gcc-4.6: fs: fix unused but set warnings
[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/memcontrol.h>
25 #include <linux/mm_inline.h>
26 #include <linux/swap.h>
27 #include <linux/writeback.h>
28 #include <linux/buffer_head.h>
29 #include <linux/module.h>
30 #include <linux/syscalls.h>
31 #include <linux/uio.h>
32 #include <linux/security.h>
33 #include <linux/gfp.h>
34
35 /*
36  * Attempt to steal a page from a pipe buffer. This should perhaps go into
37  * a vm helper function, it's already simplified quite a bit by the
38  * addition of remove_mapping(). If success is returned, the caller may
39  * attempt to reuse this page for another destination.
40  */
41 static int page_cache_pipe_buf_steal(struct pipe_inode_info *pipe,
42                                      struct pipe_buffer *buf)
43 {
44         struct page *page = buf->page;
45         struct address_space *mapping;
46
47         lock_page(page);
48
49         mapping = page_mapping(page);
50         if (mapping) {
51                 WARN_ON(!PageUptodate(page));
52
53                 /*
54                  * At least for ext2 with nobh option, we need to wait on
55                  * writeback completing on this page, since we'll remove it
56                  * from the pagecache.  Otherwise truncate wont wait on the
57                  * page, allowing the disk blocks to be reused by someone else
58                  * before we actually wrote our data to them. fs corruption
59                  * ensues.
60                  */
61                 wait_on_page_writeback(page);
62
63                 if (page_has_private(page) &&
64                     !try_to_release_page(page, GFP_KERNEL))
65                         goto out_unlock;
66
67                 /*
68                  * If we succeeded in removing the mapping, set LRU flag
69                  * and return good.
70                  */
71                 if (remove_mapping(mapping, page)) {
72                         buf->flags |= PIPE_BUF_FLAG_LRU;
73                         return 0;
74                 }
75         }
76
77         /*
78          * Raced with truncate or failed to remove page from current
79          * address space, unlock and return failure.
80          */
81 out_unlock:
82         unlock_page(page);
83         return 1;
84 }
85
86 static void page_cache_pipe_buf_release(struct pipe_inode_info *pipe,
87                                         struct pipe_buffer *buf)
88 {
89         page_cache_release(buf->page);
90         buf->flags &= ~PIPE_BUF_FLAG_LRU;
91 }
92
93 /*
94  * Check whether the contents of buf is OK to access. Since the content
95  * is a page cache page, IO may be in flight.
96  */
97 static int page_cache_pipe_buf_confirm(struct pipe_inode_info *pipe,
98                                        struct pipe_buffer *buf)
99 {
100         struct page *page = buf->page;
101         int err;
102
103         if (!PageUptodate(page)) {
104                 lock_page(page);
105
106                 /*
107                  * Page got truncated/unhashed. This will cause a 0-byte
108                  * splice, if this is the first page.
109                  */
110                 if (!page->mapping) {
111                         err = -ENODATA;
112                         goto error;
113                 }
114
115                 /*
116                  * Uh oh, read-error from disk.
117                  */
118                 if (!PageUptodate(page)) {
119                         err = -EIO;
120                         goto error;
121                 }
122
123                 /*
124                  * Page is ok afterall, we are done.
125                  */
126                 unlock_page(page);
127         }
128
129         return 0;
130 error:
131         unlock_page(page);
132         return err;
133 }
134
135 static const struct pipe_buf_operations page_cache_pipe_buf_ops = {
136         .can_merge = 0,
137         .map = generic_pipe_buf_map,
138         .unmap = generic_pipe_buf_unmap,
139         .confirm = page_cache_pipe_buf_confirm,
140         .release = page_cache_pipe_buf_release,
141         .steal = page_cache_pipe_buf_steal,
142         .get = generic_pipe_buf_get,
143 };
144
145 static int user_page_pipe_buf_steal(struct pipe_inode_info *pipe,
146                                     struct pipe_buffer *buf)
147 {
148         if (!(buf->flags & PIPE_BUF_FLAG_GIFT))
149                 return 1;
150
151         buf->flags |= PIPE_BUF_FLAG_LRU;
152         return generic_pipe_buf_steal(pipe, buf);
153 }
154
155 static const struct pipe_buf_operations user_page_pipe_buf_ops = {
156         .can_merge = 0,
157         .map = generic_pipe_buf_map,
158         .unmap = generic_pipe_buf_unmap,
159         .confirm = generic_pipe_buf_confirm,
160         .release = page_cache_pipe_buf_release,
161         .steal = user_page_pipe_buf_steal,
162         .get = generic_pipe_buf_get,
163 };
164
165 /**
166  * splice_to_pipe - fill passed data into a pipe
167  * @pipe:       pipe to fill
168  * @spd:        data to fill
169  *
170  * Description:
171  *    @spd contains a map of pages and len/offset tuples, along with
172  *    the struct pipe_buf_operations associated with these pages. This
173  *    function will link that data to the pipe.
174  *
175  */
176 ssize_t splice_to_pipe(struct pipe_inode_info *pipe,
177                        struct splice_pipe_desc *spd)
178 {
179         unsigned int spd_pages = spd->nr_pages;
180         int ret, do_wakeup, page_nr;
181
182         ret = 0;
183         do_wakeup = 0;
184         page_nr = 0;
185
186         pipe_lock(pipe);
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->private = spd->partial[page_nr].private;
204                         buf->ops = spd->ops;
205                         if (spd->flags & SPLICE_F_GIFT)
206                                 buf->flags |= PIPE_BUF_FLAG_GIFT;
207
208                         pipe->nrbufs++;
209                         page_nr++;
210                         ret += buf->len;
211
212                         if (pipe->inode)
213                                 do_wakeup = 1;
214
215                         if (!--spd->nr_pages)
216                                 break;
217                         if (pipe->nrbufs < pipe->buffers)
218                                 continue;
219
220                         break;
221                 }
222
223                 if (spd->flags & SPLICE_F_NONBLOCK) {
224                         if (!ret)
225                                 ret = -EAGAIN;
226                         break;
227                 }
228
229                 if (signal_pending(current)) {
230                         if (!ret)
231                                 ret = -ERESTARTSYS;
232                         break;
233                 }
234
235                 if (do_wakeup) {
236                         smp_mb();
237                         if (waitqueue_active(&pipe->wait))
238                                 wake_up_interruptible_sync(&pipe->wait);
239                         kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
240                         do_wakeup = 0;
241                 }
242
243                 pipe->waiting_writers++;
244                 pipe_wait(pipe);
245                 pipe->waiting_writers--;
246         }
247
248         pipe_unlock(pipe);
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_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 /*
269  * Check if we need to grow the arrays holding pages and partial page
270  * descriptions.
271  */
272 int splice_grow_spd(struct pipe_inode_info *pipe, struct splice_pipe_desc *spd)
273 {
274         if (pipe->buffers <= PIPE_DEF_BUFFERS)
275                 return 0;
276
277         spd->pages = kmalloc(pipe->buffers * sizeof(struct page *), GFP_KERNEL);
278         spd->partial = kmalloc(pipe->buffers * sizeof(struct partial_page), GFP_KERNEL);
279
280         if (spd->pages && spd->partial)
281                 return 0;
282
283         kfree(spd->pages);
284         kfree(spd->partial);
285         return -ENOMEM;
286 }
287
288 void splice_shrink_spd(struct pipe_inode_info *pipe,
289                        struct splice_pipe_desc *spd)
290 {
291         if (pipe->buffers <= PIPE_DEF_BUFFERS)
292                 return;
293
294         kfree(spd->pages);
295         kfree(spd->partial);
296 }
297
298 static int
299 __generic_file_splice_read(struct file *in, loff_t *ppos,
300                            struct pipe_inode_info *pipe, size_t len,
301                            unsigned int flags)
302 {
303         struct address_space *mapping = in->f_mapping;
304         unsigned int loff, nr_pages, req_pages;
305         struct page *pages[PIPE_DEF_BUFFERS];
306         struct partial_page partial[PIPE_DEF_BUFFERS];
307         struct page *page;
308         pgoff_t index, end_index;
309         loff_t isize;
310         int error, page_nr;
311         struct splice_pipe_desc spd = {
312                 .pages = pages,
313                 .partial = partial,
314                 .flags = flags,
315                 .ops = &page_cache_pipe_buf_ops,
316                 .spd_release = spd_release_page,
317         };
318
319         if (splice_grow_spd(pipe, &spd))
320                 return -ENOMEM;
321
322         index = *ppos >> PAGE_CACHE_SHIFT;
323         loff = *ppos & ~PAGE_CACHE_MASK;
324         req_pages = (len + loff + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
325         nr_pages = min(req_pages, pipe->buffers);
326
327         /*
328          * Lookup the (hopefully) full range of pages we need.
329          */
330         spd.nr_pages = find_get_pages_contig(mapping, index, nr_pages, spd.pages);
331         index += spd.nr_pages;
332
333         /*
334          * If find_get_pages_contig() returned fewer pages than we needed,
335          * readahead/allocate the rest and fill in the holes.
336          */
337         if (spd.nr_pages < nr_pages)
338                 page_cache_sync_readahead(mapping, &in->f_ra, in,
339                                 index, req_pages - spd.nr_pages);
340
341         error = 0;
342         while (spd.nr_pages < nr_pages) {
343                 /*
344                  * Page could be there, find_get_pages_contig() breaks on
345                  * the first hole.
346                  */
347                 page = find_get_page(mapping, index);
348                 if (!page) {
349                         /*
350                          * page didn't exist, allocate one.
351                          */
352                         page = page_cache_alloc_cold(mapping);
353                         if (!page)
354                                 break;
355
356                         error = add_to_page_cache_lru(page, mapping, index,
357                                                 GFP_KERNEL);
358                         if (unlikely(error)) {
359                                 page_cache_release(page);
360                                 if (error == -EEXIST)
361                                         continue;
362                                 break;
363                         }
364                         /*
365                          * add_to_page_cache() locks the page, unlock it
366                          * to avoid convoluting the logic below even more.
367                          */
368                         unlock_page(page);
369                 }
370
371                 spd.pages[spd.nr_pages++] = page;
372                 index++;
373         }
374
375         /*
376          * Now loop over the map and see if we need to start IO on any
377          * pages, fill in the partial map, etc.
378          */
379         index = *ppos >> PAGE_CACHE_SHIFT;
380         nr_pages = spd.nr_pages;
381         spd.nr_pages = 0;
382         for (page_nr = 0; page_nr < nr_pages; page_nr++) {
383                 unsigned int this_len;
384
385                 if (!len)
386                         break;
387
388                 /*
389                  * this_len is the max we'll use from this page
390                  */
391                 this_len = min_t(unsigned long, len, PAGE_CACHE_SIZE - loff);
392                 page = spd.pages[page_nr];
393
394                 if (PageReadahead(page))
395                         page_cache_async_readahead(mapping, &in->f_ra, in,
396                                         page, index, req_pages - page_nr);
397
398                 /*
399                  * If the page isn't uptodate, we may need to start io on it
400                  */
401                 if (!PageUptodate(page)) {
402                         /*
403                          * If in nonblock mode then dont block on waiting
404                          * for an in-flight io page
405                          */
406                         if (flags & SPLICE_F_NONBLOCK) {
407                                 if (!trylock_page(page)) {
408                                         error = -EAGAIN;
409                                         break;
410                                 }
411                         } else
412                                 lock_page(page);
413
414                         /*
415                          * Page was truncated, or invalidated by the
416                          * filesystem.  Redo the find/create, but this time the
417                          * page is kept locked, so there's no chance of another
418                          * race with truncate/invalidate.
419                          */
420                         if (!page->mapping) {
421                                 unlock_page(page);
422                                 page = find_or_create_page(mapping, index,
423                                                 mapping_gfp_mask(mapping));
424
425                                 if (!page) {
426                                         error = -ENOMEM;
427                                         break;
428                                 }
429                                 page_cache_release(spd.pages[page_nr]);
430                                 spd.pages[page_nr] = page;
431                         }
432                         /*
433                          * page was already under io and is now done, great
434                          */
435                         if (PageUptodate(page)) {
436                                 unlock_page(page);
437                                 goto fill_it;
438                         }
439
440                         /*
441                          * need to read in the page
442                          */
443                         error = mapping->a_ops->readpage(in, page);
444                         if (unlikely(error)) {
445                                 /*
446                                  * We really should re-lookup the page here,
447                                  * but it complicates things a lot. Instead
448                                  * lets just do what we already stored, and
449                                  * we'll get it the next time we are called.
450                                  */
451                                 if (error == AOP_TRUNCATED_PAGE)
452                                         error = 0;
453
454                                 break;
455                         }
456                 }
457 fill_it:
458                 /*
459                  * i_size must be checked after PageUptodate.
460                  */
461                 isize = i_size_read(mapping->host);
462                 end_index = (isize - 1) >> PAGE_CACHE_SHIFT;
463                 if (unlikely(!isize || index > end_index))
464                         break;
465
466                 /*
467                  * if this is the last page, see if we need to shrink
468                  * the length and stop
469                  */
470                 if (end_index == index) {
471                         unsigned int plen;
472
473                         /*
474                          * max good bytes in this page
475                          */
476                         plen = ((isize - 1) & ~PAGE_CACHE_MASK) + 1;
477                         if (plen <= loff)
478                                 break;
479
480                         /*
481                          * force quit after adding this page
482                          */
483                         this_len = min(this_len, plen - loff);
484                         len = this_len;
485                 }
486
487                 spd.partial[page_nr].offset = loff;
488                 spd.partial[page_nr].len = this_len;
489                 len -= this_len;
490                 loff = 0;
491                 spd.nr_pages++;
492                 index++;
493         }
494
495         /*
496          * Release any pages at the end, if we quit early. 'page_nr' is how far
497          * we got, 'nr_pages' is how many pages are in the map.
498          */
499         while (page_nr < nr_pages)
500                 page_cache_release(spd.pages[page_nr++]);
501         in->f_ra.prev_pos = (loff_t)index << PAGE_CACHE_SHIFT;
502
503         if (spd.nr_pages)
504                 error = splice_to_pipe(pipe, &spd);
505
506         splice_shrink_spd(pipe, &spd);
507         return error;
508 }
509
510 /**
511  * generic_file_splice_read - splice data from file to a pipe
512  * @in:         file to splice from
513  * @ppos:       position in @in
514  * @pipe:       pipe to splice to
515  * @len:        number of bytes to splice
516  * @flags:      splice modifier flags
517  *
518  * Description:
519  *    Will read pages from given file and fill them into a pipe. Can be
520  *    used as long as the address_space operations for the source implements
521  *    a readpage() hook.
522  *
523  */
524 ssize_t generic_file_splice_read(struct file *in, loff_t *ppos,
525                                  struct pipe_inode_info *pipe, size_t len,
526                                  unsigned int flags)
527 {
528         loff_t isize, left;
529         int ret;
530
531         isize = i_size_read(in->f_mapping->host);
532         if (unlikely(*ppos >= isize))
533                 return 0;
534
535         left = isize - *ppos;
536         if (unlikely(left < len))
537                 len = left;
538
539         ret = __generic_file_splice_read(in, ppos, pipe, len, flags);
540         if (ret > 0) {
541                 *ppos += ret;
542                 file_accessed(in);
543         }
544
545         return ret;
546 }
547 EXPORT_SYMBOL(generic_file_splice_read);
548
549 static const struct pipe_buf_operations default_pipe_buf_ops = {
550         .can_merge = 0,
551         .map = generic_pipe_buf_map,
552         .unmap = generic_pipe_buf_unmap,
553         .confirm = generic_pipe_buf_confirm,
554         .release = generic_pipe_buf_release,
555         .steal = generic_pipe_buf_steal,
556         .get = generic_pipe_buf_get,
557 };
558
559 static ssize_t kernel_readv(struct file *file, const struct iovec *vec,
560                             unsigned long vlen, loff_t offset)
561 {
562         mm_segment_t old_fs;
563         loff_t pos = offset;
564         ssize_t res;
565
566         old_fs = get_fs();
567         set_fs(get_ds());
568         /* The cast to a user pointer is valid due to the set_fs() */
569         res = vfs_readv(file, (const struct iovec __user *)vec, vlen, &pos);
570         set_fs(old_fs);
571
572         return res;
573 }
574
575 static ssize_t kernel_write(struct file *file, const char *buf, size_t count,
576                             loff_t pos)
577 {
578         mm_segment_t old_fs;
579         ssize_t res;
580
581         old_fs = get_fs();
582         set_fs(get_ds());
583         /* The cast to a user pointer is valid due to the set_fs() */
584         res = vfs_write(file, (const char __user *)buf, count, &pos);
585         set_fs(old_fs);
586
587         return res;
588 }
589
590 ssize_t default_file_splice_read(struct file *in, loff_t *ppos,
591                                  struct pipe_inode_info *pipe, size_t len,
592                                  unsigned int flags)
593 {
594         unsigned int nr_pages;
595         unsigned int nr_freed;
596         size_t offset;
597         struct page *pages[PIPE_DEF_BUFFERS];
598         struct partial_page partial[PIPE_DEF_BUFFERS];
599         struct iovec *vec, __vec[PIPE_DEF_BUFFERS];
600         ssize_t res;
601         size_t this_len;
602         int error;
603         int i;
604         struct splice_pipe_desc spd = {
605                 .pages = pages,
606                 .partial = partial,
607                 .flags = flags,
608                 .ops = &default_pipe_buf_ops,
609                 .spd_release = spd_release_page,
610         };
611
612         if (splice_grow_spd(pipe, &spd))
613                 return -ENOMEM;
614
615         res = -ENOMEM;
616         vec = __vec;
617         if (pipe->buffers > PIPE_DEF_BUFFERS) {
618                 vec = kmalloc(pipe->buffers * sizeof(struct iovec), GFP_KERNEL);
619                 if (!vec)
620                         goto shrink_ret;
621         }
622
623         offset = *ppos & ~PAGE_CACHE_MASK;
624         nr_pages = (len + offset + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
625
626         for (i = 0; i < nr_pages && i < pipe->buffers && len; i++) {
627                 struct page *page;
628
629                 page = alloc_page(GFP_USER);
630                 error = -ENOMEM;
631                 if (!page)
632                         goto err;
633
634                 this_len = min_t(size_t, len, PAGE_CACHE_SIZE - offset);
635                 vec[i].iov_base = (void __user *) page_address(page);
636                 vec[i].iov_len = this_len;
637                 spd.pages[i] = page;
638                 spd.nr_pages++;
639                 len -= this_len;
640                 offset = 0;
641         }
642
643         res = kernel_readv(in, vec, spd.nr_pages, *ppos);
644         if (res < 0) {
645                 error = res;
646                 goto err;
647         }
648
649         error = 0;
650         if (!res)
651                 goto err;
652
653         nr_freed = 0;
654         for (i = 0; i < spd.nr_pages; i++) {
655                 this_len = min_t(size_t, vec[i].iov_len, res);
656                 spd.partial[i].offset = 0;
657                 spd.partial[i].len = this_len;
658                 if (!this_len) {
659                         __free_page(spd.pages[i]);
660                         spd.pages[i] = NULL;
661                         nr_freed++;
662                 }
663                 res -= this_len;
664         }
665         spd.nr_pages -= nr_freed;
666
667         res = splice_to_pipe(pipe, &spd);
668         if (res > 0)
669                 *ppos += res;
670
671 shrink_ret:
672         if (vec != __vec)
673                 kfree(vec);
674         splice_shrink_spd(pipe, &spd);
675         return res;
676
677 err:
678         for (i = 0; i < spd.nr_pages; i++)
679                 __free_page(spd.pages[i]);
680
681         res = error;
682         goto shrink_ret;
683 }
684 EXPORT_SYMBOL(default_file_splice_read);
685
686 /*
687  * Send 'sd->len' bytes to socket from 'sd->file' at position 'sd->pos'
688  * using sendpage(). Return the number of bytes sent.
689  */
690 static int pipe_to_sendpage(struct pipe_inode_info *pipe,
691                             struct pipe_buffer *buf, struct splice_desc *sd)
692 {
693         struct file *file = sd->u.file;
694         loff_t pos = sd->pos;
695         int ret, more;
696
697         ret = buf->ops->confirm(pipe, buf);
698         if (!ret) {
699                 more = (sd->flags & SPLICE_F_MORE) || sd->len < sd->total_len;
700                 if (file->f_op && file->f_op->sendpage)
701                         ret = file->f_op->sendpage(file, buf->page, buf->offset,
702                                                    sd->len, &pos, more);
703                 else
704                         ret = -EINVAL;
705         }
706
707         return ret;
708 }
709
710 /*
711  * This is a little more tricky than the file -> pipe splicing. There are
712  * basically three cases:
713  *
714  *      - Destination page already exists in the address space and there
715  *        are users of it. For that case we have no other option that
716  *        copying the data. Tough luck.
717  *      - Destination page already exists in the address space, but there
718  *        are no users of it. Make sure it's uptodate, then drop it. Fall
719  *        through to last case.
720  *      - Destination page does not exist, we can add the pipe page to
721  *        the page cache and avoid the copy.
722  *
723  * If asked to move pages to the output file (SPLICE_F_MOVE is set in
724  * sd->flags), we attempt to migrate pages from the pipe to the output
725  * file address space page cache. This is possible if no one else has
726  * the pipe page referenced outside of the pipe and page cache. If
727  * SPLICE_F_MOVE isn't set, or we cannot move the page, we simply create
728  * a new page in the output file page cache and fill/dirty that.
729  */
730 int pipe_to_file(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
731                  struct splice_desc *sd)
732 {
733         struct file *file = sd->u.file;
734         struct address_space *mapping = file->f_mapping;
735         unsigned int offset, this_len;
736         struct page *page;
737         void *fsdata;
738         int ret;
739
740         /*
741          * make sure the data in this buffer is uptodate
742          */
743         ret = buf->ops->confirm(pipe, buf);
744         if (unlikely(ret))
745                 return ret;
746
747         offset = sd->pos & ~PAGE_CACHE_MASK;
748
749         this_len = sd->len;
750         if (this_len + offset > PAGE_CACHE_SIZE)
751                 this_len = PAGE_CACHE_SIZE - offset;
752
753         ret = pagecache_write_begin(file, mapping, sd->pos, this_len,
754                                 AOP_FLAG_UNINTERRUPTIBLE, &page, &fsdata);
755         if (unlikely(ret))
756                 goto out;
757
758         if (buf->page != page) {
759                 /*
760                  * Careful, ->map() uses KM_USER0!
761                  */
762                 char *src = buf->ops->map(pipe, buf, 1);
763                 char *dst = kmap_atomic(page, KM_USER1);
764
765                 memcpy(dst + offset, src + buf->offset, this_len);
766                 flush_dcache_page(page);
767                 kunmap_atomic(dst, KM_USER1);
768                 buf->ops->unmap(pipe, buf, src);
769         }
770         ret = pagecache_write_end(file, mapping, sd->pos, this_len, this_len,
771                                 page, fsdata);
772 out:
773         return ret;
774 }
775 EXPORT_SYMBOL(pipe_to_file);
776
777 static void wakeup_pipe_writers(struct pipe_inode_info *pipe)
778 {
779         smp_mb();
780         if (waitqueue_active(&pipe->wait))
781                 wake_up_interruptible(&pipe->wait);
782         kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
783 }
784
785 /**
786  * splice_from_pipe_feed - feed available data from a pipe to a file
787  * @pipe:       pipe to splice from
788  * @sd:         information to @actor
789  * @actor:      handler that splices the data
790  *
791  * Description:
792  *    This function loops over the pipe and calls @actor to do the
793  *    actual moving of a single struct pipe_buffer to the desired
794  *    destination.  It returns when there's no more buffers left in
795  *    the pipe or if the requested number of bytes (@sd->total_len)
796  *    have been copied.  It returns a positive number (one) if the
797  *    pipe needs to be filled with more data, zero if the required
798  *    number of bytes have been copied and -errno on error.
799  *
800  *    This, together with splice_from_pipe_{begin,end,next}, may be
801  *    used to implement the functionality of __splice_from_pipe() when
802  *    locking is required around copying the pipe buffers to the
803  *    destination.
804  */
805 int splice_from_pipe_feed(struct pipe_inode_info *pipe, struct splice_desc *sd,
806                           splice_actor *actor)
807 {
808         int ret;
809
810         while (pipe->nrbufs) {
811                 struct pipe_buffer *buf = pipe->bufs + pipe->curbuf;
812                 const struct pipe_buf_operations *ops = buf->ops;
813
814                 sd->len = buf->len;
815                 if (sd->len > sd->total_len)
816                         sd->len = sd->total_len;
817
818                 ret = actor(pipe, buf, sd);
819                 if (ret <= 0) {
820                         if (ret == -ENODATA)
821                                 ret = 0;
822                         return ret;
823                 }
824                 buf->offset += ret;
825                 buf->len -= ret;
826
827                 sd->num_spliced += ret;
828                 sd->len -= ret;
829                 sd->pos += ret;
830                 sd->total_len -= ret;
831
832                 if (!buf->len) {
833                         buf->ops = NULL;
834                         ops->release(pipe, buf);
835                         pipe->curbuf = (pipe->curbuf + 1) & (pipe->buffers - 1);
836                         pipe->nrbufs--;
837                         if (pipe->inode)
838                                 sd->need_wakeup = true;
839                 }
840
841                 if (!sd->total_len)
842                         return 0;
843         }
844
845         return 1;
846 }
847 EXPORT_SYMBOL(splice_from_pipe_feed);
848
849 /**
850  * splice_from_pipe_next - wait for some data to splice from
851  * @pipe:       pipe to splice from
852  * @sd:         information about the splice operation
853  *
854  * Description:
855  *    This function will wait for some data and return a positive
856  *    value (one) if pipe buffers are available.  It will return zero
857  *    or -errno if no more data needs to be spliced.
858  */
859 int splice_from_pipe_next(struct pipe_inode_info *pipe, struct splice_desc *sd)
860 {
861         while (!pipe->nrbufs) {
862                 if (!pipe->writers)
863                         return 0;
864
865                 if (!pipe->waiting_writers && sd->num_spliced)
866                         return 0;
867
868                 if (sd->flags & SPLICE_F_NONBLOCK)
869                         return -EAGAIN;
870
871                 if (signal_pending(current))
872                         return -ERESTARTSYS;
873
874                 if (sd->need_wakeup) {
875                         wakeup_pipe_writers(pipe);
876                         sd->need_wakeup = false;
877                 }
878
879                 pipe_wait(pipe);
880         }
881
882         return 1;
883 }
884 EXPORT_SYMBOL(splice_from_pipe_next);
885
886 /**
887  * splice_from_pipe_begin - start splicing from pipe
888  * @sd:         information about the splice operation
889  *
890  * Description:
891  *    This function should be called before a loop containing
892  *    splice_from_pipe_next() and splice_from_pipe_feed() to
893  *    initialize the necessary fields of @sd.
894  */
895 void splice_from_pipe_begin(struct splice_desc *sd)
896 {
897         sd->num_spliced = 0;
898         sd->need_wakeup = false;
899 }
900 EXPORT_SYMBOL(splice_from_pipe_begin);
901
902 /**
903  * splice_from_pipe_end - finish splicing from pipe
904  * @pipe:       pipe to splice from
905  * @sd:         information about the splice operation
906  *
907  * Description:
908  *    This function will wake up pipe writers if necessary.  It should
909  *    be called after a loop containing splice_from_pipe_next() and
910  *    splice_from_pipe_feed().
911  */
912 void splice_from_pipe_end(struct pipe_inode_info *pipe, struct splice_desc *sd)
913 {
914         if (sd->need_wakeup)
915                 wakeup_pipe_writers(pipe);
916 }
917 EXPORT_SYMBOL(splice_from_pipe_end);
918
919 /**
920  * __splice_from_pipe - splice data from a pipe to given actor
921  * @pipe:       pipe to splice from
922  * @sd:         information to @actor
923  * @actor:      handler that splices the data
924  *
925  * Description:
926  *    This function does little more than loop over the pipe and call
927  *    @actor to do the actual moving of a single struct pipe_buffer to
928  *    the desired destination. See pipe_to_file, pipe_to_sendpage, or
929  *    pipe_to_user.
930  *
931  */
932 ssize_t __splice_from_pipe(struct pipe_inode_info *pipe, struct splice_desc *sd,
933                            splice_actor *actor)
934 {
935         int ret;
936
937         splice_from_pipe_begin(sd);
938         do {
939                 ret = splice_from_pipe_next(pipe, sd);
940                 if (ret > 0)
941                         ret = splice_from_pipe_feed(pipe, sd, actor);
942         } while (ret > 0);
943         splice_from_pipe_end(pipe, sd);
944
945         return sd->num_spliced ? sd->num_spliced : ret;
946 }
947 EXPORT_SYMBOL(__splice_from_pipe);
948
949 /**
950  * splice_from_pipe - splice data from a pipe to a file
951  * @pipe:       pipe to splice from
952  * @out:        file to splice to
953  * @ppos:       position in @out
954  * @len:        how many bytes to splice
955  * @flags:      splice modifier flags
956  * @actor:      handler that splices the data
957  *
958  * Description:
959  *    See __splice_from_pipe. This function locks the pipe inode,
960  *    otherwise it's identical to __splice_from_pipe().
961  *
962  */
963 ssize_t splice_from_pipe(struct pipe_inode_info *pipe, struct file *out,
964                          loff_t *ppos, size_t len, unsigned int flags,
965                          splice_actor *actor)
966 {
967         ssize_t ret;
968         struct splice_desc sd = {
969                 .total_len = len,
970                 .flags = flags,
971                 .pos = *ppos,
972                 .u.file = out,
973         };
974
975         pipe_lock(pipe);
976         ret = __splice_from_pipe(pipe, &sd, actor);
977         pipe_unlock(pipe);
978
979         return ret;
980 }
981
982 /**
983  * generic_file_splice_write - splice data from a pipe to a file
984  * @pipe:       pipe info
985  * @out:        file to write to
986  * @ppos:       position in @out
987  * @len:        number of bytes to splice
988  * @flags:      splice modifier flags
989  *
990  * Description:
991  *    Will either move or copy pages (determined by @flags options) from
992  *    the given pipe inode to the given file.
993  *
994  */
995 ssize_t
996 generic_file_splice_write(struct pipe_inode_info *pipe, struct file *out,
997                           loff_t *ppos, size_t len, unsigned int flags)
998 {
999         struct address_space *mapping = out->f_mapping;
1000         struct inode *inode = mapping->host;
1001         struct splice_desc sd = {
1002                 .total_len = len,
1003                 .flags = flags,
1004                 .pos = *ppos,
1005                 .u.file = out,
1006         };
1007         ssize_t ret;
1008
1009         pipe_lock(pipe);
1010
1011         splice_from_pipe_begin(&sd);
1012         do {
1013                 ret = splice_from_pipe_next(pipe, &sd);
1014                 if (ret <= 0)
1015                         break;
1016
1017                 mutex_lock_nested(&inode->i_mutex, I_MUTEX_CHILD);
1018                 ret = file_remove_suid(out);
1019                 if (!ret) {
1020                         file_update_time(out);
1021                         ret = splice_from_pipe_feed(pipe, &sd, pipe_to_file);
1022                 }
1023                 mutex_unlock(&inode->i_mutex);
1024         } while (ret > 0);
1025         splice_from_pipe_end(pipe, &sd);
1026
1027         pipe_unlock(pipe);
1028
1029         if (sd.num_spliced)
1030                 ret = sd.num_spliced;
1031
1032         if (ret > 0) {
1033                 unsigned long nr_pages;
1034                 int err;
1035
1036                 nr_pages = (ret + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
1037
1038                 err = generic_write_sync(out, *ppos, ret);
1039                 if (err)
1040                         ret = err;
1041                 else
1042                         *ppos += ret;
1043                 balance_dirty_pages_ratelimited_nr(mapping, nr_pages);
1044         }
1045
1046         return ret;
1047 }
1048
1049 EXPORT_SYMBOL(generic_file_splice_write);
1050
1051 static int write_pipe_buf(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
1052                           struct splice_desc *sd)
1053 {
1054         int ret;
1055         void *data;
1056
1057         ret = buf->ops->confirm(pipe, buf);
1058         if (ret)
1059                 return ret;
1060
1061         data = buf->ops->map(pipe, buf, 0);
1062         ret = kernel_write(sd->u.file, data + buf->offset, sd->len, sd->pos);
1063         buf->ops->unmap(pipe, buf, data);
1064
1065         return ret;
1066 }
1067
1068 static ssize_t default_file_splice_write(struct pipe_inode_info *pipe,
1069                                          struct file *out, loff_t *ppos,
1070                                          size_t len, unsigned int flags)
1071 {
1072         ssize_t ret;
1073
1074         ret = splice_from_pipe(pipe, out, ppos, len, flags, write_pipe_buf);
1075         if (ret > 0)
1076                 *ppos += ret;
1077
1078         return ret;
1079 }
1080
1081 /**
1082  * generic_splice_sendpage - splice data from a pipe to a socket
1083  * @pipe:       pipe to splice from
1084  * @out:        socket to write to
1085  * @ppos:       position in @out
1086  * @len:        number of bytes to splice
1087  * @flags:      splice modifier flags
1088  *
1089  * Description:
1090  *    Will send @len bytes from the pipe to a network socket. No data copying
1091  *    is involved.
1092  *
1093  */
1094 ssize_t generic_splice_sendpage(struct pipe_inode_info *pipe, struct file *out,
1095                                 loff_t *ppos, size_t len, unsigned int flags)
1096 {
1097         return splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_sendpage);
1098 }
1099
1100 EXPORT_SYMBOL(generic_splice_sendpage);
1101
1102 /*
1103  * Attempt to initiate a splice from pipe to file.
1104  */
1105 static long do_splice_from(struct pipe_inode_info *pipe, struct file *out,
1106                            loff_t *ppos, size_t len, unsigned int flags)
1107 {
1108         ssize_t (*splice_write)(struct pipe_inode_info *, struct file *,
1109                                 loff_t *, size_t, unsigned int);
1110         int ret;
1111
1112         if (unlikely(!(out->f_mode & FMODE_WRITE)))
1113                 return -EBADF;
1114
1115         if (unlikely(out->f_flags & O_APPEND))
1116                 return -EINVAL;
1117
1118         ret = rw_verify_area(WRITE, out, ppos, len);
1119         if (unlikely(ret < 0))
1120                 return ret;
1121
1122         if (out->f_op && out->f_op->splice_write)
1123                 splice_write = out->f_op->splice_write;
1124         else
1125                 splice_write = default_file_splice_write;
1126
1127         return splice_write(pipe, out, ppos, len, flags);
1128 }
1129
1130 /*
1131  * Attempt to initiate a splice from a file to a pipe.
1132  */
1133 static long do_splice_to(struct file *in, loff_t *ppos,
1134                          struct pipe_inode_info *pipe, size_t len,
1135                          unsigned int flags)
1136 {
1137         ssize_t (*splice_read)(struct file *, loff_t *,
1138                                struct pipe_inode_info *, size_t, unsigned int);
1139         int ret;
1140
1141         if (unlikely(!(in->f_mode & FMODE_READ)))
1142                 return -EBADF;
1143
1144         ret = rw_verify_area(READ, in, ppos, len);
1145         if (unlikely(ret < 0))
1146                 return ret;
1147
1148         if (in->f_op && in->f_op->splice_read)
1149                 splice_read = in->f_op->splice_read;
1150         else
1151                 splice_read = default_file_splice_read;
1152
1153         return splice_read(in, ppos, pipe, len, flags);
1154 }
1155
1156 /**
1157  * splice_direct_to_actor - splices data directly between two non-pipes
1158  * @in:         file to splice from
1159  * @sd:         actor information on where to splice to
1160  * @actor:      handles the data splicing
1161  *
1162  * Description:
1163  *    This is a special case helper to splice directly between two
1164  *    points, without requiring an explicit pipe. Internally an allocated
1165  *    pipe is cached in the process, and reused during the lifetime of
1166  *    that process.
1167  *
1168  */
1169 ssize_t splice_direct_to_actor(struct file *in, struct splice_desc *sd,
1170                                splice_direct_actor *actor)
1171 {
1172         struct pipe_inode_info *pipe;
1173         long ret, bytes;
1174         umode_t i_mode;
1175         size_t len;
1176         int i, flags;
1177
1178         /*
1179          * We require the input being a regular file, as we don't want to
1180          * randomly drop data for eg socket -> socket splicing. Use the
1181          * piped splicing for that!
1182          */
1183         i_mode = in->f_path.dentry->d_inode->i_mode;
1184         if (unlikely(!S_ISREG(i_mode) && !S_ISBLK(i_mode)))
1185                 return -EINVAL;
1186
1187         /*
1188          * neither in nor out is a pipe, setup an internal pipe attached to
1189          * 'out' and transfer the wanted data from 'in' to 'out' through that
1190          */
1191         pipe = current->splice_pipe;
1192         if (unlikely(!pipe)) {
1193                 pipe = alloc_pipe_info(NULL);
1194                 if (!pipe)
1195                         return -ENOMEM;
1196
1197                 /*
1198                  * We don't have an immediate reader, but we'll read the stuff
1199                  * out of the pipe right after the splice_to_pipe(). So set
1200                  * PIPE_READERS appropriately.
1201                  */
1202                 pipe->readers = 1;
1203
1204                 current->splice_pipe = pipe;
1205         }
1206
1207         /*
1208          * Do the splice.
1209          */
1210         ret = 0;
1211         bytes = 0;
1212         len = sd->total_len;
1213         flags = sd->flags;
1214
1215         /*
1216          * Don't block on output, we have to drain the direct pipe.
1217          */
1218         sd->flags &= ~SPLICE_F_NONBLOCK;
1219
1220         while (len) {
1221                 size_t read_len;
1222                 loff_t pos = sd->pos, prev_pos = pos;
1223
1224                 ret = do_splice_to(in, &pos, pipe, len, flags);
1225                 if (unlikely(ret <= 0))
1226                         goto out_release;
1227
1228                 read_len = ret;
1229                 sd->total_len = read_len;
1230
1231                 /*
1232                  * NOTE: nonblocking mode only applies to the input. We
1233                  * must not do the output in nonblocking mode as then we
1234                  * could get stuck data in the internal pipe:
1235                  */
1236                 ret = actor(pipe, sd);
1237                 if (unlikely(ret <= 0)) {
1238                         sd->pos = prev_pos;
1239                         goto out_release;
1240                 }
1241
1242                 bytes += ret;
1243                 len -= ret;
1244                 sd->pos = pos;
1245
1246                 if (ret < read_len) {
1247                         sd->pos = prev_pos + ret;
1248                         goto out_release;
1249                 }
1250         }
1251
1252 done:
1253         pipe->nrbufs = pipe->curbuf = 0;
1254         file_accessed(in);
1255         return bytes;
1256
1257 out_release:
1258         /*
1259          * If we did an incomplete transfer we must release
1260          * the pipe buffers in question:
1261          */
1262         for (i = 0; i < pipe->buffers; i++) {
1263                 struct pipe_buffer *buf = pipe->bufs + i;
1264
1265                 if (buf->ops) {
1266                         buf->ops->release(pipe, buf);
1267                         buf->ops = NULL;
1268                 }
1269         }
1270
1271         if (!bytes)
1272                 bytes = ret;
1273
1274         goto done;
1275 }
1276 EXPORT_SYMBOL(splice_direct_to_actor);
1277
1278 static int direct_splice_actor(struct pipe_inode_info *pipe,
1279                                struct splice_desc *sd)
1280 {
1281         struct file *file = sd->u.file;
1282
1283         return do_splice_from(pipe, file, &file->f_pos, sd->total_len,
1284                               sd->flags);
1285 }
1286
1287 /**
1288  * do_splice_direct - splices data directly between two files
1289  * @in:         file to splice from
1290  * @ppos:       input file offset
1291  * @out:        file to splice to
1292  * @len:        number of bytes to splice
1293  * @flags:      splice modifier flags
1294  *
1295  * Description:
1296  *    For use by do_sendfile(). splice can easily emulate sendfile, but
1297  *    doing it in the application would incur an extra system call
1298  *    (splice in + splice out, as compared to just sendfile()). So this helper
1299  *    can splice directly through a process-private pipe.
1300  *
1301  */
1302 long do_splice_direct(struct file *in, loff_t *ppos, struct file *out,
1303                       size_t len, unsigned int flags)
1304 {
1305         struct splice_desc sd = {
1306                 .len            = len,
1307                 .total_len      = len,
1308                 .flags          = flags,
1309                 .pos            = *ppos,
1310                 .u.file         = out,
1311         };
1312         long ret;
1313
1314         ret = splice_direct_to_actor(in, &sd, direct_splice_actor);
1315         if (ret > 0)
1316                 *ppos = sd.pos;
1317
1318         return ret;
1319 }
1320
1321 static int splice_pipe_to_pipe(struct pipe_inode_info *ipipe,
1322                                struct pipe_inode_info *opipe,
1323                                size_t len, unsigned int flags);
1324 /*
1325  * After the inode slimming patch, i_pipe/i_bdev/i_cdev share the same
1326  * location, so checking ->i_pipe is not enough to verify that this is a
1327  * pipe.
1328  */
1329 static inline struct pipe_inode_info *pipe_info(struct inode *inode)
1330 {
1331         if (S_ISFIFO(inode->i_mode))
1332                 return inode->i_pipe;
1333
1334         return NULL;
1335 }
1336
1337 /*
1338  * Determine where to splice to/from.
1339  */
1340 static long do_splice(struct file *in, loff_t __user *off_in,
1341                       struct file *out, loff_t __user *off_out,
1342                       size_t len, unsigned int flags)
1343 {
1344         struct pipe_inode_info *ipipe;
1345         struct pipe_inode_info *opipe;
1346         loff_t offset, *off;
1347         long ret;
1348
1349         ipipe = pipe_info(in->f_path.dentry->d_inode);
1350         opipe = pipe_info(out->f_path.dentry->d_inode);
1351
1352         if (ipipe && opipe) {
1353                 if (off_in || off_out)
1354                         return -ESPIPE;
1355
1356                 if (!(in->f_mode & FMODE_READ))
1357                         return -EBADF;
1358
1359                 if (!(out->f_mode & FMODE_WRITE))
1360                         return -EBADF;
1361
1362                 /* Splicing to self would be fun, but... */
1363                 if (ipipe == opipe)
1364                         return -EINVAL;
1365
1366                 return splice_pipe_to_pipe(ipipe, opipe, len, flags);
1367         }
1368
1369         if (ipipe) {
1370                 if (off_in)
1371                         return -ESPIPE;
1372                 if (off_out) {
1373                         if (!(out->f_mode & FMODE_PWRITE))
1374                                 return -EINVAL;
1375                         if (copy_from_user(&offset, off_out, sizeof(loff_t)))
1376                                 return -EFAULT;
1377                         off = &offset;
1378                 } else
1379                         off = &out->f_pos;
1380
1381                 ret = do_splice_from(ipipe, out, off, len, flags);
1382
1383                 if (off_out && copy_to_user(off_out, off, sizeof(loff_t)))
1384                         ret = -EFAULT;
1385
1386                 return ret;
1387         }
1388
1389         if (opipe) {
1390                 if (off_out)
1391                         return -ESPIPE;
1392                 if (off_in) {
1393                         if (!(in->f_mode & FMODE_PREAD))
1394                                 return -EINVAL;
1395                         if (copy_from_user(&offset, off_in, sizeof(loff_t)))
1396                                 return -EFAULT;
1397                         off = &offset;
1398                 } else
1399                         off = &in->f_pos;
1400
1401                 ret = do_splice_to(in, off, opipe, len, flags);
1402
1403                 if (off_in && copy_to_user(off_in, off, sizeof(loff_t)))
1404                         ret = -EFAULT;
1405
1406                 return ret;
1407         }
1408
1409         return -EINVAL;
1410 }
1411
1412 /*
1413  * Map an iov into an array of pages and offset/length tupples. With the
1414  * partial_page structure, we can map several non-contiguous ranges into
1415  * our ones pages[] map instead of splitting that operation into pieces.
1416  * Could easily be exported as a generic helper for other users, in which
1417  * case one would probably want to add a 'max_nr_pages' parameter as well.
1418  */
1419 static int get_iovec_page_array(const struct iovec __user *iov,
1420                                 unsigned int nr_vecs, struct page **pages,
1421                                 struct partial_page *partial, int aligned,
1422                                 unsigned int pipe_buffers)
1423 {
1424         int buffers = 0, error = 0;
1425
1426         while (nr_vecs) {
1427                 unsigned long off, npages;
1428                 struct iovec entry;
1429                 void __user *base;
1430                 size_t len;
1431                 int i;
1432
1433                 error = -EFAULT;
1434                 if (copy_from_user(&entry, iov, sizeof(entry)))
1435                         break;
1436
1437                 base = entry.iov_base;
1438                 len = entry.iov_len;
1439
1440                 /*
1441                  * Sanity check this iovec. 0 read succeeds.
1442                  */
1443                 error = 0;
1444                 if (unlikely(!len))
1445                         break;
1446                 error = -EFAULT;
1447                 if (!access_ok(VERIFY_READ, base, len))
1448                         break;
1449
1450                 /*
1451                  * Get this base offset and number of pages, then map
1452                  * in the user pages.
1453                  */
1454                 off = (unsigned long) base & ~PAGE_MASK;
1455
1456                 /*
1457                  * If asked for alignment, the offset must be zero and the
1458                  * length a multiple of the PAGE_SIZE.
1459                  */
1460                 error = -EINVAL;
1461                 if (aligned && (off || len & ~PAGE_MASK))
1462                         break;
1463
1464                 npages = (off + len + PAGE_SIZE - 1) >> PAGE_SHIFT;
1465                 if (npages > pipe_buffers - buffers)
1466                         npages = pipe_buffers - buffers;
1467
1468                 error = get_user_pages_fast((unsigned long)base, npages,
1469                                         0, &pages[buffers]);
1470
1471                 if (unlikely(error <= 0))
1472                         break;
1473
1474                 /*
1475                  * Fill this contiguous range into the partial page map.
1476                  */
1477                 for (i = 0; i < error; i++) {
1478                         const int plen = min_t(size_t, len, PAGE_SIZE - off);
1479
1480                         partial[buffers].offset = off;
1481                         partial[buffers].len = plen;
1482
1483                         off = 0;
1484                         len -= plen;
1485                         buffers++;
1486                 }
1487
1488                 /*
1489                  * We didn't complete this iov, stop here since it probably
1490                  * means we have to move some of this into a pipe to
1491                  * be able to continue.
1492                  */
1493                 if (len)
1494                         break;
1495
1496                 /*
1497                  * Don't continue if we mapped fewer pages than we asked for,
1498                  * or if we mapped the max number of pages that we have
1499                  * room for.
1500                  */
1501                 if (error < npages || buffers == pipe_buffers)
1502                         break;
1503
1504                 nr_vecs--;
1505                 iov++;
1506         }
1507
1508         if (buffers)
1509                 return buffers;
1510
1511         return error;
1512 }
1513
1514 static int pipe_to_user(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
1515                         struct splice_desc *sd)
1516 {
1517         char *src;
1518         int ret;
1519
1520         ret = buf->ops->confirm(pipe, buf);
1521         if (unlikely(ret))
1522                 return ret;
1523
1524         /*
1525          * See if we can use the atomic maps, by prefaulting in the
1526          * pages and doing an atomic copy
1527          */
1528         if (!fault_in_pages_writeable(sd->u.userptr, sd->len)) {
1529                 src = buf->ops->map(pipe, buf, 1);
1530                 ret = __copy_to_user_inatomic(sd->u.userptr, src + buf->offset,
1531                                                         sd->len);
1532                 buf->ops->unmap(pipe, buf, src);
1533                 if (!ret) {
1534                         ret = sd->len;
1535                         goto out;
1536                 }
1537         }
1538
1539         /*
1540          * No dice, use slow non-atomic map and copy
1541          */
1542         src = buf->ops->map(pipe, buf, 0);
1543
1544         ret = sd->len;
1545         if (copy_to_user(sd->u.userptr, src + buf->offset, sd->len))
1546                 ret = -EFAULT;
1547
1548         buf->ops->unmap(pipe, buf, src);
1549 out:
1550         if (ret > 0)
1551                 sd->u.userptr += ret;
1552         return ret;
1553 }
1554
1555 /*
1556  * For lack of a better implementation, implement vmsplice() to userspace
1557  * as a simple copy of the pipes pages to the user iov.
1558  */
1559 static long vmsplice_to_user(struct file *file, const struct iovec __user *iov,
1560                              unsigned long nr_segs, unsigned int flags)
1561 {
1562         struct pipe_inode_info *pipe;
1563         struct splice_desc sd;
1564         ssize_t size;
1565         int error;
1566         long ret;
1567
1568         pipe = pipe_info(file->f_path.dentry->d_inode);
1569         if (!pipe)
1570                 return -EBADF;
1571
1572         pipe_lock(pipe);
1573
1574         error = ret = 0;
1575         while (nr_segs) {
1576                 void __user *base;
1577                 size_t len;
1578
1579                 /*
1580                  * Get user address base and length for this iovec.
1581                  */
1582                 error = get_user(base, &iov->iov_base);
1583                 if (unlikely(error))
1584                         break;
1585                 error = get_user(len, &iov->iov_len);
1586                 if (unlikely(error))
1587                         break;
1588
1589                 /*
1590                  * Sanity check this iovec. 0 read succeeds.
1591                  */
1592                 if (unlikely(!len))
1593                         break;
1594                 if (unlikely(!base)) {
1595                         error = -EFAULT;
1596                         break;
1597                 }
1598
1599                 if (unlikely(!access_ok(VERIFY_WRITE, base, len))) {
1600                         error = -EFAULT;
1601                         break;
1602                 }
1603
1604                 sd.len = 0;
1605                 sd.total_len = len;
1606                 sd.flags = flags;
1607                 sd.u.userptr = base;
1608                 sd.pos = 0;
1609
1610                 size = __splice_from_pipe(pipe, &sd, pipe_to_user);
1611                 if (size < 0) {
1612                         if (!ret)
1613                                 ret = size;
1614
1615                         break;
1616                 }
1617
1618                 ret += size;
1619
1620                 if (size < len)
1621                         break;
1622
1623                 nr_segs--;
1624                 iov++;
1625         }
1626
1627         pipe_unlock(pipe);
1628
1629         if (!ret)
1630                 ret = error;
1631
1632         return ret;
1633 }
1634
1635 /*
1636  * vmsplice splices a user address range into a pipe. It can be thought of
1637  * as splice-from-memory, where the regular splice is splice-from-file (or
1638  * to file). In both cases the output is a pipe, naturally.
1639  */
1640 static long vmsplice_to_pipe(struct file *file, const struct iovec __user *iov,
1641                              unsigned long nr_segs, unsigned int flags)
1642 {
1643         struct pipe_inode_info *pipe;
1644         struct page *pages[PIPE_DEF_BUFFERS];
1645         struct partial_page partial[PIPE_DEF_BUFFERS];
1646         struct splice_pipe_desc spd = {
1647                 .pages = pages,
1648                 .partial = partial,
1649                 .flags = flags,
1650                 .ops = &user_page_pipe_buf_ops,
1651                 .spd_release = spd_release_page,
1652         };
1653         long ret;
1654
1655         pipe = pipe_info(file->f_path.dentry->d_inode);
1656         if (!pipe)
1657                 return -EBADF;
1658
1659         if (splice_grow_spd(pipe, &spd))
1660                 return -ENOMEM;
1661
1662         spd.nr_pages = get_iovec_page_array(iov, nr_segs, spd.pages,
1663                                             spd.partial, flags & SPLICE_F_GIFT,
1664                                             pipe->buffers);
1665         if (spd.nr_pages <= 0)
1666                 ret = spd.nr_pages;
1667         else
1668                 ret = splice_to_pipe(pipe, &spd);
1669
1670         splice_shrink_spd(pipe, &spd);
1671         return ret;
1672 }
1673
1674 /*
1675  * Note that vmsplice only really supports true splicing _from_ user memory
1676  * to a pipe, not the other way around. Splicing from user memory is a simple
1677  * operation that can be supported without any funky alignment restrictions
1678  * or nasty vm tricks. We simply map in the user memory and fill them into
1679  * a pipe. The reverse isn't quite as easy, though. There are two possible
1680  * solutions for that:
1681  *
1682  *      - memcpy() the data internally, at which point we might as well just
1683  *        do a regular read() on the buffer anyway.
1684  *      - Lots of nasty vm tricks, that are neither fast nor flexible (it
1685  *        has restriction limitations on both ends of the pipe).
1686  *
1687  * Currently we punt and implement it as a normal copy, see pipe_to_user().
1688  *
1689  */
1690 SYSCALL_DEFINE4(vmsplice, int, fd, const struct iovec __user *, iov,
1691                 unsigned long, nr_segs, unsigned int, flags)
1692 {
1693         struct file *file;
1694         long error;
1695         int fput;
1696
1697         if (unlikely(nr_segs > UIO_MAXIOV))
1698                 return -EINVAL;
1699         else if (unlikely(!nr_segs))
1700                 return 0;
1701
1702         error = -EBADF;
1703         file = fget_light(fd, &fput);
1704         if (file) {
1705                 if (file->f_mode & FMODE_WRITE)
1706                         error = vmsplice_to_pipe(file, iov, nr_segs, flags);
1707                 else if (file->f_mode & FMODE_READ)
1708                         error = vmsplice_to_user(file, iov, nr_segs, flags);
1709
1710                 fput_light(file, fput);
1711         }
1712
1713         return error;
1714 }
1715
1716 SYSCALL_DEFINE6(splice, int, fd_in, loff_t __user *, off_in,
1717                 int, fd_out, loff_t __user *, off_out,
1718                 size_t, len, unsigned int, flags)
1719 {
1720         long error;
1721         struct file *in, *out;
1722         int fput_in, fput_out;
1723
1724         if (unlikely(!len))
1725                 return 0;
1726
1727         error = -EBADF;
1728         in = fget_light(fd_in, &fput_in);
1729         if (in) {
1730                 if (in->f_mode & FMODE_READ) {
1731                         out = fget_light(fd_out, &fput_out);
1732                         if (out) {
1733                                 if (out->f_mode & FMODE_WRITE)
1734                                         error = do_splice(in, off_in,
1735                                                           out, off_out,
1736                                                           len, flags);
1737                                 fput_light(out, fput_out);
1738                         }
1739                 }
1740
1741                 fput_light(in, fput_in);
1742         }
1743
1744         return error;
1745 }
1746
1747 /*
1748  * Make sure there's data to read. Wait for input if we can, otherwise
1749  * return an appropriate error.
1750  */
1751 static int ipipe_prep(struct pipe_inode_info *pipe, unsigned int flags)
1752 {
1753         int ret;
1754
1755         /*
1756          * Check ->nrbufs without the inode lock first. This function
1757          * is speculative anyways, so missing one is ok.
1758          */
1759         if (pipe->nrbufs)
1760                 return 0;
1761
1762         ret = 0;
1763         pipe_lock(pipe);
1764
1765         while (!pipe->nrbufs) {
1766                 if (signal_pending(current)) {
1767                         ret = -ERESTARTSYS;
1768                         break;
1769                 }
1770                 if (!pipe->writers)
1771                         break;
1772                 if (!pipe->waiting_writers) {
1773                         if (flags & SPLICE_F_NONBLOCK) {
1774                                 ret = -EAGAIN;
1775                                 break;
1776                         }
1777                 }
1778                 pipe_wait(pipe);
1779         }
1780
1781         pipe_unlock(pipe);
1782         return ret;
1783 }
1784
1785 /*
1786  * Make sure there's writeable room. Wait for room if we can, otherwise
1787  * return an appropriate error.
1788  */
1789 static int opipe_prep(struct pipe_inode_info *pipe, unsigned int flags)
1790 {
1791         int ret;
1792
1793         /*
1794          * Check ->nrbufs without the inode lock first. This function
1795          * is speculative anyways, so missing one is ok.
1796          */
1797         if (pipe->nrbufs < pipe->buffers)
1798                 return 0;
1799
1800         ret = 0;
1801         pipe_lock(pipe);
1802
1803         while (pipe->nrbufs >= pipe->buffers) {
1804                 if (!pipe->readers) {
1805                         send_sig(SIGPIPE, current, 0);
1806                         ret = -EPIPE;
1807                         break;
1808                 }
1809                 if (flags & SPLICE_F_NONBLOCK) {
1810                         ret = -EAGAIN;
1811                         break;
1812                 }
1813                 if (signal_pending(current)) {
1814                         ret = -ERESTARTSYS;
1815                         break;
1816                 }
1817                 pipe->waiting_writers++;
1818                 pipe_wait(pipe);
1819                 pipe->waiting_writers--;
1820         }
1821
1822         pipe_unlock(pipe);
1823         return ret;
1824 }
1825
1826 /*
1827  * Splice contents of ipipe to opipe.
1828  */
1829 static int splice_pipe_to_pipe(struct pipe_inode_info *ipipe,
1830                                struct pipe_inode_info *opipe,
1831                                size_t len, unsigned int flags)
1832 {
1833         struct pipe_buffer *ibuf, *obuf;
1834         int ret = 0, nbuf;
1835         bool input_wakeup = false;
1836
1837
1838 retry:
1839         ret = ipipe_prep(ipipe, flags);
1840         if (ret)
1841                 return ret;
1842
1843         ret = opipe_prep(opipe, flags);
1844         if (ret)
1845                 return ret;
1846
1847         /*
1848          * Potential ABBA deadlock, work around it by ordering lock
1849          * grabbing by pipe info address. Otherwise two different processes
1850          * could deadlock (one doing tee from A -> B, the other from B -> A).
1851          */
1852         pipe_double_lock(ipipe, opipe);
1853
1854         do {
1855                 if (!opipe->readers) {
1856                         send_sig(SIGPIPE, current, 0);
1857                         if (!ret)
1858                                 ret = -EPIPE;
1859                         break;
1860                 }
1861
1862                 if (!ipipe->nrbufs && !ipipe->writers)
1863                         break;
1864
1865                 /*
1866                  * Cannot make any progress, because either the input
1867                  * pipe is empty or the output pipe is full.
1868                  */
1869                 if (!ipipe->nrbufs || opipe->nrbufs >= opipe->buffers) {
1870                         /* Already processed some buffers, break */
1871                         if (ret)
1872                                 break;
1873
1874                         if (flags & SPLICE_F_NONBLOCK) {
1875                                 ret = -EAGAIN;
1876                                 break;
1877                         }
1878
1879                         /*
1880                          * We raced with another reader/writer and haven't
1881                          * managed to process any buffers.  A zero return
1882                          * value means EOF, so retry instead.
1883                          */
1884                         pipe_unlock(ipipe);
1885                         pipe_unlock(opipe);
1886                         goto retry;
1887                 }
1888
1889                 ibuf = ipipe->bufs + ipipe->curbuf;
1890                 nbuf = (opipe->curbuf + opipe->nrbufs) & (opipe->buffers - 1);
1891                 obuf = opipe->bufs + nbuf;
1892
1893                 if (len >= ibuf->len) {
1894                         /*
1895                          * Simply move the whole buffer from ipipe to opipe
1896                          */
1897                         *obuf = *ibuf;
1898                         ibuf->ops = NULL;
1899                         opipe->nrbufs++;
1900                         ipipe->curbuf = (ipipe->curbuf + 1) & (ipipe->buffers - 1);
1901                         ipipe->nrbufs--;
1902                         input_wakeup = true;
1903                 } else {
1904                         /*
1905                          * Get a reference to this pipe buffer,
1906                          * so we can copy the contents over.
1907                          */
1908                         ibuf->ops->get(ipipe, ibuf);
1909                         *obuf = *ibuf;
1910
1911                         /*
1912                          * Don't inherit the gift flag, we need to
1913                          * prevent multiple steals of this page.
1914                          */
1915                         obuf->flags &= ~PIPE_BUF_FLAG_GIFT;
1916
1917                         obuf->len = len;
1918                         opipe->nrbufs++;
1919                         ibuf->offset += obuf->len;
1920                         ibuf->len -= obuf->len;
1921                 }
1922                 ret += obuf->len;
1923                 len -= obuf->len;
1924         } while (len);
1925
1926         pipe_unlock(ipipe);
1927         pipe_unlock(opipe);
1928
1929         /*
1930          * If we put data in the output pipe, wakeup any potential readers.
1931          */
1932         if (ret > 0) {
1933                 smp_mb();
1934                 if (waitqueue_active(&opipe->wait))
1935                         wake_up_interruptible(&opipe->wait);
1936                 kill_fasync(&opipe->fasync_readers, SIGIO, POLL_IN);
1937         }
1938         if (input_wakeup)
1939                 wakeup_pipe_writers(ipipe);
1940
1941         return ret;
1942 }
1943
1944 /*
1945  * Link contents of ipipe to opipe.
1946  */
1947 static int link_pipe(struct pipe_inode_info *ipipe,
1948                      struct pipe_inode_info *opipe,
1949                      size_t len, unsigned int flags)
1950 {
1951         struct pipe_buffer *ibuf, *obuf;
1952         int ret = 0, i = 0, nbuf;
1953
1954         /*
1955          * Potential ABBA deadlock, work around it by ordering lock
1956          * grabbing by pipe info address. Otherwise two different processes
1957          * could deadlock (one doing tee from A -> B, the other from B -> A).
1958          */
1959         pipe_double_lock(ipipe, opipe);
1960
1961         do {
1962                 if (!opipe->readers) {
1963                         send_sig(SIGPIPE, current, 0);
1964                         if (!ret)
1965                                 ret = -EPIPE;
1966                         break;
1967                 }
1968
1969                 /*
1970                  * If we have iterated all input buffers or ran out of
1971                  * output room, break.
1972                  */
1973                 if (i >= ipipe->nrbufs || opipe->nrbufs >= opipe->buffers)
1974                         break;
1975
1976                 ibuf = ipipe->bufs + ((ipipe->curbuf + i) & (ipipe->buffers-1));
1977                 nbuf = (opipe->curbuf + opipe->nrbufs) & (opipe->buffers - 1);
1978
1979                 /*
1980                  * Get a reference to this pipe buffer,
1981                  * so we can copy the contents over.
1982                  */
1983                 ibuf->ops->get(ipipe, ibuf);
1984
1985                 obuf = opipe->bufs + nbuf;
1986                 *obuf = *ibuf;
1987
1988                 /*
1989                  * Don't inherit the gift flag, we need to
1990                  * prevent multiple steals of this page.
1991                  */
1992                 obuf->flags &= ~PIPE_BUF_FLAG_GIFT;
1993
1994                 if (obuf->len > len)
1995                         obuf->len = len;
1996
1997                 opipe->nrbufs++;
1998                 ret += obuf->len;
1999                 len -= obuf->len;
2000                 i++;
2001         } while (len);
2002
2003         /*
2004          * return EAGAIN if we have the potential of some data in the
2005          * future, otherwise just return 0
2006          */
2007         if (!ret && ipipe->waiting_writers && (flags & SPLICE_F_NONBLOCK))
2008                 ret = -EAGAIN;
2009
2010         pipe_unlock(ipipe);
2011         pipe_unlock(opipe);
2012
2013         /*
2014          * If we put data in the output pipe, wakeup any potential readers.
2015          */
2016         if (ret > 0) {
2017                 smp_mb();
2018                 if (waitqueue_active(&opipe->wait))
2019                         wake_up_interruptible(&opipe->wait);
2020                 kill_fasync(&opipe->fasync_readers, SIGIO, POLL_IN);
2021         }
2022
2023         return ret;
2024 }
2025
2026 /*
2027  * This is a tee(1) implementation that works on pipes. It doesn't copy
2028  * any data, it simply references the 'in' pages on the 'out' pipe.
2029  * The 'flags' used are the SPLICE_F_* variants, currently the only
2030  * applicable one is SPLICE_F_NONBLOCK.
2031  */
2032 static long do_tee(struct file *in, struct file *out, size_t len,
2033                    unsigned int flags)
2034 {
2035         struct pipe_inode_info *ipipe = pipe_info(in->f_path.dentry->d_inode);
2036         struct pipe_inode_info *opipe = pipe_info(out->f_path.dentry->d_inode);
2037         int ret = -EINVAL;
2038
2039         /*
2040          * Duplicate the contents of ipipe to opipe without actually
2041          * copying the data.
2042          */
2043         if (ipipe && opipe && ipipe != opipe) {
2044                 /*
2045                  * Keep going, unless we encounter an error. The ipipe/opipe
2046                  * ordering doesn't really matter.
2047                  */
2048                 ret = ipipe_prep(ipipe, flags);
2049                 if (!ret) {
2050                         ret = opipe_prep(opipe, flags);
2051                         if (!ret)
2052                                 ret = link_pipe(ipipe, opipe, len, flags);
2053                 }
2054         }
2055
2056         return ret;
2057 }
2058
2059 SYSCALL_DEFINE4(tee, int, fdin, int, fdout, size_t, len, unsigned int, flags)
2060 {
2061         struct file *in;
2062         int error, fput_in;
2063
2064         if (unlikely(!len))
2065                 return 0;
2066
2067         error = -EBADF;
2068         in = fget_light(fdin, &fput_in);
2069         if (in) {
2070                 if (in->f_mode & FMODE_READ) {
2071                         int fput_out;
2072                         struct file *out = fget_light(fdout, &fput_out);
2073
2074                         if (out) {
2075                                 if (out->f_mode & FMODE_WRITE)
2076                                         error = do_tee(in, out, len, flags);
2077                                 fput_light(out, fput_out);
2078                         }
2079                 }
2080                 fput_light(in, fput_in);
2081         }
2082
2083         return error;
2084 }