splice: direct_splice_actor() should not use pos in sd
[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         pgoff_t index;
601         ssize_t res;
602         size_t this_len;
603         int error;
604         int i;
605         struct splice_pipe_desc spd = {
606                 .pages = pages,
607                 .partial = partial,
608                 .flags = flags,
609                 .ops = &default_pipe_buf_ops,
610                 .spd_release = spd_release_page,
611         };
612
613         if (splice_grow_spd(pipe, &spd))
614                 return -ENOMEM;
615
616         res = -ENOMEM;
617         vec = __vec;
618         if (pipe->buffers > PIPE_DEF_BUFFERS) {
619                 vec = kmalloc(pipe->buffers * sizeof(struct iovec), GFP_KERNEL);
620                 if (!vec)
621                         goto shrink_ret;
622         }
623
624         index = *ppos >> PAGE_CACHE_SHIFT;
625         offset = *ppos & ~PAGE_CACHE_MASK;
626         nr_pages = (len + offset + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
627
628         for (i = 0; i < nr_pages && i < pipe->buffers && len; i++) {
629                 struct page *page;
630
631                 page = alloc_page(GFP_USER);
632                 error = -ENOMEM;
633                 if (!page)
634                         goto err;
635
636                 this_len = min_t(size_t, len, PAGE_CACHE_SIZE - offset);
637                 vec[i].iov_base = (void __user *) page_address(page);
638                 vec[i].iov_len = this_len;
639                 spd.pages[i] = page;
640                 spd.nr_pages++;
641                 len -= this_len;
642                 offset = 0;
643         }
644
645         res = kernel_readv(in, vec, spd.nr_pages, *ppos);
646         if (res < 0) {
647                 error = res;
648                 goto err;
649         }
650
651         error = 0;
652         if (!res)
653                 goto err;
654
655         nr_freed = 0;
656         for (i = 0; i < spd.nr_pages; i++) {
657                 this_len = min_t(size_t, vec[i].iov_len, res);
658                 spd.partial[i].offset = 0;
659                 spd.partial[i].len = this_len;
660                 if (!this_len) {
661                         __free_page(spd.pages[i]);
662                         spd.pages[i] = NULL;
663                         nr_freed++;
664                 }
665                 res -= this_len;
666         }
667         spd.nr_pages -= nr_freed;
668
669         res = splice_to_pipe(pipe, &spd);
670         if (res > 0)
671                 *ppos += res;
672
673 shrink_ret:
674         if (vec != __vec)
675                 kfree(vec);
676         splice_shrink_spd(pipe, &spd);
677         return res;
678
679 err:
680         for (i = 0; i < spd.nr_pages; i++)
681                 __free_page(spd.pages[i]);
682
683         res = error;
684         goto shrink_ret;
685 }
686 EXPORT_SYMBOL(default_file_splice_read);
687
688 /*
689  * Send 'sd->len' bytes to socket from 'sd->file' at position 'sd->pos'
690  * using sendpage(). Return the number of bytes sent.
691  */
692 static int pipe_to_sendpage(struct pipe_inode_info *pipe,
693                             struct pipe_buffer *buf, struct splice_desc *sd)
694 {
695         struct file *file = sd->u.file;
696         loff_t pos = sd->pos;
697         int ret, more;
698
699         ret = buf->ops->confirm(pipe, buf);
700         if (!ret) {
701                 more = (sd->flags & SPLICE_F_MORE) || sd->len < sd->total_len;
702                 if (file->f_op && file->f_op->sendpage)
703                         ret = file->f_op->sendpage(file, buf->page, buf->offset,
704                                                    sd->len, &pos, more);
705                 else
706                         ret = -EINVAL;
707         }
708
709         return ret;
710 }
711
712 /*
713  * This is a little more tricky than the file -> pipe splicing. There are
714  * basically three cases:
715  *
716  *      - Destination page already exists in the address space and there
717  *        are users of it. For that case we have no other option that
718  *        copying the data. Tough luck.
719  *      - Destination page already exists in the address space, but there
720  *        are no users of it. Make sure it's uptodate, then drop it. Fall
721  *        through to last case.
722  *      - Destination page does not exist, we can add the pipe page to
723  *        the page cache and avoid the copy.
724  *
725  * If asked to move pages to the output file (SPLICE_F_MOVE is set in
726  * sd->flags), we attempt to migrate pages from the pipe to the output
727  * file address space page cache. This is possible if no one else has
728  * the pipe page referenced outside of the pipe and page cache. If
729  * SPLICE_F_MOVE isn't set, or we cannot move the page, we simply create
730  * a new page in the output file page cache and fill/dirty that.
731  */
732 int pipe_to_file(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
733                  struct splice_desc *sd)
734 {
735         struct file *file = sd->u.file;
736         struct address_space *mapping = file->f_mapping;
737         unsigned int offset, this_len;
738         struct page *page;
739         void *fsdata;
740         int ret;
741
742         /*
743          * make sure the data in this buffer is uptodate
744          */
745         ret = buf->ops->confirm(pipe, buf);
746         if (unlikely(ret))
747                 return ret;
748
749         offset = sd->pos & ~PAGE_CACHE_MASK;
750
751         this_len = sd->len;
752         if (this_len + offset > PAGE_CACHE_SIZE)
753                 this_len = PAGE_CACHE_SIZE - offset;
754
755         ret = pagecache_write_begin(file, mapping, sd->pos, this_len,
756                                 AOP_FLAG_UNINTERRUPTIBLE, &page, &fsdata);
757         if (unlikely(ret))
758                 goto out;
759
760         if (buf->page != page) {
761                 /*
762                  * Careful, ->map() uses KM_USER0!
763                  */
764                 char *src = buf->ops->map(pipe, buf, 1);
765                 char *dst = kmap_atomic(page, KM_USER1);
766
767                 memcpy(dst + offset, src + buf->offset, this_len);
768                 flush_dcache_page(page);
769                 kunmap_atomic(dst, KM_USER1);
770                 buf->ops->unmap(pipe, buf, src);
771         }
772         ret = pagecache_write_end(file, mapping, sd->pos, this_len, this_len,
773                                 page, fsdata);
774 out:
775         return ret;
776 }
777 EXPORT_SYMBOL(pipe_to_file);
778
779 static void wakeup_pipe_writers(struct pipe_inode_info *pipe)
780 {
781         smp_mb();
782         if (waitqueue_active(&pipe->wait))
783                 wake_up_interruptible(&pipe->wait);
784         kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
785 }
786
787 /**
788  * splice_from_pipe_feed - feed available data from a pipe to a file
789  * @pipe:       pipe to splice from
790  * @sd:         information to @actor
791  * @actor:      handler that splices the data
792  *
793  * Description:
794  *    This function loops over the pipe and calls @actor to do the
795  *    actual moving of a single struct pipe_buffer to the desired
796  *    destination.  It returns when there's no more buffers left in
797  *    the pipe or if the requested number of bytes (@sd->total_len)
798  *    have been copied.  It returns a positive number (one) if the
799  *    pipe needs to be filled with more data, zero if the required
800  *    number of bytes have been copied and -errno on error.
801  *
802  *    This, together with splice_from_pipe_{begin,end,next}, may be
803  *    used to implement the functionality of __splice_from_pipe() when
804  *    locking is required around copying the pipe buffers to the
805  *    destination.
806  */
807 int splice_from_pipe_feed(struct pipe_inode_info *pipe, struct splice_desc *sd,
808                           splice_actor *actor)
809 {
810         int ret;
811
812         while (pipe->nrbufs) {
813                 struct pipe_buffer *buf = pipe->bufs + pipe->curbuf;
814                 const struct pipe_buf_operations *ops = buf->ops;
815
816                 sd->len = buf->len;
817                 if (sd->len > sd->total_len)
818                         sd->len = sd->total_len;
819
820                 ret = actor(pipe, buf, sd);
821                 if (ret <= 0) {
822                         if (ret == -ENODATA)
823                                 ret = 0;
824                         return ret;
825                 }
826                 buf->offset += ret;
827                 buf->len -= ret;
828
829                 sd->num_spliced += ret;
830                 sd->len -= ret;
831                 sd->pos += ret;
832                 sd->total_len -= ret;
833
834                 if (!buf->len) {
835                         buf->ops = NULL;
836                         ops->release(pipe, buf);
837                         pipe->curbuf = (pipe->curbuf + 1) & (pipe->buffers - 1);
838                         pipe->nrbufs--;
839                         if (pipe->inode)
840                                 sd->need_wakeup = true;
841                 }
842
843                 if (!sd->total_len)
844                         return 0;
845         }
846
847         return 1;
848 }
849 EXPORT_SYMBOL(splice_from_pipe_feed);
850
851 /**
852  * splice_from_pipe_next - wait for some data to splice from
853  * @pipe:       pipe to splice from
854  * @sd:         information about the splice operation
855  *
856  * Description:
857  *    This function will wait for some data and return a positive
858  *    value (one) if pipe buffers are available.  It will return zero
859  *    or -errno if no more data needs to be spliced.
860  */
861 int splice_from_pipe_next(struct pipe_inode_info *pipe, struct splice_desc *sd)
862 {
863         while (!pipe->nrbufs) {
864                 if (!pipe->writers)
865                         return 0;
866
867                 if (!pipe->waiting_writers && sd->num_spliced)
868                         return 0;
869
870                 if (sd->flags & SPLICE_F_NONBLOCK)
871                         return -EAGAIN;
872
873                 if (signal_pending(current))
874                         return -ERESTARTSYS;
875
876                 if (sd->need_wakeup) {
877                         wakeup_pipe_writers(pipe);
878                         sd->need_wakeup = false;
879                 }
880
881                 pipe_wait(pipe);
882         }
883
884         return 1;
885 }
886 EXPORT_SYMBOL(splice_from_pipe_next);
887
888 /**
889  * splice_from_pipe_begin - start splicing from pipe
890  * @sd:         information about the splice operation
891  *
892  * Description:
893  *    This function should be called before a loop containing
894  *    splice_from_pipe_next() and splice_from_pipe_feed() to
895  *    initialize the necessary fields of @sd.
896  */
897 void splice_from_pipe_begin(struct splice_desc *sd)
898 {
899         sd->num_spliced = 0;
900         sd->need_wakeup = false;
901 }
902 EXPORT_SYMBOL(splice_from_pipe_begin);
903
904 /**
905  * splice_from_pipe_end - finish splicing from pipe
906  * @pipe:       pipe to splice from
907  * @sd:         information about the splice operation
908  *
909  * Description:
910  *    This function will wake up pipe writers if necessary.  It should
911  *    be called after a loop containing splice_from_pipe_next() and
912  *    splice_from_pipe_feed().
913  */
914 void splice_from_pipe_end(struct pipe_inode_info *pipe, struct splice_desc *sd)
915 {
916         if (sd->need_wakeup)
917                 wakeup_pipe_writers(pipe);
918 }
919 EXPORT_SYMBOL(splice_from_pipe_end);
920
921 /**
922  * __splice_from_pipe - splice data from a pipe to given actor
923  * @pipe:       pipe to splice from
924  * @sd:         information to @actor
925  * @actor:      handler that splices the data
926  *
927  * Description:
928  *    This function does little more than loop over the pipe and call
929  *    @actor to do the actual moving of a single struct pipe_buffer to
930  *    the desired destination. See pipe_to_file, pipe_to_sendpage, or
931  *    pipe_to_user.
932  *
933  */
934 ssize_t __splice_from_pipe(struct pipe_inode_info *pipe, struct splice_desc *sd,
935                            splice_actor *actor)
936 {
937         int ret;
938
939         splice_from_pipe_begin(sd);
940         do {
941                 ret = splice_from_pipe_next(pipe, sd);
942                 if (ret > 0)
943                         ret = splice_from_pipe_feed(pipe, sd, actor);
944         } while (ret > 0);
945         splice_from_pipe_end(pipe, sd);
946
947         return sd->num_spliced ? sd->num_spliced : ret;
948 }
949 EXPORT_SYMBOL(__splice_from_pipe);
950
951 /**
952  * splice_from_pipe - splice data from a pipe to a file
953  * @pipe:       pipe to splice from
954  * @out:        file to splice to
955  * @ppos:       position in @out
956  * @len:        how many bytes to splice
957  * @flags:      splice modifier flags
958  * @actor:      handler that splices the data
959  *
960  * Description:
961  *    See __splice_from_pipe. This function locks the pipe inode,
962  *    otherwise it's identical to __splice_from_pipe().
963  *
964  */
965 ssize_t splice_from_pipe(struct pipe_inode_info *pipe, struct file *out,
966                          loff_t *ppos, size_t len, unsigned int flags,
967                          splice_actor *actor)
968 {
969         ssize_t ret;
970         struct splice_desc sd = {
971                 .total_len = len,
972                 .flags = flags,
973                 .pos = *ppos,
974                 .u.file = out,
975         };
976
977         pipe_lock(pipe);
978         ret = __splice_from_pipe(pipe, &sd, actor);
979         pipe_unlock(pipe);
980
981         return ret;
982 }
983
984 /**
985  * generic_file_splice_write - splice data from a pipe to a file
986  * @pipe:       pipe info
987  * @out:        file to write to
988  * @ppos:       position in @out
989  * @len:        number of bytes to splice
990  * @flags:      splice modifier flags
991  *
992  * Description:
993  *    Will either move or copy pages (determined by @flags options) from
994  *    the given pipe inode to the given file.
995  *
996  */
997 ssize_t
998 generic_file_splice_write(struct pipe_inode_info *pipe, struct file *out,
999                           loff_t *ppos, size_t len, unsigned int flags)
1000 {
1001         struct address_space *mapping = out->f_mapping;
1002         struct inode *inode = mapping->host;
1003         struct splice_desc sd = {
1004                 .total_len = len,
1005                 .flags = flags,
1006                 .pos = *ppos,
1007                 .u.file = out,
1008         };
1009         ssize_t ret;
1010
1011         pipe_lock(pipe);
1012
1013         splice_from_pipe_begin(&sd);
1014         do {
1015                 ret = splice_from_pipe_next(pipe, &sd);
1016                 if (ret <= 0)
1017                         break;
1018
1019                 mutex_lock_nested(&inode->i_mutex, I_MUTEX_CHILD);
1020                 ret = file_remove_suid(out);
1021                 if (!ret) {
1022                         file_update_time(out);
1023                         ret = splice_from_pipe_feed(pipe, &sd, pipe_to_file);
1024                 }
1025                 mutex_unlock(&inode->i_mutex);
1026         } while (ret > 0);
1027         splice_from_pipe_end(pipe, &sd);
1028
1029         pipe_unlock(pipe);
1030
1031         if (sd.num_spliced)
1032                 ret = sd.num_spliced;
1033
1034         if (ret > 0) {
1035                 unsigned long nr_pages;
1036                 int err;
1037
1038                 nr_pages = (ret + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
1039
1040                 err = generic_write_sync(out, *ppos, ret);
1041                 if (err)
1042                         ret = err;
1043                 else
1044                         *ppos += ret;
1045                 balance_dirty_pages_ratelimited_nr(mapping, nr_pages);
1046         }
1047
1048         return ret;
1049 }
1050
1051 EXPORT_SYMBOL(generic_file_splice_write);
1052
1053 static int write_pipe_buf(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
1054                           struct splice_desc *sd)
1055 {
1056         int ret;
1057         void *data;
1058
1059         ret = buf->ops->confirm(pipe, buf);
1060         if (ret)
1061                 return ret;
1062
1063         data = buf->ops->map(pipe, buf, 0);
1064         ret = kernel_write(sd->u.file, data + buf->offset, sd->len, sd->pos);
1065         buf->ops->unmap(pipe, buf, data);
1066
1067         return ret;
1068 }
1069
1070 static ssize_t default_file_splice_write(struct pipe_inode_info *pipe,
1071                                          struct file *out, loff_t *ppos,
1072                                          size_t len, unsigned int flags)
1073 {
1074         ssize_t ret;
1075
1076         ret = splice_from_pipe(pipe, out, ppos, len, flags, write_pipe_buf);
1077         if (ret > 0)
1078                 *ppos += ret;
1079
1080         return ret;
1081 }
1082
1083 /**
1084  * generic_splice_sendpage - splice data from a pipe to a socket
1085  * @pipe:       pipe to splice from
1086  * @out:        socket to write to
1087  * @ppos:       position in @out
1088  * @len:        number of bytes to splice
1089  * @flags:      splice modifier flags
1090  *
1091  * Description:
1092  *    Will send @len bytes from the pipe to a network socket. No data copying
1093  *    is involved.
1094  *
1095  */
1096 ssize_t generic_splice_sendpage(struct pipe_inode_info *pipe, struct file *out,
1097                                 loff_t *ppos, size_t len, unsigned int flags)
1098 {
1099         return splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_sendpage);
1100 }
1101
1102 EXPORT_SYMBOL(generic_splice_sendpage);
1103
1104 /*
1105  * Attempt to initiate a splice from pipe to file.
1106  */
1107 static long do_splice_from(struct pipe_inode_info *pipe, struct file *out,
1108                            loff_t *ppos, size_t len, unsigned int flags)
1109 {
1110         ssize_t (*splice_write)(struct pipe_inode_info *, struct file *,
1111                                 loff_t *, size_t, unsigned int);
1112         int ret;
1113
1114         if (unlikely(!(out->f_mode & FMODE_WRITE)))
1115                 return -EBADF;
1116
1117         if (unlikely(out->f_flags & O_APPEND))
1118                 return -EINVAL;
1119
1120         ret = rw_verify_area(WRITE, out, ppos, len);
1121         if (unlikely(ret < 0))
1122                 return ret;
1123
1124         if (out->f_op && out->f_op->splice_write)
1125                 splice_write = out->f_op->splice_write;
1126         else
1127                 splice_write = default_file_splice_write;
1128
1129         return splice_write(pipe, out, ppos, len, flags);
1130 }
1131
1132 /*
1133  * Attempt to initiate a splice from a file to a pipe.
1134  */
1135 static long do_splice_to(struct file *in, loff_t *ppos,
1136                          struct pipe_inode_info *pipe, size_t len,
1137                          unsigned int flags)
1138 {
1139         ssize_t (*splice_read)(struct file *, loff_t *,
1140                                struct pipe_inode_info *, size_t, unsigned int);
1141         int ret;
1142
1143         if (unlikely(!(in->f_mode & FMODE_READ)))
1144                 return -EBADF;
1145
1146         ret = rw_verify_area(READ, in, ppos, len);
1147         if (unlikely(ret < 0))
1148                 return ret;
1149
1150         if (in->f_op && in->f_op->splice_read)
1151                 splice_read = in->f_op->splice_read;
1152         else
1153                 splice_read = default_file_splice_read;
1154
1155         return splice_read(in, ppos, pipe, len, flags);
1156 }
1157
1158 /**
1159  * splice_direct_to_actor - splices data directly between two non-pipes
1160  * @in:         file to splice from
1161  * @sd:         actor information on where to splice to
1162  * @actor:      handles the data splicing
1163  *
1164  * Description:
1165  *    This is a special case helper to splice directly between two
1166  *    points, without requiring an explicit pipe. Internally an allocated
1167  *    pipe is cached in the process, and reused during the lifetime of
1168  *    that process.
1169  *
1170  */
1171 ssize_t splice_direct_to_actor(struct file *in, struct splice_desc *sd,
1172                                splice_direct_actor *actor)
1173 {
1174         struct pipe_inode_info *pipe;
1175         long ret, bytes;
1176         umode_t i_mode;
1177         size_t len;
1178         int i, flags;
1179
1180         /*
1181          * We require the input being a regular file, as we don't want to
1182          * randomly drop data for eg socket -> socket splicing. Use the
1183          * piped splicing for that!
1184          */
1185         i_mode = in->f_path.dentry->d_inode->i_mode;
1186         if (unlikely(!S_ISREG(i_mode) && !S_ISBLK(i_mode)))
1187                 return -EINVAL;
1188
1189         /*
1190          * neither in nor out is a pipe, setup an internal pipe attached to
1191          * 'out' and transfer the wanted data from 'in' to 'out' through that
1192          */
1193         pipe = current->splice_pipe;
1194         if (unlikely(!pipe)) {
1195                 pipe = alloc_pipe_info(NULL);
1196                 if (!pipe)
1197                         return -ENOMEM;
1198
1199                 /*
1200                  * We don't have an immediate reader, but we'll read the stuff
1201                  * out of the pipe right after the splice_to_pipe(). So set
1202                  * PIPE_READERS appropriately.
1203                  */
1204                 pipe->readers = 1;
1205
1206                 current->splice_pipe = pipe;
1207         }
1208
1209         /*
1210          * Do the splice.
1211          */
1212         ret = 0;
1213         bytes = 0;
1214         len = sd->total_len;
1215         flags = sd->flags;
1216
1217         /*
1218          * Don't block on output, we have to drain the direct pipe.
1219          */
1220         sd->flags &= ~SPLICE_F_NONBLOCK;
1221
1222         while (len) {
1223                 size_t read_len;
1224                 loff_t pos = sd->pos, prev_pos = pos;
1225
1226                 ret = do_splice_to(in, &pos, pipe, len, flags);
1227                 if (unlikely(ret <= 0))
1228                         goto out_release;
1229
1230                 read_len = ret;
1231                 sd->total_len = read_len;
1232
1233                 /*
1234                  * NOTE: nonblocking mode only applies to the input. We
1235                  * must not do the output in nonblocking mode as then we
1236                  * could get stuck data in the internal pipe:
1237                  */
1238                 ret = actor(pipe, sd);
1239                 if (unlikely(ret <= 0)) {
1240                         sd->pos = prev_pos;
1241                         goto out_release;
1242                 }
1243
1244                 bytes += ret;
1245                 len -= ret;
1246                 sd->pos = pos;
1247
1248                 if (ret < read_len) {
1249                         sd->pos = prev_pos + ret;
1250                         goto out_release;
1251                 }
1252         }
1253
1254 done:
1255         pipe->nrbufs = pipe->curbuf = 0;
1256         file_accessed(in);
1257         return bytes;
1258
1259 out_release:
1260         /*
1261          * If we did an incomplete transfer we must release
1262          * the pipe buffers in question:
1263          */
1264         for (i = 0; i < pipe->buffers; i++) {
1265                 struct pipe_buffer *buf = pipe->bufs + i;
1266
1267                 if (buf->ops) {
1268                         buf->ops->release(pipe, buf);
1269                         buf->ops = NULL;
1270                 }
1271         }
1272
1273         if (!bytes)
1274                 bytes = ret;
1275
1276         goto done;
1277 }
1278 EXPORT_SYMBOL(splice_direct_to_actor);
1279
1280 static int direct_splice_actor(struct pipe_inode_info *pipe,
1281                                struct splice_desc *sd)
1282 {
1283         struct file *file = sd->u.file;
1284
1285         return do_splice_from(pipe, file, &file->f_pos, sd->total_len,
1286                               sd->flags);
1287 }
1288
1289 /**
1290  * do_splice_direct - splices data directly between two files
1291  * @in:         file to splice from
1292  * @ppos:       input file offset
1293  * @out:        file to splice to
1294  * @len:        number of bytes to splice
1295  * @flags:      splice modifier flags
1296  *
1297  * Description:
1298  *    For use by do_sendfile(). splice can easily emulate sendfile, but
1299  *    doing it in the application would incur an extra system call
1300  *    (splice in + splice out, as compared to just sendfile()). So this helper
1301  *    can splice directly through a process-private pipe.
1302  *
1303  */
1304 long do_splice_direct(struct file *in, loff_t *ppos, struct file *out,
1305                       size_t len, unsigned int flags)
1306 {
1307         struct splice_desc sd = {
1308                 .len            = len,
1309                 .total_len      = len,
1310                 .flags          = flags,
1311                 .pos            = *ppos,
1312                 .u.file         = out,
1313         };
1314         long ret;
1315
1316         ret = splice_direct_to_actor(in, &sd, direct_splice_actor);
1317         if (ret > 0)
1318                 *ppos = sd.pos;
1319
1320         return ret;
1321 }
1322
1323 static int splice_pipe_to_pipe(struct pipe_inode_info *ipipe,
1324                                struct pipe_inode_info *opipe,
1325                                size_t len, unsigned int flags);
1326 /*
1327  * After the inode slimming patch, i_pipe/i_bdev/i_cdev share the same
1328  * location, so checking ->i_pipe is not enough to verify that this is a
1329  * pipe.
1330  */
1331 static inline struct pipe_inode_info *pipe_info(struct inode *inode)
1332 {
1333         if (S_ISFIFO(inode->i_mode))
1334                 return inode->i_pipe;
1335
1336         return NULL;
1337 }
1338
1339 /*
1340  * Determine where to splice to/from.
1341  */
1342 static long do_splice(struct file *in, loff_t __user *off_in,
1343                       struct file *out, loff_t __user *off_out,
1344                       size_t len, unsigned int flags)
1345 {
1346         struct pipe_inode_info *ipipe;
1347         struct pipe_inode_info *opipe;
1348         loff_t offset, *off;
1349         long ret;
1350
1351         ipipe = pipe_info(in->f_path.dentry->d_inode);
1352         opipe = pipe_info(out->f_path.dentry->d_inode);
1353
1354         if (ipipe && opipe) {
1355                 if (off_in || off_out)
1356                         return -ESPIPE;
1357
1358                 if (!(in->f_mode & FMODE_READ))
1359                         return -EBADF;
1360
1361                 if (!(out->f_mode & FMODE_WRITE))
1362                         return -EBADF;
1363
1364                 /* Splicing to self would be fun, but... */
1365                 if (ipipe == opipe)
1366                         return -EINVAL;
1367
1368                 return splice_pipe_to_pipe(ipipe, opipe, len, flags);
1369         }
1370
1371         if (ipipe) {
1372                 if (off_in)
1373                         return -ESPIPE;
1374                 if (off_out) {
1375                         if (!out->f_op || !out->f_op->llseek ||
1376                             out->f_op->llseek == no_llseek)
1377                                 return -EINVAL;
1378                         if (copy_from_user(&offset, off_out, sizeof(loff_t)))
1379                                 return -EFAULT;
1380                         off = &offset;
1381                 } else
1382                         off = &out->f_pos;
1383
1384                 ret = do_splice_from(ipipe, out, off, len, flags);
1385
1386                 if (off_out && copy_to_user(off_out, off, sizeof(loff_t)))
1387                         ret = -EFAULT;
1388
1389                 return ret;
1390         }
1391
1392         if (opipe) {
1393                 if (off_out)
1394                         return -ESPIPE;
1395                 if (off_in) {
1396                         if (!in->f_op || !in->f_op->llseek ||
1397                             in->f_op->llseek == no_llseek)
1398                                 return -EINVAL;
1399                         if (copy_from_user(&offset, off_in, sizeof(loff_t)))
1400                                 return -EFAULT;
1401                         off = &offset;
1402                 } else
1403                         off = &in->f_pos;
1404
1405                 ret = do_splice_to(in, off, opipe, len, flags);
1406
1407                 if (off_in && copy_to_user(off_in, off, sizeof(loff_t)))
1408                         ret = -EFAULT;
1409
1410                 return ret;
1411         }
1412
1413         return -EINVAL;
1414 }
1415
1416 /*
1417  * Map an iov into an array of pages and offset/length tupples. With the
1418  * partial_page structure, we can map several non-contiguous ranges into
1419  * our ones pages[] map instead of splitting that operation into pieces.
1420  * Could easily be exported as a generic helper for other users, in which
1421  * case one would probably want to add a 'max_nr_pages' parameter as well.
1422  */
1423 static int get_iovec_page_array(const struct iovec __user *iov,
1424                                 unsigned int nr_vecs, struct page **pages,
1425                                 struct partial_page *partial, int aligned,
1426                                 unsigned int pipe_buffers)
1427 {
1428         int buffers = 0, error = 0;
1429
1430         while (nr_vecs) {
1431                 unsigned long off, npages;
1432                 struct iovec entry;
1433                 void __user *base;
1434                 size_t len;
1435                 int i;
1436
1437                 error = -EFAULT;
1438                 if (copy_from_user(&entry, iov, sizeof(entry)))
1439                         break;
1440
1441                 base = entry.iov_base;
1442                 len = entry.iov_len;
1443
1444                 /*
1445                  * Sanity check this iovec. 0 read succeeds.
1446                  */
1447                 error = 0;
1448                 if (unlikely(!len))
1449                         break;
1450                 error = -EFAULT;
1451                 if (!access_ok(VERIFY_READ, base, len))
1452                         break;
1453
1454                 /*
1455                  * Get this base offset and number of pages, then map
1456                  * in the user pages.
1457                  */
1458                 off = (unsigned long) base & ~PAGE_MASK;
1459
1460                 /*
1461                  * If asked for alignment, the offset must be zero and the
1462                  * length a multiple of the PAGE_SIZE.
1463                  */
1464                 error = -EINVAL;
1465                 if (aligned && (off || len & ~PAGE_MASK))
1466                         break;
1467
1468                 npages = (off + len + PAGE_SIZE - 1) >> PAGE_SHIFT;
1469                 if (npages > pipe_buffers - buffers)
1470                         npages = pipe_buffers - buffers;
1471
1472                 error = get_user_pages_fast((unsigned long)base, npages,
1473                                         0, &pages[buffers]);
1474
1475                 if (unlikely(error <= 0))
1476                         break;
1477
1478                 /*
1479                  * Fill this contiguous range into the partial page map.
1480                  */
1481                 for (i = 0; i < error; i++) {
1482                         const int plen = min_t(size_t, len, PAGE_SIZE - off);
1483
1484                         partial[buffers].offset = off;
1485                         partial[buffers].len = plen;
1486
1487                         off = 0;
1488                         len -= plen;
1489                         buffers++;
1490                 }
1491
1492                 /*
1493                  * We didn't complete this iov, stop here since it probably
1494                  * means we have to move some of this into a pipe to
1495                  * be able to continue.
1496                  */
1497                 if (len)
1498                         break;
1499
1500                 /*
1501                  * Don't continue if we mapped fewer pages than we asked for,
1502                  * or if we mapped the max number of pages that we have
1503                  * room for.
1504                  */
1505                 if (error < npages || buffers == pipe_buffers)
1506                         break;
1507
1508                 nr_vecs--;
1509                 iov++;
1510         }
1511
1512         if (buffers)
1513                 return buffers;
1514
1515         return error;
1516 }
1517
1518 static int pipe_to_user(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
1519                         struct splice_desc *sd)
1520 {
1521         char *src;
1522         int ret;
1523
1524         ret = buf->ops->confirm(pipe, buf);
1525         if (unlikely(ret))
1526                 return ret;
1527
1528         /*
1529          * See if we can use the atomic maps, by prefaulting in the
1530          * pages and doing an atomic copy
1531          */
1532         if (!fault_in_pages_writeable(sd->u.userptr, sd->len)) {
1533                 src = buf->ops->map(pipe, buf, 1);
1534                 ret = __copy_to_user_inatomic(sd->u.userptr, src + buf->offset,
1535                                                         sd->len);
1536                 buf->ops->unmap(pipe, buf, src);
1537                 if (!ret) {
1538                         ret = sd->len;
1539                         goto out;
1540                 }
1541         }
1542
1543         /*
1544          * No dice, use slow non-atomic map and copy
1545          */
1546         src = buf->ops->map(pipe, buf, 0);
1547
1548         ret = sd->len;
1549         if (copy_to_user(sd->u.userptr, src + buf->offset, sd->len))
1550                 ret = -EFAULT;
1551
1552         buf->ops->unmap(pipe, buf, src);
1553 out:
1554         if (ret > 0)
1555                 sd->u.userptr += ret;
1556         return ret;
1557 }
1558
1559 /*
1560  * For lack of a better implementation, implement vmsplice() to userspace
1561  * as a simple copy of the pipes pages to the user iov.
1562  */
1563 static long vmsplice_to_user(struct file *file, const struct iovec __user *iov,
1564                              unsigned long nr_segs, unsigned int flags)
1565 {
1566         struct pipe_inode_info *pipe;
1567         struct splice_desc sd;
1568         ssize_t size;
1569         int error;
1570         long ret;
1571
1572         pipe = pipe_info(file->f_path.dentry->d_inode);
1573         if (!pipe)
1574                 return -EBADF;
1575
1576         pipe_lock(pipe);
1577
1578         error = ret = 0;
1579         while (nr_segs) {
1580                 void __user *base;
1581                 size_t len;
1582
1583                 /*
1584                  * Get user address base and length for this iovec.
1585                  */
1586                 error = get_user(base, &iov->iov_base);
1587                 if (unlikely(error))
1588                         break;
1589                 error = get_user(len, &iov->iov_len);
1590                 if (unlikely(error))
1591                         break;
1592
1593                 /*
1594                  * Sanity check this iovec. 0 read succeeds.
1595                  */
1596                 if (unlikely(!len))
1597                         break;
1598                 if (unlikely(!base)) {
1599                         error = -EFAULT;
1600                         break;
1601                 }
1602
1603                 if (unlikely(!access_ok(VERIFY_WRITE, base, len))) {
1604                         error = -EFAULT;
1605                         break;
1606                 }
1607
1608                 sd.len = 0;
1609                 sd.total_len = len;
1610                 sd.flags = flags;
1611                 sd.u.userptr = base;
1612                 sd.pos = 0;
1613
1614                 size = __splice_from_pipe(pipe, &sd, pipe_to_user);
1615                 if (size < 0) {
1616                         if (!ret)
1617                                 ret = size;
1618
1619                         break;
1620                 }
1621
1622                 ret += size;
1623
1624                 if (size < len)
1625                         break;
1626
1627                 nr_segs--;
1628                 iov++;
1629         }
1630
1631         pipe_unlock(pipe);
1632
1633         if (!ret)
1634                 ret = error;
1635
1636         return ret;
1637 }
1638
1639 /*
1640  * vmsplice splices a user address range into a pipe. It can be thought of
1641  * as splice-from-memory, where the regular splice is splice-from-file (or
1642  * to file). In both cases the output is a pipe, naturally.
1643  */
1644 static long vmsplice_to_pipe(struct file *file, const struct iovec __user *iov,
1645                              unsigned long nr_segs, unsigned int flags)
1646 {
1647         struct pipe_inode_info *pipe;
1648         struct page *pages[PIPE_DEF_BUFFERS];
1649         struct partial_page partial[PIPE_DEF_BUFFERS];
1650         struct splice_pipe_desc spd = {
1651                 .pages = pages,
1652                 .partial = partial,
1653                 .flags = flags,
1654                 .ops = &user_page_pipe_buf_ops,
1655                 .spd_release = spd_release_page,
1656         };
1657         long ret;
1658
1659         pipe = pipe_info(file->f_path.dentry->d_inode);
1660         if (!pipe)
1661                 return -EBADF;
1662
1663         if (splice_grow_spd(pipe, &spd))
1664                 return -ENOMEM;
1665
1666         spd.nr_pages = get_iovec_page_array(iov, nr_segs, spd.pages,
1667                                             spd.partial, flags & SPLICE_F_GIFT,
1668                                             pipe->buffers);
1669         if (spd.nr_pages <= 0)
1670                 ret = spd.nr_pages;
1671         else
1672                 ret = splice_to_pipe(pipe, &spd);
1673
1674         splice_shrink_spd(pipe, &spd);
1675         return ret;
1676 }
1677
1678 /*
1679  * Note that vmsplice only really supports true splicing _from_ user memory
1680  * to a pipe, not the other way around. Splicing from user memory is a simple
1681  * operation that can be supported without any funky alignment restrictions
1682  * or nasty vm tricks. We simply map in the user memory and fill them into
1683  * a pipe. The reverse isn't quite as easy, though. There are two possible
1684  * solutions for that:
1685  *
1686  *      - memcpy() the data internally, at which point we might as well just
1687  *        do a regular read() on the buffer anyway.
1688  *      - Lots of nasty vm tricks, that are neither fast nor flexible (it
1689  *        has restriction limitations on both ends of the pipe).
1690  *
1691  * Currently we punt and implement it as a normal copy, see pipe_to_user().
1692  *
1693  */
1694 SYSCALL_DEFINE4(vmsplice, int, fd, const struct iovec __user *, iov,
1695                 unsigned long, nr_segs, unsigned int, flags)
1696 {
1697         struct file *file;
1698         long error;
1699         int fput;
1700
1701         if (unlikely(nr_segs > UIO_MAXIOV))
1702                 return -EINVAL;
1703         else if (unlikely(!nr_segs))
1704                 return 0;
1705
1706         error = -EBADF;
1707         file = fget_light(fd, &fput);
1708         if (file) {
1709                 if (file->f_mode & FMODE_WRITE)
1710                         error = vmsplice_to_pipe(file, iov, nr_segs, flags);
1711                 else if (file->f_mode & FMODE_READ)
1712                         error = vmsplice_to_user(file, iov, nr_segs, flags);
1713
1714                 fput_light(file, fput);
1715         }
1716
1717         return error;
1718 }
1719
1720 SYSCALL_DEFINE6(splice, int, fd_in, loff_t __user *, off_in,
1721                 int, fd_out, loff_t __user *, off_out,
1722                 size_t, len, unsigned int, flags)
1723 {
1724         long error;
1725         struct file *in, *out;
1726         int fput_in, fput_out;
1727
1728         if (unlikely(!len))
1729                 return 0;
1730
1731         error = -EBADF;
1732         in = fget_light(fd_in, &fput_in);
1733         if (in) {
1734                 if (in->f_mode & FMODE_READ) {
1735                         out = fget_light(fd_out, &fput_out);
1736                         if (out) {
1737                                 if (out->f_mode & FMODE_WRITE)
1738                                         error = do_splice(in, off_in,
1739                                                           out, off_out,
1740                                                           len, flags);
1741                                 fput_light(out, fput_out);
1742                         }
1743                 }
1744
1745                 fput_light(in, fput_in);
1746         }
1747
1748         return error;
1749 }
1750
1751 /*
1752  * Make sure there's data to read. Wait for input if we can, otherwise
1753  * return an appropriate error.
1754  */
1755 static int ipipe_prep(struct pipe_inode_info *pipe, unsigned int flags)
1756 {
1757         int ret;
1758
1759         /*
1760          * Check ->nrbufs without the inode lock first. This function
1761          * is speculative anyways, so missing one is ok.
1762          */
1763         if (pipe->nrbufs)
1764                 return 0;
1765
1766         ret = 0;
1767         pipe_lock(pipe);
1768
1769         while (!pipe->nrbufs) {
1770                 if (signal_pending(current)) {
1771                         ret = -ERESTARTSYS;
1772                         break;
1773                 }
1774                 if (!pipe->writers)
1775                         break;
1776                 if (!pipe->waiting_writers) {
1777                         if (flags & SPLICE_F_NONBLOCK) {
1778                                 ret = -EAGAIN;
1779                                 break;
1780                         }
1781                 }
1782                 pipe_wait(pipe);
1783         }
1784
1785         pipe_unlock(pipe);
1786         return ret;
1787 }
1788
1789 /*
1790  * Make sure there's writeable room. Wait for room if we can, otherwise
1791  * return an appropriate error.
1792  */
1793 static int opipe_prep(struct pipe_inode_info *pipe, unsigned int flags)
1794 {
1795         int ret;
1796
1797         /*
1798          * Check ->nrbufs without the inode lock first. This function
1799          * is speculative anyways, so missing one is ok.
1800          */
1801         if (pipe->nrbufs < pipe->buffers)
1802                 return 0;
1803
1804         ret = 0;
1805         pipe_lock(pipe);
1806
1807         while (pipe->nrbufs >= pipe->buffers) {
1808                 if (!pipe->readers) {
1809                         send_sig(SIGPIPE, current, 0);
1810                         ret = -EPIPE;
1811                         break;
1812                 }
1813                 if (flags & SPLICE_F_NONBLOCK) {
1814                         ret = -EAGAIN;
1815                         break;
1816                 }
1817                 if (signal_pending(current)) {
1818                         ret = -ERESTARTSYS;
1819                         break;
1820                 }
1821                 pipe->waiting_writers++;
1822                 pipe_wait(pipe);
1823                 pipe->waiting_writers--;
1824         }
1825
1826         pipe_unlock(pipe);
1827         return ret;
1828 }
1829
1830 /*
1831  * Splice contents of ipipe to opipe.
1832  */
1833 static int splice_pipe_to_pipe(struct pipe_inode_info *ipipe,
1834                                struct pipe_inode_info *opipe,
1835                                size_t len, unsigned int flags)
1836 {
1837         struct pipe_buffer *ibuf, *obuf;
1838         int ret = 0, nbuf;
1839         bool input_wakeup = false;
1840
1841
1842 retry:
1843         ret = ipipe_prep(ipipe, flags);
1844         if (ret)
1845                 return ret;
1846
1847         ret = opipe_prep(opipe, flags);
1848         if (ret)
1849                 return ret;
1850
1851         /*
1852          * Potential ABBA deadlock, work around it by ordering lock
1853          * grabbing by pipe info address. Otherwise two different processes
1854          * could deadlock (one doing tee from A -> B, the other from B -> A).
1855          */
1856         pipe_double_lock(ipipe, opipe);
1857
1858         do {
1859                 if (!opipe->readers) {
1860                         send_sig(SIGPIPE, current, 0);
1861                         if (!ret)
1862                                 ret = -EPIPE;
1863                         break;
1864                 }
1865
1866                 if (!ipipe->nrbufs && !ipipe->writers)
1867                         break;
1868
1869                 /*
1870                  * Cannot make any progress, because either the input
1871                  * pipe is empty or the output pipe is full.
1872                  */
1873                 if (!ipipe->nrbufs || opipe->nrbufs >= opipe->buffers) {
1874                         /* Already processed some buffers, break */
1875                         if (ret)
1876                                 break;
1877
1878                         if (flags & SPLICE_F_NONBLOCK) {
1879                                 ret = -EAGAIN;
1880                                 break;
1881                         }
1882
1883                         /*
1884                          * We raced with another reader/writer and haven't
1885                          * managed to process any buffers.  A zero return
1886                          * value means EOF, so retry instead.
1887                          */
1888                         pipe_unlock(ipipe);
1889                         pipe_unlock(opipe);
1890                         goto retry;
1891                 }
1892
1893                 ibuf = ipipe->bufs + ipipe->curbuf;
1894                 nbuf = (opipe->curbuf + opipe->nrbufs) & (opipe->buffers - 1);
1895                 obuf = opipe->bufs + nbuf;
1896
1897                 if (len >= ibuf->len) {
1898                         /*
1899                          * Simply move the whole buffer from ipipe to opipe
1900                          */
1901                         *obuf = *ibuf;
1902                         ibuf->ops = NULL;
1903                         opipe->nrbufs++;
1904                         ipipe->curbuf = (ipipe->curbuf + 1) & (ipipe->buffers - 1);
1905                         ipipe->nrbufs--;
1906                         input_wakeup = true;
1907                 } else {
1908                         /*
1909                          * Get a reference to this pipe buffer,
1910                          * so we can copy the contents over.
1911                          */
1912                         ibuf->ops->get(ipipe, ibuf);
1913                         *obuf = *ibuf;
1914
1915                         /*
1916                          * Don't inherit the gift flag, we need to
1917                          * prevent multiple steals of this page.
1918                          */
1919                         obuf->flags &= ~PIPE_BUF_FLAG_GIFT;
1920
1921                         obuf->len = len;
1922                         opipe->nrbufs++;
1923                         ibuf->offset += obuf->len;
1924                         ibuf->len -= obuf->len;
1925                 }
1926                 ret += obuf->len;
1927                 len -= obuf->len;
1928         } while (len);
1929
1930         pipe_unlock(ipipe);
1931         pipe_unlock(opipe);
1932
1933         /*
1934          * If we put data in the output pipe, wakeup any potential readers.
1935          */
1936         if (ret > 0) {
1937                 smp_mb();
1938                 if (waitqueue_active(&opipe->wait))
1939                         wake_up_interruptible(&opipe->wait);
1940                 kill_fasync(&opipe->fasync_readers, SIGIO, POLL_IN);
1941         }
1942         if (input_wakeup)
1943                 wakeup_pipe_writers(ipipe);
1944
1945         return ret;
1946 }
1947
1948 /*
1949  * Link contents of ipipe to opipe.
1950  */
1951 static int link_pipe(struct pipe_inode_info *ipipe,
1952                      struct pipe_inode_info *opipe,
1953                      size_t len, unsigned int flags)
1954 {
1955         struct pipe_buffer *ibuf, *obuf;
1956         int ret = 0, i = 0, nbuf;
1957
1958         /*
1959          * Potential ABBA deadlock, work around it by ordering lock
1960          * grabbing by pipe info address. Otherwise two different processes
1961          * could deadlock (one doing tee from A -> B, the other from B -> A).
1962          */
1963         pipe_double_lock(ipipe, opipe);
1964
1965         do {
1966                 if (!opipe->readers) {
1967                         send_sig(SIGPIPE, current, 0);
1968                         if (!ret)
1969                                 ret = -EPIPE;
1970                         break;
1971                 }
1972
1973                 /*
1974                  * If we have iterated all input buffers or ran out of
1975                  * output room, break.
1976                  */
1977                 if (i >= ipipe->nrbufs || opipe->nrbufs >= opipe->buffers)
1978                         break;
1979
1980                 ibuf = ipipe->bufs + ((ipipe->curbuf + i) & (ipipe->buffers-1));
1981                 nbuf = (opipe->curbuf + opipe->nrbufs) & (opipe->buffers - 1);
1982
1983                 /*
1984                  * Get a reference to this pipe buffer,
1985                  * so we can copy the contents over.
1986                  */
1987                 ibuf->ops->get(ipipe, ibuf);
1988
1989                 obuf = opipe->bufs + nbuf;
1990                 *obuf = *ibuf;
1991
1992                 /*
1993                  * Don't inherit the gift flag, we need to
1994                  * prevent multiple steals of this page.
1995                  */
1996                 obuf->flags &= ~PIPE_BUF_FLAG_GIFT;
1997
1998                 if (obuf->len > len)
1999                         obuf->len = len;
2000
2001                 opipe->nrbufs++;
2002                 ret += obuf->len;
2003                 len -= obuf->len;
2004                 i++;
2005         } while (len);
2006
2007         /*
2008          * return EAGAIN if we have the potential of some data in the
2009          * future, otherwise just return 0
2010          */
2011         if (!ret && ipipe->waiting_writers && (flags & SPLICE_F_NONBLOCK))
2012                 ret = -EAGAIN;
2013
2014         pipe_unlock(ipipe);
2015         pipe_unlock(opipe);
2016
2017         /*
2018          * If we put data in the output pipe, wakeup any potential readers.
2019          */
2020         if (ret > 0) {
2021                 smp_mb();
2022                 if (waitqueue_active(&opipe->wait))
2023                         wake_up_interruptible(&opipe->wait);
2024                 kill_fasync(&opipe->fasync_readers, SIGIO, POLL_IN);
2025         }
2026
2027         return ret;
2028 }
2029
2030 /*
2031  * This is a tee(1) implementation that works on pipes. It doesn't copy
2032  * any data, it simply references the 'in' pages on the 'out' pipe.
2033  * The 'flags' used are the SPLICE_F_* variants, currently the only
2034  * applicable one is SPLICE_F_NONBLOCK.
2035  */
2036 static long do_tee(struct file *in, struct file *out, size_t len,
2037                    unsigned int flags)
2038 {
2039         struct pipe_inode_info *ipipe = pipe_info(in->f_path.dentry->d_inode);
2040         struct pipe_inode_info *opipe = pipe_info(out->f_path.dentry->d_inode);
2041         int ret = -EINVAL;
2042
2043         /*
2044          * Duplicate the contents of ipipe to opipe without actually
2045          * copying the data.
2046          */
2047         if (ipipe && opipe && ipipe != opipe) {
2048                 /*
2049                  * Keep going, unless we encounter an error. The ipipe/opipe
2050                  * ordering doesn't really matter.
2051                  */
2052                 ret = ipipe_prep(ipipe, flags);
2053                 if (!ret) {
2054                         ret = opipe_prep(opipe, flags);
2055                         if (!ret)
2056                                 ret = link_pipe(ipipe, opipe, len, flags);
2057                 }
2058         }
2059
2060         return ret;
2061 }
2062
2063 SYSCALL_DEFINE4(tee, int, fdin, int, fdout, size_t, len, unsigned int, flags)
2064 {
2065         struct file *in;
2066         int error, fput_in;
2067
2068         if (unlikely(!len))
2069                 return 0;
2070
2071         error = -EBADF;
2072         in = fget_light(fdin, &fput_in);
2073         if (in) {
2074                 if (in->f_mode & FMODE_READ) {
2075                         int fput_out;
2076                         struct file *out = fget_light(fdout, &fput_out);
2077
2078                         if (out) {
2079                                 if (out->f_mode & FMODE_WRITE)
2080                                         error = do_tee(in, out, len, flags);
2081                                 fput_light(out, fput_out);
2082                         }
2083                 }
2084                 fput_light(in, fput_in);
2085         }
2086
2087         return error;
2088 }