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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 */
10#include <linux/slab.h>
11
12#include "blk.h"
13
14/*
15 * For io context allocations
16 */
17static struct kmem_cache *iocontext_cachep;
18
19static void cfq_dtor(struct io_context *ioc)
20{
21 if (!hlist_empty(&ioc->cic_list)) {
22 struct cfq_io_context *cic;
23
24 cic = hlist_entry(ioc->cic_list.first, struct cfq_io_context,
25 cic_list);
26 cic->dtor(ioc);
27 }
28}
29
30/*
31 * IO Context helper functions. put_io_context() returns 1 if there are no
32 * more users of this io context, 0 otherwise.
33 */
34int put_io_context(struct io_context *ioc)
35{
36 if (ioc == NULL)
37 return 1;
38
39 BUG_ON(atomic_long_read(&ioc->refcount) == 0);
40
41 if (atomic_long_dec_and_test(&ioc->refcount)) {
42 rcu_read_lock();
43 cfq_dtor(ioc);
44 rcu_read_unlock();
45
46 kmem_cache_free(iocontext_cachep, ioc);
47 return 1;
48 }
49 return 0;
50}
51EXPORT_SYMBOL(put_io_context);
52
53static void cfq_exit(struct io_context *ioc)
54{
55 rcu_read_lock();
56
57 if (!hlist_empty(&ioc->cic_list)) {
58 struct cfq_io_context *cic;
59
60 cic = hlist_entry(ioc->cic_list.first, struct cfq_io_context,
61 cic_list);
62 cic->exit(ioc);
63 }
64 rcu_read_unlock();
65}
66
67/* Called by the exiting task */
68void exit_io_context(struct task_struct *task)
69{
70 struct io_context *ioc;
71
72 task_lock(task);
73 ioc = task->io_context;
74 task->io_context = NULL;
75 task_unlock(task);
76
77 if (atomic_dec_and_test(&ioc->nr_tasks))
78 cfq_exit(ioc);
79
80 put_io_context(ioc);
81}
82
83struct io_context *alloc_io_context(gfp_t gfp_flags, int node)
84{
85 struct io_context *ioc;
86
87 ioc = kmem_cache_alloc_node(iocontext_cachep, gfp_flags, node);
88 if (ioc) {
89 atomic_long_set(&ioc->refcount, 1);
90 atomic_set(&ioc->nr_tasks, 1);
91 spin_lock_init(&ioc->lock);
92 ioc->ioprio_changed = 0;
93 ioc->ioprio = 0;
94 ioc->last_waited = 0; /* doesn't matter... */
95 ioc->nr_batch_requests = 0; /* because this is 0 */
96 INIT_RADIX_TREE(&ioc->radix_root, GFP_ATOMIC | __GFP_HIGH);
97 INIT_HLIST_HEAD(&ioc->cic_list);
98 ioc->ioc_data = NULL;
99#if defined(CONFIG_BLK_CGROUP) || defined(CONFIG_BLK_CGROUP_MODULE)
100 ioc->cgroup_changed = 0;
101#endif
102 }
103
104 return ioc;
105}
106
107/*
108 * If the current task has no IO context then create one and initialise it.
109 * Otherwise, return its existing IO context.
110 *
111 * This returned IO context doesn't have a specifically elevated refcount,
112 * but since the current task itself holds a reference, the context can be
113 * used in general code, so long as it stays within `current` context.
114 */
115struct io_context *current_io_context(gfp_t gfp_flags, int node)
116{
117 struct task_struct *tsk = current;
118 struct io_context *ret;
119
120 ret = tsk->io_context;
121 if (likely(ret))
122 return ret;
123
124 ret = alloc_io_context(gfp_flags, node);
125 if (ret) {
126 /* make sure set_task_ioprio() sees the settings above */
127 smp_wmb();
128 tsk->io_context = ret;
129 }
130
131 return ret;
132}
133
134/*
135 * If the current task has no IO context then create one and initialise it.
136 * If it does have a context, take a ref on it.
137 *
138 * This is always called in the context of the task which submitted the I/O.
139 */
140struct io_context *get_io_context(gfp_t gfp_flags, int node)
141{
142 struct io_context *ioc = NULL;
143
144 /*
145 * Check for unlikely race with exiting task. ioc ref count is
146 * zero when ioc is being detached.
147 */
148 do {
149 ioc = current_io_context(gfp_flags, node);
150 if (unlikely(!ioc))
151 break;
152 } while (!atomic_long_inc_not_zero(&ioc->refcount));
153
154 return ioc;
155}
156EXPORT_SYMBOL(get_io_context);
157
158static int __init blk_ioc_init(void)
159{
160 iocontext_cachep = kmem_cache_create("blkdev_ioc",
161 sizeof(struct io_context), 0, SLAB_PANIC, NULL);
162 return 0;
163}
164subsys_initcall(blk_ioc_init);
1// SPDX-License-Identifier: GPL-2.0
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>
10#include <linux/slab.h>
11#include <linux/security.h>
12#include <linux/sched/task.h>
13
14#include "blk.h"
15#include "blk-mq-sched.h"
16
17/*
18 * For io context allocations
19 */
20static struct kmem_cache *iocontext_cachep;
21
22#ifdef CONFIG_BLK_ICQ
23/**
24 * get_io_context - increment reference count to io_context
25 * @ioc: io_context to get
26 *
27 * Increment reference count to @ioc.
28 */
29static void get_io_context(struct io_context *ioc)
30{
31 BUG_ON(atomic_long_read(&ioc->refcount) <= 0);
32 atomic_long_inc(&ioc->refcount);
33}
34
35static void icq_free_icq_rcu(struct rcu_head *head)
36{
37 struct io_cq *icq = container_of(head, struct io_cq, __rcu_head);
38
39 kmem_cache_free(icq->__rcu_icq_cache, icq);
40}
41
42/*
43 * Exit an icq. Called with ioc locked for blk-mq, and with both ioc
44 * and queue locked for legacy.
45 */
46static void ioc_exit_icq(struct io_cq *icq)
47{
48 struct elevator_type *et = icq->q->elevator->type;
49
50 if (icq->flags & ICQ_EXITED)
51 return;
52
53 if (et->ops.exit_icq)
54 et->ops.exit_icq(icq);
55
56 icq->flags |= ICQ_EXITED;
57}
58
59static void ioc_exit_icqs(struct io_context *ioc)
60{
61 struct io_cq *icq;
62
63 spin_lock_irq(&ioc->lock);
64 hlist_for_each_entry(icq, &ioc->icq_list, ioc_node)
65 ioc_exit_icq(icq);
66 spin_unlock_irq(&ioc->lock);
67}
68
69/*
70 * Release an icq. Called with ioc locked for blk-mq, and with both ioc
71 * and queue locked for legacy.
72 */
73static void ioc_destroy_icq(struct io_cq *icq)
74{
75 struct io_context *ioc = icq->ioc;
76 struct request_queue *q = icq->q;
77 struct elevator_type *et = q->elevator->type;
78
79 lockdep_assert_held(&ioc->lock);
80 lockdep_assert_held(&q->queue_lock);
81
82 if (icq->flags & ICQ_DESTROYED)
83 return;
84
85 radix_tree_delete(&ioc->icq_tree, icq->q->id);
86 hlist_del_init(&icq->ioc_node);
87 list_del_init(&icq->q_node);
88
89 /*
90 * Both setting lookup hint to and clearing it from @icq are done
91 * under queue_lock. If it's not pointing to @icq now, it never
92 * will. Hint assignment itself can race safely.
93 */
94 if (rcu_access_pointer(ioc->icq_hint) == icq)
95 rcu_assign_pointer(ioc->icq_hint, NULL);
96
97 ioc_exit_icq(icq);
98
99 /*
100 * @icq->q might have gone away by the time RCU callback runs
101 * making it impossible to determine icq_cache. Record it in @icq.
102 */
103 icq->__rcu_icq_cache = et->icq_cache;
104 icq->flags |= ICQ_DESTROYED;
105 call_rcu(&icq->__rcu_head, icq_free_icq_rcu);
106}
107
108/*
109 * Slow path for ioc release in put_io_context(). Performs double-lock
110 * dancing to unlink all icq's and then frees ioc.
111 */
112static void ioc_release_fn(struct work_struct *work)
113{
114 struct io_context *ioc = container_of(work, struct io_context,
115 release_work);
116 spin_lock_irq(&ioc->lock);
117
118 while (!hlist_empty(&ioc->icq_list)) {
119 struct io_cq *icq = hlist_entry(ioc->icq_list.first,
120 struct io_cq, ioc_node);
121 struct request_queue *q = icq->q;
122
123 if (spin_trylock(&q->queue_lock)) {
124 ioc_destroy_icq(icq);
125 spin_unlock(&q->queue_lock);
126 } else {
127 /* Make sure q and icq cannot be freed. */
128 rcu_read_lock();
129
130 /* Re-acquire the locks in the correct order. */
131 spin_unlock(&ioc->lock);
132 spin_lock(&q->queue_lock);
133 spin_lock(&ioc->lock);
134
135 ioc_destroy_icq(icq);
136
137 spin_unlock(&q->queue_lock);
138 rcu_read_unlock();
139 }
140 }
141
142 spin_unlock_irq(&ioc->lock);
143
144 kmem_cache_free(iocontext_cachep, ioc);
145}
146
147/*
148 * Releasing icqs requires reverse order double locking and we may already be
149 * holding a queue_lock. Do it asynchronously from a workqueue.
150 */
151static bool ioc_delay_free(struct io_context *ioc)
152{
153 unsigned long flags;
154
155 spin_lock_irqsave(&ioc->lock, flags);
156 if (!hlist_empty(&ioc->icq_list)) {
157 queue_work(system_power_efficient_wq, &ioc->release_work);
158 spin_unlock_irqrestore(&ioc->lock, flags);
159 return true;
160 }
161 spin_unlock_irqrestore(&ioc->lock, flags);
162 return false;
163}
164
165/**
166 * ioc_clear_queue - break any ioc association with the specified queue
167 * @q: request_queue being cleared
168 *
169 * Walk @q->icq_list and exit all io_cq's.
170 */
171void ioc_clear_queue(struct request_queue *q)
172{
173 spin_lock_irq(&q->queue_lock);
174 while (!list_empty(&q->icq_list)) {
175 struct io_cq *icq =
176 list_first_entry(&q->icq_list, struct io_cq, q_node);
177
178 /*
179 * Other context won't hold ioc lock to wait for queue_lock, see
180 * details in ioc_release_fn().
181 */
182 spin_lock(&icq->ioc->lock);
183 ioc_destroy_icq(icq);
184 spin_unlock(&icq->ioc->lock);
185 }
186 spin_unlock_irq(&q->queue_lock);
187}
188#else /* CONFIG_BLK_ICQ */
189static inline void ioc_exit_icqs(struct io_context *ioc)
190{
191}
192static inline bool ioc_delay_free(struct io_context *ioc)
193{
194 return false;
195}
196#endif /* CONFIG_BLK_ICQ */
197
198/**
199 * put_io_context - put a reference of io_context
200 * @ioc: io_context to put
201 *
202 * Decrement reference count of @ioc and release it if the count reaches
203 * zero.
204 */
205void put_io_context(struct io_context *ioc)
206{
207 BUG_ON(atomic_long_read(&ioc->refcount) <= 0);
208 if (atomic_long_dec_and_test(&ioc->refcount) && !ioc_delay_free(ioc))
209 kmem_cache_free(iocontext_cachep, ioc);
210}
211EXPORT_SYMBOL_GPL(put_io_context);
212
213/* Called by the exiting task */
214void 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 if (atomic_dec_and_test(&ioc->active_ref)) {
224 ioc_exit_icqs(ioc);
225 put_io_context(ioc);
226 }
227}
228
229static struct io_context *alloc_io_context(gfp_t gfp_flags, int node)
230{
231 struct io_context *ioc;
232
233 ioc = kmem_cache_alloc_node(iocontext_cachep, gfp_flags | __GFP_ZERO,
234 node);
235 if (unlikely(!ioc))
236 return NULL;
237
238 atomic_long_set(&ioc->refcount, 1);
239 atomic_set(&ioc->active_ref, 1);
240#ifdef CONFIG_BLK_ICQ
241 spin_lock_init(&ioc->lock);
242 INIT_RADIX_TREE(&ioc->icq_tree, GFP_ATOMIC);
243 INIT_HLIST_HEAD(&ioc->icq_list);
244 INIT_WORK(&ioc->release_work, ioc_release_fn);
245#endif
246 ioc->ioprio = IOPRIO_DEFAULT;
247
248 return ioc;
249}
250
251int set_task_ioprio(struct task_struct *task, int ioprio)
252{
253 int err;
254 const struct cred *cred = current_cred(), *tcred;
255
256 rcu_read_lock();
257 tcred = __task_cred(task);
258 if (!uid_eq(tcred->uid, cred->euid) &&
259 !uid_eq(tcred->uid, cred->uid) && !capable(CAP_SYS_NICE)) {
260 rcu_read_unlock();
261 return -EPERM;
262 }
263 rcu_read_unlock();
264
265 err = security_task_setioprio(task, ioprio);
266 if (err)
267 return err;
268
269 task_lock(task);
270 if (unlikely(!task->io_context)) {
271 struct io_context *ioc;
272
273 task_unlock(task);
274
275 ioc = alloc_io_context(GFP_ATOMIC, NUMA_NO_NODE);
276 if (!ioc)
277 return -ENOMEM;
278
279 task_lock(task);
280 if (task->flags & PF_EXITING) {
281 kmem_cache_free(iocontext_cachep, ioc);
282 goto out;
283 }
284 if (task->io_context)
285 kmem_cache_free(iocontext_cachep, ioc);
286 else
287 task->io_context = ioc;
288 }
289 task->io_context->ioprio = ioprio;
290out:
291 task_unlock(task);
292 return 0;
293}
294EXPORT_SYMBOL_GPL(set_task_ioprio);
295
296int __copy_io(unsigned long clone_flags, struct task_struct *tsk)
297{
298 struct io_context *ioc = current->io_context;
299
300 /*
301 * Share io context with parent, if CLONE_IO is set
302 */
303 if (clone_flags & CLONE_IO) {
304 atomic_inc(&ioc->active_ref);
305 tsk->io_context = ioc;
306 } else if (ioprio_valid(ioc->ioprio)) {
307 tsk->io_context = alloc_io_context(GFP_KERNEL, NUMA_NO_NODE);
308 if (!tsk->io_context)
309 return -ENOMEM;
310 tsk->io_context->ioprio = ioc->ioprio;
311 }
312
313 return 0;
314}
315
316#ifdef CONFIG_BLK_ICQ
317/**
318 * ioc_lookup_icq - lookup io_cq from ioc
319 * @q: the associated request_queue
320 *
321 * Look up io_cq associated with @ioc - @q pair from @ioc. Must be called
322 * with @q->queue_lock held.
323 */
324struct io_cq *ioc_lookup_icq(struct request_queue *q)
325{
326 struct io_context *ioc = current->io_context;
327 struct io_cq *icq;
328
329 lockdep_assert_held(&q->queue_lock);
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;
347out:
348 rcu_read_unlock();
349 return icq;
350}
351EXPORT_SYMBOL(ioc_lookup_icq);
352
353/**
354 * ioc_create_icq - create and link io_cq
355 * @q: request_queue of interest
356 *
357 * Make sure io_cq linking @ioc and @q exists. If icq doesn't exist, they
358 * will be created using @gfp_mask.
359 *
360 * The caller is responsible for ensuring @ioc won't go away and @q is
361 * alive and will stay alive until this function returns.
362 */
363static struct io_cq *ioc_create_icq(struct request_queue *q)
364{
365 struct io_context *ioc = current->io_context;
366 struct elevator_type *et = q->elevator->type;
367 struct io_cq *icq;
368
369 /* allocate stuff */
370 icq = kmem_cache_alloc_node(et->icq_cache, GFP_ATOMIC | __GFP_ZERO,
371 q->node);
372 if (!icq)
373 return NULL;
374
375 if (radix_tree_maybe_preload(GFP_ATOMIC) < 0) {
376 kmem_cache_free(et->icq_cache, icq);
377 return NULL;
378 }
379
380 icq->ioc = ioc;
381 icq->q = q;
382 INIT_LIST_HEAD(&icq->q_node);
383 INIT_HLIST_NODE(&icq->ioc_node);
384
385 /* lock both q and ioc and try to link @icq */
386 spin_lock_irq(&q->queue_lock);
387 spin_lock(&ioc->lock);
388
389 if (likely(!radix_tree_insert(&ioc->icq_tree, q->id, icq))) {
390 hlist_add_head(&icq->ioc_node, &ioc->icq_list);
391 list_add(&icq->q_node, &q->icq_list);
392 if (et->ops.init_icq)
393 et->ops.init_icq(icq);
394 } else {
395 kmem_cache_free(et->icq_cache, icq);
396 icq = ioc_lookup_icq(q);
397 if (!icq)
398 printk(KERN_ERR "cfq: icq link failed!\n");
399 }
400
401 spin_unlock(&ioc->lock);
402 spin_unlock_irq(&q->queue_lock);
403 radix_tree_preload_end();
404 return icq;
405}
406
407struct io_cq *ioc_find_get_icq(struct request_queue *q)
408{
409 struct io_context *ioc = current->io_context;
410 struct io_cq *icq = NULL;
411
412 if (unlikely(!ioc)) {
413 ioc = alloc_io_context(GFP_ATOMIC, q->node);
414 if (!ioc)
415 return NULL;
416
417 task_lock(current);
418 if (current->io_context) {
419 kmem_cache_free(iocontext_cachep, ioc);
420 ioc = current->io_context;
421 } else {
422 current->io_context = ioc;
423 }
424
425 get_io_context(ioc);
426 task_unlock(current);
427 } else {
428 get_io_context(ioc);
429
430 spin_lock_irq(&q->queue_lock);
431 icq = ioc_lookup_icq(q);
432 spin_unlock_irq(&q->queue_lock);
433 }
434
435 if (!icq) {
436 icq = ioc_create_icq(q);
437 if (!icq) {
438 put_io_context(ioc);
439 return NULL;
440 }
441 }
442 return icq;
443}
444EXPORT_SYMBOL_GPL(ioc_find_get_icq);
445#endif /* CONFIG_BLK_ICQ */
446
447static int __init blk_ioc_init(void)
448{
449 iocontext_cachep = kmem_cache_create("blkdev_ioc",
450 sizeof(struct io_context), 0, SLAB_PANIC, NULL);
451 return 0;
452}
453subsys_initcall(blk_ioc_init);