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 get_user_pages(). This determines
46 : * 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 : dio_submit_t *submit_io; /* IO submition function */
90 :
91 : loff_t logical_offset_in_bio; /* current first logical block in bio */
92 : sector_t final_block_in_bio; /* current final block in bio + 1 */
93 : sector_t next_block_for_io; /* next block to be put under IO,
94 : in dio_blocks units */
95 :
96 : /*
97 : * Deferred addition of a page to the dio. These variables are
98 : * private to dio_send_cur_page(), submit_page_section() and
99 : * dio_bio_add_page().
100 : */
101 : struct page *cur_page; /* The page */
102 : unsigned cur_page_offset; /* Offset into it, in bytes */
103 : unsigned cur_page_len; /* Nr of bytes at cur_page_offset */
104 : sector_t cur_page_block; /* Where it starts */
105 : loff_t cur_page_fs_offset; /* Offset in file */
106 :
107 : struct iov_iter *iter;
108 : /*
109 : * Page queue. These variables belong to dio_refill_pages() and
110 : * dio_get_page().
111 : */
112 : unsigned head; /* next page to process */
113 : unsigned tail; /* last valid page + 1 */
114 : size_t from, to;
115 : };
116 :
117 : /* dio_state communicated between submission path and end_io */
118 : struct dio {
119 : int flags; /* doesn't change */
120 : int op;
121 : int op_flags;
122 : blk_qc_t bio_cookie;
123 : struct gendisk *bio_disk;
124 : struct inode *inode;
125 : loff_t i_size; /* i_size when submitted */
126 : dio_iodone_t *end_io; /* IO completion function */
127 :
128 : void *private; /* copy from map_bh.b_private */
129 :
130 : /* BIO completion state */
131 : spinlock_t bio_lock; /* protects BIO fields below */
132 : int page_errors; /* errno from get_user_pages() */
133 : int is_async; /* is IO async ? */
134 : bool defer_completion; /* defer AIO completion to workqueue? */
135 : bool should_dirty; /* if pages should be dirtied */
136 : int io_error; /* IO error in completion path */
137 : unsigned long refcount; /* direct_io_worker() and bios */
138 : struct bio *bio_list; /* singly linked via bi_private */
139 : struct task_struct *waiter; /* waiting task (NULL if none) */
140 :
141 : /* AIO related stuff */
142 : struct kiocb *iocb; /* kiocb */
143 : ssize_t result; /* IO result */
144 :
145 : /*
146 : * pages[] (and any fields placed after it) are not zeroed out at
147 : * allocation time. Don't add new fields after pages[] unless you
148 : * wish that they not be zeroed.
149 : */
150 : union {
151 : struct page *pages[DIO_PAGES]; /* page buffer */
152 : struct work_struct complete_work;/* deferred AIO completion */
153 : };
154 : } ____cacheline_aligned_in_smp;
155 :
156 : static struct kmem_cache *dio_cache __read_mostly;
157 :
158 : /*
159 : * How many pages are in the queue?
160 : */
161 0 : static inline unsigned dio_pages_present(struct dio_submit *sdio)
162 : {
163 0 : return sdio->tail - sdio->head;
164 : }
165 :
166 : /*
167 : * Go grab and pin some userspace pages. Typically we'll get 64 at a time.
168 : */
169 0 : static inline int dio_refill_pages(struct dio *dio, struct dio_submit *sdio)
170 : {
171 0 : ssize_t ret;
172 :
173 0 : ret = iov_iter_get_pages(sdio->iter, dio->pages, LONG_MAX, DIO_PAGES,
174 : &sdio->from);
175 :
176 0 : if (ret < 0 && sdio->blocks_available && (dio->op == REQ_OP_WRITE)) {
177 0 : struct page *page = ZERO_PAGE(0);
178 : /*
179 : * A memory fault, but the filesystem has some outstanding
180 : * mapped blocks. We need to use those blocks up to avoid
181 : * leaking stale data in the file.
182 : */
183 0 : if (dio->page_errors == 0)
184 0 : dio->page_errors = ret;
185 0 : get_page(page);
186 0 : dio->pages[0] = page;
187 0 : sdio->head = 0;
188 0 : sdio->tail = 1;
189 0 : sdio->from = 0;
190 0 : sdio->to = PAGE_SIZE;
191 0 : return 0;
192 : }
193 :
194 0 : if (ret >= 0) {
195 0 : iov_iter_advance(sdio->iter, ret);
196 0 : ret += sdio->from;
197 0 : sdio->head = 0;
198 0 : sdio->tail = (ret + PAGE_SIZE - 1) / PAGE_SIZE;
199 0 : sdio->to = ((ret - 1) & (PAGE_SIZE - 1)) + 1;
200 0 : return 0;
201 : }
202 0 : return ret;
203 : }
204 :
205 : /*
206 : * Get another userspace page. Returns an ERR_PTR on error. Pages are
207 : * buffered inside the dio so that we can call get_user_pages() against a
208 : * decent number of pages, less frequently. To provide nicer use of the
209 : * L1 cache.
210 : */
211 0 : static inline struct page *dio_get_page(struct dio *dio,
212 : struct dio_submit *sdio)
213 : {
214 0 : if (dio_pages_present(sdio) == 0) {
215 0 : int ret;
216 :
217 0 : ret = dio_refill_pages(dio, sdio);
218 0 : if (ret)
219 0 : return ERR_PTR(ret);
220 0 : BUG_ON(dio_pages_present(sdio) == 0);
221 : }
222 0 : return dio->pages[sdio->head];
223 : }
224 :
225 : /*
226 : * dio_complete() - called when all DIO BIO I/O has been completed
227 : *
228 : * This drops i_dio_count, lets interested parties know that a DIO operation
229 : * has completed, and calculates the resulting return code for the operation.
230 : *
231 : * It lets the filesystem know if it registered an interest earlier via
232 : * get_block. Pass the private field of the map buffer_head so that
233 : * filesystems can use it to hold additional state between get_block calls and
234 : * dio_complete.
235 : */
236 0 : static ssize_t dio_complete(struct dio *dio, ssize_t ret, unsigned int flags)
237 : {
238 0 : loff_t offset = dio->iocb->ki_pos;
239 0 : ssize_t transferred = 0;
240 0 : int err;
241 :
242 : /*
243 : * AIO submission can race with bio completion to get here while
244 : * expecting to have the last io completed by bio completion.
245 : * In that case -EIOCBQUEUED is in fact not an error we want
246 : * to preserve through this call.
247 : */
248 0 : if (ret == -EIOCBQUEUED)
249 0 : ret = 0;
250 :
251 0 : if (dio->result) {
252 0 : transferred = dio->result;
253 :
254 : /* Check for short read case */
255 0 : if ((dio->op == REQ_OP_READ) &&
256 0 : ((offset + transferred) > dio->i_size))
257 0 : transferred = dio->i_size - offset;
258 : /* ignore EFAULT if some IO has been done */
259 0 : if (unlikely(ret == -EFAULT) && transferred)
260 : ret = 0;
261 : }
262 :
263 0 : if (ret == 0)
264 0 : ret = dio->page_errors;
265 0 : if (ret == 0)
266 0 : ret = dio->io_error;
267 0 : if (ret == 0)
268 0 : ret = transferred;
269 :
270 0 : if (dio->end_io) {
271 : // XXX: ki_pos??
272 0 : err = dio->end_io(dio->iocb, offset, ret, dio->private);
273 0 : if (err)
274 0 : ret = err;
275 : }
276 :
277 : /*
278 : * Try again to invalidate clean pages which might have been cached by
279 : * non-direct readahead, or faulted in by get_user_pages() if the source
280 : * of the write was an mmap'ed region of the file we're writing. Either
281 : * one is a pretty crazy thing to do, so we don't support it 100%. If
282 : * this invalidation fails, tough, the write still worked...
283 : *
284 : * And this page cache invalidation has to be after dio->end_io(), as
285 : * some filesystems convert unwritten extents to real allocations in
286 : * end_io() when necessary, otherwise a racing buffer read would cache
287 : * zeros from unwritten extents.
288 : */
289 0 : if (flags & DIO_COMPLETE_INVALIDATE &&
290 0 : ret > 0 && dio->op == REQ_OP_WRITE &&
291 0 : dio->inode->i_mapping->nrpages) {
292 0 : err = invalidate_inode_pages2_range(dio->inode->i_mapping,
293 0 : offset >> PAGE_SHIFT,
294 0 : (offset + ret - 1) >> PAGE_SHIFT);
295 0 : if (err)
296 0 : dio_warn_stale_pagecache(dio->iocb->ki_filp);
297 : }
298 :
299 0 : inode_dio_end(dio->inode);
300 :
301 0 : if (flags & DIO_COMPLETE_ASYNC) {
302 : /*
303 : * generic_write_sync expects ki_pos to have been updated
304 : * already, but the submission path only does this for
305 : * synchronous I/O.
306 : */
307 0 : dio->iocb->ki_pos += transferred;
308 :
309 0 : if (ret > 0 && dio->op == REQ_OP_WRITE)
310 0 : ret = generic_write_sync(dio->iocb, ret);
311 0 : dio->iocb->ki_complete(dio->iocb, ret, 0);
312 : }
313 :
314 0 : kmem_cache_free(dio_cache, dio);
315 0 : return ret;
316 : }
317 :
318 0 : static void dio_aio_complete_work(struct work_struct *work)
319 : {
320 0 : struct dio *dio = container_of(work, struct dio, complete_work);
321 :
322 0 : dio_complete(dio, 0, DIO_COMPLETE_ASYNC | DIO_COMPLETE_INVALIDATE);
323 0 : }
324 :
325 : static blk_status_t dio_bio_complete(struct dio *dio, struct bio *bio);
326 :
327 : /*
328 : * Asynchronous IO callback.
329 : */
330 0 : static void dio_bio_end_aio(struct bio *bio)
331 : {
332 0 : struct dio *dio = bio->bi_private;
333 0 : unsigned long remaining;
334 0 : unsigned long flags;
335 0 : bool defer_completion = false;
336 :
337 : /* cleanup the bio */
338 0 : dio_bio_complete(dio, bio);
339 :
340 0 : spin_lock_irqsave(&dio->bio_lock, flags);
341 0 : remaining = --dio->refcount;
342 0 : if (remaining == 1 && dio->waiter)
343 0 : wake_up_process(dio->waiter);
344 0 : spin_unlock_irqrestore(&dio->bio_lock, flags);
345 :
346 0 : if (remaining == 0) {
347 : /*
348 : * Defer completion when defer_completion is set or
349 : * when the inode has pages mapped and this is AIO write.
350 : * We need to invalidate those pages because there is a
351 : * chance they contain stale data in the case buffered IO
352 : * went in between AIO submission and completion into the
353 : * same region.
354 : */
355 0 : if (dio->result)
356 0 : defer_completion = dio->defer_completion ||
357 0 : (dio->op == REQ_OP_WRITE &&
358 0 : dio->inode->i_mapping->nrpages);
359 0 : if (defer_completion) {
360 0 : INIT_WORK(&dio->complete_work, dio_aio_complete_work);
361 0 : queue_work(dio->inode->i_sb->s_dio_done_wq,
362 : &dio->complete_work);
363 : } else {
364 0 : dio_complete(dio, 0, DIO_COMPLETE_ASYNC);
365 : }
366 : }
367 0 : }
368 :
369 : /*
370 : * The BIO completion handler simply queues the BIO up for the process-context
371 : * handler.
372 : *
373 : * During I/O bi_private points at the dio. After I/O, bi_private is used to
374 : * implement a singly-linked list of completed BIOs, at dio->bio_list.
375 : */
376 0 : static void dio_bio_end_io(struct bio *bio)
377 : {
378 0 : struct dio *dio = bio->bi_private;
379 0 : unsigned long flags;
380 :
381 0 : spin_lock_irqsave(&dio->bio_lock, flags);
382 0 : bio->bi_private = dio->bio_list;
383 0 : dio->bio_list = bio;
384 0 : if (--dio->refcount == 1 && dio->waiter)
385 0 : wake_up_process(dio->waiter);
386 0 : spin_unlock_irqrestore(&dio->bio_lock, flags);
387 0 : }
388 :
389 : static inline void
390 0 : dio_bio_alloc(struct dio *dio, struct dio_submit *sdio,
391 : struct block_device *bdev,
392 : sector_t first_sector, int nr_vecs)
393 : {
394 0 : struct bio *bio;
395 :
396 : /*
397 : * bio_alloc() is guaranteed to return a bio when allowed to sleep and
398 : * we request a valid number of vectors.
399 : */
400 0 : bio = bio_alloc(GFP_KERNEL, nr_vecs);
401 :
402 0 : bio_set_dev(bio, bdev);
403 0 : bio->bi_iter.bi_sector = first_sector;
404 0 : bio_set_op_attrs(bio, dio->op, dio->op_flags);
405 0 : if (dio->is_async)
406 0 : bio->bi_end_io = dio_bio_end_aio;
407 : else
408 0 : bio->bi_end_io = dio_bio_end_io;
409 :
410 0 : bio->bi_write_hint = dio->iocb->ki_hint;
411 :
412 0 : sdio->bio = bio;
413 0 : sdio->logical_offset_in_bio = sdio->cur_page_fs_offset;
414 0 : }
415 :
416 : /*
417 : * In the AIO read case we speculatively dirty the pages before starting IO.
418 : * During IO completion, any of these pages which happen to have been written
419 : * back will be redirtied by bio_check_pages_dirty().
420 : *
421 : * bios hold a dio reference between submit_bio and ->end_io.
422 : */
423 0 : static inline void dio_bio_submit(struct dio *dio, struct dio_submit *sdio)
424 : {
425 0 : struct bio *bio = sdio->bio;
426 0 : unsigned long flags;
427 :
428 0 : bio->bi_private = dio;
429 : /* don't account direct I/O as memory stall */
430 0 : bio_clear_flag(bio, BIO_WORKINGSET);
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 : if (sdio->submit_io) {
442 0 : sdio->submit_io(bio, dio->inode, sdio->logical_offset_in_bio);
443 0 : dio->bio_cookie = BLK_QC_T_NONE;
444 : } else
445 0 : dio->bio_cookie = submit_bio(bio);
446 :
447 0 : sdio->bio = NULL;
448 0 : sdio->boundary = 0;
449 0 : sdio->logical_offset_in_bio = 0;
450 0 : }
451 :
452 : /*
453 : * Release any resources in case of a failure
454 : */
455 0 : static inline void dio_cleanup(struct dio *dio, struct dio_submit *sdio)
456 : {
457 0 : while (sdio->head < sdio->tail)
458 0 : put_page(dio->pages[sdio->head++]);
459 0 : }
460 :
461 : /*
462 : * Wait for the next BIO to complete. Remove it and return it. NULL is
463 : * returned once all BIOs have been completed. This must only be called once
464 : * all bios have been issued so that dio->refcount can only decrease. This
465 : * requires that the caller hold a reference on the dio.
466 : */
467 0 : static struct bio *dio_await_one(struct dio *dio)
468 : {
469 0 : unsigned long flags;
470 0 : struct bio *bio = NULL;
471 :
472 0 : spin_lock_irqsave(&dio->bio_lock, flags);
473 :
474 : /*
475 : * Wait as long as the list is empty and there are bios in flight. bio
476 : * completion drops the count, maybe adds to the list, and wakes while
477 : * holding the bio_lock so we don't need set_current_state()'s barrier
478 : * and can call it after testing our condition.
479 : */
480 0 : while (dio->refcount > 1 && dio->bio_list == NULL) {
481 0 : __set_current_state(TASK_UNINTERRUPTIBLE);
482 0 : dio->waiter = current;
483 0 : spin_unlock_irqrestore(&dio->bio_lock, flags);
484 0 : if (!(dio->iocb->ki_flags & IOCB_HIPRI) ||
485 0 : !blk_poll(dio->bio_disk->queue, dio->bio_cookie, true))
486 0 : blk_io_schedule();
487 : /* wake up sets us TASK_RUNNING */
488 0 : spin_lock_irqsave(&dio->bio_lock, flags);
489 0 : dio->waiter = NULL;
490 : }
491 0 : if (dio->bio_list) {
492 0 : bio = dio->bio_list;
493 0 : dio->bio_list = bio->bi_private;
494 : }
495 0 : spin_unlock_irqrestore(&dio->bio_lock, flags);
496 0 : return bio;
497 : }
498 :
499 : /*
500 : * Process one completed BIO. No locks are held.
501 : */
502 0 : static blk_status_t dio_bio_complete(struct dio *dio, struct bio *bio)
503 : {
504 0 : blk_status_t err = bio->bi_status;
505 0 : bool should_dirty = dio->op == REQ_OP_READ && dio->should_dirty;
506 :
507 0 : if (err) {
508 0 : if (err == BLK_STS_AGAIN && (bio->bi_opf & REQ_NOWAIT))
509 0 : dio->io_error = -EAGAIN;
510 : else
511 0 : dio->io_error = -EIO;
512 : }
513 :
514 0 : if (dio->is_async && should_dirty) {
515 0 : bio_check_pages_dirty(bio); /* transfers ownership */
516 : } else {
517 0 : bio_release_pages(bio, should_dirty);
518 0 : bio_put(bio);
519 : }
520 0 : return err;
521 : }
522 :
523 : /*
524 : * Wait on and process all in-flight BIOs. This must only be called once
525 : * all bios have been issued so that the refcount can only decrease.
526 : * This just waits for all bios to make it through dio_bio_complete. IO
527 : * errors are propagated through dio->io_error and should be propagated via
528 : * dio_complete().
529 : */
530 0 : static void dio_await_completion(struct dio *dio)
531 : {
532 0 : struct bio *bio;
533 0 : do {
534 0 : bio = dio_await_one(dio);
535 0 : if (bio)
536 0 : dio_bio_complete(dio, bio);
537 0 : } while (bio);
538 0 : }
539 :
540 : /*
541 : * A really large O_DIRECT read or write can generate a lot of BIOs. So
542 : * to keep the memory consumption sane we periodically reap any completed BIOs
543 : * during the BIO generation phase.
544 : *
545 : * This also helps to limit the peak amount of pinned userspace memory.
546 : */
547 0 : static inline int dio_bio_reap(struct dio *dio, struct dio_submit *sdio)
548 : {
549 0 : int ret = 0;
550 :
551 0 : if (sdio->reap_counter++ >= 64) {
552 0 : while (dio->bio_list) {
553 0 : unsigned long flags;
554 0 : struct bio *bio;
555 0 : int ret2;
556 :
557 0 : spin_lock_irqsave(&dio->bio_lock, flags);
558 0 : bio = dio->bio_list;
559 0 : dio->bio_list = bio->bi_private;
560 0 : spin_unlock_irqrestore(&dio->bio_lock, flags);
561 0 : ret2 = blk_status_to_errno(dio_bio_complete(dio, bio));
562 0 : if (ret == 0)
563 0 : ret = ret2;
564 : }
565 0 : sdio->reap_counter = 0;
566 : }
567 0 : return ret;
568 : }
569 :
570 : /*
571 : * Create workqueue for deferred direct IO completions. We allocate the
572 : * workqueue when it's first needed. This avoids creating workqueue for
573 : * filesystems that don't need it and also allows us to create the workqueue
574 : * late enough so the we can include s_id in the name of the workqueue.
575 : */
576 0 : int sb_init_dio_done_wq(struct super_block *sb)
577 : {
578 0 : struct workqueue_struct *old;
579 0 : struct workqueue_struct *wq = alloc_workqueue("dio/%s",
580 : WQ_MEM_RECLAIM, 0,
581 0 : sb->s_id);
582 0 : if (!wq)
583 : return -ENOMEM;
584 : /*
585 : * This has to be atomic as more DIOs can race to create the workqueue
586 : */
587 0 : old = cmpxchg(&sb->s_dio_done_wq, NULL, wq);
588 : /* Someone created workqueue before us? Free ours... */
589 0 : if (old)
590 0 : destroy_workqueue(wq);
591 : return 0;
592 : }
593 :
594 0 : static int dio_set_defer_completion(struct dio *dio)
595 : {
596 0 : struct super_block *sb = dio->inode->i_sb;
597 :
598 0 : if (dio->defer_completion)
599 : return 0;
600 0 : dio->defer_completion = true;
601 0 : if (!sb->s_dio_done_wq)
602 0 : return sb_init_dio_done_wq(sb);
603 : return 0;
604 : }
605 :
606 : /*
607 : * Call into the fs to map some more disk blocks. We record the current number
608 : * of available blocks at sdio->blocks_available. These are in units of the
609 : * fs blocksize, i_blocksize(inode).
610 : *
611 : * The fs is allowed to map lots of blocks at once. If it wants to do that,
612 : * it uses the passed inode-relative block number as the file offset, as usual.
613 : *
614 : * get_block() is passed the number of i_blkbits-sized blocks which direct_io
615 : * has remaining to do. The fs should not map more than this number of blocks.
616 : *
617 : * If the fs has mapped a lot of blocks, it should populate bh->b_size to
618 : * indicate how much contiguous disk space has been made available at
619 : * bh->b_blocknr.
620 : *
621 : * If *any* of the mapped blocks are new, then the fs must set buffer_new().
622 : * This isn't very efficient...
623 : *
624 : * In the case of filesystem holes: the fs may return an arbitrarily-large
625 : * hole by returning an appropriate value in b_size and by clearing
626 : * buffer_mapped(). However the direct-io code will only process holes one
627 : * block at a time - it will repeatedly call get_block() as it walks the hole.
628 : */
629 0 : static int get_more_blocks(struct dio *dio, struct dio_submit *sdio,
630 : struct buffer_head *map_bh)
631 : {
632 0 : int ret;
633 0 : sector_t fs_startblk; /* Into file, in filesystem-sized blocks */
634 0 : sector_t fs_endblk; /* Into file, in filesystem-sized blocks */
635 0 : unsigned long fs_count; /* Number of filesystem-sized blocks */
636 0 : int create;
637 0 : unsigned int i_blkbits = sdio->blkbits + sdio->blkfactor;
638 0 : loff_t i_size;
639 :
640 : /*
641 : * If there was a memory error and we've overwritten all the
642 : * mapped blocks then we can now return that memory error
643 : */
644 0 : ret = dio->page_errors;
645 0 : if (ret == 0) {
646 0 : BUG_ON(sdio->block_in_file >= sdio->final_block_in_request);
647 0 : fs_startblk = sdio->block_in_file >> sdio->blkfactor;
648 0 : fs_endblk = (sdio->final_block_in_request - 1) >>
649 : sdio->blkfactor;
650 0 : fs_count = fs_endblk - fs_startblk + 1;
651 :
652 0 : map_bh->b_state = 0;
653 0 : map_bh->b_size = fs_count << i_blkbits;
654 :
655 : /*
656 : * For writes that could fill holes inside i_size on a
657 : * DIO_SKIP_HOLES filesystem we forbid block creations: only
658 : * overwrites are permitted. We will return early to the caller
659 : * once we see an unmapped buffer head returned, and the caller
660 : * will fall back to buffered I/O.
661 : *
662 : * Otherwise the decision is left to the get_blocks method,
663 : * which may decide to handle it or also return an unmapped
664 : * buffer head.
665 : */
666 0 : create = dio->op == REQ_OP_WRITE;
667 0 : if (dio->flags & DIO_SKIP_HOLES) {
668 0 : i_size = i_size_read(dio->inode);
669 0 : if (i_size && fs_startblk <= (i_size - 1) >> i_blkbits)
670 0 : create = 0;
671 : }
672 :
673 0 : ret = (*sdio->get_block)(dio->inode, fs_startblk,
674 : map_bh, create);
675 :
676 : /* Store for completion */
677 0 : dio->private = map_bh->b_private;
678 :
679 0 : if (ret == 0 && buffer_defer_completion(map_bh))
680 0 : ret = dio_set_defer_completion(dio);
681 : }
682 0 : return ret;
683 : }
684 :
685 : /*
686 : * There is no bio. Make one now.
687 : */
688 0 : static inline int dio_new_bio(struct dio *dio, struct dio_submit *sdio,
689 : sector_t start_sector, struct buffer_head *map_bh)
690 : {
691 0 : sector_t sector;
692 0 : int ret, nr_pages;
693 :
694 0 : ret = dio_bio_reap(dio, sdio);
695 0 : if (ret)
696 0 : goto out;
697 0 : sector = start_sector << (sdio->blkbits - 9);
698 0 : nr_pages = bio_max_segs(sdio->pages_in_io);
699 0 : BUG_ON(nr_pages <= 0);
700 0 : dio_bio_alloc(dio, sdio, map_bh->b_bdev, sector, nr_pages);
701 0 : sdio->boundary = 0;
702 0 : out:
703 0 : return ret;
704 : }
705 :
706 : /*
707 : * Attempt to put the current chunk of 'cur_page' into the current BIO. If
708 : * that was successful then update final_block_in_bio and take a ref against
709 : * the just-added page.
710 : *
711 : * Return zero on success. Non-zero means the caller needs to start a new BIO.
712 : */
713 0 : static inline int dio_bio_add_page(struct dio_submit *sdio)
714 : {
715 0 : int ret;
716 :
717 0 : ret = bio_add_page(sdio->bio, sdio->cur_page,
718 : sdio->cur_page_len, sdio->cur_page_offset);
719 0 : if (ret == sdio->cur_page_len) {
720 : /*
721 : * Decrement count only, if we are done with this page
722 : */
723 0 : if ((sdio->cur_page_len + sdio->cur_page_offset) == PAGE_SIZE)
724 0 : sdio->pages_in_io--;
725 0 : get_page(sdio->cur_page);
726 0 : sdio->final_block_in_bio = sdio->cur_page_block +
727 0 : (sdio->cur_page_len >> sdio->blkbits);
728 0 : ret = 0;
729 : } else {
730 : ret = 1;
731 : }
732 0 : return ret;
733 : }
734 :
735 : /*
736 : * Put cur_page under IO. The section of cur_page which is described by
737 : * cur_page_offset,cur_page_len is put into a BIO. The section of cur_page
738 : * starts on-disk at cur_page_block.
739 : *
740 : * We take a ref against the page here (on behalf of its presence in the bio).
741 : *
742 : * The caller of this function is responsible for removing cur_page from the
743 : * dio, and for dropping the refcount which came from that presence.
744 : */
745 0 : static inline int dio_send_cur_page(struct dio *dio, struct dio_submit *sdio,
746 : struct buffer_head *map_bh)
747 : {
748 0 : int ret = 0;
749 :
750 0 : if (sdio->bio) {
751 0 : loff_t cur_offset = sdio->cur_page_fs_offset;
752 0 : loff_t bio_next_offset = sdio->logical_offset_in_bio +
753 0 : sdio->bio->bi_iter.bi_size;
754 :
755 : /*
756 : * See whether this new request is contiguous with the old.
757 : *
758 : * Btrfs cannot handle having logically non-contiguous requests
759 : * submitted. For example if you have
760 : *
761 : * Logical: [0-4095][HOLE][8192-12287]
762 : * Physical: [0-4095] [4096-8191]
763 : *
764 : * We cannot submit those pages together as one BIO. So if our
765 : * current logical offset in the file does not equal what would
766 : * be the next logical offset in the bio, submit the bio we
767 : * have.
768 : */
769 0 : if (sdio->final_block_in_bio != sdio->cur_page_block ||
770 : cur_offset != bio_next_offset)
771 0 : dio_bio_submit(dio, sdio);
772 : }
773 :
774 0 : if (sdio->bio == NULL) {
775 0 : ret = dio_new_bio(dio, sdio, sdio->cur_page_block, map_bh);
776 0 : if (ret)
777 0 : goto out;
778 : }
779 :
780 0 : if (dio_bio_add_page(sdio) != 0) {
781 0 : dio_bio_submit(dio, sdio);
782 0 : ret = dio_new_bio(dio, sdio, sdio->cur_page_block, map_bh);
783 0 : if (ret == 0) {
784 0 : ret = dio_bio_add_page(sdio);
785 0 : BUG_ON(ret != 0);
786 : }
787 : }
788 0 : out:
789 0 : return ret;
790 : }
791 :
792 : /*
793 : * An autonomous function to put a chunk of a page under deferred IO.
794 : *
795 : * The caller doesn't actually know (or care) whether this piece of page is in
796 : * a BIO, or is under IO or whatever. We just take care of all possible
797 : * situations here. The separation between the logic of do_direct_IO() and
798 : * that of submit_page_section() is important for clarity. Please don't break.
799 : *
800 : * The chunk of page starts on-disk at blocknr.
801 : *
802 : * We perform deferred IO, by recording the last-submitted page inside our
803 : * private part of the dio structure. If possible, we just expand the IO
804 : * across that page here.
805 : *
806 : * If that doesn't work out then we put the old page into the bio and add this
807 : * page to the dio instead.
808 : */
809 : static inline int
810 0 : submit_page_section(struct dio *dio, struct dio_submit *sdio, struct page *page,
811 : unsigned offset, unsigned len, sector_t blocknr,
812 : struct buffer_head *map_bh)
813 : {
814 0 : int ret = 0;
815 :
816 0 : if (dio->op == REQ_OP_WRITE) {
817 : /*
818 : * Read accounting is performed in submit_bio()
819 : */
820 0 : task_io_account_write(len);
821 : }
822 :
823 : /*
824 : * Can we just grow the current page's presence in the dio?
825 : */
826 0 : if (sdio->cur_page == page &&
827 0 : sdio->cur_page_offset + sdio->cur_page_len == offset &&
828 0 : sdio->cur_page_block +
829 0 : (sdio->cur_page_len >> sdio->blkbits) == blocknr) {
830 0 : sdio->cur_page_len += len;
831 0 : goto out;
832 : }
833 :
834 : /*
835 : * If there's a deferred page already there then send it.
836 : */
837 0 : if (sdio->cur_page) {
838 0 : ret = dio_send_cur_page(dio, sdio, map_bh);
839 0 : put_page(sdio->cur_page);
840 0 : sdio->cur_page = NULL;
841 0 : if (ret)
842 : return ret;
843 : }
844 :
845 0 : get_page(page); /* It is in dio */
846 0 : sdio->cur_page = page;
847 0 : sdio->cur_page_offset = offset;
848 0 : sdio->cur_page_len = len;
849 0 : sdio->cur_page_block = blocknr;
850 0 : sdio->cur_page_fs_offset = sdio->block_in_file << sdio->blkbits;
851 0 : out:
852 : /*
853 : * If sdio->boundary then we want to schedule the IO now to
854 : * avoid metadata seeks.
855 : */
856 0 : if (sdio->boundary) {
857 0 : ret = dio_send_cur_page(dio, sdio, map_bh);
858 0 : if (sdio->bio)
859 0 : dio_bio_submit(dio, sdio);
860 0 : put_page(sdio->cur_page);
861 0 : sdio->cur_page = NULL;
862 : }
863 : return ret;
864 : }
865 :
866 : /*
867 : * If we are not writing the entire block and get_block() allocated
868 : * the block for us, we need to fill-in the unused portion of the
869 : * block with zeros. This happens only if user-buffer, fileoffset or
870 : * io length is not filesystem block-size multiple.
871 : *
872 : * `end' is zero if we're doing the start of the IO, 1 at the end of the
873 : * IO.
874 : */
875 0 : static inline void dio_zero_block(struct dio *dio, struct dio_submit *sdio,
876 : int end, struct buffer_head *map_bh)
877 : {
878 0 : unsigned dio_blocks_per_fs_block;
879 0 : unsigned this_chunk_blocks; /* In dio_blocks */
880 0 : unsigned this_chunk_bytes;
881 0 : struct page *page;
882 :
883 0 : sdio->start_zero_done = 1;
884 0 : if (!sdio->blkfactor || !buffer_new(map_bh))
885 0 : return;
886 :
887 0 : dio_blocks_per_fs_block = 1 << sdio->blkfactor;
888 0 : this_chunk_blocks = sdio->block_in_file & (dio_blocks_per_fs_block - 1);
889 :
890 0 : if (!this_chunk_blocks)
891 : return;
892 :
893 : /*
894 : * We need to zero out part of an fs block. It is either at the
895 : * beginning or the end of the fs block.
896 : */
897 0 : if (end)
898 0 : this_chunk_blocks = dio_blocks_per_fs_block - this_chunk_blocks;
899 :
900 0 : this_chunk_bytes = this_chunk_blocks << sdio->blkbits;
901 :
902 0 : page = ZERO_PAGE(0);
903 0 : if (submit_page_section(dio, sdio, page, 0, this_chunk_bytes,
904 : sdio->next_block_for_io, map_bh))
905 : return;
906 :
907 0 : sdio->next_block_for_io += this_chunk_blocks;
908 : }
909 :
910 : /*
911 : * Walk the user pages, and the file, mapping blocks to disk and generating
912 : * a sequence of (page,offset,len,block) mappings. These mappings are injected
913 : * into submit_page_section(), which takes care of the next stage of submission
914 : *
915 : * Direct IO against a blockdev is different from a file. Because we can
916 : * happily perform page-sized but 512-byte aligned IOs. It is important that
917 : * blockdev IO be able to have fine alignment and large sizes.
918 : *
919 : * So what we do is to permit the ->get_block function to populate bh.b_size
920 : * with the size of IO which is permitted at this offset and this i_blkbits.
921 : *
922 : * For best results, the blockdev should be set up with 512-byte i_blkbits and
923 : * it should set b_size to PAGE_SIZE or more inside get_block(). This gives
924 : * fine alignment but still allows this function to work in PAGE_SIZE units.
925 : */
926 0 : static int do_direct_IO(struct dio *dio, struct dio_submit *sdio,
927 : struct buffer_head *map_bh)
928 : {
929 0 : const unsigned blkbits = sdio->blkbits;
930 0 : const unsigned i_blkbits = blkbits + sdio->blkfactor;
931 0 : int ret = 0;
932 :
933 0 : while (sdio->block_in_file < sdio->final_block_in_request) {
934 0 : struct page *page;
935 0 : size_t from, to;
936 :
937 0 : page = dio_get_page(dio, sdio);
938 0 : if (IS_ERR(page)) {
939 0 : ret = PTR_ERR(page);
940 0 : goto out;
941 : }
942 0 : from = sdio->head ? 0 : sdio->from;
943 0 : to = (sdio->head == sdio->tail - 1) ? sdio->to : PAGE_SIZE;
944 0 : sdio->head++;
945 :
946 0 : while (from < to) {
947 0 : unsigned this_chunk_bytes; /* # of bytes mapped */
948 0 : unsigned this_chunk_blocks; /* # of blocks */
949 0 : unsigned u;
950 :
951 0 : if (sdio->blocks_available == 0) {
952 : /*
953 : * Need to go and map some more disk
954 : */
955 0 : unsigned long blkmask;
956 0 : unsigned long dio_remainder;
957 :
958 0 : ret = get_more_blocks(dio, sdio, map_bh);
959 0 : if (ret) {
960 0 : put_page(page);
961 0 : goto out;
962 : }
963 0 : if (!buffer_mapped(map_bh))
964 0 : goto do_holes;
965 :
966 0 : sdio->blocks_available =
967 0 : map_bh->b_size >> blkbits;
968 0 : sdio->next_block_for_io =
969 0 : map_bh->b_blocknr << sdio->blkfactor;
970 0 : if (buffer_new(map_bh)) {
971 0 : clean_bdev_aliases(
972 : map_bh->b_bdev,
973 : map_bh->b_blocknr,
974 0 : map_bh->b_size >> i_blkbits);
975 : }
976 :
977 0 : if (!sdio->blkfactor)
978 0 : goto do_holes;
979 :
980 0 : blkmask = (1 << sdio->blkfactor) - 1;
981 0 : dio_remainder = (sdio->block_in_file & blkmask);
982 :
983 : /*
984 : * If we are at the start of IO and that IO
985 : * starts partway into a fs-block,
986 : * dio_remainder will be non-zero. If the IO
987 : * is a read then we can simply advance the IO
988 : * cursor to the first block which is to be
989 : * read. But if the IO is a write and the
990 : * block was newly allocated we cannot do that;
991 : * the start of the fs block must be zeroed out
992 : * on-disk
993 : */
994 0 : if (!buffer_new(map_bh))
995 0 : sdio->next_block_for_io += dio_remainder;
996 0 : sdio->blocks_available -= dio_remainder;
997 : }
998 0 : do_holes:
999 : /* Handle holes */
1000 0 : if (!buffer_mapped(map_bh)) {
1001 0 : loff_t i_size_aligned;
1002 :
1003 : /* AKPM: eargh, -ENOTBLK is a hack */
1004 0 : if (dio->op == REQ_OP_WRITE) {
1005 0 : put_page(page);
1006 0 : return -ENOTBLK;
1007 : }
1008 :
1009 : /*
1010 : * Be sure to account for a partial block as the
1011 : * last block in the file
1012 : */
1013 0 : i_size_aligned = ALIGN(i_size_read(dio->inode),
1014 : 1 << blkbits);
1015 0 : if (sdio->block_in_file >=
1016 0 : i_size_aligned >> blkbits) {
1017 : /* We hit eof */
1018 0 : put_page(page);
1019 0 : goto out;
1020 : }
1021 0 : zero_user(page, from, 1 << blkbits);
1022 0 : sdio->block_in_file++;
1023 0 : from += 1 << blkbits;
1024 0 : dio->result += 1 << blkbits;
1025 0 : goto next_block;
1026 : }
1027 :
1028 : /*
1029 : * If we're performing IO which has an alignment which
1030 : * is finer than the underlying fs, go check to see if
1031 : * we must zero out the start of this block.
1032 : */
1033 0 : if (unlikely(sdio->blkfactor && !sdio->start_zero_done))
1034 0 : dio_zero_block(dio, sdio, 0, map_bh);
1035 :
1036 : /*
1037 : * Work out, in this_chunk_blocks, how much disk we
1038 : * can add to this page
1039 : */
1040 0 : this_chunk_blocks = sdio->blocks_available;
1041 0 : u = (to - from) >> blkbits;
1042 0 : if (this_chunk_blocks > u)
1043 : this_chunk_blocks = u;
1044 0 : u = sdio->final_block_in_request - sdio->block_in_file;
1045 0 : if (this_chunk_blocks > u)
1046 : this_chunk_blocks = u;
1047 0 : this_chunk_bytes = this_chunk_blocks << blkbits;
1048 0 : BUG_ON(this_chunk_bytes == 0);
1049 :
1050 0 : if (this_chunk_blocks == sdio->blocks_available)
1051 0 : sdio->boundary = buffer_boundary(map_bh);
1052 0 : ret = submit_page_section(dio, sdio, page,
1053 : from,
1054 : this_chunk_bytes,
1055 : sdio->next_block_for_io,
1056 : map_bh);
1057 0 : if (ret) {
1058 0 : put_page(page);
1059 0 : goto out;
1060 : }
1061 0 : sdio->next_block_for_io += this_chunk_blocks;
1062 :
1063 0 : sdio->block_in_file += this_chunk_blocks;
1064 0 : from += this_chunk_bytes;
1065 0 : dio->result += this_chunk_bytes;
1066 0 : sdio->blocks_available -= this_chunk_blocks;
1067 0 : next_block:
1068 0 : BUG_ON(sdio->block_in_file > sdio->final_block_in_request);
1069 0 : if (sdio->block_in_file == sdio->final_block_in_request)
1070 : break;
1071 : }
1072 :
1073 : /* Drop the ref which was taken in get_user_pages() */
1074 0 : put_page(page);
1075 : }
1076 0 : out:
1077 : return ret;
1078 : }
1079 :
1080 0 : static inline int drop_refcount(struct dio *dio)
1081 : {
1082 0 : int ret2;
1083 0 : unsigned long flags;
1084 :
1085 : /*
1086 : * Sync will always be dropping the final ref and completing the
1087 : * operation. AIO can if it was a broken operation described above or
1088 : * in fact if all the bios race to complete before we get here. In
1089 : * that case dio_complete() translates the EIOCBQUEUED into the proper
1090 : * return code that the caller will hand to ->complete().
1091 : *
1092 : * This is managed by the bio_lock instead of being an atomic_t so that
1093 : * completion paths can drop their ref and use the remaining count to
1094 : * decide to wake the submission path atomically.
1095 : */
1096 0 : spin_lock_irqsave(&dio->bio_lock, flags);
1097 0 : ret2 = --dio->refcount;
1098 0 : spin_unlock_irqrestore(&dio->bio_lock, flags);
1099 0 : return ret2;
1100 : }
1101 :
1102 : /*
1103 : * This is a library function for use by filesystem drivers.
1104 : *
1105 : * The locking rules are governed by the flags parameter:
1106 : * - if the flags value contains DIO_LOCKING we use a fancy locking
1107 : * scheme for dumb filesystems.
1108 : * For writes this function is called under i_mutex and returns with
1109 : * i_mutex held, for reads, i_mutex is not held on entry, but it is
1110 : * taken and dropped again before returning.
1111 : * - if the flags value does NOT contain DIO_LOCKING we don't use any
1112 : * internal locking but rather rely on the filesystem to synchronize
1113 : * direct I/O reads/writes versus each other and truncate.
1114 : *
1115 : * To help with locking against truncate we incremented the i_dio_count
1116 : * counter before starting direct I/O, and decrement it once we are done.
1117 : * Truncate can wait for it to reach zero to provide exclusion. It is
1118 : * expected that filesystem provide exclusion between new direct I/O
1119 : * and truncates. For DIO_LOCKING filesystems this is done by i_mutex,
1120 : * but other filesystems need to take care of this on their own.
1121 : *
1122 : * NOTE: if you pass "sdio" to anything by pointer make sure that function
1123 : * is always inlined. Otherwise gcc is unable to split the structure into
1124 : * individual fields and will generate much worse code. This is important
1125 : * for the whole file.
1126 : */
1127 : static inline ssize_t
1128 0 : do_blockdev_direct_IO(struct kiocb *iocb, struct inode *inode,
1129 : struct block_device *bdev, struct iov_iter *iter,
1130 : get_block_t get_block, dio_iodone_t end_io,
1131 : dio_submit_t submit_io, int flags)
1132 : {
1133 0 : unsigned i_blkbits = READ_ONCE(inode->i_blkbits);
1134 0 : unsigned blkbits = i_blkbits;
1135 0 : unsigned blocksize_mask = (1 << blkbits) - 1;
1136 0 : ssize_t retval = -EINVAL;
1137 0 : const size_t count = iov_iter_count(iter);
1138 0 : loff_t offset = iocb->ki_pos;
1139 0 : const loff_t end = offset + count;
1140 0 : struct dio *dio;
1141 0 : struct dio_submit sdio = { 0, };
1142 0 : struct buffer_head map_bh = { 0, };
1143 0 : struct blk_plug plug;
1144 0 : unsigned long align = offset | iov_iter_alignment(iter);
1145 :
1146 : /*
1147 : * Avoid references to bdev if not absolutely needed to give
1148 : * the early prefetch in the caller enough time.
1149 : */
1150 :
1151 : /* watch out for a 0 len io from a tricksy fs */
1152 0 : if (iov_iter_rw(iter) == READ && !count)
1153 : return 0;
1154 :
1155 0 : dio = kmem_cache_alloc(dio_cache, GFP_KERNEL);
1156 0 : if (!dio)
1157 : return -ENOMEM;
1158 : /*
1159 : * Believe it or not, zeroing out the page array caused a .5%
1160 : * performance regression in a database benchmark. So, we take
1161 : * care to only zero out what's needed.
1162 : */
1163 0 : memset(dio, 0, offsetof(struct dio, pages));
1164 :
1165 0 : dio->flags = flags;
1166 0 : if (dio->flags & DIO_LOCKING && iov_iter_rw(iter) == READ) {
1167 : /* will be released by direct_io_worker */
1168 0 : inode_lock(inode);
1169 : }
1170 :
1171 : /* Once we sampled i_size check for reads beyond EOF */
1172 0 : dio->i_size = i_size_read(inode);
1173 0 : if (iov_iter_rw(iter) == READ && offset >= dio->i_size) {
1174 0 : retval = 0;
1175 0 : goto fail_dio;
1176 : }
1177 :
1178 0 : if (align & blocksize_mask) {
1179 0 : if (bdev)
1180 0 : blkbits = blksize_bits(bdev_logical_block_size(bdev));
1181 0 : blocksize_mask = (1 << blkbits) - 1;
1182 0 : if (align & blocksize_mask)
1183 0 : goto fail_dio;
1184 : }
1185 :
1186 0 : if (dio->flags & DIO_LOCKING && iov_iter_rw(iter) == READ) {
1187 0 : struct address_space *mapping = iocb->ki_filp->f_mapping;
1188 :
1189 0 : retval = filemap_write_and_wait_range(mapping, offset, end - 1);
1190 0 : if (retval)
1191 0 : goto fail_dio;
1192 : }
1193 :
1194 : /*
1195 : * For file extending writes updating i_size before data writeouts
1196 : * complete can expose uninitialized blocks in dumb filesystems.
1197 : * In that case we need to wait for I/O completion even if asked
1198 : * for an asynchronous write.
1199 : */
1200 0 : if (is_sync_kiocb(iocb))
1201 0 : dio->is_async = false;
1202 0 : else if (iov_iter_rw(iter) == WRITE && end > i_size_read(inode))
1203 0 : dio->is_async = false;
1204 : else
1205 0 : dio->is_async = true;
1206 :
1207 0 : dio->inode = inode;
1208 0 : if (iov_iter_rw(iter) == WRITE) {
1209 0 : dio->op = REQ_OP_WRITE;
1210 0 : dio->op_flags = REQ_SYNC | REQ_IDLE;
1211 0 : if (iocb->ki_flags & IOCB_NOWAIT)
1212 0 : dio->op_flags |= REQ_NOWAIT;
1213 : } else {
1214 0 : dio->op = REQ_OP_READ;
1215 : }
1216 0 : if (iocb->ki_flags & IOCB_HIPRI)
1217 0 : dio->op_flags |= REQ_HIPRI;
1218 :
1219 : /*
1220 : * For AIO O_(D)SYNC writes we need to defer completions to a workqueue
1221 : * so that we can call ->fsync.
1222 : */
1223 0 : if (dio->is_async && iov_iter_rw(iter) == WRITE) {
1224 0 : retval = 0;
1225 0 : if (iocb->ki_flags & IOCB_DSYNC)
1226 0 : retval = dio_set_defer_completion(dio);
1227 0 : else if (!dio->inode->i_sb->s_dio_done_wq) {
1228 : /*
1229 : * In case of AIO write racing with buffered read we
1230 : * need to defer completion. We can't decide this now,
1231 : * however the workqueue needs to be initialized here.
1232 : */
1233 0 : retval = sb_init_dio_done_wq(dio->inode->i_sb);
1234 : }
1235 0 : if (retval)
1236 0 : goto fail_dio;
1237 : }
1238 :
1239 : /*
1240 : * Will be decremented at I/O completion time.
1241 : */
1242 0 : inode_dio_begin(inode);
1243 :
1244 0 : retval = 0;
1245 0 : sdio.blkbits = blkbits;
1246 0 : sdio.blkfactor = i_blkbits - blkbits;
1247 0 : sdio.block_in_file = offset >> blkbits;
1248 :
1249 0 : sdio.get_block = get_block;
1250 0 : dio->end_io = end_io;
1251 0 : sdio.submit_io = submit_io;
1252 0 : sdio.final_block_in_bio = -1;
1253 0 : sdio.next_block_for_io = -1;
1254 :
1255 0 : dio->iocb = iocb;
1256 :
1257 0 : spin_lock_init(&dio->bio_lock);
1258 0 : dio->refcount = 1;
1259 :
1260 0 : dio->should_dirty = iter_is_iovec(iter) && iov_iter_rw(iter) == READ;
1261 0 : sdio.iter = iter;
1262 0 : sdio.final_block_in_request = end >> blkbits;
1263 :
1264 : /*
1265 : * In case of non-aligned buffers, we may need 2 more
1266 : * pages since we need to zero out first and last block.
1267 : */
1268 0 : if (unlikely(sdio.blkfactor))
1269 0 : sdio.pages_in_io = 2;
1270 :
1271 0 : sdio.pages_in_io += iov_iter_npages(iter, INT_MAX);
1272 :
1273 0 : blk_start_plug(&plug);
1274 :
1275 0 : retval = do_direct_IO(dio, &sdio, &map_bh);
1276 0 : if (retval)
1277 0 : dio_cleanup(dio, &sdio);
1278 :
1279 0 : if (retval == -ENOTBLK) {
1280 : /*
1281 : * The remaining part of the request will be
1282 : * handled by buffered I/O when we return
1283 : */
1284 0 : retval = 0;
1285 : }
1286 : /*
1287 : * There may be some unwritten disk at the end of a part-written
1288 : * fs-block-sized block. Go zero that now.
1289 : */
1290 0 : dio_zero_block(dio, &sdio, 1, &map_bh);
1291 :
1292 0 : if (sdio.cur_page) {
1293 0 : ssize_t ret2;
1294 :
1295 0 : ret2 = dio_send_cur_page(dio, &sdio, &map_bh);
1296 0 : if (retval == 0)
1297 0 : retval = ret2;
1298 0 : put_page(sdio.cur_page);
1299 0 : sdio.cur_page = NULL;
1300 : }
1301 0 : if (sdio.bio)
1302 0 : dio_bio_submit(dio, &sdio);
1303 :
1304 0 : blk_finish_plug(&plug);
1305 :
1306 : /*
1307 : * It is possible that, we return short IO due to end of file.
1308 : * In that case, we need to release all the pages we got hold on.
1309 : */
1310 0 : dio_cleanup(dio, &sdio);
1311 :
1312 : /*
1313 : * All block lookups have been performed. For READ requests
1314 : * we can let i_mutex go now that its achieved its purpose
1315 : * of protecting us from looking up uninitialized blocks.
1316 : */
1317 0 : if (iov_iter_rw(iter) == READ && (dio->flags & DIO_LOCKING))
1318 0 : inode_unlock(dio->inode);
1319 :
1320 : /*
1321 : * The only time we want to leave bios in flight is when a successful
1322 : * partial aio read or full aio write have been setup. In that case
1323 : * bio completion will call aio_complete. The only time it's safe to
1324 : * call aio_complete is when we return -EIOCBQUEUED, so we key on that.
1325 : * This had *better* be the only place that raises -EIOCBQUEUED.
1326 : */
1327 0 : BUG_ON(retval == -EIOCBQUEUED);
1328 0 : if (dio->is_async && retval == 0 && dio->result &&
1329 0 : (iov_iter_rw(iter) == READ || dio->result == count))
1330 : retval = -EIOCBQUEUED;
1331 : else
1332 0 : dio_await_completion(dio);
1333 :
1334 0 : if (drop_refcount(dio) == 0) {
1335 0 : retval = dio_complete(dio, retval, DIO_COMPLETE_INVALIDATE);
1336 : } else
1337 0 : BUG_ON(retval != -EIOCBQUEUED);
1338 :
1339 : return retval;
1340 :
1341 0 : fail_dio:
1342 0 : if (dio->flags & DIO_LOCKING && iov_iter_rw(iter) == READ)
1343 0 : inode_unlock(inode);
1344 :
1345 0 : kmem_cache_free(dio_cache, dio);
1346 0 : return retval;
1347 : }
1348 :
1349 0 : ssize_t __blockdev_direct_IO(struct kiocb *iocb, struct inode *inode,
1350 : struct block_device *bdev, struct iov_iter *iter,
1351 : get_block_t get_block,
1352 : dio_iodone_t end_io, dio_submit_t submit_io,
1353 : int flags)
1354 : {
1355 : /*
1356 : * The block device state is needed in the end to finally
1357 : * submit everything. Since it's likely to be cache cold
1358 : * prefetch it here as first thing to hide some of the
1359 : * latency.
1360 : *
1361 : * Attempt to prefetch the pieces we likely need later.
1362 : */
1363 0 : prefetch(&bdev->bd_disk->part_tbl);
1364 0 : prefetch(bdev->bd_disk->queue);
1365 0 : prefetch((char *)bdev->bd_disk->queue + SMP_CACHE_BYTES);
1366 :
1367 0 : return do_blockdev_direct_IO(iocb, inode, bdev, iter, get_block,
1368 : end_io, submit_io, flags);
1369 : }
1370 :
1371 : EXPORT_SYMBOL(__blockdev_direct_IO);
1372 :
1373 1 : static __init int dio_init(void)
1374 : {
1375 1 : dio_cache = KMEM_CACHE(dio, SLAB_PANIC);
1376 1 : return 0;
1377 : }
1378 : module_init(dio_init)
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