ia64/linux-2.6.18-xen.hg

view fs/splice.c @ 524:7f8b544237bf

netfront: Allow netfront in domain 0.

This is useful if your physical network device is in a utility domain.

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
author Keir Fraser <keir.fraser@citrix.com>
date Tue Apr 15 15:18:58 2008 +0100 (2008-04-15)
parents 08e85e79c65d
children
line source
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, network, direct splicing, etc and
13 * fixing lots of bugs.
14 *
15 * Copyright (C) 2005-2006 Jens Axboe <axboe@suse.de>
16 * Copyright (C) 2005-2006 Linus Torvalds <torvalds@osdl.org>
17 * Copyright (C) 2006 Ingo Molnar <mingo@elte.hu>
18 *
19 */
20 #include <linux/fs.h>
21 #include <linux/file.h>
22 #include <linux/pagemap.h>
23 #include <linux/pipe_fs_i.h>
24 #include <linux/mm_inline.h>
25 #include <linux/swap.h>
26 #include <linux/writeback.h>
27 #include <linux/buffer_head.h>
28 #include <linux/module.h>
29 #include <linux/syscalls.h>
30 #include <linux/uio.h>
32 struct partial_page {
33 unsigned int offset;
34 unsigned int len;
35 };
37 /*
38 * Passed to splice_to_pipe
39 */
40 struct splice_pipe_desc {
41 struct page **pages; /* page map */
42 struct partial_page *partial; /* pages[] may not be contig */
43 int nr_pages; /* number of pages in map */
44 unsigned int flags; /* splice flags */
45 struct pipe_buf_operations *ops;/* ops associated with output pipe */
46 };
48 /*
49 * Attempt to steal a page from a pipe buffer. This should perhaps go into
50 * a vm helper function, it's already simplified quite a bit by the
51 * addition of remove_mapping(). If success is returned, the caller may
52 * attempt to reuse this page for another destination.
53 */
54 static int page_cache_pipe_buf_steal(struct pipe_inode_info *pipe,
55 struct pipe_buffer *buf)
56 {
57 struct page *page = buf->page;
58 struct address_space *mapping;
60 lock_page(page);
62 mapping = page_mapping(page);
63 if (mapping) {
64 WARN_ON(!PageUptodate(page));
66 /*
67 * At least for ext2 with nobh option, we need to wait on
68 * writeback completing on this page, since we'll remove it
69 * from the pagecache. Otherwise truncate wont wait on the
70 * page, allowing the disk blocks to be reused by someone else
71 * before we actually wrote our data to them. fs corruption
72 * ensues.
73 */
74 wait_on_page_writeback(page);
76 if (PagePrivate(page))
77 try_to_release_page(page, mapping_gfp_mask(mapping));
79 /*
80 * If we succeeded in removing the mapping, set LRU flag
81 * and return good.
82 */
83 if (remove_mapping(mapping, page)) {
84 buf->flags |= PIPE_BUF_FLAG_LRU;
85 return 0;
86 }
87 }
89 /*
90 * Raced with truncate or failed to remove page from current
91 * address space, unlock and return failure.
92 */
93 unlock_page(page);
94 return 1;
95 }
97 static void page_cache_pipe_buf_release(struct pipe_inode_info *pipe,
98 struct pipe_buffer *buf)
99 {
100 page_cache_release(buf->page);
101 buf->flags &= ~PIPE_BUF_FLAG_LRU;
102 }
104 static int page_cache_pipe_buf_pin(struct pipe_inode_info *pipe,
105 struct pipe_buffer *buf)
106 {
107 struct page *page = buf->page;
108 int err;
110 if (!PageUptodate(page)) {
111 lock_page(page);
113 /*
114 * Page got truncated/unhashed. This will cause a 0-byte
115 * splice, if this is the first page.
116 */
117 if (!page->mapping) {
118 err = -ENODATA;
119 goto error;
120 }
122 /*
123 * Uh oh, read-error from disk.
124 */
125 if (!PageUptodate(page)) {
126 err = -EIO;
127 goto error;
128 }
130 /*
131 * Page is ok afterall, we are done.
132 */
133 unlock_page(page);
134 }
136 return 0;
137 error:
138 unlock_page(page);
139 return err;
140 }
142 static struct pipe_buf_operations page_cache_pipe_buf_ops = {
143 .can_merge = 0,
144 .map = generic_pipe_buf_map,
145 .unmap = generic_pipe_buf_unmap,
146 .pin = page_cache_pipe_buf_pin,
147 .release = page_cache_pipe_buf_release,
148 .steal = page_cache_pipe_buf_steal,
149 .get = generic_pipe_buf_get,
150 };
152 static int user_page_pipe_buf_steal(struct pipe_inode_info *pipe,
153 struct pipe_buffer *buf)
154 {
155 if (!(buf->flags & PIPE_BUF_FLAG_GIFT))
156 return 1;
158 buf->flags |= PIPE_BUF_FLAG_LRU;
159 return generic_pipe_buf_steal(pipe, buf);
160 }
162 static struct pipe_buf_operations user_page_pipe_buf_ops = {
163 .can_merge = 0,
164 .map = generic_pipe_buf_map,
165 .unmap = generic_pipe_buf_unmap,
166 .pin = generic_pipe_buf_pin,
167 .release = page_cache_pipe_buf_release,
168 .steal = user_page_pipe_buf_steal,
169 .get = generic_pipe_buf_get,
170 };
172 /*
173 * Pipe output worker. This sets up our pipe format with the page cache
174 * pipe buffer operations. Otherwise very similar to the regular pipe_writev().
175 */
176 static ssize_t splice_to_pipe(struct pipe_inode_info *pipe,
177 struct splice_pipe_desc *spd)
178 {
179 int ret, do_wakeup, page_nr;
181 ret = 0;
182 do_wakeup = 0;
183 page_nr = 0;
185 if (pipe->inode)
186 mutex_lock(&pipe->inode->i_mutex);
188 for (;;) {
189 if (!pipe->readers) {
190 send_sig(SIGPIPE, current, 0);
191 if (!ret)
192 ret = -EPIPE;
193 break;
194 }
196 if (pipe->nrbufs < PIPE_BUFFERS) {
197 int newbuf = (pipe->curbuf + pipe->nrbufs) & (PIPE_BUFFERS - 1);
198 struct pipe_buffer *buf = pipe->bufs + newbuf;
200 buf->page = spd->pages[page_nr];
201 buf->offset = spd->partial[page_nr].offset;
202 buf->len = spd->partial[page_nr].len;
203 buf->ops = spd->ops;
204 if (spd->flags & SPLICE_F_GIFT)
205 buf->flags |= PIPE_BUF_FLAG_GIFT;
207 pipe->nrbufs++;
208 page_nr++;
209 ret += buf->len;
211 if (pipe->inode)
212 do_wakeup = 1;
214 if (!--spd->nr_pages)
215 break;
216 if (pipe->nrbufs < PIPE_BUFFERS)
217 continue;
219 break;
220 }
222 if (spd->flags & SPLICE_F_NONBLOCK) {
223 if (!ret)
224 ret = -EAGAIN;
225 break;
226 }
228 if (signal_pending(current)) {
229 if (!ret)
230 ret = -ERESTARTSYS;
231 break;
232 }
234 if (do_wakeup) {
235 smp_mb();
236 if (waitqueue_active(&pipe->wait))
237 wake_up_interruptible_sync(&pipe->wait);
238 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
239 do_wakeup = 0;
240 }
242 pipe->waiting_writers++;
243 pipe_wait(pipe);
244 pipe->waiting_writers--;
245 }
247 if (pipe->inode)
248 mutex_unlock(&pipe->inode->i_mutex);
250 if (do_wakeup) {
251 smp_mb();
252 if (waitqueue_active(&pipe->wait))
253 wake_up_interruptible(&pipe->wait);
254 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
255 }
257 while (page_nr < spd->nr_pages)
258 page_cache_release(spd->pages[page_nr++]);
260 return ret;
261 }
263 static int
264 __generic_file_splice_read(struct file *in, loff_t *ppos,
265 struct pipe_inode_info *pipe, size_t len,
266 unsigned int flags)
267 {
268 struct address_space *mapping = in->f_mapping;
269 unsigned int loff, nr_pages;
270 struct page *pages[PIPE_BUFFERS];
271 struct partial_page partial[PIPE_BUFFERS];
272 struct page *page;
273 pgoff_t index, end_index;
274 loff_t isize;
275 size_t total_len;
276 int error, page_nr;
277 struct splice_pipe_desc spd = {
278 .pages = pages,
279 .partial = partial,
280 .flags = flags,
281 .ops = &page_cache_pipe_buf_ops,
282 };
284 index = *ppos >> PAGE_CACHE_SHIFT;
285 loff = *ppos & ~PAGE_CACHE_MASK;
286 nr_pages = (len + loff + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
288 if (nr_pages > PIPE_BUFFERS)
289 nr_pages = PIPE_BUFFERS;
291 /*
292 * Initiate read-ahead on this page range. however, don't call into
293 * read-ahead if this is a non-zero offset (we are likely doing small
294 * chunk splice and the page is already there) for a single page.
295 */
296 if (!loff || nr_pages > 1)
297 page_cache_readahead(mapping, &in->f_ra, in, index, nr_pages);
299 /*
300 * Now fill in the holes:
301 */
302 error = 0;
303 total_len = 0;
305 /*
306 * Lookup the (hopefully) full range of pages we need.
307 */
308 spd.nr_pages = find_get_pages_contig(mapping, index, nr_pages, pages);
310 /*
311 * If find_get_pages_contig() returned fewer pages than we needed,
312 * allocate the rest.
313 */
314 index += spd.nr_pages;
315 while (spd.nr_pages < nr_pages) {
316 /*
317 * Page could be there, find_get_pages_contig() breaks on
318 * the first hole.
319 */
320 page = find_get_page(mapping, index);
321 if (!page) {
322 /*
323 * Make sure the read-ahead engine is notified
324 * about this failure.
325 */
326 handle_ra_miss(mapping, &in->f_ra, index);
328 /*
329 * page didn't exist, allocate one.
330 */
331 page = page_cache_alloc_cold(mapping);
332 if (!page)
333 break;
335 error = add_to_page_cache_lru(page, mapping, index,
336 mapping_gfp_mask(mapping));
337 if (unlikely(error)) {
338 page_cache_release(page);
339 if (error == -EEXIST)
340 continue;
341 break;
342 }
343 /*
344 * add_to_page_cache() locks the page, unlock it
345 * to avoid convoluting the logic below even more.
346 */
347 unlock_page(page);
348 }
350 pages[spd.nr_pages++] = page;
351 index++;
352 }
354 /*
355 * Now loop over the map and see if we need to start IO on any
356 * pages, fill in the partial map, etc.
357 */
358 index = *ppos >> PAGE_CACHE_SHIFT;
359 nr_pages = spd.nr_pages;
360 spd.nr_pages = 0;
361 for (page_nr = 0; page_nr < nr_pages; page_nr++) {
362 unsigned int this_len;
364 if (!len)
365 break;
367 /*
368 * this_len is the max we'll use from this page
369 */
370 this_len = min_t(unsigned long, len, PAGE_CACHE_SIZE - loff);
371 page = pages[page_nr];
373 /*
374 * If the page isn't uptodate, we may need to start io on it
375 */
376 if (!PageUptodate(page)) {
377 /*
378 * If in nonblock mode then dont block on waiting
379 * for an in-flight io page
380 */
381 if (flags & SPLICE_F_NONBLOCK)
382 break;
384 lock_page(page);
386 /*
387 * page was truncated, stop here. if this isn't the
388 * first page, we'll just complete what we already
389 * added
390 */
391 if (!page->mapping) {
392 unlock_page(page);
393 break;
394 }
395 /*
396 * page was already under io and is now done, great
397 */
398 if (PageUptodate(page)) {
399 unlock_page(page);
400 goto fill_it;
401 }
403 /*
404 * need to read in the page
405 */
406 error = mapping->a_ops->readpage(in, page);
407 if (unlikely(error)) {
408 /*
409 * We really should re-lookup the page here,
410 * but it complicates things a lot. Instead
411 * lets just do what we already stored, and
412 * we'll get it the next time we are called.
413 */
414 if (error == AOP_TRUNCATED_PAGE)
415 error = 0;
417 break;
418 }
420 /*
421 * i_size must be checked after ->readpage().
422 */
423 isize = i_size_read(mapping->host);
424 end_index = (isize - 1) >> PAGE_CACHE_SHIFT;
425 if (unlikely(!isize || index > end_index))
426 break;
428 /*
429 * if this is the last page, see if we need to shrink
430 * the length and stop
431 */
432 if (end_index == index) {
433 loff = PAGE_CACHE_SIZE - (isize & ~PAGE_CACHE_MASK);
434 if (total_len + loff > isize)
435 break;
436 /*
437 * force quit after adding this page
438 */
439 len = this_len;
440 this_len = min(this_len, loff);
441 loff = 0;
442 }
443 }
444 fill_it:
445 partial[page_nr].offset = loff;
446 partial[page_nr].len = this_len;
447 len -= this_len;
448 total_len += this_len;
449 loff = 0;
450 spd.nr_pages++;
451 index++;
452 }
454 /*
455 * Release any pages at the end, if we quit early. 'i' is how far
456 * we got, 'nr_pages' is how many pages are in the map.
457 */
458 while (page_nr < nr_pages)
459 page_cache_release(pages[page_nr++]);
461 if (spd.nr_pages)
462 return splice_to_pipe(pipe, &spd);
464 return error;
465 }
467 /**
468 * generic_file_splice_read - splice data from file to a pipe
469 * @in: file to splice from
470 * @pipe: pipe to splice to
471 * @len: number of bytes to splice
472 * @flags: splice modifier flags
473 *
474 * Will read pages from given file and fill them into a pipe.
475 */
476 ssize_t generic_file_splice_read(struct file *in, loff_t *ppos,
477 struct pipe_inode_info *pipe, size_t len,
478 unsigned int flags)
479 {
480 ssize_t spliced;
481 int ret;
483 ret = 0;
484 spliced = 0;
486 while (len) {
487 ret = __generic_file_splice_read(in, ppos, pipe, len, flags);
489 if (ret < 0)
490 break;
491 else if (!ret) {
492 if (spliced)
493 break;
494 if (flags & SPLICE_F_NONBLOCK) {
495 ret = -EAGAIN;
496 break;
497 }
498 }
500 *ppos += ret;
501 len -= ret;
502 spliced += ret;
503 }
505 if (spliced)
506 return spliced;
508 return ret;
509 }
511 EXPORT_SYMBOL(generic_file_splice_read);
513 /*
514 * Send 'sd->len' bytes to socket from 'sd->file' at position 'sd->pos'
515 * using sendpage(). Return the number of bytes sent.
516 */
517 static int pipe_to_sendpage(struct pipe_inode_info *pipe,
518 struct pipe_buffer *buf, struct splice_desc *sd)
519 {
520 struct file *file = sd->file;
521 loff_t pos = sd->pos;
522 int ret, more;
524 ret = buf->ops->pin(pipe, buf);
525 if (!ret) {
526 more = (sd->flags & SPLICE_F_MORE) || sd->len < sd->total_len;
528 ret = file->f_op->sendpage(file, buf->page, buf->offset,
529 sd->len, &pos, more);
530 }
532 return ret;
533 }
535 /*
536 * This is a little more tricky than the file -> pipe splicing. There are
537 * basically three cases:
538 *
539 * - Destination page already exists in the address space and there
540 * are users of it. For that case we have no other option that
541 * copying the data. Tough luck.
542 * - Destination page already exists in the address space, but there
543 * are no users of it. Make sure it's uptodate, then drop it. Fall
544 * through to last case.
545 * - Destination page does not exist, we can add the pipe page to
546 * the page cache and avoid the copy.
547 *
548 * If asked to move pages to the output file (SPLICE_F_MOVE is set in
549 * sd->flags), we attempt to migrate pages from the pipe to the output
550 * file address space page cache. This is possible if no one else has
551 * the pipe page referenced outside of the pipe and page cache. If
552 * SPLICE_F_MOVE isn't set, or we cannot move the page, we simply create
553 * a new page in the output file page cache and fill/dirty that.
554 */
555 static int pipe_to_file(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
556 struct splice_desc *sd)
557 {
558 struct file *file = sd->file;
559 struct address_space *mapping = file->f_mapping;
560 gfp_t gfp_mask = mapping_gfp_mask(mapping);
561 unsigned int offset, this_len;
562 struct page *page;
563 pgoff_t index;
564 int ret;
566 /*
567 * make sure the data in this buffer is uptodate
568 */
569 ret = buf->ops->pin(pipe, buf);
570 if (unlikely(ret))
571 return ret;
573 index = sd->pos >> PAGE_CACHE_SHIFT;
574 offset = sd->pos & ~PAGE_CACHE_MASK;
576 this_len = sd->len;
577 if (this_len + offset > PAGE_CACHE_SIZE)
578 this_len = PAGE_CACHE_SIZE - offset;
580 /*
581 * Reuse buf page, if SPLICE_F_MOVE is set and we are doing a full
582 * page.
583 */
584 if ((sd->flags & SPLICE_F_MOVE) && this_len == PAGE_CACHE_SIZE) {
585 /*
586 * If steal succeeds, buf->page is now pruned from the
587 * pagecache and we can reuse it. The page will also be
588 * locked on successful return.
589 */
590 if (buf->ops->steal(pipe, buf))
591 goto find_page;
593 page = buf->page;
594 if (add_to_page_cache(page, mapping, index, gfp_mask)) {
595 unlock_page(page);
596 goto find_page;
597 }
599 page_cache_get(page);
601 if (!(buf->flags & PIPE_BUF_FLAG_LRU))
602 lru_cache_add(page);
603 } else {
604 find_page:
605 page = find_lock_page(mapping, index);
606 if (!page) {
607 ret = -ENOMEM;
608 page = page_cache_alloc_cold(mapping);
609 if (unlikely(!page))
610 goto out_ret;
612 /*
613 * This will also lock the page
614 */
615 ret = add_to_page_cache_lru(page, mapping, index,
616 gfp_mask);
617 if (unlikely(ret))
618 goto out;
619 }
621 /*
622 * We get here with the page locked. If the page is also
623 * uptodate, we don't need to do more. If it isn't, we
624 * may need to bring it in if we are not going to overwrite
625 * the full page.
626 */
627 if (!PageUptodate(page)) {
628 if (this_len < PAGE_CACHE_SIZE) {
629 ret = mapping->a_ops->readpage(file, page);
630 if (unlikely(ret))
631 goto out;
633 lock_page(page);
635 if (!PageUptodate(page)) {
636 /*
637 * Page got invalidated, repeat.
638 */
639 if (!page->mapping) {
640 unlock_page(page);
641 page_cache_release(page);
642 goto find_page;
643 }
644 ret = -EIO;
645 goto out;
646 }
647 } else
648 SetPageUptodate(page);
649 }
650 }
652 ret = mapping->a_ops->prepare_write(file, page, offset, offset+this_len);
653 if (unlikely(ret)) {
654 loff_t isize = i_size_read(mapping->host);
656 if (ret != AOP_TRUNCATED_PAGE)
657 unlock_page(page);
658 page_cache_release(page);
659 if (ret == AOP_TRUNCATED_PAGE)
660 goto find_page;
662 /*
663 * prepare_write() may have instantiated a few blocks
664 * outside i_size. Trim these off again.
665 */
666 if (sd->pos + this_len > isize)
667 vmtruncate(mapping->host, isize);
669 goto out_ret;
670 }
672 if (buf->page != page) {
673 /*
674 * Careful, ->map() uses KM_USER0!
675 */
676 char *src = buf->ops->map(pipe, buf, 1);
677 char *dst = kmap_atomic(page, KM_USER1);
679 memcpy(dst + offset, src + buf->offset, this_len);
680 flush_dcache_page(page);
681 kunmap_atomic(dst, KM_USER1);
682 buf->ops->unmap(pipe, buf, src);
683 }
685 ret = mapping->a_ops->commit_write(file, page, offset, offset+this_len);
686 if (!ret) {
687 /*
688 * Return the number of bytes written and mark page as
689 * accessed, we are now done!
690 */
691 ret = this_len;
692 mark_page_accessed(page);
693 balance_dirty_pages_ratelimited(mapping);
694 } else if (ret == AOP_TRUNCATED_PAGE) {
695 page_cache_release(page);
696 goto find_page;
697 }
698 out:
699 page_cache_release(page);
700 unlock_page(page);
701 out_ret:
702 return ret;
703 }
705 /*
706 * Pipe input worker. Most of this logic works like a regular pipe, the
707 * key here is the 'actor' worker passed in that actually moves the data
708 * to the wanted destination. See pipe_to_file/pipe_to_sendpage above.
709 */
710 ssize_t splice_from_pipe(struct pipe_inode_info *pipe, struct file *out,
711 loff_t *ppos, size_t len, unsigned int flags,
712 splice_actor *actor)
713 {
714 int ret, do_wakeup, err;
715 struct splice_desc sd;
717 ret = 0;
718 do_wakeup = 0;
720 sd.total_len = len;
721 sd.flags = flags;
722 sd.file = out;
723 sd.pos = *ppos;
725 if (pipe->inode)
726 mutex_lock(&pipe->inode->i_mutex);
728 for (;;) {
729 if (pipe->nrbufs) {
730 struct pipe_buffer *buf = pipe->bufs + pipe->curbuf;
731 struct pipe_buf_operations *ops = buf->ops;
733 sd.len = buf->len;
734 if (sd.len > sd.total_len)
735 sd.len = sd.total_len;
737 err = actor(pipe, buf, &sd);
738 if (err <= 0) {
739 if (!ret && err != -ENODATA)
740 ret = err;
742 break;
743 }
745 ret += err;
746 buf->offset += err;
747 buf->len -= err;
749 sd.len -= err;
750 sd.pos += err;
751 sd.total_len -= err;
752 if (sd.len)
753 continue;
755 if (!buf->len) {
756 buf->ops = NULL;
757 ops->release(pipe, buf);
758 pipe->curbuf = (pipe->curbuf + 1) & (PIPE_BUFFERS - 1);
759 pipe->nrbufs--;
760 if (pipe->inode)
761 do_wakeup = 1;
762 }
764 if (!sd.total_len)
765 break;
766 }
768 if (pipe->nrbufs)
769 continue;
770 if (!pipe->writers)
771 break;
772 if (!pipe->waiting_writers) {
773 if (ret)
774 break;
775 }
777 if (flags & SPLICE_F_NONBLOCK) {
778 if (!ret)
779 ret = -EAGAIN;
780 break;
781 }
783 if (signal_pending(current)) {
784 if (!ret)
785 ret = -ERESTARTSYS;
786 break;
787 }
789 if (do_wakeup) {
790 smp_mb();
791 if (waitqueue_active(&pipe->wait))
792 wake_up_interruptible_sync(&pipe->wait);
793 kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
794 do_wakeup = 0;
795 }
797 pipe_wait(pipe);
798 }
800 if (pipe->inode)
801 mutex_unlock(&pipe->inode->i_mutex);
803 if (do_wakeup) {
804 smp_mb();
805 if (waitqueue_active(&pipe->wait))
806 wake_up_interruptible(&pipe->wait);
807 kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
808 }
810 return ret;
811 }
813 /**
814 * generic_file_splice_write - splice data from a pipe to a file
815 * @pipe: pipe info
816 * @out: file to write to
817 * @len: number of bytes to splice
818 * @flags: splice modifier flags
819 *
820 * Will either move or copy pages (determined by @flags options) from
821 * the given pipe inode to the given file.
822 *
823 */
824 ssize_t
825 generic_file_splice_write(struct pipe_inode_info *pipe, struct file *out,
826 loff_t *ppos, size_t len, unsigned int flags)
827 {
828 struct address_space *mapping = out->f_mapping;
829 ssize_t ret;
831 ret = splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_file);
832 if (ret > 0) {
833 struct inode *inode = mapping->host;
835 *ppos += ret;
837 /*
838 * If file or inode is SYNC and we actually wrote some data,
839 * sync it.
840 */
841 if (unlikely((out->f_flags & O_SYNC) || IS_SYNC(inode))) {
842 int err;
844 mutex_lock(&inode->i_mutex);
845 err = generic_osync_inode(inode, mapping,
846 OSYNC_METADATA|OSYNC_DATA);
847 mutex_unlock(&inode->i_mutex);
849 if (err)
850 ret = err;
851 }
852 }
854 return ret;
855 }
857 EXPORT_SYMBOL(generic_file_splice_write);
859 /**
860 * generic_splice_sendpage - splice data from a pipe to a socket
861 * @inode: pipe inode
862 * @out: socket to write to
863 * @len: number of bytes to splice
864 * @flags: splice modifier flags
865 *
866 * Will send @len bytes from the pipe to a network socket. No data copying
867 * is involved.
868 *
869 */
870 ssize_t generic_splice_sendpage(struct pipe_inode_info *pipe, struct file *out,
871 loff_t *ppos, size_t len, unsigned int flags)
872 {
873 return splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_sendpage);
874 }
876 EXPORT_SYMBOL(generic_splice_sendpage);
878 /*
879 * Attempt to initiate a splice from pipe to file.
880 */
881 static long do_splice_from(struct pipe_inode_info *pipe, struct file *out,
882 loff_t *ppos, size_t len, unsigned int flags)
883 {
884 int ret;
886 if (unlikely(!out->f_op || !out->f_op->splice_write))
887 return -EINVAL;
889 if (unlikely(!(out->f_mode & FMODE_WRITE)))
890 return -EBADF;
892 ret = rw_verify_area(WRITE, out, ppos, len);
893 if (unlikely(ret < 0))
894 return ret;
896 return out->f_op->splice_write(pipe, out, ppos, len, flags);
897 }
899 /*
900 * Attempt to initiate a splice from a file to a pipe.
901 */
902 static long do_splice_to(struct file *in, loff_t *ppos,
903 struct pipe_inode_info *pipe, size_t len,
904 unsigned int flags)
905 {
906 loff_t isize, left;
907 int ret;
909 if (unlikely(!in->f_op || !in->f_op->splice_read))
910 return -EINVAL;
912 if (unlikely(!(in->f_mode & FMODE_READ)))
913 return -EBADF;
915 ret = rw_verify_area(READ, in, ppos, len);
916 if (unlikely(ret < 0))
917 return ret;
919 isize = i_size_read(in->f_mapping->host);
920 if (unlikely(*ppos >= isize))
921 return 0;
923 left = isize - *ppos;
924 if (unlikely(left < len))
925 len = left;
927 return in->f_op->splice_read(in, ppos, pipe, len, flags);
928 }
930 long do_splice_direct(struct file *in, loff_t *ppos, struct file *out,
931 size_t len, unsigned int flags)
932 {
933 struct pipe_inode_info *pipe;
934 long ret, bytes;
935 loff_t out_off;
936 umode_t i_mode;
937 int i;
939 /*
940 * We require the input being a regular file, as we don't want to
941 * randomly drop data for eg socket -> socket splicing. Use the
942 * piped splicing for that!
943 */
944 i_mode = in->f_dentry->d_inode->i_mode;
945 if (unlikely(!S_ISREG(i_mode) && !S_ISBLK(i_mode)))
946 return -EINVAL;
948 /*
949 * neither in nor out is a pipe, setup an internal pipe attached to
950 * 'out' and transfer the wanted data from 'in' to 'out' through that
951 */
952 pipe = current->splice_pipe;
953 if (unlikely(!pipe)) {
954 pipe = alloc_pipe_info(NULL);
955 if (!pipe)
956 return -ENOMEM;
958 /*
959 * We don't have an immediate reader, but we'll read the stuff
960 * out of the pipe right after the splice_to_pipe(). So set
961 * PIPE_READERS appropriately.
962 */
963 pipe->readers = 1;
965 current->splice_pipe = pipe;
966 }
968 /*
969 * Do the splice.
970 */
971 ret = 0;
972 bytes = 0;
973 out_off = 0;
975 while (len) {
976 size_t read_len, max_read_len;
978 /*
979 * Do at most PIPE_BUFFERS pages worth of transfer:
980 */
981 max_read_len = min(len, (size_t)(PIPE_BUFFERS*PAGE_SIZE));
983 ret = do_splice_to(in, ppos, pipe, max_read_len, flags);
984 if (unlikely(ret < 0))
985 goto out_release;
987 read_len = ret;
989 /*
990 * NOTE: nonblocking mode only applies to the input. We
991 * must not do the output in nonblocking mode as then we
992 * could get stuck data in the internal pipe:
993 */
994 ret = do_splice_from(pipe, out, &out_off, read_len,
995 flags & ~SPLICE_F_NONBLOCK);
996 if (unlikely(ret < 0))
997 goto out_release;
999 bytes += ret;
1000 len -= ret;
1002 /*
1003 * In nonblocking mode, if we got back a short read then
1004 * that was due to either an IO error or due to the
1005 * pagecache entry not being there. In the IO error case
1006 * the _next_ splice attempt will produce a clean IO error
1007 * return value (not a short read), so in both cases it's
1008 * correct to break out of the loop here:
1009 */
1010 if ((flags & SPLICE_F_NONBLOCK) && (read_len < max_read_len))
1011 break;
1014 pipe->nrbufs = pipe->curbuf = 0;
1016 return bytes;
1018 out_release:
1019 /*
1020 * If we did an incomplete transfer we must release
1021 * the pipe buffers in question:
1022 */
1023 for (i = 0; i < PIPE_BUFFERS; i++) {
1024 struct pipe_buffer *buf = pipe->bufs + i;
1026 if (buf->ops) {
1027 buf->ops->release(pipe, buf);
1028 buf->ops = NULL;
1031 pipe->nrbufs = pipe->curbuf = 0;
1033 /*
1034 * If we transferred some data, return the number of bytes:
1035 */
1036 if (bytes > 0)
1037 return bytes;
1039 return ret;
1042 EXPORT_SYMBOL(do_splice_direct);
1044 /*
1045 * Determine where to splice to/from.
1046 */
1047 static long do_splice(struct file *in, loff_t __user *off_in,
1048 struct file *out, loff_t __user *off_out,
1049 size_t len, unsigned int flags)
1051 struct pipe_inode_info *pipe;
1052 loff_t offset, *off;
1053 long ret;
1055 pipe = in->f_dentry->d_inode->i_pipe;
1056 if (pipe) {
1057 if (off_in)
1058 return -ESPIPE;
1059 if (off_out) {
1060 if (out->f_op->llseek == no_llseek)
1061 return -EINVAL;
1062 if (copy_from_user(&offset, off_out, sizeof(loff_t)))
1063 return -EFAULT;
1064 off = &offset;
1065 } else
1066 off = &out->f_pos;
1068 ret = do_splice_from(pipe, out, off, len, flags);
1070 if (off_out && copy_to_user(off_out, off, sizeof(loff_t)))
1071 ret = -EFAULT;
1073 return ret;
1076 pipe = out->f_dentry->d_inode->i_pipe;
1077 if (pipe) {
1078 if (off_out)
1079 return -ESPIPE;
1080 if (off_in) {
1081 if (in->f_op->llseek == no_llseek)
1082 return -EINVAL;
1083 if (copy_from_user(&offset, off_in, sizeof(loff_t)))
1084 return -EFAULT;
1085 off = &offset;
1086 } else
1087 off = &in->f_pos;
1089 ret = do_splice_to(in, off, pipe, len, flags);
1091 if (off_in && copy_to_user(off_in, off, sizeof(loff_t)))
1092 ret = -EFAULT;
1094 return ret;
1097 return -EINVAL;
1100 /*
1101 * Map an iov into an array of pages and offset/length tupples. With the
1102 * partial_page structure, we can map several non-contiguous ranges into
1103 * our ones pages[] map instead of splitting that operation into pieces.
1104 * Could easily be exported as a generic helper for other users, in which
1105 * case one would probably want to add a 'max_nr_pages' parameter as well.
1106 */
1107 static int get_iovec_page_array(const struct iovec __user *iov,
1108 unsigned int nr_vecs, struct page **pages,
1109 struct partial_page *partial, int aligned)
1111 int buffers = 0, error = 0;
1113 /*
1114 * It's ok to take the mmap_sem for reading, even
1115 * across a "get_user()".
1116 */
1117 down_read(&current->mm->mmap_sem);
1119 while (nr_vecs) {
1120 unsigned long off, npages;
1121 void __user *base;
1122 size_t len;
1123 int i;
1125 /*
1126 * Get user address base and length for this iovec.
1127 */
1128 error = get_user(base, &iov->iov_base);
1129 if (unlikely(error))
1130 break;
1131 error = get_user(len, &iov->iov_len);
1132 if (unlikely(error))
1133 break;
1135 /*
1136 * Sanity check this iovec. 0 read succeeds.
1137 */
1138 if (unlikely(!len))
1139 break;
1140 error = -EFAULT;
1141 if (unlikely(!base))
1142 break;
1144 if (unlikely(!access_ok(VERIFY_READ, base, len)))
1145 break;
1147 /*
1148 * Get this base offset and number of pages, then map
1149 * in the user pages.
1150 */
1151 off = (unsigned long) base & ~PAGE_MASK;
1153 /*
1154 * If asked for alignment, the offset must be zero and the
1155 * length a multiple of the PAGE_SIZE.
1156 */
1157 error = -EINVAL;
1158 if (aligned && (off || len & ~PAGE_MASK))
1159 break;
1161 npages = (off + len + PAGE_SIZE - 1) >> PAGE_SHIFT;
1162 if (npages > PIPE_BUFFERS - buffers)
1163 npages = PIPE_BUFFERS - buffers;
1165 error = get_user_pages(current, current->mm,
1166 (unsigned long) base, npages, 0, 0,
1167 &pages[buffers], NULL);
1169 if (unlikely(error <= 0))
1170 break;
1172 /*
1173 * Fill this contiguous range into the partial page map.
1174 */
1175 for (i = 0; i < error; i++) {
1176 const int plen = min_t(size_t, len, PAGE_SIZE - off);
1178 partial[buffers].offset = off;
1179 partial[buffers].len = plen;
1181 off = 0;
1182 len -= plen;
1183 buffers++;
1186 /*
1187 * We didn't complete this iov, stop here since it probably
1188 * means we have to move some of this into a pipe to
1189 * be able to continue.
1190 */
1191 if (len)
1192 break;
1194 /*
1195 * Don't continue if we mapped fewer pages than we asked for,
1196 * or if we mapped the max number of pages that we have
1197 * room for.
1198 */
1199 if (error < npages || buffers == PIPE_BUFFERS)
1200 break;
1202 nr_vecs--;
1203 iov++;
1206 up_read(&current->mm->mmap_sem);
1208 if (buffers)
1209 return buffers;
1211 return error;
1214 /*
1215 * vmsplice splices a user address range into a pipe. It can be thought of
1216 * as splice-from-memory, where the regular splice is splice-from-file (or
1217 * to file). In both cases the output is a pipe, naturally.
1219 * Note that vmsplice only supports splicing _from_ user memory to a pipe,
1220 * not the other way around. Splicing from user memory is a simple operation
1221 * that can be supported without any funky alignment restrictions or nasty
1222 * vm tricks. We simply map in the user memory and fill them into a pipe.
1223 * The reverse isn't quite as easy, though. There are two possible solutions
1224 * for that:
1226 * - memcpy() the data internally, at which point we might as well just
1227 * do a regular read() on the buffer anyway.
1228 * - Lots of nasty vm tricks, that are neither fast nor flexible (it
1229 * has restriction limitations on both ends of the pipe).
1231 * Alas, it isn't here.
1233 */
1234 static long do_vmsplice(struct file *file, const struct iovec __user *iov,
1235 unsigned long nr_segs, unsigned int flags)
1237 struct pipe_inode_info *pipe = file->f_dentry->d_inode->i_pipe;
1238 struct page *pages[PIPE_BUFFERS];
1239 struct partial_page partial[PIPE_BUFFERS];
1240 struct splice_pipe_desc spd = {
1241 .pages = pages,
1242 .partial = partial,
1243 .flags = flags,
1244 .ops = &user_page_pipe_buf_ops,
1245 };
1247 if (unlikely(!pipe))
1248 return -EBADF;
1249 if (unlikely(nr_segs > UIO_MAXIOV))
1250 return -EINVAL;
1251 else if (unlikely(!nr_segs))
1252 return 0;
1254 spd.nr_pages = get_iovec_page_array(iov, nr_segs, pages, partial,
1255 flags & SPLICE_F_GIFT);
1256 if (spd.nr_pages <= 0)
1257 return spd.nr_pages;
1259 return splice_to_pipe(pipe, &spd);
1262 asmlinkage long sys_vmsplice(int fd, const struct iovec __user *iov,
1263 unsigned long nr_segs, unsigned int flags)
1265 struct file *file;
1266 long error;
1267 int fput;
1269 error = -EBADF;
1270 file = fget_light(fd, &fput);
1271 if (file) {
1272 if (file->f_mode & FMODE_WRITE)
1273 error = do_vmsplice(file, iov, nr_segs, flags);
1275 fput_light(file, fput);
1278 return error;
1281 asmlinkage long sys_splice(int fd_in, loff_t __user *off_in,
1282 int fd_out, loff_t __user *off_out,
1283 size_t len, unsigned int flags)
1285 long error;
1286 struct file *in, *out;
1287 int fput_in, fput_out;
1289 if (unlikely(!len))
1290 return 0;
1292 error = -EBADF;
1293 in = fget_light(fd_in, &fput_in);
1294 if (in) {
1295 if (in->f_mode & FMODE_READ) {
1296 out = fget_light(fd_out, &fput_out);
1297 if (out) {
1298 if (out->f_mode & FMODE_WRITE)
1299 error = do_splice(in, off_in,
1300 out, off_out,
1301 len, flags);
1302 fput_light(out, fput_out);
1306 fput_light(in, fput_in);
1309 return error;
1312 /*
1313 * Make sure there's data to read. Wait for input if we can, otherwise
1314 * return an appropriate error.
1315 */
1316 static int link_ipipe_prep(struct pipe_inode_info *pipe, unsigned int flags)
1318 int ret;
1320 /*
1321 * Check ->nrbufs without the inode lock first. This function
1322 * is speculative anyways, so missing one is ok.
1323 */
1324 if (pipe->nrbufs)
1325 return 0;
1327 ret = 0;
1328 mutex_lock(&pipe->inode->i_mutex);
1330 while (!pipe->nrbufs) {
1331 if (signal_pending(current)) {
1332 ret = -ERESTARTSYS;
1333 break;
1335 if (!pipe->writers)
1336 break;
1337 if (!pipe->waiting_writers) {
1338 if (flags & SPLICE_F_NONBLOCK) {
1339 ret = -EAGAIN;
1340 break;
1343 pipe_wait(pipe);
1346 mutex_unlock(&pipe->inode->i_mutex);
1347 return ret;
1350 /*
1351 * Make sure there's writeable room. Wait for room if we can, otherwise
1352 * return an appropriate error.
1353 */
1354 static int link_opipe_prep(struct pipe_inode_info *pipe, unsigned int flags)
1356 int ret;
1358 /*
1359 * Check ->nrbufs without the inode lock first. This function
1360 * is speculative anyways, so missing one is ok.
1361 */
1362 if (pipe->nrbufs < PIPE_BUFFERS)
1363 return 0;
1365 ret = 0;
1366 mutex_lock(&pipe->inode->i_mutex);
1368 while (pipe->nrbufs >= PIPE_BUFFERS) {
1369 if (!pipe->readers) {
1370 send_sig(SIGPIPE, current, 0);
1371 ret = -EPIPE;
1372 break;
1374 if (flags & SPLICE_F_NONBLOCK) {
1375 ret = -EAGAIN;
1376 break;
1378 if (signal_pending(current)) {
1379 ret = -ERESTARTSYS;
1380 break;
1382 pipe->waiting_writers++;
1383 pipe_wait(pipe);
1384 pipe->waiting_writers--;
1387 mutex_unlock(&pipe->inode->i_mutex);
1388 return ret;
1391 /*
1392 * Link contents of ipipe to opipe.
1393 */
1394 static int link_pipe(struct pipe_inode_info *ipipe,
1395 struct pipe_inode_info *opipe,
1396 size_t len, unsigned int flags)
1398 struct pipe_buffer *ibuf, *obuf;
1399 int ret = 0, i = 0, nbuf;
1401 /*
1402 * Potential ABBA deadlock, work around it by ordering lock
1403 * grabbing by inode address. Otherwise two different processes
1404 * could deadlock (one doing tee from A -> B, the other from B -> A).
1405 */
1406 if (ipipe->inode < opipe->inode) {
1407 mutex_lock_nested(&ipipe->inode->i_mutex, I_MUTEX_PARENT);
1408 mutex_lock_nested(&opipe->inode->i_mutex, I_MUTEX_CHILD);
1409 } else {
1410 mutex_lock_nested(&opipe->inode->i_mutex, I_MUTEX_PARENT);
1411 mutex_lock_nested(&ipipe->inode->i_mutex, I_MUTEX_CHILD);
1414 do {
1415 if (!opipe->readers) {
1416 send_sig(SIGPIPE, current, 0);
1417 if (!ret)
1418 ret = -EPIPE;
1419 break;
1422 /*
1423 * If we have iterated all input buffers or ran out of
1424 * output room, break.
1425 */
1426 if (i >= ipipe->nrbufs || opipe->nrbufs >= PIPE_BUFFERS)
1427 break;
1429 ibuf = ipipe->bufs + ((ipipe->curbuf + i) & (PIPE_BUFFERS - 1));
1430 nbuf = (opipe->curbuf + opipe->nrbufs) & (PIPE_BUFFERS - 1);
1432 /*
1433 * Get a reference to this pipe buffer,
1434 * so we can copy the contents over.
1435 */
1436 ibuf->ops->get(ipipe, ibuf);
1438 obuf = opipe->bufs + nbuf;
1439 *obuf = *ibuf;
1441 /*
1442 * Don't inherit the gift flag, we need to
1443 * prevent multiple steals of this page.
1444 */
1445 obuf->flags &= ~PIPE_BUF_FLAG_GIFT;
1447 if (obuf->len > len)
1448 obuf->len = len;
1450 opipe->nrbufs++;
1451 ret += obuf->len;
1452 len -= obuf->len;
1453 i++;
1454 } while (len);
1456 mutex_unlock(&ipipe->inode->i_mutex);
1457 mutex_unlock(&opipe->inode->i_mutex);
1459 /*
1460 * If we put data in the output pipe, wakeup any potential readers.
1461 */
1462 if (ret > 0) {
1463 smp_mb();
1464 if (waitqueue_active(&opipe->wait))
1465 wake_up_interruptible(&opipe->wait);
1466 kill_fasync(&opipe->fasync_readers, SIGIO, POLL_IN);
1469 return ret;
1472 /*
1473 * This is a tee(1) implementation that works on pipes. It doesn't copy
1474 * any data, it simply references the 'in' pages on the 'out' pipe.
1475 * The 'flags' used are the SPLICE_F_* variants, currently the only
1476 * applicable one is SPLICE_F_NONBLOCK.
1477 */
1478 static long do_tee(struct file *in, struct file *out, size_t len,
1479 unsigned int flags)
1481 struct pipe_inode_info *ipipe = in->f_dentry->d_inode->i_pipe;
1482 struct pipe_inode_info *opipe = out->f_dentry->d_inode->i_pipe;
1483 int ret = -EINVAL;
1485 /*
1486 * Duplicate the contents of ipipe to opipe without actually
1487 * copying the data.
1488 */
1489 if (ipipe && opipe && ipipe != opipe) {
1490 /*
1491 * Keep going, unless we encounter an error. The ipipe/opipe
1492 * ordering doesn't really matter.
1493 */
1494 ret = link_ipipe_prep(ipipe, flags);
1495 if (!ret) {
1496 ret = link_opipe_prep(opipe, flags);
1497 if (!ret) {
1498 ret = link_pipe(ipipe, opipe, len, flags);
1499 if (!ret && (flags & SPLICE_F_NONBLOCK))
1500 ret = -EAGAIN;
1505 return ret;
1508 asmlinkage long sys_tee(int fdin, int fdout, size_t len, unsigned int flags)
1510 struct file *in;
1511 int error, fput_in;
1513 if (unlikely(!len))
1514 return 0;
1516 error = -EBADF;
1517 in = fget_light(fdin, &fput_in);
1518 if (in) {
1519 if (in->f_mode & FMODE_READ) {
1520 int fput_out;
1521 struct file *out = fget_light(fdout, &fput_out);
1523 if (out) {
1524 if (out->f_mode & FMODE_WRITE)
1525 error = do_tee(in, out, len, flags);
1526 fput_light(out, fput_out);
1529 fput_light(in, fput_in);
1532 return error;