From: Andrea Parri <andrea.parri@amarulasolutions.com>
Date: Mon, 20 May 2019 17:23:57 +0000 (+0200)
Subject: sbitmap: fix improper use of smp_mb__before_atomic()
X-Git-Tag: Ubuntu-4.15.0-61.68~1621
X-Git-Url: https://git.proxmox.com/?p=mirror_ubuntu-bionic-kernel.git;a=commitdiff_plain;h=980ab6cc318c7357e9b139819fb3065dc0e8750d

sbitmap: fix improper use of smp_mb__before_atomic()

BugLink: https://bugs.launchpad.net/bugs/1838700

commit a0934fd2b1208458e55fc4b48f55889809fce666 upstream.

This barrier only applies to the read-modify-write operations; in
particular, it does not apply to the atomic_set() primitive.

Replace the barrier with an smp_mb().

Fixes: 6c0ca7ae292ad ("sbitmap: fix wakeup hang after sbq resize")
Cc: stable@vger.kernel.org
Reported-by: "Paul E. McKenney" <paulmck@linux.ibm.com>
Reported-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Andrea Parri <andrea.parri@amarulasolutions.com>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Omar Sandoval <osandov@fb.com>
Cc: Ming Lei <ming.lei@redhat.com>
Cc: linux-block@vger.kernel.org
Cc: "Paul E. McKenney" <paulmck@linux.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>
---

diff --git a/lib/sbitmap.c b/lib/sbitmap.c
index 80aa8d5463fa..8e467917e0d1 100644
--- a/lib/sbitmap.c
+++ b/lib/sbitmap.c
@@ -338,7 +338,7 @@ void sbitmap_queue_resize(struct sbitmap_queue *sbq, unsigned int depth)
 		 * Pairs with the memory barrier in sbq_wake_up() to ensure that
 		 * the batch size is updated before the wait counts.
 		 */
-		smp_mb__before_atomic();
+		smp_mb();
 		for (i = 0; i < SBQ_WAIT_QUEUES; i++)
 			atomic_set(&sbq->ws[i].wait_cnt, 1);
 	}