[PATCH v2] xfs: fix the extent count when allocating an new indirection array entry

[Jeff Liu]

From: Jie Liu <jeff.liu at oracle.com>

At xfs_iext_add(), if extent(s) are being appended to the last page in
the indirection array and the new extent(s) don't fit in the page, the
number of extents(erp->er_extcount) in a new allocated entry should be
the minimum value between count and XFS_LINEAR_EXTS, instead of count.

For now, there is no existing test case can demonstrates a problem with
the er_extcount being set incorrectly here, but it obviously like a bug.

Signed-off-by: Jie Liu <jeff.liu at oracle.com>
---
v2: * Declare count to uint as it will be decreased to 0 and XFS_LINEAR_EXTS
      can be uint because of a case in the macro.
    * Convert MIN() to min().
    * Revise the commits log to indicate there is no existing test case can
      reflect this issue for future tracking up.

 fs/xfs/xfs_inode_fork.c |    9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/fs/xfs/xfs_inode_fork.c b/fs/xfs/xfs_inode_fork.c
index 22c9837..cfee14a 100644
--- a/fs/xfs/xfs_inode_fork.c
+++ b/fs/xfs/xfs_inode_fork.c
@@ -1021,15 +1021,14 @@ xfs_iext_add(
 		 * the next index needed in the indirection array.
 		 */
 		else {
-			int	count = ext_diff;
+			uint	count = ext_diff;
 
 			while (count) {
 				erp = xfs_iext_irec_new(ifp, erp_idx);
-				erp->er_extcount = count;
-				count -= MIN(count, (int)XFS_LINEAR_EXTS);
-				if (count) {
+				erp->er_extcount = min(count, XFS_LINEAR_EXTS);
+				count -= erp->er_extcount;
+				if (count)
 					erp_idx++;
-				}
 			}
 		}
 	}
-- 
1.7.9.5