Re: [PATCH 2/8] xfs: remove a racy if_bytes check in xfs_reflink_end_cow_extent

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

On Mon, Apr 29, 2024 at 06:49:11AM +0200, Christoph Hellwig wrote:
> Accessing if_bytes without the ilock is racy.  Remove the initial
> if_bytes == 0 check in xfs_reflink_end_cow_extent and let
> ext_iext_lookup_extent fail for this case after we've taken the ilock.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>

I wonder if this has any practical (mal)effects on the system?

Regardless,
Reviewed-by: Darrick J. Wong <djwong@kernel.org>

--D

> ---
>  fs/xfs/xfs_reflink.c | 6 ------
>  1 file changed, 6 deletions(-)
> 
> diff --git a/fs/xfs/xfs_reflink.c b/fs/xfs/xfs_reflink.c
> index 9ce37d366534c3..0ab2ef5b58f6c4 100644
> --- a/fs/xfs/xfs_reflink.c
> +++ b/fs/xfs/xfs_reflink.c
> @@ -731,12 +731,6 @@ xfs_reflink_end_cow_extent(
>  	int			nmaps;
>  	int			error;
>  
> -	/* No COW extents?  That's easy! */
> -	if (ifp->if_bytes == 0) {
> -		*offset_fsb = end_fsb;
> -		return 0;
> -	}
> -
>  	resblks = XFS_EXTENTADD_SPACE_RES(mp, XFS_DATA_FORK);
>  	error = xfs_trans_alloc(mp, &M_RES(mp)->tr_write, resblks, 0,
>  			XFS_TRANS_RESERVE, &tp);
> -- 
> 2.39.2
> 
>