xref: /openbmc/linux/fs/splice.c (revision 643d1f7f)
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/fs.h>
21 #include <linux/file.h>
22 #include <linux/pagemap.h>
23 #include <linux/splice.h>
24 #include <linux/mm_inline.h>
25 #include <linux/swap.h>
26 #include <linux/writeback.h>
27 #include <linux/buffer_head.h>
28 #include <linux/module.h>
29 #include <linux/syscalls.h>
30 #include <linux/uio.h>
31 #include <linux/security.h>
32 
33 /*
34  * Attempt to steal a page from a pipe buffer. This should perhaps go into
35  * a vm helper function, it's already simplified quite a bit by the
36  * addition of remove_mapping(). If success is returned, the caller may
37  * attempt to reuse this page for another destination.
38  */
39 static int page_cache_pipe_buf_steal(struct pipe_inode_info *pipe,
40 				     struct pipe_buffer *buf)
41 {
42 	struct page *page = buf->page;
43 	struct address_space *mapping;
44 
45 	lock_page(page);
46 
47 	mapping = page_mapping(page);
48 	if (mapping) {
49 		WARN_ON(!PageUptodate(page));
50 
51 		/*
52 		 * At least for ext2 with nobh option, we need to wait on
53 		 * writeback completing on this page, since we'll remove it
54 		 * from the pagecache.  Otherwise truncate wont wait on the
55 		 * page, allowing the disk blocks to be reused by someone else
56 		 * before we actually wrote our data to them. fs corruption
57 		 * ensues.
58 		 */
59 		wait_on_page_writeback(page);
60 
61 		if (PagePrivate(page))
62 			try_to_release_page(page, GFP_KERNEL);
63 
64 		/*
65 		 * If we succeeded in removing the mapping, set LRU flag
66 		 * and return good.
67 		 */
68 		if (remove_mapping(mapping, page)) {
69 			buf->flags |= PIPE_BUF_FLAG_LRU;
70 			return 0;
71 		}
72 	}
73 
74 	/*
75 	 * Raced with truncate or failed to remove page from current
76 	 * address space, unlock and return failure.
77 	 */
78 	unlock_page(page);
79 	return 1;
80 }
81 
82 static void page_cache_pipe_buf_release(struct pipe_inode_info *pipe,
83 					struct pipe_buffer *buf)
84 {
85 	page_cache_release(buf->page);
86 	buf->flags &= ~PIPE_BUF_FLAG_LRU;
87 }
88 
89 /*
90  * Check whether the contents of buf is OK to access. Since the content
91  * is a page cache page, IO may be in flight.
92  */
93 static int page_cache_pipe_buf_confirm(struct pipe_inode_info *pipe,
94 				       struct pipe_buffer *buf)
95 {
96 	struct page *page = buf->page;
97 	int err;
98 
99 	if (!PageUptodate(page)) {
100 		lock_page(page);
101 
102 		/*
103 		 * Page got truncated/unhashed. This will cause a 0-byte
104 		 * splice, if this is the first page.
105 		 */
106 		if (!page->mapping) {
107 			err = -ENODATA;
108 			goto error;
109 		}
110 
111 		/*
112 		 * Uh oh, read-error from disk.
113 		 */
114 		if (!PageUptodate(page)) {
115 			err = -EIO;
116 			goto error;
117 		}
118 
119 		/*
120 		 * Page is ok afterall, we are done.
121 		 */
122 		unlock_page(page);
123 	}
124 
125 	return 0;
126 error:
127 	unlock_page(page);
128 	return err;
129 }
130 
131 static const struct pipe_buf_operations page_cache_pipe_buf_ops = {
132 	.can_merge = 0,
133 	.map = generic_pipe_buf_map,
134 	.unmap = generic_pipe_buf_unmap,
135 	.confirm = page_cache_pipe_buf_confirm,
136 	.release = page_cache_pipe_buf_release,
137 	.steal = page_cache_pipe_buf_steal,
138 	.get = generic_pipe_buf_get,
139 };
140 
141 static int user_page_pipe_buf_steal(struct pipe_inode_info *pipe,
142 				    struct pipe_buffer *buf)
143 {
144 	if (!(buf->flags & PIPE_BUF_FLAG_GIFT))
145 		return 1;
146 
147 	buf->flags |= PIPE_BUF_FLAG_LRU;
148 	return generic_pipe_buf_steal(pipe, buf);
149 }
150 
151 static const struct pipe_buf_operations user_page_pipe_buf_ops = {
152 	.can_merge = 0,
153 	.map = generic_pipe_buf_map,
154 	.unmap = generic_pipe_buf_unmap,
155 	.confirm = generic_pipe_buf_confirm,
156 	.release = page_cache_pipe_buf_release,
157 	.steal = user_page_pipe_buf_steal,
158 	.get = generic_pipe_buf_get,
159 };
160 
161 /**
162  * splice_to_pipe - fill passed data into a pipe
163  * @pipe:	pipe to fill
164  * @spd:	data to fill
165  *
166  * Description:
167  *    @spd contains a map of pages and len/offset tuples, along with
168  *    the struct pipe_buf_operations associated with these pages. This
169  *    function will link that data to the pipe.
170  *
171  */
172 ssize_t splice_to_pipe(struct pipe_inode_info *pipe,
173 		       struct splice_pipe_desc *spd)
174 {
175 	unsigned int spd_pages = spd->nr_pages;
176 	int ret, do_wakeup, page_nr;
177 
178 	ret = 0;
179 	do_wakeup = 0;
180 	page_nr = 0;
181 
182 	if (pipe->inode)
183 		mutex_lock(&pipe->inode->i_mutex);
184 
185 	for (;;) {
186 		if (!pipe->readers) {
187 			send_sig(SIGPIPE, current, 0);
188 			if (!ret)
189 				ret = -EPIPE;
190 			break;
191 		}
192 
193 		if (pipe->nrbufs < PIPE_BUFFERS) {
194 			int newbuf = (pipe->curbuf + pipe->nrbufs) & (PIPE_BUFFERS - 1);
195 			struct pipe_buffer *buf = pipe->bufs + newbuf;
196 
197 			buf->page = spd->pages[page_nr];
198 			buf->offset = spd->partial[page_nr].offset;
199 			buf->len = spd->partial[page_nr].len;
200 			buf->private = spd->partial[page_nr].private;
201 			buf->ops = spd->ops;
202 			if (spd->flags & SPLICE_F_GIFT)
203 				buf->flags |= PIPE_BUF_FLAG_GIFT;
204 
205 			pipe->nrbufs++;
206 			page_nr++;
207 			ret += buf->len;
208 
209 			if (pipe->inode)
210 				do_wakeup = 1;
211 
212 			if (!--spd->nr_pages)
213 				break;
214 			if (pipe->nrbufs < PIPE_BUFFERS)
215 				continue;
216 
217 			break;
218 		}
219 
220 		if (spd->flags & SPLICE_F_NONBLOCK) {
221 			if (!ret)
222 				ret = -EAGAIN;
223 			break;
224 		}
225 
226 		if (signal_pending(current)) {
227 			if (!ret)
228 				ret = -ERESTARTSYS;
229 			break;
230 		}
231 
232 		if (do_wakeup) {
233 			smp_mb();
234 			if (waitqueue_active(&pipe->wait))
235 				wake_up_interruptible_sync(&pipe->wait);
236 			kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
237 			do_wakeup = 0;
238 		}
239 
240 		pipe->waiting_writers++;
241 		pipe_wait(pipe);
242 		pipe->waiting_writers--;
243 	}
244 
245 	if (pipe->inode) {
246 		mutex_unlock(&pipe->inode->i_mutex);
247 
248 		if (do_wakeup) {
249 			smp_mb();
250 			if (waitqueue_active(&pipe->wait))
251 				wake_up_interruptible(&pipe->wait);
252 			kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
253 		}
254 	}
255 
256 	while (page_nr < spd_pages)
257 		spd->spd_release(spd, page_nr++);
258 
259 	return ret;
260 }
261 
262 static void spd_release_page(struct splice_pipe_desc *spd, unsigned int i)
263 {
264 	page_cache_release(spd->pages[i]);
265 }
266 
267 static int
268 __generic_file_splice_read(struct file *in, loff_t *ppos,
269 			   struct pipe_inode_info *pipe, size_t len,
270 			   unsigned int flags)
271 {
272 	struct address_space *mapping = in->f_mapping;
273 	unsigned int loff, nr_pages, req_pages;
274 	struct page *pages[PIPE_BUFFERS];
275 	struct partial_page partial[PIPE_BUFFERS];
276 	struct page *page;
277 	pgoff_t index, end_index;
278 	loff_t isize;
279 	int error, page_nr;
280 	struct splice_pipe_desc spd = {
281 		.pages = pages,
282 		.partial = partial,
283 		.flags = flags,
284 		.ops = &page_cache_pipe_buf_ops,
285 		.spd_release = spd_release_page,
286 	};
287 
288 	index = *ppos >> PAGE_CACHE_SHIFT;
289 	loff = *ppos & ~PAGE_CACHE_MASK;
290 	req_pages = (len + loff + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
291 	nr_pages = min(req_pages, (unsigned)PIPE_BUFFERS);
292 
293 	/*
294 	 * Lookup the (hopefully) full range of pages we need.
295 	 */
296 	spd.nr_pages = find_get_pages_contig(mapping, index, nr_pages, pages);
297 	index += spd.nr_pages;
298 
299 	/*
300 	 * If find_get_pages_contig() returned fewer pages than we needed,
301 	 * readahead/allocate the rest and fill in the holes.
302 	 */
303 	if (spd.nr_pages < nr_pages)
304 		page_cache_sync_readahead(mapping, &in->f_ra, in,
305 				index, req_pages - spd.nr_pages);
306 
307 	error = 0;
308 	while (spd.nr_pages < nr_pages) {
309 		/*
310 		 * Page could be there, find_get_pages_contig() breaks on
311 		 * the first hole.
312 		 */
313 		page = find_get_page(mapping, index);
314 		if (!page) {
315 			/*
316 			 * page didn't exist, allocate one.
317 			 */
318 			page = page_cache_alloc_cold(mapping);
319 			if (!page)
320 				break;
321 
322 			error = add_to_page_cache_lru(page, mapping, index,
323 					      GFP_KERNEL);
324 			if (unlikely(error)) {
325 				page_cache_release(page);
326 				if (error == -EEXIST)
327 					continue;
328 				break;
329 			}
330 			/*
331 			 * add_to_page_cache() locks the page, unlock it
332 			 * to avoid convoluting the logic below even more.
333 			 */
334 			unlock_page(page);
335 		}
336 
337 		pages[spd.nr_pages++] = page;
338 		index++;
339 	}
340 
341 	/*
342 	 * Now loop over the map and see if we need to start IO on any
343 	 * pages, fill in the partial map, etc.
344 	 */
345 	index = *ppos >> PAGE_CACHE_SHIFT;
346 	nr_pages = spd.nr_pages;
347 	spd.nr_pages = 0;
348 	for (page_nr = 0; page_nr < nr_pages; page_nr++) {
349 		unsigned int this_len;
350 
351 		if (!len)
352 			break;
353 
354 		/*
355 		 * this_len is the max we'll use from this page
356 		 */
357 		this_len = min_t(unsigned long, len, PAGE_CACHE_SIZE - loff);
358 		page = pages[page_nr];
359 
360 		if (PageReadahead(page))
361 			page_cache_async_readahead(mapping, &in->f_ra, in,
362 					page, index, req_pages - page_nr);
363 
364 		/*
365 		 * If the page isn't uptodate, we may need to start io on it
366 		 */
367 		if (!PageUptodate(page)) {
368 			/*
369 			 * If in nonblock mode then dont block on waiting
370 			 * for an in-flight io page
371 			 */
372 			if (flags & SPLICE_F_NONBLOCK) {
373 				if (TestSetPageLocked(page))
374 					break;
375 			} else
376 				lock_page(page);
377 
378 			/*
379 			 * page was truncated, stop here. if this isn't the
380 			 * first page, we'll just complete what we already
381 			 * added
382 			 */
383 			if (!page->mapping) {
384 				unlock_page(page);
385 				break;
386 			}
387 			/*
388 			 * page was already under io and is now done, great
389 			 */
390 			if (PageUptodate(page)) {
391 				unlock_page(page);
392 				goto fill_it;
393 			}
394 
395 			/*
396 			 * need to read in the page
397 			 */
398 			error = mapping->a_ops->readpage(in, page);
399 			if (unlikely(error)) {
400 				/*
401 				 * We really should re-lookup the page here,
402 				 * but it complicates things a lot. Instead
403 				 * lets just do what we already stored, and
404 				 * we'll get it the next time we are called.
405 				 */
406 				if (error == AOP_TRUNCATED_PAGE)
407 					error = 0;
408 
409 				break;
410 			}
411 		}
412 fill_it:
413 		/*
414 		 * i_size must be checked after PageUptodate.
415 		 */
416 		isize = i_size_read(mapping->host);
417 		end_index = (isize - 1) >> PAGE_CACHE_SHIFT;
418 		if (unlikely(!isize || index > end_index))
419 			break;
420 
421 		/*
422 		 * if this is the last page, see if we need to shrink
423 		 * the length and stop
424 		 */
425 		if (end_index == index) {
426 			unsigned int plen;
427 
428 			/*
429 			 * max good bytes in this page
430 			 */
431 			plen = ((isize - 1) & ~PAGE_CACHE_MASK) + 1;
432 			if (plen <= loff)
433 				break;
434 
435 			/*
436 			 * force quit after adding this page
437 			 */
438 			this_len = min(this_len, plen - loff);
439 			len = this_len;
440 		}
441 
442 		partial[page_nr].offset = loff;
443 		partial[page_nr].len = this_len;
444 		len -= this_len;
445 		loff = 0;
446 		spd.nr_pages++;
447 		index++;
448 	}
449 
450 	/*
451 	 * Release any pages at the end, if we quit early. 'page_nr' is how far
452 	 * we got, 'nr_pages' is how many pages are in the map.
453 	 */
454 	while (page_nr < nr_pages)
455 		page_cache_release(pages[page_nr++]);
456 	in->f_ra.prev_pos = (loff_t)index << PAGE_CACHE_SHIFT;
457 
458 	if (spd.nr_pages)
459 		return splice_to_pipe(pipe, &spd);
460 
461 	return error;
462 }
463 
464 /**
465  * generic_file_splice_read - splice data from file to a pipe
466  * @in:		file to splice from
467  * @ppos:	position in @in
468  * @pipe:	pipe to splice to
469  * @len:	number of bytes to splice
470  * @flags:	splice modifier flags
471  *
472  * Description:
473  *    Will read pages from given file and fill them into a pipe. Can be
474  *    used as long as the address_space operations for the source implements
475  *    a readpage() hook.
476  *
477  */
478 ssize_t generic_file_splice_read(struct file *in, loff_t *ppos,
479 				 struct pipe_inode_info *pipe, size_t len,
480 				 unsigned int flags)
481 {
482 	ssize_t spliced;
483 	int ret;
484 	loff_t isize, left;
485 
486 	isize = i_size_read(in->f_mapping->host);
487 	if (unlikely(*ppos >= isize))
488 		return 0;
489 
490 	left = isize - *ppos;
491 	if (unlikely(left < len))
492 		len = left;
493 
494 	ret = 0;
495 	spliced = 0;
496 	while (len && !spliced) {
497 		ret = __generic_file_splice_read(in, ppos, pipe, len, flags);
498 
499 		if (ret < 0)
500 			break;
501 		else if (!ret) {
502 			if (spliced)
503 				break;
504 			if (flags & SPLICE_F_NONBLOCK) {
505 				ret = -EAGAIN;
506 				break;
507 			}
508 		}
509 
510 		*ppos += ret;
511 		len -= ret;
512 		spliced += ret;
513 	}
514 
515 	if (spliced)
516 		return spliced;
517 
518 	return ret;
519 }
520 
521 EXPORT_SYMBOL(generic_file_splice_read);
522 
523 /*
524  * Send 'sd->len' bytes to socket from 'sd->file' at position 'sd->pos'
525  * using sendpage(). Return the number of bytes sent.
526  */
527 static int pipe_to_sendpage(struct pipe_inode_info *pipe,
528 			    struct pipe_buffer *buf, struct splice_desc *sd)
529 {
530 	struct file *file = sd->u.file;
531 	loff_t pos = sd->pos;
532 	int ret, more;
533 
534 	ret = buf->ops->confirm(pipe, buf);
535 	if (!ret) {
536 		more = (sd->flags & SPLICE_F_MORE) || sd->len < sd->total_len;
537 
538 		ret = file->f_op->sendpage(file, buf->page, buf->offset,
539 					   sd->len, &pos, more);
540 	}
541 
542 	return ret;
543 }
544 
545 /*
546  * This is a little more tricky than the file -> pipe splicing. There are
547  * basically three cases:
548  *
549  *	- Destination page already exists in the address space and there
550  *	  are users of it. For that case we have no other option that
551  *	  copying the data. Tough luck.
552  *	- Destination page already exists in the address space, but there
553  *	  are no users of it. Make sure it's uptodate, then drop it. Fall
554  *	  through to last case.
555  *	- Destination page does not exist, we can add the pipe page to
556  *	  the page cache and avoid the copy.
557  *
558  * If asked to move pages to the output file (SPLICE_F_MOVE is set in
559  * sd->flags), we attempt to migrate pages from the pipe to the output
560  * file address space page cache. This is possible if no one else has
561  * the pipe page referenced outside of the pipe and page cache. If
562  * SPLICE_F_MOVE isn't set, or we cannot move the page, we simply create
563  * a new page in the output file page cache and fill/dirty that.
564  */
565 static int pipe_to_file(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
566 			struct splice_desc *sd)
567 {
568 	struct file *file = sd->u.file;
569 	struct address_space *mapping = file->f_mapping;
570 	unsigned int offset, this_len;
571 	struct page *page;
572 	void *fsdata;
573 	int ret;
574 
575 	/*
576 	 * make sure the data in this buffer is uptodate
577 	 */
578 	ret = buf->ops->confirm(pipe, buf);
579 	if (unlikely(ret))
580 		return ret;
581 
582 	offset = sd->pos & ~PAGE_CACHE_MASK;
583 
584 	this_len = sd->len;
585 	if (this_len + offset > PAGE_CACHE_SIZE)
586 		this_len = PAGE_CACHE_SIZE - offset;
587 
588 	ret = pagecache_write_begin(file, mapping, sd->pos, this_len,
589 				AOP_FLAG_UNINTERRUPTIBLE, &page, &fsdata);
590 	if (unlikely(ret))
591 		goto out;
592 
593 	if (buf->page != page) {
594 		/*
595 		 * Careful, ->map() uses KM_USER0!
596 		 */
597 		char *src = buf->ops->map(pipe, buf, 1);
598 		char *dst = kmap_atomic(page, KM_USER1);
599 
600 		memcpy(dst + offset, src + buf->offset, this_len);
601 		flush_dcache_page(page);
602 		kunmap_atomic(dst, KM_USER1);
603 		buf->ops->unmap(pipe, buf, src);
604 	}
605 	ret = pagecache_write_end(file, mapping, sd->pos, this_len, this_len,
606 				page, fsdata);
607 out:
608 	return ret;
609 }
610 
611 /**
612  * __splice_from_pipe - splice data from a pipe to given actor
613  * @pipe:	pipe to splice from
614  * @sd:		information to @actor
615  * @actor:	handler that splices the data
616  *
617  * Description:
618  *    This function does little more than loop over the pipe and call
619  *    @actor to do the actual moving of a single struct pipe_buffer to
620  *    the desired destination. See pipe_to_file, pipe_to_sendpage, or
621  *    pipe_to_user.
622  *
623  */
624 ssize_t __splice_from_pipe(struct pipe_inode_info *pipe, struct splice_desc *sd,
625 			   splice_actor *actor)
626 {
627 	int ret, do_wakeup, err;
628 
629 	ret = 0;
630 	do_wakeup = 0;
631 
632 	for (;;) {
633 		if (pipe->nrbufs) {
634 			struct pipe_buffer *buf = pipe->bufs + pipe->curbuf;
635 			const struct pipe_buf_operations *ops = buf->ops;
636 
637 			sd->len = buf->len;
638 			if (sd->len > sd->total_len)
639 				sd->len = sd->total_len;
640 
641 			err = actor(pipe, buf, sd);
642 			if (err <= 0) {
643 				if (!ret && err != -ENODATA)
644 					ret = err;
645 
646 				break;
647 			}
648 
649 			ret += err;
650 			buf->offset += err;
651 			buf->len -= err;
652 
653 			sd->len -= err;
654 			sd->pos += err;
655 			sd->total_len -= err;
656 			if (sd->len)
657 				continue;
658 
659 			if (!buf->len) {
660 				buf->ops = NULL;
661 				ops->release(pipe, buf);
662 				pipe->curbuf = (pipe->curbuf + 1) & (PIPE_BUFFERS - 1);
663 				pipe->nrbufs--;
664 				if (pipe->inode)
665 					do_wakeup = 1;
666 			}
667 
668 			if (!sd->total_len)
669 				break;
670 		}
671 
672 		if (pipe->nrbufs)
673 			continue;
674 		if (!pipe->writers)
675 			break;
676 		if (!pipe->waiting_writers) {
677 			if (ret)
678 				break;
679 		}
680 
681 		if (sd->flags & SPLICE_F_NONBLOCK) {
682 			if (!ret)
683 				ret = -EAGAIN;
684 			break;
685 		}
686 
687 		if (signal_pending(current)) {
688 			if (!ret)
689 				ret = -ERESTARTSYS;
690 			break;
691 		}
692 
693 		if (do_wakeup) {
694 			smp_mb();
695 			if (waitqueue_active(&pipe->wait))
696 				wake_up_interruptible_sync(&pipe->wait);
697 			kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
698 			do_wakeup = 0;
699 		}
700 
701 		pipe_wait(pipe);
702 	}
703 
704 	if (do_wakeup) {
705 		smp_mb();
706 		if (waitqueue_active(&pipe->wait))
707 			wake_up_interruptible(&pipe->wait);
708 		kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
709 	}
710 
711 	return ret;
712 }
713 EXPORT_SYMBOL(__splice_from_pipe);
714 
715 /**
716  * splice_from_pipe - splice data from a pipe to a file
717  * @pipe:	pipe to splice from
718  * @out:	file to splice to
719  * @ppos:	position in @out
720  * @len:	how many bytes to splice
721  * @flags:	splice modifier flags
722  * @actor:	handler that splices the data
723  *
724  * Description:
725  *    See __splice_from_pipe. This function locks the input and output inodes,
726  *    otherwise it's identical to __splice_from_pipe().
727  *
728  */
729 ssize_t splice_from_pipe(struct pipe_inode_info *pipe, struct file *out,
730 			 loff_t *ppos, size_t len, unsigned int flags,
731 			 splice_actor *actor)
732 {
733 	ssize_t ret;
734 	struct inode *inode = out->f_mapping->host;
735 	struct splice_desc sd = {
736 		.total_len = len,
737 		.flags = flags,
738 		.pos = *ppos,
739 		.u.file = out,
740 	};
741 
742 	/*
743 	 * The actor worker might be calling ->prepare_write and
744 	 * ->commit_write. Most of the time, these expect i_mutex to
745 	 * be held. Since this may result in an ABBA deadlock with
746 	 * pipe->inode, we have to order lock acquiry here.
747 	 */
748 	inode_double_lock(inode, pipe->inode);
749 	ret = __splice_from_pipe(pipe, &sd, actor);
750 	inode_double_unlock(inode, pipe->inode);
751 
752 	return ret;
753 }
754 
755 /**
756  * generic_file_splice_write_nolock - generic_file_splice_write without mutexes
757  * @pipe:	pipe info
758  * @out:	file to write to
759  * @ppos:	position in @out
760  * @len:	number of bytes to splice
761  * @flags:	splice modifier flags
762  *
763  * Description:
764  *    Will either move or copy pages (determined by @flags options) from
765  *    the given pipe inode to the given file. The caller is responsible
766  *    for acquiring i_mutex on both inodes.
767  *
768  */
769 ssize_t
770 generic_file_splice_write_nolock(struct pipe_inode_info *pipe, struct file *out,
771 				 loff_t *ppos, size_t len, unsigned int flags)
772 {
773 	struct address_space *mapping = out->f_mapping;
774 	struct inode *inode = mapping->host;
775 	struct splice_desc sd = {
776 		.total_len = len,
777 		.flags = flags,
778 		.pos = *ppos,
779 		.u.file = out,
780 	};
781 	ssize_t ret;
782 	int err;
783 
784 	err = remove_suid(out->f_path.dentry);
785 	if (unlikely(err))
786 		return err;
787 
788 	ret = __splice_from_pipe(pipe, &sd, pipe_to_file);
789 	if (ret > 0) {
790 		unsigned long nr_pages;
791 
792 		*ppos += ret;
793 		nr_pages = (ret + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
794 
795 		/*
796 		 * If file or inode is SYNC and we actually wrote some data,
797 		 * sync it.
798 		 */
799 		if (unlikely((out->f_flags & O_SYNC) || IS_SYNC(inode))) {
800 			err = generic_osync_inode(inode, mapping,
801 						  OSYNC_METADATA|OSYNC_DATA);
802 
803 			if (err)
804 				ret = err;
805 		}
806 		balance_dirty_pages_ratelimited_nr(mapping, nr_pages);
807 	}
808 
809 	return ret;
810 }
811 
812 EXPORT_SYMBOL(generic_file_splice_write_nolock);
813 
814 /**
815  * generic_file_splice_write - splice data from a pipe to a file
816  * @pipe:	pipe info
817  * @out:	file to write to
818  * @ppos:	position in @out
819  * @len:	number of bytes to splice
820  * @flags:	splice modifier flags
821  *
822  * Description:
823  *    Will either move or copy pages (determined by @flags options) from
824  *    the given pipe inode to the given file.
825  *
826  */
827 ssize_t
828 generic_file_splice_write(struct pipe_inode_info *pipe, struct file *out,
829 			  loff_t *ppos, size_t len, unsigned int flags)
830 {
831 	struct address_space *mapping = out->f_mapping;
832 	struct inode *inode = mapping->host;
833 	int killsuid, killpriv;
834 	ssize_t ret;
835 	int err = 0;
836 
837 	killpriv = security_inode_need_killpriv(out->f_path.dentry);
838 	killsuid = should_remove_suid(out->f_path.dentry);
839 	if (unlikely(killsuid || killpriv)) {
840 		mutex_lock(&inode->i_mutex);
841 		if (killpriv)
842 			err = security_inode_killpriv(out->f_path.dentry);
843 		if (!err && killsuid)
844 			err = __remove_suid(out->f_path.dentry, killsuid);
845 		mutex_unlock(&inode->i_mutex);
846 		if (err)
847 			return err;
848 	}
849 
850 	ret = splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_file);
851 	if (ret > 0) {
852 		unsigned long nr_pages;
853 
854 		*ppos += ret;
855 		nr_pages = (ret + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
856 
857 		/*
858 		 * If file or inode is SYNC and we actually wrote some data,
859 		 * sync it.
860 		 */
861 		if (unlikely((out->f_flags & O_SYNC) || IS_SYNC(inode))) {
862 			mutex_lock(&inode->i_mutex);
863 			err = generic_osync_inode(inode, mapping,
864 						  OSYNC_METADATA|OSYNC_DATA);
865 			mutex_unlock(&inode->i_mutex);
866 
867 			if (err)
868 				ret = err;
869 		}
870 		balance_dirty_pages_ratelimited_nr(mapping, nr_pages);
871 	}
872 
873 	return ret;
874 }
875 
876 EXPORT_SYMBOL(generic_file_splice_write);
877 
878 /**
879  * generic_splice_sendpage - splice data from a pipe to a socket
880  * @pipe:	pipe to splice from
881  * @out:	socket to write to
882  * @ppos:	position in @out
883  * @len:	number of bytes to splice
884  * @flags:	splice modifier flags
885  *
886  * Description:
887  *    Will send @len bytes from the pipe to a network socket. No data copying
888  *    is involved.
889  *
890  */
891 ssize_t generic_splice_sendpage(struct pipe_inode_info *pipe, struct file *out,
892 				loff_t *ppos, size_t len, unsigned int flags)
893 {
894 	return splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_sendpage);
895 }
896 
897 EXPORT_SYMBOL(generic_splice_sendpage);
898 
899 /*
900  * Attempt to initiate a splice from pipe to file.
901  */
902 static long do_splice_from(struct pipe_inode_info *pipe, struct file *out,
903 			   loff_t *ppos, size_t len, unsigned int flags)
904 {
905 	int ret;
906 
907 	if (unlikely(!out->f_op || !out->f_op->splice_write))
908 		return -EINVAL;
909 
910 	if (unlikely(!(out->f_mode & FMODE_WRITE)))
911 		return -EBADF;
912 
913 	ret = rw_verify_area(WRITE, out, ppos, len);
914 	if (unlikely(ret < 0))
915 		return ret;
916 
917 	return out->f_op->splice_write(pipe, out, ppos, len, flags);
918 }
919 
920 /*
921  * Attempt to initiate a splice from a file to a pipe.
922  */
923 static long do_splice_to(struct file *in, loff_t *ppos,
924 			 struct pipe_inode_info *pipe, size_t len,
925 			 unsigned int flags)
926 {
927 	int ret;
928 
929 	if (unlikely(!in->f_op || !in->f_op->splice_read))
930 		return -EINVAL;
931 
932 	if (unlikely(!(in->f_mode & FMODE_READ)))
933 		return -EBADF;
934 
935 	ret = rw_verify_area(READ, in, ppos, len);
936 	if (unlikely(ret < 0))
937 		return ret;
938 
939 	return in->f_op->splice_read(in, ppos, pipe, len, flags);
940 }
941 
942 /**
943  * splice_direct_to_actor - splices data directly between two non-pipes
944  * @in:		file to splice from
945  * @sd:		actor information on where to splice to
946  * @actor:	handles the data splicing
947  *
948  * Description:
949  *    This is a special case helper to splice directly between two
950  *    points, without requiring an explicit pipe. Internally an allocated
951  *    pipe is cached in the process, and reused during the lifetime of
952  *    that process.
953  *
954  */
955 ssize_t splice_direct_to_actor(struct file *in, struct splice_desc *sd,
956 			       splice_direct_actor *actor)
957 {
958 	struct pipe_inode_info *pipe;
959 	long ret, bytes;
960 	umode_t i_mode;
961 	size_t len;
962 	int i, flags;
963 
964 	/*
965 	 * We require the input being a regular file, as we don't want to
966 	 * randomly drop data for eg socket -> socket splicing. Use the
967 	 * piped splicing for that!
968 	 */
969 	i_mode = in->f_path.dentry->d_inode->i_mode;
970 	if (unlikely(!S_ISREG(i_mode) && !S_ISBLK(i_mode)))
971 		return -EINVAL;
972 
973 	/*
974 	 * neither in nor out is a pipe, setup an internal pipe attached to
975 	 * 'out' and transfer the wanted data from 'in' to 'out' through that
976 	 */
977 	pipe = current->splice_pipe;
978 	if (unlikely(!pipe)) {
979 		pipe = alloc_pipe_info(NULL);
980 		if (!pipe)
981 			return -ENOMEM;
982 
983 		/*
984 		 * We don't have an immediate reader, but we'll read the stuff
985 		 * out of the pipe right after the splice_to_pipe(). So set
986 		 * PIPE_READERS appropriately.
987 		 */
988 		pipe->readers = 1;
989 
990 		current->splice_pipe = pipe;
991 	}
992 
993 	/*
994 	 * Do the splice.
995 	 */
996 	ret = 0;
997 	bytes = 0;
998 	len = sd->total_len;
999 	flags = sd->flags;
1000 
1001 	/*
1002 	 * Don't block on output, we have to drain the direct pipe.
1003 	 */
1004 	sd->flags &= ~SPLICE_F_NONBLOCK;
1005 
1006 	while (len) {
1007 		size_t read_len;
1008 		loff_t pos = sd->pos;
1009 
1010 		ret = do_splice_to(in, &pos, pipe, len, flags);
1011 		if (unlikely(ret <= 0))
1012 			goto out_release;
1013 
1014 		read_len = ret;
1015 		sd->total_len = read_len;
1016 
1017 		/*
1018 		 * NOTE: nonblocking mode only applies to the input. We
1019 		 * must not do the output in nonblocking mode as then we
1020 		 * could get stuck data in the internal pipe:
1021 		 */
1022 		ret = actor(pipe, sd);
1023 		if (unlikely(ret <= 0))
1024 			goto out_release;
1025 
1026 		bytes += ret;
1027 		len -= ret;
1028 		sd->pos = pos;
1029 
1030 		if (ret < read_len)
1031 			goto out_release;
1032 	}
1033 
1034 done:
1035 	pipe->nrbufs = pipe->curbuf = 0;
1036 	file_accessed(in);
1037 	return bytes;
1038 
1039 out_release:
1040 	/*
1041 	 * If we did an incomplete transfer we must release
1042 	 * the pipe buffers in question:
1043 	 */
1044 	for (i = 0; i < PIPE_BUFFERS; i++) {
1045 		struct pipe_buffer *buf = pipe->bufs + i;
1046 
1047 		if (buf->ops) {
1048 			buf->ops->release(pipe, buf);
1049 			buf->ops = NULL;
1050 		}
1051 	}
1052 
1053 	if (!bytes)
1054 		bytes = ret;
1055 
1056 	goto done;
1057 }
1058 EXPORT_SYMBOL(splice_direct_to_actor);
1059 
1060 static int direct_splice_actor(struct pipe_inode_info *pipe,
1061 			       struct splice_desc *sd)
1062 {
1063 	struct file *file = sd->u.file;
1064 
1065 	return do_splice_from(pipe, file, &sd->pos, sd->total_len, sd->flags);
1066 }
1067 
1068 /**
1069  * do_splice_direct - splices data directly between two files
1070  * @in:		file to splice from
1071  * @ppos:	input file offset
1072  * @out:	file to splice to
1073  * @len:	number of bytes to splice
1074  * @flags:	splice modifier flags
1075  *
1076  * Description:
1077  *    For use by do_sendfile(). splice can easily emulate sendfile, but
1078  *    doing it in the application would incur an extra system call
1079  *    (splice in + splice out, as compared to just sendfile()). So this helper
1080  *    can splice directly through a process-private pipe.
1081  *
1082  */
1083 long do_splice_direct(struct file *in, loff_t *ppos, struct file *out,
1084 		      size_t len, unsigned int flags)
1085 {
1086 	struct splice_desc sd = {
1087 		.len		= len,
1088 		.total_len	= len,
1089 		.flags		= flags,
1090 		.pos		= *ppos,
1091 		.u.file		= out,
1092 	};
1093 	long ret;
1094 
1095 	ret = splice_direct_to_actor(in, &sd, direct_splice_actor);
1096 	if (ret > 0)
1097 		*ppos += ret;
1098 
1099 	return ret;
1100 }
1101 
1102 /*
1103  * After the inode slimming patch, i_pipe/i_bdev/i_cdev share the same
1104  * location, so checking ->i_pipe is not enough to verify that this is a
1105  * pipe.
1106  */
1107 static inline struct pipe_inode_info *pipe_info(struct inode *inode)
1108 {
1109 	if (S_ISFIFO(inode->i_mode))
1110 		return inode->i_pipe;
1111 
1112 	return NULL;
1113 }
1114 
1115 /*
1116  * Determine where to splice to/from.
1117  */
1118 static long do_splice(struct file *in, loff_t __user *off_in,
1119 		      struct file *out, loff_t __user *off_out,
1120 		      size_t len, unsigned int flags)
1121 {
1122 	struct pipe_inode_info *pipe;
1123 	loff_t offset, *off;
1124 	long ret;
1125 
1126 	pipe = pipe_info(in->f_path.dentry->d_inode);
1127 	if (pipe) {
1128 		if (off_in)
1129 			return -ESPIPE;
1130 		if (off_out) {
1131 			if (out->f_op->llseek == no_llseek)
1132 				return -EINVAL;
1133 			if (copy_from_user(&offset, off_out, sizeof(loff_t)))
1134 				return -EFAULT;
1135 			off = &offset;
1136 		} else
1137 			off = &out->f_pos;
1138 
1139 		ret = do_splice_from(pipe, out, off, len, flags);
1140 
1141 		if (off_out && copy_to_user(off_out, off, sizeof(loff_t)))
1142 			ret = -EFAULT;
1143 
1144 		return ret;
1145 	}
1146 
1147 	pipe = pipe_info(out->f_path.dentry->d_inode);
1148 	if (pipe) {
1149 		if (off_out)
1150 			return -ESPIPE;
1151 		if (off_in) {
1152 			if (in->f_op->llseek == no_llseek)
1153 				return -EINVAL;
1154 			if (copy_from_user(&offset, off_in, sizeof(loff_t)))
1155 				return -EFAULT;
1156 			off = &offset;
1157 		} else
1158 			off = &in->f_pos;
1159 
1160 		ret = do_splice_to(in, off, pipe, len, flags);
1161 
1162 		if (off_in && copy_to_user(off_in, off, sizeof(loff_t)))
1163 			ret = -EFAULT;
1164 
1165 		return ret;
1166 	}
1167 
1168 	return -EINVAL;
1169 }
1170 
1171 /*
1172  * Do a copy-from-user while holding the mmap_semaphore for reading, in a
1173  * manner safe from deadlocking with simultaneous mmap() (grabbing mmap_sem
1174  * for writing) and page faulting on the user memory pointed to by src.
1175  * This assumes that we will very rarely hit the partial != 0 path, or this
1176  * will not be a win.
1177  */
1178 static int copy_from_user_mmap_sem(void *dst, const void __user *src, size_t n)
1179 {
1180 	int partial;
1181 
1182 	pagefault_disable();
1183 	partial = __copy_from_user_inatomic(dst, src, n);
1184 	pagefault_enable();
1185 
1186 	/*
1187 	 * Didn't copy everything, drop the mmap_sem and do a faulting copy
1188 	 */
1189 	if (unlikely(partial)) {
1190 		up_read(&current->mm->mmap_sem);
1191 		partial = copy_from_user(dst, src, n);
1192 		down_read(&current->mm->mmap_sem);
1193 	}
1194 
1195 	return partial;
1196 }
1197 
1198 /*
1199  * Map an iov into an array of pages and offset/length tupples. With the
1200  * partial_page structure, we can map several non-contiguous ranges into
1201  * our ones pages[] map instead of splitting that operation into pieces.
1202  * Could easily be exported as a generic helper for other users, in which
1203  * case one would probably want to add a 'max_nr_pages' parameter as well.
1204  */
1205 static int get_iovec_page_array(const struct iovec __user *iov,
1206 				unsigned int nr_vecs, struct page **pages,
1207 				struct partial_page *partial, int aligned)
1208 {
1209 	int buffers = 0, error = 0;
1210 
1211 	down_read(&current->mm->mmap_sem);
1212 
1213 	while (nr_vecs) {
1214 		unsigned long off, npages;
1215 		struct iovec entry;
1216 		void __user *base;
1217 		size_t len;
1218 		int i;
1219 
1220 		error = -EFAULT;
1221 		if (copy_from_user_mmap_sem(&entry, iov, sizeof(entry)))
1222 			break;
1223 
1224 		base = entry.iov_base;
1225 		len = entry.iov_len;
1226 
1227 		/*
1228 		 * Sanity check this iovec. 0 read succeeds.
1229 		 */
1230 		error = 0;
1231 		if (unlikely(!len))
1232 			break;
1233 		error = -EFAULT;
1234 		if (unlikely(!base))
1235 			break;
1236 
1237 		/*
1238 		 * Get this base offset and number of pages, then map
1239 		 * in the user pages.
1240 		 */
1241 		off = (unsigned long) base & ~PAGE_MASK;
1242 
1243 		/*
1244 		 * If asked for alignment, the offset must be zero and the
1245 		 * length a multiple of the PAGE_SIZE.
1246 		 */
1247 		error = -EINVAL;
1248 		if (aligned && (off || len & ~PAGE_MASK))
1249 			break;
1250 
1251 		npages = (off + len + PAGE_SIZE - 1) >> PAGE_SHIFT;
1252 		if (npages > PIPE_BUFFERS - buffers)
1253 			npages = PIPE_BUFFERS - buffers;
1254 
1255 		error = get_user_pages(current, current->mm,
1256 				       (unsigned long) base, npages, 0, 0,
1257 				       &pages[buffers], NULL);
1258 
1259 		if (unlikely(error <= 0))
1260 			break;
1261 
1262 		/*
1263 		 * Fill this contiguous range into the partial page map.
1264 		 */
1265 		for (i = 0; i < error; i++) {
1266 			const int plen = min_t(size_t, len, PAGE_SIZE - off);
1267 
1268 			partial[buffers].offset = off;
1269 			partial[buffers].len = plen;
1270 
1271 			off = 0;
1272 			len -= plen;
1273 			buffers++;
1274 		}
1275 
1276 		/*
1277 		 * We didn't complete this iov, stop here since it probably
1278 		 * means we have to move some of this into a pipe to
1279 		 * be able to continue.
1280 		 */
1281 		if (len)
1282 			break;
1283 
1284 		/*
1285 		 * Don't continue if we mapped fewer pages than we asked for,
1286 		 * or if we mapped the max number of pages that we have
1287 		 * room for.
1288 		 */
1289 		if (error < npages || buffers == PIPE_BUFFERS)
1290 			break;
1291 
1292 		nr_vecs--;
1293 		iov++;
1294 	}
1295 
1296 	up_read(&current->mm->mmap_sem);
1297 
1298 	if (buffers)
1299 		return buffers;
1300 
1301 	return error;
1302 }
1303 
1304 static int pipe_to_user(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
1305 			struct splice_desc *sd)
1306 {
1307 	char *src;
1308 	int ret;
1309 
1310 	ret = buf->ops->confirm(pipe, buf);
1311 	if (unlikely(ret))
1312 		return ret;
1313 
1314 	/*
1315 	 * See if we can use the atomic maps, by prefaulting in the
1316 	 * pages and doing an atomic copy
1317 	 */
1318 	if (!fault_in_pages_writeable(sd->u.userptr, sd->len)) {
1319 		src = buf->ops->map(pipe, buf, 1);
1320 		ret = __copy_to_user_inatomic(sd->u.userptr, src + buf->offset,
1321 							sd->len);
1322 		buf->ops->unmap(pipe, buf, src);
1323 		if (!ret) {
1324 			ret = sd->len;
1325 			goto out;
1326 		}
1327 	}
1328 
1329 	/*
1330 	 * No dice, use slow non-atomic map and copy
1331  	 */
1332 	src = buf->ops->map(pipe, buf, 0);
1333 
1334 	ret = sd->len;
1335 	if (copy_to_user(sd->u.userptr, src + buf->offset, sd->len))
1336 		ret = -EFAULT;
1337 
1338 	buf->ops->unmap(pipe, buf, src);
1339 out:
1340 	if (ret > 0)
1341 		sd->u.userptr += ret;
1342 	return ret;
1343 }
1344 
1345 /*
1346  * For lack of a better implementation, implement vmsplice() to userspace
1347  * as a simple copy of the pipes pages to the user iov.
1348  */
1349 static long vmsplice_to_user(struct file *file, const struct iovec __user *iov,
1350 			     unsigned long nr_segs, unsigned int flags)
1351 {
1352 	struct pipe_inode_info *pipe;
1353 	struct splice_desc sd;
1354 	ssize_t size;
1355 	int error;
1356 	long ret;
1357 
1358 	pipe = pipe_info(file->f_path.dentry->d_inode);
1359 	if (!pipe)
1360 		return -EBADF;
1361 
1362 	if (pipe->inode)
1363 		mutex_lock(&pipe->inode->i_mutex);
1364 
1365 	error = ret = 0;
1366 	while (nr_segs) {
1367 		void __user *base;
1368 		size_t len;
1369 
1370 		/*
1371 		 * Get user address base and length for this iovec.
1372 		 */
1373 		error = get_user(base, &iov->iov_base);
1374 		if (unlikely(error))
1375 			break;
1376 		error = get_user(len, &iov->iov_len);
1377 		if (unlikely(error))
1378 			break;
1379 
1380 		/*
1381 		 * Sanity check this iovec. 0 read succeeds.
1382 		 */
1383 		if (unlikely(!len))
1384 			break;
1385 		if (unlikely(!base)) {
1386 			error = -EFAULT;
1387 			break;
1388 		}
1389 
1390 		sd.len = 0;
1391 		sd.total_len = len;
1392 		sd.flags = flags;
1393 		sd.u.userptr = base;
1394 		sd.pos = 0;
1395 
1396 		size = __splice_from_pipe(pipe, &sd, pipe_to_user);
1397 		if (size < 0) {
1398 			if (!ret)
1399 				ret = size;
1400 
1401 			break;
1402 		}
1403 
1404 		ret += size;
1405 
1406 		if (size < len)
1407 			break;
1408 
1409 		nr_segs--;
1410 		iov++;
1411 	}
1412 
1413 	if (pipe->inode)
1414 		mutex_unlock(&pipe->inode->i_mutex);
1415 
1416 	if (!ret)
1417 		ret = error;
1418 
1419 	return ret;
1420 }
1421 
1422 /*
1423  * vmsplice splices a user address range into a pipe. It can be thought of
1424  * as splice-from-memory, where the regular splice is splice-from-file (or
1425  * to file). In both cases the output is a pipe, naturally.
1426  */
1427 static long vmsplice_to_pipe(struct file *file, const struct iovec __user *iov,
1428 			     unsigned long nr_segs, unsigned int flags)
1429 {
1430 	struct pipe_inode_info *pipe;
1431 	struct page *pages[PIPE_BUFFERS];
1432 	struct partial_page partial[PIPE_BUFFERS];
1433 	struct splice_pipe_desc spd = {
1434 		.pages = pages,
1435 		.partial = partial,
1436 		.flags = flags,
1437 		.ops = &user_page_pipe_buf_ops,
1438 		.spd_release = spd_release_page,
1439 	};
1440 
1441 	pipe = pipe_info(file->f_path.dentry->d_inode);
1442 	if (!pipe)
1443 		return -EBADF;
1444 
1445 	spd.nr_pages = get_iovec_page_array(iov, nr_segs, pages, partial,
1446 					    flags & SPLICE_F_GIFT);
1447 	if (spd.nr_pages <= 0)
1448 		return spd.nr_pages;
1449 
1450 	return splice_to_pipe(pipe, &spd);
1451 }
1452 
1453 /*
1454  * Note that vmsplice only really supports true splicing _from_ user memory
1455  * to a pipe, not the other way around. Splicing from user memory is a simple
1456  * operation that can be supported without any funky alignment restrictions
1457  * or nasty vm tricks. We simply map in the user memory and fill them into
1458  * a pipe. The reverse isn't quite as easy, though. There are two possible
1459  * solutions for that:
1460  *
1461  *	- memcpy() the data internally, at which point we might as well just
1462  *	  do a regular read() on the buffer anyway.
1463  *	- Lots of nasty vm tricks, that are neither fast nor flexible (it
1464  *	  has restriction limitations on both ends of the pipe).
1465  *
1466  * Currently we punt and implement it as a normal copy, see pipe_to_user().
1467  *
1468  */
1469 asmlinkage long sys_vmsplice(int fd, const struct iovec __user *iov,
1470 			     unsigned long nr_segs, unsigned int flags)
1471 {
1472 	struct file *file;
1473 	long error;
1474 	int fput;
1475 
1476 	if (unlikely(nr_segs > UIO_MAXIOV))
1477 		return -EINVAL;
1478 	else if (unlikely(!nr_segs))
1479 		return 0;
1480 
1481 	error = -EBADF;
1482 	file = fget_light(fd, &fput);
1483 	if (file) {
1484 		if (file->f_mode & FMODE_WRITE)
1485 			error = vmsplice_to_pipe(file, iov, nr_segs, flags);
1486 		else if (file->f_mode & FMODE_READ)
1487 			error = vmsplice_to_user(file, iov, nr_segs, flags);
1488 
1489 		fput_light(file, fput);
1490 	}
1491 
1492 	return error;
1493 }
1494 
1495 asmlinkage long sys_splice(int fd_in, loff_t __user *off_in,
1496 			   int fd_out, loff_t __user *off_out,
1497 			   size_t len, unsigned int flags)
1498 {
1499 	long error;
1500 	struct file *in, *out;
1501 	int fput_in, fput_out;
1502 
1503 	if (unlikely(!len))
1504 		return 0;
1505 
1506 	error = -EBADF;
1507 	in = fget_light(fd_in, &fput_in);
1508 	if (in) {
1509 		if (in->f_mode & FMODE_READ) {
1510 			out = fget_light(fd_out, &fput_out);
1511 			if (out) {
1512 				if (out->f_mode & FMODE_WRITE)
1513 					error = do_splice(in, off_in,
1514 							  out, off_out,
1515 							  len, flags);
1516 				fput_light(out, fput_out);
1517 			}
1518 		}
1519 
1520 		fput_light(in, fput_in);
1521 	}
1522 
1523 	return error;
1524 }
1525 
1526 /*
1527  * Make sure there's data to read. Wait for input if we can, otherwise
1528  * return an appropriate error.
1529  */
1530 static int link_ipipe_prep(struct pipe_inode_info *pipe, unsigned int flags)
1531 {
1532 	int ret;
1533 
1534 	/*
1535 	 * Check ->nrbufs without the inode lock first. This function
1536 	 * is speculative anyways, so missing one is ok.
1537 	 */
1538 	if (pipe->nrbufs)
1539 		return 0;
1540 
1541 	ret = 0;
1542 	mutex_lock(&pipe->inode->i_mutex);
1543 
1544 	while (!pipe->nrbufs) {
1545 		if (signal_pending(current)) {
1546 			ret = -ERESTARTSYS;
1547 			break;
1548 		}
1549 		if (!pipe->writers)
1550 			break;
1551 		if (!pipe->waiting_writers) {
1552 			if (flags & SPLICE_F_NONBLOCK) {
1553 				ret = -EAGAIN;
1554 				break;
1555 			}
1556 		}
1557 		pipe_wait(pipe);
1558 	}
1559 
1560 	mutex_unlock(&pipe->inode->i_mutex);
1561 	return ret;
1562 }
1563 
1564 /*
1565  * Make sure there's writeable room. Wait for room if we can, otherwise
1566  * return an appropriate error.
1567  */
1568 static int link_opipe_prep(struct pipe_inode_info *pipe, unsigned int flags)
1569 {
1570 	int ret;
1571 
1572 	/*
1573 	 * Check ->nrbufs without the inode lock first. This function
1574 	 * is speculative anyways, so missing one is ok.
1575 	 */
1576 	if (pipe->nrbufs < PIPE_BUFFERS)
1577 		return 0;
1578 
1579 	ret = 0;
1580 	mutex_lock(&pipe->inode->i_mutex);
1581 
1582 	while (pipe->nrbufs >= PIPE_BUFFERS) {
1583 		if (!pipe->readers) {
1584 			send_sig(SIGPIPE, current, 0);
1585 			ret = -EPIPE;
1586 			break;
1587 		}
1588 		if (flags & SPLICE_F_NONBLOCK) {
1589 			ret = -EAGAIN;
1590 			break;
1591 		}
1592 		if (signal_pending(current)) {
1593 			ret = -ERESTARTSYS;
1594 			break;
1595 		}
1596 		pipe->waiting_writers++;
1597 		pipe_wait(pipe);
1598 		pipe->waiting_writers--;
1599 	}
1600 
1601 	mutex_unlock(&pipe->inode->i_mutex);
1602 	return ret;
1603 }
1604 
1605 /*
1606  * Link contents of ipipe to opipe.
1607  */
1608 static int link_pipe(struct pipe_inode_info *ipipe,
1609 		     struct pipe_inode_info *opipe,
1610 		     size_t len, unsigned int flags)
1611 {
1612 	struct pipe_buffer *ibuf, *obuf;
1613 	int ret = 0, i = 0, nbuf;
1614 
1615 	/*
1616 	 * Potential ABBA deadlock, work around it by ordering lock
1617 	 * grabbing by inode address. Otherwise two different processes
1618 	 * could deadlock (one doing tee from A -> B, the other from B -> A).
1619 	 */
1620 	inode_double_lock(ipipe->inode, opipe->inode);
1621 
1622 	do {
1623 		if (!opipe->readers) {
1624 			send_sig(SIGPIPE, current, 0);
1625 			if (!ret)
1626 				ret = -EPIPE;
1627 			break;
1628 		}
1629 
1630 		/*
1631 		 * If we have iterated all input buffers or ran out of
1632 		 * output room, break.
1633 		 */
1634 		if (i >= ipipe->nrbufs || opipe->nrbufs >= PIPE_BUFFERS)
1635 			break;
1636 
1637 		ibuf = ipipe->bufs + ((ipipe->curbuf + i) & (PIPE_BUFFERS - 1));
1638 		nbuf = (opipe->curbuf + opipe->nrbufs) & (PIPE_BUFFERS - 1);
1639 
1640 		/*
1641 		 * Get a reference to this pipe buffer,
1642 		 * so we can copy the contents over.
1643 		 */
1644 		ibuf->ops->get(ipipe, ibuf);
1645 
1646 		obuf = opipe->bufs + nbuf;
1647 		*obuf = *ibuf;
1648 
1649 		/*
1650 		 * Don't inherit the gift flag, we need to
1651 		 * prevent multiple steals of this page.
1652 		 */
1653 		obuf->flags &= ~PIPE_BUF_FLAG_GIFT;
1654 
1655 		if (obuf->len > len)
1656 			obuf->len = len;
1657 
1658 		opipe->nrbufs++;
1659 		ret += obuf->len;
1660 		len -= obuf->len;
1661 		i++;
1662 	} while (len);
1663 
1664 	inode_double_unlock(ipipe->inode, opipe->inode);
1665 
1666 	/*
1667 	 * If we put data in the output pipe, wakeup any potential readers.
1668 	 */
1669 	if (ret > 0) {
1670 		smp_mb();
1671 		if (waitqueue_active(&opipe->wait))
1672 			wake_up_interruptible(&opipe->wait);
1673 		kill_fasync(&opipe->fasync_readers, SIGIO, POLL_IN);
1674 	}
1675 
1676 	return ret;
1677 }
1678 
1679 /*
1680  * This is a tee(1) implementation that works on pipes. It doesn't copy
1681  * any data, it simply references the 'in' pages on the 'out' pipe.
1682  * The 'flags' used are the SPLICE_F_* variants, currently the only
1683  * applicable one is SPLICE_F_NONBLOCK.
1684  */
1685 static long do_tee(struct file *in, struct file *out, size_t len,
1686 		   unsigned int flags)
1687 {
1688 	struct pipe_inode_info *ipipe = pipe_info(in->f_path.dentry->d_inode);
1689 	struct pipe_inode_info *opipe = pipe_info(out->f_path.dentry->d_inode);
1690 	int ret = -EINVAL;
1691 
1692 	/*
1693 	 * Duplicate the contents of ipipe to opipe without actually
1694 	 * copying the data.
1695 	 */
1696 	if (ipipe && opipe && ipipe != opipe) {
1697 		/*
1698 		 * Keep going, unless we encounter an error. The ipipe/opipe
1699 		 * ordering doesn't really matter.
1700 		 */
1701 		ret = link_ipipe_prep(ipipe, flags);
1702 		if (!ret) {
1703 			ret = link_opipe_prep(opipe, flags);
1704 			if (!ret) {
1705 				ret = link_pipe(ipipe, opipe, len, flags);
1706 				if (!ret && (flags & SPLICE_F_NONBLOCK))
1707 					ret = -EAGAIN;
1708 			}
1709 		}
1710 	}
1711 
1712 	return ret;
1713 }
1714 
1715 asmlinkage long sys_tee(int fdin, int fdout, size_t len, unsigned int flags)
1716 {
1717 	struct file *in;
1718 	int error, fput_in;
1719 
1720 	if (unlikely(!len))
1721 		return 0;
1722 
1723 	error = -EBADF;
1724 	in = fget_light(fdin, &fput_in);
1725 	if (in) {
1726 		if (in->f_mode & FMODE_READ) {
1727 			int fput_out;
1728 			struct file *out = fget_light(fdout, &fput_out);
1729 
1730 			if (out) {
1731 				if (out->f_mode & FMODE_WRITE)
1732 					error = do_tee(in, out, len, flags);
1733 				fput_light(out, fput_out);
1734 			}
1735 		}
1736  		fput_light(in, fput_in);
1737  	}
1738 
1739 	return error;
1740 }
1741