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Linux/fs/splice.c

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  1 // SPDX-License-Identifier: GPL-2.0-only
  2 /*
  3  * "splice": joining two ropes together by interweaving their strands.
  4  *
  5  * This is the "extended pipe" functionality, where a pipe is used as
  6  * an arbitrary in-memory buffer. Think of a pipe as a small kernel
  7  * buffer that you can use to transfer data from one end to the other.
  8  *
  9  * The traditional unix read/write is extended with a "splice()" operation
 10  * that transfers data buffers to or from a pipe buffer.
 11  *
 12  * Named by Larry McVoy, original implementation from Linus, extended by
 13  * Jens to support splicing to files, network, direct splicing, etc and
 14  * fixing lots of bugs.
 15  *
 16  * Copyright (C) 2005-2006 Jens Axboe <axboe@kernel.dk>
 17  * Copyright (C) 2005-2006 Linus Torvalds <torvalds@osdl.org>
 18  * Copyright (C) 2006 Ingo Molnar <mingo@elte.hu>
 19  *
 20  */
 21 #include <linux/bvec.h>
 22 #include <linux/fs.h>
 23 #include <linux/file.h>
 24 #include <linux/pagemap.h>
 25 #include <linux/splice.h>
 26 #include <linux/memcontrol.h>
 27 #include <linux/mm_inline.h>
 28 #include <linux/swap.h>
 29 #include <linux/writeback.h>
 30 #include <linux/export.h>
 31 #include <linux/syscalls.h>
 32 #include <linux/uio.h>
 33 #include <linux/security.h>
 34 #include <linux/gfp.h>
 35 #include <linux/socket.h>
 36 #include <linux/compat.h>
 37 #include <linux/sched/signal.h>
 38 
 39 #include "internal.h"
 40 
 41 /*
 42  * Attempt to steal a page from a pipe buffer. This should perhaps go into
 43  * a vm helper function, it's already simplified quite a bit by the
 44  * addition of remove_mapping(). If success is returned, the caller may
 45  * attempt to reuse this page for another destination.
 46  */
 47 static int page_cache_pipe_buf_steal(struct pipe_inode_info *pipe,
 48                                      struct pipe_buffer *buf)
 49 {
 50         struct page *page = buf->page;
 51         struct address_space *mapping;
 52 
 53         lock_page(page);
 54 
 55         mapping = page_mapping(page);
 56         if (mapping) {
 57                 WARN_ON(!PageUptodate(page));
 58 
 59                 /*
 60                  * At least for ext2 with nobh option, we need to wait on
 61                  * writeback completing on this page, since we'll remove it
 62                  * from the pagecache.  Otherwise truncate wont wait on the
 63                  * page, allowing the disk blocks to be reused by someone else
 64                  * before we actually wrote our data to them. fs corruption
 65                  * ensues.
 66                  */
 67                 wait_on_page_writeback(page);
 68 
 69                 if (page_has_private(page) &&
 70                     !try_to_release_page(page, GFP_KERNEL))
 71                         goto out_unlock;
 72 
 73                 /*
 74                  * If we succeeded in removing the mapping, set LRU flag
 75                  * and return good.
 76                  */
 77                 if (remove_mapping(mapping, page)) {
 78                         buf->flags |= PIPE_BUF_FLAG_LRU;
 79                         return 0;
 80                 }
 81         }
 82 
 83         /*
 84          * Raced with truncate or failed to remove page from current
 85          * address space, unlock and return failure.
 86          */
 87 out_unlock:
 88         unlock_page(page);
 89         return 1;
 90 }
 91 
 92 static void page_cache_pipe_buf_release(struct pipe_inode_info *pipe,
 93                                         struct pipe_buffer *buf)
 94 {
 95         put_page(buf->page);
 96         buf->flags &= ~PIPE_BUF_FLAG_LRU;
 97 }
 98 
 99 /*
100  * Check whether the contents of buf is OK to access. Since the content
101  * is a page cache page, IO may be in flight.
102  */
103 static int page_cache_pipe_buf_confirm(struct pipe_inode_info *pipe,
104                                        struct pipe_buffer *buf)
105 {
106         struct page *page = buf->page;
107         int err;
108 
109         if (!PageUptodate(page)) {
110                 lock_page(page);
111 
112                 /*
113                  * Page got truncated/unhashed. This will cause a 0-byte
114                  * splice, if this is the first page.
115                  */
116                 if (!page->mapping) {
117                         err = -ENODATA;
118                         goto error;
119                 }
120 
121                 /*
122                  * Uh oh, read-error from disk.
123                  */
124                 if (!PageUptodate(page)) {
125                         err = -EIO;
126                         goto error;
127                 }
128 
129                 /*
130                  * Page is ok afterall, we are done.
131                  */
132                 unlock_page(page);
133         }
134 
135         return 0;
136 error:
137         unlock_page(page);
138         return err;
139 }
140 
141 const struct pipe_buf_operations page_cache_pipe_buf_ops = {
142         .confirm = page_cache_pipe_buf_confirm,
143         .release = page_cache_pipe_buf_release,
144         .steal = page_cache_pipe_buf_steal,
145         .get = generic_pipe_buf_get,
146 };
147 
148 static int user_page_pipe_buf_steal(struct pipe_inode_info *pipe,
149                                     struct pipe_buffer *buf)
150 {
151         if (!(buf->flags & PIPE_BUF_FLAG_GIFT))
152                 return 1;
153 
154         buf->flags |= PIPE_BUF_FLAG_LRU;
155         return generic_pipe_buf_steal(pipe, buf);
156 }
157 
158 static const struct pipe_buf_operations user_page_pipe_buf_ops = {
159         .confirm = generic_pipe_buf_confirm,
160         .release = page_cache_pipe_buf_release,
161         .steal = user_page_pipe_buf_steal,
162         .get = generic_pipe_buf_get,
163 };
164 
165 static void wakeup_pipe_readers(struct pipe_inode_info *pipe)
166 {
167         smp_mb();
168         if (waitqueue_active(&pipe->wait))
169                 wake_up_interruptible(&pipe->wait);
170         kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
171 }
172 
173 /**
174  * splice_to_pipe - fill passed data into a pipe
175  * @pipe:       pipe to fill
176  * @spd:        data to fill
177  *
178  * Description:
179  *    @spd contains a map of pages and len/offset tuples, along with
180  *    the struct pipe_buf_operations associated with these pages. This
181  *    function will link that data to the pipe.
182  *
183  */
184 ssize_t splice_to_pipe(struct pipe_inode_info *pipe,
185                        struct splice_pipe_desc *spd)
186 {
187         unsigned int spd_pages = spd->nr_pages;
188         int ret = 0, page_nr = 0;
189 
190         if (!spd_pages)
191                 return 0;
192 
193         if (unlikely(!pipe->readers)) {
194                 send_sig(SIGPIPE, current, 0);
195                 ret = -EPIPE;
196                 goto out;
197         }
198 
199         while (pipe->nrbufs < pipe->buffers) {
200                 int newbuf = (pipe->curbuf + pipe->nrbufs) & (pipe->buffers - 1);
201                 struct pipe_buffer *buf = pipe->bufs + newbuf;
202 
203                 buf->page = spd->pages[page_nr];
204                 buf->offset = spd->partial[page_nr].offset;
205                 buf->len = spd->partial[page_nr].len;
206                 buf->private = spd->partial[page_nr].private;
207                 buf->ops = spd->ops;
208                 buf->flags = 0;
209 
210                 pipe->nrbufs++;
211                 page_nr++;
212                 ret += buf->len;
213 
214                 if (!--spd->nr_pages)
215                         break;
216         }
217 
218         if (!ret)
219                 ret = -EAGAIN;
220 
221 out:
222         while (page_nr < spd_pages)
223                 spd->spd_release(spd, page_nr++);
224 
225         return ret;
226 }
227 EXPORT_SYMBOL_GPL(splice_to_pipe);
228 
229 ssize_t add_to_pipe(struct pipe_inode_info *pipe, struct pipe_buffer *buf)
230 {
231         int ret;
232 
233         if (unlikely(!pipe->readers)) {
234                 send_sig(SIGPIPE, current, 0);
235                 ret = -EPIPE;
236         } else if (pipe->nrbufs == pipe->buffers) {
237                 ret = -EAGAIN;
238         } else {
239                 int newbuf = (pipe->curbuf + pipe->nrbufs) & (pipe->buffers - 1);
240                 pipe->bufs[newbuf] = *buf;
241                 pipe->nrbufs++;
242                 return buf->len;
243         }
244         pipe_buf_release(pipe, buf);
245         return ret;
246 }
247 EXPORT_SYMBOL(add_to_pipe);
248 
249 /*
250  * Check if we need to grow the arrays holding pages and partial page
251  * descriptions.
252  */
253 int splice_grow_spd(const struct pipe_inode_info *pipe, struct splice_pipe_desc *spd)
254 {
255         unsigned int buffers = READ_ONCE(pipe->buffers);
256 
257         spd->nr_pages_max = buffers;
258         if (buffers <= PIPE_DEF_BUFFERS)
259                 return 0;
260 
261         spd->pages = kmalloc_array(buffers, sizeof(struct page *), GFP_KERNEL);
262         spd->partial = kmalloc_array(buffers, sizeof(struct partial_page),
263                                      GFP_KERNEL);
264 
265         if (spd->pages && spd->partial)
266                 return 0;
267 
268         kfree(spd->pages);
269         kfree(spd->partial);
270         return -ENOMEM;
271 }
272 
273 void splice_shrink_spd(struct splice_pipe_desc *spd)
274 {
275         if (spd->nr_pages_max <= PIPE_DEF_BUFFERS)
276                 return;
277 
278         kfree(spd->pages);
279         kfree(spd->partial);
280 }
281 
282 /**
283  * generic_file_splice_read - splice data from file to a pipe
284  * @in:         file to splice from
285  * @ppos:       position in @in
286  * @pipe:       pipe to splice to
287  * @len:        number of bytes to splice
288  * @flags:      splice modifier flags
289  *
290  * Description:
291  *    Will read pages from given file and fill them into a pipe. Can be
292  *    used as long as it has more or less sane ->read_iter().
293  *
294  */
295 ssize_t generic_file_splice_read(struct file *in, loff_t *ppos,
296                                  struct pipe_inode_info *pipe, size_t len,
297                                  unsigned int flags)
298 {
299         struct iov_iter to;
300         struct kiocb kiocb;
301         int idx, ret;
302 
303         iov_iter_pipe(&to, READ, pipe, len);
304         idx = to.idx;
305         init_sync_kiocb(&kiocb, in);
306         kiocb.ki_pos = *ppos;
307         ret = call_read_iter(in, &kiocb, &to);
308         if (ret > 0) {
309                 *ppos = kiocb.ki_pos;
310                 file_accessed(in);
311         } else if (ret < 0) {
312                 to.idx = idx;
313                 to.iov_offset = 0;
314                 iov_iter_advance(&to, 0); /* to free what was emitted */
315                 /*
316                  * callers of ->splice_read() expect -EAGAIN on
317                  * "can't put anything in there", rather than -EFAULT.
318                  */
319                 if (ret == -EFAULT)
320                         ret = -EAGAIN;
321         }
322 
323         return ret;
324 }
325 EXPORT_SYMBOL(generic_file_splice_read);
326 
327 const struct pipe_buf_operations default_pipe_buf_ops = {
328         .confirm = generic_pipe_buf_confirm,
329         .release = generic_pipe_buf_release,
330         .steal = generic_pipe_buf_steal,
331         .get = generic_pipe_buf_get,
332 };
333 
334 int generic_pipe_buf_nosteal(struct pipe_inode_info *pipe,
335                              struct pipe_buffer *buf)
336 {
337         return 1;
338 }
339 
340 /* Pipe buffer operations for a socket and similar. */
341 const struct pipe_buf_operations nosteal_pipe_buf_ops = {
342         .confirm = generic_pipe_buf_confirm,
343         .release = generic_pipe_buf_release,
344         .steal = generic_pipe_buf_nosteal,
345         .get = generic_pipe_buf_get,
346 };
347 EXPORT_SYMBOL(nosteal_pipe_buf_ops);
348 
349 static ssize_t kernel_readv(struct file *file, const struct kvec *vec,
350                             unsigned long vlen, loff_t offset)
351 {
352         mm_segment_t old_fs;
353         loff_t pos = offset;
354         ssize_t res;
355 
356         old_fs = get_fs();
357         set_fs(KERNEL_DS);
358         /* The cast to a user pointer is valid due to the set_fs() */
359         res = vfs_readv(file, (const struct iovec __user *)vec, vlen, &pos, 0);
360         set_fs(old_fs);
361 
362         return res;
363 }
364 
365 static ssize_t default_file_splice_read(struct file *in, loff_t *ppos,
366                                  struct pipe_inode_info *pipe, size_t len,
367                                  unsigned int flags)
368 {
369         struct kvec *vec, __vec[PIPE_DEF_BUFFERS];
370         struct iov_iter to;
371         struct page **pages;
372         unsigned int nr_pages;
373         size_t offset, base, copied = 0;
374         ssize_t res;
375         int i;
376 
377         if (pipe->nrbufs == pipe->buffers)
378                 return -EAGAIN;
379 
380         /*
381          * Try to keep page boundaries matching to source pagecache ones -
382          * it probably won't be much help, but...
383          */
384         offset = *ppos & ~PAGE_MASK;
385 
386         iov_iter_pipe(&to, READ, pipe, len + offset);
387 
388         res = iov_iter_get_pages_alloc(&to, &pages, len + offset, &base);
389         if (res <= 0)
390                 return -ENOMEM;
391 
392         nr_pages = DIV_ROUND_UP(res + base, PAGE_SIZE);
393 
394         vec = __vec;
395         if (nr_pages > PIPE_DEF_BUFFERS) {
396                 vec = kmalloc_array(nr_pages, sizeof(struct kvec), GFP_KERNEL);
397                 if (unlikely(!vec)) {
398                         res = -ENOMEM;
399                         goto out;
400                 }
401         }
402 
403         pipe->bufs[to.idx].offset = offset;
404         pipe->bufs[to.idx].len -= offset;
405 
406         for (i = 0; i < nr_pages; i++) {
407                 size_t this_len = min_t(size_t, len, PAGE_SIZE - offset);
408                 vec[i].iov_base = page_address(pages[i]) + offset;
409                 vec[i].iov_len = this_len;
410                 len -= this_len;
411                 offset = 0;
412         }
413 
414         res = kernel_readv(in, vec, nr_pages, *ppos);
415         if (res > 0) {
416                 copied = res;
417                 *ppos += res;
418         }
419 
420         if (vec != __vec)
421                 kfree(vec);
422 out:
423         for (i = 0; i < nr_pages; i++)
424                 put_page(pages[i]);
425         kvfree(pages);
426         iov_iter_advance(&to, copied);  /* truncates and discards */
427         return res;
428 }
429 
430 /*
431  * Send 'sd->len' bytes to socket from 'sd->file' at position 'sd->pos'
432  * using sendpage(). Return the number of bytes sent.
433  */
434 static int pipe_to_sendpage(struct pipe_inode_info *pipe,
435                             struct pipe_buffer *buf, struct splice_desc *sd)
436 {
437         struct file *file = sd->u.file;
438         loff_t pos = sd->pos;
439         int more;
440 
441         if (!likely(file->f_op->sendpage))
442                 return -EINVAL;
443 
444         more = (sd->flags & SPLICE_F_MORE) ? MSG_MORE : 0;
445 
446         if (sd->len < sd->total_len && pipe->nrbufs > 1)
447                 more |= MSG_SENDPAGE_NOTLAST;
448 
449         return file->f_op->sendpage(file, buf->page, buf->offset,
450                                     sd->len, &pos, more);
451 }
452 
453 static void wakeup_pipe_writers(struct pipe_inode_info *pipe)
454 {
455         smp_mb();
456         if (waitqueue_active(&pipe->wait))
457                 wake_up_interruptible(&pipe->wait);
458         kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
459 }
460 
461 /**
462  * splice_from_pipe_feed - feed available data from a pipe to a file
463  * @pipe:       pipe to splice from
464  * @sd:         information to @actor
465  * @actor:      handler that splices the data
466  *
467  * Description:
468  *    This function loops over the pipe and calls @actor to do the
469  *    actual moving of a single struct pipe_buffer to the desired
470  *    destination.  It returns when there's no more buffers left in
471  *    the pipe or if the requested number of bytes (@sd->total_len)
472  *    have been copied.  It returns a positive number (one) if the
473  *    pipe needs to be filled with more data, zero if the required
474  *    number of bytes have been copied and -errno on error.
475  *
476  *    This, together with splice_from_pipe_{begin,end,next}, may be
477  *    used to implement the functionality of __splice_from_pipe() when
478  *    locking is required around copying the pipe buffers to the
479  *    destination.
480  */
481 static int splice_from_pipe_feed(struct pipe_inode_info *pipe, struct splice_desc *sd,
482                           splice_actor *actor)
483 {
484         int ret;
485 
486         while (pipe->nrbufs) {
487                 struct pipe_buffer *buf = pipe->bufs + pipe->curbuf;
488 
489                 sd->len = buf->len;
490                 if (sd->len > sd->total_len)
491                         sd->len = sd->total_len;
492 
493                 ret = pipe_buf_confirm(pipe, buf);
494                 if (unlikely(ret)) {
495                         if (ret == -ENODATA)
496                                 ret = 0;
497                         return ret;
498                 }
499 
500                 ret = actor(pipe, buf, sd);
501                 if (ret <= 0)
502                         return ret;
503 
504                 buf->offset += ret;
505                 buf->len -= ret;
506 
507                 sd->num_spliced += ret;
508                 sd->len -= ret;
509                 sd->pos += ret;
510                 sd->total_len -= ret;
511 
512                 if (!buf->len) {
513                         pipe_buf_release(pipe, buf);
514                         pipe->curbuf = (pipe->curbuf + 1) & (pipe->buffers - 1);
515                         pipe->nrbufs--;
516                         if (pipe->files)
517                                 sd->need_wakeup = true;
518                 }
519 
520                 if (!sd->total_len)
521                         return 0;
522         }
523 
524         return 1;
525 }
526 
527 /**
528  * splice_from_pipe_next - wait for some data to splice from
529  * @pipe:       pipe to splice from
530  * @sd:         information about the splice operation
531  *
532  * Description:
533  *    This function will wait for some data and return a positive
534  *    value (one) if pipe buffers are available.  It will return zero
535  *    or -errno if no more data needs to be spliced.
536  */
537 static int splice_from_pipe_next(struct pipe_inode_info *pipe, struct splice_desc *sd)
538 {
539         /*
540          * Check for signal early to make process killable when there are
541          * always buffers available
542          */
543         if (signal_pending(current))
544                 return -ERESTARTSYS;
545 
546         while (!pipe->nrbufs) {
547                 if (!pipe->writers)
548                         return 0;
549 
550                 if (!pipe->waiting_writers && sd->num_spliced)
551                         return 0;
552 
553                 if (sd->flags & SPLICE_F_NONBLOCK)
554                         return -EAGAIN;
555 
556                 if (signal_pending(current))
557                         return -ERESTARTSYS;
558 
559                 if (sd->need_wakeup) {
560                         wakeup_pipe_writers(pipe);
561                         sd->need_wakeup = false;
562                 }
563 
564                 pipe_wait(pipe);
565         }
566 
567         return 1;
568 }
569 
570 /**
571  * splice_from_pipe_begin - start splicing from pipe
572  * @sd:         information about the splice operation
573  *
574  * Description:
575  *    This function should be called before a loop containing
576  *    splice_from_pipe_next() and splice_from_pipe_feed() to
577  *    initialize the necessary fields of @sd.
578  */
579 static void splice_from_pipe_begin(struct splice_desc *sd)
580 {
581         sd->num_spliced = 0;
582         sd->need_wakeup = false;
583 }
584 
585 /**
586  * splice_from_pipe_end - finish splicing from pipe
587  * @pipe:       pipe to splice from
588  * @sd:         information about the splice operation
589  *
590  * Description:
591  *    This function will wake up pipe writers if necessary.  It should
592  *    be called after a loop containing splice_from_pipe_next() and
593  *    splice_from_pipe_feed().
594  */
595 static void splice_from_pipe_end(struct pipe_inode_info *pipe, struct splice_desc *sd)
596 {
597         if (sd->need_wakeup)
598                 wakeup_pipe_writers(pipe);
599 }
600 
601 /**
602  * __splice_from_pipe - splice data from a pipe to given actor
603  * @pipe:       pipe to splice from
604  * @sd:         information to @actor
605  * @actor:      handler that splices the data
606  *
607  * Description:
608  *    This function does little more than loop over the pipe and call
609  *    @actor to do the actual moving of a single struct pipe_buffer to
610  *    the desired destination. See pipe_to_file, pipe_to_sendpage, or
611  *    pipe_to_user.
612  *
613  */
614 ssize_t __splice_from_pipe(struct pipe_inode_info *pipe, struct splice_desc *sd,
615                            splice_actor *actor)
616 {
617         int ret;
618 
619         splice_from_pipe_begin(sd);
620         do {
621                 cond_resched();
622                 ret = splice_from_pipe_next(pipe, sd);
623                 if (ret > 0)
624                         ret = splice_from_pipe_feed(pipe, sd, actor);
625         } while (ret > 0);
626         splice_from_pipe_end(pipe, sd);
627 
628         return sd->num_spliced ? sd->num_spliced : ret;
629 }
630 EXPORT_SYMBOL(__splice_from_pipe);
631 
632 /**
633  * splice_from_pipe - splice data from a pipe to a file
634  * @pipe:       pipe to splice from
635  * @out:        file to splice to
636  * @ppos:       position in @out
637  * @len:        how many bytes to splice
638  * @flags:      splice modifier flags
639  * @actor:      handler that splices the data
640  *
641  * Description:
642  *    See __splice_from_pipe. This function locks the pipe inode,
643  *    otherwise it's identical to __splice_from_pipe().
644  *
645  */
646 ssize_t splice_from_pipe(struct pipe_inode_info *pipe, struct file *out,
647                          loff_t *ppos, size_t len, unsigned int flags,
648                          splice_actor *actor)
649 {
650         ssize_t ret;
651         struct splice_desc sd = {
652                 .total_len = len,
653                 .flags = flags,
654                 .pos = *ppos,
655                 .u.file = out,
656         };
657 
658         pipe_lock(pipe);
659         ret = __splice_from_pipe(pipe, &sd, actor);
660         pipe_unlock(pipe);
661 
662         return ret;
663 }
664 
665 /**
666  * iter_file_splice_write - splice data from a pipe to a file
667  * @pipe:       pipe info
668  * @out:        file to write to
669  * @ppos:       position in @out
670  * @len:        number of bytes to splice
671  * @flags:      splice modifier flags
672  *
673  * Description:
674  *    Will either move or copy pages (determined by @flags options) from
675  *    the given pipe inode to the given file.
676  *    This one is ->write_iter-based.
677  *
678  */
679 ssize_t
680 iter_file_splice_write(struct pipe_inode_info *pipe, struct file *out,
681                           loff_t *ppos, size_t len, unsigned int flags)
682 {
683         struct splice_desc sd = {
684                 .total_len = len,
685                 .flags = flags,
686                 .pos = *ppos,
687                 .u.file = out,
688         };
689         int nbufs = pipe->buffers;
690         struct bio_vec *array = kcalloc(nbufs, sizeof(struct bio_vec),
691                                         GFP_KERNEL);
692         ssize_t ret;
693 
694         if (unlikely(!array))
695                 return -ENOMEM;
696 
697         pipe_lock(pipe);
698 
699         splice_from_pipe_begin(&sd);
700         while (sd.total_len) {
701                 struct iov_iter from;
702                 size_t left;
703                 int n, idx;
704 
705                 ret = splice_from_pipe_next(pipe, &sd);
706                 if (ret <= 0)
707                         break;
708 
709                 if (unlikely(nbufs < pipe->buffers)) {
710                         kfree(array);
711                         nbufs = pipe->buffers;
712                         array = kcalloc(nbufs, sizeof(struct bio_vec),
713                                         GFP_KERNEL);
714                         if (!array) {
715                                 ret = -ENOMEM;
716                                 break;
717                         }
718                 }
719 
720                 /* build the vector */
721                 left = sd.total_len;
722                 for (n = 0, idx = pipe->curbuf; left && n < pipe->nrbufs; n++, idx++) {
723                         struct pipe_buffer *buf = pipe->bufs + idx;
724                         size_t this_len = buf->len;
725 
726                         if (this_len > left)
727                                 this_len = left;
728 
729                         if (idx == pipe->buffers - 1)
730                                 idx = -1;
731 
732                         ret = pipe_buf_confirm(pipe, buf);
733                         if (unlikely(ret)) {
734                                 if (ret == -ENODATA)
735                                         ret = 0;
736                                 goto done;
737                         }
738 
739                         array[n].bv_page = buf->page;
740                         array[n].bv_len = this_len;
741                         array[n].bv_offset = buf->offset;
742                         left -= this_len;
743                 }
744 
745                 iov_iter_bvec(&from, WRITE, array, n, sd.total_len - left);
746                 ret = vfs_iter_write(out, &from, &sd.pos, 0);
747                 if (ret <= 0)
748                         break;
749 
750                 sd.num_spliced += ret;
751                 sd.total_len -= ret;
752                 *ppos = sd.pos;
753 
754                 /* dismiss the fully eaten buffers, adjust the partial one */
755                 while (ret) {
756                         struct pipe_buffer *buf = pipe->bufs + pipe->curbuf;
757                         if (ret >= buf->len) {
758                                 ret -= buf->len;
759                                 buf->len = 0;
760                                 pipe_buf_release(pipe, buf);
761                                 pipe->curbuf = (pipe->curbuf + 1) & (pipe->buffers - 1);
762                                 pipe->nrbufs--;
763                                 if (pipe->files)
764                                         sd.need_wakeup = true;
765                         } else {
766                                 buf->offset += ret;
767                                 buf->len -= ret;
768                                 ret = 0;
769                         }
770                 }
771         }
772 done:
773         kfree(array);
774         splice_from_pipe_end(pipe, &sd);
775 
776         pipe_unlock(pipe);
777 
778         if (sd.num_spliced)
779                 ret = sd.num_spliced;
780 
781         return ret;
782 }
783 
784 EXPORT_SYMBOL(iter_file_splice_write);
785 
786 static int write_pipe_buf(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
787                           struct splice_desc *sd)
788 {
789         int ret;
790         void *data;
791         loff_t tmp = sd->pos;
792 
793         data = kmap(buf->page);
794         ret = __kernel_write(sd->u.file, data + buf->offset, sd->len, &tmp);
795         kunmap(buf->page);
796 
797         return ret;
798 }
799 
800 static ssize_t default_file_splice_write(struct pipe_inode_info *pipe,
801                                          struct file *out, loff_t *ppos,
802                                          size_t len, unsigned int flags)
803 {
804         ssize_t ret;
805 
806         ret = splice_from_pipe(pipe, out, ppos, len, flags, write_pipe_buf);
807         if (ret > 0)
808                 *ppos += ret;
809 
810         return ret;
811 }
812 
813 /**
814  * generic_splice_sendpage - splice data from a pipe to a socket
815  * @pipe:       pipe to splice from
816  * @out:        socket to write to
817  * @ppos:       position in @out
818  * @len:        number of bytes to splice
819  * @flags:      splice modifier flags
820  *
821  * Description:
822  *    Will send @len bytes from the pipe to a network socket. No data copying
823  *    is involved.
824  *
825  */
826 ssize_t generic_splice_sendpage(struct pipe_inode_info *pipe, struct file *out,
827                                 loff_t *ppos, size_t len, unsigned int flags)
828 {
829         return splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_sendpage);
830 }
831 
832 EXPORT_SYMBOL(generic_splice_sendpage);
833 
834 /*
835  * Attempt to initiate a splice from pipe to file.
836  */
837 static long do_splice_from(struct pipe_inode_info *pipe, struct file *out,
838                            loff_t *ppos, size_t len, unsigned int flags)
839 {
840         ssize_t (*splice_write)(struct pipe_inode_info *, struct file *,
841                                 loff_t *, size_t, unsigned int);
842 
843         if (out->f_op->splice_write)
844                 splice_write = out->f_op->splice_write;
845         else
846                 splice_write = default_file_splice_write;
847 
848         return splice_write(pipe, out, ppos, len, flags);
849 }
850 
851 /*
852  * Attempt to initiate a splice from a file to a pipe.
853  */
854 static long do_splice_to(struct file *in, loff_t *ppos,
855                          struct pipe_inode_info *pipe, size_t len,
856                          unsigned int flags)
857 {
858         ssize_t (*splice_read)(struct file *, loff_t *,
859                                struct pipe_inode_info *, size_t, unsigned int);
860         int ret;
861 
862         if (unlikely(!(in->f_mode & FMODE_READ)))
863                 return -EBADF;
864 
865         ret = rw_verify_area(READ, in, ppos, len);
866         if (unlikely(ret < 0))
867                 return ret;
868 
869         if (unlikely(len > MAX_RW_COUNT))
870                 len = MAX_RW_COUNT;
871 
872         if (in->f_op->splice_read)
873                 splice_read = in->f_op->splice_read;
874         else
875                 splice_read = default_file_splice_read;
876 
877         return splice_read(in, ppos, pipe, len, flags);
878 }
879 
880 /**
881  * splice_direct_to_actor - splices data directly between two non-pipes
882  * @in:         file to splice from
883  * @sd:         actor information on where to splice to
884  * @actor:      handles the data splicing
885  *
886  * Description:
887  *    This is a special case helper to splice directly between two
888  *    points, without requiring an explicit pipe. Internally an allocated
889  *    pipe is cached in the process, and reused during the lifetime of
890  *    that process.
891  *
892  */
893 ssize_t splice_direct_to_actor(struct file *in, struct splice_desc *sd,
894                                splice_direct_actor *actor)
895 {
896         struct pipe_inode_info *pipe;
897         long ret, bytes;
898         umode_t i_mode;
899         size_t len;
900         int i, flags, more;
901 
902         /*
903          * We require the input being a regular file, as we don't want to
904          * randomly drop data for eg socket -> socket splicing. Use the
905          * piped splicing for that!
906          */
907         i_mode = file_inode(in)->i_mode;
908         if (unlikely(!S_ISREG(i_mode) && !S_ISBLK(i_mode)))
909                 return -EINVAL;
910 
911         /*
912          * neither in nor out is a pipe, setup an internal pipe attached to
913          * 'out' and transfer the wanted data from 'in' to 'out' through that
914          */
915         pipe = current->splice_pipe;
916         if (unlikely(!pipe)) {
917                 pipe = alloc_pipe_info();
918                 if (!pipe)
919                         return -ENOMEM;
920 
921                 /*
922                  * We don't have an immediate reader, but we'll read the stuff
923                  * out of the pipe right after the splice_to_pipe(). So set
924                  * PIPE_READERS appropriately.
925                  */
926                 pipe->readers = 1;
927 
928                 current->splice_pipe = pipe;
929         }
930 
931         /*
932          * Do the splice.
933          */
934         ret = 0;
935         bytes = 0;
936         len = sd->total_len;
937         flags = sd->flags;
938 
939         /*
940          * Don't block on output, we have to drain the direct pipe.
941          */
942         sd->flags &= ~SPLICE_F_NONBLOCK;
943         more = sd->flags & SPLICE_F_MORE;
944 
945         WARN_ON_ONCE(pipe->nrbufs != 0);
946 
947         while (len) {
948                 unsigned int pipe_pages;
949                 size_t read_len;
950                 loff_t pos = sd->pos, prev_pos = pos;
951 
952                 /* Don't try to read more the pipe has space for. */
953                 pipe_pages = pipe->buffers - pipe->nrbufs;
954                 read_len = min(len, (size_t)pipe_pages << PAGE_SHIFT);
955                 ret = do_splice_to(in, &pos, pipe, read_len, flags);
956                 if (unlikely(ret <= 0))
957                         goto out_release;
958 
959                 read_len = ret;
960                 sd->total_len = read_len;
961 
962                 /*
963                  * If more data is pending, set SPLICE_F_MORE
964                  * If this is the last data and SPLICE_F_MORE was not set
965                  * initially, clears it.
966                  */
967                 if (read_len < len)
968                         sd->flags |= SPLICE_F_MORE;
969                 else if (!more)
970                         sd->flags &= ~SPLICE_F_MORE;
971                 /*
972                  * NOTE: nonblocking mode only applies to the input. We
973                  * must not do the output in nonblocking mode as then we
974                  * could get stuck data in the internal pipe:
975                  */
976                 ret = actor(pipe, sd);
977                 if (unlikely(ret <= 0)) {
978                         sd->pos = prev_pos;
979                         goto out_release;
980                 }
981 
982                 bytes += ret;
983                 len -= ret;
984                 sd->pos = pos;
985 
986                 if (ret < read_len) {
987                         sd->pos = prev_pos + ret;
988                         goto out_release;
989                 }
990         }
991 
992 done:
993         pipe->nrbufs = pipe->curbuf = 0;
994         file_accessed(in);
995         return bytes;
996 
997 out_release:
998         /*
999          * If we did an incomplete transfer we must release
1000          * the pipe buffers in question:
1001          */
1002         for (i = 0; i < pipe->buffers; i++) {
1003                 struct pipe_buffer *buf = pipe->bufs + i;
1004 
1005                 if (buf->ops)
1006                         pipe_buf_release(pipe, buf);
1007         }
1008 
1009         if (!bytes)
1010                 bytes = ret;
1011 
1012         goto done;
1013 }
1014 EXPORT_SYMBOL(splice_direct_to_actor);
1015 
1016 static int direct_splice_actor(struct pipe_inode_info *pipe,
1017                                struct splice_desc *sd)
1018 {
1019         struct file *file = sd->u.file;
1020 
1021         return do_splice_from(pipe, file, sd->opos, sd->total_len,
1022                               sd->flags);
1023 }
1024 
1025 /**
1026  * do_splice_direct - splices data directly between two files
1027  * @in:         file to splice from
1028  * @ppos:       input file offset
1029  * @out:        file to splice to
1030  * @opos:       output file offset
1031  * @len:        number of bytes to splice
1032  * @flags:      splice modifier flags
1033  *
1034  * Description:
1035  *    For use by do_sendfile(). splice can easily emulate sendfile, but
1036  *    doing it in the application would incur an extra system call
1037  *    (splice in + splice out, as compared to just sendfile()). So this helper
1038  *    can splice directly through a process-private pipe.
1039  *
1040  */
1041 long do_splice_direct(struct file *in, loff_t *ppos, struct file *out,
1042                       loff_t *opos, size_t len, unsigned int flags)
1043 {
1044         struct splice_desc sd = {
1045                 .len            = len,
1046                 .total_len      = len,
1047                 .flags          = flags,
1048                 .pos            = *ppos,
1049                 .u.file         = out,
1050                 .opos           = opos,
1051         };
1052         long ret;
1053 
1054         if (unlikely(!(out->f_mode & FMODE_WRITE)))
1055                 return -EBADF;
1056 
1057         if (unlikely(out->f_flags & O_APPEND))
1058                 return -EINVAL;
1059 
1060         ret = rw_verify_area(WRITE, out, opos, len);
1061         if (unlikely(ret < 0))
1062                 return ret;
1063 
1064         ret = splice_direct_to_actor(in, &sd, direct_splice_actor);
1065         if (ret > 0)
1066                 *ppos = sd.pos;
1067 
1068         return ret;
1069 }
1070 EXPORT_SYMBOL(do_splice_direct);
1071 
1072 static int wait_for_space(struct pipe_inode_info *pipe, unsigned flags)
1073 {
1074         for (;;) {
1075                 if (unlikely(!pipe->readers)) {
1076                         send_sig(SIGPIPE, current, 0);
1077                         return -EPIPE;
1078                 }
1079                 if (pipe->nrbufs != pipe->buffers)
1080                         return 0;
1081                 if (flags & SPLICE_F_NONBLOCK)
1082                         return -EAGAIN;
1083                 if (signal_pending(current))
1084                         return -ERESTARTSYS;
1085                 pipe->waiting_writers++;
1086                 pipe_wait(pipe);
1087                 pipe->waiting_writers--;
1088         }
1089 }
1090 
1091 static int splice_pipe_to_pipe(struct pipe_inode_info *ipipe,
1092                                struct pipe_inode_info *opipe,
1093                                size_t len, unsigned int flags);
1094 
1095 /*
1096  * Determine where to splice to/from.
1097  */
1098 static long do_splice(struct file *in, loff_t __user *off_in,
1099                       struct file *out, loff_t __user *off_out,
1100                       size_t len, unsigned int flags)
1101 {
1102         struct pipe_inode_info *ipipe;
1103         struct pipe_inode_info *opipe;
1104         loff_t offset;
1105         long ret;
1106 
1107         ipipe = get_pipe_info(in);
1108         opipe = get_pipe_info(out);
1109 
1110         if (ipipe && opipe) {
1111                 if (off_in || off_out)
1112                         return -ESPIPE;
1113 
1114                 if (!(in->f_mode & FMODE_READ))
1115                         return -EBADF;
1116 
1117                 if (!(out->f_mode & FMODE_WRITE))
1118                         return -EBADF;
1119 
1120                 /* Splicing to self would be fun, but... */
1121                 if (ipipe == opipe)
1122                         return -EINVAL;
1123 
1124                 if ((in->f_flags | out->f_flags) & O_NONBLOCK)
1125                         flags |= SPLICE_F_NONBLOCK;
1126 
1127                 return splice_pipe_to_pipe(ipipe, opipe, len, flags);
1128         }
1129 
1130         if (ipipe) {
1131                 if (off_in)
1132                         return -ESPIPE;
1133                 if (off_out) {
1134                         if (!(out->f_mode & FMODE_PWRITE))
1135                                 return -EINVAL;
1136                         if (copy_from_user(&offset, off_out, sizeof(loff_t)))
1137                                 return -EFAULT;
1138                 } else {
1139                         offset = out->f_pos;
1140                 }
1141 
1142                 if (unlikely(!(out->f_mode & FMODE_WRITE)))
1143                         return -EBADF;
1144 
1145                 if (unlikely(out->f_flags & O_APPEND))
1146                         return -EINVAL;
1147 
1148                 ret = rw_verify_area(WRITE, out, &offset, len);
1149                 if (unlikely(ret < 0))
1150                         return ret;
1151 
1152                 if (in->f_flags & O_NONBLOCK)
1153                         flags |= SPLICE_F_NONBLOCK;
1154 
1155                 file_start_write(out);
1156                 ret = do_splice_from(ipipe, out, &offset, len, flags);
1157                 file_end_write(out);
1158 
1159                 if (!off_out)
1160                         out->f_pos = offset;
1161                 else if (copy_to_user(off_out, &offset, sizeof(loff_t)))
1162                         ret = -EFAULT;
1163 
1164                 return ret;
1165         }
1166 
1167         if (opipe) {
1168                 if (off_out)
1169                         return -ESPIPE;
1170                 if (off_in) {
1171                         if (!(in->f_mode & FMODE_PREAD))
1172                                 return -EINVAL;
1173                         if (copy_from_user(&offset, off_in, sizeof(loff_t)))
1174                                 return -EFAULT;
1175                 } else {
1176                         offset = in->f_pos;
1177                 }
1178 
1179                 if (out->f_flags & O_NONBLOCK)
1180                         flags |= SPLICE_F_NONBLOCK;
1181 
1182                 pipe_lock(opipe);
1183                 ret = wait_for_space(opipe, flags);
1184                 if (!ret) {
1185                         unsigned int pipe_pages;
1186 
1187                         /* Don't try to read more the pipe has space for. */
1188                         pipe_pages = opipe->buffers - opipe->nrbufs;
1189                         len = min(len, (size_t)pipe_pages << PAGE_SHIFT);
1190 
1191                         ret = do_splice_to(in, &offset, opipe, len, flags);
1192                 }
1193                 pipe_unlock(opipe);
1194                 if (ret > 0)
1195                         wakeup_pipe_readers(opipe);
1196                 if (!off_in)
1197                         in->f_pos = offset;
1198                 else if (copy_to_user(off_in, &offset, sizeof(loff_t)))
1199                         ret = -EFAULT;
1200 
1201                 return ret;
1202         }
1203 
1204         return -EINVAL;
1205 }
1206 
1207 static int iter_to_pipe(struct iov_iter *from,
1208                         struct pipe_inode_info *pipe,
1209                         unsigned flags)
1210 {
1211         struct pipe_buffer buf = {
1212                 .ops = &user_page_pipe_buf_ops,
1213                 .flags = flags
1214         };
1215         size_t total = 0;
1216         int ret = 0;
1217         bool failed = false;
1218 
1219         while (iov_iter_count(from) && !failed) {
1220                 struct page *pages[16];
1221                 ssize_t copied;
1222                 size_t start;
1223                 int n;
1224 
1225                 copied = iov_iter_get_pages(from, pages, ~0UL, 16, &start);
1226                 if (copied <= 0) {
1227                         ret = copied;
1228                         break;
1229                 }
1230 
1231                 for (n = 0; copied; n++, start = 0) {
1232                         int size = min_t(int, copied, PAGE_SIZE - start);
1233                         if (!failed) {
1234                                 buf.page = pages[n];
1235                                 buf.offset = start;
1236                                 buf.len = size;
1237                                 ret = add_to_pipe(pipe, &buf);
1238                                 if (unlikely(ret < 0)) {
1239                                         failed = true;
1240                                 } else {
1241                                         iov_iter_advance(from, ret);
1242                                         total += ret;
1243                                 }
1244                         } else {
1245                                 put_page(pages[n]);
1246                         }
1247                         copied -= size;
1248                 }
1249         }
1250         return total ? total : ret;
1251 }
1252 
1253 static int pipe_to_user(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
1254                         struct splice_desc *sd)
1255 {
1256         int n = copy_page_to_iter(buf->page, buf->offset, sd->len, sd->u.data);
1257         return n == sd->len ? n : -EFAULT;
1258 }
1259 
1260 /*
1261  * For lack of a better implementation, implement vmsplice() to userspace
1262  * as a simple copy of the pipes pages to the user iov.
1263  */
1264 static long vmsplice_to_user(struct file *file, struct iov_iter *iter,
1265                              unsigned int flags)
1266 {
1267         struct pipe_inode_info *pipe = get_pipe_info(file);
1268         struct splice_desc sd = {
1269                 .total_len = iov_iter_count(iter),
1270                 .flags = flags,
1271                 .u.data = iter
1272         };
1273         long ret = 0;
1274 
1275         if (!pipe)
1276                 return -EBADF;
1277 
1278         if (sd.total_len) {
1279                 pipe_lock(pipe);
1280                 ret = __splice_from_pipe(pipe, &sd, pipe_to_user);
1281                 pipe_unlock(pipe);
1282         }
1283 
1284         return ret;
1285 }
1286 
1287 /*
1288  * vmsplice splices a user address range into a pipe. It can be thought of
1289  * as splice-from-memory, where the regular splice is splice-from-file (or
1290  * to file). In both cases the output is a pipe, naturally.
1291  */
1292 static long vmsplice_to_pipe(struct file *file, struct iov_iter *iter,
1293                              unsigned int flags)
1294 {
1295         struct pipe_inode_info *pipe;
1296         long ret = 0;
1297         unsigned buf_flag = 0;
1298 
1299         if (flags & SPLICE_F_GIFT)
1300                 buf_flag = PIPE_BUF_FLAG_GIFT;
1301 
1302         pipe = get_pipe_info(file);
1303         if (!pipe)
1304                 return -EBADF;
1305 
1306         pipe_lock(pipe);
1307         ret = wait_for_space(pipe, flags);
1308         if (!ret)
1309                 ret = iter_to_pipe(iter, pipe, buf_flag);
1310         pipe_unlock(pipe);
1311         if (ret > 0)
1312                 wakeup_pipe_readers(pipe);
1313         return ret;
1314 }
1315 
1316 static int vmsplice_type(struct fd f, int *type)
1317 {
1318         if (!f.file)
1319                 return -EBADF;
1320         if (f.file->f_mode & FMODE_WRITE) {
1321                 *type = WRITE;
1322         } else if (f.file->f_mode & FMODE_READ) {
1323                 *type = READ;
1324         } else {
1325                 fdput(f);
1326                 return -EBADF;
1327         }
1328         return 0;
1329 }
1330 
1331 /*
1332  * Note that vmsplice only really supports true splicing _from_ user memory
1333  * to a pipe, not the other way around. Splicing from user memory is a simple
1334  * operation that can be supported without any funky alignment restrictions
1335  * or nasty vm tricks. We simply map in the user memory and fill them into
1336  * a pipe. The reverse isn't quite as easy, though. There are two possible
1337  * solutions for that:
1338  *
1339  *      - memcpy() the data internally, at which point we might as well just
1340  *        do a regular read() on the buffer anyway.
1341  *      - Lots of nasty vm tricks, that are neither fast nor flexible (it
1342  *        has restriction limitations on both ends of the pipe).
1343  *
1344  * Currently we punt and implement it as a normal copy, see pipe_to_user().
1345  *
1346  */
1347 static long do_vmsplice(struct file *f, struct iov_iter *iter, unsigned int flags)
1348 {
1349         if (unlikely(flags & ~SPLICE_F_ALL))
1350                 return -EINVAL;
1351 
1352         if (!iov_iter_count(iter))
1353                 return 0;
1354 
1355         if (iov_iter_rw(iter) == WRITE)
1356                 return vmsplice_to_pipe(f, iter, flags);
1357         else
1358                 return vmsplice_to_user(f, iter, flags);
1359 }
1360 
1361 SYSCALL_DEFINE4(vmsplice, int, fd, const struct iovec __user *, uiov,
1362                 unsigned long, nr_segs, unsigned int, flags)
1363 {
1364         struct iovec iovstack[UIO_FASTIOV];
1365         struct iovec *iov = iovstack;
1366         struct iov_iter iter;
1367         ssize_t error;
1368         struct fd f;
1369         int type;
1370 
1371         f = fdget(fd);
1372         error = vmsplice_type(f, &type);
1373         if (error)
1374                 return error;
1375 
1376         error = import_iovec(type, uiov, nr_segs,
1377                              ARRAY_SIZE(iovstack), &iov, &iter);
1378         if (error >= 0) {
1379                 error = do_vmsplice(f.file, &iter, flags);
1380                 kfree(iov);
1381         }
1382         fdput(f);
1383         return error;
1384 }
1385 
1386 #ifdef CONFIG_COMPAT
1387 COMPAT_SYSCALL_DEFINE4(vmsplice, int, fd, const struct compat_iovec __user *, iov32,
1388                     unsigned int, nr_segs, unsigned int, flags)
1389 {
1390         struct iovec iovstack[UIO_FASTIOV];
1391         struct iovec *iov = iovstack;
1392         struct iov_iter iter;
1393         ssize_t error;
1394         struct fd f;
1395         int type;
1396 
1397         f = fdget(fd);
1398         error = vmsplice_type(f, &type);
1399         if (error)
1400                 return error;
1401 
1402         error = compat_import_iovec(type, iov32, nr_segs,
1403                              ARRAY_SIZE(iovstack), &iov, &iter);
1404         if (error >= 0) {
1405                 error = do_vmsplice(f.file, &iter, flags);
1406                 kfree(iov);
1407         }
1408         fdput(f);
1409         return error;
1410 }
1411 #endif
1412 
1413 SYSCALL_DEFINE6(splice, int, fd_in, loff_t __user *, off_in,
1414                 int, fd_out, loff_t __user *, off_out,
1415                 size_t, len, unsigned int, flags)
1416 {
1417         struct fd in, out;
1418         long error;
1419 
1420         if (unlikely(!len))
1421                 return 0;
1422 
1423         if (unlikely(flags & ~SPLICE_F_ALL))
1424                 return -EINVAL;
1425 
1426         error = -EBADF;
1427         in = fdget(fd_in);
1428         if (in.file) {
1429                 if (in.file->f_mode & FMODE_READ) {
1430                         out = fdget(fd_out);
1431                         if (out.file) {
1432                                 if (out.file->f_mode & FMODE_WRITE)
1433                                         error = do_splice(in.file, off_in,
1434                                                           out.file, off_out,
1435                                                           len, flags);
1436                                 fdput(out);
1437                         }
1438                 }
1439                 fdput(in);
1440         }
1441         return error;
1442 }
1443 
1444 /*
1445  * Make sure there's data to read. Wait for input if we can, otherwise
1446  * return an appropriate error.
1447  */
1448 static int ipipe_prep(struct pipe_inode_info *pipe, unsigned int flags)
1449 {
1450         int ret;
1451 
1452         /*
1453          * Check ->nrbufs without the inode lock first. This function
1454          * is speculative anyways, so missing one is ok.
1455          */
1456         if (pipe->nrbufs)
1457                 return 0;
1458 
1459         ret = 0;
1460         pipe_lock(pipe);
1461 
1462         while (!pipe->nrbufs) {
1463                 if (signal_pending(current)) {
1464                         ret = -ERESTARTSYS;
1465                         break;
1466                 }
1467                 if (!pipe->writers)
1468                         break;
1469                 if (!pipe->waiting_writers) {
1470                         if (flags & SPLICE_F_NONBLOCK) {
1471                                 ret = -EAGAIN;
1472                                 break;
1473                         }
1474                 }
1475                 pipe_wait(pipe);
1476         }
1477 
1478         pipe_unlock(pipe);
1479         return ret;
1480 }
1481 
1482 /*
1483  * Make sure there's writeable room. Wait for room if we can, otherwise
1484  * return an appropriate error.
1485  */
1486 static int opipe_prep(struct pipe_inode_info *pipe, unsigned int flags)
1487 {
1488         int ret;
1489 
1490         /*
1491          * Check ->nrbufs without the inode lock first. This function
1492          * is speculative anyways, so missing one is ok.
1493          */
1494         if (pipe->nrbufs < pipe->buffers)
1495                 return 0;
1496 
1497         ret = 0;
1498         pipe_lock(pipe);
1499 
1500         while (pipe->nrbufs >= pipe->buffers) {
1501                 if (!pipe->readers) {
1502                         send_sig(SIGPIPE, current, 0);
1503                         ret = -EPIPE;
1504                         break;
1505                 }
1506                 if (flags & SPLICE_F_NONBLOCK) {
1507                         ret = -EAGAIN;
1508                         break;
1509                 }
1510                 if (signal_pending(current)) {
1511                         ret = -ERESTARTSYS;
1512                         break;
1513                 }
1514                 pipe->waiting_writers++;
1515                 pipe_wait(pipe);
1516                 pipe->waiting_writers--;
1517         }
1518 
1519         pipe_unlock(pipe);
1520         return ret;
1521 }
1522 
1523 /*
1524  * Splice contents of ipipe to opipe.
1525  */
1526 static int splice_pipe_to_pipe(struct pipe_inode_info *ipipe,
1527                                struct pipe_inode_info *opipe,
1528                                size_t len, unsigned int flags)
1529 {
1530         struct pipe_buffer *ibuf, *obuf;
1531         int ret = 0, nbuf;
1532         bool input_wakeup = false;
1533 
1534 
1535 retry:
1536         ret = ipipe_prep(ipipe, flags);
1537         if (ret)
1538                 return ret;
1539 
1540         ret = opipe_prep(opipe, flags);
1541         if (ret)
1542                 return ret;
1543 
1544         /*
1545          * Potential ABBA deadlock, work around it by ordering lock
1546          * grabbing by pipe info address. Otherwise two different processes
1547          * could deadlock (one doing tee from A -> B, the other from B -> A).
1548          */
1549         pipe_double_lock(ipipe, opipe);
1550 
1551         do {
1552                 if (!opipe->readers) {
1553                         send_sig(SIGPIPE, current, 0);
1554                         if (!ret)
1555                                 ret = -EPIPE;
1556                         break;
1557                 }
1558 
1559                 if (!ipipe->nrbufs && !ipipe->writers)
1560                         break;
1561 
1562                 /*
1563                  * Cannot make any progress, because either the input
1564                  * pipe is empty or the output pipe is full.
1565                  */
1566                 if (!ipipe->nrbufs || opipe->nrbufs >= opipe->buffers) {
1567                         /* Already processed some buffers, break */
1568                         if (ret)
1569                                 break;
1570 
1571                         if (flags & SPLICE_F_NONBLOCK) {
1572                                 ret = -EAGAIN;
1573                                 break;
1574                         }
1575 
1576                         /*
1577                          * We raced with another reader/writer and haven't
1578                          * managed to process any buffers.  A zero return
1579                          * value means EOF, so retry instead.
1580                          */
1581                         pipe_unlock(ipipe);
1582                         pipe_unlock(opipe);
1583                         goto retry;
1584                 }
1585 
1586                 ibuf = ipipe->bufs + ipipe->curbuf;
1587                 nbuf = (opipe->curbuf + opipe->nrbufs) & (opipe->buffers - 1);
1588                 obuf = opipe->bufs + nbuf;
1589 
1590                 if (len >= ibuf->len) {
1591                         /*
1592                          * Simply move the whole buffer from ipipe to opipe
1593                          */
1594                         *obuf = *ibuf;
1595                         ibuf->ops = NULL;
1596                         opipe->nrbufs++;
1597                         ipipe->curbuf = (ipipe->curbuf + 1) & (ipipe->buffers - 1);
1598                         ipipe->nrbufs--;
1599                         input_wakeup = true;
1600                 } else {
1601                         /*
1602                          * Get a reference to this pipe buffer,
1603                          * so we can copy the contents over.
1604                          */
1605                         if (!pipe_buf_get(ipipe, ibuf)) {
1606                                 if (ret == 0)
1607                                         ret = -EFAULT;
1608                                 break;
1609                         }
1610                         *obuf = *ibuf;
1611 
1612                         /*
1613                          * Don't inherit the gift flag, we need to
1614                          * prevent multiple steals of this page.
1615                          */
1616                         obuf->flags &= ~PIPE_BUF_FLAG_GIFT;
1617 
1618                         pipe_buf_mark_unmergeable(obuf);
1619 
1620                         obuf->len = len;
1621                         opipe->nrbufs++;
1622                         ibuf->offset += obuf->len;
1623                         ibuf->len -= obuf->len;
1624                 }
1625                 ret += obuf->len;
1626                 len -= obuf->len;
1627         } while (len);
1628 
1629         pipe_unlock(ipipe);
1630         pipe_unlock(opipe);
1631 
1632         /*
1633          * If we put data in the output pipe, wakeup any potential readers.
1634          */
1635         if (ret > 0)
1636                 wakeup_pipe_readers(opipe);
1637 
1638         if (input_wakeup)
1639                 wakeup_pipe_writers(ipipe);
1640 
1641         return ret;
1642 }
1643 
1644 /*
1645  * Link contents of ipipe to opipe.
1646  */
1647 static int link_pipe(struct pipe_inode_info *ipipe,
1648                      struct pipe_inode_info *opipe,
1649                      size_t len, unsigned int flags)
1650 {
1651         struct pipe_buffer *ibuf, *obuf;
1652         int ret = 0, i = 0, nbuf;
1653 
1654         /*
1655          * Potential ABBA deadlock, work around it by ordering lock
1656          * grabbing by pipe info address. Otherwise two different processes
1657          * could deadlock (one doing tee from A -> B, the other from B -> A).
1658          */
1659         pipe_double_lock(ipipe, opipe);
1660 
1661         do {
1662                 if (!opipe->readers) {
1663                         send_sig(SIGPIPE, current, 0);
1664                         if (!ret)
1665                                 ret = -EPIPE;
1666                         break;
1667                 }
1668 
1669                 /*
1670                  * If we have iterated all input buffers or ran out of
1671                  * output room, break.
1672                  */
1673                 if (i >= ipipe->nrbufs || opipe->nrbufs >= opipe->buffers)
1674                         break;
1675 
1676                 ibuf = ipipe->bufs + ((ipipe->curbuf + i) & (ipipe->buffers-1));
1677                 nbuf = (opipe->curbuf + opipe->nrbufs) & (opipe->buffers - 1);
1678 
1679                 /*
1680                  * Get a reference to this pipe buffer,
1681                  * so we can copy the contents over.
1682                  */
1683                 if (!pipe_buf_get(ipipe, ibuf)) {
1684                         if (ret == 0)
1685                                 ret = -EFAULT;
1686                         break;
1687                 }
1688 
1689                 obuf = opipe->bufs + nbuf;
1690                 *obuf = *ibuf;
1691 
1692                 /*
1693                  * Don't inherit the gift flag, we need to
1694                  * prevent multiple steals of this page.
1695                  */
1696                 obuf->flags &= ~PIPE_BUF_FLAG_GIFT;
1697 
1698                 pipe_buf_mark_unmergeable(obuf);
1699 
1700                 if (obuf->len > len)
1701                         obuf->len = len;
1702 
1703                 opipe->nrbufs++;
1704                 ret += obuf->len;
1705                 len -= obuf->len;
1706                 i++;
1707         } while (len);
1708 
1709         /*
1710          * return EAGAIN if we have the potential of some data in the
1711          * future, otherwise just return 0
1712          */
1713         if (!ret && ipipe->waiting_writers && (flags & SPLICE_F_NONBLOCK))
1714                 ret = -EAGAIN;
1715 
1716         pipe_unlock(ipipe);
1717         pipe_unlock(opipe);
1718 
1719         /*
1720          * If we put data in the output pipe, wakeup any potential readers.
1721          */
1722         if (ret > 0)
1723                 wakeup_pipe_readers(opipe);
1724 
1725         return ret;
1726 }
1727 
1728 /*
1729  * This is a tee(1) implementation that works on pipes. It doesn't copy
1730  * any data, it simply references the 'in' pages on the 'out' pipe.
1731  * The 'flags' used are the SPLICE_F_* variants, currently the only
1732  * applicable one is SPLICE_F_NONBLOCK.
1733  */
1734 static long do_tee(struct file *in, struct file *out, size_t len,
1735                    unsigned int flags)
1736 {
1737         struct pipe_inode_info *ipipe = get_pipe_info(in);
1738         struct pipe_inode_info *opipe = get_pipe_info(out);
1739         int ret = -EINVAL;
1740 
1741         /*
1742          * Duplicate the contents of ipipe to opipe without actually
1743          * copying the data.
1744          */
1745         if (ipipe && opipe && ipipe != opipe) {
1746                 if ((in->f_flags | out->f_flags) & O_NONBLOCK)
1747                         flags |= SPLICE_F_NONBLOCK;
1748 
1749                 /*
1750                  * Keep going, unless we encounter an error. The ipipe/opipe
1751                  * ordering doesn't really matter.
1752                  */
1753                 ret = ipipe_prep(ipipe, flags);
1754                 if (!ret) {
1755                         ret = opipe_prep(opipe, flags);
1756                         if (!ret)
1757                                 ret = link_pipe(ipipe, opipe, len, flags);
1758                 }
1759         }
1760 
1761         return ret;
1762 }
1763 
1764 SYSCALL_DEFINE4(tee, int, fdin, int, fdout, size_t, len, unsigned int, flags)
1765 {
1766         struct fd in;
1767         int error;
1768 
1769         if (unlikely(flags & ~SPLICE_F_ALL))
1770                 return -EINVAL;
1771 
1772         if (unlikely(!len))
1773                 return 0;
1774 
1775         error = -EBADF;
1776         in = fdget(fdin);
1777         if (in.file) {
1778                 if (in.file->f_mode & FMODE_READ) {
1779                         struct fd out = fdget(fdout);
1780                         if (out.file) {
1781                                 if (out.file->f_mode & FMODE_WRITE)
1782                                         error = do_tee(in.file, out.file,
1783                                                         len, flags);
1784                                 fdput(out);
1785                         }
1786                 }
1787                 fdput(in);
1788         }
1789 
1790         return error;
1791 }
1792 

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