Don't allow splice() to files opened with O_APPEND
[linux-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/fs.h>
21 #include <linux/file.h>
22 #include <linux/pagemap.h>
23 #include <linux/splice.h>
24 #include <linux/mm_inline.h>
25 #include <linux/swap.h>
26 #include <linux/writeback.h>
27 #include <linux/buffer_head.h>
28 #include <linux/module.h>
29 #include <linux/syscalls.h>
30 #include <linux/uio.h>
31 #include <linux/security.h>
32
33 /*
34  * Attempt to steal a page from a pipe buffer. This should perhaps go into
35  * a vm helper function, it's already simplified quite a bit by the
36  * addition of remove_mapping(). If success is returned, the caller may
37  * attempt to reuse this page for another destination.
38  */
39 static int page_cache_pipe_buf_steal(struct pipe_inode_info *pipe,
40                                      struct pipe_buffer *buf)
41 {
42         struct page *page = buf->page;
43         struct address_space *mapping;
44
45         lock_page(page);
46
47         mapping = page_mapping(page);
48         if (mapping) {
49                 WARN_ON(!PageUptodate(page));
50
51                 /*
52                  * At least for ext2 with nobh option, we need to wait on
53                  * writeback completing on this page, since we'll remove it
54                  * from the pagecache.  Otherwise truncate wont wait on the
55                  * page, allowing the disk blocks to be reused by someone else
56                  * before we actually wrote our data to them. fs corruption
57                  * ensues.
58                  */
59                 wait_on_page_writeback(page);
60
61                 if (PagePrivate(page) && !try_to_release_page(page, GFP_KERNEL))
62                         goto out_unlock;
63
64                 /*
65                  * If we succeeded in removing the mapping, set LRU flag
66                  * and return good.
67                  */
68                 if (remove_mapping(mapping, page)) {
69                         buf->flags |= PIPE_BUF_FLAG_LRU;
70                         return 0;
71                 }
72         }
73
74         /*
75          * Raced with truncate or failed to remove page from current
76          * address space, unlock and return failure.
77          */
78 out_unlock:
79         unlock_page(page);
80         return 1;
81 }
82
83 static void page_cache_pipe_buf_release(struct pipe_inode_info *pipe,
84                                         struct pipe_buffer *buf)
85 {
86         page_cache_release(buf->page);
87         buf->flags &= ~PIPE_BUF_FLAG_LRU;
88 }
89
90 /*
91  * Check whether the contents of buf is OK to access. Since the content
92  * is a page cache page, IO may be in flight.
93  */
94 static int page_cache_pipe_buf_confirm(struct pipe_inode_info *pipe,
95                                        struct pipe_buffer *buf)
96 {
97         struct page *page = buf->page;
98         int err;
99
100         if (!PageUptodate(page)) {
101                 lock_page(page);
102
103                 /*
104                  * Page got truncated/unhashed. This will cause a 0-byte
105                  * splice, if this is the first page.
106                  */
107                 if (!page->mapping) {
108                         err = -ENODATA;
109                         goto error;
110                 }
111
112                 /*
113                  * Uh oh, read-error from disk.
114                  */
115                 if (!PageUptodate(page)) {
116                         err = -EIO;
117                         goto error;
118                 }
119
120                 /*
121                  * Page is ok afterall, we are done.
122                  */
123                 unlock_page(page);
124         }
125
126         return 0;
127 error:
128         unlock_page(page);
129         return err;
130 }
131
132 static const struct pipe_buf_operations page_cache_pipe_buf_ops = {
133         .can_merge = 0,
134         .map = generic_pipe_buf_map,
135         .unmap = generic_pipe_buf_unmap,
136         .confirm = page_cache_pipe_buf_confirm,
137         .release = page_cache_pipe_buf_release,
138         .steal = page_cache_pipe_buf_steal,
139         .get = generic_pipe_buf_get,
140 };
141
142 static int user_page_pipe_buf_steal(struct pipe_inode_info *pipe,
143                                     struct pipe_buffer *buf)
144 {
145         if (!(buf->flags & PIPE_BUF_FLAG_GIFT))
146                 return 1;
147
148         buf->flags |= PIPE_BUF_FLAG_LRU;
149         return generic_pipe_buf_steal(pipe, buf);
150 }
151
152 static const struct pipe_buf_operations user_page_pipe_buf_ops = {
153         .can_merge = 0,
154         .map = generic_pipe_buf_map,
155         .unmap = generic_pipe_buf_unmap,
156         .confirm = generic_pipe_buf_confirm,
157         .release = page_cache_pipe_buf_release,
158         .steal = user_page_pipe_buf_steal,
159         .get = generic_pipe_buf_get,
160 };
161
162 /**
163  * splice_to_pipe - fill passed data into a pipe
164  * @pipe:       pipe to fill
165  * @spd:        data to fill
166  *
167  * Description:
168  *    @spd contains a map of pages and len/offset tuples, along with
169  *    the struct pipe_buf_operations associated with these pages. This
170  *    function will link that data to the pipe.
171  *
172  */
173 ssize_t splice_to_pipe(struct pipe_inode_info *pipe,
174                        struct splice_pipe_desc *spd)
175 {
176         unsigned int spd_pages = spd->nr_pages;
177         int ret, do_wakeup, page_nr;
178
179         ret = 0;
180         do_wakeup = 0;
181         page_nr = 0;
182
183         if (pipe->inode)
184                 mutex_lock(&pipe->inode->i_mutex);
185
186         for (;;) {
187                 if (!pipe->readers) {
188                         send_sig(SIGPIPE, current, 0);
189                         if (!ret)
190                                 ret = -EPIPE;
191                         break;
192                 }
193
194                 if (pipe->nrbufs < PIPE_BUFFERS) {
195                         int newbuf = (pipe->curbuf + pipe->nrbufs) & (PIPE_BUFFERS - 1);
196                         struct pipe_buffer *buf = pipe->bufs + newbuf;
197
198                         buf->page = spd->pages[page_nr];
199                         buf->offset = spd->partial[page_nr].offset;
200                         buf->len = spd->partial[page_nr].len;
201                         buf->private = spd->partial[page_nr].private;
202                         buf->ops = spd->ops;
203                         if (spd->flags & SPLICE_F_GIFT)
204                                 buf->flags |= PIPE_BUF_FLAG_GIFT;
205
206                         pipe->nrbufs++;
207                         page_nr++;
208                         ret += buf->len;
209
210                         if (pipe->inode)
211                                 do_wakeup = 1;
212
213                         if (!--spd->nr_pages)
214                                 break;
215                         if (pipe->nrbufs < PIPE_BUFFERS)
216                                 continue;
217
218                         break;
219                 }
220
221                 if (spd->flags & SPLICE_F_NONBLOCK) {
222                         if (!ret)
223                                 ret = -EAGAIN;
224                         break;
225                 }
226
227                 if (signal_pending(current)) {
228                         if (!ret)
229                                 ret = -ERESTARTSYS;
230                         break;
231                 }
232
233                 if (do_wakeup) {
234                         smp_mb();
235                         if (waitqueue_active(&pipe->wait))
236                                 wake_up_interruptible_sync(&pipe->wait);
237                         kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
238                         do_wakeup = 0;
239                 }
240
241                 pipe->waiting_writers++;
242                 pipe_wait(pipe);
243                 pipe->waiting_writers--;
244         }
245
246         if (pipe->inode) {
247                 mutex_unlock(&pipe->inode->i_mutex);
248
249                 if (do_wakeup) {
250                         smp_mb();
251                         if (waitqueue_active(&pipe->wait))
252                                 wake_up_interruptible(&pipe->wait);
253                         kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
254                 }
255         }
256
257         while (page_nr < spd_pages)
258                 spd->spd_release(spd, page_nr++);
259
260         return ret;
261 }
262
263 static void spd_release_page(struct splice_pipe_desc *spd, unsigned int i)
264 {
265         page_cache_release(spd->pages[i]);
266 }
267
268 static int
269 __generic_file_splice_read(struct file *in, loff_t *ppos,
270                            struct pipe_inode_info *pipe, size_t len,
271                            unsigned int flags)
272 {
273         struct address_space *mapping = in->f_mapping;
274         unsigned int loff, nr_pages, req_pages;
275         struct page *pages[PIPE_BUFFERS];
276         struct partial_page partial[PIPE_BUFFERS];
277         struct page *page;
278         pgoff_t index, end_index;
279         loff_t isize;
280         int error, page_nr;
281         struct splice_pipe_desc spd = {
282                 .pages = pages,
283                 .partial = partial,
284                 .flags = flags,
285                 .ops = &page_cache_pipe_buf_ops,
286                 .spd_release = spd_release_page,
287         };
288
289         index = *ppos >> PAGE_CACHE_SHIFT;
290         loff = *ppos & ~PAGE_CACHE_MASK;
291         req_pages = (len + loff + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
292         nr_pages = min(req_pages, (unsigned)PIPE_BUFFERS);
293
294         /*
295          * Lookup the (hopefully) full range of pages we need.
296          */
297         spd.nr_pages = find_get_pages_contig(mapping, index, nr_pages, pages);
298         index += spd.nr_pages;
299
300         /*
301          * If find_get_pages_contig() returned fewer pages than we needed,
302          * readahead/allocate the rest and fill in the holes.
303          */
304         if (spd.nr_pages < nr_pages)
305                 page_cache_sync_readahead(mapping, &in->f_ra, in,
306                                 index, req_pages - spd.nr_pages);
307
308         error = 0;
309         while (spd.nr_pages < nr_pages) {
310                 /*
311                  * Page could be there, find_get_pages_contig() breaks on
312                  * the first hole.
313                  */
314                 page = find_get_page(mapping, index);
315                 if (!page) {
316                         /*
317                          * page didn't exist, allocate one.
318                          */
319                         page = page_cache_alloc_cold(mapping);
320                         if (!page)
321                                 break;
322
323                         error = add_to_page_cache_lru(page, mapping, index,
324                                                 mapping_gfp_mask(mapping));
325                         if (unlikely(error)) {
326                                 page_cache_release(page);
327                                 if (error == -EEXIST)
328                                         continue;
329                                 break;
330                         }
331                         /*
332                          * add_to_page_cache() locks the page, unlock it
333                          * to avoid convoluting the logic below even more.
334                          */
335                         unlock_page(page);
336                 }
337
338                 pages[spd.nr_pages++] = page;
339                 index++;
340         }
341
342         /*
343          * Now loop over the map and see if we need to start IO on any
344          * pages, fill in the partial map, etc.
345          */
346         index = *ppos >> PAGE_CACHE_SHIFT;
347         nr_pages = spd.nr_pages;
348         spd.nr_pages = 0;
349         for (page_nr = 0; page_nr < nr_pages; page_nr++) {
350                 unsigned int this_len;
351
352                 if (!len)
353                         break;
354
355                 /*
356                  * this_len is the max we'll use from this page
357                  */
358                 this_len = min_t(unsigned long, len, PAGE_CACHE_SIZE - loff);
359                 page = pages[page_nr];
360
361                 if (PageReadahead(page))
362                         page_cache_async_readahead(mapping, &in->f_ra, in,
363                                         page, index, req_pages - page_nr);
364
365                 /*
366                  * If the page isn't uptodate, we may need to start io on it
367                  */
368                 if (!PageUptodate(page)) {
369                         /*
370                          * If in nonblock mode then dont block on waiting
371                          * for an in-flight io page
372                          */
373                         if (flags & SPLICE_F_NONBLOCK) {
374                                 if (!trylock_page(page)) {
375                                         error = -EAGAIN;
376                                         break;
377                                 }
378                         } else
379                                 lock_page(page);
380
381                         /*
382                          * Page was truncated, or invalidated by the
383                          * filesystem.  Redo the find/create, but this time the
384                          * page is kept locked, so there's no chance of another
385                          * race with truncate/invalidate.
386                          */
387                         if (!page->mapping) {
388                                 unlock_page(page);
389                                 page = find_or_create_page(mapping, index,
390                                                 mapping_gfp_mask(mapping));
391
392                                 if (!page) {
393                                         error = -ENOMEM;
394                                         break;
395                                 }
396                                 page_cache_release(pages[page_nr]);
397                                 pages[page_nr] = page;
398                         }
399                         /*
400                          * page was already under io and is now done, great
401                          */
402                         if (PageUptodate(page)) {
403                                 unlock_page(page);
404                                 goto fill_it;
405                         }
406
407                         /*
408                          * need to read in the page
409                          */
410                         error = mapping->a_ops->readpage(in, page);
411                         if (unlikely(error)) {
412                                 /*
413                                  * We really should re-lookup the page here,
414                                  * but it complicates things a lot. Instead
415                                  * lets just do what we already stored, and
416                                  * we'll get it the next time we are called.
417                                  */
418                                 if (error == AOP_TRUNCATED_PAGE)
419                                         error = 0;
420
421                                 break;
422                         }
423                 }
424 fill_it:
425                 /*
426                  * i_size must be checked after PageUptodate.
427                  */
428                 isize = i_size_read(mapping->host);
429                 end_index = (isize - 1) >> PAGE_CACHE_SHIFT;
430                 if (unlikely(!isize || index > end_index))
431                         break;
432
433                 /*
434                  * if this is the last page, see if we need to shrink
435                  * the length and stop
436                  */
437                 if (end_index == index) {
438                         unsigned int plen;
439
440                         /*
441                          * max good bytes in this page
442                          */
443                         plen = ((isize - 1) & ~PAGE_CACHE_MASK) + 1;
444                         if (plen <= loff)
445                                 break;
446
447                         /*
448                          * force quit after adding this page
449                          */
450                         this_len = min(this_len, plen - loff);
451                         len = this_len;
452                 }
453
454                 partial[page_nr].offset = loff;
455                 partial[page_nr].len = this_len;
456                 len -= this_len;
457                 loff = 0;
458                 spd.nr_pages++;
459                 index++;
460         }
461
462         /*
463          * Release any pages at the end, if we quit early. 'page_nr' is how far
464          * we got, 'nr_pages' is how many pages are in the map.
465          */
466         while (page_nr < nr_pages)
467                 page_cache_release(pages[page_nr++]);
468         in->f_ra.prev_pos = (loff_t)index << PAGE_CACHE_SHIFT;
469
470         if (spd.nr_pages)
471                 return splice_to_pipe(pipe, &spd);
472
473         return error;
474 }
475
476 /**
477  * generic_file_splice_read - splice data from file to a pipe
478  * @in:         file to splice from
479  * @ppos:       position in @in
480  * @pipe:       pipe to splice to
481  * @len:        number of bytes to splice
482  * @flags:      splice modifier flags
483  *
484  * Description:
485  *    Will read pages from given file and fill them into a pipe. Can be
486  *    used as long as the address_space operations for the source implements
487  *    a readpage() hook.
488  *
489  */
490 ssize_t generic_file_splice_read(struct file *in, loff_t *ppos,
491                                  struct pipe_inode_info *pipe, size_t len,
492                                  unsigned int flags)
493 {
494         loff_t isize, left;
495         int ret;
496
497         isize = i_size_read(in->f_mapping->host);
498         if (unlikely(*ppos >= isize))
499                 return 0;
500
501         left = isize - *ppos;
502         if (unlikely(left < len))
503                 len = left;
504
505         ret = __generic_file_splice_read(in, ppos, pipe, len, flags);
506         if (ret > 0)
507                 *ppos += ret;
508
509         return ret;
510 }
511
512 EXPORT_SYMBOL(generic_file_splice_read);
513
514 /*
515  * Send 'sd->len' bytes to socket from 'sd->file' at position 'sd->pos'
516  * using sendpage(). Return the number of bytes sent.
517  */
518 static int pipe_to_sendpage(struct pipe_inode_info *pipe,
519                             struct pipe_buffer *buf, struct splice_desc *sd)
520 {
521         struct file *file = sd->u.file;
522         loff_t pos = sd->pos;
523         int ret, more;
524
525         ret = buf->ops->confirm(pipe, buf);
526         if (!ret) {
527                 more = (sd->flags & SPLICE_F_MORE) || sd->len < sd->total_len;
528
529                 ret = file->f_op->sendpage(file, buf->page, buf->offset,
530                                            sd->len, &pos, more);
531         }
532
533         return ret;
534 }
535
536 /*
537  * This is a little more tricky than the file -> pipe splicing. There are
538  * basically three cases:
539  *
540  *      - Destination page already exists in the address space and there
541  *        are users of it. For that case we have no other option that
542  *        copying the data. Tough luck.
543  *      - Destination page already exists in the address space, but there
544  *        are no users of it. Make sure it's uptodate, then drop it. Fall
545  *        through to last case.
546  *      - Destination page does not exist, we can add the pipe page to
547  *        the page cache and avoid the copy.
548  *
549  * If asked to move pages to the output file (SPLICE_F_MOVE is set in
550  * sd->flags), we attempt to migrate pages from the pipe to the output
551  * file address space page cache. This is possible if no one else has
552  * the pipe page referenced outside of the pipe and page cache. If
553  * SPLICE_F_MOVE isn't set, or we cannot move the page, we simply create
554  * a new page in the output file page cache and fill/dirty that.
555  */
556 static int pipe_to_file(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
557                         struct splice_desc *sd)
558 {
559         struct file *file = sd->u.file;
560         struct address_space *mapping = file->f_mapping;
561         unsigned int offset, this_len;
562         struct page *page;
563         void *fsdata;
564         int ret;
565
566         /*
567          * make sure the data in this buffer is uptodate
568          */
569         ret = buf->ops->confirm(pipe, buf);
570         if (unlikely(ret))
571                 return ret;
572
573         offset = sd->pos & ~PAGE_CACHE_MASK;
574
575         this_len = sd->len;
576         if (this_len + offset > PAGE_CACHE_SIZE)
577                 this_len = PAGE_CACHE_SIZE - offset;
578
579         ret = pagecache_write_begin(file, mapping, sd->pos, this_len,
580                                 AOP_FLAG_UNINTERRUPTIBLE, &page, &fsdata);
581         if (unlikely(ret))
582                 goto out;
583
584         if (buf->page != page) {
585                 /*
586                  * Careful, ->map() uses KM_USER0!
587                  */
588                 char *src = buf->ops->map(pipe, buf, 1);
589                 char *dst = kmap_atomic(page, KM_USER1);
590
591                 memcpy(dst + offset, src + buf->offset, this_len);
592                 flush_dcache_page(page);
593                 kunmap_atomic(dst, KM_USER1);
594                 buf->ops->unmap(pipe, buf, src);
595         }
596         ret = pagecache_write_end(file, mapping, sd->pos, this_len, this_len,
597                                 page, fsdata);
598 out:
599         return ret;
600 }
601
602 /**
603  * __splice_from_pipe - splice data from a pipe to given actor
604  * @pipe:       pipe to splice from
605  * @sd:         information to @actor
606  * @actor:      handler that splices the data
607  *
608  * Description:
609  *    This function does little more than loop over the pipe and call
610  *    @actor to do the actual moving of a single struct pipe_buffer to
611  *    the desired destination. See pipe_to_file, pipe_to_sendpage, or
612  *    pipe_to_user.
613  *
614  */
615 ssize_t __splice_from_pipe(struct pipe_inode_info *pipe, struct splice_desc *sd,
616                            splice_actor *actor)
617 {
618         int ret, do_wakeup, err;
619
620         ret = 0;
621         do_wakeup = 0;
622
623         for (;;) {
624                 if (pipe->nrbufs) {
625                         struct pipe_buffer *buf = pipe->bufs + pipe->curbuf;
626                         const struct pipe_buf_operations *ops = buf->ops;
627
628                         sd->len = buf->len;
629                         if (sd->len > sd->total_len)
630                                 sd->len = sd->total_len;
631
632                         err = actor(pipe, buf, sd);
633                         if (err <= 0) {
634                                 if (!ret && err != -ENODATA)
635                                         ret = err;
636
637                                 break;
638                         }
639
640                         ret += err;
641                         buf->offset += err;
642                         buf->len -= err;
643
644                         sd->len -= err;
645                         sd->pos += err;
646                         sd->total_len -= err;
647                         if (sd->len)
648                                 continue;
649
650                         if (!buf->len) {
651                                 buf->ops = NULL;
652                                 ops->release(pipe, buf);
653                                 pipe->curbuf = (pipe->curbuf + 1) & (PIPE_BUFFERS - 1);
654                                 pipe->nrbufs--;
655                                 if (pipe->inode)
656                                         do_wakeup = 1;
657                         }
658
659                         if (!sd->total_len)
660                                 break;
661                 }
662
663                 if (pipe->nrbufs)
664                         continue;
665                 if (!pipe->writers)
666                         break;
667                 if (!pipe->waiting_writers) {
668                         if (ret)
669                                 break;
670                 }
671
672                 if (sd->flags & SPLICE_F_NONBLOCK) {
673                         if (!ret)
674                                 ret = -EAGAIN;
675                         break;
676                 }
677
678                 if (signal_pending(current)) {
679                         if (!ret)
680                                 ret = -ERESTARTSYS;
681                         break;
682                 }
683
684                 if (do_wakeup) {
685                         smp_mb();
686                         if (waitqueue_active(&pipe->wait))
687                                 wake_up_interruptible_sync(&pipe->wait);
688                         kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
689                         do_wakeup = 0;
690                 }
691
692                 pipe_wait(pipe);
693         }
694
695         if (do_wakeup) {
696                 smp_mb();
697                 if (waitqueue_active(&pipe->wait))
698                         wake_up_interruptible(&pipe->wait);
699                 kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
700         }
701
702         return ret;
703 }
704 EXPORT_SYMBOL(__splice_from_pipe);
705
706 /**
707  * splice_from_pipe - splice data from a pipe to a file
708  * @pipe:       pipe to splice from
709  * @out:        file to splice to
710  * @ppos:       position in @out
711  * @len:        how many bytes to splice
712  * @flags:      splice modifier flags
713  * @actor:      handler that splices the data
714  *
715  * Description:
716  *    See __splice_from_pipe. This function locks the input and output inodes,
717  *    otherwise it's identical to __splice_from_pipe().
718  *
719  */
720 ssize_t splice_from_pipe(struct pipe_inode_info *pipe, struct file *out,
721                          loff_t *ppos, size_t len, unsigned int flags,
722                          splice_actor *actor)
723 {
724         ssize_t ret;
725         struct inode *inode = out->f_mapping->host;
726         struct splice_desc sd = {
727                 .total_len = len,
728                 .flags = flags,
729                 .pos = *ppos,
730                 .u.file = out,
731         };
732
733         /*
734          * The actor worker might be calling ->prepare_write and
735          * ->commit_write. Most of the time, these expect i_mutex to
736          * be held. Since this may result in an ABBA deadlock with
737          * pipe->inode, we have to order lock acquiry here.
738          */
739         inode_double_lock(inode, pipe->inode);
740         ret = __splice_from_pipe(pipe, &sd, actor);
741         inode_double_unlock(inode, pipe->inode);
742
743         return ret;
744 }
745
746 /**
747  * generic_file_splice_write_nolock - generic_file_splice_write without mutexes
748  * @pipe:       pipe info
749  * @out:        file to write to
750  * @ppos:       position in @out
751  * @len:        number of bytes to splice
752  * @flags:      splice modifier flags
753  *
754  * Description:
755  *    Will either move or copy pages (determined by @flags options) from
756  *    the given pipe inode to the given file. The caller is responsible
757  *    for acquiring i_mutex on both inodes.
758  *
759  */
760 ssize_t
761 generic_file_splice_write_nolock(struct pipe_inode_info *pipe, struct file *out,
762                                  loff_t *ppos, size_t len, unsigned int flags)
763 {
764         struct address_space *mapping = out->f_mapping;
765         struct inode *inode = mapping->host;
766         struct splice_desc sd = {
767                 .total_len = len,
768                 .flags = flags,
769                 .pos = *ppos,
770                 .u.file = out,
771         };
772         ssize_t ret;
773         int err;
774
775         err = file_remove_suid(out);
776         if (unlikely(err))
777                 return err;
778
779         ret = __splice_from_pipe(pipe, &sd, pipe_to_file);
780         if (ret > 0) {
781                 unsigned long nr_pages;
782
783                 *ppos += ret;
784                 nr_pages = (ret + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
785
786                 /*
787                  * If file or inode is SYNC and we actually wrote some data,
788                  * sync it.
789                  */
790                 if (unlikely((out->f_flags & O_SYNC) || IS_SYNC(inode))) {
791                         err = generic_osync_inode(inode, mapping,
792                                                   OSYNC_METADATA|OSYNC_DATA);
793
794                         if (err)
795                                 ret = err;
796                 }
797                 balance_dirty_pages_ratelimited_nr(mapping, nr_pages);
798         }
799
800         return ret;
801 }
802
803 EXPORT_SYMBOL(generic_file_splice_write_nolock);
804
805 /**
806  * generic_file_splice_write - splice data from a pipe to a file
807  * @pipe:       pipe info
808  * @out:        file to write to
809  * @ppos:       position in @out
810  * @len:        number of bytes to splice
811  * @flags:      splice modifier flags
812  *
813  * Description:
814  *    Will either move or copy pages (determined by @flags options) from
815  *    the given pipe inode to the given file.
816  *
817  */
818 ssize_t
819 generic_file_splice_write(struct pipe_inode_info *pipe, struct file *out,
820                           loff_t *ppos, size_t len, unsigned int flags)
821 {
822         struct address_space *mapping = out->f_mapping;
823         struct inode *inode = mapping->host;
824         struct splice_desc sd = {
825                 .total_len = len,
826                 .flags = flags,
827                 .pos = *ppos,
828                 .u.file = out,
829         };
830         ssize_t ret;
831
832         inode_double_lock(inode, pipe->inode);
833         ret = file_remove_suid(out);
834         if (likely(!ret))
835                 ret = __splice_from_pipe(pipe, &sd, pipe_to_file);
836         inode_double_unlock(inode, pipe->inode);
837         if (ret > 0) {
838                 unsigned long nr_pages;
839
840                 *ppos += ret;
841                 nr_pages = (ret + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
842
843                 /*
844                  * If file or inode is SYNC and we actually wrote some data,
845                  * sync it.
846                  */
847                 if (unlikely((out->f_flags & O_SYNC) || IS_SYNC(inode))) {
848                         int err;
849
850                         mutex_lock(&inode->i_mutex);
851                         err = generic_osync_inode(inode, mapping,
852                                                   OSYNC_METADATA|OSYNC_DATA);
853                         mutex_unlock(&inode->i_mutex);
854
855                         if (err)
856                                 ret = err;
857                 }
858                 balance_dirty_pages_ratelimited_nr(mapping, nr_pages);
859         }
860
861         return ret;
862 }
863
864 EXPORT_SYMBOL(generic_file_splice_write);
865
866 /**
867  * generic_splice_sendpage - splice data from a pipe to a socket
868  * @pipe:       pipe to splice from
869  * @out:        socket to write to
870  * @ppos:       position in @out
871  * @len:        number of bytes to splice
872  * @flags:      splice modifier flags
873  *
874  * Description:
875  *    Will send @len bytes from the pipe to a network socket. No data copying
876  *    is involved.
877  *
878  */
879 ssize_t generic_splice_sendpage(struct pipe_inode_info *pipe, struct file *out,
880                                 loff_t *ppos, size_t len, unsigned int flags)
881 {
882         return splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_sendpage);
883 }
884
885 EXPORT_SYMBOL(generic_splice_sendpage);
886
887 /*
888  * Attempt to initiate a splice from pipe to file.
889  */
890 static long do_splice_from(struct pipe_inode_info *pipe, struct file *out,
891                            loff_t *ppos, size_t len, unsigned int flags)
892 {
893         int ret;
894
895         if (unlikely(!out->f_op || !out->f_op->splice_write))
896                 return -EINVAL;
897
898         if (unlikely(!(out->f_mode & FMODE_WRITE)))
899                 return -EBADF;
900
901         if (unlikely(out->f_flags & O_APPEND))
902                 return -EINVAL;
903
904         ret = rw_verify_area(WRITE, out, ppos, len);
905         if (unlikely(ret < 0))
906                 return ret;
907
908         return out->f_op->splice_write(pipe, out, ppos, len, flags);
909 }
910
911 /*
912  * Attempt to initiate a splice from a file to a pipe.
913  */
914 static long do_splice_to(struct file *in, loff_t *ppos,
915                          struct pipe_inode_info *pipe, size_t len,
916                          unsigned int flags)
917 {
918         int ret;
919
920         if (unlikely(!in->f_op || !in->f_op->splice_read))
921                 return -EINVAL;
922
923         if (unlikely(!(in->f_mode & FMODE_READ)))
924                 return -EBADF;
925
926         ret = rw_verify_area(READ, in, ppos, len);
927         if (unlikely(ret < 0))
928                 return ret;
929
930         return in->f_op->splice_read(in, ppos, pipe, len, flags);
931 }
932
933 /**
934  * splice_direct_to_actor - splices data directly between two non-pipes
935  * @in:         file to splice from
936  * @sd:         actor information on where to splice to
937  * @actor:      handles the data splicing
938  *
939  * Description:
940  *    This is a special case helper to splice directly between two
941  *    points, without requiring an explicit pipe. Internally an allocated
942  *    pipe is cached in the process, and reused during the lifetime of
943  *    that process.
944  *
945  */
946 ssize_t splice_direct_to_actor(struct file *in, struct splice_desc *sd,
947                                splice_direct_actor *actor)
948 {
949         struct pipe_inode_info *pipe;
950         long ret, bytes;
951         umode_t i_mode;
952         size_t len;
953         int i, flags;
954
955         /*
956          * We require the input being a regular file, as we don't want to
957          * randomly drop data for eg socket -> socket splicing. Use the
958          * piped splicing for that!
959          */
960         i_mode = in->f_path.dentry->d_inode->i_mode;
961         if (unlikely(!S_ISREG(i_mode) && !S_ISBLK(i_mode)))
962                 return -EINVAL;
963
964         /*
965          * neither in nor out is a pipe, setup an internal pipe attached to
966          * 'out' and transfer the wanted data from 'in' to 'out' through that
967          */
968         pipe = current->splice_pipe;
969         if (unlikely(!pipe)) {
970                 pipe = alloc_pipe_info(NULL);
971                 if (!pipe)
972                         return -ENOMEM;
973
974                 /*
975                  * We don't have an immediate reader, but we'll read the stuff
976                  * out of the pipe right after the splice_to_pipe(). So set
977                  * PIPE_READERS appropriately.
978                  */
979                 pipe->readers = 1;
980
981                 current->splice_pipe = pipe;
982         }
983
984         /*
985          * Do the splice.
986          */
987         ret = 0;
988         bytes = 0;
989         len = sd->total_len;
990         flags = sd->flags;
991
992         /*
993          * Don't block on output, we have to drain the direct pipe.
994          */
995         sd->flags &= ~SPLICE_F_NONBLOCK;
996
997         while (len) {
998                 size_t read_len;
999                 loff_t pos = sd->pos, prev_pos = pos;
1000
1001                 ret = do_splice_to(in, &pos, pipe, len, flags);
1002                 if (unlikely(ret <= 0))
1003                         goto out_release;
1004
1005                 read_len = ret;
1006                 sd->total_len = read_len;
1007
1008                 /*
1009                  * NOTE: nonblocking mode only applies to the input. We
1010                  * must not do the output in nonblocking mode as then we
1011                  * could get stuck data in the internal pipe:
1012                  */
1013                 ret = actor(pipe, sd);
1014                 if (unlikely(ret <= 0)) {
1015                         sd->pos = prev_pos;
1016                         goto out_release;
1017                 }
1018
1019                 bytes += ret;
1020                 len -= ret;
1021                 sd->pos = pos;
1022
1023                 if (ret < read_len) {
1024                         sd->pos = prev_pos + ret;
1025                         goto out_release;
1026                 }
1027         }
1028
1029 done:
1030         pipe->nrbufs = pipe->curbuf = 0;
1031         file_accessed(in);
1032         return bytes;
1033
1034 out_release:
1035         /*
1036          * If we did an incomplete transfer we must release
1037          * the pipe buffers in question:
1038          */
1039         for (i = 0; i < PIPE_BUFFERS; i++) {
1040                 struct pipe_buffer *buf = pipe->bufs + i;
1041
1042                 if (buf->ops) {
1043                         buf->ops->release(pipe, buf);
1044                         buf->ops = NULL;
1045                 }
1046         }
1047
1048         if (!bytes)
1049                 bytes = ret;
1050
1051         goto done;
1052 }
1053 EXPORT_SYMBOL(splice_direct_to_actor);
1054
1055 static int direct_splice_actor(struct pipe_inode_info *pipe,
1056                                struct splice_desc *sd)
1057 {
1058         struct file *file = sd->u.file;
1059
1060         return do_splice_from(pipe, file, &sd->pos, sd->total_len, sd->flags);
1061 }
1062
1063 /**
1064  * do_splice_direct - splices data directly between two files
1065  * @in:         file to splice from
1066  * @ppos:       input file offset
1067  * @out:        file to splice to
1068  * @len:        number of bytes to splice
1069  * @flags:      splice modifier flags
1070  *
1071  * Description:
1072  *    For use by do_sendfile(). splice can easily emulate sendfile, but
1073  *    doing it in the application would incur an extra system call
1074  *    (splice in + splice out, as compared to just sendfile()). So this helper
1075  *    can splice directly through a process-private pipe.
1076  *
1077  */
1078 long do_splice_direct(struct file *in, loff_t *ppos, struct file *out,
1079                       size_t len, unsigned int flags)
1080 {
1081         struct splice_desc sd = {
1082                 .len            = len,
1083                 .total_len      = len,
1084                 .flags          = flags,
1085                 .pos            = *ppos,
1086                 .u.file         = out,
1087         };
1088         long ret;
1089
1090         ret = splice_direct_to_actor(in, &sd, direct_splice_actor);
1091         if (ret > 0)
1092                 *ppos = sd.pos;
1093
1094         return ret;
1095 }
1096
1097 /*
1098  * After the inode slimming patch, i_pipe/i_bdev/i_cdev share the same
1099  * location, so checking ->i_pipe is not enough to verify that this is a
1100  * pipe.
1101  */
1102 static inline struct pipe_inode_info *pipe_info(struct inode *inode)
1103 {
1104         if (S_ISFIFO(inode->i_mode))
1105                 return inode->i_pipe;
1106
1107         return NULL;
1108 }
1109
1110 /*
1111  * Determine where to splice to/from.
1112  */
1113 static long do_splice(struct file *in, loff_t __user *off_in,
1114                       struct file *out, loff_t __user *off_out,
1115                       size_t len, unsigned int flags)
1116 {
1117         struct pipe_inode_info *pipe;
1118         loff_t offset, *off;
1119         long ret;
1120
1121         pipe = pipe_info(in->f_path.dentry->d_inode);
1122         if (pipe) {
1123                 if (off_in)
1124                         return -ESPIPE;
1125                 if (off_out) {
1126                         if (out->f_op->llseek == no_llseek)
1127                                 return -EINVAL;
1128                         if (copy_from_user(&offset, off_out, sizeof(loff_t)))
1129                                 return -EFAULT;
1130                         off = &offset;
1131                 } else
1132                         off = &out->f_pos;
1133
1134                 ret = do_splice_from(pipe, out, off, len, flags);
1135
1136                 if (off_out && copy_to_user(off_out, off, sizeof(loff_t)))
1137                         ret = -EFAULT;
1138
1139                 return ret;
1140         }
1141
1142         pipe = pipe_info(out->f_path.dentry->d_inode);
1143         if (pipe) {
1144                 if (off_out)
1145                         return -ESPIPE;
1146                 if (off_in) {
1147                         if (in->f_op->llseek == no_llseek)
1148                                 return -EINVAL;
1149                         if (copy_from_user(&offset, off_in, sizeof(loff_t)))
1150                                 return -EFAULT;
1151                         off = &offset;
1152                 } else
1153                         off = &in->f_pos;
1154
1155                 ret = do_splice_to(in, off, pipe, len, flags);
1156
1157                 if (off_in && copy_to_user(off_in, off, sizeof(loff_t)))
1158                         ret = -EFAULT;
1159
1160                 return ret;
1161         }
1162
1163         return -EINVAL;
1164 }
1165
1166 /*
1167  * Map an iov into an array of pages and offset/length tupples. With the
1168  * partial_page structure, we can map several non-contiguous ranges into
1169  * our ones pages[] map instead of splitting that operation into pieces.
1170  * Could easily be exported as a generic helper for other users, in which
1171  * case one would probably want to add a 'max_nr_pages' parameter as well.
1172  */
1173 static int get_iovec_page_array(const struct iovec __user *iov,
1174                                 unsigned int nr_vecs, struct page **pages,
1175                                 struct partial_page *partial, int aligned)
1176 {
1177         int buffers = 0, error = 0;
1178
1179         while (nr_vecs) {
1180                 unsigned long off, npages;
1181                 struct iovec entry;
1182                 void __user *base;
1183                 size_t len;
1184                 int i;
1185
1186                 error = -EFAULT;
1187                 if (copy_from_user(&entry, iov, sizeof(entry)))
1188                         break;
1189
1190                 base = entry.iov_base;
1191                 len = entry.iov_len;
1192
1193                 /*
1194                  * Sanity check this iovec. 0 read succeeds.
1195                  */
1196                 error = 0;
1197                 if (unlikely(!len))
1198                         break;
1199                 error = -EFAULT;
1200                 if (!access_ok(VERIFY_READ, base, len))
1201                         break;
1202
1203                 /*
1204                  * Get this base offset and number of pages, then map
1205                  * in the user pages.
1206                  */
1207                 off = (unsigned long) base & ~PAGE_MASK;
1208
1209                 /*
1210                  * If asked for alignment, the offset must be zero and the
1211                  * length a multiple of the PAGE_SIZE.
1212                  */
1213                 error = -EINVAL;
1214                 if (aligned && (off || len & ~PAGE_MASK))
1215                         break;
1216
1217                 npages = (off + len + PAGE_SIZE - 1) >> PAGE_SHIFT;
1218                 if (npages > PIPE_BUFFERS - buffers)
1219                         npages = PIPE_BUFFERS - buffers;
1220
1221                 error = get_user_pages_fast((unsigned long)base, npages,
1222                                         0, &pages[buffers]);
1223
1224                 if (unlikely(error <= 0))
1225                         break;
1226
1227                 /*
1228                  * Fill this contiguous range into the partial page map.
1229                  */
1230                 for (i = 0; i < error; i++) {
1231                         const int plen = min_t(size_t, len, PAGE_SIZE - off);
1232
1233                         partial[buffers].offset = off;
1234                         partial[buffers].len = plen;
1235
1236                         off = 0;
1237                         len -= plen;
1238                         buffers++;
1239                 }
1240
1241                 /*
1242                  * We didn't complete this iov, stop here since it probably
1243                  * means we have to move some of this into a pipe to
1244                  * be able to continue.
1245                  */
1246                 if (len)
1247                         break;
1248
1249                 /*
1250                  * Don't continue if we mapped fewer pages than we asked for,
1251                  * or if we mapped the max number of pages that we have
1252                  * room for.
1253                  */
1254                 if (error < npages || buffers == PIPE_BUFFERS)
1255                         break;
1256
1257                 nr_vecs--;
1258                 iov++;
1259         }
1260
1261         if (buffers)
1262                 return buffers;
1263
1264         return error;
1265 }
1266
1267 static int pipe_to_user(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
1268                         struct splice_desc *sd)
1269 {
1270         char *src;
1271         int ret;
1272
1273         ret = buf->ops->confirm(pipe, buf);
1274         if (unlikely(ret))
1275                 return ret;
1276
1277         /*
1278          * See if we can use the atomic maps, by prefaulting in the
1279          * pages and doing an atomic copy
1280          */
1281         if (!fault_in_pages_writeable(sd->u.userptr, sd->len)) {
1282                 src = buf->ops->map(pipe, buf, 1);
1283                 ret = __copy_to_user_inatomic(sd->u.userptr, src + buf->offset,
1284                                                         sd->len);
1285                 buf->ops->unmap(pipe, buf, src);
1286                 if (!ret) {
1287                         ret = sd->len;
1288                         goto out;
1289                 }
1290         }
1291
1292         /*
1293          * No dice, use slow non-atomic map and copy
1294          */
1295         src = buf->ops->map(pipe, buf, 0);
1296
1297         ret = sd->len;
1298         if (copy_to_user(sd->u.userptr, src + buf->offset, sd->len))
1299                 ret = -EFAULT;
1300
1301         buf->ops->unmap(pipe, buf, src);
1302 out:
1303         if (ret > 0)
1304                 sd->u.userptr += ret;
1305         return ret;
1306 }
1307
1308 /*
1309  * For lack of a better implementation, implement vmsplice() to userspace
1310  * as a simple copy of the pipes pages to the user iov.
1311  */
1312 static long vmsplice_to_user(struct file *file, const struct iovec __user *iov,
1313                              unsigned long nr_segs, unsigned int flags)
1314 {
1315         struct pipe_inode_info *pipe;
1316         struct splice_desc sd;
1317         ssize_t size;
1318         int error;
1319         long ret;
1320
1321         pipe = pipe_info(file->f_path.dentry->d_inode);
1322         if (!pipe)
1323                 return -EBADF;
1324
1325         if (pipe->inode)
1326                 mutex_lock(&pipe->inode->i_mutex);
1327
1328         error = ret = 0;
1329         while (nr_segs) {
1330                 void __user *base;
1331                 size_t len;
1332
1333                 /*
1334                  * Get user address base and length for this iovec.
1335                  */
1336                 error = get_user(base, &iov->iov_base);
1337                 if (unlikely(error))
1338                         break;
1339                 error = get_user(len, &iov->iov_len);
1340                 if (unlikely(error))
1341                         break;
1342
1343                 /*
1344                  * Sanity check this iovec. 0 read succeeds.
1345                  */
1346                 if (unlikely(!len))
1347                         break;
1348                 if (unlikely(!base)) {
1349                         error = -EFAULT;
1350                         break;
1351                 }
1352
1353                 if (unlikely(!access_ok(VERIFY_WRITE, base, len))) {
1354                         error = -EFAULT;
1355                         break;
1356                 }
1357
1358                 sd.len = 0;
1359                 sd.total_len = len;
1360                 sd.flags = flags;
1361                 sd.u.userptr = base;
1362                 sd.pos = 0;
1363
1364                 size = __splice_from_pipe(pipe, &sd, pipe_to_user);
1365                 if (size < 0) {
1366                         if (!ret)
1367                                 ret = size;
1368
1369                         break;
1370                 }
1371
1372                 ret += size;
1373
1374                 if (size < len)
1375                         break;
1376
1377                 nr_segs--;
1378                 iov++;
1379         }
1380
1381         if (pipe->inode)
1382                 mutex_unlock(&pipe->inode->i_mutex);
1383
1384         if (!ret)
1385                 ret = error;
1386
1387         return ret;
1388 }
1389
1390 /*
1391  * vmsplice splices a user address range into a pipe. It can be thought of
1392  * as splice-from-memory, where the regular splice is splice-from-file (or
1393  * to file). In both cases the output is a pipe, naturally.
1394  */
1395 static long vmsplice_to_pipe(struct file *file, const struct iovec __user *iov,
1396                              unsigned long nr_segs, unsigned int flags)
1397 {
1398         struct pipe_inode_info *pipe;
1399         struct page *pages[PIPE_BUFFERS];
1400         struct partial_page partial[PIPE_BUFFERS];
1401         struct splice_pipe_desc spd = {
1402                 .pages = pages,
1403                 .partial = partial,
1404                 .flags = flags,
1405                 .ops = &user_page_pipe_buf_ops,
1406                 .spd_release = spd_release_page,
1407         };
1408
1409         pipe = pipe_info(file->f_path.dentry->d_inode);
1410         if (!pipe)
1411                 return -EBADF;
1412
1413         spd.nr_pages = get_iovec_page_array(iov, nr_segs, pages, partial,
1414                                             flags & SPLICE_F_GIFT);
1415         if (spd.nr_pages <= 0)
1416                 return spd.nr_pages;
1417
1418         return splice_to_pipe(pipe, &spd);
1419 }
1420
1421 /*
1422  * Note that vmsplice only really supports true splicing _from_ user memory
1423  * to a pipe, not the other way around. Splicing from user memory is a simple
1424  * operation that can be supported without any funky alignment restrictions
1425  * or nasty vm tricks. We simply map in the user memory and fill them into
1426  * a pipe. The reverse isn't quite as easy, though. There are two possible
1427  * solutions for that:
1428  *
1429  *      - memcpy() the data internally, at which point we might as well just
1430  *        do a regular read() on the buffer anyway.
1431  *      - Lots of nasty vm tricks, that are neither fast nor flexible (it
1432  *        has restriction limitations on both ends of the pipe).
1433  *
1434  * Currently we punt and implement it as a normal copy, see pipe_to_user().
1435  *
1436  */
1437 asmlinkage long sys_vmsplice(int fd, const struct iovec __user *iov,
1438                              unsigned long nr_segs, unsigned int flags)
1439 {
1440         struct file *file;
1441         long error;
1442         int fput;
1443
1444         if (unlikely(nr_segs > UIO_MAXIOV))
1445                 return -EINVAL;
1446         else if (unlikely(!nr_segs))
1447                 return 0;
1448
1449         error = -EBADF;
1450         file = fget_light(fd, &fput);
1451         if (file) {
1452                 if (file->f_mode & FMODE_WRITE)
1453                         error = vmsplice_to_pipe(file, iov, nr_segs, flags);
1454                 else if (file->f_mode & FMODE_READ)
1455                         error = vmsplice_to_user(file, iov, nr_segs, flags);
1456
1457                 fput_light(file, fput);
1458         }
1459
1460         return error;
1461 }
1462
1463 asmlinkage long sys_splice(int fd_in, loff_t __user *off_in,
1464                            int fd_out, loff_t __user *off_out,
1465                            size_t len, unsigned int flags)
1466 {
1467         long error;
1468         struct file *in, *out;
1469         int fput_in, fput_out;
1470
1471         if (unlikely(!len))
1472                 return 0;
1473
1474         error = -EBADF;
1475         in = fget_light(fd_in, &fput_in);
1476         if (in) {
1477                 if (in->f_mode & FMODE_READ) {
1478                         out = fget_light(fd_out, &fput_out);
1479                         if (out) {
1480                                 if (out->f_mode & FMODE_WRITE)
1481                                         error = do_splice(in, off_in,
1482                                                           out, off_out,
1483                                                           len, flags);
1484                                 fput_light(out, fput_out);
1485                         }
1486                 }
1487
1488                 fput_light(in, fput_in);
1489         }
1490
1491         return error;
1492 }
1493
1494 /*
1495  * Make sure there's data to read. Wait for input if we can, otherwise
1496  * return an appropriate error.
1497  */
1498 static int link_ipipe_prep(struct pipe_inode_info *pipe, unsigned int flags)
1499 {
1500         int ret;
1501
1502         /*
1503          * Check ->nrbufs without the inode lock first. This function
1504          * is speculative anyways, so missing one is ok.
1505          */
1506         if (pipe->nrbufs)
1507                 return 0;
1508
1509         ret = 0;
1510         mutex_lock(&pipe->inode->i_mutex);
1511
1512         while (!pipe->nrbufs) {
1513                 if (signal_pending(current)) {
1514                         ret = -ERESTARTSYS;
1515                         break;
1516                 }
1517                 if (!pipe->writers)
1518                         break;
1519                 if (!pipe->waiting_writers) {
1520                         if (flags & SPLICE_F_NONBLOCK) {
1521                                 ret = -EAGAIN;
1522                                 break;
1523                         }
1524                 }
1525                 pipe_wait(pipe);
1526         }
1527
1528         mutex_unlock(&pipe->inode->i_mutex);
1529         return ret;
1530 }
1531
1532 /*
1533  * Make sure there's writeable room. Wait for room if we can, otherwise
1534  * return an appropriate error.
1535  */
1536 static int link_opipe_prep(struct pipe_inode_info *pipe, unsigned int flags)
1537 {
1538         int ret;
1539
1540         /*
1541          * Check ->nrbufs without the inode lock first. This function
1542          * is speculative anyways, so missing one is ok.
1543          */
1544         if (pipe->nrbufs < PIPE_BUFFERS)
1545                 return 0;
1546
1547         ret = 0;
1548         mutex_lock(&pipe->inode->i_mutex);
1549
1550         while (pipe->nrbufs >= PIPE_BUFFERS) {
1551                 if (!pipe->readers) {
1552                         send_sig(SIGPIPE, current, 0);
1553                         ret = -EPIPE;
1554                         break;
1555                 }
1556                 if (flags & SPLICE_F_NONBLOCK) {
1557                         ret = -EAGAIN;
1558                         break;
1559                 }
1560                 if (signal_pending(current)) {
1561                         ret = -ERESTARTSYS;
1562                         break;
1563                 }
1564                 pipe->waiting_writers++;
1565                 pipe_wait(pipe);
1566                 pipe->waiting_writers--;
1567         }
1568
1569         mutex_unlock(&pipe->inode->i_mutex);
1570         return ret;
1571 }
1572
1573 /*
1574  * Link contents of ipipe to opipe.
1575  */
1576 static int link_pipe(struct pipe_inode_info *ipipe,
1577                      struct pipe_inode_info *opipe,
1578                      size_t len, unsigned int flags)
1579 {
1580         struct pipe_buffer *ibuf, *obuf;
1581         int ret = 0, i = 0, nbuf;
1582
1583         /*
1584          * Potential ABBA deadlock, work around it by ordering lock
1585          * grabbing by inode address. Otherwise two different processes
1586          * could deadlock (one doing tee from A -> B, the other from B -> A).
1587          */
1588         inode_double_lock(ipipe->inode, opipe->inode);
1589
1590         do {
1591                 if (!opipe->readers) {
1592                         send_sig(SIGPIPE, current, 0);
1593                         if (!ret)
1594                                 ret = -EPIPE;
1595                         break;
1596                 }
1597
1598                 /*
1599                  * If we have iterated all input buffers or ran out of
1600                  * output room, break.
1601                  */
1602                 if (i >= ipipe->nrbufs || opipe->nrbufs >= PIPE_BUFFERS)
1603                         break;
1604
1605                 ibuf = ipipe->bufs + ((ipipe->curbuf + i) & (PIPE_BUFFERS - 1));
1606                 nbuf = (opipe->curbuf + opipe->nrbufs) & (PIPE_BUFFERS - 1);
1607
1608                 /*
1609                  * Get a reference to this pipe buffer,
1610                  * so we can copy the contents over.
1611                  */
1612                 ibuf->ops->get(ipipe, ibuf);
1613
1614                 obuf = opipe->bufs + nbuf;
1615                 *obuf = *ibuf;
1616
1617                 /*
1618                  * Don't inherit the gift flag, we need to
1619                  * prevent multiple steals of this page.
1620                  */
1621                 obuf->flags &= ~PIPE_BUF_FLAG_GIFT;
1622
1623                 if (obuf->len > len)
1624                         obuf->len = len;
1625
1626                 opipe->nrbufs++;
1627                 ret += obuf->len;
1628                 len -= obuf->len;
1629                 i++;
1630         } while (len);
1631
1632         /*
1633          * return EAGAIN if we have the potential of some data in the
1634          * future, otherwise just return 0
1635          */
1636         if (!ret && ipipe->waiting_writers && (flags & SPLICE_F_NONBLOCK))
1637                 ret = -EAGAIN;
1638
1639         inode_double_unlock(ipipe->inode, opipe->inode);
1640
1641         /*
1642          * If we put data in the output pipe, wakeup any potential readers.
1643          */
1644         if (ret > 0) {
1645                 smp_mb();
1646                 if (waitqueue_active(&opipe->wait))
1647                         wake_up_interruptible(&opipe->wait);
1648                 kill_fasync(&opipe->fasync_readers, SIGIO, POLL_IN);
1649         }
1650
1651         return ret;
1652 }
1653
1654 /*
1655  * This is a tee(1) implementation that works on pipes. It doesn't copy
1656  * any data, it simply references the 'in' pages on the 'out' pipe.
1657  * The 'flags' used are the SPLICE_F_* variants, currently the only
1658  * applicable one is SPLICE_F_NONBLOCK.
1659  */
1660 static long do_tee(struct file *in, struct file *out, size_t len,
1661                    unsigned int flags)
1662 {
1663         struct pipe_inode_info *ipipe = pipe_info(in->f_path.dentry->d_inode);
1664         struct pipe_inode_info *opipe = pipe_info(out->f_path.dentry->d_inode);
1665         int ret = -EINVAL;
1666
1667         /*
1668          * Duplicate the contents of ipipe to opipe without actually
1669          * copying the data.
1670          */
1671         if (ipipe && opipe && ipipe != opipe) {
1672                 /*
1673                  * Keep going, unless we encounter an error. The ipipe/opipe
1674                  * ordering doesn't really matter.
1675                  */
1676                 ret = link_ipipe_prep(ipipe, flags);
1677                 if (!ret) {
1678                         ret = link_opipe_prep(opipe, flags);
1679                         if (!ret)
1680                                 ret = link_pipe(ipipe, opipe, len, flags);
1681                 }
1682         }
1683
1684         return ret;
1685 }
1686
1687 asmlinkage long sys_tee(int fdin, int fdout, size_t len, unsigned int flags)
1688 {
1689         struct file *in;
1690         int error, fput_in;
1691
1692         if (unlikely(!len))
1693                 return 0;
1694
1695         error = -EBADF;
1696         in = fget_light(fdin, &fput_in);
1697         if (in) {
1698                 if (in->f_mode & FMODE_READ) {
1699                         int fput_out;
1700                         struct file *out = fget_light(fdout, &fput_out);
1701
1702                         if (out) {
1703                                 if (out->f_mode & FMODE_WRITE)
1704                                         error = do_tee(in, out, len, flags);
1705                                 fput_light(out, fput_out);
1706                         }
1707                 }
1708                 fput_light(in, fput_in);
1709         }
1710
1711         return error;
1712 }