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Commit 52f1acc8 authored by Jeff Liu's avatar Jeff Liu Committed by Ben Myers
Browse files

xfs: xfs_seek_data() refinement with unwritten extents check up from page cache 



xfs_seek_data() refinement with unwritten extents check up from page cache.

Signed-off-by: default avatarJie Liu <jeff.liu@oracle.com>
Reviewed-by: default avatarMark Tinguely <tinguely@sgi.com>
Reviewed-by: default avatarDave Chinner <dchinner@redhat.com>
Signed-off-by: default avatarBen Myers <bpm@sgi.com>
parent d126d43f

fs/xfs/xfs_file.c

+54 −18
Original line number Diff line number Diff line
@@ -1186,8 +1186,6 @@ xfs_seek_data( 
	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;
@@ -1203,36 +1201,74 @@ xfs_seek_data( 
		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.

	 */

	fsbno = XFS_B_TO_FSBT(mp, start);

	end = XFS_B_TO_FSB(mp, isize);

	for (;;) {

		struct xfs_bmbt_irec	map[2];

		int			nmap = 2;

		unsigned int		i;



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

				       XFS_BMAPI_ENTIRE);

		if (error)

			goto out_unlock;



		/* No extents at given offset, must be beyond EOF */

		if (nmap == 0) {

			error = ENXIO;

			goto out_unlock;

		}



		for (i = 0; i < nmap; i++) {

			offset = max_t(loff_t, start,

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



			/* Landed in a data extent */

			if (map[i].br_startblock == DELAYSTARTBLOCK ||

			    (map[i].br_state == XFS_EXT_NORM &&

			     !isnullstartblock(map[i].br_startblock)))

				goto out;



			/*

	 * Treat unwritten extent as data extent since it might

	 * contains dirty data in page cache.

			 * Landed in an unwritten extent, try to search data

			 * from page cache.

			 */

			if (map[i].br_state == XFS_EXT_UNWRITTEN) {

				if (xfs_find_get_desired_pgoff(inode, &map[i],

							DATA_OFF, &offset))

					goto out;

			}

		}



		/*

		 * map[0] is hole or its an unwritten extent but

		 * without data in page cache.  Probably means that

		 * we are reading after EOF if nothing in map[1].

		 */

	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));

		ASSERT(i > 1);



		/*

		 * Nothing was found, proceed to the next round of search

		 * if reading offset not beyond or hit EOF.

		 */

		fsbno = map[i - 1].br_startoff + map[i - 1].br_blockcount;

		start = XFS_FSB_TO_B(mp, fsbno);

		if (start >= isize) {

			error = ENXIO;

			goto out_unlock;

		}

	}



out:

	if (offset != file->f_pos)

		file->f_pos = offset;