bcache: only clear BTREE_NODE_dirty bit when it is set

In bch_btree_cache_free() and btree_node_free(), BTREE_NODE_dirty is
always set no matter btree node is dirty or not. The code looks like
this,
	if (btree_node_dirty(b))
		btree_complete_write(b, btree_current_write(b));
	clear_bit(BTREE_NODE_dirty, &b->flags);

Indeed if btree_node_dirty(b) returns false, it means BTREE_NODE_dirty
bit is cleared, then it is unnecessary to clear the bit again.

This patch only clears BTREE_NODE_dirty when btree_node_dirty(b) is
true (the bit is set), to save a few CPU cycles.

Signed-off-by: Coly Li <colyli@suse.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/drivers/md/bcache/btree.c b/drivers/md/bcache/btree.c
index cf38a1b..88e5aa3 100644 (file)
--- a/drivers/md/bcache/btree.c
+++ b/drivers/md/bcache/btree.c
@@ -782,10 +782,10 @@ void bch_btree_cache_free(struct cache_set *c)
        while (!list_empty(&c->btree_cache)) {
                b = list_first_entry(&c->btree_cache, struct btree, list);
 
-               if (btree_node_dirty(b))
+               if (btree_node_dirty(b)) {
                        btree_complete_write(b, btree_current_write(b));
-               clear_bit(BTREE_NODE_dirty, &b->flags);
-
+                       clear_bit(BTREE_NODE_dirty, &b->flags);
+               }
                mca_data_free(b);
        }
 
@@ -1073,9 +1073,10 @@ static void btree_node_free(struct btree *b)
 
        mutex_lock(&b->write_lock);
 
-       if (btree_node_dirty(b))
+       if (btree_node_dirty(b)) {
                btree_complete_write(b, btree_current_write(b));
-       clear_bit(BTREE_NODE_dirty, &b->flags);
+               clear_bit(BTREE_NODE_dirty, &b->flags);
+       }
 
        mutex_unlock(&b->write_lock);