bcachefs: port block device access to file

[thirdparty/linux.git] / fs / bcachefs / super-io.c

// SPDX-License-Identifier: GPL-2.0

#include "bcachefs.h"
#include "checksum.h"
#include "disk_groups.h"
#include "ec.h"
#include "error.h"
#include "journal.h"
#include "journal_sb.h"
#include "journal_seq_blacklist.h"
#include "recovery.h"
#include "replicas.h"
#include "quota.h"
#include "sb-clean.h"
#include "sb-counters.h"
#include "sb-downgrade.h"
#include "sb-errors.h"
#include "sb-members.h"
#include "super-io.h"
#include "super.h"
#include "trace.h"
#include "vstructs.h"

#include <linux/backing-dev.h>
#include <linux/sort.h>

static const struct blk_holder_ops bch2_sb_handle_bdev_ops = {
};

struct bch2_metadata_version {
        u16             version;
        const char      *name;
};

static const struct bch2_metadata_version bch2_metadata_versions[] = {
#define x(n, v) {               \
        .version = v,                           \
        .name = #n,                             \
},
        BCH_METADATA_VERSIONS()
#undef x
};

void bch2_version_to_text(struct printbuf *out, unsigned v)
{
        const char *str = "(unknown version)";

        for (unsigned i = 0; i < ARRAY_SIZE(bch2_metadata_versions); i++)
                if (bch2_metadata_versions[i].version == v) {
                        str = bch2_metadata_versions[i].name;
                        break;
                }

        prt_printf(out, "%u.%u: %s", BCH_VERSION_MAJOR(v), BCH_VERSION_MINOR(v), str);
}

unsigned bch2_latest_compatible_version(unsigned v)
{
        if (!BCH_VERSION_MAJOR(v))
                return v;

        for (unsigned i = 0; i < ARRAY_SIZE(bch2_metadata_versions); i++)
                if (bch2_metadata_versions[i].version > v &&
                    BCH_VERSION_MAJOR(bch2_metadata_versions[i].version) ==
                    BCH_VERSION_MAJOR(v))
                        v = bch2_metadata_versions[i].version;

        return v;
}

const char * const bch2_sb_fields[] = {
#define x(name, nr)     #name,
        BCH_SB_FIELDS()
#undef x
        NULL
};

static int bch2_sb_field_validate(struct bch_sb *, struct bch_sb_field *,
                                  struct printbuf *);

struct bch_sb_field *bch2_sb_field_get_id(struct bch_sb *sb,
                                      enum bch_sb_field_type type)
{
        /* XXX: need locking around superblock to access optional fields */

        vstruct_for_each(sb, f)
                if (le32_to_cpu(f->type) == type)
                        return f;
        return NULL;
}

static struct bch_sb_field *__bch2_sb_field_resize(struct bch_sb_handle *sb,
                                                   struct bch_sb_field *f,
                                                   unsigned u64s)
{
        unsigned old_u64s = f ? le32_to_cpu(f->u64s) : 0;
        unsigned sb_u64s = le32_to_cpu(sb->sb->u64s) + u64s - old_u64s;

        BUG_ON(__vstruct_bytes(struct bch_sb, sb_u64s) > sb->buffer_size);

        if (!f && !u64s) {
                /* nothing to do: */
        } else if (!f) {
                f = vstruct_last(sb->sb);
                memset(f, 0, sizeof(u64) * u64s);
                f->u64s = cpu_to_le32(u64s);
                f->type = 0;
        } else {
                void *src, *dst;

                src = vstruct_end(f);

                if (u64s) {
                        f->u64s = cpu_to_le32(u64s);
                        dst = vstruct_end(f);
                } else {
                        dst = f;
                }

                memmove(dst, src, vstruct_end(sb->sb) - src);

                if (dst > src)
                        memset(src, 0, dst - src);
        }

        sb->sb->u64s = cpu_to_le32(sb_u64s);

        return u64s ? f : NULL;
}

void bch2_sb_field_delete(struct bch_sb_handle *sb,
                          enum bch_sb_field_type type)
{
        struct bch_sb_field *f = bch2_sb_field_get_id(sb->sb, type);

        if (f)
                __bch2_sb_field_resize(sb, f, 0);
}

/* Superblock realloc/free: */

void bch2_free_super(struct bch_sb_handle *sb)
{
        kfree(sb->bio);
        if (!IS_ERR_OR_NULL(sb->s_bdev_file))
                fput(sb->s_bdev_file);
        kfree(sb->holder);
        kfree(sb->sb_name);

        kfree(sb->sb);
        memset(sb, 0, sizeof(*sb));
}

int bch2_sb_realloc(struct bch_sb_handle *sb, unsigned u64s)
{
        size_t new_bytes = __vstruct_bytes(struct bch_sb, u64s);
        size_t new_buffer_size;
        struct bch_sb *new_sb;
        struct bio *bio;

        if (sb->bdev)
                new_bytes = max_t(size_t, new_bytes, bdev_logical_block_size(sb->bdev));

        new_buffer_size = roundup_pow_of_two(new_bytes);

        if (sb->sb && sb->buffer_size >= new_buffer_size)
                return 0;

        if (sb->sb && sb->have_layout) {
                u64 max_bytes = 512 << sb->sb->layout.sb_max_size_bits;

                if (new_bytes > max_bytes) {
                        struct printbuf buf = PRINTBUF;

                        prt_bdevname(&buf, sb->bdev);
                        prt_printf(&buf, ": superblock too big: want %zu but have %llu", new_bytes, max_bytes);
                        pr_err("%s", buf.buf);
                        printbuf_exit(&buf);
                        return -BCH_ERR_ENOSPC_sb;
                }
        }

        if (sb->buffer_size >= new_buffer_size && sb->sb)
                return 0;

        if (dynamic_fault("bcachefs:add:super_realloc"))
                return -BCH_ERR_ENOMEM_sb_realloc_injected;

        new_sb = krealloc(sb->sb, new_buffer_size, GFP_NOFS|__GFP_ZERO);
        if (!new_sb)
                return -BCH_ERR_ENOMEM_sb_buf_realloc;

        sb->sb = new_sb;

        if (sb->have_bio) {
                unsigned nr_bvecs = buf_pages(sb->sb, new_buffer_size);

                bio = bio_kmalloc(nr_bvecs, GFP_KERNEL);
                if (!bio)
                        return -BCH_ERR_ENOMEM_sb_bio_realloc;

                bio_init(bio, NULL, bio->bi_inline_vecs, nr_bvecs, 0);

                kfree(sb->bio);
                sb->bio = bio;
        }

        sb->buffer_size = new_buffer_size;

        return 0;
}

struct bch_sb_field *bch2_sb_field_resize_id(struct bch_sb_handle *sb,
                                          enum bch_sb_field_type type,
                                          unsigned u64s)
{
        struct bch_sb_field *f = bch2_sb_field_get_id(sb->sb, type);
        ssize_t old_u64s = f ? le32_to_cpu(f->u64s) : 0;
        ssize_t d = -old_u64s + u64s;

        if (bch2_sb_realloc(sb, le32_to_cpu(sb->sb->u64s) + d))
                return NULL;

        if (sb->fs_sb) {
                struct bch_fs *c = container_of(sb, struct bch_fs, disk_sb);

                lockdep_assert_held(&c->sb_lock);

                /* XXX: we're not checking that offline device have enough space */

                for_each_online_member(c, ca) {
                        struct bch_sb_handle *dev_sb = &ca->disk_sb;

                        if (bch2_sb_realloc(dev_sb, le32_to_cpu(dev_sb->sb->u64s) + d)) {
                                percpu_ref_put(&ca->ref);
                                return NULL;
                        }
                }
        }

        f = bch2_sb_field_get_id(sb->sb, type);
        f = __bch2_sb_field_resize(sb, f, u64s);
        if (f)
                f->type = cpu_to_le32(type);
        return f;
}

struct bch_sb_field *bch2_sb_field_get_minsize_id(struct bch_sb_handle *sb,
                                                  enum bch_sb_field_type type,
                                                  unsigned u64s)
{
        struct bch_sb_field *f = bch2_sb_field_get_id(sb->sb, type);

        if (!f || le32_to_cpu(f->u64s) < u64s)
                f = bch2_sb_field_resize_id(sb, type, u64s);
        return f;
}

/* Superblock validate: */

static int validate_sb_layout(struct bch_sb_layout *layout, struct printbuf *out)
{
        u64 offset, prev_offset, max_sectors;
        unsigned i;

        BUILD_BUG_ON(sizeof(struct bch_sb_layout) != 512);

        if (!uuid_equal(&layout->magic, &BCACHE_MAGIC) &&
            !uuid_equal(&layout->magic, &BCHFS_MAGIC)) {
                prt_printf(out, "Not a bcachefs superblock layout");
                return -BCH_ERR_invalid_sb_layout;
        }

        if (layout->layout_type != 0) {
                prt_printf(out, "Invalid superblock layout type %u",
                       layout->layout_type);
                return -BCH_ERR_invalid_sb_layout_type;
        }

        if (!layout->nr_superblocks) {
                prt_printf(out, "Invalid superblock layout: no superblocks");
                return -BCH_ERR_invalid_sb_layout_nr_superblocks;
        }

        if (layout->nr_superblocks > ARRAY_SIZE(layout->sb_offset)) {
                prt_printf(out, "Invalid superblock layout: too many superblocks");
                return -BCH_ERR_invalid_sb_layout_nr_superblocks;
        }

        max_sectors = 1 << layout->sb_max_size_bits;

        prev_offset = le64_to_cpu(layout->sb_offset[0]);

        for (i = 1; i < layout->nr_superblocks; i++) {
                offset = le64_to_cpu(layout->sb_offset[i]);

                if (offset < prev_offset + max_sectors) {
                        prt_printf(out, "Invalid superblock layout: superblocks overlap\n"
                               "  (sb %u ends at %llu next starts at %llu",
                               i - 1, prev_offset + max_sectors, offset);
                        return -BCH_ERR_invalid_sb_layout_superblocks_overlap;
                }
                prev_offset = offset;
        }

        return 0;
}

static int bch2_sb_compatible(struct bch_sb *sb, struct printbuf *out)
{
        u16 version             = le16_to_cpu(sb->version);
        u16 version_min         = le16_to_cpu(sb->version_min);

        if (!bch2_version_compatible(version)) {
                prt_str(out, "Unsupported superblock version ");
                bch2_version_to_text(out, version);
                prt_str(out, " (min ");
                bch2_version_to_text(out, bcachefs_metadata_version_min);
                prt_str(out, ", max ");
                bch2_version_to_text(out, bcachefs_metadata_version_current);
                prt_str(out, ")");
                return -BCH_ERR_invalid_sb_version;
        }

        if (!bch2_version_compatible(version_min)) {
                prt_str(out, "Unsupported superblock version_min ");
                bch2_version_to_text(out, version_min);
                prt_str(out, " (min ");
                bch2_version_to_text(out, bcachefs_metadata_version_min);
                prt_str(out, ", max ");
                bch2_version_to_text(out, bcachefs_metadata_version_current);
                prt_str(out, ")");
                return -BCH_ERR_invalid_sb_version;
        }

        if (version_min > version) {
                prt_str(out, "Bad minimum version ");
                bch2_version_to_text(out, version_min);
                prt_str(out, ", greater than version field ");
                bch2_version_to_text(out, version);
                return -BCH_ERR_invalid_sb_version;
        }

        return 0;
}

static int bch2_sb_validate(struct bch_sb_handle *disk_sb, struct printbuf *out,
                            int rw)
{
        struct bch_sb *sb = disk_sb->sb;
        struct bch_sb_field_members_v1 *mi;
        enum bch_opt_id opt_id;
        u16 block_size;
        int ret;

        ret = bch2_sb_compatible(sb, out);
        if (ret)
                return ret;

        if (sb->features[1] ||
            (le64_to_cpu(sb->features[0]) & (~0ULL << BCH_FEATURE_NR))) {
                prt_printf(out, "Filesystem has incompatible features");
                return -BCH_ERR_invalid_sb_features;
        }

        block_size = le16_to_cpu(sb->block_size);

        if (block_size > PAGE_SECTORS) {
                prt_printf(out, "Block size too big (got %u, max %u)",
                       block_size, PAGE_SECTORS);
                return -BCH_ERR_invalid_sb_block_size;
        }

        if (bch2_is_zero(sb->user_uuid.b, sizeof(sb->user_uuid))) {
                prt_printf(out, "Bad user UUID (got zeroes)");
                return -BCH_ERR_invalid_sb_uuid;
        }

        if (bch2_is_zero(sb->uuid.b, sizeof(sb->uuid))) {
                prt_printf(out, "Bad internal UUID (got zeroes)");
                return -BCH_ERR_invalid_sb_uuid;
        }

        if (!sb->nr_devices ||
            sb->nr_devices > BCH_SB_MEMBERS_MAX) {
                prt_printf(out, "Bad number of member devices %u (max %u)",
                       sb->nr_devices, BCH_SB_MEMBERS_MAX);
                return -BCH_ERR_invalid_sb_too_many_members;
        }

        if (sb->dev_idx >= sb->nr_devices) {
                prt_printf(out, "Bad dev_idx (got %u, nr_devices %u)",
                       sb->dev_idx, sb->nr_devices);
                return -BCH_ERR_invalid_sb_dev_idx;
        }

        if (!sb->time_precision ||
            le32_to_cpu(sb->time_precision) > NSEC_PER_SEC) {
                prt_printf(out, "Invalid time precision: %u (min 1, max %lu)",
                       le32_to_cpu(sb->time_precision), NSEC_PER_SEC);
                return -BCH_ERR_invalid_sb_time_precision;
        }

        if (rw == READ) {
                /*
                 * Been seeing a bug where these are getting inexplicably
                 * zeroed, so we're now validating them, but we have to be
                 * careful not to preven people's filesystems from mounting:
                 */
                if (!BCH_SB_JOURNAL_FLUSH_DELAY(sb))
                        SET_BCH_SB_JOURNAL_FLUSH_DELAY(sb, 1000);
                if (!BCH_SB_JOURNAL_RECLAIM_DELAY(sb))
                        SET_BCH_SB_JOURNAL_RECLAIM_DELAY(sb, 1000);

                if (!BCH_SB_VERSION_UPGRADE_COMPLETE(sb))
                        SET_BCH_SB_VERSION_UPGRADE_COMPLETE(sb, le16_to_cpu(sb->version));
        }

        for (opt_id = 0; opt_id < bch2_opts_nr; opt_id++) {
                const struct bch_option *opt = bch2_opt_table + opt_id;

                if (opt->get_sb != BCH2_NO_SB_OPT) {
                        u64 v = bch2_opt_from_sb(sb, opt_id);

                        prt_printf(out, "Invalid option ");
                        ret = bch2_opt_validate(opt, v, out);
                        if (ret)
                                return ret;

                        printbuf_reset(out);
                }
        }

        /* validate layout */
        ret = validate_sb_layout(&sb->layout, out);
        if (ret)
                return ret;

        vstruct_for_each(sb, f) {
                if (!f->u64s) {
                        prt_printf(out, "Invalid superblock: optional field with size 0 (type %u)",
                               le32_to_cpu(f->type));
                        return -BCH_ERR_invalid_sb_field_size;
                }

                if (vstruct_next(f) > vstruct_last(sb)) {
                        prt_printf(out, "Invalid superblock: optional field extends past end of superblock (type %u)",
                               le32_to_cpu(f->type));
                        return -BCH_ERR_invalid_sb_field_size;
                }
        }

        /* members must be validated first: */
        mi = bch2_sb_field_get(sb, members_v1);
        if (!mi) {
                prt_printf(out, "Invalid superblock: member info area missing");
                return -BCH_ERR_invalid_sb_members_missing;
        }

        ret = bch2_sb_field_validate(sb, &mi->field, out);
        if (ret)
                return ret;

        vstruct_for_each(sb, f) {
                if (le32_to_cpu(f->type) == BCH_SB_FIELD_members_v1)
                        continue;

                ret = bch2_sb_field_validate(sb, f, out);
                if (ret)
                        return ret;
        }

        return 0;
}

/* device open: */

static unsigned long le_ulong_to_cpu(unsigned long v)
{
        return sizeof(unsigned long) == 8
                ? le64_to_cpu(v)
                : le32_to_cpu(v);
}

static void le_bitvector_to_cpu(unsigned long *dst, unsigned long *src, unsigned nr)
{
        BUG_ON(nr & (BITS_PER_TYPE(long) - 1));

        for (unsigned i = 0; i < BITS_TO_LONGS(nr); i++)
                dst[i] = le_ulong_to_cpu(src[i]);
}

static void bch2_sb_update(struct bch_fs *c)
{
        struct bch_sb *src = c->disk_sb.sb;

        lockdep_assert_held(&c->sb_lock);

        c->sb.uuid              = src->uuid;
        c->sb.user_uuid         = src->user_uuid;
        c->sb.version           = le16_to_cpu(src->version);
        c->sb.version_min       = le16_to_cpu(src->version_min);
        c->sb.version_upgrade_complete = BCH_SB_VERSION_UPGRADE_COMPLETE(src);
        c->sb.nr_devices        = src->nr_devices;
        c->sb.clean             = BCH_SB_CLEAN(src);
        c->sb.encryption_type   = BCH_SB_ENCRYPTION_TYPE(src);

        c->sb.nsec_per_time_unit = le32_to_cpu(src->time_precision);
        c->sb.time_units_per_sec = NSEC_PER_SEC / c->sb.nsec_per_time_unit;

        /* XXX this is wrong, we need a 96 or 128 bit integer type */
        c->sb.time_base_lo      = div_u64(le64_to_cpu(src->time_base_lo),
                                          c->sb.nsec_per_time_unit);
        c->sb.time_base_hi      = le32_to_cpu(src->time_base_hi);

        c->sb.features          = le64_to_cpu(src->features[0]);
        c->sb.compat            = le64_to_cpu(src->compat[0]);

        memset(c->sb.errors_silent, 0, sizeof(c->sb.errors_silent));

        struct bch_sb_field_ext *ext = bch2_sb_field_get(src, ext);
        if (ext)
                le_bitvector_to_cpu(c->sb.errors_silent, (void *) ext->errors_silent,
                                    sizeof(c->sb.errors_silent) * 8);

        for_each_member_device(c, ca) {
                struct bch_member m = bch2_sb_member_get(src, ca->dev_idx);
                ca->mi = bch2_mi_to_cpu(&m);
        }
}

static int __copy_super(struct bch_sb_handle *dst_handle, struct bch_sb *src)
{
        struct bch_sb_field *src_f, *dst_f;
        struct bch_sb *dst = dst_handle->sb;
        unsigned i;

        dst->version            = src->version;
        dst->version_min        = src->version_min;
        dst->seq                = src->seq;
        dst->uuid               = src->uuid;
        dst->user_uuid          = src->user_uuid;
        memcpy(dst->label,      src->label, sizeof(dst->label));

        dst->block_size         = src->block_size;
        dst->nr_devices         = src->nr_devices;

        dst->time_base_lo       = src->time_base_lo;
        dst->time_base_hi       = src->time_base_hi;
        dst->time_precision     = src->time_precision;
        dst->write_time         = src->write_time;

        memcpy(dst->flags,      src->flags,     sizeof(dst->flags));
        memcpy(dst->features,   src->features,  sizeof(dst->features));
        memcpy(dst->compat,     src->compat,    sizeof(dst->compat));

        for (i = 0; i < BCH_SB_FIELD_NR; i++) {
                int d;

                if ((1U << i) & BCH_SINGLE_DEVICE_SB_FIELDS)
                        continue;

                src_f = bch2_sb_field_get_id(src, i);
                dst_f = bch2_sb_field_get_id(dst, i);

                d = (src_f ? le32_to_cpu(src_f->u64s) : 0) -
                    (dst_f ? le32_to_cpu(dst_f->u64s) : 0);
                if (d > 0) {
                        int ret = bch2_sb_realloc(dst_handle,
                                        le32_to_cpu(dst_handle->sb->u64s) + d);

                        if (ret)
                                return ret;

                        dst = dst_handle->sb;
                        dst_f = bch2_sb_field_get_id(dst, i);
                }

                dst_f = __bch2_sb_field_resize(dst_handle, dst_f,
                                src_f ? le32_to_cpu(src_f->u64s) : 0);

                if (src_f)
                        memcpy(dst_f, src_f, vstruct_bytes(src_f));
        }

        return 0;
}

int bch2_sb_to_fs(struct bch_fs *c, struct bch_sb *src)
{
        int ret;

        lockdep_assert_held(&c->sb_lock);

        ret =   bch2_sb_realloc(&c->disk_sb, 0) ?:
                __copy_super(&c->disk_sb, src) ?:
                bch2_sb_replicas_to_cpu_replicas(c) ?:
                bch2_sb_disk_groups_to_cpu(c);
        if (ret)
                return ret;

        bch2_sb_update(c);
        return 0;
}

int bch2_sb_from_fs(struct bch_fs *c, struct bch_dev *ca)
{
        return __copy_super(&ca->disk_sb, c->disk_sb.sb);
}

/* read superblock: */

static int read_one_super(struct bch_sb_handle *sb, u64 offset, struct printbuf *err)
{
        size_t bytes;
        int ret;
reread:
        bio_reset(sb->bio, sb->bdev, REQ_OP_READ|REQ_SYNC|REQ_META);
        sb->bio->bi_iter.bi_sector = offset;
        bch2_bio_map(sb->bio, sb->sb, sb->buffer_size);

        ret = submit_bio_wait(sb->bio);
        if (ret) {
                prt_printf(err, "IO error: %i", ret);
                return ret;
        }

        if (!uuid_equal(&sb->sb->magic, &BCACHE_MAGIC) &&
            !uuid_equal(&sb->sb->magic, &BCHFS_MAGIC)) {
                prt_str(err, "Not a bcachefs superblock (got magic ");
                pr_uuid(err, sb->sb->magic.b);
                prt_str(err, ")");
                return -BCH_ERR_invalid_sb_magic;
        }

        ret = bch2_sb_compatible(sb->sb, err);
        if (ret)
                return ret;

        bytes = vstruct_bytes(sb->sb);

        if (bytes > 512 << sb->sb->layout.sb_max_size_bits) {
                prt_printf(err, "Invalid superblock: too big (got %zu bytes, layout max %lu)",
                       bytes, 512UL << sb->sb->layout.sb_max_size_bits);
                return -BCH_ERR_invalid_sb_too_big;
        }

        if (bytes > sb->buffer_size) {
                ret = bch2_sb_realloc(sb, le32_to_cpu(sb->sb->u64s));
                if (ret)
                        return ret;
                goto reread;
        }

        enum bch_csum_type csum_type = BCH_SB_CSUM_TYPE(sb->sb);
        if (csum_type >= BCH_CSUM_NR) {
                prt_printf(err, "unknown checksum type %llu", BCH_SB_CSUM_TYPE(sb->sb));
                return -BCH_ERR_invalid_sb_csum_type;
        }

        /* XXX: verify MACs */
        struct bch_csum csum = csum_vstruct(NULL, csum_type, null_nonce(), sb->sb);
        if (bch2_crc_cmp(csum, sb->sb->csum)) {
                bch2_csum_err_msg(err, csum_type, sb->sb->csum, csum);
                return -BCH_ERR_invalid_sb_csum;
        }

        sb->seq = le64_to_cpu(sb->sb->seq);

        return 0;
}

static int __bch2_read_super(const char *path, struct bch_opts *opts,
                    struct bch_sb_handle *sb, bool ignore_notbchfs_msg)
{
        u64 offset = opt_get(*opts, sb);
        struct bch_sb_layout layout;
        struct printbuf err = PRINTBUF;
        struct printbuf err2 = PRINTBUF;
        __le64 *i;
        int ret;
#ifndef __KERNEL__
retry:
#endif
        memset(sb, 0, sizeof(*sb));
        sb->mode        = BLK_OPEN_READ;
        sb->have_bio    = true;
        sb->holder      = kmalloc(1, GFP_KERNEL);
        if (!sb->holder)
                return -ENOMEM;

        sb->sb_name = kstrdup(path, GFP_KERNEL);
        if (!sb->sb_name)
                return -ENOMEM;

#ifndef __KERNEL__
        if (opt_get(*opts, direct_io) == false)
                sb->mode |= BLK_OPEN_BUFFERED;
#endif

        if (!opt_get(*opts, noexcl))
                sb->mode |= BLK_OPEN_EXCL;

        if (!opt_get(*opts, nochanges))
                sb->mode |= BLK_OPEN_WRITE;

        sb->s_bdev_file = bdev_file_open_by_path(path, sb->mode, sb->holder, &bch2_sb_handle_bdev_ops);
        if (IS_ERR(sb->s_bdev_file) &&
            PTR_ERR(sb->s_bdev_file) == -EACCES &&
            opt_get(*opts, read_only)) {
                sb->mode &= ~BLK_OPEN_WRITE;

                sb->s_bdev_file = bdev_file_open_by_path(path, sb->mode, sb->holder, &bch2_sb_handle_bdev_ops);
                if (!IS_ERR(sb->s_bdev_file))
                        opt_set(*opts, nochanges, true);
        }

        if (IS_ERR(sb->s_bdev_file)) {
                ret = PTR_ERR(sb->s_bdev_file);
                goto out;
        }
        sb->bdev = file_bdev(sb->s_bdev_file);

        ret = bch2_sb_realloc(sb, 0);
        if (ret) {
                prt_printf(&err, "error allocating memory for superblock");
                goto err;
        }

        if (bch2_fs_init_fault("read_super")) {
                prt_printf(&err, "dynamic fault");
                ret = -EFAULT;
                goto err;
        }

        ret = read_one_super(sb, offset, &err);
        if (!ret)
                goto got_super;

        if (opt_defined(*opts, sb))
                goto err;

        prt_printf(&err2, "bcachefs (%s): error reading default superblock: %s\n",
               path, err.buf);
        if (ret == -BCH_ERR_invalid_sb_magic && ignore_notbchfs_msg)
                printk(KERN_INFO "%s", err2.buf);
        else
                printk(KERN_ERR "%s", err2.buf);

        printbuf_exit(&err2);
        printbuf_reset(&err);

        /*
         * Error reading primary superblock - read location of backup
         * superblocks:
         */
        bio_reset(sb->bio, sb->bdev, REQ_OP_READ|REQ_SYNC|REQ_META);
        sb->bio->bi_iter.bi_sector = BCH_SB_LAYOUT_SECTOR;
        /*
         * use sb buffer to read layout, since sb buffer is page aligned but
         * layout won't be:
         */
        bch2_bio_map(sb->bio, sb->sb, sizeof(struct bch_sb_layout));

        ret = submit_bio_wait(sb->bio);
        if (ret) {
                prt_printf(&err, "IO error: %i", ret);
                goto err;
        }

        memcpy(&layout, sb->sb, sizeof(layout));
        ret = validate_sb_layout(&layout, &err);
        if (ret)
                goto err;

        for (i = layout.sb_offset;
             i < layout.sb_offset + layout.nr_superblocks; i++) {
                offset = le64_to_cpu(*i);

                if (offset == opt_get(*opts, sb))
                        continue;

                ret = read_one_super(sb, offset, &err);
                if (!ret)
                        goto got_super;
        }

        goto err;

got_super:
        if (le16_to_cpu(sb->sb->block_size) << 9 <
            bdev_logical_block_size(sb->bdev) &&
            opt_get(*opts, direct_io)) {
#ifndef __KERNEL__
                opt_set(*opts, direct_io, false);
                bch2_free_super(sb);
                goto retry;
#endif
                prt_printf(&err, "block size (%u) smaller than device block size (%u)",
                       le16_to_cpu(sb->sb->block_size) << 9,
                       bdev_logical_block_size(sb->bdev));
                ret = -BCH_ERR_block_size_too_small;
                goto err;
        }

        ret = 0;
        sb->have_layout = true;

        ret = bch2_sb_validate(sb, &err, READ);
        if (ret) {
                printk(KERN_ERR "bcachefs (%s): error validating superblock: %s\n",
                       path, err.buf);
                goto err_no_print;
        }
out:
        printbuf_exit(&err);
        return ret;
err:
        printk(KERN_ERR "bcachefs (%s): error reading superblock: %s\n",
               path, err.buf);
err_no_print:
        bch2_free_super(sb);
        goto out;
}

int bch2_read_super(const char *path, struct bch_opts *opts,
                    struct bch_sb_handle *sb)
{
        return __bch2_read_super(path, opts, sb, false);
}

/* provide a silenced version for mount.bcachefs */

int bch2_read_super_silent(const char *path, struct bch_opts *opts,
                    struct bch_sb_handle *sb)
{
        return __bch2_read_super(path, opts, sb, true);
}

/* write superblock: */

static void write_super_endio(struct bio *bio)
{
        struct bch_dev *ca = bio->bi_private;

        /* XXX: return errors directly */

        if (bch2_dev_io_err_on(bio->bi_status, ca,
                               bio_data_dir(bio)
                               ? BCH_MEMBER_ERROR_write
                               : BCH_MEMBER_ERROR_read,
                               "superblock %s error: %s",
                               bio_data_dir(bio) ? "write" : "read",
                               bch2_blk_status_to_str(bio->bi_status)))
                ca->sb_write_error = 1;

        closure_put(&ca->fs->sb_write);
        percpu_ref_put(&ca->io_ref);
}

static void read_back_super(struct bch_fs *c, struct bch_dev *ca)
{
        struct bch_sb *sb = ca->disk_sb.sb;
        struct bio *bio = ca->disk_sb.bio;

        bio_reset(bio, ca->disk_sb.bdev, REQ_OP_READ|REQ_SYNC|REQ_META);
        bio->bi_iter.bi_sector  = le64_to_cpu(sb->layout.sb_offset[0]);
        bio->bi_end_io          = write_super_endio;
        bio->bi_private         = ca;
        bch2_bio_map(bio, ca->sb_read_scratch, PAGE_SIZE);

        this_cpu_add(ca->io_done->sectors[READ][BCH_DATA_sb],
                     bio_sectors(bio));

        percpu_ref_get(&ca->io_ref);
        closure_bio_submit(bio, &c->sb_write);
}

static void write_one_super(struct bch_fs *c, struct bch_dev *ca, unsigned idx)
{
        struct bch_sb *sb = ca->disk_sb.sb;
        struct bio *bio = ca->disk_sb.bio;

        sb->offset = sb->layout.sb_offset[idx];

        SET_BCH_SB_CSUM_TYPE(sb, bch2_csum_opt_to_type(c->opts.metadata_checksum, false));
        sb->csum = csum_vstruct(c, BCH_SB_CSUM_TYPE(sb),
                                null_nonce(), sb);

        bio_reset(bio, ca->disk_sb.bdev, REQ_OP_WRITE|REQ_SYNC|REQ_META);
        bio->bi_iter.bi_sector  = le64_to_cpu(sb->offset);
        bio->bi_end_io          = write_super_endio;
        bio->bi_private         = ca;
        bch2_bio_map(bio, sb,
                     roundup((size_t) vstruct_bytes(sb),
                             bdev_logical_block_size(ca->disk_sb.bdev)));

        this_cpu_add(ca->io_done->sectors[WRITE][BCH_DATA_sb],
                     bio_sectors(bio));

        percpu_ref_get(&ca->io_ref);
        closure_bio_submit(bio, &c->sb_write);
}

int bch2_write_super(struct bch_fs *c)
{
        struct closure *cl = &c->sb_write;
        struct printbuf err = PRINTBUF;
        unsigned sb = 0, nr_wrote;
        struct bch_devs_mask sb_written;
        bool wrote, can_mount_without_written, can_mount_with_written;
        unsigned degraded_flags = BCH_FORCE_IF_DEGRADED;
        int ret = 0;

        trace_and_count(c, write_super, c, _RET_IP_);

        if (c->opts.very_degraded)
                degraded_flags |= BCH_FORCE_IF_LOST;

        lockdep_assert_held(&c->sb_lock);

        closure_init_stack(cl);
        memset(&sb_written, 0, sizeof(sb_written));

        /* Make sure we're using the new magic numbers: */
        c->disk_sb.sb->magic = BCHFS_MAGIC;
        c->disk_sb.sb->layout.magic = BCHFS_MAGIC;

        le64_add_cpu(&c->disk_sb.sb->seq, 1);

        struct bch_sb_field_members_v2 *mi = bch2_sb_field_get(c->disk_sb.sb, members_v2);
        for_each_online_member(c, ca)
                __bch2_members_v2_get_mut(mi, ca->dev_idx)->seq = c->disk_sb.sb->seq;
        c->disk_sb.sb->write_time = cpu_to_le64(ktime_get_real_seconds());

        if (test_bit(BCH_FS_error, &c->flags))
                SET_BCH_SB_HAS_ERRORS(c->disk_sb.sb, 1);
        if (test_bit(BCH_FS_topology_error, &c->flags))
                SET_BCH_SB_HAS_TOPOLOGY_ERRORS(c->disk_sb.sb, 1);

        SET_BCH_SB_BIG_ENDIAN(c->disk_sb.sb, CPU_BIG_ENDIAN);

        bch2_sb_counters_from_cpu(c);
        bch2_sb_members_from_cpu(c);
        bch2_sb_members_cpy_v2_v1(&c->disk_sb);
        bch2_sb_errors_from_cpu(c);
        bch2_sb_downgrade_update(c);

        for_each_online_member(c, ca)
                bch2_sb_from_fs(c, ca);

        for_each_online_member(c, ca) {
                printbuf_reset(&err);

                ret = bch2_sb_validate(&ca->disk_sb, &err, WRITE);
                if (ret) {
                        bch2_fs_inconsistent(c, "sb invalid before write: %s", err.buf);
                        percpu_ref_put(&ca->io_ref);
                        goto out;
                }
        }

        if (c->opts.nochanges)
                goto out;

        /*
         * Defer writing the superblock until filesystem initialization is
         * complete - don't write out a partly initialized superblock:
         */
        if (!BCH_SB_INITIALIZED(c->disk_sb.sb))
                goto out;

        if (le16_to_cpu(c->disk_sb.sb->version) > bcachefs_metadata_version_current) {
                struct printbuf buf = PRINTBUF;
                prt_printf(&buf, "attempting to write superblock that wasn't version downgraded (");
                bch2_version_to_text(&buf, le16_to_cpu(c->disk_sb.sb->version));
                prt_str(&buf, " > ");
                bch2_version_to_text(&buf, bcachefs_metadata_version_current);
                prt_str(&buf, ")");
                bch2_fs_fatal_error(c, "%s", buf.buf);
                printbuf_exit(&buf);
                return -BCH_ERR_sb_not_downgraded;
        }

        for_each_online_member(c, ca) {
                __set_bit(ca->dev_idx, sb_written.d);
                ca->sb_write_error = 0;
        }

        for_each_online_member(c, ca)
                read_back_super(c, ca);
        closure_sync(cl);

        for_each_online_member(c, ca) {
                if (ca->sb_write_error)
                        continue;

                if (le64_to_cpu(ca->sb_read_scratch->seq) < ca->disk_sb.seq) {
                        bch2_fs_fatal_error(c,
                                "Superblock write was silently dropped! (seq %llu expected %llu)",
                                le64_to_cpu(ca->sb_read_scratch->seq),
                                ca->disk_sb.seq);
                        percpu_ref_put(&ca->io_ref);
                        ret = -BCH_ERR_erofs_sb_err;
                        goto out;
                }

                if (le64_to_cpu(ca->sb_read_scratch->seq) > ca->disk_sb.seq) {
                        bch2_fs_fatal_error(c,
                                "Superblock modified by another process (seq %llu expected %llu)",
                                le64_to_cpu(ca->sb_read_scratch->seq),
                                ca->disk_sb.seq);
                        percpu_ref_put(&ca->io_ref);
                        ret = -BCH_ERR_erofs_sb_err;
                        goto out;
                }
        }

        do {
                wrote = false;
                for_each_online_member(c, ca)
                        if (!ca->sb_write_error &&
                            sb < ca->disk_sb.sb->layout.nr_superblocks) {
                                write_one_super(c, ca, sb);
                                wrote = true;
                        }
                closure_sync(cl);
                sb++;
        } while (wrote);

        for_each_online_member(c, ca) {
                if (ca->sb_write_error)
                        __clear_bit(ca->dev_idx, sb_written.d);
                else
                        ca->disk_sb.seq = le64_to_cpu(ca->disk_sb.sb->seq);
        }

        nr_wrote = dev_mask_nr(&sb_written);

        can_mount_with_written =
                bch2_have_enough_devs(c, sb_written, degraded_flags, false);

        for (unsigned i = 0; i < ARRAY_SIZE(sb_written.d); i++)
                sb_written.d[i] = ~sb_written.d[i];

        can_mount_without_written =
                bch2_have_enough_devs(c, sb_written, degraded_flags, false);

        /*
         * If we would be able to mount _without_ the devices we successfully
         * wrote superblocks to, we weren't able to write to enough devices:
         *
         * Exception: if we can mount without the successes because we haven't
         * written anything (new filesystem), we continue if we'd be able to
         * mount with the devices we did successfully write to:
         */
        if (bch2_fs_fatal_err_on(!nr_wrote ||
                                 !can_mount_with_written ||
                                 (can_mount_without_written &&
                                  !can_mount_with_written), c,
                "Unable to write superblock to sufficient devices (from %ps)",
                (void *) _RET_IP_))
                ret = -1;
out:
        /* Make new options visible after they're persistent: */
        bch2_sb_update(c);
        printbuf_exit(&err);
        return ret;
}

void __bch2_check_set_feature(struct bch_fs *c, unsigned feat)
{
        mutex_lock(&c->sb_lock);
        if (!(c->sb.features & (1ULL << feat))) {
                c->disk_sb.sb->features[0] |= cpu_to_le64(1ULL << feat);

                bch2_write_super(c);
        }
        mutex_unlock(&c->sb_lock);
}

/* Downgrade if superblock is at a higher version than currently supported: */
bool bch2_check_version_downgrade(struct bch_fs *c)
{
        bool ret = bcachefs_metadata_version_current < c->sb.version;

        lockdep_assert_held(&c->sb_lock);

        /*
         * Downgrade, if superblock is at a higher version than currently
         * supported:
         *
         * c->sb will be checked before we write the superblock, so update it as
         * well:
         */
        if (BCH_SB_VERSION_UPGRADE_COMPLETE(c->disk_sb.sb) > bcachefs_metadata_version_current) {
                SET_BCH_SB_VERSION_UPGRADE_COMPLETE(c->disk_sb.sb, bcachefs_metadata_version_current);
                c->sb.version_upgrade_complete = bcachefs_metadata_version_current;
        }
        if (c->sb.version > bcachefs_metadata_version_current) {
                c->disk_sb.sb->version = cpu_to_le16(bcachefs_metadata_version_current);
                c->sb.version = bcachefs_metadata_version_current;
        }
        if (c->sb.version_min > bcachefs_metadata_version_current) {
                c->disk_sb.sb->version_min = cpu_to_le16(bcachefs_metadata_version_current);
                c->sb.version_min = bcachefs_metadata_version_current;
        }
        c->disk_sb.sb->compat[0] &= cpu_to_le64((1ULL << BCH_COMPAT_NR) - 1);
        return ret;
}

void bch2_sb_upgrade(struct bch_fs *c, unsigned new_version)
{
        lockdep_assert_held(&c->sb_lock);

        if (BCH_VERSION_MAJOR(new_version) >
            BCH_VERSION_MAJOR(le16_to_cpu(c->disk_sb.sb->version)))
                bch2_sb_field_resize(&c->disk_sb, downgrade, 0);

        c->disk_sb.sb->version = cpu_to_le16(new_version);
        c->disk_sb.sb->features[0] |= cpu_to_le64(BCH_SB_FEATURES_ALL);
}

static int bch2_sb_ext_validate(struct bch_sb *sb, struct bch_sb_field *f,
                                struct printbuf *err)
{
        if (vstruct_bytes(f) < 88) {
                prt_printf(err, "field too small (%zu < %u)", vstruct_bytes(f), 88);
                return -BCH_ERR_invalid_sb_ext;
        }

        return 0;
}

static void bch2_sb_ext_to_text(struct printbuf *out, struct bch_sb *sb,
                                struct bch_sb_field *f)
{
        struct bch_sb_field_ext *e = field_to_type(f, ext);

        prt_printf(out, "Recovery passes required:");
        prt_tab(out);
        prt_bitflags(out, bch2_recovery_passes,
                     bch2_recovery_passes_from_stable(le64_to_cpu(e->recovery_passes_required[0])));
        prt_newline(out);

        unsigned long *errors_silent = kmalloc(sizeof(e->errors_silent), GFP_KERNEL);
        if (errors_silent) {
                le_bitvector_to_cpu(errors_silent, (void *) e->errors_silent, sizeof(e->errors_silent) * 8);

                prt_printf(out, "Errors to silently fix:");
                prt_tab(out);
                prt_bitflags_vector(out, bch2_sb_error_strs, errors_silent, sizeof(e->errors_silent) * 8);
                prt_newline(out);

                kfree(errors_silent);
        }
}

static const struct bch_sb_field_ops bch_sb_field_ops_ext = {
        .validate       = bch2_sb_ext_validate,
        .to_text        = bch2_sb_ext_to_text,
};

static const struct bch_sb_field_ops *bch2_sb_field_ops[] = {
#define x(f, nr)                                        \
        [BCH_SB_FIELD_##f] = &bch_sb_field_ops_##f,
        BCH_SB_FIELDS()
#undef x
};

static const struct bch_sb_field_ops bch2_sb_field_null_ops;

static const struct bch_sb_field_ops *bch2_sb_field_type_ops(unsigned type)
{
        return likely(type < ARRAY_SIZE(bch2_sb_field_ops))
                ? bch2_sb_field_ops[type]
                : &bch2_sb_field_null_ops;
}

static int bch2_sb_field_validate(struct bch_sb *sb, struct bch_sb_field *f,
                                  struct printbuf *err)
{
        unsigned type = le32_to_cpu(f->type);
        struct printbuf field_err = PRINTBUF;
        const struct bch_sb_field_ops *ops = bch2_sb_field_type_ops(type);
        int ret;

        ret = ops->validate ? ops->validate(sb, f, &field_err) : 0;
        if (ret) {
                prt_printf(err, "Invalid superblock section %s: %s",
                           bch2_sb_fields[type], field_err.buf);
                prt_newline(err);
                bch2_sb_field_to_text(err, sb, f);
        }

        printbuf_exit(&field_err);
        return ret;
}

void __bch2_sb_field_to_text(struct printbuf *out, struct bch_sb *sb,
                             struct bch_sb_field *f)
{
        unsigned type = le32_to_cpu(f->type);
        const struct bch_sb_field_ops *ops = bch2_sb_field_type_ops(type);

        if (!out->nr_tabstops)
                printbuf_tabstop_push(out, 32);

        if (ops->to_text)
                ops->to_text(out, sb, f);
}

void bch2_sb_field_to_text(struct printbuf *out, struct bch_sb *sb,
                           struct bch_sb_field *f)
{
        unsigned type = le32_to_cpu(f->type);

        if (type < BCH_SB_FIELD_NR)
                prt_printf(out, "%s", bch2_sb_fields[type]);
        else
                prt_printf(out, "(unknown field %u)", type);

        prt_printf(out, " (size %zu):", vstruct_bytes(f));
        prt_newline(out);

        __bch2_sb_field_to_text(out, sb, f);
}

void bch2_sb_layout_to_text(struct printbuf *out, struct bch_sb_layout *l)
{
        unsigned i;

        prt_printf(out, "Type:                    %u", l->layout_type);
        prt_newline(out);

        prt_str(out, "Superblock max size:     ");
        prt_units_u64(out, 512 << l->sb_max_size_bits);
        prt_newline(out);

        prt_printf(out, "Nr superblocks:          %u", l->nr_superblocks);
        prt_newline(out);

        prt_str(out, "Offsets:                 ");
        for (i = 0; i < l->nr_superblocks; i++) {
                if (i)
                        prt_str(out, ", ");
                prt_printf(out, "%llu", le64_to_cpu(l->sb_offset[i]));
        }
        prt_newline(out);
}

void bch2_sb_to_text(struct printbuf *out, struct bch_sb *sb,
                     bool print_layout, unsigned fields)
{
        u64 fields_have = 0;
        unsigned nr_devices = 0;

        if (!out->nr_tabstops)
                printbuf_tabstop_push(out, 44);

        for (int i = 0; i < sb->nr_devices; i++)
                nr_devices += bch2_dev_exists(sb, i);

        prt_printf(out, "External UUID:");
        prt_tab(out);
        pr_uuid(out, sb->user_uuid.b);
        prt_newline(out);

        prt_printf(out, "Internal UUID:");
        prt_tab(out);
        pr_uuid(out, sb->uuid.b);
        prt_newline(out);

        prt_printf(out, "Magic number:");
        prt_tab(out);
        pr_uuid(out, sb->magic.b);
        prt_newline(out);

        prt_str(out, "Device index:");
        prt_tab(out);
        prt_printf(out, "%u", sb->dev_idx);
        prt_newline(out);

        prt_str(out, "Label:");
        prt_tab(out);
        prt_printf(out, "%.*s", (int) sizeof(sb->label), sb->label);
        prt_newline(out);

        prt_str(out, "Version:");
        prt_tab(out);
        bch2_version_to_text(out, le16_to_cpu(sb->version));
        prt_newline(out);

        prt_str(out, "Version upgrade complete:");
        prt_tab(out);
        bch2_version_to_text(out, BCH_SB_VERSION_UPGRADE_COMPLETE(sb));
        prt_newline(out);

        prt_printf(out, "Oldest version on disk:");
        prt_tab(out);
        bch2_version_to_text(out, le16_to_cpu(sb->version_min));
        prt_newline(out);

        prt_printf(out, "Created:");
        prt_tab(out);
        if (sb->time_base_lo)
                bch2_prt_datetime(out, div_u64(le64_to_cpu(sb->time_base_lo), NSEC_PER_SEC));
        else
                prt_printf(out, "(not set)");
        prt_newline(out);

        prt_printf(out, "Sequence number:");
        prt_tab(out);
        prt_printf(out, "%llu", le64_to_cpu(sb->seq));
        prt_newline(out);

        prt_printf(out, "Time of last write:");
        prt_tab(out);
        bch2_prt_datetime(out, le64_to_cpu(sb->write_time));
        prt_newline(out);

        prt_printf(out, "Superblock size:");
        prt_tab(out);
        prt_units_u64(out, vstruct_bytes(sb));
        prt_str(out, "/");
        prt_units_u64(out, 512ULL << sb->layout.sb_max_size_bits);
        prt_newline(out);

        prt_printf(out, "Clean:");
        prt_tab(out);
        prt_printf(out, "%llu", BCH_SB_CLEAN(sb));
        prt_newline(out);

        prt_printf(out, "Devices:");
        prt_tab(out);
        prt_printf(out, "%u", nr_devices);
        prt_newline(out);

        prt_printf(out, "Sections:");
        vstruct_for_each(sb, f)
                fields_have |= 1 << le32_to_cpu(f->type);
        prt_tab(out);
        prt_bitflags(out, bch2_sb_fields, fields_have);
        prt_newline(out);

        prt_printf(out, "Features:");
        prt_tab(out);
        prt_bitflags(out, bch2_sb_features, le64_to_cpu(sb->features[0]));
        prt_newline(out);

        prt_printf(out, "Compat features:");
        prt_tab(out);
        prt_bitflags(out, bch2_sb_compat, le64_to_cpu(sb->compat[0]));
        prt_newline(out);

        prt_newline(out);
        prt_printf(out, "Options:");
        prt_newline(out);
        printbuf_indent_add(out, 2);
        {
                enum bch_opt_id id;

                for (id = 0; id < bch2_opts_nr; id++) {
                        const struct bch_option *opt = bch2_opt_table + id;

                        if (opt->get_sb != BCH2_NO_SB_OPT) {
                                u64 v = bch2_opt_from_sb(sb, id);

                                prt_printf(out, "%s:", opt->attr.name);
                                prt_tab(out);
                                bch2_opt_to_text(out, NULL, sb, opt, v,
                                                 OPT_HUMAN_READABLE|OPT_SHOW_FULL_LIST);
                                prt_newline(out);
                        }
                }
        }

        printbuf_indent_sub(out, 2);

        if (print_layout) {
                prt_newline(out);
                prt_printf(out, "layout:");
                prt_newline(out);
                printbuf_indent_add(out, 2);
                bch2_sb_layout_to_text(out, &sb->layout);
                printbuf_indent_sub(out, 2);
        }

        vstruct_for_each(sb, f)
                if (fields & (1 << le32_to_cpu(f->type))) {
                        prt_newline(out);
                        bch2_sb_field_to_text(out, sb, f);
                }
}