Commit | Line | Data |
---|---|---|
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 | ||
39 | /* | |
40 | * Exit and free an icq. Called with both ioc and q locked. | |
41 | */ | |
42 | static void ioc_exit_icq(struct io_cq *icq) | |
43 | { | |
44 | struct io_context *ioc = icq->ioc; | |
45 | struct request_queue *q = icq->q; | |
46 | struct elevator_type *et = q->elevator->type; | |
47 | ||
48 | lockdep_assert_held(&ioc->lock); | |
49 | lockdep_assert_held(q->queue_lock); | |
50 | ||
51 | radix_tree_delete(&ioc->icq_tree, icq->q->id); | |
52 | hlist_del_init(&icq->ioc_node); | |
53 | list_del_init(&icq->q_node); | |
54 | ||
55 | /* | |
56 | * Both setting lookup hint to and clearing it from @icq are done | |
57 | * under queue_lock. If it's not pointing to @icq now, it never | |
58 | * will. Hint assignment itself can race safely. | |
59 | */ | |
60 | if (rcu_dereference_raw(ioc->icq_hint) == icq) | |
61 | rcu_assign_pointer(ioc->icq_hint, NULL); | |
62 | ||
11a3122f | 63 | if (et->ops.elevator_exit_icq_fn) |
7e5a8794 | 64 | et->ops.elevator_exit_icq_fn(icq); |
7e5a8794 TH |
65 | |
66 | /* | |
67 | * @icq->q might have gone away by the time RCU callback runs | |
68 | * making it impossible to determine icq_cache. Record it in @icq. | |
69 | */ | |
70 | icq->__rcu_icq_cache = et->icq_cache; | |
71 | call_rcu(&icq->__rcu_head, icq_free_icq_rcu); | |
72 | } | |
73 | ||
b2efa052 TH |
74 | /* |
75 | * Slow path for ioc release in put_io_context(). Performs double-lock | |
c5869807 | 76 | * dancing to unlink all icq's and then frees ioc. |
b2efa052 TH |
77 | */ |
78 | static void ioc_release_fn(struct work_struct *work) | |
86db1e29 | 79 | { |
b2efa052 TH |
80 | struct io_context *ioc = container_of(work, struct io_context, |
81 | release_work); | |
82 | struct request_queue *last_q = NULL; | |
d8c66c5d | 83 | unsigned long flags; |
b2efa052 | 84 | |
d8c66c5d TH |
85 | /* |
86 | * Exiting icq may call into put_io_context() through elevator | |
87 | * which will trigger lockdep warning. The ioc's are guaranteed to | |
88 | * be different, use a different locking subclass here. Use | |
89 | * irqsave variant as there's no spin_lock_irq_nested(). | |
90 | */ | |
91 | spin_lock_irqsave_nested(&ioc->lock, flags, 1); | |
b2efa052 | 92 | |
c5869807 TH |
93 | while (!hlist_empty(&ioc->icq_list)) { |
94 | struct io_cq *icq = hlist_entry(ioc->icq_list.first, | |
95 | struct io_cq, ioc_node); | |
96 | struct request_queue *this_q = icq->q; | |
b2efa052 TH |
97 | |
98 | if (this_q != last_q) { | |
99 | /* | |
100 | * Need to switch to @this_q. Once we release | |
101 | * @ioc->lock, it can go away along with @cic. | |
102 | * Hold on to it. | |
103 | */ | |
104 | __blk_get_queue(this_q); | |
105 | ||
106 | /* | |
107 | * blk_put_queue() might sleep thanks to kobject | |
108 | * idiocy. Always release both locks, put and | |
109 | * restart. | |
110 | */ | |
111 | if (last_q) { | |
112 | spin_unlock(last_q->queue_lock); | |
d8c66c5d | 113 | spin_unlock_irqrestore(&ioc->lock, flags); |
b2efa052 TH |
114 | blk_put_queue(last_q); |
115 | } else { | |
d8c66c5d | 116 | spin_unlock_irqrestore(&ioc->lock, flags); |
b2efa052 TH |
117 | } |
118 | ||
119 | last_q = this_q; | |
d8c66c5d TH |
120 | spin_lock_irqsave(this_q->queue_lock, flags); |
121 | spin_lock_nested(&ioc->lock, 1); | |
b2efa052 TH |
122 | continue; |
123 | } | |
7e5a8794 | 124 | ioc_exit_icq(icq); |
b2efa052 | 125 | } |
ffc4e759 | 126 | |
b2efa052 TH |
127 | if (last_q) { |
128 | spin_unlock(last_q->queue_lock); | |
d8c66c5d | 129 | spin_unlock_irqrestore(&ioc->lock, flags); |
b2efa052 TH |
130 | blk_put_queue(last_q); |
131 | } else { | |
d8c66c5d | 132 | spin_unlock_irqrestore(&ioc->lock, flags); |
ffc4e759 | 133 | } |
b2efa052 TH |
134 | |
135 | kmem_cache_free(iocontext_cachep, ioc); | |
86db1e29 JA |
136 | } |
137 | ||
42ec57a8 TH |
138 | /** |
139 | * put_io_context - put a reference of io_context | |
140 | * @ioc: io_context to put | |
141 | * | |
142 | * Decrement reference count of @ioc and release it if the count reaches | |
11a3122f | 143 | * zero. |
86db1e29 | 144 | */ |
11a3122f | 145 | void put_io_context(struct io_context *ioc) |
86db1e29 | 146 | { |
b2efa052 TH |
147 | unsigned long flags; |
148 | ||
86db1e29 | 149 | if (ioc == NULL) |
42ec57a8 | 150 | return; |
86db1e29 | 151 | |
42ec57a8 | 152 | BUG_ON(atomic_long_read(&ioc->refcount) <= 0); |
86db1e29 | 153 | |
b2efa052 | 154 | /* |
11a3122f TH |
155 | * Releasing ioc requires reverse order double locking and we may |
156 | * already be holding a queue_lock. Do it asynchronously from wq. | |
b2efa052 | 157 | */ |
11a3122f TH |
158 | if (atomic_long_dec_and_test(&ioc->refcount)) { |
159 | spin_lock_irqsave(&ioc->lock, flags); | |
160 | if (!hlist_empty(&ioc->icq_list)) | |
161 | schedule_work(&ioc->release_work); | |
162 | spin_unlock_irqrestore(&ioc->lock, flags); | |
b2efa052 | 163 | } |
86db1e29 | 164 | } |
b2efa052 | 165 | EXPORT_SYMBOL(put_io_context); |
86db1e29 | 166 | |
27667c99 | 167 | /* Called by the exiting task */ |
b69f2292 | 168 | void exit_io_context(struct task_struct *task) |
86db1e29 JA |
169 | { |
170 | struct io_context *ioc; | |
171 | ||
b69f2292 LR |
172 | task_lock(task); |
173 | ioc = task->io_context; | |
174 | task->io_context = NULL; | |
175 | task_unlock(task); | |
86db1e29 | 176 | |
b2efa052 | 177 | atomic_dec(&ioc->nr_tasks); |
11a3122f | 178 | put_io_context(ioc); |
86db1e29 JA |
179 | } |
180 | ||
7e5a8794 TH |
181 | /** |
182 | * ioc_clear_queue - break any ioc association with the specified queue | |
183 | * @q: request_queue being cleared | |
184 | * | |
185 | * Walk @q->icq_list and exit all io_cq's. Must be called with @q locked. | |
186 | */ | |
187 | void ioc_clear_queue(struct request_queue *q) | |
188 | { | |
189 | lockdep_assert_held(q->queue_lock); | |
190 | ||
191 | while (!list_empty(&q->icq_list)) { | |
192 | struct io_cq *icq = list_entry(q->icq_list.next, | |
193 | struct io_cq, q_node); | |
194 | struct io_context *ioc = icq->ioc; | |
195 | ||
196 | spin_lock(&ioc->lock); | |
197 | ioc_exit_icq(icq); | |
198 | spin_unlock(&ioc->lock); | |
199 | } | |
200 | } | |
201 | ||
f2dbd76a TH |
202 | void create_io_context_slowpath(struct task_struct *task, gfp_t gfp_flags, |
203 | int node) | |
86db1e29 | 204 | { |
df415656 | 205 | struct io_context *ioc; |
86db1e29 | 206 | |
42ec57a8 TH |
207 | ioc = kmem_cache_alloc_node(iocontext_cachep, gfp_flags | __GFP_ZERO, |
208 | node); | |
209 | if (unlikely(!ioc)) | |
f2dbd76a | 210 | return; |
42ec57a8 TH |
211 | |
212 | /* initialize */ | |
213 | atomic_long_set(&ioc->refcount, 1); | |
214 | atomic_set(&ioc->nr_tasks, 1); | |
215 | spin_lock_init(&ioc->lock); | |
c5869807 TH |
216 | INIT_RADIX_TREE(&ioc->icq_tree, GFP_ATOMIC | __GFP_HIGH); |
217 | INIT_HLIST_HEAD(&ioc->icq_list); | |
b2efa052 | 218 | INIT_WORK(&ioc->release_work, ioc_release_fn); |
86db1e29 | 219 | |
fd638368 TH |
220 | /* |
221 | * Try to install. ioc shouldn't be installed if someone else | |
222 | * already did or @task, which isn't %current, is exiting. Note | |
223 | * that we need to allow ioc creation on exiting %current as exit | |
224 | * path may issue IOs from e.g. exit_files(). The exit path is | |
225 | * responsible for not issuing IO after exit_io_context(). | |
226 | */ | |
6e736be7 | 227 | task_lock(task); |
fd638368 TH |
228 | if (!task->io_context && |
229 | (task == current || !(task->flags & PF_EXITING))) | |
6e736be7 | 230 | task->io_context = ioc; |
f2dbd76a | 231 | else |
6e736be7 | 232 | kmem_cache_free(iocontext_cachep, ioc); |
6e736be7 | 233 | task_unlock(task); |
86db1e29 | 234 | } |
86db1e29 | 235 | |
6e736be7 TH |
236 | /** |
237 | * get_task_io_context - get io_context of a task | |
238 | * @task: task of interest | |
239 | * @gfp_flags: allocation flags, used if allocation is necessary | |
240 | * @node: allocation node, used if allocation is necessary | |
241 | * | |
242 | * Return io_context of @task. If it doesn't exist, it is created with | |
243 | * @gfp_flags and @node. The returned io_context has its reference count | |
244 | * incremented. | |
86db1e29 | 245 | * |
6e736be7 | 246 | * This function always goes through task_lock() and it's better to use |
f2dbd76a | 247 | * %current->io_context + get_io_context() for %current. |
86db1e29 | 248 | */ |
6e736be7 TH |
249 | struct io_context *get_task_io_context(struct task_struct *task, |
250 | gfp_t gfp_flags, int node) | |
86db1e29 | 251 | { |
6e736be7 | 252 | struct io_context *ioc; |
86db1e29 | 253 | |
6e736be7 TH |
254 | might_sleep_if(gfp_flags & __GFP_WAIT); |
255 | ||
f2dbd76a TH |
256 | do { |
257 | task_lock(task); | |
258 | ioc = task->io_context; | |
259 | if (likely(ioc)) { | |
260 | get_io_context(ioc); | |
261 | task_unlock(task); | |
262 | return ioc; | |
263 | } | |
6e736be7 | 264 | task_unlock(task); |
f2dbd76a | 265 | } while (create_io_context(task, gfp_flags, node)); |
6e736be7 | 266 | |
f2dbd76a | 267 | return NULL; |
86db1e29 | 268 | } |
6e736be7 | 269 | EXPORT_SYMBOL(get_task_io_context); |
86db1e29 | 270 | |
47fdd4ca TH |
271 | /** |
272 | * ioc_lookup_icq - lookup io_cq from ioc | |
273 | * @ioc: the associated io_context | |
274 | * @q: the associated request_queue | |
275 | * | |
276 | * Look up io_cq associated with @ioc - @q pair from @ioc. Must be called | |
277 | * with @q->queue_lock held. | |
278 | */ | |
279 | struct io_cq *ioc_lookup_icq(struct io_context *ioc, struct request_queue *q) | |
280 | { | |
281 | struct io_cq *icq; | |
282 | ||
283 | lockdep_assert_held(q->queue_lock); | |
284 | ||
285 | /* | |
286 | * icq's are indexed from @ioc using radix tree and hint pointer, | |
287 | * both of which are protected with RCU. All removals are done | |
288 | * holding both q and ioc locks, and we're holding q lock - if we | |
289 | * find a icq which points to us, it's guaranteed to be valid. | |
290 | */ | |
291 | rcu_read_lock(); | |
292 | icq = rcu_dereference(ioc->icq_hint); | |
293 | if (icq && icq->q == q) | |
294 | goto out; | |
295 | ||
296 | icq = radix_tree_lookup(&ioc->icq_tree, q->id); | |
297 | if (icq && icq->q == q) | |
298 | rcu_assign_pointer(ioc->icq_hint, icq); /* allowed to race */ | |
299 | else | |
300 | icq = NULL; | |
301 | out: | |
302 | rcu_read_unlock(); | |
303 | return icq; | |
304 | } | |
305 | EXPORT_SYMBOL(ioc_lookup_icq); | |
306 | ||
f1f8cc94 TH |
307 | /** |
308 | * ioc_create_icq - create and link io_cq | |
309 | * @q: request_queue of interest | |
310 | * @gfp_mask: allocation mask | |
311 | * | |
312 | * Make sure io_cq linking %current->io_context and @q exists. If either | |
313 | * io_context and/or icq don't exist, they will be created using @gfp_mask. | |
314 | * | |
315 | * The caller is responsible for ensuring @ioc won't go away and @q is | |
316 | * alive and will stay alive until this function returns. | |
317 | */ | |
318 | struct io_cq *ioc_create_icq(struct request_queue *q, gfp_t gfp_mask) | |
319 | { | |
320 | struct elevator_type *et = q->elevator->type; | |
321 | struct io_context *ioc; | |
322 | struct io_cq *icq; | |
323 | ||
324 | /* allocate stuff */ | |
325 | ioc = create_io_context(current, gfp_mask, q->node); | |
326 | if (!ioc) | |
327 | return NULL; | |
328 | ||
329 | icq = kmem_cache_alloc_node(et->icq_cache, gfp_mask | __GFP_ZERO, | |
330 | q->node); | |
331 | if (!icq) | |
332 | return NULL; | |
333 | ||
334 | if (radix_tree_preload(gfp_mask) < 0) { | |
335 | kmem_cache_free(et->icq_cache, icq); | |
336 | return NULL; | |
337 | } | |
338 | ||
339 | icq->ioc = ioc; | |
340 | icq->q = q; | |
341 | INIT_LIST_HEAD(&icq->q_node); | |
342 | INIT_HLIST_NODE(&icq->ioc_node); | |
343 | ||
344 | /* lock both q and ioc and try to link @icq */ | |
345 | spin_lock_irq(q->queue_lock); | |
346 | spin_lock(&ioc->lock); | |
347 | ||
348 | if (likely(!radix_tree_insert(&ioc->icq_tree, q->id, icq))) { | |
349 | hlist_add_head(&icq->ioc_node, &ioc->icq_list); | |
350 | list_add(&icq->q_node, &q->icq_list); | |
351 | if (et->ops.elevator_init_icq_fn) | |
352 | et->ops.elevator_init_icq_fn(icq); | |
353 | } else { | |
354 | kmem_cache_free(et->icq_cache, icq); | |
355 | icq = ioc_lookup_icq(ioc, q); | |
356 | if (!icq) | |
357 | printk(KERN_ERR "cfq: icq link failed!\n"); | |
358 | } | |
359 | ||
360 | spin_unlock(&ioc->lock); | |
361 | spin_unlock_irq(q->queue_lock); | |
362 | radix_tree_preload_end(); | |
363 | return icq; | |
364 | } | |
365 | ||
dc86900e TH |
366 | void ioc_set_changed(struct io_context *ioc, int which) |
367 | { | |
c5869807 | 368 | struct io_cq *icq; |
dc86900e TH |
369 | struct hlist_node *n; |
370 | ||
c5869807 TH |
371 | hlist_for_each_entry(icq, n, &ioc->icq_list, ioc_node) |
372 | set_bit(which, &icq->changed); | |
dc86900e TH |
373 | } |
374 | ||
375 | /** | |
376 | * ioc_ioprio_changed - notify ioprio change | |
377 | * @ioc: io_context of interest | |
378 | * @ioprio: new ioprio | |
379 | * | |
c5869807 TH |
380 | * @ioc's ioprio has changed to @ioprio. Set %ICQ_IOPRIO_CHANGED for all |
381 | * icq's. iosched is responsible for checking the bit and applying it on | |
dc86900e TH |
382 | * request issue path. |
383 | */ | |
384 | void ioc_ioprio_changed(struct io_context *ioc, int ioprio) | |
385 | { | |
386 | unsigned long flags; | |
387 | ||
388 | spin_lock_irqsave(&ioc->lock, flags); | |
389 | ioc->ioprio = ioprio; | |
c5869807 | 390 | ioc_set_changed(ioc, ICQ_IOPRIO_CHANGED); |
dc86900e TH |
391 | spin_unlock_irqrestore(&ioc->lock, flags); |
392 | } | |
393 | ||
394 | /** | |
395 | * ioc_cgroup_changed - notify cgroup change | |
396 | * @ioc: io_context of interest | |
397 | * | |
c5869807 | 398 | * @ioc's cgroup has changed. Set %ICQ_CGROUP_CHANGED for all icq's. |
dc86900e TH |
399 | * iosched is responsible for checking the bit and applying it on request |
400 | * issue path. | |
401 | */ | |
402 | void ioc_cgroup_changed(struct io_context *ioc) | |
403 | { | |
404 | unsigned long flags; | |
405 | ||
406 | spin_lock_irqsave(&ioc->lock, flags); | |
c5869807 | 407 | ioc_set_changed(ioc, ICQ_CGROUP_CHANGED); |
dc86900e TH |
408 | spin_unlock_irqrestore(&ioc->lock, flags); |
409 | } | |
64c42998 | 410 | EXPORT_SYMBOL(ioc_cgroup_changed); |
dc86900e | 411 | |
13341598 | 412 | static int __init blk_ioc_init(void) |
86db1e29 JA |
413 | { |
414 | iocontext_cachep = kmem_cache_create("blkdev_ioc", | |
415 | sizeof(struct io_context), 0, SLAB_PANIC, NULL); | |
416 | return 0; | |
417 | } | |
418 | subsys_initcall(blk_ioc_init); |