5 files changed, 107 insertions, 68 deletions

diff --git a/block/as-iosched.c b/block/as-iosched.c
index e25a5d79ab27..a7caf35ca0c2 100644
--- a/block/as-iosched.c
+++ b/block/as-iosched.c
@@ -1648,17 +1648,17 @@ static void as_exit_queue(elevator_t *e)
  * initialize elevator private data (as_data), and alloc a arq for
  * each request on the free lists
  */
-static int as_init_queue(request_queue_t *q, elevator_t *e)
+static void *as_init_queue(request_queue_t *q, elevator_t *e)
 {
         struct as_data *ad;
         int i;
 
         if (!arq_pool)
-                return -ENOMEM;
+                return NULL;
 
         ad = kmalloc_node(sizeof(*ad), GFP_KERNEL, q->node);
         if (!ad)
-                return -ENOMEM;
+                return NULL;
         memset(ad, 0, sizeof(*ad));
 
         ad->q = q; /* Identify what queue the data belongs to */
@@ -1667,7 +1667,7 @@ static int as_init_queue(request_queue_t *q, elevator_t *e)
                                 GFP_KERNEL, q->node);
         if (!ad->hash) {
                 kfree(ad);
-                return -ENOMEM;
+                return NULL;
         }
 
         ad->arq_pool = mempool_create_node(BLKDEV_MIN_RQ, mempool_alloc_slab,
@@ -1675,7 +1675,7 @@ static int as_init_queue(request_queue_t *q, elevator_t *e)
         if (!ad->arq_pool) {
                 kfree(ad->hash);
                 kfree(ad);
-                return -ENOMEM;
+                return NULL;
         }
 
         /* anticipatory scheduling helpers */
@@ -1696,14 +1696,13 @@ static int as_init_queue(request_queue_t *q, elevator_t *e)
         ad->antic_expire = default_antic_expire;
         ad->batch_expire[REQ_SYNC] = default_read_batch_expire;
         ad->batch_expire[REQ_ASYNC] = default_write_batch_expire;
-        e->elevator_data = ad;
 
         ad->current_batch_expires = jiffies + ad->batch_expire[REQ_SYNC];
         ad->write_batch_count = ad->batch_expire[REQ_ASYNC] / 10;
         if (ad->write_batch_count < 2)
                 ad->write_batch_count = 2;
 
-        return 0;
+        return ad;
 }
 
 /*
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 2540dfaa3e38..a46d030e092a 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -33,7 +33,7 @@ static int cfq_slice_idle = HZ / 70;
 
 #define CFQ_KEY_ASYNC           (0)
 
-static DEFINE_RWLOCK(cfq_exit_lock);
+static DEFINE_SPINLOCK(cfq_exit_lock);
 
 /*
  * for the hash of cfqq inside the cfqd
@@ -133,6 +133,7 @@ struct cfq_data {
         mempool_t *crq_pool;
 
         int rq_in_driver;
+        int hw_tag;
 
         /*
          * schedule slice state info
@@ -500,10 +501,13 @@ static void cfq_resort_rr_list(struct cfq_queue *cfqq, int preempted)
 
         /*
          * if queue was preempted, just add to front to be fair. busy_rr
-         * isn't sorted.
+         * isn't sorted, but insert at the back for fairness.
          */
         if (preempted || list == &cfqd->busy_rr) {
-                list_add(&cfqq->cfq_list, list);
+                if (preempted)
+                        list = list->prev;
+
+                list_add_tail(&cfqq->cfq_list, list);
                 return;
         }
 
@@ -664,6 +668,15 @@ static void cfq_activate_request(request_queue_t *q, struct request *rq)
         struct cfq_data *cfqd = q->elevator->elevator_data;
 
         cfqd->rq_in_driver++;
+
+        /*
+         * If the depth is larger 1, it really could be queueing. But lets
+         * make the mark a little higher - idling could still be good for
+         * low queueing, and a low queueing number could also just indicate
+         * a SCSI mid layer like behaviour where limit+1 is often seen.
+         */
+        if (!cfqd->hw_tag && cfqd->rq_in_driver > 4)
+                cfqd->hw_tag = 1;
 }
 
 static void cfq_deactivate_request(request_queue_t *q, struct request *rq)
@@ -879,6 +892,13 @@ static struct cfq_queue *cfq_set_active_queue(struct cfq_data *cfqd)
                 cfqq = list_entry_cfqq(cfqd->cur_rr.next);
 
         /*
+         * If no new queues are available, check if the busy list has some
+         * before falling back to idle io.
+         */
+        if (!cfqq && !list_empty(&cfqd->busy_rr))
+                cfqq = list_entry_cfqq(cfqd->busy_rr.next);
+
+        /*
          * if we have idle queues and no rt or be queues had pending
          * requests, either allow immediate service if the grace period
          * has passed or arm the idle grace timer
@@ -1284,7 +1304,7 @@ static void cfq_exit_io_context(struct io_context *ioc)
         /*
          * put the reference this task is holding to the various queues
          */
-        read_lock_irqsave(&cfq_exit_lock, flags);
+        spin_lock_irqsave(&cfq_exit_lock, flags);
 
         n = rb_first(&ioc->cic_root);
         while (n != NULL) {
@@ -1294,7 +1314,7 @@ static void cfq_exit_io_context(struct io_context *ioc)
                 n = rb_next(n);
         }
 
-        read_unlock_irqrestore(&cfq_exit_lock, flags);
+        spin_unlock_irqrestore(&cfq_exit_lock, flags);
 }
 
 static struct cfq_io_context *
@@ -1400,17 +1420,17 @@ static int cfq_ioc_set_ioprio(struct io_context *ioc, unsigned int ioprio)
         struct cfq_io_context *cic;
         struct rb_node *n;
 
-        write_lock(&cfq_exit_lock);
+        spin_lock(&cfq_exit_lock);
 
         n = rb_first(&ioc->cic_root);
         while (n != NULL) {
                 cic = rb_entry(n, struct cfq_io_context, rb_node);
- 
+
                 changed_ioprio(cic);
                 n = rb_next(n);
         }
 
-        write_unlock(&cfq_exit_lock);
+        spin_unlock(&cfq_exit_lock);
 
         return 0;
 }
@@ -1458,7 +1478,8 @@ retry:
                  * set ->slice_left to allow preemption for a new process
                  */
                 cfqq->slice_left = 2 * cfqd->cfq_slice_idle;
-                cfq_mark_cfqq_idle_window(cfqq);
+                if (!cfqd->hw_tag)
+                        cfq_mark_cfqq_idle_window(cfqq);
                 cfq_mark_cfqq_prio_changed(cfqq);
                 cfq_init_prio_data(cfqq);
         }
@@ -1475,9 +1496,10 @@ out:
 static void
 cfq_drop_dead_cic(struct io_context *ioc, struct cfq_io_context *cic)
 {
-        read_lock(&cfq_exit_lock);
+        spin_lock(&cfq_exit_lock);
         rb_erase(&cic->rb_node, &ioc->cic_root);
-        read_unlock(&cfq_exit_lock);
+        list_del_init(&cic->queue_list);
+        spin_unlock(&cfq_exit_lock);
         kmem_cache_free(cfq_ioc_pool, cic);
         atomic_dec(&ioc_count);
 }
@@ -1545,11 +1567,11 @@ restart:
                         BUG();
         }
 
-        read_lock(&cfq_exit_lock);
+        spin_lock(&cfq_exit_lock);
         rb_link_node(&cic->rb_node, parent, p);
         rb_insert_color(&cic->rb_node, &ioc->cic_root);
         list_add(&cic->queue_list, &cfqd->cic_list);
-        read_unlock(&cfq_exit_lock);
+        spin_unlock(&cfq_exit_lock);
 }
 
 /*
@@ -1648,7 +1670,7 @@ cfq_update_idle_window(struct cfq_data *cfqd, struct cfq_queue *cfqq,
 {
         int enable_idle = cfq_cfqq_idle_window(cfqq);
 
-        if (!cic->ioc->task || !cfqd->cfq_slice_idle)
+        if (!cic->ioc->task || !cfqd->cfq_slice_idle || cfqd->hw_tag)
                 enable_idle = 0;
         else if (sample_valid(cic->ttime_samples)) {
                 if (cic->ttime_mean > cfqd->cfq_slice_idle)
@@ -1739,14 +1761,24 @@ cfq_crq_enqueued(struct cfq_data *cfqd, struct cfq_queue *cfqq,
 
         cfqq->next_crq = cfq_choose_req(cfqd, cfqq->next_crq, crq);
 
+        cic = crq->io_context;
+
         /*
          * we never wait for an async request and we don't allow preemption
          * of an async request. so just return early
          */
-        if (!cfq_crq_is_sync(crq))
+        if (!cfq_crq_is_sync(crq)) {
+                /*
+                 * sync process issued an async request, if it's waiting
+                 * then expire it and kick rq handling.
+                 */
+                if (cic == cfqd->active_cic &&
+                    del_timer(&cfqd->idle_slice_timer)) {
+                        cfq_slice_expired(cfqd, 0);
+                        cfq_start_queueing(cfqd, cfqq);
+                }
                 return;
-
-        cic = crq->io_context;
+        }
 
         cfq_update_io_thinktime(cfqd, cic);
         cfq_update_io_seektime(cfqd, cic, crq);
@@ -2164,10 +2196,9 @@ static void cfq_idle_class_timer(unsigned long data)
          * race with a non-idle queue, reset timer
          */
         end = cfqd->last_end_request + CFQ_IDLE_GRACE;
-        if (!time_after_eq(jiffies, end)) {
-                cfqd->idle_class_timer.expires = end;
-                add_timer(&cfqd->idle_class_timer);
-        } else
+        if (!time_after_eq(jiffies, end))
+                mod_timer(&cfqd->idle_class_timer, end);
+        else
                 cfq_schedule_dispatch(cfqd);
 
         spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
@@ -2187,7 +2218,7 @@ static void cfq_exit_queue(elevator_t *e)
 
         cfq_shutdown_timer_wq(cfqd);
 
-        write_lock(&cfq_exit_lock);
+        spin_lock(&cfq_exit_lock);
         spin_lock_irq(q->queue_lock);
 
         if (cfqd->active_queue)
@@ -2210,7 +2241,7 @@ static void cfq_exit_queue(elevator_t *e)
         }
 
         spin_unlock_irq(q->queue_lock);
-        write_unlock(&cfq_exit_lock);
+        spin_unlock(&cfq_exit_lock);
 
         cfq_shutdown_timer_wq(cfqd);
 
@@ -2220,14 +2251,14 @@ static void cfq_exit_queue(elevator_t *e)
         kfree(cfqd);
 }
 
-static int cfq_init_queue(request_queue_t *q, elevator_t *e)
+static void *cfq_init_queue(request_queue_t *q, elevator_t *e)
 {
         struct cfq_data *cfqd;
         int i;
 
         cfqd = kmalloc(sizeof(*cfqd), GFP_KERNEL);
         if (!cfqd)
-                return -ENOMEM;
+                return NULL;
 
         memset(cfqd, 0, sizeof(*cfqd));
 
@@ -2257,8 +2288,6 @@ static int cfq_init_queue(request_queue_t *q, elevator_t *e)
         for (i = 0; i < CFQ_QHASH_ENTRIES; i++)
                 INIT_HLIST_HEAD(&cfqd->cfq_hash[i]);
 
-        e->elevator_data = cfqd;
-
         cfqd->queue = q;
 
         cfqd->max_queued = q->nr_requests / 4;
@@ -2285,14 +2314,14 @@ static int cfq_init_queue(request_queue_t *q, elevator_t *e)
         cfqd->cfq_slice_async_rq = cfq_slice_async_rq;
         cfqd->cfq_slice_idle = cfq_slice_idle;
 
-        return 0;
+        return cfqd;
 out_crqpool:
         kfree(cfqd->cfq_hash);
 out_cfqhash:
         kfree(cfqd->crq_hash);
 out_crqhash:
         kfree(cfqd);
-        return -ENOMEM;
+        return NULL;
 }
 
 static void cfq_slab_kill(void)
diff --git a/block/deadline-iosched.c b/block/deadline-iosched.c
index 399fa1e60e1f..3bd0415a9828 100644
--- a/block/deadline-iosched.c
+++ b/block/deadline-iosched.c
@@ -613,24 +613,24 @@ static void deadline_exit_queue(elevator_t *e)
  * initialize elevator private data (deadline_data), and alloc a drq for
  * each request on the free lists
  */
-static int deadline_init_queue(request_queue_t *q, elevator_t *e)
+static void *deadline_init_queue(request_queue_t *q, elevator_t *e)
 {
         struct deadline_data *dd;
         int i;
 
         if (!drq_pool)
-                return -ENOMEM;
+                return NULL;
 
         dd = kmalloc_node(sizeof(*dd), GFP_KERNEL, q->node);
         if (!dd)
-                return -ENOMEM;
+                return NULL;
         memset(dd, 0, sizeof(*dd));
 
         dd->hash = kmalloc_node(sizeof(struct list_head)*DL_HASH_ENTRIES,
                                 GFP_KERNEL, q->node);
         if (!dd->hash) {
                 kfree(dd);
-                return -ENOMEM;
+                return NULL;
         }
 
         dd->drq_pool = mempool_create_node(BLKDEV_MIN_RQ, mempool_alloc_slab,
@@ -638,7 +638,7 @@ static int deadline_init_queue(request_queue_t *q, elevator_t *e)
         if (!dd->drq_pool) {
                 kfree(dd->hash);
                 kfree(dd);
-                return -ENOMEM;
+                return NULL;
         }
 
         for (i = 0; i < DL_HASH_ENTRIES; i++)
@@ -653,8 +653,7 @@ static int deadline_init_queue(request_queue_t *q, elevator_t *e)
         dd->writes_starved = writes_starved;
         dd->front_merges = 1;
         dd->fifo_batch = fifo_batch;
-        e->elevator_data = dd;
-        return 0;
+        return dd;
 }
 
 static void deadline_put_request(request_queue_t *q, struct request *rq)
diff --git a/block/elevator.c b/block/elevator.c
index 8768a367fdde..a0afdd317cef 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -121,16 +121,16 @@ static struct elevator_type *elevator_get(const char *name)
         return e;
 }
 
-static int elevator_attach(request_queue_t *q, struct elevator_queue *eq)
+static void *elevator_init_queue(request_queue_t *q, struct elevator_queue *eq)
 {
-        int ret = 0;
+        return eq->ops->elevator_init_fn(q, eq);
+}
 
+static void elevator_attach(request_queue_t *q, struct elevator_queue *eq,
+                           void *data)
+{
         q->elevator = eq;
-
-        if (eq->ops->elevator_init_fn)
-                ret = eq->ops->elevator_init_fn(q, eq);
-
-        return ret;
+        eq->elevator_data = data;
 }
 
 static char chosen_elevator[16];
@@ -181,6 +181,7 @@ int elevator_init(request_queue_t *q, char *name)
         struct elevator_type *e = NULL;
         struct elevator_queue *eq;
         int ret = 0;
+        void *data;
 
         INIT_LIST_HEAD(&q->queue_head);
         q->last_merge = NULL;
@@ -202,10 +203,13 @@ int elevator_init(request_queue_t *q, char *name)
         if (!eq)
                 return -ENOMEM;
 
-        ret = elevator_attach(q, eq);
-        if (ret)
+        data = elevator_init_queue(q, eq);
+        if (!data) {
                 kobject_put(&eq->kobj);
+                return -ENOMEM;
+        }
 
+        elevator_attach(q, eq, data);
         return ret;
 }
 
@@ -722,13 +726,16 @@ int elv_register_queue(struct request_queue *q)
         return error;
 }
 
+static void __elv_unregister_queue(elevator_t *e)
+{
+        kobject_uevent(&e->kobj, KOBJ_REMOVE);
+        kobject_del(&e->kobj);
+}
+
 void elv_unregister_queue(struct request_queue *q)
 {
-        if (q) {
-                elevator_t *e = q->elevator;
-                kobject_uevent(&e->kobj, KOBJ_REMOVE);
-                kobject_del(&e->kobj);
-        }
+        if (q)
+                __elv_unregister_queue(q->elevator);
 }
 
 int elv_register(struct elevator_type *e)
@@ -780,6 +787,7 @@ EXPORT_SYMBOL_GPL(elv_unregister);
 static int elevator_switch(request_queue_t *q, struct elevator_type *new_e)
 {
         elevator_t *old_elevator, *e;
+        void *data;
 
         /*
          * Allocate new elevator
@@ -788,6 +796,12 @@ static int elevator_switch(request_queue_t *q, struct elevator_type *new_e)
         if (!e)
                 return 0;
 
+        data = elevator_init_queue(q, e);
+        if (!data) {
+                kobject_put(&e->kobj);
+                return 0;
+        }
+
         /*
          * Turn on BYPASS and drain all requests w/ elevator private data
          */
@@ -806,19 +820,19 @@ static int elevator_switch(request_queue_t *q, struct elevator_type *new_e)
                 elv_drain_elevator(q);
         }
 
-        spin_unlock_irq(q->queue_lock);
-
         /*
-         * unregister old elevator data
+         * Remember old elevator.
          */
-        elv_unregister_queue(q);
         old_elevator = q->elevator;
 
         /*
          * attach and start new elevator
          */
-        if (elevator_attach(q, e))
-                goto fail;
+        elevator_attach(q, e, data);
+
+        spin_unlock_irq(q->queue_lock);
+
+        __elv_unregister_queue(old_elevator);
 
         if (elv_register_queue(q))
                 goto fail_register;
@@ -837,7 +851,6 @@ fail_register:
          */
         elevator_exit(e);
         e = NULL;
-fail:
         q->elevator = old_elevator;
         elv_register_queue(q);
         clear_bit(QUEUE_FLAG_ELVSWITCH, &q->queue_flags);
diff --git a/block/noop-iosched.c b/block/noop-iosched.c
index f370e4a7fe6d..56a7c620574f 100644
--- a/block/noop-iosched.c
+++ b/block/noop-iosched.c
@@ -65,16 +65,15 @@ noop_latter_request(request_queue_t *q, struct request *rq)
         return list_entry(rq->queuelist.next, struct request, queuelist);
 }
 
-static int noop_init_queue(request_queue_t *q, elevator_t *e)
+static void *noop_init_queue(request_queue_t *q, elevator_t *e)
 {
         struct noop_data *nd;
 
         nd = kmalloc(sizeof(*nd), GFP_KERNEL);
         if (!nd)
-                return -ENOMEM;
+                return NULL;
         INIT_LIST_HEAD(&nd->queue);
-        e->elevator_data = nd;
-        return 0;
+        return nd;
 }
 
 static void noop_exit_queue(elevator_t *e)