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>
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/buffer_head.h>
29 #include <linux/module.h>
30 #include <linux/syscalls.h>
31 #include <linux/uio.h>
32 #include <linux/security.h>
35 * Attempt to steal a page from a pipe buffer. This should perhaps go into
36 * a vm helper function, it's already simplified quite a bit by the
37 * addition of remove_mapping(). If success is returned, the caller may
38 * attempt to reuse this page for another destination.
40 static int page_cache_pipe_buf_steal(struct pipe_inode_info *pipe,
41 struct pipe_buffer *buf)
43 struct page *page = buf->page;
44 struct address_space *mapping;
48 mapping = page_mapping(page);
50 WARN_ON(!PageUptodate(page));
53 * At least for ext2 with nobh option, we need to wait on
54 * writeback completing on this page, since we'll remove it
55 * from the pagecache. Otherwise truncate wont wait on the
56 * page, allowing the disk blocks to be reused by someone else
57 * before we actually wrote our data to them. fs corruption
60 wait_on_page_writeback(page);
62 if (page_has_private(page) &&
63 !try_to_release_page(page, GFP_KERNEL))
67 * If we succeeded in removing the mapping, set LRU flag
70 if (remove_mapping(mapping, page)) {
71 buf->flags |= PIPE_BUF_FLAG_LRU;
77 * Raced with truncate or failed to remove page from current
78 * address space, unlock and return failure.
85 static void page_cache_pipe_buf_release(struct pipe_inode_info *pipe,
86 struct pipe_buffer *buf)
88 page_cache_release(buf->page);
89 buf->flags &= ~PIPE_BUF_FLAG_LRU;
93 * Check whether the contents of buf is OK to access. Since the content
94 * is a page cache page, IO may be in flight.
96 static int page_cache_pipe_buf_confirm(struct pipe_inode_info *pipe,
97 struct pipe_buffer *buf)
99 struct page *page = buf->page;
102 if (!PageUptodate(page)) {
106 * Page got truncated/unhashed. This will cause a 0-byte
107 * splice, if this is the first page.
109 if (!page->mapping) {
115 * Uh oh, read-error from disk.
117 if (!PageUptodate(page)) {
123 * Page is ok afterall, we are done.
134 static const struct pipe_buf_operations page_cache_pipe_buf_ops = {
136 .map = generic_pipe_buf_map,
137 .unmap = generic_pipe_buf_unmap,
138 .confirm = page_cache_pipe_buf_confirm,
139 .release = page_cache_pipe_buf_release,
140 .steal = page_cache_pipe_buf_steal,
141 .get = generic_pipe_buf_get,
144 static int user_page_pipe_buf_steal(struct pipe_inode_info *pipe,
145 struct pipe_buffer *buf)
147 if (!(buf->flags & PIPE_BUF_FLAG_GIFT))
150 buf->flags |= PIPE_BUF_FLAG_LRU;
151 return generic_pipe_buf_steal(pipe, buf);
154 static const struct pipe_buf_operations user_page_pipe_buf_ops = {
156 .map = generic_pipe_buf_map,
157 .unmap = generic_pipe_buf_unmap,
158 .confirm = generic_pipe_buf_confirm,
159 .release = page_cache_pipe_buf_release,
160 .steal = user_page_pipe_buf_steal,
161 .get = generic_pipe_buf_get,
165 * splice_to_pipe - fill passed data into a pipe
166 * @pipe: pipe to fill
170 * @spd contains a map of pages and len/offset tuples, along with
171 * the struct pipe_buf_operations associated with these pages. This
172 * function will link that data to the pipe.
175 ssize_t splice_to_pipe(struct pipe_inode_info *pipe,
176 struct splice_pipe_desc *spd)
178 unsigned int spd_pages = spd->nr_pages;
179 int ret, do_wakeup, page_nr;
188 if (!pipe->readers) {
189 send_sig(SIGPIPE, current, 0);
195 if (pipe->nrbufs < PIPE_BUFFERS) {
196 int newbuf = (pipe->curbuf + pipe->nrbufs) & (PIPE_BUFFERS - 1);
197 struct pipe_buffer *buf = pipe->bufs + newbuf;
199 buf->page = spd->pages[page_nr];
200 buf->offset = spd->partial[page_nr].offset;
201 buf->len = spd->partial[page_nr].len;
202 buf->private = spd->partial[page_nr].private;
204 if (spd->flags & SPLICE_F_GIFT)
205 buf->flags |= PIPE_BUF_FLAG_GIFT;
214 if (!--spd->nr_pages)
216 if (pipe->nrbufs < PIPE_BUFFERS)
222 if (spd->flags & SPLICE_F_NONBLOCK) {
228 if (signal_pending(current)) {
236 if (waitqueue_active(&pipe->wait))
237 wake_up_interruptible_sync(&pipe->wait);
238 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
242 pipe->waiting_writers++;
244 pipe->waiting_writers--;
251 if (waitqueue_active(&pipe->wait))
252 wake_up_interruptible(&pipe->wait);
253 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
256 while (page_nr < spd_pages)
257 spd->spd_release(spd, page_nr++);
262 static void spd_release_page(struct splice_pipe_desc *spd, unsigned int i)
264 page_cache_release(spd->pages[i]);
268 __generic_file_splice_read(struct file *in, loff_t *ppos,
269 struct pipe_inode_info *pipe, size_t len,
272 struct address_space *mapping = in->f_mapping;
273 unsigned int loff, nr_pages, req_pages;
274 struct page *pages[PIPE_BUFFERS];
275 struct partial_page partial[PIPE_BUFFERS];
277 pgoff_t index, end_index;
280 struct splice_pipe_desc spd = {
284 .ops = &page_cache_pipe_buf_ops,
285 .spd_release = spd_release_page,
288 index = *ppos >> PAGE_CACHE_SHIFT;
289 loff = *ppos & ~PAGE_CACHE_MASK;
290 req_pages = (len + loff + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
291 nr_pages = min(req_pages, (unsigned)PIPE_BUFFERS);
294 * Lookup the (hopefully) full range of pages we need.
296 spd.nr_pages = find_get_pages_contig(mapping, index, nr_pages, pages);
297 index += spd.nr_pages;
300 * If find_get_pages_contig() returned fewer pages than we needed,
301 * readahead/allocate the rest and fill in the holes.
303 if (spd.nr_pages < nr_pages)
304 page_cache_sync_readahead(mapping, &in->f_ra, in,
305 index, req_pages - spd.nr_pages);
308 while (spd.nr_pages < nr_pages) {
310 * Page could be there, find_get_pages_contig() breaks on
313 page = find_get_page(mapping, index);
316 * page didn't exist, allocate one.
318 page = page_cache_alloc_cold(mapping);
322 error = add_to_page_cache_lru(page, mapping, index,
323 mapping_gfp_mask(mapping));
324 if (unlikely(error)) {
325 page_cache_release(page);
326 if (error == -EEXIST)
331 * add_to_page_cache() locks the page, unlock it
332 * to avoid convoluting the logic below even more.
337 pages[spd.nr_pages++] = page;
342 * Now loop over the map and see if we need to start IO on any
343 * pages, fill in the partial map, etc.
345 index = *ppos >> PAGE_CACHE_SHIFT;
346 nr_pages = spd.nr_pages;
348 for (page_nr = 0; page_nr < nr_pages; page_nr++) {
349 unsigned int this_len;
355 * this_len is the max we'll use from this page
357 this_len = min_t(unsigned long, len, PAGE_CACHE_SIZE - loff);
358 page = pages[page_nr];
360 if (PageReadahead(page))
361 page_cache_async_readahead(mapping, &in->f_ra, in,
362 page, index, req_pages - page_nr);
365 * If the page isn't uptodate, we may need to start io on it
367 if (!PageUptodate(page)) {
371 * Page was truncated, or invalidated by the
372 * filesystem. Redo the find/create, but this time the
373 * page is kept locked, so there's no chance of another
374 * race with truncate/invalidate.
376 if (!page->mapping) {
378 page = find_or_create_page(mapping, index,
379 mapping_gfp_mask(mapping));
385 page_cache_release(pages[page_nr]);
386 pages[page_nr] = page;
389 * page was already under io and is now done, great
391 if (PageUptodate(page)) {
397 * need to read in the page
399 error = mapping->a_ops->readpage(in, page);
400 if (unlikely(error)) {
402 * We really should re-lookup the page here,
403 * but it complicates things a lot. Instead
404 * lets just do what we already stored, and
405 * we'll get it the next time we are called.
407 if (error == AOP_TRUNCATED_PAGE)
415 * i_size must be checked after PageUptodate.
417 isize = i_size_read(mapping->host);
418 end_index = (isize - 1) >> PAGE_CACHE_SHIFT;
419 if (unlikely(!isize || index > end_index))
423 * if this is the last page, see if we need to shrink
424 * the length and stop
426 if (end_index == index) {
430 * max good bytes in this page
432 plen = ((isize - 1) & ~PAGE_CACHE_MASK) + 1;
437 * force quit after adding this page
439 this_len = min(this_len, plen - loff);
443 partial[page_nr].offset = loff;
444 partial[page_nr].len = this_len;
452 * Release any pages at the end, if we quit early. 'page_nr' is how far
453 * we got, 'nr_pages' is how many pages are in the map.
455 while (page_nr < nr_pages)
456 page_cache_release(pages[page_nr++]);
457 in->f_ra.prev_pos = (loff_t)index << PAGE_CACHE_SHIFT;
460 return splice_to_pipe(pipe, &spd);
466 * generic_file_splice_read - splice data from file to a pipe
467 * @in: file to splice from
468 * @ppos: position in @in
469 * @pipe: pipe to splice to
470 * @len: number of bytes to splice
471 * @flags: splice modifier flags
474 * Will read pages from given file and fill them into a pipe. Can be
475 * used as long as the address_space operations for the source implements
479 ssize_t generic_file_splice_read(struct file *in, loff_t *ppos,
480 struct pipe_inode_info *pipe, size_t len,
486 isize = i_size_read(in->f_mapping->host);
487 if (unlikely(*ppos >= isize))
490 left = isize - *ppos;
491 if (unlikely(left < len))
494 ret = __generic_file_splice_read(in, ppos, pipe, len, flags);
502 EXPORT_SYMBOL(generic_file_splice_read);
504 static const struct pipe_buf_operations default_pipe_buf_ops = {
506 .map = generic_pipe_buf_map,
507 .unmap = generic_pipe_buf_unmap,
508 .confirm = generic_pipe_buf_confirm,
509 .release = generic_pipe_buf_release,
510 .steal = generic_pipe_buf_steal,
511 .get = generic_pipe_buf_get,
514 static ssize_t kernel_readv(struct file *file, const struct iovec *vec,
515 unsigned long vlen, loff_t offset)
523 /* The cast to a user pointer is valid due to the set_fs() */
524 res = vfs_readv(file, (const struct iovec __user *)vec, vlen, &pos);
530 static ssize_t kernel_write(struct file *file, const char *buf, size_t count,
538 /* The cast to a user pointer is valid due to the set_fs() */
539 res = vfs_write(file, (const char __user *)buf, count, &pos);
545 ssize_t default_file_splice_read(struct file *in, loff_t *ppos,
546 struct pipe_inode_info *pipe, size_t len,
549 unsigned int nr_pages;
550 unsigned int nr_freed;
552 struct page *pages[PIPE_BUFFERS];
553 struct partial_page partial[PIPE_BUFFERS];
554 struct iovec vec[PIPE_BUFFERS];
560 struct splice_pipe_desc spd = {
564 .ops = &default_pipe_buf_ops,
565 .spd_release = spd_release_page,
568 index = *ppos >> PAGE_CACHE_SHIFT;
569 offset = *ppos & ~PAGE_CACHE_MASK;
570 nr_pages = (len + offset + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
572 for (i = 0; i < nr_pages && i < PIPE_BUFFERS && len; i++) {
575 page = alloc_page(GFP_USER);
580 this_len = min_t(size_t, len, PAGE_CACHE_SIZE - offset);
581 vec[i].iov_base = (void __user *) page_address(page);
582 vec[i].iov_len = this_len;
589 res = kernel_readv(in, vec, spd.nr_pages, *ppos);
600 for (i = 0; i < spd.nr_pages; i++) {
601 this_len = min_t(size_t, vec[i].iov_len, res);
602 partial[i].offset = 0;
603 partial[i].len = this_len;
605 __free_page(pages[i]);
611 spd.nr_pages -= nr_freed;
613 res = splice_to_pipe(pipe, &spd);
620 for (i = 0; i < spd.nr_pages; i++)
621 __free_page(pages[i]);
625 EXPORT_SYMBOL(default_file_splice_read);
628 * Send 'sd->len' bytes to socket from 'sd->file' at position 'sd->pos'
629 * using sendpage(). Return the number of bytes sent.
631 static int pipe_to_sendpage(struct pipe_inode_info *pipe,
632 struct pipe_buffer *buf, struct splice_desc *sd)
634 struct file *file = sd->u.file;
635 loff_t pos = sd->pos;
638 ret = buf->ops->confirm(pipe, buf);
640 more = (sd->flags & SPLICE_F_MORE) || sd->len < sd->total_len;
642 ret = file->f_op->sendpage(file, buf->page, buf->offset,
643 sd->len, &pos, more);
650 * This is a little more tricky than the file -> pipe splicing. There are
651 * basically three cases:
653 * - Destination page already exists in the address space and there
654 * are users of it. For that case we have no other option that
655 * copying the data. Tough luck.
656 * - Destination page already exists in the address space, but there
657 * are no users of it. Make sure it's uptodate, then drop it. Fall
658 * through to last case.
659 * - Destination page does not exist, we can add the pipe page to
660 * the page cache and avoid the copy.
662 * If asked to move pages to the output file (SPLICE_F_MOVE is set in
663 * sd->flags), we attempt to migrate pages from the pipe to the output
664 * file address space page cache. This is possible if no one else has
665 * the pipe page referenced outside of the pipe and page cache. If
666 * SPLICE_F_MOVE isn't set, or we cannot move the page, we simply create
667 * a new page in the output file page cache and fill/dirty that.
669 int pipe_to_file(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
670 struct splice_desc *sd)
672 struct file *file = sd->u.file;
673 struct address_space *mapping = file->f_mapping;
674 unsigned int offset, this_len;
680 * make sure the data in this buffer is uptodate
682 ret = buf->ops->confirm(pipe, buf);
686 offset = sd->pos & ~PAGE_CACHE_MASK;
689 if (this_len + offset > PAGE_CACHE_SIZE)
690 this_len = PAGE_CACHE_SIZE - offset;
692 ret = pagecache_write_begin(file, mapping, sd->pos, this_len,
693 AOP_FLAG_UNINTERRUPTIBLE, &page, &fsdata);
697 if (buf->page != page) {
699 * Careful, ->map() uses KM_USER0!
701 char *src = buf->ops->map(pipe, buf, 1);
702 char *dst = kmap_atomic(page, KM_USER1);
704 memcpy(dst + offset, src + buf->offset, this_len);
705 flush_dcache_page(page);
706 kunmap_atomic(dst, KM_USER1);
707 buf->ops->unmap(pipe, buf, src);
709 ret = pagecache_write_end(file, mapping, sd->pos, this_len, this_len,
714 EXPORT_SYMBOL(pipe_to_file);
716 static void wakeup_pipe_writers(struct pipe_inode_info *pipe)
719 if (waitqueue_active(&pipe->wait))
720 wake_up_interruptible(&pipe->wait);
721 kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
725 * splice_from_pipe_feed - feed available data from a pipe to a file
726 * @pipe: pipe to splice from
727 * @sd: information to @actor
728 * @actor: handler that splices the data
731 * This function loops over the pipe and calls @actor to do the
732 * actual moving of a single struct pipe_buffer to the desired
733 * destination. It returns when there's no more buffers left in
734 * the pipe or if the requested number of bytes (@sd->total_len)
735 * have been copied. It returns a positive number (one) if the
736 * pipe needs to be filled with more data, zero if the required
737 * number of bytes have been copied and -errno on error.
739 * This, together with splice_from_pipe_{begin,end,next}, may be
740 * used to implement the functionality of __splice_from_pipe() when
741 * locking is required around copying the pipe buffers to the
744 int splice_from_pipe_feed(struct pipe_inode_info *pipe, struct splice_desc *sd,
749 while (pipe->nrbufs) {
750 struct pipe_buffer *buf = pipe->bufs + pipe->curbuf;
751 const struct pipe_buf_operations *ops = buf->ops;
754 if (sd->len > sd->total_len)
755 sd->len = sd->total_len;
757 ret = actor(pipe, buf, sd);
766 sd->num_spliced += ret;
769 sd->total_len -= ret;
773 ops->release(pipe, buf);
774 pipe->curbuf = (pipe->curbuf + 1) & (PIPE_BUFFERS - 1);
777 sd->need_wakeup = true;
786 EXPORT_SYMBOL(splice_from_pipe_feed);
789 * splice_from_pipe_next - wait for some data to splice from
790 * @pipe: pipe to splice from
791 * @sd: information about the splice operation
794 * This function will wait for some data and return a positive
795 * value (one) if pipe buffers are available. It will return zero
796 * or -errno if no more data needs to be spliced.
798 int splice_from_pipe_next(struct pipe_inode_info *pipe, struct splice_desc *sd)
800 while (!pipe->nrbufs) {
804 if (!pipe->waiting_writers && sd->num_spliced)
807 if (sd->flags & SPLICE_F_NONBLOCK)
810 if (signal_pending(current))
813 if (sd->need_wakeup) {
814 wakeup_pipe_writers(pipe);
815 sd->need_wakeup = false;
823 EXPORT_SYMBOL(splice_from_pipe_next);
826 * splice_from_pipe_begin - start splicing from pipe
827 * @sd: information about the splice operation
830 * This function should be called before a loop containing
831 * splice_from_pipe_next() and splice_from_pipe_feed() to
832 * initialize the necessary fields of @sd.
834 void splice_from_pipe_begin(struct splice_desc *sd)
837 sd->need_wakeup = false;
839 EXPORT_SYMBOL(splice_from_pipe_begin);
842 * splice_from_pipe_end - finish splicing from pipe
843 * @pipe: pipe to splice from
844 * @sd: information about the splice operation
847 * This function will wake up pipe writers if necessary. It should
848 * be called after a loop containing splice_from_pipe_next() and
849 * splice_from_pipe_feed().
851 void splice_from_pipe_end(struct pipe_inode_info *pipe, struct splice_desc *sd)
854 wakeup_pipe_writers(pipe);
856 EXPORT_SYMBOL(splice_from_pipe_end);
859 * __splice_from_pipe - splice data from a pipe to given actor
860 * @pipe: pipe to splice from
861 * @sd: information to @actor
862 * @actor: handler that splices the data
865 * This function does little more than loop over the pipe and call
866 * @actor to do the actual moving of a single struct pipe_buffer to
867 * the desired destination. See pipe_to_file, pipe_to_sendpage, or
871 ssize_t __splice_from_pipe(struct pipe_inode_info *pipe, struct splice_desc *sd,
876 splice_from_pipe_begin(sd);
878 ret = splice_from_pipe_next(pipe, sd);
880 ret = splice_from_pipe_feed(pipe, sd, actor);
882 splice_from_pipe_end(pipe, sd);
884 return sd->num_spliced ? sd->num_spliced : ret;
886 EXPORT_SYMBOL(__splice_from_pipe);
889 * splice_from_pipe - splice data from a pipe to a file
890 * @pipe: pipe to splice from
891 * @out: file to splice to
892 * @ppos: position in @out
893 * @len: how many bytes to splice
894 * @flags: splice modifier flags
895 * @actor: handler that splices the data
898 * See __splice_from_pipe. This function locks the pipe inode,
899 * otherwise it's identical to __splice_from_pipe().
902 ssize_t splice_from_pipe(struct pipe_inode_info *pipe, struct file *out,
903 loff_t *ppos, size_t len, unsigned int flags,
907 struct splice_desc sd = {
915 ret = __splice_from_pipe(pipe, &sd, actor);
922 * generic_file_splice_write - splice data from a pipe to a file
924 * @out: file to write to
925 * @ppos: position in @out
926 * @len: number of bytes to splice
927 * @flags: splice modifier flags
930 * Will either move or copy pages (determined by @flags options) from
931 * the given pipe inode to the given file.
935 generic_file_splice_write(struct pipe_inode_info *pipe, struct file *out,
936 loff_t *ppos, size_t len, unsigned int flags)
938 struct address_space *mapping = out->f_mapping;
939 struct inode *inode = mapping->host;
940 struct splice_desc sd = {
950 splice_from_pipe_begin(&sd);
952 ret = splice_from_pipe_next(pipe, &sd);
956 mutex_lock_nested(&inode->i_mutex, I_MUTEX_CHILD);
957 ret = file_remove_suid(out);
959 file_update_time(out);
960 ret = splice_from_pipe_feed(pipe, &sd, pipe_to_file);
962 mutex_unlock(&inode->i_mutex);
964 splice_from_pipe_end(pipe, &sd);
969 ret = sd.num_spliced;
972 unsigned long nr_pages;
975 nr_pages = (ret + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
977 err = generic_write_sync(out, *ppos, ret);
982 balance_dirty_pages_ratelimited_nr(mapping, nr_pages);
988 EXPORT_SYMBOL(generic_file_splice_write);
990 static int write_pipe_buf(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
991 struct splice_desc *sd)
996 ret = buf->ops->confirm(pipe, buf);
1000 data = buf->ops->map(pipe, buf, 0);
1001 ret = kernel_write(sd->u.file, data + buf->offset, sd->len, sd->pos);
1002 buf->ops->unmap(pipe, buf, data);
1007 static ssize_t default_file_splice_write(struct pipe_inode_info *pipe,
1008 struct file *out, loff_t *ppos,
1009 size_t len, unsigned int flags)
1013 ret = splice_from_pipe(pipe, out, ppos, len, flags, write_pipe_buf);
1021 * generic_splice_sendpage - splice data from a pipe to a socket
1022 * @pipe: pipe to splice from
1023 * @out: socket to write to
1024 * @ppos: position in @out
1025 * @len: number of bytes to splice
1026 * @flags: splice modifier flags
1029 * Will send @len bytes from the pipe to a network socket. No data copying
1033 ssize_t generic_splice_sendpage(struct pipe_inode_info *pipe, struct file *out,
1034 loff_t *ppos, size_t len, unsigned int flags)
1036 return splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_sendpage);
1039 EXPORT_SYMBOL(generic_splice_sendpage);
1042 * Attempt to initiate a splice from pipe to file.
1044 static long do_splice_from(struct pipe_inode_info *pipe, struct file *out,
1045 loff_t *ppos, size_t len, unsigned int flags)
1047 ssize_t (*splice_write)(struct pipe_inode_info *, struct file *,
1048 loff_t *, size_t, unsigned int);
1051 if (unlikely(!(out->f_mode & FMODE_WRITE)))
1054 if (unlikely(out->f_flags & O_APPEND))
1057 ret = rw_verify_area(WRITE, out, ppos, len);
1058 if (unlikely(ret < 0))
1061 splice_write = out->f_op->splice_write;
1063 splice_write = default_file_splice_write;
1065 return splice_write(pipe, out, ppos, len, flags);
1069 * Attempt to initiate a splice from a file to a pipe.
1071 static long do_splice_to(struct file *in, loff_t *ppos,
1072 struct pipe_inode_info *pipe, size_t len,
1075 ssize_t (*splice_read)(struct file *, loff_t *,
1076 struct pipe_inode_info *, size_t, unsigned int);
1079 if (unlikely(!(in->f_mode & FMODE_READ)))
1082 ret = rw_verify_area(READ, in, ppos, len);
1083 if (unlikely(ret < 0))
1086 splice_read = in->f_op->splice_read;
1088 splice_read = default_file_splice_read;
1090 return splice_read(in, ppos, pipe, len, flags);
1094 * splice_direct_to_actor - splices data directly between two non-pipes
1095 * @in: file to splice from
1096 * @sd: actor information on where to splice to
1097 * @actor: handles the data splicing
1100 * This is a special case helper to splice directly between two
1101 * points, without requiring an explicit pipe. Internally an allocated
1102 * pipe is cached in the process, and reused during the lifetime of
1106 ssize_t splice_direct_to_actor(struct file *in, struct splice_desc *sd,
1107 splice_direct_actor *actor)
1109 struct pipe_inode_info *pipe;
1116 * We require the input being a regular file, as we don't want to
1117 * randomly drop data for eg socket -> socket splicing. Use the
1118 * piped splicing for that!
1120 i_mode = in->f_path.dentry->d_inode->i_mode;
1121 if (unlikely(!S_ISREG(i_mode) && !S_ISBLK(i_mode)))
1125 * neither in nor out is a pipe, setup an internal pipe attached to
1126 * 'out' and transfer the wanted data from 'in' to 'out' through that
1128 pipe = current->splice_pipe;
1129 if (unlikely(!pipe)) {
1130 pipe = alloc_pipe_info(NULL);
1135 * We don't have an immediate reader, but we'll read the stuff
1136 * out of the pipe right after the splice_to_pipe(). So set
1137 * PIPE_READERS appropriately.
1141 current->splice_pipe = pipe;
1149 len = sd->total_len;
1153 * Don't block on output, we have to drain the direct pipe.
1155 sd->flags &= ~SPLICE_F_NONBLOCK;
1159 loff_t pos = sd->pos, prev_pos = pos;
1161 ret = do_splice_to(in, &pos, pipe, len, flags);
1162 if (unlikely(ret <= 0))
1166 sd->total_len = read_len;
1169 * NOTE: nonblocking mode only applies to the input. We
1170 * must not do the output in nonblocking mode as then we
1171 * could get stuck data in the internal pipe:
1173 ret = actor(pipe, sd);
1174 if (unlikely(ret <= 0)) {
1183 if (ret < read_len) {
1184 sd->pos = prev_pos + ret;
1190 pipe->nrbufs = pipe->curbuf = 0;
1196 * If we did an incomplete transfer we must release
1197 * the pipe buffers in question:
1199 for (i = 0; i < PIPE_BUFFERS; i++) {
1200 struct pipe_buffer *buf = pipe->bufs + i;
1203 buf->ops->release(pipe, buf);
1213 EXPORT_SYMBOL(splice_direct_to_actor);
1215 static int direct_splice_actor(struct pipe_inode_info *pipe,
1216 struct splice_desc *sd)
1218 struct file *file = sd->u.file;
1220 return do_splice_from(pipe, file, &sd->pos, sd->total_len, sd->flags);
1224 * do_splice_direct - splices data directly between two files
1225 * @in: file to splice from
1226 * @ppos: input file offset
1227 * @out: file to splice to
1228 * @len: number of bytes to splice
1229 * @flags: splice modifier flags
1232 * For use by do_sendfile(). splice can easily emulate sendfile, but
1233 * doing it in the application would incur an extra system call
1234 * (splice in + splice out, as compared to just sendfile()). So this helper
1235 * can splice directly through a process-private pipe.
1238 long do_splice_direct(struct file *in, loff_t *ppos, struct file *out,
1239 size_t len, unsigned int flags)
1241 struct splice_desc sd = {
1250 ret = splice_direct_to_actor(in, &sd, direct_splice_actor);
1257 static int splice_pipe_to_pipe(struct pipe_inode_info *ipipe,
1258 struct pipe_inode_info *opipe,
1259 size_t len, unsigned int flags);
1261 * After the inode slimming patch, i_pipe/i_bdev/i_cdev share the same
1262 * location, so checking ->i_pipe is not enough to verify that this is a
1265 static inline struct pipe_inode_info *pipe_info(struct inode *inode)
1267 if (S_ISFIFO(inode->i_mode))
1268 return inode->i_pipe;
1274 * Determine where to splice to/from.
1276 static long do_splice(struct file *in, loff_t __user *off_in,
1277 struct file *out, loff_t __user *off_out,
1278 size_t len, unsigned int flags)
1280 struct pipe_inode_info *ipipe;
1281 struct pipe_inode_info *opipe;
1282 loff_t offset, *off;
1285 ipipe = pipe_info(in->f_path.dentry->d_inode);
1286 opipe = pipe_info(out->f_path.dentry->d_inode);
1288 if (ipipe && opipe) {
1289 if (off_in || off_out)
1292 if (!(in->f_mode & FMODE_READ))
1295 if (!(out->f_mode & FMODE_WRITE))
1298 /* Splicing to self would be fun, but... */
1302 return splice_pipe_to_pipe(ipipe, opipe, len, flags);
1309 if (out->f_op->llseek == no_llseek)
1311 if (copy_from_user(&offset, off_out, sizeof(loff_t)))
1317 ret = do_splice_from(ipipe, out, off, len, flags);
1319 if (off_out && copy_to_user(off_out, off, sizeof(loff_t)))
1329 if (in->f_op->llseek == no_llseek)
1331 if (copy_from_user(&offset, off_in, sizeof(loff_t)))
1337 ret = do_splice_to(in, off, opipe, len, flags);
1339 if (off_in && copy_to_user(off_in, off, sizeof(loff_t)))
1349 * Map an iov into an array of pages and offset/length tupples. With the
1350 * partial_page structure, we can map several non-contiguous ranges into
1351 * our ones pages[] map instead of splitting that operation into pieces.
1352 * Could easily be exported as a generic helper for other users, in which
1353 * case one would probably want to add a 'max_nr_pages' parameter as well.
1355 static int get_iovec_page_array(const struct iovec __user *iov,
1356 unsigned int nr_vecs, struct page **pages,
1357 struct partial_page *partial, int aligned)
1359 int buffers = 0, error = 0;
1362 unsigned long off, npages;
1369 if (copy_from_user(&entry, iov, sizeof(entry)))
1372 base = entry.iov_base;
1373 len = entry.iov_len;
1376 * Sanity check this iovec. 0 read succeeds.
1382 if (!access_ok(VERIFY_READ, base, len))
1386 * Get this base offset and number of pages, then map
1387 * in the user pages.
1389 off = (unsigned long) base & ~PAGE_MASK;
1392 * If asked for alignment, the offset must be zero and the
1393 * length a multiple of the PAGE_SIZE.
1396 if (aligned && (off || len & ~PAGE_MASK))
1399 npages = (off + len + PAGE_SIZE - 1) >> PAGE_SHIFT;
1400 if (npages > PIPE_BUFFERS - buffers)
1401 npages = PIPE_BUFFERS - buffers;
1403 error = get_user_pages_fast((unsigned long)base, npages,
1404 0, &pages[buffers]);
1406 if (unlikely(error <= 0))
1410 * Fill this contiguous range into the partial page map.
1412 for (i = 0; i < error; i++) {
1413 const int plen = min_t(size_t, len, PAGE_SIZE - off);
1415 partial[buffers].offset = off;
1416 partial[buffers].len = plen;
1424 * We didn't complete this iov, stop here since it probably
1425 * means we have to move some of this into a pipe to
1426 * be able to continue.
1432 * Don't continue if we mapped fewer pages than we asked for,
1433 * or if we mapped the max number of pages that we have
1436 if (error < npages || buffers == PIPE_BUFFERS)
1449 static int pipe_to_user(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
1450 struct splice_desc *sd)
1455 ret = buf->ops->confirm(pipe, buf);
1460 * See if we can use the atomic maps, by prefaulting in the
1461 * pages and doing an atomic copy
1463 if (!fault_in_pages_writeable(sd->u.userptr, sd->len)) {
1464 src = buf->ops->map(pipe, buf, 1);
1465 ret = __copy_to_user_inatomic(sd->u.userptr, src + buf->offset,
1467 buf->ops->unmap(pipe, buf, src);
1475 * No dice, use slow non-atomic map and copy
1477 src = buf->ops->map(pipe, buf, 0);
1480 if (copy_to_user(sd->u.userptr, src + buf->offset, sd->len))
1483 buf->ops->unmap(pipe, buf, src);
1486 sd->u.userptr += ret;
1491 * For lack of a better implementation, implement vmsplice() to userspace
1492 * as a simple copy of the pipes pages to the user iov.
1494 static long vmsplice_to_user(struct file *file, const struct iovec __user *iov,
1495 unsigned long nr_segs, unsigned int flags)
1497 struct pipe_inode_info *pipe;
1498 struct splice_desc sd;
1503 pipe = pipe_info(file->f_path.dentry->d_inode);
1515 * Get user address base and length for this iovec.
1517 error = get_user(base, &iov->iov_base);
1518 if (unlikely(error))
1520 error = get_user(len, &iov->iov_len);
1521 if (unlikely(error))
1525 * Sanity check this iovec. 0 read succeeds.
1529 if (unlikely(!base)) {
1534 if (unlikely(!access_ok(VERIFY_WRITE, base, len))) {
1542 sd.u.userptr = base;
1545 size = __splice_from_pipe(pipe, &sd, pipe_to_user);
1571 * vmsplice splices a user address range into a pipe. It can be thought of
1572 * as splice-from-memory, where the regular splice is splice-from-file (or
1573 * to file). In both cases the output is a pipe, naturally.
1575 static long vmsplice_to_pipe(struct file *file, const struct iovec __user *iov,
1576 unsigned long nr_segs, unsigned int flags)
1578 struct pipe_inode_info *pipe;
1579 struct page *pages[PIPE_BUFFERS];
1580 struct partial_page partial[PIPE_BUFFERS];
1581 struct splice_pipe_desc spd = {
1585 .ops = &user_page_pipe_buf_ops,
1586 .spd_release = spd_release_page,
1589 pipe = pipe_info(file->f_path.dentry->d_inode);
1593 spd.nr_pages = get_iovec_page_array(iov, nr_segs, pages, partial,
1594 flags & SPLICE_F_GIFT);
1595 if (spd.nr_pages <= 0)
1596 return spd.nr_pages;
1598 return splice_to_pipe(pipe, &spd);
1602 * Note that vmsplice only really supports true splicing _from_ user memory
1603 * to a pipe, not the other way around. Splicing from user memory is a simple
1604 * operation that can be supported without any funky alignment restrictions
1605 * or nasty vm tricks. We simply map in the user memory and fill them into
1606 * a pipe. The reverse isn't quite as easy, though. There are two possible
1607 * solutions for that:
1609 * - memcpy() the data internally, at which point we might as well just
1610 * do a regular read() on the buffer anyway.
1611 * - Lots of nasty vm tricks, that are neither fast nor flexible (it
1612 * has restriction limitations on both ends of the pipe).
1614 * Currently we punt and implement it as a normal copy, see pipe_to_user().
1617 SYSCALL_DEFINE4(vmsplice, int, fd, const struct iovec __user *, iov,
1618 unsigned long, nr_segs, unsigned int, flags)
1624 if (unlikely(nr_segs > UIO_MAXIOV))
1626 else if (unlikely(!nr_segs))
1630 file = fget_light(fd, &fput);
1632 if (file->f_mode & FMODE_WRITE)
1633 error = vmsplice_to_pipe(file, iov, nr_segs, flags);
1634 else if (file->f_mode & FMODE_READ)
1635 error = vmsplice_to_user(file, iov, nr_segs, flags);
1637 fput_light(file, fput);
1643 SYSCALL_DEFINE6(splice, int, fd_in, loff_t __user *, off_in,
1644 int, fd_out, loff_t __user *, off_out,
1645 size_t, len, unsigned int, flags)
1648 struct file *in, *out;
1649 int fput_in, fput_out;
1655 in = fget_light(fd_in, &fput_in);
1657 if (in->f_mode & FMODE_READ) {
1658 out = fget_light(fd_out, &fput_out);
1660 if (out->f_mode & FMODE_WRITE)
1661 error = do_splice(in, off_in,
1664 fput_light(out, fput_out);
1668 fput_light(in, fput_in);
1675 * Make sure there's data to read. Wait for input if we can, otherwise
1676 * return an appropriate error.
1678 static int ipipe_prep(struct pipe_inode_info *pipe, unsigned int flags)
1683 * Check ->nrbufs without the inode lock first. This function
1684 * is speculative anyways, so missing one is ok.
1692 while (!pipe->nrbufs) {
1693 if (signal_pending(current)) {
1699 if (!pipe->waiting_writers) {
1700 if (flags & SPLICE_F_NONBLOCK) {
1713 * Make sure there's writeable room. Wait for room if we can, otherwise
1714 * return an appropriate error.
1716 static int opipe_prep(struct pipe_inode_info *pipe, unsigned int flags)
1721 * Check ->nrbufs without the inode lock first. This function
1722 * is speculative anyways, so missing one is ok.
1724 if (pipe->nrbufs < PIPE_BUFFERS)
1730 while (pipe->nrbufs >= PIPE_BUFFERS) {
1731 if (!pipe->readers) {
1732 send_sig(SIGPIPE, current, 0);
1736 if (flags & SPLICE_F_NONBLOCK) {
1740 if (signal_pending(current)) {
1744 pipe->waiting_writers++;
1746 pipe->waiting_writers--;
1754 * Splice contents of ipipe to opipe.
1756 static int splice_pipe_to_pipe(struct pipe_inode_info *ipipe,
1757 struct pipe_inode_info *opipe,
1758 size_t len, unsigned int flags)
1760 struct pipe_buffer *ibuf, *obuf;
1762 bool input_wakeup = false;
1766 ret = ipipe_prep(ipipe, flags);
1770 ret = opipe_prep(opipe, flags);
1775 * Potential ABBA deadlock, work around it by ordering lock
1776 * grabbing by pipe info address. Otherwise two different processes
1777 * could deadlock (one doing tee from A -> B, the other from B -> A).
1779 pipe_double_lock(ipipe, opipe);
1782 if (!opipe->readers) {
1783 send_sig(SIGPIPE, current, 0);
1789 if (!ipipe->nrbufs && !ipipe->writers)
1793 * Cannot make any progress, because either the input
1794 * pipe is empty or the output pipe is full.
1796 if (!ipipe->nrbufs || opipe->nrbufs >= PIPE_BUFFERS) {
1797 /* Already processed some buffers, break */
1801 if (flags & SPLICE_F_NONBLOCK) {
1807 * We raced with another reader/writer and haven't
1808 * managed to process any buffers. A zero return
1809 * value means EOF, so retry instead.
1816 ibuf = ipipe->bufs + ipipe->curbuf;
1817 nbuf = (opipe->curbuf + opipe->nrbufs) % PIPE_BUFFERS;
1818 obuf = opipe->bufs + nbuf;
1820 if (len >= ibuf->len) {
1822 * Simply move the whole buffer from ipipe to opipe
1827 ipipe->curbuf = (ipipe->curbuf + 1) % PIPE_BUFFERS;
1829 input_wakeup = true;
1832 * Get a reference to this pipe buffer,
1833 * so we can copy the contents over.
1835 ibuf->ops->get(ipipe, ibuf);
1839 * Don't inherit the gift flag, we need to
1840 * prevent multiple steals of this page.
1842 obuf->flags &= ~PIPE_BUF_FLAG_GIFT;
1846 ibuf->offset += obuf->len;
1847 ibuf->len -= obuf->len;
1857 * If we put data in the output pipe, wakeup any potential readers.
1861 if (waitqueue_active(&opipe->wait))
1862 wake_up_interruptible(&opipe->wait);
1863 kill_fasync(&opipe->fasync_readers, SIGIO, POLL_IN);
1866 wakeup_pipe_writers(ipipe);
1872 * Link contents of ipipe to opipe.
1874 static int link_pipe(struct pipe_inode_info *ipipe,
1875 struct pipe_inode_info *opipe,
1876 size_t len, unsigned int flags)
1878 struct pipe_buffer *ibuf, *obuf;
1879 int ret = 0, i = 0, nbuf;
1882 * Potential ABBA deadlock, work around it by ordering lock
1883 * grabbing by pipe info address. Otherwise two different processes
1884 * could deadlock (one doing tee from A -> B, the other from B -> A).
1886 pipe_double_lock(ipipe, opipe);
1889 if (!opipe->readers) {
1890 send_sig(SIGPIPE, current, 0);
1897 * If we have iterated all input buffers or ran out of
1898 * output room, break.
1900 if (i >= ipipe->nrbufs || opipe->nrbufs >= PIPE_BUFFERS)
1903 ibuf = ipipe->bufs + ((ipipe->curbuf + i) & (PIPE_BUFFERS - 1));
1904 nbuf = (opipe->curbuf + opipe->nrbufs) & (PIPE_BUFFERS - 1);
1907 * Get a reference to this pipe buffer,
1908 * so we can copy the contents over.
1910 ibuf->ops->get(ipipe, ibuf);
1912 obuf = opipe->bufs + nbuf;
1916 * Don't inherit the gift flag, we need to
1917 * prevent multiple steals of this page.
1919 obuf->flags &= ~PIPE_BUF_FLAG_GIFT;
1921 if (obuf->len > len)
1931 * return EAGAIN if we have the potential of some data in the
1932 * future, otherwise just return 0
1934 if (!ret && ipipe->waiting_writers && (flags & SPLICE_F_NONBLOCK))
1941 * If we put data in the output pipe, wakeup any potential readers.
1945 if (waitqueue_active(&opipe->wait))
1946 wake_up_interruptible(&opipe->wait);
1947 kill_fasync(&opipe->fasync_readers, SIGIO, POLL_IN);
1954 * This is a tee(1) implementation that works on pipes. It doesn't copy
1955 * any data, it simply references the 'in' pages on the 'out' pipe.
1956 * The 'flags' used are the SPLICE_F_* variants, currently the only
1957 * applicable one is SPLICE_F_NONBLOCK.
1959 static long do_tee(struct file *in, struct file *out, size_t len,
1962 struct pipe_inode_info *ipipe = pipe_info(in->f_path.dentry->d_inode);
1963 struct pipe_inode_info *opipe = pipe_info(out->f_path.dentry->d_inode);
1967 * Duplicate the contents of ipipe to opipe without actually
1970 if (ipipe && opipe && ipipe != opipe) {
1972 * Keep going, unless we encounter an error. The ipipe/opipe
1973 * ordering doesn't really matter.
1975 ret = ipipe_prep(ipipe, flags);
1977 ret = opipe_prep(opipe, flags);
1979 ret = link_pipe(ipipe, opipe, len, flags);
1986 SYSCALL_DEFINE4(tee, int, fdin, int, fdout, size_t, len, unsigned int, flags)
1995 in = fget_light(fdin, &fput_in);
1997 if (in->f_mode & FMODE_READ) {
1999 struct file *out = fget_light(fdout, &fput_out);
2002 if (out->f_mode & FMODE_WRITE)
2003 error = do_tee(in, out, len, flags);
2004 fput_light(out, fput_out);
2007 fput_light(in, fput_in);