linux-kernel - Re: [PATCH 10/13] xfs: Unmap blocks according to forcealign

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Date: Fri, 21 Jun 2024 12:12:47 -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 10/13] xfs: Unmap blocks according to forcealign

On Fri, Jun 21, 2024 at 10:05:37AM +0000, John Garry wrote:
> For when forcealign is enabled, blocks in an inode need to be unmapped
> according to extent alignment, like what is already done for rtvol.
> 
> Signed-off-by: John Garry <john.g.garry@...cle.com>
> ---
>  fs/xfs/libxfs/xfs_bmap.c | 38 +++++++++++++++++++++++++++++++++-----
>  1 file changed, 33 insertions(+), 5 deletions(-)
> 
> diff --git a/fs/xfs/libxfs/xfs_bmap.c b/fs/xfs/libxfs/xfs_bmap.c
> index c9cf138e13c4..ebeb2969b289 100644
> --- a/fs/xfs/libxfs/xfs_bmap.c
> +++ b/fs/xfs/libxfs/xfs_bmap.c
> @@ -5380,6 +5380,25 @@ xfs_bmap_del_extent_real(
>  	return 0;
>  }
>  
> +static xfs_extlen_t
> +xfs_bunmapi_align(
> +	struct xfs_inode	*ip,
> +	xfs_fsblock_t		bno)
> +{
> +	struct xfs_mount	*mp = ip->i_mount;
> +	xfs_agblock_t		agbno;
> +
> +	if (xfs_inode_has_forcealign(ip)) {
> +		if (is_power_of_2(ip->i_extsize))
> +			return bno & (ip->i_extsize - 1);
> +
> +		agbno = XFS_FSB_TO_AGBNO(mp, bno);
> +		return do_div(agbno, ip->i_extsize);

Huh.  The inode verifier allows realtime forcealign files, but this code
will not handle that properly.  Either don't allow realtime files, or
make this handle them correctly:

	if (XFS_IS_REALTIME_INODE(ip)) {
		if (xfs_inode_has_forcealign(ip))
			return offset_in_block(bno, ip->i_extsize);
		return xfs_rtb_to_rtxoff(ip->i_mount, bno);
	} else if (xfs_inode_has_forcealign(ip)) {
		xfs_agblock_t	agbno = XFS_FSB_TO_AGBNO(mp, bno);

		return offset_in_block(agbno, ip->i_extsize);
	}

	return 1; /* or assert, or whatever */

> +	}
> +	ASSERT(XFS_IS_REALTIME_INODE(ip));
> +	return xfs_rtb_to_rtxoff(ip->i_mount, bno);
> +}
> +
>  /*
>   * Unmap (remove) blocks from a file.
>   * If nexts is nonzero then the number of extents to remove is limited to
> @@ -5402,6 +5421,7 @@ __xfs_bunmapi(
>  	struct xfs_bmbt_irec	got;		/* current extent record */
>  	struct xfs_ifork	*ifp;		/* inode fork pointer */
>  	int			isrt;		/* freeing in rt area */
> +	int			isforcealign;	/* freeing for inode with forcealign */
>  	int			logflags;	/* transaction logging flags */
>  	xfs_extlen_t		mod;		/* rt extent offset */
>  	struct xfs_mount	*mp = ip->i_mount;
> @@ -5439,6 +5459,8 @@ __xfs_bunmapi(
>  	}
>  	XFS_STATS_INC(mp, xs_blk_unmap);
>  	isrt = xfs_ifork_is_realtime(ip, whichfork);
> +	isforcealign = (whichfork != XFS_ATTR_FORK) &&
> +			xfs_inode_has_forcealign(ip);
>  	end = start + len;
>  
>  	if (!xfs_iext_lookup_extent_before(ip, ifp, &end, &icur, &got)) {
> @@ -5490,11 +5512,10 @@ __xfs_bunmapi(
>  		if (del.br_startoff + del.br_blockcount > end + 1)
>  			del.br_blockcount = end + 1 - del.br_startoff;
>  
> -		if (!isrt || (flags & XFS_BMAPI_REMAP))
> +		if ((!isrt && !isforcealign) || (flags & XFS_BMAPI_REMAP))
>  			goto delete;
>  
> -		mod = xfs_rtb_to_rtxoff(mp,
> -				del.br_startblock + del.br_blockcount);
> +		mod = xfs_bunmapi_align(ip, del.br_startblock + del.br_blockcount);
>  		if (mod) {
>  			/*
>  			 * Realtime extent not lined up at the end.

"Not aligned to allocation unit on the end." ?

> @@ -5542,9 +5563,16 @@ __xfs_bunmapi(
>  			goto nodelete;
>  		}
>  
> -		mod = xfs_rtb_to_rtxoff(mp, del.br_startblock);
> +		mod = xfs_bunmapi_align(ip, del.br_startblock);
>  		if (mod) {
> -			xfs_extlen_t off = mp->m_sb.sb_rextsize - mod;
> +			xfs_extlen_t off;
> +
> +			if (isforcealign) {
> +				off = ip->i_extsize - mod;
> +			} else {
> +				ASSERT(isrt);
> +				off = mp->m_sb.sb_rextsize - mod;
> +			}
>  
>  			/*
>  			 * Realtime extent is lined up at the end but not

Same here -- now this code is handling more than just rt extents.

--D

> -- 
> 2.31.1
> 
>