Commit | Line | Data |
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1da177e4 LT |
1 | /* |
2 | * fs/direct-io.c | |
3 | * | |
4 | * Copyright (C) 2002, Linus Torvalds. | |
5 | * | |
6 | * O_DIRECT | |
7 | * | |
8 | * 04Jul2002 akpm@zip.com.au | |
9 | * Initial version | |
10 | * 11Sep2002 janetinc@us.ibm.com | |
11 | * added readv/writev support. | |
12 | * 29Oct2002 akpm@zip.com.au | |
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/bio.h> | |
31 | #include <linux/wait.h> | |
32 | #include <linux/err.h> | |
33 | #include <linux/blkdev.h> | |
34 | #include <linux/buffer_head.h> | |
35 | #include <linux/rwsem.h> | |
36 | #include <linux/uio.h> | |
37 | #include <asm/atomic.h> | |
38 | ||
39 | /* | |
40 | * How many user pages to map in one call to get_user_pages(). This determines | |
41 | * the size of a structure on the stack. | |
42 | */ | |
43 | #define DIO_PAGES 64 | |
44 | ||
45 | /* | |
46 | * This code generally works in units of "dio_blocks". A dio_block is | |
47 | * somewhere between the hard sector size and the filesystem block size. it | |
48 | * is determined on a per-invocation basis. When talking to the filesystem | |
49 | * we need to convert dio_blocks to fs_blocks by scaling the dio_block quantity | |
50 | * down by dio->blkfactor. Similarly, fs-blocksize quantities are converted | |
51 | * to bio_block quantities by shifting left by blkfactor. | |
52 | * | |
53 | * If blkfactor is zero then the user's request was aligned to the filesystem's | |
54 | * blocksize. | |
55 | * | |
56 | * lock_type is DIO_LOCKING for regular files on direct-IO-naive filesystems. | |
57 | * This determines whether we need to do the fancy locking which prevents | |
58 | * direct-IO from being able to read uninitialised disk blocks. If its zero | |
59 | * (blockdev) this locking is not done, and if it is DIO_OWN_LOCKING i_sem is | |
60 | * not held for the entire direct write (taken briefly, initially, during a | |
61 | * direct read though, but its never held for the duration of a direct-IO). | |
62 | */ | |
63 | ||
64 | struct dio { | |
65 | /* BIO submission state */ | |
66 | struct bio *bio; /* bio under assembly */ | |
67 | struct inode *inode; | |
68 | int rw; | |
69 | int lock_type; /* doesn't change */ | |
70 | unsigned blkbits; /* doesn't change */ | |
71 | unsigned blkfactor; /* When we're using an alignment which | |
72 | is finer than the filesystem's soft | |
73 | blocksize, this specifies how much | |
74 | finer. blkfactor=2 means 1/4-block | |
75 | alignment. Does not change */ | |
76 | unsigned start_zero_done; /* flag: sub-blocksize zeroing has | |
77 | been performed at the start of a | |
78 | write */ | |
79 | int pages_in_io; /* approximate total IO pages */ | |
80 | size_t size; /* total request size (doesn't change)*/ | |
81 | sector_t block_in_file; /* Current offset into the underlying | |
82 | file in dio_block units. */ | |
83 | unsigned blocks_available; /* At block_in_file. changes */ | |
84 | sector_t final_block_in_request;/* doesn't change */ | |
85 | unsigned first_block_in_page; /* doesn't change, Used only once */ | |
86 | int boundary; /* prev block is at a boundary */ | |
87 | int reap_counter; /* rate limit reaping */ | |
88 | get_blocks_t *get_blocks; /* block mapping function */ | |
89 | dio_iodone_t *end_io; /* IO completion function */ | |
90 | sector_t final_block_in_bio; /* current final block in bio + 1 */ | |
91 | sector_t next_block_for_io; /* next block to be put under IO, | |
92 | in dio_blocks units */ | |
93 | struct buffer_head map_bh; /* last get_blocks() result */ | |
94 | ||
95 | /* | |
96 | * Deferred addition of a page to the dio. These variables are | |
97 | * private to dio_send_cur_page(), submit_page_section() and | |
98 | * dio_bio_add_page(). | |
99 | */ | |
100 | struct page *cur_page; /* The page */ | |
101 | unsigned cur_page_offset; /* Offset into it, in bytes */ | |
102 | unsigned cur_page_len; /* Nr of bytes at cur_page_offset */ | |
103 | sector_t cur_page_block; /* Where it starts */ | |
104 | ||
105 | /* | |
106 | * Page fetching state. These variables belong to dio_refill_pages(). | |
107 | */ | |
108 | int curr_page; /* changes */ | |
109 | int total_pages; /* doesn't change */ | |
110 | unsigned long curr_user_address;/* changes */ | |
111 | ||
112 | /* | |
113 | * Page queue. These variables belong to dio_refill_pages() and | |
114 | * dio_get_page(). | |
115 | */ | |
116 | struct page *pages[DIO_PAGES]; /* page buffer */ | |
117 | unsigned head; /* next page to process */ | |
118 | unsigned tail; /* last valid page + 1 */ | |
119 | int page_errors; /* errno from get_user_pages() */ | |
120 | ||
121 | /* BIO completion state */ | |
122 | spinlock_t bio_lock; /* protects BIO fields below */ | |
123 | int bio_count; /* nr bios to be completed */ | |
124 | int bios_in_flight; /* nr bios in flight */ | |
125 | struct bio *bio_list; /* singly linked via bi_private */ | |
126 | struct task_struct *waiter; /* waiting task (NULL if none) */ | |
127 | ||
128 | /* AIO related stuff */ | |
129 | struct kiocb *iocb; /* kiocb */ | |
130 | int is_async; /* is IO async ? */ | |
131 | ssize_t result; /* IO result */ | |
132 | }; | |
133 | ||
134 | /* | |
135 | * How many pages are in the queue? | |
136 | */ | |
137 | static inline unsigned dio_pages_present(struct dio *dio) | |
138 | { | |
139 | return dio->tail - dio->head; | |
140 | } | |
141 | ||
142 | /* | |
143 | * Go grab and pin some userspace pages. Typically we'll get 64 at a time. | |
144 | */ | |
145 | static int dio_refill_pages(struct dio *dio) | |
146 | { | |
147 | int ret; | |
148 | int nr_pages; | |
149 | ||
150 | nr_pages = min(dio->total_pages - dio->curr_page, DIO_PAGES); | |
151 | down_read(¤t->mm->mmap_sem); | |
152 | ret = get_user_pages( | |
153 | current, /* Task for fault acounting */ | |
154 | current->mm, /* whose pages? */ | |
155 | dio->curr_user_address, /* Where from? */ | |
156 | nr_pages, /* How many pages? */ | |
157 | dio->rw == READ, /* Write to memory? */ | |
158 | 0, /* force (?) */ | |
159 | &dio->pages[0], | |
160 | NULL); /* vmas */ | |
161 | up_read(¤t->mm->mmap_sem); | |
162 | ||
163 | if (ret < 0 && dio->blocks_available && (dio->rw == WRITE)) { | |
164 | /* | |
165 | * A memory fault, but the filesystem has some outstanding | |
166 | * mapped blocks. We need to use those blocks up to avoid | |
167 | * leaking stale data in the file. | |
168 | */ | |
169 | if (dio->page_errors == 0) | |
170 | dio->page_errors = ret; | |
171 | dio->pages[0] = ZERO_PAGE(dio->curr_user_address); | |
172 | dio->head = 0; | |
173 | dio->tail = 1; | |
174 | ret = 0; | |
175 | goto out; | |
176 | } | |
177 | ||
178 | if (ret >= 0) { | |
179 | dio->curr_user_address += ret * PAGE_SIZE; | |
180 | dio->curr_page += ret; | |
181 | dio->head = 0; | |
182 | dio->tail = ret; | |
183 | ret = 0; | |
184 | } | |
185 | out: | |
186 | return ret; | |
187 | } | |
188 | ||
189 | /* | |
190 | * Get another userspace page. Returns an ERR_PTR on error. Pages are | |
191 | * buffered inside the dio so that we can call get_user_pages() against a | |
192 | * decent number of pages, less frequently. To provide nicer use of the | |
193 | * L1 cache. | |
194 | */ | |
195 | static struct page *dio_get_page(struct dio *dio) | |
196 | { | |
197 | if (dio_pages_present(dio) == 0) { | |
198 | int ret; | |
199 | ||
200 | ret = dio_refill_pages(dio); | |
201 | if (ret) | |
202 | return ERR_PTR(ret); | |
203 | BUG_ON(dio_pages_present(dio) == 0); | |
204 | } | |
205 | return dio->pages[dio->head++]; | |
206 | } | |
207 | ||
208 | /* | |
209 | * Called when all DIO BIO I/O has been completed - let the filesystem | |
210 | * know, if it registered an interest earlier via get_blocks. Pass the | |
211 | * private field of the map buffer_head so that filesystems can use it | |
212 | * to hold additional state between get_blocks calls and dio_complete. | |
213 | */ | |
214 | static void dio_complete(struct dio *dio, loff_t offset, ssize_t bytes) | |
215 | { | |
216 | if (dio->end_io && dio->result) | |
217 | dio->end_io(dio->inode, offset, bytes, dio->map_bh.b_private); | |
218 | if (dio->lock_type == DIO_LOCKING) | |
219 | up_read(&dio->inode->i_alloc_sem); | |
220 | } | |
221 | ||
222 | /* | |
223 | * Called when a BIO has been processed. If the count goes to zero then IO is | |
224 | * complete and we can signal this to the AIO layer. | |
225 | */ | |
226 | static void finished_one_bio(struct dio *dio) | |
227 | { | |
228 | unsigned long flags; | |
229 | ||
230 | spin_lock_irqsave(&dio->bio_lock, flags); | |
231 | if (dio->bio_count == 1) { | |
232 | if (dio->is_async) { | |
233 | /* | |
234 | * Last reference to the dio is going away. | |
235 | * Drop spinlock and complete the DIO. | |
236 | */ | |
237 | spin_unlock_irqrestore(&dio->bio_lock, flags); | |
238 | dio_complete(dio, dio->block_in_file << dio->blkbits, | |
239 | dio->result); | |
240 | /* Complete AIO later if falling back to buffered i/o */ | |
241 | if (dio->result == dio->size || | |
242 | ((dio->rw == READ) && dio->result)) { | |
243 | aio_complete(dio->iocb, dio->result, 0); | |
244 | kfree(dio); | |
245 | return; | |
246 | } else { | |
247 | /* | |
248 | * Falling back to buffered | |
249 | */ | |
250 | spin_lock_irqsave(&dio->bio_lock, flags); | |
251 | dio->bio_count--; | |
252 | if (dio->waiter) | |
253 | wake_up_process(dio->waiter); | |
254 | spin_unlock_irqrestore(&dio->bio_lock, flags); | |
255 | return; | |
256 | } | |
257 | } | |
258 | } | |
259 | dio->bio_count--; | |
260 | spin_unlock_irqrestore(&dio->bio_lock, flags); | |
261 | } | |
262 | ||
263 | static int dio_bio_complete(struct dio *dio, struct bio *bio); | |
264 | /* | |
265 | * Asynchronous IO callback. | |
266 | */ | |
267 | static int dio_bio_end_aio(struct bio *bio, unsigned int bytes_done, int error) | |
268 | { | |
269 | struct dio *dio = bio->bi_private; | |
270 | ||
271 | if (bio->bi_size) | |
272 | return 1; | |
273 | ||
274 | /* cleanup the bio */ | |
275 | dio_bio_complete(dio, bio); | |
276 | return 0; | |
277 | } | |
278 | ||
279 | /* | |
280 | * The BIO completion handler simply queues the BIO up for the process-context | |
281 | * handler. | |
282 | * | |
283 | * During I/O bi_private points at the dio. After I/O, bi_private is used to | |
284 | * implement a singly-linked list of completed BIOs, at dio->bio_list. | |
285 | */ | |
286 | static int dio_bio_end_io(struct bio *bio, unsigned int bytes_done, int error) | |
287 | { | |
288 | struct dio *dio = bio->bi_private; | |
289 | unsigned long flags; | |
290 | ||
291 | if (bio->bi_size) | |
292 | return 1; | |
293 | ||
294 | spin_lock_irqsave(&dio->bio_lock, flags); | |
295 | bio->bi_private = dio->bio_list; | |
296 | dio->bio_list = bio; | |
297 | dio->bios_in_flight--; | |
298 | if (dio->waiter && dio->bios_in_flight == 0) | |
299 | wake_up_process(dio->waiter); | |
300 | spin_unlock_irqrestore(&dio->bio_lock, flags); | |
301 | return 0; | |
302 | } | |
303 | ||
304 | static int | |
305 | dio_bio_alloc(struct dio *dio, struct block_device *bdev, | |
306 | sector_t first_sector, int nr_vecs) | |
307 | { | |
308 | struct bio *bio; | |
309 | ||
310 | bio = bio_alloc(GFP_KERNEL, nr_vecs); | |
311 | if (bio == NULL) | |
312 | return -ENOMEM; | |
313 | ||
314 | bio->bi_bdev = bdev; | |
315 | bio->bi_sector = first_sector; | |
316 | if (dio->is_async) | |
317 | bio->bi_end_io = dio_bio_end_aio; | |
318 | else | |
319 | bio->bi_end_io = dio_bio_end_io; | |
320 | ||
321 | dio->bio = bio; | |
322 | return 0; | |
323 | } | |
324 | ||
325 | /* | |
326 | * In the AIO read case we speculatively dirty the pages before starting IO. | |
327 | * During IO completion, any of these pages which happen to have been written | |
328 | * back will be redirtied by bio_check_pages_dirty(). | |
329 | */ | |
330 | static void dio_bio_submit(struct dio *dio) | |
331 | { | |
332 | struct bio *bio = dio->bio; | |
333 | unsigned long flags; | |
334 | ||
335 | bio->bi_private = dio; | |
336 | spin_lock_irqsave(&dio->bio_lock, flags); | |
337 | dio->bio_count++; | |
338 | dio->bios_in_flight++; | |
339 | spin_unlock_irqrestore(&dio->bio_lock, flags); | |
340 | if (dio->is_async && dio->rw == READ) | |
341 | bio_set_pages_dirty(bio); | |
342 | submit_bio(dio->rw, bio); | |
343 | ||
344 | dio->bio = NULL; | |
345 | dio->boundary = 0; | |
346 | } | |
347 | ||
348 | /* | |
349 | * Release any resources in case of a failure | |
350 | */ | |
351 | static void dio_cleanup(struct dio *dio) | |
352 | { | |
353 | while (dio_pages_present(dio)) | |
354 | page_cache_release(dio_get_page(dio)); | |
355 | } | |
356 | ||
357 | /* | |
358 | * Wait for the next BIO to complete. Remove it and return it. | |
359 | */ | |
360 | static struct bio *dio_await_one(struct dio *dio) | |
361 | { | |
362 | unsigned long flags; | |
363 | struct bio *bio; | |
364 | ||
365 | spin_lock_irqsave(&dio->bio_lock, flags); | |
366 | while (dio->bio_list == NULL) { | |
367 | set_current_state(TASK_UNINTERRUPTIBLE); | |
368 | if (dio->bio_list == NULL) { | |
369 | dio->waiter = current; | |
370 | spin_unlock_irqrestore(&dio->bio_lock, flags); | |
371 | blk_run_address_space(dio->inode->i_mapping); | |
372 | io_schedule(); | |
373 | spin_lock_irqsave(&dio->bio_lock, flags); | |
374 | dio->waiter = NULL; | |
375 | } | |
376 | set_current_state(TASK_RUNNING); | |
377 | } | |
378 | bio = dio->bio_list; | |
379 | dio->bio_list = bio->bi_private; | |
380 | spin_unlock_irqrestore(&dio->bio_lock, flags); | |
381 | return bio; | |
382 | } | |
383 | ||
384 | /* | |
385 | * Process one completed BIO. No locks are held. | |
386 | */ | |
387 | static int dio_bio_complete(struct dio *dio, struct bio *bio) | |
388 | { | |
389 | const int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags); | |
390 | struct bio_vec *bvec = bio->bi_io_vec; | |
391 | int page_no; | |
392 | ||
393 | if (!uptodate) | |
394 | dio->result = -EIO; | |
395 | ||
396 | if (dio->is_async && dio->rw == READ) { | |
397 | bio_check_pages_dirty(bio); /* transfers ownership */ | |
398 | } else { | |
399 | for (page_no = 0; page_no < bio->bi_vcnt; page_no++) { | |
400 | struct page *page = bvec[page_no].bv_page; | |
401 | ||
402 | if (dio->rw == READ && !PageCompound(page)) | |
403 | set_page_dirty_lock(page); | |
404 | page_cache_release(page); | |
405 | } | |
406 | bio_put(bio); | |
407 | } | |
408 | finished_one_bio(dio); | |
409 | return uptodate ? 0 : -EIO; | |
410 | } | |
411 | ||
412 | /* | |
413 | * Wait on and process all in-flight BIOs. | |
414 | */ | |
415 | static int dio_await_completion(struct dio *dio) | |
416 | { | |
417 | int ret = 0; | |
418 | ||
419 | if (dio->bio) | |
420 | dio_bio_submit(dio); | |
421 | ||
422 | /* | |
423 | * The bio_lock is not held for the read of bio_count. | |
424 | * This is ok since it is the dio_bio_complete() that changes | |
425 | * bio_count. | |
426 | */ | |
427 | while (dio->bio_count) { | |
428 | struct bio *bio = dio_await_one(dio); | |
429 | int ret2; | |
430 | ||
431 | ret2 = dio_bio_complete(dio, bio); | |
432 | if (ret == 0) | |
433 | ret = ret2; | |
434 | } | |
435 | return ret; | |
436 | } | |
437 | ||
438 | /* | |
439 | * A really large O_DIRECT read or write can generate a lot of BIOs. So | |
440 | * to keep the memory consumption sane we periodically reap any completed BIOs | |
441 | * during the BIO generation phase. | |
442 | * | |
443 | * This also helps to limit the peak amount of pinned userspace memory. | |
444 | */ | |
445 | static int dio_bio_reap(struct dio *dio) | |
446 | { | |
447 | int ret = 0; | |
448 | ||
449 | if (dio->reap_counter++ >= 64) { | |
450 | while (dio->bio_list) { | |
451 | unsigned long flags; | |
452 | struct bio *bio; | |
453 | int ret2; | |
454 | ||
455 | spin_lock_irqsave(&dio->bio_lock, flags); | |
456 | bio = dio->bio_list; | |
457 | dio->bio_list = bio->bi_private; | |
458 | spin_unlock_irqrestore(&dio->bio_lock, flags); | |
459 | ret2 = dio_bio_complete(dio, bio); | |
460 | if (ret == 0) | |
461 | ret = ret2; | |
462 | } | |
463 | dio->reap_counter = 0; | |
464 | } | |
465 | return ret; | |
466 | } | |
467 | ||
468 | /* | |
469 | * Call into the fs to map some more disk blocks. We record the current number | |
470 | * of available blocks at dio->blocks_available. These are in units of the | |
471 | * fs blocksize, (1 << inode->i_blkbits). | |
472 | * | |
473 | * The fs is allowed to map lots of blocks at once. If it wants to do that, | |
474 | * it uses the passed inode-relative block number as the file offset, as usual. | |
475 | * | |
476 | * get_blocks() is passed the number of i_blkbits-sized blocks which direct_io | |
477 | * has remaining to do. The fs should not map more than this number of blocks. | |
478 | * | |
479 | * If the fs has mapped a lot of blocks, it should populate bh->b_size to | |
480 | * indicate how much contiguous disk space has been made available at | |
481 | * bh->b_blocknr. | |
482 | * | |
483 | * If *any* of the mapped blocks are new, then the fs must set buffer_new(). | |
484 | * This isn't very efficient... | |
485 | * | |
486 | * In the case of filesystem holes: the fs may return an arbitrarily-large | |
487 | * hole by returning an appropriate value in b_size and by clearing | |
488 | * buffer_mapped(). However the direct-io code will only process holes one | |
489 | * block at a time - it will repeatedly call get_blocks() as it walks the hole. | |
490 | */ | |
491 | static int get_more_blocks(struct dio *dio) | |
492 | { | |
493 | int ret; | |
494 | struct buffer_head *map_bh = &dio->map_bh; | |
495 | sector_t fs_startblk; /* Into file, in filesystem-sized blocks */ | |
496 | unsigned long fs_count; /* Number of filesystem-sized blocks */ | |
497 | unsigned long dio_count;/* Number of dio_block-sized blocks */ | |
498 | unsigned long blkmask; | |
499 | int create; | |
500 | ||
501 | /* | |
502 | * If there was a memory error and we've overwritten all the | |
503 | * mapped blocks then we can now return that memory error | |
504 | */ | |
505 | ret = dio->page_errors; | |
506 | if (ret == 0) { | |
507 | map_bh->b_state = 0; | |
508 | map_bh->b_size = 0; | |
509 | BUG_ON(dio->block_in_file >= dio->final_block_in_request); | |
510 | fs_startblk = dio->block_in_file >> dio->blkfactor; | |
511 | dio_count = dio->final_block_in_request - dio->block_in_file; | |
512 | fs_count = dio_count >> dio->blkfactor; | |
513 | blkmask = (1 << dio->blkfactor) - 1; | |
514 | if (dio_count & blkmask) | |
515 | fs_count++; | |
516 | ||
517 | create = dio->rw == WRITE; | |
518 | if (dio->lock_type == DIO_LOCKING) { | |
519 | if (dio->block_in_file < (i_size_read(dio->inode) >> | |
520 | dio->blkbits)) | |
521 | create = 0; | |
522 | } else if (dio->lock_type == DIO_NO_LOCKING) { | |
523 | create = 0; | |
524 | } | |
525 | /* | |
526 | * For writes inside i_size we forbid block creations: only | |
527 | * overwrites are permitted. We fall back to buffered writes | |
528 | * at a higher level for inside-i_size block-instantiating | |
529 | * writes. | |
530 | */ | |
531 | ret = (*dio->get_blocks)(dio->inode, fs_startblk, fs_count, | |
532 | map_bh, create); | |
533 | } | |
534 | return ret; | |
535 | } | |
536 | ||
537 | /* | |
538 | * There is no bio. Make one now. | |
539 | */ | |
540 | static int dio_new_bio(struct dio *dio, sector_t start_sector) | |
541 | { | |
542 | sector_t sector; | |
543 | int ret, nr_pages; | |
544 | ||
545 | ret = dio_bio_reap(dio); | |
546 | if (ret) | |
547 | goto out; | |
548 | sector = start_sector << (dio->blkbits - 9); | |
549 | nr_pages = min(dio->pages_in_io, bio_get_nr_vecs(dio->map_bh.b_bdev)); | |
550 | BUG_ON(nr_pages <= 0); | |
551 | ret = dio_bio_alloc(dio, dio->map_bh.b_bdev, sector, nr_pages); | |
552 | dio->boundary = 0; | |
553 | out: | |
554 | return ret; | |
555 | } | |
556 | ||
557 | /* | |
558 | * Attempt to put the current chunk of 'cur_page' into the current BIO. If | |
559 | * that was successful then update final_block_in_bio and take a ref against | |
560 | * the just-added page. | |
561 | * | |
562 | * Return zero on success. Non-zero means the caller needs to start a new BIO. | |
563 | */ | |
564 | static int dio_bio_add_page(struct dio *dio) | |
565 | { | |
566 | int ret; | |
567 | ||
568 | ret = bio_add_page(dio->bio, dio->cur_page, | |
569 | dio->cur_page_len, dio->cur_page_offset); | |
570 | if (ret == dio->cur_page_len) { | |
571 | /* | |
572 | * Decrement count only, if we are done with this page | |
573 | */ | |
574 | if ((dio->cur_page_len + dio->cur_page_offset) == PAGE_SIZE) | |
575 | dio->pages_in_io--; | |
576 | page_cache_get(dio->cur_page); | |
577 | dio->final_block_in_bio = dio->cur_page_block + | |
578 | (dio->cur_page_len >> dio->blkbits); | |
579 | ret = 0; | |
580 | } else { | |
581 | ret = 1; | |
582 | } | |
583 | return ret; | |
584 | } | |
585 | ||
586 | /* | |
587 | * Put cur_page under IO. The section of cur_page which is described by | |
588 | * cur_page_offset,cur_page_len is put into a BIO. The section of cur_page | |
589 | * starts on-disk at cur_page_block. | |
590 | * | |
591 | * We take a ref against the page here (on behalf of its presence in the bio). | |
592 | * | |
593 | * The caller of this function is responsible for removing cur_page from the | |
594 | * dio, and for dropping the refcount which came from that presence. | |
595 | */ | |
596 | static int dio_send_cur_page(struct dio *dio) | |
597 | { | |
598 | int ret = 0; | |
599 | ||
600 | if (dio->bio) { | |
601 | /* | |
602 | * See whether this new request is contiguous with the old | |
603 | */ | |
604 | if (dio->final_block_in_bio != dio->cur_page_block) | |
605 | dio_bio_submit(dio); | |
606 | /* | |
607 | * Submit now if the underlying fs is about to perform a | |
608 | * metadata read | |
609 | */ | |
610 | if (dio->boundary) | |
611 | dio_bio_submit(dio); | |
612 | } | |
613 | ||
614 | if (dio->bio == NULL) { | |
615 | ret = dio_new_bio(dio, dio->cur_page_block); | |
616 | if (ret) | |
617 | goto out; | |
618 | } | |
619 | ||
620 | if (dio_bio_add_page(dio) != 0) { | |
621 | dio_bio_submit(dio); | |
622 | ret = dio_new_bio(dio, dio->cur_page_block); | |
623 | if (ret == 0) { | |
624 | ret = dio_bio_add_page(dio); | |
625 | BUG_ON(ret != 0); | |
626 | } | |
627 | } | |
628 | out: | |
629 | return ret; | |
630 | } | |
631 | ||
632 | /* | |
633 | * An autonomous function to put a chunk of a page under deferred IO. | |
634 | * | |
635 | * The caller doesn't actually know (or care) whether this piece of page is in | |
636 | * a BIO, or is under IO or whatever. We just take care of all possible | |
637 | * situations here. The separation between the logic of do_direct_IO() and | |
638 | * that of submit_page_section() is important for clarity. Please don't break. | |
639 | * | |
640 | * The chunk of page starts on-disk at blocknr. | |
641 | * | |
642 | * We perform deferred IO, by recording the last-submitted page inside our | |
643 | * private part of the dio structure. If possible, we just expand the IO | |
644 | * across that page here. | |
645 | * | |
646 | * If that doesn't work out then we put the old page into the bio and add this | |
647 | * page to the dio instead. | |
648 | */ | |
649 | static int | |
650 | submit_page_section(struct dio *dio, struct page *page, | |
651 | unsigned offset, unsigned len, sector_t blocknr) | |
652 | { | |
653 | int ret = 0; | |
654 | ||
655 | /* | |
656 | * Can we just grow the current page's presence in the dio? | |
657 | */ | |
658 | if ( (dio->cur_page == page) && | |
659 | (dio->cur_page_offset + dio->cur_page_len == offset) && | |
660 | (dio->cur_page_block + | |
661 | (dio->cur_page_len >> dio->blkbits) == blocknr)) { | |
662 | dio->cur_page_len += len; | |
663 | ||
664 | /* | |
665 | * If dio->boundary then we want to schedule the IO now to | |
666 | * avoid metadata seeks. | |
667 | */ | |
668 | if (dio->boundary) { | |
669 | ret = dio_send_cur_page(dio); | |
670 | page_cache_release(dio->cur_page); | |
671 | dio->cur_page = NULL; | |
672 | } | |
673 | goto out; | |
674 | } | |
675 | ||
676 | /* | |
677 | * If there's a deferred page already there then send it. | |
678 | */ | |
679 | if (dio->cur_page) { | |
680 | ret = dio_send_cur_page(dio); | |
681 | page_cache_release(dio->cur_page); | |
682 | dio->cur_page = NULL; | |
683 | if (ret) | |
684 | goto out; | |
685 | } | |
686 | ||
687 | page_cache_get(page); /* It is in dio */ | |
688 | dio->cur_page = page; | |
689 | dio->cur_page_offset = offset; | |
690 | dio->cur_page_len = len; | |
691 | dio->cur_page_block = blocknr; | |
692 | out: | |
693 | return ret; | |
694 | } | |
695 | ||
696 | /* | |
697 | * Clean any dirty buffers in the blockdev mapping which alias newly-created | |
698 | * file blocks. Only called for S_ISREG files - blockdevs do not set | |
699 | * buffer_new | |
700 | */ | |
701 | static void clean_blockdev_aliases(struct dio *dio) | |
702 | { | |
703 | unsigned i; | |
704 | unsigned nblocks; | |
705 | ||
706 | nblocks = dio->map_bh.b_size >> dio->inode->i_blkbits; | |
707 | ||
708 | for (i = 0; i < nblocks; i++) { | |
709 | unmap_underlying_metadata(dio->map_bh.b_bdev, | |
710 | dio->map_bh.b_blocknr + i); | |
711 | } | |
712 | } | |
713 | ||
714 | /* | |
715 | * If we are not writing the entire block and get_block() allocated | |
716 | * the block for us, we need to fill-in the unused portion of the | |
717 | * block with zeros. This happens only if user-buffer, fileoffset or | |
718 | * io length is not filesystem block-size multiple. | |
719 | * | |
720 | * `end' is zero if we're doing the start of the IO, 1 at the end of the | |
721 | * IO. | |
722 | */ | |
723 | static void dio_zero_block(struct dio *dio, int end) | |
724 | { | |
725 | unsigned dio_blocks_per_fs_block; | |
726 | unsigned this_chunk_blocks; /* In dio_blocks */ | |
727 | unsigned this_chunk_bytes; | |
728 | struct page *page; | |
729 | ||
730 | dio->start_zero_done = 1; | |
731 | if (!dio->blkfactor || !buffer_new(&dio->map_bh)) | |
732 | return; | |
733 | ||
734 | dio_blocks_per_fs_block = 1 << dio->blkfactor; | |
735 | this_chunk_blocks = dio->block_in_file & (dio_blocks_per_fs_block - 1); | |
736 | ||
737 | if (!this_chunk_blocks) | |
738 | return; | |
739 | ||
740 | /* | |
741 | * We need to zero out part of an fs block. It is either at the | |
742 | * beginning or the end of the fs block. | |
743 | */ | |
744 | if (end) | |
745 | this_chunk_blocks = dio_blocks_per_fs_block - this_chunk_blocks; | |
746 | ||
747 | this_chunk_bytes = this_chunk_blocks << dio->blkbits; | |
748 | ||
749 | page = ZERO_PAGE(dio->curr_user_address); | |
750 | if (submit_page_section(dio, page, 0, this_chunk_bytes, | |
751 | dio->next_block_for_io)) | |
752 | return; | |
753 | ||
754 | dio->next_block_for_io += this_chunk_blocks; | |
755 | } | |
756 | ||
757 | /* | |
758 | * Walk the user pages, and the file, mapping blocks to disk and generating | |
759 | * a sequence of (page,offset,len,block) mappings. These mappings are injected | |
760 | * into submit_page_section(), which takes care of the next stage of submission | |
761 | * | |
762 | * Direct IO against a blockdev is different from a file. Because we can | |
763 | * happily perform page-sized but 512-byte aligned IOs. It is important that | |
764 | * blockdev IO be able to have fine alignment and large sizes. | |
765 | * | |
766 | * So what we do is to permit the ->get_blocks function to populate bh.b_size | |
767 | * with the size of IO which is permitted at this offset and this i_blkbits. | |
768 | * | |
769 | * For best results, the blockdev should be set up with 512-byte i_blkbits and | |
770 | * it should set b_size to PAGE_SIZE or more inside get_blocks(). This gives | |
771 | * fine alignment but still allows this function to work in PAGE_SIZE units. | |
772 | */ | |
773 | static int do_direct_IO(struct dio *dio) | |
774 | { | |
775 | const unsigned blkbits = dio->blkbits; | |
776 | const unsigned blocks_per_page = PAGE_SIZE >> blkbits; | |
777 | struct page *page; | |
778 | unsigned block_in_page; | |
779 | struct buffer_head *map_bh = &dio->map_bh; | |
780 | int ret = 0; | |
781 | ||
782 | /* The I/O can start at any block offset within the first page */ | |
783 | block_in_page = dio->first_block_in_page; | |
784 | ||
785 | while (dio->block_in_file < dio->final_block_in_request) { | |
786 | page = dio_get_page(dio); | |
787 | if (IS_ERR(page)) { | |
788 | ret = PTR_ERR(page); | |
789 | goto out; | |
790 | } | |
791 | ||
792 | while (block_in_page < blocks_per_page) { | |
793 | unsigned offset_in_page = block_in_page << blkbits; | |
794 | unsigned this_chunk_bytes; /* # of bytes mapped */ | |
795 | unsigned this_chunk_blocks; /* # of blocks */ | |
796 | unsigned u; | |
797 | ||
798 | if (dio->blocks_available == 0) { | |
799 | /* | |
800 | * Need to go and map some more disk | |
801 | */ | |
802 | unsigned long blkmask; | |
803 | unsigned long dio_remainder; | |
804 | ||
805 | ret = get_more_blocks(dio); | |
806 | if (ret) { | |
807 | page_cache_release(page); | |
808 | goto out; | |
809 | } | |
810 | if (!buffer_mapped(map_bh)) | |
811 | goto do_holes; | |
812 | ||
813 | dio->blocks_available = | |
814 | map_bh->b_size >> dio->blkbits; | |
815 | dio->next_block_for_io = | |
816 | map_bh->b_blocknr << dio->blkfactor; | |
817 | if (buffer_new(map_bh)) | |
818 | clean_blockdev_aliases(dio); | |
819 | ||
820 | if (!dio->blkfactor) | |
821 | goto do_holes; | |
822 | ||
823 | blkmask = (1 << dio->blkfactor) - 1; | |
824 | dio_remainder = (dio->block_in_file & blkmask); | |
825 | ||
826 | /* | |
827 | * If we are at the start of IO and that IO | |
828 | * starts partway into a fs-block, | |
829 | * dio_remainder will be non-zero. If the IO | |
830 | * is a read then we can simply advance the IO | |
831 | * cursor to the first block which is to be | |
832 | * read. But if the IO is a write and the | |
833 | * block was newly allocated we cannot do that; | |
834 | * the start of the fs block must be zeroed out | |
835 | * on-disk | |
836 | */ | |
837 | if (!buffer_new(map_bh)) | |
838 | dio->next_block_for_io += dio_remainder; | |
839 | dio->blocks_available -= dio_remainder; | |
840 | } | |
841 | do_holes: | |
842 | /* Handle holes */ | |
843 | if (!buffer_mapped(map_bh)) { | |
844 | char *kaddr; | |
845 | ||
846 | /* AKPM: eargh, -ENOTBLK is a hack */ | |
847 | if (dio->rw == WRITE) { | |
848 | page_cache_release(page); | |
849 | return -ENOTBLK; | |
850 | } | |
851 | ||
852 | if (dio->block_in_file >= | |
853 | i_size_read(dio->inode)>>blkbits) { | |
854 | /* We hit eof */ | |
855 | page_cache_release(page); | |
856 | goto out; | |
857 | } | |
858 | kaddr = kmap_atomic(page, KM_USER0); | |
859 | memset(kaddr + (block_in_page << blkbits), | |
860 | 0, 1 << blkbits); | |
861 | flush_dcache_page(page); | |
862 | kunmap_atomic(kaddr, KM_USER0); | |
863 | dio->block_in_file++; | |
864 | block_in_page++; | |
865 | goto next_block; | |
866 | } | |
867 | ||
868 | /* | |
869 | * If we're performing IO which has an alignment which | |
870 | * is finer than the underlying fs, go check to see if | |
871 | * we must zero out the start of this block. | |
872 | */ | |
873 | if (unlikely(dio->blkfactor && !dio->start_zero_done)) | |
874 | dio_zero_block(dio, 0); | |
875 | ||
876 | /* | |
877 | * Work out, in this_chunk_blocks, how much disk we | |
878 | * can add to this page | |
879 | */ | |
880 | this_chunk_blocks = dio->blocks_available; | |
881 | u = (PAGE_SIZE - offset_in_page) >> blkbits; | |
882 | if (this_chunk_blocks > u) | |
883 | this_chunk_blocks = u; | |
884 | u = dio->final_block_in_request - dio->block_in_file; | |
885 | if (this_chunk_blocks > u) | |
886 | this_chunk_blocks = u; | |
887 | this_chunk_bytes = this_chunk_blocks << blkbits; | |
888 | BUG_ON(this_chunk_bytes == 0); | |
889 | ||
890 | dio->boundary = buffer_boundary(map_bh); | |
891 | ret = submit_page_section(dio, page, offset_in_page, | |
892 | this_chunk_bytes, dio->next_block_for_io); | |
893 | if (ret) { | |
894 | page_cache_release(page); | |
895 | goto out; | |
896 | } | |
897 | dio->next_block_for_io += this_chunk_blocks; | |
898 | ||
899 | dio->block_in_file += this_chunk_blocks; | |
900 | block_in_page += this_chunk_blocks; | |
901 | dio->blocks_available -= this_chunk_blocks; | |
902 | next_block: | |
903 | if (dio->block_in_file > dio->final_block_in_request) | |
904 | BUG(); | |
905 | if (dio->block_in_file == dio->final_block_in_request) | |
906 | break; | |
907 | } | |
908 | ||
909 | /* Drop the ref which was taken in get_user_pages() */ | |
910 | page_cache_release(page); | |
911 | block_in_page = 0; | |
912 | } | |
913 | out: | |
914 | return ret; | |
915 | } | |
916 | ||
917 | /* | |
918 | * Releases both i_sem and i_alloc_sem | |
919 | */ | |
920 | static ssize_t | |
921 | direct_io_worker(int rw, struct kiocb *iocb, struct inode *inode, | |
922 | const struct iovec *iov, loff_t offset, unsigned long nr_segs, | |
923 | unsigned blkbits, get_blocks_t get_blocks, dio_iodone_t end_io, | |
924 | struct dio *dio) | |
925 | { | |
926 | unsigned long user_addr; | |
927 | int seg; | |
928 | ssize_t ret = 0; | |
929 | ssize_t ret2; | |
930 | size_t bytes; | |
931 | ||
932 | dio->bio = NULL; | |
933 | dio->inode = inode; | |
934 | dio->rw = rw; | |
935 | dio->blkbits = blkbits; | |
936 | dio->blkfactor = inode->i_blkbits - blkbits; | |
937 | dio->start_zero_done = 0; | |
938 | dio->size = 0; | |
939 | dio->block_in_file = offset >> blkbits; | |
940 | dio->blocks_available = 0; | |
941 | dio->cur_page = NULL; | |
942 | ||
943 | dio->boundary = 0; | |
944 | dio->reap_counter = 0; | |
945 | dio->get_blocks = get_blocks; | |
946 | dio->end_io = end_io; | |
947 | dio->map_bh.b_private = NULL; | |
948 | dio->final_block_in_bio = -1; | |
949 | dio->next_block_for_io = -1; | |
950 | ||
951 | dio->page_errors = 0; | |
952 | dio->result = 0; | |
953 | dio->iocb = iocb; | |
954 | ||
955 | /* | |
956 | * BIO completion state. | |
957 | * | |
958 | * ->bio_count starts out at one, and we decrement it to zero after all | |
959 | * BIOs are submitted. This to avoid the situation where a really fast | |
960 | * (or synchronous) device could take the count to zero while we're | |
961 | * still submitting BIOs. | |
962 | */ | |
963 | dio->bio_count = 1; | |
964 | dio->bios_in_flight = 0; | |
965 | spin_lock_init(&dio->bio_lock); | |
966 | dio->bio_list = NULL; | |
967 | dio->waiter = NULL; | |
968 | ||
969 | /* | |
970 | * In case of non-aligned buffers, we may need 2 more | |
971 | * pages since we need to zero out first and last block. | |
972 | */ | |
973 | if (unlikely(dio->blkfactor)) | |
974 | dio->pages_in_io = 2; | |
975 | else | |
976 | dio->pages_in_io = 0; | |
977 | ||
978 | for (seg = 0; seg < nr_segs; seg++) { | |
979 | user_addr = (unsigned long)iov[seg].iov_base; | |
980 | dio->pages_in_io += | |
981 | ((user_addr+iov[seg].iov_len +PAGE_SIZE-1)/PAGE_SIZE | |
982 | - user_addr/PAGE_SIZE); | |
983 | } | |
984 | ||
985 | for (seg = 0; seg < nr_segs; seg++) { | |
986 | user_addr = (unsigned long)iov[seg].iov_base; | |
987 | dio->size += bytes = iov[seg].iov_len; | |
988 | ||
989 | /* Index into the first page of the first block */ | |
990 | dio->first_block_in_page = (user_addr & ~PAGE_MASK) >> blkbits; | |
991 | dio->final_block_in_request = dio->block_in_file + | |
992 | (bytes >> blkbits); | |
993 | /* Page fetching state */ | |
994 | dio->head = 0; | |
995 | dio->tail = 0; | |
996 | dio->curr_page = 0; | |
997 | ||
998 | dio->total_pages = 0; | |
999 | if (user_addr & (PAGE_SIZE-1)) { | |
1000 | dio->total_pages++; | |
1001 | bytes -= PAGE_SIZE - (user_addr & (PAGE_SIZE - 1)); | |
1002 | } | |
1003 | dio->total_pages += (bytes + PAGE_SIZE - 1) / PAGE_SIZE; | |
1004 | dio->curr_user_address = user_addr; | |
1005 | ||
1006 | ret = do_direct_IO(dio); | |
1007 | ||
1008 | dio->result += iov[seg].iov_len - | |
1009 | ((dio->final_block_in_request - dio->block_in_file) << | |
1010 | blkbits); | |
1011 | ||
1012 | if (ret) { | |
1013 | dio_cleanup(dio); | |
1014 | break; | |
1015 | } | |
1016 | } /* end iovec loop */ | |
1017 | ||
1018 | if (ret == -ENOTBLK && rw == WRITE) { | |
1019 | /* | |
1020 | * The remaining part of the request will be | |
1021 | * be handled by buffered I/O when we return | |
1022 | */ | |
1023 | ret = 0; | |
1024 | } | |
1025 | /* | |
1026 | * There may be some unwritten disk at the end of a part-written | |
1027 | * fs-block-sized block. Go zero that now. | |
1028 | */ | |
1029 | dio_zero_block(dio, 1); | |
1030 | ||
1031 | if (dio->cur_page) { | |
1032 | ret2 = dio_send_cur_page(dio); | |
1033 | if (ret == 0) | |
1034 | ret = ret2; | |
1035 | page_cache_release(dio->cur_page); | |
1036 | dio->cur_page = NULL; | |
1037 | } | |
1038 | if (dio->bio) | |
1039 | dio_bio_submit(dio); | |
1040 | ||
1041 | /* | |
1042 | * It is possible that, we return short IO due to end of file. | |
1043 | * In that case, we need to release all the pages we got hold on. | |
1044 | */ | |
1045 | dio_cleanup(dio); | |
1046 | ||
1047 | /* | |
1048 | * All block lookups have been performed. For READ requests | |
1049 | * we can let i_sem go now that its achieved its purpose | |
1050 | * of protecting us from looking up uninitialized blocks. | |
1051 | */ | |
1052 | if ((rw == READ) && (dio->lock_type == DIO_LOCKING)) | |
1053 | up(&dio->inode->i_sem); | |
1054 | ||
1055 | /* | |
1056 | * OK, all BIOs are submitted, so we can decrement bio_count to truly | |
1057 | * reflect the number of to-be-processed BIOs. | |
1058 | */ | |
1059 | if (dio->is_async) { | |
1060 | int should_wait = 0; | |
1061 | ||
1062 | if (dio->result < dio->size && rw == WRITE) { | |
1063 | dio->waiter = current; | |
1064 | should_wait = 1; | |
1065 | } | |
1066 | if (ret == 0) | |
1067 | ret = dio->result; | |
1068 | finished_one_bio(dio); /* This can free the dio */ | |
1069 | blk_run_address_space(inode->i_mapping); | |
1070 | if (should_wait) { | |
1071 | unsigned long flags; | |
1072 | /* | |
1073 | * Wait for already issued I/O to drain out and | |
1074 | * release its references to user-space pages | |
1075 | * before returning to fallback on buffered I/O | |
1076 | */ | |
1077 | ||
1078 | spin_lock_irqsave(&dio->bio_lock, flags); | |
1079 | set_current_state(TASK_UNINTERRUPTIBLE); | |
1080 | while (dio->bio_count) { | |
1081 | spin_unlock_irqrestore(&dio->bio_lock, flags); | |
1082 | io_schedule(); | |
1083 | spin_lock_irqsave(&dio->bio_lock, flags); | |
1084 | set_current_state(TASK_UNINTERRUPTIBLE); | |
1085 | } | |
1086 | spin_unlock_irqrestore(&dio->bio_lock, flags); | |
1087 | set_current_state(TASK_RUNNING); | |
1088 | kfree(dio); | |
1089 | } | |
1090 | } else { | |
1091 | ssize_t transferred = 0; | |
1092 | ||
1093 | finished_one_bio(dio); | |
1094 | ret2 = dio_await_completion(dio); | |
1095 | if (ret == 0) | |
1096 | ret = ret2; | |
1097 | if (ret == 0) | |
1098 | ret = dio->page_errors; | |
1099 | if (dio->result) { | |
1100 | loff_t i_size = i_size_read(inode); | |
1101 | ||
1102 | transferred = dio->result; | |
1103 | /* | |
1104 | * Adjust the return value if the read crossed a | |
1105 | * non-block-aligned EOF. | |
1106 | */ | |
1107 | if (rw == READ && (offset + transferred > i_size)) | |
1108 | transferred = i_size - offset; | |
1109 | } | |
1110 | dio_complete(dio, offset, transferred); | |
1111 | if (ret == 0) | |
1112 | ret = transferred; | |
1113 | ||
1114 | /* We could have also come here on an AIO file extend */ | |
1115 | if (!is_sync_kiocb(iocb) && rw == WRITE && | |
1116 | ret >= 0 && dio->result == dio->size) | |
1117 | /* | |
1118 | * For AIO writes where we have completed the | |
1119 | * i/o, we have to mark the the aio complete. | |
1120 | */ | |
1121 | aio_complete(iocb, ret, 0); | |
1122 | kfree(dio); | |
1123 | } | |
1124 | return ret; | |
1125 | } | |
1126 | ||
1127 | /* | |
1128 | * This is a library function for use by filesystem drivers. | |
1129 | * The locking rules are governed by the dio_lock_type parameter. | |
1130 | * | |
1131 | * DIO_NO_LOCKING (no locking, for raw block device access) | |
1132 | * For writes, i_sem is not held on entry; it is never taken. | |
1133 | * | |
1134 | * DIO_LOCKING (simple locking for regular files) | |
1135 | * For writes we are called under i_sem and return with i_sem held, even though | |
1136 | * it is internally dropped. | |
1137 | * For reads, i_sem is not held on entry, but it is taken and dropped before | |
1138 | * returning. | |
1139 | * | |
1140 | * DIO_OWN_LOCKING (filesystem provides synchronisation and handling of | |
1141 | * uninitialised data, allowing parallel direct readers and writers) | |
1142 | * For writes we are called without i_sem, return without it, never touch it. | |
1143 | * For reads, i_sem is held on entry and will be released before returning. | |
1144 | * | |
1145 | * Additional i_alloc_sem locking requirements described inline below. | |
1146 | */ | |
1147 | ssize_t | |
1148 | __blockdev_direct_IO(int rw, struct kiocb *iocb, struct inode *inode, | |
1149 | struct block_device *bdev, const struct iovec *iov, loff_t offset, | |
1150 | unsigned long nr_segs, get_blocks_t get_blocks, dio_iodone_t end_io, | |
1151 | int dio_lock_type) | |
1152 | { | |
1153 | int seg; | |
1154 | size_t size; | |
1155 | unsigned long addr; | |
1156 | unsigned blkbits = inode->i_blkbits; | |
1157 | unsigned bdev_blkbits = 0; | |
1158 | unsigned blocksize_mask = (1 << blkbits) - 1; | |
1159 | ssize_t retval = -EINVAL; | |
1160 | loff_t end = offset; | |
1161 | struct dio *dio; | |
1162 | int reader_with_isem = (rw == READ && dio_lock_type == DIO_OWN_LOCKING); | |
1163 | ||
1164 | if (rw & WRITE) | |
1165 | current->flags |= PF_SYNCWRITE; | |
1166 | ||
1167 | if (bdev) | |
1168 | bdev_blkbits = blksize_bits(bdev_hardsect_size(bdev)); | |
1169 | ||
1170 | if (offset & blocksize_mask) { | |
1171 | if (bdev) | |
1172 | blkbits = bdev_blkbits; | |
1173 | blocksize_mask = (1 << blkbits) - 1; | |
1174 | if (offset & blocksize_mask) | |
1175 | goto out; | |
1176 | } | |
1177 | ||
1178 | /* Check the memory alignment. Blocks cannot straddle pages */ | |
1179 | for (seg = 0; seg < nr_segs; seg++) { | |
1180 | addr = (unsigned long)iov[seg].iov_base; | |
1181 | size = iov[seg].iov_len; | |
1182 | end += size; | |
1183 | if ((addr & blocksize_mask) || (size & blocksize_mask)) { | |
1184 | if (bdev) | |
1185 | blkbits = bdev_blkbits; | |
1186 | blocksize_mask = (1 << blkbits) - 1; | |
1187 | if ((addr & blocksize_mask) || (size & blocksize_mask)) | |
1188 | goto out; | |
1189 | } | |
1190 | } | |
1191 | ||
1192 | dio = kmalloc(sizeof(*dio), GFP_KERNEL); | |
1193 | retval = -ENOMEM; | |
1194 | if (!dio) | |
1195 | goto out; | |
1196 | ||
1197 | /* | |
1198 | * For block device access DIO_NO_LOCKING is used, | |
1199 | * neither readers nor writers do any locking at all | |
1200 | * For regular files using DIO_LOCKING, | |
1201 | * readers need to grab i_sem and i_alloc_sem | |
1202 | * writers need to grab i_alloc_sem only (i_sem is already held) | |
1203 | * For regular files using DIO_OWN_LOCKING, | |
1204 | * neither readers nor writers take any locks here | |
1205 | * (i_sem is already held and release for writers here) | |
1206 | */ | |
1207 | dio->lock_type = dio_lock_type; | |
1208 | if (dio_lock_type != DIO_NO_LOCKING) { | |
1209 | /* watch out for a 0 len io from a tricksy fs */ | |
1210 | if (rw == READ && end > offset) { | |
1211 | struct address_space *mapping; | |
1212 | ||
1213 | mapping = iocb->ki_filp->f_mapping; | |
1214 | if (dio_lock_type != DIO_OWN_LOCKING) { | |
1215 | down(&inode->i_sem); | |
1216 | reader_with_isem = 1; | |
1217 | } | |
1218 | ||
1219 | retval = filemap_write_and_wait_range(mapping, offset, | |
1220 | end - 1); | |
1221 | if (retval) { | |
1222 | kfree(dio); | |
1223 | goto out; | |
1224 | } | |
1225 | ||
1226 | if (dio_lock_type == DIO_OWN_LOCKING) { | |
1227 | up(&inode->i_sem); | |
1228 | reader_with_isem = 0; | |
1229 | } | |
1230 | } | |
1231 | ||
1232 | if (dio_lock_type == DIO_LOCKING) | |
1233 | down_read(&inode->i_alloc_sem); | |
1234 | } | |
1235 | ||
1236 | /* | |
1237 | * For file extending writes updating i_size before data | |
1238 | * writeouts complete can expose uninitialized blocks. So | |
1239 | * even for AIO, we need to wait for i/o to complete before | |
1240 | * returning in this case. | |
1241 | */ | |
1242 | dio->is_async = !is_sync_kiocb(iocb) && !((rw == WRITE) && | |
1243 | (end > i_size_read(inode))); | |
1244 | ||
1245 | retval = direct_io_worker(rw, iocb, inode, iov, offset, | |
1246 | nr_segs, blkbits, get_blocks, end_io, dio); | |
1247 | ||
1248 | if (rw == READ && dio_lock_type == DIO_LOCKING) | |
1249 | reader_with_isem = 0; | |
1250 | ||
1251 | out: | |
1252 | if (reader_with_isem) | |
1253 | up(&inode->i_sem); | |
1254 | if (rw & WRITE) | |
1255 | current->flags &= ~PF_SYNCWRITE; | |
1256 | return retval; | |
1257 | } | |
1258 | EXPORT_SYMBOL(__blockdev_direct_IO); |