xref: /openbmc/linux/fs/splice.c (revision 67e2fae3)
1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * "splice": joining two ropes together by interweaving their strands.
4  *
5  * This is the "extended pipe" functionality, where a pipe is used as
6  * an arbitrary in-memory buffer. Think of a pipe as a small kernel
7  * buffer that you can use to transfer data from one end to the other.
8  *
9  * The traditional unix read/write is extended with a "splice()" operation
10  * that transfers data buffers to or from a pipe buffer.
11  *
12  * Named by Larry McVoy, original implementation from Linus, extended by
13  * Jens to support splicing to files, network, direct splicing, etc and
14  * fixing lots of bugs.
15  *
16  * Copyright (C) 2005-2006 Jens Axboe <axboe@kernel.dk>
17  * Copyright (C) 2005-2006 Linus Torvalds <torvalds@osdl.org>
18  * Copyright (C) 2006 Ingo Molnar <mingo@elte.hu>
19  *
20  */
21 #include <linux/bvec.h>
22 #include <linux/fs.h>
23 #include <linux/file.h>
24 #include <linux/pagemap.h>
25 #include <linux/splice.h>
26 #include <linux/memcontrol.h>
27 #include <linux/mm_inline.h>
28 #include <linux/swap.h>
29 #include <linux/writeback.h>
30 #include <linux/export.h>
31 #include <linux/syscalls.h>
32 #include <linux/uio.h>
33 #include <linux/security.h>
34 #include <linux/gfp.h>
35 #include <linux/socket.h>
36 #include <linux/compat.h>
37 #include <linux/sched/signal.h>
38 
39 #include "internal.h"
40 
41 /*
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.
46  */
47 static bool page_cache_pipe_buf_try_steal(struct pipe_inode_info *pipe,
48 		struct pipe_buffer *buf)
49 {
50 	struct page *page = buf->page;
51 	struct address_space *mapping;
52 
53 	lock_page(page);
54 
55 	mapping = page_mapping(page);
56 	if (mapping) {
57 		WARN_ON(!PageUptodate(page));
58 
59 		/*
60 		 * At least for ext2 with nobh option, we need to wait on
61 		 * writeback completing on this page, since we'll remove it
62 		 * from the pagecache.  Otherwise truncate wont wait on the
63 		 * page, allowing the disk blocks to be reused by someone else
64 		 * before we actually wrote our data to them. fs corruption
65 		 * ensues.
66 		 */
67 		wait_on_page_writeback(page);
68 
69 		if (page_has_private(page) &&
70 		    !try_to_release_page(page, GFP_KERNEL))
71 			goto out_unlock;
72 
73 		/*
74 		 * If we succeeded in removing the mapping, set LRU flag
75 		 * and return good.
76 		 */
77 		if (remove_mapping(mapping, page)) {
78 			buf->flags |= PIPE_BUF_FLAG_LRU;
79 			return true;
80 		}
81 	}
82 
83 	/*
84 	 * Raced with truncate or failed to remove page from current
85 	 * address space, unlock and return failure.
86 	 */
87 out_unlock:
88 	unlock_page(page);
89 	return false;
90 }
91 
92 static void page_cache_pipe_buf_release(struct pipe_inode_info *pipe,
93 					struct pipe_buffer *buf)
94 {
95 	put_page(buf->page);
96 	buf->flags &= ~PIPE_BUF_FLAG_LRU;
97 }
98 
99 /*
100  * Check whether the contents of buf is OK to access. Since the content
101  * is a page cache page, IO may be in flight.
102  */
103 static int page_cache_pipe_buf_confirm(struct pipe_inode_info *pipe,
104 				       struct pipe_buffer *buf)
105 {
106 	struct page *page = buf->page;
107 	int err;
108 
109 	if (!PageUptodate(page)) {
110 		lock_page(page);
111 
112 		/*
113 		 * Page got truncated/unhashed. This will cause a 0-byte
114 		 * splice, if this is the first page.
115 		 */
116 		if (!page->mapping) {
117 			err = -ENODATA;
118 			goto error;
119 		}
120 
121 		/*
122 		 * Uh oh, read-error from disk.
123 		 */
124 		if (!PageUptodate(page)) {
125 			err = -EIO;
126 			goto error;
127 		}
128 
129 		/*
130 		 * Page is ok afterall, we are done.
131 		 */
132 		unlock_page(page);
133 	}
134 
135 	return 0;
136 error:
137 	unlock_page(page);
138 	return err;
139 }
140 
141 const struct pipe_buf_operations page_cache_pipe_buf_ops = {
142 	.confirm	= page_cache_pipe_buf_confirm,
143 	.release	= page_cache_pipe_buf_release,
144 	.try_steal	= page_cache_pipe_buf_try_steal,
145 	.get		= generic_pipe_buf_get,
146 };
147 
148 static bool user_page_pipe_buf_try_steal(struct pipe_inode_info *pipe,
149 		struct pipe_buffer *buf)
150 {
151 	if (!(buf->flags & PIPE_BUF_FLAG_GIFT))
152 		return false;
153 
154 	buf->flags |= PIPE_BUF_FLAG_LRU;
155 	return generic_pipe_buf_try_steal(pipe, buf);
156 }
157 
158 static const struct pipe_buf_operations user_page_pipe_buf_ops = {
159 	.release	= page_cache_pipe_buf_release,
160 	.try_steal	= user_page_pipe_buf_try_steal,
161 	.get		= generic_pipe_buf_get,
162 };
163 
164 static void wakeup_pipe_readers(struct pipe_inode_info *pipe)
165 {
166 	smp_mb();
167 	if (waitqueue_active(&pipe->rd_wait))
168 		wake_up_interruptible(&pipe->rd_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  */
183 ssize_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 	unsigned int tail = pipe->tail;
188 	unsigned int head = pipe->head;
189 	unsigned int mask = pipe->ring_size - 1;
190 	int ret = 0, page_nr = 0;
191 
192 	if (!spd_pages)
193 		return 0;
194 
195 	if (unlikely(!pipe->readers)) {
196 		send_sig(SIGPIPE, current, 0);
197 		ret = -EPIPE;
198 		goto out;
199 	}
200 
201 	while (!pipe_full(head, tail, pipe->max_usage)) {
202 		struct pipe_buffer *buf = &pipe->bufs[head & mask];
203 
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;
210 
211 		head++;
212 		pipe->head = head;
213 		page_nr++;
214 		ret += buf->len;
215 
216 		if (!--spd->nr_pages)
217 			break;
218 	}
219 
220 	if (!ret)
221 		ret = -EAGAIN;
222 
223 out:
224 	while (page_nr < spd_pages)
225 		spd->spd_release(spd, page_nr++);
226 
227 	return ret;
228 }
229 EXPORT_SYMBOL_GPL(splice_to_pipe);
230 
231 ssize_t add_to_pipe(struct pipe_inode_info *pipe, struct pipe_buffer *buf)
232 {
233 	unsigned int head = pipe->head;
234 	unsigned int tail = pipe->tail;
235 	unsigned int mask = pipe->ring_size - 1;
236 	int ret;
237 
238 	if (unlikely(!pipe->readers)) {
239 		send_sig(SIGPIPE, current, 0);
240 		ret = -EPIPE;
241 	} else if (pipe_full(head, tail, pipe->max_usage)) {
242 		ret = -EAGAIN;
243 	} else {
244 		pipe->bufs[head & mask] = *buf;
245 		pipe->head = head + 1;
246 		return buf->len;
247 	}
248 	pipe_buf_release(pipe, buf);
249 	return ret;
250 }
251 EXPORT_SYMBOL(add_to_pipe);
252 
253 /*
254  * Check if we need to grow the arrays holding pages and partial page
255  * descriptions.
256  */
257 int splice_grow_spd(const struct pipe_inode_info *pipe, struct splice_pipe_desc *spd)
258 {
259 	unsigned int max_usage = READ_ONCE(pipe->max_usage);
260 
261 	spd->nr_pages_max = max_usage;
262 	if (max_usage <= PIPE_DEF_BUFFERS)
263 		return 0;
264 
265 	spd->pages = kmalloc_array(max_usage, sizeof(struct page *), GFP_KERNEL);
266 	spd->partial = kmalloc_array(max_usage, sizeof(struct partial_page),
267 				     GFP_KERNEL);
268 
269 	if (spd->pages && spd->partial)
270 		return 0;
271 
272 	kfree(spd->pages);
273 	kfree(spd->partial);
274 	return -ENOMEM;
275 }
276 
277 void splice_shrink_spd(struct splice_pipe_desc *spd)
278 {
279 	if (spd->nr_pages_max <= PIPE_DEF_BUFFERS)
280 		return;
281 
282 	kfree(spd->pages);
283 	kfree(spd->partial);
284 }
285 
286 /**
287  * generic_file_splice_read - splice data from file to a pipe
288  * @in:		file to splice from
289  * @ppos:	position in @in
290  * @pipe:	pipe to splice to
291  * @len:	number of bytes to splice
292  * @flags:	splice modifier flags
293  *
294  * Description:
295  *    Will read pages from given file and fill them into a pipe. Can be
296  *    used as long as it has more or less sane ->read_iter().
297  *
298  */
299 ssize_t generic_file_splice_read(struct file *in, loff_t *ppos,
300 				 struct pipe_inode_info *pipe, size_t len,
301 				 unsigned int flags)
302 {
303 	struct iov_iter to;
304 	struct kiocb kiocb;
305 	unsigned int i_head;
306 	int ret;
307 
308 	iov_iter_pipe(&to, READ, pipe, len);
309 	i_head = to.head;
310 	init_sync_kiocb(&kiocb, in);
311 	kiocb.ki_pos = *ppos;
312 	ret = call_read_iter(in, &kiocb, &to);
313 	if (ret > 0) {
314 		*ppos = kiocb.ki_pos;
315 		file_accessed(in);
316 	} else if (ret < 0) {
317 		to.head = i_head;
318 		to.iov_offset = 0;
319 		iov_iter_advance(&to, 0); /* to free what was emitted */
320 		/*
321 		 * callers of ->splice_read() expect -EAGAIN on
322 		 * "can't put anything in there", rather than -EFAULT.
323 		 */
324 		if (ret == -EFAULT)
325 			ret = -EAGAIN;
326 	}
327 
328 	return ret;
329 }
330 EXPORT_SYMBOL(generic_file_splice_read);
331 
332 const struct pipe_buf_operations default_pipe_buf_ops = {
333 	.release	= generic_pipe_buf_release,
334 	.try_steal	= generic_pipe_buf_try_steal,
335 	.get		= generic_pipe_buf_get,
336 };
337 
338 /* Pipe buffer operations for a socket and similar. */
339 const struct pipe_buf_operations nosteal_pipe_buf_ops = {
340 	.release	= generic_pipe_buf_release,
341 	.get		= generic_pipe_buf_get,
342 };
343 EXPORT_SYMBOL(nosteal_pipe_buf_ops);
344 
345 static ssize_t kernel_readv(struct file *file, const struct kvec *vec,
346 			    unsigned long vlen, loff_t offset)
347 {
348 	mm_segment_t old_fs;
349 	loff_t pos = offset;
350 	ssize_t res;
351 
352 	old_fs = get_fs();
353 	set_fs(KERNEL_DS);
354 	/* The cast to a user pointer is valid due to the set_fs() */
355 	res = vfs_readv(file, (const struct iovec __user *)vec, vlen, &pos, 0);
356 	set_fs(old_fs);
357 
358 	return res;
359 }
360 
361 static ssize_t default_file_splice_read(struct file *in, loff_t *ppos,
362 				 struct pipe_inode_info *pipe, size_t len,
363 				 unsigned int flags)
364 {
365 	struct kvec *vec, __vec[PIPE_DEF_BUFFERS];
366 	struct iov_iter to;
367 	struct page **pages;
368 	unsigned int nr_pages;
369 	unsigned int mask;
370 	size_t offset, base, copied = 0;
371 	ssize_t res;
372 	int i;
373 
374 	if (pipe_full(pipe->head, pipe->tail, pipe->max_usage))
375 		return -EAGAIN;
376 
377 	/*
378 	 * Try to keep page boundaries matching to source pagecache ones -
379 	 * it probably won't be much help, but...
380 	 */
381 	offset = *ppos & ~PAGE_MASK;
382 
383 	iov_iter_pipe(&to, READ, pipe, len + offset);
384 
385 	res = iov_iter_get_pages_alloc(&to, &pages, len + offset, &base);
386 	if (res <= 0)
387 		return -ENOMEM;
388 
389 	nr_pages = DIV_ROUND_UP(res + base, PAGE_SIZE);
390 
391 	vec = __vec;
392 	if (nr_pages > PIPE_DEF_BUFFERS) {
393 		vec = kmalloc_array(nr_pages, sizeof(struct kvec), GFP_KERNEL);
394 		if (unlikely(!vec)) {
395 			res = -ENOMEM;
396 			goto out;
397 		}
398 	}
399 
400 	mask = pipe->ring_size - 1;
401 	pipe->bufs[to.head & mask].offset = offset;
402 	pipe->bufs[to.head & mask].len -= offset;
403 
404 	for (i = 0; i < nr_pages; i++) {
405 		size_t this_len = min_t(size_t, len, PAGE_SIZE - offset);
406 		vec[i].iov_base = page_address(pages[i]) + offset;
407 		vec[i].iov_len = this_len;
408 		len -= this_len;
409 		offset = 0;
410 	}
411 
412 	res = kernel_readv(in, vec, nr_pages, *ppos);
413 	if (res > 0) {
414 		copied = res;
415 		*ppos += res;
416 	}
417 
418 	if (vec != __vec)
419 		kfree(vec);
420 out:
421 	for (i = 0; i < nr_pages; i++)
422 		put_page(pages[i]);
423 	kvfree(pages);
424 	iov_iter_advance(&to, copied);	/* truncates and discards */
425 	return res;
426 }
427 
428 /*
429  * Send 'sd->len' bytes to socket from 'sd->file' at position 'sd->pos'
430  * using sendpage(). Return the number of bytes sent.
431  */
432 static int pipe_to_sendpage(struct pipe_inode_info *pipe,
433 			    struct pipe_buffer *buf, struct splice_desc *sd)
434 {
435 	struct file *file = sd->u.file;
436 	loff_t pos = sd->pos;
437 	int more;
438 
439 	if (!likely(file->f_op->sendpage))
440 		return -EINVAL;
441 
442 	more = (sd->flags & SPLICE_F_MORE) ? MSG_MORE : 0;
443 
444 	if (sd->len < sd->total_len &&
445 	    pipe_occupancy(pipe->head, pipe->tail) > 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 
452 static void wakeup_pipe_writers(struct pipe_inode_info *pipe)
453 {
454 	smp_mb();
455 	if (waitqueue_active(&pipe->wr_wait))
456 		wake_up_interruptible(&pipe->wr_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  */
480 static int splice_from_pipe_feed(struct pipe_inode_info *pipe, struct splice_desc *sd,
481 			  splice_actor *actor)
482 {
483 	unsigned int head = pipe->head;
484 	unsigned int tail = pipe->tail;
485 	unsigned int mask = pipe->ring_size - 1;
486 	int ret;
487 
488 	while (!pipe_empty(head, tail)) {
489 		struct pipe_buffer *buf = &pipe->bufs[tail & mask];
490 
491 		sd->len = buf->len;
492 		if (sd->len > sd->total_len)
493 			sd->len = sd->total_len;
494 
495 		ret = pipe_buf_confirm(pipe, buf);
496 		if (unlikely(ret)) {
497 			if (ret == -ENODATA)
498 				ret = 0;
499 			return ret;
500 		}
501 
502 		ret = actor(pipe, buf, sd);
503 		if (ret <= 0)
504 			return ret;
505 
506 		buf->offset += ret;
507 		buf->len -= ret;
508 
509 		sd->num_spliced += ret;
510 		sd->len -= ret;
511 		sd->pos += ret;
512 		sd->total_len -= ret;
513 
514 		if (!buf->len) {
515 			pipe_buf_release(pipe, buf);
516 			tail++;
517 			pipe->tail = tail;
518 			if (pipe->files)
519 				sd->need_wakeup = true;
520 		}
521 
522 		if (!sd->total_len)
523 			return 0;
524 	}
525 
526 	return 1;
527 }
528 
529 /**
530  * splice_from_pipe_next - wait for some data to splice from
531  * @pipe:	pipe to splice from
532  * @sd:		information about the splice operation
533  *
534  * Description:
535  *    This function will wait for some data and return a positive
536  *    value (one) if pipe buffers are available.  It will return zero
537  *    or -errno if no more data needs to be spliced.
538  */
539 static int splice_from_pipe_next(struct pipe_inode_info *pipe, struct splice_desc *sd)
540 {
541 	/*
542 	 * Check for signal early to make process killable when there are
543 	 * always buffers available
544 	 */
545 	if (signal_pending(current))
546 		return -ERESTARTSYS;
547 
548 	while (pipe_empty(pipe->head, pipe->tail)) {
549 		if (!pipe->writers)
550 			return 0;
551 
552 		if (sd->num_spliced)
553 			return 0;
554 
555 		if (sd->flags & SPLICE_F_NONBLOCK)
556 			return -EAGAIN;
557 
558 		if (signal_pending(current))
559 			return -ERESTARTSYS;
560 
561 		if (sd->need_wakeup) {
562 			wakeup_pipe_writers(pipe);
563 			sd->need_wakeup = false;
564 		}
565 
566 		pipe_wait(pipe);
567 	}
568 
569 	return 1;
570 }
571 
572 /**
573  * splice_from_pipe_begin - start splicing from pipe
574  * @sd:		information about the splice operation
575  *
576  * Description:
577  *    This function should be called before a loop containing
578  *    splice_from_pipe_next() and splice_from_pipe_feed() to
579  *    initialize the necessary fields of @sd.
580  */
581 static void splice_from_pipe_begin(struct splice_desc *sd)
582 {
583 	sd->num_spliced = 0;
584 	sd->need_wakeup = false;
585 }
586 
587 /**
588  * splice_from_pipe_end - finish splicing from pipe
589  * @pipe:	pipe to splice from
590  * @sd:		information about the splice operation
591  *
592  * Description:
593  *    This function will wake up pipe writers if necessary.  It should
594  *    be called after a loop containing splice_from_pipe_next() and
595  *    splice_from_pipe_feed().
596  */
597 static void splice_from_pipe_end(struct pipe_inode_info *pipe, struct splice_desc *sd)
598 {
599 	if (sd->need_wakeup)
600 		wakeup_pipe_writers(pipe);
601 }
602 
603 /**
604  * __splice_from_pipe - splice data from a pipe to given actor
605  * @pipe:	pipe to splice from
606  * @sd:		information to @actor
607  * @actor:	handler that splices the data
608  *
609  * Description:
610  *    This function does little more than loop over the pipe and call
611  *    @actor to do the actual moving of a single struct pipe_buffer to
612  *    the desired destination. See pipe_to_file, pipe_to_sendpage, or
613  *    pipe_to_user.
614  *
615  */
616 ssize_t __splice_from_pipe(struct pipe_inode_info *pipe, struct splice_desc *sd,
617 			   splice_actor *actor)
618 {
619 	int ret;
620 
621 	splice_from_pipe_begin(sd);
622 	do {
623 		cond_resched();
624 		ret = splice_from_pipe_next(pipe, sd);
625 		if (ret > 0)
626 			ret = splice_from_pipe_feed(pipe, sd, actor);
627 	} while (ret > 0);
628 	splice_from_pipe_end(pipe, sd);
629 
630 	return sd->num_spliced ? sd->num_spliced : ret;
631 }
632 EXPORT_SYMBOL(__splice_from_pipe);
633 
634 /**
635  * splice_from_pipe - splice data from a pipe to a file
636  * @pipe:	pipe to splice from
637  * @out:	file to splice to
638  * @ppos:	position in @out
639  * @len:	how many bytes to splice
640  * @flags:	splice modifier flags
641  * @actor:	handler that splices the data
642  *
643  * Description:
644  *    See __splice_from_pipe. This function locks the pipe inode,
645  *    otherwise it's identical to __splice_from_pipe().
646  *
647  */
648 ssize_t splice_from_pipe(struct pipe_inode_info *pipe, struct file *out,
649 			 loff_t *ppos, size_t len, unsigned int flags,
650 			 splice_actor *actor)
651 {
652 	ssize_t ret;
653 	struct splice_desc sd = {
654 		.total_len = len,
655 		.flags = flags,
656 		.pos = *ppos,
657 		.u.file = out,
658 	};
659 
660 	pipe_lock(pipe);
661 	ret = __splice_from_pipe(pipe, &sd, actor);
662 	pipe_unlock(pipe);
663 
664 	return ret;
665 }
666 
667 /**
668  * iter_file_splice_write - splice data from a pipe to a file
669  * @pipe:	pipe info
670  * @out:	file to write to
671  * @ppos:	position in @out
672  * @len:	number of bytes to splice
673  * @flags:	splice modifier flags
674  *
675  * Description:
676  *    Will either move or copy pages (determined by @flags options) from
677  *    the given pipe inode to the given file.
678  *    This one is ->write_iter-based.
679  *
680  */
681 ssize_t
682 iter_file_splice_write(struct pipe_inode_info *pipe, struct file *out,
683 			  loff_t *ppos, size_t len, unsigned int flags)
684 {
685 	struct splice_desc sd = {
686 		.total_len = len,
687 		.flags = flags,
688 		.pos = *ppos,
689 		.u.file = out,
690 	};
691 	int nbufs = pipe->max_usage;
692 	struct bio_vec *array = kcalloc(nbufs, sizeof(struct bio_vec),
693 					GFP_KERNEL);
694 	ssize_t ret;
695 
696 	if (unlikely(!array))
697 		return -ENOMEM;
698 
699 	pipe_lock(pipe);
700 
701 	splice_from_pipe_begin(&sd);
702 	while (sd.total_len) {
703 		struct iov_iter from;
704 		unsigned int head, tail, mask;
705 		size_t left;
706 		int n;
707 
708 		ret = splice_from_pipe_next(pipe, &sd);
709 		if (ret <= 0)
710 			break;
711 
712 		if (unlikely(nbufs < pipe->max_usage)) {
713 			kfree(array);
714 			nbufs = pipe->max_usage;
715 			array = kcalloc(nbufs, sizeof(struct bio_vec),
716 					GFP_KERNEL);
717 			if (!array) {
718 				ret = -ENOMEM;
719 				break;
720 			}
721 		}
722 
723 		head = pipe->head;
724 		tail = pipe->tail;
725 		mask = pipe->ring_size - 1;
726 
727 		/* build the vector */
728 		left = sd.total_len;
729 		for (n = 0; !pipe_empty(head, tail) && left && n < nbufs; tail++, n++) {
730 			struct pipe_buffer *buf = &pipe->bufs[tail & mask];
731 			size_t this_len = buf->len;
732 
733 			if (this_len > left)
734 				this_len = left;
735 
736 			ret = pipe_buf_confirm(pipe, buf);
737 			if (unlikely(ret)) {
738 				if (ret == -ENODATA)
739 					ret = 0;
740 				goto done;
741 			}
742 
743 			array[n].bv_page = buf->page;
744 			array[n].bv_len = this_len;
745 			array[n].bv_offset = buf->offset;
746 			left -= this_len;
747 		}
748 
749 		iov_iter_bvec(&from, WRITE, array, n, sd.total_len - left);
750 		ret = vfs_iter_write(out, &from, &sd.pos, 0);
751 		if (ret <= 0)
752 			break;
753 
754 		sd.num_spliced += ret;
755 		sd.total_len -= ret;
756 		*ppos = sd.pos;
757 
758 		/* dismiss the fully eaten buffers, adjust the partial one */
759 		tail = pipe->tail;
760 		while (ret) {
761 			struct pipe_buffer *buf = &pipe->bufs[tail & mask];
762 			if (ret >= buf->len) {
763 				ret -= buf->len;
764 				buf->len = 0;
765 				pipe_buf_release(pipe, buf);
766 				tail++;
767 				pipe->tail = tail;
768 				if (pipe->files)
769 					sd.need_wakeup = true;
770 			} else {
771 				buf->offset += ret;
772 				buf->len -= ret;
773 				ret = 0;
774 			}
775 		}
776 	}
777 done:
778 	kfree(array);
779 	splice_from_pipe_end(pipe, &sd);
780 
781 	pipe_unlock(pipe);
782 
783 	if (sd.num_spliced)
784 		ret = sd.num_spliced;
785 
786 	return ret;
787 }
788 
789 EXPORT_SYMBOL(iter_file_splice_write);
790 
791 static int write_pipe_buf(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
792 			  struct splice_desc *sd)
793 {
794 	int ret;
795 	void *data;
796 	loff_t tmp = sd->pos;
797 
798 	data = kmap(buf->page);
799 	ret = __kernel_write(sd->u.file, data + buf->offset, sd->len, &tmp);
800 	kunmap(buf->page);
801 
802 	return ret;
803 }
804 
805 static ssize_t default_file_splice_write(struct pipe_inode_info *pipe,
806 					 struct file *out, loff_t *ppos,
807 					 size_t len, unsigned int flags)
808 {
809 	ssize_t ret;
810 
811 	ret = splice_from_pipe(pipe, out, ppos, len, flags, write_pipe_buf);
812 	if (ret > 0)
813 		*ppos += ret;
814 
815 	return ret;
816 }
817 
818 /**
819  * generic_splice_sendpage - splice data from a pipe to a socket
820  * @pipe:	pipe to splice from
821  * @out:	socket to write to
822  * @ppos:	position in @out
823  * @len:	number of bytes to splice
824  * @flags:	splice modifier flags
825  *
826  * Description:
827  *    Will send @len bytes from the pipe to a network socket. No data copying
828  *    is involved.
829  *
830  */
831 ssize_t generic_splice_sendpage(struct pipe_inode_info *pipe, struct file *out,
832 				loff_t *ppos, size_t len, unsigned int flags)
833 {
834 	return splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_sendpage);
835 }
836 
837 EXPORT_SYMBOL(generic_splice_sendpage);
838 
839 /*
840  * Attempt to initiate a splice from pipe to file.
841  */
842 static long do_splice_from(struct pipe_inode_info *pipe, struct file *out,
843 			   loff_t *ppos, size_t len, unsigned int flags)
844 {
845 	if (out->f_op->splice_write)
846 		return out->f_op->splice_write(pipe, out, ppos, len, flags);
847 	return default_file_splice_write(pipe, out, ppos, len, flags);
848 }
849 
850 /*
851  * Attempt to initiate a splice from a file to a pipe.
852  */
853 static 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 	int ret;
858 
859 	if (unlikely(!(in->f_mode & FMODE_READ)))
860 		return -EBADF;
861 
862 	ret = rw_verify_area(READ, in, ppos, len);
863 	if (unlikely(ret < 0))
864 		return ret;
865 
866 	if (unlikely(len > MAX_RW_COUNT))
867 		len = MAX_RW_COUNT;
868 
869 	if (in->f_op->splice_read)
870 		return in->f_op->splice_read(in, ppos, pipe, len, flags);
871 	return default_file_splice_read(in, ppos, pipe, len, flags);
872 }
873 
874 /**
875  * splice_direct_to_actor - splices data directly between two non-pipes
876  * @in:		file to splice from
877  * @sd:		actor information on where to splice to
878  * @actor:	handles the data splicing
879  *
880  * Description:
881  *    This is a special case helper to splice directly between two
882  *    points, without requiring an explicit pipe. Internally an allocated
883  *    pipe is cached in the process, and reused during the lifetime of
884  *    that process.
885  *
886  */
887 ssize_t splice_direct_to_actor(struct file *in, struct splice_desc *sd,
888 			       splice_direct_actor *actor)
889 {
890 	struct pipe_inode_info *pipe;
891 	long ret, bytes;
892 	umode_t i_mode;
893 	size_t len;
894 	int i, flags, more;
895 
896 	/*
897 	 * We require the input being a regular file, as we don't want to
898 	 * randomly drop data for eg socket -> socket splicing. Use the
899 	 * piped splicing for that!
900 	 */
901 	i_mode = file_inode(in)->i_mode;
902 	if (unlikely(!S_ISREG(i_mode) && !S_ISBLK(i_mode)))
903 		return -EINVAL;
904 
905 	/*
906 	 * neither in nor out is a pipe, setup an internal pipe attached to
907 	 * 'out' and transfer the wanted data from 'in' to 'out' through that
908 	 */
909 	pipe = current->splice_pipe;
910 	if (unlikely(!pipe)) {
911 		pipe = alloc_pipe_info();
912 		if (!pipe)
913 			return -ENOMEM;
914 
915 		/*
916 		 * We don't have an immediate reader, but we'll read the stuff
917 		 * out of the pipe right after the splice_to_pipe(). So set
918 		 * PIPE_READERS appropriately.
919 		 */
920 		pipe->readers = 1;
921 
922 		current->splice_pipe = pipe;
923 	}
924 
925 	/*
926 	 * Do the splice.
927 	 */
928 	ret = 0;
929 	bytes = 0;
930 	len = sd->total_len;
931 	flags = sd->flags;
932 
933 	/*
934 	 * Don't block on output, we have to drain the direct pipe.
935 	 */
936 	sd->flags &= ~SPLICE_F_NONBLOCK;
937 	more = sd->flags & SPLICE_F_MORE;
938 
939 	WARN_ON_ONCE(!pipe_empty(pipe->head, pipe->tail));
940 
941 	while (len) {
942 		unsigned int p_space;
943 		size_t read_len;
944 		loff_t pos = sd->pos, prev_pos = pos;
945 
946 		/* Don't try to read more the pipe has space for. */
947 		p_space = pipe->max_usage -
948 			pipe_occupancy(pipe->head, pipe->tail);
949 		read_len = min_t(size_t, len, p_space << PAGE_SHIFT);
950 		ret = do_splice_to(in, &pos, pipe, read_len, flags);
951 		if (unlikely(ret <= 0))
952 			goto out_release;
953 
954 		read_len = ret;
955 		sd->total_len = read_len;
956 
957 		/*
958 		 * If more data is pending, set SPLICE_F_MORE
959 		 * If this is the last data and SPLICE_F_MORE was not set
960 		 * initially, clears it.
961 		 */
962 		if (read_len < len)
963 			sd->flags |= SPLICE_F_MORE;
964 		else if (!more)
965 			sd->flags &= ~SPLICE_F_MORE;
966 		/*
967 		 * NOTE: nonblocking mode only applies to the input. We
968 		 * must not do the output in nonblocking mode as then we
969 		 * could get stuck data in the internal pipe:
970 		 */
971 		ret = actor(pipe, sd);
972 		if (unlikely(ret <= 0)) {
973 			sd->pos = prev_pos;
974 			goto out_release;
975 		}
976 
977 		bytes += ret;
978 		len -= ret;
979 		sd->pos = pos;
980 
981 		if (ret < read_len) {
982 			sd->pos = prev_pos + ret;
983 			goto out_release;
984 		}
985 	}
986 
987 done:
988 	pipe->tail = pipe->head = 0;
989 	file_accessed(in);
990 	return bytes;
991 
992 out_release:
993 	/*
994 	 * If we did an incomplete transfer we must release
995 	 * the pipe buffers in question:
996 	 */
997 	for (i = 0; i < pipe->ring_size; i++) {
998 		struct pipe_buffer *buf = &pipe->bufs[i];
999 
1000 		if (buf->ops)
1001 			pipe_buf_release(pipe, buf);
1002 	}
1003 
1004 	if (!bytes)
1005 		bytes = ret;
1006 
1007 	goto done;
1008 }
1009 EXPORT_SYMBOL(splice_direct_to_actor);
1010 
1011 static int direct_splice_actor(struct pipe_inode_info *pipe,
1012 			       struct splice_desc *sd)
1013 {
1014 	struct file *file = sd->u.file;
1015 
1016 	return do_splice_from(pipe, file, sd->opos, sd->total_len,
1017 			      sd->flags);
1018 }
1019 
1020 /**
1021  * do_splice_direct - splices data directly between two files
1022  * @in:		file to splice from
1023  * @ppos:	input file offset
1024  * @out:	file to splice to
1025  * @opos:	output file offset
1026  * @len:	number of bytes to splice
1027  * @flags:	splice modifier flags
1028  *
1029  * Description:
1030  *    For use by do_sendfile(). splice can easily emulate sendfile, but
1031  *    doing it in the application would incur an extra system call
1032  *    (splice in + splice out, as compared to just sendfile()). So this helper
1033  *    can splice directly through a process-private pipe.
1034  *
1035  */
1036 long do_splice_direct(struct file *in, loff_t *ppos, struct file *out,
1037 		      loff_t *opos, size_t len, unsigned int flags)
1038 {
1039 	struct splice_desc sd = {
1040 		.len		= len,
1041 		.total_len	= len,
1042 		.flags		= flags,
1043 		.pos		= *ppos,
1044 		.u.file		= out,
1045 		.opos		= opos,
1046 	};
1047 	long ret;
1048 
1049 	if (unlikely(!(out->f_mode & FMODE_WRITE)))
1050 		return -EBADF;
1051 
1052 	if (unlikely(out->f_flags & O_APPEND))
1053 		return -EINVAL;
1054 
1055 	ret = rw_verify_area(WRITE, out, opos, len);
1056 	if (unlikely(ret < 0))
1057 		return ret;
1058 
1059 	ret = splice_direct_to_actor(in, &sd, direct_splice_actor);
1060 	if (ret > 0)
1061 		*ppos = sd.pos;
1062 
1063 	return ret;
1064 }
1065 EXPORT_SYMBOL(do_splice_direct);
1066 
1067 static int wait_for_space(struct pipe_inode_info *pipe, unsigned flags)
1068 {
1069 	for (;;) {
1070 		if (unlikely(!pipe->readers)) {
1071 			send_sig(SIGPIPE, current, 0);
1072 			return -EPIPE;
1073 		}
1074 		if (!pipe_full(pipe->head, pipe->tail, pipe->max_usage))
1075 			return 0;
1076 		if (flags & SPLICE_F_NONBLOCK)
1077 			return -EAGAIN;
1078 		if (signal_pending(current))
1079 			return -ERESTARTSYS;
1080 		pipe_wait(pipe);
1081 	}
1082 }
1083 
1084 static int splice_pipe_to_pipe(struct pipe_inode_info *ipipe,
1085 			       struct pipe_inode_info *opipe,
1086 			       size_t len, unsigned int flags);
1087 
1088 /*
1089  * Determine where to splice to/from.
1090  */
1091 long do_splice(struct file *in, loff_t __user *off_in,
1092 		struct file *out, loff_t __user *off_out,
1093 		size_t len, unsigned int flags)
1094 {
1095 	struct pipe_inode_info *ipipe;
1096 	struct pipe_inode_info *opipe;
1097 	loff_t offset;
1098 	long ret;
1099 
1100 	if (unlikely(!(in->f_mode & FMODE_READ) ||
1101 		     !(out->f_mode & FMODE_WRITE)))
1102 		return -EBADF;
1103 
1104 	ipipe = get_pipe_info(in, true);
1105 	opipe = get_pipe_info(out, true);
1106 
1107 	if (ipipe && opipe) {
1108 		if (off_in || off_out)
1109 			return -ESPIPE;
1110 
1111 		/* Splicing to self would be fun, but... */
1112 		if (ipipe == opipe)
1113 			return -EINVAL;
1114 
1115 		if ((in->f_flags | out->f_flags) & O_NONBLOCK)
1116 			flags |= SPLICE_F_NONBLOCK;
1117 
1118 		return splice_pipe_to_pipe(ipipe, opipe, len, flags);
1119 	}
1120 
1121 	if (ipipe) {
1122 		if (off_in)
1123 			return -ESPIPE;
1124 		if (off_out) {
1125 			if (!(out->f_mode & FMODE_PWRITE))
1126 				return -EINVAL;
1127 			if (copy_from_user(&offset, off_out, sizeof(loff_t)))
1128 				return -EFAULT;
1129 		} else {
1130 			offset = out->f_pos;
1131 		}
1132 
1133 		if (unlikely(out->f_flags & O_APPEND))
1134 			return -EINVAL;
1135 
1136 		ret = rw_verify_area(WRITE, out, &offset, len);
1137 		if (unlikely(ret < 0))
1138 			return ret;
1139 
1140 		if (in->f_flags & O_NONBLOCK)
1141 			flags |= SPLICE_F_NONBLOCK;
1142 
1143 		file_start_write(out);
1144 		ret = do_splice_from(ipipe, out, &offset, len, flags);
1145 		file_end_write(out);
1146 
1147 		if (!off_out)
1148 			out->f_pos = offset;
1149 		else if (copy_to_user(off_out, &offset, sizeof(loff_t)))
1150 			ret = -EFAULT;
1151 
1152 		return ret;
1153 	}
1154 
1155 	if (opipe) {
1156 		if (off_out)
1157 			return -ESPIPE;
1158 		if (off_in) {
1159 			if (!(in->f_mode & FMODE_PREAD))
1160 				return -EINVAL;
1161 			if (copy_from_user(&offset, off_in, sizeof(loff_t)))
1162 				return -EFAULT;
1163 		} else {
1164 			offset = in->f_pos;
1165 		}
1166 
1167 		if (out->f_flags & O_NONBLOCK)
1168 			flags |= SPLICE_F_NONBLOCK;
1169 
1170 		pipe_lock(opipe);
1171 		ret = wait_for_space(opipe, flags);
1172 		if (!ret) {
1173 			unsigned int p_space;
1174 
1175 			/* Don't try to read more the pipe has space for. */
1176 			p_space = opipe->max_usage - pipe_occupancy(opipe->head, opipe->tail);
1177 			len = min_t(size_t, len, p_space << PAGE_SHIFT);
1178 
1179 			ret = do_splice_to(in, &offset, opipe, len, flags);
1180 		}
1181 		pipe_unlock(opipe);
1182 		if (ret > 0)
1183 			wakeup_pipe_readers(opipe);
1184 		if (!off_in)
1185 			in->f_pos = offset;
1186 		else if (copy_to_user(off_in, &offset, sizeof(loff_t)))
1187 			ret = -EFAULT;
1188 
1189 		return ret;
1190 	}
1191 
1192 	return -EINVAL;
1193 }
1194 
1195 static int iter_to_pipe(struct iov_iter *from,
1196 			struct pipe_inode_info *pipe,
1197 			unsigned flags)
1198 {
1199 	struct pipe_buffer buf = {
1200 		.ops = &user_page_pipe_buf_ops,
1201 		.flags = flags
1202 	};
1203 	size_t total = 0;
1204 	int ret = 0;
1205 	bool failed = false;
1206 
1207 	while (iov_iter_count(from) && !failed) {
1208 		struct page *pages[16];
1209 		ssize_t copied;
1210 		size_t start;
1211 		int n;
1212 
1213 		copied = iov_iter_get_pages(from, pages, ~0UL, 16, &start);
1214 		if (copied <= 0) {
1215 			ret = copied;
1216 			break;
1217 		}
1218 
1219 		for (n = 0; copied; n++, start = 0) {
1220 			int size = min_t(int, copied, PAGE_SIZE - start);
1221 			if (!failed) {
1222 				buf.page = pages[n];
1223 				buf.offset = start;
1224 				buf.len = size;
1225 				ret = add_to_pipe(pipe, &buf);
1226 				if (unlikely(ret < 0)) {
1227 					failed = true;
1228 				} else {
1229 					iov_iter_advance(from, ret);
1230 					total += ret;
1231 				}
1232 			} else {
1233 				put_page(pages[n]);
1234 			}
1235 			copied -= size;
1236 		}
1237 	}
1238 	return total ? total : ret;
1239 }
1240 
1241 static int pipe_to_user(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
1242 			struct splice_desc *sd)
1243 {
1244 	int n = copy_page_to_iter(buf->page, buf->offset, sd->len, sd->u.data);
1245 	return n == sd->len ? n : -EFAULT;
1246 }
1247 
1248 /*
1249  * For lack of a better implementation, implement vmsplice() to userspace
1250  * as a simple copy of the pipes pages to the user iov.
1251  */
1252 static long vmsplice_to_user(struct file *file, struct iov_iter *iter,
1253 			     unsigned int flags)
1254 {
1255 	struct pipe_inode_info *pipe = get_pipe_info(file, true);
1256 	struct splice_desc sd = {
1257 		.total_len = iov_iter_count(iter),
1258 		.flags = flags,
1259 		.u.data = iter
1260 	};
1261 	long ret = 0;
1262 
1263 	if (!pipe)
1264 		return -EBADF;
1265 
1266 	if (sd.total_len) {
1267 		pipe_lock(pipe);
1268 		ret = __splice_from_pipe(pipe, &sd, pipe_to_user);
1269 		pipe_unlock(pipe);
1270 	}
1271 
1272 	return ret;
1273 }
1274 
1275 /*
1276  * vmsplice splices a user address range into a pipe. It can be thought of
1277  * as splice-from-memory, where the regular splice is splice-from-file (or
1278  * to file). In both cases the output is a pipe, naturally.
1279  */
1280 static long vmsplice_to_pipe(struct file *file, struct iov_iter *iter,
1281 			     unsigned int flags)
1282 {
1283 	struct pipe_inode_info *pipe;
1284 	long ret = 0;
1285 	unsigned buf_flag = 0;
1286 
1287 	if (flags & SPLICE_F_GIFT)
1288 		buf_flag = PIPE_BUF_FLAG_GIFT;
1289 
1290 	pipe = get_pipe_info(file, true);
1291 	if (!pipe)
1292 		return -EBADF;
1293 
1294 	pipe_lock(pipe);
1295 	ret = wait_for_space(pipe, flags);
1296 	if (!ret)
1297 		ret = iter_to_pipe(iter, pipe, buf_flag);
1298 	pipe_unlock(pipe);
1299 	if (ret > 0)
1300 		wakeup_pipe_readers(pipe);
1301 	return ret;
1302 }
1303 
1304 static int vmsplice_type(struct fd f, int *type)
1305 {
1306 	if (!f.file)
1307 		return -EBADF;
1308 	if (f.file->f_mode & FMODE_WRITE) {
1309 		*type = WRITE;
1310 	} else if (f.file->f_mode & FMODE_READ) {
1311 		*type = READ;
1312 	} else {
1313 		fdput(f);
1314 		return -EBADF;
1315 	}
1316 	return 0;
1317 }
1318 
1319 /*
1320  * Note that vmsplice only really supports true splicing _from_ user memory
1321  * to a pipe, not the other way around. Splicing from user memory is a simple
1322  * operation that can be supported without any funky alignment restrictions
1323  * or nasty vm tricks. We simply map in the user memory and fill them into
1324  * a pipe. The reverse isn't quite as easy, though. There are two possible
1325  * solutions for that:
1326  *
1327  *	- memcpy() the data internally, at which point we might as well just
1328  *	  do a regular read() on the buffer anyway.
1329  *	- Lots of nasty vm tricks, that are neither fast nor flexible (it
1330  *	  has restriction limitations on both ends of the pipe).
1331  *
1332  * Currently we punt and implement it as a normal copy, see pipe_to_user().
1333  *
1334  */
1335 static long do_vmsplice(struct file *f, struct iov_iter *iter, unsigned int flags)
1336 {
1337 	if (unlikely(flags & ~SPLICE_F_ALL))
1338 		return -EINVAL;
1339 
1340 	if (!iov_iter_count(iter))
1341 		return 0;
1342 
1343 	if (iov_iter_rw(iter) == WRITE)
1344 		return vmsplice_to_pipe(f, iter, flags);
1345 	else
1346 		return vmsplice_to_user(f, iter, flags);
1347 }
1348 
1349 SYSCALL_DEFINE4(vmsplice, int, fd, const struct iovec __user *, uiov,
1350 		unsigned long, nr_segs, unsigned int, flags)
1351 {
1352 	struct iovec iovstack[UIO_FASTIOV];
1353 	struct iovec *iov = iovstack;
1354 	struct iov_iter iter;
1355 	ssize_t error;
1356 	struct fd f;
1357 	int type;
1358 
1359 	f = fdget(fd);
1360 	error = vmsplice_type(f, &type);
1361 	if (error)
1362 		return error;
1363 
1364 	error = import_iovec(type, uiov, nr_segs,
1365 			     ARRAY_SIZE(iovstack), &iov, &iter);
1366 	if (error >= 0) {
1367 		error = do_vmsplice(f.file, &iter, flags);
1368 		kfree(iov);
1369 	}
1370 	fdput(f);
1371 	return error;
1372 }
1373 
1374 #ifdef CONFIG_COMPAT
1375 COMPAT_SYSCALL_DEFINE4(vmsplice, int, fd, const struct compat_iovec __user *, iov32,
1376 		    unsigned int, nr_segs, unsigned int, flags)
1377 {
1378 	struct iovec iovstack[UIO_FASTIOV];
1379 	struct iovec *iov = iovstack;
1380 	struct iov_iter iter;
1381 	ssize_t error;
1382 	struct fd f;
1383 	int type;
1384 
1385 	f = fdget(fd);
1386 	error = vmsplice_type(f, &type);
1387 	if (error)
1388 		return error;
1389 
1390 	error = compat_import_iovec(type, iov32, nr_segs,
1391 			     ARRAY_SIZE(iovstack), &iov, &iter);
1392 	if (error >= 0) {
1393 		error = do_vmsplice(f.file, &iter, flags);
1394 		kfree(iov);
1395 	}
1396 	fdput(f);
1397 	return error;
1398 }
1399 #endif
1400 
1401 SYSCALL_DEFINE6(splice, int, fd_in, loff_t __user *, off_in,
1402 		int, fd_out, loff_t __user *, off_out,
1403 		size_t, len, unsigned int, flags)
1404 {
1405 	struct fd in, out;
1406 	long error;
1407 
1408 	if (unlikely(!len))
1409 		return 0;
1410 
1411 	if (unlikely(flags & ~SPLICE_F_ALL))
1412 		return -EINVAL;
1413 
1414 	error = -EBADF;
1415 	in = fdget(fd_in);
1416 	if (in.file) {
1417 		out = fdget(fd_out);
1418 		if (out.file) {
1419 			error = do_splice(in.file, off_in, out.file, off_out,
1420 					  len, flags);
1421 			fdput(out);
1422 		}
1423 		fdput(in);
1424 	}
1425 	return error;
1426 }
1427 
1428 /*
1429  * Make sure there's data to read. Wait for input if we can, otherwise
1430  * return an appropriate error.
1431  */
1432 static int ipipe_prep(struct pipe_inode_info *pipe, unsigned int flags)
1433 {
1434 	int ret;
1435 
1436 	/*
1437 	 * Check the pipe occupancy without the inode lock first. This function
1438 	 * is speculative anyways, so missing one is ok.
1439 	 */
1440 	if (!pipe_empty(pipe->head, pipe->tail))
1441 		return 0;
1442 
1443 	ret = 0;
1444 	pipe_lock(pipe);
1445 
1446 	while (pipe_empty(pipe->head, pipe->tail)) {
1447 		if (signal_pending(current)) {
1448 			ret = -ERESTARTSYS;
1449 			break;
1450 		}
1451 		if (!pipe->writers)
1452 			break;
1453 		if (flags & SPLICE_F_NONBLOCK) {
1454 			ret = -EAGAIN;
1455 			break;
1456 		}
1457 		pipe_wait(pipe);
1458 	}
1459 
1460 	pipe_unlock(pipe);
1461 	return ret;
1462 }
1463 
1464 /*
1465  * Make sure there's writeable room. Wait for room if we can, otherwise
1466  * return an appropriate error.
1467  */
1468 static int opipe_prep(struct pipe_inode_info *pipe, unsigned int flags)
1469 {
1470 	int ret;
1471 
1472 	/*
1473 	 * Check pipe occupancy without the inode lock first. This function
1474 	 * is speculative anyways, so missing one is ok.
1475 	 */
1476 	if (!pipe_full(pipe->head, pipe->tail, pipe->max_usage))
1477 		return 0;
1478 
1479 	ret = 0;
1480 	pipe_lock(pipe);
1481 
1482 	while (pipe_full(pipe->head, pipe->tail, pipe->max_usage)) {
1483 		if (!pipe->readers) {
1484 			send_sig(SIGPIPE, current, 0);
1485 			ret = -EPIPE;
1486 			break;
1487 		}
1488 		if (flags & SPLICE_F_NONBLOCK) {
1489 			ret = -EAGAIN;
1490 			break;
1491 		}
1492 		if (signal_pending(current)) {
1493 			ret = -ERESTARTSYS;
1494 			break;
1495 		}
1496 		pipe_wait(pipe);
1497 	}
1498 
1499 	pipe_unlock(pipe);
1500 	return ret;
1501 }
1502 
1503 /*
1504  * Splice contents of ipipe to opipe.
1505  */
1506 static int splice_pipe_to_pipe(struct pipe_inode_info *ipipe,
1507 			       struct pipe_inode_info *opipe,
1508 			       size_t len, unsigned int flags)
1509 {
1510 	struct pipe_buffer *ibuf, *obuf;
1511 	unsigned int i_head, o_head;
1512 	unsigned int i_tail, o_tail;
1513 	unsigned int i_mask, o_mask;
1514 	int ret = 0;
1515 	bool input_wakeup = false;
1516 
1517 
1518 retry:
1519 	ret = ipipe_prep(ipipe, flags);
1520 	if (ret)
1521 		return ret;
1522 
1523 	ret = opipe_prep(opipe, flags);
1524 	if (ret)
1525 		return ret;
1526 
1527 	/*
1528 	 * Potential ABBA deadlock, work around it by ordering lock
1529 	 * grabbing by pipe info address. Otherwise two different processes
1530 	 * could deadlock (one doing tee from A -> B, the other from B -> A).
1531 	 */
1532 	pipe_double_lock(ipipe, opipe);
1533 
1534 	i_tail = ipipe->tail;
1535 	i_mask = ipipe->ring_size - 1;
1536 	o_head = opipe->head;
1537 	o_mask = opipe->ring_size - 1;
1538 
1539 	do {
1540 		size_t o_len;
1541 
1542 		if (!opipe->readers) {
1543 			send_sig(SIGPIPE, current, 0);
1544 			if (!ret)
1545 				ret = -EPIPE;
1546 			break;
1547 		}
1548 
1549 		i_head = ipipe->head;
1550 		o_tail = opipe->tail;
1551 
1552 		if (pipe_empty(i_head, i_tail) && !ipipe->writers)
1553 			break;
1554 
1555 		/*
1556 		 * Cannot make any progress, because either the input
1557 		 * pipe is empty or the output pipe is full.
1558 		 */
1559 		if (pipe_empty(i_head, i_tail) ||
1560 		    pipe_full(o_head, o_tail, opipe->max_usage)) {
1561 			/* Already processed some buffers, break */
1562 			if (ret)
1563 				break;
1564 
1565 			if (flags & SPLICE_F_NONBLOCK) {
1566 				ret = -EAGAIN;
1567 				break;
1568 			}
1569 
1570 			/*
1571 			 * We raced with another reader/writer and haven't
1572 			 * managed to process any buffers.  A zero return
1573 			 * value means EOF, so retry instead.
1574 			 */
1575 			pipe_unlock(ipipe);
1576 			pipe_unlock(opipe);
1577 			goto retry;
1578 		}
1579 
1580 		ibuf = &ipipe->bufs[i_tail & i_mask];
1581 		obuf = &opipe->bufs[o_head & o_mask];
1582 
1583 		if (len >= ibuf->len) {
1584 			/*
1585 			 * Simply move the whole buffer from ipipe to opipe
1586 			 */
1587 			*obuf = *ibuf;
1588 			ibuf->ops = NULL;
1589 			i_tail++;
1590 			ipipe->tail = i_tail;
1591 			input_wakeup = true;
1592 			o_len = obuf->len;
1593 			o_head++;
1594 			opipe->head = o_head;
1595 		} else {
1596 			/*
1597 			 * Get a reference to this pipe buffer,
1598 			 * so we can copy the contents over.
1599 			 */
1600 			if (!pipe_buf_get(ipipe, ibuf)) {
1601 				if (ret == 0)
1602 					ret = -EFAULT;
1603 				break;
1604 			}
1605 			*obuf = *ibuf;
1606 
1607 			/*
1608 			 * Don't inherit the gift and merge flags, we need to
1609 			 * prevent multiple steals of this page.
1610 			 */
1611 			obuf->flags &= ~PIPE_BUF_FLAG_GIFT;
1612 			obuf->flags &= ~PIPE_BUF_FLAG_CAN_MERGE;
1613 
1614 			obuf->len = len;
1615 			ibuf->offset += len;
1616 			ibuf->len -= len;
1617 			o_len = len;
1618 			o_head++;
1619 			opipe->head = o_head;
1620 		}
1621 		ret += o_len;
1622 		len -= o_len;
1623 	} while (len);
1624 
1625 	pipe_unlock(ipipe);
1626 	pipe_unlock(opipe);
1627 
1628 	/*
1629 	 * If we put data in the output pipe, wakeup any potential readers.
1630 	 */
1631 	if (ret > 0)
1632 		wakeup_pipe_readers(opipe);
1633 
1634 	if (input_wakeup)
1635 		wakeup_pipe_writers(ipipe);
1636 
1637 	return ret;
1638 }
1639 
1640 /*
1641  * Link contents of ipipe to opipe.
1642  */
1643 static int link_pipe(struct pipe_inode_info *ipipe,
1644 		     struct pipe_inode_info *opipe,
1645 		     size_t len, unsigned int flags)
1646 {
1647 	struct pipe_buffer *ibuf, *obuf;
1648 	unsigned int i_head, o_head;
1649 	unsigned int i_tail, o_tail;
1650 	unsigned int i_mask, o_mask;
1651 	int ret = 0;
1652 
1653 	/*
1654 	 * Potential ABBA deadlock, work around it by ordering lock
1655 	 * grabbing by pipe info address. Otherwise two different processes
1656 	 * could deadlock (one doing tee from A -> B, the other from B -> A).
1657 	 */
1658 	pipe_double_lock(ipipe, opipe);
1659 
1660 	i_tail = ipipe->tail;
1661 	i_mask = ipipe->ring_size - 1;
1662 	o_head = opipe->head;
1663 	o_mask = opipe->ring_size - 1;
1664 
1665 	do {
1666 		if (!opipe->readers) {
1667 			send_sig(SIGPIPE, current, 0);
1668 			if (!ret)
1669 				ret = -EPIPE;
1670 			break;
1671 		}
1672 
1673 		i_head = ipipe->head;
1674 		o_tail = opipe->tail;
1675 
1676 		/*
1677 		 * If we have iterated all input buffers or run out of
1678 		 * output room, break.
1679 		 */
1680 		if (pipe_empty(i_head, i_tail) ||
1681 		    pipe_full(o_head, o_tail, opipe->max_usage))
1682 			break;
1683 
1684 		ibuf = &ipipe->bufs[i_tail & i_mask];
1685 		obuf = &opipe->bufs[o_head & o_mask];
1686 
1687 		/*
1688 		 * Get a reference to this pipe buffer,
1689 		 * so we can copy the contents over.
1690 		 */
1691 		if (!pipe_buf_get(ipipe, ibuf)) {
1692 			if (ret == 0)
1693 				ret = -EFAULT;
1694 			break;
1695 		}
1696 
1697 		*obuf = *ibuf;
1698 
1699 		/*
1700 		 * Don't inherit the gift and merge flag, we need to prevent
1701 		 * multiple steals of this page.
1702 		 */
1703 		obuf->flags &= ~PIPE_BUF_FLAG_GIFT;
1704 		obuf->flags &= ~PIPE_BUF_FLAG_CAN_MERGE;
1705 
1706 		if (obuf->len > len)
1707 			obuf->len = len;
1708 		ret += obuf->len;
1709 		len -= obuf->len;
1710 
1711 		o_head++;
1712 		opipe->head = o_head;
1713 		i_tail++;
1714 	} while (len);
1715 
1716 	pipe_unlock(ipipe);
1717 	pipe_unlock(opipe);
1718 
1719 	/*
1720 	 * If we put data in the output pipe, wakeup any potential readers.
1721 	 */
1722 	if (ret > 0)
1723 		wakeup_pipe_readers(opipe);
1724 
1725 	return ret;
1726 }
1727 
1728 /*
1729  * This is a tee(1) implementation that works on pipes. It doesn't copy
1730  * any data, it simply references the 'in' pages on the 'out' pipe.
1731  * The 'flags' used are the SPLICE_F_* variants, currently the only
1732  * applicable one is SPLICE_F_NONBLOCK.
1733  */
1734 long do_tee(struct file *in, struct file *out, size_t len, unsigned int flags)
1735 {
1736 	struct pipe_inode_info *ipipe = get_pipe_info(in, true);
1737 	struct pipe_inode_info *opipe = get_pipe_info(out, true);
1738 	int ret = -EINVAL;
1739 
1740 	if (unlikely(!(in->f_mode & FMODE_READ) ||
1741 		     !(out->f_mode & FMODE_WRITE)))
1742 		return -EBADF;
1743 
1744 	/*
1745 	 * Duplicate the contents of ipipe to opipe without actually
1746 	 * copying the data.
1747 	 */
1748 	if (ipipe && opipe && ipipe != opipe) {
1749 		if ((in->f_flags | out->f_flags) & O_NONBLOCK)
1750 			flags |= SPLICE_F_NONBLOCK;
1751 
1752 		/*
1753 		 * Keep going, unless we encounter an error. The ipipe/opipe
1754 		 * ordering doesn't really matter.
1755 		 */
1756 		ret = ipipe_prep(ipipe, flags);
1757 		if (!ret) {
1758 			ret = opipe_prep(opipe, flags);
1759 			if (!ret)
1760 				ret = link_pipe(ipipe, opipe, len, flags);
1761 		}
1762 	}
1763 
1764 	return ret;
1765 }
1766 
1767 SYSCALL_DEFINE4(tee, int, fdin, int, fdout, size_t, len, unsigned int, flags)
1768 {
1769 	struct fd in, out;
1770 	int error;
1771 
1772 	if (unlikely(flags & ~SPLICE_F_ALL))
1773 		return -EINVAL;
1774 
1775 	if (unlikely(!len))
1776 		return 0;
1777 
1778 	error = -EBADF;
1779 	in = fdget(fdin);
1780 	if (in.file) {
1781 		out = fdget(fdout);
1782 		if (out.file) {
1783 			error = do_tee(in.file, out.file, len, flags);
1784 			fdput(out);
1785 		}
1786  		fdput(in);
1787  	}
1788 
1789 	return error;
1790 }
1791