linux-kernel - Re: [PATCH v3 10/14] xfs: Do not free EOF blocks for forcealign

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Message-ID: <20240806192441.GM623936@frogsfrogsfrogs>
Date: Tue, 6 Aug 2024 12:24:41 -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 v3 10/14] xfs: Do not free EOF blocks for forcealign

On Thu, Aug 01, 2024 at 04:30:53PM +0000, John Garry wrote:
> For when forcealign is enabled, we want the EOF to be aligned as well, so
> do not free EOF blocks.
> 
> Reviewed-by: "Darrick J. Wong" <djwong@...nel.org> #earlier version
> Signed-off-by: John Garry <john.g.garry@...cle.com>
> ---
>  fs/xfs/xfs_bmap_util.c |  7 +++++--
>  fs/xfs/xfs_inode.c     | 14 ++++++++++++++
>  fs/xfs/xfs_inode.h     |  2 ++
>  3 files changed, 21 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/xfs/xfs_bmap_util.c b/fs/xfs/xfs_bmap_util.c
> index fe2e2c930975..60389ac8bd45 100644
> --- a/fs/xfs/xfs_bmap_util.c
> +++ b/fs/xfs/xfs_bmap_util.c
> @@ -496,6 +496,7 @@ xfs_can_free_eofblocks(
>  	struct xfs_mount	*mp = ip->i_mount;
>  	xfs_fileoff_t		end_fsb;
>  	xfs_fileoff_t		last_fsb;
> +	xfs_fileoff_t		dummy_fsb;
>  	int			nimaps = 1;
>  	int			error;
>  
> @@ -537,8 +538,10 @@ xfs_can_free_eofblocks(
>  	 * forever.
>  	 */
>  	end_fsb = XFS_B_TO_FSB(mp, (xfs_ufsize_t)XFS_ISIZE(ip));
> -	if (xfs_inode_has_bigrtalloc(ip))
> -		end_fsb = xfs_rtb_roundup_rtx(mp, end_fsb);
> +
> +	/* Only try to free beyond the allocation unit that crosses EOF */
> +	xfs_roundout_to_alloc_fsbsize(ip, &dummy_fsb, &end_fsb);
> +
>  	last_fsb = XFS_B_TO_FSB(mp, mp->m_super->s_maxbytes);
>  	if (last_fsb <= end_fsb)
>  		return false;
> diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c
> index 5af12f35062d..d765dedebc15 100644
> --- a/fs/xfs/xfs_inode.c
> +++ b/fs/xfs/xfs_inode.c
> @@ -3129,6 +3129,20 @@ xfs_inode_alloc_unitsize(
>  	return XFS_FSB_TO_B(ip->i_mount, xfs_inode_alloc_fsbsize(ip));
>  }
>  
> +void
> +xfs_roundout_to_alloc_fsbsize(
> +	struct xfs_inode	*ip,
> +	xfs_fileoff_t		*start,
> +	xfs_fileoff_t		*end)
> +{
> +	unsigned int		blocks = xfs_inode_alloc_fsbsize(ip);
> +
> +	if (blocks == 1)
> +		return;
> +	*start = rounddown_64(*start, blocks);
> +	*end = roundup_64(*end, blocks);
> +}

This is probably going to start another round of shouting, but I think
it's silly to do two rounding operations when you only care about one
value.  In patch 12 it results in a bunch more dummy variables that you
then ignore.

Can't this be:

static inline xfs_fileoff_t
xfs_inode_rounddown_alloc_unit(
	struct xfs_inode	*ip,
	xfs_fileoff		off)
{
	unsigned int		rounding = xfs_inode_alloc_fsbsize(ip);

	if (rounding == 1)
		return off;
	return rounddown_64(off, rounding);
}

static inline xfs_fileoff_t
xfs_inode_roundup_alloc_unit(
	struct xfs_inode	*ip,
	xfs_fileoff		off)
{
	unsigned int		rounding = xfs_inode_alloc_fsbsize(ip);

	if (rounding == 1)
		return off;
	return roundup_64(off, rounding);
}

Then that callsite can be:

	end_fsb = xfs_inode_roundup_alloc_unit(ip,
			XFS_B_TO_FSB(mp, (xfs_ufsize_t)XFS_ISIZE(ip)));

--D

> +
>  /* Should we always be using copy on write for file writes? */
>  bool
>  xfs_is_always_cow_inode(
> diff --git a/fs/xfs/xfs_inode.h b/fs/xfs/xfs_inode.h
> index 158afad8c7a4..7f86c4781bd8 100644
> --- a/fs/xfs/xfs_inode.h
> +++ b/fs/xfs/xfs_inode.h
> @@ -643,6 +643,8 @@ void xfs_inode_count_blocks(struct xfs_trans *tp, struct xfs_inode *ip,
>  		xfs_filblks_t *dblocks, xfs_filblks_t *rblocks);
>  unsigned int xfs_inode_alloc_fsbsize(struct xfs_inode *ip);
>  unsigned int xfs_inode_alloc_unitsize(struct xfs_inode *ip);
> +void xfs_roundout_to_alloc_fsbsize(struct xfs_inode *ip,
> +		xfs_fileoff_t *start, xfs_fileoff_t *end);
>  
>  int xfs_icreate_dqalloc(const struct xfs_icreate_args *args,
>  		struct xfs_dquot **udqpp, struct xfs_dquot **gdqpp,
> -- 
> 2.31.1
> 
>