Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit f73c35d9 authored by Coly Li's avatar Coly Li Committed by Greg Kroah-Hartman
Browse files

bcache: add comments for mutex_lock(&b->write_lock) 



[ Upstream commit 41508bb7d46b74dba631017e5a702a86caf1db8c ]

When accessing or modifying BTREE_NODE_dirty bit, it is not always
necessary to acquire b->write_lock. In bch_btree_cache_free() and
mca_reap() acquiring b->write_lock is necessary, and this patch adds
comments to explain why mutex_lock(&b->write_lock) is necessary for
checking or clearing BTREE_NODE_dirty bit there.

Signed-off-by: default avatarColy Li <colyli@suse.de>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
Signed-off-by: default avatarSasha Levin <sashal@kernel.org>
parent 7989a502

drivers/md/bcache/btree.c

+10 −0
Original line number Diff line number Diff line
@@ -649,6 +649,11 @@ static int mca_reap(struct btree *b, unsigned int min_order, bool flush) 
		up(&b->io_mutex);

	}



	/*

	 * BTREE_NODE_dirty might be cleared in btree_flush_btree() by

	 * __bch_btree_node_write(). To avoid an extra flush, acquire

	 * b->write_lock before checking BTREE_NODE_dirty bit.

	 */

	mutex_lock(&b->write_lock);

	if (btree_node_dirty(b))

		__bch_btree_node_write(b, &cl);
@@ -772,6 +777,11 @@ 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);



		/*

		 * This function is called by cache_set_free(), no I/O

		 * request on cache now, it is unnecessary to acquire

		 * b->write_lock before clearing BTREE_NODE_dirty anymore.

		 */

		if (btree_node_dirty(b)) {

			btree_complete_write(b, btree_current_write(b));

			clear_bit(BTREE_NODE_dirty, &b->flags);