linux-kernel - [PATCH 5.8 159/186] blk-iocost: ioc_pd_free() shouldnt assume irq disabled

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Message-Id: <20200908152249.370435259@linuxfoundation.org>
Date:   Tue,  8 Sep 2020 17:25:01 +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, Tejun Heo <tj@...nel.org>,
        Jens Axboe <axboe@...nel.dk>
Subject: [PATCH 5.8 159/186] blk-iocost: ioc_pd_free() shouldnt assume irq disabled

From: Tejun Heo <tj@...nel.org>

commit 5aeac7c4b16069aae49005f0a8d4526baa83341b upstream.

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+
Signed-off-by: Jens Axboe <axboe@...nel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 block/blk-iocost.c |    5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

--- a/block/blk-iocost.c
+++ b/block/blk-iocost.c
@@ -2094,14 +2094,15 @@ static void ioc_pd_free(struct blkg_poli
 {
 	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);