Linux 4.4.3
[linux/fpc-iii.git] / fs / splice.c
blob4cf700d50b4037e6c334b0647cdb81b816f9ef65
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/memcontrol.h>
25 #include <linux/mm_inline.h>
26 #include <linux/swap.h>
27 #include <linux/writeback.h>
28 #include <linux/export.h>
29 #include <linux/syscalls.h>
30 #include <linux/uio.h>
31 #include <linux/security.h>
32 #include <linux/gfp.h>
33 #include <linux/socket.h>
34 #include <linux/compat.h>
35 #include "internal.h"
38 * Attempt to steal a page from a pipe buffer. This should perhaps go into
39 * a vm helper function, it's already simplified quite a bit by the
40 * addition of remove_mapping(). If success is returned, the caller may
41 * attempt to reuse this page for another destination.
43 static int page_cache_pipe_buf_steal(struct pipe_inode_info *pipe,
44 struct pipe_buffer *buf)
46 struct page *page = buf->page;
47 struct address_space *mapping;
49 lock_page(page);
51 mapping = page_mapping(page);
52 if (mapping) {
53 WARN_ON(!PageUptodate(page));
56 * At least for ext2 with nobh option, we need to wait on
57 * writeback completing on this page, since we'll remove it
58 * from the pagecache. Otherwise truncate wont wait on the
59 * page, allowing the disk blocks to be reused by someone else
60 * before we actually wrote our data to them. fs corruption
61 * ensues.
63 wait_on_page_writeback(page);
65 if (page_has_private(page) &&
66 !try_to_release_page(page, GFP_KERNEL))
67 goto out_unlock;
70 * If we succeeded in removing the mapping, set LRU flag
71 * and return good.
73 if (remove_mapping(mapping, page)) {
74 buf->flags |= PIPE_BUF_FLAG_LRU;
75 return 0;
80 * Raced with truncate or failed to remove page from current
81 * address space, unlock and return failure.
83 out_unlock:
84 unlock_page(page);
85 return 1;
88 static void page_cache_pipe_buf_release(struct pipe_inode_info *pipe,
89 struct pipe_buffer *buf)
91 page_cache_release(buf->page);
92 buf->flags &= ~PIPE_BUF_FLAG_LRU;
96 * Check whether the contents of buf is OK to access. Since the content
97 * is a page cache page, IO may be in flight.
99 static int page_cache_pipe_buf_confirm(struct pipe_inode_info *pipe,
100 struct pipe_buffer *buf)
102 struct page *page = buf->page;
103 int err;
105 if (!PageUptodate(page)) {
106 lock_page(page);
109 * Page got truncated/unhashed. This will cause a 0-byte
110 * splice, if this is the first page.
112 if (!page->mapping) {
113 err = -ENODATA;
114 goto error;
118 * Uh oh, read-error from disk.
120 if (!PageUptodate(page)) {
121 err = -EIO;
122 goto error;
126 * Page is ok afterall, we are done.
128 unlock_page(page);
131 return 0;
132 error:
133 unlock_page(page);
134 return err;
137 const struct pipe_buf_operations page_cache_pipe_buf_ops = {
138 .can_merge = 0,
139 .confirm = page_cache_pipe_buf_confirm,
140 .release = page_cache_pipe_buf_release,
141 .steal = page_cache_pipe_buf_steal,
142 .get = generic_pipe_buf_get,
145 static int user_page_pipe_buf_steal(struct pipe_inode_info *pipe,
146 struct pipe_buffer *buf)
148 if (!(buf->flags & PIPE_BUF_FLAG_GIFT))
149 return 1;
151 buf->flags |= PIPE_BUF_FLAG_LRU;
152 return generic_pipe_buf_steal(pipe, buf);
155 static const struct pipe_buf_operations user_page_pipe_buf_ops = {
156 .can_merge = 0,
157 .confirm = generic_pipe_buf_confirm,
158 .release = page_cache_pipe_buf_release,
159 .steal = user_page_pipe_buf_steal,
160 .get = generic_pipe_buf_get,
163 static void wakeup_pipe_readers(struct pipe_inode_info *pipe)
165 smp_mb();
166 if (waitqueue_active(&pipe->wait))
167 wake_up_interruptible(&pipe->wait);
168 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
172 * splice_to_pipe - fill passed data into a pipe
173 * @pipe: pipe to fill
174 * @spd: data to fill
176 * Description:
177 * @spd contains a map of pages and len/offset tuples, along with
178 * the struct pipe_buf_operations associated with these pages. This
179 * function will link that data to the pipe.
182 ssize_t splice_to_pipe(struct pipe_inode_info *pipe,
183 struct splice_pipe_desc *spd)
185 unsigned int spd_pages = spd->nr_pages;
186 int ret, do_wakeup, page_nr;
188 ret = 0;
189 do_wakeup = 0;
190 page_nr = 0;
192 pipe_lock(pipe);
194 for (;;) {
195 if (!pipe->readers) {
196 send_sig(SIGPIPE, current, 0);
197 if (!ret)
198 ret = -EPIPE;
199 break;
202 if (pipe->nrbufs < pipe->buffers) {
203 int newbuf = (pipe->curbuf + pipe->nrbufs) & (pipe->buffers - 1);
204 struct pipe_buffer *buf = pipe->bufs + newbuf;
206 buf->page = spd->pages[page_nr];
207 buf->offset = spd->partial[page_nr].offset;
208 buf->len = spd->partial[page_nr].len;
209 buf->private = spd->partial[page_nr].private;
210 buf->ops = spd->ops;
211 if (spd->flags & SPLICE_F_GIFT)
212 buf->flags |= PIPE_BUF_FLAG_GIFT;
214 pipe->nrbufs++;
215 page_nr++;
216 ret += buf->len;
218 if (pipe->files)
219 do_wakeup = 1;
221 if (!--spd->nr_pages)
222 break;
223 if (pipe->nrbufs < pipe->buffers)
224 continue;
226 break;
229 if (spd->flags & SPLICE_F_NONBLOCK) {
230 if (!ret)
231 ret = -EAGAIN;
232 break;
235 if (signal_pending(current)) {
236 if (!ret)
237 ret = -ERESTARTSYS;
238 break;
241 if (do_wakeup) {
242 smp_mb();
243 if (waitqueue_active(&pipe->wait))
244 wake_up_interruptible_sync(&pipe->wait);
245 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
246 do_wakeup = 0;
249 pipe->waiting_writers++;
250 pipe_wait(pipe);
251 pipe->waiting_writers--;
254 pipe_unlock(pipe);
256 if (do_wakeup)
257 wakeup_pipe_readers(pipe);
259 while (page_nr < spd_pages)
260 spd->spd_release(spd, page_nr++);
262 return ret;
264 EXPORT_SYMBOL_GPL(splice_to_pipe);
266 void spd_release_page(struct splice_pipe_desc *spd, unsigned int i)
268 page_cache_release(spd->pages[i]);
272 * Check if we need to grow the arrays holding pages and partial page
273 * descriptions.
275 int splice_grow_spd(const struct pipe_inode_info *pipe, struct splice_pipe_desc *spd)
277 unsigned int buffers = ACCESS_ONCE(pipe->buffers);
279 spd->nr_pages_max = buffers;
280 if (buffers <= PIPE_DEF_BUFFERS)
281 return 0;
283 spd->pages = kmalloc(buffers * sizeof(struct page *), GFP_KERNEL);
284 spd->partial = kmalloc(buffers * sizeof(struct partial_page), GFP_KERNEL);
286 if (spd->pages && spd->partial)
287 return 0;
289 kfree(spd->pages);
290 kfree(spd->partial);
291 return -ENOMEM;
294 void splice_shrink_spd(struct splice_pipe_desc *spd)
296 if (spd->nr_pages_max <= PIPE_DEF_BUFFERS)
297 return;
299 kfree(spd->pages);
300 kfree(spd->partial);
303 static int
304 __generic_file_splice_read(struct file *in, loff_t *ppos,
305 struct pipe_inode_info *pipe, size_t len,
306 unsigned int flags)
308 struct address_space *mapping = in->f_mapping;
309 unsigned int loff, nr_pages, req_pages;
310 struct page *pages[PIPE_DEF_BUFFERS];
311 struct partial_page partial[PIPE_DEF_BUFFERS];
312 struct page *page;
313 pgoff_t index, end_index;
314 loff_t isize;
315 int error, page_nr;
316 struct splice_pipe_desc spd = {
317 .pages = pages,
318 .partial = partial,
319 .nr_pages_max = PIPE_DEF_BUFFERS,
320 .flags = flags,
321 .ops = &page_cache_pipe_buf_ops,
322 .spd_release = spd_release_page,
325 if (splice_grow_spd(pipe, &spd))
326 return -ENOMEM;
328 index = *ppos >> PAGE_CACHE_SHIFT;
329 loff = *ppos & ~PAGE_CACHE_MASK;
330 req_pages = (len + loff + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
331 nr_pages = min(req_pages, spd.nr_pages_max);
334 * Lookup the (hopefully) full range of pages we need.
336 spd.nr_pages = find_get_pages_contig(mapping, index, nr_pages, spd.pages);
337 index += spd.nr_pages;
340 * If find_get_pages_contig() returned fewer pages than we needed,
341 * readahead/allocate the rest and fill in the holes.
343 if (spd.nr_pages < nr_pages)
344 page_cache_sync_readahead(mapping, &in->f_ra, in,
345 index, req_pages - spd.nr_pages);
347 error = 0;
348 while (spd.nr_pages < nr_pages) {
350 * Page could be there, find_get_pages_contig() breaks on
351 * the first hole.
353 page = find_get_page(mapping, index);
354 if (!page) {
356 * page didn't exist, allocate one.
358 page = page_cache_alloc_cold(mapping);
359 if (!page)
360 break;
362 error = add_to_page_cache_lru(page, mapping, index,
363 mapping_gfp_constraint(mapping, GFP_KERNEL));
364 if (unlikely(error)) {
365 page_cache_release(page);
366 if (error == -EEXIST)
367 continue;
368 break;
371 * add_to_page_cache() locks the page, unlock it
372 * to avoid convoluting the logic below even more.
374 unlock_page(page);
377 spd.pages[spd.nr_pages++] = page;
378 index++;
382 * Now loop over the map and see if we need to start IO on any
383 * pages, fill in the partial map, etc.
385 index = *ppos >> PAGE_CACHE_SHIFT;
386 nr_pages = spd.nr_pages;
387 spd.nr_pages = 0;
388 for (page_nr = 0; page_nr < nr_pages; page_nr++) {
389 unsigned int this_len;
391 if (!len)
392 break;
395 * this_len is the max we'll use from this page
397 this_len = min_t(unsigned long, len, PAGE_CACHE_SIZE - loff);
398 page = spd.pages[page_nr];
400 if (PageReadahead(page))
401 page_cache_async_readahead(mapping, &in->f_ra, in,
402 page, index, req_pages - page_nr);
405 * If the page isn't uptodate, we may need to start io on it
407 if (!PageUptodate(page)) {
408 lock_page(page);
411 * Page was truncated, or invalidated by the
412 * filesystem. Redo the find/create, but this time the
413 * page is kept locked, so there's no chance of another
414 * race with truncate/invalidate.
416 if (!page->mapping) {
417 unlock_page(page);
418 page = find_or_create_page(mapping, index,
419 mapping_gfp_mask(mapping));
421 if (!page) {
422 error = -ENOMEM;
423 break;
425 page_cache_release(spd.pages[page_nr]);
426 spd.pages[page_nr] = page;
429 * page was already under io and is now done, great
431 if (PageUptodate(page)) {
432 unlock_page(page);
433 goto fill_it;
437 * need to read in the page
439 error = mapping->a_ops->readpage(in, page);
440 if (unlikely(error)) {
442 * We really should re-lookup the page here,
443 * but it complicates things a lot. Instead
444 * lets just do what we already stored, and
445 * we'll get it the next time we are called.
447 if (error == AOP_TRUNCATED_PAGE)
448 error = 0;
450 break;
453 fill_it:
455 * i_size must be checked after PageUptodate.
457 isize = i_size_read(mapping->host);
458 end_index = (isize - 1) >> PAGE_CACHE_SHIFT;
459 if (unlikely(!isize || index > end_index))
460 break;
463 * if this is the last page, see if we need to shrink
464 * the length and stop
466 if (end_index == index) {
467 unsigned int plen;
470 * max good bytes in this page
472 plen = ((isize - 1) & ~PAGE_CACHE_MASK) + 1;
473 if (plen <= loff)
474 break;
477 * force quit after adding this page
479 this_len = min(this_len, plen - loff);
480 len = this_len;
483 spd.partial[page_nr].offset = loff;
484 spd.partial[page_nr].len = this_len;
485 len -= this_len;
486 loff = 0;
487 spd.nr_pages++;
488 index++;
492 * Release any pages at the end, if we quit early. 'page_nr' is how far
493 * we got, 'nr_pages' is how many pages are in the map.
495 while (page_nr < nr_pages)
496 page_cache_release(spd.pages[page_nr++]);
497 in->f_ra.prev_pos = (loff_t)index << PAGE_CACHE_SHIFT;
499 if (spd.nr_pages)
500 error = splice_to_pipe(pipe, &spd);
502 splice_shrink_spd(&spd);
503 return error;
507 * generic_file_splice_read - splice data from file to a pipe
508 * @in: file to splice from
509 * @ppos: position in @in
510 * @pipe: pipe to splice to
511 * @len: number of bytes to splice
512 * @flags: splice modifier flags
514 * Description:
515 * Will read pages from given file and fill them into a pipe. Can be
516 * used as long as the address_space operations for the source implements
517 * a readpage() hook.
520 ssize_t generic_file_splice_read(struct file *in, loff_t *ppos,
521 struct pipe_inode_info *pipe, size_t len,
522 unsigned int flags)
524 loff_t isize, left;
525 int ret;
527 if (IS_DAX(in->f_mapping->host))
528 return default_file_splice_read(in, ppos, pipe, len, flags);
530 isize = i_size_read(in->f_mapping->host);
531 if (unlikely(*ppos >= isize))
532 return 0;
534 left = isize - *ppos;
535 if (unlikely(left < len))
536 len = left;
538 ret = __generic_file_splice_read(in, ppos, pipe, len, flags);
539 if (ret > 0) {
540 *ppos += ret;
541 file_accessed(in);
544 return ret;
546 EXPORT_SYMBOL(generic_file_splice_read);
548 static const struct pipe_buf_operations default_pipe_buf_ops = {
549 .can_merge = 0,
550 .confirm = generic_pipe_buf_confirm,
551 .release = generic_pipe_buf_release,
552 .steal = generic_pipe_buf_steal,
553 .get = generic_pipe_buf_get,
556 static int generic_pipe_buf_nosteal(struct pipe_inode_info *pipe,
557 struct pipe_buffer *buf)
559 return 1;
562 /* Pipe buffer operations for a socket and similar. */
563 const struct pipe_buf_operations nosteal_pipe_buf_ops = {
564 .can_merge = 0,
565 .confirm = generic_pipe_buf_confirm,
566 .release = generic_pipe_buf_release,
567 .steal = generic_pipe_buf_nosteal,
568 .get = generic_pipe_buf_get,
570 EXPORT_SYMBOL(nosteal_pipe_buf_ops);
572 static ssize_t kernel_readv(struct file *file, const struct iovec *vec,
573 unsigned long vlen, loff_t offset)
575 mm_segment_t old_fs;
576 loff_t pos = offset;
577 ssize_t res;
579 old_fs = get_fs();
580 set_fs(get_ds());
581 /* The cast to a user pointer is valid due to the set_fs() */
582 res = vfs_readv(file, (const struct iovec __user *)vec, vlen, &pos);
583 set_fs(old_fs);
585 return res;
588 ssize_t kernel_write(struct file *file, const char *buf, size_t count,
589 loff_t pos)
591 mm_segment_t old_fs;
592 ssize_t res;
594 old_fs = get_fs();
595 set_fs(get_ds());
596 /* The cast to a user pointer is valid due to the set_fs() */
597 res = vfs_write(file, (__force const char __user *)buf, count, &pos);
598 set_fs(old_fs);
600 return res;
602 EXPORT_SYMBOL(kernel_write);
604 ssize_t default_file_splice_read(struct file *in, loff_t *ppos,
605 struct pipe_inode_info *pipe, size_t len,
606 unsigned int flags)
608 unsigned int nr_pages;
609 unsigned int nr_freed;
610 size_t offset;
611 struct page *pages[PIPE_DEF_BUFFERS];
612 struct partial_page partial[PIPE_DEF_BUFFERS];
613 struct iovec *vec, __vec[PIPE_DEF_BUFFERS];
614 ssize_t res;
615 size_t this_len;
616 int error;
617 int i;
618 struct splice_pipe_desc spd = {
619 .pages = pages,
620 .partial = partial,
621 .nr_pages_max = PIPE_DEF_BUFFERS,
622 .flags = flags,
623 .ops = &default_pipe_buf_ops,
624 .spd_release = spd_release_page,
627 if (splice_grow_spd(pipe, &spd))
628 return -ENOMEM;
630 res = -ENOMEM;
631 vec = __vec;
632 if (spd.nr_pages_max > PIPE_DEF_BUFFERS) {
633 vec = kmalloc(spd.nr_pages_max * sizeof(struct iovec), GFP_KERNEL);
634 if (!vec)
635 goto shrink_ret;
638 offset = *ppos & ~PAGE_CACHE_MASK;
639 nr_pages = (len + offset + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
641 for (i = 0; i < nr_pages && i < spd.nr_pages_max && len; i++) {
642 struct page *page;
644 page = alloc_page(GFP_USER);
645 error = -ENOMEM;
646 if (!page)
647 goto err;
649 this_len = min_t(size_t, len, PAGE_CACHE_SIZE - offset);
650 vec[i].iov_base = (void __user *) page_address(page);
651 vec[i].iov_len = this_len;
652 spd.pages[i] = page;
653 spd.nr_pages++;
654 len -= this_len;
655 offset = 0;
658 res = kernel_readv(in, vec, spd.nr_pages, *ppos);
659 if (res < 0) {
660 error = res;
661 goto err;
664 error = 0;
665 if (!res)
666 goto err;
668 nr_freed = 0;
669 for (i = 0; i < spd.nr_pages; i++) {
670 this_len = min_t(size_t, vec[i].iov_len, res);
671 spd.partial[i].offset = 0;
672 spd.partial[i].len = this_len;
673 if (!this_len) {
674 __free_page(spd.pages[i]);
675 spd.pages[i] = NULL;
676 nr_freed++;
678 res -= this_len;
680 spd.nr_pages -= nr_freed;
682 res = splice_to_pipe(pipe, &spd);
683 if (res > 0)
684 *ppos += res;
686 shrink_ret:
687 if (vec != __vec)
688 kfree(vec);
689 splice_shrink_spd(&spd);
690 return res;
692 err:
693 for (i = 0; i < spd.nr_pages; i++)
694 __free_page(spd.pages[i]);
696 res = error;
697 goto shrink_ret;
699 EXPORT_SYMBOL(default_file_splice_read);
702 * Send 'sd->len' bytes to socket from 'sd->file' at position 'sd->pos'
703 * using sendpage(). Return the number of bytes sent.
705 static int pipe_to_sendpage(struct pipe_inode_info *pipe,
706 struct pipe_buffer *buf, struct splice_desc *sd)
708 struct file *file = sd->u.file;
709 loff_t pos = sd->pos;
710 int more;
712 if (!likely(file->f_op->sendpage))
713 return -EINVAL;
715 more = (sd->flags & SPLICE_F_MORE) ? MSG_MORE : 0;
717 if (sd->len < sd->total_len && pipe->nrbufs > 1)
718 more |= MSG_SENDPAGE_NOTLAST;
720 return file->f_op->sendpage(file, buf->page, buf->offset,
721 sd->len, &pos, more);
724 static void wakeup_pipe_writers(struct pipe_inode_info *pipe)
726 smp_mb();
727 if (waitqueue_active(&pipe->wait))
728 wake_up_interruptible(&pipe->wait);
729 kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
733 * splice_from_pipe_feed - feed available data from a pipe to a file
734 * @pipe: pipe to splice from
735 * @sd: information to @actor
736 * @actor: handler that splices the data
738 * Description:
739 * This function loops over the pipe and calls @actor to do the
740 * actual moving of a single struct pipe_buffer to the desired
741 * destination. It returns when there's no more buffers left in
742 * the pipe or if the requested number of bytes (@sd->total_len)
743 * have been copied. It returns a positive number (one) if the
744 * pipe needs to be filled with more data, zero if the required
745 * number of bytes have been copied and -errno on error.
747 * This, together with splice_from_pipe_{begin,end,next}, may be
748 * used to implement the functionality of __splice_from_pipe() when
749 * locking is required around copying the pipe buffers to the
750 * destination.
752 static int splice_from_pipe_feed(struct pipe_inode_info *pipe, struct splice_desc *sd,
753 splice_actor *actor)
755 int ret;
757 while (pipe->nrbufs) {
758 struct pipe_buffer *buf = pipe->bufs + pipe->curbuf;
759 const struct pipe_buf_operations *ops = buf->ops;
761 sd->len = buf->len;
762 if (sd->len > sd->total_len)
763 sd->len = sd->total_len;
765 ret = buf->ops->confirm(pipe, buf);
766 if (unlikely(ret)) {
767 if (ret == -ENODATA)
768 ret = 0;
769 return ret;
772 ret = actor(pipe, buf, sd);
773 if (ret <= 0)
774 return ret;
776 buf->offset += ret;
777 buf->len -= ret;
779 sd->num_spliced += ret;
780 sd->len -= ret;
781 sd->pos += ret;
782 sd->total_len -= ret;
784 if (!buf->len) {
785 buf->ops = NULL;
786 ops->release(pipe, buf);
787 pipe->curbuf = (pipe->curbuf + 1) & (pipe->buffers - 1);
788 pipe->nrbufs--;
789 if (pipe->files)
790 sd->need_wakeup = true;
793 if (!sd->total_len)
794 return 0;
797 return 1;
801 * splice_from_pipe_next - wait for some data to splice from
802 * @pipe: pipe to splice from
803 * @sd: information about the splice operation
805 * Description:
806 * This function will wait for some data and return a positive
807 * value (one) if pipe buffers are available. It will return zero
808 * or -errno if no more data needs to be spliced.
810 static int splice_from_pipe_next(struct pipe_inode_info *pipe, struct splice_desc *sd)
813 * Check for signal early to make process killable when there are
814 * always buffers available
816 if (signal_pending(current))
817 return -ERESTARTSYS;
819 while (!pipe->nrbufs) {
820 if (!pipe->writers)
821 return 0;
823 if (!pipe->waiting_writers && sd->num_spliced)
824 return 0;
826 if (sd->flags & SPLICE_F_NONBLOCK)
827 return -EAGAIN;
829 if (signal_pending(current))
830 return -ERESTARTSYS;
832 if (sd->need_wakeup) {
833 wakeup_pipe_writers(pipe);
834 sd->need_wakeup = false;
837 pipe_wait(pipe);
840 return 1;
844 * splice_from_pipe_begin - start splicing from pipe
845 * @sd: information about the splice operation
847 * Description:
848 * This function should be called before a loop containing
849 * splice_from_pipe_next() and splice_from_pipe_feed() to
850 * initialize the necessary fields of @sd.
852 static void splice_from_pipe_begin(struct splice_desc *sd)
854 sd->num_spliced = 0;
855 sd->need_wakeup = false;
859 * splice_from_pipe_end - finish splicing from pipe
860 * @pipe: pipe to splice from
861 * @sd: information about the splice operation
863 * Description:
864 * This function will wake up pipe writers if necessary. It should
865 * be called after a loop containing splice_from_pipe_next() and
866 * splice_from_pipe_feed().
868 static void splice_from_pipe_end(struct pipe_inode_info *pipe, struct splice_desc *sd)
870 if (sd->need_wakeup)
871 wakeup_pipe_writers(pipe);
875 * __splice_from_pipe - splice data from a pipe to given actor
876 * @pipe: pipe to splice from
877 * @sd: information to @actor
878 * @actor: handler that splices the data
880 * Description:
881 * This function does little more than loop over the pipe and call
882 * @actor to do the actual moving of a single struct pipe_buffer to
883 * the desired destination. See pipe_to_file, pipe_to_sendpage, or
884 * pipe_to_user.
887 ssize_t __splice_from_pipe(struct pipe_inode_info *pipe, struct splice_desc *sd,
888 splice_actor *actor)
890 int ret;
892 splice_from_pipe_begin(sd);
893 do {
894 cond_resched();
895 ret = splice_from_pipe_next(pipe, sd);
896 if (ret > 0)
897 ret = splice_from_pipe_feed(pipe, sd, actor);
898 } while (ret > 0);
899 splice_from_pipe_end(pipe, sd);
901 return sd->num_spliced ? sd->num_spliced : ret;
903 EXPORT_SYMBOL(__splice_from_pipe);
906 * splice_from_pipe - splice data from a pipe to a file
907 * @pipe: pipe to splice from
908 * @out: file to splice to
909 * @ppos: position in @out
910 * @len: how many bytes to splice
911 * @flags: splice modifier flags
912 * @actor: handler that splices the data
914 * Description:
915 * See __splice_from_pipe. This function locks the pipe inode,
916 * otherwise it's identical to __splice_from_pipe().
919 ssize_t splice_from_pipe(struct pipe_inode_info *pipe, struct file *out,
920 loff_t *ppos, size_t len, unsigned int flags,
921 splice_actor *actor)
923 ssize_t ret;
924 struct splice_desc sd = {
925 .total_len = len,
926 .flags = flags,
927 .pos = *ppos,
928 .u.file = out,
931 pipe_lock(pipe);
932 ret = __splice_from_pipe(pipe, &sd, actor);
933 pipe_unlock(pipe);
935 return ret;
939 * iter_file_splice_write - splice data from a pipe to a file
940 * @pipe: pipe info
941 * @out: file to write to
942 * @ppos: position in @out
943 * @len: number of bytes to splice
944 * @flags: splice modifier flags
946 * Description:
947 * Will either move or copy pages (determined by @flags options) from
948 * the given pipe inode to the given file.
949 * This one is ->write_iter-based.
952 ssize_t
953 iter_file_splice_write(struct pipe_inode_info *pipe, struct file *out,
954 loff_t *ppos, size_t len, unsigned int flags)
956 struct splice_desc sd = {
957 .total_len = len,
958 .flags = flags,
959 .pos = *ppos,
960 .u.file = out,
962 int nbufs = pipe->buffers;
963 struct bio_vec *array = kcalloc(nbufs, sizeof(struct bio_vec),
964 GFP_KERNEL);
965 ssize_t ret;
967 if (unlikely(!array))
968 return -ENOMEM;
970 pipe_lock(pipe);
972 splice_from_pipe_begin(&sd);
973 while (sd.total_len) {
974 struct iov_iter from;
975 size_t left;
976 int n, idx;
978 ret = splice_from_pipe_next(pipe, &sd);
979 if (ret <= 0)
980 break;
982 if (unlikely(nbufs < pipe->buffers)) {
983 kfree(array);
984 nbufs = pipe->buffers;
985 array = kcalloc(nbufs, sizeof(struct bio_vec),
986 GFP_KERNEL);
987 if (!array) {
988 ret = -ENOMEM;
989 break;
993 /* build the vector */
994 left = sd.total_len;
995 for (n = 0, idx = pipe->curbuf; left && n < pipe->nrbufs; n++, idx++) {
996 struct pipe_buffer *buf = pipe->bufs + idx;
997 size_t this_len = buf->len;
999 if (this_len > left)
1000 this_len = left;
1002 if (idx == pipe->buffers - 1)
1003 idx = -1;
1005 ret = buf->ops->confirm(pipe, buf);
1006 if (unlikely(ret)) {
1007 if (ret == -ENODATA)
1008 ret = 0;
1009 goto done;
1012 array[n].bv_page = buf->page;
1013 array[n].bv_len = this_len;
1014 array[n].bv_offset = buf->offset;
1015 left -= this_len;
1018 iov_iter_bvec(&from, ITER_BVEC | WRITE, array, n,
1019 sd.total_len - left);
1020 ret = vfs_iter_write(out, &from, &sd.pos);
1021 if (ret <= 0)
1022 break;
1024 sd.num_spliced += ret;
1025 sd.total_len -= ret;
1026 *ppos = sd.pos;
1028 /* dismiss the fully eaten buffers, adjust the partial one */
1029 while (ret) {
1030 struct pipe_buffer *buf = pipe->bufs + pipe->curbuf;
1031 if (ret >= buf->len) {
1032 const struct pipe_buf_operations *ops = buf->ops;
1033 ret -= buf->len;
1034 buf->len = 0;
1035 buf->ops = NULL;
1036 ops->release(pipe, buf);
1037 pipe->curbuf = (pipe->curbuf + 1) & (pipe->buffers - 1);
1038 pipe->nrbufs--;
1039 if (pipe->files)
1040 sd.need_wakeup = true;
1041 } else {
1042 buf->offset += ret;
1043 buf->len -= ret;
1044 ret = 0;
1048 done:
1049 kfree(array);
1050 splice_from_pipe_end(pipe, &sd);
1052 pipe_unlock(pipe);
1054 if (sd.num_spliced)
1055 ret = sd.num_spliced;
1057 return ret;
1060 EXPORT_SYMBOL(iter_file_splice_write);
1062 static int write_pipe_buf(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
1063 struct splice_desc *sd)
1065 int ret;
1066 void *data;
1067 loff_t tmp = sd->pos;
1069 data = kmap(buf->page);
1070 ret = __kernel_write(sd->u.file, data + buf->offset, sd->len, &tmp);
1071 kunmap(buf->page);
1073 return ret;
1076 static ssize_t default_file_splice_write(struct pipe_inode_info *pipe,
1077 struct file *out, loff_t *ppos,
1078 size_t len, unsigned int flags)
1080 ssize_t ret;
1082 ret = splice_from_pipe(pipe, out, ppos, len, flags, write_pipe_buf);
1083 if (ret > 0)
1084 *ppos += ret;
1086 return ret;
1090 * generic_splice_sendpage - splice data from a pipe to a socket
1091 * @pipe: pipe to splice from
1092 * @out: socket to write to
1093 * @ppos: position in @out
1094 * @len: number of bytes to splice
1095 * @flags: splice modifier flags
1097 * Description:
1098 * Will send @len bytes from the pipe to a network socket. No data copying
1099 * is involved.
1102 ssize_t generic_splice_sendpage(struct pipe_inode_info *pipe, struct file *out,
1103 loff_t *ppos, size_t len, unsigned int flags)
1105 return splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_sendpage);
1108 EXPORT_SYMBOL(generic_splice_sendpage);
1111 * Attempt to initiate a splice from pipe to file.
1113 static long do_splice_from(struct pipe_inode_info *pipe, struct file *out,
1114 loff_t *ppos, size_t len, unsigned int flags)
1116 ssize_t (*splice_write)(struct pipe_inode_info *, struct file *,
1117 loff_t *, size_t, unsigned int);
1119 if (out->f_op->splice_write)
1120 splice_write = out->f_op->splice_write;
1121 else
1122 splice_write = default_file_splice_write;
1124 return splice_write(pipe, out, ppos, len, flags);
1128 * Attempt to initiate a splice from a file to a pipe.
1130 static long do_splice_to(struct file *in, loff_t *ppos,
1131 struct pipe_inode_info *pipe, size_t len,
1132 unsigned int flags)
1134 ssize_t (*splice_read)(struct file *, loff_t *,
1135 struct pipe_inode_info *, size_t, unsigned int);
1136 int ret;
1138 if (unlikely(!(in->f_mode & FMODE_READ)))
1139 return -EBADF;
1141 ret = rw_verify_area(READ, in, ppos, len);
1142 if (unlikely(ret < 0))
1143 return ret;
1145 if (in->f_op->splice_read)
1146 splice_read = in->f_op->splice_read;
1147 else
1148 splice_read = default_file_splice_read;
1150 return splice_read(in, ppos, pipe, len, flags);
1154 * splice_direct_to_actor - splices data directly between two non-pipes
1155 * @in: file to splice from
1156 * @sd: actor information on where to splice to
1157 * @actor: handles the data splicing
1159 * Description:
1160 * This is a special case helper to splice directly between two
1161 * points, without requiring an explicit pipe. Internally an allocated
1162 * pipe is cached in the process, and reused during the lifetime of
1163 * that process.
1166 ssize_t splice_direct_to_actor(struct file *in, struct splice_desc *sd,
1167 splice_direct_actor *actor)
1169 struct pipe_inode_info *pipe;
1170 long ret, bytes;
1171 umode_t i_mode;
1172 size_t len;
1173 int i, flags, more;
1176 * We require the input being a regular file, as we don't want to
1177 * randomly drop data for eg socket -> socket splicing. Use the
1178 * piped splicing for that!
1180 i_mode = file_inode(in)->i_mode;
1181 if (unlikely(!S_ISREG(i_mode) && !S_ISBLK(i_mode)))
1182 return -EINVAL;
1185 * neither in nor out is a pipe, setup an internal pipe attached to
1186 * 'out' and transfer the wanted data from 'in' to 'out' through that
1188 pipe = current->splice_pipe;
1189 if (unlikely(!pipe)) {
1190 pipe = alloc_pipe_info();
1191 if (!pipe)
1192 return -ENOMEM;
1195 * We don't have an immediate reader, but we'll read the stuff
1196 * out of the pipe right after the splice_to_pipe(). So set
1197 * PIPE_READERS appropriately.
1199 pipe->readers = 1;
1201 current->splice_pipe = pipe;
1205 * Do the splice.
1207 ret = 0;
1208 bytes = 0;
1209 len = sd->total_len;
1210 flags = sd->flags;
1213 * Don't block on output, we have to drain the direct pipe.
1215 sd->flags &= ~SPLICE_F_NONBLOCK;
1216 more = sd->flags & SPLICE_F_MORE;
1218 while (len) {
1219 size_t read_len;
1220 loff_t pos = sd->pos, prev_pos = pos;
1222 ret = do_splice_to(in, &pos, pipe, len, flags);
1223 if (unlikely(ret <= 0))
1224 goto out_release;
1226 read_len = ret;
1227 sd->total_len = read_len;
1230 * If more data is pending, set SPLICE_F_MORE
1231 * If this is the last data and SPLICE_F_MORE was not set
1232 * initially, clears it.
1234 if (read_len < len)
1235 sd->flags |= SPLICE_F_MORE;
1236 else if (!more)
1237 sd->flags &= ~SPLICE_F_MORE;
1239 * NOTE: nonblocking mode only applies to the input. We
1240 * must not do the output in nonblocking mode as then we
1241 * could get stuck data in the internal pipe:
1243 ret = actor(pipe, sd);
1244 if (unlikely(ret <= 0)) {
1245 sd->pos = prev_pos;
1246 goto out_release;
1249 bytes += ret;
1250 len -= ret;
1251 sd->pos = pos;
1253 if (ret < read_len) {
1254 sd->pos = prev_pos + ret;
1255 goto out_release;
1259 done:
1260 pipe->nrbufs = pipe->curbuf = 0;
1261 file_accessed(in);
1262 return bytes;
1264 out_release:
1266 * If we did an incomplete transfer we must release
1267 * the pipe buffers in question:
1269 for (i = 0; i < pipe->buffers; i++) {
1270 struct pipe_buffer *buf = pipe->bufs + i;
1272 if (buf->ops) {
1273 buf->ops->release(pipe, buf);
1274 buf->ops = NULL;
1278 if (!bytes)
1279 bytes = ret;
1281 goto done;
1283 EXPORT_SYMBOL(splice_direct_to_actor);
1285 static int direct_splice_actor(struct pipe_inode_info *pipe,
1286 struct splice_desc *sd)
1288 struct file *file = sd->u.file;
1290 return do_splice_from(pipe, file, sd->opos, sd->total_len,
1291 sd->flags);
1295 * do_splice_direct - splices data directly between two files
1296 * @in: file to splice from
1297 * @ppos: input file offset
1298 * @out: file to splice to
1299 * @opos: output file offset
1300 * @len: number of bytes to splice
1301 * @flags: splice modifier flags
1303 * Description:
1304 * For use by do_sendfile(). splice can easily emulate sendfile, but
1305 * doing it in the application would incur an extra system call
1306 * (splice in + splice out, as compared to just sendfile()). So this helper
1307 * can splice directly through a process-private pipe.
1310 long do_splice_direct(struct file *in, loff_t *ppos, struct file *out,
1311 loff_t *opos, size_t len, unsigned int flags)
1313 struct splice_desc sd = {
1314 .len = len,
1315 .total_len = len,
1316 .flags = flags,
1317 .pos = *ppos,
1318 .u.file = out,
1319 .opos = opos,
1321 long ret;
1323 if (unlikely(!(out->f_mode & FMODE_WRITE)))
1324 return -EBADF;
1326 if (unlikely(out->f_flags & O_APPEND))
1327 return -EINVAL;
1329 ret = rw_verify_area(WRITE, out, opos, len);
1330 if (unlikely(ret < 0))
1331 return ret;
1333 ret = splice_direct_to_actor(in, &sd, direct_splice_actor);
1334 if (ret > 0)
1335 *ppos = sd.pos;
1337 return ret;
1339 EXPORT_SYMBOL(do_splice_direct);
1341 static int splice_pipe_to_pipe(struct pipe_inode_info *ipipe,
1342 struct pipe_inode_info *opipe,
1343 size_t len, unsigned int flags);
1346 * Determine where to splice to/from.
1348 static long do_splice(struct file *in, loff_t __user *off_in,
1349 struct file *out, loff_t __user *off_out,
1350 size_t len, unsigned int flags)
1352 struct pipe_inode_info *ipipe;
1353 struct pipe_inode_info *opipe;
1354 loff_t offset;
1355 long ret;
1357 ipipe = get_pipe_info(in);
1358 opipe = get_pipe_info(out);
1360 if (ipipe && opipe) {
1361 if (off_in || off_out)
1362 return -ESPIPE;
1364 if (!(in->f_mode & FMODE_READ))
1365 return -EBADF;
1367 if (!(out->f_mode & FMODE_WRITE))
1368 return -EBADF;
1370 /* Splicing to self would be fun, but... */
1371 if (ipipe == opipe)
1372 return -EINVAL;
1374 return splice_pipe_to_pipe(ipipe, opipe, len, flags);
1377 if (ipipe) {
1378 if (off_in)
1379 return -ESPIPE;
1380 if (off_out) {
1381 if (!(out->f_mode & FMODE_PWRITE))
1382 return -EINVAL;
1383 if (copy_from_user(&offset, off_out, sizeof(loff_t)))
1384 return -EFAULT;
1385 } else {
1386 offset = out->f_pos;
1389 if (unlikely(!(out->f_mode & FMODE_WRITE)))
1390 return -EBADF;
1392 if (unlikely(out->f_flags & O_APPEND))
1393 return -EINVAL;
1395 ret = rw_verify_area(WRITE, out, &offset, len);
1396 if (unlikely(ret < 0))
1397 return ret;
1399 file_start_write(out);
1400 ret = do_splice_from(ipipe, out, &offset, len, flags);
1401 file_end_write(out);
1403 if (!off_out)
1404 out->f_pos = offset;
1405 else if (copy_to_user(off_out, &offset, sizeof(loff_t)))
1406 ret = -EFAULT;
1408 return ret;
1411 if (opipe) {
1412 if (off_out)
1413 return -ESPIPE;
1414 if (off_in) {
1415 if (!(in->f_mode & FMODE_PREAD))
1416 return -EINVAL;
1417 if (copy_from_user(&offset, off_in, sizeof(loff_t)))
1418 return -EFAULT;
1419 } else {
1420 offset = in->f_pos;
1423 ret = do_splice_to(in, &offset, opipe, len, flags);
1425 if (!off_in)
1426 in->f_pos = offset;
1427 else if (copy_to_user(off_in, &offset, sizeof(loff_t)))
1428 ret = -EFAULT;
1430 return ret;
1433 return -EINVAL;
1437 * Map an iov into an array of pages and offset/length tupples. With the
1438 * partial_page structure, we can map several non-contiguous ranges into
1439 * our ones pages[] map instead of splitting that operation into pieces.
1440 * Could easily be exported as a generic helper for other users, in which
1441 * case one would probably want to add a 'max_nr_pages' parameter as well.
1443 static int get_iovec_page_array(const struct iovec __user *iov,
1444 unsigned int nr_vecs, struct page **pages,
1445 struct partial_page *partial, bool aligned,
1446 unsigned int pipe_buffers)
1448 int buffers = 0, error = 0;
1450 while (nr_vecs) {
1451 unsigned long off, npages;
1452 struct iovec entry;
1453 void __user *base;
1454 size_t len;
1455 int i;
1457 error = -EFAULT;
1458 if (copy_from_user(&entry, iov, sizeof(entry)))
1459 break;
1461 base = entry.iov_base;
1462 len = entry.iov_len;
1465 * Sanity check this iovec. 0 read succeeds.
1467 error = 0;
1468 if (unlikely(!len))
1469 break;
1470 error = -EFAULT;
1471 if (!access_ok(VERIFY_READ, base, len))
1472 break;
1475 * Get this base offset and number of pages, then map
1476 * in the user pages.
1478 off = (unsigned long) base & ~PAGE_MASK;
1481 * If asked for alignment, the offset must be zero and the
1482 * length a multiple of the PAGE_SIZE.
1484 error = -EINVAL;
1485 if (aligned && (off || len & ~PAGE_MASK))
1486 break;
1488 npages = (off + len + PAGE_SIZE - 1) >> PAGE_SHIFT;
1489 if (npages > pipe_buffers - buffers)
1490 npages = pipe_buffers - buffers;
1492 error = get_user_pages_fast((unsigned long)base, npages,
1493 0, &pages[buffers]);
1495 if (unlikely(error <= 0))
1496 break;
1499 * Fill this contiguous range into the partial page map.
1501 for (i = 0; i < error; i++) {
1502 const int plen = min_t(size_t, len, PAGE_SIZE - off);
1504 partial[buffers].offset = off;
1505 partial[buffers].len = plen;
1507 off = 0;
1508 len -= plen;
1509 buffers++;
1513 * We didn't complete this iov, stop here since it probably
1514 * means we have to move some of this into a pipe to
1515 * be able to continue.
1517 if (len)
1518 break;
1521 * Don't continue if we mapped fewer pages than we asked for,
1522 * or if we mapped the max number of pages that we have
1523 * room for.
1525 if (error < npages || buffers == pipe_buffers)
1526 break;
1528 nr_vecs--;
1529 iov++;
1532 if (buffers)
1533 return buffers;
1535 return error;
1538 static int pipe_to_user(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
1539 struct splice_desc *sd)
1541 int n = copy_page_to_iter(buf->page, buf->offset, sd->len, sd->u.data);
1542 return n == sd->len ? n : -EFAULT;
1546 * For lack of a better implementation, implement vmsplice() to userspace
1547 * as a simple copy of the pipes pages to the user iov.
1549 static long vmsplice_to_user(struct file *file, const struct iovec __user *uiov,
1550 unsigned long nr_segs, unsigned int flags)
1552 struct pipe_inode_info *pipe;
1553 struct splice_desc sd;
1554 long ret;
1555 struct iovec iovstack[UIO_FASTIOV];
1556 struct iovec *iov = iovstack;
1557 struct iov_iter iter;
1559 pipe = get_pipe_info(file);
1560 if (!pipe)
1561 return -EBADF;
1563 ret = import_iovec(READ, uiov, nr_segs,
1564 ARRAY_SIZE(iovstack), &iov, &iter);
1565 if (ret < 0)
1566 return ret;
1568 sd.total_len = iov_iter_count(&iter);
1569 sd.len = 0;
1570 sd.flags = flags;
1571 sd.u.data = &iter;
1572 sd.pos = 0;
1574 if (sd.total_len) {
1575 pipe_lock(pipe);
1576 ret = __splice_from_pipe(pipe, &sd, pipe_to_user);
1577 pipe_unlock(pipe);
1580 kfree(iov);
1581 return ret;
1585 * vmsplice splices a user address range into a pipe. It can be thought of
1586 * as splice-from-memory, where the regular splice is splice-from-file (or
1587 * to file). In both cases the output is a pipe, naturally.
1589 static long vmsplice_to_pipe(struct file *file, const struct iovec __user *iov,
1590 unsigned long nr_segs, unsigned int flags)
1592 struct pipe_inode_info *pipe;
1593 struct page *pages[PIPE_DEF_BUFFERS];
1594 struct partial_page partial[PIPE_DEF_BUFFERS];
1595 struct splice_pipe_desc spd = {
1596 .pages = pages,
1597 .partial = partial,
1598 .nr_pages_max = PIPE_DEF_BUFFERS,
1599 .flags = flags,
1600 .ops = &user_page_pipe_buf_ops,
1601 .spd_release = spd_release_page,
1603 long ret;
1605 pipe = get_pipe_info(file);
1606 if (!pipe)
1607 return -EBADF;
1609 if (splice_grow_spd(pipe, &spd))
1610 return -ENOMEM;
1612 spd.nr_pages = get_iovec_page_array(iov, nr_segs, spd.pages,
1613 spd.partial, false,
1614 spd.nr_pages_max);
1615 if (spd.nr_pages <= 0)
1616 ret = spd.nr_pages;
1617 else
1618 ret = splice_to_pipe(pipe, &spd);
1620 splice_shrink_spd(&spd);
1621 return ret;
1625 * Note that vmsplice only really supports true splicing _from_ user memory
1626 * to a pipe, not the other way around. Splicing from user memory is a simple
1627 * operation that can be supported without any funky alignment restrictions
1628 * or nasty vm tricks. We simply map in the user memory and fill them into
1629 * a pipe. The reverse isn't quite as easy, though. There are two possible
1630 * solutions for that:
1632 * - memcpy() the data internally, at which point we might as well just
1633 * do a regular read() on the buffer anyway.
1634 * - Lots of nasty vm tricks, that are neither fast nor flexible (it
1635 * has restriction limitations on both ends of the pipe).
1637 * Currently we punt and implement it as a normal copy, see pipe_to_user().
1640 SYSCALL_DEFINE4(vmsplice, int, fd, const struct iovec __user *, iov,
1641 unsigned long, nr_segs, unsigned int, flags)
1643 struct fd f;
1644 long error;
1646 if (unlikely(nr_segs > UIO_MAXIOV))
1647 return -EINVAL;
1648 else if (unlikely(!nr_segs))
1649 return 0;
1651 error = -EBADF;
1652 f = fdget(fd);
1653 if (f.file) {
1654 if (f.file->f_mode & FMODE_WRITE)
1655 error = vmsplice_to_pipe(f.file, iov, nr_segs, flags);
1656 else if (f.file->f_mode & FMODE_READ)
1657 error = vmsplice_to_user(f.file, iov, nr_segs, flags);
1659 fdput(f);
1662 return error;
1665 #ifdef CONFIG_COMPAT
1666 COMPAT_SYSCALL_DEFINE4(vmsplice, int, fd, const struct compat_iovec __user *, iov32,
1667 unsigned int, nr_segs, unsigned int, flags)
1669 unsigned i;
1670 struct iovec __user *iov;
1671 if (nr_segs > UIO_MAXIOV)
1672 return -EINVAL;
1673 iov = compat_alloc_user_space(nr_segs * sizeof(struct iovec));
1674 for (i = 0; i < nr_segs; i++) {
1675 struct compat_iovec v;
1676 if (get_user(v.iov_base, &iov32[i].iov_base) ||
1677 get_user(v.iov_len, &iov32[i].iov_len) ||
1678 put_user(compat_ptr(v.iov_base), &iov[i].iov_base) ||
1679 put_user(v.iov_len, &iov[i].iov_len))
1680 return -EFAULT;
1682 return sys_vmsplice(fd, iov, nr_segs, flags);
1684 #endif
1686 SYSCALL_DEFINE6(splice, int, fd_in, loff_t __user *, off_in,
1687 int, fd_out, loff_t __user *, off_out,
1688 size_t, len, unsigned int, flags)
1690 struct fd in, out;
1691 long error;
1693 if (unlikely(!len))
1694 return 0;
1696 error = -EBADF;
1697 in = fdget(fd_in);
1698 if (in.file) {
1699 if (in.file->f_mode & FMODE_READ) {
1700 out = fdget(fd_out);
1701 if (out.file) {
1702 if (out.file->f_mode & FMODE_WRITE)
1703 error = do_splice(in.file, off_in,
1704 out.file, off_out,
1705 len, flags);
1706 fdput(out);
1709 fdput(in);
1711 return error;
1715 * Make sure there's data to read. Wait for input if we can, otherwise
1716 * return an appropriate error.
1718 static int ipipe_prep(struct pipe_inode_info *pipe, unsigned int flags)
1720 int ret;
1723 * Check ->nrbufs without the inode lock first. This function
1724 * is speculative anyways, so missing one is ok.
1726 if (pipe->nrbufs)
1727 return 0;
1729 ret = 0;
1730 pipe_lock(pipe);
1732 while (!pipe->nrbufs) {
1733 if (signal_pending(current)) {
1734 ret = -ERESTARTSYS;
1735 break;
1737 if (!pipe->writers)
1738 break;
1739 if (!pipe->waiting_writers) {
1740 if (flags & SPLICE_F_NONBLOCK) {
1741 ret = -EAGAIN;
1742 break;
1745 pipe_wait(pipe);
1748 pipe_unlock(pipe);
1749 return ret;
1753 * Make sure there's writeable room. Wait for room if we can, otherwise
1754 * return an appropriate error.
1756 static int opipe_prep(struct pipe_inode_info *pipe, unsigned int flags)
1758 int ret;
1761 * Check ->nrbufs without the inode lock first. This function
1762 * is speculative anyways, so missing one is ok.
1764 if (pipe->nrbufs < pipe->buffers)
1765 return 0;
1767 ret = 0;
1768 pipe_lock(pipe);
1770 while (pipe->nrbufs >= pipe->buffers) {
1771 if (!pipe->readers) {
1772 send_sig(SIGPIPE, current, 0);
1773 ret = -EPIPE;
1774 break;
1776 if (flags & SPLICE_F_NONBLOCK) {
1777 ret = -EAGAIN;
1778 break;
1780 if (signal_pending(current)) {
1781 ret = -ERESTARTSYS;
1782 break;
1784 pipe->waiting_writers++;
1785 pipe_wait(pipe);
1786 pipe->waiting_writers--;
1789 pipe_unlock(pipe);
1790 return ret;
1794 * Splice contents of ipipe to opipe.
1796 static int splice_pipe_to_pipe(struct pipe_inode_info *ipipe,
1797 struct pipe_inode_info *opipe,
1798 size_t len, unsigned int flags)
1800 struct pipe_buffer *ibuf, *obuf;
1801 int ret = 0, nbuf;
1802 bool input_wakeup = false;
1805 retry:
1806 ret = ipipe_prep(ipipe, flags);
1807 if (ret)
1808 return ret;
1810 ret = opipe_prep(opipe, flags);
1811 if (ret)
1812 return ret;
1815 * Potential ABBA deadlock, work around it by ordering lock
1816 * grabbing by pipe info address. Otherwise two different processes
1817 * could deadlock (one doing tee from A -> B, the other from B -> A).
1819 pipe_double_lock(ipipe, opipe);
1821 do {
1822 if (!opipe->readers) {
1823 send_sig(SIGPIPE, current, 0);
1824 if (!ret)
1825 ret = -EPIPE;
1826 break;
1829 if (!ipipe->nrbufs && !ipipe->writers)
1830 break;
1833 * Cannot make any progress, because either the input
1834 * pipe is empty or the output pipe is full.
1836 if (!ipipe->nrbufs || opipe->nrbufs >= opipe->buffers) {
1837 /* Already processed some buffers, break */
1838 if (ret)
1839 break;
1841 if (flags & SPLICE_F_NONBLOCK) {
1842 ret = -EAGAIN;
1843 break;
1847 * We raced with another reader/writer and haven't
1848 * managed to process any buffers. A zero return
1849 * value means EOF, so retry instead.
1851 pipe_unlock(ipipe);
1852 pipe_unlock(opipe);
1853 goto retry;
1856 ibuf = ipipe->bufs + ipipe->curbuf;
1857 nbuf = (opipe->curbuf + opipe->nrbufs) & (opipe->buffers - 1);
1858 obuf = opipe->bufs + nbuf;
1860 if (len >= ibuf->len) {
1862 * Simply move the whole buffer from ipipe to opipe
1864 *obuf = *ibuf;
1865 ibuf->ops = NULL;
1866 opipe->nrbufs++;
1867 ipipe->curbuf = (ipipe->curbuf + 1) & (ipipe->buffers - 1);
1868 ipipe->nrbufs--;
1869 input_wakeup = true;
1870 } else {
1872 * Get a reference to this pipe buffer,
1873 * so we can copy the contents over.
1875 ibuf->ops->get(ipipe, ibuf);
1876 *obuf = *ibuf;
1879 * Don't inherit the gift flag, we need to
1880 * prevent multiple steals of this page.
1882 obuf->flags &= ~PIPE_BUF_FLAG_GIFT;
1884 obuf->len = len;
1885 opipe->nrbufs++;
1886 ibuf->offset += obuf->len;
1887 ibuf->len -= obuf->len;
1889 ret += obuf->len;
1890 len -= obuf->len;
1891 } while (len);
1893 pipe_unlock(ipipe);
1894 pipe_unlock(opipe);
1897 * If we put data in the output pipe, wakeup any potential readers.
1899 if (ret > 0)
1900 wakeup_pipe_readers(opipe);
1902 if (input_wakeup)
1903 wakeup_pipe_writers(ipipe);
1905 return ret;
1909 * Link contents of ipipe to opipe.
1911 static int link_pipe(struct pipe_inode_info *ipipe,
1912 struct pipe_inode_info *opipe,
1913 size_t len, unsigned int flags)
1915 struct pipe_buffer *ibuf, *obuf;
1916 int ret = 0, i = 0, nbuf;
1919 * Potential ABBA deadlock, work around it by ordering lock
1920 * grabbing by pipe info address. Otherwise two different processes
1921 * could deadlock (one doing tee from A -> B, the other from B -> A).
1923 pipe_double_lock(ipipe, opipe);
1925 do {
1926 if (!opipe->readers) {
1927 send_sig(SIGPIPE, current, 0);
1928 if (!ret)
1929 ret = -EPIPE;
1930 break;
1934 * If we have iterated all input buffers or ran out of
1935 * output room, break.
1937 if (i >= ipipe->nrbufs || opipe->nrbufs >= opipe->buffers)
1938 break;
1940 ibuf = ipipe->bufs + ((ipipe->curbuf + i) & (ipipe->buffers-1));
1941 nbuf = (opipe->curbuf + opipe->nrbufs) & (opipe->buffers - 1);
1944 * Get a reference to this pipe buffer,
1945 * so we can copy the contents over.
1947 ibuf->ops->get(ipipe, ibuf);
1949 obuf = opipe->bufs + nbuf;
1950 *obuf = *ibuf;
1953 * Don't inherit the gift flag, we need to
1954 * prevent multiple steals of this page.
1956 obuf->flags &= ~PIPE_BUF_FLAG_GIFT;
1958 if (obuf->len > len)
1959 obuf->len = len;
1961 opipe->nrbufs++;
1962 ret += obuf->len;
1963 len -= obuf->len;
1964 i++;
1965 } while (len);
1968 * return EAGAIN if we have the potential of some data in the
1969 * future, otherwise just return 0
1971 if (!ret && ipipe->waiting_writers && (flags & SPLICE_F_NONBLOCK))
1972 ret = -EAGAIN;
1974 pipe_unlock(ipipe);
1975 pipe_unlock(opipe);
1978 * If we put data in the output pipe, wakeup any potential readers.
1980 if (ret > 0)
1981 wakeup_pipe_readers(opipe);
1983 return ret;
1987 * This is a tee(1) implementation that works on pipes. It doesn't copy
1988 * any data, it simply references the 'in' pages on the 'out' pipe.
1989 * The 'flags' used are the SPLICE_F_* variants, currently the only
1990 * applicable one is SPLICE_F_NONBLOCK.
1992 static long do_tee(struct file *in, struct file *out, size_t len,
1993 unsigned int flags)
1995 struct pipe_inode_info *ipipe = get_pipe_info(in);
1996 struct pipe_inode_info *opipe = get_pipe_info(out);
1997 int ret = -EINVAL;
2000 * Duplicate the contents of ipipe to opipe without actually
2001 * copying the data.
2003 if (ipipe && opipe && ipipe != opipe) {
2005 * Keep going, unless we encounter an error. The ipipe/opipe
2006 * ordering doesn't really matter.
2008 ret = ipipe_prep(ipipe, flags);
2009 if (!ret) {
2010 ret = opipe_prep(opipe, flags);
2011 if (!ret)
2012 ret = link_pipe(ipipe, opipe, len, flags);
2016 return ret;
2019 SYSCALL_DEFINE4(tee, int, fdin, int, fdout, size_t, len, unsigned int, flags)
2021 struct fd in;
2022 int error;
2024 if (unlikely(!len))
2025 return 0;
2027 error = -EBADF;
2028 in = fdget(fdin);
2029 if (in.file) {
2030 if (in.file->f_mode & FMODE_READ) {
2031 struct fd out = fdget(fdout);
2032 if (out.file) {
2033 if (out.file->f_mode & FMODE_WRITE)
2034 error = do_tee(in.file, out.file,
2035 len, flags);
2036 fdput(out);
2039 fdput(in);
2042 return error;