linux-kernel - Re: [PATCH 12/13] xfs: Don't revert allocated offset for forcealign

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Date: Fri, 21 Jun 2024 12:13:57 -0700
From: "Darrick J. Wong" <djwong@...nel.org>
To: John Garry <john.g.garry@...cle.com>
Cc: chandan.babu@...cle.com, dchinner@...hat.com, hch@....de,
	viro@...iv.linux.org.uk, brauner@...nel.org, jack@...e.cz,
	linux-xfs@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-fsdevel@...r.kernel.org, catherine.hoang@...cle.com,
	martin.petersen@...cle.com
Subject: Re: [PATCH 12/13] xfs: Don't revert allocated offset for forcealign

On Fri, Jun 21, 2024 at 10:05:39AM +0000, John Garry wrote:
> In xfs_bmap_process_allocated_extent(), for when we found that we could not
> provide the requested length completely, the mapping is moved so that we
> can provide as much as possible for the original request.
> 
> For forcealign, this would mean ignoring alignment guaranteed, so don't do
> this.
> 
> Signed-off-by: John Garry <john.g.garry@...cle.com>

Makes sense,
Reviewed-by: Darrick J. Wong <djwong@...nel.org>

--D

> ---
>  fs/xfs/libxfs/xfs_bmap.c | 12 ++++++++----
>  1 file changed, 8 insertions(+), 4 deletions(-)
> 
> diff --git a/fs/xfs/libxfs/xfs_bmap.c b/fs/xfs/libxfs/xfs_bmap.c
> index ebeb2969b289..42f3582c1574 100644
> --- a/fs/xfs/libxfs/xfs_bmap.c
> +++ b/fs/xfs/libxfs/xfs_bmap.c
> @@ -3492,11 +3492,15 @@ xfs_bmap_process_allocated_extent(
>  	 * original request as possible.  Free space is apparently
>  	 * very fragmented so we're unlikely to be able to satisfy the
>  	 * hints anyway.
> +	 * However, for an inode with forcealign, continue with the
> +	 * found offset as we need to honour the alignment hint.
>  	 */
> -	if (ap->length <= orig_length)
> -		ap->offset = orig_offset;
> -	else if (ap->offset + ap->length < orig_offset + orig_length)
> -		ap->offset = orig_offset + orig_length - ap->length;
> +	if (!xfs_inode_has_forcealign(ap->ip)) {
> +		if (ap->length <= orig_length)
> +			ap->offset = orig_offset;
> +		else if (ap->offset + ap->length < orig_offset + orig_length)
> +			ap->offset = orig_offset + orig_length - ap->length;
> +	}
>  	xfs_bmap_alloc_account(ap);
>  }
>  
> -- 
> 2.31.1
> 
>