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
;
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
;
203 buf
->private = spd
->partial
[page_nr
].private;
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
);
259 while (page_nr
< spd_pages
)
260 spd
->spd_release(spd
, page_nr
++);
265 static void spd_release_page(struct splice_pipe_desc
*spd
, unsigned int i
)
267 page_cache_release(spd
->pages
[i
]);
271 __generic_file_splice_read(struct file
*in
, loff_t
*ppos
,
272 struct pipe_inode_info
*pipe
, size_t len
,
275 struct address_space
*mapping
= in
->f_mapping
;
276 unsigned int loff
, nr_pages
, req_pages
;
277 struct page
*pages
[PIPE_BUFFERS
];
278 struct partial_page partial
[PIPE_BUFFERS
];
280 pgoff_t index
, end_index
;
283 struct splice_pipe_desc spd
= {
287 .ops
= &page_cache_pipe_buf_ops
,
288 .spd_release
= spd_release_page
,
291 index
= *ppos
>> PAGE_CACHE_SHIFT
;
292 loff
= *ppos
& ~PAGE_CACHE_MASK
;
293 req_pages
= (len
+ loff
+ PAGE_CACHE_SIZE
- 1) >> PAGE_CACHE_SHIFT
;
294 nr_pages
= min(req_pages
, (unsigned)PIPE_BUFFERS
);
297 * Lookup the (hopefully) full range of pages we need.
299 spd
.nr_pages
= find_get_pages_contig(mapping
, index
, nr_pages
, pages
);
300 index
+= spd
.nr_pages
;
303 * If find_get_pages_contig() returned fewer pages than we needed,
304 * readahead/allocate the rest and fill in the holes.
306 if (spd
.nr_pages
< nr_pages
)
307 page_cache_sync_readahead(mapping
, &in
->f_ra
, in
,
308 index
, req_pages
- 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 * page didn't exist, allocate one.
321 page
= page_cache_alloc_cold(mapping
);
325 error
= add_to_page_cache_lru(page
, mapping
, index
,
326 mapping_gfp_mask(mapping
));
327 if (unlikely(error
)) {
328 page_cache_release(page
);
329 if (error
== -EEXIST
)
334 * add_to_page_cache() locks the page, unlock it
335 * to avoid convoluting the logic below even more.
340 pages
[spd
.nr_pages
++] = page
;
345 * Now loop over the map and see if we need to start IO on any
346 * pages, fill in the partial map, etc.
348 index
= *ppos
>> PAGE_CACHE_SHIFT
;
349 nr_pages
= spd
.nr_pages
;
351 for (page_nr
= 0; page_nr
< nr_pages
; page_nr
++) {
352 unsigned int this_len
;
358 * this_len is the max we'll use from this page
360 this_len
= min_t(unsigned long, len
, PAGE_CACHE_SIZE
- loff
);
361 page
= pages
[page_nr
];
363 if (PageReadahead(page
))
364 page_cache_async_readahead(mapping
, &in
->f_ra
, in
,
365 page
, index
, req_pages
- page_nr
);
368 * If the page isn't uptodate, we may need to start io on it
370 if (!PageUptodate(page
)) {
372 * If in nonblock mode then dont block on waiting
373 * for an in-flight io page
375 if (flags
& SPLICE_F_NONBLOCK
) {
376 if (!trylock_page(page
)) {
384 * Page was truncated, or invalidated by the
385 * filesystem. Redo the find/create, but this time the
386 * page is kept locked, so there's no chance of another
387 * race with truncate/invalidate.
389 if (!page
->mapping
) {
391 page
= find_or_create_page(mapping
, index
,
392 mapping_gfp_mask(mapping
));
398 page_cache_release(pages
[page_nr
]);
399 pages
[page_nr
] = page
;
402 * page was already under io and is now done, great
404 if (PageUptodate(page
)) {
410 * need to read in the page
412 error
= mapping
->a_ops
->readpage(in
, page
);
413 if (unlikely(error
)) {
415 * We really should re-lookup the page here,
416 * but it complicates things a lot. Instead
417 * lets just do what we already stored, and
418 * we'll get it the next time we are called.
420 if (error
== AOP_TRUNCATED_PAGE
)
428 * i_size must be checked after PageUptodate.
430 isize
= i_size_read(mapping
->host
);
431 end_index
= (isize
- 1) >> PAGE_CACHE_SHIFT
;
432 if (unlikely(!isize
|| index
> end_index
))
436 * if this is the last page, see if we need to shrink
437 * the length and stop
439 if (end_index
== index
) {
443 * max good bytes in this page
445 plen
= ((isize
- 1) & ~PAGE_CACHE_MASK
) + 1;
450 * force quit after adding this page
452 this_len
= min(this_len
, plen
- loff
);
456 partial
[page_nr
].offset
= loff
;
457 partial
[page_nr
].len
= this_len
;
465 * Release any pages at the end, if we quit early. 'page_nr' is how far
466 * we got, 'nr_pages' is how many pages are in the map.
468 while (page_nr
< nr_pages
)
469 page_cache_release(pages
[page_nr
++]);
470 in
->f_ra
.prev_pos
= (loff_t
)index
<< PAGE_CACHE_SHIFT
;
473 return splice_to_pipe(pipe
, &spd
);
479 * generic_file_splice_read - splice data from file to a pipe
480 * @in: file to splice from
481 * @ppos: position in @in
482 * @pipe: pipe to splice to
483 * @len: number of bytes to splice
484 * @flags: splice modifier flags
487 * Will read pages from given file and fill them into a pipe. Can be
488 * used as long as the address_space operations for the source implements
492 ssize_t
generic_file_splice_read(struct file
*in
, loff_t
*ppos
,
493 struct pipe_inode_info
*pipe
, size_t len
,
499 isize
= i_size_read(in
->f_mapping
->host
);
500 if (unlikely(*ppos
>= isize
))
503 left
= isize
- *ppos
;
504 if (unlikely(left
< len
))
507 ret
= __generic_file_splice_read(in
, ppos
, pipe
, len
, flags
);
514 EXPORT_SYMBOL(generic_file_splice_read
);
517 * Send 'sd->len' bytes to socket from 'sd->file' at position 'sd->pos'
518 * using sendpage(). Return the number of bytes sent.
520 static int pipe_to_sendpage(struct pipe_inode_info
*pipe
,
521 struct pipe_buffer
*buf
, struct splice_desc
*sd
)
523 struct file
*file
= sd
->u
.file
;
524 loff_t pos
= sd
->pos
;
527 ret
= buf
->ops
->confirm(pipe
, buf
);
529 more
= (sd
->flags
& SPLICE_F_MORE
) || sd
->len
< sd
->total_len
;
531 ret
= file
->f_op
->sendpage(file
, buf
->page
, buf
->offset
,
532 sd
->len
, &pos
, more
);
539 * This is a little more tricky than the file -> pipe splicing. There are
540 * basically three cases:
542 * - Destination page already exists in the address space and there
543 * are users of it. For that case we have no other option that
544 * copying the data. Tough luck.
545 * - Destination page already exists in the address space, but there
546 * are no users of it. Make sure it's uptodate, then drop it. Fall
547 * through to last case.
548 * - Destination page does not exist, we can add the pipe page to
549 * the page cache and avoid the copy.
551 * If asked to move pages to the output file (SPLICE_F_MOVE is set in
552 * sd->flags), we attempt to migrate pages from the pipe to the output
553 * file address space page cache. This is possible if no one else has
554 * the pipe page referenced outside of the pipe and page cache. If
555 * SPLICE_F_MOVE isn't set, or we cannot move the page, we simply create
556 * a new page in the output file page cache and fill/dirty that.
558 static int pipe_to_file(struct pipe_inode_info
*pipe
, struct pipe_buffer
*buf
,
559 struct splice_desc
*sd
)
561 struct file
*file
= sd
->u
.file
;
562 struct address_space
*mapping
= file
->f_mapping
;
563 unsigned int offset
, this_len
;
569 * make sure the data in this buffer is uptodate
571 ret
= buf
->ops
->confirm(pipe
, buf
);
575 offset
= sd
->pos
& ~PAGE_CACHE_MASK
;
578 if (this_len
+ offset
> PAGE_CACHE_SIZE
)
579 this_len
= PAGE_CACHE_SIZE
- offset
;
581 ret
= pagecache_write_begin(file
, mapping
, sd
->pos
, this_len
,
582 AOP_FLAG_UNINTERRUPTIBLE
, &page
, &fsdata
);
586 if (buf
->page
!= page
) {
588 * Careful, ->map() uses KM_USER0!
590 char *src
= buf
->ops
->map(pipe
, buf
, 1);
591 char *dst
= kmap_atomic(page
, KM_USER1
);
593 memcpy(dst
+ offset
, src
+ buf
->offset
, this_len
);
594 flush_dcache_page(page
);
595 kunmap_atomic(dst
, KM_USER1
);
596 buf
->ops
->unmap(pipe
, buf
, src
);
598 ret
= pagecache_write_end(file
, mapping
, sd
->pos
, this_len
, this_len
,
604 static void wakeup_pipe_writers(struct pipe_inode_info
*pipe
)
607 if (waitqueue_active(&pipe
->wait
))
608 wake_up_interruptible(&pipe
->wait
);
609 kill_fasync(&pipe
->fasync_writers
, SIGIO
, POLL_OUT
);
613 * splice_from_pipe_feed - feed available data from a pipe to a file
614 * @pipe: pipe to splice from
615 * @sd: information to @actor
616 * @actor: handler that splices the data
620 * This function loops over the pipe and calls @actor to do the
621 * actual moving of a single struct pipe_buffer to the desired
622 * destination. It returns when there's no more buffers left in
623 * the pipe or if the requested number of bytes (@sd->total_len)
624 * have been copied. It returns a positive number (one) if the
625 * pipe needs to be filled with more data, zero if the required
626 * number of bytes have been copied and -errno on error.
628 * This, together with splice_from_pipe_{begin,end,next}, may be
629 * used to implement the functionality of __splice_from_pipe() when
630 * locking is required around copying the pipe buffers to the
633 int splice_from_pipe_feed(struct pipe_inode_info
*pipe
, struct splice_desc
*sd
,
638 while (pipe
->nrbufs
) {
639 struct pipe_buffer
*buf
= pipe
->bufs
+ pipe
->curbuf
;
640 const struct pipe_buf_operations
*ops
= buf
->ops
;
643 if (sd
->len
> sd
->total_len
)
644 sd
->len
= sd
->total_len
;
646 ret
= actor(pipe
, buf
, sd
);
655 sd
->num_spliced
+= ret
;
658 sd
->total_len
-= ret
;
662 ops
->release(pipe
, buf
);
663 pipe
->curbuf
= (pipe
->curbuf
+ 1) & (PIPE_BUFFERS
- 1);
666 sd
->need_wakeup
= true;
675 EXPORT_SYMBOL(splice_from_pipe_feed
);
678 * splice_from_pipe_next - wait for some data to splice from
679 * @pipe: pipe to splice from
680 * @sd: information about the splice operation
683 * This function will wait for some data and return a positive
684 * value (one) if pipe buffers are available. It will return zero
685 * or -errno if no more data needs to be spliced.
687 int splice_from_pipe_next(struct pipe_inode_info
*pipe
, struct splice_desc
*sd
)
689 while (!pipe
->nrbufs
) {
693 if (!pipe
->waiting_writers
&& sd
->num_spliced
)
696 if (sd
->flags
& SPLICE_F_NONBLOCK
)
699 if (signal_pending(current
))
702 if (sd
->need_wakeup
) {
703 wakeup_pipe_writers(pipe
);
704 sd
->need_wakeup
= false;
712 EXPORT_SYMBOL(splice_from_pipe_next
);
715 * splice_from_pipe_begin - start splicing from pipe
716 * @pipe: pipe to splice from
719 * This function should be called before a loop containing
720 * splice_from_pipe_next() and splice_from_pipe_feed() to
721 * initialize the necessary fields of @sd.
723 void splice_from_pipe_begin(struct splice_desc
*sd
)
726 sd
->need_wakeup
= false;
728 EXPORT_SYMBOL(splice_from_pipe_begin
);
731 * splice_from_pipe_end - finish splicing from pipe
732 * @pipe: pipe to splice from
733 * @sd: information about the splice operation
736 * This function will wake up pipe writers if necessary. It should
737 * be called after a loop containing splice_from_pipe_next() and
738 * splice_from_pipe_feed().
740 void splice_from_pipe_end(struct pipe_inode_info
*pipe
, struct splice_desc
*sd
)
743 wakeup_pipe_writers(pipe
);
745 EXPORT_SYMBOL(splice_from_pipe_end
);
748 * __splice_from_pipe - splice data from a pipe to given actor
749 * @pipe: pipe to splice from
750 * @sd: information to @actor
751 * @actor: handler that splices the data
754 * This function does little more than loop over the pipe and call
755 * @actor to do the actual moving of a single struct pipe_buffer to
756 * the desired destination. See pipe_to_file, pipe_to_sendpage, or
760 ssize_t
__splice_from_pipe(struct pipe_inode_info
*pipe
, struct splice_desc
*sd
,
765 splice_from_pipe_begin(sd
);
767 ret
= splice_from_pipe_next(pipe
, sd
);
769 ret
= splice_from_pipe_feed(pipe
, sd
, actor
);
771 splice_from_pipe_end(pipe
, sd
);
773 return sd
->num_spliced
? sd
->num_spliced
: ret
;
775 EXPORT_SYMBOL(__splice_from_pipe
);
778 * splice_from_pipe - splice data from a pipe to a file
779 * @pipe: pipe to splice from
780 * @out: file to splice to
781 * @ppos: position in @out
782 * @len: how many bytes to splice
783 * @flags: splice modifier flags
784 * @actor: handler that splices the data
787 * See __splice_from_pipe. This function locks the pipe inode,
788 * otherwise it's identical to __splice_from_pipe().
791 ssize_t
splice_from_pipe(struct pipe_inode_info
*pipe
, struct file
*out
,
792 loff_t
*ppos
, size_t len
, unsigned int flags
,
796 struct splice_desc sd
= {
804 mutex_lock(&pipe
->inode
->i_mutex
);
805 ret
= __splice_from_pipe(pipe
, &sd
, actor
);
807 mutex_unlock(&pipe
->inode
->i_mutex
);
813 * generic_file_splice_write_nolock - generic_file_splice_write without mutexes
815 * @out: file to write to
816 * @ppos: position in @out
817 * @len: number of bytes to splice
818 * @flags: splice modifier flags
821 * Will either move or copy pages (determined by @flags options) from
822 * the given pipe inode to the given file. The caller is responsible
823 * for acquiring i_mutex on both inodes.
827 generic_file_splice_write_nolock(struct pipe_inode_info
*pipe
, struct file
*out
,
828 loff_t
*ppos
, size_t len
, unsigned int flags
)
830 struct address_space
*mapping
= out
->f_mapping
;
831 struct inode
*inode
= mapping
->host
;
832 struct splice_desc sd
= {
841 err
= file_remove_suid(out
);
845 ret
= __splice_from_pipe(pipe
, &sd
, pipe_to_file
);
847 unsigned long nr_pages
;
850 nr_pages
= (ret
+ PAGE_CACHE_SIZE
- 1) >> PAGE_CACHE_SHIFT
;
853 * If file or inode is SYNC and we actually wrote some data,
856 if (unlikely((out
->f_flags
& O_SYNC
) || IS_SYNC(inode
))) {
857 err
= generic_osync_inode(inode
, mapping
,
858 OSYNC_METADATA
|OSYNC_DATA
);
863 balance_dirty_pages_ratelimited_nr(mapping
, nr_pages
);
869 EXPORT_SYMBOL(generic_file_splice_write_nolock
);
872 * generic_file_splice_write - splice data from a pipe to a file
874 * @out: file to write to
875 * @ppos: position in @out
876 * @len: number of bytes to splice
877 * @flags: splice modifier flags
880 * Will either move or copy pages (determined by @flags options) from
881 * the given pipe inode to the given file.
885 generic_file_splice_write(struct pipe_inode_info
*pipe
, struct file
*out
,
886 loff_t
*ppos
, size_t len
, unsigned int flags
)
888 struct address_space
*mapping
= out
->f_mapping
;
889 struct inode
*inode
= mapping
->host
;
890 struct splice_desc sd
= {
898 WARN_ON(S_ISFIFO(inode
->i_mode
));
899 mutex_lock_nested(&inode
->i_mutex
, I_MUTEX_PARENT
);
900 ret
= file_remove_suid(out
);
903 mutex_lock_nested(&pipe
->inode
->i_mutex
, I_MUTEX_CHILD
);
904 ret
= __splice_from_pipe(pipe
, &sd
, pipe_to_file
);
906 mutex_unlock(&pipe
->inode
->i_mutex
);
908 mutex_unlock(&inode
->i_mutex
);
910 unsigned long nr_pages
;
913 nr_pages
= (ret
+ PAGE_CACHE_SIZE
- 1) >> PAGE_CACHE_SHIFT
;
916 * If file or inode is SYNC and we actually wrote some data,
919 if (unlikely((out
->f_flags
& O_SYNC
) || IS_SYNC(inode
))) {
922 mutex_lock(&inode
->i_mutex
);
923 err
= generic_osync_inode(inode
, mapping
,
924 OSYNC_METADATA
|OSYNC_DATA
);
925 mutex_unlock(&inode
->i_mutex
);
930 balance_dirty_pages_ratelimited_nr(mapping
, nr_pages
);
936 EXPORT_SYMBOL(generic_file_splice_write
);
939 * generic_splice_sendpage - splice data from a pipe to a socket
940 * @pipe: pipe to splice from
941 * @out: socket to write to
942 * @ppos: position in @out
943 * @len: number of bytes to splice
944 * @flags: splice modifier flags
947 * Will send @len bytes from the pipe to a network socket. No data copying
951 ssize_t
generic_splice_sendpage(struct pipe_inode_info
*pipe
, struct file
*out
,
952 loff_t
*ppos
, size_t len
, unsigned int flags
)
954 return splice_from_pipe(pipe
, out
, ppos
, len
, flags
, pipe_to_sendpage
);
957 EXPORT_SYMBOL(generic_splice_sendpage
);
960 * Attempt to initiate a splice from pipe to file.
962 static long do_splice_from(struct pipe_inode_info
*pipe
, struct file
*out
,
963 loff_t
*ppos
, size_t len
, unsigned int flags
)
967 if (unlikely(!out
->f_op
|| !out
->f_op
->splice_write
))
970 if (unlikely(!(out
->f_mode
& FMODE_WRITE
)))
973 if (unlikely(out
->f_flags
& O_APPEND
))
976 ret
= rw_verify_area(WRITE
, out
, ppos
, len
);
977 if (unlikely(ret
< 0))
980 return out
->f_op
->splice_write(pipe
, out
, ppos
, len
, flags
);
984 * Attempt to initiate a splice from a file to a pipe.
986 static long do_splice_to(struct file
*in
, loff_t
*ppos
,
987 struct pipe_inode_info
*pipe
, size_t len
,
992 if (unlikely(!in
->f_op
|| !in
->f_op
->splice_read
))
995 if (unlikely(!(in
->f_mode
& FMODE_READ
)))
998 ret
= rw_verify_area(READ
, in
, ppos
, len
);
999 if (unlikely(ret
< 0))
1002 return in
->f_op
->splice_read(in
, ppos
, pipe
, len
, flags
);
1006 * splice_direct_to_actor - splices data directly between two non-pipes
1007 * @in: file to splice from
1008 * @sd: actor information on where to splice to
1009 * @actor: handles the data splicing
1012 * This is a special case helper to splice directly between two
1013 * points, without requiring an explicit pipe. Internally an allocated
1014 * pipe is cached in the process, and reused during the lifetime of
1018 ssize_t
splice_direct_to_actor(struct file
*in
, struct splice_desc
*sd
,
1019 splice_direct_actor
*actor
)
1021 struct pipe_inode_info
*pipe
;
1028 * We require the input being a regular file, as we don't want to
1029 * randomly drop data for eg socket -> socket splicing. Use the
1030 * piped splicing for that!
1032 i_mode
= in
->f_path
.dentry
->d_inode
->i_mode
;
1033 if (unlikely(!S_ISREG(i_mode
) && !S_ISBLK(i_mode
)))
1037 * neither in nor out is a pipe, setup an internal pipe attached to
1038 * 'out' and transfer the wanted data from 'in' to 'out' through that
1040 pipe
= current
->splice_pipe
;
1041 if (unlikely(!pipe
)) {
1042 pipe
= alloc_pipe_info(NULL
);
1047 * We don't have an immediate reader, but we'll read the stuff
1048 * out of the pipe right after the splice_to_pipe(). So set
1049 * PIPE_READERS appropriately.
1053 current
->splice_pipe
= pipe
;
1061 len
= sd
->total_len
;
1065 * Don't block on output, we have to drain the direct pipe.
1067 sd
->flags
&= ~SPLICE_F_NONBLOCK
;
1071 loff_t pos
= sd
->pos
, prev_pos
= pos
;
1073 ret
= do_splice_to(in
, &pos
, pipe
, len
, flags
);
1074 if (unlikely(ret
<= 0))
1078 sd
->total_len
= read_len
;
1081 * NOTE: nonblocking mode only applies to the input. We
1082 * must not do the output in nonblocking mode as then we
1083 * could get stuck data in the internal pipe:
1085 ret
= actor(pipe
, sd
);
1086 if (unlikely(ret
<= 0)) {
1095 if (ret
< read_len
) {
1096 sd
->pos
= prev_pos
+ ret
;
1102 pipe
->nrbufs
= pipe
->curbuf
= 0;
1108 * If we did an incomplete transfer we must release
1109 * the pipe buffers in question:
1111 for (i
= 0; i
< PIPE_BUFFERS
; i
++) {
1112 struct pipe_buffer
*buf
= pipe
->bufs
+ i
;
1115 buf
->ops
->release(pipe
, buf
);
1125 EXPORT_SYMBOL(splice_direct_to_actor
);
1127 static int direct_splice_actor(struct pipe_inode_info
*pipe
,
1128 struct splice_desc
*sd
)
1130 struct file
*file
= sd
->u
.file
;
1132 return do_splice_from(pipe
, file
, &sd
->pos
, sd
->total_len
, sd
->flags
);
1136 * do_splice_direct - splices data directly between two files
1137 * @in: file to splice from
1138 * @ppos: input file offset
1139 * @out: file to splice to
1140 * @len: number of bytes to splice
1141 * @flags: splice modifier flags
1144 * For use by do_sendfile(). splice can easily emulate sendfile, but
1145 * doing it in the application would incur an extra system call
1146 * (splice in + splice out, as compared to just sendfile()). So this helper
1147 * can splice directly through a process-private pipe.
1150 long do_splice_direct(struct file
*in
, loff_t
*ppos
, struct file
*out
,
1151 size_t len
, unsigned int flags
)
1153 struct splice_desc sd
= {
1162 ret
= splice_direct_to_actor(in
, &sd
, direct_splice_actor
);
1170 * After the inode slimming patch, i_pipe/i_bdev/i_cdev share the same
1171 * location, so checking ->i_pipe is not enough to verify that this is a
1174 static inline struct pipe_inode_info
*pipe_info(struct inode
*inode
)
1176 if (S_ISFIFO(inode
->i_mode
))
1177 return inode
->i_pipe
;
1183 * Determine where to splice to/from.
1185 static long do_splice(struct file
*in
, loff_t __user
*off_in
,
1186 struct file
*out
, loff_t __user
*off_out
,
1187 size_t len
, unsigned int flags
)
1189 struct pipe_inode_info
*pipe
;
1190 loff_t offset
, *off
;
1193 pipe
= pipe_info(in
->f_path
.dentry
->d_inode
);
1198 if (out
->f_op
->llseek
== no_llseek
)
1200 if (copy_from_user(&offset
, off_out
, sizeof(loff_t
)))
1206 ret
= do_splice_from(pipe
, out
, off
, len
, flags
);
1208 if (off_out
&& copy_to_user(off_out
, off
, sizeof(loff_t
)))
1214 pipe
= pipe_info(out
->f_path
.dentry
->d_inode
);
1219 if (in
->f_op
->llseek
== no_llseek
)
1221 if (copy_from_user(&offset
, off_in
, sizeof(loff_t
)))
1227 ret
= do_splice_to(in
, off
, pipe
, len
, flags
);
1229 if (off_in
&& copy_to_user(off_in
, off
, sizeof(loff_t
)))
1239 * Map an iov into an array of pages and offset/length tupples. With the
1240 * partial_page structure, we can map several non-contiguous ranges into
1241 * our ones pages[] map instead of splitting that operation into pieces.
1242 * Could easily be exported as a generic helper for other users, in which
1243 * case one would probably want to add a 'max_nr_pages' parameter as well.
1245 static int get_iovec_page_array(const struct iovec __user
*iov
,
1246 unsigned int nr_vecs
, struct page
**pages
,
1247 struct partial_page
*partial
, int aligned
)
1249 int buffers
= 0, error
= 0;
1252 unsigned long off
, npages
;
1259 if (copy_from_user(&entry
, iov
, sizeof(entry
)))
1262 base
= entry
.iov_base
;
1263 len
= entry
.iov_len
;
1266 * Sanity check this iovec. 0 read succeeds.
1272 if (!access_ok(VERIFY_READ
, base
, len
))
1276 * Get this base offset and number of pages, then map
1277 * in the user pages.
1279 off
= (unsigned long) base
& ~PAGE_MASK
;
1282 * If asked for alignment, the offset must be zero and the
1283 * length a multiple of the PAGE_SIZE.
1286 if (aligned
&& (off
|| len
& ~PAGE_MASK
))
1289 npages
= (off
+ len
+ PAGE_SIZE
- 1) >> PAGE_SHIFT
;
1290 if (npages
> PIPE_BUFFERS
- buffers
)
1291 npages
= PIPE_BUFFERS
- buffers
;
1293 error
= get_user_pages_fast((unsigned long)base
, npages
,
1294 0, &pages
[buffers
]);
1296 if (unlikely(error
<= 0))
1300 * Fill this contiguous range into the partial page map.
1302 for (i
= 0; i
< error
; i
++) {
1303 const int plen
= min_t(size_t, len
, PAGE_SIZE
- off
);
1305 partial
[buffers
].offset
= off
;
1306 partial
[buffers
].len
= plen
;
1314 * We didn't complete this iov, stop here since it probably
1315 * means we have to move some of this into a pipe to
1316 * be able to continue.
1322 * Don't continue if we mapped fewer pages than we asked for,
1323 * or if we mapped the max number of pages that we have
1326 if (error
< npages
|| buffers
== PIPE_BUFFERS
)
1339 static int pipe_to_user(struct pipe_inode_info
*pipe
, struct pipe_buffer
*buf
,
1340 struct splice_desc
*sd
)
1345 ret
= buf
->ops
->confirm(pipe
, buf
);
1350 * See if we can use the atomic maps, by prefaulting in the
1351 * pages and doing an atomic copy
1353 if (!fault_in_pages_writeable(sd
->u
.userptr
, sd
->len
)) {
1354 src
= buf
->ops
->map(pipe
, buf
, 1);
1355 ret
= __copy_to_user_inatomic(sd
->u
.userptr
, src
+ buf
->offset
,
1357 buf
->ops
->unmap(pipe
, buf
, src
);
1365 * No dice, use slow non-atomic map and copy
1367 src
= buf
->ops
->map(pipe
, buf
, 0);
1370 if (copy_to_user(sd
->u
.userptr
, src
+ buf
->offset
, sd
->len
))
1373 buf
->ops
->unmap(pipe
, buf
, src
);
1376 sd
->u
.userptr
+= ret
;
1381 * For lack of a better implementation, implement vmsplice() to userspace
1382 * as a simple copy of the pipes pages to the user iov.
1384 static long vmsplice_to_user(struct file
*file
, const struct iovec __user
*iov
,
1385 unsigned long nr_segs
, unsigned int flags
)
1387 struct pipe_inode_info
*pipe
;
1388 struct splice_desc sd
;
1393 pipe
= pipe_info(file
->f_path
.dentry
->d_inode
);
1398 mutex_lock(&pipe
->inode
->i_mutex
);
1406 * Get user address base and length for this iovec.
1408 error
= get_user(base
, &iov
->iov_base
);
1409 if (unlikely(error
))
1411 error
= get_user(len
, &iov
->iov_len
);
1412 if (unlikely(error
))
1416 * Sanity check this iovec. 0 read succeeds.
1420 if (unlikely(!base
)) {
1425 if (unlikely(!access_ok(VERIFY_WRITE
, base
, len
))) {
1433 sd
.u
.userptr
= base
;
1436 size
= __splice_from_pipe(pipe
, &sd
, pipe_to_user
);
1454 mutex_unlock(&pipe
->inode
->i_mutex
);
1463 * vmsplice splices a user address range into a pipe. It can be thought of
1464 * as splice-from-memory, where the regular splice is splice-from-file (or
1465 * to file). In both cases the output is a pipe, naturally.
1467 static long vmsplice_to_pipe(struct file
*file
, const struct iovec __user
*iov
,
1468 unsigned long nr_segs
, unsigned int flags
)
1470 struct pipe_inode_info
*pipe
;
1471 struct page
*pages
[PIPE_BUFFERS
];
1472 struct partial_page partial
[PIPE_BUFFERS
];
1473 struct splice_pipe_desc spd
= {
1477 .ops
= &user_page_pipe_buf_ops
,
1478 .spd_release
= spd_release_page
,
1481 pipe
= pipe_info(file
->f_path
.dentry
->d_inode
);
1485 spd
.nr_pages
= get_iovec_page_array(iov
, nr_segs
, pages
, partial
,
1486 flags
& SPLICE_F_GIFT
);
1487 if (spd
.nr_pages
<= 0)
1488 return spd
.nr_pages
;
1490 return splice_to_pipe(pipe
, &spd
);
1494 * Note that vmsplice only really supports true splicing _from_ user memory
1495 * to a pipe, not the other way around. Splicing from user memory is a simple
1496 * operation that can be supported without any funky alignment restrictions
1497 * or nasty vm tricks. We simply map in the user memory and fill them into
1498 * a pipe. The reverse isn't quite as easy, though. There are two possible
1499 * solutions for that:
1501 * - memcpy() the data internally, at which point we might as well just
1502 * do a regular read() on the buffer anyway.
1503 * - Lots of nasty vm tricks, that are neither fast nor flexible (it
1504 * has restriction limitations on both ends of the pipe).
1506 * Currently we punt and implement it as a normal copy, see pipe_to_user().
1509 SYSCALL_DEFINE4(vmsplice
, int, fd
, const struct iovec __user
*, iov
,
1510 unsigned long, nr_segs
, unsigned int, flags
)
1516 if (unlikely(nr_segs
> UIO_MAXIOV
))
1518 else if (unlikely(!nr_segs
))
1522 file
= fget_light(fd
, &fput
);
1524 if (file
->f_mode
& FMODE_WRITE
)
1525 error
= vmsplice_to_pipe(file
, iov
, nr_segs
, flags
);
1526 else if (file
->f_mode
& FMODE_READ
)
1527 error
= vmsplice_to_user(file
, iov
, nr_segs
, flags
);
1529 fput_light(file
, fput
);
1535 SYSCALL_DEFINE6(splice
, int, fd_in
, loff_t __user
*, off_in
,
1536 int, fd_out
, loff_t __user
*, off_out
,
1537 size_t, len
, unsigned int, flags
)
1540 struct file
*in
, *out
;
1541 int fput_in
, fput_out
;
1547 in
= fget_light(fd_in
, &fput_in
);
1549 if (in
->f_mode
& FMODE_READ
) {
1550 out
= fget_light(fd_out
, &fput_out
);
1552 if (out
->f_mode
& FMODE_WRITE
)
1553 error
= do_splice(in
, off_in
,
1556 fput_light(out
, fput_out
);
1560 fput_light(in
, fput_in
);
1567 * Make sure there's data to read. Wait for input if we can, otherwise
1568 * return an appropriate error.
1570 static int link_ipipe_prep(struct pipe_inode_info
*pipe
, unsigned int flags
)
1575 * Check ->nrbufs without the inode lock first. This function
1576 * is speculative anyways, so missing one is ok.
1582 mutex_lock(&pipe
->inode
->i_mutex
);
1584 while (!pipe
->nrbufs
) {
1585 if (signal_pending(current
)) {
1591 if (!pipe
->waiting_writers
) {
1592 if (flags
& SPLICE_F_NONBLOCK
) {
1600 mutex_unlock(&pipe
->inode
->i_mutex
);
1605 * Make sure there's writeable room. Wait for room if we can, otherwise
1606 * return an appropriate error.
1608 static int link_opipe_prep(struct pipe_inode_info
*pipe
, unsigned int flags
)
1613 * Check ->nrbufs without the inode lock first. This function
1614 * is speculative anyways, so missing one is ok.
1616 if (pipe
->nrbufs
< PIPE_BUFFERS
)
1620 mutex_lock(&pipe
->inode
->i_mutex
);
1622 while (pipe
->nrbufs
>= PIPE_BUFFERS
) {
1623 if (!pipe
->readers
) {
1624 send_sig(SIGPIPE
, current
, 0);
1628 if (flags
& SPLICE_F_NONBLOCK
) {
1632 if (signal_pending(current
)) {
1636 pipe
->waiting_writers
++;
1638 pipe
->waiting_writers
--;
1641 mutex_unlock(&pipe
->inode
->i_mutex
);
1646 * Link contents of ipipe to opipe.
1648 static int link_pipe(struct pipe_inode_info
*ipipe
,
1649 struct pipe_inode_info
*opipe
,
1650 size_t len
, unsigned int flags
)
1652 struct pipe_buffer
*ibuf
, *obuf
;
1653 int ret
= 0, i
= 0, nbuf
;
1656 * Potential ABBA deadlock, work around it by ordering lock
1657 * grabbing by inode address. Otherwise two different processes
1658 * could deadlock (one doing tee from A -> B, the other from B -> A).
1660 inode_double_lock(ipipe
->inode
, opipe
->inode
);
1663 if (!opipe
->readers
) {
1664 send_sig(SIGPIPE
, current
, 0);
1671 * If we have iterated all input buffers or ran out of
1672 * output room, break.
1674 if (i
>= ipipe
->nrbufs
|| opipe
->nrbufs
>= PIPE_BUFFERS
)
1677 ibuf
= ipipe
->bufs
+ ((ipipe
->curbuf
+ i
) & (PIPE_BUFFERS
- 1));
1678 nbuf
= (opipe
->curbuf
+ opipe
->nrbufs
) & (PIPE_BUFFERS
- 1);
1681 * Get a reference to this pipe buffer,
1682 * so we can copy the contents over.
1684 ibuf
->ops
->get(ipipe
, ibuf
);
1686 obuf
= opipe
->bufs
+ nbuf
;
1690 * Don't inherit the gift flag, we need to
1691 * prevent multiple steals of this page.
1693 obuf
->flags
&= ~PIPE_BUF_FLAG_GIFT
;
1695 if (obuf
->len
> len
)
1705 * return EAGAIN if we have the potential of some data in the
1706 * future, otherwise just return 0
1708 if (!ret
&& ipipe
->waiting_writers
&& (flags
& SPLICE_F_NONBLOCK
))
1711 inode_double_unlock(ipipe
->inode
, opipe
->inode
);
1714 * If we put data in the output pipe, wakeup any potential readers.
1718 if (waitqueue_active(&opipe
->wait
))
1719 wake_up_interruptible(&opipe
->wait
);
1720 kill_fasync(&opipe
->fasync_readers
, SIGIO
, POLL_IN
);
1727 * This is a tee(1) implementation that works on pipes. It doesn't copy
1728 * any data, it simply references the 'in' pages on the 'out' pipe.
1729 * The 'flags' used are the SPLICE_F_* variants, currently the only
1730 * applicable one is SPLICE_F_NONBLOCK.
1732 static long do_tee(struct file
*in
, struct file
*out
, size_t len
,
1735 struct pipe_inode_info
*ipipe
= pipe_info(in
->f_path
.dentry
->d_inode
);
1736 struct pipe_inode_info
*opipe
= pipe_info(out
->f_path
.dentry
->d_inode
);
1740 * Duplicate the contents of ipipe to opipe without actually
1743 if (ipipe
&& opipe
&& ipipe
!= opipe
) {
1745 * Keep going, unless we encounter an error. The ipipe/opipe
1746 * ordering doesn't really matter.
1748 ret
= link_ipipe_prep(ipipe
, flags
);
1750 ret
= link_opipe_prep(opipe
, flags
);
1752 ret
= link_pipe(ipipe
, opipe
, len
, flags
);
1759 SYSCALL_DEFINE4(tee
, int, fdin
, int, fdout
, size_t, len
, unsigned int, flags
)
1768 in
= fget_light(fdin
, &fput_in
);
1770 if (in
->f_mode
& FMODE_READ
) {
1772 struct file
*out
= fget_light(fdout
, &fput_out
);
1775 if (out
->f_mode
& FMODE_WRITE
)
1776 error
= do_tee(in
, out
, len
, flags
);
1777 fput_light(out
, fput_out
);
1780 fput_light(in
, fput_in
);