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 void page_cache_pipe_buf_get(struct pipe_inode_info
*info
,
129 struct pipe_buffer
*buf
)
131 page_cache_get(buf
->page
);
134 static struct pipe_buf_operations page_cache_pipe_buf_ops
= {
136 .map
= page_cache_pipe_buf_map
,
137 .unmap
= page_cache_pipe_buf_unmap
,
138 .release
= page_cache_pipe_buf_release
,
139 .steal
= page_cache_pipe_buf_steal
,
140 .get
= page_cache_pipe_buf_get
,
144 * Pipe output worker. This sets up our pipe format with the page cache
145 * pipe buffer operations. Otherwise very similar to the regular pipe_writev().
147 static ssize_t
move_to_pipe(struct pipe_inode_info
*pipe
, struct page
**pages
,
148 int nr_pages
, unsigned long len
,
149 unsigned int offset
, unsigned int flags
)
151 int ret
, do_wakeup
, i
;
158 mutex_lock(&pipe
->inode
->i_mutex
);
161 if (!pipe
->readers
) {
162 send_sig(SIGPIPE
, current
, 0);
168 if (pipe
->nrbufs
< PIPE_BUFFERS
) {
169 int newbuf
= (pipe
->curbuf
+ pipe
->nrbufs
) & (PIPE_BUFFERS
- 1);
170 struct pipe_buffer
*buf
= pipe
->bufs
+ newbuf
;
171 struct page
*page
= pages
[i
++];
172 unsigned long this_len
;
174 this_len
= PAGE_CACHE_SIZE
- offset
;
179 buf
->offset
= offset
;
181 buf
->ops
= &page_cache_pipe_buf_ops
;
193 if (pipe
->nrbufs
< PIPE_BUFFERS
)
199 if (flags
& SPLICE_F_NONBLOCK
) {
205 if (signal_pending(current
)) {
213 if (waitqueue_active(&pipe
->wait
))
214 wake_up_interruptible_sync(&pipe
->wait
);
215 kill_fasync(&pipe
->fasync_readers
, SIGIO
, POLL_IN
);
219 pipe
->waiting_writers
++;
221 pipe
->waiting_writers
--;
225 mutex_unlock(&pipe
->inode
->i_mutex
);
229 if (waitqueue_active(&pipe
->wait
))
230 wake_up_interruptible(&pipe
->wait
);
231 kill_fasync(&pipe
->fasync_readers
, SIGIO
, POLL_IN
);
235 page_cache_release(pages
[i
++]);
241 __generic_file_splice_read(struct file
*in
, loff_t
*ppos
,
242 struct pipe_inode_info
*pipe
, size_t len
,
245 struct address_space
*mapping
= in
->f_mapping
;
246 unsigned int loff
, offset
, nr_pages
;
247 struct page
*pages
[PIPE_BUFFERS
];
249 pgoff_t index
, end_index
;
254 index
= *ppos
>> PAGE_CACHE_SHIFT
;
255 loff
= offset
= *ppos
& ~PAGE_CACHE_MASK
;
256 nr_pages
= (len
+ offset
+ PAGE_CACHE_SIZE
- 1) >> PAGE_CACHE_SHIFT
;
258 if (nr_pages
> PIPE_BUFFERS
)
259 nr_pages
= PIPE_BUFFERS
;
262 * Initiate read-ahead on this page range. however, don't call into
263 * read-ahead if this is a non-zero offset (we are likely doing small
264 * chunk splice and the page is already there) for a single page.
266 if (!offset
|| nr_pages
> 1)
267 do_page_cache_readahead(mapping
, in
, index
, nr_pages
);
270 * Now fill in the holes:
274 for (i
= 0; i
< nr_pages
; i
++, index
++) {
277 * lookup the page for this index
279 page
= find_get_page(mapping
, index
);
282 * page didn't exist, allocate one
284 page
= page_cache_alloc_cold(mapping
);
288 error
= add_to_page_cache_lru(page
, mapping
, index
,
289 mapping_gfp_mask(mapping
));
290 if (unlikely(error
)) {
291 page_cache_release(page
);
299 * If the page isn't uptodate, we may need to start io on it
301 if (!PageUptodate(page
)) {
303 * If in nonblock mode then dont block on waiting
304 * for an in-flight io page
306 if (flags
& SPLICE_F_NONBLOCK
)
312 * page was truncated, stop here. if this isn't the
313 * first page, we'll just complete what we already
316 if (!page
->mapping
) {
318 page_cache_release(page
);
322 * page was already under io and is now done, great
324 if (PageUptodate(page
)) {
331 * need to read in the page
333 error
= mapping
->a_ops
->readpage(in
, page
);
335 if (unlikely(error
)) {
336 page_cache_release(page
);
337 if (error
== AOP_TRUNCATED_PAGE
)
343 * i_size must be checked after ->readpage().
345 isize
= i_size_read(mapping
->host
);
346 end_index
= (isize
- 1) >> PAGE_CACHE_SHIFT
;
347 if (unlikely(!isize
|| index
> end_index
)) {
348 page_cache_release(page
);
353 * if this is the last page, see if we need to shrink
354 * the length and stop
356 if (end_index
== index
) {
357 loff
= PAGE_CACHE_SIZE
- (isize
& ~PAGE_CACHE_MASK
);
358 if (bytes
+ loff
> isize
) {
359 page_cache_release(page
);
363 * force quit after adding this page
370 bytes
+= PAGE_CACHE_SIZE
- loff
;
375 return move_to_pipe(pipe
, pages
, i
, bytes
, offset
, flags
);
381 * generic_file_splice_read - splice data from file to a pipe
382 * @in: file to splice from
383 * @pipe: pipe to splice to
384 * @len: number of bytes to splice
385 * @flags: splice modifier flags
387 * Will read pages from given file and fill them into a pipe.
389 ssize_t
generic_file_splice_read(struct file
*in
, loff_t
*ppos
,
390 struct pipe_inode_info
*pipe
, size_t len
,
400 ret
= __generic_file_splice_read(in
, ppos
, pipe
, len
, flags
);
407 if (flags
& SPLICE_F_NONBLOCK
) {
424 EXPORT_SYMBOL(generic_file_splice_read
);
427 * Send 'sd->len' bytes to socket from 'sd->file' at position 'sd->pos'
430 static int pipe_to_sendpage(struct pipe_inode_info
*info
,
431 struct pipe_buffer
*buf
, struct splice_desc
*sd
)
433 struct file
*file
= sd
->file
;
434 loff_t pos
= sd
->pos
;
441 * Sub-optimal, but we are limited by the pipe ->map. We don't
442 * need a kmap'ed buffer here, we just want to make sure we
443 * have the page pinned if the pipe page originates from the
446 ptr
= buf
->ops
->map(file
, info
, buf
);
450 offset
= pos
& ~PAGE_CACHE_MASK
;
451 more
= (sd
->flags
& SPLICE_F_MORE
) || sd
->len
< sd
->total_len
;
453 ret
= file
->f_op
->sendpage(file
, buf
->page
, offset
, sd
->len
, &pos
,more
);
455 buf
->ops
->unmap(info
, buf
);
463 * This is a little more tricky than the file -> pipe splicing. There are
464 * basically three cases:
466 * - Destination page already exists in the address space and there
467 * are users of it. For that case we have no other option that
468 * copying the data. Tough luck.
469 * - Destination page already exists in the address space, but there
470 * are no users of it. Make sure it's uptodate, then drop it. Fall
471 * through to last case.
472 * - Destination page does not exist, we can add the pipe page to
473 * the page cache and avoid the copy.
475 * If asked to move pages to the output file (SPLICE_F_MOVE is set in
476 * sd->flags), we attempt to migrate pages from the pipe to the output
477 * file address space page cache. This is possible if no one else has
478 * the pipe page referenced outside of the pipe and page cache. If
479 * SPLICE_F_MOVE isn't set, or we cannot move the page, we simply create
480 * a new page in the output file page cache and fill/dirty that.
482 static int pipe_to_file(struct pipe_inode_info
*info
, struct pipe_buffer
*buf
,
483 struct splice_desc
*sd
)
485 struct file
*file
= sd
->file
;
486 struct address_space
*mapping
= file
->f_mapping
;
487 gfp_t gfp_mask
= mapping_gfp_mask(mapping
);
495 * make sure the data in this buffer is uptodate
497 src
= buf
->ops
->map(file
, info
, buf
);
501 index
= sd
->pos
>> PAGE_CACHE_SHIFT
;
502 offset
= sd
->pos
& ~PAGE_CACHE_MASK
;
505 * Reuse buf page, if SPLICE_F_MOVE is set.
507 if (sd
->flags
& SPLICE_F_MOVE
) {
509 * If steal succeeds, buf->page is now pruned from the vm
510 * side (LRU and page cache) and we can reuse it.
512 if (buf
->ops
->steal(info
, buf
))
516 * this will also set the page locked
519 if (add_to_page_cache(page
, mapping
, index
, gfp_mask
))
522 if (!(buf
->flags
& PIPE_BUF_FLAG_LRU
))
527 page
= find_or_create_page(mapping
, index
, gfp_mask
);
532 * If the page is uptodate, it is also locked. If it isn't
533 * uptodate, we can mark it uptodate if we are filling the
534 * full page. Otherwise we need to read it in first...
536 if (!PageUptodate(page
)) {
537 if (sd
->len
< PAGE_CACHE_SIZE
) {
538 ret
= mapping
->a_ops
->readpage(file
, page
);
544 if (!PageUptodate(page
)) {
546 * Page got invalidated, repeat.
548 if (!page
->mapping
) {
550 page_cache_release(page
);
557 WARN_ON(!PageLocked(page
));
558 SetPageUptodate(page
);
563 ret
= mapping
->a_ops
->prepare_write(file
, page
, 0, sd
->len
);
564 if (ret
== AOP_TRUNCATED_PAGE
) {
565 page_cache_release(page
);
570 if (!(buf
->flags
& PIPE_BUF_FLAG_STOLEN
)) {
571 char *dst
= kmap_atomic(page
, KM_USER0
);
573 memcpy(dst
+ offset
, src
+ buf
->offset
, sd
->len
);
574 flush_dcache_page(page
);
575 kunmap_atomic(dst
, KM_USER0
);
578 ret
= mapping
->a_ops
->commit_write(file
, page
, 0, sd
->len
);
579 if (ret
== AOP_TRUNCATED_PAGE
) {
580 page_cache_release(page
);
585 mark_page_accessed(page
);
586 balance_dirty_pages_ratelimited(mapping
);
588 if (!(buf
->flags
& PIPE_BUF_FLAG_STOLEN
)) {
589 page_cache_release(page
);
593 buf
->ops
->unmap(info
, buf
);
597 typedef int (splice_actor
)(struct pipe_inode_info
*, struct pipe_buffer
*,
598 struct splice_desc
*);
601 * Pipe input worker. Most of this logic works like a regular pipe, the
602 * key here is the 'actor' worker passed in that actually moves the data
603 * to the wanted destination. See pipe_to_file/pipe_to_sendpage above.
605 static ssize_t
move_from_pipe(struct pipe_inode_info
*pipe
, struct file
*out
,
606 loff_t
*ppos
, size_t len
, unsigned int flags
,
609 int ret
, do_wakeup
, err
;
610 struct splice_desc sd
;
621 mutex_lock(&pipe
->inode
->i_mutex
);
625 struct pipe_buffer
*buf
= pipe
->bufs
+ pipe
->curbuf
;
626 struct pipe_buf_operations
*ops
= buf
->ops
;
629 if (sd
.len
> sd
.total_len
)
630 sd
.len
= sd
.total_len
;
632 err
= actor(pipe
, buf
, &sd
);
634 if (!ret
&& err
!= -ENODATA
)
641 buf
->offset
+= sd
.len
;
646 ops
->release(pipe
, buf
);
647 pipe
->curbuf
= (pipe
->curbuf
+ 1) & (PIPE_BUFFERS
- 1);
654 sd
.total_len
-= sd
.len
;
663 if (!pipe
->waiting_writers
) {
668 if (flags
& SPLICE_F_NONBLOCK
) {
674 if (signal_pending(current
)) {
682 if (waitqueue_active(&pipe
->wait
))
683 wake_up_interruptible_sync(&pipe
->wait
);
684 kill_fasync(&pipe
->fasync_writers
, SIGIO
, POLL_OUT
);
692 mutex_unlock(&pipe
->inode
->i_mutex
);
696 if (waitqueue_active(&pipe
->wait
))
697 wake_up_interruptible(&pipe
->wait
);
698 kill_fasync(&pipe
->fasync_writers
, SIGIO
, POLL_OUT
);
705 * generic_file_splice_write - splice data from a pipe to a file
707 * @out: file to write to
708 * @len: number of bytes to splice
709 * @flags: splice modifier flags
711 * Will either move or copy pages (determined by @flags options) from
712 * the given pipe inode to the given file.
716 generic_file_splice_write(struct pipe_inode_info
*pipe
, struct file
*out
,
717 loff_t
*ppos
, size_t len
, unsigned int flags
)
719 struct address_space
*mapping
= out
->f_mapping
;
722 ret
= move_from_pipe(pipe
, out
, ppos
, len
, flags
, pipe_to_file
);
725 * If file or inode is SYNC and we actually wrote some data, sync it.
727 if (unlikely((out
->f_flags
& O_SYNC
) || IS_SYNC(mapping
->host
))
729 struct inode
*inode
= mapping
->host
;
732 mutex_lock(&inode
->i_mutex
);
733 err
= generic_osync_inode(mapping
->host
, mapping
,
734 OSYNC_METADATA
|OSYNC_DATA
);
735 mutex_unlock(&inode
->i_mutex
);
744 EXPORT_SYMBOL(generic_file_splice_write
);
747 * generic_splice_sendpage - splice data from a pipe to a socket
749 * @out: socket to write to
750 * @len: number of bytes to splice
751 * @flags: splice modifier flags
753 * Will send @len bytes from the pipe to a network socket. No data copying
757 ssize_t
generic_splice_sendpage(struct pipe_inode_info
*pipe
, struct file
*out
,
758 loff_t
*ppos
, size_t len
, unsigned int flags
)
760 return move_from_pipe(pipe
, out
, ppos
, len
, flags
, pipe_to_sendpage
);
763 EXPORT_SYMBOL(generic_splice_sendpage
);
766 * Attempt to initiate a splice from pipe to file.
768 static long do_splice_from(struct pipe_inode_info
*pipe
, struct file
*out
,
769 loff_t
*ppos
, size_t len
, unsigned int flags
)
773 if (unlikely(!out
->f_op
|| !out
->f_op
->splice_write
))
776 if (unlikely(!(out
->f_mode
& FMODE_WRITE
)))
779 ret
= rw_verify_area(WRITE
, out
, ppos
, len
);
780 if (unlikely(ret
< 0))
783 return out
->f_op
->splice_write(pipe
, out
, ppos
, len
, flags
);
787 * Attempt to initiate a splice from a file to a pipe.
789 static long do_splice_to(struct file
*in
, loff_t
*ppos
,
790 struct pipe_inode_info
*pipe
, size_t len
,
796 if (unlikely(!in
->f_op
|| !in
->f_op
->splice_read
))
799 if (unlikely(!(in
->f_mode
& FMODE_READ
)))
802 ret
= rw_verify_area(READ
, in
, ppos
, len
);
803 if (unlikely(ret
< 0))
806 isize
= i_size_read(in
->f_mapping
->host
);
807 if (unlikely(*ppos
>= isize
))
810 left
= isize
- *ppos
;
811 if (unlikely(left
< len
))
814 return in
->f_op
->splice_read(in
, ppos
, pipe
, len
, flags
);
817 long do_splice_direct(struct file
*in
, loff_t
*ppos
, struct file
*out
,
818 size_t len
, unsigned int flags
)
820 struct pipe_inode_info
*pipe
;
827 * We require the input being a regular file, as we don't want to
828 * randomly drop data for eg socket -> socket splicing. Use the
829 * piped splicing for that!
831 i_mode
= in
->f_dentry
->d_inode
->i_mode
;
832 if (unlikely(!S_ISREG(i_mode
) && !S_ISBLK(i_mode
)))
836 * neither in nor out is a pipe, setup an internal pipe attached to
837 * 'out' and transfer the wanted data from 'in' to 'out' through that
839 pipe
= current
->splice_pipe
;
840 if (unlikely(!pipe
)) {
841 pipe
= alloc_pipe_info(NULL
);
846 * We don't have an immediate reader, but we'll read the stuff
847 * out of the pipe right after the move_to_pipe(). So set
848 * PIPE_READERS appropriately.
852 current
->splice_pipe
= pipe
;
863 size_t read_len
, max_read_len
;
866 * Do at most PIPE_BUFFERS pages worth of transfer:
868 max_read_len
= min(len
, (size_t)(PIPE_BUFFERS
*PAGE_SIZE
));
870 ret
= do_splice_to(in
, ppos
, pipe
, max_read_len
, flags
);
871 if (unlikely(ret
< 0))
877 * NOTE: nonblocking mode only applies to the input. We
878 * must not do the output in nonblocking mode as then we
879 * could get stuck data in the internal pipe:
881 ret
= do_splice_from(pipe
, out
, &out_off
, read_len
,
882 flags
& ~SPLICE_F_NONBLOCK
);
883 if (unlikely(ret
< 0))
890 * In nonblocking mode, if we got back a short read then
891 * that was due to either an IO error or due to the
892 * pagecache entry not being there. In the IO error case
893 * the _next_ splice attempt will produce a clean IO error
894 * return value (not a short read), so in both cases it's
895 * correct to break out of the loop here:
897 if ((flags
& SPLICE_F_NONBLOCK
) && (read_len
< max_read_len
))
901 pipe
->nrbufs
= pipe
->curbuf
= 0;
907 * If we did an incomplete transfer we must release
908 * the pipe buffers in question:
910 for (i
= 0; i
< PIPE_BUFFERS
; i
++) {
911 struct pipe_buffer
*buf
= pipe
->bufs
+ i
;
914 buf
->ops
->release(pipe
, buf
);
918 pipe
->nrbufs
= pipe
->curbuf
= 0;
921 * If we transferred some data, return the number of bytes:
929 EXPORT_SYMBOL(do_splice_direct
);
932 * Determine where to splice to/from.
934 static long do_splice(struct file
*in
, loff_t __user
*off_in
,
935 struct file
*out
, loff_t __user
*off_out
,
936 size_t len
, unsigned int flags
)
938 struct pipe_inode_info
*pipe
;
941 pipe
= in
->f_dentry
->d_inode
->i_pipe
;
946 if (out
->f_op
->llseek
== no_llseek
)
948 if (copy_from_user(&offset
, off_out
, sizeof(loff_t
)))
954 return do_splice_from(pipe
, out
, off
, len
, flags
);
957 pipe
= out
->f_dentry
->d_inode
->i_pipe
;
962 if (in
->f_op
->llseek
== no_llseek
)
964 if (copy_from_user(&offset
, off_in
, sizeof(loff_t
)))
970 return do_splice_to(in
, off
, pipe
, len
, flags
);
976 asmlinkage
long sys_splice(int fd_in
, loff_t __user
*off_in
,
977 int fd_out
, loff_t __user
*off_out
,
978 size_t len
, unsigned int flags
)
981 struct file
*in
, *out
;
982 int fput_in
, fput_out
;
988 in
= fget_light(fd_in
, &fput_in
);
990 if (in
->f_mode
& FMODE_READ
) {
991 out
= fget_light(fd_out
, &fput_out
);
993 if (out
->f_mode
& FMODE_WRITE
)
994 error
= do_splice(in
, off_in
,
997 fput_light(out
, fput_out
);
1001 fput_light(in
, fput_in
);
1008 * Link contents of ipipe to opipe.
1010 static int link_pipe(struct pipe_inode_info
*ipipe
,
1011 struct pipe_inode_info
*opipe
,
1012 size_t len
, unsigned int flags
)
1014 struct pipe_buffer
*ibuf
, *obuf
;
1015 int ret
, do_wakeup
, i
, ipipe_first
;
1017 ret
= do_wakeup
= ipipe_first
= 0;
1020 * Potential ABBA deadlock, work around it by ordering lock
1021 * grabbing by inode address. Otherwise two different processes
1022 * could deadlock (one doing tee from A -> B, the other from B -> A).
1024 if (ipipe
->inode
< opipe
->inode
) {
1026 mutex_lock(&ipipe
->inode
->i_mutex
);
1027 mutex_lock(&opipe
->inode
->i_mutex
);
1029 mutex_lock(&opipe
->inode
->i_mutex
);
1030 mutex_lock(&ipipe
->inode
->i_mutex
);
1034 if (!opipe
->readers
) {
1035 send_sig(SIGPIPE
, current
, 0);
1040 if (ipipe
->nrbufs
- i
) {
1041 ibuf
= ipipe
->bufs
+ ((ipipe
->curbuf
+ i
) & (PIPE_BUFFERS
- 1));
1044 * If we have room, fill this buffer
1046 if (opipe
->nrbufs
< PIPE_BUFFERS
) {
1047 int nbuf
= (opipe
->curbuf
+ opipe
->nrbufs
) & (PIPE_BUFFERS
- 1);
1050 * Get a reference to this pipe buffer,
1051 * so we can copy the contents over.
1053 ibuf
->ops
->get(ipipe
, ibuf
);
1055 obuf
= opipe
->bufs
+ nbuf
;
1058 if (obuf
->len
> len
)
1068 if (opipe
->nrbufs
< PIPE_BUFFERS
)
1073 * We have input available, but no output room.
1074 * If we already copied data, return that. If we
1075 * need to drop the opipe lock, it must be ordered
1076 * last to avoid deadlocks.
1078 if ((flags
& SPLICE_F_NONBLOCK
) || !ipipe_first
) {
1083 if (signal_pending(current
)) {
1090 if (waitqueue_active(&opipe
->wait
))
1091 wake_up_interruptible(&opipe
->wait
);
1092 kill_fasync(&opipe
->fasync_readers
, SIGIO
, POLL_IN
);
1096 opipe
->waiting_writers
++;
1098 opipe
->waiting_writers
--;
1103 * No input buffers, do the usual checks for available
1104 * writers and blocking and wait if necessary
1106 if (!ipipe
->writers
)
1108 if (!ipipe
->waiting_writers
) {
1113 * pipe_wait() drops the ipipe mutex. To avoid deadlocks
1114 * with another process, we can only safely do that if
1115 * the ipipe lock is ordered last.
1117 if ((flags
& SPLICE_F_NONBLOCK
) || ipipe_first
) {
1122 if (signal_pending(current
)) {
1128 if (waitqueue_active(&ipipe
->wait
))
1129 wake_up_interruptible_sync(&ipipe
->wait
);
1130 kill_fasync(&ipipe
->fasync_writers
, SIGIO
, POLL_OUT
);
1135 mutex_unlock(&ipipe
->inode
->i_mutex
);
1136 mutex_unlock(&opipe
->inode
->i_mutex
);
1140 if (waitqueue_active(&opipe
->wait
))
1141 wake_up_interruptible(&opipe
->wait
);
1142 kill_fasync(&opipe
->fasync_readers
, SIGIO
, POLL_IN
);
1149 * This is a tee(1) implementation that works on pipes. It doesn't copy
1150 * any data, it simply references the 'in' pages on the 'out' pipe.
1151 * The 'flags' used are the SPLICE_F_* variants, currently the only
1152 * applicable one is SPLICE_F_NONBLOCK.
1154 static long do_tee(struct file
*in
, struct file
*out
, size_t len
,
1157 struct pipe_inode_info
*ipipe
= in
->f_dentry
->d_inode
->i_pipe
;
1158 struct pipe_inode_info
*opipe
= out
->f_dentry
->d_inode
->i_pipe
;
1161 * Link ipipe to the two output pipes, consuming as we go along.
1164 return link_pipe(ipipe
, opipe
, len
, flags
);
1169 asmlinkage
long sys_tee(int fdin
, int fdout
, size_t len
, unsigned int flags
)
1178 in
= fget_light(fdin
, &fput_in
);
1180 if (in
->f_mode
& FMODE_READ
) {
1182 struct file
*out
= fget_light(fdout
, &fput_out
);
1185 if (out
->f_mode
& FMODE_WRITE
)
1186 error
= do_tee(in
, out
, len
, flags
);
1187 fput_light(out
, fput_out
);
1190 fput_light(in
, fput_in
);