From: Bart Van Assche <bart.vanassche@wdc.com>
Date: Mon, 19 Mar 2018 11:46:13 -0700
Subject: [PATCH] block: Change a rcu_read_{lock,unlock}_sched() pair into rcu_read_{lock,unlock}()
Git-commit: 818e0fa293ca836eba515615c64680ea916fd7cd
Patch-mainline: v4.17-rc1
References: bsc#1104967,FATE#325924
scsi_device_quiesce() uses synchronize_rcu() to guarantee that the
effect of blk_set_preempt_only() will be visible for percpu_ref_tryget()
calls that occur after the queue unfreeze by using the approach
explained in https://lwn.net/Articles/573497/. The rcu read lock and
unlock calls in blk_queue_enter() form a pair with the synchronize_rcu()
call in scsi_device_quiesce(). Both scsi_device_quiesce() and
blk_queue_enter() must either use regular RCU or RCU-sched.
Since neither the RCU-protected code in blk_queue_enter() nor
blk_queue_usage_counter_release() sleeps, regular RCU protection
is sufficient. Note: scsi_device_quiesce() does not have to be
modified since it already uses synchronize_rcu().
Reported-by: Tejun Heo <tj@kernel.org>
Fixes: 3a0a529971ec ("block, scsi: Make SCSI quiesce and resume work reliably")
Signed-off-by: Bart Van Assche <bart.vanassche@wdc.com>
Acked-by: Tejun Heo <tj@kernel.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: Hannes Reinecke <hare@suse.com>
Cc: Ming Lei <ming.lei@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Johannes Thumshirn <jthumshirn@suse.de>
Cc: Oleksandr Natalenko <oleksandr@natalenko.name>
Cc: Martin Steigerwald <martin@lichtvoll.de>
Cc: stable@vger.kernel.org # v4.15
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Acked-by: Hannes Reinecke <hare@suse.com>
---
block/blk-core.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/block/blk-core.c b/block/blk-core.c
index 5e88c579e896..a0f675f84f86 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -917,7 +917,7 @@ int blk_queue_enter(struct request_queue *q, blk_mq_req_flags_t flags)
bool success = false;
int ret;
- rcu_read_lock_sched();
+ rcu_read_lock();
if (percpu_ref_tryget_live(&q->q_usage_counter)) {
/*
* The code that sets the PREEMPT_ONLY flag is
@@ -930,7 +930,7 @@ int blk_queue_enter(struct request_queue *q, blk_mq_req_flags_t flags)
percpu_ref_put(&q->q_usage_counter);
}
}
- rcu_read_unlock_sched();
+ rcu_read_unlock();
if (success)
return 0;
--
2.16.4