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