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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/bootmem.h> /* for max_pfn/max_low_pfn */
10#include <linux/slab.h>
11
12#include "blk.h"
13
14/*
15 * For io context allocations
16 */
17static struct kmem_cache *iocontext_cachep;
18
19/**
20 * get_io_context - increment reference count to io_context
21 * @ioc: io_context to get
22 *
23 * Increment reference count to @ioc.
24 */
25void get_io_context(struct io_context *ioc)
26{
27 BUG_ON(atomic_long_read(&ioc->refcount) <= 0);
28 atomic_long_inc(&ioc->refcount);
29}
30EXPORT_SYMBOL(get_io_context);
31
32static void icq_free_icq_rcu(struct rcu_head *head)
33{
34 struct io_cq *icq = container_of(head, struct io_cq, __rcu_head);
35
36 kmem_cache_free(icq->__rcu_icq_cache, icq);
37}
38
39/* Exit an icq. Called with both ioc and q locked. */
40static void ioc_exit_icq(struct io_cq *icq)
41{
42 struct elevator_type *et = icq->q->elevator->type;
43
44 if (icq->flags & ICQ_EXITED)
45 return;
46
47 if (et->ops.elevator_exit_icq_fn)
48 et->ops.elevator_exit_icq_fn(icq);
49
50 icq->flags |= ICQ_EXITED;
51}
52
53/* Release an icq. Called with both ioc and q locked. */
54static void ioc_destroy_icq(struct io_cq *icq)
55{
56 struct io_context *ioc = icq->ioc;
57 struct request_queue *q = icq->q;
58 struct elevator_type *et = q->elevator->type;
59
60 lockdep_assert_held(&ioc->lock);
61 lockdep_assert_held(q->queue_lock);
62
63 radix_tree_delete(&ioc->icq_tree, icq->q->id);
64 hlist_del_init(&icq->ioc_node);
65 list_del_init(&icq->q_node);
66
67 /*
68 * Both setting lookup hint to and clearing it from @icq are done
69 * under queue_lock. If it's not pointing to @icq now, it never
70 * will. Hint assignment itself can race safely.
71 */
72 if (rcu_dereference_raw(ioc->icq_hint) == icq)
73 rcu_assign_pointer(ioc->icq_hint, NULL);
74
75 ioc_exit_icq(icq);
76
77 /*
78 * @icq->q might have gone away by the time RCU callback runs
79 * making it impossible to determine icq_cache. Record it in @icq.
80 */
81 icq->__rcu_icq_cache = et->icq_cache;
82 call_rcu(&icq->__rcu_head, icq_free_icq_rcu);
83}
84
85/*
86 * Slow path for ioc release in put_io_context(). Performs double-lock
87 * dancing to unlink all icq's and then frees ioc.
88 */
89static void ioc_release_fn(struct work_struct *work)
90{
91 struct io_context *ioc = container_of(work, struct io_context,
92 release_work);
93 unsigned long flags;
94
95 /*
96 * Exiting icq may call into put_io_context() through elevator
97 * which will trigger lockdep warning. The ioc's are guaranteed to
98 * be different, use a different locking subclass here. Use
99 * irqsave variant as there's no spin_lock_irq_nested().
100 */
101 spin_lock_irqsave_nested(&ioc->lock, flags, 1);
102
103 while (!hlist_empty(&ioc->icq_list)) {
104 struct io_cq *icq = hlist_entry(ioc->icq_list.first,
105 struct io_cq, ioc_node);
106 struct request_queue *q = icq->q;
107
108 if (spin_trylock(q->queue_lock)) {
109 ioc_destroy_icq(icq);
110 spin_unlock(q->queue_lock);
111 } else {
112 spin_unlock_irqrestore(&ioc->lock, flags);
113 cpu_relax();
114 spin_lock_irqsave_nested(&ioc->lock, flags, 1);
115 }
116 }
117
118 spin_unlock_irqrestore(&ioc->lock, flags);
119
120 kmem_cache_free(iocontext_cachep, ioc);
121}
122
123/**
124 * put_io_context - put a reference of io_context
125 * @ioc: io_context to put
126 *
127 * Decrement reference count of @ioc and release it if the count reaches
128 * zero.
129 */
130void put_io_context(struct io_context *ioc)
131{
132 unsigned long flags;
133 bool free_ioc = false;
134
135 if (ioc == NULL)
136 return;
137
138 BUG_ON(atomic_long_read(&ioc->refcount) <= 0);
139
140 /*
141 * Releasing ioc requires reverse order double locking and we may
142 * already be holding a queue_lock. Do it asynchronously from wq.
143 */
144 if (atomic_long_dec_and_test(&ioc->refcount)) {
145 spin_lock_irqsave(&ioc->lock, flags);
146 if (!hlist_empty(&ioc->icq_list))
147 schedule_work(&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 struct hlist_node *n;
168 unsigned long flags;
169 struct io_cq *icq;
170
171 if (!atomic_dec_and_test(&ioc->active_ref)) {
172 put_io_context(ioc);
173 return;
174 }
175
176 /*
177 * Need ioc lock to walk icq_list and q lock to exit icq. Perform
178 * reverse double locking. Read comment in ioc_release_fn() for
179 * explanation on the nested locking annotation.
180 */
181retry:
182 spin_lock_irqsave_nested(&ioc->lock, flags, 1);
183 hlist_for_each_entry(icq, n, &ioc->icq_list, ioc_node) {
184 if (icq->flags & ICQ_EXITED)
185 continue;
186 if (spin_trylock(icq->q->queue_lock)) {
187 ioc_exit_icq(icq);
188 spin_unlock(icq->q->queue_lock);
189 } else {
190 spin_unlock_irqrestore(&ioc->lock, flags);
191 cpu_relax();
192 goto retry;
193 }
194 }
195 spin_unlock_irqrestore(&ioc->lock, flags);
196
197 put_io_context(ioc);
198}
199
200/* Called by the exiting task */
201void exit_io_context(struct task_struct *task)
202{
203 struct io_context *ioc;
204
205 task_lock(task);
206 ioc = task->io_context;
207 task->io_context = NULL;
208 task_unlock(task);
209
210 atomic_dec(&ioc->nr_tasks);
211 put_io_context_active(ioc);
212}
213
214/**
215 * ioc_clear_queue - break any ioc association with the specified queue
216 * @q: request_queue being cleared
217 *
218 * Walk @q->icq_list and exit all io_cq's. Must be called with @q locked.
219 */
220void ioc_clear_queue(struct request_queue *q)
221{
222 lockdep_assert_held(q->queue_lock);
223
224 while (!list_empty(&q->icq_list)) {
225 struct io_cq *icq = list_entry(q->icq_list.next,
226 struct io_cq, q_node);
227 struct io_context *ioc = icq->ioc;
228
229 spin_lock(&ioc->lock);
230 ioc_destroy_icq(icq);
231 spin_unlock(&ioc->lock);
232 }
233}
234
235int create_task_io_context(struct task_struct *task, gfp_t gfp_flags, int node)
236{
237 struct io_context *ioc;
238 int ret;
239
240 ioc = kmem_cache_alloc_node(iocontext_cachep, gfp_flags | __GFP_ZERO,
241 node);
242 if (unlikely(!ioc))
243 return -ENOMEM;
244
245 /* initialize */
246 atomic_long_set(&ioc->refcount, 1);
247 atomic_set(&ioc->nr_tasks, 1);
248 atomic_set(&ioc->active_ref, 1);
249 spin_lock_init(&ioc->lock);
250 INIT_RADIX_TREE(&ioc->icq_tree, GFP_ATOMIC | __GFP_HIGH);
251 INIT_HLIST_HEAD(&ioc->icq_list);
252 INIT_WORK(&ioc->release_work, ioc_release_fn);
253
254 /*
255 * Try to install. ioc shouldn't be installed if someone else
256 * already did or @task, which isn't %current, is exiting. Note
257 * that we need to allow ioc creation on exiting %current as exit
258 * path may issue IOs from e.g. exit_files(). The exit path is
259 * responsible for not issuing IO after exit_io_context().
260 */
261 task_lock(task);
262 if (!task->io_context &&
263 (task == current || !(task->flags & PF_EXITING)))
264 task->io_context = ioc;
265 else
266 kmem_cache_free(iocontext_cachep, ioc);
267
268 ret = task->io_context ? 0 : -EBUSY;
269
270 task_unlock(task);
271
272 return ret;
273}
274
275/**
276 * get_task_io_context - get io_context of a task
277 * @task: task of interest
278 * @gfp_flags: allocation flags, used if allocation is necessary
279 * @node: allocation node, used if allocation is necessary
280 *
281 * Return io_context of @task. If it doesn't exist, it is created with
282 * @gfp_flags and @node. The returned io_context has its reference count
283 * incremented.
284 *
285 * This function always goes through task_lock() and it's better to use
286 * %current->io_context + get_io_context() for %current.
287 */
288struct io_context *get_task_io_context(struct task_struct *task,
289 gfp_t gfp_flags, int node)
290{
291 struct io_context *ioc;
292
293 might_sleep_if(gfp_flags & __GFP_WAIT);
294
295 do {
296 task_lock(task);
297 ioc = task->io_context;
298 if (likely(ioc)) {
299 get_io_context(ioc);
300 task_unlock(task);
301 return ioc;
302 }
303 task_unlock(task);
304 } while (!create_task_io_context(task, gfp_flags, node));
305
306 return NULL;
307}
308EXPORT_SYMBOL(get_task_io_context);
309
310/**
311 * ioc_lookup_icq - lookup io_cq from ioc
312 * @ioc: the associated io_context
313 * @q: the associated request_queue
314 *
315 * Look up io_cq associated with @ioc - @q pair from @ioc. Must be called
316 * with @q->queue_lock held.
317 */
318struct io_cq *ioc_lookup_icq(struct io_context *ioc, struct request_queue *q)
319{
320 struct io_cq *icq;
321
322 lockdep_assert_held(q->queue_lock);
323
324 /*
325 * icq's are indexed from @ioc using radix tree and hint pointer,
326 * both of which are protected with RCU. All removals are done
327 * holding both q and ioc locks, and we're holding q lock - if we
328 * find a icq which points to us, it's guaranteed to be valid.
329 */
330 rcu_read_lock();
331 icq = rcu_dereference(ioc->icq_hint);
332 if (icq && icq->q == q)
333 goto out;
334
335 icq = radix_tree_lookup(&ioc->icq_tree, q->id);
336 if (icq && icq->q == q)
337 rcu_assign_pointer(ioc->icq_hint, icq); /* allowed to race */
338 else
339 icq = NULL;
340out:
341 rcu_read_unlock();
342 return icq;
343}
344EXPORT_SYMBOL(ioc_lookup_icq);
345
346/**
347 * ioc_create_icq - create and link io_cq
348 * @ioc: io_context of interest
349 * @q: request_queue of interest
350 * @gfp_mask: allocation mask
351 *
352 * Make sure io_cq linking @ioc and @q exists. If icq doesn't exist, they
353 * will be created using @gfp_mask.
354 *
355 * The caller is responsible for ensuring @ioc won't go away and @q is
356 * alive and will stay alive until this function returns.
357 */
358struct io_cq *ioc_create_icq(struct io_context *ioc, struct request_queue *q,
359 gfp_t gfp_mask)
360{
361 struct elevator_type *et = q->elevator->type;
362 struct io_cq *icq;
363
364 /* allocate stuff */
365 icq = kmem_cache_alloc_node(et->icq_cache, gfp_mask | __GFP_ZERO,
366 q->node);
367 if (!icq)
368 return NULL;
369
370 if (radix_tree_preload(gfp_mask) < 0) {
371 kmem_cache_free(et->icq_cache, icq);
372 return NULL;
373 }
374
375 icq->ioc = ioc;
376 icq->q = q;
377 INIT_LIST_HEAD(&icq->q_node);
378 INIT_HLIST_NODE(&icq->ioc_node);
379
380 /* lock both q and ioc and try to link @icq */
381 spin_lock_irq(q->queue_lock);
382 spin_lock(&ioc->lock);
383
384 if (likely(!radix_tree_insert(&ioc->icq_tree, q->id, icq))) {
385 hlist_add_head(&icq->ioc_node, &ioc->icq_list);
386 list_add(&icq->q_node, &q->icq_list);
387 if (et->ops.elevator_init_icq_fn)
388 et->ops.elevator_init_icq_fn(icq);
389 } else {
390 kmem_cache_free(et->icq_cache, icq);
391 icq = ioc_lookup_icq(ioc, q);
392 if (!icq)
393 printk(KERN_ERR "cfq: icq link failed!\n");
394 }
395
396 spin_unlock(&ioc->lock);
397 spin_unlock_irq(q->queue_lock);
398 radix_tree_preload_end();
399 return icq;
400}
401
402static int __init blk_ioc_init(void)
403{
404 iocontext_cachep = kmem_cache_create("blkdev_ioc",
405 sizeof(struct io_context), 0, SLAB_PANIC, NULL);
406 return 0;
407}
408subsys_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/security.h>
12#include <linux/sched/task.h>
13
14#include "blk.h"
15#include "blk-mq-sched.h"
16
17/*
18 * For io context allocations
19 */
20static struct kmem_cache *iocontext_cachep;
21
22#ifdef CONFIG_BLK_ICQ
23/**
24 * get_io_context - increment reference count to io_context
25 * @ioc: io_context to get
26 *
27 * Increment reference count to @ioc.
28 */
29static void get_io_context(struct io_context *ioc)
30{
31 BUG_ON(atomic_long_read(&ioc->refcount) <= 0);
32 atomic_long_inc(&ioc->refcount);
33}
34
35static void icq_free_icq_rcu(struct rcu_head *head)
36{
37 struct io_cq *icq = container_of(head, struct io_cq, __rcu_head);
38
39 kmem_cache_free(icq->__rcu_icq_cache, icq);
40}
41
42/*
43 * Exit an icq. Called with ioc locked for blk-mq, and with both ioc
44 * and queue locked for legacy.
45 */
46static void ioc_exit_icq(struct io_cq *icq)
47{
48 struct elevator_type *et = icq->q->elevator->type;
49
50 if (icq->flags & ICQ_EXITED)
51 return;
52
53 if (et->ops.exit_icq)
54 et->ops.exit_icq(icq);
55
56 icq->flags |= ICQ_EXITED;
57}
58
59static void ioc_exit_icqs(struct io_context *ioc)
60{
61 struct io_cq *icq;
62
63 spin_lock_irq(&ioc->lock);
64 hlist_for_each_entry(icq, &ioc->icq_list, ioc_node)
65 ioc_exit_icq(icq);
66 spin_unlock_irq(&ioc->lock);
67}
68
69/*
70 * Release an icq. Called with ioc locked for blk-mq, and with both ioc
71 * and queue locked for legacy.
72 */
73static void ioc_destroy_icq(struct io_cq *icq)
74{
75 struct io_context *ioc = icq->ioc;
76 struct request_queue *q = icq->q;
77 struct elevator_type *et = q->elevator->type;
78
79 lockdep_assert_held(&ioc->lock);
80 lockdep_assert_held(&q->queue_lock);
81
82 if (icq->flags & ICQ_DESTROYED)
83 return;
84
85 radix_tree_delete(&ioc->icq_tree, icq->q->id);
86 hlist_del_init(&icq->ioc_node);
87 list_del_init(&icq->q_node);
88
89 /*
90 * Both setting lookup hint to and clearing it from @icq are done
91 * under queue_lock. If it's not pointing to @icq now, it never
92 * will. Hint assignment itself can race safely.
93 */
94 if (rcu_access_pointer(ioc->icq_hint) == icq)
95 rcu_assign_pointer(ioc->icq_hint, NULL);
96
97 ioc_exit_icq(icq);
98
99 /*
100 * @icq->q might have gone away by the time RCU callback runs
101 * making it impossible to determine icq_cache. Record it in @icq.
102 */
103 icq->__rcu_icq_cache = et->icq_cache;
104 icq->flags |= ICQ_DESTROYED;
105 call_rcu(&icq->__rcu_head, icq_free_icq_rcu);
106}
107
108/*
109 * Slow path for ioc release in put_io_context(). Performs double-lock
110 * dancing to unlink all icq's and then frees ioc.
111 */
112static void ioc_release_fn(struct work_struct *work)
113{
114 struct io_context *ioc = container_of(work, struct io_context,
115 release_work);
116 spin_lock_irq(&ioc->lock);
117
118 while (!hlist_empty(&ioc->icq_list)) {
119 struct io_cq *icq = hlist_entry(ioc->icq_list.first,
120 struct io_cq, ioc_node);
121 struct request_queue *q = icq->q;
122
123 if (spin_trylock(&q->queue_lock)) {
124 ioc_destroy_icq(icq);
125 spin_unlock(&q->queue_lock);
126 } else {
127 /* Make sure q and icq cannot be freed. */
128 rcu_read_lock();
129
130 /* Re-acquire the locks in the correct order. */
131 spin_unlock(&ioc->lock);
132 spin_lock(&q->queue_lock);
133 spin_lock(&ioc->lock);
134
135 ioc_destroy_icq(icq);
136
137 spin_unlock(&q->queue_lock);
138 rcu_read_unlock();
139 }
140 }
141
142 spin_unlock_irq(&ioc->lock);
143
144 kmem_cache_free(iocontext_cachep, ioc);
145}
146
147/*
148 * Releasing icqs requires reverse order double locking and we may already be
149 * holding a queue_lock. Do it asynchronously from a workqueue.
150 */
151static bool ioc_delay_free(struct io_context *ioc)
152{
153 unsigned long flags;
154
155 spin_lock_irqsave(&ioc->lock, flags);
156 if (!hlist_empty(&ioc->icq_list)) {
157 queue_work(system_power_efficient_wq, &ioc->release_work);
158 spin_unlock_irqrestore(&ioc->lock, flags);
159 return true;
160 }
161 spin_unlock_irqrestore(&ioc->lock, flags);
162 return false;
163}
164
165/**
166 * ioc_clear_queue - break any ioc association with the specified queue
167 * @q: request_queue being cleared
168 *
169 * Walk @q->icq_list and exit all io_cq's.
170 */
171void ioc_clear_queue(struct request_queue *q)
172{
173 spin_lock_irq(&q->queue_lock);
174 while (!list_empty(&q->icq_list)) {
175 struct io_cq *icq =
176 list_first_entry(&q->icq_list, struct io_cq, q_node);
177
178 /*
179 * Other context won't hold ioc lock to wait for queue_lock, see
180 * details in ioc_release_fn().
181 */
182 spin_lock(&icq->ioc->lock);
183 ioc_destroy_icq(icq);
184 spin_unlock(&icq->ioc->lock);
185 }
186 spin_unlock_irq(&q->queue_lock);
187}
188#else /* CONFIG_BLK_ICQ */
189static inline void ioc_exit_icqs(struct io_context *ioc)
190{
191}
192static inline bool ioc_delay_free(struct io_context *ioc)
193{
194 return false;
195}
196#endif /* CONFIG_BLK_ICQ */
197
198/**
199 * put_io_context - put a reference of io_context
200 * @ioc: io_context to put
201 *
202 * Decrement reference count of @ioc and release it if the count reaches
203 * zero.
204 */
205void put_io_context(struct io_context *ioc)
206{
207 BUG_ON(atomic_long_read(&ioc->refcount) <= 0);
208 if (atomic_long_dec_and_test(&ioc->refcount) && !ioc_delay_free(ioc))
209 kmem_cache_free(iocontext_cachep, ioc);
210}
211EXPORT_SYMBOL_GPL(put_io_context);
212
213/* Called by the exiting task */
214void exit_io_context(struct task_struct *task)
215{
216 struct io_context *ioc;
217
218 task_lock(task);
219 ioc = task->io_context;
220 task->io_context = NULL;
221 task_unlock(task);
222
223 if (atomic_dec_and_test(&ioc->active_ref)) {
224 ioc_exit_icqs(ioc);
225 put_io_context(ioc);
226 }
227}
228
229static struct io_context *alloc_io_context(gfp_t gfp_flags, int node)
230{
231 struct io_context *ioc;
232
233 ioc = kmem_cache_alloc_node(iocontext_cachep, gfp_flags | __GFP_ZERO,
234 node);
235 if (unlikely(!ioc))
236 return NULL;
237
238 atomic_long_set(&ioc->refcount, 1);
239 atomic_set(&ioc->active_ref, 1);
240#ifdef CONFIG_BLK_ICQ
241 spin_lock_init(&ioc->lock);
242 INIT_RADIX_TREE(&ioc->icq_tree, GFP_ATOMIC);
243 INIT_HLIST_HEAD(&ioc->icq_list);
244 INIT_WORK(&ioc->release_work, ioc_release_fn);
245#endif
246 ioc->ioprio = IOPRIO_DEFAULT;
247
248 return ioc;
249}
250
251int set_task_ioprio(struct task_struct *task, int ioprio)
252{
253 int err;
254 const struct cred *cred = current_cred(), *tcred;
255
256 rcu_read_lock();
257 tcred = __task_cred(task);
258 if (!uid_eq(tcred->uid, cred->euid) &&
259 !uid_eq(tcred->uid, cred->uid) && !capable(CAP_SYS_NICE)) {
260 rcu_read_unlock();
261 return -EPERM;
262 }
263 rcu_read_unlock();
264
265 err = security_task_setioprio(task, ioprio);
266 if (err)
267 return err;
268
269 task_lock(task);
270 if (unlikely(!task->io_context)) {
271 struct io_context *ioc;
272
273 task_unlock(task);
274
275 ioc = alloc_io_context(GFP_ATOMIC, NUMA_NO_NODE);
276 if (!ioc)
277 return -ENOMEM;
278
279 task_lock(task);
280 if (task->flags & PF_EXITING) {
281 kmem_cache_free(iocontext_cachep, ioc);
282 goto out;
283 }
284 if (task->io_context)
285 kmem_cache_free(iocontext_cachep, ioc);
286 else
287 task->io_context = ioc;
288 }
289 task->io_context->ioprio = ioprio;
290out:
291 task_unlock(task);
292 return 0;
293}
294EXPORT_SYMBOL_GPL(set_task_ioprio);
295
296int __copy_io(unsigned long clone_flags, struct task_struct *tsk)
297{
298 struct io_context *ioc = current->io_context;
299
300 /*
301 * Share io context with parent, if CLONE_IO is set
302 */
303 if (clone_flags & CLONE_IO) {
304 atomic_inc(&ioc->active_ref);
305 tsk->io_context = ioc;
306 } else if (ioprio_valid(ioc->ioprio)) {
307 tsk->io_context = alloc_io_context(GFP_KERNEL, NUMA_NO_NODE);
308 if (!tsk->io_context)
309 return -ENOMEM;
310 tsk->io_context->ioprio = ioc->ioprio;
311 }
312
313 return 0;
314}
315
316#ifdef CONFIG_BLK_ICQ
317/**
318 * ioc_lookup_icq - lookup io_cq from ioc
319 * @q: the associated request_queue
320 *
321 * Look up io_cq associated with @ioc - @q pair from @ioc. Must be called
322 * with @q->queue_lock held.
323 */
324struct io_cq *ioc_lookup_icq(struct request_queue *q)
325{
326 struct io_context *ioc = current->io_context;
327 struct io_cq *icq;
328
329 lockdep_assert_held(&q->queue_lock);
330
331 /*
332 * icq's are indexed from @ioc using radix tree and hint pointer,
333 * both of which are protected with RCU. All removals are done
334 * holding both q and ioc locks, and we're holding q lock - if we
335 * find a icq which points to us, it's guaranteed to be valid.
336 */
337 rcu_read_lock();
338 icq = rcu_dereference(ioc->icq_hint);
339 if (icq && icq->q == q)
340 goto out;
341
342 icq = radix_tree_lookup(&ioc->icq_tree, q->id);
343 if (icq && icq->q == q)
344 rcu_assign_pointer(ioc->icq_hint, icq); /* allowed to race */
345 else
346 icq = NULL;
347out:
348 rcu_read_unlock();
349 return icq;
350}
351EXPORT_SYMBOL(ioc_lookup_icq);
352
353/**
354 * ioc_create_icq - create and link io_cq
355 * @q: request_queue of interest
356 *
357 * Make sure io_cq linking @ioc and @q exists. If icq doesn't exist, they
358 * will be created using @gfp_mask.
359 *
360 * The caller is responsible for ensuring @ioc won't go away and @q is
361 * alive and will stay alive until this function returns.
362 */
363static struct io_cq *ioc_create_icq(struct request_queue *q)
364{
365 struct io_context *ioc = current->io_context;
366 struct elevator_type *et = q->elevator->type;
367 struct io_cq *icq;
368
369 /* allocate stuff */
370 icq = kmem_cache_alloc_node(et->icq_cache, GFP_ATOMIC | __GFP_ZERO,
371 q->node);
372 if (!icq)
373 return NULL;
374
375 if (radix_tree_maybe_preload(GFP_ATOMIC) < 0) {
376 kmem_cache_free(et->icq_cache, icq);
377 return NULL;
378 }
379
380 icq->ioc = ioc;
381 icq->q = q;
382 INIT_LIST_HEAD(&icq->q_node);
383 INIT_HLIST_NODE(&icq->ioc_node);
384
385 /* lock both q and ioc and try to link @icq */
386 spin_lock_irq(&q->queue_lock);
387 spin_lock(&ioc->lock);
388
389 if (likely(!radix_tree_insert(&ioc->icq_tree, q->id, icq))) {
390 hlist_add_head(&icq->ioc_node, &ioc->icq_list);
391 list_add(&icq->q_node, &q->icq_list);
392 if (et->ops.init_icq)
393 et->ops.init_icq(icq);
394 } else {
395 kmem_cache_free(et->icq_cache, icq);
396 icq = ioc_lookup_icq(q);
397 if (!icq)
398 printk(KERN_ERR "cfq: icq link failed!\n");
399 }
400
401 spin_unlock(&ioc->lock);
402 spin_unlock_irq(&q->queue_lock);
403 radix_tree_preload_end();
404 return icq;
405}
406
407struct io_cq *ioc_find_get_icq(struct request_queue *q)
408{
409 struct io_context *ioc = current->io_context;
410 struct io_cq *icq = NULL;
411
412 if (unlikely(!ioc)) {
413 ioc = alloc_io_context(GFP_ATOMIC, q->node);
414 if (!ioc)
415 return NULL;
416
417 task_lock(current);
418 if (current->io_context) {
419 kmem_cache_free(iocontext_cachep, ioc);
420 ioc = current->io_context;
421 } else {
422 current->io_context = ioc;
423 }
424
425 get_io_context(ioc);
426 task_unlock(current);
427 } else {
428 get_io_context(ioc);
429
430 spin_lock_irq(&q->queue_lock);
431 icq = ioc_lookup_icq(q);
432 spin_unlock_irq(&q->queue_lock);
433 }
434
435 if (!icq) {
436 icq = ioc_create_icq(q);
437 if (!icq) {
438 put_io_context(ioc);
439 return NULL;
440 }
441 }
442 return icq;
443}
444EXPORT_SYMBOL_GPL(ioc_find_get_icq);
445#endif /* CONFIG_BLK_ICQ */
446
447static int __init blk_ioc_init(void)
448{
449 iocontext_cachep = kmem_cache_create("blkdev_ioc",
450 sizeof(struct io_context), 0, SLAB_PANIC, NULL);
451 return 0;
452}
453subsys_initcall(blk_ioc_init);