1/*
2 * "splice": joining two ropes together by interweaving their strands.
3 *
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.
7 *
8 * The traditional unix read/write is extended with a "splice()" operation
9 * that transfers data buffers to or from a pipe buffer.
10 *
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.
14 *
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>
18 *
19 */
20#include <linux/bvec.h>
21#include <linux/fs.h>
22#include <linux/file.h>
23#include <linux/pagemap.h>
24#include <linux/splice.h>
25#include <linux/memcontrol.h>
26#include <linux/mm_inline.h>
27#include <linux/swap.h>
28#include <linux/writeback.h>
29#include <linux/export.h>
30#include <linux/syscalls.h>
31#include <linux/uio.h>
32#include <linux/security.h>
33#include <linux/gfp.h>
34#include <linux/socket.h>
35#include <linux/compat.h>
36#include <linux/sched/signal.h>
37
38#include "internal.h"
39
40/*
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.
45 */
46static int page_cache_pipe_buf_steal(struct pipe_inode_info *pipe,
47 struct pipe_buffer *buf)
48{
49 struct page *page = buf->page;
50 struct address_space *mapping;
51
52 lock_page(page);
53
54 mapping = page_mapping(page);
55 if (mapping) {
56 WARN_ON(!PageUptodate(page));
57
58 /*
59 * At least for ext2 with nobh option, we need to wait on
60 * writeback completing on this page, since we'll remove it
61 * from the pagecache. Otherwise truncate wont wait on the
62 * page, allowing the disk blocks to be reused by someone else
63 * before we actually wrote our data to them. fs corruption
64 * ensues.
65 */
66 wait_on_page_writeback(page);
67
68 if (page_has_private(page) &&
69 !try_to_release_page(page, GFP_KERNEL))
70 goto out_unlock;
71
72 /*
73 * If we succeeded in removing the mapping, set LRU flag
74 * and return good.
75 */
76 if (remove_mapping(mapping, page)) {
77 buf->flags |= PIPE_BUF_FLAG_LRU;
78 return 0;
79 }
80 }
81
82 /*
83 * Raced with truncate or failed to remove page from current
84 * address space, unlock and return failure.
85 */
86out_unlock:
87 unlock_page(page);
88 return 1;
89}
90
91static void page_cache_pipe_buf_release(struct pipe_inode_info *pipe,
92 struct pipe_buffer *buf)
93{
94 put_page(buf->page);
95 buf->flags &= ~PIPE_BUF_FLAG_LRU;
96}
97
98/*
99 * Check whether the contents of buf is OK to access. Since the content
100 * is a page cache page, IO may be in flight.
101 */
102static int page_cache_pipe_buf_confirm(struct pipe_inode_info *pipe,
103 struct pipe_buffer *buf)
104{
105 struct page *page = buf->page;
106 int err;
107
108 if (!PageUptodate(page)) {
109 lock_page(page);
110
111 /*
112 * Page got truncated/unhashed. This will cause a 0-byte
113 * splice, if this is the first page.
114 */
115 if (!page->mapping) {
116 err = -ENODATA;
117 goto error;
118 }
119
120 /*
121 * Uh oh, read-error from disk.
122 */
123 if (!PageUptodate(page)) {
124 err = -EIO;
125 goto error;
126 }
127
128 /*
129 * Page is ok afterall, we are done.
130 */
131 unlock_page(page);
132 }
133
134 return 0;
135error:
136 unlock_page(page);
137 return err;
138}
139
140const struct pipe_buf_operations page_cache_pipe_buf_ops = {
141 .confirm = page_cache_pipe_buf_confirm,
142 .release = page_cache_pipe_buf_release,
143 .steal = page_cache_pipe_buf_steal,
144 .get = generic_pipe_buf_get,
145};
146
147static int user_page_pipe_buf_steal(struct pipe_inode_info *pipe,
148 struct pipe_buffer *buf)
149{
150 if (!(buf->flags & PIPE_BUF_FLAG_GIFT))
151 return 1;
152
153 buf->flags |= PIPE_BUF_FLAG_LRU;
154 return generic_pipe_buf_steal(pipe, buf);
155}
156
157static const struct pipe_buf_operations user_page_pipe_buf_ops = {
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,
162};
163
164static void wakeup_pipe_readers(struct pipe_inode_info *pipe)
165{
166 smp_mb();
167 if (waitqueue_active(&pipe->wait))
168 wake_up_interruptible(&pipe->wait);
169 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
170}
171
172/**
173 * splice_to_pipe - fill passed data into a pipe
174 * @pipe: pipe to fill
175 * @spd: data to fill
176 *
177 * Description:
178 * @spd contains a map of pages and len/offset tuples, along with
179 * the struct pipe_buf_operations associated with these pages. This
180 * function will link that data to the pipe.
181 *
182 */
183ssize_t splice_to_pipe(struct pipe_inode_info *pipe,
184 struct splice_pipe_desc *spd)
185{
186 unsigned int spd_pages = spd->nr_pages;
187 int ret = 0, page_nr = 0;
188
189 if (!spd_pages)
190 return 0;
191
192 if (unlikely(!pipe->readers)) {
193 send_sig(SIGPIPE, current, 0);
194 ret = -EPIPE;
195 goto out;
196 }
197
198 while (pipe->nrbufs < pipe->buffers) {
199 int newbuf = (pipe->curbuf + pipe->nrbufs) & (pipe->buffers - 1);
200 struct pipe_buffer *buf = pipe->bufs + newbuf;
201
202 buf->page = spd->pages[page_nr];
203 buf->offset = spd->partial[page_nr].offset;
204 buf->len = spd->partial[page_nr].len;
205 buf->private = spd->partial[page_nr].private;
206 buf->ops = spd->ops;
207 buf->flags = 0;
208
209 pipe->nrbufs++;
210 page_nr++;
211 ret += buf->len;
212
213 if (!--spd->nr_pages)
214 break;
215 }
216
217 if (!ret)
218 ret = -EAGAIN;
219
220out:
221 while (page_nr < spd_pages)
222 spd->spd_release(spd, page_nr++);
223
224 return ret;
225}
226EXPORT_SYMBOL_GPL(splice_to_pipe);
227
228ssize_t add_to_pipe(struct pipe_inode_info *pipe, struct pipe_buffer *buf)
229{
230 int ret;
231
232 if (unlikely(!pipe->readers)) {
233 send_sig(SIGPIPE, current, 0);
234 ret = -EPIPE;
235 } else if (pipe->nrbufs == pipe->buffers) {
236 ret = -EAGAIN;
237 } else {
238 int newbuf = (pipe->curbuf + pipe->nrbufs) & (pipe->buffers - 1);
239 pipe->bufs[newbuf] = *buf;
240 pipe->nrbufs++;
241 return buf->len;
242 }
243 pipe_buf_release(pipe, buf);
244 return ret;
245}
246EXPORT_SYMBOL(add_to_pipe);
247
248/*
249 * Check if we need to grow the arrays holding pages and partial page
250 * descriptions.
251 */
252int splice_grow_spd(const struct pipe_inode_info *pipe, struct splice_pipe_desc *spd)
253{
254 unsigned int buffers = READ_ONCE(pipe->buffers);
255
256 spd->nr_pages_max = buffers;
257 if (buffers <= PIPE_DEF_BUFFERS)
258 return 0;
259
260 spd->pages = kmalloc_array(buffers, sizeof(struct page *), GFP_KERNEL);
261 spd->partial = kmalloc_array(buffers, sizeof(struct partial_page),
262 GFP_KERNEL);
263
264 if (spd->pages && spd->partial)
265 return 0;
266
267 kfree(spd->pages);
268 kfree(spd->partial);
269 return -ENOMEM;
270}
271
272void splice_shrink_spd(struct splice_pipe_desc *spd)
273{
274 if (spd->nr_pages_max <= PIPE_DEF_BUFFERS)
275 return;
276
277 kfree(spd->pages);
278 kfree(spd->partial);
279}
280
281/**
282 * generic_file_splice_read - splice data from file to a pipe
283 * @in: file to splice from
284 * @ppos: position in @in
285 * @pipe: pipe to splice to
286 * @len: number of bytes to splice
287 * @flags: splice modifier flags
288 *
289 * Description:
290 * Will read pages from given file and fill them into a pipe. Can be
291 * used as long as it has more or less sane ->read_iter().
292 *
293 */
294ssize_t generic_file_splice_read(struct file *in, loff_t *ppos,
295 struct pipe_inode_info *pipe, size_t len,
296 unsigned int flags)
297{
298 struct iov_iter to;
299 struct kiocb kiocb;
300 int idx, ret;
301
302 iov_iter_pipe(&to, READ, pipe, len);
303 idx = to.idx;
304 init_sync_kiocb(&kiocb, in);
305 kiocb.ki_pos = *ppos;
306 ret = call_read_iter(in, &kiocb, &to);
307 if (ret > 0) {
308 *ppos = kiocb.ki_pos;
309 file_accessed(in);
310 } else if (ret < 0) {
311 to.idx = idx;
312 to.iov_offset = 0;
313 iov_iter_advance(&to, 0); /* to free what was emitted */
314 /*
315 * callers of ->splice_read() expect -EAGAIN on
316 * "can't put anything in there", rather than -EFAULT.
317 */
318 if (ret == -EFAULT)
319 ret = -EAGAIN;
320 }
321
322 return ret;
323}
324EXPORT_SYMBOL(generic_file_splice_read);
325
326const struct pipe_buf_operations default_pipe_buf_ops = {
327 .confirm = generic_pipe_buf_confirm,
328 .release = generic_pipe_buf_release,
329 .steal = generic_pipe_buf_steal,
330 .get = generic_pipe_buf_get,
331};
332
333static int generic_pipe_buf_nosteal(struct pipe_inode_info *pipe,
334 struct pipe_buffer *buf)
335{
336 return 1;
337}
338
339/* Pipe buffer operations for a socket and similar. */
340const struct pipe_buf_operations nosteal_pipe_buf_ops = {
341 .confirm = generic_pipe_buf_confirm,
342 .release = generic_pipe_buf_release,
343 .steal = generic_pipe_buf_nosteal,
344 .get = generic_pipe_buf_get,
345};
346EXPORT_SYMBOL(nosteal_pipe_buf_ops);
347
348static ssize_t kernel_readv(struct file *file, const struct kvec *vec,
349 unsigned long vlen, loff_t offset)
350{
351 mm_segment_t old_fs;
352 loff_t pos = offset;
353 ssize_t res;
354
355 old_fs = get_fs();
356 set_fs(KERNEL_DS);
357 /* The cast to a user pointer is valid due to the set_fs() */
358 res = vfs_readv(file, (const struct iovec __user *)vec, vlen, &pos, 0);
359 set_fs(old_fs);
360
361 return res;
362}
363
364static ssize_t default_file_splice_read(struct file *in, loff_t *ppos,
365 struct pipe_inode_info *pipe, size_t len,
366 unsigned int flags)
367{
368 struct kvec *vec, __vec[PIPE_DEF_BUFFERS];
369 struct iov_iter to;
370 struct page **pages;
371 unsigned int nr_pages;
372 size_t offset, base, copied = 0;
373 ssize_t res;
374 int i;
375
376 if (pipe->nrbufs == pipe->buffers)
377 return -EAGAIN;
378
379 /*
380 * Try to keep page boundaries matching to source pagecache ones -
381 * it probably won't be much help, but...
382 */
383 offset = *ppos & ~PAGE_MASK;
384
385 iov_iter_pipe(&to, READ, pipe, len + offset);
386
387 res = iov_iter_get_pages_alloc(&to, &pages, len + offset, &base);
388 if (res <= 0)
389 return -ENOMEM;
390
391 nr_pages = DIV_ROUND_UP(res + base, PAGE_SIZE);
392
393 vec = __vec;
394 if (nr_pages > PIPE_DEF_BUFFERS) {
395 vec = kmalloc_array(nr_pages, sizeof(struct kvec), GFP_KERNEL);
396 if (unlikely(!vec)) {
397 res = -ENOMEM;
398 goto out;
399 }
400 }
401
402 pipe->bufs[to.idx].offset = offset;
403 pipe->bufs[to.idx].len -= offset;
404
405 for (i = 0; i < nr_pages; i++) {
406 size_t this_len = min_t(size_t, len, PAGE_SIZE - offset);
407 vec[i].iov_base = page_address(pages[i]) + offset;
408 vec[i].iov_len = this_len;
409 len -= this_len;
410 offset = 0;
411 }
412
413 res = kernel_readv(in, vec, nr_pages, *ppos);
414 if (res > 0) {
415 copied = res;
416 *ppos += res;
417 }
418
419 if (vec != __vec)
420 kfree(vec);
421out:
422 for (i = 0; i < nr_pages; i++)
423 put_page(pages[i]);
424 kvfree(pages);
425 iov_iter_advance(&to, copied); /* truncates and discards */
426 return res;
427}
428
429/*
430 * Send 'sd->len' bytes to socket from 'sd->file' at position 'sd->pos'
431 * using sendpage(). Return the number of bytes sent.
432 */
433static int pipe_to_sendpage(struct pipe_inode_info *pipe,
434 struct pipe_buffer *buf, struct splice_desc *sd)
435{
436 struct file *file = sd->u.file;
437 loff_t pos = sd->pos;
438 int more;
439
440 if (!likely(file->f_op->sendpage))
441 return -EINVAL;
442
443 more = (sd->flags & SPLICE_F_MORE) ? MSG_MORE : 0;
444
445 if (sd->len < sd->total_len && pipe->nrbufs > 1)
446 more |= MSG_SENDPAGE_NOTLAST;
447
448 return file->f_op->sendpage(file, buf->page, buf->offset,
449 sd->len, &pos, more);
450}
451
452static void wakeup_pipe_writers(struct pipe_inode_info *pipe)
453{
454 smp_mb();
455 if (waitqueue_active(&pipe->wait))
456 wake_up_interruptible(&pipe->wait);
457 kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
458}
459
460/**
461 * splice_from_pipe_feed - feed available data from a pipe to a file
462 * @pipe: pipe to splice from
463 * @sd: information to @actor
464 * @actor: handler that splices the data
465 *
466 * Description:
467 * This function loops over the pipe and calls @actor to do the
468 * actual moving of a single struct pipe_buffer to the desired
469 * destination. It returns when there's no more buffers left in
470 * the pipe or if the requested number of bytes (@sd->total_len)
471 * have been copied. It returns a positive number (one) if the
472 * pipe needs to be filled with more data, zero if the required
473 * number of bytes have been copied and -errno on error.
474 *
475 * This, together with splice_from_pipe_{begin,end,next}, may be
476 * used to implement the functionality of __splice_from_pipe() when
477 * locking is required around copying the pipe buffers to the
478 * destination.
479 */
480static int splice_from_pipe_feed(struct pipe_inode_info *pipe, struct splice_desc *sd,
481 splice_actor *actor)
482{
483 int ret;
484
485 while (pipe->nrbufs) {
486 struct pipe_buffer *buf = pipe->bufs + pipe->curbuf;
487
488 sd->len = buf->len;
489 if (sd->len > sd->total_len)
490 sd->len = sd->total_len;
491
492 ret = pipe_buf_confirm(pipe, buf);
493 if (unlikely(ret)) {
494 if (ret == -ENODATA)
495 ret = 0;
496 return ret;
497 }
498
499 ret = actor(pipe, buf, sd);
500 if (ret <= 0)
501 return ret;
502
503 buf->offset += ret;
504 buf->len -= ret;
505
506 sd->num_spliced += ret;
507 sd->len -= ret;
508 sd->pos += ret;
509 sd->total_len -= ret;
510
511 if (!buf->len) {
512 pipe_buf_release(pipe, buf);
513 pipe->curbuf = (pipe->curbuf + 1) & (pipe->buffers - 1);
514 pipe->nrbufs--;
515 if (pipe->files)
516 sd->need_wakeup = true;
517 }
518
519 if (!sd->total_len)
520 return 0;
521 }
522
523 return 1;
524}
525
526/**
527 * splice_from_pipe_next - wait for some data to splice from
528 * @pipe: pipe to splice from
529 * @sd: information about the splice operation
530 *
531 * Description:
532 * This function will wait for some data and return a positive
533 * value (one) if pipe buffers are available. It will return zero
534 * or -errno if no more data needs to be spliced.
535 */
536static int splice_from_pipe_next(struct pipe_inode_info *pipe, struct splice_desc *sd)
537{
538 /*
539 * Check for signal early to make process killable when there are
540 * always buffers available
541 */
542 if (signal_pending(current))
543 return -ERESTARTSYS;
544
545 while (!pipe->nrbufs) {
546 if (!pipe->writers)
547 return 0;
548
549 if (!pipe->waiting_writers && sd->num_spliced)
550 return 0;
551
552 if (sd->flags & SPLICE_F_NONBLOCK)
553 return -EAGAIN;
554
555 if (signal_pending(current))
556 return -ERESTARTSYS;
557
558 if (sd->need_wakeup) {
559 wakeup_pipe_writers(pipe);
560 sd->need_wakeup = false;
561 }
562
563 pipe_wait(pipe);
564 }
565
566 return 1;
567}
568
569/**
570 * splice_from_pipe_begin - start splicing from pipe
571 * @sd: information about the splice operation
572 *
573 * Description:
574 * This function should be called before a loop containing
575 * splice_from_pipe_next() and splice_from_pipe_feed() to
576 * initialize the necessary fields of @sd.
577 */
578static void splice_from_pipe_begin(struct splice_desc *sd)
579{
580 sd->num_spliced = 0;
581 sd->need_wakeup = false;
582}
583
584/**
585 * splice_from_pipe_end - finish splicing from pipe
586 * @pipe: pipe to splice from
587 * @sd: information about the splice operation
588 *
589 * Description:
590 * This function will wake up pipe writers if necessary. It should
591 * be called after a loop containing splice_from_pipe_next() and
592 * splice_from_pipe_feed().
593 */
594static void splice_from_pipe_end(struct pipe_inode_info *pipe, struct splice_desc *sd)
595{
596 if (sd->need_wakeup)
597 wakeup_pipe_writers(pipe);
598}
599
600/**
601 * __splice_from_pipe - splice data from a pipe to given actor
602 * @pipe: pipe to splice from
603 * @sd: information to @actor
604 * @actor: handler that splices the data
605 *
606 * Description:
607 * This function does little more than loop over the pipe and call
608 * @actor to do the actual moving of a single struct pipe_buffer to
609 * the desired destination. See pipe_to_file, pipe_to_sendpage, or
610 * pipe_to_user.
611 *
612 */
613ssize_t __splice_from_pipe(struct pipe_inode_info *pipe, struct splice_desc *sd,
614 splice_actor *actor)
615{
616 int ret;
617
618 splice_from_pipe_begin(sd);
619 do {
620 cond_resched();
621 ret = splice_from_pipe_next(pipe, sd);
622 if (ret > 0)
623 ret = splice_from_pipe_feed(pipe, sd, actor);
624 } while (ret > 0);
625 splice_from_pipe_end(pipe, sd);
626
627 return sd->num_spliced ? sd->num_spliced : ret;
628}
629EXPORT_SYMBOL(__splice_from_pipe);
630
631/**
632 * splice_from_pipe - splice data from a pipe to a file
633 * @pipe: pipe to splice from
634 * @out: file to splice to
635 * @ppos: position in @out
636 * @len: how many bytes to splice
637 * @flags: splice modifier flags
638 * @actor: handler that splices the data
639 *
640 * Description:
641 * See __splice_from_pipe. This function locks the pipe inode,
642 * otherwise it's identical to __splice_from_pipe().
643 *
644 */
645ssize_t splice_from_pipe(struct pipe_inode_info *pipe, struct file *out,
646 loff_t *ppos, size_t len, unsigned int flags,
647 splice_actor *actor)
648{
649 ssize_t ret;
650 struct splice_desc sd = {
651 .total_len = len,
652 .flags = flags,
653 .pos = *ppos,
654 .u.file = out,
655 };
656
657 pipe_lock(pipe);
658 ret = __splice_from_pipe(pipe, &sd, actor);
659 pipe_unlock(pipe);
660
661 return ret;
662}
663
664/**
665 * iter_file_splice_write - splice data from a pipe to a file
666 * @pipe: pipe info
667 * @out: file to write to
668 * @ppos: position in @out
669 * @len: number of bytes to splice
670 * @flags: splice modifier flags
671 *
672 * Description:
673 * Will either move or copy pages (determined by @flags options) from
674 * the given pipe inode to the given file.
675 * This one is ->write_iter-based.
676 *
677 */
678ssize_t
679iter_file_splice_write(struct pipe_inode_info *pipe, struct file *out,
680 loff_t *ppos, size_t len, unsigned int flags)
681{
682 struct splice_desc sd = {
683 .total_len = len,
684 .flags = flags,
685 .pos = *ppos,
686 .u.file = out,
687 };
688 int nbufs = pipe->buffers;
689 struct bio_vec *array = kcalloc(nbufs, sizeof(struct bio_vec),
690 GFP_KERNEL);
691 ssize_t ret;
692
693 if (unlikely(!array))
694 return -ENOMEM;
695
696 pipe_lock(pipe);
697
698 splice_from_pipe_begin(&sd);
699 while (sd.total_len) {
700 struct iov_iter from;
701 size_t left;
702 int n, idx;
703
704 ret = splice_from_pipe_next(pipe, &sd);
705 if (ret <= 0)
706 break;
707
708 if (unlikely(nbufs < pipe->buffers)) {
709 kfree(array);
710 nbufs = pipe->buffers;
711 array = kcalloc(nbufs, sizeof(struct bio_vec),
712 GFP_KERNEL);
713 if (!array) {
714 ret = -ENOMEM;
715 break;
716 }
717 }
718
719 /* build the vector */
720 left = sd.total_len;
721 for (n = 0, idx = pipe->curbuf; left && n < pipe->nrbufs; n++, idx++) {
722 struct pipe_buffer *buf = pipe->bufs + idx;
723 size_t this_len = buf->len;
724
725 if (this_len > left)
726 this_len = left;
727
728 if (idx == pipe->buffers - 1)
729 idx = -1;
730
731 ret = pipe_buf_confirm(pipe, buf);
732 if (unlikely(ret)) {
733 if (ret == -ENODATA)
734 ret = 0;
735 goto done;
736 }
737
738 array[n].bv_page = buf->page;
739 array[n].bv_len = this_len;
740 array[n].bv_offset = buf->offset;
741 left -= this_len;
742 }
743
744 iov_iter_bvec(&from, WRITE, array, n, sd.total_len - left);
745 ret = vfs_iter_write(out, &from, &sd.pos, 0);
746 if (ret <= 0)
747 break;
748
749 sd.num_spliced += ret;
750 sd.total_len -= ret;
751 *ppos = sd.pos;
752
753 /* dismiss the fully eaten buffers, adjust the partial one */
754 while (ret) {
755 struct pipe_buffer *buf = pipe->bufs + pipe->curbuf;
756 if (ret >= buf->len) {
757 ret -= buf->len;
758 buf->len = 0;
759 pipe_buf_release(pipe, buf);
760 pipe->curbuf = (pipe->curbuf + 1) & (pipe->buffers - 1);
761 pipe->nrbufs--;
762 if (pipe->files)
763 sd.need_wakeup = true;
764 } else {
765 buf->offset += ret;
766 buf->len -= ret;
767 ret = 0;
768 }
769 }
770 }
771done:
772 kfree(array);
773 splice_from_pipe_end(pipe, &sd);
774
775 pipe_unlock(pipe);
776
777 if (sd.num_spliced)
778 ret = sd.num_spliced;
779
780 return ret;
781}
782
783EXPORT_SYMBOL(iter_file_splice_write);
784
785static int write_pipe_buf(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
786 struct splice_desc *sd)
787{
788 int ret;
789 void *data;
790 loff_t tmp = sd->pos;
791
792 data = kmap(buf->page);
793 ret = __kernel_write(sd->u.file, data + buf->offset, sd->len, &tmp);
794 kunmap(buf->page);
795
796 return ret;
797}
798
799static ssize_t default_file_splice_write(struct pipe_inode_info *pipe,
800 struct file *out, loff_t *ppos,
801 size_t len, unsigned int flags)
802{
803 ssize_t ret;
804
805 ret = splice_from_pipe(pipe, out, ppos, len, flags, write_pipe_buf);
806 if (ret > 0)
807 *ppos += ret;
808
809 return ret;
810}
811
812/**
813 * generic_splice_sendpage - splice data from a pipe to a socket
814 * @pipe: pipe to splice from
815 * @out: socket to write to
816 * @ppos: position in @out
817 * @len: number of bytes to splice
818 * @flags: splice modifier flags
819 *
820 * Description:
821 * Will send @len bytes from the pipe to a network socket. No data copying
822 * is involved.
823 *
824 */
825ssize_t generic_splice_sendpage(struct pipe_inode_info *pipe, struct file *out,
826 loff_t *ppos, size_t len, unsigned int flags)
827{
828 return splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_sendpage);
829}
830
831EXPORT_SYMBOL(generic_splice_sendpage);
832
833/*
834 * Attempt to initiate a splice from pipe to file.
835 */
836static long do_splice_from(struct pipe_inode_info *pipe, struct file *out,
837 loff_t *ppos, size_t len, unsigned int flags)
838{
839 ssize_t (*splice_write)(struct pipe_inode_info *, struct file *,
840 loff_t *, size_t, unsigned int);
841
842 if (out->f_op->splice_write)
843 splice_write = out->f_op->splice_write;
844 else
845 splice_write = default_file_splice_write;
846
847 return splice_write(pipe, out, ppos, len, flags);
848}
849
850/*
851 * Attempt to initiate a splice from a file to a pipe.
852 */
853static long do_splice_to(struct file *in, loff_t *ppos,
854 struct pipe_inode_info *pipe, size_t len,
855 unsigned int flags)
856{
857 ssize_t (*splice_read)(struct file *, loff_t *,
858 struct pipe_inode_info *, size_t, unsigned int);
859 int ret;
860
861 if (unlikely(!(in->f_mode & FMODE_READ)))
862 return -EBADF;
863
864 ret = rw_verify_area(READ, in, ppos, len);
865 if (unlikely(ret < 0))
866 return ret;
867
868 if (unlikely(len > MAX_RW_COUNT))
869 len = MAX_RW_COUNT;
870
871 if (in->f_op->splice_read)
872 splice_read = in->f_op->splice_read;
873 else
874 splice_read = default_file_splice_read;
875
876 return splice_read(in, ppos, pipe, len, flags);
877}
878
879/**
880 * splice_direct_to_actor - splices data directly between two non-pipes
881 * @in: file to splice from
882 * @sd: actor information on where to splice to
883 * @actor: handles the data splicing
884 *
885 * Description:
886 * This is a special case helper to splice directly between two
887 * points, without requiring an explicit pipe. Internally an allocated
888 * pipe is cached in the process, and reused during the lifetime of
889 * that process.
890 *
891 */
892ssize_t splice_direct_to_actor(struct file *in, struct splice_desc *sd,
893 splice_direct_actor *actor)
894{
895 struct pipe_inode_info *pipe;
896 long ret, bytes;
897 umode_t i_mode;
898 size_t len;
899 int i, flags, more;
900
901 /*
902 * We require the input being a regular file, as we don't want to
903 * randomly drop data for eg socket -> socket splicing. Use the
904 * piped splicing for that!
905 */
906 i_mode = file_inode(in)->i_mode;
907 if (unlikely(!S_ISREG(i_mode) && !S_ISBLK(i_mode)))
908 return -EINVAL;
909
910 /*
911 * neither in nor out is a pipe, setup an internal pipe attached to
912 * 'out' and transfer the wanted data from 'in' to 'out' through that
913 */
914 pipe = current->splice_pipe;
915 if (unlikely(!pipe)) {
916 pipe = alloc_pipe_info();
917 if (!pipe)
918 return -ENOMEM;
919
920 /*
921 * We don't have an immediate reader, but we'll read the stuff
922 * out of the pipe right after the splice_to_pipe(). So set
923 * PIPE_READERS appropriately.
924 */
925 pipe->readers = 1;
926
927 current->splice_pipe = pipe;
928 }
929
930 /*
931 * Do the splice.
932 */
933 ret = 0;
934 bytes = 0;
935 len = sd->total_len;
936 flags = sd->flags;
937
938 /*
939 * Don't block on output, we have to drain the direct pipe.
940 */
941 sd->flags &= ~SPLICE_F_NONBLOCK;
942 more = sd->flags & SPLICE_F_MORE;
943
944 WARN_ON_ONCE(pipe->nrbufs != 0);
945
946 while (len) {
947 size_t read_len;
948 loff_t pos = sd->pos, prev_pos = pos;
949
950 /* Don't try to read more the pipe has space for. */
951 read_len = min_t(size_t, len,
952 (pipe->buffers - pipe->nrbufs) << PAGE_SHIFT);
953 ret = do_splice_to(in, &pos, pipe, read_len, flags);
954 if (unlikely(ret <= 0))
955 goto out_release;
956
957 read_len = ret;
958 sd->total_len = read_len;
959
960 /*
961 * If more data is pending, set SPLICE_F_MORE
962 * If this is the last data and SPLICE_F_MORE was not set
963 * initially, clears it.
964 */
965 if (read_len < len)
966 sd->flags |= SPLICE_F_MORE;
967 else if (!more)
968 sd->flags &= ~SPLICE_F_MORE;
969 /*
970 * NOTE: nonblocking mode only applies to the input. We
971 * must not do the output in nonblocking mode as then we
972 * could get stuck data in the internal pipe:
973 */
974 ret = actor(pipe, sd);
975 if (unlikely(ret <= 0)) {
976 sd->pos = prev_pos;
977 goto out_release;
978 }
979
980 bytes += ret;
981 len -= ret;
982 sd->pos = pos;
983
984 if (ret < read_len) {
985 sd->pos = prev_pos + ret;
986 goto out_release;
987 }
988 }
989
990done:
991 pipe->nrbufs = pipe->curbuf = 0;
992 file_accessed(in);
993 return bytes;
994
995out_release:
996 /*
997 * If we did an incomplete transfer we must release
998 * the pipe buffers in question:
999 */
1000 for (i = 0; i < pipe->buffers; i++) {
1001 struct pipe_buffer *buf = pipe->bufs + i;
1002
1003 if (buf->ops)
1004 pipe_buf_release(pipe, buf);
1005 }
1006
1007 if (!bytes)
1008 bytes = ret;
1009
1010 goto done;
1011}
1012EXPORT_SYMBOL(splice_direct_to_actor);
1013
1014static int direct_splice_actor(struct pipe_inode_info *pipe,
1015 struct splice_desc *sd)
1016{
1017 struct file *file = sd->u.file;
1018
1019 return do_splice_from(pipe, file, sd->opos, sd->total_len,
1020 sd->flags);
1021}
1022
1023/**
1024 * do_splice_direct - splices data directly between two files
1025 * @in: file to splice from
1026 * @ppos: input file offset
1027 * @out: file to splice to
1028 * @opos: output file offset
1029 * @len: number of bytes to splice
1030 * @flags: splice modifier flags
1031 *
1032 * Description:
1033 * For use by do_sendfile(). splice can easily emulate sendfile, but
1034 * doing it in the application would incur an extra system call
1035 * (splice in + splice out, as compared to just sendfile()). So this helper
1036 * can splice directly through a process-private pipe.
1037 *
1038 */
1039long do_splice_direct(struct file *in, loff_t *ppos, struct file *out,
1040 loff_t *opos, size_t len, unsigned int flags)
1041{
1042 struct splice_desc sd = {
1043 .len = len,
1044 .total_len = len,
1045 .flags = flags,
1046 .pos = *ppos,
1047 .u.file = out,
1048 .opos = opos,
1049 };
1050 long ret;
1051
1052 if (unlikely(!(out->f_mode & FMODE_WRITE)))
1053 return -EBADF;
1054
1055 if (unlikely(out->f_flags & O_APPEND))
1056 return -EINVAL;
1057
1058 ret = rw_verify_area(WRITE, out, opos, len);
1059 if (unlikely(ret < 0))
1060 return ret;
1061
1062 ret = splice_direct_to_actor(in, &sd, direct_splice_actor);
1063 if (ret > 0)
1064 *ppos = sd.pos;
1065
1066 return ret;
1067}
1068EXPORT_SYMBOL(do_splice_direct);
1069
1070static int wait_for_space(struct pipe_inode_info *pipe, unsigned flags)
1071{
1072 for (;;) {
1073 if (unlikely(!pipe->readers)) {
1074 send_sig(SIGPIPE, current, 0);
1075 return -EPIPE;
1076 }
1077 if (pipe->nrbufs != pipe->buffers)
1078 return 0;
1079 if (flags & SPLICE_F_NONBLOCK)
1080 return -EAGAIN;
1081 if (signal_pending(current))
1082 return -ERESTARTSYS;
1083 pipe->waiting_writers++;
1084 pipe_wait(pipe);
1085 pipe->waiting_writers--;
1086 }
1087}
1088
1089static int splice_pipe_to_pipe(struct pipe_inode_info *ipipe,
1090 struct pipe_inode_info *opipe,
1091 size_t len, unsigned int flags);
1092
1093/*
1094 * Determine where to splice to/from.
1095 */
1096static long do_splice(struct file *in, loff_t __user *off_in,
1097 struct file *out, loff_t __user *off_out,
1098 size_t len, unsigned int flags)
1099{
1100 struct pipe_inode_info *ipipe;
1101 struct pipe_inode_info *opipe;
1102 loff_t offset;
1103 long ret;
1104
1105 ipipe = get_pipe_info(in);
1106 opipe = get_pipe_info(out);
1107
1108 if (ipipe && opipe) {
1109 if (off_in || off_out)
1110 return -ESPIPE;
1111
1112 if (!(in->f_mode & FMODE_READ))
1113 return -EBADF;
1114
1115 if (!(out->f_mode & FMODE_WRITE))
1116 return -EBADF;
1117
1118 /* Splicing to self would be fun, but... */
1119 if (ipipe == opipe)
1120 return -EINVAL;
1121
1122 if ((in->f_flags | out->f_flags) & O_NONBLOCK)
1123 flags |= SPLICE_F_NONBLOCK;
1124
1125 return splice_pipe_to_pipe(ipipe, opipe, len, flags);
1126 }
1127
1128 if (ipipe) {
1129 if (off_in)
1130 return -ESPIPE;
1131 if (off_out) {
1132 if (!(out->f_mode & FMODE_PWRITE))
1133 return -EINVAL;
1134 if (copy_from_user(&offset, off_out, sizeof(loff_t)))
1135 return -EFAULT;
1136 } else {
1137 offset = out->f_pos;
1138 }
1139
1140 if (unlikely(!(out->f_mode & FMODE_WRITE)))
1141 return -EBADF;
1142
1143 if (unlikely(out->f_flags & O_APPEND))
1144 return -EINVAL;
1145
1146 ret = rw_verify_area(WRITE, out, &offset, len);
1147 if (unlikely(ret < 0))
1148 return ret;
1149
1150 if (in->f_flags & O_NONBLOCK)
1151 flags |= SPLICE_F_NONBLOCK;
1152
1153 file_start_write(out);
1154 ret = do_splice_from(ipipe, out, &offset, len, flags);
1155 file_end_write(out);
1156
1157 if (!off_out)
1158 out->f_pos = offset;
1159 else if (copy_to_user(off_out, &offset, sizeof(loff_t)))
1160 ret = -EFAULT;
1161
1162 return ret;
1163 }
1164
1165 if (opipe) {
1166 if (off_out)
1167 return -ESPIPE;
1168 if (off_in) {
1169 if (!(in->f_mode & FMODE_PREAD))
1170 return -EINVAL;
1171 if (copy_from_user(&offset, off_in, sizeof(loff_t)))
1172 return -EFAULT;
1173 } else {
1174 offset = in->f_pos;
1175 }
1176
1177 if (out->f_flags & O_NONBLOCK)
1178 flags |= SPLICE_F_NONBLOCK;
1179
1180 pipe_lock(opipe);
1181 ret = wait_for_space(opipe, flags);
1182 if (!ret)
1183 ret = do_splice_to(in, &offset, opipe, len, flags);
1184 pipe_unlock(opipe);
1185 if (ret > 0)
1186 wakeup_pipe_readers(opipe);
1187 if (!off_in)
1188 in->f_pos = offset;
1189 else if (copy_to_user(off_in, &offset, sizeof(loff_t)))
1190 ret = -EFAULT;
1191
1192 return ret;
1193 }
1194
1195 return -EINVAL;
1196}
1197
1198static int iter_to_pipe(struct iov_iter *from,
1199 struct pipe_inode_info *pipe,
1200 unsigned flags)
1201{
1202 struct pipe_buffer buf = {
1203 .ops = &user_page_pipe_buf_ops,
1204 .flags = flags
1205 };
1206 size_t total = 0;
1207 int ret = 0;
1208 bool failed = false;
1209
1210 while (iov_iter_count(from) && !failed) {
1211 struct page *pages[16];
1212 ssize_t copied;
1213 size_t start;
1214 int n;
1215
1216 copied = iov_iter_get_pages(from, pages, ~0UL, 16, &start);
1217 if (copied <= 0) {
1218 ret = copied;
1219 break;
1220 }
1221
1222 for (n = 0; copied; n++, start = 0) {
1223 int size = min_t(int, copied, PAGE_SIZE - start);
1224 if (!failed) {
1225 buf.page = pages[n];
1226 buf.offset = start;
1227 buf.len = size;
1228 ret = add_to_pipe(pipe, &buf);
1229 if (unlikely(ret < 0)) {
1230 failed = true;
1231 } else {
1232 iov_iter_advance(from, ret);
1233 total += ret;
1234 }
1235 } else {
1236 put_page(pages[n]);
1237 }
1238 copied -= size;
1239 }
1240 }
1241 return total ? total : ret;
1242}
1243
1244static int pipe_to_user(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
1245 struct splice_desc *sd)
1246{
1247 int n = copy_page_to_iter(buf->page, buf->offset, sd->len, sd->u.data);
1248 return n == sd->len ? n : -EFAULT;
1249}
1250
1251/*
1252 * For lack of a better implementation, implement vmsplice() to userspace
1253 * as a simple copy of the pipes pages to the user iov.
1254 */
1255static long vmsplice_to_user(struct file *file, struct iov_iter *iter,
1256 unsigned int flags)
1257{
1258 struct pipe_inode_info *pipe = get_pipe_info(file);
1259 struct splice_desc sd = {
1260 .total_len = iov_iter_count(iter),
1261 .flags = flags,
1262 .u.data = iter
1263 };
1264 long ret = 0;
1265
1266 if (!pipe)
1267 return -EBADF;
1268
1269 if (sd.total_len) {
1270 pipe_lock(pipe);
1271 ret = __splice_from_pipe(pipe, &sd, pipe_to_user);
1272 pipe_unlock(pipe);
1273 }
1274
1275 return ret;
1276}
1277
1278/*
1279 * vmsplice splices a user address range into a pipe. It can be thought of
1280 * as splice-from-memory, where the regular splice is splice-from-file (or
1281 * to file). In both cases the output is a pipe, naturally.
1282 */
1283static long vmsplice_to_pipe(struct file *file, struct iov_iter *iter,
1284 unsigned int flags)
1285{
1286 struct pipe_inode_info *pipe;
1287 long ret = 0;
1288 unsigned buf_flag = 0;
1289
1290 if (flags & SPLICE_F_GIFT)
1291 buf_flag = PIPE_BUF_FLAG_GIFT;
1292
1293 pipe = get_pipe_info(file);
1294 if (!pipe)
1295 return -EBADF;
1296
1297 pipe_lock(pipe);
1298 ret = wait_for_space(pipe, flags);
1299 if (!ret)
1300 ret = iter_to_pipe(iter, pipe, buf_flag);
1301 pipe_unlock(pipe);
1302 if (ret > 0)
1303 wakeup_pipe_readers(pipe);
1304 return ret;
1305}
1306
1307static int vmsplice_type(struct fd f, int *type)
1308{
1309 if (!f.file)
1310 return -EBADF;
1311 if (f.file->f_mode & FMODE_WRITE) {
1312 *type = WRITE;
1313 } else if (f.file->f_mode & FMODE_READ) {
1314 *type = READ;
1315 } else {
1316 fdput(f);
1317 return -EBADF;
1318 }
1319 return 0;
1320}
1321
1322/*
1323 * Note that vmsplice only really supports true splicing _from_ user memory
1324 * to a pipe, not the other way around. Splicing from user memory is a simple
1325 * operation that can be supported without any funky alignment restrictions
1326 * or nasty vm tricks. We simply map in the user memory and fill them into
1327 * a pipe. The reverse isn't quite as easy, though. There are two possible
1328 * solutions for that:
1329 *
1330 * - memcpy() the data internally, at which point we might as well just
1331 * do a regular read() on the buffer anyway.
1332 * - Lots of nasty vm tricks, that are neither fast nor flexible (it
1333 * has restriction limitations on both ends of the pipe).
1334 *
1335 * Currently we punt and implement it as a normal copy, see pipe_to_user().
1336 *
1337 */
1338static long do_vmsplice(struct file *f, struct iov_iter *iter, unsigned int flags)
1339{
1340 if (unlikely(flags & ~SPLICE_F_ALL))
1341 return -EINVAL;
1342
1343 if (!iov_iter_count(iter))
1344 return 0;
1345
1346 if (iov_iter_rw(iter) == WRITE)
1347 return vmsplice_to_pipe(f, iter, flags);
1348 else
1349 return vmsplice_to_user(f, iter, flags);
1350}
1351
1352SYSCALL_DEFINE4(vmsplice, int, fd, const struct iovec __user *, uiov,
1353 unsigned long, nr_segs, unsigned int, flags)
1354{
1355 struct iovec iovstack[UIO_FASTIOV];
1356 struct iovec *iov = iovstack;
1357 struct iov_iter iter;
1358 long error;
1359 struct fd f;
1360 int type;
1361
1362 f = fdget(fd);
1363 error = vmsplice_type(f, &type);
1364 if (error)
1365 return error;
1366
1367 error = import_iovec(type, uiov, nr_segs,
1368 ARRAY_SIZE(iovstack), &iov, &iter);
1369 if (!error) {
1370 error = do_vmsplice(f.file, &iter, flags);
1371 kfree(iov);
1372 }
1373 fdput(f);
1374 return error;
1375}
1376
1377#ifdef CONFIG_COMPAT
1378COMPAT_SYSCALL_DEFINE4(vmsplice, int, fd, const struct compat_iovec __user *, iov32,
1379 unsigned int, nr_segs, unsigned int, flags)
1380{
1381 struct iovec iovstack[UIO_FASTIOV];
1382 struct iovec *iov = iovstack;
1383 struct iov_iter iter;
1384 long error;
1385 struct fd f;
1386 int type;
1387
1388 f = fdget(fd);
1389 error = vmsplice_type(f, &type);
1390 if (error)
1391 return error;
1392
1393 error = compat_import_iovec(type, iov32, nr_segs,
1394 ARRAY_SIZE(iovstack), &iov, &iter);
1395 if (!error) {
1396 error = do_vmsplice(f.file, &iter, flags);
1397 kfree(iov);
1398 }
1399 fdput(f);
1400 return error;
1401}
1402#endif
1403
1404SYSCALL_DEFINE6(splice, int, fd_in, loff_t __user *, off_in,
1405 int, fd_out, loff_t __user *, off_out,
1406 size_t, len, unsigned int, flags)
1407{
1408 struct fd in, out;
1409 long error;
1410
1411 if (unlikely(!len))
1412 return 0;
1413
1414 if (unlikely(flags & ~SPLICE_F_ALL))
1415 return -EINVAL;
1416
1417 error = -EBADF;
1418 in = fdget(fd_in);
1419 if (in.file) {
1420 if (in.file->f_mode & FMODE_READ) {
1421 out = fdget(fd_out);
1422 if (out.file) {
1423 if (out.file->f_mode & FMODE_WRITE)
1424 error = do_splice(in.file, off_in,
1425 out.file, off_out,
1426 len, flags);
1427 fdput(out);
1428 }
1429 }
1430 fdput(in);
1431 }
1432 return error;
1433}
1434
1435/*
1436 * Make sure there's data to read. Wait for input if we can, otherwise
1437 * return an appropriate error.
1438 */
1439static int ipipe_prep(struct pipe_inode_info *pipe, unsigned int flags)
1440{
1441 int ret;
1442
1443 /*
1444 * Check ->nrbufs without the inode lock first. This function
1445 * is speculative anyways, so missing one is ok.
1446 */
1447 if (pipe->nrbufs)
1448 return 0;
1449
1450 ret = 0;
1451 pipe_lock(pipe);
1452
1453 while (!pipe->nrbufs) {
1454 if (signal_pending(current)) {
1455 ret = -ERESTARTSYS;
1456 break;
1457 }
1458 if (!pipe->writers)
1459 break;
1460 if (!pipe->waiting_writers) {
1461 if (flags & SPLICE_F_NONBLOCK) {
1462 ret = -EAGAIN;
1463 break;
1464 }
1465 }
1466 pipe_wait(pipe);
1467 }
1468
1469 pipe_unlock(pipe);
1470 return ret;
1471}
1472
1473/*
1474 * Make sure there's writeable room. Wait for room if we can, otherwise
1475 * return an appropriate error.
1476 */
1477static int opipe_prep(struct pipe_inode_info *pipe, unsigned int flags)
1478{
1479 int ret;
1480
1481 /*
1482 * Check ->nrbufs without the inode lock first. This function
1483 * is speculative anyways, so missing one is ok.
1484 */
1485 if (pipe->nrbufs < pipe->buffers)
1486 return 0;
1487
1488 ret = 0;
1489 pipe_lock(pipe);
1490
1491 while (pipe->nrbufs >= pipe->buffers) {
1492 if (!pipe->readers) {
1493 send_sig(SIGPIPE, current, 0);
1494 ret = -EPIPE;
1495 break;
1496 }
1497 if (flags & SPLICE_F_NONBLOCK) {
1498 ret = -EAGAIN;
1499 break;
1500 }
1501 if (signal_pending(current)) {
1502 ret = -ERESTARTSYS;
1503 break;
1504 }
1505 pipe->waiting_writers++;
1506 pipe_wait(pipe);
1507 pipe->waiting_writers--;
1508 }
1509
1510 pipe_unlock(pipe);
1511 return ret;
1512}
1513
1514/*
1515 * Splice contents of ipipe to opipe.
1516 */
1517static int splice_pipe_to_pipe(struct pipe_inode_info *ipipe,
1518 struct pipe_inode_info *opipe,
1519 size_t len, unsigned int flags)
1520{
1521 struct pipe_buffer *ibuf, *obuf;
1522 int ret = 0, nbuf;
1523 bool input_wakeup = false;
1524
1525
1526retry:
1527 ret = ipipe_prep(ipipe, flags);
1528 if (ret)
1529 return ret;
1530
1531 ret = opipe_prep(opipe, flags);
1532 if (ret)
1533 return ret;
1534
1535 /*
1536 * Potential ABBA deadlock, work around it by ordering lock
1537 * grabbing by pipe info address. Otherwise two different processes
1538 * could deadlock (one doing tee from A -> B, the other from B -> A).
1539 */
1540 pipe_double_lock(ipipe, opipe);
1541
1542 do {
1543 if (!opipe->readers) {
1544 send_sig(SIGPIPE, current, 0);
1545 if (!ret)
1546 ret = -EPIPE;
1547 break;
1548 }
1549
1550 if (!ipipe->nrbufs && !ipipe->writers)
1551 break;
1552
1553 /*
1554 * Cannot make any progress, because either the input
1555 * pipe is empty or the output pipe is full.
1556 */
1557 if (!ipipe->nrbufs || opipe->nrbufs >= opipe->buffers) {
1558 /* Already processed some buffers, break */
1559 if (ret)
1560 break;
1561
1562 if (flags & SPLICE_F_NONBLOCK) {
1563 ret = -EAGAIN;
1564 break;
1565 }
1566
1567 /*
1568 * We raced with another reader/writer and haven't
1569 * managed to process any buffers. A zero return
1570 * value means EOF, so retry instead.
1571 */
1572 pipe_unlock(ipipe);
1573 pipe_unlock(opipe);
1574 goto retry;
1575 }
1576
1577 ibuf = ipipe->bufs + ipipe->curbuf;
1578 nbuf = (opipe->curbuf + opipe->nrbufs) & (opipe->buffers - 1);
1579 obuf = opipe->bufs + nbuf;
1580
1581 if (len >= ibuf->len) {
1582 /*
1583 * Simply move the whole buffer from ipipe to opipe
1584 */
1585 *obuf = *ibuf;
1586 ibuf->ops = NULL;
1587 opipe->nrbufs++;
1588 ipipe->curbuf = (ipipe->curbuf + 1) & (ipipe->buffers - 1);
1589 ipipe->nrbufs--;
1590 input_wakeup = true;
1591 } else {
1592 /*
1593 * Get a reference to this pipe buffer,
1594 * so we can copy the contents over.
1595 */
1596 pipe_buf_get(ipipe, ibuf);
1597 *obuf = *ibuf;
1598
1599 /*
1600 * Don't inherit the gift flag, we need to
1601 * prevent multiple steals of this page.
1602 */
1603 obuf->flags &= ~PIPE_BUF_FLAG_GIFT;
1604
1605 pipe_buf_mark_unmergeable(obuf);
1606
1607 obuf->len = len;
1608 opipe->nrbufs++;
1609 ibuf->offset += obuf->len;
1610 ibuf->len -= obuf->len;
1611 }
1612 ret += obuf->len;
1613 len -= obuf->len;
1614 } while (len);
1615
1616 pipe_unlock(ipipe);
1617 pipe_unlock(opipe);
1618
1619 /*
1620 * If we put data in the output pipe, wakeup any potential readers.
1621 */
1622 if (ret > 0)
1623 wakeup_pipe_readers(opipe);
1624
1625 if (input_wakeup)
1626 wakeup_pipe_writers(ipipe);
1627
1628 return ret;
1629}
1630
1631/*
1632 * Link contents of ipipe to opipe.
1633 */
1634static int link_pipe(struct pipe_inode_info *ipipe,
1635 struct pipe_inode_info *opipe,
1636 size_t len, unsigned int flags)
1637{
1638 struct pipe_buffer *ibuf, *obuf;
1639 int ret = 0, i = 0, nbuf;
1640
1641 /*
1642 * Potential ABBA deadlock, work around it by ordering lock
1643 * grabbing by pipe info address. Otherwise two different processes
1644 * could deadlock (one doing tee from A -> B, the other from B -> A).
1645 */
1646 pipe_double_lock(ipipe, opipe);
1647
1648 do {
1649 if (!opipe->readers) {
1650 send_sig(SIGPIPE, current, 0);
1651 if (!ret)
1652 ret = -EPIPE;
1653 break;
1654 }
1655
1656 /*
1657 * If we have iterated all input buffers or ran out of
1658 * output room, break.
1659 */
1660 if (i >= ipipe->nrbufs || opipe->nrbufs >= opipe->buffers)
1661 break;
1662
1663 ibuf = ipipe->bufs + ((ipipe->curbuf + i) & (ipipe->buffers-1));
1664 nbuf = (opipe->curbuf + opipe->nrbufs) & (opipe->buffers - 1);
1665
1666 /*
1667 * Get a reference to this pipe buffer,
1668 * so we can copy the contents over.
1669 */
1670 pipe_buf_get(ipipe, ibuf);
1671
1672 obuf = opipe->bufs + nbuf;
1673 *obuf = *ibuf;
1674
1675 /*
1676 * Don't inherit the gift flag, we need to
1677 * prevent multiple steals of this page.
1678 */
1679 obuf->flags &= ~PIPE_BUF_FLAG_GIFT;
1680
1681 pipe_buf_mark_unmergeable(obuf);
1682
1683 if (obuf->len > len)
1684 obuf->len = len;
1685
1686 opipe->nrbufs++;
1687 ret += obuf->len;
1688 len -= obuf->len;
1689 i++;
1690 } while (len);
1691
1692 /*
1693 * return EAGAIN if we have the potential of some data in the
1694 * future, otherwise just return 0
1695 */
1696 if (!ret && ipipe->waiting_writers && (flags & SPLICE_F_NONBLOCK))
1697 ret = -EAGAIN;
1698
1699 pipe_unlock(ipipe);
1700 pipe_unlock(opipe);
1701
1702 /*
1703 * If we put data in the output pipe, wakeup any potential readers.
1704 */
1705 if (ret > 0)
1706 wakeup_pipe_readers(opipe);
1707
1708 return ret;
1709}
1710
1711/*
1712 * This is a tee(1) implementation that works on pipes. It doesn't copy
1713 * any data, it simply references the 'in' pages on the 'out' pipe.
1714 * The 'flags' used are the SPLICE_F_* variants, currently the only
1715 * applicable one is SPLICE_F_NONBLOCK.
1716 */
1717static long do_tee(struct file *in, struct file *out, size_t len,
1718 unsigned int flags)
1719{
1720 struct pipe_inode_info *ipipe = get_pipe_info(in);
1721 struct pipe_inode_info *opipe = get_pipe_info(out);
1722 int ret = -EINVAL;
1723
1724 /*
1725 * Duplicate the contents of ipipe to opipe without actually
1726 * copying the data.
1727 */
1728 if (ipipe && opipe && ipipe != opipe) {
1729 if ((in->f_flags | out->f_flags) & O_NONBLOCK)
1730 flags |= SPLICE_F_NONBLOCK;
1731
1732 /*
1733 * Keep going, unless we encounter an error. The ipipe/opipe
1734 * ordering doesn't really matter.
1735 */
1736 ret = ipipe_prep(ipipe, flags);
1737 if (!ret) {
1738 ret = opipe_prep(opipe, flags);
1739 if (!ret)
1740 ret = link_pipe(ipipe, opipe, len, flags);
1741 }
1742 }
1743
1744 return ret;
1745}
1746
1747SYSCALL_DEFINE4(tee, int, fdin, int, fdout, size_t, len, unsigned int, flags)
1748{
1749 struct fd in;
1750 int error;
1751
1752 if (unlikely(flags & ~SPLICE_F_ALL))
1753 return -EINVAL;
1754
1755 if (unlikely(!len))
1756 return 0;
1757
1758 error = -EBADF;
1759 in = fdget(fdin);
1760 if (in.file) {
1761 if (in.file->f_mode & FMODE_READ) {
1762 struct fd out = fdget(fdout);
1763 if (out.file) {
1764 if (out.file->f_mode & FMODE_WRITE)
1765 error = do_tee(in.file, out.file,
1766 len, flags);
1767 fdput(out);
1768 }
1769 }
1770 fdput(in);
1771 }
1772
1773 return error;
1774}
1775