Commit | Line | Data |
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b2441318 | 1 | // SPDX-License-Identifier: GPL-2.0 |
86db1e29 JA |
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> | |
5a0e3ad6 | 10 | #include <linux/slab.h> |
f719ff9b | 11 | #include <linux/sched/task.h> |
86db1e29 JA |
12 | |
13 | #include "blk.h" | |
2aa7745b | 14 | #include "blk-mq-sched.h" |
86db1e29 JA |
15 | |
16 | /* | |
17 | * For io context allocations | |
18 | */ | |
19 | static struct kmem_cache *iocontext_cachep; | |
20 | ||
6e736be7 TH |
21 | /** |
22 | * get_io_context - increment reference count to io_context | |
23 | * @ioc: io_context to get | |
24 | * | |
25 | * Increment reference count to @ioc. | |
26 | */ | |
87dd1d63 | 27 | static void get_io_context(struct io_context *ioc) |
6e736be7 TH |
28 | { |
29 | BUG_ON(atomic_long_read(&ioc->refcount) <= 0); | |
30 | atomic_long_inc(&ioc->refcount); | |
31 | } | |
6e736be7 | 32 | |
7e5a8794 TH |
33 | static 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 | ||
3d492c2e | 40 | /* |
7b36a718 JA |
41 | * Exit an icq. Called with ioc locked for blk-mq, and with both ioc |
42 | * and queue locked for legacy. | |
3d492c2e | 43 | */ |
7e5a8794 | 44 | static void ioc_exit_icq(struct io_cq *icq) |
621032ad TH |
45 | { |
46 | struct elevator_type *et = icq->q->elevator->type; | |
47 | ||
48 | if (icq->flags & ICQ_EXITED) | |
49 | return; | |
50 | ||
f9cd4bfe JA |
51 | if (et->ops.exit_icq) |
52 | et->ops.exit_icq(icq); | |
621032ad TH |
53 | |
54 | icq->flags |= ICQ_EXITED; | |
55 | } | |
56 | ||
7b36a718 JA |
57 | /* |
58 | * Release an icq. Called with ioc locked for blk-mq, and with both ioc | |
59 | * and queue locked for legacy. | |
60 | */ | |
621032ad | 61 | static void ioc_destroy_icq(struct io_cq *icq) |
7e5a8794 TH |
62 | { |
63 | struct io_context *ioc = icq->ioc; | |
64 | struct request_queue *q = icq->q; | |
65 | struct elevator_type *et = q->elevator->type; | |
66 | ||
67 | lockdep_assert_held(&ioc->lock); | |
7e5a8794 TH |
68 | |
69 | radix_tree_delete(&ioc->icq_tree, icq->q->id); | |
70 | hlist_del_init(&icq->ioc_node); | |
71 | list_del_init(&icq->q_node); | |
72 | ||
73 | /* | |
74 | * Both setting lookup hint to and clearing it from @icq are done | |
75 | * under queue_lock. If it's not pointing to @icq now, it never | |
76 | * will. Hint assignment itself can race safely. | |
77 | */ | |
ec6c676a | 78 | if (rcu_access_pointer(ioc->icq_hint) == icq) |
7e5a8794 TH |
79 | rcu_assign_pointer(ioc->icq_hint, NULL); |
80 | ||
621032ad | 81 | ioc_exit_icq(icq); |
7e5a8794 TH |
82 | |
83 | /* | |
84 | * @icq->q might have gone away by the time RCU callback runs | |
85 | * making it impossible to determine icq_cache. Record it in @icq. | |
86 | */ | |
87 | icq->__rcu_icq_cache = et->icq_cache; | |
30a2da7b | 88 | icq->flags |= ICQ_DESTROYED; |
7e5a8794 TH |
89 | call_rcu(&icq->__rcu_head, icq_free_icq_rcu); |
90 | } | |
91 | ||
b2efa052 TH |
92 | /* |
93 | * Slow path for ioc release in put_io_context(). Performs double-lock | |
c5869807 | 94 | * dancing to unlink all icq's and then frees ioc. |
b2efa052 TH |
95 | */ |
96 | static void ioc_release_fn(struct work_struct *work) | |
86db1e29 | 97 | { |
b2efa052 TH |
98 | struct io_context *ioc = container_of(work, struct io_context, |
99 | release_work); | |
a43f085f | 100 | spin_lock_irq(&ioc->lock); |
b2efa052 | 101 | |
c5869807 TH |
102 | while (!hlist_empty(&ioc->icq_list)) { |
103 | struct io_cq *icq = hlist_entry(ioc->icq_list.first, | |
104 | struct io_cq, ioc_node); | |
2274b029 TH |
105 | struct request_queue *q = icq->q; |
106 | ||
0d945c1f | 107 | if (spin_trylock(&q->queue_lock)) { |
621032ad | 108 | ioc_destroy_icq(icq); |
0d945c1f | 109 | spin_unlock(&q->queue_lock); |
2274b029 | 110 | } else { |
ab96bbab JO |
111 | /* Make sure q and icq cannot be freed. */ |
112 | rcu_read_lock(); | |
113 | ||
114 | /* Re-acquire the locks in the correct order. */ | |
115 | spin_unlock(&ioc->lock); | |
116 | spin_lock(&q->queue_lock); | |
117 | spin_lock(&ioc->lock); | |
118 | ||
119 | /* | |
120 | * The icq may have been destroyed when the ioc lock | |
121 | * was released. | |
122 | */ | |
123 | if (!(icq->flags & ICQ_DESTROYED)) | |
124 | ioc_destroy_icq(icq); | |
125 | ||
126 | spin_unlock(&q->queue_lock); | |
127 | rcu_read_unlock(); | |
b2efa052 | 128 | } |
b2efa052 | 129 | } |
ffc4e759 | 130 | |
a43f085f | 131 | spin_unlock_irq(&ioc->lock); |
b2efa052 TH |
132 | |
133 | kmem_cache_free(iocontext_cachep, ioc); | |
86db1e29 JA |
134 | } |
135 | ||
42ec57a8 TH |
136 | /** |
137 | * put_io_context - put a reference of io_context | |
138 | * @ioc: io_context to put | |
139 | * | |
140 | * Decrement reference count of @ioc and release it if the count reaches | |
11a3122f | 141 | * zero. |
86db1e29 | 142 | */ |
11a3122f | 143 | void put_io_context(struct io_context *ioc) |
86db1e29 | 144 | { |
b2efa052 | 145 | unsigned long flags; |
ff8c1474 | 146 | bool free_ioc = false; |
b2efa052 | 147 | |
86db1e29 | 148 | if (ioc == NULL) |
42ec57a8 | 149 | return; |
86db1e29 | 150 | |
42ec57a8 | 151 | BUG_ON(atomic_long_read(&ioc->refcount) <= 0); |
86db1e29 | 152 | |
b2efa052 | 153 | /* |
11a3122f TH |
154 | * Releasing ioc requires reverse order double locking and we may |
155 | * already be holding a queue_lock. Do it asynchronously from wq. | |
b2efa052 | 156 | */ |
11a3122f TH |
157 | if (atomic_long_dec_and_test(&ioc->refcount)) { |
158 | spin_lock_irqsave(&ioc->lock, flags); | |
159 | if (!hlist_empty(&ioc->icq_list)) | |
695588f9 VK |
160 | queue_work(system_power_efficient_wq, |
161 | &ioc->release_work); | |
ff8c1474 XF |
162 | else |
163 | free_ioc = true; | |
11a3122f | 164 | spin_unlock_irqrestore(&ioc->lock, flags); |
b2efa052 | 165 | } |
ff8c1474 XF |
166 | |
167 | if (free_ioc) | |
168 | kmem_cache_free(iocontext_cachep, ioc); | |
86db1e29 | 169 | } |
222ee581 | 170 | EXPORT_SYMBOL_GPL(put_io_context); |
86db1e29 | 171 | |
f6e8d01b TH |
172 | /** |
173 | * put_io_context_active - put active reference on ioc | |
174 | * @ioc: ioc of interest | |
175 | * | |
50569c24 | 176 | * Put an active reference to an ioc. If active reference reaches zero after |
f6e8d01b TH |
177 | * put, @ioc can never issue further IOs and ioscheds are notified. |
178 | */ | |
33047425 | 179 | static void put_io_context_active(struct io_context *ioc) |
86db1e29 | 180 | { |
f6e8d01b | 181 | struct io_cq *icq; |
86db1e29 | 182 | |
0aed2f16 | 183 | if (!atomic_dec_and_test(&ioc->active_ref)) |
621032ad | 184 | return; |
621032ad | 185 | |
a43f085f | 186 | spin_lock_irq(&ioc->lock); |
b67bfe0d | 187 | hlist_for_each_entry(icq, &ioc->icq_list, ioc_node) { |
621032ad TH |
188 | if (icq->flags & ICQ_EXITED) |
189 | continue; | |
3d492c2e | 190 | |
a1ce35fa | 191 | ioc_exit_icq(icq); |
621032ad | 192 | } |
a43f085f | 193 | spin_unlock_irq(&ioc->lock); |
621032ad | 194 | |
11a3122f | 195 | put_io_context(ioc); |
86db1e29 JA |
196 | } |
197 | ||
f6e8d01b TH |
198 | /* Called by the exiting task */ |
199 | void exit_io_context(struct task_struct *task) | |
200 | { | |
201 | struct io_context *ioc; | |
202 | ||
203 | task_lock(task); | |
204 | ioc = task->io_context; | |
205 | task->io_context = NULL; | |
206 | task_unlock(task); | |
207 | ||
f6e8d01b TH |
208 | put_io_context_active(ioc); |
209 | } | |
210 | ||
7b36a718 JA |
211 | static void __ioc_clear_queue(struct list_head *icq_list) |
212 | { | |
213 | unsigned long flags; | |
214 | ||
30a2da7b | 215 | rcu_read_lock(); |
7b36a718 JA |
216 | while (!list_empty(icq_list)) { |
217 | struct io_cq *icq = list_entry(icq_list->next, | |
a1ce35fa | 218 | struct io_cq, q_node); |
7b36a718 JA |
219 | struct io_context *ioc = icq->ioc; |
220 | ||
221 | spin_lock_irqsave(&ioc->lock, flags); | |
30a2da7b ST |
222 | if (icq->flags & ICQ_DESTROYED) { |
223 | spin_unlock_irqrestore(&ioc->lock, flags); | |
224 | continue; | |
225 | } | |
7b36a718 JA |
226 | ioc_destroy_icq(icq); |
227 | spin_unlock_irqrestore(&ioc->lock, flags); | |
228 | } | |
30a2da7b | 229 | rcu_read_unlock(); |
7b36a718 JA |
230 | } |
231 | ||
7e5a8794 TH |
232 | /** |
233 | * ioc_clear_queue - break any ioc association with the specified queue | |
234 | * @q: request_queue being cleared | |
235 | * | |
7b36a718 | 236 | * Walk @q->icq_list and exit all io_cq's. |
7e5a8794 TH |
237 | */ |
238 | void ioc_clear_queue(struct request_queue *q) | |
239 | { | |
7b36a718 | 240 | LIST_HEAD(icq_list); |
7e5a8794 | 241 | |
0d945c1f | 242 | spin_lock_irq(&q->queue_lock); |
7b36a718 | 243 | list_splice_init(&q->icq_list, &icq_list); |
0d945c1f | 244 | spin_unlock_irq(&q->queue_lock); |
7e5a8794 | 245 | |
a1ce35fa | 246 | __ioc_clear_queue(&icq_list); |
7e5a8794 TH |
247 | } |
248 | ||
a0f14d8b | 249 | static struct io_context *alloc_io_context(gfp_t gfp_flags, int node) |
86db1e29 | 250 | { |
df415656 | 251 | struct io_context *ioc; |
86db1e29 | 252 | |
42ec57a8 TH |
253 | ioc = kmem_cache_alloc_node(iocontext_cachep, gfp_flags | __GFP_ZERO, |
254 | node); | |
255 | if (unlikely(!ioc)) | |
a0f14d8b | 256 | return NULL; |
42ec57a8 | 257 | |
42ec57a8 | 258 | atomic_long_set(&ioc->refcount, 1); |
f6e8d01b | 259 | atomic_set(&ioc->active_ref, 1); |
42ec57a8 | 260 | spin_lock_init(&ioc->lock); |
c137969b | 261 | INIT_RADIX_TREE(&ioc->icq_tree, GFP_ATOMIC); |
c5869807 | 262 | INIT_HLIST_HEAD(&ioc->icq_list); |
b2efa052 | 263 | INIT_WORK(&ioc->release_work, ioc_release_fn); |
a0f14d8b CH |
264 | return ioc; |
265 | } | |
266 | ||
d538ea4c CH |
267 | static struct io_context *create_task_io_context(struct task_struct *task, |
268 | gfp_t gfp_flags, int node) | |
a0f14d8b CH |
269 | { |
270 | struct io_context *ioc; | |
a0f14d8b CH |
271 | |
272 | ioc = alloc_io_context(gfp_flags, node); | |
273 | if (!ioc) | |
d538ea4c | 274 | return NULL; |
86db1e29 | 275 | |
fd638368 TH |
276 | /* |
277 | * Try to install. ioc shouldn't be installed if someone else | |
278 | * already did or @task, which isn't %current, is exiting. Note | |
279 | * that we need to allow ioc creation on exiting %current as exit | |
280 | * path may issue IOs from e.g. exit_files(). The exit path is | |
281 | * responsible for not issuing IO after exit_io_context(). | |
282 | */ | |
6e736be7 | 283 | task_lock(task); |
fd638368 TH |
284 | if (!task->io_context && |
285 | (task == current || !(task->flags & PF_EXITING))) | |
6e736be7 | 286 | task->io_context = ioc; |
f2dbd76a | 287 | else |
6e736be7 | 288 | kmem_cache_free(iocontext_cachep, ioc); |
3c9c708c | 289 | |
d538ea4c CH |
290 | ioc = task->io_context; |
291 | if (ioc) | |
292 | get_io_context(ioc); | |
6e736be7 | 293 | task_unlock(task); |
d538ea4c | 294 | return ioc; |
86db1e29 | 295 | } |
86db1e29 | 296 | |
6e736be7 TH |
297 | /** |
298 | * get_task_io_context - get io_context of a task | |
299 | * @task: task of interest | |
300 | * @gfp_flags: allocation flags, used if allocation is necessary | |
301 | * @node: allocation node, used if allocation is necessary | |
302 | * | |
303 | * Return io_context of @task. If it doesn't exist, it is created with | |
304 | * @gfp_flags and @node. The returned io_context has its reference count | |
305 | * incremented. | |
86db1e29 | 306 | * |
6e736be7 | 307 | * This function always goes through task_lock() and it's better to use |
f2dbd76a | 308 | * %current->io_context + get_io_context() for %current. |
86db1e29 | 309 | */ |
6e736be7 TH |
310 | struct io_context *get_task_io_context(struct task_struct *task, |
311 | gfp_t gfp_flags, int node) | |
86db1e29 | 312 | { |
6e736be7 | 313 | struct io_context *ioc; |
86db1e29 | 314 | |
d0164adc | 315 | might_sleep_if(gfpflags_allow_blocking(gfp_flags)); |
6e736be7 | 316 | |
d538ea4c CH |
317 | task_lock(task); |
318 | ioc = task->io_context; | |
319 | if (unlikely(!ioc)) { | |
6e736be7 | 320 | task_unlock(task); |
d538ea4c CH |
321 | return create_task_io_context(task, gfp_flags, node); |
322 | } | |
323 | get_io_context(ioc); | |
324 | task_unlock(task); | |
325 | return ioc; | |
86db1e29 | 326 | } |
86db1e29 | 327 | |
88c9a2ce CH |
328 | int __copy_io(unsigned long clone_flags, struct task_struct *tsk) |
329 | { | |
330 | struct io_context *ioc = current->io_context; | |
88c9a2ce CH |
331 | |
332 | /* | |
333 | * Share io context with parent, if CLONE_IO is set | |
334 | */ | |
335 | if (clone_flags & CLONE_IO) { | |
50569c24 | 336 | atomic_inc(&ioc->active_ref); |
88c9a2ce CH |
337 | tsk->io_context = ioc; |
338 | } else if (ioprio_valid(ioc->ioprio)) { | |
8ffc1368 CH |
339 | tsk->io_context = alloc_io_context(GFP_KERNEL, NUMA_NO_NODE); |
340 | if (!tsk->io_context) | |
88c9a2ce | 341 | return -ENOMEM; |
8ffc1368 | 342 | tsk->io_context->ioprio = ioc->ioprio; |
88c9a2ce CH |
343 | } |
344 | ||
345 | return 0; | |
346 | } | |
347 | ||
47fdd4ca TH |
348 | /** |
349 | * ioc_lookup_icq - lookup io_cq from ioc | |
47fdd4ca TH |
350 | * @q: the associated request_queue |
351 | * | |
352 | * Look up io_cq associated with @ioc - @q pair from @ioc. Must be called | |
353 | * with @q->queue_lock held. | |
354 | */ | |
eca5892a | 355 | struct io_cq *ioc_lookup_icq(struct request_queue *q) |
47fdd4ca | 356 | { |
eca5892a | 357 | struct io_context *ioc = current->io_context; |
47fdd4ca TH |
358 | struct io_cq *icq; |
359 | ||
0d945c1f | 360 | lockdep_assert_held(&q->queue_lock); |
47fdd4ca TH |
361 | |
362 | /* | |
363 | * icq's are indexed from @ioc using radix tree and hint pointer, | |
364 | * both of which are protected with RCU. All removals are done | |
365 | * holding both q and ioc locks, and we're holding q lock - if we | |
366 | * find a icq which points to us, it's guaranteed to be valid. | |
367 | */ | |
368 | rcu_read_lock(); | |
369 | icq = rcu_dereference(ioc->icq_hint); | |
370 | if (icq && icq->q == q) | |
371 | goto out; | |
372 | ||
373 | icq = radix_tree_lookup(&ioc->icq_tree, q->id); | |
374 | if (icq && icq->q == q) | |
375 | rcu_assign_pointer(ioc->icq_hint, icq); /* allowed to race */ | |
376 | else | |
377 | icq = NULL; | |
378 | out: | |
379 | rcu_read_unlock(); | |
380 | return icq; | |
381 | } | |
382 | EXPORT_SYMBOL(ioc_lookup_icq); | |
383 | ||
f1f8cc94 TH |
384 | /** |
385 | * ioc_create_icq - create and link io_cq | |
386 | * @q: request_queue of interest | |
f1f8cc94 | 387 | * |
24acfc34 TH |
388 | * Make sure io_cq linking @ioc and @q exists. If icq doesn't exist, they |
389 | * will be created using @gfp_mask. | |
f1f8cc94 TH |
390 | * |
391 | * The caller is responsible for ensuring @ioc won't go away and @q is | |
392 | * alive and will stay alive until this function returns. | |
393 | */ | |
18b74c4d | 394 | static struct io_cq *ioc_create_icq(struct request_queue *q) |
f1f8cc94 | 395 | { |
18b74c4d | 396 | struct io_context *ioc = current->io_context; |
f1f8cc94 | 397 | struct elevator_type *et = q->elevator->type; |
f1f8cc94 TH |
398 | struct io_cq *icq; |
399 | ||
400 | /* allocate stuff */ | |
18b74c4d | 401 | icq = kmem_cache_alloc_node(et->icq_cache, GFP_ATOMIC | __GFP_ZERO, |
f1f8cc94 TH |
402 | q->node); |
403 | if (!icq) | |
404 | return NULL; | |
405 | ||
18b74c4d | 406 | if (radix_tree_maybe_preload(GFP_ATOMIC) < 0) { |
f1f8cc94 TH |
407 | kmem_cache_free(et->icq_cache, icq); |
408 | return NULL; | |
409 | } | |
410 | ||
411 | icq->ioc = ioc; | |
412 | icq->q = q; | |
413 | INIT_LIST_HEAD(&icq->q_node); | |
414 | INIT_HLIST_NODE(&icq->ioc_node); | |
415 | ||
416 | /* lock both q and ioc and try to link @icq */ | |
0d945c1f | 417 | spin_lock_irq(&q->queue_lock); |
f1f8cc94 TH |
418 | spin_lock(&ioc->lock); |
419 | ||
420 | if (likely(!radix_tree_insert(&ioc->icq_tree, q->id, icq))) { | |
421 | hlist_add_head(&icq->ioc_node, &ioc->icq_list); | |
422 | list_add(&icq->q_node, &q->icq_list); | |
f9cd4bfe JA |
423 | if (et->ops.init_icq) |
424 | et->ops.init_icq(icq); | |
f1f8cc94 TH |
425 | } else { |
426 | kmem_cache_free(et->icq_cache, icq); | |
eca5892a | 427 | icq = ioc_lookup_icq(q); |
f1f8cc94 TH |
428 | if (!icq) |
429 | printk(KERN_ERR "cfq: icq link failed!\n"); | |
430 | } | |
431 | ||
432 | spin_unlock(&ioc->lock); | |
0d945c1f | 433 | spin_unlock_irq(&q->queue_lock); |
f1f8cc94 TH |
434 | radix_tree_preload_end(); |
435 | return icq; | |
436 | } | |
437 | ||
87dd1d63 CH |
438 | struct io_cq *ioc_find_get_icq(struct request_queue *q) |
439 | { | |
d538ea4c CH |
440 | struct io_context *ioc = current->io_context; |
441 | struct io_cq *icq = NULL; | |
87dd1d63 | 442 | |
d538ea4c CH |
443 | if (unlikely(!ioc)) { |
444 | ioc = create_task_io_context(current, GFP_ATOMIC, q->node); | |
445 | if (!ioc) | |
446 | return NULL; | |
447 | } else { | |
448 | get_io_context(ioc); | |
87dd1d63 | 449 | |
d538ea4c | 450 | spin_lock_irq(&q->queue_lock); |
eca5892a | 451 | icq = ioc_lookup_icq(q); |
d538ea4c CH |
452 | spin_unlock_irq(&q->queue_lock); |
453 | } | |
87dd1d63 CH |
454 | |
455 | if (!icq) { | |
18b74c4d | 456 | icq = ioc_create_icq(q); |
d538ea4c CH |
457 | if (!icq) { |
458 | put_io_context(ioc); | |
87dd1d63 | 459 | return NULL; |
d538ea4c | 460 | } |
87dd1d63 | 461 | } |
87dd1d63 CH |
462 | return icq; |
463 | } | |
464 | EXPORT_SYMBOL_GPL(ioc_find_get_icq); | |
465 | ||
13341598 | 466 | static int __init blk_ioc_init(void) |
86db1e29 JA |
467 | { |
468 | iocontext_cachep = kmem_cache_create("blkdev_ioc", | |
469 | sizeof(struct io_context), 0, SLAB_PANIC, NULL); | |
470 | return 0; | |
471 | } | |
472 | subsys_initcall(blk_ioc_init); |