dm writecache: add unlikely for returned value of rb_next/prev

In functions writecache_discard() and writecache_find_entry() there is a
high probablity that the pointer of structure rb_node won't equal NULL.
Add unlikely for the pointer node NULL.

Signed-off-by: Huaisheng Ye <yehs1@lenovo.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>

diff --git a/drivers/md/dm-writecache.c b/drivers/md/dm-writecache.c
index 5b4d1c11eff14ac7430a15c6136037dd9bfa3eab..cfbbfbc028f97176a16245feb21183e698431a24 100644 (file)
--- a/drivers/md/dm-writecache.c
+++ b/drivers/md/dm-writecache.c
@@ -571,7 +571,7 @@ static struct wc_entry *writecache_find_entry(struct dm_writecache *wc,
                        node = rb_prev(&e->rb_node);
                else
                        node = rb_next(&e->rb_node);
-               if (!node)
+               if (unlikely(!node))
                        return e;
                e2 = container_of(node, struct wc_entry, rb_node);
                if (read_original_sector(wc, e2) != block)
@@ -804,7 +804,7 @@ static void writecache_discard(struct dm_writecache *wc, sector_t start, sector_
                        writecache_free_entry(wc, e);
                }
 
-               if (!node)
+               if (unlikely(!node))
                        break;
 
                e = container_of(node, struct wc_entry, rb_node);