xref: /openbmc/linux/fs/splice.c (revision 495311927ffbe3604e915aeafdf03325e9925b9d)
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 #include <linux/gfp.h>
34 
35 /*
36  * Attempt to steal a page from a pipe buffer. This should perhaps go into
37  * a vm helper function, it's already simplified quite a bit by the
38  * addition of remove_mapping(). If success is returned, the caller may
39  * attempt to reuse this page for another destination.
40  */
41 static int page_cache_pipe_buf_steal(struct pipe_inode_info *pipe,
42 				     struct pipe_buffer *buf)
43 {
44 	struct page *page = buf->page;
45 	struct address_space *mapping;
46 
47 	lock_page(page);
48 
49 	mapping = page_mapping(page);
50 	if (mapping) {
51 		WARN_ON(!PageUptodate(page));
52 
53 		/*
54 		 * At least for ext2 with nobh option, we need to wait on
55 		 * writeback completing on this page, since we'll remove it
56 		 * from the pagecache.  Otherwise truncate wont wait on the
57 		 * page, allowing the disk blocks to be reused by someone else
58 		 * before we actually wrote our data to them. fs corruption
59 		 * ensues.
60 		 */
61 		wait_on_page_writeback(page);
62 
63 		if (page_has_private(page) &&
64 		    !try_to_release_page(page, GFP_KERNEL))
65 			goto out_unlock;
66 
67 		/*
68 		 * If we succeeded in removing the mapping, set LRU flag
69 		 * and return good.
70 		 */
71 		if (remove_mapping(mapping, page)) {
72 			buf->flags |= PIPE_BUF_FLAG_LRU;
73 			return 0;
74 		}
75 	}
76 
77 	/*
78 	 * Raced with truncate or failed to remove page from current
79 	 * address space, unlock and return failure.
80 	 */
81 out_unlock:
82 	unlock_page(page);
83 	return 1;
84 }
85 
86 static void page_cache_pipe_buf_release(struct pipe_inode_info *pipe,
87 					struct pipe_buffer *buf)
88 {
89 	page_cache_release(buf->page);
90 	buf->flags &= ~PIPE_BUF_FLAG_LRU;
91 }
92 
93 /*
94  * Check whether the contents of buf is OK to access. Since the content
95  * is a page cache page, IO may be in flight.
96  */
97 static int page_cache_pipe_buf_confirm(struct pipe_inode_info *pipe,
98 				       struct pipe_buffer *buf)
99 {
100 	struct page *page = buf->page;
101 	int err;
102 
103 	if (!PageUptodate(page)) {
104 		lock_page(page);
105 
106 		/*
107 		 * Page got truncated/unhashed. This will cause a 0-byte
108 		 * splice, if this is the first page.
109 		 */
110 		if (!page->mapping) {
111 			err = -ENODATA;
112 			goto error;
113 		}
114 
115 		/*
116 		 * Uh oh, read-error from disk.
117 		 */
118 		if (!PageUptodate(page)) {
119 			err = -EIO;
120 			goto error;
121 		}
122 
123 		/*
124 		 * Page is ok afterall, we are done.
125 		 */
126 		unlock_page(page);
127 	}
128 
129 	return 0;
130 error:
131 	unlock_page(page);
132 	return err;
133 }
134 
135 static const struct pipe_buf_operations page_cache_pipe_buf_ops = {
136 	.can_merge = 0,
137 	.map = generic_pipe_buf_map,
138 	.unmap = generic_pipe_buf_unmap,
139 	.confirm = page_cache_pipe_buf_confirm,
140 	.release = page_cache_pipe_buf_release,
141 	.steal = page_cache_pipe_buf_steal,
142 	.get = generic_pipe_buf_get,
143 };
144 
145 static int user_page_pipe_buf_steal(struct pipe_inode_info *pipe,
146 				    struct pipe_buffer *buf)
147 {
148 	if (!(buf->flags & PIPE_BUF_FLAG_GIFT))
149 		return 1;
150 
151 	buf->flags |= PIPE_BUF_FLAG_LRU;
152 	return generic_pipe_buf_steal(pipe, buf);
153 }
154 
155 static const struct pipe_buf_operations user_page_pipe_buf_ops = {
156 	.can_merge = 0,
157 	.map = generic_pipe_buf_map,
158 	.unmap = generic_pipe_buf_unmap,
159 	.confirm = generic_pipe_buf_confirm,
160 	.release = page_cache_pipe_buf_release,
161 	.steal = user_page_pipe_buf_steal,
162 	.get = generic_pipe_buf_get,
163 };
164 
165 /**
166  * splice_to_pipe - fill passed data into a pipe
167  * @pipe:	pipe to fill
168  * @spd:	data to fill
169  *
170  * Description:
171  *    @spd contains a map of pages and len/offset tuples, along with
172  *    the struct pipe_buf_operations associated with these pages. This
173  *    function will link that data to the pipe.
174  *
175  */
176 ssize_t splice_to_pipe(struct pipe_inode_info *pipe,
177 		       struct splice_pipe_desc *spd)
178 {
179 	unsigned int spd_pages = spd->nr_pages;
180 	int ret, do_wakeup, page_nr;
181 
182 	ret = 0;
183 	do_wakeup = 0;
184 	page_nr = 0;
185 
186 	pipe_lock(pipe);
187 
188 	for (;;) {
189 		if (!pipe->readers) {
190 			send_sig(SIGPIPE, current, 0);
191 			if (!ret)
192 				ret = -EPIPE;
193 			break;
194 		}
195 
196 		if (pipe->nrbufs < pipe->buffers) {
197 			int newbuf = (pipe->curbuf + pipe->nrbufs) & (pipe->buffers - 1);
198 			struct pipe_buffer *buf = pipe->bufs + newbuf;
199 
200 			buf->page = spd->pages[page_nr];
201 			buf->offset = spd->partial[page_nr].offset;
202 			buf->len = spd->partial[page_nr].len;
203 			buf->private = spd->partial[page_nr].private;
204 			buf->ops = spd->ops;
205 			if (spd->flags & SPLICE_F_GIFT)
206 				buf->flags |= PIPE_BUF_FLAG_GIFT;
207 
208 			pipe->nrbufs++;
209 			page_nr++;
210 			ret += buf->len;
211 
212 			if (pipe->inode)
213 				do_wakeup = 1;
214 
215 			if (!--spd->nr_pages)
216 				break;
217 			if (pipe->nrbufs < pipe->buffers)
218 				continue;
219 
220 			break;
221 		}
222 
223 		if (spd->flags & SPLICE_F_NONBLOCK) {
224 			if (!ret)
225 				ret = -EAGAIN;
226 			break;
227 		}
228 
229 		if (signal_pending(current)) {
230 			if (!ret)
231 				ret = -ERESTARTSYS;
232 			break;
233 		}
234 
235 		if (do_wakeup) {
236 			smp_mb();
237 			if (waitqueue_active(&pipe->wait))
238 				wake_up_interruptible_sync(&pipe->wait);
239 			kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
240 			do_wakeup = 0;
241 		}
242 
243 		pipe->waiting_writers++;
244 		pipe_wait(pipe);
245 		pipe->waiting_writers--;
246 	}
247 
248 	pipe_unlock(pipe);
249 
250 	if (do_wakeup) {
251 		smp_mb();
252 		if (waitqueue_active(&pipe->wait))
253 			wake_up_interruptible(&pipe->wait);
254 		kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
255 	}
256 
257 	while (page_nr < spd_pages)
258 		spd->spd_release(spd, page_nr++);
259 
260 	return ret;
261 }
262 
263 static void spd_release_page(struct splice_pipe_desc *spd, unsigned int i)
264 {
265 	page_cache_release(spd->pages[i]);
266 }
267 
268 /*
269  * Check if we need to grow the arrays holding pages and partial page
270  * descriptions.
271  */
272 int splice_grow_spd(struct pipe_inode_info *pipe, struct splice_pipe_desc *spd)
273 {
274 	if (pipe->buffers <= PIPE_DEF_BUFFERS)
275 		return 0;
276 
277 	spd->pages = kmalloc(pipe->buffers * sizeof(struct page *), GFP_KERNEL);
278 	spd->partial = kmalloc(pipe->buffers * sizeof(struct partial_page), GFP_KERNEL);
279 
280 	if (spd->pages && spd->partial)
281 		return 0;
282 
283 	kfree(spd->pages);
284 	kfree(spd->partial);
285 	return -ENOMEM;
286 }
287 
288 void splice_shrink_spd(struct pipe_inode_info *pipe,
289 		       struct splice_pipe_desc *spd)
290 {
291 	if (pipe->buffers <= PIPE_DEF_BUFFERS)
292 		return;
293 
294 	kfree(spd->pages);
295 	kfree(spd->partial);
296 }
297 
298 static int
299 __generic_file_splice_read(struct file *in, loff_t *ppos,
300 			   struct pipe_inode_info *pipe, size_t len,
301 			   unsigned int flags)
302 {
303 	struct address_space *mapping = in->f_mapping;
304 	unsigned int loff, nr_pages, req_pages;
305 	struct page *pages[PIPE_DEF_BUFFERS];
306 	struct partial_page partial[PIPE_DEF_BUFFERS];
307 	struct page *page;
308 	pgoff_t index, end_index;
309 	loff_t isize;
310 	int error, page_nr;
311 	struct splice_pipe_desc spd = {
312 		.pages = pages,
313 		.partial = partial,
314 		.flags = flags,
315 		.ops = &page_cache_pipe_buf_ops,
316 		.spd_release = spd_release_page,
317 	};
318 
319 	if (splice_grow_spd(pipe, &spd))
320 		return -ENOMEM;
321 
322 	index = *ppos >> PAGE_CACHE_SHIFT;
323 	loff = *ppos & ~PAGE_CACHE_MASK;
324 	req_pages = (len + loff + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
325 	nr_pages = min(req_pages, pipe->buffers);
326 
327 	/*
328 	 * Lookup the (hopefully) full range of pages we need.
329 	 */
330 	spd.nr_pages = find_get_pages_contig(mapping, index, nr_pages, spd.pages);
331 	index += spd.nr_pages;
332 
333 	/*
334 	 * If find_get_pages_contig() returned fewer pages than we needed,
335 	 * readahead/allocate the rest and fill in the holes.
336 	 */
337 	if (spd.nr_pages < nr_pages)
338 		page_cache_sync_readahead(mapping, &in->f_ra, in,
339 				index, req_pages - spd.nr_pages);
340 
341 	error = 0;
342 	while (spd.nr_pages < nr_pages) {
343 		/*
344 		 * Page could be there, find_get_pages_contig() breaks on
345 		 * the first hole.
346 		 */
347 		page = find_get_page(mapping, index);
348 		if (!page) {
349 			/*
350 			 * page didn't exist, allocate one.
351 			 */
352 			page = page_cache_alloc_cold(mapping);
353 			if (!page)
354 				break;
355 
356 			error = add_to_page_cache_lru(page, mapping, index,
357 						GFP_KERNEL);
358 			if (unlikely(error)) {
359 				page_cache_release(page);
360 				if (error == -EEXIST)
361 					continue;
362 				break;
363 			}
364 			/*
365 			 * add_to_page_cache() locks the page, unlock it
366 			 * to avoid convoluting the logic below even more.
367 			 */
368 			unlock_page(page);
369 		}
370 
371 		spd.pages[spd.nr_pages++] = page;
372 		index++;
373 	}
374 
375 	/*
376 	 * Now loop over the map and see if we need to start IO on any
377 	 * pages, fill in the partial map, etc.
378 	 */
379 	index = *ppos >> PAGE_CACHE_SHIFT;
380 	nr_pages = spd.nr_pages;
381 	spd.nr_pages = 0;
382 	for (page_nr = 0; page_nr < nr_pages; page_nr++) {
383 		unsigned int this_len;
384 
385 		if (!len)
386 			break;
387 
388 		/*
389 		 * this_len is the max we'll use from this page
390 		 */
391 		this_len = min_t(unsigned long, len, PAGE_CACHE_SIZE - loff);
392 		page = spd.pages[page_nr];
393 
394 		if (PageReadahead(page))
395 			page_cache_async_readahead(mapping, &in->f_ra, in,
396 					page, index, req_pages - page_nr);
397 
398 		/*
399 		 * If the page isn't uptodate, we may need to start io on it
400 		 */
401 		if (!PageUptodate(page)) {
402 			/*
403 			 * If in nonblock mode then dont block on waiting
404 			 * for an in-flight io page
405 			 */
406 			if (flags & SPLICE_F_NONBLOCK) {
407 				if (!trylock_page(page)) {
408 					error = -EAGAIN;
409 					break;
410 				}
411 			} else
412 				lock_page(page);
413 
414 			/*
415 			 * Page was truncated, or invalidated by the
416 			 * filesystem.  Redo the find/create, but this time the
417 			 * page is kept locked, so there's no chance of another
418 			 * race with truncate/invalidate.
419 			 */
420 			if (!page->mapping) {
421 				unlock_page(page);
422 				page = find_or_create_page(mapping, index,
423 						mapping_gfp_mask(mapping));
424 
425 				if (!page) {
426 					error = -ENOMEM;
427 					break;
428 				}
429 				page_cache_release(spd.pages[page_nr]);
430 				spd.pages[page_nr] = page;
431 			}
432 			/*
433 			 * page was already under io and is now done, great
434 			 */
435 			if (PageUptodate(page)) {
436 				unlock_page(page);
437 				goto fill_it;
438 			}
439 
440 			/*
441 			 * need to read in the page
442 			 */
443 			error = mapping->a_ops->readpage(in, page);
444 			if (unlikely(error)) {
445 				/*
446 				 * We really should re-lookup the page here,
447 				 * but it complicates things a lot. Instead
448 				 * lets just do what we already stored, and
449 				 * we'll get it the next time we are called.
450 				 */
451 				if (error == AOP_TRUNCATED_PAGE)
452 					error = 0;
453 
454 				break;
455 			}
456 		}
457 fill_it:
458 		/*
459 		 * i_size must be checked after PageUptodate.
460 		 */
461 		isize = i_size_read(mapping->host);
462 		end_index = (isize - 1) >> PAGE_CACHE_SHIFT;
463 		if (unlikely(!isize || index > end_index))
464 			break;
465 
466 		/*
467 		 * if this is the last page, see if we need to shrink
468 		 * the length and stop
469 		 */
470 		if (end_index == index) {
471 			unsigned int plen;
472 
473 			/*
474 			 * max good bytes in this page
475 			 */
476 			plen = ((isize - 1) & ~PAGE_CACHE_MASK) + 1;
477 			if (plen <= loff)
478 				break;
479 
480 			/*
481 			 * force quit after adding this page
482 			 */
483 			this_len = min(this_len, plen - loff);
484 			len = this_len;
485 		}
486 
487 		spd.partial[page_nr].offset = loff;
488 		spd.partial[page_nr].len = this_len;
489 		len -= this_len;
490 		loff = 0;
491 		spd.nr_pages++;
492 		index++;
493 	}
494 
495 	/*
496 	 * Release any pages at the end, if we quit early. 'page_nr' is how far
497 	 * we got, 'nr_pages' is how many pages are in the map.
498 	 */
499 	while (page_nr < nr_pages)
500 		page_cache_release(spd.pages[page_nr++]);
501 	in->f_ra.prev_pos = (loff_t)index << PAGE_CACHE_SHIFT;
502 
503 	if (spd.nr_pages)
504 		error = splice_to_pipe(pipe, &spd);
505 
506 	splice_shrink_spd(pipe, &spd);
507 	return error;
508 }
509 
510 /**
511  * generic_file_splice_read - splice data from file to a pipe
512  * @in:		file to splice from
513  * @ppos:	position in @in
514  * @pipe:	pipe to splice to
515  * @len:	number of bytes to splice
516  * @flags:	splice modifier flags
517  *
518  * Description:
519  *    Will read pages from given file and fill them into a pipe. Can be
520  *    used as long as the address_space operations for the source implements
521  *    a readpage() hook.
522  *
523  */
524 ssize_t generic_file_splice_read(struct file *in, loff_t *ppos,
525 				 struct pipe_inode_info *pipe, size_t len,
526 				 unsigned int flags)
527 {
528 	loff_t isize, left;
529 	int ret;
530 
531 	isize = i_size_read(in->f_mapping->host);
532 	if (unlikely(*ppos >= isize))
533 		return 0;
534 
535 	left = isize - *ppos;
536 	if (unlikely(left < len))
537 		len = left;
538 
539 	ret = __generic_file_splice_read(in, ppos, pipe, len, flags);
540 	if (ret > 0) {
541 		*ppos += ret;
542 		file_accessed(in);
543 	}
544 
545 	return ret;
546 }
547 EXPORT_SYMBOL(generic_file_splice_read);
548 
549 static const struct pipe_buf_operations default_pipe_buf_ops = {
550 	.can_merge = 0,
551 	.map = generic_pipe_buf_map,
552 	.unmap = generic_pipe_buf_unmap,
553 	.confirm = generic_pipe_buf_confirm,
554 	.release = generic_pipe_buf_release,
555 	.steal = generic_pipe_buf_steal,
556 	.get = generic_pipe_buf_get,
557 };
558 
559 static ssize_t kernel_readv(struct file *file, const struct iovec *vec,
560 			    unsigned long vlen, loff_t offset)
561 {
562 	mm_segment_t old_fs;
563 	loff_t pos = offset;
564 	ssize_t res;
565 
566 	old_fs = get_fs();
567 	set_fs(get_ds());
568 	/* The cast to a user pointer is valid due to the set_fs() */
569 	res = vfs_readv(file, (const struct iovec __user *)vec, vlen, &pos);
570 	set_fs(old_fs);
571 
572 	return res;
573 }
574 
575 static ssize_t kernel_write(struct file *file, const char *buf, size_t count,
576 			    loff_t pos)
577 {
578 	mm_segment_t old_fs;
579 	ssize_t res;
580 
581 	old_fs = get_fs();
582 	set_fs(get_ds());
583 	/* The cast to a user pointer is valid due to the set_fs() */
584 	res = vfs_write(file, (const char __user *)buf, count, &pos);
585 	set_fs(old_fs);
586 
587 	return res;
588 }
589 
590 ssize_t default_file_splice_read(struct file *in, loff_t *ppos,
591 				 struct pipe_inode_info *pipe, size_t len,
592 				 unsigned int flags)
593 {
594 	unsigned int nr_pages;
595 	unsigned int nr_freed;
596 	size_t offset;
597 	struct page *pages[PIPE_DEF_BUFFERS];
598 	struct partial_page partial[PIPE_DEF_BUFFERS];
599 	struct iovec *vec, __vec[PIPE_DEF_BUFFERS];
600 	pgoff_t index;
601 	ssize_t res;
602 	size_t this_len;
603 	int error;
604 	int i;
605 	struct splice_pipe_desc spd = {
606 		.pages = pages,
607 		.partial = partial,
608 		.flags = flags,
609 		.ops = &default_pipe_buf_ops,
610 		.spd_release = spd_release_page,
611 	};
612 
613 	if (splice_grow_spd(pipe, &spd))
614 		return -ENOMEM;
615 
616 	res = -ENOMEM;
617 	vec = __vec;
618 	if (pipe->buffers > PIPE_DEF_BUFFERS) {
619 		vec = kmalloc(pipe->buffers * sizeof(struct iovec), GFP_KERNEL);
620 		if (!vec)
621 			goto shrink_ret;
622 	}
623 
624 	index = *ppos >> PAGE_CACHE_SHIFT;
625 	offset = *ppos & ~PAGE_CACHE_MASK;
626 	nr_pages = (len + offset + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
627 
628 	for (i = 0; i < nr_pages && i < pipe->buffers && len; i++) {
629 		struct page *page;
630 
631 		page = alloc_page(GFP_USER);
632 		error = -ENOMEM;
633 		if (!page)
634 			goto err;
635 
636 		this_len = min_t(size_t, len, PAGE_CACHE_SIZE - offset);
637 		vec[i].iov_base = (void __user *) page_address(page);
638 		vec[i].iov_len = this_len;
639 		spd.pages[i] = page;
640 		spd.nr_pages++;
641 		len -= this_len;
642 		offset = 0;
643 	}
644 
645 	res = kernel_readv(in, vec, spd.nr_pages, *ppos);
646 	if (res < 0) {
647 		error = res;
648 		goto err;
649 	}
650 
651 	error = 0;
652 	if (!res)
653 		goto err;
654 
655 	nr_freed = 0;
656 	for (i = 0; i < spd.nr_pages; i++) {
657 		this_len = min_t(size_t, vec[i].iov_len, res);
658 		spd.partial[i].offset = 0;
659 		spd.partial[i].len = this_len;
660 		if (!this_len) {
661 			__free_page(spd.pages[i]);
662 			spd.pages[i] = NULL;
663 			nr_freed++;
664 		}
665 		res -= this_len;
666 	}
667 	spd.nr_pages -= nr_freed;
668 
669 	res = splice_to_pipe(pipe, &spd);
670 	if (res > 0)
671 		*ppos += res;
672 
673 shrink_ret:
674 	if (vec != __vec)
675 		kfree(vec);
676 	splice_shrink_spd(pipe, &spd);
677 	return res;
678 
679 err:
680 	for (i = 0; i < spd.nr_pages; i++)
681 		__free_page(spd.pages[i]);
682 
683 	res = error;
684 	goto shrink_ret;
685 }
686 EXPORT_SYMBOL(default_file_splice_read);
687 
688 /*
689  * Send 'sd->len' bytes to socket from 'sd->file' at position 'sd->pos'
690  * using sendpage(). Return the number of bytes sent.
691  */
692 static int pipe_to_sendpage(struct pipe_inode_info *pipe,
693 			    struct pipe_buffer *buf, struct splice_desc *sd)
694 {
695 	struct file *file = sd->u.file;
696 	loff_t pos = sd->pos;
697 	int ret, more;
698 
699 	ret = buf->ops->confirm(pipe, buf);
700 	if (!ret) {
701 		more = (sd->flags & SPLICE_F_MORE) || sd->len < sd->total_len;
702 		if (file->f_op && file->f_op->sendpage)
703 			ret = file->f_op->sendpage(file, buf->page, buf->offset,
704 						   sd->len, &pos, more);
705 		else
706 			ret = -EINVAL;
707 	}
708 
709 	return ret;
710 }
711 
712 /*
713  * This is a little more tricky than the file -> pipe splicing. There are
714  * basically three cases:
715  *
716  *	- Destination page already exists in the address space and there
717  *	  are users of it. For that case we have no other option that
718  *	  copying the data. Tough luck.
719  *	- Destination page already exists in the address space, but there
720  *	  are no users of it. Make sure it's uptodate, then drop it. Fall
721  *	  through to last case.
722  *	- Destination page does not exist, we can add the pipe page to
723  *	  the page cache and avoid the copy.
724  *
725  * If asked to move pages to the output file (SPLICE_F_MOVE is set in
726  * sd->flags), we attempt to migrate pages from the pipe to the output
727  * file address space page cache. This is possible if no one else has
728  * the pipe page referenced outside of the pipe and page cache. If
729  * SPLICE_F_MOVE isn't set, or we cannot move the page, we simply create
730  * a new page in the output file page cache and fill/dirty that.
731  */
732 int pipe_to_file(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
733 		 struct splice_desc *sd)
734 {
735 	struct file *file = sd->u.file;
736 	struct address_space *mapping = file->f_mapping;
737 	unsigned int offset, this_len;
738 	struct page *page;
739 	void *fsdata;
740 	int ret;
741 
742 	/*
743 	 * make sure the data in this buffer is uptodate
744 	 */
745 	ret = buf->ops->confirm(pipe, buf);
746 	if (unlikely(ret))
747 		return ret;
748 
749 	offset = sd->pos & ~PAGE_CACHE_MASK;
750 
751 	this_len = sd->len;
752 	if (this_len + offset > PAGE_CACHE_SIZE)
753 		this_len = PAGE_CACHE_SIZE - offset;
754 
755 	ret = pagecache_write_begin(file, mapping, sd->pos, this_len,
756 				AOP_FLAG_UNINTERRUPTIBLE, &page, &fsdata);
757 	if (unlikely(ret))
758 		goto out;
759 
760 	if (buf->page != page) {
761 		/*
762 		 * Careful, ->map() uses KM_USER0!
763 		 */
764 		char *src = buf->ops->map(pipe, buf, 1);
765 		char *dst = kmap_atomic(page, KM_USER1);
766 
767 		memcpy(dst + offset, src + buf->offset, this_len);
768 		flush_dcache_page(page);
769 		kunmap_atomic(dst, KM_USER1);
770 		buf->ops->unmap(pipe, buf, src);
771 	}
772 	ret = pagecache_write_end(file, mapping, sd->pos, this_len, this_len,
773 				page, fsdata);
774 out:
775 	return ret;
776 }
777 EXPORT_SYMBOL(pipe_to_file);
778 
779 static void wakeup_pipe_writers(struct pipe_inode_info *pipe)
780 {
781 	smp_mb();
782 	if (waitqueue_active(&pipe->wait))
783 		wake_up_interruptible(&pipe->wait);
784 	kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
785 }
786 
787 /**
788  * splice_from_pipe_feed - feed available data from a pipe to a file
789  * @pipe:	pipe to splice from
790  * @sd:		information to @actor
791  * @actor:	handler that splices the data
792  *
793  * Description:
794  *    This function loops over the pipe and calls @actor to do the
795  *    actual moving of a single struct pipe_buffer to the desired
796  *    destination.  It returns when there's no more buffers left in
797  *    the pipe or if the requested number of bytes (@sd->total_len)
798  *    have been copied.  It returns a positive number (one) if the
799  *    pipe needs to be filled with more data, zero if the required
800  *    number of bytes have been copied and -errno on error.
801  *
802  *    This, together with splice_from_pipe_{begin,end,next}, may be
803  *    used to implement the functionality of __splice_from_pipe() when
804  *    locking is required around copying the pipe buffers to the
805  *    destination.
806  */
807 int splice_from_pipe_feed(struct pipe_inode_info *pipe, struct splice_desc *sd,
808 			  splice_actor *actor)
809 {
810 	int ret;
811 
812 	while (pipe->nrbufs) {
813 		struct pipe_buffer *buf = pipe->bufs + pipe->curbuf;
814 		const struct pipe_buf_operations *ops = buf->ops;
815 
816 		sd->len = buf->len;
817 		if (sd->len > sd->total_len)
818 			sd->len = sd->total_len;
819 
820 		ret = actor(pipe, buf, sd);
821 		if (ret <= 0) {
822 			if (ret == -ENODATA)
823 				ret = 0;
824 			return ret;
825 		}
826 		buf->offset += ret;
827 		buf->len -= ret;
828 
829 		sd->num_spliced += ret;
830 		sd->len -= ret;
831 		sd->pos += ret;
832 		sd->total_len -= ret;
833 
834 		if (!buf->len) {
835 			buf->ops = NULL;
836 			ops->release(pipe, buf);
837 			pipe->curbuf = (pipe->curbuf + 1) & (pipe->buffers - 1);
838 			pipe->nrbufs--;
839 			if (pipe->inode)
840 				sd->need_wakeup = true;
841 		}
842 
843 		if (!sd->total_len)
844 			return 0;
845 	}
846 
847 	return 1;
848 }
849 EXPORT_SYMBOL(splice_from_pipe_feed);
850 
851 /**
852  * splice_from_pipe_next - wait for some data to splice from
853  * @pipe:	pipe to splice from
854  * @sd:		information about the splice operation
855  *
856  * Description:
857  *    This function will wait for some data and return a positive
858  *    value (one) if pipe buffers are available.  It will return zero
859  *    or -errno if no more data needs to be spliced.
860  */
861 int splice_from_pipe_next(struct pipe_inode_info *pipe, struct splice_desc *sd)
862 {
863 	while (!pipe->nrbufs) {
864 		if (!pipe->writers)
865 			return 0;
866 
867 		if (!pipe->waiting_writers && sd->num_spliced)
868 			return 0;
869 
870 		if (sd->flags & SPLICE_F_NONBLOCK)
871 			return -EAGAIN;
872 
873 		if (signal_pending(current))
874 			return -ERESTARTSYS;
875 
876 		if (sd->need_wakeup) {
877 			wakeup_pipe_writers(pipe);
878 			sd->need_wakeup = false;
879 		}
880 
881 		pipe_wait(pipe);
882 	}
883 
884 	return 1;
885 }
886 EXPORT_SYMBOL(splice_from_pipe_next);
887 
888 /**
889  * splice_from_pipe_begin - start splicing from pipe
890  * @sd:		information about the splice operation
891  *
892  * Description:
893  *    This function should be called before a loop containing
894  *    splice_from_pipe_next() and splice_from_pipe_feed() to
895  *    initialize the necessary fields of @sd.
896  */
897 void splice_from_pipe_begin(struct splice_desc *sd)
898 {
899 	sd->num_spliced = 0;
900 	sd->need_wakeup = false;
901 }
902 EXPORT_SYMBOL(splice_from_pipe_begin);
903 
904 /**
905  * splice_from_pipe_end - finish splicing from pipe
906  * @pipe:	pipe to splice from
907  * @sd:		information about the splice operation
908  *
909  * Description:
910  *    This function will wake up pipe writers if necessary.  It should
911  *    be called after a loop containing splice_from_pipe_next() and
912  *    splice_from_pipe_feed().
913  */
914 void splice_from_pipe_end(struct pipe_inode_info *pipe, struct splice_desc *sd)
915 {
916 	if (sd->need_wakeup)
917 		wakeup_pipe_writers(pipe);
918 }
919 EXPORT_SYMBOL(splice_from_pipe_end);
920 
921 /**
922  * __splice_from_pipe - splice data from a pipe to given actor
923  * @pipe:	pipe to splice from
924  * @sd:		information to @actor
925  * @actor:	handler that splices the data
926  *
927  * Description:
928  *    This function does little more than loop over the pipe and call
929  *    @actor to do the actual moving of a single struct pipe_buffer to
930  *    the desired destination. See pipe_to_file, pipe_to_sendpage, or
931  *    pipe_to_user.
932  *
933  */
934 ssize_t __splice_from_pipe(struct pipe_inode_info *pipe, struct splice_desc *sd,
935 			   splice_actor *actor)
936 {
937 	int ret;
938 
939 	splice_from_pipe_begin(sd);
940 	do {
941 		ret = splice_from_pipe_next(pipe, sd);
942 		if (ret > 0)
943 			ret = splice_from_pipe_feed(pipe, sd, actor);
944 	} while (ret > 0);
945 	splice_from_pipe_end(pipe, sd);
946 
947 	return sd->num_spliced ? sd->num_spliced : ret;
948 }
949 EXPORT_SYMBOL(__splice_from_pipe);
950 
951 /**
952  * splice_from_pipe - splice data from a pipe to a file
953  * @pipe:	pipe to splice from
954  * @out:	file to splice to
955  * @ppos:	position in @out
956  * @len:	how many bytes to splice
957  * @flags:	splice modifier flags
958  * @actor:	handler that splices the data
959  *
960  * Description:
961  *    See __splice_from_pipe. This function locks the pipe inode,
962  *    otherwise it's identical to __splice_from_pipe().
963  *
964  */
965 ssize_t splice_from_pipe(struct pipe_inode_info *pipe, struct file *out,
966 			 loff_t *ppos, size_t len, unsigned int flags,
967 			 splice_actor *actor)
968 {
969 	ssize_t ret;
970 	struct splice_desc sd = {
971 		.total_len = len,
972 		.flags = flags,
973 		.pos = *ppos,
974 		.u.file = out,
975 	};
976 
977 	pipe_lock(pipe);
978 	ret = __splice_from_pipe(pipe, &sd, actor);
979 	pipe_unlock(pipe);
980 
981 	return ret;
982 }
983 
984 /**
985  * generic_file_splice_write - splice data from a pipe to a file
986  * @pipe:	pipe info
987  * @out:	file to write to
988  * @ppos:	position in @out
989  * @len:	number of bytes to splice
990  * @flags:	splice modifier flags
991  *
992  * Description:
993  *    Will either move or copy pages (determined by @flags options) from
994  *    the given pipe inode to the given file.
995  *
996  */
997 ssize_t
998 generic_file_splice_write(struct pipe_inode_info *pipe, struct file *out,
999 			  loff_t *ppos, size_t len, unsigned int flags)
1000 {
1001 	struct address_space *mapping = out->f_mapping;
1002 	struct inode *inode = mapping->host;
1003 	struct splice_desc sd = {
1004 		.total_len = len,
1005 		.flags = flags,
1006 		.pos = *ppos,
1007 		.u.file = out,
1008 	};
1009 	ssize_t ret;
1010 
1011 	pipe_lock(pipe);
1012 
1013 	splice_from_pipe_begin(&sd);
1014 	do {
1015 		ret = splice_from_pipe_next(pipe, &sd);
1016 		if (ret <= 0)
1017 			break;
1018 
1019 		mutex_lock_nested(&inode->i_mutex, I_MUTEX_CHILD);
1020 		ret = file_remove_suid(out);
1021 		if (!ret) {
1022 			file_update_time(out);
1023 			ret = splice_from_pipe_feed(pipe, &sd, pipe_to_file);
1024 		}
1025 		mutex_unlock(&inode->i_mutex);
1026 	} while (ret > 0);
1027 	splice_from_pipe_end(pipe, &sd);
1028 
1029 	pipe_unlock(pipe);
1030 
1031 	if (sd.num_spliced)
1032 		ret = sd.num_spliced;
1033 
1034 	if (ret > 0) {
1035 		unsigned long nr_pages;
1036 		int err;
1037 
1038 		nr_pages = (ret + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
1039 
1040 		err = generic_write_sync(out, *ppos, ret);
1041 		if (err)
1042 			ret = err;
1043 		else
1044 			*ppos += ret;
1045 		balance_dirty_pages_ratelimited_nr(mapping, nr_pages);
1046 	}
1047 
1048 	return ret;
1049 }
1050 
1051 EXPORT_SYMBOL(generic_file_splice_write);
1052 
1053 static int write_pipe_buf(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
1054 			  struct splice_desc *sd)
1055 {
1056 	int ret;
1057 	void *data;
1058 
1059 	ret = buf->ops->confirm(pipe, buf);
1060 	if (ret)
1061 		return ret;
1062 
1063 	data = buf->ops->map(pipe, buf, 0);
1064 	ret = kernel_write(sd->u.file, data + buf->offset, sd->len, sd->pos);
1065 	buf->ops->unmap(pipe, buf, data);
1066 
1067 	return ret;
1068 }
1069 
1070 static ssize_t default_file_splice_write(struct pipe_inode_info *pipe,
1071 					 struct file *out, loff_t *ppos,
1072 					 size_t len, unsigned int flags)
1073 {
1074 	ssize_t ret;
1075 
1076 	ret = splice_from_pipe(pipe, out, ppos, len, flags, write_pipe_buf);
1077 	if (ret > 0)
1078 		*ppos += ret;
1079 
1080 	return ret;
1081 }
1082 
1083 /**
1084  * generic_splice_sendpage - splice data from a pipe to a socket
1085  * @pipe:	pipe to splice from
1086  * @out:	socket to write to
1087  * @ppos:	position in @out
1088  * @len:	number of bytes to splice
1089  * @flags:	splice modifier flags
1090  *
1091  * Description:
1092  *    Will send @len bytes from the pipe to a network socket. No data copying
1093  *    is involved.
1094  *
1095  */
1096 ssize_t generic_splice_sendpage(struct pipe_inode_info *pipe, struct file *out,
1097 				loff_t *ppos, size_t len, unsigned int flags)
1098 {
1099 	return splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_sendpage);
1100 }
1101 
1102 EXPORT_SYMBOL(generic_splice_sendpage);
1103 
1104 /*
1105  * Attempt to initiate a splice from pipe to file.
1106  */
1107 static long do_splice_from(struct pipe_inode_info *pipe, struct file *out,
1108 			   loff_t *ppos, size_t len, unsigned int flags)
1109 {
1110 	ssize_t (*splice_write)(struct pipe_inode_info *, struct file *,
1111 				loff_t *, size_t, unsigned int);
1112 	int ret;
1113 
1114 	if (unlikely(!(out->f_mode & FMODE_WRITE)))
1115 		return -EBADF;
1116 
1117 	if (unlikely(out->f_flags & O_APPEND))
1118 		return -EINVAL;
1119 
1120 	ret = rw_verify_area(WRITE, out, ppos, len);
1121 	if (unlikely(ret < 0))
1122 		return ret;
1123 
1124 	if (out->f_op && out->f_op->splice_write)
1125 		splice_write = out->f_op->splice_write;
1126 	else
1127 		splice_write = default_file_splice_write;
1128 
1129 	return splice_write(pipe, out, ppos, len, flags);
1130 }
1131 
1132 /*
1133  * Attempt to initiate a splice from a file to a pipe.
1134  */
1135 static long do_splice_to(struct file *in, loff_t *ppos,
1136 			 struct pipe_inode_info *pipe, size_t len,
1137 			 unsigned int flags)
1138 {
1139 	ssize_t (*splice_read)(struct file *, loff_t *,
1140 			       struct pipe_inode_info *, size_t, unsigned int);
1141 	int ret;
1142 
1143 	if (unlikely(!(in->f_mode & FMODE_READ)))
1144 		return -EBADF;
1145 
1146 	ret = rw_verify_area(READ, in, ppos, len);
1147 	if (unlikely(ret < 0))
1148 		return ret;
1149 
1150 	if (in->f_op && in->f_op->splice_read)
1151 		splice_read = in->f_op->splice_read;
1152 	else
1153 		splice_read = default_file_splice_read;
1154 
1155 	return splice_read(in, ppos, pipe, len, flags);
1156 }
1157 
1158 /**
1159  * splice_direct_to_actor - splices data directly between two non-pipes
1160  * @in:		file to splice from
1161  * @sd:		actor information on where to splice to
1162  * @actor:	handles the data splicing
1163  *
1164  * Description:
1165  *    This is a special case helper to splice directly between two
1166  *    points, without requiring an explicit pipe. Internally an allocated
1167  *    pipe is cached in the process, and reused during the lifetime of
1168  *    that process.
1169  *
1170  */
1171 ssize_t splice_direct_to_actor(struct file *in, struct splice_desc *sd,
1172 			       splice_direct_actor *actor)
1173 {
1174 	struct pipe_inode_info *pipe;
1175 	long ret, bytes;
1176 	umode_t i_mode;
1177 	size_t len;
1178 	int i, flags;
1179 
1180 	/*
1181 	 * We require the input being a regular file, as we don't want to
1182 	 * randomly drop data for eg socket -> socket splicing. Use the
1183 	 * piped splicing for that!
1184 	 */
1185 	i_mode = in->f_path.dentry->d_inode->i_mode;
1186 	if (unlikely(!S_ISREG(i_mode) && !S_ISBLK(i_mode)))
1187 		return -EINVAL;
1188 
1189 	/*
1190 	 * neither in nor out is a pipe, setup an internal pipe attached to
1191 	 * 'out' and transfer the wanted data from 'in' to 'out' through that
1192 	 */
1193 	pipe = current->splice_pipe;
1194 	if (unlikely(!pipe)) {
1195 		pipe = alloc_pipe_info(NULL);
1196 		if (!pipe)
1197 			return -ENOMEM;
1198 
1199 		/*
1200 		 * We don't have an immediate reader, but we'll read the stuff
1201 		 * out of the pipe right after the splice_to_pipe(). So set
1202 		 * PIPE_READERS appropriately.
1203 		 */
1204 		pipe->readers = 1;
1205 
1206 		current->splice_pipe = pipe;
1207 	}
1208 
1209 	/*
1210 	 * Do the splice.
1211 	 */
1212 	ret = 0;
1213 	bytes = 0;
1214 	len = sd->total_len;
1215 	flags = sd->flags;
1216 
1217 	/*
1218 	 * Don't block on output, we have to drain the direct pipe.
1219 	 */
1220 	sd->flags &= ~SPLICE_F_NONBLOCK;
1221 
1222 	while (len) {
1223 		size_t read_len;
1224 		loff_t pos = sd->pos, prev_pos = pos;
1225 
1226 		ret = do_splice_to(in, &pos, pipe, len, flags);
1227 		if (unlikely(ret <= 0))
1228 			goto out_release;
1229 
1230 		read_len = ret;
1231 		sd->total_len = read_len;
1232 
1233 		/*
1234 		 * NOTE: nonblocking mode only applies to the input. We
1235 		 * must not do the output in nonblocking mode as then we
1236 		 * could get stuck data in the internal pipe:
1237 		 */
1238 		ret = actor(pipe, sd);
1239 		if (unlikely(ret <= 0)) {
1240 			sd->pos = prev_pos;
1241 			goto out_release;
1242 		}
1243 
1244 		bytes += ret;
1245 		len -= ret;
1246 		sd->pos = pos;
1247 
1248 		if (ret < read_len) {
1249 			sd->pos = prev_pos + ret;
1250 			goto out_release;
1251 		}
1252 	}
1253 
1254 done:
1255 	pipe->nrbufs = pipe->curbuf = 0;
1256 	file_accessed(in);
1257 	return bytes;
1258 
1259 out_release:
1260 	/*
1261 	 * If we did an incomplete transfer we must release
1262 	 * the pipe buffers in question:
1263 	 */
1264 	for (i = 0; i < pipe->buffers; i++) {
1265 		struct pipe_buffer *buf = pipe->bufs + i;
1266 
1267 		if (buf->ops) {
1268 			buf->ops->release(pipe, buf);
1269 			buf->ops = NULL;
1270 		}
1271 	}
1272 
1273 	if (!bytes)
1274 		bytes = ret;
1275 
1276 	goto done;
1277 }
1278 EXPORT_SYMBOL(splice_direct_to_actor);
1279 
1280 static int direct_splice_actor(struct pipe_inode_info *pipe,
1281 			       struct splice_desc *sd)
1282 {
1283 	struct file *file = sd->u.file;
1284 
1285 	return do_splice_from(pipe, file, &file->f_pos, sd->total_len,
1286 			      sd->flags);
1287 }
1288 
1289 /**
1290  * do_splice_direct - splices data directly between two files
1291  * @in:		file to splice from
1292  * @ppos:	input file offset
1293  * @out:	file to splice to
1294  * @len:	number of bytes to splice
1295  * @flags:	splice modifier flags
1296  *
1297  * Description:
1298  *    For use by do_sendfile(). splice can easily emulate sendfile, but
1299  *    doing it in the application would incur an extra system call
1300  *    (splice in + splice out, as compared to just sendfile()). So this helper
1301  *    can splice directly through a process-private pipe.
1302  *
1303  */
1304 long do_splice_direct(struct file *in, loff_t *ppos, struct file *out,
1305 		      size_t len, unsigned int flags)
1306 {
1307 	struct splice_desc sd = {
1308 		.len		= len,
1309 		.total_len	= len,
1310 		.flags		= flags,
1311 		.pos		= *ppos,
1312 		.u.file		= out,
1313 	};
1314 	long ret;
1315 
1316 	ret = splice_direct_to_actor(in, &sd, direct_splice_actor);
1317 	if (ret > 0)
1318 		*ppos = sd.pos;
1319 
1320 	return ret;
1321 }
1322 
1323 static int splice_pipe_to_pipe(struct pipe_inode_info *ipipe,
1324 			       struct pipe_inode_info *opipe,
1325 			       size_t len, unsigned int flags);
1326 /*
1327  * After the inode slimming patch, i_pipe/i_bdev/i_cdev share the same
1328  * location, so checking ->i_pipe is not enough to verify that this is a
1329  * pipe.
1330  */
1331 static inline struct pipe_inode_info *pipe_info(struct inode *inode)
1332 {
1333 	if (S_ISFIFO(inode->i_mode))
1334 		return inode->i_pipe;
1335 
1336 	return NULL;
1337 }
1338 
1339 /*
1340  * Determine where to splice to/from.
1341  */
1342 static long do_splice(struct file *in, loff_t __user *off_in,
1343 		      struct file *out, loff_t __user *off_out,
1344 		      size_t len, unsigned int flags)
1345 {
1346 	struct pipe_inode_info *ipipe;
1347 	struct pipe_inode_info *opipe;
1348 	loff_t offset, *off;
1349 	long ret;
1350 
1351 	ipipe = pipe_info(in->f_path.dentry->d_inode);
1352 	opipe = pipe_info(out->f_path.dentry->d_inode);
1353 
1354 	if (ipipe && opipe) {
1355 		if (off_in || off_out)
1356 			return -ESPIPE;
1357 
1358 		if (!(in->f_mode & FMODE_READ))
1359 			return -EBADF;
1360 
1361 		if (!(out->f_mode & FMODE_WRITE))
1362 			return -EBADF;
1363 
1364 		/* Splicing to self would be fun, but... */
1365 		if (ipipe == opipe)
1366 			return -EINVAL;
1367 
1368 		return splice_pipe_to_pipe(ipipe, opipe, len, flags);
1369 	}
1370 
1371 	if (ipipe) {
1372 		if (off_in)
1373 			return -ESPIPE;
1374 		if (off_out) {
1375 			if (!(out->f_mode & FMODE_PWRITE))
1376 				return -EINVAL;
1377 			if (copy_from_user(&offset, off_out, sizeof(loff_t)))
1378 				return -EFAULT;
1379 			off = &offset;
1380 		} else
1381 			off = &out->f_pos;
1382 
1383 		ret = do_splice_from(ipipe, out, off, len, flags);
1384 
1385 		if (off_out && copy_to_user(off_out, off, sizeof(loff_t)))
1386 			ret = -EFAULT;
1387 
1388 		return ret;
1389 	}
1390 
1391 	if (opipe) {
1392 		if (off_out)
1393 			return -ESPIPE;
1394 		if (off_in) {
1395 			if (!(in->f_mode & FMODE_PREAD))
1396 				return -EINVAL;
1397 			if (copy_from_user(&offset, off_in, sizeof(loff_t)))
1398 				return -EFAULT;
1399 			off = &offset;
1400 		} else
1401 			off = &in->f_pos;
1402 
1403 		ret = do_splice_to(in, off, opipe, len, flags);
1404 
1405 		if (off_in && copy_to_user(off_in, off, sizeof(loff_t)))
1406 			ret = -EFAULT;
1407 
1408 		return ret;
1409 	}
1410 
1411 	return -EINVAL;
1412 }
1413 
1414 /*
1415  * Map an iov into an array of pages and offset/length tupples. With the
1416  * partial_page structure, we can map several non-contiguous ranges into
1417  * our ones pages[] map instead of splitting that operation into pieces.
1418  * Could easily be exported as a generic helper for other users, in which
1419  * case one would probably want to add a 'max_nr_pages' parameter as well.
1420  */
1421 static int get_iovec_page_array(const struct iovec __user *iov,
1422 				unsigned int nr_vecs, struct page **pages,
1423 				struct partial_page *partial, int aligned,
1424 				unsigned int pipe_buffers)
1425 {
1426 	int buffers = 0, error = 0;
1427 
1428 	while (nr_vecs) {
1429 		unsigned long off, npages;
1430 		struct iovec entry;
1431 		void __user *base;
1432 		size_t len;
1433 		int i;
1434 
1435 		error = -EFAULT;
1436 		if (copy_from_user(&entry, iov, sizeof(entry)))
1437 			break;
1438 
1439 		base = entry.iov_base;
1440 		len = entry.iov_len;
1441 
1442 		/*
1443 		 * Sanity check this iovec. 0 read succeeds.
1444 		 */
1445 		error = 0;
1446 		if (unlikely(!len))
1447 			break;
1448 		error = -EFAULT;
1449 		if (!access_ok(VERIFY_READ, base, len))
1450 			break;
1451 
1452 		/*
1453 		 * Get this base offset and number of pages, then map
1454 		 * in the user pages.
1455 		 */
1456 		off = (unsigned long) base & ~PAGE_MASK;
1457 
1458 		/*
1459 		 * If asked for alignment, the offset must be zero and the
1460 		 * length a multiple of the PAGE_SIZE.
1461 		 */
1462 		error = -EINVAL;
1463 		if (aligned && (off || len & ~PAGE_MASK))
1464 			break;
1465 
1466 		npages = (off + len + PAGE_SIZE - 1) >> PAGE_SHIFT;
1467 		if (npages > pipe_buffers - buffers)
1468 			npages = pipe_buffers - buffers;
1469 
1470 		error = get_user_pages_fast((unsigned long)base, npages,
1471 					0, &pages[buffers]);
1472 
1473 		if (unlikely(error <= 0))
1474 			break;
1475 
1476 		/*
1477 		 * Fill this contiguous range into the partial page map.
1478 		 */
1479 		for (i = 0; i < error; i++) {
1480 			const int plen = min_t(size_t, len, PAGE_SIZE - off);
1481 
1482 			partial[buffers].offset = off;
1483 			partial[buffers].len = plen;
1484 
1485 			off = 0;
1486 			len -= plen;
1487 			buffers++;
1488 		}
1489 
1490 		/*
1491 		 * We didn't complete this iov, stop here since it probably
1492 		 * means we have to move some of this into a pipe to
1493 		 * be able to continue.
1494 		 */
1495 		if (len)
1496 			break;
1497 
1498 		/*
1499 		 * Don't continue if we mapped fewer pages than we asked for,
1500 		 * or if we mapped the max number of pages that we have
1501 		 * room for.
1502 		 */
1503 		if (error < npages || buffers == pipe_buffers)
1504 			break;
1505 
1506 		nr_vecs--;
1507 		iov++;
1508 	}
1509 
1510 	if (buffers)
1511 		return buffers;
1512 
1513 	return error;
1514 }
1515 
1516 static int pipe_to_user(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
1517 			struct splice_desc *sd)
1518 {
1519 	char *src;
1520 	int ret;
1521 
1522 	ret = buf->ops->confirm(pipe, buf);
1523 	if (unlikely(ret))
1524 		return ret;
1525 
1526 	/*
1527 	 * See if we can use the atomic maps, by prefaulting in the
1528 	 * pages and doing an atomic copy
1529 	 */
1530 	if (!fault_in_pages_writeable(sd->u.userptr, sd->len)) {
1531 		src = buf->ops->map(pipe, buf, 1);
1532 		ret = __copy_to_user_inatomic(sd->u.userptr, src + buf->offset,
1533 							sd->len);
1534 		buf->ops->unmap(pipe, buf, src);
1535 		if (!ret) {
1536 			ret = sd->len;
1537 			goto out;
1538 		}
1539 	}
1540 
1541 	/*
1542 	 * No dice, use slow non-atomic map and copy
1543  	 */
1544 	src = buf->ops->map(pipe, buf, 0);
1545 
1546 	ret = sd->len;
1547 	if (copy_to_user(sd->u.userptr, src + buf->offset, sd->len))
1548 		ret = -EFAULT;
1549 
1550 	buf->ops->unmap(pipe, buf, src);
1551 out:
1552 	if (ret > 0)
1553 		sd->u.userptr += ret;
1554 	return ret;
1555 }
1556 
1557 /*
1558  * For lack of a better implementation, implement vmsplice() to userspace
1559  * as a simple copy of the pipes pages to the user iov.
1560  */
1561 static long vmsplice_to_user(struct file *file, const struct iovec __user *iov,
1562 			     unsigned long nr_segs, unsigned int flags)
1563 {
1564 	struct pipe_inode_info *pipe;
1565 	struct splice_desc sd;
1566 	ssize_t size;
1567 	int error;
1568 	long ret;
1569 
1570 	pipe = pipe_info(file->f_path.dentry->d_inode);
1571 	if (!pipe)
1572 		return -EBADF;
1573 
1574 	pipe_lock(pipe);
1575 
1576 	error = ret = 0;
1577 	while (nr_segs) {
1578 		void __user *base;
1579 		size_t len;
1580 
1581 		/*
1582 		 * Get user address base and length for this iovec.
1583 		 */
1584 		error = get_user(base, &iov->iov_base);
1585 		if (unlikely(error))
1586 			break;
1587 		error = get_user(len, &iov->iov_len);
1588 		if (unlikely(error))
1589 			break;
1590 
1591 		/*
1592 		 * Sanity check this iovec. 0 read succeeds.
1593 		 */
1594 		if (unlikely(!len))
1595 			break;
1596 		if (unlikely(!base)) {
1597 			error = -EFAULT;
1598 			break;
1599 		}
1600 
1601 		if (unlikely(!access_ok(VERIFY_WRITE, base, len))) {
1602 			error = -EFAULT;
1603 			break;
1604 		}
1605 
1606 		sd.len = 0;
1607 		sd.total_len = len;
1608 		sd.flags = flags;
1609 		sd.u.userptr = base;
1610 		sd.pos = 0;
1611 
1612 		size = __splice_from_pipe(pipe, &sd, pipe_to_user);
1613 		if (size < 0) {
1614 			if (!ret)
1615 				ret = size;
1616 
1617 			break;
1618 		}
1619 
1620 		ret += size;
1621 
1622 		if (size < len)
1623 			break;
1624 
1625 		nr_segs--;
1626 		iov++;
1627 	}
1628 
1629 	pipe_unlock(pipe);
1630 
1631 	if (!ret)
1632 		ret = error;
1633 
1634 	return ret;
1635 }
1636 
1637 /*
1638  * vmsplice splices a user address range into a pipe. It can be thought of
1639  * as splice-from-memory, where the regular splice is splice-from-file (or
1640  * to file). In both cases the output is a pipe, naturally.
1641  */
1642 static long vmsplice_to_pipe(struct file *file, const struct iovec __user *iov,
1643 			     unsigned long nr_segs, unsigned int flags)
1644 {
1645 	struct pipe_inode_info *pipe;
1646 	struct page *pages[PIPE_DEF_BUFFERS];
1647 	struct partial_page partial[PIPE_DEF_BUFFERS];
1648 	struct splice_pipe_desc spd = {
1649 		.pages = pages,
1650 		.partial = partial,
1651 		.flags = flags,
1652 		.ops = &user_page_pipe_buf_ops,
1653 		.spd_release = spd_release_page,
1654 	};
1655 	long ret;
1656 
1657 	pipe = pipe_info(file->f_path.dentry->d_inode);
1658 	if (!pipe)
1659 		return -EBADF;
1660 
1661 	if (splice_grow_spd(pipe, &spd))
1662 		return -ENOMEM;
1663 
1664 	spd.nr_pages = get_iovec_page_array(iov, nr_segs, spd.pages,
1665 					    spd.partial, flags & SPLICE_F_GIFT,
1666 					    pipe->buffers);
1667 	if (spd.nr_pages <= 0)
1668 		ret = spd.nr_pages;
1669 	else
1670 		ret = splice_to_pipe(pipe, &spd);
1671 
1672 	splice_shrink_spd(pipe, &spd);
1673 	return ret;
1674 }
1675 
1676 /*
1677  * Note that vmsplice only really supports true splicing _from_ user memory
1678  * to a pipe, not the other way around. Splicing from user memory is a simple
1679  * operation that can be supported without any funky alignment restrictions
1680  * or nasty vm tricks. We simply map in the user memory and fill them into
1681  * a pipe. The reverse isn't quite as easy, though. There are two possible
1682  * solutions for that:
1683  *
1684  *	- memcpy() the data internally, at which point we might as well just
1685  *	  do a regular read() on the buffer anyway.
1686  *	- Lots of nasty vm tricks, that are neither fast nor flexible (it
1687  *	  has restriction limitations on both ends of the pipe).
1688  *
1689  * Currently we punt and implement it as a normal copy, see pipe_to_user().
1690  *
1691  */
1692 SYSCALL_DEFINE4(vmsplice, int, fd, const struct iovec __user *, iov,
1693 		unsigned long, nr_segs, unsigned int, flags)
1694 {
1695 	struct file *file;
1696 	long error;
1697 	int fput;
1698 
1699 	if (unlikely(nr_segs > UIO_MAXIOV))
1700 		return -EINVAL;
1701 	else if (unlikely(!nr_segs))
1702 		return 0;
1703 
1704 	error = -EBADF;
1705 	file = fget_light(fd, &fput);
1706 	if (file) {
1707 		if (file->f_mode & FMODE_WRITE)
1708 			error = vmsplice_to_pipe(file, iov, nr_segs, flags);
1709 		else if (file->f_mode & FMODE_READ)
1710 			error = vmsplice_to_user(file, iov, nr_segs, flags);
1711 
1712 		fput_light(file, fput);
1713 	}
1714 
1715 	return error;
1716 }
1717 
1718 SYSCALL_DEFINE6(splice, int, fd_in, loff_t __user *, off_in,
1719 		int, fd_out, loff_t __user *, off_out,
1720 		size_t, len, unsigned int, flags)
1721 {
1722 	long error;
1723 	struct file *in, *out;
1724 	int fput_in, fput_out;
1725 
1726 	if (unlikely(!len))
1727 		return 0;
1728 
1729 	error = -EBADF;
1730 	in = fget_light(fd_in, &fput_in);
1731 	if (in) {
1732 		if (in->f_mode & FMODE_READ) {
1733 			out = fget_light(fd_out, &fput_out);
1734 			if (out) {
1735 				if (out->f_mode & FMODE_WRITE)
1736 					error = do_splice(in, off_in,
1737 							  out, off_out,
1738 							  len, flags);
1739 				fput_light(out, fput_out);
1740 			}
1741 		}
1742 
1743 		fput_light(in, fput_in);
1744 	}
1745 
1746 	return error;
1747 }
1748 
1749 /*
1750  * Make sure there's data to read. Wait for input if we can, otherwise
1751  * return an appropriate error.
1752  */
1753 static int ipipe_prep(struct pipe_inode_info *pipe, unsigned int flags)
1754 {
1755 	int ret;
1756 
1757 	/*
1758 	 * Check ->nrbufs without the inode lock first. This function
1759 	 * is speculative anyways, so missing one is ok.
1760 	 */
1761 	if (pipe->nrbufs)
1762 		return 0;
1763 
1764 	ret = 0;
1765 	pipe_lock(pipe);
1766 
1767 	while (!pipe->nrbufs) {
1768 		if (signal_pending(current)) {
1769 			ret = -ERESTARTSYS;
1770 			break;
1771 		}
1772 		if (!pipe->writers)
1773 			break;
1774 		if (!pipe->waiting_writers) {
1775 			if (flags & SPLICE_F_NONBLOCK) {
1776 				ret = -EAGAIN;
1777 				break;
1778 			}
1779 		}
1780 		pipe_wait(pipe);
1781 	}
1782 
1783 	pipe_unlock(pipe);
1784 	return ret;
1785 }
1786 
1787 /*
1788  * Make sure there's writeable room. Wait for room if we can, otherwise
1789  * return an appropriate error.
1790  */
1791 static int opipe_prep(struct pipe_inode_info *pipe, unsigned int flags)
1792 {
1793 	int ret;
1794 
1795 	/*
1796 	 * Check ->nrbufs without the inode lock first. This function
1797 	 * is speculative anyways, so missing one is ok.
1798 	 */
1799 	if (pipe->nrbufs < pipe->buffers)
1800 		return 0;
1801 
1802 	ret = 0;
1803 	pipe_lock(pipe);
1804 
1805 	while (pipe->nrbufs >= pipe->buffers) {
1806 		if (!pipe->readers) {
1807 			send_sig(SIGPIPE, current, 0);
1808 			ret = -EPIPE;
1809 			break;
1810 		}
1811 		if (flags & SPLICE_F_NONBLOCK) {
1812 			ret = -EAGAIN;
1813 			break;
1814 		}
1815 		if (signal_pending(current)) {
1816 			ret = -ERESTARTSYS;
1817 			break;
1818 		}
1819 		pipe->waiting_writers++;
1820 		pipe_wait(pipe);
1821 		pipe->waiting_writers--;
1822 	}
1823 
1824 	pipe_unlock(pipe);
1825 	return ret;
1826 }
1827 
1828 /*
1829  * Splice contents of ipipe to opipe.
1830  */
1831 static int splice_pipe_to_pipe(struct pipe_inode_info *ipipe,
1832 			       struct pipe_inode_info *opipe,
1833 			       size_t len, unsigned int flags)
1834 {
1835 	struct pipe_buffer *ibuf, *obuf;
1836 	int ret = 0, nbuf;
1837 	bool input_wakeup = false;
1838 
1839 
1840 retry:
1841 	ret = ipipe_prep(ipipe, flags);
1842 	if (ret)
1843 		return ret;
1844 
1845 	ret = opipe_prep(opipe, flags);
1846 	if (ret)
1847 		return ret;
1848 
1849 	/*
1850 	 * Potential ABBA deadlock, work around it by ordering lock
1851 	 * grabbing by pipe info address. Otherwise two different processes
1852 	 * could deadlock (one doing tee from A -> B, the other from B -> A).
1853 	 */
1854 	pipe_double_lock(ipipe, opipe);
1855 
1856 	do {
1857 		if (!opipe->readers) {
1858 			send_sig(SIGPIPE, current, 0);
1859 			if (!ret)
1860 				ret = -EPIPE;
1861 			break;
1862 		}
1863 
1864 		if (!ipipe->nrbufs && !ipipe->writers)
1865 			break;
1866 
1867 		/*
1868 		 * Cannot make any progress, because either the input
1869 		 * pipe is empty or the output pipe is full.
1870 		 */
1871 		if (!ipipe->nrbufs || opipe->nrbufs >= opipe->buffers) {
1872 			/* Already processed some buffers, break */
1873 			if (ret)
1874 				break;
1875 
1876 			if (flags & SPLICE_F_NONBLOCK) {
1877 				ret = -EAGAIN;
1878 				break;
1879 			}
1880 
1881 			/*
1882 			 * We raced with another reader/writer and haven't
1883 			 * managed to process any buffers.  A zero return
1884 			 * value means EOF, so retry instead.
1885 			 */
1886 			pipe_unlock(ipipe);
1887 			pipe_unlock(opipe);
1888 			goto retry;
1889 		}
1890 
1891 		ibuf = ipipe->bufs + ipipe->curbuf;
1892 		nbuf = (opipe->curbuf + opipe->nrbufs) & (opipe->buffers - 1);
1893 		obuf = opipe->bufs + nbuf;
1894 
1895 		if (len >= ibuf->len) {
1896 			/*
1897 			 * Simply move the whole buffer from ipipe to opipe
1898 			 */
1899 			*obuf = *ibuf;
1900 			ibuf->ops = NULL;
1901 			opipe->nrbufs++;
1902 			ipipe->curbuf = (ipipe->curbuf + 1) & (ipipe->buffers - 1);
1903 			ipipe->nrbufs--;
1904 			input_wakeup = true;
1905 		} else {
1906 			/*
1907 			 * Get a reference to this pipe buffer,
1908 			 * so we can copy the contents over.
1909 			 */
1910 			ibuf->ops->get(ipipe, ibuf);
1911 			*obuf = *ibuf;
1912 
1913 			/*
1914 			 * Don't inherit the gift flag, we need to
1915 			 * prevent multiple steals of this page.
1916 			 */
1917 			obuf->flags &= ~PIPE_BUF_FLAG_GIFT;
1918 
1919 			obuf->len = len;
1920 			opipe->nrbufs++;
1921 			ibuf->offset += obuf->len;
1922 			ibuf->len -= obuf->len;
1923 		}
1924 		ret += obuf->len;
1925 		len -= obuf->len;
1926 	} while (len);
1927 
1928 	pipe_unlock(ipipe);
1929 	pipe_unlock(opipe);
1930 
1931 	/*
1932 	 * If we put data in the output pipe, wakeup any potential readers.
1933 	 */
1934 	if (ret > 0) {
1935 		smp_mb();
1936 		if (waitqueue_active(&opipe->wait))
1937 			wake_up_interruptible(&opipe->wait);
1938 		kill_fasync(&opipe->fasync_readers, SIGIO, POLL_IN);
1939 	}
1940 	if (input_wakeup)
1941 		wakeup_pipe_writers(ipipe);
1942 
1943 	return ret;
1944 }
1945 
1946 /*
1947  * Link contents of ipipe to opipe.
1948  */
1949 static int link_pipe(struct pipe_inode_info *ipipe,
1950 		     struct pipe_inode_info *opipe,
1951 		     size_t len, unsigned int flags)
1952 {
1953 	struct pipe_buffer *ibuf, *obuf;
1954 	int ret = 0, i = 0, nbuf;
1955 
1956 	/*
1957 	 * Potential ABBA deadlock, work around it by ordering lock
1958 	 * grabbing by pipe info address. Otherwise two different processes
1959 	 * could deadlock (one doing tee from A -> B, the other from B -> A).
1960 	 */
1961 	pipe_double_lock(ipipe, opipe);
1962 
1963 	do {
1964 		if (!opipe->readers) {
1965 			send_sig(SIGPIPE, current, 0);
1966 			if (!ret)
1967 				ret = -EPIPE;
1968 			break;
1969 		}
1970 
1971 		/*
1972 		 * If we have iterated all input buffers or ran out of
1973 		 * output room, break.
1974 		 */
1975 		if (i >= ipipe->nrbufs || opipe->nrbufs >= opipe->buffers)
1976 			break;
1977 
1978 		ibuf = ipipe->bufs + ((ipipe->curbuf + i) & (ipipe->buffers-1));
1979 		nbuf = (opipe->curbuf + opipe->nrbufs) & (opipe->buffers - 1);
1980 
1981 		/*
1982 		 * Get a reference to this pipe buffer,
1983 		 * so we can copy the contents over.
1984 		 */
1985 		ibuf->ops->get(ipipe, ibuf);
1986 
1987 		obuf = opipe->bufs + nbuf;
1988 		*obuf = *ibuf;
1989 
1990 		/*
1991 		 * Don't inherit the gift flag, we need to
1992 		 * prevent multiple steals of this page.
1993 		 */
1994 		obuf->flags &= ~PIPE_BUF_FLAG_GIFT;
1995 
1996 		if (obuf->len > len)
1997 			obuf->len = len;
1998 
1999 		opipe->nrbufs++;
2000 		ret += obuf->len;
2001 		len -= obuf->len;
2002 		i++;
2003 	} while (len);
2004 
2005 	/*
2006 	 * return EAGAIN if we have the potential of some data in the
2007 	 * future, otherwise just return 0
2008 	 */
2009 	if (!ret && ipipe->waiting_writers && (flags & SPLICE_F_NONBLOCK))
2010 		ret = -EAGAIN;
2011 
2012 	pipe_unlock(ipipe);
2013 	pipe_unlock(opipe);
2014 
2015 	/*
2016 	 * If we put data in the output pipe, wakeup any potential readers.
2017 	 */
2018 	if (ret > 0) {
2019 		smp_mb();
2020 		if (waitqueue_active(&opipe->wait))
2021 			wake_up_interruptible(&opipe->wait);
2022 		kill_fasync(&opipe->fasync_readers, SIGIO, POLL_IN);
2023 	}
2024 
2025 	return ret;
2026 }
2027 
2028 /*
2029  * This is a tee(1) implementation that works on pipes. It doesn't copy
2030  * any data, it simply references the 'in' pages on the 'out' pipe.
2031  * The 'flags' used are the SPLICE_F_* variants, currently the only
2032  * applicable one is SPLICE_F_NONBLOCK.
2033  */
2034 static long do_tee(struct file *in, struct file *out, size_t len,
2035 		   unsigned int flags)
2036 {
2037 	struct pipe_inode_info *ipipe = pipe_info(in->f_path.dentry->d_inode);
2038 	struct pipe_inode_info *opipe = pipe_info(out->f_path.dentry->d_inode);
2039 	int ret = -EINVAL;
2040 
2041 	/*
2042 	 * Duplicate the contents of ipipe to opipe without actually
2043 	 * copying the data.
2044 	 */
2045 	if (ipipe && opipe && ipipe != opipe) {
2046 		/*
2047 		 * Keep going, unless we encounter an error. The ipipe/opipe
2048 		 * ordering doesn't really matter.
2049 		 */
2050 		ret = ipipe_prep(ipipe, flags);
2051 		if (!ret) {
2052 			ret = opipe_prep(opipe, flags);
2053 			if (!ret)
2054 				ret = link_pipe(ipipe, opipe, len, flags);
2055 		}
2056 	}
2057 
2058 	return ret;
2059 }
2060 
2061 SYSCALL_DEFINE4(tee, int, fdin, int, fdout, size_t, len, unsigned int, flags)
2062 {
2063 	struct file *in;
2064 	int error, fput_in;
2065 
2066 	if (unlikely(!len))
2067 		return 0;
2068 
2069 	error = -EBADF;
2070 	in = fget_light(fdin, &fput_in);
2071 	if (in) {
2072 		if (in->f_mode & FMODE_READ) {
2073 			int fput_out;
2074 			struct file *out = fget_light(fdout, &fput_out);
2075 
2076 			if (out) {
2077 				if (out->f_mode & FMODE_WRITE)
2078 					error = do_tee(in, out, len, flags);
2079 				fput_light(out, fput_out);
2080 			}
2081 		}
2082  		fput_light(in, fput_in);
2083  	}
2084 
2085 	return error;
2086 }
2087