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