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Date: Mon, 18 Jun 2018 10:10:26 +0200 From: Greg Kroah-Hartman <gregkh@...uxfoundation.org> To: linux-kernel@...r.kernel.org Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>, stable@...r.kernel.org, Jiang Biao <jiang.biao2@....com.cn>, Wen Yang <wen.yang99@....com.cn>, Tejun Heo <tj@...nel.org>, Jens Axboe <axboe@...nel.dk>, Sasha Levin <alexander.levin@...rosoft.com> Subject: [PATCH 4.16 041/279] blkcg: dont hold blkcg lock when deactivating policy 4.16-stable review patch. If anyone has any objections, please let me know. ------------------ From: Jiang Biao <jiang.biao2@....com.cn> [ Upstream commit 946b81da114b8ba5c74bb01e57c0c6eca2bdc801 ] 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@....com.cn> Signed-off-by: Wen Yang <wen.yang99@....com.cn> CC: Tejun Heo <tj@...nel.org> Signed-off-by: Jens Axboe <axboe@...nel.dk> Signed-off-by: Sasha Levin <alexander.levin@...rosoft.com> Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org> --- block/blk-cgroup.c | 5 ----- 1 file changed, 5 deletions(-) --- a/block/blk-cgroup.c +++ b/block/blk-cgroup.c @@ -1367,17 +1367,12 @@ void blkcg_deactivate_policy(struct requ __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 (pol->pd_offline_fn) pol->pd_offline_fn(blkg->pd[pol->plid]); pol->pd_free_fn(blkg->pd[pol->plid]); blkg->pd[pol->plid] = NULL; } - - spin_unlock(&blkg->blkcg->lock); } spin_unlock_irq(q->queue_lock);
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