1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * Copyright (C) 2010 Red Hat, Inc.
4  * Copyright (c) 2016-2018 Christoph Hellwig.
5  */
6 #include <linux/module.h>
7 #include <linux/compiler.h>
8 #include <linux/fs.h>
9 #include <linux/iomap.h>
10 #include <linux/backing-dev.h>
11 #include <linux/uio.h>
12 #include <linux/task_io_accounting_ops.h>
13 #include "trace.h"
14 
15 #include "../internal.h"
16 
17 /*
18  * Private flags for iomap_dio, must not overlap with the public ones in
19  * iomap.h:
20  */
21 #define IOMAP_DIO_WRITE_FUA	(1 << 28)
22 #define IOMAP_DIO_NEED_SYNC	(1 << 29)
23 #define IOMAP_DIO_WRITE		(1 << 30)
24 #define IOMAP_DIO_DIRTY		(1 << 31)
25 
26 struct iomap_dio {
27 	struct kiocb		*iocb;
28 	const struct iomap_dio_ops *dops;
29 	loff_t			i_size;
30 	loff_t			size;
31 	atomic_t		ref;
32 	unsigned		flags;
33 	int			error;
34 	bool			wait_for_completion;
35 
36 	union {
37 		/* used during submission and for synchronous completion: */
38 		struct {
39 			struct iov_iter		*iter;
40 			struct task_struct	*waiter;
41 			struct request_queue	*last_queue;
42 			blk_qc_t		cookie;
43 		} submit;
44 
45 		/* used for aio completion: */
46 		struct {
47 			struct work_struct	work;
48 		} aio;
49 	};
50 };
51 
iomap_dio_iopoll(struct kiocb * kiocb,bool spin)52 int iomap_dio_iopoll(struct kiocb *kiocb, bool spin)
53 {
54 	struct request_queue *q = READ_ONCE(kiocb->private);
55 
56 	if (!q)
57 		return 0;
58 	return blk_poll(q, READ_ONCE(kiocb->ki_cookie), spin);
59 }
60 EXPORT_SYMBOL_GPL(iomap_dio_iopoll);
61 
iomap_dio_submit_bio(struct iomap_dio * dio,struct iomap * iomap,struct bio * bio,loff_t pos)62 static void iomap_dio_submit_bio(struct iomap_dio *dio, struct iomap *iomap,
63 		struct bio *bio, loff_t pos)
64 {
65 	atomic_inc(&dio->ref);
66 
67 	if (dio->iocb->ki_flags & IOCB_HIPRI)
68 		bio_set_polled(bio, dio->iocb);
69 
70 	dio->submit.last_queue = bdev_get_queue(iomap->bdev);
71 	if (dio->dops && dio->dops->submit_io)
72 		dio->submit.cookie = dio->dops->submit_io(
73 				file_inode(dio->iocb->ki_filp),
74 				iomap, bio, pos);
75 	else
76 		dio->submit.cookie = submit_bio(bio);
77 }
78 
iomap_dio_complete(struct iomap_dio * dio)79 ssize_t iomap_dio_complete(struct iomap_dio *dio)
80 {
81 	const struct iomap_dio_ops *dops = dio->dops;
82 	struct kiocb *iocb = dio->iocb;
83 	struct inode *inode = file_inode(iocb->ki_filp);
84 	loff_t offset = iocb->ki_pos;
85 	ssize_t ret = dio->error;
86 
87 	if (dops && dops->end_io)
88 		ret = dops->end_io(iocb, dio->size, ret, dio->flags);
89 
90 	if (likely(!ret)) {
91 		ret = dio->size;
92 		/* check for short read */
93 		if (offset + ret > dio->i_size &&
94 		    !(dio->flags & IOMAP_DIO_WRITE))
95 			ret = dio->i_size - offset;
96 		iocb->ki_pos += ret;
97 	}
98 
99 	/*
100 	 * Try again to invalidate clean pages which might have been cached by
101 	 * non-direct readahead, or faulted in by get_user_pages() if the source
102 	 * of the write was an mmap'ed region of the file we're writing.  Either
103 	 * one is a pretty crazy thing to do, so we don't support it 100%.  If
104 	 * this invalidation fails, tough, the write still worked...
105 	 *
106 	 * And this page cache invalidation has to be after ->end_io(), as some
107 	 * filesystems convert unwritten extents to real allocations in
108 	 * ->end_io() when necessary, otherwise a racing buffer read would cache
109 	 * zeros from unwritten extents.
110 	 */
111 	if (!dio->error && dio->size &&
112 	    (dio->flags & IOMAP_DIO_WRITE) && inode->i_mapping->nrpages) {
113 		int err;
114 		err = invalidate_inode_pages2_range(inode->i_mapping,
115 				offset >> PAGE_SHIFT,
116 				(offset + dio->size - 1) >> PAGE_SHIFT);
117 		if (err)
118 			dio_warn_stale_pagecache(iocb->ki_filp);
119 	}
120 
121 	inode_dio_end(file_inode(iocb->ki_filp));
122 	/*
123 	 * If this is a DSYNC write, make sure we push it to stable storage now
124 	 * that we've written data.
125 	 */
126 	if (ret > 0 && (dio->flags & IOMAP_DIO_NEED_SYNC))
127 		ret = generic_write_sync(iocb, ret);
128 
129 	kfree(dio);
130 
131 	return ret;
132 }
133 EXPORT_SYMBOL_GPL(iomap_dio_complete);
134 
iomap_dio_complete_work(struct work_struct * work)135 static void iomap_dio_complete_work(struct work_struct *work)
136 {
137 	struct iomap_dio *dio = container_of(work, struct iomap_dio, aio.work);
138 	struct kiocb *iocb = dio->iocb;
139 
140 	iocb->ki_complete(iocb, iomap_dio_complete(dio), 0);
141 }
142 
143 /*
144  * Set an error in the dio if none is set yet.  We have to use cmpxchg
145  * as the submission context and the completion context(s) can race to
146  * update the error.
147  */
iomap_dio_set_error(struct iomap_dio * dio,int ret)148 static inline void iomap_dio_set_error(struct iomap_dio *dio, int ret)
149 {
150 	cmpxchg(&dio->error, 0, ret);
151 }
152 
iomap_dio_bio_end_io(struct bio * bio)153 static void iomap_dio_bio_end_io(struct bio *bio)
154 {
155 	struct iomap_dio *dio = bio->bi_private;
156 	bool should_dirty = (dio->flags & IOMAP_DIO_DIRTY);
157 
158 	if (bio->bi_status)
159 		iomap_dio_set_error(dio, blk_status_to_errno(bio->bi_status));
160 
161 	if (atomic_dec_and_test(&dio->ref)) {
162 		if (dio->wait_for_completion) {
163 			struct task_struct *waiter = dio->submit.waiter;
164 			WRITE_ONCE(dio->submit.waiter, NULL);
165 			blk_wake_io_task(waiter);
166 		} else if (dio->flags & IOMAP_DIO_WRITE) {
167 			struct inode *inode = file_inode(dio->iocb->ki_filp);
168 
169 			INIT_WORK(&dio->aio.work, iomap_dio_complete_work);
170 			queue_work(inode->i_sb->s_dio_done_wq, &dio->aio.work);
171 		} else {
172 			iomap_dio_complete_work(&dio->aio.work);
173 		}
174 	}
175 
176 	if (should_dirty) {
177 		bio_check_pages_dirty(bio);
178 	} else {
179 		bio_release_pages(bio, false);
180 		bio_put(bio);
181 	}
182 }
183 
184 static void
iomap_dio_zero(struct iomap_dio * dio,struct iomap * iomap,loff_t pos,unsigned len)185 iomap_dio_zero(struct iomap_dio *dio, struct iomap *iomap, loff_t pos,
186 		unsigned len)
187 {
188 	struct page *page = ZERO_PAGE(0);
189 	int flags = REQ_SYNC | REQ_IDLE;
190 	struct bio *bio;
191 
192 	bio = bio_alloc(GFP_KERNEL, 1);
193 	bio_set_dev(bio, iomap->bdev);
194 	bio->bi_iter.bi_sector = iomap_sector(iomap, pos);
195 	bio->bi_private = dio;
196 	bio->bi_end_io = iomap_dio_bio_end_io;
197 
198 	get_page(page);
199 	__bio_add_page(bio, page, len, 0);
200 	bio_set_op_attrs(bio, REQ_OP_WRITE, flags);
201 	iomap_dio_submit_bio(dio, iomap, bio, pos);
202 }
203 
204 /*
205  * Figure out the bio's operation flags from the dio request, the
206  * mapping, and whether or not we want FUA.  Note that we can end up
207  * clearing the WRITE_FUA flag in the dio request.
208  */
209 static inline unsigned int
iomap_dio_bio_opflags(struct iomap_dio * dio,struct iomap * iomap,bool use_fua)210 iomap_dio_bio_opflags(struct iomap_dio *dio, struct iomap *iomap, bool use_fua)
211 {
212 	unsigned int opflags = REQ_SYNC | REQ_IDLE;
213 
214 	if (!(dio->flags & IOMAP_DIO_WRITE)) {
215 		WARN_ON_ONCE(iomap->flags & IOMAP_F_ZONE_APPEND);
216 		return REQ_OP_READ;
217 	}
218 
219 	if (iomap->flags & IOMAP_F_ZONE_APPEND)
220 		opflags |= REQ_OP_ZONE_APPEND;
221 	else
222 		opflags |= REQ_OP_WRITE;
223 
224 	if (use_fua)
225 		opflags |= REQ_FUA;
226 	else
227 		dio->flags &= ~IOMAP_DIO_WRITE_FUA;
228 
229 	return opflags;
230 }
231 
232 static loff_t
iomap_dio_bio_actor(struct inode * inode,loff_t pos,loff_t length,struct iomap_dio * dio,struct iomap * iomap)233 iomap_dio_bio_actor(struct inode *inode, loff_t pos, loff_t length,
234 		struct iomap_dio *dio, struct iomap *iomap)
235 {
236 	unsigned int blkbits = blksize_bits(bdev_logical_block_size(iomap->bdev));
237 	unsigned int fs_block_size = i_blocksize(inode), pad;
238 	unsigned int align = iov_iter_alignment(dio->submit.iter);
239 	unsigned int bio_opf;
240 	struct bio *bio;
241 	bool need_zeroout = false;
242 	bool use_fua = false;
243 	int nr_pages, ret = 0;
244 	size_t copied = 0;
245 	size_t orig_count;
246 
247 	if ((pos | length | align) & ((1 << blkbits) - 1))
248 		return -EINVAL;
249 
250 	if (iomap->type == IOMAP_UNWRITTEN) {
251 		dio->flags |= IOMAP_DIO_UNWRITTEN;
252 		need_zeroout = true;
253 	}
254 
255 	if (iomap->flags & IOMAP_F_SHARED)
256 		dio->flags |= IOMAP_DIO_COW;
257 
258 	if (iomap->flags & IOMAP_F_NEW) {
259 		need_zeroout = true;
260 	} else if (iomap->type == IOMAP_MAPPED) {
261 		/*
262 		 * Use a FUA write if we need datasync semantics, this is a pure
263 		 * data IO that doesn't require any metadata updates (including
264 		 * after IO completion such as unwritten extent conversion) and
265 		 * the underlying device supports FUA. This allows us to avoid
266 		 * cache flushes on IO completion.
267 		 */
268 		if (!(iomap->flags & (IOMAP_F_SHARED|IOMAP_F_DIRTY)) &&
269 		    (dio->flags & IOMAP_DIO_WRITE_FUA) &&
270 		    blk_queue_fua(bdev_get_queue(iomap->bdev)))
271 			use_fua = true;
272 	}
273 
274 	/*
275 	 * Save the original count and trim the iter to just the extent we
276 	 * are operating on right now.  The iter will be re-expanded once
277 	 * we are done.
278 	 */
279 	orig_count = iov_iter_count(dio->submit.iter);
280 	iov_iter_truncate(dio->submit.iter, length);
281 
282 	if (!iov_iter_count(dio->submit.iter))
283 		goto out;
284 
285 	if (need_zeroout) {
286 		/* zero out from the start of the block to the write offset */
287 		pad = pos & (fs_block_size - 1);
288 		if (pad)
289 			iomap_dio_zero(dio, iomap, pos - pad, pad);
290 	}
291 
292 	/*
293 	 * Set the operation flags early so that bio_iov_iter_get_pages
294 	 * can set up the page vector appropriately for a ZONE_APPEND
295 	 * operation.
296 	 */
297 	bio_opf = iomap_dio_bio_opflags(dio, iomap, use_fua);
298 
299 	nr_pages = bio_iov_vecs_to_alloc(dio->submit.iter, BIO_MAX_VECS);
300 	do {
301 		size_t n;
302 		if (dio->error) {
303 			iov_iter_revert(dio->submit.iter, copied);
304 			copied = ret = 0;
305 			goto out;
306 		}
307 
308 		bio = bio_alloc(GFP_KERNEL, nr_pages);
309 		bio_set_dev(bio, iomap->bdev);
310 		bio->bi_iter.bi_sector = iomap_sector(iomap, pos);
311 		bio->bi_write_hint = dio->iocb->ki_hint;
312 		bio->bi_ioprio = dio->iocb->ki_ioprio;
313 		bio->bi_private = dio;
314 		bio->bi_end_io = iomap_dio_bio_end_io;
315 		bio->bi_opf = bio_opf;
316 
317 		ret = bio_iov_iter_get_pages(bio, dio->submit.iter);
318 		if (unlikely(ret)) {
319 			/*
320 			 * We have to stop part way through an IO. We must fall
321 			 * through to the sub-block tail zeroing here, otherwise
322 			 * this short IO may expose stale data in the tail of
323 			 * the block we haven't written data to.
324 			 */
325 			bio_put(bio);
326 			goto zero_tail;
327 		}
328 
329 		n = bio->bi_iter.bi_size;
330 		if (dio->flags & IOMAP_DIO_WRITE) {
331 			task_io_account_write(n);
332 		} else {
333 			if (dio->flags & IOMAP_DIO_DIRTY)
334 				bio_set_pages_dirty(bio);
335 		}
336 
337 		dio->size += n;
338 		copied += n;
339 
340 		nr_pages = bio_iov_vecs_to_alloc(dio->submit.iter,
341 						 BIO_MAX_VECS);
342 		iomap_dio_submit_bio(dio, iomap, bio, pos);
343 		pos += n;
344 	} while (nr_pages);
345 
346 	/*
347 	 * We need to zeroout the tail of a sub-block write if the extent type
348 	 * requires zeroing or the write extends beyond EOF. If we don't zero
349 	 * the block tail in the latter case, we can expose stale data via mmap
350 	 * reads of the EOF block.
351 	 */
352 zero_tail:
353 	if (need_zeroout ||
354 	    ((dio->flags & IOMAP_DIO_WRITE) && pos >= i_size_read(inode))) {
355 		/* zero out from the end of the write to the end of the block */
356 		pad = pos & (fs_block_size - 1);
357 		if (pad)
358 			iomap_dio_zero(dio, iomap, pos, fs_block_size - pad);
359 	}
360 out:
361 	/* Undo iter limitation to current extent */
362 	iov_iter_reexpand(dio->submit.iter, orig_count - copied);
363 	if (copied)
364 		return copied;
365 	return ret;
366 }
367 
368 static loff_t
iomap_dio_hole_actor(loff_t length,struct iomap_dio * dio)369 iomap_dio_hole_actor(loff_t length, struct iomap_dio *dio)
370 {
371 	length = iov_iter_zero(length, dio->submit.iter);
372 	dio->size += length;
373 	return length;
374 }
375 
376 static loff_t
iomap_dio_inline_actor(struct inode * inode,loff_t pos,loff_t length,struct iomap_dio * dio,struct iomap * iomap)377 iomap_dio_inline_actor(struct inode *inode, loff_t pos, loff_t length,
378 		struct iomap_dio *dio, struct iomap *iomap)
379 {
380 	struct iov_iter *iter = dio->submit.iter;
381 	size_t copied;
382 
383 	BUG_ON(pos + length > PAGE_SIZE - offset_in_page(iomap->inline_data));
384 
385 	if (dio->flags & IOMAP_DIO_WRITE) {
386 		loff_t size = inode->i_size;
387 
388 		if (pos > size)
389 			memset(iomap->inline_data + size, 0, pos - size);
390 		copied = copy_from_iter(iomap->inline_data + pos, length, iter);
391 		if (copied) {
392 			if (pos + copied > size)
393 				i_size_write(inode, pos + copied);
394 			mark_inode_dirty(inode);
395 		}
396 	} else {
397 		copied = copy_to_iter(iomap->inline_data + pos, length, iter);
398 	}
399 	dio->size += copied;
400 	return copied;
401 }
402 
403 static loff_t
iomap_dio_actor(struct inode * inode,loff_t pos,loff_t length,void * data,struct iomap * iomap,struct iomap * srcmap)404 iomap_dio_actor(struct inode *inode, loff_t pos, loff_t length,
405 		void *data, struct iomap *iomap, struct iomap *srcmap)
406 {
407 	struct iomap_dio *dio = data;
408 
409 	switch (iomap->type) {
410 	case IOMAP_HOLE:
411 		if (WARN_ON_ONCE(dio->flags & IOMAP_DIO_WRITE))
412 			return -EIO;
413 		return iomap_dio_hole_actor(length, dio);
414 	case IOMAP_UNWRITTEN:
415 		if (!(dio->flags & IOMAP_DIO_WRITE))
416 			return iomap_dio_hole_actor(length, dio);
417 		return iomap_dio_bio_actor(inode, pos, length, dio, iomap);
418 	case IOMAP_MAPPED:
419 		return iomap_dio_bio_actor(inode, pos, length, dio, iomap);
420 	case IOMAP_INLINE:
421 		return iomap_dio_inline_actor(inode, pos, length, dio, iomap);
422 	case IOMAP_DELALLOC:
423 		/*
424 		 * DIO is not serialised against mmap() access at all, and so
425 		 * if the page_mkwrite occurs between the writeback and the
426 		 * iomap_apply() call in the DIO path, then it will see the
427 		 * DELALLOC block that the page-mkwrite allocated.
428 		 */
429 		pr_warn_ratelimited("Direct I/O collision with buffered writes! File: %pD4 Comm: %.20s\n",
430 				    dio->iocb->ki_filp, current->comm);
431 		return -EIO;
432 	default:
433 		WARN_ON_ONCE(1);
434 		return -EIO;
435 	}
436 }
437 
438 /*
439  * iomap_dio_rw() always completes O_[D]SYNC writes regardless of whether the IO
440  * is being issued as AIO or not.  This allows us to optimise pure data writes
441  * to use REQ_FUA rather than requiring generic_write_sync() to issue a
442  * REQ_FLUSH post write. This is slightly tricky because a single request here
443  * can be mapped into multiple disjoint IOs and only a subset of the IOs issued
444  * may be pure data writes. In that case, we still need to do a full data sync
445  * completion.
446  *
447  * Returns -ENOTBLK In case of a page invalidation invalidation failure for
448  * writes.  The callers needs to fall back to buffered I/O in this case.
449  */
450 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)451 __iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
452 		const struct iomap_ops *ops, const struct iomap_dio_ops *dops,
453 		unsigned int dio_flags)
454 {
455 	struct address_space *mapping = iocb->ki_filp->f_mapping;
456 	struct inode *inode = file_inode(iocb->ki_filp);
457 	size_t count = iov_iter_count(iter);
458 	loff_t pos = iocb->ki_pos;
459 	loff_t end = iocb->ki_pos + count - 1, ret = 0;
460 	bool wait_for_completion =
461 		is_sync_kiocb(iocb) || (dio_flags & IOMAP_DIO_FORCE_WAIT);
462 	unsigned int iomap_flags = IOMAP_DIRECT;
463 	struct blk_plug plug;
464 	struct iomap_dio *dio;
465 
466 	if (!count)
467 		return NULL;
468 
469 	dio = kmalloc(sizeof(*dio), GFP_KERNEL);
470 	if (!dio)
471 		return ERR_PTR(-ENOMEM);
472 
473 	dio->iocb = iocb;
474 	atomic_set(&dio->ref, 1);
475 	dio->size = 0;
476 	dio->i_size = i_size_read(inode);
477 	dio->dops = dops;
478 	dio->error = 0;
479 	dio->flags = 0;
480 
481 	dio->submit.iter = iter;
482 	dio->submit.waiter = current;
483 	dio->submit.cookie = BLK_QC_T_NONE;
484 	dio->submit.last_queue = NULL;
485 
486 	if (iov_iter_rw(iter) == READ) {
487 		if (pos >= dio->i_size)
488 			goto out_free_dio;
489 
490 		if (iocb->ki_flags & IOCB_NOWAIT) {
491 			if (filemap_range_needs_writeback(mapping, pos, end)) {
492 				ret = -EAGAIN;
493 				goto out_free_dio;
494 			}
495 			iomap_flags |= IOMAP_NOWAIT;
496 		}
497 
498 		if (iter_is_iovec(iter))
499 			dio->flags |= IOMAP_DIO_DIRTY;
500 	} else {
501 		iomap_flags |= IOMAP_WRITE;
502 		dio->flags |= IOMAP_DIO_WRITE;
503 
504 		if (iocb->ki_flags & IOCB_NOWAIT) {
505 			if (filemap_range_has_page(mapping, pos, end)) {
506 				ret = -EAGAIN;
507 				goto out_free_dio;
508 			}
509 			iomap_flags |= IOMAP_NOWAIT;
510 		}
511 
512 		/* for data sync or sync, we need sync completion processing */
513 		if (iocb->ki_flags & IOCB_DSYNC)
514 			dio->flags |= IOMAP_DIO_NEED_SYNC;
515 
516 		/*
517 		 * For datasync only writes, we optimistically try using FUA for
518 		 * this IO.  Any non-FUA write that occurs will clear this flag,
519 		 * hence we know before completion whether a cache flush is
520 		 * necessary.
521 		 */
522 		if ((iocb->ki_flags & (IOCB_DSYNC | IOCB_SYNC)) == IOCB_DSYNC)
523 			dio->flags |= IOMAP_DIO_WRITE_FUA;
524 	}
525 
526 	if (dio_flags & IOMAP_DIO_OVERWRITE_ONLY) {
527 		ret = -EAGAIN;
528 		if (pos >= dio->i_size || pos + count > dio->i_size)
529 			goto out_free_dio;
530 		iomap_flags |= IOMAP_OVERWRITE_ONLY;
531 	}
532 
533 	ret = filemap_write_and_wait_range(mapping, pos, end);
534 	if (ret)
535 		goto out_free_dio;
536 
537 	if (iov_iter_rw(iter) == WRITE) {
538 		/*
539 		 * Try to invalidate cache pages for the range we are writing.
540 		 * If this invalidation fails, let the caller fall back to
541 		 * buffered I/O.
542 		 */
543 		if (invalidate_inode_pages2_range(mapping, pos >> PAGE_SHIFT,
544 				end >> PAGE_SHIFT)) {
545 			trace_iomap_dio_invalidate_fail(inode, pos, count);
546 			ret = -ENOTBLK;
547 			goto out_free_dio;
548 		}
549 
550 		if (!wait_for_completion && !inode->i_sb->s_dio_done_wq) {
551 			ret = sb_init_dio_done_wq(inode->i_sb);
552 			if (ret < 0)
553 				goto out_free_dio;
554 		}
555 	}
556 
557 	inode_dio_begin(inode);
558 
559 	blk_start_plug(&plug);
560 	do {
561 		ret = iomap_apply(inode, pos, count, iomap_flags, ops, dio,
562 				iomap_dio_actor);
563 		if (ret <= 0) {
564 			/* magic error code to fall back to buffered I/O */
565 			if (ret == -ENOTBLK) {
566 				wait_for_completion = true;
567 				ret = 0;
568 			}
569 			break;
570 		}
571 		pos += ret;
572 
573 		if (iov_iter_rw(iter) == READ && pos >= dio->i_size) {
574 			/*
575 			 * We only report that we've read data up to i_size.
576 			 * Revert iter to a state corresponding to that as
577 			 * some callers (such as splice code) rely on it.
578 			 */
579 			iov_iter_revert(iter, pos - dio->i_size);
580 			break;
581 		}
582 	} while ((count = iov_iter_count(iter)) > 0);
583 	blk_finish_plug(&plug);
584 
585 	if (ret < 0)
586 		iomap_dio_set_error(dio, ret);
587 
588 	/*
589 	 * If all the writes we issued were FUA, we don't need to flush the
590 	 * cache on IO completion. Clear the sync flag for this case.
591 	 */
592 	if (dio->flags & IOMAP_DIO_WRITE_FUA)
593 		dio->flags &= ~IOMAP_DIO_NEED_SYNC;
594 
595 	WRITE_ONCE(iocb->ki_cookie, dio->submit.cookie);
596 	WRITE_ONCE(iocb->private, dio->submit.last_queue);
597 
598 	/*
599 	 * We are about to drop our additional submission reference, which
600 	 * might be the last reference to the dio.  There are three different
601 	 * ways we can progress here:
602 	 *
603 	 *  (a) If this is the last reference we will always complete and free
604 	 *	the dio ourselves.
605 	 *  (b) If this is not the last reference, and we serve an asynchronous
606 	 *	iocb, we must never touch the dio after the decrement, the
607 	 *	I/O completion handler will complete and free it.
608 	 *  (c) If this is not the last reference, but we serve a synchronous
609 	 *	iocb, the I/O completion handler will wake us up on the drop
610 	 *	of the final reference, and we will complete and free it here
611 	 *	after we got woken by the I/O completion handler.
612 	 */
613 	dio->wait_for_completion = wait_for_completion;
614 	if (!atomic_dec_and_test(&dio->ref)) {
615 		if (!wait_for_completion)
616 			return ERR_PTR(-EIOCBQUEUED);
617 
618 		for (;;) {
619 			set_current_state(TASK_UNINTERRUPTIBLE);
620 			if (!READ_ONCE(dio->submit.waiter))
621 				break;
622 
623 			if (!(iocb->ki_flags & IOCB_HIPRI) ||
624 			    !dio->submit.last_queue ||
625 			    !blk_poll(dio->submit.last_queue,
626 					 dio->submit.cookie, true))
627 				blk_io_schedule();
628 		}
629 		__set_current_state(TASK_RUNNING);
630 	}
631 
632 	return dio;
633 
634 out_free_dio:
635 	kfree(dio);
636 	if (ret)
637 		return ERR_PTR(ret);
638 	return NULL;
639 }
640 EXPORT_SYMBOL_GPL(__iomap_dio_rw);
641 
642 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)643 iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
644 		const struct iomap_ops *ops, const struct iomap_dio_ops *dops,
645 		unsigned int dio_flags)
646 {
647 	struct iomap_dio *dio;
648 
649 	dio = __iomap_dio_rw(iocb, iter, ops, dops, dio_flags);
650 	if (IS_ERR_OR_NULL(dio))
651 		return PTR_ERR_OR_ZERO(dio);
652 	return iomap_dio_complete(dio);
653 }
654 EXPORT_SYMBOL_GPL(iomap_dio_rw);
655