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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
81 radix_tree_delete(&ioc->icq_tree, icq->q->id);
82 hlist_del_init(&icq->ioc_node);
83 list_del_init(&icq->q_node);
84
85 /*
86 * Both setting lookup hint to and clearing it from @icq are done
87 * under queue_lock. If it's not pointing to @icq now, it never
88 * will. Hint assignment itself can race safely.
89 */
90 if (rcu_access_pointer(ioc->icq_hint) == icq)
91 rcu_assign_pointer(ioc->icq_hint, NULL);
92
93 ioc_exit_icq(icq);
94
95 /*
96 * @icq->q might have gone away by the time RCU callback runs
97 * making it impossible to determine icq_cache. Record it in @icq.
98 */
99 icq->__rcu_icq_cache = et->icq_cache;
100 icq->flags |= ICQ_DESTROYED;
101 call_rcu(&icq->__rcu_head, icq_free_icq_rcu);
102}
103
104/*
105 * Slow path for ioc release in put_io_context(). Performs double-lock
106 * dancing to unlink all icq's and then frees ioc.
107 */
108static void ioc_release_fn(struct work_struct *work)
109{
110 struct io_context *ioc = container_of(work, struct io_context,
111 release_work);
112 spin_lock_irq(&ioc->lock);
113
114 while (!hlist_empty(&ioc->icq_list)) {
115 struct io_cq *icq = hlist_entry(ioc->icq_list.first,
116 struct io_cq, ioc_node);
117 struct request_queue *q = icq->q;
118
119 if (spin_trylock(&q->queue_lock)) {
120 ioc_destroy_icq(icq);
121 spin_unlock(&q->queue_lock);
122 } else {
123 /* Make sure q and icq cannot be freed. */
124 rcu_read_lock();
125
126 /* Re-acquire the locks in the correct order. */
127 spin_unlock(&ioc->lock);
128 spin_lock(&q->queue_lock);
129 spin_lock(&ioc->lock);
130
131 /*
132 * The icq may have been destroyed when the ioc lock
133 * was released.
134 */
135 if (!(icq->flags & ICQ_DESTROYED))
136 ioc_destroy_icq(icq);
137
138 spin_unlock(&q->queue_lock);
139 rcu_read_unlock();
140 }
141 }
142
143 spin_unlock_irq(&ioc->lock);
144
145 kmem_cache_free(iocontext_cachep, ioc);
146}
147
148/*
149 * Releasing icqs requires reverse order double locking and we may already be
150 * holding a queue_lock. Do it asynchronously from a workqueue.
151 */
152static bool ioc_delay_free(struct io_context *ioc)
153{
154 unsigned long flags;
155
156 spin_lock_irqsave(&ioc->lock, flags);
157 if (!hlist_empty(&ioc->icq_list)) {
158 queue_work(system_power_efficient_wq, &ioc->release_work);
159 spin_unlock_irqrestore(&ioc->lock, flags);
160 return true;
161 }
162 spin_unlock_irqrestore(&ioc->lock, flags);
163 return false;
164}
165
166/**
167 * ioc_clear_queue - break any ioc association with the specified queue
168 * @q: request_queue being cleared
169 *
170 * Walk @q->icq_list and exit all io_cq's.
171 */
172void ioc_clear_queue(struct request_queue *q)
173{
174 LIST_HEAD(icq_list);
175
176 spin_lock_irq(&q->queue_lock);
177 list_splice_init(&q->icq_list, &icq_list);
178 spin_unlock_irq(&q->queue_lock);
179
180 rcu_read_lock();
181 while (!list_empty(&icq_list)) {
182 struct io_cq *icq =
183 list_entry(icq_list.next, struct io_cq, q_node);
184
185 spin_lock_irq(&icq->ioc->lock);
186 if (!(icq->flags & ICQ_DESTROYED))
187 ioc_destroy_icq(icq);
188 spin_unlock_irq(&icq->ioc->lock);
189 }
190 rcu_read_unlock();
191}
192#else /* CONFIG_BLK_ICQ */
193static inline void ioc_exit_icqs(struct io_context *ioc)
194{
195}
196static inline bool ioc_delay_free(struct io_context *ioc)
197{
198 return false;
199}
200#endif /* CONFIG_BLK_ICQ */
201
202/**
203 * put_io_context - put a reference of io_context
204 * @ioc: io_context to put
205 *
206 * Decrement reference count of @ioc and release it if the count reaches
207 * zero.
208 */
209void put_io_context(struct io_context *ioc)
210{
211 BUG_ON(atomic_long_read(&ioc->refcount) <= 0);
212 if (atomic_long_dec_and_test(&ioc->refcount) && !ioc_delay_free(ioc))
213 kmem_cache_free(iocontext_cachep, ioc);
214}
215EXPORT_SYMBOL_GPL(put_io_context);
216
217/* Called by the exiting task */
218void exit_io_context(struct task_struct *task)
219{
220 struct io_context *ioc;
221
222 task_lock(task);
223 ioc = task->io_context;
224 task->io_context = NULL;
225 task_unlock(task);
226
227 if (atomic_dec_and_test(&ioc->active_ref)) {
228 ioc_exit_icqs(ioc);
229 put_io_context(ioc);
230 }
231}
232
233static struct io_context *alloc_io_context(gfp_t gfp_flags, int node)
234{
235 struct io_context *ioc;
236
237 ioc = kmem_cache_alloc_node(iocontext_cachep, gfp_flags | __GFP_ZERO,
238 node);
239 if (unlikely(!ioc))
240 return NULL;
241
242 atomic_long_set(&ioc->refcount, 1);
243 atomic_set(&ioc->active_ref, 1);
244#ifdef CONFIG_BLK_ICQ
245 spin_lock_init(&ioc->lock);
246 INIT_RADIX_TREE(&ioc->icq_tree, GFP_ATOMIC);
247 INIT_HLIST_HEAD(&ioc->icq_list);
248 INIT_WORK(&ioc->release_work, ioc_release_fn);
249#endif
250 ioc->ioprio = IOPRIO_DEFAULT;
251
252 return ioc;
253}
254
255int set_task_ioprio(struct task_struct *task, int ioprio)
256{
257 int err;
258 const struct cred *cred = current_cred(), *tcred;
259
260 rcu_read_lock();
261 tcred = __task_cred(task);
262 if (!uid_eq(tcred->uid, cred->euid) &&
263 !uid_eq(tcred->uid, cred->uid) && !capable(CAP_SYS_NICE)) {
264 rcu_read_unlock();
265 return -EPERM;
266 }
267 rcu_read_unlock();
268
269 err = security_task_setioprio(task, ioprio);
270 if (err)
271 return err;
272
273 task_lock(task);
274 if (unlikely(!task->io_context)) {
275 struct io_context *ioc;
276
277 task_unlock(task);
278
279 ioc = alloc_io_context(GFP_ATOMIC, NUMA_NO_NODE);
280 if (!ioc)
281 return -ENOMEM;
282
283 task_lock(task);
284 if (task->flags & PF_EXITING) {
285 kmem_cache_free(iocontext_cachep, ioc);
286 goto out;
287 }
288 if (task->io_context)
289 kmem_cache_free(iocontext_cachep, ioc);
290 else
291 task->io_context = ioc;
292 }
293 task->io_context->ioprio = ioprio;
294out:
295 task_unlock(task);
296 return 0;
297}
298EXPORT_SYMBOL_GPL(set_task_ioprio);
299
300int __copy_io(unsigned long clone_flags, struct task_struct *tsk)
301{
302 struct io_context *ioc = current->io_context;
303
304 /*
305 * Share io context with parent, if CLONE_IO is set
306 */
307 if (clone_flags & CLONE_IO) {
308 atomic_inc(&ioc->active_ref);
309 tsk->io_context = ioc;
310 } else if (ioprio_valid(ioc->ioprio)) {
311 tsk->io_context = alloc_io_context(GFP_KERNEL, NUMA_NO_NODE);
312 if (!tsk->io_context)
313 return -ENOMEM;
314 tsk->io_context->ioprio = ioc->ioprio;
315 }
316
317 return 0;
318}
319
320#ifdef CONFIG_BLK_ICQ
321/**
322 * ioc_lookup_icq - lookup io_cq from ioc
323 * @q: the associated request_queue
324 *
325 * Look up io_cq associated with @ioc - @q pair from @ioc. Must be called
326 * with @q->queue_lock held.
327 */
328struct io_cq *ioc_lookup_icq(struct request_queue *q)
329{
330 struct io_context *ioc = current->io_context;
331 struct io_cq *icq;
332
333 lockdep_assert_held(&q->queue_lock);
334
335 /*
336 * icq's are indexed from @ioc using radix tree and hint pointer,
337 * both of which are protected with RCU. All removals are done
338 * holding both q and ioc locks, and we're holding q lock - if we
339 * find a icq which points to us, it's guaranteed to be valid.
340 */
341 rcu_read_lock();
342 icq = rcu_dereference(ioc->icq_hint);
343 if (icq && icq->q == q)
344 goto out;
345
346 icq = radix_tree_lookup(&ioc->icq_tree, q->id);
347 if (icq && icq->q == q)
348 rcu_assign_pointer(ioc->icq_hint, icq); /* allowed to race */
349 else
350 icq = NULL;
351out:
352 rcu_read_unlock();
353 return icq;
354}
355EXPORT_SYMBOL(ioc_lookup_icq);
356
357/**
358 * ioc_create_icq - create and link io_cq
359 * @q: request_queue of interest
360 *
361 * Make sure io_cq linking @ioc and @q exists. If icq doesn't exist, they
362 * will be created using @gfp_mask.
363 *
364 * The caller is responsible for ensuring @ioc won't go away and @q is
365 * alive and will stay alive until this function returns.
366 */
367static struct io_cq *ioc_create_icq(struct request_queue *q)
368{
369 struct io_context *ioc = current->io_context;
370 struct elevator_type *et = q->elevator->type;
371 struct io_cq *icq;
372
373 /* allocate stuff */
374 icq = kmem_cache_alloc_node(et->icq_cache, GFP_ATOMIC | __GFP_ZERO,
375 q->node);
376 if (!icq)
377 return NULL;
378
379 if (radix_tree_maybe_preload(GFP_ATOMIC) < 0) {
380 kmem_cache_free(et->icq_cache, icq);
381 return NULL;
382 }
383
384 icq->ioc = ioc;
385 icq->q = q;
386 INIT_LIST_HEAD(&icq->q_node);
387 INIT_HLIST_NODE(&icq->ioc_node);
388
389 /* lock both q and ioc and try to link @icq */
390 spin_lock_irq(&q->queue_lock);
391 spin_lock(&ioc->lock);
392
393 if (likely(!radix_tree_insert(&ioc->icq_tree, q->id, icq))) {
394 hlist_add_head(&icq->ioc_node, &ioc->icq_list);
395 list_add(&icq->q_node, &q->icq_list);
396 if (et->ops.init_icq)
397 et->ops.init_icq(icq);
398 } else {
399 kmem_cache_free(et->icq_cache, icq);
400 icq = ioc_lookup_icq(q);
401 if (!icq)
402 printk(KERN_ERR "cfq: icq link failed!\n");
403 }
404
405 spin_unlock(&ioc->lock);
406 spin_unlock_irq(&q->queue_lock);
407 radix_tree_preload_end();
408 return icq;
409}
410
411struct io_cq *ioc_find_get_icq(struct request_queue *q)
412{
413 struct io_context *ioc = current->io_context;
414 struct io_cq *icq = NULL;
415
416 if (unlikely(!ioc)) {
417 ioc = alloc_io_context(GFP_ATOMIC, q->node);
418 if (!ioc)
419 return NULL;
420
421 task_lock(current);
422 if (current->io_context) {
423 kmem_cache_free(iocontext_cachep, ioc);
424 ioc = current->io_context;
425 } else {
426 current->io_context = ioc;
427 }
428
429 get_io_context(ioc);
430 task_unlock(current);
431 } else {
432 get_io_context(ioc);
433
434 spin_lock_irq(&q->queue_lock);
435 icq = ioc_lookup_icq(q);
436 spin_unlock_irq(&q->queue_lock);
437 }
438
439 if (!icq) {
440 icq = ioc_create_icq(q);
441 if (!icq) {
442 put_io_context(ioc);
443 return NULL;
444 }
445 }
446 return icq;
447}
448EXPORT_SYMBOL_GPL(ioc_find_get_icq);
449#endif /* CONFIG_BLK_ICQ */
450
451static int __init blk_ioc_init(void)
452{
453 iocontext_cachep = kmem_cache_create("blkdev_ioc",
454 sizeof(struct io_context), 0, SLAB_PANIC, NULL);
455 return 0;
456}
457subsys_initcall(blk_ioc_init);