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 | * | |
e1f8e874 | 8 | * 04Jul2002 Andrew Morton |
1da177e4 LT |
9 | * Initial version |
10 | * 11Sep2002 janetinc@us.ibm.com | |
11 | * added readv/writev support. | |
e1f8e874 | 12 | * 29Oct2002 Andrew Morton |
1da177e4 LT |
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. | |
1da177e4 LT |
56 | */ |
57 | ||
58 | struct dio { | |
59 | /* BIO submission state */ | |
60 | struct bio *bio; /* bio under assembly */ | |
61 | struct inode *inode; | |
62 | int rw; | |
29504ff3 | 63 | loff_t i_size; /* i_size when submitted */ |
1e431f5c | 64 | int flags; /* doesn't change */ |
1da177e4 LT |
65 | unsigned blkbits; /* doesn't change */ |
66 | unsigned blkfactor; /* When we're using an alignment which | |
67 | is finer than the filesystem's soft | |
68 | blocksize, this specifies how much | |
69 | finer. blkfactor=2 means 1/4-block | |
70 | alignment. Does not change */ | |
71 | unsigned start_zero_done; /* flag: sub-blocksize zeroing has | |
72 | been performed at the start of a | |
73 | write */ | |
74 | int pages_in_io; /* approximate total IO pages */ | |
75 | size_t size; /* total request size (doesn't change)*/ | |
76 | sector_t block_in_file; /* Current offset into the underlying | |
77 | file in dio_block units. */ | |
78 | unsigned blocks_available; /* At block_in_file. changes */ | |
79 | sector_t final_block_in_request;/* doesn't change */ | |
80 | unsigned first_block_in_page; /* doesn't change, Used only once */ | |
81 | int boundary; /* prev block is at a boundary */ | |
82 | int reap_counter; /* rate limit reaping */ | |
1d8fa7a2 | 83 | get_block_t *get_block; /* block mapping function */ |
1da177e4 LT |
84 | dio_iodone_t *end_io; /* IO completion function */ |
85 | sector_t final_block_in_bio; /* current final block in bio + 1 */ | |
86 | sector_t next_block_for_io; /* next block to be put under IO, | |
87 | in dio_blocks units */ | |
1d8fa7a2 | 88 | struct buffer_head map_bh; /* last get_block() result */ |
1da177e4 LT |
89 | |
90 | /* | |
91 | * Deferred addition of a page to the dio. These variables are | |
92 | * private to dio_send_cur_page(), submit_page_section() and | |
93 | * dio_bio_add_page(). | |
94 | */ | |
95 | struct page *cur_page; /* The page */ | |
96 | unsigned cur_page_offset; /* Offset into it, in bytes */ | |
97 | unsigned cur_page_len; /* Nr of bytes at cur_page_offset */ | |
98 | sector_t cur_page_block; /* Where it starts */ | |
99 | ||
100 | /* | |
101 | * Page fetching state. These variables belong to dio_refill_pages(). | |
102 | */ | |
103 | int curr_page; /* changes */ | |
104 | int total_pages; /* doesn't change */ | |
105 | unsigned long curr_user_address;/* changes */ | |
106 | ||
107 | /* | |
108 | * Page queue. These variables belong to dio_refill_pages() and | |
109 | * dio_get_page(). | |
110 | */ | |
111 | struct page *pages[DIO_PAGES]; /* page buffer */ | |
112 | unsigned head; /* next page to process */ | |
113 | unsigned tail; /* last valid page + 1 */ | |
114 | int page_errors; /* errno from get_user_pages() */ | |
115 | ||
116 | /* BIO completion state */ | |
117 | spinlock_t bio_lock; /* protects BIO fields below */ | |
5eb6c7a2 | 118 | unsigned long refcount; /* direct_io_worker() and bios */ |
1da177e4 LT |
119 | struct bio *bio_list; /* singly linked via bi_private */ |
120 | struct task_struct *waiter; /* waiting task (NULL if none) */ | |
121 | ||
122 | /* AIO related stuff */ | |
123 | struct kiocb *iocb; /* kiocb */ | |
124 | int is_async; /* is IO async ? */ | |
174e27c6 | 125 | int io_error; /* IO error in completion path */ |
1da177e4 LT |
126 | ssize_t result; /* IO result */ |
127 | }; | |
128 | ||
129 | /* | |
130 | * How many pages are in the queue? | |
131 | */ | |
132 | static inline unsigned dio_pages_present(struct dio *dio) | |
133 | { | |
134 | return dio->tail - dio->head; | |
135 | } | |
136 | ||
137 | /* | |
138 | * Go grab and pin some userspace pages. Typically we'll get 64 at a time. | |
139 | */ | |
140 | static int dio_refill_pages(struct dio *dio) | |
141 | { | |
142 | int ret; | |
143 | int nr_pages; | |
144 | ||
145 | nr_pages = min(dio->total_pages - dio->curr_page, DIO_PAGES); | |
f5dd33c4 | 146 | ret = get_user_pages_fast( |
1da177e4 LT |
147 | dio->curr_user_address, /* Where from? */ |
148 | nr_pages, /* How many pages? */ | |
149 | dio->rw == READ, /* Write to memory? */ | |
f5dd33c4 | 150 | &dio->pages[0]); /* Put results here */ |
1da177e4 | 151 | |
b31dc66a | 152 | if (ret < 0 && dio->blocks_available && (dio->rw & WRITE)) { |
557ed1fa | 153 | struct page *page = ZERO_PAGE(0); |
1da177e4 LT |
154 | /* |
155 | * A memory fault, but the filesystem has some outstanding | |
156 | * mapped blocks. We need to use those blocks up to avoid | |
157 | * leaking stale data in the file. | |
158 | */ | |
159 | if (dio->page_errors == 0) | |
160 | dio->page_errors = ret; | |
b5810039 NP |
161 | page_cache_get(page); |
162 | dio->pages[0] = page; | |
1da177e4 LT |
163 | dio->head = 0; |
164 | dio->tail = 1; | |
165 | ret = 0; | |
166 | goto out; | |
167 | } | |
168 | ||
169 | if (ret >= 0) { | |
170 | dio->curr_user_address += ret * PAGE_SIZE; | |
171 | dio->curr_page += ret; | |
172 | dio->head = 0; | |
173 | dio->tail = ret; | |
174 | ret = 0; | |
175 | } | |
176 | out: | |
177 | return ret; | |
178 | } | |
179 | ||
180 | /* | |
181 | * Get another userspace page. Returns an ERR_PTR on error. Pages are | |
182 | * buffered inside the dio so that we can call get_user_pages() against a | |
183 | * decent number of pages, less frequently. To provide nicer use of the | |
184 | * L1 cache. | |
185 | */ | |
186 | static struct page *dio_get_page(struct dio *dio) | |
187 | { | |
188 | if (dio_pages_present(dio) == 0) { | |
189 | int ret; | |
190 | ||
191 | ret = dio_refill_pages(dio); | |
192 | if (ret) | |
193 | return ERR_PTR(ret); | |
194 | BUG_ON(dio_pages_present(dio) == 0); | |
195 | } | |
196 | return dio->pages[dio->head++]; | |
197 | } | |
198 | ||
6d544bb4 ZB |
199 | /** |
200 | * dio_complete() - called when all DIO BIO I/O has been completed | |
201 | * @offset: the byte offset in the file of the completed operation | |
202 | * | |
203 | * This releases locks as dictated by the locking type, lets interested parties | |
204 | * know that a DIO operation has completed, and calculates the resulting return | |
205 | * code for the operation. | |
206 | * | |
207 | * It lets the filesystem know if it registered an interest earlier via | |
208 | * get_block. Pass the private field of the map buffer_head so that | |
209 | * filesystems can use it to hold additional state between get_block calls and | |
210 | * dio_complete. | |
1da177e4 | 211 | */ |
6d544bb4 | 212 | static int dio_complete(struct dio *dio, loff_t offset, int ret) |
1da177e4 | 213 | { |
6d544bb4 ZB |
214 | ssize_t transferred = 0; |
215 | ||
8459d86a ZB |
216 | /* |
217 | * AIO submission can race with bio completion to get here while | |
218 | * expecting to have the last io completed by bio completion. | |
219 | * In that case -EIOCBQUEUED is in fact not an error we want | |
220 | * to preserve through this call. | |
221 | */ | |
222 | if (ret == -EIOCBQUEUED) | |
223 | ret = 0; | |
224 | ||
6d544bb4 ZB |
225 | if (dio->result) { |
226 | transferred = dio->result; | |
227 | ||
228 | /* Check for short read case */ | |
229 | if ((dio->rw == READ) && ((offset + transferred) > dio->i_size)) | |
230 | transferred = dio->i_size - offset; | |
231 | } | |
232 | ||
1da177e4 | 233 | if (dio->end_io && dio->result) |
6d544bb4 ZB |
234 | dio->end_io(dio->iocb, offset, transferred, |
235 | dio->map_bh.b_private); | |
1e431f5c CH |
236 | |
237 | if (dio->flags & DIO_LOCKING) | |
d8aa905b IM |
238 | /* lockdep: non-owner release */ |
239 | up_read_non_owner(&dio->inode->i_alloc_sem); | |
6d544bb4 ZB |
240 | |
241 | if (ret == 0) | |
242 | ret = dio->page_errors; | |
243 | if (ret == 0) | |
244 | ret = dio->io_error; | |
245 | if (ret == 0) | |
246 | ret = transferred; | |
247 | ||
248 | return ret; | |
1da177e4 LT |
249 | } |
250 | ||
1da177e4 LT |
251 | static int dio_bio_complete(struct dio *dio, struct bio *bio); |
252 | /* | |
253 | * Asynchronous IO callback. | |
254 | */ | |
6712ecf8 | 255 | static void dio_bio_end_aio(struct bio *bio, int error) |
1da177e4 LT |
256 | { |
257 | struct dio *dio = bio->bi_private; | |
5eb6c7a2 ZB |
258 | unsigned long remaining; |
259 | unsigned long flags; | |
1da177e4 | 260 | |
1da177e4 LT |
261 | /* cleanup the bio */ |
262 | dio_bio_complete(dio, bio); | |
0273201e | 263 | |
5eb6c7a2 ZB |
264 | spin_lock_irqsave(&dio->bio_lock, flags); |
265 | remaining = --dio->refcount; | |
266 | if (remaining == 1 && dio->waiter) | |
20258b2b | 267 | wake_up_process(dio->waiter); |
5eb6c7a2 | 268 | spin_unlock_irqrestore(&dio->bio_lock, flags); |
20258b2b | 269 | |
8459d86a ZB |
270 | if (remaining == 0) { |
271 | int ret = dio_complete(dio, dio->iocb->ki_pos, 0); | |
272 | aio_complete(dio->iocb, ret, 0); | |
273 | kfree(dio); | |
274 | } | |
1da177e4 LT |
275 | } |
276 | ||
277 | /* | |
278 | * The BIO completion handler simply queues the BIO up for the process-context | |
279 | * handler. | |
280 | * | |
281 | * During I/O bi_private points at the dio. After I/O, bi_private is used to | |
282 | * implement a singly-linked list of completed BIOs, at dio->bio_list. | |
283 | */ | |
6712ecf8 | 284 | static void dio_bio_end_io(struct bio *bio, int error) |
1da177e4 LT |
285 | { |
286 | struct dio *dio = bio->bi_private; | |
287 | unsigned long flags; | |
288 | ||
1da177e4 LT |
289 | spin_lock_irqsave(&dio->bio_lock, flags); |
290 | bio->bi_private = dio->bio_list; | |
291 | dio->bio_list = bio; | |
5eb6c7a2 | 292 | if (--dio->refcount == 1 && dio->waiter) |
1da177e4 LT |
293 | wake_up_process(dio->waiter); |
294 | spin_unlock_irqrestore(&dio->bio_lock, flags); | |
1da177e4 LT |
295 | } |
296 | ||
297 | static int | |
298 | dio_bio_alloc(struct dio *dio, struct block_device *bdev, | |
299 | sector_t first_sector, int nr_vecs) | |
300 | { | |
301 | struct bio *bio; | |
302 | ||
303 | bio = bio_alloc(GFP_KERNEL, nr_vecs); | |
1da177e4 LT |
304 | |
305 | bio->bi_bdev = bdev; | |
306 | bio->bi_sector = first_sector; | |
307 | if (dio->is_async) | |
308 | bio->bi_end_io = dio_bio_end_aio; | |
309 | else | |
310 | bio->bi_end_io = dio_bio_end_io; | |
311 | ||
312 | dio->bio = bio; | |
313 | return 0; | |
314 | } | |
315 | ||
316 | /* | |
317 | * In the AIO read case we speculatively dirty the pages before starting IO. | |
318 | * During IO completion, any of these pages which happen to have been written | |
319 | * back will be redirtied by bio_check_pages_dirty(). | |
0273201e ZB |
320 | * |
321 | * bios hold a dio reference between submit_bio and ->end_io. | |
1da177e4 LT |
322 | */ |
323 | static void dio_bio_submit(struct dio *dio) | |
324 | { | |
325 | struct bio *bio = dio->bio; | |
5eb6c7a2 | 326 | unsigned long flags; |
1da177e4 LT |
327 | |
328 | bio->bi_private = dio; | |
5eb6c7a2 ZB |
329 | |
330 | spin_lock_irqsave(&dio->bio_lock, flags); | |
331 | dio->refcount++; | |
332 | spin_unlock_irqrestore(&dio->bio_lock, flags); | |
333 | ||
1da177e4 LT |
334 | if (dio->is_async && dio->rw == READ) |
335 | bio_set_pages_dirty(bio); | |
5eb6c7a2 | 336 | |
1da177e4 LT |
337 | submit_bio(dio->rw, bio); |
338 | ||
339 | dio->bio = NULL; | |
340 | dio->boundary = 0; | |
341 | } | |
342 | ||
343 | /* | |
344 | * Release any resources in case of a failure | |
345 | */ | |
346 | static void dio_cleanup(struct dio *dio) | |
347 | { | |
348 | while (dio_pages_present(dio)) | |
349 | page_cache_release(dio_get_page(dio)); | |
350 | } | |
351 | ||
352 | /* | |
0273201e ZB |
353 | * Wait for the next BIO to complete. Remove it and return it. NULL is |
354 | * returned once all BIOs have been completed. This must only be called once | |
355 | * all bios have been issued so that dio->refcount can only decrease. This | |
356 | * requires that that the caller hold a reference on the dio. | |
1da177e4 LT |
357 | */ |
358 | static struct bio *dio_await_one(struct dio *dio) | |
359 | { | |
360 | unsigned long flags; | |
0273201e | 361 | struct bio *bio = NULL; |
1da177e4 LT |
362 | |
363 | spin_lock_irqsave(&dio->bio_lock, flags); | |
5eb6c7a2 ZB |
364 | |
365 | /* | |
366 | * Wait as long as the list is empty and there are bios in flight. bio | |
367 | * completion drops the count, maybe adds to the list, and wakes while | |
368 | * holding the bio_lock so we don't need set_current_state()'s barrier | |
369 | * and can call it after testing our condition. | |
370 | */ | |
371 | while (dio->refcount > 1 && dio->bio_list == NULL) { | |
372 | __set_current_state(TASK_UNINTERRUPTIBLE); | |
373 | dio->waiter = current; | |
374 | spin_unlock_irqrestore(&dio->bio_lock, flags); | |
375 | io_schedule(); | |
376 | /* wake up sets us TASK_RUNNING */ | |
377 | spin_lock_irqsave(&dio->bio_lock, flags); | |
378 | dio->waiter = NULL; | |
1da177e4 | 379 | } |
0273201e ZB |
380 | if (dio->bio_list) { |
381 | bio = dio->bio_list; | |
382 | dio->bio_list = bio->bi_private; | |
383 | } | |
1da177e4 LT |
384 | spin_unlock_irqrestore(&dio->bio_lock, flags); |
385 | return bio; | |
386 | } | |
387 | ||
388 | /* | |
389 | * Process one completed BIO. No locks are held. | |
390 | */ | |
391 | static int dio_bio_complete(struct dio *dio, struct bio *bio) | |
392 | { | |
393 | const int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags); | |
394 | struct bio_vec *bvec = bio->bi_io_vec; | |
395 | int page_no; | |
396 | ||
397 | if (!uptodate) | |
174e27c6 | 398 | dio->io_error = -EIO; |
1da177e4 LT |
399 | |
400 | if (dio->is_async && dio->rw == READ) { | |
401 | bio_check_pages_dirty(bio); /* transfers ownership */ | |
402 | } else { | |
403 | for (page_no = 0; page_no < bio->bi_vcnt; page_no++) { | |
404 | struct page *page = bvec[page_no].bv_page; | |
405 | ||
406 | if (dio->rw == READ && !PageCompound(page)) | |
407 | set_page_dirty_lock(page); | |
408 | page_cache_release(page); | |
409 | } | |
410 | bio_put(bio); | |
411 | } | |
1da177e4 LT |
412 | return uptodate ? 0 : -EIO; |
413 | } | |
414 | ||
415 | /* | |
0273201e ZB |
416 | * Wait on and process all in-flight BIOs. This must only be called once |
417 | * all bios have been issued so that the refcount can only decrease. | |
418 | * This just waits for all bios to make it through dio_bio_complete. IO | |
beb7dd86 | 419 | * errors are propagated through dio->io_error and should be propagated via |
0273201e | 420 | * dio_complete(). |
1da177e4 | 421 | */ |
6d544bb4 | 422 | static void dio_await_completion(struct dio *dio) |
1da177e4 | 423 | { |
0273201e ZB |
424 | struct bio *bio; |
425 | do { | |
426 | bio = dio_await_one(dio); | |
427 | if (bio) | |
428 | dio_bio_complete(dio, bio); | |
429 | } while (bio); | |
1da177e4 LT |
430 | } |
431 | ||
432 | /* | |
433 | * A really large O_DIRECT read or write can generate a lot of BIOs. So | |
434 | * to keep the memory consumption sane we periodically reap any completed BIOs | |
435 | * during the BIO generation phase. | |
436 | * | |
437 | * This also helps to limit the peak amount of pinned userspace memory. | |
438 | */ | |
439 | static int dio_bio_reap(struct dio *dio) | |
440 | { | |
441 | int ret = 0; | |
442 | ||
443 | if (dio->reap_counter++ >= 64) { | |
444 | while (dio->bio_list) { | |
445 | unsigned long flags; | |
446 | struct bio *bio; | |
447 | int ret2; | |
448 | ||
449 | spin_lock_irqsave(&dio->bio_lock, flags); | |
450 | bio = dio->bio_list; | |
451 | dio->bio_list = bio->bi_private; | |
452 | spin_unlock_irqrestore(&dio->bio_lock, flags); | |
453 | ret2 = dio_bio_complete(dio, bio); | |
454 | if (ret == 0) | |
455 | ret = ret2; | |
456 | } | |
457 | dio->reap_counter = 0; | |
458 | } | |
459 | return ret; | |
460 | } | |
461 | ||
462 | /* | |
463 | * Call into the fs to map some more disk blocks. We record the current number | |
464 | * of available blocks at dio->blocks_available. These are in units of the | |
465 | * fs blocksize, (1 << inode->i_blkbits). | |
466 | * | |
467 | * The fs is allowed to map lots of blocks at once. If it wants to do that, | |
468 | * it uses the passed inode-relative block number as the file offset, as usual. | |
469 | * | |
1d8fa7a2 | 470 | * get_block() is passed the number of i_blkbits-sized blocks which direct_io |
1da177e4 LT |
471 | * has remaining to do. The fs should not map more than this number of blocks. |
472 | * | |
473 | * If the fs has mapped a lot of blocks, it should populate bh->b_size to | |
474 | * indicate how much contiguous disk space has been made available at | |
475 | * bh->b_blocknr. | |
476 | * | |
477 | * If *any* of the mapped blocks are new, then the fs must set buffer_new(). | |
478 | * This isn't very efficient... | |
479 | * | |
480 | * In the case of filesystem holes: the fs may return an arbitrarily-large | |
481 | * hole by returning an appropriate value in b_size and by clearing | |
482 | * buffer_mapped(). However the direct-io code will only process holes one | |
1d8fa7a2 | 483 | * block at a time - it will repeatedly call get_block() as it walks the hole. |
1da177e4 LT |
484 | */ |
485 | static int get_more_blocks(struct dio *dio) | |
486 | { | |
487 | int ret; | |
488 | struct buffer_head *map_bh = &dio->map_bh; | |
489 | sector_t fs_startblk; /* Into file, in filesystem-sized blocks */ | |
490 | unsigned long fs_count; /* Number of filesystem-sized blocks */ | |
491 | unsigned long dio_count;/* Number of dio_block-sized blocks */ | |
492 | unsigned long blkmask; | |
493 | int create; | |
494 | ||
495 | /* | |
496 | * If there was a memory error and we've overwritten all the | |
497 | * mapped blocks then we can now return that memory error | |
498 | */ | |
499 | ret = dio->page_errors; | |
500 | if (ret == 0) { | |
1da177e4 LT |
501 | BUG_ON(dio->block_in_file >= dio->final_block_in_request); |
502 | fs_startblk = dio->block_in_file >> dio->blkfactor; | |
503 | dio_count = dio->final_block_in_request - dio->block_in_file; | |
504 | fs_count = dio_count >> dio->blkfactor; | |
505 | blkmask = (1 << dio->blkfactor) - 1; | |
506 | if (dio_count & blkmask) | |
507 | fs_count++; | |
508 | ||
3c674e74 NS |
509 | map_bh->b_state = 0; |
510 | map_bh->b_size = fs_count << dio->inode->i_blkbits; | |
511 | ||
1e431f5c CH |
512 | /* |
513 | * For writes inside i_size on a DIO_SKIP_HOLES filesystem we | |
514 | * forbid block creations: only overwrites are permitted. | |
515 | * We will return early to the caller once we see an | |
516 | * unmapped buffer head returned, and the caller will fall | |
517 | * back to buffered I/O. | |
518 | * | |
519 | * Otherwise the decision is left to the get_blocks method, | |
520 | * which may decide to handle it or also return an unmapped | |
521 | * buffer head. | |
522 | */ | |
b31dc66a | 523 | create = dio->rw & WRITE; |
1e431f5c | 524 | if (dio->flags & DIO_SKIP_HOLES) { |
1da177e4 LT |
525 | if (dio->block_in_file < (i_size_read(dio->inode) >> |
526 | dio->blkbits)) | |
527 | create = 0; | |
1da177e4 | 528 | } |
3c674e74 | 529 | |
1d8fa7a2 | 530 | ret = (*dio->get_block)(dio->inode, fs_startblk, |
1da177e4 LT |
531 | map_bh, create); |
532 | } | |
533 | return ret; | |
534 | } | |
535 | ||
536 | /* | |
537 | * There is no bio. Make one now. | |
538 | */ | |
539 | static int dio_new_bio(struct dio *dio, sector_t start_sector) | |
540 | { | |
541 | sector_t sector; | |
542 | int ret, nr_pages; | |
543 | ||
544 | ret = dio_bio_reap(dio); | |
545 | if (ret) | |
546 | goto out; | |
547 | sector = start_sector << (dio->blkbits - 9); | |
548 | nr_pages = min(dio->pages_in_io, bio_get_nr_vecs(dio->map_bh.b_bdev)); | |
549 | BUG_ON(nr_pages <= 0); | |
550 | ret = dio_bio_alloc(dio, dio->map_bh.b_bdev, sector, nr_pages); | |
551 | dio->boundary = 0; | |
552 | out: | |
553 | return ret; | |
554 | } | |
555 | ||
556 | /* | |
557 | * Attempt to put the current chunk of 'cur_page' into the current BIO. If | |
558 | * that was successful then update final_block_in_bio and take a ref against | |
559 | * the just-added page. | |
560 | * | |
561 | * Return zero on success. Non-zero means the caller needs to start a new BIO. | |
562 | */ | |
563 | static int dio_bio_add_page(struct dio *dio) | |
564 | { | |
565 | int ret; | |
566 | ||
567 | ret = bio_add_page(dio->bio, dio->cur_page, | |
568 | dio->cur_page_len, dio->cur_page_offset); | |
569 | if (ret == dio->cur_page_len) { | |
570 | /* | |
571 | * Decrement count only, if we are done with this page | |
572 | */ | |
573 | if ((dio->cur_page_len + dio->cur_page_offset) == PAGE_SIZE) | |
574 | dio->pages_in_io--; | |
575 | page_cache_get(dio->cur_page); | |
576 | dio->final_block_in_bio = dio->cur_page_block + | |
577 | (dio->cur_page_len >> dio->blkbits); | |
578 | ret = 0; | |
579 | } else { | |
580 | ret = 1; | |
581 | } | |
582 | return ret; | |
583 | } | |
584 | ||
585 | /* | |
586 | * Put cur_page under IO. The section of cur_page which is described by | |
587 | * cur_page_offset,cur_page_len is put into a BIO. The section of cur_page | |
588 | * starts on-disk at cur_page_block. | |
589 | * | |
590 | * We take a ref against the page here (on behalf of its presence in the bio). | |
591 | * | |
592 | * The caller of this function is responsible for removing cur_page from the | |
593 | * dio, and for dropping the refcount which came from that presence. | |
594 | */ | |
595 | static int dio_send_cur_page(struct dio *dio) | |
596 | { | |
597 | int ret = 0; | |
598 | ||
599 | if (dio->bio) { | |
600 | /* | |
601 | * See whether this new request is contiguous with the old | |
602 | */ | |
603 | if (dio->final_block_in_bio != dio->cur_page_block) | |
604 | dio_bio_submit(dio); | |
605 | /* | |
606 | * Submit now if the underlying fs is about to perform a | |
607 | * metadata read | |
608 | */ | |
609 | if (dio->boundary) | |
610 | dio_bio_submit(dio); | |
611 | } | |
612 | ||
613 | if (dio->bio == NULL) { | |
614 | ret = dio_new_bio(dio, dio->cur_page_block); | |
615 | if (ret) | |
616 | goto out; | |
617 | } | |
618 | ||
619 | if (dio_bio_add_page(dio) != 0) { | |
620 | dio_bio_submit(dio); | |
621 | ret = dio_new_bio(dio, dio->cur_page_block); | |
622 | if (ret == 0) { | |
623 | ret = dio_bio_add_page(dio); | |
624 | BUG_ON(ret != 0); | |
625 | } | |
626 | } | |
627 | out: | |
628 | return ret; | |
629 | } | |
630 | ||
631 | /* | |
632 | * An autonomous function to put a chunk of a page under deferred IO. | |
633 | * | |
634 | * The caller doesn't actually know (or care) whether this piece of page is in | |
635 | * a BIO, or is under IO or whatever. We just take care of all possible | |
636 | * situations here. The separation between the logic of do_direct_IO() and | |
637 | * that of submit_page_section() is important for clarity. Please don't break. | |
638 | * | |
639 | * The chunk of page starts on-disk at blocknr. | |
640 | * | |
641 | * We perform deferred IO, by recording the last-submitted page inside our | |
642 | * private part of the dio structure. If possible, we just expand the IO | |
643 | * across that page here. | |
644 | * | |
645 | * If that doesn't work out then we put the old page into the bio and add this | |
646 | * page to the dio instead. | |
647 | */ | |
648 | static int | |
649 | submit_page_section(struct dio *dio, struct page *page, | |
650 | unsigned offset, unsigned len, sector_t blocknr) | |
651 | { | |
652 | int ret = 0; | |
653 | ||
98c4d57d AM |
654 | if (dio->rw & WRITE) { |
655 | /* | |
656 | * Read accounting is performed in submit_bio() | |
657 | */ | |
658 | task_io_account_write(len); | |
659 | } | |
660 | ||
1da177e4 LT |
661 | /* |
662 | * Can we just grow the current page's presence in the dio? | |
663 | */ | |
664 | if ( (dio->cur_page == page) && | |
665 | (dio->cur_page_offset + dio->cur_page_len == offset) && | |
666 | (dio->cur_page_block + | |
667 | (dio->cur_page_len >> dio->blkbits) == blocknr)) { | |
668 | dio->cur_page_len += len; | |
669 | ||
670 | /* | |
671 | * If dio->boundary then we want to schedule the IO now to | |
672 | * avoid metadata seeks. | |
673 | */ | |
674 | if (dio->boundary) { | |
675 | ret = dio_send_cur_page(dio); | |
676 | page_cache_release(dio->cur_page); | |
677 | dio->cur_page = NULL; | |
678 | } | |
679 | goto out; | |
680 | } | |
681 | ||
682 | /* | |
683 | * If there's a deferred page already there then send it. | |
684 | */ | |
685 | if (dio->cur_page) { | |
686 | ret = dio_send_cur_page(dio); | |
687 | page_cache_release(dio->cur_page); | |
688 | dio->cur_page = NULL; | |
689 | if (ret) | |
690 | goto out; | |
691 | } | |
692 | ||
693 | page_cache_get(page); /* It is in dio */ | |
694 | dio->cur_page = page; | |
695 | dio->cur_page_offset = offset; | |
696 | dio->cur_page_len = len; | |
697 | dio->cur_page_block = blocknr; | |
698 | out: | |
699 | return ret; | |
700 | } | |
701 | ||
702 | /* | |
703 | * Clean any dirty buffers in the blockdev mapping which alias newly-created | |
704 | * file blocks. Only called for S_ISREG files - blockdevs do not set | |
705 | * buffer_new | |
706 | */ | |
707 | static void clean_blockdev_aliases(struct dio *dio) | |
708 | { | |
709 | unsigned i; | |
710 | unsigned nblocks; | |
711 | ||
712 | nblocks = dio->map_bh.b_size >> dio->inode->i_blkbits; | |
713 | ||
714 | for (i = 0; i < nblocks; i++) { | |
715 | unmap_underlying_metadata(dio->map_bh.b_bdev, | |
716 | dio->map_bh.b_blocknr + i); | |
717 | } | |
718 | } | |
719 | ||
720 | /* | |
721 | * If we are not writing the entire block and get_block() allocated | |
722 | * the block for us, we need to fill-in the unused portion of the | |
723 | * block with zeros. This happens only if user-buffer, fileoffset or | |
724 | * io length is not filesystem block-size multiple. | |
725 | * | |
726 | * `end' is zero if we're doing the start of the IO, 1 at the end of the | |
727 | * IO. | |
728 | */ | |
729 | static void dio_zero_block(struct dio *dio, int end) | |
730 | { | |
731 | unsigned dio_blocks_per_fs_block; | |
732 | unsigned this_chunk_blocks; /* In dio_blocks */ | |
733 | unsigned this_chunk_bytes; | |
734 | struct page *page; | |
735 | ||
736 | dio->start_zero_done = 1; | |
737 | if (!dio->blkfactor || !buffer_new(&dio->map_bh)) | |
738 | return; | |
739 | ||
740 | dio_blocks_per_fs_block = 1 << dio->blkfactor; | |
741 | this_chunk_blocks = dio->block_in_file & (dio_blocks_per_fs_block - 1); | |
742 | ||
743 | if (!this_chunk_blocks) | |
744 | return; | |
745 | ||
746 | /* | |
747 | * We need to zero out part of an fs block. It is either at the | |
748 | * beginning or the end of the fs block. | |
749 | */ | |
750 | if (end) | |
751 | this_chunk_blocks = dio_blocks_per_fs_block - this_chunk_blocks; | |
752 | ||
753 | this_chunk_bytes = this_chunk_blocks << dio->blkbits; | |
754 | ||
557ed1fa | 755 | page = ZERO_PAGE(0); |
1da177e4 LT |
756 | if (submit_page_section(dio, page, 0, this_chunk_bytes, |
757 | dio->next_block_for_io)) | |
758 | return; | |
759 | ||
760 | dio->next_block_for_io += this_chunk_blocks; | |
761 | } | |
762 | ||
763 | /* | |
764 | * Walk the user pages, and the file, mapping blocks to disk and generating | |
765 | * a sequence of (page,offset,len,block) mappings. These mappings are injected | |
766 | * into submit_page_section(), which takes care of the next stage of submission | |
767 | * | |
768 | * Direct IO against a blockdev is different from a file. Because we can | |
769 | * happily perform page-sized but 512-byte aligned IOs. It is important that | |
770 | * blockdev IO be able to have fine alignment and large sizes. | |
771 | * | |
1d8fa7a2 | 772 | * So what we do is to permit the ->get_block function to populate bh.b_size |
1da177e4 LT |
773 | * with the size of IO which is permitted at this offset and this i_blkbits. |
774 | * | |
775 | * For best results, the blockdev should be set up with 512-byte i_blkbits and | |
1d8fa7a2 | 776 | * it should set b_size to PAGE_SIZE or more inside get_block(). This gives |
1da177e4 LT |
777 | * fine alignment but still allows this function to work in PAGE_SIZE units. |
778 | */ | |
779 | static int do_direct_IO(struct dio *dio) | |
780 | { | |
781 | const unsigned blkbits = dio->blkbits; | |
782 | const unsigned blocks_per_page = PAGE_SIZE >> blkbits; | |
783 | struct page *page; | |
784 | unsigned block_in_page; | |
785 | struct buffer_head *map_bh = &dio->map_bh; | |
786 | int ret = 0; | |
787 | ||
788 | /* The I/O can start at any block offset within the first page */ | |
789 | block_in_page = dio->first_block_in_page; | |
790 | ||
791 | while (dio->block_in_file < dio->final_block_in_request) { | |
792 | page = dio_get_page(dio); | |
793 | if (IS_ERR(page)) { | |
794 | ret = PTR_ERR(page); | |
795 | goto out; | |
796 | } | |
797 | ||
798 | while (block_in_page < blocks_per_page) { | |
799 | unsigned offset_in_page = block_in_page << blkbits; | |
800 | unsigned this_chunk_bytes; /* # of bytes mapped */ | |
801 | unsigned this_chunk_blocks; /* # of blocks */ | |
802 | unsigned u; | |
803 | ||
804 | if (dio->blocks_available == 0) { | |
805 | /* | |
806 | * Need to go and map some more disk | |
807 | */ | |
808 | unsigned long blkmask; | |
809 | unsigned long dio_remainder; | |
810 | ||
811 | ret = get_more_blocks(dio); | |
812 | if (ret) { | |
813 | page_cache_release(page); | |
814 | goto out; | |
815 | } | |
816 | if (!buffer_mapped(map_bh)) | |
817 | goto do_holes; | |
818 | ||
819 | dio->blocks_available = | |
820 | map_bh->b_size >> dio->blkbits; | |
821 | dio->next_block_for_io = | |
822 | map_bh->b_blocknr << dio->blkfactor; | |
823 | if (buffer_new(map_bh)) | |
824 | clean_blockdev_aliases(dio); | |
825 | ||
826 | if (!dio->blkfactor) | |
827 | goto do_holes; | |
828 | ||
829 | blkmask = (1 << dio->blkfactor) - 1; | |
830 | dio_remainder = (dio->block_in_file & blkmask); | |
831 | ||
832 | /* | |
833 | * If we are at the start of IO and that IO | |
834 | * starts partway into a fs-block, | |
835 | * dio_remainder will be non-zero. If the IO | |
836 | * is a read then we can simply advance the IO | |
837 | * cursor to the first block which is to be | |
838 | * read. But if the IO is a write and the | |
839 | * block was newly allocated we cannot do that; | |
840 | * the start of the fs block must be zeroed out | |
841 | * on-disk | |
842 | */ | |
843 | if (!buffer_new(map_bh)) | |
844 | dio->next_block_for_io += dio_remainder; | |
845 | dio->blocks_available -= dio_remainder; | |
846 | } | |
847 | do_holes: | |
848 | /* Handle holes */ | |
849 | if (!buffer_mapped(map_bh)) { | |
35dc8161 | 850 | loff_t i_size_aligned; |
1da177e4 LT |
851 | |
852 | /* AKPM: eargh, -ENOTBLK is a hack */ | |
b31dc66a | 853 | if (dio->rw & WRITE) { |
1da177e4 LT |
854 | page_cache_release(page); |
855 | return -ENOTBLK; | |
856 | } | |
857 | ||
35dc8161 JM |
858 | /* |
859 | * Be sure to account for a partial block as the | |
860 | * last block in the file | |
861 | */ | |
862 | i_size_aligned = ALIGN(i_size_read(dio->inode), | |
863 | 1 << blkbits); | |
1da177e4 | 864 | if (dio->block_in_file >= |
35dc8161 | 865 | i_size_aligned >> blkbits) { |
1da177e4 LT |
866 | /* We hit eof */ |
867 | page_cache_release(page); | |
868 | goto out; | |
869 | } | |
eebd2aa3 CL |
870 | zero_user(page, block_in_page << blkbits, |
871 | 1 << blkbits); | |
1da177e4 LT |
872 | dio->block_in_file++; |
873 | block_in_page++; | |
874 | goto next_block; | |
875 | } | |
876 | ||
877 | /* | |
878 | * If we're performing IO which has an alignment which | |
879 | * is finer than the underlying fs, go check to see if | |
880 | * we must zero out the start of this block. | |
881 | */ | |
882 | if (unlikely(dio->blkfactor && !dio->start_zero_done)) | |
883 | dio_zero_block(dio, 0); | |
884 | ||
885 | /* | |
886 | * Work out, in this_chunk_blocks, how much disk we | |
887 | * can add to this page | |
888 | */ | |
889 | this_chunk_blocks = dio->blocks_available; | |
890 | u = (PAGE_SIZE - offset_in_page) >> blkbits; | |
891 | if (this_chunk_blocks > u) | |
892 | this_chunk_blocks = u; | |
893 | u = dio->final_block_in_request - dio->block_in_file; | |
894 | if (this_chunk_blocks > u) | |
895 | this_chunk_blocks = u; | |
896 | this_chunk_bytes = this_chunk_blocks << blkbits; | |
897 | BUG_ON(this_chunk_bytes == 0); | |
898 | ||
899 | dio->boundary = buffer_boundary(map_bh); | |
900 | ret = submit_page_section(dio, page, offset_in_page, | |
901 | this_chunk_bytes, dio->next_block_for_io); | |
902 | if (ret) { | |
903 | page_cache_release(page); | |
904 | goto out; | |
905 | } | |
906 | dio->next_block_for_io += this_chunk_blocks; | |
907 | ||
908 | dio->block_in_file += this_chunk_blocks; | |
909 | block_in_page += this_chunk_blocks; | |
910 | dio->blocks_available -= this_chunk_blocks; | |
911 | next_block: | |
d4569d2e | 912 | BUG_ON(dio->block_in_file > dio->final_block_in_request); |
1da177e4 LT |
913 | if (dio->block_in_file == dio->final_block_in_request) |
914 | break; | |
915 | } | |
916 | ||
917 | /* Drop the ref which was taken in get_user_pages() */ | |
918 | page_cache_release(page); | |
919 | block_in_page = 0; | |
920 | } | |
921 | out: | |
922 | return ret; | |
923 | } | |
924 | ||
925 | /* | |
1b1dcc1b | 926 | * Releases both i_mutex and i_alloc_sem |
1da177e4 LT |
927 | */ |
928 | static ssize_t | |
929 | direct_io_worker(int rw, struct kiocb *iocb, struct inode *inode, | |
930 | const struct iovec *iov, loff_t offset, unsigned long nr_segs, | |
1d8fa7a2 | 931 | unsigned blkbits, get_block_t get_block, dio_iodone_t end_io, |
1da177e4 LT |
932 | struct dio *dio) |
933 | { | |
934 | unsigned long user_addr; | |
5eb6c7a2 | 935 | unsigned long flags; |
1da177e4 LT |
936 | int seg; |
937 | ssize_t ret = 0; | |
938 | ssize_t ret2; | |
939 | size_t bytes; | |
940 | ||
1da177e4 LT |
941 | dio->inode = inode; |
942 | dio->rw = rw; | |
943 | dio->blkbits = blkbits; | |
944 | dio->blkfactor = inode->i_blkbits - blkbits; | |
1da177e4 | 945 | dio->block_in_file = offset >> blkbits; |
1da177e4 | 946 | |
1d8fa7a2 | 947 | dio->get_block = get_block; |
1da177e4 | 948 | dio->end_io = end_io; |
1da177e4 LT |
949 | dio->final_block_in_bio = -1; |
950 | dio->next_block_for_io = -1; | |
951 | ||
1da177e4 | 952 | dio->iocb = iocb; |
29504ff3 | 953 | dio->i_size = i_size_read(inode); |
1da177e4 | 954 | |
1da177e4 | 955 | spin_lock_init(&dio->bio_lock); |
5eb6c7a2 | 956 | dio->refcount = 1; |
1da177e4 LT |
957 | |
958 | /* | |
959 | * In case of non-aligned buffers, we may need 2 more | |
960 | * pages since we need to zero out first and last block. | |
961 | */ | |
962 | if (unlikely(dio->blkfactor)) | |
963 | dio->pages_in_io = 2; | |
1da177e4 LT |
964 | |
965 | for (seg = 0; seg < nr_segs; seg++) { | |
966 | user_addr = (unsigned long)iov[seg].iov_base; | |
967 | dio->pages_in_io += | |
968 | ((user_addr+iov[seg].iov_len +PAGE_SIZE-1)/PAGE_SIZE | |
969 | - user_addr/PAGE_SIZE); | |
970 | } | |
971 | ||
972 | for (seg = 0; seg < nr_segs; seg++) { | |
973 | user_addr = (unsigned long)iov[seg].iov_base; | |
974 | dio->size += bytes = iov[seg].iov_len; | |
975 | ||
976 | /* Index into the first page of the first block */ | |
977 | dio->first_block_in_page = (user_addr & ~PAGE_MASK) >> blkbits; | |
978 | dio->final_block_in_request = dio->block_in_file + | |
979 | (bytes >> blkbits); | |
980 | /* Page fetching state */ | |
981 | dio->head = 0; | |
982 | dio->tail = 0; | |
983 | dio->curr_page = 0; | |
984 | ||
985 | dio->total_pages = 0; | |
986 | if (user_addr & (PAGE_SIZE-1)) { | |
987 | dio->total_pages++; | |
988 | bytes -= PAGE_SIZE - (user_addr & (PAGE_SIZE - 1)); | |
989 | } | |
990 | dio->total_pages += (bytes + PAGE_SIZE - 1) / PAGE_SIZE; | |
991 | dio->curr_user_address = user_addr; | |
992 | ||
993 | ret = do_direct_IO(dio); | |
994 | ||
995 | dio->result += iov[seg].iov_len - | |
996 | ((dio->final_block_in_request - dio->block_in_file) << | |
997 | blkbits); | |
998 | ||
999 | if (ret) { | |
1000 | dio_cleanup(dio); | |
1001 | break; | |
1002 | } | |
1003 | } /* end iovec loop */ | |
1004 | ||
b31dc66a | 1005 | if (ret == -ENOTBLK && (rw & WRITE)) { |
1da177e4 LT |
1006 | /* |
1007 | * The remaining part of the request will be | |
1008 | * be handled by buffered I/O when we return | |
1009 | */ | |
1010 | ret = 0; | |
1011 | } | |
1012 | /* | |
1013 | * There may be some unwritten disk at the end of a part-written | |
1014 | * fs-block-sized block. Go zero that now. | |
1015 | */ | |
1016 | dio_zero_block(dio, 1); | |
1017 | ||
1018 | if (dio->cur_page) { | |
1019 | ret2 = dio_send_cur_page(dio); | |
1020 | if (ret == 0) | |
1021 | ret = ret2; | |
1022 | page_cache_release(dio->cur_page); | |
1023 | dio->cur_page = NULL; | |
1024 | } | |
1025 | if (dio->bio) | |
1026 | dio_bio_submit(dio); | |
1027 | ||
1028 | /* | |
1029 | * It is possible that, we return short IO due to end of file. | |
1030 | * In that case, we need to release all the pages we got hold on. | |
1031 | */ | |
1032 | dio_cleanup(dio); | |
1033 | ||
1034 | /* | |
1035 | * All block lookups have been performed. For READ requests | |
1b1dcc1b | 1036 | * we can let i_mutex go now that its achieved its purpose |
1da177e4 LT |
1037 | * of protecting us from looking up uninitialized blocks. |
1038 | */ | |
1e431f5c | 1039 | if (rw == READ && (dio->flags & DIO_LOCKING)) |
1b1dcc1b | 1040 | mutex_unlock(&dio->inode->i_mutex); |
1da177e4 LT |
1041 | |
1042 | /* | |
8459d86a ZB |
1043 | * The only time we want to leave bios in flight is when a successful |
1044 | * partial aio read or full aio write have been setup. In that case | |
1045 | * bio completion will call aio_complete. The only time it's safe to | |
1046 | * call aio_complete is when we return -EIOCBQUEUED, so we key on that. | |
1047 | * This had *better* be the only place that raises -EIOCBQUEUED. | |
1da177e4 | 1048 | */ |
8459d86a ZB |
1049 | BUG_ON(ret == -EIOCBQUEUED); |
1050 | if (dio->is_async && ret == 0 && dio->result && | |
1051 | ((rw & READ) || (dio->result == dio->size))) | |
1052 | ret = -EIOCBQUEUED; | |
0273201e | 1053 | |
cfb1e33e JM |
1054 | if (ret != -EIOCBQUEUED) { |
1055 | /* All IO is now issued, send it on its way */ | |
1056 | blk_run_address_space(inode->i_mapping); | |
6d544bb4 | 1057 | dio_await_completion(dio); |
cfb1e33e | 1058 | } |
1da177e4 | 1059 | |
8459d86a ZB |
1060 | /* |
1061 | * Sync will always be dropping the final ref and completing the | |
5eb6c7a2 ZB |
1062 | * operation. AIO can if it was a broken operation described above or |
1063 | * in fact if all the bios race to complete before we get here. In | |
1064 | * that case dio_complete() translates the EIOCBQUEUED into the proper | |
1065 | * return code that the caller will hand to aio_complete(). | |
1066 | * | |
1067 | * This is managed by the bio_lock instead of being an atomic_t so that | |
1068 | * completion paths can drop their ref and use the remaining count to | |
1069 | * decide to wake the submission path atomically. | |
8459d86a | 1070 | */ |
5eb6c7a2 ZB |
1071 | spin_lock_irqsave(&dio->bio_lock, flags); |
1072 | ret2 = --dio->refcount; | |
1073 | spin_unlock_irqrestore(&dio->bio_lock, flags); | |
fcb82f88 | 1074 | |
5eb6c7a2 | 1075 | if (ret2 == 0) { |
6d544bb4 | 1076 | ret = dio_complete(dio, offset, ret); |
8459d86a ZB |
1077 | kfree(dio); |
1078 | } else | |
1079 | BUG_ON(ret != -EIOCBQUEUED); | |
1da177e4 | 1080 | |
1da177e4 LT |
1081 | return ret; |
1082 | } | |
1083 | ||
1084 | /* | |
1085 | * This is a library function for use by filesystem drivers. | |
1da177e4 | 1086 | * |
1e431f5c CH |
1087 | * The locking rules are governed by the flags parameter: |
1088 | * - if the flags value contains DIO_LOCKING we use a fancy locking | |
1089 | * scheme for dumb filesystems. | |
1090 | * For writes this function is called under i_mutex and returns with | |
1091 | * i_mutex held, for reads, i_mutex is not held on entry, but it is | |
1092 | * taken and dropped again before returning. | |
1093 | * For reads and writes i_alloc_sem is taken in shared mode and released | |
1094 | * on I/O completion (which may happen asynchronously after returning to | |
1095 | * the caller). | |
1da177e4 | 1096 | * |
1e431f5c CH |
1097 | * - if the flags value does NOT contain DIO_LOCKING we don't use any |
1098 | * internal locking but rather rely on the filesystem to synchronize | |
1099 | * direct I/O reads/writes versus each other and truncate. | |
1100 | * For reads and writes both i_mutex and i_alloc_sem are not held on | |
1101 | * entry and are never taken. | |
1da177e4 LT |
1102 | */ |
1103 | ssize_t | |
1104 | __blockdev_direct_IO(int rw, struct kiocb *iocb, struct inode *inode, | |
1105 | struct block_device *bdev, const struct iovec *iov, loff_t offset, | |
1d8fa7a2 | 1106 | unsigned long nr_segs, get_block_t get_block, dio_iodone_t end_io, |
1e431f5c | 1107 | int flags) |
1da177e4 LT |
1108 | { |
1109 | int seg; | |
1110 | size_t size; | |
1111 | unsigned long addr; | |
1112 | unsigned blkbits = inode->i_blkbits; | |
1113 | unsigned bdev_blkbits = 0; | |
1114 | unsigned blocksize_mask = (1 << blkbits) - 1; | |
1115 | ssize_t retval = -EINVAL; | |
1116 | loff_t end = offset; | |
1117 | struct dio *dio; | |
1da177e4 LT |
1118 | |
1119 | if (rw & WRITE) | |
d9449ce3 | 1120 | rw = WRITE_ODIRECT_PLUG; |
1da177e4 LT |
1121 | |
1122 | if (bdev) | |
e1defc4f | 1123 | bdev_blkbits = blksize_bits(bdev_logical_block_size(bdev)); |
1da177e4 LT |
1124 | |
1125 | if (offset & blocksize_mask) { | |
1126 | if (bdev) | |
1127 | blkbits = bdev_blkbits; | |
1128 | blocksize_mask = (1 << blkbits) - 1; | |
1129 | if (offset & blocksize_mask) | |
1130 | goto out; | |
1131 | } | |
1132 | ||
1133 | /* Check the memory alignment. Blocks cannot straddle pages */ | |
1134 | for (seg = 0; seg < nr_segs; seg++) { | |
1135 | addr = (unsigned long)iov[seg].iov_base; | |
1136 | size = iov[seg].iov_len; | |
1137 | end += size; | |
1138 | if ((addr & blocksize_mask) || (size & blocksize_mask)) { | |
1139 | if (bdev) | |
1140 | blkbits = bdev_blkbits; | |
1141 | blocksize_mask = (1 << blkbits) - 1; | |
1142 | if ((addr & blocksize_mask) || (size & blocksize_mask)) | |
1143 | goto out; | |
1144 | } | |
1145 | } | |
1146 | ||
848c4dd5 | 1147 | dio = kzalloc(sizeof(*dio), GFP_KERNEL); |
1da177e4 LT |
1148 | retval = -ENOMEM; |
1149 | if (!dio) | |
1150 | goto out; | |
1151 | ||
1e431f5c CH |
1152 | dio->flags = flags; |
1153 | if (dio->flags & DIO_LOCKING) { | |
1da177e4 LT |
1154 | /* watch out for a 0 len io from a tricksy fs */ |
1155 | if (rw == READ && end > offset) { | |
1e431f5c CH |
1156 | struct address_space *mapping = |
1157 | iocb->ki_filp->f_mapping; | |
1da177e4 | 1158 | |
1e431f5c CH |
1159 | /* will be released by direct_io_worker */ |
1160 | mutex_lock(&inode->i_mutex); | |
1da177e4 LT |
1161 | |
1162 | retval = filemap_write_and_wait_range(mapping, offset, | |
1163 | end - 1); | |
1164 | if (retval) { | |
1e431f5c | 1165 | mutex_unlock(&inode->i_mutex); |
1da177e4 LT |
1166 | kfree(dio); |
1167 | goto out; | |
1168 | } | |
1da177e4 LT |
1169 | } |
1170 | ||
1e431f5c CH |
1171 | /* |
1172 | * Will be released at I/O completion, possibly in a | |
1173 | * different thread. | |
1174 | */ | |
1175 | down_read_non_owner(&inode->i_alloc_sem); | |
1da177e4 LT |
1176 | } |
1177 | ||
1178 | /* | |
1179 | * For file extending writes updating i_size before data | |
1180 | * writeouts complete can expose uninitialized blocks. So | |
1181 | * even for AIO, we need to wait for i/o to complete before | |
1182 | * returning in this case. | |
1183 | */ | |
b31dc66a | 1184 | dio->is_async = !is_sync_kiocb(iocb) && !((rw & WRITE) && |
1da177e4 LT |
1185 | (end > i_size_read(inode))); |
1186 | ||
1187 | retval = direct_io_worker(rw, iocb, inode, iov, offset, | |
1d8fa7a2 | 1188 | nr_segs, blkbits, get_block, end_io, dio); |
1da177e4 | 1189 | |
0f64415d DM |
1190 | /* |
1191 | * In case of error extending write may have instantiated a few | |
1192 | * blocks outside i_size. Trim these off again for DIO_LOCKING. | |
1e431f5c CH |
1193 | * |
1194 | * NOTE: filesystems with their own locking have to handle this | |
1195 | * on their own. | |
0f64415d | 1196 | */ |
1e431f5c CH |
1197 | if (dio->flags & DIO_LOCKING) { |
1198 | if (unlikely((rw & WRITE) && retval < 0)) { | |
1199 | loff_t isize = i_size_read(inode); | |
1200 | if (end > isize ) | |
1201 | vmtruncate(inode, isize); | |
1202 | } | |
0f64415d DM |
1203 | } |
1204 | ||
1da177e4 | 1205 | out: |
1da177e4 LT |
1206 | return retval; |
1207 | } | |
1208 | EXPORT_SYMBOL(__blockdev_direct_IO); |