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>
26 * Passed to the actors
29 unsigned int len
, total_len
; /* current and remaining length */
30 unsigned int flags
; /* splice flags */
31 struct file
*file
; /* file to read/write */
32 loff_t pos
; /* file position */
35 static void page_cache_pipe_buf_release(struct pipe_inode_info
*info
,
36 struct pipe_buffer
*buf
)
38 page_cache_release(buf
->page
);
42 static void *page_cache_pipe_buf_map(struct file
*file
,
43 struct pipe_inode_info
*info
,
44 struct pipe_buffer
*buf
)
46 struct page
*page
= buf
->page
;
50 if (!PageUptodate(page
)) {
57 return ERR_PTR(-ENODATA
);
60 return kmap(buf
->page
);
63 static void page_cache_pipe_buf_unmap(struct pipe_inode_info
*info
,
64 struct pipe_buffer
*buf
)
66 unlock_page(buf
->page
);
70 static struct pipe_buf_operations page_cache_pipe_buf_ops
= {
72 .map
= page_cache_pipe_buf_map
,
73 .unmap
= page_cache_pipe_buf_unmap
,
74 .release
= page_cache_pipe_buf_release
,
77 static ssize_t
move_to_pipe(struct inode
*inode
, struct page
**pages
,
78 int nr_pages
, unsigned long offset
,
81 struct pipe_inode_info
*info
;
82 int ret
, do_wakeup
, i
;
88 mutex_lock(PIPE_MUTEX(*inode
));
94 if (!PIPE_READERS(*inode
)) {
95 send_sig(SIGPIPE
, current
, 0);
102 if (bufs
< PIPE_BUFFERS
) {
103 int newbuf
= (info
->curbuf
+ bufs
) & (PIPE_BUFFERS
- 1);
104 struct pipe_buffer
*buf
= info
->bufs
+ newbuf
;
105 struct page
*page
= pages
[i
++];
106 unsigned long this_len
;
108 this_len
= PAGE_CACHE_SIZE
- offset
;
113 buf
->offset
= offset
;
115 buf
->ops
= &page_cache_pipe_buf_ops
;
116 info
->nrbufs
= ++bufs
;
126 if (bufs
< PIPE_BUFFERS
)
132 if (signal_pending(current
)) {
139 wake_up_interruptible_sync(PIPE_WAIT(*inode
));
140 kill_fasync(PIPE_FASYNC_READERS(*inode
), SIGIO
,
145 PIPE_WAITING_WRITERS(*inode
)++;
147 PIPE_WAITING_WRITERS(*inode
)--;
150 mutex_unlock(PIPE_MUTEX(*inode
));
153 wake_up_interruptible(PIPE_WAIT(*inode
));
154 kill_fasync(PIPE_FASYNC_READERS(*inode
), SIGIO
, POLL_IN
);
158 page_cache_release(pages
[i
++]);
163 static int __generic_file_splice_read(struct file
*in
, struct inode
*pipe
,
166 struct address_space
*mapping
= in
->f_mapping
;
167 unsigned int offset
, nr_pages
;
168 struct page
*pages
[PIPE_BUFFERS
], *shadow
[PIPE_BUFFERS
];
173 index
= in
->f_pos
>> PAGE_CACHE_SHIFT
;
174 offset
= in
->f_pos
& ~PAGE_CACHE_MASK
;
175 nr_pages
= (len
+ offset
+ PAGE_CACHE_SIZE
- 1) >> PAGE_CACHE_SHIFT
;
177 if (nr_pages
> PIPE_BUFFERS
)
178 nr_pages
= PIPE_BUFFERS
;
181 * initiate read-ahead on this page range
183 do_page_cache_readahead(mapping
, in
, index
, nr_pages
);
186 * Get as many pages from the page cache as possible..
187 * Start IO on the page cache entries we create (we
188 * can assume that any pre-existing ones we find have
189 * already had IO started on them).
191 i
= find_get_pages(mapping
, index
, nr_pages
, pages
);
194 * common case - we found all pages and they are contiguous,
197 if (i
&& (pages
[i
- 1]->index
== index
+ i
- 1))
201 * fill shadow[] with pages at the right locations, so we only
204 memset(shadow
, 0, i
* sizeof(struct page
*));
205 for (j
= 0, pidx
= index
; j
< i
; pidx
++, j
++)
206 shadow
[pages
[j
]->index
- pidx
] = pages
[j
];
209 * now fill in the holes
211 for (i
= 0, pidx
= index
; i
< nr_pages
; pidx
++, i
++) {
218 * no page there, look one up / create it
220 page
= find_or_create_page(mapping
, pidx
,
221 mapping_gfp_mask(mapping
));
225 if (PageUptodate(page
))
228 error
= mapping
->a_ops
->readpage(in
, page
);
230 if (unlikely(error
)) {
231 page_cache_release(page
);
239 for (i
= 0; i
< nr_pages
; i
++) {
241 page_cache_release(shadow
[i
]);
246 memcpy(pages
, shadow
, i
* sizeof(struct page
*));
249 * Now we splice them into the pipe..
252 return move_to_pipe(pipe
, pages
, i
, offset
, len
);
255 ssize_t
generic_file_splice_read(struct file
*in
, struct inode
*pipe
,
256 size_t len
, unsigned int flags
)
264 ret
= __generic_file_splice_read(in
, pipe
, len
);
281 * Send 'len' bytes to socket from 'file' at position 'pos' using sendpage().
283 static int pipe_to_sendpage(struct pipe_inode_info
*info
,
284 struct pipe_buffer
*buf
, struct splice_desc
*sd
)
286 struct file
*file
= sd
->file
;
287 loff_t pos
= sd
->pos
;
293 * sub-optimal, but we are limited by the pipe ->map. we don't
294 * need a kmap'ed buffer here, we just want to make sure we
295 * have the page pinned if the pipe page originates from the
298 ptr
= buf
->ops
->map(file
, info
, buf
);
302 offset
= pos
& ~PAGE_CACHE_MASK
;
304 ret
= file
->f_op
->sendpage(file
, buf
->page
, offset
, sd
->len
, &pos
,
305 sd
->len
< sd
->total_len
);
307 buf
->ops
->unmap(info
, buf
);
315 * This is a little more tricky than the file -> pipe splicing. There are
316 * basically three cases:
318 * - Destination page already exists in the address space and there
319 * are users of it. For that case we have no other option that
320 * copying the data. Tough luck.
321 * - Destination page already exists in the address space, but there
322 * are no users of it. Make sure it's uptodate, then drop it. Fall
323 * through to last case.
324 * - Destination page does not exist, we can add the pipe page to
325 * the page cache and avoid the copy.
327 * For now we just do the slower thing and always copy pages over, it's
328 * easier than migrating pages from the pipe to the target file. For the
329 * case of doing file | file splicing, the migrate approach had some LRU
332 static int pipe_to_file(struct pipe_inode_info
*info
, struct pipe_buffer
*buf
,
333 struct splice_desc
*sd
)
335 struct file
*file
= sd
->file
;
336 struct address_space
*mapping
= file
->f_mapping
;
344 * after this, page will be locked and unmapped
346 src
= buf
->ops
->map(file
, info
, buf
);
350 index
= sd
->pos
>> PAGE_CACHE_SHIFT
;
351 offset
= sd
->pos
& ~PAGE_CACHE_MASK
;
355 page
= find_or_create_page(mapping
, index
, mapping_gfp_mask(mapping
));
360 * If the page is uptodate, it is also locked. If it isn't
361 * uptodate, we can mark it uptodate if we are filling the
362 * full page. Otherwise we need to read it in first...
364 if (!PageUptodate(page
)) {
365 if (sd
->len
< PAGE_CACHE_SIZE
) {
366 ret
= mapping
->a_ops
->readpage(file
, page
);
372 if (!PageUptodate(page
)) {
374 * page got invalidated, repeat
376 if (!page
->mapping
) {
378 page_cache_release(page
);
385 WARN_ON(!PageLocked(page
));
386 SetPageUptodate(page
);
390 ret
= mapping
->a_ops
->prepare_write(file
, page
, 0, sd
->len
);
394 dst
= kmap_atomic(page
, KM_USER0
);
395 memcpy(dst
+ offset
, src
+ buf
->offset
, sd
->len
);
396 flush_dcache_page(page
);
397 kunmap_atomic(dst
, KM_USER0
);
399 ret
= mapping
->a_ops
->commit_write(file
, page
, 0, sd
->len
);
403 set_page_dirty(page
);
404 ret
= write_one_page(page
, 0);
408 page_cache_release(page
);
409 buf
->ops
->unmap(info
, buf
);
413 typedef int (splice_actor
)(struct pipe_inode_info
*, struct pipe_buffer
*,
414 struct splice_desc
*);
416 static ssize_t
move_from_pipe(struct inode
*inode
, struct file
*out
,
417 size_t len
, unsigned int flags
,
420 struct pipe_inode_info
*info
;
421 int ret
, do_wakeup
, err
;
422 struct splice_desc sd
;
432 mutex_lock(PIPE_MUTEX(*inode
));
434 info
= inode
->i_pipe
;
436 int bufs
= info
->nrbufs
;
439 int curbuf
= info
->curbuf
;
440 struct pipe_buffer
*buf
= info
->bufs
+ curbuf
;
441 struct pipe_buf_operations
*ops
= buf
->ops
;
444 if (sd
.len
> sd
.total_len
)
445 sd
.len
= sd
.total_len
;
447 err
= actor(info
, buf
, &sd
);
449 if (!ret
&& err
!= -ENODATA
)
456 buf
->offset
+= sd
.len
;
460 ops
->release(info
, buf
);
461 curbuf
= (curbuf
+ 1) & (PIPE_BUFFERS
- 1);
462 info
->curbuf
= curbuf
;
463 info
->nrbufs
= --bufs
;
468 sd
.total_len
-= sd
.len
;
475 if (!PIPE_WRITERS(*inode
))
477 if (!PIPE_WAITING_WRITERS(*inode
)) {
482 if (signal_pending(current
)) {
489 wake_up_interruptible_sync(PIPE_WAIT(*inode
));
490 kill_fasync(PIPE_FASYNC_WRITERS(*inode
),SIGIO
,POLL_OUT
);
497 mutex_unlock(PIPE_MUTEX(*inode
));
500 wake_up_interruptible(PIPE_WAIT(*inode
));
501 kill_fasync(PIPE_FASYNC_WRITERS(*inode
), SIGIO
, POLL_OUT
);
504 mutex_lock(&out
->f_mapping
->host
->i_mutex
);
506 mutex_unlock(&out
->f_mapping
->host
->i_mutex
);
511 ssize_t
generic_file_splice_write(struct inode
*inode
, struct file
*out
,
512 size_t len
, unsigned int flags
)
514 return move_from_pipe(inode
, out
, len
, flags
, pipe_to_file
);
517 ssize_t
generic_splice_sendpage(struct inode
*inode
, struct file
*out
,
518 size_t len
, unsigned int flags
)
520 return move_from_pipe(inode
, out
, len
, flags
, pipe_to_sendpage
);
523 static long do_splice_from(struct inode
*pipe
, struct file
*out
, size_t len
,
529 if (!out
->f_op
|| !out
->f_op
->splice_write
)
532 if (!(out
->f_mode
& FMODE_WRITE
))
536 ret
= rw_verify_area(WRITE
, out
, &pos
, len
);
537 if (unlikely(ret
< 0))
540 return out
->f_op
->splice_write(pipe
, out
, len
, flags
);
543 static long do_splice_to(struct file
*in
, struct inode
*pipe
, size_t len
,
546 loff_t pos
, isize
, left
;
549 if (!in
->f_op
|| !in
->f_op
->splice_read
)
552 if (!(in
->f_mode
& FMODE_READ
))
556 ret
= rw_verify_area(READ
, in
, &pos
, len
);
557 if (unlikely(ret
< 0))
560 isize
= i_size_read(in
->f_mapping
->host
);
561 if (unlikely(in
->f_pos
>= isize
))
564 left
= isize
- in
->f_pos
;
568 return in
->f_op
->splice_read(in
, pipe
, len
, flags
);
571 static long do_splice(struct file
*in
, struct file
*out
, size_t len
,
576 pipe
= in
->f_dentry
->d_inode
;
578 return do_splice_from(pipe
, out
, len
, flags
);
580 pipe
= out
->f_dentry
->d_inode
;
582 return do_splice_to(in
, pipe
, len
, flags
);
587 asmlinkage
long sys_splice(int fdin
, int fdout
, size_t len
, unsigned int flags
)
590 struct file
*in
, *out
;
591 int fput_in
, fput_out
;
597 in
= fget_light(fdin
, &fput_in
);
599 if (in
->f_mode
& FMODE_READ
) {
600 out
= fget_light(fdout
, &fput_out
);
602 if (out
->f_mode
& FMODE_WRITE
)
603 error
= do_splice(in
, out
, len
, flags
);
604 fput_light(out
, fput_out
);
608 fput_light(in
, fput_in
);