block, cfq: move icq cache management to block core
Tejun Heo [Tue, 13 Dec 2011 23:33:42 +0000 (00:33 +0100)]
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>

block/cfq-iosched.c
block/deadline-iosched.c
block/elevator.c
block/noop-iosched.c
include/linux/elevator.h

index 048fa69..06e59ab 100644 (file)
@@ -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);
index c644137..7bf12d7 100644 (file)
@@ -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)
index c5c6214..cca049f 100644 (file)
@@ -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);
 
index 06389e9..413a0b1 100644 (file)
@@ -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)
index 04958ef..d3d3e28 100644 (file)
@@ -78,10 +78,19 @@ struct elv_fs_entry {
  */
 struct elevator_type
 {
+       /* managed by elevator core */
+       struct kmem_cache *icq_cache;
+
+       /* fields provided by elevator implementation */
        struct elevator_ops ops;
+       size_t icq_size;
+       size_t icq_align;
        struct elv_fs_entry *elevator_attrs;
        char elevator_name[ELV_NAME_MAX];
        struct module *elevator_owner;
+
+       /* managed by elevator core */
+       char icq_cache_name[ELV_NAME_MAX + 5];  /* elvname + "_io_cq" */
        struct list_head list;
 };
 
@@ -127,7 +136,7 @@ extern void elv_drain_elevator(struct request_queue *);
 /*
  * io scheduler registration
  */
-extern void elv_register(struct elevator_type *);
+extern int elv_register(struct elevator_type *);
 extern void elv_unregister(struct elevator_type *);
 
 /*