Commit 3fe3e6b1 authored by Jeff Liu's avatar Jeff Liu Committed by Ben Myers
Browse files

xfs: introduce SEEK_DATA/SEEK_HOLE support 



This patch adds lseek(2) SEEK_DATA/SEEK_HOLE functionality to xfs.

Signed-off-by: default avatarJie Liu <jeff.liu@oracle.com>
Reviewed-by: default avatarMark Tinguely <tinguely@sgi.com>
Signed-off-by: default avatarBen Myers <bpm@sgi.com>
parent e700a06c

fs/xfs/xfs_file.c

+142 −1
Original line number Diff line number Diff line
@@ -963,8 +963,149 @@ xfs_vm_page_mkwrite( 
	return block_page_mkwrite(vma, vmf, xfs_get_blocks);

}



STATIC loff_t

xfs_seek_data(

	struct file		*file,

	loff_t			start,

	u32			type)

{

	struct inode		*inode = file->f_mapping->host;

	struct xfs_inode	*ip = XFS_I(inode);

	struct xfs_mount	*mp = ip->i_mount;

	struct xfs_bmbt_irec	map[2];

	int			nmap = 2;

	loff_t			uninitialized_var(offset);

	xfs_fsize_t		isize;

	xfs_fileoff_t		fsbno;

	xfs_filblks_t		end;

	uint			lock;

	int			error;



	lock = xfs_ilock_map_shared(ip);



	isize = i_size_read(inode);

	if (start >= isize) {

		error = ENXIO;

		goto out_unlock;

	}



	fsbno = XFS_B_TO_FSBT(mp, start);



	/*

	 * Try to read extents from the first block indicated

	 * by fsbno to the end block of the file.

	 */

	end = XFS_B_TO_FSB(mp, isize);



	error = xfs_bmapi_read(ip, fsbno, end - fsbno, map, &nmap,

			       XFS_BMAPI_ENTIRE);

	if (error)

		goto out_unlock;



	/*

	 * Treat unwritten extent as data extent since it might

	 * contains dirty data in page cache.

	 */

	if (map[0].br_startblock != HOLESTARTBLOCK) {

		offset = max_t(loff_t, start,

			       XFS_FSB_TO_B(mp, map[0].br_startoff));

	} else {

		if (nmap == 1) {

			error = ENXIO;

			goto out_unlock;

		}



		offset = max_t(loff_t, start,

			       XFS_FSB_TO_B(mp, map[1].br_startoff));

	}



	if (offset != file->f_pos)

		file->f_pos = offset;



out_unlock:

	xfs_iunlock_map_shared(ip, lock);



	if (error)

		return -error;

	return offset;

}



STATIC loff_t

xfs_seek_hole(

	struct file		*file,

	loff_t			start,

	u32			type)

{

	struct inode		*inode = file->f_mapping->host;

	struct xfs_inode	*ip = XFS_I(inode);

	struct xfs_mount	*mp = ip->i_mount;

	loff_t			uninitialized_var(offset);

	loff_t			holeoff;

	xfs_fsize_t		isize;

	xfs_fileoff_t		fsbno;

	uint			lock;

	int			error;



	if (XFS_FORCED_SHUTDOWN(mp))

		return -XFS_ERROR(EIO);



	lock = xfs_ilock_map_shared(ip);



	isize = i_size_read(inode);

	if (start >= isize) {

		error = ENXIO;

		goto out_unlock;

	}



	fsbno = XFS_B_TO_FSBT(mp, start);

	error = xfs_bmap_first_unused(NULL, ip, 1, &fsbno, XFS_DATA_FORK);

	if (error)

		goto out_unlock;



	holeoff = XFS_FSB_TO_B(mp, fsbno);

	if (holeoff <= start)

		offset = start;

	else {

		/*

		 * xfs_bmap_first_unused() could return a value bigger than

		 * isize if there are no more holes past the supplied offset.

		 */

		offset = min_t(loff_t, holeoff, isize);

	}



	if (offset != file->f_pos)

		file->f_pos = offset;



out_unlock:

	xfs_iunlock_map_shared(ip, lock);



	if (error)

		return -error;

	return offset;

}



STATIC loff_t

xfs_file_llseek(

	struct file	*file,

	loff_t		offset,

	int		origin)

{

	switch (origin) {

	case SEEK_END:

	case SEEK_CUR:

	case SEEK_SET:

		return generic_file_llseek(file, offset, origin);

	case SEEK_DATA:

		return xfs_seek_data(file, offset, origin);

	case SEEK_HOLE:

		return xfs_seek_hole(file, offset, origin);

	default:

		return -EINVAL;

	}

}



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,