From: Stefan Haberland <sth@linux.vnet.ibm.com>
Date: Tue, 12 Sep 2017 15:22:42 +0000 (+0200)
Subject: s390/dasd: fix race during dasd initialization
X-Git-Tag: v4.14-rc2~26^2~6
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=673514aff5d797b0cdb3f09097ae0e253b5667c3;p=platform%2Fkernel%2Flinux-rpi3.git

s390/dasd: fix race during dasd initialization

Fix a panic in blk_mq_hctx_has_pending() that is caused by a racy call to
blk_mq_run_hw_queues in a dasd function that might get called with the
request queue not yet initialized during initialization.

Signed-off-by: Stefan Haberland <sth@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
---

diff --git a/drivers/s390/block/dasd.c b/drivers/s390/block/dasd.c
index ea19b4f..29f35e2 100644
--- a/drivers/s390/block/dasd.c
+++ b/drivers/s390/block/dasd.c
@@ -1644,7 +1644,9 @@ void dasd_generic_handle_state_change(struct dasd_device *device)
 	dasd_schedule_device_bh(device);
 	if (device->block) {
 		dasd_schedule_block_bh(device->block);
-		blk_mq_run_hw_queues(device->block->request_queue, true);
+		if (device->block->request_queue)
+			blk_mq_run_hw_queues(device->block->request_queue,
+					     true);
 	}
 }
 EXPORT_SYMBOL_GPL(dasd_generic_handle_state_change);
@@ -3759,7 +3761,9 @@ int dasd_generic_path_operational(struct dasd_device *device)
 	dasd_schedule_device_bh(device);
 	if (device->block) {
 		dasd_schedule_block_bh(device->block);
-		blk_mq_run_hw_queues(device->block->request_queue, true);
+		if (device->block->request_queue)
+			blk_mq_run_hw_queues(device->block->request_queue,
+					     true);
 		}
 
 	if (!device->stopped)
@@ -4025,7 +4029,9 @@ int dasd_generic_restore_device(struct ccw_device *cdev)
 
 	if (device->block) {
 		dasd_schedule_block_bh(device->block);
-		blk_mq_run_hw_queues(device->block->request_queue, true);
+		if (device->block->request_queue)
+			blk_mq_run_hw_queues(device->block->request_queue,
+					     true);
 	}
 
 	clear_bit(DASD_FLAG_SUSPENDED, &device->flags);