From: Heiko Carstens <heiko.carstens@de.ibm.com>
Date: Thu, 31 Oct 2013 12:24:28 +0000 (+0100)
Subject: s390/dasd: hold request queue sysfs lock when calling elevator_init()
X-Git-Url: http://git.mmlx.us/?a=commitdiff_plain;h=ed93fb01a3991ced713a37bc844ed2f2abef8ea8;p=linux-edison.git

s390/dasd: hold request queue sysfs lock when calling elevator_init()

commit ef0899410ff630b2e75306da49996dbbfa318165 upstream.

"elevator: Fix a race in elevator switching and md device initialization"
changed the semantics of elevator_init() in a way that now enforces to hold
the corresponding request queue's sysfs_lock when calling elevator_init()
to fix a race.
The patch did not convert the s390 dasd device driver which is the only
device driver which also calls elevator_init(). So add the missing locking.

Cc: Tomoki Sekiyama <tomoki.sekiyama@hds.com>
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Cc: Christian Borntraeger <christian@borntraeger.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---

diff --git a/drivers/s390/block/dasd.c b/drivers/s390/block/dasd.c
index d72a9216ee2..e91ec8cd9b0 100644
--- a/drivers/s390/block/dasd.c
+++ b/drivers/s390/block/dasd.c
@@ -2879,12 +2879,12 @@ static int dasd_alloc_queue(struct dasd_block *block)
 
 	elevator_exit(block->request_queue->elevator);
 	block->request_queue->elevator = NULL;
+	mutex_lock(&block->request_queue->sysfs_lock);
 	rc = elevator_init(block->request_queue, "deadline");
-	if (rc) {
+	if (rc)
 		blk_cleanup_queue(block->request_queue);
-		return rc;
-	}
-	return 0;
+	mutex_unlock(&block->request_queue->sysfs_lock);
+	return rc;
 }
 
 /*