1 | // SPDX-License-Identifier: GPL-2.0-only |
2 | /* |
3 | * fs/direct-io.c |
4 | * |
5 | * Copyright (C) 2002, Linus Torvalds. |
6 | * |
7 | * O_DIRECT |
8 | * |
9 | * 04Jul2002 Andrew Morton |
10 | * Initial version |
11 | * 11Sep2002 janetinc@us.ibm.com |
12 | * added readv/writev support. |
13 | * 29Oct2002 Andrew Morton |
14 | * rewrote bio_add_page() support. |
15 | * 30Oct2002 pbadari@us.ibm.com |
16 | * added support for non-aligned IO. |
17 | * 06Nov2002 pbadari@us.ibm.com |
18 | * added asynchronous IO support. |
19 | * 21Jul2003 nathans@sgi.com |
20 | * added IO completion notifier. |
21 | */ |
22 | |
23 | #include <linux/kernel.h> |
24 | #include <linux/module.h> |
25 | #include <linux/types.h> |
26 | #include <linux/fs.h> |
27 | #include <linux/mm.h> |
28 | #include <linux/slab.h> |
29 | #include <linux/highmem.h> |
30 | #include <linux/pagemap.h> |
31 | #include <linux/task_io_accounting_ops.h> |
32 | #include <linux/bio.h> |
33 | #include <linux/wait.h> |
34 | #include <linux/err.h> |
35 | #include <linux/blkdev.h> |
36 | #include <linux/buffer_head.h> |
37 | #include <linux/rwsem.h> |
38 | #include <linux/uio.h> |
39 | #include <linux/atomic.h> |
40 | #include <linux/prefetch.h> |
41 | |
42 | #include "internal.h" |
43 | |
44 | /* |
45 | * How many user pages to map in one call to iov_iter_extract_pages(). This |
46 | * determines the size of a structure in the slab cache |
47 | */ |
48 | #define DIO_PAGES 64 |
49 | |
50 | /* |
51 | * Flags for dio_complete() |
52 | */ |
53 | #define DIO_COMPLETE_ASYNC 0x01 /* This is async IO */ |
54 | #define DIO_COMPLETE_INVALIDATE 0x02 /* Can invalidate pages */ |
55 | |
56 | /* |
57 | * This code generally works in units of "dio_blocks". A dio_block is |
58 | * somewhere between the hard sector size and the filesystem block size. it |
59 | * is determined on a per-invocation basis. When talking to the filesystem |
60 | * we need to convert dio_blocks to fs_blocks by scaling the dio_block quantity |
61 | * down by dio->blkfactor. Similarly, fs-blocksize quantities are converted |
62 | * to bio_block quantities by shifting left by blkfactor. |
63 | * |
64 | * If blkfactor is zero then the user's request was aligned to the filesystem's |
65 | * blocksize. |
66 | */ |
67 | |
68 | /* dio_state only used in the submission path */ |
69 | |
70 | struct dio_submit { |
71 | struct bio *bio; /* bio under assembly */ |
72 | unsigned blkbits; /* doesn't change */ |
73 | unsigned blkfactor; /* When we're using an alignment which |
74 | is finer than the filesystem's soft |
75 | blocksize, this specifies how much |
76 | finer. blkfactor=2 means 1/4-block |
77 | alignment. Does not change */ |
78 | unsigned start_zero_done; /* flag: sub-blocksize zeroing has |
79 | been performed at the start of a |
80 | write */ |
81 | int pages_in_io; /* approximate total IO pages */ |
82 | sector_t block_in_file; /* Current offset into the underlying |
83 | file in dio_block units. */ |
84 | unsigned blocks_available; /* At block_in_file. changes */ |
85 | int reap_counter; /* rate limit reaping */ |
86 | sector_t final_block_in_request;/* doesn't change */ |
87 | int boundary; /* prev block is at a boundary */ |
88 | get_block_t *get_block; /* block mapping function */ |
89 | |
90 | loff_t logical_offset_in_bio; /* current first logical block in bio */ |
91 | sector_t final_block_in_bio; /* current final block in bio + 1 */ |
92 | sector_t next_block_for_io; /* next block to be put under IO, |
93 | in dio_blocks units */ |
94 | |
95 | /* |
96 | * Deferred addition of a page to the dio. These variables are |
97 | * private to dio_send_cur_page(), submit_page_section() and |
98 | * dio_bio_add_page(). |
99 | */ |
100 | struct page *cur_page; /* The page */ |
101 | unsigned cur_page_offset; /* Offset into it, in bytes */ |
102 | unsigned cur_page_len; /* Nr of bytes at cur_page_offset */ |
103 | sector_t cur_page_block; /* Where it starts */ |
104 | loff_t cur_page_fs_offset; /* Offset in file */ |
105 | |
106 | struct iov_iter *iter; |
107 | /* |
108 | * Page queue. These variables belong to dio_refill_pages() and |
109 | * dio_get_page(). |
110 | */ |
111 | unsigned head; /* next page to process */ |
112 | unsigned tail; /* last valid page + 1 */ |
113 | size_t from, to; |
114 | }; |
115 | |
116 | /* dio_state communicated between submission path and end_io */ |
117 | struct dio { |
118 | int flags; /* doesn't change */ |
119 | blk_opf_t opf; /* request operation type and flags */ |
120 | struct gendisk *bio_disk; |
121 | struct inode *inode; |
122 | loff_t i_size; /* i_size when submitted */ |
123 | dio_iodone_t *end_io; /* IO completion function */ |
124 | bool is_pinned; /* T if we have pins on the pages */ |
125 | |
126 | void *private; /* copy from map_bh.b_private */ |
127 | |
128 | /* BIO completion state */ |
129 | spinlock_t bio_lock; /* protects BIO fields below */ |
130 | int page_errors; /* err from iov_iter_extract_pages() */ |
131 | int is_async; /* is IO async ? */ |
132 | bool defer_completion; /* defer AIO completion to workqueue? */ |
133 | bool should_dirty; /* if pages should be dirtied */ |
134 | int io_error; /* IO error in completion path */ |
135 | unsigned long refcount; /* direct_io_worker() and bios */ |
136 | struct bio *bio_list; /* singly linked via bi_private */ |
137 | struct task_struct *waiter; /* waiting task (NULL if none) */ |
138 | |
139 | /* AIO related stuff */ |
140 | struct kiocb *iocb; /* kiocb */ |
141 | ssize_t result; /* IO result */ |
142 | |
143 | /* |
144 | * pages[] (and any fields placed after it) are not zeroed out at |
145 | * allocation time. Don't add new fields after pages[] unless you |
146 | * wish that they not be zeroed. |
147 | */ |
148 | union { |
149 | struct page *pages[DIO_PAGES]; /* page buffer */ |
150 | struct work_struct complete_work;/* deferred AIO completion */ |
151 | }; |
152 | } ____cacheline_aligned_in_smp; |
153 | |
154 | static struct kmem_cache *dio_cache __ro_after_init; |
155 | |
156 | /* |
157 | * How many pages are in the queue? |
158 | */ |
159 | static inline unsigned dio_pages_present(struct dio_submit *sdio) |
160 | { |
161 | return sdio->tail - sdio->head; |
162 | } |
163 | |
164 | /* |
165 | * Go grab and pin some userspace pages. Typically we'll get 64 at a time. |
166 | */ |
167 | static inline int dio_refill_pages(struct dio *dio, struct dio_submit *sdio) |
168 | { |
169 | struct page **pages = dio->pages; |
170 | const enum req_op dio_op = dio->opf & REQ_OP_MASK; |
171 | ssize_t ret; |
172 | |
173 | ret = iov_iter_extract_pages(i: sdio->iter, pages: &pages, LONG_MAX, |
174 | DIO_PAGES, extraction_flags: 0, offset0: &sdio->from); |
175 | |
176 | if (ret < 0 && sdio->blocks_available && dio_op == REQ_OP_WRITE) { |
177 | /* |
178 | * A memory fault, but the filesystem has some outstanding |
179 | * mapped blocks. We need to use those blocks up to avoid |
180 | * leaking stale data in the file. |
181 | */ |
182 | if (dio->page_errors == 0) |
183 | dio->page_errors = ret; |
184 | dio->pages[0] = ZERO_PAGE(0); |
185 | sdio->head = 0; |
186 | sdio->tail = 1; |
187 | sdio->from = 0; |
188 | sdio->to = PAGE_SIZE; |
189 | return 0; |
190 | } |
191 | |
192 | if (ret >= 0) { |
193 | ret += sdio->from; |
194 | sdio->head = 0; |
195 | sdio->tail = (ret + PAGE_SIZE - 1) / PAGE_SIZE; |
196 | sdio->to = ((ret - 1) & (PAGE_SIZE - 1)) + 1; |
197 | return 0; |
198 | } |
199 | return ret; |
200 | } |
201 | |
202 | /* |
203 | * Get another userspace page. Returns an ERR_PTR on error. Pages are |
204 | * buffered inside the dio so that we can call iov_iter_extract_pages() |
205 | * against a decent number of pages, less frequently. To provide nicer use of |
206 | * the L1 cache. |
207 | */ |
208 | static inline struct page *dio_get_page(struct dio *dio, |
209 | struct dio_submit *sdio) |
210 | { |
211 | if (dio_pages_present(sdio) == 0) { |
212 | int ret; |
213 | |
214 | ret = dio_refill_pages(dio, sdio); |
215 | if (ret) |
216 | return ERR_PTR(error: ret); |
217 | BUG_ON(dio_pages_present(sdio) == 0); |
218 | } |
219 | return dio->pages[sdio->head]; |
220 | } |
221 | |
222 | static void dio_pin_page(struct dio *dio, struct page *page) |
223 | { |
224 | if (dio->is_pinned) |
225 | folio_add_pin(page_folio(page)); |
226 | } |
227 | |
228 | static void dio_unpin_page(struct dio *dio, struct page *page) |
229 | { |
230 | if (dio->is_pinned) |
231 | unpin_user_page(page); |
232 | } |
233 | |
234 | /* |
235 | * dio_complete() - called when all DIO BIO I/O has been completed |
236 | * |
237 | * This drops i_dio_count, lets interested parties know that a DIO operation |
238 | * has completed, and calculates the resulting return code for the operation. |
239 | * |
240 | * It lets the filesystem know if it registered an interest earlier via |
241 | * get_block. Pass the private field of the map buffer_head so that |
242 | * filesystems can use it to hold additional state between get_block calls and |
243 | * dio_complete. |
244 | */ |
245 | static ssize_t dio_complete(struct dio *dio, ssize_t ret, unsigned int flags) |
246 | { |
247 | const enum req_op dio_op = dio->opf & REQ_OP_MASK; |
248 | loff_t offset = dio->iocb->ki_pos; |
249 | ssize_t transferred = 0; |
250 | int err; |
251 | |
252 | /* |
253 | * AIO submission can race with bio completion to get here while |
254 | * expecting to have the last io completed by bio completion. |
255 | * In that case -EIOCBQUEUED is in fact not an error we want |
256 | * to preserve through this call. |
257 | */ |
258 | if (ret == -EIOCBQUEUED) |
259 | ret = 0; |
260 | |
261 | if (dio->result) { |
262 | transferred = dio->result; |
263 | |
264 | /* Check for short read case */ |
265 | if (dio_op == REQ_OP_READ && |
266 | ((offset + transferred) > dio->i_size)) |
267 | transferred = dio->i_size - offset; |
268 | /* ignore EFAULT if some IO has been done */ |
269 | if (unlikely(ret == -EFAULT) && transferred) |
270 | ret = 0; |
271 | } |
272 | |
273 | if (ret == 0) |
274 | ret = dio->page_errors; |
275 | if (ret == 0) |
276 | ret = dio->io_error; |
277 | if (ret == 0) |
278 | ret = transferred; |
279 | |
280 | if (dio->end_io) { |
281 | // XXX: ki_pos?? |
282 | err = dio->end_io(dio->iocb, offset, ret, dio->private); |
283 | if (err) |
284 | ret = err; |
285 | } |
286 | |
287 | /* |
288 | * Try again to invalidate clean pages which might have been cached by |
289 | * non-direct readahead, or faulted in by get_user_pages() if the source |
290 | * of the write was an mmap'ed region of the file we're writing. Either |
291 | * one is a pretty crazy thing to do, so we don't support it 100%. If |
292 | * this invalidation fails, tough, the write still worked... |
293 | * |
294 | * And this page cache invalidation has to be after dio->end_io(), as |
295 | * some filesystems convert unwritten extents to real allocations in |
296 | * end_io() when necessary, otherwise a racing buffer read would cache |
297 | * zeros from unwritten extents. |
298 | */ |
299 | if (flags & DIO_COMPLETE_INVALIDATE && |
300 | ret > 0 && dio_op == REQ_OP_WRITE) |
301 | kiocb_invalidate_post_direct_write(iocb: dio->iocb, count: ret); |
302 | |
303 | inode_dio_end(inode: dio->inode); |
304 | |
305 | if (flags & DIO_COMPLETE_ASYNC) { |
306 | /* |
307 | * generic_write_sync expects ki_pos to have been updated |
308 | * already, but the submission path only does this for |
309 | * synchronous I/O. |
310 | */ |
311 | dio->iocb->ki_pos += transferred; |
312 | |
313 | if (ret > 0 && dio_op == REQ_OP_WRITE) |
314 | ret = generic_write_sync(iocb: dio->iocb, count: ret); |
315 | dio->iocb->ki_complete(dio->iocb, ret); |
316 | } |
317 | |
318 | kmem_cache_free(s: dio_cache, objp: dio); |
319 | return ret; |
320 | } |
321 | |
322 | static void dio_aio_complete_work(struct work_struct *work) |
323 | { |
324 | struct dio *dio = container_of(work, struct dio, complete_work); |
325 | |
326 | dio_complete(dio, ret: 0, DIO_COMPLETE_ASYNC | DIO_COMPLETE_INVALIDATE); |
327 | } |
328 | |
329 | static blk_status_t dio_bio_complete(struct dio *dio, struct bio *bio); |
330 | |
331 | /* |
332 | * Asynchronous IO callback. |
333 | */ |
334 | static void dio_bio_end_aio(struct bio *bio) |
335 | { |
336 | struct dio *dio = bio->bi_private; |
337 | const enum req_op dio_op = dio->opf & REQ_OP_MASK; |
338 | unsigned long remaining; |
339 | unsigned long flags; |
340 | bool defer_completion = false; |
341 | |
342 | /* cleanup the bio */ |
343 | dio_bio_complete(dio, bio); |
344 | |
345 | spin_lock_irqsave(&dio->bio_lock, flags); |
346 | remaining = --dio->refcount; |
347 | if (remaining == 1 && dio->waiter) |
348 | wake_up_process(tsk: dio->waiter); |
349 | spin_unlock_irqrestore(lock: &dio->bio_lock, flags); |
350 | |
351 | if (remaining == 0) { |
352 | /* |
353 | * Defer completion when defer_completion is set or |
354 | * when the inode has pages mapped and this is AIO write. |
355 | * We need to invalidate those pages because there is a |
356 | * chance they contain stale data in the case buffered IO |
357 | * went in between AIO submission and completion into the |
358 | * same region. |
359 | */ |
360 | if (dio->result) |
361 | defer_completion = dio->defer_completion || |
362 | (dio_op == REQ_OP_WRITE && |
363 | dio->inode->i_mapping->nrpages); |
364 | if (defer_completion) { |
365 | INIT_WORK(&dio->complete_work, dio_aio_complete_work); |
366 | queue_work(wq: dio->inode->i_sb->s_dio_done_wq, |
367 | work: &dio->complete_work); |
368 | } else { |
369 | dio_complete(dio, ret: 0, DIO_COMPLETE_ASYNC); |
370 | } |
371 | } |
372 | } |
373 | |
374 | /* |
375 | * The BIO completion handler simply queues the BIO up for the process-context |
376 | * handler. |
377 | * |
378 | * During I/O bi_private points at the dio. After I/O, bi_private is used to |
379 | * implement a singly-linked list of completed BIOs, at dio->bio_list. |
380 | */ |
381 | static void dio_bio_end_io(struct bio *bio) |
382 | { |
383 | struct dio *dio = bio->bi_private; |
384 | unsigned long flags; |
385 | |
386 | spin_lock_irqsave(&dio->bio_lock, flags); |
387 | bio->bi_private = dio->bio_list; |
388 | dio->bio_list = bio; |
389 | if (--dio->refcount == 1 && dio->waiter) |
390 | wake_up_process(tsk: dio->waiter); |
391 | spin_unlock_irqrestore(lock: &dio->bio_lock, flags); |
392 | } |
393 | |
394 | static inline void |
395 | dio_bio_alloc(struct dio *dio, struct dio_submit *sdio, |
396 | struct block_device *bdev, |
397 | sector_t first_sector, int nr_vecs) |
398 | { |
399 | struct bio *bio; |
400 | |
401 | /* |
402 | * bio_alloc() is guaranteed to return a bio when allowed to sleep and |
403 | * we request a valid number of vectors. |
404 | */ |
405 | bio = bio_alloc(bdev, nr_vecs, opf: dio->opf, GFP_KERNEL); |
406 | bio->bi_iter.bi_sector = first_sector; |
407 | if (dio->is_async) |
408 | bio->bi_end_io = dio_bio_end_aio; |
409 | else |
410 | bio->bi_end_io = dio_bio_end_io; |
411 | if (dio->is_pinned) |
412 | bio_set_flag(bio, bit: BIO_PAGE_PINNED); |
413 | sdio->bio = bio; |
414 | sdio->logical_offset_in_bio = sdio->cur_page_fs_offset; |
415 | } |
416 | |
417 | /* |
418 | * In the AIO read case we speculatively dirty the pages before starting IO. |
419 | * During IO completion, any of these pages which happen to have been written |
420 | * back will be redirtied by bio_check_pages_dirty(). |
421 | * |
422 | * bios hold a dio reference between submit_bio and ->end_io. |
423 | */ |
424 | static inline void dio_bio_submit(struct dio *dio, struct dio_submit *sdio) |
425 | { |
426 | const enum req_op dio_op = dio->opf & REQ_OP_MASK; |
427 | struct bio *bio = sdio->bio; |
428 | unsigned long flags; |
429 | |
430 | bio->bi_private = dio; |
431 | |
432 | spin_lock_irqsave(&dio->bio_lock, flags); |
433 | dio->refcount++; |
434 | spin_unlock_irqrestore(lock: &dio->bio_lock, flags); |
435 | |
436 | if (dio->is_async && dio_op == REQ_OP_READ && dio->should_dirty) |
437 | bio_set_pages_dirty(bio); |
438 | |
439 | dio->bio_disk = bio->bi_bdev->bd_disk; |
440 | |
441 | submit_bio(bio); |
442 | |
443 | sdio->bio = NULL; |
444 | sdio->boundary = 0; |
445 | sdio->logical_offset_in_bio = 0; |
446 | } |
447 | |
448 | /* |
449 | * Release any resources in case of a failure |
450 | */ |
451 | static inline void dio_cleanup(struct dio *dio, struct dio_submit *sdio) |
452 | { |
453 | if (dio->is_pinned) |
454 | unpin_user_pages(pages: dio->pages + sdio->head, |
455 | npages: sdio->tail - sdio->head); |
456 | sdio->head = sdio->tail; |
457 | } |
458 | |
459 | /* |
460 | * Wait for the next BIO to complete. Remove it and return it. NULL is |
461 | * returned once all BIOs have been completed. This must only be called once |
462 | * all bios have been issued so that dio->refcount can only decrease. This |
463 | * requires that the caller hold a reference on the dio. |
464 | */ |
465 | static struct bio *dio_await_one(struct dio *dio) |
466 | { |
467 | unsigned long flags; |
468 | struct bio *bio = NULL; |
469 | |
470 | spin_lock_irqsave(&dio->bio_lock, flags); |
471 | |
472 | /* |
473 | * Wait as long as the list is empty and there are bios in flight. bio |
474 | * completion drops the count, maybe adds to the list, and wakes while |
475 | * holding the bio_lock so we don't need set_current_state()'s barrier |
476 | * and can call it after testing our condition. |
477 | */ |
478 | while (dio->refcount > 1 && dio->bio_list == NULL) { |
479 | __set_current_state(TASK_UNINTERRUPTIBLE); |
480 | dio->waiter = current; |
481 | spin_unlock_irqrestore(lock: &dio->bio_lock, flags); |
482 | blk_io_schedule(); |
483 | /* wake up sets us TASK_RUNNING */ |
484 | spin_lock_irqsave(&dio->bio_lock, flags); |
485 | dio->waiter = NULL; |
486 | } |
487 | if (dio->bio_list) { |
488 | bio = dio->bio_list; |
489 | dio->bio_list = bio->bi_private; |
490 | } |
491 | spin_unlock_irqrestore(lock: &dio->bio_lock, flags); |
492 | return bio; |
493 | } |
494 | |
495 | /* |
496 | * Process one completed BIO. No locks are held. |
497 | */ |
498 | static blk_status_t dio_bio_complete(struct dio *dio, struct bio *bio) |
499 | { |
500 | blk_status_t err = bio->bi_status; |
501 | const enum req_op dio_op = dio->opf & REQ_OP_MASK; |
502 | bool should_dirty = dio_op == REQ_OP_READ && dio->should_dirty; |
503 | |
504 | if (err) { |
505 | if (err == BLK_STS_AGAIN && (bio->bi_opf & REQ_NOWAIT)) |
506 | dio->io_error = -EAGAIN; |
507 | else |
508 | dio->io_error = -EIO; |
509 | } |
510 | |
511 | if (dio->is_async && should_dirty) { |
512 | bio_check_pages_dirty(bio); /* transfers ownership */ |
513 | } else { |
514 | bio_release_pages(bio, mark_dirty: should_dirty); |
515 | bio_put(bio); |
516 | } |
517 | return err; |
518 | } |
519 | |
520 | /* |
521 | * Wait on and process all in-flight BIOs. This must only be called once |
522 | * all bios have been issued so that the refcount can only decrease. |
523 | * This just waits for all bios to make it through dio_bio_complete. IO |
524 | * errors are propagated through dio->io_error and should be propagated via |
525 | * dio_complete(). |
526 | */ |
527 | static void dio_await_completion(struct dio *dio) |
528 | { |
529 | struct bio *bio; |
530 | do { |
531 | bio = dio_await_one(dio); |
532 | if (bio) |
533 | dio_bio_complete(dio, bio); |
534 | } while (bio); |
535 | } |
536 | |
537 | /* |
538 | * A really large O_DIRECT read or write can generate a lot of BIOs. So |
539 | * to keep the memory consumption sane we periodically reap any completed BIOs |
540 | * during the BIO generation phase. |
541 | * |
542 | * This also helps to limit the peak amount of pinned userspace memory. |
543 | */ |
544 | static inline int dio_bio_reap(struct dio *dio, struct dio_submit *sdio) |
545 | { |
546 | int ret = 0; |
547 | |
548 | if (sdio->reap_counter++ >= 64) { |
549 | while (dio->bio_list) { |
550 | unsigned long flags; |
551 | struct bio *bio; |
552 | int ret2; |
553 | |
554 | spin_lock_irqsave(&dio->bio_lock, flags); |
555 | bio = dio->bio_list; |
556 | dio->bio_list = bio->bi_private; |
557 | spin_unlock_irqrestore(lock: &dio->bio_lock, flags); |
558 | ret2 = blk_status_to_errno(status: dio_bio_complete(dio, bio)); |
559 | if (ret == 0) |
560 | ret = ret2; |
561 | } |
562 | sdio->reap_counter = 0; |
563 | } |
564 | return ret; |
565 | } |
566 | |
567 | static int dio_set_defer_completion(struct dio *dio) |
568 | { |
569 | struct super_block *sb = dio->inode->i_sb; |
570 | |
571 | if (dio->defer_completion) |
572 | return 0; |
573 | dio->defer_completion = true; |
574 | if (!sb->s_dio_done_wq) |
575 | return sb_init_dio_done_wq(sb); |
576 | return 0; |
577 | } |
578 | |
579 | /* |
580 | * Call into the fs to map some more disk blocks. We record the current number |
581 | * of available blocks at sdio->blocks_available. These are in units of the |
582 | * fs blocksize, i_blocksize(inode). |
583 | * |
584 | * The fs is allowed to map lots of blocks at once. If it wants to do that, |
585 | * it uses the passed inode-relative block number as the file offset, as usual. |
586 | * |
587 | * get_block() is passed the number of i_blkbits-sized blocks which direct_io |
588 | * has remaining to do. The fs should not map more than this number of blocks. |
589 | * |
590 | * If the fs has mapped a lot of blocks, it should populate bh->b_size to |
591 | * indicate how much contiguous disk space has been made available at |
592 | * bh->b_blocknr. |
593 | * |
594 | * If *any* of the mapped blocks are new, then the fs must set buffer_new(). |
595 | * This isn't very efficient... |
596 | * |
597 | * In the case of filesystem holes: the fs may return an arbitrarily-large |
598 | * hole by returning an appropriate value in b_size and by clearing |
599 | * buffer_mapped(). However the direct-io code will only process holes one |
600 | * block at a time - it will repeatedly call get_block() as it walks the hole. |
601 | */ |
602 | static int get_more_blocks(struct dio *dio, struct dio_submit *sdio, |
603 | struct buffer_head *map_bh) |
604 | { |
605 | const enum req_op dio_op = dio->opf & REQ_OP_MASK; |
606 | int ret; |
607 | sector_t fs_startblk; /* Into file, in filesystem-sized blocks */ |
608 | sector_t fs_endblk; /* Into file, in filesystem-sized blocks */ |
609 | unsigned long fs_count; /* Number of filesystem-sized blocks */ |
610 | int create; |
611 | unsigned int i_blkbits = sdio->blkbits + sdio->blkfactor; |
612 | loff_t i_size; |
613 | |
614 | /* |
615 | * If there was a memory error and we've overwritten all the |
616 | * mapped blocks then we can now return that memory error |
617 | */ |
618 | ret = dio->page_errors; |
619 | if (ret == 0) { |
620 | BUG_ON(sdio->block_in_file >= sdio->final_block_in_request); |
621 | fs_startblk = sdio->block_in_file >> sdio->blkfactor; |
622 | fs_endblk = (sdio->final_block_in_request - 1) >> |
623 | sdio->blkfactor; |
624 | fs_count = fs_endblk - fs_startblk + 1; |
625 | |
626 | map_bh->b_state = 0; |
627 | map_bh->b_size = fs_count << i_blkbits; |
628 | |
629 | /* |
630 | * For writes that could fill holes inside i_size on a |
631 | * DIO_SKIP_HOLES filesystem we forbid block creations: only |
632 | * overwrites are permitted. We will return early to the caller |
633 | * once we see an unmapped buffer head returned, and the caller |
634 | * will fall back to buffered I/O. |
635 | * |
636 | * Otherwise the decision is left to the get_blocks method, |
637 | * which may decide to handle it or also return an unmapped |
638 | * buffer head. |
639 | */ |
640 | create = dio_op == REQ_OP_WRITE; |
641 | if (dio->flags & DIO_SKIP_HOLES) { |
642 | i_size = i_size_read(inode: dio->inode); |
643 | if (i_size && fs_startblk <= (i_size - 1) >> i_blkbits) |
644 | create = 0; |
645 | } |
646 | |
647 | ret = (*sdio->get_block)(dio->inode, fs_startblk, |
648 | map_bh, create); |
649 | |
650 | /* Store for completion */ |
651 | dio->private = map_bh->b_private; |
652 | |
653 | if (ret == 0 && buffer_defer_completion(bh: map_bh)) |
654 | ret = dio_set_defer_completion(dio); |
655 | } |
656 | return ret; |
657 | } |
658 | |
659 | /* |
660 | * There is no bio. Make one now. |
661 | */ |
662 | static inline int dio_new_bio(struct dio *dio, struct dio_submit *sdio, |
663 | sector_t start_sector, struct buffer_head *map_bh) |
664 | { |
665 | sector_t sector; |
666 | int ret, nr_pages; |
667 | |
668 | ret = dio_bio_reap(dio, sdio); |
669 | if (ret) |
670 | goto out; |
671 | sector = start_sector << (sdio->blkbits - 9); |
672 | nr_pages = bio_max_segs(nr_segs: sdio->pages_in_io); |
673 | BUG_ON(nr_pages <= 0); |
674 | dio_bio_alloc(dio, sdio, bdev: map_bh->b_bdev, first_sector: sector, nr_vecs: nr_pages); |
675 | sdio->boundary = 0; |
676 | out: |
677 | return ret; |
678 | } |
679 | |
680 | /* |
681 | * Attempt to put the current chunk of 'cur_page' into the current BIO. If |
682 | * that was successful then update final_block_in_bio and take a ref against |
683 | * the just-added page. |
684 | * |
685 | * Return zero on success. Non-zero means the caller needs to start a new BIO. |
686 | */ |
687 | static inline int dio_bio_add_page(struct dio *dio, struct dio_submit *sdio) |
688 | { |
689 | int ret; |
690 | |
691 | ret = bio_add_page(bio: sdio->bio, page: sdio->cur_page, |
692 | len: sdio->cur_page_len, off: sdio->cur_page_offset); |
693 | if (ret == sdio->cur_page_len) { |
694 | /* |
695 | * Decrement count only, if we are done with this page |
696 | */ |
697 | if ((sdio->cur_page_len + sdio->cur_page_offset) == PAGE_SIZE) |
698 | sdio->pages_in_io--; |
699 | dio_pin_page(dio, page: sdio->cur_page); |
700 | sdio->final_block_in_bio = sdio->cur_page_block + |
701 | (sdio->cur_page_len >> sdio->blkbits); |
702 | ret = 0; |
703 | } else { |
704 | ret = 1; |
705 | } |
706 | return ret; |
707 | } |
708 | |
709 | /* |
710 | * Put cur_page under IO. The section of cur_page which is described by |
711 | * cur_page_offset,cur_page_len is put into a BIO. The section of cur_page |
712 | * starts on-disk at cur_page_block. |
713 | * |
714 | * We take a ref against the page here (on behalf of its presence in the bio). |
715 | * |
716 | * The caller of this function is responsible for removing cur_page from the |
717 | * dio, and for dropping the refcount which came from that presence. |
718 | */ |
719 | static inline int dio_send_cur_page(struct dio *dio, struct dio_submit *sdio, |
720 | struct buffer_head *map_bh) |
721 | { |
722 | int ret = 0; |
723 | |
724 | if (sdio->bio) { |
725 | loff_t cur_offset = sdio->cur_page_fs_offset; |
726 | loff_t bio_next_offset = sdio->logical_offset_in_bio + |
727 | sdio->bio->bi_iter.bi_size; |
728 | |
729 | /* |
730 | * See whether this new request is contiguous with the old. |
731 | * |
732 | * Btrfs cannot handle having logically non-contiguous requests |
733 | * submitted. For example if you have |
734 | * |
735 | * Logical: [0-4095][HOLE][8192-12287] |
736 | * Physical: [0-4095] [4096-8191] |
737 | * |
738 | * We cannot submit those pages together as one BIO. So if our |
739 | * current logical offset in the file does not equal what would |
740 | * be the next logical offset in the bio, submit the bio we |
741 | * have. |
742 | */ |
743 | if (sdio->final_block_in_bio != sdio->cur_page_block || |
744 | cur_offset != bio_next_offset) |
745 | dio_bio_submit(dio, sdio); |
746 | } |
747 | |
748 | if (sdio->bio == NULL) { |
749 | ret = dio_new_bio(dio, sdio, start_sector: sdio->cur_page_block, map_bh); |
750 | if (ret) |
751 | goto out; |
752 | } |
753 | |
754 | if (dio_bio_add_page(dio, sdio) != 0) { |
755 | dio_bio_submit(dio, sdio); |
756 | ret = dio_new_bio(dio, sdio, start_sector: sdio->cur_page_block, map_bh); |
757 | if (ret == 0) { |
758 | ret = dio_bio_add_page(dio, sdio); |
759 | BUG_ON(ret != 0); |
760 | } |
761 | } |
762 | out: |
763 | return ret; |
764 | } |
765 | |
766 | /* |
767 | * An autonomous function to put a chunk of a page under deferred IO. |
768 | * |
769 | * The caller doesn't actually know (or care) whether this piece of page is in |
770 | * a BIO, or is under IO or whatever. We just take care of all possible |
771 | * situations here. The separation between the logic of do_direct_IO() and |
772 | * that of submit_page_section() is important for clarity. Please don't break. |
773 | * |
774 | * The chunk of page starts on-disk at blocknr. |
775 | * |
776 | * We perform deferred IO, by recording the last-submitted page inside our |
777 | * private part of the dio structure. If possible, we just expand the IO |
778 | * across that page here. |
779 | * |
780 | * If that doesn't work out then we put the old page into the bio and add this |
781 | * page to the dio instead. |
782 | */ |
783 | static inline int |
784 | submit_page_section(struct dio *dio, struct dio_submit *sdio, struct page *page, |
785 | unsigned offset, unsigned len, sector_t blocknr, |
786 | struct buffer_head *map_bh) |
787 | { |
788 | const enum req_op dio_op = dio->opf & REQ_OP_MASK; |
789 | int ret = 0; |
790 | int boundary = sdio->boundary; /* dio_send_cur_page may clear it */ |
791 | |
792 | if (dio_op == REQ_OP_WRITE) { |
793 | /* |
794 | * Read accounting is performed in submit_bio() |
795 | */ |
796 | task_io_account_write(bytes: len); |
797 | } |
798 | |
799 | /* |
800 | * Can we just grow the current page's presence in the dio? |
801 | */ |
802 | if (sdio->cur_page == page && |
803 | sdio->cur_page_offset + sdio->cur_page_len == offset && |
804 | sdio->cur_page_block + |
805 | (sdio->cur_page_len >> sdio->blkbits) == blocknr) { |
806 | sdio->cur_page_len += len; |
807 | goto out; |
808 | } |
809 | |
810 | /* |
811 | * If there's a deferred page already there then send it. |
812 | */ |
813 | if (sdio->cur_page) { |
814 | ret = dio_send_cur_page(dio, sdio, map_bh); |
815 | dio_unpin_page(dio, page: sdio->cur_page); |
816 | sdio->cur_page = NULL; |
817 | if (ret) |
818 | return ret; |
819 | } |
820 | |
821 | dio_pin_page(dio, page); /* It is in dio */ |
822 | sdio->cur_page = page; |
823 | sdio->cur_page_offset = offset; |
824 | sdio->cur_page_len = len; |
825 | sdio->cur_page_block = blocknr; |
826 | sdio->cur_page_fs_offset = sdio->block_in_file << sdio->blkbits; |
827 | out: |
828 | /* |
829 | * If boundary then we want to schedule the IO now to |
830 | * avoid metadata seeks. |
831 | */ |
832 | if (boundary) { |
833 | ret = dio_send_cur_page(dio, sdio, map_bh); |
834 | if (sdio->bio) |
835 | dio_bio_submit(dio, sdio); |
836 | dio_unpin_page(dio, page: sdio->cur_page); |
837 | sdio->cur_page = NULL; |
838 | } |
839 | return ret; |
840 | } |
841 | |
842 | /* |
843 | * If we are not writing the entire block and get_block() allocated |
844 | * the block for us, we need to fill-in the unused portion of the |
845 | * block with zeros. This happens only if user-buffer, fileoffset or |
846 | * io length is not filesystem block-size multiple. |
847 | * |
848 | * `end' is zero if we're doing the start of the IO, 1 at the end of the |
849 | * IO. |
850 | */ |
851 | static inline void dio_zero_block(struct dio *dio, struct dio_submit *sdio, |
852 | int end, struct buffer_head *map_bh) |
853 | { |
854 | unsigned dio_blocks_per_fs_block; |
855 | unsigned this_chunk_blocks; /* In dio_blocks */ |
856 | unsigned this_chunk_bytes; |
857 | struct page *page; |
858 | |
859 | sdio->start_zero_done = 1; |
860 | if (!sdio->blkfactor || !buffer_new(bh: map_bh)) |
861 | return; |
862 | |
863 | dio_blocks_per_fs_block = 1 << sdio->blkfactor; |
864 | this_chunk_blocks = sdio->block_in_file & (dio_blocks_per_fs_block - 1); |
865 | |
866 | if (!this_chunk_blocks) |
867 | return; |
868 | |
869 | /* |
870 | * We need to zero out part of an fs block. It is either at the |
871 | * beginning or the end of the fs block. |
872 | */ |
873 | if (end) |
874 | this_chunk_blocks = dio_blocks_per_fs_block - this_chunk_blocks; |
875 | |
876 | this_chunk_bytes = this_chunk_blocks << sdio->blkbits; |
877 | |
878 | page = ZERO_PAGE(0); |
879 | if (submit_page_section(dio, sdio, page, offset: 0, len: this_chunk_bytes, |
880 | blocknr: sdio->next_block_for_io, map_bh)) |
881 | return; |
882 | |
883 | sdio->next_block_for_io += this_chunk_blocks; |
884 | } |
885 | |
886 | /* |
887 | * Walk the user pages, and the file, mapping blocks to disk and generating |
888 | * a sequence of (page,offset,len,block) mappings. These mappings are injected |
889 | * into submit_page_section(), which takes care of the next stage of submission |
890 | * |
891 | * Direct IO against a blockdev is different from a file. Because we can |
892 | * happily perform page-sized but 512-byte aligned IOs. It is important that |
893 | * blockdev IO be able to have fine alignment and large sizes. |
894 | * |
895 | * So what we do is to permit the ->get_block function to populate bh.b_size |
896 | * with the size of IO which is permitted at this offset and this i_blkbits. |
897 | * |
898 | * For best results, the blockdev should be set up with 512-byte i_blkbits and |
899 | * it should set b_size to PAGE_SIZE or more inside get_block(). This gives |
900 | * fine alignment but still allows this function to work in PAGE_SIZE units. |
901 | */ |
902 | static int do_direct_IO(struct dio *dio, struct dio_submit *sdio, |
903 | struct buffer_head *map_bh) |
904 | { |
905 | const enum req_op dio_op = dio->opf & REQ_OP_MASK; |
906 | const unsigned blkbits = sdio->blkbits; |
907 | const unsigned i_blkbits = blkbits + sdio->blkfactor; |
908 | int ret = 0; |
909 | |
910 | while (sdio->block_in_file < sdio->final_block_in_request) { |
911 | struct page *page; |
912 | size_t from, to; |
913 | |
914 | page = dio_get_page(dio, sdio); |
915 | if (IS_ERR(ptr: page)) { |
916 | ret = PTR_ERR(ptr: page); |
917 | goto out; |
918 | } |
919 | from = sdio->head ? 0 : sdio->from; |
920 | to = (sdio->head == sdio->tail - 1) ? sdio->to : PAGE_SIZE; |
921 | sdio->head++; |
922 | |
923 | while (from < to) { |
924 | unsigned this_chunk_bytes; /* # of bytes mapped */ |
925 | unsigned this_chunk_blocks; /* # of blocks */ |
926 | unsigned u; |
927 | |
928 | if (sdio->blocks_available == 0) { |
929 | /* |
930 | * Need to go and map some more disk |
931 | */ |
932 | unsigned long blkmask; |
933 | unsigned long dio_remainder; |
934 | |
935 | ret = get_more_blocks(dio, sdio, map_bh); |
936 | if (ret) { |
937 | dio_unpin_page(dio, page); |
938 | goto out; |
939 | } |
940 | if (!buffer_mapped(bh: map_bh)) |
941 | goto do_holes; |
942 | |
943 | sdio->blocks_available = |
944 | map_bh->b_size >> blkbits; |
945 | sdio->next_block_for_io = |
946 | map_bh->b_blocknr << sdio->blkfactor; |
947 | if (buffer_new(bh: map_bh)) { |
948 | clean_bdev_aliases( |
949 | bdev: map_bh->b_bdev, |
950 | block: map_bh->b_blocknr, |
951 | len: map_bh->b_size >> i_blkbits); |
952 | } |
953 | |
954 | if (!sdio->blkfactor) |
955 | goto do_holes; |
956 | |
957 | blkmask = (1 << sdio->blkfactor) - 1; |
958 | dio_remainder = (sdio->block_in_file & blkmask); |
959 | |
960 | /* |
961 | * If we are at the start of IO and that IO |
962 | * starts partway into a fs-block, |
963 | * dio_remainder will be non-zero. If the IO |
964 | * is a read then we can simply advance the IO |
965 | * cursor to the first block which is to be |
966 | * read. But if the IO is a write and the |
967 | * block was newly allocated we cannot do that; |
968 | * the start of the fs block must be zeroed out |
969 | * on-disk |
970 | */ |
971 | if (!buffer_new(bh: map_bh)) |
972 | sdio->next_block_for_io += dio_remainder; |
973 | sdio->blocks_available -= dio_remainder; |
974 | } |
975 | do_holes: |
976 | /* Handle holes */ |
977 | if (!buffer_mapped(bh: map_bh)) { |
978 | loff_t i_size_aligned; |
979 | |
980 | /* AKPM: eargh, -ENOTBLK is a hack */ |
981 | if (dio_op == REQ_OP_WRITE) { |
982 | dio_unpin_page(dio, page); |
983 | return -ENOTBLK; |
984 | } |
985 | |
986 | /* |
987 | * Be sure to account for a partial block as the |
988 | * last block in the file |
989 | */ |
990 | i_size_aligned = ALIGN(i_size_read(dio->inode), |
991 | 1 << blkbits); |
992 | if (sdio->block_in_file >= |
993 | i_size_aligned >> blkbits) { |
994 | /* We hit eof */ |
995 | dio_unpin_page(dio, page); |
996 | goto out; |
997 | } |
998 | zero_user(page, start: from, size: 1 << blkbits); |
999 | sdio->block_in_file++; |
1000 | from += 1 << blkbits; |
1001 | dio->result += 1 << blkbits; |
1002 | goto next_block; |
1003 | } |
1004 | |
1005 | /* |
1006 | * If we're performing IO which has an alignment which |
1007 | * is finer than the underlying fs, go check to see if |
1008 | * we must zero out the start of this block. |
1009 | */ |
1010 | if (unlikely(sdio->blkfactor && !sdio->start_zero_done)) |
1011 | dio_zero_block(dio, sdio, end: 0, map_bh); |
1012 | |
1013 | /* |
1014 | * Work out, in this_chunk_blocks, how much disk we |
1015 | * can add to this page |
1016 | */ |
1017 | this_chunk_blocks = sdio->blocks_available; |
1018 | u = (to - from) >> blkbits; |
1019 | if (this_chunk_blocks > u) |
1020 | this_chunk_blocks = u; |
1021 | u = sdio->final_block_in_request - sdio->block_in_file; |
1022 | if (this_chunk_blocks > u) |
1023 | this_chunk_blocks = u; |
1024 | this_chunk_bytes = this_chunk_blocks << blkbits; |
1025 | BUG_ON(this_chunk_bytes == 0); |
1026 | |
1027 | if (this_chunk_blocks == sdio->blocks_available) |
1028 | sdio->boundary = buffer_boundary(bh: map_bh); |
1029 | ret = submit_page_section(dio, sdio, page, |
1030 | offset: from, |
1031 | len: this_chunk_bytes, |
1032 | blocknr: sdio->next_block_for_io, |
1033 | map_bh); |
1034 | if (ret) { |
1035 | dio_unpin_page(dio, page); |
1036 | goto out; |
1037 | } |
1038 | sdio->next_block_for_io += this_chunk_blocks; |
1039 | |
1040 | sdio->block_in_file += this_chunk_blocks; |
1041 | from += this_chunk_bytes; |
1042 | dio->result += this_chunk_bytes; |
1043 | sdio->blocks_available -= this_chunk_blocks; |
1044 | next_block: |
1045 | BUG_ON(sdio->block_in_file > sdio->final_block_in_request); |
1046 | if (sdio->block_in_file == sdio->final_block_in_request) |
1047 | break; |
1048 | } |
1049 | |
1050 | /* Drop the pin which was taken in get_user_pages() */ |
1051 | dio_unpin_page(dio, page); |
1052 | } |
1053 | out: |
1054 | return ret; |
1055 | } |
1056 | |
1057 | static inline int drop_refcount(struct dio *dio) |
1058 | { |
1059 | int ret2; |
1060 | unsigned long flags; |
1061 | |
1062 | /* |
1063 | * Sync will always be dropping the final ref and completing the |
1064 | * operation. AIO can if it was a broken operation described above or |
1065 | * in fact if all the bios race to complete before we get here. In |
1066 | * that case dio_complete() translates the EIOCBQUEUED into the proper |
1067 | * return code that the caller will hand to ->complete(). |
1068 | * |
1069 | * This is managed by the bio_lock instead of being an atomic_t so that |
1070 | * completion paths can drop their ref and use the remaining count to |
1071 | * decide to wake the submission path atomically. |
1072 | */ |
1073 | spin_lock_irqsave(&dio->bio_lock, flags); |
1074 | ret2 = --dio->refcount; |
1075 | spin_unlock_irqrestore(lock: &dio->bio_lock, flags); |
1076 | return ret2; |
1077 | } |
1078 | |
1079 | /* |
1080 | * This is a library function for use by filesystem drivers. |
1081 | * |
1082 | * The locking rules are governed by the flags parameter: |
1083 | * - if the flags value contains DIO_LOCKING we use a fancy locking |
1084 | * scheme for dumb filesystems. |
1085 | * For writes this function is called under i_mutex and returns with |
1086 | * i_mutex held, for reads, i_mutex is not held on entry, but it is |
1087 | * taken and dropped again before returning. |
1088 | * - if the flags value does NOT contain DIO_LOCKING we don't use any |
1089 | * internal locking but rather rely on the filesystem to synchronize |
1090 | * direct I/O reads/writes versus each other and truncate. |
1091 | * |
1092 | * To help with locking against truncate we incremented the i_dio_count |
1093 | * counter before starting direct I/O, and decrement it once we are done. |
1094 | * Truncate can wait for it to reach zero to provide exclusion. It is |
1095 | * expected that filesystem provide exclusion between new direct I/O |
1096 | * and truncates. For DIO_LOCKING filesystems this is done by i_mutex, |
1097 | * but other filesystems need to take care of this on their own. |
1098 | * |
1099 | * NOTE: if you pass "sdio" to anything by pointer make sure that function |
1100 | * is always inlined. Otherwise gcc is unable to split the structure into |
1101 | * individual fields and will generate much worse code. This is important |
1102 | * for the whole file. |
1103 | */ |
1104 | ssize_t __blockdev_direct_IO(struct kiocb *iocb, struct inode *inode, |
1105 | struct block_device *bdev, struct iov_iter *iter, |
1106 | get_block_t get_block, dio_iodone_t end_io, |
1107 | int flags) |
1108 | { |
1109 | unsigned i_blkbits = READ_ONCE(inode->i_blkbits); |
1110 | unsigned blkbits = i_blkbits; |
1111 | unsigned blocksize_mask = (1 << blkbits) - 1; |
1112 | ssize_t retval = -EINVAL; |
1113 | const size_t count = iov_iter_count(i: iter); |
1114 | loff_t offset = iocb->ki_pos; |
1115 | const loff_t end = offset + count; |
1116 | struct dio *dio; |
1117 | struct dio_submit sdio = { 0, }; |
1118 | struct buffer_head map_bh = { 0, }; |
1119 | struct blk_plug plug; |
1120 | unsigned long align = offset | iov_iter_alignment(i: iter); |
1121 | |
1122 | /* |
1123 | * Avoid references to bdev if not absolutely needed to give |
1124 | * the early prefetch in the caller enough time. |
1125 | */ |
1126 | |
1127 | /* watch out for a 0 len io from a tricksy fs */ |
1128 | if (iov_iter_rw(i: iter) == READ && !count) |
1129 | return 0; |
1130 | |
1131 | dio = kmem_cache_alloc(cachep: dio_cache, GFP_KERNEL); |
1132 | if (!dio) |
1133 | return -ENOMEM; |
1134 | /* |
1135 | * Believe it or not, zeroing out the page array caused a .5% |
1136 | * performance regression in a database benchmark. So, we take |
1137 | * care to only zero out what's needed. |
1138 | */ |
1139 | memset(dio, 0, offsetof(struct dio, pages)); |
1140 | |
1141 | dio->flags = flags; |
1142 | if (dio->flags & DIO_LOCKING && iov_iter_rw(i: iter) == READ) { |
1143 | /* will be released by direct_io_worker */ |
1144 | inode_lock(inode); |
1145 | } |
1146 | dio->is_pinned = iov_iter_extract_will_pin(iter); |
1147 | |
1148 | /* Once we sampled i_size check for reads beyond EOF */ |
1149 | dio->i_size = i_size_read(inode); |
1150 | if (iov_iter_rw(i: iter) == READ && offset >= dio->i_size) { |
1151 | retval = 0; |
1152 | goto fail_dio; |
1153 | } |
1154 | |
1155 | if (align & blocksize_mask) { |
1156 | if (bdev) |
1157 | blkbits = blksize_bits(size: bdev_logical_block_size(bdev)); |
1158 | blocksize_mask = (1 << blkbits) - 1; |
1159 | if (align & blocksize_mask) |
1160 | goto fail_dio; |
1161 | } |
1162 | |
1163 | if (dio->flags & DIO_LOCKING && iov_iter_rw(i: iter) == READ) { |
1164 | struct address_space *mapping = iocb->ki_filp->f_mapping; |
1165 | |
1166 | retval = filemap_write_and_wait_range(mapping, lstart: offset, lend: end - 1); |
1167 | if (retval) |
1168 | goto fail_dio; |
1169 | } |
1170 | |
1171 | /* |
1172 | * For file extending writes updating i_size before data writeouts |
1173 | * complete can expose uninitialized blocks in dumb filesystems. |
1174 | * In that case we need to wait for I/O completion even if asked |
1175 | * for an asynchronous write. |
1176 | */ |
1177 | if (is_sync_kiocb(kiocb: iocb)) |
1178 | dio->is_async = false; |
1179 | else if (iov_iter_rw(i: iter) == WRITE && end > i_size_read(inode)) |
1180 | dio->is_async = false; |
1181 | else |
1182 | dio->is_async = true; |
1183 | |
1184 | dio->inode = inode; |
1185 | if (iov_iter_rw(i: iter) == WRITE) { |
1186 | dio->opf = REQ_OP_WRITE | REQ_SYNC | REQ_IDLE; |
1187 | if (iocb->ki_flags & IOCB_NOWAIT) |
1188 | dio->opf |= REQ_NOWAIT; |
1189 | } else { |
1190 | dio->opf = REQ_OP_READ; |
1191 | } |
1192 | |
1193 | /* |
1194 | * For AIO O_(D)SYNC writes we need to defer completions to a workqueue |
1195 | * so that we can call ->fsync. |
1196 | */ |
1197 | if (dio->is_async && iov_iter_rw(i: iter) == WRITE) { |
1198 | retval = 0; |
1199 | if (iocb_is_dsync(iocb)) |
1200 | retval = dio_set_defer_completion(dio); |
1201 | else if (!dio->inode->i_sb->s_dio_done_wq) { |
1202 | /* |
1203 | * In case of AIO write racing with buffered read we |
1204 | * need to defer completion. We can't decide this now, |
1205 | * however the workqueue needs to be initialized here. |
1206 | */ |
1207 | retval = sb_init_dio_done_wq(sb: dio->inode->i_sb); |
1208 | } |
1209 | if (retval) |
1210 | goto fail_dio; |
1211 | } |
1212 | |
1213 | /* |
1214 | * Will be decremented at I/O completion time. |
1215 | */ |
1216 | inode_dio_begin(inode); |
1217 | |
1218 | retval = 0; |
1219 | sdio.blkbits = blkbits; |
1220 | sdio.blkfactor = i_blkbits - blkbits; |
1221 | sdio.block_in_file = offset >> blkbits; |
1222 | |
1223 | sdio.get_block = get_block; |
1224 | dio->end_io = end_io; |
1225 | sdio.final_block_in_bio = -1; |
1226 | sdio.next_block_for_io = -1; |
1227 | |
1228 | dio->iocb = iocb; |
1229 | |
1230 | spin_lock_init(&dio->bio_lock); |
1231 | dio->refcount = 1; |
1232 | |
1233 | dio->should_dirty = user_backed_iter(i: iter) && iov_iter_rw(i: iter) == READ; |
1234 | sdio.iter = iter; |
1235 | sdio.final_block_in_request = end >> blkbits; |
1236 | |
1237 | /* |
1238 | * In case of non-aligned buffers, we may need 2 more |
1239 | * pages since we need to zero out first and last block. |
1240 | */ |
1241 | if (unlikely(sdio.blkfactor)) |
1242 | sdio.pages_in_io = 2; |
1243 | |
1244 | sdio.pages_in_io += iov_iter_npages(i: iter, INT_MAX); |
1245 | |
1246 | blk_start_plug(&plug); |
1247 | |
1248 | retval = do_direct_IO(dio, sdio: &sdio, map_bh: &map_bh); |
1249 | if (retval) |
1250 | dio_cleanup(dio, sdio: &sdio); |
1251 | |
1252 | if (retval == -ENOTBLK) { |
1253 | /* |
1254 | * The remaining part of the request will be |
1255 | * handled by buffered I/O when we return |
1256 | */ |
1257 | retval = 0; |
1258 | } |
1259 | /* |
1260 | * There may be some unwritten disk at the end of a part-written |
1261 | * fs-block-sized block. Go zero that now. |
1262 | */ |
1263 | dio_zero_block(dio, sdio: &sdio, end: 1, map_bh: &map_bh); |
1264 | |
1265 | if (sdio.cur_page) { |
1266 | ssize_t ret2; |
1267 | |
1268 | ret2 = dio_send_cur_page(dio, sdio: &sdio, map_bh: &map_bh); |
1269 | if (retval == 0) |
1270 | retval = ret2; |
1271 | dio_unpin_page(dio, page: sdio.cur_page); |
1272 | sdio.cur_page = NULL; |
1273 | } |
1274 | if (sdio.bio) |
1275 | dio_bio_submit(dio, sdio: &sdio); |
1276 | |
1277 | blk_finish_plug(&plug); |
1278 | |
1279 | /* |
1280 | * It is possible that, we return short IO due to end of file. |
1281 | * In that case, we need to release all the pages we got hold on. |
1282 | */ |
1283 | dio_cleanup(dio, sdio: &sdio); |
1284 | |
1285 | /* |
1286 | * All block lookups have been performed. For READ requests |
1287 | * we can let i_mutex go now that its achieved its purpose |
1288 | * of protecting us from looking up uninitialized blocks. |
1289 | */ |
1290 | if (iov_iter_rw(i: iter) == READ && (dio->flags & DIO_LOCKING)) |
1291 | inode_unlock(inode: dio->inode); |
1292 | |
1293 | /* |
1294 | * The only time we want to leave bios in flight is when a successful |
1295 | * partial aio read or full aio write have been setup. In that case |
1296 | * bio completion will call aio_complete. The only time it's safe to |
1297 | * call aio_complete is when we return -EIOCBQUEUED, so we key on that. |
1298 | * This had *better* be the only place that raises -EIOCBQUEUED. |
1299 | */ |
1300 | BUG_ON(retval == -EIOCBQUEUED); |
1301 | if (dio->is_async && retval == 0 && dio->result && |
1302 | (iov_iter_rw(i: iter) == READ || dio->result == count)) |
1303 | retval = -EIOCBQUEUED; |
1304 | else |
1305 | dio_await_completion(dio); |
1306 | |
1307 | if (drop_refcount(dio) == 0) { |
1308 | retval = dio_complete(dio, ret: retval, DIO_COMPLETE_INVALIDATE); |
1309 | } else |
1310 | BUG_ON(retval != -EIOCBQUEUED); |
1311 | |
1312 | return retval; |
1313 | |
1314 | fail_dio: |
1315 | if (dio->flags & DIO_LOCKING && iov_iter_rw(i: iter) == READ) |
1316 | inode_unlock(inode); |
1317 | |
1318 | kmem_cache_free(s: dio_cache, objp: dio); |
1319 | return retval; |
1320 | } |
1321 | EXPORT_SYMBOL(__blockdev_direct_IO); |
1322 | |
1323 | static __init int dio_init(void) |
1324 | { |
1325 | dio_cache = KMEM_CACHE(dio, SLAB_PANIC); |
1326 | return 0; |
1327 | } |
1328 | module_init(dio_init) |
1329 | |