lkml.org 
[lkml]   [2022]   [Oct]   [24]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Subject[PATCH 5.10 351/390] btrfs: scrub: try to fix super block errors
    Date
    From: Qu Wenruo <wqu@suse.com>

    [ Upstream commit f9eab5f0bba76742af654f33d517bf62a0db8f12 ]

    [BUG]
    The following script shows that, although scrub can detect super block
    errors, it never tries to fix it:

    mkfs.btrfs -f -d raid1 -m raid1 $dev1 $dev2
    xfs_io -c "pwrite 67108864 4k" $dev2

    mount $dev1 $mnt
    btrfs scrub start -B $dev2
    btrfs scrub start -Br $dev2
    umount $mnt

    The first scrub reports the super error correctly:

    scrub done for f3289218-abd3-41ac-a630-202f766c0859
    Scrub started: Tue Aug 2 14:44:11 2022
    Status: finished
    Duration: 0:00:00
    Total to scrub: 1.26GiB
    Rate: 0.00B/s
    Error summary: super=1
    Corrected: 0
    Uncorrectable: 0
    Unverified: 0

    But the second read-only scrub still reports the same super error:

    Scrub started: Tue Aug 2 14:44:11 2022
    Status: finished
    Duration: 0:00:00
    Total to scrub: 1.26GiB
    Rate: 0.00B/s
    Error summary: super=1
    Corrected: 0
    Uncorrectable: 0
    Unverified: 0

    [CAUSE]
    The comments already shows that super block can be easily fixed by
    committing a transaction:

    /*
    * If we find an error in a super block, we just report it.
    * They will get written with the next transaction commit
    * anyway
    */

    But the truth is, such assumption is not always true, and since scrub
    should try to repair every error it found (except for read-only scrub),
    we should really actively commit a transaction to fix this.

    [FIX]
    Just commit a transaction if we found any super block errors, after
    everything else is done.

    We cannot do this just after scrub_supers(), as
    btrfs_commit_transaction() will try to pause and wait for the running
    scrub, thus we can not call it with scrub_lock hold.

    Signed-off-by: Qu Wenruo <wqu@suse.com>
    Reviewed-by: David Sterba <dsterba@suse.com>
    Signed-off-by: David Sterba <dsterba@suse.com>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    fs/btrfs/scrub.c | 36 ++++++++++++++++++++++++++++++++++++
    1 file changed, 36 insertions(+)

    diff --git a/fs/btrfs/scrub.c b/fs/btrfs/scrub.c
    index 0392c556af60..88b9a5394561 100644
    --- a/fs/btrfs/scrub.c
    +++ b/fs/btrfs/scrub.c
    @@ -3811,6 +3811,7 @@ int btrfs_scrub_dev(struct btrfs_fs_info *fs_info, u64 devid, u64 start,
    int ret;
    struct btrfs_device *dev;
    unsigned int nofs_flag;
    + bool need_commit = false;

    if (btrfs_fs_closing(fs_info))
    return -EAGAIN;
    @@ -3924,6 +3925,12 @@ int btrfs_scrub_dev(struct btrfs_fs_info *fs_info, u64 devid, u64 start,
    */
    nofs_flag = memalloc_nofs_save();
    if (!is_dev_replace) {
    + u64 old_super_errors;
    +
    + spin_lock(&sctx->stat_lock);
    + old_super_errors = sctx->stat.super_errors;
    + spin_unlock(&sctx->stat_lock);
    +
    btrfs_info(fs_info, "scrub: started on devid %llu", devid);
    /*
    * by holding device list mutex, we can
    @@ -3932,6 +3939,16 @@ int btrfs_scrub_dev(struct btrfs_fs_info *fs_info, u64 devid, u64 start,
    mutex_lock(&fs_info->fs_devices->device_list_mutex);
    ret = scrub_supers(sctx, dev);
    mutex_unlock(&fs_info->fs_devices->device_list_mutex);
    +
    + spin_lock(&sctx->stat_lock);
    + /*
    + * Super block errors found, but we can not commit transaction
    + * at current context, since btrfs_commit_transaction() needs
    + * to pause the current running scrub (hold by ourselves).
    + */
    + if (sctx->stat.super_errors > old_super_errors && !sctx->readonly)
    + need_commit = true;
    + spin_unlock(&sctx->stat_lock);
    }

    if (!ret)
    @@ -3958,6 +3975,25 @@ int btrfs_scrub_dev(struct btrfs_fs_info *fs_info, u64 devid, u64 start,
    scrub_workers_put(fs_info);
    scrub_put_ctx(sctx);

    + /*
    + * We found some super block errors before, now try to force a
    + * transaction commit, as scrub has finished.
    + */
    + if (need_commit) {
    + struct btrfs_trans_handle *trans;
    +
    + trans = btrfs_start_transaction(fs_info->tree_root, 0);
    + if (IS_ERR(trans)) {
    + ret = PTR_ERR(trans);
    + btrfs_err(fs_info,
    + "scrub: failed to start transaction to fix super block errors: %d", ret);
    + return ret;
    + }
    + ret = btrfs_commit_transaction(trans);
    + if (ret < 0)
    + btrfs_err(fs_info,
    + "scrub: failed to commit transaction to fix super block errors: %d", ret);
    + }
    return ret;
    out:
    scrub_workers_put(fs_info);
    --
    2.35.1


    \
     
     \ /
      Last update: 2022-10-24 17:59    [W:2.269 / U:0.032 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site