GNU Linux-libre 5.19-rc6-gnu
[releases.git] / fs / splice.c
1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * "splice": joining two ropes together by interweaving their strands.
4  *
5  * This is the "extended pipe" functionality, where a pipe is used as
6  * an arbitrary in-memory buffer. Think of a pipe as a small kernel
7  * buffer that you can use to transfer data from one end to the other.
8  *
9  * The traditional unix read/write is extended with a "splice()" operation
10  * that transfers data buffers to or from a pipe buffer.
11  *
12  * Named by Larry McVoy, original implementation from Linus, extended by
13  * Jens to support splicing to files, network, direct splicing, etc and
14  * fixing lots of bugs.
15  *
16  * Copyright (C) 2005-2006 Jens Axboe <axboe@kernel.dk>
17  * Copyright (C) 2005-2006 Linus Torvalds <torvalds@osdl.org>
18  * Copyright (C) 2006 Ingo Molnar <mingo@elte.hu>
19  *
20  */
21 #include <linux/bvec.h>
22 #include <linux/fs.h>
23 #include <linux/file.h>
24 #include <linux/pagemap.h>
25 #include <linux/splice.h>
26 #include <linux/memcontrol.h>
27 #include <linux/mm_inline.h>
28 #include <linux/swap.h>
29 #include <linux/writeback.h>
30 #include <linux/export.h>
31 #include <linux/syscalls.h>
32 #include <linux/uio.h>
33 #include <linux/security.h>
34 #include <linux/gfp.h>
35 #include <linux/socket.h>
36 #include <linux/sched/signal.h>
37
38 #include "internal.h"
39
40 /*
41  * Attempt to steal a page from a pipe buffer. This should perhaps go into
42  * a vm helper function, it's already simplified quite a bit by the
43  * addition of remove_mapping(). If success is returned, the caller may
44  * attempt to reuse this page for another destination.
45  */
46 static bool page_cache_pipe_buf_try_steal(struct pipe_inode_info *pipe,
47                 struct pipe_buffer *buf)
48 {
49         struct folio *folio = page_folio(buf->page);
50         struct address_space *mapping;
51
52         folio_lock(folio);
53
54         mapping = folio_mapping(folio);
55         if (mapping) {
56                 WARN_ON(!folio_test_uptodate(folio));
57
58                 /*
59                  * At least for ext2 with nobh option, we need to wait on
60                  * writeback completing on this folio, since we'll remove it
61                  * from the pagecache.  Otherwise truncate wont wait on the
62                  * folio, allowing the disk blocks to be reused by someone else
63                  * before we actually wrote our data to them. fs corruption
64                  * ensues.
65                  */
66                 folio_wait_writeback(folio);
67
68                 if (folio_has_private(folio) &&
69                     !filemap_release_folio(folio, GFP_KERNEL))
70                         goto out_unlock;
71
72                 /*
73                  * If we succeeded in removing the mapping, set LRU flag
74                  * and return good.
75                  */
76                 if (remove_mapping(mapping, folio)) {
77                         buf->flags |= PIPE_BUF_FLAG_LRU;
78                         return true;
79                 }
80         }
81
82         /*
83          * Raced with truncate or failed to remove folio from current
84          * address space, unlock and return failure.
85          */
86 out_unlock:
87         folio_unlock(folio);
88         return false;
89 }
90
91 static void page_cache_pipe_buf_release(struct pipe_inode_info *pipe,
92                                         struct pipe_buffer *buf)
93 {
94         put_page(buf->page);
95         buf->flags &= ~PIPE_BUF_FLAG_LRU;
96 }
97
98 /*
99  * Check whether the contents of buf is OK to access. Since the content
100  * is a page cache page, IO may be in flight.
101  */
102 static int page_cache_pipe_buf_confirm(struct pipe_inode_info *pipe,
103                                        struct pipe_buffer *buf)
104 {
105         struct page *page = buf->page;
106         int err;
107
108         if (!PageUptodate(page)) {
109                 lock_page(page);
110
111                 /*
112                  * Page got truncated/unhashed. This will cause a 0-byte
113                  * splice, if this is the first page.
114                  */
115                 if (!page->mapping) {
116                         err = -ENODATA;
117                         goto error;
118                 }
119
120                 /*
121                  * Uh oh, read-error from disk.
122                  */
123                 if (!PageUptodate(page)) {
124                         err = -EIO;
125                         goto error;
126                 }
127
128                 /*
129                  * Page is ok afterall, we are done.
130                  */
131                 unlock_page(page);
132         }
133
134         return 0;
135 error:
136         unlock_page(page);
137         return err;
138 }
139
140 const struct pipe_buf_operations page_cache_pipe_buf_ops = {
141         .confirm        = page_cache_pipe_buf_confirm,
142         .release        = page_cache_pipe_buf_release,
143         .try_steal      = page_cache_pipe_buf_try_steal,
144         .get            = generic_pipe_buf_get,
145 };
146
147 static bool user_page_pipe_buf_try_steal(struct pipe_inode_info *pipe,
148                 struct pipe_buffer *buf)
149 {
150         if (!(buf->flags & PIPE_BUF_FLAG_GIFT))
151                 return false;
152
153         buf->flags |= PIPE_BUF_FLAG_LRU;
154         return generic_pipe_buf_try_steal(pipe, buf);
155 }
156
157 static const struct pipe_buf_operations user_page_pipe_buf_ops = {
158         .release        = page_cache_pipe_buf_release,
159         .try_steal      = user_page_pipe_buf_try_steal,
160         .get            = generic_pipe_buf_get,
161 };
162
163 static void wakeup_pipe_readers(struct pipe_inode_info *pipe)
164 {
165         smp_mb();
166         if (waitqueue_active(&pipe->rd_wait))
167                 wake_up_interruptible(&pipe->rd_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  */
182 ssize_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         unsigned int tail = pipe->tail;
187         unsigned int head = pipe->head;
188         unsigned int mask = pipe->ring_size - 1;
189         int ret = 0, page_nr = 0;
190
191         if (!spd_pages)
192                 return 0;
193
194         if (unlikely(!pipe->readers)) {
195                 send_sig(SIGPIPE, current, 0);
196                 ret = -EPIPE;
197                 goto out;
198         }
199
200         while (!pipe_full(head, tail, pipe->max_usage)) {
201                 struct pipe_buffer *buf = &pipe->bufs[head & mask];
202
203                 buf->page = spd->pages[page_nr];
204                 buf->offset = spd->partial[page_nr].offset;
205                 buf->len = spd->partial[page_nr].len;
206                 buf->private = spd->partial[page_nr].private;
207                 buf->ops = spd->ops;
208                 buf->flags = 0;
209
210                 head++;
211                 pipe->head = head;
212                 page_nr++;
213                 ret += buf->len;
214
215                 if (!--spd->nr_pages)
216                         break;
217         }
218
219         if (!ret)
220                 ret = -EAGAIN;
221
222 out:
223         while (page_nr < spd_pages)
224                 spd->spd_release(spd, page_nr++);
225
226         return ret;
227 }
228 EXPORT_SYMBOL_GPL(splice_to_pipe);
229
230 ssize_t add_to_pipe(struct pipe_inode_info *pipe, struct pipe_buffer *buf)
231 {
232         unsigned int head = pipe->head;
233         unsigned int tail = pipe->tail;
234         unsigned int mask = pipe->ring_size - 1;
235         int ret;
236
237         if (unlikely(!pipe->readers)) {
238                 send_sig(SIGPIPE, current, 0);
239                 ret = -EPIPE;
240         } else if (pipe_full(head, tail, pipe->max_usage)) {
241                 ret = -EAGAIN;
242         } else {
243                 pipe->bufs[head & mask] = *buf;
244                 pipe->head = head + 1;
245                 return buf->len;
246         }
247         pipe_buf_release(pipe, buf);
248         return ret;
249 }
250 EXPORT_SYMBOL(add_to_pipe);
251
252 /*
253  * Check if we need to grow the arrays holding pages and partial page
254  * descriptions.
255  */
256 int splice_grow_spd(const struct pipe_inode_info *pipe, struct splice_pipe_desc *spd)
257 {
258         unsigned int max_usage = READ_ONCE(pipe->max_usage);
259
260         spd->nr_pages_max = max_usage;
261         if (max_usage <= PIPE_DEF_BUFFERS)
262                 return 0;
263
264         spd->pages = kmalloc_array(max_usage, sizeof(struct page *), GFP_KERNEL);
265         spd->partial = kmalloc_array(max_usage, sizeof(struct partial_page),
266                                      GFP_KERNEL);
267
268         if (spd->pages && spd->partial)
269                 return 0;
270
271         kfree(spd->pages);
272         kfree(spd->partial);
273         return -ENOMEM;
274 }
275
276 void splice_shrink_spd(struct splice_pipe_desc *spd)
277 {
278         if (spd->nr_pages_max <= PIPE_DEF_BUFFERS)
279                 return;
280
281         kfree(spd->pages);
282         kfree(spd->partial);
283 }
284
285 /**
286  * generic_file_splice_read - splice data from file to a pipe
287  * @in:         file to splice from
288  * @ppos:       position in @in
289  * @pipe:       pipe to splice to
290  * @len:        number of bytes to splice
291  * @flags:      splice modifier flags
292  *
293  * Description:
294  *    Will read pages from given file and fill them into a pipe. Can be
295  *    used as long as it has more or less sane ->read_iter().
296  *
297  */
298 ssize_t generic_file_splice_read(struct file *in, loff_t *ppos,
299                                  struct pipe_inode_info *pipe, size_t len,
300                                  unsigned int flags)
301 {
302         struct iov_iter to;
303         struct kiocb kiocb;
304         unsigned int i_head;
305         int ret;
306
307         iov_iter_pipe(&to, READ, pipe, len);
308         i_head = to.head;
309         init_sync_kiocb(&kiocb, in);
310         kiocb.ki_pos = *ppos;
311         ret = call_read_iter(in, &kiocb, &to);
312         if (ret > 0) {
313                 *ppos = kiocb.ki_pos;
314                 file_accessed(in);
315         } else if (ret < 0) {
316                 to.head = i_head;
317                 to.iov_offset = 0;
318                 iov_iter_advance(&to, 0); /* to free what was emitted */
319                 /*
320                  * callers of ->splice_read() expect -EAGAIN on
321                  * "can't put anything in there", rather than -EFAULT.
322                  */
323                 if (ret == -EFAULT)
324                         ret = -EAGAIN;
325         }
326
327         return ret;
328 }
329 EXPORT_SYMBOL(generic_file_splice_read);
330
331 const struct pipe_buf_operations default_pipe_buf_ops = {
332         .release        = generic_pipe_buf_release,
333         .try_steal      = generic_pipe_buf_try_steal,
334         .get            = generic_pipe_buf_get,
335 };
336
337 /* Pipe buffer operations for a socket and similar. */
338 const struct pipe_buf_operations nosteal_pipe_buf_ops = {
339         .release        = generic_pipe_buf_release,
340         .get            = generic_pipe_buf_get,
341 };
342 EXPORT_SYMBOL(nosteal_pipe_buf_ops);
343
344 /*
345  * Send 'sd->len' bytes to socket from 'sd->file' at position 'sd->pos'
346  * using sendpage(). Return the number of bytes sent.
347  */
348 static int pipe_to_sendpage(struct pipe_inode_info *pipe,
349                             struct pipe_buffer *buf, struct splice_desc *sd)
350 {
351         struct file *file = sd->u.file;
352         loff_t pos = sd->pos;
353         int more;
354
355         if (!likely(file->f_op->sendpage))
356                 return -EINVAL;
357
358         more = (sd->flags & SPLICE_F_MORE) ? MSG_MORE : 0;
359
360         if (sd->len < sd->total_len &&
361             pipe_occupancy(pipe->head, pipe->tail) > 1)
362                 more |= MSG_SENDPAGE_NOTLAST;
363
364         return file->f_op->sendpage(file, buf->page, buf->offset,
365                                     sd->len, &pos, more);
366 }
367
368 static void wakeup_pipe_writers(struct pipe_inode_info *pipe)
369 {
370         smp_mb();
371         if (waitqueue_active(&pipe->wr_wait))
372                 wake_up_interruptible(&pipe->wr_wait);
373         kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
374 }
375
376 /**
377  * splice_from_pipe_feed - feed available data from a pipe to a file
378  * @pipe:       pipe to splice from
379  * @sd:         information to @actor
380  * @actor:      handler that splices the data
381  *
382  * Description:
383  *    This function loops over the pipe and calls @actor to do the
384  *    actual moving of a single struct pipe_buffer to the desired
385  *    destination.  It returns when there's no more buffers left in
386  *    the pipe or if the requested number of bytes (@sd->total_len)
387  *    have been copied.  It returns a positive number (one) if the
388  *    pipe needs to be filled with more data, zero if the required
389  *    number of bytes have been copied and -errno on error.
390  *
391  *    This, together with splice_from_pipe_{begin,end,next}, may be
392  *    used to implement the functionality of __splice_from_pipe() when
393  *    locking is required around copying the pipe buffers to the
394  *    destination.
395  */
396 static int splice_from_pipe_feed(struct pipe_inode_info *pipe, struct splice_desc *sd,
397                           splice_actor *actor)
398 {
399         unsigned int head = pipe->head;
400         unsigned int tail = pipe->tail;
401         unsigned int mask = pipe->ring_size - 1;
402         int ret;
403
404         while (!pipe_empty(head, tail)) {
405                 struct pipe_buffer *buf = &pipe->bufs[tail & mask];
406
407                 sd->len = buf->len;
408                 if (sd->len > sd->total_len)
409                         sd->len = sd->total_len;
410
411                 ret = pipe_buf_confirm(pipe, buf);
412                 if (unlikely(ret)) {
413                         if (ret == -ENODATA)
414                                 ret = 0;
415                         return ret;
416                 }
417
418                 ret = actor(pipe, buf, sd);
419                 if (ret <= 0)
420                         return ret;
421
422                 buf->offset += ret;
423                 buf->len -= ret;
424
425                 sd->num_spliced += ret;
426                 sd->len -= ret;
427                 sd->pos += ret;
428                 sd->total_len -= ret;
429
430                 if (!buf->len) {
431                         pipe_buf_release(pipe, buf);
432                         tail++;
433                         pipe->tail = tail;
434                         if (pipe->files)
435                                 sd->need_wakeup = true;
436                 }
437
438                 if (!sd->total_len)
439                         return 0;
440         }
441
442         return 1;
443 }
444
445 /* We know we have a pipe buffer, but maybe it's empty? */
446 static inline bool eat_empty_buffer(struct pipe_inode_info *pipe)
447 {
448         unsigned int tail = pipe->tail;
449         unsigned int mask = pipe->ring_size - 1;
450         struct pipe_buffer *buf = &pipe->bufs[tail & mask];
451
452         if (unlikely(!buf->len)) {
453                 pipe_buf_release(pipe, buf);
454                 pipe->tail = tail+1;
455                 return true;
456         }
457
458         return false;
459 }
460
461 /**
462  * splice_from_pipe_next - wait for some data to splice from
463  * @pipe:       pipe to splice from
464  * @sd:         information about the splice operation
465  *
466  * Description:
467  *    This function will wait for some data and return a positive
468  *    value (one) if pipe buffers are available.  It will return zero
469  *    or -errno if no more data needs to be spliced.
470  */
471 static int splice_from_pipe_next(struct pipe_inode_info *pipe, struct splice_desc *sd)
472 {
473         /*
474          * Check for signal early to make process killable when there are
475          * always buffers available
476          */
477         if (signal_pending(current))
478                 return -ERESTARTSYS;
479
480 repeat:
481         while (pipe_empty(pipe->head, pipe->tail)) {
482                 if (!pipe->writers)
483                         return 0;
484
485                 if (sd->num_spliced)
486                         return 0;
487
488                 if (sd->flags & SPLICE_F_NONBLOCK)
489                         return -EAGAIN;
490
491                 if (signal_pending(current))
492                         return -ERESTARTSYS;
493
494                 if (sd->need_wakeup) {
495                         wakeup_pipe_writers(pipe);
496                         sd->need_wakeup = false;
497                 }
498
499                 pipe_wait_readable(pipe);
500         }
501
502         if (eat_empty_buffer(pipe))
503                 goto repeat;
504
505         return 1;
506 }
507
508 /**
509  * splice_from_pipe_begin - start splicing from pipe
510  * @sd:         information about the splice operation
511  *
512  * Description:
513  *    This function should be called before a loop containing
514  *    splice_from_pipe_next() and splice_from_pipe_feed() to
515  *    initialize the necessary fields of @sd.
516  */
517 static void splice_from_pipe_begin(struct splice_desc *sd)
518 {
519         sd->num_spliced = 0;
520         sd->need_wakeup = false;
521 }
522
523 /**
524  * splice_from_pipe_end - finish splicing from pipe
525  * @pipe:       pipe to splice from
526  * @sd:         information about the splice operation
527  *
528  * Description:
529  *    This function will wake up pipe writers if necessary.  It should
530  *    be called after a loop containing splice_from_pipe_next() and
531  *    splice_from_pipe_feed().
532  */
533 static void splice_from_pipe_end(struct pipe_inode_info *pipe, struct splice_desc *sd)
534 {
535         if (sd->need_wakeup)
536                 wakeup_pipe_writers(pipe);
537 }
538
539 /**
540  * __splice_from_pipe - splice data from a pipe to given actor
541  * @pipe:       pipe to splice from
542  * @sd:         information to @actor
543  * @actor:      handler that splices the data
544  *
545  * Description:
546  *    This function does little more than loop over the pipe and call
547  *    @actor to do the actual moving of a single struct pipe_buffer to
548  *    the desired destination. See pipe_to_file, pipe_to_sendpage, or
549  *    pipe_to_user.
550  *
551  */
552 ssize_t __splice_from_pipe(struct pipe_inode_info *pipe, struct splice_desc *sd,
553                            splice_actor *actor)
554 {
555         int ret;
556
557         splice_from_pipe_begin(sd);
558         do {
559                 cond_resched();
560                 ret = splice_from_pipe_next(pipe, sd);
561                 if (ret > 0)
562                         ret = splice_from_pipe_feed(pipe, sd, actor);
563         } while (ret > 0);
564         splice_from_pipe_end(pipe, sd);
565
566         return sd->num_spliced ? sd->num_spliced : ret;
567 }
568 EXPORT_SYMBOL(__splice_from_pipe);
569
570 /**
571  * splice_from_pipe - splice data from a pipe to a file
572  * @pipe:       pipe to splice from
573  * @out:        file to splice to
574  * @ppos:       position in @out
575  * @len:        how many bytes to splice
576  * @flags:      splice modifier flags
577  * @actor:      handler that splices the data
578  *
579  * Description:
580  *    See __splice_from_pipe. This function locks the pipe inode,
581  *    otherwise it's identical to __splice_from_pipe().
582  *
583  */
584 ssize_t splice_from_pipe(struct pipe_inode_info *pipe, struct file *out,
585                          loff_t *ppos, size_t len, unsigned int flags,
586                          splice_actor *actor)
587 {
588         ssize_t ret;
589         struct splice_desc sd = {
590                 .total_len = len,
591                 .flags = flags,
592                 .pos = *ppos,
593                 .u.file = out,
594         };
595
596         pipe_lock(pipe);
597         ret = __splice_from_pipe(pipe, &sd, actor);
598         pipe_unlock(pipe);
599
600         return ret;
601 }
602
603 /**
604  * iter_file_splice_write - splice data from a pipe to a file
605  * @pipe:       pipe info
606  * @out:        file to write to
607  * @ppos:       position in @out
608  * @len:        number of bytes to splice
609  * @flags:      splice modifier flags
610  *
611  * Description:
612  *    Will either move or copy pages (determined by @flags options) from
613  *    the given pipe inode to the given file.
614  *    This one is ->write_iter-based.
615  *
616  */
617 ssize_t
618 iter_file_splice_write(struct pipe_inode_info *pipe, struct file *out,
619                           loff_t *ppos, size_t len, unsigned int flags)
620 {
621         struct splice_desc sd = {
622                 .total_len = len,
623                 .flags = flags,
624                 .pos = *ppos,
625                 .u.file = out,
626         };
627         int nbufs = pipe->max_usage;
628         struct bio_vec *array = kcalloc(nbufs, sizeof(struct bio_vec),
629                                         GFP_KERNEL);
630         ssize_t ret;
631
632         if (unlikely(!array))
633                 return -ENOMEM;
634
635         pipe_lock(pipe);
636
637         splice_from_pipe_begin(&sd);
638         while (sd.total_len) {
639                 struct iov_iter from;
640                 unsigned int head, tail, mask;
641                 size_t left;
642                 int n;
643
644                 ret = splice_from_pipe_next(pipe, &sd);
645                 if (ret <= 0)
646                         break;
647
648                 if (unlikely(nbufs < pipe->max_usage)) {
649                         kfree(array);
650                         nbufs = pipe->max_usage;
651                         array = kcalloc(nbufs, sizeof(struct bio_vec),
652                                         GFP_KERNEL);
653                         if (!array) {
654                                 ret = -ENOMEM;
655                                 break;
656                         }
657                 }
658
659                 head = pipe->head;
660                 tail = pipe->tail;
661                 mask = pipe->ring_size - 1;
662
663                 /* build the vector */
664                 left = sd.total_len;
665                 for (n = 0; !pipe_empty(head, tail) && left && n < nbufs; tail++) {
666                         struct pipe_buffer *buf = &pipe->bufs[tail & mask];
667                         size_t this_len = buf->len;
668
669                         /* zero-length bvecs are not supported, skip them */
670                         if (!this_len)
671                                 continue;
672                         this_len = min(this_len, left);
673
674                         ret = pipe_buf_confirm(pipe, buf);
675                         if (unlikely(ret)) {
676                                 if (ret == -ENODATA)
677                                         ret = 0;
678                                 goto done;
679                         }
680
681                         array[n].bv_page = buf->page;
682                         array[n].bv_len = this_len;
683                         array[n].bv_offset = buf->offset;
684                         left -= this_len;
685                         n++;
686                 }
687
688                 iov_iter_bvec(&from, WRITE, array, n, sd.total_len - left);
689                 ret = vfs_iter_write(out, &from, &sd.pos, 0);
690                 if (ret <= 0)
691                         break;
692
693                 sd.num_spliced += ret;
694                 sd.total_len -= ret;
695                 *ppos = sd.pos;
696
697                 /* dismiss the fully eaten buffers, adjust the partial one */
698                 tail = pipe->tail;
699                 while (ret) {
700                         struct pipe_buffer *buf = &pipe->bufs[tail & mask];
701                         if (ret >= buf->len) {
702                                 ret -= buf->len;
703                                 buf->len = 0;
704                                 pipe_buf_release(pipe, buf);
705                                 tail++;
706                                 pipe->tail = tail;
707                                 if (pipe->files)
708                                         sd.need_wakeup = true;
709                         } else {
710                                 buf->offset += ret;
711                                 buf->len -= ret;
712                                 ret = 0;
713                         }
714                 }
715         }
716 done:
717         kfree(array);
718         splice_from_pipe_end(pipe, &sd);
719
720         pipe_unlock(pipe);
721
722         if (sd.num_spliced)
723                 ret = sd.num_spliced;
724
725         return ret;
726 }
727
728 EXPORT_SYMBOL(iter_file_splice_write);
729
730 /**
731  * generic_splice_sendpage - splice data from a pipe to a socket
732  * @pipe:       pipe to splice from
733  * @out:        socket to write to
734  * @ppos:       position in @out
735  * @len:        number of bytes to splice
736  * @flags:      splice modifier flags
737  *
738  * Description:
739  *    Will send @len bytes from the pipe to a network socket. No data copying
740  *    is involved.
741  *
742  */
743 ssize_t generic_splice_sendpage(struct pipe_inode_info *pipe, struct file *out,
744                                 loff_t *ppos, size_t len, unsigned int flags)
745 {
746         return splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_sendpage);
747 }
748
749 EXPORT_SYMBOL(generic_splice_sendpage);
750
751 static int warn_unsupported(struct file *file, const char *op)
752 {
753         pr_debug_ratelimited(
754                 "splice %s not supported for file %pD4 (pid: %d comm: %.20s)\n",
755                 op, file, current->pid, current->comm);
756         return -EINVAL;
757 }
758
759 /*
760  * Attempt to initiate a splice from pipe to file.
761  */
762 static long do_splice_from(struct pipe_inode_info *pipe, struct file *out,
763                            loff_t *ppos, size_t len, unsigned int flags)
764 {
765         if (unlikely(!out->f_op->splice_write))
766                 return warn_unsupported(out, "write");
767         return out->f_op->splice_write(pipe, out, ppos, len, flags);
768 }
769
770 /*
771  * Attempt to initiate a splice from a file to a pipe.
772  */
773 static long do_splice_to(struct file *in, loff_t *ppos,
774                          struct pipe_inode_info *pipe, size_t len,
775                          unsigned int flags)
776 {
777         unsigned int p_space;
778         int ret;
779
780         if (unlikely(!(in->f_mode & FMODE_READ)))
781                 return -EBADF;
782
783         /* Don't try to read more the pipe has space for. */
784         p_space = pipe->max_usage - pipe_occupancy(pipe->head, pipe->tail);
785         len = min_t(size_t, len, p_space << PAGE_SHIFT);
786
787         ret = rw_verify_area(READ, in, ppos, len);
788         if (unlikely(ret < 0))
789                 return ret;
790
791         if (unlikely(len > MAX_RW_COUNT))
792                 len = MAX_RW_COUNT;
793
794         if (unlikely(!in->f_op->splice_read))
795                 return warn_unsupported(in, "read");
796         return in->f_op->splice_read(in, ppos, pipe, len, flags);
797 }
798
799 /**
800  * splice_direct_to_actor - splices data directly between two non-pipes
801  * @in:         file to splice from
802  * @sd:         actor information on where to splice to
803  * @actor:      handles the data splicing
804  *
805  * Description:
806  *    This is a special case helper to splice directly between two
807  *    points, without requiring an explicit pipe. Internally an allocated
808  *    pipe is cached in the process, and reused during the lifetime of
809  *    that process.
810  *
811  */
812 ssize_t splice_direct_to_actor(struct file *in, struct splice_desc *sd,
813                                splice_direct_actor *actor)
814 {
815         struct pipe_inode_info *pipe;
816         long ret, bytes;
817         umode_t i_mode;
818         size_t len;
819         int i, flags, more;
820
821         /*
822          * We require the input being a regular file, as we don't want to
823          * randomly drop data for eg socket -> socket splicing. Use the
824          * piped splicing for that!
825          */
826         i_mode = file_inode(in)->i_mode;
827         if (unlikely(!S_ISREG(i_mode) && !S_ISBLK(i_mode)))
828                 return -EINVAL;
829
830         /*
831          * neither in nor out is a pipe, setup an internal pipe attached to
832          * 'out' and transfer the wanted data from 'in' to 'out' through that
833          */
834         pipe = current->splice_pipe;
835         if (unlikely(!pipe)) {
836                 pipe = alloc_pipe_info();
837                 if (!pipe)
838                         return -ENOMEM;
839
840                 /*
841                  * We don't have an immediate reader, but we'll read the stuff
842                  * out of the pipe right after the splice_to_pipe(). So set
843                  * PIPE_READERS appropriately.
844                  */
845                 pipe->readers = 1;
846
847                 current->splice_pipe = pipe;
848         }
849
850         /*
851          * Do the splice.
852          */
853         ret = 0;
854         bytes = 0;
855         len = sd->total_len;
856         flags = sd->flags;
857
858         /*
859          * Don't block on output, we have to drain the direct pipe.
860          */
861         sd->flags &= ~SPLICE_F_NONBLOCK;
862         more = sd->flags & SPLICE_F_MORE;
863
864         WARN_ON_ONCE(!pipe_empty(pipe->head, pipe->tail));
865
866         while (len) {
867                 size_t read_len;
868                 loff_t pos = sd->pos, prev_pos = pos;
869
870                 ret = do_splice_to(in, &pos, pipe, len, flags);
871                 if (unlikely(ret <= 0))
872                         goto out_release;
873
874                 read_len = ret;
875                 sd->total_len = read_len;
876
877                 /*
878                  * If more data is pending, set SPLICE_F_MORE
879                  * If this is the last data and SPLICE_F_MORE was not set
880                  * initially, clears it.
881                  */
882                 if (read_len < len)
883                         sd->flags |= SPLICE_F_MORE;
884                 else if (!more)
885                         sd->flags &= ~SPLICE_F_MORE;
886                 /*
887                  * NOTE: nonblocking mode only applies to the input. We
888                  * must not do the output in nonblocking mode as then we
889                  * could get stuck data in the internal pipe:
890                  */
891                 ret = actor(pipe, sd);
892                 if (unlikely(ret <= 0)) {
893                         sd->pos = prev_pos;
894                         goto out_release;
895                 }
896
897                 bytes += ret;
898                 len -= ret;
899                 sd->pos = pos;
900
901                 if (ret < read_len) {
902                         sd->pos = prev_pos + ret;
903                         goto out_release;
904                 }
905         }
906
907 done:
908         pipe->tail = pipe->head = 0;
909         file_accessed(in);
910         return bytes;
911
912 out_release:
913         /*
914          * If we did an incomplete transfer we must release
915          * the pipe buffers in question:
916          */
917         for (i = 0; i < pipe->ring_size; i++) {
918                 struct pipe_buffer *buf = &pipe->bufs[i];
919
920                 if (buf->ops)
921                         pipe_buf_release(pipe, buf);
922         }
923
924         if (!bytes)
925                 bytes = ret;
926
927         goto done;
928 }
929 EXPORT_SYMBOL(splice_direct_to_actor);
930
931 static int direct_splice_actor(struct pipe_inode_info *pipe,
932                                struct splice_desc *sd)
933 {
934         struct file *file = sd->u.file;
935
936         return do_splice_from(pipe, file, sd->opos, sd->total_len,
937                               sd->flags);
938 }
939
940 /**
941  * do_splice_direct - splices data directly between two files
942  * @in:         file to splice from
943  * @ppos:       input file offset
944  * @out:        file to splice to
945  * @opos:       output file offset
946  * @len:        number of bytes to splice
947  * @flags:      splice modifier flags
948  *
949  * Description:
950  *    For use by do_sendfile(). splice can easily emulate sendfile, but
951  *    doing it in the application would incur an extra system call
952  *    (splice in + splice out, as compared to just sendfile()). So this helper
953  *    can splice directly through a process-private pipe.
954  *
955  */
956 long do_splice_direct(struct file *in, loff_t *ppos, struct file *out,
957                       loff_t *opos, size_t len, unsigned int flags)
958 {
959         struct splice_desc sd = {
960                 .len            = len,
961                 .total_len      = len,
962                 .flags          = flags,
963                 .pos            = *ppos,
964                 .u.file         = out,
965                 .opos           = opos,
966         };
967         long ret;
968
969         if (unlikely(!(out->f_mode & FMODE_WRITE)))
970                 return -EBADF;
971
972         if (unlikely(out->f_flags & O_APPEND))
973                 return -EINVAL;
974
975         ret = rw_verify_area(WRITE, out, opos, len);
976         if (unlikely(ret < 0))
977                 return ret;
978
979         ret = splice_direct_to_actor(in, &sd, direct_splice_actor);
980         if (ret > 0)
981                 *ppos = sd.pos;
982
983         return ret;
984 }
985 EXPORT_SYMBOL(do_splice_direct);
986
987 static int wait_for_space(struct pipe_inode_info *pipe, unsigned flags)
988 {
989         for (;;) {
990                 if (unlikely(!pipe->readers)) {
991                         send_sig(SIGPIPE, current, 0);
992                         return -EPIPE;
993                 }
994                 if (!pipe_full(pipe->head, pipe->tail, pipe->max_usage))
995                         return 0;
996                 if (flags & SPLICE_F_NONBLOCK)
997                         return -EAGAIN;
998                 if (signal_pending(current))
999                         return -ERESTARTSYS;
1000                 pipe_wait_writable(pipe);
1001         }
1002 }
1003
1004 static int splice_pipe_to_pipe(struct pipe_inode_info *ipipe,
1005                                struct pipe_inode_info *opipe,
1006                                size_t len, unsigned int flags);
1007
1008 long splice_file_to_pipe(struct file *in,
1009                          struct pipe_inode_info *opipe,
1010                          loff_t *offset,
1011                          size_t len, unsigned int flags)
1012 {
1013         long ret;
1014
1015         pipe_lock(opipe);
1016         ret = wait_for_space(opipe, flags);
1017         if (!ret)
1018                 ret = do_splice_to(in, offset, opipe, len, flags);
1019         pipe_unlock(opipe);
1020         if (ret > 0)
1021                 wakeup_pipe_readers(opipe);
1022         return ret;
1023 }
1024
1025 /*
1026  * Determine where to splice to/from.
1027  */
1028 long do_splice(struct file *in, loff_t *off_in, struct file *out,
1029                loff_t *off_out, size_t len, unsigned int flags)
1030 {
1031         struct pipe_inode_info *ipipe;
1032         struct pipe_inode_info *opipe;
1033         loff_t offset;
1034         long ret;
1035
1036         if (unlikely(!(in->f_mode & FMODE_READ) ||
1037                      !(out->f_mode & FMODE_WRITE)))
1038                 return -EBADF;
1039
1040         ipipe = get_pipe_info(in, true);
1041         opipe = get_pipe_info(out, true);
1042
1043         if (ipipe && opipe) {
1044                 if (off_in || off_out)
1045                         return -ESPIPE;
1046
1047                 /* Splicing to self would be fun, but... */
1048                 if (ipipe == opipe)
1049                         return -EINVAL;
1050
1051                 if ((in->f_flags | out->f_flags) & O_NONBLOCK)
1052                         flags |= SPLICE_F_NONBLOCK;
1053
1054                 return splice_pipe_to_pipe(ipipe, opipe, len, flags);
1055         }
1056
1057         if (ipipe) {
1058                 if (off_in)
1059                         return -ESPIPE;
1060                 if (off_out) {
1061                         if (!(out->f_mode & FMODE_PWRITE))
1062                                 return -EINVAL;
1063                         offset = *off_out;
1064                 } else {
1065                         offset = out->f_pos;
1066                 }
1067
1068                 if (unlikely(out->f_flags & O_APPEND))
1069                         return -EINVAL;
1070
1071                 ret = rw_verify_area(WRITE, out, &offset, len);
1072                 if (unlikely(ret < 0))
1073                         return ret;
1074
1075                 if (in->f_flags & O_NONBLOCK)
1076                         flags |= SPLICE_F_NONBLOCK;
1077
1078                 file_start_write(out);
1079                 ret = do_splice_from(ipipe, out, &offset, len, flags);
1080                 file_end_write(out);
1081
1082                 if (!off_out)
1083                         out->f_pos = offset;
1084                 else
1085                         *off_out = offset;
1086
1087                 return ret;
1088         }
1089
1090         if (opipe) {
1091                 if (off_out)
1092                         return -ESPIPE;
1093                 if (off_in) {
1094                         if (!(in->f_mode & FMODE_PREAD))
1095                                 return -EINVAL;
1096                         offset = *off_in;
1097                 } else {
1098                         offset = in->f_pos;
1099                 }
1100
1101                 if (out->f_flags & O_NONBLOCK)
1102                         flags |= SPLICE_F_NONBLOCK;
1103
1104                 ret = splice_file_to_pipe(in, opipe, &offset, len, flags);
1105                 if (!off_in)
1106                         in->f_pos = offset;
1107                 else
1108                         *off_in = offset;
1109
1110                 return ret;
1111         }
1112
1113         return -EINVAL;
1114 }
1115
1116 static long __do_splice(struct file *in, loff_t __user *off_in,
1117                         struct file *out, loff_t __user *off_out,
1118                         size_t len, unsigned int flags)
1119 {
1120         struct pipe_inode_info *ipipe;
1121         struct pipe_inode_info *opipe;
1122         loff_t offset, *__off_in = NULL, *__off_out = NULL;
1123         long ret;
1124
1125         ipipe = get_pipe_info(in, true);
1126         opipe = get_pipe_info(out, true);
1127
1128         if (ipipe && off_in)
1129                 return -ESPIPE;
1130         if (opipe && off_out)
1131                 return -ESPIPE;
1132
1133         if (off_out) {
1134                 if (copy_from_user(&offset, off_out, sizeof(loff_t)))
1135                         return -EFAULT;
1136                 __off_out = &offset;
1137         }
1138         if (off_in) {
1139                 if (copy_from_user(&offset, off_in, sizeof(loff_t)))
1140                         return -EFAULT;
1141                 __off_in = &offset;
1142         }
1143
1144         ret = do_splice(in, __off_in, out, __off_out, len, flags);
1145         if (ret < 0)
1146                 return ret;
1147
1148         if (__off_out && copy_to_user(off_out, __off_out, sizeof(loff_t)))
1149                 return -EFAULT;
1150         if (__off_in && copy_to_user(off_in, __off_in, sizeof(loff_t)))
1151                 return -EFAULT;
1152
1153         return ret;
1154 }
1155
1156 static int iter_to_pipe(struct iov_iter *from,
1157                         struct pipe_inode_info *pipe,
1158                         unsigned flags)
1159 {
1160         struct pipe_buffer buf = {
1161                 .ops = &user_page_pipe_buf_ops,
1162                 .flags = flags
1163         };
1164         size_t total = 0;
1165         int ret = 0;
1166         bool failed = false;
1167
1168         while (iov_iter_count(from) && !failed) {
1169                 struct page *pages[16];
1170                 ssize_t copied;
1171                 size_t start;
1172                 int n;
1173
1174                 copied = iov_iter_get_pages(from, pages, ~0UL, 16, &start);
1175                 if (copied <= 0) {
1176                         ret = copied;
1177                         break;
1178                 }
1179
1180                 for (n = 0; copied; n++, start = 0) {
1181                         int size = min_t(int, copied, PAGE_SIZE - start);
1182                         if (!failed) {
1183                                 buf.page = pages[n];
1184                                 buf.offset = start;
1185                                 buf.len = size;
1186                                 ret = add_to_pipe(pipe, &buf);
1187                                 if (unlikely(ret < 0)) {
1188                                         failed = true;
1189                                 } else {
1190                                         iov_iter_advance(from, ret);
1191                                         total += ret;
1192                                 }
1193                         } else {
1194                                 put_page(pages[n]);
1195                         }
1196                         copied -= size;
1197                 }
1198         }
1199         return total ? total : ret;
1200 }
1201
1202 static int pipe_to_user(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
1203                         struct splice_desc *sd)
1204 {
1205         int n = copy_page_to_iter(buf->page, buf->offset, sd->len, sd->u.data);
1206         return n == sd->len ? n : -EFAULT;
1207 }
1208
1209 /*
1210  * For lack of a better implementation, implement vmsplice() to userspace
1211  * as a simple copy of the pipes pages to the user iov.
1212  */
1213 static long vmsplice_to_user(struct file *file, struct iov_iter *iter,
1214                              unsigned int flags)
1215 {
1216         struct pipe_inode_info *pipe = get_pipe_info(file, true);
1217         struct splice_desc sd = {
1218                 .total_len = iov_iter_count(iter),
1219                 .flags = flags,
1220                 .u.data = iter
1221         };
1222         long ret = 0;
1223
1224         if (!pipe)
1225                 return -EBADF;
1226
1227         if (sd.total_len) {
1228                 pipe_lock(pipe);
1229                 ret = __splice_from_pipe(pipe, &sd, pipe_to_user);
1230                 pipe_unlock(pipe);
1231         }
1232
1233         return ret;
1234 }
1235
1236 /*
1237  * vmsplice splices a user address range into a pipe. It can be thought of
1238  * as splice-from-memory, where the regular splice is splice-from-file (or
1239  * to file). In both cases the output is a pipe, naturally.
1240  */
1241 static long vmsplice_to_pipe(struct file *file, struct iov_iter *iter,
1242                              unsigned int flags)
1243 {
1244         struct pipe_inode_info *pipe;
1245         long ret = 0;
1246         unsigned buf_flag = 0;
1247
1248         if (flags & SPLICE_F_GIFT)
1249                 buf_flag = PIPE_BUF_FLAG_GIFT;
1250
1251         pipe = get_pipe_info(file, true);
1252         if (!pipe)
1253                 return -EBADF;
1254
1255         pipe_lock(pipe);
1256         ret = wait_for_space(pipe, flags);
1257         if (!ret)
1258                 ret = iter_to_pipe(iter, pipe, buf_flag);
1259         pipe_unlock(pipe);
1260         if (ret > 0)
1261                 wakeup_pipe_readers(pipe);
1262         return ret;
1263 }
1264
1265 static int vmsplice_type(struct fd f, int *type)
1266 {
1267         if (!f.file)
1268                 return -EBADF;
1269         if (f.file->f_mode & FMODE_WRITE) {
1270                 *type = WRITE;
1271         } else if (f.file->f_mode & FMODE_READ) {
1272                 *type = READ;
1273         } else {
1274                 fdput(f);
1275                 return -EBADF;
1276         }
1277         return 0;
1278 }
1279
1280 /*
1281  * Note that vmsplice only really supports true splicing _from_ user memory
1282  * to a pipe, not the other way around. Splicing from user memory is a simple
1283  * operation that can be supported without any funky alignment restrictions
1284  * or nasty vm tricks. We simply map in the user memory and fill them into
1285  * a pipe. The reverse isn't quite as easy, though. There are two possible
1286  * solutions for that:
1287  *
1288  *      - memcpy() the data internally, at which point we might as well just
1289  *        do a regular read() on the buffer anyway.
1290  *      - Lots of nasty vm tricks, that are neither fast nor flexible (it
1291  *        has restriction limitations on both ends of the pipe).
1292  *
1293  * Currently we punt and implement it as a normal copy, see pipe_to_user().
1294  *
1295  */
1296 SYSCALL_DEFINE4(vmsplice, int, fd, const struct iovec __user *, uiov,
1297                 unsigned long, nr_segs, unsigned int, flags)
1298 {
1299         struct iovec iovstack[UIO_FASTIOV];
1300         struct iovec *iov = iovstack;
1301         struct iov_iter iter;
1302         ssize_t error;
1303         struct fd f;
1304         int type;
1305
1306         if (unlikely(flags & ~SPLICE_F_ALL))
1307                 return -EINVAL;
1308
1309         f = fdget(fd);
1310         error = vmsplice_type(f, &type);
1311         if (error)
1312                 return error;
1313
1314         error = import_iovec(type, uiov, nr_segs,
1315                              ARRAY_SIZE(iovstack), &iov, &iter);
1316         if (error < 0)
1317                 goto out_fdput;
1318
1319         if (!iov_iter_count(&iter))
1320                 error = 0;
1321         else if (iov_iter_rw(&iter) == WRITE)
1322                 error = vmsplice_to_pipe(f.file, &iter, flags);
1323         else
1324                 error = vmsplice_to_user(f.file, &iter, flags);
1325
1326         kfree(iov);
1327 out_fdput:
1328         fdput(f);
1329         return error;
1330 }
1331
1332 SYSCALL_DEFINE6(splice, int, fd_in, loff_t __user *, off_in,
1333                 int, fd_out, loff_t __user *, off_out,
1334                 size_t, len, unsigned int, flags)
1335 {
1336         struct fd in, out;
1337         long error;
1338
1339         if (unlikely(!len))
1340                 return 0;
1341
1342         if (unlikely(flags & ~SPLICE_F_ALL))
1343                 return -EINVAL;
1344
1345         error = -EBADF;
1346         in = fdget(fd_in);
1347         if (in.file) {
1348                 out = fdget(fd_out);
1349                 if (out.file) {
1350                         error = __do_splice(in.file, off_in, out.file, off_out,
1351                                                 len, flags);
1352                         fdput(out);
1353                 }
1354                 fdput(in);
1355         }
1356         return error;
1357 }
1358
1359 /*
1360  * Make sure there's data to read. Wait for input if we can, otherwise
1361  * return an appropriate error.
1362  */
1363 static int ipipe_prep(struct pipe_inode_info *pipe, unsigned int flags)
1364 {
1365         int ret;
1366
1367         /*
1368          * Check the pipe occupancy without the inode lock first. This function
1369          * is speculative anyways, so missing one is ok.
1370          */
1371         if (!pipe_empty(pipe->head, pipe->tail))
1372                 return 0;
1373
1374         ret = 0;
1375         pipe_lock(pipe);
1376
1377         while (pipe_empty(pipe->head, pipe->tail)) {
1378                 if (signal_pending(current)) {
1379                         ret = -ERESTARTSYS;
1380                         break;
1381                 }
1382                 if (!pipe->writers)
1383                         break;
1384                 if (flags & SPLICE_F_NONBLOCK) {
1385                         ret = -EAGAIN;
1386                         break;
1387                 }
1388                 pipe_wait_readable(pipe);
1389         }
1390
1391         pipe_unlock(pipe);
1392         return ret;
1393 }
1394
1395 /*
1396  * Make sure there's writeable room. Wait for room if we can, otherwise
1397  * return an appropriate error.
1398  */
1399 static int opipe_prep(struct pipe_inode_info *pipe, unsigned int flags)
1400 {
1401         int ret;
1402
1403         /*
1404          * Check pipe occupancy without the inode lock first. This function
1405          * is speculative anyways, so missing one is ok.
1406          */
1407         if (!pipe_full(pipe->head, pipe->tail, pipe->max_usage))
1408                 return 0;
1409
1410         ret = 0;
1411         pipe_lock(pipe);
1412
1413         while (pipe_full(pipe->head, pipe->tail, pipe->max_usage)) {
1414                 if (!pipe->readers) {
1415                         send_sig(SIGPIPE, current, 0);
1416                         ret = -EPIPE;
1417                         break;
1418                 }
1419                 if (flags & SPLICE_F_NONBLOCK) {
1420                         ret = -EAGAIN;
1421                         break;
1422                 }
1423                 if (signal_pending(current)) {
1424                         ret = -ERESTARTSYS;
1425                         break;
1426                 }
1427                 pipe_wait_writable(pipe);
1428         }
1429
1430         pipe_unlock(pipe);
1431         return ret;
1432 }
1433
1434 /*
1435  * Splice contents of ipipe to opipe.
1436  */
1437 static int splice_pipe_to_pipe(struct pipe_inode_info *ipipe,
1438                                struct pipe_inode_info *opipe,
1439                                size_t len, unsigned int flags)
1440 {
1441         struct pipe_buffer *ibuf, *obuf;
1442         unsigned int i_head, o_head;
1443         unsigned int i_tail, o_tail;
1444         unsigned int i_mask, o_mask;
1445         int ret = 0;
1446         bool input_wakeup = false;
1447
1448
1449 retry:
1450         ret = ipipe_prep(ipipe, flags);
1451         if (ret)
1452                 return ret;
1453
1454         ret = opipe_prep(opipe, flags);
1455         if (ret)
1456                 return ret;
1457
1458         /*
1459          * Potential ABBA deadlock, work around it by ordering lock
1460          * grabbing by pipe info address. Otherwise two different processes
1461          * could deadlock (one doing tee from A -> B, the other from B -> A).
1462          */
1463         pipe_double_lock(ipipe, opipe);
1464
1465         i_tail = ipipe->tail;
1466         i_mask = ipipe->ring_size - 1;
1467         o_head = opipe->head;
1468         o_mask = opipe->ring_size - 1;
1469
1470         do {
1471                 size_t o_len;
1472
1473                 if (!opipe->readers) {
1474                         send_sig(SIGPIPE, current, 0);
1475                         if (!ret)
1476                                 ret = -EPIPE;
1477                         break;
1478                 }
1479
1480                 i_head = ipipe->head;
1481                 o_tail = opipe->tail;
1482
1483                 if (pipe_empty(i_head, i_tail) && !ipipe->writers)
1484                         break;
1485
1486                 /*
1487                  * Cannot make any progress, because either the input
1488                  * pipe is empty or the output pipe is full.
1489                  */
1490                 if (pipe_empty(i_head, i_tail) ||
1491                     pipe_full(o_head, o_tail, opipe->max_usage)) {
1492                         /* Already processed some buffers, break */
1493                         if (ret)
1494                                 break;
1495
1496                         if (flags & SPLICE_F_NONBLOCK) {
1497                                 ret = -EAGAIN;
1498                                 break;
1499                         }
1500
1501                         /*
1502                          * We raced with another reader/writer and haven't
1503                          * managed to process any buffers.  A zero return
1504                          * value means EOF, so retry instead.
1505                          */
1506                         pipe_unlock(ipipe);
1507                         pipe_unlock(opipe);
1508                         goto retry;
1509                 }
1510
1511                 ibuf = &ipipe->bufs[i_tail & i_mask];
1512                 obuf = &opipe->bufs[o_head & o_mask];
1513
1514                 if (len >= ibuf->len) {
1515                         /*
1516                          * Simply move the whole buffer from ipipe to opipe
1517                          */
1518                         *obuf = *ibuf;
1519                         ibuf->ops = NULL;
1520                         i_tail++;
1521                         ipipe->tail = i_tail;
1522                         input_wakeup = true;
1523                         o_len = obuf->len;
1524                         o_head++;
1525                         opipe->head = o_head;
1526                 } else {
1527                         /*
1528                          * Get a reference to this pipe buffer,
1529                          * so we can copy the contents over.
1530                          */
1531                         if (!pipe_buf_get(ipipe, ibuf)) {
1532                                 if (ret == 0)
1533                                         ret = -EFAULT;
1534                                 break;
1535                         }
1536                         *obuf = *ibuf;
1537
1538                         /*
1539                          * Don't inherit the gift and merge flags, we need to
1540                          * prevent multiple steals of this page.
1541                          */
1542                         obuf->flags &= ~PIPE_BUF_FLAG_GIFT;
1543                         obuf->flags &= ~PIPE_BUF_FLAG_CAN_MERGE;
1544
1545                         obuf->len = len;
1546                         ibuf->offset += len;
1547                         ibuf->len -= len;
1548                         o_len = len;
1549                         o_head++;
1550                         opipe->head = o_head;
1551                 }
1552                 ret += o_len;
1553                 len -= o_len;
1554         } while (len);
1555
1556         pipe_unlock(ipipe);
1557         pipe_unlock(opipe);
1558
1559         /*
1560          * If we put data in the output pipe, wakeup any potential readers.
1561          */
1562         if (ret > 0)
1563                 wakeup_pipe_readers(opipe);
1564
1565         if (input_wakeup)
1566                 wakeup_pipe_writers(ipipe);
1567
1568         return ret;
1569 }
1570
1571 /*
1572  * Link contents of ipipe to opipe.
1573  */
1574 static int link_pipe(struct pipe_inode_info *ipipe,
1575                      struct pipe_inode_info *opipe,
1576                      size_t len, unsigned int flags)
1577 {
1578         struct pipe_buffer *ibuf, *obuf;
1579         unsigned int i_head, o_head;
1580         unsigned int i_tail, o_tail;
1581         unsigned int i_mask, o_mask;
1582         int ret = 0;
1583
1584         /*
1585          * Potential ABBA deadlock, work around it by ordering lock
1586          * grabbing by pipe info address. Otherwise two different processes
1587          * could deadlock (one doing tee from A -> B, the other from B -> A).
1588          */
1589         pipe_double_lock(ipipe, opipe);
1590
1591         i_tail = ipipe->tail;
1592         i_mask = ipipe->ring_size - 1;
1593         o_head = opipe->head;
1594         o_mask = opipe->ring_size - 1;
1595
1596         do {
1597                 if (!opipe->readers) {
1598                         send_sig(SIGPIPE, current, 0);
1599                         if (!ret)
1600                                 ret = -EPIPE;
1601                         break;
1602                 }
1603
1604                 i_head = ipipe->head;
1605                 o_tail = opipe->tail;
1606
1607                 /*
1608                  * If we have iterated all input buffers or run out of
1609                  * output room, break.
1610                  */
1611                 if (pipe_empty(i_head, i_tail) ||
1612                     pipe_full(o_head, o_tail, opipe->max_usage))
1613                         break;
1614
1615                 ibuf = &ipipe->bufs[i_tail & i_mask];
1616                 obuf = &opipe->bufs[o_head & o_mask];
1617
1618                 /*
1619                  * Get a reference to this pipe buffer,
1620                  * so we can copy the contents over.
1621                  */
1622                 if (!pipe_buf_get(ipipe, ibuf)) {
1623                         if (ret == 0)
1624                                 ret = -EFAULT;
1625                         break;
1626                 }
1627
1628                 *obuf = *ibuf;
1629
1630                 /*
1631                  * Don't inherit the gift and merge flag, we need to prevent
1632                  * multiple steals of this page.
1633                  */
1634                 obuf->flags &= ~PIPE_BUF_FLAG_GIFT;
1635                 obuf->flags &= ~PIPE_BUF_FLAG_CAN_MERGE;
1636
1637                 if (obuf->len > len)
1638                         obuf->len = len;
1639                 ret += obuf->len;
1640                 len -= obuf->len;
1641
1642                 o_head++;
1643                 opipe->head = o_head;
1644                 i_tail++;
1645         } while (len);
1646
1647         pipe_unlock(ipipe);
1648         pipe_unlock(opipe);
1649
1650         /*
1651          * If we put data in the output pipe, wakeup any potential readers.
1652          */
1653         if (ret > 0)
1654                 wakeup_pipe_readers(opipe);
1655
1656         return ret;
1657 }
1658
1659 /*
1660  * This is a tee(1) implementation that works on pipes. It doesn't copy
1661  * any data, it simply references the 'in' pages on the 'out' pipe.
1662  * The 'flags' used are the SPLICE_F_* variants, currently the only
1663  * applicable one is SPLICE_F_NONBLOCK.
1664  */
1665 long do_tee(struct file *in, struct file *out, size_t len, unsigned int flags)
1666 {
1667         struct pipe_inode_info *ipipe = get_pipe_info(in, true);
1668         struct pipe_inode_info *opipe = get_pipe_info(out, true);
1669         int ret = -EINVAL;
1670
1671         if (unlikely(!(in->f_mode & FMODE_READ) ||
1672                      !(out->f_mode & FMODE_WRITE)))
1673                 return -EBADF;
1674
1675         /*
1676          * Duplicate the contents of ipipe to opipe without actually
1677          * copying the data.
1678          */
1679         if (ipipe && opipe && ipipe != opipe) {
1680                 if ((in->f_flags | out->f_flags) & O_NONBLOCK)
1681                         flags |= SPLICE_F_NONBLOCK;
1682
1683                 /*
1684                  * Keep going, unless we encounter an error. The ipipe/opipe
1685                  * ordering doesn't really matter.
1686                  */
1687                 ret = ipipe_prep(ipipe, flags);
1688                 if (!ret) {
1689                         ret = opipe_prep(opipe, flags);
1690                         if (!ret)
1691                                 ret = link_pipe(ipipe, opipe, len, flags);
1692                 }
1693         }
1694
1695         return ret;
1696 }
1697
1698 SYSCALL_DEFINE4(tee, int, fdin, int, fdout, size_t, len, unsigned int, flags)
1699 {
1700         struct fd in, out;
1701         int error;
1702
1703         if (unlikely(flags & ~SPLICE_F_ALL))
1704                 return -EINVAL;
1705
1706         if (unlikely(!len))
1707                 return 0;
1708
1709         error = -EBADF;
1710         in = fdget(fdin);
1711         if (in.file) {
1712                 out = fdget(fdout);
1713                 if (out.file) {
1714                         error = do_tee(in.file, out.file, len, flags);
1715                         fdput(out);
1716                 }
1717                 fdput(in);
1718         }
1719
1720         return error;
1721 }