Merge branch 'work.compat' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs
[sfrench/cifs-2.6.git] / fs / splice.c
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/bvec.h>
21 #include <linux/fs.h>
22 #include <linux/file.h>
23 #include <linux/pagemap.h>
24 #include <linux/splice.h>
25 #include <linux/memcontrol.h>
26 #include <linux/mm_inline.h>
27 #include <linux/swap.h>
28 #include <linux/writeback.h>
29 #include <linux/export.h>
30 #include <linux/syscalls.h>
31 #include <linux/uio.h>
32 #include <linux/security.h>
33 #include <linux/gfp.h>
34 #include <linux/socket.h>
35 #include <linux/compat.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 int page_cache_pipe_buf_steal(struct pipe_inode_info *pipe,
47                                      struct pipe_buffer *buf)
48 {
49         struct page *page = buf->page;
50         struct address_space *mapping;
51
52         lock_page(page);
53
54         mapping = page_mapping(page);
55         if (mapping) {
56                 WARN_ON(!PageUptodate(page));
57
58                 /*
59                  * At least for ext2 with nobh option, we need to wait on
60                  * writeback completing on this page, since we'll remove it
61                  * from the pagecache.  Otherwise truncate wont wait on the
62                  * page, 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                 wait_on_page_writeback(page);
67
68                 if (page_has_private(page) &&
69                     !try_to_release_page(page, 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, page)) {
77                         buf->flags |= PIPE_BUF_FLAG_LRU;
78                         return 0;
79                 }
80         }
81
82         /*
83          * Raced with truncate or failed to remove page from current
84          * address space, unlock and return failure.
85          */
86 out_unlock:
87         unlock_page(page);
88         return 1;
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         .can_merge = 0,
142         .confirm = page_cache_pipe_buf_confirm,
143         .release = page_cache_pipe_buf_release,
144         .steal = page_cache_pipe_buf_steal,
145         .get = generic_pipe_buf_get,
146 };
147
148 static int user_page_pipe_buf_steal(struct pipe_inode_info *pipe,
149                                     struct pipe_buffer *buf)
150 {
151         if (!(buf->flags & PIPE_BUF_FLAG_GIFT))
152                 return 1;
153
154         buf->flags |= PIPE_BUF_FLAG_LRU;
155         return generic_pipe_buf_steal(pipe, buf);
156 }
157
158 static const struct pipe_buf_operations user_page_pipe_buf_ops = {
159         .can_merge = 0,
160         .confirm = generic_pipe_buf_confirm,
161         .release = page_cache_pipe_buf_release,
162         .steal = user_page_pipe_buf_steal,
163         .get = generic_pipe_buf_get,
164 };
165
166 static void wakeup_pipe_readers(struct pipe_inode_info *pipe)
167 {
168         smp_mb();
169         if (waitqueue_active(&pipe->wait))
170                 wake_up_interruptible(&pipe->wait);
171         kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
172 }
173
174 /**
175  * splice_to_pipe - fill passed data into a pipe
176  * @pipe:       pipe to fill
177  * @spd:        data to fill
178  *
179  * Description:
180  *    @spd contains a map of pages and len/offset tuples, along with
181  *    the struct pipe_buf_operations associated with these pages. This
182  *    function will link that data to the pipe.
183  *
184  */
185 ssize_t splice_to_pipe(struct pipe_inode_info *pipe,
186                        struct splice_pipe_desc *spd)
187 {
188         unsigned int spd_pages = spd->nr_pages;
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->nrbufs < pipe->buffers) {
201                 int newbuf = (pipe->curbuf + pipe->nrbufs) & (pipe->buffers - 1);
202                 struct pipe_buffer *buf = pipe->bufs + newbuf;
203
204                 buf->page = spd->pages[page_nr];
205                 buf->offset = spd->partial[page_nr].offset;
206                 buf->len = spd->partial[page_nr].len;
207                 buf->private = spd->partial[page_nr].private;
208                 buf->ops = spd->ops;
209                 buf->flags = 0;
210
211                 pipe->nrbufs++;
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         int ret;
233
234         if (unlikely(!pipe->readers)) {
235                 send_sig(SIGPIPE, current, 0);
236                 ret = -EPIPE;
237         } else if (pipe->nrbufs == pipe->buffers) {
238                 ret = -EAGAIN;
239         } else {
240                 int newbuf = (pipe->curbuf + pipe->nrbufs) & (pipe->buffers - 1);
241                 pipe->bufs[newbuf] = *buf;
242                 pipe->nrbufs++;
243                 return buf->len;
244         }
245         pipe_buf_release(pipe, buf);
246         return ret;
247 }
248 EXPORT_SYMBOL(add_to_pipe);
249
250 /*
251  * Check if we need to grow the arrays holding pages and partial page
252  * descriptions.
253  */
254 int splice_grow_spd(const struct pipe_inode_info *pipe, struct splice_pipe_desc *spd)
255 {
256         unsigned int buffers = READ_ONCE(pipe->buffers);
257
258         spd->nr_pages_max = buffers;
259         if (buffers <= PIPE_DEF_BUFFERS)
260                 return 0;
261
262         spd->pages = kmalloc_array(buffers, sizeof(struct page *), GFP_KERNEL);
263         spd->partial = kmalloc_array(buffers, sizeof(struct partial_page),
264                                      GFP_KERNEL);
265
266         if (spd->pages && spd->partial)
267                 return 0;
268
269         kfree(spd->pages);
270         kfree(spd->partial);
271         return -ENOMEM;
272 }
273
274 void splice_shrink_spd(struct splice_pipe_desc *spd)
275 {
276         if (spd->nr_pages_max <= PIPE_DEF_BUFFERS)
277                 return;
278
279         kfree(spd->pages);
280         kfree(spd->partial);
281 }
282
283 /**
284  * generic_file_splice_read - splice data from file to a pipe
285  * @in:         file to splice from
286  * @ppos:       position in @in
287  * @pipe:       pipe to splice to
288  * @len:        number of bytes to splice
289  * @flags:      splice modifier flags
290  *
291  * Description:
292  *    Will read pages from given file and fill them into a pipe. Can be
293  *    used as long as it has more or less sane ->read_iter().
294  *
295  */
296 ssize_t generic_file_splice_read(struct file *in, loff_t *ppos,
297                                  struct pipe_inode_info *pipe, size_t len,
298                                  unsigned int flags)
299 {
300         struct iov_iter to;
301         struct kiocb kiocb;
302         int idx, ret;
303
304         iov_iter_pipe(&to, ITER_PIPE | READ, pipe, len);
305         idx = to.idx;
306         init_sync_kiocb(&kiocb, in);
307         kiocb.ki_pos = *ppos;
308         ret = call_read_iter(in, &kiocb, &to);
309         if (ret > 0) {
310                 *ppos = kiocb.ki_pos;
311                 file_accessed(in);
312         } else if (ret < 0) {
313                 to.idx = idx;
314                 to.iov_offset = 0;
315                 iov_iter_advance(&to, 0); /* to free what was emitted */
316                 /*
317                  * callers of ->splice_read() expect -EAGAIN on
318                  * "can't put anything in there", rather than -EFAULT.
319                  */
320                 if (ret == -EFAULT)
321                         ret = -EAGAIN;
322         }
323
324         return ret;
325 }
326 EXPORT_SYMBOL(generic_file_splice_read);
327
328 const struct pipe_buf_operations default_pipe_buf_ops = {
329         .can_merge = 0,
330         .confirm = generic_pipe_buf_confirm,
331         .release = generic_pipe_buf_release,
332         .steal = generic_pipe_buf_steal,
333         .get = generic_pipe_buf_get,
334 };
335
336 static int generic_pipe_buf_nosteal(struct pipe_inode_info *pipe,
337                                     struct pipe_buffer *buf)
338 {
339         return 1;
340 }
341
342 /* Pipe buffer operations for a socket and similar. */
343 const struct pipe_buf_operations nosteal_pipe_buf_ops = {
344         .can_merge = 0,
345         .confirm = generic_pipe_buf_confirm,
346         .release = generic_pipe_buf_release,
347         .steal = generic_pipe_buf_nosteal,
348         .get = generic_pipe_buf_get,
349 };
350 EXPORT_SYMBOL(nosteal_pipe_buf_ops);
351
352 static ssize_t kernel_readv(struct file *file, const struct kvec *vec,
353                             unsigned long vlen, loff_t offset)
354 {
355         mm_segment_t old_fs;
356         loff_t pos = offset;
357         ssize_t res;
358
359         old_fs = get_fs();
360         set_fs(get_ds());
361         /* The cast to a user pointer is valid due to the set_fs() */
362         res = vfs_readv(file, (const struct iovec __user *)vec, vlen, &pos, 0);
363         set_fs(old_fs);
364
365         return res;
366 }
367
368 static ssize_t default_file_splice_read(struct file *in, loff_t *ppos,
369                                  struct pipe_inode_info *pipe, size_t len,
370                                  unsigned int flags)
371 {
372         struct kvec *vec, __vec[PIPE_DEF_BUFFERS];
373         struct iov_iter to;
374         struct page **pages;
375         unsigned int nr_pages;
376         size_t offset, base, copied = 0;
377         ssize_t res;
378         int i;
379
380         if (pipe->nrbufs == pipe->buffers)
381                 return -EAGAIN;
382
383         /*
384          * Try to keep page boundaries matching to source pagecache ones -
385          * it probably won't be much help, but...
386          */
387         offset = *ppos & ~PAGE_MASK;
388
389         iov_iter_pipe(&to, ITER_PIPE | READ, pipe, len + offset);
390
391         res = iov_iter_get_pages_alloc(&to, &pages, len + offset, &base);
392         if (res <= 0)
393                 return -ENOMEM;
394
395         nr_pages = DIV_ROUND_UP(res + base, PAGE_SIZE);
396
397         vec = __vec;
398         if (nr_pages > PIPE_DEF_BUFFERS) {
399                 vec = kmalloc_array(nr_pages, sizeof(struct kvec), GFP_KERNEL);
400                 if (unlikely(!vec)) {
401                         res = -ENOMEM;
402                         goto out;
403                 }
404         }
405
406         pipe->bufs[to.idx].offset = offset;
407         pipe->bufs[to.idx].len -= offset;
408
409         for (i = 0; i < nr_pages; i++) {
410                 size_t this_len = min_t(size_t, len, PAGE_SIZE - offset);
411                 vec[i].iov_base = page_address(pages[i]) + offset;
412                 vec[i].iov_len = this_len;
413                 len -= this_len;
414                 offset = 0;
415         }
416
417         res = kernel_readv(in, vec, nr_pages, *ppos);
418         if (res > 0) {
419                 copied = res;
420                 *ppos += res;
421         }
422
423         if (vec != __vec)
424                 kfree(vec);
425 out:
426         for (i = 0; i < nr_pages; i++)
427                 put_page(pages[i]);
428         kvfree(pages);
429         iov_iter_advance(&to, copied);  /* truncates and discards */
430         return res;
431 }
432
433 /*
434  * Send 'sd->len' bytes to socket from 'sd->file' at position 'sd->pos'
435  * using sendpage(). Return the number of bytes sent.
436  */
437 static int pipe_to_sendpage(struct pipe_inode_info *pipe,
438                             struct pipe_buffer *buf, struct splice_desc *sd)
439 {
440         struct file *file = sd->u.file;
441         loff_t pos = sd->pos;
442         int more;
443
444         if (!likely(file->f_op->sendpage))
445                 return -EINVAL;
446
447         more = (sd->flags & SPLICE_F_MORE) ? MSG_MORE : 0;
448
449         if (sd->len < sd->total_len && pipe->nrbufs > 1)
450                 more |= MSG_SENDPAGE_NOTLAST;
451
452         return file->f_op->sendpage(file, buf->page, buf->offset,
453                                     sd->len, &pos, more);
454 }
455
456 static void wakeup_pipe_writers(struct pipe_inode_info *pipe)
457 {
458         smp_mb();
459         if (waitqueue_active(&pipe->wait))
460                 wake_up_interruptible(&pipe->wait);
461         kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
462 }
463
464 /**
465  * splice_from_pipe_feed - feed available data from a pipe to a file
466  * @pipe:       pipe to splice from
467  * @sd:         information to @actor
468  * @actor:      handler that splices the data
469  *
470  * Description:
471  *    This function loops over the pipe and calls @actor to do the
472  *    actual moving of a single struct pipe_buffer to the desired
473  *    destination.  It returns when there's no more buffers left in
474  *    the pipe or if the requested number of bytes (@sd->total_len)
475  *    have been copied.  It returns a positive number (one) if the
476  *    pipe needs to be filled with more data, zero if the required
477  *    number of bytes have been copied and -errno on error.
478  *
479  *    This, together with splice_from_pipe_{begin,end,next}, may be
480  *    used to implement the functionality of __splice_from_pipe() when
481  *    locking is required around copying the pipe buffers to the
482  *    destination.
483  */
484 static int splice_from_pipe_feed(struct pipe_inode_info *pipe, struct splice_desc *sd,
485                           splice_actor *actor)
486 {
487         int ret;
488
489         while (pipe->nrbufs) {
490                 struct pipe_buffer *buf = pipe->bufs + pipe->curbuf;
491
492                 sd->len = buf->len;
493                 if (sd->len > sd->total_len)
494                         sd->len = sd->total_len;
495
496                 ret = pipe_buf_confirm(pipe, buf);
497                 if (unlikely(ret)) {
498                         if (ret == -ENODATA)
499                                 ret = 0;
500                         return ret;
501                 }
502
503                 ret = actor(pipe, buf, sd);
504                 if (ret <= 0)
505                         return ret;
506
507                 buf->offset += ret;
508                 buf->len -= ret;
509
510                 sd->num_spliced += ret;
511                 sd->len -= ret;
512                 sd->pos += ret;
513                 sd->total_len -= ret;
514
515                 if (!buf->len) {
516                         pipe_buf_release(pipe, buf);
517                         pipe->curbuf = (pipe->curbuf + 1) & (pipe->buffers - 1);
518                         pipe->nrbufs--;
519                         if (pipe->files)
520                                 sd->need_wakeup = true;
521                 }
522
523                 if (!sd->total_len)
524                         return 0;
525         }
526
527         return 1;
528 }
529
530 /**
531  * splice_from_pipe_next - wait for some data to splice from
532  * @pipe:       pipe to splice from
533  * @sd:         information about the splice operation
534  *
535  * Description:
536  *    This function will wait for some data and return a positive
537  *    value (one) if pipe buffers are available.  It will return zero
538  *    or -errno if no more data needs to be spliced.
539  */
540 static int splice_from_pipe_next(struct pipe_inode_info *pipe, struct splice_desc *sd)
541 {
542         /*
543          * Check for signal early to make process killable when there are
544          * always buffers available
545          */
546         if (signal_pending(current))
547                 return -ERESTARTSYS;
548
549         while (!pipe->nrbufs) {
550                 if (!pipe->writers)
551                         return 0;
552
553                 if (!pipe->waiting_writers && sd->num_spliced)
554                         return 0;
555
556                 if (sd->flags & SPLICE_F_NONBLOCK)
557                         return -EAGAIN;
558
559                 if (signal_pending(current))
560                         return -ERESTARTSYS;
561
562                 if (sd->need_wakeup) {
563                         wakeup_pipe_writers(pipe);
564                         sd->need_wakeup = false;
565                 }
566
567                 pipe_wait(pipe);
568         }
569
570         return 1;
571 }
572
573 /**
574  * splice_from_pipe_begin - start splicing from pipe
575  * @sd:         information about the splice operation
576  *
577  * Description:
578  *    This function should be called before a loop containing
579  *    splice_from_pipe_next() and splice_from_pipe_feed() to
580  *    initialize the necessary fields of @sd.
581  */
582 static void splice_from_pipe_begin(struct splice_desc *sd)
583 {
584         sd->num_spliced = 0;
585         sd->need_wakeup = false;
586 }
587
588 /**
589  * splice_from_pipe_end - finish splicing from pipe
590  * @pipe:       pipe to splice from
591  * @sd:         information about the splice operation
592  *
593  * Description:
594  *    This function will wake up pipe writers if necessary.  It should
595  *    be called after a loop containing splice_from_pipe_next() and
596  *    splice_from_pipe_feed().
597  */
598 static void splice_from_pipe_end(struct pipe_inode_info *pipe, struct splice_desc *sd)
599 {
600         if (sd->need_wakeup)
601                 wakeup_pipe_writers(pipe);
602 }
603
604 /**
605  * __splice_from_pipe - splice data from a pipe to given actor
606  * @pipe:       pipe to splice from
607  * @sd:         information to @actor
608  * @actor:      handler that splices the data
609  *
610  * Description:
611  *    This function does little more than loop over the pipe and call
612  *    @actor to do the actual moving of a single struct pipe_buffer to
613  *    the desired destination. See pipe_to_file, pipe_to_sendpage, or
614  *    pipe_to_user.
615  *
616  */
617 ssize_t __splice_from_pipe(struct pipe_inode_info *pipe, struct splice_desc *sd,
618                            splice_actor *actor)
619 {
620         int ret;
621
622         splice_from_pipe_begin(sd);
623         do {
624                 cond_resched();
625                 ret = splice_from_pipe_next(pipe, sd);
626                 if (ret > 0)
627                         ret = splice_from_pipe_feed(pipe, sd, actor);
628         } while (ret > 0);
629         splice_from_pipe_end(pipe, sd);
630
631         return sd->num_spliced ? sd->num_spliced : ret;
632 }
633 EXPORT_SYMBOL(__splice_from_pipe);
634
635 /**
636  * splice_from_pipe - splice data from a pipe to a file
637  * @pipe:       pipe to splice from
638  * @out:        file to splice to
639  * @ppos:       position in @out
640  * @len:        how many bytes to splice
641  * @flags:      splice modifier flags
642  * @actor:      handler that splices the data
643  *
644  * Description:
645  *    See __splice_from_pipe. This function locks the pipe inode,
646  *    otherwise it's identical to __splice_from_pipe().
647  *
648  */
649 ssize_t splice_from_pipe(struct pipe_inode_info *pipe, struct file *out,
650                          loff_t *ppos, size_t len, unsigned int flags,
651                          splice_actor *actor)
652 {
653         ssize_t ret;
654         struct splice_desc sd = {
655                 .total_len = len,
656                 .flags = flags,
657                 .pos = *ppos,
658                 .u.file = out,
659         };
660
661         pipe_lock(pipe);
662         ret = __splice_from_pipe(pipe, &sd, actor);
663         pipe_unlock(pipe);
664
665         return ret;
666 }
667
668 /**
669  * iter_file_splice_write - splice data from a pipe to a file
670  * @pipe:       pipe info
671  * @out:        file to write to
672  * @ppos:       position in @out
673  * @len:        number of bytes to splice
674  * @flags:      splice modifier flags
675  *
676  * Description:
677  *    Will either move or copy pages (determined by @flags options) from
678  *    the given pipe inode to the given file.
679  *    This one is ->write_iter-based.
680  *
681  */
682 ssize_t
683 iter_file_splice_write(struct pipe_inode_info *pipe, struct file *out,
684                           loff_t *ppos, size_t len, unsigned int flags)
685 {
686         struct splice_desc sd = {
687                 .total_len = len,
688                 .flags = flags,
689                 .pos = *ppos,
690                 .u.file = out,
691         };
692         int nbufs = pipe->buffers;
693         struct bio_vec *array = kcalloc(nbufs, sizeof(struct bio_vec),
694                                         GFP_KERNEL);
695         ssize_t ret;
696
697         if (unlikely(!array))
698                 return -ENOMEM;
699
700         pipe_lock(pipe);
701
702         splice_from_pipe_begin(&sd);
703         while (sd.total_len) {
704                 struct iov_iter from;
705                 size_t left;
706                 int n, idx;
707
708                 ret = splice_from_pipe_next(pipe, &sd);
709                 if (ret <= 0)
710                         break;
711
712                 if (unlikely(nbufs < pipe->buffers)) {
713                         kfree(array);
714                         nbufs = pipe->buffers;
715                         array = kcalloc(nbufs, sizeof(struct bio_vec),
716                                         GFP_KERNEL);
717                         if (!array) {
718                                 ret = -ENOMEM;
719                                 break;
720                         }
721                 }
722
723                 /* build the vector */
724                 left = sd.total_len;
725                 for (n = 0, idx = pipe->curbuf; left && n < pipe->nrbufs; n++, idx++) {
726                         struct pipe_buffer *buf = pipe->bufs + idx;
727                         size_t this_len = buf->len;
728
729                         if (this_len > left)
730                                 this_len = left;
731
732                         if (idx == pipe->buffers - 1)
733                                 idx = -1;
734
735                         ret = pipe_buf_confirm(pipe, buf);
736                         if (unlikely(ret)) {
737                                 if (ret == -ENODATA)
738                                         ret = 0;
739                                 goto done;
740                         }
741
742                         array[n].bv_page = buf->page;
743                         array[n].bv_len = this_len;
744                         array[n].bv_offset = buf->offset;
745                         left -= this_len;
746                 }
747
748                 iov_iter_bvec(&from, ITER_BVEC | WRITE, array, n,
749                               sd.total_len - left);
750                 ret = vfs_iter_write(out, &from, &sd.pos, 0);
751                 if (ret <= 0)
752                         break;
753
754                 sd.num_spliced += ret;
755                 sd.total_len -= ret;
756                 *ppos = sd.pos;
757
758                 /* dismiss the fully eaten buffers, adjust the partial one */
759                 while (ret) {
760                         struct pipe_buffer *buf = pipe->bufs + pipe->curbuf;
761                         if (ret >= buf->len) {
762                                 ret -= buf->len;
763                                 buf->len = 0;
764                                 pipe_buf_release(pipe, buf);
765                                 pipe->curbuf = (pipe->curbuf + 1) & (pipe->buffers - 1);
766                                 pipe->nrbufs--;
767                                 if (pipe->files)
768                                         sd.need_wakeup = true;
769                         } else {
770                                 buf->offset += ret;
771                                 buf->len -= ret;
772                                 ret = 0;
773                         }
774                 }
775         }
776 done:
777         kfree(array);
778         splice_from_pipe_end(pipe, &sd);
779
780         pipe_unlock(pipe);
781
782         if (sd.num_spliced)
783                 ret = sd.num_spliced;
784
785         return ret;
786 }
787
788 EXPORT_SYMBOL(iter_file_splice_write);
789
790 static int write_pipe_buf(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
791                           struct splice_desc *sd)
792 {
793         int ret;
794         void *data;
795         loff_t tmp = sd->pos;
796
797         data = kmap(buf->page);
798         ret = __kernel_write(sd->u.file, data + buf->offset, sd->len, &tmp);
799         kunmap(buf->page);
800
801         return ret;
802 }
803
804 static ssize_t default_file_splice_write(struct pipe_inode_info *pipe,
805                                          struct file *out, loff_t *ppos,
806                                          size_t len, unsigned int flags)
807 {
808         ssize_t ret;
809
810         ret = splice_from_pipe(pipe, out, ppos, len, flags, write_pipe_buf);
811         if (ret > 0)
812                 *ppos += ret;
813
814         return ret;
815 }
816
817 /**
818  * generic_splice_sendpage - splice data from a pipe to a socket
819  * @pipe:       pipe to splice from
820  * @out:        socket to write to
821  * @ppos:       position in @out
822  * @len:        number of bytes to splice
823  * @flags:      splice modifier flags
824  *
825  * Description:
826  *    Will send @len bytes from the pipe to a network socket. No data copying
827  *    is involved.
828  *
829  */
830 ssize_t generic_splice_sendpage(struct pipe_inode_info *pipe, struct file *out,
831                                 loff_t *ppos, size_t len, unsigned int flags)
832 {
833         return splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_sendpage);
834 }
835
836 EXPORT_SYMBOL(generic_splice_sendpage);
837
838 /*
839  * Attempt to initiate a splice from pipe to file.
840  */
841 static long do_splice_from(struct pipe_inode_info *pipe, struct file *out,
842                            loff_t *ppos, size_t len, unsigned int flags)
843 {
844         ssize_t (*splice_write)(struct pipe_inode_info *, struct file *,
845                                 loff_t *, size_t, unsigned int);
846
847         if (out->f_op->splice_write)
848                 splice_write = out->f_op->splice_write;
849         else
850                 splice_write = default_file_splice_write;
851
852         return splice_write(pipe, out, ppos, len, flags);
853 }
854
855 /*
856  * Attempt to initiate a splice from a file to a pipe.
857  */
858 static long do_splice_to(struct file *in, loff_t *ppos,
859                          struct pipe_inode_info *pipe, size_t len,
860                          unsigned int flags)
861 {
862         ssize_t (*splice_read)(struct file *, loff_t *,
863                                struct pipe_inode_info *, size_t, unsigned int);
864         int ret;
865
866         if (unlikely(!(in->f_mode & FMODE_READ)))
867                 return -EBADF;
868
869         ret = rw_verify_area(READ, in, ppos, len);
870         if (unlikely(ret < 0))
871                 return ret;
872
873         if (unlikely(len > MAX_RW_COUNT))
874                 len = MAX_RW_COUNT;
875
876         if (in->f_op->splice_read)
877                 splice_read = in->f_op->splice_read;
878         else
879                 splice_read = default_file_splice_read;
880
881         return splice_read(in, ppos, pipe, len, flags);
882 }
883
884 /**
885  * splice_direct_to_actor - splices data directly between two non-pipes
886  * @in:         file to splice from
887  * @sd:         actor information on where to splice to
888  * @actor:      handles the data splicing
889  *
890  * Description:
891  *    This is a special case helper to splice directly between two
892  *    points, without requiring an explicit pipe. Internally an allocated
893  *    pipe is cached in the process, and reused during the lifetime of
894  *    that process.
895  *
896  */
897 ssize_t splice_direct_to_actor(struct file *in, struct splice_desc *sd,
898                                splice_direct_actor *actor)
899 {
900         struct pipe_inode_info *pipe;
901         long ret, bytes;
902         umode_t i_mode;
903         size_t len;
904         int i, flags, more;
905
906         /*
907          * We require the input being a regular file, as we don't want to
908          * randomly drop data for eg socket -> socket splicing. Use the
909          * piped splicing for that!
910          */
911         i_mode = file_inode(in)->i_mode;
912         if (unlikely(!S_ISREG(i_mode) && !S_ISBLK(i_mode)))
913                 return -EINVAL;
914
915         /*
916          * neither in nor out is a pipe, setup an internal pipe attached to
917          * 'out' and transfer the wanted data from 'in' to 'out' through that
918          */
919         pipe = current->splice_pipe;
920         if (unlikely(!pipe)) {
921                 pipe = alloc_pipe_info();
922                 if (!pipe)
923                         return -ENOMEM;
924
925                 /*
926                  * We don't have an immediate reader, but we'll read the stuff
927                  * out of the pipe right after the splice_to_pipe(). So set
928                  * PIPE_READERS appropriately.
929                  */
930                 pipe->readers = 1;
931
932                 current->splice_pipe = pipe;
933         }
934
935         /*
936          * Do the splice.
937          */
938         ret = 0;
939         bytes = 0;
940         len = sd->total_len;
941         flags = sd->flags;
942
943         /*
944          * Don't block on output, we have to drain the direct pipe.
945          */
946         sd->flags &= ~SPLICE_F_NONBLOCK;
947         more = sd->flags & SPLICE_F_MORE;
948
949         while (len) {
950                 size_t read_len;
951                 loff_t pos = sd->pos, prev_pos = pos;
952
953                 ret = do_splice_to(in, &pos, pipe, len, flags);
954                 if (unlikely(ret <= 0))
955                         goto out_release;
956
957                 read_len = ret;
958                 sd->total_len = read_len;
959
960                 /*
961                  * If more data is pending, set SPLICE_F_MORE
962                  * If this is the last data and SPLICE_F_MORE was not set
963                  * initially, clears it.
964                  */
965                 if (read_len < len)
966                         sd->flags |= SPLICE_F_MORE;
967                 else if (!more)
968                         sd->flags &= ~SPLICE_F_MORE;
969                 /*
970                  * NOTE: nonblocking mode only applies to the input. We
971                  * must not do the output in nonblocking mode as then we
972                  * could get stuck data in the internal pipe:
973                  */
974                 ret = actor(pipe, sd);
975                 if (unlikely(ret <= 0)) {
976                         sd->pos = prev_pos;
977                         goto out_release;
978                 }
979
980                 bytes += ret;
981                 len -= ret;
982                 sd->pos = pos;
983
984                 if (ret < read_len) {
985                         sd->pos = prev_pos + ret;
986                         goto out_release;
987                 }
988         }
989
990 done:
991         pipe->nrbufs = pipe->curbuf = 0;
992         file_accessed(in);
993         return bytes;
994
995 out_release:
996         /*
997          * If we did an incomplete transfer we must release
998          * the pipe buffers in question:
999          */
1000         for (i = 0; i < pipe->buffers; i++) {
1001                 struct pipe_buffer *buf = pipe->bufs + i;
1002
1003                 if (buf->ops)
1004                         pipe_buf_release(pipe, buf);
1005         }
1006
1007         if (!bytes)
1008                 bytes = ret;
1009
1010         goto done;
1011 }
1012 EXPORT_SYMBOL(splice_direct_to_actor);
1013
1014 static int direct_splice_actor(struct pipe_inode_info *pipe,
1015                                struct splice_desc *sd)
1016 {
1017         struct file *file = sd->u.file;
1018
1019         return do_splice_from(pipe, file, sd->opos, sd->total_len,
1020                               sd->flags);
1021 }
1022
1023 /**
1024  * do_splice_direct - splices data directly between two files
1025  * @in:         file to splice from
1026  * @ppos:       input file offset
1027  * @out:        file to splice to
1028  * @opos:       output file offset
1029  * @len:        number of bytes to splice
1030  * @flags:      splice modifier flags
1031  *
1032  * Description:
1033  *    For use by do_sendfile(). splice can easily emulate sendfile, but
1034  *    doing it in the application would incur an extra system call
1035  *    (splice in + splice out, as compared to just sendfile()). So this helper
1036  *    can splice directly through a process-private pipe.
1037  *
1038  */
1039 long do_splice_direct(struct file *in, loff_t *ppos, struct file *out,
1040                       loff_t *opos, size_t len, unsigned int flags)
1041 {
1042         struct splice_desc sd = {
1043                 .len            = len,
1044                 .total_len      = len,
1045                 .flags          = flags,
1046                 .pos            = *ppos,
1047                 .u.file         = out,
1048                 .opos           = opos,
1049         };
1050         long ret;
1051
1052         if (unlikely(!(out->f_mode & FMODE_WRITE)))
1053                 return -EBADF;
1054
1055         if (unlikely(out->f_flags & O_APPEND))
1056                 return -EINVAL;
1057
1058         ret = rw_verify_area(WRITE, out, opos, len);
1059         if (unlikely(ret < 0))
1060                 return ret;
1061
1062         ret = splice_direct_to_actor(in, &sd, direct_splice_actor);
1063         if (ret > 0)
1064                 *ppos = sd.pos;
1065
1066         return ret;
1067 }
1068 EXPORT_SYMBOL(do_splice_direct);
1069
1070 static int wait_for_space(struct pipe_inode_info *pipe, unsigned flags)
1071 {
1072         for (;;) {
1073                 if (unlikely(!pipe->readers)) {
1074                         send_sig(SIGPIPE, current, 0);
1075                         return -EPIPE;
1076                 }
1077                 if (pipe->nrbufs != pipe->buffers)
1078                         return 0;
1079                 if (flags & SPLICE_F_NONBLOCK)
1080                         return -EAGAIN;
1081                 if (signal_pending(current))
1082                         return -ERESTARTSYS;
1083                 pipe->waiting_writers++;
1084                 pipe_wait(pipe);
1085                 pipe->waiting_writers--;
1086         }
1087 }
1088
1089 static int splice_pipe_to_pipe(struct pipe_inode_info *ipipe,
1090                                struct pipe_inode_info *opipe,
1091                                size_t len, unsigned int flags);
1092
1093 /*
1094  * Determine where to splice to/from.
1095  */
1096 static long do_splice(struct file *in, loff_t __user *off_in,
1097                       struct file *out, loff_t __user *off_out,
1098                       size_t len, unsigned int flags)
1099 {
1100         struct pipe_inode_info *ipipe;
1101         struct pipe_inode_info *opipe;
1102         loff_t offset;
1103         long ret;
1104
1105         ipipe = get_pipe_info(in);
1106         opipe = get_pipe_info(out);
1107
1108         if (ipipe && opipe) {
1109                 if (off_in || off_out)
1110                         return -ESPIPE;
1111
1112                 if (!(in->f_mode & FMODE_READ))
1113                         return -EBADF;
1114
1115                 if (!(out->f_mode & FMODE_WRITE))
1116                         return -EBADF;
1117
1118                 /* Splicing to self would be fun, but... */
1119                 if (ipipe == opipe)
1120                         return -EINVAL;
1121
1122                 return splice_pipe_to_pipe(ipipe, opipe, len, flags);
1123         }
1124
1125         if (ipipe) {
1126                 if (off_in)
1127                         return -ESPIPE;
1128                 if (off_out) {
1129                         if (!(out->f_mode & FMODE_PWRITE))
1130                                 return -EINVAL;
1131                         if (copy_from_user(&offset, off_out, sizeof(loff_t)))
1132                                 return -EFAULT;
1133                 } else {
1134                         offset = out->f_pos;
1135                 }
1136
1137                 if (unlikely(!(out->f_mode & FMODE_WRITE)))
1138                         return -EBADF;
1139
1140                 if (unlikely(out->f_flags & O_APPEND))
1141                         return -EINVAL;
1142
1143                 ret = rw_verify_area(WRITE, out, &offset, len);
1144                 if (unlikely(ret < 0))
1145                         return ret;
1146
1147                 file_start_write(out);
1148                 ret = do_splice_from(ipipe, out, &offset, len, flags);
1149                 file_end_write(out);
1150
1151                 if (!off_out)
1152                         out->f_pos = offset;
1153                 else if (copy_to_user(off_out, &offset, sizeof(loff_t)))
1154                         ret = -EFAULT;
1155
1156                 return ret;
1157         }
1158
1159         if (opipe) {
1160                 if (off_out)
1161                         return -ESPIPE;
1162                 if (off_in) {
1163                         if (!(in->f_mode & FMODE_PREAD))
1164                                 return -EINVAL;
1165                         if (copy_from_user(&offset, off_in, sizeof(loff_t)))
1166                                 return -EFAULT;
1167                 } else {
1168                         offset = in->f_pos;
1169                 }
1170
1171                 pipe_lock(opipe);
1172                 ret = wait_for_space(opipe, flags);
1173                 if (!ret)
1174                         ret = do_splice_to(in, &offset, opipe, len, flags);
1175                 pipe_unlock(opipe);
1176                 if (ret > 0)
1177                         wakeup_pipe_readers(opipe);
1178                 if (!off_in)
1179                         in->f_pos = offset;
1180                 else if (copy_to_user(off_in, &offset, sizeof(loff_t)))
1181                         ret = -EFAULT;
1182
1183                 return ret;
1184         }
1185
1186         return -EINVAL;
1187 }
1188
1189 static int iter_to_pipe(struct iov_iter *from,
1190                         struct pipe_inode_info *pipe,
1191                         unsigned flags)
1192 {
1193         struct pipe_buffer buf = {
1194                 .ops = &user_page_pipe_buf_ops,
1195                 .flags = flags
1196         };
1197         size_t total = 0;
1198         int ret = 0;
1199         bool failed = false;
1200
1201         while (iov_iter_count(from) && !failed) {
1202                 struct page *pages[16];
1203                 ssize_t copied;
1204                 size_t start;
1205                 int n;
1206
1207                 copied = iov_iter_get_pages(from, pages, ~0UL, 16, &start);
1208                 if (copied <= 0) {
1209                         ret = copied;
1210                         break;
1211                 }
1212
1213                 for (n = 0; copied; n++, start = 0) {
1214                         int size = min_t(int, copied, PAGE_SIZE - start);
1215                         if (!failed) {
1216                                 buf.page = pages[n];
1217                                 buf.offset = start;
1218                                 buf.len = size;
1219                                 ret = add_to_pipe(pipe, &buf);
1220                                 if (unlikely(ret < 0)) {
1221                                         failed = true;
1222                                 } else {
1223                                         iov_iter_advance(from, ret);
1224                                         total += ret;
1225                                 }
1226                         } else {
1227                                 put_page(pages[n]);
1228                         }
1229                         copied -= size;
1230                 }
1231         }
1232         return total ? total : ret;
1233 }
1234
1235 static int pipe_to_user(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
1236                         struct splice_desc *sd)
1237 {
1238         int n = copy_page_to_iter(buf->page, buf->offset, sd->len, sd->u.data);
1239         return n == sd->len ? n : -EFAULT;
1240 }
1241
1242 /*
1243  * For lack of a better implementation, implement vmsplice() to userspace
1244  * as a simple copy of the pipes pages to the user iov.
1245  */
1246 static long vmsplice_to_user(struct file *file, struct iov_iter *iter,
1247                              unsigned int flags)
1248 {
1249         struct pipe_inode_info *pipe = get_pipe_info(file);
1250         struct splice_desc sd = {
1251                 .total_len = iov_iter_count(iter),
1252                 .flags = flags,
1253                 .u.data = iter
1254         };
1255         long ret = 0;
1256
1257         if (!pipe)
1258                 return -EBADF;
1259
1260         if (sd.total_len) {
1261                 pipe_lock(pipe);
1262                 ret = __splice_from_pipe(pipe, &sd, pipe_to_user);
1263                 pipe_unlock(pipe);
1264         }
1265
1266         return ret;
1267 }
1268
1269 /*
1270  * vmsplice splices a user address range into a pipe. It can be thought of
1271  * as splice-from-memory, where the regular splice is splice-from-file (or
1272  * to file). In both cases the output is a pipe, naturally.
1273  */
1274 static long vmsplice_to_pipe(struct file *file, struct iov_iter *iter,
1275                              unsigned int flags)
1276 {
1277         struct pipe_inode_info *pipe;
1278         long ret = 0;
1279         unsigned buf_flag = 0;
1280
1281         if (flags & SPLICE_F_GIFT)
1282                 buf_flag = PIPE_BUF_FLAG_GIFT;
1283
1284         pipe = get_pipe_info(file);
1285         if (!pipe)
1286                 return -EBADF;
1287
1288         pipe_lock(pipe);
1289         ret = wait_for_space(pipe, flags);
1290         if (!ret)
1291                 ret = iter_to_pipe(iter, pipe, buf_flag);
1292         pipe_unlock(pipe);
1293         if (ret > 0)
1294                 wakeup_pipe_readers(pipe);
1295         return ret;
1296 }
1297
1298 static int vmsplice_type(struct fd f, int *type)
1299 {
1300         if (!f.file)
1301                 return -EBADF;
1302         if (f.file->f_mode & FMODE_WRITE) {
1303                 *type = WRITE;
1304         } else if (f.file->f_mode & FMODE_READ) {
1305                 *type = READ;
1306         } else {
1307                 fdput(f);
1308                 return -EBADF;
1309         }
1310         return 0;
1311 }
1312
1313 /*
1314  * Note that vmsplice only really supports true splicing _from_ user memory
1315  * to a pipe, not the other way around. Splicing from user memory is a simple
1316  * operation that can be supported without any funky alignment restrictions
1317  * or nasty vm tricks. We simply map in the user memory and fill them into
1318  * a pipe. The reverse isn't quite as easy, though. There are two possible
1319  * solutions for that:
1320  *
1321  *      - memcpy() the data internally, at which point we might as well just
1322  *        do a regular read() on the buffer anyway.
1323  *      - Lots of nasty vm tricks, that are neither fast nor flexible (it
1324  *        has restriction limitations on both ends of the pipe).
1325  *
1326  * Currently we punt and implement it as a normal copy, see pipe_to_user().
1327  *
1328  */
1329 static long do_vmsplice(struct file *f, struct iov_iter *iter, unsigned int flags)
1330 {
1331         if (unlikely(flags & ~SPLICE_F_ALL))
1332                 return -EINVAL;
1333
1334         if (!iov_iter_count(iter))
1335                 return 0;
1336
1337         if (iov_iter_rw(iter) == WRITE)
1338                 return vmsplice_to_pipe(f, iter, flags);
1339         else
1340                 return vmsplice_to_user(f, iter, flags);
1341 }
1342
1343 SYSCALL_DEFINE4(vmsplice, int, fd, const struct iovec __user *, uiov,
1344                 unsigned long, nr_segs, unsigned int, flags)
1345 {
1346         struct iovec iovstack[UIO_FASTIOV];
1347         struct iovec *iov = iovstack;
1348         struct iov_iter iter;
1349         long error;
1350         struct fd f;
1351         int type;
1352
1353         f = fdget(fd);
1354         error = vmsplice_type(f, &type);
1355         if (error)
1356                 return error;
1357
1358         error = import_iovec(type, uiov, nr_segs,
1359                              ARRAY_SIZE(iovstack), &iov, &iter);
1360         if (!error) {
1361                 error = do_vmsplice(f.file, &iter, flags);
1362                 kfree(iov);
1363         }
1364         fdput(f);
1365         return error;
1366 }
1367
1368 #ifdef CONFIG_COMPAT
1369 COMPAT_SYSCALL_DEFINE4(vmsplice, int, fd, const struct compat_iovec __user *, iov32,
1370                     unsigned int, nr_segs, unsigned int, flags)
1371 {
1372         struct iovec iovstack[UIO_FASTIOV];
1373         struct iovec *iov = iovstack;
1374         struct iov_iter iter;
1375         long error;
1376         struct fd f;
1377         int type;
1378
1379         f = fdget(fd);
1380         error = vmsplice_type(f, &type);
1381         if (error)
1382                 return error;
1383
1384         error = compat_import_iovec(type, iov32, nr_segs,
1385                              ARRAY_SIZE(iovstack), &iov, &iter);
1386         if (!error) {
1387                 error = do_vmsplice(f.file, &iter, flags);
1388                 kfree(iov);
1389         }
1390         fdput(f);
1391         return error;
1392 }
1393 #endif
1394
1395 SYSCALL_DEFINE6(splice, int, fd_in, loff_t __user *, off_in,
1396                 int, fd_out, loff_t __user *, off_out,
1397                 size_t, len, unsigned int, flags)
1398 {
1399         struct fd in, out;
1400         long error;
1401
1402         if (unlikely(!len))
1403                 return 0;
1404
1405         if (unlikely(flags & ~SPLICE_F_ALL))
1406                 return -EINVAL;
1407
1408         error = -EBADF;
1409         in = fdget(fd_in);
1410         if (in.file) {
1411                 if (in.file->f_mode & FMODE_READ) {
1412                         out = fdget(fd_out);
1413                         if (out.file) {
1414                                 if (out.file->f_mode & FMODE_WRITE)
1415                                         error = do_splice(in.file, off_in,
1416                                                           out.file, off_out,
1417                                                           len, flags);
1418                                 fdput(out);
1419                         }
1420                 }
1421                 fdput(in);
1422         }
1423         return error;
1424 }
1425
1426 /*
1427  * Make sure there's data to read. Wait for input if we can, otherwise
1428  * return an appropriate error.
1429  */
1430 static int ipipe_prep(struct pipe_inode_info *pipe, unsigned int flags)
1431 {
1432         int ret;
1433
1434         /*
1435          * Check ->nrbufs without the inode lock first. This function
1436          * is speculative anyways, so missing one is ok.
1437          */
1438         if (pipe->nrbufs)
1439                 return 0;
1440
1441         ret = 0;
1442         pipe_lock(pipe);
1443
1444         while (!pipe->nrbufs) {
1445                 if (signal_pending(current)) {
1446                         ret = -ERESTARTSYS;
1447                         break;
1448                 }
1449                 if (!pipe->writers)
1450                         break;
1451                 if (!pipe->waiting_writers) {
1452                         if (flags & SPLICE_F_NONBLOCK) {
1453                                 ret = -EAGAIN;
1454                                 break;
1455                         }
1456                 }
1457                 pipe_wait(pipe);
1458         }
1459
1460         pipe_unlock(pipe);
1461         return ret;
1462 }
1463
1464 /*
1465  * Make sure there's writeable room. Wait for room if we can, otherwise
1466  * return an appropriate error.
1467  */
1468 static int opipe_prep(struct pipe_inode_info *pipe, unsigned int flags)
1469 {
1470         int ret;
1471
1472         /*
1473          * Check ->nrbufs without the inode lock first. This function
1474          * is speculative anyways, so missing one is ok.
1475          */
1476         if (pipe->nrbufs < pipe->buffers)
1477                 return 0;
1478
1479         ret = 0;
1480         pipe_lock(pipe);
1481
1482         while (pipe->nrbufs >= pipe->buffers) {
1483                 if (!pipe->readers) {
1484                         send_sig(SIGPIPE, current, 0);
1485                         ret = -EPIPE;
1486                         break;
1487                 }
1488                 if (flags & SPLICE_F_NONBLOCK) {
1489                         ret = -EAGAIN;
1490                         break;
1491                 }
1492                 if (signal_pending(current)) {
1493                         ret = -ERESTARTSYS;
1494                         break;
1495                 }
1496                 pipe->waiting_writers++;
1497                 pipe_wait(pipe);
1498                 pipe->waiting_writers--;
1499         }
1500
1501         pipe_unlock(pipe);
1502         return ret;
1503 }
1504
1505 /*
1506  * Splice contents of ipipe to opipe.
1507  */
1508 static int splice_pipe_to_pipe(struct pipe_inode_info *ipipe,
1509                                struct pipe_inode_info *opipe,
1510                                size_t len, unsigned int flags)
1511 {
1512         struct pipe_buffer *ibuf, *obuf;
1513         int ret = 0, nbuf;
1514         bool input_wakeup = false;
1515
1516
1517 retry:
1518         ret = ipipe_prep(ipipe, flags);
1519         if (ret)
1520                 return ret;
1521
1522         ret = opipe_prep(opipe, flags);
1523         if (ret)
1524                 return ret;
1525
1526         /*
1527          * Potential ABBA deadlock, work around it by ordering lock
1528          * grabbing by pipe info address. Otherwise two different processes
1529          * could deadlock (one doing tee from A -> B, the other from B -> A).
1530          */
1531         pipe_double_lock(ipipe, opipe);
1532
1533         do {
1534                 if (!opipe->readers) {
1535                         send_sig(SIGPIPE, current, 0);
1536                         if (!ret)
1537                                 ret = -EPIPE;
1538                         break;
1539                 }
1540
1541                 if (!ipipe->nrbufs && !ipipe->writers)
1542                         break;
1543
1544                 /*
1545                  * Cannot make any progress, because either the input
1546                  * pipe is empty or the output pipe is full.
1547                  */
1548                 if (!ipipe->nrbufs || opipe->nrbufs >= opipe->buffers) {
1549                         /* Already processed some buffers, break */
1550                         if (ret)
1551                                 break;
1552
1553                         if (flags & SPLICE_F_NONBLOCK) {
1554                                 ret = -EAGAIN;
1555                                 break;
1556                         }
1557
1558                         /*
1559                          * We raced with another reader/writer and haven't
1560                          * managed to process any buffers.  A zero return
1561                          * value means EOF, so retry instead.
1562                          */
1563                         pipe_unlock(ipipe);
1564                         pipe_unlock(opipe);
1565                         goto retry;
1566                 }
1567
1568                 ibuf = ipipe->bufs + ipipe->curbuf;
1569                 nbuf = (opipe->curbuf + opipe->nrbufs) & (opipe->buffers - 1);
1570                 obuf = opipe->bufs + nbuf;
1571
1572                 if (len >= ibuf->len) {
1573                         /*
1574                          * Simply move the whole buffer from ipipe to opipe
1575                          */
1576                         *obuf = *ibuf;
1577                         ibuf->ops = NULL;
1578                         opipe->nrbufs++;
1579                         ipipe->curbuf = (ipipe->curbuf + 1) & (ipipe->buffers - 1);
1580                         ipipe->nrbufs--;
1581                         input_wakeup = true;
1582                 } else {
1583                         /*
1584                          * Get a reference to this pipe buffer,
1585                          * so we can copy the contents over.
1586                          */
1587                         pipe_buf_get(ipipe, ibuf);
1588                         *obuf = *ibuf;
1589
1590                         /*
1591                          * Don't inherit the gift flag, we need to
1592                          * prevent multiple steals of this page.
1593                          */
1594                         obuf->flags &= ~PIPE_BUF_FLAG_GIFT;
1595
1596                         obuf->len = len;
1597                         opipe->nrbufs++;
1598                         ibuf->offset += obuf->len;
1599                         ibuf->len -= obuf->len;
1600                 }
1601                 ret += obuf->len;
1602                 len -= obuf->len;
1603         } while (len);
1604
1605         pipe_unlock(ipipe);
1606         pipe_unlock(opipe);
1607
1608         /*
1609          * If we put data in the output pipe, wakeup any potential readers.
1610          */
1611         if (ret > 0)
1612                 wakeup_pipe_readers(opipe);
1613
1614         if (input_wakeup)
1615                 wakeup_pipe_writers(ipipe);
1616
1617         return ret;
1618 }
1619
1620 /*
1621  * Link contents of ipipe to opipe.
1622  */
1623 static int link_pipe(struct pipe_inode_info *ipipe,
1624                      struct pipe_inode_info *opipe,
1625                      size_t len, unsigned int flags)
1626 {
1627         struct pipe_buffer *ibuf, *obuf;
1628         int ret = 0, i = 0, nbuf;
1629
1630         /*
1631          * Potential ABBA deadlock, work around it by ordering lock
1632          * grabbing by pipe info address. Otherwise two different processes
1633          * could deadlock (one doing tee from A -> B, the other from B -> A).
1634          */
1635         pipe_double_lock(ipipe, opipe);
1636
1637         do {
1638                 if (!opipe->readers) {
1639                         send_sig(SIGPIPE, current, 0);
1640                         if (!ret)
1641                                 ret = -EPIPE;
1642                         break;
1643                 }
1644
1645                 /*
1646                  * If we have iterated all input buffers or ran out of
1647                  * output room, break.
1648                  */
1649                 if (i >= ipipe->nrbufs || opipe->nrbufs >= opipe->buffers)
1650                         break;
1651
1652                 ibuf = ipipe->bufs + ((ipipe->curbuf + i) & (ipipe->buffers-1));
1653                 nbuf = (opipe->curbuf + opipe->nrbufs) & (opipe->buffers - 1);
1654
1655                 /*
1656                  * Get a reference to this pipe buffer,
1657                  * so we can copy the contents over.
1658                  */
1659                 pipe_buf_get(ipipe, ibuf);
1660
1661                 obuf = opipe->bufs + nbuf;
1662                 *obuf = *ibuf;
1663
1664                 /*
1665                  * Don't inherit the gift flag, we need to
1666                  * prevent multiple steals of this page.
1667                  */
1668                 obuf->flags &= ~PIPE_BUF_FLAG_GIFT;
1669
1670                 if (obuf->len > len)
1671                         obuf->len = len;
1672
1673                 opipe->nrbufs++;
1674                 ret += obuf->len;
1675                 len -= obuf->len;
1676                 i++;
1677         } while (len);
1678
1679         /*
1680          * return EAGAIN if we have the potential of some data in the
1681          * future, otherwise just return 0
1682          */
1683         if (!ret && ipipe->waiting_writers && (flags & SPLICE_F_NONBLOCK))
1684                 ret = -EAGAIN;
1685
1686         pipe_unlock(ipipe);
1687         pipe_unlock(opipe);
1688
1689         /*
1690          * If we put data in the output pipe, wakeup any potential readers.
1691          */
1692         if (ret > 0)
1693                 wakeup_pipe_readers(opipe);
1694
1695         return ret;
1696 }
1697
1698 /*
1699  * This is a tee(1) implementation that works on pipes. It doesn't copy
1700  * any data, it simply references the 'in' pages on the 'out' pipe.
1701  * The 'flags' used are the SPLICE_F_* variants, currently the only
1702  * applicable one is SPLICE_F_NONBLOCK.
1703  */
1704 static long do_tee(struct file *in, struct file *out, size_t len,
1705                    unsigned int flags)
1706 {
1707         struct pipe_inode_info *ipipe = get_pipe_info(in);
1708         struct pipe_inode_info *opipe = get_pipe_info(out);
1709         int ret = -EINVAL;
1710
1711         /*
1712          * Duplicate the contents of ipipe to opipe without actually
1713          * copying the data.
1714          */
1715         if (ipipe && opipe && ipipe != opipe) {
1716                 /*
1717                  * Keep going, unless we encounter an error. The ipipe/opipe
1718                  * ordering doesn't really matter.
1719                  */
1720                 ret = ipipe_prep(ipipe, flags);
1721                 if (!ret) {
1722                         ret = opipe_prep(opipe, flags);
1723                         if (!ret)
1724                                 ret = link_pipe(ipipe, opipe, len, flags);
1725                 }
1726         }
1727
1728         return ret;
1729 }
1730
1731 SYSCALL_DEFINE4(tee, int, fdin, int, fdout, size_t, len, unsigned int, flags)
1732 {
1733         struct fd in;
1734         int error;
1735
1736         if (unlikely(flags & ~SPLICE_F_ALL))
1737                 return -EINVAL;
1738
1739         if (unlikely(!len))
1740                 return 0;
1741
1742         error = -EBADF;
1743         in = fdget(fdin);
1744         if (in.file) {
1745                 if (in.file->f_mode & FMODE_READ) {
1746                         struct fd out = fdget(fdout);
1747                         if (out.file) {
1748                                 if (out.file->f_mode & FMODE_WRITE)
1749                                         error = do_tee(in.file, out.file,
1750                                                         len, flags);
1751                                 fdput(out);
1752                         }
1753                 }
1754                 fdput(in);
1755         }
1756
1757         return error;
1758 }