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; | |
87 | call_rcu(&icq->__rcu_head, icq_free_icq_rcu); | |
88 | } | |
89 | ||
b2efa052 TH |
90 | /* |
91 | * Slow path for ioc release in put_io_context(). Performs double-lock | |
c5869807 | 92 | * dancing to unlink all icq's and then frees ioc. |
b2efa052 TH |
93 | */ |
94 | static void ioc_release_fn(struct work_struct *work) | |
86db1e29 | 95 | { |
b2efa052 TH |
96 | struct io_context *ioc = container_of(work, struct io_context, |
97 | release_work); | |
d8c66c5d | 98 | unsigned long flags; |
b2efa052 | 99 | |
d8c66c5d TH |
100 | /* |
101 | * Exiting icq may call into put_io_context() through elevator | |
102 | * which will trigger lockdep warning. The ioc's are guaranteed to | |
103 | * be different, use a different locking subclass here. Use | |
104 | * irqsave variant as there's no spin_lock_irq_nested(). | |
105 | */ | |
106 | spin_lock_irqsave_nested(&ioc->lock, flags, 1); | |
b2efa052 | 107 | |
c5869807 TH |
108 | while (!hlist_empty(&ioc->icq_list)) { |
109 | struct io_cq *icq = hlist_entry(ioc->icq_list.first, | |
110 | struct io_cq, ioc_node); | |
2274b029 TH |
111 | struct request_queue *q = icq->q; |
112 | ||
0d945c1f | 113 | if (spin_trylock(&q->queue_lock)) { |
621032ad | 114 | ioc_destroy_icq(icq); |
0d945c1f | 115 | spin_unlock(&q->queue_lock); |
2274b029 TH |
116 | } else { |
117 | spin_unlock_irqrestore(&ioc->lock, flags); | |
118 | cpu_relax(); | |
119 | spin_lock_irqsave_nested(&ioc->lock, flags, 1); | |
b2efa052 | 120 | } |
b2efa052 | 121 | } |
ffc4e759 | 122 | |
2274b029 | 123 | spin_unlock_irqrestore(&ioc->lock, flags); |
b2efa052 TH |
124 | |
125 | kmem_cache_free(iocontext_cachep, ioc); | |
86db1e29 JA |
126 | } |
127 | ||
42ec57a8 TH |
128 | /** |
129 | * put_io_context - put a reference of io_context | |
130 | * @ioc: io_context to put | |
131 | * | |
132 | * Decrement reference count of @ioc and release it if the count reaches | |
11a3122f | 133 | * zero. |
86db1e29 | 134 | */ |
11a3122f | 135 | void put_io_context(struct io_context *ioc) |
86db1e29 | 136 | { |
b2efa052 | 137 | unsigned long flags; |
ff8c1474 | 138 | bool free_ioc = false; |
b2efa052 | 139 | |
86db1e29 | 140 | if (ioc == NULL) |
42ec57a8 | 141 | return; |
86db1e29 | 142 | |
42ec57a8 | 143 | BUG_ON(atomic_long_read(&ioc->refcount) <= 0); |
86db1e29 | 144 | |
b2efa052 | 145 | /* |
11a3122f TH |
146 | * Releasing ioc requires reverse order double locking and we may |
147 | * already be holding a queue_lock. Do it asynchronously from wq. | |
b2efa052 | 148 | */ |
11a3122f TH |
149 | if (atomic_long_dec_and_test(&ioc->refcount)) { |
150 | spin_lock_irqsave(&ioc->lock, flags); | |
151 | if (!hlist_empty(&ioc->icq_list)) | |
695588f9 VK |
152 | queue_work(system_power_efficient_wq, |
153 | &ioc->release_work); | |
ff8c1474 XF |
154 | else |
155 | free_ioc = true; | |
11a3122f | 156 | spin_unlock_irqrestore(&ioc->lock, flags); |
b2efa052 | 157 | } |
ff8c1474 XF |
158 | |
159 | if (free_ioc) | |
160 | kmem_cache_free(iocontext_cachep, ioc); | |
86db1e29 JA |
161 | } |
162 | ||
f6e8d01b TH |
163 | /** |
164 | * put_io_context_active - put active reference on ioc | |
165 | * @ioc: ioc of interest | |
166 | * | |
167 | * Undo get_io_context_active(). If active reference reaches zero after | |
168 | * put, @ioc can never issue further IOs and ioscheds are notified. | |
169 | */ | |
170 | void put_io_context_active(struct io_context *ioc) | |
86db1e29 | 171 | { |
621032ad | 172 | unsigned long flags; |
f6e8d01b | 173 | struct io_cq *icq; |
86db1e29 | 174 | |
f6e8d01b | 175 | if (!atomic_dec_and_test(&ioc->active_ref)) { |
621032ad TH |
176 | put_io_context(ioc); |
177 | return; | |
178 | } | |
179 | ||
180 | /* | |
181 | * Need ioc lock to walk icq_list and q lock to exit icq. Perform | |
182 | * reverse double locking. Read comment in ioc_release_fn() for | |
183 | * explanation on the nested locking annotation. | |
184 | */ | |
621032ad | 185 | spin_lock_irqsave_nested(&ioc->lock, flags, 1); |
b67bfe0d | 186 | hlist_for_each_entry(icq, &ioc->icq_list, ioc_node) { |
621032ad TH |
187 | if (icq->flags & ICQ_EXITED) |
188 | continue; | |
3d492c2e | 189 | |
a1ce35fa | 190 | ioc_exit_icq(icq); |
621032ad TH |
191 | } |
192 | spin_unlock_irqrestore(&ioc->lock, flags); | |
193 | ||
11a3122f | 194 | put_io_context(ioc); |
86db1e29 JA |
195 | } |
196 | ||
f6e8d01b TH |
197 | /* Called by the exiting task */ |
198 | void exit_io_context(struct task_struct *task) | |
199 | { | |
200 | struct io_context *ioc; | |
201 | ||
202 | task_lock(task); | |
203 | ioc = task->io_context; | |
204 | task->io_context = NULL; | |
205 | task_unlock(task); | |
206 | ||
207 | atomic_dec(&ioc->nr_tasks); | |
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 | ||
215 | while (!list_empty(icq_list)) { | |
216 | struct io_cq *icq = list_entry(icq_list->next, | |
a1ce35fa | 217 | struct io_cq, q_node); |
7b36a718 JA |
218 | struct io_context *ioc = icq->ioc; |
219 | ||
220 | spin_lock_irqsave(&ioc->lock, flags); | |
221 | ioc_destroy_icq(icq); | |
222 | spin_unlock_irqrestore(&ioc->lock, flags); | |
223 | } | |
224 | } | |
225 | ||
7e5a8794 TH |
226 | /** |
227 | * ioc_clear_queue - break any ioc association with the specified queue | |
228 | * @q: request_queue being cleared | |
229 | * | |
7b36a718 | 230 | * Walk @q->icq_list and exit all io_cq's. |
7e5a8794 TH |
231 | */ |
232 | void ioc_clear_queue(struct request_queue *q) | |
233 | { | |
7b36a718 | 234 | LIST_HEAD(icq_list); |
7e5a8794 | 235 | |
0d945c1f | 236 | spin_lock_irq(&q->queue_lock); |
7b36a718 | 237 | list_splice_init(&q->icq_list, &icq_list); |
0d945c1f | 238 | spin_unlock_irq(&q->queue_lock); |
7e5a8794 | 239 | |
a1ce35fa | 240 | __ioc_clear_queue(&icq_list); |
7e5a8794 TH |
241 | } |
242 | ||
24acfc34 | 243 | int create_task_io_context(struct task_struct *task, gfp_t gfp_flags, int node) |
86db1e29 | 244 | { |
df415656 | 245 | struct io_context *ioc; |
3c9c708c | 246 | int ret; |
86db1e29 | 247 | |
42ec57a8 TH |
248 | ioc = kmem_cache_alloc_node(iocontext_cachep, gfp_flags | __GFP_ZERO, |
249 | node); | |
250 | if (unlikely(!ioc)) | |
24acfc34 | 251 | return -ENOMEM; |
42ec57a8 TH |
252 | |
253 | /* initialize */ | |
254 | atomic_long_set(&ioc->refcount, 1); | |
4638a83e | 255 | atomic_set(&ioc->nr_tasks, 1); |
f6e8d01b | 256 | atomic_set(&ioc->active_ref, 1); |
42ec57a8 | 257 | spin_lock_init(&ioc->lock); |
c137969b | 258 | INIT_RADIX_TREE(&ioc->icq_tree, GFP_ATOMIC); |
c5869807 | 259 | INIT_HLIST_HEAD(&ioc->icq_list); |
b2efa052 | 260 | INIT_WORK(&ioc->release_work, ioc_release_fn); |
86db1e29 | 261 | |
fd638368 TH |
262 | /* |
263 | * Try to install. ioc shouldn't be installed if someone else | |
264 | * already did or @task, which isn't %current, is exiting. Note | |
265 | * that we need to allow ioc creation on exiting %current as exit | |
266 | * path may issue IOs from e.g. exit_files(). The exit path is | |
267 | * responsible for not issuing IO after exit_io_context(). | |
268 | */ | |
6e736be7 | 269 | task_lock(task); |
fd638368 TH |
270 | if (!task->io_context && |
271 | (task == current || !(task->flags & PF_EXITING))) | |
6e736be7 | 272 | task->io_context = ioc; |
f2dbd76a | 273 | else |
6e736be7 | 274 | kmem_cache_free(iocontext_cachep, ioc); |
3c9c708c ED |
275 | |
276 | ret = task->io_context ? 0 : -EBUSY; | |
277 | ||
6e736be7 | 278 | task_unlock(task); |
24acfc34 | 279 | |
3c9c708c | 280 | return ret; |
86db1e29 | 281 | } |
86db1e29 | 282 | |
6e736be7 TH |
283 | /** |
284 | * get_task_io_context - get io_context of a task | |
285 | * @task: task of interest | |
286 | * @gfp_flags: allocation flags, used if allocation is necessary | |
287 | * @node: allocation node, used if allocation is necessary | |
288 | * | |
289 | * Return io_context of @task. If it doesn't exist, it is created with | |
290 | * @gfp_flags and @node. The returned io_context has its reference count | |
291 | * incremented. | |
86db1e29 | 292 | * |
6e736be7 | 293 | * This function always goes through task_lock() and it's better to use |
f2dbd76a | 294 | * %current->io_context + get_io_context() for %current. |
86db1e29 | 295 | */ |
6e736be7 TH |
296 | struct io_context *get_task_io_context(struct task_struct *task, |
297 | gfp_t gfp_flags, int node) | |
86db1e29 | 298 | { |
6e736be7 | 299 | struct io_context *ioc; |
86db1e29 | 300 | |
d0164adc | 301 | might_sleep_if(gfpflags_allow_blocking(gfp_flags)); |
6e736be7 | 302 | |
f2dbd76a TH |
303 | do { |
304 | task_lock(task); | |
305 | ioc = task->io_context; | |
306 | if (likely(ioc)) { | |
307 | get_io_context(ioc); | |
308 | task_unlock(task); | |
309 | return ioc; | |
310 | } | |
6e736be7 | 311 | task_unlock(task); |
24acfc34 | 312 | } while (!create_task_io_context(task, gfp_flags, node)); |
6e736be7 | 313 | |
f2dbd76a | 314 | return NULL; |
86db1e29 | 315 | } |
86db1e29 | 316 | |
47fdd4ca TH |
317 | /** |
318 | * ioc_lookup_icq - lookup io_cq from ioc | |
319 | * @ioc: the associated io_context | |
320 | * @q: the associated request_queue | |
321 | * | |
322 | * Look up io_cq associated with @ioc - @q pair from @ioc. Must be called | |
323 | * with @q->queue_lock held. | |
324 | */ | |
325 | struct io_cq *ioc_lookup_icq(struct io_context *ioc, struct request_queue *q) | |
326 | { | |
327 | struct io_cq *icq; | |
328 | ||
0d945c1f | 329 | lockdep_assert_held(&q->queue_lock); |
47fdd4ca TH |
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; | |
347 | out: | |
348 | rcu_read_unlock(); | |
349 | return icq; | |
350 | } | |
351 | EXPORT_SYMBOL(ioc_lookup_icq); | |
352 | ||
f1f8cc94 TH |
353 | /** |
354 | * ioc_create_icq - create and link io_cq | |
24acfc34 | 355 | * @ioc: io_context of interest |
f1f8cc94 TH |
356 | * @q: request_queue of interest |
357 | * @gfp_mask: allocation mask | |
358 | * | |
24acfc34 TH |
359 | * Make sure io_cq linking @ioc and @q exists. If icq doesn't exist, they |
360 | * will be created using @gfp_mask. | |
f1f8cc94 TH |
361 | * |
362 | * The caller is responsible for ensuring @ioc won't go away and @q is | |
363 | * alive and will stay alive until this function returns. | |
364 | */ | |
24acfc34 TH |
365 | struct io_cq *ioc_create_icq(struct io_context *ioc, struct request_queue *q, |
366 | gfp_t gfp_mask) | |
f1f8cc94 TH |
367 | { |
368 | struct elevator_type *et = q->elevator->type; | |
f1f8cc94 TH |
369 | struct io_cq *icq; |
370 | ||
371 | /* allocate stuff */ | |
f1f8cc94 TH |
372 | icq = kmem_cache_alloc_node(et->icq_cache, gfp_mask | __GFP_ZERO, |
373 | q->node); | |
374 | if (!icq) | |
375 | return NULL; | |
376 | ||
5e4c0d97 | 377 | if (radix_tree_maybe_preload(gfp_mask) < 0) { |
f1f8cc94 TH |
378 | kmem_cache_free(et->icq_cache, icq); |
379 | return NULL; | |
380 | } | |
381 | ||
382 | icq->ioc = ioc; | |
383 | icq->q = q; | |
384 | INIT_LIST_HEAD(&icq->q_node); | |
385 | INIT_HLIST_NODE(&icq->ioc_node); | |
386 | ||
387 | /* lock both q and ioc and try to link @icq */ | |
0d945c1f | 388 | spin_lock_irq(&q->queue_lock); |
f1f8cc94 TH |
389 | spin_lock(&ioc->lock); |
390 | ||
391 | if (likely(!radix_tree_insert(&ioc->icq_tree, q->id, icq))) { | |
392 | hlist_add_head(&icq->ioc_node, &ioc->icq_list); | |
393 | list_add(&icq->q_node, &q->icq_list); | |
f9cd4bfe JA |
394 | if (et->ops.init_icq) |
395 | et->ops.init_icq(icq); | |
f1f8cc94 TH |
396 | } else { |
397 | kmem_cache_free(et->icq_cache, icq); | |
398 | icq = ioc_lookup_icq(ioc, q); | |
399 | if (!icq) | |
400 | printk(KERN_ERR "cfq: icq link failed!\n"); | |
401 | } | |
402 | ||
403 | spin_unlock(&ioc->lock); | |
0d945c1f | 404 | spin_unlock_irq(&q->queue_lock); |
f1f8cc94 TH |
405 | radix_tree_preload_end(); |
406 | return icq; | |
407 | } | |
408 | ||
13341598 | 409 | static int __init blk_ioc_init(void) |
86db1e29 JA |
410 | { |
411 | iocontext_cachep = kmem_cache_create("blkdev_ioc", | |
412 | sizeof(struct io_context), 0, SLAB_PANIC, NULL); | |
413 | return 0; | |
414 | } | |
415 | subsys_initcall(blk_ioc_init); |