xref: /openbmc/linux/fs/splice.c (revision 151f4e2b)
1 /*
2  * "splice": joining two ropes together by interweaving their strands.
3  *
4  * This is the "extended pipe" functionality, where a pipe is used as
5  * an arbitrary in-memory buffer. Think of a pipe as a small kernel
6  * buffer that you can use to transfer data from one end to the other.
7  *
8  * The traditional unix read/write is extended with a "splice()" operation
9  * that transfers data buffers to or from a pipe buffer.
10  *
11  * Named by Larry McVoy, original implementation from Linus, extended by
12  * Jens to support splicing to files, network, direct splicing, etc and
13  * fixing lots of bugs.
14  *
15  * Copyright (C) 2005-2006 Jens Axboe <axboe@kernel.dk>
16  * Copyright (C) 2005-2006 Linus Torvalds <torvalds@osdl.org>
17  * Copyright (C) 2006 Ingo Molnar <mingo@elte.hu>
18  *
19  */
20 #include <linux/bvec.h>
21 #include <linux/fs.h>
22 #include <linux/file.h>
23 #include <linux/pagemap.h>
24 #include <linux/splice.h>
25 #include <linux/memcontrol.h>
26 #include <linux/mm_inline.h>
27 #include <linux/swap.h>
28 #include <linux/writeback.h>
29 #include <linux/export.h>
30 #include <linux/syscalls.h>
31 #include <linux/uio.h>
32 #include <linux/security.h>
33 #include <linux/gfp.h>
34 #include <linux/socket.h>
35 #include <linux/compat.h>
36 #include <linux/sched/signal.h>
37 
38 #include "internal.h"
39 
40 /*
41  * Attempt to steal a page from a pipe buffer. This should perhaps go into
42  * a vm helper function, it's already simplified quite a bit by the
43  * addition of remove_mapping(). If success is returned, the caller may
44  * attempt to reuse this page for another destination.
45  */
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;
51 
52 	lock_page(page);
53 
54 	mapping = page_mapping(page);
55 	if (mapping) {
56 		WARN_ON(!PageUptodate(page));
57 
58 		/*
59 		 * At least for ext2 with nobh option, we need to wait on
60 		 * writeback completing on this page, since we'll remove it
61 		 * from the pagecache.  Otherwise truncate wont wait on the
62 		 * page, allowing the disk blocks to be reused by someone else
63 		 * before we actually wrote our data to them. fs corruption
64 		 * ensues.
65 		 */
66 		wait_on_page_writeback(page);
67 
68 		if (page_has_private(page) &&
69 		    !try_to_release_page(page, GFP_KERNEL))
70 			goto out_unlock;
71 
72 		/*
73 		 * If we succeeded in removing the mapping, set LRU flag
74 		 * and return good.
75 		 */
76 		if (remove_mapping(mapping, page)) {
77 			buf->flags |= PIPE_BUF_FLAG_LRU;
78 			return 0;
79 		}
80 	}
81 
82 	/*
83 	 * Raced with truncate or failed to remove page from current
84 	 * address space, unlock and return failure.
85 	 */
86 out_unlock:
87 	unlock_page(page);
88 	return 1;
89 }
90 
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 }
97 
98 /*
99  * Check whether the contents of buf is OK to access. Since the content
100  * is a page cache page, IO may be in flight.
101  */
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;
107 
108 	if (!PageUptodate(page)) {
109 		lock_page(page);
110 
111 		/*
112 		 * Page got truncated/unhashed. This will cause a 0-byte
113 		 * splice, if this is the first page.
114 		 */
115 		if (!page->mapping) {
116 			err = -ENODATA;
117 			goto error;
118 		}
119 
120 		/*
121 		 * Uh oh, read-error from disk.
122 		 */
123 		if (!PageUptodate(page)) {
124 			err = -EIO;
125 			goto error;
126 		}
127 
128 		/*
129 		 * Page is ok afterall, we are done.
130 		 */
131 		unlock_page(page);
132 	}
133 
134 	return 0;
135 error:
136 	unlock_page(page);
137 	return err;
138 }
139 
140 const struct pipe_buf_operations page_cache_pipe_buf_ops = {
141 	.confirm = page_cache_pipe_buf_confirm,
142 	.release = page_cache_pipe_buf_release,
143 	.steal = page_cache_pipe_buf_steal,
144 	.get = generic_pipe_buf_get,
145 };
146 
147 static int user_page_pipe_buf_steal(struct pipe_inode_info *pipe,
148 				    struct pipe_buffer *buf)
149 {
150 	if (!(buf->flags & PIPE_BUF_FLAG_GIFT))
151 		return 1;
152 
153 	buf->flags |= PIPE_BUF_FLAG_LRU;
154 	return generic_pipe_buf_steal(pipe, buf);
155 }
156 
157 static const struct pipe_buf_operations user_page_pipe_buf_ops = {
158 	.confirm = generic_pipe_buf_confirm,
159 	.release = page_cache_pipe_buf_release,
160 	.steal = user_page_pipe_buf_steal,
161 	.get = generic_pipe_buf_get,
162 };
163 
164 static void wakeup_pipe_readers(struct pipe_inode_info *pipe)
165 {
166 	smp_mb();
167 	if (waitqueue_active(&pipe->wait))
168 		wake_up_interruptible(&pipe->wait);
169 	kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
170 }
171 
172 /**
173  * splice_to_pipe - fill passed data into a pipe
174  * @pipe:	pipe to fill
175  * @spd:	data to fill
176  *
177  * Description:
178  *    @spd contains a map of pages and len/offset tuples, along with
179  *    the struct pipe_buf_operations associated with these pages. This
180  *    function will link that data to the pipe.
181  *
182  */
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 	int ret = 0, page_nr = 0;
188 
189 	if (!spd_pages)
190 		return 0;
191 
192 	if (unlikely(!pipe->readers)) {
193 		send_sig(SIGPIPE, current, 0);
194 		ret = -EPIPE;
195 		goto out;
196 	}
197 
198 	while (pipe->nrbufs < pipe->buffers) {
199 		int newbuf = (pipe->curbuf + pipe->nrbufs) & (pipe->buffers - 1);
200 		struct pipe_buffer *buf = pipe->bufs + newbuf;
201 
202 		buf->page = spd->pages[page_nr];
203 		buf->offset = spd->partial[page_nr].offset;
204 		buf->len = spd->partial[page_nr].len;
205 		buf->private = spd->partial[page_nr].private;
206 		buf->ops = spd->ops;
207 		buf->flags = 0;
208 
209 		pipe->nrbufs++;
210 		page_nr++;
211 		ret += buf->len;
212 
213 		if (!--spd->nr_pages)
214 			break;
215 	}
216 
217 	if (!ret)
218 		ret = -EAGAIN;
219 
220 out:
221 	while (page_nr < spd_pages)
222 		spd->spd_release(spd, page_nr++);
223 
224 	return ret;
225 }
226 EXPORT_SYMBOL_GPL(splice_to_pipe);
227 
228 ssize_t add_to_pipe(struct pipe_inode_info *pipe, struct pipe_buffer *buf)
229 {
230 	int ret;
231 
232 	if (unlikely(!pipe->readers)) {
233 		send_sig(SIGPIPE, current, 0);
234 		ret = -EPIPE;
235 	} else if (pipe->nrbufs == pipe->buffers) {
236 		ret = -EAGAIN;
237 	} else {
238 		int newbuf = (pipe->curbuf + pipe->nrbufs) & (pipe->buffers - 1);
239 		pipe->bufs[newbuf] = *buf;
240 		pipe->nrbufs++;
241 		return buf->len;
242 	}
243 	pipe_buf_release(pipe, buf);
244 	return ret;
245 }
246 EXPORT_SYMBOL(add_to_pipe);
247 
248 /*
249  * Check if we need to grow the arrays holding pages and partial page
250  * descriptions.
251  */
252 int splice_grow_spd(const struct pipe_inode_info *pipe, struct splice_pipe_desc *spd)
253 {
254 	unsigned int buffers = READ_ONCE(pipe->buffers);
255 
256 	spd->nr_pages_max = buffers;
257 	if (buffers <= PIPE_DEF_BUFFERS)
258 		return 0;
259 
260 	spd->pages = kmalloc_array(buffers, sizeof(struct page *), GFP_KERNEL);
261 	spd->partial = kmalloc_array(buffers, sizeof(struct partial_page),
262 				     GFP_KERNEL);
263 
264 	if (spd->pages && spd->partial)
265 		return 0;
266 
267 	kfree(spd->pages);
268 	kfree(spd->partial);
269 	return -ENOMEM;
270 }
271 
272 void splice_shrink_spd(struct splice_pipe_desc *spd)
273 {
274 	if (spd->nr_pages_max <= PIPE_DEF_BUFFERS)
275 		return;
276 
277 	kfree(spd->pages);
278 	kfree(spd->partial);
279 }
280 
281 /**
282  * generic_file_splice_read - splice data from file to a pipe
283  * @in:		file to splice from
284  * @ppos:	position in @in
285  * @pipe:	pipe to splice to
286  * @len:	number of bytes to splice
287  * @flags:	splice modifier flags
288  *
289  * Description:
290  *    Will read pages from given file and fill them into a pipe. Can be
291  *    used as long as it has more or less sane ->read_iter().
292  *
293  */
294 ssize_t generic_file_splice_read(struct file *in, loff_t *ppos,
295 				 struct pipe_inode_info *pipe, size_t len,
296 				 unsigned int flags)
297 {
298 	struct iov_iter to;
299 	struct kiocb kiocb;
300 	int idx, ret;
301 
302 	iov_iter_pipe(&to, READ, pipe, len);
303 	idx = to.idx;
304 	init_sync_kiocb(&kiocb, in);
305 	kiocb.ki_pos = *ppos;
306 	ret = call_read_iter(in, &kiocb, &to);
307 	if (ret > 0) {
308 		*ppos = kiocb.ki_pos;
309 		file_accessed(in);
310 	} else if (ret < 0) {
311 		to.idx = idx;
312 		to.iov_offset = 0;
313 		iov_iter_advance(&to, 0); /* to free what was emitted */
314 		/*
315 		 * callers of ->splice_read() expect -EAGAIN on
316 		 * "can't put anything in there", rather than -EFAULT.
317 		 */
318 		if (ret == -EFAULT)
319 			ret = -EAGAIN;
320 	}
321 
322 	return ret;
323 }
324 EXPORT_SYMBOL(generic_file_splice_read);
325 
326 const struct pipe_buf_operations default_pipe_buf_ops = {
327 	.confirm = generic_pipe_buf_confirm,
328 	.release = generic_pipe_buf_release,
329 	.steal = generic_pipe_buf_steal,
330 	.get = generic_pipe_buf_get,
331 };
332 
333 int generic_pipe_buf_nosteal(struct pipe_inode_info *pipe,
334 			     struct pipe_buffer *buf)
335 {
336 	return 1;
337 }
338 
339 /* Pipe buffer operations for a socket and similar. */
340 const struct pipe_buf_operations nosteal_pipe_buf_ops = {
341 	.confirm = generic_pipe_buf_confirm,
342 	.release = generic_pipe_buf_release,
343 	.steal = generic_pipe_buf_nosteal,
344 	.get = generic_pipe_buf_get,
345 };
346 EXPORT_SYMBOL(nosteal_pipe_buf_ops);
347 
348 static ssize_t kernel_readv(struct file *file, const struct kvec *vec,
349 			    unsigned long vlen, loff_t offset)
350 {
351 	mm_segment_t old_fs;
352 	loff_t pos = offset;
353 	ssize_t res;
354 
355 	old_fs = get_fs();
356 	set_fs(KERNEL_DS);
357 	/* The cast to a user pointer is valid due to the set_fs() */
358 	res = vfs_readv(file, (const struct iovec __user *)vec, vlen, &pos, 0);
359 	set_fs(old_fs);
360 
361 	return res;
362 }
363 
364 static ssize_t default_file_splice_read(struct file *in, loff_t *ppos,
365 				 struct pipe_inode_info *pipe, size_t len,
366 				 unsigned int flags)
367 {
368 	struct kvec *vec, __vec[PIPE_DEF_BUFFERS];
369 	struct iov_iter to;
370 	struct page **pages;
371 	unsigned int nr_pages;
372 	size_t offset, base, copied = 0;
373 	ssize_t res;
374 	int i;
375 
376 	if (pipe->nrbufs == pipe->buffers)
377 		return -EAGAIN;
378 
379 	/*
380 	 * Try to keep page boundaries matching to source pagecache ones -
381 	 * it probably won't be much help, but...
382 	 */
383 	offset = *ppos & ~PAGE_MASK;
384 
385 	iov_iter_pipe(&to, READ, pipe, len + offset);
386 
387 	res = iov_iter_get_pages_alloc(&to, &pages, len + offset, &base);
388 	if (res <= 0)
389 		return -ENOMEM;
390 
391 	nr_pages = DIV_ROUND_UP(res + base, PAGE_SIZE);
392 
393 	vec = __vec;
394 	if (nr_pages > PIPE_DEF_BUFFERS) {
395 		vec = kmalloc_array(nr_pages, sizeof(struct kvec), GFP_KERNEL);
396 		if (unlikely(!vec)) {
397 			res = -ENOMEM;
398 			goto out;
399 		}
400 	}
401 
402 	pipe->bufs[to.idx].offset = offset;
403 	pipe->bufs[to.idx].len -= offset;
404 
405 	for (i = 0; i < nr_pages; i++) {
406 		size_t this_len = min_t(size_t, len, PAGE_SIZE - offset);
407 		vec[i].iov_base = page_address(pages[i]) + offset;
408 		vec[i].iov_len = this_len;
409 		len -= this_len;
410 		offset = 0;
411 	}
412 
413 	res = kernel_readv(in, vec, nr_pages, *ppos);
414 	if (res > 0) {
415 		copied = res;
416 		*ppos += res;
417 	}
418 
419 	if (vec != __vec)
420 		kfree(vec);
421 out:
422 	for (i = 0; i < nr_pages; i++)
423 		put_page(pages[i]);
424 	kvfree(pages);
425 	iov_iter_advance(&to, copied);	/* truncates and discards */
426 	return res;
427 }
428 
429 /*
430  * Send 'sd->len' bytes to socket from 'sd->file' at position 'sd->pos'
431  * using sendpage(). Return the number of bytes sent.
432  */
433 static int pipe_to_sendpage(struct pipe_inode_info *pipe,
434 			    struct pipe_buffer *buf, struct splice_desc *sd)
435 {
436 	struct file *file = sd->u.file;
437 	loff_t pos = sd->pos;
438 	int more;
439 
440 	if (!likely(file->f_op->sendpage))
441 		return -EINVAL;
442 
443 	more = (sd->flags & SPLICE_F_MORE) ? MSG_MORE : 0;
444 
445 	if (sd->len < sd->total_len && pipe->nrbufs > 1)
446 		more |= MSG_SENDPAGE_NOTLAST;
447 
448 	return file->f_op->sendpage(file, buf->page, buf->offset,
449 				    sd->len, &pos, more);
450 }
451 
452 static void wakeup_pipe_writers(struct pipe_inode_info *pipe)
453 {
454 	smp_mb();
455 	if (waitqueue_active(&pipe->wait))
456 		wake_up_interruptible(&pipe->wait);
457 	kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
458 }
459 
460 /**
461  * splice_from_pipe_feed - feed available data from a pipe to a file
462  * @pipe:	pipe to splice from
463  * @sd:		information to @actor
464  * @actor:	handler that splices the data
465  *
466  * Description:
467  *    This function loops over the pipe and calls @actor to do the
468  *    actual moving of a single struct pipe_buffer to the desired
469  *    destination.  It returns when there's no more buffers left in
470  *    the pipe or if the requested number of bytes (@sd->total_len)
471  *    have been copied.  It returns a positive number (one) if the
472  *    pipe needs to be filled with more data, zero if the required
473  *    number of bytes have been copied and -errno on error.
474  *
475  *    This, together with splice_from_pipe_{begin,end,next}, may be
476  *    used to implement the functionality of __splice_from_pipe() when
477  *    locking is required around copying the pipe buffers to the
478  *    destination.
479  */
480 static int splice_from_pipe_feed(struct pipe_inode_info *pipe, struct splice_desc *sd,
481 			  splice_actor *actor)
482 {
483 	int ret;
484 
485 	while (pipe->nrbufs) {
486 		struct pipe_buffer *buf = pipe->bufs + pipe->curbuf;
487 
488 		sd->len = buf->len;
489 		if (sd->len > sd->total_len)
490 			sd->len = sd->total_len;
491 
492 		ret = pipe_buf_confirm(pipe, buf);
493 		if (unlikely(ret)) {
494 			if (ret == -ENODATA)
495 				ret = 0;
496 			return ret;
497 		}
498 
499 		ret = actor(pipe, buf, sd);
500 		if (ret <= 0)
501 			return ret;
502 
503 		buf->offset += ret;
504 		buf->len -= ret;
505 
506 		sd->num_spliced += ret;
507 		sd->len -= ret;
508 		sd->pos += ret;
509 		sd->total_len -= ret;
510 
511 		if (!buf->len) {
512 			pipe_buf_release(pipe, buf);
513 			pipe->curbuf = (pipe->curbuf + 1) & (pipe->buffers - 1);
514 			pipe->nrbufs--;
515 			if (pipe->files)
516 				sd->need_wakeup = true;
517 		}
518 
519 		if (!sd->total_len)
520 			return 0;
521 	}
522 
523 	return 1;
524 }
525 
526 /**
527  * splice_from_pipe_next - wait for some data to splice from
528  * @pipe:	pipe to splice from
529  * @sd:		information about the splice operation
530  *
531  * Description:
532  *    This function will wait for some data and return a positive
533  *    value (one) if pipe buffers are available.  It will return zero
534  *    or -errno if no more data needs to be spliced.
535  */
536 static int splice_from_pipe_next(struct pipe_inode_info *pipe, struct splice_desc *sd)
537 {
538 	/*
539 	 * Check for signal early to make process killable when there are
540 	 * always buffers available
541 	 */
542 	if (signal_pending(current))
543 		return -ERESTARTSYS;
544 
545 	while (!pipe->nrbufs) {
546 		if (!pipe->writers)
547 			return 0;
548 
549 		if (!pipe->waiting_writers && sd->num_spliced)
550 			return 0;
551 
552 		if (sd->flags & SPLICE_F_NONBLOCK)
553 			return -EAGAIN;
554 
555 		if (signal_pending(current))
556 			return -ERESTARTSYS;
557 
558 		if (sd->need_wakeup) {
559 			wakeup_pipe_writers(pipe);
560 			sd->need_wakeup = false;
561 		}
562 
563 		pipe_wait(pipe);
564 	}
565 
566 	return 1;
567 }
568 
569 /**
570  * splice_from_pipe_begin - start splicing from pipe
571  * @sd:		information about the splice operation
572  *
573  * Description:
574  *    This function should be called before a loop containing
575  *    splice_from_pipe_next() and splice_from_pipe_feed() to
576  *    initialize the necessary fields of @sd.
577  */
578 static void splice_from_pipe_begin(struct splice_desc *sd)
579 {
580 	sd->num_spliced = 0;
581 	sd->need_wakeup = false;
582 }
583 
584 /**
585  * splice_from_pipe_end - finish splicing from pipe
586  * @pipe:	pipe to splice from
587  * @sd:		information about the splice operation
588  *
589  * Description:
590  *    This function will wake up pipe writers if necessary.  It should
591  *    be called after a loop containing splice_from_pipe_next() and
592  *    splice_from_pipe_feed().
593  */
594 static void splice_from_pipe_end(struct pipe_inode_info *pipe, struct splice_desc *sd)
595 {
596 	if (sd->need_wakeup)
597 		wakeup_pipe_writers(pipe);
598 }
599 
600 /**
601  * __splice_from_pipe - splice data from a pipe to given actor
602  * @pipe:	pipe to splice from
603  * @sd:		information to @actor
604  * @actor:	handler that splices the data
605  *
606  * Description:
607  *    This function does little more than loop over the pipe and call
608  *    @actor to do the actual moving of a single struct pipe_buffer to
609  *    the desired destination. See pipe_to_file, pipe_to_sendpage, or
610  *    pipe_to_user.
611  *
612  */
613 ssize_t __splice_from_pipe(struct pipe_inode_info *pipe, struct splice_desc *sd,
614 			   splice_actor *actor)
615 {
616 	int ret;
617 
618 	splice_from_pipe_begin(sd);
619 	do {
620 		cond_resched();
621 		ret = splice_from_pipe_next(pipe, sd);
622 		if (ret > 0)
623 			ret = splice_from_pipe_feed(pipe, sd, actor);
624 	} while (ret > 0);
625 	splice_from_pipe_end(pipe, sd);
626 
627 	return sd->num_spliced ? sd->num_spliced : ret;
628 }
629 EXPORT_SYMBOL(__splice_from_pipe);
630 
631 /**
632  * splice_from_pipe - splice data from a pipe to a file
633  * @pipe:	pipe to splice from
634  * @out:	file to splice to
635  * @ppos:	position in @out
636  * @len:	how many bytes to splice
637  * @flags:	splice modifier flags
638  * @actor:	handler that splices the data
639  *
640  * Description:
641  *    See __splice_from_pipe. This function locks the pipe inode,
642  *    otherwise it's identical to __splice_from_pipe().
643  *
644  */
645 ssize_t splice_from_pipe(struct pipe_inode_info *pipe, struct file *out,
646 			 loff_t *ppos, size_t len, unsigned int flags,
647 			 splice_actor *actor)
648 {
649 	ssize_t ret;
650 	struct splice_desc sd = {
651 		.total_len = len,
652 		.flags = flags,
653 		.pos = *ppos,
654 		.u.file = out,
655 	};
656 
657 	pipe_lock(pipe);
658 	ret = __splice_from_pipe(pipe, &sd, actor);
659 	pipe_unlock(pipe);
660 
661 	return ret;
662 }
663 
664 /**
665  * iter_file_splice_write - splice data from a pipe to a file
666  * @pipe:	pipe info
667  * @out:	file to write to
668  * @ppos:	position in @out
669  * @len:	number of bytes to splice
670  * @flags:	splice modifier flags
671  *
672  * Description:
673  *    Will either move or copy pages (determined by @flags options) from
674  *    the given pipe inode to the given file.
675  *    This one is ->write_iter-based.
676  *
677  */
678 ssize_t
679 iter_file_splice_write(struct pipe_inode_info *pipe, struct file *out,
680 			  loff_t *ppos, size_t len, unsigned int flags)
681 {
682 	struct splice_desc sd = {
683 		.total_len = len,
684 		.flags = flags,
685 		.pos = *ppos,
686 		.u.file = out,
687 	};
688 	int nbufs = pipe->buffers;
689 	struct bio_vec *array = kcalloc(nbufs, sizeof(struct bio_vec),
690 					GFP_KERNEL);
691 	ssize_t ret;
692 
693 	if (unlikely(!array))
694 		return -ENOMEM;
695 
696 	pipe_lock(pipe);
697 
698 	splice_from_pipe_begin(&sd);
699 	while (sd.total_len) {
700 		struct iov_iter from;
701 		size_t left;
702 		int n, idx;
703 
704 		ret = splice_from_pipe_next(pipe, &sd);
705 		if (ret <= 0)
706 			break;
707 
708 		if (unlikely(nbufs < pipe->buffers)) {
709 			kfree(array);
710 			nbufs = pipe->buffers;
711 			array = kcalloc(nbufs, sizeof(struct bio_vec),
712 					GFP_KERNEL);
713 			if (!array) {
714 				ret = -ENOMEM;
715 				break;
716 			}
717 		}
718 
719 		/* build the vector */
720 		left = sd.total_len;
721 		for (n = 0, idx = pipe->curbuf; left && n < pipe->nrbufs; n++, idx++) {
722 			struct pipe_buffer *buf = pipe->bufs + idx;
723 			size_t this_len = buf->len;
724 
725 			if (this_len > left)
726 				this_len = left;
727 
728 			if (idx == pipe->buffers - 1)
729 				idx = -1;
730 
731 			ret = pipe_buf_confirm(pipe, buf);
732 			if (unlikely(ret)) {
733 				if (ret == -ENODATA)
734 					ret = 0;
735 				goto done;
736 			}
737 
738 			array[n].bv_page = buf->page;
739 			array[n].bv_len = this_len;
740 			array[n].bv_offset = buf->offset;
741 			left -= this_len;
742 		}
743 
744 		iov_iter_bvec(&from, WRITE, array, n, sd.total_len - left);
745 		ret = vfs_iter_write(out, &from, &sd.pos, 0);
746 		if (ret <= 0)
747 			break;
748 
749 		sd.num_spliced += ret;
750 		sd.total_len -= ret;
751 		*ppos = sd.pos;
752 
753 		/* dismiss the fully eaten buffers, adjust the partial one */
754 		while (ret) {
755 			struct pipe_buffer *buf = pipe->bufs + pipe->curbuf;
756 			if (ret >= buf->len) {
757 				ret -= buf->len;
758 				buf->len = 0;
759 				pipe_buf_release(pipe, buf);
760 				pipe->curbuf = (pipe->curbuf + 1) & (pipe->buffers - 1);
761 				pipe->nrbufs--;
762 				if (pipe->files)
763 					sd.need_wakeup = true;
764 			} else {
765 				buf->offset += ret;
766 				buf->len -= ret;
767 				ret = 0;
768 			}
769 		}
770 	}
771 done:
772 	kfree(array);
773 	splice_from_pipe_end(pipe, &sd);
774 
775 	pipe_unlock(pipe);
776 
777 	if (sd.num_spliced)
778 		ret = sd.num_spliced;
779 
780 	return ret;
781 }
782 
783 EXPORT_SYMBOL(iter_file_splice_write);
784 
785 static int write_pipe_buf(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
786 			  struct splice_desc *sd)
787 {
788 	int ret;
789 	void *data;
790 	loff_t tmp = sd->pos;
791 
792 	data = kmap(buf->page);
793 	ret = __kernel_write(sd->u.file, data + buf->offset, sd->len, &tmp);
794 	kunmap(buf->page);
795 
796 	return ret;
797 }
798 
799 static ssize_t default_file_splice_write(struct pipe_inode_info *pipe,
800 					 struct file *out, loff_t *ppos,
801 					 size_t len, unsigned int flags)
802 {
803 	ssize_t ret;
804 
805 	ret = splice_from_pipe(pipe, out, ppos, len, flags, write_pipe_buf);
806 	if (ret > 0)
807 		*ppos += ret;
808 
809 	return ret;
810 }
811 
812 /**
813  * generic_splice_sendpage - splice data from a pipe to a socket
814  * @pipe:	pipe to splice from
815  * @out:	socket to write to
816  * @ppos:	position in @out
817  * @len:	number of bytes to splice
818  * @flags:	splice modifier flags
819  *
820  * Description:
821  *    Will send @len bytes from the pipe to a network socket. No data copying
822  *    is involved.
823  *
824  */
825 ssize_t generic_splice_sendpage(struct pipe_inode_info *pipe, struct file *out,
826 				loff_t *ppos, size_t len, unsigned int flags)
827 {
828 	return splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_sendpage);
829 }
830 
831 EXPORT_SYMBOL(generic_splice_sendpage);
832 
833 /*
834  * Attempt to initiate a splice from pipe to file.
835  */
836 static long do_splice_from(struct pipe_inode_info *pipe, struct file *out,
837 			   loff_t *ppos, size_t len, unsigned int flags)
838 {
839 	ssize_t (*splice_write)(struct pipe_inode_info *, struct file *,
840 				loff_t *, size_t, unsigned int);
841 
842 	if (out->f_op->splice_write)
843 		splice_write = out->f_op->splice_write;
844 	else
845 		splice_write = default_file_splice_write;
846 
847 	return splice_write(pipe, out, ppos, len, flags);
848 }
849 
850 /*
851  * Attempt to initiate a splice from a file to a pipe.
852  */
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 	ssize_t (*splice_read)(struct file *, loff_t *,
858 			       struct pipe_inode_info *, size_t, unsigned int);
859 	int ret;
860 
861 	if (unlikely(!(in->f_mode & FMODE_READ)))
862 		return -EBADF;
863 
864 	ret = rw_verify_area(READ, in, ppos, len);
865 	if (unlikely(ret < 0))
866 		return ret;
867 
868 	if (unlikely(len > MAX_RW_COUNT))
869 		len = MAX_RW_COUNT;
870 
871 	if (in->f_op->splice_read)
872 		splice_read = in->f_op->splice_read;
873 	else
874 		splice_read = default_file_splice_read;
875 
876 	return splice_read(in, ppos, pipe, len, flags);
877 }
878 
879 /**
880  * splice_direct_to_actor - splices data directly between two non-pipes
881  * @in:		file to splice from
882  * @sd:		actor information on where to splice to
883  * @actor:	handles the data splicing
884  *
885  * Description:
886  *    This is a special case helper to splice directly between two
887  *    points, without requiring an explicit pipe. Internally an allocated
888  *    pipe is cached in the process, and reused during the lifetime of
889  *    that process.
890  *
891  */
892 ssize_t splice_direct_to_actor(struct file *in, struct splice_desc *sd,
893 			       splice_direct_actor *actor)
894 {
895 	struct pipe_inode_info *pipe;
896 	long ret, bytes;
897 	umode_t i_mode;
898 	size_t len;
899 	int i, flags, more;
900 
901 	/*
902 	 * We require the input being a regular file, as we don't want to
903 	 * randomly drop data for eg socket -> socket splicing. Use the
904 	 * piped splicing for that!
905 	 */
906 	i_mode = file_inode(in)->i_mode;
907 	if (unlikely(!S_ISREG(i_mode) && !S_ISBLK(i_mode)))
908 		return -EINVAL;
909 
910 	/*
911 	 * neither in nor out is a pipe, setup an internal pipe attached to
912 	 * 'out' and transfer the wanted data from 'in' to 'out' through that
913 	 */
914 	pipe = current->splice_pipe;
915 	if (unlikely(!pipe)) {
916 		pipe = alloc_pipe_info();
917 		if (!pipe)
918 			return -ENOMEM;
919 
920 		/*
921 		 * We don't have an immediate reader, but we'll read the stuff
922 		 * out of the pipe right after the splice_to_pipe(). So set
923 		 * PIPE_READERS appropriately.
924 		 */
925 		pipe->readers = 1;
926 
927 		current->splice_pipe = pipe;
928 	}
929 
930 	/*
931 	 * Do the splice.
932 	 */
933 	ret = 0;
934 	bytes = 0;
935 	len = sd->total_len;
936 	flags = sd->flags;
937 
938 	/*
939 	 * Don't block on output, we have to drain the direct pipe.
940 	 */
941 	sd->flags &= ~SPLICE_F_NONBLOCK;
942 	more = sd->flags & SPLICE_F_MORE;
943 
944 	WARN_ON_ONCE(pipe->nrbufs != 0);
945 
946 	while (len) {
947 		size_t read_len;
948 		loff_t pos = sd->pos, prev_pos = pos;
949 
950 		/* Don't try to read more the pipe has space for. */
951 		read_len = min_t(size_t, len,
952 				 (pipe->buffers - pipe->nrbufs) << PAGE_SHIFT);
953 		ret = do_splice_to(in, &pos, pipe, read_len, flags);
954 		if (unlikely(ret <= 0))
955 			goto out_release;
956 
957 		read_len = ret;
958 		sd->total_len = read_len;
959 
960 		/*
961 		 * If more data is pending, set SPLICE_F_MORE
962 		 * If this is the last data and SPLICE_F_MORE was not set
963 		 * initially, clears it.
964 		 */
965 		if (read_len < len)
966 			sd->flags |= SPLICE_F_MORE;
967 		else if (!more)
968 			sd->flags &= ~SPLICE_F_MORE;
969 		/*
970 		 * NOTE: nonblocking mode only applies to the input. We
971 		 * must not do the output in nonblocking mode as then we
972 		 * could get stuck data in the internal pipe:
973 		 */
974 		ret = actor(pipe, sd);
975 		if (unlikely(ret <= 0)) {
976 			sd->pos = prev_pos;
977 			goto out_release;
978 		}
979 
980 		bytes += ret;
981 		len -= ret;
982 		sd->pos = pos;
983 
984 		if (ret < read_len) {
985 			sd->pos = prev_pos + ret;
986 			goto out_release;
987 		}
988 	}
989 
990 done:
991 	pipe->nrbufs = pipe->curbuf = 0;
992 	file_accessed(in);
993 	return bytes;
994 
995 out_release:
996 	/*
997 	 * If we did an incomplete transfer we must release
998 	 * the pipe buffers in question:
999 	 */
1000 	for (i = 0; i < pipe->buffers; i++) {
1001 		struct pipe_buffer *buf = pipe->bufs + i;
1002 
1003 		if (buf->ops)
1004 			pipe_buf_release(pipe, buf);
1005 	}
1006 
1007 	if (!bytes)
1008 		bytes = ret;
1009 
1010 	goto done;
1011 }
1012 EXPORT_SYMBOL(splice_direct_to_actor);
1013 
1014 static int direct_splice_actor(struct pipe_inode_info *pipe,
1015 			       struct splice_desc *sd)
1016 {
1017 	struct file *file = sd->u.file;
1018 
1019 	return do_splice_from(pipe, file, sd->opos, sd->total_len,
1020 			      sd->flags);
1021 }
1022 
1023 /**
1024  * do_splice_direct - splices data directly between two files
1025  * @in:		file to splice from
1026  * @ppos:	input file offset
1027  * @out:	file to splice to
1028  * @opos:	output file offset
1029  * @len:	number of bytes to splice
1030  * @flags:	splice modifier flags
1031  *
1032  * Description:
1033  *    For use by do_sendfile(). splice can easily emulate sendfile, but
1034  *    doing it in the application would incur an extra system call
1035  *    (splice in + splice out, as compared to just sendfile()). So this helper
1036  *    can splice directly through a process-private pipe.
1037  *
1038  */
1039 long do_splice_direct(struct file *in, loff_t *ppos, struct file *out,
1040 		      loff_t *opos, size_t len, unsigned int flags)
1041 {
1042 	struct splice_desc sd = {
1043 		.len		= len,
1044 		.total_len	= len,
1045 		.flags		= flags,
1046 		.pos		= *ppos,
1047 		.u.file		= out,
1048 		.opos		= opos,
1049 	};
1050 	long ret;
1051 
1052 	if (unlikely(!(out->f_mode & FMODE_WRITE)))
1053 		return -EBADF;
1054 
1055 	if (unlikely(out->f_flags & O_APPEND))
1056 		return -EINVAL;
1057 
1058 	ret = rw_verify_area(WRITE, out, opos, len);
1059 	if (unlikely(ret < 0))
1060 		return ret;
1061 
1062 	ret = splice_direct_to_actor(in, &sd, direct_splice_actor);
1063 	if (ret > 0)
1064 		*ppos = sd.pos;
1065 
1066 	return ret;
1067 }
1068 EXPORT_SYMBOL(do_splice_direct);
1069 
1070 static int wait_for_space(struct pipe_inode_info *pipe, unsigned flags)
1071 {
1072 	for (;;) {
1073 		if (unlikely(!pipe->readers)) {
1074 			send_sig(SIGPIPE, current, 0);
1075 			return -EPIPE;
1076 		}
1077 		if (pipe->nrbufs != pipe->buffers)
1078 			return 0;
1079 		if (flags & SPLICE_F_NONBLOCK)
1080 			return -EAGAIN;
1081 		if (signal_pending(current))
1082 			return -ERESTARTSYS;
1083 		pipe->waiting_writers++;
1084 		pipe_wait(pipe);
1085 		pipe->waiting_writers--;
1086 	}
1087 }
1088 
1089 static int splice_pipe_to_pipe(struct pipe_inode_info *ipipe,
1090 			       struct pipe_inode_info *opipe,
1091 			       size_t len, unsigned int flags);
1092 
1093 /*
1094  * Determine where to splice to/from.
1095  */
1096 static long do_splice(struct file *in, loff_t __user *off_in,
1097 		      struct file *out, loff_t __user *off_out,
1098 		      size_t len, unsigned int flags)
1099 {
1100 	struct pipe_inode_info *ipipe;
1101 	struct pipe_inode_info *opipe;
1102 	loff_t offset;
1103 	long ret;
1104 
1105 	ipipe = get_pipe_info(in);
1106 	opipe = get_pipe_info(out);
1107 
1108 	if (ipipe && opipe) {
1109 		if (off_in || off_out)
1110 			return -ESPIPE;
1111 
1112 		if (!(in->f_mode & FMODE_READ))
1113 			return -EBADF;
1114 
1115 		if (!(out->f_mode & FMODE_WRITE))
1116 			return -EBADF;
1117 
1118 		/* Splicing to self would be fun, but... */
1119 		if (ipipe == opipe)
1120 			return -EINVAL;
1121 
1122 		if ((in->f_flags | out->f_flags) & O_NONBLOCK)
1123 			flags |= SPLICE_F_NONBLOCK;
1124 
1125 		return splice_pipe_to_pipe(ipipe, opipe, len, flags);
1126 	}
1127 
1128 	if (ipipe) {
1129 		if (off_in)
1130 			return -ESPIPE;
1131 		if (off_out) {
1132 			if (!(out->f_mode & FMODE_PWRITE))
1133 				return -EINVAL;
1134 			if (copy_from_user(&offset, off_out, sizeof(loff_t)))
1135 				return -EFAULT;
1136 		} else {
1137 			offset = out->f_pos;
1138 		}
1139 
1140 		if (unlikely(!(out->f_mode & FMODE_WRITE)))
1141 			return -EBADF;
1142 
1143 		if (unlikely(out->f_flags & O_APPEND))
1144 			return -EINVAL;
1145 
1146 		ret = rw_verify_area(WRITE, out, &offset, len);
1147 		if (unlikely(ret < 0))
1148 			return ret;
1149 
1150 		if (in->f_flags & O_NONBLOCK)
1151 			flags |= SPLICE_F_NONBLOCK;
1152 
1153 		file_start_write(out);
1154 		ret = do_splice_from(ipipe, out, &offset, len, flags);
1155 		file_end_write(out);
1156 
1157 		if (!off_out)
1158 			out->f_pos = offset;
1159 		else if (copy_to_user(off_out, &offset, sizeof(loff_t)))
1160 			ret = -EFAULT;
1161 
1162 		return ret;
1163 	}
1164 
1165 	if (opipe) {
1166 		if (off_out)
1167 			return -ESPIPE;
1168 		if (off_in) {
1169 			if (!(in->f_mode & FMODE_PREAD))
1170 				return -EINVAL;
1171 			if (copy_from_user(&offset, off_in, sizeof(loff_t)))
1172 				return -EFAULT;
1173 		} else {
1174 			offset = in->f_pos;
1175 		}
1176 
1177 		if (out->f_flags & O_NONBLOCK)
1178 			flags |= SPLICE_F_NONBLOCK;
1179 
1180 		pipe_lock(opipe);
1181 		ret = wait_for_space(opipe, flags);
1182 		if (!ret)
1183 			ret = do_splice_to(in, &offset, opipe, len, flags);
1184 		pipe_unlock(opipe);
1185 		if (ret > 0)
1186 			wakeup_pipe_readers(opipe);
1187 		if (!off_in)
1188 			in->f_pos = offset;
1189 		else if (copy_to_user(off_in, &offset, sizeof(loff_t)))
1190 			ret = -EFAULT;
1191 
1192 		return ret;
1193 	}
1194 
1195 	return -EINVAL;
1196 }
1197 
1198 static int iter_to_pipe(struct iov_iter *from,
1199 			struct pipe_inode_info *pipe,
1200 			unsigned flags)
1201 {
1202 	struct pipe_buffer buf = {
1203 		.ops = &user_page_pipe_buf_ops,
1204 		.flags = flags
1205 	};
1206 	size_t total = 0;
1207 	int ret = 0;
1208 	bool failed = false;
1209 
1210 	while (iov_iter_count(from) && !failed) {
1211 		struct page *pages[16];
1212 		ssize_t copied;
1213 		size_t start;
1214 		int n;
1215 
1216 		copied = iov_iter_get_pages(from, pages, ~0UL, 16, &start);
1217 		if (copied <= 0) {
1218 			ret = copied;
1219 			break;
1220 		}
1221 
1222 		for (n = 0; copied; n++, start = 0) {
1223 			int size = min_t(int, copied, PAGE_SIZE - start);
1224 			if (!failed) {
1225 				buf.page = pages[n];
1226 				buf.offset = start;
1227 				buf.len = size;
1228 				ret = add_to_pipe(pipe, &buf);
1229 				if (unlikely(ret < 0)) {
1230 					failed = true;
1231 				} else {
1232 					iov_iter_advance(from, ret);
1233 					total += ret;
1234 				}
1235 			} else {
1236 				put_page(pages[n]);
1237 			}
1238 			copied -= size;
1239 		}
1240 	}
1241 	return total ? total : ret;
1242 }
1243 
1244 static int pipe_to_user(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
1245 			struct splice_desc *sd)
1246 {
1247 	int n = copy_page_to_iter(buf->page, buf->offset, sd->len, sd->u.data);
1248 	return n == sd->len ? n : -EFAULT;
1249 }
1250 
1251 /*
1252  * For lack of a better implementation, implement vmsplice() to userspace
1253  * as a simple copy of the pipes pages to the user iov.
1254  */
1255 static long vmsplice_to_user(struct file *file, struct iov_iter *iter,
1256 			     unsigned int flags)
1257 {
1258 	struct pipe_inode_info *pipe = get_pipe_info(file);
1259 	struct splice_desc sd = {
1260 		.total_len = iov_iter_count(iter),
1261 		.flags = flags,
1262 		.u.data = iter
1263 	};
1264 	long ret = 0;
1265 
1266 	if (!pipe)
1267 		return -EBADF;
1268 
1269 	if (sd.total_len) {
1270 		pipe_lock(pipe);
1271 		ret = __splice_from_pipe(pipe, &sd, pipe_to_user);
1272 		pipe_unlock(pipe);
1273 	}
1274 
1275 	return ret;
1276 }
1277 
1278 /*
1279  * vmsplice splices a user address range into a pipe. It can be thought of
1280  * as splice-from-memory, where the regular splice is splice-from-file (or
1281  * to file). In both cases the output is a pipe, naturally.
1282  */
1283 static long vmsplice_to_pipe(struct file *file, struct iov_iter *iter,
1284 			     unsigned int flags)
1285 {
1286 	struct pipe_inode_info *pipe;
1287 	long ret = 0;
1288 	unsigned buf_flag = 0;
1289 
1290 	if (flags & SPLICE_F_GIFT)
1291 		buf_flag = PIPE_BUF_FLAG_GIFT;
1292 
1293 	pipe = get_pipe_info(file);
1294 	if (!pipe)
1295 		return -EBADF;
1296 
1297 	pipe_lock(pipe);
1298 	ret = wait_for_space(pipe, flags);
1299 	if (!ret)
1300 		ret = iter_to_pipe(iter, pipe, buf_flag);
1301 	pipe_unlock(pipe);
1302 	if (ret > 0)
1303 		wakeup_pipe_readers(pipe);
1304 	return ret;
1305 }
1306 
1307 static int vmsplice_type(struct fd f, int *type)
1308 {
1309 	if (!f.file)
1310 		return -EBADF;
1311 	if (f.file->f_mode & FMODE_WRITE) {
1312 		*type = WRITE;
1313 	} else if (f.file->f_mode & FMODE_READ) {
1314 		*type = READ;
1315 	} else {
1316 		fdput(f);
1317 		return -EBADF;
1318 	}
1319 	return 0;
1320 }
1321 
1322 /*
1323  * Note that vmsplice only really supports true splicing _from_ user memory
1324  * to a pipe, not the other way around. Splicing from user memory is a simple
1325  * operation that can be supported without any funky alignment restrictions
1326  * or nasty vm tricks. We simply map in the user memory and fill them into
1327  * a pipe. The reverse isn't quite as easy, though. There are two possible
1328  * solutions for that:
1329  *
1330  *	- memcpy() the data internally, at which point we might as well just
1331  *	  do a regular read() on the buffer anyway.
1332  *	- Lots of nasty vm tricks, that are neither fast nor flexible (it
1333  *	  has restriction limitations on both ends of the pipe).
1334  *
1335  * Currently we punt and implement it as a normal copy, see pipe_to_user().
1336  *
1337  */
1338 static long do_vmsplice(struct file *f, struct iov_iter *iter, unsigned int flags)
1339 {
1340 	if (unlikely(flags & ~SPLICE_F_ALL))
1341 		return -EINVAL;
1342 
1343 	if (!iov_iter_count(iter))
1344 		return 0;
1345 
1346 	if (iov_iter_rw(iter) == WRITE)
1347 		return vmsplice_to_pipe(f, iter, flags);
1348 	else
1349 		return vmsplice_to_user(f, iter, flags);
1350 }
1351 
1352 SYSCALL_DEFINE4(vmsplice, int, fd, const struct iovec __user *, uiov,
1353 		unsigned long, nr_segs, unsigned int, flags)
1354 {
1355 	struct iovec iovstack[UIO_FASTIOV];
1356 	struct iovec *iov = iovstack;
1357 	struct iov_iter iter;
1358 	long error;
1359 	struct fd f;
1360 	int type;
1361 
1362 	f = fdget(fd);
1363 	error = vmsplice_type(f, &type);
1364 	if (error)
1365 		return error;
1366 
1367 	error = import_iovec(type, uiov, nr_segs,
1368 			     ARRAY_SIZE(iovstack), &iov, &iter);
1369 	if (!error) {
1370 		error = do_vmsplice(f.file, &iter, flags);
1371 		kfree(iov);
1372 	}
1373 	fdput(f);
1374 	return error;
1375 }
1376 
1377 #ifdef CONFIG_COMPAT
1378 COMPAT_SYSCALL_DEFINE4(vmsplice, int, fd, const struct compat_iovec __user *, iov32,
1379 		    unsigned int, nr_segs, unsigned int, flags)
1380 {
1381 	struct iovec iovstack[UIO_FASTIOV];
1382 	struct iovec *iov = iovstack;
1383 	struct iov_iter iter;
1384 	long error;
1385 	struct fd f;
1386 	int type;
1387 
1388 	f = fdget(fd);
1389 	error = vmsplice_type(f, &type);
1390 	if (error)
1391 		return error;
1392 
1393 	error = compat_import_iovec(type, iov32, nr_segs,
1394 			     ARRAY_SIZE(iovstack), &iov, &iter);
1395 	if (!error) {
1396 		error = do_vmsplice(f.file, &iter, flags);
1397 		kfree(iov);
1398 	}
1399 	fdput(f);
1400 	return error;
1401 }
1402 #endif
1403 
1404 SYSCALL_DEFINE6(splice, int, fd_in, loff_t __user *, off_in,
1405 		int, fd_out, loff_t __user *, off_out,
1406 		size_t, len, unsigned int, flags)
1407 {
1408 	struct fd in, out;
1409 	long error;
1410 
1411 	if (unlikely(!len))
1412 		return 0;
1413 
1414 	if (unlikely(flags & ~SPLICE_F_ALL))
1415 		return -EINVAL;
1416 
1417 	error = -EBADF;
1418 	in = fdget(fd_in);
1419 	if (in.file) {
1420 		if (in.file->f_mode & FMODE_READ) {
1421 			out = fdget(fd_out);
1422 			if (out.file) {
1423 				if (out.file->f_mode & FMODE_WRITE)
1424 					error = do_splice(in.file, off_in,
1425 							  out.file, off_out,
1426 							  len, flags);
1427 				fdput(out);
1428 			}
1429 		}
1430 		fdput(in);
1431 	}
1432 	return error;
1433 }
1434 
1435 /*
1436  * Make sure there's data to read. Wait for input if we can, otherwise
1437  * return an appropriate error.
1438  */
1439 static int ipipe_prep(struct pipe_inode_info *pipe, unsigned int flags)
1440 {
1441 	int ret;
1442 
1443 	/*
1444 	 * Check ->nrbufs without the inode lock first. This function
1445 	 * is speculative anyways, so missing one is ok.
1446 	 */
1447 	if (pipe->nrbufs)
1448 		return 0;
1449 
1450 	ret = 0;
1451 	pipe_lock(pipe);
1452 
1453 	while (!pipe->nrbufs) {
1454 		if (signal_pending(current)) {
1455 			ret = -ERESTARTSYS;
1456 			break;
1457 		}
1458 		if (!pipe->writers)
1459 			break;
1460 		if (!pipe->waiting_writers) {
1461 			if (flags & SPLICE_F_NONBLOCK) {
1462 				ret = -EAGAIN;
1463 				break;
1464 			}
1465 		}
1466 		pipe_wait(pipe);
1467 	}
1468 
1469 	pipe_unlock(pipe);
1470 	return ret;
1471 }
1472 
1473 /*
1474  * Make sure there's writeable room. Wait for room if we can, otherwise
1475  * return an appropriate error.
1476  */
1477 static int opipe_prep(struct pipe_inode_info *pipe, unsigned int flags)
1478 {
1479 	int ret;
1480 
1481 	/*
1482 	 * Check ->nrbufs without the inode lock first. This function
1483 	 * is speculative anyways, so missing one is ok.
1484 	 */
1485 	if (pipe->nrbufs < pipe->buffers)
1486 		return 0;
1487 
1488 	ret = 0;
1489 	pipe_lock(pipe);
1490 
1491 	while (pipe->nrbufs >= pipe->buffers) {
1492 		if (!pipe->readers) {
1493 			send_sig(SIGPIPE, current, 0);
1494 			ret = -EPIPE;
1495 			break;
1496 		}
1497 		if (flags & SPLICE_F_NONBLOCK) {
1498 			ret = -EAGAIN;
1499 			break;
1500 		}
1501 		if (signal_pending(current)) {
1502 			ret = -ERESTARTSYS;
1503 			break;
1504 		}
1505 		pipe->waiting_writers++;
1506 		pipe_wait(pipe);
1507 		pipe->waiting_writers--;
1508 	}
1509 
1510 	pipe_unlock(pipe);
1511 	return ret;
1512 }
1513 
1514 /*
1515  * Splice contents of ipipe to opipe.
1516  */
1517 static int splice_pipe_to_pipe(struct pipe_inode_info *ipipe,
1518 			       struct pipe_inode_info *opipe,
1519 			       size_t len, unsigned int flags)
1520 {
1521 	struct pipe_buffer *ibuf, *obuf;
1522 	int ret = 0, nbuf;
1523 	bool input_wakeup = false;
1524 
1525 
1526 retry:
1527 	ret = ipipe_prep(ipipe, flags);
1528 	if (ret)
1529 		return ret;
1530 
1531 	ret = opipe_prep(opipe, flags);
1532 	if (ret)
1533 		return ret;
1534 
1535 	/*
1536 	 * Potential ABBA deadlock, work around it by ordering lock
1537 	 * grabbing by pipe info address. Otherwise two different processes
1538 	 * could deadlock (one doing tee from A -> B, the other from B -> A).
1539 	 */
1540 	pipe_double_lock(ipipe, opipe);
1541 
1542 	do {
1543 		if (!opipe->readers) {
1544 			send_sig(SIGPIPE, current, 0);
1545 			if (!ret)
1546 				ret = -EPIPE;
1547 			break;
1548 		}
1549 
1550 		if (!ipipe->nrbufs && !ipipe->writers)
1551 			break;
1552 
1553 		/*
1554 		 * Cannot make any progress, because either the input
1555 		 * pipe is empty or the output pipe is full.
1556 		 */
1557 		if (!ipipe->nrbufs || opipe->nrbufs >= opipe->buffers) {
1558 			/* Already processed some buffers, break */
1559 			if (ret)
1560 				break;
1561 
1562 			if (flags & SPLICE_F_NONBLOCK) {
1563 				ret = -EAGAIN;
1564 				break;
1565 			}
1566 
1567 			/*
1568 			 * We raced with another reader/writer and haven't
1569 			 * managed to process any buffers.  A zero return
1570 			 * value means EOF, so retry instead.
1571 			 */
1572 			pipe_unlock(ipipe);
1573 			pipe_unlock(opipe);
1574 			goto retry;
1575 		}
1576 
1577 		ibuf = ipipe->bufs + ipipe->curbuf;
1578 		nbuf = (opipe->curbuf + opipe->nrbufs) & (opipe->buffers - 1);
1579 		obuf = opipe->bufs + nbuf;
1580 
1581 		if (len >= ibuf->len) {
1582 			/*
1583 			 * Simply move the whole buffer from ipipe to opipe
1584 			 */
1585 			*obuf = *ibuf;
1586 			ibuf->ops = NULL;
1587 			opipe->nrbufs++;
1588 			ipipe->curbuf = (ipipe->curbuf + 1) & (ipipe->buffers - 1);
1589 			ipipe->nrbufs--;
1590 			input_wakeup = true;
1591 		} else {
1592 			/*
1593 			 * Get a reference to this pipe buffer,
1594 			 * so we can copy the contents over.
1595 			 */
1596 			if (!pipe_buf_get(ipipe, ibuf)) {
1597 				if (ret == 0)
1598 					ret = -EFAULT;
1599 				break;
1600 			}
1601 			*obuf = *ibuf;
1602 
1603 			/*
1604 			 * Don't inherit the gift flag, we need to
1605 			 * prevent multiple steals of this page.
1606 			 */
1607 			obuf->flags &= ~PIPE_BUF_FLAG_GIFT;
1608 
1609 			pipe_buf_mark_unmergeable(obuf);
1610 
1611 			obuf->len = len;
1612 			opipe->nrbufs++;
1613 			ibuf->offset += obuf->len;
1614 			ibuf->len -= obuf->len;
1615 		}
1616 		ret += obuf->len;
1617 		len -= obuf->len;
1618 	} while (len);
1619 
1620 	pipe_unlock(ipipe);
1621 	pipe_unlock(opipe);
1622 
1623 	/*
1624 	 * If we put data in the output pipe, wakeup any potential readers.
1625 	 */
1626 	if (ret > 0)
1627 		wakeup_pipe_readers(opipe);
1628 
1629 	if (input_wakeup)
1630 		wakeup_pipe_writers(ipipe);
1631 
1632 	return ret;
1633 }
1634 
1635 /*
1636  * Link contents of ipipe to opipe.
1637  */
1638 static int link_pipe(struct pipe_inode_info *ipipe,
1639 		     struct pipe_inode_info *opipe,
1640 		     size_t len, unsigned int flags)
1641 {
1642 	struct pipe_buffer *ibuf, *obuf;
1643 	int ret = 0, i = 0, nbuf;
1644 
1645 	/*
1646 	 * Potential ABBA deadlock, work around it by ordering lock
1647 	 * grabbing by pipe info address. Otherwise two different processes
1648 	 * could deadlock (one doing tee from A -> B, the other from B -> A).
1649 	 */
1650 	pipe_double_lock(ipipe, opipe);
1651 
1652 	do {
1653 		if (!opipe->readers) {
1654 			send_sig(SIGPIPE, current, 0);
1655 			if (!ret)
1656 				ret = -EPIPE;
1657 			break;
1658 		}
1659 
1660 		/*
1661 		 * If we have iterated all input buffers or ran out of
1662 		 * output room, break.
1663 		 */
1664 		if (i >= ipipe->nrbufs || opipe->nrbufs >= opipe->buffers)
1665 			break;
1666 
1667 		ibuf = ipipe->bufs + ((ipipe->curbuf + i) & (ipipe->buffers-1));
1668 		nbuf = (opipe->curbuf + opipe->nrbufs) & (opipe->buffers - 1);
1669 
1670 		/*
1671 		 * Get a reference to this pipe buffer,
1672 		 * so we can copy the contents over.
1673 		 */
1674 		if (!pipe_buf_get(ipipe, ibuf)) {
1675 			if (ret == 0)
1676 				ret = -EFAULT;
1677 			break;
1678 		}
1679 
1680 		obuf = opipe->bufs + nbuf;
1681 		*obuf = *ibuf;
1682 
1683 		/*
1684 		 * Don't inherit the gift flag, we need to
1685 		 * prevent multiple steals of this page.
1686 		 */
1687 		obuf->flags &= ~PIPE_BUF_FLAG_GIFT;
1688 
1689 		pipe_buf_mark_unmergeable(obuf);
1690 
1691 		if (obuf->len > len)
1692 			obuf->len = len;
1693 
1694 		opipe->nrbufs++;
1695 		ret += obuf->len;
1696 		len -= obuf->len;
1697 		i++;
1698 	} while (len);
1699 
1700 	/*
1701 	 * return EAGAIN if we have the potential of some data in the
1702 	 * future, otherwise just return 0
1703 	 */
1704 	if (!ret && ipipe->waiting_writers && (flags & SPLICE_F_NONBLOCK))
1705 		ret = -EAGAIN;
1706 
1707 	pipe_unlock(ipipe);
1708 	pipe_unlock(opipe);
1709 
1710 	/*
1711 	 * If we put data in the output pipe, wakeup any potential readers.
1712 	 */
1713 	if (ret > 0)
1714 		wakeup_pipe_readers(opipe);
1715 
1716 	return ret;
1717 }
1718 
1719 /*
1720  * This is a tee(1) implementation that works on pipes. It doesn't copy
1721  * any data, it simply references the 'in' pages on the 'out' pipe.
1722  * The 'flags' used are the SPLICE_F_* variants, currently the only
1723  * applicable one is SPLICE_F_NONBLOCK.
1724  */
1725 static long do_tee(struct file *in, struct file *out, size_t len,
1726 		   unsigned int flags)
1727 {
1728 	struct pipe_inode_info *ipipe = get_pipe_info(in);
1729 	struct pipe_inode_info *opipe = get_pipe_info(out);
1730 	int ret = -EINVAL;
1731 
1732 	/*
1733 	 * Duplicate the contents of ipipe to opipe without actually
1734 	 * copying the data.
1735 	 */
1736 	if (ipipe && opipe && ipipe != opipe) {
1737 		if ((in->f_flags | out->f_flags) & O_NONBLOCK)
1738 			flags |= SPLICE_F_NONBLOCK;
1739 
1740 		/*
1741 		 * Keep going, unless we encounter an error. The ipipe/opipe
1742 		 * ordering doesn't really matter.
1743 		 */
1744 		ret = ipipe_prep(ipipe, flags);
1745 		if (!ret) {
1746 			ret = opipe_prep(opipe, flags);
1747 			if (!ret)
1748 				ret = link_pipe(ipipe, opipe, len, flags);
1749 		}
1750 	}
1751 
1752 	return ret;
1753 }
1754 
1755 SYSCALL_DEFINE4(tee, int, fdin, int, fdout, size_t, len, unsigned int, flags)
1756 {
1757 	struct fd in;
1758 	int error;
1759 
1760 	if (unlikely(flags & ~SPLICE_F_ALL))
1761 		return -EINVAL;
1762 
1763 	if (unlikely(!len))
1764 		return 0;
1765 
1766 	error = -EBADF;
1767 	in = fdget(fdin);
1768 	if (in.file) {
1769 		if (in.file->f_mode & FMODE_READ) {
1770 			struct fd out = fdget(fdout);
1771 			if (out.file) {
1772 				if (out.file->f_mode & FMODE_WRITE)
1773 					error = do_tee(in.file, out.file,
1774 							len, flags);
1775 				fdput(out);
1776 			}
1777 		}
1778  		fdput(in);
1779  	}
1780 
1781 	return error;
1782 }
1783