2 files changed, 10 insertions, 98 deletions

diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 6cc606560402..ff44435fad50 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -2669,24 +2669,6 @@ static void cfq_put_queue(struct cfq_queue *cfqq)
         cfq_put_cfqg(cfqg);
 }
 
-/*
- * Call func for each cic attached to this ioc.
- */
-static void
-call_for_each_cic(struct io_context *ioc,
-                  void (*func)(struct io_context *, struct cfq_io_context *))
-{
-        struct cfq_io_context *cic;
-        struct hlist_node *n;
-
-        rcu_read_lock();
-
-        hlist_for_each_entry_rcu(cic, n, &ioc->cic_list, cic_list)
-                func(ioc, cic);
-
-        rcu_read_unlock();
-}
-
 static void cfq_cic_free_rcu(struct rcu_head *head)
 {
         struct cfq_io_context *cic;
@@ -2727,31 +2709,6 @@ static void cfq_release_cic(struct cfq_io_context *cic)
         cfq_cic_free(cic);
 }
 
-static void cic_free_func(struct io_context *ioc, struct cfq_io_context *cic)
-{
-        unsigned long flags;
-
-        spin_lock_irqsave(&ioc->lock, flags);
-        cfq_release_cic(cic);
-        spin_unlock_irqrestore(&ioc->lock, flags);
-}
-
-/*
- * Must be called with rcu_read_lock() held or preemption otherwise disabled.
- * Only two callers of this - ->dtor() which is called with the rcu_read_lock(),
- * and ->trim() which is called with the task lock held
- */
-static void cfq_free_io_context(struct io_context *ioc)
-{
-        /*
-         * ioc->refcount is zero here, or we are called from elv_unregister(),
-         * 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.
-         */
-        call_for_each_cic(ioc, cic_free_func);
-}
-
 static void cfq_put_cooperator(struct cfq_queue *cfqq)
 {
         struct cfq_queue *__cfqq, *next;
@@ -3037,30 +2994,6 @@ cfq_get_queue(struct cfq_data *cfqd, bool is_sync, struct io_context *ioc,
         return cfqq;
 }
 
-/*
- * We drop cfq io contexts lazily, so we may find a dead one.
- */
-static void
-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));
-        BUG_ON(cic->key != cfqd_dead_key(cfqd));
-
-        spin_lock_irqsave(&ioc->lock, flags);
-
-        BUG_ON(rcu_dereference_check(ioc->ioc_data,
-                lockdep_is_held(&ioc->lock)) == cic);
-
-        radix_tree_delete(&ioc->radix_root, cfqd->queue->id);
-        hlist_del_rcu(&cic->cic_list);
-        spin_unlock_irqrestore(&ioc->lock, flags);
-
-        cfq_cic_free(cic);
-}
-
 /**
  * cfq_cic_lookup - lookup cfq_io_context
  * @cfqd: the associated cfq_data
@@ -3078,26 +3011,22 @@ cfq_cic_lookup(struct cfq_data *cfqd, struct io_context *ioc)
         if (unlikely(!ioc))
                 return NULL;
 
-        rcu_read_lock();
-
         /*
-         * we maintain a last-hit cache, to avoid browsing over the tree
+         * cic's are indexed from @ioc using radix tree and hint pointer,
+         * both of which are protected with RCU.  All removals are done
+         * holding both q and ioc locks, and we're holding q lock - if we
+         * find a cic which points to us, it's guaranteed to be valid.
          */
+        rcu_read_lock();
         cic = rcu_dereference(ioc->ioc_data);
         if (cic && cic->key == cfqd)
                 goto out;
 
-        do {
-                cic = radix_tree_lookup(&ioc->radix_root, cfqd->queue->id);
-                if (!cic)
-                        break;
-                if (likely(cic->key == cfqd)) {
-                        /* hint assignment itself can race safely */
-                        rcu_assign_pointer(ioc->ioc_data, cic);
-                        break;
-                }
-                cfq_drop_dead_cic(cfqd, ioc, cic);
-        } while (1);
+        cic = radix_tree_lookup(&ioc->radix_root, cfqd->queue->id);
+        if (cic && cic->key == cfqd)
+                rcu_assign_pointer(ioc->ioc_data, cic); /* allowed to race */
+        else
+                cic = NULL;
 out:
         rcu_read_unlock();
         return cic;
@@ -4182,7 +4111,6 @@ static struct elevator_type iosched_cfq = {
                 .elevator_may_queue_fn =        cfq_may_queue,
                 .elevator_init_fn =             cfq_init_queue,
                 .elevator_exit_fn =             cfq_exit_queue,
-                .trim =                         cfq_free_io_context,
         },
         .elevator_attrs =       cfq_attrs,
         .elevator_name =        "cfq",
diff --git a/block/elevator.c b/block/elevator.c
index 66343d6917d0..6a343e8f8319 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -913,22 +913,6 @@ EXPORT_SYMBOL_GPL(elv_register);
 
 void elv_unregister(struct elevator_type *e)
 {
-        struct task_struct *g, *p;
-
-        /*
-         * Iterate every thread in the process to remove the io contexts.
-         */
-        if (e->ops.trim) {
-                read_lock(&tasklist_lock);
-                do_each_thread(g, p) {
-                        task_lock(p);
-                        if (p->io_context)
-                                e->ops.trim(p->io_context);
-                        task_unlock(p);
-                } while_each_thread(g, p);
-                read_unlock(&tasklist_lock);
-        }
-
         spin_lock(&elv_list_lock);
         list_del_init(&e->list);
         spin_unlock(&elv_list_lock);