dm writecache: avoid unnecessary lookups in writecache_find_entry()

This is a small optimization in writecache_find_entry().

If we go past the condition "if (unlikely(!node))", we can be certain that
there is no entry in the tree that has the block equal to the "block"
variable.

Consequently, we can return the next entry directly, we don't need to go
to the second part of the function that finds the entry with lowest or
highest seq number that matches the "block" variable.

Also, add some whitespace and cleanup needless braces.

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

diff --git a/drivers/md/dm-writecache.c b/drivers/md/dm-writecache.c
index ddf1732dae506c8a3528c6c70f375bdb94a7ce49..1cb137f0ef9d7f4b265779563273ed82d136eee3 100644 (file)
--- a/drivers/md/dm-writecache.c
+++ b/drivers/md/dm-writecache.c
@@ -545,21 +545,20 @@ static struct wc_entry *writecache_find_entry(struct dm_writecache *wc,
                e = container_of(node, struct wc_entry, rb_node);
                if (read_original_sector(wc, e) == block)
                        break;
+
                node = (read_original_sector(wc, e) >= block ?
                        e->rb_node.rb_left : e->rb_node.rb_right);
                if (unlikely(!node)) {
-                       if (!(flags & WFE_RETURN_FOLLOWING)) {
+                       if (!(flags & WFE_RETURN_FOLLOWING))
                                return NULL;
-                       }
                        if (read_original_sector(wc, e) >= block) {
-                               break;
+                               return e;
                        } else {
                                node = rb_next(&e->rb_node);
-                               if (unlikely(!node)) {
+                               if (unlikely(!node))
                                        return NULL;
-                               }
                                e = container_of(node, struct wc_entry, rb_node);
-                               break;
+                               return e;
                        }
                }
        }