Loading...
1/*
2 * Functions related to io context handling
3 */
4#include <linux/kernel.h>
5#include <linux/module.h>
6#include <linux/init.h>
7#include <linux/bio.h>
8#include <linux/blkdev.h>
9#include <linux/slab.h>
10
11#include "blk.h"
12
13/*
14 * For io context allocations
15 */
16static struct kmem_cache *iocontext_cachep;
17
18/**
19 * get_io_context - increment reference count to io_context
20 * @ioc: io_context to get
21 *
22 * Increment reference count to @ioc.
23 */
24void get_io_context(struct io_context *ioc)
25{
26 BUG_ON(atomic_long_read(&ioc->refcount) <= 0);
27 atomic_long_inc(&ioc->refcount);
28}
29EXPORT_SYMBOL(get_io_context);
30
31static void icq_free_icq_rcu(struct rcu_head *head)
32{
33 struct io_cq *icq = container_of(head, struct io_cq, __rcu_head);
34
35 kmem_cache_free(icq->__rcu_icq_cache, icq);
36}
37
38/* Exit an icq. Called with both ioc and q locked. */
39static void ioc_exit_icq(struct io_cq *icq)
40{
41 struct elevator_type *et = icq->q->elevator->type;
42
43 if (icq->flags & ICQ_EXITED)
44 return;
45
46 if (et->ops.elevator_exit_icq_fn)
47 et->ops.elevator_exit_icq_fn(icq);
48
49 icq->flags |= ICQ_EXITED;
50}
51
52/* Release an icq. Called with both ioc and q locked. */
53static void ioc_destroy_icq(struct io_cq *icq)
54{
55 struct io_context *ioc = icq->ioc;
56 struct request_queue *q = icq->q;
57 struct elevator_type *et = q->elevator->type;
58
59 lockdep_assert_held(&ioc->lock);
60 lockdep_assert_held(q->queue_lock);
61
62 radix_tree_delete(&ioc->icq_tree, icq->q->id);
63 hlist_del_init(&icq->ioc_node);
64 list_del_init(&icq->q_node);
65
66 /*
67 * Both setting lookup hint to and clearing it from @icq are done
68 * under queue_lock. If it's not pointing to @icq now, it never
69 * will. Hint assignment itself can race safely.
70 */
71 if (rcu_access_pointer(ioc->icq_hint) == icq)
72 rcu_assign_pointer(ioc->icq_hint, NULL);
73
74 ioc_exit_icq(icq);
75
76 /*
77 * @icq->q might have gone away by the time RCU callback runs
78 * making it impossible to determine icq_cache. Record it in @icq.
79 */
80 icq->__rcu_icq_cache = et->icq_cache;
81 call_rcu(&icq->__rcu_head, icq_free_icq_rcu);
82}
83
84/*
85 * Slow path for ioc release in put_io_context(). Performs double-lock
86 * dancing to unlink all icq's and then frees ioc.
87 */
88static void ioc_release_fn(struct work_struct *work)
89{
90 struct io_context *ioc = container_of(work, struct io_context,
91 release_work);
92 unsigned long flags;
93
94 /*
95 * Exiting icq may call into put_io_context() through elevator
96 * which will trigger lockdep warning. The ioc's are guaranteed to
97 * be different, use a different locking subclass here. Use
98 * irqsave variant as there's no spin_lock_irq_nested().
99 */
100 spin_lock_irqsave_nested(&ioc->lock, flags, 1);
101
102 while (!hlist_empty(&ioc->icq_list)) {
103 struct io_cq *icq = hlist_entry(ioc->icq_list.first,
104 struct io_cq, ioc_node);
105 struct request_queue *q = icq->q;
106
107 if (spin_trylock(q->queue_lock)) {
108 ioc_destroy_icq(icq);
109 spin_unlock(q->queue_lock);
110 } else {
111 spin_unlock_irqrestore(&ioc->lock, flags);
112 cpu_relax();
113 spin_lock_irqsave_nested(&ioc->lock, flags, 1);
114 }
115 }
116
117 spin_unlock_irqrestore(&ioc->lock, flags);
118
119 kmem_cache_free(iocontext_cachep, ioc);
120}
121
122/**
123 * put_io_context - put a reference of io_context
124 * @ioc: io_context to put
125 *
126 * Decrement reference count of @ioc and release it if the count reaches
127 * zero.
128 */
129void put_io_context(struct io_context *ioc)
130{
131 unsigned long flags;
132 bool free_ioc = false;
133
134 if (ioc == NULL)
135 return;
136
137 BUG_ON(atomic_long_read(&ioc->refcount) <= 0);
138
139 /*
140 * Releasing ioc requires reverse order double locking and we may
141 * already be holding a queue_lock. Do it asynchronously from wq.
142 */
143 if (atomic_long_dec_and_test(&ioc->refcount)) {
144 spin_lock_irqsave(&ioc->lock, flags);
145 if (!hlist_empty(&ioc->icq_list))
146 queue_work(system_power_efficient_wq,
147 &ioc->release_work);
148 else
149 free_ioc = true;
150 spin_unlock_irqrestore(&ioc->lock, flags);
151 }
152
153 if (free_ioc)
154 kmem_cache_free(iocontext_cachep, ioc);
155}
156EXPORT_SYMBOL(put_io_context);
157
158/**
159 * put_io_context_active - put active reference on ioc
160 * @ioc: ioc of interest
161 *
162 * Undo get_io_context_active(). If active reference reaches zero after
163 * put, @ioc can never issue further IOs and ioscheds are notified.
164 */
165void put_io_context_active(struct io_context *ioc)
166{
167 unsigned long flags;
168 struct io_cq *icq;
169
170 if (!atomic_dec_and_test(&ioc->active_ref)) {
171 put_io_context(ioc);
172 return;
173 }
174
175 /*
176 * Need ioc lock to walk icq_list and q lock to exit icq. Perform
177 * reverse double locking. Read comment in ioc_release_fn() for
178 * explanation on the nested locking annotation.
179 */
180retry:
181 spin_lock_irqsave_nested(&ioc->lock, flags, 1);
182 hlist_for_each_entry(icq, &ioc->icq_list, ioc_node) {
183 if (icq->flags & ICQ_EXITED)
184 continue;
185 if (spin_trylock(icq->q->queue_lock)) {
186 ioc_exit_icq(icq);
187 spin_unlock(icq->q->queue_lock);
188 } else {
189 spin_unlock_irqrestore(&ioc->lock, flags);
190 cpu_relax();
191 goto retry;
192 }
193 }
194 spin_unlock_irqrestore(&ioc->lock, flags);
195
196 put_io_context(ioc);
197}
198
199/* Called by the exiting task */
200void exit_io_context(struct task_struct *task)
201{
202 struct io_context *ioc;
203
204 task_lock(task);
205 ioc = task->io_context;
206 task->io_context = NULL;
207 task_unlock(task);
208
209 atomic_dec(&ioc->nr_tasks);
210 put_io_context_active(ioc);
211}
212
213/**
214 * ioc_clear_queue - break any ioc association with the specified queue
215 * @q: request_queue being cleared
216 *
217 * Walk @q->icq_list and exit all io_cq's. Must be called with @q locked.
218 */
219void ioc_clear_queue(struct request_queue *q)
220{
221 lockdep_assert_held(q->queue_lock);
222
223 while (!list_empty(&q->icq_list)) {
224 struct io_cq *icq = list_entry(q->icq_list.next,
225 struct io_cq, q_node);
226 struct io_context *ioc = icq->ioc;
227
228 spin_lock(&ioc->lock);
229 ioc_destroy_icq(icq);
230 spin_unlock(&ioc->lock);
231 }
232}
233
234int create_task_io_context(struct task_struct *task, gfp_t gfp_flags, int node)
235{
236 struct io_context *ioc;
237 int ret;
238
239 ioc = kmem_cache_alloc_node(iocontext_cachep, gfp_flags | __GFP_ZERO,
240 node);
241 if (unlikely(!ioc))
242 return -ENOMEM;
243
244 /* initialize */
245 atomic_long_set(&ioc->refcount, 1);
246 atomic_set(&ioc->nr_tasks, 1);
247 atomic_set(&ioc->active_ref, 1);
248 spin_lock_init(&ioc->lock);
249 INIT_RADIX_TREE(&ioc->icq_tree, GFP_ATOMIC | __GFP_HIGH);
250 INIT_HLIST_HEAD(&ioc->icq_list);
251 INIT_WORK(&ioc->release_work, ioc_release_fn);
252
253 /*
254 * Try to install. ioc shouldn't be installed if someone else
255 * already did or @task, which isn't %current, is exiting. Note
256 * that we need to allow ioc creation on exiting %current as exit
257 * path may issue IOs from e.g. exit_files(). The exit path is
258 * responsible for not issuing IO after exit_io_context().
259 */
260 task_lock(task);
261 if (!task->io_context &&
262 (task == current || !(task->flags & PF_EXITING)))
263 task->io_context = ioc;
264 else
265 kmem_cache_free(iocontext_cachep, ioc);
266
267 ret = task->io_context ? 0 : -EBUSY;
268
269 task_unlock(task);
270
271 return ret;
272}
273
274/**
275 * get_task_io_context - get io_context of a task
276 * @task: task of interest
277 * @gfp_flags: allocation flags, used if allocation is necessary
278 * @node: allocation node, used if allocation is necessary
279 *
280 * Return io_context of @task. If it doesn't exist, it is created with
281 * @gfp_flags and @node. The returned io_context has its reference count
282 * incremented.
283 *
284 * This function always goes through task_lock() and it's better to use
285 * %current->io_context + get_io_context() for %current.
286 */
287struct io_context *get_task_io_context(struct task_struct *task,
288 gfp_t gfp_flags, int node)
289{
290 struct io_context *ioc;
291
292 might_sleep_if(gfp_flags & __GFP_WAIT);
293
294 do {
295 task_lock(task);
296 ioc = task->io_context;
297 if (likely(ioc)) {
298 get_io_context(ioc);
299 task_unlock(task);
300 return ioc;
301 }
302 task_unlock(task);
303 } while (!create_task_io_context(task, gfp_flags, node));
304
305 return NULL;
306}
307EXPORT_SYMBOL(get_task_io_context);
308
309/**
310 * ioc_lookup_icq - lookup io_cq from ioc
311 * @ioc: the associated io_context
312 * @q: the associated request_queue
313 *
314 * Look up io_cq associated with @ioc - @q pair from @ioc. Must be called
315 * with @q->queue_lock held.
316 */
317struct io_cq *ioc_lookup_icq(struct io_context *ioc, struct request_queue *q)
318{
319 struct io_cq *icq;
320
321 lockdep_assert_held(q->queue_lock);
322
323 /*
324 * icq's are indexed from @ioc using radix tree and hint pointer,
325 * both of which are protected with RCU. All removals are done
326 * holding both q and ioc locks, and we're holding q lock - if we
327 * find a icq which points to us, it's guaranteed to be valid.
328 */
329 rcu_read_lock();
330 icq = rcu_dereference(ioc->icq_hint);
331 if (icq && icq->q == q)
332 goto out;
333
334 icq = radix_tree_lookup(&ioc->icq_tree, q->id);
335 if (icq && icq->q == q)
336 rcu_assign_pointer(ioc->icq_hint, icq); /* allowed to race */
337 else
338 icq = NULL;
339out:
340 rcu_read_unlock();
341 return icq;
342}
343EXPORT_SYMBOL(ioc_lookup_icq);
344
345/**
346 * ioc_create_icq - create and link io_cq
347 * @ioc: io_context of interest
348 * @q: request_queue of interest
349 * @gfp_mask: allocation mask
350 *
351 * Make sure io_cq linking @ioc and @q exists. If icq doesn't exist, they
352 * will be created using @gfp_mask.
353 *
354 * The caller is responsible for ensuring @ioc won't go away and @q is
355 * alive and will stay alive until this function returns.
356 */
357struct io_cq *ioc_create_icq(struct io_context *ioc, struct request_queue *q,
358 gfp_t gfp_mask)
359{
360 struct elevator_type *et = q->elevator->type;
361 struct io_cq *icq;
362
363 /* allocate stuff */
364 icq = kmem_cache_alloc_node(et->icq_cache, gfp_mask | __GFP_ZERO,
365 q->node);
366 if (!icq)
367 return NULL;
368
369 if (radix_tree_maybe_preload(gfp_mask) < 0) {
370 kmem_cache_free(et->icq_cache, icq);
371 return NULL;
372 }
373
374 icq->ioc = ioc;
375 icq->q = q;
376 INIT_LIST_HEAD(&icq->q_node);
377 INIT_HLIST_NODE(&icq->ioc_node);
378
379 /* lock both q and ioc and try to link @icq */
380 spin_lock_irq(q->queue_lock);
381 spin_lock(&ioc->lock);
382
383 if (likely(!radix_tree_insert(&ioc->icq_tree, q->id, icq))) {
384 hlist_add_head(&icq->ioc_node, &ioc->icq_list);
385 list_add(&icq->q_node, &q->icq_list);
386 if (et->ops.elevator_init_icq_fn)
387 et->ops.elevator_init_icq_fn(icq);
388 } else {
389 kmem_cache_free(et->icq_cache, icq);
390 icq = ioc_lookup_icq(ioc, q);
391 if (!icq)
392 printk(KERN_ERR "cfq: icq link failed!\n");
393 }
394
395 spin_unlock(&ioc->lock);
396 spin_unlock_irq(q->queue_lock);
397 radix_tree_preload_end();
398 return icq;
399}
400
401static int __init blk_ioc_init(void)
402{
403 iocontext_cachep = kmem_cache_create("blkdev_ioc",
404 sizeof(struct io_context), 0, SLAB_PANIC, NULL);
405 return 0;
406}
407subsys_initcall(blk_ioc_init);
1// SPDX-License-Identifier: GPL-2.0
2/*
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>
10#include <linux/slab.h>
11#include <linux/sched/task.h>
12
13#include "blk.h"
14
15/*
16 * For io context allocations
17 */
18static struct kmem_cache *iocontext_cachep;
19
20/**
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
33static 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
40/*
41 * Exit an icq. Called with ioc locked for blk-mq, and with both ioc
42 * and queue locked for legacy.
43 */
44static void ioc_exit_icq(struct io_cq *icq)
45{
46 struct elevator_type *et = icq->q->elevator->type;
47
48 if (icq->flags & ICQ_EXITED)
49 return;
50
51 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)
54 et->ops.sq.elevator_exit_icq_fn(icq);
55
56 icq->flags |= ICQ_EXITED;
57}
58
59/*
60 * Release an icq. Called with ioc locked for blk-mq, and with both ioc
61 * and queue locked for legacy.
62 */
63static void ioc_destroy_icq(struct io_cq *icq)
64{
65 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);
70
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 */
80 if (rcu_access_pointer(ioc->icq_hint) == icq)
81 rcu_assign_pointer(ioc->icq_hint, NULL);
82
83 ioc_exit_icq(icq);
84
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
93/*
94 * Slow path for ioc release in put_io_context(). Performs double-lock
95 * dancing to unlink all icq's and then frees ioc.
96 */
97static void ioc_release_fn(struct work_struct *work)
98{
99 struct io_context *ioc = container_of(work, struct io_context,
100 release_work);
101 unsigned long flags;
102
103 /*
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);
110
111 while (!hlist_empty(&ioc->icq_list)) {
112 struct io_cq *icq = hlist_entry(ioc->icq_list.first,
113 struct io_cq, ioc_node);
114 struct request_queue *q = icq->q;
115
116 if (spin_trylock(q->queue_lock)) {
117 ioc_destroy_icq(icq);
118 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);
123 }
124 }
125
126 spin_unlock_irqrestore(&ioc->lock, flags);
127
128 kmem_cache_free(iocontext_cachep, ioc);
129}
130
131/**
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
136 * zero.
137 */
138void put_io_context(struct io_context *ioc)
139{
140 unsigned long flags;
141 bool free_ioc = false;
142
143 if (ioc == NULL)
144 return;
145
146 BUG_ON(atomic_long_read(&ioc->refcount) <= 0);
147
148 /*
149 * Releasing ioc requires reverse order double locking and we may
150 * already be holding a queue_lock. Do it asynchronously from wq.
151 */
152 if (atomic_long_dec_and_test(&ioc->refcount)) {
153 spin_lock_irqsave(&ioc->lock, flags);
154 if (!hlist_empty(&ioc->icq_list))
155 queue_work(system_power_efficient_wq,
156 &ioc->release_work);
157 else
158 free_ioc = true;
159 spin_unlock_irqrestore(&ioc->lock, flags);
160 }
161
162 if (free_ioc)
163 kmem_cache_free(iocontext_cachep, ioc);
164}
165EXPORT_SYMBOL(put_io_context);
166
167/**
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)
175{
176 struct elevator_type *et;
177 unsigned long flags;
178 struct io_cq *icq;
179
180 if (!atomic_dec_and_test(&ioc->active_ref)) {
181 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);
192 hlist_for_each_entry(icq, &ioc->icq_list, ioc_node) {
193 if (icq->flags & ICQ_EXITED)
194 continue;
195
196 et = icq->q->elevator->type;
197 if (et->uses_mq) {
198 ioc_exit_icq(icq);
199 } else {
200 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 }
208 }
209 }
210 spin_unlock_irqrestore(&ioc->lock, flags);
211
212 put_io_context(ioc);
213}
214
215/* 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
229static 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
244/**
245 * ioc_clear_queue - break any ioc association with the specified queue
246 * @q: request_queue being cleared
247 *
248 * Walk @q->icq_list and exit all io_cq's.
249 */
250void ioc_clear_queue(struct request_queue *q)
251{
252 LIST_HEAD(icq_list);
253
254 spin_lock_irq(q->queue_lock);
255 list_splice_init(&q->icq_list, &icq_list);
256
257 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);
263 }
264}
265
266int create_task_io_context(struct task_struct *task, gfp_t gfp_flags, int node)
267{
268 struct io_context *ioc;
269 int ret;
270
271 ioc = kmem_cache_alloc_node(iocontext_cachep, gfp_flags | __GFP_ZERO,
272 node);
273 if (unlikely(!ioc))
274 return -ENOMEM;
275
276 /* initialize */
277 atomic_long_set(&ioc->refcount, 1);
278 atomic_set(&ioc->nr_tasks, 1);
279 atomic_set(&ioc->active_ref, 1);
280 spin_lock_init(&ioc->lock);
281 INIT_RADIX_TREE(&ioc->icq_tree, GFP_ATOMIC | __GFP_HIGH);
282 INIT_HLIST_HEAD(&ioc->icq_list);
283 INIT_WORK(&ioc->release_work, ioc_release_fn);
284
285 /*
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 */
292 task_lock(task);
293 if (!task->io_context &&
294 (task == current || !(task->flags & PF_EXITING)))
295 task->io_context = ioc;
296 else
297 kmem_cache_free(iocontext_cachep, ioc);
298
299 ret = task->io_context ? 0 : -EBUSY;
300
301 task_unlock(task);
302
303 return ret;
304}
305
306/**
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
311 *
312 * 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
317 * %current->io_context + get_io_context() for %current.
318 */
319struct io_context *get_task_io_context(struct task_struct *task,
320 gfp_t gfp_flags, int node)
321{
322 struct io_context *ioc;
323
324 might_sleep_if(gfpflags_allow_blocking(gfp_flags));
325
326 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 }
334 task_unlock(task);
335 } while (!create_task_io_context(task, gfp_flags, node));
336
337 return NULL;
338}
339EXPORT_SYMBOL(get_task_io_context);
340
341/**
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
377/**
378 * ioc_create_icq - create and link io_cq
379 * @ioc: io_context of interest
380 * @q: request_queue of interest
381 * @gfp_mask: allocation mask
382 *
383 * Make sure io_cq linking @ioc and @q exists. If icq doesn't exist, they
384 * will be created using @gfp_mask.
385 *
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 */
389struct io_cq *ioc_create_icq(struct io_context *ioc, struct request_queue *q,
390 gfp_t gfp_mask)
391{
392 struct elevator_type *et = q->elevator->type;
393 struct io_cq *icq;
394
395 /* allocate stuff */
396 icq = kmem_cache_alloc_node(et->icq_cache, gfp_mask | __GFP_ZERO,
397 q->node);
398 if (!icq)
399 return NULL;
400
401 if (radix_tree_maybe_preload(gfp_mask) < 0) {
402 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);
418 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)
421 et->ops.sq.elevator_init_icq_fn(icq);
422 } 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
435static int __init blk_ioc_init(void)
436{
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);