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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> | |
9 | #include <linux/bootmem.h> /* for max_pfn/max_low_pfn */ | |
5a0e3ad6 | 10 | #include <linux/slab.h> |
86db1e29 JA |
11 | |
12 | #include "blk.h" | |
13 | ||
14 | /* | |
15 | * For io context allocations | |
16 | */ | |
17 | static struct kmem_cache *iocontext_cachep; | |
18 | ||
6e736be7 TH |
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 | */ | |
25 | void get_io_context(struct io_context *ioc) | |
26 | { | |
27 | BUG_ON(atomic_long_read(&ioc->refcount) <= 0); | |
28 | atomic_long_inc(&ioc->refcount); | |
29 | } | |
30 | EXPORT_SYMBOL(get_io_context); | |
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 | ||
621032ad | 39 | /* Exit an icq. Called with both ioc and q locked. */ |
7e5a8794 | 40 | static void ioc_exit_icq(struct io_cq *icq) |
621032ad TH |
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. */ | |
54 | static void ioc_destroy_icq(struct io_cq *icq) | |
7e5a8794 TH |
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 | ||
621032ad | 75 | ioc_exit_icq(icq); |
7e5a8794 TH |
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 | ||
b2efa052 TH |
85 | /* |
86 | * Slow path for ioc release in put_io_context(). Performs double-lock | |
c5869807 | 87 | * dancing to unlink all icq's and then frees ioc. |
b2efa052 TH |
88 | */ |
89 | static void ioc_release_fn(struct work_struct *work) | |
86db1e29 | 90 | { |
b2efa052 TH |
91 | struct io_context *ioc = container_of(work, struct io_context, |
92 | release_work); | |
d8c66c5d | 93 | unsigned long flags; |
b2efa052 | 94 | |
d8c66c5d TH |
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); | |
b2efa052 | 102 | |
c5869807 TH |
103 | while (!hlist_empty(&ioc->icq_list)) { |
104 | struct io_cq *icq = hlist_entry(ioc->icq_list.first, | |
105 | struct io_cq, ioc_node); | |
2274b029 TH |
106 | struct request_queue *q = icq->q; |
107 | ||
108 | if (spin_trylock(q->queue_lock)) { | |
621032ad | 109 | ioc_destroy_icq(icq); |
2274b029 TH |
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); | |
b2efa052 | 115 | } |
b2efa052 | 116 | } |
ffc4e759 | 117 | |
2274b029 | 118 | spin_unlock_irqrestore(&ioc->lock, flags); |
b2efa052 TH |
119 | |
120 | kmem_cache_free(iocontext_cachep, ioc); | |
86db1e29 JA |
121 | } |
122 | ||
42ec57a8 TH |
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 | |
11a3122f | 128 | * zero. |
86db1e29 | 129 | */ |
11a3122f | 130 | void put_io_context(struct io_context *ioc) |
86db1e29 | 131 | { |
b2efa052 TH |
132 | unsigned long flags; |
133 | ||
86db1e29 | 134 | if (ioc == NULL) |
42ec57a8 | 135 | return; |
86db1e29 | 136 | |
42ec57a8 | 137 | BUG_ON(atomic_long_read(&ioc->refcount) <= 0); |
86db1e29 | 138 | |
b2efa052 | 139 | /* |
11a3122f TH |
140 | * Releasing ioc requires reverse order double locking and we may |
141 | * already be holding a queue_lock. Do it asynchronously from wq. | |
b2efa052 | 142 | */ |
11a3122f TH |
143 | if (atomic_long_dec_and_test(&ioc->refcount)) { |
144 | spin_lock_irqsave(&ioc->lock, flags); | |
145 | if (!hlist_empty(&ioc->icq_list)) | |
146 | schedule_work(&ioc->release_work); | |
147 | spin_unlock_irqrestore(&ioc->lock, flags); | |
b2efa052 | 148 | } |
86db1e29 | 149 | } |
b2efa052 | 150 | EXPORT_SYMBOL(put_io_context); |
86db1e29 | 151 | |
27667c99 | 152 | /* Called by the exiting task */ |
b69f2292 | 153 | void exit_io_context(struct task_struct *task) |
86db1e29 JA |
154 | { |
155 | struct io_context *ioc; | |
621032ad TH |
156 | struct io_cq *icq; |
157 | struct hlist_node *n; | |
158 | unsigned long flags; | |
86db1e29 | 159 | |
b69f2292 LR |
160 | task_lock(task); |
161 | ioc = task->io_context; | |
162 | task->io_context = NULL; | |
163 | task_unlock(task); | |
86db1e29 | 164 | |
621032ad TH |
165 | if (!atomic_dec_and_test(&ioc->nr_tasks)) { |
166 | put_io_context(ioc); | |
167 | return; | |
168 | } | |
169 | ||
170 | /* | |
171 | * Need ioc lock to walk icq_list and q lock to exit icq. Perform | |
172 | * reverse double locking. Read comment in ioc_release_fn() for | |
173 | * explanation on the nested locking annotation. | |
174 | */ | |
175 | retry: | |
176 | spin_lock_irqsave_nested(&ioc->lock, flags, 1); | |
177 | hlist_for_each_entry(icq, n, &ioc->icq_list, ioc_node) { | |
178 | if (icq->flags & ICQ_EXITED) | |
179 | continue; | |
180 | if (spin_trylock(icq->q->queue_lock)) { | |
181 | ioc_exit_icq(icq); | |
182 | spin_unlock(icq->q->queue_lock); | |
183 | } else { | |
184 | spin_unlock_irqrestore(&ioc->lock, flags); | |
185 | cpu_relax(); | |
186 | goto retry; | |
187 | } | |
188 | } | |
189 | spin_unlock_irqrestore(&ioc->lock, flags); | |
190 | ||
11a3122f | 191 | put_io_context(ioc); |
86db1e29 JA |
192 | } |
193 | ||
7e5a8794 TH |
194 | /** |
195 | * ioc_clear_queue - break any ioc association with the specified queue | |
196 | * @q: request_queue being cleared | |
197 | * | |
198 | * Walk @q->icq_list and exit all io_cq's. Must be called with @q locked. | |
199 | */ | |
200 | void ioc_clear_queue(struct request_queue *q) | |
201 | { | |
202 | lockdep_assert_held(q->queue_lock); | |
203 | ||
204 | while (!list_empty(&q->icq_list)) { | |
205 | struct io_cq *icq = list_entry(q->icq_list.next, | |
206 | struct io_cq, q_node); | |
207 | struct io_context *ioc = icq->ioc; | |
208 | ||
209 | spin_lock(&ioc->lock); | |
621032ad | 210 | ioc_destroy_icq(icq); |
7e5a8794 TH |
211 | spin_unlock(&ioc->lock); |
212 | } | |
213 | } | |
214 | ||
f2dbd76a TH |
215 | void create_io_context_slowpath(struct task_struct *task, gfp_t gfp_flags, |
216 | int node) | |
86db1e29 | 217 | { |
df415656 | 218 | struct io_context *ioc; |
86db1e29 | 219 | |
42ec57a8 TH |
220 | ioc = kmem_cache_alloc_node(iocontext_cachep, gfp_flags | __GFP_ZERO, |
221 | node); | |
222 | if (unlikely(!ioc)) | |
f2dbd76a | 223 | return; |
42ec57a8 TH |
224 | |
225 | /* initialize */ | |
226 | atomic_long_set(&ioc->refcount, 1); | |
227 | atomic_set(&ioc->nr_tasks, 1); | |
228 | spin_lock_init(&ioc->lock); | |
c5869807 TH |
229 | INIT_RADIX_TREE(&ioc->icq_tree, GFP_ATOMIC | __GFP_HIGH); |
230 | INIT_HLIST_HEAD(&ioc->icq_list); | |
b2efa052 | 231 | INIT_WORK(&ioc->release_work, ioc_release_fn); |
86db1e29 | 232 | |
fd638368 TH |
233 | /* |
234 | * Try to install. ioc shouldn't be installed if someone else | |
235 | * already did or @task, which isn't %current, is exiting. Note | |
236 | * that we need to allow ioc creation on exiting %current as exit | |
237 | * path may issue IOs from e.g. exit_files(). The exit path is | |
238 | * responsible for not issuing IO after exit_io_context(). | |
239 | */ | |
6e736be7 | 240 | task_lock(task); |
fd638368 TH |
241 | if (!task->io_context && |
242 | (task == current || !(task->flags & PF_EXITING))) | |
6e736be7 | 243 | task->io_context = ioc; |
f2dbd76a | 244 | else |
6e736be7 | 245 | kmem_cache_free(iocontext_cachep, ioc); |
6e736be7 | 246 | task_unlock(task); |
86db1e29 | 247 | } |
86db1e29 | 248 | |
6e736be7 TH |
249 | /** |
250 | * get_task_io_context - get io_context of a task | |
251 | * @task: task of interest | |
252 | * @gfp_flags: allocation flags, used if allocation is necessary | |
253 | * @node: allocation node, used if allocation is necessary | |
254 | * | |
255 | * Return io_context of @task. If it doesn't exist, it is created with | |
256 | * @gfp_flags and @node. The returned io_context has its reference count | |
257 | * incremented. | |
86db1e29 | 258 | * |
6e736be7 | 259 | * This function always goes through task_lock() and it's better to use |
f2dbd76a | 260 | * %current->io_context + get_io_context() for %current. |
86db1e29 | 261 | */ |
6e736be7 TH |
262 | struct io_context *get_task_io_context(struct task_struct *task, |
263 | gfp_t gfp_flags, int node) | |
86db1e29 | 264 | { |
6e736be7 | 265 | struct io_context *ioc; |
86db1e29 | 266 | |
6e736be7 TH |
267 | might_sleep_if(gfp_flags & __GFP_WAIT); |
268 | ||
f2dbd76a TH |
269 | do { |
270 | task_lock(task); | |
271 | ioc = task->io_context; | |
272 | if (likely(ioc)) { | |
273 | get_io_context(ioc); | |
274 | task_unlock(task); | |
275 | return ioc; | |
276 | } | |
6e736be7 | 277 | task_unlock(task); |
f2dbd76a | 278 | } while (create_io_context(task, gfp_flags, node)); |
6e736be7 | 279 | |
f2dbd76a | 280 | return NULL; |
86db1e29 | 281 | } |
6e736be7 | 282 | EXPORT_SYMBOL(get_task_io_context); |
86db1e29 | 283 | |
47fdd4ca TH |
284 | /** |
285 | * ioc_lookup_icq - lookup io_cq from ioc | |
286 | * @ioc: the associated io_context | |
287 | * @q: the associated request_queue | |
288 | * | |
289 | * Look up io_cq associated with @ioc - @q pair from @ioc. Must be called | |
290 | * with @q->queue_lock held. | |
291 | */ | |
292 | struct io_cq *ioc_lookup_icq(struct io_context *ioc, struct request_queue *q) | |
293 | { | |
294 | struct io_cq *icq; | |
295 | ||
296 | lockdep_assert_held(q->queue_lock); | |
297 | ||
298 | /* | |
299 | * icq's are indexed from @ioc using radix tree and hint pointer, | |
300 | * both of which are protected with RCU. All removals are done | |
301 | * holding both q and ioc locks, and we're holding q lock - if we | |
302 | * find a icq which points to us, it's guaranteed to be valid. | |
303 | */ | |
304 | rcu_read_lock(); | |
305 | icq = rcu_dereference(ioc->icq_hint); | |
306 | if (icq && icq->q == q) | |
307 | goto out; | |
308 | ||
309 | icq = radix_tree_lookup(&ioc->icq_tree, q->id); | |
310 | if (icq && icq->q == q) | |
311 | rcu_assign_pointer(ioc->icq_hint, icq); /* allowed to race */ | |
312 | else | |
313 | icq = NULL; | |
314 | out: | |
315 | rcu_read_unlock(); | |
316 | return icq; | |
317 | } | |
318 | EXPORT_SYMBOL(ioc_lookup_icq); | |
319 | ||
f1f8cc94 TH |
320 | /** |
321 | * ioc_create_icq - create and link io_cq | |
322 | * @q: request_queue of interest | |
323 | * @gfp_mask: allocation mask | |
324 | * | |
325 | * Make sure io_cq linking %current->io_context and @q exists. If either | |
326 | * io_context and/or icq don't exist, they will be created using @gfp_mask. | |
327 | * | |
328 | * The caller is responsible for ensuring @ioc won't go away and @q is | |
329 | * alive and will stay alive until this function returns. | |
330 | */ | |
331 | struct io_cq *ioc_create_icq(struct request_queue *q, gfp_t gfp_mask) | |
332 | { | |
333 | struct elevator_type *et = q->elevator->type; | |
334 | struct io_context *ioc; | |
335 | struct io_cq *icq; | |
336 | ||
337 | /* allocate stuff */ | |
338 | ioc = create_io_context(current, gfp_mask, q->node); | |
339 | if (!ioc) | |
340 | return NULL; | |
341 | ||
342 | icq = kmem_cache_alloc_node(et->icq_cache, gfp_mask | __GFP_ZERO, | |
343 | q->node); | |
344 | if (!icq) | |
345 | return NULL; | |
346 | ||
347 | if (radix_tree_preload(gfp_mask) < 0) { | |
348 | kmem_cache_free(et->icq_cache, icq); | |
349 | return NULL; | |
350 | } | |
351 | ||
352 | icq->ioc = ioc; | |
353 | icq->q = q; | |
354 | INIT_LIST_HEAD(&icq->q_node); | |
355 | INIT_HLIST_NODE(&icq->ioc_node); | |
356 | ||
357 | /* lock both q and ioc and try to link @icq */ | |
358 | spin_lock_irq(q->queue_lock); | |
359 | spin_lock(&ioc->lock); | |
360 | ||
361 | if (likely(!radix_tree_insert(&ioc->icq_tree, q->id, icq))) { | |
362 | hlist_add_head(&icq->ioc_node, &ioc->icq_list); | |
363 | list_add(&icq->q_node, &q->icq_list); | |
364 | if (et->ops.elevator_init_icq_fn) | |
365 | et->ops.elevator_init_icq_fn(icq); | |
366 | } else { | |
367 | kmem_cache_free(et->icq_cache, icq); | |
368 | icq = ioc_lookup_icq(ioc, q); | |
369 | if (!icq) | |
370 | printk(KERN_ERR "cfq: icq link failed!\n"); | |
371 | } | |
372 | ||
373 | spin_unlock(&ioc->lock); | |
374 | spin_unlock_irq(q->queue_lock); | |
375 | radix_tree_preload_end(); | |
376 | return icq; | |
377 | } | |
378 | ||
d705ae6b | 379 | void ioc_set_icq_flags(struct io_context *ioc, unsigned int flags) |
dc86900e | 380 | { |
c5869807 | 381 | struct io_cq *icq; |
dc86900e TH |
382 | struct hlist_node *n; |
383 | ||
c5869807 | 384 | hlist_for_each_entry(icq, n, &ioc->icq_list, ioc_node) |
d705ae6b | 385 | icq->flags |= flags; |
dc86900e TH |
386 | } |
387 | ||
388 | /** | |
389 | * ioc_ioprio_changed - notify ioprio change | |
390 | * @ioc: io_context of interest | |
391 | * @ioprio: new ioprio | |
392 | * | |
c5869807 TH |
393 | * @ioc's ioprio has changed to @ioprio. Set %ICQ_IOPRIO_CHANGED for all |
394 | * icq's. iosched is responsible for checking the bit and applying it on | |
dc86900e TH |
395 | * request issue path. |
396 | */ | |
397 | void ioc_ioprio_changed(struct io_context *ioc, int ioprio) | |
398 | { | |
399 | unsigned long flags; | |
400 | ||
401 | spin_lock_irqsave(&ioc->lock, flags); | |
402 | ioc->ioprio = ioprio; | |
d705ae6b | 403 | ioc_set_icq_flags(ioc, ICQ_IOPRIO_CHANGED); |
dc86900e TH |
404 | spin_unlock_irqrestore(&ioc->lock, flags); |
405 | } | |
406 | ||
407 | /** | |
408 | * ioc_cgroup_changed - notify cgroup change | |
409 | * @ioc: io_context of interest | |
410 | * | |
c5869807 | 411 | * @ioc's cgroup has changed. Set %ICQ_CGROUP_CHANGED for all icq's. |
dc86900e TH |
412 | * iosched is responsible for checking the bit and applying it on request |
413 | * issue path. | |
414 | */ | |
415 | void ioc_cgroup_changed(struct io_context *ioc) | |
416 | { | |
417 | unsigned long flags; | |
418 | ||
419 | spin_lock_irqsave(&ioc->lock, flags); | |
d705ae6b | 420 | ioc_set_icq_flags(ioc, ICQ_CGROUP_CHANGED); |
dc86900e TH |
421 | spin_unlock_irqrestore(&ioc->lock, flags); |
422 | } | |
64c42998 | 423 | EXPORT_SYMBOL(ioc_cgroup_changed); |
dc86900e | 424 | |
d705ae6b TH |
425 | /** |
426 | * icq_get_changed - fetch and clear icq changed mask | |
427 | * @icq: icq of interest | |
428 | * | |
429 | * Fetch and clear ICQ_*_CHANGED bits from @icq. Grabs and releases | |
430 | * @icq->ioc->lock. | |
431 | */ | |
432 | unsigned icq_get_changed(struct io_cq *icq) | |
433 | { | |
434 | unsigned int changed = 0; | |
435 | unsigned long flags; | |
436 | ||
437 | if (unlikely(icq->flags & ICQ_CHANGED_MASK)) { | |
438 | spin_lock_irqsave(&icq->ioc->lock, flags); | |
439 | changed = icq->flags & ICQ_CHANGED_MASK; | |
440 | icq->flags &= ~ICQ_CHANGED_MASK; | |
441 | spin_unlock_irqrestore(&icq->ioc->lock, flags); | |
442 | } | |
443 | return changed; | |
444 | } | |
445 | EXPORT_SYMBOL(icq_get_changed); | |
446 | ||
13341598 | 447 | static int __init blk_ioc_init(void) |
86db1e29 JA |
448 | { |
449 | iocontext_cachep = kmem_cache_create("blkdev_ioc", | |
450 | sizeof(struct io_context), 0, SLAB_PANIC, NULL); | |
451 | return 0; | |
452 | } | |
453 | subsys_initcall(blk_ioc_init); |