[thirdparty/kernel/stable.git] /

// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (C) 2007 Oracle.  All rights reserved.
 * Copyright (C) 2022 Christoph Hellwig.
 */

#include <linux/bio.h>
#include "bio.h"
#include "ctree.h"
#include "volumes.h"
#include "raid56.h"
#include "async-thread.h"
#include "check-integrity.h"
#include "dev-replace.h"
#include "rcu-string.h"
#include "zoned.h"
#include "file-item.h"
#include "raid-stripe-tree.h"

static struct bio_set btrfs_bioset;
static struct bio_set btrfs_clone_bioset;
static struct bio_set btrfs_repair_bioset;
static mempool_t btrfs_failed_bio_pool;

struct btrfs_failed_bio {
        struct btrfs_bio *bbio;
        int num_copies;
        atomic_t repair_count;
};

/* Is this a data path I/O that needs storage layer checksum and repair? */
static inline bool is_data_bbio(struct btrfs_bio *bbio)
{
        return bbio->inode && is_data_inode(&bbio->inode->vfs_inode);
}

static bool bbio_has_ordered_extent(struct btrfs_bio *bbio)
{
        return is_data_bbio(bbio) && btrfs_op(&bbio->bio) == BTRFS_MAP_WRITE;
}

/*
 * Initialize a btrfs_bio structure.  This skips the embedded bio itself as it
 * is already initialized by the block layer.
 */
void btrfs_bio_init(struct btrfs_bio *bbio, struct btrfs_fs_info *fs_info,
                    btrfs_bio_end_io_t end_io, void *private)
{
        memset(bbio, 0, offsetof(struct btrfs_bio, bio));
        bbio->fs_info = fs_info;
        bbio->end_io = end_io;
        bbio->private = private;
        atomic_set(&bbio->pending_ios, 1);
}

/*
 * Allocate a btrfs_bio structure.  The btrfs_bio is the main I/O container for
 * btrfs, and is used for all I/O submitted through btrfs_submit_bio.
 *
 * Just like the underlying bio_alloc_bioset it will not fail as it is backed by
 * a mempool.
 */
struct btrfs_bio *btrfs_bio_alloc(unsigned int nr_vecs, blk_opf_t opf,
                                  struct btrfs_fs_info *fs_info,
                                  btrfs_bio_end_io_t end_io, void *private)
{
        struct btrfs_bio *bbio;
        struct bio *bio;

        bio = bio_alloc_bioset(NULL, nr_vecs, opf, GFP_NOFS, &btrfs_bioset);
        bbio = btrfs_bio(bio);
        btrfs_bio_init(bbio, fs_info, end_io, private);
        return bbio;
}

static struct btrfs_bio *btrfs_split_bio(struct btrfs_fs_info *fs_info,
                                         struct btrfs_bio *orig_bbio,
                                         u64 map_length, bool use_append)
{
        struct btrfs_bio *bbio;
        struct bio *bio;

        if (use_append) {
                unsigned int nr_segs;

                bio = bio_split_rw(&orig_bbio->bio, &fs_info->limits, &nr_segs,
                                   &btrfs_clone_bioset, map_length);
        } else {
                bio = bio_split(&orig_bbio->bio, map_length >> SECTOR_SHIFT,
                                GFP_NOFS, &btrfs_clone_bioset);
        }
        bbio = btrfs_bio(bio);
        btrfs_bio_init(bbio, fs_info, NULL, orig_bbio);
        bbio->inode = orig_bbio->inode;
        bbio->file_offset = orig_bbio->file_offset;
        orig_bbio->file_offset += map_length;
        if (bbio_has_ordered_extent(bbio)) {
                refcount_inc(&orig_bbio->ordered->refs);
                bbio->ordered = orig_bbio->ordered;
        }
        atomic_inc(&orig_bbio->pending_ios);
        return bbio;
}

/* Free a bio that was never submitted to the underlying device. */
static void btrfs_cleanup_bio(struct btrfs_bio *bbio)
{
        if (bbio_has_ordered_extent(bbio))
                btrfs_put_ordered_extent(bbio->ordered);
        bio_put(&bbio->bio);
}

static void __btrfs_bio_end_io(struct btrfs_bio *bbio)
{
        if (bbio_has_ordered_extent(bbio)) {
                struct btrfs_ordered_extent *ordered = bbio->ordered;

                bbio->end_io(bbio);
                btrfs_put_ordered_extent(ordered);
        } else {
                bbio->end_io(bbio);
        }
}

static void btrfs_orig_write_end_io(struct bio *bio);

static void btrfs_bbio_propagate_error(struct btrfs_bio *bbio,
                                       struct btrfs_bio *orig_bbio)
{
        /*
         * For writes we tolerate nr_mirrors - 1 write failures, so we can't
         * just blindly propagate a write failure here.  Instead increment the
         * error count in the original I/O context so that it is guaranteed to
         * be larger than the error tolerance.
         */
        if (bbio->bio.bi_end_io == &btrfs_orig_write_end_io) {
                struct btrfs_io_stripe *orig_stripe = orig_bbio->bio.bi_private;
                struct btrfs_io_context *orig_bioc = orig_stripe->bioc;

                atomic_add(orig_bioc->max_errors, &orig_bioc->error);
        } else {
                orig_bbio->bio.bi_status = bbio->bio.bi_status;
        }
}

void btrfs_bio_end_io(struct btrfs_bio *bbio, blk_status_t status)
{
        bbio->bio.bi_status = status;
        if (bbio->bio.bi_pool == &btrfs_clone_bioset) {
                struct btrfs_bio *orig_bbio = bbio->private;

                if (bbio->bio.bi_status)
                        btrfs_bbio_propagate_error(bbio, orig_bbio);
                btrfs_cleanup_bio(bbio);
                bbio = orig_bbio;
        }

        if (atomic_dec_and_test(&bbio->pending_ios))
                __btrfs_bio_end_io(bbio);
}

static int next_repair_mirror(struct btrfs_failed_bio *fbio, int cur_mirror)
{
        if (cur_mirror == fbio->num_copies)
                return cur_mirror + 1 - fbio->num_copies;
        return cur_mirror + 1;
}

static int prev_repair_mirror(struct btrfs_failed_bio *fbio, int cur_mirror)
{
        if (cur_mirror == 1)
                return fbio->num_copies;
        return cur_mirror - 1;
}

static void btrfs_repair_done(struct btrfs_failed_bio *fbio)
{
        if (atomic_dec_and_test(&fbio->repair_count)) {
                btrfs_bio_end_io(fbio->bbio, fbio->bbio->bio.bi_status);
                mempool_free(fbio, &btrfs_failed_bio_pool);
        }
}

static void btrfs_end_repair_bio(struct btrfs_bio *repair_bbio,
                                 struct btrfs_device *dev)
{
        struct btrfs_failed_bio *fbio = repair_bbio->private;
        struct btrfs_inode *inode = repair_bbio->inode;
        struct btrfs_fs_info *fs_info = inode->root->fs_info;
        struct bio_vec *bv = bio_first_bvec_all(&repair_bbio->bio);
        int mirror = repair_bbio->mirror_num;

        if (repair_bbio->bio.bi_status ||
            !btrfs_data_csum_ok(repair_bbio, dev, 0, bv)) {
                bio_reset(&repair_bbio->bio, NULL, REQ_OP_READ);
                repair_bbio->bio.bi_iter = repair_bbio->saved_iter;

                mirror = next_repair_mirror(fbio, mirror);
                if (mirror == fbio->bbio->mirror_num) {
                        btrfs_debug(fs_info, "no mirror left");
                        fbio->bbio->bio.bi_status = BLK_STS_IOERR;
                        goto done;
                }

                btrfs_submit_bio(repair_bbio, mirror);
                return;
        }

        do {
                mirror = prev_repair_mirror(fbio, mirror);
                btrfs_repair_io_failure(fs_info, btrfs_ino(inode),
                                  repair_bbio->file_offset, fs_info->sectorsize,
                                  repair_bbio->saved_iter.bi_sector << SECTOR_SHIFT,
                                  bv->bv_page, bv->bv_offset, mirror);
        } while (mirror != fbio->bbio->mirror_num);

done:
        btrfs_repair_done(fbio);
        bio_put(&repair_bbio->bio);
}

/*
 * Try to kick off a repair read to the next available mirror for a bad sector.
 *
 * This primarily tries to recover good data to serve the actual read request,
 * but also tries to write the good data back to the bad mirror(s) when a
 * read succeeded to restore the redundancy.
 */
static struct btrfs_failed_bio *repair_one_sector(struct btrfs_bio *failed_bbio,
                                                  u32 bio_offset,
                                                  struct bio_vec *bv,
                                                  struct btrfs_failed_bio *fbio)
{
        struct btrfs_inode *inode = failed_bbio->inode;
        struct btrfs_fs_info *fs_info = inode->root->fs_info;
        const u32 sectorsize = fs_info->sectorsize;
        const u64 logical = (failed_bbio->saved_iter.bi_sector << SECTOR_SHIFT);
        struct btrfs_bio *repair_bbio;
        struct bio *repair_bio;
        int num_copies;
        int mirror;

        btrfs_debug(fs_info, "repair read error: read error at %llu",
                    failed_bbio->file_offset + bio_offset);

        num_copies = btrfs_num_copies(fs_info, logical, sectorsize);
        if (num_copies == 1) {
                btrfs_debug(fs_info, "no copy to repair from");
                failed_bbio->bio.bi_status = BLK_STS_IOERR;
                return fbio;
        }

        if (!fbio) {
                fbio = mempool_alloc(&btrfs_failed_bio_pool, GFP_NOFS);
                fbio->bbio = failed_bbio;
                fbio->num_copies = num_copies;
                atomic_set(&fbio->repair_count, 1);
        }

        atomic_inc(&fbio->repair_count);

        repair_bio = bio_alloc_bioset(NULL, 1, REQ_OP_READ, GFP_NOFS,
                                      &btrfs_repair_bioset);
        repair_bio->bi_iter.bi_sector = failed_bbio->saved_iter.bi_sector;
        __bio_add_page(repair_bio, bv->bv_page, bv->bv_len, bv->bv_offset);

        repair_bbio = btrfs_bio(repair_bio);
        btrfs_bio_init(repair_bbio, fs_info, NULL, fbio);
        repair_bbio->inode = failed_bbio->inode;
        repair_bbio->file_offset = failed_bbio->file_offset + bio_offset;

        mirror = next_repair_mirror(fbio, failed_bbio->mirror_num);
        btrfs_debug(fs_info, "submitting repair read to mirror %d", mirror);
        btrfs_submit_bio(repair_bbio, mirror);
        return fbio;
}

static void btrfs_check_read_bio(struct btrfs_bio *bbio, struct btrfs_device *dev)
{
        struct btrfs_inode *inode = bbio->inode;
        struct btrfs_fs_info *fs_info = inode->root->fs_info;
        u32 sectorsize = fs_info->sectorsize;
        struct bvec_iter *iter = &bbio->saved_iter;
        blk_status_t status = bbio->bio.bi_status;
        struct btrfs_failed_bio *fbio = NULL;
        u32 offset = 0;

        /* Read-repair requires the inode field to be set by the submitter. */
        ASSERT(inode);

        /*
         * Hand off repair bios to the repair code as there is no upper level
         * submitter for them.
         */
        if (bbio->bio.bi_pool == &btrfs_repair_bioset) {
                btrfs_end_repair_bio(bbio, dev);
                return;
        }

        /* Clear the I/O error. A failed repair will reset it. */
        bbio->bio.bi_status = BLK_STS_OK;

        while (iter->bi_size) {
                struct bio_vec bv = bio_iter_iovec(&bbio->bio, *iter);

                bv.bv_len = min(bv.bv_len, sectorsize);
                if (status || !btrfs_data_csum_ok(bbio, dev, offset, &bv))
                        fbio = repair_one_sector(bbio, offset, &bv, fbio);

                bio_advance_iter_single(&bbio->bio, iter, sectorsize);
                offset += sectorsize;
        }

        if (bbio->csum != bbio->csum_inline)
                kfree(bbio->csum);

        if (fbio)
                btrfs_repair_done(fbio);
        else
                btrfs_bio_end_io(bbio, bbio->bio.bi_status);
}

static void btrfs_log_dev_io_error(struct bio *bio, struct btrfs_device *dev)
{
        if (!dev || !dev->bdev)
                return;
        if (bio->bi_status != BLK_STS_IOERR && bio->bi_status != BLK_STS_TARGET)
                return;

        if (btrfs_op(bio) == BTRFS_MAP_WRITE)
                btrfs_dev_stat_inc_and_print(dev, BTRFS_DEV_STAT_WRITE_ERRS);
        else if (!(bio->bi_opf & REQ_RAHEAD))
                btrfs_dev_stat_inc_and_print(dev, BTRFS_DEV_STAT_READ_ERRS);
        if (bio->bi_opf & REQ_PREFLUSH)
                btrfs_dev_stat_inc_and_print(dev, BTRFS_DEV_STAT_FLUSH_ERRS);
}

static struct workqueue_struct *btrfs_end_io_wq(struct btrfs_fs_info *fs_info,
                                                struct bio *bio)
{
        if (bio->bi_opf & REQ_META)
                return fs_info->endio_meta_workers;
        return fs_info->endio_workers;
}

static void btrfs_end_bio_work(struct work_struct *work)
{
        struct btrfs_bio *bbio = container_of(work, struct btrfs_bio, end_io_work);

        /* Metadata reads are checked and repaired by the submitter. */
        if (is_data_bbio(bbio))
                btrfs_check_read_bio(bbio, bbio->bio.bi_private);
        else
                btrfs_bio_end_io(bbio, bbio->bio.bi_status);
}

static void btrfs_simple_end_io(struct bio *bio)
{
        struct btrfs_bio *bbio = btrfs_bio(bio);
        struct btrfs_device *dev = bio->bi_private;
        struct btrfs_fs_info *fs_info = bbio->fs_info;

        btrfs_bio_counter_dec(fs_info);

        if (bio->bi_status)
                btrfs_log_dev_io_error(bio, dev);

        if (bio_op(bio) == REQ_OP_READ) {
                INIT_WORK(&bbio->end_io_work, btrfs_end_bio_work);
                queue_work(btrfs_end_io_wq(fs_info, bio), &bbio->end_io_work);
        } else {
                if (bio_op(bio) == REQ_OP_ZONE_APPEND && !bio->bi_status)
                        btrfs_record_physical_zoned(bbio);
                btrfs_bio_end_io(bbio, bbio->bio.bi_status);
        }
}

static void btrfs_raid56_end_io(struct bio *bio)
{
        struct btrfs_io_context *bioc = bio->bi_private;
        struct btrfs_bio *bbio = btrfs_bio(bio);

        btrfs_bio_counter_dec(bioc->fs_info);
        bbio->mirror_num = bioc->mirror_num;
        if (bio_op(bio) == REQ_OP_READ && is_data_bbio(bbio))
                btrfs_check_read_bio(bbio, NULL);
        else
                btrfs_bio_end_io(bbio, bbio->bio.bi_status);

        btrfs_put_bioc(bioc);
}

static void btrfs_orig_write_end_io(struct bio *bio)
{
        struct btrfs_io_stripe *stripe = bio->bi_private;
        struct btrfs_io_context *bioc = stripe->bioc;
        struct btrfs_bio *bbio = btrfs_bio(bio);

        btrfs_bio_counter_dec(bioc->fs_info);

        if (bio->bi_status) {
                atomic_inc(&bioc->error);
                btrfs_log_dev_io_error(bio, stripe->dev);
        }

        /*
         * Only send an error to the higher layers if it is beyond the tolerance
         * threshold.
         */
        if (atomic_read(&bioc->error) > bioc->max_errors)
                bio->bi_status = BLK_STS_IOERR;
        else
                bio->bi_status = BLK_STS_OK;

        if (bio_op(bio) == REQ_OP_ZONE_APPEND && !bio->bi_status)
                stripe->physical = bio->bi_iter.bi_sector << SECTOR_SHIFT;

        btrfs_bio_end_io(bbio, bbio->bio.bi_status);
        btrfs_put_bioc(bioc);
}

static void btrfs_clone_write_end_io(struct bio *bio)
{
        struct btrfs_io_stripe *stripe = bio->bi_private;

        if (bio->bi_status) {
                atomic_inc(&stripe->bioc->error);
                btrfs_log_dev_io_error(bio, stripe->dev);
        } else if (bio_op(bio) == REQ_OP_ZONE_APPEND) {
                stripe->physical = bio->bi_iter.bi_sector << SECTOR_SHIFT;
        }

        /* Pass on control to the original bio this one was cloned from */
        bio_endio(stripe->bioc->orig_bio);
        bio_put(bio);
}

static void btrfs_submit_dev_bio(struct btrfs_device *dev, struct bio *bio)
{
        if (!dev || !dev->bdev ||
            test_bit(BTRFS_DEV_STATE_MISSING, &dev->dev_state) ||
            (btrfs_op(bio) == BTRFS_MAP_WRITE &&
             !test_bit(BTRFS_DEV_STATE_WRITEABLE, &dev->dev_state))) {
                bio_io_error(bio);
                return;
        }

        bio_set_dev(bio, dev->bdev);

        /*
         * For zone append writing, bi_sector must point the beginning of the
         * zone
         */
        if (bio_op(bio) == REQ_OP_ZONE_APPEND) {
                u64 physical = bio->bi_iter.bi_sector << SECTOR_SHIFT;
                u64 zone_start = round_down(physical, dev->fs_info->zone_size);

                ASSERT(btrfs_dev_is_sequential(dev, physical));
                bio->bi_iter.bi_sector = zone_start >> SECTOR_SHIFT;
        }
        btrfs_debug_in_rcu(dev->fs_info,
        "%s: rw %d 0x%x, sector=%llu, dev=%lu (%s id %llu), size=%u",
                __func__, bio_op(bio), bio->bi_opf, bio->bi_iter.bi_sector,
                (unsigned long)dev->bdev->bd_dev, btrfs_dev_name(dev),
                dev->devid, bio->bi_iter.bi_size);

        btrfsic_check_bio(bio);

        if (bio->bi_opf & REQ_BTRFS_CGROUP_PUNT)
                blkcg_punt_bio_submit(bio);
        else
                submit_bio(bio);
}

static void btrfs_submit_mirrored_bio(struct btrfs_io_context *bioc, int dev_nr)
{
        struct bio *orig_bio = bioc->orig_bio, *bio;

        ASSERT(bio_op(orig_bio) != REQ_OP_READ);

        /* Reuse the bio embedded into the btrfs_bio for the last mirror */
        if (dev_nr == bioc->num_stripes - 1) {
                bio = orig_bio;
                bio->bi_end_io = btrfs_orig_write_end_io;
        } else {
                bio = bio_alloc_clone(NULL, orig_bio, GFP_NOFS, &fs_bio_set);
                bio_inc_remaining(orig_bio);
                bio->bi_end_io = btrfs_clone_write_end_io;
        }

        bio->bi_private = &bioc->stripes[dev_nr];
        bio->bi_iter.bi_sector = bioc->stripes[dev_nr].physical >> SECTOR_SHIFT;
        bioc->stripes[dev_nr].bioc = bioc;
        bioc->size = bio->bi_iter.bi_size;
        btrfs_submit_dev_bio(bioc->stripes[dev_nr].dev, bio);
}

static void __btrfs_submit_bio(struct bio *bio, struct btrfs_io_context *bioc,
                               struct btrfs_io_stripe *smap, int mirror_num)
{
        if (!bioc) {
                /* Single mirror read/write fast path. */
                btrfs_bio(bio)->mirror_num = mirror_num;
                if (bio_op(bio) != REQ_OP_READ)
                        btrfs_bio(bio)->orig_physical = smap->physical;
                bio->bi_iter.bi_sector = smap->physical >> SECTOR_SHIFT;
                if (bio_op(bio) != REQ_OP_READ)
                        btrfs_bio(bio)->orig_physical = smap->physical;
                bio->bi_private = smap->dev;
                bio->bi_end_io = btrfs_simple_end_io;
                btrfs_submit_dev_bio(smap->dev, bio);
        } else if (bioc->map_type & BTRFS_BLOCK_GROUP_RAID56_MASK) {
                /* Parity RAID write or read recovery. */
                bio->bi_private = bioc;
                bio->bi_end_io = btrfs_raid56_end_io;
                if (bio_op(bio) == REQ_OP_READ)
                        raid56_parity_recover(bio, bioc, mirror_num);
                else
                        raid56_parity_write(bio, bioc);
        } else {
                /* Write to multiple mirrors. */
                int total_devs = bioc->num_stripes;

                bioc->orig_bio = bio;
                for (int dev_nr = 0; dev_nr < total_devs; dev_nr++)
                        btrfs_submit_mirrored_bio(bioc, dev_nr);
        }
}

static blk_status_t btrfs_bio_csum(struct btrfs_bio *bbio)
{
        if (bbio->bio.bi_opf & REQ_META)
                return btree_csum_one_bio(bbio);
        return btrfs_csum_one_bio(bbio);
}

/*
 * Async submit bios are used to offload expensive checksumming onto the worker
 * threads.
 */
struct async_submit_bio {
        struct btrfs_bio *bbio;
        struct btrfs_io_context *bioc;
        struct btrfs_io_stripe smap;
        int mirror_num;
        struct btrfs_work work;
};

/*
 * In order to insert checksums into the metadata in large chunks, we wait
 * until bio submission time.   All the pages in the bio are checksummed and
 * sums are attached onto the ordered extent record.
 *
 * At IO completion time the csums attached on the ordered extent record are
 * inserted into the btree.
 */
static void run_one_async_start(struct btrfs_work *work)
{
        struct async_submit_bio *async =
                container_of(work, struct async_submit_bio, work);
        blk_status_t ret;

        ret = btrfs_bio_csum(async->bbio);
        if (ret)
                async->bbio->bio.bi_status = ret;
}

/*
 * In order to insert checksums into the metadata in large chunks, we wait
 * until bio submission time.   All the pages in the bio are checksummed and
 * sums are attached onto the ordered extent record.
 *
 * At IO completion time the csums attached on the ordered extent record are
 * inserted into the tree.
 */
static void run_one_async_done(struct btrfs_work *work)
{
        struct async_submit_bio *async =
                container_of(work, struct async_submit_bio, work);
        struct bio *bio = &async->bbio->bio;

        /* If an error occurred we just want to clean up the bio and move on. */
        if (bio->bi_status) {
                btrfs_bio_end_io(async->bbio, async->bbio->bio.bi_status);
                return;
        }

        /*
         * All of the bios that pass through here are from async helpers.
         * Use REQ_BTRFS_CGROUP_PUNT to issue them from the owning cgroup's
         * context.  This changes nothing when cgroups aren't in use.
         */
        bio->bi_opf |= REQ_BTRFS_CGROUP_PUNT;
        __btrfs_submit_bio(bio, async->bioc, &async->smap, async->mirror_num);
}

static void run_one_async_free(struct btrfs_work *work)
{
        kfree(container_of(work, struct async_submit_bio, work));
}

static bool should_async_write(struct btrfs_bio *bbio)
{
        /* Submit synchronously if the checksum implementation is fast. */
        if (test_bit(BTRFS_FS_CSUM_IMPL_FAST, &bbio->fs_info->flags))
                return false;

        /*
         * Try to defer the submission to a workqueue to parallelize the
         * checksum calculation unless the I/O is issued synchronously.
         */
        if (op_is_sync(bbio->bio.bi_opf))
                return false;

        /* Zoned devices require I/O to be submitted in order. */
        if ((bbio->bio.bi_opf & REQ_META) && btrfs_is_zoned(bbio->fs_info))
                return false;

        return true;
}

/*
 * Submit bio to an async queue.
 *
 * Return true if the work has been succesfuly submitted, else false.
 */
static bool btrfs_wq_submit_bio(struct btrfs_bio *bbio,
                                struct btrfs_io_context *bioc,
                                struct btrfs_io_stripe *smap, int mirror_num)
{
        struct btrfs_fs_info *fs_info = bbio->fs_info;
        struct async_submit_bio *async;

        async = kmalloc(sizeof(*async), GFP_NOFS);
        if (!async)
                return false;

        async->bbio = bbio;
        async->bioc = bioc;
        async->smap = *smap;
        async->mirror_num = mirror_num;

        btrfs_init_work(&async->work, run_one_async_start, run_one_async_done,
                        run_one_async_free);
        btrfs_queue_work(fs_info->workers, &async->work);
        return true;
}

static bool btrfs_submit_chunk(struct btrfs_bio *bbio, int mirror_num)
{
        struct btrfs_inode *inode = bbio->inode;
        struct btrfs_fs_info *fs_info = bbio->fs_info;
        struct bio *bio = &bbio->bio;
        u64 logical = bio->bi_iter.bi_sector << SECTOR_SHIFT;
        u64 length = bio->bi_iter.bi_size;
        u64 map_length = length;
        bool use_append = btrfs_use_zone_append(bbio);
        struct btrfs_io_context *bioc = NULL;
        struct btrfs_io_stripe smap;
        blk_status_t ret;
        int error;

        btrfs_bio_counter_inc_blocked(fs_info);
        error = btrfs_map_block(fs_info, btrfs_op(bio), logical, &map_length,
                                &bioc, &smap, &mirror_num, 1);
        if (error) {
                ret = errno_to_blk_status(error);
                goto fail;
        }

        map_length = min(map_length, length);
        if (use_append)
                map_length = min(map_length, fs_info->max_zone_append_size);

        if (map_length < length) {
                bbio = btrfs_split_bio(fs_info, bbio, map_length, use_append);
                bio = &bbio->bio;
        }

        /*
         * Save the iter for the end_io handler and preload the checksums for
         * data reads.
         */
        if (bio_op(bio) == REQ_OP_READ && is_data_bbio(bbio)) {
                bbio->saved_iter = bio->bi_iter;
                ret = btrfs_lookup_bio_sums(bbio);
                if (ret)
                        goto fail;
        }

        if (btrfs_op(bio) == BTRFS_MAP_WRITE) {
                if (use_append) {
                        bio->bi_opf &= ~REQ_OP_WRITE;
                        bio->bi_opf |= REQ_OP_ZONE_APPEND;
                }

                if (is_data_bbio(bbio) && bioc &&
                    btrfs_need_stripe_tree_update(bioc->fs_info, bioc->map_type)) {
                        /*
                         * No locking for the list update, as we only add to
                         * the list in the I/O submission path, and list
                         * iteration only happens in the completion path, which
                         * can't happen until after the last submission.
                         */
                        btrfs_get_bioc(bioc);
                        list_add_tail(&bioc->rst_ordered_entry, &bbio->ordered->bioc_list);
                }

                /*
                 * Csum items for reloc roots have already been cloned at this
                 * point, so they are handled as part of the no-checksum case.
                 */
                if (inode && !(inode->flags & BTRFS_INODE_NODATASUM) &&
                    !test_bit(BTRFS_FS_STATE_NO_CSUMS, &fs_info->fs_state) &&
                    !btrfs_is_data_reloc_root(inode->root)) {
                        if (should_async_write(bbio) &&
                            btrfs_wq_submit_bio(bbio, bioc, &smap, mirror_num))
                                goto done;

                        ret = btrfs_bio_csum(bbio);
                        if (ret)
                                goto fail;
                } else if (use_append ||
                           (btrfs_is_zoned(fs_info) && inode &&
                            inode->flags & BTRFS_INODE_NODATASUM)) {
                        ret = btrfs_alloc_dummy_sum(bbio);
                        if (ret)
                                goto fail;
                }
        }

        __btrfs_submit_bio(bio, bioc, &smap, mirror_num);
done:
        return map_length == length;

fail:
        btrfs_bio_counter_dec(fs_info);
        /*
         * We have split the original bbio, now we have to end both the current
         * @bbio and remaining one, as the remaining one will never be submitted.
         */
        if (map_length < length) {
                struct btrfs_bio *remaining = bbio->private;

                ASSERT(bbio->bio.bi_pool == &btrfs_clone_bioset);
                ASSERT(remaining);

                btrfs_bio_end_io(remaining, ret);
        }
        btrfs_bio_end_io(bbio, ret);
        /* Do not submit another chunk */
        return true;
}

void btrfs_submit_bio(struct btrfs_bio *bbio, int mirror_num)
{
        /* If bbio->inode is not populated, its file_offset must be 0. */
        ASSERT(bbio->inode || bbio->file_offset == 0);

        while (!btrfs_submit_chunk(bbio, mirror_num))
                ;
}

/*
 * Submit a repair write.
 *
 * This bypasses btrfs_submit_bio deliberately, as that writes all copies in a
 * RAID setup.  Here we only want to write the one bad copy, so we do the
 * mapping ourselves and submit the bio directly.
 *
 * The I/O is issued synchronously to block the repair read completion from
 * freeing the bio.
 */
int btrfs_repair_io_failure(struct btrfs_fs_info *fs_info, u64 ino, u64 start,
                            u64 length, u64 logical, struct page *page,
                            unsigned int pg_offset, int mirror_num)
{
        struct btrfs_io_stripe smap = { 0 };
        struct bio_vec bvec;
        struct bio bio;
        int ret = 0;

        ASSERT(!(fs_info->sb->s_flags & SB_RDONLY));
        BUG_ON(!mirror_num);

        if (btrfs_repair_one_zone(fs_info, logical))
                return 0;

        /*
         * Avoid races with device replace and make sure our bioc has devices
         * associated to its stripes that don't go away while we are doing the
         * read repair operation.
         */
        btrfs_bio_counter_inc_blocked(fs_info);
        ret = btrfs_map_repair_block(fs_info, &smap, logical, length, mirror_num);
        if (ret < 0)
                goto out_counter_dec;

        if (!smap.dev->bdev ||
            !test_bit(BTRFS_DEV_STATE_WRITEABLE, &smap.dev->dev_state)) {
                ret = -EIO;
                goto out_counter_dec;
        }

        bio_init(&bio, smap.dev->bdev, &bvec, 1, REQ_OP_WRITE | REQ_SYNC);
        bio.bi_iter.bi_sector = smap.physical >> SECTOR_SHIFT;
        __bio_add_page(&bio, page, length, pg_offset);

        btrfsic_check_bio(&bio);
        ret = submit_bio_wait(&bio);
        if (ret) {
                /* try to remap that extent elsewhere? */
                btrfs_dev_stat_inc_and_print(smap.dev, BTRFS_DEV_STAT_WRITE_ERRS);
                goto out_bio_uninit;
        }

        btrfs_info_rl_in_rcu(fs_info,
                "read error corrected: ino %llu off %llu (dev %s sector %llu)",
                             ino, start, btrfs_dev_name(smap.dev),
                             smap.physical >> SECTOR_SHIFT);
        ret = 0;

out_bio_uninit:
        bio_uninit(&bio);
out_counter_dec:
        btrfs_bio_counter_dec(fs_info);
        return ret;
}

/*
 * Submit a btrfs_bio based repair write.
 *
 * If @dev_replace is true, the write would be submitted to dev-replace target.
 */
void btrfs_submit_repair_write(struct btrfs_bio *bbio, int mirror_num, bool dev_replace)
{
        struct btrfs_fs_info *fs_info = bbio->fs_info;
        u64 logical = bbio->bio.bi_iter.bi_sector << SECTOR_SHIFT;
        u64 length = bbio->bio.bi_iter.bi_size;
        struct btrfs_io_stripe smap = { 0 };
        int ret;

        ASSERT(fs_info);
        ASSERT(mirror_num > 0);
        ASSERT(btrfs_op(&bbio->bio) == BTRFS_MAP_WRITE);
        ASSERT(!bbio->inode);

        btrfs_bio_counter_inc_blocked(fs_info);
        ret = btrfs_map_repair_block(fs_info, &smap, logical, length, mirror_num);
        if (ret < 0)
                goto fail;

        if (dev_replace) {
                ASSERT(smap.dev == fs_info->dev_replace.srcdev);
                smap.dev = fs_info->dev_replace.tgtdev;
        }
        __btrfs_submit_bio(&bbio->bio, NULL, &smap, mirror_num);
        return;

fail:
        btrfs_bio_counter_dec(fs_info);
        btrfs_bio_end_io(bbio, errno_to_blk_status(ret));
}

int __init btrfs_bioset_init(void)
{
        if (bioset_init(&btrfs_bioset, BIO_POOL_SIZE,
                        offsetof(struct btrfs_bio, bio),
                        BIOSET_NEED_BVECS))
                return -ENOMEM;
        if (bioset_init(&btrfs_clone_bioset, BIO_POOL_SIZE,
                        offsetof(struct btrfs_bio, bio), 0))
                goto out_free_bioset;
        if (bioset_init(&btrfs_repair_bioset, BIO_POOL_SIZE,
                        offsetof(struct btrfs_bio, bio),
                        BIOSET_NEED_BVECS))
                goto out_free_clone_bioset;
        if (mempool_init_kmalloc_pool(&btrfs_failed_bio_pool, BIO_POOL_SIZE,
                                      sizeof(struct btrfs_failed_bio)))
                goto out_free_repair_bioset;
        return 0;

out_free_repair_bioset:
        bioset_exit(&btrfs_repair_bioset);
out_free_clone_bioset:
        bioset_exit(&btrfs_clone_bioset);
out_free_bioset:
        bioset_exit(&btrfs_bioset);
        return -ENOMEM;
}

void __cold btrfs_bioset_exit(void)
{
        mempool_exit(&btrfs_failed_bio_pool);
        bioset_exit(&btrfs_repair_bioset);
        bioset_exit(&btrfs_clone_bioset);
        bioset_exit(&btrfs_bioset);
}