Re: [PATCH 1/2] xfs: correct the sb_rgcount when the disk not support rt volume

["Darrick J. Wong" <djwong@kernel.org>]

On Tue, Dec 31, 2024 at 10:34:22AM +0800, Long Li wrote:
> When mounting an xfs disk that incompat with metadir and has no realtime
> subvolume, if CONFIG_XFS_RT is not enabled in the kernel, the mount will
> fail. During superblock log recovery, since mp->m_sb.sb_rgcount is greater
> than 0, updating the last rtag in-core is required, however, without
> CONFIG_XFS_RT enabled, xfs_update_last_rtgroup_size() always returns
> -EOPNOTSUPP, leading to mount failure.

Didn't we fix the xfs_update_last_rtgroup_size stub to return 0?

--D

> Initializing sb_rgcount as 1 is incorrect in this scenario. If no
> realtime subvolume exists, the value of sb_rgcount should be set
> to zero. Fix it by initializing sb_rgcount based on the actual number
> of realtime blocks.
> 
> Fixes: 87fe4c34a383 ("xfs: create incore realtime group structures")
> Signed-off-by: Long Li <leo.lilong@huawei.com>
> ---
>  fs/xfs/libxfs/xfs_sb.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/fs/xfs/libxfs/xfs_sb.c b/fs/xfs/libxfs/xfs_sb.c
> index 3b5623611eba..1ea28f04b75a 100644
> --- a/fs/xfs/libxfs/xfs_sb.c
> +++ b/fs/xfs/libxfs/xfs_sb.c
> @@ -830,7 +830,7 @@ __xfs_sb_from_disk(
>  		to->sb_rsumino = NULLFSINO;
>  	} else {
>  		to->sb_metadirino = NULLFSINO;
> -		to->sb_rgcount = 1;
> +		to->sb_rgcount = to->sb_rblocks > 0 ? 1 : 0;
>  		to->sb_rgextents = 0;
>  	}
>  }
> -- 
> 2.39.2
> 
>