Merge tag 'io_uring-6.6-2023-10-06' of git://git.kernel.dk/linux

[thirdparty/linux.git] / fs / btrfs / disk-io.c

// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (C) 2007 Oracle.  All rights reserved.
 */

#include <linux/fs.h>
#include <linux/blkdev.h>
#include <linux/radix-tree.h>
#include <linux/writeback.h>
#include <linux/workqueue.h>
#include <linux/kthread.h>
#include <linux/slab.h>
#include <linux/migrate.h>
#include <linux/ratelimit.h>
#include <linux/uuid.h>
#include <linux/semaphore.h>
#include <linux/error-injection.h>
#include <linux/crc32c.h>
#include <linux/sched/mm.h>
#include <asm/unaligned.h>
#include <crypto/hash.h>
#include "ctree.h"
#include "disk-io.h"
#include "transaction.h"
#include "btrfs_inode.h"
#include "bio.h"
#include "print-tree.h"
#include "locking.h"
#include "tree-log.h"
#include "free-space-cache.h"
#include "free-space-tree.h"
#include "check-integrity.h"
#include "rcu-string.h"
#include "dev-replace.h"
#include "raid56.h"
#include "sysfs.h"
#include "qgroup.h"
#include "compression.h"
#include "tree-checker.h"
#include "ref-verify.h"
#include "block-group.h"
#include "discard.h"
#include "space-info.h"
#include "zoned.h"
#include "subpage.h"
#include "fs.h"
#include "accessors.h"
#include "extent-tree.h"
#include "root-tree.h"
#include "defrag.h"
#include "uuid-tree.h"
#include "relocation.h"
#include "scrub.h"
#include "super.h"

#define BTRFS_SUPER_FLAG_SUPP   (BTRFS_HEADER_FLAG_WRITTEN |\
                                 BTRFS_HEADER_FLAG_RELOC |\
                                 BTRFS_SUPER_FLAG_ERROR |\
                                 BTRFS_SUPER_FLAG_SEEDING |\
                                 BTRFS_SUPER_FLAG_METADUMP |\
                                 BTRFS_SUPER_FLAG_METADUMP_V2)

static int btrfs_cleanup_transaction(struct btrfs_fs_info *fs_info);
static void btrfs_error_commit_super(struct btrfs_fs_info *fs_info);

static void btrfs_free_csum_hash(struct btrfs_fs_info *fs_info)
{
        if (fs_info->csum_shash)
                crypto_free_shash(fs_info->csum_shash);
}

/*
 * Compute the csum of a btree block and store the result to provided buffer.
 */
static void csum_tree_block(struct extent_buffer *buf, u8 *result)
{
        struct btrfs_fs_info *fs_info = buf->fs_info;
        const int num_pages = num_extent_pages(buf);
        const int first_page_part = min_t(u32, PAGE_SIZE, fs_info->nodesize);
        SHASH_DESC_ON_STACK(shash, fs_info->csum_shash);
        char *kaddr;
        int i;

        shash->tfm = fs_info->csum_shash;
        crypto_shash_init(shash);
        kaddr = page_address(buf->pages[0]) + offset_in_page(buf->start);
        crypto_shash_update(shash, kaddr + BTRFS_CSUM_SIZE,
                            first_page_part - BTRFS_CSUM_SIZE);

        for (i = 1; i < num_pages && INLINE_EXTENT_BUFFER_PAGES > 1; i++) {
                kaddr = page_address(buf->pages[i]);
                crypto_shash_update(shash, kaddr, PAGE_SIZE);
        }
        memset(result, 0, BTRFS_CSUM_SIZE);
        crypto_shash_final(shash, result);
}

/*
 * we can't consider a given block up to date unless the transid of the
 * block matches the transid in the parent node's pointer.  This is how we
 * detect blocks that either didn't get written at all or got written
 * in the wrong place.
 */
int btrfs_buffer_uptodate(struct extent_buffer *eb, u64 parent_transid, int atomic)
{
        if (!extent_buffer_uptodate(eb))
                return 0;

        if (!parent_transid || btrfs_header_generation(eb) == parent_transid)
                return 1;

        if (atomic)
                return -EAGAIN;

        if (!extent_buffer_uptodate(eb) ||
            btrfs_header_generation(eb) != parent_transid) {
                btrfs_err_rl(eb->fs_info,
"parent transid verify failed on logical %llu mirror %u wanted %llu found %llu",
                        eb->start, eb->read_mirror,
                        parent_transid, btrfs_header_generation(eb));
                clear_extent_buffer_uptodate(eb);
                return 0;
        }
        return 1;
}

static bool btrfs_supported_super_csum(u16 csum_type)
{
        switch (csum_type) {
        case BTRFS_CSUM_TYPE_CRC32:
        case BTRFS_CSUM_TYPE_XXHASH:
        case BTRFS_CSUM_TYPE_SHA256:
        case BTRFS_CSUM_TYPE_BLAKE2:
                return true;
        default:
                return false;
        }
}

/*
 * Return 0 if the superblock checksum type matches the checksum value of that
 * algorithm. Pass the raw disk superblock data.
 */
int btrfs_check_super_csum(struct btrfs_fs_info *fs_info,
                           const struct btrfs_super_block *disk_sb)
{
        char result[BTRFS_CSUM_SIZE];
        SHASH_DESC_ON_STACK(shash, fs_info->csum_shash);

        shash->tfm = fs_info->csum_shash;

        /*
         * The super_block structure does not span the whole
         * BTRFS_SUPER_INFO_SIZE range, we expect that the unused space is
         * filled with zeros and is included in the checksum.
         */
        crypto_shash_digest(shash, (const u8 *)disk_sb + BTRFS_CSUM_SIZE,
                            BTRFS_SUPER_INFO_SIZE - BTRFS_CSUM_SIZE, result);

        if (memcmp(disk_sb->csum, result, fs_info->csum_size))
                return 1;

        return 0;
}

static int btrfs_repair_eb_io_failure(const struct extent_buffer *eb,
                                      int mirror_num)
{
        struct btrfs_fs_info *fs_info = eb->fs_info;
        int i, num_pages = num_extent_pages(eb);
        int ret = 0;

        if (sb_rdonly(fs_info->sb))
                return -EROFS;

        for (i = 0; i < num_pages; i++) {
                struct page *p = eb->pages[i];
                u64 start = max_t(u64, eb->start, page_offset(p));
                u64 end = min_t(u64, eb->start + eb->len, page_offset(p) + PAGE_SIZE);
                u32 len = end - start;

                ret = btrfs_repair_io_failure(fs_info, 0, start, len,
                                start, p, offset_in_page(start), mirror_num);
                if (ret)
                        break;
        }

        return ret;
}

/*
 * helper to read a given tree block, doing retries as required when
 * the checksums don't match and we have alternate mirrors to try.
 *
 * @check:              expected tree parentness check, see the comments of the
 *                      structure for details.
 */
int btrfs_read_extent_buffer(struct extent_buffer *eb,
                             struct btrfs_tree_parent_check *check)
{
        struct btrfs_fs_info *fs_info = eb->fs_info;
        int failed = 0;
        int ret;
        int num_copies = 0;
        int mirror_num = 0;
        int failed_mirror = 0;

        ASSERT(check);

        while (1) {
                clear_bit(EXTENT_BUFFER_CORRUPT, &eb->bflags);
                ret = read_extent_buffer_pages(eb, WAIT_COMPLETE, mirror_num, check);
                if (!ret)
                        break;

                num_copies = btrfs_num_copies(fs_info,
                                              eb->start, eb->len);
                if (num_copies == 1)
                        break;

                if (!failed_mirror) {
                        failed = 1;
                        failed_mirror = eb->read_mirror;
                }

                mirror_num++;
                if (mirror_num == failed_mirror)
                        mirror_num++;

                if (mirror_num > num_copies)
                        break;
        }

        if (failed && !ret && failed_mirror)
                btrfs_repair_eb_io_failure(eb, failed_mirror);

        return ret;
}

/*
 * Checksum a dirty tree block before IO.
 */
blk_status_t btree_csum_one_bio(struct btrfs_bio *bbio)
{
        struct extent_buffer *eb = bbio->private;
        struct btrfs_fs_info *fs_info = eb->fs_info;
        u64 found_start = btrfs_header_bytenr(eb);
        u8 result[BTRFS_CSUM_SIZE];
        int ret;

        /* Btree blocks are always contiguous on disk. */
        if (WARN_ON_ONCE(bbio->file_offset != eb->start))
                return BLK_STS_IOERR;
        if (WARN_ON_ONCE(bbio->bio.bi_iter.bi_size != eb->len))
                return BLK_STS_IOERR;

        if (test_bit(EXTENT_BUFFER_NO_CHECK, &eb->bflags)) {
                WARN_ON_ONCE(found_start != 0);
                return BLK_STS_OK;
        }

        if (WARN_ON_ONCE(found_start != eb->start))
                return BLK_STS_IOERR;
        if (WARN_ON(!btrfs_page_test_uptodate(fs_info, eb->pages[0], eb->start,
                                              eb->len)))
                return BLK_STS_IOERR;

        ASSERT(memcmp_extent_buffer(eb, fs_info->fs_devices->metadata_uuid,
                                    offsetof(struct btrfs_header, fsid),
                                    BTRFS_FSID_SIZE) == 0);
        csum_tree_block(eb, result);

        if (btrfs_header_level(eb))
                ret = btrfs_check_node(eb);
        else
                ret = btrfs_check_leaf(eb);

        if (ret < 0)
                goto error;

        /*
         * Also check the generation, the eb reached here must be newer than
         * last committed. Or something seriously wrong happened.
         */
        if (unlikely(btrfs_header_generation(eb) <= fs_info->last_trans_committed)) {
                ret = -EUCLEAN;
                btrfs_err(fs_info,
                        "block=%llu bad generation, have %llu expect > %llu",
                          eb->start, btrfs_header_generation(eb),
                          fs_info->last_trans_committed);
                goto error;
        }
        write_extent_buffer(eb, result, 0, fs_info->csum_size);
        return BLK_STS_OK;

error:
        btrfs_print_tree(eb, 0);
        btrfs_err(fs_info, "block=%llu write time tree block corruption detected",
                  eb->start);
        /*
         * Be noisy if this is an extent buffer from a log tree. We don't abort
         * a transaction in case there's a bad log tree extent buffer, we just
         * fallback to a transaction commit. Still we want to know when there is
         * a bad log tree extent buffer, as that may signal a bug somewhere.
         */
        WARN_ON(IS_ENABLED(CONFIG_BTRFS_DEBUG) ||
                btrfs_header_owner(eb) == BTRFS_TREE_LOG_OBJECTID);
        return errno_to_blk_status(ret);
}

static bool check_tree_block_fsid(struct extent_buffer *eb)
{
        struct btrfs_fs_info *fs_info = eb->fs_info;
        struct btrfs_fs_devices *fs_devices = fs_info->fs_devices, *seed_devs;
        u8 fsid[BTRFS_FSID_SIZE];

        read_extent_buffer(eb, fsid, offsetof(struct btrfs_header, fsid),
                           BTRFS_FSID_SIZE);

        /*
         * alloc_fs_devices() copies the fsid into metadata_uuid if the
         * metadata_uuid is unset in the superblock, including for a seed device.
         * So, we can use fs_devices->metadata_uuid.
         */
        if (memcmp(fsid, fs_info->fs_devices->metadata_uuid, BTRFS_FSID_SIZE) == 0)
                return false;

        list_for_each_entry(seed_devs, &fs_devices->seed_list, seed_list)
                if (!memcmp(fsid, seed_devs->fsid, BTRFS_FSID_SIZE))
                        return false;

        return true;
}

/* Do basic extent buffer checks at read time */
int btrfs_validate_extent_buffer(struct extent_buffer *eb,
                                 struct btrfs_tree_parent_check *check)
{
        struct btrfs_fs_info *fs_info = eb->fs_info;
        u64 found_start;
        const u32 csum_size = fs_info->csum_size;
        u8 found_level;
        u8 result[BTRFS_CSUM_SIZE];
        const u8 *header_csum;
        int ret = 0;

        ASSERT(check);

        found_start = btrfs_header_bytenr(eb);
        if (found_start != eb->start) {
                btrfs_err_rl(fs_info,
                        "bad tree block start, mirror %u want %llu have %llu",
                             eb->read_mirror, eb->start, found_start);
                ret = -EIO;
                goto out;
        }
        if (check_tree_block_fsid(eb)) {
                btrfs_err_rl(fs_info, "bad fsid on logical %llu mirror %u",
                             eb->start, eb->read_mirror);
                ret = -EIO;
                goto out;
        }
        found_level = btrfs_header_level(eb);
        if (found_level >= BTRFS_MAX_LEVEL) {
                btrfs_err(fs_info,
                        "bad tree block level, mirror %u level %d on logical %llu",
                        eb->read_mirror, btrfs_header_level(eb), eb->start);
                ret = -EIO;
                goto out;
        }

        csum_tree_block(eb, result);
        header_csum = page_address(eb->pages[0]) +
                get_eb_offset_in_page(eb, offsetof(struct btrfs_header, csum));

        if (memcmp(result, header_csum, csum_size) != 0) {
                btrfs_warn_rl(fs_info,
"checksum verify failed on logical %llu mirror %u wanted " CSUM_FMT " found " CSUM_FMT " level %d",
                              eb->start, eb->read_mirror,
                              CSUM_FMT_VALUE(csum_size, header_csum),
                              CSUM_FMT_VALUE(csum_size, result),
                              btrfs_header_level(eb));
                ret = -EUCLEAN;
                goto out;
        }

        if (found_level != check->level) {
                btrfs_err(fs_info,
                "level verify failed on logical %llu mirror %u wanted %u found %u",
                          eb->start, eb->read_mirror, check->level, found_level);
                ret = -EIO;
                goto out;
        }
        if (unlikely(check->transid &&
                     btrfs_header_generation(eb) != check->transid)) {
                btrfs_err_rl(eb->fs_info,
"parent transid verify failed on logical %llu mirror %u wanted %llu found %llu",
                                eb->start, eb->read_mirror, check->transid,
                                btrfs_header_generation(eb));
                ret = -EIO;
                goto out;
        }
        if (check->has_first_key) {
                struct btrfs_key *expect_key = &check->first_key;
                struct btrfs_key found_key;

                if (found_level)
                        btrfs_node_key_to_cpu(eb, &found_key, 0);
                else
                        btrfs_item_key_to_cpu(eb, &found_key, 0);
                if (unlikely(btrfs_comp_cpu_keys(expect_key, &found_key))) {
                        btrfs_err(fs_info,
"tree first key mismatch detected, bytenr=%llu parent_transid=%llu key expected=(%llu,%u,%llu) has=(%llu,%u,%llu)",
                                  eb->start, check->transid,
                                  expect_key->objectid,
                                  expect_key->type, expect_key->offset,
                                  found_key.objectid, found_key.type,
                                  found_key.offset);
                        ret = -EUCLEAN;
                        goto out;
                }
        }
        if (check->owner_root) {
                ret = btrfs_check_eb_owner(eb, check->owner_root);
                if (ret < 0)
                        goto out;
        }

        /*
         * If this is a leaf block and it is corrupt, set the corrupt bit so
         * that we don't try and read the other copies of this block, just
         * return -EIO.
         */
        if (found_level == 0 && btrfs_check_leaf(eb)) {
                set_bit(EXTENT_BUFFER_CORRUPT, &eb->bflags);
                ret = -EIO;
        }

        if (found_level > 0 && btrfs_check_node(eb))
                ret = -EIO;

        if (ret)
                btrfs_err(fs_info,
                "read time tree block corruption detected on logical %llu mirror %u",
                          eb->start, eb->read_mirror);
out:
        return ret;
}

#ifdef CONFIG_MIGRATION
static int btree_migrate_folio(struct address_space *mapping,
                struct folio *dst, struct folio *src, enum migrate_mode mode)
{
        /*
         * we can't safely write a btree page from here,
         * we haven't done the locking hook
         */
        if (folio_test_dirty(src))
                return -EAGAIN;
        /*
         * Buffers may be managed in a filesystem specific way.
         * We must have no buffers or drop them.
         */
        if (folio_get_private(src) &&
            !filemap_release_folio(src, GFP_KERNEL))
                return -EAGAIN;
        return migrate_folio(mapping, dst, src, mode);
}
#else
#define btree_migrate_folio NULL
#endif

static int btree_writepages(struct address_space *mapping,
                            struct writeback_control *wbc)
{
        struct btrfs_fs_info *fs_info;
        int ret;

        if (wbc->sync_mode == WB_SYNC_NONE) {

                if (wbc->for_kupdate)
                        return 0;

                fs_info = BTRFS_I(mapping->host)->root->fs_info;
                /* this is a bit racy, but that's ok */
                ret = __percpu_counter_compare(&fs_info->dirty_metadata_bytes,
                                             BTRFS_DIRTY_METADATA_THRESH,
                                             fs_info->dirty_metadata_batch);
                if (ret < 0)
                        return 0;
        }
        return btree_write_cache_pages(mapping, wbc);
}

static bool btree_release_folio(struct folio *folio, gfp_t gfp_flags)
{
        if (folio_test_writeback(folio) || folio_test_dirty(folio))
                return false;

        return try_release_extent_buffer(&folio->page);
}

static void btree_invalidate_folio(struct folio *folio, size_t offset,
                                 size_t length)
{
        struct extent_io_tree *tree;
        tree = &BTRFS_I(folio->mapping->host)->io_tree;
        extent_invalidate_folio(tree, folio, offset);
        btree_release_folio(folio, GFP_NOFS);
        if (folio_get_private(folio)) {
                btrfs_warn(BTRFS_I(folio->mapping->host)->root->fs_info,
                           "folio private not zero on folio %llu",
                           (unsigned long long)folio_pos(folio));
                folio_detach_private(folio);
        }
}

#ifdef DEBUG
static bool btree_dirty_folio(struct address_space *mapping,
                struct folio *folio)
{
        struct btrfs_fs_info *fs_info = btrfs_sb(mapping->host->i_sb);
        struct btrfs_subpage_info *spi = fs_info->subpage_info;
        struct btrfs_subpage *subpage;
        struct extent_buffer *eb;
        int cur_bit = 0;
        u64 page_start = folio_pos(folio);

        if (fs_info->sectorsize == PAGE_SIZE) {
                eb = folio_get_private(folio);
                BUG_ON(!eb);
                BUG_ON(!test_bit(EXTENT_BUFFER_DIRTY, &eb->bflags));
                BUG_ON(!atomic_read(&eb->refs));
                btrfs_assert_tree_write_locked(eb);
                return filemap_dirty_folio(mapping, folio);
        }

        ASSERT(spi);
        subpage = folio_get_private(folio);

        for (cur_bit = spi->dirty_offset;
             cur_bit < spi->dirty_offset + spi->bitmap_nr_bits;
             cur_bit++) {
                unsigned long flags;
                u64 cur;

                spin_lock_irqsave(&subpage->lock, flags);
                if (!test_bit(cur_bit, subpage->bitmaps)) {
                        spin_unlock_irqrestore(&subpage->lock, flags);
                        continue;
                }
                spin_unlock_irqrestore(&subpage->lock, flags);
                cur = page_start + cur_bit * fs_info->sectorsize;

                eb = find_extent_buffer(fs_info, cur);
                ASSERT(eb);
                ASSERT(test_bit(EXTENT_BUFFER_DIRTY, &eb->bflags));
                ASSERT(atomic_read(&eb->refs));
                btrfs_assert_tree_write_locked(eb);
                free_extent_buffer(eb);

                cur_bit += (fs_info->nodesize >> fs_info->sectorsize_bits) - 1;
        }
        return filemap_dirty_folio(mapping, folio);
}
#else
#define btree_dirty_folio filemap_dirty_folio
#endif

static const struct address_space_operations btree_aops = {
        .writepages     = btree_writepages,
        .release_folio  = btree_release_folio,
        .invalidate_folio = btree_invalidate_folio,
        .migrate_folio  = btree_migrate_folio,
        .dirty_folio    = btree_dirty_folio,
};

struct extent_buffer *btrfs_find_create_tree_block(
                                                struct btrfs_fs_info *fs_info,
                                                u64 bytenr, u64 owner_root,
                                                int level)
{
        if (btrfs_is_testing(fs_info))
                return alloc_test_extent_buffer(fs_info, bytenr);
        return alloc_extent_buffer(fs_info, bytenr, owner_root, level);
}

/*
 * Read tree block at logical address @bytenr and do variant basic but critical
 * verification.
 *
 * @check:              expected tree parentness check, see comments of the
 *                      structure for details.
 */
struct extent_buffer *read_tree_block(struct btrfs_fs_info *fs_info, u64 bytenr,
                                      struct btrfs_tree_parent_check *check)
{
        struct extent_buffer *buf = NULL;
        int ret;

        ASSERT(check);

        buf = btrfs_find_create_tree_block(fs_info, bytenr, check->owner_root,
                                           check->level);
        if (IS_ERR(buf))
                return buf;

        ret = btrfs_read_extent_buffer(buf, check);
        if (ret) {
                free_extent_buffer_stale(buf);
                return ERR_PTR(ret);
        }
        if (btrfs_check_eb_owner(buf, check->owner_root)) {
                free_extent_buffer_stale(buf);
                return ERR_PTR(-EUCLEAN);
        }
        return buf;

}

static void __setup_root(struct btrfs_root *root, struct btrfs_fs_info *fs_info,
                         u64 objectid)
{
        bool dummy = test_bit(BTRFS_FS_STATE_DUMMY_FS_INFO, &fs_info->fs_state);

        memset(&root->root_key, 0, sizeof(root->root_key));
        memset(&root->root_item, 0, sizeof(root->root_item));
        memset(&root->defrag_progress, 0, sizeof(root->defrag_progress));
        root->fs_info = fs_info;
        root->root_key.objectid = objectid;
        root->node = NULL;
        root->commit_root = NULL;
        root->state = 0;
        RB_CLEAR_NODE(&root->rb_node);

        root->last_trans = 0;
        root->free_objectid = 0;
        root->nr_delalloc_inodes = 0;
        root->nr_ordered_extents = 0;
        root->inode_tree = RB_ROOT;
        INIT_RADIX_TREE(&root->delayed_nodes_tree, GFP_ATOMIC);

        btrfs_init_root_block_rsv(root);

        INIT_LIST_HEAD(&root->dirty_list);
        INIT_LIST_HEAD(&root->root_list);
        INIT_LIST_HEAD(&root->delalloc_inodes);
        INIT_LIST_HEAD(&root->delalloc_root);
        INIT_LIST_HEAD(&root->ordered_extents);
        INIT_LIST_HEAD(&root->ordered_root);
        INIT_LIST_HEAD(&root->reloc_dirty_list);
        INIT_LIST_HEAD(&root->logged_list[0]);
        INIT_LIST_HEAD(&root->logged_list[1]);
        spin_lock_init(&root->inode_lock);
        spin_lock_init(&root->delalloc_lock);
        spin_lock_init(&root->ordered_extent_lock);
        spin_lock_init(&root->accounting_lock);
        spin_lock_init(&root->log_extents_lock[0]);
        spin_lock_init(&root->log_extents_lock[1]);
        spin_lock_init(&root->qgroup_meta_rsv_lock);
        mutex_init(&root->objectid_mutex);
        mutex_init(&root->log_mutex);
        mutex_init(&root->ordered_extent_mutex);
        mutex_init(&root->delalloc_mutex);
        init_waitqueue_head(&root->qgroup_flush_wait);
        init_waitqueue_head(&root->log_writer_wait);
        init_waitqueue_head(&root->log_commit_wait[0]);
        init_waitqueue_head(&root->log_commit_wait[1]);
        INIT_LIST_HEAD(&root->log_ctxs[0]);
        INIT_LIST_HEAD(&root->log_ctxs[1]);
        atomic_set(&root->log_commit[0], 0);
        atomic_set(&root->log_commit[1], 0);
        atomic_set(&root->log_writers, 0);
        atomic_set(&root->log_batch, 0);
        refcount_set(&root->refs, 1);
        atomic_set(&root->snapshot_force_cow, 0);
        atomic_set(&root->nr_swapfiles, 0);
        root->log_transid = 0;
        root->log_transid_committed = -1;
        root->last_log_commit = 0;
        root->anon_dev = 0;
        if (!dummy) {
                extent_io_tree_init(fs_info, &root->dirty_log_pages,
                                    IO_TREE_ROOT_DIRTY_LOG_PAGES);
                extent_io_tree_init(fs_info, &root->log_csum_range,
                                    IO_TREE_LOG_CSUM_RANGE);
        }

        spin_lock_init(&root->root_item_lock);
        btrfs_qgroup_init_swapped_blocks(&root->swapped_blocks);
#ifdef CONFIG_BTRFS_DEBUG
        INIT_LIST_HEAD(&root->leak_list);
        spin_lock(&fs_info->fs_roots_radix_lock);
        list_add_tail(&root->leak_list, &fs_info->allocated_roots);
        spin_unlock(&fs_info->fs_roots_radix_lock);
#endif
}

static struct btrfs_root *btrfs_alloc_root(struct btrfs_fs_info *fs_info,
                                           u64 objectid, gfp_t flags)
{
        struct btrfs_root *root = kzalloc(sizeof(*root), flags);
        if (root)
                __setup_root(root, fs_info, objectid);
        return root;
}

#ifdef CONFIG_BTRFS_FS_RUN_SANITY_TESTS
/* Should only be used by the testing infrastructure */
struct btrfs_root *btrfs_alloc_dummy_root(struct btrfs_fs_info *fs_info)
{
        struct btrfs_root *root;

        if (!fs_info)
                return ERR_PTR(-EINVAL);

        root = btrfs_alloc_root(fs_info, BTRFS_ROOT_TREE_OBJECTID, GFP_KERNEL);
        if (!root)
                return ERR_PTR(-ENOMEM);

        /* We don't use the stripesize in selftest, set it as sectorsize */
        root->alloc_bytenr = 0;

        return root;
}
#endif

static int global_root_cmp(struct rb_node *a_node, const struct rb_node *b_node)
{
        const struct btrfs_root *a = rb_entry(a_node, struct btrfs_root, rb_node);
        const struct btrfs_root *b = rb_entry(b_node, struct btrfs_root, rb_node);

        return btrfs_comp_cpu_keys(&a->root_key, &b->root_key);
}

static int global_root_key_cmp(const void *k, const struct rb_node *node)
{
        const struct btrfs_key *key = k;
        const struct btrfs_root *root = rb_entry(node, struct btrfs_root, rb_node);

        return btrfs_comp_cpu_keys(key, &root->root_key);
}

int btrfs_global_root_insert(struct btrfs_root *root)
{
        struct btrfs_fs_info *fs_info = root->fs_info;
        struct rb_node *tmp;
        int ret = 0;

        write_lock(&fs_info->global_root_lock);
        tmp = rb_find_add(&root->rb_node, &fs_info->global_root_tree, global_root_cmp);
        write_unlock(&fs_info->global_root_lock);

        if (tmp) {
                ret = -EEXIST;
                btrfs_warn(fs_info, "global root %llu %llu already exists",
                                root->root_key.objectid, root->root_key.offset);
        }
        return ret;
}

void btrfs_global_root_delete(struct btrfs_root *root)
{
        struct btrfs_fs_info *fs_info = root->fs_info;

        write_lock(&fs_info->global_root_lock);
        rb_erase(&root->rb_node, &fs_info->global_root_tree);
        write_unlock(&fs_info->global_root_lock);
}

struct btrfs_root *btrfs_global_root(struct btrfs_fs_info *fs_info,
                                     struct btrfs_key *key)
{
        struct rb_node *node;
        struct btrfs_root *root = NULL;

        read_lock(&fs_info->global_root_lock);
        node = rb_find(key, &fs_info->global_root_tree, global_root_key_cmp);
        if (node)
                root = container_of(node, struct btrfs_root, rb_node);
        read_unlock(&fs_info->global_root_lock);

        return root;
}

static u64 btrfs_global_root_id(struct btrfs_fs_info *fs_info, u64 bytenr)
{
        struct btrfs_block_group *block_group;
        u64 ret;

        if (!btrfs_fs_incompat(fs_info, EXTENT_TREE_V2))
                return 0;

        if (bytenr)
                block_group = btrfs_lookup_block_group(fs_info, bytenr);
        else
                block_group = btrfs_lookup_first_block_group(fs_info, bytenr);
        ASSERT(block_group);
        if (!block_group)
                return 0;
        ret = block_group->global_root_id;
        btrfs_put_block_group(block_group);

        return ret;
}

struct btrfs_root *btrfs_csum_root(struct btrfs_fs_info *fs_info, u64 bytenr)
{
        struct btrfs_key key = {
                .objectid = BTRFS_CSUM_TREE_OBJECTID,
                .type = BTRFS_ROOT_ITEM_KEY,
                .offset = btrfs_global_root_id(fs_info, bytenr),
        };

        return btrfs_global_root(fs_info, &key);
}

struct btrfs_root *btrfs_extent_root(struct btrfs_fs_info *fs_info, u64 bytenr)
{
        struct btrfs_key key = {
                .objectid = BTRFS_EXTENT_TREE_OBJECTID,
                .type = BTRFS_ROOT_ITEM_KEY,
                .offset = btrfs_global_root_id(fs_info, bytenr),
        };

        return btrfs_global_root(fs_info, &key);
}

struct btrfs_root *btrfs_block_group_root(struct btrfs_fs_info *fs_info)
{
        if (btrfs_fs_compat_ro(fs_info, BLOCK_GROUP_TREE))
                return fs_info->block_group_root;
        return btrfs_extent_root(fs_info, 0);
}

struct btrfs_root *btrfs_create_tree(struct btrfs_trans_handle *trans,
                                     u64 objectid)
{
        struct btrfs_fs_info *fs_info = trans->fs_info;
        struct extent_buffer *leaf;
        struct btrfs_root *tree_root = fs_info->tree_root;
        struct btrfs_root *root;
        struct btrfs_key key;
        unsigned int nofs_flag;
        int ret = 0;

        /*
         * We're holding a transaction handle, so use a NOFS memory allocation
         * context to avoid deadlock if reclaim happens.
         */
        nofs_flag = memalloc_nofs_save();
        root = btrfs_alloc_root(fs_info, objectid, GFP_KERNEL);
        memalloc_nofs_restore(nofs_flag);
        if (!root)
                return ERR_PTR(-ENOMEM);

        root->root_key.objectid = objectid;
        root->root_key.type = BTRFS_ROOT_ITEM_KEY;
        root->root_key.offset = 0;

        leaf = btrfs_alloc_tree_block(trans, root, 0, objectid, NULL, 0, 0, 0,
                                      BTRFS_NESTING_NORMAL);
        if (IS_ERR(leaf)) {
                ret = PTR_ERR(leaf);
                leaf = NULL;
                goto fail;
        }

        root->node = leaf;
        btrfs_mark_buffer_dirty(leaf);

        root->commit_root = btrfs_root_node(root);
        set_bit(BTRFS_ROOT_TRACK_DIRTY, &root->state);

        btrfs_set_root_flags(&root->root_item, 0);
        btrfs_set_root_limit(&root->root_item, 0);
        btrfs_set_root_bytenr(&root->root_item, leaf->start);
        btrfs_set_root_generation(&root->root_item, trans->transid);
        btrfs_set_root_level(&root->root_item, 0);
        btrfs_set_root_refs(&root->root_item, 1);
        btrfs_set_root_used(&root->root_item, leaf->len);
        btrfs_set_root_last_snapshot(&root->root_item, 0);
        btrfs_set_root_dirid(&root->root_item, 0);
        if (is_fstree(objectid))
                generate_random_guid(root->root_item.uuid);
        else
                export_guid(root->root_item.uuid, &guid_null);
        btrfs_set_root_drop_level(&root->root_item, 0);

        btrfs_tree_unlock(leaf);

        key.objectid = objectid;
        key.type = BTRFS_ROOT_ITEM_KEY;
        key.offset = 0;
        ret = btrfs_insert_root(trans, tree_root, &key, &root->root_item);
        if (ret)
                goto fail;

        return root;

fail:
        btrfs_put_root(root);

        return ERR_PTR(ret);
}

static struct btrfs_root *alloc_log_tree(struct btrfs_trans_handle *trans,
                                         struct btrfs_fs_info *fs_info)
{
        struct btrfs_root *root;

        root = btrfs_alloc_root(fs_info, BTRFS_TREE_LOG_OBJECTID, GFP_NOFS);
        if (!root)
                return ERR_PTR(-ENOMEM);

        root->root_key.objectid = BTRFS_TREE_LOG_OBJECTID;
        root->root_key.type = BTRFS_ROOT_ITEM_KEY;
        root->root_key.offset = BTRFS_TREE_LOG_OBJECTID;

        return root;
}

int btrfs_alloc_log_tree_node(struct btrfs_trans_handle *trans,
                              struct btrfs_root *root)
{
        struct extent_buffer *leaf;

        /*
         * DON'T set SHAREABLE bit for log trees.
         *
         * Log trees are not exposed to user space thus can't be snapshotted,
         * and they go away before a real commit is actually done.
         *
         * They do store pointers to file data extents, and those reference
         * counts still get updated (along with back refs to the log tree).
         */

        leaf = btrfs_alloc_tree_block(trans, root, 0, BTRFS_TREE_LOG_OBJECTID,
                        NULL, 0, 0, 0, BTRFS_NESTING_NORMAL);
        if (IS_ERR(leaf))
                return PTR_ERR(leaf);

        root->node = leaf;

        btrfs_mark_buffer_dirty(root->node);
        btrfs_tree_unlock(root->node);

        return 0;
}

int btrfs_init_log_root_tree(struct btrfs_trans_handle *trans,
                             struct btrfs_fs_info *fs_info)
{
        struct btrfs_root *log_root;

        log_root = alloc_log_tree(trans, fs_info);
        if (IS_ERR(log_root))
                return PTR_ERR(log_root);

        if (!btrfs_is_zoned(fs_info)) {
                int ret = btrfs_alloc_log_tree_node(trans, log_root);

                if (ret) {
                        btrfs_put_root(log_root);
                        return ret;
                }
        }

        WARN_ON(fs_info->log_root_tree);
        fs_info->log_root_tree = log_root;
        return 0;
}

int btrfs_add_log_tree(struct btrfs_trans_handle *trans,
                       struct btrfs_root *root)
{
        struct btrfs_fs_info *fs_info = root->fs_info;
        struct btrfs_root *log_root;
        struct btrfs_inode_item *inode_item;
        int ret;

        log_root = alloc_log_tree(trans, fs_info);
        if (IS_ERR(log_root))
                return PTR_ERR(log_root);

        ret = btrfs_alloc_log_tree_node(trans, log_root);
        if (ret) {
                btrfs_put_root(log_root);
                return ret;
        }

        log_root->last_trans = trans->transid;
        log_root->root_key.offset = root->root_key.objectid;

        inode_item = &log_root->root_item.inode;
        btrfs_set_stack_inode_generation(inode_item, 1);
        btrfs_set_stack_inode_size(inode_item, 3);
        btrfs_set_stack_inode_nlink(inode_item, 1);
        btrfs_set_stack_inode_nbytes(inode_item,
                                     fs_info->nodesize);
        btrfs_set_stack_inode_mode(inode_item, S_IFDIR | 0755);

        btrfs_set_root_node(&log_root->root_item, log_root->node);

        WARN_ON(root->log_root);
        root->log_root = log_root;
        root->log_transid = 0;
        root->log_transid_committed = -1;
        root->last_log_commit = 0;
        return 0;
}

static struct btrfs_root *read_tree_root_path(struct btrfs_root *tree_root,
                                              struct btrfs_path *path,
                                              struct btrfs_key *key)
{
        struct btrfs_root *root;
        struct btrfs_tree_parent_check check = { 0 };
        struct btrfs_fs_info *fs_info = tree_root->fs_info;
        u64 generation;
        int ret;
        int level;

        root = btrfs_alloc_root(fs_info, key->objectid, GFP_NOFS);
        if (!root)
                return ERR_PTR(-ENOMEM);

        ret = btrfs_find_root(tree_root, key, path,
                              &root->root_item, &root->root_key);
        if (ret) {
                if (ret > 0)
                        ret = -ENOENT;
                goto fail;
        }

        generation = btrfs_root_generation(&root->root_item);
        level = btrfs_root_level(&root->root_item);
        check.level = level;
        check.transid = generation;
        check.owner_root = key->objectid;
        root->node = read_tree_block(fs_info, btrfs_root_bytenr(&root->root_item),
                                     &check);
        if (IS_ERR(root->node)) {
                ret = PTR_ERR(root->node);
                root->node = NULL;
                goto fail;
        }
        if (!btrfs_buffer_uptodate(root->node, generation, 0)) {
                ret = -EIO;
                goto fail;
        }

        /*
         * For real fs, and not log/reloc trees, root owner must
         * match its root node owner
         */
        if (!test_bit(BTRFS_FS_STATE_DUMMY_FS_INFO, &fs_info->fs_state) &&
            root->root_key.objectid != BTRFS_TREE_LOG_OBJECTID &&
            root->root_key.objectid != BTRFS_TREE_RELOC_OBJECTID &&
            root->root_key.objectid != btrfs_header_owner(root->node)) {
                btrfs_crit(fs_info,
"root=%llu block=%llu, tree root owner mismatch, have %llu expect %llu",
                           root->root_key.objectid, root->node->start,
                           btrfs_header_owner(root->node),
                           root->root_key.objectid);
                ret = -EUCLEAN;
                goto fail;
        }
        root->commit_root = btrfs_root_node(root);
        return root;
fail:
        btrfs_put_root(root);
        return ERR_PTR(ret);
}

struct btrfs_root *btrfs_read_tree_root(struct btrfs_root *tree_root,
                                        struct btrfs_key *key)
{
        struct btrfs_root *root;
        struct btrfs_path *path;

        path = btrfs_alloc_path();
        if (!path)
                return ERR_PTR(-ENOMEM);
        root = read_tree_root_path(tree_root, path, key);
        btrfs_free_path(path);

        return root;
}

/*
 * Initialize subvolume root in-memory structure
 *
 * @anon_dev:   anonymous device to attach to the root, if zero, allocate new
 */
static int btrfs_init_fs_root(struct btrfs_root *root, dev_t anon_dev)
{
        int ret;

        btrfs_drew_lock_init(&root->snapshot_lock);

        if (root->root_key.objectid != BTRFS_TREE_LOG_OBJECTID &&
            !btrfs_is_data_reloc_root(root) &&
            is_fstree(root->root_key.objectid)) {
                set_bit(BTRFS_ROOT_SHAREABLE, &root->state);
                btrfs_check_and_init_root_item(&root->root_item);
        }

        /*
         * Don't assign anonymous block device to roots that are not exposed to
         * userspace, the id pool is limited to 1M
         */
        if (is_fstree(root->root_key.objectid) &&
            btrfs_root_refs(&root->root_item) > 0) {
                if (!anon_dev) {
                        ret = get_anon_bdev(&root->anon_dev);
                        if (ret)
                                goto fail;
                } else {
                        root->anon_dev = anon_dev;
                }
        }

        mutex_lock(&root->objectid_mutex);
        ret = btrfs_init_root_free_objectid(root);
        if (ret) {
                mutex_unlock(&root->objectid_mutex);
                goto fail;
        }

        ASSERT(root->free_objectid <= BTRFS_LAST_FREE_OBJECTID);

        mutex_unlock(&root->objectid_mutex);

        return 0;
fail:
        /* The caller is responsible to call btrfs_free_fs_root */
        return ret;
}

static struct btrfs_root *btrfs_lookup_fs_root(struct btrfs_fs_info *fs_info,
                                               u64 root_id)
{
        struct btrfs_root *root;

        spin_lock(&fs_info->fs_roots_radix_lock);
        root = radix_tree_lookup(&fs_info->fs_roots_radix,
                                 (unsigned long)root_id);
        root = btrfs_grab_root(root);
        spin_unlock(&fs_info->fs_roots_radix_lock);
        return root;
}

static struct btrfs_root *btrfs_get_global_root(struct btrfs_fs_info *fs_info,
                                                u64 objectid)
{
        struct btrfs_key key = {
                .objectid = objectid,
                .type = BTRFS_ROOT_ITEM_KEY,
                .offset = 0,
        };

        switch (objectid) {
        case BTRFS_ROOT_TREE_OBJECTID:
                return btrfs_grab_root(fs_info->tree_root);
        case BTRFS_EXTENT_TREE_OBJECTID:
                return btrfs_grab_root(btrfs_global_root(fs_info, &key));
        case BTRFS_CHUNK_TREE_OBJECTID:
                return btrfs_grab_root(fs_info->chunk_root);
        case BTRFS_DEV_TREE_OBJECTID:
                return btrfs_grab_root(fs_info->dev_root);
        case BTRFS_CSUM_TREE_OBJECTID:
                return btrfs_grab_root(btrfs_global_root(fs_info, &key));
        case BTRFS_QUOTA_TREE_OBJECTID:
                return btrfs_grab_root(fs_info->quota_root);
        case BTRFS_UUID_TREE_OBJECTID:
                return btrfs_grab_root(fs_info->uuid_root);
        case BTRFS_BLOCK_GROUP_TREE_OBJECTID:
                return btrfs_grab_root(fs_info->block_group_root);
        case BTRFS_FREE_SPACE_TREE_OBJECTID:
                return btrfs_grab_root(btrfs_global_root(fs_info, &key));
        default:
                return NULL;
        }
}

int btrfs_insert_fs_root(struct btrfs_fs_info *fs_info,
                         struct btrfs_root *root)
{
        int ret;

        ret = radix_tree_preload(GFP_NOFS);
        if (ret)
                return ret;

        spin_lock(&fs_info->fs_roots_radix_lock);
        ret = radix_tree_insert(&fs_info->fs_roots_radix,
                                (unsigned long)root->root_key.objectid,
                                root);
        if (ret == 0) {
                btrfs_grab_root(root);
                set_bit(BTRFS_ROOT_IN_RADIX, &root->state);
        }
        spin_unlock(&fs_info->fs_roots_radix_lock);
        radix_tree_preload_end();

        return ret;
}

void btrfs_check_leaked_roots(struct btrfs_fs_info *fs_info)
{
#ifdef CONFIG_BTRFS_DEBUG
        struct btrfs_root *root;

        while (!list_empty(&fs_info->allocated_roots)) {
                char buf[BTRFS_ROOT_NAME_BUF_LEN];

                root = list_first_entry(&fs_info->allocated_roots,
                                        struct btrfs_root, leak_list);
                btrfs_err(fs_info, "leaked root %s refcount %d",
                          btrfs_root_name(&root->root_key, buf),
                          refcount_read(&root->refs));
                while (refcount_read(&root->refs) > 1)
                        btrfs_put_root(root);
                btrfs_put_root(root);
        }
#endif
}

static void free_global_roots(struct btrfs_fs_info *fs_info)
{
        struct btrfs_root *root;
        struct rb_node *node;

        while ((node = rb_first_postorder(&fs_info->global_root_tree)) != NULL) {
                root = rb_entry(node, struct btrfs_root, rb_node);
                rb_erase(&root->rb_node, &fs_info->global_root_tree);
                btrfs_put_root(root);
        }
}

void btrfs_free_fs_info(struct btrfs_fs_info *fs_info)
{
        percpu_counter_destroy(&fs_info->dirty_metadata_bytes);
        percpu_counter_destroy(&fs_info->delalloc_bytes);
        percpu_counter_destroy(&fs_info->ordered_bytes);
        percpu_counter_destroy(&fs_info->dev_replace.bio_counter);
        btrfs_free_csum_hash(fs_info);
        btrfs_free_stripe_hash_table(fs_info);
        btrfs_free_ref_cache(fs_info);
        kfree(fs_info->balance_ctl);
        kfree(fs_info->delayed_root);
        free_global_roots(fs_info);
        btrfs_put_root(fs_info->tree_root);
        btrfs_put_root(fs_info->chunk_root);
        btrfs_put_root(fs_info->dev_root);
        btrfs_put_root(fs_info->quota_root);
        btrfs_put_root(fs_info->uuid_root);
        btrfs_put_root(fs_info->fs_root);
        btrfs_put_root(fs_info->data_reloc_root);
        btrfs_put_root(fs_info->block_group_root);
        btrfs_check_leaked_roots(fs_info);
        btrfs_extent_buffer_leak_debug_check(fs_info);
        kfree(fs_info->super_copy);
        kfree(fs_info->super_for_commit);
        kfree(fs_info->subpage_info);
        kvfree(fs_info);
}


/*
 * Get an in-memory reference of a root structure.
 *
 * For essential trees like root/extent tree, we grab it from fs_info directly.
 * For subvolume trees, we check the cached filesystem roots first. If not
 * found, then read it from disk and add it to cached fs roots.
 *
 * Caller should release the root by calling btrfs_put_root() after the usage.
 *
 * NOTE: Reloc and log trees can't be read by this function as they share the
 *       same root objectid.
 *
 * @objectid:   root id
 * @anon_dev:   preallocated anonymous block device number for new roots,
 *              pass 0 for new allocation.
 * @check_ref:  whether to check root item references, If true, return -ENOENT
 *              for orphan roots
 */
static struct btrfs_root *btrfs_get_root_ref(struct btrfs_fs_info *fs_info,
                                             u64 objectid, dev_t anon_dev,
                                             bool check_ref)
{
        struct btrfs_root *root;
        struct btrfs_path *path;
        struct btrfs_key key;
        int ret;

        root = btrfs_get_global_root(fs_info, objectid);
        if (root)
                return root;

        /*
         * If we're called for non-subvolume trees, and above function didn't
         * find one, do not try to read it from disk.
         *
         * This is namely for free-space-tree and quota tree, which can change
         * at runtime and should only be grabbed from fs_info.
         */
        if (!is_fstree(objectid) && objectid != BTRFS_DATA_RELOC_TREE_OBJECTID)
                return ERR_PTR(-ENOENT);
again:
        root = btrfs_lookup_fs_root(fs_info, objectid);
        if (root) {
                /* Shouldn't get preallocated anon_dev for cached roots */
                ASSERT(!anon_dev);
                if (check_ref && btrfs_root_refs(&root->root_item) == 0) {
                        btrfs_put_root(root);
                        return ERR_PTR(-ENOENT);
                }
                return root;
        }

        key.objectid = objectid;
        key.type = BTRFS_ROOT_ITEM_KEY;
        key.offset = (u64)-1;
        root = btrfs_read_tree_root(fs_info->tree_root, &key);
        if (IS_ERR(root))
                return root;

        if (check_ref && btrfs_root_refs(&root->root_item) == 0) {
                ret = -ENOENT;
                goto fail;
        }

        ret = btrfs_init_fs_root(root, anon_dev);
        if (ret)
                goto fail;

        path = btrfs_alloc_path();
        if (!path) {
                ret = -ENOMEM;
                goto fail;
        }
        key.objectid = BTRFS_ORPHAN_OBJECTID;
        key.type = BTRFS_ORPHAN_ITEM_KEY;
        key.offset = objectid;

        ret = btrfs_search_slot(NULL, fs_info->tree_root, &key, path, 0, 0);
        btrfs_free_path(path);
        if (ret < 0)
                goto fail;
        if (ret == 0)
                set_bit(BTRFS_ROOT_ORPHAN_ITEM_INSERTED, &root->state);

        ret = btrfs_insert_fs_root(fs_info, root);
        if (ret) {
                if (ret == -EEXIST) {
                        btrfs_put_root(root);
                        goto again;
                }
                goto fail;
        }
        return root;
fail:
        /*
         * If our caller provided us an anonymous device, then it's his
         * responsibility to free it in case we fail. So we have to set our
         * root's anon_dev to 0 to avoid a double free, once by btrfs_put_root()
         * and once again by our caller.
         */
        if (anon_dev)
                root->anon_dev = 0;
        btrfs_put_root(root);
        return ERR_PTR(ret);
}

/*
 * Get in-memory reference of a root structure
 *
 * @objectid:   tree objectid
 * @check_ref:  if set, verify that the tree exists and the item has at least
 *              one reference
 */
struct btrfs_root *btrfs_get_fs_root(struct btrfs_fs_info *fs_info,
                                     u64 objectid, bool check_ref)
{
        return btrfs_get_root_ref(fs_info, objectid, 0, check_ref);
}

/*
 * Get in-memory reference of a root structure, created as new, optionally pass
 * the anonymous block device id
 *
 * @objectid:   tree objectid
 * @anon_dev:   if zero, allocate a new anonymous block device or use the
 *              parameter value
 */
struct btrfs_root *btrfs_get_new_fs_root(struct btrfs_fs_info *fs_info,
                                         u64 objectid, dev_t anon_dev)
{
        return btrfs_get_root_ref(fs_info, objectid, anon_dev, true);
}

/*
 * btrfs_get_fs_root_commit_root - return a root for the given objectid
 * @fs_info:    the fs_info
 * @objectid:   the objectid we need to lookup
 *
 * This is exclusively used for backref walking, and exists specifically because
 * of how qgroups does lookups.  Qgroups will do a backref lookup at delayed ref
 * creation time, which means we may have to read the tree_root in order to look
 * up a fs root that is not in memory.  If the root is not in memory we will
 * read the tree root commit root and look up the fs root from there.  This is a
 * temporary root, it will not be inserted into the radix tree as it doesn't
 * have the most uptodate information, it'll simply be discarded once the
 * backref code is finished using the root.
 */
struct btrfs_root *btrfs_get_fs_root_commit_root(struct btrfs_fs_info *fs_info,
                                                 struct btrfs_path *path,
                                                 u64 objectid)
{
        struct btrfs_root *root;
        struct btrfs_key key;

        ASSERT(path->search_commit_root && path->skip_locking);

        /*
         * This can return -ENOENT if we ask for a root that doesn't exist, but
         * since this is called via the backref walking code we won't be looking
         * up a root that doesn't exist, unless there's corruption.  So if root
         * != NULL just return it.
         */
        root = btrfs_get_global_root(fs_info, objectid);
        if (root)
                return root;

        root = btrfs_lookup_fs_root(fs_info, objectid);
        if (root)
                return root;

        key.objectid = objectid;
        key.type = BTRFS_ROOT_ITEM_KEY;
        key.offset = (u64)-1;
        root = read_tree_root_path(fs_info->tree_root, path, &key);
        btrfs_release_path(path);

        return root;
}

static int cleaner_kthread(void *arg)
{
        struct btrfs_fs_info *fs_info = arg;
        int again;

        while (1) {
                again = 0;

                set_bit(BTRFS_FS_CLEANER_RUNNING, &fs_info->flags);

                /* Make the cleaner go to sleep early. */
                if (btrfs_need_cleaner_sleep(fs_info))
                        goto sleep;

                /*
                 * Do not do anything if we might cause open_ctree() to block
                 * before we have finished mounting the filesystem.
                 */
                if (!test_bit(BTRFS_FS_OPEN, &fs_info->flags))
                        goto sleep;

                if (!mutex_trylock(&fs_info->cleaner_mutex))
                        goto sleep;

                /*
                 * Avoid the problem that we change the status of the fs
                 * during the above check and trylock.
                 */
                if (btrfs_need_cleaner_sleep(fs_info)) {
                        mutex_unlock(&fs_info->cleaner_mutex);
                        goto sleep;
                }

                if (test_and_clear_bit(BTRFS_FS_FEATURE_CHANGED, &fs_info->flags))
                        btrfs_sysfs_feature_update(fs_info);

                btrfs_run_delayed_iputs(fs_info);

                again = btrfs_clean_one_deleted_snapshot(fs_info);
                mutex_unlock(&fs_info->cleaner_mutex);

                /*
                 * The defragger has dealt with the R/O remount and umount,
                 * needn't do anything special here.
                 */
                btrfs_run_defrag_inodes(fs_info);

                /*
                 * Acquires fs_info->reclaim_bgs_lock to avoid racing
                 * with relocation (btrfs_relocate_chunk) and relocation
                 * acquires fs_info->cleaner_mutex (btrfs_relocate_block_group)
                 * after acquiring fs_info->reclaim_bgs_lock. So we
                 * can't hold, nor need to, fs_info->cleaner_mutex when deleting
                 * unused block groups.
                 */
                btrfs_delete_unused_bgs(fs_info);

                /*
                 * Reclaim block groups in the reclaim_bgs list after we deleted
                 * all unused block_groups. This possibly gives us some more free
                 * space.
                 */
                btrfs_reclaim_bgs(fs_info);
sleep:
                clear_and_wake_up_bit(BTRFS_FS_CLEANER_RUNNING, &fs_info->flags);
                if (kthread_should_park())
                        kthread_parkme();
                if (kthread_should_stop())
                        return 0;
                if (!again) {
                        set_current_state(TASK_INTERRUPTIBLE);
                        schedule();
                        __set_current_state(TASK_RUNNING);
                }
        }
}

static int transaction_kthread(void *arg)
{
        struct btrfs_root *root = arg;
        struct btrfs_fs_info *fs_info = root->fs_info;
        struct btrfs_trans_handle *trans;
        struct btrfs_transaction *cur;
        u64 transid;
        time64_t delta;
        unsigned long delay;
        bool cannot_commit;

        do {
                cannot_commit = false;
                delay = msecs_to_jiffies(fs_info->commit_interval * 1000);
                mutex_lock(&fs_info->transaction_kthread_mutex);

                spin_lock(&fs_info->trans_lock);
                cur = fs_info->running_transaction;
                if (!cur) {
                        spin_unlock(&fs_info->trans_lock);
                        goto sleep;
                }

                delta = ktime_get_seconds() - cur->start_time;
                if (!test_and_clear_bit(BTRFS_FS_COMMIT_TRANS, &fs_info->flags) &&
                    cur->state < TRANS_STATE_COMMIT_PREP &&
                    delta < fs_info->commit_interval) {
                        spin_unlock(&fs_info->trans_lock);
                        delay -= msecs_to_jiffies((delta - 1) * 1000);
                        delay = min(delay,
                                    msecs_to_jiffies(fs_info->commit_interval * 1000));
                        goto sleep;
                }
                transid = cur->transid;
                spin_unlock(&fs_info->trans_lock);

                /* If the file system is aborted, this will always fail. */
                trans = btrfs_attach_transaction(root);
                if (IS_ERR(trans)) {
                        if (PTR_ERR(trans) != -ENOENT)
                                cannot_commit = true;
                        goto sleep;
                }
                if (transid == trans->transid) {
                        btrfs_commit_transaction(trans);
                } else {
                        btrfs_end_transaction(trans);
                }
sleep:
                wake_up_process(fs_info->cleaner_kthread);
                mutex_unlock(&fs_info->transaction_kthread_mutex);

                if (BTRFS_FS_ERROR(fs_info))
                        btrfs_cleanup_transaction(fs_info);
                if (!kthread_should_stop() &&
                                (!btrfs_transaction_blocked(fs_info) ||
                                 cannot_commit))
                        schedule_timeout_interruptible(delay);
        } while (!kthread_should_stop());
        return 0;
}

/*
 * This will find the highest generation in the array of root backups.  The
 * index of the highest array is returned, or -EINVAL if we can't find
 * anything.
 *
 * We check to make sure the array is valid by comparing the
 * generation of the latest  root in the array with the generation
 * in the super block.  If they don't match we pitch it.
 */
static int find_newest_super_backup(struct btrfs_fs_info *info)
{
        const u64 newest_gen = btrfs_super_generation(info->super_copy);
        u64 cur;
        struct btrfs_root_backup *root_backup;
        int i;

        for (i = 0; i < BTRFS_NUM_BACKUP_ROOTS; i++) {
                root_backup = info->super_copy->super_roots + i;
                cur = btrfs_backup_tree_root_gen(root_backup);
                if (cur == newest_gen)
                        return i;
        }

        return -EINVAL;
}

/*
 * copy all the root pointers into the super backup array.
 * this will bump the backup pointer by one when it is
 * done
 */
static void backup_super_roots(struct btrfs_fs_info *info)
{
        const int next_backup = info->backup_root_index;
        struct btrfs_root_backup *root_backup;

        root_backup = info->super_for_commit->super_roots + next_backup;

        /*
         * make sure all of our padding and empty slots get zero filled
         * regardless of which ones we use today
         */
        memset(root_backup, 0, sizeof(*root_backup));

        info->backup_root_index = (next_backup + 1) % BTRFS_NUM_BACKUP_ROOTS;

        btrfs_set_backup_tree_root(root_backup, info->tree_root->node->start);
        btrfs_set_backup_tree_root_gen(root_backup,
                               btrfs_header_generation(info->tree_root->node));

        btrfs_set_backup_tree_root_level(root_backup,
                               btrfs_header_level(info->tree_root->node));

        btrfs_set_backup_chunk_root(root_backup, info->chunk_root->node->start);
        btrfs_set_backup_chunk_root_gen(root_backup,
                               btrfs_header_generation(info->chunk_root->node));
        btrfs_set_backup_chunk_root_level(root_backup,
                               btrfs_header_level(info->chunk_root->node));

        if (!btrfs_fs_compat_ro(info, BLOCK_GROUP_TREE)) {
                struct btrfs_root *extent_root = btrfs_extent_root(info, 0);
                struct btrfs_root *csum_root = btrfs_csum_root(info, 0);

                btrfs_set_backup_extent_root(root_backup,
                                             extent_root->node->start);
                btrfs_set_backup_extent_root_gen(root_backup,
                                btrfs_header_generation(extent_root->node));
                btrfs_set_backup_extent_root_level(root_backup,
                                        btrfs_header_level(extent_root->node));

                btrfs_set_backup_csum_root(root_backup, csum_root->node->start);
                btrfs_set_backup_csum_root_gen(root_backup,
                                               btrfs_header_generation(csum_root->node));
                btrfs_set_backup_csum_root_level(root_backup,
                                                 btrfs_header_level(csum_root->node));
        }

        /*
         * we might commit during log recovery, which happens before we set
         * the fs_root.  Make sure it is valid before we fill it in.
         */
        if (info->fs_root && info->fs_root->node) {
                btrfs_set_backup_fs_root(root_backup,
                                         info->fs_root->node->start);
                btrfs_set_backup_fs_root_gen(root_backup,
                               btrfs_header_generation(info->fs_root->node));
                btrfs_set_backup_fs_root_level(root_backup,
                               btrfs_header_level(info->fs_root->node));
        }

        btrfs_set_backup_dev_root(root_backup, info->dev_root->node->start);
        btrfs_set_backup_dev_root_gen(root_backup,
                               btrfs_header_generation(info->dev_root->node));
        btrfs_set_backup_dev_root_level(root_backup,
                                       btrfs_header_level(info->dev_root->node));

        btrfs_set_backup_total_bytes(root_backup,
                             btrfs_super_total_bytes(info->super_copy));
        btrfs_set_backup_bytes_used(root_backup,
                             btrfs_super_bytes_used(info->super_copy));
        btrfs_set_backup_num_devices(root_backup,
                             btrfs_super_num_devices(info->super_copy));

        /*
         * if we don't copy this out to the super_copy, it won't get remembered
         * for the next commit
         */
        memcpy(&info->super_copy->super_roots,
               &info->super_for_commit->super_roots,
               sizeof(*root_backup) * BTRFS_NUM_BACKUP_ROOTS);
}

/*
 * read_backup_root - Reads a backup root based on the passed priority. Prio 0
 * is the newest, prio 1/2/3 are 2nd newest/3rd newest/4th (oldest) backup roots
 *
 * fs_info - filesystem whose backup roots need to be read
 * priority - priority of backup root required
 *
 * Returns backup root index on success and -EINVAL otherwise.
 */
static int read_backup_root(struct btrfs_fs_info *fs_info, u8 priority)
{
        int backup_index = find_newest_super_backup(fs_info);
        struct btrfs_super_block *super = fs_info->super_copy;
        struct btrfs_root_backup *root_backup;

        if (priority < BTRFS_NUM_BACKUP_ROOTS && backup_index >= 0) {
                if (priority == 0)
                        return backup_index;

                backup_index = backup_index + BTRFS_NUM_BACKUP_ROOTS - priority;
                backup_index %= BTRFS_NUM_BACKUP_ROOTS;
        } else {
                return -EINVAL;
        }

        root_backup = super->super_roots + backup_index;

        btrfs_set_super_generation(super,
                                   btrfs_backup_tree_root_gen(root_backup));
        btrfs_set_super_root(super, btrfs_backup_tree_root(root_backup));
        btrfs_set_super_root_level(super,
                                   btrfs_backup_tree_root_level(root_backup));
        btrfs_set_super_bytes_used(super, btrfs_backup_bytes_used(root_backup));

        /*
         * Fixme: the total bytes and num_devices need to match or we should
         * need a fsck
         */
        btrfs_set_super_total_bytes(super, btrfs_backup_total_bytes(root_backup));
        btrfs_set_super_num_devices(super, btrfs_backup_num_devices(root_backup));

        return backup_index;
}

/* helper to cleanup workers */
static void btrfs_stop_all_workers(struct btrfs_fs_info *fs_info)
{
        btrfs_destroy_workqueue(fs_info->fixup_workers);
        btrfs_destroy_workqueue(fs_info->delalloc_workers);
        btrfs_destroy_workqueue(fs_info->workers);
        if (fs_info->endio_workers)
                destroy_workqueue(fs_info->endio_workers);
        if (fs_info->rmw_workers)
                destroy_workqueue(fs_info->rmw_workers);
        if (fs_info->compressed_write_workers)
                destroy_workqueue(fs_info->compressed_write_workers);
        btrfs_destroy_workqueue(fs_info->endio_write_workers);
        btrfs_destroy_workqueue(fs_info->endio_freespace_worker);
        btrfs_destroy_workqueue(fs_info->delayed_workers);
        btrfs_destroy_workqueue(fs_info->caching_workers);
        btrfs_destroy_workqueue(fs_info->flush_workers);
        btrfs_destroy_workqueue(fs_info->qgroup_rescan_workers);
        if (fs_info->discard_ctl.discard_workers)
                destroy_workqueue(fs_info->discard_ctl.discard_workers);
        /*
         * Now that all other work queues are destroyed, we can safely destroy
         * the queues used for metadata I/O, since tasks from those other work
         * queues can do metadata I/O operations.
         */
        if (fs_info->endio_meta_workers)
                destroy_workqueue(fs_info->endio_meta_workers);
}

static void free_root_extent_buffers(struct btrfs_root *root)
{
        if (root) {
                free_extent_buffer(root->node);
                free_extent_buffer(root->commit_root);
                root->node = NULL;
                root->commit_root = NULL;
        }
}

static void free_global_root_pointers(struct btrfs_fs_info *fs_info)
{
        struct btrfs_root *root, *tmp;

        rbtree_postorder_for_each_entry_safe(root, tmp,
                                             &fs_info->global_root_tree,
                                             rb_node)
                free_root_extent_buffers(root);
}

/* helper to cleanup tree roots */
static void free_root_pointers(struct btrfs_fs_info *info, bool free_chunk_root)
{
        free_root_extent_buffers(info->tree_root);

        free_global_root_pointers(info);
        free_root_extent_buffers(info->dev_root);
        free_root_extent_buffers(info->quota_root);
        free_root_extent_buffers(info->uuid_root);
        free_root_extent_buffers(info->fs_root);
        free_root_extent_buffers(info->data_reloc_root);
        free_root_extent_buffers(info->block_group_root);
        if (free_chunk_root)
                free_root_extent_buffers(info->chunk_root);
}

void btrfs_put_root(struct btrfs_root *root)
{
        if (!root)
                return;

        if (refcount_dec_and_test(&root->refs)) {
                WARN_ON(!RB_EMPTY_ROOT(&root->inode_tree));
                WARN_ON(test_bit(BTRFS_ROOT_DEAD_RELOC_TREE, &root->state));
                if (root->anon_dev)
                        free_anon_bdev(root->anon_dev);
                free_root_extent_buffers(root);
#ifdef CONFIG_BTRFS_DEBUG
                spin_lock(&root->fs_info->fs_roots_radix_lock);
                list_del_init(&root->leak_list);
                spin_unlock(&root->fs_info->fs_roots_radix_lock);
#endif
                kfree(root);
        }
}

void btrfs_free_fs_roots(struct btrfs_fs_info *fs_info)
{
        int ret;
        struct btrfs_root *gang[8];
        int i;

        while (!list_empty(&fs_info->dead_roots)) {
                gang[0] = list_entry(fs_info->dead_roots.next,
                                     struct btrfs_root, root_list);
                list_del(&gang[0]->root_list);

                if (test_bit(BTRFS_ROOT_IN_RADIX, &gang[0]->state))
                        btrfs_drop_and_free_fs_root(fs_info, gang[0]);
                btrfs_put_root(gang[0]);
        }

        while (1) {
                ret = radix_tree_gang_lookup(&fs_info->fs_roots_radix,
                                             (void **)gang, 0,
                                             ARRAY_SIZE(gang));
                if (!ret)
                        break;
                for (i = 0; i < ret; i++)
                        btrfs_drop_and_free_fs_root(fs_info, gang[i]);
        }
}

static void btrfs_init_scrub(struct btrfs_fs_info *fs_info)
{
        mutex_init(&fs_info->scrub_lock);
        atomic_set(&fs_info->scrubs_running, 0);
        atomic_set(&fs_info->scrub_pause_req, 0);
        atomic_set(&fs_info->scrubs_paused, 0);
        atomic_set(&fs_info->scrub_cancel_req, 0);
        init_waitqueue_head(&fs_info->scrub_pause_wait);
        refcount_set(&fs_info->scrub_workers_refcnt, 0);
}

static void btrfs_init_balance(struct btrfs_fs_info *fs_info)
{
        spin_lock_init(&fs_info->balance_lock);
        mutex_init(&fs_info->balance_mutex);
        atomic_set(&fs_info->balance_pause_req, 0);
        atomic_set(&fs_info->balance_cancel_req, 0);
        fs_info->balance_ctl = NULL;
        init_waitqueue_head(&fs_info->balance_wait_q);
        atomic_set(&fs_info->reloc_cancel_req, 0);
}

static int btrfs_init_btree_inode(struct super_block *sb)
{
        struct btrfs_fs_info *fs_info = btrfs_sb(sb);
        unsigned long hash = btrfs_inode_hash(BTRFS_BTREE_INODE_OBJECTID,
                                              fs_info->tree_root);
        struct inode *inode;

        inode = new_inode(sb);
        if (!inode)
                return -ENOMEM;

        inode->i_ino = BTRFS_BTREE_INODE_OBJECTID;
        set_nlink(inode, 1);
        /*
         * we set the i_size on the btree inode to the max possible int.
         * the real end of the address space is determined by all of
         * the devices in the system
         */
        inode->i_size = OFFSET_MAX;
        inode->i_mapping->a_ops = &btree_aops;
        mapping_set_gfp_mask(inode->i_mapping, GFP_NOFS);

        RB_CLEAR_NODE(&BTRFS_I(inode)->rb_node);
        extent_io_tree_init(fs_info, &BTRFS_I(inode)->io_tree,
                            IO_TREE_BTREE_INODE_IO);
        extent_map_tree_init(&BTRFS_I(inode)->extent_tree);

        BTRFS_I(inode)->root = btrfs_grab_root(fs_info->tree_root);
        BTRFS_I(inode)->location.objectid = BTRFS_BTREE_INODE_OBJECTID;
        BTRFS_I(inode)->location.type = 0;
        BTRFS_I(inode)->location.offset = 0;
        set_bit(BTRFS_INODE_DUMMY, &BTRFS_I(inode)->runtime_flags);
        __insert_inode_hash(inode, hash);
        fs_info->btree_inode = inode;

        return 0;
}

static void btrfs_init_dev_replace_locks(struct btrfs_fs_info *fs_info)
{
        mutex_init(&fs_info->dev_replace.lock_finishing_cancel_unmount);
        init_rwsem(&fs_info->dev_replace.rwsem);
        init_waitqueue_head(&fs_info->dev_replace.replace_wait);
}

static void btrfs_init_qgroup(struct btrfs_fs_info *fs_info)
{
        spin_lock_init(&fs_info->qgroup_lock);
        mutex_init(&fs_info->qgroup_ioctl_lock);
        fs_info->qgroup_tree = RB_ROOT;
        INIT_LIST_HEAD(&fs_info->dirty_qgroups);
        fs_info->qgroup_seq = 1;
        fs_info->qgroup_ulist = NULL;
        fs_info->qgroup_rescan_running = false;
        fs_info->qgroup_drop_subtree_thres = BTRFS_MAX_LEVEL;
        mutex_init(&fs_info->qgroup_rescan_lock);
}

static int btrfs_init_workqueues(struct btrfs_fs_info *fs_info)
{
        u32 max_active = fs_info->thread_pool_size;
        unsigned int flags = WQ_MEM_RECLAIM | WQ_FREEZABLE | WQ_UNBOUND;
        unsigned int ordered_flags = WQ_MEM_RECLAIM | WQ_FREEZABLE;

        fs_info->workers =
                btrfs_alloc_workqueue(fs_info, "worker", flags, max_active, 16);

        fs_info->delalloc_workers =
                btrfs_alloc_workqueue(fs_info, "delalloc",
                                      flags, max_active, 2);

        fs_info->flush_workers =
                btrfs_alloc_workqueue(fs_info, "flush_delalloc",
                                      flags, max_active, 0);

        fs_info->caching_workers =
                btrfs_alloc_workqueue(fs_info, "cache", flags, max_active, 0);

        fs_info->fixup_workers =
                btrfs_alloc_ordered_workqueue(fs_info, "fixup", ordered_flags);

        fs_info->endio_workers =
                alloc_workqueue("btrfs-endio", flags, max_active);
        fs_info->endio_meta_workers =
                alloc_workqueue("btrfs-endio-meta", flags, max_active);
        fs_info->rmw_workers = alloc_workqueue("btrfs-rmw", flags, max_active);
        fs_info->endio_write_workers =
                btrfs_alloc_workqueue(fs_info, "endio-write", flags,
                                      max_active, 2);
        fs_info->compressed_write_workers =
                alloc_workqueue("btrfs-compressed-write", flags, max_active);
        fs_info->endio_freespace_worker =
                btrfs_alloc_workqueue(fs_info, "freespace-write", flags,
                                      max_active, 0);
        fs_info->delayed_workers =
                btrfs_alloc_workqueue(fs_info, "delayed-meta", flags,
                                      max_active, 0);
        fs_info->qgroup_rescan_workers =
                btrfs_alloc_ordered_workqueue(fs_info, "qgroup-rescan",
                                              ordered_flags);
        fs_info->discard_ctl.discard_workers =
                alloc_ordered_workqueue("btrfs_discard", WQ_FREEZABLE);

        if (!(fs_info->workers &&
              fs_info->delalloc_workers && fs_info->flush_workers &&
              fs_info->endio_workers && fs_info->endio_meta_workers &&
              fs_info->compressed_write_workers &&
              fs_info->endio_write_workers &&
              fs_info->endio_freespace_worker && fs_info->rmw_workers &&
              fs_info->caching_workers && fs_info->fixup_workers &&
              fs_info->delayed_workers && fs_info->qgroup_rescan_workers &&
              fs_info->discard_ctl.discard_workers)) {
                return -ENOMEM;
        }

        return 0;
}

static int btrfs_init_csum_hash(struct btrfs_fs_info *fs_info, u16 csum_type)
{
        struct crypto_shash *csum_shash;
        const char *csum_driver = btrfs_super_csum_driver(csum_type);

        csum_shash = crypto_alloc_shash(csum_driver, 0, 0);

        if (IS_ERR(csum_shash)) {
                btrfs_err(fs_info, "error allocating %s hash for checksum",
                          csum_driver);
                return PTR_ERR(csum_shash);
        }

        fs_info->csum_shash = csum_shash;

        /*
         * Check if the checksum implementation is a fast accelerated one.
         * As-is this is a bit of a hack and should be replaced once the csum
         * implementations provide that information themselves.
         */
        switch (csum_type) {
        case BTRFS_CSUM_TYPE_CRC32:
                if (!strstr(crypto_shash_driver_name(csum_shash), "generic"))
                        set_bit(BTRFS_FS_CSUM_IMPL_FAST, &fs_info->flags);
                break;
        case BTRFS_CSUM_TYPE_XXHASH:
                set_bit(BTRFS_FS_CSUM_IMPL_FAST, &fs_info->flags);
                break;
        default:
                break;
        }

        btrfs_info(fs_info, "using %s (%s) checksum algorithm",
                        btrfs_super_csum_name(csum_type),
                        crypto_shash_driver_name(csum_shash));
        return 0;
}

static int btrfs_replay_log(struct btrfs_fs_info *fs_info,
                            struct btrfs_fs_devices *fs_devices)
{
        int ret;
        struct btrfs_tree_parent_check check = { 0 };
        struct btrfs_root *log_tree_root;
        struct btrfs_super_block *disk_super = fs_info->super_copy;
        u64 bytenr = btrfs_super_log_root(disk_super);
        int level = btrfs_super_log_root_level(disk_super);

        if (fs_devices->rw_devices == 0) {
                btrfs_warn(fs_info, "log replay required on RO media");
                return -EIO;
        }

        log_tree_root = btrfs_alloc_root(fs_info, BTRFS_TREE_LOG_OBJECTID,
                                         GFP_KERNEL);
        if (!log_tree_root)
                return -ENOMEM;

        check.level = level;
        check.transid = fs_info->generation + 1;
        check.owner_root = BTRFS_TREE_LOG_OBJECTID;
        log_tree_root->node = read_tree_block(fs_info, bytenr, &check);
        if (IS_ERR(log_tree_root->node)) {
                btrfs_warn(fs_info, "failed to read log tree");
                ret = PTR_ERR(log_tree_root->node);
                log_tree_root->node = NULL;
                btrfs_put_root(log_tree_root);
                return ret;
        }
        if (!extent_buffer_uptodate(log_tree_root->node)) {
                btrfs_err(fs_info, "failed to read log tree");
                btrfs_put_root(log_tree_root);
                return -EIO;
        }

        /* returns with log_tree_root freed on success */
        ret = btrfs_recover_log_trees(log_tree_root);
        if (ret) {
                btrfs_handle_fs_error(fs_info, ret,
                                      "Failed to recover log tree");
                btrfs_put_root(log_tree_root);
                return ret;
        }

        if (sb_rdonly(fs_info->sb)) {
                ret = btrfs_commit_super(fs_info);
                if (ret)
                        return ret;
        }

        return 0;
}

static int load_global_roots_objectid(struct btrfs_root *tree_root,
                                      struct btrfs_path *path, u64 objectid,
                                      const char *name)
{
        struct btrfs_fs_info *fs_info = tree_root->fs_info;
        struct btrfs_root *root;
        u64 max_global_id = 0;
        int ret;
        struct btrfs_key key = {
                .objectid = objectid,
                .type = BTRFS_ROOT_ITEM_KEY,
                .offset = 0,
        };
        bool found = false;

        /* If we have IGNOREDATACSUMS skip loading these roots. */
        if (objectid == BTRFS_CSUM_TREE_OBJECTID &&
            btrfs_test_opt(fs_info, IGNOREDATACSUMS)) {
                set_bit(BTRFS_FS_STATE_NO_CSUMS, &fs_info->fs_state);
                return 0;
        }

        while (1) {
                ret = btrfs_search_slot(NULL, tree_root, &key, path, 0, 0);
                if (ret < 0)
                        break;

                if (path->slots[0] >= btrfs_header_nritems(path->nodes[0])) {
                        ret = btrfs_next_leaf(tree_root, path);
                        if (ret) {
                                if (ret > 0)
                                        ret = 0;
                                break;
                        }
                }
                ret = 0;

                btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0]);
                if (key.objectid != objectid)
                        break;
                btrfs_release_path(path);

                /*
                 * Just worry about this for extent tree, it'll be the same for
                 * everybody.
                 */
                if (objectid == BTRFS_EXTENT_TREE_OBJECTID)
                        max_global_id = max(max_global_id, key.offset);

                found = true;
                root = read_tree_root_path(tree_root, path, &key);
                if (IS_ERR(root)) {
                        if (!btrfs_test_opt(fs_info, IGNOREBADROOTS))
                                ret = PTR_ERR(root);
                        break;
                }
                set_bit(BTRFS_ROOT_TRACK_DIRTY, &root->state);
                ret = btrfs_global_root_insert(root);
                if (ret) {
                        btrfs_put_root(root);
                        break;
                }
                key.offset++;
        }
        btrfs_release_path(path);

        if (objectid == BTRFS_EXTENT_TREE_OBJECTID)
                fs_info->nr_global_roots = max_global_id + 1;

        if (!found || ret) {
                if (objectid == BTRFS_CSUM_TREE_OBJECTID)
                        set_bit(BTRFS_FS_STATE_NO_CSUMS, &fs_info->fs_state);

                if (!btrfs_test_opt(fs_info, IGNOREBADROOTS))
                        ret = ret ? ret : -ENOENT;
                else
                        ret = 0;
                btrfs_err(fs_info, "failed to load root %s", name);
        }
        return ret;
}

static int load_global_roots(struct btrfs_root *tree_root)
{
        struct btrfs_path *path;
        int ret = 0;

        path = btrfs_alloc_path();
        if (!path)
                return -ENOMEM;

        ret = load_global_roots_objectid(tree_root, path,
                                         BTRFS_EXTENT_TREE_OBJECTID, "extent");
        if (ret)
                goto out;
        ret = load_global_roots_objectid(tree_root, path,
                                         BTRFS_CSUM_TREE_OBJECTID, "csum");
        if (ret)
                goto out;
        if (!btrfs_fs_compat_ro(tree_root->fs_info, FREE_SPACE_TREE))
                goto out;
        ret = load_global_roots_objectid(tree_root, path,
                                         BTRFS_FREE_SPACE_TREE_OBJECTID,
                                         "free space");
out:
        btrfs_free_path(path);
        return ret;
}

static int btrfs_read_roots(struct btrfs_fs_info *fs_info)
{
        struct btrfs_root *tree_root = fs_info->tree_root;
        struct btrfs_root *root;
        struct btrfs_key location;
        int ret;

        BUG_ON(!fs_info->tree_root);

        ret = load_global_roots(tree_root);
        if (ret)
                return ret;

        location.type = BTRFS_ROOT_ITEM_KEY;
        location.offset = 0;

        if (btrfs_fs_compat_ro(fs_info, BLOCK_GROUP_TREE)) {
                location.objectid = BTRFS_BLOCK_GROUP_TREE_OBJECTID;
                root = btrfs_read_tree_root(tree_root, &location);
                if (IS_ERR(root)) {
                        if (!btrfs_test_opt(fs_info, IGNOREBADROOTS)) {
                                ret = PTR_ERR(root);
                                goto out;
                        }
                } else {
                        set_bit(BTRFS_ROOT_TRACK_DIRTY, &root->state);
                        fs_info->block_group_root = root;
                }
        }

        location.objectid = BTRFS_DEV_TREE_OBJECTID;
        root = btrfs_read_tree_root(tree_root, &location);
        if (IS_ERR(root)) {
                if (!btrfs_test_opt(fs_info, IGNOREBADROOTS)) {
                        ret = PTR_ERR(root);
                        goto out;
                }
        } else {
                set_bit(BTRFS_ROOT_TRACK_DIRTY, &root->state);
                fs_info->dev_root = root;
        }
        /* Initialize fs_info for all devices in any case */
        ret = btrfs_init_devices_late(fs_info);
        if (ret)
                goto out;

        /*
         * This tree can share blocks with some other fs tree during relocation
         * and we need a proper setup by btrfs_get_fs_root
         */
        root = btrfs_get_fs_root(tree_root->fs_info,
                                 BTRFS_DATA_RELOC_TREE_OBJECTID, true);
        if (IS_ERR(root)) {
                if (!btrfs_test_opt(fs_info, IGNOREBADROOTS)) {
                        ret = PTR_ERR(root);
                        goto out;
                }
        } else {
                set_bit(BTRFS_ROOT_TRACK_DIRTY, &root->state);
                fs_info->data_reloc_root = root;
        }

        location.objectid = BTRFS_QUOTA_TREE_OBJECTID;
        root = btrfs_read_tree_root(tree_root, &location);
        if (!IS_ERR(root)) {
                set_bit(BTRFS_ROOT_TRACK_DIRTY, &root->state);
                set_bit(BTRFS_FS_QUOTA_ENABLED, &fs_info->flags);
                fs_info->quota_root = root;
        }

        location.objectid = BTRFS_UUID_TREE_OBJECTID;
        root = btrfs_read_tree_root(tree_root, &location);
        if (IS_ERR(root)) {
                if (!btrfs_test_opt(fs_info, IGNOREBADROOTS)) {
                        ret = PTR_ERR(root);
                        if (ret != -ENOENT)
                                goto out;
                }
        } else {
                set_bit(BTRFS_ROOT_TRACK_DIRTY, &root->state);
                fs_info->uuid_root = root;
        }

        return 0;
out:
        btrfs_warn(fs_info, "failed to read root (objectid=%llu): %d",
                   location.objectid, ret);
        return ret;
}

/*
 * Real super block validation
 * NOTE: super csum type and incompat features will not be checked here.
 *
 * @sb:         super block to check
 * @mirror_num: the super block number to check its bytenr:
 *              0       the primary (1st) sb
 *              1, 2    2nd and 3rd backup copy
 *             -1       skip bytenr check
 */
int btrfs_validate_super(struct btrfs_fs_info *fs_info,
                         struct btrfs_super_block *sb, int mirror_num)
{
        u64 nodesize = btrfs_super_nodesize(sb);
        u64 sectorsize = btrfs_super_sectorsize(sb);
        int ret = 0;

        if (btrfs_super_magic(sb) != BTRFS_MAGIC) {
                btrfs_err(fs_info, "no valid FS found");
                ret = -EINVAL;
        }
        if (btrfs_super_flags(sb) & ~BTRFS_SUPER_FLAG_SUPP) {
                btrfs_err(fs_info, "unrecognized or unsupported super flag: %llu",
                                btrfs_super_flags(sb) & ~BTRFS_SUPER_FLAG_SUPP);
                ret = -EINVAL;
        }
        if (btrfs_super_root_level(sb) >= BTRFS_MAX_LEVEL) {
                btrfs_err(fs_info, "tree_root level too big: %d >= %d",
                                btrfs_super_root_level(sb), BTRFS_MAX_LEVEL);
                ret = -EINVAL;
        }
        if (btrfs_super_chunk_root_level(sb) >= BTRFS_MAX_LEVEL) {
                btrfs_err(fs_info, "chunk_root level too big: %d >= %d",
                                btrfs_super_chunk_root_level(sb), BTRFS_MAX_LEVEL);
                ret = -EINVAL;
        }
        if (btrfs_super_log_root_level(sb) >= BTRFS_MAX_LEVEL) {
                btrfs_err(fs_info, "log_root level too big: %d >= %d",
                                btrfs_super_log_root_level(sb), BTRFS_MAX_LEVEL);
                ret = -EINVAL;
        }

        /*
         * Check sectorsize and nodesize first, other check will need it.
         * Check all possible sectorsize(4K, 8K, 16K, 32K, 64K) here.
         */
        if (!is_power_of_2(sectorsize) || sectorsize < 4096 ||
            sectorsize > BTRFS_MAX_METADATA_BLOCKSIZE) {
                btrfs_err(fs_info, "invalid sectorsize %llu", sectorsize);
                ret = -EINVAL;
        }

        /*
         * We only support at most two sectorsizes: 4K and PAGE_SIZE.
         *
         * We can support 16K sectorsize with 64K page size without problem,
         * but such sectorsize/pagesize combination doesn't make much sense.
         * 4K will be our future standard, PAGE_SIZE is supported from the very
         * beginning.
         */
        if (sectorsize > PAGE_SIZE || (sectorsize != SZ_4K && sectorsize != PAGE_SIZE)) {
                btrfs_err(fs_info,
                        "sectorsize %llu not yet supported for page size %lu",
                        sectorsize, PAGE_SIZE);
                ret = -EINVAL;
        }

        if (!is_power_of_2(nodesize) || nodesize < sectorsize ||
            nodesize > BTRFS_MAX_METADATA_BLOCKSIZE) {
                btrfs_err(fs_info, "invalid nodesize %llu", nodesize);
                ret = -EINVAL;
        }
        if (nodesize != le32_to_cpu(sb->__unused_leafsize)) {
                btrfs_err(fs_info, "invalid leafsize %u, should be %llu",
                          le32_to_cpu(sb->__unused_leafsize), nodesize);
                ret = -EINVAL;
        }

        /* Root alignment check */
        if (!IS_ALIGNED(btrfs_super_root(sb), sectorsize)) {
                btrfs_warn(fs_info, "tree_root block unaligned: %llu",
                           btrfs_super_root(sb));
                ret = -EINVAL;
        }
        if (!IS_ALIGNED(btrfs_super_chunk_root(sb), sectorsize)) {
                btrfs_warn(fs_info, "chunk_root block unaligned: %llu",
                           btrfs_super_chunk_root(sb));
                ret = -EINVAL;
        }
        if (!IS_ALIGNED(btrfs_super_log_root(sb), sectorsize)) {
                btrfs_warn(fs_info, "log_root block unaligned: %llu",
                           btrfs_super_log_root(sb));
                ret = -EINVAL;
        }

        if (memcmp(fs_info->fs_devices->fsid, sb->fsid, BTRFS_FSID_SIZE) != 0) {
                btrfs_err(fs_info,
                "superblock fsid doesn't match fsid of fs_devices: %pU != %pU",
                          sb->fsid, fs_info->fs_devices->fsid);
                ret = -EINVAL;
        }

        if (memcmp(fs_info->fs_devices->metadata_uuid, btrfs_sb_fsid_ptr(sb),
                   BTRFS_FSID_SIZE) != 0) {
                btrfs_err(fs_info,
"superblock metadata_uuid doesn't match metadata uuid of fs_devices: %pU != %pU",
                          btrfs_sb_fsid_ptr(sb), fs_info->fs_devices->metadata_uuid);
                ret = -EINVAL;
        }

        if (memcmp(fs_info->fs_devices->metadata_uuid, sb->dev_item.fsid,
                   BTRFS_FSID_SIZE) != 0) {
                btrfs_err(fs_info,
                        "dev_item UUID does not match metadata fsid: %pU != %pU",
                        fs_info->fs_devices->metadata_uuid, sb->dev_item.fsid);
                ret = -EINVAL;
        }

        /*
         * Artificial requirement for block-group-tree to force newer features
         * (free-space-tree, no-holes) so the test matrix is smaller.
         */
        if (btrfs_fs_compat_ro(fs_info, BLOCK_GROUP_TREE) &&
            (!btrfs_fs_compat_ro(fs_info, FREE_SPACE_TREE_VALID) ||
             !btrfs_fs_incompat(fs_info, NO_HOLES))) {
                btrfs_err(fs_info,
                "block-group-tree feature requires fres-space-tree and no-holes");
                ret = -EINVAL;
        }

        /*
         * Hint to catch really bogus numbers, bitflips or so, more exact checks are
         * done later
         */
        if (btrfs_super_bytes_used(sb) < 6 * btrfs_super_nodesize(sb)) {
                btrfs_err(fs_info, "bytes_used is too small %llu",
                          btrfs_super_bytes_used(sb));
                ret = -EINVAL;
        }
        if (!is_power_of_2(btrfs_super_stripesize(sb))) {
                btrfs_err(fs_info, "invalid stripesize %u",
                          btrfs_super_stripesize(sb));
                ret = -EINVAL;
        }
        if (btrfs_super_num_devices(sb) > (1UL << 31))
                btrfs_warn(fs_info, "suspicious number of devices: %llu",
                           btrfs_super_num_devices(sb));
        if (btrfs_super_num_devices(sb) == 0) {
                btrfs_err(fs_info, "number of devices is 0");
                ret = -EINVAL;
        }

        if (mirror_num >= 0 &&
            btrfs_super_bytenr(sb) != btrfs_sb_offset(mirror_num)) {
                btrfs_err(fs_info, "super offset mismatch %llu != %u",
                          btrfs_super_bytenr(sb), BTRFS_SUPER_INFO_OFFSET);
                ret = -EINVAL;
        }

        /*
         * Obvious sys_chunk_array corruptions, it must hold at least one key
         * and one chunk
         */
        if (btrfs_super_sys_array_size(sb) > BTRFS_SYSTEM_CHUNK_ARRAY_SIZE) {
                btrfs_err(fs_info, "system chunk array too big %u > %u",
                          btrfs_super_sys_array_size(sb),
                          BTRFS_SYSTEM_CHUNK_ARRAY_SIZE);
                ret = -EINVAL;
        }
        if (btrfs_super_sys_array_size(sb) < sizeof(struct btrfs_disk_key)
                        + sizeof(struct btrfs_chunk)) {
                btrfs_err(fs_info, "system chunk array too small %u < %zu",
                          btrfs_super_sys_array_size(sb),
                          sizeof(struct btrfs_disk_key)
                          + sizeof(struct btrfs_chunk));
                ret = -EINVAL;
        }

        /*
         * The generation is a global counter, we'll trust it more than the others
         * but it's still possible that it's the one that's wrong.
         */
        if (btrfs_super_generation(sb) < btrfs_super_chunk_root_generation(sb))
                btrfs_warn(fs_info,
                        "suspicious: generation < chunk_root_generation: %llu < %llu",
                        btrfs_super_generation(sb),
                        btrfs_super_chunk_root_generation(sb));
        if (btrfs_super_generation(sb) < btrfs_super_cache_generation(sb)
            && btrfs_super_cache_generation(sb) != (u64)-1)
                btrfs_warn(fs_info,
                        "suspicious: generation < cache_generation: %llu < %llu",
                        btrfs_super_generation(sb),
                        btrfs_super_cache_generation(sb));

        return ret;
}

/*
 * Validation of super block at mount time.
 * Some checks already done early at mount time, like csum type and incompat
 * flags will be skipped.
 */
static int btrfs_validate_mount_super(struct btrfs_fs_info *fs_info)
{
        return btrfs_validate_super(fs_info, fs_info->super_copy, 0);
}

/*
 * Validation of super block at write time.
 * Some checks like bytenr check will be skipped as their values will be
 * overwritten soon.
 * Extra checks like csum type and incompat flags will be done here.
 */
static int btrfs_validate_write_super(struct btrfs_fs_info *fs_info,
                                      struct btrfs_super_block *sb)
{
        int ret;

        ret = btrfs_validate_super(fs_info, sb, -1);
        if (ret < 0)
                goto out;
        if (!btrfs_supported_super_csum(btrfs_super_csum_type(sb))) {
                ret = -EUCLEAN;
                btrfs_err(fs_info, "invalid csum type, has %u want %u",
                          btrfs_super_csum_type(sb), BTRFS_CSUM_TYPE_CRC32);
                goto out;
        }
        if (btrfs_super_incompat_flags(sb) & ~BTRFS_FEATURE_INCOMPAT_SUPP) {
                ret = -EUCLEAN;
                btrfs_err(fs_info,
                "invalid incompat flags, has 0x%llx valid mask 0x%llx",
                          btrfs_super_incompat_flags(sb),
                          (unsigned long long)BTRFS_FEATURE_INCOMPAT_SUPP);
                goto out;
        }
out:
        if (ret < 0)
                btrfs_err(fs_info,
                "super block corruption detected before writing it to disk");
        return ret;
}

static int load_super_root(struct btrfs_root *root, u64 bytenr, u64 gen, int level)
{
        struct btrfs_tree_parent_check check = {
                .level = level,
                .transid = gen,
                .owner_root = root->root_key.objectid
        };
        int ret = 0;

        root->node = read_tree_block(root->fs_info, bytenr, &check);
        if (IS_ERR(root->node)) {
                ret = PTR_ERR(root->node);
                root->node = NULL;
                return ret;
        }
        if (!extent_buffer_uptodate(root->node)) {
                free_extent_buffer(root->node);
                root->node = NULL;
                return -EIO;
        }

        btrfs_set_root_node(&root->root_item, root->node);
        root->commit_root = btrfs_root_node(root);
        btrfs_set_root_refs(&root->root_item, 1);
        return ret;
}

static int load_important_roots(struct btrfs_fs_info *fs_info)
{
        struct btrfs_super_block *sb = fs_info->super_copy;
        u64 gen, bytenr;
        int level, ret;

        bytenr = btrfs_super_root(sb);
        gen = btrfs_super_generation(sb);
        level = btrfs_super_root_level(sb);
        ret = load_super_root(fs_info->tree_root, bytenr, gen, level);
        if (ret) {
                btrfs_warn(fs_info, "couldn't read tree root");
                return ret;
        }
        return 0;
}

static int __cold init_tree_roots(struct btrfs_fs_info *fs_info)
{
        int backup_index = find_newest_super_backup(fs_info);
        struct btrfs_super_block *sb = fs_info->super_copy;
        struct btrfs_root *tree_root = fs_info->tree_root;
        bool handle_error = false;
        int ret = 0;
        int i;

        for (i = 0; i < BTRFS_NUM_BACKUP_ROOTS; i++) {
                if (handle_error) {
                        if (!IS_ERR(tree_root->node))
                                free_extent_buffer(tree_root->node);
                        tree_root->node = NULL;

                        if (!btrfs_test_opt(fs_info, USEBACKUPROOT))
                                break;

                        free_root_pointers(fs_info, 0);

                        /*
                         * Don't use the log in recovery mode, it won't be
                         * valid
                         */
                        btrfs_set_super_log_root(sb, 0);

                        /* We can't trust the free space cache either */
                        btrfs_set_opt(fs_info->mount_opt, CLEAR_CACHE);

                        btrfs_warn(fs_info, "try to load backup roots slot %d", i);
                        ret = read_backup_root(fs_info, i);
                        backup_index = ret;
                        if (ret < 0)
                                return ret;
                }

                ret = load_important_roots(fs_info);
                if (ret) {
                        handle_error = true;
                        continue;
                }

                /*
                 * No need to hold btrfs_root::objectid_mutex since the fs
                 * hasn't been fully initialised and we are the only user
                 */
                ret = btrfs_init_root_free_objectid(tree_root);
                if (ret < 0) {
                        handle_error = true;
                        continue;
                }

                ASSERT(tree_root->free_objectid <= BTRFS_LAST_FREE_OBJECTID);

                ret = btrfs_read_roots(fs_info);
                if (ret < 0) {
                        handle_error = true;
                        continue;
                }

                /* All successful */
                fs_info->generation = btrfs_header_generation(tree_root->node);
                fs_info->last_trans_committed = fs_info->generation;
                fs_info->last_reloc_trans = 0;

                /* Always begin writing backup roots after the one being used */
                if (backup_index < 0) {
                        fs_info->backup_root_index = 0;
                } else {
                        fs_info->backup_root_index = backup_index + 1;
                        fs_info->backup_root_index %= BTRFS_NUM_BACKUP_ROOTS;
                }
                break;
        }

        return ret;
}

void btrfs_init_fs_info(struct btrfs_fs_info *fs_info)
{
        INIT_RADIX_TREE(&fs_info->fs_roots_radix, GFP_ATOMIC);
        INIT_RADIX_TREE(&fs_info->buffer_radix, GFP_ATOMIC);
        INIT_LIST_HEAD(&fs_info->trans_list);
        INIT_LIST_HEAD(&fs_info->dead_roots);
        INIT_LIST_HEAD(&fs_info->delayed_iputs);
        INIT_LIST_HEAD(&fs_info->delalloc_roots);
        INIT_LIST_HEAD(&fs_info->caching_block_groups);
        spin_lock_init(&fs_info->delalloc_root_lock);
        spin_lock_init(&fs_info->trans_lock);
        spin_lock_init(&fs_info->fs_roots_radix_lock);
        spin_lock_init(&fs_info->delayed_iput_lock);
        spin_lock_init(&fs_info->defrag_inodes_lock);
        spin_lock_init(&fs_info->super_lock);
        spin_lock_init(&fs_info->buffer_lock);
        spin_lock_init(&fs_info->unused_bgs_lock);
        spin_lock_init(&fs_info->treelog_bg_lock);
        spin_lock_init(&fs_info->zone_active_bgs_lock);
        spin_lock_init(&fs_info->relocation_bg_lock);
        rwlock_init(&fs_info->tree_mod_log_lock);
        rwlock_init(&fs_info->global_root_lock);
        mutex_init(&fs_info->unused_bg_unpin_mutex);
        mutex_init(&fs_info->reclaim_bgs_lock);
        mutex_init(&fs_info->reloc_mutex);
        mutex_init(&fs_info->delalloc_root_mutex);
        mutex_init(&fs_info->zoned_meta_io_lock);
        mutex_init(&fs_info->zoned_data_reloc_io_lock);
        seqlock_init(&fs_info->profiles_lock);

        btrfs_lockdep_init_map(fs_info, btrfs_trans_num_writers);
        btrfs_lockdep_init_map(fs_info, btrfs_trans_num_extwriters);
        btrfs_lockdep_init_map(fs_info, btrfs_trans_pending_ordered);
        btrfs_lockdep_init_map(fs_info, btrfs_ordered_extent);
        btrfs_state_lockdep_init_map(fs_info, btrfs_trans_commit_prep,
                                     BTRFS_LOCKDEP_TRANS_COMMIT_PREP);
        btrfs_state_lockdep_init_map(fs_info, btrfs_trans_unblocked,
                                     BTRFS_LOCKDEP_TRANS_UNBLOCKED);
        btrfs_state_lockdep_init_map(fs_info, btrfs_trans_super_committed,
                                     BTRFS_LOCKDEP_TRANS_SUPER_COMMITTED);
        btrfs_state_lockdep_init_map(fs_info, btrfs_trans_completed,
                                     BTRFS_LOCKDEP_TRANS_COMPLETED);

        INIT_LIST_HEAD(&fs_info->dirty_cowonly_roots);
        INIT_LIST_HEAD(&fs_info->space_info);
        INIT_LIST_HEAD(&fs_info->tree_mod_seq_list);
        INIT_LIST_HEAD(&fs_info->unused_bgs);
        INIT_LIST_HEAD(&fs_info->reclaim_bgs);
        INIT_LIST_HEAD(&fs_info->zone_active_bgs);
#ifdef CONFIG_BTRFS_DEBUG
        INIT_LIST_HEAD(&fs_info->allocated_roots);
        INIT_LIST_HEAD(&fs_info->allocated_ebs);
        spin_lock_init(&fs_info->eb_leak_lock);
#endif
        extent_map_tree_init(&fs_info->mapping_tree);
        btrfs_init_block_rsv(&fs_info->global_block_rsv,
                             BTRFS_BLOCK_RSV_GLOBAL);
        btrfs_init_block_rsv(&fs_info->trans_block_rsv, BTRFS_BLOCK_RSV_TRANS);
        btrfs_init_block_rsv(&fs_info->chunk_block_rsv, BTRFS_BLOCK_RSV_CHUNK);
        btrfs_init_block_rsv(&fs_info->empty_block_rsv, BTRFS_BLOCK_RSV_EMPTY);
        btrfs_init_block_rsv(&fs_info->delayed_block_rsv,
                             BTRFS_BLOCK_RSV_DELOPS);
        btrfs_init_block_rsv(&fs_info->delayed_refs_rsv,
                             BTRFS_BLOCK_RSV_DELREFS);

        atomic_set(&fs_info->async_delalloc_pages, 0);
        atomic_set(&fs_info->defrag_running, 0);
        atomic_set(&fs_info->nr_delayed_iputs, 0);
        atomic64_set(&fs_info->tree_mod_seq, 0);
        fs_info->global_root_tree = RB_ROOT;
        fs_info->max_inline = BTRFS_DEFAULT_MAX_INLINE;
        fs_info->metadata_ratio = 0;
        fs_info->defrag_inodes = RB_ROOT;
        atomic64_set(&fs_info->free_chunk_space, 0);
        fs_info->tree_mod_log = RB_ROOT;
        fs_info->commit_interval = BTRFS_DEFAULT_COMMIT_INTERVAL;
        btrfs_init_ref_verify(fs_info);

        fs_info->thread_pool_size = min_t(unsigned long,
                                          num_online_cpus() + 2, 8);

        INIT_LIST_HEAD(&fs_info->ordered_roots);
        spin_lock_init(&fs_info->ordered_root_lock);

        btrfs_init_scrub(fs_info);
#ifdef CONFIG_BTRFS_FS_CHECK_INTEGRITY
        fs_info->check_integrity_print_mask = 0;
#endif
        btrfs_init_balance(fs_info);
        btrfs_init_async_reclaim_work(fs_info);

        rwlock_init(&fs_info->block_group_cache_lock);
        fs_info->block_group_cache_tree = RB_ROOT_CACHED;

        extent_io_tree_init(fs_info, &fs_info->excluded_extents,
                            IO_TREE_FS_EXCLUDED_EXTENTS);

        mutex_init(&fs_info->ordered_operations_mutex);
        mutex_init(&fs_info->tree_log_mutex);
        mutex_init(&fs_info->chunk_mutex);
        mutex_init(&fs_info->transaction_kthread_mutex);
        mutex_init(&fs_info->cleaner_mutex);
        mutex_init(&fs_info->ro_block_group_mutex);
        init_rwsem(&fs_info->commit_root_sem);
        init_rwsem(&fs_info->cleanup_work_sem);
        init_rwsem(&fs_info->subvol_sem);
        sema_init(&fs_info->uuid_tree_rescan_sem, 1);

        btrfs_init_dev_replace_locks(fs_info);
        btrfs_init_qgroup(fs_info);
        btrfs_discard_init(fs_info);

        btrfs_init_free_cluster(&fs_info->meta_alloc_cluster);
        btrfs_init_free_cluster(&fs_info->data_alloc_cluster);

        init_waitqueue_head(&fs_info->transaction_throttle);
        init_waitqueue_head(&fs_info->transaction_wait);
        init_waitqueue_head(&fs_info->transaction_blocked_wait);
        init_waitqueue_head(&fs_info->async_submit_wait);
        init_waitqueue_head(&fs_info->delayed_iputs_wait);

        /* Usable values until the real ones are cached from the superblock */
        fs_info->nodesize = 4096;
        fs_info->sectorsize = 4096;
        fs_info->sectorsize_bits = ilog2(4096);
        fs_info->stripesize = 4096;

        fs_info->max_extent_size = BTRFS_MAX_EXTENT_SIZE;

        spin_lock_init(&fs_info->swapfile_pins_lock);
        fs_info->swapfile_pins = RB_ROOT;

        fs_info->bg_reclaim_threshold = BTRFS_DEFAULT_RECLAIM_THRESH;
        INIT_WORK(&fs_info->reclaim_bgs_work, btrfs_reclaim_bgs_work);
}

static int init_mount_fs_info(struct btrfs_fs_info *fs_info, struct super_block *sb)
{
        int ret;

        fs_info->sb = sb;
        sb->s_blocksize = BTRFS_BDEV_BLOCKSIZE;
        sb->s_blocksize_bits = blksize_bits(BTRFS_BDEV_BLOCKSIZE);

        ret = percpu_counter_init(&fs_info->ordered_bytes, 0, GFP_KERNEL);
        if (ret)
                return ret;

        ret = percpu_counter_init(&fs_info->dirty_metadata_bytes, 0, GFP_KERNEL);
        if (ret)
                return ret;

        fs_info->dirty_metadata_batch = PAGE_SIZE *
                                        (1 + ilog2(nr_cpu_ids));

        ret = percpu_counter_init(&fs_info->delalloc_bytes, 0, GFP_KERNEL);
        if (ret)
                return ret;

        ret = percpu_counter_init(&fs_info->dev_replace.bio_counter, 0,
                        GFP_KERNEL);
        if (ret)
                return ret;

        fs_info->delayed_root = kmalloc(sizeof(struct btrfs_delayed_root),
                                        GFP_KERNEL);
        if (!fs_info->delayed_root)
                return -ENOMEM;
        btrfs_init_delayed_root(fs_info->delayed_root);

        if (sb_rdonly(sb))
                set_bit(BTRFS_FS_STATE_RO, &fs_info->fs_state);

        return btrfs_alloc_stripe_hash_table(fs_info);
}

static int btrfs_uuid_rescan_kthread(void *data)
{
        struct btrfs_fs_info *fs_info = data;
        int ret;

        /*
         * 1st step is to iterate through the existing UUID tree and
         * to delete all entries that contain outdated data.
         * 2nd step is to add all missing entries to the UUID tree.
         */
        ret = btrfs_uuid_tree_iterate(fs_info);
        if (ret < 0) {
                if (ret != -EINTR)
                        btrfs_warn(fs_info, "iterating uuid_tree failed %d",
                                   ret);
                up(&fs_info->uuid_tree_rescan_sem);
                return ret;
        }
        return btrfs_uuid_scan_kthread(data);
}

static int btrfs_check_uuid_tree(struct btrfs_fs_info *fs_info)
{
        struct task_struct *task;

        down(&fs_info->uuid_tree_rescan_sem);
        task = kthread_run(btrfs_uuid_rescan_kthread, fs_info, "btrfs-uuid");
        if (IS_ERR(task)) {
                /* fs_info->update_uuid_tree_gen remains 0 in all error case */
                btrfs_warn(fs_info, "failed to start uuid_rescan task");
                up(&fs_info->uuid_tree_rescan_sem);
                return PTR_ERR(task);
        }

        return 0;
}

static int btrfs_cleanup_fs_roots(struct btrfs_fs_info *fs_info)
{
        u64 root_objectid = 0;
        struct btrfs_root *gang[8];
        int i = 0;
        int err = 0;
        unsigned int ret = 0;

        while (1) {
                spin_lock(&fs_info->fs_roots_radix_lock);
                ret = radix_tree_gang_lookup(&fs_info->fs_roots_radix,
                                             (void **)gang, root_objectid,
                                             ARRAY_SIZE(gang));
                if (!ret) {
                        spin_unlock(&fs_info->fs_roots_radix_lock);
                        break;
                }
                root_objectid = gang[ret - 1]->root_key.objectid + 1;

                for (i = 0; i < ret; i++) {
                        /* Avoid to grab roots in dead_roots. */
                        if (btrfs_root_refs(&gang[i]->root_item) == 0) {
                                gang[i] = NULL;
                                continue;
                        }
                        /* Grab all the search result for later use. */
                        gang[i] = btrfs_grab_root(gang[i]);
                }
                spin_unlock(&fs_info->fs_roots_radix_lock);

                for (i = 0; i < ret; i++) {
                        if (!gang[i])
                                continue;
                        root_objectid = gang[i]->root_key.objectid;
                        err = btrfs_orphan_cleanup(gang[i]);
                        if (err)
                                goto out;
                        btrfs_put_root(gang[i]);
                }
                root_objectid++;
        }
out:
        /* Release the uncleaned roots due to error. */
        for (; i < ret; i++) {
                if (gang[i])
                        btrfs_put_root(gang[i]);
        }
        return err;
}

/*
 * Some options only have meaning at mount time and shouldn't persist across
 * remounts, or be displayed. Clear these at the end of mount and remount
 * code paths.
 */
void btrfs_clear_oneshot_options(struct btrfs_fs_info *fs_info)
{
        btrfs_clear_opt(fs_info->mount_opt, USEBACKUPROOT);
        btrfs_clear_opt(fs_info->mount_opt, CLEAR_CACHE);
}

/*
 * Mounting logic specific to read-write file systems. Shared by open_ctree
 * and btrfs_remount when remounting from read-only to read-write.
 */
int btrfs_start_pre_rw_mount(struct btrfs_fs_info *fs_info)
{
        int ret;
        const bool cache_opt = btrfs_test_opt(fs_info, SPACE_CACHE);
        bool rebuild_free_space_tree = false;

        if (btrfs_test_opt(fs_info, CLEAR_CACHE) &&
            btrfs_fs_compat_ro(fs_info, FREE_SPACE_TREE)) {
                rebuild_free_space_tree = true;
        } else if (btrfs_fs_compat_ro(fs_info, FREE_SPACE_TREE) &&
                   !btrfs_fs_compat_ro(fs_info, FREE_SPACE_TREE_VALID)) {
                btrfs_warn(fs_info, "free space tree is invalid");
                rebuild_free_space_tree = true;
        }

        if (rebuild_free_space_tree) {
                btrfs_info(fs_info, "rebuilding free space tree");
                ret = btrfs_rebuild_free_space_tree(fs_info);
                if (ret) {
                        btrfs_warn(fs_info,
                                   "failed to rebuild free space tree: %d", ret);
                        goto out;
                }
        }

        if (btrfs_fs_compat_ro(fs_info, FREE_SPACE_TREE) &&
            !btrfs_test_opt(fs_info, FREE_SPACE_TREE)) {
                btrfs_info(fs_info, "disabling free space tree");
                ret = btrfs_delete_free_space_tree(fs_info);
                if (ret) {
                        btrfs_warn(fs_info,
                                   "failed to disable free space tree: %d", ret);
                        goto out;
                }
        }

        /*
         * btrfs_find_orphan_roots() is responsible for finding all the dead
         * roots (with 0 refs), flag them with BTRFS_ROOT_DEAD_TREE and load
         * them into the fs_info->fs_roots_radix tree. This must be done before
         * calling btrfs_orphan_cleanup() on the tree root. If we don't do it
         * first, then btrfs_orphan_cleanup() will delete a dead root's orphan
         * item before the root's tree is deleted - this means that if we unmount
         * or crash before the deletion completes, on the next mount we will not
         * delete what remains of the tree because the orphan item does not
         * exists anymore, which is what tells us we have a pending deletion.
         */
        ret = btrfs_find_orphan_roots(fs_info);
        if (ret)
                goto out;

        ret = btrfs_cleanup_fs_roots(fs_info);
        if (ret)
                goto out;

        down_read(&fs_info->cleanup_work_sem);
        if ((ret = btrfs_orphan_cleanup(fs_info->fs_root)) ||
            (ret = btrfs_orphan_cleanup(fs_info->tree_root))) {
                up_read(&fs_info->cleanup_work_sem);
                goto out;
        }
        up_read(&fs_info->cleanup_work_sem);

        mutex_lock(&fs_info->cleaner_mutex);
        ret = btrfs_recover_relocation(fs_info);
        mutex_unlock(&fs_info->cleaner_mutex);
        if (ret < 0) {
                btrfs_warn(fs_info, "failed to recover relocation: %d", ret);
                goto out;
        }

        if (btrfs_test_opt(fs_info, FREE_SPACE_TREE) &&
            !btrfs_fs_compat_ro(fs_info, FREE_SPACE_TREE)) {
                btrfs_info(fs_info, "creating free space tree");
                ret = btrfs_create_free_space_tree(fs_info);
                if (ret) {
                        btrfs_warn(fs_info,
                                "failed to create free space tree: %d", ret);
                        goto out;
                }
        }

        if (cache_opt != btrfs_free_space_cache_v1_active(fs_info)) {
                ret = btrfs_set_free_space_cache_v1_active(fs_info, cache_opt);
                if (ret)
                        goto out;
        }

        ret = btrfs_resume_balance_async(fs_info);
        if (ret)
                goto out;

        ret = btrfs_resume_dev_replace_async(fs_info);
        if (ret) {
                btrfs_warn(fs_info, "failed to resume dev_replace");
                goto out;
        }

        btrfs_qgroup_rescan_resume(fs_info);

        if (!fs_info->uuid_root) {
                btrfs_info(fs_info, "creating UUID tree");
                ret = btrfs_create_uuid_tree(fs_info);
                if (ret) {
                        btrfs_warn(fs_info,
                                   "failed to create the UUID tree %d", ret);
                        goto out;
                }
        }

out:
        return ret;
}

/*
 * Do various sanity and dependency checks of different features.
 *
 * @is_rw_mount:        If the mount is read-write.
 *
 * This is the place for less strict checks (like for subpage or artificial
 * feature dependencies).
 *
 * For strict checks or possible corruption detection, see
 * btrfs_validate_super().
 *
 * This should be called after btrfs_parse_options(), as some mount options
 * (space cache related) can modify on-disk format like free space tree and
 * screw up certain feature dependencies.
 */
int btrfs_check_features(struct btrfs_fs_info *fs_info, bool is_rw_mount)
{
        struct btrfs_super_block *disk_super = fs_info->super_copy;
        u64 incompat = btrfs_super_incompat_flags(disk_super);
        const u64 compat_ro = btrfs_super_compat_ro_flags(disk_super);
        const u64 compat_ro_unsupp = (compat_ro & ~BTRFS_FEATURE_COMPAT_RO_SUPP);

        if (incompat & ~BTRFS_FEATURE_INCOMPAT_SUPP) {
                btrfs_err(fs_info,
                "cannot mount because of unknown incompat features (0x%llx)",
                    incompat);
                return -EINVAL;
        }

        /* Runtime limitation for mixed block groups. */
        if ((incompat & BTRFS_FEATURE_INCOMPAT_MIXED_GROUPS) &&
            (fs_info->sectorsize != fs_info->nodesize)) {
                btrfs_err(fs_info,
"unequal nodesize/sectorsize (%u != %u) are not allowed for mixed block groups",
                        fs_info->nodesize, fs_info->sectorsize);
                return -EINVAL;
        }

        /* Mixed backref is an always-enabled feature. */
        incompat |= BTRFS_FEATURE_INCOMPAT_MIXED_BACKREF;

        /* Set compression related flags just in case. */
        if (fs_info->compress_type == BTRFS_COMPRESS_LZO)
                incompat |= BTRFS_FEATURE_INCOMPAT_COMPRESS_LZO;
        else if (fs_info->compress_type == BTRFS_COMPRESS_ZSTD)
                incompat |= BTRFS_FEATURE_INCOMPAT_COMPRESS_ZSTD;

        /*
         * An ancient flag, which should really be marked deprecated.
         * Such runtime limitation doesn't really need a incompat flag.
         */
        if (btrfs_super_nodesize(disk_super) > PAGE_SIZE)
                incompat |= BTRFS_FEATURE_INCOMPAT_BIG_METADATA;

        if (compat_ro_unsupp && is_rw_mount) {
                btrfs_err(fs_info,
        "cannot mount read-write because of unknown compat_ro features (0x%llx)",
                       compat_ro);
                return -EINVAL;
        }

        /*
         * We have unsupported RO compat features, although RO mounted, we
         * should not cause any metadata writes, including log replay.
         * Or we could screw up whatever the new feature requires.
         */
        if (compat_ro_unsupp && btrfs_super_log_root(disk_super) &&
            !btrfs_test_opt(fs_info, NOLOGREPLAY)) {
                btrfs_err(fs_info,
"cannot replay dirty log with unsupported compat_ro features (0x%llx), try rescue=nologreplay",
                          compat_ro);
                return -EINVAL;
        }

        /*
         * Artificial limitations for block group tree, to force
         * block-group-tree to rely on no-holes and free-space-tree.
         */
        if (btrfs_fs_compat_ro(fs_info, BLOCK_GROUP_TREE) &&
            (!btrfs_fs_incompat(fs_info, NO_HOLES) ||
             !btrfs_test_opt(fs_info, FREE_SPACE_TREE))) {
                btrfs_err(fs_info,
"block-group-tree feature requires no-holes and free-space-tree features");
                return -EINVAL;
        }

        /*
         * Subpage runtime limitation on v1 cache.
         *
         * V1 space cache still has some hard codeed PAGE_SIZE usage, while
         * we're already defaulting to v2 cache, no need to bother v1 as it's
         * going to be deprecated anyway.
         */
        if (fs_info->sectorsize < PAGE_SIZE && btrfs_test_opt(fs_info, SPACE_CACHE)) {
                btrfs_warn(fs_info,
        "v1 space cache is not supported for page size %lu with sectorsize %u",
                           PAGE_SIZE, fs_info->sectorsize);
                return -EINVAL;
        }

        /* This can be called by remount, we need to protect the super block. */
        spin_lock(&fs_info->super_lock);
        btrfs_set_super_incompat_flags(disk_super, incompat);
        spin_unlock(&fs_info->super_lock);

        return 0;
}

int __cold open_ctree(struct super_block *sb, struct btrfs_fs_devices *fs_devices,
                      char *options)
{
        u32 sectorsize;
        u32 nodesize;
        u32 stripesize;
        u64 generation;
        u64 features;
        u16 csum_type;
        struct btrfs_super_block *disk_super;
        struct btrfs_fs_info *fs_info = btrfs_sb(sb);
        struct btrfs_root *tree_root;
        struct btrfs_root *chunk_root;
        int ret;
        int level;

        ret = init_mount_fs_info(fs_info, sb);
        if (ret)
                goto fail;

        /* These need to be init'ed before we start creating inodes and such. */
        tree_root = btrfs_alloc_root(fs_info, BTRFS_ROOT_TREE_OBJECTID,
                                     GFP_KERNEL);
        fs_info->tree_root = tree_root;
        chunk_root = btrfs_alloc_root(fs_info, BTRFS_CHUNK_TREE_OBJECTID,
                                      GFP_KERNEL);
        fs_info->chunk_root = chunk_root;
        if (!tree_root || !chunk_root) {
                ret = -ENOMEM;
                goto fail;
        }

        ret = btrfs_init_btree_inode(sb);
        if (ret)
                goto fail;

        invalidate_bdev(fs_devices->latest_dev->bdev);

        /*
         * Read super block and check the signature bytes only
         */
        disk_super = btrfs_read_dev_super(fs_devices->latest_dev->bdev);
        if (IS_ERR(disk_super)) {
                ret = PTR_ERR(disk_super);
                goto fail_alloc;
        }

        /*
         * Verify the type first, if that or the checksum value are
         * corrupted, we'll find out
         */
        csum_type = btrfs_super_csum_type(disk_super);
        if (!btrfs_supported_super_csum(csum_type)) {
                btrfs_err(fs_info, "unsupported checksum algorithm: %u",
                          csum_type);
                ret = -EINVAL;
                btrfs_release_disk_super(disk_super);
                goto fail_alloc;
        }

        fs_info->csum_size = btrfs_super_csum_size(disk_super);

        ret = btrfs_init_csum_hash(fs_info, csum_type);
        if (ret) {
                btrfs_release_disk_super(disk_super);
                goto fail_alloc;
        }

        /*
         * We want to check superblock checksum, the type is stored inside.
         * Pass the whole disk block of size BTRFS_SUPER_INFO_SIZE (4k).
         */
        if (btrfs_check_super_csum(fs_info, disk_super)) {
                btrfs_err(fs_info, "superblock checksum mismatch");
                ret = -EINVAL;
                btrfs_release_disk_super(disk_super);
                goto fail_alloc;
        }

        /*
         * super_copy is zeroed at allocation time and we never touch the
         * following bytes up to INFO_SIZE, the checksum is calculated from
         * the whole block of INFO_SIZE
         */
        memcpy(fs_info->super_copy, disk_super, sizeof(*fs_info->super_copy));
        btrfs_release_disk_super(disk_super);

        disk_super = fs_info->super_copy;


        features = btrfs_super_flags(disk_super);
        if (features & BTRFS_SUPER_FLAG_CHANGING_FSID_V2) {
                features &= ~BTRFS_SUPER_FLAG_CHANGING_FSID_V2;
                btrfs_set_super_flags(disk_super, features);
                btrfs_info(fs_info,
                        "found metadata UUID change in progress flag, clearing");
        }

        memcpy(fs_info->super_for_commit, fs_info->super_copy,
               sizeof(*fs_info->super_for_commit));

        ret = btrfs_validate_mount_super(fs_info);
        if (ret) {
                btrfs_err(fs_info, "superblock contains fatal errors");
                ret = -EINVAL;
                goto fail_alloc;
        }

        if (!btrfs_super_root(disk_super)) {
                btrfs_err(fs_info, "invalid superblock tree root bytenr");
                ret = -EINVAL;
                goto fail_alloc;
        }

        /* check FS state, whether FS is broken. */
        if (btrfs_super_flags(disk_super) & BTRFS_SUPER_FLAG_ERROR)
                WRITE_ONCE(fs_info->fs_error, -EUCLEAN);

        /*
         * In the long term, we'll store the compression type in the super
         * block, and it'll be used for per file compression control.
         */
        fs_info->compress_type = BTRFS_COMPRESS_ZLIB;


        /* Set up fs_info before parsing mount options */
        nodesize = btrfs_super_nodesize(disk_super);
        sectorsize = btrfs_super_sectorsize(disk_super);
        stripesize = sectorsize;
        fs_info->dirty_metadata_batch = nodesize * (1 + ilog2(nr_cpu_ids));
        fs_info->delalloc_batch = sectorsize * 512 * (1 + ilog2(nr_cpu_ids));

        fs_info->nodesize = nodesize;
        fs_info->sectorsize = sectorsize;
        fs_info->sectorsize_bits = ilog2(sectorsize);
        fs_info->csums_per_leaf = BTRFS_MAX_ITEM_SIZE(fs_info) / fs_info->csum_size;
        fs_info->stripesize = stripesize;

        ret = btrfs_parse_options(fs_info, options, sb->s_flags);
        if (ret)
                goto fail_alloc;

        ret = btrfs_check_features(fs_info, !sb_rdonly(sb));
        if (ret < 0)
                goto fail_alloc;

        if (sectorsize < PAGE_SIZE) {
                struct btrfs_subpage_info *subpage_info;

                /*
                 * V1 space cache has some hardcoded PAGE_SIZE usage, and is
                 * going to be deprecated.
                 *
                 * Force to use v2 cache for subpage case.
                 */
                btrfs_clear_opt(fs_info->mount_opt, SPACE_CACHE);
                btrfs_set_and_info(fs_info, FREE_SPACE_TREE,
                        "forcing free space tree for sector size %u with page size %lu",
                        sectorsize, PAGE_SIZE);

                btrfs_warn(fs_info,
                "read-write for sector size %u with page size %lu is experimental",
                           sectorsize, PAGE_SIZE);
                subpage_info = kzalloc(sizeof(*subpage_info), GFP_KERNEL);
                if (!subpage_info) {
                        ret = -ENOMEM;
                        goto fail_alloc;
                }
                btrfs_init_subpage_info(subpage_info, sectorsize);
                fs_info->subpage_info = subpage_info;
        }

        ret = btrfs_init_workqueues(fs_info);
        if (ret)
                goto fail_sb_buffer;

        sb->s_bdi->ra_pages *= btrfs_super_num_devices(disk_super);
        sb->s_bdi->ra_pages = max(sb->s_bdi->ra_pages, SZ_4M / PAGE_SIZE);

        sb->s_blocksize = sectorsize;
        sb->s_blocksize_bits = blksize_bits(sectorsize);
        memcpy(&sb->s_uuid, fs_info->fs_devices->fsid, BTRFS_FSID_SIZE);

        mutex_lock(&fs_info->chunk_mutex);
        ret = btrfs_read_sys_array(fs_info);
        mutex_unlock(&fs_info->chunk_mutex);
        if (ret) {
                btrfs_err(fs_info, "failed to read the system array: %d", ret);
                goto fail_sb_buffer;
        }

        generation = btrfs_super_chunk_root_generation(disk_super);
        level = btrfs_super_chunk_root_level(disk_super);
        ret = load_super_root(chunk_root, btrfs_super_chunk_root(disk_super),
                              generation, level);
        if (ret) {
                btrfs_err(fs_info, "failed to read chunk root");
                goto fail_tree_roots;
        }

        read_extent_buffer(chunk_root->node, fs_info->chunk_tree_uuid,
                           offsetof(struct btrfs_header, chunk_tree_uuid),
                           BTRFS_UUID_SIZE);

        ret = btrfs_read_chunk_tree(fs_info);
        if (ret) {
                btrfs_err(fs_info, "failed to read chunk tree: %d", ret);
                goto fail_tree_roots;
        }

        /*
         * At this point we know all the devices that make this filesystem,
         * including the seed devices but we don't know yet if the replace
         * target is required. So free devices that are not part of this
         * filesystem but skip the replace target device which is checked
         * below in btrfs_init_dev_replace().
         */
        btrfs_free_extra_devids(fs_devices);
        if (!fs_devices->latest_dev->bdev) {
                btrfs_err(fs_info, "failed to read devices");
                ret = -EIO;
                goto fail_tree_roots;
        }

        ret = init_tree_roots(fs_info);
        if (ret)
                goto fail_tree_roots;

        /*
         * Get zone type information of zoned block devices. This will also
         * handle emulation of a zoned filesystem if a regular device has the
         * zoned incompat feature flag set.
         */
        ret = btrfs_get_dev_zone_info_all_devices(fs_info);
        if (ret) {
                btrfs_err(fs_info,
                          "zoned: failed to read device zone info: %d", ret);
                goto fail_block_groups;
        }

        /*
         * If we have a uuid root and we're not being told to rescan we need to
         * check the generation here so we can set the
         * BTRFS_FS_UPDATE_UUID_TREE_GEN bit.  Otherwise we could commit the
         * transaction during a balance or the log replay without updating the
         * uuid generation, and then if we crash we would rescan the uuid tree,
         * even though it was perfectly fine.
         */
        if (fs_info->uuid_root && !btrfs_test_opt(fs_info, RESCAN_UUID_TREE) &&
            fs_info->generation == btrfs_super_uuid_tree_generation(disk_super))
                set_bit(BTRFS_FS_UPDATE_UUID_TREE_GEN, &fs_info->flags);

        ret = btrfs_verify_dev_extents(fs_info);
        if (ret) {
                btrfs_err(fs_info,
                          "failed to verify dev extents against chunks: %d",
                          ret);
                goto fail_block_groups;
        }
        ret = btrfs_recover_balance(fs_info);
        if (ret) {
                btrfs_err(fs_info, "failed to recover balance: %d", ret);
                goto fail_block_groups;
        }

        ret = btrfs_init_dev_stats(fs_info);
        if (ret) {
                btrfs_err(fs_info, "failed to init dev_stats: %d", ret);
                goto fail_block_groups;
        }

        ret = btrfs_init_dev_replace(fs_info);
        if (ret) {
                btrfs_err(fs_info, "failed to init dev_replace: %d", ret);
                goto fail_block_groups;
        }

        ret = btrfs_check_zoned_mode(fs_info);
        if (ret) {
                btrfs_err(fs_info, "failed to initialize zoned mode: %d",
                          ret);
                goto fail_block_groups;
        }

        ret = btrfs_sysfs_add_fsid(fs_devices);
        if (ret) {
                btrfs_err(fs_info, "failed to init sysfs fsid interface: %d",
                                ret);
                goto fail_block_groups;
        }

        ret = btrfs_sysfs_add_mounted(fs_info);
        if (ret) {
                btrfs_err(fs_info, "failed to init sysfs interface: %d", ret);
                goto fail_fsdev_sysfs;
        }

        ret = btrfs_init_space_info(fs_info);
        if (ret) {
                btrfs_err(fs_info, "failed to initialize space info: %d", ret);
                goto fail_sysfs;
        }

        ret = btrfs_read_block_groups(fs_info);
        if (ret) {
                btrfs_err(fs_info, "failed to read block groups: %d", ret);
                goto fail_sysfs;
        }

        btrfs_free_zone_cache(fs_info);

        btrfs_check_active_zone_reservation(fs_info);

        if (!sb_rdonly(sb) && fs_info->fs_devices->missing_devices &&
            !btrfs_check_rw_degradable(fs_info, NULL)) {
                btrfs_warn(fs_info,
                "writable mount is not allowed due to too many missing devices");
                ret = -EINVAL;
                goto fail_sysfs;
        }

        fs_info->cleaner_kthread = kthread_run(cleaner_kthread, fs_info,
                                               "btrfs-cleaner");
        if (IS_ERR(fs_info->cleaner_kthread)) {
                ret = PTR_ERR(fs_info->cleaner_kthread);
                goto fail_sysfs;
        }

        fs_info->transaction_kthread = kthread_run(transaction_kthread,
                                                   tree_root,
                                                   "btrfs-transaction");
        if (IS_ERR(fs_info->transaction_kthread)) {
                ret = PTR_ERR(fs_info->transaction_kthread);
                goto fail_cleaner;
        }

        if (!btrfs_test_opt(fs_info, NOSSD) &&
            !fs_info->fs_devices->rotating) {
                btrfs_set_and_info(fs_info, SSD, "enabling ssd optimizations");
        }

        /*
         * For devices supporting discard turn on discard=async automatically,
         * unless it's already set or disabled. This could be turned off by
         * nodiscard for the same mount.
         *
         * The zoned mode piggy backs on the discard functionality for
         * resetting a zone. There is no reason to delay the zone reset as it is
         * fast enough. So, do not enable async discard for zoned mode.
         */
        if (!(btrfs_test_opt(fs_info, DISCARD_SYNC) ||
              btrfs_test_opt(fs_info, DISCARD_ASYNC) ||
              btrfs_test_opt(fs_info, NODISCARD)) &&
            fs_info->fs_devices->discardable &&
            !btrfs_is_zoned(fs_info)) {
                btrfs_set_and_info(fs_info, DISCARD_ASYNC,
                                   "auto enabling async discard");
        }

#ifdef CONFIG_BTRFS_FS_CHECK_INTEGRITY
        if (btrfs_test_opt(fs_info, CHECK_INTEGRITY)) {
                ret = btrfsic_mount(fs_info, fs_devices,
                                    btrfs_test_opt(fs_info,
                                        CHECK_INTEGRITY_DATA) ? 1 : 0,
                                    fs_info->check_integrity_print_mask);
                if (ret)
                        btrfs_warn(fs_info,
                                "failed to initialize integrity check module: %d",
                                ret);
        }
#endif
        ret = btrfs_read_qgroup_config(fs_info);
        if (ret)
                goto fail_trans_kthread;

        if (btrfs_build_ref_tree(fs_info))
                btrfs_err(fs_info, "couldn't build ref tree");

        /* do not make disk changes in broken FS or nologreplay is given */
        if (btrfs_super_log_root(disk_super) != 0 &&
            !btrfs_test_opt(fs_info, NOLOGREPLAY)) {
                btrfs_info(fs_info, "start tree-log replay");
                ret = btrfs_replay_log(fs_info, fs_devices);
                if (ret)
                        goto fail_qgroup;
        }

        fs_info->fs_root = btrfs_get_fs_root(fs_info, BTRFS_FS_TREE_OBJECTID, true);
        if (IS_ERR(fs_info->fs_root)) {
                ret = PTR_ERR(fs_info->fs_root);
                btrfs_warn(fs_info, "failed to read fs tree: %d", ret);
                fs_info->fs_root = NULL;
                goto fail_qgroup;
        }

        if (sb_rdonly(sb))
                goto clear_oneshot;

        ret = btrfs_start_pre_rw_mount(fs_info);
        if (ret) {
                close_ctree(fs_info);
                return ret;
        }
        btrfs_discard_resume(fs_info);

        if (fs_info->uuid_root &&
            (btrfs_test_opt(fs_info, RESCAN_UUID_TREE) ||
             fs_info->generation != btrfs_super_uuid_tree_generation(disk_super))) {
                btrfs_info(fs_info, "checking UUID tree");
                ret = btrfs_check_uuid_tree(fs_info);
                if (ret) {
                        btrfs_warn(fs_info,
                                "failed to check the UUID tree: %d", ret);
                        close_ctree(fs_info);
                        return ret;
                }
        }

        set_bit(BTRFS_FS_OPEN, &fs_info->flags);

        /* Kick the cleaner thread so it'll start deleting snapshots. */
        if (test_bit(BTRFS_FS_UNFINISHED_DROPS, &fs_info->flags))
                wake_up_process(fs_info->cleaner_kthread);

clear_oneshot:
        btrfs_clear_oneshot_options(fs_info);
        return 0;

fail_qgroup:
        btrfs_free_qgroup_config(fs_info);
fail_trans_kthread:
        kthread_stop(fs_info->transaction_kthread);
        btrfs_cleanup_transaction(fs_info);
        btrfs_free_fs_roots(fs_info);
fail_cleaner:
        kthread_stop(fs_info->cleaner_kthread);

        /*
         * make sure we're done with the btree inode before we stop our
         * kthreads
         */
        filemap_write_and_wait(fs_info->btree_inode->i_mapping);

fail_sysfs:
        btrfs_sysfs_remove_mounted(fs_info);

fail_fsdev_sysfs:
        btrfs_sysfs_remove_fsid(fs_info->fs_devices);

fail_block_groups:
        btrfs_put_block_group_cache(fs_info);

fail_tree_roots:
        if (fs_info->data_reloc_root)
                btrfs_drop_and_free_fs_root(fs_info, fs_info->data_reloc_root);
        free_root_pointers(fs_info, true);
        invalidate_inode_pages2(fs_info->btree_inode->i_mapping);

fail_sb_buffer:
        btrfs_stop_all_workers(fs_info);
        btrfs_free_block_groups(fs_info);
fail_alloc:
        btrfs_mapping_tree_free(&fs_info->mapping_tree);

        iput(fs_info->btree_inode);
fail:
        btrfs_close_devices(fs_info->fs_devices);
        ASSERT(ret < 0);
        return ret;
}
ALLOW_ERROR_INJECTION(open_ctree, ERRNO);

static void btrfs_end_super_write(struct bio *bio)
{
        struct btrfs_device *device = bio->bi_private;
        struct bio_vec *bvec;
        struct bvec_iter_all iter_all;
        struct page *page;

        bio_for_each_segment_all(bvec, bio, iter_all) {
                page = bvec->bv_page;

                if (bio->bi_status) {
                        btrfs_warn_rl_in_rcu(device->fs_info,
                                "lost page write due to IO error on %s (%d)",
                                btrfs_dev_name(device),
                                blk_status_to_errno(bio->bi_status));
                        ClearPageUptodate(page);
                        SetPageError(page);
                        btrfs_dev_stat_inc_and_print(device,
                                                     BTRFS_DEV_STAT_WRITE_ERRS);
                } else {
                        SetPageUptodate(page);
                }

                put_page(page);
                unlock_page(page);
        }

        bio_put(bio);
}

struct btrfs_super_block *btrfs_read_dev_one_super(struct block_device *bdev,
                                                   int copy_num, bool drop_cache)
{
        struct btrfs_super_block *super;
        struct page *page;
        u64 bytenr, bytenr_orig;
        struct address_space *mapping = bdev->bd_inode->i_mapping;
        int ret;

        bytenr_orig = btrfs_sb_offset(copy_num);
        ret = btrfs_sb_log_location_bdev(bdev, copy_num, READ, &bytenr);
        if (ret == -ENOENT)
                return ERR_PTR(-EINVAL);
        else if (ret)
                return ERR_PTR(ret);

        if (bytenr + BTRFS_SUPER_INFO_SIZE >= bdev_nr_bytes(bdev))
                return ERR_PTR(-EINVAL);

        if (drop_cache) {
                /* This should only be called with the primary sb. */
                ASSERT(copy_num == 0);

                /*
                 * Drop the page of the primary superblock, so later read will
                 * always read from the device.
                 */
                invalidate_inode_pages2_range(mapping,
                                bytenr >> PAGE_SHIFT,
                                (bytenr + BTRFS_SUPER_INFO_SIZE) >> PAGE_SHIFT);
        }

        page = read_cache_page_gfp(mapping, bytenr >> PAGE_SHIFT, GFP_NOFS);
        if (IS_ERR(page))
                return ERR_CAST(page);

        super = page_address(page);
        if (btrfs_super_magic(super) != BTRFS_MAGIC) {
                btrfs_release_disk_super(super);
                return ERR_PTR(-ENODATA);
        }

        if (btrfs_super_bytenr(super) != bytenr_orig) {
                btrfs_release_disk_super(super);
                return ERR_PTR(-EINVAL);
        }

        return super;
}


struct btrfs_super_block *btrfs_read_dev_super(struct block_device *bdev)
{
        struct btrfs_super_block *super, *latest = NULL;
        int i;
        u64 transid = 0;

        /* we would like to check all the supers, but that would make
         * a btrfs mount succeed after a mkfs from a different FS.
         * So, we need to add a special mount option to scan for
         * later supers, using BTRFS_SUPER_MIRROR_MAX instead
         */
        for (i = 0; i < 1; i++) {
                super = btrfs_read_dev_one_super(bdev, i, false);
                if (IS_ERR(super))
                        continue;

                if (!latest || btrfs_super_generation(super) > transid) {
                        if (latest)
                                btrfs_release_disk_super(super);

                        latest = super;
                        transid = btrfs_super_generation(super);
                }
        }

        return super;
}

/*
 * Write superblock @sb to the @device. Do not wait for completion, all the
 * pages we use for writing are locked.
 *
 * Write @max_mirrors copies of the superblock, where 0 means default that fit
 * the expected device size at commit time. Note that max_mirrors must be
 * same for write and wait phases.
 *
 * Return number of errors when page is not found or submission fails.
 */
static int write_dev_supers(struct btrfs_device *device,
                            struct btrfs_super_block *sb, int max_mirrors)
{
        struct btrfs_fs_info *fs_info = device->fs_info;
        struct address_space *mapping = device->bdev->bd_inode->i_mapping;
        SHASH_DESC_ON_STACK(shash, fs_info->csum_shash);
        int i;
        int errors = 0;
        int ret;
        u64 bytenr, bytenr_orig;

        if (max_mirrors == 0)
                max_mirrors = BTRFS_SUPER_MIRROR_MAX;

        shash->tfm = fs_info->csum_shash;

        for (i = 0; i < max_mirrors; i++) {
                struct page *page;
                struct bio *bio;
                struct btrfs_super_block *disk_super;

                bytenr_orig = btrfs_sb_offset(i);
                ret = btrfs_sb_log_location(device, i, WRITE, &bytenr);
                if (ret == -ENOENT) {
                        continue;
                } else if (ret < 0) {
                        btrfs_err(device->fs_info,
                                "couldn't get super block location for mirror %d",
                                i);
                        errors++;
                        continue;
                }
                if (bytenr + BTRFS_SUPER_INFO_SIZE >=
                    device->commit_total_bytes)
                        break;

                btrfs_set_super_bytenr(sb, bytenr_orig);

                crypto_shash_digest(shash, (const char *)sb + BTRFS_CSUM_SIZE,
                                    BTRFS_SUPER_INFO_SIZE - BTRFS_CSUM_SIZE,
                                    sb->csum);

                page = find_or_create_page(mapping, bytenr >> PAGE_SHIFT,
                                           GFP_NOFS);
                if (!page) {
                        btrfs_err(device->fs_info,
                            "couldn't get super block page for bytenr %llu",
                            bytenr);
                        errors++;
                        continue;
                }

                /* Bump the refcount for wait_dev_supers() */
                get_page(page);

                disk_super = page_address(page);
                memcpy(disk_super, sb, BTRFS_SUPER_INFO_SIZE);

                /*
                 * Directly use bios here instead of relying on the page cache
                 * to do I/O, so we don't lose the ability to do integrity
                 * checking.
                 */
                bio = bio_alloc(device->bdev, 1,
                                REQ_OP_WRITE | REQ_SYNC | REQ_META | REQ_PRIO,
                                GFP_NOFS);
                bio->bi_iter.bi_sector = bytenr >> SECTOR_SHIFT;
                bio->bi_private = device;
                bio->bi_end_io = btrfs_end_super_write;
                __bio_add_page(bio, page, BTRFS_SUPER_INFO_SIZE,
                               offset_in_page(bytenr));

                /*
                 * We FUA only the first super block.  The others we allow to
                 * go down lazy and there's a short window where the on-disk
                 * copies might still contain the older version.
                 */
                if (i == 0 && !btrfs_test_opt(device->fs_info, NOBARRIER))
                        bio->bi_opf |= REQ_FUA;

                btrfsic_check_bio(bio);
                submit_bio(bio);

                if (btrfs_advance_sb_log(device, i))
                        errors++;
        }
        return errors < i ? 0 : -1;
}

/*
 * Wait for write completion of superblocks done by write_dev_supers,
 * @max_mirrors same for write and wait phases.
 *
 * Return number of errors when page is not found or not marked up to
 * date.
 */
static int wait_dev_supers(struct btrfs_device *device, int max_mirrors)
{
        int i;
        int errors = 0;
        bool primary_failed = false;
        int ret;
        u64 bytenr;

        if (max_mirrors == 0)
                max_mirrors = BTRFS_SUPER_MIRROR_MAX;

        for (i = 0; i < max_mirrors; i++) {
                struct page *page;

                ret = btrfs_sb_log_location(device, i, READ, &bytenr);
                if (ret == -ENOENT) {
                        break;
                } else if (ret < 0) {
                        errors++;
                        if (i == 0)
                                primary_failed = true;
                        continue;
                }
                if (bytenr + BTRFS_SUPER_INFO_SIZE >=
                    device->commit_total_bytes)
                        break;

                page = find_get_page(device->bdev->bd_inode->i_mapping,
                                     bytenr >> PAGE_SHIFT);
                if (!page) {
                        errors++;
                        if (i == 0)
                                primary_failed = true;
                        continue;
                }
                /* Page is submitted locked and unlocked once the IO completes */
                wait_on_page_locked(page);
                if (PageError(page)) {
                        errors++;
                        if (i == 0)
                                primary_failed = true;
                }

                /* Drop our reference */
                put_page(page);

                /* Drop the reference from the writing run */
                put_page(page);
        }

        /* log error, force error return */
        if (primary_failed) {
                btrfs_err(device->fs_info, "error writing primary super block to device %llu",
                          device->devid);
                return -1;
        }

        return errors < i ? 0 : -1;
}

/*
 * endio for the write_dev_flush, this will wake anyone waiting
 * for the barrier when it is done
 */
static void btrfs_end_empty_barrier(struct bio *bio)
{
        bio_uninit(bio);
        complete(bio->bi_private);
}

/*
 * Submit a flush request to the device if it supports it. Error handling is
 * done in the waiting counterpart.
 */
static void write_dev_flush(struct btrfs_device *device)
{
        struct bio *bio = &device->flush_bio;

        device->last_flush_error = BLK_STS_OK;

#ifndef CONFIG_BTRFS_FS_CHECK_INTEGRITY
        /*
         * When a disk has write caching disabled, we skip submission of a bio
         * with flush and sync requests before writing the superblock, since
         * it's not needed. However when the integrity checker is enabled, this
         * results in reports that there are metadata blocks referred by a
         * superblock that were not properly flushed. So don't skip the bio
         * submission only when the integrity checker is enabled for the sake
         * of simplicity, since this is a debug tool and not meant for use in
         * non-debug builds.
         */
        if (!bdev_write_cache(device->bdev))
                return;
#endif

        bio_init(bio, device->bdev, NULL, 0,
                 REQ_OP_WRITE | REQ_SYNC | REQ_PREFLUSH);
        bio->bi_end_io = btrfs_end_empty_barrier;
        init_completion(&device->flush_wait);
        bio->bi_private = &device->flush_wait;

        btrfsic_check_bio(bio);
        submit_bio(bio);
        set_bit(BTRFS_DEV_STATE_FLUSH_SENT, &device->dev_state);
}

/*
 * If the flush bio has been submitted by write_dev_flush, wait for it.
 * Return true for any error, and false otherwise.
 */
static bool wait_dev_flush(struct btrfs_device *device)
{
        struct bio *bio = &device->flush_bio;

        if (!test_and_clear_bit(BTRFS_DEV_STATE_FLUSH_SENT, &device->dev_state))
                return false;

        wait_for_completion_io(&device->flush_wait);

        if (bio->bi_status) {
                device->last_flush_error = bio->bi_status;
                btrfs_dev_stat_inc_and_print(device, BTRFS_DEV_STAT_FLUSH_ERRS);
                return true;
        }

        return false;
}

/*
 * send an empty flush down to each device in parallel,
 * then wait for them
 */
static int barrier_all_devices(struct btrfs_fs_info *info)
{
        struct list_head *head;
        struct btrfs_device *dev;
        int errors_wait = 0;

        lockdep_assert_held(&info->fs_devices->device_list_mutex);
        /* send down all the barriers */
        head = &info->fs_devices->devices;
        list_for_each_entry(dev, head, dev_list) {
                if (test_bit(BTRFS_DEV_STATE_MISSING, &dev->dev_state))
                        continue;
                if (!dev->bdev)
                        continue;
                if (!test_bit(BTRFS_DEV_STATE_IN_FS_METADATA, &dev->dev_state) ||
                    !test_bit(BTRFS_DEV_STATE_WRITEABLE, &dev->dev_state))
                        continue;

                write_dev_flush(dev);
        }

        /* wait for all the barriers */
        list_for_each_entry(dev, head, dev_list) {
                if (test_bit(BTRFS_DEV_STATE_MISSING, &dev->dev_state))
                        continue;
                if (!dev->bdev) {
                        errors_wait++;
                        continue;
                }
                if (!test_bit(BTRFS_DEV_STATE_IN_FS_METADATA, &dev->dev_state) ||
                    !test_bit(BTRFS_DEV_STATE_WRITEABLE, &dev->dev_state))
                        continue;

                if (wait_dev_flush(dev))
                        errors_wait++;
        }

        /*
         * Checks last_flush_error of disks in order to determine the device
         * state.
         */
        if (errors_wait && !btrfs_check_rw_degradable(info, NULL))
                return -EIO;

        return 0;
}

int btrfs_get_num_tolerated_disk_barrier_failures(u64 flags)
{
        int raid_type;
        int min_tolerated = INT_MAX;

        if ((flags & BTRFS_BLOCK_GROUP_PROFILE_MASK) == 0 ||
            (flags & BTRFS_AVAIL_ALLOC_BIT_SINGLE))
                min_tolerated = min_t(int, min_tolerated,
                                    btrfs_raid_array[BTRFS_RAID_SINGLE].
                                    tolerated_failures);

        for (raid_type = 0; raid_type < BTRFS_NR_RAID_TYPES; raid_type++) {
                if (raid_type == BTRFS_RAID_SINGLE)
                        continue;
                if (!(flags & btrfs_raid_array[raid_type].bg_flag))
                        continue;
                min_tolerated = min_t(int, min_tolerated,
                                    btrfs_raid_array[raid_type].
                                    tolerated_failures);
        }

        if (min_tolerated == INT_MAX) {
                pr_warn("BTRFS: unknown raid flag: %llu", flags);
                min_tolerated = 0;
        }

        return min_tolerated;
}

int write_all_supers(struct btrfs_fs_info *fs_info, int max_mirrors)
{
        struct list_head *head;
        struct btrfs_device *dev;
        struct btrfs_super_block *sb;
        struct btrfs_dev_item *dev_item;
        int ret;
        int do_barriers;
        int max_errors;
        int total_errors = 0;
        u64 flags;

        do_barriers = !btrfs_test_opt(fs_info, NOBARRIER);

        /*
         * max_mirrors == 0 indicates we're from commit_transaction,
         * not from fsync where the tree roots in fs_info have not
         * been consistent on disk.
         */
        if (max_mirrors == 0)
                backup_super_roots(fs_info);

        sb = fs_info->super_for_commit;
        dev_item = &sb->dev_item;

        mutex_lock(&fs_info->fs_devices->device_list_mutex);
        head = &fs_info->fs_devices->devices;
        max_errors = btrfs_super_num_devices(fs_info->super_copy) - 1;

        if (do_barriers) {
                ret = barrier_all_devices(fs_info);
                if (ret) {
                        mutex_unlock(
                                &fs_info->fs_devices->device_list_mutex);
                        btrfs_handle_fs_error(fs_info, ret,
                                              "errors while submitting device barriers.");
                        return ret;
                }
        }

        list_for_each_entry(dev, head, dev_list) {
                if (!dev->bdev) {
                        total_errors++;
                        continue;
                }
                if (!test_bit(BTRFS_DEV_STATE_IN_FS_METADATA, &dev->dev_state) ||
                    !test_bit(BTRFS_DEV_STATE_WRITEABLE, &dev->dev_state))
                        continue;

                btrfs_set_stack_device_generation(dev_item, 0);
                btrfs_set_stack_device_type(dev_item, dev->type);
                btrfs_set_stack_device_id(dev_item, dev->devid);
                btrfs_set_stack_device_total_bytes(dev_item,
                                                   dev->commit_total_bytes);
                btrfs_set_stack_device_bytes_used(dev_item,
                                                  dev->commit_bytes_used);
                btrfs_set_stack_device_io_align(dev_item, dev->io_align);
                btrfs_set_stack_device_io_width(dev_item, dev->io_width);
                btrfs_set_stack_device_sector_size(dev_item, dev->sector_size);
                memcpy(dev_item->uuid, dev->uuid, BTRFS_UUID_SIZE);
                memcpy(dev_item->fsid, dev->fs_devices->metadata_uuid,
                       BTRFS_FSID_SIZE);

                flags = btrfs_super_flags(sb);
                btrfs_set_super_flags(sb, flags | BTRFS_HEADER_FLAG_WRITTEN);

                ret = btrfs_validate_write_super(fs_info, sb);
                if (ret < 0) {
                        mutex_unlock(&fs_info->fs_devices->device_list_mutex);
                        btrfs_handle_fs_error(fs_info, -EUCLEAN,
                                "unexpected superblock corruption detected");
                        return -EUCLEAN;
                }

                ret = write_dev_supers(dev, sb, max_mirrors);
                if (ret)
                        total_errors++;
        }
        if (total_errors > max_errors) {
                btrfs_err(fs_info, "%d errors while writing supers",
                          total_errors);
                mutex_unlock(&fs_info->fs_devices->device_list_mutex);

                /* FUA is masked off if unsupported and can't be the reason */
                btrfs_handle_fs_error(fs_info, -EIO,
                                      "%d errors while writing supers",
                                      total_errors);
                return -EIO;
        }

        total_errors = 0;
        list_for_each_entry(dev, head, dev_list) {
                if (!dev->bdev)
                        continue;
                if (!test_bit(BTRFS_DEV_STATE_IN_FS_METADATA, &dev->dev_state) ||
                    !test_bit(BTRFS_DEV_STATE_WRITEABLE, &dev->dev_state))
                        continue;

                ret = wait_dev_supers(dev, max_mirrors);
                if (ret)
                        total_errors++;
        }
        mutex_unlock(&fs_info->fs_devices->device_list_mutex);
        if (total_errors > max_errors) {
                btrfs_handle_fs_error(fs_info, -EIO,
                                      "%d errors while writing supers",
                                      total_errors);
                return -EIO;
        }
        return 0;
}

/* Drop a fs root from the radix tree and free it. */
void btrfs_drop_and_free_fs_root(struct btrfs_fs_info *fs_info,
                                  struct btrfs_root *root)
{
        bool drop_ref = false;

        spin_lock(&fs_info->fs_roots_radix_lock);
        radix_tree_delete(&fs_info->fs_roots_radix,
                          (unsigned long)root->root_key.objectid);
        if (test_and_clear_bit(BTRFS_ROOT_IN_RADIX, &root->state))
                drop_ref = true;
        spin_unlock(&fs_info->fs_roots_radix_lock);

        if (BTRFS_FS_ERROR(fs_info)) {
                ASSERT(root->log_root == NULL);
                if (root->reloc_root) {
                        btrfs_put_root(root->reloc_root);
                        root->reloc_root = NULL;
                }
        }

        if (drop_ref)
                btrfs_put_root(root);
}

int btrfs_commit_super(struct btrfs_fs_info *fs_info)
{
        struct btrfs_root *root = fs_info->tree_root;
        struct btrfs_trans_handle *trans;

        mutex_lock(&fs_info->cleaner_mutex);
        btrfs_run_delayed_iputs(fs_info);
        mutex_unlock(&fs_info->cleaner_mutex);
        wake_up_process(fs_info->cleaner_kthread);

        /* wait until ongoing cleanup work done */
        down_write(&fs_info->cleanup_work_sem);
        up_write(&fs_info->cleanup_work_sem);

        trans = btrfs_join_transaction(root);
        if (IS_ERR(trans))
                return PTR_ERR(trans);
        return btrfs_commit_transaction(trans);
}

static void warn_about_uncommitted_trans(struct btrfs_fs_info *fs_info)
{
        struct btrfs_transaction *trans;
        struct btrfs_transaction *tmp;
        bool found = false;

        if (list_empty(&fs_info->trans_list))
                return;

        /*
         * This function is only called at the very end of close_ctree(),
         * thus no other running transaction, no need to take trans_lock.
         */
        ASSERT(test_bit(BTRFS_FS_CLOSING_DONE, &fs_info->flags));
        list_for_each_entry_safe(trans, tmp, &fs_info->trans_list, list) {
                struct extent_state *cached = NULL;
                u64 dirty_bytes = 0;
                u64 cur = 0;
                u64 found_start;
                u64 found_end;

                found = true;
                while (find_first_extent_bit(&trans->dirty_pages, cur,
                        &found_start, &found_end, EXTENT_DIRTY, &cached)) {
                        dirty_bytes += found_end + 1 - found_start;
                        cur = found_end + 1;
                }
                btrfs_warn(fs_info,
        "transaction %llu (with %llu dirty metadata bytes) is not committed",
                           trans->transid, dirty_bytes);
                btrfs_cleanup_one_transaction(trans, fs_info);

                if (trans == fs_info->running_transaction)
                        fs_info->running_transaction = NULL;
                list_del_init(&trans->list);

                btrfs_put_transaction(trans);
                trace_btrfs_transaction_commit(fs_info);
        }
        ASSERT(!found);
}

void __cold close_ctree(struct btrfs_fs_info *fs_info)
{
        int ret;

        set_bit(BTRFS_FS_CLOSING_START, &fs_info->flags);

        /*
         * If we had UNFINISHED_DROPS we could still be processing them, so
         * clear that bit and wake up relocation so it can stop.
         * We must do this before stopping the block group reclaim task, because
         * at btrfs_relocate_block_group() we wait for this bit, and after the
         * wait we stop with -EINTR if btrfs_fs_closing() returns non-zero - we
         * have just set BTRFS_FS_CLOSING_START, so btrfs_fs_closing() will
         * return 1.
         */
        btrfs_wake_unfinished_drop(fs_info);

        /*
         * We may have the reclaim task running and relocating a data block group,
         * in which case it may create delayed iputs. So stop it before we park
         * the cleaner kthread otherwise we can get new delayed iputs after
         * parking the cleaner, and that can make the async reclaim task to hang
         * if it's waiting for delayed iputs to complete, since the cleaner is
         * parked and can not run delayed iputs - this will make us hang when
         * trying to stop the async reclaim task.
         */
        cancel_work_sync(&fs_info->reclaim_bgs_work);
        /*
         * We don't want the cleaner to start new transactions, add more delayed
         * iputs, etc. while we're closing. We can't use kthread_stop() yet
         * because that frees the task_struct, and the transaction kthread might
         * still try to wake up the cleaner.
         */
        kthread_park(fs_info->cleaner_kthread);

        /* wait for the qgroup rescan worker to stop */
        btrfs_qgroup_wait_for_completion(fs_info, false);

        /* wait for the uuid_scan task to finish */
        down(&fs_info->uuid_tree_rescan_sem);
        /* avoid complains from lockdep et al., set sem back to initial state */
        up(&fs_info->uuid_tree_rescan_sem);

        /* pause restriper - we want to resume on mount */
        btrfs_pause_balance(fs_info);

        btrfs_dev_replace_suspend_for_unmount(fs_info);

        btrfs_scrub_cancel(fs_info);

        /* wait for any defraggers to finish */
        wait_event(fs_info->transaction_wait,
                   (atomic_read(&fs_info->defrag_running) == 0));

        /* clear out the rbtree of defraggable inodes */
        btrfs_cleanup_defrag_inodes(fs_info);

        /*
         * After we parked the cleaner kthread, ordered extents may have
         * completed and created new delayed iputs. If one of the async reclaim
         * tasks is running and in the RUN_DELAYED_IPUTS flush state, then we
         * can hang forever trying to stop it, because if a delayed iput is
         * added after it ran btrfs_run_delayed_iputs() and before it called
         * btrfs_wait_on_delayed_iputs(), it will hang forever since there is
         * no one else to run iputs.
         *
         * So wait for all ongoing ordered extents to complete and then run
         * delayed iputs. This works because once we reach this point no one
         * can either create new ordered extents nor create delayed iputs
         * through some other means.
         *
         * Also note that btrfs_wait_ordered_roots() is not safe here, because
         * it waits for BTRFS_ORDERED_COMPLETE to be set on an ordered extent,
         * but the delayed iput for the respective inode is made only when doing
         * the final btrfs_put_ordered_extent() (which must happen at
         * btrfs_finish_ordered_io() when we are unmounting).
         */
        btrfs_flush_workqueue(fs_info->endio_write_workers);
        /* Ordered extents for free space inodes. */
        btrfs_flush_workqueue(fs_info->endio_freespace_worker);
        btrfs_run_delayed_iputs(fs_info);

        cancel_work_sync(&fs_info->async_reclaim_work);
        cancel_work_sync(&fs_info->async_data_reclaim_work);
        cancel_work_sync(&fs_info->preempt_reclaim_work);

        /* Cancel or finish ongoing discard work */
        btrfs_discard_cleanup(fs_info);

        if (!sb_rdonly(fs_info->sb)) {
                /*
                 * The cleaner kthread is stopped, so do one final pass over
                 * unused block groups.
                 */
                btrfs_delete_unused_bgs(fs_info);

                /*
                 * There might be existing delayed inode workers still running
                 * and holding an empty delayed inode item. We must wait for
                 * them to complete first because they can create a transaction.
                 * This happens when someone calls btrfs_balance_delayed_items()
                 * and then a transaction commit runs the same delayed nodes
                 * before any delayed worker has done something with the nodes.
                 * We must wait for any worker here and not at transaction
                 * commit time since that could cause a deadlock.
                 * This is a very rare case.
                 */
                btrfs_flush_workqueue(fs_info->delayed_workers);

                ret = btrfs_commit_super(fs_info);
                if (ret)
                        btrfs_err(fs_info, "commit super ret %d", ret);
        }

        if (BTRFS_FS_ERROR(fs_info))
                btrfs_error_commit_super(fs_info);

        kthread_stop(fs_info->transaction_kthread);
        kthread_stop(fs_info->cleaner_kthread);

        ASSERT(list_empty(&fs_info->delayed_iputs));
        set_bit(BTRFS_FS_CLOSING_DONE, &fs_info->flags);

        if (btrfs_check_quota_leak(fs_info)) {
                WARN_ON(IS_ENABLED(CONFIG_BTRFS_DEBUG));
                btrfs_err(fs_info, "qgroup reserved space leaked");
        }

        btrfs_free_qgroup_config(fs_info);
        ASSERT(list_empty(&fs_info->delalloc_roots));

        if (percpu_counter_sum(&fs_info->delalloc_bytes)) {
                btrfs_info(fs_info, "at unmount delalloc count %lld",
                       percpu_counter_sum(&fs_info->delalloc_bytes));
        }

        if (percpu_counter_sum(&fs_info->ordered_bytes))
                btrfs_info(fs_info, "at unmount dio bytes count %lld",
                           percpu_counter_sum(&fs_info->ordered_bytes));

        btrfs_sysfs_remove_mounted(fs_info);
        btrfs_sysfs_remove_fsid(fs_info->fs_devices);

        btrfs_put_block_group_cache(fs_info);

        /*
         * we must make sure there is not any read request to
         * submit after we stopping all workers.
         */
        invalidate_inode_pages2(fs_info->btree_inode->i_mapping);
        btrfs_stop_all_workers(fs_info);

        /* We shouldn't have any transaction open at this point */
        warn_about_uncommitted_trans(fs_info);

        clear_bit(BTRFS_FS_OPEN, &fs_info->flags);
        free_root_pointers(fs_info, true);
        btrfs_free_fs_roots(fs_info);

        /*
         * We must free the block groups after dropping the fs_roots as we could
         * have had an IO error and have left over tree log blocks that aren't
         * cleaned up until the fs roots are freed.  This makes the block group
         * accounting appear to be wrong because there's pending reserved bytes,
         * so make sure we do the block group cleanup afterwards.
         */
        btrfs_free_block_groups(fs_info);

        iput(fs_info->btree_inode);

#ifdef CONFIG_BTRFS_FS_CHECK_INTEGRITY
        if (btrfs_test_opt(fs_info, CHECK_INTEGRITY))
                btrfsic_unmount(fs_info->fs_devices);
#endif

        btrfs_mapping_tree_free(&fs_info->mapping_tree);
        btrfs_close_devices(fs_info->fs_devices);
}

void btrfs_mark_buffer_dirty(struct extent_buffer *buf)
{
        struct btrfs_fs_info *fs_info = buf->fs_info;
        u64 transid = btrfs_header_generation(buf);

#ifdef CONFIG_BTRFS_FS_RUN_SANITY_TESTS
        /*
         * This is a fast path so only do this check if we have sanity tests
         * enabled.  Normal people shouldn't be using unmapped buffers as dirty
         * outside of the sanity tests.
         */
        if (unlikely(test_bit(EXTENT_BUFFER_UNMAPPED, &buf->bflags)))
                return;
#endif
        btrfs_assert_tree_write_locked(buf);
        if (transid != fs_info->generation)
                WARN(1, KERN_CRIT "btrfs transid mismatch buffer %llu, found %llu running %llu\n",
                        buf->start, transid, fs_info->generation);
        set_extent_buffer_dirty(buf);
#ifdef CONFIG_BTRFS_FS_CHECK_INTEGRITY
        /*
         * btrfs_check_leaf() won't check item data if we don't have WRITTEN
         * set, so this will only validate the basic structure of the items.
         */
        if (btrfs_header_level(buf) == 0 && btrfs_check_leaf(buf)) {
                btrfs_print_leaf(buf);
                ASSERT(0);
        }
#endif
}

static void __btrfs_btree_balance_dirty(struct btrfs_fs_info *fs_info,
                                        int flush_delayed)
{
        /*
         * looks as though older kernels can get into trouble with
         * this code, they end up stuck in balance_dirty_pages forever
         */
        int ret;

        if (current->flags & PF_MEMALLOC)
                return;

        if (flush_delayed)
                btrfs_balance_delayed_items(fs_info);

        ret = __percpu_counter_compare(&fs_info->dirty_metadata_bytes,
                                     BTRFS_DIRTY_METADATA_THRESH,
                                     fs_info->dirty_metadata_batch);
        if (ret > 0) {
                balance_dirty_pages_ratelimited(fs_info->btree_inode->i_mapping);
        }
}

void btrfs_btree_balance_dirty(struct btrfs_fs_info *fs_info)
{
        __btrfs_btree_balance_dirty(fs_info, 1);
}

void btrfs_btree_balance_dirty_nodelay(struct btrfs_fs_info *fs_info)
{
        __btrfs_btree_balance_dirty(fs_info, 0);
}

static void btrfs_error_commit_super(struct btrfs_fs_info *fs_info)
{
        /* cleanup FS via transaction */
        btrfs_cleanup_transaction(fs_info);

        mutex_lock(&fs_info->cleaner_mutex);
        btrfs_run_delayed_iputs(fs_info);
        mutex_unlock(&fs_info->cleaner_mutex);

        down_write(&fs_info->cleanup_work_sem);
        up_write(&fs_info->cleanup_work_sem);
}

static void btrfs_drop_all_logs(struct btrfs_fs_info *fs_info)
{
        struct btrfs_root *gang[8];
        u64 root_objectid = 0;
        int ret;

        spin_lock(&fs_info->fs_roots_radix_lock);
        while ((ret = radix_tree_gang_lookup(&fs_info->fs_roots_radix,
                                             (void **)gang, root_objectid,
                                             ARRAY_SIZE(gang))) != 0) {
                int i;

                for (i = 0; i < ret; i++)
                        gang[i] = btrfs_grab_root(gang[i]);
                spin_unlock(&fs_info->fs_roots_radix_lock);

                for (i = 0; i < ret; i++) {
                        if (!gang[i])
                                continue;
                        root_objectid = gang[i]->root_key.objectid;
                        btrfs_free_log(NULL, gang[i]);
                        btrfs_put_root(gang[i]);
                }
                root_objectid++;
                spin_lock(&fs_info->fs_roots_radix_lock);
        }
        spin_unlock(&fs_info->fs_roots_radix_lock);
        btrfs_free_log_root_tree(NULL, fs_info);
}

static void btrfs_destroy_ordered_extents(struct btrfs_root *root)
{
        struct btrfs_ordered_extent *ordered;

        spin_lock(&root->ordered_extent_lock);
        /*
         * This will just short circuit the ordered completion stuff which will
         * make sure the ordered extent gets properly cleaned up.
         */
        list_for_each_entry(ordered, &root->ordered_extents,
                            root_extent_list)
                set_bit(BTRFS_ORDERED_IOERR, &ordered->flags);
        spin_unlock(&root->ordered_extent_lock);
}

static void btrfs_destroy_all_ordered_extents(struct btrfs_fs_info *fs_info)
{
        struct btrfs_root *root;
        LIST_HEAD(splice);

        spin_lock(&fs_info->ordered_root_lock);
        list_splice_init(&fs_info->ordered_roots, &splice);
        while (!list_empty(&splice)) {
                root = list_first_entry(&splice, struct btrfs_root,
                                        ordered_root);
                list_move_tail(&root->ordered_root,
                               &fs_info->ordered_roots);

                spin_unlock(&fs_info->ordered_root_lock);
                btrfs_destroy_ordered_extents(root);

                cond_resched();
                spin_lock(&fs_info->ordered_root_lock);
        }
        spin_unlock(&fs_info->ordered_root_lock);

        /*
         * We need this here because if we've been flipped read-only we won't
         * get sync() from the umount, so we need to make sure any ordered
         * extents that haven't had their dirty pages IO start writeout yet
         * actually get run and error out properly.
         */
        btrfs_wait_ordered_roots(fs_info, U64_MAX, 0, (u64)-1);
}

static void btrfs_destroy_delayed_refs(struct btrfs_transaction *trans,
                                       struct btrfs_fs_info *fs_info)
{
        struct rb_node *node;
        struct btrfs_delayed_ref_root *delayed_refs;
        struct btrfs_delayed_ref_node *ref;

        delayed_refs = &trans->delayed_refs;

        spin_lock(&delayed_refs->lock);
        if (atomic_read(&delayed_refs->num_entries) == 0) {
                spin_unlock(&delayed_refs->lock);
                btrfs_debug(fs_info, "delayed_refs has NO entry");
                return;
        }

        while ((node = rb_first_cached(&delayed_refs->href_root)) != NULL) {
                struct btrfs_delayed_ref_head *head;
                struct rb_node *n;
                bool pin_bytes = false;

                head = rb_entry(node, struct btrfs_delayed_ref_head,
                                href_node);
                if (btrfs_delayed_ref_lock(delayed_refs, head))
                        continue;

                spin_lock(&head->lock);
                while ((n = rb_first_cached(&head->ref_tree)) != NULL) {
                        ref = rb_entry(n, struct btrfs_delayed_ref_node,
                                       ref_node);
                        rb_erase_cached(&ref->ref_node, &head->ref_tree);
                        RB_CLEAR_NODE(&ref->ref_node);
                        if (!list_empty(&ref->add_list))
                                list_del(&ref->add_list);
                        atomic_dec(&delayed_refs->num_entries);
                        btrfs_put_delayed_ref(ref);
                }
                if (head->must_insert_reserved)
                        pin_bytes = true;
                btrfs_free_delayed_extent_op(head->extent_op);
                btrfs_delete_ref_head(delayed_refs, head);
                spin_unlock(&head->lock);
                spin_unlock(&delayed_refs->lock);
                mutex_unlock(&head->mutex);

                if (pin_bytes) {
                        struct btrfs_block_group *cache;

                        cache = btrfs_lookup_block_group(fs_info, head->bytenr);
                        BUG_ON(!cache);

                        spin_lock(&cache->space_info->lock);
                        spin_lock(&cache->lock);
                        cache->pinned += head->num_bytes;
                        btrfs_space_info_update_bytes_pinned(fs_info,
                                cache->space_info, head->num_bytes);
                        cache->reserved -= head->num_bytes;
                        cache->space_info->bytes_reserved -= head->num_bytes;
                        spin_unlock(&cache->lock);
                        spin_unlock(&cache->space_info->lock);

                        btrfs_put_block_group(cache);

                        btrfs_error_unpin_extent_range(fs_info, head->bytenr,
                                head->bytenr + head->num_bytes - 1);
                }
                btrfs_cleanup_ref_head_accounting(fs_info, delayed_refs, head);
                btrfs_put_delayed_ref_head(head);
                cond_resched();
                spin_lock(&delayed_refs->lock);
        }
        btrfs_qgroup_destroy_extent_records(trans);

        spin_unlock(&delayed_refs->lock);
}

static void btrfs_destroy_delalloc_inodes(struct btrfs_root *root)
{
        struct btrfs_inode *btrfs_inode;
        LIST_HEAD(splice);

        spin_lock(&root->delalloc_lock);
        list_splice_init(&root->delalloc_inodes, &splice);

        while (!list_empty(&splice)) {
                struct inode *inode = NULL;
                btrfs_inode = list_first_entry(&splice, struct btrfs_inode,
                                               delalloc_inodes);
                __btrfs_del_delalloc_inode(root, btrfs_inode);
                spin_unlock(&root->delalloc_lock);

                /*
                 * Make sure we get a live inode and that it'll not disappear
                 * meanwhile.
                 */
                inode = igrab(&btrfs_inode->vfs_inode);
                if (inode) {
                        unsigned int nofs_flag;

                        nofs_flag = memalloc_nofs_save();
                        invalidate_inode_pages2(inode->i_mapping);
                        memalloc_nofs_restore(nofs_flag);
                        iput(inode);
                }
                spin_lock(&root->delalloc_lock);
        }
        spin_unlock(&root->delalloc_lock);
}

static void btrfs_destroy_all_delalloc_inodes(struct btrfs_fs_info *fs_info)
{
        struct btrfs_root *root;
        LIST_HEAD(splice);

        spin_lock(&fs_info->delalloc_root_lock);
        list_splice_init(&fs_info->delalloc_roots, &splice);
        while (!list_empty(&splice)) {
                root = list_first_entry(&splice, struct btrfs_root,
                                         delalloc_root);
                root = btrfs_grab_root(root);
                BUG_ON(!root);
                spin_unlock(&fs_info->delalloc_root_lock);

                btrfs_destroy_delalloc_inodes(root);
                btrfs_put_root(root);

                spin_lock(&fs_info->delalloc_root_lock);
        }
        spin_unlock(&fs_info->delalloc_root_lock);
}

static void btrfs_destroy_marked_extents(struct btrfs_fs_info *fs_info,
                                         struct extent_io_tree *dirty_pages,
                                         int mark)
{
        struct extent_buffer *eb;
        u64 start = 0;
        u64 end;

        while (find_first_extent_bit(dirty_pages, start, &start, &end,
                                     mark, NULL)) {
                clear_extent_bits(dirty_pages, start, end, mark);
                while (start <= end) {
                        eb = find_extent_buffer(fs_info, start);
                        start += fs_info->nodesize;
                        if (!eb)
                                continue;

                        btrfs_tree_lock(eb);
                        wait_on_extent_buffer_writeback(eb);
                        btrfs_clear_buffer_dirty(NULL, eb);
                        btrfs_tree_unlock(eb);

                        free_extent_buffer_stale(eb);
                }
        }
}

static void btrfs_destroy_pinned_extent(struct btrfs_fs_info *fs_info,
                                        struct extent_io_tree *unpin)
{
        u64 start;
        u64 end;

        while (1) {
                struct extent_state *cached_state = NULL;

                /*
                 * The btrfs_finish_extent_commit() may get the same range as
                 * ours between find_first_extent_bit and clear_extent_dirty.
                 * Hence, hold the unused_bg_unpin_mutex to avoid double unpin
                 * the same extent range.
                 */
                mutex_lock(&fs_info->unused_bg_unpin_mutex);
                if (!find_first_extent_bit(unpin, 0, &start, &end,
                                           EXTENT_DIRTY, &cached_state)) {
                        mutex_unlock(&fs_info->unused_bg_unpin_mutex);
                        break;
                }

                clear_extent_dirty(unpin, start, end, &cached_state);
                free_extent_state(cached_state);
                btrfs_error_unpin_extent_range(fs_info, start, end);
                mutex_unlock(&fs_info->unused_bg_unpin_mutex);
                cond_resched();
        }
}

static void btrfs_cleanup_bg_io(struct btrfs_block_group *cache)
{
        struct inode *inode;

        inode = cache->io_ctl.inode;
        if (inode) {
                unsigned int nofs_flag;

                nofs_flag = memalloc_nofs_save();
                invalidate_inode_pages2(inode->i_mapping);
                memalloc_nofs_restore(nofs_flag);

                BTRFS_I(inode)->generation = 0;
                cache->io_ctl.inode = NULL;
                iput(inode);
        }
        ASSERT(cache->io_ctl.pages == NULL);
        btrfs_put_block_group(cache);
}

void btrfs_cleanup_dirty_bgs(struct btrfs_transaction *cur_trans,
                             struct btrfs_fs_info *fs_info)
{
        struct btrfs_block_group *cache;

        spin_lock(&cur_trans->dirty_bgs_lock);
        while (!list_empty(&cur_trans->dirty_bgs)) {
                cache = list_first_entry(&cur_trans->dirty_bgs,
                                         struct btrfs_block_group,
                                         dirty_list);

                if (!list_empty(&cache->io_list)) {
                        spin_unlock(&cur_trans->dirty_bgs_lock);
                        list_del_init(&cache->io_list);
                        btrfs_cleanup_bg_io(cache);
                        spin_lock(&cur_trans->dirty_bgs_lock);
                }

                list_del_init(&cache->dirty_list);
                spin_lock(&cache->lock);
                cache->disk_cache_state = BTRFS_DC_ERROR;
                spin_unlock(&cache->lock);

                spin_unlock(&cur_trans->dirty_bgs_lock);
                btrfs_put_block_group(cache);
                btrfs_delayed_refs_rsv_release(fs_info, 1);
                spin_lock(&cur_trans->dirty_bgs_lock);
        }
        spin_unlock(&cur_trans->dirty_bgs_lock);

        /*
         * Refer to the definition of io_bgs member for details why it's safe
         * to use it without any locking
         */
        while (!list_empty(&cur_trans->io_bgs)) {
                cache = list_first_entry(&cur_trans->io_bgs,
                                         struct btrfs_block_group,
                                         io_list);

                list_del_init(&cache->io_list);
                spin_lock(&cache->lock);
                cache->disk_cache_state = BTRFS_DC_ERROR;
                spin_unlock(&cache->lock);
                btrfs_cleanup_bg_io(cache);
        }
}

void btrfs_cleanup_one_transaction(struct btrfs_transaction *cur_trans,
                                   struct btrfs_fs_info *fs_info)
{
        struct btrfs_device *dev, *tmp;

        btrfs_cleanup_dirty_bgs(cur_trans, fs_info);
        ASSERT(list_empty(&cur_trans->dirty_bgs));
        ASSERT(list_empty(&cur_trans->io_bgs));

        list_for_each_entry_safe(dev, tmp, &cur_trans->dev_update_list,
                                 post_commit_list) {
                list_del_init(&dev->post_commit_list);
        }

        btrfs_destroy_delayed_refs(cur_trans, fs_info);

        cur_trans->state = TRANS_STATE_COMMIT_START;
        wake_up(&fs_info->transaction_blocked_wait);

        cur_trans->state = TRANS_STATE_UNBLOCKED;
        wake_up(&fs_info->transaction_wait);

        btrfs_destroy_delayed_inodes(fs_info);

        btrfs_destroy_marked_extents(fs_info, &cur_trans->dirty_pages,
                                     EXTENT_DIRTY);
        btrfs_destroy_pinned_extent(fs_info, &cur_trans->pinned_extents);

        cur_trans->state =TRANS_STATE_COMPLETED;
        wake_up(&cur_trans->commit_wait);
}

static int btrfs_cleanup_transaction(struct btrfs_fs_info *fs_info)
{
        struct btrfs_transaction *t;

        mutex_lock(&fs_info->transaction_kthread_mutex);

        spin_lock(&fs_info->trans_lock);
        while (!list_empty(&fs_info->trans_list)) {
                t = list_first_entry(&fs_info->trans_list,
                                     struct btrfs_transaction, list);
                if (t->state >= TRANS_STATE_COMMIT_PREP) {
                        refcount_inc(&t->use_count);
                        spin_unlock(&fs_info->trans_lock);
                        btrfs_wait_for_commit(fs_info, t->transid);
                        btrfs_put_transaction(t);
                        spin_lock(&fs_info->trans_lock);
                        continue;
                }
                if (t == fs_info->running_transaction) {
                        t->state = TRANS_STATE_COMMIT_DOING;
                        spin_unlock(&fs_info->trans_lock);
                        /*
                         * We wait for 0 num_writers since we don't hold a trans
                         * handle open currently for this transaction.
                         */
                        wait_event(t->writer_wait,
                                   atomic_read(&t->num_writers) == 0);
                } else {
                        spin_unlock(&fs_info->trans_lock);
                }
                btrfs_cleanup_one_transaction(t, fs_info);

                spin_lock(&fs_info->trans_lock);
                if (t == fs_info->running_transaction)
                        fs_info->running_transaction = NULL;
                list_del_init(&t->list);
                spin_unlock(&fs_info->trans_lock);

                btrfs_put_transaction(t);
                trace_btrfs_transaction_commit(fs_info);
                spin_lock(&fs_info->trans_lock);
        }
        spin_unlock(&fs_info->trans_lock);
        btrfs_destroy_all_ordered_extents(fs_info);
        btrfs_destroy_delayed_inodes(fs_info);
        btrfs_assert_delayed_root_empty(fs_info);
        btrfs_destroy_all_delalloc_inodes(fs_info);
        btrfs_drop_all_logs(fs_info);
        mutex_unlock(&fs_info->transaction_kthread_mutex);

        return 0;
}

int btrfs_init_root_free_objectid(struct btrfs_root *root)
{
        struct btrfs_path *path;
        int ret;
        struct extent_buffer *l;
        struct btrfs_key search_key;
        struct btrfs_key found_key;
        int slot;

        path = btrfs_alloc_path();
        if (!path)
                return -ENOMEM;

        search_key.objectid = BTRFS_LAST_FREE_OBJECTID;
        search_key.type = -1;
        search_key.offset = (u64)-1;
        ret = btrfs_search_slot(NULL, root, &search_key, path, 0, 0);
        if (ret < 0)
                goto error;
        BUG_ON(ret == 0); /* Corruption */
        if (path->slots[0] > 0) {
                slot = path->slots[0] - 1;
                l = path->nodes[0];
                btrfs_item_key_to_cpu(l, &found_key, slot);
                root->free_objectid = max_t(u64, found_key.objectid + 1,
                                            BTRFS_FIRST_FREE_OBJECTID);
        } else {
                root->free_objectid = BTRFS_FIRST_FREE_OBJECTID;
        }
        ret = 0;
error:
        btrfs_free_path(path);
        return ret;
}

int btrfs_get_free_objectid(struct btrfs_root *root, u64 *objectid)
{
        int ret;
        mutex_lock(&root->objectid_mutex);

        if (unlikely(root->free_objectid >= BTRFS_LAST_FREE_OBJECTID)) {
                btrfs_warn(root->fs_info,
                           "the objectid of root %llu reaches its highest value",
                           root->root_key.objectid);
                ret = -ENOSPC;
                goto out;
        }

        *objectid = root->free_objectid++;
        ret = 0;
out:
        mutex_unlock(&root->objectid_mutex);
        return ret;
}