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 d72a921..e91ec8c 100644 (file)
--- 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;
 }
 
 /*