Commit e5ec5f47 authored Jun 28, 2019 by Coly Li Committed by Jens Axboe Jun 28, 2019

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>

parent 249a5f6d

drivers/md/bcache/btree.c

+6 −5

Original line number	Diff line number	Diff line
		@@ -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);

		}
		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);
		}

		mutex_unlock(&b->write_lock);

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