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 unsigned int spd_pages
= spd
->nr_pages
;
180 int ret
, do_wakeup
, page_nr
;
187 mutex_lock(&pipe
->inode
->i_mutex
);
190 if (!pipe
->readers
) {
191 send_sig(SIGPIPE
, current
, 0);
197 if (pipe
->nrbufs
< PIPE_BUFFERS
) {
198 int newbuf
= (pipe
->curbuf
+ pipe
->nrbufs
) & (PIPE_BUFFERS
- 1);
199 struct pipe_buffer
*buf
= pipe
->bufs
+ newbuf
;
201 buf
->page
= spd
->pages
[page_nr
];
202 buf
->offset
= spd
->partial
[page_nr
].offset
;
203 buf
->len
= spd
->partial
[page_nr
].len
;
205 if (spd
->flags
& SPLICE_F_GIFT
)
206 buf
->flags
|= PIPE_BUF_FLAG_GIFT
;
215 if (!--spd
->nr_pages
)
217 if (pipe
->nrbufs
< PIPE_BUFFERS
)
223 if (spd
->flags
& SPLICE_F_NONBLOCK
) {
229 if (signal_pending(current
)) {
237 if (waitqueue_active(&pipe
->wait
))
238 wake_up_interruptible_sync(&pipe
->wait
);
239 kill_fasync(&pipe
->fasync_readers
, SIGIO
, POLL_IN
);
243 pipe
->waiting_writers
++;
245 pipe
->waiting_writers
--;
249 mutex_unlock(&pipe
->inode
->i_mutex
);
253 if (waitqueue_active(&pipe
->wait
))
254 wake_up_interruptible(&pipe
->wait
);
255 kill_fasync(&pipe
->fasync_readers
, SIGIO
, POLL_IN
);
258 while (page_nr
< spd_pages
)
259 page_cache_release(spd
->pages
[page_nr
++]);
265 __generic_file_splice_read(struct file
*in
, loff_t
*ppos
,
266 struct pipe_inode_info
*pipe
, size_t len
,
269 struct address_space
*mapping
= in
->f_mapping
;
270 unsigned int loff
, nr_pages
;
271 struct page
*pages
[PIPE_BUFFERS
];
272 struct partial_page partial
[PIPE_BUFFERS
];
274 pgoff_t index
, end_index
;
277 struct splice_pipe_desc spd
= {
281 .ops
= &page_cache_pipe_buf_ops
,
284 index
= *ppos
>> PAGE_CACHE_SHIFT
;
285 loff
= *ppos
& ~PAGE_CACHE_MASK
;
286 nr_pages
= (len
+ loff
+ PAGE_CACHE_SIZE
- 1) >> PAGE_CACHE_SHIFT
;
288 if (nr_pages
> PIPE_BUFFERS
)
289 nr_pages
= PIPE_BUFFERS
;
292 * Don't try to 2nd guess the read-ahead logic, call into
293 * page_cache_readahead() like the page cache reads would do.
295 page_cache_readahead(mapping
, &in
->f_ra
, in
, index
, nr_pages
);
298 * Now fill in the holes:
303 * Lookup the (hopefully) full range of pages we need.
305 spd
.nr_pages
= find_get_pages_contig(mapping
, index
, nr_pages
, pages
);
308 * If find_get_pages_contig() returned fewer pages than we needed,
311 index
+= spd
.nr_pages
;
312 while (spd
.nr_pages
< nr_pages
) {
314 * Page could be there, find_get_pages_contig() breaks on
317 page
= find_get_page(mapping
, index
);
320 * Make sure the read-ahead engine is notified
321 * about this failure.
323 handle_ra_miss(mapping
, &in
->f_ra
, index
);
326 * page didn't exist, allocate one.
328 page
= page_cache_alloc_cold(mapping
);
332 error
= add_to_page_cache_lru(page
, mapping
, index
,
334 if (unlikely(error
)) {
335 page_cache_release(page
);
336 if (error
== -EEXIST
)
341 * add_to_page_cache() locks the page, unlock it
342 * to avoid convoluting the logic below even more.
347 pages
[spd
.nr_pages
++] = page
;
352 * Now loop over the map and see if we need to start IO on any
353 * pages, fill in the partial map, etc.
355 index
= *ppos
>> PAGE_CACHE_SHIFT
;
356 nr_pages
= spd
.nr_pages
;
358 for (page_nr
= 0; page_nr
< nr_pages
; page_nr
++) {
359 unsigned int this_len
;
365 * this_len is the max we'll use from this page
367 this_len
= min_t(unsigned long, len
, PAGE_CACHE_SIZE
- loff
);
368 page
= pages
[page_nr
];
371 * If the page isn't uptodate, we may need to start io on it
373 if (!PageUptodate(page
)) {
375 * If in nonblock mode then dont block on waiting
376 * for an in-flight io page
378 if (flags
& SPLICE_F_NONBLOCK
) {
379 if (TestSetPageLocked(page
))
385 * page was truncated, stop here. if this isn't the
386 * first page, we'll just complete what we already
389 if (!page
->mapping
) {
394 * page was already under io and is now done, great
396 if (PageUptodate(page
)) {
402 * need to read in the page
404 error
= mapping
->a_ops
->readpage(in
, page
);
405 if (unlikely(error
)) {
407 * We really should re-lookup the page here,
408 * but it complicates things a lot. Instead
409 * lets just do what we already stored, and
410 * we'll get it the next time we are called.
412 if (error
== AOP_TRUNCATED_PAGE
)
420 * i_size must be checked after PageUptodate.
422 isize
= i_size_read(mapping
->host
);
423 end_index
= (isize
- 1) >> PAGE_CACHE_SHIFT
;
424 if (unlikely(!isize
|| index
> end_index
))
428 * if this is the last page, see if we need to shrink
429 * the length and stop
431 if (end_index
== index
) {
435 * max good bytes in this page
437 plen
= ((isize
- 1) & ~PAGE_CACHE_MASK
) + 1;
442 * force quit after adding this page
444 this_len
= min(this_len
, plen
- loff
);
448 partial
[page_nr
].offset
= loff
;
449 partial
[page_nr
].len
= this_len
;
457 * Release any pages at the end, if we quit early. 'page_nr' is how far
458 * we got, 'nr_pages' is how many pages are in the map.
460 while (page_nr
< nr_pages
)
461 page_cache_release(pages
[page_nr
++]);
464 return splice_to_pipe(pipe
, &spd
);
470 * generic_file_splice_read - splice data from file to a pipe
471 * @in: file to splice from
472 * @pipe: pipe to splice to
473 * @len: number of bytes to splice
474 * @flags: splice modifier flags
476 * Will read pages from given file and fill them into a pipe.
478 ssize_t
generic_file_splice_read(struct file
*in
, loff_t
*ppos
,
479 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
))
497 ret
= __generic_file_splice_read(in
, ppos
, pipe
, len
, flags
);
504 if (flags
& SPLICE_F_NONBLOCK
) {
521 EXPORT_SYMBOL(generic_file_splice_read
);
524 * Send 'sd->len' bytes to socket from 'sd->file' at position 'sd->pos'
525 * using sendpage(). Return the number of bytes sent.
527 static int pipe_to_sendpage(struct pipe_inode_info
*pipe
,
528 struct pipe_buffer
*buf
, struct splice_desc
*sd
)
530 struct file
*file
= sd
->file
;
531 loff_t pos
= sd
->pos
;
534 ret
= buf
->ops
->pin(pipe
, buf
);
536 more
= (sd
->flags
& SPLICE_F_MORE
) || sd
->len
< sd
->total_len
;
538 ret
= file
->f_op
->sendpage(file
, buf
->page
, buf
->offset
,
539 sd
->len
, &pos
, more
);
546 * This is a little more tricky than the file -> pipe splicing. There are
547 * basically three cases:
549 * - Destination page already exists in the address space and there
550 * are users of it. For that case we have no other option that
551 * copying the data. Tough luck.
552 * - Destination page already exists in the address space, but there
553 * are no users of it. Make sure it's uptodate, then drop it. Fall
554 * through to last case.
555 * - Destination page does not exist, we can add the pipe page to
556 * the page cache and avoid the copy.
558 * If asked to move pages to the output file (SPLICE_F_MOVE is set in
559 * sd->flags), we attempt to migrate pages from the pipe to the output
560 * file address space page cache. This is possible if no one else has
561 * the pipe page referenced outside of the pipe and page cache. If
562 * SPLICE_F_MOVE isn't set, or we cannot move the page, we simply create
563 * a new page in the output file page cache and fill/dirty that.
565 static int pipe_to_file(struct pipe_inode_info
*pipe
, struct pipe_buffer
*buf
,
566 struct splice_desc
*sd
)
568 struct file
*file
= sd
->file
;
569 struct address_space
*mapping
= file
->f_mapping
;
570 unsigned int offset
, this_len
;
576 * make sure the data in this buffer is uptodate
578 ret
= buf
->ops
->pin(pipe
, buf
);
582 index
= sd
->pos
>> PAGE_CACHE_SHIFT
;
583 offset
= sd
->pos
& ~PAGE_CACHE_MASK
;
586 if (this_len
+ offset
> PAGE_CACHE_SIZE
)
587 this_len
= PAGE_CACHE_SIZE
- offset
;
590 page
= find_lock_page(mapping
, index
);
593 page
= page_cache_alloc_cold(mapping
);
598 * This will also lock the page
600 ret
= add_to_page_cache_lru(page
, mapping
, index
,
606 ret
= mapping
->a_ops
->prepare_write(file
, page
, offset
, offset
+this_len
);
608 loff_t isize
= i_size_read(mapping
->host
);
610 if (ret
!= AOP_TRUNCATED_PAGE
)
612 page_cache_release(page
);
613 if (ret
== AOP_TRUNCATED_PAGE
)
617 * prepare_write() may have instantiated a few blocks
618 * outside i_size. Trim these off again.
620 if (sd
->pos
+ this_len
> isize
)
621 vmtruncate(mapping
->host
, isize
);
626 if (buf
->page
!= page
) {
628 * Careful, ->map() uses KM_USER0!
630 char *src
= buf
->ops
->map(pipe
, buf
, 1);
631 char *dst
= kmap_atomic(page
, KM_USER1
);
633 memcpy(dst
+ offset
, src
+ buf
->offset
, this_len
);
634 flush_dcache_page(page
);
635 kunmap_atomic(dst
, KM_USER1
);
636 buf
->ops
->unmap(pipe
, buf
, src
);
639 ret
= mapping
->a_ops
->commit_write(file
, page
, offset
, offset
+this_len
);
641 if (ret
== AOP_TRUNCATED_PAGE
) {
642 page_cache_release(page
);
648 * Partial write has happened, so 'ret' already initialized by
649 * number of bytes written, Where is nothing we have to do here.
654 * Return the number of bytes written and mark page as
655 * accessed, we are now done!
657 mark_page_accessed(page
);
659 page_cache_release(page
);
666 * Pipe input worker. Most of this logic works like a regular pipe, the
667 * key here is the 'actor' worker passed in that actually moves the data
668 * to the wanted destination. See pipe_to_file/pipe_to_sendpage above.
670 ssize_t
__splice_from_pipe(struct pipe_inode_info
*pipe
,
671 struct file
*out
, loff_t
*ppos
, size_t len
,
672 unsigned int flags
, splice_actor
*actor
)
674 int ret
, do_wakeup
, err
;
675 struct splice_desc sd
;
687 struct pipe_buffer
*buf
= pipe
->bufs
+ pipe
->curbuf
;
688 const struct pipe_buf_operations
*ops
= buf
->ops
;
691 if (sd
.len
> sd
.total_len
)
692 sd
.len
= sd
.total_len
;
694 err
= actor(pipe
, buf
, &sd
);
696 if (!ret
&& err
!= -ENODATA
)
714 ops
->release(pipe
, buf
);
715 pipe
->curbuf
= (pipe
->curbuf
+ 1) & (PIPE_BUFFERS
- 1);
729 if (!pipe
->waiting_writers
) {
734 if (flags
& SPLICE_F_NONBLOCK
) {
740 if (signal_pending(current
)) {
748 if (waitqueue_active(&pipe
->wait
))
749 wake_up_interruptible_sync(&pipe
->wait
);
750 kill_fasync(&pipe
->fasync_writers
, SIGIO
, POLL_OUT
);
759 if (waitqueue_active(&pipe
->wait
))
760 wake_up_interruptible(&pipe
->wait
);
761 kill_fasync(&pipe
->fasync_writers
, SIGIO
, POLL_OUT
);
766 EXPORT_SYMBOL(__splice_from_pipe
);
768 ssize_t
splice_from_pipe(struct pipe_inode_info
*pipe
, struct file
*out
,
769 loff_t
*ppos
, size_t len
, unsigned int flags
,
773 struct inode
*inode
= out
->f_mapping
->host
;
776 * The actor worker might be calling ->prepare_write and
777 * ->commit_write. Most of the time, these expect i_mutex to
778 * be held. Since this may result in an ABBA deadlock with
779 * pipe->inode, we have to order lock acquiry here.
781 inode_double_lock(inode
, pipe
->inode
);
782 ret
= __splice_from_pipe(pipe
, out
, ppos
, len
, flags
, actor
);
783 inode_double_unlock(inode
, pipe
->inode
);
789 * generic_file_splice_write_nolock - generic_file_splice_write without mutexes
791 * @out: file to write to
792 * @len: number of bytes to splice
793 * @flags: splice modifier flags
795 * Will either move or copy pages (determined by @flags options) from
796 * the given pipe inode to the given file. The caller is responsible
797 * for acquiring i_mutex on both inodes.
801 generic_file_splice_write_nolock(struct pipe_inode_info
*pipe
, struct file
*out
,
802 loff_t
*ppos
, size_t len
, unsigned int flags
)
804 struct address_space
*mapping
= out
->f_mapping
;
805 struct inode
*inode
= mapping
->host
;
809 err
= remove_suid(out
->f_path
.dentry
);
813 ret
= __splice_from_pipe(pipe
, out
, ppos
, len
, flags
, pipe_to_file
);
815 unsigned long nr_pages
;
818 nr_pages
= (ret
+ PAGE_CACHE_SIZE
- 1) >> PAGE_CACHE_SHIFT
;
821 * If file or inode is SYNC and we actually wrote some data,
824 if (unlikely((out
->f_flags
& O_SYNC
) || IS_SYNC(inode
))) {
825 err
= generic_osync_inode(inode
, mapping
,
826 OSYNC_METADATA
|OSYNC_DATA
);
831 balance_dirty_pages_ratelimited_nr(mapping
, nr_pages
);
837 EXPORT_SYMBOL(generic_file_splice_write_nolock
);
840 * generic_file_splice_write - splice data from a pipe to a file
842 * @out: file to write to
843 * @len: number of bytes to splice
844 * @flags: splice modifier flags
846 * Will either move or copy pages (determined by @flags options) from
847 * the given pipe inode to the given file.
851 generic_file_splice_write(struct pipe_inode_info
*pipe
, struct file
*out
,
852 loff_t
*ppos
, size_t len
, unsigned int flags
)
854 struct address_space
*mapping
= out
->f_mapping
;
855 struct inode
*inode
= mapping
->host
;
859 err
= should_remove_suid(out
->f_path
.dentry
);
861 mutex_lock(&inode
->i_mutex
);
862 err
= __remove_suid(out
->f_path
.dentry
, err
);
863 mutex_unlock(&inode
->i_mutex
);
868 ret
= splice_from_pipe(pipe
, out
, ppos
, len
, flags
, pipe_to_file
);
870 unsigned long nr_pages
;
873 nr_pages
= (ret
+ PAGE_CACHE_SIZE
- 1) >> PAGE_CACHE_SHIFT
;
876 * If file or inode is SYNC and we actually wrote some data,
879 if (unlikely((out
->f_flags
& O_SYNC
) || IS_SYNC(inode
))) {
880 mutex_lock(&inode
->i_mutex
);
881 err
= generic_osync_inode(inode
, mapping
,
882 OSYNC_METADATA
|OSYNC_DATA
);
883 mutex_unlock(&inode
->i_mutex
);
888 balance_dirty_pages_ratelimited_nr(mapping
, nr_pages
);
894 EXPORT_SYMBOL(generic_file_splice_write
);
897 * generic_splice_sendpage - splice data from a pipe to a socket
899 * @out: socket to write to
900 * @len: number of bytes to splice
901 * @flags: splice modifier flags
903 * Will send @len bytes from the pipe to a network socket. No data copying
907 ssize_t
generic_splice_sendpage(struct pipe_inode_info
*pipe
, struct file
*out
,
908 loff_t
*ppos
, size_t len
, unsigned int flags
)
910 return splice_from_pipe(pipe
, out
, ppos
, len
, flags
, pipe_to_sendpage
);
913 EXPORT_SYMBOL(generic_splice_sendpage
);
916 * Attempt to initiate a splice from pipe to file.
918 static long do_splice_from(struct pipe_inode_info
*pipe
, struct file
*out
,
919 loff_t
*ppos
, size_t len
, unsigned int flags
)
923 if (unlikely(!out
->f_op
|| !out
->f_op
->splice_write
))
926 if (unlikely(!(out
->f_mode
& FMODE_WRITE
)))
929 ret
= rw_verify_area(WRITE
, out
, ppos
, len
);
930 if (unlikely(ret
< 0))
933 return out
->f_op
->splice_write(pipe
, out
, ppos
, len
, flags
);
937 * Attempt to initiate a splice from a file to a pipe.
939 static long do_splice_to(struct file
*in
, loff_t
*ppos
,
940 struct pipe_inode_info
*pipe
, size_t len
,
945 if (unlikely(!in
->f_op
|| !in
->f_op
->splice_read
))
948 if (unlikely(!(in
->f_mode
& FMODE_READ
)))
951 ret
= rw_verify_area(READ
, in
, ppos
, len
);
952 if (unlikely(ret
< 0))
955 return in
->f_op
->splice_read(in
, ppos
, pipe
, len
, flags
);
958 long do_splice_direct(struct file
*in
, loff_t
*ppos
, struct file
*out
,
959 size_t len
, unsigned int flags
)
961 struct pipe_inode_info
*pipe
;
968 * We require the input being a regular file, as we don't want to
969 * randomly drop data for eg socket -> socket splicing. Use the
970 * piped splicing for that!
972 i_mode
= in
->f_path
.dentry
->d_inode
->i_mode
;
973 if (unlikely(!S_ISREG(i_mode
) && !S_ISBLK(i_mode
)))
977 * neither in nor out is a pipe, setup an internal pipe attached to
978 * 'out' and transfer the wanted data from 'in' to 'out' through that
980 pipe
= current
->splice_pipe
;
981 if (unlikely(!pipe
)) {
982 pipe
= alloc_pipe_info(NULL
);
987 * We don't have an immediate reader, but we'll read the stuff
988 * out of the pipe right after the splice_to_pipe(). So set
989 * PIPE_READERS appropriately.
993 current
->splice_pipe
= pipe
;
1004 size_t read_len
, max_read_len
;
1007 * Do at most PIPE_BUFFERS pages worth of transfer:
1009 max_read_len
= min(len
, (size_t)(PIPE_BUFFERS
*PAGE_SIZE
));
1011 ret
= do_splice_to(in
, ppos
, pipe
, max_read_len
, flags
);
1012 if (unlikely(ret
< 0))
1018 * NOTE: nonblocking mode only applies to the input. We
1019 * must not do the output in nonblocking mode as then we
1020 * could get stuck data in the internal pipe:
1022 ret
= do_splice_from(pipe
, out
, &out_off
, read_len
,
1023 flags
& ~SPLICE_F_NONBLOCK
);
1024 if (unlikely(ret
< 0))
1031 * In nonblocking mode, if we got back a short read then
1032 * that was due to either an IO error or due to the
1033 * pagecache entry not being there. In the IO error case
1034 * the _next_ splice attempt will produce a clean IO error
1035 * return value (not a short read), so in both cases it's
1036 * correct to break out of the loop here:
1038 if ((flags
& SPLICE_F_NONBLOCK
) && (read_len
< max_read_len
))
1042 pipe
->nrbufs
= pipe
->curbuf
= 0;
1048 * If we did an incomplete transfer we must release
1049 * the pipe buffers in question:
1051 for (i
= 0; i
< PIPE_BUFFERS
; i
++) {
1052 struct pipe_buffer
*buf
= pipe
->bufs
+ i
;
1055 buf
->ops
->release(pipe
, buf
);
1059 pipe
->nrbufs
= pipe
->curbuf
= 0;
1062 * If we transferred some data, return the number of bytes:
1071 * After the inode slimming patch, i_pipe/i_bdev/i_cdev share the same
1072 * location, so checking ->i_pipe is not enough to verify that this is a
1075 static inline struct pipe_inode_info
*pipe_info(struct inode
*inode
)
1077 if (S_ISFIFO(inode
->i_mode
))
1078 return inode
->i_pipe
;
1084 * Determine where to splice to/from.
1086 static long do_splice(struct file
*in
, loff_t __user
*off_in
,
1087 struct file
*out
, loff_t __user
*off_out
,
1088 size_t len
, unsigned int flags
)
1090 struct pipe_inode_info
*pipe
;
1091 loff_t offset
, *off
;
1094 pipe
= pipe_info(in
->f_path
.dentry
->d_inode
);
1099 if (out
->f_op
->llseek
== no_llseek
)
1101 if (copy_from_user(&offset
, off_out
, sizeof(loff_t
)))
1107 ret
= do_splice_from(pipe
, out
, off
, len
, flags
);
1109 if (off_out
&& copy_to_user(off_out
, off
, sizeof(loff_t
)))
1115 pipe
= pipe_info(out
->f_path
.dentry
->d_inode
);
1120 if (in
->f_op
->llseek
== no_llseek
)
1122 if (copy_from_user(&offset
, off_in
, sizeof(loff_t
)))
1128 ret
= do_splice_to(in
, off
, pipe
, len
, flags
);
1130 if (off_in
&& copy_to_user(off_in
, off
, sizeof(loff_t
)))
1140 * Map an iov into an array of pages and offset/length tupples. With the
1141 * partial_page structure, we can map several non-contiguous ranges into
1142 * our ones pages[] map instead of splitting that operation into pieces.
1143 * Could easily be exported as a generic helper for other users, in which
1144 * case one would probably want to add a 'max_nr_pages' parameter as well.
1146 static int get_iovec_page_array(const struct iovec __user
*iov
,
1147 unsigned int nr_vecs
, struct page
**pages
,
1148 struct partial_page
*partial
, int aligned
)
1150 int buffers
= 0, error
= 0;
1153 * It's ok to take the mmap_sem for reading, even
1154 * across a "get_user()".
1156 down_read(¤t
->mm
->mmap_sem
);
1159 unsigned long off
, npages
;
1165 * Get user address base and length for this iovec.
1167 error
= get_user(base
, &iov
->iov_base
);
1168 if (unlikely(error
))
1170 error
= get_user(len
, &iov
->iov_len
);
1171 if (unlikely(error
))
1175 * Sanity check this iovec. 0 read succeeds.
1180 if (unlikely(!base
))
1184 * Get this base offset and number of pages, then map
1185 * in the user pages.
1187 off
= (unsigned long) base
& ~PAGE_MASK
;
1190 * If asked for alignment, the offset must be zero and the
1191 * length a multiple of the PAGE_SIZE.
1194 if (aligned
&& (off
|| len
& ~PAGE_MASK
))
1197 npages
= (off
+ len
+ PAGE_SIZE
- 1) >> PAGE_SHIFT
;
1198 if (npages
> PIPE_BUFFERS
- buffers
)
1199 npages
= PIPE_BUFFERS
- buffers
;
1201 error
= get_user_pages(current
, current
->mm
,
1202 (unsigned long) base
, npages
, 0, 0,
1203 &pages
[buffers
], NULL
);
1205 if (unlikely(error
<= 0))
1209 * Fill this contiguous range into the partial page map.
1211 for (i
= 0; i
< error
; i
++) {
1212 const int plen
= min_t(size_t, len
, PAGE_SIZE
- off
);
1214 partial
[buffers
].offset
= off
;
1215 partial
[buffers
].len
= plen
;
1223 * We didn't complete this iov, stop here since it probably
1224 * means we have to move some of this into a pipe to
1225 * be able to continue.
1231 * Don't continue if we mapped fewer pages than we asked for,
1232 * or if we mapped the max number of pages that we have
1235 if (error
< npages
|| buffers
== PIPE_BUFFERS
)
1242 up_read(¤t
->mm
->mmap_sem
);
1251 * vmsplice splices a user address range into a pipe. It can be thought of
1252 * as splice-from-memory, where the regular splice is splice-from-file (or
1253 * to file). In both cases the output is a pipe, naturally.
1255 * Note that vmsplice only supports splicing _from_ user memory to a pipe,
1256 * not the other way around. Splicing from user memory is a simple operation
1257 * that can be supported without any funky alignment restrictions or nasty
1258 * vm tricks. We simply map in the user memory and fill them into a pipe.
1259 * The reverse isn't quite as easy, though. There are two possible solutions
1262 * - memcpy() the data internally, at which point we might as well just
1263 * do a regular read() on the buffer anyway.
1264 * - Lots of nasty vm tricks, that are neither fast nor flexible (it
1265 * has restriction limitations on both ends of the pipe).
1267 * Alas, it isn't here.
1270 static long do_vmsplice(struct file
*file
, const struct iovec __user
*iov
,
1271 unsigned long nr_segs
, unsigned int flags
)
1273 struct pipe_inode_info
*pipe
;
1274 struct page
*pages
[PIPE_BUFFERS
];
1275 struct partial_page partial
[PIPE_BUFFERS
];
1276 struct splice_pipe_desc spd
= {
1280 .ops
= &user_page_pipe_buf_ops
,
1283 pipe
= pipe_info(file
->f_path
.dentry
->d_inode
);
1286 if (unlikely(nr_segs
> UIO_MAXIOV
))
1288 else if (unlikely(!nr_segs
))
1291 spd
.nr_pages
= get_iovec_page_array(iov
, nr_segs
, pages
, partial
,
1292 flags
& SPLICE_F_GIFT
);
1293 if (spd
.nr_pages
<= 0)
1294 return spd
.nr_pages
;
1296 return splice_to_pipe(pipe
, &spd
);
1299 asmlinkage
long sys_vmsplice(int fd
, const struct iovec __user
*iov
,
1300 unsigned long nr_segs
, unsigned int flags
)
1307 file
= fget_light(fd
, &fput
);
1309 if (file
->f_mode
& FMODE_WRITE
)
1310 error
= do_vmsplice(file
, iov
, nr_segs
, flags
);
1312 fput_light(file
, fput
);
1318 asmlinkage
long sys_splice(int fd_in
, loff_t __user
*off_in
,
1319 int fd_out
, loff_t __user
*off_out
,
1320 size_t len
, unsigned int flags
)
1323 struct file
*in
, *out
;
1324 int fput_in
, fput_out
;
1330 in
= fget_light(fd_in
, &fput_in
);
1332 if (in
->f_mode
& FMODE_READ
) {
1333 out
= fget_light(fd_out
, &fput_out
);
1335 if (out
->f_mode
& FMODE_WRITE
)
1336 error
= do_splice(in
, off_in
,
1339 fput_light(out
, fput_out
);
1343 fput_light(in
, fput_in
);
1350 * Make sure there's data to read. Wait for input if we can, otherwise
1351 * return an appropriate error.
1353 static int link_ipipe_prep(struct pipe_inode_info
*pipe
, unsigned int flags
)
1358 * Check ->nrbufs without the inode lock first. This function
1359 * is speculative anyways, so missing one is ok.
1365 mutex_lock(&pipe
->inode
->i_mutex
);
1367 while (!pipe
->nrbufs
) {
1368 if (signal_pending(current
)) {
1374 if (!pipe
->waiting_writers
) {
1375 if (flags
& SPLICE_F_NONBLOCK
) {
1383 mutex_unlock(&pipe
->inode
->i_mutex
);
1388 * Make sure there's writeable room. Wait for room if we can, otherwise
1389 * return an appropriate error.
1391 static int link_opipe_prep(struct pipe_inode_info
*pipe
, unsigned int flags
)
1396 * Check ->nrbufs without the inode lock first. This function
1397 * is speculative anyways, so missing one is ok.
1399 if (pipe
->nrbufs
< PIPE_BUFFERS
)
1403 mutex_lock(&pipe
->inode
->i_mutex
);
1405 while (pipe
->nrbufs
>= PIPE_BUFFERS
) {
1406 if (!pipe
->readers
) {
1407 send_sig(SIGPIPE
, current
, 0);
1411 if (flags
& SPLICE_F_NONBLOCK
) {
1415 if (signal_pending(current
)) {
1419 pipe
->waiting_writers
++;
1421 pipe
->waiting_writers
--;
1424 mutex_unlock(&pipe
->inode
->i_mutex
);
1429 * Link contents of ipipe to opipe.
1431 static int link_pipe(struct pipe_inode_info
*ipipe
,
1432 struct pipe_inode_info
*opipe
,
1433 size_t len
, unsigned int flags
)
1435 struct pipe_buffer
*ibuf
, *obuf
;
1436 int ret
= 0, i
= 0, nbuf
;
1439 * Potential ABBA deadlock, work around it by ordering lock
1440 * grabbing by inode address. Otherwise two different processes
1441 * could deadlock (one doing tee from A -> B, the other from B -> A).
1443 inode_double_lock(ipipe
->inode
, opipe
->inode
);
1446 if (!opipe
->readers
) {
1447 send_sig(SIGPIPE
, current
, 0);
1454 * If we have iterated all input buffers or ran out of
1455 * output room, break.
1457 if (i
>= ipipe
->nrbufs
|| opipe
->nrbufs
>= PIPE_BUFFERS
)
1460 ibuf
= ipipe
->bufs
+ ((ipipe
->curbuf
+ i
) & (PIPE_BUFFERS
- 1));
1461 nbuf
= (opipe
->curbuf
+ opipe
->nrbufs
) & (PIPE_BUFFERS
- 1);
1464 * Get a reference to this pipe buffer,
1465 * so we can copy the contents over.
1467 ibuf
->ops
->get(ipipe
, ibuf
);
1469 obuf
= opipe
->bufs
+ nbuf
;
1473 * Don't inherit the gift flag, we need to
1474 * prevent multiple steals of this page.
1476 obuf
->flags
&= ~PIPE_BUF_FLAG_GIFT
;
1478 if (obuf
->len
> len
)
1487 inode_double_unlock(ipipe
->inode
, opipe
->inode
);
1490 * If we put data in the output pipe, wakeup any potential readers.
1494 if (waitqueue_active(&opipe
->wait
))
1495 wake_up_interruptible(&opipe
->wait
);
1496 kill_fasync(&opipe
->fasync_readers
, SIGIO
, POLL_IN
);
1503 * This is a tee(1) implementation that works on pipes. It doesn't copy
1504 * any data, it simply references the 'in' pages on the 'out' pipe.
1505 * The 'flags' used are the SPLICE_F_* variants, currently the only
1506 * applicable one is SPLICE_F_NONBLOCK.
1508 static long do_tee(struct file
*in
, struct file
*out
, size_t len
,
1511 struct pipe_inode_info
*ipipe
= pipe_info(in
->f_path
.dentry
->d_inode
);
1512 struct pipe_inode_info
*opipe
= pipe_info(out
->f_path
.dentry
->d_inode
);
1516 * Duplicate the contents of ipipe to opipe without actually
1519 if (ipipe
&& opipe
&& ipipe
!= opipe
) {
1521 * Keep going, unless we encounter an error. The ipipe/opipe
1522 * ordering doesn't really matter.
1524 ret
= link_ipipe_prep(ipipe
, flags
);
1526 ret
= link_opipe_prep(opipe
, flags
);
1528 ret
= link_pipe(ipipe
, opipe
, len
, flags
);
1529 if (!ret
&& (flags
& SPLICE_F_NONBLOCK
))
1538 asmlinkage
long sys_tee(int fdin
, int fdout
, size_t len
, unsigned int flags
)
1547 in
= fget_light(fdin
, &fput_in
);
1549 if (in
->f_mode
& FMODE_READ
) {
1551 struct file
*out
= fget_light(fdout
, &fput_out
);
1554 if (out
->f_mode
& FMODE_WRITE
)
1555 error
= do_tee(in
, out
, len
, flags
);
1556 fput_light(out
, fput_out
);
1559 fput_light(in
, fput_in
);