From: Darrick J. Wong <darrick.wong@oracle.com>
Date: Mon, 10 Oct 2016 05:47:40 +0000 (+1100)
Subject: xfs: reduce stack usage of _reflink_clear_inode_flag
X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=024adf48702212b0af15c682a7ff9773e1e092d6;p=linux-beck.git

xfs: reduce stack usage of _reflink_clear_inode_flag

The loop in _reflink_clear_inode_flag isn't necessary since we
jump out if any part of any extent is shared.  Remove the loop
and we no longer need two maps, so we can save some stack use.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reported-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
---

diff --git a/fs/xfs/xfs_reflink.c b/fs/xfs/xfs_reflink.c
index 9c58b4a83248..c4e35dccb803 100644
--- a/fs/xfs/xfs_reflink.c
+++ b/fs/xfs/xfs_reflink.c
@@ -1507,7 +1507,7 @@ xfs_reflink_clear_inode_flag(
 	xfs_extlen_t		aglen;
 	xfs_agblock_t		rbno;
 	xfs_extlen_t		rlen;
-	struct xfs_bmbt_irec	map[2];
+	struct xfs_bmbt_irec	map;
 	int			nmaps;
 	int			error = 0;
 
@@ -1521,37 +1521,29 @@ xfs_reflink_clear_inode_flag(
 		 * Look for extents in the file.  Skip holes, delalloc, or
 		 * unwritten extents; they can't be reflinked.
 		 */
-		error = xfs_bmapi_read(ip, fbno, end - fbno, map, &nmaps, 0);
+		error = xfs_bmapi_read(ip, fbno, end - fbno, &map, &nmaps, 0);
 		if (error)
 			return error;
 		if (nmaps == 0)
 			break;
-		if (map[0].br_startblock == HOLESTARTBLOCK ||
-		    map[0].br_startblock == DELAYSTARTBLOCK ||
-		    ISUNWRITTEN(&map[0]))
+		if (map.br_startblock == HOLESTARTBLOCK ||
+		    map.br_startblock == DELAYSTARTBLOCK ||
+		    ISUNWRITTEN(&map))
 			goto next;
 
-		map[1] = map[0];
-		while (map[1].br_blockcount) {
-			agno = XFS_FSB_TO_AGNO(mp, map[1].br_startblock);
-			agbno = XFS_FSB_TO_AGBNO(mp, map[1].br_startblock);
-			aglen = map[1].br_blockcount;
-
-			error = xfs_reflink_find_shared(mp, agno, agbno, aglen,
-					&rbno, &rlen, false);
-			if (error)
-				return error;
-			/* Is there still a shared block here? */
-			if (rbno != NULLAGBLOCK)
-				return 0;
-
-			map[1].br_blockcount -= aglen;
-			map[1].br_startoff += aglen;
-			map[1].br_startblock += aglen;
-		}
+		agno = XFS_FSB_TO_AGNO(mp, map.br_startblock);
+		agbno = XFS_FSB_TO_AGBNO(mp, map.br_startblock);
+		aglen = map.br_blockcount;
 
+		error = xfs_reflink_find_shared(mp, agno, agbno, aglen,
+				&rbno, &rlen, false);
+		if (error)
+			return error;
+		/* Is there still a shared block here? */
+		if (rbno != NULLAGBLOCK)
+			return 0;
 next:
-		fbno = map[0].br_startoff + map[0].br_blockcount;
+		fbno = map.br_startoff + map.br_blockcount;
 	}
 
 	/*