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>

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index f7c65ca056f8d498146c17182af678ce467cf434..25c422b11bdbbad4fd7fa41f3158ca4c6284b300 100644 (file)
--- 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);