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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> | |
98c4d57d | 30 | #include <linux/task_io_accounting_ops.h> |
1da177e4 LT |
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 <asm/atomic.h> | |
39 | ||
40 | /* | |
41 | * How many user pages to map in one call to get_user_pages(). This determines | |
42 | * the size of a structure on the stack. | |
43 | */ | |
44 | #define DIO_PAGES 64 | |
45 | ||
46 | /* | |
47 | * This code generally works in units of "dio_blocks". A dio_block is | |
48 | * somewhere between the hard sector size and the filesystem block size. it | |
49 | * is determined on a per-invocation basis. When talking to the filesystem | |
50 | * we need to convert dio_blocks to fs_blocks by scaling the dio_block quantity | |
51 | * down by dio->blkfactor. Similarly, fs-blocksize quantities are converted | |
52 | * to bio_block quantities by shifting left by blkfactor. | |
53 | * | |
54 | * If blkfactor is zero then the user's request was aligned to the filesystem's | |
55 | * blocksize. | |
56 | * | |
57 | * lock_type is DIO_LOCKING for regular files on direct-IO-naive filesystems. | |
58 | * This determines whether we need to do the fancy locking which prevents | |
59 | * direct-IO from being able to read uninitialised disk blocks. If its zero | |
1b1dcc1b | 60 | * (blockdev) this locking is not done, and if it is DIO_OWN_LOCKING i_mutex is |
1da177e4 LT |
61 | * not held for the entire direct write (taken briefly, initially, during a |
62 | * direct read though, but its never held for the duration of a direct-IO). | |
63 | */ | |
64 | ||
65 | struct dio { | |
66 | /* BIO submission state */ | |
67 | struct bio *bio; /* bio under assembly */ | |
68 | struct inode *inode; | |
69 | int rw; | |
29504ff3 | 70 | loff_t i_size; /* i_size when submitted */ |
1da177e4 LT |
71 | int lock_type; /* doesn't change */ |
72 | unsigned blkbits; /* doesn't change */ | |
73 | unsigned blkfactor; /* When we're using an alignment which | |
74 | is finer than the filesystem's soft | |
75 | blocksize, this specifies how much | |
76 | finer. blkfactor=2 means 1/4-block | |
77 | alignment. Does not change */ | |
78 | unsigned start_zero_done; /* flag: sub-blocksize zeroing has | |
79 | been performed at the start of a | |
80 | write */ | |
81 | int pages_in_io; /* approximate total IO pages */ | |
82 | size_t size; /* total request size (doesn't change)*/ | |
83 | sector_t block_in_file; /* Current offset into the underlying | |
84 | file in dio_block units. */ | |
85 | unsigned blocks_available; /* At block_in_file. changes */ | |
86 | sector_t final_block_in_request;/* doesn't change */ | |
87 | unsigned first_block_in_page; /* doesn't change, Used only once */ | |
88 | int boundary; /* prev block is at a boundary */ | |
89 | int reap_counter; /* rate limit reaping */ | |
1d8fa7a2 | 90 | get_block_t *get_block; /* block mapping function */ |
1da177e4 LT |
91 | dio_iodone_t *end_io; /* IO completion function */ |
92 | sector_t final_block_in_bio; /* current final block in bio + 1 */ | |
93 | sector_t next_block_for_io; /* next block to be put under IO, | |
94 | in dio_blocks units */ | |
1d8fa7a2 | 95 | struct buffer_head map_bh; /* last get_block() result */ |
1da177e4 LT |
96 | |
97 | /* | |
98 | * Deferred addition of a page to the dio. These variables are | |
99 | * private to dio_send_cur_page(), submit_page_section() and | |
100 | * dio_bio_add_page(). | |
101 | */ | |
102 | struct page *cur_page; /* The page */ | |
103 | unsigned cur_page_offset; /* Offset into it, in bytes */ | |
104 | unsigned cur_page_len; /* Nr of bytes at cur_page_offset */ | |
105 | sector_t cur_page_block; /* Where it starts */ | |
106 | ||
107 | /* | |
108 | * Page fetching state. These variables belong to dio_refill_pages(). | |
109 | */ | |
110 | int curr_page; /* changes */ | |
111 | int total_pages; /* doesn't change */ | |
112 | unsigned long curr_user_address;/* changes */ | |
113 | ||
114 | /* | |
115 | * Page queue. These variables belong to dio_refill_pages() and | |
116 | * dio_get_page(). | |
117 | */ | |
118 | struct page *pages[DIO_PAGES]; /* page buffer */ | |
119 | unsigned head; /* next page to process */ | |
120 | unsigned tail; /* last valid page + 1 */ | |
121 | int page_errors; /* errno from get_user_pages() */ | |
122 | ||
123 | /* BIO completion state */ | |
124 | spinlock_t bio_lock; /* protects BIO fields below */ | |
125 | int bio_count; /* nr bios to be completed */ | |
126 | int bios_in_flight; /* nr bios in flight */ | |
127 | struct bio *bio_list; /* singly linked via bi_private */ | |
128 | struct task_struct *waiter; /* waiting task (NULL if none) */ | |
129 | ||
130 | /* AIO related stuff */ | |
131 | struct kiocb *iocb; /* kiocb */ | |
132 | int is_async; /* is IO async ? */ | |
174e27c6 | 133 | int io_error; /* IO error in completion path */ |
1da177e4 LT |
134 | ssize_t result; /* IO result */ |
135 | }; | |
136 | ||
137 | /* | |
138 | * How many pages are in the queue? | |
139 | */ | |
140 | static inline unsigned dio_pages_present(struct dio *dio) | |
141 | { | |
142 | return dio->tail - dio->head; | |
143 | } | |
144 | ||
145 | /* | |
146 | * Go grab and pin some userspace pages. Typically we'll get 64 at a time. | |
147 | */ | |
148 | static int dio_refill_pages(struct dio *dio) | |
149 | { | |
150 | int ret; | |
151 | int nr_pages; | |
152 | ||
153 | nr_pages = min(dio->total_pages - dio->curr_page, DIO_PAGES); | |
154 | down_read(¤t->mm->mmap_sem); | |
155 | ret = get_user_pages( | |
156 | current, /* Task for fault acounting */ | |
157 | current->mm, /* whose pages? */ | |
158 | dio->curr_user_address, /* Where from? */ | |
159 | nr_pages, /* How many pages? */ | |
160 | dio->rw == READ, /* Write to memory? */ | |
161 | 0, /* force (?) */ | |
162 | &dio->pages[0], | |
163 | NULL); /* vmas */ | |
164 | up_read(¤t->mm->mmap_sem); | |
165 | ||
b31dc66a | 166 | if (ret < 0 && dio->blocks_available && (dio->rw & WRITE)) { |
b5810039 | 167 | struct page *page = ZERO_PAGE(dio->curr_user_address); |
1da177e4 LT |
168 | /* |
169 | * A memory fault, but the filesystem has some outstanding | |
170 | * mapped blocks. We need to use those blocks up to avoid | |
171 | * leaking stale data in the file. | |
172 | */ | |
173 | if (dio->page_errors == 0) | |
174 | dio->page_errors = ret; | |
b5810039 NP |
175 | page_cache_get(page); |
176 | dio->pages[0] = page; | |
1da177e4 LT |
177 | dio->head = 0; |
178 | dio->tail = 1; | |
179 | ret = 0; | |
180 | goto out; | |
181 | } | |
182 | ||
183 | if (ret >= 0) { | |
184 | dio->curr_user_address += ret * PAGE_SIZE; | |
185 | dio->curr_page += ret; | |
186 | dio->head = 0; | |
187 | dio->tail = ret; | |
188 | ret = 0; | |
189 | } | |
190 | out: | |
191 | return ret; | |
192 | } | |
193 | ||
194 | /* | |
195 | * Get another userspace page. Returns an ERR_PTR on error. Pages are | |
196 | * buffered inside the dio so that we can call get_user_pages() against a | |
197 | * decent number of pages, less frequently. To provide nicer use of the | |
198 | * L1 cache. | |
199 | */ | |
200 | static struct page *dio_get_page(struct dio *dio) | |
201 | { | |
202 | if (dio_pages_present(dio) == 0) { | |
203 | int ret; | |
204 | ||
205 | ret = dio_refill_pages(dio); | |
206 | if (ret) | |
207 | return ERR_PTR(ret); | |
208 | BUG_ON(dio_pages_present(dio) == 0); | |
209 | } | |
210 | return dio->pages[dio->head++]; | |
211 | } | |
212 | ||
213 | /* | |
214 | * Called when all DIO BIO I/O has been completed - let the filesystem | |
1d8fa7a2 | 215 | * know, if it registered an interest earlier via get_block. Pass the |
1da177e4 | 216 | * private field of the map buffer_head so that filesystems can use it |
1d8fa7a2 | 217 | * to hold additional state between get_block calls and dio_complete. |
1da177e4 LT |
218 | */ |
219 | static void dio_complete(struct dio *dio, loff_t offset, ssize_t bytes) | |
220 | { | |
221 | if (dio->end_io && dio->result) | |
92198f7e | 222 | dio->end_io(dio->iocb, offset, bytes, dio->map_bh.b_private); |
1da177e4 | 223 | if (dio->lock_type == DIO_LOCKING) |
d8aa905b IM |
224 | /* lockdep: non-owner release */ |
225 | up_read_non_owner(&dio->inode->i_alloc_sem); | |
1da177e4 LT |
226 | } |
227 | ||
228 | /* | |
229 | * Called when a BIO has been processed. If the count goes to zero then IO is | |
230 | * complete and we can signal this to the AIO layer. | |
231 | */ | |
232 | static void finished_one_bio(struct dio *dio) | |
233 | { | |
234 | unsigned long flags; | |
235 | ||
236 | spin_lock_irqsave(&dio->bio_lock, flags); | |
237 | if (dio->bio_count == 1) { | |
238 | if (dio->is_async) { | |
29504ff3 DM |
239 | ssize_t transferred; |
240 | loff_t offset; | |
241 | ||
1da177e4 LT |
242 | /* |
243 | * Last reference to the dio is going away. | |
244 | * Drop spinlock and complete the DIO. | |
245 | */ | |
246 | spin_unlock_irqrestore(&dio->bio_lock, flags); | |
29504ff3 DM |
247 | |
248 | /* Check for short read case */ | |
249 | transferred = dio->result; | |
250 | offset = dio->iocb->ki_pos; | |
251 | ||
252 | if ((dio->rw == READ) && | |
253 | ((offset + transferred) > dio->i_size)) | |
254 | transferred = dio->i_size - offset; | |
255 | ||
174e27c6 KC |
256 | /* check for error in completion path */ |
257 | if (dio->io_error) | |
258 | transferred = dio->io_error; | |
259 | ||
29504ff3 DM |
260 | dio_complete(dio, offset, transferred); |
261 | ||
1da177e4 LT |
262 | /* Complete AIO later if falling back to buffered i/o */ |
263 | if (dio->result == dio->size || | |
264 | ((dio->rw == READ) && dio->result)) { | |
29504ff3 | 265 | aio_complete(dio->iocb, transferred, 0); |
1da177e4 LT |
266 | kfree(dio); |
267 | return; | |
268 | } else { | |
269 | /* | |
270 | * Falling back to buffered | |
271 | */ | |
272 | spin_lock_irqsave(&dio->bio_lock, flags); | |
273 | dio->bio_count--; | |
274 | if (dio->waiter) | |
275 | wake_up_process(dio->waiter); | |
276 | spin_unlock_irqrestore(&dio->bio_lock, flags); | |
277 | return; | |
278 | } | |
279 | } | |
280 | } | |
281 | dio->bio_count--; | |
282 | spin_unlock_irqrestore(&dio->bio_lock, flags); | |
283 | } | |
284 | ||
285 | static int dio_bio_complete(struct dio *dio, struct bio *bio); | |
286 | /* | |
287 | * Asynchronous IO callback. | |
288 | */ | |
289 | static int dio_bio_end_aio(struct bio *bio, unsigned int bytes_done, int error) | |
290 | { | |
291 | struct dio *dio = bio->bi_private; | |
292 | ||
293 | if (bio->bi_size) | |
294 | return 1; | |
295 | ||
296 | /* cleanup the bio */ | |
297 | dio_bio_complete(dio, bio); | |
298 | return 0; | |
299 | } | |
300 | ||
301 | /* | |
302 | * The BIO completion handler simply queues the BIO up for the process-context | |
303 | * handler. | |
304 | * | |
305 | * During I/O bi_private points at the dio. After I/O, bi_private is used to | |
306 | * implement a singly-linked list of completed BIOs, at dio->bio_list. | |
307 | */ | |
308 | static int dio_bio_end_io(struct bio *bio, unsigned int bytes_done, int error) | |
309 | { | |
310 | struct dio *dio = bio->bi_private; | |
311 | unsigned long flags; | |
312 | ||
313 | if (bio->bi_size) | |
314 | return 1; | |
315 | ||
316 | spin_lock_irqsave(&dio->bio_lock, flags); | |
317 | bio->bi_private = dio->bio_list; | |
318 | dio->bio_list = bio; | |
319 | dio->bios_in_flight--; | |
320 | if (dio->waiter && dio->bios_in_flight == 0) | |
321 | wake_up_process(dio->waiter); | |
322 | spin_unlock_irqrestore(&dio->bio_lock, flags); | |
323 | return 0; | |
324 | } | |
325 | ||
326 | static int | |
327 | dio_bio_alloc(struct dio *dio, struct block_device *bdev, | |
328 | sector_t first_sector, int nr_vecs) | |
329 | { | |
330 | struct bio *bio; | |
331 | ||
332 | bio = bio_alloc(GFP_KERNEL, nr_vecs); | |
333 | if (bio == NULL) | |
334 | return -ENOMEM; | |
335 | ||
336 | bio->bi_bdev = bdev; | |
337 | bio->bi_sector = first_sector; | |
338 | if (dio->is_async) | |
339 | bio->bi_end_io = dio_bio_end_aio; | |
340 | else | |
341 | bio->bi_end_io = dio_bio_end_io; | |
342 | ||
343 | dio->bio = bio; | |
344 | return 0; | |
345 | } | |
346 | ||
347 | /* | |
348 | * In the AIO read case we speculatively dirty the pages before starting IO. | |
349 | * During IO completion, any of these pages which happen to have been written | |
350 | * back will be redirtied by bio_check_pages_dirty(). | |
351 | */ | |
352 | static void dio_bio_submit(struct dio *dio) | |
353 | { | |
354 | struct bio *bio = dio->bio; | |
355 | unsigned long flags; | |
356 | ||
357 | bio->bi_private = dio; | |
358 | spin_lock_irqsave(&dio->bio_lock, flags); | |
359 | dio->bio_count++; | |
360 | dio->bios_in_flight++; | |
361 | spin_unlock_irqrestore(&dio->bio_lock, flags); | |
362 | if (dio->is_async && dio->rw == READ) | |
363 | bio_set_pages_dirty(bio); | |
364 | submit_bio(dio->rw, bio); | |
365 | ||
366 | dio->bio = NULL; | |
367 | dio->boundary = 0; | |
368 | } | |
369 | ||
370 | /* | |
371 | * Release any resources in case of a failure | |
372 | */ | |
373 | static void dio_cleanup(struct dio *dio) | |
374 | { | |
375 | while (dio_pages_present(dio)) | |
376 | page_cache_release(dio_get_page(dio)); | |
377 | } | |
378 | ||
379 | /* | |
380 | * Wait for the next BIO to complete. Remove it and return it. | |
381 | */ | |
382 | static struct bio *dio_await_one(struct dio *dio) | |
383 | { | |
384 | unsigned long flags; | |
385 | struct bio *bio; | |
386 | ||
387 | spin_lock_irqsave(&dio->bio_lock, flags); | |
388 | while (dio->bio_list == NULL) { | |
389 | set_current_state(TASK_UNINTERRUPTIBLE); | |
390 | if (dio->bio_list == NULL) { | |
391 | dio->waiter = current; | |
392 | spin_unlock_irqrestore(&dio->bio_lock, flags); | |
393 | blk_run_address_space(dio->inode->i_mapping); | |
394 | io_schedule(); | |
395 | spin_lock_irqsave(&dio->bio_lock, flags); | |
396 | dio->waiter = NULL; | |
397 | } | |
398 | set_current_state(TASK_RUNNING); | |
399 | } | |
400 | bio = dio->bio_list; | |
401 | dio->bio_list = bio->bi_private; | |
402 | spin_unlock_irqrestore(&dio->bio_lock, flags); | |
403 | return bio; | |
404 | } | |
405 | ||
406 | /* | |
407 | * Process one completed BIO. No locks are held. | |
408 | */ | |
409 | static int dio_bio_complete(struct dio *dio, struct bio *bio) | |
410 | { | |
411 | const int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags); | |
412 | struct bio_vec *bvec = bio->bi_io_vec; | |
413 | int page_no; | |
414 | ||
415 | if (!uptodate) | |
174e27c6 | 416 | dio->io_error = -EIO; |
1da177e4 LT |
417 | |
418 | if (dio->is_async && dio->rw == READ) { | |
419 | bio_check_pages_dirty(bio); /* transfers ownership */ | |
420 | } else { | |
421 | for (page_no = 0; page_no < bio->bi_vcnt; page_no++) { | |
422 | struct page *page = bvec[page_no].bv_page; | |
423 | ||
424 | if (dio->rw == READ && !PageCompound(page)) | |
425 | set_page_dirty_lock(page); | |
426 | page_cache_release(page); | |
427 | } | |
428 | bio_put(bio); | |
429 | } | |
430 | finished_one_bio(dio); | |
431 | return uptodate ? 0 : -EIO; | |
432 | } | |
433 | ||
434 | /* | |
435 | * Wait on and process all in-flight BIOs. | |
436 | */ | |
437 | static int dio_await_completion(struct dio *dio) | |
438 | { | |
439 | int ret = 0; | |
440 | ||
441 | if (dio->bio) | |
442 | dio_bio_submit(dio); | |
443 | ||
444 | /* | |
445 | * The bio_lock is not held for the read of bio_count. | |
446 | * This is ok since it is the dio_bio_complete() that changes | |
447 | * bio_count. | |
448 | */ | |
449 | while (dio->bio_count) { | |
450 | struct bio *bio = dio_await_one(dio); | |
451 | int ret2; | |
452 | ||
453 | ret2 = dio_bio_complete(dio, bio); | |
454 | if (ret == 0) | |
455 | ret = ret2; | |
456 | } | |
457 | return ret; | |
458 | } | |
459 | ||
460 | /* | |
461 | * A really large O_DIRECT read or write can generate a lot of BIOs. So | |
462 | * to keep the memory consumption sane we periodically reap any completed BIOs | |
463 | * during the BIO generation phase. | |
464 | * | |
465 | * This also helps to limit the peak amount of pinned userspace memory. | |
466 | */ | |
467 | static int dio_bio_reap(struct dio *dio) | |
468 | { | |
469 | int ret = 0; | |
470 | ||
471 | if (dio->reap_counter++ >= 64) { | |
472 | while (dio->bio_list) { | |
473 | unsigned long flags; | |
474 | struct bio *bio; | |
475 | int ret2; | |
476 | ||
477 | spin_lock_irqsave(&dio->bio_lock, flags); | |
478 | bio = dio->bio_list; | |
479 | dio->bio_list = bio->bi_private; | |
480 | spin_unlock_irqrestore(&dio->bio_lock, flags); | |
481 | ret2 = dio_bio_complete(dio, bio); | |
482 | if (ret == 0) | |
483 | ret = ret2; | |
484 | } | |
485 | dio->reap_counter = 0; | |
486 | } | |
487 | return ret; | |
488 | } | |
489 | ||
490 | /* | |
491 | * Call into the fs to map some more disk blocks. We record the current number | |
492 | * of available blocks at dio->blocks_available. These are in units of the | |
493 | * fs blocksize, (1 << inode->i_blkbits). | |
494 | * | |
495 | * The fs is allowed to map lots of blocks at once. If it wants to do that, | |
496 | * it uses the passed inode-relative block number as the file offset, as usual. | |
497 | * | |
1d8fa7a2 | 498 | * get_block() is passed the number of i_blkbits-sized blocks which direct_io |
1da177e4 LT |
499 | * has remaining to do. The fs should not map more than this number of blocks. |
500 | * | |
501 | * If the fs has mapped a lot of blocks, it should populate bh->b_size to | |
502 | * indicate how much contiguous disk space has been made available at | |
503 | * bh->b_blocknr. | |
504 | * | |
505 | * If *any* of the mapped blocks are new, then the fs must set buffer_new(). | |
506 | * This isn't very efficient... | |
507 | * | |
508 | * In the case of filesystem holes: the fs may return an arbitrarily-large | |
509 | * hole by returning an appropriate value in b_size and by clearing | |
510 | * buffer_mapped(). However the direct-io code will only process holes one | |
1d8fa7a2 | 511 | * block at a time - it will repeatedly call get_block() as it walks the hole. |
1da177e4 LT |
512 | */ |
513 | static int get_more_blocks(struct dio *dio) | |
514 | { | |
515 | int ret; | |
516 | struct buffer_head *map_bh = &dio->map_bh; | |
517 | sector_t fs_startblk; /* Into file, in filesystem-sized blocks */ | |
518 | unsigned long fs_count; /* Number of filesystem-sized blocks */ | |
519 | unsigned long dio_count;/* Number of dio_block-sized blocks */ | |
520 | unsigned long blkmask; | |
521 | int create; | |
522 | ||
523 | /* | |
524 | * If there was a memory error and we've overwritten all the | |
525 | * mapped blocks then we can now return that memory error | |
526 | */ | |
527 | ret = dio->page_errors; | |
528 | if (ret == 0) { | |
1da177e4 LT |
529 | BUG_ON(dio->block_in_file >= dio->final_block_in_request); |
530 | fs_startblk = dio->block_in_file >> dio->blkfactor; | |
531 | dio_count = dio->final_block_in_request - dio->block_in_file; | |
532 | fs_count = dio_count >> dio->blkfactor; | |
533 | blkmask = (1 << dio->blkfactor) - 1; | |
534 | if (dio_count & blkmask) | |
535 | fs_count++; | |
536 | ||
3c674e74 NS |
537 | map_bh->b_state = 0; |
538 | map_bh->b_size = fs_count << dio->inode->i_blkbits; | |
539 | ||
b31dc66a | 540 | create = dio->rw & WRITE; |
1da177e4 LT |
541 | if (dio->lock_type == DIO_LOCKING) { |
542 | if (dio->block_in_file < (i_size_read(dio->inode) >> | |
543 | dio->blkbits)) | |
544 | create = 0; | |
545 | } else if (dio->lock_type == DIO_NO_LOCKING) { | |
546 | create = 0; | |
547 | } | |
3c674e74 | 548 | |
1da177e4 LT |
549 | /* |
550 | * For writes inside i_size we forbid block creations: only | |
551 | * overwrites are permitted. We fall back to buffered writes | |
552 | * at a higher level for inside-i_size block-instantiating | |
553 | * writes. | |
554 | */ | |
1d8fa7a2 | 555 | ret = (*dio->get_block)(dio->inode, fs_startblk, |
1da177e4 LT |
556 | map_bh, create); |
557 | } | |
558 | return ret; | |
559 | } | |
560 | ||
561 | /* | |
562 | * There is no bio. Make one now. | |
563 | */ | |
564 | static int dio_new_bio(struct dio *dio, sector_t start_sector) | |
565 | { | |
566 | sector_t sector; | |
567 | int ret, nr_pages; | |
568 | ||
569 | ret = dio_bio_reap(dio); | |
570 | if (ret) | |
571 | goto out; | |
572 | sector = start_sector << (dio->blkbits - 9); | |
573 | nr_pages = min(dio->pages_in_io, bio_get_nr_vecs(dio->map_bh.b_bdev)); | |
574 | BUG_ON(nr_pages <= 0); | |
575 | ret = dio_bio_alloc(dio, dio->map_bh.b_bdev, sector, nr_pages); | |
576 | dio->boundary = 0; | |
577 | out: | |
578 | return ret; | |
579 | } | |
580 | ||
581 | /* | |
582 | * Attempt to put the current chunk of 'cur_page' into the current BIO. If | |
583 | * that was successful then update final_block_in_bio and take a ref against | |
584 | * the just-added page. | |
585 | * | |
586 | * Return zero on success. Non-zero means the caller needs to start a new BIO. | |
587 | */ | |
588 | static int dio_bio_add_page(struct dio *dio) | |
589 | { | |
590 | int ret; | |
591 | ||
592 | ret = bio_add_page(dio->bio, dio->cur_page, | |
593 | dio->cur_page_len, dio->cur_page_offset); | |
594 | if (ret == dio->cur_page_len) { | |
595 | /* | |
596 | * Decrement count only, if we are done with this page | |
597 | */ | |
598 | if ((dio->cur_page_len + dio->cur_page_offset) == PAGE_SIZE) | |
599 | dio->pages_in_io--; | |
600 | page_cache_get(dio->cur_page); | |
601 | dio->final_block_in_bio = dio->cur_page_block + | |
602 | (dio->cur_page_len >> dio->blkbits); | |
603 | ret = 0; | |
604 | } else { | |
605 | ret = 1; | |
606 | } | |
607 | return ret; | |
608 | } | |
609 | ||
610 | /* | |
611 | * Put cur_page under IO. The section of cur_page which is described by | |
612 | * cur_page_offset,cur_page_len is put into a BIO. The section of cur_page | |
613 | * starts on-disk at cur_page_block. | |
614 | * | |
615 | * We take a ref against the page here (on behalf of its presence in the bio). | |
616 | * | |
617 | * The caller of this function is responsible for removing cur_page from the | |
618 | * dio, and for dropping the refcount which came from that presence. | |
619 | */ | |
620 | static int dio_send_cur_page(struct dio *dio) | |
621 | { | |
622 | int ret = 0; | |
623 | ||
624 | if (dio->bio) { | |
625 | /* | |
626 | * See whether this new request is contiguous with the old | |
627 | */ | |
628 | if (dio->final_block_in_bio != dio->cur_page_block) | |
629 | dio_bio_submit(dio); | |
630 | /* | |
631 | * Submit now if the underlying fs is about to perform a | |
632 | * metadata read | |
633 | */ | |
634 | if (dio->boundary) | |
635 | dio_bio_submit(dio); | |
636 | } | |
637 | ||
638 | if (dio->bio == NULL) { | |
639 | ret = dio_new_bio(dio, dio->cur_page_block); | |
640 | if (ret) | |
641 | goto out; | |
642 | } | |
643 | ||
644 | if (dio_bio_add_page(dio) != 0) { | |
645 | dio_bio_submit(dio); | |
646 | ret = dio_new_bio(dio, dio->cur_page_block); | |
647 | if (ret == 0) { | |
648 | ret = dio_bio_add_page(dio); | |
649 | BUG_ON(ret != 0); | |
650 | } | |
651 | } | |
652 | out: | |
653 | return ret; | |
654 | } | |
655 | ||
656 | /* | |
657 | * An autonomous function to put a chunk of a page under deferred IO. | |
658 | * | |
659 | * The caller doesn't actually know (or care) whether this piece of page is in | |
660 | * a BIO, or is under IO or whatever. We just take care of all possible | |
661 | * situations here. The separation between the logic of do_direct_IO() and | |
662 | * that of submit_page_section() is important for clarity. Please don't break. | |
663 | * | |
664 | * The chunk of page starts on-disk at blocknr. | |
665 | * | |
666 | * We perform deferred IO, by recording the last-submitted page inside our | |
667 | * private part of the dio structure. If possible, we just expand the IO | |
668 | * across that page here. | |
669 | * | |
670 | * If that doesn't work out then we put the old page into the bio and add this | |
671 | * page to the dio instead. | |
672 | */ | |
673 | static int | |
674 | submit_page_section(struct dio *dio, struct page *page, | |
675 | unsigned offset, unsigned len, sector_t blocknr) | |
676 | { | |
677 | int ret = 0; | |
678 | ||
98c4d57d AM |
679 | if (dio->rw & WRITE) { |
680 | /* | |
681 | * Read accounting is performed in submit_bio() | |
682 | */ | |
683 | task_io_account_write(len); | |
684 | } | |
685 | ||
1da177e4 LT |
686 | /* |
687 | * Can we just grow the current page's presence in the dio? | |
688 | */ | |
689 | if ( (dio->cur_page == page) && | |
690 | (dio->cur_page_offset + dio->cur_page_len == offset) && | |
691 | (dio->cur_page_block + | |
692 | (dio->cur_page_len >> dio->blkbits) == blocknr)) { | |
693 | dio->cur_page_len += len; | |
694 | ||
695 | /* | |
696 | * If dio->boundary then we want to schedule the IO now to | |
697 | * avoid metadata seeks. | |
698 | */ | |
699 | if (dio->boundary) { | |
700 | ret = dio_send_cur_page(dio); | |
701 | page_cache_release(dio->cur_page); | |
702 | dio->cur_page = NULL; | |
703 | } | |
704 | goto out; | |
705 | } | |
706 | ||
707 | /* | |
708 | * If there's a deferred page already there then send it. | |
709 | */ | |
710 | if (dio->cur_page) { | |
711 | ret = dio_send_cur_page(dio); | |
712 | page_cache_release(dio->cur_page); | |
713 | dio->cur_page = NULL; | |
714 | if (ret) | |
715 | goto out; | |
716 | } | |
717 | ||
718 | page_cache_get(page); /* It is in dio */ | |
719 | dio->cur_page = page; | |
720 | dio->cur_page_offset = offset; | |
721 | dio->cur_page_len = len; | |
722 | dio->cur_page_block = blocknr; | |
723 | out: | |
724 | return ret; | |
725 | } | |
726 | ||
727 | /* | |
728 | * Clean any dirty buffers in the blockdev mapping which alias newly-created | |
729 | * file blocks. Only called for S_ISREG files - blockdevs do not set | |
730 | * buffer_new | |
731 | */ | |
732 | static void clean_blockdev_aliases(struct dio *dio) | |
733 | { | |
734 | unsigned i; | |
735 | unsigned nblocks; | |
736 | ||
737 | nblocks = dio->map_bh.b_size >> dio->inode->i_blkbits; | |
738 | ||
739 | for (i = 0; i < nblocks; i++) { | |
740 | unmap_underlying_metadata(dio->map_bh.b_bdev, | |
741 | dio->map_bh.b_blocknr + i); | |
742 | } | |
743 | } | |
744 | ||
745 | /* | |
746 | * If we are not writing the entire block and get_block() allocated | |
747 | * the block for us, we need to fill-in the unused portion of the | |
748 | * block with zeros. This happens only if user-buffer, fileoffset or | |
749 | * io length is not filesystem block-size multiple. | |
750 | * | |
751 | * `end' is zero if we're doing the start of the IO, 1 at the end of the | |
752 | * IO. | |
753 | */ | |
754 | static void dio_zero_block(struct dio *dio, int end) | |
755 | { | |
756 | unsigned dio_blocks_per_fs_block; | |
757 | unsigned this_chunk_blocks; /* In dio_blocks */ | |
758 | unsigned this_chunk_bytes; | |
759 | struct page *page; | |
760 | ||
761 | dio->start_zero_done = 1; | |
762 | if (!dio->blkfactor || !buffer_new(&dio->map_bh)) | |
763 | return; | |
764 | ||
765 | dio_blocks_per_fs_block = 1 << dio->blkfactor; | |
766 | this_chunk_blocks = dio->block_in_file & (dio_blocks_per_fs_block - 1); | |
767 | ||
768 | if (!this_chunk_blocks) | |
769 | return; | |
770 | ||
771 | /* | |
772 | * We need to zero out part of an fs block. It is either at the | |
773 | * beginning or the end of the fs block. | |
774 | */ | |
775 | if (end) | |
776 | this_chunk_blocks = dio_blocks_per_fs_block - this_chunk_blocks; | |
777 | ||
778 | this_chunk_bytes = this_chunk_blocks << dio->blkbits; | |
779 | ||
780 | page = ZERO_PAGE(dio->curr_user_address); | |
781 | if (submit_page_section(dio, page, 0, this_chunk_bytes, | |
782 | dio->next_block_for_io)) | |
783 | return; | |
784 | ||
785 | dio->next_block_for_io += this_chunk_blocks; | |
786 | } | |
787 | ||
788 | /* | |
789 | * Walk the user pages, and the file, mapping blocks to disk and generating | |
790 | * a sequence of (page,offset,len,block) mappings. These mappings are injected | |
791 | * into submit_page_section(), which takes care of the next stage of submission | |
792 | * | |
793 | * Direct IO against a blockdev is different from a file. Because we can | |
794 | * happily perform page-sized but 512-byte aligned IOs. It is important that | |
795 | * blockdev IO be able to have fine alignment and large sizes. | |
796 | * | |
1d8fa7a2 | 797 | * So what we do is to permit the ->get_block function to populate bh.b_size |
1da177e4 LT |
798 | * with the size of IO which is permitted at this offset and this i_blkbits. |
799 | * | |
800 | * For best results, the blockdev should be set up with 512-byte i_blkbits and | |
1d8fa7a2 | 801 | * it should set b_size to PAGE_SIZE or more inside get_block(). This gives |
1da177e4 LT |
802 | * fine alignment but still allows this function to work in PAGE_SIZE units. |
803 | */ | |
804 | static int do_direct_IO(struct dio *dio) | |
805 | { | |
806 | const unsigned blkbits = dio->blkbits; | |
807 | const unsigned blocks_per_page = PAGE_SIZE >> blkbits; | |
808 | struct page *page; | |
809 | unsigned block_in_page; | |
810 | struct buffer_head *map_bh = &dio->map_bh; | |
811 | int ret = 0; | |
812 | ||
813 | /* The I/O can start at any block offset within the first page */ | |
814 | block_in_page = dio->first_block_in_page; | |
815 | ||
816 | while (dio->block_in_file < dio->final_block_in_request) { | |
817 | page = dio_get_page(dio); | |
818 | if (IS_ERR(page)) { | |
819 | ret = PTR_ERR(page); | |
820 | goto out; | |
821 | } | |
822 | ||
823 | while (block_in_page < blocks_per_page) { | |
824 | unsigned offset_in_page = block_in_page << blkbits; | |
825 | unsigned this_chunk_bytes; /* # of bytes mapped */ | |
826 | unsigned this_chunk_blocks; /* # of blocks */ | |
827 | unsigned u; | |
828 | ||
829 | if (dio->blocks_available == 0) { | |
830 | /* | |
831 | * Need to go and map some more disk | |
832 | */ | |
833 | unsigned long blkmask; | |
834 | unsigned long dio_remainder; | |
835 | ||
836 | ret = get_more_blocks(dio); | |
837 | if (ret) { | |
838 | page_cache_release(page); | |
839 | goto out; | |
840 | } | |
841 | if (!buffer_mapped(map_bh)) | |
842 | goto do_holes; | |
843 | ||
844 | dio->blocks_available = | |
845 | map_bh->b_size >> dio->blkbits; | |
846 | dio->next_block_for_io = | |
847 | map_bh->b_blocknr << dio->blkfactor; | |
848 | if (buffer_new(map_bh)) | |
849 | clean_blockdev_aliases(dio); | |
850 | ||
851 | if (!dio->blkfactor) | |
852 | goto do_holes; | |
853 | ||
854 | blkmask = (1 << dio->blkfactor) - 1; | |
855 | dio_remainder = (dio->block_in_file & blkmask); | |
856 | ||
857 | /* | |
858 | * If we are at the start of IO and that IO | |
859 | * starts partway into a fs-block, | |
860 | * dio_remainder will be non-zero. If the IO | |
861 | * is a read then we can simply advance the IO | |
862 | * cursor to the first block which is to be | |
863 | * read. But if the IO is a write and the | |
864 | * block was newly allocated we cannot do that; | |
865 | * the start of the fs block must be zeroed out | |
866 | * on-disk | |
867 | */ | |
868 | if (!buffer_new(map_bh)) | |
869 | dio->next_block_for_io += dio_remainder; | |
870 | dio->blocks_available -= dio_remainder; | |
871 | } | |
872 | do_holes: | |
873 | /* Handle holes */ | |
874 | if (!buffer_mapped(map_bh)) { | |
875 | char *kaddr; | |
35dc8161 | 876 | loff_t i_size_aligned; |
1da177e4 LT |
877 | |
878 | /* AKPM: eargh, -ENOTBLK is a hack */ | |
b31dc66a | 879 | if (dio->rw & WRITE) { |
1da177e4 LT |
880 | page_cache_release(page); |
881 | return -ENOTBLK; | |
882 | } | |
883 | ||
35dc8161 JM |
884 | /* |
885 | * Be sure to account for a partial block as the | |
886 | * last block in the file | |
887 | */ | |
888 | i_size_aligned = ALIGN(i_size_read(dio->inode), | |
889 | 1 << blkbits); | |
1da177e4 | 890 | if (dio->block_in_file >= |
35dc8161 | 891 | i_size_aligned >> blkbits) { |
1da177e4 LT |
892 | /* We hit eof */ |
893 | page_cache_release(page); | |
894 | goto out; | |
895 | } | |
896 | kaddr = kmap_atomic(page, KM_USER0); | |
897 | memset(kaddr + (block_in_page << blkbits), | |
898 | 0, 1 << blkbits); | |
899 | flush_dcache_page(page); | |
900 | kunmap_atomic(kaddr, KM_USER0); | |
901 | dio->block_in_file++; | |
902 | block_in_page++; | |
903 | goto next_block; | |
904 | } | |
905 | ||
906 | /* | |
907 | * If we're performing IO which has an alignment which | |
908 | * is finer than the underlying fs, go check to see if | |
909 | * we must zero out the start of this block. | |
910 | */ | |
911 | if (unlikely(dio->blkfactor && !dio->start_zero_done)) | |
912 | dio_zero_block(dio, 0); | |
913 | ||
914 | /* | |
915 | * Work out, in this_chunk_blocks, how much disk we | |
916 | * can add to this page | |
917 | */ | |
918 | this_chunk_blocks = dio->blocks_available; | |
919 | u = (PAGE_SIZE - offset_in_page) >> blkbits; | |
920 | if (this_chunk_blocks > u) | |
921 | this_chunk_blocks = u; | |
922 | u = dio->final_block_in_request - dio->block_in_file; | |
923 | if (this_chunk_blocks > u) | |
924 | this_chunk_blocks = u; | |
925 | this_chunk_bytes = this_chunk_blocks << blkbits; | |
926 | BUG_ON(this_chunk_bytes == 0); | |
927 | ||
928 | dio->boundary = buffer_boundary(map_bh); | |
929 | ret = submit_page_section(dio, page, offset_in_page, | |
930 | this_chunk_bytes, dio->next_block_for_io); | |
931 | if (ret) { | |
932 | page_cache_release(page); | |
933 | goto out; | |
934 | } | |
935 | dio->next_block_for_io += this_chunk_blocks; | |
936 | ||
937 | dio->block_in_file += this_chunk_blocks; | |
938 | block_in_page += this_chunk_blocks; | |
939 | dio->blocks_available -= this_chunk_blocks; | |
940 | next_block: | |
d4569d2e | 941 | BUG_ON(dio->block_in_file > dio->final_block_in_request); |
1da177e4 LT |
942 | if (dio->block_in_file == dio->final_block_in_request) |
943 | break; | |
944 | } | |
945 | ||
946 | /* Drop the ref which was taken in get_user_pages() */ | |
947 | page_cache_release(page); | |
948 | block_in_page = 0; | |
949 | } | |
950 | out: | |
951 | return ret; | |
952 | } | |
953 | ||
954 | /* | |
1b1dcc1b | 955 | * Releases both i_mutex and i_alloc_sem |
1da177e4 LT |
956 | */ |
957 | static ssize_t | |
958 | direct_io_worker(int rw, struct kiocb *iocb, struct inode *inode, | |
959 | const struct iovec *iov, loff_t offset, unsigned long nr_segs, | |
1d8fa7a2 | 960 | unsigned blkbits, get_block_t get_block, dio_iodone_t end_io, |
1da177e4 LT |
961 | struct dio *dio) |
962 | { | |
963 | unsigned long user_addr; | |
964 | int seg; | |
965 | ssize_t ret = 0; | |
966 | ssize_t ret2; | |
967 | size_t bytes; | |
968 | ||
969 | dio->bio = NULL; | |
970 | dio->inode = inode; | |
971 | dio->rw = rw; | |
972 | dio->blkbits = blkbits; | |
973 | dio->blkfactor = inode->i_blkbits - blkbits; | |
974 | dio->start_zero_done = 0; | |
975 | dio->size = 0; | |
976 | dio->block_in_file = offset >> blkbits; | |
977 | dio->blocks_available = 0; | |
978 | dio->cur_page = NULL; | |
979 | ||
980 | dio->boundary = 0; | |
981 | dio->reap_counter = 0; | |
1d8fa7a2 | 982 | dio->get_block = get_block; |
1da177e4 LT |
983 | dio->end_io = end_io; |
984 | dio->map_bh.b_private = NULL; | |
985 | dio->final_block_in_bio = -1; | |
986 | dio->next_block_for_io = -1; | |
987 | ||
988 | dio->page_errors = 0; | |
174e27c6 | 989 | dio->io_error = 0; |
1da177e4 LT |
990 | dio->result = 0; |
991 | dio->iocb = iocb; | |
29504ff3 | 992 | dio->i_size = i_size_read(inode); |
1da177e4 LT |
993 | |
994 | /* | |
995 | * BIO completion state. | |
996 | * | |
997 | * ->bio_count starts out at one, and we decrement it to zero after all | |
998 | * BIOs are submitted. This to avoid the situation where a really fast | |
999 | * (or synchronous) device could take the count to zero while we're | |
1000 | * still submitting BIOs. | |
1001 | */ | |
1002 | dio->bio_count = 1; | |
1003 | dio->bios_in_flight = 0; | |
1004 | spin_lock_init(&dio->bio_lock); | |
1005 | dio->bio_list = NULL; | |
1006 | dio->waiter = NULL; | |
1007 | ||
1008 | /* | |
1009 | * In case of non-aligned buffers, we may need 2 more | |
1010 | * pages since we need to zero out first and last block. | |
1011 | */ | |
1012 | if (unlikely(dio->blkfactor)) | |
1013 | dio->pages_in_io = 2; | |
1014 | else | |
1015 | dio->pages_in_io = 0; | |
1016 | ||
1017 | for (seg = 0; seg < nr_segs; seg++) { | |
1018 | user_addr = (unsigned long)iov[seg].iov_base; | |
1019 | dio->pages_in_io += | |
1020 | ((user_addr+iov[seg].iov_len +PAGE_SIZE-1)/PAGE_SIZE | |
1021 | - user_addr/PAGE_SIZE); | |
1022 | } | |
1023 | ||
1024 | for (seg = 0; seg < nr_segs; seg++) { | |
1025 | user_addr = (unsigned long)iov[seg].iov_base; | |
1026 | dio->size += bytes = iov[seg].iov_len; | |
1027 | ||
1028 | /* Index into the first page of the first block */ | |
1029 | dio->first_block_in_page = (user_addr & ~PAGE_MASK) >> blkbits; | |
1030 | dio->final_block_in_request = dio->block_in_file + | |
1031 | (bytes >> blkbits); | |
1032 | /* Page fetching state */ | |
1033 | dio->head = 0; | |
1034 | dio->tail = 0; | |
1035 | dio->curr_page = 0; | |
1036 | ||
1037 | dio->total_pages = 0; | |
1038 | if (user_addr & (PAGE_SIZE-1)) { | |
1039 | dio->total_pages++; | |
1040 | bytes -= PAGE_SIZE - (user_addr & (PAGE_SIZE - 1)); | |
1041 | } | |
1042 | dio->total_pages += (bytes + PAGE_SIZE - 1) / PAGE_SIZE; | |
1043 | dio->curr_user_address = user_addr; | |
1044 | ||
1045 | ret = do_direct_IO(dio); | |
1046 | ||
1047 | dio->result += iov[seg].iov_len - | |
1048 | ((dio->final_block_in_request - dio->block_in_file) << | |
1049 | blkbits); | |
1050 | ||
1051 | if (ret) { | |
1052 | dio_cleanup(dio); | |
1053 | break; | |
1054 | } | |
1055 | } /* end iovec loop */ | |
1056 | ||
b31dc66a | 1057 | if (ret == -ENOTBLK && (rw & WRITE)) { |
1da177e4 LT |
1058 | /* |
1059 | * The remaining part of the request will be | |
1060 | * be handled by buffered I/O when we return | |
1061 | */ | |
1062 | ret = 0; | |
1063 | } | |
1064 | /* | |
1065 | * There may be some unwritten disk at the end of a part-written | |
1066 | * fs-block-sized block. Go zero that now. | |
1067 | */ | |
1068 | dio_zero_block(dio, 1); | |
1069 | ||
1070 | if (dio->cur_page) { | |
1071 | ret2 = dio_send_cur_page(dio); | |
1072 | if (ret == 0) | |
1073 | ret = ret2; | |
1074 | page_cache_release(dio->cur_page); | |
1075 | dio->cur_page = NULL; | |
1076 | } | |
1077 | if (dio->bio) | |
1078 | dio_bio_submit(dio); | |
1079 | ||
1080 | /* | |
1081 | * It is possible that, we return short IO due to end of file. | |
1082 | * In that case, we need to release all the pages we got hold on. | |
1083 | */ | |
1084 | dio_cleanup(dio); | |
1085 | ||
1086 | /* | |
1087 | * All block lookups have been performed. For READ requests | |
1b1dcc1b | 1088 | * we can let i_mutex go now that its achieved its purpose |
1da177e4 LT |
1089 | * of protecting us from looking up uninitialized blocks. |
1090 | */ | |
1091 | if ((rw == READ) && (dio->lock_type == DIO_LOCKING)) | |
1b1dcc1b | 1092 | mutex_unlock(&dio->inode->i_mutex); |
1da177e4 LT |
1093 | |
1094 | /* | |
1095 | * OK, all BIOs are submitted, so we can decrement bio_count to truly | |
1096 | * reflect the number of to-be-processed BIOs. | |
1097 | */ | |
1098 | if (dio->is_async) { | |
1099 | int should_wait = 0; | |
1100 | ||
b31dc66a | 1101 | if (dio->result < dio->size && (rw & WRITE)) { |
1da177e4 LT |
1102 | dio->waiter = current; |
1103 | should_wait = 1; | |
1104 | } | |
1105 | if (ret == 0) | |
1106 | ret = dio->result; | |
1107 | finished_one_bio(dio); /* This can free the dio */ | |
1108 | blk_run_address_space(inode->i_mapping); | |
1109 | if (should_wait) { | |
1110 | unsigned long flags; | |
1111 | /* | |
1112 | * Wait for already issued I/O to drain out and | |
1113 | * release its references to user-space pages | |
1114 | * before returning to fallback on buffered I/O | |
1115 | */ | |
1116 | ||
1117 | spin_lock_irqsave(&dio->bio_lock, flags); | |
1118 | set_current_state(TASK_UNINTERRUPTIBLE); | |
1119 | while (dio->bio_count) { | |
1120 | spin_unlock_irqrestore(&dio->bio_lock, flags); | |
1121 | io_schedule(); | |
1122 | spin_lock_irqsave(&dio->bio_lock, flags); | |
1123 | set_current_state(TASK_UNINTERRUPTIBLE); | |
1124 | } | |
1125 | spin_unlock_irqrestore(&dio->bio_lock, flags); | |
1126 | set_current_state(TASK_RUNNING); | |
1127 | kfree(dio); | |
1128 | } | |
1129 | } else { | |
1130 | ssize_t transferred = 0; | |
1131 | ||
1132 | finished_one_bio(dio); | |
1133 | ret2 = dio_await_completion(dio); | |
1134 | if (ret == 0) | |
1135 | ret = ret2; | |
1136 | if (ret == 0) | |
1137 | ret = dio->page_errors; | |
1138 | if (dio->result) { | |
1139 | loff_t i_size = i_size_read(inode); | |
1140 | ||
1141 | transferred = dio->result; | |
1142 | /* | |
1143 | * Adjust the return value if the read crossed a | |
1144 | * non-block-aligned EOF. | |
1145 | */ | |
1146 | if (rw == READ && (offset + transferred > i_size)) | |
1147 | transferred = i_size - offset; | |
1148 | } | |
1149 | dio_complete(dio, offset, transferred); | |
1150 | if (ret == 0) | |
1151 | ret = transferred; | |
1152 | ||
1153 | /* We could have also come here on an AIO file extend */ | |
b31dc66a | 1154 | if (!is_sync_kiocb(iocb) && (rw & WRITE) && |
1da177e4 LT |
1155 | ret >= 0 && dio->result == dio->size) |
1156 | /* | |
1157 | * For AIO writes where we have completed the | |
1158 | * i/o, we have to mark the the aio complete. | |
1159 | */ | |
1160 | aio_complete(iocb, ret, 0); | |
1161 | kfree(dio); | |
1162 | } | |
1163 | return ret; | |
1164 | } | |
1165 | ||
1166 | /* | |
1167 | * This is a library function for use by filesystem drivers. | |
1168 | * The locking rules are governed by the dio_lock_type parameter. | |
1169 | * | |
1170 | * DIO_NO_LOCKING (no locking, for raw block device access) | |
1b1dcc1b | 1171 | * For writes, i_mutex is not held on entry; it is never taken. |
1da177e4 LT |
1172 | * |
1173 | * DIO_LOCKING (simple locking for regular files) | |
3fb962bd NS |
1174 | * For writes we are called under i_mutex and return with i_mutex held, even |
1175 | * though it is internally dropped. | |
1b1dcc1b | 1176 | * For reads, i_mutex is not held on entry, but it is taken and dropped before |
1da177e4 LT |
1177 | * returning. |
1178 | * | |
1179 | * DIO_OWN_LOCKING (filesystem provides synchronisation and handling of | |
1180 | * uninitialised data, allowing parallel direct readers and writers) | |
1b1dcc1b | 1181 | * For writes we are called without i_mutex, return without it, never touch it. |
3fb962bd NS |
1182 | * For reads we are called under i_mutex and return with i_mutex held, even |
1183 | * though it may be internally dropped. | |
1da177e4 LT |
1184 | * |
1185 | * Additional i_alloc_sem locking requirements described inline below. | |
1186 | */ | |
1187 | ssize_t | |
1188 | __blockdev_direct_IO(int rw, struct kiocb *iocb, struct inode *inode, | |
1189 | struct block_device *bdev, const struct iovec *iov, loff_t offset, | |
1d8fa7a2 | 1190 | unsigned long nr_segs, get_block_t get_block, dio_iodone_t end_io, |
1da177e4 LT |
1191 | int dio_lock_type) |
1192 | { | |
1193 | int seg; | |
1194 | size_t size; | |
1195 | unsigned long addr; | |
1196 | unsigned blkbits = inode->i_blkbits; | |
1197 | unsigned bdev_blkbits = 0; | |
1198 | unsigned blocksize_mask = (1 << blkbits) - 1; | |
1199 | ssize_t retval = -EINVAL; | |
1200 | loff_t end = offset; | |
1201 | struct dio *dio; | |
3fb962bd NS |
1202 | int release_i_mutex = 0; |
1203 | int acquire_i_mutex = 0; | |
1da177e4 LT |
1204 | |
1205 | if (rw & WRITE) | |
b31dc66a | 1206 | rw = WRITE_SYNC; |
1da177e4 LT |
1207 | |
1208 | if (bdev) | |
1209 | bdev_blkbits = blksize_bits(bdev_hardsect_size(bdev)); | |
1210 | ||
1211 | if (offset & blocksize_mask) { | |
1212 | if (bdev) | |
1213 | blkbits = bdev_blkbits; | |
1214 | blocksize_mask = (1 << blkbits) - 1; | |
1215 | if (offset & blocksize_mask) | |
1216 | goto out; | |
1217 | } | |
1218 | ||
1219 | /* Check the memory alignment. Blocks cannot straddle pages */ | |
1220 | for (seg = 0; seg < nr_segs; seg++) { | |
1221 | addr = (unsigned long)iov[seg].iov_base; | |
1222 | size = iov[seg].iov_len; | |
1223 | end += size; | |
1224 | if ((addr & blocksize_mask) || (size & blocksize_mask)) { | |
1225 | if (bdev) | |
1226 | blkbits = bdev_blkbits; | |
1227 | blocksize_mask = (1 << blkbits) - 1; | |
1228 | if ((addr & blocksize_mask) || (size & blocksize_mask)) | |
1229 | goto out; | |
1230 | } | |
1231 | } | |
1232 | ||
1233 | dio = kmalloc(sizeof(*dio), GFP_KERNEL); | |
1234 | retval = -ENOMEM; | |
1235 | if (!dio) | |
1236 | goto out; | |
1237 | ||
1238 | /* | |
1239 | * For block device access DIO_NO_LOCKING is used, | |
1240 | * neither readers nor writers do any locking at all | |
1241 | * For regular files using DIO_LOCKING, | |
1b1dcc1b JS |
1242 | * readers need to grab i_mutex and i_alloc_sem |
1243 | * writers need to grab i_alloc_sem only (i_mutex is already held) | |
1da177e4 LT |
1244 | * For regular files using DIO_OWN_LOCKING, |
1245 | * neither readers nor writers take any locks here | |
1da177e4 LT |
1246 | */ |
1247 | dio->lock_type = dio_lock_type; | |
1248 | if (dio_lock_type != DIO_NO_LOCKING) { | |
1249 | /* watch out for a 0 len io from a tricksy fs */ | |
1250 | if (rw == READ && end > offset) { | |
1251 | struct address_space *mapping; | |
1252 | ||
1253 | mapping = iocb->ki_filp->f_mapping; | |
1254 | if (dio_lock_type != DIO_OWN_LOCKING) { | |
1b1dcc1b | 1255 | mutex_lock(&inode->i_mutex); |
3fb962bd | 1256 | release_i_mutex = 1; |
1da177e4 LT |
1257 | } |
1258 | ||
1259 | retval = filemap_write_and_wait_range(mapping, offset, | |
1260 | end - 1); | |
1261 | if (retval) { | |
1262 | kfree(dio); | |
1263 | goto out; | |
1264 | } | |
1265 | ||
1266 | if (dio_lock_type == DIO_OWN_LOCKING) { | |
1b1dcc1b | 1267 | mutex_unlock(&inode->i_mutex); |
3fb962bd | 1268 | acquire_i_mutex = 1; |
1da177e4 LT |
1269 | } |
1270 | } | |
1271 | ||
1272 | if (dio_lock_type == DIO_LOCKING) | |
d8aa905b IM |
1273 | /* lockdep: not the owner will release it */ |
1274 | down_read_non_owner(&inode->i_alloc_sem); | |
1da177e4 LT |
1275 | } |
1276 | ||
1277 | /* | |
1278 | * For file extending writes updating i_size before data | |
1279 | * writeouts complete can expose uninitialized blocks. So | |
1280 | * even for AIO, we need to wait for i/o to complete before | |
1281 | * returning in this case. | |
1282 | */ | |
b31dc66a | 1283 | dio->is_async = !is_sync_kiocb(iocb) && !((rw & WRITE) && |
1da177e4 LT |
1284 | (end > i_size_read(inode))); |
1285 | ||
1286 | retval = direct_io_worker(rw, iocb, inode, iov, offset, | |
1d8fa7a2 | 1287 | nr_segs, blkbits, get_block, end_io, dio); |
1da177e4 LT |
1288 | |
1289 | if (rw == READ && dio_lock_type == DIO_LOCKING) | |
3fb962bd | 1290 | release_i_mutex = 0; |
1da177e4 LT |
1291 | |
1292 | out: | |
3fb962bd | 1293 | if (release_i_mutex) |
1b1dcc1b | 1294 | mutex_unlock(&inode->i_mutex); |
3fb962bd NS |
1295 | else if (acquire_i_mutex) |
1296 | mutex_lock(&inode->i_mutex); | |
1da177e4 LT |
1297 | return retval; |
1298 | } | |
1299 | EXPORT_SYMBOL(__blockdev_direct_IO); |