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);