SAFE public projects git trees. - safe/jmp/linux-2.6/blob - fs/splice.c

   1 /*
   2  * "splice": joining two ropes together by interweaving their strands.
   3  *
   4  * This is the "extended pipe" functionality, where a pipe is used as
   5  * an arbitrary in-memory buffer. Think of a pipe as a small kernel
   6  * buffer that you can use to transfer data from one end to the other.
   7  *
   8  * The traditional unix read/write is extended with a "splice()" operation
   9  * that transfers data buffers to or from a pipe buffer.
  10  *
  11  * Named by Larry McVoy, original implementation from Linus, extended by
  12  * Jens to support splicing to files, network, direct splicing, etc and
  13  * fixing lots of bugs.
  14  *
  15  * Copyright (C) 2005-2006 Jens Axboe <axboe@suse.de>
  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/pipe_fs_i.h>
  24 #include <linux/mm_inline.h>
  25 #include <linux/swap.h>
  26 #include <linux/writeback.h>
  27 #include <linux/buffer_head.h>
  28 #include <linux/module.h>
  29 #include <linux/syscalls.h>
  30 #include <linux/uio.h>
  31
  32 struct partial_page {
  33         unsigned int offset;
  34         unsigned int len;
  35 };
  36
  37 /*
  38  * Passed to splice_to_pipe
  39  */
  40 struct splice_pipe_desc {
  41         struct page **pages;            /* page map */
  42         struct partial_page *partial;   /* pages[] may not be contig */
  43         int nr_pages;                   /* number of pages in map */
  44         unsigned int flags;             /* splice flags */
  45         struct pipe_buf_operations *ops;/* ops associated with output pipe */
  46 };
  47
  48 /*
  49  * Attempt to steal a page from a pipe buffer. This should perhaps go into
  50  * a vm helper function, it's already simplified quite a bit by the
  51  * addition of remove_mapping(). If success is returned, the caller may
  52  * attempt to reuse this page for another destination.
  53  */
  54 static int page_cache_pipe_buf_steal(struct pipe_inode_info *info,
  55                                      struct pipe_buffer *buf)
  56 {
  57         struct page *page = buf->page;
  58         struct address_space *mapping = page_mapping(page);
  59
  60         lock_page(page);
  61
  62         WARN_ON(!PageUptodate(page));
  63
  64         /*
  65          * At least for ext2 with nobh option, we need to wait on writeback
  66          * completing on this page, since we'll remove it from the pagecache.
  67          * Otherwise truncate wont wait on the page, allowing the disk
  68          * blocks to be reused by someone else before we actually wrote our
  69          * data to them. fs corruption ensues.
  70          */
  71         wait_on_page_writeback(page);
  72
  73         if (PagePrivate(page))
  74                 try_to_release_page(page, mapping_gfp_mask(mapping));
  75
  76         if (!remove_mapping(mapping, page)) {
  77                 unlock_page(page);
  78                 return 1;
  79         }
  80
  81         buf->flags |= PIPE_BUF_FLAG_LRU;
  82         return 0;
  83 }
  84
  85 static void page_cache_pipe_buf_release(struct pipe_inode_info *info,
  86                                         struct pipe_buffer *buf)
  87 {
  88         page_cache_release(buf->page);
  89         buf->page = NULL;
  90         buf->flags &= ~PIPE_BUF_FLAG_LRU;
  91 }
  92
  93 static void *page_cache_pipe_buf_map(struct file *file,
  94                                      struct pipe_inode_info *info,
  95                                      struct pipe_buffer *buf)
  96 {
  97         struct page *page = buf->page;
  98         int err;
  99
 100         if (!PageUptodate(page)) {
 101                 lock_page(page);
 102
 103                 /*
 104                  * Page got truncated/unhashed. This will cause a 0-byte
 105                  * splice, if this is the first page.
 106                  */
 107                 if (!page->mapping) {
 108                         err = -ENODATA;
 109                         goto error;
 110                 }
 111
 112                 /*
 113                  * Uh oh, read-error from disk.
 114                  */
 115                 if (!PageUptodate(page)) {
 116                         err = -EIO;
 117                         goto error;
 118                 }
 119
 120                 /*
 121                  * Page is ok afterall, fall through to mapping.
 122                  */
 123                 unlock_page(page);
 124         }
 125
 126         return kmap(page);
 127 error:
 128         unlock_page(page);
 129         return ERR_PTR(err);
 130 }
 131
 132 static void page_cache_pipe_buf_unmap(struct pipe_inode_info *info,
 133                                       struct pipe_buffer *buf)
 134 {
 135         kunmap(buf->page);
 136 }
 137
 138 static void *user_page_pipe_buf_map(struct file *file,
 139                                     struct pipe_inode_info *pipe,
 140                                     struct pipe_buffer *buf)
 141 {
 142         return kmap(buf->page);
 143 }
 144
 145 static void user_page_pipe_buf_unmap(struct pipe_inode_info *pipe,
 146                                      struct pipe_buffer *buf)
 147 {
 148         kunmap(buf->page);
 149 }
 150
 151 static void page_cache_pipe_buf_get(struct pipe_inode_info *info,
 152                                     struct pipe_buffer *buf)
 153 {
 154         page_cache_get(buf->page);
 155 }
 156
 157 static struct pipe_buf_operations page_cache_pipe_buf_ops = {
 158         .can_merge = 0,
 159         .map = page_cache_pipe_buf_map,
 160         .unmap = page_cache_pipe_buf_unmap,
 161         .release = page_cache_pipe_buf_release,
 162         .steal = page_cache_pipe_buf_steal,
 163         .get = page_cache_pipe_buf_get,
 164 };
 165
 166 static int user_page_pipe_buf_steal(struct pipe_inode_info *pipe,
 167                                     struct pipe_buffer *buf)
 168 {
 169         return 1;
 170 }
 171
 172 static struct pipe_buf_operations user_page_pipe_buf_ops = {
 173         .can_merge = 0,
 174         .map = user_page_pipe_buf_map,
 175         .unmap = user_page_pipe_buf_unmap,
 176         .release = page_cache_pipe_buf_release,
 177         .steal = user_page_pipe_buf_steal,
 178         .get = page_cache_pipe_buf_get,
 179 };
 180
 181 /*
 182  * Pipe output worker. This sets up our pipe format with the page cache
 183  * pipe buffer operations. Otherwise very similar to the regular pipe_writev().
 184  */
 185 static ssize_t splice_to_pipe(struct pipe_inode_info *pipe,
 186                               struct splice_pipe_desc *spd)
 187 {
 188         int ret, do_wakeup, page_nr;
 189
 190         ret = 0;
 191         do_wakeup = 0;
 192         page_nr = 0;
 193
 194         if (pipe->inode)
 195                 mutex_lock(&pipe->inode->i_mutex);
 196
 197         for (;;) {
 198                 if (!pipe->readers) {
 199                         send_sig(SIGPIPE, current, 0);
 200                         if (!ret)
 201                                 ret = -EPIPE;
 202                         break;
 203                 }
 204
 205                 if (pipe->nrbufs < PIPE_BUFFERS) {
 206                         int newbuf = (pipe->curbuf + pipe->nrbufs) & (PIPE_BUFFERS - 1);
 207                         struct pipe_buffer *buf = pipe->bufs + newbuf;
 208
 209                         buf->page = spd->pages[page_nr];
 210                         buf->offset = spd->partial[page_nr].offset;
 211                         buf->len = spd->partial[page_nr].len;
 212                         buf->ops = spd->ops;
 213                         pipe->nrbufs++;
 214                         page_nr++;
 215                         ret += buf->len;
 216
 217                         if (pipe->inode)
 218                                 do_wakeup = 1;
 219
 220                         if (!--spd->nr_pages)
 221                                 break;
 222                         if (pipe->nrbufs < PIPE_BUFFERS)
 223                                 continue;
 224
 225                         break;
 226                 }
 227
 228                 if (spd->flags & SPLICE_F_NONBLOCK) {
 229                         if (!ret)
 230                                 ret = -EAGAIN;
 231                         break;
 232                 }
 233
 234                 if (signal_pending(current)) {
 235                         if (!ret)
 236                                 ret = -ERESTARTSYS;
 237                         break;
 238                 }
 239
 240                 if (do_wakeup) {
 241                         smp_mb();
 242                         if (waitqueue_active(&pipe->wait))
 243                                 wake_up_interruptible_sync(&pipe->wait);
 244                         kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
 245                         do_wakeup = 0;
 246                 }
 247
 248                 pipe->waiting_writers++;
 249                 pipe_wait(pipe);
 250                 pipe->waiting_writers--;
 251         }
 252
 253         if (pipe->inode)
 254                 mutex_unlock(&pipe->inode->i_mutex);
 255
 256         if (do_wakeup) {
 257                 smp_mb();
 258                 if (waitqueue_active(&pipe->wait))
 259                         wake_up_interruptible(&pipe->wait);
 260                 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
 261         }
 262
 263         while (page_nr < spd->nr_pages)
 264                 page_cache_release(spd->pages[page_nr++]);
 265
 266         return ret;
 267 }
 268
 269 static int
 270 __generic_file_splice_read(struct file *in, loff_t *ppos,
 271                            struct pipe_inode_info *pipe, size_t len,
 272                            unsigned int flags)
 273 {
 274         struct address_space *mapping = in->f_mapping;
 275         unsigned int loff, nr_pages;
 276         struct page *pages[PIPE_BUFFERS];
 277         struct partial_page partial[PIPE_BUFFERS];
 278         struct page *page;
 279         pgoff_t index, end_index;
 280         loff_t isize;
 281         size_t total_len;
 282         int error, page_nr;
 283         struct splice_pipe_desc spd = {
 284                 .pages = pages,
 285                 .partial = partial,
 286                 .flags = flags,
 287                 .ops = &page_cache_pipe_buf_ops,
 288         };
 289
 290         index = *ppos >> PAGE_CACHE_SHIFT;
 291         loff = *ppos & ~PAGE_CACHE_MASK;
 292         nr_pages = (len + loff + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
 293
 294         if (nr_pages > PIPE_BUFFERS)
 295                 nr_pages = PIPE_BUFFERS;
 296
 297         /*
 298          * Initiate read-ahead on this page range. however, don't call into
 299          * read-ahead if this is a non-zero offset (we are likely doing small
 300          * chunk splice and the page is already there) for a single page.
 301          */
 302         if (!loff || nr_pages > 1)
 303                 page_cache_readahead(mapping, &in->f_ra, in, index, nr_pages);
 304
 305         /*
 306          * Now fill in the holes:
 307          */
 308         error = 0;
 309         total_len = 0;
 310
 311         /*
 312          * Lookup the (hopefully) full range of pages we need.
 313          */
 314         spd.nr_pages = find_get_pages_contig(mapping, index, nr_pages, pages);
 315
 316         /*
 317          * If find_get_pages_contig() returned fewer pages than we needed,
 318          * allocate the rest.
 319          */
 320         index += spd.nr_pages;
 321         while (spd.nr_pages < nr_pages) {
 322                 /*
 323                  * Page could be there, find_get_pages_contig() breaks on
 324                  * the first hole.
 325                  */
 326                 page = find_get_page(mapping, index);
 327                 if (!page) {
 328                         /*
 329                          * page didn't exist, allocate one.
 330                          */
 331                         page = page_cache_alloc_cold(mapping);
 332                         if (!page)
 333                                 break;
 334
 335                         error = add_to_page_cache_lru(page, mapping, index,
 336                                               mapping_gfp_mask(mapping));
 337                         if (unlikely(error)) {
 338                                 page_cache_release(page);
 339                                 break;
 340                         }
 341                         /*
 342                          * add_to_page_cache() locks the page, unlock it
 343                          * to avoid convoluting the logic below even more.
 344                          */
 345                         unlock_page(page);
 346                 }
 347
 348                 pages[spd.nr_pages++] = page;
 349                 index++;
 350         }
 351
 352         /*
 353          * Now loop over the map and see if we need to start IO on any
 354          * pages, fill in the partial map, etc.
 355          */
 356         index = *ppos >> PAGE_CACHE_SHIFT;
 357         nr_pages = spd.nr_pages;
 358         spd.nr_pages = 0;
 359         for (page_nr = 0; page_nr < nr_pages; page_nr++) {
 360                 unsigned int this_len;
 361
 362                 if (!len)
 363                         break;
 364
 365                 /*
 366                  * this_len is the max we'll use from this page
 367                  */
 368                 this_len = min_t(unsigned long, len, PAGE_CACHE_SIZE - loff);
 369                 page = pages[page_nr];
 370
 371                 /*
 372                  * If the page isn't uptodate, we may need to start io on it
 373                  */
 374                 if (!PageUptodate(page)) {
 375                         /*
 376                          * If in nonblock mode then dont block on waiting
 377                          * for an in-flight io page
 378                          */
 379                         if (flags & SPLICE_F_NONBLOCK)
 380                                 break;
 381
 382                         lock_page(page);
 383
 384                         /*
 385                          * page was truncated, stop here. if this isn't the
 386                          * first page, we'll just complete what we already
 387                          * added
 388                          */
 389                         if (!page->mapping) {
 390                                 unlock_page(page);
 391                                 break;
 392                         }
 393                         /*
 394                          * page was already under io and is now done, great
 395                          */
 396                         if (PageUptodate(page)) {
 397                                 unlock_page(page);
 398                                 goto fill_it;
 399                         }
 400
 401                         /*
 402                          * need to read in the page
 403                          */
 404                         error = mapping->a_ops->readpage(in, page);
 405                         if (unlikely(error)) {
 406                                 /*
 407                                  * We really should re-lookup the page here,
 408                                  * but it complicates things a lot. Instead
 409                                  * lets just do what we already stored, and
 410                                  * we'll get it the next time we are called.
 411                                  */
 412                                 if (error == AOP_TRUNCATED_PAGE)
 413                                         error = 0;
 414
 415                                 break;
 416                         }
 417
 418                         /*
 419                          * i_size must be checked after ->readpage().
 420                          */
 421                         isize = i_size_read(mapping->host);
 422                         end_index = (isize - 1) >> PAGE_CACHE_SHIFT;
 423                         if (unlikely(!isize || index > end_index))
 424                                 break;
 425
 426                         /*
 427                          * if this is the last page, see if we need to shrink
 428                          * the length and stop
 429                          */
 430                         if (end_index == index) {
 431                                 loff = PAGE_CACHE_SIZE - (isize & ~PAGE_CACHE_MASK);
 432                                 if (total_len + loff > isize)
 433                                         break;
 434                                 /*
 435                                  * force quit after adding this page
 436                                  */
 437                                 len = this_len;
 438                                 this_len = min(this_len, loff);
 439                                 loff = 0;
 440                         }
 441                 }
 442 fill_it:
 443                 partial[page_nr].offset = loff;
 444                 partial[page_nr].len = this_len;
 445                 len -= this_len;
 446                 total_len += this_len;
 447                 loff = 0;
 448                 spd.nr_pages++;
 449                 index++;
 450         }
 451
 452         /*
 453          * Release any pages at the end, if we quit early. 'i' is how far
 454          * we got, 'nr_pages' is how many pages are in the map.
 455          */
 456         while (page_nr < nr_pages)
 457                 page_cache_release(pages[page_nr++]);
 458
 459         if (spd.nr_pages)
 460                 return splice_to_pipe(pipe, &spd);
 461
 462         return error;
 463 }
 464
 465 /**
 466  * generic_file_splice_read - splice data from file to a pipe
 467  * @in:         file to splice from
 468  * @pipe:       pipe to splice to
 469  * @len:        number of bytes to splice
 470  * @flags:      splice modifier flags
 471  *
 472  * Will read pages from given file and fill them into a pipe.
 473  */
 474 ssize_t generic_file_splice_read(struct file *in, loff_t *ppos,
 475                                  struct pipe_inode_info *pipe, size_t len,
 476                                  unsigned int flags)
 477 {
 478         ssize_t spliced;
 479         int ret;
 480
 481         ret = 0;
 482         spliced = 0;
 483
 484         while (len) {
 485                 ret = __generic_file_splice_read(in, ppos, pipe, len, flags);
 486
 487                 if (ret < 0)
 488                         break;
 489                 else if (!ret) {
 490                         if (spliced)
 491                                 break;
 492                         if (flags & SPLICE_F_NONBLOCK) {
 493                                 ret = -EAGAIN;
 494                                 break;
 495                         }
 496                 }
 497
 498                 *ppos += ret;
 499                 len -= ret;
 500                 spliced += ret;
 501         }
 502
 503         if (spliced)
 504                 return spliced;
 505
 506         return ret;
 507 }
 508
 509 EXPORT_SYMBOL(generic_file_splice_read);
 510
 511 /*
 512  * Send 'sd->len' bytes to socket from 'sd->file' at position 'sd->pos'
 513  * using sendpage(). Return the number of bytes sent.
 514  */
 515 static int pipe_to_sendpage(struct pipe_inode_info *info,
 516                             struct pipe_buffer *buf, struct splice_desc *sd)
 517 {
 518         struct file *file = sd->file;
 519         loff_t pos = sd->pos;
 520         ssize_t ret;
 521         void *ptr;
 522         int more;
 523
 524         /*
 525          * Sub-optimal, but we are limited by the pipe ->map. We don't
 526          * need a kmap'ed buffer here, we just want to make sure we
 527          * have the page pinned if the pipe page originates from the
 528          * page cache.
 529          */
 530         ptr = buf->ops->map(file, info, buf);
 531         if (IS_ERR(ptr))
 532                 return PTR_ERR(ptr);
 533
 534         more = (sd->flags & SPLICE_F_MORE) || sd->len < sd->total_len;
 535
 536         ret = file->f_op->sendpage(file, buf->page, buf->offset, sd->len,
 537                                    &pos, more);
 538
 539         buf->ops->unmap(info, buf);
 540         return ret;
 541 }
 542
 543 /*
 544  * This is a little more tricky than the file -> pipe splicing. There are
 545  * basically three cases:
 546  *
 547  *      - Destination page already exists in the address space and there
 548  *        are users of it. For that case we have no other option that
 549  *        copying the data. Tough luck.
 550  *      - Destination page already exists in the address space, but there
 551  *        are no users of it. Make sure it's uptodate, then drop it. Fall
 552  *        through to last case.
 553  *      - Destination page does not exist, we can add the pipe page to
 554  *        the page cache and avoid the copy.
 555  *
 556  * If asked to move pages to the output file (SPLICE_F_MOVE is set in
 557  * sd->flags), we attempt to migrate pages from the pipe to the output
 558  * file address space page cache. This is possible if no one else has
 559  * the pipe page referenced outside of the pipe and page cache. If
 560  * SPLICE_F_MOVE isn't set, or we cannot move the page, we simply create
 561  * a new page in the output file page cache and fill/dirty that.
 562  */
 563 static int pipe_to_file(struct pipe_inode_info *info, struct pipe_buffer *buf,
 564                         struct splice_desc *sd)
 565 {
 566         struct file *file = sd->file;
 567         struct address_space *mapping = file->f_mapping;
 568         gfp_t gfp_mask = mapping_gfp_mask(mapping);
 569         unsigned int offset, this_len;
 570         struct page *page;
 571         pgoff_t index;
 572         char *src;
 573         int ret;
 574
 575         /*
 576          * make sure the data in this buffer is uptodate
 577          */
 578         src = buf->ops->map(file, info, buf);
 579         if (IS_ERR(src))
 580                 return PTR_ERR(src);
 581
 582         index = sd->pos >> PAGE_CACHE_SHIFT;
 583         offset = sd->pos & ~PAGE_CACHE_MASK;
 584
 585         this_len = sd->len;
 586         if (this_len + offset > PAGE_CACHE_SIZE)
 587                 this_len = PAGE_CACHE_SIZE - offset;
 588
 589         /*
 590          * Reuse buf page, if SPLICE_F_MOVE is set and we are doing a full
 591          * page.
 592          */
 593         if ((sd->flags & SPLICE_F_MOVE) && this_len == PAGE_CACHE_SIZE) {
 594                 /*
 595                  * If steal succeeds, buf->page is now pruned from the vm
 596                  * side (LRU and page cache) and we can reuse it. The page
 597                  * will also be looked on successful return.
 598                  */
 599                 if (buf->ops->steal(info, buf))
 600                         goto find_page;
 601
 602                 page = buf->page;
 603                 if (add_to_page_cache(page, mapping, index, gfp_mask)) {
 604                         unlock_page(page);
 605                         goto find_page;
 606                 }
 607
 608                 page_cache_get(page);
 609
 610                 if (!(buf->flags & PIPE_BUF_FLAG_LRU))
 611                         lru_cache_add(page);
 612         } else {
 613 find_page:
 614                 page = find_lock_page(mapping, index);
 615                 if (!page) {
 616                         ret = -ENOMEM;
 617                         page = page_cache_alloc_cold(mapping);
 618                         if (unlikely(!page))
 619                                 goto out_nomem;
 620
 621                         /*
 622                          * This will also lock the page
 623                          */
 624                         ret = add_to_page_cache_lru(page, mapping, index,
 625                                                     gfp_mask);
 626                         if (unlikely(ret))
 627                                 goto out;
 628                 }
 629
 630                 /*
 631                  * We get here with the page locked. If the page is also
 632                  * uptodate, we don't need to do more. If it isn't, we
 633                  * may need to bring it in if we are not going to overwrite
 634                  * the full page.
 635                  */
 636                 if (!PageUptodate(page)) {
 637                         if (this_len < PAGE_CACHE_SIZE) {
 638                                 ret = mapping->a_ops->readpage(file, page);
 639                                 if (unlikely(ret))
 640                                         goto out;
 641
 642                                 lock_page(page);
 643
 644                                 if (!PageUptodate(page)) {
 645                                         /*
 646                                          * Page got invalidated, repeat.
 647                                          */
 648                                         if (!page->mapping) {
 649                                                 unlock_page(page);
 650                                                 page_cache_release(page);
 651                                                 goto find_page;
 652                                         }
 653                                         ret = -EIO;
 654                                         goto out;
 655                                 }
 656                         } else
 657                                 SetPageUptodate(page);
 658                 }
 659         }
 660
 661         ret = mapping->a_ops->prepare_write(file, page, offset, offset+this_len);
 662         if (ret == AOP_TRUNCATED_PAGE) {
 663                 page_cache_release(page);
 664                 goto find_page;
 665         } else if (ret)
 666                 goto out;
 667
 668         if (buf->page != page) {
 669                 char *dst = kmap_atomic(page, KM_USER0);
 670
 671                 memcpy(dst + offset, src + buf->offset, this_len);
 672                 flush_dcache_page(page);
 673                 kunmap_atomic(dst, KM_USER0);
 674         }
 675
 676         ret = mapping->a_ops->commit_write(file, page, offset, offset+this_len);
 677         if (!ret) {
 678                 /*
 679                  * Return the number of bytes written and mark page as
 680                  * accessed, we are now done!
 681                  */
 682                 ret = this_len;
 683                 mark_page_accessed(page);
 684                 balance_dirty_pages_ratelimited(mapping);
 685         } else if (ret == AOP_TRUNCATED_PAGE) {
 686                 page_cache_release(page);
 687                 goto find_page;
 688         }
 689 out:
 690         page_cache_release(page);
 691         unlock_page(page);
 692 out_nomem:
 693         buf->ops->unmap(info, buf);
 694         return ret;
 695 }
 696
 697 /*
 698  * Pipe input worker. Most of this logic works like a regular pipe, the
 699  * key here is the 'actor' worker passed in that actually moves the data
 700  * to the wanted destination. See pipe_to_file/pipe_to_sendpage above.
 701  */
 702 ssize_t splice_from_pipe(struct pipe_inode_info *pipe, struct file *out,
 703                          loff_t *ppos, size_t len, unsigned int flags,
 704                          splice_actor *actor)
 705 {
 706         int ret, do_wakeup, err;
 707         struct splice_desc sd;
 708
 709         ret = 0;
 710         do_wakeup = 0;
 711
 712         sd.total_len = len;
 713         sd.flags = flags;
 714         sd.file = out;
 715         sd.pos = *ppos;
 716
 717         if (pipe->inode)
 718                 mutex_lock(&pipe->inode->i_mutex);
 719
 720         for (;;) {
 721                 if (pipe->nrbufs) {
 722                         struct pipe_buffer *buf = pipe->bufs + pipe->curbuf;
 723                         struct pipe_buf_operations *ops = buf->ops;
 724
 725                         sd.len = buf->len;
 726                         if (sd.len > sd.total_len)
 727                                 sd.len = sd.total_len;
 728
 729                         err = actor(pipe, buf, &sd);
 730                         if (err <= 0) {
 731                                 if (!ret && err != -ENODATA)
 732                                         ret = err;
 733
 734                                 break;
 735                         }
 736
 737                         ret += err;
 738                         buf->offset += err;
 739                         buf->len -= err;
 740
 741                         sd.len -= err;
 742                         sd.pos += err;
 743                         sd.total_len -= err;
 744                         if (sd.len)
 745                                 continue;
 746
 747                         if (!buf->len) {
 748                                 buf->ops = NULL;
 749                                 ops->release(pipe, buf);
 750                                 pipe->curbuf = (pipe->curbuf + 1) & (PIPE_BUFFERS - 1);
 751                                 pipe->nrbufs--;
 752                                 if (pipe->inode)
 753                                         do_wakeup = 1;
 754                         }
 755
 756                         if (!sd.total_len)
 757                                 break;
 758                 }
 759
 760                 if (pipe->nrbufs)
 761                         continue;
 762                 if (!pipe->writers)
 763                         break;
 764                 if (!pipe->waiting_writers) {
 765                         if (ret)
 766                                 break;
 767                 }
 768
 769                 if (flags & SPLICE_F_NONBLOCK) {
 770                         if (!ret)
 771                                 ret = -EAGAIN;
 772                         break;
 773                 }
 774
 775                 if (signal_pending(current)) {
 776                         if (!ret)
 777                                 ret = -ERESTARTSYS;
 778                         break;
 779                 }
 780
 781                 if (do_wakeup) {
 782                         smp_mb();
 783                         if (waitqueue_active(&pipe->wait))
 784                                 wake_up_interruptible_sync(&pipe->wait);
 785                         kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
 786                         do_wakeup = 0;
 787                 }
 788
 789                 pipe_wait(pipe);
 790         }
 791
 792         if (pipe->inode)
 793                 mutex_unlock(&pipe->inode->i_mutex);
 794
 795         if (do_wakeup) {
 796                 smp_mb();
 797                 if (waitqueue_active(&pipe->wait))
 798                         wake_up_interruptible(&pipe->wait);
 799                 kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
 800         }
 801
 802         return ret;
 803 }
 804
 805 /**
 806  * generic_file_splice_write - splice data from a pipe to a file
 807  * @pipe:       pipe info
 808  * @out:        file to write to
 809  * @len:        number of bytes to splice
 810  * @flags:      splice modifier flags
 811  *
 812  * Will either move or copy pages (determined by @flags options) from
 813  * the given pipe inode to the given file.
 814  *
 815  */
 816 ssize_t
 817 generic_file_splice_write(struct pipe_inode_info *pipe, struct file *out,
 818                           loff_t *ppos, size_t len, unsigned int flags)
 819 {
 820         struct address_space *mapping = out->f_mapping;
 821         ssize_t ret;
 822
 823         ret = splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_file);
 824         if (ret > 0) {
 825                 struct inode *inode = mapping->host;
 826
 827                 *ppos += ret;
 828
 829                 /*
 830                  * If file or inode is SYNC and we actually wrote some data,
 831                  * sync it.
 832                  */
 833                 if (unlikely((out->f_flags & O_SYNC) || IS_SYNC(inode))) {
 834                         int err;
 835
 836                         mutex_lock(&inode->i_mutex);
 837                         err = generic_osync_inode(inode, mapping,
 838                                                   OSYNC_METADATA|OSYNC_DATA);
 839                         mutex_unlock(&inode->i_mutex);
 840
 841                         if (err)
 842                                 ret = err;
 843                 }
 844         }
 845
 846         return ret;
 847 }
 848
 849 EXPORT_SYMBOL(generic_file_splice_write);
 850
 851 /**
 852  * generic_splice_sendpage - splice data from a pipe to a socket
 853  * @inode:      pipe inode
 854  * @out:        socket to write to
 855  * @len:        number of bytes to splice
 856  * @flags:      splice modifier flags
 857  *
 858  * Will send @len bytes from the pipe to a network socket. No data copying
 859  * is involved.
 860  *
 861  */
 862 ssize_t generic_splice_sendpage(struct pipe_inode_info *pipe, struct file *out,
 863                                 loff_t *ppos, size_t len, unsigned int flags)
 864 {
 865         return splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_sendpage);
 866 }
 867
 868 EXPORT_SYMBOL(generic_splice_sendpage);
 869
 870 /*
 871  * Attempt to initiate a splice from pipe to file.
 872  */
 873 static long do_splice_from(struct pipe_inode_info *pipe, struct file *out,
 874                            loff_t *ppos, size_t len, unsigned int flags)
 875 {
 876         int ret;
 877
 878         if (unlikely(!out->f_op || !out->f_op->splice_write))
 879                 return -EINVAL;
 880
 881         if (unlikely(!(out->f_mode & FMODE_WRITE)))
 882                 return -EBADF;
 883
 884         ret = rw_verify_area(WRITE, out, ppos, len);
 885         if (unlikely(ret < 0))
 886                 return ret;
 887
 888         return out->f_op->splice_write(pipe, out, ppos, len, flags);
 889 }
 890
 891 /*
 892  * Attempt to initiate a splice from a file to a pipe.
 893  */
 894 static long do_splice_to(struct file *in, loff_t *ppos,
 895                          struct pipe_inode_info *pipe, size_t len,
 896                          unsigned int flags)
 897 {
 898         loff_t isize, left;
 899         int ret;
 900
 901         if (unlikely(!in->f_op || !in->f_op->splice_read))
 902                 return -EINVAL;
 903
 904         if (unlikely(!(in->f_mode & FMODE_READ)))
 905                 return -EBADF;
 906
 907         ret = rw_verify_area(READ, in, ppos, len);
 908         if (unlikely(ret < 0))
 909                 return ret;
 910
 911         isize = i_size_read(in->f_mapping->host);
 912         if (unlikely(*ppos >= isize))
 913                 return 0;
 914
 915         left = isize - *ppos;
 916         if (unlikely(left < len))
 917                 len = left;
 918
 919         return in->f_op->splice_read(in, ppos, pipe, len, flags);
 920 }
 921
 922 long do_splice_direct(struct file *in, loff_t *ppos, struct file *out,
 923                       size_t len, unsigned int flags)
 924 {
 925         struct pipe_inode_info *pipe;
 926         long ret, bytes;
 927         loff_t out_off;
 928         umode_t i_mode;
 929         int i;
 930
 931         /*
 932          * We require the input being a regular file, as we don't want to
 933          * randomly drop data for eg socket -> socket splicing. Use the
 934          * piped splicing for that!
 935          */
 936         i_mode = in->f_dentry->d_inode->i_mode;
 937         if (unlikely(!S_ISREG(i_mode) && !S_ISBLK(i_mode)))
 938                 return -EINVAL;
 939
 940         /*
 941          * neither in nor out is a pipe, setup an internal pipe attached to
 942          * 'out' and transfer the wanted data from 'in' to 'out' through that
 943          */
 944         pipe = current->splice_pipe;
 945         if (unlikely(!pipe)) {
 946                 pipe = alloc_pipe_info(NULL);
 947                 if (!pipe)
 948                         return -ENOMEM;
 949
 950                 /*
 951                  * We don't have an immediate reader, but we'll read the stuff
 952                  * out of the pipe right after the splice_to_pipe(). So set
 953                  * PIPE_READERS appropriately.
 954                  */
 955                 pipe->readers = 1;
 956
 957                 current->splice_pipe = pipe;
 958         }
 959
 960         /*
 961          * Do the splice.
 962          */
 963         ret = 0;
 964         bytes = 0;
 965         out_off = 0;
 966
 967         while (len) {
 968                 size_t read_len, max_read_len;
 969
 970                 /*
 971                  * Do at most PIPE_BUFFERS pages worth of transfer:
 972                  */
 973                 max_read_len = min(len, (size_t)(PIPE_BUFFERS*PAGE_SIZE));
 974
 975                 ret = do_splice_to(in, ppos, pipe, max_read_len, flags);
 976                 if (unlikely(ret < 0))
 977                         goto out_release;
 978
 979                 read_len = ret;
 980
 981                 /*
 982                  * NOTE: nonblocking mode only applies to the input. We
 983                  * must not do the output in nonblocking mode as then we
 984                  * could get stuck data in the internal pipe:
 985                  */
 986                 ret = do_splice_from(pipe, out, &out_off, read_len,
 987                                      flags & ~SPLICE_F_NONBLOCK);
 988                 if (unlikely(ret < 0))
 989                         goto out_release;
 990
 991                 bytes += ret;
 992                 len -= ret;
 993
 994                 /*
 995                  * In nonblocking mode, if we got back a short read then
 996                  * that was due to either an IO error or due to the
 997                  * pagecache entry not being there. In the IO error case
 998                  * the _next_ splice attempt will produce a clean IO error
 999                  * return value (not a short read), so in both cases it's
1000                  * correct to break out of the loop here:
1001                  */
1002                 if ((flags & SPLICE_F_NONBLOCK) && (read_len < max_read_len))
1003                         break;
1004         }
1005
1006         pipe->nrbufs = pipe->curbuf = 0;
1007
1008         return bytes;
1009
1010 out_release:
1011         /*
1012          * If we did an incomplete transfer we must release
1013          * the pipe buffers in question:
1014          */
1015         for (i = 0; i < PIPE_BUFFERS; i++) {
1016                 struct pipe_buffer *buf = pipe->bufs + i;
1017
1018                 if (buf->ops) {
1019                         buf->ops->release(pipe, buf);
1020                         buf->ops = NULL;
1021                 }
1022         }
1023         pipe->nrbufs = pipe->curbuf = 0;
1024
1025         /*
1026          * If we transferred some data, return the number of bytes:
1027          */
1028         if (bytes > 0)
1029                 return bytes;
1030
1031         return ret;
1032 }
1033
1034 EXPORT_SYMBOL(do_splice_direct);
1035
1036 /*
1037  * Determine where to splice to/from.
1038  */
1039 static long do_splice(struct file *in, loff_t __user *off_in,
1040                       struct file *out, loff_t __user *off_out,
1041                       size_t len, unsigned int flags)
1042 {
1043         struct pipe_inode_info *pipe;
1044         loff_t offset, *off;
1045         long ret;
1046
1047         pipe = in->f_dentry->d_inode->i_pipe;
1048         if (pipe) {
1049                 if (off_in)
1050                         return -ESPIPE;
1051                 if (off_out) {
1052                         if (out->f_op->llseek == no_llseek)
1053                                 return -EINVAL;
1054                         if (copy_from_user(&offset, off_out, sizeof(loff_t)))
1055                                 return -EFAULT;
1056                         off = &offset;
1057                 } else
1058                         off = &out->f_pos;
1059
1060                 ret = do_splice_from(pipe, out, off, len, flags);
1061
1062                 if (off_out && copy_to_user(off_out, off, sizeof(loff_t)))
1063                         ret = -EFAULT;
1064
1065                 return ret;
1066         }
1067
1068         pipe = out->f_dentry->d_inode->i_pipe;
1069         if (pipe) {
1070                 if (off_out)
1071                         return -ESPIPE;
1072                 if (off_in) {
1073                         if (in->f_op->llseek == no_llseek)
1074                                 return -EINVAL;
1075                         if (copy_from_user(&offset, off_in, sizeof(loff_t)))
1076                                 return -EFAULT;
1077                         off = &offset;
1078                 } else
1079                         off = &in->f_pos;
1080
1081                 ret = do_splice_to(in, off, pipe, len, flags);
1082
1083                 if (off_in && copy_to_user(off_in, off, sizeof(loff_t)))
1084                         ret = -EFAULT;
1085
1086                 return ret;
1087         }
1088
1089         return -EINVAL;
1090 }
1091
1092 /*
1093  * Map an iov into an array of pages and offset/length tupples. With the
1094  * partial_page structure, we can map several non-contiguous ranges into
1095  * our ones pages[] map instead of splitting that operation into pieces.
1096  * Could easily be exported as a generic helper for other users, in which
1097  * case one would probably want to add a 'max_nr_pages' parameter as well.
1098  */
1099 static int get_iovec_page_array(const struct iovec __user *iov,
1100                                 unsigned int nr_vecs, struct page **pages,
1101                                 struct partial_page *partial)
1102 {
1103         int buffers = 0, error = 0;
1104
1105         /*
1106          * It's ok to take the mmap_sem for reading, even
1107          * across a "get_user()".
1108          */
1109         down_read(&current->mm->mmap_sem);
1110
1111         while (nr_vecs) {
1112                 unsigned long off, npages;
1113                 void __user *base;
1114                 size_t len;
1115                 int i;
1116
1117                 /*
1118                  * Get user address base and length for this iovec.
1119                  */
1120                 error = get_user(base, &iov->iov_base);
1121                 if (unlikely(error))
1122                         break;
1123                 error = get_user(len, &iov->iov_len);
1124                 if (unlikely(error))
1125                         break;
1126
1127                 /*
1128                  * Sanity check this iovec. 0 read succeeds.
1129                  */
1130                 if (unlikely(!len))
1131                         break;
1132                 error = -EFAULT;
1133                 if (unlikely(!base))
1134                         break;
1135
1136                 /*
1137                  * Get this base offset and number of pages, then map
1138                  * in the user pages.
1139                  */
1140                 off = (unsigned long) base & ~PAGE_MASK;
1141                 npages = (off + len + PAGE_SIZE - 1) >> PAGE_SHIFT;
1142                 if (npages > PIPE_BUFFERS - buffers)
1143                         npages = PIPE_BUFFERS - buffers;
1144
1145                 error = get_user_pages(current, current->mm,
1146                                        (unsigned long) base, npages, 0, 0,
1147                                        &pages[buffers], NULL);
1148
1149                 if (unlikely(error <= 0))
1150                         break;
1151
1152                 /*
1153                  * Fill this contiguous range into the partial page map.
1154                  */
1155                 for (i = 0; i < error; i++) {
1156                         const int plen = min_t(size_t, len, PAGE_SIZE) - off;
1157
1158                         partial[buffers].offset = off;
1159                         partial[buffers].len = plen;
1160
1161                         off = 0;
1162                         len -= plen;
1163                         buffers++;
1164                 }
1165
1166                 /*
1167                  * We didn't complete this iov, stop here since it probably
1168                  * means we have to move some of this into a pipe to
1169                  * be able to continue.
1170                  */
1171                 if (len)
1172                         break;
1173
1174                 /*
1175                  * Don't continue if we mapped fewer pages than we asked for,
1176                  * or if we mapped the max number of pages that we have
1177                  * room for.
1178                  */
1179                 if (error < npages || buffers == PIPE_BUFFERS)
1180                         break;
1181
1182                 nr_vecs--;
1183                 iov++;
1184         }
1185
1186         up_read(&current->mm->mmap_sem);
1187
1188         if (buffers)
1189                 return buffers;
1190
1191         return error;
1192 }
1193
1194 /*
1195  * vmsplice splices a user address range into a pipe. It can be thought of
1196  * as splice-from-memory, where the regular splice is splice-from-file (or
1197  * to file). In both cases the output is a pipe, naturally.
1198  *
1199  * Note that vmsplice only supports splicing _from_ user memory to a pipe,
1200  * not the other way around. Splicing from user memory is a simple operation
1201  * that can be supported without any funky alignment restrictions or nasty
1202  * vm tricks. We simply map in the user memory and fill them into a pipe.
1203  * The reverse isn't quite as easy, though. There are two possible solutions
1204  * for that:
1205  *
1206  *      - memcpy() the data internally, at which point we might as well just
1207  *        do a regular read() on the buffer anyway.
1208  *      - Lots of nasty vm tricks, that are neither fast nor flexible (it
1209  *        has restriction limitations on both ends of the pipe).
1210  *
1211  * Alas, it isn't here.
1212  *
1213  */
1214 static long do_vmsplice(struct file *file, const struct iovec __user *iov,
1215                         unsigned long nr_segs, unsigned int flags)
1216 {
1217         struct pipe_inode_info *pipe = file->f_dentry->d_inode->i_pipe;
1218         struct page *pages[PIPE_BUFFERS];
1219         struct partial_page partial[PIPE_BUFFERS];
1220         struct splice_pipe_desc spd = {
1221                 .pages = pages,
1222                 .partial = partial,
1223                 .flags = flags,
1224                 .ops = &user_page_pipe_buf_ops,
1225         };
1226
1227         if (unlikely(!pipe))
1228                 return -EBADF;
1229         if (unlikely(nr_segs > UIO_MAXIOV))
1230                 return -EINVAL;
1231         else if (unlikely(!nr_segs))
1232                 return 0;
1233
1234         spd.nr_pages = get_iovec_page_array(iov, nr_segs, pages, partial);
1235         if (spd.nr_pages <= 0)
1236                 return spd.nr_pages;
1237
1238         return splice_to_pipe(pipe, &spd);
1239 }
1240
1241 asmlinkage long sys_vmsplice(int fd, const struct iovec __user *iov,
1242                              unsigned long nr_segs, unsigned int flags)
1243 {
1244         struct file *file;
1245         long error;
1246         int fput;
1247
1248         error = -EBADF;
1249         file = fget_light(fd, &fput);
1250         if (file) {
1251                 if (file->f_mode & FMODE_WRITE)
1252                         error = do_vmsplice(file, iov, nr_segs, flags);
1253
1254                 fput_light(file, fput);
1255         }
1256
1257         return error;
1258 }
1259
1260 asmlinkage long sys_splice(int fd_in, loff_t __user *off_in,
1261                            int fd_out, loff_t __user *off_out,
1262                            size_t len, unsigned int flags)
1263 {
1264         long error;
1265         struct file *in, *out;
1266         int fput_in, fput_out;
1267
1268         if (unlikely(!len))
1269                 return 0;
1270
1271         error = -EBADF;
1272         in = fget_light(fd_in, &fput_in);
1273         if (in) {
1274                 if (in->f_mode & FMODE_READ) {
1275                         out = fget_light(fd_out, &fput_out);
1276                         if (out) {
1277                                 if (out->f_mode & FMODE_WRITE)
1278                                         error = do_splice(in, off_in,
1279                                                           out, off_out,
1280                                                           len, flags);
1281                                 fput_light(out, fput_out);
1282                         }
1283                 }
1284
1285                 fput_light(in, fput_in);
1286         }
1287
1288         return error;
1289 }
1290
1291 /*
1292  * Link contents of ipipe to opipe.
1293  */
1294 static int link_pipe(struct pipe_inode_info *ipipe,
1295                      struct pipe_inode_info *opipe,
1296                      size_t len, unsigned int flags)
1297 {
1298         struct pipe_buffer *ibuf, *obuf;
1299         int ret, do_wakeup, i, ipipe_first;
1300
1301         ret = do_wakeup = ipipe_first = 0;
1302
1303         /*
1304          * Potential ABBA deadlock, work around it by ordering lock
1305          * grabbing by inode address. Otherwise two different processes
1306          * could deadlock (one doing tee from A -> B, the other from B -> A).
1307          */
1308         if (ipipe->inode < opipe->inode) {
1309                 ipipe_first = 1;
1310                 mutex_lock(&ipipe->inode->i_mutex);
1311                 mutex_lock(&opipe->inode->i_mutex);
1312         } else {
1313                 mutex_lock(&opipe->inode->i_mutex);
1314                 mutex_lock(&ipipe->inode->i_mutex);
1315         }
1316
1317         for (i = 0;; i++) {
1318                 if (!opipe->readers) {
1319                         send_sig(SIGPIPE, current, 0);
1320                         if (!ret)
1321                                 ret = -EPIPE;
1322                         break;
1323                 }
1324                 if (ipipe->nrbufs - i) {
1325                         ibuf = ipipe->bufs + ((ipipe->curbuf + i) & (PIPE_BUFFERS - 1));
1326
1327                         /*
1328                          * If we have room, fill this buffer
1329                          */
1330                         if (opipe->nrbufs < PIPE_BUFFERS) {
1331                                 int nbuf = (opipe->curbuf + opipe->nrbufs) & (PIPE_BUFFERS - 1);
1332
1333                                 /*
1334                                  * Get a reference to this pipe buffer,
1335                                  * so we can copy the contents over.
1336                                  */
1337                                 ibuf->ops->get(ipipe, ibuf);
1338
1339                                 obuf = opipe->bufs + nbuf;
1340                                 *obuf = *ibuf;
1341
1342                                 if (obuf->len > len)
1343                                         obuf->len = len;
1344
1345                                 opipe->nrbufs++;
1346                                 do_wakeup = 1;
1347                                 ret += obuf->len;
1348                                 len -= obuf->len;
1349
1350                                 if (!len)
1351                                         break;
1352                                 if (opipe->nrbufs < PIPE_BUFFERS)
1353                                         continue;
1354                         }
1355
1356                         /*
1357                          * We have input available, but no output room.
1358                          * If we already copied data, return that. If we
1359                          * need to drop the opipe lock, it must be ordered
1360                          * last to avoid deadlocks.
1361                          */
1362                         if ((flags & SPLICE_F_NONBLOCK) || !ipipe_first) {
1363                                 if (!ret)
1364                                         ret = -EAGAIN;
1365                                 break;
1366                         }
1367                         if (signal_pending(current)) {
1368                                 if (!ret)
1369                                         ret = -ERESTARTSYS;
1370                                 break;
1371                         }
1372                         if (do_wakeup) {
1373                                 smp_mb();
1374                                 if (waitqueue_active(&opipe->wait))
1375                                         wake_up_interruptible(&opipe->wait);
1376                                 kill_fasync(&opipe->fasync_readers, SIGIO, POLL_IN);
1377                                 do_wakeup = 0;
1378                         }
1379
1380                         opipe->waiting_writers++;
1381                         pipe_wait(opipe);
1382                         opipe->waiting_writers--;
1383                         continue;
1384                 }
1385
1386                 /*
1387                  * No input buffers, do the usual checks for available
1388                  * writers and blocking and wait if necessary
1389                  */
1390                 if (!ipipe->writers)
1391                         break;
1392                 if (!ipipe->waiting_writers) {
1393                         if (ret)
1394                                 break;
1395                 }
1396                 /*
1397                  * pipe_wait() drops the ipipe mutex. To avoid deadlocks
1398                  * with another process, we can only safely do that if
1399                  * the ipipe lock is ordered last.
1400                  */
1401                 if ((flags & SPLICE_F_NONBLOCK) || ipipe_first) {
1402                         if (!ret)
1403                                 ret = -EAGAIN;
1404                         break;
1405                 }
1406                 if (signal_pending(current)) {
1407                         if (!ret)
1408                                 ret = -ERESTARTSYS;
1409                         break;
1410                 }
1411
1412                 if (waitqueue_active(&ipipe->wait))
1413                         wake_up_interruptible_sync(&ipipe->wait);
1414                 kill_fasync(&ipipe->fasync_writers, SIGIO, POLL_OUT);
1415
1416                 pipe_wait(ipipe);
1417         }
1418
1419         mutex_unlock(&ipipe->inode->i_mutex);
1420         mutex_unlock(&opipe->inode->i_mutex);
1421
1422         if (do_wakeup) {
1423                 smp_mb();
1424                 if (waitqueue_active(&opipe->wait))
1425                         wake_up_interruptible(&opipe->wait);
1426                 kill_fasync(&opipe->fasync_readers, SIGIO, POLL_IN);
1427         }
1428
1429         return ret;
1430 }
1431
1432 /*
1433  * This is a tee(1) implementation that works on pipes. It doesn't copy
1434  * any data, it simply references the 'in' pages on the 'out' pipe.
1435  * The 'flags' used are the SPLICE_F_* variants, currently the only
1436  * applicable one is SPLICE_F_NONBLOCK.
1437  */
1438 static long do_tee(struct file *in, struct file *out, size_t len,
1439                    unsigned int flags)
1440 {
1441         struct pipe_inode_info *ipipe = in->f_dentry->d_inode->i_pipe;
1442         struct pipe_inode_info *opipe = out->f_dentry->d_inode->i_pipe;
1443
1444         /*
1445          * Link ipipe to the two output pipes, consuming as we go along.
1446          */
1447         if (ipipe && opipe)
1448                 return link_pipe(ipipe, opipe, len, flags);
1449
1450         return -EINVAL;
1451 }
1452
1453 asmlinkage long sys_tee(int fdin, int fdout, size_t len, unsigned int flags)
1454 {
1455         struct file *in;
1456         int error, fput_in;
1457
1458         if (unlikely(!len))
1459                 return 0;
1460
1461         error = -EBADF;
1462         in = fget_light(fdin, &fput_in);
1463         if (in) {
1464                 if (in->f_mode & FMODE_READ) {
1465                         int fput_out;
1466                         struct file *out = fget_light(fdout, &fput_out);
1467
1468                         if (out) {
1469                                 if (out->f_mode & FMODE_WRITE)
1470                                         error = do_tee(in, out, len, flags);
1471                                 fput_light(out, fput_out);
1472                         }
1473                 }
1474                 fput_light(in, fput_in);
1475         }
1476
1477         return error;
1478 }