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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
35/*
36 * Exit an icq. Called with ioc locked for blk-mq, and with both ioc
37 * and queue locked for legacy.
38 */
39static void ioc_exit_icq(struct io_cq *icq)
40{
41 struct elevator_type *et = icq->q->elevator->type;
42
43 if (icq->flags & ICQ_EXITED)
44 return;
45
46 if (et->ops.exit_icq)
47 et->ops.exit_icq(icq);
48
49 icq->flags |= ICQ_EXITED;
50}
51
52static void ioc_exit_icqs(struct io_context *ioc)
53{
54 struct io_cq *icq;
55
56 spin_lock_irq(&ioc->lock);
57 hlist_for_each_entry(icq, &ioc->icq_list, ioc_node)
58 ioc_exit_icq(icq);
59 spin_unlock_irq(&ioc->lock);
60}
61
62/*
63 * Release an icq. Called with ioc locked for blk-mq, and with both ioc
64 * and queue locked for legacy.
65 */
66static void ioc_destroy_icq(struct io_cq *icq)
67{
68 struct io_context *ioc = icq->ioc;
69 struct request_queue *q = icq->q;
70 struct elevator_type *et = q->elevator->type;
71
72 lockdep_assert_held(&ioc->lock);
73 lockdep_assert_held(&q->queue_lock);
74
75 if (icq->flags & ICQ_DESTROYED)
76 return;
77
78 radix_tree_delete(&ioc->icq_tree, icq->q->id);
79 hlist_del_init(&icq->ioc_node);
80 list_del_init(&icq->q_node);
81
82 /*
83 * Both setting lookup hint to and clearing it from @icq are done
84 * under queue_lock. If it's not pointing to @icq now, it never
85 * will. Hint assignment itself can race safely.
86 */
87 if (rcu_access_pointer(ioc->icq_hint) == icq)
88 rcu_assign_pointer(ioc->icq_hint, NULL);
89
90 ioc_exit_icq(icq);
91
92 /*
93 * @icq->q might have gone away by the time RCU callback runs
94 * making it impossible to determine icq_cache. Record it in @icq.
95 */
96 icq->__rcu_icq_cache = et->icq_cache;
97 icq->flags |= ICQ_DESTROYED;
98 kfree_rcu(icq, __rcu_head);
99}
100
101/*
102 * Slow path for ioc release in put_io_context(). Performs double-lock
103 * dancing to unlink all icq's and then frees ioc.
104 */
105static void ioc_release_fn(struct work_struct *work)
106{
107 struct io_context *ioc = container_of(work, struct io_context,
108 release_work);
109 spin_lock_irq(&ioc->lock);
110
111 while (!hlist_empty(&ioc->icq_list)) {
112 struct io_cq *icq = hlist_entry(ioc->icq_list.first,
113 struct io_cq, ioc_node);
114 struct request_queue *q = icq->q;
115
116 if (spin_trylock(&q->queue_lock)) {
117 ioc_destroy_icq(icq);
118 spin_unlock(&q->queue_lock);
119 } else {
120 /* Make sure q and icq cannot be freed. */
121 rcu_read_lock();
122
123 /* Re-acquire the locks in the correct order. */
124 spin_unlock(&ioc->lock);
125 spin_lock(&q->queue_lock);
126 spin_lock(&ioc->lock);
127
128 ioc_destroy_icq(icq);
129
130 spin_unlock(&q->queue_lock);
131 rcu_read_unlock();
132 }
133 }
134
135 spin_unlock_irq(&ioc->lock);
136
137 kmem_cache_free(iocontext_cachep, ioc);
138}
139
140/*
141 * Releasing icqs requires reverse order double locking and we may already be
142 * holding a queue_lock. Do it asynchronously from a workqueue.
143 */
144static bool ioc_delay_free(struct io_context *ioc)
145{
146 unsigned long flags;
147
148 spin_lock_irqsave(&ioc->lock, flags);
149 if (!hlist_empty(&ioc->icq_list)) {
150 queue_work(system_power_efficient_wq, &ioc->release_work);
151 spin_unlock_irqrestore(&ioc->lock, flags);
152 return true;
153 }
154 spin_unlock_irqrestore(&ioc->lock, flags);
155 return false;
156}
157
158/**
159 * ioc_clear_queue - break any ioc association with the specified queue
160 * @q: request_queue being cleared
161 *
162 * Walk @q->icq_list and exit all io_cq's.
163 */
164void ioc_clear_queue(struct request_queue *q)
165{
166 spin_lock_irq(&q->queue_lock);
167 while (!list_empty(&q->icq_list)) {
168 struct io_cq *icq =
169 list_first_entry(&q->icq_list, struct io_cq, q_node);
170
171 /*
172 * Other context won't hold ioc lock to wait for queue_lock, see
173 * details in ioc_release_fn().
174 */
175 spin_lock(&icq->ioc->lock);
176 ioc_destroy_icq(icq);
177 spin_unlock(&icq->ioc->lock);
178 }
179 spin_unlock_irq(&q->queue_lock);
180}
181#else /* CONFIG_BLK_ICQ */
182static inline void ioc_exit_icqs(struct io_context *ioc)
183{
184}
185static inline bool ioc_delay_free(struct io_context *ioc)
186{
187 return false;
188}
189#endif /* CONFIG_BLK_ICQ */
190
191/**
192 * put_io_context - put a reference of io_context
193 * @ioc: io_context to put
194 *
195 * Decrement reference count of @ioc and release it if the count reaches
196 * zero.
197 */
198void put_io_context(struct io_context *ioc)
199{
200 BUG_ON(atomic_long_read(&ioc->refcount) <= 0);
201 if (atomic_long_dec_and_test(&ioc->refcount) && !ioc_delay_free(ioc))
202 kmem_cache_free(iocontext_cachep, ioc);
203}
204EXPORT_SYMBOL_GPL(put_io_context);
205
206/* Called by the exiting task */
207void exit_io_context(struct task_struct *task)
208{
209 struct io_context *ioc;
210
211 task_lock(task);
212 ioc = task->io_context;
213 task->io_context = NULL;
214 task_unlock(task);
215
216 if (atomic_dec_and_test(&ioc->active_ref)) {
217 ioc_exit_icqs(ioc);
218 put_io_context(ioc);
219 }
220}
221
222static struct io_context *alloc_io_context(gfp_t gfp_flags, int node)
223{
224 struct io_context *ioc;
225
226 ioc = kmem_cache_alloc_node(iocontext_cachep, gfp_flags | __GFP_ZERO,
227 node);
228 if (unlikely(!ioc))
229 return NULL;
230
231 atomic_long_set(&ioc->refcount, 1);
232 atomic_set(&ioc->active_ref, 1);
233#ifdef CONFIG_BLK_ICQ
234 spin_lock_init(&ioc->lock);
235 INIT_RADIX_TREE(&ioc->icq_tree, GFP_ATOMIC);
236 INIT_HLIST_HEAD(&ioc->icq_list);
237 INIT_WORK(&ioc->release_work, ioc_release_fn);
238#endif
239 ioc->ioprio = IOPRIO_DEFAULT;
240
241 return ioc;
242}
243
244int set_task_ioprio(struct task_struct *task, int ioprio)
245{
246 int err;
247 const struct cred *cred = current_cred(), *tcred;
248
249 rcu_read_lock();
250 tcred = __task_cred(task);
251 if (!uid_eq(tcred->uid, cred->euid) &&
252 !uid_eq(tcred->uid, cred->uid) && !capable(CAP_SYS_NICE)) {
253 rcu_read_unlock();
254 return -EPERM;
255 }
256 rcu_read_unlock();
257
258 err = security_task_setioprio(task, ioprio);
259 if (err)
260 return err;
261
262 task_lock(task);
263 if (unlikely(!task->io_context)) {
264 struct io_context *ioc;
265
266 task_unlock(task);
267
268 ioc = alloc_io_context(GFP_ATOMIC, NUMA_NO_NODE);
269 if (!ioc)
270 return -ENOMEM;
271
272 task_lock(task);
273 if (task->flags & PF_EXITING) {
274 kmem_cache_free(iocontext_cachep, ioc);
275 goto out;
276 }
277 if (task->io_context)
278 kmem_cache_free(iocontext_cachep, ioc);
279 else
280 task->io_context = ioc;
281 }
282 task->io_context->ioprio = ioprio;
283out:
284 task_unlock(task);
285 return 0;
286}
287EXPORT_SYMBOL_GPL(set_task_ioprio);
288
289int __copy_io(unsigned long clone_flags, struct task_struct *tsk)
290{
291 struct io_context *ioc = current->io_context;
292
293 /*
294 * Share io context with parent, if CLONE_IO is set
295 */
296 if (clone_flags & CLONE_IO) {
297 atomic_inc(&ioc->active_ref);
298 tsk->io_context = ioc;
299 } else if (ioprio_valid(ioc->ioprio)) {
300 tsk->io_context = alloc_io_context(GFP_KERNEL, NUMA_NO_NODE);
301 if (!tsk->io_context)
302 return -ENOMEM;
303 tsk->io_context->ioprio = ioc->ioprio;
304 }
305
306 return 0;
307}
308
309#ifdef CONFIG_BLK_ICQ
310/**
311 * ioc_lookup_icq - lookup io_cq from ioc
312 * @q: the associated request_queue
313 *
314 * Look up io_cq associated with @ioc - @q pair from @ioc. Must be called
315 * with @q->queue_lock held.
316 */
317struct io_cq *ioc_lookup_icq(struct request_queue *q)
318{
319 struct io_context *ioc = current->io_context;
320 struct io_cq *icq;
321
322 lockdep_assert_held(&q->queue_lock);
323
324 /*
325 * icq's are indexed from @ioc using radix tree and hint pointer,
326 * both of which are protected with RCU. All removals are done
327 * holding both q and ioc locks, and we're holding q lock - if we
328 * find a icq which points to us, it's guaranteed to be valid.
329 */
330 rcu_read_lock();
331 icq = rcu_dereference(ioc->icq_hint);
332 if (icq && icq->q == q)
333 goto out;
334
335 icq = radix_tree_lookup(&ioc->icq_tree, q->id);
336 if (icq && icq->q == q)
337 rcu_assign_pointer(ioc->icq_hint, icq); /* allowed to race */
338 else
339 icq = NULL;
340out:
341 rcu_read_unlock();
342 return icq;
343}
344EXPORT_SYMBOL(ioc_lookup_icq);
345
346/**
347 * ioc_create_icq - create and link io_cq
348 * @q: request_queue of interest
349 *
350 * Make sure io_cq linking @ioc and @q exists. If icq doesn't exist, they
351 * will be created using @gfp_mask.
352 *
353 * The caller is responsible for ensuring @ioc won't go away and @q is
354 * alive and will stay alive until this function returns.
355 */
356static struct io_cq *ioc_create_icq(struct request_queue *q)
357{
358 struct io_context *ioc = current->io_context;
359 struct elevator_type *et = q->elevator->type;
360 struct io_cq *icq;
361
362 /* allocate stuff */
363 icq = kmem_cache_alloc_node(et->icq_cache, GFP_ATOMIC | __GFP_ZERO,
364 q->node);
365 if (!icq)
366 return NULL;
367
368 if (radix_tree_maybe_preload(GFP_ATOMIC) < 0) {
369 kmem_cache_free(et->icq_cache, icq);
370 return NULL;
371 }
372
373 icq->ioc = ioc;
374 icq->q = q;
375 INIT_LIST_HEAD(&icq->q_node);
376 INIT_HLIST_NODE(&icq->ioc_node);
377
378 /* lock both q and ioc and try to link @icq */
379 spin_lock_irq(&q->queue_lock);
380 spin_lock(&ioc->lock);
381
382 if (likely(!radix_tree_insert(&ioc->icq_tree, q->id, icq))) {
383 hlist_add_head(&icq->ioc_node, &ioc->icq_list);
384 list_add(&icq->q_node, &q->icq_list);
385 if (et->ops.init_icq)
386 et->ops.init_icq(icq);
387 } else {
388 kmem_cache_free(et->icq_cache, icq);
389 icq = ioc_lookup_icq(q);
390 if (!icq)
391 printk(KERN_ERR "cfq: icq link failed!\n");
392 }
393
394 spin_unlock(&ioc->lock);
395 spin_unlock_irq(&q->queue_lock);
396 radix_tree_preload_end();
397 return icq;
398}
399
400struct io_cq *ioc_find_get_icq(struct request_queue *q)
401{
402 struct io_context *ioc = current->io_context;
403 struct io_cq *icq = NULL;
404
405 if (unlikely(!ioc)) {
406 ioc = alloc_io_context(GFP_ATOMIC, q->node);
407 if (!ioc)
408 return NULL;
409
410 task_lock(current);
411 if (current->io_context) {
412 kmem_cache_free(iocontext_cachep, ioc);
413 ioc = current->io_context;
414 } else {
415 current->io_context = ioc;
416 }
417
418 get_io_context(ioc);
419 task_unlock(current);
420 } else {
421 get_io_context(ioc);
422
423 spin_lock_irq(&q->queue_lock);
424 icq = ioc_lookup_icq(q);
425 spin_unlock_irq(&q->queue_lock);
426 }
427
428 if (!icq) {
429 icq = ioc_create_icq(q);
430 if (!icq) {
431 put_io_context(ioc);
432 return NULL;
433 }
434 }
435 return icq;
436}
437EXPORT_SYMBOL_GPL(ioc_find_get_icq);
438#endif /* CONFIG_BLK_ICQ */
439
440static int __init blk_ioc_init(void)
441{
442 iocontext_cachep = kmem_cache_create("blkdev_ioc",
443 sizeof(struct io_context), 0, SLAB_PANIC, NULL);
444 return 0;
445}
446subsys_initcall(blk_ioc_init);