block: Free queue resources at blk_release_queue()

A kernel crash is observed when a mounted ext3/ext4 filesystem is
physically removed. The problem is that blk_cleanup_queue() frees up
some resources eg by calling elevator_exit(), which are not checked for
in normal operation. So we should rather move these calls to the
destructor function blk_release_queue() as at that point all remaining
references are gone. However, in doing so we have to ensure that any
externally supplied queue_lock is disconnected as the driver might free
up the lock after the call of blk_cleanup_queue(),

Signed-off-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

2 files changed, 11 insertions, 7 deletions

diff --git a/block/blk-core.c b/block/blk-core.c
index b2ed78afd9f0..d34433ae7917 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -348,9 +348,10 @@ void blk_put_queue(struct request_queue *q)
 EXPORT_SYMBOL(blk_put_queue);
 
 /*
- * Note: If a driver supplied the queue lock, it should not zap that lock
- * unexpectedly as some queue cleanup components like elevator_exit() and
- * blk_throtl_exit() need queue lock.
+ * Note: If a driver supplied the queue lock, it is disconnected
+ * by this function. The actual state of the lock doesn't matter
+ * here as the request_queue isn't accessible after this point
+ * (QUEUE_FLAG_DEAD is set) and no other requests will be queued.
  */
 void blk_cleanup_queue(struct request_queue *q)
 {
@@ -367,10 +368,8 @@ void blk_cleanup_queue(struct request_queue *q)
         queue_flag_set_unlocked(QUEUE_FLAG_DEAD, q);
         mutex_unlock(&q->sysfs_lock);
 
-        if (q->elevator)
-                elevator_exit(q->elevator);
-
-        blk_throtl_exit(q);
+        if (q->queue_lock != &q->__queue_lock)
+                q->queue_lock = &q->__queue_lock;
 
         blk_put_queue(q);
 }
diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
index e681805cdb47..60fda88c57f0 100644
--- a/block/blk-sysfs.c
+++ b/block/blk-sysfs.c
@@ -479,6 +479,11 @@ static void blk_release_queue(struct kobject *kobj)
 
         blk_sync_queue(q);
 
+        if (q->elevator)
+                elevator_exit(q->elevator);
+
+        blk_throtl_exit(q);
+
         if (rl->rq_pool)
                 mempool_destroy(rl->rq_pool);