Btrfs: Don't do btree balance_dirty_pages on old kernels, it stalls forever

Signed-off-by: Chris Mason <chris.mason@oracle.com>

1 files changed, 8 insertions, 0 deletions

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 9d5424ad01a3..c3083165b172 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -1655,6 +1655,11 @@ void btrfs_throttle(struct btrfs_root *root)
 
 void btrfs_btree_balance_dirty(struct btrfs_root *root, unsigned long nr)
 {
+        /*
+         * looks as though older kernels can get into trouble with
+         * this code, they end up stuck in balance_dirty_pages forever
+         */
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(2,6,23)
         struct extent_io_tree *tree;
         u64 num_dirty;
         u64 start = 0;
@@ -1670,6 +1675,9 @@ void btrfs_btree_balance_dirty(struct btrfs_root *root, unsigned long nr)
                 balance_dirty_pages_ratelimited_nr(
                                    root->fs_info->btree_inode->i_mapping, 1);
         }
+#else
+        return;
+#endif
 }
 
 void btrfs_set_buffer_defrag(struct extent_buffer *buf)