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>

1 files changed, 2 insertions, 2 deletions

diff --git a/drivers/md/dm-writecache.c b/drivers/md/dm-writecache.c
index 5b4d1c11eff1..cfbbfbc028f9 100644
--- 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);