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