linux-kernel - Re: [PATCH] xfs: getattr ignore blocks beyond eof

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Date:   Wed, 30 Mar 2022 17:38:26 -0700
From:   "Darrick J. Wong" <djwong@...nel.org>
To:     Yi Wang <wang.yi59@....com.cn>
Cc:     linux-xfs@...r.kernel.org, linux-kernel@...r.kernel.org,
        xue.zhihong@....com.cn, wang.liang82@....com.cn,
        Cheng Lin <cheng.lin130@....com.cn>
Subject: Re: [PATCH] xfs: getattr ignore blocks beyond eof

On Thu, Mar 31, 2022 at 04:02:56PM +0800, Yi Wang wrote:
> From: Cheng Lin <cheng.lin130@....com.cn>
> 
> Blocks beyond EOF, which preallocated, will be reclaimed at some time.
> These blocks can be ignored when getattr.
> 
> This patch will optimize query accuracy for getattr blocks.

Huh?  This subtracts posteof blocks from the query results, which makes
the results *less accurate*.  Those blocks are mapped to the file, hence
they are supposed to be counted in nblocks.

--D

> Signed-off-by: Cheng Lin <cheng.lin130@....com.cn>
> Signed-off-by: Yi Wang <wang.yi59@....com.cn>
> ---
>  fs/xfs/xfs_bmap_util.c |  1 +
>  fs/xfs/xfs_icache.c    |  1 +
>  fs/xfs/xfs_inode.h     |  1 +
>  fs/xfs/xfs_iomap.c     |  5 +++++
>  fs/xfs/xfs_iops.c      | 19 ++++++++++++++++++-
>  5 files changed, 26 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/xfs/xfs_bmap_util.c b/fs/xfs/xfs_bmap_util.c
> index eb2e387..9f4081d 100644
> --- a/fs/xfs/xfs_bmap_util.c
> +++ b/fs/xfs/xfs_bmap_util.c
> @@ -753,6 +753,7 @@
>  	if (error)
>  		goto out_unlock;
>  
> +	ip->i_last_fsb = end_fsb;
>  	xfs_inode_clear_eofblocks_tag(ip);
>  	goto out_unlock;
>  
> diff --git a/fs/xfs/xfs_icache.c b/fs/xfs/xfs_icache.c
> index 9644f93..43ffb9e 100644
> --- a/fs/xfs/xfs_icache.c
> +++ b/fs/xfs/xfs_icache.c
> @@ -102,6 +102,7 @@ struct xfs_inode *
>  	memset(&ip->i_df, 0, sizeof(ip->i_df));
>  	ip->i_flags = 0;
>  	ip->i_delayed_blks = 0;
> +	ip->i_last_fsb = 0;
>  	ip->i_diflags2 = mp->m_ino_geo.new_diflags2;
>  	ip->i_nblocks = 0;
>  	ip->i_forkoff = 0;
> diff --git a/fs/xfs/xfs_inode.h b/fs/xfs/xfs_inode.h
> index b7e8f14..56fc41b 100644
> --- a/fs/xfs/xfs_inode.h
> +++ b/fs/xfs/xfs_inode.h
> @@ -55,6 +55,7 @@
>  	unsigned long		i_flags;	/* see defined flags below */
>  	uint64_t		i_delayed_blks;	/* count of delay alloc blks */
>  	xfs_fsize_t		i_disk_size;	/* number of bytes in file */
> +	xfs_fileoff_t		i_last_fsb;	/* last fsb preallocated */
>  	xfs_rfsblock_t		i_nblocks;	/* # of direct & btree blocks */
>  	prid_t			i_projid;	/* owner's project id */
>  	xfs_extlen_t		i_extsize;	/* basic/minimum extent size */
> diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c
> index e552ce5..bd9266e 100644
> --- a/fs/xfs/xfs_iomap.c
> +++ b/fs/xfs/xfs_iomap.c
> @@ -881,6 +881,7 @@
>  	bool			eof = false, cow_eof = false, shared = false;
>  	int			allocfork = XFS_DATA_FORK;
>  	int			error = 0;
> +	xfs_fileoff_t		prealloc_last_fsb = 0;
>  
>  	if (xfs_is_shutdown(mp))
>  		return -EIO;
> @@ -1024,6 +1025,7 @@
>  				XFS_B_TO_FSB(mp, mp->m_super->s_maxbytes));
>  			ASSERT(p_end_fsb > offset_fsb);
>  			prealloc_blocks = p_end_fsb - end_fsb;
> +			prealloc_last_fsb = p_end_fsb;
>  		}
>  	}
>  
> @@ -1049,6 +1051,9 @@
>  		goto out_unlock;
>  	}
>  
> +	if (prealloc_last_fsb && prealloc_blocks)
> +		ip->i_last_fsb = prealloc_last_fsb;
> +
>  	if (allocfork == XFS_COW_FORK) {
>  		trace_xfs_iomap_alloc(ip, offset, count, allocfork, &cmap);
>  		goto found_cow;
> diff --git a/fs/xfs/xfs_iops.c b/fs/xfs/xfs_iops.c
> index b79b384..ca0372c 100644
> --- a/fs/xfs/xfs_iops.c
> +++ b/fs/xfs/xfs_iops.c
> @@ -559,8 +559,14 @@
>  	struct xfs_inode	*ip = XFS_I(inode);
>  	struct xfs_mount	*mp = ip->i_mount;
>  
> +	xfs_off_t		fsb_beyond_eof;
> +	xfs_fileoff_t		end_fsb;
> +
>  	trace_xfs_getattr(ip);
>  
> +	end_fsb = XFS_B_TO_FSB(mp, (xfs_ufsize_t)XFS_ISIZE(ip));
> +	fsb_beyond_eof = ip->i_last_fsb - end_fsb;
> +
>  	if (xfs_is_shutdown(mp))
>  		return -EIO;
>  
> @@ -574,7 +580,15 @@
>  	stat->atime = inode->i_atime;
>  	stat->mtime = inode->i_mtime;
>  	stat->ctime = inode->i_ctime;
> -	stat->blocks = XFS_FSB_TO_BB(mp, ip->i_nblocks + ip->i_delayed_blks);
> +
> +	if (fsb_beyond_eof > 0) {
> +		stat->blocks =
> +		XFS_FSB_TO_BB(mp, ip->i_nblocks + ip->i_delayed_blks)
> +				  - fsb_beyond_eof;
> +	} else {
> +		stat->blocks =
> +		XFS_FSB_TO_BB(mp, ip->i_nblocks + ip->i_delayed_blks);
> +	}
>  
>  	if (xfs_has_v3inodes(mp)) {
>  		if (request_mask & STATX_BTIME) {
> @@ -988,6 +1002,9 @@
>  	ip->i_disk_size = newsize;
>  	xfs_trans_log_inode(tp, ip, XFS_ILOG_CORE);
>  
> +	/* update i_last_fsb to newsize when truncate.*/
> +	ip->i_last_fsb = XFS_B_TO_FSB(mp, newsize);
> +
>  	if (newsize <= oldsize) {
>  		error = xfs_itruncate_extents(&tp, ip, XFS_DATA_FORK, newsize);
>  		if (error)
> -- 
> 1.8.3.1