Re: [PATCH] btrfs: fix replace/scrub failure with metadata_uuid

[Anand Jain <anand.jain@oracle.com>]

Gentle ping?

Thx.


On 28/07/2023 14:48, Anand Jain wrote:
> Fstests with POST_MKFS_CMD="btrfstune -m" (as in the mailing list)
> reported a few of the test cases failing.
> 
> The failure scenario can be summaried and simplified as follows:
> 
>    $ mkfs.btrfs -fq -draid1 -mraid1 /dev/sdb1 /dev/sdb2 :0
>    $ btrfstune -m /dev/sdb1 :0
>    $ wipefs -a /dev/sdb1 :0
>    $ mount -o degraded /dev/sdb2 /btrfs :0
>    $ btrfs replace start -B -f -r 1 /dev/sdb1 /btrfs :1
>      STDERR:
>      ERROR: ioctl(DEV_REPLACE_START) failed on "/btrfs": Input/output error
> 
>    [11290.583502] BTRFS warning (device sdb2): tree block 22036480 mirror 2 has bad fsid, has 99835c32-49f0-4668-9e66-dc277a96b4a6 want da40350c-33ac-4872-92a8-4948ed8c04d0
>    [11290.586580] BTRFS error (device sdb2): unable to fix up (regular) error at logical 22020096 on dev /dev/sdb8 physical 1048576
> 
> As above, the replace is failing because we are verifying the header with
> fs_devices::fsid instead of fs_devices::metadata_uuid, despite the
> metadata_uuid actually being present.
> 
> To fix this, use fs_devices::metadata_uuid;
> 
> (We copy fsid into fs_devices::metadata_uuid if there is no
> metadata_uuid, so its fine).
> 
> Fixes: a3ddbaebc7c9 ("btrfs: scrub: introduce a helper to verify one metadata block")
> Signed-off-by: Anand Jain <anand.jain@oracle.com>
> ---
>   fs/btrfs/scrub.c | 3 ++-
>   1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/btrfs/scrub.c b/fs/btrfs/scrub.c
> index db076e12f442..8381174bda15 100644
> --- a/fs/btrfs/scrub.c
> +++ b/fs/btrfs/scrub.c
> @@ -605,7 +605,8 @@ static void scrub_verify_one_metadata(struct scrub_stripe *stripe, int sector_nr
>   			      btrfs_stack_header_bytenr(header), logical);
>   		return;
>   	}
> -	if (memcmp(header->fsid, fs_info->fs_devices->fsid, BTRFS_FSID_SIZE) != 0) {
> +	if (memcmp(header->fsid, fs_info->fs_devices->metadata_uuid,
> +		   BTRFS_FSID_SIZE) != 0) {
>   		bitmap_set(&stripe->meta_error_bitmap, sector_nr, sectors_per_tree);
>   		bitmap_set(&stripe->error_bitmap, sector_nr, sectors_per_tree);
>   		btrfs_warn_rl(fs_info,