splice: move inode size check into generic_file_splice_read()
[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/pipe_fs_i.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
32 struct partial_page {
33         unsigned int offset;
34         unsigned int len;
35 };
36
37 /*
38  * Passed to splice_to_pipe
39  */
40 struct splice_pipe_desc {
41         struct page **pages;            /* page map */
42         struct partial_page *partial;   /* pages[] may not be contig */
43         int nr_pages;                   /* number of pages in map */
44         unsigned int flags;             /* splice flags */
45         const struct pipe_buf_operations *ops;/* ops associated with output pipe */
46 };
47
48 /*
49  * Attempt to steal a page from a pipe buffer. This should perhaps go into
50  * a vm helper function, it's already simplified quite a bit by the
51  * addition of remove_mapping(). If success is returned, the caller may
52  * attempt to reuse this page for another destination.
53  */
54 static int page_cache_pipe_buf_steal(struct pipe_inode_info *pipe,
55                                      struct pipe_buffer *buf)
56 {
57         struct page *page = buf->page;
58         struct address_space *mapping;
59
60         lock_page(page);
61
62         mapping = page_mapping(page);
63         if (mapping) {
64                 WARN_ON(!PageUptodate(page));
65
66                 /*
67                  * At least for ext2 with nobh option, we need to wait on
68                  * writeback completing on this page, since we'll remove it
69                  * from the pagecache.  Otherwise truncate wont wait on the
70                  * page, allowing the disk blocks to be reused by someone else
71                  * before we actually wrote our data to them. fs corruption
72                  * ensues.
73                  */
74                 wait_on_page_writeback(page);
75
76                 if (PagePrivate(page))
77                         try_to_release_page(page, GFP_KERNEL);
78
79                 /*
80                  * If we succeeded in removing the mapping, set LRU flag
81                  * and return good.
82                  */
83                 if (remove_mapping(mapping, page)) {
84                         buf->flags |= PIPE_BUF_FLAG_LRU;
85                         return 0;
86                 }
87         }
88
89         /*
90          * Raced with truncate or failed to remove page from current
91          * address space, unlock and return failure.
92          */
93         unlock_page(page);
94         return 1;
95 }
96
97 static void page_cache_pipe_buf_release(struct pipe_inode_info *pipe,
98                                         struct pipe_buffer *buf)
99 {
100         page_cache_release(buf->page);
101         buf->flags &= ~PIPE_BUF_FLAG_LRU;
102 }
103
104 static int page_cache_pipe_buf_pin(struct pipe_inode_info *pipe,
105                                    struct pipe_buffer *buf)
106 {
107         struct page *page = buf->page;
108         int err;
109
110         if (!PageUptodate(page)) {
111                 lock_page(page);
112
113                 /*
114                  * Page got truncated/unhashed. This will cause a 0-byte
115                  * splice, if this is the first page.
116                  */
117                 if (!page->mapping) {
118                         err = -ENODATA;
119                         goto error;
120                 }
121
122                 /*
123                  * Uh oh, read-error from disk.
124                  */
125                 if (!PageUptodate(page)) {
126                         err = -EIO;
127                         goto error;
128                 }
129
130                 /*
131                  * Page is ok afterall, we are done.
132                  */
133                 unlock_page(page);
134         }
135
136         return 0;
137 error:
138         unlock_page(page);
139         return err;
140 }
141
142 static const struct pipe_buf_operations page_cache_pipe_buf_ops = {
143         .can_merge = 0,
144         .map = generic_pipe_buf_map,
145         .unmap = generic_pipe_buf_unmap,
146         .pin = page_cache_pipe_buf_pin,
147         .release = page_cache_pipe_buf_release,
148         .steal = page_cache_pipe_buf_steal,
149         .get = generic_pipe_buf_get,
150 };
151
152 static int user_page_pipe_buf_steal(struct pipe_inode_info *pipe,
153                                     struct pipe_buffer *buf)
154 {
155         if (!(buf->flags & PIPE_BUF_FLAG_GIFT))
156                 return 1;
157
158         buf->flags |= PIPE_BUF_FLAG_LRU;
159         return generic_pipe_buf_steal(pipe, buf);
160 }
161
162 static const struct pipe_buf_operations user_page_pipe_buf_ops = {
163         .can_merge = 0,
164         .map = generic_pipe_buf_map,
165         .unmap = generic_pipe_buf_unmap,
166         .pin = generic_pipe_buf_pin,
167         .release = page_cache_pipe_buf_release,
168         .steal = user_page_pipe_buf_steal,
169         .get = generic_pipe_buf_get,
170 };
171
172 /*
173  * Pipe output worker. This sets up our pipe format with the page cache
174  * pipe buffer operations. Otherwise very similar to the regular pipe_writev().
175  */
176 static ssize_t splice_to_pipe(struct pipe_inode_info *pipe,
177                               struct splice_pipe_desc *spd)
178 {
179         int ret, do_wakeup, page_nr;
180
181         ret = 0;
182         do_wakeup = 0;
183         page_nr = 0;
184
185         if (pipe->inode)
186                 mutex_lock(&pipe->inode->i_mutex);
187
188         for (;;) {
189                 if (!pipe->readers) {
190                         send_sig(SIGPIPE, current, 0);
191                         if (!ret)
192                                 ret = -EPIPE;
193                         break;
194                 }
195
196                 if (pipe->nrbufs < PIPE_BUFFERS) {
197                         int newbuf = (pipe->curbuf + pipe->nrbufs) & (PIPE_BUFFERS - 1);
198                         struct pipe_buffer *buf = pipe->bufs + newbuf;
199
200                         buf->page = spd->pages[page_nr];
201                         buf->offset = spd->partial[page_nr].offset;
202                         buf->len = spd->partial[page_nr].len;
203                         buf->ops = spd->ops;
204                         if (spd->flags & SPLICE_F_GIFT)
205                                 buf->flags |= PIPE_BUF_FLAG_GIFT;
206
207                         pipe->nrbufs++;
208                         page_nr++;
209                         ret += buf->len;
210
211                         if (pipe->inode)
212                                 do_wakeup = 1;
213
214                         if (!--spd->nr_pages)
215                                 break;
216                         if (pipe->nrbufs < PIPE_BUFFERS)
217                                 continue;
218
219                         break;
220                 }
221
222                 if (spd->flags & SPLICE_F_NONBLOCK) {
223                         if (!ret)
224                                 ret = -EAGAIN;
225                         break;
226                 }
227
228                 if (signal_pending(current)) {
229                         if (!ret)
230                                 ret = -ERESTARTSYS;
231                         break;
232                 }
233
234                 if (do_wakeup) {
235                         smp_mb();
236                         if (waitqueue_active(&pipe->wait))
237                                 wake_up_interruptible_sync(&pipe->wait);
238                         kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
239                         do_wakeup = 0;
240                 }
241
242                 pipe->waiting_writers++;
243                 pipe_wait(pipe);
244                 pipe->waiting_writers--;
245         }
246
247         if (pipe->inode)
248                 mutex_unlock(&pipe->inode->i_mutex);
249
250         if (do_wakeup) {
251                 smp_mb();
252                 if (waitqueue_active(&pipe->wait))
253                         wake_up_interruptible(&pipe->wait);
254                 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
255         }
256
257         while (page_nr < spd->nr_pages)
258                 page_cache_release(spd->pages[page_nr++]);
259
260         return ret;
261 }
262
263 static int
264 __generic_file_splice_read(struct file *in, loff_t *ppos,
265                            struct pipe_inode_info *pipe, size_t len,
266                            unsigned int flags)
267 {
268         struct address_space *mapping = in->f_mapping;
269         unsigned int loff, nr_pages;
270         struct page *pages[PIPE_BUFFERS];
271         struct partial_page partial[PIPE_BUFFERS];
272         struct page *page;
273         pgoff_t index, end_index;
274         loff_t isize;
275         size_t total_len;
276         int error, page_nr;
277         struct splice_pipe_desc spd = {
278                 .pages = pages,
279                 .partial = partial,
280                 .flags = flags,
281                 .ops = &page_cache_pipe_buf_ops,
282         };
283
284         index = *ppos >> PAGE_CACHE_SHIFT;
285         loff = *ppos & ~PAGE_CACHE_MASK;
286         nr_pages = (len + loff + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
287
288         if (nr_pages > PIPE_BUFFERS)
289                 nr_pages = PIPE_BUFFERS;
290
291         /*
292          * Don't try to 2nd guess the read-ahead logic, call into
293          * page_cache_readahead() like the page cache reads would do.
294          */
295         page_cache_readahead(mapping, &in->f_ra, in, index, nr_pages);
296
297         /*
298          * Now fill in the holes:
299          */
300         error = 0;
301         total_len = 0;
302
303         /*
304          * Lookup the (hopefully) full range of pages we need.
305          */
306         spd.nr_pages = find_get_pages_contig(mapping, index, nr_pages, pages);
307
308         /*
309          * If find_get_pages_contig() returned fewer pages than we needed,
310          * allocate the rest.
311          */
312         index += spd.nr_pages;
313         while (spd.nr_pages < nr_pages) {
314                 /*
315                  * Page could be there, find_get_pages_contig() breaks on
316                  * the first hole.
317                  */
318                 page = find_get_page(mapping, index);
319                 if (!page) {
320                         /*
321                          * Make sure the read-ahead engine is notified
322                          * about this failure.
323                          */
324                         handle_ra_miss(mapping, &in->f_ra, index);
325
326                         /*
327                          * page didn't exist, allocate one.
328                          */
329                         page = page_cache_alloc_cold(mapping);
330                         if (!page)
331                                 break;
332
333                         error = add_to_page_cache_lru(page, mapping, index,
334                                               GFP_KERNEL);
335                         if (unlikely(error)) {
336                                 page_cache_release(page);
337                                 if (error == -EEXIST)
338                                         continue;
339                                 break;
340                         }
341                         /*
342                          * add_to_page_cache() locks the page, unlock it
343                          * to avoid convoluting the logic below even more.
344                          */
345                         unlock_page(page);
346                 }
347
348                 pages[spd.nr_pages++] = page;
349                 index++;
350         }
351
352         /*
353          * Now loop over the map and see if we need to start IO on any
354          * pages, fill in the partial map, etc.
355          */
356         index = *ppos >> PAGE_CACHE_SHIFT;
357         nr_pages = spd.nr_pages;
358         spd.nr_pages = 0;
359         for (page_nr = 0; page_nr < nr_pages; page_nr++) {
360                 unsigned int this_len;
361
362                 if (!len)
363                         break;
364
365                 /*
366                  * this_len is the max we'll use from this page
367                  */
368                 this_len = min_t(unsigned long, len, PAGE_CACHE_SIZE - loff);
369                 page = pages[page_nr];
370
371                 /*
372                  * If the page isn't uptodate, we may need to start io on it
373                  */
374                 if (!PageUptodate(page)) {
375                         /*
376                          * If in nonblock mode then dont block on waiting
377                          * for an in-flight io page
378                          */
379                         if (flags & SPLICE_F_NONBLOCK) {
380                                 if (TestSetPageLocked(page))
381                                         break;
382                         } else
383                                 lock_page(page);
384
385                         /*
386                          * page was truncated, stop here. if this isn't the
387                          * first page, we'll just complete what we already
388                          * added
389                          */
390                         if (!page->mapping) {
391                                 unlock_page(page);
392                                 break;
393                         }
394                         /*
395                          * page was already under io and is now done, great
396                          */
397                         if (PageUptodate(page)) {
398                                 unlock_page(page);
399                                 goto fill_it;
400                         }
401
402                         /*
403                          * need to read in the page
404                          */
405                         error = mapping->a_ops->readpage(in, page);
406                         if (unlikely(error)) {
407                                 /*
408                                  * We really should re-lookup the page here,
409                                  * but it complicates things a lot. Instead
410                                  * lets just do what we already stored, and
411                                  * we'll get it the next time we are called.
412                                  */
413                                 if (error == AOP_TRUNCATED_PAGE)
414                                         error = 0;
415
416                                 break;
417                         }
418
419                         /*
420                          * i_size must be checked after ->readpage().
421                          */
422                         isize = i_size_read(mapping->host);
423                         end_index = (isize - 1) >> PAGE_CACHE_SHIFT;
424                         if (unlikely(!isize || index > end_index))
425                                 break;
426
427                         /*
428                          * if this is the last page, see if we need to shrink
429                          * the length and stop
430                          */
431                         if (end_index == index) {
432                                 loff = PAGE_CACHE_SIZE - (isize & ~PAGE_CACHE_MASK);
433                                 if (total_len + loff > isize)
434                                         break;
435                                 /*
436                                  * force quit after adding this page
437                                  */
438                                 len = this_len;
439                                 this_len = min(this_len, loff);
440                                 loff = 0;
441                         }
442                 }
443 fill_it:
444                 partial[page_nr].offset = loff;
445                 partial[page_nr].len = this_len;
446                 len -= this_len;
447                 total_len += this_len;
448                 loff = 0;
449                 spd.nr_pages++;
450                 index++;
451         }
452
453         /*
454          * Release any pages at the end, if we quit early. 'i' is how far
455          * we got, 'nr_pages' is how many pages are in the map.
456          */
457         while (page_nr < nr_pages)
458                 page_cache_release(pages[page_nr++]);
459
460         if (spd.nr_pages)
461                 return splice_to_pipe(pipe, &spd);
462
463         return error;
464 }
465
466 /**
467  * generic_file_splice_read - splice data from file to a pipe
468  * @in:         file to splice from
469  * @pipe:       pipe to splice to
470  * @len:        number of bytes to splice
471  * @flags:      splice modifier flags
472  *
473  * Will read pages from given file and fill them into a pipe.
474  */
475 ssize_t generic_file_splice_read(struct file *in, loff_t *ppos,
476                                  struct pipe_inode_info *pipe, size_t len,
477                                  unsigned int flags)
478 {
479         ssize_t spliced;
480         int ret;
481         loff_t isize, left;
482
483         isize = i_size_read(in->f_mapping->host);
484         if (unlikely(*ppos >= isize))
485                 return 0;
486
487         left = isize - *ppos;
488         if (unlikely(left < len))
489                 len = left;
490
491         ret = 0;
492         spliced = 0;
493         while (len) {
494                 ret = __generic_file_splice_read(in, ppos, pipe, len, flags);
495
496                 if (ret < 0)
497                         break;
498                 else if (!ret) {
499                         if (spliced)
500                                 break;
501                         if (flags & SPLICE_F_NONBLOCK) {
502                                 ret = -EAGAIN;
503                                 break;
504                         }
505                 }
506
507                 *ppos += ret;
508                 len -= ret;
509                 spliced += ret;
510         }
511
512         if (spliced)
513                 return spliced;
514
515         return ret;
516 }
517
518 EXPORT_SYMBOL(generic_file_splice_read);
519
520 /*
521  * Send 'sd->len' bytes to socket from 'sd->file' at position 'sd->pos'
522  * using sendpage(). Return the number of bytes sent.
523  */
524 static int pipe_to_sendpage(struct pipe_inode_info *pipe,
525                             struct pipe_buffer *buf, struct splice_desc *sd)
526 {
527         struct file *file = sd->file;
528         loff_t pos = sd->pos;
529         int ret, more;
530
531         ret = buf->ops->pin(pipe, buf);
532         if (!ret) {
533                 more = (sd->flags & SPLICE_F_MORE) || sd->len < sd->total_len;
534
535                 ret = file->f_op->sendpage(file, buf->page, buf->offset,
536                                            sd->len, &pos, more);
537         }
538
539         return ret;
540 }
541
542 /*
543  * This is a little more tricky than the file -> pipe splicing. There are
544  * basically three cases:
545  *
546  *      - Destination page already exists in the address space and there
547  *        are users of it. For that case we have no other option that
548  *        copying the data. Tough luck.
549  *      - Destination page already exists in the address space, but there
550  *        are no users of it. Make sure it's uptodate, then drop it. Fall
551  *        through to last case.
552  *      - Destination page does not exist, we can add the pipe page to
553  *        the page cache and avoid the copy.
554  *
555  * If asked to move pages to the output file (SPLICE_F_MOVE is set in
556  * sd->flags), we attempt to migrate pages from the pipe to the output
557  * file address space page cache. This is possible if no one else has
558  * the pipe page referenced outside of the pipe and page cache. If
559  * SPLICE_F_MOVE isn't set, or we cannot move the page, we simply create
560  * a new page in the output file page cache and fill/dirty that.
561  */
562 static int pipe_to_file(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
563                         struct splice_desc *sd)
564 {
565         struct file *file = sd->file;
566         struct address_space *mapping = file->f_mapping;
567         unsigned int offset, this_len;
568         struct page *page;
569         pgoff_t index;
570         int ret;
571
572         /*
573          * make sure the data in this buffer is uptodate
574          */
575         ret = buf->ops->pin(pipe, buf);
576         if (unlikely(ret))
577                 return ret;
578
579         index = sd->pos >> PAGE_CACHE_SHIFT;
580         offset = sd->pos & ~PAGE_CACHE_MASK;
581
582         this_len = sd->len;
583         if (this_len + offset > PAGE_CACHE_SIZE)
584                 this_len = PAGE_CACHE_SIZE - offset;
585
586 find_page:
587         page = find_lock_page(mapping, index);
588         if (!page) {
589                 ret = -ENOMEM;
590                 page = page_cache_alloc_cold(mapping);
591                 if (unlikely(!page))
592                         goto out_ret;
593
594                 /*
595                  * This will also lock the page
596                  */
597                 ret = add_to_page_cache_lru(page, mapping, index,
598                                             GFP_KERNEL);
599                 if (unlikely(ret))
600                         goto out;
601         }
602
603         ret = mapping->a_ops->prepare_write(file, page, offset, offset+this_len);
604         if (unlikely(ret)) {
605                 loff_t isize = i_size_read(mapping->host);
606
607                 if (ret != AOP_TRUNCATED_PAGE)
608                         unlock_page(page);
609                 page_cache_release(page);
610                 if (ret == AOP_TRUNCATED_PAGE)
611                         goto find_page;
612
613                 /*
614                  * prepare_write() may have instantiated a few blocks
615                  * outside i_size.  Trim these off again.
616                  */
617                 if (sd->pos + this_len > isize)
618                         vmtruncate(mapping->host, isize);
619
620                 goto out_ret;
621         }
622
623         if (buf->page != page) {
624                 /*
625                  * Careful, ->map() uses KM_USER0!
626                  */
627                 char *src = buf->ops->map(pipe, buf, 1);
628                 char *dst = kmap_atomic(page, KM_USER1);
629
630                 memcpy(dst + offset, src + buf->offset, this_len);
631                 flush_dcache_page(page);
632                 kunmap_atomic(dst, KM_USER1);
633                 buf->ops->unmap(pipe, buf, src);
634         }
635
636         ret = mapping->a_ops->commit_write(file, page, offset, offset+this_len);
637         if (ret) {
638                 if (ret == AOP_TRUNCATED_PAGE) {
639                         page_cache_release(page);
640                         goto find_page;
641                 }
642                 if (ret < 0)
643                         goto out;
644                 /*
645                  * Partial write has happened, so 'ret' already initialized by
646                  * number of bytes written, Where is nothing we have to do here.
647                  */
648         } else
649                 ret = this_len;
650         /*
651          * Return the number of bytes written and mark page as
652          * accessed, we are now done!
653          */
654         mark_page_accessed(page);
655         balance_dirty_pages_ratelimited(mapping);
656 out:
657         page_cache_release(page);
658         unlock_page(page);
659 out_ret:
660         return ret;
661 }
662
663 /*
664  * Pipe input worker. Most of this logic works like a regular pipe, the
665  * key here is the 'actor' worker passed in that actually moves the data
666  * to the wanted destination. See pipe_to_file/pipe_to_sendpage above.
667  */
668 ssize_t __splice_from_pipe(struct pipe_inode_info *pipe,
669                            struct file *out, loff_t *ppos, size_t len,
670                            unsigned int flags, splice_actor *actor)
671 {
672         int ret, do_wakeup, err;
673         struct splice_desc sd;
674
675         ret = 0;
676         do_wakeup = 0;
677
678         sd.total_len = len;
679         sd.flags = flags;
680         sd.file = out;
681         sd.pos = *ppos;
682
683         for (;;) {
684                 if (pipe->nrbufs) {
685                         struct pipe_buffer *buf = pipe->bufs + pipe->curbuf;
686                         const struct pipe_buf_operations *ops = buf->ops;
687
688                         sd.len = buf->len;
689                         if (sd.len > sd.total_len)
690                                 sd.len = sd.total_len;
691
692                         err = actor(pipe, buf, &sd);
693                         if (err <= 0) {
694                                 if (!ret && err != -ENODATA)
695                                         ret = err;
696
697                                 break;
698                         }
699
700                         ret += err;
701                         buf->offset += err;
702                         buf->len -= err;
703
704                         sd.len -= err;
705                         sd.pos += err;
706                         sd.total_len -= err;
707                         if (sd.len)
708                                 continue;
709
710                         if (!buf->len) {
711                                 buf->ops = NULL;
712                                 ops->release(pipe, buf);
713                                 pipe->curbuf = (pipe->curbuf + 1) & (PIPE_BUFFERS - 1);
714                                 pipe->nrbufs--;
715                                 if (pipe->inode)
716                                         do_wakeup = 1;
717                         }
718
719                         if (!sd.total_len)
720                                 break;
721                 }
722
723                 if (pipe->nrbufs)
724                         continue;
725                 if (!pipe->writers)
726                         break;
727                 if (!pipe->waiting_writers) {
728                         if (ret)
729                                 break;
730                 }
731
732                 if (flags & SPLICE_F_NONBLOCK) {
733                         if (!ret)
734                                 ret = -EAGAIN;
735                         break;
736                 }
737
738                 if (signal_pending(current)) {
739                         if (!ret)
740                                 ret = -ERESTARTSYS;
741                         break;
742                 }
743
744                 if (do_wakeup) {
745                         smp_mb();
746                         if (waitqueue_active(&pipe->wait))
747                                 wake_up_interruptible_sync(&pipe->wait);
748                         kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
749                         do_wakeup = 0;
750                 }
751
752                 pipe_wait(pipe);
753         }
754
755         if (do_wakeup) {
756                 smp_mb();
757                 if (waitqueue_active(&pipe->wait))
758                         wake_up_interruptible(&pipe->wait);
759                 kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
760         }
761
762         return ret;
763 }
764 EXPORT_SYMBOL(__splice_from_pipe);
765
766 ssize_t splice_from_pipe(struct pipe_inode_info *pipe, struct file *out,
767                          loff_t *ppos, size_t len, unsigned int flags,
768                          splice_actor *actor)
769 {
770         ssize_t ret;
771         struct inode *inode = out->f_mapping->host;
772
773         /*
774          * The actor worker might be calling ->prepare_write and
775          * ->commit_write. Most of the time, these expect i_mutex to
776          * be held. Since this may result in an ABBA deadlock with
777          * pipe->inode, we have to order lock acquiry here.
778          */
779         inode_double_lock(inode, pipe->inode);
780         ret = __splice_from_pipe(pipe, out, ppos, len, flags, actor);
781         inode_double_unlock(inode, pipe->inode);
782
783         return ret;
784 }
785
786 /**
787  * generic_file_splice_write_nolock - generic_file_splice_write without mutexes
788  * @pipe:       pipe info
789  * @out:        file to write to
790  * @len:        number of bytes to splice
791  * @flags:      splice modifier flags
792  *
793  * Will either move or copy pages (determined by @flags options) from
794  * the given pipe inode to the given file. The caller is responsible
795  * for acquiring i_mutex on both inodes.
796  *
797  */
798 ssize_t
799 generic_file_splice_write_nolock(struct pipe_inode_info *pipe, struct file *out,
800                                  loff_t *ppos, size_t len, unsigned int flags)
801 {
802         struct address_space *mapping = out->f_mapping;
803         struct inode *inode = mapping->host;
804         ssize_t ret;
805         int err;
806
807         err = remove_suid(out->f_path.dentry);
808         if (unlikely(err))
809                 return err;
810
811         ret = __splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_file);
812         if (ret > 0) {
813                 *ppos += ret;
814
815                 /*
816                  * If file or inode is SYNC and we actually wrote some data,
817                  * sync it.
818                  */
819                 if (unlikely((out->f_flags & O_SYNC) || IS_SYNC(inode))) {
820                         err = generic_osync_inode(inode, mapping,
821                                                   OSYNC_METADATA|OSYNC_DATA);
822
823                         if (err)
824                                 ret = err;
825                 }
826         }
827
828         return ret;
829 }
830
831 EXPORT_SYMBOL(generic_file_splice_write_nolock);
832
833 /**
834  * generic_file_splice_write - splice data from a pipe to a file
835  * @pipe:       pipe info
836  * @out:        file to write to
837  * @len:        number of bytes to splice
838  * @flags:      splice modifier flags
839  *
840  * Will either move or copy pages (determined by @flags options) from
841  * the given pipe inode to the given file.
842  *
843  */
844 ssize_t
845 generic_file_splice_write(struct pipe_inode_info *pipe, struct file *out,
846                           loff_t *ppos, size_t len, unsigned int flags)
847 {
848         struct address_space *mapping = out->f_mapping;
849         struct inode *inode = mapping->host;
850         ssize_t ret;
851         int err;
852
853         err = should_remove_suid(out->f_path.dentry);
854         if (unlikely(err)) {
855                 mutex_lock(&inode->i_mutex);
856                 err = __remove_suid(out->f_path.dentry, err);
857                 mutex_unlock(&inode->i_mutex);
858                 if (err)
859                         return err;
860         }
861
862         ret = splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_file);
863         if (ret > 0) {
864                 *ppos += ret;
865
866                 /*
867                  * If file or inode is SYNC and we actually wrote some data,
868                  * sync it.
869                  */
870                 if (unlikely((out->f_flags & O_SYNC) || IS_SYNC(inode))) {
871                         mutex_lock(&inode->i_mutex);
872                         err = generic_osync_inode(inode, mapping,
873                                                   OSYNC_METADATA|OSYNC_DATA);
874                         mutex_unlock(&inode->i_mutex);
875
876                         if (err)
877                                 ret = err;
878                 }
879         }
880
881         return ret;
882 }
883
884 EXPORT_SYMBOL(generic_file_splice_write);
885
886 /**
887  * generic_splice_sendpage - splice data from a pipe to a socket
888  * @inode:      pipe inode
889  * @out:        socket to write to
890  * @len:        number of bytes to splice
891  * @flags:      splice modifier flags
892  *
893  * Will send @len bytes from the pipe to a network socket. No data copying
894  * is involved.
895  *
896  */
897 ssize_t generic_splice_sendpage(struct pipe_inode_info *pipe, struct file *out,
898                                 loff_t *ppos, size_t len, unsigned int flags)
899 {
900         return splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_sendpage);
901 }
902
903 EXPORT_SYMBOL(generic_splice_sendpage);
904
905 /*
906  * Attempt to initiate a splice from pipe to file.
907  */
908 static long do_splice_from(struct pipe_inode_info *pipe, struct file *out,
909                            loff_t *ppos, size_t len, unsigned int flags)
910 {
911         int ret;
912
913         if (unlikely(!out->f_op || !out->f_op->splice_write))
914                 return -EINVAL;
915
916         if (unlikely(!(out->f_mode & FMODE_WRITE)))
917                 return -EBADF;
918
919         ret = rw_verify_area(WRITE, out, ppos, len);
920         if (unlikely(ret < 0))
921                 return ret;
922
923         return out->f_op->splice_write(pipe, out, ppos, len, flags);
924 }
925
926 /*
927  * Attempt to initiate a splice from a file to a pipe.
928  */
929 static long do_splice_to(struct file *in, loff_t *ppos,
930                          struct pipe_inode_info *pipe, size_t len,
931                          unsigned int flags)
932 {
933         int ret;
934
935         if (unlikely(!in->f_op || !in->f_op->splice_read))
936                 return -EINVAL;
937
938         if (unlikely(!(in->f_mode & FMODE_READ)))
939                 return -EBADF;
940
941         ret = rw_verify_area(READ, in, ppos, len);
942         if (unlikely(ret < 0))
943                 return ret;
944
945         return in->f_op->splice_read(in, ppos, pipe, len, flags);
946 }
947
948 long do_splice_direct(struct file *in, loff_t *ppos, struct file *out,
949                       size_t len, unsigned int flags)
950 {
951         struct pipe_inode_info *pipe;
952         long ret, bytes;
953         loff_t out_off;
954         umode_t i_mode;
955         int i;
956
957         /*
958          * We require the input being a regular file, as we don't want to
959          * randomly drop data for eg socket -> socket splicing. Use the
960          * piped splicing for that!
961          */
962         i_mode = in->f_path.dentry->d_inode->i_mode;
963         if (unlikely(!S_ISREG(i_mode) && !S_ISBLK(i_mode)))
964                 return -EINVAL;
965
966         /*
967          * neither in nor out is a pipe, setup an internal pipe attached to
968          * 'out' and transfer the wanted data from 'in' to 'out' through that
969          */
970         pipe = current->splice_pipe;
971         if (unlikely(!pipe)) {
972                 pipe = alloc_pipe_info(NULL);
973                 if (!pipe)
974                         return -ENOMEM;
975
976                 /*
977                  * We don't have an immediate reader, but we'll read the stuff
978                  * out of the pipe right after the splice_to_pipe(). So set
979                  * PIPE_READERS appropriately.
980                  */
981                 pipe->readers = 1;
982
983                 current->splice_pipe = pipe;
984         }
985
986         /*
987          * Do the splice.
988          */
989         ret = 0;
990         bytes = 0;
991         out_off = 0;
992
993         while (len) {
994                 size_t read_len, max_read_len;
995
996                 /*
997                  * Do at most PIPE_BUFFERS pages worth of transfer:
998                  */
999                 max_read_len = min(len, (size_t)(PIPE_BUFFERS*PAGE_SIZE));
1000
1001                 ret = do_splice_to(in, ppos, pipe, max_read_len, flags);
1002                 if (unlikely(ret < 0))
1003                         goto out_release;
1004
1005                 read_len = ret;
1006
1007                 /*
1008                  * NOTE: nonblocking mode only applies to the input. We
1009                  * must not do the output in nonblocking mode as then we
1010                  * could get stuck data in the internal pipe:
1011                  */
1012                 ret = do_splice_from(pipe, out, &out_off, read_len,
1013                                      flags & ~SPLICE_F_NONBLOCK);
1014                 if (unlikely(ret < 0))
1015                         goto out_release;
1016
1017                 bytes += ret;
1018                 len -= ret;
1019
1020                 /*
1021                  * In nonblocking mode, if we got back a short read then
1022                  * that was due to either an IO error or due to the
1023                  * pagecache entry not being there. In the IO error case
1024                  * the _next_ splice attempt will produce a clean IO error
1025                  * return value (not a short read), so in both cases it's
1026                  * correct to break out of the loop here:
1027                  */
1028                 if ((flags & SPLICE_F_NONBLOCK) && (read_len < max_read_len))
1029                         break;
1030         }
1031
1032         pipe->nrbufs = pipe->curbuf = 0;
1033
1034         return bytes;
1035
1036 out_release:
1037         /*
1038          * If we did an incomplete transfer we must release
1039          * the pipe buffers in question:
1040          */
1041         for (i = 0; i < PIPE_BUFFERS; i++) {
1042                 struct pipe_buffer *buf = pipe->bufs + i;
1043
1044                 if (buf->ops) {
1045                         buf->ops->release(pipe, buf);
1046                         buf->ops = NULL;
1047                 }
1048         }
1049         pipe->nrbufs = pipe->curbuf = 0;
1050
1051         /*
1052          * If we transferred some data, return the number of bytes:
1053          */
1054         if (bytes > 0)
1055                 return bytes;
1056
1057         return ret;
1058 }
1059
1060 EXPORT_SYMBOL(do_splice_direct);
1061
1062 /*
1063  * After the inode slimming patch, i_pipe/i_bdev/i_cdev share the same
1064  * location, so checking ->i_pipe is not enough to verify that this is a
1065  * pipe.
1066  */
1067 static inline struct pipe_inode_info *pipe_info(struct inode *inode)
1068 {
1069         if (S_ISFIFO(inode->i_mode))
1070                 return inode->i_pipe;
1071
1072         return NULL;
1073 }
1074
1075 /*
1076  * Determine where to splice to/from.
1077  */
1078 static long do_splice(struct file *in, loff_t __user *off_in,
1079                       struct file *out, loff_t __user *off_out,
1080                       size_t len, unsigned int flags)
1081 {
1082         struct pipe_inode_info *pipe;
1083         loff_t offset, *off;
1084         long ret;
1085
1086         pipe = pipe_info(in->f_path.dentry->d_inode);
1087         if (pipe) {
1088                 if (off_in)
1089                         return -ESPIPE;
1090                 if (off_out) {
1091                         if (out->f_op->llseek == no_llseek)
1092                                 return -EINVAL;
1093                         if (copy_from_user(&offset, off_out, sizeof(loff_t)))
1094                                 return -EFAULT;
1095                         off = &offset;
1096                 } else
1097                         off = &out->f_pos;
1098
1099                 ret = do_splice_from(pipe, out, off, len, flags);
1100
1101                 if (off_out && copy_to_user(off_out, off, sizeof(loff_t)))
1102                         ret = -EFAULT;
1103
1104                 return ret;
1105         }
1106
1107         pipe = pipe_info(out->f_path.dentry->d_inode);
1108         if (pipe) {
1109                 if (off_out)
1110                         return -ESPIPE;
1111                 if (off_in) {
1112                         if (in->f_op->llseek == no_llseek)
1113                                 return -EINVAL;
1114                         if (copy_from_user(&offset, off_in, sizeof(loff_t)))
1115                                 return -EFAULT;
1116                         off = &offset;
1117                 } else
1118                         off = &in->f_pos;
1119
1120                 ret = do_splice_to(in, off, pipe, len, flags);
1121
1122                 if (off_in && copy_to_user(off_in, off, sizeof(loff_t)))
1123                         ret = -EFAULT;
1124
1125                 return ret;
1126         }
1127
1128         return -EINVAL;
1129 }
1130
1131 /*
1132  * Map an iov into an array of pages and offset/length tupples. With the
1133  * partial_page structure, we can map several non-contiguous ranges into
1134  * our ones pages[] map instead of splitting that operation into pieces.
1135  * Could easily be exported as a generic helper for other users, in which
1136  * case one would probably want to add a 'max_nr_pages' parameter as well.
1137  */
1138 static int get_iovec_page_array(const struct iovec __user *iov,
1139                                 unsigned int nr_vecs, struct page **pages,
1140                                 struct partial_page *partial, int aligned)
1141 {
1142         int buffers = 0, error = 0;
1143
1144         /*
1145          * It's ok to take the mmap_sem for reading, even
1146          * across a "get_user()".
1147          */
1148         down_read(&current->mm->mmap_sem);
1149
1150         while (nr_vecs) {
1151                 unsigned long off, npages;
1152                 void __user *base;
1153                 size_t len;
1154                 int i;
1155
1156                 /*
1157                  * Get user address base and length for this iovec.
1158                  */
1159                 error = get_user(base, &iov->iov_base);
1160                 if (unlikely(error))
1161                         break;
1162                 error = get_user(len, &iov->iov_len);
1163                 if (unlikely(error))
1164                         break;
1165
1166                 /*
1167                  * Sanity check this iovec. 0 read succeeds.
1168                  */
1169                 if (unlikely(!len))
1170                         break;
1171                 error = -EFAULT;
1172                 if (unlikely(!base))
1173                         break;
1174
1175                 /*
1176                  * Get this base offset and number of pages, then map
1177                  * in the user pages.
1178                  */
1179                 off = (unsigned long) base & ~PAGE_MASK;
1180
1181                 /*
1182                  * If asked for alignment, the offset must be zero and the
1183                  * length a multiple of the PAGE_SIZE.
1184                  */
1185                 error = -EINVAL;
1186                 if (aligned && (off || len & ~PAGE_MASK))
1187                         break;
1188
1189                 npages = (off + len + PAGE_SIZE - 1) >> PAGE_SHIFT;
1190                 if (npages > PIPE_BUFFERS - buffers)
1191                         npages = PIPE_BUFFERS - buffers;
1192
1193                 error = get_user_pages(current, current->mm,
1194                                        (unsigned long) base, npages, 0, 0,
1195                                        &pages[buffers], NULL);
1196
1197                 if (unlikely(error <= 0))
1198                         break;
1199
1200                 /*
1201                  * Fill this contiguous range into the partial page map.
1202                  */
1203                 for (i = 0; i < error; i++) {
1204                         const int plen = min_t(size_t, len, PAGE_SIZE - off);
1205
1206                         partial[buffers].offset = off;
1207                         partial[buffers].len = plen;
1208
1209                         off = 0;
1210                         len -= plen;
1211                         buffers++;
1212                 }
1213
1214                 /*
1215                  * We didn't complete this iov, stop here since it probably
1216                  * means we have to move some of this into a pipe to
1217                  * be able to continue.
1218                  */
1219                 if (len)
1220                         break;
1221
1222                 /*
1223                  * Don't continue if we mapped fewer pages than we asked for,
1224                  * or if we mapped the max number of pages that we have
1225                  * room for.
1226                  */
1227                 if (error < npages || buffers == PIPE_BUFFERS)
1228                         break;
1229
1230                 nr_vecs--;
1231                 iov++;
1232         }
1233
1234         up_read(&current->mm->mmap_sem);
1235
1236         if (buffers)
1237                 return buffers;
1238
1239         return error;
1240 }
1241
1242 /*
1243  * vmsplice splices a user address range into a pipe. It can be thought of
1244  * as splice-from-memory, where the regular splice is splice-from-file (or
1245  * to file). In both cases the output is a pipe, naturally.
1246  *
1247  * Note that vmsplice only supports splicing _from_ user memory to a pipe,
1248  * not the other way around. Splicing from user memory is a simple operation
1249  * that can be supported without any funky alignment restrictions or nasty
1250  * vm tricks. We simply map in the user memory and fill them into a pipe.
1251  * The reverse isn't quite as easy, though. There are two possible solutions
1252  * for that:
1253  *
1254  *      - memcpy() the data internally, at which point we might as well just
1255  *        do a regular read() on the buffer anyway.
1256  *      - Lots of nasty vm tricks, that are neither fast nor flexible (it
1257  *        has restriction limitations on both ends of the pipe).
1258  *
1259  * Alas, it isn't here.
1260  *
1261  */
1262 static long do_vmsplice(struct file *file, const struct iovec __user *iov,
1263                         unsigned long nr_segs, unsigned int flags)
1264 {
1265         struct pipe_inode_info *pipe;
1266         struct page *pages[PIPE_BUFFERS];
1267         struct partial_page partial[PIPE_BUFFERS];
1268         struct splice_pipe_desc spd = {
1269                 .pages = pages,
1270                 .partial = partial,
1271                 .flags = flags,
1272                 .ops = &user_page_pipe_buf_ops,
1273         };
1274
1275         pipe = pipe_info(file->f_path.dentry->d_inode);
1276         if (!pipe)
1277                 return -EBADF;
1278         if (unlikely(nr_segs > UIO_MAXIOV))
1279                 return -EINVAL;
1280         else if (unlikely(!nr_segs))
1281                 return 0;
1282
1283         spd.nr_pages = get_iovec_page_array(iov, nr_segs, pages, partial,
1284                                             flags & SPLICE_F_GIFT);
1285         if (spd.nr_pages <= 0)
1286                 return spd.nr_pages;
1287
1288         return splice_to_pipe(pipe, &spd);
1289 }
1290
1291 asmlinkage long sys_vmsplice(int fd, const struct iovec __user *iov,
1292                              unsigned long nr_segs, unsigned int flags)
1293 {
1294         struct file *file;
1295         long error;
1296         int fput;
1297
1298         error = -EBADF;
1299         file = fget_light(fd, &fput);
1300         if (file) {
1301                 if (file->f_mode & FMODE_WRITE)
1302                         error = do_vmsplice(file, iov, nr_segs, flags);
1303
1304                 fput_light(file, fput);
1305         }
1306
1307         return error;
1308 }
1309
1310 asmlinkage long sys_splice(int fd_in, loff_t __user *off_in,
1311                            int fd_out, loff_t __user *off_out,
1312                            size_t len, unsigned int flags)
1313 {
1314         long error;
1315         struct file *in, *out;
1316         int fput_in, fput_out;
1317
1318         if (unlikely(!len))
1319                 return 0;
1320
1321         error = -EBADF;
1322         in = fget_light(fd_in, &fput_in);
1323         if (in) {
1324                 if (in->f_mode & FMODE_READ) {
1325                         out = fget_light(fd_out, &fput_out);
1326                         if (out) {
1327                                 if (out->f_mode & FMODE_WRITE)
1328                                         error = do_splice(in, off_in,
1329                                                           out, off_out,
1330                                                           len, flags);
1331                                 fput_light(out, fput_out);
1332                         }
1333                 }
1334
1335                 fput_light(in, fput_in);
1336         }
1337
1338         return error;
1339 }
1340
1341 /*
1342  * Make sure there's data to read. Wait for input if we can, otherwise
1343  * return an appropriate error.
1344  */
1345 static int link_ipipe_prep(struct pipe_inode_info *pipe, unsigned int flags)
1346 {
1347         int ret;
1348
1349         /*
1350          * Check ->nrbufs without the inode lock first. This function
1351          * is speculative anyways, so missing one is ok.
1352          */
1353         if (pipe->nrbufs)
1354                 return 0;
1355
1356         ret = 0;
1357         mutex_lock(&pipe->inode->i_mutex);
1358
1359         while (!pipe->nrbufs) {
1360                 if (signal_pending(current)) {
1361                         ret = -ERESTARTSYS;
1362                         break;
1363                 }
1364                 if (!pipe->writers)
1365                         break;
1366                 if (!pipe->waiting_writers) {
1367                         if (flags & SPLICE_F_NONBLOCK) {
1368                                 ret = -EAGAIN;
1369                                 break;
1370                         }
1371                 }
1372                 pipe_wait(pipe);
1373         }
1374
1375         mutex_unlock(&pipe->inode->i_mutex);
1376         return ret;
1377 }
1378
1379 /*
1380  * Make sure there's writeable room. Wait for room if we can, otherwise
1381  * return an appropriate error.
1382  */
1383 static int link_opipe_prep(struct pipe_inode_info *pipe, unsigned int flags)
1384 {
1385         int ret;
1386
1387         /*
1388          * Check ->nrbufs without the inode lock first. This function
1389          * is speculative anyways, so missing one is ok.
1390          */
1391         if (pipe->nrbufs < PIPE_BUFFERS)
1392                 return 0;
1393
1394         ret = 0;
1395         mutex_lock(&pipe->inode->i_mutex);
1396
1397         while (pipe->nrbufs >= PIPE_BUFFERS) {
1398                 if (!pipe->readers) {
1399                         send_sig(SIGPIPE, current, 0);
1400                         ret = -EPIPE;
1401                         break;
1402                 }
1403                 if (flags & SPLICE_F_NONBLOCK) {
1404                         ret = -EAGAIN;
1405                         break;
1406                 }
1407                 if (signal_pending(current)) {
1408                         ret = -ERESTARTSYS;
1409                         break;
1410                 }
1411                 pipe->waiting_writers++;
1412                 pipe_wait(pipe);
1413                 pipe->waiting_writers--;
1414         }
1415
1416         mutex_unlock(&pipe->inode->i_mutex);
1417         return ret;
1418 }
1419
1420 /*
1421  * Link contents of ipipe to opipe.
1422  */
1423 static int link_pipe(struct pipe_inode_info *ipipe,
1424                      struct pipe_inode_info *opipe,
1425                      size_t len, unsigned int flags)
1426 {
1427         struct pipe_buffer *ibuf, *obuf;
1428         int ret = 0, i = 0, nbuf;
1429
1430         /*
1431          * Potential ABBA deadlock, work around it by ordering lock
1432          * grabbing by inode address. Otherwise two different processes
1433          * could deadlock (one doing tee from A -> B, the other from B -> A).
1434          */
1435         inode_double_lock(ipipe->inode, opipe->inode);
1436
1437         do {
1438                 if (!opipe->readers) {
1439                         send_sig(SIGPIPE, current, 0);
1440                         if (!ret)
1441                                 ret = -EPIPE;
1442                         break;
1443                 }
1444
1445                 /*
1446                  * If we have iterated all input buffers or ran out of
1447                  * output room, break.
1448                  */
1449                 if (i >= ipipe->nrbufs || opipe->nrbufs >= PIPE_BUFFERS)
1450                         break;
1451
1452                 ibuf = ipipe->bufs + ((ipipe->curbuf + i) & (PIPE_BUFFERS - 1));
1453                 nbuf = (opipe->curbuf + opipe->nrbufs) & (PIPE_BUFFERS - 1);
1454
1455                 /*
1456                  * Get a reference to this pipe buffer,
1457                  * so we can copy the contents over.
1458                  */
1459                 ibuf->ops->get(ipipe, ibuf);
1460
1461                 obuf = opipe->bufs + nbuf;
1462                 *obuf = *ibuf;
1463
1464                 /*
1465                  * Don't inherit the gift flag, we need to
1466                  * prevent multiple steals of this page.
1467                  */
1468                 obuf->flags &= ~PIPE_BUF_FLAG_GIFT;
1469
1470                 if (obuf->len > len)
1471                         obuf->len = len;
1472
1473                 opipe->nrbufs++;
1474                 ret += obuf->len;
1475                 len -= obuf->len;
1476                 i++;
1477         } while (len);
1478
1479         inode_double_unlock(ipipe->inode, opipe->inode);
1480
1481         /*
1482          * If we put data in the output pipe, wakeup any potential readers.
1483          */
1484         if (ret > 0) {
1485                 smp_mb();
1486                 if (waitqueue_active(&opipe->wait))
1487                         wake_up_interruptible(&opipe->wait);
1488                 kill_fasync(&opipe->fasync_readers, SIGIO, POLL_IN);
1489         }
1490
1491         return ret;
1492 }
1493
1494 /*
1495  * This is a tee(1) implementation that works on pipes. It doesn't copy
1496  * any data, it simply references the 'in' pages on the 'out' pipe.
1497  * The 'flags' used are the SPLICE_F_* variants, currently the only
1498  * applicable one is SPLICE_F_NONBLOCK.
1499  */
1500 static long do_tee(struct file *in, struct file *out, size_t len,
1501                    unsigned int flags)
1502 {
1503         struct pipe_inode_info *ipipe = pipe_info(in->f_path.dentry->d_inode);
1504         struct pipe_inode_info *opipe = pipe_info(out->f_path.dentry->d_inode);
1505         int ret = -EINVAL;
1506
1507         /*
1508          * Duplicate the contents of ipipe to opipe without actually
1509          * copying the data.
1510          */
1511         if (ipipe && opipe && ipipe != opipe) {
1512                 /*
1513                  * Keep going, unless we encounter an error. The ipipe/opipe
1514                  * ordering doesn't really matter.
1515                  */
1516                 ret = link_ipipe_prep(ipipe, flags);
1517                 if (!ret) {
1518                         ret = link_opipe_prep(opipe, flags);
1519                         if (!ret) {
1520                                 ret = link_pipe(ipipe, opipe, len, flags);
1521                                 if (!ret && (flags & SPLICE_F_NONBLOCK))
1522                                         ret = -EAGAIN;
1523                         }
1524                 }
1525         }
1526
1527         return ret;
1528 }
1529
1530 asmlinkage long sys_tee(int fdin, int fdout, size_t len, unsigned int flags)
1531 {
1532         struct file *in;
1533         int error, fput_in;
1534
1535         if (unlikely(!len))
1536                 return 0;
1537
1538         error = -EBADF;
1539         in = fget_light(fdin, &fput_in);
1540         if (in) {
1541                 if (in->f_mode & FMODE_READ) {
1542                         int fput_out;
1543                         struct file *out = fget_light(fdout, &fput_out);
1544
1545                         if (out) {
1546                                 if (out->f_mode & FMODE_WRITE)
1547                                         error = do_tee(in, out, len, flags);
1548                                 fput_light(out, fput_out);
1549                         }
1550                 }
1551                 fput_light(in, fput_in);
1552         }
1553
1554         return error;
1555 }