[PATCH v4 9/9] block: Do not accept any requests while suspended

From: Bart Van Assche <bvanassche@acm.org>
To: "Martin K . Petersen" <martin.petersen@oracle.com>
Cc: "James E . J . Bottomley" <jejb@linux.vnet.ibm.com>,
	Jens Axboe <axboe@kernel.dk>, Christoph Hellwig <hch@lst.de>,
	Ming Lei <ming.lei@redhat.com>,
	linux-scsi@vger.kernel.org, linux-block@vger.kernel.org,
	Bart Van Assche <bvanassche@acm.org>,
	Alan Stern <stern@rowland.harvard.edu>,
	Can Guo <cang@codeaurora.org>,
	Stanley Chu <stanley.chu@mediatek.com>,
	"Rafael J . Wysocki" <rafael.j.wysocki@intel.com>,
	Martin Kepplinger <martin.kepplinger@puri.sm>
Subject: [PATCH v4 9/9] block: Do not accept any requests while suspended
Date: Sun, 29 Nov 2020 18:46:15 -0800	[thread overview]
Message-ID: <20201130024615.29171-10-bvanassche@acm.org> (raw)
In-Reply-To: <20201130024615.29171-1-bvanassche@acm.org>

From: Alan Stern <stern@rowland.harvard.edu>

blk_queue_enter() accepts BLK_MQ_REQ_PM requests independent of the runtime
power management state. Now that SCSI domain validation no longer depends
on this behavior, modify the behavior of blk_queue_enter() as follows:
- Do not accept any requests while suspended.
- Only process power management requests while suspending or resuming.

Submitting BLK_MQ_REQ_PM requests to a device that is runtime suspended
causes runtime-suspended devices not to resume as they should. The request
which should cause a runtime resume instead gets issued directly, without
resuming the device first. Of course the device can't handle it properly,
the I/O fails, and the device remains suspended.

The problem is fixed by checking that the queue's runtime-PM status
isn't RPM_SUSPENDED before allowing a request to be issued, and
queuing a runtime-resume request if it is.  In particular, the inline
blk_pm_request_resume() routine is renamed blk_pm_resume_queue() and
the code is unified by merging the surrounding checks into the
routine.  If the queue isn't set up for runtime PM, or there currently
is no restriction on allowed requests, the request is allowed.
Likewise if the BLK_MQ_REQ_PM flag is set and the status isn't
RPM_SUSPENDED.  Otherwise a runtime resume is queued and the request
is blocked until conditions are more suitable.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Can Guo <cang@codeaurora.org>
Reviewed-by: Stanley Chu <stanley.chu@mediatek.com>
Cc: Ming Lei <ming.lei@redhat.com>
Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reported-and-tested-by: Martin Kepplinger <martin.kepplinger@puri.sm>
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
[ bvanassche: modified commit message and removed Cc: stable because without
  the previous patches from this series this patch would break parallel SCSI
  domain validation ]
---
 block/blk-core.c |  6 +++---
 block/blk-pm.h   | 14 +++++++++-----
 2 files changed, 12 insertions(+), 8 deletions(-)

diff --git a/block/blk-core.c b/block/blk-core.c
index a00bce9f46d8..230880cbf8c8 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -440,7 +440,8 @@ int blk_queue_enter(struct request_queue *q, blk_mq_req_flags_t flags)
 			 * responsible for ensuring that that counter is
 			 * globally visible before the queue is unfrozen.
 			 */
-			if (pm || !blk_queue_pm_only(q)) {
+			if ((pm && q->rpm_status != RPM_SUSPENDED) ||
+			    !blk_queue_pm_only(q)) {
 				success = true;
 			} else {
 				percpu_ref_put(&q->q_usage_counter);
@@ -465,8 +466,7 @@ int blk_queue_enter(struct request_queue *q, blk_mq_req_flags_t flags)
 
 		wait_event(q->mq_freeze_wq,
 			   (!q->mq_freeze_depth &&
-			    (pm || (blk_pm_request_resume(q),
-				    !blk_queue_pm_only(q)))) ||
+			    blk_pm_resume_queue(pm, q)) ||
 			   blk_queue_dying(q));
 		if (blk_queue_dying(q))
 			return -ENODEV;
diff --git a/block/blk-pm.h b/block/blk-pm.h
index ea5507d23e75..a2283cc9f716 100644
--- a/block/blk-pm.h
+++ b/block/blk-pm.h
@@ -6,11 +6,14 @@
 #include <linux/pm_runtime.h>
 
 #ifdef CONFIG_PM
-static inline void blk_pm_request_resume(struct request_queue *q)
+static inline int blk_pm_resume_queue(const bool pm, struct request_queue *q)
 {
-	if (q->dev && (q->rpm_status == RPM_SUSPENDED ||
-		       q->rpm_status == RPM_SUSPENDING))
-		pm_request_resume(q->dev);
+	if (!q->dev || !blk_queue_pm_only(q))
+		return 1;	/* Nothing to do */
+	if (pm && q->rpm_status != RPM_SUSPENDED)
+		return 1;	/* Request allowed */
+	pm_request_resume(q->dev);
+	return 0;
 }
 
 static inline void blk_pm_mark_last_busy(struct request *rq)
@@ -44,8 +47,9 @@ static inline void blk_pm_put_request(struct request *rq)
 		--rq->q->nr_pending;
 }
 #else
-static inline void blk_pm_request_resume(struct request_queue *q)
+static inline int blk_pm_resume_queue(const bool pm, struct request_queue *q)
 {
+	return 1;
 }
 
 static inline void blk_pm_mark_last_busy(struct request *rq)
