linux-kernel - Re: [PATCH v3 10/21] xfs: Update xfs_is_falloc

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Date: Wed, 1 May 2024 09:35:19 +1000
From: Dave Chinner <david@...morbit.com>
To: John Garry <john.g.garry@...cle.com>
Cc: djwong@...nel.org, hch@....de, viro@...iv.linux.org.uk,
	brauner@...nel.org, jack@...e.cz, chandan.babu@...cle.com,
	willy@...radead.org, axboe@...nel.dk, martin.petersen@...cle.com,
	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	tytso@....edu, jbongio@...gle.com, ojaswin@...ux.ibm.com,
	ritesh.list@...il.com, mcgrof@...nel.org, p.raghav@...sung.com,
	linux-xfs@...r.kernel.org, catherine.hoang@...cle.com
Subject: Re: [PATCH v3 10/21] xfs: Update xfs_is_falloc_aligned() mask for
 forcealign

On Mon, Apr 29, 2024 at 05:47:35PM +0000, John Garry wrote:
> For when forcealign is enabled, we want the alignment mask to cover an
> aligned extent, similar to rtvol.
> 
> Signed-off-by: John Garry <john.g.garry@...cle.com>
> ---
>  fs/xfs/xfs_file.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
> index 632653e00906..e81e01e6b22b 100644
> --- a/fs/xfs/xfs_file.c
> +++ b/fs/xfs/xfs_file.c
> @@ -61,7 +61,10 @@ xfs_is_falloc_aligned(
>  		}
>  		mask = XFS_FSB_TO_B(mp, mp->m_sb.sb_rextsize) - 1;
>  	} else {
> -		mask = mp->m_sb.sb_blocksize - 1;
> +		if (xfs_inode_has_forcealign(ip) && ip->i_extsize > 1)
> +			mask = (mp->m_sb.sb_blocksize * ip->i_extsize) - 1;
> +		else
> +			mask = mp->m_sb.sb_blocksize - 1;
>  	}
>  
>  	return !((pos | len) & mask);

I think this whole function needs to be rewritten so that
non-power-of-2 extent sizes are supported on both devices properly.

	xfs_extlen_t	fsbs = 1;
	u64		bytes;
	u32		mod;

	if (xfs_inode_has_forcealign(ip))
		fsbs = ip->i_extsize;
	else if (XFS_IS_REALTIME_INODE(ip))
		fsbs = mp->m_sb.sb_rextsize;

	bytes = XFS_FSB_TO_B(mp, fsbs);
	if (is_power_of_2(fsbs))
		return !((pos | len) & (bytes - 1));

	div_u64_rem(pos, bytes, &mod);
	if (mod)
		return false;
	div_u64_rem(len, bytes, &mod);
	return mod == 0;

-Dave.
-- 
Dave Chinner
david@...morbit.com