1 files changed, 14 insertions, 8 deletions

diff --git a/drivers/block/elevator.c b/drivers/block/elevator.c
index 6b79b4314622..f831f08f839c 100644
--- a/drivers/block/elevator.c
+++ b/drivers/block/elevator.c
@@ -220,11 +220,6 @@ void elevator_exit(elevator_t *e)
         kfree(e);
 }
 
-static int elevator_global_init(void)
-{
-        return 0;
-}
-
 int elv_merge(request_queue_t *q, struct request **req, struct bio *bio)
 {
         elevator_t *e = q->elevator;
@@ -291,6 +286,13 @@ void elv_requeue_request(request_queue_t *q, struct request *rq)
         }
 
         /*
+         * the request is prepped and may have some resources allocated.
+         * allowing unprepped requests to pass this one may cause resource
+         * deadlock.  turn on softbarrier.
+         */
+        rq->flags |= REQ_SOFTBARRIER;
+
+        /*
          * if iosched has an explicit requeue hook, then use that. otherwise
          * just put the request at the front of the queue
          */
@@ -322,7 +324,7 @@ void __elv_add_request(request_queue_t *q, struct request *rq, int where,
                         int nrq = q->rq.count[READ] + q->rq.count[WRITE]
                                   - q->in_flight;
 
-                        if (nrq == q->unplug_thresh)
+                        if (nrq >= q->unplug_thresh)
                                 __generic_unplug_device(q);
                 }
         } else
@@ -386,6 +388,12 @@ struct request *elv_next_request(request_queue_t *q)
                 if (ret == BLKPREP_OK) {
                         break;
                 } else if (ret == BLKPREP_DEFER) {
+                        /*
+                         * the request may have been (partially) prepped.
+                         * we need to keep this request in the front to
+                         * avoid resource deadlock.  turn on softbarrier.
+                         */
+                        rq->flags |= REQ_SOFTBARRIER;
                         rq = NULL;
                         break;
                 } else if (ret == BLKPREP_KILL) {
@@ -692,8 +700,6 @@ ssize_t elv_iosched_show(request_queue_t *q, char *name)
         return len;
 }
 
-module_init(elevator_global_init);
-
 EXPORT_SYMBOL(elv_add_request);
 EXPORT_SYMBOL(__elv_add_request);
 EXPORT_SYMBOL(elv_requeue_request);