[PATCH 5.2 18/37] bcache: only clear BTREE_NODE_dirty bit when it is set

[Greg Kroah-Hartman]

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 <col...@suse.de>
Signed-off-by: Jens Axboe <ax...@kernel.dk>
---
 drivers/md/bcache/btree.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/drivers/md/bcache/btree.c b/drivers/md/bcache/btree.c
index 773f5fdad25fb..3fbadf2058a65 100644
--- a/drivers/md/bcache/btree.c
+++ b/drivers/md/bcache/btree.c
@@ -778,10 +778,10 @@ 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);
        }
 
@@ -1069,9 +1069,10 @@ 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);
 
-- 
2.20.1