block: do not use interruptible wait anywhere

When blk_queue_enter() waits for a queue to unfreeze, or unset the
PREEMPT_ONLY flag, do not allow it to be interrupted by a signal.

The PREEMPT_ONLY flag was introduced later in commit 3a0a529
("block, scsi: Make SCSI quiesce and resume work reliably").  Note the SCSI
device is resumed asynchronously, i.e. after un-freezing userspace tasks.

So that commit exposed the bug as a regression in v4.15.  A mysterious
SIGBUS (or -EIO) sometimes happened during the time the device was being
resumed.  Most frequently, there was no kernel log message, and we saw Xorg
or Xwayland killed by SIGBUS.[1]

[1] E.g. https://bugzilla.redhat.com/show_bug.cgi?id=1553979

Without this fix, I get an IO error in this test:

  while killall -SIGUSR1 dd; do sleep 0.1; done & \
  echo mem > /sys/power/state ; \
  sleep 5; killall dd  # stop after 5 seconds

The interruptible wait was added to blk_queue_enter in
commit 3ef28e8 ("block: generic request_queue reference counting").
Before then, the interruptible wait was only in blk-mq, but I don't think
it could ever have been correct.

Reviewed-by: Bart Van Assche <[email protected]>
Cc: [email protected]
Signed-off-by: Alan Jenkins <[email protected]>
Signed-off-by: Jens Axboe <[email protected]>
(cherry picked from commit 1dc3039)

Orabug: 29674055

Signed-off-by: Junxiao Bi <[email protected]>
Reviewed-by: Wengang Wang <[email protected]>

 Conflicts:
	block/blk-core.c

Signed-off-by: Brian Maly <[email protected]>

Author: sourcejedi

block/blk-core.c

@@ -612,21 +612,17 @@ EXPORT_SYMBOL(blk_alloc_queue);
 int blk_queue_enter(struct request_queue *q, gfp_t gfp)
 {
 	while (true) {
-		int ret;
-
 		if (percpu_ref_tryget_live(&q->q_usage_counter))
 			return 0;
 
 		if (!(gfp & __GFP_WAIT))
 			return -EBUSY;
 
-		ret = wait_event_interruptible(q->mq_freeze_wq,
+		wait_event(q->mq_freeze_wq,
 				!atomic_read(&q->mq_freeze_depth) ||
 				blk_queue_dying(q));
 		if (blk_queue_dying(q))
 			return -ENODEV;
-		if (ret)
-			return ret;
 	}
 }