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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(u64 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 in io issue path
312 * @q: the associated request_queue
313 *
314 * Look up io_cq associated with @ioc - @q pair from @ioc. Must be called
315 * from io issue path, either return NULL if current issue io to @q for the
316 * first time, or return a valid icq.
317 */
318struct io_cq *ioc_lookup_icq(struct request_queue *q)
319{
320 struct io_context *ioc = current->io_context;
321 struct io_cq *icq;
322
323 /*
324 * icq's are indexed from @ioc using radix tree and hint pointer,
325 * both of which are protected with RCU, io issue path ensures that
326 * both request_queue and current task are valid, the found icq
327 * is guaranteed to be valid until the io is done.
328 */
329 rcu_read_lock();
330 icq = rcu_dereference(ioc->icq_hint);
331 if (icq && icq->q == q)
332 goto out;
333
334 icq = radix_tree_lookup(&ioc->icq_tree, q->id);
335 if (icq && icq->q == q)
336 rcu_assign_pointer(ioc->icq_hint, icq); /* allowed to race */
337 else
338 icq = NULL;
339out:
340 rcu_read_unlock();
341 return icq;
342}
343EXPORT_SYMBOL(ioc_lookup_icq);
344
345/**
346 * ioc_create_icq - create and link io_cq
347 * @q: request_queue of interest
348 *
349 * Make sure io_cq linking @ioc and @q exists. If icq doesn't exist, they
350 * will be created using @gfp_mask.
351 *
352 * The caller is responsible for ensuring @ioc won't go away and @q is
353 * alive and will stay alive until this function returns.
354 */
355static struct io_cq *ioc_create_icq(struct request_queue *q)
356{
357 struct io_context *ioc = current->io_context;
358 struct elevator_type *et = q->elevator->type;
359 struct io_cq *icq;
360
361 /* allocate stuff */
362 icq = kmem_cache_alloc_node(et->icq_cache, GFP_ATOMIC | __GFP_ZERO,
363 q->node);
364 if (!icq)
365 return NULL;
366
367 if (radix_tree_maybe_preload(GFP_ATOMIC) < 0) {
368 kmem_cache_free(et->icq_cache, icq);
369 return NULL;
370 }
371
372 icq->ioc = ioc;
373 icq->q = q;
374 INIT_LIST_HEAD(&icq->q_node);
375 INIT_HLIST_NODE(&icq->ioc_node);
376
377 /* lock both q and ioc and try to link @icq */
378 spin_lock_irq(&q->queue_lock);
379 spin_lock(&ioc->lock);
380
381 if (likely(!radix_tree_insert(&ioc->icq_tree, q->id, icq))) {
382 hlist_add_head(&icq->ioc_node, &ioc->icq_list);
383 list_add(&icq->q_node, &q->icq_list);
384 if (et->ops.init_icq)
385 et->ops.init_icq(icq);
386 } else {
387 kmem_cache_free(et->icq_cache, icq);
388 icq = ioc_lookup_icq(q);
389 if (!icq)
390 printk(KERN_ERR "cfq: icq link failed!\n");
391 }
392
393 spin_unlock(&ioc->lock);
394 spin_unlock_irq(&q->queue_lock);
395 radix_tree_preload_end();
396 return icq;
397}
398
399struct io_cq *ioc_find_get_icq(struct request_queue *q)
400{
401 struct io_context *ioc = current->io_context;
402 struct io_cq *icq = NULL;
403
404 if (unlikely(!ioc)) {
405 ioc = alloc_io_context(GFP_ATOMIC, q->node);
406 if (!ioc)
407 return NULL;
408
409 task_lock(current);
410 if (current->io_context) {
411 kmem_cache_free(iocontext_cachep, ioc);
412 ioc = current->io_context;
413 } else {
414 current->io_context = ioc;
415 }
416
417 get_io_context(ioc);
418 task_unlock(current);
419 } else {
420 get_io_context(ioc);
421 icq = ioc_lookup_icq(q);
422 }
423
424 if (!icq) {
425 icq = ioc_create_icq(q);
426 if (!icq) {
427 put_io_context(ioc);
428 return NULL;
429 }
430 }
431 return icq;
432}
433EXPORT_SYMBOL_GPL(ioc_find_get_icq);
434#endif /* CONFIG_BLK_ICQ */
435
436static int __init blk_ioc_init(void)
437{
438 iocontext_cachep = kmem_cache_create("blkdev_ioc",
439 sizeof(struct io_context), 0, SLAB_PANIC, NULL);
440 return 0;
441}
442subsys_initcall(blk_ioc_init);