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Commit | Line | Data |
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86db1e29 JA |
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> | |
5a0e3ad6 | 9 | #include <linux/slab.h> |
86db1e29 JA |
10 | |
11 | #include "blk.h" | |
12 | ||
13 | /* | |
14 | * For io context allocations | |
15 | */ | |
16 | static struct kmem_cache *iocontext_cachep; | |
17 | ||
6e736be7 TH |
18 | /** |
19 | * get_io_context - increment reference count to io_context | |
20 | * @ioc: io_context to get | |
21 | * | |
22 | * Increment reference count to @ioc. | |
23 | */ | |
24 | void get_io_context(struct io_context *ioc) | |
25 | { | |
26 | BUG_ON(atomic_long_read(&ioc->refcount) <= 0); | |
27 | atomic_long_inc(&ioc->refcount); | |
28 | } | |
29 | EXPORT_SYMBOL(get_io_context); | |
30 | ||
7e5a8794 TH |
31 | static void icq_free_icq_rcu(struct rcu_head *head) |
32 | { | |
33 | struct io_cq *icq = container_of(head, struct io_cq, __rcu_head); | |
34 | ||
35 | kmem_cache_free(icq->__rcu_icq_cache, icq); | |
36 | } | |
37 | ||
3d492c2e | 38 | /* |
7b36a718 JA |
39 | * Exit an icq. Called with ioc locked for blk-mq, and with both ioc |
40 | * and queue locked for legacy. | |
3d492c2e | 41 | */ |
7e5a8794 | 42 | static void ioc_exit_icq(struct io_cq *icq) |
621032ad TH |
43 | { |
44 | struct elevator_type *et = icq->q->elevator->type; | |
45 | ||
46 | if (icq->flags & ICQ_EXITED) | |
47 | return; | |
48 | ||
bd166ef1 JA |
49 | if (et->uses_mq && et->ops.mq.exit_icq) |
50 | et->ops.mq.exit_icq(icq); | |
51 | else if (!et->uses_mq && et->ops.sq.elevator_exit_icq_fn) | |
c51ca6cf | 52 | et->ops.sq.elevator_exit_icq_fn(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; | |
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); | |
d8c66c5d | 99 | unsigned long flags; |
b2efa052 | 100 | |
d8c66c5d TH |
101 | /* |
102 | * Exiting icq may call into put_io_context() through elevator | |
103 | * which will trigger lockdep warning. The ioc's are guaranteed to | |
104 | * be different, use a different locking subclass here. Use | |
105 | * irqsave variant as there's no spin_lock_irq_nested(). | |
106 | */ | |
107 | spin_lock_irqsave_nested(&ioc->lock, flags, 1); | |
b2efa052 | 108 | |
c5869807 TH |
109 | while (!hlist_empty(&ioc->icq_list)) { |
110 | struct io_cq *icq = hlist_entry(ioc->icq_list.first, | |
111 | struct io_cq, ioc_node); | |
2274b029 TH |
112 | struct request_queue *q = icq->q; |
113 | ||
114 | if (spin_trylock(q->queue_lock)) { | |
621032ad | 115 | ioc_destroy_icq(icq); |
2274b029 TH |
116 | spin_unlock(q->queue_lock); |
117 | } else { | |
118 | spin_unlock_irqrestore(&ioc->lock, flags); | |
119 | cpu_relax(); | |
120 | spin_lock_irqsave_nested(&ioc->lock, flags, 1); | |
b2efa052 | 121 | } |
b2efa052 | 122 | } |
ffc4e759 | 123 | |
2274b029 | 124 | spin_unlock_irqrestore(&ioc->lock, flags); |
b2efa052 TH |
125 | |
126 | kmem_cache_free(iocontext_cachep, ioc); | |
86db1e29 JA |
127 | } |
128 | ||
42ec57a8 TH |
129 | /** |
130 | * put_io_context - put a reference of io_context | |
131 | * @ioc: io_context to put | |
132 | * | |
133 | * Decrement reference count of @ioc and release it if the count reaches | |
11a3122f | 134 | * zero. |
86db1e29 | 135 | */ |
11a3122f | 136 | void put_io_context(struct io_context *ioc) |
86db1e29 | 137 | { |
b2efa052 | 138 | unsigned long flags; |
ff8c1474 | 139 | bool free_ioc = false; |
b2efa052 | 140 | |
86db1e29 | 141 | if (ioc == NULL) |
42ec57a8 | 142 | return; |
86db1e29 | 143 | |
42ec57a8 | 144 | BUG_ON(atomic_long_read(&ioc->refcount) <= 0); |
86db1e29 | 145 | |
b2efa052 | 146 | /* |
11a3122f TH |
147 | * Releasing ioc requires reverse order double locking and we may |
148 | * already be holding a queue_lock. Do it asynchronously from wq. | |
b2efa052 | 149 | */ |
11a3122f TH |
150 | if (atomic_long_dec_and_test(&ioc->refcount)) { |
151 | spin_lock_irqsave(&ioc->lock, flags); | |
152 | if (!hlist_empty(&ioc->icq_list)) | |
695588f9 VK |
153 | queue_work(system_power_efficient_wq, |
154 | &ioc->release_work); | |
ff8c1474 XF |
155 | else |
156 | free_ioc = true; | |
11a3122f | 157 | spin_unlock_irqrestore(&ioc->lock, flags); |
b2efa052 | 158 | } |
ff8c1474 XF |
159 | |
160 | if (free_ioc) | |
161 | kmem_cache_free(iocontext_cachep, ioc); | |
86db1e29 | 162 | } |
b2efa052 | 163 | EXPORT_SYMBOL(put_io_context); |
86db1e29 | 164 | |
f6e8d01b TH |
165 | /** |
166 | * put_io_context_active - put active reference on ioc | |
167 | * @ioc: ioc of interest | |
168 | * | |
169 | * Undo get_io_context_active(). If active reference reaches zero after | |
170 | * put, @ioc can never issue further IOs and ioscheds are notified. | |
171 | */ | |
172 | void put_io_context_active(struct io_context *ioc) | |
86db1e29 | 173 | { |
3d492c2e | 174 | struct elevator_type *et; |
621032ad | 175 | unsigned long flags; |
f6e8d01b | 176 | struct io_cq *icq; |
86db1e29 | 177 | |
f6e8d01b | 178 | if (!atomic_dec_and_test(&ioc->active_ref)) { |
621032ad TH |
179 | put_io_context(ioc); |
180 | return; | |
181 | } | |
182 | ||
183 | /* | |
184 | * Need ioc lock to walk icq_list and q lock to exit icq. Perform | |
185 | * reverse double locking. Read comment in ioc_release_fn() for | |
186 | * explanation on the nested locking annotation. | |
187 | */ | |
188 | retry: | |
189 | spin_lock_irqsave_nested(&ioc->lock, flags, 1); | |
b67bfe0d | 190 | hlist_for_each_entry(icq, &ioc->icq_list, ioc_node) { |
621032ad TH |
191 | if (icq->flags & ICQ_EXITED) |
192 | continue; | |
3d492c2e OS |
193 | |
194 | et = icq->q->elevator->type; | |
195 | if (et->uses_mq) { | |
621032ad | 196 | ioc_exit_icq(icq); |
621032ad | 197 | } else { |
3d492c2e OS |
198 | if (spin_trylock(icq->q->queue_lock)) { |
199 | ioc_exit_icq(icq); | |
200 | spin_unlock(icq->q->queue_lock); | |
201 | } else { | |
202 | spin_unlock_irqrestore(&ioc->lock, flags); | |
203 | cpu_relax(); | |
204 | goto retry; | |
205 | } | |
621032ad TH |
206 | } |
207 | } | |
208 | spin_unlock_irqrestore(&ioc->lock, flags); | |
209 | ||
11a3122f | 210 | put_io_context(ioc); |
86db1e29 JA |
211 | } |
212 | ||
f6e8d01b TH |
213 | /* Called by the exiting task */ |
214 | void 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 | atomic_dec(&ioc->nr_tasks); | |
224 | put_io_context_active(ioc); | |
225 | } | |
226 | ||
7b36a718 JA |
227 | static void __ioc_clear_queue(struct list_head *icq_list) |
228 | { | |
229 | unsigned long flags; | |
230 | ||
231 | while (!list_empty(icq_list)) { | |
232 | struct io_cq *icq = list_entry(icq_list->next, | |
233 | struct io_cq, q_node); | |
234 | struct io_context *ioc = icq->ioc; | |
235 | ||
236 | spin_lock_irqsave(&ioc->lock, flags); | |
237 | ioc_destroy_icq(icq); | |
238 | spin_unlock_irqrestore(&ioc->lock, flags); | |
239 | } | |
240 | } | |
241 | ||
7e5a8794 TH |
242 | /** |
243 | * ioc_clear_queue - break any ioc association with the specified queue | |
244 | * @q: request_queue being cleared | |
245 | * | |
7b36a718 | 246 | * Walk @q->icq_list and exit all io_cq's. |
7e5a8794 TH |
247 | */ |
248 | void ioc_clear_queue(struct request_queue *q) | |
249 | { | |
7b36a718 | 250 | LIST_HEAD(icq_list); |
7e5a8794 | 251 | |
7b36a718 JA |
252 | spin_lock_irq(q->queue_lock); |
253 | list_splice_init(&q->icq_list, &icq_list); | |
7e5a8794 | 254 | |
7b36a718 JA |
255 | if (q->mq_ops) { |
256 | spin_unlock_irq(q->queue_lock); | |
257 | __ioc_clear_queue(&icq_list); | |
258 | } else { | |
259 | __ioc_clear_queue(&icq_list); | |
260 | spin_unlock_irq(q->queue_lock); | |
7e5a8794 TH |
261 | } |
262 | } | |
263 | ||
24acfc34 | 264 | int create_task_io_context(struct task_struct *task, gfp_t gfp_flags, int node) |
86db1e29 | 265 | { |
df415656 | 266 | struct io_context *ioc; |
3c9c708c | 267 | int ret; |
86db1e29 | 268 | |
42ec57a8 TH |
269 | ioc = kmem_cache_alloc_node(iocontext_cachep, gfp_flags | __GFP_ZERO, |
270 | node); | |
271 | if (unlikely(!ioc)) | |
24acfc34 | 272 | return -ENOMEM; |
42ec57a8 TH |
273 | |
274 | /* initialize */ | |
275 | atomic_long_set(&ioc->refcount, 1); | |
4638a83e | 276 | atomic_set(&ioc->nr_tasks, 1); |
f6e8d01b | 277 | atomic_set(&ioc->active_ref, 1); |
42ec57a8 | 278 | spin_lock_init(&ioc->lock); |
c5869807 TH |
279 | INIT_RADIX_TREE(&ioc->icq_tree, GFP_ATOMIC | __GFP_HIGH); |
280 | INIT_HLIST_HEAD(&ioc->icq_list); | |
b2efa052 | 281 | INIT_WORK(&ioc->release_work, ioc_release_fn); |
86db1e29 | 282 | |
fd638368 TH |
283 | /* |
284 | * Try to install. ioc shouldn't be installed if someone else | |
285 | * already did or @task, which isn't %current, is exiting. Note | |
286 | * that we need to allow ioc creation on exiting %current as exit | |
287 | * path may issue IOs from e.g. exit_files(). The exit path is | |
288 | * responsible for not issuing IO after exit_io_context(). | |
289 | */ | |
6e736be7 | 290 | task_lock(task); |
fd638368 TH |
291 | if (!task->io_context && |
292 | (task == current || !(task->flags & PF_EXITING))) | |
6e736be7 | 293 | task->io_context = ioc; |
f2dbd76a | 294 | else |
6e736be7 | 295 | kmem_cache_free(iocontext_cachep, ioc); |
3c9c708c ED |
296 | |
297 | ret = task->io_context ? 0 : -EBUSY; | |
298 | ||
6e736be7 | 299 | task_unlock(task); |
24acfc34 | 300 | |
3c9c708c | 301 | return ret; |
86db1e29 | 302 | } |
86db1e29 | 303 | |
6e736be7 TH |
304 | /** |
305 | * get_task_io_context - get io_context of a task | |
306 | * @task: task of interest | |
307 | * @gfp_flags: allocation flags, used if allocation is necessary | |
308 | * @node: allocation node, used if allocation is necessary | |
309 | * | |
310 | * Return io_context of @task. If it doesn't exist, it is created with | |
311 | * @gfp_flags and @node. The returned io_context has its reference count | |
312 | * incremented. | |
86db1e29 | 313 | * |
6e736be7 | 314 | * This function always goes through task_lock() and it's better to use |
f2dbd76a | 315 | * %current->io_context + get_io_context() for %current. |
86db1e29 | 316 | */ |
6e736be7 TH |
317 | struct io_context *get_task_io_context(struct task_struct *task, |
318 | gfp_t gfp_flags, int node) | |
86db1e29 | 319 | { |
6e736be7 | 320 | struct io_context *ioc; |
86db1e29 | 321 | |
d0164adc | 322 | might_sleep_if(gfpflags_allow_blocking(gfp_flags)); |
6e736be7 | 323 | |
f2dbd76a TH |
324 | do { |
325 | task_lock(task); | |
326 | ioc = task->io_context; | |
327 | if (likely(ioc)) { | |
328 | get_io_context(ioc); | |
329 | task_unlock(task); | |
330 | return ioc; | |
331 | } | |
6e736be7 | 332 | task_unlock(task); |
24acfc34 | 333 | } while (!create_task_io_context(task, gfp_flags, node)); |
6e736be7 | 334 | |
f2dbd76a | 335 | return NULL; |
86db1e29 | 336 | } |
6e736be7 | 337 | EXPORT_SYMBOL(get_task_io_context); |
86db1e29 | 338 | |
47fdd4ca TH |
339 | /** |
340 | * ioc_lookup_icq - lookup io_cq from ioc | |
341 | * @ioc: the associated io_context | |
342 | * @q: the associated request_queue | |
343 | * | |
344 | * Look up io_cq associated with @ioc - @q pair from @ioc. Must be called | |
345 | * with @q->queue_lock held. | |
346 | */ | |
347 | struct io_cq *ioc_lookup_icq(struct io_context *ioc, struct request_queue *q) | |
348 | { | |
349 | struct io_cq *icq; | |
350 | ||
351 | lockdep_assert_held(q->queue_lock); | |
352 | ||
353 | /* | |
354 | * icq's are indexed from @ioc using radix tree and hint pointer, | |
355 | * both of which are protected with RCU. All removals are done | |
356 | * holding both q and ioc locks, and we're holding q lock - if we | |
357 | * find a icq which points to us, it's guaranteed to be valid. | |
358 | */ | |
359 | rcu_read_lock(); | |
360 | icq = rcu_dereference(ioc->icq_hint); | |
361 | if (icq && icq->q == q) | |
362 | goto out; | |
363 | ||
364 | icq = radix_tree_lookup(&ioc->icq_tree, q->id); | |
365 | if (icq && icq->q == q) | |
366 | rcu_assign_pointer(ioc->icq_hint, icq); /* allowed to race */ | |
367 | else | |
368 | icq = NULL; | |
369 | out: | |
370 | rcu_read_unlock(); | |
371 | return icq; | |
372 | } | |
373 | EXPORT_SYMBOL(ioc_lookup_icq); | |
374 | ||
f1f8cc94 TH |
375 | /** |
376 | * ioc_create_icq - create and link io_cq | |
24acfc34 | 377 | * @ioc: io_context of interest |
f1f8cc94 TH |
378 | * @q: request_queue of interest |
379 | * @gfp_mask: allocation mask | |
380 | * | |
24acfc34 TH |
381 | * Make sure io_cq linking @ioc and @q exists. If icq doesn't exist, they |
382 | * will be created using @gfp_mask. | |
f1f8cc94 TH |
383 | * |
384 | * The caller is responsible for ensuring @ioc won't go away and @q is | |
385 | * alive and will stay alive until this function returns. | |
386 | */ | |
24acfc34 TH |
387 | struct io_cq *ioc_create_icq(struct io_context *ioc, struct request_queue *q, |
388 | gfp_t gfp_mask) | |
f1f8cc94 TH |
389 | { |
390 | struct elevator_type *et = q->elevator->type; | |
f1f8cc94 TH |
391 | struct io_cq *icq; |
392 | ||
393 | /* allocate stuff */ | |
f1f8cc94 TH |
394 | icq = kmem_cache_alloc_node(et->icq_cache, gfp_mask | __GFP_ZERO, |
395 | q->node); | |
396 | if (!icq) | |
397 | return NULL; | |
398 | ||
5e4c0d97 | 399 | if (radix_tree_maybe_preload(gfp_mask) < 0) { |
f1f8cc94 TH |
400 | kmem_cache_free(et->icq_cache, icq); |
401 | return NULL; | |
402 | } | |
403 | ||
404 | icq->ioc = ioc; | |
405 | icq->q = q; | |
406 | INIT_LIST_HEAD(&icq->q_node); | |
407 | INIT_HLIST_NODE(&icq->ioc_node); | |
408 | ||
409 | /* lock both q and ioc and try to link @icq */ | |
410 | spin_lock_irq(q->queue_lock); | |
411 | spin_lock(&ioc->lock); | |
412 | ||
413 | if (likely(!radix_tree_insert(&ioc->icq_tree, q->id, icq))) { | |
414 | hlist_add_head(&icq->ioc_node, &ioc->icq_list); | |
415 | list_add(&icq->q_node, &q->icq_list); | |
bd166ef1 JA |
416 | if (et->uses_mq && et->ops.mq.init_icq) |
417 | et->ops.mq.init_icq(icq); | |
418 | else if (!et->uses_mq && et->ops.sq.elevator_init_icq_fn) | |
c51ca6cf | 419 | et->ops.sq.elevator_init_icq_fn(icq); |
f1f8cc94 TH |
420 | } else { |
421 | kmem_cache_free(et->icq_cache, icq); | |
422 | icq = ioc_lookup_icq(ioc, q); | |
423 | if (!icq) | |
424 | printk(KERN_ERR "cfq: icq link failed!\n"); | |
425 | } | |
426 | ||
427 | spin_unlock(&ioc->lock); | |
428 | spin_unlock_irq(q->queue_lock); | |
429 | radix_tree_preload_end(); | |
430 | return icq; | |
431 | } | |
432 | ||
13341598 | 433 | static int __init blk_ioc_init(void) |
86db1e29 JA |
434 | { |
435 | iocontext_cachep = kmem_cache_create("blkdev_ioc", | |
436 | sizeof(struct io_context), 0, SLAB_PANIC, NULL); | |
437 | return 0; | |
438 | } | |
439 | subsys_initcall(blk_ioc_init); |