diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index dba52b62cef8..8830893e062f 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -200,7 +200,7 @@ 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 io_context *, gfp_t);
-static struct cfq_io_context *cfq_cic_rb_lookup(struct cfq_data *,
+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,
@@ -609,7 +609,7 @@ 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 +721,7 @@ 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;
 
@@ -1170,29 +1170,74 @@ static void cfq_put_queue(struct cfq_queue *cfqq)
 	kmem_cache_free(cfq_pool, cfqq);
 }
 
+/*
+ * 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 *cics[CIC_GANG_NR];
+	unsigned long index = 0;
+	unsigned int called = 0;
+	int nr;
+
+	rcu_read_lock();
+
+	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)
 {
-	struct cfq_io_context *__cic;
-	struct rb_node *n;
-	int freed = 0;
+	int freed;
 
-	ioc->ioc_data = NULL;
-
-	spin_lock(&ioc->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++;
-	}
+	/*
+	 * 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);
 
 	if (ioc_gone && !elv_ioc_count_read(ioc_count))
 		complete(ioc_gone);
-
-	spin_unlock(&ioc->lock);
 }
 
 static void cfq_exit_cfqq(struct cfq_data *cfqd, struct cfq_queue *cfqq)
@@ -1209,7 +1254,12 @@ 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]) {
@@ -1223,16 +1273,18 @@ 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);
 	}
 }
 
@@ -1242,24 +1294,8 @@ 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;
-
-	spin_lock(&ioc->lock);
-	/*
-	 * 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);
-	}
-
-	spin_unlock(&ioc->lock);
+	rcu_assign_pointer(ioc->ioc_data, NULL);
+	call_for_each_cic(ioc, cfq_exit_single_io_context);
 }
 
 static struct cfq_io_context *
@@ -1323,7 +1359,8 @@ static void cfq_init_prio_data(struct cfq_queue *cfqq, struct io_context *ioc)
 	cfq_clear_cfqq_prio_changed(cfqq);
 }
 
-static inline void changed_ioprio(struct cfq_io_context *cic)
+static inline void changed_ioprio(struct io_context *ioc,
+				  struct cfq_io_context *cic)
 {
 	struct cfq_data *cfqd = cic->key;
 	struct cfq_queue *cfqq;
@@ -1353,22 +1390,8 @@ 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;
-
-	spin_lock(&ioc->lock);
-
+	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);
-	}
-
-	spin_unlock(&ioc->lock);
 }
 
 static struct cfq_queue *
@@ -1379,7 +1402,7 @@ cfq_find_alloc_queue(struct cfq_data *cfqd, int is_sync,
 	struct cfq_io_context *cic;
 
 retry:
-	cic = cfq_cic_rb_lookup(cfqd, ioc);
+	cic = cfq_cic_lookup(cfqd, ioc);
 	/* cic always exists here */
 	cfqq = cic_to_cfqq(cic, is_sync);
 
@@ -1480,28 +1503,42 @@ cfq_get_queue(struct cfq_data *cfqd, int is_sync, struct io_context *ioc,
 	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));
 
-	if (ioc->ioc_data == cic)
-		ioc->ioc_data = NULL;
+	spin_lock_irqsave(&ioc->lock, flags);
 
-	rb_erase(&cic->rb_node, &ioc->cic_root);
-	kmem_cache_free(cfq_ioc_pool, cic);
-	elv_ioc_count_dec(ioc_count);
+	if (ioc->ioc_data == cic)
+		rcu_assign_pointer(ioc->ioc_data, NULL);
+
+	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;
@@ -1509,79 +1546,65 @@ 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;
 
-	spin_lock(&ioc->lock);
-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;
-			spin_unlock(&ioc->lock);
-			return cic;
-		}
-	}
+		rcu_assign_pointer(ioc->ioc_data, cic);
+		break;
+	} while (1);
 
-	spin_unlock(&ioc->lock);
-	return NULL;
+	return cic;
 }
 
-static inline void
+/*
+ * 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 inline int
 cfq_cic_link(struct cfq_data *cfqd, struct io_context *ioc,
-	     struct cfq_io_context *cic)
+	     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;
 
-	spin_lock(&ioc->lock);
-	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);
+
+		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);
 		}
-
-		if (cic->key < k)
-			p = &(*p)->rb_left;
-		else if (cic->key > k)
-			p = &(*p)->rb_right;
-		else
-			BUG();
 	}
 
-	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);
-	spin_unlock(&ioc->lock);
+	return ret;
 }
 
 /*
@@ -1601,7 +1624,7 @@ 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;
 
@@ -1609,13 +1632,17 @@ 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;
@@ -1909,7 +1936,7 @@ 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;
 
@@ -2174,7 +2201,7 @@ 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 d4550ecae443..b901db63f6ae 100644
--- a/block/ll_rw_blk.c
+++ b/block/ll_rw_blk.c
@@ -3853,6 +3853,21 @@ 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. put_io_context() returns 1 if there are no
  * more users of this io context, 0 otherwise.
@@ -3865,18 +3880,11 @@ int put_io_context(struct io_context *ioc)
 	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;
@@ -3885,11 +3893,26 @@ int put_io_context(struct io_context *ioc)
 }
 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;
@@ -3899,11 +3922,7 @@ void exit_io_context(void)
 	if (atomic_dec_and_test(&ioc->nr_tasks)) {
 		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);
-		}
+		cfq_exit(ioc);
 
 		put_io_context(ioc);
 	}
@@ -3923,7 +3942,7 @@ struct io_context *alloc_io_context(gfp_t gfp_flags, int node)
 		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;
+		INIT_RADIX_TREE(&ret->radix_root, GFP_ATOMIC | __GFP_HIGH);
 		ret->ioc_data = NULL;
 	}
 
diff --git a/include/linux/iocontext.h b/include/linux/iocontext.h
index cd44d458124a..593b222d9dcc 100644
--- a/include/linux/iocontext.h
+++ b/include/linux/iocontext.h
@@ -1,6 +1,8 @@
 #ifndef IOCONTEXT_H
 #define IOCONTEXT_H
 
+#include <linux/radix-tree.h>
+
 /*
  * This is the per-process anticipatory I/O scheduler state.
  */
@@ -29,8 +31,8 @@ struct as_io_context {
 
 struct cfq_queue;
 struct cfq_io_context {
-	struct rb_node rb_node;
 	void *key;
+	unsigned long dead_key;
 
 	struct cfq_queue *cfqq[2];
 
@@ -74,7 +76,7 @@ struct io_context {
 	int nr_batch_requests;     /* Number of requests left in the batch */
 
 	struct as_io_context *aic;
-	struct rb_root cic_root;
+	struct radix_tree_root radix_root;
 	void *ioc_data;
 };