aio.c 47 KB
Newer Older
Linus Torvalds's avatar
Linus Torvalds committed
1
2
3
4
5
6
7
8
9
10
/*
 *	An async IO implementation for Linux
 *	Written by Benjamin LaHaise <bcrl@kvack.org>
 *
 *	Implements an efficient asynchronous io interface.
 *
 *	Copyright 2000, 2001, 2002 Red Hat, Inc.  All Rights Reserved.
 *
 *	See ../COPYING for licensing terms.
 */
Kent Overstreet's avatar
Kent Overstreet committed
11
12
#define pr_fmt(fmt) "%s: " fmt, __func__

Linus Torvalds's avatar
Linus Torvalds committed
13
14
15
16
17
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/errno.h>
#include <linux/time.h>
#include <linux/aio_abi.h>
18
#include <linux/export.h>
Linus Torvalds's avatar
Linus Torvalds committed
19
#include <linux/syscalls.h>
20
#include <linux/backing-dev.h>
21
#include <linux/uio.h>
Linus Torvalds's avatar
Linus Torvalds committed
22

23
#include <linux/sched/signal.h>
Linus Torvalds's avatar
Linus Torvalds committed
24
25
26
27
#include <linux/fs.h>
#include <linux/file.h>
#include <linux/mm.h>
#include <linux/mman.h>
28
#include <linux/mmu_context.h>
Kent Overstreet's avatar
Kent Overstreet committed
29
#include <linux/percpu.h>
Linus Torvalds's avatar
Linus Torvalds committed
30
31
32
33
34
35
#include <linux/slab.h>
#include <linux/timer.h>
#include <linux/aio.h>
#include <linux/highmem.h>
#include <linux/workqueue.h>
#include <linux/security.h>
36
#include <linux/eventfd.h>
Jeff Moyer's avatar
Jeff Moyer committed
37
#include <linux/blkdev.h>
38
#include <linux/compat.h>
39
40
#include <linux/migrate.h>
#include <linux/ramfs.h>
Kent Overstreet's avatar
Kent Overstreet committed
41
#include <linux/percpu-refcount.h>
42
#include <linux/mount.h>
Linus Torvalds's avatar
Linus Torvalds committed
43
44

#include <asm/kmap_types.h>
45
#include <linux/uaccess.h>
Linus Torvalds's avatar
Linus Torvalds committed
46

Al Viro's avatar
Al Viro committed
47
48
#include "internal.h"

49
50
51
52
53
54
#define AIO_RING_MAGIC			0xa10a10a1
#define AIO_RING_COMPAT_FEATURES	1
#define AIO_RING_INCOMPAT_FEATURES	0
struct aio_ring {
	unsigned	id;	/* kernel internal index number */
	unsigned	nr;	/* number of io_events */
55
56
	unsigned	head;	/* Written to by userland or under ring_lock
				 * mutex by aio_read_events_ring(). */
57
58
59
60
61
62
63
64
65
66
67
68
69
	unsigned	tail;

	unsigned	magic;
	unsigned	compat_features;
	unsigned	incompat_features;
	unsigned	header_length;	/* size of aio_ring */


	struct io_event		io_events[0];
}; /* 128 bytes + ring size */

#define AIO_RING_PAGES	8

70
struct kioctx_table {
71
72
73
	struct rcu_head		rcu;
	unsigned		nr;
	struct kioctx __rcu	*table[];
74
75
};

Kent Overstreet's avatar
Kent Overstreet committed
76
77
78
79
struct kioctx_cpu {
	unsigned		reqs_available;
};

80
81
82
83
84
struct ctx_rq_wait {
	struct completion comp;
	atomic_t count;
};

85
struct kioctx {
Kent Overstreet's avatar
Kent Overstreet committed
86
	struct percpu_ref	users;
Kent Overstreet's avatar
Kent Overstreet committed
87
	atomic_t		dead;
88

Kent Overstreet's avatar
Kent Overstreet committed
89
90
	struct percpu_ref	reqs;

91
92
	unsigned long		user_id;

Kent Overstreet's avatar
Kent Overstreet committed
93
94
95
96
97
98
99
	struct __percpu kioctx_cpu *cpu;

	/*
	 * For percpu reqs_available, number of slots we move to/from global
	 * counter at a time:
	 */
	unsigned		req_batch;
100
101
102
103
	/*
	 * This is what userspace passed to io_setup(), it's not used for
	 * anything but counting against the global max_reqs quota.
	 *
104
	 * The real limit is nr_events - 1, which will be larger (see
105
106
	 * aio_setup_ring())
	 */
107
108
	unsigned		max_reqs;

109
110
	/* Size of ringbuffer, in units of struct io_event */
	unsigned		nr_events;
111

112
113
114
115
116
117
	unsigned long		mmap_base;
	unsigned long		mmap_size;

	struct page		**ring_pages;
	long			nr_pages;

118
	struct rcu_work		free_rwork;	/* see free_ioctx() */
119

120
121
122
	/*
	 * signals when all in-flight requests are done
	 */
123
	struct ctx_rq_wait	*rq_wait;
124

125
	struct {
126
127
128
129
130
		/*
		 * This counts the number of available slots in the ringbuffer,
		 * so we avoid overflowing it: it's decremented (if positive)
		 * when allocating a kiocb and incremented when the resulting
		 * io_event is pulled off the ringbuffer.
Kent Overstreet's avatar
Kent Overstreet committed
131
132
		 *
		 * We batch accesses to it with a percpu version.
133
134
		 */
		atomic_t	reqs_available;
135
136
137
138
139
140
141
	} ____cacheline_aligned_in_smp;

	struct {
		spinlock_t	ctx_lock;
		struct list_head active_reqs;	/* used for cancellation */
	} ____cacheline_aligned_in_smp;

142
143
	struct {
		struct mutex	ring_lock;
144
145
		wait_queue_head_t wait;
	} ____cacheline_aligned_in_smp;
146
147
148

	struct {
		unsigned	tail;
149
		unsigned	completed_events;
150
		spinlock_t	completion_lock;
151
	} ____cacheline_aligned_in_smp;
152
153

	struct page		*internal_pages[AIO_RING_PAGES];
154
	struct file		*aio_ring_file;
155
156

	unsigned		id;
157
158
};

159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
/*
 * We use ki_cancel == KIOCB_CANCELLED to indicate that a kiocb has been either
 * cancelled or completed (this makes a certain amount of sense because
 * successful cancellation - io_cancel() - does deliver the completion to
 * userspace).
 *
 * And since most things don't implement kiocb cancellation and we'd really like
 * kiocb completion to be lockless when possible, we use ki_cancel to
 * synchronize cancellation and completion - we only set it to KIOCB_CANCELLED
 * with xchg() or cmpxchg(), see batch_complete_aio() and kiocb_cancel().
 */
#define KIOCB_CANCELLED		((void *) (~0ULL))

struct aio_kiocb {
	struct kiocb		common;

	struct kioctx		*ki_ctx;
	kiocb_cancel_fn		*ki_cancel;

	struct iocb __user	*ki_user_iocb;	/* user's aiocb */
	__u64			ki_user_data;	/* user's data for completion */

	struct list_head	ki_list;	/* the aio core uses this
						 * for cancellation */

	/*
	 * If the aio_resfd field of the userspace iocb is not zero,
	 * this is the underlying eventfd context to deliver events to.
	 */
	struct eventfd_ctx	*ki_eventfd;
};

Linus Torvalds's avatar
Linus Torvalds committed
191
/*------ sysctl variables----*/
192
193
194
static DEFINE_SPINLOCK(aio_nr_lock);
unsigned long aio_nr;		/* current system wide number of aio requests */
unsigned long aio_max_nr = 0x10000; /* system wide maximum number of aio requests */
Linus Torvalds's avatar
Linus Torvalds committed
195
196
/*----end sysctl variables---*/

197
198
static struct kmem_cache	*kiocb_cachep;
static struct kmem_cache	*kioctx_cachep;
Linus Torvalds's avatar
Linus Torvalds committed
199

200
201
202
203
204
205
206
207
208
209
210
static struct vfsmount *aio_mnt;

static const struct file_operations aio_ring_fops;
static const struct address_space_operations aio_ctx_aops;

static struct file *aio_private_file(struct kioctx *ctx, loff_t nr_pages)
{
	struct qstr this = QSTR_INIT("[aio]", 5);
	struct file *file;
	struct path path;
	struct inode *inode = alloc_anon_inode(aio_mnt->mnt_sb);
211
212
	if (IS_ERR(inode))
		return ERR_CAST(inode);
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241

	inode->i_mapping->a_ops = &aio_ctx_aops;
	inode->i_mapping->private_data = ctx;
	inode->i_size = PAGE_SIZE * nr_pages;

	path.dentry = d_alloc_pseudo(aio_mnt->mnt_sb, &this);
	if (!path.dentry) {
		iput(inode);
		return ERR_PTR(-ENOMEM);
	}
	path.mnt = mntget(aio_mnt);

	d_instantiate(path.dentry, inode);
	file = alloc_file(&path, FMODE_READ | FMODE_WRITE, &aio_ring_fops);
	if (IS_ERR(file)) {
		path_put(&path);
		return file;
	}

	file->f_flags = O_RDWR;
	return file;
}

static struct dentry *aio_mount(struct file_system_type *fs_type,
				int flags, const char *dev_name, void *data)
{
	static const struct dentry_operations ops = {
		.d_dname	= simple_dname,
	};
Jann Horn's avatar
Jann Horn committed
242
243
244
245
246
247
	struct dentry *root = mount_pseudo(fs_type, "aio:", NULL, &ops,
					   AIO_RING_MAGIC);

	if (!IS_ERR(root))
		root->d_sb->s_iflags |= SB_I_NOEXEC;
	return root;
248
249
}

Linus Torvalds's avatar
Linus Torvalds committed
250
251
252
253
254
255
/* aio_setup
 *	Creates the slab caches used by the aio routines, panic on
 *	failure as this is done early during the boot sequence.
 */
static int __init aio_setup(void)
{
256
257
258
259
260
261
262
263
264
	static struct file_system_type aio_fs = {
		.name		= "aio",
		.mount		= aio_mount,
		.kill_sb	= kill_anon_super,
	};
	aio_mnt = kern_mount(&aio_fs);
	if (IS_ERR(aio_mnt))
		panic("Failed to create aio fs mount.");

265
	kiocb_cachep = KMEM_CACHE(aio_kiocb, SLAB_HWCACHE_ALIGN|SLAB_PANIC);
266
	kioctx_cachep = KMEM_CACHE(kioctx,SLAB_HWCACHE_ALIGN|SLAB_PANIC);
Linus Torvalds's avatar
Linus Torvalds committed
267
268
	return 0;
}
269
__initcall(aio_setup);
Linus Torvalds's avatar
Linus Torvalds committed
270

271
272
273
static void put_aio_ring_file(struct kioctx *ctx)
{
	struct file *aio_ring_file = ctx->aio_ring_file;
274
275
	struct address_space *i_mapping;

276
	if (aio_ring_file) {
Al Viro's avatar
Al Viro committed
277
		truncate_setsize(file_inode(aio_ring_file), 0);
278
279

		/* Prevent further access to the kioctx from migratepages */
Al Viro's avatar
Al Viro committed
280
		i_mapping = aio_ring_file->f_mapping;
281
282
		spin_lock(&i_mapping->private_lock);
		i_mapping->private_data = NULL;
283
		ctx->aio_ring_file = NULL;
284
		spin_unlock(&i_mapping->private_lock);
285
286
287
288
289

		fput(aio_ring_file);
	}
}

Linus Torvalds's avatar
Linus Torvalds committed
290
291
static void aio_free_ring(struct kioctx *ctx)
{
292
	int i;
Linus Torvalds's avatar
Linus Torvalds committed
293

294
295
296
297
298
	/* Disconnect the kiotx from the ring file.  This prevents future
	 * accesses to the kioctx from page migration.
	 */
	put_aio_ring_file(ctx);

299
	for (i = 0; i < ctx->nr_pages; i++) {
300
		struct page *page;
301
302
		pr_debug("pid(%d) [%d] page->count=%d\n", current->pid, i,
				page_count(ctx->ring_pages[i]));
303
304
305
306
307
		page = ctx->ring_pages[i];
		if (!page)
			continue;
		ctx->ring_pages[i] = NULL;
		put_page(page);
308
	}
Linus Torvalds's avatar
Linus Torvalds committed
309

310
	if (ctx->ring_pages && ctx->ring_pages != ctx->internal_pages) {
311
		kfree(ctx->ring_pages);
312
313
		ctx->ring_pages = NULL;
	}
314
315
}

316
static int aio_ring_mremap(struct vm_area_struct *vma)
317
{
318
	struct file *file = vma->vm_file;
319
320
	struct mm_struct *mm = vma->vm_mm;
	struct kioctx_table *table;
Al Viro's avatar
Al Viro committed
321
	int i, res = -EINVAL;
322
323
324
325
326
327
328

	spin_lock(&mm->ioctx_lock);
	rcu_read_lock();
	table = rcu_dereference(mm->ioctx_table);
	for (i = 0; i < table->nr; i++) {
		struct kioctx *ctx;

329
		ctx = rcu_dereference(table->table[i]);
330
		if (ctx && ctx->aio_ring_file == file) {
Al Viro's avatar
Al Viro committed
331
332
333
334
			if (!atomic_read(&ctx->dead)) {
				ctx->user_id = ctx->mmap_base = vma->vm_start;
				res = 0;
			}
335
336
337
338
339
340
			break;
		}
	}

	rcu_read_unlock();
	spin_unlock(&mm->ioctx_lock);
Al Viro's avatar
Al Viro committed
341
	return res;
342
343
}

344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
static const struct vm_operations_struct aio_ring_vm_ops = {
	.mremap		= aio_ring_mremap,
#if IS_ENABLED(CONFIG_MMU)
	.fault		= filemap_fault,
	.map_pages	= filemap_map_pages,
	.page_mkwrite	= filemap_page_mkwrite,
#endif
};

static int aio_ring_mmap(struct file *file, struct vm_area_struct *vma)
{
	vma->vm_flags |= VM_DONTEXPAND;
	vma->vm_ops = &aio_ring_vm_ops;
	return 0;
}

360
361
362
363
static const struct file_operations aio_ring_fops = {
	.mmap = aio_ring_mmap,
};

364
#if IS_ENABLED(CONFIG_MIGRATION)
365
366
367
static int aio_migratepage(struct address_space *mapping, struct page *new,
			struct page *old, enum migrate_mode mode)
{
368
	struct kioctx *ctx;
369
	unsigned long flags;
370
	pgoff_t idx;
371
372
	int rc;

373
374
375
376
377
378
379
380
	/*
	 * We cannot support the _NO_COPY case here, because copy needs to
	 * happen under the ctx->completion_lock. That does not work with the
	 * migration workflow of MIGRATE_SYNC_NO_COPY.
	 */
	if (mode == MIGRATE_SYNC_NO_COPY)
		return -EINVAL;

381
382
	rc = 0;

383
	/* mapping->private_lock here protects against the kioctx teardown.  */
384
385
	spin_lock(&mapping->private_lock);
	ctx = mapping->private_data;
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
	if (!ctx) {
		rc = -EINVAL;
		goto out;
	}

	/* The ring_lock mutex.  The prevents aio_read_events() from writing
	 * to the ring's head, and prevents page migration from mucking in
	 * a partially initialized kiotx.
	 */
	if (!mutex_trylock(&ctx->ring_lock)) {
		rc = -EAGAIN;
		goto out;
	}

	idx = old->index;
	if (idx < (pgoff_t)ctx->nr_pages) {
		/* Make sure the old page hasn't already been changed */
		if (ctx->ring_pages[idx] != old)
			rc = -EAGAIN;
405
406
407
408
	} else
		rc = -EINVAL;

	if (rc != 0)
409
		goto out_unlock;
410

411
412
	/* Writeback must be complete */
	BUG_ON(PageWriteback(old));
413
	get_page(new);
414

415
	rc = migrate_page_move_mapping(mapping, new, old, NULL, mode, 1);
416
	if (rc != MIGRATEPAGE_SUCCESS) {
417
		put_page(new);
418
		goto out_unlock;
419
420
	}

421
422
423
	/* Take completion_lock to prevent other writes to the ring buffer
	 * while the old page is copied to the new.  This prevents new
	 * events from being lost.
424
	 */
425
426
427
428
429
	spin_lock_irqsave(&ctx->completion_lock, flags);
	migrate_page_copy(new, old);
	BUG_ON(ctx->ring_pages[idx] != old);
	ctx->ring_pages[idx] = new;
	spin_unlock_irqrestore(&ctx->completion_lock, flags);
430

431
432
	/* The old page is no longer accessible. */
	put_page(old);
433

434
435
436
437
out_unlock:
	mutex_unlock(&ctx->ring_lock);
out:
	spin_unlock(&mapping->private_lock);
438
	return rc;
Linus Torvalds's avatar
Linus Torvalds committed
439
}
440
#endif
Linus Torvalds's avatar
Linus Torvalds committed
441

442
static const struct address_space_operations aio_ctx_aops = {
443
	.set_page_dirty = __set_page_dirty_no_writeback,
444
#if IS_ENABLED(CONFIG_MIGRATION)
445
	.migratepage	= aio_migratepage,
446
#endif
447
448
};

449
static int aio_setup_ring(struct kioctx *ctx, unsigned int nr_events)
Linus Torvalds's avatar
Linus Torvalds committed
450
451
{
	struct aio_ring *ring;
Zach Brown's avatar
Zach Brown committed
452
	struct mm_struct *mm = current->mm;
453
	unsigned long size, unused;
Linus Torvalds's avatar
Linus Torvalds committed
454
	int nr_pages;
455
456
	int i;
	struct file *file;
Linus Torvalds's avatar
Linus Torvalds committed
457
458
459
460
461
462
463

	/* Compensate for the ring buffer's head/tail overlap entry */
	nr_events += 2;	/* 1 is required, 2 for good luck */

	size = sizeof(struct aio_ring);
	size += sizeof(struct io_event) * nr_events;

464
	nr_pages = PFN_UP(size);
Linus Torvalds's avatar
Linus Torvalds committed
465
466
467
	if (nr_pages < 0)
		return -EINVAL;

468
	file = aio_private_file(ctx, nr_pages);
469
470
	if (IS_ERR(file)) {
		ctx->aio_ring_file = NULL;
471
		return -ENOMEM;
472
473
	}

474
475
476
477
478
479
480
481
482
483
484
485
486
487
	ctx->aio_ring_file = file;
	nr_events = (PAGE_SIZE * nr_pages - sizeof(struct aio_ring))
			/ sizeof(struct io_event);

	ctx->ring_pages = ctx->internal_pages;
	if (nr_pages > AIO_RING_PAGES) {
		ctx->ring_pages = kcalloc(nr_pages, sizeof(struct page *),
					  GFP_KERNEL);
		if (!ctx->ring_pages) {
			put_aio_ring_file(ctx);
			return -ENOMEM;
		}
	}

488
489
	for (i = 0; i < nr_pages; i++) {
		struct page *page;
Al Viro's avatar
Al Viro committed
490
		page = find_or_create_page(file->f_mapping,
491
492
493
494
495
496
497
					   i, GFP_HIGHUSER | __GFP_ZERO);
		if (!page)
			break;
		pr_debug("pid(%d) page[%d]->count=%d\n",
			 current->pid, i, page_count(page));
		SetPageUptodate(page);
		unlock_page(page);
498
499

		ctx->ring_pages[i] = page;
500
	}
501
	ctx->nr_pages = i;
Linus Torvalds's avatar
Linus Torvalds committed
502

503
504
	if (unlikely(i != nr_pages)) {
		aio_free_ring(ctx);
505
		return -ENOMEM;
Linus Torvalds's avatar
Linus Torvalds committed
506
507
	}

508
509
	ctx->mmap_size = nr_pages * PAGE_SIZE;
	pr_debug("attempting mmap of %lu bytes\n", ctx->mmap_size);
510

511
512
513
514
515
516
	if (down_write_killable(&mm->mmap_sem)) {
		ctx->mmap_size = 0;
		aio_free_ring(ctx);
		return -EINTR;
	}

517
518
	ctx->mmap_base = do_mmap_pgoff(ctx->aio_ring_file, 0, ctx->mmap_size,
				       PROT_READ | PROT_WRITE,
519
				       MAP_SHARED, 0, &unused, NULL);
520
	up_write(&mm->mmap_sem);
521
522
	if (IS_ERR((void *)ctx->mmap_base)) {
		ctx->mmap_size = 0;
Linus Torvalds's avatar
Linus Torvalds committed
523
		aio_free_ring(ctx);
524
		return -ENOMEM;
Linus Torvalds's avatar
Linus Torvalds committed
525
526
	}

527
	pr_debug("mmap address: 0x%08lx\n", ctx->mmap_base);
528

529
530
	ctx->user_id = ctx->mmap_base;
	ctx->nr_events = nr_events; /* trusted copy */
Linus Torvalds's avatar
Linus Torvalds committed
531

532
	ring = kmap_atomic(ctx->ring_pages[0]);
Linus Torvalds's avatar
Linus Torvalds committed
533
	ring->nr = nr_events;	/* user copy */
534
	ring->id = ~0U;
Linus Torvalds's avatar
Linus Torvalds committed
535
536
537
538
539
	ring->head = ring->tail = 0;
	ring->magic = AIO_RING_MAGIC;
	ring->compat_features = AIO_RING_COMPAT_FEATURES;
	ring->incompat_features = AIO_RING_INCOMPAT_FEATURES;
	ring->header_length = sizeof(struct aio_ring);
540
	kunmap_atomic(ring);
541
	flush_dcache_page(ctx->ring_pages[0]);
Linus Torvalds's avatar
Linus Torvalds committed
542
543
544
545
546
547
548
549

	return 0;
}

#define AIO_EVENTS_PER_PAGE	(PAGE_SIZE / sizeof(struct io_event))
#define AIO_EVENTS_FIRST_PAGE	((PAGE_SIZE - sizeof(struct aio_ring)) / sizeof(struct io_event))
#define AIO_EVENTS_OFFSET	(AIO_EVENTS_PER_PAGE - AIO_EVENTS_FIRST_PAGE)

550
void kiocb_set_cancel_fn(struct kiocb *iocb, kiocb_cancel_fn *cancel)
551
{
552
	struct aio_kiocb *req = container_of(iocb, struct aio_kiocb, common);
553
554
555
	struct kioctx *ctx = req->ki_ctx;
	unsigned long flags;

556
557
	if (WARN_ON_ONCE(!list_empty(&req->ki_list)))
		return;
558

559
560
	spin_lock_irqsave(&ctx->ctx_lock, flags);
	list_add_tail(&req->ki_list, &ctx->active_reqs);
561
562
563
564
565
	req->ki_cancel = cancel;
	spin_unlock_irqrestore(&ctx->ctx_lock, flags);
}
EXPORT_SYMBOL(kiocb_set_cancel_fn);

566
static int kiocb_cancel(struct aio_kiocb *kiocb)
Kent Overstreet's avatar
Kent Overstreet committed
567
{
568
	kiocb_cancel_fn *old, *cancel;
Kent Overstreet's avatar
Kent Overstreet committed
569

570
571
572
573
574
	/*
	 * Don't want to set kiocb->ki_cancel = KIOCB_CANCELLED unless it
	 * actually has a cancel function, hence the cmpxchg()
	 */

575
	cancel = READ_ONCE(kiocb->ki_cancel);
576
577
	do {
		if (!cancel || cancel == KIOCB_CANCELLED)
Kent Overstreet's avatar
Kent Overstreet committed
578
			return -EINVAL;
Kent Overstreet's avatar
Kent Overstreet committed
579

580
581
582
		old = cancel;
		cancel = cmpxchg(&kiocb->ki_cancel, old, KIOCB_CANCELLED);
	} while (cancel != old);
Kent Overstreet's avatar
Kent Overstreet committed
583

584
	return cancel(&kiocb->common);
Kent Overstreet's avatar
Kent Overstreet committed
585
586
}

587
588
589
/*
 * free_ioctx() should be RCU delayed to synchronize against the RCU
 * protected lookup_ioctx() and also needs process context to call
590
 * aio_free_ring().  Use rcu_work.
591
 */
Kent Overstreet's avatar
Kent Overstreet committed
592
static void free_ioctx(struct work_struct *work)
Kent Overstreet's avatar
Kent Overstreet committed
593
{
594
595
	struct kioctx *ctx = container_of(to_rcu_work(work), struct kioctx,
					  free_rwork);
Kent Overstreet's avatar
Kent Overstreet committed
596
	pr_debug("freeing %p\n", ctx);
Kent Overstreet's avatar
Kent Overstreet committed
597

Kent Overstreet's avatar
Kent Overstreet committed
598
	aio_free_ring(ctx);
Kent Overstreet's avatar
Kent Overstreet committed
599
	free_percpu(ctx->cpu);
600
601
	percpu_ref_exit(&ctx->reqs);
	percpu_ref_exit(&ctx->users);
Kent Overstreet's avatar
Kent Overstreet committed
602
603
604
	kmem_cache_free(kioctx_cachep, ctx);
}

Kent Overstreet's avatar
Kent Overstreet committed
605
606
607
608
static void free_ioctx_reqs(struct percpu_ref *ref)
{
	struct kioctx *ctx = container_of(ref, struct kioctx, reqs);

609
	/* At this point we know that there are no any in-flight requests */
610
611
	if (ctx->rq_wait && atomic_dec_and_test(&ctx->rq_wait->count))
		complete(&ctx->rq_wait->comp);
612

613
	/* Synchronize against RCU protected table->table[] dereferences */
614
615
	INIT_RCU_WORK(&ctx->free_rwork, free_ioctx);
	queue_rcu_work(system_wq, &ctx->free_rwork);
Kent Overstreet's avatar
Kent Overstreet committed
616
617
}

Kent Overstreet's avatar
Kent Overstreet committed
618
619
620
621
622
/*
 * When this function runs, the kioctx has been removed from the "hash table"
 * and ctx->users has dropped to 0, so we know no more kiocbs can be submitted -
 * now it's safe to cancel any that need to be.
 */
Kent Overstreet's avatar
Kent Overstreet committed
623
static void free_ioctx_users(struct percpu_ref *ref)
Kent Overstreet's avatar
Kent Overstreet committed
624
{
Kent Overstreet's avatar
Kent Overstreet committed
625
	struct kioctx *ctx = container_of(ref, struct kioctx, users);
626
	struct aio_kiocb *req;
Kent Overstreet's avatar
Kent Overstreet committed
627
628
629
630
631

	spin_lock_irq(&ctx->ctx_lock);

	while (!list_empty(&ctx->active_reqs)) {
		req = list_first_entry(&ctx->active_reqs,
632
				       struct aio_kiocb, ki_list);
Kent Overstreet's avatar
Kent Overstreet committed
633
634

		list_del_init(&req->ki_list);
635
		kiocb_cancel(req);
Kent Overstreet's avatar
Kent Overstreet committed
636
637
638
639
	}

	spin_unlock_irq(&ctx->ctx_lock);

Kent Overstreet's avatar
Kent Overstreet committed
640
641
	percpu_ref_kill(&ctx->reqs);
	percpu_ref_put(&ctx->reqs);
Kent Overstreet's avatar
Kent Overstreet committed
642
643
}

644
645
646
647
648
649
650
static int ioctx_add_table(struct kioctx *ctx, struct mm_struct *mm)
{
	unsigned i, new_nr;
	struct kioctx_table *table, *old;
	struct aio_ring *ring;

	spin_lock(&mm->ioctx_lock);
651
	table = rcu_dereference_raw(mm->ioctx_table);
652
653
654
655

	while (1) {
		if (table)
			for (i = 0; i < table->nr; i++)
656
				if (!rcu_access_pointer(table->table[i])) {
657
					ctx->id = i;
658
					rcu_assign_pointer(table->table[i], ctx);
659
660
					spin_unlock(&mm->ioctx_lock);

661
662
663
664
					/* While kioctx setup is in progress,
					 * we are protected from page migration
					 * changes ring_pages by ->ring_lock.
					 */
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
					ring = kmap_atomic(ctx->ring_pages[0]);
					ring->id = ctx->id;
					kunmap_atomic(ring);
					return 0;
				}

		new_nr = (table ? table->nr : 1) * 4;
		spin_unlock(&mm->ioctx_lock);

		table = kzalloc(sizeof(*table) + sizeof(struct kioctx *) *
				new_nr, GFP_KERNEL);
		if (!table)
			return -ENOMEM;

		table->nr = new_nr;

		spin_lock(&mm->ioctx_lock);
682
		old = rcu_dereference_raw(mm->ioctx_table);
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698

		if (!old) {
			rcu_assign_pointer(mm->ioctx_table, table);
		} else if (table->nr > old->nr) {
			memcpy(table->table, old->table,
			       old->nr * sizeof(struct kioctx *));

			rcu_assign_pointer(mm->ioctx_table, table);
			kfree_rcu(old, rcu);
		} else {
			kfree(table);
			table = old;
		}
	}
}

Kent Overstreet's avatar
Kent Overstreet committed
699
700
701
702
703
704
705
706
707
708
static void aio_nr_sub(unsigned nr)
{
	spin_lock(&aio_nr_lock);
	if (WARN_ON(aio_nr - nr > aio_nr))
		aio_nr = 0;
	else
		aio_nr -= nr;
	spin_unlock(&aio_nr_lock);
}

Linus Torvalds's avatar
Linus Torvalds committed
709
710
711
712
713
/* ioctx_alloc
 *	Allocates and initializes an ioctx.  Returns an ERR_PTR if it failed.
 */
static struct kioctx *ioctx_alloc(unsigned nr_events)
{
Zach Brown's avatar
Zach Brown committed
714
	struct mm_struct *mm = current->mm;
Linus Torvalds's avatar
Linus Torvalds committed
715
	struct kioctx *ctx;
716
	int err = -ENOMEM;
Linus Torvalds's avatar
Linus Torvalds committed
717

718
719
720
721
722
723
	/*
	 * Store the original nr_events -- what userspace passed to io_setup(),
	 * for counting against the global limit -- before it changes.
	 */
	unsigned int max_reqs = nr_events;

Kent Overstreet's avatar
Kent Overstreet committed
724
725
726
727
728
729
730
731
732
733
734
735
	/*
	 * We keep track of the number of available ringbuffer slots, to prevent
	 * overflow (reqs_available), and we also use percpu counters for this.
	 *
	 * So since up to half the slots might be on other cpu's percpu counters
	 * and unavailable, double nr_events so userspace sees what they
	 * expected: additionally, we move req_batch slots to/from percpu
	 * counters at a time, so make sure that isn't 0:
	 */
	nr_events = max(nr_events, num_possible_cpus() * 4);
	nr_events *= 2;

Linus Torvalds's avatar
Linus Torvalds committed
736
	/* Prevent overflows */
737
	if (nr_events > (0x10000000U / sizeof(struct io_event))) {
Linus Torvalds's avatar
Linus Torvalds committed
738
739
740
741
		pr_debug("ENOMEM: nr_events too high\n");
		return ERR_PTR(-EINVAL);
	}

742
	if (!nr_events || (unsigned long)max_reqs > aio_max_nr)
Linus Torvalds's avatar
Linus Torvalds committed
743
744
		return ERR_PTR(-EAGAIN);

745
	ctx = kmem_cache_zalloc(kioctx_cachep, GFP_KERNEL);
Linus Torvalds's avatar
Linus Torvalds committed
746
747
748
	if (!ctx)
		return ERR_PTR(-ENOMEM);

749
	ctx->max_reqs = max_reqs;
Linus Torvalds's avatar
Linus Torvalds committed
750
751

	spin_lock_init(&ctx->ctx_lock);
752
	spin_lock_init(&ctx->completion_lock);
753
	mutex_init(&ctx->ring_lock);
754
755
756
	/* Protect against page migration throughout kiotx setup by keeping
	 * the ring_lock mutex held until setup is complete. */
	mutex_lock(&ctx->ring_lock);
Linus Torvalds's avatar
Linus Torvalds committed
757
758
759
760
	init_waitqueue_head(&ctx->wait);

	INIT_LIST_HEAD(&ctx->active_reqs);

761
	if (percpu_ref_init(&ctx->users, free_ioctx_users, 0, GFP_KERNEL))
762
763
		goto err;

764
	if (percpu_ref_init(&ctx->reqs, free_ioctx_reqs, 0, GFP_KERNEL))
765
766
		goto err;

Kent Overstreet's avatar
Kent Overstreet committed
767
768
	ctx->cpu = alloc_percpu(struct kioctx_cpu);
	if (!ctx->cpu)
Kent Overstreet's avatar
Kent Overstreet committed
769
		goto err;
Linus Torvalds's avatar
Linus Torvalds committed
770

771
	err = aio_setup_ring(ctx, nr_events);
772
	if (err < 0)
Kent Overstreet's avatar
Kent Overstreet committed
773
		goto err;
Kent Overstreet's avatar
Kent Overstreet committed
774

775
	atomic_set(&ctx->reqs_available, ctx->nr_events - 1);
Kent Overstreet's avatar
Kent Overstreet committed
776
	ctx->req_batch = (ctx->nr_events - 1) / (num_possible_cpus() * 4);
777
778
	if (ctx->req_batch < 1)
		ctx->req_batch = 1;
779

Linus Torvalds's avatar
Linus Torvalds committed
780
	/* limit the number of system wide aios */
781
	spin_lock(&aio_nr_lock);
782
783
	if (aio_nr + ctx->max_reqs > aio_max_nr ||
	    aio_nr + ctx->max_reqs < aio_nr) {
784
		spin_unlock(&aio_nr_lock);
Kent Overstreet's avatar
Kent Overstreet committed
785
		err = -EAGAIN;
786
		goto err_ctx;
787
788
	}
	aio_nr += ctx->max_reqs;
789
	spin_unlock(&aio_nr_lock);
Linus Torvalds's avatar
Linus Torvalds committed
790

791
792
	percpu_ref_get(&ctx->users);	/* io_setup() will drop this ref */
	percpu_ref_get(&ctx->reqs);	/* free_ioctx_users() will drop this */
Kent Overstreet's avatar
Kent Overstreet committed
793

794
795
	err = ioctx_add_table(ctx, mm);
	if (err)
Kent Overstreet's avatar
Kent Overstreet committed
796
		goto err_cleanup;
797

798
799
800
	/* Release the ring_lock mutex now that all setup is complete. */
	mutex_unlock(&ctx->ring_lock);

Kent Overstreet's avatar
Kent Overstreet committed
801
	pr_debug("allocated ioctx %p[%ld]: mm=%p mask=0x%x\n",
802
		 ctx, ctx->user_id, mm, ctx->nr_events);
Linus Torvalds's avatar
Linus Torvalds committed
803
804
	return ctx;

Kent Overstreet's avatar
Kent Overstreet committed
805
806
err_cleanup:
	aio_nr_sub(ctx->max_reqs);
807
err_ctx:
808
809
810
	atomic_set(&ctx->dead, 1);
	if (ctx->mmap_size)
		vm_munmap(ctx->mmap_base, ctx->mmap_size);
811
	aio_free_ring(ctx);
Kent Overstreet's avatar
Kent Overstreet committed
812
err:
813
	mutex_unlock(&ctx->ring_lock);
Kent Overstreet's avatar
Kent Overstreet committed
814
	free_percpu(ctx->cpu);
815
816
	percpu_ref_exit(&ctx->reqs);
	percpu_ref_exit(&ctx->users);
Linus Torvalds's avatar
Linus Torvalds committed
817
	kmem_cache_free(kioctx_cachep, ctx);
Kent Overstreet's avatar
Kent Overstreet committed
818
	pr_debug("error allocating ioctx %d\n", err);
819
	return ERR_PTR(err);
Linus Torvalds's avatar
Linus Torvalds committed
820
821
}

Kent Overstreet's avatar
Kent Overstreet committed
822
823
824
825
826
/* kill_ioctx
 *	Cancels all outstanding aio requests on an aio context.  Used
 *	when the processes owning a context have all exited to encourage
 *	the rapid destruction of the kioctx.
 */
827
static int kill_ioctx(struct mm_struct *mm, struct kioctx *ctx,
828
		      struct ctx_rq_wait *wait)
Kent Overstreet's avatar
Kent Overstreet committed
829
{
830
	struct kioctx_table *table;
831

Al Viro's avatar
Al Viro committed
832
833
834
	spin_lock(&mm->ioctx_lock);
	if (atomic_xchg(&ctx->dead, 1)) {
		spin_unlock(&mm->ioctx_lock);
835
		return -EINVAL;
Al Viro's avatar
Al Viro committed
836
	}
837

838
	table = rcu_dereference_raw(mm->ioctx_table);
839
840
	WARN_ON(ctx != rcu_access_pointer(table->table[ctx->id]));
	RCU_INIT_POINTER(table->table[ctx->id], NULL);
841
	spin_unlock(&mm->ioctx_lock);
842

843
	/* free_ioctx_reqs() will do the necessary RCU synchronization */
844
	wake_up_all(&ctx->wait);
845

846
847
848
849
850
851
852
853
	/*
	 * It'd be more correct to do this in free_ioctx(), after all
	 * the outstanding kiocbs have finished - but by then io_destroy
	 * has already returned, so io_setup() could potentially return
	 * -EAGAIN with no ioctxs actually in use (as far as userspace
	 *  could tell).
	 */
	aio_nr_sub(ctx->max_reqs);
854

855
856
	if (ctx->mmap_size)
		vm_munmap(ctx->mmap_base, ctx->mmap_size);
857

858
	ctx->rq_wait = wait;
859
860
	percpu_ref_kill(&ctx->users);
	return 0;
Linus Torvalds's avatar
Linus Torvalds committed
861
862
}

Kent Overstreet's avatar
Kent Overstreet committed
863
864
865
866
867
868
869
/*
 * exit_aio: called when the last user of mm goes away.  At this point, there is
 * no way for any new requests to be submited or any of the io_* syscalls to be
 * called on the context.
 *
 * There may be outstanding kiocbs, but free_ioctx() will explicitly wait on
 * them.
Linus Torvalds's avatar
Linus Torvalds committed
870
 */
871
void exit_aio(struct mm_struct *mm)
Linus Torvalds's avatar
Linus Torvalds committed
872
{
873
	struct kioctx_table *table = rcu_dereference_raw(mm->ioctx_table);
874
875
	struct ctx_rq_wait wait;
	int i, skipped;
876

877
878
	if (!table)
		return;
879

880
881
882
883
	atomic_set(&wait.count, table->nr);
	init_completion(&wait.comp);

	skipped = 0;
884
	for (i = 0; i < table->nr; ++i) {
885
886
		struct kioctx *ctx =
			rcu_dereference_protected(table->table[i], true);
887

888
889
		if (!ctx) {
			skipped++;
890
			continue;
891
892
		}

893
		/*
894
895
896
897
898
		 * We don't need to bother with munmap() here - exit_mmap(mm)
		 * is coming and it'll unmap everything. And we simply can't,
		 * this is not necessarily our ->mm.
		 * Since kill_ioctx() uses non-zero ->mmap_size as indicator
		 * that it needs to unmap the area, just set it to 0.
899
		 */
900
		ctx->mmap_size = 0;
901
902
		kill_ioctx(mm, ctx, &wait);
	}
Kent Overstreet's avatar
Kent Overstreet committed
903

904
	if (!atomic_sub_and_test(skipped, &wait.count)) {
905
		/* Wait until all IO for the context are done. */
906
		wait_for_completion(&wait.comp);
Linus Torvalds's avatar
Linus Torvalds committed
907
	}
908
909
910

	RCU_INIT_POINTER(mm->ioctx_table, NULL);
	kfree(table);
Linus Torvalds's avatar
Linus Torvalds committed
911
912
}

Kent Overstreet's avatar
Kent Overstreet committed
913
914
915
static void put_reqs_available(struct kioctx *ctx, unsigned nr)
{
	struct kioctx_cpu *kcpu;
916
	unsigned long flags;
Kent Overstreet's avatar
Kent Overstreet committed
917

918
	local_irq_save(flags);
919
	kcpu = this_cpu_ptr(ctx->cpu);
Kent Overstreet's avatar
Kent Overstreet committed
920
	kcpu->reqs_available += nr;
921

Kent Overstreet's avatar
Kent Overstreet committed
922
923
924
925
926
	while (kcpu->reqs_available >= ctx->req_batch * 2) {
		kcpu->reqs_available -= ctx->req_batch;
		atomic_add(ctx->req_batch, &ctx->reqs_available);
	}

927
	local_irq_restore(flags);
Kent Overstreet's avatar
Kent Overstreet committed
928
929
930
931
932
933
}

static bool get_reqs_available(struct kioctx *ctx)
{
	struct kioctx_cpu *kcpu;
	bool ret = false;
934
	unsigned long flags;
Kent Overstreet's avatar
Kent Overstreet committed
935

936
	local_irq_save(flags);
937
	kcpu = this_cpu_ptr(ctx->cpu);
Kent Overstreet's avatar
Kent Overstreet committed
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
	if (!kcpu->reqs_available) {
		int old, avail = atomic_read(&ctx->reqs_available);

		do {
			if (avail < ctx->req_batch)
				goto out;

			old = avail;
			avail = atomic_cmpxchg(&ctx->reqs_available,
					       avail, avail - ctx->req_batch);
		} while (avail != old);

		kcpu->reqs_available += ctx->req_batch;
	}

	ret = true;
	kcpu->reqs_available--;
out:
956
	local_irq_restore(flags);
Kent Overstreet's avatar
Kent Overstreet committed
957
958
959
	return ret;
}

960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
/* refill_reqs_available
 *	Updates the reqs_available reference counts used for tracking the
 *	number of free slots in the completion ring.  This can be called
 *	from aio_complete() (to optimistically update reqs_available) or
 *	from aio_get_req() (the we're out of events case).  It must be
 *	called holding ctx->completion_lock.
 */
static void refill_reqs_available(struct kioctx *ctx, unsigned head,
                                  unsigned tail)
{
	unsigned events_in_ring, completed;

	/* Clamp head since userland can write to it. */
	head %= ctx->nr_events;
	if (head <= tail)
		events_in_ring = tail - head;
	else
		events_in_ring = ctx->nr_events - (head - tail);

	completed = ctx->completed_events;
	if (events_in_ring < completed)
		completed -= events_in_ring;
	else
		completed = 0;

	if (!completed)
		return;

	ctx->completed_events -= completed;
	put_reqs_available(ctx, completed);
}

/* user_refill_reqs_available
 *	Called to refill reqs_available when aio_get_req() encounters an
 *	out of space in the completion ring.
 */
static void user_refill_reqs_available(struct kioctx *ctx)
{
	spin_lock_irq(&ctx->completion_lock);
	if (ctx->completed_events) {
		struct aio_ring *ring;
		unsigned head;

		/* Access of ring->head may race with aio_read_events_ring()
		 * here, but that's okay since whether we read the old version
		 * or the new version, and either will be valid.  The important
		 * part is that head cannot pass tail since we prevent
		 * aio_complete() from updating tail by holding
		 * ctx->completion_lock.  Even if head is invalid, the check
		 * against ctx->completed_events below will make sure we do the
		 * safe/right thing.
		 */
		ring = kmap_atomic(ctx->ring_pages[0]);
		head = ring->head;
		kunmap_atomic(ring);

		refill_reqs_available(ctx, head, ctx->tail);
	}

	spin_unlock_irq(&ctx->completion_lock);
}

Linus Torvalds's avatar
Linus Torvalds committed
1022
/* aio_get_req
Kent Overstreet's avatar
Kent Overstreet committed
1023
1024
 *	Allocate a slot for an aio request.
 * Returns NULL if no requests are free.
Linus Torvalds's avatar
Linus Torvalds committed
1025
 */
1026
static inline struct aio_kiocb *aio_get_req(struct kioctx *ctx)
Linus Torvalds's avatar
Linus Torvalds committed
1027
{
1028
	struct aio_kiocb *req;
Kent Overstreet's avatar
Kent Overstreet committed
1029

1030
1031
1032
1033
1034
	if (!get_reqs_available(ctx)) {
		user_refill_reqs_available(ctx);
		if (!get_reqs_available(ctx))
			return NULL;
	}
Kent Overstreet's avatar
Kent Overstreet committed
1035

1036
	req = kmem_cache_alloc(kiocb_cachep, GFP_KERNEL|__GFP_ZERO);
Linus Torvalds's avatar
Linus Torvalds committed
1037
	if (unlikely(!req))
Kent Overstreet's avatar
Kent Overstreet committed
1038
		goto out_put;
Linus Torvalds's avatar
Linus Torvalds committed
1039

Kent Overstreet's avatar
Kent Overstreet committed
1040
	percpu_ref_get(&ctx->reqs);
1041
	INIT_LIST_HEAD(&req->ki_list);
Linus Torvalds's avatar
Linus Torvalds committed
1042
	req->ki_ctx = ctx;
Jeff Moyer's avatar
Jeff Moyer committed
1043
	return req;
Kent Overstreet's avatar
Kent Overstreet committed
1044
out_put:
Kent Overstreet's avatar
Kent Overstreet committed
1045
	put_reqs_available(ctx, 1);
Kent Overstreet's avatar
Kent Overstreet committed
1046
	return NULL;
Linus Torvalds's avatar
Linus Torvalds committed
1047
1048
}

1049
static void kiocb_free(struct aio_kiocb *req)
Linus Torvalds's avatar
Linus Torvalds committed
1050
{
1051
1052
	if (req->common.ki_filp)
		fput(req->common.ki_filp);
1053
1054
	if (req->ki_eventfd != NULL)
		eventfd_ctx_put(req->ki_eventfd);
Linus Torvalds's avatar
Linus Torvalds committed
1055
1056
1057
	kmem_cache_free(kiocb_cachep, req);
}

1058
static struct kioctx *lookup_ioctx(unsigned long ctx_id)
Linus Torvalds's avatar
Linus Torvalds committed
1059
{
1060
	struct aio_ring __user *ring  = (void __user *)ctx_id;
1061
	struct mm_struct *mm = current->mm;
1062
	struct kioctx *ctx, *ret = NULL;
1063
1064
1065
1066
1067
	struct kioctx_table *table;
	unsigned id;

	if (get_user(id, &ring->id))
		return NULL;
Linus Torvalds's avatar
Linus Torvalds committed
1068

1069
	rcu_read_lock();
1070
	table = rcu_dereference(mm->ioctx_table);
1071

1072
1073
	if (!table || id >= table->nr)
		goto out;
Linus Torvalds's avatar
Linus Torvalds committed
1074

1075
	ctx = rcu_dereference(table->table[id]);
1076
	if (ctx && ctx->user_id == ctx_id) {
1077
1078
1079
1080
		percpu_ref_get(&ctx->users);
		ret = ctx;
	}
out:
1081
	rcu_read_unlock();
1082
	return ret;
Linus Torvalds's avatar
Linus Torvalds committed
1083
1084
1085
1086
1087
}

/* aio_complete
 *	Called when the io request on the given iocb is complete.
 */
1088
static void aio_complete(struct kiocb *kiocb, long res, long res2)
Linus Torvalds's avatar
Linus Torvalds committed
1089
{
1090
	struct aio_kiocb *iocb = container_of(kiocb, struct aio_kiocb, common);
Linus Torvalds's avatar
Linus Torvalds committed
1091
1092
	struct kioctx	*ctx = iocb->ki_ctx;
	struct aio_ring	*ring;
Kent Overstreet's avatar
Kent Overstreet committed
1093
	struct io_event	*ev_page, *event;
1094
	unsigned tail, pos, head;
Linus Torvalds's avatar
Linus Torvalds committed
1095
1096
	unsigned long	flags;

1097
1098
1099
1100
1101
1102
1103
	if (kiocb->ki_flags & IOCB_WRITE) {
		struct file *file = kiocb->ki_filp;

		/*
		 * Tell lockdep we inherited freeze protection from submission
		 * thread.
		 */
Shaohua Li's avatar
Shaohua Li committed
1104
1105
		if (S_ISREG(file_inode(file)->i_mode))
			__sb_writers_acquired(file_inode(file)->i_sb, SB_FREEZE_WRITE);
1106
1107
1108
		file_end_write(file);
	}

1109
	if (!list_empty_careful(&iocb->ki_list)) {
1110
1111
1112
1113
1114
1115
		unsigned long flags;

		spin_lock_irqsave(&ctx->ctx_lock, flags);
		list_del(&iocb