3 files changed, 439 insertions, 416 deletions

diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index f92ba2a869b4..64df3fa303b0 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -9,7 +9,6 @@
 #include <linux/module.h>
 #include <linux/blkdev.h>
 #include <linux/elevator.h>
-#include <linux/hash.h>
 #include <linux/rbtree.h>
 #include <linux/ioprio.h>
 
@@ -26,19 +25,17 @@ static int cfq_slice_async = HZ / 25;
 static const int cfq_slice_async_rq = 2;
 static int cfq_slice_idle = HZ / 125;
 
+/*
+ * grace period before allowing idle class to get disk access
+ */
 #define CFQ_IDLE_GRACE          (HZ / 10)
-#define CFQ_SLICE_SCALE         (5)
-
-#define CFQ_KEY_ASYNC           (0)
 
 /*
- * for the hash of cfqq inside the cfqd
+ * below this threshold, we consider thinktime immediate
  */
-#define CFQ_QHASH_SHIFT         6
-#define CFQ_QHASH_ENTRIES       (1 << CFQ_QHASH_SHIFT)
-#define list_entry_qhash(entry) hlist_entry((entry), struct cfq_queue, cfq_hash)
+#define CFQ_MIN_TT              (2)
 
-#define list_entry_cfqq(ptr)    list_entry((ptr), struct cfq_queue, cfq_list)
+#define CFQ_SLICE_SCALE         (5)
 
 #define RQ_CIC(rq)              ((struct cfq_io_context*)(rq)->elevator_private)
 #define RQ_CFQQ(rq)             ((rq)->elevator_private2)
@@ -56,17 +53,21 @@ static struct completion *ioc_gone;
 #define ASYNC                   (0)
 #define SYNC                    (1)
 
-#define cfq_cfqq_dispatched(cfqq)       \
-        ((cfqq)->on_dispatch[ASYNC] + (cfqq)->on_dispatch[SYNC])
-
-#define cfq_cfqq_class_sync(cfqq)       ((cfqq)->key != CFQ_KEY_ASYNC)
-
-#define cfq_cfqq_sync(cfqq)             \
-        (cfq_cfqq_class_sync(cfqq) || (cfqq)->on_dispatch[SYNC])
-
 #define sample_valid(samples)   ((samples) > 80)
 
 /*
+ * Most of our rbtree usage is for sorting with min extraction, so
+ * if we cache the leftmost node we don't have to walk down the tree
+ * to find it. Idea borrowed from Ingo Molnars CFS scheduler. We should
+ * move this into the elevator for the rq sorting as well.
+ */
+struct cfq_rb_root {
+        struct rb_root rb;
+        struct rb_node *left;
+};
+#define CFQ_RB_ROOT     (struct cfq_rb_root) { RB_ROOT, NULL, }
+
+/*
  * Per block device queue structure
  */
 struct cfq_data {
@@ -75,18 +76,11 @@ struct cfq_data {
         /*
          * rr list of queues with requests and the count of them
          */
-        struct list_head rr_list[CFQ_PRIO_LISTS];
-        struct list_head busy_rr;
-        struct list_head cur_rr;
-        struct list_head idle_rr;
+        struct cfq_rb_root service_tree;
         unsigned int busy_queues;
 
-        /*
-         * cfqq lookup hash
-         */
-        struct hlist_head *cfq_hash;
-
         int rq_in_driver;
+        int sync_flight;
         int hw_tag;
 
         /*
@@ -97,12 +91,10 @@ struct cfq_data {
 
         struct cfq_queue *active_queue;
         struct cfq_io_context *active_cic;
-        int cur_prio, cur_end_prio;
-        unsigned int dispatch_slice;
 
         struct timer_list idle_class_timer;
 
-        sector_t last_sector;
+        sector_t last_position;
         unsigned long last_end_request;
 
         /*
@@ -117,6 +109,9 @@ struct cfq_data {
         unsigned int cfq_slice_idle;
 
         struct list_head cic_list;
+
+        sector_t new_seek_mean;
+        u64 new_seek_total;
 };
 
 /*
@@ -127,12 +122,10 @@ struct cfq_queue {
         atomic_t ref;
         /* parent cfq_data */
         struct cfq_data *cfqd;
-        /* cfqq lookup hash */
-        struct hlist_node cfq_hash;
-        /* hash key */
-        unsigned int key;
-        /* member of the rr/busy/cur/idle cfqd list */
-        struct list_head cfq_list;
+        /* service_tree member */
+        struct rb_node rb_node;
+        /* service_tree key */
+        unsigned long rb_key;
         /* sorted list of pending requests */
         struct rb_root sort_list;
         /* if fifo isn't expired, next request to serve */
@@ -147,11 +140,10 @@ struct cfq_queue {
         struct list_head fifo;
 
         unsigned long slice_end;
-        unsigned long service_last;
         long slice_resid;
 
-        /* number of requests that are on the dispatch list */
-        int on_dispatch[2];
+        /* number of requests that are on the dispatch list or inside driver */
+        int dispatched;
 
         /* io prio of this group */
         unsigned short ioprio, org_ioprio;
@@ -159,6 +151,8 @@ struct cfq_queue {
 
         /* various state flags, see below */
         unsigned int flags;
+
+        sector_t last_request_pos;
 };
 
 enum cfqq_state_flags {
@@ -172,6 +166,7 @@ enum cfqq_state_flags {
         CFQ_CFQQ_FLAG_prio_changed,     /* task priority has changed */
         CFQ_CFQQ_FLAG_queue_new,        /* queue never been serviced */
         CFQ_CFQQ_FLAG_slice_new,        /* no requests dispatched in slice */
+        CFQ_CFQQ_FLAG_sync,             /* synchronous queue */
 };
 
 #define CFQ_CFQQ_FNS(name)                                              \
@@ -198,11 +193,38 @@ CFQ_CFQQ_FNS(idle_window);
 CFQ_CFQQ_FNS(prio_changed);
 CFQ_CFQQ_FNS(queue_new);
 CFQ_CFQQ_FNS(slice_new);
+CFQ_CFQQ_FNS(sync);
 #undef CFQ_CFQQ_FNS
 
-static struct cfq_queue *cfq_find_cfq_hash(struct cfq_data *, unsigned int, unsigned short);
 static void cfq_dispatch_insert(request_queue_t *, struct request *);
-static struct cfq_queue *cfq_get_queue(struct cfq_data *cfqd, unsigned int key, struct task_struct *tsk, gfp_t gfp_mask);
+static struct cfq_queue *cfq_get_queue(struct cfq_data *, int,
+                                       struct task_struct *, gfp_t);
+static struct cfq_io_context *cfq_cic_rb_lookup(struct cfq_data *,
+                                                struct io_context *);
+
+static inline struct cfq_queue *cic_to_cfqq(struct cfq_io_context *cic,
+                                            int is_sync)
+{
+        return cic->cfqq[!!is_sync];
+}
+
+static inline void cic_set_cfqq(struct cfq_io_context *cic,
+                                struct cfq_queue *cfqq, int is_sync)
+{
+        cic->cfqq[!!is_sync] = cfqq;
+}
+
+/*
+ * We regard a request as SYNC, if it's either a read or has the SYNC bit
+ * set (in which case it could also be direct WRITE).
+ */
+static inline int cfq_bio_sync(struct bio *bio)
+{
+        if (bio_data_dir(bio) == READ || bio_sync(bio))
+                return 1;
+
+        return 0;
+}
 
 /*
  * scheduler run of queue, if there are requests pending and no one in the
@@ -221,44 +243,31 @@ static int cfq_queue_empty(request_queue_t *q)
         return !cfqd->busy_queues;
 }
 
-static inline pid_t cfq_queue_pid(struct task_struct *task, int rw, int is_sync)
-{
-        /*
-         * Use the per-process queue, for read requests and syncronous writes
-         */
-        if (!(rw & REQ_RW) || is_sync)
-                return task->pid;
-
-        return CFQ_KEY_ASYNC;
-}
-
 /*
  * Scale schedule slice based on io priority. Use the sync time slice only
  * if a queue is marked sync and has sync io queued. A sync queue with async
  * io only, should not get full sync slice length.
  */
-static inline int
-cfq_prio_to_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq)
+static inline int cfq_prio_slice(struct cfq_data *cfqd, int sync,
+                                 unsigned short prio)
 {
-        const int base_slice = cfqd->cfq_slice[cfq_cfqq_sync(cfqq)];
+        const int base_slice = cfqd->cfq_slice[sync];
 
-        WARN_ON(cfqq->ioprio >= IOPRIO_BE_NR);
+        WARN_ON(prio >= IOPRIO_BE_NR);
+
+        return base_slice + (base_slice/CFQ_SLICE_SCALE * (4 - prio));
+}
 
-        return base_slice + (base_slice/CFQ_SLICE_SCALE * (4 - cfqq->ioprio));
+static inline int
+cfq_prio_to_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq)
+{
+        return cfq_prio_slice(cfqd, cfq_cfqq_sync(cfqq), cfqq->ioprio);
 }
 
 static inline void
 cfq_set_prio_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq)
 {
         cfqq->slice_end = cfq_prio_to_slice(cfqd, cfqq) + jiffies;
-        cfqq->slice_end += cfqq->slice_resid;
-
-        /*
-         * Don't carry over residual for more than one slice, we only want
-         * to slightly correct the fairness. Carrying over forever would
-         * easily introduce oscillations.
-         */
-        cfqq->slice_resid = 0;
 }
 
 /*
@@ -307,7 +316,7 @@ cfq_choose_req(struct cfq_data *cfqd, struct request *rq1, struct request *rq2)
         s1 = rq1->sector;
         s2 = rq2->sector;
 
-        last = cfqd->last_sector;
+        last = cfqd->last_position;
 
         /*
          * by definition, 1KiB is 2 sectors
@@ -372,6 +381,26 @@ cfq_choose_req(struct cfq_data *cfqd, struct request *rq1, struct request *rq2)
 }
 
 /*
+ * The below is leftmost cache rbtree addon
+ */
+static struct rb_node *cfq_rb_first(struct cfq_rb_root *root)
+{
+        if (!root->left)
+                root->left = rb_first(&root->rb);
+
+        return root->left;
+}
+
+static void cfq_rb_erase(struct rb_node *n, struct cfq_rb_root *root)
+{
+        if (root->left == n)
+                root->left = NULL;
+
+        rb_erase(n, &root->rb);
+        RB_CLEAR_NODE(n);
+}
+
+/*
  * would be nice to take fifo expire time into account as well
  */
 static struct request *
@@ -398,78 +427,96 @@ cfq_find_next_rq(struct cfq_data *cfqd, struct cfq_queue *cfqq,
         return cfq_choose_req(cfqd, next, prev);
 }
 
-static void cfq_resort_rr_list(struct cfq_queue *cfqq, int preempted)
+static unsigned long cfq_slice_offset(struct cfq_data *cfqd,
+                                      struct cfq_queue *cfqq)
 {
-        struct cfq_data *cfqd = cfqq->cfqd;
-        struct list_head *list, *n;
-        struct cfq_queue *__cfqq;
-
         /*
-         * Resorting requires the cfqq to be on the RR list already.
+         * just an approximation, should be ok.
          */
-        if (!cfq_cfqq_on_rr(cfqq))
-                return;
+        return (cfqd->busy_queues - 1) * (cfq_prio_slice(cfqd, 1, 0) -
+                       cfq_prio_slice(cfqd, cfq_cfqq_sync(cfqq), cfqq->ioprio));
+}
 
-        list_del(&cfqq->cfq_list);
+/*
+ * The cfqd->service_tree holds all pending cfq_queue's that have
+ * requests waiting to be processed. It is sorted in the order that
+ * we will service the queues.
+ */
+static void cfq_service_tree_add(struct cfq_data *cfqd,
+                                    struct cfq_queue *cfqq, int add_front)
+{
+        struct rb_node **p = &cfqd->service_tree.rb.rb_node;
+        struct rb_node *parent = NULL;
+        unsigned long rb_key;
+        int left;
+
+        if (!add_front) {
+                rb_key = cfq_slice_offset(cfqd, cfqq) + jiffies;
+                rb_key += cfqq->slice_resid;
+                cfqq->slice_resid = 0;
+        } else
+                rb_key = 0;
 
-        if (cfq_class_rt(cfqq))
-                list = &cfqd->cur_rr;
-        else if (cfq_class_idle(cfqq))
-                list = &cfqd->idle_rr;
-        else {
+        if (!RB_EMPTY_NODE(&cfqq->rb_node)) {
                 /*
-                 * if cfqq has requests in flight, don't allow it to be
-                 * found in cfq_set_active_queue before it has finished them.
-                 * this is done to increase fairness between a process that
-                 * has lots of io pending vs one that only generates one
-                 * sporadically or synchronously
+                 * same position, nothing more to do
                  */
-                if (cfq_cfqq_dispatched(cfqq))
-                        list = &cfqd->busy_rr;
-                else
-                        list = &cfqd->rr_list[cfqq->ioprio];
+                if (rb_key == cfqq->rb_key)
+                        return;
+
+                cfq_rb_erase(&cfqq->rb_node, &cfqd->service_tree);
         }
 
-        if (preempted || cfq_cfqq_queue_new(cfqq)) {
-                /*
-                 * If this queue was preempted or is new (never been serviced),
-                 * let it be added first for fairness but beind other new
-                 * queues.
-                 */
-                n = list;
-                while (n->next != list) {
-                        __cfqq = list_entry_cfqq(n->next);
-                        if (!cfq_cfqq_queue_new(__cfqq))
-                                break;
+        left = 1;
+        while (*p) {
+                struct cfq_queue *__cfqq;
+                struct rb_node **n;
+
+                parent = *p;
+                __cfqq = rb_entry(parent, struct cfq_queue, rb_node);
 
-                        n = n->next;
-                }
-                list_add_tail(&cfqq->cfq_list, n);
-        } else if (!cfq_cfqq_class_sync(cfqq)) {
-                /*
-                 * async queue always goes to the end. this wont be overly
-                 * unfair to writes, as the sort of the sync queue wont be
-                 * allowed to pass the async queue again.
-                 */
-                list_add_tail(&cfqq->cfq_list, list);
-        } else {
                 /*
-                 * sort by last service, but don't cross a new or async
-                 * queue. we don't cross a new queue because it hasn't been
-                 * service before, and we don't cross an async queue because
-                 * it gets added to the end on expire.
+                 * sort RT queues first, we always want to give
+                 * preference to them. IDLE queues goes to the back.
+                 * after that, sort on the next service time.
                  */
-                n = list;
-                while ((n = n->prev) != list) {
-                        struct cfq_queue *__cfqq = list_entry_cfqq(n);
+                if (cfq_class_rt(cfqq) > cfq_class_rt(__cfqq))
+                        n = &(*p)->rb_left;
+                else if (cfq_class_rt(cfqq) < cfq_class_rt(__cfqq))
+                        n = &(*p)->rb_right;
+                else if (cfq_class_idle(cfqq) < cfq_class_idle(__cfqq))
+                        n = &(*p)->rb_left;
+                else if (cfq_class_idle(cfqq) > cfq_class_idle(__cfqq))
+                        n = &(*p)->rb_right;
+                else if (rb_key < __cfqq->rb_key)
+                        n = &(*p)->rb_left;
+                else
+                        n = &(*p)->rb_right;
 
-                        if (!cfq_cfqq_class_sync(cfqq) || !__cfqq->service_last)
-                                break;
-                        if (time_before(__cfqq->service_last, cfqq->service_last))
-                                break;
-                }
-                list_add(&cfqq->cfq_list, n);
+                if (n == &(*p)->rb_right)
+                        left = 0;
+
+                p = n;
         }
+
+        if (left)
+                cfqd->service_tree.left = &cfqq->rb_node;
+
+        cfqq->rb_key = rb_key;
+        rb_link_node(&cfqq->rb_node, parent, p);
+        rb_insert_color(&cfqq->rb_node, &cfqd->service_tree.rb);
+}
+
+/*
+ * Update cfqq's position in the service tree.
+ */
+static void cfq_resort_rr_list(struct cfq_data *cfqd, struct cfq_queue *cfqq)
+{
+        /*
+         * Resorting requires the cfqq to be on the RR list already.
+         */
+        if (cfq_cfqq_on_rr(cfqq))
+                cfq_service_tree_add(cfqd, cfqq, 0);
 }
 
 /*
@@ -483,15 +530,21 @@ cfq_add_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
         cfq_mark_cfqq_on_rr(cfqq);
         cfqd->busy_queues++;
 
-        cfq_resort_rr_list(cfqq, 0);
+        cfq_resort_rr_list(cfqd, cfqq);
 }
 
+/*
+ * Called when the cfqq no longer has requests pending, remove it from
+ * the service tree.
+ */
 static inline void
 cfq_del_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
 {
         BUG_ON(!cfq_cfqq_on_rr(cfqq));
         cfq_clear_cfqq_on_rr(cfqq);
-        list_del_init(&cfqq->cfq_list);
+
+        if (!RB_EMPTY_NODE(&cfqq->rb_node))
+                cfq_rb_erase(&cfqq->rb_node, &cfqd->service_tree);
 
         BUG_ON(!cfqd->busy_queues);
         cfqd->busy_queues--;
@@ -552,10 +605,14 @@ static struct request *
 cfq_find_rq_fmerge(struct cfq_data *cfqd, struct bio *bio)
 {
         struct task_struct *tsk = current;
-        pid_t key = cfq_queue_pid(tsk, bio_data_dir(bio), bio_sync(bio));
+        struct cfq_io_context *cic;
         struct cfq_queue *cfqq;
 
-        cfqq = cfq_find_cfq_hash(cfqd, key, tsk->ioprio);
+        cic = cfq_cic_rb_lookup(cfqd, tsk->io_context);
+        if (!cic)
+                return NULL;
+
+        cfqq = cic_to_cfqq(cic, cfq_bio_sync(bio));
         if (cfqq) {
                 sector_t sector = bio->bi_sector + bio_sectors(bio);
 
@@ -579,6 +636,8 @@ static void cfq_activate_request(request_queue_t *q, struct request *rq)
          */
         if (!cfqd->hw_tag && cfqd->rq_in_driver > 4)
                 cfqd->hw_tag = 1;
+
+        cfqd->last_position = rq->hard_sector + rq->hard_nr_sectors;
 }
 
 static void cfq_deactivate_request(request_queue_t *q, struct request *rq)
@@ -605,8 +664,7 @@ static void cfq_remove_request(struct request *rq)
         }
 }
 
-static int
-cfq_merge(request_queue_t *q, struct request **req, struct bio *bio)
+static int cfq_merge(request_queue_t *q, struct request **req, struct bio *bio)
 {
         struct cfq_data *cfqd = q->elevator->elevator_data;
         struct request *__rq;
@@ -648,23 +706,24 @@ static int cfq_allow_merge(request_queue_t *q, struct request *rq,
                            struct bio *bio)
 {
         struct cfq_data *cfqd = q->elevator->elevator_data;
-        const int rw = bio_data_dir(bio);
+        struct cfq_io_context *cic;
         struct cfq_queue *cfqq;
-        pid_t key;
 
         /*
          * Disallow merge of a sync bio into an async request.
          */
-        if ((bio_data_dir(bio) == READ || bio_sync(bio)) && !rq_is_sync(rq))
+        if (cfq_bio_sync(bio) && !rq_is_sync(rq))
                 return 0;
 
         /*
          * Lookup the cfqq that this bio will be queued with. Allow
          * merge only if rq is queued there.
          */
-        key = cfq_queue_pid(current, rw, bio_sync(bio));
-        cfqq = cfq_find_cfq_hash(cfqd, key, current->ioprio);
+        cic = cfq_cic_rb_lookup(cfqd, current->io_context);
+        if (!cic)
+                return 0;
 
+        cfqq = cic_to_cfqq(cic, cfq_bio_sync(bio));
         if (cfqq == RQ_CFQQ(rq))
                 return 1;
 
@@ -684,6 +743,7 @@ __cfq_set_active_queue(struct cfq_data *cfqd, struct cfq_queue *cfqq)
                 cfq_clear_cfqq_must_alloc_slice(cfqq);
                 cfq_clear_cfqq_fifo_expire(cfqq);
                 cfq_mark_cfqq_slice_new(cfqq);
+                cfq_clear_cfqq_queue_new(cfqq);
         }
 
         cfqd->active_queue = cfqq;
@@ -694,23 +754,21 @@ __cfq_set_active_queue(struct cfq_data *cfqd, struct cfq_queue *cfqq)
  */
 static void
 __cfq_slice_expired(struct cfq_data *cfqd, struct cfq_queue *cfqq,
-                    int preempted, int timed_out)
+                    int timed_out)
 {
         if (cfq_cfqq_wait_request(cfqq))
                 del_timer(&cfqd->idle_slice_timer);
 
         cfq_clear_cfqq_must_dispatch(cfqq);
         cfq_clear_cfqq_wait_request(cfqq);
-        cfq_clear_cfqq_queue_new(cfqq);
 
         /*
-         * store what was left of this slice, if the queue idled out
-         * or was preempted
+         * store what was left of this slice, if the queue idled/timed out
          */
         if (timed_out && !cfq_cfqq_slice_new(cfqq))
                 cfqq->slice_resid = cfqq->slice_end - jiffies;
 
-        cfq_resort_rr_list(cfqq, preempted);
+        cfq_resort_rr_list(cfqd, cfqq);
 
         if (cfqq == cfqd->active_queue)
                 cfqd->active_queue = NULL;
@@ -719,163 +777,152 @@ __cfq_slice_expired(struct cfq_data *cfqd, struct cfq_queue *cfqq,
                 put_io_context(cfqd->active_cic->ioc);
                 cfqd->active_cic = NULL;
         }
-
-        cfqd->dispatch_slice = 0;
 }
 
-static inline void cfq_slice_expired(struct cfq_data *cfqd, int preempted,
-                                     int timed_out)
+static inline void cfq_slice_expired(struct cfq_data *cfqd, int timed_out)
 {
         struct cfq_queue *cfqq = cfqd->active_queue;
 
         if (cfqq)
-                __cfq_slice_expired(cfqd, cfqq, preempted, timed_out);
+                __cfq_slice_expired(cfqd, cfqq, timed_out);
 }
 
 /*
- * 0
- * 0,1
- * 0,1,2
- * 0,1,2,3
- * 0,1,2,3,4
- * 0,1,2,3,4,5
- * 0,1,2,3,4,5,6
- * 0,1,2,3,4,5,6,7
+ * Get next queue for service. Unless we have a queue preemption,
+ * we'll simply select the first cfqq in the service tree.
  */
-static int cfq_get_next_prio_level(struct cfq_data *cfqd)
+static struct cfq_queue *cfq_get_next_queue(struct cfq_data *cfqd)
 {
-        int prio, wrap;
+        struct cfq_queue *cfqq;
+        struct rb_node *n;
 
-        prio = -1;
-        wrap = 0;
-        do {
-                int p;
+        if (RB_EMPTY_ROOT(&cfqd->service_tree.rb))
+                return NULL;
 
-                for (p = cfqd->cur_prio; p <= cfqd->cur_end_prio; p++) {
-                        if (!list_empty(&cfqd->rr_list[p])) {
-                                prio = p;
-                                break;
-                        }
-                }
+        n = cfq_rb_first(&cfqd->service_tree);
+        cfqq = rb_entry(n, struct cfq_queue, rb_node);
 
-                if (prio != -1)
-                        break;
-                cfqd->cur_prio = 0;
-                if (++cfqd->cur_end_prio == CFQ_PRIO_LISTS) {
-                        cfqd->cur_end_prio = 0;
-                        if (wrap)
-                                break;
-                        wrap = 1;
-                }
-        } while (1);
+        if (cfq_class_idle(cfqq)) {
+                unsigned long end;
 
-        if (unlikely(prio == -1))
-                return -1;
+                /*
+                 * 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
+                 */
+                end = cfqd->last_end_request + CFQ_IDLE_GRACE;
+                if (time_before(jiffies, end)) {
+                        mod_timer(&cfqd->idle_class_timer, end);
+                        cfqq = NULL;
+                }
+        }
 
-        BUG_ON(prio >= CFQ_PRIO_LISTS);
+        return cfqq;
+}
 
-        list_splice_init(&cfqd->rr_list[prio], &cfqd->cur_rr);
+/*
+ * Get and set a new active queue for service.
+ */
+static struct cfq_queue *cfq_set_active_queue(struct cfq_data *cfqd)
+{
+        struct cfq_queue *cfqq;
 
-        cfqd->cur_prio = prio + 1;
-        if (cfqd->cur_prio > cfqd->cur_end_prio) {
-                cfqd->cur_end_prio = cfqd->cur_prio;
-                cfqd->cur_prio = 0;
-        }
-        if (cfqd->cur_end_prio == CFQ_PRIO_LISTS) {
-                cfqd->cur_prio = 0;
-                cfqd->cur_end_prio = 0;
-        }
+        cfqq = cfq_get_next_queue(cfqd);
+        __cfq_set_active_queue(cfqd, cfqq);
+        return cfqq;
+}
 
-        return prio;
+static inline sector_t cfq_dist_from_last(struct cfq_data *cfqd,
+                                          struct request *rq)
+{
+        if (rq->sector >= cfqd->last_position)
+                return rq->sector - cfqd->last_position;
+        else
+                return cfqd->last_position - rq->sector;
 }
 
-static struct cfq_queue *cfq_set_active_queue(struct cfq_data *cfqd)
+static inline int cfq_rq_close(struct cfq_data *cfqd, struct request *rq)
 {
-        struct cfq_queue *cfqq = NULL;
+        struct cfq_io_context *cic = cfqd->active_cic;
 
-        if (!list_empty(&cfqd->cur_rr) || cfq_get_next_prio_level(cfqd) != -1) {
-                /*
-                 * if current list is non-empty, grab first entry. if it is
-                 * empty, get next prio level and grab first entry then if any
-                 * are spliced
-                 */
-                cfqq = list_entry_cfqq(cfqd->cur_rr.next);
-        } else if (!list_empty(&cfqd->busy_rr)) {
-                /*
-                 * If no new queues are available, check if the busy list has
-                 * some before falling back to idle io.
-                 */
-                cfqq = list_entry_cfqq(cfqd->busy_rr.next);
-        } else if (!list_empty(&cfqd->idle_rr)) {
-                /*
-                 * 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
-                 */
-                unsigned long end = cfqd->last_end_request + CFQ_IDLE_GRACE;
+        if (!sample_valid(cic->seek_samples))
+                return 0;
 
-                if (time_after_eq(jiffies, end))
-                        cfqq = list_entry_cfqq(cfqd->idle_rr.next);
-                else
-                        mod_timer(&cfqd->idle_class_timer, end);
-        }
+        return cfq_dist_from_last(cfqd, rq) <= cic->seek_mean;
+}
 
-        __cfq_set_active_queue(cfqd, cfqq);
-        return cfqq;
+static int cfq_close_cooperator(struct cfq_data *cfq_data,
+                                struct cfq_queue *cfqq)
+{
+        /*
+         * We should notice if some of the queues are cooperating, eg
+         * working closely on the same area of the disk. In that case,
+         * we can group them together and don't waste time idling.
+         */
+        return 0;
 }
 
-#define CIC_SEEKY(cic) ((cic)->seek_mean > (128 * 1024))
+#define CIC_SEEKY(cic) ((cic)->seek_mean > (8 * 1024))
 
-static int cfq_arm_slice_timer(struct cfq_data *cfqd)
+static void cfq_arm_slice_timer(struct cfq_data *cfqd)
 {
         struct cfq_queue *cfqq = cfqd->active_queue;
         struct cfq_io_context *cic;
         unsigned long sl;
 
         WARN_ON(!RB_EMPTY_ROOT(&cfqq->sort_list));
+        WARN_ON(cfq_cfqq_slice_new(cfqq));
 
         /*
          * idle is disabled, either manually or by past process history
          */
-        if (!cfqd->cfq_slice_idle)
-                return 0;
-        if (!cfq_cfqq_idle_window(cfqq))
-                return 0;
+        if (!cfqd->cfq_slice_idle || !cfq_cfqq_idle_window(cfqq))
+                return;
+
         /*
          * task has exited, don't wait
          */
         cic = cfqd->active_cic;
         if (!cic || !cic->ioc->task)
-                return 0;
+                return;
+
+        /*
+         * See if this prio level has a good candidate
+         */
+        if (cfq_close_cooperator(cfqd, cfqq) &&
+            (sample_valid(cic->ttime_samples) && cic->ttime_mean > 2))
+                return;
 
         cfq_mark_cfqq_must_dispatch(cfqq);
         cfq_mark_cfqq_wait_request(cfqq);
 
-        sl = min(cfqq->slice_end - 1, (unsigned long) cfqd->cfq_slice_idle);
-
         /*
          * we don't want to idle for seeks, but we do want to allow
          * fair distribution of slice time for a process doing back-to-back
          * seeks. so allow a little bit of time for him to submit a new rq
          */
+        sl = cfqd->cfq_slice_idle;
         if (sample_valid(cic->seek_samples) && CIC_SEEKY(cic))
-                sl = min(sl, msecs_to_jiffies(2));
+                sl = min(sl, msecs_to_jiffies(CFQ_MIN_TT));
 
         mod_timer(&cfqd->idle_slice_timer, jiffies + sl);
-        return 1;
 }
 
+/*
+ * Move request from internal lists to the request queue dispatch list.
+ */
 static void cfq_dispatch_insert(request_queue_t *q, struct request *rq)
 {
         struct cfq_data *cfqd = q->elevator->elevator_data;
         struct cfq_queue *cfqq = RQ_CFQQ(rq);
 
         cfq_remove_request(rq);
-        cfqq->on_dispatch[rq_is_sync(rq)]++;
+        cfqq->dispatched++;
         elv_dispatch_sort(q, rq);
 
-        rq = list_entry(q->queue_head.prev, struct request, queuelist);
-        cfqd->last_sector = rq->sector + rq->nr_sectors;
+        if (cfq_cfqq_sync(cfqq))
+                cfqd->sync_flight++;
 }
 
 /*
@@ -895,13 +942,13 @@ static inline struct request *cfq_check_fifo(struct cfq_queue *cfqq)
         if (list_empty(&cfqq->fifo))
                 return NULL;
 
-        fifo = cfq_cfqq_class_sync(cfqq);
+        fifo = cfq_cfqq_sync(cfqq);
         rq = rq_entry_fifo(cfqq->fifo.next);
 
-        if (time_after(jiffies, rq->start_time + cfqd->cfq_fifo_expire[fifo]))
-                return rq;
+        if (time_before(jiffies, rq->start_time + cfqd->cfq_fifo_expire[fifo]))
+                return NULL;
 
-        return NULL;
+        return rq;
 }
 
 static inline int
@@ -915,7 +962,8 @@ cfq_prio_to_maxrq(struct cfq_data *cfqd, struct cfq_queue *cfqq)
 }
 
 /*
- * get next queue for service
+ * Select a queue for service. If we have a current active queue,
+ * check whether to continue servicing it, or retrieve and set a new one.
  */
 static struct cfq_queue *cfq_select_queue(struct cfq_data *cfqd)
 {
@@ -926,33 +974,41 @@ static struct cfq_queue *cfq_select_queue(struct cfq_data *cfqd)
                 goto new_queue;
 
         /*
-         * slice has expired
+         * The active queue has run out of time, expire it and select new.
          */
-        if (!cfq_cfqq_must_dispatch(cfqq) && cfq_slice_used(cfqq))
+        if (cfq_slice_used(cfqq))
                 goto expire;
 
         /*
-         * if queue has requests, dispatch one. if not, check if
-         * enough slice is left to wait for one
+         * The active queue has requests and isn't expired, allow it to
+         * dispatch.
          */
         if (!RB_EMPTY_ROOT(&cfqq->sort_list))
                 goto keep_queue;
-        else if (cfq_cfqq_slice_new(cfqq) || cfq_cfqq_dispatched(cfqq)) {
+
+        /*
+         * No requests pending. If the active queue still has requests in
+         * flight or is idling for a new request, allow either of these
+         * conditions to happen (or time out) before selecting a new queue.
+         */
+        if (timer_pending(&cfqd->idle_slice_timer) ||
+            (cfqq->dispatched && cfq_cfqq_idle_window(cfqq))) {
                 cfqq = NULL;
                 goto keep_queue;
-        } else if (cfq_cfqq_class_sync(cfqq)) {
-                if (cfq_arm_slice_timer(cfqd))
-                        return NULL;
         }
 
 expire:
-        cfq_slice_expired(cfqd, 0, 0);
+        cfq_slice_expired(cfqd, 0);
 new_queue:
         cfqq = cfq_set_active_queue(cfqd);
 keep_queue:
         return cfqq;
 }
 
+/*
+ * Dispatch some requests from cfqq, moving them to the request queue
+ * dispatch list.
+ */
 static int
 __cfq_dispatch_requests(struct cfq_data *cfqd, struct cfq_queue *cfqq,
                         int max_dispatch)
@@ -975,7 +1031,6 @@ __cfq_dispatch_requests(struct cfq_data *cfqd, struct cfq_queue *cfqq,
                  */
                 cfq_dispatch_insert(cfqd->queue, rq);
 
-                cfqd->dispatch_slice++;
                 dispatched++;
 
                 if (!cfqd->active_cic) {
@@ -993,57 +1048,54 @@ __cfq_dispatch_requests(struct cfq_data *cfqd, struct cfq_queue *cfqq,
          * queue always expire after 1 dispatch round.
          */
         if (cfqd->busy_queues > 1 && ((!cfq_cfqq_sync(cfqq) &&
-            cfqd->dispatch_slice >= cfq_prio_to_maxrq(cfqd, cfqq)) ||
+            dispatched >= cfq_prio_to_maxrq(cfqd, cfqq)) ||
             cfq_class_idle(cfqq))) {
                 cfqq->slice_end = jiffies + 1;
-                cfq_slice_expired(cfqd, 0, 0);
+                cfq_slice_expired(cfqd, 0);
         }
 
         return dispatched;
 }
 
-static int
-cfq_forced_dispatch_cfqqs(struct list_head *list)
+static inline int __cfq_forced_dispatch_cfqq(struct cfq_queue *cfqq)
 {
-        struct cfq_queue *cfqq, *next;
-        int dispatched;
+        int dispatched = 0;
 
-        dispatched = 0;
-        list_for_each_entry_safe(cfqq, next, list, cfq_list) {
-                while (cfqq->next_rq) {
-                        cfq_dispatch_insert(cfqq->cfqd->queue, cfqq->next_rq);
-                        dispatched++;
-                }
-                BUG_ON(!list_empty(&cfqq->fifo));
+        while (cfqq->next_rq) {
+                cfq_dispatch_insert(cfqq->cfqd->queue, cfqq->next_rq);
+                dispatched++;
         }
 
+        BUG_ON(!list_empty(&cfqq->fifo));
         return dispatched;
 }
 
-static int
-cfq_forced_dispatch(struct cfq_data *cfqd)
+/*
+ * Drain our current requests. Used for barriers and when switching
+ * io schedulers on-the-fly.
+ */
+static int cfq_forced_dispatch(struct cfq_data *cfqd)
 {
-        int i, dispatched = 0;
+        int dispatched = 0;
+        struct rb_node *n;
 
-        for (i = 0; i < CFQ_PRIO_LISTS; i++)
-                dispatched += cfq_forced_dispatch_cfqqs(&cfqd->rr_list[i]);
+        while ((n = cfq_rb_first(&cfqd->service_tree)) != NULL) {
+                struct cfq_queue *cfqq = rb_entry(n, struct cfq_queue, rb_node);
 
-        dispatched += cfq_forced_dispatch_cfqqs(&cfqd->busy_rr);
-        dispatched += cfq_forced_dispatch_cfqqs(&cfqd->cur_rr);
-        dispatched += cfq_forced_dispatch_cfqqs(&cfqd->idle_rr);
+                dispatched += __cfq_forced_dispatch_cfqq(cfqq);
+        }
 
-        cfq_slice_expired(cfqd, 0, 0);
+        cfq_slice_expired(cfqd, 0);
 
         BUG_ON(cfqd->busy_queues);
 
         return dispatched;
 }
 
-static int
-cfq_dispatch_requests(request_queue_t *q, int force)
+static int cfq_dispatch_requests(request_queue_t *q, int force)
 {
         struct cfq_data *cfqd = q->elevator->elevator_data;
-        struct cfq_queue *cfqq, *prev_cfqq;
+        struct cfq_queue *cfqq;
         int dispatched;
 
         if (!cfqd->busy_queues)
@@ -1053,36 +1105,28 @@ cfq_dispatch_requests(request_queue_t *q, int force)
                 return cfq_forced_dispatch(cfqd);
 
         dispatched = 0;
-        prev_cfqq = NULL;
         while ((cfqq = cfq_select_queue(cfqd)) != NULL) {
                 int max_dispatch;
 
-                if (cfqd->busy_queues > 1) {
-                        /*
-                         * Don't repeat dispatch from the previous queue.
-                         */
-                        if (prev_cfqq == cfqq)
-                                break;
+                max_dispatch = cfqd->cfq_quantum;
+                if (cfq_class_idle(cfqq))
+                        max_dispatch = 1;
 
-                        /*
-                         * So we have dispatched before in this round, if the
-                         * next queue has idling enabled (must be sync), don't
-                         * allow it service until the previous have continued.
-                         */
-                        if (cfqd->rq_in_driver && cfq_cfqq_idle_window(cfqq))
+                if (cfqq->dispatched >= max_dispatch) {
+                        if (cfqd->busy_queues > 1)
+                                break;
+                        if (cfqq->dispatched >= 4 * max_dispatch)
                                 break;
                 }
 
+                if (cfqd->sync_flight && !cfq_cfqq_sync(cfqq))
+                        break;
+
                 cfq_clear_cfqq_must_dispatch(cfqq);
                 cfq_clear_cfqq_wait_request(cfqq);
                 del_timer(&cfqd->idle_slice_timer);
 
-                max_dispatch = cfqd->cfq_quantum;
-                if (cfq_class_idle(cfqq))
-                        max_dispatch = 1;
-
                 dispatched += __cfq_dispatch_requests(cfqd, cfqq, max_dispatch);
-                prev_cfqq = cfqq;
         }
 
         return dispatched;
@@ -1108,48 +1152,21 @@ static void cfq_put_queue(struct cfq_queue *cfqq)
         BUG_ON(cfq_cfqq_on_rr(cfqq));
 
         if (unlikely(cfqd->active_queue == cfqq)) {
-                __cfq_slice_expired(cfqd, cfqq, 0, 0);
+                __cfq_slice_expired(cfqd, cfqq, 0);
                 cfq_schedule_dispatch(cfqd);
         }
 
-        /*
-         * it's on the empty list and still hashed
-         */
-        list_del(&cfqq->cfq_list);
-        hlist_del(&cfqq->cfq_hash);
         kmem_cache_free(cfq_pool, cfqq);
 }
 
-static struct cfq_queue *
-__cfq_find_cfq_hash(struct cfq_data *cfqd, unsigned int key, unsigned int prio,
-                    const int hashval)
-{
-        struct hlist_head *hash_list = &cfqd->cfq_hash[hashval];
-        struct hlist_node *entry;
-        struct cfq_queue *__cfqq;
-
-        hlist_for_each_entry(__cfqq, entry, hash_list, cfq_hash) {
-                const unsigned short __p = IOPRIO_PRIO_VALUE(__cfqq->org_ioprio_class, __cfqq->org_ioprio);
-
-                if (__cfqq->key == key && (__p == prio || !prio))
-                        return __cfqq;
-        }
-
-        return NULL;
-}
-
-static struct cfq_queue *
-cfq_find_cfq_hash(struct cfq_data *cfqd, unsigned int key, unsigned short prio)
-{
-        return __cfq_find_cfq_hash(cfqd, key, prio, hash_long(key, CFQ_QHASH_SHIFT));
-}
-
 static void cfq_free_io_context(struct io_context *ioc)
 {
         struct cfq_io_context *__cic;
         struct rb_node *n;
         int freed = 0;
 
+        ioc->ioc_data = NULL;
+
         while ((n = rb_first(&ioc->cic_root)) != NULL) {
                 __cic = rb_entry(n, struct cfq_io_context, rb_node);
                 rb_erase(&__cic->rb_node, &ioc->cic_root);
@@ -1166,7 +1183,7 @@ static void cfq_free_io_context(struct io_context *ioc)
 static void cfq_exit_cfqq(struct cfq_data *cfqd, struct cfq_queue *cfqq)
 {
         if (unlikely(cfqq == cfqd->active_queue)) {
-                __cfq_slice_expired(cfqd, cfqq, 0, 0);
+                __cfq_slice_expired(cfqd, cfqq, 0);
                 cfq_schedule_dispatch(cfqd);
         }
 
@@ -1191,10 +1208,6 @@ static void __cfq_exit_single_io_context(struct cfq_data *cfqd,
         }
 }
 
-
-/*
- * Called with interrupts disabled
- */
 static void cfq_exit_single_io_context(struct cfq_io_context *cic)
 {
         struct cfq_data *cfqd = cic->key;
@@ -1208,15 +1221,20 @@ static void cfq_exit_single_io_context(struct cfq_io_context *cic)
         }
 }
 
+/*
+ * The process that ioc belongs to has exited, we need to clean up
+ * and put the internal structures we have that belongs to that process.
+ */
 static void cfq_exit_io_context(struct io_context *ioc)
 {
         struct cfq_io_context *__cic;
         struct rb_node *n;
 
+        ioc->ioc_data = NULL;
+
         /*
          * put the reference this task is holding to the various queues
          */
-
         n = rb_first(&ioc->cic_root);
         while (n != NULL) {
                 __cic = rb_entry(n, struct cfq_io_context, rb_node);
@@ -1284,8 +1302,6 @@ static void cfq_init_prio_data(struct cfq_queue *cfqq)
          */
         cfqq->org_ioprio = cfqq->ioprio;
         cfqq->org_ioprio_class = cfqq->ioprio_class;
-
-        cfq_resort_rr_list(cfqq, 0);
         cfq_clear_cfqq_prio_changed(cfqq);
 }
 
@@ -1303,7 +1319,7 @@ static inline void changed_ioprio(struct cfq_io_context *cic)
         cfqq = cic->cfqq[ASYNC];
         if (cfqq) {
                 struct cfq_queue *new_cfqq;
-                new_cfqq = cfq_get_queue(cfqd, CFQ_KEY_ASYNC, cic->ioc->task,
+                new_cfqq = cfq_get_queue(cfqd, ASYNC, cic->ioc->task,
                                          GFP_ATOMIC);
                 if (new_cfqq) {
                         cic->cfqq[ASYNC] = new_cfqq;
@@ -1335,16 +1351,16 @@ static void cfq_ioc_set_ioprio(struct io_context *ioc)
 }
 
 static struct cfq_queue *
-cfq_get_queue(struct cfq_data *cfqd, unsigned int key, struct task_struct *tsk,
+cfq_get_queue(struct cfq_data *cfqd, int is_sync, struct task_struct *tsk,
               gfp_t gfp_mask)
 {
-        const int hashval = hash_long(key, CFQ_QHASH_SHIFT);
         struct cfq_queue *cfqq, *new_cfqq = NULL;
-        unsigned short ioprio;
+        struct cfq_io_context *cic;
 
 retry:
-        ioprio = tsk->ioprio;
-        cfqq = __cfq_find_cfq_hash(cfqd, key, ioprio, hashval);
+        cic = cfq_cic_rb_lookup(cfqd, tsk->io_context);
+        /* cic always exists here */
+        cfqq = cic_to_cfqq(cic, is_sync);
 
         if (!cfqq) {
                 if (new_cfqq) {
@@ -1369,20 +1385,20 @@ retry:
 
                 memset(cfqq, 0, sizeof(*cfqq));
 
-                INIT_HLIST_NODE(&cfqq->cfq_hash);
-                INIT_LIST_HEAD(&cfqq->cfq_list);
+                RB_CLEAR_NODE(&cfqq->rb_node);
                 INIT_LIST_HEAD(&cfqq->fifo);
 
-                cfqq->key = key;
-                hlist_add_head(&cfqq->cfq_hash, &cfqd->cfq_hash[hashval]);
                 atomic_set(&cfqq->ref, 0);
                 cfqq->cfqd = cfqd;
 
-                if (key != CFQ_KEY_ASYNC)
+                if (is_sync) {
                         cfq_mark_cfqq_idle_window(cfqq);
+                        cfq_mark_cfqq_sync(cfqq);
+                }
 
                 cfq_mark_cfqq_prio_changed(cfqq);
                 cfq_mark_cfqq_queue_new(cfqq);
+
                 cfq_init_prio_data(cfqq);
         }
 
@@ -1395,10 +1411,17 @@ out:
         return cfqq;
 }
 
+/*
+ * We drop cfq io contexts lazily, so we may find a dead one.
+ */
 static void
 cfq_drop_dead_cic(struct io_context *ioc, struct cfq_io_context *cic)
 {
         WARN_ON(!list_empty(&cic->queue_list));
+
+        if (ioc->ioc_data == cic)
+                ioc->ioc_data = NULL;
+
         rb_erase(&cic->rb_node, &ioc->cic_root);
         kmem_cache_free(cfq_ioc_pool, cic);
         elv_ioc_count_dec(ioc_count);
@@ -1411,6 +1434,16 @@ cfq_cic_rb_lookup(struct cfq_data *cfqd, struct io_context *ioc)
         struct cfq_io_context *cic;
         void *k, *key = cfqd;
 
+        if (unlikely(!ioc))
+                return NULL;
+
+        /*
+         * we maintain a last-hit cache, to avoid browsing over the tree
+         */
+        cic = ioc->ioc_data;
+        if (cic && cic->key == cfqd)
+                return cic;
+
 restart:
         n = ioc->cic_root.rb_node;
         while (n) {
@@ -1426,8 +1459,10 @@ restart:
                         n = n->rb_left;
                 else if (key > k)
                         n = n->rb_right;
-                else
+                else {
+                        ioc->ioc_data = cic;
                         return cic;
+                }
         }
 
         return NULL;
@@ -1524,7 +1559,8 @@ cfq_update_io_thinktime(struct cfq_data *cfqd, struct cfq_io_context *cic)
 }
 
 static void
-cfq_update_io_seektime(struct cfq_io_context *cic, struct request *rq)
+cfq_update_io_seektime(struct cfq_data *cfqd, struct cfq_io_context *cic,
+                       struct request *rq)
 {
         sector_t sdist;
         u64 total;
@@ -1534,6 +1570,11 @@ cfq_update_io_seektime(struct cfq_io_context *cic, struct request *rq)
         else
                 sdist = cic->last_request_pos - rq->sector;
 
+        if (!cic->seek_samples) {
+                cfqd->new_seek_total = (7*cic->seek_total + (u64)256*sdist) / 8;
+                cfqd->new_seek_mean = cfqd->new_seek_total / 256;
+        }
+
         /*
          * Don't allow the seek distance to get too large from the
          * odd fragment, pagein, etc
@@ -1558,7 +1599,12 @@ static void
 cfq_update_idle_window(struct cfq_data *cfqd, struct cfq_queue *cfqq,
                        struct cfq_io_context *cic)
 {
-        int enable_idle = cfq_cfqq_idle_window(cfqq);
+        int enable_idle;
+
+        if (!cfq_cfqq_sync(cfqq))
+                return;
+
+        enable_idle = cfq_cfqq_idle_window(cfqq);
 
         if (!cic->ioc->task || !cfqd->cfq_slice_idle ||
             (cfqd->hw_tag && CIC_SEEKY(cic)))
@@ -1584,24 +1630,28 @@ static int
 cfq_should_preempt(struct cfq_data *cfqd, struct cfq_queue *new_cfqq,
                    struct request *rq)
 {
-        struct cfq_queue *cfqq = cfqd->active_queue;
+        struct cfq_queue *cfqq;
 
-        if (cfq_class_idle(new_cfqq))
+        cfqq = cfqd->active_queue;
+        if (!cfqq)
                 return 0;
 
-        if (!cfqq)
+        if (cfq_slice_used(cfqq))
+                return 1;
+
+        if (cfq_class_idle(new_cfqq))
                 return 0;
 
         if (cfq_class_idle(cfqq))
                 return 1;
-        if (!cfq_cfqq_wait_request(new_cfqq))
-                return 0;
+
         /*
          * if the new request is sync, but the currently running queue is
          * not, let the sync request have priority.
          */
         if (rq_is_sync(rq) && !cfq_cfqq_sync(cfqq))
                 return 1;
+
         /*
          * So both queues are sync. Let the new request get disk time if
          * it's a metadata request and the current queue is doing regular IO.
@@ -1609,6 +1659,16 @@ cfq_should_preempt(struct cfq_data *cfqd, struct cfq_queue *new_cfqq,
         if (rq_is_meta(rq) && !cfqq->meta_pending)
                 return 1;
 
+        if (!cfqd->active_cic || !cfq_cfqq_wait_request(cfqq))
+                return 0;
+
+        /*
+         * if this request is as-good as one we would expect from the
+         * current cfqq, let it preempt
+         */
+        if (cfq_rq_close(cfqd, rq))
+                return 1;
+
         return 0;
 }
 
@@ -1618,14 +1678,15 @@ cfq_should_preempt(struct cfq_data *cfqd, struct cfq_queue *new_cfqq,
  */
 static void cfq_preempt_queue(struct cfq_data *cfqd, struct cfq_queue *cfqq)
 {
-        cfq_slice_expired(cfqd, 1, 1);
+        cfq_slice_expired(cfqd, 1);
 
         /*
          * Put the new queue at the front of the of the current list,
          * so we know that it will be selected next.
          */
         BUG_ON(!cfq_cfqq_on_rr(cfqq));
-        list_move(&cfqq->cfq_list, &cfqd->cur_rr);
+
+        cfq_service_tree_add(cfqd, cfqq, 1);
 
         cfqq->slice_end = 0;
         cfq_mark_cfqq_slice_new(cfqq);
@@ -1644,28 +1705,12 @@ cfq_rq_enqueued(struct cfq_data *cfqd, struct cfq_queue *cfqq,
         if (rq_is_meta(rq))
                 cfqq->meta_pending++;
 
-        /*
-         * we never wait for an async request and we don't allow preemption
-         * of an async request. so just return early
-         */
-        if (!rq_is_sync(rq)) {
-                /*
-                 * 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, 0);
-                        blk_start_queueing(cfqd->queue);
-                }
-                return;
-        }
-
         cfq_update_io_thinktime(cfqd, cic);
-        cfq_update_io_seektime(cic, rq);
+        cfq_update_io_seektime(cfqd, cic, rq);
         cfq_update_idle_window(cfqd, cfqq, cic);
 
         cic->last_request_pos = rq->sector + rq->nr_sectors;
+        cfqq->last_request_pos = cic->last_request_pos;
 
         if (cfqq == cfqd->active_queue) {
                 /*
@@ -1714,16 +1759,16 @@ static void cfq_completed_request(request_queue_t *q, struct request *rq)
         now = jiffies;
 
         WARN_ON(!cfqd->rq_in_driver);
-        WARN_ON(!cfqq->on_dispatch[sync]);
+        WARN_ON(!cfqq->dispatched);
         cfqd->rq_in_driver--;
-        cfqq->on_dispatch[sync]--;
-        cfqq->service_last = now;
+        cfqq->dispatched--;
+
+        if (cfq_cfqq_sync(cfqq))
+                cfqd->sync_flight--;
 
         if (!cfq_class_idle(cfqq))
                 cfqd->last_end_request = now;
 
-        cfq_resort_rr_list(cfqq, 0);
-
         if (sync)
                 RQ_CIC(rq)->last_end_request = now;
 
@@ -1737,12 +1782,13 @@ static void cfq_completed_request(request_queue_t *q, struct request *rq)
                         cfq_clear_cfqq_slice_new(cfqq);
                 }
                 if (cfq_slice_used(cfqq))
-                        cfq_slice_expired(cfqd, 0, 1);
-                else if (sync && RB_EMPTY_ROOT(&cfqq->sort_list)) {
-                        if (!cfq_arm_slice_timer(cfqd))
-                                cfq_schedule_dispatch(cfqd);
-                }
+                        cfq_slice_expired(cfqd, 1);
+                else if (sync && RB_EMPTY_ROOT(&cfqq->sort_list))
+                        cfq_arm_slice_timer(cfqd);
         }
+
+        if (!cfqd->rq_in_driver)
+                cfq_schedule_dispatch(cfqd);
 }
 
 /*
@@ -1751,9 +1797,6 @@ static void cfq_completed_request(request_queue_t *q, struct request *rq)
  */
 static void cfq_prio_boost(struct cfq_queue *cfqq)
 {
-        const int ioprio_class = cfqq->ioprio_class;
-        const int ioprio = cfqq->ioprio;
-
         if (has_fs_excl()) {
                 /*
                  * boost idle prio on transactions that would lock out other
@@ -1772,12 +1815,6 @@ static void cfq_prio_boost(struct cfq_queue *cfqq)
                 if (cfqq->ioprio != cfqq->org_ioprio)
                         cfqq->ioprio = cfqq->org_ioprio;
         }
-
-        /*
-         * refile between round-robin lists if we moved the priority class
-         */
-        if ((ioprio_class != cfqq->ioprio_class || ioprio != cfqq->ioprio))
-                cfq_resort_rr_list(cfqq, 0);
 }
 
 static inline int __cfq_may_queue(struct cfq_queue *cfqq)
@@ -1795,10 +1832,8 @@ static int cfq_may_queue(request_queue_t *q, int rw)
 {
         struct cfq_data *cfqd = q->elevator->elevator_data;
         struct task_struct *tsk = current;
+        struct cfq_io_context *cic;
         struct cfq_queue *cfqq;
-        unsigned int key;
-
-        key = cfq_queue_pid(tsk, rw, rw & REQ_RW_SYNC);
 
         /*
          * don't force setup of a queue from here, as a call to may_queue
@@ -1806,7 +1841,11 @@ static int cfq_may_queue(request_queue_t *q, int rw)
          * so just lookup a possibly existing queue, or return 'may queue'
          * if that fails
          */
-        cfqq = cfq_find_cfq_hash(cfqd, key, tsk->ioprio);
+        cic = cfq_cic_rb_lookup(cfqd, tsk->io_context);
+        if (!cic)
+                return ELV_MQUEUE_MAY;
+
+        cfqq = cic_to_cfqq(cic, rw & REQ_RW_SYNC);
         if (cfqq) {
                 cfq_init_prio_data(cfqq);
                 cfq_prio_boost(cfqq);
@@ -1850,7 +1889,6 @@ cfq_set_request(request_queue_t *q, struct request *rq, gfp_t gfp_mask)
         struct cfq_io_context *cic;
         const int rw = rq_data_dir(rq);
         const int is_sync = rq_is_sync(rq);
-        pid_t key = cfq_queue_pid(tsk, rw, is_sync);
         struct cfq_queue *cfqq;
         unsigned long flags;
 
@@ -1863,14 +1901,15 @@ cfq_set_request(request_queue_t *q, struct request *rq, gfp_t gfp_mask)
         if (!cic)
                 goto queue_fail;
 
-        if (!cic->cfqq[is_sync]) {
-                cfqq = cfq_get_queue(cfqd, key, tsk, gfp_mask);
+        cfqq = cic_to_cfqq(cic, is_sync);
+        if (!cfqq) {
+                cfqq = cfq_get_queue(cfqd, is_sync, tsk, gfp_mask);
+
                 if (!cfqq)
                         goto queue_fail;
 
-                cic->cfqq[is_sync] = cfqq;
-        } else
-                cfqq = cic->cfqq[is_sync];
+                cic_set_cfqq(cic, cfqq, is_sync);
+        }
 
         cfqq->allocated[rw]++;
         cfq_clear_cfqq_must_alloc(cfqq);
@@ -1940,7 +1979,7 @@ static void cfq_idle_slice_timer(unsigned long data)
                 }
         }
 expire:
-        cfq_slice_expired(cfqd, 0, timed_out);
+        cfq_slice_expired(cfqd, timed_out);
 out_kick:
         cfq_schedule_dispatch(cfqd);
 out_cont:
@@ -1986,7 +2025,7 @@ static void cfq_exit_queue(elevator_t *e)
         spin_lock_irq(q->queue_lock);
 
         if (cfqd->active_queue)
-                __cfq_slice_expired(cfqd, cfqd->active_queue, 0, 0);
+                __cfq_slice_expired(cfqd, cfqd->active_queue, 0);
 
         while (!list_empty(&cfqd->cic_list)) {
                 struct cfq_io_context *cic = list_entry(cfqd->cic_list.next,
@@ -2000,14 +2039,12 @@ static void cfq_exit_queue(elevator_t *e)
 
         cfq_shutdown_timer_wq(cfqd);
 
-        kfree(cfqd->cfq_hash);
         kfree(cfqd);
 }
 
 static void *cfq_init_queue(request_queue_t *q)
 {
         struct cfq_data *cfqd;
-        int i;
 
         cfqd = kmalloc_node(sizeof(*cfqd), GFP_KERNEL, q->node);
         if (!cfqd)
@@ -2015,21 +2052,9 @@ static void *cfq_init_queue(request_queue_t *q)
 
         memset(cfqd, 0, sizeof(*cfqd));
 
-        for (i = 0; i < CFQ_PRIO_LISTS; i++)
-                INIT_LIST_HEAD(&cfqd->rr_list[i]);
-
-        INIT_LIST_HEAD(&cfqd->busy_rr);
-        INIT_LIST_HEAD(&cfqd->cur_rr);
-        INIT_LIST_HEAD(&cfqd->idle_rr);
+        cfqd->service_tree = CFQ_RB_ROOT;
         INIT_LIST_HEAD(&cfqd->cic_list);
 
-        cfqd->cfq_hash = kmalloc_node(sizeof(struct hlist_head) * CFQ_QHASH_ENTRIES, GFP_KERNEL, q->node);
-        if (!cfqd->cfq_hash)
-                goto out_free;
-
-        for (i = 0; i < CFQ_QHASH_ENTRIES; i++)
-                INIT_HLIST_HEAD(&cfqd->cfq_hash[i]);
-
         cfqd->queue = q;
 
         init_timer(&cfqd->idle_slice_timer);
@@ -2053,9 +2078,6 @@ static void *cfq_init_queue(request_queue_t *q)
         cfqd->cfq_slice_idle = cfq_slice_idle;
 
         return cfqd;
-out_free:
-        kfree(cfqd);
-        return NULL;
 }
 
 static void cfq_slab_kill(void)
@@ -2087,7 +2109,6 @@ fail:
 /*
  * sysfs parts below -->
  */
-
 static ssize_t
 cfq_var_show(unsigned int var, char *page)
 {
diff --git a/block/ll_rw_blk.c b/block/ll_rw_blk.c
index 3de06953ac33..123003a90477 100644
--- a/block/ll_rw_blk.c
+++ b/block/ll_rw_blk.c
@@ -3741,6 +3741,7 @@ static struct io_context *current_io_context(gfp_t gfp_flags, int node)
                 ret->nr_batch_requests = 0; /* because this is 0 */
                 ret->aic = NULL;
                 ret->cic_root.rb_node = NULL;
+                ret->ioc_data = NULL;
                 /* make sure set_task_ioprio() sees the settings above */
                 smp_wmb();
                 tsk->io_context = ret;
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 83dcd8c0e974..a686eabe22d6 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -116,6 +116,7 @@ struct io_context {
 
         struct as_io_context *aic;
         struct rb_root cic_root;
+        void *ioc_data;
 };
 
 void put_io_context(struct io_context *ioc);