summaryrefslogtreecommitdiffstats
path: root/fs/iomap/direct-io.c
blob: 9398b8c31323b39278144bf8cbaa1ba5d0f94180 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
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
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
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
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (C) 2010 Red Hat, Inc.
 * Copyright (c) 2016-2018 Christoph Hellwig.
 */
#include <linux/module.h>
#include <linux/compiler.h>
#include <linux/fs.h>
#include <linux/iomap.h>
#include <linux/backing-dev.h>
#include <linux/uio.h>
#include <linux/task_io_accounting_ops.h>
#include "trace.h"

#include "../internal.h"

/*
 * Private flags for iomap_dio, must not overlap with the public ones in
 * iomap.h:
 */
#define IOMAP_DIO_WRITE_FUA	(1 << 28)
#define IOMAP_DIO_NEED_SYNC	(1 << 29)
#define IOMAP_DIO_WRITE		(1 << 30)
#define IOMAP_DIO_DIRTY		(1 << 31)

struct iomap_dio {
	struct kiocb		*iocb;
	const struct iomap_dio_ops *dops;
	loff_t			i_size;
	loff_t			size;
	atomic_t		ref;
	unsigned		flags;
	int			error;
	bool			wait_for_completion;

	union {
		/* used during submission and for synchronous completion: */
		struct {
			struct iov_iter		*iter;
			struct task_struct	*waiter;
			struct request_queue	*last_queue;
			blk_qc_t		cookie;
		} submit;

		/* used for aio completion: */
		struct {
			struct work_struct	work;
		} aio;
	};
};

int iomap_dio_iopoll(struct kiocb *kiocb, bool spin)
{
	struct request_queue *q = READ_ONCE(kiocb->private);

	if (!q)
		return 0;
	return blk_poll(q, READ_ONCE(kiocb->ki_cookie), spin);
}
EXPORT_SYMBOL_GPL(iomap_dio_iopoll);

static void iomap_dio_submit_bio(struct iomap_dio *dio, struct iomap *iomap,
		struct bio *bio, loff_t pos)
{
	atomic_inc(&dio->ref);

	if (dio->iocb->ki_flags & IOCB_HIPRI)
		bio_set_polled(bio, dio->iocb);

	dio->submit.last_queue = bdev_get_queue(iomap->bdev);
	if (dio->dops && dio->dops->submit_io)
		dio->submit.cookie = dio->dops->submit_io(
				file_inode(dio->iocb->ki_filp),
				iomap, bio, pos);
	else
		dio->submit.cookie = submit_bio(bio);
}

ssize_t iomap_dio_complete(struct iomap_dio *dio)
{
	const struct iomap_dio_ops *dops = dio->dops;
	struct kiocb *iocb = dio->iocb;
	struct inode *inode = file_inode(iocb->ki_filp);
	loff_t offset = iocb->ki_pos;
	ssize_t ret = dio->error;

	if (dops && dops->end_io)
		ret = dops->end_io(iocb, dio->size, ret, dio->flags);

	if (likely(!ret)) {
		ret = dio->size;
		/* check for short read */
		if (offset + ret > dio->i_size &&
		    !(dio->flags & IOMAP_DIO_WRITE))
			ret = dio->i_size - offset;
		iocb->ki_pos += ret;
	}

	/*
	 * Try again to invalidate clean pages which might have been cached by
	 * non-direct readahead, or faulted in by get_user_pages() if the source
	 * of the write was an mmap'ed region of the file we're writing.  Either
	 * one is a pretty crazy thing to do, so we don't support it 100%.  If
	 * this invalidation fails, tough, the write still worked...
	 *
	 * And this page cache invalidation has to be after ->end_io(), as some
	 * filesystems convert unwritten extents to real allocations in
	 * ->end_io() when necessary, otherwise a racing buffer read would cache
	 * zeros from unwritten extents.
	 */
	if (!dio->error && dio->size &&
	    (dio->flags & IOMAP_DIO_WRITE) && inode->i_mapping->nrpages) {
		int err;
		err = invalidate_inode_pages2_range(inode->i_mapping,
				offset >> PAGE_SHIFT,
				(offset + dio->size - 1) >> PAGE_SHIFT);
		if (err)
			dio_warn_stale_pagecache(iocb->ki_filp);
	}

	inode_dio_end(file_inode(iocb->ki_filp));
	/*
	 * If this is a DSYNC write, make sure we push it to stable storage now
	 * that we've written data.
	 */
	if (ret > 0 && (dio->flags & IOMAP_DIO_NEED_SYNC))
		ret = generic_write_sync(iocb, ret);

	kfree(dio);

	return ret;
}
EXPORT_SYMBOL_GPL(iomap_dio_complete);

static void iomap_dio_complete_work(struct work_struct *work)
{
	struct iomap_dio *dio = container_of(work, struct iomap_dio, aio.work);
	struct kiocb *iocb = dio->iocb;

	iocb->ki_complete(iocb, iomap_dio_complete(dio), 0);
}

/*
 * Set an error in the dio if none is set yet.  We have to use cmpxchg
 * as the submission context and the completion context(s) can race to
 * update the error.
 */
static inline void iomap_dio_set_error(struct iomap_dio *dio, int ret)
{
	cmpxchg(&dio->error, 0, ret);
}

static void iomap_dio_bio_end_io(struct bio *bio)
{
	struct iomap_dio *dio = bio->bi_private;
	bool should_dirty = (dio->flags & IOMAP_DIO_DIRTY);

	if (bio->bi_status)
		iomap_dio_set_error(dio, blk_status_to_errno(bio->bi_status));

	if (atomic_dec_and_test(&dio->ref)) {
		if (dio->wait_for_completion) {
			struct task_struct *waiter = dio->submit.waiter;
			WRITE_ONCE(dio->submit.waiter, NULL);
			blk_wake_io_task(waiter);
		} else if (dio->flags & IOMAP_DIO_WRITE) {
			struct inode *inode = file_inode(dio->iocb->ki_filp);

			INIT_WORK(&dio->aio.work, iomap_dio_complete_work);
			queue_work(inode->i_sb->s_dio_done_wq, &dio->aio.work);
		} else {
			iomap_dio_complete_work(&dio->aio.work);
		}
	}

	if (should_dirty) {
		bio_check_pages_dirty(bio);
	} else {
		bio_release_pages(bio, false);
		bio_put(bio);
	}
}

static void
iomap_dio_zero(struct iomap_dio *dio, struct iomap *iomap, loff_t pos,
		unsigned len)
{
	struct page *page = ZERO_PAGE(0);
	int flags = REQ_SYNC | REQ_IDLE;
	struct bio *bio;

	bio = bio_alloc(GFP_KERNEL, 1);
	bio_set_dev(bio, iomap->bdev);
	bio->bi_iter.bi_sector = iomap_sector(iomap, pos);
	bio->bi_private = dio;
	bio->bi_end_io = iomap_dio_bio_end_io;

	get_page(page);
	__bio_add_page(bio, page, len, 0);
	bio_set_op_attrs(bio, REQ_OP_WRITE, flags);
	iomap_dio_submit_bio(dio, iomap, bio, pos);
}

/*
 * Figure out the bio's operation flags from the dio request, the
 * mapping, and whether or not we want FUA.  Note that we can end up
 * clearing the WRITE_FUA flag in the dio request.
 */
static inline unsigned int
iomap_dio_bio_opflags(struct iomap_dio *dio, struct iomap *iomap, bool use_fua)
{
	unsigned int opflags = REQ_SYNC | REQ_IDLE;

	if (!(dio->flags & IOMAP_DIO_WRITE)) {
		WARN_ON_ONCE(iomap->flags & IOMAP_F_ZONE_APPEND);
		return REQ_OP_READ;
	}

	if (iomap->flags & IOMAP_F_ZONE_APPEND)
		opflags |= REQ_OP_ZONE_APPEND;
	else
		opflags |= REQ_OP_WRITE;

	if (use_fua)
		opflags |= REQ_FUA;
	else
		dio->flags &= ~IOMAP_DIO_WRITE_FUA;

	return opflags;
}

static loff_t
iomap_dio_bio_actor(struct inode *inode, loff_t pos, loff_t length,
		struct iomap_dio *dio, struct iomap *iomap)
{
	unsigned int blkbits = blksize_bits(bdev_logical_block_size(iomap->bdev));
	unsigned int fs_block_size = i_blocksize(inode), pad;
	unsigned int align = iov_iter_alignment(dio->submit.iter);
	unsigned int bio_opf;
	struct bio *bio;
	bool need_zeroout = false;
	bool use_fua = false;
	int nr_pages, ret = 0;
	size_t copied = 0;
	size_t orig_count;

	if ((pos | length | align) & ((1 << blkbits) - 1))
		return -EINVAL;

	if (iomap->type == IOMAP_UNWRITTEN) {
		dio->flags |= IOMAP_DIO_UNWRITTEN;
		need_zeroout = true;
	}

	if (iomap->flags & IOMAP_F_SHARED)
		dio->flags |= IOMAP_DIO_COW;

	if (iomap->flags & IOMAP_F_NEW) {
		need_zeroout = true;
	} else if (iomap->type == IOMAP_MAPPED) {
		/*
		 * Use a FUA write if we need datasync semantics, this is a pure
		 * data IO that doesn't require any metadata updates (including
		 * after IO completion such as unwritten extent conversion) and
		 * the underlying device supports FUA. This allows us to avoid
		 * cache flushes on IO completion.
		 */
		if (!(iomap->flags & (IOMAP_F_SHARED|IOMAP_F_DIRTY)) &&
		    (dio->flags & IOMAP_DIO_WRITE_FUA) &&
		    blk_queue_fua(bdev_get_queue(iomap->bdev)))
			use_fua = true;
	}

	/*
	 * Save the original count and trim the iter to just the extent we
	 * are operating on right now.  The iter will be re-expanded once
	 * we are done.
	 */
	orig_count = iov_iter_count(dio->submit.iter);
	iov_iter_truncate(dio->submit.iter, length);

	if (!iov_iter_count(dio->submit.iter))
		goto out;

	if (need_zeroout) {
		/* zero out from the start of the block to the write offset */
		pad = pos & (fs_block_size - 1);
		if (pad)
			iomap_dio_zero(dio, iomap, pos - pad, pad);
	}

	/*
	 * Set the operation flags early so that bio_iov_iter_get_pages
	 * can set up the page vector appropriately for a ZONE_APPEND
	 * operation.
	 */
	bio_opf = iomap_dio_bio_opflags(dio, iomap, use_fua);

	nr_pages = bio_iov_vecs_to_alloc(dio->submit.iter, BIO_MAX_VECS);
	do {
		size_t n;
		if (dio->error) {
			iov_iter_revert(dio->submit.iter, copied);
			copied = ret = 0;
			goto out;
		}

		bio = bio_alloc(GFP_KERNEL, nr_pages);
		bio_set_dev(bio, iomap->bdev);
		bio->bi_iter.bi_sector = iomap_sector(iomap, pos);
		bio->bi_write_hint = dio->iocb->ki_hint;
		bio->bi_ioprio = dio->iocb->ki_ioprio;
		bio->bi_private = dio;
		bio->bi_end_io = iomap_dio_bio_end_io;
		bio->bi_opf = bio_opf;

		ret = bio_iov_iter_get_pages(bio, dio->submit.iter);
		if (unlikely(ret)) {
			/*
			 * We have to stop part way through an IO. We must fall
			 * through to the sub-block tail zeroing here, otherwise
			 * this short IO may expose stale data in the tail of
			 * the block we haven't written data to.
			 */
			bio_put(bio);
			goto zero_tail;
		}

		n = bio->bi_iter.bi_size;
		if (dio->flags & IOMAP_DIO_WRITE) {
			task_io_account_write(n);
		} else {
			if (dio->flags & IOMAP_DIO_DIRTY)
				bio_set_pages_dirty(bio);
		}

		dio->size += n;
		copied += n;

		nr_pages = bio_iov_vecs_to_alloc(dio->submit.iter,
						 BIO_MAX_VECS);
		iomap_dio_submit_bio(dio, iomap, bio, pos);
		pos += n;
	} while (nr_pages);

	/*
	 * We need to zeroout the tail of a sub-block write if the extent type
	 * requires zeroing or the write extends beyond EOF. If we don't zero
	 * the block tail in the latter case, we can expose stale data via mmap
	 * reads of the EOF block.
	 */
zero_tail:
	if (need_zeroout ||
	    ((dio->flags & IOMAP_DIO_WRITE) && pos >= i_size_read(inode))) {
		/* zero out from the end of the write to the end of the block */
		pad = pos & (fs_block_size - 1);
		if (pad)
			iomap_dio_zero(dio, iomap, pos, fs_block_size - pad);
	}
out:
	/* Undo iter limitation to current extent */
	iov_iter_reexpand(dio->submit.iter, orig_count - copied);
	if (copied)
		return copied;
	return ret;
}

static loff_t
iomap_dio_hole_actor(loff_t length, struct iomap_dio *dio)
{
	length = iov_iter_zero(length, dio->submit.iter);
	dio->size += length;
	return length;
}

static loff_t
iomap_dio_inline_actor(struct inode *inode, loff_t pos, loff_t length,
		struct iomap_dio *dio, struct iomap *iomap)
{
	struct iov_iter *iter = dio->submit.iter;
	size_t copied;

	BUG_ON(pos + length > PAGE_SIZE - offset_in_page(iomap->inline_data));

	if (dio->flags & IOMAP_DIO_WRITE) {
		loff_t size = inode->i_size;

		if (pos > size)
			memset(iomap->inline_data + size, 0, pos - size);
		copied = copy_from_iter(iomap->inline_data + pos, length, iter);
		if (copied) {
			if (pos + copied > size)
				i_size_write(inode, pos + copied);
			mark_inode_dirty(inode);
		}
	} else {
		copied = copy_to_iter(iomap->inline_data + pos, length, iter);
	}
	dio->size += copied;
	return copied;
}

static loff_t
iomap_dio_actor(struct inode *inode, loff_t pos, loff_t length,
		void *data, struct iomap *iomap, struct iomap *srcmap)
{
	struct iomap_dio *dio = data;

	switch (iomap->type) {
	case IOMAP_HOLE:
		if (WARN_ON_ONCE(dio->flags & IOMAP_DIO_WRITE))
			return -EIO;
		return iomap_dio_hole_actor(length, dio);
	case IOMAP_UNWRITTEN:
		if (!(dio->flags & IOMAP_DIO_WRITE))
			return iomap_dio_hole_actor(length, dio);
		return iomap_dio_bio_actor(inode, pos, length, dio, iomap);
	case IOMAP_MAPPED:
		return iomap_dio_bio_actor(inode, pos, length, dio, iomap);
	case IOMAP_INLINE:
		return iomap_dio_inline_actor(inode, pos, length, dio, iomap);
	case IOMAP_DELALLOC:
		/*
		 * DIO is not serialised against mmap() access at all, and so
		 * if the page_mkwrite occurs between the writeback and the
		 * iomap_apply() call in the DIO path, then it will see the
		 * DELALLOC block that the page-mkwrite allocated.
		 */
		pr_warn_ratelimited("Direct I/O collision with buffered writes! File: %pD4 Comm: %.20s\n",
				    dio->iocb->ki_filp, current->comm);
		return -EIO;
	default:
		WARN_ON_ONCE(1);
		return -EIO;
	}
}

/*
 * iomap_dio_rw() always completes O_[D]SYNC writes regardless of whether the IO
 * is being issued as AIO or not.  This allows us to optimise pure data writes
 * to use REQ_FUA rather than requiring generic_write_sync() to issue a
 * REQ_FLUSH post write. This is slightly tricky because a single request here
 * can be mapped into multiple disjoint IOs and only a subset of the IOs issued
 * may be pure data writes. In that case, we still need to do a full data sync
 * completion.
 *
 * Returns -ENOTBLK In case of a page invalidation invalidation failure for
 * writes.  The callers needs to fall back to buffered I/O in this case.
 */
struct iomap_dio *
__iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
		const struct iomap_ops *ops, const struct iomap_dio_ops *dops,
		unsigned int dio_flags)
{
	struct address_space *mapping = iocb->ki_filp->f_mapping;
	struct inode *inode = file_inode(iocb->ki_filp);
	size_t count = iov_iter_count(iter);
	loff_t pos = iocb->ki_pos;
	loff_t end = iocb->ki_pos + count - 1, ret = 0;
	bool wait_for_completion =
		is_sync_kiocb(iocb) || (dio_flags & IOMAP_DIO_FORCE_WAIT);
	unsigned int iomap_flags = IOMAP_DIRECT;
	struct blk_plug plug;
	struct iomap_dio *dio;

	if (!count)
		return NULL;

	dio = kmalloc(sizeof(*dio), GFP_KERNEL);
	if (!dio)
		return ERR_PTR(-ENOMEM);

	dio->iocb = iocb;
	atomic_set(&dio->ref, 1);
	dio->size = 0;
	dio->i_size = i_size_read(inode);
	dio->dops = dops;
	dio->error = 0;
	dio->flags = 0;

	dio->submit.iter = iter;
	dio->submit.waiter = current;
	dio->submit.cookie = BLK_QC_T_NONE;
	dio->submit.last_queue = NULL;

	if (iov_iter_rw(iter) == READ) {
		if (pos >= dio->i_size)
			goto out_free_dio;

		if (iocb->ki_flags & IOCB_NOWAIT) {
			if (filemap_range_needs_writeback(mapping, pos, end)) {
				ret = -EAGAIN;
				goto out_free_dio;
			}
			iomap_flags |= IOMAP_NOWAIT;
		}

		if (iter_is_iovec(iter))
			dio->flags |= IOMAP_DIO_DIRTY;
	} else {
		iomap_flags |= IOMAP_WRITE;
		dio->flags |= IOMAP_DIO_WRITE;

		if (iocb->ki_flags & IOCB_NOWAIT) {
			if (filemap_range_has_page(mapping, pos, end)) {
				ret = -EAGAIN;
				goto out_free_dio;
			}
			iomap_flags |= IOMAP_NOWAIT;
		}

		/* for data sync or sync, we need sync completion processing */
		if (iocb->ki_flags & IOCB_DSYNC)
			dio->flags |= IOMAP_DIO_NEED_SYNC;

		/*
		 * For datasync only writes, we optimistically try using FUA for
		 * this IO.  Any non-FUA write that occurs will clear this flag,
		 * hence we know before completion whether a cache flush is
		 * necessary.
		 */
		if ((iocb->ki_flags & (IOCB_DSYNC | IOCB_SYNC)) == IOCB_DSYNC)
			dio->flags |= IOMAP_DIO_WRITE_FUA;
	}

	if (dio_flags & IOMAP_DIO_OVERWRITE_ONLY) {
		ret = -EAGAIN;
		if (pos >= dio->i_size || pos + count > dio->i_size)
			goto out_free_dio;
		iomap_flags |= IOMAP_OVERWRITE_ONLY;
	}

	ret = filemap_write_and_wait_range(mapping, pos, end);
	if (ret)
		goto out_free_dio;

	if (iov_iter_rw(iter) == WRITE) {
		/*
		 * Try to invalidate cache pages for the range we are writing.
		 * If this invalidation fails, let the caller fall back to
		 * buffered I/O.
		 */
		if (invalidate_inode_pages2_range(mapping, pos >> PAGE_SHIFT,
				end >> PAGE_SHIFT)) {
			trace_iomap_dio_invalidate_fail(inode, pos, count);
			ret = -ENOTBLK;
			goto out_free_dio;
		}

		if (!wait_for_completion && !inode->i_sb->s_dio_done_wq) {
			ret = sb_init_dio_done_wq(inode->i_sb);
			if (ret < 0)
				goto out_free_dio;
		}
	}

	inode_dio_begin(inode);

	blk_start_plug(&plug);
	do {
		ret = iomap_apply(inode, pos, count, iomap_flags, ops, dio,
				iomap_dio_actor);
		if (ret <= 0) {
			/* magic error code to fall back to buffered I/O */
			if (ret == -ENOTBLK) {
				wait_for_completion = true;
				ret = 0;
			}
			break;
		}
		pos += ret;

		if (iov_iter_rw(iter) == READ && pos >= dio->i_size) {
			/*
			 * We only report that we've read data up to i_size.
			 * Revert iter to a state corresponding to that as
			 * some callers (such as splice code) rely on it.
			 */
			iov_iter_revert(iter, pos - dio->i_size);
			break;
		}
	} while ((count = iov_iter_count(iter)) > 0);
	blk_finish_plug(&plug);

	if (ret < 0)
		iomap_dio_set_error(dio, ret);

	/*
	 * If all the writes we issued were FUA, we don't need to flush the
	 * cache on IO completion. Clear the sync flag for this case.
	 */
	if (dio->flags & IOMAP_DIO_WRITE_FUA)
		dio->flags &= ~IOMAP_DIO_NEED_SYNC;

	WRITE_ONCE(iocb->ki_cookie, dio->submit.cookie);
	WRITE_ONCE(iocb->private, dio->submit.last_queue);

	/*
	 * We are about to drop our additional submission reference, which
	 * might be the last reference to the dio.  There are three different
	 * ways we can progress here:
	 *
	 *  (a) If this is the last reference we will always complete and free
	 *	the dio ourselves.
	 *  (b) If this is not the last reference, and we serve an asynchronous
	 *	iocb, we must never touch the dio after the decrement, the
	 *	I/O completion handler will complete and free it.
	 *  (c) If this is not the last reference, but we serve a synchronous
	 *	iocb, the I/O completion handler will wake us up on the drop
	 *	of the final reference, and we will complete and free it here
	 *	after we got woken by the I/O completion handler.
	 */
	dio->wait_for_completion = wait_for_completion;
	if (!atomic_dec_and_test(&dio->ref)) {
		if (!wait_for_completion)
			return ERR_PTR(-EIOCBQUEUED);

		for (;;) {
			set_current_state(TASK_UNINTERRUPTIBLE);
			if (!READ_ONCE(dio->submit.waiter))
				break;

			if (!(iocb->ki_flags & IOCB_HIPRI) ||
			    !dio->submit.last_queue ||
			    !blk_poll(dio->submit.last_queue,
					 dio->submit.cookie, true))
				blk_io_schedule();
		}
		__set_current_state(TASK_RUNNING);
	}

	return dio;

out_free_dio:
	kfree(dio);
	if (ret)
		return ERR_PTR(ret);
	return NULL;
}
EXPORT_SYMBOL_GPL(__iomap_dio_rw);

ssize_t
iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
		const struct iomap_ops *ops, const struct iomap_dio_ops *dops,
		unsigned int dio_flags)
{
	struct iomap_dio *dio;

	dio = __iomap_dio_rw(iocb, iter, ops, dops, dio_flags);
	if (IS_ERR_OR_NULL(dio))
		return PTR_ERR_OR_ZERO(dio);
	return iomap_dio_complete(dio);
}
EXPORT_SYMBOL_GPL(iomap_dio_rw);