Line data Source code
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 __read_mostly;
155 :
156 : /*
157 : * How many pages are in the queue?
158 : */
159 : static inline unsigned dio_pages_present(struct dio_submit *sdio)
160 : {
161 0 : 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 0 : static inline int dio_refill_pages(struct dio *dio, struct dio_submit *sdio)
168 : {
169 0 : struct page **pages = dio->pages;
170 0 : const enum req_op dio_op = dio->opf & REQ_OP_MASK;
171 0 : ssize_t ret;
172 :
173 0 : ret = iov_iter_extract_pages(sdio->iter, &pages, LONG_MAX,
174 : DIO_PAGES, 0, &sdio->from);
175 :
176 0 : 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 0 : if (dio->page_errors == 0)
183 0 : dio->page_errors = ret;
184 0 : dio->pages[0] = ZERO_PAGE(0);
185 0 : sdio->head = 0;
186 0 : sdio->tail = 1;
187 0 : sdio->from = 0;
188 0 : sdio->to = PAGE_SIZE;
189 0 : return 0;
190 : }
191 :
192 0 : if (ret >= 0) {
193 0 : ret += sdio->from;
194 0 : sdio->head = 0;
195 0 : sdio->tail = (ret + PAGE_SIZE - 1) / PAGE_SIZE;
196 0 : sdio->to = ((ret - 1) & (PAGE_SIZE - 1)) + 1;
197 0 : return 0;
198 : }
199 0 : 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 0 : static inline struct page *dio_get_page(struct dio *dio,
209 : struct dio_submit *sdio)
210 : {
211 0 : if (dio_pages_present(sdio) == 0) {
212 0 : int ret;
213 :
214 0 : ret = dio_refill_pages(dio, sdio);
215 0 : if (ret)
216 0 : return ERR_PTR(ret);
217 0 : BUG_ON(dio_pages_present(sdio) == 0);
218 : }
219 0 : return dio->pages[sdio->head];
220 : }
221 :
222 0 : static void dio_pin_page(struct dio *dio, struct page *page)
223 : {
224 0 : if (dio->is_pinned)
225 0 : folio_add_pin(page_folio(page));
226 0 : }
227 :
228 0 : static void dio_unpin_page(struct dio *dio, struct page *page)
229 : {
230 0 : if (dio->is_pinned)
231 0 : unpin_user_page(page);
232 0 : }
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 0 : static ssize_t dio_complete(struct dio *dio, ssize_t ret, unsigned int flags)
246 : {
247 0 : const enum req_op dio_op = dio->opf & REQ_OP_MASK;
248 0 : loff_t offset = dio->iocb->ki_pos;
249 0 : ssize_t transferred = 0;
250 0 : 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 0 : if (ret == -EIOCBQUEUED)
259 0 : ret = 0;
260 :
261 0 : if (dio->result) {
262 0 : transferred = dio->result;
263 :
264 : /* Check for short read case */
265 0 : if (dio_op == REQ_OP_READ &&
266 0 : ((offset + transferred) > dio->i_size))
267 0 : transferred = dio->i_size - offset;
268 : /* ignore EFAULT if some IO has been done */
269 0 : if (unlikely(ret == -EFAULT) && transferred)
270 : ret = 0;
271 : }
272 :
273 0 : if (ret == 0)
274 0 : ret = dio->page_errors;
275 0 : if (ret == 0)
276 0 : ret = dio->io_error;
277 0 : if (ret == 0)
278 0 : ret = transferred;
279 :
280 0 : if (dio->end_io) {
281 : // XXX: ki_pos??
282 0 : err = dio->end_io(dio->iocb, offset, ret, dio->private);
283 0 : if (err)
284 0 : 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 0 : if (flags & DIO_COMPLETE_INVALIDATE &&
300 0 : ret > 0 && dio_op == REQ_OP_WRITE)
301 0 : kiocb_invalidate_post_direct_write(dio->iocb, ret);
302 :
303 0 : inode_dio_end(dio->inode);
304 :
305 0 : 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 0 : dio->iocb->ki_pos += transferred;
312 :
313 0 : if (ret > 0 && dio_op == REQ_OP_WRITE)
314 0 : ret = generic_write_sync(dio->iocb, ret);
315 0 : dio->iocb->ki_complete(dio->iocb, ret);
316 : }
317 :
318 0 : kmem_cache_free(dio_cache, dio);
319 0 : return ret;
320 : }
321 :
322 0 : static void dio_aio_complete_work(struct work_struct *work)
323 : {
324 0 : struct dio *dio = container_of(work, struct dio, complete_work);
325 :
326 0 : dio_complete(dio, 0, DIO_COMPLETE_ASYNC | DIO_COMPLETE_INVALIDATE);
327 0 : }
328 :
329 : static blk_status_t dio_bio_complete(struct dio *dio, struct bio *bio);
330 :
331 : /*
332 : * Asynchronous IO callback.
333 : */
334 0 : static void dio_bio_end_aio(struct bio *bio)
335 : {
336 0 : struct dio *dio = bio->bi_private;
337 0 : const enum req_op dio_op = dio->opf & REQ_OP_MASK;
338 0 : unsigned long remaining;
339 0 : unsigned long flags;
340 0 : bool defer_completion = false;
341 :
342 : /* cleanup the bio */
343 0 : dio_bio_complete(dio, bio);
344 :
345 0 : spin_lock_irqsave(&dio->bio_lock, flags);
346 0 : remaining = --dio->refcount;
347 0 : if (remaining == 1 && dio->waiter)
348 0 : wake_up_process(dio->waiter);
349 0 : spin_unlock_irqrestore(&dio->bio_lock, flags);
350 :
351 0 : 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 0 : if (dio->result)
361 0 : defer_completion = dio->defer_completion ||
362 0 : (dio_op == REQ_OP_WRITE &&
363 0 : dio->inode->i_mapping->nrpages);
364 0 : if (defer_completion) {
365 0 : INIT_WORK(&dio->complete_work, dio_aio_complete_work);
366 0 : queue_work(dio->inode->i_sb->s_dio_done_wq,
367 : &dio->complete_work);
368 : } else {
369 0 : dio_complete(dio, 0, DIO_COMPLETE_ASYNC);
370 : }
371 : }
372 0 : }
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 0 : static void dio_bio_end_io(struct bio *bio)
382 : {
383 0 : struct dio *dio = bio->bi_private;
384 0 : unsigned long flags;
385 :
386 0 : spin_lock_irqsave(&dio->bio_lock, flags);
387 0 : bio->bi_private = dio->bio_list;
388 0 : dio->bio_list = bio;
389 0 : if (--dio->refcount == 1 && dio->waiter)
390 0 : wake_up_process(dio->waiter);
391 0 : spin_unlock_irqrestore(&dio->bio_lock, flags);
392 0 : }
393 :
394 : static inline void
395 0 : 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 0 : 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 0 : bio = bio_alloc(bdev, nr_vecs, dio->opf, GFP_KERNEL);
406 0 : bio->bi_iter.bi_sector = first_sector;
407 0 : if (dio->is_async)
408 0 : bio->bi_end_io = dio_bio_end_aio;
409 : else
410 0 : bio->bi_end_io = dio_bio_end_io;
411 0 : if (dio->is_pinned)
412 0 : bio_set_flag(bio, BIO_PAGE_PINNED);
413 0 : sdio->bio = bio;
414 0 : sdio->logical_offset_in_bio = sdio->cur_page_fs_offset;
415 0 : }
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 0 : static inline void dio_bio_submit(struct dio *dio, struct dio_submit *sdio)
425 : {
426 0 : const enum req_op dio_op = dio->opf & REQ_OP_MASK;
427 0 : struct bio *bio = sdio->bio;
428 0 : unsigned long flags;
429 :
430 0 : bio->bi_private = dio;
431 :
432 0 : spin_lock_irqsave(&dio->bio_lock, flags);
433 0 : dio->refcount++;
434 0 : spin_unlock_irqrestore(&dio->bio_lock, flags);
435 :
436 0 : if (dio->is_async && dio_op == REQ_OP_READ && dio->should_dirty)
437 0 : bio_set_pages_dirty(bio);
438 :
439 0 : dio->bio_disk = bio->bi_bdev->bd_disk;
440 :
441 0 : submit_bio(bio);
442 :
443 0 : sdio->bio = NULL;
444 0 : sdio->boundary = 0;
445 0 : sdio->logical_offset_in_bio = 0;
446 0 : }
447 :
448 : /*
449 : * Release any resources in case of a failure
450 : */
451 0 : static inline void dio_cleanup(struct dio *dio, struct dio_submit *sdio)
452 : {
453 0 : if (dio->is_pinned)
454 0 : unpin_user_pages(dio->pages + sdio->head,
455 0 : sdio->tail - sdio->head);
456 0 : sdio->head = sdio->tail;
457 0 : }
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 0 : static struct bio *dio_await_one(struct dio *dio)
466 : {
467 0 : unsigned long flags;
468 0 : struct bio *bio = NULL;
469 :
470 0 : 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 0 : while (dio->refcount > 1 && dio->bio_list == NULL) {
479 0 : __set_current_state(TASK_UNINTERRUPTIBLE);
480 0 : dio->waiter = current;
481 0 : spin_unlock_irqrestore(&dio->bio_lock, flags);
482 0 : blk_io_schedule();
483 : /* wake up sets us TASK_RUNNING */
484 0 : spin_lock_irqsave(&dio->bio_lock, flags);
485 0 : dio->waiter = NULL;
486 : }
487 0 : if (dio->bio_list) {
488 0 : bio = dio->bio_list;
489 0 : dio->bio_list = bio->bi_private;
490 : }
491 0 : spin_unlock_irqrestore(&dio->bio_lock, flags);
492 0 : return bio;
493 : }
494 :
495 : /*
496 : * Process one completed BIO. No locks are held.
497 : */
498 0 : static blk_status_t dio_bio_complete(struct dio *dio, struct bio *bio)
499 : {
500 0 : blk_status_t err = bio->bi_status;
501 0 : const enum req_op dio_op = dio->opf & REQ_OP_MASK;
502 0 : bool should_dirty = dio_op == REQ_OP_READ && dio->should_dirty;
503 :
504 0 : if (err) {
505 0 : if (err == BLK_STS_AGAIN && (bio->bi_opf & REQ_NOWAIT))
506 0 : dio->io_error = -EAGAIN;
507 : else
508 0 : dio->io_error = -EIO;
509 : }
510 :
511 0 : if (dio->is_async && should_dirty) {
512 0 : bio_check_pages_dirty(bio); /* transfers ownership */
513 : } else {
514 0 : bio_release_pages(bio, should_dirty);
515 0 : bio_put(bio);
516 : }
517 0 : 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 0 : static void dio_await_completion(struct dio *dio)
528 : {
529 0 : struct bio *bio;
530 0 : do {
531 0 : bio = dio_await_one(dio);
532 0 : if (bio)
533 0 : dio_bio_complete(dio, bio);
534 0 : } while (bio);
535 0 : }
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 0 : static inline int dio_bio_reap(struct dio *dio, struct dio_submit *sdio)
545 : {
546 0 : int ret = 0;
547 :
548 0 : if (sdio->reap_counter++ >= 64) {
549 0 : while (dio->bio_list) {
550 0 : unsigned long flags;
551 0 : struct bio *bio;
552 0 : int ret2;
553 :
554 0 : spin_lock_irqsave(&dio->bio_lock, flags);
555 0 : bio = dio->bio_list;
556 0 : dio->bio_list = bio->bi_private;
557 0 : spin_unlock_irqrestore(&dio->bio_lock, flags);
558 0 : ret2 = blk_status_to_errno(dio_bio_complete(dio, bio));
559 0 : if (ret == 0)
560 0 : ret = ret2;
561 : }
562 0 : sdio->reap_counter = 0;
563 : }
564 0 : return ret;
565 : }
566 :
567 0 : static int dio_set_defer_completion(struct dio *dio)
568 : {
569 0 : struct super_block *sb = dio->inode->i_sb;
570 :
571 0 : if (dio->defer_completion)
572 : return 0;
573 0 : dio->defer_completion = true;
574 0 : if (!sb->s_dio_done_wq)
575 0 : 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 0 : static int get_more_blocks(struct dio *dio, struct dio_submit *sdio,
603 : struct buffer_head *map_bh)
604 : {
605 0 : const enum req_op dio_op = dio->opf & REQ_OP_MASK;
606 0 : int ret;
607 0 : sector_t fs_startblk; /* Into file, in filesystem-sized blocks */
608 0 : sector_t fs_endblk; /* Into file, in filesystem-sized blocks */
609 0 : unsigned long fs_count; /* Number of filesystem-sized blocks */
610 0 : int create;
611 0 : unsigned int i_blkbits = sdio->blkbits + sdio->blkfactor;
612 0 : 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 0 : ret = dio->page_errors;
619 0 : if (ret == 0) {
620 0 : BUG_ON(sdio->block_in_file >= sdio->final_block_in_request);
621 0 : fs_startblk = sdio->block_in_file >> sdio->blkfactor;
622 0 : fs_endblk = (sdio->final_block_in_request - 1) >>
623 0 : sdio->blkfactor;
624 0 : fs_count = fs_endblk - fs_startblk + 1;
625 :
626 0 : map_bh->b_state = 0;
627 0 : 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 0 : create = dio_op == REQ_OP_WRITE;
641 0 : if (dio->flags & DIO_SKIP_HOLES) {
642 0 : i_size = i_size_read(dio->inode);
643 0 : if (i_size && fs_startblk <= (i_size - 1) >> i_blkbits)
644 0 : create = 0;
645 : }
646 :
647 0 : ret = (*sdio->get_block)(dio->inode, fs_startblk,
648 : map_bh, create);
649 :
650 : /* Store for completion */
651 0 : dio->private = map_bh->b_private;
652 :
653 0 : if (ret == 0 && buffer_defer_completion(map_bh))
654 0 : ret = dio_set_defer_completion(dio);
655 : }
656 0 : return ret;
657 : }
658 :
659 : /*
660 : * There is no bio. Make one now.
661 : */
662 0 : 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 0 : sector_t sector;
666 0 : int ret, nr_pages;
667 :
668 0 : ret = dio_bio_reap(dio, sdio);
669 0 : if (ret)
670 0 : goto out;
671 0 : sector = start_sector << (sdio->blkbits - 9);
672 0 : nr_pages = bio_max_segs(sdio->pages_in_io);
673 0 : BUG_ON(nr_pages <= 0);
674 0 : dio_bio_alloc(dio, sdio, map_bh->b_bdev, sector, nr_pages);
675 0 : sdio->boundary = 0;
676 0 : out:
677 0 : 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 0 : static inline int dio_bio_add_page(struct dio *dio, struct dio_submit *sdio)
688 : {
689 0 : int ret;
690 :
691 0 : ret = bio_add_page(sdio->bio, sdio->cur_page,
692 : sdio->cur_page_len, sdio->cur_page_offset);
693 0 : if (ret == sdio->cur_page_len) {
694 : /*
695 : * Decrement count only, if we are done with this page
696 : */
697 0 : if ((sdio->cur_page_len + sdio->cur_page_offset) == PAGE_SIZE)
698 0 : sdio->pages_in_io--;
699 0 : dio_pin_page(dio, sdio->cur_page);
700 0 : sdio->final_block_in_bio = sdio->cur_page_block +
701 0 : (sdio->cur_page_len >> sdio->blkbits);
702 0 : ret = 0;
703 : } else {
704 : ret = 1;
705 : }
706 0 : 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 0 : static inline int dio_send_cur_page(struct dio *dio, struct dio_submit *sdio,
720 : struct buffer_head *map_bh)
721 : {
722 0 : int ret = 0;
723 :
724 0 : if (sdio->bio) {
725 0 : loff_t cur_offset = sdio->cur_page_fs_offset;
726 0 : loff_t bio_next_offset = sdio->logical_offset_in_bio +
727 0 : 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 0 : if (sdio->final_block_in_bio != sdio->cur_page_block ||
744 : cur_offset != bio_next_offset)
745 0 : dio_bio_submit(dio, sdio);
746 : }
747 :
748 0 : if (sdio->bio == NULL) {
749 0 : ret = dio_new_bio(dio, sdio, sdio->cur_page_block, map_bh);
750 0 : if (ret)
751 0 : goto out;
752 : }
753 :
754 0 : if (dio_bio_add_page(dio, sdio) != 0) {
755 0 : dio_bio_submit(dio, sdio);
756 0 : ret = dio_new_bio(dio, sdio, sdio->cur_page_block, map_bh);
757 0 : if (ret == 0) {
758 0 : ret = dio_bio_add_page(dio, sdio);
759 0 : BUG_ON(ret != 0);
760 : }
761 : }
762 0 : out:
763 0 : 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 0 : 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 0 : const enum req_op dio_op = dio->opf & REQ_OP_MASK;
789 0 : int ret = 0;
790 0 : int boundary = sdio->boundary; /* dio_send_cur_page may clear it */
791 :
792 0 : if (dio_op == REQ_OP_WRITE) {
793 : /*
794 : * Read accounting is performed in submit_bio()
795 : */
796 0 : task_io_account_write(len);
797 : }
798 :
799 : /*
800 : * Can we just grow the current page's presence in the dio?
801 : */
802 0 : if (sdio->cur_page == page &&
803 0 : sdio->cur_page_offset + sdio->cur_page_len == offset &&
804 0 : sdio->cur_page_block +
805 0 : (sdio->cur_page_len >> sdio->blkbits) == blocknr) {
806 0 : sdio->cur_page_len += len;
807 0 : goto out;
808 : }
809 :
810 : /*
811 : * If there's a deferred page already there then send it.
812 : */
813 0 : if (sdio->cur_page) {
814 0 : ret = dio_send_cur_page(dio, sdio, map_bh);
815 0 : dio_unpin_page(dio, sdio->cur_page);
816 0 : sdio->cur_page = NULL;
817 0 : if (ret)
818 : return ret;
819 : }
820 :
821 0 : dio_pin_page(dio, page); /* It is in dio */
822 0 : sdio->cur_page = page;
823 0 : sdio->cur_page_offset = offset;
824 0 : sdio->cur_page_len = len;
825 0 : sdio->cur_page_block = blocknr;
826 0 : sdio->cur_page_fs_offset = sdio->block_in_file << sdio->blkbits;
827 0 : out:
828 : /*
829 : * If boundary then we want to schedule the IO now to
830 : * avoid metadata seeks.
831 : */
832 0 : if (boundary) {
833 0 : ret = dio_send_cur_page(dio, sdio, map_bh);
834 0 : if (sdio->bio)
835 0 : dio_bio_submit(dio, sdio);
836 0 : dio_unpin_page(dio, sdio->cur_page);
837 0 : 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 0 : static inline void dio_zero_block(struct dio *dio, struct dio_submit *sdio,
852 : int end, struct buffer_head *map_bh)
853 : {
854 0 : unsigned dio_blocks_per_fs_block;
855 0 : unsigned this_chunk_blocks; /* In dio_blocks */
856 0 : unsigned this_chunk_bytes;
857 0 : struct page *page;
858 :
859 0 : sdio->start_zero_done = 1;
860 0 : if (!sdio->blkfactor || !buffer_new(map_bh))
861 : return;
862 :
863 0 : dio_blocks_per_fs_block = 1 << sdio->blkfactor;
864 0 : this_chunk_blocks = sdio->block_in_file & (dio_blocks_per_fs_block - 1);
865 :
866 0 : 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 0 : if (end)
874 0 : this_chunk_blocks = dio_blocks_per_fs_block - this_chunk_blocks;
875 :
876 0 : this_chunk_bytes = this_chunk_blocks << sdio->blkbits;
877 :
878 0 : page = ZERO_PAGE(0);
879 0 : if (submit_page_section(dio, sdio, page, 0, this_chunk_bytes,
880 : sdio->next_block_for_io, map_bh))
881 : return;
882 :
883 0 : 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 0 : static int do_direct_IO(struct dio *dio, struct dio_submit *sdio,
903 : struct buffer_head *map_bh)
904 : {
905 0 : const enum req_op dio_op = dio->opf & REQ_OP_MASK;
906 0 : const unsigned blkbits = sdio->blkbits;
907 0 : const unsigned i_blkbits = blkbits + sdio->blkfactor;
908 0 : int ret = 0;
909 :
910 0 : while (sdio->block_in_file < sdio->final_block_in_request) {
911 0 : struct page *page;
912 0 : size_t from, to;
913 :
914 0 : page = dio_get_page(dio, sdio);
915 0 : if (IS_ERR(page)) {
916 0 : ret = PTR_ERR(page);
917 0 : goto out;
918 : }
919 0 : from = sdio->head ? 0 : sdio->from;
920 0 : to = (sdio->head == sdio->tail - 1) ? sdio->to : PAGE_SIZE;
921 0 : sdio->head++;
922 :
923 0 : while (from < to) {
924 0 : unsigned this_chunk_bytes; /* # of bytes mapped */
925 0 : unsigned this_chunk_blocks; /* # of blocks */
926 0 : unsigned u;
927 :
928 0 : if (sdio->blocks_available == 0) {
929 : /*
930 : * Need to go and map some more disk
931 : */
932 0 : unsigned long blkmask;
933 0 : unsigned long dio_remainder;
934 :
935 0 : ret = get_more_blocks(dio, sdio, map_bh);
936 0 : if (ret) {
937 0 : dio_unpin_page(dio, page);
938 0 : goto out;
939 : }
940 0 : if (!buffer_mapped(map_bh))
941 0 : goto do_holes;
942 :
943 0 : sdio->blocks_available =
944 0 : map_bh->b_size >> blkbits;
945 0 : sdio->next_block_for_io =
946 0 : map_bh->b_blocknr << sdio->blkfactor;
947 0 : if (buffer_new(map_bh)) {
948 0 : clean_bdev_aliases(
949 : map_bh->b_bdev,
950 : map_bh->b_blocknr,
951 0 : map_bh->b_size >> i_blkbits);
952 : }
953 :
954 0 : if (!sdio->blkfactor)
955 0 : goto do_holes;
956 :
957 0 : blkmask = (1 << sdio->blkfactor) - 1;
958 0 : 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 0 : if (!buffer_new(map_bh))
972 0 : sdio->next_block_for_io += dio_remainder;
973 0 : sdio->blocks_available -= dio_remainder;
974 : }
975 0 : do_holes:
976 : /* Handle holes */
977 0 : if (!buffer_mapped(map_bh)) {
978 0 : loff_t i_size_aligned;
979 :
980 : /* AKPM: eargh, -ENOTBLK is a hack */
981 0 : if (dio_op == REQ_OP_WRITE) {
982 0 : dio_unpin_page(dio, page);
983 0 : return -ENOTBLK;
984 : }
985 :
986 : /*
987 : * Be sure to account for a partial block as the
988 : * last block in the file
989 : */
990 0 : i_size_aligned = ALIGN(i_size_read(dio->inode),
991 : 1 << blkbits);
992 0 : if (sdio->block_in_file >=
993 0 : i_size_aligned >> blkbits) {
994 : /* We hit eof */
995 0 : dio_unpin_page(dio, page);
996 0 : goto out;
997 : }
998 0 : zero_user(page, from, 1 << blkbits);
999 0 : sdio->block_in_file++;
1000 0 : from += 1 << blkbits;
1001 0 : dio->result += 1 << blkbits;
1002 0 : 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 0 : if (unlikely(sdio->blkfactor && !sdio->start_zero_done))
1011 0 : dio_zero_block(dio, sdio, 0, map_bh);
1012 :
1013 : /*
1014 : * Work out, in this_chunk_blocks, how much disk we
1015 : * can add to this page
1016 : */
1017 0 : this_chunk_blocks = sdio->blocks_available;
1018 0 : u = (to - from) >> blkbits;
1019 0 : if (this_chunk_blocks > u)
1020 : this_chunk_blocks = u;
1021 0 : u = sdio->final_block_in_request - sdio->block_in_file;
1022 0 : if (this_chunk_blocks > u)
1023 : this_chunk_blocks = u;
1024 0 : this_chunk_bytes = this_chunk_blocks << blkbits;
1025 0 : BUG_ON(this_chunk_bytes == 0);
1026 :
1027 0 : if (this_chunk_blocks == sdio->blocks_available)
1028 0 : sdio->boundary = buffer_boundary(map_bh);
1029 0 : ret = submit_page_section(dio, sdio, page,
1030 : from,
1031 : this_chunk_bytes,
1032 : sdio->next_block_for_io,
1033 : map_bh);
1034 0 : if (ret) {
1035 0 : dio_unpin_page(dio, page);
1036 0 : goto out;
1037 : }
1038 0 : sdio->next_block_for_io += this_chunk_blocks;
1039 :
1040 0 : sdio->block_in_file += this_chunk_blocks;
1041 0 : from += this_chunk_bytes;
1042 0 : dio->result += this_chunk_bytes;
1043 0 : sdio->blocks_available -= this_chunk_blocks;
1044 0 : next_block:
1045 0 : BUG_ON(sdio->block_in_file > sdio->final_block_in_request);
1046 0 : 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 0 : dio_unpin_page(dio, page);
1052 : }
1053 0 : out:
1054 : return ret;
1055 : }
1056 :
1057 0 : static inline int drop_refcount(struct dio *dio)
1058 : {
1059 0 : int ret2;
1060 0 : 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 0 : spin_lock_irqsave(&dio->bio_lock, flags);
1074 0 : ret2 = --dio->refcount;
1075 0 : spin_unlock_irqrestore(&dio->bio_lock, flags);
1076 0 : 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 0 : 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 0 : unsigned i_blkbits = READ_ONCE(inode->i_blkbits);
1110 0 : unsigned blkbits = i_blkbits;
1111 0 : unsigned blocksize_mask = (1 << blkbits) - 1;
1112 0 : ssize_t retval = -EINVAL;
1113 0 : const size_t count = iov_iter_count(iter);
1114 0 : loff_t offset = iocb->ki_pos;
1115 0 : const loff_t end = offset + count;
1116 0 : struct dio *dio;
1117 0 : struct dio_submit sdio = { 0, };
1118 0 : struct buffer_head map_bh = { 0, };
1119 0 : struct blk_plug plug;
1120 0 : unsigned long align = offset | iov_iter_alignment(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 0 : if (iov_iter_rw(iter) == READ && !count)
1129 : return 0;
1130 :
1131 0 : dio = kmem_cache_alloc(dio_cache, GFP_KERNEL);
1132 0 : 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 0 : memset(dio, 0, offsetof(struct dio, pages));
1140 :
1141 0 : dio->flags = flags;
1142 0 : if (dio->flags & DIO_LOCKING && iov_iter_rw(iter) == READ) {
1143 : /* will be released by direct_io_worker */
1144 0 : inode_lock(inode);
1145 : }
1146 0 : dio->is_pinned = iov_iter_extract_will_pin(iter);
1147 :
1148 : /* Once we sampled i_size check for reads beyond EOF */
1149 0 : dio->i_size = i_size_read(inode);
1150 0 : if (iov_iter_rw(iter) == READ && offset >= dio->i_size) {
1151 0 : retval = 0;
1152 0 : goto fail_dio;
1153 : }
1154 :
1155 0 : if (align & blocksize_mask) {
1156 0 : if (bdev)
1157 0 : blkbits = blksize_bits(bdev_logical_block_size(bdev));
1158 0 : blocksize_mask = (1 << blkbits) - 1;
1159 0 : if (align & blocksize_mask)
1160 0 : goto fail_dio;
1161 : }
1162 :
1163 0 : if (dio->flags & DIO_LOCKING && iov_iter_rw(iter) == READ) {
1164 0 : struct address_space *mapping = iocb->ki_filp->f_mapping;
1165 :
1166 0 : retval = filemap_write_and_wait_range(mapping, offset, end - 1);
1167 0 : if (retval)
1168 0 : 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 0 : if (is_sync_kiocb(iocb))
1178 0 : dio->is_async = false;
1179 0 : else if (iov_iter_rw(iter) == WRITE && end > i_size_read(inode))
1180 0 : dio->is_async = false;
1181 : else
1182 0 : dio->is_async = true;
1183 :
1184 0 : dio->inode = inode;
1185 0 : if (iov_iter_rw(iter) == WRITE) {
1186 0 : dio->opf = REQ_OP_WRITE | REQ_SYNC | REQ_IDLE;
1187 0 : if (iocb->ki_flags & IOCB_NOWAIT)
1188 0 : dio->opf |= REQ_NOWAIT;
1189 : } else {
1190 0 : 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 0 : if (dio->is_async && iov_iter_rw(iter) == WRITE) {
1198 0 : retval = 0;
1199 0 : if (iocb_is_dsync(iocb))
1200 0 : retval = dio_set_defer_completion(dio);
1201 0 : 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 0 : retval = sb_init_dio_done_wq(dio->inode->i_sb);
1208 : }
1209 0 : if (retval)
1210 0 : goto fail_dio;
1211 : }
1212 :
1213 : /*
1214 : * Will be decremented at I/O completion time.
1215 : */
1216 0 : inode_dio_begin(inode);
1217 :
1218 0 : retval = 0;
1219 0 : sdio.blkbits = blkbits;
1220 0 : sdio.blkfactor = i_blkbits - blkbits;
1221 0 : sdio.block_in_file = offset >> blkbits;
1222 :
1223 0 : sdio.get_block = get_block;
1224 0 : dio->end_io = end_io;
1225 0 : sdio.final_block_in_bio = -1;
1226 0 : sdio.next_block_for_io = -1;
1227 :
1228 0 : dio->iocb = iocb;
1229 :
1230 0 : spin_lock_init(&dio->bio_lock);
1231 0 : dio->refcount = 1;
1232 :
1233 0 : dio->should_dirty = user_backed_iter(iter) && iov_iter_rw(iter) == READ;
1234 0 : sdio.iter = iter;
1235 0 : 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 0 : if (unlikely(sdio.blkfactor))
1242 0 : sdio.pages_in_io = 2;
1243 :
1244 0 : sdio.pages_in_io += iov_iter_npages(iter, INT_MAX);
1245 :
1246 0 : blk_start_plug(&plug);
1247 :
1248 0 : retval = do_direct_IO(dio, &sdio, &map_bh);
1249 0 : if (retval)
1250 0 : dio_cleanup(dio, &sdio);
1251 :
1252 0 : if (retval == -ENOTBLK) {
1253 : /*
1254 : * The remaining part of the request will be
1255 : * handled by buffered I/O when we return
1256 : */
1257 0 : 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 0 : dio_zero_block(dio, &sdio, 1, &map_bh);
1264 :
1265 0 : if (sdio.cur_page) {
1266 0 : ssize_t ret2;
1267 :
1268 0 : ret2 = dio_send_cur_page(dio, &sdio, &map_bh);
1269 0 : if (retval == 0)
1270 0 : retval = ret2;
1271 0 : dio_unpin_page(dio, sdio.cur_page);
1272 0 : sdio.cur_page = NULL;
1273 : }
1274 0 : if (sdio.bio)
1275 0 : dio_bio_submit(dio, &sdio);
1276 :
1277 0 : 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 0 : dio_cleanup(dio, &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 0 : if (iov_iter_rw(iter) == READ && (dio->flags & DIO_LOCKING))
1291 0 : inode_unlock(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 0 : BUG_ON(retval == -EIOCBQUEUED);
1301 0 : if (dio->is_async && retval == 0 && dio->result &&
1302 0 : (iov_iter_rw(iter) == READ || dio->result == count))
1303 : retval = -EIOCBQUEUED;
1304 : else
1305 0 : dio_await_completion(dio);
1306 :
1307 0 : if (drop_refcount(dio) == 0) {
1308 0 : retval = dio_complete(dio, retval, DIO_COMPLETE_INVALIDATE);
1309 : } else
1310 0 : BUG_ON(retval != -EIOCBQUEUED);
1311 :
1312 : return retval;
1313 :
1314 0 : fail_dio:
1315 0 : if (dio->flags & DIO_LOCKING && iov_iter_rw(iter) == READ)
1316 0 : inode_unlock(inode);
1317 :
1318 0 : kmem_cache_free(dio_cache, dio);
1319 0 : return retval;
1320 : }
1321 : EXPORT_SYMBOL(__blockdev_direct_IO);
1322 :
1323 0 : static __init int dio_init(void)
1324 : {
1325 0 : dio_cache = KMEM_CACHE(dio, SLAB_PANIC);
1326 0 : return 0;
1327 : }
1328 : module_init(dio_init)
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