xfs: Check for extent overflow when punching a hole

The extent mapping the file offset at which a hole has to be
inserted will be split into two extents causing extent count to
increase by 1.
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Chandan Babu R <chandanrlinux@gmail.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>

fs/xfs/libxfs/xfs_inode_fork.h

@@ -40,6 +40,13 @@ struct xfs_ifork {
  */
 #define XFS_IEXT_ADD_NOSPLIT_CNT	(1)
 
+/*
+ * Punching out an extent from the middle of an existing extent can cause the
+ * extent count to increase by 1.
+ * i.e. | Old extent | Hole | Old extent |
+ */
+#define XFS_IEXT_PUNCH_HOLE_CNT		(1)
+
 /*
  * Fork handling.
  */

fs/xfs/xfs_bmap_item.c

@@ -471,6 +471,7 @@ xfs_bui_item_recover(
 	xfs_exntst_t			state;
 	unsigned int			bui_type;
 	int				whichfork;
+	int				iext_delta;
 	int				error = 0;
 
 	if (!xfs_bui_validate(mp, buip)) {
@@ -508,12 +509,14 @@ xfs_bui_item_recover(
 	xfs_ilock(ip, XFS_ILOCK_EXCL);
 	xfs_trans_ijoin(tp, ip, 0);
 
-	if (bui_type == XFS_BMAP_MAP) {
-		error = xfs_iext_count_may_overflow(ip, whichfork,
-				XFS_IEXT_ADD_NOSPLIT_CNT);
+	if (bui_type == XFS_BMAP_MAP)
+		iext_delta = XFS_IEXT_ADD_NOSPLIT_CNT;
+	else
+		iext_delta = XFS_IEXT_PUNCH_HOLE_CNT;
+
+	error = xfs_iext_count_may_overflow(ip, whichfork, iext_delta);
 	if (error)
 		goto err_cancel;
-	}
 
 	count = bmap->me_len;
 	error = xfs_trans_log_finish_bmap_update(tp, budp, bui_type, ip,

fs/xfs/xfs_bmap_util.c

@@ -891,6 +891,11 @@ xfs_unmap_extent(
 
 	xfs_trans_ijoin(tp, ip, 0);
 
+	error = xfs_iext_count_may_overflow(ip, XFS_DATA_FORK,
+			XFS_IEXT_PUNCH_HOLE_CNT);
+	if (error)
+		goto out_trans_cancel;
+
 	error = xfs_bunmapi(tp, ip, startoffset_fsb, len_fsb, 0, 2, done);
 	if (error)
 		goto out_trans_cancel;
@@ -1168,6 +1173,11 @@ xfs_insert_file_space(
 	xfs_ilock(ip, XFS_ILOCK_EXCL);
 	xfs_trans_ijoin(tp, ip, 0);
 
+	error = xfs_iext_count_may_overflow(ip, XFS_DATA_FORK,
+			XFS_IEXT_PUNCH_HOLE_CNT);
+	if (error)
+		goto out_trans_cancel;
+
 	/*
 	 * The extent shifting code works on extent granularity. So, if stop_fsb
 	 * is not the starting block of extent, we need to split the extent at