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1 | /* |
2 | * fs/direct-io.c |
3 | * |
4 | * Copyright (C) 2002, Linus Torvalds. |
5 | * |
6 | * O_DIRECT |
7 | * |
8 | * 04Jul2002 Andrew Morton |
9 | * Initial version |
10 | * 11Sep2002 janetinc@us.ibm.com |
11 | * added readv/writev support. |
12 | * 29Oct2002 Andrew Morton |
13 | * rewrote bio_add_page() support. |
14 | * 30Oct2002 pbadari@us.ibm.com |
15 | * added support for non-aligned IO. |
16 | * 06Nov2002 pbadari@us.ibm.com |
17 | * added asynchronous IO support. |
18 | * 21Jul2003 nathans@sgi.com |
19 | * added IO completion notifier. |
20 | */ |
21 | |
22 | #include <linux/kernel.h> |
23 | #include <linux/module.h> |
24 | #include <linux/types.h> |
25 | #include <linux/fs.h> |
26 | #include <linux/mm.h> |
27 | #include <linux/slab.h> |
28 | #include <linux/highmem.h> |
29 | #include <linux/pagemap.h> |
30 | #include <linux/task_io_accounting_ops.h> |
31 | #include <linux/bio.h> |
32 | #include <linux/wait.h> |
33 | #include <linux/err.h> |
34 | #include <linux/blkdev.h> |
35 | #include <linux/buffer_head.h> |
36 | #include <linux/rwsem.h> |
37 | #include <linux/uio.h> |
38 | #include <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 | |
58 | struct dio { |
59 | /* BIO submission state */ |
60 | struct bio *bio; /* bio under assembly */ |
61 | struct inode *inode; |
62 | int rw; |
63 | loff_t i_size; /* i_size when submitted */ |
64 | int flags; /* doesn't change */ |
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 */ |
83 | get_block_t *get_block; /* block mapping function */ |
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 */ |
88 | struct buffer_head map_bh; /* last get_block() result */ |
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 | /* BIO completion state */ |
101 | spinlock_t bio_lock; /* protects BIO fields below */ |
102 | unsigned long refcount; /* direct_io_worker() and bios */ |
103 | struct bio *bio_list; /* singly linked via bi_private */ |
104 | struct task_struct *waiter; /* waiting task (NULL if none) */ |
105 | |
106 | /* AIO related stuff */ |
107 | struct kiocb *iocb; /* kiocb */ |
108 | int is_async; /* is IO async ? */ |
109 | int io_error; /* IO error in completion path */ |
110 | ssize_t result; /* IO result */ |
111 | |
112 | /* |
113 | * Page fetching state. These variables belong to dio_refill_pages(). |
114 | */ |
115 | int curr_page; /* changes */ |
116 | int total_pages; /* doesn't change */ |
117 | unsigned long curr_user_address;/* changes */ |
118 | |
119 | /* |
120 | * Page queue. These variables belong to dio_refill_pages() and |
121 | * dio_get_page(). |
122 | */ |
123 | unsigned head; /* next page to process */ |
124 | unsigned tail; /* last valid page + 1 */ |
125 | int page_errors; /* errno from get_user_pages() */ |
126 | |
127 | /* |
128 | * pages[] (and any fields placed after it) are not zeroed out at |
129 | * allocation time. Don't add new fields after pages[] unless you |
130 | * wish that they not be zeroed. |
131 | */ |
132 | struct page *pages[DIO_PAGES]; /* page buffer */ |
133 | }; |
134 | |
135 | /* |
136 | * How many pages are in the queue? |
137 | */ |
138 | static inline unsigned dio_pages_present(struct dio *dio) |
139 | { |
140 | return dio->tail - dio->head; |
141 | } |
142 | |
143 | /* |
144 | * Go grab and pin some userspace pages. Typically we'll get 64 at a time. |
145 | */ |
146 | static int dio_refill_pages(struct dio *dio) |
147 | { |
148 | int ret; |
149 | int nr_pages; |
150 | |
151 | nr_pages = min(dio->total_pages - dio->curr_page, DIO_PAGES); |
152 | ret = get_user_pages_fast( |
153 | dio->curr_user_address, /* Where from? */ |
154 | nr_pages, /* How many pages? */ |
155 | dio->rw == READ, /* Write to memory? */ |
156 | &dio->pages[0]); /* Put results here */ |
157 | |
158 | if (ret < 0 && dio->blocks_available && (dio->rw & WRITE)) { |
159 | struct page *page = ZERO_PAGE(0); |
160 | /* |
161 | * A memory fault, but the filesystem has some outstanding |
162 | * mapped blocks. We need to use those blocks up to avoid |
163 | * leaking stale data in the file. |
164 | */ |
165 | if (dio->page_errors == 0) |
166 | dio->page_errors = ret; |
167 | page_cache_get(page); |
168 | dio->pages[0] = page; |
169 | dio->head = 0; |
170 | dio->tail = 1; |
171 | ret = 0; |
172 | goto out; |
173 | } |
174 | |
175 | if (ret >= 0) { |
176 | dio->curr_user_address += ret * PAGE_SIZE; |
177 | dio->curr_page += ret; |
178 | dio->head = 0; |
179 | dio->tail = ret; |
180 | ret = 0; |
181 | } |
182 | out: |
183 | return ret; |
184 | } |
185 | |
186 | /* |
187 | * Get another userspace page. Returns an ERR_PTR on error. Pages are |
188 | * buffered inside the dio so that we can call get_user_pages() against a |
189 | * decent number of pages, less frequently. To provide nicer use of the |
190 | * L1 cache. |
191 | */ |
192 | static struct page *dio_get_page(struct dio *dio) |
193 | { |
194 | if (dio_pages_present(dio) == 0) { |
195 | int ret; |
196 | |
197 | ret = dio_refill_pages(dio); |
198 | if (ret) |
199 | return ERR_PTR(ret); |
200 | BUG_ON(dio_pages_present(dio) == 0); |
201 | } |
202 | return dio->pages[dio->head++]; |
203 | } |
204 | |
205 | /** |
206 | * dio_complete() - called when all DIO BIO I/O has been completed |
207 | * @offset: the byte offset in the file of the completed operation |
208 | * |
209 | * This releases locks as dictated by the locking type, lets interested parties |
210 | * know that a DIO operation has completed, and calculates the resulting return |
211 | * code for the operation. |
212 | * |
213 | * It lets the filesystem know if it registered an interest earlier via |
214 | * get_block. Pass the private field of the map buffer_head so that |
215 | * filesystems can use it to hold additional state between get_block calls and |
216 | * dio_complete. |
217 | */ |
218 | static int dio_complete(struct dio *dio, loff_t offset, int ret) |
219 | { |
220 | ssize_t transferred = 0; |
221 | |
222 | /* |
223 | * AIO submission can race with bio completion to get here while |
224 | * expecting to have the last io completed by bio completion. |
225 | * In that case -EIOCBQUEUED is in fact not an error we want |
226 | * to preserve through this call. |
227 | */ |
228 | if (ret == -EIOCBQUEUED) |
229 | ret = 0; |
230 | |
231 | if (dio->result) { |
232 | transferred = dio->result; |
233 | |
234 | /* Check for short read case */ |
235 | if ((dio->rw == READ) && ((offset + transferred) > dio->i_size)) |
236 | transferred = dio->i_size - offset; |
237 | } |
238 | |
239 | if (dio->end_io && dio->result) |
240 | dio->end_io(dio->iocb, offset, transferred, |
241 | dio->map_bh.b_private); |
242 | |
243 | if (dio->flags & DIO_LOCKING) |
244 | /* lockdep: non-owner release */ |
245 | up_read_non_owner(&dio->inode->i_alloc_sem); |
246 | |
247 | if (ret == 0) |
248 | ret = dio->page_errors; |
249 | if (ret == 0) |
250 | ret = dio->io_error; |
251 | if (ret == 0) |
252 | ret = transferred; |
253 | |
254 | return ret; |
255 | } |
256 | |
257 | static int dio_bio_complete(struct dio *dio, struct bio *bio); |
258 | /* |
259 | * Asynchronous IO callback. |
260 | */ |
261 | static void dio_bio_end_aio(struct bio *bio, int error) |
262 | { |
263 | struct dio *dio = bio->bi_private; |
264 | unsigned long remaining; |
265 | unsigned long flags; |
266 | |
267 | /* cleanup the bio */ |
268 | dio_bio_complete(dio, bio); |
269 | |
270 | spin_lock_irqsave(&dio->bio_lock, flags); |
271 | remaining = --dio->refcount; |
272 | if (remaining == 1 && dio->waiter) |
273 | wake_up_process(dio->waiter); |
274 | spin_unlock_irqrestore(&dio->bio_lock, flags); |
275 | |
276 | if (remaining == 0) { |
277 | int ret = dio_complete(dio, dio->iocb->ki_pos, 0); |
278 | aio_complete(dio->iocb, ret, 0); |
279 | kfree(dio); |
280 | } |
281 | } |
282 | |
283 | /* |
284 | * The BIO completion handler simply queues the BIO up for the process-context |
285 | * handler. |
286 | * |
287 | * During I/O bi_private points at the dio. After I/O, bi_private is used to |
288 | * implement a singly-linked list of completed BIOs, at dio->bio_list. |
289 | */ |
290 | static void dio_bio_end_io(struct bio *bio, int error) |
291 | { |
292 | struct dio *dio = bio->bi_private; |
293 | unsigned long flags; |
294 | |
295 | spin_lock_irqsave(&dio->bio_lock, flags); |
296 | bio->bi_private = dio->bio_list; |
297 | dio->bio_list = bio; |
298 | if (--dio->refcount == 1 && dio->waiter) |
299 | wake_up_process(dio->waiter); |
300 | spin_unlock_irqrestore(&dio->bio_lock, flags); |
301 | } |
302 | |
303 | static int |
304 | dio_bio_alloc(struct dio *dio, struct block_device *bdev, |
305 | sector_t first_sector, int nr_vecs) |
306 | { |
307 | struct bio *bio; |
308 | |
309 | bio = bio_alloc(GFP_KERNEL, nr_vecs); |
310 | |
311 | bio->bi_bdev = bdev; |
312 | bio->bi_sector = first_sector; |
313 | if (dio->is_async) |
314 | bio->bi_end_io = dio_bio_end_aio; |
315 | else |
316 | bio->bi_end_io = dio_bio_end_io; |
317 | |
318 | dio->bio = bio; |
319 | return 0; |
320 | } |
321 | |
322 | /* |
323 | * In the AIO read case we speculatively dirty the pages before starting IO. |
324 | * During IO completion, any of these pages which happen to have been written |
325 | * back will be redirtied by bio_check_pages_dirty(). |
326 | * |
327 | * bios hold a dio reference between submit_bio and ->end_io. |
328 | */ |
329 | static void dio_bio_submit(struct dio *dio) |
330 | { |
331 | struct bio *bio = dio->bio; |
332 | unsigned long flags; |
333 | |
334 | bio->bi_private = dio; |
335 | |
336 | spin_lock_irqsave(&dio->bio_lock, flags); |
337 | dio->refcount++; |
338 | spin_unlock_irqrestore(&dio->bio_lock, flags); |
339 | |
340 | if (dio->is_async && dio->rw == READ) |
341 | bio_set_pages_dirty(bio); |
342 | |
343 | submit_bio(dio->rw, bio); |
344 | |
345 | dio->bio = NULL; |
346 | dio->boundary = 0; |
347 | } |
348 | |
349 | /* |
350 | * Release any resources in case of a failure |
351 | */ |
352 | static void dio_cleanup(struct dio *dio) |
353 | { |
354 | while (dio_pages_present(dio)) |
355 | page_cache_release(dio_get_page(dio)); |
356 | } |
357 | |
358 | /* |
359 | * Wait for the next BIO to complete. Remove it and return it. NULL is |
360 | * returned once all BIOs have been completed. This must only be called once |
361 | * all bios have been issued so that dio->refcount can only decrease. This |
362 | * requires that that the caller hold a reference on the dio. |
363 | */ |
364 | static struct bio *dio_await_one(struct dio *dio) |
365 | { |
366 | unsigned long flags; |
367 | struct bio *bio = NULL; |
368 | |
369 | spin_lock_irqsave(&dio->bio_lock, flags); |
370 | |
371 | /* |
372 | * Wait as long as the list is empty and there are bios in flight. bio |
373 | * completion drops the count, maybe adds to the list, and wakes while |
374 | * holding the bio_lock so we don't need set_current_state()'s barrier |
375 | * and can call it after testing our condition. |
376 | */ |
377 | while (dio->refcount > 1 && dio->bio_list == NULL) { |
378 | __set_current_state(TASK_UNINTERRUPTIBLE); |
379 | dio->waiter = current; |
380 | spin_unlock_irqrestore(&dio->bio_lock, flags); |
381 | io_schedule(); |
382 | /* wake up sets us TASK_RUNNING */ |
383 | spin_lock_irqsave(&dio->bio_lock, flags); |
384 | dio->waiter = NULL; |
385 | } |
386 | if (dio->bio_list) { |
387 | bio = dio->bio_list; |
388 | dio->bio_list = bio->bi_private; |
389 | } |
390 | spin_unlock_irqrestore(&dio->bio_lock, flags); |
391 | return bio; |
392 | } |
393 | |
394 | /* |
395 | * Process one completed BIO. No locks are held. |
396 | */ |
397 | static int dio_bio_complete(struct dio *dio, struct bio *bio) |
398 | { |
399 | const int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags); |
400 | struct bio_vec *bvec = bio->bi_io_vec; |
401 | int page_no; |
402 | |
403 | if (!uptodate) |
404 | dio->io_error = -EIO; |
405 | |
406 | if (dio->is_async && dio->rw == READ) { |
407 | bio_check_pages_dirty(bio); /* transfers ownership */ |
408 | } else { |
409 | for (page_no = 0; page_no < bio->bi_vcnt; page_no++) { |
410 | struct page *page = bvec[page_no].bv_page; |
411 | |
412 | if (dio->rw == READ && !PageCompound(page)) |
413 | set_page_dirty_lock(page); |
414 | page_cache_release(page); |
415 | } |
416 | bio_put(bio); |
417 | } |
418 | return uptodate ? 0 : -EIO; |
419 | } |
420 | |
421 | /* |
422 | * Wait on and process all in-flight BIOs. This must only be called once |
423 | * all bios have been issued so that the refcount can only decrease. |
424 | * This just waits for all bios to make it through dio_bio_complete. IO |
425 | * errors are propagated through dio->io_error and should be propagated via |
426 | * dio_complete(). |
427 | */ |
428 | static void dio_await_completion(struct dio *dio) |
429 | { |
430 | struct bio *bio; |
431 | do { |
432 | bio = dio_await_one(dio); |
433 | if (bio) |
434 | dio_bio_complete(dio, bio); |
435 | } while (bio); |
436 | } |
437 | |
438 | /* |
439 | * A really large O_DIRECT read or write can generate a lot of BIOs. So |
440 | * to keep the memory consumption sane we periodically reap any completed BIOs |
441 | * during the BIO generation phase. |
442 | * |
443 | * This also helps to limit the peak amount of pinned userspace memory. |
444 | */ |
445 | static int dio_bio_reap(struct dio *dio) |
446 | { |
447 | int ret = 0; |
448 | |
449 | if (dio->reap_counter++ >= 64) { |
450 | while (dio->bio_list) { |
451 | unsigned long flags; |
452 | struct bio *bio; |
453 | int ret2; |
454 | |
455 | spin_lock_irqsave(&dio->bio_lock, flags); |
456 | bio = dio->bio_list; |
457 | dio->bio_list = bio->bi_private; |
458 | spin_unlock_irqrestore(&dio->bio_lock, flags); |
459 | ret2 = dio_bio_complete(dio, bio); |
460 | if (ret == 0) |
461 | ret = ret2; |
462 | } |
463 | dio->reap_counter = 0; |
464 | } |
465 | return ret; |
466 | } |
467 | |
468 | /* |
469 | * Call into the fs to map some more disk blocks. We record the current number |
470 | * of available blocks at dio->blocks_available. These are in units of the |
471 | * fs blocksize, (1 << inode->i_blkbits). |
472 | * |
473 | * The fs is allowed to map lots of blocks at once. If it wants to do that, |
474 | * it uses the passed inode-relative block number as the file offset, as usual. |
475 | * |
476 | * get_block() is passed the number of i_blkbits-sized blocks which direct_io |
477 | * has remaining to do. The fs should not map more than this number of blocks. |
478 | * |
479 | * If the fs has mapped a lot of blocks, it should populate bh->b_size to |
480 | * indicate how much contiguous disk space has been made available at |
481 | * bh->b_blocknr. |
482 | * |
483 | * If *any* of the mapped blocks are new, then the fs must set buffer_new(). |
484 | * This isn't very efficient... |
485 | * |
486 | * In the case of filesystem holes: the fs may return an arbitrarily-large |
487 | * hole by returning an appropriate value in b_size and by clearing |
488 | * buffer_mapped(). However the direct-io code will only process holes one |
489 | * block at a time - it will repeatedly call get_block() as it walks the hole. |
490 | */ |
491 | static int get_more_blocks(struct dio *dio) |
492 | { |
493 | int ret; |
494 | struct buffer_head *map_bh = &dio->map_bh; |
495 | sector_t fs_startblk; /* Into file, in filesystem-sized blocks */ |
496 | unsigned long fs_count; /* Number of filesystem-sized blocks */ |
497 | unsigned long dio_count;/* Number of dio_block-sized blocks */ |
498 | unsigned long blkmask; |
499 | int create; |
500 | |
501 | /* |
502 | * If there was a memory error and we've overwritten all the |
503 | * mapped blocks then we can now return that memory error |
504 | */ |
505 | ret = dio->page_errors; |
506 | if (ret == 0) { |
507 | BUG_ON(dio->block_in_file >= dio->final_block_in_request); |
508 | fs_startblk = dio->block_in_file >> dio->blkfactor; |
509 | dio_count = dio->final_block_in_request - dio->block_in_file; |
510 | fs_count = dio_count >> dio->blkfactor; |
511 | blkmask = (1 << dio->blkfactor) - 1; |
512 | if (dio_count & blkmask) |
513 | fs_count++; |
514 | |
515 | map_bh->b_state = 0; |
516 | map_bh->b_size = fs_count << dio->inode->i_blkbits; |
517 | |
518 | /* |
519 | * For writes inside i_size on a DIO_SKIP_HOLES filesystem we |
520 | * forbid block creations: only overwrites are permitted. |
521 | * We will return early to the caller once we see an |
522 | * unmapped buffer head returned, and the caller will fall |
523 | * back to buffered I/O. |
524 | * |
525 | * Otherwise the decision is left to the get_blocks method, |
526 | * which may decide to handle it or also return an unmapped |
527 | * buffer head. |
528 | */ |
529 | create = dio->rw & WRITE; |
530 | if (dio->flags & DIO_SKIP_HOLES) { |
531 | if (dio->block_in_file < (i_size_read(dio->inode) >> |
532 | dio->blkbits)) |
533 | create = 0; |
534 | } |
535 | |
536 | ret = (*dio->get_block)(dio->inode, fs_startblk, |
537 | map_bh, create); |
538 | } |
539 | return ret; |
540 | } |
541 | |
542 | /* |
543 | * There is no bio. Make one now. |
544 | */ |
545 | static int dio_new_bio(struct dio *dio, sector_t start_sector) |
546 | { |
547 | sector_t sector; |
548 | int ret, nr_pages; |
549 | |
550 | ret = dio_bio_reap(dio); |
551 | if (ret) |
552 | goto out; |
553 | sector = start_sector << (dio->blkbits - 9); |
554 | nr_pages = min(dio->pages_in_io, bio_get_nr_vecs(dio->map_bh.b_bdev)); |
555 | BUG_ON(nr_pages <= 0); |
556 | ret = dio_bio_alloc(dio, dio->map_bh.b_bdev, sector, nr_pages); |
557 | dio->boundary = 0; |
558 | out: |
559 | return ret; |
560 | } |
561 | |
562 | /* |
563 | * Attempt to put the current chunk of 'cur_page' into the current BIO. If |
564 | * that was successful then update final_block_in_bio and take a ref against |
565 | * the just-added page. |
566 | * |
567 | * Return zero on success. Non-zero means the caller needs to start a new BIO. |
568 | */ |
569 | static int dio_bio_add_page(struct dio *dio) |
570 | { |
571 | int ret; |
572 | |
573 | ret = bio_add_page(dio->bio, dio->cur_page, |
574 | dio->cur_page_len, dio->cur_page_offset); |
575 | if (ret == dio->cur_page_len) { |
576 | /* |
577 | * Decrement count only, if we are done with this page |
578 | */ |
579 | if ((dio->cur_page_len + dio->cur_page_offset) == PAGE_SIZE) |
580 | dio->pages_in_io--; |
581 | page_cache_get(dio->cur_page); |
582 | dio->final_block_in_bio = dio->cur_page_block + |
583 | (dio->cur_page_len >> dio->blkbits); |
584 | ret = 0; |
585 | } else { |
586 | ret = 1; |
587 | } |
588 | return ret; |
589 | } |
590 | |
591 | /* |
592 | * Put cur_page under IO. The section of cur_page which is described by |
593 | * cur_page_offset,cur_page_len is put into a BIO. The section of cur_page |
594 | * starts on-disk at cur_page_block. |
595 | * |
596 | * We take a ref against the page here (on behalf of its presence in the bio). |
597 | * |
598 | * The caller of this function is responsible for removing cur_page from the |
599 | * dio, and for dropping the refcount which came from that presence. |
600 | */ |
601 | static int dio_send_cur_page(struct dio *dio) |
602 | { |
603 | int ret = 0; |
604 | |
605 | if (dio->bio) { |
606 | /* |
607 | * See whether this new request is contiguous with the old |
608 | */ |
609 | if (dio->final_block_in_bio != dio->cur_page_block) |
610 | dio_bio_submit(dio); |
611 | /* |
612 | * Submit now if the underlying fs is about to perform a |
613 | * metadata read |
614 | */ |
615 | if (dio->boundary) |
616 | dio_bio_submit(dio); |
617 | } |
618 | |
619 | if (dio->bio == NULL) { |
620 | ret = dio_new_bio(dio, dio->cur_page_block); |
621 | if (ret) |
622 | goto out; |
623 | } |
624 | |
625 | if (dio_bio_add_page(dio) != 0) { |
626 | dio_bio_submit(dio); |
627 | ret = dio_new_bio(dio, dio->cur_page_block); |
628 | if (ret == 0) { |
629 | ret = dio_bio_add_page(dio); |
630 | BUG_ON(ret != 0); |
631 | } |
632 | } |
633 | out: |
634 | return ret; |
635 | } |
636 | |
637 | /* |
638 | * An autonomous function to put a chunk of a page under deferred IO. |
639 | * |
640 | * The caller doesn't actually know (or care) whether this piece of page is in |
641 | * a BIO, or is under IO or whatever. We just take care of all possible |
642 | * situations here. The separation between the logic of do_direct_IO() and |
643 | * that of submit_page_section() is important for clarity. Please don't break. |
644 | * |
645 | * The chunk of page starts on-disk at blocknr. |
646 | * |
647 | * We perform deferred IO, by recording the last-submitted page inside our |
648 | * private part of the dio structure. If possible, we just expand the IO |
649 | * across that page here. |
650 | * |
651 | * If that doesn't work out then we put the old page into the bio and add this |
652 | * page to the dio instead. |
653 | */ |
654 | static int |
655 | submit_page_section(struct dio *dio, struct page *page, |
656 | unsigned offset, unsigned len, sector_t blocknr) |
657 | { |
658 | int ret = 0; |
659 | |
660 | if (dio->rw & WRITE) { |
661 | /* |
662 | * Read accounting is performed in submit_bio() |
663 | */ |
664 | task_io_account_write(len); |
665 | } |
666 | |
667 | /* |
668 | * Can we just grow the current page's presence in the dio? |
669 | */ |
670 | if ( (dio->cur_page == page) && |
671 | (dio->cur_page_offset + dio->cur_page_len == offset) && |
672 | (dio->cur_page_block + |
673 | (dio->cur_page_len >> dio->blkbits) == blocknr)) { |
674 | dio->cur_page_len += len; |
675 | |
676 | /* |
677 | * If dio->boundary then we want to schedule the IO now to |
678 | * avoid metadata seeks. |
679 | */ |
680 | if (dio->boundary) { |
681 | ret = dio_send_cur_page(dio); |
682 | page_cache_release(dio->cur_page); |
683 | dio->cur_page = NULL; |
684 | } |
685 | goto out; |
686 | } |
687 | |
688 | /* |
689 | * If there's a deferred page already there then send it. |
690 | */ |
691 | if (dio->cur_page) { |
692 | ret = dio_send_cur_page(dio); |
693 | page_cache_release(dio->cur_page); |
694 | dio->cur_page = NULL; |
695 | if (ret) |
696 | goto out; |
697 | } |
698 | |
699 | page_cache_get(page); /* It is in dio */ |
700 | dio->cur_page = page; |
701 | dio->cur_page_offset = offset; |
702 | dio->cur_page_len = len; |
703 | dio->cur_page_block = blocknr; |
704 | out: |
705 | return ret; |
706 | } |
707 | |
708 | /* |
709 | * Clean any dirty buffers in the blockdev mapping which alias newly-created |
710 | * file blocks. Only called for S_ISREG files - blockdevs do not set |
711 | * buffer_new |
712 | */ |
713 | static void clean_blockdev_aliases(struct dio *dio) |
714 | { |
715 | unsigned i; |
716 | unsigned nblocks; |
717 | |
718 | nblocks = dio->map_bh.b_size >> dio->inode->i_blkbits; |
719 | |
720 | for (i = 0; i < nblocks; i++) { |
721 | unmap_underlying_metadata(dio->map_bh.b_bdev, |
722 | dio->map_bh.b_blocknr + i); |
723 | } |
724 | } |
725 | |
726 | /* |
727 | * If we are not writing the entire block and get_block() allocated |
728 | * the block for us, we need to fill-in the unused portion of the |
729 | * block with zeros. This happens only if user-buffer, fileoffset or |
730 | * io length is not filesystem block-size multiple. |
731 | * |
732 | * `end' is zero if we're doing the start of the IO, 1 at the end of the |
733 | * IO. |
734 | */ |
735 | static void dio_zero_block(struct dio *dio, int end) |
736 | { |
737 | unsigned dio_blocks_per_fs_block; |
738 | unsigned this_chunk_blocks; /* In dio_blocks */ |
739 | unsigned this_chunk_bytes; |
740 | struct page *page; |
741 | |
742 | dio->start_zero_done = 1; |
743 | if (!dio->blkfactor || !buffer_new(&dio->map_bh)) |
744 | return; |
745 | |
746 | dio_blocks_per_fs_block = 1 << dio->blkfactor; |
747 | this_chunk_blocks = dio->block_in_file & (dio_blocks_per_fs_block - 1); |
748 | |
749 | if (!this_chunk_blocks) |
750 | return; |
751 | |
752 | /* |
753 | * We need to zero out part of an fs block. It is either at the |
754 | * beginning or the end of the fs block. |
755 | */ |
756 | if (end) |
757 | this_chunk_blocks = dio_blocks_per_fs_block - this_chunk_blocks; |
758 | |
759 | this_chunk_bytes = this_chunk_blocks << dio->blkbits; |
760 | |
761 | page = ZERO_PAGE(0); |
762 | if (submit_page_section(dio, page, 0, this_chunk_bytes, |
763 | dio->next_block_for_io)) |
764 | return; |
765 | |
766 | dio->next_block_for_io += this_chunk_blocks; |
767 | } |
768 | |
769 | /* |
770 | * Walk the user pages, and the file, mapping blocks to disk and generating |
771 | * a sequence of (page,offset,len,block) mappings. These mappings are injected |
772 | * into submit_page_section(), which takes care of the next stage of submission |
773 | * |
774 | * Direct IO against a blockdev is different from a file. Because we can |
775 | * happily perform page-sized but 512-byte aligned IOs. It is important that |
776 | * blockdev IO be able to have fine alignment and large sizes. |
777 | * |
778 | * So what we do is to permit the ->get_block function to populate bh.b_size |
779 | * with the size of IO which is permitted at this offset and this i_blkbits. |
780 | * |
781 | * For best results, the blockdev should be set up with 512-byte i_blkbits and |
782 | * it should set b_size to PAGE_SIZE or more inside get_block(). This gives |
783 | * fine alignment but still allows this function to work in PAGE_SIZE units. |
784 | */ |
785 | static int do_direct_IO(struct dio *dio) |
786 | { |
787 | const unsigned blkbits = dio->blkbits; |
788 | const unsigned blocks_per_page = PAGE_SIZE >> blkbits; |
789 | struct page *page; |
790 | unsigned block_in_page; |
791 | struct buffer_head *map_bh = &dio->map_bh; |
792 | int ret = 0; |
793 | |
794 | /* The I/O can start at any block offset within the first page */ |
795 | block_in_page = dio->first_block_in_page; |
796 | |
797 | while (dio->block_in_file < dio->final_block_in_request) { |
798 | page = dio_get_page(dio); |
799 | if (IS_ERR(page)) { |
800 | ret = PTR_ERR(page); |
801 | goto out; |
802 | } |
803 | |
804 | while (block_in_page < blocks_per_page) { |
805 | unsigned offset_in_page = block_in_page << blkbits; |
806 | unsigned this_chunk_bytes; /* # of bytes mapped */ |
807 | unsigned this_chunk_blocks; /* # of blocks */ |
808 | unsigned u; |
809 | |
810 | if (dio->blocks_available == 0) { |
811 | /* |
812 | * Need to go and map some more disk |
813 | */ |
814 | unsigned long blkmask; |
815 | unsigned long dio_remainder; |
816 | |
817 | ret = get_more_blocks(dio); |
818 | if (ret) { |
819 | page_cache_release(page); |
820 | goto out; |
821 | } |
822 | if (!buffer_mapped(map_bh)) |
823 | goto do_holes; |
824 | |
825 | dio->blocks_available = |
826 | map_bh->b_size >> dio->blkbits; |
827 | dio->next_block_for_io = |
828 | map_bh->b_blocknr << dio->blkfactor; |
829 | if (buffer_new(map_bh)) |
830 | clean_blockdev_aliases(dio); |
831 | |
832 | if (!dio->blkfactor) |
833 | goto do_holes; |
834 | |
835 | blkmask = (1 << dio->blkfactor) - 1; |
836 | dio_remainder = (dio->block_in_file & blkmask); |
837 | |
838 | /* |
839 | * If we are at the start of IO and that IO |
840 | * starts partway into a fs-block, |
841 | * dio_remainder will be non-zero. If the IO |
842 | * is a read then we can simply advance the IO |
843 | * cursor to the first block which is to be |
844 | * read. But if the IO is a write and the |
845 | * block was newly allocated we cannot do that; |
846 | * the start of the fs block must be zeroed out |
847 | * on-disk |
848 | */ |
849 | if (!buffer_new(map_bh)) |
850 | dio->next_block_for_io += dio_remainder; |
851 | dio->blocks_available -= dio_remainder; |
852 | } |
853 | do_holes: |
854 | /* Handle holes */ |
855 | if (!buffer_mapped(map_bh)) { |
856 | loff_t i_size_aligned; |
857 | |
858 | /* AKPM: eargh, -ENOTBLK is a hack */ |
859 | if (dio->rw & WRITE) { |
860 | page_cache_release(page); |
861 | return -ENOTBLK; |
862 | } |
863 | |
864 | /* |
865 | * Be sure to account for a partial block as the |
866 | * last block in the file |
867 | */ |
868 | i_size_aligned = ALIGN(i_size_read(dio->inode), |
869 | 1 << blkbits); |
870 | if (dio->block_in_file >= |
871 | i_size_aligned >> blkbits) { |
872 | /* We hit eof */ |
873 | page_cache_release(page); |
874 | goto out; |
875 | } |
876 | zero_user(page, block_in_page << blkbits, |
877 | 1 << blkbits); |
878 | dio->block_in_file++; |
879 | block_in_page++; |
880 | goto next_block; |
881 | } |
882 | |
883 | /* |
884 | * If we're performing IO which has an alignment which |
885 | * is finer than the underlying fs, go check to see if |
886 | * we must zero out the start of this block. |
887 | */ |
888 | if (unlikely(dio->blkfactor && !dio->start_zero_done)) |
889 | dio_zero_block(dio, 0); |
890 | |
891 | /* |
892 | * Work out, in this_chunk_blocks, how much disk we |
893 | * can add to this page |
894 | */ |
895 | this_chunk_blocks = dio->blocks_available; |
896 | u = (PAGE_SIZE - offset_in_page) >> blkbits; |
897 | if (this_chunk_blocks > u) |
898 | this_chunk_blocks = u; |
899 | u = dio->final_block_in_request - dio->block_in_file; |
900 | if (this_chunk_blocks > u) |
901 | this_chunk_blocks = u; |
902 | this_chunk_bytes = this_chunk_blocks << blkbits; |
903 | BUG_ON(this_chunk_bytes == 0); |
904 | |
905 | dio->boundary = buffer_boundary(map_bh); |
906 | ret = submit_page_section(dio, page, offset_in_page, |
907 | this_chunk_bytes, dio->next_block_for_io); |
908 | if (ret) { |
909 | page_cache_release(page); |
910 | goto out; |
911 | } |
912 | dio->next_block_for_io += this_chunk_blocks; |
913 | |
914 | dio->block_in_file += this_chunk_blocks; |
915 | block_in_page += this_chunk_blocks; |
916 | dio->blocks_available -= this_chunk_blocks; |
917 | next_block: |
918 | BUG_ON(dio->block_in_file > dio->final_block_in_request); |
919 | if (dio->block_in_file == dio->final_block_in_request) |
920 | break; |
921 | } |
922 | |
923 | /* Drop the ref which was taken in get_user_pages() */ |
924 | page_cache_release(page); |
925 | block_in_page = 0; |
926 | } |
927 | out: |
928 | return ret; |
929 | } |
930 | |
931 | /* |
932 | * Releases both i_mutex and i_alloc_sem |
933 | */ |
934 | static ssize_t |
935 | direct_io_worker(int rw, struct kiocb *iocb, struct inode *inode, |
936 | const struct iovec *iov, loff_t offset, unsigned long nr_segs, |
937 | unsigned blkbits, get_block_t get_block, dio_iodone_t end_io, |
938 | struct dio *dio) |
939 | { |
940 | unsigned long user_addr; |
941 | unsigned long flags; |
942 | int seg; |
943 | ssize_t ret = 0; |
944 | ssize_t ret2; |
945 | size_t bytes; |
946 | |
947 | dio->inode = inode; |
948 | dio->rw = rw; |
949 | dio->blkbits = blkbits; |
950 | dio->blkfactor = inode->i_blkbits - blkbits; |
951 | dio->block_in_file = offset >> blkbits; |
952 | |
953 | dio->get_block = get_block; |
954 | dio->end_io = end_io; |
955 | dio->final_block_in_bio = -1; |
956 | dio->next_block_for_io = -1; |
957 | |
958 | dio->iocb = iocb; |
959 | dio->i_size = i_size_read(inode); |
960 | |
961 | spin_lock_init(&dio->bio_lock); |
962 | dio->refcount = 1; |
963 | |
964 | /* |
965 | * In case of non-aligned buffers, we may need 2 more |
966 | * pages since we need to zero out first and last block. |
967 | */ |
968 | if (unlikely(dio->blkfactor)) |
969 | dio->pages_in_io = 2; |
970 | |
971 | for (seg = 0; seg < nr_segs; seg++) { |
972 | user_addr = (unsigned long)iov[seg].iov_base; |
973 | dio->pages_in_io += |
974 | ((user_addr+iov[seg].iov_len +PAGE_SIZE-1)/PAGE_SIZE |
975 | - user_addr/PAGE_SIZE); |
976 | } |
977 | |
978 | for (seg = 0; seg < nr_segs; seg++) { |
979 | user_addr = (unsigned long)iov[seg].iov_base; |
980 | dio->size += bytes = iov[seg].iov_len; |
981 | |
982 | /* Index into the first page of the first block */ |
983 | dio->first_block_in_page = (user_addr & ~PAGE_MASK) >> blkbits; |
984 | dio->final_block_in_request = dio->block_in_file + |
985 | (bytes >> blkbits); |
986 | /* Page fetching state */ |
987 | dio->head = 0; |
988 | dio->tail = 0; |
989 | dio->curr_page = 0; |
990 | |
991 | dio->total_pages = 0; |
992 | if (user_addr & (PAGE_SIZE-1)) { |
993 | dio->total_pages++; |
994 | bytes -= PAGE_SIZE - (user_addr & (PAGE_SIZE - 1)); |
995 | } |
996 | dio->total_pages += (bytes + PAGE_SIZE - 1) / PAGE_SIZE; |
997 | dio->curr_user_address = user_addr; |
998 | |
999 | ret = do_direct_IO(dio); |
1000 | |
1001 | dio->result += iov[seg].iov_len - |
1002 | ((dio->final_block_in_request - dio->block_in_file) << |
1003 | blkbits); |
1004 | |
1005 | if (ret) { |
1006 | dio_cleanup(dio); |
1007 | break; |
1008 | } |
1009 | } /* end iovec loop */ |
1010 | |
1011 | if (ret == -ENOTBLK && (rw & WRITE)) { |
1012 | /* |
1013 | * The remaining part of the request will be |
1014 | * be handled by buffered I/O when we return |
1015 | */ |
1016 | ret = 0; |
1017 | } |
1018 | /* |
1019 | * There may be some unwritten disk at the end of a part-written |
1020 | * fs-block-sized block. Go zero that now. |
1021 | */ |
1022 | dio_zero_block(dio, 1); |
1023 | |
1024 | if (dio->cur_page) { |
1025 | ret2 = dio_send_cur_page(dio); |
1026 | if (ret == 0) |
1027 | ret = ret2; |
1028 | page_cache_release(dio->cur_page); |
1029 | dio->cur_page = NULL; |
1030 | } |
1031 | if (dio->bio) |
1032 | dio_bio_submit(dio); |
1033 | |
1034 | /* |
1035 | * It is possible that, we return short IO due to end of file. |
1036 | * In that case, we need to release all the pages we got hold on. |
1037 | */ |
1038 | dio_cleanup(dio); |
1039 | |
1040 | /* |
1041 | * All block lookups have been performed. For READ requests |
1042 | * we can let i_mutex go now that its achieved its purpose |
1043 | * of protecting us from looking up uninitialized blocks. |
1044 | */ |
1045 | if (rw == READ && (dio->flags & DIO_LOCKING)) |
1046 | mutex_unlock(&dio->inode->i_mutex); |
1047 | |
1048 | /* |
1049 | * The only time we want to leave bios in flight is when a successful |
1050 | * partial aio read or full aio write have been setup. In that case |
1051 | * bio completion will call aio_complete. The only time it's safe to |
1052 | * call aio_complete is when we return -EIOCBQUEUED, so we key on that. |
1053 | * This had *better* be the only place that raises -EIOCBQUEUED. |
1054 | */ |
1055 | BUG_ON(ret == -EIOCBQUEUED); |
1056 | if (dio->is_async && ret == 0 && dio->result && |
1057 | ((rw & READ) || (dio->result == dio->size))) |
1058 | ret = -EIOCBQUEUED; |
1059 | |
1060 | if (ret != -EIOCBQUEUED) { |
1061 | /* All IO is now issued, send it on its way */ |
1062 | blk_run_address_space(inode->i_mapping); |
1063 | dio_await_completion(dio); |
1064 | } |
1065 | |
1066 | /* |
1067 | * Sync will always be dropping the final ref and completing the |
1068 | * operation. AIO can if it was a broken operation described above or |
1069 | * in fact if all the bios race to complete before we get here. In |
1070 | * that case dio_complete() translates the EIOCBQUEUED into the proper |
1071 | * return code that the caller will hand to aio_complete(). |
1072 | * |
1073 | * This is managed by the bio_lock instead of being an atomic_t so that |
1074 | * completion paths can drop their ref and use the remaining count to |
1075 | * decide to wake the submission path atomically. |
1076 | */ |
1077 | spin_lock_irqsave(&dio->bio_lock, flags); |
1078 | ret2 = --dio->refcount; |
1079 | spin_unlock_irqrestore(&dio->bio_lock, flags); |
1080 | |
1081 | if (ret2 == 0) { |
1082 | ret = dio_complete(dio, offset, ret); |
1083 | kfree(dio); |
1084 | } else |
1085 | BUG_ON(ret != -EIOCBQUEUED); |
1086 | |
1087 | return ret; |
1088 | } |
1089 | |
1090 | /* |
1091 | * This is a library function for use by filesystem drivers. |
1092 | * |
1093 | * The locking rules are governed by the flags parameter: |
1094 | * - if the flags value contains DIO_LOCKING we use a fancy locking |
1095 | * scheme for dumb filesystems. |
1096 | * For writes this function is called under i_mutex and returns with |
1097 | * i_mutex held, for reads, i_mutex is not held on entry, but it is |
1098 | * taken and dropped again before returning. |
1099 | * For reads and writes i_alloc_sem is taken in shared mode and released |
1100 | * on I/O completion (which may happen asynchronously after returning to |
1101 | * the caller). |
1102 | * |
1103 | * - if the flags value does NOT contain DIO_LOCKING we don't use any |
1104 | * internal locking but rather rely on the filesystem to synchronize |
1105 | * direct I/O reads/writes versus each other and truncate. |
1106 | * For reads and writes both i_mutex and i_alloc_sem are not held on |
1107 | * entry and are never taken. |
1108 | */ |
1109 | ssize_t |
1110 | __blockdev_direct_IO(int rw, struct kiocb *iocb, struct inode *inode, |
1111 | struct block_device *bdev, const struct iovec *iov, loff_t offset, |
1112 | unsigned long nr_segs, get_block_t get_block, dio_iodone_t end_io, |
1113 | int flags) |
1114 | { |
1115 | int seg; |
1116 | size_t size; |
1117 | unsigned long addr; |
1118 | unsigned blkbits = inode->i_blkbits; |
1119 | unsigned bdev_blkbits = 0; |
1120 | unsigned blocksize_mask = (1 << blkbits) - 1; |
1121 | ssize_t retval = -EINVAL; |
1122 | loff_t end = offset; |
1123 | struct dio *dio; |
1124 | |
1125 | if (rw & WRITE) |
1126 | rw = WRITE_ODIRECT_PLUG; |
1127 | |
1128 | if (bdev) |
1129 | bdev_blkbits = blksize_bits(bdev_logical_block_size(bdev)); |
1130 | |
1131 | if (offset & blocksize_mask) { |
1132 | if (bdev) |
1133 | blkbits = bdev_blkbits; |
1134 | blocksize_mask = (1 << blkbits) - 1; |
1135 | if (offset & blocksize_mask) |
1136 | goto out; |
1137 | } |
1138 | |
1139 | /* Check the memory alignment. Blocks cannot straddle pages */ |
1140 | for (seg = 0; seg < nr_segs; seg++) { |
1141 | addr = (unsigned long)iov[seg].iov_base; |
1142 | size = iov[seg].iov_len; |
1143 | end += size; |
1144 | if ((addr & blocksize_mask) || (size & blocksize_mask)) { |
1145 | if (bdev) |
1146 | blkbits = bdev_blkbits; |
1147 | blocksize_mask = (1 << blkbits) - 1; |
1148 | if ((addr & blocksize_mask) || (size & blocksize_mask)) |
1149 | goto out; |
1150 | } |
1151 | } |
1152 | |
1153 | dio = kmalloc(sizeof(*dio), GFP_KERNEL); |
1154 | retval = -ENOMEM; |
1155 | if (!dio) |
1156 | goto out; |
1157 | /* |
1158 | * Believe it or not, zeroing out the page array caused a .5% |
1159 | * performance regression in a database benchmark. So, we take |
1160 | * care to only zero out what's needed. |
1161 | */ |
1162 | memset(dio, 0, offsetof(struct dio, pages)); |
1163 | |
1164 | dio->flags = flags; |
1165 | if (dio->flags & DIO_LOCKING) { |
1166 | /* watch out for a 0 len io from a tricksy fs */ |
1167 | if (rw == READ && end > offset) { |
1168 | struct address_space *mapping = |
1169 | iocb->ki_filp->f_mapping; |
1170 | |
1171 | /* will be released by direct_io_worker */ |
1172 | mutex_lock(&inode->i_mutex); |
1173 | |
1174 | retval = filemap_write_and_wait_range(mapping, offset, |
1175 | end - 1); |
1176 | if (retval) { |
1177 | mutex_unlock(&inode->i_mutex); |
1178 | kfree(dio); |
1179 | goto out; |
1180 | } |
1181 | } |
1182 | |
1183 | /* |
1184 | * Will be released at I/O completion, possibly in a |
1185 | * different thread. |
1186 | */ |
1187 | down_read_non_owner(&inode->i_alloc_sem); |
1188 | } |
1189 | |
1190 | /* |
1191 | * For file extending writes updating i_size before data |
1192 | * writeouts complete can expose uninitialized blocks. So |
1193 | * even for AIO, we need to wait for i/o to complete before |
1194 | * returning in this case. |
1195 | */ |
1196 | dio->is_async = !is_sync_kiocb(iocb) && !((rw & WRITE) && |
1197 | (end > i_size_read(inode))); |
1198 | |
1199 | retval = direct_io_worker(rw, iocb, inode, iov, offset, |
1200 | nr_segs, blkbits, get_block, end_io, dio); |
1201 | |
1202 | /* |
1203 | * In case of error extending write may have instantiated a few |
1204 | * blocks outside i_size. Trim these off again for DIO_LOCKING. |
1205 | * |
1206 | * NOTE: filesystems with their own locking have to handle this |
1207 | * on their own. |
1208 | */ |
1209 | if (flags & DIO_LOCKING) { |
1210 | if (unlikely((rw & WRITE) && retval < 0)) { |
1211 | loff_t isize = i_size_read(inode); |
1212 | if (end > isize) |
1213 | vmtruncate(inode, isize); |
1214 | } |
1215 | } |
1216 | |
1217 | out: |
1218 | return retval; |
1219 | } |
1220 | EXPORT_SYMBOL(__blockdev_direct_IO); |
1221 |
Branches:
ben-wpan
ben-wpan-stefan
javiroman/ks7010
jz-2.6.34
jz-2.6.34-rc5
jz-2.6.34-rc6
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jz-2.6.35
jz-2.6.36
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jz-3.11
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jz-3.3
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jz-3.5
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jz-3.6-rc2-pwm
jz-3.9
jz-3.9-clk
jz-3.9-rc8
jz47xx
jz47xx-2.6.38
master
Tags:
od-2011-09-04
od-2011-09-18
v2.6.34-rc5
v2.6.34-rc6
v2.6.34-rc7
v3.9