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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/export.h>
29 #include <linux/syscalls.h>
30 #include <linux/uio.h>
31 #include <linux/security.h>
32 #include <linux/gfp.h>
33 #include <linux/socket.h>
34 #include <linux/compat.h>
35 #include <linux/aio.h>
36 #include "internal.h"
37
38 /*
39 * Attempt to steal a page from a pipe buffer. This should perhaps go into
40 * a vm helper function, it's already simplified quite a bit by the
41 * addition of remove_mapping(). If success is returned, the caller may
42 * attempt to reuse this page for another destination.
43 */
44 static int page_cache_pipe_buf_steal(struct pipe_inode_info *pipe,
45 struct pipe_buffer *buf)
46 {
47 struct page *page = buf->page;
48 struct address_space *mapping;
49
50 lock_page(page);
51
52 mapping = page_mapping(page);
53 if (mapping) {
54 WARN_ON(!PageUptodate(page));
55
56 /*
57 * At least for ext2 with nobh option, we need to wait on
58 * writeback completing on this page, since we'll remove it
59 * from the pagecache. Otherwise truncate wont wait on the
60 * page, allowing the disk blocks to be reused by someone else
61 * before we actually wrote our data to them. fs corruption
62 * ensues.
63 */
64 wait_on_page_writeback(page);
65
66 if (page_has_private(page) &&
67 !try_to_release_page(page, GFP_KERNEL))
68 goto out_unlock;
69
70 /*
71 * If we succeeded in removing the mapping, set LRU flag
72 * and return good.
73 */
74 if (remove_mapping(mapping, page)) {
75 buf->flags |= PIPE_BUF_FLAG_LRU;
76 return 0;
77 }
78 }
79
80 /*
81 * Raced with truncate or failed to remove page from current
82 * address space, unlock and return failure.
83 */
84 out_unlock:
85 unlock_page(page);
86 return 1;
87 }
88
89 static void page_cache_pipe_buf_release(struct pipe_inode_info *pipe,
90 struct pipe_buffer *buf)
91 {
92 page_cache_release(buf->page);
93 buf->flags &= ~PIPE_BUF_FLAG_LRU;
94 }
95
96 /*
97 * Check whether the contents of buf is OK to access. Since the content
98 * is a page cache page, IO may be in flight.
99 */
100 static int page_cache_pipe_buf_confirm(struct pipe_inode_info *pipe,
101 struct pipe_buffer *buf)
102 {
103 struct page *page = buf->page;
104 int err;
105
106 if (!PageUptodate(page)) {
107 lock_page(page);
108
109 /*
110 * Page got truncated/unhashed. This will cause a 0-byte
111 * splice, if this is the first page.
112 */
113 if (!page->mapping) {
114 err = -ENODATA;
115 goto error;
116 }
117
118 /*
119 * Uh oh, read-error from disk.
120 */
121 if (!PageUptodate(page)) {
122 err = -EIO;
123 goto error;
124 }
125
126 /*
127 * Page is ok afterall, we are done.
128 */
129 unlock_page(page);
130 }
131
132 return 0;
133 error:
134 unlock_page(page);
135 return err;
136 }
137
138 const struct pipe_buf_operations page_cache_pipe_buf_ops = {
139 .can_merge = 0,
140 .confirm = page_cache_pipe_buf_confirm,
141 .release = page_cache_pipe_buf_release,
142 .steal = page_cache_pipe_buf_steal,
143 .get = generic_pipe_buf_get,
144 };
145
146 static int user_page_pipe_buf_steal(struct pipe_inode_info *pipe,
147 struct pipe_buffer *buf)
148 {
149 if (!(buf->flags & PIPE_BUF_FLAG_GIFT))
150 return 1;
151
152 buf->flags |= PIPE_BUF_FLAG_LRU;
153 return generic_pipe_buf_steal(pipe, buf);
154 }
155
156 static const struct pipe_buf_operations user_page_pipe_buf_ops = {
157 .can_merge = 0,
158 .confirm = generic_pipe_buf_confirm,
159 .release = page_cache_pipe_buf_release,
160 .steal = user_page_pipe_buf_steal,
161 .get = generic_pipe_buf_get,
162 };
163
164 static void wakeup_pipe_readers(struct pipe_inode_info *pipe)
165 {
166 smp_mb();
167 if (waitqueue_active(&pipe->wait))
168 wake_up_interruptible(&pipe->wait);
169 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
170 }
171
172 /**
173 * splice_to_pipe - fill passed data into a pipe
174 * @pipe: pipe to fill
175 * @spd: data to fill
176 *
177 * Description:
178 * @spd contains a map of pages and len/offset tuples, along with
179 * the struct pipe_buf_operations associated with these pages. This
180 * function will link that data to the pipe.
181 *
182 */
183 ssize_t splice_to_pipe(struct pipe_inode_info *pipe,
184 struct splice_pipe_desc *spd)
185 {
186 unsigned int spd_pages = spd->nr_pages;
187 int ret, do_wakeup, page_nr;
188
189 ret = 0;
190 do_wakeup = 0;
191 page_nr = 0;
192
193 pipe_lock(pipe);
194
195 for (;;) {
196 if (!pipe->readers) {
197 send_sig(SIGPIPE, current, 0);
198 if (!ret)
199 ret = -EPIPE;
200 break;
201 }
202
203 if (pipe->nrbufs < pipe->buffers) {
204 int newbuf = (pipe->curbuf + pipe->nrbufs) & (pipe->buffers - 1);
205 struct pipe_buffer *buf = pipe->bufs + newbuf;
206
207 buf->page = spd->pages[page_nr];
208 buf->offset = spd->partial[page_nr].offset;
209 buf->len = spd->partial[page_nr].len;
210 buf->private = spd->partial[page_nr].private;
211 buf->ops = spd->ops;
212 if (spd->flags & SPLICE_F_GIFT)
213 buf->flags |= PIPE_BUF_FLAG_GIFT;
214
215 pipe->nrbufs++;
216 page_nr++;
217 ret += buf->len;
218
219 if (pipe->files)
220 do_wakeup = 1;
221
222 if (!--spd->nr_pages)
223 break;
224 if (pipe->nrbufs < pipe->buffers)
225 continue;
226
227 break;
228 }
229
230 if (spd->flags & SPLICE_F_NONBLOCK) {
231 if (!ret)
232 ret = -EAGAIN;
233 break;
234 }
235
236 if (signal_pending(current)) {
237 if (!ret)
238 ret = -ERESTARTSYS;
239 break;
240 }
241
242 if (do_wakeup) {
243 smp_mb();
244 if (waitqueue_active(&pipe->wait))
245 wake_up_interruptible_sync(&pipe->wait);
246 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
247 do_wakeup = 0;
248 }
249
250 pipe->waiting_writers++;
251 pipe_wait(pipe);
252 pipe->waiting_writers--;
253 }
254
255 pipe_unlock(pipe);
256
257 if (do_wakeup)
258 wakeup_pipe_readers(pipe);
259
260 while (page_nr < spd_pages)
261 spd->spd_release(spd, page_nr++);
262
263 return ret;
264 }
265
266 void spd_release_page(struct splice_pipe_desc *spd, unsigned int i)
267 {
268 page_cache_release(spd->pages[i]);
269 }
270
271 /*
272 * Check if we need to grow the arrays holding pages and partial page
273 * descriptions.
274 */
275 int splice_grow_spd(const struct pipe_inode_info *pipe, struct splice_pipe_desc *spd)
276 {
277 unsigned int buffers = ACCESS_ONCE(pipe->buffers);
278
279 spd->nr_pages_max = buffers;
280 if (buffers <= PIPE_DEF_BUFFERS)
281 return 0;
282
283 spd->pages = kmalloc(buffers * sizeof(struct page *), GFP_KERNEL);
284 spd->partial = kmalloc(buffers * sizeof(struct partial_page), GFP_KERNEL);
285
286 if (spd->pages && spd->partial)
287 return 0;
288
289 kfree(spd->pages);
290 kfree(spd->partial);
291 return -ENOMEM;
292 }
293
294 void splice_shrink_spd(struct splice_pipe_desc *spd)
295 {
296 if (spd->nr_pages_max <= PIPE_DEF_BUFFERS)
297 return;
298
299 kfree(spd->pages);
300 kfree(spd->partial);
301 }
302
303 static int
304 __generic_file_splice_read(struct file *in, loff_t *ppos,
305 struct pipe_inode_info *pipe, size_t len,
306 unsigned int flags)
307 {
308 struct address_space *mapping = in->f_mapping;
309 unsigned int loff, nr_pages, req_pages;
310 struct page *pages[PIPE_DEF_BUFFERS];
311 struct partial_page partial[PIPE_DEF_BUFFERS];
312 struct page *page;
313 pgoff_t index, end_index;
314 loff_t isize;
315 int error, page_nr;
316 struct splice_pipe_desc spd = {
317 .pages = pages,
318 .partial = partial,
319 .nr_pages_max = PIPE_DEF_BUFFERS,
320 .flags = flags,
321 .ops = &page_cache_pipe_buf_ops,
322 .spd_release = spd_release_page,
323 };
324
325 if (splice_grow_spd(pipe, &spd))
326 return -ENOMEM;
327
328 index = *ppos >> PAGE_CACHE_SHIFT;
329 loff = *ppos & ~PAGE_CACHE_MASK;
330 req_pages = (len + loff + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
331 nr_pages = min(req_pages, spd.nr_pages_max);
332
333 /*
334 * Lookup the (hopefully) full range of pages we need.
335 */
336 spd.nr_pages = find_get_pages_contig(mapping, index, nr_pages, spd.pages);
337 index += spd.nr_pages;
338
339 /*
340 * If find_get_pages_contig() returned fewer pages than we needed,
341 * readahead/allocate the rest and fill in the holes.
342 */
343 if (spd.nr_pages < nr_pages)
344 page_cache_sync_readahead(mapping, &in->f_ra, in,
345 index, req_pages - spd.nr_pages);
346
347 error = 0;
348 while (spd.nr_pages < nr_pages) {
349 /*
350 * Page could be there, find_get_pages_contig() breaks on
351 * the first hole.
352 */
353 page = find_get_page(mapping, index);
354 if (!page) {
355 /*
356 * page didn't exist, allocate one.
357 */
358 page = page_cache_alloc_cold(mapping);
359 if (!page)
360 break;
361
362 error = add_to_page_cache_lru(page, mapping, index,
363 GFP_KERNEL);
364 if (unlikely(error)) {
365 page_cache_release(page);
366 if (error == -EEXIST)
367 continue;
368 break;
369 }
370 /*
371 * add_to_page_cache() locks the page, unlock it
372 * to avoid convoluting the logic below even more.
373 */
374 unlock_page(page);
375 }
376
377 spd.pages[spd.nr_pages++] = page;
378 index++;
379 }
380
381 /*
382 * Now loop over the map and see if we need to start IO on any
383 * pages, fill in the partial map, etc.
384 */
385 index = *ppos >> PAGE_CACHE_SHIFT;
386 nr_pages = spd.nr_pages;
387 spd.nr_pages = 0;
388 for (page_nr = 0; page_nr < nr_pages; page_nr++) {
389 unsigned int this_len;
390
391 if (!len)
392 break;
393
394 /*
395 * this_len is the max we'll use from this page
396 */
397 this_len = min_t(unsigned long, len, PAGE_CACHE_SIZE - loff);
398 page = spd.pages[page_nr];
399
400 if (PageReadahead(page))
401 page_cache_async_readahead(mapping, &in->f_ra, in,
402 page, index, req_pages - page_nr);
403
404 /*
405 * If the page isn't uptodate, we may need to start io on it
406 */
407 if (!PageUptodate(page)) {
408 lock_page(page);
409
410 /*
411 * Page was truncated, or invalidated by the
412 * filesystem. Redo the find/create, but this time the
413 * page is kept locked, so there's no chance of another
414 * race with truncate/invalidate.
415 */
416 if (!page->mapping) {
417 unlock_page(page);
418 page = find_or_create_page(mapping, index,
419 mapping_gfp_mask(mapping));
420
421 if (!page) {
422 error = -ENOMEM;
423 break;
424 }
425 page_cache_release(spd.pages[page_nr]);
426 spd.pages[page_nr] = page;
427 }
428 /*
429 * page was already under io and is now done, great
430 */
431 if (PageUptodate(page)) {
432 unlock_page(page);
433 goto fill_it;
434 }
435
436 /*
437 * need to read in the page
438 */
439 error = mapping->a_ops->readpage(in, page);
440 if (unlikely(error)) {
441 /*
442 * We really should re-lookup the page here,
443 * but it complicates things a lot. Instead
444 * lets just do what we already stored, and
445 * we'll get it the next time we are called.
446 */
447 if (error == AOP_TRUNCATED_PAGE)
448 error = 0;
449
450 break;
451 }
452 }
453 fill_it:
454 /*
455 * i_size must be checked after PageUptodate.
456 */
457 isize = i_size_read(mapping->host);
458 end_index = (isize - 1) >> PAGE_CACHE_SHIFT;
459 if (unlikely(!isize || index > end_index))
460 break;
461
462 /*
463 * if this is the last page, see if we need to shrink
464 * the length and stop
465 */
466 if (end_index == index) {
467 unsigned int plen;
468
469 /*
470 * max good bytes in this page
471 */
472 plen = ((isize - 1) & ~PAGE_CACHE_MASK) + 1;
473 if (plen <= loff)
474 break;
475
476 /*
477 * force quit after adding this page
478 */
479 this_len = min(this_len, plen - loff);
480 len = this_len;
481 }
482
483 spd.partial[page_nr].offset = loff;
484 spd.partial[page_nr].len = this_len;
485 len -= this_len;
486 loff = 0;
487 spd.nr_pages++;
488 index++;
489 }
490
491 /*
492 * Release any pages at the end, if we quit early. 'page_nr' is how far
493 * we got, 'nr_pages' is how many pages are in the map.
494 */
495 while (page_nr < nr_pages)
496 page_cache_release(spd.pages[page_nr++]);
497 in->f_ra.prev_pos = (loff_t)index << PAGE_CACHE_SHIFT;
498
499 if (spd.nr_pages)
500 error = splice_to_pipe(pipe, &spd);
501
502 splice_shrink_spd(&spd);
503 return error;
504 }
505
506 /**
507 * generic_file_splice_read - splice data from file to a pipe
508 * @in: file to splice from
509 * @ppos: position in @in
510 * @pipe: pipe to splice to
511 * @len: number of bytes to splice
512 * @flags: splice modifier flags
513 *
514 * Description:
515 * Will read pages from given file and fill them into a pipe. Can be
516 * used as long as the address_space operations for the source implements
517 * a readpage() hook.
518 *
519 */
520 ssize_t generic_file_splice_read(struct file *in, loff_t *ppos,
521 struct pipe_inode_info *pipe, size_t len,
522 unsigned int flags)
523 {
524 loff_t isize, left;
525 int ret;
526
527 isize = i_size_read(in->f_mapping->host);
528 if (unlikely(*ppos >= isize))
529 return 0;
530
531 left = isize - *ppos;
532 if (unlikely(left < len))
533 len = left;
534
535 ret = __generic_file_splice_read(in, ppos, pipe, len, flags);
536 if (ret > 0) {
537 *ppos += ret;
538 file_accessed(in);
539 }
540
541 return ret;
542 }
543 EXPORT_SYMBOL(generic_file_splice_read);
544
545 static const struct pipe_buf_operations default_pipe_buf_ops = {
546 .can_merge = 0,
547 .confirm = generic_pipe_buf_confirm,
548 .release = generic_pipe_buf_release,
549 .steal = generic_pipe_buf_steal,
550 .get = generic_pipe_buf_get,
551 };
552
553 static int generic_pipe_buf_nosteal(struct pipe_inode_info *pipe,
554 struct pipe_buffer *buf)
555 {
556 return 1;
557 }
558
559 /* Pipe buffer operations for a socket and similar. */
560 const struct pipe_buf_operations nosteal_pipe_buf_ops = {
561 .can_merge = 0,
562 .confirm = generic_pipe_buf_confirm,
563 .release = generic_pipe_buf_release,
564 .steal = generic_pipe_buf_nosteal,
565 .get = generic_pipe_buf_get,
566 };
567 EXPORT_SYMBOL(nosteal_pipe_buf_ops);
568
569 static ssize_t kernel_readv(struct file *file, const struct iovec *vec,
570 unsigned long vlen, loff_t offset)
571 {
572 mm_segment_t old_fs;
573 loff_t pos = offset;
574 ssize_t res;
575
576 old_fs = get_fs();
577 set_fs(get_ds());
578 /* The cast to a user pointer is valid due to the set_fs() */
579 res = vfs_readv(file, (const struct iovec __user *)vec, vlen, &pos);
580 set_fs(old_fs);
581
582 return res;
583 }
584
585 ssize_t kernel_write(struct file *file, const char *buf, size_t count,
586 loff_t pos)
587 {
588 mm_segment_t old_fs;
589 ssize_t res;
590
591 old_fs = get_fs();
592 set_fs(get_ds());
593 /* The cast to a user pointer is valid due to the set_fs() */
594 res = vfs_write(file, (__force const char __user *)buf, count, &pos);
595 set_fs(old_fs);
596
597 return res;
598 }
599 EXPORT_SYMBOL(kernel_write);
600
601 ssize_t default_file_splice_read(struct file *in, loff_t *ppos,
602 struct pipe_inode_info *pipe, size_t len,
603 unsigned int flags)
604 {
605 unsigned int nr_pages;
606 unsigned int nr_freed;
607 size_t offset;
608 struct page *pages[PIPE_DEF_BUFFERS];
609 struct partial_page partial[PIPE_DEF_BUFFERS];
610 struct iovec *vec, __vec[PIPE_DEF_BUFFERS];
611 ssize_t res;
612 size_t this_len;
613 int error;
614 int i;
615 struct splice_pipe_desc spd = {
616 .pages = pages,
617 .partial = partial,
618 .nr_pages_max = PIPE_DEF_BUFFERS,
619 .flags = flags,
620 .ops = &default_pipe_buf_ops,
621 .spd_release = spd_release_page,
622 };
623
624 if (splice_grow_spd(pipe, &spd))
625 return -ENOMEM;
626
627 res = -ENOMEM;
628 vec = __vec;
629 if (spd.nr_pages_max > PIPE_DEF_BUFFERS) {
630 vec = kmalloc(spd.nr_pages_max * sizeof(struct iovec), GFP_KERNEL);
631 if (!vec)
632 goto shrink_ret;
633 }
634
635 offset = *ppos & ~PAGE_CACHE_MASK;
636 nr_pages = (len + offset + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
637
638 for (i = 0; i < nr_pages && i < spd.nr_pages_max && len; i++) {
639 struct page *page;
640
641 page = alloc_page(GFP_USER);
642 error = -ENOMEM;
643 if (!page)
644 goto err;
645
646 this_len = min_t(size_t, len, PAGE_CACHE_SIZE - offset);
647 vec[i].iov_base = (void __user *) page_address(page);
648 vec[i].iov_len = this_len;
649 spd.pages[i] = page;
650 spd.nr_pages++;
651 len -= this_len;
652 offset = 0;
653 }
654
655 res = kernel_readv(in, vec, spd.nr_pages, *ppos);
656 if (res < 0) {
657 error = res;
658 goto err;
659 }
660
661 error = 0;
662 if (!res)
663 goto err;
664
665 nr_freed = 0;
666 for (i = 0; i < spd.nr_pages; i++) {
667 this_len = min_t(size_t, vec[i].iov_len, res);
668 spd.partial[i].offset = 0;
669 spd.partial[i].len = this_len;
670 if (!this_len) {
671 __free_page(spd.pages[i]);
672 spd.pages[i] = NULL;
673 nr_freed++;
674 }
675 res -= this_len;
676 }
677 spd.nr_pages -= nr_freed;
678
679 res = splice_to_pipe(pipe, &spd);
680 if (res > 0)
681 *ppos += res;
682
683 shrink_ret:
684 if (vec != __vec)
685 kfree(vec);
686 splice_shrink_spd(&spd);
687 return res;
688
689 err:
690 for (i = 0; i < spd.nr_pages; i++)
691 __free_page(spd.pages[i]);
692
693 res = error;
694 goto shrink_ret;
695 }
696 EXPORT_SYMBOL(default_file_splice_read);
697
698 /*
699 * Send 'sd->len' bytes to socket from 'sd->file' at position 'sd->pos'
700 * using sendpage(). Return the number of bytes sent.
701 */
702 static int pipe_to_sendpage(struct pipe_inode_info *pipe,
703 struct pipe_buffer *buf, struct splice_desc *sd)
704 {
705 struct file *file = sd->u.file;
706 loff_t pos = sd->pos;
707 int more;
708
709 if (!likely(file->f_op->sendpage))
710 return -EINVAL;
711
712 more = (sd->flags & SPLICE_F_MORE) ? MSG_MORE : 0;
713
714 if (sd->len < sd->total_len && pipe->nrbufs > 1)
715 more |= MSG_SENDPAGE_NOTLAST;
716
717 return file->f_op->sendpage(file, buf->page, buf->offset,
718 sd->len, &pos, more);
719 }
720
721 static void wakeup_pipe_writers(struct pipe_inode_info *pipe)
722 {
723 smp_mb();
724 if (waitqueue_active(&pipe->wait))
725 wake_up_interruptible(&pipe->wait);
726 kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
727 }
728
729 /**
730 * splice_from_pipe_feed - feed available data from a pipe to a file
731 * @pipe: pipe to splice from
732 * @sd: information to @actor
733 * @actor: handler that splices the data
734 *
735 * Description:
736 * This function loops over the pipe and calls @actor to do the
737 * actual moving of a single struct pipe_buffer to the desired
738 * destination. It returns when there's no more buffers left in
739 * the pipe or if the requested number of bytes (@sd->total_len)
740 * have been copied. It returns a positive number (one) if the
741 * pipe needs to be filled with more data, zero if the required
742 * number of bytes have been copied and -errno on error.
743 *
744 * This, together with splice_from_pipe_{begin,end,next}, may be
745 * used to implement the functionality of __splice_from_pipe() when
746 * locking is required around copying the pipe buffers to the
747 * destination.
748 */
749 static int splice_from_pipe_feed(struct pipe_inode_info *pipe, struct splice_desc *sd,
750 splice_actor *actor)
751 {
752 int ret;
753
754 while (pipe->nrbufs) {
755 struct pipe_buffer *buf = pipe->bufs + pipe->curbuf;
756 const struct pipe_buf_operations *ops = buf->ops;
757
758 sd->len = buf->len;
759 if (sd->len > sd->total_len)
760 sd->len = sd->total_len;
761
762 ret = buf->ops->confirm(pipe, buf);
763 if (unlikely(ret)) {
764 if (ret == -ENODATA)
765 ret = 0;
766 return ret;
767 }
768
769 ret = actor(pipe, buf, sd);
770 if (ret <= 0)
771 return ret;
772
773 buf->offset += ret;
774 buf->len -= ret;
775
776 sd->num_spliced += ret;
777 sd->len -= ret;
778 sd->pos += ret;
779 sd->total_len -= ret;
780
781 if (!buf->len) {
782 buf->ops = NULL;
783 ops->release(pipe, buf);
784 pipe->curbuf = (pipe->curbuf + 1) & (pipe->buffers - 1);
785 pipe->nrbufs--;
786 if (pipe->files)
787 sd->need_wakeup = true;
788 }
789
790 if (!sd->total_len)
791 return 0;
792 }
793
794 return 1;
795 }
796
797 /**
798 * splice_from_pipe_next - wait for some data to splice from
799 * @pipe: pipe to splice from
800 * @sd: information about the splice operation
801 *
802 * Description:
803 * This function will wait for some data and return a positive
804 * value (one) if pipe buffers are available. It will return zero
805 * or -errno if no more data needs to be spliced.
806 */
807 static int splice_from_pipe_next(struct pipe_inode_info *pipe, struct splice_desc *sd)
808 {
809 while (!pipe->nrbufs) {
810 if (!pipe->writers)
811 return 0;
812
813 if (!pipe->waiting_writers && sd->num_spliced)
814 return 0;
815
816 if (sd->flags & SPLICE_F_NONBLOCK)
817 return -EAGAIN;
818
819 if (signal_pending(current))
820 return -ERESTARTSYS;
821
822 if (sd->need_wakeup) {
823 wakeup_pipe_writers(pipe);
824 sd->need_wakeup = false;
825 }
826
827 pipe_wait(pipe);
828 }
829
830 return 1;
831 }
832
833 /**
834 * splice_from_pipe_begin - start splicing from pipe
835 * @sd: information about the splice operation
836 *
837 * Description:
838 * This function should be called before a loop containing
839 * splice_from_pipe_next() and splice_from_pipe_feed() to
840 * initialize the necessary fields of @sd.
841 */
842 static void splice_from_pipe_begin(struct splice_desc *sd)
843 {
844 sd->num_spliced = 0;
845 sd->need_wakeup = false;
846 }
847
848 /**
849 * splice_from_pipe_end - finish splicing from pipe
850 * @pipe: pipe to splice from
851 * @sd: information about the splice operation
852 *
853 * Description:
854 * This function will wake up pipe writers if necessary. It should
855 * be called after a loop containing splice_from_pipe_next() and
856 * splice_from_pipe_feed().
857 */
858 static void splice_from_pipe_end(struct pipe_inode_info *pipe, struct splice_desc *sd)
859 {
860 if (sd->need_wakeup)
861 wakeup_pipe_writers(pipe);
862 }
863
864 /**
865 * __splice_from_pipe - splice data from a pipe to given actor
866 * @pipe: pipe to splice from
867 * @sd: information to @actor
868 * @actor: handler that splices the data
869 *
870 * Description:
871 * This function does little more than loop over the pipe and call
872 * @actor to do the actual moving of a single struct pipe_buffer to
873 * the desired destination. See pipe_to_file, pipe_to_sendpage, or
874 * pipe_to_user.
875 *
876 */
877 ssize_t __splice_from_pipe(struct pipe_inode_info *pipe, struct splice_desc *sd,
878 splice_actor *actor)
879 {
880 int ret;
881
882 splice_from_pipe_begin(sd);
883 do {
884 ret = splice_from_pipe_next(pipe, sd);
885 if (ret > 0)
886 ret = splice_from_pipe_feed(pipe, sd, actor);
887 } while (ret > 0);
888 splice_from_pipe_end(pipe, sd);
889
890 return sd->num_spliced ? sd->num_spliced : ret;
891 }
892 EXPORT_SYMBOL(__splice_from_pipe);
893
894 /**
895 * splice_from_pipe - splice data from a pipe to a file
896 * @pipe: pipe to splice from
897 * @out: file to splice to
898 * @ppos: position in @out
899 * @len: how many bytes to splice
900 * @flags: splice modifier flags
901 * @actor: handler that splices the data
902 *
903 * Description:
904 * See __splice_from_pipe. This function locks the pipe inode,
905 * otherwise it's identical to __splice_from_pipe().
906 *
907 */
908 ssize_t splice_from_pipe(struct pipe_inode_info *pipe, struct file *out,
909 loff_t *ppos, size_t len, unsigned int flags,
910 splice_actor *actor)
911 {
912 ssize_t ret;
913 struct splice_desc sd = {
914 .total_len = len,
915 .flags = flags,
916 .pos = *ppos,
917 .u.file = out,
918 };
919
920 pipe_lock(pipe);
921 ret = __splice_from_pipe(pipe, &sd, actor);
922 pipe_unlock(pipe);
923
924 return ret;
925 }
926
927 /**
928 * iter_file_splice_write - splice data from a pipe to a file
929 * @pipe: pipe info
930 * @out: file to write to
931 * @ppos: position in @out
932 * @len: number of bytes to splice
933 * @flags: splice modifier flags
934 *
935 * Description:
936 * Will either move or copy pages (determined by @flags options) from
937 * the given pipe inode to the given file.
938 * This one is ->write_iter-based.
939 *
940 */
941 ssize_t
942 iter_file_splice_write(struct pipe_inode_info *pipe, struct file *out,
943 loff_t *ppos, size_t len, unsigned int flags)
944 {
945 struct splice_desc sd = {
946 .total_len = len,
947 .flags = flags,
948 .pos = *ppos,
949 .u.file = out,
950 };
951 int nbufs = pipe->buffers;
952 struct bio_vec *array = kcalloc(nbufs, sizeof(struct bio_vec),
953 GFP_KERNEL);
954 ssize_t ret;
955
956 if (unlikely(!array))
957 return -ENOMEM;
958
959 pipe_lock(pipe);
960
961 splice_from_pipe_begin(&sd);
962 while (sd.total_len) {
963 struct iov_iter from;
964 size_t left;
965 int n, idx;
966
967 ret = splice_from_pipe_next(pipe, &sd);
968 if (ret <= 0)
969 break;
970
971 if (unlikely(nbufs < pipe->buffers)) {
972 kfree(array);
973 nbufs = pipe->buffers;
974 array = kcalloc(nbufs, sizeof(struct bio_vec),
975 GFP_KERNEL);
976 if (!array) {
977 ret = -ENOMEM;
978 break;
979 }
980 }
981
982 /* build the vector */
983 left = sd.total_len;
984 for (n = 0, idx = pipe->curbuf; left && n < pipe->nrbufs; n++, idx++) {
985 struct pipe_buffer *buf = pipe->bufs + idx;
986 size_t this_len = buf->len;
987
988 if (this_len > left)
989 this_len = left;
990
991 if (idx == pipe->buffers - 1)
992 idx = -1;
993
994 ret = buf->ops->confirm(pipe, buf);
995 if (unlikely(ret)) {
996 if (ret == -ENODATA)
997 ret = 0;
998 goto done;
999 }
1000
1001 array[n].bv_page = buf->page;
1002 array[n].bv_len = this_len;
1003 array[n].bv_offset = buf->offset;
1004 left -= this_len;
1005 }
1006
1007 iov_iter_bvec(&from, ITER_BVEC | WRITE, array, n,
1008 sd.total_len - left);
1009 ret = vfs_iter_write(out, &from, &sd.pos);
1010 if (ret <= 0)
1011 break;
1012
1013 sd.num_spliced += ret;
1014 sd.total_len -= ret;
1015 *ppos = sd.pos;
1016
1017 /* dismiss the fully eaten buffers, adjust the partial one */
1018 while (ret) {
1019 struct pipe_buffer *buf = pipe->bufs + pipe->curbuf;
1020 if (ret >= buf->len) {
1021 const struct pipe_buf_operations *ops = buf->ops;
1022 ret -= buf->len;
1023 buf->len = 0;
1024 buf->ops = NULL;
1025 ops->release(pipe, buf);
1026 pipe->curbuf = (pipe->curbuf + 1) & (pipe->buffers - 1);
1027 pipe->nrbufs--;
1028 if (pipe->files)
1029 sd.need_wakeup = true;
1030 } else {
1031 buf->offset += ret;
1032 buf->len -= ret;
1033 ret = 0;
1034 }
1035 }
1036 }
1037 done:
1038 kfree(array);
1039 splice_from_pipe_end(pipe, &sd);
1040
1041 pipe_unlock(pipe);
1042
1043 if (sd.num_spliced)
1044 ret = sd.num_spliced;
1045
1046 return ret;
1047 }
1048
1049 EXPORT_SYMBOL(iter_file_splice_write);
1050
1051 static int write_pipe_buf(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
1052 struct splice_desc *sd)
1053 {
1054 int ret;
1055 void *data;
1056 loff_t tmp = sd->pos;
1057
1058 data = kmap(buf->page);
1059 ret = __kernel_write(sd->u.file, data + buf->offset, sd->len, &tmp);
1060 kunmap(buf->page);
1061
1062 return ret;
1063 }
1064
1065 static ssize_t default_file_splice_write(struct pipe_inode_info *pipe,
1066 struct file *out, loff_t *ppos,
1067 size_t len, unsigned int flags)
1068 {
1069 ssize_t ret;
1070
1071 ret = splice_from_pipe(pipe, out, ppos, len, flags, write_pipe_buf);
1072 if (ret > 0)
1073 *ppos += ret;
1074
1075 return ret;
1076 }
1077
1078 /**
1079 * generic_splice_sendpage - splice data from a pipe to a socket
1080 * @pipe: pipe to splice from
1081 * @out: socket to write to
1082 * @ppos: position in @out
1083 * @len: number of bytes to splice
1084 * @flags: splice modifier flags
1085 *
1086 * Description:
1087 * Will send @len bytes from the pipe to a network socket. No data copying
1088 * is involved.
1089 *
1090 */
1091 ssize_t generic_splice_sendpage(struct pipe_inode_info *pipe, struct file *out,
1092 loff_t *ppos, size_t len, unsigned int flags)
1093 {
1094 return splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_sendpage);
1095 }
1096
1097 EXPORT_SYMBOL(generic_splice_sendpage);
1098
1099 /*
1100 * Attempt to initiate a splice from pipe to file.
1101 */
1102 static long do_splice_from(struct pipe_inode_info *pipe, struct file *out,
1103 loff_t *ppos, size_t len, unsigned int flags)
1104 {
1105 ssize_t (*splice_write)(struct pipe_inode_info *, struct file *,
1106 loff_t *, size_t, unsigned int);
1107
1108 if (out->f_op->splice_write)
1109 splice_write = out->f_op->splice_write;
1110 else
1111 splice_write = default_file_splice_write;
1112
1113 return splice_write(pipe, out, ppos, len, flags);
1114 }
1115
1116 /*
1117 * Attempt to initiate a splice from a file to a pipe.
1118 */
1119 static long do_splice_to(struct file *in, loff_t *ppos,
1120 struct pipe_inode_info *pipe, size_t len,
1121 unsigned int flags)
1122 {
1123 ssize_t (*splice_read)(struct file *, loff_t *,
1124 struct pipe_inode_info *, size_t, unsigned int);
1125 int ret;
1126
1127 if (unlikely(!(in->f_mode & FMODE_READ)))
1128 return -EBADF;
1129
1130 ret = rw_verify_area(READ, in, ppos, len);
1131 if (unlikely(ret < 0))
1132 return ret;
1133
1134 if (in->f_op->splice_read)
1135 splice_read = in->f_op->splice_read;
1136 else
1137 splice_read = default_file_splice_read;
1138
1139 return splice_read(in, ppos, pipe, len, flags);
1140 }
1141
1142 /**
1143 * splice_direct_to_actor - splices data directly between two non-pipes
1144 * @in: file to splice from
1145 * @sd: actor information on where to splice to
1146 * @actor: handles the data splicing
1147 *
1148 * Description:
1149 * This is a special case helper to splice directly between two
1150 * points, without requiring an explicit pipe. Internally an allocated
1151 * pipe is cached in the process, and reused during the lifetime of
1152 * that process.
1153 *
1154 */
1155 ssize_t splice_direct_to_actor(struct file *in, struct splice_desc *sd,
1156 splice_direct_actor *actor)
1157 {
1158 struct pipe_inode_info *pipe;
1159 long ret, bytes;
1160 umode_t i_mode;
1161 size_t len;
1162 int i, flags;
1163
1164 /*
1165 * We require the input being a regular file, as we don't want to
1166 * randomly drop data for eg socket -> socket splicing. Use the
1167 * piped splicing for that!
1168 */
1169 i_mode = file_inode(in)->i_mode;
1170 if (unlikely(!S_ISREG(i_mode) && !S_ISBLK(i_mode)))
1171 return -EINVAL;
1172
1173 /*
1174 * neither in nor out is a pipe, setup an internal pipe attached to
1175 * 'out' and transfer the wanted data from 'in' to 'out' through that
1176 */
1177 pipe = current->splice_pipe;
1178 if (unlikely(!pipe)) {
1179 pipe = alloc_pipe_info();
1180 if (!pipe)
1181 return -ENOMEM;
1182
1183 /*
1184 * We don't have an immediate reader, but we'll read the stuff
1185 * out of the pipe right after the splice_to_pipe(). So set
1186 * PIPE_READERS appropriately.
1187 */
1188 pipe->readers = 1;
1189
1190 current->splice_pipe = pipe;
1191 }
1192
1193 /*
1194 * Do the splice.
1195 */
1196 ret = 0;
1197 bytes = 0;
1198 len = sd->total_len;
1199 flags = sd->flags;
1200
1201 /*
1202 * Don't block on output, we have to drain the direct pipe.
1203 */
1204 sd->flags &= ~SPLICE_F_NONBLOCK;
1205
1206 while (len) {
1207 size_t read_len;
1208 loff_t pos = sd->pos, prev_pos = pos;
1209
1210 ret = do_splice_to(in, &pos, pipe, len, flags);
1211 if (unlikely(ret <= 0))
1212 goto out_release;
1213
1214 read_len = ret;
1215 sd->total_len = read_len;
1216
1217 /*
1218 * NOTE: nonblocking mode only applies to the input. We
1219 * must not do the output in nonblocking mode as then we
1220 * could get stuck data in the internal pipe:
1221 */
1222 ret = actor(pipe, sd);
1223 if (unlikely(ret <= 0)) {
1224 sd->pos = prev_pos;
1225 goto out_release;
1226 }
1227
1228 bytes += ret;
1229 len -= ret;
1230 sd->pos = pos;
1231
1232 if (ret < read_len) {
1233 sd->pos = prev_pos + ret;
1234 goto out_release;
1235 }
1236 }
1237
1238 done:
1239 pipe->nrbufs = pipe->curbuf = 0;
1240 file_accessed(in);
1241 return bytes;
1242
1243 out_release:
1244 /*
1245 * If we did an incomplete transfer we must release
1246 * the pipe buffers in question:
1247 */
1248 for (i = 0; i < pipe->buffers; i++) {
1249 struct pipe_buffer *buf = pipe->bufs + i;
1250
1251 if (buf->ops) {
1252 buf->ops->release(pipe, buf);
1253 buf->ops = NULL;
1254 }
1255 }
1256
1257 if (!bytes)
1258 bytes = ret;
1259
1260 goto done;
1261 }
1262 EXPORT_SYMBOL(splice_direct_to_actor);
1263
1264 static int direct_splice_actor(struct pipe_inode_info *pipe,
1265 struct splice_desc *sd)
1266 {
1267 struct file *file = sd->u.file;
1268
1269 return do_splice_from(pipe, file, sd->opos, sd->total_len,
1270 sd->flags);
1271 }
1272
1273 /**
1274 * do_splice_direct - splices data directly between two files
1275 * @in: file to splice from
1276 * @ppos: input file offset
1277 * @out: file to splice to
1278 * @opos: output file offset
1279 * @len: number of bytes to splice
1280 * @flags: splice modifier flags
1281 *
1282 * Description:
1283 * For use by do_sendfile(). splice can easily emulate sendfile, but
1284 * doing it in the application would incur an extra system call
1285 * (splice in + splice out, as compared to just sendfile()). So this helper
1286 * can splice directly through a process-private pipe.
1287 *
1288 */
1289 long do_splice_direct(struct file *in, loff_t *ppos, struct file *out,
1290 loff_t *opos, size_t len, unsigned int flags)
1291 {
1292 struct splice_desc sd = {
1293 .len = len,
1294 .total_len = len,
1295 .flags = flags,
1296 .pos = *ppos,
1297 .u.file = out,
1298 .opos = opos,
1299 };
1300 long ret;
1301
1302 if (unlikely(!(out->f_mode & FMODE_WRITE)))
1303 return -EBADF;
1304
1305 if (unlikely(out->f_flags & O_APPEND))
1306 return -EINVAL;
1307
1308 ret = rw_verify_area(WRITE, out, opos, len);
1309 if (unlikely(ret < 0))
1310 return ret;
1311
1312 ret = splice_direct_to_actor(in, &sd, direct_splice_actor);
1313 if (ret > 0)
1314 *ppos = sd.pos;
1315
1316 return ret;
1317 }
1318 EXPORT_SYMBOL(do_splice_direct);
1319
1320 static int splice_pipe_to_pipe(struct pipe_inode_info *ipipe,
1321 struct pipe_inode_info *opipe,
1322 size_t len, unsigned int flags);
1323
1324 /*
1325 * Determine where to splice to/from.
1326 */
1327 static long do_splice(struct file *in, loff_t __user *off_in,
1328 struct file *out, loff_t __user *off_out,
1329 size_t len, unsigned int flags)
1330 {
1331 struct pipe_inode_info *ipipe;
1332 struct pipe_inode_info *opipe;
1333 loff_t offset;
1334 long ret;
1335
1336 ipipe = get_pipe_info(in);
1337 opipe = get_pipe_info(out);
1338
1339 if (ipipe && opipe) {
1340 if (off_in || off_out)
1341 return -ESPIPE;
1342
1343 if (!(in->f_mode & FMODE_READ))
1344 return -EBADF;
1345
1346 if (!(out->f_mode & FMODE_WRITE))
1347 return -EBADF;
1348
1349 /* Splicing to self would be fun, but... */
1350 if (ipipe == opipe)
1351 return -EINVAL;
1352
1353 return splice_pipe_to_pipe(ipipe, opipe, len, flags);
1354 }
1355
1356 if (ipipe) {
1357 if (off_in)
1358 return -ESPIPE;
1359 if (off_out) {
1360 if (!(out->f_mode & FMODE_PWRITE))
1361 return -EINVAL;
1362 if (copy_from_user(&offset, off_out, sizeof(loff_t)))
1363 return -EFAULT;
1364 } else {
1365 offset = out->f_pos;
1366 }
1367
1368 if (unlikely(!(out->f_mode & FMODE_WRITE)))
1369 return -EBADF;
1370
1371 if (unlikely(out->f_flags & O_APPEND))
1372 return -EINVAL;
1373
1374 ret = rw_verify_area(WRITE, out, &offset, len);
1375 if (unlikely(ret < 0))
1376 return ret;
1377
1378 file_start_write(out);
1379 ret = do_splice_from(ipipe, out, &offset, len, flags);
1380 file_end_write(out);
1381
1382 if (!off_out)
1383 out->f_pos = offset;
1384 else if (copy_to_user(off_out, &offset, sizeof(loff_t)))
1385 ret = -EFAULT;
1386
1387 return ret;
1388 }
1389
1390 if (opipe) {
1391 if (off_out)
1392 return -ESPIPE;
1393 if (off_in) {
1394 if (!(in->f_mode & FMODE_PREAD))
1395 return -EINVAL;
1396 if (copy_from_user(&offset, off_in, sizeof(loff_t)))
1397 return -EFAULT;
1398 } else {
1399 offset = in->f_pos;
1400 }
1401
1402 ret = do_splice_to(in, &offset, opipe, len, flags);
1403
1404 if (!off_in)
1405 in->f_pos = offset;
1406 else if (copy_to_user(off_in, &offset, sizeof(loff_t)))
1407 ret = -EFAULT;
1408
1409 return ret;
1410 }
1411
1412 return -EINVAL;
1413 }
1414
1415 /*
1416 * Map an iov into an array of pages and offset/length tupples. With the
1417 * partial_page structure, we can map several non-contiguous ranges into
1418 * our ones pages[] map instead of splitting that operation into pieces.
1419 * Could easily be exported as a generic helper for other users, in which
1420 * case one would probably want to add a 'max_nr_pages' parameter as well.
1421 */
1422 static int get_iovec_page_array(const struct iovec __user *iov,
1423 unsigned int nr_vecs, struct page **pages,
1424 struct partial_page *partial, bool aligned,
1425 unsigned int pipe_buffers)
1426 {
1427 int buffers = 0, error = 0;
1428
1429 while (nr_vecs) {
1430 unsigned long off, npages;
1431 struct iovec entry;
1432 void __user *base;
1433 size_t len;
1434 int i;
1435
1436 error = -EFAULT;
1437 if (copy_from_user(&entry, iov, sizeof(entry)))
1438 break;
1439
1440 base = entry.iov_base;
1441 len = entry.iov_len;
1442
1443 /*
1444 * Sanity check this iovec. 0 read succeeds.
1445 */
1446 error = 0;
1447 if (unlikely(!len))
1448 break;
1449 error = -EFAULT;
1450 if (!access_ok(VERIFY_READ, base, len))
1451 break;
1452
1453 /*
1454 * Get this base offset and number of pages, then map
1455 * in the user pages.
1456 */
1457 off = (unsigned long) base & ~PAGE_MASK;
1458
1459 /*
1460 * If asked for alignment, the offset must be zero and the
1461 * length a multiple of the PAGE_SIZE.
1462 */
1463 error = -EINVAL;
1464 if (aligned && (off || len & ~PAGE_MASK))
1465 break;
1466
1467 npages = (off + len + PAGE_SIZE - 1) >> PAGE_SHIFT;
1468 if (npages > pipe_buffers - buffers)
1469 npages = pipe_buffers - buffers;
1470
1471 error = get_user_pages_fast((unsigned long)base, npages,
1472 0, &pages[buffers]);
1473
1474 if (unlikely(error <= 0))
1475 break;
1476
1477 /*
1478 * Fill this contiguous range into the partial page map.
1479 */
1480 for (i = 0; i < error; i++) {
1481 const int plen = min_t(size_t, len, PAGE_SIZE - off);
1482
1483 partial[buffers].offset = off;
1484 partial[buffers].len = plen;
1485
1486 off = 0;
1487 len -= plen;
1488 buffers++;
1489 }
1490
1491 /*
1492 * We didn't complete this iov, stop here since it probably
1493 * means we have to move some of this into a pipe to
1494 * be able to continue.
1495 */
1496 if (len)
1497 break;
1498
1499 /*
1500 * Don't continue if we mapped fewer pages than we asked for,
1501 * or if we mapped the max number of pages that we have
1502 * room for.
1503 */
1504 if (error < npages || buffers == pipe_buffers)
1505 break;
1506
1507 nr_vecs--;
1508 iov++;
1509 }
1510
1511 if (buffers)
1512 return buffers;
1513
1514 return error;
1515 }
1516
1517 static int pipe_to_user(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
1518 struct splice_desc *sd)
1519 {
1520 int n = copy_page_to_iter(buf->page, buf->offset, sd->len, sd->u.data);
1521 return n == sd->len ? n : -EFAULT;
1522 }
1523
1524 /*
1525 * For lack of a better implementation, implement vmsplice() to userspace
1526 * as a simple copy of the pipes pages to the user iov.
1527 */
1528 static long vmsplice_to_user(struct file *file, const struct iovec __user *uiov,
1529 unsigned long nr_segs, unsigned int flags)
1530 {
1531 struct pipe_inode_info *pipe;
1532 struct splice_desc sd;
1533 long ret;
1534 struct iovec iovstack[UIO_FASTIOV];
1535 struct iovec *iov = iovstack;
1536 struct iov_iter iter;
1537 ssize_t count;
1538
1539 pipe = get_pipe_info(file);
1540 if (!pipe)
1541 return -EBADF;
1542
1543 ret = rw_copy_check_uvector(READ, uiov, nr_segs,
1544 ARRAY_SIZE(iovstack), iovstack, &iov);
1545 if (ret <= 0)
1546 goto out;
1547
1548 count = ret;
1549 iov_iter_init(&iter, READ, iov, nr_segs, count);
1550
1551 sd.len = 0;
1552 sd.total_len = count;
1553 sd.flags = flags;
1554 sd.u.data = &iter;
1555 sd.pos = 0;
1556
1557 pipe_lock(pipe);
1558 ret = __splice_from_pipe(pipe, &sd, pipe_to_user);
1559 pipe_unlock(pipe);
1560
1561 out:
1562 if (iov != iovstack)
1563 kfree(iov);
1564
1565 return ret;
1566 }
1567
1568 /*
1569 * vmsplice splices a user address range into a pipe. It can be thought of
1570 * as splice-from-memory, where the regular splice is splice-from-file (or
1571 * to file). In both cases the output is a pipe, naturally.
1572 */
1573 static long vmsplice_to_pipe(struct file *file, const struct iovec __user *iov,
1574 unsigned long nr_segs, unsigned int flags)
1575 {
1576 struct pipe_inode_info *pipe;
1577 struct page *pages[PIPE_DEF_BUFFERS];
1578 struct partial_page partial[PIPE_DEF_BUFFERS];
1579 struct splice_pipe_desc spd = {
1580 .pages = pages,
1581 .partial = partial,
1582 .nr_pages_max = PIPE_DEF_BUFFERS,
1583 .flags = flags,
1584 .ops = &user_page_pipe_buf_ops,
1585 .spd_release = spd_release_page,
1586 };
1587 long ret;
1588
1589 pipe = get_pipe_info(file);
1590 if (!pipe)
1591 return -EBADF;
1592
1593 if (splice_grow_spd(pipe, &spd))
1594 return -ENOMEM;
1595
1596 spd.nr_pages = get_iovec_page_array(iov, nr_segs, spd.pages,
1597 spd.partial, false,
1598 spd.nr_pages_max);
1599 if (spd.nr_pages <= 0)
1600 ret = spd.nr_pages;
1601 else
1602 ret = splice_to_pipe(pipe, &spd);
1603
1604 splice_shrink_spd(&spd);
1605 return ret;
1606 }
1607
1608 /*
1609 * Note that vmsplice only really supports true splicing _from_ user memory
1610 * to a pipe, not the other way around. Splicing from user memory is a simple
1611 * operation that can be supported without any funky alignment restrictions
1612 * or nasty vm tricks. We simply map in the user memory and fill them into
1613 * a pipe. The reverse isn't quite as easy, though. There are two possible
1614 * solutions for that:
1615 *
1616 * - memcpy() the data internally, at which point we might as well just
1617 * do a regular read() on the buffer anyway.
1618 * - Lots of nasty vm tricks, that are neither fast nor flexible (it
1619 * has restriction limitations on both ends of the pipe).
1620 *
1621 * Currently we punt and implement it as a normal copy, see pipe_to_user().
1622 *
1623 */
1624 SYSCALL_DEFINE4(vmsplice, int, fd, const struct iovec __user *, iov,
1625 unsigned long, nr_segs, unsigned int, flags)
1626 {
1627 struct fd f;
1628 long error;
1629
1630 if (unlikely(nr_segs > UIO_MAXIOV))
1631 return -EINVAL;
1632 else if (unlikely(!nr_segs))
1633 return 0;
1634
1635 error = -EBADF;
1636 f = fdget(fd);
1637 if (f.file) {
1638 if (f.file->f_mode & FMODE_WRITE)
1639 error = vmsplice_to_pipe(f.file, iov, nr_segs, flags);
1640 else if (f.file->f_mode & FMODE_READ)
1641 error = vmsplice_to_user(f.file, iov, nr_segs, flags);
1642
1643 fdput(f);
1644 }
1645
1646 return error;
1647 }
1648
1649 #ifdef CONFIG_COMPAT
1650 COMPAT_SYSCALL_DEFINE4(vmsplice, int, fd, const struct compat_iovec __user *, iov32,
1651 unsigned int, nr_segs, unsigned int, flags)
1652 {
1653 unsigned i;
1654 struct iovec __user *iov;
1655 if (nr_segs > UIO_MAXIOV)
1656 return -EINVAL;
1657 iov = compat_alloc_user_space(nr_segs * sizeof(struct iovec));
1658 for (i = 0; i < nr_segs; i++) {
1659 struct compat_iovec v;
1660 if (get_user(v.iov_base, &iov32[i].iov_base) ||
1661 get_user(v.iov_len, &iov32[i].iov_len) ||
1662 put_user(compat_ptr(v.iov_base), &iov[i].iov_base) ||
1663 put_user(v.iov_len, &iov[i].iov_len))
1664 return -EFAULT;
1665 }
1666 return sys_vmsplice(fd, iov, nr_segs, flags);
1667 }
1668 #endif
1669
1670 SYSCALL_DEFINE6(splice, int, fd_in, loff_t __user *, off_in,
1671 int, fd_out, loff_t __user *, off_out,
1672 size_t, len, unsigned int, flags)
1673 {
1674 struct fd in, out;
1675 long error;
1676
1677 if (unlikely(!len))
1678 return 0;
1679
1680 error = -EBADF;
1681 in = fdget(fd_in);
1682 if (in.file) {
1683 if (in.file->f_mode & FMODE_READ) {
1684 out = fdget(fd_out);
1685 if (out.file) {
1686 if (out.file->f_mode & FMODE_WRITE)
1687 error = do_splice(in.file, off_in,
1688 out.file, off_out,
1689 len, flags);
1690 fdput(out);
1691 }
1692 }
1693 fdput(in);
1694 }
1695 return error;
1696 }
1697
1698 /*
1699 * Make sure there's data to read. Wait for input if we can, otherwise
1700 * return an appropriate error.
1701 */
1702 static int ipipe_prep(struct pipe_inode_info *pipe, unsigned int flags)
1703 {
1704 int ret;
1705
1706 /*
1707 * Check ->nrbufs without the inode lock first. This function
1708 * is speculative anyways, so missing one is ok.
1709 */
1710 if (pipe->nrbufs)
1711 return 0;
1712
1713 ret = 0;
1714 pipe_lock(pipe);
1715
1716 while (!pipe->nrbufs) {
1717 if (signal_pending(current)) {
1718 ret = -ERESTARTSYS;
1719 break;
1720 }
1721 if (!pipe->writers)
1722 break;
1723 if (!pipe->waiting_writers) {
1724 if (flags & SPLICE_F_NONBLOCK) {
1725 ret = -EAGAIN;
1726 break;
1727 }
1728 }
1729 pipe_wait(pipe);
1730 }
1731
1732 pipe_unlock(pipe);
1733 return ret;
1734 }
1735
1736 /*
1737 * Make sure there's writeable room. Wait for room if we can, otherwise
1738 * return an appropriate error.
1739 */
1740 static int opipe_prep(struct pipe_inode_info *pipe, unsigned int flags)
1741 {
1742 int ret;
1743
1744 /*
1745 * Check ->nrbufs without the inode lock first. This function
1746 * is speculative anyways, so missing one is ok.
1747 */
1748 if (pipe->nrbufs < pipe->buffers)
1749 return 0;
1750
1751 ret = 0;
1752 pipe_lock(pipe);
1753
1754 while (pipe->nrbufs >= pipe->buffers) {
1755 if (!pipe->readers) {
1756 send_sig(SIGPIPE, current, 0);
1757 ret = -EPIPE;
1758 break;
1759 }
1760 if (flags & SPLICE_F_NONBLOCK) {
1761 ret = -EAGAIN;
1762 break;
1763 }
1764 if (signal_pending(current)) {
1765 ret = -ERESTARTSYS;
1766 break;
1767 }
1768 pipe->waiting_writers++;
1769 pipe_wait(pipe);
1770 pipe->waiting_writers--;
1771 }
1772
1773 pipe_unlock(pipe);
1774 return ret;
1775 }
1776
1777 /*
1778 * Splice contents of ipipe to opipe.
1779 */
1780 static int splice_pipe_to_pipe(struct pipe_inode_info *ipipe,
1781 struct pipe_inode_info *opipe,
1782 size_t len, unsigned int flags)
1783 {
1784 struct pipe_buffer *ibuf, *obuf;
1785 int ret = 0, nbuf;
1786 bool input_wakeup = false;
1787
1788
1789 retry:
1790 ret = ipipe_prep(ipipe, flags);
1791 if (ret)
1792 return ret;
1793
1794 ret = opipe_prep(opipe, flags);
1795 if (ret)
1796 return ret;
1797
1798 /*
1799 * Potential ABBA deadlock, work around it by ordering lock
1800 * grabbing by pipe info address. Otherwise two different processes
1801 * could deadlock (one doing tee from A -> B, the other from B -> A).
1802 */
1803 pipe_double_lock(ipipe, opipe);
1804
1805 do {
1806 if (!opipe->readers) {
1807 send_sig(SIGPIPE, current, 0);
1808 if (!ret)
1809 ret = -EPIPE;
1810 break;
1811 }
1812
1813 if (!ipipe->nrbufs && !ipipe->writers)
1814 break;
1815
1816 /*
1817 * Cannot make any progress, because either the input
1818 * pipe is empty or the output pipe is full.
1819 */
1820 if (!ipipe->nrbufs || opipe->nrbufs >= opipe->buffers) {
1821 /* Already processed some buffers, break */
1822 if (ret)
1823 break;
1824
1825 if (flags & SPLICE_F_NONBLOCK) {
1826 ret = -EAGAIN;
1827 break;
1828 }
1829
1830 /*
1831 * We raced with another reader/writer and haven't
1832 * managed to process any buffers. A zero return
1833 * value means EOF, so retry instead.
1834 */
1835 pipe_unlock(ipipe);
1836 pipe_unlock(opipe);
1837 goto retry;
1838 }
1839
1840 ibuf = ipipe->bufs + ipipe->curbuf;
1841 nbuf = (opipe->curbuf + opipe->nrbufs) & (opipe->buffers - 1);
1842 obuf = opipe->bufs + nbuf;
1843
1844 if (len >= ibuf->len) {
1845 /*
1846 * Simply move the whole buffer from ipipe to opipe
1847 */
1848 *obuf = *ibuf;
1849 ibuf->ops = NULL;
1850 opipe->nrbufs++;
1851 ipipe->curbuf = (ipipe->curbuf + 1) & (ipipe->buffers - 1);
1852 ipipe->nrbufs--;
1853 input_wakeup = true;
1854 } else {
1855 /*
1856 * Get a reference to this pipe buffer,
1857 * so we can copy the contents over.
1858 */
1859 ibuf->ops->get(ipipe, ibuf);
1860 *obuf = *ibuf;
1861
1862 /*
1863 * Don't inherit the gift flag, we need to
1864 * prevent multiple steals of this page.
1865 */
1866 obuf->flags &= ~PIPE_BUF_FLAG_GIFT;
1867
1868 obuf->len = len;
1869 opipe->nrbufs++;
1870 ibuf->offset += obuf->len;
1871 ibuf->len -= obuf->len;
1872 }
1873 ret += obuf->len;
1874 len -= obuf->len;
1875 } while (len);
1876
1877 pipe_unlock(ipipe);
1878 pipe_unlock(opipe);
1879
1880 /*
1881 * If we put data in the output pipe, wakeup any potential readers.
1882 */
1883 if (ret > 0)
1884 wakeup_pipe_readers(opipe);
1885
1886 if (input_wakeup)
1887 wakeup_pipe_writers(ipipe);
1888
1889 return ret;
1890 }
1891
1892 /*
1893 * Link contents of ipipe to opipe.
1894 */
1895 static int link_pipe(struct pipe_inode_info *ipipe,
1896 struct pipe_inode_info *opipe,
1897 size_t len, unsigned int flags)
1898 {
1899 struct pipe_buffer *ibuf, *obuf;
1900 int ret = 0, i = 0, nbuf;
1901
1902 /*
1903 * Potential ABBA deadlock, work around it by ordering lock
1904 * grabbing by pipe info address. Otherwise two different processes
1905 * could deadlock (one doing tee from A -> B, the other from B -> A).
1906 */
1907 pipe_double_lock(ipipe, opipe);
1908
1909 do {
1910 if (!opipe->readers) {
1911 send_sig(SIGPIPE, current, 0);
1912 if (!ret)
1913 ret = -EPIPE;
1914 break;
1915 }
1916
1917 /*
1918 * If we have iterated all input buffers or ran out of
1919 * output room, break.
1920 */
1921 if (i >= ipipe->nrbufs || opipe->nrbufs >= opipe->buffers)
1922 break;
1923
1924 ibuf = ipipe->bufs + ((ipipe->curbuf + i) & (ipipe->buffers-1));
1925 nbuf = (opipe->curbuf + opipe->nrbufs) & (opipe->buffers - 1);
1926
1927 /*
1928 * Get a reference to this pipe buffer,
1929 * so we can copy the contents over.
1930 */
1931 ibuf->ops->get(ipipe, ibuf);
1932
1933 obuf = opipe->bufs + nbuf;
1934 *obuf = *ibuf;
1935
1936 /*
1937 * Don't inherit the gift flag, we need to
1938 * prevent multiple steals of this page.
1939 */
1940 obuf->flags &= ~PIPE_BUF_FLAG_GIFT;
1941
1942 if (obuf->len > len)
1943 obuf->len = len;
1944
1945 opipe->nrbufs++;
1946 ret += obuf->len;
1947 len -= obuf->len;
1948 i++;
1949 } while (len);
1950
1951 /*
1952 * return EAGAIN if we have the potential of some data in the
1953 * future, otherwise just return 0
1954 */
1955 if (!ret && ipipe->waiting_writers && (flags & SPLICE_F_NONBLOCK))
1956 ret = -EAGAIN;
1957
1958 pipe_unlock(ipipe);
1959 pipe_unlock(opipe);
1960
1961 /*
1962 * If we put data in the output pipe, wakeup any potential readers.
1963 */
1964 if (ret > 0)
1965 wakeup_pipe_readers(opipe);
1966
1967 return ret;
1968 }
1969
1970 /*
1971 * This is a tee(1) implementation that works on pipes. It doesn't copy
1972 * any data, it simply references the 'in' pages on the 'out' pipe.
1973 * The 'flags' used are the SPLICE_F_* variants, currently the only
1974 * applicable one is SPLICE_F_NONBLOCK.
1975 */
1976 static long do_tee(struct file *in, struct file *out, size_t len,
1977 unsigned int flags)
1978 {
1979 struct pipe_inode_info *ipipe = get_pipe_info(in);
1980 struct pipe_inode_info *opipe = get_pipe_info(out);
1981 int ret = -EINVAL;
1982
1983 /*
1984 * Duplicate the contents of ipipe to opipe without actually
1985 * copying the data.
1986 */
1987 if (ipipe && opipe && ipipe != opipe) {
1988 /*
1989 * Keep going, unless we encounter an error. The ipipe/opipe
1990 * ordering doesn't really matter.
1991 */
1992 ret = ipipe_prep(ipipe, flags);
1993 if (!ret) {
1994 ret = opipe_prep(opipe, flags);
1995 if (!ret)
1996 ret = link_pipe(ipipe, opipe, len, flags);
1997 }
1998 }
1999
2000 return ret;
2001 }
2002
2003 SYSCALL_DEFINE4(tee, int, fdin, int, fdout, size_t, len, unsigned int, flags)
2004 {
2005 struct fd in;
2006 int error;
2007
2008 if (unlikely(!len))
2009 return 0;
2010
2011 error = -EBADF;
2012 in = fdget(fdin);
2013 if (in.file) {
2014 if (in.file->f_mode & FMODE_READ) {
2015 struct fd out = fdget(fdout);
2016 if (out.file) {
2017 if (out.file->f_mode & FMODE_WRITE)
2018 error = do_tee(in.file, out.file,
2019 len, flags);
2020 fdput(out);
2021 }
2022 }
2023 fdput(in);
2024 }
2025
2026 return error;
2027 }