ARM: tegra11: clock: Update EMC clock mux
[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/export.h>
29 #include <linux/syscalls.h>
30 #include <linux/uio.h>
31 #include <linux/security.h>
32 #include <linux/gfp.h>
33 #include <linux/socket.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 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 static void wakeup_pipe_readers(struct pipe_inode_info *pipe)
166 {
167         smp_mb();
168         if (waitqueue_active(&pipe->wait))
169                 wake_up_interruptible(&pipe->wait);
170         kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
171 }
172
173 /**
174  * splice_to_pipe - fill passed data into a pipe
175  * @pipe:       pipe to fill
176  * @spd:        data to fill
177  *
178  * Description:
179  *    @spd contains a map of pages and len/offset tuples, along with
180  *    the struct pipe_buf_operations associated with these pages. This
181  *    function will link that data to the pipe.
182  *
183  */
184 ssize_t splice_to_pipe(struct pipe_inode_info *pipe,
185                        struct splice_pipe_desc *spd)
186 {
187         unsigned int spd_pages = spd->nr_pages;
188         int ret, do_wakeup, page_nr;
189
190         ret = 0;
191         do_wakeup = 0;
192         page_nr = 0;
193
194         pipe_lock(pipe);
195
196         for (;;) {
197                 if (!pipe->readers) {
198                         send_sig(SIGPIPE, current, 0);
199                         if (!ret)
200                                 ret = -EPIPE;
201                         break;
202                 }
203
204                 if (pipe->nrbufs < pipe->buffers) {
205                         int newbuf = (pipe->curbuf + pipe->nrbufs) & (pipe->buffers - 1);
206                         struct pipe_buffer *buf = pipe->bufs + newbuf;
207
208                         buf->page = spd->pages[page_nr];
209                         buf->offset = spd->partial[page_nr].offset;
210                         buf->len = spd->partial[page_nr].len;
211                         buf->private = spd->partial[page_nr].private;
212                         buf->ops = spd->ops;
213                         if (spd->flags & SPLICE_F_GIFT)
214                                 buf->flags |= PIPE_BUF_FLAG_GIFT;
215
216                         pipe->nrbufs++;
217                         page_nr++;
218                         ret += buf->len;
219
220                         if (pipe->inode)
221                                 do_wakeup = 1;
222
223                         if (!--spd->nr_pages)
224                                 break;
225                         if (pipe->nrbufs < pipe->buffers)
226                                 continue;
227
228                         break;
229                 }
230
231                 if (spd->flags & SPLICE_F_NONBLOCK) {
232                         if (!ret)
233                                 ret = -EAGAIN;
234                         break;
235                 }
236
237                 if (signal_pending(current)) {
238                         if (!ret)
239                                 ret = -ERESTARTSYS;
240                         break;
241                 }
242
243                 if (do_wakeup) {
244                         smp_mb();
245                         if (waitqueue_active(&pipe->wait))
246                                 wake_up_interruptible_sync(&pipe->wait);
247                         kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
248                         do_wakeup = 0;
249                 }
250
251                 pipe->waiting_writers++;
252                 pipe_wait(pipe);
253                 pipe->waiting_writers--;
254         }
255
256         pipe_unlock(pipe);
257
258         if (do_wakeup)
259                 wakeup_pipe_readers(pipe);
260
261         while (page_nr < spd_pages)
262                 spd->spd_release(spd, page_nr++);
263
264         return ret;
265 }
266
267 void spd_release_page(struct splice_pipe_desc *spd, unsigned int i)
268 {
269         page_cache_release(spd->pages[i]);
270 }
271
272 /*
273  * Check if we need to grow the arrays holding pages and partial page
274  * descriptions.
275  */
276 int splice_grow_spd(const struct pipe_inode_info *pipe, struct splice_pipe_desc *spd)
277 {
278         unsigned int buffers = ACCESS_ONCE(pipe->buffers);
279
280         spd->nr_pages_max = buffers;
281         if (buffers <= PIPE_DEF_BUFFERS)
282                 return 0;
283
284         spd->pages = kmalloc(buffers * sizeof(struct page *), GFP_KERNEL);
285         spd->partial = kmalloc(buffers * sizeof(struct partial_page), GFP_KERNEL);
286
287         if (spd->pages && spd->partial)
288                 return 0;
289
290         kfree(spd->pages);
291         kfree(spd->partial);
292         return -ENOMEM;
293 }
294
295 void splice_shrink_spd(struct splice_pipe_desc *spd)
296 {
297         if (spd->nr_pages_max <= PIPE_DEF_BUFFERS)
298                 return;
299
300         kfree(spd->pages);
301         kfree(spd->partial);
302 }
303
304 static int
305 __generic_file_splice_read(struct file *in, loff_t *ppos,
306                            struct pipe_inode_info *pipe, size_t len,
307                            unsigned int flags)
308 {
309         struct address_space *mapping = in->f_mapping;
310         unsigned int loff, nr_pages, req_pages;
311         struct page *pages[PIPE_DEF_BUFFERS];
312         struct partial_page partial[PIPE_DEF_BUFFERS];
313         struct page *page;
314         pgoff_t index, end_index;
315         loff_t isize;
316         int error, page_nr;
317         struct splice_pipe_desc spd = {
318                 .pages = pages,
319                 .partial = partial,
320                 .nr_pages_max = PIPE_DEF_BUFFERS,
321                 .flags = flags,
322                 .ops = &page_cache_pipe_buf_ops,
323                 .spd_release = spd_release_page,
324         };
325
326         if (splice_grow_spd(pipe, &spd))
327                 return -ENOMEM;
328
329         index = *ppos >> PAGE_CACHE_SHIFT;
330         loff = *ppos & ~PAGE_CACHE_MASK;
331         req_pages = (len + loff + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
332         nr_pages = min(req_pages, spd.nr_pages_max);
333
334         /*
335          * Lookup the (hopefully) full range of pages we need.
336          */
337         spd.nr_pages = find_get_pages_contig(mapping, index, nr_pages, spd.pages);
338         index += spd.nr_pages;
339
340         /*
341          * If find_get_pages_contig() returned fewer pages than we needed,
342          * readahead/allocate the rest and fill in the holes.
343          */
344         if (spd.nr_pages < nr_pages)
345                 page_cache_sync_readahead(mapping, &in->f_ra, in,
346                                 index, req_pages - spd.nr_pages);
347
348         error = 0;
349         while (spd.nr_pages < nr_pages) {
350                 /*
351                  * Page could be there, find_get_pages_contig() breaks on
352                  * the first hole.
353                  */
354                 page = find_get_page(mapping, index);
355                 if (!page) {
356                         /*
357                          * page didn't exist, allocate one.
358                          */
359                         page = page_cache_alloc_cold(mapping);
360                         if (!page)
361                                 break;
362
363                         error = add_to_page_cache_lru(page, mapping, index,
364                                                 GFP_KERNEL);
365                         if (unlikely(error)) {
366                                 page_cache_release(page);
367                                 if (error == -EEXIST)
368                                         continue;
369                                 break;
370                         }
371                         /*
372                          * add_to_page_cache() locks the page, unlock it
373                          * to avoid convoluting the logic below even more.
374                          */
375                         unlock_page(page);
376                 }
377
378                 spd.pages[spd.nr_pages++] = page;
379                 index++;
380         }
381
382         /*
383          * Now loop over the map and see if we need to start IO on any
384          * pages, fill in the partial map, etc.
385          */
386         index = *ppos >> PAGE_CACHE_SHIFT;
387         nr_pages = spd.nr_pages;
388         spd.nr_pages = 0;
389         for (page_nr = 0; page_nr < nr_pages; page_nr++) {
390                 unsigned int this_len;
391
392                 if (!len)
393                         break;
394
395                 /*
396                  * this_len is the max we'll use from this page
397                  */
398                 this_len = min_t(unsigned long, len, PAGE_CACHE_SIZE - loff);
399                 page = spd.pages[page_nr];
400
401                 if (PageReadahead(page))
402                         page_cache_async_readahead(mapping, &in->f_ra, in,
403                                         page, index, req_pages - page_nr);
404
405                 /*
406                  * If the page isn't uptodate, we may need to start io on it
407                  */
408                 if (!PageUptodate(page)) {
409                         lock_page(page);
410
411                         /*
412                          * Page was truncated, or invalidated by the
413                          * filesystem.  Redo the find/create, but this time the
414                          * page is kept locked, so there's no chance of another
415                          * race with truncate/invalidate.
416                          */
417                         if (!page->mapping) {
418                                 unlock_page(page);
419                                 page = find_or_create_page(mapping, index,
420                                                 mapping_gfp_mask(mapping));
421
422                                 if (!page) {
423                                         error = -ENOMEM;
424                                         break;
425                                 }
426                                 page_cache_release(spd.pages[page_nr]);
427                                 spd.pages[page_nr] = page;
428                         }
429                         /*
430                          * page was already under io and is now done, great
431                          */
432                         if (PageUptodate(page)) {
433                                 unlock_page(page);
434                                 goto fill_it;
435                         }
436
437                         /*
438                          * need to read in the page
439                          */
440                         error = mapping->a_ops->readpage(in, page);
441                         if (unlikely(error)) {
442                                 /*
443                                  * We really should re-lookup the page here,
444                                  * but it complicates things a lot. Instead
445                                  * lets just do what we already stored, and
446                                  * we'll get it the next time we are called.
447                                  */
448                                 if (error == AOP_TRUNCATED_PAGE)
449                                         error = 0;
450
451                                 break;
452                         }
453                 }
454 fill_it:
455                 /*
456                  * i_size must be checked after PageUptodate.
457                  */
458                 isize = i_size_read(mapping->host);
459                 end_index = (isize - 1) >> PAGE_CACHE_SHIFT;
460                 if (unlikely(!isize || index > end_index))
461                         break;
462
463                 /*
464                  * if this is the last page, see if we need to shrink
465                  * the length and stop
466                  */
467                 if (end_index == index) {
468                         unsigned int plen;
469
470                         /*
471                          * max good bytes in this page
472                          */
473                         plen = ((isize - 1) & ~PAGE_CACHE_MASK) + 1;
474                         if (plen <= loff)
475                                 break;
476
477                         /*
478                          * force quit after adding this page
479                          */
480                         this_len = min(this_len, plen - loff);
481                         len = this_len;
482                 }
483
484                 spd.partial[page_nr].offset = loff;
485                 spd.partial[page_nr].len = this_len;
486                 len -= this_len;
487                 loff = 0;
488                 spd.nr_pages++;
489                 index++;
490         }
491
492         /*
493          * Release any pages at the end, if we quit early. 'page_nr' is how far
494          * we got, 'nr_pages' is how many pages are in the map.
495          */
496         while (page_nr < nr_pages)
497                 page_cache_release(spd.pages[page_nr++]);
498         in->f_ra.prev_pos = (loff_t)index << PAGE_CACHE_SHIFT;
499
500         if (spd.nr_pages)
501                 error = splice_to_pipe(pipe, &spd);
502
503         splice_shrink_spd(&spd);
504         return error;
505 }
506
507 /**
508  * generic_file_splice_read - splice data from file to a pipe
509  * @in:         file to splice from
510  * @ppos:       position in @in
511  * @pipe:       pipe to splice to
512  * @len:        number of bytes to splice
513  * @flags:      splice modifier flags
514  *
515  * Description:
516  *    Will read pages from given file and fill them into a pipe. Can be
517  *    used as long as the address_space operations for the source implements
518  *    a readpage() hook.
519  *
520  */
521 ssize_t generic_file_splice_read(struct file *in, loff_t *ppos,
522                                  struct pipe_inode_info *pipe, size_t len,
523                                  unsigned int flags)
524 {
525         loff_t isize, left;
526         int ret;
527
528         isize = i_size_read(in->f_mapping->host);
529         if (unlikely(*ppos >= isize))
530                 return 0;
531
532         left = isize - *ppos;
533         if (unlikely(left < len))
534                 len = left;
535
536         ret = __generic_file_splice_read(in, ppos, pipe, len, flags);
537         if (ret > 0) {
538                 *ppos += ret;
539                 file_accessed(in);
540         }
541
542         return ret;
543 }
544 EXPORT_SYMBOL(generic_file_splice_read);
545
546 static const struct pipe_buf_operations default_pipe_buf_ops = {
547         .can_merge = 0,
548         .map = generic_pipe_buf_map,
549         .unmap = generic_pipe_buf_unmap,
550         .confirm = generic_pipe_buf_confirm,
551         .release = generic_pipe_buf_release,
552         .steal = generic_pipe_buf_steal,
553         .get = generic_pipe_buf_get,
554 };
555
556 static ssize_t kernel_readv(struct file *file, const struct iovec *vec,
557                             unsigned long vlen, loff_t offset)
558 {
559         mm_segment_t old_fs;
560         loff_t pos = offset;
561         ssize_t res;
562
563         old_fs = get_fs();
564         set_fs(get_ds());
565         /* The cast to a user pointer is valid due to the set_fs() */
566         res = vfs_readv(file, (const struct iovec __user *)vec, vlen, &pos);
567         set_fs(old_fs);
568
569         return res;
570 }
571
572 static ssize_t kernel_write(struct file *file, const char *buf, size_t count,
573                             loff_t pos)
574 {
575         mm_segment_t old_fs;
576         ssize_t res;
577
578         old_fs = get_fs();
579         set_fs(get_ds());
580         /* The cast to a user pointer is valid due to the set_fs() */
581         res = vfs_write(file, (const char __user *)buf, count, &pos);
582         set_fs(old_fs);
583
584         return res;
585 }
586
587 ssize_t default_file_splice_read(struct file *in, loff_t *ppos,
588                                  struct pipe_inode_info *pipe, size_t len,
589                                  unsigned int flags)
590 {
591         unsigned int nr_pages;
592         unsigned int nr_freed;
593         size_t offset;
594         struct page *pages[PIPE_DEF_BUFFERS];
595         struct partial_page partial[PIPE_DEF_BUFFERS];
596         struct iovec *vec, __vec[PIPE_DEF_BUFFERS];
597         ssize_t res;
598         size_t this_len;
599         int error;
600         int i;
601         struct splice_pipe_desc spd = {
602                 .pages = pages,
603                 .partial = partial,
604                 .nr_pages_max = PIPE_DEF_BUFFERS,
605                 .flags = flags,
606                 .ops = &default_pipe_buf_ops,
607                 .spd_release = spd_release_page,
608         };
609
610         if (splice_grow_spd(pipe, &spd))
611                 return -ENOMEM;
612
613         res = -ENOMEM;
614         vec = __vec;
615         if (spd.nr_pages_max > PIPE_DEF_BUFFERS) {
616                 vec = kmalloc(spd.nr_pages_max * sizeof(struct iovec), GFP_KERNEL);
617                 if (!vec)
618                         goto shrink_ret;
619         }
620
621         offset = *ppos & ~PAGE_CACHE_MASK;
622         nr_pages = (len + offset + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
623
624         for (i = 0; i < nr_pages && i < spd.nr_pages_max && len; i++) {
625                 struct page *page;
626
627                 page = alloc_page(GFP_USER);
628                 error = -ENOMEM;
629                 if (!page)
630                         goto err;
631
632                 this_len = min_t(size_t, len, PAGE_CACHE_SIZE - offset);
633                 vec[i].iov_base = (void __user *) page_address(page);
634                 vec[i].iov_len = this_len;
635                 spd.pages[i] = page;
636                 spd.nr_pages++;
637                 len -= this_len;
638                 offset = 0;
639         }
640
641         res = kernel_readv(in, vec, spd.nr_pages, *ppos);
642         if (res < 0) {
643                 error = res;
644                 goto err;
645         }
646
647         error = 0;
648         if (!res)
649                 goto err;
650
651         nr_freed = 0;
652         for (i = 0; i < spd.nr_pages; i++) {
653                 this_len = min_t(size_t, vec[i].iov_len, res);
654                 spd.partial[i].offset = 0;
655                 spd.partial[i].len = this_len;
656                 if (!this_len) {
657                         __free_page(spd.pages[i]);
658                         spd.pages[i] = NULL;
659                         nr_freed++;
660                 }
661                 res -= this_len;
662         }
663         spd.nr_pages -= nr_freed;
664
665         res = splice_to_pipe(pipe, &spd);
666         if (res > 0)
667                 *ppos += res;
668
669 shrink_ret:
670         if (vec != __vec)
671                 kfree(vec);
672         splice_shrink_spd(&spd);
673         return res;
674
675 err:
676         for (i = 0; i < spd.nr_pages; i++)
677                 __free_page(spd.pages[i]);
678
679         res = error;
680         goto shrink_ret;
681 }
682 EXPORT_SYMBOL(default_file_splice_read);
683
684 /*
685  * Send 'sd->len' bytes to socket from 'sd->file' at position 'sd->pos'
686  * using sendpage(). Return the number of bytes sent.
687  */
688 static int pipe_to_sendpage(struct pipe_inode_info *pipe,
689                             struct pipe_buffer *buf, struct splice_desc *sd)
690 {
691         struct file *file = sd->u.file;
692         loff_t pos = sd->pos;
693         int more;
694
695         if (!likely(file->f_op && file->f_op->sendpage))
696                 return -EINVAL;
697
698         more = (sd->flags & SPLICE_F_MORE) ? MSG_MORE : 0;
699         if (sd->len < sd->total_len)
700                 more |= MSG_SENDPAGE_NOTLAST;
701         return file->f_op->sendpage(file, buf->page, buf->offset,
702                                     sd->len, &pos, more);
703 }
704
705 /*
706  * This is a little more tricky than the file -> pipe splicing. There are
707  * basically three cases:
708  *
709  *      - Destination page already exists in the address space and there
710  *        are users of it. For that case we have no other option that
711  *        copying the data. Tough luck.
712  *      - Destination page already exists in the address space, but there
713  *        are no users of it. Make sure it's uptodate, then drop it. Fall
714  *        through to last case.
715  *      - Destination page does not exist, we can add the pipe page to
716  *        the page cache and avoid the copy.
717  *
718  * If asked to move pages to the output file (SPLICE_F_MOVE is set in
719  * sd->flags), we attempt to migrate pages from the pipe to the output
720  * file address space page cache. This is possible if no one else has
721  * the pipe page referenced outside of the pipe and page cache. If
722  * SPLICE_F_MOVE isn't set, or we cannot move the page, we simply create
723  * a new page in the output file page cache and fill/dirty that.
724  */
725 int pipe_to_file(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
726                  struct splice_desc *sd)
727 {
728         struct file *file = sd->u.file;
729         struct address_space *mapping = file->f_mapping;
730         unsigned int offset, this_len;
731         struct page *page;
732         void *fsdata;
733         int ret;
734
735         offset = sd->pos & ~PAGE_CACHE_MASK;
736
737         this_len = sd->len;
738         if (this_len + offset > PAGE_CACHE_SIZE)
739                 this_len = PAGE_CACHE_SIZE - offset;
740
741         ret = pagecache_write_begin(file, mapping, sd->pos, this_len,
742                                 AOP_FLAG_UNINTERRUPTIBLE, &page, &fsdata);
743         if (unlikely(ret))
744                 goto out;
745
746         if (buf->page != page) {
747                 char *src = buf->ops->map(pipe, buf, 1);
748                 char *dst = kmap_atomic(page);
749
750                 memcpy(dst + offset, src + buf->offset, this_len);
751                 flush_dcache_page(page);
752                 kunmap_atomic(dst);
753                 buf->ops->unmap(pipe, buf, src);
754         }
755         ret = pagecache_write_end(file, mapping, sd->pos, this_len, this_len,
756                                 page, fsdata);
757 out:
758         return ret;
759 }
760 EXPORT_SYMBOL(pipe_to_file);
761
762 static void wakeup_pipe_writers(struct pipe_inode_info *pipe)
763 {
764         smp_mb();
765         if (waitqueue_active(&pipe->wait))
766                 wake_up_interruptible(&pipe->wait);
767         kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
768 }
769
770 /**
771  * splice_from_pipe_feed - feed available data from a pipe to a file
772  * @pipe:       pipe to splice from
773  * @sd:         information to @actor
774  * @actor:      handler that splices the data
775  *
776  * Description:
777  *    This function loops over the pipe and calls @actor to do the
778  *    actual moving of a single struct pipe_buffer to the desired
779  *    destination.  It returns when there's no more buffers left in
780  *    the pipe or if the requested number of bytes (@sd->total_len)
781  *    have been copied.  It returns a positive number (one) if the
782  *    pipe needs to be filled with more data, zero if the required
783  *    number of bytes have been copied and -errno on error.
784  *
785  *    This, together with splice_from_pipe_{begin,end,next}, may be
786  *    used to implement the functionality of __splice_from_pipe() when
787  *    locking is required around copying the pipe buffers to the
788  *    destination.
789  */
790 int splice_from_pipe_feed(struct pipe_inode_info *pipe, struct splice_desc *sd,
791                           splice_actor *actor)
792 {
793         int ret;
794
795         while (pipe->nrbufs) {
796                 struct pipe_buffer *buf = pipe->bufs + pipe->curbuf;
797                 const struct pipe_buf_operations *ops = buf->ops;
798
799                 sd->len = buf->len;
800                 if (sd->len > sd->total_len)
801                         sd->len = sd->total_len;
802
803                 ret = buf->ops->confirm(pipe, buf);
804                 if (unlikely(ret)) {
805                         if (ret == -ENODATA)
806                                 ret = 0;
807                         return ret;
808                 }
809
810                 ret = actor(pipe, buf, sd);
811                 if (ret <= 0)
812                         return ret;
813
814                 buf->offset += ret;
815                 buf->len -= ret;
816
817                 sd->num_spliced += ret;
818                 sd->len -= ret;
819                 sd->pos += ret;
820                 sd->total_len -= ret;
821
822                 if (!buf->len) {
823                         buf->ops = NULL;
824                         ops->release(pipe, buf);
825                         pipe->curbuf = (pipe->curbuf + 1) & (pipe->buffers - 1);
826                         pipe->nrbufs--;
827                         if (pipe->inode)
828                                 sd->need_wakeup = true;
829                 }
830
831                 if (!sd->total_len)
832                         return 0;
833         }
834
835         return 1;
836 }
837 EXPORT_SYMBOL(splice_from_pipe_feed);
838
839 /**
840  * splice_from_pipe_next - wait for some data to splice from
841  * @pipe:       pipe to splice from
842  * @sd:         information about the splice operation
843  *
844  * Description:
845  *    This function will wait for some data and return a positive
846  *    value (one) if pipe buffers are available.  It will return zero
847  *    or -errno if no more data needs to be spliced.
848  */
849 int splice_from_pipe_next(struct pipe_inode_info *pipe, struct splice_desc *sd)
850 {
851         while (!pipe->nrbufs) {
852                 if (!pipe->writers)
853                         return 0;
854
855                 if (!pipe->waiting_writers && sd->num_spliced)
856                         return 0;
857
858                 if (sd->flags & SPLICE_F_NONBLOCK)
859                         return -EAGAIN;
860
861                 if (signal_pending(current))
862                         return -ERESTARTSYS;
863
864                 if (sd->need_wakeup) {
865                         wakeup_pipe_writers(pipe);
866                         sd->need_wakeup = false;
867                 }
868
869                 pipe_wait(pipe);
870         }
871
872         return 1;
873 }
874 EXPORT_SYMBOL(splice_from_pipe_next);
875
876 /**
877  * splice_from_pipe_begin - start splicing from pipe
878  * @sd:         information about the splice operation
879  *
880  * Description:
881  *    This function should be called before a loop containing
882  *    splice_from_pipe_next() and splice_from_pipe_feed() to
883  *    initialize the necessary fields of @sd.
884  */
885 void splice_from_pipe_begin(struct splice_desc *sd)
886 {
887         sd->num_spliced = 0;
888         sd->need_wakeup = false;
889 }
890 EXPORT_SYMBOL(splice_from_pipe_begin);
891
892 /**
893  * splice_from_pipe_end - finish splicing from pipe
894  * @pipe:       pipe to splice from
895  * @sd:         information about the splice operation
896  *
897  * Description:
898  *    This function will wake up pipe writers if necessary.  It should
899  *    be called after a loop containing splice_from_pipe_next() and
900  *    splice_from_pipe_feed().
901  */
902 void splice_from_pipe_end(struct pipe_inode_info *pipe, struct splice_desc *sd)
903 {
904         if (sd->need_wakeup)
905                 wakeup_pipe_writers(pipe);
906 }
907 EXPORT_SYMBOL(splice_from_pipe_end);
908
909 /**
910  * __splice_from_pipe - splice data from a pipe to given actor
911  * @pipe:       pipe to splice from
912  * @sd:         information to @actor
913  * @actor:      handler that splices the data
914  *
915  * Description:
916  *    This function does little more than loop over the pipe and call
917  *    @actor to do the actual moving of a single struct pipe_buffer to
918  *    the desired destination. See pipe_to_file, pipe_to_sendpage, or
919  *    pipe_to_user.
920  *
921  */
922 ssize_t __splice_from_pipe(struct pipe_inode_info *pipe, struct splice_desc *sd,
923                            splice_actor *actor)
924 {
925         int ret;
926
927         splice_from_pipe_begin(sd);
928         do {
929                 ret = splice_from_pipe_next(pipe, sd);
930                 if (ret > 0)
931                         ret = splice_from_pipe_feed(pipe, sd, actor);
932         } while (ret > 0);
933         splice_from_pipe_end(pipe, sd);
934
935         return sd->num_spliced ? sd->num_spliced : ret;
936 }
937 EXPORT_SYMBOL(__splice_from_pipe);
938
939 /**
940  * splice_from_pipe - splice data from a pipe to a file
941  * @pipe:       pipe to splice from
942  * @out:        file to splice to
943  * @ppos:       position in @out
944  * @len:        how many bytes to splice
945  * @flags:      splice modifier flags
946  * @actor:      handler that splices the data
947  *
948  * Description:
949  *    See __splice_from_pipe. This function locks the pipe inode,
950  *    otherwise it's identical to __splice_from_pipe().
951  *
952  */
953 ssize_t splice_from_pipe(struct pipe_inode_info *pipe, struct file *out,
954                          loff_t *ppos, size_t len, unsigned int flags,
955                          splice_actor *actor)
956 {
957         ssize_t ret;
958         struct splice_desc sd = {
959                 .total_len = len,
960                 .flags = flags,
961                 .pos = *ppos,
962                 .u.file = out,
963         };
964
965         pipe_lock(pipe);
966         ret = __splice_from_pipe(pipe, &sd, actor);
967         pipe_unlock(pipe);
968
969         return ret;
970 }
971
972 /**
973  * generic_file_splice_write - splice data from a pipe to a file
974  * @pipe:       pipe info
975  * @out:        file to write to
976  * @ppos:       position in @out
977  * @len:        number of bytes to splice
978  * @flags:      splice modifier flags
979  *
980  * Description:
981  *    Will either move or copy pages (determined by @flags options) from
982  *    the given pipe inode to the given file.
983  *
984  */
985 ssize_t
986 generic_file_splice_write(struct pipe_inode_info *pipe, struct file *out,
987                           loff_t *ppos, size_t len, unsigned int flags)
988 {
989         struct address_space *mapping = out->f_mapping;
990         struct inode *inode = mapping->host;
991         struct splice_desc sd = {
992                 .total_len = len,
993                 .flags = flags,
994                 .pos = *ppos,
995                 .u.file = out,
996         };
997         ssize_t ret;
998
999         pipe_lock(pipe);
1000
1001         splice_from_pipe_begin(&sd);
1002         do {
1003                 ret = splice_from_pipe_next(pipe, &sd);
1004                 if (ret <= 0)
1005                         break;
1006
1007                 mutex_lock_nested(&inode->i_mutex, I_MUTEX_CHILD);
1008                 ret = file_remove_suid(out);
1009                 if (!ret) {
1010                         file_update_time(out);
1011                         ret = splice_from_pipe_feed(pipe, &sd, pipe_to_file);
1012                 }
1013                 mutex_unlock(&inode->i_mutex);
1014         } while (ret > 0);
1015         splice_from_pipe_end(pipe, &sd);
1016
1017         pipe_unlock(pipe);
1018
1019         if (sd.num_spliced)
1020                 ret = sd.num_spliced;
1021
1022         if (ret > 0) {
1023                 unsigned long nr_pages;
1024                 int err;
1025
1026                 nr_pages = (ret + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
1027
1028                 err = generic_write_sync(out, *ppos, ret);
1029                 if (err)
1030                         ret = err;
1031                 else
1032                         *ppos += ret;
1033                 balance_dirty_pages_ratelimited_nr(mapping, nr_pages);
1034         }
1035
1036         return ret;
1037 }
1038
1039 EXPORT_SYMBOL(generic_file_splice_write);
1040
1041 static int write_pipe_buf(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
1042                           struct splice_desc *sd)
1043 {
1044         int ret;
1045         void *data;
1046
1047         data = buf->ops->map(pipe, buf, 0);
1048         ret = kernel_write(sd->u.file, data + buf->offset, sd->len, sd->pos);
1049         buf->ops->unmap(pipe, buf, data);
1050
1051         return ret;
1052 }
1053
1054 static ssize_t default_file_splice_write(struct pipe_inode_info *pipe,
1055                                          struct file *out, loff_t *ppos,
1056                                          size_t len, unsigned int flags)
1057 {
1058         ssize_t ret;
1059
1060         ret = splice_from_pipe(pipe, out, ppos, len, flags, write_pipe_buf);
1061         if (ret > 0)
1062                 *ppos += ret;
1063
1064         return ret;
1065 }
1066
1067 /**
1068  * generic_splice_sendpage - splice data from a pipe to a socket
1069  * @pipe:       pipe to splice from
1070  * @out:        socket to write to
1071  * @ppos:       position in @out
1072  * @len:        number of bytes to splice
1073  * @flags:      splice modifier flags
1074  *
1075  * Description:
1076  *    Will send @len bytes from the pipe to a network socket. No data copying
1077  *    is involved.
1078  *
1079  */
1080 ssize_t generic_splice_sendpage(struct pipe_inode_info *pipe, struct file *out,
1081                                 loff_t *ppos, size_t len, unsigned int flags)
1082 {
1083         return splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_sendpage);
1084 }
1085
1086 EXPORT_SYMBOL(generic_splice_sendpage);
1087
1088 /*
1089  * Attempt to initiate a splice from pipe to file.
1090  */
1091 static long do_splice_from(struct pipe_inode_info *pipe, struct file *out,
1092                            loff_t *ppos, size_t len, unsigned int flags)
1093 {
1094         ssize_t (*splice_write)(struct pipe_inode_info *, struct file *,
1095                                 loff_t *, size_t, unsigned int);
1096         int ret;
1097
1098         if (unlikely(!(out->f_mode & FMODE_WRITE)))
1099                 return -EBADF;
1100
1101         if (unlikely(out->f_flags & O_APPEND))
1102                 return -EINVAL;
1103
1104         ret = rw_verify_area(WRITE, out, ppos, len);
1105         if (unlikely(ret < 0))
1106                 return ret;
1107
1108         if (out->f_op && out->f_op->splice_write)
1109                 splice_write = out->f_op->splice_write;
1110         else
1111                 splice_write = default_file_splice_write;
1112
1113         return splice_write(pipe, out, ppos, len, flags);
1114 }
1115
1116 /*
1117  * Attempt to initiate a splice from a file to a pipe.
1118  */
1119 static long do_splice_to(struct file *in, loff_t *ppos,
1120                          struct pipe_inode_info *pipe, size_t len,
1121                          unsigned int flags)
1122 {
1123         ssize_t (*splice_read)(struct file *, loff_t *,
1124                                struct pipe_inode_info *, size_t, unsigned int);
1125         int ret;
1126
1127         if (unlikely(!(in->f_mode & FMODE_READ)))
1128                 return -EBADF;
1129
1130         ret = rw_verify_area(READ, in, ppos, len);
1131         if (unlikely(ret < 0))
1132                 return ret;
1133
1134         if (in->f_op && in->f_op->splice_read)
1135                 splice_read = in->f_op->splice_read;
1136         else
1137                 splice_read = default_file_splice_read;
1138
1139         return splice_read(in, ppos, pipe, len, flags);
1140 }
1141
1142 /**
1143  * splice_direct_to_actor - splices data directly between two non-pipes
1144  * @in:         file to splice from
1145  * @sd:         actor information on where to splice to
1146  * @actor:      handles the data splicing
1147  *
1148  * Description:
1149  *    This is a special case helper to splice directly between two
1150  *    points, without requiring an explicit pipe. Internally an allocated
1151  *    pipe is cached in the process, and reused during the lifetime of
1152  *    that process.
1153  *
1154  */
1155 ssize_t splice_direct_to_actor(struct file *in, struct splice_desc *sd,
1156                                splice_direct_actor *actor)
1157 {
1158         struct pipe_inode_info *pipe;
1159         long ret, bytes;
1160         umode_t i_mode;
1161         size_t len;
1162         int i, flags;
1163
1164         /*
1165          * We require the input being a regular file, as we don't want to
1166          * randomly drop data for eg socket -> socket splicing. Use the
1167          * piped splicing for that!
1168          */
1169         i_mode = in->f_path.dentry->d_inode->i_mode;
1170         if (unlikely(!S_ISREG(i_mode) && !S_ISBLK(i_mode)))
1171                 return -EINVAL;
1172
1173         /*
1174          * neither in nor out is a pipe, setup an internal pipe attached to
1175          * 'out' and transfer the wanted data from 'in' to 'out' through that
1176          */
1177         pipe = current->splice_pipe;
1178         if (unlikely(!pipe)) {
1179                 pipe = alloc_pipe_info(NULL);
1180                 if (!pipe)
1181                         return -ENOMEM;
1182
1183                 /*
1184                  * We don't have an immediate reader, but we'll read the stuff
1185                  * out of the pipe right after the splice_to_pipe(). So set
1186                  * PIPE_READERS appropriately.
1187                  */
1188                 pipe->readers = 1;
1189
1190                 current->splice_pipe = pipe;
1191         }
1192
1193         /*
1194          * Do the splice.
1195          */
1196         ret = 0;
1197         bytes = 0;
1198         len = sd->total_len;
1199         flags = sd->flags;
1200
1201         /*
1202          * Don't block on output, we have to drain the direct pipe.
1203          */
1204         sd->flags &= ~SPLICE_F_NONBLOCK;
1205
1206         while (len) {
1207                 size_t read_len;
1208                 loff_t pos = sd->pos, prev_pos = pos;
1209
1210                 ret = do_splice_to(in, &pos, pipe, len, flags);
1211                 if (unlikely(ret <= 0))
1212                         goto out_release;
1213
1214                 read_len = ret;
1215                 sd->total_len = read_len;
1216
1217                 /*
1218                  * NOTE: nonblocking mode only applies to the input. We
1219                  * must not do the output in nonblocking mode as then we
1220                  * could get stuck data in the internal pipe:
1221                  */
1222                 ret = actor(pipe, sd);
1223                 if (unlikely(ret <= 0)) {
1224                         sd->pos = prev_pos;
1225                         goto out_release;
1226                 }
1227
1228                 bytes += ret;
1229                 len -= ret;
1230                 sd->pos = pos;
1231
1232                 if (ret < read_len) {
1233                         sd->pos = prev_pos + ret;
1234                         goto out_release;
1235                 }
1236         }
1237
1238 done:
1239         pipe->nrbufs = pipe->curbuf = 0;
1240         file_accessed(in);
1241         return bytes;
1242
1243 out_release:
1244         /*
1245          * If we did an incomplete transfer we must release
1246          * the pipe buffers in question:
1247          */
1248         for (i = 0; i < pipe->buffers; i++) {
1249                 struct pipe_buffer *buf = pipe->bufs + i;
1250
1251                 if (buf->ops) {
1252                         buf->ops->release(pipe, buf);
1253                         buf->ops = NULL;
1254                 }
1255         }
1256
1257         if (!bytes)
1258                 bytes = ret;
1259
1260         goto done;
1261 }
1262 EXPORT_SYMBOL(splice_direct_to_actor);
1263
1264 static int direct_splice_actor(struct pipe_inode_info *pipe,
1265                                struct splice_desc *sd)
1266 {
1267         struct file *file = sd->u.file;
1268
1269         return do_splice_from(pipe, file, &file->f_pos, sd->total_len,
1270                               sd->flags);
1271 }
1272
1273 /**
1274  * do_splice_direct - splices data directly between two files
1275  * @in:         file to splice from
1276  * @ppos:       input file offset
1277  * @out:        file to splice to
1278  * @len:        number of bytes to splice
1279  * @flags:      splice modifier flags
1280  *
1281  * Description:
1282  *    For use by do_sendfile(). splice can easily emulate sendfile, but
1283  *    doing it in the application would incur an extra system call
1284  *    (splice in + splice out, as compared to just sendfile()). So this helper
1285  *    can splice directly through a process-private pipe.
1286  *
1287  */
1288 long do_splice_direct(struct file *in, loff_t *ppos, struct file *out,
1289                       size_t len, unsigned int flags)
1290 {
1291         struct splice_desc sd = {
1292                 .len            = len,
1293                 .total_len      = len,
1294                 .flags          = flags,
1295                 .pos            = *ppos,
1296                 .u.file         = out,
1297         };
1298         long ret;
1299
1300         ret = splice_direct_to_actor(in, &sd, direct_splice_actor);
1301         if (ret > 0)
1302                 *ppos = sd.pos;
1303
1304         return ret;
1305 }
1306
1307 static int splice_pipe_to_pipe(struct pipe_inode_info *ipipe,
1308                                struct pipe_inode_info *opipe,
1309                                size_t len, unsigned int flags);
1310
1311 /*
1312  * Determine where to splice to/from.
1313  */
1314 static long do_splice(struct file *in, loff_t __user *off_in,
1315                       struct file *out, loff_t __user *off_out,
1316                       size_t len, unsigned int flags)
1317 {
1318         struct pipe_inode_info *ipipe;
1319         struct pipe_inode_info *opipe;
1320         loff_t offset, *off;
1321         long ret;
1322
1323         ipipe = get_pipe_info(in);
1324         opipe = get_pipe_info(out);
1325
1326         if (ipipe && opipe) {
1327                 if (off_in || off_out)
1328                         return -ESPIPE;
1329
1330                 if (!(in->f_mode & FMODE_READ))
1331                         return -EBADF;
1332
1333                 if (!(out->f_mode & FMODE_WRITE))
1334                         return -EBADF;
1335
1336                 /* Splicing to self would be fun, but... */
1337                 if (ipipe == opipe)
1338                         return -EINVAL;
1339
1340                 return splice_pipe_to_pipe(ipipe, opipe, len, flags);
1341         }
1342
1343         if (ipipe) {
1344                 if (off_in)
1345                         return -ESPIPE;
1346                 if (off_out) {
1347                         if (!(out->f_mode & FMODE_PWRITE))
1348                                 return -EINVAL;
1349                         if (copy_from_user(&offset, off_out, sizeof(loff_t)))
1350                                 return -EFAULT;
1351                         off = &offset;
1352                 } else
1353                         off = &out->f_pos;
1354
1355                 ret = do_splice_from(ipipe, out, off, len, flags);
1356
1357                 if (off_out && copy_to_user(off_out, off, sizeof(loff_t)))
1358                         ret = -EFAULT;
1359
1360                 return ret;
1361         }
1362
1363         if (opipe) {
1364                 if (off_out)
1365                         return -ESPIPE;
1366                 if (off_in) {
1367                         if (!(in->f_mode & FMODE_PREAD))
1368                                 return -EINVAL;
1369                         if (copy_from_user(&offset, off_in, sizeof(loff_t)))
1370                                 return -EFAULT;
1371                         off = &offset;
1372                 } else
1373                         off = &in->f_pos;
1374
1375                 ret = do_splice_to(in, off, opipe, len, flags);
1376
1377                 if (off_in && copy_to_user(off_in, off, sizeof(loff_t)))
1378                         ret = -EFAULT;
1379
1380                 return ret;
1381         }
1382
1383         return -EINVAL;
1384 }
1385
1386 /*
1387  * Map an iov into an array of pages and offset/length tupples. With the
1388  * partial_page structure, we can map several non-contiguous ranges into
1389  * our ones pages[] map instead of splitting that operation into pieces.
1390  * Could easily be exported as a generic helper for other users, in which
1391  * case one would probably want to add a 'max_nr_pages' parameter as well.
1392  */
1393 static int get_iovec_page_array(const struct iovec __user *iov,
1394                                 unsigned int nr_vecs, struct page **pages,
1395                                 struct partial_page *partial, int aligned,
1396                                 unsigned int pipe_buffers)
1397 {
1398         int buffers = 0, error = 0;
1399
1400         while (nr_vecs) {
1401                 unsigned long off, npages;
1402                 struct iovec entry;
1403                 void __user *base;
1404                 size_t len;
1405                 int i;
1406
1407                 error = -EFAULT;
1408                 if (copy_from_user(&entry, iov, sizeof(entry)))
1409                         break;
1410
1411                 base = entry.iov_base;
1412                 len = entry.iov_len;
1413
1414                 /*
1415                  * Sanity check this iovec. 0 read succeeds.
1416                  */
1417                 error = 0;
1418                 if (unlikely(!len))
1419                         break;
1420                 error = -EFAULT;
1421                 if (!access_ok(VERIFY_READ, base, len))
1422                         break;
1423
1424                 /*
1425                  * Get this base offset and number of pages, then map
1426                  * in the user pages.
1427                  */
1428                 off = (unsigned long) base & ~PAGE_MASK;
1429
1430                 /*
1431                  * If asked for alignment, the offset must be zero and the
1432                  * length a multiple of the PAGE_SIZE.
1433                  */
1434                 error = -EINVAL;
1435                 if (aligned && (off || len & ~PAGE_MASK))
1436                         break;
1437
1438                 npages = (off + len + PAGE_SIZE - 1) >> PAGE_SHIFT;
1439                 if (npages > pipe_buffers - buffers)
1440                         npages = pipe_buffers - buffers;
1441
1442                 error = get_user_pages_fast((unsigned long)base, npages,
1443                                         0, &pages[buffers]);
1444
1445                 if (unlikely(error <= 0))
1446                         break;
1447
1448                 /*
1449                  * Fill this contiguous range into the partial page map.
1450                  */
1451                 for (i = 0; i < error; i++) {
1452                         const int plen = min_t(size_t, len, PAGE_SIZE - off);
1453
1454                         partial[buffers].offset = off;
1455                         partial[buffers].len = plen;
1456
1457                         off = 0;
1458                         len -= plen;
1459                         buffers++;
1460                 }
1461
1462                 /*
1463                  * We didn't complete this iov, stop here since it probably
1464                  * means we have to move some of this into a pipe to
1465                  * be able to continue.
1466                  */
1467                 if (len)
1468                         break;
1469
1470                 /*
1471                  * Don't continue if we mapped fewer pages than we asked for,
1472                  * or if we mapped the max number of pages that we have
1473                  * room for.
1474                  */
1475                 if (error < npages || buffers == pipe_buffers)
1476                         break;
1477
1478                 nr_vecs--;
1479                 iov++;
1480         }
1481
1482         if (buffers)
1483                 return buffers;
1484
1485         return error;
1486 }
1487
1488 static int pipe_to_user(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
1489                         struct splice_desc *sd)
1490 {
1491         char *src;
1492         int ret;
1493
1494         /*
1495          * See if we can use the atomic maps, by prefaulting in the
1496          * pages and doing an atomic copy
1497          */
1498         if (!fault_in_pages_writeable(sd->u.userptr, sd->len)) {
1499                 src = buf->ops->map(pipe, buf, 1);
1500                 ret = __copy_to_user_inatomic(sd->u.userptr, src + buf->offset,
1501                                                         sd->len);
1502                 buf->ops->unmap(pipe, buf, src);
1503                 if (!ret) {
1504                         ret = sd->len;
1505                         goto out;
1506                 }
1507         }
1508
1509         /*
1510          * No dice, use slow non-atomic map and copy
1511          */
1512         src = buf->ops->map(pipe, buf, 0);
1513
1514         ret = sd->len;
1515         if (copy_to_user(sd->u.userptr, src + buf->offset, sd->len))
1516                 ret = -EFAULT;
1517
1518         buf->ops->unmap(pipe, buf, src);
1519 out:
1520         if (ret > 0)
1521                 sd->u.userptr += ret;
1522         return ret;
1523 }
1524
1525 /*
1526  * For lack of a better implementation, implement vmsplice() to userspace
1527  * as a simple copy of the pipes pages to the user iov.
1528  */
1529 static long vmsplice_to_user(struct file *file, const struct iovec __user *iov,
1530                              unsigned long nr_segs, unsigned int flags)
1531 {
1532         struct pipe_inode_info *pipe;
1533         struct splice_desc sd;
1534         ssize_t size;
1535         int error;
1536         long ret;
1537
1538         pipe = get_pipe_info(file);
1539         if (!pipe)
1540                 return -EBADF;
1541
1542         pipe_lock(pipe);
1543
1544         error = ret = 0;
1545         while (nr_segs) {
1546                 void __user *base;
1547                 size_t len;
1548
1549                 /*
1550                  * Get user address base and length for this iovec.
1551                  */
1552                 error = get_user(base, &iov->iov_base);
1553                 if (unlikely(error))
1554                         break;
1555                 error = get_user(len, &iov->iov_len);
1556                 if (unlikely(error))
1557                         break;
1558
1559                 /*
1560                  * Sanity check this iovec. 0 read succeeds.
1561                  */
1562                 if (unlikely(!len))
1563                         break;
1564                 if (unlikely(!base)) {
1565                         error = -EFAULT;
1566                         break;
1567                 }
1568
1569                 if (unlikely(!access_ok(VERIFY_WRITE, base, len))) {
1570                         error = -EFAULT;
1571                         break;
1572                 }
1573
1574                 sd.len = 0;
1575                 sd.total_len = len;
1576                 sd.flags = flags;
1577                 sd.u.userptr = base;
1578                 sd.pos = 0;
1579
1580                 size = __splice_from_pipe(pipe, &sd, pipe_to_user);
1581                 if (size < 0) {
1582                         if (!ret)
1583                                 ret = size;
1584
1585                         break;
1586                 }
1587
1588                 ret += size;
1589
1590                 if (size < len)
1591                         break;
1592
1593                 nr_segs--;
1594                 iov++;
1595         }
1596
1597         pipe_unlock(pipe);
1598
1599         if (!ret)
1600                 ret = error;
1601
1602         return ret;
1603 }
1604
1605 /*
1606  * vmsplice splices a user address range into a pipe. It can be thought of
1607  * as splice-from-memory, where the regular splice is splice-from-file (or
1608  * to file). In both cases the output is a pipe, naturally.
1609  */
1610 static long vmsplice_to_pipe(struct file *file, const struct iovec __user *iov,
1611                              unsigned long nr_segs, unsigned int flags)
1612 {
1613         struct pipe_inode_info *pipe;
1614         struct page *pages[PIPE_DEF_BUFFERS];
1615         struct partial_page partial[PIPE_DEF_BUFFERS];
1616         struct splice_pipe_desc spd = {
1617                 .pages = pages,
1618                 .partial = partial,
1619                 .nr_pages_max = PIPE_DEF_BUFFERS,
1620                 .flags = flags,
1621                 .ops = &user_page_pipe_buf_ops,
1622                 .spd_release = spd_release_page,
1623         };
1624         long ret;
1625
1626         pipe = get_pipe_info(file);
1627         if (!pipe)
1628                 return -EBADF;
1629
1630         if (splice_grow_spd(pipe, &spd))
1631                 return -ENOMEM;
1632
1633         spd.nr_pages = get_iovec_page_array(iov, nr_segs, spd.pages,
1634                                             spd.partial, flags & SPLICE_F_GIFT,
1635                                             spd.nr_pages_max);
1636         if (spd.nr_pages <= 0)
1637                 ret = spd.nr_pages;
1638         else
1639                 ret = splice_to_pipe(pipe, &spd);
1640
1641         splice_shrink_spd(&spd);
1642         return ret;
1643 }
1644
1645 /*
1646  * Note that vmsplice only really supports true splicing _from_ user memory
1647  * to a pipe, not the other way around. Splicing from user memory is a simple
1648  * operation that can be supported without any funky alignment restrictions
1649  * or nasty vm tricks. We simply map in the user memory and fill them into
1650  * a pipe. The reverse isn't quite as easy, though. There are two possible
1651  * solutions for that:
1652  *
1653  *      - memcpy() the data internally, at which point we might as well just
1654  *        do a regular read() on the buffer anyway.
1655  *      - Lots of nasty vm tricks, that are neither fast nor flexible (it
1656  *        has restriction limitations on both ends of the pipe).
1657  *
1658  * Currently we punt and implement it as a normal copy, see pipe_to_user().
1659  *
1660  */
1661 SYSCALL_DEFINE4(vmsplice, int, fd, const struct iovec __user *, iov,
1662                 unsigned long, nr_segs, unsigned int, flags)
1663 {
1664         struct file *file;
1665         long error;
1666         int fput;
1667
1668         if (unlikely(nr_segs > UIO_MAXIOV))
1669                 return -EINVAL;
1670         else if (unlikely(!nr_segs))
1671                 return 0;
1672
1673         error = -EBADF;
1674         file = fget_light(fd, &fput);
1675         if (file) {
1676                 if (file->f_mode & FMODE_WRITE)
1677                         error = vmsplice_to_pipe(file, iov, nr_segs, flags);
1678                 else if (file->f_mode & FMODE_READ)
1679                         error = vmsplice_to_user(file, iov, nr_segs, flags);
1680
1681                 fput_light(file, fput);
1682         }
1683
1684         return error;
1685 }
1686
1687 SYSCALL_DEFINE6(splice, int, fd_in, loff_t __user *, off_in,
1688                 int, fd_out, loff_t __user *, off_out,
1689                 size_t, len, unsigned int, flags)
1690 {
1691         long error;
1692         struct file *in, *out;
1693         int fput_in, fput_out;
1694
1695         if (unlikely(!len))
1696                 return 0;
1697
1698         error = -EBADF;
1699         in = fget_light(fd_in, &fput_in);
1700         if (in) {
1701                 if (in->f_mode & FMODE_READ) {
1702                         out = fget_light(fd_out, &fput_out);
1703                         if (out) {
1704                                 if (out->f_mode & FMODE_WRITE)
1705                                         error = do_splice(in, off_in,
1706                                                           out, off_out,
1707                                                           len, flags);
1708                                 fput_light(out, fput_out);
1709                         }
1710                 }
1711
1712                 fput_light(in, fput_in);
1713         }
1714
1715         return error;
1716 }
1717
1718 /*
1719  * Make sure there's data to read. Wait for input if we can, otherwise
1720  * return an appropriate error.
1721  */
1722 static int ipipe_prep(struct pipe_inode_info *pipe, unsigned int flags)
1723 {
1724         int ret;
1725
1726         /*
1727          * Check ->nrbufs without the inode lock first. This function
1728          * is speculative anyways, so missing one is ok.
1729          */
1730         if (pipe->nrbufs)
1731                 return 0;
1732
1733         ret = 0;
1734         pipe_lock(pipe);
1735
1736         while (!pipe->nrbufs) {
1737                 if (signal_pending(current)) {
1738                         ret = -ERESTARTSYS;
1739                         break;
1740                 }
1741                 if (!pipe->writers)
1742                         break;
1743                 if (!pipe->waiting_writers) {
1744                         if (flags & SPLICE_F_NONBLOCK) {
1745                                 ret = -EAGAIN;
1746                                 break;
1747                         }
1748                 }
1749                 pipe_wait(pipe);
1750         }
1751
1752         pipe_unlock(pipe);
1753         return ret;
1754 }
1755
1756 /*
1757  * Make sure there's writeable room. Wait for room if we can, otherwise
1758  * return an appropriate error.
1759  */
1760 static int opipe_prep(struct pipe_inode_info *pipe, unsigned int flags)
1761 {
1762         int ret;
1763
1764         /*
1765          * Check ->nrbufs without the inode lock first. This function
1766          * is speculative anyways, so missing one is ok.
1767          */
1768         if (pipe->nrbufs < pipe->buffers)
1769                 return 0;
1770
1771         ret = 0;
1772         pipe_lock(pipe);
1773
1774         while (pipe->nrbufs >= pipe->buffers) {
1775                 if (!pipe->readers) {
1776                         send_sig(SIGPIPE, current, 0);
1777                         ret = -EPIPE;
1778                         break;
1779                 }
1780                 if (flags & SPLICE_F_NONBLOCK) {
1781                         ret = -EAGAIN;
1782                         break;
1783                 }
1784                 if (signal_pending(current)) {
1785                         ret = -ERESTARTSYS;
1786                         break;
1787                 }
1788                 pipe->waiting_writers++;
1789                 pipe_wait(pipe);
1790                 pipe->waiting_writers--;
1791         }
1792
1793         pipe_unlock(pipe);
1794         return ret;
1795 }
1796
1797 /*
1798  * Splice contents of ipipe to opipe.
1799  */
1800 static int splice_pipe_to_pipe(struct pipe_inode_info *ipipe,
1801                                struct pipe_inode_info *opipe,
1802                                size_t len, unsigned int flags)
1803 {
1804         struct pipe_buffer *ibuf, *obuf;
1805         int ret = 0, nbuf;
1806         bool input_wakeup = false;
1807
1808
1809 retry:
1810         ret = ipipe_prep(ipipe, flags);
1811         if (ret)
1812                 return ret;
1813
1814         ret = opipe_prep(opipe, flags);
1815         if (ret)
1816                 return ret;
1817
1818         /*
1819          * Potential ABBA deadlock, work around it by ordering lock
1820          * grabbing by pipe info address. Otherwise two different processes
1821          * could deadlock (one doing tee from A -> B, the other from B -> A).
1822          */
1823         pipe_double_lock(ipipe, opipe);
1824
1825         do {
1826                 if (!opipe->readers) {
1827                         send_sig(SIGPIPE, current, 0);
1828                         if (!ret)
1829                                 ret = -EPIPE;
1830                         break;
1831                 }
1832
1833                 if (!ipipe->nrbufs && !ipipe->writers)
1834                         break;
1835
1836                 /*
1837                  * Cannot make any progress, because either the input
1838                  * pipe is empty or the output pipe is full.
1839                  */
1840                 if (!ipipe->nrbufs || opipe->nrbufs >= opipe->buffers) {
1841                         /* Already processed some buffers, break */
1842                         if (ret)
1843                                 break;
1844
1845                         if (flags & SPLICE_F_NONBLOCK) {
1846                                 ret = -EAGAIN;
1847                                 break;
1848                         }
1849
1850                         /*
1851                          * We raced with another reader/writer and haven't
1852                          * managed to process any buffers.  A zero return
1853                          * value means EOF, so retry instead.
1854                          */
1855                         pipe_unlock(ipipe);
1856                         pipe_unlock(opipe);
1857                         goto retry;
1858                 }
1859
1860                 ibuf = ipipe->bufs + ipipe->curbuf;
1861                 nbuf = (opipe->curbuf + opipe->nrbufs) & (opipe->buffers - 1);
1862                 obuf = opipe->bufs + nbuf;
1863
1864                 if (len >= ibuf->len) {
1865                         /*
1866                          * Simply move the whole buffer from ipipe to opipe
1867                          */
1868                         *obuf = *ibuf;
1869                         ibuf->ops = NULL;
1870                         opipe->nrbufs++;
1871                         ipipe->curbuf = (ipipe->curbuf + 1) & (ipipe->buffers - 1);
1872                         ipipe->nrbufs--;
1873                         input_wakeup = true;
1874                 } else {
1875                         /*
1876                          * Get a reference to this pipe buffer,
1877                          * so we can copy the contents over.
1878                          */
1879                         ibuf->ops->get(ipipe, ibuf);
1880                         *obuf = *ibuf;
1881
1882                         /*
1883                          * Don't inherit the gift flag, we need to
1884                          * prevent multiple steals of this page.
1885                          */
1886                         obuf->flags &= ~PIPE_BUF_FLAG_GIFT;
1887
1888                         obuf->len = len;
1889                         opipe->nrbufs++;
1890                         ibuf->offset += obuf->len;
1891                         ibuf->len -= obuf->len;
1892                 }
1893                 ret += obuf->len;
1894                 len -= obuf->len;
1895         } while (len);
1896
1897         pipe_unlock(ipipe);
1898         pipe_unlock(opipe);
1899
1900         /*
1901          * If we put data in the output pipe, wakeup any potential readers.
1902          */
1903         if (ret > 0)
1904                 wakeup_pipe_readers(opipe);
1905
1906         if (input_wakeup)
1907                 wakeup_pipe_writers(ipipe);
1908
1909         return ret;
1910 }
1911
1912 /*
1913  * Link contents of ipipe to opipe.
1914  */
1915 static int link_pipe(struct pipe_inode_info *ipipe,
1916                      struct pipe_inode_info *opipe,
1917                      size_t len, unsigned int flags)
1918 {
1919         struct pipe_buffer *ibuf, *obuf;
1920         int ret = 0, i = 0, nbuf;
1921
1922         /*
1923          * Potential ABBA deadlock, work around it by ordering lock
1924          * grabbing by pipe info address. Otherwise two different processes
1925          * could deadlock (one doing tee from A -> B, the other from B -> A).
1926          */
1927         pipe_double_lock(ipipe, opipe);
1928
1929         do {
1930                 if (!opipe->readers) {
1931                         send_sig(SIGPIPE, current, 0);
1932                         if (!ret)
1933                                 ret = -EPIPE;
1934                         break;
1935                 }
1936
1937                 /*
1938                  * If we have iterated all input buffers or ran out of
1939                  * output room, break.
1940                  */
1941                 if (i >= ipipe->nrbufs || opipe->nrbufs >= opipe->buffers)
1942                         break;
1943
1944                 ibuf = ipipe->bufs + ((ipipe->curbuf + i) & (ipipe->buffers-1));
1945                 nbuf = (opipe->curbuf + opipe->nrbufs) & (opipe->buffers - 1);
1946
1947                 /*
1948                  * Get a reference to this pipe buffer,
1949                  * so we can copy the contents over.
1950                  */
1951                 ibuf->ops->get(ipipe, ibuf);
1952
1953                 obuf = opipe->bufs + nbuf;
1954                 *obuf = *ibuf;
1955
1956                 /*
1957                  * Don't inherit the gift flag, we need to
1958                  * prevent multiple steals of this page.
1959                  */
1960                 obuf->flags &= ~PIPE_BUF_FLAG_GIFT;
1961
1962                 if (obuf->len > len)
1963                         obuf->len = len;
1964
1965                 opipe->nrbufs++;
1966                 ret += obuf->len;
1967                 len -= obuf->len;
1968                 i++;
1969         } while (len);
1970
1971         /*
1972          * return EAGAIN if we have the potential of some data in the
1973          * future, otherwise just return 0
1974          */
1975         if (!ret && ipipe->waiting_writers && (flags & SPLICE_F_NONBLOCK))
1976                 ret = -EAGAIN;
1977
1978         pipe_unlock(ipipe);
1979         pipe_unlock(opipe);
1980
1981         /*
1982          * If we put data in the output pipe, wakeup any potential readers.
1983          */
1984         if (ret > 0)
1985                 wakeup_pipe_readers(opipe);
1986
1987         return ret;
1988 }
1989
1990 /*
1991  * This is a tee(1) implementation that works on pipes. It doesn't copy
1992  * any data, it simply references the 'in' pages on the 'out' pipe.
1993  * The 'flags' used are the SPLICE_F_* variants, currently the only
1994  * applicable one is SPLICE_F_NONBLOCK.
1995  */
1996 static long do_tee(struct file *in, struct file *out, size_t len,
1997                    unsigned int flags)
1998 {
1999         struct pipe_inode_info *ipipe = get_pipe_info(in);
2000         struct pipe_inode_info *opipe = get_pipe_info(out);
2001         int ret = -EINVAL;
2002
2003         /*
2004          * Duplicate the contents of ipipe to opipe without actually
2005          * copying the data.
2006          */
2007         if (ipipe && opipe && ipipe != opipe) {
2008                 /*
2009                  * Keep going, unless we encounter an error. The ipipe/opipe
2010                  * ordering doesn't really matter.
2011                  */
2012                 ret = ipipe_prep(ipipe, flags);
2013                 if (!ret) {
2014                         ret = opipe_prep(opipe, flags);
2015                         if (!ret)
2016                                 ret = link_pipe(ipipe, opipe, len, flags);
2017                 }
2018         }
2019
2020         return ret;
2021 }
2022
2023 SYSCALL_DEFINE4(tee, int, fdin, int, fdout, size_t, len, unsigned int, flags)
2024 {
2025         struct file *in;
2026         int error, fput_in;
2027
2028         if (unlikely(!len))
2029                 return 0;
2030
2031         error = -EBADF;
2032         in = fget_light(fdin, &fput_in);
2033         if (in) {
2034                 if (in->f_mode & FMODE_READ) {
2035                         int fput_out;
2036                         struct file *out = fget_light(fdout, &fput_out);
2037
2038                         if (out) {
2039                                 if (out->f_mode & FMODE_WRITE)
2040                                         error = do_tee(in, out, len, flags);
2041                                 fput_light(out, fput_out);
2042                         }
2043                 }
2044                 fput_light(in, fput_in);
2045         }
2046
2047         return error;
2048 }