Merge branch 'cfq-ioc-share' of git://git.kernel.dk/linux-2.6-block

* 'cfq-ioc-share' of git://git.kernel.dk/linux-2.6-block:
  cfq-iosched: kill some big inlines
  cfq-iosched: relax IOPRIO_CLASS_IDLE restrictions
  kernel: add CLONE_IO to specifically request sharing of IO contexts
  io_context sharing - anticipatory changes
  block: cfq: make the io contect sharing lockless
  io_context sharing - cfq changes
  io context sharing: preliminary support
  ioprio: move io priority from task_struct to io_context

10 files changed, 474 insertions, 355 deletions

diff --git a/block/as-iosched.c b/block/as-iosched.c
index cb5e53b05c7c..b201d16a7102 100644
--- a/block/as-iosched.c
+++ b/block/as-iosched.c
@@ -170,9 +170,11 @@ static void free_as_io_context(struct as_io_context *aic)
 
 static void as_trim(struct io_context *ioc)
 {
+        spin_lock(&ioc->lock);
         if (ioc->aic)
                 free_as_io_context(ioc->aic);
         ioc->aic = NULL;
+        spin_unlock(&ioc->lock);
 }
 
 /* Called when the task exits */
@@ -462,7 +464,9 @@ static void as_antic_timeout(unsigned long data)
         spin_lock_irqsave(q->queue_lock, flags);
         if (ad->antic_status == ANTIC_WAIT_REQ
                         || ad->antic_status == ANTIC_WAIT_NEXT) {
-                struct as_io_context *aic = ad->io_context->aic;
+                struct as_io_context *aic;
+                spin_lock(&ad->io_context->lock);
+                aic = ad->io_context->aic;
 
                 ad->antic_status = ANTIC_FINISHED;
                 kblockd_schedule_work(&ad->antic_work);
@@ -475,6 +479,7 @@ static void as_antic_timeout(unsigned long data)
                         /* process not "saved" by a cooperating request */
                         ad->exit_no_coop = (7*ad->exit_no_coop + 256)/8;
                 }
+                spin_unlock(&ad->io_context->lock);
         }
         spin_unlock_irqrestore(q->queue_lock, flags);
 }
@@ -635,9 +640,11 @@ static int as_can_break_anticipation(struct as_data *ad, struct request *rq)
 
         ioc = ad->io_context;
         BUG_ON(!ioc);
+        spin_lock(&ioc->lock);
 
         if (rq && ioc == RQ_IOC(rq)) {
                 /* request from same process */
+                spin_unlock(&ioc->lock);
                 return 1;
         }
 
@@ -646,20 +653,25 @@ static int as_can_break_anticipation(struct as_data *ad, struct request *rq)
                  * In this situation status should really be FINISHED,
                  * however the timer hasn't had the chance to run yet.
                  */
+                spin_unlock(&ioc->lock);
                 return 1;
         }
 
         aic = ioc->aic;
-        if (!aic)
+        if (!aic) {
+                spin_unlock(&ioc->lock);
                 return 0;
+        }
 
         if (atomic_read(&aic->nr_queued) > 0) {
                 /* process has more requests queued */
+                spin_unlock(&ioc->lock);
                 return 1;
         }
 
         if (atomic_read(&aic->nr_dispatched) > 0) {
                 /* process has more requests dispatched */
+                spin_unlock(&ioc->lock);
                 return 1;
         }
 
@@ -680,6 +692,7 @@ static int as_can_break_anticipation(struct as_data *ad, struct request *rq)
                 }
 
                 as_update_iohist(ad, aic, rq);
+                spin_unlock(&ioc->lock);
                 return 1;
         }
 
@@ -688,20 +701,27 @@ static int as_can_break_anticipation(struct as_data *ad, struct request *rq)
                 if (aic->ttime_samples == 0)
                         ad->exit_prob = (7*ad->exit_prob + 256)/8;
 
-                if (ad->exit_no_coop > 128)
+                if (ad->exit_no_coop > 128) {
+                        spin_unlock(&ioc->lock);
                         return 1;
+                }
         }
 
         if (aic->ttime_samples == 0) {
-                if (ad->new_ttime_mean > ad->antic_expire)
+                if (ad->new_ttime_mean > ad->antic_expire) {
+                        spin_unlock(&ioc->lock);
                         return 1;
-                if (ad->exit_prob * ad->exit_no_coop > 128*256)
+                }
+                if (ad->exit_prob * ad->exit_no_coop > 128*256) {
+                        spin_unlock(&ioc->lock);
                         return 1;
+                }
         } else if (aic->ttime_mean > ad->antic_expire) {
                 /* the process thinks too much between requests */
+                spin_unlock(&ioc->lock);
                 return 1;
         }
-
+        spin_unlock(&ioc->lock);
         return 0;
 }
 
@@ -1255,7 +1275,9 @@ static void as_merged_requests(struct request_queue *q, struct request *req,
                          * Don't copy here but swap, because when anext is
                          * removed below, it must contain the unused context
                          */
+                        double_spin_lock(&rioc->lock, &nioc->lock, rioc < nioc);
                         swap_io_context(&rioc, &nioc);
+                        double_spin_unlock(&rioc->lock, &nioc->lock, rioc < nioc);
                 }
         }
 
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 13553e015d72..f28d1fb30608 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -26,9 +26,9 @@ 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
+ * offset from end of service tree
  */
-#define CFQ_IDLE_GRACE          (HZ / 10)
+#define CFQ_IDLE_DELAY          (HZ / 5)
 
 /*
  * below this threshold, we consider thinktime immediate
@@ -98,8 +98,6 @@ struct cfq_data {
         struct cfq_queue *async_cfqq[2][IOPRIO_BE_NR];
         struct cfq_queue *async_idle_cfqq;
 
-        struct timer_list idle_class_timer;
-
         sector_t last_position;
         unsigned long last_end_request;
 
@@ -199,8 +197,8 @@ CFQ_CFQQ_FNS(sync);
 
 static void cfq_dispatch_insert(struct request_queue *, struct request *);
 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 *, gfp_t);
+static struct cfq_io_context *cfq_cic_lookup(struct cfq_data *,
                                                 struct io_context *);
 
 static inline struct cfq_queue *cic_to_cfqq(struct cfq_io_context *cic,
@@ -384,12 +382,15 @@ 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)
+static struct cfq_queue *cfq_rb_first(struct cfq_rb_root *root)
 {
         if (!root->left)
                 root->left = rb_first(&root->rb);
 
-        return root->left;
+        if (root->left)
+                return rb_entry(root->left, struct cfq_queue, rb_node);
+
+        return NULL;
 }
 
 static void cfq_rb_erase(struct rb_node *n, struct cfq_rb_root *root)
@@ -446,12 +447,20 @@ static unsigned long cfq_slice_offset(struct cfq_data *cfqd,
 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;
+        struct rb_node **p, *parent;
+        struct cfq_queue *__cfqq;
         unsigned long rb_key;
         int left;
 
-        if (!add_front) {
+        if (cfq_class_idle(cfqq)) {
+                rb_key = CFQ_IDLE_DELAY;
+                parent = rb_last(&cfqd->service_tree.rb);
+                if (parent && parent != &cfqq->rb_node) {
+                        __cfqq = rb_entry(parent, struct cfq_queue, rb_node);
+                        rb_key += __cfqq->rb_key;
+                } else
+                        rb_key += jiffies;
+        } else if (!add_front) {
                 rb_key = cfq_slice_offset(cfqd, cfqq) + jiffies;
                 rb_key += cfqq->slice_resid;
                 cfqq->slice_resid = 0;
@@ -469,8 +478,9 @@ static void cfq_service_tree_add(struct cfq_data *cfqd,
         }
 
         left = 1;
+        parent = NULL;
+        p = &cfqd->service_tree.rb.rb_node;
         while (*p) {
-                struct cfq_queue *__cfqq;
                 struct rb_node **n;
 
                 parent = *p;
@@ -524,8 +534,7 @@ static void cfq_resort_rr_list(struct cfq_data *cfqd, struct cfq_queue *cfqq)
  * add to busy list of queues for service, trying to be fair in ordering
  * the pending list according to last request service
  */
-static inline void
-cfq_add_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
+static void cfq_add_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
 {
         BUG_ON(cfq_cfqq_on_rr(cfqq));
         cfq_mark_cfqq_on_rr(cfqq);
@@ -538,8 +547,7 @@ cfq_add_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *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)
+static 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);
@@ -554,7 +562,7 @@ cfq_del_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
 /*
  * rb tree support functions
  */
-static inline void cfq_del_rq_rb(struct request *rq)
+static void cfq_del_rq_rb(struct request *rq)
 {
         struct cfq_queue *cfqq = RQ_CFQQ(rq);
         struct cfq_data *cfqd = cfqq->cfqd;
@@ -594,8 +602,7 @@ static void cfq_add_rq_rb(struct request *rq)
         BUG_ON(!cfqq->next_rq);
 }
 
-static inline void
-cfq_reposition_rq_rb(struct cfq_queue *cfqq, struct request *rq)
+static void cfq_reposition_rq_rb(struct cfq_queue *cfqq, struct request *rq)
 {
         elv_rb_del(&cfqq->sort_list, rq);
         cfqq->queued[rq_is_sync(rq)]--;
@@ -609,7 +616,7 @@ cfq_find_rq_fmerge(struct cfq_data *cfqd, struct bio *bio)
         struct cfq_io_context *cic;
         struct cfq_queue *cfqq;
 
-        cic = cfq_cic_rb_lookup(cfqd, tsk->io_context);
+        cic = cfq_cic_lookup(cfqd, tsk->io_context);
         if (!cic)
                 return NULL;
 
@@ -721,7 +728,7 @@ static int cfq_allow_merge(struct request_queue *q, struct request *rq,
          * Lookup the cfqq that this bio will be queued with. Allow
          * merge only if rq is queued there.
          */
-        cic = cfq_cic_rb_lookup(cfqd, current->io_context);
+        cic = cfq_cic_lookup(cfqd, current->io_context);
         if (!cic)
                 return 0;
 
@@ -732,15 +739,10 @@ static int cfq_allow_merge(struct request_queue *q, struct request *rq,
         return 0;
 }
 
-static inline void
-__cfq_set_active_queue(struct cfq_data *cfqd, struct cfq_queue *cfqq)
+static void __cfq_set_active_queue(struct cfq_data *cfqd,
+                                   struct cfq_queue *cfqq)
 {
         if (cfqq) {
-                /*
-                 * stop potential idle class queues waiting service
-                 */
-                del_timer(&cfqd->idle_class_timer);
-
                 cfqq->slice_end = 0;
                 cfq_clear_cfqq_must_alloc_slice(cfqq);
                 cfq_clear_cfqq_fifo_expire(cfqq);
@@ -789,47 +791,16 @@ static inline void cfq_slice_expired(struct cfq_data *cfqd, int timed_out)
                 __cfq_slice_expired(cfqd, cfqq, timed_out);
 }
 
-static int start_idle_class_timer(struct cfq_data *cfqd)
-{
-        unsigned long end = cfqd->last_end_request + CFQ_IDLE_GRACE;
-        unsigned long now = jiffies;
-
-        if (time_before(now, end) &&
-            time_after_eq(now, cfqd->last_end_request)) {
-                mod_timer(&cfqd->idle_class_timer, end);
-                return 1;
-        }
-
-        return 0;
-}
-
 /*
  * Get next queue for service. Unless we have a queue preemption,
  * we'll simply select the first cfqq in the service tree.
  */
 static struct cfq_queue *cfq_get_next_queue(struct cfq_data *cfqd)
 {
-        struct cfq_queue *cfqq;
-        struct rb_node *n;
-
         if (RB_EMPTY_ROOT(&cfqd->service_tree.rb))
                 return NULL;
 
-        n = cfq_rb_first(&cfqd->service_tree);
-        cfqq = rb_entry(n, struct cfq_queue, rb_node);
-
-        if (cfq_class_idle(cfqq)) {
-                /*
-                 * 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
-                 */
-                if (start_idle_class_timer(cfqd))
-                        cfqq = NULL;
-        }
-
-        return cfqq;
+        return cfq_rb_first(&cfqd->service_tree);
 }
 
 /*
@@ -895,7 +866,7 @@ static void cfq_arm_slice_timer(struct cfq_data *cfqd)
          * task has exited, don't wait
          */
         cic = cfqd->active_cic;
-        if (!cic || !cic->ioc->task)
+        if (!cic || !atomic_read(&cic->ioc->nr_tasks))
                 return;
 
         /*
@@ -939,7 +910,7 @@ static void cfq_dispatch_insert(struct request_queue *q, struct request *rq)
 /*
  * return expired entry, or NULL to just start from scratch in rbtree
  */
-static inline struct request *cfq_check_fifo(struct cfq_queue *cfqq)
+static struct request *cfq_check_fifo(struct cfq_queue *cfqq)
 {
         struct cfq_data *cfqd = cfqq->cfqd;
         struct request *rq;
@@ -1068,7 +1039,7 @@ __cfq_dispatch_requests(struct cfq_data *cfqd, struct cfq_queue *cfqq,
         return dispatched;
 }
 
-static inline int __cfq_forced_dispatch_cfqq(struct cfq_queue *cfqq)
+static int __cfq_forced_dispatch_cfqq(struct cfq_queue *cfqq)
 {
         int dispatched = 0;
 
@@ -1087,14 +1058,11 @@ static inline int __cfq_forced_dispatch_cfqq(struct cfq_queue *cfqq)
  */
 static int cfq_forced_dispatch(struct cfq_data *cfqd)
 {
+        struct cfq_queue *cfqq;
         int dispatched = 0;
-        struct rb_node *n;
-
-        while ((n = cfq_rb_first(&cfqd->service_tree)) != NULL) {
-                struct cfq_queue *cfqq = rb_entry(n, struct cfq_queue, rb_node);
 
+        while ((cfqq = cfq_rb_first(&cfqd->service_tree)) != NULL)
                 dispatched += __cfq_forced_dispatch_cfqq(cfqq);
-        }
 
         cfq_slice_expired(cfqd, 0);
 
@@ -1170,20 +1138,69 @@ static void cfq_put_queue(struct cfq_queue *cfqq)
         kmem_cache_free(cfq_pool, cfqq);
 }
 
-static void cfq_free_io_context(struct io_context *ioc)
+/*
+ * Call func for each cic attached to this ioc. Returns number of cic's seen.
+ */
+#define CIC_GANG_NR     16
+static unsigned int
+call_for_each_cic(struct io_context *ioc,
+                  void (*func)(struct io_context *, struct cfq_io_context *))
 {
-        struct cfq_io_context *__cic;
-        struct rb_node *n;
-        int freed = 0;
+        struct cfq_io_context *cics[CIC_GANG_NR];
+        unsigned long index = 0;
+        unsigned int called = 0;
+        int nr;
 
-        ioc->ioc_data = NULL;
+        rcu_read_lock();
 
-        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);
-                kmem_cache_free(cfq_ioc_pool, __cic);
-                freed++;
-        }
+        do {
+                int i;
+
+                /*
+                 * Perhaps there's a better way - this just gang lookups from
+                 * 0 to the end, restarting after each CIC_GANG_NR from the
+                 * last key + 1.
+                 */
+                nr = radix_tree_gang_lookup(&ioc->radix_root, (void **) cics,
+                                                index, CIC_GANG_NR);
+                if (!nr)
+                        break;
+
+                called += nr;
+                index = 1 + (unsigned long) cics[nr - 1]->key;
+
+                for (i = 0; i < nr; i++)
+                        func(ioc, cics[i]);
+        } while (nr == CIC_GANG_NR);
+
+        rcu_read_unlock();
+
+        return called;
+}
+
+static void cic_free_func(struct io_context *ioc, struct cfq_io_context *cic)
+{
+        unsigned long flags;
+
+        BUG_ON(!cic->dead_key);
+
+        spin_lock_irqsave(&ioc->lock, flags);
+        radix_tree_delete(&ioc->radix_root, cic->dead_key);
+        spin_unlock_irqrestore(&ioc->lock, flags);
+
+        kmem_cache_free(cfq_ioc_pool, cic);
+}
+
+static void cfq_free_io_context(struct io_context *ioc)
+{
+        int freed;
+
+        /*
+         * ioc->refcount is zero here, so no more cic's are allowed to be
+         * linked into this ioc. So it should be ok to iterate over the known
+         * list, we will see all cic's since no new ones are added.
+         */
+        freed = call_for_each_cic(ioc, cic_free_func);
 
         elv_ioc_count_mod(ioc_count, -freed);
 
@@ -1205,7 +1222,12 @@ static void __cfq_exit_single_io_context(struct cfq_data *cfqd,
                                          struct cfq_io_context *cic)
 {
         list_del_init(&cic->queue_list);
+
+        /*
+         * Make sure key == NULL is seen for dead queues
+         */
         smp_wmb();
+        cic->dead_key = (unsigned long) cic->key;
         cic->key = NULL;
 
         if (cic->cfqq[ASYNC]) {
@@ -1219,16 +1241,18 @@ static void __cfq_exit_single_io_context(struct cfq_data *cfqd,
         }
 }
 
-static void cfq_exit_single_io_context(struct cfq_io_context *cic)
+static void cfq_exit_single_io_context(struct io_context *ioc,
+                                       struct cfq_io_context *cic)
 {
         struct cfq_data *cfqd = cic->key;
 
         if (cfqd) {
                 struct request_queue *q = cfqd->queue;
+                unsigned long flags;
 
-                spin_lock_irq(q->queue_lock);
+                spin_lock_irqsave(q->queue_lock, flags);
                 __cfq_exit_single_io_context(cfqd, cic);
-                spin_unlock_irq(q->queue_lock);
+                spin_unlock_irqrestore(q->queue_lock, flags);
         }
 }
 
@@ -1238,21 +1262,8 @@ static void cfq_exit_single_io_context(struct cfq_io_context *cic)
  */
 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);
-
-                cfq_exit_single_io_context(__cic);
-                n = rb_next(n);
-        }
+        rcu_assign_pointer(ioc->ioc_data, NULL);
+        call_for_each_cic(ioc, cfq_exit_single_io_context);
 }
 
 static struct cfq_io_context *
@@ -1273,7 +1284,7 @@ cfq_alloc_io_context(struct cfq_data *cfqd, gfp_t gfp_mask)
         return cic;
 }
 
-static void cfq_init_prio_data(struct cfq_queue *cfqq)
+static void cfq_init_prio_data(struct cfq_queue *cfqq, struct io_context *ioc)
 {
         struct task_struct *tsk = current;
         int ioprio_class;
@@ -1281,7 +1292,7 @@ static void cfq_init_prio_data(struct cfq_queue *cfqq)
         if (!cfq_cfqq_prio_changed(cfqq))
                 return;
 
-        ioprio_class = IOPRIO_PRIO_CLASS(tsk->ioprio);
+        ioprio_class = IOPRIO_PRIO_CLASS(ioc->ioprio);
         switch (ioprio_class) {
                 default:
                         printk(KERN_ERR "cfq: bad prio %x\n", ioprio_class);
@@ -1293,11 +1304,11 @@ static void cfq_init_prio_data(struct cfq_queue *cfqq)
                         cfqq->ioprio_class = IOPRIO_CLASS_BE;
                         break;
                 case IOPRIO_CLASS_RT:
-                        cfqq->ioprio = task_ioprio(tsk);
+                        cfqq->ioprio = task_ioprio(ioc);
                         cfqq->ioprio_class = IOPRIO_CLASS_RT;
                         break;
                 case IOPRIO_CLASS_BE:
-                        cfqq->ioprio = task_ioprio(tsk);
+                        cfqq->ioprio = task_ioprio(ioc);
                         cfqq->ioprio_class = IOPRIO_CLASS_BE;
                         break;
                 case IOPRIO_CLASS_IDLE:
@@ -1316,7 +1327,7 @@ static void cfq_init_prio_data(struct cfq_queue *cfqq)
         cfq_clear_cfqq_prio_changed(cfqq);
 }
 
-static inline void changed_ioprio(struct cfq_io_context *cic)
+static void changed_ioprio(struct io_context *ioc, struct cfq_io_context *cic)
 {
         struct cfq_data *cfqd = cic->key;
         struct cfq_queue *cfqq;
@@ -1330,8 +1341,7 @@ 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, ASYNC, cic->ioc->task,
-                                         GFP_ATOMIC);
+                new_cfqq = cfq_get_queue(cfqd, ASYNC, cic->ioc, GFP_ATOMIC);
                 if (new_cfqq) {
                         cic->cfqq[ASYNC] = new_cfqq;
                         cfq_put_queue(cfqq);
@@ -1347,29 +1357,19 @@ static inline void changed_ioprio(struct cfq_io_context *cic)
 
 static void cfq_ioc_set_ioprio(struct io_context *ioc)
 {
-        struct cfq_io_context *cic;
-        struct rb_node *n;
-
+        call_for_each_cic(ioc, changed_ioprio);
         ioc->ioprio_changed = 0;
-
-        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);
-        }
 }
 
 static struct cfq_queue *
 cfq_find_alloc_queue(struct cfq_data *cfqd, int is_sync,
-                     struct task_struct *tsk, gfp_t gfp_mask)
+                     struct io_context *ioc, gfp_t gfp_mask)
 {
         struct cfq_queue *cfqq, *new_cfqq = NULL;
         struct cfq_io_context *cic;
 
 retry:
-        cic = cfq_cic_rb_lookup(cfqd, tsk->io_context);
+        cic = cfq_cic_lookup(cfqd, ioc);
         /* cic always exists here */
         cfqq = cic_to_cfqq(cic, is_sync);
 
@@ -1404,15 +1404,16 @@ retry:
                 atomic_set(&cfqq->ref, 0);
                 cfqq->cfqd = cfqd;
 
-                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);
+                cfq_init_prio_data(cfqq, ioc);
+
+                if (is_sync) {
+                        if (!cfq_class_idle(cfqq))
+                                cfq_mark_cfqq_idle_window(cfqq);
+                        cfq_mark_cfqq_sync(cfqq);
+                }
         }
 
         if (new_cfqq)
@@ -1439,11 +1440,11 @@ cfq_async_queue_prio(struct cfq_data *cfqd, int ioprio_class, int ioprio)
 }
 
 static struct cfq_queue *
-cfq_get_queue(struct cfq_data *cfqd, int is_sync, struct task_struct *tsk,
+cfq_get_queue(struct cfq_data *cfqd, int is_sync, struct io_context *ioc,
               gfp_t gfp_mask)
 {
-        const int ioprio = task_ioprio(tsk);
-        const int ioprio_class = task_ioprio_class(tsk);
+        const int ioprio = task_ioprio(ioc);
+        const int ioprio_class = task_ioprio_class(ioc);
         struct cfq_queue **async_cfqq = NULL;
         struct cfq_queue *cfqq = NULL;
 
@@ -1453,7 +1454,7 @@ cfq_get_queue(struct cfq_data *cfqd, int is_sync, struct task_struct *tsk,
         }
 
         if (!cfqq) {
-                cfqq = cfq_find_alloc_queue(cfqd, is_sync, tsk, gfp_mask);
+                cfqq = cfq_find_alloc_queue(cfqd, is_sync, ioc, gfp_mask);
                 if (!cfqq)
                         return NULL;
         }
@@ -1470,28 +1471,42 @@ cfq_get_queue(struct cfq_data *cfqd, int is_sync, struct task_struct *tsk,
         return cfqq;
 }
 
+static void cfq_cic_free(struct cfq_io_context *cic)
+{
+        kmem_cache_free(cfq_ioc_pool, cic);
+        elv_ioc_count_dec(ioc_count);
+
+        if (ioc_gone && !elv_ioc_count_read(ioc_count))
+                complete(ioc_gone);
+}
+
 /*
  * 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)
+cfq_drop_dead_cic(struct cfq_data *cfqd, struct io_context *ioc,
+                  struct cfq_io_context *cic)
 {
+        unsigned long flags;
+
         WARN_ON(!list_empty(&cic->queue_list));
 
+        spin_lock_irqsave(&ioc->lock, flags);
+
         if (ioc->ioc_data == cic)
-                ioc->ioc_data = NULL;
+                rcu_assign_pointer(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);
+        radix_tree_delete(&ioc->radix_root, (unsigned long) cfqd);
+        spin_unlock_irqrestore(&ioc->lock, flags);
+
+        cfq_cic_free(cic);
 }
 
 static struct cfq_io_context *
-cfq_cic_rb_lookup(struct cfq_data *cfqd, struct io_context *ioc)
+cfq_cic_lookup(struct cfq_data *cfqd, struct io_context *ioc)
 {
-        struct rb_node *n;
         struct cfq_io_context *cic;
-        void *k, *key = cfqd;
+        void *k;
 
         if (unlikely(!ioc))
                 return NULL;
@@ -1499,74 +1514,64 @@ cfq_cic_rb_lookup(struct cfq_data *cfqd, struct io_context *ioc)
         /*
          * we maintain a last-hit cache, to avoid browsing over the tree
          */
-        cic = ioc->ioc_data;
+        cic = rcu_dereference(ioc->ioc_data);
         if (cic && cic->key == cfqd)
                 return cic;
 
-restart:
-        n = ioc->cic_root.rb_node;
-        while (n) {
-                cic = rb_entry(n, struct cfq_io_context, rb_node);
+        do {
+                rcu_read_lock();
+                cic = radix_tree_lookup(&ioc->radix_root, (unsigned long) cfqd);
+                rcu_read_unlock();
+                if (!cic)
+                        break;
                 /* ->key must be copied to avoid race with cfq_exit_queue() */
                 k = cic->key;
                 if (unlikely(!k)) {
-                        cfq_drop_dead_cic(ioc, cic);
-                        goto restart;
+                        cfq_drop_dead_cic(cfqd, ioc, cic);
+                        continue;
                 }
 
-                if (key < k)
-                        n = n->rb_left;
-                else if (key > k)
-                        n = n->rb_right;
-                else {
-                        ioc->ioc_data = cic;
-                        return cic;
-                }
-        }
+                rcu_assign_pointer(ioc->ioc_data, cic);
+                break;
+        } while (1);
 
-        return NULL;
+        return cic;
 }
 
-static inline void
-cfq_cic_link(struct cfq_data *cfqd, struct io_context *ioc,
-             struct cfq_io_context *cic)
+/*
+ * Add cic into ioc, using cfqd as the search key. This enables us to lookup
+ * the process specific cfq io context when entered from the block layer.
+ * Also adds the cic to a per-cfqd list, used when this queue is removed.
+ */
+static int cfq_cic_link(struct cfq_data *cfqd, struct io_context *ioc,
+                        struct cfq_io_context *cic, gfp_t gfp_mask)
 {
-        struct rb_node **p;
-        struct rb_node *parent;
-        struct cfq_io_context *__cic;
         unsigned long flags;
-        void *k;
+        int ret;
 
-        cic->ioc = ioc;
-        cic->key = cfqd;
+        ret = radix_tree_preload(gfp_mask);
+        if (!ret) {
+                cic->ioc = ioc;
+                cic->key = cfqd;
 
-restart:
-        parent = NULL;
-        p = &ioc->cic_root.rb_node;
-        while (*p) {
-                parent = *p;
-                __cic = rb_entry(parent, struct cfq_io_context, rb_node);
-                /* ->key must be copied to avoid race with cfq_exit_queue() */
-                k = __cic->key;
-                if (unlikely(!k)) {
-                        cfq_drop_dead_cic(ioc, __cic);
-                        goto restart;
-                }
+                spin_lock_irqsave(&ioc->lock, flags);
+                ret = radix_tree_insert(&ioc->radix_root,
+                                                (unsigned long) cfqd, cic);
+                spin_unlock_irqrestore(&ioc->lock, flags);
 
-                if (cic->key < k)
-                        p = &(*p)->rb_left;
-                else if (cic->key > k)
-                        p = &(*p)->rb_right;
-                else
-                        BUG();
+                radix_tree_preload_end();
+
+                if (!ret) {
+                        spin_lock_irqsave(cfqd->queue->queue_lock, flags);
+                        list_add(&cic->queue_list, &cfqd->cic_list);
+                        spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
+                }
         }
 
-        rb_link_node(&cic->rb_node, parent, p);
-        rb_insert_color(&cic->rb_node, &ioc->cic_root);
+        if (ret)
+                printk(KERN_ERR "cfq: cic link failed!\n");
 
-        spin_lock_irqsave(cfqd->queue->queue_lock, flags);
-        list_add(&cic->queue_list, &cfqd->cic_list);
-        spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
+        return ret;
 }
 
 /*
@@ -1586,7 +1591,7 @@ cfq_get_io_context(struct cfq_data *cfqd, gfp_t gfp_mask)
         if (!ioc)
                 return NULL;
 
-        cic = cfq_cic_rb_lookup(cfqd, ioc);
+        cic = cfq_cic_lookup(cfqd, ioc);
         if (cic)
                 goto out;
 
@@ -1594,13 +1599,17 @@ cfq_get_io_context(struct cfq_data *cfqd, gfp_t gfp_mask)
         if (cic == NULL)
                 goto err;
 
-        cfq_cic_link(cfqd, ioc, cic);
+        if (cfq_cic_link(cfqd, ioc, cic, gfp_mask))
+                goto err_free;
+
 out:
         smp_read_barrier_depends();
         if (unlikely(ioc->ioprio_changed))
                 cfq_ioc_set_ioprio(ioc);
 
         return cic;
+err_free:
+        cfq_cic_free(cic);
 err:
         put_io_context(ioc);
         return NULL;
@@ -1655,12 +1664,15 @@ cfq_update_idle_window(struct cfq_data *cfqd, struct cfq_queue *cfqq,
 {
         int enable_idle;
 
-        if (!cfq_cfqq_sync(cfqq))
+        /*
+         * Don't idle for async or idle io prio class
+         */
+        if (!cfq_cfqq_sync(cfqq) || cfq_class_idle(cfqq))
                 return;
 
         enable_idle = cfq_cfqq_idle_window(cfqq);
 
-        if (!cic->ioc->task || !cfqd->cfq_slice_idle ||
+        if (!atomic_read(&cic->ioc->nr_tasks) || !cfqd->cfq_slice_idle ||
             (cfqd->hw_tag && CIC_SEEKY(cic)))
                 enable_idle = 0;
         else if (sample_valid(cic->ttime_samples)) {
@@ -1793,7 +1805,7 @@ static void cfq_insert_request(struct request_queue *q, struct request *rq)
         struct cfq_data *cfqd = q->elevator->elevator_data;
         struct cfq_queue *cfqq = RQ_CFQQ(rq);
 
-        cfq_init_prio_data(cfqq);
+        cfq_init_prio_data(cfqq, RQ_CIC(rq)->ioc);
 
         cfq_add_rq_rb(rq);
 
@@ -1834,7 +1846,7 @@ static void cfq_completed_request(struct request_queue *q, struct request *rq)
                         cfq_set_prio_slice(cfqd, cfqq);
                         cfq_clear_cfqq_slice_new(cfqq);
                 }
-                if (cfq_slice_used(cfqq))
+                if (cfq_slice_used(cfqq) || cfq_class_idle(cfqq))
                         cfq_slice_expired(cfqd, 1);
                 else if (sync && RB_EMPTY_ROOT(&cfqq->sort_list))
                         cfq_arm_slice_timer(cfqd);
@@ -1894,13 +1906,13 @@ static int cfq_may_queue(struct request_queue *q, int rw)
          * so just lookup a possibly existing queue, or return 'may queue'
          * if that fails
          */
-        cic = cfq_cic_rb_lookup(cfqd, tsk->io_context);
+        cic = cfq_cic_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_init_prio_data(cfqq, cic->ioc);
                 cfq_prio_boost(cfqq);
 
                 return __cfq_may_queue(cfqq);
@@ -1938,7 +1950,6 @@ static int
 cfq_set_request(struct request_queue *q, struct request *rq, gfp_t gfp_mask)
 {
         struct cfq_data *cfqd = q->elevator->elevator_data;
-        struct task_struct *tsk = current;
         struct cfq_io_context *cic;
         const int rw = rq_data_dir(rq);
         const int is_sync = rq_is_sync(rq);
@@ -1956,7 +1967,7 @@ cfq_set_request(struct request_queue *q, struct request *rq, gfp_t gfp_mask)
 
         cfqq = cic_to_cfqq(cic, is_sync);
         if (!cfqq) {
-                cfqq = cfq_get_queue(cfqd, is_sync, tsk, gfp_mask);
+                cfqq = cfq_get_queue(cfqd, is_sync, cic->ioc, gfp_mask);
 
                 if (!cfqq)
                         goto queue_fail;
@@ -2039,29 +2050,9 @@ out_cont:
         spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
 }
 
-/*
- * Timer running if an idle class queue is waiting for service
- */
-static void cfq_idle_class_timer(unsigned long data)
-{
-        struct cfq_data *cfqd = (struct cfq_data *) data;
-        unsigned long flags;
-
-        spin_lock_irqsave(cfqd->queue->queue_lock, flags);
-
-        /*
-         * race with a non-idle queue, reset timer
-         */
-        if (!start_idle_class_timer(cfqd))
-                cfq_schedule_dispatch(cfqd);
-
-        spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
-}
-
 static void cfq_shutdown_timer_wq(struct cfq_data *cfqd)
 {
         del_timer_sync(&cfqd->idle_slice_timer);
-        del_timer_sync(&cfqd->idle_class_timer);
         kblockd_flush_work(&cfqd->unplug_work);
 }
 
@@ -2126,10 +2117,6 @@ static void *cfq_init_queue(struct request_queue *q)
         cfqd->idle_slice_timer.function = cfq_idle_slice_timer;
         cfqd->idle_slice_timer.data = (unsigned long) cfqd;
 
-        init_timer(&cfqd->idle_class_timer);
-        cfqd->idle_class_timer.function = cfq_idle_class_timer;
-        cfqd->idle_class_timer.data = (unsigned long) cfqd;
-
         INIT_WORK(&cfqd->unplug_work, cfq_kick_queue);
 
         cfqd->last_end_request = jiffies;
@@ -2160,7 +2147,7 @@ static int __init cfq_slab_setup(void)
         if (!cfq_pool)
                 goto fail;
 
-        cfq_ioc_pool = KMEM_CACHE(cfq_io_context, 0);
+        cfq_ioc_pool = KMEM_CACHE(cfq_io_context, SLAB_DESTROY_BY_RCU);
         if (!cfq_ioc_pool)
                 goto fail;
 
diff --git a/block/ll_rw_blk.c b/block/ll_rw_blk.c
index 3d0422f48453..b901db63f6ae 100644
--- a/block/ll_rw_blk.c
+++ b/block/ll_rw_blk.c
@@ -3853,55 +3853,100 @@ int __init blk_dev_init(void)
         return 0;
 }
 
+static void cfq_dtor(struct io_context *ioc)
+{
+        struct cfq_io_context *cic[1];
+        int r;
+
+        /*
+         * We don't have a specific key to lookup with, so use the gang
+         * lookup to just retrieve the first item stored. The cfq exit
+         * function will iterate the full tree, so any member will do.
+         */
+        r = radix_tree_gang_lookup(&ioc->radix_root, (void **) cic, 0, 1);
+        if (r > 0)
+                cic[0]->dtor(ioc);
+}
+
 /*
- * IO Context helper functions
+ * IO Context helper functions. put_io_context() returns 1 if there are no
+ * more users of this io context, 0 otherwise.
  */
-void put_io_context(struct io_context *ioc)
+int put_io_context(struct io_context *ioc)
 {
         if (ioc == NULL)
-                return;
+                return 1;
 
         BUG_ON(atomic_read(&ioc->refcount) == 0);
 
         if (atomic_dec_and_test(&ioc->refcount)) {
-                struct cfq_io_context *cic;
-
                 rcu_read_lock();
                 if (ioc->aic && ioc->aic->dtor)
                         ioc->aic->dtor(ioc->aic);
-                if (ioc->cic_root.rb_node != NULL) {
-                        struct rb_node *n = rb_first(&ioc->cic_root);
-
-                        cic = rb_entry(n, struct cfq_io_context, rb_node);
-                        cic->dtor(ioc);
-                }
                 rcu_read_unlock();
+                cfq_dtor(ioc);
 
                 kmem_cache_free(iocontext_cachep, ioc);
+                return 1;
         }
+        return 0;
 }
 EXPORT_SYMBOL(put_io_context);
 
+static void cfq_exit(struct io_context *ioc)
+{
+        struct cfq_io_context *cic[1];
+        int r;
+
+        rcu_read_lock();
+        /*
+         * See comment for cfq_dtor()
+         */
+        r = radix_tree_gang_lookup(&ioc->radix_root, (void **) cic, 0, 1);
+        rcu_read_unlock();
+
+        if (r > 0)
+                cic[0]->exit(ioc);
+}
+
 /* Called by the exitting task */
 void exit_io_context(void)
 {
         struct io_context *ioc;
-        struct cfq_io_context *cic;
 
         task_lock(current);
         ioc = current->io_context;
         current->io_context = NULL;
         task_unlock(current);
 
-        ioc->task = NULL;
-        if (ioc->aic && ioc->aic->exit)
-                ioc->aic->exit(ioc->aic);
-        if (ioc->cic_root.rb_node != NULL) {
-                cic = rb_entry(rb_first(&ioc->cic_root), struct cfq_io_context, rb_node);
-                cic->exit(ioc);
+        if (atomic_dec_and_test(&ioc->nr_tasks)) {
+                if (ioc->aic && ioc->aic->exit)
+                        ioc->aic->exit(ioc->aic);
+                cfq_exit(ioc);
+
+                put_io_context(ioc);
         }
+}
+
+struct io_context *alloc_io_context(gfp_t gfp_flags, int node)
+{
+        struct io_context *ret;
 
-        put_io_context(ioc);
+        ret = kmem_cache_alloc_node(iocontext_cachep, gfp_flags, node);
+        if (ret) {
+                atomic_set(&ret->refcount, 1);
+                atomic_set(&ret->nr_tasks, 1);
+                spin_lock_init(&ret->lock);
+                ret->ioprio_changed = 0;
+                ret->ioprio = 0;
+                ret->last_waited = jiffies; /* doesn't matter... */
+                ret->nr_batch_requests = 0; /* because this is 0 */
+                ret->aic = NULL;
+                INIT_RADIX_TREE(&ret->radix_root, GFP_ATOMIC | __GFP_HIGH);
+                ret->ioc_data = NULL;
+        }
+
+        return ret;
 }
 
 /*
@@ -3921,16 +3966,8 @@ static struct io_context *current_io_context(gfp_t gfp_flags, int node)
         if (likely(ret))
                 return ret;
 
-        ret = kmem_cache_alloc_node(iocontext_cachep, gfp_flags, node);
+        ret = alloc_io_context(gfp_flags, node);
         if (ret) {
-                atomic_set(&ret->refcount, 1);
-                ret->task = current;
-                ret->ioprio_changed = 0;
-                ret->last_waited = jiffies; /* doesn't matter... */
-                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;
@@ -3947,10 +3984,18 @@ static struct io_context *current_io_context(gfp_t gfp_flags, int node)
  */
 struct io_context *get_io_context(gfp_t gfp_flags, int node)
 {
-        struct io_context *ret;
-        ret = current_io_context(gfp_flags, node);
-        if (likely(ret))
-                atomic_inc(&ret->refcount);
+        struct io_context *ret = NULL;
+
+        /*
+         * Check for unlikely race with exiting task. ioc ref count is
+         * zero when ioc is being detached.
+         */
+        do {
+                ret = current_io_context(gfp_flags, node);
+                if (unlikely(!ret))
+                        break;
+        } while (!atomic_inc_not_zero(&ret->refcount));
+
         return ret;
 }
 EXPORT_SYMBOL(get_io_context);
diff --git a/fs/ioprio.c b/fs/ioprio.c
index e4e01bc7f338..c4a1c3c65aac 100644
--- a/fs/ioprio.c
+++ b/fs/ioprio.c
@@ -41,18 +41,28 @@ static int set_task_ioprio(struct task_struct *task, int ioprio)
                 return err;
 
         task_lock(task);
+        do {
+                ioc = task->io_context;
+                /* see wmb() in current_io_context() */
+                smp_read_barrier_depends();
+                if (ioc)
+                        break;
 
-        task->ioprio = ioprio;
-
-        ioc = task->io_context;
-        /* see wmb() in current_io_context() */
-        smp_read_barrier_depends();
+                ioc = alloc_io_context(GFP_ATOMIC, -1);
+                if (!ioc) {
+                        err = -ENOMEM;
+                        break;
+                }
+                task->io_context = ioc;
+        } while (1);
 
-        if (ioc)
+        if (!err) {
+                ioc->ioprio = ioprio;
                 ioc->ioprio_changed = 1;
+        }
 
         task_unlock(task);
-        return 0;
+        return err;
 }
 
 asmlinkage long sys_ioprio_set(int which, int who, int ioprio)
@@ -75,8 +85,6 @@ asmlinkage long sys_ioprio_set(int which, int who, int ioprio)
 
                         break;
                 case IOPRIO_CLASS_IDLE:
-                        if (!capable(CAP_SYS_ADMIN))
-                                return -EPERM;
                         break;
                 case IOPRIO_CLASS_NONE:
                         if (data)
@@ -148,7 +156,9 @@ static int get_task_ioprio(struct task_struct *p)
         ret = security_task_getioprio(p);
         if (ret)
                 goto out;
-        ret = p->ioprio;
+        ret = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_NONE, IOPRIO_NORM);
+        if (p->io_context)
+                ret = p->io_context->ioprio;
 out:
         return ret;
 }
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 49b7a4c31a6d..2483a05231c7 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -34,83 +34,10 @@ struct sg_io_hdr;
 #define BLKDEV_MIN_RQ   4
 #define BLKDEV_MAX_RQ   128     /* Default maximum */
 
-/*
- * This is the per-process anticipatory I/O scheduler state.
- */
-struct as_io_context {
-        spinlock_t lock;
-
-        void (*dtor)(struct as_io_context *aic); /* destructor */
-        void (*exit)(struct as_io_context *aic); /* called on task exit */
-
-        unsigned long state;
-        atomic_t nr_queued; /* queued reads & sync writes */
-        atomic_t nr_dispatched; /* number of requests gone to the drivers */
-
-        /* IO History tracking */
-        /* Thinktime */
-        unsigned long last_end_request;
-        unsigned long ttime_total;
-        unsigned long ttime_samples;
-        unsigned long ttime_mean;
-        /* Layout pattern */
-        unsigned int seek_samples;
-        sector_t last_request_pos;
-        u64 seek_total;
-        sector_t seek_mean;
-};
-
-struct cfq_queue;
-struct cfq_io_context {
-        struct rb_node rb_node;
-        void *key;
-
-        struct cfq_queue *cfqq[2];
-
-        struct io_context *ioc;
-
-        unsigned long last_end_request;
-        sector_t last_request_pos;
-
-        unsigned long ttime_total;
-        unsigned long ttime_samples;
-        unsigned long ttime_mean;
-
-        unsigned int seek_samples;
-        u64 seek_total;
-        sector_t seek_mean;
-
-        struct list_head queue_list;
-
-        void (*dtor)(struct io_context *); /* destructor */
-        void (*exit)(struct io_context *); /* called on task exit */
-};
-
-/*
- * This is the per-process I/O subsystem state.  It is refcounted and
- * kmalloc'ed. Currently all fields are modified in process io context
- * (apart from the atomic refcount), so require no locking.
- */
-struct io_context {
-        atomic_t refcount;
-        struct task_struct *task;
-
-        unsigned int ioprio_changed;
-
-        /*
-         * For request batching
-         */
-        unsigned long last_waited; /* Time last woken after wait for request */
-        int nr_batch_requests;     /* Number of requests left in the batch */
-
-        struct as_io_context *aic;
-        struct rb_root cic_root;
-        void *ioc_data;
-};
-
-void put_io_context(struct io_context *ioc);
+int put_io_context(struct io_context *ioc);
 void exit_io_context(void);
 struct io_context *get_io_context(gfp_t gfp_flags, int node);
+struct io_context *alloc_io_context(gfp_t gfp_flags, int node);
 void copy_io_context(struct io_context **pdst, struct io_context **psrc);
 void swap_io_context(struct io_context **ioc1, struct io_context **ioc2);
 
@@ -894,6 +821,12 @@ static inline void exit_io_context(void)
 {
 }
 
+static inline int put_io_context(struct io_context *ioc)
+{
+        return 1;
+}
+
+
 #endif /* CONFIG_BLOCK */
 
 #endif
diff --git a/include/linux/init_task.h b/include/linux/init_task.h
index 796019b22b6f..e6b3f7080679 100644
--- a/include/linux/init_task.h
+++ b/include/linux/init_task.h
@@ -137,7 +137,6 @@ extern struct group_info init_groups;
                 .time_slice     = HZ,                                   \
                 .nr_cpus_allowed = NR_CPUS,                             \
         },                                                              \
-        .ioprio         = 0,                                            \
         .tasks          = LIST_HEAD_INIT(tsk.tasks),                    \
         .ptrace_children= LIST_HEAD_INIT(tsk.ptrace_children),          \
         .ptrace_list    = LIST_HEAD_INIT(tsk.ptrace_list),              \
diff --git a/include/linux/iocontext.h b/include/linux/iocontext.h
new file mode 100644
index 000000000000..593b222d9dcc
--- /dev/null
+++ b/include/linux/iocontext.h
@@ -0,0 +1,95 @@
+#ifndef IOCONTEXT_H
+#define IOCONTEXT_H
+
+#include <linux/radix-tree.h>
+
+/*
+ * This is the per-process anticipatory I/O scheduler state.
+ */
+struct as_io_context {
+        spinlock_t lock;
+
+        void (*dtor)(struct as_io_context *aic); /* destructor */
+        void (*exit)(struct as_io_context *aic); /* called on task exit */
+
+        unsigned long state;
+        atomic_t nr_queued; /* queued reads & sync writes */
+        atomic_t nr_dispatched; /* number of requests gone to the drivers */
+
+        /* IO History tracking */
+        /* Thinktime */
+        unsigned long last_end_request;
+        unsigned long ttime_total;
+        unsigned long ttime_samples;
+        unsigned long ttime_mean;
+        /* Layout pattern */
+        unsigned int seek_samples;
+        sector_t last_request_pos;
+        u64 seek_total;
+        sector_t seek_mean;
+};
+
+struct cfq_queue;
+struct cfq_io_context {
+        void *key;
+        unsigned long dead_key;
+
+        struct cfq_queue *cfqq[2];
+
+        struct io_context *ioc;
+
+        unsigned long last_end_request;
+        sector_t last_request_pos;
+
+        unsigned long ttime_total;
+        unsigned long ttime_samples;
+        unsigned long ttime_mean;
+
+        unsigned int seek_samples;
+        u64 seek_total;
+        sector_t seek_mean;
+
+        struct list_head queue_list;
+
+        void (*dtor)(struct io_context *); /* destructor */
+        void (*exit)(struct io_context *); /* called on task exit */
+};
+
+/*
+ * I/O subsystem state of the associated processes.  It is refcounted
+ * and kmalloc'ed. These could be shared between processes.
+ */
+struct io_context {
+        atomic_t refcount;
+        atomic_t nr_tasks;
+
+        /* all the fields below are protected by this lock */
+        spinlock_t lock;
+
+        unsigned short ioprio;
+        unsigned short ioprio_changed;
+
+        /*
+         * For request batching
+         */
+        unsigned long last_waited; /* Time last woken after wait for request */
+        int nr_batch_requests;     /* Number of requests left in the batch */
+
+        struct as_io_context *aic;
+        struct radix_tree_root radix_root;
+        void *ioc_data;
+};
+
+static inline struct io_context *ioc_task_link(struct io_context *ioc)
+{
+        /*
+         * if ref count is zero, don't allow sharing (ioc is going away, it's
+         * a race).
+         */
+        if (ioc && atomic_inc_not_zero(&ioc->refcount))
+                return ioc;
+
+        return NULL;
+}
+
+#endif
diff --git a/include/linux/ioprio.h b/include/linux/ioprio.h
index baf29387cab4..2a3bb1bb7433 100644
--- a/include/linux/ioprio.h
+++ b/include/linux/ioprio.h
@@ -2,6 +2,7 @@
 #define IOPRIO_H
 
 #include <linux/sched.h>
+#include <linux/iocontext.h>
 
 /*
  * Gives us 8 prio classes with 13-bits of data for each class
@@ -45,18 +46,18 @@ enum {
  * the cpu scheduler nice value to an io priority
  */
 #define IOPRIO_NORM     (4)
-static inline int task_ioprio(struct task_struct *task)
+static inline int task_ioprio(struct io_context *ioc)
 {
-        if (ioprio_valid(task->ioprio))
-                return IOPRIO_PRIO_DATA(task->ioprio);
+        if (ioprio_valid(ioc->ioprio))
+                return IOPRIO_PRIO_DATA(ioc->ioprio);
 
         return IOPRIO_NORM;
 }
 
-static inline int task_ioprio_class(struct task_struct *task)
+static inline int task_ioprio_class(struct io_context *ioc)
 {
-        if (ioprio_valid(task->ioprio))
-                return IOPRIO_PRIO_CLASS(task->ioprio);
+        if (ioprio_valid(ioc->ioprio))
+                return IOPRIO_PRIO_CLASS(ioc->ioprio);
 
         return IOPRIO_CLASS_BE;
 }
diff --git a/include/linux/sched.h b/include/linux/sched.h
index df5b24ee80b3..2d0546e884ea 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -27,6 +27,7 @@
 #define CLONE_NEWUSER           0x10000000      /* New user namespace */
 #define CLONE_NEWPID            0x20000000      /* New pid namespace */
 #define CLONE_NEWNET            0x40000000      /* New network namespace */
+#define CLONE_IO                0x80000000      /* Clone io context */
 
 /*
  * Scheduling policies
@@ -975,7 +976,6 @@ struct task_struct {
         struct hlist_head preempt_notifiers;
 #endif
 
-        unsigned short ioprio;
         /*
          * fpu_counter contains the number of consecutive context switches
          * that the FPU is used. If this is over a threshold, the lazy fpu
diff --git a/kernel/fork.c b/kernel/fork.c
index 39d22b3357de..314f5101d2b0 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -51,6 +51,7 @@
 #include <linux/random.h>
 #include <linux/tty.h>
 #include <linux/proc_fs.h>
+#include <linux/blkdev.h>
 
 #include <asm/pgtable.h>
 #include <asm/pgalloc.h>
@@ -791,6 +792,31 @@ out:
         return error;
 }
 
+static int copy_io(unsigned long clone_flags, struct task_struct *tsk)
+{
+#ifdef CONFIG_BLOCK
+        struct io_context *ioc = current->io_context;
+
+        if (!ioc)
+                return 0;
+        /*
+         * Share io context with parent, if CLONE_IO is set
+         */
+        if (clone_flags & CLONE_IO) {
+                tsk->io_context = ioc_task_link(ioc);
+                if (unlikely(!tsk->io_context))
+                        return -ENOMEM;
+        } else if (ioprio_valid(ioc->ioprio)) {
+                tsk->io_context = alloc_io_context(GFP_KERNEL, -1);
+                if (unlikely(!tsk->io_context))
+                        return -ENOMEM;
+
+                tsk->io_context->ioprio = ioc->ioprio;
+        }
+#endif
+        return 0;
+}
+
 /*
  *      Helper to unshare the files of the current task.
  *      We don't want to expose copy_files internals to
@@ -1156,15 +1182,17 @@ static struct task_struct *copy_process(unsigned long clone_flags,
                 goto bad_fork_cleanup_mm;
         if ((retval = copy_namespaces(clone_flags, p)))
                 goto bad_fork_cleanup_keys;
+        if ((retval = copy_io(clone_flags, p)))
+                goto bad_fork_cleanup_namespaces;
         retval = copy_thread(0, clone_flags, stack_start, stack_size, p, regs);
         if (retval)
-                goto bad_fork_cleanup_namespaces;
+                goto bad_fork_cleanup_io;
 
         if (pid != &init_struct_pid) {
                 retval = -ENOMEM;
                 pid = alloc_pid(task_active_pid_ns(p));
                 if (!pid)
-                        goto bad_fork_cleanup_namespaces;
+                        goto bad_fork_cleanup_io;
 
                 if (clone_flags & CLONE_NEWPID) {
                         retval = pid_ns_prepare_proc(task_active_pid_ns(p));
@@ -1234,9 +1262,6 @@ static struct task_struct *copy_process(unsigned long clone_flags,
         /* Need tasklist lock for parent etc handling! */
         write_lock_irq(&tasklist_lock);
 
-        /* for sys_ioprio_set(IOPRIO_WHO_PGRP) */
-        p->ioprio = current->ioprio;
-
         /*
          * The task hasn't been attached yet, so its cpus_allowed mask will
          * not be changed, nor will its assigned CPU.
@@ -1328,6 +1353,8 @@ static struct task_struct *copy_process(unsigned long clone_flags,
 bad_fork_free_pid:
         if (pid != &init_struct_pid)
                 free_pid(pid);
+bad_fork_cleanup_io:
+        put_io_context(p->io_context);
 bad_fork_cleanup_namespaces:
         exit_task_namespaces(p);
 bad_fork_cleanup_keys: