Btrfs: btrfs_defrag_file: Fix ra_index computation.

Read-ahead is done for the pages in the range [ra_index, ra_index + cluster -
1]. So the next read-ahead should be starting from the page at index 'ra_index
+ cluster' (unless we deemed that the extent at 'ra_index + cluster' as
non-defraggable) rather than from the page at index 'ra_index +
max_cluster'. This patch fixes this. I did run the xfstests suite to make sure
that the code does not regress.

Signed-off-by: Chandan Rajendra <chandan@linux.vnet.ibm.com>
Signed-off-by: Chris Mason <clm@fb.com>

1 files changed, 1 insertions, 1 deletions

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index f7c65ca..25c422b 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -1368,7 +1368,7 @@ int btrfs_defrag_file(struct inode *inode, struct file *file,
 			ra_index = max(i, ra_index);
 			btrfs_force_ra(inode->i_mapping, ra, file, ra_index,
 				       cluster);
-			ra_index += max_cluster;
+			ra_index += cluster;
 		}
 
 		mutex_lock(&inode->i_mutex);