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@suse.de>
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>
32 * Passed to the actors
35 unsigned int len
, total_len
; /* current and remaining length */
36 unsigned int flags
; /* splice flags */
37 struct file
*file
; /* file to read/write */
38 loff_t pos
; /* file position */
42 * Attempt to steal a page from a pipe buffer. This should perhaps go into
43 * a vm helper function, it's already simplified quite a bit by the
44 * addition of remove_mapping(). If success is returned, the caller may
45 * attempt to reuse this page for another destination.
47 static int page_cache_pipe_buf_steal(struct pipe_inode_info
*info
,
48 struct pipe_buffer
*buf
)
50 struct page
*page
= buf
->page
;
51 struct address_space
*mapping
= page_mapping(page
);
53 WARN_ON(!PageLocked(page
));
54 WARN_ON(!PageUptodate(page
));
57 * At least for ext2 with nobh option, we need to wait on writeback
58 * completing on this page, since we'll remove it from the pagecache.
59 * Otherwise truncate wont wait on the page, allowing the disk
60 * blocks to be reused by someone else before we actually wrote our
61 * data to them. fs corruption ensues.
63 wait_on_page_writeback(page
);
65 if (PagePrivate(page
))
66 try_to_release_page(page
, mapping_gfp_mask(mapping
));
68 if (!remove_mapping(mapping
, page
))
71 buf
->flags
|= PIPE_BUF_FLAG_STOLEN
| PIPE_BUF_FLAG_LRU
;
75 static void page_cache_pipe_buf_release(struct pipe_inode_info
*info
,
76 struct pipe_buffer
*buf
)
78 page_cache_release(buf
->page
);
80 buf
->flags
&= ~(PIPE_BUF_FLAG_STOLEN
| PIPE_BUF_FLAG_LRU
);
83 static void *page_cache_pipe_buf_map(struct file
*file
,
84 struct pipe_inode_info
*info
,
85 struct pipe_buffer
*buf
)
87 struct page
*page
= buf
->page
;
90 if (!PageUptodate(page
)) {
94 * Page got truncated/unhashed. This will cause a 0-byte
95 * splice, if this is the first page.
103 * Uh oh, read-error from disk.
105 if (!PageUptodate(page
)) {
111 * Page is ok afterall, fall through to mapping.
122 static void page_cache_pipe_buf_unmap(struct pipe_inode_info
*info
,
123 struct pipe_buffer
*buf
)
128 static struct pipe_buf_operations page_cache_pipe_buf_ops
= {
130 .map
= page_cache_pipe_buf_map
,
131 .unmap
= page_cache_pipe_buf_unmap
,
132 .release
= page_cache_pipe_buf_release
,
133 .steal
= page_cache_pipe_buf_steal
,
137 * Pipe output worker. This sets up our pipe format with the page cache
138 * pipe buffer operations. Otherwise very similar to the regular pipe_writev().
140 static ssize_t
move_to_pipe(struct pipe_inode_info
*pipe
, struct page
**pages
,
141 int nr_pages
, unsigned long offset
,
142 unsigned long len
, unsigned int flags
)
144 int ret
, do_wakeup
, i
;
151 mutex_lock(&pipe
->inode
->i_mutex
);
154 if (!pipe
->readers
) {
155 send_sig(SIGPIPE
, current
, 0);
161 if (pipe
->nrbufs
< PIPE_BUFFERS
) {
162 int newbuf
= (pipe
->curbuf
+ pipe
->nrbufs
) & (PIPE_BUFFERS
- 1);
163 struct pipe_buffer
*buf
= pipe
->bufs
+ newbuf
;
164 struct page
*page
= pages
[i
++];
165 unsigned long this_len
;
167 this_len
= PAGE_CACHE_SIZE
- offset
;
172 buf
->offset
= offset
;
174 buf
->ops
= &page_cache_pipe_buf_ops
;
186 if (pipe
->nrbufs
< PIPE_BUFFERS
)
192 if (flags
& SPLICE_F_NONBLOCK
) {
198 if (signal_pending(current
)) {
206 if (waitqueue_active(&pipe
->wait
))
207 wake_up_interruptible_sync(&pipe
->wait
);
208 kill_fasync(&pipe
->fasync_readers
, SIGIO
, POLL_IN
);
212 pipe
->waiting_writers
++;
214 pipe
->waiting_writers
--;
218 mutex_unlock(&pipe
->inode
->i_mutex
);
222 if (waitqueue_active(&pipe
->wait
))
223 wake_up_interruptible(&pipe
->wait
);
224 kill_fasync(&pipe
->fasync_readers
, SIGIO
, POLL_IN
);
228 page_cache_release(pages
[i
++]);
234 __generic_file_splice_read(struct file
*in
, struct pipe_inode_info
*pipe
,
235 size_t len
, unsigned int flags
)
237 struct address_space
*mapping
= in
->f_mapping
;
238 unsigned int offset
, nr_pages
;
239 struct page
*pages
[PIPE_BUFFERS
];
244 index
= in
->f_pos
>> PAGE_CACHE_SHIFT
;
245 offset
= in
->f_pos
& ~PAGE_CACHE_MASK
;
246 nr_pages
= (len
+ offset
+ PAGE_CACHE_SIZE
- 1) >> PAGE_CACHE_SHIFT
;
248 if (nr_pages
> PIPE_BUFFERS
)
249 nr_pages
= PIPE_BUFFERS
;
252 * Initiate read-ahead on this page range. however, don't call into
253 * read-ahead if this is a non-zero offset (we are likely doing small
254 * chunk splice and the page is already there) for a single page.
256 if (!offset
|| nr_pages
> 1)
257 do_page_cache_readahead(mapping
, in
, index
, nr_pages
);
260 * Now fill in the holes:
263 for (i
= 0; i
< nr_pages
; i
++, index
++) {
266 * lookup the page for this index
268 page
= find_get_page(mapping
, index
);
271 * If in nonblock mode then dont block on
272 * readpage (we've kicked readahead so there
273 * will be asynchronous progress):
275 if (flags
& SPLICE_F_NONBLOCK
)
279 * page didn't exist, allocate one
281 page
= page_cache_alloc_cold(mapping
);
285 error
= add_to_page_cache_lru(page
, mapping
, index
,
286 mapping_gfp_mask(mapping
));
287 if (unlikely(error
)) {
288 page_cache_release(page
);
296 * If the page isn't uptodate, we may need to start io on it
298 if (!PageUptodate(page
)) {
302 * page was truncated, stop here. if this isn't the
303 * first page, we'll just complete what we already
306 if (!page
->mapping
) {
308 page_cache_release(page
);
312 * page was already under io and is now done, great
314 if (PageUptodate(page
)) {
321 * need to read in the page
323 error
= mapping
->a_ops
->readpage(in
, page
);
325 if (unlikely(error
)) {
326 page_cache_release(page
);
327 if (error
== AOP_TRUNCATED_PAGE
)
337 return move_to_pipe(pipe
, pages
, i
, offset
, len
, flags
);
343 * generic_file_splice_read - splice data from file to a pipe
344 * @in: file to splice from
345 * @pipe: pipe to splice to
346 * @len: number of bytes to splice
347 * @flags: splice modifier flags
349 * Will read pages from given file and fill them into a pipe.
351 ssize_t
generic_file_splice_read(struct file
*in
, struct pipe_inode_info
*pipe
,
352 size_t len
, unsigned int flags
)
361 ret
= __generic_file_splice_read(in
, pipe
, len
, flags
);
370 if (!(flags
& SPLICE_F_NONBLOCK
))
382 EXPORT_SYMBOL(generic_file_splice_read
);
385 * Send 'sd->len' bytes to socket from 'sd->file' at position 'sd->pos'
388 static int pipe_to_sendpage(struct pipe_inode_info
*info
,
389 struct pipe_buffer
*buf
, struct splice_desc
*sd
)
391 struct file
*file
= sd
->file
;
392 loff_t pos
= sd
->pos
;
399 * Sub-optimal, but we are limited by the pipe ->map. We don't
400 * need a kmap'ed buffer here, we just want to make sure we
401 * have the page pinned if the pipe page originates from the
404 ptr
= buf
->ops
->map(file
, info
, buf
);
408 offset
= pos
& ~PAGE_CACHE_MASK
;
409 more
= (sd
->flags
& SPLICE_F_MORE
) || sd
->len
< sd
->total_len
;
411 ret
= file
->f_op
->sendpage(file
, buf
->page
, offset
, sd
->len
, &pos
,more
);
413 buf
->ops
->unmap(info
, buf
);
421 * This is a little more tricky than the file -> pipe splicing. There are
422 * basically three cases:
424 * - Destination page already exists in the address space and there
425 * are users of it. For that case we have no other option that
426 * copying the data. Tough luck.
427 * - Destination page already exists in the address space, but there
428 * are no users of it. Make sure it's uptodate, then drop it. Fall
429 * through to last case.
430 * - Destination page does not exist, we can add the pipe page to
431 * the page cache and avoid the copy.
433 * If asked to move pages to the output file (SPLICE_F_MOVE is set in
434 * sd->flags), we attempt to migrate pages from the pipe to the output
435 * file address space page cache. This is possible if no one else has
436 * the pipe page referenced outside of the pipe and page cache. If
437 * SPLICE_F_MOVE isn't set, or we cannot move the page, we simply create
438 * a new page in the output file page cache and fill/dirty that.
440 static int pipe_to_file(struct pipe_inode_info
*info
, struct pipe_buffer
*buf
,
441 struct splice_desc
*sd
)
443 struct file
*file
= sd
->file
;
444 struct address_space
*mapping
= file
->f_mapping
;
445 gfp_t gfp_mask
= mapping_gfp_mask(mapping
);
453 * make sure the data in this buffer is uptodate
455 src
= buf
->ops
->map(file
, info
, buf
);
459 index
= sd
->pos
>> PAGE_CACHE_SHIFT
;
460 offset
= sd
->pos
& ~PAGE_CACHE_MASK
;
463 * Reuse buf page, if SPLICE_F_MOVE is set.
465 if (sd
->flags
& SPLICE_F_MOVE
) {
467 * If steal succeeds, buf->page is now pruned from the vm
468 * side (LRU and page cache) and we can reuse it.
470 if (buf
->ops
->steal(info
, buf
))
474 * this will also set the page locked
477 if (add_to_page_cache(page
, mapping
, index
, gfp_mask
))
480 if (!(buf
->flags
& PIPE_BUF_FLAG_LRU
))
485 page
= find_or_create_page(mapping
, index
, gfp_mask
);
490 * If the page is uptodate, it is also locked. If it isn't
491 * uptodate, we can mark it uptodate if we are filling the
492 * full page. Otherwise we need to read it in first...
494 if (!PageUptodate(page
)) {
495 if (sd
->len
< PAGE_CACHE_SIZE
) {
496 ret
= mapping
->a_ops
->readpage(file
, page
);
502 if (!PageUptodate(page
)) {
504 * Page got invalidated, repeat.
506 if (!page
->mapping
) {
508 page_cache_release(page
);
515 WARN_ON(!PageLocked(page
));
516 SetPageUptodate(page
);
521 ret
= mapping
->a_ops
->prepare_write(file
, page
, 0, sd
->len
);
522 if (ret
== AOP_TRUNCATED_PAGE
) {
523 page_cache_release(page
);
528 if (!(buf
->flags
& PIPE_BUF_FLAG_STOLEN
)) {
529 char *dst
= kmap_atomic(page
, KM_USER0
);
531 memcpy(dst
+ offset
, src
+ buf
->offset
, sd
->len
);
532 flush_dcache_page(page
);
533 kunmap_atomic(dst
, KM_USER0
);
536 ret
= mapping
->a_ops
->commit_write(file
, page
, 0, sd
->len
);
537 if (ret
== AOP_TRUNCATED_PAGE
) {
538 page_cache_release(page
);
543 mark_page_accessed(page
);
544 balance_dirty_pages_ratelimited(mapping
);
546 if (!(buf
->flags
& PIPE_BUF_FLAG_STOLEN
)) {
547 page_cache_release(page
);
551 buf
->ops
->unmap(info
, buf
);
555 typedef int (splice_actor
)(struct pipe_inode_info
*, struct pipe_buffer
*,
556 struct splice_desc
*);
559 * Pipe input worker. Most of this logic works like a regular pipe, the
560 * key here is the 'actor' worker passed in that actually moves the data
561 * to the wanted destination. See pipe_to_file/pipe_to_sendpage above.
563 static ssize_t
move_from_pipe(struct pipe_inode_info
*pipe
, struct file
*out
,
564 size_t len
, unsigned int flags
,
567 int ret
, do_wakeup
, err
;
568 struct splice_desc sd
;
579 mutex_lock(&pipe
->inode
->i_mutex
);
583 struct pipe_buffer
*buf
= pipe
->bufs
+ pipe
->curbuf
;
584 struct pipe_buf_operations
*ops
= buf
->ops
;
587 if (sd
.len
> sd
.total_len
)
588 sd
.len
= sd
.total_len
;
590 err
= actor(pipe
, buf
, &sd
);
592 if (!ret
&& err
!= -ENODATA
)
599 buf
->offset
+= sd
.len
;
604 ops
->release(pipe
, buf
);
605 pipe
->curbuf
= (pipe
->curbuf
+ 1) & (PIPE_BUFFERS
- 1);
612 sd
.total_len
-= sd
.len
;
621 if (!pipe
->waiting_writers
) {
626 if (flags
& SPLICE_F_NONBLOCK
) {
632 if (signal_pending(current
)) {
640 if (waitqueue_active(&pipe
->wait
))
641 wake_up_interruptible_sync(&pipe
->wait
);
642 kill_fasync(&pipe
->fasync_writers
, SIGIO
, POLL_OUT
);
650 mutex_unlock(&pipe
->inode
->i_mutex
);
654 if (waitqueue_active(&pipe
->wait
))
655 wake_up_interruptible(&pipe
->wait
);
656 kill_fasync(&pipe
->fasync_writers
, SIGIO
, POLL_OUT
);
665 * generic_file_splice_write - splice data from a pipe to a file
667 * @out: file to write to
668 * @len: number of bytes to splice
669 * @flags: splice modifier flags
671 * Will either move or copy pages (determined by @flags options) from
672 * the given pipe inode to the given file.
676 generic_file_splice_write(struct pipe_inode_info
*pipe
, struct file
*out
,
677 size_t len
, unsigned int flags
)
679 struct address_space
*mapping
= out
->f_mapping
;
682 ret
= move_from_pipe(pipe
, out
, len
, flags
, pipe_to_file
);
685 * If file or inode is SYNC and we actually wrote some data, sync it.
687 if (unlikely((out
->f_flags
& O_SYNC
) || IS_SYNC(mapping
->host
))
689 struct inode
*inode
= mapping
->host
;
692 mutex_lock(&inode
->i_mutex
);
693 err
= generic_osync_inode(mapping
->host
, mapping
,
694 OSYNC_METADATA
|OSYNC_DATA
);
695 mutex_unlock(&inode
->i_mutex
);
704 EXPORT_SYMBOL(generic_file_splice_write
);
707 * generic_splice_sendpage - splice data from a pipe to a socket
709 * @out: socket to write to
710 * @len: number of bytes to splice
711 * @flags: splice modifier flags
713 * Will send @len bytes from the pipe to a network socket. No data copying
717 ssize_t
generic_splice_sendpage(struct pipe_inode_info
*pipe
, struct file
*out
,
718 size_t len
, unsigned int flags
)
720 return move_from_pipe(pipe
, out
, len
, flags
, pipe_to_sendpage
);
723 EXPORT_SYMBOL(generic_splice_sendpage
);
726 * Attempt to initiate a splice from pipe to file.
728 static long do_splice_from(struct pipe_inode_info
*pipe
, struct file
*out
,
729 size_t len
, unsigned int flags
)
734 if (unlikely(!out
->f_op
|| !out
->f_op
->splice_write
))
737 if (unlikely(!(out
->f_mode
& FMODE_WRITE
)))
742 ret
= rw_verify_area(WRITE
, out
, &pos
, len
);
743 if (unlikely(ret
< 0))
746 return out
->f_op
->splice_write(pipe
, out
, len
, flags
);
750 * Attempt to initiate a splice from a file to a pipe.
752 static long do_splice_to(struct file
*in
, struct pipe_inode_info
*pipe
,
753 size_t len
, unsigned int flags
)
755 loff_t pos
, isize
, left
;
758 if (unlikely(!in
->f_op
|| !in
->f_op
->splice_read
))
761 if (unlikely(!(in
->f_mode
& FMODE_READ
)))
766 ret
= rw_verify_area(READ
, in
, &pos
, len
);
767 if (unlikely(ret
< 0))
770 isize
= i_size_read(in
->f_mapping
->host
);
771 if (unlikely(in
->f_pos
>= isize
))
774 left
= isize
- in
->f_pos
;
775 if (unlikely(left
< len
))
778 return in
->f_op
->splice_read(in
, pipe
, len
, flags
);
781 long do_splice_direct(struct file
*in
, struct file
*out
, size_t len
,
784 struct pipe_inode_info
*pipe
;
790 * We require the input being a regular file, as we don't want to
791 * randomly drop data for eg socket -> socket splicing. Use the
792 * piped splicing for that!
794 i_mode
= in
->f_dentry
->d_inode
->i_mode
;
795 if (unlikely(!S_ISREG(i_mode
) && !S_ISBLK(i_mode
)))
799 * neither in nor out is a pipe, setup an internal pipe attached to
800 * 'out' and transfer the wanted data from 'in' to 'out' through that
802 pipe
= current
->splice_pipe
;
803 if (unlikely(!pipe
)) {
804 pipe
= alloc_pipe_info(NULL
);
809 * We don't have an immediate reader, but we'll read the stuff
810 * out of the pipe right after the move_to_pipe(). So set
811 * PIPE_READERS appropriately.
815 current
->splice_pipe
= pipe
;
825 size_t read_len
, max_read_len
;
828 * Do at most PIPE_BUFFERS pages worth of transfer:
830 max_read_len
= min(len
, (size_t)(PIPE_BUFFERS
*PAGE_SIZE
));
832 ret
= do_splice_to(in
, pipe
, max_read_len
, flags
);
833 if (unlikely(ret
< 0))
839 * NOTE: nonblocking mode only applies to the input. We
840 * must not do the output in nonblocking mode as then we
841 * could get stuck data in the internal pipe:
843 ret
= do_splice_from(pipe
, out
, read_len
,
844 flags
& ~SPLICE_F_NONBLOCK
);
845 if (unlikely(ret
< 0))
852 * In nonblocking mode, if we got back a short read then
853 * that was due to either an IO error or due to the
854 * pagecache entry not being there. In the IO error case
855 * the _next_ splice attempt will produce a clean IO error
856 * return value (not a short read), so in both cases it's
857 * correct to break out of the loop here:
859 if ((flags
& SPLICE_F_NONBLOCK
) && (read_len
< max_read_len
))
863 pipe
->nrbufs
= pipe
->curbuf
= 0;
869 * If we did an incomplete transfer we must release
870 * the pipe buffers in question:
872 for (i
= 0; i
< PIPE_BUFFERS
; i
++) {
873 struct pipe_buffer
*buf
= pipe
->bufs
+ i
;
876 buf
->ops
->release(pipe
, buf
);
880 pipe
->nrbufs
= pipe
->curbuf
= 0;
883 * If we transferred some data, return the number of bytes:
891 EXPORT_SYMBOL(do_splice_direct
);
894 * Determine where to splice to/from.
896 static long do_splice(struct file
*in
, loff_t __user
*off_in
,
897 struct file
*out
, loff_t __user
*off_out
,
898 size_t len
, unsigned int flags
)
900 struct pipe_inode_info
*pipe
;
902 pipe
= in
->f_dentry
->d_inode
->i_pipe
;
907 if (out
->f_op
->llseek
== no_llseek
)
909 if (copy_from_user(&out
->f_pos
, off_out
,
914 return do_splice_from(pipe
, out
, len
, flags
);
917 pipe
= out
->f_dentry
->d_inode
->i_pipe
;
922 if (in
->f_op
->llseek
== no_llseek
)
924 if (copy_from_user(&in
->f_pos
, off_in
, sizeof(loff_t
)))
928 return do_splice_to(in
, pipe
, len
, flags
);
934 asmlinkage
long sys_splice(int fd_in
, loff_t __user
*off_in
,
935 int fd_out
, loff_t __user
*off_out
,
936 size_t len
, unsigned int flags
)
939 struct file
*in
, *out
;
940 int fput_in
, fput_out
;
946 in
= fget_light(fd_in
, &fput_in
);
948 if (in
->f_mode
& FMODE_READ
) {
949 out
= fget_light(fd_out
, &fput_out
);
951 if (out
->f_mode
& FMODE_WRITE
)
952 error
= do_splice(in
, off_in
,
955 fput_light(out
, fput_out
);
959 fput_light(in
, fput_in
);