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" | |
14 | ||
15 | /* | |
16 | * For io context allocations | |
17 | */ | |
18 | static struct kmem_cache *iocontext_cachep; | |
19 | ||
6e736be7 TH |
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 | */ | |
26 | void get_io_context(struct io_context *ioc) | |
27 | { | |
28 | BUG_ON(atomic_long_read(&ioc->refcount) <= 0); | |
29 | atomic_long_inc(&ioc->refcount); | |
30 | } | |
6e736be7 | 31 | |
7e5a8794 TH |
32 | static 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 | ||
3d492c2e | 39 | /* |
7b36a718 JA |
40 | * Exit an icq. Called with ioc locked for blk-mq, and with both ioc |
41 | * and queue locked for legacy. | |
3d492c2e | 42 | */ |
7e5a8794 | 43 | static void ioc_exit_icq(struct io_cq *icq) |
621032ad TH |
44 | { |
45 | struct elevator_type *et = icq->q->elevator->type; | |
46 | ||
47 | if (icq->flags & ICQ_EXITED) | |
48 | return; | |
49 | ||
f9cd4bfe JA |
50 | if (et->ops.exit_icq) |
51 | et->ops.exit_icq(icq); | |
621032ad TH |
52 | |
53 | icq->flags |= ICQ_EXITED; | |
54 | } | |
55 | ||
7b36a718 JA |
56 | /* |
57 | * Release an icq. Called with ioc locked for blk-mq, and with both ioc | |
58 | * and queue locked for legacy. | |
59 | */ | |
621032ad | 60 | static void ioc_destroy_icq(struct io_cq *icq) |
7e5a8794 TH |
61 | { |
62 | struct io_context *ioc = icq->ioc; | |
63 | struct request_queue *q = icq->q; | |
64 | struct elevator_type *et = q->elevator->type; | |
65 | ||
66 | lockdep_assert_held(&ioc->lock); | |
7e5a8794 TH |
67 | |
68 | radix_tree_delete(&ioc->icq_tree, icq->q->id); | |
69 | hlist_del_init(&icq->ioc_node); | |
70 | list_del_init(&icq->q_node); | |
71 | ||
72 | /* | |
73 | * Both setting lookup hint to and clearing it from @icq are done | |
74 | * under queue_lock. If it's not pointing to @icq now, it never | |
75 | * will. Hint assignment itself can race safely. | |
76 | */ | |
ec6c676a | 77 | if (rcu_access_pointer(ioc->icq_hint) == icq) |
7e5a8794 TH |
78 | rcu_assign_pointer(ioc->icq_hint, NULL); |
79 | ||
621032ad | 80 | ioc_exit_icq(icq); |
7e5a8794 TH |
81 | |
82 | /* | |
83 | * @icq->q might have gone away by the time RCU callback runs | |
84 | * making it impossible to determine icq_cache. Record it in @icq. | |
85 | */ | |
86 | icq->__rcu_icq_cache = et->icq_cache; | |
30a2da7b | 87 | icq->flags |= ICQ_DESTROYED; |
7e5a8794 TH |
88 | call_rcu(&icq->__rcu_head, icq_free_icq_rcu); |
89 | } | |
90 | ||
b2efa052 TH |
91 | /* |
92 | * Slow path for ioc release in put_io_context(). Performs double-lock | |
c5869807 | 93 | * dancing to unlink all icq's and then frees ioc. |
b2efa052 TH |
94 | */ |
95 | static void ioc_release_fn(struct work_struct *work) | |
86db1e29 | 96 | { |
b2efa052 TH |
97 | struct io_context *ioc = container_of(work, struct io_context, |
98 | release_work); | |
a43f085f | 99 | spin_lock_irq(&ioc->lock); |
b2efa052 | 100 | |
c5869807 TH |
101 | while (!hlist_empty(&ioc->icq_list)) { |
102 | struct io_cq *icq = hlist_entry(ioc->icq_list.first, | |
103 | struct io_cq, ioc_node); | |
2274b029 TH |
104 | struct request_queue *q = icq->q; |
105 | ||
0d945c1f | 106 | if (spin_trylock(&q->queue_lock)) { |
621032ad | 107 | ioc_destroy_icq(icq); |
0d945c1f | 108 | spin_unlock(&q->queue_lock); |
2274b029 | 109 | } else { |
ab96bbab JO |
110 | /* Make sure q and icq cannot be freed. */ |
111 | rcu_read_lock(); | |
112 | ||
113 | /* Re-acquire the locks in the correct order. */ | |
114 | spin_unlock(&ioc->lock); | |
115 | spin_lock(&q->queue_lock); | |
116 | spin_lock(&ioc->lock); | |
117 | ||
118 | /* | |
119 | * The icq may have been destroyed when the ioc lock | |
120 | * was released. | |
121 | */ | |
122 | if (!(icq->flags & ICQ_DESTROYED)) | |
123 | ioc_destroy_icq(icq); | |
124 | ||
125 | spin_unlock(&q->queue_lock); | |
126 | rcu_read_unlock(); | |
b2efa052 | 127 | } |
b2efa052 | 128 | } |
ffc4e759 | 129 | |
a43f085f | 130 | spin_unlock_irq(&ioc->lock); |
b2efa052 TH |
131 | |
132 | kmem_cache_free(iocontext_cachep, ioc); | |
86db1e29 JA |
133 | } |
134 | ||
42ec57a8 TH |
135 | /** |
136 | * put_io_context - put a reference of io_context | |
137 | * @ioc: io_context to put | |
138 | * | |
139 | * Decrement reference count of @ioc and release it if the count reaches | |
11a3122f | 140 | * zero. |
86db1e29 | 141 | */ |
11a3122f | 142 | void put_io_context(struct io_context *ioc) |
86db1e29 | 143 | { |
b2efa052 | 144 | unsigned long flags; |
ff8c1474 | 145 | bool free_ioc = false; |
b2efa052 | 146 | |
86db1e29 | 147 | if (ioc == NULL) |
42ec57a8 | 148 | return; |
86db1e29 | 149 | |
42ec57a8 | 150 | BUG_ON(atomic_long_read(&ioc->refcount) <= 0); |
86db1e29 | 151 | |
b2efa052 | 152 | /* |
11a3122f TH |
153 | * Releasing ioc requires reverse order double locking and we may |
154 | * already be holding a queue_lock. Do it asynchronously from wq. | |
b2efa052 | 155 | */ |
11a3122f TH |
156 | if (atomic_long_dec_and_test(&ioc->refcount)) { |
157 | spin_lock_irqsave(&ioc->lock, flags); | |
158 | if (!hlist_empty(&ioc->icq_list)) | |
695588f9 VK |
159 | queue_work(system_power_efficient_wq, |
160 | &ioc->release_work); | |
ff8c1474 XF |
161 | else |
162 | free_ioc = true; | |
11a3122f | 163 | spin_unlock_irqrestore(&ioc->lock, flags); |
b2efa052 | 164 | } |
ff8c1474 XF |
165 | |
166 | if (free_ioc) | |
167 | kmem_cache_free(iocontext_cachep, ioc); | |
86db1e29 JA |
168 | } |
169 | ||
f6e8d01b TH |
170 | /** |
171 | * put_io_context_active - put active reference on ioc | |
172 | * @ioc: ioc of interest | |
173 | * | |
174 | * Undo get_io_context_active(). If active reference reaches zero after | |
175 | * put, @ioc can never issue further IOs and ioscheds are notified. | |
176 | */ | |
177 | void put_io_context_active(struct io_context *ioc) | |
86db1e29 | 178 | { |
f6e8d01b | 179 | struct io_cq *icq; |
86db1e29 | 180 | |
f6e8d01b | 181 | if (!atomic_dec_and_test(&ioc->active_ref)) { |
621032ad TH |
182 | put_io_context(ioc); |
183 | return; | |
184 | } | |
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 | ||
208 | atomic_dec(&ioc->nr_tasks); | |
209 | put_io_context_active(ioc); | |
210 | } | |
211 | ||
7b36a718 JA |
212 | static void __ioc_clear_queue(struct list_head *icq_list) |
213 | { | |
214 | unsigned long flags; | |
215 | ||
30a2da7b | 216 | rcu_read_lock(); |
7b36a718 JA |
217 | while (!list_empty(icq_list)) { |
218 | struct io_cq *icq = list_entry(icq_list->next, | |
a1ce35fa | 219 | struct io_cq, q_node); |
7b36a718 JA |
220 | struct io_context *ioc = icq->ioc; |
221 | ||
222 | spin_lock_irqsave(&ioc->lock, flags); | |
30a2da7b ST |
223 | if (icq->flags & ICQ_DESTROYED) { |
224 | spin_unlock_irqrestore(&ioc->lock, flags); | |
225 | continue; | |
226 | } | |
7b36a718 JA |
227 | ioc_destroy_icq(icq); |
228 | spin_unlock_irqrestore(&ioc->lock, flags); | |
229 | } | |
30a2da7b | 230 | rcu_read_unlock(); |
7b36a718 JA |
231 | } |
232 | ||
7e5a8794 TH |
233 | /** |
234 | * ioc_clear_queue - break any ioc association with the specified queue | |
235 | * @q: request_queue being cleared | |
236 | * | |
7b36a718 | 237 | * Walk @q->icq_list and exit all io_cq's. |
7e5a8794 TH |
238 | */ |
239 | void ioc_clear_queue(struct request_queue *q) | |
240 | { | |
7b36a718 | 241 | LIST_HEAD(icq_list); |
7e5a8794 | 242 | |
0d945c1f | 243 | spin_lock_irq(&q->queue_lock); |
7b36a718 | 244 | list_splice_init(&q->icq_list, &icq_list); |
0d945c1f | 245 | spin_unlock_irq(&q->queue_lock); |
7e5a8794 | 246 | |
a1ce35fa | 247 | __ioc_clear_queue(&icq_list); |
7e5a8794 TH |
248 | } |
249 | ||
24acfc34 | 250 | int create_task_io_context(struct task_struct *task, gfp_t gfp_flags, int node) |
86db1e29 | 251 | { |
df415656 | 252 | struct io_context *ioc; |
3c9c708c | 253 | int ret; |
86db1e29 | 254 | |
42ec57a8 TH |
255 | ioc = kmem_cache_alloc_node(iocontext_cachep, gfp_flags | __GFP_ZERO, |
256 | node); | |
257 | if (unlikely(!ioc)) | |
24acfc34 | 258 | return -ENOMEM; |
42ec57a8 TH |
259 | |
260 | /* initialize */ | |
261 | atomic_long_set(&ioc->refcount, 1); | |
4638a83e | 262 | atomic_set(&ioc->nr_tasks, 1); |
f6e8d01b | 263 | atomic_set(&ioc->active_ref, 1); |
42ec57a8 | 264 | spin_lock_init(&ioc->lock); |
c137969b | 265 | INIT_RADIX_TREE(&ioc->icq_tree, GFP_ATOMIC); |
c5869807 | 266 | INIT_HLIST_HEAD(&ioc->icq_list); |
b2efa052 | 267 | INIT_WORK(&ioc->release_work, ioc_release_fn); |
86db1e29 | 268 | |
fd638368 TH |
269 | /* |
270 | * Try to install. ioc shouldn't be installed if someone else | |
271 | * already did or @task, which isn't %current, is exiting. Note | |
272 | * that we need to allow ioc creation on exiting %current as exit | |
273 | * path may issue IOs from e.g. exit_files(). The exit path is | |
274 | * responsible for not issuing IO after exit_io_context(). | |
275 | */ | |
6e736be7 | 276 | task_lock(task); |
fd638368 TH |
277 | if (!task->io_context && |
278 | (task == current || !(task->flags & PF_EXITING))) | |
6e736be7 | 279 | task->io_context = ioc; |
f2dbd76a | 280 | else |
6e736be7 | 281 | kmem_cache_free(iocontext_cachep, ioc); |
3c9c708c ED |
282 | |
283 | ret = task->io_context ? 0 : -EBUSY; | |
284 | ||
6e736be7 | 285 | task_unlock(task); |
24acfc34 | 286 | |
3c9c708c | 287 | return ret; |
86db1e29 | 288 | } |
86db1e29 | 289 | |
6e736be7 TH |
290 | /** |
291 | * get_task_io_context - get io_context of a task | |
292 | * @task: task of interest | |
293 | * @gfp_flags: allocation flags, used if allocation is necessary | |
294 | * @node: allocation node, used if allocation is necessary | |
295 | * | |
296 | * Return io_context of @task. If it doesn't exist, it is created with | |
297 | * @gfp_flags and @node. The returned io_context has its reference count | |
298 | * incremented. | |
86db1e29 | 299 | * |
6e736be7 | 300 | * This function always goes through task_lock() and it's better to use |
f2dbd76a | 301 | * %current->io_context + get_io_context() for %current. |
86db1e29 | 302 | */ |
6e736be7 TH |
303 | struct io_context *get_task_io_context(struct task_struct *task, |
304 | gfp_t gfp_flags, int node) | |
86db1e29 | 305 | { |
6e736be7 | 306 | struct io_context *ioc; |
86db1e29 | 307 | |
d0164adc | 308 | might_sleep_if(gfpflags_allow_blocking(gfp_flags)); |
6e736be7 | 309 | |
f2dbd76a TH |
310 | do { |
311 | task_lock(task); | |
312 | ioc = task->io_context; | |
313 | if (likely(ioc)) { | |
314 | get_io_context(ioc); | |
315 | task_unlock(task); | |
316 | return ioc; | |
317 | } | |
6e736be7 | 318 | task_unlock(task); |
24acfc34 | 319 | } while (!create_task_io_context(task, gfp_flags, node)); |
6e736be7 | 320 | |
f2dbd76a | 321 | return NULL; |
86db1e29 | 322 | } |
86db1e29 | 323 | |
47fdd4ca TH |
324 | /** |
325 | * ioc_lookup_icq - lookup io_cq from ioc | |
326 | * @ioc: the associated io_context | |
327 | * @q: the associated request_queue | |
328 | * | |
329 | * Look up io_cq associated with @ioc - @q pair from @ioc. Must be called | |
330 | * with @q->queue_lock held. | |
331 | */ | |
332 | struct io_cq *ioc_lookup_icq(struct io_context *ioc, struct request_queue *q) | |
333 | { | |
334 | struct io_cq *icq; | |
335 | ||
0d945c1f | 336 | lockdep_assert_held(&q->queue_lock); |
47fdd4ca TH |
337 | |
338 | /* | |
339 | * icq's are indexed from @ioc using radix tree and hint pointer, | |
340 | * both of which are protected with RCU. All removals are done | |
341 | * holding both q and ioc locks, and we're holding q lock - if we | |
342 | * find a icq which points to us, it's guaranteed to be valid. | |
343 | */ | |
344 | rcu_read_lock(); | |
345 | icq = rcu_dereference(ioc->icq_hint); | |
346 | if (icq && icq->q == q) | |
347 | goto out; | |
348 | ||
349 | icq = radix_tree_lookup(&ioc->icq_tree, q->id); | |
350 | if (icq && icq->q == q) | |
351 | rcu_assign_pointer(ioc->icq_hint, icq); /* allowed to race */ | |
352 | else | |
353 | icq = NULL; | |
354 | out: | |
355 | rcu_read_unlock(); | |
356 | return icq; | |
357 | } | |
358 | EXPORT_SYMBOL(ioc_lookup_icq); | |
359 | ||
f1f8cc94 TH |
360 | /** |
361 | * ioc_create_icq - create and link io_cq | |
24acfc34 | 362 | * @ioc: io_context of interest |
f1f8cc94 TH |
363 | * @q: request_queue of interest |
364 | * @gfp_mask: allocation mask | |
365 | * | |
24acfc34 TH |
366 | * Make sure io_cq linking @ioc and @q exists. If icq doesn't exist, they |
367 | * will be created using @gfp_mask. | |
f1f8cc94 TH |
368 | * |
369 | * The caller is responsible for ensuring @ioc won't go away and @q is | |
370 | * alive and will stay alive until this function returns. | |
371 | */ | |
24acfc34 TH |
372 | struct io_cq *ioc_create_icq(struct io_context *ioc, struct request_queue *q, |
373 | gfp_t gfp_mask) | |
f1f8cc94 TH |
374 | { |
375 | struct elevator_type *et = q->elevator->type; | |
f1f8cc94 TH |
376 | struct io_cq *icq; |
377 | ||
378 | /* allocate stuff */ | |
f1f8cc94 TH |
379 | icq = kmem_cache_alloc_node(et->icq_cache, gfp_mask | __GFP_ZERO, |
380 | q->node); | |
381 | if (!icq) | |
382 | return NULL; | |
383 | ||
5e4c0d97 | 384 | if (radix_tree_maybe_preload(gfp_mask) < 0) { |
f1f8cc94 TH |
385 | kmem_cache_free(et->icq_cache, icq); |
386 | return NULL; | |
387 | } | |
388 | ||
389 | icq->ioc = ioc; | |
390 | icq->q = q; | |
391 | INIT_LIST_HEAD(&icq->q_node); | |
392 | INIT_HLIST_NODE(&icq->ioc_node); | |
393 | ||
394 | /* lock both q and ioc and try to link @icq */ | |
0d945c1f | 395 | spin_lock_irq(&q->queue_lock); |
f1f8cc94 TH |
396 | spin_lock(&ioc->lock); |
397 | ||
398 | if (likely(!radix_tree_insert(&ioc->icq_tree, q->id, icq))) { | |
399 | hlist_add_head(&icq->ioc_node, &ioc->icq_list); | |
400 | list_add(&icq->q_node, &q->icq_list); | |
f9cd4bfe JA |
401 | if (et->ops.init_icq) |
402 | et->ops.init_icq(icq); | |
f1f8cc94 TH |
403 | } else { |
404 | kmem_cache_free(et->icq_cache, icq); | |
405 | icq = ioc_lookup_icq(ioc, q); | |
406 | if (!icq) | |
407 | printk(KERN_ERR "cfq: icq link failed!\n"); | |
408 | } | |
409 | ||
410 | spin_unlock(&ioc->lock); | |
0d945c1f | 411 | spin_unlock_irq(&q->queue_lock); |
f1f8cc94 TH |
412 | radix_tree_preload_end(); |
413 | return icq; | |
414 | } | |
415 | ||
13341598 | 416 | static int __init blk_ioc_init(void) |
86db1e29 JA |
417 | { |
418 | iocontext_cachep = kmem_cache_create("blkdev_ioc", | |
419 | sizeof(struct io_context), 0, SLAB_PANIC, NULL); | |
420 | return 0; | |
421 | } | |
422 | subsys_initcall(blk_ioc_init); |