xref: /openbmc/linux/fs/splice.c (revision 9d56dd3b083a3bec56e9da35ce07baca81030b03)
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/memcontrol.h>
25 #include <linux/mm_inline.h>
26 #include <linux/swap.h>
27 #include <linux/writeback.h>
28 #include <linux/buffer_head.h>
29 #include <linux/module.h>
30 #include <linux/syscalls.h>
31 #include <linux/uio.h>
32 #include <linux/security.h>
33 
34 /*
35  * Attempt to steal a page from a pipe buffer. This should perhaps go into
36  * a vm helper function, it's already simplified quite a bit by the
37  * addition of remove_mapping(). If success is returned, the caller may
38  * attempt to reuse this page for another destination.
39  */
40 static int page_cache_pipe_buf_steal(struct pipe_inode_info *pipe,
41 				     struct pipe_buffer *buf)
42 {
43 	struct page *page = buf->page;
44 	struct address_space *mapping;
45 
46 	lock_page(page);
47 
48 	mapping = page_mapping(page);
49 	if (mapping) {
50 		WARN_ON(!PageUptodate(page));
51 
52 		/*
53 		 * At least for ext2 with nobh option, we need to wait on
54 		 * writeback completing on this page, since we'll remove it
55 		 * from the pagecache.  Otherwise truncate wont wait on the
56 		 * page, allowing the disk blocks to be reused by someone else
57 		 * before we actually wrote our data to them. fs corruption
58 		 * ensues.
59 		 */
60 		wait_on_page_writeback(page);
61 
62 		if (page_has_private(page) &&
63 		    !try_to_release_page(page, GFP_KERNEL))
64 			goto out_unlock;
65 
66 		/*
67 		 * If we succeeded in removing the mapping, set LRU flag
68 		 * and return good.
69 		 */
70 		if (remove_mapping(mapping, page)) {
71 			buf->flags |= PIPE_BUF_FLAG_LRU;
72 			return 0;
73 		}
74 	}
75 
76 	/*
77 	 * Raced with truncate or failed to remove page from current
78 	 * address space, unlock and return failure.
79 	 */
80 out_unlock:
81 	unlock_page(page);
82 	return 1;
83 }
84 
85 static void page_cache_pipe_buf_release(struct pipe_inode_info *pipe,
86 					struct pipe_buffer *buf)
87 {
88 	page_cache_release(buf->page);
89 	buf->flags &= ~PIPE_BUF_FLAG_LRU;
90 }
91 
92 /*
93  * Check whether the contents of buf is OK to access. Since the content
94  * is a page cache page, IO may be in flight.
95  */
96 static int page_cache_pipe_buf_confirm(struct pipe_inode_info *pipe,
97 				       struct pipe_buffer *buf)
98 {
99 	struct page *page = buf->page;
100 	int err;
101 
102 	if (!PageUptodate(page)) {
103 		lock_page(page);
104 
105 		/*
106 		 * Page got truncated/unhashed. This will cause a 0-byte
107 		 * splice, if this is the first page.
108 		 */
109 		if (!page->mapping) {
110 			err = -ENODATA;
111 			goto error;
112 		}
113 
114 		/*
115 		 * Uh oh, read-error from disk.
116 		 */
117 		if (!PageUptodate(page)) {
118 			err = -EIO;
119 			goto error;
120 		}
121 
122 		/*
123 		 * Page is ok afterall, we are done.
124 		 */
125 		unlock_page(page);
126 	}
127 
128 	return 0;
129 error:
130 	unlock_page(page);
131 	return err;
132 }
133 
134 static const struct pipe_buf_operations page_cache_pipe_buf_ops = {
135 	.can_merge = 0,
136 	.map = generic_pipe_buf_map,
137 	.unmap = generic_pipe_buf_unmap,
138 	.confirm = page_cache_pipe_buf_confirm,
139 	.release = page_cache_pipe_buf_release,
140 	.steal = page_cache_pipe_buf_steal,
141 	.get = generic_pipe_buf_get,
142 };
143 
144 static int user_page_pipe_buf_steal(struct pipe_inode_info *pipe,
145 				    struct pipe_buffer *buf)
146 {
147 	if (!(buf->flags & PIPE_BUF_FLAG_GIFT))
148 		return 1;
149 
150 	buf->flags |= PIPE_BUF_FLAG_LRU;
151 	return generic_pipe_buf_steal(pipe, buf);
152 }
153 
154 static const struct pipe_buf_operations user_page_pipe_buf_ops = {
155 	.can_merge = 0,
156 	.map = generic_pipe_buf_map,
157 	.unmap = generic_pipe_buf_unmap,
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 /**
165  * splice_to_pipe - fill passed data into a pipe
166  * @pipe:	pipe to fill
167  * @spd:	data to fill
168  *
169  * Description:
170  *    @spd contains a map of pages and len/offset tuples, along with
171  *    the struct pipe_buf_operations associated with these pages. This
172  *    function will link that data to the pipe.
173  *
174  */
175 ssize_t splice_to_pipe(struct pipe_inode_info *pipe,
176 		       struct splice_pipe_desc *spd)
177 {
178 	unsigned int spd_pages = spd->nr_pages;
179 	int ret, do_wakeup, page_nr;
180 
181 	ret = 0;
182 	do_wakeup = 0;
183 	page_nr = 0;
184 
185 	pipe_lock(pipe);
186 
187 	for (;;) {
188 		if (!pipe->readers) {
189 			send_sig(SIGPIPE, current, 0);
190 			if (!ret)
191 				ret = -EPIPE;
192 			break;
193 		}
194 
195 		if (pipe->nrbufs < PIPE_BUFFERS) {
196 			int newbuf = (pipe->curbuf + pipe->nrbufs) & (PIPE_BUFFERS - 1);
197 			struct pipe_buffer *buf = pipe->bufs + newbuf;
198 
199 			buf->page = spd->pages[page_nr];
200 			buf->offset = spd->partial[page_nr].offset;
201 			buf->len = spd->partial[page_nr].len;
202 			buf->private = spd->partial[page_nr].private;
203 			buf->ops = spd->ops;
204 			if (spd->flags & SPLICE_F_GIFT)
205 				buf->flags |= PIPE_BUF_FLAG_GIFT;
206 
207 			pipe->nrbufs++;
208 			page_nr++;
209 			ret += buf->len;
210 
211 			if (pipe->inode)
212 				do_wakeup = 1;
213 
214 			if (!--spd->nr_pages)
215 				break;
216 			if (pipe->nrbufs < PIPE_BUFFERS)
217 				continue;
218 
219 			break;
220 		}
221 
222 		if (spd->flags & SPLICE_F_NONBLOCK) {
223 			if (!ret)
224 				ret = -EAGAIN;
225 			break;
226 		}
227 
228 		if (signal_pending(current)) {
229 			if (!ret)
230 				ret = -ERESTARTSYS;
231 			break;
232 		}
233 
234 		if (do_wakeup) {
235 			smp_mb();
236 			if (waitqueue_active(&pipe->wait))
237 				wake_up_interruptible_sync(&pipe->wait);
238 			kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
239 			do_wakeup = 0;
240 		}
241 
242 		pipe->waiting_writers++;
243 		pipe_wait(pipe);
244 		pipe->waiting_writers--;
245 	}
246 
247 	pipe_unlock(pipe);
248 
249 	if (do_wakeup) {
250 		smp_mb();
251 		if (waitqueue_active(&pipe->wait))
252 			wake_up_interruptible(&pipe->wait);
253 		kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
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 						mapping_gfp_mask(mapping));
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 (!trylock_page(page)) {
374 					error = -EAGAIN;
375 					break;
376 				}
377 			} else
378 				lock_page(page);
379 
380 			/*
381 			 * Page was truncated, or invalidated by the
382 			 * filesystem.  Redo the find/create, but this time the
383 			 * page is kept locked, so there's no chance of another
384 			 * race with truncate/invalidate.
385 			 */
386 			if (!page->mapping) {
387 				unlock_page(page);
388 				page = find_or_create_page(mapping, index,
389 						mapping_gfp_mask(mapping));
390 
391 				if (!page) {
392 					error = -ENOMEM;
393 					break;
394 				}
395 				page_cache_release(pages[page_nr]);
396 				pages[page_nr] = page;
397 			}
398 			/*
399 			 * page was already under io and is now done, great
400 			 */
401 			if (PageUptodate(page)) {
402 				unlock_page(page);
403 				goto fill_it;
404 			}
405 
406 			/*
407 			 * need to read in the page
408 			 */
409 			error = mapping->a_ops->readpage(in, page);
410 			if (unlikely(error)) {
411 				/*
412 				 * We really should re-lookup the page here,
413 				 * but it complicates things a lot. Instead
414 				 * lets just do what we already stored, and
415 				 * we'll get it the next time we are called.
416 				 */
417 				if (error == AOP_TRUNCATED_PAGE)
418 					error = 0;
419 
420 				break;
421 			}
422 		}
423 fill_it:
424 		/*
425 		 * i_size must be checked after PageUptodate.
426 		 */
427 		isize = i_size_read(mapping->host);
428 		end_index = (isize - 1) >> PAGE_CACHE_SHIFT;
429 		if (unlikely(!isize || index > end_index))
430 			break;
431 
432 		/*
433 		 * if this is the last page, see if we need to shrink
434 		 * the length and stop
435 		 */
436 		if (end_index == index) {
437 			unsigned int plen;
438 
439 			/*
440 			 * max good bytes in this page
441 			 */
442 			plen = ((isize - 1) & ~PAGE_CACHE_MASK) + 1;
443 			if (plen <= loff)
444 				break;
445 
446 			/*
447 			 * force quit after adding this page
448 			 */
449 			this_len = min(this_len, plen - loff);
450 			len = this_len;
451 		}
452 
453 		partial[page_nr].offset = loff;
454 		partial[page_nr].len = this_len;
455 		len -= this_len;
456 		loff = 0;
457 		spd.nr_pages++;
458 		index++;
459 	}
460 
461 	/*
462 	 * Release any pages at the end, if we quit early. 'page_nr' is how far
463 	 * we got, 'nr_pages' is how many pages are in the map.
464 	 */
465 	while (page_nr < nr_pages)
466 		page_cache_release(pages[page_nr++]);
467 	in->f_ra.prev_pos = (loff_t)index << PAGE_CACHE_SHIFT;
468 
469 	if (spd.nr_pages)
470 		return splice_to_pipe(pipe, &spd);
471 
472 	return error;
473 }
474 
475 /**
476  * generic_file_splice_read - splice data from file to a pipe
477  * @in:		file to splice from
478  * @ppos:	position in @in
479  * @pipe:	pipe to splice to
480  * @len:	number of bytes to splice
481  * @flags:	splice modifier flags
482  *
483  * Description:
484  *    Will read pages from given file and fill them into a pipe. Can be
485  *    used as long as the address_space operations for the source implements
486  *    a readpage() hook.
487  *
488  */
489 ssize_t generic_file_splice_read(struct file *in, loff_t *ppos,
490 				 struct pipe_inode_info *pipe, size_t len,
491 				 unsigned int flags)
492 {
493 	loff_t isize, left;
494 	int ret;
495 
496 	isize = i_size_read(in->f_mapping->host);
497 	if (unlikely(*ppos >= isize))
498 		return 0;
499 
500 	left = isize - *ppos;
501 	if (unlikely(left < len))
502 		len = left;
503 
504 	ret = __generic_file_splice_read(in, ppos, pipe, len, flags);
505 	if (ret > 0) {
506 		*ppos += ret;
507 		file_accessed(in);
508 	}
509 
510 	return ret;
511 }
512 EXPORT_SYMBOL(generic_file_splice_read);
513 
514 static const struct pipe_buf_operations default_pipe_buf_ops = {
515 	.can_merge = 0,
516 	.map = generic_pipe_buf_map,
517 	.unmap = generic_pipe_buf_unmap,
518 	.confirm = generic_pipe_buf_confirm,
519 	.release = generic_pipe_buf_release,
520 	.steal = generic_pipe_buf_steal,
521 	.get = generic_pipe_buf_get,
522 };
523 
524 static ssize_t kernel_readv(struct file *file, const struct iovec *vec,
525 			    unsigned long vlen, loff_t offset)
526 {
527 	mm_segment_t old_fs;
528 	loff_t pos = offset;
529 	ssize_t res;
530 
531 	old_fs = get_fs();
532 	set_fs(get_ds());
533 	/* The cast to a user pointer is valid due to the set_fs() */
534 	res = vfs_readv(file, (const struct iovec __user *)vec, vlen, &pos);
535 	set_fs(old_fs);
536 
537 	return res;
538 }
539 
540 static ssize_t kernel_write(struct file *file, const char *buf, size_t count,
541 			    loff_t pos)
542 {
543 	mm_segment_t old_fs;
544 	ssize_t res;
545 
546 	old_fs = get_fs();
547 	set_fs(get_ds());
548 	/* The cast to a user pointer is valid due to the set_fs() */
549 	res = vfs_write(file, (const char __user *)buf, count, &pos);
550 	set_fs(old_fs);
551 
552 	return res;
553 }
554 
555 ssize_t default_file_splice_read(struct file *in, loff_t *ppos,
556 				 struct pipe_inode_info *pipe, size_t len,
557 				 unsigned int flags)
558 {
559 	unsigned int nr_pages;
560 	unsigned int nr_freed;
561 	size_t offset;
562 	struct page *pages[PIPE_BUFFERS];
563 	struct partial_page partial[PIPE_BUFFERS];
564 	struct iovec vec[PIPE_BUFFERS];
565 	pgoff_t index;
566 	ssize_t res;
567 	size_t this_len;
568 	int error;
569 	int i;
570 	struct splice_pipe_desc spd = {
571 		.pages = pages,
572 		.partial = partial,
573 		.flags = flags,
574 		.ops = &default_pipe_buf_ops,
575 		.spd_release = spd_release_page,
576 	};
577 
578 	index = *ppos >> PAGE_CACHE_SHIFT;
579 	offset = *ppos & ~PAGE_CACHE_MASK;
580 	nr_pages = (len + offset + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
581 
582 	for (i = 0; i < nr_pages && i < PIPE_BUFFERS && len; i++) {
583 		struct page *page;
584 
585 		page = alloc_page(GFP_USER);
586 		error = -ENOMEM;
587 		if (!page)
588 			goto err;
589 
590 		this_len = min_t(size_t, len, PAGE_CACHE_SIZE - offset);
591 		vec[i].iov_base = (void __user *) page_address(page);
592 		vec[i].iov_len = this_len;
593 		pages[i] = page;
594 		spd.nr_pages++;
595 		len -= this_len;
596 		offset = 0;
597 	}
598 
599 	res = kernel_readv(in, vec, spd.nr_pages, *ppos);
600 	if (res < 0) {
601 		error = res;
602 		goto err;
603 	}
604 
605 	error = 0;
606 	if (!res)
607 		goto err;
608 
609 	nr_freed = 0;
610 	for (i = 0; i < spd.nr_pages; i++) {
611 		this_len = min_t(size_t, vec[i].iov_len, res);
612 		partial[i].offset = 0;
613 		partial[i].len = this_len;
614 		if (!this_len) {
615 			__free_page(pages[i]);
616 			pages[i] = NULL;
617 			nr_freed++;
618 		}
619 		res -= this_len;
620 	}
621 	spd.nr_pages -= nr_freed;
622 
623 	res = splice_to_pipe(pipe, &spd);
624 	if (res > 0)
625 		*ppos += res;
626 
627 	return res;
628 
629 err:
630 	for (i = 0; i < spd.nr_pages; i++)
631 		__free_page(pages[i]);
632 
633 	return error;
634 }
635 EXPORT_SYMBOL(default_file_splice_read);
636 
637 /*
638  * Send 'sd->len' bytes to socket from 'sd->file' at position 'sd->pos'
639  * using sendpage(). Return the number of bytes sent.
640  */
641 static int pipe_to_sendpage(struct pipe_inode_info *pipe,
642 			    struct pipe_buffer *buf, struct splice_desc *sd)
643 {
644 	struct file *file = sd->u.file;
645 	loff_t pos = sd->pos;
646 	int ret, more;
647 
648 	ret = buf->ops->confirm(pipe, buf);
649 	if (!ret) {
650 		more = (sd->flags & SPLICE_F_MORE) || sd->len < sd->total_len;
651 		if (file->f_op && file->f_op->sendpage)
652 			ret = file->f_op->sendpage(file, buf->page, buf->offset,
653 						   sd->len, &pos, more);
654 		else
655 			ret = -EINVAL;
656 	}
657 
658 	return ret;
659 }
660 
661 /*
662  * This is a little more tricky than the file -> pipe splicing. There are
663  * basically three cases:
664  *
665  *	- Destination page already exists in the address space and there
666  *	  are users of it. For that case we have no other option that
667  *	  copying the data. Tough luck.
668  *	- Destination page already exists in the address space, but there
669  *	  are no users of it. Make sure it's uptodate, then drop it. Fall
670  *	  through to last case.
671  *	- Destination page does not exist, we can add the pipe page to
672  *	  the page cache and avoid the copy.
673  *
674  * If asked to move pages to the output file (SPLICE_F_MOVE is set in
675  * sd->flags), we attempt to migrate pages from the pipe to the output
676  * file address space page cache. This is possible if no one else has
677  * the pipe page referenced outside of the pipe and page cache. If
678  * SPLICE_F_MOVE isn't set, or we cannot move the page, we simply create
679  * a new page in the output file page cache and fill/dirty that.
680  */
681 int pipe_to_file(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
682 		 struct splice_desc *sd)
683 {
684 	struct file *file = sd->u.file;
685 	struct address_space *mapping = file->f_mapping;
686 	unsigned int offset, this_len;
687 	struct page *page;
688 	void *fsdata;
689 	int ret;
690 
691 	/*
692 	 * make sure the data in this buffer is uptodate
693 	 */
694 	ret = buf->ops->confirm(pipe, buf);
695 	if (unlikely(ret))
696 		return ret;
697 
698 	offset = sd->pos & ~PAGE_CACHE_MASK;
699 
700 	this_len = sd->len;
701 	if (this_len + offset > PAGE_CACHE_SIZE)
702 		this_len = PAGE_CACHE_SIZE - offset;
703 
704 	ret = pagecache_write_begin(file, mapping, sd->pos, this_len,
705 				AOP_FLAG_UNINTERRUPTIBLE, &page, &fsdata);
706 	if (unlikely(ret))
707 		goto out;
708 
709 	if (buf->page != page) {
710 		/*
711 		 * Careful, ->map() uses KM_USER0!
712 		 */
713 		char *src = buf->ops->map(pipe, buf, 1);
714 		char *dst = kmap_atomic(page, KM_USER1);
715 
716 		memcpy(dst + offset, src + buf->offset, this_len);
717 		flush_dcache_page(page);
718 		kunmap_atomic(dst, KM_USER1);
719 		buf->ops->unmap(pipe, buf, src);
720 	}
721 	ret = pagecache_write_end(file, mapping, sd->pos, this_len, this_len,
722 				page, fsdata);
723 out:
724 	return ret;
725 }
726 EXPORT_SYMBOL(pipe_to_file);
727 
728 static void wakeup_pipe_writers(struct pipe_inode_info *pipe)
729 {
730 	smp_mb();
731 	if (waitqueue_active(&pipe->wait))
732 		wake_up_interruptible(&pipe->wait);
733 	kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
734 }
735 
736 /**
737  * splice_from_pipe_feed - feed available data from a pipe to a file
738  * @pipe:	pipe to splice from
739  * @sd:		information to @actor
740  * @actor:	handler that splices the data
741  *
742  * Description:
743  *    This function loops over the pipe and calls @actor to do the
744  *    actual moving of a single struct pipe_buffer to the desired
745  *    destination.  It returns when there's no more buffers left in
746  *    the pipe or if the requested number of bytes (@sd->total_len)
747  *    have been copied.  It returns a positive number (one) if the
748  *    pipe needs to be filled with more data, zero if the required
749  *    number of bytes have been copied and -errno on error.
750  *
751  *    This, together with splice_from_pipe_{begin,end,next}, may be
752  *    used to implement the functionality of __splice_from_pipe() when
753  *    locking is required around copying the pipe buffers to the
754  *    destination.
755  */
756 int splice_from_pipe_feed(struct pipe_inode_info *pipe, struct splice_desc *sd,
757 			  splice_actor *actor)
758 {
759 	int ret;
760 
761 	while (pipe->nrbufs) {
762 		struct pipe_buffer *buf = pipe->bufs + pipe->curbuf;
763 		const struct pipe_buf_operations *ops = buf->ops;
764 
765 		sd->len = buf->len;
766 		if (sd->len > sd->total_len)
767 			sd->len = sd->total_len;
768 
769 		ret = actor(pipe, buf, sd);
770 		if (ret <= 0) {
771 			if (ret == -ENODATA)
772 				ret = 0;
773 			return ret;
774 		}
775 		buf->offset += ret;
776 		buf->len -= ret;
777 
778 		sd->num_spliced += ret;
779 		sd->len -= ret;
780 		sd->pos += ret;
781 		sd->total_len -= ret;
782 
783 		if (!buf->len) {
784 			buf->ops = NULL;
785 			ops->release(pipe, buf);
786 			pipe->curbuf = (pipe->curbuf + 1) & (PIPE_BUFFERS - 1);
787 			pipe->nrbufs--;
788 			if (pipe->inode)
789 				sd->need_wakeup = true;
790 		}
791 
792 		if (!sd->total_len)
793 			return 0;
794 	}
795 
796 	return 1;
797 }
798 EXPORT_SYMBOL(splice_from_pipe_feed);
799 
800 /**
801  * splice_from_pipe_next - wait for some data to splice from
802  * @pipe:	pipe to splice from
803  * @sd:		information about the splice operation
804  *
805  * Description:
806  *    This function will wait for some data and return a positive
807  *    value (one) if pipe buffers are available.  It will return zero
808  *    or -errno if no more data needs to be spliced.
809  */
810 int splice_from_pipe_next(struct pipe_inode_info *pipe, struct splice_desc *sd)
811 {
812 	while (!pipe->nrbufs) {
813 		if (!pipe->writers)
814 			return 0;
815 
816 		if (!pipe->waiting_writers && sd->num_spliced)
817 			return 0;
818 
819 		if (sd->flags & SPLICE_F_NONBLOCK)
820 			return -EAGAIN;
821 
822 		if (signal_pending(current))
823 			return -ERESTARTSYS;
824 
825 		if (sd->need_wakeup) {
826 			wakeup_pipe_writers(pipe);
827 			sd->need_wakeup = false;
828 		}
829 
830 		pipe_wait(pipe);
831 	}
832 
833 	return 1;
834 }
835 EXPORT_SYMBOL(splice_from_pipe_next);
836 
837 /**
838  * splice_from_pipe_begin - start splicing from pipe
839  * @sd:		information about the splice operation
840  *
841  * Description:
842  *    This function should be called before a loop containing
843  *    splice_from_pipe_next() and splice_from_pipe_feed() to
844  *    initialize the necessary fields of @sd.
845  */
846 void splice_from_pipe_begin(struct splice_desc *sd)
847 {
848 	sd->num_spliced = 0;
849 	sd->need_wakeup = false;
850 }
851 EXPORT_SYMBOL(splice_from_pipe_begin);
852 
853 /**
854  * splice_from_pipe_end - finish splicing from pipe
855  * @pipe:	pipe to splice from
856  * @sd:		information about the splice operation
857  *
858  * Description:
859  *    This function will wake up pipe writers if necessary.  It should
860  *    be called after a loop containing splice_from_pipe_next() and
861  *    splice_from_pipe_feed().
862  */
863 void splice_from_pipe_end(struct pipe_inode_info *pipe, struct splice_desc *sd)
864 {
865 	if (sd->need_wakeup)
866 		wakeup_pipe_writers(pipe);
867 }
868 EXPORT_SYMBOL(splice_from_pipe_end);
869 
870 /**
871  * __splice_from_pipe - splice data from a pipe to given actor
872  * @pipe:	pipe to splice from
873  * @sd:		information to @actor
874  * @actor:	handler that splices the data
875  *
876  * Description:
877  *    This function does little more than loop over the pipe and call
878  *    @actor to do the actual moving of a single struct pipe_buffer to
879  *    the desired destination. See pipe_to_file, pipe_to_sendpage, or
880  *    pipe_to_user.
881  *
882  */
883 ssize_t __splice_from_pipe(struct pipe_inode_info *pipe, struct splice_desc *sd,
884 			   splice_actor *actor)
885 {
886 	int ret;
887 
888 	splice_from_pipe_begin(sd);
889 	do {
890 		ret = splice_from_pipe_next(pipe, sd);
891 		if (ret > 0)
892 			ret = splice_from_pipe_feed(pipe, sd, actor);
893 	} while (ret > 0);
894 	splice_from_pipe_end(pipe, sd);
895 
896 	return sd->num_spliced ? sd->num_spliced : ret;
897 }
898 EXPORT_SYMBOL(__splice_from_pipe);
899 
900 /**
901  * splice_from_pipe - splice data from a pipe to a file
902  * @pipe:	pipe to splice from
903  * @out:	file to splice to
904  * @ppos:	position in @out
905  * @len:	how many bytes to splice
906  * @flags:	splice modifier flags
907  * @actor:	handler that splices the data
908  *
909  * Description:
910  *    See __splice_from_pipe. This function locks the pipe inode,
911  *    otherwise it's identical to __splice_from_pipe().
912  *
913  */
914 ssize_t splice_from_pipe(struct pipe_inode_info *pipe, struct file *out,
915 			 loff_t *ppos, size_t len, unsigned int flags,
916 			 splice_actor *actor)
917 {
918 	ssize_t ret;
919 	struct splice_desc sd = {
920 		.total_len = len,
921 		.flags = flags,
922 		.pos = *ppos,
923 		.u.file = out,
924 	};
925 
926 	pipe_lock(pipe);
927 	ret = __splice_from_pipe(pipe, &sd, actor);
928 	pipe_unlock(pipe);
929 
930 	return ret;
931 }
932 
933 /**
934  * generic_file_splice_write - splice data from a pipe to a file
935  * @pipe:	pipe info
936  * @out:	file to write to
937  * @ppos:	position in @out
938  * @len:	number of bytes to splice
939  * @flags:	splice modifier flags
940  *
941  * Description:
942  *    Will either move or copy pages (determined by @flags options) from
943  *    the given pipe inode to the given file.
944  *
945  */
946 ssize_t
947 generic_file_splice_write(struct pipe_inode_info *pipe, struct file *out,
948 			  loff_t *ppos, size_t len, unsigned int flags)
949 {
950 	struct address_space *mapping = out->f_mapping;
951 	struct inode *inode = mapping->host;
952 	struct splice_desc sd = {
953 		.total_len = len,
954 		.flags = flags,
955 		.pos = *ppos,
956 		.u.file = out,
957 	};
958 	ssize_t ret;
959 
960 	pipe_lock(pipe);
961 
962 	splice_from_pipe_begin(&sd);
963 	do {
964 		ret = splice_from_pipe_next(pipe, &sd);
965 		if (ret <= 0)
966 			break;
967 
968 		mutex_lock_nested(&inode->i_mutex, I_MUTEX_CHILD);
969 		ret = file_remove_suid(out);
970 		if (!ret) {
971 			file_update_time(out);
972 			ret = splice_from_pipe_feed(pipe, &sd, pipe_to_file);
973 		}
974 		mutex_unlock(&inode->i_mutex);
975 	} while (ret > 0);
976 	splice_from_pipe_end(pipe, &sd);
977 
978 	pipe_unlock(pipe);
979 
980 	if (sd.num_spliced)
981 		ret = sd.num_spliced;
982 
983 	if (ret > 0) {
984 		unsigned long nr_pages;
985 		int err;
986 
987 		nr_pages = (ret + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
988 
989 		err = generic_write_sync(out, *ppos, ret);
990 		if (err)
991 			ret = err;
992 		else
993 			*ppos += ret;
994 		balance_dirty_pages_ratelimited_nr(mapping, nr_pages);
995 	}
996 
997 	return ret;
998 }
999 
1000 EXPORT_SYMBOL(generic_file_splice_write);
1001 
1002 static int write_pipe_buf(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
1003 			  struct splice_desc *sd)
1004 {
1005 	int ret;
1006 	void *data;
1007 
1008 	ret = buf->ops->confirm(pipe, buf);
1009 	if (ret)
1010 		return ret;
1011 
1012 	data = buf->ops->map(pipe, buf, 0);
1013 	ret = kernel_write(sd->u.file, data + buf->offset, sd->len, sd->pos);
1014 	buf->ops->unmap(pipe, buf, data);
1015 
1016 	return ret;
1017 }
1018 
1019 static ssize_t default_file_splice_write(struct pipe_inode_info *pipe,
1020 					 struct file *out, loff_t *ppos,
1021 					 size_t len, unsigned int flags)
1022 {
1023 	ssize_t ret;
1024 
1025 	ret = splice_from_pipe(pipe, out, ppos, len, flags, write_pipe_buf);
1026 	if (ret > 0)
1027 		*ppos += ret;
1028 
1029 	return ret;
1030 }
1031 
1032 /**
1033  * generic_splice_sendpage - splice data from a pipe to a socket
1034  * @pipe:	pipe to splice from
1035  * @out:	socket to write to
1036  * @ppos:	position in @out
1037  * @len:	number of bytes to splice
1038  * @flags:	splice modifier flags
1039  *
1040  * Description:
1041  *    Will send @len bytes from the pipe to a network socket. No data copying
1042  *    is involved.
1043  *
1044  */
1045 ssize_t generic_splice_sendpage(struct pipe_inode_info *pipe, struct file *out,
1046 				loff_t *ppos, size_t len, unsigned int flags)
1047 {
1048 	return splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_sendpage);
1049 }
1050 
1051 EXPORT_SYMBOL(generic_splice_sendpage);
1052 
1053 /*
1054  * Attempt to initiate a splice from pipe to file.
1055  */
1056 static long do_splice_from(struct pipe_inode_info *pipe, struct file *out,
1057 			   loff_t *ppos, size_t len, unsigned int flags)
1058 {
1059 	ssize_t (*splice_write)(struct pipe_inode_info *, struct file *,
1060 				loff_t *, size_t, unsigned int);
1061 	int ret;
1062 
1063 	if (unlikely(!(out->f_mode & FMODE_WRITE)))
1064 		return -EBADF;
1065 
1066 	if (unlikely(out->f_flags & O_APPEND))
1067 		return -EINVAL;
1068 
1069 	ret = rw_verify_area(WRITE, out, ppos, len);
1070 	if (unlikely(ret < 0))
1071 		return ret;
1072 
1073 	if (out->f_op && out->f_op->splice_write)
1074 		splice_write = out->f_op->splice_write;
1075 	else
1076 		splice_write = default_file_splice_write;
1077 
1078 	return splice_write(pipe, out, ppos, len, flags);
1079 }
1080 
1081 /*
1082  * Attempt to initiate a splice from a file to a pipe.
1083  */
1084 static long do_splice_to(struct file *in, loff_t *ppos,
1085 			 struct pipe_inode_info *pipe, size_t len,
1086 			 unsigned int flags)
1087 {
1088 	ssize_t (*splice_read)(struct file *, loff_t *,
1089 			       struct pipe_inode_info *, size_t, unsigned int);
1090 	int ret;
1091 
1092 	if (unlikely(!(in->f_mode & FMODE_READ)))
1093 		return -EBADF;
1094 
1095 	ret = rw_verify_area(READ, in, ppos, len);
1096 	if (unlikely(ret < 0))
1097 		return ret;
1098 
1099 	if (in->f_op && in->f_op->splice_read)
1100 		splice_read = in->f_op->splice_read;
1101 	else
1102 		splice_read = default_file_splice_read;
1103 
1104 	return splice_read(in, ppos, pipe, len, flags);
1105 }
1106 
1107 /**
1108  * splice_direct_to_actor - splices data directly between two non-pipes
1109  * @in:		file to splice from
1110  * @sd:		actor information on where to splice to
1111  * @actor:	handles the data splicing
1112  *
1113  * Description:
1114  *    This is a special case helper to splice directly between two
1115  *    points, without requiring an explicit pipe. Internally an allocated
1116  *    pipe is cached in the process, and reused during the lifetime of
1117  *    that process.
1118  *
1119  */
1120 ssize_t splice_direct_to_actor(struct file *in, struct splice_desc *sd,
1121 			       splice_direct_actor *actor)
1122 {
1123 	struct pipe_inode_info *pipe;
1124 	long ret, bytes;
1125 	umode_t i_mode;
1126 	size_t len;
1127 	int i, flags;
1128 
1129 	/*
1130 	 * We require the input being a regular file, as we don't want to
1131 	 * randomly drop data for eg socket -> socket splicing. Use the
1132 	 * piped splicing for that!
1133 	 */
1134 	i_mode = in->f_path.dentry->d_inode->i_mode;
1135 	if (unlikely(!S_ISREG(i_mode) && !S_ISBLK(i_mode)))
1136 		return -EINVAL;
1137 
1138 	/*
1139 	 * neither in nor out is a pipe, setup an internal pipe attached to
1140 	 * 'out' and transfer the wanted data from 'in' to 'out' through that
1141 	 */
1142 	pipe = current->splice_pipe;
1143 	if (unlikely(!pipe)) {
1144 		pipe = alloc_pipe_info(NULL);
1145 		if (!pipe)
1146 			return -ENOMEM;
1147 
1148 		/*
1149 		 * We don't have an immediate reader, but we'll read the stuff
1150 		 * out of the pipe right after the splice_to_pipe(). So set
1151 		 * PIPE_READERS appropriately.
1152 		 */
1153 		pipe->readers = 1;
1154 
1155 		current->splice_pipe = pipe;
1156 	}
1157 
1158 	/*
1159 	 * Do the splice.
1160 	 */
1161 	ret = 0;
1162 	bytes = 0;
1163 	len = sd->total_len;
1164 	flags = sd->flags;
1165 
1166 	/*
1167 	 * Don't block on output, we have to drain the direct pipe.
1168 	 */
1169 	sd->flags &= ~SPLICE_F_NONBLOCK;
1170 
1171 	while (len) {
1172 		size_t read_len;
1173 		loff_t pos = sd->pos, prev_pos = pos;
1174 
1175 		ret = do_splice_to(in, &pos, pipe, len, flags);
1176 		if (unlikely(ret <= 0))
1177 			goto out_release;
1178 
1179 		read_len = ret;
1180 		sd->total_len = read_len;
1181 
1182 		/*
1183 		 * NOTE: nonblocking mode only applies to the input. We
1184 		 * must not do the output in nonblocking mode as then we
1185 		 * could get stuck data in the internal pipe:
1186 		 */
1187 		ret = actor(pipe, sd);
1188 		if (unlikely(ret <= 0)) {
1189 			sd->pos = prev_pos;
1190 			goto out_release;
1191 		}
1192 
1193 		bytes += ret;
1194 		len -= ret;
1195 		sd->pos = pos;
1196 
1197 		if (ret < read_len) {
1198 			sd->pos = prev_pos + ret;
1199 			goto out_release;
1200 		}
1201 	}
1202 
1203 done:
1204 	pipe->nrbufs = pipe->curbuf = 0;
1205 	file_accessed(in);
1206 	return bytes;
1207 
1208 out_release:
1209 	/*
1210 	 * If we did an incomplete transfer we must release
1211 	 * the pipe buffers in question:
1212 	 */
1213 	for (i = 0; i < PIPE_BUFFERS; i++) {
1214 		struct pipe_buffer *buf = pipe->bufs + i;
1215 
1216 		if (buf->ops) {
1217 			buf->ops->release(pipe, buf);
1218 			buf->ops = NULL;
1219 		}
1220 	}
1221 
1222 	if (!bytes)
1223 		bytes = ret;
1224 
1225 	goto done;
1226 }
1227 EXPORT_SYMBOL(splice_direct_to_actor);
1228 
1229 static int direct_splice_actor(struct pipe_inode_info *pipe,
1230 			       struct splice_desc *sd)
1231 {
1232 	struct file *file = sd->u.file;
1233 
1234 	return do_splice_from(pipe, file, &sd->pos, sd->total_len, sd->flags);
1235 }
1236 
1237 /**
1238  * do_splice_direct - splices data directly between two files
1239  * @in:		file to splice from
1240  * @ppos:	input file offset
1241  * @out:	file to splice to
1242  * @len:	number of bytes to splice
1243  * @flags:	splice modifier flags
1244  *
1245  * Description:
1246  *    For use by do_sendfile(). splice can easily emulate sendfile, but
1247  *    doing it in the application would incur an extra system call
1248  *    (splice in + splice out, as compared to just sendfile()). So this helper
1249  *    can splice directly through a process-private pipe.
1250  *
1251  */
1252 long do_splice_direct(struct file *in, loff_t *ppos, struct file *out,
1253 		      size_t len, unsigned int flags)
1254 {
1255 	struct splice_desc sd = {
1256 		.len		= len,
1257 		.total_len	= len,
1258 		.flags		= flags,
1259 		.pos		= *ppos,
1260 		.u.file		= out,
1261 	};
1262 	long ret;
1263 
1264 	ret = splice_direct_to_actor(in, &sd, direct_splice_actor);
1265 	if (ret > 0)
1266 		*ppos = sd.pos;
1267 
1268 	return ret;
1269 }
1270 
1271 static int splice_pipe_to_pipe(struct pipe_inode_info *ipipe,
1272 			       struct pipe_inode_info *opipe,
1273 			       size_t len, unsigned int flags);
1274 /*
1275  * After the inode slimming patch, i_pipe/i_bdev/i_cdev share the same
1276  * location, so checking ->i_pipe is not enough to verify that this is a
1277  * pipe.
1278  */
1279 static inline struct pipe_inode_info *pipe_info(struct inode *inode)
1280 {
1281 	if (S_ISFIFO(inode->i_mode))
1282 		return inode->i_pipe;
1283 
1284 	return NULL;
1285 }
1286 
1287 /*
1288  * Determine where to splice to/from.
1289  */
1290 static long do_splice(struct file *in, loff_t __user *off_in,
1291 		      struct file *out, loff_t __user *off_out,
1292 		      size_t len, unsigned int flags)
1293 {
1294 	struct pipe_inode_info *ipipe;
1295 	struct pipe_inode_info *opipe;
1296 	loff_t offset, *off;
1297 	long ret;
1298 
1299 	ipipe = pipe_info(in->f_path.dentry->d_inode);
1300 	opipe = pipe_info(out->f_path.dentry->d_inode);
1301 
1302 	if (ipipe && opipe) {
1303 		if (off_in || off_out)
1304 			return -ESPIPE;
1305 
1306 		if (!(in->f_mode & FMODE_READ))
1307 			return -EBADF;
1308 
1309 		if (!(out->f_mode & FMODE_WRITE))
1310 			return -EBADF;
1311 
1312 		/* Splicing to self would be fun, but... */
1313 		if (ipipe == opipe)
1314 			return -EINVAL;
1315 
1316 		return splice_pipe_to_pipe(ipipe, opipe, len, flags);
1317 	}
1318 
1319 	if (ipipe) {
1320 		if (off_in)
1321 			return -ESPIPE;
1322 		if (off_out) {
1323 			if (!out->f_op || !out->f_op->llseek ||
1324 			    out->f_op->llseek == no_llseek)
1325 				return -EINVAL;
1326 			if (copy_from_user(&offset, off_out, sizeof(loff_t)))
1327 				return -EFAULT;
1328 			off = &offset;
1329 		} else
1330 			off = &out->f_pos;
1331 
1332 		ret = do_splice_from(ipipe, out, off, len, flags);
1333 
1334 		if (off_out && copy_to_user(off_out, off, sizeof(loff_t)))
1335 			ret = -EFAULT;
1336 
1337 		return ret;
1338 	}
1339 
1340 	if (opipe) {
1341 		if (off_out)
1342 			return -ESPIPE;
1343 		if (off_in) {
1344 			if (!in->f_op || !in->f_op->llseek ||
1345 			    in->f_op->llseek == no_llseek)
1346 				return -EINVAL;
1347 			if (copy_from_user(&offset, off_in, sizeof(loff_t)))
1348 				return -EFAULT;
1349 			off = &offset;
1350 		} else
1351 			off = &in->f_pos;
1352 
1353 		ret = do_splice_to(in, off, opipe, len, flags);
1354 
1355 		if (off_in && copy_to_user(off_in, off, sizeof(loff_t)))
1356 			ret = -EFAULT;
1357 
1358 		return ret;
1359 	}
1360 
1361 	return -EINVAL;
1362 }
1363 
1364 /*
1365  * Map an iov into an array of pages and offset/length tupples. With the
1366  * partial_page structure, we can map several non-contiguous ranges into
1367  * our ones pages[] map instead of splitting that operation into pieces.
1368  * Could easily be exported as a generic helper for other users, in which
1369  * case one would probably want to add a 'max_nr_pages' parameter as well.
1370  */
1371 static int get_iovec_page_array(const struct iovec __user *iov,
1372 				unsigned int nr_vecs, struct page **pages,
1373 				struct partial_page *partial, int aligned)
1374 {
1375 	int buffers = 0, error = 0;
1376 
1377 	while (nr_vecs) {
1378 		unsigned long off, npages;
1379 		struct iovec entry;
1380 		void __user *base;
1381 		size_t len;
1382 		int i;
1383 
1384 		error = -EFAULT;
1385 		if (copy_from_user(&entry, iov, sizeof(entry)))
1386 			break;
1387 
1388 		base = entry.iov_base;
1389 		len = entry.iov_len;
1390 
1391 		/*
1392 		 * Sanity check this iovec. 0 read succeeds.
1393 		 */
1394 		error = 0;
1395 		if (unlikely(!len))
1396 			break;
1397 		error = -EFAULT;
1398 		if (!access_ok(VERIFY_READ, base, len))
1399 			break;
1400 
1401 		/*
1402 		 * Get this base offset and number of pages, then map
1403 		 * in the user pages.
1404 		 */
1405 		off = (unsigned long) base & ~PAGE_MASK;
1406 
1407 		/*
1408 		 * If asked for alignment, the offset must be zero and the
1409 		 * length a multiple of the PAGE_SIZE.
1410 		 */
1411 		error = -EINVAL;
1412 		if (aligned && (off || len & ~PAGE_MASK))
1413 			break;
1414 
1415 		npages = (off + len + PAGE_SIZE - 1) >> PAGE_SHIFT;
1416 		if (npages > PIPE_BUFFERS - buffers)
1417 			npages = PIPE_BUFFERS - buffers;
1418 
1419 		error = get_user_pages_fast((unsigned long)base, npages,
1420 					0, &pages[buffers]);
1421 
1422 		if (unlikely(error <= 0))
1423 			break;
1424 
1425 		/*
1426 		 * Fill this contiguous range into the partial page map.
1427 		 */
1428 		for (i = 0; i < error; i++) {
1429 			const int plen = min_t(size_t, len, PAGE_SIZE - off);
1430 
1431 			partial[buffers].offset = off;
1432 			partial[buffers].len = plen;
1433 
1434 			off = 0;
1435 			len -= plen;
1436 			buffers++;
1437 		}
1438 
1439 		/*
1440 		 * We didn't complete this iov, stop here since it probably
1441 		 * means we have to move some of this into a pipe to
1442 		 * be able to continue.
1443 		 */
1444 		if (len)
1445 			break;
1446 
1447 		/*
1448 		 * Don't continue if we mapped fewer pages than we asked for,
1449 		 * or if we mapped the max number of pages that we have
1450 		 * room for.
1451 		 */
1452 		if (error < npages || buffers == PIPE_BUFFERS)
1453 			break;
1454 
1455 		nr_vecs--;
1456 		iov++;
1457 	}
1458 
1459 	if (buffers)
1460 		return buffers;
1461 
1462 	return error;
1463 }
1464 
1465 static int pipe_to_user(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
1466 			struct splice_desc *sd)
1467 {
1468 	char *src;
1469 	int ret;
1470 
1471 	ret = buf->ops->confirm(pipe, buf);
1472 	if (unlikely(ret))
1473 		return ret;
1474 
1475 	/*
1476 	 * See if we can use the atomic maps, by prefaulting in the
1477 	 * pages and doing an atomic copy
1478 	 */
1479 	if (!fault_in_pages_writeable(sd->u.userptr, sd->len)) {
1480 		src = buf->ops->map(pipe, buf, 1);
1481 		ret = __copy_to_user_inatomic(sd->u.userptr, src + buf->offset,
1482 							sd->len);
1483 		buf->ops->unmap(pipe, buf, src);
1484 		if (!ret) {
1485 			ret = sd->len;
1486 			goto out;
1487 		}
1488 	}
1489 
1490 	/*
1491 	 * No dice, use slow non-atomic map and copy
1492  	 */
1493 	src = buf->ops->map(pipe, buf, 0);
1494 
1495 	ret = sd->len;
1496 	if (copy_to_user(sd->u.userptr, src + buf->offset, sd->len))
1497 		ret = -EFAULT;
1498 
1499 	buf->ops->unmap(pipe, buf, src);
1500 out:
1501 	if (ret > 0)
1502 		sd->u.userptr += ret;
1503 	return ret;
1504 }
1505 
1506 /*
1507  * For lack of a better implementation, implement vmsplice() to userspace
1508  * as a simple copy of the pipes pages to the user iov.
1509  */
1510 static long vmsplice_to_user(struct file *file, const struct iovec __user *iov,
1511 			     unsigned long nr_segs, unsigned int flags)
1512 {
1513 	struct pipe_inode_info *pipe;
1514 	struct splice_desc sd;
1515 	ssize_t size;
1516 	int error;
1517 	long ret;
1518 
1519 	pipe = pipe_info(file->f_path.dentry->d_inode);
1520 	if (!pipe)
1521 		return -EBADF;
1522 
1523 	pipe_lock(pipe);
1524 
1525 	error = ret = 0;
1526 	while (nr_segs) {
1527 		void __user *base;
1528 		size_t len;
1529 
1530 		/*
1531 		 * Get user address base and length for this iovec.
1532 		 */
1533 		error = get_user(base, &iov->iov_base);
1534 		if (unlikely(error))
1535 			break;
1536 		error = get_user(len, &iov->iov_len);
1537 		if (unlikely(error))
1538 			break;
1539 
1540 		/*
1541 		 * Sanity check this iovec. 0 read succeeds.
1542 		 */
1543 		if (unlikely(!len))
1544 			break;
1545 		if (unlikely(!base)) {
1546 			error = -EFAULT;
1547 			break;
1548 		}
1549 
1550 		if (unlikely(!access_ok(VERIFY_WRITE, base, len))) {
1551 			error = -EFAULT;
1552 			break;
1553 		}
1554 
1555 		sd.len = 0;
1556 		sd.total_len = len;
1557 		sd.flags = flags;
1558 		sd.u.userptr = base;
1559 		sd.pos = 0;
1560 
1561 		size = __splice_from_pipe(pipe, &sd, pipe_to_user);
1562 		if (size < 0) {
1563 			if (!ret)
1564 				ret = size;
1565 
1566 			break;
1567 		}
1568 
1569 		ret += size;
1570 
1571 		if (size < len)
1572 			break;
1573 
1574 		nr_segs--;
1575 		iov++;
1576 	}
1577 
1578 	pipe_unlock(pipe);
1579 
1580 	if (!ret)
1581 		ret = error;
1582 
1583 	return ret;
1584 }
1585 
1586 /*
1587  * vmsplice splices a user address range into a pipe. It can be thought of
1588  * as splice-from-memory, where the regular splice is splice-from-file (or
1589  * to file). In both cases the output is a pipe, naturally.
1590  */
1591 static long vmsplice_to_pipe(struct file *file, const struct iovec __user *iov,
1592 			     unsigned long nr_segs, unsigned int flags)
1593 {
1594 	struct pipe_inode_info *pipe;
1595 	struct page *pages[PIPE_BUFFERS];
1596 	struct partial_page partial[PIPE_BUFFERS];
1597 	struct splice_pipe_desc spd = {
1598 		.pages = pages,
1599 		.partial = partial,
1600 		.flags = flags,
1601 		.ops = &user_page_pipe_buf_ops,
1602 		.spd_release = spd_release_page,
1603 	};
1604 
1605 	pipe = pipe_info(file->f_path.dentry->d_inode);
1606 	if (!pipe)
1607 		return -EBADF;
1608 
1609 	spd.nr_pages = get_iovec_page_array(iov, nr_segs, pages, partial,
1610 					    flags & SPLICE_F_GIFT);
1611 	if (spd.nr_pages <= 0)
1612 		return spd.nr_pages;
1613 
1614 	return splice_to_pipe(pipe, &spd);
1615 }
1616 
1617 /*
1618  * Note that vmsplice only really supports true splicing _from_ user memory
1619  * to a pipe, not the other way around. Splicing from user memory is a simple
1620  * operation that can be supported without any funky alignment restrictions
1621  * or nasty vm tricks. We simply map in the user memory and fill them into
1622  * a pipe. The reverse isn't quite as easy, though. There are two possible
1623  * solutions for that:
1624  *
1625  *	- memcpy() the data internally, at which point we might as well just
1626  *	  do a regular read() on the buffer anyway.
1627  *	- Lots of nasty vm tricks, that are neither fast nor flexible (it
1628  *	  has restriction limitations on both ends of the pipe).
1629  *
1630  * Currently we punt and implement it as a normal copy, see pipe_to_user().
1631  *
1632  */
1633 SYSCALL_DEFINE4(vmsplice, int, fd, const struct iovec __user *, iov,
1634 		unsigned long, nr_segs, unsigned int, flags)
1635 {
1636 	struct file *file;
1637 	long error;
1638 	int fput;
1639 
1640 	if (unlikely(nr_segs > UIO_MAXIOV))
1641 		return -EINVAL;
1642 	else if (unlikely(!nr_segs))
1643 		return 0;
1644 
1645 	error = -EBADF;
1646 	file = fget_light(fd, &fput);
1647 	if (file) {
1648 		if (file->f_mode & FMODE_WRITE)
1649 			error = vmsplice_to_pipe(file, iov, nr_segs, flags);
1650 		else if (file->f_mode & FMODE_READ)
1651 			error = vmsplice_to_user(file, iov, nr_segs, flags);
1652 
1653 		fput_light(file, fput);
1654 	}
1655 
1656 	return error;
1657 }
1658 
1659 SYSCALL_DEFINE6(splice, int, fd_in, loff_t __user *, off_in,
1660 		int, fd_out, loff_t __user *, off_out,
1661 		size_t, len, unsigned int, flags)
1662 {
1663 	long error;
1664 	struct file *in, *out;
1665 	int fput_in, fput_out;
1666 
1667 	if (unlikely(!len))
1668 		return 0;
1669 
1670 	error = -EBADF;
1671 	in = fget_light(fd_in, &fput_in);
1672 	if (in) {
1673 		if (in->f_mode & FMODE_READ) {
1674 			out = fget_light(fd_out, &fput_out);
1675 			if (out) {
1676 				if (out->f_mode & FMODE_WRITE)
1677 					error = do_splice(in, off_in,
1678 							  out, off_out,
1679 							  len, flags);
1680 				fput_light(out, fput_out);
1681 			}
1682 		}
1683 
1684 		fput_light(in, fput_in);
1685 	}
1686 
1687 	return error;
1688 }
1689 
1690 /*
1691  * Make sure there's data to read. Wait for input if we can, otherwise
1692  * return an appropriate error.
1693  */
1694 static int ipipe_prep(struct pipe_inode_info *pipe, unsigned int flags)
1695 {
1696 	int ret;
1697 
1698 	/*
1699 	 * Check ->nrbufs without the inode lock first. This function
1700 	 * is speculative anyways, so missing one is ok.
1701 	 */
1702 	if (pipe->nrbufs)
1703 		return 0;
1704 
1705 	ret = 0;
1706 	pipe_lock(pipe);
1707 
1708 	while (!pipe->nrbufs) {
1709 		if (signal_pending(current)) {
1710 			ret = -ERESTARTSYS;
1711 			break;
1712 		}
1713 		if (!pipe->writers)
1714 			break;
1715 		if (!pipe->waiting_writers) {
1716 			if (flags & SPLICE_F_NONBLOCK) {
1717 				ret = -EAGAIN;
1718 				break;
1719 			}
1720 		}
1721 		pipe_wait(pipe);
1722 	}
1723 
1724 	pipe_unlock(pipe);
1725 	return ret;
1726 }
1727 
1728 /*
1729  * Make sure there's writeable room. Wait for room if we can, otherwise
1730  * return an appropriate error.
1731  */
1732 static int opipe_prep(struct pipe_inode_info *pipe, unsigned int flags)
1733 {
1734 	int ret;
1735 
1736 	/*
1737 	 * Check ->nrbufs without the inode lock first. This function
1738 	 * is speculative anyways, so missing one is ok.
1739 	 */
1740 	if (pipe->nrbufs < PIPE_BUFFERS)
1741 		return 0;
1742 
1743 	ret = 0;
1744 	pipe_lock(pipe);
1745 
1746 	while (pipe->nrbufs >= PIPE_BUFFERS) {
1747 		if (!pipe->readers) {
1748 			send_sig(SIGPIPE, current, 0);
1749 			ret = -EPIPE;
1750 			break;
1751 		}
1752 		if (flags & SPLICE_F_NONBLOCK) {
1753 			ret = -EAGAIN;
1754 			break;
1755 		}
1756 		if (signal_pending(current)) {
1757 			ret = -ERESTARTSYS;
1758 			break;
1759 		}
1760 		pipe->waiting_writers++;
1761 		pipe_wait(pipe);
1762 		pipe->waiting_writers--;
1763 	}
1764 
1765 	pipe_unlock(pipe);
1766 	return ret;
1767 }
1768 
1769 /*
1770  * Splice contents of ipipe to opipe.
1771  */
1772 static int splice_pipe_to_pipe(struct pipe_inode_info *ipipe,
1773 			       struct pipe_inode_info *opipe,
1774 			       size_t len, unsigned int flags)
1775 {
1776 	struct pipe_buffer *ibuf, *obuf;
1777 	int ret = 0, nbuf;
1778 	bool input_wakeup = false;
1779 
1780 
1781 retry:
1782 	ret = ipipe_prep(ipipe, flags);
1783 	if (ret)
1784 		return ret;
1785 
1786 	ret = opipe_prep(opipe, flags);
1787 	if (ret)
1788 		return ret;
1789 
1790 	/*
1791 	 * Potential ABBA deadlock, work around it by ordering lock
1792 	 * grabbing by pipe info address. Otherwise two different processes
1793 	 * could deadlock (one doing tee from A -> B, the other from B -> A).
1794 	 */
1795 	pipe_double_lock(ipipe, opipe);
1796 
1797 	do {
1798 		if (!opipe->readers) {
1799 			send_sig(SIGPIPE, current, 0);
1800 			if (!ret)
1801 				ret = -EPIPE;
1802 			break;
1803 		}
1804 
1805 		if (!ipipe->nrbufs && !ipipe->writers)
1806 			break;
1807 
1808 		/*
1809 		 * Cannot make any progress, because either the input
1810 		 * pipe is empty or the output pipe is full.
1811 		 */
1812 		if (!ipipe->nrbufs || opipe->nrbufs >= PIPE_BUFFERS) {
1813 			/* Already processed some buffers, break */
1814 			if (ret)
1815 				break;
1816 
1817 			if (flags & SPLICE_F_NONBLOCK) {
1818 				ret = -EAGAIN;
1819 				break;
1820 			}
1821 
1822 			/*
1823 			 * We raced with another reader/writer and haven't
1824 			 * managed to process any buffers.  A zero return
1825 			 * value means EOF, so retry instead.
1826 			 */
1827 			pipe_unlock(ipipe);
1828 			pipe_unlock(opipe);
1829 			goto retry;
1830 		}
1831 
1832 		ibuf = ipipe->bufs + ipipe->curbuf;
1833 		nbuf = (opipe->curbuf + opipe->nrbufs) % PIPE_BUFFERS;
1834 		obuf = opipe->bufs + nbuf;
1835 
1836 		if (len >= ibuf->len) {
1837 			/*
1838 			 * Simply move the whole buffer from ipipe to opipe
1839 			 */
1840 			*obuf = *ibuf;
1841 			ibuf->ops = NULL;
1842 			opipe->nrbufs++;
1843 			ipipe->curbuf = (ipipe->curbuf + 1) % PIPE_BUFFERS;
1844 			ipipe->nrbufs--;
1845 			input_wakeup = true;
1846 		} else {
1847 			/*
1848 			 * Get a reference to this pipe buffer,
1849 			 * so we can copy the contents over.
1850 			 */
1851 			ibuf->ops->get(ipipe, ibuf);
1852 			*obuf = *ibuf;
1853 
1854 			/*
1855 			 * Don't inherit the gift flag, we need to
1856 			 * prevent multiple steals of this page.
1857 			 */
1858 			obuf->flags &= ~PIPE_BUF_FLAG_GIFT;
1859 
1860 			obuf->len = len;
1861 			opipe->nrbufs++;
1862 			ibuf->offset += obuf->len;
1863 			ibuf->len -= obuf->len;
1864 		}
1865 		ret += obuf->len;
1866 		len -= obuf->len;
1867 	} while (len);
1868 
1869 	pipe_unlock(ipipe);
1870 	pipe_unlock(opipe);
1871 
1872 	/*
1873 	 * If we put data in the output pipe, wakeup any potential readers.
1874 	 */
1875 	if (ret > 0) {
1876 		smp_mb();
1877 		if (waitqueue_active(&opipe->wait))
1878 			wake_up_interruptible(&opipe->wait);
1879 		kill_fasync(&opipe->fasync_readers, SIGIO, POLL_IN);
1880 	}
1881 	if (input_wakeup)
1882 		wakeup_pipe_writers(ipipe);
1883 
1884 	return ret;
1885 }
1886 
1887 /*
1888  * Link contents of ipipe to opipe.
1889  */
1890 static int link_pipe(struct pipe_inode_info *ipipe,
1891 		     struct pipe_inode_info *opipe,
1892 		     size_t len, unsigned int flags)
1893 {
1894 	struct pipe_buffer *ibuf, *obuf;
1895 	int ret = 0, i = 0, nbuf;
1896 
1897 	/*
1898 	 * Potential ABBA deadlock, work around it by ordering lock
1899 	 * grabbing by pipe info address. Otherwise two different processes
1900 	 * could deadlock (one doing tee from A -> B, the other from B -> A).
1901 	 */
1902 	pipe_double_lock(ipipe, opipe);
1903 
1904 	do {
1905 		if (!opipe->readers) {
1906 			send_sig(SIGPIPE, current, 0);
1907 			if (!ret)
1908 				ret = -EPIPE;
1909 			break;
1910 		}
1911 
1912 		/*
1913 		 * If we have iterated all input buffers or ran out of
1914 		 * output room, break.
1915 		 */
1916 		if (i >= ipipe->nrbufs || opipe->nrbufs >= PIPE_BUFFERS)
1917 			break;
1918 
1919 		ibuf = ipipe->bufs + ((ipipe->curbuf + i) & (PIPE_BUFFERS - 1));
1920 		nbuf = (opipe->curbuf + opipe->nrbufs) & (PIPE_BUFFERS - 1);
1921 
1922 		/*
1923 		 * Get a reference to this pipe buffer,
1924 		 * so we can copy the contents over.
1925 		 */
1926 		ibuf->ops->get(ipipe, ibuf);
1927 
1928 		obuf = opipe->bufs + nbuf;
1929 		*obuf = *ibuf;
1930 
1931 		/*
1932 		 * Don't inherit the gift flag, we need to
1933 		 * prevent multiple steals of this page.
1934 		 */
1935 		obuf->flags &= ~PIPE_BUF_FLAG_GIFT;
1936 
1937 		if (obuf->len > len)
1938 			obuf->len = len;
1939 
1940 		opipe->nrbufs++;
1941 		ret += obuf->len;
1942 		len -= obuf->len;
1943 		i++;
1944 	} while (len);
1945 
1946 	/*
1947 	 * return EAGAIN if we have the potential of some data in the
1948 	 * future, otherwise just return 0
1949 	 */
1950 	if (!ret && ipipe->waiting_writers && (flags & SPLICE_F_NONBLOCK))
1951 		ret = -EAGAIN;
1952 
1953 	pipe_unlock(ipipe);
1954 	pipe_unlock(opipe);
1955 
1956 	/*
1957 	 * If we put data in the output pipe, wakeup any potential readers.
1958 	 */
1959 	if (ret > 0) {
1960 		smp_mb();
1961 		if (waitqueue_active(&opipe->wait))
1962 			wake_up_interruptible(&opipe->wait);
1963 		kill_fasync(&opipe->fasync_readers, SIGIO, POLL_IN);
1964 	}
1965 
1966 	return ret;
1967 }
1968 
1969 /*
1970  * This is a tee(1) implementation that works on pipes. It doesn't copy
1971  * any data, it simply references the 'in' pages on the 'out' pipe.
1972  * The 'flags' used are the SPLICE_F_* variants, currently the only
1973  * applicable one is SPLICE_F_NONBLOCK.
1974  */
1975 static long do_tee(struct file *in, struct file *out, size_t len,
1976 		   unsigned int flags)
1977 {
1978 	struct pipe_inode_info *ipipe = pipe_info(in->f_path.dentry->d_inode);
1979 	struct pipe_inode_info *opipe = pipe_info(out->f_path.dentry->d_inode);
1980 	int ret = -EINVAL;
1981 
1982 	/*
1983 	 * Duplicate the contents of ipipe to opipe without actually
1984 	 * copying the data.
1985 	 */
1986 	if (ipipe && opipe && ipipe != opipe) {
1987 		/*
1988 		 * Keep going, unless we encounter an error. The ipipe/opipe
1989 		 * ordering doesn't really matter.
1990 		 */
1991 		ret = ipipe_prep(ipipe, flags);
1992 		if (!ret) {
1993 			ret = opipe_prep(opipe, flags);
1994 			if (!ret)
1995 				ret = link_pipe(ipipe, opipe, len, flags);
1996 		}
1997 	}
1998 
1999 	return ret;
2000 }
2001 
2002 SYSCALL_DEFINE4(tee, int, fdin, int, fdout, size_t, len, unsigned int, flags)
2003 {
2004 	struct file *in;
2005 	int error, fput_in;
2006 
2007 	if (unlikely(!len))
2008 		return 0;
2009 
2010 	error = -EBADF;
2011 	in = fget_light(fdin, &fput_in);
2012 	if (in) {
2013 		if (in->f_mode & FMODE_READ) {
2014 			int fput_out;
2015 			struct file *out = fget_light(fdout, &fput_out);
2016 
2017 			if (out) {
2018 				if (out->f_mode & FMODE_WRITE)
2019 					error = do_tee(in, out, len, flags);
2020 				fput_light(out, fput_out);
2021 			}
2022 		}
2023  		fput_light(in, fput_in);
2024  	}
2025 
2026 	return error;
2027 }
2028