Re: [PATCH] Introduce SEEK_DATA/SEEK_HOLE to XFS V2

[Jeff Liu <jeff.liu@oracle.com>]

CC to Dave.

Thanks,
-Jeff

On 11/22/2011 04:19 PM, Jeff Liu wrote:

> Hello,
> 
> This is the V2 attempt to add SEEK_DATA/SEEK_HOLE to XFS.
> 
> Changes:
> ========
> 1. Merge xfs_find_desired_extent() and xfs_seek_data_hole() into xfs_seek_extent(), and place it at xfs_file.c.
> 2. Using two different routines xfs_seek_data()/xfs_seek_hole() to handle SEEK_DATA/SEEK_HOLE requests respectively.
> 3. Remove some worthless result checking code from xfs_file_llseek().
> 4. s/xfs_mount_t/struct xfs_mount/g.
> 
> Tests:
> ======
> In addition to the seek_test.c I have used previously, I have also done a large sparse file copy tests, it works to me.
> 
> Hope I have not made obvious stupid mistakes this time. :-P.
> Any comments are appreciated!
> 
> 
> Signed-off-by: Jie Liu <jeff.liu@oracle.com>
> 
> ---
>  fs/xfs/xfs_file.c |  188 ++++++++++++++++++++++++++++++++++++++++++++++++++++-
>  1 files changed, 187 insertions(+), 1 deletions(-)
> 
> diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
> index 753ed9b..bb2be00 100644
> --- a/fs/xfs/xfs_file.c
> +++ b/fs/xfs/xfs_file.c
> @@ -1141,8 +1141,194 @@ xfs_vm_page_mkwrite(
>  	return block_page_mkwrite(vma, vmf, xfs_get_blocks);
>  }
>  
> +STATIC int
> +xfs_seek_data(
> +	struct xfs_inode *ip,
> +	loff_t *start)
> +{
> +	struct xfs_mount	*mp = ip->i_mount;
> +	struct xfs_ifork	*ifp;
> +	xfs_fileoff_t		fsbno;
> +	xfs_filblks_t		len;
> +	loff_t			startoff = *start;
> +	int			error = 0;
> +
> +	fsbno = XFS_B_TO_FSBT(mp, *start);
> +	ifp = XFS_IFORK_PTR(ip, XFS_DATA_FORK);
> +	len = XFS_B_TO_FSB(mp, ip->i_size);
> +
> +	for (;;) {
> +		struct xfs_bmbt_irec	map[2];
> +		int			nmap = 2;
> +		loff_t			seekoff;
> +
> +		error = xfs_bmapi_read(ip, fsbno, len - fsbno, map, &nmap,
> +				       XFS_BMAPI_ENTIRE);
> +		if (error)
> +			break;
> +
> +		/* No extents at given offset, must be beyond EOF */
> +		if (!nmap) {
> +			error = ENXIO;
> +			break;
> +		}
> +
> +		seekoff = XFS_FSB_TO_B(mp, fsbno);
> +
> +		/*
> +		 * Hole handling for unwritten extents landed in a hole.
> +		 * If the next extent is a data  extent, then return the
> +		 * start of it, otherwise we need to move the start offset
> +		 * and map more blocks.
> +		 */
> +		if (map[0].br_startblock == HOLESTARTBLOCK) {
> +			if (map[1].br_startblock == HOLESTARTBLOCK) {
> +				fsbno = map[1].br_startoff +
> +					map[1].br_blockcount;
> +			} else {
> +				*start = max_t(loff_t, seekoff,
> +				       XFS_FSB_TO_B(mp, map[1].br_startoff));
> +				break;
> +			}
> +		}
> +
> +		/*
> +		 * Landed in an in-memory data extent or in an allocated
> +		 * extent.
> +		 */
> +		if (map[0].br_startoff == DELAYSTARTBLOCK ||
> +		    map[0].br_state == XFS_EXT_NORM) {
> +			*start = max_t(loff_t, seekoff,
> +				       XFS_FSB_TO_B(mp, map[0].br_startoff));
> +			break;
> +		}
> +
> +		/* return ENXIO if beyond eof */
> +		if (XFS_FSB_TO_B(mp, fsbno) > ip->i_size) {
> +			error = ENXIO;
> +			break;
> +		}
> +	}
> +
> +	if (*start < startoff)
> +		*start = startoff;
> +
> +	return error;
> +}
> +
> +STATIC int
> +xfs_seek_hole(
> +	struct xfs_inode *ip,
> +	loff_t *start)
> +{
> +	struct xfs_mount	*mp = ip->i_mount;
> +	int			error = 0;
> +	loff_t			seekoff = *start;
> +	loff_t			holeoff;
> +	xfs_fileoff_t		fsbno;
> +
> +	fsbno = XFS_B_TO_FSBT(mp, *start);
> +	error = xfs_bmap_first_unused(NULL, ip, 1, &fsbno, XFS_DATA_FORK);
> +	if (error)
> +		return error;
> +
> +	holeoff = XFS_FSB_TO_B(mp, fsbno);
> +	if (holeoff <= seekoff)
> +		*start = seekoff;
> +	else
> +		*start = min_t(loff_t, holeoff, ip->i_size);
> +
> +	return error;
> +}
> +
> +STATIC int
> +xfs_seek_extent(
> +	struct inode		*inode,
> +	loff_t			*start,
> +	u32			type)
> +{
> +	struct xfs_inode	*ip = XFS_I(inode);
> +	struct xfs_mount	*mp = ip->i_mount;
> +	struct xfs_ifork	*ifp;
> +	int			lock;
> +	int			error = 0;
> +
> +	if (ip->i_d.di_format != XFS_DINODE_FMT_EXTENTS &&
> +	    ip->i_d.di_format != XFS_DINODE_FMT_BTREE &&
> +	    ip->i_d.di_format != XFS_DINODE_FMT_LOCAL)
> +		return XFS_ERROR(EINVAL);
> +
> +	lock = xfs_ilock_map_shared(ip);
> +
> +	if (XFS_FORCED_SHUTDOWN(mp)) {
> +		error = EIO;
> +		goto out_lock;
> +	}
> +
> +	XFS_STATS_INC(xs_blk_mapr);
> +	ifp = XFS_IFORK_PTR(ip, XFS_DATA_FORK);
> +
> +	ASSERT(ifp->if_ext_max ==
> +	      XFS_IFORK_SIZE(ip, XFS_DATA_FORK) / (uint)sizeof(xfs_bmbt_rec_t));
> +
> +	if (!(ifp->if_flags & XFS_IFEXTENTS)) {
> +		error = xfs_iread_extents(NULL, ip, XFS_DATA_FORK);
> +		if (error)
> +			goto out_lock;
> +	}
> +
> +	if (type == SEEK_HOLE)
> +		error = xfs_seek_hole(ip, start);
> +	else
> +		error = xfs_seek_data(ip, start);
> +
> +out_lock:
> +	xfs_iunlock_map_shared(ip, lock);
> +
> +	if (error)
> +		return -error;
> +
> +	return 0;
> +}
> +
> +STATIC loff_t
> +xfs_file_llseek(
> +	struct file *file,
> +	loff_t offset,
> +	int origin)
> +{
> +	struct inode *inode = file->f_mapping->host;
> +	int ret;
> +
> +	switch (origin) {
> +	case SEEK_END:
> +	case SEEK_CUR:
> +		offset = generic_file_llseek(file, offset, origin);
> +		goto out;
> +	case SEEK_DATA:
> +	case SEEK_HOLE:
> +		if (offset >= i_size_read(inode)) {
> +			ret = -ENXIO;
> +			goto error;
> +		}
> +
> +		ret = xfs_seek_extent(inode, &offset, origin);
> +		if (ret)
> +			goto error;
> +	}
> +
> +	if (offset != file->f_pos)
> +		file->f_pos = offset;
> +
> +out:
> +	return offset;
> +
> +error:
> +	return ret;
> +}
> +
>  const struct file_operations xfs_file_operations = {
> -	.llseek		= generic_file_llseek,
> +	.llseek		= xfs_file_llseek,
>  	.read		= do_sync_read,
>  	.write		= do_sync_write,
>  	.aio_read	= xfs_file_aio_read,


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