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