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);
454