2 files changed, 113 insertions, 17 deletions

diff --git a/block/elevator.c b/block/elevator.c
index cff1102dac9d..cbbc36ba016a 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -239,6 +239,8 @@ int elevator_init(request_queue_t *q, char *name)
         return ret;
 }
 
+EXPORT_SYMBOL(elevator_init);
+
 void elevator_exit(elevator_t *e)
 {
         mutex_lock(&e->sysfs_lock);
@@ -250,6 +252,8 @@ void elevator_exit(elevator_t *e)
         kobject_put(&e->kobj);
 }
 
+EXPORT_SYMBOL(elevator_exit);
+
 static inline void __elv_rqhash_del(struct request *rq)
 {
         hlist_del_init(&rq->hash);
@@ -298,9 +302,68 @@ static struct request *elv_rqhash_find(request_queue_t *q, sector_t offset)
 }
 
 /*
+ * RB-tree support functions for inserting/lookup/removal of requests
+ * in a sorted RB tree.
+ */
+struct request *elv_rb_add(struct rb_root *root, struct request *rq)
+{
+        struct rb_node **p = &root->rb_node;
+        struct rb_node *parent = NULL;
+        struct request *__rq;
+
+        while (*p) {
+                parent = *p;
+                __rq = rb_entry(parent, struct request, rb_node);
+
+                if (rq->sector < __rq->sector)
+                        p = &(*p)->rb_left;
+                else if (rq->sector > __rq->sector)
+                        p = &(*p)->rb_right;
+                else
+                        return __rq;
+        }
+
+        rb_link_node(&rq->rb_node, parent, p);
+        rb_insert_color(&rq->rb_node, root);
+        return NULL;
+}
+
+EXPORT_SYMBOL(elv_rb_add);
+
+void elv_rb_del(struct rb_root *root, struct request *rq)
+{
+        BUG_ON(RB_EMPTY_NODE(&rq->rb_node));
+        rb_erase(&rq->rb_node, root);
+        RB_CLEAR_NODE(&rq->rb_node);
+}
+
+EXPORT_SYMBOL(elv_rb_del);
+
+struct request *elv_rb_find(struct rb_root *root, sector_t sector)
+{
+        struct rb_node *n = root->rb_node;
+        struct request *rq;
+
+        while (n) {
+                rq = rb_entry(n, struct request, rb_node);
+
+                if (sector < rq->sector)
+                        n = n->rb_left;
+                else if (sector > rq->sector)
+                        n = n->rb_right;
+                else
+                        return rq;
+        }
+
+        return NULL;
+}
+
+EXPORT_SYMBOL(elv_rb_find);
+
+/*
  * Insert rq into dispatch queue of q.  Queue lock must be held on
- * entry.  If sort != 0, rq is sort-inserted; otherwise, rq will be
- * appended to the dispatch queue.  To be used by specific elevators.
+ * entry.  rq is sort insted into the dispatch queue. To be used by
+ * specific elevators.
  */
 void elv_dispatch_sort(request_queue_t *q, struct request *rq)
 {
@@ -335,8 +398,12 @@ void elv_dispatch_sort(request_queue_t *q, struct request *rq)
         list_add(&rq->queuelist, entry);
 }
 
+EXPORT_SYMBOL(elv_dispatch_sort);
+
 /*
- * This should be in elevator.h, but that requires pulling in rq and q
+ * Insert rq into dispatch queue of q.  Queue lock must be held on
+ * entry.  rq is added to the back of the dispatch queue. To be used by
+ * specific elevators.
  */
 void elv_dispatch_add_tail(struct request_queue *q, struct request *rq)
 {
@@ -352,6 +419,8 @@ void elv_dispatch_add_tail(struct request_queue *q, struct request *rq)
         list_add_tail(&rq->queuelist, &q->queue_head);
 }
 
+EXPORT_SYMBOL(elv_dispatch_add_tail);
+
 int elv_merge(request_queue_t *q, struct request **req, struct bio *bio)
 {
         elevator_t *e = q->elevator;
@@ -384,14 +453,15 @@ int elv_merge(request_queue_t *q, struct request **req, struct bio *bio)
         return ELEVATOR_NO_MERGE;
 }
 
-void elv_merged_request(request_queue_t *q, struct request *rq)
+void elv_merged_request(request_queue_t *q, struct request *rq, int type)
 {
         elevator_t *e = q->elevator;
 
         if (e->ops->elevator_merged_fn)
-                e->ops->elevator_merged_fn(q, rq);
+                e->ops->elevator_merged_fn(q, rq, type);
 
-        elv_rqhash_reposition(q, rq);
+        if (type == ELEVATOR_BACK_MERGE)
+                elv_rqhash_reposition(q, rq);
 
         q->last_merge = rq;
 }
@@ -577,6 +647,8 @@ void __elv_add_request(request_queue_t *q, struct request *rq, int where,
         elv_insert(q, rq, where);
 }
 
+EXPORT_SYMBOL(__elv_add_request);
+
 void elv_add_request(request_queue_t *q, struct request *rq, int where,
                      int plug)
 {
@@ -587,6 +659,8 @@ void elv_add_request(request_queue_t *q, struct request *rq, int where,
         spin_unlock_irqrestore(q->queue_lock, flags);
 }
 
+EXPORT_SYMBOL(elv_add_request);
+
 static inline struct request *__elv_next_request(request_queue_t *q)
 {
         struct request *rq;
@@ -670,6 +744,8 @@ struct request *elv_next_request(request_queue_t *q)
         return rq;
 }
 
+EXPORT_SYMBOL(elv_next_request);
+
 void elv_dequeue_request(request_queue_t *q, struct request *rq)
 {
         BUG_ON(list_empty(&rq->queuelist));
@@ -686,6 +762,8 @@ void elv_dequeue_request(request_queue_t *q, struct request *rq)
                 q->in_flight++;
 }
 
+EXPORT_SYMBOL(elv_dequeue_request);
+
 int elv_queue_empty(request_queue_t *q)
 {
         elevator_t *e = q->elevator;
@@ -699,6 +777,8 @@ int elv_queue_empty(request_queue_t *q)
         return 1;
 }
 
+EXPORT_SYMBOL(elv_queue_empty);
+
 struct request *elv_latter_request(request_queue_t *q, struct request *rq)
 {
         elevator_t *e = q->elevator;
@@ -1025,11 +1105,26 @@ ssize_t elv_iosched_show(request_queue_t *q, char *name)
         return len;
 }
 
-EXPORT_SYMBOL(elv_dispatch_sort);
-EXPORT_SYMBOL(elv_add_request);
-EXPORT_SYMBOL(__elv_add_request);
-EXPORT_SYMBOL(elv_next_request);
-EXPORT_SYMBOL(elv_dequeue_request);
-EXPORT_SYMBOL(elv_queue_empty);
-EXPORT_SYMBOL(elevator_exit);
-EXPORT_SYMBOL(elevator_init);
+struct request *elv_rb_former_request(request_queue_t *q, struct request *rq)
+{
+        struct rb_node *rbprev = rb_prev(&rq->rb_node);
+
+        if (rbprev)
+                return rb_entry_rq(rbprev);
+
+        return NULL;
+}
+
+EXPORT_SYMBOL(elv_rb_former_request);
+
+struct request *elv_rb_latter_request(request_queue_t *q, struct request *rq)
+{
+        struct rb_node *rbnext = rb_next(&rq->rb_node);
+
+        if (rbnext)
+                return rb_entry_rq(rbnext);
+
+        return NULL;
+}
+
+EXPORT_SYMBOL(elv_rb_latter_request);
diff --git a/block/ll_rw_blk.c b/block/ll_rw_blk.c
index 9cbf7b550c78..d388486e98bb 100644
--- a/block/ll_rw_blk.c
+++ b/block/ll_rw_blk.c
@@ -281,11 +281,12 @@ static inline void rq_init(request_queue_t *q, struct request *rq)
 {
         INIT_LIST_HEAD(&rq->queuelist);
         INIT_LIST_HEAD(&rq->donelist);
-        INIT_HLIST_NODE(&rq->hash);
 
         rq->errors = 0;
         rq->rq_status = RQ_ACTIVE;
         rq->bio = rq->biotail = NULL;
+        INIT_HLIST_NODE(&rq->hash);
+        RB_CLEAR_NODE(&rq->rb_node);
         rq->ioprio = 0;
         rq->buffer = NULL;
         rq->ref_count = 1;
@@ -2943,7 +2944,7 @@ static int __make_request(request_queue_t *q, struct bio *bio)
                         req->ioprio = ioprio_best(req->ioprio, prio);
                         drive_stat_acct(req, nr_sectors, 0);
                         if (!attempt_back_merge(q, req))
-                                elv_merged_request(q, req);
+                                elv_merged_request(q, req, el_ret);
                         goto out;
 
                 case ELEVATOR_FRONT_MERGE:
@@ -2970,7 +2971,7 @@ static int __make_request(request_queue_t *q, struct bio *bio)
                         req->ioprio = ioprio_best(req->ioprio, prio);
                         drive_stat_acct(req, nr_sectors, 0);
                         if (!attempt_front_merge(q, req))
-                                elv_merged_request(q, req);
+                                elv_merged_request(q, req, el_ret);
                         goto out;
 
                 /* ELV_NO_MERGE: elevator says don't/can't merge. */