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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 : : /**
390 : : * dio_end_io - handle the end io action for the given bio
391 : : * @bio: The direct io bio thats being completed
392 : : *
393 : : * This is meant to be called by any filesystem that uses their own dio_submit_t
394 : : * so that the DIO specific endio actions are dealt with after the filesystem
395 : : * has done it's completion work.
396 : : */
397 : 0 : void dio_end_io(struct bio *bio)
398 : : {
399 : 0 : struct dio *dio = bio->bi_private;
400 : :
401 [ # # ]: 0 : if (dio->is_async)
402 : 0 : dio_bio_end_aio(bio);
403 : : else
404 : 0 : dio_bio_end_io(bio);
405 : 0 : }
406 : : EXPORT_SYMBOL_GPL(dio_end_io);
407 : :
408 : : static inline void
409 : : dio_bio_alloc(struct dio *dio, struct dio_submit *sdio,
410 : : struct block_device *bdev,
411 : : sector_t first_sector, int nr_vecs)
412 : : {
413 : : struct bio *bio;
414 : :
415 : : /*
416 : : * bio_alloc() is guaranteed to return a bio when allowed to sleep and
417 : : * we request a valid number of vectors.
418 : : */
419 : : bio = bio_alloc(GFP_KERNEL, nr_vecs);
420 : :
421 : : bio_set_dev(bio, bdev);
422 : : bio->bi_iter.bi_sector = first_sector;
423 : : bio_set_op_attrs(bio, dio->op, dio->op_flags);
424 : : if (dio->is_async)
425 : : bio->bi_end_io = dio_bio_end_aio;
426 : : else
427 : : bio->bi_end_io = dio_bio_end_io;
428 : :
429 : : bio->bi_write_hint = dio->iocb->ki_hint;
430 : :
431 : : sdio->bio = bio;
432 : : sdio->logical_offset_in_bio = sdio->cur_page_fs_offset;
433 : : }
434 : :
435 : : /*
436 : : * In the AIO read case we speculatively dirty the pages before starting IO.
437 : : * During IO completion, any of these pages which happen to have been written
438 : : * back will be redirtied by bio_check_pages_dirty().
439 : : *
440 : : * bios hold a dio reference between submit_bio and ->end_io.
441 : : */
442 : 0 : static inline void dio_bio_submit(struct dio *dio, struct dio_submit *sdio)
443 : : {
444 : 0 : struct bio *bio = sdio->bio;
445 : 0 : unsigned long flags;
446 : :
447 : 0 : bio->bi_private = dio;
448 : :
449 : 0 : spin_lock_irqsave(&dio->bio_lock, flags);
450 : 0 : dio->refcount++;
451 : 0 : spin_unlock_irqrestore(&dio->bio_lock, flags);
452 : :
453 [ # # # # : 0 : if (dio->is_async && dio->op == REQ_OP_READ && dio->should_dirty)
# # ]
454 : 0 : bio_set_pages_dirty(bio);
455 : :
456 : 0 : dio->bio_disk = bio->bi_disk;
457 : :
458 [ # # ]: 0 : if (sdio->submit_io) {
459 : 0 : sdio->submit_io(bio, dio->inode, sdio->logical_offset_in_bio);
460 : 0 : dio->bio_cookie = BLK_QC_T_NONE;
461 : : } else
462 : 0 : dio->bio_cookie = submit_bio(bio);
463 : :
464 : 0 : sdio->bio = NULL;
465 : 0 : sdio->boundary = 0;
466 : 0 : sdio->logical_offset_in_bio = 0;
467 : 0 : }
468 : :
469 : : /*
470 : : * Release any resources in case of a failure
471 : : */
472 : 0 : static inline void dio_cleanup(struct dio *dio, struct dio_submit *sdio)
473 : : {
474 [ # # # # ]: 0 : while (sdio->head < sdio->tail)
475 : 0 : put_page(dio->pages[sdio->head++]);
476 : : }
477 : :
478 : : /*
479 : : * Wait for the next BIO to complete. Remove it and return it. NULL is
480 : : * returned once all BIOs have been completed. This must only be called once
481 : : * all bios have been issued so that dio->refcount can only decrease. This
482 : : * requires that that the caller hold a reference on the dio.
483 : : */
484 : 0 : static struct bio *dio_await_one(struct dio *dio)
485 : : {
486 : 0 : unsigned long flags;
487 : 0 : struct bio *bio = NULL;
488 : :
489 : 0 : spin_lock_irqsave(&dio->bio_lock, flags);
490 : :
491 : : /*
492 : : * Wait as long as the list is empty and there are bios in flight. bio
493 : : * completion drops the count, maybe adds to the list, and wakes while
494 : : * holding the bio_lock so we don't need set_current_state()'s barrier
495 : : * and can call it after testing our condition.
496 : : */
497 [ # # # # ]: 0 : while (dio->refcount > 1 && dio->bio_list == NULL) {
498 : 0 : __set_current_state(TASK_UNINTERRUPTIBLE);
499 : 0 : dio->waiter = current;
500 : 0 : spin_unlock_irqrestore(&dio->bio_lock, flags);
501 [ # # # # ]: 0 : if (!(dio->iocb->ki_flags & IOCB_HIPRI) ||
502 : 0 : !blk_poll(dio->bio_disk->queue, dio->bio_cookie, true))
503 : 0 : io_schedule();
504 : : /* wake up sets us TASK_RUNNING */
505 : 0 : spin_lock_irqsave(&dio->bio_lock, flags);
506 : 0 : dio->waiter = NULL;
507 : : }
508 [ # # ]: 0 : if (dio->bio_list) {
509 : 0 : bio = dio->bio_list;
510 : 0 : dio->bio_list = bio->bi_private;
511 : : }
512 : 0 : spin_unlock_irqrestore(&dio->bio_lock, flags);
513 : 0 : return bio;
514 : : }
515 : :
516 : : /*
517 : : * Process one completed BIO. No locks are held.
518 : : */
519 : 0 : static blk_status_t dio_bio_complete(struct dio *dio, struct bio *bio)
520 : : {
521 : 0 : blk_status_t err = bio->bi_status;
522 [ # # # # ]: 0 : bool should_dirty = dio->op == REQ_OP_READ && dio->should_dirty;
523 : :
524 [ # # ]: 0 : if (err) {
525 [ # # # # ]: 0 : if (err == BLK_STS_AGAIN && (bio->bi_opf & REQ_NOWAIT))
526 : 0 : dio->io_error = -EAGAIN;
527 : : else
528 : 0 : dio->io_error = -EIO;
529 : : }
530 : :
531 [ # # # # ]: 0 : if (dio->is_async && should_dirty) {
532 : 0 : bio_check_pages_dirty(bio); /* transfers ownership */
533 : : } else {
534 : 0 : bio_release_pages(bio, should_dirty);
535 : 0 : bio_put(bio);
536 : : }
537 : 0 : return err;
538 : : }
539 : :
540 : : /*
541 : : * Wait on and process all in-flight BIOs. This must only be called once
542 : : * all bios have been issued so that the refcount can only decrease.
543 : : * This just waits for all bios to make it through dio_bio_complete. IO
544 : : * errors are propagated through dio->io_error and should be propagated via
545 : : * dio_complete().
546 : : */
547 : 0 : static void dio_await_completion(struct dio *dio)
548 : : {
549 : 0 : struct bio *bio;
550 : 0 : do {
551 : 0 : bio = dio_await_one(dio);
552 [ # # ]: 0 : if (bio)
553 : 0 : dio_bio_complete(dio, bio);
554 [ # # ]: 0 : } while (bio);
555 : 0 : }
556 : :
557 : : /*
558 : : * A really large O_DIRECT read or write can generate a lot of BIOs. So
559 : : * to keep the memory consumption sane we periodically reap any completed BIOs
560 : : * during the BIO generation phase.
561 : : *
562 : : * This also helps to limit the peak amount of pinned userspace memory.
563 : : */
564 : : static inline int dio_bio_reap(struct dio *dio, struct dio_submit *sdio)
565 : : {
566 : : int ret = 0;
567 : :
568 : : if (sdio->reap_counter++ >= 64) {
569 : : while (dio->bio_list) {
570 : : unsigned long flags;
571 : : struct bio *bio;
572 : : int ret2;
573 : :
574 : : spin_lock_irqsave(&dio->bio_lock, flags);
575 : : bio = dio->bio_list;
576 : : dio->bio_list = bio->bi_private;
577 : : spin_unlock_irqrestore(&dio->bio_lock, flags);
578 : : ret2 = blk_status_to_errno(dio_bio_complete(dio, bio));
579 : : if (ret == 0)
580 : : ret = ret2;
581 : : }
582 : : sdio->reap_counter = 0;
583 : : }
584 : : return ret;
585 : : }
586 : :
587 : : /*
588 : : * Create workqueue for deferred direct IO completions. We allocate the
589 : : * workqueue when it's first needed. This avoids creating workqueue for
590 : : * filesystems that don't need it and also allows us to create the workqueue
591 : : * late enough so the we can include s_id in the name of the workqueue.
592 : : */
593 : 0 : int sb_init_dio_done_wq(struct super_block *sb)
594 : : {
595 : 0 : struct workqueue_struct *old;
596 : 0 : struct workqueue_struct *wq = alloc_workqueue("dio/%s",
597 : : WQ_MEM_RECLAIM, 0,
598 : 0 : sb->s_id);
599 [ # # ]: 0 : if (!wq)
600 : : return -ENOMEM;
601 : : /*
602 : : * This has to be atomic as more DIOs can race to create the workqueue
603 : : */
604 : 0 : old = cmpxchg(&sb->s_dio_done_wq, NULL, wq);
605 : : /* Someone created workqueue before us? Free ours... */
606 [ # # ]: 0 : if (old)
607 : 0 : destroy_workqueue(wq);
608 : : return 0;
609 : : }
610 : :
611 : 0 : static int dio_set_defer_completion(struct dio *dio)
612 : : {
613 : 0 : struct super_block *sb = dio->inode->i_sb;
614 : :
615 : 0 : if (dio->defer_completion)
616 : : return 0;
617 : 0 : dio->defer_completion = true;
618 [ # # # # ]: 0 : if (!sb->s_dio_done_wq)
619 : 0 : return sb_init_dio_done_wq(sb);
620 : : return 0;
621 : : }
622 : :
623 : : /*
624 : : * Call into the fs to map some more disk blocks. We record the current number
625 : : * of available blocks at sdio->blocks_available. These are in units of the
626 : : * fs blocksize, i_blocksize(inode).
627 : : *
628 : : * The fs is allowed to map lots of blocks at once. If it wants to do that,
629 : : * it uses the passed inode-relative block number as the file offset, as usual.
630 : : *
631 : : * get_block() is passed the number of i_blkbits-sized blocks which direct_io
632 : : * has remaining to do. The fs should not map more than this number of blocks.
633 : : *
634 : : * If the fs has mapped a lot of blocks, it should populate bh->b_size to
635 : : * indicate how much contiguous disk space has been made available at
636 : : * bh->b_blocknr.
637 : : *
638 : : * If *any* of the mapped blocks are new, then the fs must set buffer_new().
639 : : * This isn't very efficient...
640 : : *
641 : : * In the case of filesystem holes: the fs may return an arbitrarily-large
642 : : * hole by returning an appropriate value in b_size and by clearing
643 : : * buffer_mapped(). However the direct-io code will only process holes one
644 : : * block at a time - it will repeatedly call get_block() as it walks the hole.
645 : : */
646 : 0 : static int get_more_blocks(struct dio *dio, struct dio_submit *sdio,
647 : : struct buffer_head *map_bh)
648 : : {
649 : 0 : int ret;
650 : 0 : sector_t fs_startblk; /* Into file, in filesystem-sized blocks */
651 : 0 : sector_t fs_endblk; /* Into file, in filesystem-sized blocks */
652 : 0 : unsigned long fs_count; /* Number of filesystem-sized blocks */
653 : 0 : int create;
654 : 0 : unsigned int i_blkbits = sdio->blkbits + sdio->blkfactor;
655 : 0 : loff_t i_size;
656 : :
657 : : /*
658 : : * If there was a memory error and we've overwritten all the
659 : : * mapped blocks then we can now return that memory error
660 : : */
661 : 0 : ret = dio->page_errors;
662 [ # # ]: 0 : if (ret == 0) {
663 [ # # ]: 0 : BUG_ON(sdio->block_in_file >= sdio->final_block_in_request);
664 : 0 : fs_startblk = sdio->block_in_file >> sdio->blkfactor;
665 : 0 : fs_endblk = (sdio->final_block_in_request - 1) >>
666 : : sdio->blkfactor;
667 : 0 : fs_count = fs_endblk - fs_startblk + 1;
668 : :
669 : 0 : map_bh->b_state = 0;
670 : 0 : map_bh->b_size = fs_count << i_blkbits;
671 : :
672 : : /*
673 : : * For writes that could fill holes inside i_size on a
674 : : * DIO_SKIP_HOLES filesystem we forbid block creations: only
675 : : * overwrites are permitted. We will return early to the caller
676 : : * once we see an unmapped buffer head returned, and the caller
677 : : * will fall back to buffered I/O.
678 : : *
679 : : * Otherwise the decision is left to the get_blocks method,
680 : : * which may decide to handle it or also return an unmapped
681 : : * buffer head.
682 : : */
683 : 0 : create = dio->op == REQ_OP_WRITE;
684 [ # # ]: 0 : if (dio->flags & DIO_SKIP_HOLES) {
685 [ # # ]: 0 : i_size = i_size_read(dio->inode);
686 [ # # # # ]: 0 : if (i_size && fs_startblk <= (i_size - 1) >> i_blkbits)
687 : 0 : create = 0;
688 : : }
689 : :
690 : 0 : ret = (*sdio->get_block)(dio->inode, fs_startblk,
691 : : map_bh, create);
692 : :
693 : : /* Store for completion */
694 : 0 : dio->private = map_bh->b_private;
695 : :
696 [ # # # # ]: 0 : if (ret == 0 && buffer_defer_completion(map_bh))
697 [ # # ]: 0 : ret = dio_set_defer_completion(dio);
698 : : }
699 : 0 : return ret;
700 : : }
701 : :
702 : : /*
703 : : * There is no bio. Make one now.
704 : : */
705 : : static inline int dio_new_bio(struct dio *dio, struct dio_submit *sdio,
706 : : sector_t start_sector, struct buffer_head *map_bh)
707 : : {
708 : : sector_t sector;
709 : : int ret, nr_pages;
710 : :
711 : : ret = dio_bio_reap(dio, sdio);
712 : : if (ret)
713 : : goto out;
714 : : sector = start_sector << (sdio->blkbits - 9);
715 : : nr_pages = min(sdio->pages_in_io, BIO_MAX_PAGES);
716 : : BUG_ON(nr_pages <= 0);
717 : : dio_bio_alloc(dio, sdio, map_bh->b_bdev, sector, nr_pages);
718 : : sdio->boundary = 0;
719 : : out:
720 : : return ret;
721 : : }
722 : :
723 : : /*
724 : : * Attempt to put the current chunk of 'cur_page' into the current BIO. If
725 : : * that was successful then update final_block_in_bio and take a ref against
726 : : * the just-added page.
727 : : *
728 : : * Return zero on success. Non-zero means the caller needs to start a new BIO.
729 : : */
730 : 0 : static inline int dio_bio_add_page(struct dio_submit *sdio)
731 : : {
732 : 0 : int ret;
733 : :
734 : 0 : ret = bio_add_page(sdio->bio, sdio->cur_page,
735 : : sdio->cur_page_len, sdio->cur_page_offset);
736 [ # # ]: 0 : if (ret == sdio->cur_page_len) {
737 : : /*
738 : : * Decrement count only, if we are done with this page
739 : : */
740 [ # # ]: 0 : if ((sdio->cur_page_len + sdio->cur_page_offset) == PAGE_SIZE)
741 : 0 : sdio->pages_in_io--;
742 [ # # ]: 0 : get_page(sdio->cur_page);
743 : 0 : sdio->final_block_in_bio = sdio->cur_page_block +
744 : 0 : (sdio->cur_page_len >> sdio->blkbits);
745 : 0 : ret = 0;
746 : : } else {
747 : : ret = 1;
748 : : }
749 : 0 : return ret;
750 : : }
751 : :
752 : : /*
753 : : * Put cur_page under IO. The section of cur_page which is described by
754 : : * cur_page_offset,cur_page_len is put into a BIO. The section of cur_page
755 : : * starts on-disk at cur_page_block.
756 : : *
757 : : * We take a ref against the page here (on behalf of its presence in the bio).
758 : : *
759 : : * The caller of this function is responsible for removing cur_page from the
760 : : * dio, and for dropping the refcount which came from that presence.
761 : : */
762 : 0 : static inline int dio_send_cur_page(struct dio *dio, struct dio_submit *sdio,
763 : : struct buffer_head *map_bh)
764 : : {
765 : 0 : int ret = 0;
766 : :
767 [ # # ]: 0 : if (sdio->bio) {
768 : 0 : loff_t cur_offset = sdio->cur_page_fs_offset;
769 : 0 : loff_t bio_next_offset = sdio->logical_offset_in_bio +
770 : 0 : sdio->bio->bi_iter.bi_size;
771 : :
772 : : /*
773 : : * See whether this new request is contiguous with the old.
774 : : *
775 : : * Btrfs cannot handle having logically non-contiguous requests
776 : : * submitted. For example if you have
777 : : *
778 : : * Logical: [0-4095][HOLE][8192-12287]
779 : : * Physical: [0-4095] [4096-8191]
780 : : *
781 : : * We cannot submit those pages together as one BIO. So if our
782 : : * current logical offset in the file does not equal what would
783 : : * be the next logical offset in the bio, submit the bio we
784 : : * have.
785 : : */
786 [ # # # # ]: 0 : if (sdio->final_block_in_bio != sdio->cur_page_block ||
787 : : cur_offset != bio_next_offset)
788 : 0 : dio_bio_submit(dio, sdio);
789 : : }
790 : :
791 [ # # ]: 0 : if (sdio->bio == NULL) {
792 : 0 : ret = dio_new_bio(dio, sdio, sdio->cur_page_block, map_bh);
793 [ # # ]: 0 : if (ret)
794 : 0 : goto out;
795 : : }
796 : :
797 [ # # ]: 0 : if (dio_bio_add_page(sdio) != 0) {
798 : 0 : dio_bio_submit(dio, sdio);
799 : 0 : ret = dio_new_bio(dio, sdio, sdio->cur_page_block, map_bh);
800 [ # # ]: 0 : if (ret == 0) {
801 : 0 : ret = dio_bio_add_page(sdio);
802 [ # # ]: 0 : BUG_ON(ret != 0);
803 : : }
804 : : }
805 : 0 : out:
806 : 0 : return ret;
807 : : }
808 : :
809 : : /*
810 : : * An autonomous function to put a chunk of a page under deferred IO.
811 : : *
812 : : * The caller doesn't actually know (or care) whether this piece of page is in
813 : : * a BIO, or is under IO or whatever. We just take care of all possible
814 : : * situations here. The separation between the logic of do_direct_IO() and
815 : : * that of submit_page_section() is important for clarity. Please don't break.
816 : : *
817 : : * The chunk of page starts on-disk at blocknr.
818 : : *
819 : : * We perform deferred IO, by recording the last-submitted page inside our
820 : : * private part of the dio structure. If possible, we just expand the IO
821 : : * across that page here.
822 : : *
823 : : * If that doesn't work out then we put the old page into the bio and add this
824 : : * page to the dio instead.
825 : : */
826 : : static inline int
827 : 0 : submit_page_section(struct dio *dio, struct dio_submit *sdio, struct page *page,
828 : : unsigned offset, unsigned len, sector_t blocknr,
829 : : struct buffer_head *map_bh)
830 : : {
831 : 0 : int ret = 0;
832 : :
833 [ # # ]: 0 : if (dio->op == REQ_OP_WRITE) {
834 : : /*
835 : : * Read accounting is performed in submit_bio()
836 : : */
837 : 0 : task_io_account_write(len);
838 : : }
839 : :
840 : : /*
841 : : * Can we just grow the current page's presence in the dio?
842 : : */
843 [ # # ]: 0 : if (sdio->cur_page == page &&
844 [ # # ]: 0 : sdio->cur_page_offset + sdio->cur_page_len == offset &&
845 : 0 : sdio->cur_page_block +
846 [ # # ]: 0 : (sdio->cur_page_len >> sdio->blkbits) == blocknr) {
847 : 0 : sdio->cur_page_len += len;
848 : 0 : goto out;
849 : : }
850 : :
851 : : /*
852 : : * If there's a deferred page already there then send it.
853 : : */
854 [ # # ]: 0 : if (sdio->cur_page) {
855 : 0 : ret = dio_send_cur_page(dio, sdio, map_bh);
856 : 0 : put_page(sdio->cur_page);
857 : 0 : sdio->cur_page = NULL;
858 [ # # ]: 0 : if (ret)
859 : : return ret;
860 : : }
861 : :
862 [ # # ]: 0 : get_page(page); /* It is in dio */
863 : 0 : sdio->cur_page = page;
864 : 0 : sdio->cur_page_offset = offset;
865 : 0 : sdio->cur_page_len = len;
866 : 0 : sdio->cur_page_block = blocknr;
867 : 0 : sdio->cur_page_fs_offset = sdio->block_in_file << sdio->blkbits;
868 : 0 : out:
869 : : /*
870 : : * If sdio->boundary then we want to schedule the IO now to
871 : : * avoid metadata seeks.
872 : : */
873 [ # # ]: 0 : if (sdio->boundary) {
874 : 0 : ret = dio_send_cur_page(dio, sdio, map_bh);
875 [ # # ]: 0 : if (sdio->bio)
876 : 0 : dio_bio_submit(dio, sdio);
877 : 0 : put_page(sdio->cur_page);
878 : 0 : sdio->cur_page = NULL;
879 : : }
880 : : return ret;
881 : : }
882 : :
883 : : /*
884 : : * If we are not writing the entire block and get_block() allocated
885 : : * the block for us, we need to fill-in the unused portion of the
886 : : * block with zeros. This happens only if user-buffer, fileoffset or
887 : : * io length is not filesystem block-size multiple.
888 : : *
889 : : * `end' is zero if we're doing the start of the IO, 1 at the end of the
890 : : * IO.
891 : : */
892 : 0 : static inline void dio_zero_block(struct dio *dio, struct dio_submit *sdio,
893 : : int end, struct buffer_head *map_bh)
894 : : {
895 : 0 : unsigned dio_blocks_per_fs_block;
896 : 0 : unsigned this_chunk_blocks; /* In dio_blocks */
897 : 0 : unsigned this_chunk_bytes;
898 : 0 : struct page *page;
899 : :
900 : 0 : sdio->start_zero_done = 1;
901 [ # # # # ]: 0 : if (!sdio->blkfactor || !buffer_new(map_bh))
902 : 0 : return;
903 : :
904 : 0 : dio_blocks_per_fs_block = 1 << sdio->blkfactor;
905 : 0 : this_chunk_blocks = sdio->block_in_file & (dio_blocks_per_fs_block - 1);
906 : :
907 [ # # ]: 0 : if (!this_chunk_blocks)
908 : : return;
909 : :
910 : : /*
911 : : * We need to zero out part of an fs block. It is either at the
912 : : * beginning or the end of the fs block.
913 : : */
914 [ # # ]: 0 : if (end)
915 : 0 : this_chunk_blocks = dio_blocks_per_fs_block - this_chunk_blocks;
916 : :
917 : 0 : this_chunk_bytes = this_chunk_blocks << sdio->blkbits;
918 : :
919 [ # # ]: 0 : page = ZERO_PAGE(0);
920 [ # # ]: 0 : if (submit_page_section(dio, sdio, page, 0, this_chunk_bytes,
921 : : sdio->next_block_for_io, map_bh))
922 : : return;
923 : :
924 : 0 : sdio->next_block_for_io += this_chunk_blocks;
925 : : }
926 : :
927 : : /*
928 : : * Walk the user pages, and the file, mapping blocks to disk and generating
929 : : * a sequence of (page,offset,len,block) mappings. These mappings are injected
930 : : * into submit_page_section(), which takes care of the next stage of submission
931 : : *
932 : : * Direct IO against a blockdev is different from a file. Because we can
933 : : * happily perform page-sized but 512-byte aligned IOs. It is important that
934 : : * blockdev IO be able to have fine alignment and large sizes.
935 : : *
936 : : * So what we do is to permit the ->get_block function to populate bh.b_size
937 : : * with the size of IO which is permitted at this offset and this i_blkbits.
938 : : *
939 : : * For best results, the blockdev should be set up with 512-byte i_blkbits and
940 : : * it should set b_size to PAGE_SIZE or more inside get_block(). This gives
941 : : * fine alignment but still allows this function to work in PAGE_SIZE units.
942 : : */
943 : 0 : static int do_direct_IO(struct dio *dio, struct dio_submit *sdio,
944 : : struct buffer_head *map_bh)
945 : : {
946 : 0 : const unsigned blkbits = sdio->blkbits;
947 : 0 : const unsigned i_blkbits = blkbits + sdio->blkfactor;
948 : 0 : int ret = 0;
949 : :
950 [ # # ]: 0 : while (sdio->block_in_file < sdio->final_block_in_request) {
951 : 0 : struct page *page;
952 : 0 : size_t from, to;
953 : :
954 : 0 : page = dio_get_page(dio, sdio);
955 [ # # ]: 0 : if (IS_ERR(page)) {
956 : 0 : ret = PTR_ERR(page);
957 : 0 : goto out;
958 : : }
959 [ # # ]: 0 : from = sdio->head ? 0 : sdio->from;
960 [ # # ]: 0 : to = (sdio->head == sdio->tail - 1) ? sdio->to : PAGE_SIZE;
961 : 0 : sdio->head++;
962 : :
963 [ # # ]: 0 : while (from < to) {
964 : 0 : unsigned this_chunk_bytes; /* # of bytes mapped */
965 : 0 : unsigned this_chunk_blocks; /* # of blocks */
966 : 0 : unsigned u;
967 : :
968 [ # # ]: 0 : if (sdio->blocks_available == 0) {
969 : : /*
970 : : * Need to go and map some more disk
971 : : */
972 : 0 : unsigned long blkmask;
973 : 0 : unsigned long dio_remainder;
974 : :
975 : 0 : ret = get_more_blocks(dio, sdio, map_bh);
976 [ # # ]: 0 : if (ret) {
977 : 0 : put_page(page);
978 : 0 : goto out;
979 : : }
980 [ # # ]: 0 : if (!buffer_mapped(map_bh))
981 : 0 : goto do_holes;
982 : :
983 : 0 : sdio->blocks_available =
984 : 0 : map_bh->b_size >> blkbits;
985 : 0 : sdio->next_block_for_io =
986 : 0 : map_bh->b_blocknr << sdio->blkfactor;
987 [ # # ]: 0 : if (buffer_new(map_bh)) {
988 : 0 : clean_bdev_aliases(
989 : : map_bh->b_bdev,
990 : : map_bh->b_blocknr,
991 : 0 : map_bh->b_size >> i_blkbits);
992 : : }
993 : :
994 [ # # ]: 0 : if (!sdio->blkfactor)
995 : 0 : goto do_holes;
996 : :
997 : 0 : blkmask = (1 << sdio->blkfactor) - 1;
998 : 0 : dio_remainder = (sdio->block_in_file & blkmask);
999 : :
1000 : : /*
1001 : : * If we are at the start of IO and that IO
1002 : : * starts partway into a fs-block,
1003 : : * dio_remainder will be non-zero. If the IO
1004 : : * is a read then we can simply advance the IO
1005 : : * cursor to the first block which is to be
1006 : : * read. But if the IO is a write and the
1007 : : * block was newly allocated we cannot do that;
1008 : : * the start of the fs block must be zeroed out
1009 : : * on-disk
1010 : : */
1011 [ # # ]: 0 : if (!buffer_new(map_bh))
1012 : 0 : sdio->next_block_for_io += dio_remainder;
1013 : 0 : sdio->blocks_available -= dio_remainder;
1014 : : }
1015 : 0 : do_holes:
1016 : : /* Handle holes */
1017 [ # # ]: 0 : if (!buffer_mapped(map_bh)) {
1018 : 0 : loff_t i_size_aligned;
1019 : :
1020 : : /* AKPM: eargh, -ENOTBLK is a hack */
1021 [ # # ]: 0 : if (dio->op == REQ_OP_WRITE) {
1022 : 0 : put_page(page);
1023 : 0 : return -ENOTBLK;
1024 : : }
1025 : :
1026 : : /*
1027 : : * Be sure to account for a partial block as the
1028 : : * last block in the file
1029 : : */
1030 [ # # ]: 0 : i_size_aligned = ALIGN(i_size_read(dio->inode),
1031 : : 1 << blkbits);
1032 : 0 : if (sdio->block_in_file >=
1033 [ # # ]: 0 : i_size_aligned >> blkbits) {
1034 : : /* We hit eof */
1035 : 0 : put_page(page);
1036 : 0 : goto out;
1037 : : }
1038 : 0 : zero_user(page, from, 1 << blkbits);
1039 : 0 : sdio->block_in_file++;
1040 : 0 : from += 1 << blkbits;
1041 : 0 : dio->result += 1 << blkbits;
1042 : 0 : goto next_block;
1043 : : }
1044 : :
1045 : : /*
1046 : : * If we're performing IO which has an alignment which
1047 : : * is finer than the underlying fs, go check to see if
1048 : : * we must zero out the start of this block.
1049 : : */
1050 [ # # # # ]: 0 : if (unlikely(sdio->blkfactor && !sdio->start_zero_done))
1051 : 0 : dio_zero_block(dio, sdio, 0, map_bh);
1052 : :
1053 : : /*
1054 : : * Work out, in this_chunk_blocks, how much disk we
1055 : : * can add to this page
1056 : : */
1057 : 0 : this_chunk_blocks = sdio->blocks_available;
1058 : 0 : u = (to - from) >> blkbits;
1059 : 0 : if (this_chunk_blocks > u)
1060 : : this_chunk_blocks = u;
1061 : 0 : u = sdio->final_block_in_request - sdio->block_in_file;
1062 : 0 : if (this_chunk_blocks > u)
1063 : : this_chunk_blocks = u;
1064 : 0 : this_chunk_bytes = this_chunk_blocks << blkbits;
1065 [ # # ]: 0 : BUG_ON(this_chunk_bytes == 0);
1066 : :
1067 [ # # ]: 0 : if (this_chunk_blocks == sdio->blocks_available)
1068 : 0 : sdio->boundary = buffer_boundary(map_bh);
1069 : 0 : ret = submit_page_section(dio, sdio, page,
1070 : : from,
1071 : : this_chunk_bytes,
1072 : : sdio->next_block_for_io,
1073 : : map_bh);
1074 [ # # ]: 0 : if (ret) {
1075 : 0 : put_page(page);
1076 : 0 : goto out;
1077 : : }
1078 : 0 : sdio->next_block_for_io += this_chunk_blocks;
1079 : :
1080 : 0 : sdio->block_in_file += this_chunk_blocks;
1081 : 0 : from += this_chunk_bytes;
1082 : 0 : dio->result += this_chunk_bytes;
1083 : 0 : sdio->blocks_available -= this_chunk_blocks;
1084 : 0 : next_block:
1085 [ # # ]: 0 : BUG_ON(sdio->block_in_file > sdio->final_block_in_request);
1086 [ # # ]: 0 : if (sdio->block_in_file == sdio->final_block_in_request)
1087 : : break;
1088 : : }
1089 : :
1090 : : /* Drop the ref which was taken in get_user_pages() */
1091 : 0 : put_page(page);
1092 : : }
1093 : 0 : out:
1094 : : return ret;
1095 : : }
1096 : :
1097 : 0 : static inline int drop_refcount(struct dio *dio)
1098 : : {
1099 : 0 : int ret2;
1100 : 0 : unsigned long flags;
1101 : :
1102 : : /*
1103 : : * Sync will always be dropping the final ref and completing the
1104 : : * operation. AIO can if it was a broken operation described above or
1105 : : * in fact if all the bios race to complete before we get here. In
1106 : : * that case dio_complete() translates the EIOCBQUEUED into the proper
1107 : : * return code that the caller will hand to ->complete().
1108 : : *
1109 : : * This is managed by the bio_lock instead of being an atomic_t so that
1110 : : * completion paths can drop their ref and use the remaining count to
1111 : : * decide to wake the submission path atomically.
1112 : : */
1113 : 0 : spin_lock_irqsave(&dio->bio_lock, flags);
1114 : 0 : ret2 = --dio->refcount;
1115 : 0 : spin_unlock_irqrestore(&dio->bio_lock, flags);
1116 : 0 : return ret2;
1117 : : }
1118 : :
1119 : : /*
1120 : : * This is a library function for use by filesystem drivers.
1121 : : *
1122 : : * The locking rules are governed by the flags parameter:
1123 : : * - if the flags value contains DIO_LOCKING we use a fancy locking
1124 : : * scheme for dumb filesystems.
1125 : : * For writes this function is called under i_mutex and returns with
1126 : : * i_mutex held, for reads, i_mutex is not held on entry, but it is
1127 : : * taken and dropped again before returning.
1128 : : * - if the flags value does NOT contain DIO_LOCKING we don't use any
1129 : : * internal locking but rather rely on the filesystem to synchronize
1130 : : * direct I/O reads/writes versus each other and truncate.
1131 : : *
1132 : : * To help with locking against truncate we incremented the i_dio_count
1133 : : * counter before starting direct I/O, and decrement it once we are done.
1134 : : * Truncate can wait for it to reach zero to provide exclusion. It is
1135 : : * expected that filesystem provide exclusion between new direct I/O
1136 : : * and truncates. For DIO_LOCKING filesystems this is done by i_mutex,
1137 : : * but other filesystems need to take care of this on their own.
1138 : : *
1139 : : * NOTE: if you pass "sdio" to anything by pointer make sure that function
1140 : : * is always inlined. Otherwise gcc is unable to split the structure into
1141 : : * individual fields and will generate much worse code. This is important
1142 : : * for the whole file.
1143 : : */
1144 : : static inline ssize_t
1145 : 0 : do_blockdev_direct_IO(struct kiocb *iocb, struct inode *inode,
1146 : : struct block_device *bdev, struct iov_iter *iter,
1147 : : get_block_t get_block, dio_iodone_t end_io,
1148 : : dio_submit_t submit_io, int flags)
1149 : : {
1150 : 0 : unsigned i_blkbits = READ_ONCE(inode->i_blkbits);
1151 : 0 : unsigned blkbits = i_blkbits;
1152 : 0 : unsigned blocksize_mask = (1 << blkbits) - 1;
1153 : 0 : ssize_t retval = -EINVAL;
1154 : 0 : const size_t count = iov_iter_count(iter);
1155 : 0 : loff_t offset = iocb->ki_pos;
1156 : 0 : const loff_t end = offset + count;
1157 : 0 : struct dio *dio;
1158 : 0 : struct dio_submit sdio = { 0, };
1159 : 0 : struct buffer_head map_bh = { 0, };
1160 : 0 : struct blk_plug plug;
1161 : 0 : unsigned long align = offset | iov_iter_alignment(iter);
1162 : :
1163 : : /*
1164 : : * Avoid references to bdev if not absolutely needed to give
1165 : : * the early prefetch in the caller enough time.
1166 : : */
1167 : :
1168 [ # # ]: 0 : if (align & blocksize_mask) {
1169 [ # # ]: 0 : if (bdev)
1170 [ # # ]: 0 : blkbits = blksize_bits(bdev_logical_block_size(bdev));
1171 : 0 : blocksize_mask = (1 << blkbits) - 1;
1172 [ # # ]: 0 : if (align & blocksize_mask)
1173 : 0 : goto out;
1174 : : }
1175 : :
1176 : : /* watch out for a 0 len io from a tricksy fs */
1177 [ # # # # ]: 0 : if (iov_iter_rw(iter) == READ && !count)
1178 : : return 0;
1179 : :
1180 : 0 : dio = kmem_cache_alloc(dio_cache, GFP_KERNEL);
1181 : 0 : retval = -ENOMEM;
1182 [ # # ]: 0 : if (!dio)
1183 : 0 : goto out;
1184 : : /*
1185 : : * Believe it or not, zeroing out the page array caused a .5%
1186 : : * performance regression in a database benchmark. So, we take
1187 : : * care to only zero out what's needed.
1188 : : */
1189 : 0 : memset(dio, 0, offsetof(struct dio, pages));
1190 : :
1191 : 0 : dio->flags = flags;
1192 [ # # ]: 0 : if (dio->flags & DIO_LOCKING) {
1193 [ # # ]: 0 : if (iov_iter_rw(iter) == READ) {
1194 : 0 : struct address_space *mapping =
1195 : 0 : iocb->ki_filp->f_mapping;
1196 : :
1197 : : /* will be released by direct_io_worker */
1198 : 0 : inode_lock(inode);
1199 : :
1200 : 0 : retval = filemap_write_and_wait_range(mapping, offset,
1201 : : end - 1);
1202 [ # # ]: 0 : if (retval) {
1203 : 0 : inode_unlock(inode);
1204 : 0 : kmem_cache_free(dio_cache, dio);
1205 : 0 : goto out;
1206 : : }
1207 : : }
1208 : : }
1209 : :
1210 : : /* Once we sampled i_size check for reads beyond EOF */
1211 [ # # ]: 0 : dio->i_size = i_size_read(inode);
1212 [ # # # # ]: 0 : if (iov_iter_rw(iter) == READ && offset >= dio->i_size) {
1213 [ # # ]: 0 : if (dio->flags & DIO_LOCKING)
1214 : 0 : inode_unlock(inode);
1215 : 0 : kmem_cache_free(dio_cache, dio);
1216 : 0 : retval = 0;
1217 : 0 : goto out;
1218 : : }
1219 : :
1220 : : /*
1221 : : * For file extending writes updating i_size before data writeouts
1222 : : * complete can expose uninitialized blocks in dumb filesystems.
1223 : : * In that case we need to wait for I/O completion even if asked
1224 : : * for an asynchronous write.
1225 : : */
1226 [ # # ]: 0 : if (is_sync_kiocb(iocb))
1227 : 0 : dio->is_async = false;
1228 [ # # # # ]: 0 : else if (iov_iter_rw(iter) == WRITE && end > i_size_read(inode))
1229 : 0 : dio->is_async = false;
1230 : : else
1231 : 0 : dio->is_async = true;
1232 : :
1233 : 0 : dio->inode = inode;
1234 [ # # ]: 0 : if (iov_iter_rw(iter) == WRITE) {
1235 : 0 : dio->op = REQ_OP_WRITE;
1236 : 0 : dio->op_flags = REQ_SYNC | REQ_IDLE;
1237 [ # # ]: 0 : if (iocb->ki_flags & IOCB_NOWAIT)
1238 : 0 : dio->op_flags |= REQ_NOWAIT;
1239 : : } else {
1240 : 0 : dio->op = REQ_OP_READ;
1241 : : }
1242 [ # # ]: 0 : if (iocb->ki_flags & IOCB_HIPRI)
1243 : 0 : dio->op_flags |= REQ_HIPRI;
1244 : :
1245 : : /*
1246 : : * For AIO O_(D)SYNC writes we need to defer completions to a workqueue
1247 : : * so that we can call ->fsync.
1248 : : */
1249 [ # # # # ]: 0 : if (dio->is_async && iov_iter_rw(iter) == WRITE) {
1250 : 0 : retval = 0;
1251 [ # # ]: 0 : if (iocb->ki_flags & IOCB_DSYNC)
1252 [ # # ]: 0 : retval = dio_set_defer_completion(dio);
1253 [ # # ]: 0 : else if (!dio->inode->i_sb->s_dio_done_wq) {
1254 : : /*
1255 : : * In case of AIO write racing with buffered read we
1256 : : * need to defer completion. We can't decide this now,
1257 : : * however the workqueue needs to be initialized here.
1258 : : */
1259 : 0 : retval = sb_init_dio_done_wq(dio->inode->i_sb);
1260 : : }
1261 [ # # ]: 0 : if (retval) {
1262 : : /*
1263 : : * We grab i_mutex only for reads so we don't have
1264 : : * to release it here
1265 : : */
1266 : 0 : kmem_cache_free(dio_cache, dio);
1267 : 0 : goto out;
1268 : : }
1269 : : }
1270 : :
1271 : : /*
1272 : : * Will be decremented at I/O completion time.
1273 : : */
1274 : 0 : inode_dio_begin(inode);
1275 : :
1276 : 0 : retval = 0;
1277 : 0 : sdio.blkbits = blkbits;
1278 : 0 : sdio.blkfactor = i_blkbits - blkbits;
1279 : 0 : sdio.block_in_file = offset >> blkbits;
1280 : :
1281 : 0 : sdio.get_block = get_block;
1282 : 0 : dio->end_io = end_io;
1283 : 0 : sdio.submit_io = submit_io;
1284 : 0 : sdio.final_block_in_bio = -1;
1285 : 0 : sdio.next_block_for_io = -1;
1286 : :
1287 : 0 : dio->iocb = iocb;
1288 : :
1289 [ # # ]: 0 : spin_lock_init(&dio->bio_lock);
1290 : 0 : dio->refcount = 1;
1291 : :
1292 [ # # ]: 0 : dio->should_dirty = iter_is_iovec(iter) && iov_iter_rw(iter) == READ;
1293 : 0 : sdio.iter = iter;
1294 : 0 : sdio.final_block_in_request = end >> blkbits;
1295 : :
1296 : : /*
1297 : : * In case of non-aligned buffers, we may need 2 more
1298 : : * pages since we need to zero out first and last block.
1299 : : */
1300 [ # # ]: 0 : if (unlikely(sdio.blkfactor))
1301 : 0 : sdio.pages_in_io = 2;
1302 : :
1303 : 0 : sdio.pages_in_io += iov_iter_npages(iter, INT_MAX);
1304 : :
1305 : 0 : blk_start_plug(&plug);
1306 : :
1307 : 0 : retval = do_direct_IO(dio, &sdio, &map_bh);
1308 [ # # ]: 0 : if (retval)
1309 : : dio_cleanup(dio, &sdio);
1310 : :
1311 [ # # ]: 0 : if (retval == -ENOTBLK) {
1312 : : /*
1313 : : * The remaining part of the request will be
1314 : : * be handled by buffered I/O when we return
1315 : : */
1316 : 0 : retval = 0;
1317 : : }
1318 : : /*
1319 : : * There may be some unwritten disk at the end of a part-written
1320 : : * fs-block-sized block. Go zero that now.
1321 : : */
1322 : 0 : dio_zero_block(dio, &sdio, 1, &map_bh);
1323 : :
1324 [ # # ]: 0 : if (sdio.cur_page) {
1325 : 0 : ssize_t ret2;
1326 : :
1327 : 0 : ret2 = dio_send_cur_page(dio, &sdio, &map_bh);
1328 [ # # ]: 0 : if (retval == 0)
1329 : 0 : retval = ret2;
1330 : 0 : put_page(sdio.cur_page);
1331 : 0 : sdio.cur_page = NULL;
1332 : : }
1333 [ # # ]: 0 : if (sdio.bio)
1334 : 0 : dio_bio_submit(dio, &sdio);
1335 : :
1336 : 0 : blk_finish_plug(&plug);
1337 : :
1338 : : /*
1339 : : * It is possible that, we return short IO due to end of file.
1340 : : * In that case, we need to release all the pages we got hold on.
1341 : : */
1342 : 0 : dio_cleanup(dio, &sdio);
1343 : :
1344 : : /*
1345 : : * All block lookups have been performed. For READ requests
1346 : : * we can let i_mutex go now that its achieved its purpose
1347 : : * of protecting us from looking up uninitialized blocks.
1348 : : */
1349 [ # # # # ]: 0 : if (iov_iter_rw(iter) == READ && (dio->flags & DIO_LOCKING))
1350 : 0 : inode_unlock(dio->inode);
1351 : :
1352 : : /*
1353 : : * The only time we want to leave bios in flight is when a successful
1354 : : * partial aio read or full aio write have been setup. In that case
1355 : : * bio completion will call aio_complete. The only time it's safe to
1356 : : * call aio_complete is when we return -EIOCBQUEUED, so we key on that.
1357 : : * This had *better* be the only place that raises -EIOCBQUEUED.
1358 : : */
1359 [ # # ]: 0 : BUG_ON(retval == -EIOCBQUEUED);
1360 [ # # # # : 0 : if (dio->is_async && retval == 0 && dio->result &&
# # # # ]
1361 [ # # # # ]: 0 : (iov_iter_rw(iter) == READ || dio->result == count))
1362 : : retval = -EIOCBQUEUED;
1363 : : else
1364 : 0 : dio_await_completion(dio);
1365 : :
1366 [ # # ]: 0 : if (drop_refcount(dio) == 0) {
1367 : 0 : retval = dio_complete(dio, retval, DIO_COMPLETE_INVALIDATE);
1368 : : } else
1369 [ # # ]: 0 : BUG_ON(retval != -EIOCBQUEUED);
1370 : :
1371 : 0 : out:
1372 : : return retval;
1373 : : }
1374 : :
1375 : 0 : ssize_t __blockdev_direct_IO(struct kiocb *iocb, struct inode *inode,
1376 : : struct block_device *bdev, struct iov_iter *iter,
1377 : : get_block_t get_block,
1378 : : dio_iodone_t end_io, dio_submit_t submit_io,
1379 : : int flags)
1380 : : {
1381 : : /*
1382 : : * The block device state is needed in the end to finally
1383 : : * submit everything. Since it's likely to be cache cold
1384 : : * prefetch it here as first thing to hide some of the
1385 : : * latency.
1386 : : *
1387 : : * Attempt to prefetch the pieces we likely need later.
1388 : : */
1389 : 0 : prefetch(&bdev->bd_disk->part_tbl);
1390 : 0 : prefetch(bdev->bd_queue);
1391 : 0 : prefetch((char *)bdev->bd_queue + SMP_CACHE_BYTES);
1392 : :
1393 : 0 : return do_blockdev_direct_IO(iocb, inode, bdev, iter, get_block,
1394 : : end_io, submit_io, flags);
1395 : : }
1396 : :
1397 : : EXPORT_SYMBOL(__blockdev_direct_IO);
1398 : :
1399 : 28 : static __init int dio_init(void)
1400 : : {
1401 : 28 : dio_cache = KMEM_CACHE(dio, SLAB_PANIC);
1402 : 28 : return 0;
1403 : : }
1404 : : module_init(dio_init)
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