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5274f052 JA |
1 | /* |
2 | * "splice": joining two ropes together by interweaving their strands. | |
3 | * | |
4 | * This is the "extended pipe" functionality, where a pipe is used as | |
5 | * an arbitrary in-memory buffer. Think of a pipe as a small kernel | |
6 | * buffer that you can use to transfer data from one end to the other. | |
7 | * | |
8 | * The traditional unix read/write is extended with a "splice()" operation | |
9 | * that transfers data buffers to or from a pipe buffer. | |
10 | * | |
11 | * Named by Larry McVoy, original implementation from Linus, extended by | |
12 | * Jens to support splicing to files and fixing the initial implementation | |
13 | * bugs. | |
14 | * | |
15 | * Copyright (C) 2005 Jens Axboe <axboe@suse.de> | |
16 | * Copyright (C) 2005 Linus Torvalds <torvalds@osdl.org> | |
17 | * | |
18 | */ | |
19 | #include <linux/fs.h> | |
20 | #include <linux/file.h> | |
21 | #include <linux/pagemap.h> | |
22 | #include <linux/pipe_fs_i.h> | |
23 | #include <linux/mm_inline.h> | |
24 | ||
25 | /* | |
26 | * Passed to the actors | |
27 | */ | |
28 | struct splice_desc { | |
29 | unsigned int len, total_len; /* current and remaining length */ | |
30 | unsigned int flags; /* splice flags */ | |
31 | struct file *file; /* file to read/write */ | |
32 | loff_t pos; /* file position */ | |
33 | }; | |
34 | ||
35 | static void page_cache_pipe_buf_release(struct pipe_inode_info *info, | |
36 | struct pipe_buffer *buf) | |
37 | { | |
38 | page_cache_release(buf->page); | |
39 | buf->page = NULL; | |
40 | } | |
41 | ||
42 | static void *page_cache_pipe_buf_map(struct file *file, | |
43 | struct pipe_inode_info *info, | |
44 | struct pipe_buffer *buf) | |
45 | { | |
46 | struct page *page = buf->page; | |
47 | ||
48 | lock_page(page); | |
49 | ||
50 | if (!PageUptodate(page)) { | |
51 | unlock_page(page); | |
52 | return ERR_PTR(-EIO); | |
53 | } | |
54 | ||
55 | if (!page->mapping) { | |
56 | unlock_page(page); | |
57 | return ERR_PTR(-ENODATA); | |
58 | } | |
59 | ||
60 | return kmap(buf->page); | |
61 | } | |
62 | ||
63 | static void page_cache_pipe_buf_unmap(struct pipe_inode_info *info, | |
64 | struct pipe_buffer *buf) | |
65 | { | |
66 | unlock_page(buf->page); | |
67 | kunmap(buf->page); | |
68 | } | |
69 | ||
70 | static struct pipe_buf_operations page_cache_pipe_buf_ops = { | |
71 | .can_merge = 0, | |
72 | .map = page_cache_pipe_buf_map, | |
73 | .unmap = page_cache_pipe_buf_unmap, | |
74 | .release = page_cache_pipe_buf_release, | |
75 | }; | |
76 | ||
77 | static ssize_t move_to_pipe(struct inode *inode, struct page **pages, | |
78 | int nr_pages, unsigned long offset, | |
79 | unsigned long len) | |
80 | { | |
81 | struct pipe_inode_info *info; | |
82 | int ret, do_wakeup, i; | |
83 | ||
84 | ret = 0; | |
85 | do_wakeup = 0; | |
86 | i = 0; | |
87 | ||
88 | mutex_lock(PIPE_MUTEX(*inode)); | |
89 | ||
90 | info = inode->i_pipe; | |
91 | for (;;) { | |
92 | int bufs; | |
93 | ||
94 | if (!PIPE_READERS(*inode)) { | |
95 | send_sig(SIGPIPE, current, 0); | |
96 | if (!ret) | |
97 | ret = -EPIPE; | |
98 | break; | |
99 | } | |
100 | ||
101 | bufs = info->nrbufs; | |
102 | if (bufs < PIPE_BUFFERS) { | |
103 | int newbuf = (info->curbuf + bufs) & (PIPE_BUFFERS - 1); | |
104 | struct pipe_buffer *buf = info->bufs + newbuf; | |
105 | struct page *page = pages[i++]; | |
106 | unsigned long this_len; | |
107 | ||
108 | this_len = PAGE_CACHE_SIZE - offset; | |
109 | if (this_len > len) | |
110 | this_len = len; | |
111 | ||
112 | buf->page = page; | |
113 | buf->offset = offset; | |
114 | buf->len = this_len; | |
115 | buf->ops = &page_cache_pipe_buf_ops; | |
116 | info->nrbufs = ++bufs; | |
117 | do_wakeup = 1; | |
118 | ||
119 | ret += this_len; | |
120 | len -= this_len; | |
121 | offset = 0; | |
122 | if (!--nr_pages) | |
123 | break; | |
124 | if (!len) | |
125 | break; | |
126 | if (bufs < PIPE_BUFFERS) | |
127 | continue; | |
128 | ||
129 | break; | |
130 | } | |
131 | ||
132 | if (signal_pending(current)) { | |
133 | if (!ret) | |
134 | ret = -ERESTARTSYS; | |
135 | break; | |
136 | } | |
137 | ||
138 | if (do_wakeup) { | |
139 | wake_up_interruptible_sync(PIPE_WAIT(*inode)); | |
140 | kill_fasync(PIPE_FASYNC_READERS(*inode), SIGIO, | |
141 | POLL_IN); | |
142 | do_wakeup = 0; | |
143 | } | |
144 | ||
145 | PIPE_WAITING_WRITERS(*inode)++; | |
146 | pipe_wait(inode); | |
147 | PIPE_WAITING_WRITERS(*inode)--; | |
148 | } | |
149 | ||
150 | mutex_unlock(PIPE_MUTEX(*inode)); | |
151 | ||
152 | if (do_wakeup) { | |
153 | wake_up_interruptible(PIPE_WAIT(*inode)); | |
154 | kill_fasync(PIPE_FASYNC_READERS(*inode), SIGIO, POLL_IN); | |
155 | } | |
156 | ||
157 | while (i < nr_pages) | |
158 | page_cache_release(pages[i++]); | |
159 | ||
160 | return ret; | |
161 | } | |
162 | ||
163 | static int __generic_file_splice_read(struct file *in, struct inode *pipe, | |
164 | size_t len) | |
165 | { | |
166 | struct address_space *mapping = in->f_mapping; | |
167 | unsigned int offset, nr_pages; | |
168 | struct page *pages[PIPE_BUFFERS], *shadow[PIPE_BUFFERS]; | |
169 | struct page *page; | |
170 | pgoff_t index, pidx; | |
171 | int i, j; | |
172 | ||
173 | index = in->f_pos >> PAGE_CACHE_SHIFT; | |
174 | offset = in->f_pos & ~PAGE_CACHE_MASK; | |
175 | nr_pages = (len + offset + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT; | |
176 | ||
177 | if (nr_pages > PIPE_BUFFERS) | |
178 | nr_pages = PIPE_BUFFERS; | |
179 | ||
180 | /* | |
181 | * initiate read-ahead on this page range | |
182 | */ | |
183 | do_page_cache_readahead(mapping, in, index, nr_pages); | |
184 | ||
185 | /* | |
186 | * Get as many pages from the page cache as possible.. | |
187 | * Start IO on the page cache entries we create (we | |
188 | * can assume that any pre-existing ones we find have | |
189 | * already had IO started on them). | |
190 | */ | |
191 | i = find_get_pages(mapping, index, nr_pages, pages); | |
192 | ||
193 | /* | |
194 | * common case - we found all pages and they are contiguous, | |
195 | * kick them off | |
196 | */ | |
197 | if (i && (pages[i - 1]->index == index + i - 1)) | |
198 | goto splice_them; | |
199 | ||
200 | /* | |
201 | * fill shadow[] with pages at the right locations, so we only | |
202 | * have to fill holes | |
203 | */ | |
204 | memset(shadow, 0, i * sizeof(struct page *)); | |
205 | for (j = 0, pidx = index; j < i; pidx++, j++) | |
206 | shadow[pages[j]->index - pidx] = pages[j]; | |
207 | ||
208 | /* | |
209 | * now fill in the holes | |
210 | */ | |
211 | for (i = 0, pidx = index; i < nr_pages; pidx++, i++) { | |
212 | int error; | |
213 | ||
214 | if (shadow[i]) | |
215 | continue; | |
216 | ||
217 | /* | |
218 | * no page there, look one up / create it | |
219 | */ | |
220 | page = find_or_create_page(mapping, pidx, | |
221 | mapping_gfp_mask(mapping)); | |
222 | if (!page) | |
223 | break; | |
224 | ||
225 | if (PageUptodate(page)) | |
226 | unlock_page(page); | |
227 | else { | |
228 | error = mapping->a_ops->readpage(in, page); | |
229 | ||
230 | if (unlikely(error)) { | |
231 | page_cache_release(page); | |
232 | break; | |
233 | } | |
234 | } | |
235 | shadow[i] = page; | |
236 | } | |
237 | ||
238 | if (!i) { | |
239 | for (i = 0; i < nr_pages; i++) { | |
240 | if (shadow[i]) | |
241 | page_cache_release(shadow[i]); | |
242 | } | |
243 | return 0; | |
244 | } | |
245 | ||
246 | memcpy(pages, shadow, i * sizeof(struct page *)); | |
247 | ||
248 | /* | |
249 | * Now we splice them into the pipe.. | |
250 | */ | |
251 | splice_them: | |
252 | return move_to_pipe(pipe, pages, i, offset, len); | |
253 | } | |
254 | ||
255 | ssize_t generic_file_splice_read(struct file *in, struct inode *pipe, | |
256 | size_t len, unsigned int flags) | |
257 | { | |
258 | ssize_t spliced; | |
259 | int ret; | |
260 | ||
261 | ret = 0; | |
262 | spliced = 0; | |
263 | while (len) { | |
264 | ret = __generic_file_splice_read(in, pipe, len); | |
265 | ||
266 | if (ret <= 0) | |
267 | break; | |
268 | ||
269 | in->f_pos += ret; | |
270 | len -= ret; | |
271 | spliced += ret; | |
272 | } | |
273 | ||
274 | if (spliced) | |
275 | return spliced; | |
276 | ||
277 | return ret; | |
278 | } | |
279 | ||
280 | /* | |
281 | * Send 'len' bytes to socket from 'file' at position 'pos' using sendpage(). | |
282 | */ | |
283 | static int pipe_to_sendpage(struct pipe_inode_info *info, | |
284 | struct pipe_buffer *buf, struct splice_desc *sd) | |
285 | { | |
286 | struct file *file = sd->file; | |
287 | loff_t pos = sd->pos; | |
288 | unsigned int offset; | |
289 | ssize_t ret; | |
290 | void *ptr; | |
291 | ||
292 | /* | |
293 | * sub-optimal, but we are limited by the pipe ->map. we don't | |
294 | * need a kmap'ed buffer here, we just want to make sure we | |
295 | * have the page pinned if the pipe page originates from the | |
296 | * page cache | |
297 | */ | |
298 | ptr = buf->ops->map(file, info, buf); | |
299 | if (IS_ERR(ptr)) | |
300 | return PTR_ERR(ptr); | |
301 | ||
302 | offset = pos & ~PAGE_CACHE_MASK; | |
303 | ||
304 | ret = file->f_op->sendpage(file, buf->page, offset, sd->len, &pos, | |
305 | sd->len < sd->total_len); | |
306 | ||
307 | buf->ops->unmap(info, buf); | |
308 | if (ret == sd->len) | |
309 | return 0; | |
310 | ||
311 | return -EIO; | |
312 | } | |
313 | ||
314 | /* | |
315 | * This is a little more tricky than the file -> pipe splicing. There are | |
316 | * basically three cases: | |
317 | * | |
318 | * - Destination page already exists in the address space and there | |
319 | * are users of it. For that case we have no other option that | |
320 | * copying the data. Tough luck. | |
321 | * - Destination page already exists in the address space, but there | |
322 | * are no users of it. Make sure it's uptodate, then drop it. Fall | |
323 | * through to last case. | |
324 | * - Destination page does not exist, we can add the pipe page to | |
325 | * the page cache and avoid the copy. | |
326 | * | |
327 | * For now we just do the slower thing and always copy pages over, it's | |
328 | * easier than migrating pages from the pipe to the target file. For the | |
329 | * case of doing file | file splicing, the migrate approach had some LRU | |
330 | * nastiness... | |
331 | */ | |
332 | static int pipe_to_file(struct pipe_inode_info *info, struct pipe_buffer *buf, | |
333 | struct splice_desc *sd) | |
334 | { | |
335 | struct file *file = sd->file; | |
336 | struct address_space *mapping = file->f_mapping; | |
337 | unsigned int offset; | |
338 | struct page *page; | |
339 | char *src, *dst; | |
340 | pgoff_t index; | |
341 | int ret; | |
342 | ||
343 | /* | |
344 | * after this, page will be locked and unmapped | |
345 | */ | |
346 | src = buf->ops->map(file, info, buf); | |
347 | if (IS_ERR(src)) | |
348 | return PTR_ERR(src); | |
349 | ||
350 | index = sd->pos >> PAGE_CACHE_SHIFT; | |
351 | offset = sd->pos & ~PAGE_CACHE_MASK; | |
352 | ||
353 | find_page: | |
354 | ret = -ENOMEM; | |
355 | page = find_or_create_page(mapping, index, mapping_gfp_mask(mapping)); | |
356 | if (!page) | |
357 | goto out; | |
358 | ||
359 | /* | |
360 | * If the page is uptodate, it is also locked. If it isn't | |
361 | * uptodate, we can mark it uptodate if we are filling the | |
362 | * full page. Otherwise we need to read it in first... | |
363 | */ | |
364 | if (!PageUptodate(page)) { | |
365 | if (sd->len < PAGE_CACHE_SIZE) { | |
366 | ret = mapping->a_ops->readpage(file, page); | |
367 | if (unlikely(ret)) | |
368 | goto out; | |
369 | ||
370 | lock_page(page); | |
371 | ||
372 | if (!PageUptodate(page)) { | |
373 | /* | |
374 | * page got invalidated, repeat | |
375 | */ | |
376 | if (!page->mapping) { | |
377 | unlock_page(page); | |
378 | page_cache_release(page); | |
379 | goto find_page; | |
380 | } | |
381 | ret = -EIO; | |
382 | goto out; | |
383 | } | |
384 | } else { | |
385 | WARN_ON(!PageLocked(page)); | |
386 | SetPageUptodate(page); | |
387 | } | |
388 | } | |
389 | ||
390 | ret = mapping->a_ops->prepare_write(file, page, 0, sd->len); | |
391 | if (ret) | |
392 | goto out; | |
393 | ||
394 | dst = kmap_atomic(page, KM_USER0); | |
395 | memcpy(dst + offset, src + buf->offset, sd->len); | |
396 | flush_dcache_page(page); | |
397 | kunmap_atomic(dst, KM_USER0); | |
398 | ||
399 | ret = mapping->a_ops->commit_write(file, page, 0, sd->len); | |
400 | if (ret < 0) | |
401 | goto out; | |
402 | ||
403 | set_page_dirty(page); | |
404 | ret = write_one_page(page, 0); | |
405 | out: | |
406 | if (ret < 0) | |
407 | unlock_page(page); | |
408 | page_cache_release(page); | |
409 | buf->ops->unmap(info, buf); | |
410 | return ret; | |
411 | } | |
412 | ||
413 | typedef int (splice_actor)(struct pipe_inode_info *, struct pipe_buffer *, | |
414 | struct splice_desc *); | |
415 | ||
416 | static ssize_t move_from_pipe(struct inode *inode, struct file *out, | |
417 | size_t len, unsigned int flags, | |
418 | splice_actor *actor) | |
419 | { | |
420 | struct pipe_inode_info *info; | |
421 | int ret, do_wakeup, err; | |
422 | struct splice_desc sd; | |
423 | ||
424 | ret = 0; | |
425 | do_wakeup = 0; | |
426 | ||
427 | sd.total_len = len; | |
428 | sd.flags = flags; | |
429 | sd.file = out; | |
430 | sd.pos = out->f_pos; | |
431 | ||
432 | mutex_lock(PIPE_MUTEX(*inode)); | |
433 | ||
434 | info = inode->i_pipe; | |
435 | for (;;) { | |
436 | int bufs = info->nrbufs; | |
437 | ||
438 | if (bufs) { | |
439 | int curbuf = info->curbuf; | |
440 | struct pipe_buffer *buf = info->bufs + curbuf; | |
441 | struct pipe_buf_operations *ops = buf->ops; | |
442 | ||
443 | sd.len = buf->len; | |
444 | if (sd.len > sd.total_len) | |
445 | sd.len = sd.total_len; | |
446 | ||
447 | err = actor(info, buf, &sd); | |
448 | if (err) { | |
449 | if (!ret && err != -ENODATA) | |
450 | ret = err; | |
451 | ||
452 | break; | |
453 | } | |
454 | ||
455 | ret += sd.len; | |
456 | buf->offset += sd.len; | |
457 | buf->len -= sd.len; | |
458 | if (!buf->len) { | |
459 | buf->ops = NULL; | |
460 | ops->release(info, buf); | |
461 | curbuf = (curbuf + 1) & (PIPE_BUFFERS - 1); | |
462 | info->curbuf = curbuf; | |
463 | info->nrbufs = --bufs; | |
464 | do_wakeup = 1; | |
465 | } | |
466 | ||
467 | sd.pos += sd.len; | |
468 | sd.total_len -= sd.len; | |
469 | if (!sd.total_len) | |
470 | break; | |
471 | } | |
472 | ||
473 | if (bufs) | |
474 | continue; | |
475 | if (!PIPE_WRITERS(*inode)) | |
476 | break; | |
477 | if (!PIPE_WAITING_WRITERS(*inode)) { | |
478 | if (ret) | |
479 | break; | |
480 | } | |
481 | ||
482 | if (signal_pending(current)) { | |
483 | if (!ret) | |
484 | ret = -ERESTARTSYS; | |
485 | break; | |
486 | } | |
487 | ||
488 | if (do_wakeup) { | |
489 | wake_up_interruptible_sync(PIPE_WAIT(*inode)); | |
490 | kill_fasync(PIPE_FASYNC_WRITERS(*inode),SIGIO,POLL_OUT); | |
491 | do_wakeup = 0; | |
492 | } | |
493 | ||
494 | pipe_wait(inode); | |
495 | } | |
496 | ||
497 | mutex_unlock(PIPE_MUTEX(*inode)); | |
498 | ||
499 | if (do_wakeup) { | |
500 | wake_up_interruptible(PIPE_WAIT(*inode)); | |
501 | kill_fasync(PIPE_FASYNC_WRITERS(*inode), SIGIO, POLL_OUT); | |
502 | } | |
503 | ||
504 | mutex_lock(&out->f_mapping->host->i_mutex); | |
505 | out->f_pos = sd.pos; | |
506 | mutex_unlock(&out->f_mapping->host->i_mutex); | |
507 | return ret; | |
508 | ||
509 | } | |
510 | ||
511 | ssize_t generic_file_splice_write(struct inode *inode, struct file *out, | |
512 | size_t len, unsigned int flags) | |
513 | { | |
514 | return move_from_pipe(inode, out, len, flags, pipe_to_file); | |
515 | } | |
516 | ||
517 | ssize_t generic_splice_sendpage(struct inode *inode, struct file *out, | |
518 | size_t len, unsigned int flags) | |
519 | { | |
520 | return move_from_pipe(inode, out, len, flags, pipe_to_sendpage); | |
521 | } | |
522 | ||
523 | static long do_splice_from(struct inode *pipe, struct file *out, size_t len, | |
524 | unsigned int flags) | |
525 | { | |
526 | loff_t pos; | |
527 | int ret; | |
528 | ||
529 | if (!out->f_op || !out->f_op->splice_write) | |
530 | return -EINVAL; | |
531 | ||
532 | if (!(out->f_mode & FMODE_WRITE)) | |
533 | return -EBADF; | |
534 | ||
535 | pos = out->f_pos; | |
536 | ret = rw_verify_area(WRITE, out, &pos, len); | |
537 | if (unlikely(ret < 0)) | |
538 | return ret; | |
539 | ||
540 | return out->f_op->splice_write(pipe, out, len, flags); | |
541 | } | |
542 | ||
543 | static long do_splice_to(struct file *in, struct inode *pipe, size_t len, | |
544 | unsigned int flags) | |
545 | { | |
546 | loff_t pos, isize, left; | |
547 | int ret; | |
548 | ||
549 | if (!in->f_op || !in->f_op->splice_read) | |
550 | return -EINVAL; | |
551 | ||
552 | if (!(in->f_mode & FMODE_READ)) | |
553 | return -EBADF; | |
554 | ||
555 | pos = in->f_pos; | |
556 | ret = rw_verify_area(READ, in, &pos, len); | |
557 | if (unlikely(ret < 0)) | |
558 | return ret; | |
559 | ||
560 | isize = i_size_read(in->f_mapping->host); | |
561 | if (unlikely(in->f_pos >= isize)) | |
562 | return 0; | |
563 | ||
564 | left = isize - in->f_pos; | |
565 | if (left < len) | |
566 | len = left; | |
567 | ||
568 | return in->f_op->splice_read(in, pipe, len, flags); | |
569 | } | |
570 | ||
571 | static long do_splice(struct file *in, struct file *out, size_t len, | |
572 | unsigned int flags) | |
573 | { | |
574 | struct inode *pipe; | |
575 | ||
576 | pipe = in->f_dentry->d_inode; | |
577 | if (pipe->i_pipe) | |
578 | return do_splice_from(pipe, out, len, flags); | |
579 | ||
580 | pipe = out->f_dentry->d_inode; | |
581 | if (pipe->i_pipe) | |
582 | return do_splice_to(in, pipe, len, flags); | |
583 | ||
584 | return -EINVAL; | |
585 | } | |
586 | ||
587 | asmlinkage long sys_splice(int fdin, int fdout, size_t len, unsigned int flags) | |
588 | { | |
589 | long error; | |
590 | struct file *in, *out; | |
591 | int fput_in, fput_out; | |
592 | ||
593 | if (unlikely(!len)) | |
594 | return 0; | |
595 | ||
596 | error = -EBADF; | |
597 | in = fget_light(fdin, &fput_in); | |
598 | if (in) { | |
599 | if (in->f_mode & FMODE_READ) { | |
600 | out = fget_light(fdout, &fput_out); | |
601 | if (out) { | |
602 | if (out->f_mode & FMODE_WRITE) | |
603 | error = do_splice(in, out, len, flags); | |
604 | fput_light(out, fput_out); | |
605 | } | |
606 | } | |
607 | ||
608 | fput_light(in, fput_in); | |
609 | } | |
610 | ||
611 | return error; | |
612 | } |