GFS2: Improve statfs and quota usability
[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
34 /*
35  * Attempt to steal a page from a pipe buffer. This should perhaps go into
36  * a vm helper function, it's already simplified quite a bit by the
37  * addition of remove_mapping(). If success is returned, the caller may
38  * attempt to reuse this page for another destination.
39  */
40 static int page_cache_pipe_buf_steal(struct pipe_inode_info *pipe,
41                                      struct pipe_buffer *buf)
42 {
43         struct page *page = buf->page;
44         struct address_space *mapping;
45
46         lock_page(page);
47
48         mapping = page_mapping(page);
49         if (mapping) {
50                 WARN_ON(!PageUptodate(page));
51
52                 /*
53                  * At least for ext2 with nobh option, we need to wait on
54                  * writeback completing on this page, since we'll remove it
55                  * from the pagecache.  Otherwise truncate wont wait on the
56                  * page, allowing the disk blocks to be reused by someone else
57                  * before we actually wrote our data to them. fs corruption
58                  * ensues.
59                  */
60                 wait_on_page_writeback(page);
61
62                 if (page_has_private(page) &&
63                     !try_to_release_page(page, GFP_KERNEL))
64                         goto out_unlock;
65
66                 /*
67                  * If we succeeded in removing the mapping, set LRU flag
68                  * and return good.
69                  */
70                 if (remove_mapping(mapping, page)) {
71                         buf->flags |= PIPE_BUF_FLAG_LRU;
72                         return 0;
73                 }
74         }
75
76         /*
77          * Raced with truncate or failed to remove page from current
78          * address space, unlock and return failure.
79          */
80 out_unlock:
81         unlock_page(page);
82         return 1;
83 }
84
85 static void page_cache_pipe_buf_release(struct pipe_inode_info *pipe,
86                                         struct pipe_buffer *buf)
87 {
88         page_cache_release(buf->page);
89         buf->flags &= ~PIPE_BUF_FLAG_LRU;
90 }
91
92 /*
93  * Check whether the contents of buf is OK to access. Since the content
94  * is a page cache page, IO may be in flight.
95  */
96 static int page_cache_pipe_buf_confirm(struct pipe_inode_info *pipe,
97                                        struct pipe_buffer *buf)
98 {
99         struct page *page = buf->page;
100         int err;
101
102         if (!PageUptodate(page)) {
103                 lock_page(page);
104
105                 /*
106                  * Page got truncated/unhashed. This will cause a 0-byte
107                  * splice, if this is the first page.
108                  */
109                 if (!page->mapping) {
110                         err = -ENODATA;
111                         goto error;
112                 }
113
114                 /*
115                  * Uh oh, read-error from disk.
116                  */
117                 if (!PageUptodate(page)) {
118                         err = -EIO;
119                         goto error;
120                 }
121
122                 /*
123                  * Page is ok afterall, we are done.
124                  */
125                 unlock_page(page);
126         }
127
128         return 0;
129 error:
130         unlock_page(page);
131         return err;
132 }
133
134 static const struct pipe_buf_operations page_cache_pipe_buf_ops = {
135         .can_merge = 0,
136         .map = generic_pipe_buf_map,
137         .unmap = generic_pipe_buf_unmap,
138         .confirm = page_cache_pipe_buf_confirm,
139         .release = page_cache_pipe_buf_release,
140         .steal = page_cache_pipe_buf_steal,
141         .get = generic_pipe_buf_get,
142 };
143
144 static int user_page_pipe_buf_steal(struct pipe_inode_info *pipe,
145                                     struct pipe_buffer *buf)
146 {
147         if (!(buf->flags & PIPE_BUF_FLAG_GIFT))
148                 return 1;
149
150         buf->flags |= PIPE_BUF_FLAG_LRU;
151         return generic_pipe_buf_steal(pipe, buf);
152 }
153
154 static const struct pipe_buf_operations user_page_pipe_buf_ops = {
155         .can_merge = 0,
156         .map = generic_pipe_buf_map,
157         .unmap = generic_pipe_buf_unmap,
158         .confirm = generic_pipe_buf_confirm,
159         .release = page_cache_pipe_buf_release,
160         .steal = user_page_pipe_buf_steal,
161         .get = generic_pipe_buf_get,
162 };
163
164 /**
165  * splice_to_pipe - fill passed data into a pipe
166  * @pipe:       pipe to fill
167  * @spd:        data to fill
168  *
169  * Description:
170  *    @spd contains a map of pages and len/offset tuples, along with
171  *    the struct pipe_buf_operations associated with these pages. This
172  *    function will link that data to the pipe.
173  *
174  */
175 ssize_t splice_to_pipe(struct pipe_inode_info *pipe,
176                        struct splice_pipe_desc *spd)
177 {
178         unsigned int spd_pages = spd->nr_pages;
179         int ret, do_wakeup, page_nr;
180
181         ret = 0;
182         do_wakeup = 0;
183         page_nr = 0;
184
185         pipe_lock(pipe);
186
187         for (;;) {
188                 if (!pipe->readers) {
189                         send_sig(SIGPIPE, current, 0);
190                         if (!ret)
191                                 ret = -EPIPE;
192                         break;
193                 }
194
195                 if (pipe->nrbufs < PIPE_BUFFERS) {
196                         int newbuf = (pipe->curbuf + pipe->nrbufs) & (PIPE_BUFFERS - 1);
197                         struct pipe_buffer *buf = pipe->bufs + newbuf;
198
199                         buf->page = spd->pages[page_nr];
200                         buf->offset = spd->partial[page_nr].offset;
201                         buf->len = spd->partial[page_nr].len;
202                         buf->private = spd->partial[page_nr].private;
203                         buf->ops = spd->ops;
204                         if (spd->flags & SPLICE_F_GIFT)
205                                 buf->flags |= PIPE_BUF_FLAG_GIFT;
206
207                         pipe->nrbufs++;
208                         page_nr++;
209                         ret += buf->len;
210
211                         if (pipe->inode)
212                                 do_wakeup = 1;
213
214                         if (!--spd->nr_pages)
215                                 break;
216                         if (pipe->nrbufs < PIPE_BUFFERS)
217                                 continue;
218
219                         break;
220                 }
221
222                 if (spd->flags & SPLICE_F_NONBLOCK) {
223                         if (!ret)
224                                 ret = -EAGAIN;
225                         break;
226                 }
227
228                 if (signal_pending(current)) {
229                         if (!ret)
230                                 ret = -ERESTARTSYS;
231                         break;
232                 }
233
234                 if (do_wakeup) {
235                         smp_mb();
236                         if (waitqueue_active(&pipe->wait))
237                                 wake_up_interruptible_sync(&pipe->wait);
238                         kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
239                         do_wakeup = 0;
240                 }
241
242                 pipe->waiting_writers++;
243                 pipe_wait(pipe);
244                 pipe->waiting_writers--;
245         }
246
247         pipe_unlock(pipe);
248
249         if (do_wakeup) {
250                 smp_mb();
251                 if (waitqueue_active(&pipe->wait))
252                         wake_up_interruptible(&pipe->wait);
253                 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
254         }
255
256         while (page_nr < spd_pages)
257                 spd->spd_release(spd, page_nr++);
258
259         return ret;
260 }
261
262 static void spd_release_page(struct splice_pipe_desc *spd, unsigned int i)
263 {
264         page_cache_release(spd->pages[i]);
265 }
266
267 static int
268 __generic_file_splice_read(struct file *in, loff_t *ppos,
269                            struct pipe_inode_info *pipe, size_t len,
270                            unsigned int flags)
271 {
272         struct address_space *mapping = in->f_mapping;
273         unsigned int loff, nr_pages, req_pages;
274         struct page *pages[PIPE_BUFFERS];
275         struct partial_page partial[PIPE_BUFFERS];
276         struct page *page;
277         pgoff_t index, end_index;
278         loff_t isize;
279         int error, page_nr;
280         struct splice_pipe_desc spd = {
281                 .pages = pages,
282                 .partial = partial,
283                 .flags = flags,
284                 .ops = &page_cache_pipe_buf_ops,
285                 .spd_release = spd_release_page,
286         };
287
288         index = *ppos >> PAGE_CACHE_SHIFT;
289         loff = *ppos & ~PAGE_CACHE_MASK;
290         req_pages = (len + loff + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
291         nr_pages = min(req_pages, (unsigned)PIPE_BUFFERS);
292
293         /*
294          * Lookup the (hopefully) full range of pages we need.
295          */
296         spd.nr_pages = find_get_pages_contig(mapping, index, nr_pages, pages);
297         index += spd.nr_pages;
298
299         /*
300          * If find_get_pages_contig() returned fewer pages than we needed,
301          * readahead/allocate the rest and fill in the holes.
302          */
303         if (spd.nr_pages < nr_pages)
304                 page_cache_sync_readahead(mapping, &in->f_ra, in,
305                                 index, req_pages - spd.nr_pages);
306
307         error = 0;
308         while (spd.nr_pages < nr_pages) {
309                 /*
310                  * Page could be there, find_get_pages_contig() breaks on
311                  * the first hole.
312                  */
313                 page = find_get_page(mapping, index);
314                 if (!page) {
315                         /*
316                          * page didn't exist, allocate one.
317                          */
318                         page = page_cache_alloc_cold(mapping);
319                         if (!page)
320                                 break;
321
322                         error = add_to_page_cache_lru(page, mapping, index,
323                                                 mapping_gfp_mask(mapping));
324                         if (unlikely(error)) {
325                                 page_cache_release(page);
326                                 if (error == -EEXIST)
327                                         continue;
328                                 break;
329                         }
330                         /*
331                          * add_to_page_cache() locks the page, unlock it
332                          * to avoid convoluting the logic below even more.
333                          */
334                         unlock_page(page);
335                 }
336
337                 pages[spd.nr_pages++] = page;
338                 index++;
339         }
340
341         /*
342          * Now loop over the map and see if we need to start IO on any
343          * pages, fill in the partial map, etc.
344          */
345         index = *ppos >> PAGE_CACHE_SHIFT;
346         nr_pages = spd.nr_pages;
347         spd.nr_pages = 0;
348         for (page_nr = 0; page_nr < nr_pages; page_nr++) {
349                 unsigned int this_len;
350
351                 if (!len)
352                         break;
353
354                 /*
355                  * this_len is the max we'll use from this page
356                  */
357                 this_len = min_t(unsigned long, len, PAGE_CACHE_SIZE - loff);
358                 page = pages[page_nr];
359
360                 if (PageReadahead(page))
361                         page_cache_async_readahead(mapping, &in->f_ra, in,
362                                         page, index, req_pages - page_nr);
363
364                 /*
365                  * If the page isn't uptodate, we may need to start io on it
366                  */
367                 if (!PageUptodate(page)) {
368                         /*
369                          * If in nonblock mode then dont block on waiting
370                          * for an in-flight io page
371                          */
372                         if (flags & SPLICE_F_NONBLOCK) {
373                                 if (!trylock_page(page)) {
374                                         error = -EAGAIN;
375                                         break;
376                                 }
377                         } else
378                                 lock_page(page);
379
380                         /*
381                          * Page was truncated, or invalidated by the
382                          * filesystem.  Redo the find/create, but this time the
383                          * page is kept locked, so there's no chance of another
384                          * race with truncate/invalidate.
385                          */
386                         if (!page->mapping) {
387                                 unlock_page(page);
388                                 page = find_or_create_page(mapping, index,
389                                                 mapping_gfp_mask(mapping));
390
391                                 if (!page) {
392                                         error = -ENOMEM;
393                                         break;
394                                 }
395                                 page_cache_release(pages[page_nr]);
396                                 pages[page_nr] = page;
397                         }
398                         /*
399                          * page was already under io and is now done, great
400                          */
401                         if (PageUptodate(page)) {
402                                 unlock_page(page);
403                                 goto fill_it;
404                         }
405
406                         /*
407                          * need to read in the page
408                          */
409                         error = mapping->a_ops->readpage(in, page);
410                         if (unlikely(error)) {
411                                 /*
412                                  * We really should re-lookup the page here,
413                                  * but it complicates things a lot. Instead
414                                  * lets just do what we already stored, and
415                                  * we'll get it the next time we are called.
416                                  */
417                                 if (error == AOP_TRUNCATED_PAGE)
418                                         error = 0;
419
420                                 break;
421                         }
422                 }
423 fill_it:
424                 /*
425                  * i_size must be checked after PageUptodate.
426                  */
427                 isize = i_size_read(mapping->host);
428                 end_index = (isize - 1) >> PAGE_CACHE_SHIFT;
429                 if (unlikely(!isize || index > end_index))
430                         break;
431
432                 /*
433                  * if this is the last page, see if we need to shrink
434                  * the length and stop
435                  */
436                 if (end_index == index) {
437                         unsigned int plen;
438
439                         /*
440                          * max good bytes in this page
441                          */
442                         plen = ((isize - 1) & ~PAGE_CACHE_MASK) + 1;
443                         if (plen <= loff)
444                                 break;
445
446                         /*
447                          * force quit after adding this page
448                          */
449                         this_len = min(this_len, plen - loff);
450                         len = this_len;
451                 }
452
453                 partial[page_nr].offset = loff;
454                 partial[page_nr].len = this_len;
455                 len -= this_len;
456                 loff = 0;
457                 spd.nr_pages++;
458                 index++;
459         }
460
461         /*
462          * Release any pages at the end, if we quit early. 'page_nr' is how far
463          * we got, 'nr_pages' is how many pages are in the map.
464          */
465         while (page_nr < nr_pages)
466                 page_cache_release(pages[page_nr++]);
467         in->f_ra.prev_pos = (loff_t)index << PAGE_CACHE_SHIFT;
468
469         if (spd.nr_pages)
470                 return splice_to_pipe(pipe, &spd);
471
472         return error;
473 }
474
475 /**
476  * generic_file_splice_read - splice data from file to a pipe
477  * @in:         file to splice from
478  * @ppos:       position in @in
479  * @pipe:       pipe to splice to
480  * @len:        number of bytes to splice
481  * @flags:      splice modifier flags
482  *
483  * Description:
484  *    Will read pages from given file and fill them into a pipe. Can be
485  *    used as long as the address_space operations for the source implements
486  *    a readpage() hook.
487  *
488  */
489 ssize_t generic_file_splice_read(struct file *in, loff_t *ppos,
490                                  struct pipe_inode_info *pipe, size_t len,
491                                  unsigned int flags)
492 {
493         loff_t isize, left;
494         int ret;
495
496         isize = i_size_read(in->f_mapping->host);
497         if (unlikely(*ppos >= isize))
498                 return 0;
499
500         left = isize - *ppos;
501         if (unlikely(left < len))
502                 len = left;
503
504         ret = __generic_file_splice_read(in, ppos, pipe, len, flags);
505         if (ret > 0) {
506                 *ppos += ret;
507                 file_accessed(in);
508         }
509
510         return ret;
511 }
512 EXPORT_SYMBOL(generic_file_splice_read);
513
514 static const struct pipe_buf_operations default_pipe_buf_ops = {
515         .can_merge = 0,
516         .map = generic_pipe_buf_map,
517         .unmap = generic_pipe_buf_unmap,
518         .confirm = generic_pipe_buf_confirm,
519         .release = generic_pipe_buf_release,
520         .steal = generic_pipe_buf_steal,
521         .get = generic_pipe_buf_get,
522 };
523
524 static ssize_t kernel_readv(struct file *file, const struct iovec *vec,
525                             unsigned long vlen, loff_t offset)
526 {
527         mm_segment_t old_fs;
528         loff_t pos = offset;
529         ssize_t res;
530
531         old_fs = get_fs();
532         set_fs(get_ds());
533         /* The cast to a user pointer is valid due to the set_fs() */
534         res = vfs_readv(file, (const struct iovec __user *)vec, vlen, &pos);
535         set_fs(old_fs);
536
537         return res;
538 }
539
540 static ssize_t kernel_write(struct file *file, const char *buf, size_t count,
541                             loff_t pos)
542 {
543         mm_segment_t old_fs;
544         ssize_t res;
545
546         old_fs = get_fs();
547         set_fs(get_ds());
548         /* The cast to a user pointer is valid due to the set_fs() */
549         res = vfs_write(file, (const char __user *)buf, count, &pos);
550         set_fs(old_fs);
551
552         return res;
553 }
554
555 ssize_t default_file_splice_read(struct file *in, loff_t *ppos,
556                                  struct pipe_inode_info *pipe, size_t len,
557                                  unsigned int flags)
558 {
559         unsigned int nr_pages;
560         unsigned int nr_freed;
561         size_t offset;
562         struct page *pages[PIPE_BUFFERS];
563         struct partial_page partial[PIPE_BUFFERS];
564         struct iovec vec[PIPE_BUFFERS];
565         pgoff_t index;
566         ssize_t res;
567         size_t this_len;
568         int error;
569         int i;
570         struct splice_pipe_desc spd = {
571                 .pages = pages,
572                 .partial = partial,
573                 .flags = flags,
574                 .ops = &default_pipe_buf_ops,
575                 .spd_release = spd_release_page,
576         };
577
578         index = *ppos >> PAGE_CACHE_SHIFT;
579         offset = *ppos & ~PAGE_CACHE_MASK;
580         nr_pages = (len + offset + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
581
582         for (i = 0; i < nr_pages && i < PIPE_BUFFERS && len; i++) {
583                 struct page *page;
584
585                 page = alloc_page(GFP_USER);
586                 error = -ENOMEM;
587                 if (!page)
588                         goto err;
589
590                 this_len = min_t(size_t, len, PAGE_CACHE_SIZE - offset);
591                 vec[i].iov_base = (void __user *) page_address(page);
592                 vec[i].iov_len = this_len;
593                 pages[i] = page;
594                 spd.nr_pages++;
595                 len -= this_len;
596                 offset = 0;
597         }
598
599         res = kernel_readv(in, vec, spd.nr_pages, *ppos);
600         if (res < 0) {
601                 error = res;
602                 goto err;
603         }
604
605         error = 0;
606         if (!res)
607                 goto err;
608
609         nr_freed = 0;
610         for (i = 0; i < spd.nr_pages; i++) {
611                 this_len = min_t(size_t, vec[i].iov_len, res);
612                 partial[i].offset = 0;
613                 partial[i].len = this_len;
614                 if (!this_len) {
615                         __free_page(pages[i]);
616                         pages[i] = NULL;
617                         nr_freed++;
618                 }
619                 res -= this_len;
620         }
621         spd.nr_pages -= nr_freed;
622
623         res = splice_to_pipe(pipe, &spd);
624         if (res > 0)
625                 *ppos += res;
626
627         return res;
628
629 err:
630         for (i = 0; i < spd.nr_pages; i++)
631                 __free_page(pages[i]);
632
633         return error;
634 }
635 EXPORT_SYMBOL(default_file_splice_read);
636
637 /*
638  * Send 'sd->len' bytes to socket from 'sd->file' at position 'sd->pos'
639  * using sendpage(). Return the number of bytes sent.
640  */
641 static int pipe_to_sendpage(struct pipe_inode_info *pipe,
642                             struct pipe_buffer *buf, struct splice_desc *sd)
643 {
644         struct file *file = sd->u.file;
645         loff_t pos = sd->pos;
646         int ret, more;
647
648         ret = buf->ops->confirm(pipe, buf);
649         if (!ret) {
650                 more = (sd->flags & SPLICE_F_MORE) || sd->len < sd->total_len;
651
652                 ret = file->f_op->sendpage(file, buf->page, buf->offset,
653                                            sd->len, &pos, more);
654         }
655
656         return ret;
657 }
658
659 /*
660  * This is a little more tricky than the file -> pipe splicing. There are
661  * basically three cases:
662  *
663  *      - Destination page already exists in the address space and there
664  *        are users of it. For that case we have no other option that
665  *        copying the data. Tough luck.
666  *      - Destination page already exists in the address space, but there
667  *        are no users of it. Make sure it's uptodate, then drop it. Fall
668  *        through to last case.
669  *      - Destination page does not exist, we can add the pipe page to
670  *        the page cache and avoid the copy.
671  *
672  * If asked to move pages to the output file (SPLICE_F_MOVE is set in
673  * sd->flags), we attempt to migrate pages from the pipe to the output
674  * file address space page cache. This is possible if no one else has
675  * the pipe page referenced outside of the pipe and page cache. If
676  * SPLICE_F_MOVE isn't set, or we cannot move the page, we simply create
677  * a new page in the output file page cache and fill/dirty that.
678  */
679 int pipe_to_file(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
680                  struct splice_desc *sd)
681 {
682         struct file *file = sd->u.file;
683         struct address_space *mapping = file->f_mapping;
684         unsigned int offset, this_len;
685         struct page *page;
686         void *fsdata;
687         int ret;
688
689         /*
690          * make sure the data in this buffer is uptodate
691          */
692         ret = buf->ops->confirm(pipe, buf);
693         if (unlikely(ret))
694                 return ret;
695
696         offset = sd->pos & ~PAGE_CACHE_MASK;
697
698         this_len = sd->len;
699         if (this_len + offset > PAGE_CACHE_SIZE)
700                 this_len = PAGE_CACHE_SIZE - offset;
701
702         ret = pagecache_write_begin(file, mapping, sd->pos, this_len,
703                                 AOP_FLAG_UNINTERRUPTIBLE, &page, &fsdata);
704         if (unlikely(ret))
705                 goto out;
706
707         if (buf->page != page) {
708                 /*
709                  * Careful, ->map() uses KM_USER0!
710                  */
711                 char *src = buf->ops->map(pipe, buf, 1);
712                 char *dst = kmap_atomic(page, KM_USER1);
713
714                 memcpy(dst + offset, src + buf->offset, this_len);
715                 flush_dcache_page(page);
716                 kunmap_atomic(dst, KM_USER1);
717                 buf->ops->unmap(pipe, buf, src);
718         }
719         ret = pagecache_write_end(file, mapping, sd->pos, this_len, this_len,
720                                 page, fsdata);
721 out:
722         return ret;
723 }
724 EXPORT_SYMBOL(pipe_to_file);
725
726 static void wakeup_pipe_writers(struct pipe_inode_info *pipe)
727 {
728         smp_mb();
729         if (waitqueue_active(&pipe->wait))
730                 wake_up_interruptible(&pipe->wait);
731         kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
732 }
733
734 /**
735  * splice_from_pipe_feed - feed available data from a pipe to a file
736  * @pipe:       pipe to splice from
737  * @sd:         information to @actor
738  * @actor:      handler that splices the data
739  *
740  * Description:
741  *    This function loops over the pipe and calls @actor to do the
742  *    actual moving of a single struct pipe_buffer to the desired
743  *    destination.  It returns when there's no more buffers left in
744  *    the pipe or if the requested number of bytes (@sd->total_len)
745  *    have been copied.  It returns a positive number (one) if the
746  *    pipe needs to be filled with more data, zero if the required
747  *    number of bytes have been copied and -errno on error.
748  *
749  *    This, together with splice_from_pipe_{begin,end,next}, may be
750  *    used to implement the functionality of __splice_from_pipe() when
751  *    locking is required around copying the pipe buffers to the
752  *    destination.
753  */
754 int splice_from_pipe_feed(struct pipe_inode_info *pipe, struct splice_desc *sd,
755                           splice_actor *actor)
756 {
757         int ret;
758
759         while (pipe->nrbufs) {
760                 struct pipe_buffer *buf = pipe->bufs + pipe->curbuf;
761                 const struct pipe_buf_operations *ops = buf->ops;
762
763                 sd->len = buf->len;
764                 if (sd->len > sd->total_len)
765                         sd->len = sd->total_len;
766
767                 ret = actor(pipe, buf, sd);
768                 if (ret <= 0) {
769                         if (ret == -ENODATA)
770                                 ret = 0;
771                         return ret;
772                 }
773                 buf->offset += ret;
774                 buf->len -= ret;
775
776                 sd->num_spliced += ret;
777                 sd->len -= ret;
778                 sd->pos += ret;
779                 sd->total_len -= ret;
780
781                 if (!buf->len) {
782                         buf->ops = NULL;
783                         ops->release(pipe, buf);
784                         pipe->curbuf = (pipe->curbuf + 1) & (PIPE_BUFFERS - 1);
785                         pipe->nrbufs--;
786                         if (pipe->inode)
787                                 sd->need_wakeup = true;
788                 }
789
790                 if (!sd->total_len)
791                         return 0;
792         }
793
794         return 1;
795 }
796 EXPORT_SYMBOL(splice_from_pipe_feed);
797
798 /**
799  * splice_from_pipe_next - wait for some data to splice from
800  * @pipe:       pipe to splice from
801  * @sd:         information about the splice operation
802  *
803  * Description:
804  *    This function will wait for some data and return a positive
805  *    value (one) if pipe buffers are available.  It will return zero
806  *    or -errno if no more data needs to be spliced.
807  */
808 int splice_from_pipe_next(struct pipe_inode_info *pipe, struct splice_desc *sd)
809 {
810         while (!pipe->nrbufs) {
811                 if (!pipe->writers)
812                         return 0;
813
814                 if (!pipe->waiting_writers && sd->num_spliced)
815                         return 0;
816
817                 if (sd->flags & SPLICE_F_NONBLOCK)
818                         return -EAGAIN;
819
820                 if (signal_pending(current))
821                         return -ERESTARTSYS;
822
823                 if (sd->need_wakeup) {
824                         wakeup_pipe_writers(pipe);
825                         sd->need_wakeup = false;
826                 }
827
828                 pipe_wait(pipe);
829         }
830
831         return 1;
832 }
833 EXPORT_SYMBOL(splice_from_pipe_next);
834
835 /**
836  * splice_from_pipe_begin - start splicing from pipe
837  * @sd:         information about the splice operation
838  *
839  * Description:
840  *    This function should be called before a loop containing
841  *    splice_from_pipe_next() and splice_from_pipe_feed() to
842  *    initialize the necessary fields of @sd.
843  */
844 void splice_from_pipe_begin(struct splice_desc *sd)
845 {
846         sd->num_spliced = 0;
847         sd->need_wakeup = false;
848 }
849 EXPORT_SYMBOL(splice_from_pipe_begin);
850
851 /**
852  * splice_from_pipe_end - finish splicing from pipe
853  * @pipe:       pipe to splice from
854  * @sd:         information about the splice operation
855  *
856  * Description:
857  *    This function will wake up pipe writers if necessary.  It should
858  *    be called after a loop containing splice_from_pipe_next() and
859  *    splice_from_pipe_feed().
860  */
861 void splice_from_pipe_end(struct pipe_inode_info *pipe, struct splice_desc *sd)
862 {
863         if (sd->need_wakeup)
864                 wakeup_pipe_writers(pipe);
865 }
866 EXPORT_SYMBOL(splice_from_pipe_end);
867
868 /**
869  * __splice_from_pipe - splice data from a pipe to given actor
870  * @pipe:       pipe to splice from
871  * @sd:         information to @actor
872  * @actor:      handler that splices the data
873  *
874  * Description:
875  *    This function does little more than loop over the pipe and call
876  *    @actor to do the actual moving of a single struct pipe_buffer to
877  *    the desired destination. See pipe_to_file, pipe_to_sendpage, or
878  *    pipe_to_user.
879  *
880  */
881 ssize_t __splice_from_pipe(struct pipe_inode_info *pipe, struct splice_desc *sd,
882                            splice_actor *actor)
883 {
884         int ret;
885
886         splice_from_pipe_begin(sd);
887         do {
888                 ret = splice_from_pipe_next(pipe, sd);
889                 if (ret > 0)
890                         ret = splice_from_pipe_feed(pipe, sd, actor);
891         } while (ret > 0);
892         splice_from_pipe_end(pipe, sd);
893
894         return sd->num_spliced ? sd->num_spliced : ret;
895 }
896 EXPORT_SYMBOL(__splice_from_pipe);
897
898 /**
899  * splice_from_pipe - splice data from a pipe to a file
900  * @pipe:       pipe to splice from
901  * @out:        file to splice to
902  * @ppos:       position in @out
903  * @len:        how many bytes to splice
904  * @flags:      splice modifier flags
905  * @actor:      handler that splices the data
906  *
907  * Description:
908  *    See __splice_from_pipe. This function locks the pipe inode,
909  *    otherwise it's identical to __splice_from_pipe().
910  *
911  */
912 ssize_t splice_from_pipe(struct pipe_inode_info *pipe, struct file *out,
913                          loff_t *ppos, size_t len, unsigned int flags,
914                          splice_actor *actor)
915 {
916         ssize_t ret;
917         struct splice_desc sd = {
918                 .total_len = len,
919                 .flags = flags,
920                 .pos = *ppos,
921                 .u.file = out,
922         };
923
924         pipe_lock(pipe);
925         ret = __splice_from_pipe(pipe, &sd, actor);
926         pipe_unlock(pipe);
927
928         return ret;
929 }
930
931 /**
932  * generic_file_splice_write - splice data from a pipe to a file
933  * @pipe:       pipe info
934  * @out:        file to write to
935  * @ppos:       position in @out
936  * @len:        number of bytes to splice
937  * @flags:      splice modifier flags
938  *
939  * Description:
940  *    Will either move or copy pages (determined by @flags options) from
941  *    the given pipe inode to the given file.
942  *
943  */
944 ssize_t
945 generic_file_splice_write(struct pipe_inode_info *pipe, struct file *out,
946                           loff_t *ppos, size_t len, unsigned int flags)
947 {
948         struct address_space *mapping = out->f_mapping;
949         struct inode *inode = mapping->host;
950         struct splice_desc sd = {
951                 .total_len = len,
952                 .flags = flags,
953                 .pos = *ppos,
954                 .u.file = out,
955         };
956         ssize_t ret;
957
958         pipe_lock(pipe);
959
960         splice_from_pipe_begin(&sd);
961         do {
962                 ret = splice_from_pipe_next(pipe, &sd);
963                 if (ret <= 0)
964                         break;
965
966                 mutex_lock_nested(&inode->i_mutex, I_MUTEX_CHILD);
967                 ret = file_remove_suid(out);
968                 if (!ret) {
969                         file_update_time(out);
970                         ret = splice_from_pipe_feed(pipe, &sd, pipe_to_file);
971                 }
972                 mutex_unlock(&inode->i_mutex);
973         } while (ret > 0);
974         splice_from_pipe_end(pipe, &sd);
975
976         pipe_unlock(pipe);
977
978         if (sd.num_spliced)
979                 ret = sd.num_spliced;
980
981         if (ret > 0) {
982                 unsigned long nr_pages;
983                 int err;
984
985                 nr_pages = (ret + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
986
987                 err = generic_write_sync(out, *ppos, ret);
988                 if (err)
989                         ret = err;
990                 else
991                         *ppos += ret;
992                 balance_dirty_pages_ratelimited_nr(mapping, nr_pages);
993         }
994
995         return ret;
996 }
997
998 EXPORT_SYMBOL(generic_file_splice_write);
999
1000 static int write_pipe_buf(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
1001                           struct splice_desc *sd)
1002 {
1003         int ret;
1004         void *data;
1005
1006         ret = buf->ops->confirm(pipe, buf);
1007         if (ret)
1008                 return ret;
1009
1010         data = buf->ops->map(pipe, buf, 0);
1011         ret = kernel_write(sd->u.file, data + buf->offset, sd->len, sd->pos);
1012         buf->ops->unmap(pipe, buf, data);
1013
1014         return ret;
1015 }
1016
1017 static ssize_t default_file_splice_write(struct pipe_inode_info *pipe,
1018                                          struct file *out, loff_t *ppos,
1019                                          size_t len, unsigned int flags)
1020 {
1021         ssize_t ret;
1022
1023         ret = splice_from_pipe(pipe, out, ppos, len, flags, write_pipe_buf);
1024         if (ret > 0)
1025                 *ppos += ret;
1026
1027         return ret;
1028 }
1029
1030 /**
1031  * generic_splice_sendpage - splice data from a pipe to a socket
1032  * @pipe:       pipe to splice from
1033  * @out:        socket to write to
1034  * @ppos:       position in @out
1035  * @len:        number of bytes to splice
1036  * @flags:      splice modifier flags
1037  *
1038  * Description:
1039  *    Will send @len bytes from the pipe to a network socket. No data copying
1040  *    is involved.
1041  *
1042  */
1043 ssize_t generic_splice_sendpage(struct pipe_inode_info *pipe, struct file *out,
1044                                 loff_t *ppos, size_t len, unsigned int flags)
1045 {
1046         return splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_sendpage);
1047 }
1048
1049 EXPORT_SYMBOL(generic_splice_sendpage);
1050
1051 /*
1052  * Attempt to initiate a splice from pipe to file.
1053  */
1054 static long do_splice_from(struct pipe_inode_info *pipe, struct file *out,
1055                            loff_t *ppos, size_t len, unsigned int flags)
1056 {
1057         ssize_t (*splice_write)(struct pipe_inode_info *, struct file *,
1058                                 loff_t *, size_t, unsigned int);
1059         int ret;
1060
1061         if (unlikely(!(out->f_mode & FMODE_WRITE)))
1062                 return -EBADF;
1063
1064         if (unlikely(out->f_flags & O_APPEND))
1065                 return -EINVAL;
1066
1067         ret = rw_verify_area(WRITE, out, ppos, len);
1068         if (unlikely(ret < 0))
1069                 return ret;
1070
1071         splice_write = out->f_op->splice_write;
1072         if (!splice_write)
1073                 splice_write = default_file_splice_write;
1074
1075         return splice_write(pipe, out, ppos, len, flags);
1076 }
1077
1078 /*
1079  * Attempt to initiate a splice from a file to a pipe.
1080  */
1081 static long do_splice_to(struct file *in, loff_t *ppos,
1082                          struct pipe_inode_info *pipe, size_t len,
1083                          unsigned int flags)
1084 {
1085         ssize_t (*splice_read)(struct file *, loff_t *,
1086                                struct pipe_inode_info *, size_t, unsigned int);
1087         int ret;
1088
1089         if (unlikely(!(in->f_mode & FMODE_READ)))
1090                 return -EBADF;
1091
1092         ret = rw_verify_area(READ, in, ppos, len);
1093         if (unlikely(ret < 0))
1094                 return ret;
1095
1096         splice_read = in->f_op->splice_read;
1097         if (!splice_read)
1098                 splice_read = default_file_splice_read;
1099
1100         return splice_read(in, ppos, pipe, len, flags);
1101 }
1102
1103 /**
1104  * splice_direct_to_actor - splices data directly between two non-pipes
1105  * @in:         file to splice from
1106  * @sd:         actor information on where to splice to
1107  * @actor:      handles the data splicing
1108  *
1109  * Description:
1110  *    This is a special case helper to splice directly between two
1111  *    points, without requiring an explicit pipe. Internally an allocated
1112  *    pipe is cached in the process, and reused during the lifetime of
1113  *    that process.
1114  *
1115  */
1116 ssize_t splice_direct_to_actor(struct file *in, struct splice_desc *sd,
1117                                splice_direct_actor *actor)
1118 {
1119         struct pipe_inode_info *pipe;
1120         long ret, bytes;
1121         umode_t i_mode;
1122         size_t len;
1123         int i, flags;
1124
1125         /*
1126          * We require the input being a regular file, as we don't want to
1127          * randomly drop data for eg socket -> socket splicing. Use the
1128          * piped splicing for that!
1129          */
1130         i_mode = in->f_path.dentry->d_inode->i_mode;
1131         if (unlikely(!S_ISREG(i_mode) && !S_ISBLK(i_mode)))
1132                 return -EINVAL;
1133
1134         /*
1135          * neither in nor out is a pipe, setup an internal pipe attached to
1136          * 'out' and transfer the wanted data from 'in' to 'out' through that
1137          */
1138         pipe = current->splice_pipe;
1139         if (unlikely(!pipe)) {
1140                 pipe = alloc_pipe_info(NULL);
1141                 if (!pipe)
1142                         return -ENOMEM;
1143
1144                 /*
1145                  * We don't have an immediate reader, but we'll read the stuff
1146                  * out of the pipe right after the splice_to_pipe(). So set
1147                  * PIPE_READERS appropriately.
1148                  */
1149                 pipe->readers = 1;
1150
1151                 current->splice_pipe = pipe;
1152         }
1153
1154         /*
1155          * Do the splice.
1156          */
1157         ret = 0;
1158         bytes = 0;
1159         len = sd->total_len;
1160         flags = sd->flags;
1161
1162         /*
1163          * Don't block on output, we have to drain the direct pipe.
1164          */
1165         sd->flags &= ~SPLICE_F_NONBLOCK;
1166
1167         while (len) {
1168                 size_t read_len;
1169                 loff_t pos = sd->pos, prev_pos = pos;
1170
1171                 ret = do_splice_to(in, &pos, pipe, len, flags);
1172                 if (unlikely(ret <= 0))
1173                         goto out_release;
1174
1175                 read_len = ret;
1176                 sd->total_len = read_len;
1177
1178                 /*
1179                  * NOTE: nonblocking mode only applies to the input. We
1180                  * must not do the output in nonblocking mode as then we
1181                  * could get stuck data in the internal pipe:
1182                  */
1183                 ret = actor(pipe, sd);
1184                 if (unlikely(ret <= 0)) {
1185                         sd->pos = prev_pos;
1186                         goto out_release;
1187                 }
1188
1189                 bytes += ret;
1190                 len -= ret;
1191                 sd->pos = pos;
1192
1193                 if (ret < read_len) {
1194                         sd->pos = prev_pos + ret;
1195                         goto out_release;
1196                 }
1197         }
1198
1199 done:
1200         pipe->nrbufs = pipe->curbuf = 0;
1201         file_accessed(in);
1202         return bytes;
1203
1204 out_release:
1205         /*
1206          * If we did an incomplete transfer we must release
1207          * the pipe buffers in question:
1208          */
1209         for (i = 0; i < PIPE_BUFFERS; i++) {
1210                 struct pipe_buffer *buf = pipe->bufs + i;
1211
1212                 if (buf->ops) {
1213                         buf->ops->release(pipe, buf);
1214                         buf->ops = NULL;
1215                 }
1216         }
1217
1218         if (!bytes)
1219                 bytes = ret;
1220
1221         goto done;
1222 }
1223 EXPORT_SYMBOL(splice_direct_to_actor);
1224
1225 static int direct_splice_actor(struct pipe_inode_info *pipe,
1226                                struct splice_desc *sd)
1227 {
1228         struct file *file = sd->u.file;
1229
1230         return do_splice_from(pipe, file, &sd->pos, sd->total_len, sd->flags);
1231 }
1232
1233 /**
1234  * do_splice_direct - splices data directly between two files
1235  * @in:         file to splice from
1236  * @ppos:       input file offset
1237  * @out:        file to splice to
1238  * @len:        number of bytes to splice
1239  * @flags:      splice modifier flags
1240  *
1241  * Description:
1242  *    For use by do_sendfile(). splice can easily emulate sendfile, but
1243  *    doing it in the application would incur an extra system call
1244  *    (splice in + splice out, as compared to just sendfile()). So this helper
1245  *    can splice directly through a process-private pipe.
1246  *
1247  */
1248 long do_splice_direct(struct file *in, loff_t *ppos, struct file *out,
1249                       size_t len, unsigned int flags)
1250 {
1251         struct splice_desc sd = {
1252                 .len            = len,
1253                 .total_len      = len,
1254                 .flags          = flags,
1255                 .pos            = *ppos,
1256                 .u.file         = out,
1257         };
1258         long ret;
1259
1260         ret = splice_direct_to_actor(in, &sd, direct_splice_actor);
1261         if (ret > 0)
1262                 *ppos = sd.pos;
1263
1264         return ret;
1265 }
1266
1267 static int splice_pipe_to_pipe(struct pipe_inode_info *ipipe,
1268                                struct pipe_inode_info *opipe,
1269                                size_t len, unsigned int flags);
1270 /*
1271  * After the inode slimming patch, i_pipe/i_bdev/i_cdev share the same
1272  * location, so checking ->i_pipe is not enough to verify that this is a
1273  * pipe.
1274  */
1275 static inline struct pipe_inode_info *pipe_info(struct inode *inode)
1276 {
1277         if (S_ISFIFO(inode->i_mode))
1278                 return inode->i_pipe;
1279
1280         return NULL;
1281 }
1282
1283 /*
1284  * Determine where to splice to/from.
1285  */
1286 static long do_splice(struct file *in, loff_t __user *off_in,
1287                       struct file *out, loff_t __user *off_out,
1288                       size_t len, unsigned int flags)
1289 {
1290         struct pipe_inode_info *ipipe;
1291         struct pipe_inode_info *opipe;
1292         loff_t offset, *off;
1293         long ret;
1294
1295         ipipe = pipe_info(in->f_path.dentry->d_inode);
1296         opipe = pipe_info(out->f_path.dentry->d_inode);
1297
1298         if (ipipe && opipe) {
1299                 if (off_in || off_out)
1300                         return -ESPIPE;
1301
1302                 if (!(in->f_mode & FMODE_READ))
1303                         return -EBADF;
1304
1305                 if (!(out->f_mode & FMODE_WRITE))
1306                         return -EBADF;
1307
1308                 /* Splicing to self would be fun, but... */
1309                 if (ipipe == opipe)
1310                         return -EINVAL;
1311
1312                 return splice_pipe_to_pipe(ipipe, opipe, len, flags);
1313         }
1314
1315         if (ipipe) {
1316                 if (off_in)
1317                         return -ESPIPE;
1318                 if (off_out) {
1319                         if (out->f_op->llseek == no_llseek)
1320                                 return -EINVAL;
1321                         if (copy_from_user(&offset, off_out, sizeof(loff_t)))
1322                                 return -EFAULT;
1323                         off = &offset;
1324                 } else
1325                         off = &out->f_pos;
1326
1327                 ret = do_splice_from(ipipe, out, off, len, flags);
1328
1329                 if (off_out && copy_to_user(off_out, off, sizeof(loff_t)))
1330                         ret = -EFAULT;
1331
1332                 return ret;
1333         }
1334
1335         if (opipe) {
1336                 if (off_out)
1337                         return -ESPIPE;
1338                 if (off_in) {
1339                         if (in->f_op->llseek == no_llseek)
1340                                 return -EINVAL;
1341                         if (copy_from_user(&offset, off_in, sizeof(loff_t)))
1342                                 return -EFAULT;
1343                         off = &offset;
1344                 } else
1345                         off = &in->f_pos;
1346
1347                 ret = do_splice_to(in, off, opipe, len, flags);
1348
1349                 if (off_in && copy_to_user(off_in, off, sizeof(loff_t)))
1350                         ret = -EFAULT;
1351
1352                 return ret;
1353         }
1354
1355         return -EINVAL;
1356 }
1357
1358 /*
1359  * Map an iov into an array of pages and offset/length tupples. With the
1360  * partial_page structure, we can map several non-contiguous ranges into
1361  * our ones pages[] map instead of splitting that operation into pieces.
1362  * Could easily be exported as a generic helper for other users, in which
1363  * case one would probably want to add a 'max_nr_pages' parameter as well.
1364  */
1365 static int get_iovec_page_array(const struct iovec __user *iov,
1366                                 unsigned int nr_vecs, struct page **pages,
1367                                 struct partial_page *partial, int aligned)
1368 {
1369         int buffers = 0, error = 0;
1370
1371         while (nr_vecs) {
1372                 unsigned long off, npages;
1373                 struct iovec entry;
1374                 void __user *base;
1375                 size_t len;
1376                 int i;
1377
1378                 error = -EFAULT;
1379                 if (copy_from_user(&entry, iov, sizeof(entry)))
1380                         break;
1381
1382                 base = entry.iov_base;
1383                 len = entry.iov_len;
1384
1385                 /*
1386                  * Sanity check this iovec. 0 read succeeds.
1387                  */
1388                 error = 0;
1389                 if (unlikely(!len))
1390                         break;
1391                 error = -EFAULT;
1392                 if (!access_ok(VERIFY_READ, base, len))
1393                         break;
1394
1395                 /*
1396                  * Get this base offset and number of pages, then map
1397                  * in the user pages.
1398                  */
1399                 off = (unsigned long) base & ~PAGE_MASK;
1400
1401                 /*
1402                  * If asked for alignment, the offset must be zero and the
1403                  * length a multiple of the PAGE_SIZE.
1404                  */
1405                 error = -EINVAL;
1406                 if (aligned && (off || len & ~PAGE_MASK))
1407                         break;
1408
1409                 npages = (off + len + PAGE_SIZE - 1) >> PAGE_SHIFT;
1410                 if (npages > PIPE_BUFFERS - buffers)
1411                         npages = PIPE_BUFFERS - buffers;
1412
1413                 error = get_user_pages_fast((unsigned long)base, npages,
1414                                         0, &pages[buffers]);
1415
1416                 if (unlikely(error <= 0))
1417                         break;
1418
1419                 /*
1420                  * Fill this contiguous range into the partial page map.
1421                  */
1422                 for (i = 0; i < error; i++) {
1423                         const int plen = min_t(size_t, len, PAGE_SIZE - off);
1424
1425                         partial[buffers].offset = off;
1426                         partial[buffers].len = plen;
1427
1428                         off = 0;
1429                         len -= plen;
1430                         buffers++;
1431                 }
1432
1433                 /*
1434                  * We didn't complete this iov, stop here since it probably
1435                  * means we have to move some of this into a pipe to
1436                  * be able to continue.
1437                  */
1438                 if (len)
1439                         break;
1440
1441                 /*
1442                  * Don't continue if we mapped fewer pages than we asked for,
1443                  * or if we mapped the max number of pages that we have
1444                  * room for.
1445                  */
1446                 if (error < npages || buffers == PIPE_BUFFERS)
1447                         break;
1448
1449                 nr_vecs--;
1450                 iov++;
1451         }
1452
1453         if (buffers)
1454                 return buffers;
1455
1456         return error;
1457 }
1458
1459 static int pipe_to_user(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
1460                         struct splice_desc *sd)
1461 {
1462         char *src;
1463         int ret;
1464
1465         ret = buf->ops->confirm(pipe, buf);
1466         if (unlikely(ret))
1467                 return ret;
1468
1469         /*
1470          * See if we can use the atomic maps, by prefaulting in the
1471          * pages and doing an atomic copy
1472          */
1473         if (!fault_in_pages_writeable(sd->u.userptr, sd->len)) {
1474                 src = buf->ops->map(pipe, buf, 1);
1475                 ret = __copy_to_user_inatomic(sd->u.userptr, src + buf->offset,
1476                                                         sd->len);
1477                 buf->ops->unmap(pipe, buf, src);
1478                 if (!ret) {
1479                         ret = sd->len;
1480                         goto out;
1481                 }
1482         }
1483
1484         /*
1485          * No dice, use slow non-atomic map and copy
1486          */
1487         src = buf->ops->map(pipe, buf, 0);
1488
1489         ret = sd->len;
1490         if (copy_to_user(sd->u.userptr, src + buf->offset, sd->len))
1491                 ret = -EFAULT;
1492
1493         buf->ops->unmap(pipe, buf, src);
1494 out:
1495         if (ret > 0)
1496                 sd->u.userptr += ret;
1497         return ret;
1498 }
1499
1500 /*
1501  * For lack of a better implementation, implement vmsplice() to userspace
1502  * as a simple copy of the pipes pages to the user iov.
1503  */
1504 static long vmsplice_to_user(struct file *file, const struct iovec __user *iov,
1505                              unsigned long nr_segs, unsigned int flags)
1506 {
1507         struct pipe_inode_info *pipe;
1508         struct splice_desc sd;
1509         ssize_t size;
1510         int error;
1511         long ret;
1512
1513         pipe = pipe_info(file->f_path.dentry->d_inode);
1514         if (!pipe)
1515                 return -EBADF;
1516
1517         pipe_lock(pipe);
1518
1519         error = ret = 0;
1520         while (nr_segs) {
1521                 void __user *base;
1522                 size_t len;
1523
1524                 /*
1525                  * Get user address base and length for this iovec.
1526                  */
1527                 error = get_user(base, &iov->iov_base);
1528                 if (unlikely(error))
1529                         break;
1530                 error = get_user(len, &iov->iov_len);
1531                 if (unlikely(error))
1532                         break;
1533
1534                 /*
1535                  * Sanity check this iovec. 0 read succeeds.
1536                  */
1537                 if (unlikely(!len))
1538                         break;
1539                 if (unlikely(!base)) {
1540                         error = -EFAULT;
1541                         break;
1542                 }
1543
1544                 if (unlikely(!access_ok(VERIFY_WRITE, base, len))) {
1545                         error = -EFAULT;
1546                         break;
1547                 }
1548
1549                 sd.len = 0;
1550                 sd.total_len = len;
1551                 sd.flags = flags;
1552                 sd.u.userptr = base;
1553                 sd.pos = 0;
1554
1555                 size = __splice_from_pipe(pipe, &sd, pipe_to_user);
1556                 if (size < 0) {
1557                         if (!ret)
1558                                 ret = size;
1559
1560                         break;
1561                 }
1562
1563                 ret += size;
1564
1565                 if (size < len)
1566                         break;
1567
1568                 nr_segs--;
1569                 iov++;
1570         }
1571
1572         pipe_unlock(pipe);
1573
1574         if (!ret)
1575                 ret = error;
1576
1577         return ret;
1578 }
1579
1580 /*
1581  * vmsplice splices a user address range into a pipe. It can be thought of
1582  * as splice-from-memory, where the regular splice is splice-from-file (or
1583  * to file). In both cases the output is a pipe, naturally.
1584  */
1585 static long vmsplice_to_pipe(struct file *file, const struct iovec __user *iov,
1586                              unsigned long nr_segs, unsigned int flags)
1587 {
1588         struct pipe_inode_info *pipe;
1589         struct page *pages[PIPE_BUFFERS];
1590         struct partial_page partial[PIPE_BUFFERS];
1591         struct splice_pipe_desc spd = {
1592                 .pages = pages,
1593                 .partial = partial,
1594                 .flags = flags,
1595                 .ops = &user_page_pipe_buf_ops,
1596                 .spd_release = spd_release_page,
1597         };
1598
1599         pipe = pipe_info(file->f_path.dentry->d_inode);
1600         if (!pipe)
1601                 return -EBADF;
1602
1603         spd.nr_pages = get_iovec_page_array(iov, nr_segs, pages, partial,
1604                                             flags & SPLICE_F_GIFT);
1605         if (spd.nr_pages <= 0)
1606                 return spd.nr_pages;
1607
1608         return splice_to_pipe(pipe, &spd);
1609 }
1610
1611 /*
1612  * Note that vmsplice only really supports true splicing _from_ user memory
1613  * to a pipe, not the other way around. Splicing from user memory is a simple
1614  * operation that can be supported without any funky alignment restrictions
1615  * or nasty vm tricks. We simply map in the user memory and fill them into
1616  * a pipe. The reverse isn't quite as easy, though. There are two possible
1617  * solutions for that:
1618  *
1619  *      - memcpy() the data internally, at which point we might as well just
1620  *        do a regular read() on the buffer anyway.
1621  *      - Lots of nasty vm tricks, that are neither fast nor flexible (it
1622  *        has restriction limitations on both ends of the pipe).
1623  *
1624  * Currently we punt and implement it as a normal copy, see pipe_to_user().
1625  *
1626  */
1627 SYSCALL_DEFINE4(vmsplice, int, fd, const struct iovec __user *, iov,
1628                 unsigned long, nr_segs, unsigned int, flags)
1629 {
1630         struct file *file;
1631         long error;
1632         int fput;
1633
1634         if (unlikely(nr_segs > UIO_MAXIOV))
1635                 return -EINVAL;
1636         else if (unlikely(!nr_segs))
1637                 return 0;
1638
1639         error = -EBADF;
1640         file = fget_light(fd, &fput);
1641         if (file) {
1642                 if (file->f_mode & FMODE_WRITE)
1643                         error = vmsplice_to_pipe(file, iov, nr_segs, flags);
1644                 else if (file->f_mode & FMODE_READ)
1645                         error = vmsplice_to_user(file, iov, nr_segs, flags);
1646
1647                 fput_light(file, fput);
1648         }
1649
1650         return error;
1651 }
1652
1653 SYSCALL_DEFINE6(splice, int, fd_in, loff_t __user *, off_in,
1654                 int, fd_out, loff_t __user *, off_out,
1655                 size_t, len, unsigned int, flags)
1656 {
1657         long error;
1658         struct file *in, *out;
1659         int fput_in, fput_out;
1660
1661         if (unlikely(!len))
1662                 return 0;
1663
1664         error = -EBADF;
1665         in = fget_light(fd_in, &fput_in);
1666         if (in) {
1667                 if (in->f_mode & FMODE_READ) {
1668                         out = fget_light(fd_out, &fput_out);
1669                         if (out) {
1670                                 if (out->f_mode & FMODE_WRITE)
1671                                         error = do_splice(in, off_in,
1672                                                           out, off_out,
1673                                                           len, flags);
1674                                 fput_light(out, fput_out);
1675                         }
1676                 }
1677
1678                 fput_light(in, fput_in);
1679         }
1680
1681         return error;
1682 }
1683
1684 /*
1685  * Make sure there's data to read. Wait for input if we can, otherwise
1686  * return an appropriate error.
1687  */
1688 static int ipipe_prep(struct pipe_inode_info *pipe, unsigned int flags)
1689 {
1690         int ret;
1691
1692         /*
1693          * Check ->nrbufs without the inode lock first. This function
1694          * is speculative anyways, so missing one is ok.
1695          */
1696         if (pipe->nrbufs)
1697                 return 0;
1698
1699         ret = 0;
1700         pipe_lock(pipe);
1701
1702         while (!pipe->nrbufs) {
1703                 if (signal_pending(current)) {
1704                         ret = -ERESTARTSYS;
1705                         break;
1706                 }
1707                 if (!pipe->writers)
1708                         break;
1709                 if (!pipe->waiting_writers) {
1710                         if (flags & SPLICE_F_NONBLOCK) {
1711                                 ret = -EAGAIN;
1712                                 break;
1713                         }
1714                 }
1715                 pipe_wait(pipe);
1716         }
1717
1718         pipe_unlock(pipe);
1719         return ret;
1720 }
1721
1722 /*
1723  * Make sure there's writeable room. Wait for room if we can, otherwise
1724  * return an appropriate error.
1725  */
1726 static int opipe_prep(struct pipe_inode_info *pipe, unsigned int flags)
1727 {
1728         int ret;
1729
1730         /*
1731          * Check ->nrbufs without the inode lock first. This function
1732          * is speculative anyways, so missing one is ok.
1733          */
1734         if (pipe->nrbufs < PIPE_BUFFERS)
1735                 return 0;
1736
1737         ret = 0;
1738         pipe_lock(pipe);
1739
1740         while (pipe->nrbufs >= PIPE_BUFFERS) {
1741                 if (!pipe->readers) {
1742                         send_sig(SIGPIPE, current, 0);
1743                         ret = -EPIPE;
1744                         break;
1745                 }
1746                 if (flags & SPLICE_F_NONBLOCK) {
1747                         ret = -EAGAIN;
1748                         break;
1749                 }
1750                 if (signal_pending(current)) {
1751                         ret = -ERESTARTSYS;
1752                         break;
1753                 }
1754                 pipe->waiting_writers++;
1755                 pipe_wait(pipe);
1756                 pipe->waiting_writers--;
1757         }
1758
1759         pipe_unlock(pipe);
1760         return ret;
1761 }
1762
1763 /*
1764  * Splice contents of ipipe to opipe.
1765  */
1766 static int splice_pipe_to_pipe(struct pipe_inode_info *ipipe,
1767                                struct pipe_inode_info *opipe,
1768                                size_t len, unsigned int flags)
1769 {
1770         struct pipe_buffer *ibuf, *obuf;
1771         int ret = 0, nbuf;
1772         bool input_wakeup = false;
1773
1774
1775 retry:
1776         ret = ipipe_prep(ipipe, flags);
1777         if (ret)
1778                 return ret;
1779
1780         ret = opipe_prep(opipe, flags);
1781         if (ret)
1782                 return ret;
1783
1784         /*
1785          * Potential ABBA deadlock, work around it by ordering lock
1786          * grabbing by pipe info address. Otherwise two different processes
1787          * could deadlock (one doing tee from A -> B, the other from B -> A).
1788          */
1789         pipe_double_lock(ipipe, opipe);
1790
1791         do {
1792                 if (!opipe->readers) {
1793                         send_sig(SIGPIPE, current, 0);
1794                         if (!ret)
1795                                 ret = -EPIPE;
1796                         break;
1797                 }
1798
1799                 if (!ipipe->nrbufs && !ipipe->writers)
1800                         break;
1801
1802                 /*
1803                  * Cannot make any progress, because either the input
1804                  * pipe is empty or the output pipe is full.
1805                  */
1806                 if (!ipipe->nrbufs || opipe->nrbufs >= PIPE_BUFFERS) {
1807                         /* Already processed some buffers, break */
1808                         if (ret)
1809                                 break;
1810
1811                         if (flags & SPLICE_F_NONBLOCK) {
1812                                 ret = -EAGAIN;
1813                                 break;
1814                         }
1815
1816                         /*
1817                          * We raced with another reader/writer and haven't
1818                          * managed to process any buffers.  A zero return
1819                          * value means EOF, so retry instead.
1820                          */
1821                         pipe_unlock(ipipe);
1822                         pipe_unlock(opipe);
1823                         goto retry;
1824                 }
1825
1826                 ibuf = ipipe->bufs + ipipe->curbuf;
1827                 nbuf = (opipe->curbuf + opipe->nrbufs) % PIPE_BUFFERS;
1828                 obuf = opipe->bufs + nbuf;
1829
1830                 if (len >= ibuf->len) {
1831                         /*
1832                          * Simply move the whole buffer from ipipe to opipe
1833                          */
1834                         *obuf = *ibuf;
1835                         ibuf->ops = NULL;
1836                         opipe->nrbufs++;
1837                         ipipe->curbuf = (ipipe->curbuf + 1) % PIPE_BUFFERS;
1838                         ipipe->nrbufs--;
1839                         input_wakeup = true;
1840                 } else {
1841                         /*
1842                          * Get a reference to this pipe buffer,
1843                          * so we can copy the contents over.
1844                          */
1845                         ibuf->ops->get(ipipe, ibuf);
1846                         *obuf = *ibuf;
1847
1848                         /*
1849                          * Don't inherit the gift flag, we need to
1850                          * prevent multiple steals of this page.
1851                          */
1852                         obuf->flags &= ~PIPE_BUF_FLAG_GIFT;
1853
1854                         obuf->len = len;
1855                         opipe->nrbufs++;
1856                         ibuf->offset += obuf->len;
1857                         ibuf->len -= obuf->len;
1858                 }
1859                 ret += obuf->len;
1860                 len -= obuf->len;
1861         } while (len);
1862
1863         pipe_unlock(ipipe);
1864         pipe_unlock(opipe);
1865
1866         /*
1867          * If we put data in the output pipe, wakeup any potential readers.
1868          */
1869         if (ret > 0) {
1870                 smp_mb();
1871                 if (waitqueue_active(&opipe->wait))
1872                         wake_up_interruptible(&opipe->wait);
1873                 kill_fasync(&opipe->fasync_readers, SIGIO, POLL_IN);
1874         }
1875         if (input_wakeup)
1876                 wakeup_pipe_writers(ipipe);
1877
1878         return ret;
1879 }
1880
1881 /*
1882  * Link contents of ipipe to opipe.
1883  */
1884 static int link_pipe(struct pipe_inode_info *ipipe,
1885                      struct pipe_inode_info *opipe,
1886                      size_t len, unsigned int flags)
1887 {
1888         struct pipe_buffer *ibuf, *obuf;
1889         int ret = 0, i = 0, nbuf;
1890
1891         /*
1892          * Potential ABBA deadlock, work around it by ordering lock
1893          * grabbing by pipe info address. Otherwise two different processes
1894          * could deadlock (one doing tee from A -> B, the other from B -> A).
1895          */
1896         pipe_double_lock(ipipe, opipe);
1897
1898         do {
1899                 if (!opipe->readers) {
1900                         send_sig(SIGPIPE, current, 0);
1901                         if (!ret)
1902                                 ret = -EPIPE;
1903                         break;
1904                 }
1905
1906                 /*
1907                  * If we have iterated all input buffers or ran out of
1908                  * output room, break.
1909                  */
1910                 if (i >= ipipe->nrbufs || opipe->nrbufs >= PIPE_BUFFERS)
1911                         break;
1912
1913                 ibuf = ipipe->bufs + ((ipipe->curbuf + i) & (PIPE_BUFFERS - 1));
1914                 nbuf = (opipe->curbuf + opipe->nrbufs) & (PIPE_BUFFERS - 1);
1915
1916                 /*
1917                  * Get a reference to this pipe buffer,
1918                  * so we can copy the contents over.
1919                  */
1920                 ibuf->ops->get(ipipe, ibuf);
1921
1922                 obuf = opipe->bufs + nbuf;
1923                 *obuf = *ibuf;
1924
1925                 /*
1926                  * Don't inherit the gift flag, we need to
1927                  * prevent multiple steals of this page.
1928                  */
1929                 obuf->flags &= ~PIPE_BUF_FLAG_GIFT;
1930
1931                 if (obuf->len > len)
1932                         obuf->len = len;
1933
1934                 opipe->nrbufs++;
1935                 ret += obuf->len;
1936                 len -= obuf->len;
1937                 i++;
1938         } while (len);
1939
1940         /*
1941          * return EAGAIN if we have the potential of some data in the
1942          * future, otherwise just return 0
1943          */
1944         if (!ret && ipipe->waiting_writers && (flags & SPLICE_F_NONBLOCK))
1945                 ret = -EAGAIN;
1946
1947         pipe_unlock(ipipe);
1948         pipe_unlock(opipe);
1949
1950         /*
1951          * If we put data in the output pipe, wakeup any potential readers.
1952          */
1953         if (ret > 0) {
1954                 smp_mb();
1955                 if (waitqueue_active(&opipe->wait))
1956                         wake_up_interruptible(&opipe->wait);
1957                 kill_fasync(&opipe->fasync_readers, SIGIO, POLL_IN);
1958         }
1959
1960         return ret;
1961 }
1962
1963 /*
1964  * This is a tee(1) implementation that works on pipes. It doesn't copy
1965  * any data, it simply references the 'in' pages on the 'out' pipe.
1966  * The 'flags' used are the SPLICE_F_* variants, currently the only
1967  * applicable one is SPLICE_F_NONBLOCK.
1968  */
1969 static long do_tee(struct file *in, struct file *out, size_t len,
1970                    unsigned int flags)
1971 {
1972         struct pipe_inode_info *ipipe = pipe_info(in->f_path.dentry->d_inode);
1973         struct pipe_inode_info *opipe = pipe_info(out->f_path.dentry->d_inode);
1974         int ret = -EINVAL;
1975
1976         /*
1977          * Duplicate the contents of ipipe to opipe without actually
1978          * copying the data.
1979          */
1980         if (ipipe && opipe && ipipe != opipe) {
1981                 /*
1982                  * Keep going, unless we encounter an error. The ipipe/opipe
1983                  * ordering doesn't really matter.
1984                  */
1985                 ret = ipipe_prep(ipipe, flags);
1986                 if (!ret) {
1987                         ret = opipe_prep(opipe, flags);
1988                         if (!ret)
1989                                 ret = link_pipe(ipipe, opipe, len, flags);
1990                 }
1991         }
1992
1993         return ret;
1994 }
1995
1996 SYSCALL_DEFINE4(tee, int, fdin, int, fdout, size_t, len, unsigned int, flags)
1997 {
1998         struct file *in;
1999         int error, fput_in;
2000
2001         if (unlikely(!len))
2002                 return 0;
2003
2004         error = -EBADF;
2005         in = fget_light(fdin, &fput_in);
2006         if (in) {
2007                 if (in->f_mode & FMODE_READ) {
2008                         int fput_out;
2009                         struct file *out = fget_light(fdout, &fput_out);
2010
2011                         if (out) {
2012                                 if (out->f_mode & FMODE_WRITE)
2013                                         error = do_tee(in, out, len, flags);
2014                                 fput_light(out, fput_out);
2015                         }
2016                 }
2017                 fput_light(in, fput_in);
2018         }
2019
2020         return error;
2021 }