Commit 946b81da authored Apr 18, 2018 by Jiang Biao Committed by Jens Axboe Apr 18, 2018

blkcg: don't hold blkcg lock when deactivating policy



As described in the comment of blkcg_activate_policy(),
*Update of each blkg is protected by both queue and blkcg locks so
that holding either lock and testing blkcg_policy_enabled() is
always enough for dereferencing policy data.*
with queue lock held, there is no need to hold blkcg lock in
blkcg_deactivate_policy(). Similar case is in
blkcg_activate_policy(), which has removed holding of blkcg lock in
commit 4c55f4f9.

Signed-off-by: Jiang Biao <jiang.biao2@zte.com.cn>
Signed-off-by: Wen Yang <wen.yang99@zte.com.cn>
CC: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

parent 0ce91444

block/blk-cgroup.c

+0 −5

Original line number	Diff line number	Diff line
		@@ -1410,9 +1410,6 @@ void blkcg_deactivate_policy(struct request_queue *q,
		__clear_bit(pol->plid, q->blkcg_pols);

		list_for_each_entry(blkg, &q->blkg_list, q_node) {
		/* grab blkcg lock too while removing @pd from @blkg */
		spin_lock(&blkg->blkcg->lock);

		if (blkg->pd[pol->plid]) {
		if (!blkg->pd[pol->plid]->offline &&
		pol->pd_offline_fn) {
		@@ -1422,8 +1419,6 @@ void blkcg_deactivate_policy(struct request_queue *q,
		pol->pd_free_fn(blkg->pd[pol->plid]);
		blkg->pd[pol->plid] = NULL;
		}

		spin_unlock(&blkg->blkcg->lock);
		}

		spin_unlock_irq(q->queue_lock);