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1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Copyright (C) 2010 Red Hat, Inc.
4 * Copyright (c) 2016-2021 Christoph Hellwig.
5 */
6#include <linux/module.h>
7#include <linux/compiler.h>
8#include <linux/fs.h>
9#include <linux/fscrypt.h>
10#include <linux/pagemap.h>
11#include <linux/iomap.h>
12#include <linux/backing-dev.h>
13#include <linux/uio.h>
14#include <linux/task_io_accounting_ops.h>
15#include "trace.h"
16
17#include "../internal.h"
18
19/*
20 * Private flags for iomap_dio, must not overlap with the public ones in
21 * iomap.h:
22 */
23#define IOMAP_DIO_CALLER_COMP (1U << 26)
24#define IOMAP_DIO_INLINE_COMP (1U << 27)
25#define IOMAP_DIO_WRITE_THROUGH (1U << 28)
26#define IOMAP_DIO_NEED_SYNC (1U << 29)
27#define IOMAP_DIO_WRITE (1U << 30)
28#define IOMAP_DIO_DIRTY (1U << 31)
29
30/*
31 * Used for sub block zeroing in iomap_dio_zero()
32 */
33#define IOMAP_ZERO_PAGE_SIZE (SZ_64K)
34#define IOMAP_ZERO_PAGE_ORDER (get_order(IOMAP_ZERO_PAGE_SIZE))
35static struct page *zero_page;
36
37struct iomap_dio {
38 struct kiocb *iocb;
39 const struct iomap_dio_ops *dops;
40 loff_t i_size;
41 loff_t size;
42 atomic_t ref;
43 unsigned flags;
44 int error;
45 size_t done_before;
46 bool wait_for_completion;
47
48 union {
49 /* used during submission and for synchronous completion: */
50 struct {
51 struct iov_iter *iter;
52 struct task_struct *waiter;
53 } submit;
54
55 /* used for aio completion: */
56 struct {
57 struct work_struct work;
58 } aio;
59 };
60};
61
62static struct bio *iomap_dio_alloc_bio(const struct iomap_iter *iter,
63 struct iomap_dio *dio, unsigned short nr_vecs, blk_opf_t opf)
64{
65 if (dio->dops && dio->dops->bio_set)
66 return bio_alloc_bioset(iter->iomap.bdev, nr_vecs, opf,
67 GFP_KERNEL, dio->dops->bio_set);
68 return bio_alloc(iter->iomap.bdev, nr_vecs, opf, GFP_KERNEL);
69}
70
71static void iomap_dio_submit_bio(const struct iomap_iter *iter,
72 struct iomap_dio *dio, struct bio *bio, loff_t pos)
73{
74 struct kiocb *iocb = dio->iocb;
75
76 atomic_inc(&dio->ref);
77
78 /* Sync dio can't be polled reliably */
79 if ((iocb->ki_flags & IOCB_HIPRI) && !is_sync_kiocb(iocb)) {
80 bio_set_polled(bio, iocb);
81 WRITE_ONCE(iocb->private, bio);
82 }
83
84 if (dio->dops && dio->dops->submit_io)
85 dio->dops->submit_io(iter, bio, pos);
86 else
87 submit_bio(bio);
88}
89
90ssize_t iomap_dio_complete(struct iomap_dio *dio)
91{
92 const struct iomap_dio_ops *dops = dio->dops;
93 struct kiocb *iocb = dio->iocb;
94 loff_t offset = iocb->ki_pos;
95 ssize_t ret = dio->error;
96
97 if (dops && dops->end_io)
98 ret = dops->end_io(iocb, dio->size, ret, dio->flags);
99
100 if (likely(!ret)) {
101 ret = dio->size;
102 /* check for short read */
103 if (offset + ret > dio->i_size &&
104 !(dio->flags & IOMAP_DIO_WRITE))
105 ret = dio->i_size - offset;
106 }
107
108 /*
109 * Try again to invalidate clean pages which might have been cached by
110 * non-direct readahead, or faulted in by get_user_pages() if the source
111 * of the write was an mmap'ed region of the file we're writing. Either
112 * one is a pretty crazy thing to do, so we don't support it 100%. If
113 * this invalidation fails, tough, the write still worked...
114 *
115 * And this page cache invalidation has to be after ->end_io(), as some
116 * filesystems convert unwritten extents to real allocations in
117 * ->end_io() when necessary, otherwise a racing buffer read would cache
118 * zeros from unwritten extents.
119 */
120 if (!dio->error && dio->size && (dio->flags & IOMAP_DIO_WRITE))
121 kiocb_invalidate_post_direct_write(iocb, dio->size);
122
123 inode_dio_end(file_inode(iocb->ki_filp));
124
125 if (ret > 0) {
126 iocb->ki_pos += ret;
127
128 /*
129 * If this is a DSYNC write, make sure we push it to stable
130 * storage now that we've written data.
131 */
132 if (dio->flags & IOMAP_DIO_NEED_SYNC)
133 ret = generic_write_sync(iocb, ret);
134 if (ret > 0)
135 ret += dio->done_before;
136 }
137 trace_iomap_dio_complete(iocb, dio->error, ret);
138 kfree(dio);
139 return ret;
140}
141EXPORT_SYMBOL_GPL(iomap_dio_complete);
142
143static ssize_t iomap_dio_deferred_complete(void *data)
144{
145 return iomap_dio_complete(data);
146}
147
148static void iomap_dio_complete_work(struct work_struct *work)
149{
150 struct iomap_dio *dio = container_of(work, struct iomap_dio, aio.work);
151 struct kiocb *iocb = dio->iocb;
152
153 iocb->ki_complete(iocb, iomap_dio_complete(dio));
154}
155
156/*
157 * Set an error in the dio if none is set yet. We have to use cmpxchg
158 * as the submission context and the completion context(s) can race to
159 * update the error.
160 */
161static inline void iomap_dio_set_error(struct iomap_dio *dio, int ret)
162{
163 cmpxchg(&dio->error, 0, ret);
164}
165
166void iomap_dio_bio_end_io(struct bio *bio)
167{
168 struct iomap_dio *dio = bio->bi_private;
169 bool should_dirty = (dio->flags & IOMAP_DIO_DIRTY);
170 struct kiocb *iocb = dio->iocb;
171
172 if (bio->bi_status)
173 iomap_dio_set_error(dio, blk_status_to_errno(bio->bi_status));
174 if (!atomic_dec_and_test(&dio->ref))
175 goto release_bio;
176
177 /*
178 * Synchronous dio, task itself will handle any completion work
179 * that needs after IO. All we need to do is wake the task.
180 */
181 if (dio->wait_for_completion) {
182 struct task_struct *waiter = dio->submit.waiter;
183
184 WRITE_ONCE(dio->submit.waiter, NULL);
185 blk_wake_io_task(waiter);
186 goto release_bio;
187 }
188
189 /*
190 * Flagged with IOMAP_DIO_INLINE_COMP, we can complete it inline
191 */
192 if (dio->flags & IOMAP_DIO_INLINE_COMP) {
193 WRITE_ONCE(iocb->private, NULL);
194 iomap_dio_complete_work(&dio->aio.work);
195 goto release_bio;
196 }
197
198 /*
199 * If this dio is flagged with IOMAP_DIO_CALLER_COMP, then schedule
200 * our completion that way to avoid an async punt to a workqueue.
201 */
202 if (dio->flags & IOMAP_DIO_CALLER_COMP) {
203 /* only polled IO cares about private cleared */
204 iocb->private = dio;
205 iocb->dio_complete = iomap_dio_deferred_complete;
206
207 /*
208 * Invoke ->ki_complete() directly. We've assigned our
209 * dio_complete callback handler, and since the issuer set
210 * IOCB_DIO_CALLER_COMP, we know their ki_complete handler will
211 * notice ->dio_complete being set and will defer calling that
212 * handler until it can be done from a safe task context.
213 *
214 * Note that the 'res' being passed in here is not important
215 * for this case. The actual completion value of the request
216 * will be gotten from dio_complete when that is run by the
217 * issuer.
218 */
219 iocb->ki_complete(iocb, 0);
220 goto release_bio;
221 }
222
223 /*
224 * Async DIO completion that requires filesystem level completion work
225 * gets punted to a work queue to complete as the operation may require
226 * more IO to be issued to finalise filesystem metadata changes or
227 * guarantee data integrity.
228 */
229 INIT_WORK(&dio->aio.work, iomap_dio_complete_work);
230 queue_work(file_inode(iocb->ki_filp)->i_sb->s_dio_done_wq,
231 &dio->aio.work);
232release_bio:
233 if (should_dirty) {
234 bio_check_pages_dirty(bio);
235 } else {
236 bio_release_pages(bio, false);
237 bio_put(bio);
238 }
239}
240EXPORT_SYMBOL_GPL(iomap_dio_bio_end_io);
241
242static int iomap_dio_zero(const struct iomap_iter *iter, struct iomap_dio *dio,
243 loff_t pos, unsigned len)
244{
245 struct inode *inode = file_inode(dio->iocb->ki_filp);
246 struct bio *bio;
247
248 if (!len)
249 return 0;
250 /*
251 * Max block size supported is 64k
252 */
253 if (WARN_ON_ONCE(len > IOMAP_ZERO_PAGE_SIZE))
254 return -EINVAL;
255
256 bio = iomap_dio_alloc_bio(iter, dio, 1, REQ_OP_WRITE | REQ_SYNC | REQ_IDLE);
257 fscrypt_set_bio_crypt_ctx(bio, inode, pos >> inode->i_blkbits,
258 GFP_KERNEL);
259 bio->bi_iter.bi_sector = iomap_sector(&iter->iomap, pos);
260 bio->bi_private = dio;
261 bio->bi_end_io = iomap_dio_bio_end_io;
262
263 __bio_add_page(bio, zero_page, len, 0);
264 iomap_dio_submit_bio(iter, dio, bio, pos);
265 return 0;
266}
267
268/*
269 * Figure out the bio's operation flags from the dio request, the
270 * mapping, and whether or not we want FUA. Note that we can end up
271 * clearing the WRITE_THROUGH flag in the dio request.
272 */
273static inline blk_opf_t iomap_dio_bio_opflags(struct iomap_dio *dio,
274 const struct iomap *iomap, bool use_fua, bool atomic)
275{
276 blk_opf_t opflags = REQ_SYNC | REQ_IDLE;
277
278 if (!(dio->flags & IOMAP_DIO_WRITE))
279 return REQ_OP_READ;
280
281 opflags |= REQ_OP_WRITE;
282 if (use_fua)
283 opflags |= REQ_FUA;
284 else
285 dio->flags &= ~IOMAP_DIO_WRITE_THROUGH;
286 if (atomic)
287 opflags |= REQ_ATOMIC;
288
289 return opflags;
290}
291
292static loff_t iomap_dio_bio_iter(const struct iomap_iter *iter,
293 struct iomap_dio *dio)
294{
295 const struct iomap *iomap = &iter->iomap;
296 struct inode *inode = iter->inode;
297 unsigned int fs_block_size = i_blocksize(inode), pad;
298 const loff_t length = iomap_length(iter);
299 bool atomic = iter->flags & IOMAP_ATOMIC;
300 loff_t pos = iter->pos;
301 blk_opf_t bio_opf;
302 struct bio *bio;
303 bool need_zeroout = false;
304 bool use_fua = false;
305 int nr_pages, ret = 0;
306 size_t copied = 0;
307 size_t orig_count;
308
309 if (atomic && length != fs_block_size)
310 return -EINVAL;
311
312 if ((pos | length) & (bdev_logical_block_size(iomap->bdev) - 1) ||
313 !bdev_iter_is_aligned(iomap->bdev, dio->submit.iter))
314 return -EINVAL;
315
316 if (iomap->type == IOMAP_UNWRITTEN) {
317 dio->flags |= IOMAP_DIO_UNWRITTEN;
318 need_zeroout = true;
319 }
320
321 if (iomap->flags & IOMAP_F_SHARED)
322 dio->flags |= IOMAP_DIO_COW;
323
324 if (iomap->flags & IOMAP_F_NEW) {
325 need_zeroout = true;
326 } else if (iomap->type == IOMAP_MAPPED) {
327 /*
328 * Use a FUA write if we need datasync semantics, this is a pure
329 * data IO that doesn't require any metadata updates (including
330 * after IO completion such as unwritten extent conversion) and
331 * the underlying device either supports FUA or doesn't have
332 * a volatile write cache. This allows us to avoid cache flushes
333 * on IO completion. If we can't use writethrough and need to
334 * sync, disable in-task completions as dio completion will
335 * need to call generic_write_sync() which will do a blocking
336 * fsync / cache flush call.
337 */
338 if (!(iomap->flags & (IOMAP_F_SHARED|IOMAP_F_DIRTY)) &&
339 (dio->flags & IOMAP_DIO_WRITE_THROUGH) &&
340 (bdev_fua(iomap->bdev) || !bdev_write_cache(iomap->bdev)))
341 use_fua = true;
342 else if (dio->flags & IOMAP_DIO_NEED_SYNC)
343 dio->flags &= ~IOMAP_DIO_CALLER_COMP;
344 }
345
346 /*
347 * Save the original count and trim the iter to just the extent we
348 * are operating on right now. The iter will be re-expanded once
349 * we are done.
350 */
351 orig_count = iov_iter_count(dio->submit.iter);
352 iov_iter_truncate(dio->submit.iter, length);
353
354 if (!iov_iter_count(dio->submit.iter))
355 goto out;
356
357 /*
358 * We can only do deferred completion for pure overwrites that
359 * don't require additional IO at completion. This rules out
360 * writes that need zeroing or extent conversion, extend
361 * the file size, or issue journal IO or cache flushes
362 * during completion processing.
363 */
364 if (need_zeroout ||
365 ((dio->flags & IOMAP_DIO_NEED_SYNC) && !use_fua) ||
366 ((dio->flags & IOMAP_DIO_WRITE) && pos >= i_size_read(inode)))
367 dio->flags &= ~IOMAP_DIO_CALLER_COMP;
368
369 /*
370 * The rules for polled IO completions follow the guidelines as the
371 * ones we set for inline and deferred completions. If none of those
372 * are available for this IO, clear the polled flag.
373 */
374 if (!(dio->flags & (IOMAP_DIO_INLINE_COMP|IOMAP_DIO_CALLER_COMP)))
375 dio->iocb->ki_flags &= ~IOCB_HIPRI;
376
377 if (need_zeroout) {
378 /* zero out from the start of the block to the write offset */
379 pad = pos & (fs_block_size - 1);
380
381 ret = iomap_dio_zero(iter, dio, pos - pad, pad);
382 if (ret)
383 goto out;
384 }
385
386 bio_opf = iomap_dio_bio_opflags(dio, iomap, use_fua, atomic);
387
388 nr_pages = bio_iov_vecs_to_alloc(dio->submit.iter, BIO_MAX_VECS);
389 do {
390 size_t n;
391 if (dio->error) {
392 iov_iter_revert(dio->submit.iter, copied);
393 copied = ret = 0;
394 goto out;
395 }
396
397 bio = iomap_dio_alloc_bio(iter, dio, nr_pages, bio_opf);
398 fscrypt_set_bio_crypt_ctx(bio, inode, pos >> inode->i_blkbits,
399 GFP_KERNEL);
400 bio->bi_iter.bi_sector = iomap_sector(iomap, pos);
401 bio->bi_write_hint = inode->i_write_hint;
402 bio->bi_ioprio = dio->iocb->ki_ioprio;
403 bio->bi_private = dio;
404 bio->bi_end_io = iomap_dio_bio_end_io;
405
406 ret = bio_iov_iter_get_pages(bio, dio->submit.iter);
407 if (unlikely(ret)) {
408 /*
409 * We have to stop part way through an IO. We must fall
410 * through to the sub-block tail zeroing here, otherwise
411 * this short IO may expose stale data in the tail of
412 * the block we haven't written data to.
413 */
414 bio_put(bio);
415 goto zero_tail;
416 }
417
418 n = bio->bi_iter.bi_size;
419 if (WARN_ON_ONCE(atomic && n != length)) {
420 /*
421 * This bio should have covered the complete length,
422 * which it doesn't, so error. We may need to zero out
423 * the tail (complete FS block), similar to when
424 * bio_iov_iter_get_pages() returns an error, above.
425 */
426 ret = -EINVAL;
427 bio_put(bio);
428 goto zero_tail;
429 }
430 if (dio->flags & IOMAP_DIO_WRITE) {
431 task_io_account_write(n);
432 } else {
433 if (dio->flags & IOMAP_DIO_DIRTY)
434 bio_set_pages_dirty(bio);
435 }
436
437 dio->size += n;
438 copied += n;
439
440 nr_pages = bio_iov_vecs_to_alloc(dio->submit.iter,
441 BIO_MAX_VECS);
442 /*
443 * We can only poll for single bio I/Os.
444 */
445 if (nr_pages)
446 dio->iocb->ki_flags &= ~IOCB_HIPRI;
447 iomap_dio_submit_bio(iter, dio, bio, pos);
448 pos += n;
449 } while (nr_pages);
450
451 /*
452 * We need to zeroout the tail of a sub-block write if the extent type
453 * requires zeroing or the write extends beyond EOF. If we don't zero
454 * the block tail in the latter case, we can expose stale data via mmap
455 * reads of the EOF block.
456 */
457zero_tail:
458 if (need_zeroout ||
459 ((dio->flags & IOMAP_DIO_WRITE) && pos >= i_size_read(inode))) {
460 /* zero out from the end of the write to the end of the block */
461 pad = pos & (fs_block_size - 1);
462 if (pad)
463 ret = iomap_dio_zero(iter, dio, pos,
464 fs_block_size - pad);
465 }
466out:
467 /* Undo iter limitation to current extent */
468 iov_iter_reexpand(dio->submit.iter, orig_count - copied);
469 if (copied)
470 return copied;
471 return ret;
472}
473
474static loff_t iomap_dio_hole_iter(const struct iomap_iter *iter,
475 struct iomap_dio *dio)
476{
477 loff_t length = iov_iter_zero(iomap_length(iter), dio->submit.iter);
478
479 dio->size += length;
480 if (!length)
481 return -EFAULT;
482 return length;
483}
484
485static loff_t iomap_dio_inline_iter(const struct iomap_iter *iomi,
486 struct iomap_dio *dio)
487{
488 const struct iomap *iomap = &iomi->iomap;
489 struct iov_iter *iter = dio->submit.iter;
490 void *inline_data = iomap_inline_data(iomap, iomi->pos);
491 loff_t length = iomap_length(iomi);
492 loff_t pos = iomi->pos;
493 size_t copied;
494
495 if (WARN_ON_ONCE(!iomap_inline_data_valid(iomap)))
496 return -EIO;
497
498 if (dio->flags & IOMAP_DIO_WRITE) {
499 loff_t size = iomi->inode->i_size;
500
501 if (pos > size)
502 memset(iomap_inline_data(iomap, size), 0, pos - size);
503 copied = copy_from_iter(inline_data, length, iter);
504 if (copied) {
505 if (pos + copied > size)
506 i_size_write(iomi->inode, pos + copied);
507 mark_inode_dirty(iomi->inode);
508 }
509 } else {
510 copied = copy_to_iter(inline_data, length, iter);
511 }
512 dio->size += copied;
513 if (!copied)
514 return -EFAULT;
515 return copied;
516}
517
518static loff_t iomap_dio_iter(const struct iomap_iter *iter,
519 struct iomap_dio *dio)
520{
521 switch (iter->iomap.type) {
522 case IOMAP_HOLE:
523 if (WARN_ON_ONCE(dio->flags & IOMAP_DIO_WRITE))
524 return -EIO;
525 return iomap_dio_hole_iter(iter, dio);
526 case IOMAP_UNWRITTEN:
527 if (!(dio->flags & IOMAP_DIO_WRITE))
528 return iomap_dio_hole_iter(iter, dio);
529 return iomap_dio_bio_iter(iter, dio);
530 case IOMAP_MAPPED:
531 return iomap_dio_bio_iter(iter, dio);
532 case IOMAP_INLINE:
533 return iomap_dio_inline_iter(iter, dio);
534 case IOMAP_DELALLOC:
535 /*
536 * DIO is not serialised against mmap() access at all, and so
537 * if the page_mkwrite occurs between the writeback and the
538 * iomap_iter() call in the DIO path, then it will see the
539 * DELALLOC block that the page-mkwrite allocated.
540 */
541 pr_warn_ratelimited("Direct I/O collision with buffered writes! File: %pD4 Comm: %.20s\n",
542 dio->iocb->ki_filp, current->comm);
543 return -EIO;
544 default:
545 WARN_ON_ONCE(1);
546 return -EIO;
547 }
548}
549
550/*
551 * iomap_dio_rw() always completes O_[D]SYNC writes regardless of whether the IO
552 * is being issued as AIO or not. This allows us to optimise pure data writes
553 * to use REQ_FUA rather than requiring generic_write_sync() to issue a
554 * REQ_FLUSH post write. This is slightly tricky because a single request here
555 * can be mapped into multiple disjoint IOs and only a subset of the IOs issued
556 * may be pure data writes. In that case, we still need to do a full data sync
557 * completion.
558 *
559 * When page faults are disabled and @dio_flags includes IOMAP_DIO_PARTIAL,
560 * __iomap_dio_rw can return a partial result if it encounters a non-resident
561 * page in @iter after preparing a transfer. In that case, the non-resident
562 * pages can be faulted in and the request resumed with @done_before set to the
563 * number of bytes previously transferred. The request will then complete with
564 * the correct total number of bytes transferred; this is essential for
565 * completing partial requests asynchronously.
566 *
567 * Returns -ENOTBLK In case of a page invalidation invalidation failure for
568 * writes. The callers needs to fall back to buffered I/O in this case.
569 */
570struct iomap_dio *
571__iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
572 const struct iomap_ops *ops, const struct iomap_dio_ops *dops,
573 unsigned int dio_flags, void *private, size_t done_before)
574{
575 struct inode *inode = file_inode(iocb->ki_filp);
576 struct iomap_iter iomi = {
577 .inode = inode,
578 .pos = iocb->ki_pos,
579 .len = iov_iter_count(iter),
580 .flags = IOMAP_DIRECT,
581 .private = private,
582 };
583 bool wait_for_completion =
584 is_sync_kiocb(iocb) || (dio_flags & IOMAP_DIO_FORCE_WAIT);
585 struct blk_plug plug;
586 struct iomap_dio *dio;
587 loff_t ret = 0;
588
589 trace_iomap_dio_rw_begin(iocb, iter, dio_flags, done_before);
590
591 if (!iomi.len)
592 return NULL;
593
594 dio = kmalloc(sizeof(*dio), GFP_KERNEL);
595 if (!dio)
596 return ERR_PTR(-ENOMEM);
597
598 dio->iocb = iocb;
599 atomic_set(&dio->ref, 1);
600 dio->size = 0;
601 dio->i_size = i_size_read(inode);
602 dio->dops = dops;
603 dio->error = 0;
604 dio->flags = 0;
605 dio->done_before = done_before;
606
607 dio->submit.iter = iter;
608 dio->submit.waiter = current;
609
610 if (iocb->ki_flags & IOCB_NOWAIT)
611 iomi.flags |= IOMAP_NOWAIT;
612
613 if (iocb->ki_flags & IOCB_ATOMIC)
614 iomi.flags |= IOMAP_ATOMIC;
615
616 if (iov_iter_rw(iter) == READ) {
617 /* reads can always complete inline */
618 dio->flags |= IOMAP_DIO_INLINE_COMP;
619
620 if (iomi.pos >= dio->i_size)
621 goto out_free_dio;
622
623 if (user_backed_iter(iter))
624 dio->flags |= IOMAP_DIO_DIRTY;
625
626 ret = kiocb_write_and_wait(iocb, iomi.len);
627 if (ret)
628 goto out_free_dio;
629 } else {
630 iomi.flags |= IOMAP_WRITE;
631 dio->flags |= IOMAP_DIO_WRITE;
632
633 /*
634 * Flag as supporting deferred completions, if the issuer
635 * groks it. This can avoid a workqueue punt for writes.
636 * We may later clear this flag if we need to do other IO
637 * as part of this IO completion.
638 */
639 if (iocb->ki_flags & IOCB_DIO_CALLER_COMP)
640 dio->flags |= IOMAP_DIO_CALLER_COMP;
641
642 if (dio_flags & IOMAP_DIO_OVERWRITE_ONLY) {
643 ret = -EAGAIN;
644 if (iomi.pos >= dio->i_size ||
645 iomi.pos + iomi.len > dio->i_size)
646 goto out_free_dio;
647 iomi.flags |= IOMAP_OVERWRITE_ONLY;
648 }
649
650 /* for data sync or sync, we need sync completion processing */
651 if (iocb_is_dsync(iocb)) {
652 dio->flags |= IOMAP_DIO_NEED_SYNC;
653
654 /*
655 * For datasync only writes, we optimistically try using
656 * WRITE_THROUGH for this IO. This flag requires either
657 * FUA writes through the device's write cache, or a
658 * normal write to a device without a volatile write
659 * cache. For the former, Any non-FUA write that occurs
660 * will clear this flag, hence we know before completion
661 * whether a cache flush is necessary.
662 */
663 if (!(iocb->ki_flags & IOCB_SYNC))
664 dio->flags |= IOMAP_DIO_WRITE_THROUGH;
665 }
666
667 /*
668 * Try to invalidate cache pages for the range we are writing.
669 * If this invalidation fails, let the caller fall back to
670 * buffered I/O.
671 */
672 ret = kiocb_invalidate_pages(iocb, iomi.len);
673 if (ret) {
674 if (ret != -EAGAIN) {
675 trace_iomap_dio_invalidate_fail(inode, iomi.pos,
676 iomi.len);
677 if (iocb->ki_flags & IOCB_ATOMIC) {
678 /*
679 * folio invalidation failed, maybe
680 * this is transient, unlock and see if
681 * the caller tries again.
682 */
683 ret = -EAGAIN;
684 } else {
685 /* fall back to buffered write */
686 ret = -ENOTBLK;
687 }
688 }
689 goto out_free_dio;
690 }
691
692 if (!wait_for_completion && !inode->i_sb->s_dio_done_wq) {
693 ret = sb_init_dio_done_wq(inode->i_sb);
694 if (ret < 0)
695 goto out_free_dio;
696 }
697 }
698
699 inode_dio_begin(inode);
700
701 blk_start_plug(&plug);
702 while ((ret = iomap_iter(&iomi, ops)) > 0) {
703 iomi.processed = iomap_dio_iter(&iomi, dio);
704
705 /*
706 * We can only poll for single bio I/Os.
707 */
708 iocb->ki_flags &= ~IOCB_HIPRI;
709 }
710
711 blk_finish_plug(&plug);
712
713 /*
714 * We only report that we've read data up to i_size.
715 * Revert iter to a state corresponding to that as some callers (such
716 * as the splice code) rely on it.
717 */
718 if (iov_iter_rw(iter) == READ && iomi.pos >= dio->i_size)
719 iov_iter_revert(iter, iomi.pos - dio->i_size);
720
721 if (ret == -EFAULT && dio->size && (dio_flags & IOMAP_DIO_PARTIAL)) {
722 if (!(iocb->ki_flags & IOCB_NOWAIT))
723 wait_for_completion = true;
724 ret = 0;
725 }
726
727 /* magic error code to fall back to buffered I/O */
728 if (ret == -ENOTBLK) {
729 wait_for_completion = true;
730 ret = 0;
731 }
732 if (ret < 0)
733 iomap_dio_set_error(dio, ret);
734
735 /*
736 * If all the writes we issued were already written through to the
737 * media, we don't need to flush the cache on IO completion. Clear the
738 * sync flag for this case.
739 */
740 if (dio->flags & IOMAP_DIO_WRITE_THROUGH)
741 dio->flags &= ~IOMAP_DIO_NEED_SYNC;
742
743 /*
744 * We are about to drop our additional submission reference, which
745 * might be the last reference to the dio. There are three different
746 * ways we can progress here:
747 *
748 * (a) If this is the last reference we will always complete and free
749 * the dio ourselves.
750 * (b) If this is not the last reference, and we serve an asynchronous
751 * iocb, we must never touch the dio after the decrement, the
752 * I/O completion handler will complete and free it.
753 * (c) If this is not the last reference, but we serve a synchronous
754 * iocb, the I/O completion handler will wake us up on the drop
755 * of the final reference, and we will complete and free it here
756 * after we got woken by the I/O completion handler.
757 */
758 dio->wait_for_completion = wait_for_completion;
759 if (!atomic_dec_and_test(&dio->ref)) {
760 if (!wait_for_completion) {
761 trace_iomap_dio_rw_queued(inode, iomi.pos, iomi.len);
762 return ERR_PTR(-EIOCBQUEUED);
763 }
764
765 for (;;) {
766 set_current_state(TASK_UNINTERRUPTIBLE);
767 if (!READ_ONCE(dio->submit.waiter))
768 break;
769
770 blk_io_schedule();
771 }
772 __set_current_state(TASK_RUNNING);
773 }
774
775 return dio;
776
777out_free_dio:
778 kfree(dio);
779 if (ret)
780 return ERR_PTR(ret);
781 return NULL;
782}
783EXPORT_SYMBOL_GPL(__iomap_dio_rw);
784
785ssize_t
786iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
787 const struct iomap_ops *ops, const struct iomap_dio_ops *dops,
788 unsigned int dio_flags, void *private, size_t done_before)
789{
790 struct iomap_dio *dio;
791
792 dio = __iomap_dio_rw(iocb, iter, ops, dops, dio_flags, private,
793 done_before);
794 if (IS_ERR_OR_NULL(dio))
795 return PTR_ERR_OR_ZERO(dio);
796 return iomap_dio_complete(dio);
797}
798EXPORT_SYMBOL_GPL(iomap_dio_rw);
799
800static int __init iomap_dio_init(void)
801{
802 zero_page = alloc_pages(GFP_KERNEL | __GFP_ZERO,
803 IOMAP_ZERO_PAGE_ORDER);
804
805 if (!zero_page)
806 return -ENOMEM;
807
808 return 0;
809}
810fs_initcall(iomap_dio_init);