aio.c 49.6 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
#define KIOCB_KEY		0

51
52
53
54
55
56
#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 */
57
58
	unsigned	head;	/* Written to by userland or under ring_lock
				 * mutex by aio_read_events_ring(). */
59
60
61
62
63
64
65
66
67
68
69
70
71
	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

72
struct kioctx_table {
73
74
75
	struct rcu_head		rcu;
	unsigned		nr;
	struct kioctx __rcu	*table[];
76
77
};

Kent Overstreet's avatar
Kent Overstreet committed
78
79
80
81
struct kioctx_cpu {
	unsigned		reqs_available;
};

82
83
84
85
86
struct ctx_rq_wait {
	struct completion comp;
	atomic_t count;
};

87
struct kioctx {
Kent Overstreet's avatar
Kent Overstreet committed
88
	struct percpu_ref	users;
Kent Overstreet's avatar
Kent Overstreet committed
89
	atomic_t		dead;
90

Kent Overstreet's avatar
Kent Overstreet committed
91
92
	struct percpu_ref	reqs;

93
94
	unsigned long		user_id;

Kent Overstreet's avatar
Kent Overstreet committed
95
96
97
98
99
100
101
	struct __percpu kioctx_cpu *cpu;

	/*
	 * For percpu reqs_available, number of slots we move to/from global
	 * counter at a time:
	 */
	unsigned		req_batch;
102
103
104
105
	/*
	 * This is what userspace passed to io_setup(), it's not used for
	 * anything but counting against the global max_reqs quota.
	 *
106
	 * The real limit is nr_events - 1, which will be larger (see
107
108
	 * aio_setup_ring())
	 */
109
110
	unsigned		max_reqs;

111
112
	/* Size of ringbuffer, in units of struct io_event */
	unsigned		nr_events;
113

114
115
116
117
118
119
	unsigned long		mmap_base;
	unsigned long		mmap_size;

	struct page		**ring_pages;
	long			nr_pages;

120
	struct rcu_work		free_rwork;	/* see free_ioctx() */
121

122
123
124
	/*
	 * signals when all in-flight requests are done
	 */
125
	struct ctx_rq_wait	*rq_wait;
126

127
	struct {
128
129
130
131
132
		/*
		 * 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
133
134
		 *
		 * We batch accesses to it with a percpu version.
135
136
		 */
		atomic_t	reqs_available;
137
138
139
140
141
142
143
	} ____cacheline_aligned_in_smp;

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

144
145
	struct {
		struct mutex	ring_lock;
146
147
		wait_queue_head_t wait;
	} ____cacheline_aligned_in_smp;
148
149
150

	struct {
		unsigned	tail;
151
		unsigned	completed_events;
152
		spinlock_t	completion_lock;
153
	} ____cacheline_aligned_in_smp;
154
155

	struct page		*internal_pages[AIO_RING_PAGES];
156
	struct file		*aio_ring_file;
157
158

	unsigned		id;
159
160
};

161
162
163
164
165
166
struct fsync_iocb {
	struct work_struct	work;
	struct file		*file;
	bool			datasync;
};

167
struct aio_kiocb {
168
169
	union {
		struct kiocb		rw;
170
		struct fsync_iocb	fsync;
171
	};
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188

	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
189
/*------ sysctl variables----*/
190
191
192
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
193
194
/*----end sysctl variables---*/

195
196
static struct kmem_cache	*kiocb_cachep;
static struct kmem_cache	*kioctx_cachep;
Linus Torvalds's avatar
Linus Torvalds committed
197

198
199
200
201
202
203
204
205
206
207
208
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);
209
210
	if (IS_ERR(inode))
		return ERR_CAST(inode);
211
212
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

	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
240
241
242
243
244
245
	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;
246
247
}

Linus Torvalds's avatar
Linus Torvalds committed
248
249
250
251
252
253
/* 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)
{
254
255
256
257
258
259
260
261
262
	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.");

263
	kiocb_cachep = KMEM_CACHE(aio_kiocb, SLAB_HWCACHE_ALIGN|SLAB_PANIC);
264
	kioctx_cachep = KMEM_CACHE(kioctx,SLAB_HWCACHE_ALIGN|SLAB_PANIC);
Linus Torvalds's avatar
Linus Torvalds committed
265
266
	return 0;
}
267
__initcall(aio_setup);
Linus Torvalds's avatar
Linus Torvalds committed
268

269
270
271
static void put_aio_ring_file(struct kioctx *ctx)
{
	struct file *aio_ring_file = ctx->aio_ring_file;
272
273
	struct address_space *i_mapping;

274
	if (aio_ring_file) {
Al Viro's avatar
Al Viro committed
275
		truncate_setsize(file_inode(aio_ring_file), 0);
276
277

		/* Prevent further access to the kioctx from migratepages */
Al Viro's avatar
Al Viro committed
278
		i_mapping = aio_ring_file->f_mapping;
279
280
		spin_lock(&i_mapping->private_lock);
		i_mapping->private_data = NULL;
281
		ctx->aio_ring_file = NULL;
282
		spin_unlock(&i_mapping->private_lock);
283
284
285
286
287

		fput(aio_ring_file);
	}
}

Linus Torvalds's avatar
Linus Torvalds committed
288
289
static void aio_free_ring(struct kioctx *ctx)
{
290
	int i;
Linus Torvalds's avatar
Linus Torvalds committed
291

292
293
294
295
296
	/* Disconnect the kiotx from the ring file.  This prevents future
	 * accesses to the kioctx from page migration.
	 */
	put_aio_ring_file(ctx);

297
	for (i = 0; i < ctx->nr_pages; i++) {
298
		struct page *page;
299
300
		pr_debug("pid(%d) [%d] page->count=%d\n", current->pid, i,
				page_count(ctx->ring_pages[i]));
301
302
303
304
305
		page = ctx->ring_pages[i];
		if (!page)
			continue;
		ctx->ring_pages[i] = NULL;
		put_page(page);
306
	}
Linus Torvalds's avatar
Linus Torvalds committed
307

308
	if (ctx->ring_pages && ctx->ring_pages != ctx->internal_pages) {
309
		kfree(ctx->ring_pages);
310
311
		ctx->ring_pages = NULL;
	}
312
313
}

314
static int aio_ring_mremap(struct vm_area_struct *vma)
315
{
316
	struct file *file = vma->vm_file;
317
318
	struct mm_struct *mm = vma->vm_mm;
	struct kioctx_table *table;
Al Viro's avatar
Al Viro committed
319
	int i, res = -EINVAL;
320
321
322
323
324
325
326

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

327
		ctx = rcu_dereference(table->table[i]);
328
		if (ctx && ctx->aio_ring_file == file) {
Al Viro's avatar
Al Viro committed
329
330
331
332
			if (!atomic_read(&ctx->dead)) {
				ctx->user_id = ctx->mmap_base = vma->vm_start;
				res = 0;
			}
333
334
335
336
337
338
			break;
		}
	}

	rcu_read_unlock();
	spin_unlock(&mm->ioctx_lock);
Al Viro's avatar
Al Viro committed
339
	return res;
340
341
}

342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
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;
}

358
359
360
361
static const struct file_operations aio_ring_fops = {
	.mmap = aio_ring_mmap,
};

362
#if IS_ENABLED(CONFIG_MIGRATION)
363
364
365
static int aio_migratepage(struct address_space *mapping, struct page *new,
			struct page *old, enum migrate_mode mode)
{
366
	struct kioctx *ctx;
367
	unsigned long flags;
368
	pgoff_t idx;
369
370
	int rc;

371
372
373
374
375
376
377
378
	/*
	 * 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;

379
380
	rc = 0;

381
	/* mapping->private_lock here protects against the kioctx teardown.  */
382
383
	spin_lock(&mapping->private_lock);
	ctx = mapping->private_data;
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
	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;
403
404
405
406
	} else
		rc = -EINVAL;

	if (rc != 0)
407
		goto out_unlock;
408

409
410
	/* Writeback must be complete */
	BUG_ON(PageWriteback(old));
411
	get_page(new);
412

413
	rc = migrate_page_move_mapping(mapping, new, old, NULL, mode, 1);
414
	if (rc != MIGRATEPAGE_SUCCESS) {
415
		put_page(new);
416
		goto out_unlock;
417
418
	}

419
420
421
	/* 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.
422
	 */
423
424
425
426
427
	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);
428

429
430
	/* The old page is no longer accessible. */
	put_page(old);
431

432
433
434
435
out_unlock:
	mutex_unlock(&ctx->ring_lock);
out:
	spin_unlock(&mapping->private_lock);
436
	return rc;
Linus Torvalds's avatar
Linus Torvalds committed
437
}
438
#endif
Linus Torvalds's avatar
Linus Torvalds committed
439

440
static const struct address_space_operations aio_ctx_aops = {
441
	.set_page_dirty = __set_page_dirty_no_writeback,
442
#if IS_ENABLED(CONFIG_MIGRATION)
443
	.migratepage	= aio_migratepage,
444
#endif
445
446
};

447
static int aio_setup_ring(struct kioctx *ctx, unsigned int nr_events)
Linus Torvalds's avatar
Linus Torvalds committed
448
449
{
	struct aio_ring *ring;
Zach Brown's avatar
Zach Brown committed
450
	struct mm_struct *mm = current->mm;
451
	unsigned long size, unused;
Linus Torvalds's avatar
Linus Torvalds committed
452
	int nr_pages;
453
454
	int i;
	struct file *file;
Linus Torvalds's avatar
Linus Torvalds committed
455
456
457
458
459
460
461

	/* 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;

462
	nr_pages = PFN_UP(size);
Linus Torvalds's avatar
Linus Torvalds committed
463
464
465
	if (nr_pages < 0)
		return -EINVAL;

466
	file = aio_private_file(ctx, nr_pages);
467
468
	if (IS_ERR(file)) {
		ctx->aio_ring_file = NULL;
469
		return -ENOMEM;
470
471
	}

472
473
474
475
476
477
478
479
480
481
482
483
484
485
	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;
		}
	}

486
487
	for (i = 0; i < nr_pages; i++) {
		struct page *page;
Al Viro's avatar
Al Viro committed
488
		page = find_or_create_page(file->f_mapping,
489
490
491
492
493
494
495
					   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);
496
497

		ctx->ring_pages[i] = page;
498
	}
499
	ctx->nr_pages = i;
Linus Torvalds's avatar
Linus Torvalds committed
500

501
502
	if (unlikely(i != nr_pages)) {
		aio_free_ring(ctx);
503
		return -ENOMEM;
Linus Torvalds's avatar
Linus Torvalds committed
504
505
	}

506
507
	ctx->mmap_size = nr_pages * PAGE_SIZE;
	pr_debug("attempting mmap of %lu bytes\n", ctx->mmap_size);
508

509
510
511
512
513
514
	if (down_write_killable(&mm->mmap_sem)) {
		ctx->mmap_size = 0;
		aio_free_ring(ctx);
		return -EINTR;
	}

515
516
	ctx->mmap_base = do_mmap_pgoff(ctx->aio_ring_file, 0, ctx->mmap_size,
				       PROT_READ | PROT_WRITE,
517
				       MAP_SHARED, 0, &unused, NULL);
518
	up_write(&mm->mmap_sem);
519
520
	if (IS_ERR((void *)ctx->mmap_base)) {
		ctx->mmap_size = 0;
Linus Torvalds's avatar
Linus Torvalds committed
521
		aio_free_ring(ctx);
522
		return -ENOMEM;
Linus Torvalds's avatar
Linus Torvalds committed
523
524
	}

525
	pr_debug("mmap address: 0x%08lx\n", ctx->mmap_base);
526

527
528
	ctx->user_id = ctx->mmap_base;
	ctx->nr_events = nr_events; /* trusted copy */
Linus Torvalds's avatar
Linus Torvalds committed
529

530
	ring = kmap_atomic(ctx->ring_pages[0]);
Linus Torvalds's avatar
Linus Torvalds committed
531
	ring->nr = nr_events;	/* user copy */
532
	ring->id = ~0U;
Linus Torvalds's avatar
Linus Torvalds committed
533
534
535
536
537
	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);
538
	kunmap_atomic(ring);
539
	flush_dcache_page(ctx->ring_pages[0]);
Linus Torvalds's avatar
Linus Torvalds committed
540
541
542
543
544
545
546
547

	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)

548
void kiocb_set_cancel_fn(struct kiocb *iocb, kiocb_cancel_fn *cancel)
549
{
550
	struct aio_kiocb *req = container_of(iocb, struct aio_kiocb, rw);
551
552
553
	struct kioctx *ctx = req->ki_ctx;
	unsigned long flags;

554
555
	if (WARN_ON_ONCE(!list_empty(&req->ki_list)))
		return;
556

557
558
	spin_lock_irqsave(&ctx->ctx_lock, flags);
	list_add_tail(&req->ki_list, &ctx->active_reqs);
559
560
561
562
563
	req->ki_cancel = cancel;
	spin_unlock_irqrestore(&ctx->ctx_lock, flags);
}
EXPORT_SYMBOL(kiocb_set_cancel_fn);

564
565
566
/*
 * free_ioctx() should be RCU delayed to synchronize against the RCU
 * protected lookup_ioctx() and also needs process context to call
567
 * aio_free_ring().  Use rcu_work.
568
 */
Kent Overstreet's avatar
Kent Overstreet committed
569
static void free_ioctx(struct work_struct *work)
Kent Overstreet's avatar
Kent Overstreet committed
570
{
571
572
	struct kioctx *ctx = container_of(to_rcu_work(work), struct kioctx,
					  free_rwork);
Kent Overstreet's avatar
Kent Overstreet committed
573
	pr_debug("freeing %p\n", ctx);
Kent Overstreet's avatar
Kent Overstreet committed
574

Kent Overstreet's avatar
Kent Overstreet committed
575
	aio_free_ring(ctx);
Kent Overstreet's avatar
Kent Overstreet committed
576
	free_percpu(ctx->cpu);
577
578
	percpu_ref_exit(&ctx->reqs);
	percpu_ref_exit(&ctx->users);
Kent Overstreet's avatar
Kent Overstreet committed
579
580
581
	kmem_cache_free(kioctx_cachep, ctx);
}

Kent Overstreet's avatar
Kent Overstreet committed
582
583
584
585
static void free_ioctx_reqs(struct percpu_ref *ref)
{
	struct kioctx *ctx = container_of(ref, struct kioctx, reqs);

586
	/* At this point we know that there are no any in-flight requests */
587
588
	if (ctx->rq_wait && atomic_dec_and_test(&ctx->rq_wait->count))
		complete(&ctx->rq_wait->comp);
589

590
	/* Synchronize against RCU protected table->table[] dereferences */
591
592
	INIT_RCU_WORK(&ctx->free_rwork, free_ioctx);
	queue_rcu_work(system_wq, &ctx->free_rwork);
Kent Overstreet's avatar
Kent Overstreet committed
593
594
}

Kent Overstreet's avatar
Kent Overstreet committed
595
596
597
598
599
/*
 * 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
600
static void free_ioctx_users(struct percpu_ref *ref)
Kent Overstreet's avatar
Kent Overstreet committed
601
{
Kent Overstreet's avatar
Kent Overstreet committed
602
	struct kioctx *ctx = container_of(ref, struct kioctx, users);
603
	struct aio_kiocb *req;
Kent Overstreet's avatar
Kent Overstreet committed
604
605
606
607
608

	spin_lock_irq(&ctx->ctx_lock);

	while (!list_empty(&ctx->active_reqs)) {
		req = list_first_entry(&ctx->active_reqs,
609
				       struct aio_kiocb, ki_list);
Christoph Hellwig's avatar
Christoph Hellwig committed
610
		req->ki_cancel(&req->rw);
Al Viro's avatar
Al Viro committed
611
		list_del_init(&req->ki_list);
Kent Overstreet's avatar
Kent Overstreet committed
612
613
614
615
	}

	spin_unlock_irq(&ctx->ctx_lock);

Kent Overstreet's avatar
Kent Overstreet committed
616
617
	percpu_ref_kill(&ctx->reqs);
	percpu_ref_put(&ctx->reqs);
Kent Overstreet's avatar
Kent Overstreet committed
618
619
}

620
621
622
623
624
625
626
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);
627
	table = rcu_dereference_raw(mm->ioctx_table);
628
629
630
631

	while (1) {
		if (table)
			for (i = 0; i < table->nr; i++)
632
				if (!rcu_access_pointer(table->table[i])) {
633
					ctx->id = i;
634
					rcu_assign_pointer(table->table[i], ctx);
635
636
					spin_unlock(&mm->ioctx_lock);

637
638
639
640
					/* While kioctx setup is in progress,
					 * we are protected from page migration
					 * changes ring_pages by ->ring_lock.
					 */
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
					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);
658
		old = rcu_dereference_raw(mm->ioctx_table);
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674

		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
675
676
677
678
679
680
681
682
683
684
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
685
686
687
688
689
/* 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
690
	struct mm_struct *mm = current->mm;
Linus Torvalds's avatar
Linus Torvalds committed
691
	struct kioctx *ctx;
692
	int err = -ENOMEM;
Linus Torvalds's avatar
Linus Torvalds committed
693

694
695
696
697
698
699
	/*
	 * 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
700
701
702
703
704
705
706
707
708
709
710
711
	/*
	 * 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
712
	/* Prevent overflows */
713
	if (nr_events > (0x10000000U / sizeof(struct io_event))) {
Linus Torvalds's avatar
Linus Torvalds committed
714
715
716
717
		pr_debug("ENOMEM: nr_events too high\n");
		return ERR_PTR(-EINVAL);
	}

718
	if (!nr_events || (unsigned long)max_reqs > aio_max_nr)
Linus Torvalds's avatar
Linus Torvalds committed
719
720
		return ERR_PTR(-EAGAIN);

721
	ctx = kmem_cache_zalloc(kioctx_cachep, GFP_KERNEL);
Linus Torvalds's avatar
Linus Torvalds committed
722
723
724
	if (!ctx)
		return ERR_PTR(-ENOMEM);

725
	ctx->max_reqs = max_reqs;
Linus Torvalds's avatar
Linus Torvalds committed
726
727

	spin_lock_init(&ctx->ctx_lock);
728
	spin_lock_init(&ctx->completion_lock);
729
	mutex_init(&ctx->ring_lock);
730
731
732
	/* 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
733
734
735
736
	init_waitqueue_head(&ctx->wait);

	INIT_LIST_HEAD(&ctx->active_reqs);

737
	if (percpu_ref_init(&ctx->users, free_ioctx_users, 0, GFP_KERNEL))
738
739
		goto err;

740
	if (percpu_ref_init(&ctx->reqs, free_ioctx_reqs, 0, GFP_KERNEL))
741
742
		goto err;

Kent Overstreet's avatar
Kent Overstreet committed
743
744
	ctx->cpu = alloc_percpu(struct kioctx_cpu);
	if (!ctx->cpu)
Kent Overstreet's avatar
Kent Overstreet committed
745
		goto err;
Linus Torvalds's avatar
Linus Torvalds committed
746

747
	err = aio_setup_ring(ctx, nr_events);
748
	if (err < 0)
Kent Overstreet's avatar
Kent Overstreet committed
749
		goto err;
Kent Overstreet's avatar
Kent Overstreet committed
750

751
	atomic_set(&ctx->reqs_available, ctx->nr_events - 1);
Kent Overstreet's avatar
Kent Overstreet committed
752
	ctx->req_batch = (ctx->nr_events - 1) / (num_possible_cpus() * 4);
753
754
	if (ctx->req_batch < 1)
		ctx->req_batch = 1;
755

Linus Torvalds's avatar
Linus Torvalds committed
756
	/* limit the number of system wide aios */
757
	spin_lock(&aio_nr_lock);
758
759
	if (aio_nr + ctx->max_reqs > aio_max_nr ||
	    aio_nr + ctx->max_reqs < aio_nr) {
760
		spin_unlock(&aio_nr_lock);
Kent Overstreet's avatar
Kent Overstreet committed
761
		err = -EAGAIN;
762
		goto err_ctx;
763
764
	}
	aio_nr += ctx->max_reqs;
765
	spin_unlock(&aio_nr_lock);
Linus Torvalds's avatar
Linus Torvalds committed
766

767
768
	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
769

770
771
	err = ioctx_add_table(ctx, mm);
	if (err)
Kent Overstreet's avatar
Kent Overstreet committed
772
		goto err_cleanup;
773

774
775
776
	/* Release the ring_lock mutex now that all setup is complete. */
	mutex_unlock(&ctx->ring_lock);

Kent Overstreet's avatar
Kent Overstreet committed
777
	pr_debug("allocated ioctx %p[%ld]: mm=%p mask=0x%x\n",
778
		 ctx, ctx->user_id, mm, ctx->nr_events);
Linus Torvalds's avatar
Linus Torvalds committed
779
780
	return ctx;

Kent Overstreet's avatar
Kent Overstreet committed
781
782
err_cleanup:
	aio_nr_sub(ctx->max_reqs);
783
err_ctx:
784
785
786
	atomic_set(&ctx->dead, 1);
	if (ctx->mmap_size)
		vm_munmap(ctx->mmap_base, ctx->mmap_size);
787
	aio_free_ring(ctx);
Kent Overstreet's avatar
Kent Overstreet committed
788
err:
789
	mutex_unlock(&ctx->ring_lock);
Kent Overstreet's avatar
Kent Overstreet committed
790
	free_percpu(ctx->cpu);
791
792
	percpu_ref_exit(&ctx->reqs);
	percpu_ref_exit(&ctx->users);
Linus Torvalds's avatar
Linus Torvalds committed
793
	kmem_cache_free(kioctx_cachep, ctx);
Kent Overstreet's avatar
Kent Overstreet committed
794
	pr_debug("error allocating ioctx %d\n", err);
795
	return ERR_PTR(err);
Linus Torvalds's avatar
Linus Torvalds committed
796
797
}

Kent Overstreet's avatar
Kent Overstreet committed
798
799
800
801
802
/* 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.
 */
803
static int kill_ioctx(struct mm_struct *mm, struct kioctx *ctx,
804
		      struct ctx_rq_wait *wait)
Kent Overstreet's avatar
Kent Overstreet committed
805
{
806
	struct kioctx_table *table;
807

Al Viro's avatar
Al Viro committed
808
809
810
	spin_lock(&mm->ioctx_lock);
	if (atomic_xchg(&ctx->dead, 1)) {
		spin_unlock(&mm->ioctx_lock);
811
		return -EINVAL;
Al Viro's avatar
Al Viro committed
812
	}
813

814
	table = rcu_dereference_raw(mm->ioctx_table);
815
816
	WARN_ON(ctx != rcu_access_pointer(table->table[ctx->id]));
	RCU_INIT_POINTER(table->table[ctx->id], NULL);
817
	spin_unlock(&mm->ioctx_lock);
818

819
	/* free_ioctx_reqs() will do the necessary RCU synchronization */
820
	wake_up_all(&ctx->wait);
821

822
823
824
825
826
827
828
829
	/*
	 * 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);
830

831
832
	if (ctx->mmap_size)
		vm_munmap(ctx->mmap_base, ctx->mmap_size);
833

834
	ctx->rq_wait = wait;
835
836
	percpu_ref_kill(&ctx->users);
	return 0;
Linus Torvalds's avatar
Linus Torvalds committed
837
838
}

Kent Overstreet's avatar
Kent Overstreet committed
839
840
841
842
843
844
845
/*
 * 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
846
 */
847
void exit_aio(struct mm_struct *mm)
Linus Torvalds's avatar
Linus Torvalds committed
848
{
849
	struct kioctx_table *table = rcu_dereference_raw(mm->ioctx_table);
850
851
	struct ctx_rq_wait wait;
	int i, skipped;
852

853
854
	if (!table)
		return;
855

856
857
858
859
	atomic_set(&wait.count, table->nr);
	init_completion(&wait.comp);

	skipped = 0;
860
	for (i = 0; i < table->nr; ++i) {
861
862
		struct kioctx *ctx =
			rcu_dereference_protected(table->table[i], true);
863

864
865
		if (!ctx) {
			skipped++;
866
			continue;
867
868
		}

869
		/*
870
871
872
873
874
		 * 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.
875
		 */
876
		ctx->mmap_size = 0;
877
878
		kill_ioctx(mm, ctx, &wait);
	}
Kent Overstreet's avatar
Kent Overstreet committed
879

880
	if (!atomic_sub_and_test(skipped, &wait.count)) {
881
		/* Wait until all IO for the context are done. */
882
		wait_for_completion(&wait.comp);
Linus Torvalds's avatar
Linus Torvalds committed
883
	}
884
885
886

	RCU_INIT_POINTER(mm->ioctx_table, NULL);
	kfree(table);
Linus Torvalds's avatar
Linus Torvalds committed
887
888
}

Kent Overstreet's avatar
Kent Overstreet committed
889
890
891
static void put_reqs_available(struct kioctx *ctx, unsigned nr)
{
	struct kioctx_cpu *kcpu;
892
	unsigned long flags;
Kent Overstreet's avatar
Kent Overstreet committed
893

894
	local_irq_save(flags);
895
	kcpu = this_cpu_ptr(ctx->cpu);
Kent Overstreet's avatar
Kent Overstreet committed
896
	kcpu->reqs_available += nr;
897

Kent Overstreet's avatar
Kent Overstreet committed
898
899
900
901
902
	while (kcpu->reqs_available >= ctx->req_batch * 2) {
		kcpu->reqs_available -= ctx->req_batch;
		atomic_add(ctx->req_batch, &ctx->reqs_available);
	}

903
	local_irq_restore(flags);
Kent Overstreet's avatar
Kent Overstreet committed
904
905
906
907
908
909
}

static bool get_reqs_available(struct kioctx *ctx)
{
	struct kioctx_cpu *kcpu;
	bool ret = false;
910
	unsigned long flags;
Kent Overstreet's avatar
Kent Overstreet committed
911

912
	local_irq_save(flags);
913
	kcpu = this_cpu_ptr(ctx->cpu);
Kent Overstreet's avatar
Kent Overstreet committed
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
	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:
932
	local_irq_restore(flags);
Kent Overstreet's avatar
Kent Overstreet committed
933
934
935
	return ret;
}

936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
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
/* 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
998
/* aio_get_req
Kent Overstreet's avatar
Kent Overstreet committed
999
1000
 *	Allocate a slot for an aio request.
 * Returns NULL if no requests are free.
Linus Torvalds's avatar
Linus Torvalds committed
1001
 */
1002
static inline struct aio_kiocb *aio_get_req(struct kioctx *ctx)
Linus Torvalds's avatar
Linus Torvalds committed
1003
{
1004
	struct aio_kiocb *req;
Kent Overstreet's avatar
Kent Overstreet committed
1005

1006
1007
1008
1009
1010
	if (!get_reqs_available(ctx)) {
		user_refill_reqs_available(ctx);
		if (!get_reqs_available(ctx))
			return NULL;
	}
Kent Overstreet's avatar
Kent Overstreet committed
1011

1012
	req = kmem_cache_alloc(kiocb_cachep, GFP_KERNEL|__GFP_ZERO);
Linus Torvalds's avatar
Linus Torvalds committed
1013
	if (unlikely(!req))
Kent Overstreet's avatar
Kent Overstreet committed
1014
		goto out_put;
Linus Torvalds's avatar
Linus Torvalds committed
1015

Kent Overstreet's avatar
Kent Overstreet committed
1016
	percpu_ref_get(&ctx->reqs);
1017
	INIT_LIST_HEAD(&req->ki_list);
Linus Torvalds's avatar
Linus Torvalds committed
1018
	req->ki_ctx = ctx;
Jeff Moyer's avatar
Jeff Moyer committed
1019
	return req;
Kent Overstreet's avatar
Kent Overstreet committed
1020
out_put:
Kent Overstreet's avatar
Kent Overstreet committed
1021
	put_reqs_available(ctx, 1);
Kent Overstreet's avatar
Kent Overstreet committed
1022
	return NULL;
Linus Torvalds's avatar
Linus Torvalds committed
1023
1024
}

1025
static struct kioctx *lookup_ioctx(unsigned long ctx_id)
Linus Torvalds's avatar
Linus Torvalds committed
1026
{
1027
	struct aio_ring __user *ring  = (void __user *)ctx_id;
1028
	struct mm_struct *mm = current->mm;
1029
	struct kioctx *ctx, *ret = NULL;
1030
1031
1032
1033
1034
	struct kioctx_table *table;
	unsigned id;

	if (get_user(id, &ring->id))
		return NULL;
Linus Torvalds's avatar
Linus Torvalds committed
1035

1036
	rcu_read_lock();
1037
	table = rcu_dereference(mm->ioctx_table);
1038

1039
1040
	if (!table || id >= table->nr)
		goto out;
Linus Torvalds's avatar
Linus Torvalds committed
1041

1042
	ctx = rcu_dereference(table->table[id]);
1043
	if (ctx && ctx->user_id == ctx_id) {
1044
1045
		if (percpu_ref_tryget_live(&ctx->users))
			ret = ctx;
1046
1047
	}
out:
1048
	rcu_read_unlock();
1049
	return ret;
Linus Torvalds's avatar
Linus Torvalds committed
1050
1051
1052
1053
1054
}

/* aio_complete
 *	Called when the io request on the given iocb is complete.
 */
1055
static void aio_complete(struct aio_kiocb *iocb, long res, long res2)
Linus Torvalds's avatar
Linus Torvalds committed
1056
1057
1058
{
	struct kioctx	*ctx = iocb->ki_ctx;
	struct aio_ring	*ring;
Kent Overstreet's avatar
Kent Overstreet committed
1059
	struct io_event	*ev_page, *event;
1060
	unsigned tail, pos, head;
Linus Torvalds's avatar
Linus Torvalds committed
1061
1062
	unsigned long	flags;

1063
1064
	/*
	 * Add a completion event to the ring buffer. Must be done holding
1065
	 * ctx->completion_lock to prevent other code from messing with the tail
1066
1067
1068
1069
	 * pointer since we might be called from irq context.
	 */
	spin_lock_irqsave(&ctx->completion_lock, flags);

1070
	tail = ctx->tail;
Kent Overstreet's avatar
Kent Overstreet committed
1071
1072
	pos = tail + AIO_EVENTS_OFFSET;

1073
	if (++tail >= ctx->nr_events)
1074
		tail = 0;
Linus Torvalds's avatar
Linus Torvalds committed
1075

1076
	ev_page = kmap_atomic(ctx->ring_pages[pos / AIO_EVENTS_PER_PAGE]);
Kent Overstreet's avatar
Kent Overstreet committed
1077
1078
	event = ev_page + pos % AIO_EVENTS_PER_PAGE;

1079
	event->obj = (u64)(unsigned long)iocb->ki_user_iocb;
Linus Torvalds's avatar
Linus Torvalds committed
1080
1081
1082
1083
	event->data = iocb->ki_user_data;
	event->res = res;
	event->res2 = res2;

Kent Overstreet's avatar
Kent Overstreet committed
1084
	kunmap_atomic(ev_page);
1085
	flush_dcache_page(ctx->ring_pages[pos / AIO_EVENTS_PER_PAGE]);
Kent Overstreet's avatar
Kent Overstreet committed
1086
1087

	pr_debug("%p[%u]: %p: %p %Lx %lx %lx\n",
1088
		 ctx, tail, iocb, iocb->ki_user_iocb, iocb->ki_user_data,
Kent Overstreet's avatar
Kent Overstreet committed
1089
		 res, res2);
Linus Torvalds's avatar
Linus Torvalds committed
1090
1091
1092
1093
1094
1095

	/* after flagging the request as done, we
	 * must never even look at it again
	 */
	smp_wmb();	/* make event visible before updating tail */

1096
	ctx->tail = tail;
Linus Torvalds's avatar
Linus Torvalds committed
1097

1098
	ring = kmap_atomic(ctx->ring_pages[0]);