block, cfq: move icq cache management to block core

Let elevators set ->icq_size and ->icq_align in elevator_type and
elv_register() and elv_unregister() respectively create and destroy
kmem_cache for icq.

* elv_register() now can return failure.  All callers updated.

* icq caches are automatically named "ELVNAME_io_cq".

* cfq_slab_setup/kill() are collapsed into cfq_init/exit().

* While at it, minor indentation change for iosched_cfq.elevator_name
  for consistency.

This will help moving icq management to block core.  This doesn't
introduce any functional change.

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

4 files changed, 52 insertions, 41 deletions

diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 048fa699adf9..06e59abcb57f 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -3914,34 +3914,6 @@ static void *cfq_init_queue(struct request_queue *q)
         return cfqd;
 }
 
-static void cfq_slab_kill(void)
-{
-        /*
-         * Caller already ensured that pending RCU callbacks are completed,
-         * so we should have no busy allocations at this point.
-         */
-        if (cfq_pool)
-                kmem_cache_destroy(cfq_pool);
-        if (cfq_icq_pool)
-                kmem_cache_destroy(cfq_icq_pool);
-}
-
-static int __init cfq_slab_setup(void)
-{
-        cfq_pool = KMEM_CACHE(cfq_queue, 0);
-        if (!cfq_pool)
-                goto fail;
-
-        cfq_icq_pool = KMEM_CACHE(cfq_io_cq, 0);
-        if (!cfq_icq_pool)
-                goto fail;
-
-        return 0;
-fail:
-        cfq_slab_kill();
-        return -ENOMEM;
-}
-
 /*
  * sysfs parts below -->
  */
@@ -4053,8 +4025,10 @@ static struct elevator_type iosched_cfq = {
                 .elevator_init_fn =             cfq_init_queue,
                 .elevator_exit_fn =             cfq_exit_queue,
         },
+        .icq_size       =       sizeof(struct cfq_io_cq),
+        .icq_align      =       __alignof__(struct cfq_io_cq),
         .elevator_attrs =       cfq_attrs,
-        .elevator_name =        "cfq",
+        .elevator_name  =       "cfq",
         .elevator_owner =       THIS_MODULE,
 };
 
@@ -4072,6 +4046,8 @@ static struct blkio_policy_type blkio_policy_cfq;
 
 static int __init cfq_init(void)
 {
+        int ret;
+
         /*
          * could be 0 on HZ < 1000 setups
          */
@@ -4086,10 +4062,17 @@ static int __init cfq_init(void)
 #else
                 cfq_group_idle = 0;
 #endif
-        if (cfq_slab_setup())
+        cfq_pool = KMEM_CACHE(cfq_queue, 0);
+        if (!cfq_pool)
                 return -ENOMEM;
 
-        elv_register(&iosched_cfq);
+        ret = elv_register(&iosched_cfq);
+        if (ret) {
+                kmem_cache_destroy(cfq_pool);
+                return ret;
+        }
+        cfq_icq_pool = iosched_cfq.icq_cache;
+
         blkio_policy_register(&blkio_policy_cfq);
 
         return 0;
@@ -4099,8 +4082,7 @@ static void __exit cfq_exit(void)
 {
         blkio_policy_unregister(&blkio_policy_cfq);
         elv_unregister(&iosched_cfq);
-        rcu_barrier();  /* make sure all cic RCU frees are complete */
-        cfq_slab_kill();
+        kmem_cache_destroy(cfq_pool);
 }
 
 module_init(cfq_init);
diff --git a/block/deadline-iosched.c b/block/deadline-iosched.c
index c644137d9cd6..7bf12d793fcd 100644
--- a/block/deadline-iosched.c
+++ b/block/deadline-iosched.c
@@ -448,9 +448,7 @@ static struct elevator_type iosched_deadline = {
 
 static int __init deadline_init(void)
 {
-        elv_register(&iosched_deadline);
-
-        return 0;
+        return elv_register(&iosched_deadline);
 }
 
 static void __exit deadline_exit(void)
diff --git a/block/elevator.c b/block/elevator.c
index c5c6214829cb..cca049fb45c8 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -886,15 +886,36 @@ void elv_unregister_queue(struct request_queue *q)
 }
 EXPORT_SYMBOL(elv_unregister_queue);
 
-void elv_register(struct elevator_type *e)
+int elv_register(struct elevator_type *e)
 {
         char *def = "";
 
+        /* create icq_cache if requested */
+        if (e->icq_size) {
+                if (WARN_ON(e->icq_size < sizeof(struct io_cq)) ||
+                    WARN_ON(e->icq_align < __alignof__(struct io_cq)))
+                        return -EINVAL;
+
+                snprintf(e->icq_cache_name, sizeof(e->icq_cache_name),
+                         "%s_io_cq", e->elevator_name);
+                e->icq_cache = kmem_cache_create(e->icq_cache_name, e->icq_size,
+                                                 e->icq_align, 0, NULL);
+                if (!e->icq_cache)
+                        return -ENOMEM;
+        }
+
+        /* register, don't allow duplicate names */
         spin_lock(&elv_list_lock);
-        BUG_ON(elevator_find(e->elevator_name));
+        if (elevator_find(e->elevator_name)) {
+                spin_unlock(&elv_list_lock);
+                if (e->icq_cache)
+                        kmem_cache_destroy(e->icq_cache);
+                return -EBUSY;
+        }
         list_add_tail(&e->list, &elv_list);
         spin_unlock(&elv_list_lock);
 
+        /* print pretty message */
         if (!strcmp(e->elevator_name, chosen_elevator) ||
                         (!*chosen_elevator &&
                          !strcmp(e->elevator_name, CONFIG_DEFAULT_IOSCHED)))
@@ -902,14 +923,26 @@ void elv_register(struct elevator_type *e)
 
         printk(KERN_INFO "io scheduler %s registered%s\n", e->elevator_name,
                                                                 def);
+        return 0;
 }
 EXPORT_SYMBOL_GPL(elv_register);
 
 void elv_unregister(struct elevator_type *e)
 {
+        /* unregister */
         spin_lock(&elv_list_lock);
         list_del_init(&e->list);
         spin_unlock(&elv_list_lock);
+
+        /*
+         * Destroy icq_cache if it exists.  icq's are RCU managed.  Make
+         * sure all RCU operations are complete before proceeding.
+         */
+        if (e->icq_cache) {
+                rcu_barrier();
+                kmem_cache_destroy(e->icq_cache);
+                e->icq_cache = NULL;
+        }
 }
 EXPORT_SYMBOL_GPL(elv_unregister);
 
diff --git a/block/noop-iosched.c b/block/noop-iosched.c
index 06389e9ef96d..413a0b1d788c 100644
--- a/block/noop-iosched.c
+++ b/block/noop-iosched.c
@@ -94,9 +94,7 @@ static struct elevator_type elevator_noop = {
 
 static int __init noop_init(void)
 {
-        elv_register(&elevator_noop);
-
-        return 0;
+        return elv_register(&elevator_noop);
 }
 
 static void __exit noop_exit(void)