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 4c55f4f9ad3001ac1fefdd8d8ca7641d18558e23.

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>

1 files changed, 0 insertions, 5 deletions

diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index 1c16694ae145..21bc449d01c0 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -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);