The Design and Implementation of the FreeBSD Operating System, Second Edition
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FreeBSD/Linux Kernel Cross Reference
sys/fs/splice.c

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    1 /*
    2  * "splice": joining two ropes together by interweaving their strands.
    3  *
    4  * This is the "extended pipe" functionality, where a pipe is used as
    5  * an arbitrary in-memory buffer. Think of a pipe as a small kernel
    6  * buffer that you can use to transfer data from one end to the other.
    7  *
    8  * The traditional unix read/write is extended with a "splice()" operation
    9  * that transfers data buffers to or from a pipe buffer.
   10  *
   11  * Named by Larry McVoy, original implementation from Linus, extended by
   12  * Jens to support splicing to files, network, direct splicing, etc and
   13  * fixing lots of bugs.
   14  *
   15  * Copyright (C) 2005-2006 Jens Axboe <axboe@kernel.dk>
   16  * Copyright (C) 2005-2006 Linus Torvalds <torvalds@osdl.org>
   17  * Copyright (C) 2006 Ingo Molnar <mingo@elte.hu>
   18  *
   19  */
   20 #include <linux/fs.h>
   21 #include <linux/file.h>
   22 #include <linux/pagemap.h>
   23 #include <linux/splice.h>
   24 #include <linux/memcontrol.h>
   25 #include <linux/mm_inline.h>
   26 #include <linux/swap.h>
   27 #include <linux/writeback.h>
   28 #include <linux/export.h>
   29 #include <linux/syscalls.h>
   30 #include <linux/uio.h>
   31 #include <linux/security.h>
   32 #include <linux/gfp.h>
   33 #include <linux/socket.h>
   34 
   35 /*
   36  * Attempt to steal a page from a pipe buffer. This should perhaps go into
   37  * a vm helper function, it's already simplified quite a bit by the
   38  * addition of remove_mapping(). If success is returned, the caller may
   39  * attempt to reuse this page for another destination.
   40  */
   41 static int page_cache_pipe_buf_steal(struct pipe_inode_info *pipe,
   42                                      struct pipe_buffer *buf)
   43 {
   44         struct page *page = buf->page;
   45         struct address_space *mapping;
   46 
   47         lock_page(page);
   48 
   49         mapping = page_mapping(page);
   50         if (mapping) {
   51                 WARN_ON(!PageUptodate(page));
   52 
   53                 /*
   54                  * At least for ext2 with nobh option, we need to wait on
   55                  * writeback completing on this page, since we'll remove it
   56                  * from the pagecache.  Otherwise truncate wont wait on the
   57                  * page, allowing the disk blocks to be reused by someone else
   58                  * before we actually wrote our data to them. fs corruption
   59                  * ensues.
   60                  */
   61                 wait_on_page_writeback(page);
   62 
   63                 if (page_has_private(page) &&
   64                     !try_to_release_page(page, GFP_KERNEL))
   65                         goto out_unlock;
   66 
   67                 /*
   68                  * If we succeeded in removing the mapping, set LRU flag
   69                  * and return good.
   70                  */
   71                 if (remove_mapping(mapping, page)) {
   72                         buf->flags |= PIPE_BUF_FLAG_LRU;
   73                         return 0;
   74                 }
   75         }
   76 
   77         /*
   78          * Raced with truncate or failed to remove page from current
   79          * address space, unlock and return failure.
   80          */
   81 out_unlock:
   82         unlock_page(page);
   83         return 1;
   84 }
   85 
   86 static void page_cache_pipe_buf_release(struct pipe_inode_info *pipe,
   87                                         struct pipe_buffer *buf)
   88 {
   89         page_cache_release(buf->page);
   90         buf->flags &= ~PIPE_BUF_FLAG_LRU;
   91 }
   92 
   93 /*
   94  * Check whether the contents of buf is OK to access. Since the content
   95  * is a page cache page, IO may be in flight.
   96  */
   97 static int page_cache_pipe_buf_confirm(struct pipe_inode_info *pipe,
   98                                        struct pipe_buffer *buf)
   99 {
  100         struct page *page = buf->page;
  101         int err;
  102 
  103         if (!PageUptodate(page)) {
  104                 lock_page(page);
  105 
  106                 /*
  107                  * Page got truncated/unhashed. This will cause a 0-byte
  108                  * splice, if this is the first page.
  109                  */
  110                 if (!page->mapping) {
  111                         err = -ENODATA;
  112                         goto error;
  113                 }
  114 
  115                 /*
  116                  * Uh oh, read-error from disk.
  117                  */
  118                 if (!PageUptodate(page)) {
  119                         err = -EIO;
  120                         goto error;
  121                 }
  122 
  123                 /*
  124                  * Page is ok afterall, we are done.
  125                  */
  126                 unlock_page(page);
  127         }
  128 
  129         return 0;
  130 error:
  131         unlock_page(page);
  132         return err;
  133 }
  134 
  135 const struct pipe_buf_operations page_cache_pipe_buf_ops = {
  136         .can_merge = 0,
  137         .map = generic_pipe_buf_map,
  138         .unmap = generic_pipe_buf_unmap,
  139         .confirm = page_cache_pipe_buf_confirm,
  140         .release = page_cache_pipe_buf_release,
  141         .steal = page_cache_pipe_buf_steal,
  142         .get = generic_pipe_buf_get,
  143 };
  144 
  145 static int user_page_pipe_buf_steal(struct pipe_inode_info *pipe,
  146                                     struct pipe_buffer *buf)
  147 {
  148         if (!(buf->flags & PIPE_BUF_FLAG_GIFT))
  149                 return 1;
  150 
  151         buf->flags |= PIPE_BUF_FLAG_LRU;
  152         return generic_pipe_buf_steal(pipe, buf);
  153 }
  154 
  155 static const struct pipe_buf_operations user_page_pipe_buf_ops = {
  156         .can_merge = 0,
  157         .map = generic_pipe_buf_map,
  158         .unmap = generic_pipe_buf_unmap,
  159         .confirm = generic_pipe_buf_confirm,
  160         .release = page_cache_pipe_buf_release,
  161         .steal = user_page_pipe_buf_steal,
  162         .get = generic_pipe_buf_get,
  163 };
  164 
  165 static void wakeup_pipe_readers(struct pipe_inode_info *pipe)
  166 {
  167         smp_mb();
  168         if (waitqueue_active(&pipe->wait))
  169                 wake_up_interruptible(&pipe->wait);
  170         kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
  171 }
  172 
  173 /**
  174  * splice_to_pipe - fill passed data into a pipe
  175  * @pipe:       pipe to fill
  176  * @spd:        data to fill
  177  *
  178  * Description:
  179  *    @spd contains a map of pages and len/offset tuples, along with
  180  *    the struct pipe_buf_operations associated with these pages. This
  181  *    function will link that data to the pipe.
  182  *
  183  */
  184 ssize_t splice_to_pipe(struct pipe_inode_info *pipe,
  185                        struct splice_pipe_desc *spd)
  186 {
  187         unsigned int spd_pages = spd->nr_pages;
  188         int ret, do_wakeup, page_nr;
  189 
  190         ret = 0;
  191         do_wakeup = 0;
  192         page_nr = 0;
  193 
  194         pipe_lock(pipe);
  195 
  196         for (;;) {
  197                 if (!pipe->readers) {
  198                         send_sig(SIGPIPE, current, 0);
  199                         if (!ret)
  200                                 ret = -EPIPE;
  201                         break;
  202                 }
  203 
  204                 if (pipe->nrbufs < pipe->buffers) {
  205                         int newbuf = (pipe->curbuf + pipe->nrbufs) & (pipe->buffers - 1);
  206                         struct pipe_buffer *buf = pipe->bufs + newbuf;
  207 
  208                         buf->page = spd->pages[page_nr];
  209                         buf->offset = spd->partial[page_nr].offset;
  210                         buf->len = spd->partial[page_nr].len;
  211                         buf->private = spd->partial[page_nr].private;
  212                         buf->ops = spd->ops;
  213                         if (spd->flags & SPLICE_F_GIFT)
  214                                 buf->flags |= PIPE_BUF_FLAG_GIFT;
  215 
  216                         pipe->nrbufs++;
  217                         page_nr++;
  218                         ret += buf->len;
  219 
  220                         if (pipe->inode)
  221                                 do_wakeup = 1;
  222 
  223                         if (!--spd->nr_pages)
  224                                 break;
  225                         if (pipe->nrbufs < pipe->buffers)
  226                                 continue;
  227 
  228                         break;
  229                 }
  230 
  231                 if (spd->flags & SPLICE_F_NONBLOCK) {
  232                         if (!ret)
  233                                 ret = -EAGAIN;
  234                         break;
  235                 }
  236 
  237                 if (signal_pending(current)) {
  238                         if (!ret)
  239                                 ret = -ERESTARTSYS;
  240                         break;
  241                 }
  242 
  243                 if (do_wakeup) {
  244                         smp_mb();
  245                         if (waitqueue_active(&pipe->wait))
  246                                 wake_up_interruptible_sync(&pipe->wait);
  247                         kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
  248                         do_wakeup = 0;
  249                 }
  250 
  251                 pipe->waiting_writers++;
  252                 pipe_wait(pipe);
  253                 pipe->waiting_writers--;
  254         }
  255 
  256         pipe_unlock(pipe);
  257 
  258         if (do_wakeup)
  259                 wakeup_pipe_readers(pipe);
  260 
  261         while (page_nr < spd_pages)
  262                 spd->spd_release(spd, page_nr++);
  263 
  264         return ret;
  265 }
  266 
  267 void spd_release_page(struct splice_pipe_desc *spd, unsigned int i)
  268 {
  269         page_cache_release(spd->pages[i]);
  270 }
  271 
  272 /*
  273  * Check if we need to grow the arrays holding pages and partial page
  274  * descriptions.
  275  */
  276 int splice_grow_spd(const struct pipe_inode_info *pipe, struct splice_pipe_desc *spd)
  277 {
  278         unsigned int buffers = ACCESS_ONCE(pipe->buffers);
  279 
  280         spd->nr_pages_max = buffers;
  281         if (buffers <= PIPE_DEF_BUFFERS)
  282                 return 0;
  283 
  284         spd->pages = kmalloc(buffers * sizeof(struct page *), GFP_KERNEL);
  285         spd->partial = kmalloc(buffers * sizeof(struct partial_page), GFP_KERNEL);
  286 
  287         if (spd->pages && spd->partial)
  288                 return 0;
  289 
  290         kfree(spd->pages);
  291         kfree(spd->partial);
  292         return -ENOMEM;
  293 }
  294 
  295 void splice_shrink_spd(struct splice_pipe_desc *spd)
  296 {
  297         if (spd->nr_pages_max <= PIPE_DEF_BUFFERS)
  298                 return;
  299 
  300         kfree(spd->pages);
  301         kfree(spd->partial);
  302 }
  303 
  304 static int
  305 __generic_file_splice_read(struct file *in, loff_t *ppos,
  306                            struct pipe_inode_info *pipe, size_t len,
  307                            unsigned int flags)
  308 {
  309         struct address_space *mapping = in->f_mapping;
  310         unsigned int loff, nr_pages, req_pages;
  311         struct page *pages[PIPE_DEF_BUFFERS];
  312         struct partial_page partial[PIPE_DEF_BUFFERS];
  313         struct page *page;
  314         pgoff_t index, end_index;
  315         loff_t isize;
  316         int error, page_nr;
  317         struct splice_pipe_desc spd = {
  318                 .pages = pages,
  319                 .partial = partial,
  320                 .nr_pages_max = PIPE_DEF_BUFFERS,
  321                 .flags = flags,
  322                 .ops = &page_cache_pipe_buf_ops,
  323                 .spd_release = spd_release_page,
  324         };
  325 
  326         if (splice_grow_spd(pipe, &spd))
  327                 return -ENOMEM;
  328 
  329         index = *ppos >> PAGE_CACHE_SHIFT;
  330         loff = *ppos & ~PAGE_CACHE_MASK;
  331         req_pages = (len + loff + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
  332         nr_pages = min(req_pages, spd.nr_pages_max);
  333 
  334         /*
  335          * Lookup the (hopefully) full range of pages we need.
  336          */
  337         spd.nr_pages = find_get_pages_contig(mapping, index, nr_pages, spd.pages);
  338         index += spd.nr_pages;
  339 
  340         /*
  341          * If find_get_pages_contig() returned fewer pages than we needed,
  342          * readahead/allocate the rest and fill in the holes.
  343          */
  344         if (spd.nr_pages < nr_pages)
  345                 page_cache_sync_readahead(mapping, &in->f_ra, in,
  346                                 index, req_pages - spd.nr_pages);
  347 
  348         error = 0;
  349         while (spd.nr_pages < nr_pages) {
  350                 /*
  351                  * Page could be there, find_get_pages_contig() breaks on
  352                  * the first hole.
  353                  */
  354                 page = find_get_page(mapping, index);
  355                 if (!page) {
  356                         /*
  357                          * page didn't exist, allocate one.
  358                          */
  359                         page = page_cache_alloc_cold(mapping);
  360                         if (!page)
  361                                 break;
  362 
  363                         error = add_to_page_cache_lru(page, mapping, index,
  364                                                 GFP_KERNEL);
  365                         if (unlikely(error)) {
  366                                 page_cache_release(page);
  367                                 if (error == -EEXIST)
  368                                         continue;
  369                                 break;
  370                         }
  371                         /*
  372                          * add_to_page_cache() locks the page, unlock it
  373                          * to avoid convoluting the logic below even more.
  374                          */
  375                         unlock_page(page);
  376                 }
  377 
  378                 spd.pages[spd.nr_pages++] = page;
  379                 index++;
  380         }
  381 
  382         /*
  383          * Now loop over the map and see if we need to start IO on any
  384          * pages, fill in the partial map, etc.
  385          */
  386         index = *ppos >> PAGE_CACHE_SHIFT;
  387         nr_pages = spd.nr_pages;
  388         spd.nr_pages = 0;
  389         for (page_nr = 0; page_nr < nr_pages; page_nr++) {
  390                 unsigned int this_len;
  391 
  392                 if (!len)
  393                         break;
  394 
  395                 /*
  396                  * this_len is the max we'll use from this page
  397                  */
  398                 this_len = min_t(unsigned long, len, PAGE_CACHE_SIZE - loff);
  399                 page = spd.pages[page_nr];
  400 
  401                 if (PageReadahead(page))
  402                         page_cache_async_readahead(mapping, &in->f_ra, in,
  403                                         page, index, req_pages - page_nr);
  404 
  405                 /*
  406                  * If the page isn't uptodate, we may need to start io on it
  407                  */
  408                 if (!PageUptodate(page)) {
  409                         lock_page(page);
  410 
  411                         /*
  412                          * Page was truncated, or invalidated by the
  413                          * filesystem.  Redo the find/create, but this time the
  414                          * page is kept locked, so there's no chance of another
  415                          * race with truncate/invalidate.
  416                          */
  417                         if (!page->mapping) {
  418                                 unlock_page(page);
  419                                 page = find_or_create_page(mapping, index,
  420                                                 mapping_gfp_mask(mapping));
  421 
  422                                 if (!page) {
  423                                         error = -ENOMEM;
  424                                         break;
  425                                 }
  426                                 page_cache_release(spd.pages[page_nr]);
  427                                 spd.pages[page_nr] = page;
  428                         }
  429                         /*
  430                          * page was already under io and is now done, great
  431                          */
  432                         if (PageUptodate(page)) {
  433                                 unlock_page(page);
  434                                 goto fill_it;
  435                         }
  436 
  437                         /*
  438                          * need to read in the page
  439                          */
  440                         error = mapping->a_ops->readpage(in, page);
  441                         if (unlikely(error)) {
  442                                 /*
  443                                  * We really should re-lookup the page here,
  444                                  * but it complicates things a lot. Instead
  445                                  * lets just do what we already stored, and
  446                                  * we'll get it the next time we are called.
  447                                  */
  448                                 if (error == AOP_TRUNCATED_PAGE)
  449                                         error = 0;
  450 
  451                                 break;
  452                         }
  453                 }
  454 fill_it:
  455                 /*
  456                  * i_size must be checked after PageUptodate.
  457                  */
  458                 isize = i_size_read(mapping->host);
  459                 end_index = (isize - 1) >> PAGE_CACHE_SHIFT;
  460                 if (unlikely(!isize || index > end_index))
  461                         break;
  462 
  463                 /*
  464                  * if this is the last page, see if we need to shrink
  465                  * the length and stop
  466                  */
  467                 if (end_index == index) {
  468                         unsigned int plen;
  469 
  470                         /*
  471                          * max good bytes in this page
  472                          */
  473                         plen = ((isize - 1) & ~PAGE_CACHE_MASK) + 1;
  474                         if (plen <= loff)
  475                                 break;
  476 
  477                         /*
  478                          * force quit after adding this page
  479                          */
  480                         this_len = min(this_len, plen - loff);
  481                         len = this_len;
  482                 }
  483 
  484                 spd.partial[page_nr].offset = loff;
  485                 spd.partial[page_nr].len = this_len;
  486                 len -= this_len;
  487                 loff = 0;
  488                 spd.nr_pages++;
  489                 index++;
  490         }
  491 
  492         /*
  493          * Release any pages at the end, if we quit early. 'page_nr' is how far
  494          * we got, 'nr_pages' is how many pages are in the map.
  495          */
  496         while (page_nr < nr_pages)
  497                 page_cache_release(spd.pages[page_nr++]);
  498         in->f_ra.prev_pos = (loff_t)index << PAGE_CACHE_SHIFT;
  499 
  500         if (spd.nr_pages)
  501                 error = splice_to_pipe(pipe, &spd);
  502 
  503         splice_shrink_spd(&spd);
  504         return error;
  505 }
  506 
  507 /**
  508  * generic_file_splice_read - splice data from file to a pipe
  509  * @in:         file to splice from
  510  * @ppos:       position in @in
  511  * @pipe:       pipe to splice to
  512  * @len:        number of bytes to splice
  513  * @flags:      splice modifier flags
  514  *
  515  * Description:
  516  *    Will read pages from given file and fill them into a pipe. Can be
  517  *    used as long as the address_space operations for the source implements
  518  *    a readpage() hook.
  519  *
  520  */
  521 ssize_t generic_file_splice_read(struct file *in, loff_t *ppos,
  522                                  struct pipe_inode_info *pipe, size_t len,
  523                                  unsigned int flags)
  524 {
  525         loff_t isize, left;
  526         int ret;
  527 
  528         isize = i_size_read(in->f_mapping->host);
  529         if (unlikely(*ppos >= isize))
  530                 return 0;
  531 
  532         left = isize - *ppos;
  533         if (unlikely(left < len))
  534                 len = left;
  535 
  536         ret = __generic_file_splice_read(in, ppos, pipe, len, flags);
  537         if (ret > 0) {
  538                 *ppos += ret;
  539                 file_accessed(in);
  540         }
  541 
  542         return ret;
  543 }
  544 EXPORT_SYMBOL(generic_file_splice_read);
  545 
  546 static const struct pipe_buf_operations default_pipe_buf_ops = {
  547         .can_merge = 0,
  548         .map = generic_pipe_buf_map,
  549         .unmap = generic_pipe_buf_unmap,
  550         .confirm = generic_pipe_buf_confirm,
  551         .release = generic_pipe_buf_release,
  552         .steal = generic_pipe_buf_steal,
  553         .get = generic_pipe_buf_get,
  554 };
  555 
  556 static ssize_t kernel_readv(struct file *file, const struct iovec *vec,
  557                             unsigned long vlen, loff_t offset)
  558 {
  559         mm_segment_t old_fs;
  560         loff_t pos = offset;
  561         ssize_t res;
  562 
  563         old_fs = get_fs();
  564         set_fs(get_ds());
  565         /* The cast to a user pointer is valid due to the set_fs() */
  566         res = vfs_readv(file, (const struct iovec __user *)vec, vlen, &pos);
  567         set_fs(old_fs);
  568 
  569         return res;
  570 }
  571 
  572 static ssize_t kernel_write(struct file *file, const char *buf, size_t count,
  573                             loff_t pos)
  574 {
  575         mm_segment_t old_fs;
  576         ssize_t res;
  577 
  578         old_fs = get_fs();
  579         set_fs(get_ds());
  580         /* The cast to a user pointer is valid due to the set_fs() */
  581         res = vfs_write(file, (const char __user *)buf, count, &pos);
  582         set_fs(old_fs);
  583 
  584         return res;
  585 }
  586 
  587 ssize_t default_file_splice_read(struct file *in, loff_t *ppos,
  588                                  struct pipe_inode_info *pipe, size_t len,
  589                                  unsigned int flags)
  590 {
  591         unsigned int nr_pages;
  592         unsigned int nr_freed;
  593         size_t offset;
  594         struct page *pages[PIPE_DEF_BUFFERS];
  595         struct partial_page partial[PIPE_DEF_BUFFERS];
  596         struct iovec *vec, __vec[PIPE_DEF_BUFFERS];
  597         ssize_t res;
  598         size_t this_len;
  599         int error;
  600         int i;
  601         struct splice_pipe_desc spd = {
  602                 .pages = pages,
  603                 .partial = partial,
  604                 .nr_pages_max = PIPE_DEF_BUFFERS,
  605                 .flags = flags,
  606                 .ops = &default_pipe_buf_ops,
  607                 .spd_release = spd_release_page,
  608         };
  609 
  610         if (splice_grow_spd(pipe, &spd))
  611                 return -ENOMEM;
  612 
  613         res = -ENOMEM;
  614         vec = __vec;
  615         if (spd.nr_pages_max > PIPE_DEF_BUFFERS) {
  616                 vec = kmalloc(spd.nr_pages_max * sizeof(struct iovec), GFP_KERNEL);
  617                 if (!vec)
  618                         goto shrink_ret;
  619         }
  620 
  621         offset = *ppos & ~PAGE_CACHE_MASK;
  622         nr_pages = (len + offset + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
  623 
  624         for (i = 0; i < nr_pages && i < spd.nr_pages_max && len; i++) {
  625                 struct page *page;
  626 
  627                 page = alloc_page(GFP_USER);
  628                 error = -ENOMEM;
  629                 if (!page)
  630                         goto err;
  631 
  632                 this_len = min_t(size_t, len, PAGE_CACHE_SIZE - offset);
  633                 vec[i].iov_base = (void __user *) page_address(page);
  634                 vec[i].iov_len = this_len;
  635                 spd.pages[i] = page;
  636                 spd.nr_pages++;
  637                 len -= this_len;
  638                 offset = 0;
  639         }
  640 
  641         res = kernel_readv(in, vec, spd.nr_pages, *ppos);
  642         if (res < 0) {
  643                 error = res;
  644                 goto err;
  645         }
  646 
  647         error = 0;
  648         if (!res)
  649                 goto err;
  650 
  651         nr_freed = 0;
  652         for (i = 0; i < spd.nr_pages; i++) {
  653                 this_len = min_t(size_t, vec[i].iov_len, res);
  654                 spd.partial[i].offset = 0;
  655                 spd.partial[i].len = this_len;
  656                 if (!this_len) {
  657                         __free_page(spd.pages[i]);
  658                         spd.pages[i] = NULL;
  659                         nr_freed++;
  660                 }
  661                 res -= this_len;
  662         }
  663         spd.nr_pages -= nr_freed;
  664 
  665         res = splice_to_pipe(pipe, &spd);
  666         if (res > 0)
  667                 *ppos += res;
  668 
  669 shrink_ret:
  670         if (vec != __vec)
  671                 kfree(vec);
  672         splice_shrink_spd(&spd);
  673         return res;
  674 
  675 err:
  676         for (i = 0; i < spd.nr_pages; i++)
  677                 __free_page(spd.pages[i]);
  678 
  679         res = error;
  680         goto shrink_ret;
  681 }
  682 EXPORT_SYMBOL(default_file_splice_read);
  683 
  684 /*
  685  * Send 'sd->len' bytes to socket from 'sd->file' at position 'sd->pos'
  686  * using sendpage(). Return the number of bytes sent.
  687  */
  688 static int pipe_to_sendpage(struct pipe_inode_info *pipe,
  689                             struct pipe_buffer *buf, struct splice_desc *sd)
  690 {
  691         struct file *file = sd->u.file;
  692         loff_t pos = sd->pos;
  693         int more;
  694 
  695         if (!likely(file->f_op && file->f_op->sendpage))
  696                 return -EINVAL;
  697 
  698         more = (sd->flags & SPLICE_F_MORE) ? MSG_MORE : 0;
  699 
  700         if (sd->len < sd->total_len && pipe->nrbufs > 1)
  701                 more |= MSG_SENDPAGE_NOTLAST;
  702 
  703         return file->f_op->sendpage(file, buf->page, buf->offset,
  704                                     sd->len, &pos, more);
  705 }
  706 
  707 /*
  708  * This is a little more tricky than the file -> pipe splicing. There are
  709  * basically three cases:
  710  *
  711  *      - Destination page already exists in the address space and there
  712  *        are users of it. For that case we have no other option that
  713  *        copying the data. Tough luck.
  714  *      - Destination page already exists in the address space, but there
  715  *        are no users of it. Make sure it's uptodate, then drop it. Fall
  716  *        through to last case.
  717  *      - Destination page does not exist, we can add the pipe page to
  718  *        the page cache and avoid the copy.
  719  *
  720  * If asked to move pages to the output file (SPLICE_F_MOVE is set in
  721  * sd->flags), we attempt to migrate pages from the pipe to the output
  722  * file address space page cache. This is possible if no one else has
  723  * the pipe page referenced outside of the pipe and page cache. If
  724  * SPLICE_F_MOVE isn't set, or we cannot move the page, we simply create
  725  * a new page in the output file page cache and fill/dirty that.
  726  */
  727 int pipe_to_file(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
  728                  struct splice_desc *sd)
  729 {
  730         struct file *file = sd->u.file;
  731         struct address_space *mapping = file->f_mapping;
  732         unsigned int offset, this_len;
  733         struct page *page;
  734         void *fsdata;
  735         int ret;
  736 
  737         offset = sd->pos & ~PAGE_CACHE_MASK;
  738 
  739         this_len = sd->len;
  740         if (this_len + offset > PAGE_CACHE_SIZE)
  741                 this_len = PAGE_CACHE_SIZE - offset;
  742 
  743         ret = pagecache_write_begin(file, mapping, sd->pos, this_len,
  744                                 AOP_FLAG_UNINTERRUPTIBLE, &page, &fsdata);
  745         if (unlikely(ret))
  746                 goto out;
  747 
  748         if (buf->page != page) {
  749                 char *src = buf->ops->map(pipe, buf, 1);
  750                 char *dst = kmap_atomic(page);
  751 
  752                 memcpy(dst + offset, src + buf->offset, this_len);
  753                 flush_dcache_page(page);
  754                 kunmap_atomic(dst);
  755                 buf->ops->unmap(pipe, buf, src);
  756         }
  757         ret = pagecache_write_end(file, mapping, sd->pos, this_len, this_len,
  758                                 page, fsdata);
  759 out:
  760         return ret;
  761 }
  762 EXPORT_SYMBOL(pipe_to_file);
  763 
  764 static void wakeup_pipe_writers(struct pipe_inode_info *pipe)
  765 {
  766         smp_mb();
  767         if (waitqueue_active(&pipe->wait))
  768                 wake_up_interruptible(&pipe->wait);
  769         kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
  770 }
  771 
  772 /**
  773  * splice_from_pipe_feed - feed available data from a pipe to a file
  774  * @pipe:       pipe to splice from
  775  * @sd:         information to @actor
  776  * @actor:      handler that splices the data
  777  *
  778  * Description:
  779  *    This function loops over the pipe and calls @actor to do the
  780  *    actual moving of a single struct pipe_buffer to the desired
  781  *    destination.  It returns when there's no more buffers left in
  782  *    the pipe or if the requested number of bytes (@sd->total_len)
  783  *    have been copied.  It returns a positive number (one) if the
  784  *    pipe needs to be filled with more data, zero if the required
  785  *    number of bytes have been copied and -errno on error.
  786  *
  787  *    This, together with splice_from_pipe_{begin,end,next}, may be
  788  *    used to implement the functionality of __splice_from_pipe() when
  789  *    locking is required around copying the pipe buffers to the
  790  *    destination.
  791  */
  792 int splice_from_pipe_feed(struct pipe_inode_info *pipe, struct splice_desc *sd,
  793                           splice_actor *actor)
  794 {
  795         int ret;
  796 
  797         while (pipe->nrbufs) {
  798                 struct pipe_buffer *buf = pipe->bufs + pipe->curbuf;
  799                 const struct pipe_buf_operations *ops = buf->ops;
  800 
  801                 sd->len = buf->len;
  802                 if (sd->len > sd->total_len)
  803                         sd->len = sd->total_len;
  804 
  805                 ret = buf->ops->confirm(pipe, buf);
  806                 if (unlikely(ret)) {
  807                         if (ret == -ENODATA)
  808                                 ret = 0;
  809                         return ret;
  810                 }
  811 
  812                 ret = actor(pipe, buf, sd);
  813                 if (ret <= 0)
  814                         return ret;
  815 
  816                 buf->offset += ret;
  817                 buf->len -= ret;
  818 
  819                 sd->num_spliced += ret;
  820                 sd->len -= ret;
  821                 sd->pos += ret;
  822                 sd->total_len -= ret;
  823 
  824                 if (!buf->len) {
  825                         buf->ops = NULL;
  826                         ops->release(pipe, buf);
  827                         pipe->curbuf = (pipe->curbuf + 1) & (pipe->buffers - 1);
  828                         pipe->nrbufs--;
  829                         if (pipe->inode)
  830                                 sd->need_wakeup = true;
  831                 }
  832 
  833                 if (!sd->total_len)
  834                         return 0;
  835         }
  836 
  837         return 1;
  838 }
  839 EXPORT_SYMBOL(splice_from_pipe_feed);
  840 
  841 /**
  842  * splice_from_pipe_next - wait for some data to splice from
  843  * @pipe:       pipe to splice from
  844  * @sd:         information about the splice operation
  845  *
  846  * Description:
  847  *    This function will wait for some data and return a positive
  848  *    value (one) if pipe buffers are available.  It will return zero
  849  *    or -errno if no more data needs to be spliced.
  850  */
  851 int splice_from_pipe_next(struct pipe_inode_info *pipe, struct splice_desc *sd)
  852 {
  853         while (!pipe->nrbufs) {
  854                 if (!pipe->writers)
  855                         return 0;
  856 
  857                 if (!pipe->waiting_writers && sd->num_spliced)
  858                         return 0;
  859 
  860                 if (sd->flags & SPLICE_F_NONBLOCK)
  861                         return -EAGAIN;
  862 
  863                 if (signal_pending(current))
  864                         return -ERESTARTSYS;
  865 
  866                 if (sd->need_wakeup) {
  867                         wakeup_pipe_writers(pipe);
  868                         sd->need_wakeup = false;
  869                 }
  870 
  871                 pipe_wait(pipe);
  872         }
  873 
  874         return 1;
  875 }
  876 EXPORT_SYMBOL(splice_from_pipe_next);
  877 
  878 /**
  879  * splice_from_pipe_begin - start splicing from pipe
  880  * @sd:         information about the splice operation
  881  *
  882  * Description:
  883  *    This function should be called before a loop containing
  884  *    splice_from_pipe_next() and splice_from_pipe_feed() to
  885  *    initialize the necessary fields of @sd.
  886  */
  887 void splice_from_pipe_begin(struct splice_desc *sd)
  888 {
  889         sd->num_spliced = 0;
  890         sd->need_wakeup = false;
  891 }
  892 EXPORT_SYMBOL(splice_from_pipe_begin);
  893 
  894 /**
  895  * splice_from_pipe_end - finish splicing from pipe
  896  * @pipe:       pipe to splice from
  897  * @sd:         information about the splice operation
  898  *
  899  * Description:
  900  *    This function will wake up pipe writers if necessary.  It should
  901  *    be called after a loop containing splice_from_pipe_next() and
  902  *    splice_from_pipe_feed().
  903  */
  904 void splice_from_pipe_end(struct pipe_inode_info *pipe, struct splice_desc *sd)
  905 {
  906         if (sd->need_wakeup)
  907                 wakeup_pipe_writers(pipe);
  908 }
  909 EXPORT_SYMBOL(splice_from_pipe_end);
  910 
  911 /**
  912  * __splice_from_pipe - splice data from a pipe to given actor
  913  * @pipe:       pipe to splice from
  914  * @sd:         information to @actor
  915  * @actor:      handler that splices the data
  916  *
  917  * Description:
  918  *    This function does little more than loop over the pipe and call
  919  *    @actor to do the actual moving of a single struct pipe_buffer to
  920  *    the desired destination. See pipe_to_file, pipe_to_sendpage, or
  921  *    pipe_to_user.
  922  *
  923  */
  924 ssize_t __splice_from_pipe(struct pipe_inode_info *pipe, struct splice_desc *sd,
  925                            splice_actor *actor)
  926 {
  927         int ret;
  928 
  929         splice_from_pipe_begin(sd);
  930         do {
  931                 ret = splice_from_pipe_next(pipe, sd);
  932                 if (ret > 0)
  933                         ret = splice_from_pipe_feed(pipe, sd, actor);
  934         } while (ret > 0);
  935         splice_from_pipe_end(pipe, sd);
  936 
  937         return sd->num_spliced ? sd->num_spliced : ret;
  938 }
  939 EXPORT_SYMBOL(__splice_from_pipe);
  940 
  941 /**
  942  * splice_from_pipe - splice data from a pipe to a file
  943  * @pipe:       pipe to splice from
  944  * @out:        file to splice to
  945  * @ppos:       position in @out
  946  * @len:        how many bytes to splice
  947  * @flags:      splice modifier flags
  948  * @actor:      handler that splices the data
  949  *
  950  * Description:
  951  *    See __splice_from_pipe. This function locks the pipe inode,
  952  *    otherwise it's identical to __splice_from_pipe().
  953  *
  954  */
  955 ssize_t splice_from_pipe(struct pipe_inode_info *pipe, struct file *out,
  956                          loff_t *ppos, size_t len, unsigned int flags,
  957                          splice_actor *actor)
  958 {
  959         ssize_t ret;
  960         struct splice_desc sd = {
  961                 .total_len = len,
  962                 .flags = flags,
  963                 .pos = *ppos,
  964                 .u.file = out,
  965         };
  966 
  967         pipe_lock(pipe);
  968         ret = __splice_from_pipe(pipe, &sd, actor);
  969         pipe_unlock(pipe);
  970 
  971         return ret;
  972 }
  973 
  974 /**
  975  * generic_file_splice_write - splice data from a pipe to a file
  976  * @pipe:       pipe info
  977  * @out:        file to write to
  978  * @ppos:       position in @out
  979  * @len:        number of bytes to splice
  980  * @flags:      splice modifier flags
  981  *
  982  * Description:
  983  *    Will either move or copy pages (determined by @flags options) from
  984  *    the given pipe inode to the given file.
  985  *
  986  */
  987 ssize_t
  988 generic_file_splice_write(struct pipe_inode_info *pipe, struct file *out,
  989                           loff_t *ppos, size_t len, unsigned int flags)
  990 {
  991         struct address_space *mapping = out->f_mapping;
  992         struct inode *inode = mapping->host;
  993         struct splice_desc sd = {
  994                 .total_len = len,
  995                 .flags = flags,
  996                 .pos = *ppos,
  997                 .u.file = out,
  998         };
  999         ssize_t ret;
 1000 
 1001         sb_start_write(inode->i_sb);
 1002 
 1003         pipe_lock(pipe);
 1004 
 1005         splice_from_pipe_begin(&sd);
 1006         do {
 1007                 ret = splice_from_pipe_next(pipe, &sd);
 1008                 if (ret <= 0)
 1009                         break;
 1010 
 1011                 mutex_lock_nested(&inode->i_mutex, I_MUTEX_CHILD);
 1012                 ret = file_remove_suid(out);
 1013                 if (!ret) {
 1014                         ret = file_update_time(out);
 1015                         if (!ret)
 1016                                 ret = splice_from_pipe_feed(pipe, &sd,
 1017                                                             pipe_to_file);
 1018                 }
 1019                 mutex_unlock(&inode->i_mutex);
 1020         } while (ret > 0);
 1021         splice_from_pipe_end(pipe, &sd);
 1022 
 1023         pipe_unlock(pipe);
 1024 
 1025         if (sd.num_spliced)
 1026                 ret = sd.num_spliced;
 1027 
 1028         if (ret > 0) {
 1029                 int err;
 1030 
 1031                 err = generic_write_sync(out, *ppos, ret);
 1032                 if (err)
 1033                         ret = err;
 1034                 else
 1035                         *ppos += ret;
 1036                 balance_dirty_pages_ratelimited(mapping);
 1037         }
 1038         sb_end_write(inode->i_sb);
 1039 
 1040         return ret;
 1041 }
 1042 
 1043 EXPORT_SYMBOL(generic_file_splice_write);
 1044 
 1045 static int write_pipe_buf(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
 1046                           struct splice_desc *sd)
 1047 {
 1048         int ret;
 1049         void *data;
 1050 
 1051         data = buf->ops->map(pipe, buf, 0);
 1052         ret = kernel_write(sd->u.file, data + buf->offset, sd->len, sd->pos);
 1053         buf->ops->unmap(pipe, buf, data);
 1054 
 1055         return ret;
 1056 }
 1057 
 1058 static ssize_t default_file_splice_write(struct pipe_inode_info *pipe,
 1059                                          struct file *out, loff_t *ppos,
 1060                                          size_t len, unsigned int flags)
 1061 {
 1062         ssize_t ret;
 1063 
 1064         ret = splice_from_pipe(pipe, out, ppos, len, flags, write_pipe_buf);
 1065         if (ret > 0)
 1066                 *ppos += ret;
 1067 
 1068         return ret;
 1069 }
 1070 
 1071 /**
 1072  * generic_splice_sendpage - splice data from a pipe to a socket
 1073  * @pipe:       pipe to splice from
 1074  * @out:        socket to write to
 1075  * @ppos:       position in @out
 1076  * @len:        number of bytes to splice
 1077  * @flags:      splice modifier flags
 1078  *
 1079  * Description:
 1080  *    Will send @len bytes from the pipe to a network socket. No data copying
 1081  *    is involved.
 1082  *
 1083  */
 1084 ssize_t generic_splice_sendpage(struct pipe_inode_info *pipe, struct file *out,
 1085                                 loff_t *ppos, size_t len, unsigned int flags)
 1086 {
 1087         return splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_sendpage);
 1088 }
 1089 
 1090 EXPORT_SYMBOL(generic_splice_sendpage);
 1091 
 1092 /*
 1093  * Attempt to initiate a splice from pipe to file.
 1094  */
 1095 static long do_splice_from(struct pipe_inode_info *pipe, struct file *out,
 1096                            loff_t *ppos, size_t len, unsigned int flags)
 1097 {
 1098         ssize_t (*splice_write)(struct pipe_inode_info *, struct file *,
 1099                                 loff_t *, size_t, unsigned int);
 1100         int ret;
 1101 
 1102         if (unlikely(!(out->f_mode & FMODE_WRITE)))
 1103                 return -EBADF;
 1104 
 1105         if (unlikely(out->f_flags & O_APPEND))
 1106                 return -EINVAL;
 1107 
 1108         ret = rw_verify_area(WRITE, out, ppos, len);
 1109         if (unlikely(ret < 0))
 1110                 return ret;
 1111 
 1112         if (out->f_op && out->f_op->splice_write)
 1113                 splice_write = out->f_op->splice_write;
 1114         else
 1115                 splice_write = default_file_splice_write;
 1116 
 1117         return splice_write(pipe, out, ppos, len, flags);
 1118 }
 1119 
 1120 /*
 1121  * Attempt to initiate a splice from a file to a pipe.
 1122  */
 1123 static long do_splice_to(struct file *in, loff_t *ppos,
 1124                          struct pipe_inode_info *pipe, size_t len,
 1125                          unsigned int flags)
 1126 {
 1127         ssize_t (*splice_read)(struct file *, loff_t *,
 1128                                struct pipe_inode_info *, size_t, unsigned int);
 1129         int ret;
 1130 
 1131         if (unlikely(!(in->f_mode & FMODE_READ)))
 1132                 return -EBADF;
 1133 
 1134         ret = rw_verify_area(READ, in, ppos, len);
 1135         if (unlikely(ret < 0))
 1136                 return ret;
 1137 
 1138         if (in->f_op && in->f_op->splice_read)
 1139                 splice_read = in->f_op->splice_read;
 1140         else
 1141                 splice_read = default_file_splice_read;
 1142 
 1143         return splice_read(in, ppos, pipe, len, flags);
 1144 }
 1145 
 1146 /**
 1147  * splice_direct_to_actor - splices data directly between two non-pipes
 1148  * @in:         file to splice from
 1149  * @sd:         actor information on where to splice to
 1150  * @actor:      handles the data splicing
 1151  *
 1152  * Description:
 1153  *    This is a special case helper to splice directly between two
 1154  *    points, without requiring an explicit pipe. Internally an allocated
 1155  *    pipe is cached in the process, and reused during the lifetime of
 1156  *    that process.
 1157  *
 1158  */
 1159 ssize_t splice_direct_to_actor(struct file *in, struct splice_desc *sd,
 1160                                splice_direct_actor *actor)
 1161 {
 1162         struct pipe_inode_info *pipe;
 1163         long ret, bytes;
 1164         umode_t i_mode;
 1165         size_t len;
 1166         int i, flags;
 1167 
 1168         /*
 1169          * We require the input being a regular file, as we don't want to
 1170          * randomly drop data for eg socket -> socket splicing. Use the
 1171          * piped splicing for that!
 1172          */
 1173         i_mode = in->f_path.dentry->d_inode->i_mode;
 1174         if (unlikely(!S_ISREG(i_mode) && !S_ISBLK(i_mode)))
 1175                 return -EINVAL;
 1176 
 1177         /*
 1178          * neither in nor out is a pipe, setup an internal pipe attached to
 1179          * 'out' and transfer the wanted data from 'in' to 'out' through that
 1180          */
 1181         pipe = current->splice_pipe;
 1182         if (unlikely(!pipe)) {
 1183                 pipe = alloc_pipe_info(NULL);
 1184                 if (!pipe)
 1185                         return -ENOMEM;
 1186 
 1187                 /*
 1188                  * We don't have an immediate reader, but we'll read the stuff
 1189                  * out of the pipe right after the splice_to_pipe(). So set
 1190                  * PIPE_READERS appropriately.
 1191                  */
 1192                 pipe->readers = 1;
 1193 
 1194                 current->splice_pipe = pipe;
 1195         }
 1196 
 1197         /*
 1198          * Do the splice.
 1199          */
 1200         ret = 0;
 1201         bytes = 0;
 1202         len = sd->total_len;
 1203         flags = sd->flags;
 1204 
 1205         /*
 1206          * Don't block on output, we have to drain the direct pipe.
 1207          */
 1208         sd->flags &= ~SPLICE_F_NONBLOCK;
 1209 
 1210         while (len) {
 1211                 size_t read_len;
 1212                 loff_t pos = sd->pos, prev_pos = pos;
 1213 
 1214                 ret = do_splice_to(in, &pos, pipe, len, flags);
 1215                 if (unlikely(ret <= 0))
 1216                         goto out_release;
 1217 
 1218                 read_len = ret;
 1219                 sd->total_len = read_len;
 1220 
 1221                 /*
 1222                  * NOTE: nonblocking mode only applies to the input. We
 1223                  * must not do the output in nonblocking mode as then we
 1224                  * could get stuck data in the internal pipe:
 1225                  */
 1226                 ret = actor(pipe, sd);
 1227                 if (unlikely(ret <= 0)) {
 1228                         sd->pos = prev_pos;
 1229                         goto out_release;
 1230                 }
 1231 
 1232                 bytes += ret;
 1233                 len -= ret;
 1234                 sd->pos = pos;
 1235 
 1236                 if (ret < read_len) {
 1237                         sd->pos = prev_pos + ret;
 1238                         goto out_release;
 1239                 }
 1240         }
 1241 
 1242 done:
 1243         pipe->nrbufs = pipe->curbuf = 0;
 1244         file_accessed(in);
 1245         return bytes;
 1246 
 1247 out_release:
 1248         /*
 1249          * If we did an incomplete transfer we must release
 1250          * the pipe buffers in question:
 1251          */
 1252         for (i = 0; i < pipe->buffers; i++) {
 1253                 struct pipe_buffer *buf = pipe->bufs + i;
 1254 
 1255                 if (buf->ops) {
 1256                         buf->ops->release(pipe, buf);
 1257                         buf->ops = NULL;
 1258                 }
 1259         }
 1260 
 1261         if (!bytes)
 1262                 bytes = ret;
 1263 
 1264         goto done;
 1265 }
 1266 EXPORT_SYMBOL(splice_direct_to_actor);
 1267 
 1268 static int direct_splice_actor(struct pipe_inode_info *pipe,
 1269                                struct splice_desc *sd)
 1270 {
 1271         struct file *file = sd->u.file;
 1272 
 1273         return do_splice_from(pipe, file, &file->f_pos, sd->total_len,
 1274                               sd->flags);
 1275 }
 1276 
 1277 /**
 1278  * do_splice_direct - splices data directly between two files
 1279  * @in:         file to splice from
 1280  * @ppos:       input file offset
 1281  * @out:        file to splice to
 1282  * @len:        number of bytes to splice
 1283  * @flags:      splice modifier flags
 1284  *
 1285  * Description:
 1286  *    For use by do_sendfile(). splice can easily emulate sendfile, but
 1287  *    doing it in the application would incur an extra system call
 1288  *    (splice in + splice out, as compared to just sendfile()). So this helper
 1289  *    can splice directly through a process-private pipe.
 1290  *
 1291  */
 1292 long do_splice_direct(struct file *in, loff_t *ppos, struct file *out,
 1293                       size_t len, unsigned int flags)
 1294 {
 1295         struct splice_desc sd = {
 1296                 .len            = len,
 1297                 .total_len      = len,
 1298                 .flags          = flags,
 1299                 .pos            = *ppos,
 1300                 .u.file         = out,
 1301         };
 1302         long ret;
 1303 
 1304         ret = splice_direct_to_actor(in, &sd, direct_splice_actor);
 1305         if (ret > 0)
 1306                 *ppos = sd.pos;
 1307 
 1308         return ret;
 1309 }
 1310 
 1311 static int splice_pipe_to_pipe(struct pipe_inode_info *ipipe,
 1312                                struct pipe_inode_info *opipe,
 1313                                size_t len, unsigned int flags);
 1314 
 1315 /*
 1316  * Determine where to splice to/from.
 1317  */
 1318 static long do_splice(struct file *in, loff_t __user *off_in,
 1319                       struct file *out, loff_t __user *off_out,
 1320                       size_t len, unsigned int flags)
 1321 {
 1322         struct pipe_inode_info *ipipe;
 1323         struct pipe_inode_info *opipe;
 1324         loff_t offset, *off;
 1325         long ret;
 1326 
 1327         ipipe = get_pipe_info(in);
 1328         opipe = get_pipe_info(out);
 1329 
 1330         if (ipipe && opipe) {
 1331                 if (off_in || off_out)
 1332                         return -ESPIPE;
 1333 
 1334                 if (!(in->f_mode & FMODE_READ))
 1335                         return -EBADF;
 1336 
 1337                 if (!(out->f_mode & FMODE_WRITE))
 1338                         return -EBADF;
 1339 
 1340                 /* Splicing to self would be fun, but... */
 1341                 if (ipipe == opipe)
 1342                         return -EINVAL;
 1343 
 1344                 return splice_pipe_to_pipe(ipipe, opipe, len, flags);
 1345         }
 1346 
 1347         if (ipipe) {
 1348                 if (off_in)
 1349                         return -ESPIPE;
 1350                 if (off_out) {
 1351                         if (!(out->f_mode & FMODE_PWRITE))
 1352                                 return -EINVAL;
 1353                         if (copy_from_user(&offset, off_out, sizeof(loff_t)))
 1354                                 return -EFAULT;
 1355                         off = &offset;
 1356                 } else
 1357                         off = &out->f_pos;
 1358 
 1359                 ret = do_splice_from(ipipe, out, off, len, flags);
 1360 
 1361                 if (off_out && copy_to_user(off_out, off, sizeof(loff_t)))
 1362                         ret = -EFAULT;
 1363 
 1364                 return ret;
 1365         }
 1366 
 1367         if (opipe) {
 1368                 if (off_out)
 1369                         return -ESPIPE;
 1370                 if (off_in) {
 1371                         if (!(in->f_mode & FMODE_PREAD))
 1372                                 return -EINVAL;
 1373                         if (copy_from_user(&offset, off_in, sizeof(loff_t)))
 1374                                 return -EFAULT;
 1375                         off = &offset;
 1376                 } else
 1377                         off = &in->f_pos;
 1378 
 1379                 ret = do_splice_to(in, off, opipe, len, flags);
 1380 
 1381                 if (off_in && copy_to_user(off_in, off, sizeof(loff_t)))
 1382                         ret = -EFAULT;
 1383 
 1384                 return ret;
 1385         }
 1386 
 1387         return -EINVAL;
 1388 }
 1389 
 1390 /*
 1391  * Map an iov into an array of pages and offset/length tupples. With the
 1392  * partial_page structure, we can map several non-contiguous ranges into
 1393  * our ones pages[] map instead of splitting that operation into pieces.
 1394  * Could easily be exported as a generic helper for other users, in which
 1395  * case one would probably want to add a 'max_nr_pages' parameter as well.
 1396  */
 1397 static int get_iovec_page_array(const struct iovec __user *iov,
 1398                                 unsigned int nr_vecs, struct page **pages,
 1399                                 struct partial_page *partial, bool aligned,
 1400                                 unsigned int pipe_buffers)
 1401 {
 1402         int buffers = 0, error = 0;
 1403 
 1404         while (nr_vecs) {
 1405                 unsigned long off, npages;
 1406                 struct iovec entry;
 1407                 void __user *base;
 1408                 size_t len;
 1409                 int i;
 1410 
 1411                 error = -EFAULT;
 1412                 if (copy_from_user(&entry, iov, sizeof(entry)))
 1413                         break;
 1414 
 1415                 base = entry.iov_base;
 1416                 len = entry.iov_len;
 1417 
 1418                 /*
 1419                  * Sanity check this iovec. 0 read succeeds.
 1420                  */
 1421                 error = 0;
 1422                 if (unlikely(!len))
 1423                         break;
 1424                 error = -EFAULT;
 1425                 if (!access_ok(VERIFY_READ, base, len))
 1426                         break;
 1427 
 1428                 /*
 1429                  * Get this base offset and number of pages, then map
 1430                  * in the user pages.
 1431                  */
 1432                 off = (unsigned long) base & ~PAGE_MASK;
 1433 
 1434                 /*
 1435                  * If asked for alignment, the offset must be zero and the
 1436                  * length a multiple of the PAGE_SIZE.
 1437                  */
 1438                 error = -EINVAL;
 1439                 if (aligned && (off || len & ~PAGE_MASK))
 1440                         break;
 1441 
 1442                 npages = (off + len + PAGE_SIZE - 1) >> PAGE_SHIFT;
 1443                 if (npages > pipe_buffers - buffers)
 1444                         npages = pipe_buffers - buffers;
 1445 
 1446                 error = get_user_pages_fast((unsigned long)base, npages,
 1447                                         0, &pages[buffers]);
 1448 
 1449                 if (unlikely(error <= 0))
 1450                         break;
 1451 
 1452                 /*
 1453                  * Fill this contiguous range into the partial page map.
 1454                  */
 1455                 for (i = 0; i < error; i++) {
 1456                         const int plen = min_t(size_t, len, PAGE_SIZE - off);
 1457 
 1458                         partial[buffers].offset = off;
 1459                         partial[buffers].len = plen;
 1460 
 1461                         off = 0;
 1462                         len -= plen;
 1463                         buffers++;
 1464                 }
 1465 
 1466                 /*
 1467                  * We didn't complete this iov, stop here since it probably
 1468                  * means we have to move some of this into a pipe to
 1469                  * be able to continue.
 1470                  */
 1471                 if (len)
 1472                         break;
 1473 
 1474                 /*
 1475                  * Don't continue if we mapped fewer pages than we asked for,
 1476                  * or if we mapped the max number of pages that we have
 1477                  * room for.
 1478                  */
 1479                 if (error < npages || buffers == pipe_buffers)
 1480                         break;
 1481 
 1482                 nr_vecs--;
 1483                 iov++;
 1484         }
 1485 
 1486         if (buffers)
 1487                 return buffers;
 1488 
 1489         return error;
 1490 }
 1491 
 1492 static int pipe_to_user(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
 1493                         struct splice_desc *sd)
 1494 {
 1495         char *src;
 1496         int ret;
 1497 
 1498         /*
 1499          * See if we can use the atomic maps, by prefaulting in the
 1500          * pages and doing an atomic copy
 1501          */
 1502         if (!fault_in_pages_writeable(sd->u.userptr, sd->len)) {
 1503                 src = buf->ops->map(pipe, buf, 1);
 1504                 ret = __copy_to_user_inatomic(sd->u.userptr, src + buf->offset,
 1505                                                         sd->len);
 1506                 buf->ops->unmap(pipe, buf, src);
 1507                 if (!ret) {
 1508                         ret = sd->len;
 1509                         goto out;
 1510                 }
 1511         }
 1512 
 1513         /*
 1514          * No dice, use slow non-atomic map and copy
 1515          */
 1516         src = buf->ops->map(pipe, buf, 0);
 1517 
 1518         ret = sd->len;
 1519         if (copy_to_user(sd->u.userptr, src + buf->offset, sd->len))
 1520                 ret = -EFAULT;
 1521 
 1522         buf->ops->unmap(pipe, buf, src);
 1523 out:
 1524         if (ret > 0)
 1525                 sd->u.userptr += ret;
 1526         return ret;
 1527 }
 1528 
 1529 /*
 1530  * For lack of a better implementation, implement vmsplice() to userspace
 1531  * as a simple copy of the pipes pages to the user iov.
 1532  */
 1533 static long vmsplice_to_user(struct file *file, const struct iovec __user *iov,
 1534                              unsigned long nr_segs, unsigned int flags)
 1535 {
 1536         struct pipe_inode_info *pipe;
 1537         struct splice_desc sd;
 1538         ssize_t size;
 1539         int error;
 1540         long ret;
 1541 
 1542         pipe = get_pipe_info(file);
 1543         if (!pipe)
 1544                 return -EBADF;
 1545 
 1546         pipe_lock(pipe);
 1547 
 1548         error = ret = 0;
 1549         while (nr_segs) {
 1550                 void __user *base;
 1551                 size_t len;
 1552 
 1553                 /*
 1554                  * Get user address base and length for this iovec.
 1555                  */
 1556                 error = get_user(base, &iov->iov_base);
 1557                 if (unlikely(error))
 1558                         break;
 1559                 error = get_user(len, &iov->iov_len);
 1560                 if (unlikely(error))
 1561                         break;
 1562 
 1563                 /*
 1564                  * Sanity check this iovec. 0 read succeeds.
 1565                  */
 1566                 if (unlikely(!len))
 1567                         break;
 1568                 if (unlikely(!base)) {
 1569                         error = -EFAULT;
 1570                         break;
 1571                 }
 1572 
 1573                 if (unlikely(!access_ok(VERIFY_WRITE, base, len))) {
 1574                         error = -EFAULT;
 1575                         break;
 1576                 }
 1577 
 1578                 sd.len = 0;
 1579                 sd.total_len = len;
 1580                 sd.flags = flags;
 1581                 sd.u.userptr = base;
 1582                 sd.pos = 0;
 1583 
 1584                 size = __splice_from_pipe(pipe, &sd, pipe_to_user);
 1585                 if (size < 0) {
 1586                         if (!ret)
 1587                                 ret = size;
 1588 
 1589                         break;
 1590                 }
 1591 
 1592                 ret += size;
 1593 
 1594                 if (size < len)
 1595                         break;
 1596 
 1597                 nr_segs--;
 1598                 iov++;
 1599         }
 1600 
 1601         pipe_unlock(pipe);
 1602 
 1603         if (!ret)
 1604                 ret = error;
 1605 
 1606         return ret;
 1607 }
 1608 
 1609 /*
 1610  * vmsplice splices a user address range into a pipe. It can be thought of
 1611  * as splice-from-memory, where the regular splice is splice-from-file (or
 1612  * to file). In both cases the output is a pipe, naturally.
 1613  */
 1614 static long vmsplice_to_pipe(struct file *file, const struct iovec __user *iov,
 1615                              unsigned long nr_segs, unsigned int flags)
 1616 {
 1617         struct pipe_inode_info *pipe;
 1618         struct page *pages[PIPE_DEF_BUFFERS];
 1619         struct partial_page partial[PIPE_DEF_BUFFERS];
 1620         struct splice_pipe_desc spd = {
 1621                 .pages = pages,
 1622                 .partial = partial,
 1623                 .nr_pages_max = PIPE_DEF_BUFFERS,
 1624                 .flags = flags,
 1625                 .ops = &user_page_pipe_buf_ops,
 1626                 .spd_release = spd_release_page,
 1627         };
 1628         long ret;
 1629 
 1630         pipe = get_pipe_info(file);
 1631         if (!pipe)
 1632                 return -EBADF;
 1633 
 1634         if (splice_grow_spd(pipe, &spd))
 1635                 return -ENOMEM;
 1636 
 1637         spd.nr_pages = get_iovec_page_array(iov, nr_segs, spd.pages,
 1638                                             spd.partial, false,
 1639                                             spd.nr_pages_max);
 1640         if (spd.nr_pages <= 0)
 1641                 ret = spd.nr_pages;
 1642         else
 1643                 ret = splice_to_pipe(pipe, &spd);
 1644 
 1645         splice_shrink_spd(&spd);
 1646         return ret;
 1647 }
 1648 
 1649 /*
 1650  * Note that vmsplice only really supports true splicing _from_ user memory
 1651  * to a pipe, not the other way around. Splicing from user memory is a simple
 1652  * operation that can be supported without any funky alignment restrictions
 1653  * or nasty vm tricks. We simply map in the user memory and fill them into
 1654  * a pipe. The reverse isn't quite as easy, though. There are two possible
 1655  * solutions for that:
 1656  *
 1657  *      - memcpy() the data internally, at which point we might as well just
 1658  *        do a regular read() on the buffer anyway.
 1659  *      - Lots of nasty vm tricks, that are neither fast nor flexible (it
 1660  *        has restriction limitations on both ends of the pipe).
 1661  *
 1662  * Currently we punt and implement it as a normal copy, see pipe_to_user().
 1663  *
 1664  */
 1665 SYSCALL_DEFINE4(vmsplice, int, fd, const struct iovec __user *, iov,
 1666                 unsigned long, nr_segs, unsigned int, flags)
 1667 {
 1668         struct fd f;
 1669         long error;
 1670 
 1671         if (unlikely(nr_segs > UIO_MAXIOV))
 1672                 return -EINVAL;
 1673         else if (unlikely(!nr_segs))
 1674                 return 0;
 1675 
 1676         error = -EBADF;
 1677         f = fdget(fd);
 1678         if (f.file) {
 1679                 if (f.file->f_mode & FMODE_WRITE)
 1680                         error = vmsplice_to_pipe(f.file, iov, nr_segs, flags);
 1681                 else if (f.file->f_mode & FMODE_READ)
 1682                         error = vmsplice_to_user(f.file, iov, nr_segs, flags);
 1683 
 1684                 fdput(f);
 1685         }
 1686 
 1687         return error;
 1688 }
 1689 
 1690 SYSCALL_DEFINE6(splice, int, fd_in, loff_t __user *, off_in,
 1691                 int, fd_out, loff_t __user *, off_out,
 1692                 size_t, len, unsigned int, flags)
 1693 {
 1694         struct fd in, out;
 1695         long error;
 1696 
 1697         if (unlikely(!len))
 1698                 return 0;
 1699 
 1700         error = -EBADF;
 1701         in = fdget(fd_in);
 1702         if (in.file) {
 1703                 if (in.file->f_mode & FMODE_READ) {
 1704                         out = fdget(fd_out);
 1705                         if (out.file) {
 1706                                 if (out.file->f_mode & FMODE_WRITE)
 1707                                         error = do_splice(in.file, off_in,
 1708                                                           out.file, off_out,
 1709                                                           len, flags);
 1710                                 fdput(out);
 1711                         }
 1712                 }
 1713                 fdput(in);
 1714         }
 1715         return error;
 1716 }
 1717 
 1718 /*
 1719  * Make sure there's data to read. Wait for input if we can, otherwise
 1720  * return an appropriate error.
 1721  */
 1722 static int ipipe_prep(struct pipe_inode_info *pipe, unsigned int flags)
 1723 {
 1724         int ret;
 1725 
 1726         /*
 1727          * Check ->nrbufs without the inode lock first. This function
 1728          * is speculative anyways, so missing one is ok.
 1729          */
 1730         if (pipe->nrbufs)
 1731                 return 0;
 1732 
 1733         ret = 0;
 1734         pipe_lock(pipe);
 1735 
 1736         while (!pipe->nrbufs) {
 1737                 if (signal_pending(current)) {
 1738                         ret = -ERESTARTSYS;
 1739                         break;
 1740                 }
 1741                 if (!pipe->writers)
 1742                         break;
 1743                 if (!pipe->waiting_writers) {
 1744                         if (flags & SPLICE_F_NONBLOCK) {
 1745                                 ret = -EAGAIN;
 1746                                 break;
 1747                         }
 1748                 }
 1749                 pipe_wait(pipe);
 1750         }
 1751 
 1752         pipe_unlock(pipe);
 1753         return ret;
 1754 }
 1755 
 1756 /*
 1757  * Make sure there's writeable room. Wait for room if we can, otherwise
 1758  * return an appropriate error.
 1759  */
 1760 static int opipe_prep(struct pipe_inode_info *pipe, unsigned int flags)
 1761 {
 1762         int ret;
 1763 
 1764         /*
 1765          * Check ->nrbufs without the inode lock first. This function
 1766          * is speculative anyways, so missing one is ok.
 1767          */
 1768         if (pipe->nrbufs < pipe->buffers)
 1769                 return 0;
 1770 
 1771         ret = 0;
 1772         pipe_lock(pipe);
 1773 
 1774         while (pipe->nrbufs >= pipe->buffers) {
 1775                 if (!pipe->readers) {
 1776                         send_sig(SIGPIPE, current, 0);
 1777                         ret = -EPIPE;
 1778                         break;
 1779                 }
 1780                 if (flags & SPLICE_F_NONBLOCK) {
 1781                         ret = -EAGAIN;
 1782                         break;
 1783                 }
 1784                 if (signal_pending(current)) {
 1785                         ret = -ERESTARTSYS;
 1786                         break;
 1787                 }
 1788                 pipe->waiting_writers++;
 1789                 pipe_wait(pipe);
 1790                 pipe->waiting_writers--;
 1791         }
 1792 
 1793         pipe_unlock(pipe);
 1794         return ret;
 1795 }
 1796 
 1797 /*
 1798  * Splice contents of ipipe to opipe.
 1799  */
 1800 static int splice_pipe_to_pipe(struct pipe_inode_info *ipipe,
 1801                                struct pipe_inode_info *opipe,
 1802                                size_t len, unsigned int flags)
 1803 {
 1804         struct pipe_buffer *ibuf, *obuf;
 1805         int ret = 0, nbuf;
 1806         bool input_wakeup = false;
 1807 
 1808 
 1809 retry:
 1810         ret = ipipe_prep(ipipe, flags);
 1811         if (ret)
 1812                 return ret;
 1813 
 1814         ret = opipe_prep(opipe, flags);
 1815         if (ret)
 1816                 return ret;
 1817 
 1818         /*
 1819          * Potential ABBA deadlock, work around it by ordering lock
 1820          * grabbing by pipe info address. Otherwise two different processes
 1821          * could deadlock (one doing tee from A -> B, the other from B -> A).
 1822          */
 1823         pipe_double_lock(ipipe, opipe);
 1824 
 1825         do {
 1826                 if (!opipe->readers) {
 1827                         send_sig(SIGPIPE, current, 0);
 1828                         if (!ret)
 1829                                 ret = -EPIPE;
 1830                         break;
 1831                 }
 1832 
 1833                 if (!ipipe->nrbufs && !ipipe->writers)
 1834                         break;
 1835 
 1836                 /*
 1837                  * Cannot make any progress, because either the input
 1838                  * pipe is empty or the output pipe is full.
 1839                  */
 1840                 if (!ipipe->nrbufs || opipe->nrbufs >= opipe->buffers) {
 1841                         /* Already processed some buffers, break */
 1842                         if (ret)
 1843                                 break;
 1844 
 1845                         if (flags & SPLICE_F_NONBLOCK) {
 1846                                 ret = -EAGAIN;
 1847                                 break;
 1848                         }
 1849 
 1850                         /*
 1851                          * We raced with another reader/writer and haven't
 1852                          * managed to process any buffers.  A zero return
 1853                          * value means EOF, so retry instead.
 1854                          */
 1855                         pipe_unlock(ipipe);
 1856                         pipe_unlock(opipe);
 1857                         goto retry;
 1858                 }
 1859 
 1860                 ibuf = ipipe->bufs + ipipe->curbuf;
 1861                 nbuf = (opipe->curbuf + opipe->nrbufs) & (opipe->buffers - 1);
 1862                 obuf = opipe->bufs + nbuf;
 1863 
 1864                 if (len >= ibuf->len) {
 1865                         /*
 1866                          * Simply move the whole buffer from ipipe to opipe
 1867                          */
 1868                         *obuf = *ibuf;
 1869                         ibuf->ops = NULL;
 1870                         opipe->nrbufs++;
 1871                         ipipe->curbuf = (ipipe->curbuf + 1) & (ipipe->buffers - 1);
 1872                         ipipe->nrbufs--;
 1873                         input_wakeup = true;
 1874                 } else {
 1875                         /*
 1876                          * Get a reference to this pipe buffer,
 1877                          * so we can copy the contents over.
 1878                          */
 1879                         ibuf->ops->get(ipipe, ibuf);
 1880                         *obuf = *ibuf;
 1881 
 1882                         /*
 1883                          * Don't inherit the gift flag, we need to
 1884                          * prevent multiple steals of this page.
 1885                          */
 1886                         obuf->flags &= ~PIPE_BUF_FLAG_GIFT;
 1887 
 1888                         obuf->len = len;
 1889                         opipe->nrbufs++;
 1890                         ibuf->offset += obuf->len;
 1891                         ibuf->len -= obuf->len;
 1892                 }
 1893                 ret += obuf->len;
 1894                 len -= obuf->len;
 1895         } while (len);
 1896 
 1897         pipe_unlock(ipipe);
 1898         pipe_unlock(opipe);
 1899 
 1900         /*
 1901          * If we put data in the output pipe, wakeup any potential readers.
 1902          */
 1903         if (ret > 0)
 1904                 wakeup_pipe_readers(opipe);
 1905 
 1906         if (input_wakeup)
 1907                 wakeup_pipe_writers(ipipe);
 1908 
 1909         return ret;
 1910 }
 1911 
 1912 /*
 1913  * Link contents of ipipe to opipe.
 1914  */
 1915 static int link_pipe(struct pipe_inode_info *ipipe,
 1916                      struct pipe_inode_info *opipe,
 1917                      size_t len, unsigned int flags)
 1918 {
 1919         struct pipe_buffer *ibuf, *obuf;
 1920         int ret = 0, i = 0, nbuf;
 1921 
 1922         /*
 1923          * Potential ABBA deadlock, work around it by ordering lock
 1924          * grabbing by pipe info address. Otherwise two different processes
 1925          * could deadlock (one doing tee from A -> B, the other from B -> A).
 1926          */
 1927         pipe_double_lock(ipipe, opipe);
 1928 
 1929         do {
 1930                 if (!opipe->readers) {
 1931                         send_sig(SIGPIPE, current, 0);
 1932                         if (!ret)
 1933                                 ret = -EPIPE;
 1934                         break;
 1935                 }
 1936 
 1937                 /*
 1938                  * If we have iterated all input buffers or ran out of
 1939                  * output room, break.
 1940                  */
 1941                 if (i >= ipipe->nrbufs || opipe->nrbufs >= opipe->buffers)
 1942                         break;
 1943 
 1944                 ibuf = ipipe->bufs + ((ipipe->curbuf + i) & (ipipe->buffers-1));
 1945                 nbuf = (opipe->curbuf + opipe->nrbufs) & (opipe->buffers - 1);
 1946 
 1947                 /*
 1948                  * Get a reference to this pipe buffer,
 1949                  * so we can copy the contents over.
 1950                  */
 1951                 ibuf->ops->get(ipipe, ibuf);
 1952 
 1953                 obuf = opipe->bufs + nbuf;
 1954                 *obuf = *ibuf;
 1955 
 1956                 /*
 1957                  * Don't inherit the gift flag, we need to
 1958                  * prevent multiple steals of this page.
 1959                  */
 1960                 obuf->flags &= ~PIPE_BUF_FLAG_GIFT;
 1961 
 1962                 if (obuf->len > len)
 1963                         obuf->len = len;
 1964 
 1965                 opipe->nrbufs++;
 1966                 ret += obuf->len;
 1967                 len -= obuf->len;
 1968                 i++;
 1969         } while (len);
 1970 
 1971         /*
 1972          * return EAGAIN if we have the potential of some data in the
 1973          * future, otherwise just return 0
 1974          */
 1975         if (!ret && ipipe->waiting_writers && (flags & SPLICE_F_NONBLOCK))
 1976                 ret = -EAGAIN;
 1977 
 1978         pipe_unlock(ipipe);
 1979         pipe_unlock(opipe);
 1980 
 1981         /*
 1982          * If we put data in the output pipe, wakeup any potential readers.
 1983          */
 1984         if (ret > 0)
 1985                 wakeup_pipe_readers(opipe);
 1986 
 1987         return ret;
 1988 }
 1989 
 1990 /*
 1991  * This is a tee(1) implementation that works on pipes. It doesn't copy
 1992  * any data, it simply references the 'in' pages on the 'out' pipe.
 1993  * The 'flags' used are the SPLICE_F_* variants, currently the only
 1994  * applicable one is SPLICE_F_NONBLOCK.
 1995  */
 1996 static long do_tee(struct file *in, struct file *out, size_t len,
 1997                    unsigned int flags)
 1998 {
 1999         struct pipe_inode_info *ipipe = get_pipe_info(in);
 2000         struct pipe_inode_info *opipe = get_pipe_info(out);
 2001         int ret = -EINVAL;
 2002 
 2003         /*
 2004          * Duplicate the contents of ipipe to opipe without actually
 2005          * copying the data.
 2006          */
 2007         if (ipipe && opipe && ipipe != opipe) {
 2008                 /*
 2009                  * Keep going, unless we encounter an error. The ipipe/opipe
 2010                  * ordering doesn't really matter.
 2011                  */
 2012                 ret = ipipe_prep(ipipe, flags);
 2013                 if (!ret) {
 2014                         ret = opipe_prep(opipe, flags);
 2015                         if (!ret)
 2016                                 ret = link_pipe(ipipe, opipe, len, flags);
 2017                 }
 2018         }
 2019 
 2020         return ret;
 2021 }
 2022 
 2023 SYSCALL_DEFINE4(tee, int, fdin, int, fdout, size_t, len, unsigned int, flags)
 2024 {
 2025         struct fd in;
 2026         int error;
 2027 
 2028         if (unlikely(!len))
 2029                 return 0;
 2030 
 2031         error = -EBADF;
 2032         in = fdget(fdin);
 2033         if (in.file) {
 2034                 if (in.file->f_mode & FMODE_READ) {
 2035                         struct fd out = fdget(fdout);
 2036                         if (out.file) {
 2037                                 if (out.file->f_mode & FMODE_WRITE)
 2038                                         error = do_tee(in.file, out.file,
 2039                                                         len, flags);
 2040                                 fdput(out);
 2041                         }
 2042                 }
 2043                 fdput(in);
 2044         }
 2045 
 2046         return error;
 2047 }

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