blob: f23311e4b201fe60a6cf460a5c194cf43fd8f65b [file] [log] [blame]
Greg Kroah-Hartmanb2441312017-11-01 15:07:57 +01001// SPDX-License-Identifier: GPL-2.0
Jens Axboe86db1e22008-01-29 14:53:40 +01002/*
3 * Functions related to io context handling
4 */
5#include <linux/kernel.h>
6#include <linux/module.h>
7#include <linux/init.h>
8#include <linux/bio.h>
9#include <linux/blkdev.h>
Tejun Heo5a0e3ad2010-03-24 17:04:11 +090010#include <linux/slab.h>
Ingo Molnarf719ff92017-02-06 10:57:33 +010011#include <linux/sched/task.h>
Jens Axboe86db1e22008-01-29 14:53:40 +010012
13#include "blk.h"
14
15/*
16 * For io context allocations
17 */
18static struct kmem_cache *iocontext_cachep;
19
Tejun Heo6e736be2011-12-14 00:33:38 +010020/**
21 * get_io_context - increment reference count to io_context
22 * @ioc: io_context to get
23 *
24 * Increment reference count to @ioc.
25 */
26void get_io_context(struct io_context *ioc)
27{
28 BUG_ON(atomic_long_read(&ioc->refcount) <= 0);
29 atomic_long_inc(&ioc->refcount);
30}
31EXPORT_SYMBOL(get_io_context);
32
Tejun Heo7e5a8792011-12-14 00:33:42 +010033static void icq_free_icq_rcu(struct rcu_head *head)
34{
35 struct io_cq *icq = container_of(head, struct io_cq, __rcu_head);
36
37 kmem_cache_free(icq->__rcu_icq_cache, icq);
38}
39
Omar Sandoval3d492c22017-02-10 10:32:34 -080040/*
Jens Axboe7b36a712017-03-02 13:59:08 -070041 * Exit an icq. Called with ioc locked for blk-mq, and with both ioc
42 * and queue locked for legacy.
Omar Sandoval3d492c22017-02-10 10:32:34 -080043 */
Tejun Heo7e5a8792011-12-14 00:33:42 +010044static void ioc_exit_icq(struct io_cq *icq)
45{
Tejun Heo621032a2012-02-15 09:45:53 +010046 struct elevator_type *et = icq->q->elevator->type;
47
48 if (icq->flags & ICQ_EXITED)
49 return;
50
Jens Axboebd166ef2017-01-17 06:03:22 -070051 if (et->uses_mq && et->ops.mq.exit_icq)
52 et->ops.mq.exit_icq(icq);
53 else if (!et->uses_mq && et->ops.sq.elevator_exit_icq_fn)
Jens Axboec51ca6c2016-12-10 15:13:59 -070054 et->ops.sq.elevator_exit_icq_fn(icq);
Tejun Heo621032a2012-02-15 09:45:53 +010055
56 icq->flags |= ICQ_EXITED;
57}
58
Jens Axboe7b36a712017-03-02 13:59:08 -070059/*
60 * Release an icq. Called with ioc locked for blk-mq, and with both ioc
61 * and queue locked for legacy.
62 */
Tejun Heo621032a2012-02-15 09:45:53 +010063static void ioc_destroy_icq(struct io_cq *icq)
64{
Tejun Heo7e5a8792011-12-14 00:33:42 +010065 struct io_context *ioc = icq->ioc;
66 struct request_queue *q = icq->q;
67 struct elevator_type *et = q->elevator->type;
68
69 lockdep_assert_held(&ioc->lock);
Tejun Heo7e5a8792011-12-14 00:33:42 +010070
71 radix_tree_delete(&ioc->icq_tree, icq->q->id);
72 hlist_del_init(&icq->ioc_node);
73 list_del_init(&icq->q_node);
74
75 /*
76 * Both setting lookup hint to and clearing it from @icq are done
77 * under queue_lock. If it's not pointing to @icq now, it never
78 * will. Hint assignment itself can race safely.
79 */
Paul E. McKenneyec6c6762014-02-17 13:35:57 -080080 if (rcu_access_pointer(ioc->icq_hint) == icq)
Tejun Heo7e5a8792011-12-14 00:33:42 +010081 rcu_assign_pointer(ioc->icq_hint, NULL);
82
Tejun Heo621032a2012-02-15 09:45:53 +010083 ioc_exit_icq(icq);
Tejun Heo7e5a8792011-12-14 00:33:42 +010084
85 /*
86 * @icq->q might have gone away by the time RCU callback runs
87 * making it impossible to determine icq_cache. Record it in @icq.
88 */
89 icq->__rcu_icq_cache = et->icq_cache;
90 call_rcu(&icq->__rcu_head, icq_free_icq_rcu);
91}
92
Tejun Heob2efa052011-12-14 00:33:39 +010093/*
94 * Slow path for ioc release in put_io_context(). Performs double-lock
Tejun Heoc5869802011-12-14 00:33:41 +010095 * dancing to unlink all icq's and then frees ioc.
Tejun Heob2efa052011-12-14 00:33:39 +010096 */
97static void ioc_release_fn(struct work_struct *work)
98{
99 struct io_context *ioc = container_of(work, struct io_context,
100 release_work);
Tejun Heod8c66c52012-02-11 12:37:25 +0100101 unsigned long flags;
Tejun Heob2efa052011-12-14 00:33:39 +0100102
Tejun Heod8c66c52012-02-11 12:37:25 +0100103 /*
104 * Exiting icq may call into put_io_context() through elevator
105 * which will trigger lockdep warning. The ioc's are guaranteed to
106 * be different, use a different locking subclass here. Use
107 * irqsave variant as there's no spin_lock_irq_nested().
108 */
109 spin_lock_irqsave_nested(&ioc->lock, flags, 1);
Tejun Heob2efa052011-12-14 00:33:39 +0100110
Tejun Heoc5869802011-12-14 00:33:41 +0100111 while (!hlist_empty(&ioc->icq_list)) {
112 struct io_cq *icq = hlist_entry(ioc->icq_list.first,
113 struct io_cq, ioc_node);
Tejun Heo2274b022012-02-15 09:45:52 +0100114 struct request_queue *q = icq->q;
Tejun Heob2efa052011-12-14 00:33:39 +0100115
Tejun Heo2274b022012-02-15 09:45:52 +0100116 if (spin_trylock(q->queue_lock)) {
Tejun Heo621032a2012-02-15 09:45:53 +0100117 ioc_destroy_icq(icq);
Tejun Heo2274b022012-02-15 09:45:52 +0100118 spin_unlock(q->queue_lock);
119 } else {
120 spin_unlock_irqrestore(&ioc->lock, flags);
121 cpu_relax();
122 spin_lock_irqsave_nested(&ioc->lock, flags, 1);
Tejun Heob2efa052011-12-14 00:33:39 +0100123 }
Jens Axboeffc4e752008-02-19 10:02:29 +0100124 }
Tejun Heob2efa052011-12-14 00:33:39 +0100125
Tejun Heo2274b022012-02-15 09:45:52 +0100126 spin_unlock_irqrestore(&ioc->lock, flags);
Tejun Heob2efa052011-12-14 00:33:39 +0100127
128 kmem_cache_free(iocontext_cachep, ioc);
Jens Axboe86db1e22008-01-29 14:53:40 +0100129}
130
Tejun Heo42ec57a2011-12-14 00:33:37 +0100131/**
132 * put_io_context - put a reference of io_context
133 * @ioc: io_context to put
134 *
135 * Decrement reference count of @ioc and release it if the count reaches
Tejun Heo11a31222012-02-07 07:51:30 +0100136 * zero.
Jens Axboe86db1e22008-01-29 14:53:40 +0100137 */
Tejun Heo11a31222012-02-07 07:51:30 +0100138void put_io_context(struct io_context *ioc)
Jens Axboe86db1e22008-01-29 14:53:40 +0100139{
Tejun Heob2efa052011-12-14 00:33:39 +0100140 unsigned long flags;
Xiaotian Fengff8c1472012-03-14 15:34:48 +0100141 bool free_ioc = false;
Tejun Heob2efa052011-12-14 00:33:39 +0100142
Jens Axboe86db1e22008-01-29 14:53:40 +0100143 if (ioc == NULL)
Tejun Heo42ec57a2011-12-14 00:33:37 +0100144 return;
Jens Axboe86db1e22008-01-29 14:53:40 +0100145
Tejun Heo42ec57a2011-12-14 00:33:37 +0100146 BUG_ON(atomic_long_read(&ioc->refcount) <= 0);
Jens Axboe86db1e22008-01-29 14:53:40 +0100147
Tejun Heob2efa052011-12-14 00:33:39 +0100148 /*
Tejun Heo11a31222012-02-07 07:51:30 +0100149 * Releasing ioc requires reverse order double locking and we may
150 * already be holding a queue_lock. Do it asynchronously from wq.
Tejun Heob2efa052011-12-14 00:33:39 +0100151 */
Tejun Heo11a31222012-02-07 07:51:30 +0100152 if (atomic_long_dec_and_test(&ioc->refcount)) {
153 spin_lock_irqsave(&ioc->lock, flags);
154 if (!hlist_empty(&ioc->icq_list))
Viresh Kumar695588f2013-04-24 17:12:56 +0530155 queue_work(system_power_efficient_wq,
156 &ioc->release_work);
Xiaotian Fengff8c1472012-03-14 15:34:48 +0100157 else
158 free_ioc = true;
Tejun Heo11a31222012-02-07 07:51:30 +0100159 spin_unlock_irqrestore(&ioc->lock, flags);
Tejun Heob2efa052011-12-14 00:33:39 +0100160 }
Xiaotian Fengff8c1472012-03-14 15:34:48 +0100161
162 if (free_ioc)
163 kmem_cache_free(iocontext_cachep, ioc);
Jens Axboe86db1e22008-01-29 14:53:40 +0100164}
165EXPORT_SYMBOL(put_io_context);
166
Tejun Heof6e8d012012-03-05 13:15:26 -0800167/**
168 * put_io_context_active - put active reference on ioc
169 * @ioc: ioc of interest
170 *
171 * Undo get_io_context_active(). If active reference reaches zero after
172 * put, @ioc can never issue further IOs and ioscheds are notified.
173 */
174void put_io_context_active(struct io_context *ioc)
Jens Axboe86db1e22008-01-29 14:53:40 +0100175{
Omar Sandoval3d492c22017-02-10 10:32:34 -0800176 struct elevator_type *et;
Tejun Heo621032a2012-02-15 09:45:53 +0100177 unsigned long flags;
Tejun Heof6e8d012012-03-05 13:15:26 -0800178 struct io_cq *icq;
Jens Axboe86db1e22008-01-29 14:53:40 +0100179
Tejun Heof6e8d012012-03-05 13:15:26 -0800180 if (!atomic_dec_and_test(&ioc->active_ref)) {
Tejun Heo621032a2012-02-15 09:45:53 +0100181 put_io_context(ioc);
182 return;
183 }
184
185 /*
186 * Need ioc lock to walk icq_list and q lock to exit icq. Perform
187 * reverse double locking. Read comment in ioc_release_fn() for
188 * explanation on the nested locking annotation.
189 */
190retry:
191 spin_lock_irqsave_nested(&ioc->lock, flags, 1);
Sasha Levinb67bfe02013-02-27 17:06:00 -0800192 hlist_for_each_entry(icq, &ioc->icq_list, ioc_node) {
Tejun Heo621032a2012-02-15 09:45:53 +0100193 if (icq->flags & ICQ_EXITED)
194 continue;
Omar Sandoval3d492c22017-02-10 10:32:34 -0800195
196 et = icq->q->elevator->type;
197 if (et->uses_mq) {
Tejun Heo621032a2012-02-15 09:45:53 +0100198 ioc_exit_icq(icq);
Tejun Heo621032a2012-02-15 09:45:53 +0100199 } else {
Omar Sandoval3d492c22017-02-10 10:32:34 -0800200 if (spin_trylock(icq->q->queue_lock)) {
201 ioc_exit_icq(icq);
202 spin_unlock(icq->q->queue_lock);
203 } else {
204 spin_unlock_irqrestore(&ioc->lock, flags);
205 cpu_relax();
206 goto retry;
207 }
Tejun Heo621032a2012-02-15 09:45:53 +0100208 }
209 }
210 spin_unlock_irqrestore(&ioc->lock, flags);
211
Tejun Heo11a31222012-02-07 07:51:30 +0100212 put_io_context(ioc);
Jens Axboe86db1e22008-01-29 14:53:40 +0100213}
214
Tejun Heof6e8d012012-03-05 13:15:26 -0800215/* Called by the exiting task */
216void exit_io_context(struct task_struct *task)
217{
218 struct io_context *ioc;
219
220 task_lock(task);
221 ioc = task->io_context;
222 task->io_context = NULL;
223 task_unlock(task);
224
225 atomic_dec(&ioc->nr_tasks);
226 put_io_context_active(ioc);
227}
228
Jens Axboe7b36a712017-03-02 13:59:08 -0700229static void __ioc_clear_queue(struct list_head *icq_list)
230{
231 unsigned long flags;
232
233 while (!list_empty(icq_list)) {
234 struct io_cq *icq = list_entry(icq_list->next,
235 struct io_cq, q_node);
236 struct io_context *ioc = icq->ioc;
237
238 spin_lock_irqsave(&ioc->lock, flags);
239 ioc_destroy_icq(icq);
240 spin_unlock_irqrestore(&ioc->lock, flags);
241 }
242}
243
Tejun Heo7e5a8792011-12-14 00:33:42 +0100244/**
245 * ioc_clear_queue - break any ioc association with the specified queue
246 * @q: request_queue being cleared
247 *
Jens Axboe7b36a712017-03-02 13:59:08 -0700248 * Walk @q->icq_list and exit all io_cq's.
Tejun Heo7e5a8792011-12-14 00:33:42 +0100249 */
250void ioc_clear_queue(struct request_queue *q)
251{
Jens Axboe7b36a712017-03-02 13:59:08 -0700252 LIST_HEAD(icq_list);
Tejun Heo7e5a8792011-12-14 00:33:42 +0100253
Jens Axboe7b36a712017-03-02 13:59:08 -0700254 spin_lock_irq(q->queue_lock);
255 list_splice_init(&q->icq_list, &icq_list);
Tejun Heo7e5a8792011-12-14 00:33:42 +0100256
Jens Axboe7b36a712017-03-02 13:59:08 -0700257 if (q->mq_ops) {
258 spin_unlock_irq(q->queue_lock);
259 __ioc_clear_queue(&icq_list);
260 } else {
261 __ioc_clear_queue(&icq_list);
262 spin_unlock_irq(q->queue_lock);
Tejun Heo7e5a8792011-12-14 00:33:42 +0100263 }
264}
265
Tejun Heo24acfc32012-03-05 13:15:24 -0800266int create_task_io_context(struct task_struct *task, gfp_t gfp_flags, int node)
Jens Axboe86db1e22008-01-29 14:53:40 +0100267{
Paul Bolledf415652011-06-06 05:11:34 +0200268 struct io_context *ioc;
Eric Dumazet3c9c7082012-05-31 13:39:05 +0200269 int ret;
Jens Axboe86db1e22008-01-29 14:53:40 +0100270
Tejun Heo42ec57a2011-12-14 00:33:37 +0100271 ioc = kmem_cache_alloc_node(iocontext_cachep, gfp_flags | __GFP_ZERO,
272 node);
273 if (unlikely(!ioc))
Tejun Heo24acfc32012-03-05 13:15:24 -0800274 return -ENOMEM;
Tejun Heo42ec57a2011-12-14 00:33:37 +0100275
276 /* initialize */
277 atomic_long_set(&ioc->refcount, 1);
Olof Johansson4638a832012-08-01 12:17:27 +0200278 atomic_set(&ioc->nr_tasks, 1);
Tejun Heof6e8d012012-03-05 13:15:26 -0800279 atomic_set(&ioc->active_ref, 1);
Tejun Heo42ec57a2011-12-14 00:33:37 +0100280 spin_lock_init(&ioc->lock);
Tejun Heoc5869802011-12-14 00:33:41 +0100281 INIT_RADIX_TREE(&ioc->icq_tree, GFP_ATOMIC | __GFP_HIGH);
282 INIT_HLIST_HEAD(&ioc->icq_list);
Tejun Heob2efa052011-12-14 00:33:39 +0100283 INIT_WORK(&ioc->release_work, ioc_release_fn);
Jens Axboe86db1e22008-01-29 14:53:40 +0100284
Tejun Heofd638362011-12-25 14:29:14 +0100285 /*
286 * Try to install. ioc shouldn't be installed if someone else
287 * already did or @task, which isn't %current, is exiting. Note
288 * that we need to allow ioc creation on exiting %current as exit
289 * path may issue IOs from e.g. exit_files(). The exit path is
290 * responsible for not issuing IO after exit_io_context().
291 */
Tejun Heo6e736be2011-12-14 00:33:38 +0100292 task_lock(task);
Tejun Heofd638362011-12-25 14:29:14 +0100293 if (!task->io_context &&
294 (task == current || !(task->flags & PF_EXITING)))
Tejun Heo6e736be2011-12-14 00:33:38 +0100295 task->io_context = ioc;
Tejun Heof2dbd762011-12-14 00:33:40 +0100296 else
Tejun Heo6e736be2011-12-14 00:33:38 +0100297 kmem_cache_free(iocontext_cachep, ioc);
Eric Dumazet3c9c7082012-05-31 13:39:05 +0200298
299 ret = task->io_context ? 0 : -EBUSY;
300
Tejun Heo6e736be2011-12-14 00:33:38 +0100301 task_unlock(task);
Tejun Heo24acfc32012-03-05 13:15:24 -0800302
Eric Dumazet3c9c7082012-05-31 13:39:05 +0200303 return ret;
Jens Axboe86db1e22008-01-29 14:53:40 +0100304}
Jens Axboe86db1e22008-01-29 14:53:40 +0100305
Tejun Heo6e736be2011-12-14 00:33:38 +0100306/**
307 * get_task_io_context - get io_context of a task
308 * @task: task of interest
309 * @gfp_flags: allocation flags, used if allocation is necessary
310 * @node: allocation node, used if allocation is necessary
Jens Axboe86db1e22008-01-29 14:53:40 +0100311 *
Tejun Heo6e736be2011-12-14 00:33:38 +0100312 * Return io_context of @task. If it doesn't exist, it is created with
313 * @gfp_flags and @node. The returned io_context has its reference count
314 * incremented.
315 *
316 * This function always goes through task_lock() and it's better to use
Tejun Heof2dbd762011-12-14 00:33:40 +0100317 * %current->io_context + get_io_context() for %current.
Jens Axboe86db1e22008-01-29 14:53:40 +0100318 */
Tejun Heo6e736be2011-12-14 00:33:38 +0100319struct io_context *get_task_io_context(struct task_struct *task,
320 gfp_t gfp_flags, int node)
Jens Axboe86db1e22008-01-29 14:53:40 +0100321{
Tejun Heo6e736be2011-12-14 00:33:38 +0100322 struct io_context *ioc;
Jens Axboe86db1e22008-01-29 14:53:40 +0100323
Mel Gormand0164ad2015-11-06 16:28:21 -0800324 might_sleep_if(gfpflags_allow_blocking(gfp_flags));
Jens Axboe86db1e22008-01-29 14:53:40 +0100325
Tejun Heof2dbd762011-12-14 00:33:40 +0100326 do {
327 task_lock(task);
328 ioc = task->io_context;
329 if (likely(ioc)) {
330 get_io_context(ioc);
331 task_unlock(task);
332 return ioc;
333 }
Tejun Heo6e736be2011-12-14 00:33:38 +0100334 task_unlock(task);
Tejun Heo24acfc32012-03-05 13:15:24 -0800335 } while (!create_task_io_context(task, gfp_flags, node));
Tejun Heo6e736be2011-12-14 00:33:38 +0100336
Tejun Heof2dbd762011-12-14 00:33:40 +0100337 return NULL;
Jens Axboe86db1e22008-01-29 14:53:40 +0100338}
Tejun Heo6e736be2011-12-14 00:33:38 +0100339EXPORT_SYMBOL(get_task_io_context);
Jens Axboe86db1e22008-01-29 14:53:40 +0100340
Tejun Heo47fdd4c2011-12-14 00:33:42 +0100341/**
342 * ioc_lookup_icq - lookup io_cq from ioc
343 * @ioc: the associated io_context
344 * @q: the associated request_queue
345 *
346 * Look up io_cq associated with @ioc - @q pair from @ioc. Must be called
347 * with @q->queue_lock held.
348 */
349struct io_cq *ioc_lookup_icq(struct io_context *ioc, struct request_queue *q)
350{
351 struct io_cq *icq;
352
353 lockdep_assert_held(q->queue_lock);
354
355 /*
356 * icq's are indexed from @ioc using radix tree and hint pointer,
357 * both of which are protected with RCU. All removals are done
358 * holding both q and ioc locks, and we're holding q lock - if we
359 * find a icq which points to us, it's guaranteed to be valid.
360 */
361 rcu_read_lock();
362 icq = rcu_dereference(ioc->icq_hint);
363 if (icq && icq->q == q)
364 goto out;
365
366 icq = radix_tree_lookup(&ioc->icq_tree, q->id);
367 if (icq && icq->q == q)
368 rcu_assign_pointer(ioc->icq_hint, icq); /* allowed to race */
369 else
370 icq = NULL;
371out:
372 rcu_read_unlock();
373 return icq;
374}
375EXPORT_SYMBOL(ioc_lookup_icq);
376
Tejun Heof1f8cc92011-12-14 00:33:42 +0100377/**
378 * ioc_create_icq - create and link io_cq
Tejun Heo24acfc32012-03-05 13:15:24 -0800379 * @ioc: io_context of interest
Tejun Heof1f8cc92011-12-14 00:33:42 +0100380 * @q: request_queue of interest
381 * @gfp_mask: allocation mask
382 *
Tejun Heo24acfc32012-03-05 13:15:24 -0800383 * Make sure io_cq linking @ioc and @q exists. If icq doesn't exist, they
384 * will be created using @gfp_mask.
Tejun Heof1f8cc92011-12-14 00:33:42 +0100385 *
386 * The caller is responsible for ensuring @ioc won't go away and @q is
387 * alive and will stay alive until this function returns.
388 */
Tejun Heo24acfc32012-03-05 13:15:24 -0800389struct io_cq *ioc_create_icq(struct io_context *ioc, struct request_queue *q,
390 gfp_t gfp_mask)
Tejun Heof1f8cc92011-12-14 00:33:42 +0100391{
392 struct elevator_type *et = q->elevator->type;
Tejun Heof1f8cc92011-12-14 00:33:42 +0100393 struct io_cq *icq;
394
395 /* allocate stuff */
Tejun Heof1f8cc92011-12-14 00:33:42 +0100396 icq = kmem_cache_alloc_node(et->icq_cache, gfp_mask | __GFP_ZERO,
397 q->node);
398 if (!icq)
399 return NULL;
400
Jan Kara5e4c0d972013-09-11 14:26:05 -0700401 if (radix_tree_maybe_preload(gfp_mask) < 0) {
Tejun Heof1f8cc92011-12-14 00:33:42 +0100402 kmem_cache_free(et->icq_cache, icq);
403 return NULL;
404 }
405
406 icq->ioc = ioc;
407 icq->q = q;
408 INIT_LIST_HEAD(&icq->q_node);
409 INIT_HLIST_NODE(&icq->ioc_node);
410
411 /* lock both q and ioc and try to link @icq */
412 spin_lock_irq(q->queue_lock);
413 spin_lock(&ioc->lock);
414
415 if (likely(!radix_tree_insert(&ioc->icq_tree, q->id, icq))) {
416 hlist_add_head(&icq->ioc_node, &ioc->icq_list);
417 list_add(&icq->q_node, &q->icq_list);
Jens Axboebd166ef2017-01-17 06:03:22 -0700418 if (et->uses_mq && et->ops.mq.init_icq)
419 et->ops.mq.init_icq(icq);
420 else if (!et->uses_mq && et->ops.sq.elevator_init_icq_fn)
Jens Axboec51ca6c2016-12-10 15:13:59 -0700421 et->ops.sq.elevator_init_icq_fn(icq);
Tejun Heof1f8cc92011-12-14 00:33:42 +0100422 } else {
423 kmem_cache_free(et->icq_cache, icq);
424 icq = ioc_lookup_icq(ioc, q);
425 if (!icq)
426 printk(KERN_ERR "cfq: icq link failed!\n");
427 }
428
429 spin_unlock(&ioc->lock);
430 spin_unlock_irq(q->queue_lock);
431 radix_tree_preload_end();
432 return icq;
433}
434
Adrian Bunk13341592008-02-18 13:45:53 +0100435static int __init blk_ioc_init(void)
Jens Axboe86db1e22008-01-29 14:53:40 +0100436{
437 iocontext_cachep = kmem_cache_create("blkdev_ioc",
438 sizeof(struct io_context), 0, SLAB_PANIC, NULL);
439 return 0;
440}
441subsys_initcall(blk_ioc_init);