1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * Copyright (C) 2010 Red Hat, Inc.
4 * Copyright (c) 2016-2025 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 "internal.h"
16 #include "trace.h"
17
18 #include "../internal.h"
19
20 /*
21 * Private flags for iomap_dio, must not overlap with the public ones in
22 * iomap.h:
23 */
24 #define IOMAP_DIO_NO_INVALIDATE (1U << 25)
25 #define IOMAP_DIO_CALLER_COMP (1U << 26)
26 #define IOMAP_DIO_INLINE_COMP (1U << 27)
27 #define IOMAP_DIO_WRITE_THROUGH (1U << 28)
28 #define IOMAP_DIO_NEED_SYNC (1U << 29)
29 #define IOMAP_DIO_WRITE (1U << 30)
30 #define IOMAP_DIO_DIRTY (1U << 31)
31
32 /*
33 * Used for sub block zeroing in iomap_dio_zero()
34 */
35 #define IOMAP_ZERO_PAGE_SIZE (SZ_64K)
36 #define IOMAP_ZERO_PAGE_ORDER (get_order(IOMAP_ZERO_PAGE_SIZE))
37 static struct page *zero_page;
38
39 struct iomap_dio {
40 struct kiocb *iocb;
41 const struct iomap_dio_ops *dops;
42 loff_t i_size;
43 loff_t size;
44 atomic_t ref;
45 unsigned flags;
46 int error;
47 size_t done_before;
48 bool wait_for_completion;
49
50 union {
51 /* used during submission and for synchronous completion: */
52 struct {
53 struct iov_iter *iter;
54 struct task_struct *waiter;
55 } submit;
56
57 /* used for aio completion: */
58 struct {
59 struct work_struct work;
60 } aio;
61 };
62 };
63
iomap_dio_alloc_bio(const struct iomap_iter * iter,struct iomap_dio * dio,unsigned short nr_vecs,blk_opf_t opf)64 static struct bio *iomap_dio_alloc_bio(const struct iomap_iter *iter,
65 struct iomap_dio *dio, unsigned short nr_vecs, blk_opf_t opf)
66 {
67 if (dio->dops && dio->dops->bio_set)
68 return bio_alloc_bioset(iter->iomap.bdev, nr_vecs, opf,
69 GFP_KERNEL, dio->dops->bio_set);
70 return bio_alloc(iter->iomap.bdev, nr_vecs, opf, GFP_KERNEL);
71 }
72
iomap_dio_submit_bio(const struct iomap_iter * iter,struct iomap_dio * dio,struct bio * bio,loff_t pos)73 static void iomap_dio_submit_bio(const struct iomap_iter *iter,
74 struct iomap_dio *dio, struct bio *bio, loff_t pos)
75 {
76 struct kiocb *iocb = dio->iocb;
77
78 atomic_inc(&dio->ref);
79
80 /* Sync dio can't be polled reliably */
81 if ((iocb->ki_flags & IOCB_HIPRI) && !is_sync_kiocb(iocb)) {
82 bio_set_polled(bio, iocb);
83 WRITE_ONCE(iocb->private, bio);
84 }
85
86 if (dio->dops && dio->dops->submit_io) {
87 dio->dops->submit_io(iter, bio, pos);
88 } else {
89 WARN_ON_ONCE(iter->iomap.flags & IOMAP_F_ANON_WRITE);
90 submit_bio(bio);
91 }
92 }
93
iomap_dio_complete(struct iomap_dio * dio)94 ssize_t iomap_dio_complete(struct iomap_dio *dio)
95 {
96 const struct iomap_dio_ops *dops = dio->dops;
97 struct kiocb *iocb = dio->iocb;
98 loff_t offset = iocb->ki_pos;
99 ssize_t ret = dio->error;
100
101 if (dops && dops->end_io)
102 ret = dops->end_io(iocb, dio->size, ret, dio->flags);
103
104 if (likely(!ret)) {
105 ret = dio->size;
106 /* check for short read */
107 if (offset + ret > dio->i_size &&
108 !(dio->flags & IOMAP_DIO_WRITE))
109 ret = dio->i_size - offset;
110 }
111
112 /*
113 * Try again to invalidate clean pages which might have been cached by
114 * non-direct readahead, or faulted in by get_user_pages() if the source
115 * of the write was an mmap'ed region of the file we're writing. Either
116 * one is a pretty crazy thing to do, so we don't support it 100%. If
117 * this invalidation fails, tough, the write still worked...
118 *
119 * And this page cache invalidation has to be after ->end_io(), as some
120 * filesystems convert unwritten extents to real allocations in
121 * ->end_io() when necessary, otherwise a racing buffer read would cache
122 * zeros from unwritten extents.
123 */
124 if (!dio->error && dio->size && (dio->flags & IOMAP_DIO_WRITE) &&
125 !(dio->flags & IOMAP_DIO_NO_INVALIDATE))
126 kiocb_invalidate_post_direct_write(iocb, dio->size);
127
128 inode_dio_end(file_inode(iocb->ki_filp));
129
130 if (ret > 0) {
131 iocb->ki_pos += ret;
132
133 /*
134 * If this is a DSYNC write, make sure we push it to stable
135 * storage now that we've written data.
136 */
137 if (dio->flags & IOMAP_DIO_NEED_SYNC)
138 ret = generic_write_sync(iocb, ret);
139 if (ret > 0)
140 ret += dio->done_before;
141 }
142 trace_iomap_dio_complete(iocb, dio->error, ret);
143 kfree(dio);
144 return ret;
145 }
146 EXPORT_SYMBOL_GPL(iomap_dio_complete);
147
iomap_dio_deferred_complete(void * data)148 static ssize_t iomap_dio_deferred_complete(void *data)
149 {
150 return iomap_dio_complete(data);
151 }
152
iomap_dio_complete_work(struct work_struct * work)153 static void iomap_dio_complete_work(struct work_struct *work)
154 {
155 struct iomap_dio *dio = container_of(work, struct iomap_dio, aio.work);
156 struct kiocb *iocb = dio->iocb;
157
158 iocb->ki_complete(iocb, iomap_dio_complete(dio));
159 }
160
161 /*
162 * Set an error in the dio if none is set yet. We have to use cmpxchg
163 * as the submission context and the completion context(s) can race to
164 * update the error.
165 */
iomap_dio_set_error(struct iomap_dio * dio,int ret)166 static inline void iomap_dio_set_error(struct iomap_dio *dio, int ret)
167 {
168 cmpxchg(&dio->error, 0, ret);
169 }
170
171 /*
172 * Called when dio->ref reaches zero from an I/O completion.
173 */
iomap_dio_done(struct iomap_dio * dio)174 static void iomap_dio_done(struct iomap_dio *dio)
175 {
176 struct kiocb *iocb = dio->iocb;
177
178 if (dio->wait_for_completion) {
179 /*
180 * Synchronous I/O, task itself will handle any completion work
181 * that needs after IO. All we need to do is wake the task.
182 */
183 struct task_struct *waiter = dio->submit.waiter;
184
185 WRITE_ONCE(dio->submit.waiter, NULL);
186 blk_wake_io_task(waiter);
187 } else if (dio->flags & IOMAP_DIO_INLINE_COMP) {
188 WRITE_ONCE(iocb->private, NULL);
189 iomap_dio_complete_work(&dio->aio.work);
190 } else if (dio->flags & IOMAP_DIO_CALLER_COMP) {
191 /*
192 * If this dio is flagged with IOMAP_DIO_CALLER_COMP, then
193 * schedule our completion that way to avoid an async punt to a
194 * workqueue.
195 */
196 /* only polled IO cares about private cleared */
197 iocb->private = dio;
198 iocb->dio_complete = iomap_dio_deferred_complete;
199
200 /*
201 * Invoke ->ki_complete() directly. We've assigned our
202 * dio_complete callback handler, and since the issuer set
203 * IOCB_DIO_CALLER_COMP, we know their ki_complete handler will
204 * notice ->dio_complete being set and will defer calling that
205 * handler until it can be done from a safe task context.
206 *
207 * Note that the 'res' being passed in here is not important
208 * for this case. The actual completion value of the request
209 * will be gotten from dio_complete when that is run by the
210 * issuer.
211 */
212 iocb->ki_complete(iocb, 0);
213 } else {
214 struct inode *inode = file_inode(iocb->ki_filp);
215
216 /*
217 * Async DIO completion that requires filesystem level
218 * completion work gets punted to a work queue to complete as
219 * the operation may require more IO to be issued to finalise
220 * filesystem metadata changes or guarantee data integrity.
221 */
222 INIT_WORK(&dio->aio.work, iomap_dio_complete_work);
223 queue_work(inode->i_sb->s_dio_done_wq, &dio->aio.work);
224 }
225 }
226
iomap_dio_bio_end_io(struct bio * bio)227 void iomap_dio_bio_end_io(struct bio *bio)
228 {
229 struct iomap_dio *dio = bio->bi_private;
230 bool should_dirty = (dio->flags & IOMAP_DIO_DIRTY);
231
232 if (bio->bi_status)
233 iomap_dio_set_error(dio, blk_status_to_errno(bio->bi_status));
234
235 if (atomic_dec_and_test(&dio->ref))
236 iomap_dio_done(dio);
237
238 if (should_dirty) {
239 bio_check_pages_dirty(bio);
240 } else {
241 bio_release_pages(bio, false);
242 bio_put(bio);
243 }
244 }
245 EXPORT_SYMBOL_GPL(iomap_dio_bio_end_io);
246
iomap_finish_ioend_direct(struct iomap_ioend * ioend)247 u32 iomap_finish_ioend_direct(struct iomap_ioend *ioend)
248 {
249 struct iomap_dio *dio = ioend->io_bio.bi_private;
250 bool should_dirty = (dio->flags & IOMAP_DIO_DIRTY);
251 u32 vec_count = ioend->io_bio.bi_vcnt;
252
253 if (ioend->io_error)
254 iomap_dio_set_error(dio, ioend->io_error);
255
256 if (atomic_dec_and_test(&dio->ref)) {
257 /*
258 * Try to avoid another context switch for the completion given
259 * that we are already called from the ioend completion
260 * workqueue, but never invalidate pages from this thread to
261 * avoid deadlocks with buffered I/O completions. Tough luck if
262 * you hit the tiny race with someone dirtying the range now
263 * between this check and the actual completion.
264 */
265 if (!dio->iocb->ki_filp->f_mapping->nrpages) {
266 dio->flags |= IOMAP_DIO_INLINE_COMP;
267 dio->flags |= IOMAP_DIO_NO_INVALIDATE;
268 }
269 dio->flags &= ~IOMAP_DIO_CALLER_COMP;
270 iomap_dio_done(dio);
271 }
272
273 if (should_dirty) {
274 bio_check_pages_dirty(&ioend->io_bio);
275 } else {
276 bio_release_pages(&ioend->io_bio, false);
277 bio_put(&ioend->io_bio);
278 }
279
280 /*
281 * Return the number of bvecs completed as even direct I/O completions
282 * do significant per-folio work and we'll still want to give up the
283 * CPU after a lot of completions.
284 */
285 return vec_count;
286 }
287
iomap_dio_zero(const struct iomap_iter * iter,struct iomap_dio * dio,loff_t pos,unsigned len)288 static int iomap_dio_zero(const struct iomap_iter *iter, struct iomap_dio *dio,
289 loff_t pos, unsigned len)
290 {
291 struct inode *inode = file_inode(dio->iocb->ki_filp);
292 struct bio *bio;
293
294 if (!len)
295 return 0;
296 /*
297 * Max block size supported is 64k
298 */
299 if (WARN_ON_ONCE(len > IOMAP_ZERO_PAGE_SIZE))
300 return -EINVAL;
301
302 bio = iomap_dio_alloc_bio(iter, dio, 1, REQ_OP_WRITE | REQ_SYNC | REQ_IDLE);
303 fscrypt_set_bio_crypt_ctx(bio, inode, pos >> inode->i_blkbits,
304 GFP_KERNEL);
305 bio->bi_iter.bi_sector = iomap_sector(&iter->iomap, pos);
306 bio->bi_private = dio;
307 bio->bi_end_io = iomap_dio_bio_end_io;
308
309 __bio_add_page(bio, zero_page, len, 0);
310 iomap_dio_submit_bio(iter, dio, bio, pos);
311 return 0;
312 }
313
314 /*
315 * Use a FUA write if we need datasync semantics and this is a pure data I/O
316 * that doesn't require any metadata updates (including after I/O completion
317 * such as unwritten extent conversion) and the underlying device either
318 * doesn't have a volatile write cache or supports FUA.
319 * This allows us to avoid cache flushes on I/O completion.
320 */
iomap_dio_can_use_fua(const struct iomap * iomap,struct iomap_dio * dio)321 static inline bool iomap_dio_can_use_fua(const struct iomap *iomap,
322 struct iomap_dio *dio)
323 {
324 if (iomap->flags & (IOMAP_F_SHARED | IOMAP_F_DIRTY))
325 return false;
326 if (!(dio->flags & IOMAP_DIO_WRITE_THROUGH))
327 return false;
328 return !bdev_write_cache(iomap->bdev) || bdev_fua(iomap->bdev);
329 }
330
iomap_dio_bio_iter(struct iomap_iter * iter,struct iomap_dio * dio)331 static int iomap_dio_bio_iter(struct iomap_iter *iter, struct iomap_dio *dio)
332 {
333 const struct iomap *iomap = &iter->iomap;
334 struct inode *inode = iter->inode;
335 unsigned int fs_block_size = i_blocksize(inode), pad;
336 const loff_t length = iomap_length(iter);
337 loff_t pos = iter->pos;
338 blk_opf_t bio_opf = REQ_SYNC | REQ_IDLE;
339 struct bio *bio;
340 bool need_zeroout = false;
341 int nr_pages, ret = 0;
342 u64 copied = 0;
343 size_t orig_count;
344
345 if ((pos | length) & (bdev_logical_block_size(iomap->bdev) - 1) ||
346 !bdev_iter_is_aligned(iomap->bdev, dio->submit.iter))
347 return -EINVAL;
348
349 if (dio->flags & IOMAP_DIO_WRITE) {
350 bio_opf |= REQ_OP_WRITE;
351
352 if (iomap->flags & IOMAP_F_ATOMIC_BIO) {
353 /*
354 * Ensure that the mapping covers the full write
355 * length, otherwise it won't be submitted as a single
356 * bio, which is required to use hardware atomics.
357 */
358 if (length != iter->len)
359 return -EINVAL;
360 bio_opf |= REQ_ATOMIC;
361 }
362
363 if (iomap->type == IOMAP_UNWRITTEN) {
364 dio->flags |= IOMAP_DIO_UNWRITTEN;
365 need_zeroout = true;
366 }
367
368 if (iomap->flags & IOMAP_F_SHARED)
369 dio->flags |= IOMAP_DIO_COW;
370
371 if (iomap->flags & IOMAP_F_NEW) {
372 need_zeroout = true;
373 } else if (iomap->type == IOMAP_MAPPED) {
374 if (iomap_dio_can_use_fua(iomap, dio))
375 bio_opf |= REQ_FUA;
376 else
377 dio->flags &= ~IOMAP_DIO_WRITE_THROUGH;
378 }
379
380 /*
381 * We can only do deferred completion for pure overwrites that
382 * don't require additional I/O at completion time.
383 *
384 * This rules out writes that need zeroing or extent conversion,
385 * extend the file size, or issue metadata I/O or cache flushes
386 * during completion processing.
387 */
388 if (need_zeroout || (pos >= i_size_read(inode)) ||
389 ((dio->flags & IOMAP_DIO_NEED_SYNC) &&
390 !(bio_opf & REQ_FUA)))
391 dio->flags &= ~IOMAP_DIO_CALLER_COMP;
392 } else {
393 bio_opf |= REQ_OP_READ;
394 }
395
396 /*
397 * Save the original count and trim the iter to just the extent we
398 * are operating on right now. The iter will be re-expanded once
399 * we are done.
400 */
401 orig_count = iov_iter_count(dio->submit.iter);
402 iov_iter_truncate(dio->submit.iter, length);
403
404 if (!iov_iter_count(dio->submit.iter))
405 goto out;
406
407 /*
408 * The rules for polled IO completions follow the guidelines as the
409 * ones we set for inline and deferred completions. If none of those
410 * are available for this IO, clear the polled flag.
411 */
412 if (!(dio->flags & (IOMAP_DIO_INLINE_COMP|IOMAP_DIO_CALLER_COMP)))
413 dio->iocb->ki_flags &= ~IOCB_HIPRI;
414
415 if (need_zeroout) {
416 /* zero out from the start of the block to the write offset */
417 pad = pos & (fs_block_size - 1);
418
419 ret = iomap_dio_zero(iter, dio, pos - pad, pad);
420 if (ret)
421 goto out;
422 }
423
424 nr_pages = bio_iov_vecs_to_alloc(dio->submit.iter, BIO_MAX_VECS);
425 do {
426 size_t n;
427 if (dio->error) {
428 iov_iter_revert(dio->submit.iter, copied);
429 copied = ret = 0;
430 goto out;
431 }
432
433 bio = iomap_dio_alloc_bio(iter, dio, nr_pages, bio_opf);
434 fscrypt_set_bio_crypt_ctx(bio, inode, pos >> inode->i_blkbits,
435 GFP_KERNEL);
436 bio->bi_iter.bi_sector = iomap_sector(iomap, pos);
437 bio->bi_write_hint = inode->i_write_hint;
438 bio->bi_ioprio = dio->iocb->ki_ioprio;
439 bio->bi_private = dio;
440 bio->bi_end_io = iomap_dio_bio_end_io;
441
442 ret = bio_iov_iter_get_pages(bio, dio->submit.iter);
443 if (unlikely(ret)) {
444 /*
445 * We have to stop part way through an IO. We must fall
446 * through to the sub-block tail zeroing here, otherwise
447 * this short IO may expose stale data in the tail of
448 * the block we haven't written data to.
449 */
450 bio_put(bio);
451 goto zero_tail;
452 }
453
454 n = bio->bi_iter.bi_size;
455 if (WARN_ON_ONCE((bio_opf & REQ_ATOMIC) && n != length)) {
456 /*
457 * An atomic write bio must cover the complete length,
458 * which it doesn't, so error. We may need to zero out
459 * the tail (complete FS block), similar to when
460 * bio_iov_iter_get_pages() returns an error, above.
461 */
462 ret = -EINVAL;
463 bio_put(bio);
464 goto zero_tail;
465 }
466 if (dio->flags & IOMAP_DIO_WRITE)
467 task_io_account_write(n);
468 else if (dio->flags & IOMAP_DIO_DIRTY)
469 bio_set_pages_dirty(bio);
470
471 dio->size += n;
472 copied += n;
473
474 nr_pages = bio_iov_vecs_to_alloc(dio->submit.iter,
475 BIO_MAX_VECS);
476 /*
477 * We can only poll for single bio I/Os.
478 */
479 if (nr_pages)
480 dio->iocb->ki_flags &= ~IOCB_HIPRI;
481 iomap_dio_submit_bio(iter, dio, bio, pos);
482 pos += n;
483 } while (nr_pages);
484
485 /*
486 * We need to zeroout the tail of a sub-block write if the extent type
487 * requires zeroing or the write extends beyond EOF. If we don't zero
488 * the block tail in the latter case, we can expose stale data via mmap
489 * reads of the EOF block.
490 */
491 zero_tail:
492 if (need_zeroout ||
493 ((dio->flags & IOMAP_DIO_WRITE) && pos >= i_size_read(inode))) {
494 /* zero out from the end of the write to the end of the block */
495 pad = pos & (fs_block_size - 1);
496 if (pad)
497 ret = iomap_dio_zero(iter, dio, pos,
498 fs_block_size - pad);
499 }
500 out:
501 /* Undo iter limitation to current extent */
502 iov_iter_reexpand(dio->submit.iter, orig_count - copied);
503 if (copied)
504 return iomap_iter_advance(iter, &copied);
505 return ret;
506 }
507
iomap_dio_hole_iter(struct iomap_iter * iter,struct iomap_dio * dio)508 static int iomap_dio_hole_iter(struct iomap_iter *iter, struct iomap_dio *dio)
509 {
510 loff_t length = iov_iter_zero(iomap_length(iter), dio->submit.iter);
511
512 dio->size += length;
513 if (!length)
514 return -EFAULT;
515 return iomap_iter_advance(iter, &length);
516 }
517
iomap_dio_inline_iter(struct iomap_iter * iomi,struct iomap_dio * dio)518 static int iomap_dio_inline_iter(struct iomap_iter *iomi, struct iomap_dio *dio)
519 {
520 const struct iomap *iomap = &iomi->iomap;
521 struct iov_iter *iter = dio->submit.iter;
522 void *inline_data = iomap_inline_data(iomap, iomi->pos);
523 loff_t length = iomap_length(iomi);
524 loff_t pos = iomi->pos;
525 u64 copied;
526
527 if (WARN_ON_ONCE(!iomap_inline_data_valid(iomap)))
528 return -EIO;
529
530 if (dio->flags & IOMAP_DIO_WRITE) {
531 loff_t size = iomi->inode->i_size;
532
533 if (pos > size)
534 memset(iomap_inline_data(iomap, size), 0, pos - size);
535 copied = copy_from_iter(inline_data, length, iter);
536 if (copied) {
537 if (pos + copied > size)
538 i_size_write(iomi->inode, pos + copied);
539 mark_inode_dirty(iomi->inode);
540 }
541 } else {
542 copied = copy_to_iter(inline_data, length, iter);
543 }
544 dio->size += copied;
545 if (!copied)
546 return -EFAULT;
547 return iomap_iter_advance(iomi, &copied);
548 }
549
iomap_dio_iter(struct iomap_iter * iter,struct iomap_dio * dio)550 static int iomap_dio_iter(struct iomap_iter *iter, struct iomap_dio *dio)
551 {
552 switch (iter->iomap.type) {
553 case IOMAP_HOLE:
554 if (WARN_ON_ONCE(dio->flags & IOMAP_DIO_WRITE))
555 return -EIO;
556 return iomap_dio_hole_iter(iter, dio);
557 case IOMAP_UNWRITTEN:
558 if (!(dio->flags & IOMAP_DIO_WRITE))
559 return iomap_dio_hole_iter(iter, dio);
560 return iomap_dio_bio_iter(iter, dio);
561 case IOMAP_MAPPED:
562 return iomap_dio_bio_iter(iter, dio);
563 case IOMAP_INLINE:
564 return iomap_dio_inline_iter(iter, dio);
565 case IOMAP_DELALLOC:
566 /*
567 * DIO is not serialised against mmap() access at all, and so
568 * if the page_mkwrite occurs between the writeback and the
569 * iomap_iter() call in the DIO path, then it will see the
570 * DELALLOC block that the page-mkwrite allocated.
571 */
572 pr_warn_ratelimited("Direct I/O collision with buffered writes! File: %pD4 Comm: %.20s\n",
573 dio->iocb->ki_filp, current->comm);
574 return -EIO;
575 default:
576 WARN_ON_ONCE(1);
577 return -EIO;
578 }
579 }
580
581 /*
582 * iomap_dio_rw() always completes O_[D]SYNC writes regardless of whether the IO
583 * is being issued as AIO or not. This allows us to optimise pure data writes
584 * to use REQ_FUA rather than requiring generic_write_sync() to issue a
585 * REQ_FLUSH post write. This is slightly tricky because a single request here
586 * can be mapped into multiple disjoint IOs and only a subset of the IOs issued
587 * may be pure data writes. In that case, we still need to do a full data sync
588 * completion.
589 *
590 * When page faults are disabled and @dio_flags includes IOMAP_DIO_PARTIAL,
591 * __iomap_dio_rw can return a partial result if it encounters a non-resident
592 * page in @iter after preparing a transfer. In that case, the non-resident
593 * pages can be faulted in and the request resumed with @done_before set to the
594 * number of bytes previously transferred. The request will then complete with
595 * the correct total number of bytes transferred; this is essential for
596 * completing partial requests asynchronously.
597 *
598 * Returns -ENOTBLK In case of a page invalidation invalidation failure for
599 * writes. The callers needs to fall back to buffered I/O in this case.
600 */
601 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,void * private,size_t done_before)602 __iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
603 const struct iomap_ops *ops, const struct iomap_dio_ops *dops,
604 unsigned int dio_flags, void *private, size_t done_before)
605 {
606 struct inode *inode = file_inode(iocb->ki_filp);
607 struct iomap_iter iomi = {
608 .inode = inode,
609 .pos = iocb->ki_pos,
610 .len = iov_iter_count(iter),
611 .flags = IOMAP_DIRECT,
612 .private = private,
613 };
614 bool wait_for_completion =
615 is_sync_kiocb(iocb) || (dio_flags & IOMAP_DIO_FORCE_WAIT);
616 struct blk_plug plug;
617 struct iomap_dio *dio;
618 loff_t ret = 0;
619
620 trace_iomap_dio_rw_begin(iocb, iter, dio_flags, done_before);
621
622 if (!iomi.len)
623 return NULL;
624
625 dio = kmalloc(sizeof(*dio), GFP_KERNEL);
626 if (!dio)
627 return ERR_PTR(-ENOMEM);
628
629 dio->iocb = iocb;
630 atomic_set(&dio->ref, 1);
631 dio->size = 0;
632 dio->i_size = i_size_read(inode);
633 dio->dops = dops;
634 dio->error = 0;
635 dio->flags = 0;
636 dio->done_before = done_before;
637
638 dio->submit.iter = iter;
639 dio->submit.waiter = current;
640
641 if (iocb->ki_flags & IOCB_NOWAIT)
642 iomi.flags |= IOMAP_NOWAIT;
643
644 if (iov_iter_rw(iter) == READ) {
645 /* reads can always complete inline */
646 dio->flags |= IOMAP_DIO_INLINE_COMP;
647
648 if (iomi.pos >= dio->i_size)
649 goto out_free_dio;
650
651 if (user_backed_iter(iter))
652 dio->flags |= IOMAP_DIO_DIRTY;
653
654 ret = kiocb_write_and_wait(iocb, iomi.len);
655 if (ret)
656 goto out_free_dio;
657 } else {
658 iomi.flags |= IOMAP_WRITE;
659 dio->flags |= IOMAP_DIO_WRITE;
660
661 /*
662 * Flag as supporting deferred completions, if the issuer
663 * groks it. This can avoid a workqueue punt for writes.
664 * We may later clear this flag if we need to do other IO
665 * as part of this IO completion.
666 */
667 if (iocb->ki_flags & IOCB_DIO_CALLER_COMP)
668 dio->flags |= IOMAP_DIO_CALLER_COMP;
669
670 if (dio_flags & IOMAP_DIO_OVERWRITE_ONLY) {
671 ret = -EAGAIN;
672 if (iomi.pos >= dio->i_size ||
673 iomi.pos + iomi.len > dio->i_size)
674 goto out_free_dio;
675 iomi.flags |= IOMAP_OVERWRITE_ONLY;
676 }
677
678 if (iocb->ki_flags & IOCB_ATOMIC)
679 iomi.flags |= IOMAP_ATOMIC;
680
681 /* for data sync or sync, we need sync completion processing */
682 if (iocb_is_dsync(iocb)) {
683 dio->flags |= IOMAP_DIO_NEED_SYNC;
684
685 /*
686 * For datasync only writes, we optimistically try using
687 * WRITE_THROUGH for this IO. This flag requires either
688 * FUA writes through the device's write cache, or a
689 * normal write to a device without a volatile write
690 * cache. For the former, Any non-FUA write that occurs
691 * will clear this flag, hence we know before completion
692 * whether a cache flush is necessary.
693 */
694 if (!(iocb->ki_flags & IOCB_SYNC))
695 dio->flags |= IOMAP_DIO_WRITE_THROUGH;
696 }
697
698 /*
699 * Try to invalidate cache pages for the range we are writing.
700 * If this invalidation fails, let the caller fall back to
701 * buffered I/O.
702 */
703 ret = kiocb_invalidate_pages(iocb, iomi.len);
704 if (ret) {
705 if (ret != -EAGAIN) {
706 trace_iomap_dio_invalidate_fail(inode, iomi.pos,
707 iomi.len);
708 if (iocb->ki_flags & IOCB_ATOMIC) {
709 /*
710 * folio invalidation failed, maybe
711 * this is transient, unlock and see if
712 * the caller tries again.
713 */
714 ret = -EAGAIN;
715 } else {
716 /* fall back to buffered write */
717 ret = -ENOTBLK;
718 }
719 }
720 goto out_free_dio;
721 }
722
723 if (!wait_for_completion && !inode->i_sb->s_dio_done_wq) {
724 ret = sb_init_dio_done_wq(inode->i_sb);
725 if (ret < 0)
726 goto out_free_dio;
727 }
728 }
729
730 inode_dio_begin(inode);
731
732 blk_start_plug(&plug);
733 while ((ret = iomap_iter(&iomi, ops)) > 0) {
734 iomi.status = iomap_dio_iter(&iomi, dio);
735
736 /*
737 * We can only poll for single bio I/Os.
738 */
739 iocb->ki_flags &= ~IOCB_HIPRI;
740 }
741
742 blk_finish_plug(&plug);
743
744 /*
745 * We only report that we've read data up to i_size.
746 * Revert iter to a state corresponding to that as some callers (such
747 * as the splice code) rely on it.
748 */
749 if (iov_iter_rw(iter) == READ && iomi.pos >= dio->i_size)
750 iov_iter_revert(iter, iomi.pos - dio->i_size);
751
752 if (ret == -EFAULT && dio->size && (dio_flags & IOMAP_DIO_PARTIAL)) {
753 if (!(iocb->ki_flags & IOCB_NOWAIT))
754 wait_for_completion = true;
755 ret = 0;
756 }
757
758 /* magic error code to fall back to buffered I/O */
759 if (ret == -ENOTBLK) {
760 wait_for_completion = true;
761 ret = 0;
762 }
763 if (ret < 0)
764 iomap_dio_set_error(dio, ret);
765
766 /*
767 * If all the writes we issued were already written through to the
768 * media, we don't need to flush the cache on IO completion. Clear the
769 * sync flag for this case.
770 */
771 if (dio->flags & IOMAP_DIO_WRITE_THROUGH)
772 dio->flags &= ~IOMAP_DIO_NEED_SYNC;
773
774 /*
775 * We are about to drop our additional submission reference, which
776 * might be the last reference to the dio. There are three different
777 * ways we can progress here:
778 *
779 * (a) If this is the last reference we will always complete and free
780 * the dio ourselves.
781 * (b) If this is not the last reference, and we serve an asynchronous
782 * iocb, we must never touch the dio after the decrement, the
783 * I/O completion handler will complete and free it.
784 * (c) If this is not the last reference, but we serve a synchronous
785 * iocb, the I/O completion handler will wake us up on the drop
786 * of the final reference, and we will complete and free it here
787 * after we got woken by the I/O completion handler.
788 */
789 dio->wait_for_completion = wait_for_completion;
790 if (!atomic_dec_and_test(&dio->ref)) {
791 if (!wait_for_completion) {
792 trace_iomap_dio_rw_queued(inode, iomi.pos, iomi.len);
793 return ERR_PTR(-EIOCBQUEUED);
794 }
795
796 for (;;) {
797 set_current_state(TASK_UNINTERRUPTIBLE);
798 if (!READ_ONCE(dio->submit.waiter))
799 break;
800
801 blk_io_schedule();
802 }
803 __set_current_state(TASK_RUNNING);
804 }
805
806 return dio;
807
808 out_free_dio:
809 kfree(dio);
810 if (ret)
811 return ERR_PTR(ret);
812 return NULL;
813 }
814 EXPORT_SYMBOL_GPL(__iomap_dio_rw);
815
816 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,void * private,size_t done_before)817 iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
818 const struct iomap_ops *ops, const struct iomap_dio_ops *dops,
819 unsigned int dio_flags, void *private, size_t done_before)
820 {
821 struct iomap_dio *dio;
822
823 dio = __iomap_dio_rw(iocb, iter, ops, dops, dio_flags, private,
824 done_before);
825 if (IS_ERR_OR_NULL(dio))
826 return PTR_ERR_OR_ZERO(dio);
827 return iomap_dio_complete(dio);
828 }
829 EXPORT_SYMBOL_GPL(iomap_dio_rw);
830
iomap_dio_init(void)831 static int __init iomap_dio_init(void)
832 {
833 zero_page = alloc_pages(GFP_KERNEL | __GFP_ZERO,
834 IOMAP_ZERO_PAGE_ORDER);
835
836 if (!zero_page)
837 return -ENOMEM;
838
839 return 0;
840 }
841 fs_initcall(iomap_dio_init);
842