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List:       linux-xfs
Subject:    Re: [PATCH v3 09/21] xfs: Do not free EOF blocks for forcealign
From:       Dave Chinner <david () fromorbit ! com>
Date:       2024-04-30 22:54:06
Message-ID: ZjF2jjtsA/C6ajtb () dread ! disaster ! area
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On Mon, Apr 29, 2024 at 05:47:34PM +0000, John Garry wrote:
> For when forcealign is enabled, we want the EOF to be aligned as well, so
> do not free EOF blocks.

This is doesn't match what the code does. The code is correct - it
rounds the range to be trimmed up to the aligned offset beyond EOF
and then frees them. The description needs to be updated to reflect
this.

> 
> Signed-off-by: John Garry <john.g.garry@oracle.com>
> ---
>  fs/xfs/xfs_bmap_util.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/xfs/xfs_bmap_util.c b/fs/xfs/xfs_bmap_util.c
> index 19e11d1da660..f26d1570b9bd 100644
> --- a/fs/xfs/xfs_bmap_util.c
> +++ b/fs/xfs/xfs_bmap_util.c
> @@ -542,8 +542,13 @@ 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)
> +
> +	/* Do not free blocks when forcing extent sizes */
> +	if (xfs_inode_has_forcealign(ip) && ip->i_extsize > 1)

I see this sort of check all through the remaining patches.

Given there are significant restrictions on forced alignment,
shouldn't this all the details be pushed inside the helper function?
e.g.

/*
 * Forced extent alignment is dependent on extent size hints being
 * set to define the alignment. Alignment is only necessary when the
 * extent size hint is larger than a single block.
 *
 * If reflink is enabled on the file or we are in always_cow mode,
 * we can't easily do forced alignment.
 *
 * We don't support forced alignment on realtime files.
 * XXX(dgc): why not?
 */
static inline bool
xfs_inode_has_forcealign(struct xfs_inode *ip)
{
	if (!(ip->di_flags & XFS_DIFLAG_EXTSIZE))
		return false;
	if (ip->i_extsize <= 1)
		return false;

	if (xfs_is_cow_inode(ip))
		return false;
	if (ip->di_flags & XFS_DIFLAG_REALTIME)
		return false;

	return ip->di_flags2 & XFS_DIFLAG2_FORCEALIGN;
}

-Dave.
-- 
Dave Chinner
david@fromorbit.com

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