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 /*
43 * How many user pages to map in one call to get_user_pages(). This determines
44 * the size of a structure in the slab cache
45 */
46 #define DIO_PAGES 64
47
48 /*
49 * Flags for dio_complete()
50 */
51 #define DIO_COMPLETE_ASYNC 0x01 /* This is async IO */
52 #define DIO_COMPLETE_INVALIDATE 0x02 /* Can invalidate pages */
53
54 /*
55 * This code generally works in units of "dio_blocks". A dio_block is
56 * somewhere between the hard sector size and the filesystem block size. it
57 * is determined on a per-invocation basis. When talking to the filesystem
58 * we need to convert dio_blocks to fs_blocks by scaling the dio_block quantity
59 * down by dio->blkfactor. Similarly, fs-blocksize quantities are converted
60 * to bio_block quantities by shifting left by blkfactor.
61 *
62 * If blkfactor is zero then the user's request was aligned to the filesystem's
63 * blocksize.
64 */
65
66 /* dio_state only used in the submission path */
67
68 struct dio_submit {
69 struct bio *bio; /* bio under assembly */
70 unsigned blkbits; /* doesn't change */
71 unsigned blkfactor; /* When we're using an alignment which
72 is finer than the filesystem's soft
73 blocksize, this specifies how much
74 finer. blkfactor=2 means 1/4-block
75 alignment. Does not change */
76 unsigned start_zero_done; /* flag: sub-blocksize zeroing has
77 been performed at the start of a
78 write */
79 int pages_in_io; /* approximate total IO pages */
80 sector_t block_in_file; /* Current offset into the underlying
81 file in dio_block units. */
82 unsigned blocks_available; /* At block_in_file. changes */
83 int reap_counter; /* rate limit reaping */
84 sector_t final_block_in_request;/* doesn't change */
85 int boundary; /* prev block is at a boundary */
86 get_block_t *get_block; /* block mapping function */
87 dio_submit_t *submit_io; /* IO submition function */
88
89 loff_t logical_offset_in_bio; /* current first logical block in bio */
90 sector_t final_block_in_bio; /* current final block in bio + 1 */
91 sector_t next_block_for_io; /* next block to be put under IO,
92 in dio_blocks units */
93
94 /*
95 * Deferred addition of a page to the dio. These variables are
96 * private to dio_send_cur_page(), submit_page_section() and
97 * dio_bio_add_page().
98 */
99 struct page *cur_page; /* The page */
100 unsigned cur_page_offset; /* Offset into it, in bytes */
101 unsigned cur_page_len; /* Nr of bytes at cur_page_offset */
102 sector_t cur_page_block; /* Where it starts */
103 loff_t cur_page_fs_offset; /* Offset in file */
104
105 struct iov_iter *iter;
106 /*
107 * Page queue. These variables belong to dio_refill_pages() and
108 * dio_get_page().
109 */
110 unsigned head; /* next page to process */
111 unsigned tail; /* last valid page + 1 */
112 size_t from, to;
113 };
114
115 /* dio_state communicated between submission path and end_io */
116 struct dio {
117 int flags; /* doesn't change */
118 int op;
119 int op_flags;
120 blk_qc_t bio_cookie;
121 struct gendisk *bio_disk;
122 struct inode *inode;
123 loff_t i_size; /* i_size when submitted */
124 dio_iodone_t *end_io; /* IO completion function */
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; /* errno from get_user_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 return sdio->tail - sdio->head;
162 }
163
164 /*
165 * Go grab and pin some userspace pages. Typically we'll get 64 at a time.
166 */
167 static inline int dio_refill_pages(struct dio *dio, struct dio_submit *sdio)
168 {
169 ssize_t ret;
170
171 ret = iov_iter_get_pages(sdio->iter, dio->pages, LONG_MAX, DIO_PAGES,
172 &sdio->from);
173
174 if (ret < 0 && sdio->blocks_available && (dio->op == REQ_OP_WRITE)) {
175 struct page *page = ZERO_PAGE(0);
176 /*
177 * A memory fault, but the filesystem has some outstanding
178 * mapped blocks. We need to use those blocks up to avoid
179 * leaking stale data in the file.
180 */
181 if (dio->page_errors == 0)
182 dio->page_errors = ret;
183 get_page(page);
184 dio->pages[0] = page;
185 sdio->head = 0;
186 sdio->tail = 1;
187 sdio->from = 0;
188 sdio->to = PAGE_SIZE;
189 return 0;
190 }
191
192 if (ret >= 0) {
193 iov_iter_advance(sdio->iter, ret);
194 ret += sdio->from;
195 sdio->head = 0;
196 sdio->tail = (ret + PAGE_SIZE - 1) / PAGE_SIZE;
197 sdio->to = ((ret - 1) & (PAGE_SIZE - 1)) + 1;
198 return 0;
199 }
200 return ret;
201 }
202
203 /*
204 * Get another userspace page. Returns an ERR_PTR on error. Pages are
205 * buffered inside the dio so that we can call get_user_pages() against a
206 * decent number of pages, less frequently. To provide nicer use of the
207 * L1 cache.
208 */
209 static inline struct page *dio_get_page(struct dio *dio,
210 struct dio_submit *sdio)
211 {
212 if (dio_pages_present(sdio) == 0) {
213 int ret;
214
215 ret = dio_refill_pages(dio, sdio);
216 if (ret)
217 return ERR_PTR(ret);
218 BUG_ON(dio_pages_present(sdio) == 0);
219 }
220 return dio->pages[sdio->head];
221 }
222
223 /*
224 * Warn about a page cache invalidation failure during a direct io write.
225 */
226 void dio_warn_stale_pagecache(struct file *filp)
227 {
228 static DEFINE_RATELIMIT_STATE(_rs, 86400 * HZ, DEFAULT_RATELIMIT_BURST);
229 char pathname[128];
230 struct inode *inode = file_inode(filp);
231 char *path;
232
233 errseq_set(&inode->i_mapping->wb_err, -EIO);
234 if (__ratelimit(&_rs)) {
235 path = file_path(filp, pathname, sizeof(pathname));
236 if (IS_ERR(path))
237 path = "(unknown)";
238 pr_crit("Page cache invalidation failure on direct I/O. Possible data corruption due to collision with buffered I/O!\n");
239 pr_crit("File: %s PID: %d Comm: %.20s\n", path, current->pid,
240 current->comm);
241 }
242 }
243
244 /*
245 * dio_complete() - called when all DIO BIO I/O has been completed
246 *
247 * This drops i_dio_count, lets interested parties know that a DIO operation
248 * has completed, and calculates the resulting return code for the operation.
249 *
250 * It lets the filesystem know if it registered an interest earlier via
251 * get_block. Pass the private field of the map buffer_head so that
252 * filesystems can use it to hold additional state between get_block calls and
253 * dio_complete.
254 */
255 static ssize_t dio_complete(struct dio *dio, ssize_t ret, unsigned int flags)
256 {
257 loff_t offset = dio->iocb->ki_pos;
258 ssize_t transferred = 0;
259 int err;
260
261 /*
262 * AIO submission can race with bio completion to get here while
263 * expecting to have the last io completed by bio completion.
264 * In that case -EIOCBQUEUED is in fact not an error we want
265 * to preserve through this call.
266 */
267 if (ret == -EIOCBQUEUED)
268 ret = 0;
269
270 if (dio->result) {
271 transferred = dio->result;
272
273 /* Check for short read case */
274 if ((dio->op == REQ_OP_READ) &&
275 ((offset + transferred) > dio->i_size))
276 transferred = dio->i_size - offset;
277 /* ignore EFAULT if some IO has been done */
278 if (unlikely(ret == -EFAULT) && transferred)
279 ret = 0;
280 }
281
282 if (ret == 0)
283 ret = dio->page_errors;
284 if (ret == 0)
285 ret = dio->io_error;
286 if (ret == 0)
287 ret = transferred;
288
289 if (dio->end_io) {
290 // XXX: ki_pos??
291 err = dio->end_io(dio->iocb, offset, ret, dio->private);
292 if (err)
293 ret = err;
294 }
295
296 /*
297 * Try again to invalidate clean pages which might have been cached by
298 * non-direct readahead, or faulted in by get_user_pages() if the source
299 * of the write was an mmap'ed region of the file we're writing. Either
300 * one is a pretty crazy thing to do, so we don't support it 100%. If
301 * this invalidation fails, tough, the write still worked...
302 *
303 * And this page cache invalidation has to be after dio->end_io(), as
304 * some filesystems convert unwritten extents to real allocations in
305 * end_io() when necessary, otherwise a racing buffer read would cache
306 * zeros from unwritten extents.
307 */
308 if (flags & DIO_COMPLETE_INVALIDATE &&
309 ret > 0 && dio->op == REQ_OP_WRITE &&
310 dio->inode->i_mapping->nrpages) {
311 err = invalidate_inode_pages2_range(dio->inode->i_mapping,
312 offset >> PAGE_SHIFT,
313 (offset + ret - 1) >> PAGE_SHIFT);
314 if (err)
315 dio_warn_stale_pagecache(dio->iocb->ki_filp);
316 }
317
318 inode_dio_end(dio->inode);
319
320 if (flags & DIO_COMPLETE_ASYNC) {
321 /*
322 * generic_write_sync expects ki_pos to have been updated
323 * already, but the submission path only does this for
324 * synchronous I/O.
325 */
326 dio->iocb->ki_pos += transferred;
327
328 if (ret > 0 && dio->op == REQ_OP_WRITE)
329 ret = generic_write_sync(dio->iocb, ret);
330 dio->iocb->ki_complete(dio->iocb, ret, 0);
331 }
332
333 kmem_cache_free(dio_cache, dio);
334 return ret;
335 }
336
337 static void dio_aio_complete_work(struct work_struct *work)
338 {
339 struct dio *dio = container_of(work, struct dio, complete_work);
340
341 dio_complete(dio, 0, DIO_COMPLETE_ASYNC | DIO_COMPLETE_INVALIDATE);
342 }
343
344 static blk_status_t dio_bio_complete(struct dio *dio, struct bio *bio);
345
346 /*
347 * Asynchronous IO callback.
348 */
349 static void dio_bio_end_aio(struct bio *bio)
350 {
351 struct dio *dio = bio->bi_private;
352 unsigned long remaining;
353 unsigned long flags;
354 bool defer_completion = false;
355
356 /* cleanup the bio */
357 dio_bio_complete(dio, bio);
358
359 spin_lock_irqsave(&dio->bio_lock, flags);
360 remaining = --dio->refcount;
361 if (remaining == 1 && dio->waiter)
362 wake_up_process(dio->waiter);
363 spin_unlock_irqrestore(&dio->bio_lock, flags);
364
365 if (remaining == 0) {
366 /*
367 * Defer completion when defer_completion is set or
368 * when the inode has pages mapped and this is AIO write.
369 * We need to invalidate those pages because there is a
370 * chance they contain stale data in the case buffered IO
371 * went in between AIO submission and completion into the
372 * same region.
373 */
374 if (dio->result)
375 defer_completion = dio->defer_completion ||
376 (dio->op == REQ_OP_WRITE &&
377 dio->inode->i_mapping->nrpages);
378 if (defer_completion) {
379 INIT_WORK(&dio->complete_work, dio_aio_complete_work);
380 queue_work(dio->inode->i_sb->s_dio_done_wq,
381 &dio->complete_work);
382 } else {
383 dio_complete(dio, 0, DIO_COMPLETE_ASYNC);
384 }
385 }
386 }
387
388 /*
389 * The BIO completion handler simply queues the BIO up for the process-context
390 * handler.
391 *
392 * During I/O bi_private points at the dio. After I/O, bi_private is used to
393 * implement a singly-linked list of completed BIOs, at dio->bio_list.
394 */
395 static void dio_bio_end_io(struct bio *bio)
396 {
397 struct dio *dio = bio->bi_private;
398 unsigned long flags;
399
400 spin_lock_irqsave(&dio->bio_lock, flags);
401 bio->bi_private = dio->bio_list;
402 dio->bio_list = bio;
403 if (--dio->refcount == 1 && dio->waiter)
404 wake_up_process(dio->waiter);
405 spin_unlock_irqrestore(&dio->bio_lock, flags);
406 }
407
408 /**
409 * dio_end_io - handle the end io action for the given bio
410 * @bio: The direct io bio thats being completed
411 *
412 * This is meant to be called by any filesystem that uses their own dio_submit_t
413 * so that the DIO specific endio actions are dealt with after the filesystem
414 * has done it's completion work.
415 */
416 void dio_end_io(struct bio *bio)
417 {
418 struct dio *dio = bio->bi_private;
419
420 if (dio->is_async)
421 dio_bio_end_aio(bio);
422 else
423 dio_bio_end_io(bio);
424 }
425 EXPORT_SYMBOL_GPL(dio_end_io);
426
427 static inline void
428 dio_bio_alloc(struct dio *dio, struct dio_submit *sdio,
429 struct block_device *bdev,
430 sector_t first_sector, int nr_vecs)
431 {
432 struct bio *bio;
433
434 /*
435 * bio_alloc() is guaranteed to return a bio when allowed to sleep and
436 * we request a valid number of vectors.
437 */
438 bio = bio_alloc(GFP_KERNEL, nr_vecs);
439
440 bio_set_dev(bio, bdev);
441 bio->bi_iter.bi_sector = first_sector;
442 bio_set_op_attrs(bio, dio->op, dio->op_flags);
443 if (dio->is_async)
444 bio->bi_end_io = dio_bio_end_aio;
445 else
446 bio->bi_end_io = dio_bio_end_io;
447
448 bio->bi_write_hint = dio->iocb->ki_hint;
449
450 sdio->bio = bio;
451 sdio->logical_offset_in_bio = sdio->cur_page_fs_offset;
452 }
453
454 /*
455 * In the AIO read case we speculatively dirty the pages before starting IO.
456 * During IO completion, any of these pages which happen to have been written
457 * back will be redirtied by bio_check_pages_dirty().
458 *
459 * bios hold a dio reference between submit_bio and ->end_io.
460 */
461 static inline void dio_bio_submit(struct dio *dio, struct dio_submit *sdio)
462 {
463 struct bio *bio = sdio->bio;
464 unsigned long flags;
465
466 bio->bi_private = dio;
467
468 spin_lock_irqsave(&dio->bio_lock, flags);
469 dio->refcount++;
470 spin_unlock_irqrestore(&dio->bio_lock, flags);
471
472 if (dio->is_async && dio->op == REQ_OP_READ && dio->should_dirty)
473 bio_set_pages_dirty(bio);
474
475 dio->bio_disk = bio->bi_disk;
476
477 if (sdio->submit_io) {
478 sdio->submit_io(bio, dio->inode, sdio->logical_offset_in_bio);
479 dio->bio_cookie = BLK_QC_T_NONE;
480 } else
481 dio->bio_cookie = submit_bio(bio);
482
483 sdio->bio = NULL;
484 sdio->boundary = 0;
485 sdio->logical_offset_in_bio = 0;
486 }
487
488 /*
489 * Release any resources in case of a failure
490 */
491 static inline void dio_cleanup(struct dio *dio, struct dio_submit *sdio)
492 {
493 while (sdio->head < sdio->tail)
494 put_page(dio->pages[sdio->head++]);
495 }
496
497 /*
498 * Wait for the next BIO to complete. Remove it and return it. NULL is
499 * returned once all BIOs have been completed. This must only be called once
500 * all bios have been issued so that dio->refcount can only decrease. This
501 * requires that that the caller hold a reference on the dio.
502 */
503 static struct bio *dio_await_one(struct dio *dio)
504 {
505 unsigned long flags;
506 struct bio *bio = NULL;
507
508 spin_lock_irqsave(&dio->bio_lock, flags);
509
510 /*
511 * Wait as long as the list is empty and there are bios in flight. bio
512 * completion drops the count, maybe adds to the list, and wakes while
513 * holding the bio_lock so we don't need set_current_state()'s barrier
514 * and can call it after testing our condition.
515 */
516 while (dio->refcount > 1 && dio->bio_list == NULL) {
517 __set_current_state(TASK_UNINTERRUPTIBLE);
518 dio->waiter = current;
519 spin_unlock_irqrestore(&dio->bio_lock, flags);
520 if (!(dio->iocb->ki_flags & IOCB_HIPRI) ||
521 !blk_poll(dio->bio_disk->queue, dio->bio_cookie, true))
522 io_schedule();
523 /* wake up sets us TASK_RUNNING */
524 spin_lock_irqsave(&dio->bio_lock, flags);
525 dio->waiter = NULL;
526 }
527 if (dio->bio_list) {
528 bio = dio->bio_list;
529 dio->bio_list = bio->bi_private;
530 }
531 spin_unlock_irqrestore(&dio->bio_lock, flags);
532 return bio;
533 }
534
535 /*
536 * Process one completed BIO. No locks are held.
537 */
538 static blk_status_t dio_bio_complete(struct dio *dio, struct bio *bio)
539 {
540 blk_status_t err = bio->bi_status;
541 bool should_dirty = dio->op == REQ_OP_READ && dio->should_dirty;
542
543 if (err) {
544 if (err == BLK_STS_AGAIN && (bio->bi_opf & REQ_NOWAIT))
545 dio->io_error = -EAGAIN;
546 else
547 dio->io_error = -EIO;
548 }
549
550 if (dio->is_async && should_dirty) {
551 bio_check_pages_dirty(bio); /* transfers ownership */
552 } else {
553 bio_release_pages(bio, should_dirty);
554 bio_put(bio);
555 }
556 return err;
557 }
558
559 /*
560 * Wait on and process all in-flight BIOs. This must only be called once
561 * all bios have been issued so that the refcount can only decrease.
562 * This just waits for all bios to make it through dio_bio_complete. IO
563 * errors are propagated through dio->io_error and should be propagated via
564 * dio_complete().
565 */
566 static void dio_await_completion(struct dio *dio)
567 {
568 struct bio *bio;
569 do {
570 bio = dio_await_one(dio);
571 if (bio)
572 dio_bio_complete(dio, bio);
573 } while (bio);
574 }
575
576 /*
577 * A really large O_DIRECT read or write can generate a lot of BIOs. So
578 * to keep the memory consumption sane we periodically reap any completed BIOs
579 * during the BIO generation phase.
580 *
581 * This also helps to limit the peak amount of pinned userspace memory.
582 */
583 static inline int dio_bio_reap(struct dio *dio, struct dio_submit *sdio)
584 {
585 int ret = 0;
586
587 if (sdio->reap_counter++ >= 64) {
588 while (dio->bio_list) {
589 unsigned long flags;
590 struct bio *bio;
591 int ret2;
592
593 spin_lock_irqsave(&dio->bio_lock, flags);
594 bio = dio->bio_list;
595 dio->bio_list = bio->bi_private;
596 spin_unlock_irqrestore(&dio->bio_lock, flags);
597 ret2 = blk_status_to_errno(dio_bio_complete(dio, bio));
598 if (ret == 0)
599 ret = ret2;
600 }
601 sdio->reap_counter = 0;
602 }
603 return ret;
604 }
605
606 /*
607 * Create workqueue for deferred direct IO completions. We allocate the
608 * workqueue when it's first needed. This avoids creating workqueue for
609 * filesystems that don't need it and also allows us to create the workqueue
610 * late enough so the we can include s_id in the name of the workqueue.
611 */
612 int sb_init_dio_done_wq(struct super_block *sb)
613 {
614 struct workqueue_struct *old;
615 struct workqueue_struct *wq = alloc_workqueue("dio/%s",
616 WQ_MEM_RECLAIM, 0,
617 sb->s_id);
618 if (!wq)
619 return -ENOMEM;
620 /*
621 * This has to be atomic as more DIOs can race to create the workqueue
622 */
623 old = cmpxchg(&sb->s_dio_done_wq, NULL, wq);
624 /* Someone created workqueue before us? Free ours... */
625 if (old)
626 destroy_workqueue(wq);
627 return 0;
628 }
629
630 static int dio_set_defer_completion(struct dio *dio)
631 {
632 struct super_block *sb = dio->inode->i_sb;
633
634 if (dio->defer_completion)
635 return 0;
636 dio->defer_completion = true;
637 if (!sb->s_dio_done_wq)
638 return sb_init_dio_done_wq(sb);
639 return 0;
640 }
641
642 /*
643 * Call into the fs to map some more disk blocks. We record the current number
644 * of available blocks at sdio->blocks_available. These are in units of the
645 * fs blocksize, i_blocksize(inode).
646 *
647 * The fs is allowed to map lots of blocks at once. If it wants to do that,
648 * it uses the passed inode-relative block number as the file offset, as usual.
649 *
650 * get_block() is passed the number of i_blkbits-sized blocks which direct_io
651 * has remaining to do. The fs should not map more than this number of blocks.
652 *
653 * If the fs has mapped a lot of blocks, it should populate bh->b_size to
654 * indicate how much contiguous disk space has been made available at
655 * bh->b_blocknr.
656 *
657 * If *any* of the mapped blocks are new, then the fs must set buffer_new().
658 * This isn't very efficient...
659 *
660 * In the case of filesystem holes: the fs may return an arbitrarily-large
661 * hole by returning an appropriate value in b_size and by clearing
662 * buffer_mapped(). However the direct-io code will only process holes one
663 * block at a time - it will repeatedly call get_block() as it walks the hole.
664 */
665 static int get_more_blocks(struct dio *dio, struct dio_submit *sdio,
666 struct buffer_head *map_bh)
667 {
668 int ret;
669 sector_t fs_startblk; /* Into file, in filesystem-sized blocks */
670 sector_t fs_endblk; /* Into file, in filesystem-sized blocks */
671 unsigned long fs_count; /* Number of filesystem-sized blocks */
672 int create;
673 unsigned int i_blkbits = sdio->blkbits + sdio->blkfactor;
674 loff_t i_size;
675
676 /*
677 * If there was a memory error and we've overwritten all the
678 * mapped blocks then we can now return that memory error
679 */
680 ret = dio->page_errors;
681 if (ret == 0) {
682 BUG_ON(sdio->block_in_file >= sdio->final_block_in_request);
683 fs_startblk = sdio->block_in_file >> sdio->blkfactor;
684 fs_endblk = (sdio->final_block_in_request - 1) >>
685 sdio->blkfactor;
686 fs_count = fs_endblk - fs_startblk + 1;
687
688 map_bh->b_state = 0;
689 map_bh->b_size = fs_count << i_blkbits;
690
691 /*
692 * For writes that could fill holes inside i_size on a
693 * DIO_SKIP_HOLES filesystem we forbid block creations: only
694 * overwrites are permitted. We will return early to the caller
695 * once we see an unmapped buffer head returned, and the caller
696 * will fall back to buffered I/O.
697 *
698 * Otherwise the decision is left to the get_blocks method,
699 * which may decide to handle it or also return an unmapped
700 * buffer head.
701 */
702 create = dio->op == REQ_OP_WRITE;
703 if (dio->flags & DIO_SKIP_HOLES) {
704 i_size = i_size_read(dio->inode);
705 if (i_size && fs_startblk <= (i_size - 1) >> i_blkbits)
706 create = 0;
707 }
708
709 ret = (*sdio->get_block)(dio->inode, fs_startblk,
710 map_bh, create);
711
712 /* Store for completion */
713 dio->private = map_bh->b_private;
714
715 if (ret == 0 && buffer_defer_completion(map_bh))
716 ret = dio_set_defer_completion(dio);
717 }
718 return ret;
719 }
720
721 /*
722 * There is no bio. Make one now.
723 */
724 static inline int dio_new_bio(struct dio *dio, struct dio_submit *sdio,
725 sector_t start_sector, struct buffer_head *map_bh)
726 {
727 sector_t sector;
728 int ret, nr_pages;
729
730 ret = dio_bio_reap(dio, sdio);
731 if (ret)
732 goto out;
733 sector = start_sector << (sdio->blkbits - 9);
734 nr_pages = min(sdio->pages_in_io, BIO_MAX_PAGES);
735 BUG_ON(nr_pages <= 0);
736 dio_bio_alloc(dio, sdio, map_bh->b_bdev, sector, nr_pages);
737 sdio->boundary = 0;
738 out:
739 return ret;
740 }
741
742 /*
743 * Attempt to put the current chunk of 'cur_page' into the current BIO. If
744 * that was successful then update final_block_in_bio and take a ref against
745 * the just-added page.
746 *
747 * Return zero on success. Non-zero means the caller needs to start a new BIO.
748 */
749 static inline int dio_bio_add_page(struct dio_submit *sdio)
750 {
751 int ret;
752
753 ret = bio_add_page(sdio->bio, sdio->cur_page,
754 sdio->cur_page_len, sdio->cur_page_offset);
755 if (ret == sdio->cur_page_len) {
756 /*
757 * Decrement count only, if we are done with this page
758 */
759 if ((sdio->cur_page_len + sdio->cur_page_offset) == PAGE_SIZE)
760 sdio->pages_in_io--;
761 get_page(sdio->cur_page);
762 sdio->final_block_in_bio = sdio->cur_page_block +
763 (sdio->cur_page_len >> sdio->blkbits);
764 ret = 0;
765 } else {
766 ret = 1;
767 }
768 return ret;
769 }
770
771 /*
772 * Put cur_page under IO. The section of cur_page which is described by
773 * cur_page_offset,cur_page_len is put into a BIO. The section of cur_page
774 * starts on-disk at cur_page_block.
775 *
776 * We take a ref against the page here (on behalf of its presence in the bio).
777 *
778 * The caller of this function is responsible for removing cur_page from the
779 * dio, and for dropping the refcount which came from that presence.
780 */
781 static inline int dio_send_cur_page(struct dio *dio, struct dio_submit *sdio,
782 struct buffer_head *map_bh)
783 {
784 int ret = 0;
785
786 if (sdio->bio) {
787 loff_t cur_offset = sdio->cur_page_fs_offset;
788 loff_t bio_next_offset = sdio->logical_offset_in_bio +
789 sdio->bio->bi_iter.bi_size;
790
791 /*
792 * See whether this new request is contiguous with the old.
793 *
794 * Btrfs cannot handle having logically non-contiguous requests
795 * submitted. For example if you have
796 *
797 * Logical: [0-4095][HOLE][8192-12287]
798 * Physical: [0-4095] [4096-8191]
799 *
800 * We cannot submit those pages together as one BIO. So if our
801 * current logical offset in the file does not equal what would
802 * be the next logical offset in the bio, submit the bio we
803 * have.
804 */
805 if (sdio->final_block_in_bio != sdio->cur_page_block ||
806 cur_offset != bio_next_offset)
807 dio_bio_submit(dio, sdio);
808 }
809
810 if (sdio->bio == NULL) {
811 ret = dio_new_bio(dio, sdio, sdio->cur_page_block, map_bh);
812 if (ret)
813 goto out;
814 }
815
816 if (dio_bio_add_page(sdio) != 0) {
817 dio_bio_submit(dio, sdio);
818 ret = dio_new_bio(dio, sdio, sdio->cur_page_block, map_bh);
819 if (ret == 0) {
820 ret = dio_bio_add_page(sdio);
821 BUG_ON(ret != 0);
822 }
823 }
824 out:
825 return ret;
826 }
827
828 /*
829 * An autonomous function to put a chunk of a page under deferred IO.
830 *
831 * The caller doesn't actually know (or care) whether this piece of page is in
832 * a BIO, or is under IO or whatever. We just take care of all possible
833 * situations here. The separation between the logic of do_direct_IO() and
834 * that of submit_page_section() is important for clarity. Please don't break.
835 *
836 * The chunk of page starts on-disk at blocknr.
837 *
838 * We perform deferred IO, by recording the last-submitted page inside our
839 * private part of the dio structure. If possible, we just expand the IO
840 * across that page here.
841 *
842 * If that doesn't work out then we put the old page into the bio and add this
843 * page to the dio instead.
844 */
845 static inline int
846 submit_page_section(struct dio *dio, struct dio_submit *sdio, struct page *page,
847 unsigned offset, unsigned len, sector_t blocknr,
848 struct buffer_head *map_bh)
849 {
850 int ret = 0;
851
852 if (dio->op == REQ_OP_WRITE) {
853 /*
854 * Read accounting is performed in submit_bio()
855 */
856 task_io_account_write(len);
857 }
858
859 /*
860 * Can we just grow the current page's presence in the dio?
861 */
862 if (sdio->cur_page == page &&
863 sdio->cur_page_offset + sdio->cur_page_len == offset &&
864 sdio->cur_page_block +
865 (sdio->cur_page_len >> sdio->blkbits) == blocknr) {
866 sdio->cur_page_len += len;
867 goto out;
868 }
869
870 /*
871 * If there's a deferred page already there then send it.
872 */
873 if (sdio->cur_page) {
874 ret = dio_send_cur_page(dio, sdio, map_bh);
875 put_page(sdio->cur_page);
876 sdio->cur_page = NULL;
877 if (ret)
878 return ret;
879 }
880
881 get_page(page); /* It is in dio */
882 sdio->cur_page = page;
883 sdio->cur_page_offset = offset;
884 sdio->cur_page_len = len;
885 sdio->cur_page_block = blocknr;
886 sdio->cur_page_fs_offset = sdio->block_in_file << sdio->blkbits;
887 out:
888 /*
889 * If sdio->boundary then we want to schedule the IO now to
890 * avoid metadata seeks.
891 */
892 if (sdio->boundary) {
893 ret = dio_send_cur_page(dio, sdio, map_bh);
894 if (sdio->bio)
895 dio_bio_submit(dio, sdio);
896 put_page(sdio->cur_page);
897 sdio->cur_page = NULL;
898 }
899 return ret;
900 }
901
902 /*
903 * If we are not writing the entire block and get_block() allocated
904 * the block for us, we need to fill-in the unused portion of the
905 * block with zeros. This happens only if user-buffer, fileoffset or
906 * io length is not filesystem block-size multiple.
907 *
908 * `end' is zero if we're doing the start of the IO, 1 at the end of the
909 * IO.
910 */
911 static inline void dio_zero_block(struct dio *dio, struct dio_submit *sdio,
912 int end, struct buffer_head *map_bh)
913 {
914 unsigned dio_blocks_per_fs_block;
915 unsigned this_chunk_blocks; /* In dio_blocks */
916 unsigned this_chunk_bytes;
917 struct page *page;
918
919 sdio->start_zero_done = 1;
920 if (!sdio->blkfactor || !buffer_new(map_bh))
921 return;
922
923 dio_blocks_per_fs_block = 1 << sdio->blkfactor;
924 this_chunk_blocks = sdio->block_in_file & (dio_blocks_per_fs_block - 1);
925
926 if (!this_chunk_blocks)
927 return;
928
929 /*
930 * We need to zero out part of an fs block. It is either at the
931 * beginning or the end of the fs block.
932 */
933 if (end)
934 this_chunk_blocks = dio_blocks_per_fs_block - this_chunk_blocks;
935
936 this_chunk_bytes = this_chunk_blocks << sdio->blkbits;
937
938 page = ZERO_PAGE(0);
939 if (submit_page_section(dio, sdio, page, 0, this_chunk_bytes,
940 sdio->next_block_for_io, map_bh))
941 return;
942
943 sdio->next_block_for_io += this_chunk_blocks;
944 }
945
946 /*
947 * Walk the user pages, and the file, mapping blocks to disk and generating
948 * a sequence of (page,offset,len,block) mappings. These mappings are injected
949 * into submit_page_section(), which takes care of the next stage of submission
950 *
951 * Direct IO against a blockdev is different from a file. Because we can
952 * happily perform page-sized but 512-byte aligned IOs. It is important that
953 * blockdev IO be able to have fine alignment and large sizes.
954 *
955 * So what we do is to permit the ->get_block function to populate bh.b_size
956 * with the size of IO which is permitted at this offset and this i_blkbits.
957 *
958 * For best results, the blockdev should be set up with 512-byte i_blkbits and
959 * it should set b_size to PAGE_SIZE or more inside get_block(). This gives
960 * fine alignment but still allows this function to work in PAGE_SIZE units.
961 */
962 static int do_direct_IO(struct dio *dio, struct dio_submit *sdio,
963 struct buffer_head *map_bh)
964 {
965 const unsigned blkbits = sdio->blkbits;
966 const unsigned i_blkbits = blkbits + sdio->blkfactor;
967 int ret = 0;
968
969 while (sdio->block_in_file < sdio->final_block_in_request) {
970 struct page *page;
971 size_t from, to;
972
973 page = dio_get_page(dio, sdio);
974 if (IS_ERR(page)) {
975 ret = PTR_ERR(page);
976 goto out;
977 }
978 from = sdio->head ? 0 : sdio->from;
979 to = (sdio->head == sdio->tail - 1) ? sdio->to : PAGE_SIZE;
980 sdio->head++;
981
982 while (from < to) {
983 unsigned this_chunk_bytes; /* # of bytes mapped */
984 unsigned this_chunk_blocks; /* # of blocks */
985 unsigned u;
986
987 if (sdio->blocks_available == 0) {
988 /*
989 * Need to go and map some more disk
990 */
991 unsigned long blkmask;
992 unsigned long dio_remainder;
993
994 ret = get_more_blocks(dio, sdio, map_bh);
995 if (ret) {
996 put_page(page);
997 goto out;
998 }
999 if (!buffer_mapped(map_bh))
1000 goto do_holes;
1001
1002 sdio->blocks_available =
1003 map_bh->b_size >> blkbits;
1004 sdio->next_block_for_io =
1005 map_bh->b_blocknr << sdio->blkfactor;
1006 if (buffer_new(map_bh)) {
1007 clean_bdev_aliases(
1008 map_bh->b_bdev,
1009 map_bh->b_blocknr,
1010 map_bh->b_size >> i_blkbits);
1011 }
1012
1013 if (!sdio->blkfactor)
1014 goto do_holes;
1015
1016 blkmask = (1 << sdio->blkfactor) - 1;
1017 dio_remainder = (sdio->block_in_file & blkmask);
1018
1019 /*
1020 * If we are at the start of IO and that IO
1021 * starts partway into a fs-block,
1022 * dio_remainder will be non-zero. If the IO
1023 * is a read then we can simply advance the IO
1024 * cursor to the first block which is to be
1025 * read. But if the IO is a write and the
1026 * block was newly allocated we cannot do that;
1027 * the start of the fs block must be zeroed out
1028 * on-disk
1029 */
1030 if (!buffer_new(map_bh))
1031 sdio->next_block_for_io += dio_remainder;
1032 sdio->blocks_available -= dio_remainder;
1033 }
1034 do_holes:
1035 /* Handle holes */
1036 if (!buffer_mapped(map_bh)) {
1037 loff_t i_size_aligned;
1038
1039 /* AKPM: eargh, -ENOTBLK is a hack */
1040 if (dio->op == REQ_OP_WRITE) {
1041 put_page(page);
1042 return -ENOTBLK;
1043 }
1044
1045 /*
1046 * Be sure to account for a partial block as the
1047 * last block in the file
1048 */
1049 i_size_aligned = ALIGN(i_size_read(dio->inode),
1050 1 << blkbits);
1051 if (sdio->block_in_file >=
1052 i_size_aligned >> blkbits) {
1053 /* We hit eof */
1054 put_page(page);
1055 goto out;
1056 }
1057 zero_user(page, from, 1 << blkbits);
1058 sdio->block_in_file++;
1059 from += 1 << blkbits;
1060 dio->result += 1 << blkbits;
1061 goto next_block;
1062 }
1063
1064 /*
1065 * If we're performing IO which has an alignment which
1066 * is finer than the underlying fs, go check to see if
1067 * we must zero out the start of this block.
1068 */
1069 if (unlikely(sdio->blkfactor && !sdio->start_zero_done))
1070 dio_zero_block(dio, sdio, 0, map_bh);
1071
1072 /*
1073 * Work out, in this_chunk_blocks, how much disk we
1074 * can add to this page
1075 */
1076 this_chunk_blocks = sdio->blocks_available;
1077 u = (to - from) >> blkbits;
1078 if (this_chunk_blocks > u)
1079 this_chunk_blocks = u;
1080 u = sdio->final_block_in_request - sdio->block_in_file;
1081 if (this_chunk_blocks > u)
1082 this_chunk_blocks = u;
1083 this_chunk_bytes = this_chunk_blocks << blkbits;
1084 BUG_ON(this_chunk_bytes == 0);
1085
1086 if (this_chunk_blocks == sdio->blocks_available)
1087 sdio->boundary = buffer_boundary(map_bh);
1088 ret = submit_page_section(dio, sdio, page,
1089 from,
1090 this_chunk_bytes,
1091 sdio->next_block_for_io,
1092 map_bh);
1093 if (ret) {
1094 put_page(page);
1095 goto out;
1096 }
1097 sdio->next_block_for_io += this_chunk_blocks;
1098
1099 sdio->block_in_file += this_chunk_blocks;
1100 from += this_chunk_bytes;
1101 dio->result += this_chunk_bytes;
1102 sdio->blocks_available -= this_chunk_blocks;
1103 next_block:
1104 BUG_ON(sdio->block_in_file > sdio->final_block_in_request);
1105 if (sdio->block_in_file == sdio->final_block_in_request)
1106 break;
1107 }
1108
1109 /* Drop the ref which was taken in get_user_pages() */
1110 put_page(page);
1111 }
1112 out:
1113 return ret;
1114 }
1115
1116 static inline int drop_refcount(struct dio *dio)
1117 {
1118 int ret2;
1119 unsigned long flags;
1120
1121 /*
1122 * Sync will always be dropping the final ref and completing the
1123 * operation. AIO can if it was a broken operation described above or
1124 * in fact if all the bios race to complete before we get here. In
1125 * that case dio_complete() translates the EIOCBQUEUED into the proper
1126 * return code that the caller will hand to ->complete().
1127 *
1128 * This is managed by the bio_lock instead of being an atomic_t so that
1129 * completion paths can drop their ref and use the remaining count to
1130 * decide to wake the submission path atomically.
1131 */
1132 spin_lock_irqsave(&dio->bio_lock, flags);
1133 ret2 = --dio->refcount;
1134 spin_unlock_irqrestore(&dio->bio_lock, flags);
1135 return ret2;
1136 }
1137
1138 /*
1139 * This is a library function for use by filesystem drivers.
1140 *
1141 * The locking rules are governed by the flags parameter:
1142 * - if the flags value contains DIO_LOCKING we use a fancy locking
1143 * scheme for dumb filesystems.
1144 * For writes this function is called under i_mutex and returns with
1145 * i_mutex held, for reads, i_mutex is not held on entry, but it is
1146 * taken and dropped again before returning.
1147 * - if the flags value does NOT contain DIO_LOCKING we don't use any
1148 * internal locking but rather rely on the filesystem to synchronize
1149 * direct I/O reads/writes versus each other and truncate.
1150 *
1151 * To help with locking against truncate we incremented the i_dio_count
1152 * counter before starting direct I/O, and decrement it once we are done.
1153 * Truncate can wait for it to reach zero to provide exclusion. It is
1154 * expected that filesystem provide exclusion between new direct I/O
1155 * and truncates. For DIO_LOCKING filesystems this is done by i_mutex,
1156 * but other filesystems need to take care of this on their own.
1157 *
1158 * NOTE: if you pass "sdio" to anything by pointer make sure that function
1159 * is always inlined. Otherwise gcc is unable to split the structure into
1160 * individual fields and will generate much worse code. This is important
1161 * for the whole file.
1162 */
1163 static inline ssize_t
1164 do_blockdev_direct_IO(struct kiocb *iocb, struct inode *inode,
1165 struct block_device *bdev, struct iov_iter *iter,
1166 get_block_t get_block, dio_iodone_t end_io,
1167 dio_submit_t submit_io, int flags)
1168 {
1169 unsigned i_blkbits = READ_ONCE(inode->i_blkbits);
1170 unsigned blkbits = i_blkbits;
1171 unsigned blocksize_mask = (1 << blkbits) - 1;
1172 ssize_t retval = -EINVAL;
1173 const size_t count = iov_iter_count(iter);
1174 loff_t offset = iocb->ki_pos;
1175 const loff_t end = offset + count;
1176 struct dio *dio;
1177 struct dio_submit sdio = { 0, };
1178 struct buffer_head map_bh = { 0, };
1179 struct blk_plug plug;
1180 unsigned long align = offset | iov_iter_alignment(iter);
1181
1182 /*
1183 * Avoid references to bdev if not absolutely needed to give
1184 * the early prefetch in the caller enough time.
1185 */
1186
1187 if (align & blocksize_mask) {
1188 if (bdev)
1189 blkbits = blksize_bits(bdev_logical_block_size(bdev));
1190 blocksize_mask = (1 << blkbits) - 1;
1191 if (align & blocksize_mask)
1192 goto out;
1193 }
1194
1195 /* watch out for a 0 len io from a tricksy fs */
1196 if (iov_iter_rw(iter) == READ && !count)
1197 return 0;
1198
1199 dio = kmem_cache_alloc(dio_cache, GFP_KERNEL);
1200 retval = -ENOMEM;
1201 if (!dio)
1202 goto out;
1203 /*
1204 * Believe it or not, zeroing out the page array caused a .5%
1205 * performance regression in a database benchmark. So, we take
1206 * care to only zero out what's needed.
1207 */
1208 memset(dio, 0, offsetof(struct dio, pages));
1209
1210 dio->flags = flags;
1211 if (dio->flags & DIO_LOCKING) {
1212 if (iov_iter_rw(iter) == READ) {
1213 struct address_space *mapping =
1214 iocb->ki_filp->f_mapping;
1215
1216 /* will be released by direct_io_worker */
1217 inode_lock(inode);
1218
1219 retval = filemap_write_and_wait_range(mapping, offset,
1220 end - 1);
1221 if (retval) {
1222 inode_unlock(inode);
1223 kmem_cache_free(dio_cache, dio);
1224 goto out;
1225 }
1226 }
1227 }
1228
1229 /* Once we sampled i_size check for reads beyond EOF */
1230 dio->i_size = i_size_read(inode);
1231 if (iov_iter_rw(iter) == READ && offset >= dio->i_size) {
1232 if (dio->flags & DIO_LOCKING)
1233 inode_unlock(inode);
1234 kmem_cache_free(dio_cache, dio);
1235 retval = 0;
1236 goto out;
1237 }
1238
1239 /*
1240 * For file extending writes updating i_size before data writeouts
1241 * complete can expose uninitialized blocks in dumb filesystems.
1242 * In that case we need to wait for I/O completion even if asked
1243 * for an asynchronous write.
1244 */
1245 if (is_sync_kiocb(iocb))
1246 dio->is_async = false;
1247 else if (iov_iter_rw(iter) == WRITE && end > i_size_read(inode))
1248 dio->is_async = false;
1249 else
1250 dio->is_async = true;
1251
1252 dio->inode = inode;
1253 if (iov_iter_rw(iter) == WRITE) {
1254 dio->op = REQ_OP_WRITE;
1255 dio->op_flags = REQ_SYNC | REQ_IDLE;
1256 if (iocb->ki_flags & IOCB_NOWAIT)
1257 dio->op_flags |= REQ_NOWAIT;
1258 } else {
1259 dio->op = REQ_OP_READ;
1260 }
1261 if (iocb->ki_flags & IOCB_HIPRI)
1262 dio->op_flags |= REQ_HIPRI;
1263
1264 /*
1265 * For AIO O_(D)SYNC writes we need to defer completions to a workqueue
1266 * so that we can call ->fsync.
1267 */
1268 if (dio->is_async && iov_iter_rw(iter) == WRITE) {
1269 retval = 0;
1270 if (iocb->ki_flags & IOCB_DSYNC)
1271 retval = dio_set_defer_completion(dio);
1272 else if (!dio->inode->i_sb->s_dio_done_wq) {
1273 /*
1274 * In case of AIO write racing with buffered read we
1275 * need to defer completion. We can't decide this now,
1276 * however the workqueue needs to be initialized here.
1277 */
1278 retval = sb_init_dio_done_wq(dio->inode->i_sb);
1279 }
1280 if (retval) {
1281 /*
1282 * We grab i_mutex only for reads so we don't have
1283 * to release it here
1284 */
1285 kmem_cache_free(dio_cache, dio);
1286 goto out;
1287 }
1288 }
1289
1290 /*
1291 * Will be decremented at I/O completion time.
1292 */
1293 inode_dio_begin(inode);
1294
1295 retval = 0;
1296 sdio.blkbits = blkbits;
1297 sdio.blkfactor = i_blkbits - blkbits;
1298 sdio.block_in_file = offset >> blkbits;
1299
1300 sdio.get_block = get_block;
1301 dio->end_io = end_io;
1302 sdio.submit_io = submit_io;
1303 sdio.final_block_in_bio = -1;
1304 sdio.next_block_for_io = -1;
1305
1306 dio->iocb = iocb;
1307
1308 spin_lock_init(&dio->bio_lock);
1309 dio->refcount = 1;
1310
1311 dio->should_dirty = iter_is_iovec(iter) && iov_iter_rw(iter) == READ;
1312 sdio.iter = iter;
1313 sdio.final_block_in_request = end >> blkbits;
1314
1315 /*
1316 * In case of non-aligned buffers, we may need 2 more
1317 * pages since we need to zero out first and last block.
1318 */
1319 if (unlikely(sdio.blkfactor))
1320 sdio.pages_in_io = 2;
1321
1322 sdio.pages_in_io += iov_iter_npages(iter, INT_MAX);
1323
1324 blk_start_plug(&plug);
1325
1326 retval = do_direct_IO(dio, &sdio, &map_bh);
1327 if (retval)
1328 dio_cleanup(dio, &sdio);
1329
1330 if (retval == -ENOTBLK) {
1331 /*
1332 * The remaining part of the request will be
1333 * be handled by buffered I/O when we return
1334 */
1335 retval = 0;
1336 }
1337 /*
1338 * There may be some unwritten disk at the end of a part-written
1339 * fs-block-sized block. Go zero that now.
1340 */
1341 dio_zero_block(dio, &sdio, 1, &map_bh);
1342
1343 if (sdio.cur_page) {
1344 ssize_t ret2;
1345
1346 ret2 = dio_send_cur_page(dio, &sdio, &map_bh);
1347 if (retval == 0)
1348 retval = ret2;
1349 put_page(sdio.cur_page);
1350 sdio.cur_page = NULL;
1351 }
1352 if (sdio.bio)
1353 dio_bio_submit(dio, &sdio);
1354
1355 blk_finish_plug(&plug);
1356
1357 /*
1358 * It is possible that, we return short IO due to end of file.
1359 * In that case, we need to release all the pages we got hold on.
1360 */
1361 dio_cleanup(dio, &sdio);
1362
1363 /*
1364 * All block lookups have been performed. For READ requests
1365 * we can let i_mutex go now that its achieved its purpose
1366 * of protecting us from looking up uninitialized blocks.
1367 */
1368 if (iov_iter_rw(iter) == READ && (dio->flags & DIO_LOCKING))
1369 inode_unlock(dio->inode);
1370
1371 /*
1372 * The only time we want to leave bios in flight is when a successful
1373 * partial aio read or full aio write have been setup. In that case
1374 * bio completion will call aio_complete. The only time it's safe to
1375 * call aio_complete is when we return -EIOCBQUEUED, so we key on that.
1376 * This had *better* be the only place that raises -EIOCBQUEUED.
1377 */
1378 BUG_ON(retval == -EIOCBQUEUED);
1379 if (dio->is_async && retval == 0 && dio->result &&
1380 (iov_iter_rw(iter) == READ || dio->result == count))
1381 retval = -EIOCBQUEUED;
1382 else
1383 dio_await_completion(dio);
1384
1385 if (drop_refcount(dio) == 0) {
1386 retval = dio_complete(dio, retval, DIO_COMPLETE_INVALIDATE);
1387 } else
1388 BUG_ON(retval != -EIOCBQUEUED);
1389
1390 out:
1391 return retval;
1392 }
1393
1394 ssize_t __blockdev_direct_IO(struct kiocb *iocb, struct inode *inode,
1395 struct block_device *bdev, struct iov_iter *iter,
1396 get_block_t get_block,
1397 dio_iodone_t end_io, dio_submit_t submit_io,
1398 int flags)
1399 {
1400 /*
1401 * The block device state is needed in the end to finally
1402 * submit everything. Since it's likely to be cache cold
1403 * prefetch it here as first thing to hide some of the
1404 * latency.
1405 *
1406 * Attempt to prefetch the pieces we likely need later.
1407 */
1408 prefetch(&bdev->bd_disk->part_tbl);
1409 prefetch(bdev->bd_queue);
1410 prefetch((char *)bdev->bd_queue + SMP_CACHE_BYTES);
1411
1412 return do_blockdev_direct_IO(iocb, inode, bdev, iter, get_block,
1413 end_io, submit_io, flags);
1414 }
1415
1416 EXPORT_SYMBOL(__blockdev_direct_IO);
1417
1418 static __init int dio_init(void)
1419 {
1420 dio_cache = KMEM_CACHE(dio, SLAB_PANIC);
1421 return 0;
1422 }
1423 module_init(dio_init)