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/pipe_fs_i.h>
24 #include <linux/mm_inline.h>
25 #include <linux/swap.h>
26 #include <linux/writeback.h>
27 #include <linux/buffer_head.h>
28 #include <linux/module.h>
29 #include <linux/syscalls.h>
30 #include <linux/uio.h>
38 * Passed to splice_to_pipe
40 struct splice_pipe_desc {
41 struct page **pages; /* page map */
42 struct partial_page *partial; /* pages[] may not be contig */
43 int nr_pages; /* number of pages in map */
44 unsigned int flags; /* splice flags */
45 const struct pipe_buf_operations *ops;/* ops associated with output pipe */
49 * Attempt to steal a page from a pipe buffer. This should perhaps go into
50 * a vm helper function, it's already simplified quite a bit by the
51 * addition of remove_mapping(). If success is returned, the caller may
52 * attempt to reuse this page for another destination.
54 static int page_cache_pipe_buf_steal(struct pipe_inode_info *pipe,
55 struct pipe_buffer *buf)
57 struct page *page = buf->page;
58 struct address_space *mapping;
62 mapping = page_mapping(page);
64 WARN_ON(!PageUptodate(page));
67 * At least for ext2 with nobh option, we need to wait on
68 * writeback completing on this page, since we'll remove it
69 * from the pagecache. Otherwise truncate wont wait on the
70 * page, allowing the disk blocks to be reused by someone else
71 * before we actually wrote our data to them. fs corruption
74 wait_on_page_writeback(page);
76 if (PagePrivate(page))
77 try_to_release_page(page, GFP_KERNEL);
80 * If we succeeded in removing the mapping, set LRU flag
83 if (remove_mapping(mapping, page)) {
84 buf->flags |= PIPE_BUF_FLAG_LRU;
90 * Raced with truncate or failed to remove page from current
91 * address space, unlock and return failure.
97 static void page_cache_pipe_buf_release(struct pipe_inode_info *pipe,
98 struct pipe_buffer *buf)
100 page_cache_release(buf->page);
101 buf->flags &= ~PIPE_BUF_FLAG_LRU;
104 static int page_cache_pipe_buf_pin(struct pipe_inode_info *pipe,
105 struct pipe_buffer *buf)
107 struct page *page = buf->page;
110 if (!PageUptodate(page)) {
114 * Page got truncated/unhashed. This will cause a 0-byte
115 * splice, if this is the first page.
117 if (!page->mapping) {
123 * Uh oh, read-error from disk.
125 if (!PageUptodate(page)) {
131 * Page is ok afterall, we are done.
142 static const struct pipe_buf_operations page_cache_pipe_buf_ops = {
144 .map = generic_pipe_buf_map,
145 .unmap = generic_pipe_buf_unmap,
146 .pin = page_cache_pipe_buf_pin,
147 .release = page_cache_pipe_buf_release,
148 .steal = page_cache_pipe_buf_steal,
149 .get = generic_pipe_buf_get,
152 static int user_page_pipe_buf_steal(struct pipe_inode_info *pipe,
153 struct pipe_buffer *buf)
155 if (!(buf->flags & PIPE_BUF_FLAG_GIFT))
158 buf->flags |= PIPE_BUF_FLAG_LRU;
159 return generic_pipe_buf_steal(pipe, buf);
162 static const struct pipe_buf_operations user_page_pipe_buf_ops = {
164 .map = generic_pipe_buf_map,
165 .unmap = generic_pipe_buf_unmap,
166 .pin = generic_pipe_buf_pin,
167 .release = page_cache_pipe_buf_release,
168 .steal = user_page_pipe_buf_steal,
169 .get = generic_pipe_buf_get,
173 * Pipe output worker. This sets up our pipe format with the page cache
174 * pipe buffer operations. Otherwise very similar to the regular pipe_writev().
176 static ssize_t splice_to_pipe(struct pipe_inode_info *pipe,
177 struct splice_pipe_desc *spd)
179 int ret, do_wakeup, page_nr;
186 mutex_lock(&pipe->inode->i_mutex);
189 if (!pipe->readers) {
190 send_sig(SIGPIPE, current, 0);
196 if (pipe->nrbufs < PIPE_BUFFERS) {
197 int newbuf = (pipe->curbuf + pipe->nrbufs) & (PIPE_BUFFERS - 1);
198 struct pipe_buffer *buf = pipe->bufs + newbuf;
200 buf->page = spd->pages[page_nr];
201 buf->offset = spd->partial[page_nr].offset;
202 buf->len = spd->partial[page_nr].len;
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--;
248 mutex_unlock(&pipe->inode->i_mutex);
252 if (waitqueue_active(&pipe->wait))
253 wake_up_interruptible(&pipe->wait);
254 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
257 while (page_nr < spd->nr_pages)
258 page_cache_release(spd->pages[page_nr++]);
264 __generic_file_splice_read(struct file *in, loff_t *ppos,
265 struct pipe_inode_info *pipe, size_t len,
268 struct address_space *mapping = in->f_mapping;
269 unsigned int loff, nr_pages;
270 struct page *pages[PIPE_BUFFERS];
271 struct partial_page partial[PIPE_BUFFERS];
273 pgoff_t index, end_index;
276 struct splice_pipe_desc spd = {
280 .ops = &page_cache_pipe_buf_ops,
283 index = *ppos >> PAGE_CACHE_SHIFT;
284 loff = *ppos & ~PAGE_CACHE_MASK;
285 nr_pages = (len + loff + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
287 if (nr_pages > PIPE_BUFFERS)
288 nr_pages = PIPE_BUFFERS;
291 * Don't try to 2nd guess the read-ahead logic, call into
292 * page_cache_readahead() like the page cache reads would do.
294 page_cache_readahead(mapping, &in->f_ra, in, index, nr_pages);
297 * Now fill in the holes:
302 * Lookup the (hopefully) full range of pages we need.
304 spd.nr_pages = find_get_pages_contig(mapping, index, nr_pages, pages);
307 * If find_get_pages_contig() returned fewer pages than we needed,
310 index += spd.nr_pages;
311 while (spd.nr_pages < nr_pages) {
313 * Page could be there, find_get_pages_contig() breaks on
316 page = find_get_page(mapping, index);
319 * Make sure the read-ahead engine is notified
320 * about this failure.
322 handle_ra_miss(mapping, &in->f_ra, index);
325 * page didn't exist, allocate one.
327 page = page_cache_alloc_cold(mapping);
331 error = add_to_page_cache_lru(page, mapping, index,
333 if (unlikely(error)) {
334 page_cache_release(page);
335 if (error == -EEXIST)
340 * add_to_page_cache() locks the page, unlock it
341 * to avoid convoluting the logic below even more.
346 pages[spd.nr_pages++] = page;
351 * Now loop over the map and see if we need to start IO on any
352 * pages, fill in the partial map, etc.
354 index = *ppos >> PAGE_CACHE_SHIFT;
355 nr_pages = spd.nr_pages;
357 for (page_nr = 0; page_nr < nr_pages; page_nr++) {
358 unsigned int this_len;
364 * this_len is the max we'll use from this page
366 this_len = min_t(unsigned long, len, PAGE_CACHE_SIZE - loff);
367 page = pages[page_nr];
370 * If the page isn't uptodate, we may need to start io on it
372 if (!PageUptodate(page)) {
374 * If in nonblock mode then dont block on waiting
375 * for an in-flight io page
377 if (flags & SPLICE_F_NONBLOCK) {
378 if (TestSetPageLocked(page))
384 * page was truncated, stop here. if this isn't the
385 * first page, we'll just complete what we already
388 if (!page->mapping) {
393 * page was already under io and is now done, great
395 if (PageUptodate(page)) {
401 * need to read in the page
403 error = mapping->a_ops->readpage(in, page);
404 if (unlikely(error)) {
406 * We really should re-lookup the page here,
407 * but it complicates things a lot. Instead
408 * lets just do what we already stored, and
409 * we'll get it the next time we are called.
411 if (error == AOP_TRUNCATED_PAGE)
419 * i_size must be checked after PageUptodate.
421 isize = i_size_read(mapping->host);
422 end_index = (isize - 1) >> PAGE_CACHE_SHIFT;
423 if (unlikely(!isize || index > end_index))
427 * if this is the last page, see if we need to shrink
428 * the length and stop
430 if (end_index == index) {
434 * max good bytes in this page
436 plen = ((isize - 1) & ~PAGE_CACHE_MASK) + 1;
441 * force quit after adding this page
443 this_len = min(this_len, plen - loff);
447 partial[page_nr].offset = loff;
448 partial[page_nr].len = this_len;
456 * Release any pages at the end, if we quit early. 'page_nr' is how far
457 * we got, 'nr_pages' is how many pages are in the map.
459 while (page_nr < nr_pages)
460 page_cache_release(pages[page_nr++]);
463 return splice_to_pipe(pipe, &spd);
469 * generic_file_splice_read - splice data from file to a pipe
470 * @in: file to splice from
471 * @pipe: pipe to splice to
472 * @len: number of bytes to splice
473 * @flags: splice modifier flags
475 * Will read pages from given file and fill them into a pipe.
477 ssize_t generic_file_splice_read(struct file *in, loff_t *ppos,
478 struct pipe_inode_info *pipe, size_t len,
485 isize = i_size_read(in->f_mapping->host);
486 if (unlikely(*ppos >= isize))
489 left = isize - *ppos;
490 if (unlikely(left < len))
496 ret = __generic_file_splice_read(in, ppos, pipe, len, flags);
503 if (flags & SPLICE_F_NONBLOCK) {
520 EXPORT_SYMBOL(generic_file_splice_read);
523 * Send 'sd->len' bytes to socket from 'sd->file' at position 'sd->pos'
524 * using sendpage(). Return the number of bytes sent.
526 static int pipe_to_sendpage(struct pipe_inode_info *pipe,
527 struct pipe_buffer *buf, struct splice_desc *sd)
529 struct file *file = sd->file;
530 loff_t pos = sd->pos;
533 ret = buf->ops->pin(pipe, buf);
535 more = (sd->flags & SPLICE_F_MORE) || sd->len < sd->total_len;
537 ret = file->f_op->sendpage(file, buf->page, buf->offset,
538 sd->len, &pos, more);
545 * This is a little more tricky than the file -> pipe splicing. There are
546 * basically three cases:
548 * - Destination page already exists in the address space and there
549 * are users of it. For that case we have no other option that
550 * copying the data. Tough luck.
551 * - Destination page already exists in the address space, but there
552 * are no users of it. Make sure it's uptodate, then drop it. Fall
553 * through to last case.
554 * - Destination page does not exist, we can add the pipe page to
555 * the page cache and avoid the copy.
557 * If asked to move pages to the output file (SPLICE_F_MOVE is set in
558 * sd->flags), we attempt to migrate pages from the pipe to the output
559 * file address space page cache. This is possible if no one else has
560 * the pipe page referenced outside of the pipe and page cache. If
561 * SPLICE_F_MOVE isn't set, or we cannot move the page, we simply create
562 * a new page in the output file page cache and fill/dirty that.
564 static int pipe_to_file(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
565 struct splice_desc *sd)
567 struct file *file = sd->file;
568 struct address_space *mapping = file->f_mapping;
569 unsigned int offset, this_len;
575 * make sure the data in this buffer is uptodate
577 ret = buf->ops->pin(pipe, buf);
581 index = sd->pos >> PAGE_CACHE_SHIFT;
582 offset = sd->pos & ~PAGE_CACHE_MASK;
585 if (this_len + offset > PAGE_CACHE_SIZE)
586 this_len = PAGE_CACHE_SIZE - offset;
589 page = find_lock_page(mapping, index);
592 page = page_cache_alloc_cold(mapping);
597 * This will also lock the page
599 ret = add_to_page_cache_lru(page, mapping, index,
605 ret = mapping->a_ops->prepare_write(file, page, offset, offset+this_len);
607 loff_t isize = i_size_read(mapping->host);
609 if (ret != AOP_TRUNCATED_PAGE)
611 page_cache_release(page);
612 if (ret == AOP_TRUNCATED_PAGE)
616 * prepare_write() may have instantiated a few blocks
617 * outside i_size. Trim these off again.
619 if (sd->pos + this_len > isize)
620 vmtruncate(mapping->host, isize);
625 if (buf->page != page) {
627 * Careful, ->map() uses KM_USER0!
629 char *src = buf->ops->map(pipe, buf, 1);
630 char *dst = kmap_atomic(page, KM_USER1);
632 memcpy(dst + offset, src + buf->offset, this_len);
633 flush_dcache_page(page);
634 kunmap_atomic(dst, KM_USER1);
635 buf->ops->unmap(pipe, buf, src);
638 ret = mapping->a_ops->commit_write(file, page, offset, offset+this_len);
640 if (ret == AOP_TRUNCATED_PAGE) {
641 page_cache_release(page);
647 * Partial write has happened, so 'ret' already initialized by
648 * number of bytes written, Where is nothing we have to do here.
653 * Return the number of bytes written and mark page as
654 * accessed, we are now done!
656 mark_page_accessed(page);
658 page_cache_release(page);
665 * Pipe input worker. Most of this logic works like a regular pipe, the
666 * key here is the 'actor' worker passed in that actually moves the data
667 * to the wanted destination. See pipe_to_file/pipe_to_sendpage above.
669 ssize_t __splice_from_pipe(struct pipe_inode_info *pipe,
670 struct file *out, loff_t *ppos, size_t len,
671 unsigned int flags, splice_actor *actor)
673 int ret, do_wakeup, err;
674 struct splice_desc sd;
686 struct pipe_buffer *buf = pipe->bufs + pipe->curbuf;
687 const struct pipe_buf_operations *ops = buf->ops;
690 if (sd.len > sd.total_len)
691 sd.len = sd.total_len;
693 err = actor(pipe, buf, &sd);
695 if (!ret && err != -ENODATA)
713 ops->release(pipe, buf);
714 pipe->curbuf = (pipe->curbuf + 1) & (PIPE_BUFFERS - 1);
728 if (!pipe->waiting_writers) {
733 if (flags & SPLICE_F_NONBLOCK) {
739 if (signal_pending(current)) {
747 if (waitqueue_active(&pipe->wait))
748 wake_up_interruptible_sync(&pipe->wait);
749 kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
758 if (waitqueue_active(&pipe->wait))
759 wake_up_interruptible(&pipe->wait);
760 kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
765 EXPORT_SYMBOL(__splice_from_pipe);
767 ssize_t splice_from_pipe(struct pipe_inode_info *pipe, struct file *out,
768 loff_t *ppos, size_t len, unsigned int flags,
772 struct inode *inode = out->f_mapping->host;
775 * The actor worker might be calling ->prepare_write and
776 * ->commit_write. Most of the time, these expect i_mutex to
777 * be held. Since this may result in an ABBA deadlock with
778 * pipe->inode, we have to order lock acquiry here.
780 inode_double_lock(inode, pipe->inode);
781 ret = __splice_from_pipe(pipe, out, ppos, len, flags, actor);
782 inode_double_unlock(inode, pipe->inode);
788 * generic_file_splice_write_nolock - generic_file_splice_write without mutexes
790 * @out: file to write to
791 * @len: number of bytes to splice
792 * @flags: splice modifier flags
794 * Will either move or copy pages (determined by @flags options) from
795 * the given pipe inode to the given file. The caller is responsible
796 * for acquiring i_mutex on both inodes.
800 generic_file_splice_write_nolock(struct pipe_inode_info *pipe, struct file *out,
801 loff_t *ppos, size_t len, unsigned int flags)
803 struct address_space *mapping = out->f_mapping;
804 struct inode *inode = mapping->host;
808 err = remove_suid(out->f_path.dentry);
812 ret = __splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_file);
814 unsigned long nr_pages;
817 nr_pages = (ret + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
820 * If file or inode is SYNC and we actually wrote some data,
823 if (unlikely((out->f_flags & O_SYNC) || IS_SYNC(inode))) {
824 err = generic_osync_inode(inode, mapping,
825 OSYNC_METADATA|OSYNC_DATA);
830 balance_dirty_pages_ratelimited_nr(mapping, nr_pages);
836 EXPORT_SYMBOL(generic_file_splice_write_nolock);
839 * generic_file_splice_write - splice data from a pipe to a file
841 * @out: file to write to
842 * @len: number of bytes to splice
843 * @flags: splice modifier flags
845 * Will either move or copy pages (determined by @flags options) from
846 * the given pipe inode to the given file.
850 generic_file_splice_write(struct pipe_inode_info *pipe, struct file *out,
851 loff_t *ppos, size_t len, unsigned int flags)
853 struct address_space *mapping = out->f_mapping;
854 struct inode *inode = mapping->host;
858 err = should_remove_suid(out->f_path.dentry);
860 mutex_lock(&inode->i_mutex);
861 err = __remove_suid(out->f_path.dentry, err);
862 mutex_unlock(&inode->i_mutex);
867 ret = splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_file);
869 unsigned long nr_pages;
872 nr_pages = (ret + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
875 * If file or inode is SYNC and we actually wrote some data,
878 if (unlikely((out->f_flags & O_SYNC) || IS_SYNC(inode))) {
879 mutex_lock(&inode->i_mutex);
880 err = generic_osync_inode(inode, mapping,
881 OSYNC_METADATA|OSYNC_DATA);
882 mutex_unlock(&inode->i_mutex);
887 balance_dirty_pages_ratelimited_nr(mapping, nr_pages);
893 EXPORT_SYMBOL(generic_file_splice_write);
896 * generic_splice_sendpage - splice data from a pipe to a socket
898 * @out: socket to write to
899 * @len: number of bytes to splice
900 * @flags: splice modifier flags
902 * Will send @len bytes from the pipe to a network socket. No data copying
906 ssize_t generic_splice_sendpage(struct pipe_inode_info *pipe, struct file *out,
907 loff_t *ppos, size_t len, unsigned int flags)
909 return splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_sendpage);
912 EXPORT_SYMBOL(generic_splice_sendpage);
915 * Attempt to initiate a splice from pipe to file.
917 static long do_splice_from(struct pipe_inode_info *pipe, struct file *out,
918 loff_t *ppos, size_t len, unsigned int flags)
922 if (unlikely(!out->f_op || !out->f_op->splice_write))
925 if (unlikely(!(out->f_mode & FMODE_WRITE)))
928 ret = rw_verify_area(WRITE, out, ppos, len);
929 if (unlikely(ret < 0))
932 return out->f_op->splice_write(pipe, out, ppos, len, flags);
936 * Attempt to initiate a splice from a file to a pipe.
938 static long do_splice_to(struct file *in, loff_t *ppos,
939 struct pipe_inode_info *pipe, size_t len,
944 if (unlikely(!in->f_op || !in->f_op->splice_read))
947 if (unlikely(!(in->f_mode & FMODE_READ)))
950 ret = rw_verify_area(READ, in, ppos, len);
951 if (unlikely(ret < 0))
954 return in->f_op->splice_read(in, ppos, pipe, len, flags);
957 long do_splice_direct(struct file *in, loff_t *ppos, struct file *out,
958 size_t len, unsigned int flags)
960 struct pipe_inode_info *pipe;
967 * We require the input being a regular file, as we don't want to
968 * randomly drop data for eg socket -> socket splicing. Use the
969 * piped splicing for that!
971 i_mode = in->f_path.dentry->d_inode->i_mode;
972 if (unlikely(!S_ISREG(i_mode) && !S_ISBLK(i_mode)))
976 * neither in nor out is a pipe, setup an internal pipe attached to
977 * 'out' and transfer the wanted data from 'in' to 'out' through that
979 pipe = current->splice_pipe;
980 if (unlikely(!pipe)) {
981 pipe = alloc_pipe_info(NULL);
986 * We don't have an immediate reader, but we'll read the stuff
987 * out of the pipe right after the splice_to_pipe(). So set
988 * PIPE_READERS appropriately.
992 current->splice_pipe = pipe;
1003 size_t read_len, max_read_len;
1006 * Do at most PIPE_BUFFERS pages worth of transfer:
1008 max_read_len = min(len, (size_t)(PIPE_BUFFERS*PAGE_SIZE));
1010 ret = do_splice_to(in, ppos, pipe, max_read_len, flags);
1011 if (unlikely(ret < 0))
1017 * NOTE: nonblocking mode only applies to the input. We
1018 * must not do the output in nonblocking mode as then we
1019 * could get stuck data in the internal pipe:
1021 ret = do_splice_from(pipe, out, &out_off, read_len,
1022 flags & ~SPLICE_F_NONBLOCK);
1023 if (unlikely(ret < 0))
1030 * In nonblocking mode, if we got back a short read then
1031 * that was due to either an IO error or due to the
1032 * pagecache entry not being there. In the IO error case
1033 * the _next_ splice attempt will produce a clean IO error
1034 * return value (not a short read), so in both cases it's
1035 * correct to break out of the loop here:
1037 if ((flags & SPLICE_F_NONBLOCK) && (read_len < max_read_len))
1041 pipe->nrbufs = pipe->curbuf = 0;
1047 * If we did an incomplete transfer we must release
1048 * the pipe buffers in question:
1050 for (i = 0; i < PIPE_BUFFERS; i++) {
1051 struct pipe_buffer *buf = pipe->bufs + i;
1054 buf->ops->release(pipe, buf);
1058 pipe->nrbufs = pipe->curbuf = 0;
1061 * If we transferred some data, return the number of bytes:
1070 * After the inode slimming patch, i_pipe/i_bdev/i_cdev share the same
1071 * location, so checking ->i_pipe is not enough to verify that this is a
1074 static inline struct pipe_inode_info *pipe_info(struct inode *inode)
1076 if (S_ISFIFO(inode->i_mode))
1077 return inode->i_pipe;
1083 * Determine where to splice to/from.
1085 static long do_splice(struct file *in, loff_t __user *off_in,
1086 struct file *out, loff_t __user *off_out,
1087 size_t len, unsigned int flags)
1089 struct pipe_inode_info *pipe;
1090 loff_t offset, *off;
1093 pipe = pipe_info(in->f_path.dentry->d_inode);
1098 if (out->f_op->llseek == no_llseek)
1100 if (copy_from_user(&offset, off_out, sizeof(loff_t)))
1106 ret = do_splice_from(pipe, out, off, len, flags);
1108 if (off_out && copy_to_user(off_out, off, sizeof(loff_t)))
1114 pipe = pipe_info(out->f_path.dentry->d_inode);
1119 if (in->f_op->llseek == no_llseek)
1121 if (copy_from_user(&offset, off_in, sizeof(loff_t)))
1127 ret = do_splice_to(in, off, pipe, len, flags);
1129 if (off_in && copy_to_user(off_in, off, sizeof(loff_t)))
1139 * Map an iov into an array of pages and offset/length tupples. With the
1140 * partial_page structure, we can map several non-contiguous ranges into
1141 * our ones pages[] map instead of splitting that operation into pieces.
1142 * Could easily be exported as a generic helper for other users, in which
1143 * case one would probably want to add a 'max_nr_pages' parameter as well.
1145 static int get_iovec_page_array(const struct iovec __user *iov,
1146 unsigned int nr_vecs, struct page **pages,
1147 struct partial_page *partial, int aligned)
1149 int buffers = 0, error = 0;
1152 * It's ok to take the mmap_sem for reading, even
1153 * across a "get_user()".
1155 down_read(¤t->mm->mmap_sem);
1158 unsigned long off, npages;
1164 * Get user address base and length for this iovec.
1166 error = get_user(base, &iov->iov_base);
1167 if (unlikely(error))
1169 error = get_user(len, &iov->iov_len);
1170 if (unlikely(error))
1174 * Sanity check this iovec. 0 read succeeds.
1179 if (unlikely(!base))
1183 * Get this base offset and number of pages, then map
1184 * in the user pages.
1186 off = (unsigned long) base & ~PAGE_MASK;
1189 * If asked for alignment, the offset must be zero and the
1190 * length a multiple of the PAGE_SIZE.
1193 if (aligned && (off || len & ~PAGE_MASK))
1196 npages = (off + len + PAGE_SIZE - 1) >> PAGE_SHIFT;
1197 if (npages > PIPE_BUFFERS - buffers)
1198 npages = PIPE_BUFFERS - buffers;
1200 error = get_user_pages(current, current->mm,
1201 (unsigned long) base, npages, 0, 0,
1202 &pages[buffers], NULL);
1204 if (unlikely(error <= 0))
1208 * Fill this contiguous range into the partial page map.
1210 for (i = 0; i < error; i++) {
1211 const int plen = min_t(size_t, len, PAGE_SIZE - off);
1213 partial[buffers].offset = off;
1214 partial[buffers].len = plen;
1222 * We didn't complete this iov, stop here since it probably
1223 * means we have to move some of this into a pipe to
1224 * be able to continue.
1230 * Don't continue if we mapped fewer pages than we asked for,
1231 * or if we mapped the max number of pages that we have
1234 if (error < npages || buffers == PIPE_BUFFERS)
1241 up_read(¤t->mm->mmap_sem);
1250 * vmsplice splices a user address range into a pipe. It can be thought of
1251 * as splice-from-memory, where the regular splice is splice-from-file (or
1252 * to file). In both cases the output is a pipe, naturally.
1254 * Note that vmsplice only supports splicing _from_ user memory to a pipe,
1255 * not the other way around. Splicing from user memory is a simple operation
1256 * that can be supported without any funky alignment restrictions or nasty
1257 * vm tricks. We simply map in the user memory and fill them into a pipe.
1258 * The reverse isn't quite as easy, though. There are two possible solutions
1261 * - memcpy() the data internally, at which point we might as well just
1262 * do a regular read() on the buffer anyway.
1263 * - Lots of nasty vm tricks, that are neither fast nor flexible (it
1264 * has restriction limitations on both ends of the pipe).
1266 * Alas, it isn't here.
1269 static long do_vmsplice(struct file *file, const struct iovec __user *iov,
1270 unsigned long nr_segs, unsigned int flags)
1272 struct pipe_inode_info *pipe;
1273 struct page *pages[PIPE_BUFFERS];
1274 struct partial_page partial[PIPE_BUFFERS];
1275 struct splice_pipe_desc spd = {
1279 .ops = &user_page_pipe_buf_ops,
1282 pipe = pipe_info(file->f_path.dentry->d_inode);
1285 if (unlikely(nr_segs > UIO_MAXIOV))
1287 else if (unlikely(!nr_segs))
1290 spd.nr_pages = get_iovec_page_array(iov, nr_segs, pages, partial,
1291 flags & SPLICE_F_GIFT);
1292 if (spd.nr_pages <= 0)
1293 return spd.nr_pages;
1295 return splice_to_pipe(pipe, &spd);
1298 asmlinkage long sys_vmsplice(int fd, const struct iovec __user *iov,
1299 unsigned long nr_segs, unsigned int flags)
1306 file = fget_light(fd, &fput);
1308 if (file->f_mode & FMODE_WRITE)
1309 error = do_vmsplice(file, iov, nr_segs, flags);
1311 fput_light(file, fput);
1317 asmlinkage long sys_splice(int fd_in, loff_t __user *off_in,
1318 int fd_out, loff_t __user *off_out,
1319 size_t len, unsigned int flags)
1322 struct file *in, *out;
1323 int fput_in, fput_out;
1329 in = fget_light(fd_in, &fput_in);
1331 if (in->f_mode & FMODE_READ) {
1332 out = fget_light(fd_out, &fput_out);
1334 if (out->f_mode & FMODE_WRITE)
1335 error = do_splice(in, off_in,
1338 fput_light(out, fput_out);
1342 fput_light(in, fput_in);
1349 * Make sure there's data to read. Wait for input if we can, otherwise
1350 * return an appropriate error.
1352 static int link_ipipe_prep(struct pipe_inode_info *pipe, unsigned int flags)
1357 * Check ->nrbufs without the inode lock first. This function
1358 * is speculative anyways, so missing one is ok.
1364 mutex_lock(&pipe->inode->i_mutex);
1366 while (!pipe->nrbufs) {
1367 if (signal_pending(current)) {
1373 if (!pipe->waiting_writers) {
1374 if (flags & SPLICE_F_NONBLOCK) {
1382 mutex_unlock(&pipe->inode->i_mutex);
1387 * Make sure there's writeable room. Wait for room if we can, otherwise
1388 * return an appropriate error.
1390 static int link_opipe_prep(struct pipe_inode_info *pipe, unsigned int flags)
1395 * Check ->nrbufs without the inode lock first. This function
1396 * is speculative anyways, so missing one is ok.
1398 if (pipe->nrbufs < PIPE_BUFFERS)
1402 mutex_lock(&pipe->inode->i_mutex);
1404 while (pipe->nrbufs >= PIPE_BUFFERS) {
1405 if (!pipe->readers) {
1406 send_sig(SIGPIPE, current, 0);
1410 if (flags & SPLICE_F_NONBLOCK) {
1414 if (signal_pending(current)) {
1418 pipe->waiting_writers++;
1420 pipe->waiting_writers--;
1423 mutex_unlock(&pipe->inode->i_mutex);
1428 * Link contents of ipipe to opipe.
1430 static int link_pipe(struct pipe_inode_info *ipipe,
1431 struct pipe_inode_info *opipe,
1432 size_t len, unsigned int flags)
1434 struct pipe_buffer *ibuf, *obuf;
1435 int ret = 0, i = 0, nbuf;
1438 * Potential ABBA deadlock, work around it by ordering lock
1439 * grabbing by inode address. Otherwise two different processes
1440 * could deadlock (one doing tee from A -> B, the other from B -> A).
1442 inode_double_lock(ipipe->inode, opipe->inode);
1445 if (!opipe->readers) {
1446 send_sig(SIGPIPE, current, 0);
1453 * If we have iterated all input buffers or ran out of
1454 * output room, break.
1456 if (i >= ipipe->nrbufs || opipe->nrbufs >= PIPE_BUFFERS)
1459 ibuf = ipipe->bufs + ((ipipe->curbuf + i) & (PIPE_BUFFERS - 1));
1460 nbuf = (opipe->curbuf + opipe->nrbufs) & (PIPE_BUFFERS - 1);
1463 * Get a reference to this pipe buffer,
1464 * so we can copy the contents over.
1466 ibuf->ops->get(ipipe, ibuf);
1468 obuf = opipe->bufs + nbuf;
1472 * Don't inherit the gift flag, we need to
1473 * prevent multiple steals of this page.
1475 obuf->flags &= ~PIPE_BUF_FLAG_GIFT;
1477 if (obuf->len > len)
1486 inode_double_unlock(ipipe->inode, opipe->inode);
1489 * If we put data in the output pipe, wakeup any potential readers.
1493 if (waitqueue_active(&opipe->wait))
1494 wake_up_interruptible(&opipe->wait);
1495 kill_fasync(&opipe->fasync_readers, SIGIO, POLL_IN);
1502 * This is a tee(1) implementation that works on pipes. It doesn't copy
1503 * any data, it simply references the 'in' pages on the 'out' pipe.
1504 * The 'flags' used are the SPLICE_F_* variants, currently the only
1505 * applicable one is SPLICE_F_NONBLOCK.
1507 static long do_tee(struct file *in, struct file *out, size_t len,
1510 struct pipe_inode_info *ipipe = pipe_info(in->f_path.dentry->d_inode);
1511 struct pipe_inode_info *opipe = pipe_info(out->f_path.dentry->d_inode);
1515 * Duplicate the contents of ipipe to opipe without actually
1518 if (ipipe && opipe && ipipe != opipe) {
1520 * Keep going, unless we encounter an error. The ipipe/opipe
1521 * ordering doesn't really matter.
1523 ret = link_ipipe_prep(ipipe, flags);
1525 ret = link_opipe_prep(opipe, flags);
1527 ret = link_pipe(ipipe, opipe, len, flags);
1528 if (!ret && (flags & SPLICE_F_NONBLOCK))
1537 asmlinkage long sys_tee(int fdin, int fdout, size_t len, unsigned int flags)
1546 in = fget_light(fdin, &fput_in);
1548 if (in->f_mode & FMODE_READ) {
1550 struct file *out = fget_light(fdout, &fput_out);
1553 if (out->f_mode & FMODE_WRITE)
1554 error = do_tee(in, out, len, flags);
1555 fput_light(out, fput_out);
1558 fput_light(in, fput_in);