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db074436 DW |
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 | ||
14 | #include "../internal.h" | |
15 | ||
16 | /* | |
17 | * Private flags for iomap_dio, must not overlap with the public ones in | |
18 | * iomap.h: | |
19 | */ | |
20 | #define IOMAP_DIO_WRITE_FUA (1 << 28) | |
21 | #define IOMAP_DIO_NEED_SYNC (1 << 29) | |
22 | #define IOMAP_DIO_WRITE (1 << 30) | |
23 | #define IOMAP_DIO_DIRTY (1 << 31) | |
24 | ||
25 | struct iomap_dio { | |
26 | struct kiocb *iocb; | |
838c4f3d | 27 | const struct iomap_dio_ops *dops; |
db074436 DW |
28 | loff_t i_size; |
29 | loff_t size; | |
30 | atomic_t ref; | |
31 | unsigned flags; | |
32 | int error; | |
33 | bool wait_for_completion; | |
34 | ||
35 | union { | |
36 | /* used during submission and for synchronous completion: */ | |
37 | struct { | |
38 | struct iov_iter *iter; | |
39 | struct task_struct *waiter; | |
40 | struct request_queue *last_queue; | |
41 | blk_qc_t cookie; | |
42 | } submit; | |
43 | ||
44 | /* used for aio completion: */ | |
45 | struct { | |
46 | struct work_struct work; | |
47 | } aio; | |
48 | }; | |
49 | }; | |
50 | ||
51 | int iomap_dio_iopoll(struct kiocb *kiocb, bool spin) | |
52 | { | |
53 | struct request_queue *q = READ_ONCE(kiocb->private); | |
54 | ||
55 | if (!q) | |
56 | return 0; | |
57 | return blk_poll(q, READ_ONCE(kiocb->ki_cookie), spin); | |
58 | } | |
59 | EXPORT_SYMBOL_GPL(iomap_dio_iopoll); | |
60 | ||
61 | static void iomap_dio_submit_bio(struct iomap_dio *dio, struct iomap *iomap, | |
62 | struct bio *bio) | |
63 | { | |
64 | atomic_inc(&dio->ref); | |
65 | ||
66 | if (dio->iocb->ki_flags & IOCB_HIPRI) | |
67 | bio_set_polled(bio, dio->iocb); | |
68 | ||
69 | dio->submit.last_queue = bdev_get_queue(iomap->bdev); | |
70 | dio->submit.cookie = submit_bio(bio); | |
71 | } | |
72 | ||
73 | static ssize_t iomap_dio_complete(struct iomap_dio *dio) | |
74 | { | |
838c4f3d | 75 | const struct iomap_dio_ops *dops = dio->dops; |
db074436 DW |
76 | struct kiocb *iocb = dio->iocb; |
77 | struct inode *inode = file_inode(iocb->ki_filp); | |
78 | loff_t offset = iocb->ki_pos; | |
838c4f3d | 79 | ssize_t ret = dio->error; |
db074436 | 80 | |
838c4f3d CH |
81 | if (dops && dops->end_io) |
82 | ret = dops->end_io(iocb, dio->size, ret, dio->flags); | |
db074436 DW |
83 | |
84 | if (likely(!ret)) { | |
85 | ret = dio->size; | |
86 | /* check for short read */ | |
87 | if (offset + ret > dio->i_size && | |
88 | !(dio->flags & IOMAP_DIO_WRITE)) | |
89 | ret = dio->i_size - offset; | |
90 | iocb->ki_pos += ret; | |
91 | } | |
92 | ||
93 | /* | |
94 | * Try again to invalidate clean pages which might have been cached by | |
95 | * non-direct readahead, or faulted in by get_user_pages() if the source | |
96 | * of the write was an mmap'ed region of the file we're writing. Either | |
97 | * one is a pretty crazy thing to do, so we don't support it 100%. If | |
98 | * this invalidation fails, tough, the write still worked... | |
99 | * | |
838c4f3d CH |
100 | * And this page cache invalidation has to be after ->end_io(), as some |
101 | * filesystems convert unwritten extents to real allocations in | |
102 | * ->end_io() when necessary, otherwise a racing buffer read would cache | |
db074436 DW |
103 | * zeros from unwritten extents. |
104 | */ | |
105 | if (!dio->error && | |
106 | (dio->flags & IOMAP_DIO_WRITE) && inode->i_mapping->nrpages) { | |
107 | int err; | |
108 | err = invalidate_inode_pages2_range(inode->i_mapping, | |
109 | offset >> PAGE_SHIFT, | |
110 | (offset + dio->size - 1) >> PAGE_SHIFT); | |
111 | if (err) | |
112 | dio_warn_stale_pagecache(iocb->ki_filp); | |
113 | } | |
114 | ||
115 | /* | |
116 | * If this is a DSYNC write, make sure we push it to stable storage now | |
117 | * that we've written data. | |
118 | */ | |
119 | if (ret > 0 && (dio->flags & IOMAP_DIO_NEED_SYNC)) | |
120 | ret = generic_write_sync(iocb, ret); | |
121 | ||
122 | inode_dio_end(file_inode(iocb->ki_filp)); | |
123 | kfree(dio); | |
124 | ||
125 | return ret; | |
126 | } | |
127 | ||
128 | static void iomap_dio_complete_work(struct work_struct *work) | |
129 | { | |
130 | struct iomap_dio *dio = container_of(work, struct iomap_dio, aio.work); | |
131 | struct kiocb *iocb = dio->iocb; | |
132 | ||
133 | iocb->ki_complete(iocb, iomap_dio_complete(dio), 0); | |
134 | } | |
135 | ||
136 | /* | |
137 | * Set an error in the dio if none is set yet. We have to use cmpxchg | |
138 | * as the submission context and the completion context(s) can race to | |
139 | * update the error. | |
140 | */ | |
141 | static inline void iomap_dio_set_error(struct iomap_dio *dio, int ret) | |
142 | { | |
143 | cmpxchg(&dio->error, 0, ret); | |
144 | } | |
145 | ||
146 | static void iomap_dio_bio_end_io(struct bio *bio) | |
147 | { | |
148 | struct iomap_dio *dio = bio->bi_private; | |
149 | bool should_dirty = (dio->flags & IOMAP_DIO_DIRTY); | |
150 | ||
151 | if (bio->bi_status) | |
152 | iomap_dio_set_error(dio, blk_status_to_errno(bio->bi_status)); | |
153 | ||
154 | if (atomic_dec_and_test(&dio->ref)) { | |
155 | if (dio->wait_for_completion) { | |
156 | struct task_struct *waiter = dio->submit.waiter; | |
157 | WRITE_ONCE(dio->submit.waiter, NULL); | |
158 | blk_wake_io_task(waiter); | |
159 | } else if (dio->flags & IOMAP_DIO_WRITE) { | |
160 | struct inode *inode = file_inode(dio->iocb->ki_filp); | |
161 | ||
162 | INIT_WORK(&dio->aio.work, iomap_dio_complete_work); | |
163 | queue_work(inode->i_sb->s_dio_done_wq, &dio->aio.work); | |
164 | } else { | |
165 | iomap_dio_complete_work(&dio->aio.work); | |
166 | } | |
167 | } | |
168 | ||
169 | if (should_dirty) { | |
170 | bio_check_pages_dirty(bio); | |
171 | } else { | |
172 | bio_release_pages(bio, false); | |
173 | bio_put(bio); | |
174 | } | |
175 | } | |
176 | ||
177 | static void | |
178 | iomap_dio_zero(struct iomap_dio *dio, struct iomap *iomap, loff_t pos, | |
179 | unsigned len) | |
180 | { | |
181 | struct page *page = ZERO_PAGE(0); | |
182 | int flags = REQ_SYNC | REQ_IDLE; | |
183 | struct bio *bio; | |
184 | ||
185 | bio = bio_alloc(GFP_KERNEL, 1); | |
186 | bio_set_dev(bio, iomap->bdev); | |
187 | bio->bi_iter.bi_sector = iomap_sector(iomap, pos); | |
188 | bio->bi_private = dio; | |
189 | bio->bi_end_io = iomap_dio_bio_end_io; | |
190 | ||
191 | get_page(page); | |
192 | __bio_add_page(bio, page, len, 0); | |
193 | bio_set_op_attrs(bio, REQ_OP_WRITE, flags); | |
194 | iomap_dio_submit_bio(dio, iomap, bio); | |
195 | } | |
196 | ||
197 | static loff_t | |
198 | iomap_dio_bio_actor(struct inode *inode, loff_t pos, loff_t length, | |
199 | struct iomap_dio *dio, struct iomap *iomap) | |
200 | { | |
201 | unsigned int blkbits = blksize_bits(bdev_logical_block_size(iomap->bdev)); | |
202 | unsigned int fs_block_size = i_blocksize(inode), pad; | |
203 | unsigned int align = iov_iter_alignment(dio->submit.iter); | |
db074436 DW |
204 | struct bio *bio; |
205 | bool need_zeroout = false; | |
206 | bool use_fua = false; | |
207 | int nr_pages, ret = 0; | |
208 | size_t copied = 0; | |
f550ee9b | 209 | size_t orig_count; |
db074436 DW |
210 | |
211 | if ((pos | length | align) & ((1 << blkbits) - 1)) | |
212 | return -EINVAL; | |
213 | ||
214 | if (iomap->type == IOMAP_UNWRITTEN) { | |
215 | dio->flags |= IOMAP_DIO_UNWRITTEN; | |
216 | need_zeroout = true; | |
217 | } | |
218 | ||
219 | if (iomap->flags & IOMAP_F_SHARED) | |
220 | dio->flags |= IOMAP_DIO_COW; | |
221 | ||
222 | if (iomap->flags & IOMAP_F_NEW) { | |
223 | need_zeroout = true; | |
224 | } else if (iomap->type == IOMAP_MAPPED) { | |
225 | /* | |
226 | * Use a FUA write if we need datasync semantics, this is a pure | |
227 | * data IO that doesn't require any metadata updates (including | |
228 | * after IO completion such as unwritten extent conversion) and | |
229 | * the underlying device supports FUA. This allows us to avoid | |
230 | * cache flushes on IO completion. | |
231 | */ | |
232 | if (!(iomap->flags & (IOMAP_F_SHARED|IOMAP_F_DIRTY)) && | |
233 | (dio->flags & IOMAP_DIO_WRITE_FUA) && | |
234 | blk_queue_fua(bdev_get_queue(iomap->bdev))) | |
235 | use_fua = true; | |
236 | } | |
237 | ||
238 | /* | |
f550ee9b JK |
239 | * Save the original count and trim the iter to just the extent we |
240 | * are operating on right now. The iter will be re-expanded once | |
241 | * we are done. | |
db074436 | 242 | */ |
f550ee9b JK |
243 | orig_count = iov_iter_count(dio->submit.iter); |
244 | iov_iter_truncate(dio->submit.iter, length); | |
db074436 | 245 | |
f550ee9b JK |
246 | nr_pages = iov_iter_npages(dio->submit.iter, BIO_MAX_PAGES); |
247 | if (nr_pages <= 0) { | |
248 | ret = nr_pages; | |
249 | goto out; | |
250 | } | |
db074436 DW |
251 | |
252 | if (need_zeroout) { | |
253 | /* zero out from the start of the block to the write offset */ | |
254 | pad = pos & (fs_block_size - 1); | |
255 | if (pad) | |
256 | iomap_dio_zero(dio, iomap, pos - pad, pad); | |
257 | } | |
258 | ||
259 | do { | |
260 | size_t n; | |
261 | if (dio->error) { | |
262 | iov_iter_revert(dio->submit.iter, copied); | |
f550ee9b JK |
263 | copied = ret = 0; |
264 | goto out; | |
db074436 DW |
265 | } |
266 | ||
267 | bio = bio_alloc(GFP_KERNEL, nr_pages); | |
268 | bio_set_dev(bio, iomap->bdev); | |
269 | bio->bi_iter.bi_sector = iomap_sector(iomap, pos); | |
270 | bio->bi_write_hint = dio->iocb->ki_hint; | |
271 | bio->bi_ioprio = dio->iocb->ki_ioprio; | |
272 | bio->bi_private = dio; | |
273 | bio->bi_end_io = iomap_dio_bio_end_io; | |
274 | ||
f550ee9b | 275 | ret = bio_iov_iter_get_pages(bio, dio->submit.iter); |
db074436 DW |
276 | if (unlikely(ret)) { |
277 | /* | |
278 | * We have to stop part way through an IO. We must fall | |
279 | * through to the sub-block tail zeroing here, otherwise | |
280 | * this short IO may expose stale data in the tail of | |
281 | * the block we haven't written data to. | |
282 | */ | |
283 | bio_put(bio); | |
284 | goto zero_tail; | |
285 | } | |
286 | ||
287 | n = bio->bi_iter.bi_size; | |
288 | if (dio->flags & IOMAP_DIO_WRITE) { | |
289 | bio->bi_opf = REQ_OP_WRITE | REQ_SYNC | REQ_IDLE; | |
290 | if (use_fua) | |
291 | bio->bi_opf |= REQ_FUA; | |
292 | else | |
293 | dio->flags &= ~IOMAP_DIO_WRITE_FUA; | |
294 | task_io_account_write(n); | |
295 | } else { | |
296 | bio->bi_opf = REQ_OP_READ; | |
297 | if (dio->flags & IOMAP_DIO_DIRTY) | |
298 | bio_set_pages_dirty(bio); | |
299 | } | |
300 | ||
db074436 DW |
301 | dio->size += n; |
302 | pos += n; | |
303 | copied += n; | |
304 | ||
f550ee9b | 305 | nr_pages = iov_iter_npages(dio->submit.iter, BIO_MAX_PAGES); |
db074436 DW |
306 | iomap_dio_submit_bio(dio, iomap, bio); |
307 | } while (nr_pages); | |
308 | ||
309 | /* | |
310 | * We need to zeroout the tail of a sub-block write if the extent type | |
311 | * requires zeroing or the write extends beyond EOF. If we don't zero | |
312 | * the block tail in the latter case, we can expose stale data via mmap | |
313 | * reads of the EOF block. | |
314 | */ | |
315 | zero_tail: | |
316 | if (need_zeroout || | |
317 | ((dio->flags & IOMAP_DIO_WRITE) && pos >= i_size_read(inode))) { | |
318 | /* zero out from the end of the write to the end of the block */ | |
319 | pad = pos & (fs_block_size - 1); | |
320 | if (pad) | |
321 | iomap_dio_zero(dio, iomap, pos, fs_block_size - pad); | |
322 | } | |
f550ee9b JK |
323 | out: |
324 | /* Undo iter limitation to current extent */ | |
325 | iov_iter_reexpand(dio->submit.iter, orig_count - copied); | |
e9f930ac JS |
326 | if (copied) |
327 | return copied; | |
328 | return ret; | |
db074436 DW |
329 | } |
330 | ||
331 | static loff_t | |
332 | iomap_dio_hole_actor(loff_t length, struct iomap_dio *dio) | |
333 | { | |
334 | length = iov_iter_zero(length, dio->submit.iter); | |
335 | dio->size += length; | |
336 | return length; | |
337 | } | |
338 | ||
339 | static loff_t | |
340 | iomap_dio_inline_actor(struct inode *inode, loff_t pos, loff_t length, | |
341 | struct iomap_dio *dio, struct iomap *iomap) | |
342 | { | |
343 | struct iov_iter *iter = dio->submit.iter; | |
344 | size_t copied; | |
345 | ||
346 | BUG_ON(pos + length > PAGE_SIZE - offset_in_page(iomap->inline_data)); | |
347 | ||
348 | if (dio->flags & IOMAP_DIO_WRITE) { | |
349 | loff_t size = inode->i_size; | |
350 | ||
351 | if (pos > size) | |
352 | memset(iomap->inline_data + size, 0, pos - size); | |
353 | copied = copy_from_iter(iomap->inline_data + pos, length, iter); | |
354 | if (copied) { | |
355 | if (pos + copied > size) | |
356 | i_size_write(inode, pos + copied); | |
357 | mark_inode_dirty(inode); | |
358 | } | |
359 | } else { | |
360 | copied = copy_to_iter(iomap->inline_data + pos, length, iter); | |
361 | } | |
362 | dio->size += copied; | |
363 | return copied; | |
364 | } | |
365 | ||
366 | static loff_t | |
367 | iomap_dio_actor(struct inode *inode, loff_t pos, loff_t length, | |
c039b997 | 368 | void *data, struct iomap *iomap, struct iomap *srcmap) |
db074436 DW |
369 | { |
370 | struct iomap_dio *dio = data; | |
371 | ||
372 | switch (iomap->type) { | |
373 | case IOMAP_HOLE: | |
374 | if (WARN_ON_ONCE(dio->flags & IOMAP_DIO_WRITE)) | |
375 | return -EIO; | |
376 | return iomap_dio_hole_actor(length, dio); | |
377 | case IOMAP_UNWRITTEN: | |
378 | if (!(dio->flags & IOMAP_DIO_WRITE)) | |
379 | return iomap_dio_hole_actor(length, dio); | |
380 | return iomap_dio_bio_actor(inode, pos, length, dio, iomap); | |
381 | case IOMAP_MAPPED: | |
382 | return iomap_dio_bio_actor(inode, pos, length, dio, iomap); | |
383 | case IOMAP_INLINE: | |
384 | return iomap_dio_inline_actor(inode, pos, length, dio, iomap); | |
385 | default: | |
386 | WARN_ON_ONCE(1); | |
387 | return -EIO; | |
388 | } | |
389 | } | |
390 | ||
391 | /* | |
392 | * iomap_dio_rw() always completes O_[D]SYNC writes regardless of whether the IO | |
393 | * is being issued as AIO or not. This allows us to optimise pure data writes | |
394 | * to use REQ_FUA rather than requiring generic_write_sync() to issue a | |
395 | * REQ_FLUSH post write. This is slightly tricky because a single request here | |
396 | * can be mapped into multiple disjoint IOs and only a subset of the IOs issued | |
397 | * may be pure data writes. In that case, we still need to do a full data sync | |
398 | * completion. | |
399 | */ | |
400 | ssize_t | |
401 | iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter, | |
13ef9544 JK |
402 | const struct iomap_ops *ops, const struct iomap_dio_ops *dops, |
403 | bool wait_for_completion) | |
db074436 DW |
404 | { |
405 | struct address_space *mapping = iocb->ki_filp->f_mapping; | |
406 | struct inode *inode = file_inode(iocb->ki_filp); | |
407 | size_t count = iov_iter_count(iter); | |
88cfd30e | 408 | loff_t pos = iocb->ki_pos; |
db074436 DW |
409 | loff_t end = iocb->ki_pos + count - 1, ret = 0; |
410 | unsigned int flags = IOMAP_DIRECT; | |
db074436 DW |
411 | struct blk_plug plug; |
412 | struct iomap_dio *dio; | |
413 | ||
414 | lockdep_assert_held(&inode->i_rwsem); | |
415 | ||
416 | if (!count) | |
417 | return 0; | |
418 | ||
13ef9544 JK |
419 | if (WARN_ON(is_sync_kiocb(iocb) && !wait_for_completion)) |
420 | return -EIO; | |
421 | ||
db074436 DW |
422 | dio = kmalloc(sizeof(*dio), GFP_KERNEL); |
423 | if (!dio) | |
424 | return -ENOMEM; | |
425 | ||
426 | dio->iocb = iocb; | |
427 | atomic_set(&dio->ref, 1); | |
428 | dio->size = 0; | |
429 | dio->i_size = i_size_read(inode); | |
838c4f3d | 430 | dio->dops = dops; |
db074436 DW |
431 | dio->error = 0; |
432 | dio->flags = 0; | |
433 | ||
434 | dio->submit.iter = iter; | |
435 | dio->submit.waiter = current; | |
436 | dio->submit.cookie = BLK_QC_T_NONE; | |
437 | dio->submit.last_queue = NULL; | |
438 | ||
439 | if (iov_iter_rw(iter) == READ) { | |
440 | if (pos >= dio->i_size) | |
441 | goto out_free_dio; | |
442 | ||
a9010042 | 443 | if (iter_is_iovec(iter)) |
db074436 DW |
444 | dio->flags |= IOMAP_DIO_DIRTY; |
445 | } else { | |
446 | flags |= IOMAP_WRITE; | |
447 | dio->flags |= IOMAP_DIO_WRITE; | |
448 | ||
449 | /* for data sync or sync, we need sync completion processing */ | |
450 | if (iocb->ki_flags & IOCB_DSYNC) | |
451 | dio->flags |= IOMAP_DIO_NEED_SYNC; | |
452 | ||
453 | /* | |
454 | * For datasync only writes, we optimistically try using FUA for | |
455 | * this IO. Any non-FUA write that occurs will clear this flag, | |
456 | * hence we know before completion whether a cache flush is | |
457 | * necessary. | |
458 | */ | |
459 | if ((iocb->ki_flags & (IOCB_DSYNC | IOCB_SYNC)) == IOCB_DSYNC) | |
460 | dio->flags |= IOMAP_DIO_WRITE_FUA; | |
461 | } | |
462 | ||
463 | if (iocb->ki_flags & IOCB_NOWAIT) { | |
88cfd30e | 464 | if (filemap_range_has_page(mapping, pos, end)) { |
db074436 DW |
465 | ret = -EAGAIN; |
466 | goto out_free_dio; | |
467 | } | |
468 | flags |= IOMAP_NOWAIT; | |
469 | } | |
470 | ||
88cfd30e | 471 | ret = filemap_write_and_wait_range(mapping, pos, end); |
db074436 DW |
472 | if (ret) |
473 | goto out_free_dio; | |
474 | ||
475 | /* | |
476 | * Try to invalidate cache pages for the range we're direct | |
477 | * writing. If this invalidation fails, tough, the write will | |
478 | * still work, but racing two incompatible write paths is a | |
479 | * pretty crazy thing to do, so we don't support it 100%. | |
480 | */ | |
481 | ret = invalidate_inode_pages2_range(mapping, | |
88cfd30e | 482 | pos >> PAGE_SHIFT, end >> PAGE_SHIFT); |
db074436 DW |
483 | if (ret) |
484 | dio_warn_stale_pagecache(iocb->ki_filp); | |
485 | ret = 0; | |
486 | ||
487 | if (iov_iter_rw(iter) == WRITE && !wait_for_completion && | |
488 | !inode->i_sb->s_dio_done_wq) { | |
489 | ret = sb_init_dio_done_wq(inode->i_sb); | |
490 | if (ret < 0) | |
491 | goto out_free_dio; | |
492 | } | |
493 | ||
494 | inode_dio_begin(inode); | |
495 | ||
496 | blk_start_plug(&plug); | |
497 | do { | |
498 | ret = iomap_apply(inode, pos, count, flags, ops, dio, | |
499 | iomap_dio_actor); | |
500 | if (ret <= 0) { | |
501 | /* magic error code to fall back to buffered I/O */ | |
502 | if (ret == -ENOTBLK) { | |
503 | wait_for_completion = true; | |
504 | ret = 0; | |
505 | } | |
506 | break; | |
507 | } | |
508 | pos += ret; | |
509 | ||
419e9c38 JK |
510 | if (iov_iter_rw(iter) == READ && pos >= dio->i_size) { |
511 | /* | |
512 | * We only report that we've read data up to i_size. | |
513 | * Revert iter to a state corresponding to that as | |
514 | * some callers (such as splice code) rely on it. | |
515 | */ | |
516 | iov_iter_revert(iter, pos - dio->i_size); | |
db074436 | 517 | break; |
419e9c38 | 518 | } |
db074436 DW |
519 | } while ((count = iov_iter_count(iter)) > 0); |
520 | blk_finish_plug(&plug); | |
521 | ||
522 | if (ret < 0) | |
523 | iomap_dio_set_error(dio, ret); | |
524 | ||
525 | /* | |
526 | * If all the writes we issued were FUA, we don't need to flush the | |
527 | * cache on IO completion. Clear the sync flag for this case. | |
528 | */ | |
529 | if (dio->flags & IOMAP_DIO_WRITE_FUA) | |
530 | dio->flags &= ~IOMAP_DIO_NEED_SYNC; | |
531 | ||
532 | WRITE_ONCE(iocb->ki_cookie, dio->submit.cookie); | |
533 | WRITE_ONCE(iocb->private, dio->submit.last_queue); | |
534 | ||
535 | /* | |
536 | * We are about to drop our additional submission reference, which | |
537 | * might be the last reference to the dio. There are three three | |
538 | * different ways we can progress here: | |
539 | * | |
540 | * (a) If this is the last reference we will always complete and free | |
541 | * the dio ourselves. | |
542 | * (b) If this is not the last reference, and we serve an asynchronous | |
543 | * iocb, we must never touch the dio after the decrement, the | |
544 | * I/O completion handler will complete and free it. | |
545 | * (c) If this is not the last reference, but we serve a synchronous | |
546 | * iocb, the I/O completion handler will wake us up on the drop | |
547 | * of the final reference, and we will complete and free it here | |
548 | * after we got woken by the I/O completion handler. | |
549 | */ | |
550 | dio->wait_for_completion = wait_for_completion; | |
551 | if (!atomic_dec_and_test(&dio->ref)) { | |
552 | if (!wait_for_completion) | |
553 | return -EIOCBQUEUED; | |
554 | ||
555 | for (;;) { | |
556 | set_current_state(TASK_UNINTERRUPTIBLE); | |
557 | if (!READ_ONCE(dio->submit.waiter)) | |
558 | break; | |
559 | ||
560 | if (!(iocb->ki_flags & IOCB_HIPRI) || | |
561 | !dio->submit.last_queue || | |
562 | !blk_poll(dio->submit.last_queue, | |
563 | dio->submit.cookie, true)) | |
564 | io_schedule(); | |
565 | } | |
566 | __set_current_state(TASK_RUNNING); | |
567 | } | |
568 | ||
569 | return iomap_dio_complete(dio); | |
570 | ||
571 | out_free_dio: | |
572 | kfree(dio); | |
573 | return ret; | |
574 | } | |
575 | EXPORT_SYMBOL_GPL(iomap_dio_rw); |