1 files changed, 33 insertions, 27 deletions

diff --git a/block/elevator.c b/block/elevator.c
index d4a49a3df829..e4c58827bb46 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -155,9 +155,10 @@ static void elevator_setup_default(void)
         /*
          * If the given scheduler is not available, fall back to no-op.
          */
-        if (!(e = elevator_find(chosen_elevator)))
+        if ((e = elevator_find(chosen_elevator)))
+                elevator_put(e);
+        else
                 strcpy(chosen_elevator, "noop");
-        elevator_put(e);
 }
 
 static int __init elevator_setup(char *str)
@@ -190,14 +191,14 @@ int elevator_init(request_queue_t *q, char *name)
 
         eq = kmalloc(sizeof(struct elevator_queue), GFP_KERNEL);
         if (!eq) {
-                elevator_put(e->elevator_type);
+                elevator_put(e);
                 return -ENOMEM;
         }
 
         ret = elevator_attach(q, e, eq);
         if (ret) {
                 kfree(eq);
-                elevator_put(e->elevator_type);
+                elevator_put(e);
         }
 
         return ret;
@@ -225,6 +226,7 @@ void elv_dispatch_sort(request_queue_t *q, struct request *rq)
 
         if (q->last_merge == rq)
                 q->last_merge = NULL;
+        q->nr_sorted--;
 
         boundary = q->end_sector;
 
@@ -283,6 +285,7 @@ void elv_merge_requests(request_queue_t *q, struct request *rq,
 
         if (e->ops->elevator_merge_req_fn)
                 e->ops->elevator_merge_req_fn(q, rq, next);
+        q->nr_sorted--;
 
         q->last_merge = rq;
 }
@@ -314,6 +317,20 @@ void elv_requeue_request(request_queue_t *q, struct request *rq)
         __elv_add_request(q, rq, ELEVATOR_INSERT_FRONT, 0);
 }
 
+static void elv_drain_elevator(request_queue_t *q)
+{
+        static int printed;
+        while (q->elevator->ops->elevator_dispatch_fn(q, 1))
+                ;
+        if (q->nr_sorted == 0)
+                return;
+        if (printed++ < 10) {
+                printk(KERN_ERR "%s: forced dispatching is broken "
+                       "(nr_sorted=%u), please report this\n",
+                       q->elevator->elevator_type->elevator_name, q->nr_sorted);
+        }
+}
+
 void __elv_add_request(request_queue_t *q, struct request *rq, int where,
                        int plug)
 {
@@ -348,9 +365,7 @@ void __elv_add_request(request_queue_t *q, struct request *rq, int where,
 
         case ELEVATOR_INSERT_BACK:
                 rq->flags |= REQ_SOFTBARRIER;
-
-                while (q->elevator->ops->elevator_dispatch_fn(q, 1))
-                        ;
+                elv_drain_elevator(q);
                 list_add_tail(&rq->queuelist, &q->queue_head);
                 /*
                  * We kick the queue here for the following reasons.
@@ -369,6 +384,7 @@ void __elv_add_request(request_queue_t *q, struct request *rq, int where,
         case ELEVATOR_INSERT_SORT:
                 BUG_ON(!blk_fs_request(rq));
                 rq->flags |= REQ_SORTED;
+                q->nr_sorted++;
                 if (q->last_merge == NULL && rq_mergeable(rq))
                         q->last_merge = rq;
                 /*
@@ -525,33 +541,19 @@ int elv_queue_empty(request_queue_t *q)
 
 struct request *elv_latter_request(request_queue_t *q, struct request *rq)
 {
-        struct list_head *next;
-
         elevator_t *e = q->elevator;
 
         if (e->ops->elevator_latter_req_fn)
                 return e->ops->elevator_latter_req_fn(q, rq);
-
-        next = rq->queuelist.next;
-        if (next != &q->queue_head && next != &rq->queuelist)
-                return list_entry_rq(next);
-
         return NULL;
 }
 
 struct request *elv_former_request(request_queue_t *q, struct request *rq)
 {
-        struct list_head *prev;
-
         elevator_t *e = q->elevator;
 
         if (e->ops->elevator_former_req_fn)
                 return e->ops->elevator_former_req_fn(q, rq);
-
-        prev = rq->queuelist.prev;
-        if (prev != &q->queue_head && prev != &rq->queuelist)
-                return list_entry_rq(prev);
-
         return NULL;
 }
 
@@ -691,13 +693,15 @@ static void elevator_switch(request_queue_t *q, struct elevator_type *new_e)
 
         set_bit(QUEUE_FLAG_ELVSWITCH, &q->queue_flags);
 
-        while (q->elevator->ops->elevator_dispatch_fn(q, 1))
-                ;
+        elv_drain_elevator(q);
 
         while (q->rq.elvpriv) {
+                blk_remove_plug(q);
+                q->request_fn(q);
                 spin_unlock_irq(q->queue_lock);
                 msleep(10);
                 spin_lock_irq(q->queue_lock);
+                elv_drain_elevator(q);
         }
 
         spin_unlock_irq(q->queue_lock);
@@ -744,13 +748,15 @@ error:
 ssize_t elv_iosched_store(request_queue_t *q, const char *name, size_t count)
 {
         char elevator_name[ELV_NAME_MAX];
+        size_t len;
         struct elevator_type *e;
 
-        memset(elevator_name, 0, sizeof(elevator_name));
-        strncpy(elevator_name, name, sizeof(elevator_name));
+        elevator_name[sizeof(elevator_name) - 1] = '\0';
+        strncpy(elevator_name, name, sizeof(elevator_name) - 1);
+        len = strlen(elevator_name);
 
-        if (elevator_name[strlen(elevator_name) - 1] == '\n')
-                elevator_name[strlen(elevator_name) - 1] = '\0';
+        if (len && elevator_name[len - 1] == '\n')
+                elevator_name[len - 1] = '\0';
 
         e = elevator_get(elevator_name);
         if (!e) {