1 files changed, 132 insertions, 15 deletions

diff --git a/block/elevator.c b/block/elevator.c
index 4ac97b642042..cff1102dac9d 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -33,6 +33,7 @@
 #include <linux/compiler.h>
 #include <linux/delay.h>
 #include <linux/blktrace_api.h>
+#include <linux/hash.h>
 
 #include <asm/uaccess.h>
 
@@ -40,6 +41,16 @@ static DEFINE_SPINLOCK(elv_list_lock);
 static LIST_HEAD(elv_list);
 
 /*
+ * Merge hash stuff.
+ */
+static const int elv_hash_shift = 6;
+#define ELV_HASH_BLOCK(sec)     ((sec) >> 3)
+#define ELV_HASH_FN(sec)        (hash_long(ELV_HASH_BLOCK((sec)), elv_hash_shift))
+#define ELV_HASH_ENTRIES        (1 << elv_hash_shift)
+#define rq_hash_key(rq)         ((rq)->sector + (rq)->nr_sectors)
+#define ELV_ON_HASH(rq)         (!hlist_unhashed(&(rq)->hash))
+
+/*
  * can we safely merge with this request?
  */
 inline int elv_rq_merge_ok(struct request *rq, struct bio *bio)
@@ -153,25 +164,41 @@ static struct kobj_type elv_ktype;
 
 static elevator_t *elevator_alloc(struct elevator_type *e)
 {
-        elevator_t *eq = kmalloc(sizeof(elevator_t), GFP_KERNEL);
-        if (eq) {
-                memset(eq, 0, sizeof(*eq));
-                eq->ops = &e->ops;
-                eq->elevator_type = e;
-                kobject_init(&eq->kobj);
-                snprintf(eq->kobj.name, KOBJ_NAME_LEN, "%s", "iosched");
-                eq->kobj.ktype = &elv_ktype;
-                mutex_init(&eq->sysfs_lock);
-        } else {
-                elevator_put(e);
-        }
+        elevator_t *eq;
+        int i;
+
+        eq = kmalloc(sizeof(elevator_t), GFP_KERNEL);
+        if (unlikely(!eq))
+                goto err;
+
+        memset(eq, 0, sizeof(*eq));
+        eq->ops = &e->ops;
+        eq->elevator_type = e;
+        kobject_init(&eq->kobj);
+        snprintf(eq->kobj.name, KOBJ_NAME_LEN, "%s", "iosched");
+        eq->kobj.ktype = &elv_ktype;
+        mutex_init(&eq->sysfs_lock);
+
+        eq->hash = kmalloc(sizeof(struct hlist_head) * ELV_HASH_ENTRIES, GFP_KERNEL);
+        if (!eq->hash)
+                goto err;
+
+        for (i = 0; i < ELV_HASH_ENTRIES; i++)
+                INIT_HLIST_HEAD(&eq->hash[i]);
+
         return eq;
+err:
+        kfree(eq);
+        elevator_put(e);
+        return NULL;
 }
 
 static void elevator_release(struct kobject *kobj)
 {
         elevator_t *e = container_of(kobj, elevator_t, kobj);
+
         elevator_put(e->elevator_type);
+        kfree(e->hash);
         kfree(e);
 }
 
@@ -223,6 +250,53 @@ void elevator_exit(elevator_t *e)
         kobject_put(&e->kobj);
 }
 
+static inline void __elv_rqhash_del(struct request *rq)
+{
+        hlist_del_init(&rq->hash);
+}
+
+static void elv_rqhash_del(request_queue_t *q, struct request *rq)
+{
+        if (ELV_ON_HASH(rq))
+                __elv_rqhash_del(rq);
+}
+
+static void elv_rqhash_add(request_queue_t *q, struct request *rq)
+{
+        elevator_t *e = q->elevator;
+
+        BUG_ON(ELV_ON_HASH(rq));
+        hlist_add_head(&rq->hash, &e->hash[ELV_HASH_FN(rq_hash_key(rq))]);
+}
+
+static void elv_rqhash_reposition(request_queue_t *q, struct request *rq)
+{
+        __elv_rqhash_del(rq);
+        elv_rqhash_add(q, rq);
+}
+
+static struct request *elv_rqhash_find(request_queue_t *q, sector_t offset)
+{
+        elevator_t *e = q->elevator;
+        struct hlist_head *hash_list = &e->hash[ELV_HASH_FN(offset)];
+        struct hlist_node *entry, *next;
+        struct request *rq;
+
+        hlist_for_each_entry_safe(rq, entry, next, hash_list, hash) {
+                BUG_ON(!ELV_ON_HASH(rq));
+
+                if (unlikely(!rq_mergeable(rq))) {
+                        __elv_rqhash_del(rq);
+                        continue;
+                }
+
+                if (rq_hash_key(rq) == offset)
+                        return rq;
+        }
+
+        return NULL;
+}
+
 /*
  * 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
@@ -235,6 +309,9 @@ void elv_dispatch_sort(request_queue_t *q, struct request *rq)
 
         if (q->last_merge == rq)
                 q->last_merge = NULL;
+
+        elv_rqhash_del(q, rq);
+
         q->nr_sorted--;
 
         boundary = q->end_sector;
@@ -258,11 +335,32 @@ void elv_dispatch_sort(request_queue_t *q, struct request *rq)
         list_add(&rq->queuelist, entry);
 }
 
+/*
+ * This should be in elevator.h, but that requires pulling in rq and q
+ */
+void elv_dispatch_add_tail(struct request_queue *q, struct request *rq)
+{
+        if (q->last_merge == rq)
+                q->last_merge = NULL;
+
+        elv_rqhash_del(q, rq);
+
+        q->nr_sorted--;
+
+        q->end_sector = rq_end_sector(rq);
+        q->boundary_rq = rq;
+        list_add_tail(&rq->queuelist, &q->queue_head);
+}
+
 int elv_merge(request_queue_t *q, struct request **req, struct bio *bio)
 {
         elevator_t *e = q->elevator;
+        struct request *__rq;
         int ret;
 
+        /*
+         * First try one-hit cache.
+         */
         if (q->last_merge) {
                 ret = elv_try_merge(q->last_merge, bio);
                 if (ret != ELEVATOR_NO_MERGE) {
@@ -271,6 +369,15 @@ int elv_merge(request_queue_t *q, struct request **req, struct bio *bio)
                 }
         }
 
+        /*
+         * See if our hash lookup can find a potential backmerge.
+         */
+        __rq = elv_rqhash_find(q, bio->bi_sector);
+        if (__rq && elv_rq_merge_ok(__rq, bio)) {
+                *req = __rq;
+                return ELEVATOR_BACK_MERGE;
+        }
+
         if (e->ops->elevator_merge_fn)
                 return e->ops->elevator_merge_fn(q, req, bio);
 
@@ -284,6 +391,8 @@ void elv_merged_request(request_queue_t *q, struct request *rq)
         if (e->ops->elevator_merged_fn)
                 e->ops->elevator_merged_fn(q, rq);
 
+        elv_rqhash_reposition(q, rq);
+
         q->last_merge = rq;
 }
 
@@ -294,8 +403,11 @@ 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--;
 
+        elv_rqhash_reposition(q, rq);
+        elv_rqhash_del(q, next);
+
+        q->nr_sorted--;
         q->last_merge = rq;
 }
 
@@ -371,8 +483,12 @@ void elv_insert(request_queue_t *q, struct request *rq, int where)
                 BUG_ON(!blk_fs_request(rq));
                 rq->cmd_flags |= REQ_SORTED;
                 q->nr_sorted++;
-                if (q->last_merge == NULL && rq_mergeable(rq))
-                        q->last_merge = rq;
+                if (rq_mergeable(rq)) {
+                        elv_rqhash_add(q, rq);
+                        if (!q->last_merge)
+                                q->last_merge = rq;
+                }
+
                 /*
                  * Some ioscheds (cfq) run q->request_fn directly, so
                  * rq cannot be accessed after calling
@@ -557,6 +673,7 @@ struct request *elv_next_request(request_queue_t *q)
 void elv_dequeue_request(request_queue_t *q, struct request *rq)
 {
         BUG_ON(list_empty(&rq->queuelist));
+        BUG_ON(ELV_ON_HASH(rq));
 
         list_del_init(&rq->queuelist);