Re: [PATCH 3/3] xfs: dont treat rt extents beyond EOF as eofblocks to be cleared

[Dave Chinner <david@fromorbit.com>]

On Sun, Jun 26, 2022 at 03:04:04PM -0700, Darrick J. Wong wrote:
> From: Darrick J. Wong <djwong@kernel.org>
> 
> On a system with a realtime volume and a 28k realtime extent,
> generic/491 fails because the test opens a file on a frozen filesystem
> and closing it causes xfs_release -> xfs_can_free_eofblocks to
> mistakenly think that the the blocks of the realtime extent beyond EOF
> are posteof blocks to be freed.  Realtime extents cannot be partially
> unmapped, so this is pointless.  Worse yet, this triggers posteof
> cleanup, which stalls on a transaction allocation, which is why the test
> fails.
> 
> Teach the predicate to account for realtime extents properly.
> 
> Signed-off-by: Darrick J. Wong <djwong@kernel.org>
> ---
>  fs/xfs/xfs_bmap_util.c |    2 ++
>  1 file changed, 2 insertions(+)
> 
> 
> diff --git a/fs/xfs/xfs_bmap_util.c b/fs/xfs/xfs_bmap_util.c
> index 52be58372c63..85e1a26c92e8 100644
> --- a/fs/xfs/xfs_bmap_util.c
> +++ b/fs/xfs/xfs_bmap_util.c
> @@ -686,6 +686,8 @@ xfs_can_free_eofblocks(
>  	 * forever.
>  	 */
>  	end_fsb = XFS_B_TO_FSB(mp, (xfs_ufsize_t)XFS_ISIZE(ip));
> +	if (XFS_IS_REALTIME_INODE(ip) && mp->m_sb.sb_rextsize > 1)
> +		end_fsb = roundup_64(end_fsb, mp->m_sb.sb_rextsize);
>  	last_fsb = XFS_B_TO_FSB(mp, mp->m_super->s_maxbytes);
>  	if (last_fsb <= end_fsb)
>  		return false;

Ok, that works.

However, I was looking at xfs_can_free_eofblocks() w.r.t. freeze a
couple of days ago and wondering why there isn't a freeze/RO state
check in xfs_can_free_eofblocks(). Shouldn't we have one here so
that we never try to run xfs_free_eofblocks() on RO/frozen
filesystems regardless of unexpected state/alignment issues?

Cheers,

Dave.


-- 
Dave Chinner
david@fromorbit.com