fs/splice.c

   1 /*
   2  * "splice": joining two ropes together by interweaving their strands.
   3  *
   4  * This is the "extended pipe" functionality, where a pipe is used as
   5  * an arbitrary in-memory buffer. Think of a pipe as a small kernel
   6  * buffer that you can use to transfer data from one end to the other.
   7  *
   8  * The traditional unix read/write is extended with a "splice()" operation
   9  * that transfers data buffers to or from a pipe buffer.
  10  *
  11  * Named by Larry McVoy, original implementation from Linus, extended by
  12  * Jens to support splicing to files, network, direct splicing, etc and
  13  * fixing lots of bugs.
  14  *
  15  * Copyright (C) 2005-2006 Jens Axboe <axboe@kernel.dk>
  16  * Copyright (C) 2005-2006 Linus Torvalds <torvalds@osdl.org>
  17  * Copyright (C) 2006 Ingo Molnar <mingo@elte.hu>
  18  *
  19  */
  20 #include <linux/fs.h>
  21 #include <linux/file.h>
  22 #include <linux/pagemap.h>
  23 #include <linux/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         const 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 *pipe,
  55                                      struct pipe_buffer *buf)
  56 {
  57         struct page *page = buf->page;
  58         struct address_space *mapping;
  59
  60         lock_page(page);
  61
  62         mapping = page_mapping(page);
  63         if (mapping) {
  64                 WARN_ON(!PageUptodate(page));
  65
  66                 /*
  67                  * At least for ext2 with nobh option, we need to wait on
  68                  * writeback completing on this page, since we'll remove it
  69                  * from the pagecache.  Otherwise truncate wont wait on the
  70                  * page, allowing the disk blocks to be reused by someone else
  71                  * before we actually wrote our data to them. fs corruption
  72                  * ensues.
  73                  */
  74                 wait_on_page_writeback(page);
  75
  76                 if (PagePrivate(page))
  77                         try_to_release_page(page, GFP_KERNEL);
  78
  79                 /*
  80                  * If we succeeded in removing the mapping, set LRU flag
  81                  * and return good.
  82                  */
  83                 if (remove_mapping(mapping, page)) {
  84                         buf->flags |= PIPE_BUF_FLAG_LRU;
  85                         return 0;
  86                 }
  87         }
  88
  89         /*
  90          * Raced with truncate or failed to remove page from current
  91          * address space, unlock and return failure.
  92          */
  93         unlock_page(page);
  94         return 1;
  95 }
  96
  97 static void page_cache_pipe_buf_release(struct pipe_inode_info *pipe,
  98                                         struct pipe_buffer *buf)
  99 {
 100         page_cache_release(buf->page);
 101         buf->flags &= ~PIPE_BUF_FLAG_LRU;
 102 }
 103
 104 static int page_cache_pipe_buf_pin(struct pipe_inode_info *pipe,
 105                                    struct pipe_buffer *buf)
 106 {
 107         struct page *page = buf->page;
 108         int err;
 109
 110         if (!PageUptodate(page)) {
 111                 lock_page(page);
 112
 113                 /*
 114                  * Page got truncated/unhashed. This will cause a 0-byte
 115                  * splice, if this is the first page.
 116                  */
 117                 if (!page->mapping) {
 118                         err = -ENODATA;
 119                         goto error;
 120                 }
 121
 122                 /*
 123                  * Uh oh, read-error from disk.
 124                  */
 125                 if (!PageUptodate(page)) {
 126                         err = -EIO;
 127                         goto error;
 128                 }
 129
 130                 /*
 131                  * Page is ok afterall, we are done.
 132                  */
 133                 unlock_page(page);
 134         }
 135
 136         return 0;
 137 error:
 138         unlock_page(page);
 139         return err;
 140 }
 141
 142 static const struct pipe_buf_operations page_cache_pipe_buf_ops = {
 143         .can_merge = 0,
 144         .map = generic_pipe_buf_map,
 145         .unmap = generic_pipe_buf_unmap,
 146         .pin = page_cache_pipe_buf_pin,
 147         .release = page_cache_pipe_buf_release,
 148         .steal = page_cache_pipe_buf_steal,
 149         .get = generic_pipe_buf_get,
 150 };
 151
 152 static int user_page_pipe_buf_steal(struct pipe_inode_info *pipe,
 153                                     struct pipe_buffer *buf)
 154 {
 155         if (!(buf->flags & PIPE_BUF_FLAG_GIFT))
 156                 return 1;
 157
 158         buf->flags |= PIPE_BUF_FLAG_LRU;
 159         return generic_pipe_buf_steal(pipe, buf);
 160 }
 161
 162 static const struct pipe_buf_operations user_page_pipe_buf_ops = {
 163         .can_merge = 0,
 164         .map = generic_pipe_buf_map,
 165         .unmap = generic_pipe_buf_unmap,
 166         .pin = generic_pipe_buf_pin,
 167         .release = page_cache_pipe_buf_release,
 168         .steal = user_page_pipe_buf_steal,
 169         .get = generic_pipe_buf_get,
 170 };
 171
 172 /*
 173  * Pipe output worker. This sets up our pipe format with the page cache
 174  * pipe buffer operations. Otherwise very similar to the regular pipe_writev().
 175  */
 176 static ssize_t splice_to_pipe(struct pipe_inode_info *pipe,
 177                               struct splice_pipe_desc *spd)
 178 {
 179         int ret, do_wakeup, page_nr;
 180
 181         ret = 0;
 182         do_wakeup = 0;
 183         page_nr = 0;
 184
 185         if (pipe->inode)
 186                 mutex_lock(&pipe->inode->i_mutex);
 187
 188         for (;;) {
 189                 if (!pipe->readers) {
 190                         send_sig(SIGPIPE, current, 0);
 191                         if (!ret)
 192                                 ret = -EPIPE;
 193                         break;
 194                 }
 195
 196                 if (pipe->nrbufs < PIPE_BUFFERS) {
 197                         int newbuf = (pipe->curbuf + pipe->nrbufs) & (PIPE_BUFFERS - 1);
 198                         struct pipe_buffer *buf = pipe->bufs + newbuf;
 199
 200                         buf->page = spd->pages[page_nr];
 201                         buf->offset = spd->partial[page_nr].offset;
 202                         buf->len = spd->partial[page_nr].len;
 203                         buf->ops = spd->ops;
 204                         if (spd->flags & SPLICE_F_GIFT)
 205                                 buf->flags |= PIPE_BUF_FLAG_GIFT;
 206
 207                         pipe->nrbufs++;
 208                         page_nr++;
 209                         ret += buf->len;
 210
 211                         if (pipe->inode)
 212                                 do_wakeup = 1;
 213
 214                         if (!--spd->nr_pages)
 215                                 break;
 216                         if (pipe->nrbufs < PIPE_BUFFERS)
 217                                 continue;
 218
 219                         break;
 220                 }
 221
 222                 if (spd->flags & SPLICE_F_NONBLOCK) {
 223                         if (!ret)
 224                                 ret = -EAGAIN;
 225                         break;
 226                 }
 227
 228                 if (signal_pending(current)) {
 229                         if (!ret)
 230                                 ret = -ERESTARTSYS;
 231                         break;
 232                 }
 233
 234                 if (do_wakeup) {
 235                         smp_mb();
 236                         if (waitqueue_active(&pipe->wait))
 237                                 wake_up_interruptible_sync(&pipe->wait);
 238                         kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
 239                         do_wakeup = 0;
 240                 }
 241
 242                 pipe->waiting_writers++;
 243                 pipe_wait(pipe);
 244                 pipe->waiting_writers--;
 245         }
 246
 247         if (pipe->inode)
 248                 mutex_unlock(&pipe->inode->i_mutex);
 249
 250         if (do_wakeup) {
 251                 smp_mb();
 252                 if (waitqueue_active(&pipe->wait))
 253                         wake_up_interruptible(&pipe->wait);
 254                 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
 255         }
 256
 257         while (page_nr < spd->nr_pages)
 258                 page_cache_release(spd->pages[page_nr++]);
 259
 260         return ret;
 261 }
 262
 263 static int
 264 __generic_file_splice_read(struct file *in, loff_t *ppos,
 265                            struct pipe_inode_info *pipe, size_t len,
 266                            unsigned int flags)
 267 {
 268         struct address_space *mapping = in->f_mapping;
 269         unsigned int loff, nr_pages;
 270         struct page *pages[PIPE_BUFFERS];
 271         struct partial_page partial[PIPE_BUFFERS];
 272         struct page *page;
 273         pgoff_t index, end_index;
 274         loff_t isize;
 275         size_t total_len;
 276         int error, page_nr;
 277         struct splice_pipe_desc spd = {
 278                 .pages = pages,
 279                 .partial = partial,
 280                 .flags = flags,
 281                 .ops = &page_cache_pipe_buf_ops,
 282         };
 283
 284         index = *ppos >> PAGE_CACHE_SHIFT;
 285         loff = *ppos & ~PAGE_CACHE_MASK;
 286         nr_pages = (len + loff + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
 287
 288         if (nr_pages > PIPE_BUFFERS)
 289                 nr_pages = PIPE_BUFFERS;
 290
 291         /*
 292          * Initiate read-ahead on this page range. however, don't call into
 293          * read-ahead if this is a non-zero offset (we are likely doing small
 294          * chunk splice and the page is already there) for a single page.
 295          */
 296         if (!loff || nr_pages > 1)
 297                 page_cache_readahead(mapping, &in->f_ra, in, index, nr_pages);
 298
 299         /*
 300          * Now fill in the holes:
 301          */
 302         error = 0;
 303         total_len = 0;
 304
 305         /*
 306          * Lookup the (hopefully) full range of pages we need.
 307          */
 308         spd.nr_pages = find_get_pages_contig(mapping, index, nr_pages, pages);
 309
 310         /*
 311          * If find_get_pages_contig() returned fewer pages than we needed,
 312          * allocate the rest.
 313          */
 314         index += spd.nr_pages;
 315         while (spd.nr_pages < nr_pages) {
 316                 /*
 317                  * Page could be there, find_get_pages_contig() breaks on
 318                  * the first hole.
 319                  */
 320                 page = find_get_page(mapping, index);
 321                 if (!page) {
 322                         /*
 323                          * Make sure the read-ahead engine is notified
 324                          * about this failure.
 325                          */
 326                         handle_ra_miss(mapping, &in->f_ra, index);
 327
 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                                               GFP_KERNEL);
 337                         if (unlikely(error)) {
 338                                 page_cache_release(page);
 339                                 if (error == -EEXIST)
 340                                         continue;
 341                                 break;
 342                         }
 343                         /*
 344                          * add_to_page_cache() locks the page, unlock it
 345                          * to avoid convoluting the logic below even more.
 346                          */
 347                         unlock_page(page);
 348                 }
 349
 350                 pages[spd.nr_pages++] = page;
 351                 index++;
 352         }
 353
 354         /*
 355          * Now loop over the map and see if we need to start IO on any
 356          * pages, fill in the partial map, etc.
 357          */
 358         index = *ppos >> PAGE_CACHE_SHIFT;
 359         nr_pages = spd.nr_pages;
 360         spd.nr_pages = 0;
 361         for (page_nr = 0; page_nr < nr_pages; page_nr++) {
 362                 unsigned int this_len;
 363
 364                 if (!len)
 365                         break;
 366
 367                 /*
 368                  * this_len is the max we'll use from this page
 369                  */
 370                 this_len = min_t(unsigned long, len, PAGE_CACHE_SIZE - loff);
 371                 page = pages[page_nr];
 372
 373                 /*
 374                  * If the page isn't uptodate, we may need to start io on it
 375                  */
 376                 if (!PageUptodate(page)) {
 377                         /*
 378                          * If in nonblock mode then dont block on waiting
 379                          * for an in-flight io page
 380                          */
 381                         if (flags & SPLICE_F_NONBLOCK)
 382                                 break;
 383
 384                         lock_page(page);
 385
 386                         /*
 387                          * page was truncated, stop here. if this isn't the
 388                          * first page, we'll just complete what we already
 389                          * added
 390                          */
 391                         if (!page->mapping) {
 392                                 unlock_page(page);
 393                                 break;
 394                         }
 395                         /*
 396                          * page was already under io and is now done, great
 397                          */
 398                         if (PageUptodate(page)) {
 399                                 unlock_page(page);
 400                                 goto fill_it;
 401                         }
 402
 403                         /*
 404                          * need to read in the page
 405                          */
 406                         error = mapping->a_ops->readpage(in, page);
 407                         if (unlikely(error)) {
 408                                 /*
 409                                  * We really should re-lookup the page here,
 410                                  * but it complicates things a lot. Instead
 411                                  * lets just do what we already stored, and
 412                                  * we'll get it the next time we are called.
 413                                  */
 414                                 if (error == AOP_TRUNCATED_PAGE)
 415                                         error = 0;
 416
 417                                 break;
 418                         }
 419
 420                         /*
 421                          * i_size must be checked after ->readpage().
 422                          */
 423                         isize = i_size_read(mapping->host);
 424                         end_index = (isize - 1) >> PAGE_CACHE_SHIFT;
 425                         if (unlikely(!isize || index > end_index))
 426                                 break;
 427
 428                         /*
 429                          * if this is the last page, see if we need to shrink
 430                          * the length and stop
 431                          */
 432                         if (end_index == index) {
 433                                 loff = PAGE_CACHE_SIZE - (isize & ~PAGE_CACHE_MASK);
 434                                 if (total_len + loff > isize)
 435                                         break;
 436                                 /*
 437                                  * force quit after adding this page
 438                                  */
 439                                 len = this_len;
 440                                 this_len = min(this_len, loff);
 441                                 loff = 0;
 442                         }
 443                 }
 444 fill_it:
 445                 partial[page_nr].offset = loff;
 446                 partial[page_nr].len = this_len;
 447                 len -= this_len;
 448                 total_len += this_len;
 449                 loff = 0;
 450                 spd.nr_pages++;
 451                 index++;
 452         }
 453
 454         /*
 455          * Release any pages at the end, if we quit early. 'i' is how far
 456          * we got, 'nr_pages' is how many pages are in the map.
 457          */
 458         while (page_nr < nr_pages)
 459                 page_cache_release(pages[page_nr++]);
 460
 461         if (spd.nr_pages)
 462                 return splice_to_pipe(pipe, &spd);
 463
 464         return error;
 465 }
 466
 467 /**
 468  * generic_file_splice_read - splice data from file to a pipe
 469  * @in:         file to splice from
 470  * @pipe:       pipe to splice to
 471  * @len:        number of bytes to splice
 472  * @flags:      splice modifier flags
 473  *
 474  * Will read pages from given file and fill them into a pipe.
 475  */
 476 ssize_t generic_file_splice_read(struct file *in, loff_t *ppos,
 477                                  struct pipe_inode_info *pipe, size_t len,
 478                                  unsigned int flags)
 479 {
 480         ssize_t spliced;
 481         int ret;
 482
 483         ret = 0;
 484         spliced = 0;
 485
 486         while (len) {
 487                 ret = __generic_file_splice_read(in, ppos, pipe, len, flags);
 488
 489                 if (ret < 0)
 490                         break;
 491                 else if (!ret) {
 492                         if (spliced)
 493                                 break;
 494                         if (flags & SPLICE_F_NONBLOCK) {
 495                                 ret = -EAGAIN;
 496                                 break;
 497                         }
 498                 }
 499
 500                 *ppos += ret;
 501                 len -= ret;
 502                 spliced += ret;
 503         }
 504
 505         if (spliced)
 506                 return spliced;
 507
 508         return ret;
 509 }
 510
 511 EXPORT_SYMBOL(generic_file_splice_read);
 512
 513 /*
 514  * Send 'sd->len' bytes to socket from 'sd->file' at position 'sd->pos'
 515  * using sendpage(). Return the number of bytes sent.
 516  */
 517 static int pipe_to_sendpage(struct pipe_inode_info *pipe,
 518                             struct pipe_buffer *buf, struct splice_desc *sd)
 519 {
 520         struct file *file = sd->file;
 521         loff_t pos = sd->pos;
 522         int ret, more;
 523
 524         ret = buf->ops->pin(pipe, buf);
 525         if (!ret) {
 526                 more = (sd->flags & SPLICE_F_MORE) || sd->len < sd->total_len;
 527
 528                 ret = file->f_op->sendpage(file, buf->page, buf->offset,
 529                                            sd->len, &pos, more);
 530         }
 531
 532         return ret;
 533 }
 534
 535 /*
 536  * This is a little more tricky than the file -> pipe splicing. There are
 537  * basically three cases:
 538  *
 539  *      - Destination page already exists in the address space and there
 540  *        are users of it. For that case we have no other option that
 541  *        copying the data. Tough luck.
 542  *      - Destination page already exists in the address space, but there
 543  *        are no users of it. Make sure it's uptodate, then drop it. Fall
 544  *        through to last case.
 545  *      - Destination page does not exist, we can add the pipe page to
 546  *        the page cache and avoid the copy.
 547  *
 548  * If asked to move pages to the output file (SPLICE_F_MOVE is set in
 549  * sd->flags), we attempt to migrate pages from the pipe to the output
 550  * file address space page cache. This is possible if no one else has
 551  * the pipe page referenced outside of the pipe and page cache. If
 552  * SPLICE_F_MOVE isn't set, or we cannot move the page, we simply create
 553  * a new page in the output file page cache and fill/dirty that.
 554  */
 555 static int pipe_to_file(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
 556                         struct splice_desc *sd)
 557 {
 558         struct file *file = sd->file;
 559         struct address_space *mapping = file->f_mapping;
 560         unsigned int offset, this_len;
 561         struct page *page;
 562         pgoff_t index;
 563         int ret;
 564
 565         /*
 566          * make sure the data in this buffer is uptodate
 567          */
 568         ret = buf->ops->pin(pipe, buf);
 569         if (unlikely(ret))
 570                 return ret;
 571
 572         index = sd->pos >> PAGE_CACHE_SHIFT;
 573         offset = sd->pos & ~PAGE_CACHE_MASK;
 574
 575         this_len = sd->len;
 576         if (this_len + offset > PAGE_CACHE_SIZE)
 577                 this_len = PAGE_CACHE_SIZE - offset;
 578
 579         /*
 580          * Reuse buf page, if SPLICE_F_MOVE is set and we are doing a full
 581          * page.
 582          */
 583         if ((sd->flags & SPLICE_F_MOVE) && this_len == PAGE_CACHE_SIZE) {
 584                 /*
 585                  * If steal succeeds, buf->page is now pruned from the
 586                  * pagecache and we can reuse it. The page will also be
 587                  * locked on successful return.
 588                  */
 589                 if (buf->ops->steal(pipe, buf))
 590                         goto find_page;
 591
 592                 page = buf->page;
 593                 if (add_to_page_cache(page, mapping, index, GFP_KERNEL)) {
 594                         unlock_page(page);
 595                         goto find_page;
 596                 }
 597
 598                 page_cache_get(page);
 599
 600                 if (!(buf->flags & PIPE_BUF_FLAG_LRU))
 601                         lru_cache_add(page);
 602         } else {
 603 find_page:
 604                 page = find_lock_page(mapping, index);
 605                 if (!page) {
 606                         ret = -ENOMEM;
 607                         page = page_cache_alloc_cold(mapping);
 608                         if (unlikely(!page))
 609                                 goto out_ret;
 610
 611                         /*
 612                          * This will also lock the page
 613                          */
 614                         ret = add_to_page_cache_lru(page, mapping, index,
 615                                                     GFP_KERNEL);
 616                         if (unlikely(ret))
 617                                 goto out;
 618                 }
 619
 620                 /*
 621                  * We get here with the page locked. If the page is also
 622                  * uptodate, we don't need to do more. If it isn't, we
 623                  * may need to bring it in if we are not going to overwrite
 624                  * the full page.
 625                  */
 626                 if (!PageUptodate(page)) {
 627                         if (this_len < PAGE_CACHE_SIZE) {
 628                                 ret = mapping->a_ops->readpage(file, page);
 629                                 if (unlikely(ret))
 630                                         goto out;
 631
 632                                 lock_page(page);
 633
 634                                 if (!PageUptodate(page)) {
 635                                         /*
 636                                          * Page got invalidated, repeat.
 637                                          */
 638                                         if (!page->mapping) {
 639                                                 unlock_page(page);
 640                                                 page_cache_release(page);
 641                                                 goto find_page;
 642                                         }
 643                                         ret = -EIO;
 644                                         goto out;
 645                                 }
 646                         } else
 647                                 SetPageUptodate(page);
 648                 }
 649         }
 650
 651         ret = mapping->a_ops->prepare_write(file, page, offset, offset+this_len);
 652         if (unlikely(ret)) {
 653                 loff_t isize = i_size_read(mapping->host);
 654
 655                 if (ret != AOP_TRUNCATED_PAGE)
 656                         unlock_page(page);
 657                 page_cache_release(page);
 658                 if (ret == AOP_TRUNCATED_PAGE)
 659                         goto find_page;
 660
 661                 /*
 662                  * prepare_write() may have instantiated a few blocks
 663                  * outside i_size.  Trim these off again.
 664                  */
 665                 if (sd->pos + this_len > isize)
 666                         vmtruncate(mapping->host, isize);
 667
 668                 goto out_ret;
 669         }
 670
 671         if (buf->page != page) {
 672                 /*
 673                  * Careful, ->map() uses KM_USER0!
 674                  */
 675                 char *src = buf->ops->map(pipe, buf, 1);
 676                 char *dst = kmap_atomic(page, KM_USER1);
 677
 678                 memcpy(dst + offset, src + buf->offset, this_len);
 679                 flush_dcache_page(page);
 680                 kunmap_atomic(dst, KM_USER1);
 681                 buf->ops->unmap(pipe, buf, src);
 682         }
 683
 684         ret = mapping->a_ops->commit_write(file, page, offset, offset+this_len);
 685         if (!ret) {
 686                 /*
 687                  * Return the number of bytes written and mark page as
 688                  * accessed, we are now done!
 689                  */
 690                 ret = this_len;
 691                 mark_page_accessed(page);
 692                 balance_dirty_pages_ratelimited(mapping);
 693         } else if (ret == AOP_TRUNCATED_PAGE) {
 694                 page_cache_release(page);
 695                 goto find_page;
 696         }
 697 out:
 698         page_cache_release(page);
 699         unlock_page(page);
 700 out_ret:
 701         return ret;
 702 }
 703
 704 /*
 705  * Pipe input worker. Most of this logic works like a regular pipe, the
 706  * key here is the 'actor' worker passed in that actually moves the data
 707  * to the wanted destination. See pipe_to_file/pipe_to_sendpage above.
 708  */
 709 static ssize_t __splice_from_pipe(struct pipe_inode_info *pipe,
 710                                   struct file *out, loff_t *ppos, size_t len,
 711                                   unsigned int flags, splice_actor *actor)
 712 {
 713         int ret, do_wakeup, err;
 714         struct splice_desc sd;
 715
 716         ret = 0;
 717         do_wakeup = 0;
 718
 719         sd.total_len = len;
 720         sd.flags = flags;
 721         sd.file = out;
 722         sd.pos = *ppos;
 723
 724         for (;;) {
 725                 if (pipe->nrbufs) {
 726                         struct pipe_buffer *buf = pipe->bufs + pipe->curbuf;
 727                         const struct pipe_buf_operations *ops = buf->ops;
 728
 729                         sd.len = buf->len;
 730                         if (sd.len > sd.total_len)
 731                                 sd.len = sd.total_len;
 732
 733                         err = actor(pipe, buf, &sd);
 734                         if (err <= 0) {
 735                                 if (!ret && err != -ENODATA)
 736                                         ret = err;
 737
 738                                 break;
 739                         }
 740
 741                         ret += err;
 742                         buf->offset += err;
 743                         buf->len -= err;
 744
 745                         sd.len -= err;
 746                         sd.pos += err;
 747                         sd.total_len -= err;
 748                         if (sd.len)
 749                                 continue;
 750
 751                         if (!buf->len) {
 752                                 buf->ops = NULL;
 753                                 ops->release(pipe, buf);
 754                                 pipe->curbuf = (pipe->curbuf + 1) & (PIPE_BUFFERS - 1);
 755                                 pipe->nrbufs--;
 756                                 if (pipe->inode)
 757                                         do_wakeup = 1;
 758                         }
 759
 760                         if (!sd.total_len)
 761                                 break;
 762                 }
 763
 764                 if (pipe->nrbufs)
 765                         continue;
 766                 if (!pipe->writers)
 767                         break;
 768                 if (!pipe->waiting_writers) {
 769                         if (ret)
 770                                 break;
 771                 }
 772
 773                 if (flags & SPLICE_F_NONBLOCK) {
 774                         if (!ret)
 775                                 ret = -EAGAIN;
 776                         break;
 777                 }
 778
 779                 if (signal_pending(current)) {
 780                         if (!ret)
 781                                 ret = -ERESTARTSYS;
 782                         break;
 783                 }
 784
 785                 if (do_wakeup) {
 786                         smp_mb();
 787                         if (waitqueue_active(&pipe->wait))
 788                                 wake_up_interruptible_sync(&pipe->wait);
 789                         kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
 790                         do_wakeup = 0;
 791                 }
 792
 793                 pipe_wait(pipe);
 794         }
 795
 796         if (do_wakeup) {
 797                 smp_mb();
 798                 if (waitqueue_active(&pipe->wait))
 799                         wake_up_interruptible(&pipe->wait);
 800                 kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
 801         }
 802
 803         return ret;
 804 }
 805
 806 ssize_t splice_from_pipe(struct pipe_inode_info *pipe, struct file *out,
 807                          loff_t *ppos, size_t len, unsigned int flags,
 808                          splice_actor *actor)
 809 {
 810         ssize_t ret;
 811         struct inode *inode = out->f_mapping->host;
 812
 813         /*
 814          * The actor worker might be calling ->prepare_write and
 815          * ->commit_write. Most of the time, these expect i_mutex to
 816          * be held. Since this may result in an ABBA deadlock with
 817          * pipe->inode, we have to order lock acquiry here.
 818          */
 819         inode_double_lock(inode, pipe->inode);
 820         ret = __splice_from_pipe(pipe, out, ppos, len, flags, actor);
 821         inode_double_unlock(inode, pipe->inode);
 822
 823         return ret;
 824 }
 825
 826 /**
 827  * generic_file_splice_write_nolock - generic_file_splice_write without mutexes
 828  * @pipe:       pipe info
 829  * @out:        file to write to
 830  * @len:        number of bytes to splice
 831  * @flags:      splice modifier flags
 832  *
 833  * Will either move or copy pages (determined by @flags options) from
 834  * the given pipe inode to the given file. The caller is responsible
 835  * for acquiring i_mutex on both inodes.
 836  *
 837  */
 838 ssize_t
 839 generic_file_splice_write_nolock(struct pipe_inode_info *pipe, struct file *out,
 840                                  loff_t *ppos, size_t len, unsigned int flags)
 841 {
 842         struct address_space *mapping = out->f_mapping;
 843         struct inode *inode = mapping->host;
 844         ssize_t ret;
 845         int err;
 846
 847         err = remove_suid(out->f_path.dentry);
 848         if (unlikely(err))
 849                 return err;
 850
 851         ret = __splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_file);
 852         if (ret > 0) {
 853                 *ppos += ret;
 854
 855                 /*
 856                  * If file or inode is SYNC and we actually wrote some data,
 857                  * sync it.
 858                  */
 859                 if (unlikely((out->f_flags & O_SYNC) || IS_SYNC(inode))) {
 860                         err = generic_osync_inode(inode, mapping,
 861                                                   OSYNC_METADATA|OSYNC_DATA);
 862
 863                         if (err)
 864                                 ret = err;
 865                 }
 866         }
 867
 868         return ret;
 869 }
 870
 871 EXPORT_SYMBOL(generic_file_splice_write_nolock);
 872
 873 /**
 874  * generic_file_splice_write - splice data from a pipe to a file
 875  * @pipe:       pipe info
 876  * @out:        file to write to
 877  * @len:        number of bytes to splice
 878  * @flags:      splice modifier flags
 879  *
 880  * Will either move or copy pages (determined by @flags options) from
 881  * the given pipe inode to the given file.
 882  *
 883  */
 884 ssize_t
 885 generic_file_splice_write(struct pipe_inode_info *pipe, struct file *out,
 886                           loff_t *ppos, size_t len, unsigned int flags)
 887 {
 888         struct address_space *mapping = out->f_mapping;
 889         struct inode *inode = mapping->host;
 890         ssize_t ret;
 891         int err;
 892
 893         err = should_remove_suid(out->f_path.dentry);
 894         if (unlikely(err)) {
 895                 mutex_lock(&inode->i_mutex);
 896                 err = __remove_suid(out->f_path.dentry, err);
 897                 mutex_unlock(&inode->i_mutex);
 898                 if (err)
 899                         return err;
 900         }
 901
 902         ret = splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_file);
 903         if (ret > 0) {
 904                 *ppos += ret;
 905
 906                 /*
 907                  * If file or inode is SYNC and we actually wrote some data,
 908                  * sync it.
 909                  */
 910                 if (unlikely((out->f_flags & O_SYNC) || IS_SYNC(inode))) {
 911                         mutex_lock(&inode->i_mutex);
 912                         err = generic_osync_inode(inode, mapping,
 913                                                   OSYNC_METADATA|OSYNC_DATA);
 914                         mutex_unlock(&inode->i_mutex);
 915
 916                         if (err)
 917                                 ret = err;
 918                 }
 919         }
 920
 921         return ret;
 922 }
 923
 924 EXPORT_SYMBOL(generic_file_splice_write);
 925
 926 /**
 927  * generic_splice_sendpage - splice data from a pipe to a socket
 928  * @inode:      pipe inode
 929  * @out:        socket to write to
 930  * @len:        number of bytes to splice
 931  * @flags:      splice modifier flags
 932  *
 933  * Will send @len bytes from the pipe to a network socket. No data copying
 934  * is involved.
 935  *
 936  */
 937 ssize_t generic_splice_sendpage(struct pipe_inode_info *pipe, struct file *out,
 938                                 loff_t *ppos, size_t len, unsigned int flags)
 939 {
 940         return splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_sendpage);
 941 }
 942
 943 EXPORT_SYMBOL(generic_splice_sendpage);
 944
 945 /*
 946  * Attempt to initiate a splice from pipe to file.
 947  */
 948 static long do_splice_from(struct pipe_inode_info *pipe, struct file *out,
 949                            loff_t *ppos, size_t len, unsigned int flags)
 950 {
 951         int ret;
 952
 953         if (unlikely(!out->f_op || !out->f_op->splice_write))
 954                 return -EINVAL;
 955
 956         if (unlikely(!(out->f_mode & FMODE_WRITE)))
 957                 return -EBADF;
 958
 959         ret = rw_verify_area(WRITE, out, ppos, len);
 960         if (unlikely(ret < 0))
 961                 return ret;
 962
 963         return out->f_op->splice_write(pipe, out, ppos, len, flags);
 964 }
 965
 966 /*
 967  * Attempt to initiate a splice from a file to a pipe.
 968  */
 969 static long do_splice_to(struct file *in, loff_t *ppos,
 970                          struct pipe_inode_info *pipe, size_t len,
 971                          unsigned int flags)
 972 {
 973         loff_t isize, left;
 974         int ret;
 975
 976         if (unlikely(!in->f_op || !in->f_op->splice_read))
 977                 return -EINVAL;
 978
 979         if (unlikely(!(in->f_mode & FMODE_READ)))
 980                 return -EBADF;
 981
 982         ret = rw_verify_area(READ, in, ppos, len);
 983         if (unlikely(ret < 0))
 984                 return ret;
 985
 986         isize = i_size_read(in->f_mapping->host);
 987         if (unlikely(*ppos >= isize))
 988                 return 0;
 989
 990         left = isize - *ppos;
 991         if (unlikely(left < len))
 992                 len = left;
 993
 994         return in->f_op->splice_read(in, ppos, pipe, len, flags);
 995 }
 996
 997 long do_splice_direct(struct file *in, loff_t *ppos, struct file *out,
 998                       size_t len, unsigned int flags)
 999 {
1000         struct pipe_inode_info *pipe;
1001         long ret, bytes;
1002         loff_t out_off;
1003         umode_t i_mode;
1004         int i;
1005
1006         /*
1007          * We require the input being a regular file, as we don't want to
1008          * randomly drop data for eg socket -> socket splicing. Use the
1009          * piped splicing for that!
1010          */
1011         i_mode = in->f_path.dentry->d_inode->i_mode;
1012         if (unlikely(!S_ISREG(i_mode) && !S_ISBLK(i_mode)))
1013                 return -EINVAL;
1014
1015         /*
1016          * neither in nor out is a pipe, setup an internal pipe attached to
1017          * 'out' and transfer the wanted data from 'in' to 'out' through that
1018          */
1019         pipe = current->splice_pipe;
1020         if (unlikely(!pipe)) {
1021                 pipe = alloc_pipe_info(NULL);
1022                 if (!pipe)
1023                         return -ENOMEM;
1024
1025                 /*
1026                  * We don't have an immediate reader, but we'll read the stuff
1027                  * out of the pipe right after the splice_to_pipe(). So set
1028                  * PIPE_READERS appropriately.
1029                  */
1030                 pipe->readers = 1;
1031
1032                 current->splice_pipe = pipe;
1033         }
1034
1035         /*
1036          * Do the splice.
1037          */
1038         ret = 0;
1039         bytes = 0;
1040         out_off = 0;
1041
1042         while (len) {
1043                 size_t read_len, max_read_len;
1044
1045                 /*
1046                  * Do at most PIPE_BUFFERS pages worth of transfer:
1047                  */
1048                 max_read_len = min(len, (size_t)(PIPE_BUFFERS*PAGE_SIZE));
1049
1050                 ret = do_splice_to(in, ppos, pipe, max_read_len, flags);
1051                 if (unlikely(ret < 0))
1052                         goto out_release;
1053
1054                 read_len = ret;
1055
1056                 /*
1057                  * NOTE: nonblocking mode only applies to the input. We
1058                  * must not do the output in nonblocking mode as then we
1059                  * could get stuck data in the internal pipe:
1060                  */
1061                 ret = do_splice_from(pipe, out, &out_off, read_len,
1062                                      flags & ~SPLICE_F_NONBLOCK);
1063                 if (unlikely(ret < 0))
1064                         goto out_release;
1065
1066                 bytes += ret;
1067                 len -= ret;
1068
1069                 /*
1070                  * In nonblocking mode, if we got back a short read then
1071                  * that was due to either an IO error or due to the
1072                  * pagecache entry not being there. In the IO error case
1073                  * the _next_ splice attempt will produce a clean IO error
1074                  * return value (not a short read), so in both cases it's
1075                  * correct to break out of the loop here:
1076                  */
1077                 if ((flags & SPLICE_F_NONBLOCK) && (read_len < max_read_len))
1078                         break;
1079         }
1080
1081         pipe->nrbufs = pipe->curbuf = 0;
1082
1083         return bytes;
1084
1085 out_release:
1086         /*
1087          * If we did an incomplete transfer we must release
1088          * the pipe buffers in question:
1089          */
1090         for (i = 0; i < PIPE_BUFFERS; i++) {
1091                 struct pipe_buffer *buf = pipe->bufs + i;
1092
1093                 if (buf->ops) {
1094                         buf->ops->release(pipe, buf);
1095                         buf->ops = NULL;
1096                 }
1097         }
1098         pipe->nrbufs = pipe->curbuf = 0;
1099
1100         /*
1101          * If we transferred some data, return the number of bytes:
1102          */
1103         if (bytes > 0)
1104                 return bytes;
1105
1106         return ret;
1107 }
1108
1109 EXPORT_SYMBOL(do_splice_direct);
1110
1111 /*
1112  * After the inode slimming patch, i_pipe/i_bdev/i_cdev share the same
1113  * location, so checking ->i_pipe is not enough to verify that this is a
1114  * pipe.
1115  */
1116 static inline struct pipe_inode_info *pipe_info(struct inode *inode)
1117 {
1118         if (S_ISFIFO(inode->i_mode))
1119                 return inode->i_pipe;
1120
1121         return NULL;
1122 }
1123
1124 /*
1125  * Determine where to splice to/from.
1126  */
1127 static long do_splice(struct file *in, loff_t __user *off_in,
1128                       struct file *out, loff_t __user *off_out,
1129                       size_t len, unsigned int flags)
1130 {
1131         struct pipe_inode_info *pipe;
1132         loff_t offset, *off;
1133         long ret;
1134
1135         pipe = pipe_info(in->f_path.dentry->d_inode);
1136         if (pipe) {
1137                 if (off_in)
1138                         return -ESPIPE;
1139                 if (off_out) {
1140                         if (out->f_op->llseek == no_llseek)
1141                                 return -EINVAL;
1142                         if (copy_from_user(&offset, off_out, sizeof(loff_t)))
1143                                 return -EFAULT;
1144                         off = &offset;
1145                 } else
1146                         off = &out->f_pos;
1147
1148                 ret = do_splice_from(pipe, out, off, len, flags);
1149
1150                 if (off_out && copy_to_user(off_out, off, sizeof(loff_t)))
1151                         ret = -EFAULT;
1152
1153                 return ret;
1154         }
1155
1156         pipe = pipe_info(out->f_path.dentry->d_inode);
1157         if (pipe) {
1158                 if (off_out)
1159                         return -ESPIPE;
1160                 if (off_in) {
1161                         if (in->f_op->llseek == no_llseek)
1162                                 return -EINVAL;
1163                         if (copy_from_user(&offset, off_in, sizeof(loff_t)))
1164                                 return -EFAULT;
1165                         off = &offset;
1166                 } else
1167                         off = &in->f_pos;
1168
1169                 ret = do_splice_to(in, off, pipe, len, flags);
1170
1171                 if (off_in && copy_to_user(off_in, off, sizeof(loff_t)))
1172                         ret = -EFAULT;
1173
1174                 return ret;
1175         }
1176
1177         return -EINVAL;
1178 }
1179
1180 /*
1181  * Map an iov into an array of pages and offset/length tupples. With the
1182  * partial_page structure, we can map several non-contiguous ranges into
1183  * our ones pages[] map instead of splitting that operation into pieces.
1184  * Could easily be exported as a generic helper for other users, in which
1185  * case one would probably want to add a 'max_nr_pages' parameter as well.
1186  */
1187 static int get_iovec_page_array(const struct iovec __user *iov,
1188                                 unsigned int nr_vecs, struct page **pages,
1189                                 struct partial_page *partial, int aligned)
1190 {
1191         int buffers = 0, error = 0;
1192
1193         /*
1194          * It's ok to take the mmap_sem for reading, even
1195          * across a "get_user()".
1196          */
1197         down_read(&current->mm->mmap_sem);
1198
1199         while (nr_vecs) {
1200                 unsigned long off, npages;
1201                 void __user *base;
1202                 size_t len;
1203                 int i;
1204
1205                 /*
1206                  * Get user address base and length for this iovec.
1207                  */
1208                 error = get_user(base, &iov->iov_base);
1209                 if (unlikely(error))
1210                         break;
1211                 error = get_user(len, &iov->iov_len);
1212                 if (unlikely(error))
1213                         break;
1214
1215                 /*
1216                  * Sanity check this iovec. 0 read succeeds.
1217                  */
1218                 if (unlikely(!len))
1219                         break;
1220                 error = -EFAULT;
1221                 if (unlikely(!base))
1222                         break;
1223
1224                 /*
1225                  * Get this base offset and number of pages, then map
1226                  * in the user pages.
1227                  */
1228                 off = (unsigned long) base & ~PAGE_MASK;
1229
1230                 /*
1231                  * If asked for alignment, the offset must be zero and the
1232                  * length a multiple of the PAGE_SIZE.
1233                  */
1234                 error = -EINVAL;
1235                 if (aligned && (off || len & ~PAGE_MASK))
1236                         break;
1237
1238                 npages = (off + len + PAGE_SIZE - 1) >> PAGE_SHIFT;
1239                 if (npages > PIPE_BUFFERS - buffers)
1240                         npages = PIPE_BUFFERS - buffers;
1241
1242                 error = get_user_pages(current, current->mm,
1243                                        (unsigned long) base, npages, 0, 0,
1244                                        &pages[buffers], NULL);
1245
1246                 if (unlikely(error <= 0))
1247                         break;
1248
1249                 /*
1250                  * Fill this contiguous range into the partial page map.
1251                  */
1252                 for (i = 0; i < error; i++) {
1253                         const int plen = min_t(size_t, len, PAGE_SIZE - off);
1254
1255                         partial[buffers].offset = off;
1256                         partial[buffers].len = plen;
1257
1258                         off = 0;
1259                         len -= plen;
1260                         buffers++;
1261                 }
1262
1263                 /*
1264                  * We didn't complete this iov, stop here since it probably
1265                  * means we have to move some of this into a pipe to
1266                  * be able to continue.
1267                  */
1268                 if (len)
1269                         break;
1270
1271                 /*
1272                  * Don't continue if we mapped fewer pages than we asked for,
1273                  * or if we mapped the max number of pages that we have
1274                  * room for.
1275                  */
1276                 if (error < npages || buffers == PIPE_BUFFERS)
1277                         break;
1278
1279                 nr_vecs--;
1280                 iov++;
1281         }
1282
1283         up_read(&current->mm->mmap_sem);
1284
1285         if (buffers)
1286                 return buffers;
1287
1288         return error;
1289 }
1290
1291 /*
1292  * vmsplice splices a user address range into a pipe. It can be thought of
1293  * as splice-from-memory, where the regular splice is splice-from-file (or
1294  * to file). In both cases the output is a pipe, naturally.
1295  *
1296  * Note that vmsplice only supports splicing _from_ user memory to a pipe,
1297  * not the other way around. Splicing from user memory is a simple operation
1298  * that can be supported without any funky alignment restrictions or nasty
1299  * vm tricks. We simply map in the user memory and fill them into a pipe.
1300  * The reverse isn't quite as easy, though. There are two possible solutions
1301  * for that:
1302  *
1303  *      - memcpy() the data internally, at which point we might as well just
1304  *        do a regular read() on the buffer anyway.
1305  *      - Lots of nasty vm tricks, that are neither fast nor flexible (it
1306  *        has restriction limitations on both ends of the pipe).
1307  *
1308  * Alas, it isn't here.
1309  *
1310  */
1311 static long do_vmsplice(struct file *file, const struct iovec __user *iov,
1312                         unsigned long nr_segs, unsigned int flags)
1313 {
1314         struct pipe_inode_info *pipe;
1315         struct page *pages[PIPE_BUFFERS];
1316         struct partial_page partial[PIPE_BUFFERS];
1317         struct splice_pipe_desc spd = {
1318                 .pages = pages,
1319                 .partial = partial,
1320                 .flags = flags,
1321                 .ops = &user_page_pipe_buf_ops,
1322         };
1323
1324         pipe = pipe_info(file->f_path.dentry->d_inode);
1325         if (!pipe)
1326                 return -EBADF;
1327         if (unlikely(nr_segs > UIO_MAXIOV))
1328                 return -EINVAL;
1329         else if (unlikely(!nr_segs))
1330                 return 0;
1331
1332         spd.nr_pages = get_iovec_page_array(iov, nr_segs, pages, partial,
1333                                             flags & SPLICE_F_GIFT);
1334         if (spd.nr_pages <= 0)
1335                 return spd.nr_pages;
1336
1337         return splice_to_pipe(pipe, &spd);
1338 }
1339
1340 asmlinkage long sys_vmsplice(int fd, const struct iovec __user *iov,
1341                              unsigned long nr_segs, unsigned int flags)
1342 {
1343         struct file *file;
1344         long error;
1345         int fput;
1346
1347         error = -EBADF;
1348         file = fget_light(fd, &fput);
1349         if (file) {
1350                 if (file->f_mode & FMODE_WRITE)
1351                         error = do_vmsplice(file, iov, nr_segs, flags);
1352
1353                 fput_light(file, fput);
1354         }
1355
1356         return error;
1357 }
1358
1359 asmlinkage long sys_splice(int fd_in, loff_t __user *off_in,
1360                            int fd_out, loff_t __user *off_out,
1361                            size_t len, unsigned int flags)
1362 {
1363         long error;
1364         struct file *in, *out;
1365         int fput_in, fput_out;
1366
1367         if (unlikely(!len))
1368                 return 0;
1369
1370         error = -EBADF;
1371         in = fget_light(fd_in, &fput_in);
1372         if (in) {
1373                 if (in->f_mode & FMODE_READ) {
1374                         out = fget_light(fd_out, &fput_out);
1375                         if (out) {
1376                                 if (out->f_mode & FMODE_WRITE)
1377                                         error = do_splice(in, off_in,
1378                                                           out, off_out,
1379                                                           len, flags);
1380                                 fput_light(out, fput_out);
1381                         }
1382                 }
1383
1384                 fput_light(in, fput_in);
1385         }
1386
1387         return error;
1388 }
1389
1390 /*
1391  * Make sure there's data to read. Wait for input if we can, otherwise
1392  * return an appropriate error.
1393  */
1394 static int link_ipipe_prep(struct pipe_inode_info *pipe, unsigned int flags)
1395 {
1396         int ret;
1397
1398         /*
1399          * Check ->nrbufs without the inode lock first. This function
1400          * is speculative anyways, so missing one is ok.
1401          */
1402         if (pipe->nrbufs)
1403                 return 0;
1404
1405         ret = 0;
1406         mutex_lock(&pipe->inode->i_mutex);
1407
1408         while (!pipe->nrbufs) {
1409                 if (signal_pending(current)) {
1410                         ret = -ERESTARTSYS;
1411                         break;
1412                 }
1413                 if (!pipe->writers)
1414                         break;
1415                 if (!pipe->waiting_writers) {
1416                         if (flags & SPLICE_F_NONBLOCK) {
1417                                 ret = -EAGAIN;
1418                                 break;
1419                         }
1420                 }
1421                 pipe_wait(pipe);
1422         }
1423
1424         mutex_unlock(&pipe->inode->i_mutex);
1425         return ret;
1426 }
1427
1428 /*
1429  * Make sure there's writeable room. Wait for room if we can, otherwise
1430  * return an appropriate error.
1431  */
1432 static int link_opipe_prep(struct pipe_inode_info *pipe, unsigned int flags)
1433 {
1434         int ret;
1435
1436         /*
1437          * Check ->nrbufs without the inode lock first. This function
1438          * is speculative anyways, so missing one is ok.
1439          */
1440         if (pipe->nrbufs < PIPE_BUFFERS)
1441                 return 0;
1442
1443         ret = 0;
1444         mutex_lock(&pipe->inode->i_mutex);
1445
1446         while (pipe->nrbufs >= PIPE_BUFFERS) {
1447                 if (!pipe->readers) {
1448                         send_sig(SIGPIPE, current, 0);
1449                         ret = -EPIPE;
1450                         break;
1451                 }
1452                 if (flags & SPLICE_F_NONBLOCK) {
1453                         ret = -EAGAIN;
1454                         break;
1455                 }
1456                 if (signal_pending(current)) {
1457                         ret = -ERESTARTSYS;
1458                         break;
1459                 }
1460                 pipe->waiting_writers++;
1461                 pipe_wait(pipe);
1462                 pipe->waiting_writers--;
1463         }
1464
1465         mutex_unlock(&pipe->inode->i_mutex);
1466         return ret;
1467 }
1468
1469 /*
1470  * Link contents of ipipe to opipe.
1471  */
1472 static int link_pipe(struct pipe_inode_info *ipipe,
1473                      struct pipe_inode_info *opipe,
1474                      size_t len, unsigned int flags)
1475 {
1476         struct pipe_buffer *ibuf, *obuf;
1477         int ret = 0, i = 0, nbuf;
1478
1479         /*
1480          * Potential ABBA deadlock, work around it by ordering lock
1481          * grabbing by inode address. Otherwise two different processes
1482          * could deadlock (one doing tee from A -> B, the other from B -> A).
1483          */
1484         inode_double_lock(ipipe->inode, opipe->inode);
1485
1486         do {
1487                 if (!opipe->readers) {
1488                         send_sig(SIGPIPE, current, 0);
1489                         if (!ret)
1490                                 ret = -EPIPE;
1491                         break;
1492                 }
1493
1494                 /*
1495                  * If we have iterated all input buffers or ran out of
1496                  * output room, break.
1497                  */
1498                 if (i >= ipipe->nrbufs || opipe->nrbufs >= PIPE_BUFFERS)
1499                         break;
1500
1501                 ibuf = ipipe->bufs + ((ipipe->curbuf + i) & (PIPE_BUFFERS - 1));
1502                 nbuf = (opipe->curbuf + opipe->nrbufs) & (PIPE_BUFFERS - 1);
1503
1504                 /*
1505                  * Get a reference to this pipe buffer,
1506                  * so we can copy the contents over.
1507                  */
1508                 ibuf->ops->get(ipipe, ibuf);
1509
1510                 obuf = opipe->bufs + nbuf;
1511                 *obuf = *ibuf;
1512
1513                 /*
1514                  * Don't inherit the gift flag, we need to
1515                  * prevent multiple steals of this page.
1516                  */
1517                 obuf->flags &= ~PIPE_BUF_FLAG_GIFT;
1518
1519                 if (obuf->len > len)
1520                         obuf->len = len;
1521
1522                 opipe->nrbufs++;
1523                 ret += obuf->len;
1524                 len -= obuf->len;
1525                 i++;
1526         } while (len);
1527
1528         inode_double_unlock(ipipe->inode, opipe->inode);
1529
1530         /*
1531          * If we put data in the output pipe, wakeup any potential readers.
1532          */
1533         if (ret > 0) {
1534                 smp_mb();
1535                 if (waitqueue_active(&opipe->wait))
1536                         wake_up_interruptible(&opipe->wait);
1537                 kill_fasync(&opipe->fasync_readers, SIGIO, POLL_IN);
1538         }
1539
1540         return ret;
1541 }
1542
1543 /*
1544  * This is a tee(1) implementation that works on pipes. It doesn't copy
1545  * any data, it simply references the 'in' pages on the 'out' pipe.
1546  * The 'flags' used are the SPLICE_F_* variants, currently the only
1547  * applicable one is SPLICE_F_NONBLOCK.
1548  */
1549 static long do_tee(struct file *in, struct file *out, size_t len,
1550                    unsigned int flags)
1551 {
1552         struct pipe_inode_info *ipipe = pipe_info(in->f_path.dentry->d_inode);
1553         struct pipe_inode_info *opipe = pipe_info(out->f_path.dentry->d_inode);
1554         int ret = -EINVAL;
1555
1556         /*
1557          * Duplicate the contents of ipipe to opipe without actually
1558          * copying the data.
1559          */
1560         if (ipipe && opipe && ipipe != opipe) {
1561                 /*
1562                  * Keep going, unless we encounter an error. The ipipe/opipe
1563                  * ordering doesn't really matter.
1564                  */
1565                 ret = link_ipipe_prep(ipipe, flags);
1566                 if (!ret) {
1567                         ret = link_opipe_prep(opipe, flags);
1568                         if (!ret) {
1569                                 ret = link_pipe(ipipe, opipe, len, flags);
1570                                 if (!ret && (flags & SPLICE_F_NONBLOCK))
1571                                         ret = -EAGAIN;
1572                         }
1573                 }
1574         }
1575
1576         return ret;
1577 }
1578
1579 asmlinkage long sys_tee(int fdin, int fdout, size_t len, unsigned int flags)
1580 {
1581         struct file *in;
1582         int error, fput_in;
1583
1584         if (unlikely(!len))
1585                 return 0;
1586
1587         error = -EBADF;
1588         in = fget_light(fdin, &fput_in);
1589         if (in) {
1590                 if (in->f_mode & FMODE_READ) {
1591                         int fput_out;
1592                         struct file *out = fget_light(fdout, &fput_out);
1593
1594                         if (out) {
1595                                 if (out->f_mode & FMODE_WRITE)
1596                                         error = do_tee(in, out, len, flags);
1597                                 fput_light(out, fput_out);
1598                         }
1599                 }
1600                 fput_light(in, fput_in);
1601         }
1602
1603         return error;
1604 }