Btrfs: more efficient io tree navigation on wait_extent_bit

If we don't reschedule use rb_next to find the next extent state
instead of a full tree search, which is more efficient and safe
since we didn't release the io tree's lock.

Signed-off-by: Filipe David Borba Manana <fdmanana@gmail.com>
Signed-off-by: Chris Mason <clm@fb.com>

1 files changed, 5 insertions, 1 deletions

diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index d35a3ca15fb5..0c4389634985 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -749,6 +749,7 @@ again:
                  * our range starts
                  */
                 node = tree_search(tree, start);
+process_node:
                 if (!node)
                         break;
 
@@ -769,7 +770,10 @@ again:
                 if (start > end)
                         break;
 
-                cond_resched_lock(&tree->lock);
+                if (!cond_resched_lock(&tree->lock)) {
+                        node = rb_next(node);
+                        goto process_node;
+                }
         }
 out:
         spin_unlock(&tree->lock);