can: Fix raw_getname() leak
[linux-2.6/linux-acpi-2.6/ibm-acpi-2.6.git] / fs / splice.c
blob2f2d8c1e7a2817b2a0ff5eb6733d4a312803f996
1 /*
2 * "splice": joining two ropes together by interweaving their strands.
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.
8 * The traditional unix read/write is extended with a "splice()" operation
9 * that transfers data buffers to or from a pipe buffer.
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.
15 * Copyright (C) 2005-2006 Jens Axboe <axboe@kernel.dk>
16 * Copyright (C) 2005-2006 Linus Torvalds <torvalds@osdl.org>
17 * Copyright (C) 2006 Ingo Molnar <mingo@elte.hu>
20 #include <linux/fs.h>
21 #include <linux/file.h>
22 #include <linux/pagemap.h>
23 #include <linux/splice.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>
31 #include <linux/security.h>
34 * Attempt to steal a page from a pipe buffer. This should perhaps go into
35 * a vm helper function, it's already simplified quite a bit by the
36 * addition of remove_mapping(). If success is returned, the caller may
37 * attempt to reuse this page for another destination.
39 static int page_cache_pipe_buf_steal(struct pipe_inode_info *pipe,
40 struct pipe_buffer *buf)
42 struct page *page = buf->page;
43 struct address_space *mapping;
45 lock_page(page);
47 mapping = page_mapping(page);
48 if (mapping) {
49 WARN_ON(!PageUptodate(page));
52 * At least for ext2 with nobh option, we need to wait on
53 * writeback completing on this page, since we'll remove it
54 * from the pagecache. Otherwise truncate wont wait on the
55 * page, allowing the disk blocks to be reused by someone else
56 * before we actually wrote our data to them. fs corruption
57 * ensues.
59 wait_on_page_writeback(page);
61 if (PagePrivate(page) && !try_to_release_page(page, GFP_KERNEL))
62 goto out_unlock;
65 * If we succeeded in removing the mapping, set LRU flag
66 * and return good.
68 if (remove_mapping(mapping, page)) {
69 buf->flags |= PIPE_BUF_FLAG_LRU;
70 return 0;
75 * Raced with truncate or failed to remove page from current
76 * address space, unlock and return failure.
78 out_unlock:
79 unlock_page(page);
80 return 1;
83 static void page_cache_pipe_buf_release(struct pipe_inode_info *pipe,
84 struct pipe_buffer *buf)
86 page_cache_release(buf->page);
87 buf->flags &= ~PIPE_BUF_FLAG_LRU;
91 * Check whether the contents of buf is OK to access. Since the content
92 * is a page cache page, IO may be in flight.
94 static int page_cache_pipe_buf_confirm(struct pipe_inode_info *pipe,
95 struct pipe_buffer *buf)
97 struct page *page = buf->page;
98 int err;
100 if (!PageUptodate(page)) {
101 lock_page(page);
104 * Page got truncated/unhashed. This will cause a 0-byte
105 * splice, if this is the first page.
107 if (!page->mapping) {
108 err = -ENODATA;
109 goto error;
113 * Uh oh, read-error from disk.
115 if (!PageUptodate(page)) {
116 err = -EIO;
117 goto error;
121 * Page is ok afterall, we are done.
123 unlock_page(page);
126 return 0;
127 error:
128 unlock_page(page);
129 return err;
132 static const struct pipe_buf_operations page_cache_pipe_buf_ops = {
133 .can_merge = 0,
134 .map = generic_pipe_buf_map,
135 .unmap = generic_pipe_buf_unmap,
136 .confirm = page_cache_pipe_buf_confirm,
137 .release = page_cache_pipe_buf_release,
138 .steal = page_cache_pipe_buf_steal,
139 .get = generic_pipe_buf_get,
142 static int user_page_pipe_buf_steal(struct pipe_inode_info *pipe,
143 struct pipe_buffer *buf)
145 if (!(buf->flags & PIPE_BUF_FLAG_GIFT))
146 return 1;
148 buf->flags |= PIPE_BUF_FLAG_LRU;
149 return generic_pipe_buf_steal(pipe, buf);
152 static const struct pipe_buf_operations user_page_pipe_buf_ops = {
153 .can_merge = 0,
154 .map = generic_pipe_buf_map,
155 .unmap = generic_pipe_buf_unmap,
156 .confirm = generic_pipe_buf_confirm,
157 .release = page_cache_pipe_buf_release,
158 .steal = user_page_pipe_buf_steal,
159 .get = generic_pipe_buf_get,
163 * splice_to_pipe - fill passed data into a pipe
164 * @pipe: pipe to fill
165 * @spd: data to fill
167 * Description:
168 * @spd contains a map of pages and len/offset tuples, along with
169 * the struct pipe_buf_operations associated with these pages. This
170 * function will link that data to the pipe.
173 ssize_t splice_to_pipe(struct pipe_inode_info *pipe,
174 struct splice_pipe_desc *spd)
176 unsigned int spd_pages = spd->nr_pages;
177 int ret, do_wakeup, page_nr;
179 ret = 0;
180 do_wakeup = 0;
181 page_nr = 0;
183 if (pipe->inode)
184 mutex_lock(&pipe->inode->i_mutex);
186 for (;;) {
187 if (!pipe->readers) {
188 send_sig(SIGPIPE, current, 0);
189 if (!ret)
190 ret = -EPIPE;
191 break;
194 if (pipe->nrbufs < PIPE_BUFFERS) {
195 int newbuf = (pipe->curbuf + pipe->nrbufs) & (PIPE_BUFFERS - 1);
196 struct pipe_buffer *buf = pipe->bufs + newbuf;
198 buf->page = spd->pages[page_nr];
199 buf->offset = spd->partial[page_nr].offset;
200 buf->len = spd->partial[page_nr].len;
201 buf->private = spd->partial[page_nr].private;
202 buf->ops = spd->ops;
203 if (spd->flags & SPLICE_F_GIFT)
204 buf->flags |= PIPE_BUF_FLAG_GIFT;
206 pipe->nrbufs++;
207 page_nr++;
208 ret += buf->len;
210 if (pipe->inode)
211 do_wakeup = 1;
213 if (!--spd->nr_pages)
214 break;
215 if (pipe->nrbufs < PIPE_BUFFERS)
216 continue;
218 break;
221 if (spd->flags & SPLICE_F_NONBLOCK) {
222 if (!ret)
223 ret = -EAGAIN;
224 break;
227 if (signal_pending(current)) {
228 if (!ret)
229 ret = -ERESTARTSYS;
230 break;
233 if (do_wakeup) {
234 smp_mb();
235 if (waitqueue_active(&pipe->wait))
236 wake_up_interruptible_sync(&pipe->wait);
237 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
238 do_wakeup = 0;
241 pipe->waiting_writers++;
242 pipe_wait(pipe);
243 pipe->waiting_writers--;
246 if (pipe->inode) {
247 mutex_unlock(&pipe->inode->i_mutex);
249 if (do_wakeup) {
250 smp_mb();
251 if (waitqueue_active(&pipe->wait))
252 wake_up_interruptible(&pipe->wait);
253 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
257 while (page_nr < spd_pages)
258 spd->spd_release(spd, page_nr++);
260 return ret;
263 static void spd_release_page(struct splice_pipe_desc *spd, unsigned int i)
265 page_cache_release(spd->pages[i]);
268 static int
269 __generic_file_splice_read(struct file *in, loff_t *ppos,
270 struct pipe_inode_info *pipe, size_t len,
271 unsigned int flags)
273 struct address_space *mapping = in->f_mapping;
274 unsigned int loff, nr_pages, req_pages;
275 struct page *pages[PIPE_BUFFERS];
276 struct partial_page partial[PIPE_BUFFERS];
277 struct page *page;
278 pgoff_t index, end_index;
279 loff_t isize;
280 int error, page_nr;
281 struct splice_pipe_desc spd = {
282 .pages = pages,
283 .partial = partial,
284 .flags = flags,
285 .ops = &page_cache_pipe_buf_ops,
286 .spd_release = spd_release_page,
289 index = *ppos >> PAGE_CACHE_SHIFT;
290 loff = *ppos & ~PAGE_CACHE_MASK;
291 req_pages = (len + loff + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
292 nr_pages = min(req_pages, (unsigned)PIPE_BUFFERS);
295 * Lookup the (hopefully) full range of pages we need.
297 spd.nr_pages = find_get_pages_contig(mapping, index, nr_pages, pages);
298 index += spd.nr_pages;
301 * If find_get_pages_contig() returned fewer pages than we needed,
302 * readahead/allocate the rest and fill in the holes.
304 if (spd.nr_pages < nr_pages)
305 page_cache_sync_readahead(mapping, &in->f_ra, in,
306 index, req_pages - spd.nr_pages);
308 error = 0;
309 while (spd.nr_pages < nr_pages) {
311 * Page could be there, find_get_pages_contig() breaks on
312 * the first hole.
314 page = find_get_page(mapping, index);
315 if (!page) {
317 * page didn't exist, allocate one.
319 page = page_cache_alloc_cold(mapping);
320 if (!page)
321 break;
323 error = add_to_page_cache_lru(page, mapping, index,
324 mapping_gfp_mask(mapping));
325 if (unlikely(error)) {
326 page_cache_release(page);
327 if (error == -EEXIST)
328 continue;
329 break;
332 * add_to_page_cache() locks the page, unlock it
333 * to avoid convoluting the logic below even more.
335 unlock_page(page);
338 pages[spd.nr_pages++] = page;
339 index++;
343 * Now loop over the map and see if we need to start IO on any
344 * pages, fill in the partial map, etc.
346 index = *ppos >> PAGE_CACHE_SHIFT;
347 nr_pages = spd.nr_pages;
348 spd.nr_pages = 0;
349 for (page_nr = 0; page_nr < nr_pages; page_nr++) {
350 unsigned int this_len;
352 if (!len)
353 break;
356 * this_len is the max we'll use from this page
358 this_len = min_t(unsigned long, len, PAGE_CACHE_SIZE - loff);
359 page = pages[page_nr];
361 if (PageReadahead(page))
362 page_cache_async_readahead(mapping, &in->f_ra, in,
363 page, index, req_pages - page_nr);
366 * If the page isn't uptodate, we may need to start io on it
368 if (!PageUptodate(page)) {
370 * If in nonblock mode then dont block on waiting
371 * for an in-flight io page
373 if (flags & SPLICE_F_NONBLOCK) {
374 if (!trylock_page(page)) {
375 error = -EAGAIN;
376 break;
378 } else
379 lock_page(page);
382 * Page was truncated, or invalidated by the
383 * filesystem. Redo the find/create, but this time the
384 * page is kept locked, so there's no chance of another
385 * race with truncate/invalidate.
387 if (!page->mapping) {
388 unlock_page(page);
389 page = find_or_create_page(mapping, index,
390 mapping_gfp_mask(mapping));
392 if (!page) {
393 error = -ENOMEM;
394 break;
396 page_cache_release(pages[page_nr]);
397 pages[page_nr] = page;
400 * page was already under io and is now done, great
402 if (PageUptodate(page)) {
403 unlock_page(page);
404 goto fill_it;
408 * need to read in the page
410 error = mapping->a_ops->readpage(in, page);
411 if (unlikely(error)) {
413 * We really should re-lookup the page here,
414 * but it complicates things a lot. Instead
415 * lets just do what we already stored, and
416 * we'll get it the next time we are called.
418 if (error == AOP_TRUNCATED_PAGE)
419 error = 0;
421 break;
424 fill_it:
426 * i_size must be checked after PageUptodate.
428 isize = i_size_read(mapping->host);
429 end_index = (isize - 1) >> PAGE_CACHE_SHIFT;
430 if (unlikely(!isize || index > end_index))
431 break;
434 * if this is the last page, see if we need to shrink
435 * the length and stop
437 if (end_index == index) {
438 unsigned int plen;
441 * max good bytes in this page
443 plen = ((isize - 1) & ~PAGE_CACHE_MASK) + 1;
444 if (plen <= loff)
445 break;
448 * force quit after adding this page
450 this_len = min(this_len, plen - loff);
451 len = this_len;
454 partial[page_nr].offset = loff;
455 partial[page_nr].len = this_len;
456 len -= this_len;
457 loff = 0;
458 spd.nr_pages++;
459 index++;
463 * Release any pages at the end, if we quit early. 'page_nr' is how far
464 * we got, 'nr_pages' is how many pages are in the map.
466 while (page_nr < nr_pages)
467 page_cache_release(pages[page_nr++]);
468 in->f_ra.prev_pos = (loff_t)index << PAGE_CACHE_SHIFT;
470 if (spd.nr_pages)
471 return splice_to_pipe(pipe, &spd);
473 return error;
477 * generic_file_splice_read - splice data from file to a pipe
478 * @in: file to splice from
479 * @ppos: position in @in
480 * @pipe: pipe to splice to
481 * @len: number of bytes to splice
482 * @flags: splice modifier flags
484 * Description:
485 * Will read pages from given file and fill them into a pipe. Can be
486 * used as long as the address_space operations for the source implements
487 * a readpage() hook.
490 ssize_t generic_file_splice_read(struct file *in, loff_t *ppos,
491 struct pipe_inode_info *pipe, size_t len,
492 unsigned int flags)
494 loff_t isize, left;
495 int ret;
497 isize = i_size_read(in->f_mapping->host);
498 if (unlikely(*ppos >= isize))
499 return 0;
501 left = isize - *ppos;
502 if (unlikely(left < len))
503 len = left;
505 ret = __generic_file_splice_read(in, ppos, pipe, len, flags);
506 if (ret > 0)
507 *ppos += ret;
509 return ret;
512 EXPORT_SYMBOL(generic_file_splice_read);
515 * Send 'sd->len' bytes to socket from 'sd->file' at position 'sd->pos'
516 * using sendpage(). Return the number of bytes sent.
518 static int pipe_to_sendpage(struct pipe_inode_info *pipe,
519 struct pipe_buffer *buf, struct splice_desc *sd)
521 struct file *file = sd->u.file;
522 loff_t pos = sd->pos;
523 int ret, more;
525 ret = buf->ops->confirm(pipe, buf);
526 if (!ret) {
527 more = (sd->flags & SPLICE_F_MORE) || sd->len < sd->total_len;
529 ret = file->f_op->sendpage(file, buf->page, buf->offset,
530 sd->len, &pos, more);
533 return ret;
537 * This is a little more tricky than the file -> pipe splicing. There are
538 * basically three cases:
540 * - Destination page already exists in the address space and there
541 * are users of it. For that case we have no other option that
542 * copying the data. Tough luck.
543 * - Destination page already exists in the address space, but there
544 * are no users of it. Make sure it's uptodate, then drop it. Fall
545 * through to last case.
546 * - Destination page does not exist, we can add the pipe page to
547 * the page cache and avoid the copy.
549 * If asked to move pages to the output file (SPLICE_F_MOVE is set in
550 * sd->flags), we attempt to migrate pages from the pipe to the output
551 * file address space page cache. This is possible if no one else has
552 * the pipe page referenced outside of the pipe and page cache. If
553 * SPLICE_F_MOVE isn't set, or we cannot move the page, we simply create
554 * a new page in the output file page cache and fill/dirty that.
556 int pipe_to_file(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
557 struct splice_desc *sd)
559 struct file *file = sd->u.file;
560 struct address_space *mapping = file->f_mapping;
561 unsigned int offset, this_len;
562 struct page *page;
563 void *fsdata;
564 int ret;
567 * make sure the data in this buffer is uptodate
569 ret = buf->ops->confirm(pipe, buf);
570 if (unlikely(ret))
571 return ret;
573 offset = sd->pos & ~PAGE_CACHE_MASK;
575 this_len = sd->len;
576 if (this_len + offset > PAGE_CACHE_SIZE)
577 this_len = PAGE_CACHE_SIZE - offset;
579 ret = pagecache_write_begin(file, mapping, sd->pos, this_len,
580 AOP_FLAG_UNINTERRUPTIBLE, &page, &fsdata);
581 if (unlikely(ret))
582 goto out;
584 if (buf->page != page) {
586 * Careful, ->map() uses KM_USER0!
588 char *src = buf->ops->map(pipe, buf, 1);
589 char *dst = kmap_atomic(page, KM_USER1);
591 memcpy(dst + offset, src + buf->offset, this_len);
592 flush_dcache_page(page);
593 kunmap_atomic(dst, KM_USER1);
594 buf->ops->unmap(pipe, buf, src);
596 ret = pagecache_write_end(file, mapping, sd->pos, this_len, this_len,
597 page, fsdata);
598 out:
599 return ret;
601 EXPORT_SYMBOL(pipe_to_file);
603 static void wakeup_pipe_writers(struct pipe_inode_info *pipe)
605 smp_mb();
606 if (waitqueue_active(&pipe->wait))
607 wake_up_interruptible(&pipe->wait);
608 kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
612 * splice_from_pipe_feed - feed available data from a pipe to a file
613 * @pipe: pipe to splice from
614 * @sd: information to @actor
615 * @actor: handler that splices the data
617 * Description:
619 * This function loops over the pipe and calls @actor to do the
620 * actual moving of a single struct pipe_buffer to the desired
621 * destination. It returns when there's no more buffers left in
622 * the pipe or if the requested number of bytes (@sd->total_len)
623 * have been copied. It returns a positive number (one) if the
624 * pipe needs to be filled with more data, zero if the required
625 * number of bytes have been copied and -errno on error.
627 * This, together with splice_from_pipe_{begin,end,next}, may be
628 * used to implement the functionality of __splice_from_pipe() when
629 * locking is required around copying the pipe buffers to the
630 * destination.
632 int splice_from_pipe_feed(struct pipe_inode_info *pipe, struct splice_desc *sd,
633 splice_actor *actor)
635 int ret;
637 while (pipe->nrbufs) {
638 struct pipe_buffer *buf = pipe->bufs + pipe->curbuf;
639 const struct pipe_buf_operations *ops = buf->ops;
641 sd->len = buf->len;
642 if (sd->len > sd->total_len)
643 sd->len = sd->total_len;
645 ret = actor(pipe, buf, sd);
646 if (ret <= 0) {
647 if (ret == -ENODATA)
648 ret = 0;
649 return ret;
651 buf->offset += ret;
652 buf->len -= ret;
654 sd->num_spliced += ret;
655 sd->len -= ret;
656 sd->pos += ret;
657 sd->total_len -= ret;
659 if (!buf->len) {
660 buf->ops = NULL;
661 ops->release(pipe, buf);
662 pipe->curbuf = (pipe->curbuf + 1) & (PIPE_BUFFERS - 1);
663 pipe->nrbufs--;
664 if (pipe->inode)
665 sd->need_wakeup = true;
668 if (!sd->total_len)
669 return 0;
672 return 1;
674 EXPORT_SYMBOL(splice_from_pipe_feed);
677 * splice_from_pipe_next - wait for some data to splice from
678 * @pipe: pipe to splice from
679 * @sd: information about the splice operation
681 * Description:
682 * This function will wait for some data and return a positive
683 * value (one) if pipe buffers are available. It will return zero
684 * or -errno if no more data needs to be spliced.
686 int splice_from_pipe_next(struct pipe_inode_info *pipe, struct splice_desc *sd)
688 while (!pipe->nrbufs) {
689 if (!pipe->writers)
690 return 0;
692 if (!pipe->waiting_writers && sd->num_spliced)
693 return 0;
695 if (sd->flags & SPLICE_F_NONBLOCK)
696 return -EAGAIN;
698 if (signal_pending(current))
699 return -ERESTARTSYS;
701 if (sd->need_wakeup) {
702 wakeup_pipe_writers(pipe);
703 sd->need_wakeup = false;
706 pipe_wait(pipe);
709 return 1;
711 EXPORT_SYMBOL(splice_from_pipe_next);
714 * splice_from_pipe_begin - start splicing from pipe
715 * @pipe: pipe to splice from
717 * Description:
718 * This function should be called before a loop containing
719 * splice_from_pipe_next() and splice_from_pipe_feed() to
720 * initialize the necessary fields of @sd.
722 void splice_from_pipe_begin(struct splice_desc *sd)
724 sd->num_spliced = 0;
725 sd->need_wakeup = false;
727 EXPORT_SYMBOL(splice_from_pipe_begin);
730 * splice_from_pipe_end - finish splicing from pipe
731 * @pipe: pipe to splice from
732 * @sd: information about the splice operation
734 * Description:
735 * This function will wake up pipe writers if necessary. It should
736 * be called after a loop containing splice_from_pipe_next() and
737 * splice_from_pipe_feed().
739 void splice_from_pipe_end(struct pipe_inode_info *pipe, struct splice_desc *sd)
741 if (sd->need_wakeup)
742 wakeup_pipe_writers(pipe);
744 EXPORT_SYMBOL(splice_from_pipe_end);
747 * __splice_from_pipe - splice data from a pipe to given actor
748 * @pipe: pipe to splice from
749 * @sd: information to @actor
750 * @actor: handler that splices the data
752 * Description:
753 * This function does little more than loop over the pipe and call
754 * @actor to do the actual moving of a single struct pipe_buffer to
755 * the desired destination. See pipe_to_file, pipe_to_sendpage, or
756 * pipe_to_user.
759 ssize_t __splice_from_pipe(struct pipe_inode_info *pipe, struct splice_desc *sd,
760 splice_actor *actor)
762 int ret;
764 splice_from_pipe_begin(sd);
765 do {
766 ret = splice_from_pipe_next(pipe, sd);
767 if (ret > 0)
768 ret = splice_from_pipe_feed(pipe, sd, actor);
769 } while (ret > 0);
770 splice_from_pipe_end(pipe, sd);
772 return sd->num_spliced ? sd->num_spliced : ret;
774 EXPORT_SYMBOL(__splice_from_pipe);
777 * splice_from_pipe - splice data from a pipe to a file
778 * @pipe: pipe to splice from
779 * @out: file to splice to
780 * @ppos: position in @out
781 * @len: how many bytes to splice
782 * @flags: splice modifier flags
783 * @actor: handler that splices the data
785 * Description:
786 * See __splice_from_pipe. This function locks the pipe inode,
787 * otherwise it's identical to __splice_from_pipe().
790 ssize_t splice_from_pipe(struct pipe_inode_info *pipe, struct file *out,
791 loff_t *ppos, size_t len, unsigned int flags,
792 splice_actor *actor)
794 ssize_t ret;
795 struct splice_desc sd = {
796 .total_len = len,
797 .flags = flags,
798 .pos = *ppos,
799 .u.file = out,
802 if (pipe->inode)
803 mutex_lock(&pipe->inode->i_mutex);
804 ret = __splice_from_pipe(pipe, &sd, actor);
805 if (pipe->inode)
806 mutex_unlock(&pipe->inode->i_mutex);
808 return ret;
812 * generic_file_splice_write_nolock - generic_file_splice_write without mutexes
813 * @pipe: pipe info
814 * @out: file to write to
815 * @ppos: position in @out
816 * @len: number of bytes to splice
817 * @flags: splice modifier flags
819 * Description:
820 * Will either move or copy pages (determined by @flags options) from
821 * the given pipe inode to the given file. The caller is responsible
822 * for acquiring i_mutex on both inodes.
825 ssize_t
826 generic_file_splice_write_nolock(struct pipe_inode_info *pipe, struct file *out,
827 loff_t *ppos, size_t len, unsigned int flags)
829 struct address_space *mapping = out->f_mapping;
830 struct inode *inode = mapping->host;
831 struct splice_desc sd = {
832 .total_len = len,
833 .flags = flags,
834 .pos = *ppos,
835 .u.file = out,
837 ssize_t ret;
838 int err;
840 err = file_remove_suid(out);
841 if (unlikely(err))
842 return err;
844 ret = __splice_from_pipe(pipe, &sd, pipe_to_file);
845 if (ret > 0) {
846 unsigned long nr_pages;
848 *ppos += ret;
849 nr_pages = (ret + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
852 * If file or inode is SYNC and we actually wrote some data,
853 * sync it.
855 if (unlikely((out->f_flags & O_SYNC) || IS_SYNC(inode))) {
856 err = generic_osync_inode(inode, mapping,
857 OSYNC_METADATA|OSYNC_DATA);
859 if (err)
860 ret = err;
862 balance_dirty_pages_ratelimited_nr(mapping, nr_pages);
865 return ret;
868 EXPORT_SYMBOL(generic_file_splice_write_nolock);
871 * generic_file_splice_write - splice data from a pipe to a file
872 * @pipe: pipe info
873 * @out: file to write to
874 * @ppos: position in @out
875 * @len: number of bytes to splice
876 * @flags: splice modifier flags
878 * Description:
879 * Will either move or copy pages (determined by @flags options) from
880 * the given pipe inode to the given file.
883 ssize_t
884 generic_file_splice_write(struct pipe_inode_info *pipe, struct file *out,
885 loff_t *ppos, size_t len, unsigned int flags)
887 struct address_space *mapping = out->f_mapping;
888 struct inode *inode = mapping->host;
889 struct splice_desc sd = {
890 .total_len = len,
891 .flags = flags,
892 .pos = *ppos,
893 .u.file = out,
895 ssize_t ret;
897 if (pipe->inode)
898 mutex_lock_nested(&pipe->inode->i_mutex, I_MUTEX_PARENT);
900 splice_from_pipe_begin(&sd);
901 do {
902 ret = splice_from_pipe_next(pipe, &sd);
903 if (ret <= 0)
904 break;
906 mutex_lock_nested(&inode->i_mutex, I_MUTEX_CHILD);
907 ret = file_remove_suid(out);
908 if (!ret)
909 ret = splice_from_pipe_feed(pipe, &sd, pipe_to_file);
910 mutex_unlock(&inode->i_mutex);
911 } while (ret > 0);
912 splice_from_pipe_end(pipe, &sd);
914 if (pipe->inode)
915 mutex_unlock(&pipe->inode->i_mutex);
917 if (sd.num_spliced)
918 ret = sd.num_spliced;
920 if (ret > 0) {
921 unsigned long nr_pages;
923 *ppos += ret;
924 nr_pages = (ret + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
927 * If file or inode is SYNC and we actually wrote some data,
928 * sync it.
930 if (unlikely((out->f_flags & O_SYNC) || IS_SYNC(inode))) {
931 int err;
933 mutex_lock(&inode->i_mutex);
934 err = generic_osync_inode(inode, mapping,
935 OSYNC_METADATA|OSYNC_DATA);
936 mutex_unlock(&inode->i_mutex);
938 if (err)
939 ret = err;
941 balance_dirty_pages_ratelimited_nr(mapping, nr_pages);
944 return ret;
947 EXPORT_SYMBOL(generic_file_splice_write);
950 * generic_splice_sendpage - splice data from a pipe to a socket
951 * @pipe: pipe to splice from
952 * @out: socket to write to
953 * @ppos: position in @out
954 * @len: number of bytes to splice
955 * @flags: splice modifier flags
957 * Description:
958 * Will send @len bytes from the pipe to a network socket. No data copying
959 * is involved.
962 ssize_t generic_splice_sendpage(struct pipe_inode_info *pipe, struct file *out,
963 loff_t *ppos, size_t len, unsigned int flags)
965 return splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_sendpage);
968 EXPORT_SYMBOL(generic_splice_sendpage);
971 * Attempt to initiate a splice from pipe to file.
973 static long do_splice_from(struct pipe_inode_info *pipe, struct file *out,
974 loff_t *ppos, size_t len, unsigned int flags)
976 int ret;
978 if (unlikely(!out->f_op || !out->f_op->splice_write))
979 return -EINVAL;
981 if (unlikely(!(out->f_mode & FMODE_WRITE)))
982 return -EBADF;
984 if (unlikely(out->f_flags & O_APPEND))
985 return -EINVAL;
987 ret = rw_verify_area(WRITE, out, ppos, len);
988 if (unlikely(ret < 0))
989 return ret;
991 return out->f_op->splice_write(pipe, out, ppos, len, flags);
995 * Attempt to initiate a splice from a file to a pipe.
997 static long do_splice_to(struct file *in, loff_t *ppos,
998 struct pipe_inode_info *pipe, size_t len,
999 unsigned int flags)
1001 int ret;
1003 if (unlikely(!in->f_op || !in->f_op->splice_read))
1004 return -EINVAL;
1006 if (unlikely(!(in->f_mode & FMODE_READ)))
1007 return -EBADF;
1009 ret = rw_verify_area(READ, in, ppos, len);
1010 if (unlikely(ret < 0))
1011 return ret;
1013 return in->f_op->splice_read(in, ppos, pipe, len, flags);
1017 * splice_direct_to_actor - splices data directly between two non-pipes
1018 * @in: file to splice from
1019 * @sd: actor information on where to splice to
1020 * @actor: handles the data splicing
1022 * Description:
1023 * This is a special case helper to splice directly between two
1024 * points, without requiring an explicit pipe. Internally an allocated
1025 * pipe is cached in the process, and reused during the lifetime of
1026 * that process.
1029 ssize_t splice_direct_to_actor(struct file *in, struct splice_desc *sd,
1030 splice_direct_actor *actor)
1032 struct pipe_inode_info *pipe;
1033 long ret, bytes;
1034 umode_t i_mode;
1035 size_t len;
1036 int i, flags;
1039 * We require the input being a regular file, as we don't want to
1040 * randomly drop data for eg socket -> socket splicing. Use the
1041 * piped splicing for that!
1043 i_mode = in->f_path.dentry->d_inode->i_mode;
1044 if (unlikely(!S_ISREG(i_mode) && !S_ISBLK(i_mode)))
1045 return -EINVAL;
1048 * neither in nor out is a pipe, setup an internal pipe attached to
1049 * 'out' and transfer the wanted data from 'in' to 'out' through that
1051 pipe = current->splice_pipe;
1052 if (unlikely(!pipe)) {
1053 pipe = alloc_pipe_info(NULL);
1054 if (!pipe)
1055 return -ENOMEM;
1058 * We don't have an immediate reader, but we'll read the stuff
1059 * out of the pipe right after the splice_to_pipe(). So set
1060 * PIPE_READERS appropriately.
1062 pipe->readers = 1;
1064 current->splice_pipe = pipe;
1068 * Do the splice.
1070 ret = 0;
1071 bytes = 0;
1072 len = sd->total_len;
1073 flags = sd->flags;
1076 * Don't block on output, we have to drain the direct pipe.
1078 sd->flags &= ~SPLICE_F_NONBLOCK;
1080 while (len) {
1081 size_t read_len;
1082 loff_t pos = sd->pos, prev_pos = pos;
1084 ret = do_splice_to(in, &pos, pipe, len, flags);
1085 if (unlikely(ret <= 0))
1086 goto out_release;
1088 read_len = ret;
1089 sd->total_len = read_len;
1092 * NOTE: nonblocking mode only applies to the input. We
1093 * must not do the output in nonblocking mode as then we
1094 * could get stuck data in the internal pipe:
1096 ret = actor(pipe, sd);
1097 if (unlikely(ret <= 0)) {
1098 sd->pos = prev_pos;
1099 goto out_release;
1102 bytes += ret;
1103 len -= ret;
1104 sd->pos = pos;
1106 if (ret < read_len) {
1107 sd->pos = prev_pos + ret;
1108 goto out_release;
1112 done:
1113 pipe->nrbufs = pipe->curbuf = 0;
1114 file_accessed(in);
1115 return bytes;
1117 out_release:
1119 * If we did an incomplete transfer we must release
1120 * the pipe buffers in question:
1122 for (i = 0; i < PIPE_BUFFERS; i++) {
1123 struct pipe_buffer *buf = pipe->bufs + i;
1125 if (buf->ops) {
1126 buf->ops->release(pipe, buf);
1127 buf->ops = NULL;
1131 if (!bytes)
1132 bytes = ret;
1134 goto done;
1136 EXPORT_SYMBOL(splice_direct_to_actor);
1138 static int direct_splice_actor(struct pipe_inode_info *pipe,
1139 struct splice_desc *sd)
1141 struct file *file = sd->u.file;
1143 return do_splice_from(pipe, file, &sd->pos, sd->total_len, sd->flags);
1147 * do_splice_direct - splices data directly between two files
1148 * @in: file to splice from
1149 * @ppos: input file offset
1150 * @out: file to splice to
1151 * @len: number of bytes to splice
1152 * @flags: splice modifier flags
1154 * Description:
1155 * For use by do_sendfile(). splice can easily emulate sendfile, but
1156 * doing it in the application would incur an extra system call
1157 * (splice in + splice out, as compared to just sendfile()). So this helper
1158 * can splice directly through a process-private pipe.
1161 long do_splice_direct(struct file *in, loff_t *ppos, struct file *out,
1162 size_t len, unsigned int flags)
1164 struct splice_desc sd = {
1165 .len = len,
1166 .total_len = len,
1167 .flags = flags,
1168 .pos = *ppos,
1169 .u.file = out,
1171 long ret;
1173 ret = splice_direct_to_actor(in, &sd, direct_splice_actor);
1174 if (ret > 0)
1175 *ppos = sd.pos;
1177 return ret;
1181 * After the inode slimming patch, i_pipe/i_bdev/i_cdev share the same
1182 * location, so checking ->i_pipe is not enough to verify that this is a
1183 * pipe.
1185 static inline struct pipe_inode_info *pipe_info(struct inode *inode)
1187 if (S_ISFIFO(inode->i_mode))
1188 return inode->i_pipe;
1190 return NULL;
1194 * Determine where to splice to/from.
1196 static long do_splice(struct file *in, loff_t __user *off_in,
1197 struct file *out, loff_t __user *off_out,
1198 size_t len, unsigned int flags)
1200 struct pipe_inode_info *pipe;
1201 loff_t offset, *off;
1202 long ret;
1204 pipe = pipe_info(in->f_path.dentry->d_inode);
1205 if (pipe) {
1206 if (off_in)
1207 return -ESPIPE;
1208 if (off_out) {
1209 if (out->f_op->llseek == no_llseek)
1210 return -EINVAL;
1211 if (copy_from_user(&offset, off_out, sizeof(loff_t)))
1212 return -EFAULT;
1213 off = &offset;
1214 } else
1215 off = &out->f_pos;
1217 ret = do_splice_from(pipe, out, off, len, flags);
1219 if (off_out && copy_to_user(off_out, off, sizeof(loff_t)))
1220 ret = -EFAULT;
1222 return ret;
1225 pipe = pipe_info(out->f_path.dentry->d_inode);
1226 if (pipe) {
1227 if (off_out)
1228 return -ESPIPE;
1229 if (off_in) {
1230 if (in->f_op->llseek == no_llseek)
1231 return -EINVAL;
1232 if (copy_from_user(&offset, off_in, sizeof(loff_t)))
1233 return -EFAULT;
1234 off = &offset;
1235 } else
1236 off = &in->f_pos;
1238 ret = do_splice_to(in, off, pipe, len, flags);
1240 if (off_in && copy_to_user(off_in, off, sizeof(loff_t)))
1241 ret = -EFAULT;
1243 return ret;
1246 return -EINVAL;
1250 * Map an iov into an array of pages and offset/length tupples. With the
1251 * partial_page structure, we can map several non-contiguous ranges into
1252 * our ones pages[] map instead of splitting that operation into pieces.
1253 * Could easily be exported as a generic helper for other users, in which
1254 * case one would probably want to add a 'max_nr_pages' parameter as well.
1256 static int get_iovec_page_array(const struct iovec __user *iov,
1257 unsigned int nr_vecs, struct page **pages,
1258 struct partial_page *partial, int aligned)
1260 int buffers = 0, error = 0;
1262 while (nr_vecs) {
1263 unsigned long off, npages;
1264 struct iovec entry;
1265 void __user *base;
1266 size_t len;
1267 int i;
1269 error = -EFAULT;
1270 if (copy_from_user(&entry, iov, sizeof(entry)))
1271 break;
1273 base = entry.iov_base;
1274 len = entry.iov_len;
1277 * Sanity check this iovec. 0 read succeeds.
1279 error = 0;
1280 if (unlikely(!len))
1281 break;
1282 error = -EFAULT;
1283 if (!access_ok(VERIFY_READ, base, len))
1284 break;
1287 * Get this base offset and number of pages, then map
1288 * in the user pages.
1290 off = (unsigned long) base & ~PAGE_MASK;
1293 * If asked for alignment, the offset must be zero and the
1294 * length a multiple of the PAGE_SIZE.
1296 error = -EINVAL;
1297 if (aligned && (off || len & ~PAGE_MASK))
1298 break;
1300 npages = (off + len + PAGE_SIZE - 1) >> PAGE_SHIFT;
1301 if (npages > PIPE_BUFFERS - buffers)
1302 npages = PIPE_BUFFERS - buffers;
1304 error = get_user_pages_fast((unsigned long)base, npages,
1305 0, &pages[buffers]);
1307 if (unlikely(error <= 0))
1308 break;
1311 * Fill this contiguous range into the partial page map.
1313 for (i = 0; i < error; i++) {
1314 const int plen = min_t(size_t, len, PAGE_SIZE - off);
1316 partial[buffers].offset = off;
1317 partial[buffers].len = plen;
1319 off = 0;
1320 len -= plen;
1321 buffers++;
1325 * We didn't complete this iov, stop here since it probably
1326 * means we have to move some of this into a pipe to
1327 * be able to continue.
1329 if (len)
1330 break;
1333 * Don't continue if we mapped fewer pages than we asked for,
1334 * or if we mapped the max number of pages that we have
1335 * room for.
1337 if (error < npages || buffers == PIPE_BUFFERS)
1338 break;
1340 nr_vecs--;
1341 iov++;
1344 if (buffers)
1345 return buffers;
1347 return error;
1350 static int pipe_to_user(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
1351 struct splice_desc *sd)
1353 char *src;
1354 int ret;
1356 ret = buf->ops->confirm(pipe, buf);
1357 if (unlikely(ret))
1358 return ret;
1361 * See if we can use the atomic maps, by prefaulting in the
1362 * pages and doing an atomic copy
1364 if (!fault_in_pages_writeable(sd->u.userptr, sd->len)) {
1365 src = buf->ops->map(pipe, buf, 1);
1366 ret = __copy_to_user_inatomic(sd->u.userptr, src + buf->offset,
1367 sd->len);
1368 buf->ops->unmap(pipe, buf, src);
1369 if (!ret) {
1370 ret = sd->len;
1371 goto out;
1376 * No dice, use slow non-atomic map and copy
1378 src = buf->ops->map(pipe, buf, 0);
1380 ret = sd->len;
1381 if (copy_to_user(sd->u.userptr, src + buf->offset, sd->len))
1382 ret = -EFAULT;
1384 buf->ops->unmap(pipe, buf, src);
1385 out:
1386 if (ret > 0)
1387 sd->u.userptr += ret;
1388 return ret;
1392 * For lack of a better implementation, implement vmsplice() to userspace
1393 * as a simple copy of the pipes pages to the user iov.
1395 static long vmsplice_to_user(struct file *file, const struct iovec __user *iov,
1396 unsigned long nr_segs, unsigned int flags)
1398 struct pipe_inode_info *pipe;
1399 struct splice_desc sd;
1400 ssize_t size;
1401 int error;
1402 long ret;
1404 pipe = pipe_info(file->f_path.dentry->d_inode);
1405 if (!pipe)
1406 return -EBADF;
1408 if (pipe->inode)
1409 mutex_lock(&pipe->inode->i_mutex);
1411 error = ret = 0;
1412 while (nr_segs) {
1413 void __user *base;
1414 size_t len;
1417 * Get user address base and length for this iovec.
1419 error = get_user(base, &iov->iov_base);
1420 if (unlikely(error))
1421 break;
1422 error = get_user(len, &iov->iov_len);
1423 if (unlikely(error))
1424 break;
1427 * Sanity check this iovec. 0 read succeeds.
1429 if (unlikely(!len))
1430 break;
1431 if (unlikely(!base)) {
1432 error = -EFAULT;
1433 break;
1436 if (unlikely(!access_ok(VERIFY_WRITE, base, len))) {
1437 error = -EFAULT;
1438 break;
1441 sd.len = 0;
1442 sd.total_len = len;
1443 sd.flags = flags;
1444 sd.u.userptr = base;
1445 sd.pos = 0;
1447 size = __splice_from_pipe(pipe, &sd, pipe_to_user);
1448 if (size < 0) {
1449 if (!ret)
1450 ret = size;
1452 break;
1455 ret += size;
1457 if (size < len)
1458 break;
1460 nr_segs--;
1461 iov++;
1464 if (pipe->inode)
1465 mutex_unlock(&pipe->inode->i_mutex);
1467 if (!ret)
1468 ret = error;
1470 return ret;
1474 * vmsplice splices a user address range into a pipe. It can be thought of
1475 * as splice-from-memory, where the regular splice is splice-from-file (or
1476 * to file). In both cases the output is a pipe, naturally.
1478 static long vmsplice_to_pipe(struct file *file, const struct iovec __user *iov,
1479 unsigned long nr_segs, unsigned int flags)
1481 struct pipe_inode_info *pipe;
1482 struct page *pages[PIPE_BUFFERS];
1483 struct partial_page partial[PIPE_BUFFERS];
1484 struct splice_pipe_desc spd = {
1485 .pages = pages,
1486 .partial = partial,
1487 .flags = flags,
1488 .ops = &user_page_pipe_buf_ops,
1489 .spd_release = spd_release_page,
1492 pipe = pipe_info(file->f_path.dentry->d_inode);
1493 if (!pipe)
1494 return -EBADF;
1496 spd.nr_pages = get_iovec_page_array(iov, nr_segs, pages, partial,
1497 flags & SPLICE_F_GIFT);
1498 if (spd.nr_pages <= 0)
1499 return spd.nr_pages;
1501 return splice_to_pipe(pipe, &spd);
1505 * Note that vmsplice only really supports true splicing _from_ user memory
1506 * to a pipe, not the other way around. Splicing from user memory is a simple
1507 * operation that can be supported without any funky alignment restrictions
1508 * or nasty vm tricks. We simply map in the user memory and fill them into
1509 * a pipe. The reverse isn't quite as easy, though. There are two possible
1510 * solutions for that:
1512 * - memcpy() the data internally, at which point we might as well just
1513 * do a regular read() on the buffer anyway.
1514 * - Lots of nasty vm tricks, that are neither fast nor flexible (it
1515 * has restriction limitations on both ends of the pipe).
1517 * Currently we punt and implement it as a normal copy, see pipe_to_user().
1520 SYSCALL_DEFINE4(vmsplice, int, fd, const struct iovec __user *, iov,
1521 unsigned long, nr_segs, unsigned int, flags)
1523 struct file *file;
1524 long error;
1525 int fput;
1527 if (unlikely(nr_segs > UIO_MAXIOV))
1528 return -EINVAL;
1529 else if (unlikely(!nr_segs))
1530 return 0;
1532 error = -EBADF;
1533 file = fget_light(fd, &fput);
1534 if (file) {
1535 if (file->f_mode & FMODE_WRITE)
1536 error = vmsplice_to_pipe(file, iov, nr_segs, flags);
1537 else if (file->f_mode & FMODE_READ)
1538 error = vmsplice_to_user(file, iov, nr_segs, flags);
1540 fput_light(file, fput);
1543 return error;
1546 SYSCALL_DEFINE6(splice, int, fd_in, loff_t __user *, off_in,
1547 int, fd_out, loff_t __user *, off_out,
1548 size_t, len, unsigned int, flags)
1550 long error;
1551 struct file *in, *out;
1552 int fput_in, fput_out;
1554 if (unlikely(!len))
1555 return 0;
1557 error = -EBADF;
1558 in = fget_light(fd_in, &fput_in);
1559 if (in) {
1560 if (in->f_mode & FMODE_READ) {
1561 out = fget_light(fd_out, &fput_out);
1562 if (out) {
1563 if (out->f_mode & FMODE_WRITE)
1564 error = do_splice(in, off_in,
1565 out, off_out,
1566 len, flags);
1567 fput_light(out, fput_out);
1571 fput_light(in, fput_in);
1574 return error;
1578 * Make sure there's data to read. Wait for input if we can, otherwise
1579 * return an appropriate error.
1581 static int link_ipipe_prep(struct pipe_inode_info *pipe, unsigned int flags)
1583 int ret;
1586 * Check ->nrbufs without the inode lock first. This function
1587 * is speculative anyways, so missing one is ok.
1589 if (pipe->nrbufs)
1590 return 0;
1592 ret = 0;
1593 mutex_lock(&pipe->inode->i_mutex);
1595 while (!pipe->nrbufs) {
1596 if (signal_pending(current)) {
1597 ret = -ERESTARTSYS;
1598 break;
1600 if (!pipe->writers)
1601 break;
1602 if (!pipe->waiting_writers) {
1603 if (flags & SPLICE_F_NONBLOCK) {
1604 ret = -EAGAIN;
1605 break;
1608 pipe_wait(pipe);
1611 mutex_unlock(&pipe->inode->i_mutex);
1612 return ret;
1616 * Make sure there's writeable room. Wait for room if we can, otherwise
1617 * return an appropriate error.
1619 static int link_opipe_prep(struct pipe_inode_info *pipe, unsigned int flags)
1621 int ret;
1624 * Check ->nrbufs without the inode lock first. This function
1625 * is speculative anyways, so missing one is ok.
1627 if (pipe->nrbufs < PIPE_BUFFERS)
1628 return 0;
1630 ret = 0;
1631 mutex_lock(&pipe->inode->i_mutex);
1633 while (pipe->nrbufs >= PIPE_BUFFERS) {
1634 if (!pipe->readers) {
1635 send_sig(SIGPIPE, current, 0);
1636 ret = -EPIPE;
1637 break;
1639 if (flags & SPLICE_F_NONBLOCK) {
1640 ret = -EAGAIN;
1641 break;
1643 if (signal_pending(current)) {
1644 ret = -ERESTARTSYS;
1645 break;
1647 pipe->waiting_writers++;
1648 pipe_wait(pipe);
1649 pipe->waiting_writers--;
1652 mutex_unlock(&pipe->inode->i_mutex);
1653 return ret;
1657 * Link contents of ipipe to opipe.
1659 static int link_pipe(struct pipe_inode_info *ipipe,
1660 struct pipe_inode_info *opipe,
1661 size_t len, unsigned int flags)
1663 struct pipe_buffer *ibuf, *obuf;
1664 int ret = 0, i = 0, nbuf;
1667 * Potential ABBA deadlock, work around it by ordering lock
1668 * grabbing by inode address. Otherwise two different processes
1669 * could deadlock (one doing tee from A -> B, the other from B -> A).
1671 inode_double_lock(ipipe->inode, opipe->inode);
1673 do {
1674 if (!opipe->readers) {
1675 send_sig(SIGPIPE, current, 0);
1676 if (!ret)
1677 ret = -EPIPE;
1678 break;
1682 * If we have iterated all input buffers or ran out of
1683 * output room, break.
1685 if (i >= ipipe->nrbufs || opipe->nrbufs >= PIPE_BUFFERS)
1686 break;
1688 ibuf = ipipe->bufs + ((ipipe->curbuf + i) & (PIPE_BUFFERS - 1));
1689 nbuf = (opipe->curbuf + opipe->nrbufs) & (PIPE_BUFFERS - 1);
1692 * Get a reference to this pipe buffer,
1693 * so we can copy the contents over.
1695 ibuf->ops->get(ipipe, ibuf);
1697 obuf = opipe->bufs + nbuf;
1698 *obuf = *ibuf;
1701 * Don't inherit the gift flag, we need to
1702 * prevent multiple steals of this page.
1704 obuf->flags &= ~PIPE_BUF_FLAG_GIFT;
1706 if (obuf->len > len)
1707 obuf->len = len;
1709 opipe->nrbufs++;
1710 ret += obuf->len;
1711 len -= obuf->len;
1712 i++;
1713 } while (len);
1716 * return EAGAIN if we have the potential of some data in the
1717 * future, otherwise just return 0
1719 if (!ret && ipipe->waiting_writers && (flags & SPLICE_F_NONBLOCK))
1720 ret = -EAGAIN;
1722 inode_double_unlock(ipipe->inode, opipe->inode);
1725 * If we put data in the output pipe, wakeup any potential readers.
1727 if (ret > 0) {
1728 smp_mb();
1729 if (waitqueue_active(&opipe->wait))
1730 wake_up_interruptible(&opipe->wait);
1731 kill_fasync(&opipe->fasync_readers, SIGIO, POLL_IN);
1734 return ret;
1738 * This is a tee(1) implementation that works on pipes. It doesn't copy
1739 * any data, it simply references the 'in' pages on the 'out' pipe.
1740 * The 'flags' used are the SPLICE_F_* variants, currently the only
1741 * applicable one is SPLICE_F_NONBLOCK.
1743 static long do_tee(struct file *in, struct file *out, size_t len,
1744 unsigned int flags)
1746 struct pipe_inode_info *ipipe = pipe_info(in->f_path.dentry->d_inode);
1747 struct pipe_inode_info *opipe = pipe_info(out->f_path.dentry->d_inode);
1748 int ret = -EINVAL;
1751 * Duplicate the contents of ipipe to opipe without actually
1752 * copying the data.
1754 if (ipipe && opipe && ipipe != opipe) {
1756 * Keep going, unless we encounter an error. The ipipe/opipe
1757 * ordering doesn't really matter.
1759 ret = link_ipipe_prep(ipipe, flags);
1760 if (!ret) {
1761 ret = link_opipe_prep(opipe, flags);
1762 if (!ret)
1763 ret = link_pipe(ipipe, opipe, len, flags);
1767 return ret;
1770 SYSCALL_DEFINE4(tee, int, fdin, int, fdout, size_t, len, unsigned int, flags)
1772 struct file *in;
1773 int error, fput_in;
1775 if (unlikely(!len))
1776 return 0;
1778 error = -EBADF;
1779 in = fget_light(fdin, &fput_in);
1780 if (in) {
1781 if (in->f_mode & FMODE_READ) {
1782 int fput_out;
1783 struct file *out = fget_light(fdout, &fput_out);
1785 if (out) {
1786 if (out->f_mode & FMODE_WRITE)
1787 error = do_tee(in, out, len, flags);
1788 fput_light(out, fput_out);
1791 fput_light(in, fput_in);
1794 return error;