block, cfq: move io_cq exit/release to blk-ioc.c

With kmem_cache managed by blk-ioc, io_cq exit/release can be moved to
blk-ioc too.  The odd ->io_cq->exit/release() callbacks are replaced
with elevator_ops->elevator_exit_icq_fn() with unlinking from both ioc
and q, and freeing automatically handled by blk-ioc.  The elevator
operation only need to perform exit operation specific to the elevator
- in cfq's case, exiting the cfqq's.

Also, clearing of io_cq's on q detach is moved to block core and
automatically performed on elevator switch and q release.

Because the q io_cq points to might be freed before RCU callback for
the io_cq runs, blk-ioc code should remember to which cache the io_cq
needs to be freed when the io_cq is released.  New field
io_cq->__rcu_icq_cache is added for this purpose.  As both the new
field and rcu_head are used only after io_cq is released and the
q/ioc_node fields aren't, they are put into unions.

Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 2 insertions, 45 deletions

diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 06e59abcb57f..f6d315551496 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -2674,26 +2674,6 @@ static void cfq_put_queue(struct cfq_queue *cfqq)
         cfq_put_cfqg(cfqg);
 }
 
-static void cfq_icq_free_rcu(struct rcu_head *head)
-{
-        kmem_cache_free(cfq_icq_pool,
-                        icq_to_cic(container_of(head, struct io_cq, rcu_head)));
-}
-
-static void cfq_icq_free(struct io_cq *icq)
-{
-        call_rcu(&icq->rcu_head, cfq_icq_free_rcu);
-}
-
-static void cfq_release_icq(struct io_cq *icq)
-{
-        struct io_context *ioc = icq->ioc;
-
-        radix_tree_delete(&ioc->icq_tree, icq->q->id);
-        hlist_del(&icq->ioc_node);
-        cfq_icq_free(icq);
-}
-
 static void cfq_put_cooperator(struct cfq_queue *cfqq)
 {
         struct cfq_queue *__cfqq, *next;
@@ -2731,17 +2711,6 @@ static void cfq_exit_icq(struct io_cq *icq)
 {
         struct cfq_io_cq *cic = icq_to_cic(icq);
         struct cfq_data *cfqd = cic_to_cfqd(cic);
-        struct io_context *ioc = icq->ioc;
-
-        list_del_init(&icq->q_node);
-
-        /*
-         * Both setting lookup hint to and clearing it from @icq are done
-         * under queue_lock.  If it's not pointing to @icq now, it never
-         * will.  Hint assignment itself can race safely.
-         */
-        if (rcu_dereference_raw(ioc->icq_hint) == icq)
-                rcu_assign_pointer(ioc->icq_hint, NULL);
 
         if (cic->cfqq[BLK_RW_ASYNC]) {
                 cfq_exit_cfqq(cfqd, cic->cfqq[BLK_RW_ASYNC]);
@@ -2764,8 +2733,6 @@ static struct cfq_io_cq *cfq_alloc_cic(struct cfq_data *cfqd, gfp_t gfp_mask)
                 cic->ttime.last_end_request = jiffies;
                 INIT_LIST_HEAD(&cic->icq.q_node);
                 INIT_HLIST_NODE(&cic->icq.ioc_node);
-                cic->icq.exit = cfq_exit_icq;
-                cic->icq.release = cfq_release_icq;
         }
 
         return cic;
@@ -3034,7 +3001,7 @@ out:
         if (ret)
                 printk(KERN_ERR "cfq: icq link failed!\n");
         if (icq)
-                cfq_icq_free(icq);
+                kmem_cache_free(cfq_icq_pool, icq);
         return ret;
 }
 
@@ -3774,17 +3741,6 @@ static void cfq_exit_queue(struct elevator_queue *e)
         if (cfqd->active_queue)
                 __cfq_slice_expired(cfqd, cfqd->active_queue, 0);
 
-        while (!list_empty(&q->icq_list)) {
-                struct io_cq *icq = list_entry(q->icq_list.next,
-                                               struct io_cq, q_node);
-                struct io_context *ioc = icq->ioc;
-
-                spin_lock(&ioc->lock);
-                cfq_exit_icq(icq);
-                cfq_release_icq(icq);
-                spin_unlock(&ioc->lock);
-        }
-
         cfq_put_async_queues(cfqd);
         cfq_release_cfq_groups(cfqd);
 
@@ -4019,6 +3975,7 @@ static struct elevator_type iosched_cfq = {
                 .elevator_completed_req_fn =    cfq_completed_request,
                 .elevator_former_req_fn =       elv_rb_former_request,
                 .elevator_latter_req_fn =       elv_rb_latter_request,
+                .elevator_exit_icq_fn =         cfq_exit_icq,
                 .elevator_set_req_fn =          cfq_set_request,
                 .elevator_put_req_fn =          cfq_put_request,
                 .elevator_may_queue_fn =        cfq_may_queue,