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

"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>

1 files changed, 4 insertions, 4 deletions

diff --git a/drivers/s390/block/dasd.c b/drivers/s390/block/dasd.c
index 451bf99582ff..846d5c6609d8 100644
--- a/drivers/s390/block/dasd.c
+++ b/drivers/s390/block/dasd.c
@@ -2978,12 +2978,12 @@ 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;
 }
 
 /*