Re: [PATCH 5.10 CANDIDATE 09/11] xfs: only bother with sync_filesystem during readonly remount

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

On Fri, Jun 17, 2022 at 01:06:39PM +0300, Amir Goldstein wrote:
> From: "Darrick J. Wong" <djwong@kernel.org>
> 
> commit b97cca3ba9098522e5a1c3388764ead42640c1a5 upstream.
> 
> In commit 02b9984d6408, we pushed a sync_filesystem() call from the VFS
> into xfs_fs_remount.  The only time that we ever need to push dirty file
> data or metadata to disk for a remount is if we're remounting the
> filesystem read only, so this really could be moved to xfs_remount_ro.
> 
> Once we've moved the call site, actually check the return value from
> sync_filesystem.
> 
> Fixes: 02b9984d6408 ("fs: push sync_filesystem() down to the file system's remount_fs()")
> Signed-off-by: Darrick J. Wong <djwong@kernel.org>
> Reviewed-by: Dave Chinner <dchinner@redhat.com>
> Signed-off-by: Amir Goldstein <amir73il@gmail.com>
> ---
>  fs/xfs/xfs_super.c | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c
> index 6323974d6b3e..dd0439ae6732 100644
> --- a/fs/xfs/xfs_super.c
> +++ b/fs/xfs/xfs_super.c
> @@ -1716,6 +1716,11 @@ xfs_remount_ro(
>  	};
>  	int			error;
>  
> +	/* Flush all the dirty data to disk. */
> +	error = sync_filesystem(mp->m_super);

Looking at 5.10.124's fsync.c and xfs_super.c:

https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/tree/fs/sync.c?h=v5.10.124#n31
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/tree/fs/xfs/xfs_super.c?h=v5.10.124#n755

I think this kernel needs the patch(es) that make __sync_filesystem return
the errors passed back by ->sync_fs, and I think also the patch that
makes xfs_fs_sync_fs return errors encountered by xfs_log_force, right?

--D

> +	if (error)
> +		return error;
> +
>  	/*
>  	 * Cancel background eofb scanning so it cannot race with the final
>  	 * log force+buftarg wait and deadlock the remount.
> @@ -1786,8 +1791,6 @@ xfs_fc_reconfigure(
>  	if (error)
>  		return error;
>  
> -	sync_filesystem(mp->m_super);
> -
>  	/* inode32 -> inode64 */
>  	if ((mp->m_flags & XFS_MOUNT_SMALL_INUMS) &&
>  	    !(new_mp->m_flags & XFS_MOUNT_SMALL_INUMS)) {
> -- 
> 2.25.1
>