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
);