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 and fixing the initial implementation
15 * Copyright (C) 2005 Jens Axboe <axboe@suse.de>
16 * Copyright (C) 2005 Linus Torvalds <torvalds@osdl.org>
20 #include <linux/file.h>
21 #include <linux/pagemap.h>
22 #include <linux/pipe_fs_i.h>
23 #include <linux/mm_inline.h>
24 #include <linux/swap.h>
25 #include <linux/writeback.h>
26 #include <linux/buffer_head.h>
27 #include <linux/module.h>
28 #include <linux/syscalls.h>
31 * Passed to the actors
34 unsigned int len
, total_len
; /* current and remaining length */
35 unsigned int flags
; /* splice flags */
36 struct file
*file
; /* file to read/write */
37 loff_t pos
; /* file position */
41 * Attempt to steal a page from a pipe buffer. This should perhaps go into
42 * a vm helper function, it's already simplified quite a bit by the
43 * addition of remove_mapping(). If success is returned, the caller may
44 * attempt to reuse this page for another destination.
46 static int page_cache_pipe_buf_steal(struct pipe_inode_info
*info
,
47 struct pipe_buffer
*buf
)
49 struct page
*page
= buf
->page
;
50 struct address_space
*mapping
= page_mapping(page
);
52 WARN_ON(!PageLocked(page
));
53 WARN_ON(!PageUptodate(page
));
56 * At least for ext2 with nobh option, we need to wait on writeback
57 * completing on this page, since we'll remove it from the pagecache.
58 * Otherwise truncate wont wait on the page, allowing the disk
59 * blocks to be reused by someone else before we actually wrote our
60 * data to them. fs corruption ensues.
62 wait_on_page_writeback(page
);
64 if (PagePrivate(page
))
65 try_to_release_page(page
, mapping_gfp_mask(mapping
));
67 if (!remove_mapping(mapping
, page
))
70 buf
->flags
|= PIPE_BUF_FLAG_STOLEN
| PIPE_BUF_FLAG_LRU
;
74 static void page_cache_pipe_buf_release(struct pipe_inode_info
*info
,
75 struct pipe_buffer
*buf
)
77 page_cache_release(buf
->page
);
79 buf
->flags
&= ~(PIPE_BUF_FLAG_STOLEN
| PIPE_BUF_FLAG_LRU
);
82 static void *page_cache_pipe_buf_map(struct file
*file
,
83 struct pipe_inode_info
*info
,
84 struct pipe_buffer
*buf
)
86 struct page
*page
= buf
->page
;
89 if (!PageUptodate(page
)) {
93 * Page got truncated/unhashed. This will cause a 0-byte
94 * splice, if this is the first page
102 * uh oh, read-error from disk
104 if (!PageUptodate(page
)) {
110 * page is ok afterall, fall through to mapping
121 static void page_cache_pipe_buf_unmap(struct pipe_inode_info
*info
,
122 struct pipe_buffer
*buf
)
127 static struct pipe_buf_operations page_cache_pipe_buf_ops
= {
129 .map
= page_cache_pipe_buf_map
,
130 .unmap
= page_cache_pipe_buf_unmap
,
131 .release
= page_cache_pipe_buf_release
,
132 .steal
= page_cache_pipe_buf_steal
,
136 * Pipe output worker. This sets up our pipe format with the page cache
137 * pipe buffer operations. Otherwise very similar to the regular pipe_writev().
139 static ssize_t
move_to_pipe(struct inode
*inode
, struct page
**pages
,
140 int nr_pages
, unsigned long offset
,
141 unsigned long len
, unsigned int flags
)
143 struct pipe_inode_info
*info
;
144 int ret
, do_wakeup
, i
;
150 mutex_lock(PIPE_MUTEX(*inode
));
152 info
= inode
->i_pipe
;
156 if (!PIPE_READERS(*inode
)) {
157 send_sig(SIGPIPE
, current
, 0);
164 if (bufs
< PIPE_BUFFERS
) {
165 int newbuf
= (info
->curbuf
+ bufs
) & (PIPE_BUFFERS
- 1);
166 struct pipe_buffer
*buf
= info
->bufs
+ newbuf
;
167 struct page
*page
= pages
[i
++];
168 unsigned long this_len
;
170 this_len
= PAGE_CACHE_SIZE
- offset
;
175 buf
->offset
= offset
;
177 buf
->ops
= &page_cache_pipe_buf_ops
;
178 info
->nrbufs
= ++bufs
;
188 if (bufs
< PIPE_BUFFERS
)
194 if (flags
& SPLICE_F_NONBLOCK
) {
200 if (signal_pending(current
)) {
208 if (waitqueue_active(PIPE_WAIT(*inode
)))
209 wake_up_interruptible_sync(PIPE_WAIT(*inode
));
210 kill_fasync(PIPE_FASYNC_READERS(*inode
), SIGIO
,
215 PIPE_WAITING_WRITERS(*inode
)++;
217 PIPE_WAITING_WRITERS(*inode
)--;
220 mutex_unlock(PIPE_MUTEX(*inode
));
224 if (waitqueue_active(PIPE_WAIT(*inode
)))
225 wake_up_interruptible(PIPE_WAIT(*inode
));
226 kill_fasync(PIPE_FASYNC_READERS(*inode
), SIGIO
, POLL_IN
);
230 page_cache_release(pages
[i
++]);
235 static int __generic_file_splice_read(struct file
*in
, struct inode
*pipe
,
236 size_t len
, unsigned int flags
)
238 struct address_space
*mapping
= in
->f_mapping
;
239 unsigned int offset
, nr_pages
;
240 struct page
*pages
[PIPE_BUFFERS
];
245 index
= in
->f_pos
>> PAGE_CACHE_SHIFT
;
246 offset
= in
->f_pos
& ~PAGE_CACHE_MASK
;
247 nr_pages
= (len
+ offset
+ PAGE_CACHE_SIZE
- 1) >> PAGE_CACHE_SHIFT
;
249 if (nr_pages
> PIPE_BUFFERS
)
250 nr_pages
= PIPE_BUFFERS
;
253 * initiate read-ahead on this page range. however, don't call into
254 * read-ahead if this is a non-zero offset (we are likely doing small
255 * chunk splice and the page is already there) for a single page.
257 if (!offset
|| nr_pages
> 1)
258 do_page_cache_readahead(mapping
, in
, index
, nr_pages
);
261 * now fill in the holes
263 for (i
= 0; i
< nr_pages
; i
++, index
++) {
265 * no page there, look one up / create it
267 page
= find_or_create_page(mapping
, index
,
268 mapping_gfp_mask(mapping
));
272 if (PageUptodate(page
))
275 int error
= mapping
->a_ops
->readpage(in
, page
);
277 if (unlikely(error
)) {
278 page_cache_release(page
);
286 return move_to_pipe(pipe
, pages
, i
, offset
, len
, flags
);
292 * generic_file_splice_read - splice data from file to a pipe
293 * @in: file to splice from
294 * @pipe: pipe to splice to
295 * @len: number of bytes to splice
296 * @flags: splice modifier flags
298 * Will read pages from given file and fill them into a pipe.
301 ssize_t
generic_file_splice_read(struct file
*in
, struct inode
*pipe
,
302 size_t len
, unsigned int flags
)
310 ret
= __generic_file_splice_read(in
, pipe
, len
, flags
);
319 if (!(flags
& SPLICE_F_NONBLOCK
))
331 EXPORT_SYMBOL(generic_file_splice_read
);
334 * Send 'sd->len' bytes to socket from 'sd->file' at position 'sd->pos'
337 static int pipe_to_sendpage(struct pipe_inode_info
*info
,
338 struct pipe_buffer
*buf
, struct splice_desc
*sd
)
340 struct file
*file
= sd
->file
;
341 loff_t pos
= sd
->pos
;
348 * sub-optimal, but we are limited by the pipe ->map. we don't
349 * need a kmap'ed buffer here, we just want to make sure we
350 * have the page pinned if the pipe page originates from the
353 ptr
= buf
->ops
->map(file
, info
, buf
);
357 offset
= pos
& ~PAGE_CACHE_MASK
;
358 more
= (sd
->flags
& SPLICE_F_MORE
) || sd
->len
< sd
->total_len
;
360 ret
= file
->f_op
->sendpage(file
, buf
->page
, offset
, sd
->len
, &pos
,more
);
362 buf
->ops
->unmap(info
, buf
);
370 * This is a little more tricky than the file -> pipe splicing. There are
371 * basically three cases:
373 * - Destination page already exists in the address space and there
374 * are users of it. For that case we have no other option that
375 * copying the data. Tough luck.
376 * - Destination page already exists in the address space, but there
377 * are no users of it. Make sure it's uptodate, then drop it. Fall
378 * through to last case.
379 * - Destination page does not exist, we can add the pipe page to
380 * the page cache and avoid the copy.
382 * If asked to move pages to the output file (SPLICE_F_MOVE is set in
383 * sd->flags), we attempt to migrate pages from the pipe to the output
384 * file address space page cache. This is possible if no one else has
385 * the pipe page referenced outside of the pipe and page cache. If
386 * SPLICE_F_MOVE isn't set, or we cannot move the page, we simply create
387 * a new page in the output file page cache and fill/dirty that.
389 static int pipe_to_file(struct pipe_inode_info
*info
, struct pipe_buffer
*buf
,
390 struct splice_desc
*sd
)
392 struct file
*file
= sd
->file
;
393 struct address_space
*mapping
= file
->f_mapping
;
394 gfp_t gfp_mask
= mapping_gfp_mask(mapping
);
402 * make sure the data in this buffer is uptodate
404 src
= buf
->ops
->map(file
, info
, buf
);
408 index
= sd
->pos
>> PAGE_CACHE_SHIFT
;
409 offset
= sd
->pos
& ~PAGE_CACHE_MASK
;
412 * reuse buf page, if SPLICE_F_MOVE is set
414 if (sd
->flags
& SPLICE_F_MOVE
) {
416 * If steal succeeds, buf->page is now pruned from the vm
417 * side (LRU and page cache) and we can reuse it.
419 if (buf
->ops
->steal(info
, buf
))
423 * this will also set the page locked
426 if (add_to_page_cache(page
, mapping
, index
, gfp_mask
))
429 if (!(buf
->flags
& PIPE_BUF_FLAG_LRU
))
434 page
= find_or_create_page(mapping
, index
, gfp_mask
);
439 * If the page is uptodate, it is also locked. If it isn't
440 * uptodate, we can mark it uptodate if we are filling the
441 * full page. Otherwise we need to read it in first...
443 if (!PageUptodate(page
)) {
444 if (sd
->len
< PAGE_CACHE_SIZE
) {
445 ret
= mapping
->a_ops
->readpage(file
, page
);
451 if (!PageUptodate(page
)) {
453 * page got invalidated, repeat
455 if (!page
->mapping
) {
457 page_cache_release(page
);
464 WARN_ON(!PageLocked(page
));
465 SetPageUptodate(page
);
470 ret
= mapping
->a_ops
->prepare_write(file
, page
, 0, sd
->len
);
471 if (ret
== AOP_TRUNCATED_PAGE
) {
472 page_cache_release(page
);
477 if (!(buf
->flags
& PIPE_BUF_FLAG_STOLEN
)) {
478 char *dst
= kmap_atomic(page
, KM_USER0
);
480 memcpy(dst
+ offset
, src
+ buf
->offset
, sd
->len
);
481 flush_dcache_page(page
);
482 kunmap_atomic(dst
, KM_USER0
);
485 ret
= mapping
->a_ops
->commit_write(file
, page
, 0, sd
->len
);
486 if (ret
== AOP_TRUNCATED_PAGE
) {
487 page_cache_release(page
);
492 mark_page_accessed(page
);
493 balance_dirty_pages_ratelimited(mapping
);
495 if (!(buf
->flags
& PIPE_BUF_FLAG_STOLEN
)) {
496 page_cache_release(page
);
500 buf
->ops
->unmap(info
, buf
);
504 typedef int (splice_actor
)(struct pipe_inode_info
*, struct pipe_buffer
*,
505 struct splice_desc
*);
508 * Pipe input worker. Most of this logic works like a regular pipe, the
509 * key here is the 'actor' worker passed in that actually moves the data
510 * to the wanted destination. See pipe_to_file/pipe_to_sendpage above.
512 static ssize_t
move_from_pipe(struct inode
*inode
, struct file
*out
,
513 size_t len
, unsigned int flags
,
516 struct pipe_inode_info
*info
;
517 int ret
, do_wakeup
, err
;
518 struct splice_desc sd
;
528 mutex_lock(PIPE_MUTEX(*inode
));
530 info
= inode
->i_pipe
;
532 int bufs
= info
->nrbufs
;
535 int curbuf
= info
->curbuf
;
536 struct pipe_buffer
*buf
= info
->bufs
+ curbuf
;
537 struct pipe_buf_operations
*ops
= buf
->ops
;
540 if (sd
.len
> sd
.total_len
)
541 sd
.len
= sd
.total_len
;
543 err
= actor(info
, buf
, &sd
);
545 if (!ret
&& err
!= -ENODATA
)
552 buf
->offset
+= sd
.len
;
556 ops
->release(info
, buf
);
557 curbuf
= (curbuf
+ 1) & (PIPE_BUFFERS
- 1);
558 info
->curbuf
= curbuf
;
559 info
->nrbufs
= --bufs
;
564 sd
.total_len
-= sd
.len
;
571 if (!PIPE_WRITERS(*inode
))
573 if (!PIPE_WAITING_WRITERS(*inode
)) {
578 if (flags
& SPLICE_F_NONBLOCK
) {
584 if (signal_pending(current
)) {
592 if (waitqueue_active(PIPE_WAIT(*inode
)))
593 wake_up_interruptible_sync(PIPE_WAIT(*inode
));
594 kill_fasync(PIPE_FASYNC_WRITERS(*inode
),SIGIO
,POLL_OUT
);
601 mutex_unlock(PIPE_MUTEX(*inode
));
605 if (waitqueue_active(PIPE_WAIT(*inode
)))
606 wake_up_interruptible(PIPE_WAIT(*inode
));
607 kill_fasync(PIPE_FASYNC_WRITERS(*inode
), SIGIO
, POLL_OUT
);
610 mutex_lock(&out
->f_mapping
->host
->i_mutex
);
612 mutex_unlock(&out
->f_mapping
->host
->i_mutex
);
618 * generic_file_splice_write - splice data from a pipe to a file
620 * @out: file to write to
621 * @len: number of bytes to splice
622 * @flags: splice modifier flags
624 * Will either move or copy pages (determined by @flags options) from
625 * the given pipe inode to the given file.
628 ssize_t
generic_file_splice_write(struct inode
*inode
, struct file
*out
,
629 size_t len
, unsigned int flags
)
631 struct address_space
*mapping
= out
->f_mapping
;
632 ssize_t ret
= move_from_pipe(inode
, out
, len
, flags
, pipe_to_file
);
635 * if file or inode is SYNC and we actually wrote some data, sync it
637 if (unlikely((out
->f_flags
& O_SYNC
) || IS_SYNC(mapping
->host
))
639 struct inode
*inode
= mapping
->host
;
642 mutex_lock(&inode
->i_mutex
);
643 err
= generic_osync_inode(mapping
->host
, mapping
,
644 OSYNC_METADATA
|OSYNC_DATA
);
645 mutex_unlock(&inode
->i_mutex
);
654 EXPORT_SYMBOL(generic_file_splice_write
);
657 * generic_splice_sendpage - splice data from a pipe to a socket
659 * @out: socket to write to
660 * @len: number of bytes to splice
661 * @flags: splice modifier flags
663 * Will send @len bytes from the pipe to a network socket. No data copying
667 ssize_t
generic_splice_sendpage(struct inode
*inode
, struct file
*out
,
668 size_t len
, unsigned int flags
)
670 return move_from_pipe(inode
, out
, len
, flags
, pipe_to_sendpage
);
673 EXPORT_SYMBOL(generic_splice_sendpage
);
676 * Attempt to initiate a splice from pipe to file.
678 static long do_splice_from(struct inode
*pipe
, struct file
*out
, size_t len
,
684 if (!out
->f_op
|| !out
->f_op
->splice_write
)
687 if (!(out
->f_mode
& FMODE_WRITE
))
691 ret
= rw_verify_area(WRITE
, out
, &pos
, len
);
692 if (unlikely(ret
< 0))
695 return out
->f_op
->splice_write(pipe
, out
, len
, flags
);
699 * Attempt to initiate a splice from a file to a pipe.
701 static long do_splice_to(struct file
*in
, struct inode
*pipe
, size_t len
,
704 loff_t pos
, isize
, left
;
707 if (!in
->f_op
|| !in
->f_op
->splice_read
)
710 if (!(in
->f_mode
& FMODE_READ
))
714 ret
= rw_verify_area(READ
, in
, &pos
, len
);
715 if (unlikely(ret
< 0))
718 isize
= i_size_read(in
->f_mapping
->host
);
719 if (unlikely(in
->f_pos
>= isize
))
722 left
= isize
- in
->f_pos
;
726 return in
->f_op
->splice_read(in
, pipe
, len
, flags
);
730 * Determine where to splice to/from.
732 static long do_splice(struct file
*in
, struct file
*out
, size_t len
,
737 pipe
= in
->f_dentry
->d_inode
;
739 return do_splice_from(pipe
, out
, len
, flags
);
741 pipe
= out
->f_dentry
->d_inode
;
743 return do_splice_to(in
, pipe
, len
, flags
);
748 asmlinkage
long sys_splice(int fdin
, int fdout
, size_t len
, unsigned int flags
)
751 struct file
*in
, *out
;
752 int fput_in
, fput_out
;
758 in
= fget_light(fdin
, &fput_in
);
760 if (in
->f_mode
& FMODE_READ
) {
761 out
= fget_light(fdout
, &fput_out
);
763 if (out
->f_mode
& FMODE_WRITE
)
764 error
= do_splice(in
, out
, len
, flags
);
765 fput_light(out
, fput_out
);
769 fput_light(in
, fput_in
);