linux-kernel - [PATCH 01/27] blk-iocost: ioc_pd_free() shouldn't assume irq disabled

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Message-Id: <20200901185257.645114-2-tj@kernel.org>
Date:   Tue,  1 Sep 2020 14:52:31 -0400
From:   Tejun Heo <tj@...nel.org>
To:     axboe@...nel.dk
Cc:     linux-block@...r.kernel.org, cgroups@...r.kernel.org,
        linux-kernel@...r.kernel.org, kernel-team@...com, newella@...com,
        Tejun Heo <tj@...nel.org>, stable@...r.kernel.org
Subject: [PATCH 01/27] blk-iocost: ioc_pd_free() shouldn't assume irq disabled

ioc_pd_free() grabs irq-safe ioc->lock without ensuring that irq is disabled
when it can be called with irq disabled or enabled. This has a small chance
of causing A-A deadlocks and triggers lockdep splats. Use irqsave operations
instead.

Signed-off-by: Tejun Heo <tj@...nel.org>
Fixes: 7caa47151ab2 ("blkcg: implement blk-iocost")
Cc: stable@...r.kernel.org # v5.4+
---
 block/blk-iocost.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/block/blk-iocost.c b/block/blk-iocost.c
index 413e0b5c8e6b..d37b55db2409 100644
--- a/block/blk-iocost.c
+++ b/block/blk-iocost.c
@@ -2092,14 +2092,15 @@ static void ioc_pd_free(struct blkg_policy_data *pd)
 {
 	struct ioc_gq *iocg = pd_to_iocg(pd);
 	struct ioc *ioc = iocg->ioc;
+	unsigned long flags;
 
 	if (ioc) {
-		spin_lock(&ioc->lock);
+		spin_lock_irqsave(&ioc->lock, flags);
 		if (!list_empty(&iocg->active_list)) {
 			propagate_active_weight(iocg, 0, 0);
 			list_del_init(&iocg->active_list);
 		}
-		spin_unlock(&ioc->lock);
+		spin_unlock_irqrestore(&ioc->lock, flags);
 
 		hrtimer_cancel(&iocg->waitq_timer);
 		hrtimer_cancel(&iocg->delay_timer);
-- 
2.26.2