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path: root/fs/splice.c (plain)
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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 "internal.h"
36
37/*
38 * Attempt to steal a page from a pipe buffer. This should perhaps go into
39 * a vm helper function, it's already simplified quite a bit by the
40 * addition of remove_mapping(). If success is returned, the caller may
41 * attempt to reuse this page for another destination.
42 */
43static int page_cache_pipe_buf_steal(struct pipe_inode_info *pipe,
44 struct pipe_buffer *buf)
45{
46 struct page *page = buf->page;
47 struct address_space *mapping;
48
49 lock_page(page);
50
51 mapping = page_mapping(page);
52 if (mapping) {
53 WARN_ON(!PageUptodate(page));
54
55 /*
56 * At least for ext2 with nobh option, we need to wait on
57 * writeback completing on this page, since we'll remove it
58 * from the pagecache. Otherwise truncate wont wait on the
59 * page, allowing the disk blocks to be reused by someone else
60 * before we actually wrote our data to them. fs corruption
61 * ensues.
62 */
63 wait_on_page_writeback(page);
64
65 if (page_has_private(page) &&
66 !try_to_release_page(page, GFP_KERNEL))
67 goto out_unlock;
68
69 /*
70 * If we succeeded in removing the mapping, set LRU flag
71 * and return good.
72 */
73 if (remove_mapping(mapping, page)) {
74 buf->flags |= PIPE_BUF_FLAG_LRU;
75 return 0;
76 }
77 }
78
79 /*
80 * Raced with truncate or failed to remove page from current
81 * address space, unlock and return failure.
82 */
83out_unlock:
84 unlock_page(page);
85 return 1;
86}
87
88static void page_cache_pipe_buf_release(struct pipe_inode_info *pipe,
89 struct pipe_buffer *buf)
90{
91 put_page(buf->page);
92 buf->flags &= ~PIPE_BUF_FLAG_LRU;
93}
94
95/*
96 * Check whether the contents of buf is OK to access. Since the content
97 * is a page cache page, IO may be in flight.
98 */
99static int page_cache_pipe_buf_confirm(struct pipe_inode_info *pipe,
100 struct pipe_buffer *buf)
101{
102 struct page *page = buf->page;
103 int err;
104
105 if (!PageUptodate(page)) {
106 lock_page(page);
107
108 /*
109 * Page got truncated/unhashed. This will cause a 0-byte
110 * splice, if this is the first page.
111 */
112 if (!page->mapping) {
113 err = -ENODATA;
114 goto error;
115 }
116
117 /*
118 * Uh oh, read-error from disk.
119 */
120 if (!PageUptodate(page)) {
121 err = -EIO;
122 goto error;
123 }
124
125 /*
126 * Page is ok afterall, we are done.
127 */
128 unlock_page(page);
129 }
130
131 return 0;
132error:
133 unlock_page(page);
134 return err;
135}
136
137const struct pipe_buf_operations page_cache_pipe_buf_ops = {
138 .can_merge = 0,
139 .confirm = page_cache_pipe_buf_confirm,
140 .release = page_cache_pipe_buf_release,
141 .steal = page_cache_pipe_buf_steal,
142 .get = generic_pipe_buf_get,
143};
144
145static int user_page_pipe_buf_steal(struct pipe_inode_info *pipe,
146 struct pipe_buffer *buf)
147{
148 if (!(buf->flags & PIPE_BUF_FLAG_GIFT))
149 return 1;
150
151 buf->flags |= PIPE_BUF_FLAG_LRU;
152 return generic_pipe_buf_steal(pipe, buf);
153}
154
155static const struct pipe_buf_operations user_page_pipe_buf_ops = {
156 .can_merge = 0,
157 .confirm = generic_pipe_buf_confirm,
158 .release = page_cache_pipe_buf_release,
159 .steal = user_page_pipe_buf_steal,
160 .get = generic_pipe_buf_get,
161};
162
163static void wakeup_pipe_readers(struct pipe_inode_info *pipe)
164{
165 smp_mb();
166 if (waitqueue_active(&pipe->wait))
167 wake_up_interruptible(&pipe->wait);
168 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
169}
170
171/**
172 * splice_to_pipe - fill passed data into a pipe
173 * @pipe: pipe to fill
174 * @spd: data to fill
175 *
176 * Description:
177 * @spd contains a map of pages and len/offset tuples, along with
178 * the struct pipe_buf_operations associated with these pages. This
179 * function will link that data to the pipe.
180 *
181 */
182ssize_t splice_to_pipe(struct pipe_inode_info *pipe,
183 struct splice_pipe_desc *spd)
184{
185 unsigned int spd_pages = spd->nr_pages;
186 int ret = 0, page_nr = 0;
187
188 if (!spd_pages)
189 return 0;
190
191 if (unlikely(!pipe->readers)) {
192 send_sig(SIGPIPE, current, 0);
193 ret = -EPIPE;
194 goto out;
195 }
196
197 while (pipe->nrbufs < pipe->buffers) {
198 int newbuf = (pipe->curbuf + pipe->nrbufs) & (pipe->buffers - 1);
199 struct pipe_buffer *buf = pipe->bufs + newbuf;
200
201 buf->page = spd->pages[page_nr];
202 buf->offset = spd->partial[page_nr].offset;
203 buf->len = spd->partial[page_nr].len;
204 buf->private = spd->partial[page_nr].private;
205 buf->ops = spd->ops;
206 buf->flags = 0;
207
208 pipe->nrbufs++;
209 page_nr++;
210 ret += buf->len;
211
212 if (!--spd->nr_pages)
213 break;
214 }
215
216 if (!ret)
217 ret = -EAGAIN;
218
219out:
220 while (page_nr < spd_pages)
221 spd->spd_release(spd, page_nr++);
222
223 return ret;
224}
225EXPORT_SYMBOL_GPL(splice_to_pipe);
226
227ssize_t add_to_pipe(struct pipe_inode_info *pipe, struct pipe_buffer *buf)
228{
229 int ret;
230
231 if (unlikely(!pipe->readers)) {
232 send_sig(SIGPIPE, current, 0);
233 ret = -EPIPE;
234 } else if (pipe->nrbufs == pipe->buffers) {
235 ret = -EAGAIN;
236 } else {
237 int newbuf = (pipe->curbuf + pipe->nrbufs) & (pipe->buffers - 1);
238 pipe->bufs[newbuf] = *buf;
239 pipe->nrbufs++;
240 return buf->len;
241 }
242 pipe_buf_release(pipe, buf);
243 return ret;
244}
245EXPORT_SYMBOL(add_to_pipe);
246
247void spd_release_page(struct splice_pipe_desc *spd, unsigned int i)
248{
249 put_page(spd->pages[i]);
250}
251
252/*
253 * Check if we need to grow the arrays holding pages and partial page
254 * descriptions.
255 */
256int splice_grow_spd(const struct pipe_inode_info *pipe, struct splice_pipe_desc *spd)
257{
258 unsigned int buffers = ACCESS_ONCE(pipe->buffers);
259
260 spd->nr_pages_max = buffers;
261 if (buffers <= PIPE_DEF_BUFFERS)
262 return 0;
263
264 spd->pages = kmalloc(buffers * sizeof(struct page *), GFP_KERNEL);
265 spd->partial = kmalloc(buffers * sizeof(struct partial_page), GFP_KERNEL);
266
267 if (spd->pages && spd->partial)
268 return 0;
269
270 kfree(spd->pages);
271 kfree(spd->partial);
272 return -ENOMEM;
273}
274
275void splice_shrink_spd(struct splice_pipe_desc *spd)
276{
277 if (spd->nr_pages_max <= PIPE_DEF_BUFFERS)
278 return;
279
280 kfree(spd->pages);
281 kfree(spd->partial);
282}
283
284/**
285 * generic_file_splice_read - splice data from file to a pipe
286 * @in: file to splice from
287 * @ppos: position in @in
288 * @pipe: pipe to splice to
289 * @len: number of bytes to splice
290 * @flags: splice modifier flags
291 *
292 * Description:
293 * Will read pages from given file and fill them into a pipe. Can be
294 * used as long as it has more or less sane ->read_iter().
295 *
296 */
297ssize_t generic_file_splice_read(struct file *in, loff_t *ppos,
298 struct pipe_inode_info *pipe, size_t len,
299 unsigned int flags)
300{
301 struct iov_iter to;
302 struct kiocb kiocb;
303 int idx, ret;
304
305 iov_iter_pipe(&to, ITER_PIPE | READ, pipe, len);
306 idx = to.idx;
307 init_sync_kiocb(&kiocb, in);
308 kiocb.ki_pos = *ppos;
309 ret = in->f_op->read_iter(&kiocb, &to);
310 if (ret > 0) {
311 *ppos = kiocb.ki_pos;
312 file_accessed(in);
313 } else if (ret < 0) {
314 to.idx = idx;
315 to.iov_offset = 0;
316 iov_iter_advance(&to, 0); /* to free what was emitted */
317 /*
318 * callers of ->splice_read() expect -EAGAIN on
319 * "can't put anything in there", rather than -EFAULT.
320 */
321 if (ret == -EFAULT)
322 ret = -EAGAIN;
323 }
324
325 return ret;
326}
327EXPORT_SYMBOL(generic_file_splice_read);
328
329const struct pipe_buf_operations default_pipe_buf_ops = {
330 .can_merge = 0,
331 .confirm = generic_pipe_buf_confirm,
332 .release = generic_pipe_buf_release,
333 .steal = generic_pipe_buf_steal,
334 .get = generic_pipe_buf_get,
335};
336
337static int generic_pipe_buf_nosteal(struct pipe_inode_info *pipe,
338 struct pipe_buffer *buf)
339{
340 return 1;
341}
342
343/* Pipe buffer operations for a socket and similar. */
344const struct pipe_buf_operations nosteal_pipe_buf_ops = {
345 .can_merge = 0,
346 .confirm = generic_pipe_buf_confirm,
347 .release = generic_pipe_buf_release,
348 .steal = generic_pipe_buf_nosteal,
349 .get = generic_pipe_buf_get,
350};
351EXPORT_SYMBOL(nosteal_pipe_buf_ops);
352
353static ssize_t kernel_readv(struct file *file, const struct kvec *vec,
354 unsigned long vlen, loff_t offset)
355{
356 mm_segment_t old_fs;
357 loff_t pos = offset;
358 ssize_t res;
359
360 old_fs = get_fs();
361 set_fs(get_ds());
362 /* The cast to a user pointer is valid due to the set_fs() */
363 res = vfs_readv(file, (const struct iovec __user *)vec, vlen, &pos, 0);
364 set_fs(old_fs);
365
366 return res;
367}
368
369ssize_t kernel_write(struct file *file, const char *buf, size_t count,
370 loff_t pos)
371{
372 mm_segment_t old_fs;
373 ssize_t res;
374
375 old_fs = get_fs();
376 set_fs(get_ds());
377 /* The cast to a user pointer is valid due to the set_fs() */
378 res = vfs_write(file, (__force const char __user *)buf, count, &pos);
379 set_fs(old_fs);
380
381 return res;
382}
383EXPORT_SYMBOL(kernel_write);
384
385static ssize_t default_file_splice_read(struct file *in, loff_t *ppos,
386 struct pipe_inode_info *pipe, size_t len,
387 unsigned int flags)
388{
389 struct kvec *vec, __vec[PIPE_DEF_BUFFERS];
390 struct iov_iter to;
391 struct page **pages;
392 unsigned int nr_pages;
393 size_t offset, dummy, copied = 0;
394 ssize_t res;
395 int i;
396
397 if (pipe->nrbufs == pipe->buffers)
398 return -EAGAIN;
399
400 /*
401 * Try to keep page boundaries matching to source pagecache ones -
402 * it probably won't be much help, but...
403 */
404 offset = *ppos & ~PAGE_MASK;
405
406 iov_iter_pipe(&to, ITER_PIPE | READ, pipe, len + offset);
407
408 res = iov_iter_get_pages_alloc(&to, &pages, len + offset, &dummy);
409 if (res <= 0)
410 return -ENOMEM;
411
412 BUG_ON(dummy);
413 nr_pages = DIV_ROUND_UP(res, PAGE_SIZE);
414
415 vec = __vec;
416 if (nr_pages > PIPE_DEF_BUFFERS) {
417 vec = kmalloc(nr_pages * sizeof(struct kvec), GFP_KERNEL);
418 if (unlikely(!vec)) {
419 res = -ENOMEM;
420 goto out;
421 }
422 }
423
424 pipe->bufs[to.idx].offset = offset;
425 pipe->bufs[to.idx].len -= offset;
426
427 for (i = 0; i < nr_pages; i++) {
428 size_t this_len = min_t(size_t, len, PAGE_SIZE - offset);
429 vec[i].iov_base = page_address(pages[i]) + offset;
430 vec[i].iov_len = this_len;
431 len -= this_len;
432 offset = 0;
433 }
434
435 res = kernel_readv(in, vec, nr_pages, *ppos);
436 if (res > 0) {
437 copied = res;
438 *ppos += res;
439 }
440
441 if (vec != __vec)
442 kfree(vec);
443out:
444 for (i = 0; i < nr_pages; i++)
445 put_page(pages[i]);
446 kvfree(pages);
447 iov_iter_advance(&to, copied); /* truncates and discards */
448 return res;
449}
450
451/*
452 * Send 'sd->len' bytes to socket from 'sd->file' at position 'sd->pos'
453 * using sendpage(). Return the number of bytes sent.
454 */
455static int pipe_to_sendpage(struct pipe_inode_info *pipe,
456 struct pipe_buffer *buf, struct splice_desc *sd)
457{
458 struct file *file = sd->u.file;
459 loff_t pos = sd->pos;
460 int more;
461
462 if (!likely(file->f_op->sendpage))
463 return -EINVAL;
464
465 more = (sd->flags & SPLICE_F_MORE) ? MSG_MORE : 0;
466
467 if (sd->len < sd->total_len && pipe->nrbufs > 1)
468 more |= MSG_SENDPAGE_NOTLAST;
469
470 return file->f_op->sendpage(file, buf->page, buf->offset,
471 sd->len, &pos, more);
472}
473
474static void wakeup_pipe_writers(struct pipe_inode_info *pipe)
475{
476 smp_mb();
477 if (waitqueue_active(&pipe->wait))
478 wake_up_interruptible(&pipe->wait);
479 kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
480}
481
482/**
483 * splice_from_pipe_feed - feed available data from a pipe to a file
484 * @pipe: pipe to splice from
485 * @sd: information to @actor
486 * @actor: handler that splices the data
487 *
488 * Description:
489 * This function loops over the pipe and calls @actor to do the
490 * actual moving of a single struct pipe_buffer to the desired
491 * destination. It returns when there's no more buffers left in
492 * the pipe or if the requested number of bytes (@sd->total_len)
493 * have been copied. It returns a positive number (one) if the
494 * pipe needs to be filled with more data, zero if the required
495 * number of bytes have been copied and -errno on error.
496 *
497 * This, together with splice_from_pipe_{begin,end,next}, may be
498 * used to implement the functionality of __splice_from_pipe() when
499 * locking is required around copying the pipe buffers to the
500 * destination.
501 */
502static int splice_from_pipe_feed(struct pipe_inode_info *pipe, struct splice_desc *sd,
503 splice_actor *actor)
504{
505 int ret;
506
507 while (pipe->nrbufs) {
508 struct pipe_buffer *buf = pipe->bufs + pipe->curbuf;
509
510 sd->len = buf->len;
511 if (sd->len > sd->total_len)
512 sd->len = sd->total_len;
513
514 ret = pipe_buf_confirm(pipe, buf);
515 if (unlikely(ret)) {
516 if (ret == -ENODATA)
517 ret = 0;
518 return ret;
519 }
520
521 ret = actor(pipe, buf, sd);
522 if (ret <= 0)
523 return ret;
524
525 buf->offset += ret;
526 buf->len -= ret;
527
528 sd->num_spliced += ret;
529 sd->len -= ret;
530 sd->pos += ret;
531 sd->total_len -= ret;
532
533 if (!buf->len) {
534 pipe_buf_release(pipe, buf);
535 pipe->curbuf = (pipe->curbuf + 1) & (pipe->buffers - 1);
536 pipe->nrbufs--;
537 if (pipe->files)
538 sd->need_wakeup = true;
539 }
540
541 if (!sd->total_len)
542 return 0;
543 }
544
545 return 1;
546}
547
548/**
549 * splice_from_pipe_next - wait for some data to splice from
550 * @pipe: pipe to splice from
551 * @sd: information about the splice operation
552 *
553 * Description:
554 * This function will wait for some data and return a positive
555 * value (one) if pipe buffers are available. It will return zero
556 * or -errno if no more data needs to be spliced.
557 */
558static int splice_from_pipe_next(struct pipe_inode_info *pipe, struct splice_desc *sd)
559{
560 /*
561 * Check for signal early to make process killable when there are
562 * always buffers available
563 */
564 if (signal_pending(current))
565 return -ERESTARTSYS;
566
567 while (!pipe->nrbufs) {
568 if (!pipe->writers)
569 return 0;
570
571 if (!pipe->waiting_writers && sd->num_spliced)
572 return 0;
573
574 if (sd->flags & SPLICE_F_NONBLOCK)
575 return -EAGAIN;
576
577 if (signal_pending(current))
578 return -ERESTARTSYS;
579
580 if (sd->need_wakeup) {
581 wakeup_pipe_writers(pipe);
582 sd->need_wakeup = false;
583 }
584
585 pipe_wait(pipe);
586 }
587
588 return 1;
589}
590
591/**
592 * splice_from_pipe_begin - start splicing from pipe
593 * @sd: information about the splice operation
594 *
595 * Description:
596 * This function should be called before a loop containing
597 * splice_from_pipe_next() and splice_from_pipe_feed() to
598 * initialize the necessary fields of @sd.
599 */
600static void splice_from_pipe_begin(struct splice_desc *sd)
601{
602 sd->num_spliced = 0;
603 sd->need_wakeup = false;
604}
605
606/**
607 * splice_from_pipe_end - finish splicing from pipe
608 * @pipe: pipe to splice from
609 * @sd: information about the splice operation
610 *
611 * Description:
612 * This function will wake up pipe writers if necessary. It should
613 * be called after a loop containing splice_from_pipe_next() and
614 * splice_from_pipe_feed().
615 */
616static void splice_from_pipe_end(struct pipe_inode_info *pipe, struct splice_desc *sd)
617{
618 if (sd->need_wakeup)
619 wakeup_pipe_writers(pipe);
620}
621
622/**
623 * __splice_from_pipe - splice data from a pipe to given actor
624 * @pipe: pipe to splice from
625 * @sd: information to @actor
626 * @actor: handler that splices the data
627 *
628 * Description:
629 * This function does little more than loop over the pipe and call
630 * @actor to do the actual moving of a single struct pipe_buffer to
631 * the desired destination. See pipe_to_file, pipe_to_sendpage, or
632 * pipe_to_user.
633 *
634 */
635ssize_t __splice_from_pipe(struct pipe_inode_info *pipe, struct splice_desc *sd,
636 splice_actor *actor)
637{
638 int ret;
639
640 splice_from_pipe_begin(sd);
641 do {
642 cond_resched();
643 ret = splice_from_pipe_next(pipe, sd);
644 if (ret > 0)
645 ret = splice_from_pipe_feed(pipe, sd, actor);
646 } while (ret > 0);
647 splice_from_pipe_end(pipe, sd);
648
649 return sd->num_spliced ? sd->num_spliced : ret;
650}
651EXPORT_SYMBOL(__splice_from_pipe);
652
653/**
654 * splice_from_pipe - splice data from a pipe to a file
655 * @pipe: pipe to splice from
656 * @out: file to splice to
657 * @ppos: position in @out
658 * @len: how many bytes to splice
659 * @flags: splice modifier flags
660 * @actor: handler that splices the data
661 *
662 * Description:
663 * See __splice_from_pipe. This function locks the pipe inode,
664 * otherwise it's identical to __splice_from_pipe().
665 *
666 */
667ssize_t splice_from_pipe(struct pipe_inode_info *pipe, struct file *out,
668 loff_t *ppos, size_t len, unsigned int flags,
669 splice_actor *actor)
670{
671 ssize_t ret;
672 struct splice_desc sd = {
673 .total_len = len,
674 .flags = flags,
675 .pos = *ppos,
676 .u.file = out,
677 };
678
679 pipe_lock(pipe);
680 ret = __splice_from_pipe(pipe, &sd, actor);
681 pipe_unlock(pipe);
682
683 return ret;
684}
685
686/**
687 * iter_file_splice_write - splice data from a pipe to a file
688 * @pipe: pipe info
689 * @out: file to write to
690 * @ppos: position in @out
691 * @len: number of bytes to splice
692 * @flags: splice modifier flags
693 *
694 * Description:
695 * Will either move or copy pages (determined by @flags options) from
696 * the given pipe inode to the given file.
697 * This one is ->write_iter-based.
698 *
699 */
700ssize_t
701iter_file_splice_write(struct pipe_inode_info *pipe, struct file *out,
702 loff_t *ppos, size_t len, unsigned int flags)
703{
704 struct splice_desc sd = {
705 .total_len = len,
706 .flags = flags,
707 .pos = *ppos,
708 .u.file = out,
709 };
710 int nbufs = pipe->buffers;
711 struct bio_vec *array = kcalloc(nbufs, sizeof(struct bio_vec),
712 GFP_KERNEL);
713 ssize_t ret;
714
715 if (unlikely(!array))
716 return -ENOMEM;
717
718 pipe_lock(pipe);
719
720 splice_from_pipe_begin(&sd);
721 while (sd.total_len) {
722 struct iov_iter from;
723 size_t left;
724 int n, idx;
725
726 ret = splice_from_pipe_next(pipe, &sd);
727 if (ret <= 0)
728 break;
729
730 if (unlikely(nbufs < pipe->buffers)) {
731 kfree(array);
732 nbufs = pipe->buffers;
733 array = kcalloc(nbufs, sizeof(struct bio_vec),
734 GFP_KERNEL);
735 if (!array) {
736 ret = -ENOMEM;
737 break;
738 }
739 }
740
741 /* build the vector */
742 left = sd.total_len;
743 for (n = 0, idx = pipe->curbuf; left && n < pipe->nrbufs; n++, idx++) {
744 struct pipe_buffer *buf = pipe->bufs + idx;
745 size_t this_len = buf->len;
746
747 if (this_len > left)
748 this_len = left;
749
750 if (idx == pipe->buffers - 1)
751 idx = -1;
752
753 ret = pipe_buf_confirm(pipe, buf);
754 if (unlikely(ret)) {
755 if (ret == -ENODATA)
756 ret = 0;
757 goto done;
758 }
759
760 array[n].bv_page = buf->page;
761 array[n].bv_len = this_len;
762 array[n].bv_offset = buf->offset;
763 left -= this_len;
764 }
765
766 iov_iter_bvec(&from, ITER_BVEC | WRITE, array, n,
767 sd.total_len - left);
768 ret = vfs_iter_write(out, &from, &sd.pos);
769 if (ret <= 0)
770 break;
771
772 sd.num_spliced += ret;
773 sd.total_len -= ret;
774 *ppos = sd.pos;
775
776 /* dismiss the fully eaten buffers, adjust the partial one */
777 while (ret) {
778 struct pipe_buffer *buf = pipe->bufs + pipe->curbuf;
779 if (ret >= buf->len) {
780 ret -= buf->len;
781 buf->len = 0;
782 pipe_buf_release(pipe, buf);
783 pipe->curbuf = (pipe->curbuf + 1) & (pipe->buffers - 1);
784 pipe->nrbufs--;
785 if (pipe->files)
786 sd.need_wakeup = true;
787 } else {
788 buf->offset += ret;
789 buf->len -= ret;
790 ret = 0;
791 }
792 }
793 }
794done:
795 kfree(array);
796 splice_from_pipe_end(pipe, &sd);
797
798 pipe_unlock(pipe);
799
800 if (sd.num_spliced)
801 ret = sd.num_spliced;
802
803 return ret;
804}
805
806EXPORT_SYMBOL(iter_file_splice_write);
807
808static int write_pipe_buf(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
809 struct splice_desc *sd)
810{
811 int ret;
812 void *data;
813 loff_t tmp = sd->pos;
814
815 data = kmap(buf->page);
816 ret = __kernel_write(sd->u.file, data + buf->offset, sd->len, &tmp);
817 kunmap(buf->page);
818
819 return ret;
820}
821
822static ssize_t default_file_splice_write(struct pipe_inode_info *pipe,
823 struct file *out, loff_t *ppos,
824 size_t len, unsigned int flags)
825{
826 ssize_t ret;
827
828 ret = splice_from_pipe(pipe, out, ppos, len, flags, write_pipe_buf);
829 if (ret > 0)
830 *ppos += ret;
831
832 return ret;
833}
834
835/**
836 * generic_splice_sendpage - splice data from a pipe to a socket
837 * @pipe: pipe to splice from
838 * @out: socket to write to
839 * @ppos: position in @out
840 * @len: number of bytes to splice
841 * @flags: splice modifier flags
842 *
843 * Description:
844 * Will send @len bytes from the pipe to a network socket. No data copying
845 * is involved.
846 *
847 */
848ssize_t generic_splice_sendpage(struct pipe_inode_info *pipe, struct file *out,
849 loff_t *ppos, size_t len, unsigned int flags)
850{
851 return splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_sendpage);
852}
853
854EXPORT_SYMBOL(generic_splice_sendpage);
855
856/*
857 * Attempt to initiate a splice from pipe to file.
858 */
859static long do_splice_from(struct pipe_inode_info *pipe, struct file *out,
860 loff_t *ppos, size_t len, unsigned int flags)
861{
862 ssize_t (*splice_write)(struct pipe_inode_info *, struct file *,
863 loff_t *, size_t, unsigned int);
864
865 if (out->f_op->splice_write)
866 splice_write = out->f_op->splice_write;
867 else
868 splice_write = default_file_splice_write;
869
870 return splice_write(pipe, out, ppos, len, flags);
871}
872
873/*
874 * Attempt to initiate a splice from a file to a pipe.
875 */
876static long do_splice_to(struct file *in, loff_t *ppos,
877 struct pipe_inode_info *pipe, size_t len,
878 unsigned int flags)
879{
880 ssize_t (*splice_read)(struct file *, loff_t *,
881 struct pipe_inode_info *, size_t, unsigned int);
882 int ret;
883
884 if (unlikely(!(in->f_mode & FMODE_READ)))
885 return -EBADF;
886
887 ret = rw_verify_area(READ, in, ppos, len);
888 if (unlikely(ret < 0))
889 return ret;
890
891 if (unlikely(len > MAX_RW_COUNT))
892 len = MAX_RW_COUNT;
893
894 if (in->f_op->splice_read)
895 splice_read = in->f_op->splice_read;
896 else
897 splice_read = default_file_splice_read;
898
899 return splice_read(in, ppos, pipe, len, flags);
900}
901
902/**
903 * splice_direct_to_actor - splices data directly between two non-pipes
904 * @in: file to splice from
905 * @sd: actor information on where to splice to
906 * @actor: handles the data splicing
907 *
908 * Description:
909 * This is a special case helper to splice directly between two
910 * points, without requiring an explicit pipe. Internally an allocated
911 * pipe is cached in the process, and reused during the lifetime of
912 * that process.
913 *
914 */
915ssize_t splice_direct_to_actor(struct file *in, struct splice_desc *sd,
916 splice_direct_actor *actor)
917{
918 struct pipe_inode_info *pipe;
919 long ret, bytes;
920 umode_t i_mode;
921 size_t len;
922 int i, flags, more;
923
924 /*
925 * We require the input being a regular file, as we don't want to
926 * randomly drop data for eg socket -> socket splicing. Use the
927 * piped splicing for that!
928 */
929 i_mode = file_inode(in)->i_mode;
930 if (unlikely(!S_ISREG(i_mode) && !S_ISBLK(i_mode)))
931 return -EINVAL;
932
933 /*
934 * neither in nor out is a pipe, setup an internal pipe attached to
935 * 'out' and transfer the wanted data from 'in' to 'out' through that
936 */
937 pipe = current->splice_pipe;
938 if (unlikely(!pipe)) {
939 pipe = alloc_pipe_info();
940 if (!pipe)
941 return -ENOMEM;
942
943 /*
944 * We don't have an immediate reader, but we'll read the stuff
945 * out of the pipe right after the splice_to_pipe(). So set
946 * PIPE_READERS appropriately.
947 */
948 pipe->readers = 1;
949
950 current->splice_pipe = pipe;
951 }
952
953 /*
954 * Do the splice.
955 */
956 ret = 0;
957 bytes = 0;
958 len = sd->total_len;
959 flags = sd->flags;
960
961 /*
962 * Don't block on output, we have to drain the direct pipe.
963 */
964 sd->flags &= ~SPLICE_F_NONBLOCK;
965 more = sd->flags & SPLICE_F_MORE;
966
967 while (len) {
968 size_t read_len;
969 loff_t pos = sd->pos, prev_pos = pos;
970
971 ret = do_splice_to(in, &pos, pipe, len, flags);
972 if (unlikely(ret <= 0))
973 goto out_release;
974
975 read_len = ret;
976 sd->total_len = read_len;
977
978 /*
979 * If more data is pending, set SPLICE_F_MORE
980 * If this is the last data and SPLICE_F_MORE was not set
981 * initially, clears it.
982 */
983 if (read_len < len)
984 sd->flags |= SPLICE_F_MORE;
985 else if (!more)
986 sd->flags &= ~SPLICE_F_MORE;
987 /*
988 * NOTE: nonblocking mode only applies to the input. We
989 * must not do the output in nonblocking mode as then we
990 * could get stuck data in the internal pipe:
991 */
992 ret = actor(pipe, sd);
993 if (unlikely(ret <= 0)) {
994 sd->pos = prev_pos;
995 goto out_release;
996 }
997
998 bytes += ret;
999 len -= ret;
1000 sd->pos = pos;
1001
1002 if (ret < read_len) {
1003 sd->pos = prev_pos + ret;
1004 goto out_release;
1005 }
1006 }
1007
1008done:
1009 pipe->nrbufs = pipe->curbuf = 0;
1010 file_accessed(in);
1011 return bytes;
1012
1013out_release:
1014 /*
1015 * If we did an incomplete transfer we must release
1016 * the pipe buffers in question:
1017 */
1018 for (i = 0; i < pipe->buffers; i++) {
1019 struct pipe_buffer *buf = pipe->bufs + i;
1020
1021 if (buf->ops)
1022 pipe_buf_release(pipe, buf);
1023 }
1024
1025 if (!bytes)
1026 bytes = ret;
1027
1028 goto done;
1029}
1030EXPORT_SYMBOL(splice_direct_to_actor);
1031
1032static int direct_splice_actor(struct pipe_inode_info *pipe,
1033 struct splice_desc *sd)
1034{
1035 struct file *file = sd->u.file;
1036
1037 return do_splice_from(pipe, file, sd->opos, sd->total_len,
1038 sd->flags);
1039}
1040
1041/**
1042 * do_splice_direct - splices data directly between two files
1043 * @in: file to splice from
1044 * @ppos: input file offset
1045 * @out: file to splice to
1046 * @opos: output file offset
1047 * @len: number of bytes to splice
1048 * @flags: splice modifier flags
1049 *
1050 * Description:
1051 * For use by do_sendfile(). splice can easily emulate sendfile, but
1052 * doing it in the application would incur an extra system call
1053 * (splice in + splice out, as compared to just sendfile()). So this helper
1054 * can splice directly through a process-private pipe.
1055 *
1056 */
1057long do_splice_direct(struct file *in, loff_t *ppos, struct file *out,
1058 loff_t *opos, size_t len, unsigned int flags)
1059{
1060 struct splice_desc sd = {
1061 .len = len,
1062 .total_len = len,
1063 .flags = flags,
1064 .pos = *ppos,
1065 .u.file = out,
1066 .opos = opos,
1067 };
1068 long ret;
1069
1070 if (unlikely(!(out->f_mode & FMODE_WRITE)))
1071 return -EBADF;
1072
1073 if (unlikely(out->f_flags & O_APPEND))
1074 return -EINVAL;
1075
1076 ret = rw_verify_area(WRITE, out, opos, len);
1077 if (unlikely(ret < 0))
1078 return ret;
1079
1080 ret = splice_direct_to_actor(in, &sd, direct_splice_actor);
1081 if (ret > 0)
1082 *ppos = sd.pos;
1083
1084 return ret;
1085}
1086EXPORT_SYMBOL(do_splice_direct);
1087
1088static int wait_for_space(struct pipe_inode_info *pipe, unsigned flags)
1089{
1090 for (;;) {
1091 if (unlikely(!pipe->readers)) {
1092 send_sig(SIGPIPE, current, 0);
1093 return -EPIPE;
1094 }
1095 if (pipe->nrbufs != pipe->buffers)
1096 return 0;
1097 if (flags & SPLICE_F_NONBLOCK)
1098 return -EAGAIN;
1099 if (signal_pending(current))
1100 return -ERESTARTSYS;
1101 pipe->waiting_writers++;
1102 pipe_wait(pipe);
1103 pipe->waiting_writers--;
1104 }
1105}
1106
1107static int splice_pipe_to_pipe(struct pipe_inode_info *ipipe,
1108 struct pipe_inode_info *opipe,
1109 size_t len, unsigned int flags);
1110
1111/*
1112 * Determine where to splice to/from.
1113 */
1114static long do_splice(struct file *in, loff_t __user *off_in,
1115 struct file *out, loff_t __user *off_out,
1116 size_t len, unsigned int flags)
1117{
1118 struct pipe_inode_info *ipipe;
1119 struct pipe_inode_info *opipe;
1120 loff_t offset;
1121 long ret;
1122
1123 ipipe = get_pipe_info(in);
1124 opipe = get_pipe_info(out);
1125
1126 if (ipipe && opipe) {
1127 if (off_in || off_out)
1128 return -ESPIPE;
1129
1130 if (!(in->f_mode & FMODE_READ))
1131 return -EBADF;
1132
1133 if (!(out->f_mode & FMODE_WRITE))
1134 return -EBADF;
1135
1136 /* Splicing to self would be fun, but... */
1137 if (ipipe == opipe)
1138 return -EINVAL;
1139
1140 return splice_pipe_to_pipe(ipipe, opipe, len, flags);
1141 }
1142
1143 if (ipipe) {
1144 if (off_in)
1145 return -ESPIPE;
1146 if (off_out) {
1147 if (!(out->f_mode & FMODE_PWRITE))
1148 return -EINVAL;
1149 if (copy_from_user(&offset, off_out, sizeof(loff_t)))
1150 return -EFAULT;
1151 } else {
1152 offset = out->f_pos;
1153 }
1154
1155 if (unlikely(!(out->f_mode & FMODE_WRITE)))
1156 return -EBADF;
1157
1158 if (unlikely(out->f_flags & O_APPEND))
1159 return -EINVAL;
1160
1161 ret = rw_verify_area(WRITE, out, &offset, len);
1162 if (unlikely(ret < 0))
1163 return ret;
1164
1165 file_start_write(out);
1166 ret = do_splice_from(ipipe, out, &offset, len, flags);
1167 file_end_write(out);
1168
1169 if (!off_out)
1170 out->f_pos = offset;
1171 else if (copy_to_user(off_out, &offset, sizeof(loff_t)))
1172 ret = -EFAULT;
1173
1174 return ret;
1175 }
1176
1177 if (opipe) {
1178 if (off_out)
1179 return -ESPIPE;
1180 if (off_in) {
1181 if (!(in->f_mode & FMODE_PREAD))
1182 return -EINVAL;
1183 if (copy_from_user(&offset, off_in, sizeof(loff_t)))
1184 return -EFAULT;
1185 } else {
1186 offset = in->f_pos;
1187 }
1188
1189 pipe_lock(opipe);
1190 ret = wait_for_space(opipe, flags);
1191 if (!ret)
1192 ret = do_splice_to(in, &offset, opipe, len, flags);
1193 pipe_unlock(opipe);
1194 if (ret > 0)
1195 wakeup_pipe_readers(opipe);
1196 if (!off_in)
1197 in->f_pos = offset;
1198 else if (copy_to_user(off_in, &offset, sizeof(loff_t)))
1199 ret = -EFAULT;
1200
1201 return ret;
1202 }
1203
1204 return -EINVAL;
1205}
1206
1207static int iter_to_pipe(struct iov_iter *from,
1208 struct pipe_inode_info *pipe,
1209 unsigned flags)
1210{
1211 struct pipe_buffer buf = {
1212 .ops = &user_page_pipe_buf_ops,
1213 .flags = flags
1214 };
1215 size_t total = 0;
1216 int ret = 0;
1217 bool failed = false;
1218
1219 while (iov_iter_count(from) && !failed) {
1220 struct page *pages[16];
1221 ssize_t copied;
1222 size_t start;
1223 int n;
1224
1225 copied = iov_iter_get_pages(from, pages, ~0UL, 16, &start);
1226 if (copied <= 0) {
1227 ret = copied;
1228 break;
1229 }
1230
1231 for (n = 0; copied; n++, start = 0) {
1232 int size = min_t(int, copied, PAGE_SIZE - start);
1233 if (!failed) {
1234 buf.page = pages[n];
1235 buf.offset = start;
1236 buf.len = size;
1237 ret = add_to_pipe(pipe, &buf);
1238 if (unlikely(ret < 0)) {
1239 failed = true;
1240 } else {
1241 iov_iter_advance(from, ret);
1242 total += ret;
1243 }
1244 } else {
1245 put_page(pages[n]);
1246 }
1247 copied -= size;
1248 }
1249 }
1250 return total ? total : ret;
1251}
1252
1253static int pipe_to_user(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
1254 struct splice_desc *sd)
1255{
1256 int n = copy_page_to_iter(buf->page, buf->offset, sd->len, sd->u.data);
1257 return n == sd->len ? n : -EFAULT;
1258}
1259
1260/*
1261 * For lack of a better implementation, implement vmsplice() to userspace
1262 * as a simple copy of the pipes pages to the user iov.
1263 */
1264static long vmsplice_to_user(struct file *file, const struct iovec __user *uiov,
1265 unsigned long nr_segs, unsigned int flags)
1266{
1267 struct pipe_inode_info *pipe;
1268 struct splice_desc sd;
1269 long ret;
1270 struct iovec iovstack[UIO_FASTIOV];
1271 struct iovec *iov = iovstack;
1272 struct iov_iter iter;
1273
1274 pipe = get_pipe_info(file);
1275 if (!pipe)
1276 return -EBADF;
1277
1278 ret = import_iovec(READ, uiov, nr_segs,
1279 ARRAY_SIZE(iovstack), &iov, &iter);
1280 if (ret < 0)
1281 return ret;
1282
1283 sd.total_len = iov_iter_count(&iter);
1284 sd.len = 0;
1285 sd.flags = flags;
1286 sd.u.data = &iter;
1287 sd.pos = 0;
1288
1289 if (sd.total_len) {
1290 pipe_lock(pipe);
1291 ret = __splice_from_pipe(pipe, &sd, pipe_to_user);
1292 pipe_unlock(pipe);
1293 }
1294
1295 kfree(iov);
1296 return ret;
1297}
1298
1299/*
1300 * vmsplice splices a user address range into a pipe. It can be thought of
1301 * as splice-from-memory, where the regular splice is splice-from-file (or
1302 * to file). In both cases the output is a pipe, naturally.
1303 */
1304static long vmsplice_to_pipe(struct file *file, const struct iovec __user *uiov,
1305 unsigned long nr_segs, unsigned int flags)
1306{
1307 struct pipe_inode_info *pipe;
1308 struct iovec iovstack[UIO_FASTIOV];
1309 struct iovec *iov = iovstack;
1310 struct iov_iter from;
1311 long ret;
1312 unsigned buf_flag = 0;
1313
1314 if (flags & SPLICE_F_GIFT)
1315 buf_flag = PIPE_BUF_FLAG_GIFT;
1316
1317 pipe = get_pipe_info(file);
1318 if (!pipe)
1319 return -EBADF;
1320
1321 ret = import_iovec(WRITE, uiov, nr_segs,
1322 ARRAY_SIZE(iovstack), &iov, &from);
1323 if (ret < 0)
1324 return ret;
1325
1326 pipe_lock(pipe);
1327 ret = wait_for_space(pipe, flags);
1328 if (!ret)
1329 ret = iter_to_pipe(&from, pipe, buf_flag);
1330 pipe_unlock(pipe);
1331 if (ret > 0)
1332 wakeup_pipe_readers(pipe);
1333 kfree(iov);
1334 return ret;
1335}
1336
1337/*
1338 * Note that vmsplice only really supports true splicing _from_ user memory
1339 * to a pipe, not the other way around. Splicing from user memory is a simple
1340 * operation that can be supported without any funky alignment restrictions
1341 * or nasty vm tricks. We simply map in the user memory and fill them into
1342 * a pipe. The reverse isn't quite as easy, though. There are two possible
1343 * solutions for that:
1344 *
1345 * - memcpy() the data internally, at which point we might as well just
1346 * do a regular read() on the buffer anyway.
1347 * - Lots of nasty vm tricks, that are neither fast nor flexible (it
1348 * has restriction limitations on both ends of the pipe).
1349 *
1350 * Currently we punt and implement it as a normal copy, see pipe_to_user().
1351 *
1352 */
1353SYSCALL_DEFINE4(vmsplice, int, fd, const struct iovec __user *, iov,
1354 unsigned long, nr_segs, unsigned int, flags)
1355{
1356 struct fd f;
1357 long error;
1358
1359 if (unlikely(nr_segs > UIO_MAXIOV))
1360 return -EINVAL;
1361 else if (unlikely(!nr_segs))
1362 return 0;
1363
1364 error = -EBADF;
1365 f = fdget(fd);
1366 if (f.file) {
1367 if (f.file->f_mode & FMODE_WRITE)
1368 error = vmsplice_to_pipe(f.file, iov, nr_segs, flags);
1369 else if (f.file->f_mode & FMODE_READ)
1370 error = vmsplice_to_user(f.file, iov, nr_segs, flags);
1371
1372 fdput(f);
1373 }
1374
1375 return error;
1376}
1377
1378#ifdef CONFIG_COMPAT
1379COMPAT_SYSCALL_DEFINE4(vmsplice, int, fd, const struct compat_iovec __user *, iov32,
1380 unsigned int, nr_segs, unsigned int, flags)
1381{
1382 unsigned i;
1383 struct iovec __user *iov;
1384 if (nr_segs > UIO_MAXIOV)
1385 return -EINVAL;
1386 iov = compat_alloc_user_space(nr_segs * sizeof(struct iovec));
1387 for (i = 0; i < nr_segs; i++) {
1388 struct compat_iovec v;
1389 if (get_user(v.iov_base, &iov32[i].iov_base) ||
1390 get_user(v.iov_len, &iov32[i].iov_len) ||
1391 put_user(compat_ptr(v.iov_base), &iov[i].iov_base) ||
1392 put_user(v.iov_len, &iov[i].iov_len))
1393 return -EFAULT;
1394 }
1395 return sys_vmsplice(fd, iov, nr_segs, flags);
1396}
1397#endif
1398
1399SYSCALL_DEFINE6(splice, int, fd_in, loff_t __user *, off_in,
1400 int, fd_out, loff_t __user *, off_out,
1401 size_t, len, unsigned int, flags)
1402{
1403 struct fd in, out;
1404 long error;
1405
1406 if (unlikely(!len))
1407 return 0;
1408
1409 error = -EBADF;
1410 in = fdget(fd_in);
1411 if (in.file) {
1412 if (in.file->f_mode & FMODE_READ) {
1413 out = fdget(fd_out);
1414 if (out.file) {
1415 if (out.file->f_mode & FMODE_WRITE)
1416 error = do_splice(in.file, off_in,
1417 out.file, off_out,
1418 len, flags);
1419 fdput(out);
1420 }
1421 }
1422 fdput(in);
1423 }
1424 return error;
1425}
1426
1427/*
1428 * Make sure there's data to read. Wait for input if we can, otherwise
1429 * return an appropriate error.
1430 */
1431static int ipipe_prep(struct pipe_inode_info *pipe, unsigned int flags)
1432{
1433 int ret;
1434
1435 /*
1436 * Check ->nrbufs without the inode lock first. This function
1437 * is speculative anyways, so missing one is ok.
1438 */
1439 if (pipe->nrbufs)
1440 return 0;
1441
1442 ret = 0;
1443 pipe_lock(pipe);
1444
1445 while (!pipe->nrbufs) {
1446 if (signal_pending(current)) {
1447 ret = -ERESTARTSYS;
1448 break;
1449 }
1450 if (!pipe->writers)
1451 break;
1452 if (!pipe->waiting_writers) {
1453 if (flags & SPLICE_F_NONBLOCK) {
1454 ret = -EAGAIN;
1455 break;
1456 }
1457 }
1458 pipe_wait(pipe);
1459 }
1460
1461 pipe_unlock(pipe);
1462 return ret;
1463}
1464
1465/*
1466 * Make sure there's writeable room. Wait for room if we can, otherwise
1467 * return an appropriate error.
1468 */
1469static int opipe_prep(struct pipe_inode_info *pipe, unsigned int flags)
1470{
1471 int ret;
1472
1473 /*
1474 * Check ->nrbufs without the inode lock first. This function
1475 * is speculative anyways, so missing one is ok.
1476 */
1477 if (pipe->nrbufs < pipe->buffers)
1478 return 0;
1479
1480 ret = 0;
1481 pipe_lock(pipe);
1482
1483 while (pipe->nrbufs >= pipe->buffers) {
1484 if (!pipe->readers) {
1485 send_sig(SIGPIPE, current, 0);
1486 ret = -EPIPE;
1487 break;
1488 }
1489 if (flags & SPLICE_F_NONBLOCK) {
1490 ret = -EAGAIN;
1491 break;
1492 }
1493 if (signal_pending(current)) {
1494 ret = -ERESTARTSYS;
1495 break;
1496 }
1497 pipe->waiting_writers++;
1498 pipe_wait(pipe);
1499 pipe->waiting_writers--;
1500 }
1501
1502 pipe_unlock(pipe);
1503 return ret;
1504}
1505
1506/*
1507 * Splice contents of ipipe to opipe.
1508 */
1509static int splice_pipe_to_pipe(struct pipe_inode_info *ipipe,
1510 struct pipe_inode_info *opipe,
1511 size_t len, unsigned int flags)
1512{
1513 struct pipe_buffer *ibuf, *obuf;
1514 int ret = 0, nbuf;
1515 bool input_wakeup = false;
1516
1517
1518retry:
1519 ret = ipipe_prep(ipipe, flags);
1520 if (ret)
1521 return ret;
1522
1523 ret = opipe_prep(opipe, flags);
1524 if (ret)
1525 return ret;
1526
1527 /*
1528 * Potential ABBA deadlock, work around it by ordering lock
1529 * grabbing by pipe info address. Otherwise two different processes
1530 * could deadlock (one doing tee from A -> B, the other from B -> A).
1531 */
1532 pipe_double_lock(ipipe, opipe);
1533
1534 do {
1535 if (!opipe->readers) {
1536 send_sig(SIGPIPE, current, 0);
1537 if (!ret)
1538 ret = -EPIPE;
1539 break;
1540 }
1541
1542 if (!ipipe->nrbufs && !ipipe->writers)
1543 break;
1544
1545 /*
1546 * Cannot make any progress, because either the input
1547 * pipe is empty or the output pipe is full.
1548 */
1549 if (!ipipe->nrbufs || opipe->nrbufs >= opipe->buffers) {
1550 /* Already processed some buffers, break */
1551 if (ret)
1552 break;
1553
1554 if (flags & SPLICE_F_NONBLOCK) {
1555 ret = -EAGAIN;
1556 break;
1557 }
1558
1559 /*
1560 * We raced with another reader/writer and haven't
1561 * managed to process any buffers. A zero return
1562 * value means EOF, so retry instead.
1563 */
1564 pipe_unlock(ipipe);
1565 pipe_unlock(opipe);
1566 goto retry;
1567 }
1568
1569 ibuf = ipipe->bufs + ipipe->curbuf;
1570 nbuf = (opipe->curbuf + opipe->nrbufs) & (opipe->buffers - 1);
1571 obuf = opipe->bufs + nbuf;
1572
1573 if (len >= ibuf->len) {
1574 /*
1575 * Simply move the whole buffer from ipipe to opipe
1576 */
1577 *obuf = *ibuf;
1578 ibuf->ops = NULL;
1579 opipe->nrbufs++;
1580 ipipe->curbuf = (ipipe->curbuf + 1) & (ipipe->buffers - 1);
1581 ipipe->nrbufs--;
1582 input_wakeup = true;
1583 } else {
1584 /*
1585 * Get a reference to this pipe buffer,
1586 * so we can copy the contents over.
1587 */
1588 pipe_buf_get(ipipe, ibuf);
1589 *obuf = *ibuf;
1590
1591 /*
1592 * Don't inherit the gift flag, we need to
1593 * prevent multiple steals of this page.
1594 */
1595 obuf->flags &= ~PIPE_BUF_FLAG_GIFT;
1596
1597 pipe_buf_mark_unmergeable(obuf);
1598
1599 obuf->len = len;
1600 opipe->nrbufs++;
1601 ibuf->offset += obuf->len;
1602 ibuf->len -= obuf->len;
1603 }
1604 ret += obuf->len;
1605 len -= obuf->len;
1606 } while (len);
1607
1608 pipe_unlock(ipipe);
1609 pipe_unlock(opipe);
1610
1611 /*
1612 * If we put data in the output pipe, wakeup any potential readers.
1613 */
1614 if (ret > 0)
1615 wakeup_pipe_readers(opipe);
1616
1617 if (input_wakeup)
1618 wakeup_pipe_writers(ipipe);
1619
1620 return ret;
1621}
1622
1623/*
1624 * Link contents of ipipe to opipe.
1625 */
1626static int link_pipe(struct pipe_inode_info *ipipe,
1627 struct pipe_inode_info *opipe,
1628 size_t len, unsigned int flags)
1629{
1630 struct pipe_buffer *ibuf, *obuf;
1631 int ret = 0, i = 0, nbuf;
1632
1633 /*
1634 * Potential ABBA deadlock, work around it by ordering lock
1635 * grabbing by pipe info address. Otherwise two different processes
1636 * could deadlock (one doing tee from A -> B, the other from B -> A).
1637 */
1638 pipe_double_lock(ipipe, opipe);
1639
1640 do {
1641 if (!opipe->readers) {
1642 send_sig(SIGPIPE, current, 0);
1643 if (!ret)
1644 ret = -EPIPE;
1645 break;
1646 }
1647
1648 /*
1649 * If we have iterated all input buffers or ran out of
1650 * output room, break.
1651 */
1652 if (i >= ipipe->nrbufs || opipe->nrbufs >= opipe->buffers)
1653 break;
1654
1655 ibuf = ipipe->bufs + ((ipipe->curbuf + i) & (ipipe->buffers-1));
1656 nbuf = (opipe->curbuf + opipe->nrbufs) & (opipe->buffers - 1);
1657
1658 /*
1659 * Get a reference to this pipe buffer,
1660 * so we can copy the contents over.
1661 */
1662 pipe_buf_get(ipipe, ibuf);
1663
1664 obuf = opipe->bufs + nbuf;
1665 *obuf = *ibuf;
1666
1667 /*
1668 * Don't inherit the gift flag, we need to
1669 * prevent multiple steals of this page.
1670 */
1671 obuf->flags &= ~PIPE_BUF_FLAG_GIFT;
1672
1673 pipe_buf_mark_unmergeable(obuf);
1674
1675 if (obuf->len > len)
1676 obuf->len = len;
1677
1678 opipe->nrbufs++;
1679 ret += obuf->len;
1680 len -= obuf->len;
1681 i++;
1682 } while (len);
1683
1684 /*
1685 * return EAGAIN if we have the potential of some data in the
1686 * future, otherwise just return 0
1687 */
1688 if (!ret && ipipe->waiting_writers && (flags & SPLICE_F_NONBLOCK))
1689 ret = -EAGAIN;
1690
1691 pipe_unlock(ipipe);
1692 pipe_unlock(opipe);
1693
1694 /*
1695 * If we put data in the output pipe, wakeup any potential readers.
1696 */
1697 if (ret > 0)
1698 wakeup_pipe_readers(opipe);
1699
1700 return ret;
1701}
1702
1703/*
1704 * This is a tee(1) implementation that works on pipes. It doesn't copy
1705 * any data, it simply references the 'in' pages on the 'out' pipe.
1706 * The 'flags' used are the SPLICE_F_* variants, currently the only
1707 * applicable one is SPLICE_F_NONBLOCK.
1708 */
1709static long do_tee(struct file *in, struct file *out, size_t len,
1710 unsigned int flags)
1711{
1712 struct pipe_inode_info *ipipe = get_pipe_info(in);
1713 struct pipe_inode_info *opipe = get_pipe_info(out);
1714 int ret = -EINVAL;
1715
1716 /*
1717 * Duplicate the contents of ipipe to opipe without actually
1718 * copying the data.
1719 */
1720 if (ipipe && opipe && ipipe != opipe) {
1721 /*
1722 * Keep going, unless we encounter an error. The ipipe/opipe
1723 * ordering doesn't really matter.
1724 */
1725 ret = ipipe_prep(ipipe, flags);
1726 if (!ret) {
1727 ret = opipe_prep(opipe, flags);
1728 if (!ret)
1729 ret = link_pipe(ipipe, opipe, len, flags);
1730 }
1731 }
1732
1733 return ret;
1734}
1735
1736SYSCALL_DEFINE4(tee, int, fdin, int, fdout, size_t, len, unsigned int, flags)
1737{
1738 struct fd in;
1739 int error;
1740
1741 if (unlikely(!len))
1742 return 0;
1743
1744 error = -EBADF;
1745 in = fdget(fdin);
1746 if (in.file) {
1747 if (in.file->f_mode & FMODE_READ) {
1748 struct fd out = fdget(fdout);
1749 if (out.file) {
1750 if (out.file->f_mode & FMODE_WRITE)
1751 error = do_tee(in.file, out.file,
1752 len, flags);
1753 fdput(out);
1754 }
1755 }
1756 fdput(in);
1757 }
1758
1759 return error;
1760}
1761
generated by cgit at 2024-05-18 12:00:52 (GMT)