]> git.proxmox.com Git - mirror_ubuntu-artful-kernel.git/blob - fs/direct-io.c
Merge branch 'kbuild' of git://git.kernel.org/pub/scm/linux/kernel/git/mmarek/kbuild
[mirror_ubuntu-artful-kernel.git] / fs / direct-io.c
1 /*
2 * fs/direct-io.c
3 *
4 * Copyright (C) 2002, Linus Torvalds.
5 *
6 * O_DIRECT
7 *
8 * 04Jul2002 Andrew Morton
9 * Initial version
10 * 11Sep2002 janetinc@us.ibm.com
11 * added readv/writev support.
12 * 29Oct2002 Andrew Morton
13 * rewrote bio_add_page() support.
14 * 30Oct2002 pbadari@us.ibm.com
15 * added support for non-aligned IO.
16 * 06Nov2002 pbadari@us.ibm.com
17 * added asynchronous IO support.
18 * 21Jul2003 nathans@sgi.com
19 * added IO completion notifier.
20 */
21
22 #include <linux/kernel.h>
23 #include <linux/module.h>
24 #include <linux/types.h>
25 #include <linux/fs.h>
26 #include <linux/mm.h>
27 #include <linux/slab.h>
28 #include <linux/highmem.h>
29 #include <linux/pagemap.h>
30 #include <linux/task_io_accounting_ops.h>
31 #include <linux/bio.h>
32 #include <linux/wait.h>
33 #include <linux/err.h>
34 #include <linux/blkdev.h>
35 #include <linux/buffer_head.h>
36 #include <linux/rwsem.h>
37 #include <linux/uio.h>
38 #include <linux/atomic.h>
39 #include <linux/prefetch.h>
40
41 /*
42 * How many user pages to map in one call to get_user_pages(). This determines
43 * the size of a structure in the slab cache
44 */
45 #define DIO_PAGES 64
46
47 /*
48 * This code generally works in units of "dio_blocks". A dio_block is
49 * somewhere between the hard sector size and the filesystem block size. it
50 * is determined on a per-invocation basis. When talking to the filesystem
51 * we need to convert dio_blocks to fs_blocks by scaling the dio_block quantity
52 * down by dio->blkfactor. Similarly, fs-blocksize quantities are converted
53 * to bio_block quantities by shifting left by blkfactor.
54 *
55 * If blkfactor is zero then the user's request was aligned to the filesystem's
56 * blocksize.
57 */
58
59 /* dio_state only used in the submission path */
60
61 struct dio_submit {
62 struct bio *bio; /* bio under assembly */
63 unsigned blkbits; /* doesn't change */
64 unsigned blkfactor; /* When we're using an alignment which
65 is finer than the filesystem's soft
66 blocksize, this specifies how much
67 finer. blkfactor=2 means 1/4-block
68 alignment. Does not change */
69 unsigned start_zero_done; /* flag: sub-blocksize zeroing has
70 been performed at the start of a
71 write */
72 int pages_in_io; /* approximate total IO pages */
73 sector_t block_in_file; /* Current offset into the underlying
74 file in dio_block units. */
75 unsigned blocks_available; /* At block_in_file. changes */
76 int reap_counter; /* rate limit reaping */
77 sector_t final_block_in_request;/* doesn't change */
78 int boundary; /* prev block is at a boundary */
79 get_block_t *get_block; /* block mapping function */
80 dio_submit_t *submit_io; /* IO submition function */
81
82 loff_t logical_offset_in_bio; /* current first logical block in bio */
83 sector_t final_block_in_bio; /* current final block in bio + 1 */
84 sector_t next_block_for_io; /* next block to be put under IO,
85 in dio_blocks units */
86
87 /*
88 * Deferred addition of a page to the dio. These variables are
89 * private to dio_send_cur_page(), submit_page_section() and
90 * dio_bio_add_page().
91 */
92 struct page *cur_page; /* The page */
93 unsigned cur_page_offset; /* Offset into it, in bytes */
94 unsigned cur_page_len; /* Nr of bytes at cur_page_offset */
95 sector_t cur_page_block; /* Where it starts */
96 loff_t cur_page_fs_offset; /* Offset in file */
97
98 struct iov_iter *iter;
99 /*
100 * Page queue. These variables belong to dio_refill_pages() and
101 * dio_get_page().
102 */
103 unsigned head; /* next page to process */
104 unsigned tail; /* last valid page + 1 */
105 size_t from, to;
106 };
107
108 /* dio_state communicated between submission path and end_io */
109 struct dio {
110 int flags; /* doesn't change */
111 int op;
112 int op_flags;
113 blk_qc_t bio_cookie;
114 struct block_device *bio_bdev;
115 struct inode *inode;
116 loff_t i_size; /* i_size when submitted */
117 dio_iodone_t *end_io; /* IO completion function */
118
119 void *private; /* copy from map_bh.b_private */
120
121 /* BIO completion state */
122 spinlock_t bio_lock; /* protects BIO fields below */
123 int page_errors; /* errno from get_user_pages() */
124 int is_async; /* is IO async ? */
125 bool defer_completion; /* defer AIO completion to workqueue? */
126 bool should_dirty; /* if pages should be dirtied */
127 int io_error; /* IO error in completion path */
128 unsigned long refcount; /* direct_io_worker() and bios */
129 struct bio *bio_list; /* singly linked via bi_private */
130 struct task_struct *waiter; /* waiting task (NULL if none) */
131
132 /* AIO related stuff */
133 struct kiocb *iocb; /* kiocb */
134 ssize_t result; /* IO result */
135
136 /*
137 * pages[] (and any fields placed after it) are not zeroed out at
138 * allocation time. Don't add new fields after pages[] unless you
139 * wish that they not be zeroed.
140 */
141 union {
142 struct page *pages[DIO_PAGES]; /* page buffer */
143 struct work_struct complete_work;/* deferred AIO completion */
144 };
145 } ____cacheline_aligned_in_smp;
146
147 static struct kmem_cache *dio_cache __read_mostly;
148
149 /*
150 * How many pages are in the queue?
151 */
152 static inline unsigned dio_pages_present(struct dio_submit *sdio)
153 {
154 return sdio->tail - sdio->head;
155 }
156
157 /*
158 * Go grab and pin some userspace pages. Typically we'll get 64 at a time.
159 */
160 static inline int dio_refill_pages(struct dio *dio, struct dio_submit *sdio)
161 {
162 ssize_t ret;
163
164 ret = iov_iter_get_pages(sdio->iter, dio->pages, LONG_MAX, DIO_PAGES,
165 &sdio->from);
166
167 if (ret < 0 && sdio->blocks_available && (dio->op == REQ_OP_WRITE)) {
168 struct page *page = ZERO_PAGE(0);
169 /*
170 * A memory fault, but the filesystem has some outstanding
171 * mapped blocks. We need to use those blocks up to avoid
172 * leaking stale data in the file.
173 */
174 if (dio->page_errors == 0)
175 dio->page_errors = ret;
176 get_page(page);
177 dio->pages[0] = page;
178 sdio->head = 0;
179 sdio->tail = 1;
180 sdio->from = 0;
181 sdio->to = PAGE_SIZE;
182 return 0;
183 }
184
185 if (ret >= 0) {
186 iov_iter_advance(sdio->iter, ret);
187 ret += sdio->from;
188 sdio->head = 0;
189 sdio->tail = (ret + PAGE_SIZE - 1) / PAGE_SIZE;
190 sdio->to = ((ret - 1) & (PAGE_SIZE - 1)) + 1;
191 return 0;
192 }
193 return ret;
194 }
195
196 /*
197 * Get another userspace page. Returns an ERR_PTR on error. Pages are
198 * buffered inside the dio so that we can call get_user_pages() against a
199 * decent number of pages, less frequently. To provide nicer use of the
200 * L1 cache.
201 */
202 static inline struct page *dio_get_page(struct dio *dio,
203 struct dio_submit *sdio)
204 {
205 if (dio_pages_present(sdio) == 0) {
206 int ret;
207
208 ret = dio_refill_pages(dio, sdio);
209 if (ret)
210 return ERR_PTR(ret);
211 BUG_ON(dio_pages_present(sdio) == 0);
212 }
213 return dio->pages[sdio->head];
214 }
215
216 /**
217 * dio_complete() - called when all DIO BIO I/O has been completed
218 * @offset: the byte offset in the file of the completed operation
219 *
220 * This drops i_dio_count, lets interested parties know that a DIO operation
221 * has completed, and calculates the resulting return code for the operation.
222 *
223 * It lets the filesystem know if it registered an interest earlier via
224 * get_block. Pass the private field of the map buffer_head so that
225 * filesystems can use it to hold additional state between get_block calls and
226 * dio_complete.
227 */
228 static ssize_t dio_complete(struct dio *dio, ssize_t ret, bool is_async)
229 {
230 loff_t offset = dio->iocb->ki_pos;
231 ssize_t transferred = 0;
232
233 /*
234 * AIO submission can race with bio completion to get here while
235 * expecting to have the last io completed by bio completion.
236 * In that case -EIOCBQUEUED is in fact not an error we want
237 * to preserve through this call.
238 */
239 if (ret == -EIOCBQUEUED)
240 ret = 0;
241
242 if (dio->result) {
243 transferred = dio->result;
244
245 /* Check for short read case */
246 if ((dio->op == REQ_OP_READ) &&
247 ((offset + transferred) > dio->i_size))
248 transferred = dio->i_size - offset;
249 /* ignore EFAULT if some IO has been done */
250 if (unlikely(ret == -EFAULT) && transferred)
251 ret = 0;
252 }
253
254 if (ret == 0)
255 ret = dio->page_errors;
256 if (ret == 0)
257 ret = dio->io_error;
258 if (ret == 0)
259 ret = transferred;
260
261 if (dio->end_io) {
262 int err;
263
264 // XXX: ki_pos??
265 err = dio->end_io(dio->iocb, offset, ret, dio->private);
266 if (err)
267 ret = err;
268 }
269
270 if (!(dio->flags & DIO_SKIP_DIO_COUNT))
271 inode_dio_end(dio->inode);
272
273 if (is_async) {
274 /*
275 * generic_write_sync expects ki_pos to have been updated
276 * already, but the submission path only does this for
277 * synchronous I/O.
278 */
279 dio->iocb->ki_pos += transferred;
280
281 if (dio->op == REQ_OP_WRITE)
282 ret = generic_write_sync(dio->iocb, transferred);
283 dio->iocb->ki_complete(dio->iocb, ret, 0);
284 }
285
286 kmem_cache_free(dio_cache, dio);
287 return ret;
288 }
289
290 static void dio_aio_complete_work(struct work_struct *work)
291 {
292 struct dio *dio = container_of(work, struct dio, complete_work);
293
294 dio_complete(dio, 0, true);
295 }
296
297 static int dio_bio_complete(struct dio *dio, struct bio *bio);
298
299 /*
300 * Asynchronous IO callback.
301 */
302 static void dio_bio_end_aio(struct bio *bio)
303 {
304 struct dio *dio = bio->bi_private;
305 unsigned long remaining;
306 unsigned long flags;
307
308 /* cleanup the bio */
309 dio_bio_complete(dio, bio);
310
311 spin_lock_irqsave(&dio->bio_lock, flags);
312 remaining = --dio->refcount;
313 if (remaining == 1 && dio->waiter)
314 wake_up_process(dio->waiter);
315 spin_unlock_irqrestore(&dio->bio_lock, flags);
316
317 if (remaining == 0) {
318 if (dio->result && dio->defer_completion) {
319 INIT_WORK(&dio->complete_work, dio_aio_complete_work);
320 queue_work(dio->inode->i_sb->s_dio_done_wq,
321 &dio->complete_work);
322 } else {
323 dio_complete(dio, 0, true);
324 }
325 }
326 }
327
328 /*
329 * The BIO completion handler simply queues the BIO up for the process-context
330 * handler.
331 *
332 * During I/O bi_private points at the dio. After I/O, bi_private is used to
333 * implement a singly-linked list of completed BIOs, at dio->bio_list.
334 */
335 static void dio_bio_end_io(struct bio *bio)
336 {
337 struct dio *dio = bio->bi_private;
338 unsigned long flags;
339
340 spin_lock_irqsave(&dio->bio_lock, flags);
341 bio->bi_private = dio->bio_list;
342 dio->bio_list = bio;
343 if (--dio->refcount == 1 && dio->waiter)
344 wake_up_process(dio->waiter);
345 spin_unlock_irqrestore(&dio->bio_lock, flags);
346 }
347
348 /**
349 * dio_end_io - handle the end io action for the given bio
350 * @bio: The direct io bio thats being completed
351 * @error: Error if there was one
352 *
353 * This is meant to be called by any filesystem that uses their own dio_submit_t
354 * so that the DIO specific endio actions are dealt with after the filesystem
355 * has done it's completion work.
356 */
357 void dio_end_io(struct bio *bio, int error)
358 {
359 struct dio *dio = bio->bi_private;
360
361 if (dio->is_async)
362 dio_bio_end_aio(bio);
363 else
364 dio_bio_end_io(bio);
365 }
366 EXPORT_SYMBOL_GPL(dio_end_io);
367
368 static inline void
369 dio_bio_alloc(struct dio *dio, struct dio_submit *sdio,
370 struct block_device *bdev,
371 sector_t first_sector, int nr_vecs)
372 {
373 struct bio *bio;
374
375 /*
376 * bio_alloc() is guaranteed to return a bio when called with
377 * __GFP_RECLAIM and we request a valid number of vectors.
378 */
379 bio = bio_alloc(GFP_KERNEL, nr_vecs);
380
381 bio->bi_bdev = bdev;
382 bio->bi_iter.bi_sector = first_sector;
383 bio_set_op_attrs(bio, dio->op, dio->op_flags);
384 if (dio->is_async)
385 bio->bi_end_io = dio_bio_end_aio;
386 else
387 bio->bi_end_io = dio_bio_end_io;
388
389 sdio->bio = bio;
390 sdio->logical_offset_in_bio = sdio->cur_page_fs_offset;
391 }
392
393 /*
394 * In the AIO read case we speculatively dirty the pages before starting IO.
395 * During IO completion, any of these pages which happen to have been written
396 * back will be redirtied by bio_check_pages_dirty().
397 *
398 * bios hold a dio reference between submit_bio and ->end_io.
399 */
400 static inline void dio_bio_submit(struct dio *dio, struct dio_submit *sdio)
401 {
402 struct bio *bio = sdio->bio;
403 unsigned long flags;
404
405 bio->bi_private = dio;
406
407 spin_lock_irqsave(&dio->bio_lock, flags);
408 dio->refcount++;
409 spin_unlock_irqrestore(&dio->bio_lock, flags);
410
411 if (dio->is_async && dio->op == REQ_OP_READ && dio->should_dirty)
412 bio_set_pages_dirty(bio);
413
414 dio->bio_bdev = bio->bi_bdev;
415
416 if (sdio->submit_io) {
417 sdio->submit_io(bio, dio->inode, sdio->logical_offset_in_bio);
418 dio->bio_cookie = BLK_QC_T_NONE;
419 } else
420 dio->bio_cookie = submit_bio(bio);
421
422 sdio->bio = NULL;
423 sdio->boundary = 0;
424 sdio->logical_offset_in_bio = 0;
425 }
426
427 /*
428 * Release any resources in case of a failure
429 */
430 static inline void dio_cleanup(struct dio *dio, struct dio_submit *sdio)
431 {
432 while (sdio->head < sdio->tail)
433 put_page(dio->pages[sdio->head++]);
434 }
435
436 /*
437 * Wait for the next BIO to complete. Remove it and return it. NULL is
438 * returned once all BIOs have been completed. This must only be called once
439 * all bios have been issued so that dio->refcount can only decrease. This
440 * requires that that the caller hold a reference on the dio.
441 */
442 static struct bio *dio_await_one(struct dio *dio)
443 {
444 unsigned long flags;
445 struct bio *bio = NULL;
446
447 spin_lock_irqsave(&dio->bio_lock, flags);
448
449 /*
450 * Wait as long as the list is empty and there are bios in flight. bio
451 * completion drops the count, maybe adds to the list, and wakes while
452 * holding the bio_lock so we don't need set_current_state()'s barrier
453 * and can call it after testing our condition.
454 */
455 while (dio->refcount > 1 && dio->bio_list == NULL) {
456 __set_current_state(TASK_UNINTERRUPTIBLE);
457 dio->waiter = current;
458 spin_unlock_irqrestore(&dio->bio_lock, flags);
459 if (!(dio->iocb->ki_flags & IOCB_HIPRI) ||
460 !blk_poll(bdev_get_queue(dio->bio_bdev), dio->bio_cookie))
461 io_schedule();
462 /* wake up sets us TASK_RUNNING */
463 spin_lock_irqsave(&dio->bio_lock, flags);
464 dio->waiter = NULL;
465 }
466 if (dio->bio_list) {
467 bio = dio->bio_list;
468 dio->bio_list = bio->bi_private;
469 }
470 spin_unlock_irqrestore(&dio->bio_lock, flags);
471 return bio;
472 }
473
474 /*
475 * Process one completed BIO. No locks are held.
476 */
477 static int dio_bio_complete(struct dio *dio, struct bio *bio)
478 {
479 struct bio_vec *bvec;
480 unsigned i;
481 int err;
482
483 if (bio->bi_error)
484 dio->io_error = -EIO;
485
486 if (dio->is_async && dio->op == REQ_OP_READ && dio->should_dirty) {
487 err = bio->bi_error;
488 bio_check_pages_dirty(bio); /* transfers ownership */
489 } else {
490 bio_for_each_segment_all(bvec, bio, i) {
491 struct page *page = bvec->bv_page;
492
493 if (dio->op == REQ_OP_READ && !PageCompound(page) &&
494 dio->should_dirty)
495 set_page_dirty_lock(page);
496 put_page(page);
497 }
498 err = bio->bi_error;
499 bio_put(bio);
500 }
501 return err;
502 }
503
504 /*
505 * Wait on and process all in-flight BIOs. This must only be called once
506 * all bios have been issued so that the refcount can only decrease.
507 * This just waits for all bios to make it through dio_bio_complete. IO
508 * errors are propagated through dio->io_error and should be propagated via
509 * dio_complete().
510 */
511 static void dio_await_completion(struct dio *dio)
512 {
513 struct bio *bio;
514 do {
515 bio = dio_await_one(dio);
516 if (bio)
517 dio_bio_complete(dio, bio);
518 } while (bio);
519 }
520
521 /*
522 * A really large O_DIRECT read or write can generate a lot of BIOs. So
523 * to keep the memory consumption sane we periodically reap any completed BIOs
524 * during the BIO generation phase.
525 *
526 * This also helps to limit the peak amount of pinned userspace memory.
527 */
528 static inline int dio_bio_reap(struct dio *dio, struct dio_submit *sdio)
529 {
530 int ret = 0;
531
532 if (sdio->reap_counter++ >= 64) {
533 while (dio->bio_list) {
534 unsigned long flags;
535 struct bio *bio;
536 int ret2;
537
538 spin_lock_irqsave(&dio->bio_lock, flags);
539 bio = dio->bio_list;
540 dio->bio_list = bio->bi_private;
541 spin_unlock_irqrestore(&dio->bio_lock, flags);
542 ret2 = dio_bio_complete(dio, bio);
543 if (ret == 0)
544 ret = ret2;
545 }
546 sdio->reap_counter = 0;
547 }
548 return ret;
549 }
550
551 /*
552 * Create workqueue for deferred direct IO completions. We allocate the
553 * workqueue when it's first needed. This avoids creating workqueue for
554 * filesystems that don't need it and also allows us to create the workqueue
555 * late enough so the we can include s_id in the name of the workqueue.
556 */
557 static int sb_init_dio_done_wq(struct super_block *sb)
558 {
559 struct workqueue_struct *old;
560 struct workqueue_struct *wq = alloc_workqueue("dio/%s",
561 WQ_MEM_RECLAIM, 0,
562 sb->s_id);
563 if (!wq)
564 return -ENOMEM;
565 /*
566 * This has to be atomic as more DIOs can race to create the workqueue
567 */
568 old = cmpxchg(&sb->s_dio_done_wq, NULL, wq);
569 /* Someone created workqueue before us? Free ours... */
570 if (old)
571 destroy_workqueue(wq);
572 return 0;
573 }
574
575 static int dio_set_defer_completion(struct dio *dio)
576 {
577 struct super_block *sb = dio->inode->i_sb;
578
579 if (dio->defer_completion)
580 return 0;
581 dio->defer_completion = true;
582 if (!sb->s_dio_done_wq)
583 return sb_init_dio_done_wq(sb);
584 return 0;
585 }
586
587 /*
588 * Call into the fs to map some more disk blocks. We record the current number
589 * of available blocks at sdio->blocks_available. These are in units of the
590 * fs blocksize, (1 << inode->i_blkbits).
591 *
592 * The fs is allowed to map lots of blocks at once. If it wants to do that,
593 * it uses the passed inode-relative block number as the file offset, as usual.
594 *
595 * get_block() is passed the number of i_blkbits-sized blocks which direct_io
596 * has remaining to do. The fs should not map more than this number of blocks.
597 *
598 * If the fs has mapped a lot of blocks, it should populate bh->b_size to
599 * indicate how much contiguous disk space has been made available at
600 * bh->b_blocknr.
601 *
602 * If *any* of the mapped blocks are new, then the fs must set buffer_new().
603 * This isn't very efficient...
604 *
605 * In the case of filesystem holes: the fs may return an arbitrarily-large
606 * hole by returning an appropriate value in b_size and by clearing
607 * buffer_mapped(). However the direct-io code will only process holes one
608 * block at a time - it will repeatedly call get_block() as it walks the hole.
609 */
610 static int get_more_blocks(struct dio *dio, struct dio_submit *sdio,
611 struct buffer_head *map_bh)
612 {
613 int ret;
614 sector_t fs_startblk; /* Into file, in filesystem-sized blocks */
615 sector_t fs_endblk; /* Into file, in filesystem-sized blocks */
616 unsigned long fs_count; /* Number of filesystem-sized blocks */
617 int create;
618 unsigned int i_blkbits = sdio->blkbits + sdio->blkfactor;
619
620 /*
621 * If there was a memory error and we've overwritten all the
622 * mapped blocks then we can now return that memory error
623 */
624 ret = dio->page_errors;
625 if (ret == 0) {
626 BUG_ON(sdio->block_in_file >= sdio->final_block_in_request);
627 fs_startblk = sdio->block_in_file >> sdio->blkfactor;
628 fs_endblk = (sdio->final_block_in_request - 1) >>
629 sdio->blkfactor;
630 fs_count = fs_endblk - fs_startblk + 1;
631
632 map_bh->b_state = 0;
633 map_bh->b_size = fs_count << i_blkbits;
634
635 /*
636 * For writes that could fill holes inside i_size on a
637 * DIO_SKIP_HOLES filesystem we forbid block creations: only
638 * overwrites are permitted. We will return early to the caller
639 * once we see an unmapped buffer head returned, and the caller
640 * will fall back to buffered I/O.
641 *
642 * Otherwise the decision is left to the get_blocks method,
643 * which may decide to handle it or also return an unmapped
644 * buffer head.
645 */
646 create = dio->op == REQ_OP_WRITE;
647 if (dio->flags & DIO_SKIP_HOLES) {
648 if (fs_startblk <= ((i_size_read(dio->inode) - 1) >>
649 i_blkbits))
650 create = 0;
651 }
652
653 ret = (*sdio->get_block)(dio->inode, fs_startblk,
654 map_bh, create);
655
656 /* Store for completion */
657 dio->private = map_bh->b_private;
658
659 if (ret == 0 && buffer_defer_completion(map_bh))
660 ret = dio_set_defer_completion(dio);
661 }
662 return ret;
663 }
664
665 /*
666 * There is no bio. Make one now.
667 */
668 static inline int dio_new_bio(struct dio *dio, struct dio_submit *sdio,
669 sector_t start_sector, struct buffer_head *map_bh)
670 {
671 sector_t sector;
672 int ret, nr_pages;
673
674 ret = dio_bio_reap(dio, sdio);
675 if (ret)
676 goto out;
677 sector = start_sector << (sdio->blkbits - 9);
678 nr_pages = min(sdio->pages_in_io, BIO_MAX_PAGES);
679 BUG_ON(nr_pages <= 0);
680 dio_bio_alloc(dio, sdio, map_bh->b_bdev, sector, nr_pages);
681 sdio->boundary = 0;
682 out:
683 return ret;
684 }
685
686 /*
687 * Attempt to put the current chunk of 'cur_page' into the current BIO. If
688 * that was successful then update final_block_in_bio and take a ref against
689 * the just-added page.
690 *
691 * Return zero on success. Non-zero means the caller needs to start a new BIO.
692 */
693 static inline int dio_bio_add_page(struct dio_submit *sdio)
694 {
695 int ret;
696
697 ret = bio_add_page(sdio->bio, sdio->cur_page,
698 sdio->cur_page_len, sdio->cur_page_offset);
699 if (ret == sdio->cur_page_len) {
700 /*
701 * Decrement count only, if we are done with this page
702 */
703 if ((sdio->cur_page_len + sdio->cur_page_offset) == PAGE_SIZE)
704 sdio->pages_in_io--;
705 get_page(sdio->cur_page);
706 sdio->final_block_in_bio = sdio->cur_page_block +
707 (sdio->cur_page_len >> sdio->blkbits);
708 ret = 0;
709 } else {
710 ret = 1;
711 }
712 return ret;
713 }
714
715 /*
716 * Put cur_page under IO. The section of cur_page which is described by
717 * cur_page_offset,cur_page_len is put into a BIO. The section of cur_page
718 * starts on-disk at cur_page_block.
719 *
720 * We take a ref against the page here (on behalf of its presence in the bio).
721 *
722 * The caller of this function is responsible for removing cur_page from the
723 * dio, and for dropping the refcount which came from that presence.
724 */
725 static inline int dio_send_cur_page(struct dio *dio, struct dio_submit *sdio,
726 struct buffer_head *map_bh)
727 {
728 int ret = 0;
729
730 if (sdio->bio) {
731 loff_t cur_offset = sdio->cur_page_fs_offset;
732 loff_t bio_next_offset = sdio->logical_offset_in_bio +
733 sdio->bio->bi_iter.bi_size;
734
735 /*
736 * See whether this new request is contiguous with the old.
737 *
738 * Btrfs cannot handle having logically non-contiguous requests
739 * submitted. For example if you have
740 *
741 * Logical: [0-4095][HOLE][8192-12287]
742 * Physical: [0-4095] [4096-8191]
743 *
744 * We cannot submit those pages together as one BIO. So if our
745 * current logical offset in the file does not equal what would
746 * be the next logical offset in the bio, submit the bio we
747 * have.
748 */
749 if (sdio->final_block_in_bio != sdio->cur_page_block ||
750 cur_offset != bio_next_offset)
751 dio_bio_submit(dio, sdio);
752 }
753
754 if (sdio->bio == NULL) {
755 ret = dio_new_bio(dio, sdio, sdio->cur_page_block, map_bh);
756 if (ret)
757 goto out;
758 }
759
760 if (dio_bio_add_page(sdio) != 0) {
761 dio_bio_submit(dio, sdio);
762 ret = dio_new_bio(dio, sdio, sdio->cur_page_block, map_bh);
763 if (ret == 0) {
764 ret = dio_bio_add_page(sdio);
765 BUG_ON(ret != 0);
766 }
767 }
768 out:
769 return ret;
770 }
771
772 /*
773 * An autonomous function to put a chunk of a page under deferred IO.
774 *
775 * The caller doesn't actually know (or care) whether this piece of page is in
776 * a BIO, or is under IO or whatever. We just take care of all possible
777 * situations here. The separation between the logic of do_direct_IO() and
778 * that of submit_page_section() is important for clarity. Please don't break.
779 *
780 * The chunk of page starts on-disk at blocknr.
781 *
782 * We perform deferred IO, by recording the last-submitted page inside our
783 * private part of the dio structure. If possible, we just expand the IO
784 * across that page here.
785 *
786 * If that doesn't work out then we put the old page into the bio and add this
787 * page to the dio instead.
788 */
789 static inline int
790 submit_page_section(struct dio *dio, struct dio_submit *sdio, struct page *page,
791 unsigned offset, unsigned len, sector_t blocknr,
792 struct buffer_head *map_bh)
793 {
794 int ret = 0;
795
796 if (dio->op == REQ_OP_WRITE) {
797 /*
798 * Read accounting is performed in submit_bio()
799 */
800 task_io_account_write(len);
801 }
802
803 /*
804 * Can we just grow the current page's presence in the dio?
805 */
806 if (sdio->cur_page == page &&
807 sdio->cur_page_offset + sdio->cur_page_len == offset &&
808 sdio->cur_page_block +
809 (sdio->cur_page_len >> sdio->blkbits) == blocknr) {
810 sdio->cur_page_len += len;
811 goto out;
812 }
813
814 /*
815 * If there's a deferred page already there then send it.
816 */
817 if (sdio->cur_page) {
818 ret = dio_send_cur_page(dio, sdio, map_bh);
819 put_page(sdio->cur_page);
820 sdio->cur_page = NULL;
821 if (ret)
822 return ret;
823 }
824
825 get_page(page); /* It is in dio */
826 sdio->cur_page = page;
827 sdio->cur_page_offset = offset;
828 sdio->cur_page_len = len;
829 sdio->cur_page_block = blocknr;
830 sdio->cur_page_fs_offset = sdio->block_in_file << sdio->blkbits;
831 out:
832 /*
833 * If sdio->boundary then we want to schedule the IO now to
834 * avoid metadata seeks.
835 */
836 if (sdio->boundary) {
837 ret = dio_send_cur_page(dio, sdio, map_bh);
838 dio_bio_submit(dio, sdio);
839 put_page(sdio->cur_page);
840 sdio->cur_page = NULL;
841 }
842 return ret;
843 }
844
845 /*
846 * Clean any dirty buffers in the blockdev mapping which alias newly-created
847 * file blocks. Only called for S_ISREG files - blockdevs do not set
848 * buffer_new
849 */
850 static void clean_blockdev_aliases(struct dio *dio, struct buffer_head *map_bh)
851 {
852 unsigned i;
853 unsigned nblocks;
854
855 nblocks = map_bh->b_size >> dio->inode->i_blkbits;
856
857 for (i = 0; i < nblocks; i++) {
858 unmap_underlying_metadata(map_bh->b_bdev,
859 map_bh->b_blocknr + i);
860 }
861 }
862
863 /*
864 * If we are not writing the entire block and get_block() allocated
865 * the block for us, we need to fill-in the unused portion of the
866 * block with zeros. This happens only if user-buffer, fileoffset or
867 * io length is not filesystem block-size multiple.
868 *
869 * `end' is zero if we're doing the start of the IO, 1 at the end of the
870 * IO.
871 */
872 static inline void dio_zero_block(struct dio *dio, struct dio_submit *sdio,
873 int end, struct buffer_head *map_bh)
874 {
875 unsigned dio_blocks_per_fs_block;
876 unsigned this_chunk_blocks; /* In dio_blocks */
877 unsigned this_chunk_bytes;
878 struct page *page;
879
880 sdio->start_zero_done = 1;
881 if (!sdio->blkfactor || !buffer_new(map_bh))
882 return;
883
884 dio_blocks_per_fs_block = 1 << sdio->blkfactor;
885 this_chunk_blocks = sdio->block_in_file & (dio_blocks_per_fs_block - 1);
886
887 if (!this_chunk_blocks)
888 return;
889
890 /*
891 * We need to zero out part of an fs block. It is either at the
892 * beginning or the end of the fs block.
893 */
894 if (end)
895 this_chunk_blocks = dio_blocks_per_fs_block - this_chunk_blocks;
896
897 this_chunk_bytes = this_chunk_blocks << sdio->blkbits;
898
899 page = ZERO_PAGE(0);
900 if (submit_page_section(dio, sdio, page, 0, this_chunk_bytes,
901 sdio->next_block_for_io, map_bh))
902 return;
903
904 sdio->next_block_for_io += this_chunk_blocks;
905 }
906
907 /*
908 * Walk the user pages, and the file, mapping blocks to disk and generating
909 * a sequence of (page,offset,len,block) mappings. These mappings are injected
910 * into submit_page_section(), which takes care of the next stage of submission
911 *
912 * Direct IO against a blockdev is different from a file. Because we can
913 * happily perform page-sized but 512-byte aligned IOs. It is important that
914 * blockdev IO be able to have fine alignment and large sizes.
915 *
916 * So what we do is to permit the ->get_block function to populate bh.b_size
917 * with the size of IO which is permitted at this offset and this i_blkbits.
918 *
919 * For best results, the blockdev should be set up with 512-byte i_blkbits and
920 * it should set b_size to PAGE_SIZE or more inside get_block(). This gives
921 * fine alignment but still allows this function to work in PAGE_SIZE units.
922 */
923 static int do_direct_IO(struct dio *dio, struct dio_submit *sdio,
924 struct buffer_head *map_bh)
925 {
926 const unsigned blkbits = sdio->blkbits;
927 int ret = 0;
928
929 while (sdio->block_in_file < sdio->final_block_in_request) {
930 struct page *page;
931 size_t from, to;
932
933 page = dio_get_page(dio, sdio);
934 if (IS_ERR(page)) {
935 ret = PTR_ERR(page);
936 goto out;
937 }
938 from = sdio->head ? 0 : sdio->from;
939 to = (sdio->head == sdio->tail - 1) ? sdio->to : PAGE_SIZE;
940 sdio->head++;
941
942 while (from < to) {
943 unsigned this_chunk_bytes; /* # of bytes mapped */
944 unsigned this_chunk_blocks; /* # of blocks */
945 unsigned u;
946
947 if (sdio->blocks_available == 0) {
948 /*
949 * Need to go and map some more disk
950 */
951 unsigned long blkmask;
952 unsigned long dio_remainder;
953
954 ret = get_more_blocks(dio, sdio, map_bh);
955 if (ret) {
956 put_page(page);
957 goto out;
958 }
959 if (!buffer_mapped(map_bh))
960 goto do_holes;
961
962 sdio->blocks_available =
963 map_bh->b_size >> sdio->blkbits;
964 sdio->next_block_for_io =
965 map_bh->b_blocknr << sdio->blkfactor;
966 if (buffer_new(map_bh))
967 clean_blockdev_aliases(dio, map_bh);
968
969 if (!sdio->blkfactor)
970 goto do_holes;
971
972 blkmask = (1 << sdio->blkfactor) - 1;
973 dio_remainder = (sdio->block_in_file & blkmask);
974
975 /*
976 * If we are at the start of IO and that IO
977 * starts partway into a fs-block,
978 * dio_remainder will be non-zero. If the IO
979 * is a read then we can simply advance the IO
980 * cursor to the first block which is to be
981 * read. But if the IO is a write and the
982 * block was newly allocated we cannot do that;
983 * the start of the fs block must be zeroed out
984 * on-disk
985 */
986 if (!buffer_new(map_bh))
987 sdio->next_block_for_io += dio_remainder;
988 sdio->blocks_available -= dio_remainder;
989 }
990 do_holes:
991 /* Handle holes */
992 if (!buffer_mapped(map_bh)) {
993 loff_t i_size_aligned;
994
995 /* AKPM: eargh, -ENOTBLK is a hack */
996 if (dio->op == REQ_OP_WRITE) {
997 put_page(page);
998 return -ENOTBLK;
999 }
1000
1001 /*
1002 * Be sure to account for a partial block as the
1003 * last block in the file
1004 */
1005 i_size_aligned = ALIGN(i_size_read(dio->inode),
1006 1 << blkbits);
1007 if (sdio->block_in_file >=
1008 i_size_aligned >> blkbits) {
1009 /* We hit eof */
1010 put_page(page);
1011 goto out;
1012 }
1013 zero_user(page, from, 1 << blkbits);
1014 sdio->block_in_file++;
1015 from += 1 << blkbits;
1016 dio->result += 1 << blkbits;
1017 goto next_block;
1018 }
1019
1020 /*
1021 * If we're performing IO which has an alignment which
1022 * is finer than the underlying fs, go check to see if
1023 * we must zero out the start of this block.
1024 */
1025 if (unlikely(sdio->blkfactor && !sdio->start_zero_done))
1026 dio_zero_block(dio, sdio, 0, map_bh);
1027
1028 /*
1029 * Work out, in this_chunk_blocks, how much disk we
1030 * can add to this page
1031 */
1032 this_chunk_blocks = sdio->blocks_available;
1033 u = (to - from) >> blkbits;
1034 if (this_chunk_blocks > u)
1035 this_chunk_blocks = u;
1036 u = sdio->final_block_in_request - sdio->block_in_file;
1037 if (this_chunk_blocks > u)
1038 this_chunk_blocks = u;
1039 this_chunk_bytes = this_chunk_blocks << blkbits;
1040 BUG_ON(this_chunk_bytes == 0);
1041
1042 if (this_chunk_blocks == sdio->blocks_available)
1043 sdio->boundary = buffer_boundary(map_bh);
1044 ret = submit_page_section(dio, sdio, page,
1045 from,
1046 this_chunk_bytes,
1047 sdio->next_block_for_io,
1048 map_bh);
1049 if (ret) {
1050 put_page(page);
1051 goto out;
1052 }
1053 sdio->next_block_for_io += this_chunk_blocks;
1054
1055 sdio->block_in_file += this_chunk_blocks;
1056 from += this_chunk_bytes;
1057 dio->result += this_chunk_bytes;
1058 sdio->blocks_available -= this_chunk_blocks;
1059 next_block:
1060 BUG_ON(sdio->block_in_file > sdio->final_block_in_request);
1061 if (sdio->block_in_file == sdio->final_block_in_request)
1062 break;
1063 }
1064
1065 /* Drop the ref which was taken in get_user_pages() */
1066 put_page(page);
1067 }
1068 out:
1069 return ret;
1070 }
1071
1072 static inline int drop_refcount(struct dio *dio)
1073 {
1074 int ret2;
1075 unsigned long flags;
1076
1077 /*
1078 * Sync will always be dropping the final ref and completing the
1079 * operation. AIO can if it was a broken operation described above or
1080 * in fact if all the bios race to complete before we get here. In
1081 * that case dio_complete() translates the EIOCBQUEUED into the proper
1082 * return code that the caller will hand to ->complete().
1083 *
1084 * This is managed by the bio_lock instead of being an atomic_t so that
1085 * completion paths can drop their ref and use the remaining count to
1086 * decide to wake the submission path atomically.
1087 */
1088 spin_lock_irqsave(&dio->bio_lock, flags);
1089 ret2 = --dio->refcount;
1090 spin_unlock_irqrestore(&dio->bio_lock, flags);
1091 return ret2;
1092 }
1093
1094 /*
1095 * This is a library function for use by filesystem drivers.
1096 *
1097 * The locking rules are governed by the flags parameter:
1098 * - if the flags value contains DIO_LOCKING we use a fancy locking
1099 * scheme for dumb filesystems.
1100 * For writes this function is called under i_mutex and returns with
1101 * i_mutex held, for reads, i_mutex is not held on entry, but it is
1102 * taken and dropped again before returning.
1103 * - if the flags value does NOT contain DIO_LOCKING we don't use any
1104 * internal locking but rather rely on the filesystem to synchronize
1105 * direct I/O reads/writes versus each other and truncate.
1106 *
1107 * To help with locking against truncate we incremented the i_dio_count
1108 * counter before starting direct I/O, and decrement it once we are done.
1109 * Truncate can wait for it to reach zero to provide exclusion. It is
1110 * expected that filesystem provide exclusion between new direct I/O
1111 * and truncates. For DIO_LOCKING filesystems this is done by i_mutex,
1112 * but other filesystems need to take care of this on their own.
1113 *
1114 * NOTE: if you pass "sdio" to anything by pointer make sure that function
1115 * is always inlined. Otherwise gcc is unable to split the structure into
1116 * individual fields and will generate much worse code. This is important
1117 * for the whole file.
1118 */
1119 static inline ssize_t
1120 do_blockdev_direct_IO(struct kiocb *iocb, struct inode *inode,
1121 struct block_device *bdev, struct iov_iter *iter,
1122 get_block_t get_block, dio_iodone_t end_io,
1123 dio_submit_t submit_io, int flags)
1124 {
1125 unsigned i_blkbits = ACCESS_ONCE(inode->i_blkbits);
1126 unsigned blkbits = i_blkbits;
1127 unsigned blocksize_mask = (1 << blkbits) - 1;
1128 ssize_t retval = -EINVAL;
1129 size_t count = iov_iter_count(iter);
1130 loff_t offset = iocb->ki_pos;
1131 loff_t end = offset + count;
1132 struct dio *dio;
1133 struct dio_submit sdio = { 0, };
1134 struct buffer_head map_bh = { 0, };
1135 struct blk_plug plug;
1136 unsigned long align = offset | iov_iter_alignment(iter);
1137
1138 /*
1139 * Avoid references to bdev if not absolutely needed to give
1140 * the early prefetch in the caller enough time.
1141 */
1142
1143 if (align & blocksize_mask) {
1144 if (bdev)
1145 blkbits = blksize_bits(bdev_logical_block_size(bdev));
1146 blocksize_mask = (1 << blkbits) - 1;
1147 if (align & blocksize_mask)
1148 goto out;
1149 }
1150
1151 /* watch out for a 0 len io from a tricksy fs */
1152 if (iov_iter_rw(iter) == READ && !iov_iter_count(iter))
1153 return 0;
1154
1155 dio = kmem_cache_alloc(dio_cache, GFP_KERNEL);
1156 retval = -ENOMEM;
1157 if (!dio)
1158 goto out;
1159 /*
1160 * Believe it or not, zeroing out the page array caused a .5%
1161 * performance regression in a database benchmark. So, we take
1162 * care to only zero out what's needed.
1163 */
1164 memset(dio, 0, offsetof(struct dio, pages));
1165
1166 dio->flags = flags;
1167 if (dio->flags & DIO_LOCKING) {
1168 if (iov_iter_rw(iter) == READ) {
1169 struct address_space *mapping =
1170 iocb->ki_filp->f_mapping;
1171
1172 /* will be released by direct_io_worker */
1173 inode_lock(inode);
1174
1175 retval = filemap_write_and_wait_range(mapping, offset,
1176 end - 1);
1177 if (retval) {
1178 inode_unlock(inode);
1179 kmem_cache_free(dio_cache, dio);
1180 goto out;
1181 }
1182 }
1183 }
1184
1185 /* Once we sampled i_size check for reads beyond EOF */
1186 dio->i_size = i_size_read(inode);
1187 if (iov_iter_rw(iter) == READ && offset >= dio->i_size) {
1188 if (dio->flags & DIO_LOCKING)
1189 inode_unlock(inode);
1190 kmem_cache_free(dio_cache, dio);
1191 retval = 0;
1192 goto out;
1193 }
1194
1195 /*
1196 * For file extending writes updating i_size before data writeouts
1197 * complete can expose uninitialized blocks in dumb filesystems.
1198 * In that case we need to wait for I/O completion even if asked
1199 * for an asynchronous write.
1200 */
1201 if (is_sync_kiocb(iocb))
1202 dio->is_async = false;
1203 else if (!(dio->flags & DIO_ASYNC_EXTEND) &&
1204 iov_iter_rw(iter) == WRITE && end > i_size_read(inode))
1205 dio->is_async = false;
1206 else
1207 dio->is_async = true;
1208
1209 dio->inode = inode;
1210 if (iov_iter_rw(iter) == WRITE) {
1211 dio->op = REQ_OP_WRITE;
1212 dio->op_flags = WRITE_ODIRECT;
1213 } else {
1214 dio->op = REQ_OP_READ;
1215 }
1216
1217 /*
1218 * For AIO O_(D)SYNC writes we need to defer completions to a workqueue
1219 * so that we can call ->fsync.
1220 */
1221 if (dio->is_async && iov_iter_rw(iter) == WRITE &&
1222 ((iocb->ki_filp->f_flags & O_DSYNC) ||
1223 IS_SYNC(iocb->ki_filp->f_mapping->host))) {
1224 retval = dio_set_defer_completion(dio);
1225 if (retval) {
1226 /*
1227 * We grab i_mutex only for reads so we don't have
1228 * to release it here
1229 */
1230 kmem_cache_free(dio_cache, dio);
1231 goto out;
1232 }
1233 }
1234
1235 /*
1236 * Will be decremented at I/O completion time.
1237 */
1238 if (!(dio->flags & DIO_SKIP_DIO_COUNT))
1239 inode_dio_begin(inode);
1240
1241 retval = 0;
1242 sdio.blkbits = blkbits;
1243 sdio.blkfactor = i_blkbits - blkbits;
1244 sdio.block_in_file = offset >> blkbits;
1245
1246 sdio.get_block = get_block;
1247 dio->end_io = end_io;
1248 sdio.submit_io = submit_io;
1249 sdio.final_block_in_bio = -1;
1250 sdio.next_block_for_io = -1;
1251
1252 dio->iocb = iocb;
1253
1254 spin_lock_init(&dio->bio_lock);
1255 dio->refcount = 1;
1256
1257 dio->should_dirty = (iter->type == ITER_IOVEC);
1258 sdio.iter = iter;
1259 sdio.final_block_in_request =
1260 (offset + iov_iter_count(iter)) >> blkbits;
1261
1262 /*
1263 * In case of non-aligned buffers, we may need 2 more
1264 * pages since we need to zero out first and last block.
1265 */
1266 if (unlikely(sdio.blkfactor))
1267 sdio.pages_in_io = 2;
1268
1269 sdio.pages_in_io += iov_iter_npages(iter, INT_MAX);
1270
1271 blk_start_plug(&plug);
1272
1273 retval = do_direct_IO(dio, &sdio, &map_bh);
1274 if (retval)
1275 dio_cleanup(dio, &sdio);
1276
1277 if (retval == -ENOTBLK) {
1278 /*
1279 * The remaining part of the request will be
1280 * be handled by buffered I/O when we return
1281 */
1282 retval = 0;
1283 }
1284 /*
1285 * There may be some unwritten disk at the end of a part-written
1286 * fs-block-sized block. Go zero that now.
1287 */
1288 dio_zero_block(dio, &sdio, 1, &map_bh);
1289
1290 if (sdio.cur_page) {
1291 ssize_t ret2;
1292
1293 ret2 = dio_send_cur_page(dio, &sdio, &map_bh);
1294 if (retval == 0)
1295 retval = ret2;
1296 put_page(sdio.cur_page);
1297 sdio.cur_page = NULL;
1298 }
1299 if (sdio.bio)
1300 dio_bio_submit(dio, &sdio);
1301
1302 blk_finish_plug(&plug);
1303
1304 /*
1305 * It is possible that, we return short IO due to end of file.
1306 * In that case, we need to release all the pages we got hold on.
1307 */
1308 dio_cleanup(dio, &sdio);
1309
1310 /*
1311 * All block lookups have been performed. For READ requests
1312 * we can let i_mutex go now that its achieved its purpose
1313 * of protecting us from looking up uninitialized blocks.
1314 */
1315 if (iov_iter_rw(iter) == READ && (dio->flags & DIO_LOCKING))
1316 inode_unlock(dio->inode);
1317
1318 /*
1319 * The only time we want to leave bios in flight is when a successful
1320 * partial aio read or full aio write have been setup. In that case
1321 * bio completion will call aio_complete. The only time it's safe to
1322 * call aio_complete is when we return -EIOCBQUEUED, so we key on that.
1323 * This had *better* be the only place that raises -EIOCBQUEUED.
1324 */
1325 BUG_ON(retval == -EIOCBQUEUED);
1326 if (dio->is_async && retval == 0 && dio->result &&
1327 (iov_iter_rw(iter) == READ || dio->result == count))
1328 retval = -EIOCBQUEUED;
1329 else
1330 dio_await_completion(dio);
1331
1332 if (drop_refcount(dio) == 0) {
1333 retval = dio_complete(dio, retval, false);
1334 } else
1335 BUG_ON(retval != -EIOCBQUEUED);
1336
1337 out:
1338 return retval;
1339 }
1340
1341 ssize_t __blockdev_direct_IO(struct kiocb *iocb, struct inode *inode,
1342 struct block_device *bdev, struct iov_iter *iter,
1343 get_block_t get_block,
1344 dio_iodone_t end_io, dio_submit_t submit_io,
1345 int flags)
1346 {
1347 /*
1348 * The block device state is needed in the end to finally
1349 * submit everything. Since it's likely to be cache cold
1350 * prefetch it here as first thing to hide some of the
1351 * latency.
1352 *
1353 * Attempt to prefetch the pieces we likely need later.
1354 */
1355 prefetch(&bdev->bd_disk->part_tbl);
1356 prefetch(bdev->bd_queue);
1357 prefetch((char *)bdev->bd_queue + SMP_CACHE_BYTES);
1358
1359 return do_blockdev_direct_IO(iocb, inode, bdev, iter, get_block,
1360 end_io, submit_io, flags);
1361 }
1362
1363 EXPORT_SYMBOL(__blockdev_direct_IO);
1364
1365 static __init int dio_init(void)
1366 {
1367 dio_cache = KMEM_CACHE(dio, SLAB_PANIC);
1368 return 0;
1369 }
1370 module_init(dio_init)