git.oblomov.eu Git - 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@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          * Don't try to 2nd guess the read-ahead logic, call into
 293          * page_cache_readahead() like the page cache reads would do.
 294          */
 295         page_cache_readahead(mapping, &in->f_ra, in, index, nr_pages);
 296
 297         /*
 298          * Now fill in the holes:
 299          */
 300         error = 0;
 301         total_len = 0;
 302
 303         /*
 304          * Lookup the (hopefully) full range of pages we need.
 305          */
 306         spd.nr_pages = find_get_pages_contig(mapping, index, nr_pages, pages);
 307
 308         /*
 309          * If find_get_pages_contig() returned fewer pages than we needed,
 310          * allocate the rest.
 311          */
 312         index += spd.nr_pages;
 313         while (spd.nr_pages < nr_pages) {
 314                 /*
 315                  * Page could be there, find_get_pages_contig() breaks on
 316                  * the first hole.
 317                  */
 318                 page = find_get_page(mapping, index);
 319                 if (!page) {
 320                         /*
 321                          * Make sure the read-ahead engine is notified
 322                          * about this failure.
 323                          */
 324                         handle_ra_miss(mapping, &in->f_ra, index);
 325
 326                         /*
 327                          * page didn't exist, allocate one.
 328                          */
 329                         page = page_cache_alloc_cold(mapping);
 330                         if (!page)
 331                                 break;
 332
 333                         error = add_to_page_cache_lru(page, mapping, index,
 334                                               GFP_KERNEL);
 335                         if (unlikely(error)) {
 336                                 page_cache_release(page);
 337                                 if (error == -EEXIST)
 338                                         continue;
 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                                 if (TestSetPageLocked(page))
 381                                         break;
 382                         } else
 383                                 lock_page(page);
 384
 385                         /*
 386                          * page was truncated, stop here. if this isn't the
 387                          * first page, we'll just complete what we already
 388                          * added
 389                          */
 390                         if (!page->mapping) {
 391                                 unlock_page(page);
 392                                 break;
 393                         }
 394                         /*
 395                          * page was already under io and is now done, great
 396                          */
 397                         if (PageUptodate(page)) {
 398                                 unlock_page(page);
 399                                 goto fill_it;
 400                         }
 401
 402                         /*
 403                          * need to read in the page
 404                          */
 405                         error = mapping->a_ops->readpage(in, page);
 406                         if (unlikely(error)) {
 407                                 /*
 408                                  * We really should re-lookup the page here,
 409                                  * but it complicates things a lot. Instead
 410                                  * lets just do what we already stored, and
 411                                  * we'll get it the next time we are called.
 412                                  */
 413                                 if (error == AOP_TRUNCATED_PAGE)
 414                                         error = 0;
 415
 416                                 break;
 417                         }
 418
 419                         /*
 420                          * i_size must be checked after ->readpage().
 421                          */
 422                         isize = i_size_read(mapping->host);
 423                         end_index = (isize - 1) >> PAGE_CACHE_SHIFT;
 424                         if (unlikely(!isize || index > end_index))
 425                                 break;
 426
 427                         /*
 428                          * if this is the last page, see if we need to shrink
 429                          * the length and stop
 430                          */
 431                         if (end_index == index) {
 432                                 loff = PAGE_CACHE_SIZE - (isize & ~PAGE_CACHE_MASK);
 433                                 if (total_len + loff > isize)
 434                                         break;
 435                                 /*
 436                                  * force quit after adding this page
 437                                  */
 438                                 len = this_len;
 439                                 this_len = min(this_len, loff);
 440                                 loff = 0;
 441                         }
 442                 }
 443 fill_it:
 444                 partial[page_nr].offset = loff;
 445                 partial[page_nr].len = this_len;
 446                 len -= this_len;
 447                 total_len += this_len;
 448                 loff = 0;
 449                 spd.nr_pages++;
 450                 index++;
 451         }
 452
 453         /*
 454          * Release any pages at the end, if we quit early. 'i' is how far
 455          * we got, 'nr_pages' is how many pages are in the map.
 456          */
 457         while (page_nr < nr_pages)
 458                 page_cache_release(pages[page_nr++]);
 459
 460         if (spd.nr_pages)
 461                 return splice_to_pipe(pipe, &spd);
 462
 463         return error;
 464 }
 465
 466 /**
 467  * generic_file_splice_read - splice data from file to a pipe
 468  * @in:         file to splice from
 469  * @pipe:       pipe to splice to
 470  * @len:        number of bytes to splice
 471  * @flags:      splice modifier flags
 472  *
 473  * Will read pages from given file and fill them into a pipe.
 474  */
 475 ssize_t generic_file_splice_read(struct file *in, loff_t *ppos,
 476                                  struct pipe_inode_info *pipe, size_t len,
 477                                  unsigned int flags)
 478 {
 479         ssize_t spliced;
 480         int ret;
 481
 482         ret = 0;
 483         spliced = 0;
 484
 485         while (len) {
 486                 ret = __generic_file_splice_read(in, ppos, pipe, len, flags);
 487
 488                 if (ret < 0)
 489                         break;
 490                 else if (!ret) {
 491                         if (spliced)
 492                                 break;
 493                         if (flags & SPLICE_F_NONBLOCK) {
 494                                 ret = -EAGAIN;
 495                                 break;
 496                         }
 497                 }
 498
 499                 *ppos += ret;
 500                 len -= ret;
 501                 spliced += ret;
 502         }
 503
 504         if (spliced)
 505                 return spliced;
 506
 507         return ret;
 508 }
 509
 510 EXPORT_SYMBOL(generic_file_splice_read);
 511
 512 /*
 513  * Send 'sd->len' bytes to socket from 'sd->file' at position 'sd->pos'
 514  * using sendpage(). Return the number of bytes sent.
 515  */
 516 static int pipe_to_sendpage(struct pipe_inode_info *pipe,
 517                             struct pipe_buffer *buf, struct splice_desc *sd)
 518 {
 519         struct file *file = sd->file;
 520         loff_t pos = sd->pos;
 521         int ret, more;
 522
 523         ret = buf->ops->pin(pipe, buf);
 524         if (!ret) {
 525                 more = (sd->flags & SPLICE_F_MORE) || sd->len < sd->total_len;
 526
 527                 ret = file->f_op->sendpage(file, buf->page, buf->offset,
 528                                            sd->len, &pos, more);
 529         }
 530
 531         return ret;
 532 }
 533
 534 /*
 535  * This is a little more tricky than the file -> pipe splicing. There are
 536  * basically three cases:
 537  *
 538  *      - Destination page already exists in the address space and there
 539  *        are users of it. For that case we have no other option that
 540  *        copying the data. Tough luck.
 541  *      - Destination page already exists in the address space, but there
 542  *        are no users of it. Make sure it's uptodate, then drop it. Fall
 543  *        through to last case.
 544  *      - Destination page does not exist, we can add the pipe page to
 545  *        the page cache and avoid the copy.
 546  *
 547  * If asked to move pages to the output file (SPLICE_F_MOVE is set in
 548  * sd->flags), we attempt to migrate pages from the pipe to the output
 549  * file address space page cache. This is possible if no one else has
 550  * the pipe page referenced outside of the pipe and page cache. If
 551  * SPLICE_F_MOVE isn't set, or we cannot move the page, we simply create
 552  * a new page in the output file page cache and fill/dirty that.
 553  */
 554 static int pipe_to_file(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
 555                         struct splice_desc *sd)
 556 {
 557         struct file *file = sd->file;
 558         struct address_space *mapping = file->f_mapping;
 559         unsigned int offset, this_len;
 560         struct page *page;
 561         pgoff_t index;
 562         int ret;
 563
 564         /*
 565          * make sure the data in this buffer is uptodate
 566          */
 567         ret = buf->ops->pin(pipe, buf);
 568         if (unlikely(ret))
 569                 return ret;
 570
 571         index = sd->pos >> PAGE_CACHE_SHIFT;
 572         offset = sd->pos & ~PAGE_CACHE_MASK;
 573
 574         this_len = sd->len;
 575         if (this_len + offset > PAGE_CACHE_SIZE)
 576                 this_len = PAGE_CACHE_SIZE - offset;
 577
 578 find_page:
 579         page = find_lock_page(mapping, index);
 580         if (!page) {
 581                 ret = -ENOMEM;
 582                 page = page_cache_alloc_cold(mapping);
 583                 if (unlikely(!page))
 584                         goto out_ret;
 585
 586                 /*
 587                  * This will also lock the page
 588                  */
 589                 ret = add_to_page_cache_lru(page, mapping, index,
 590                                             GFP_KERNEL);
 591                 if (unlikely(ret))
 592                         goto out;
 593         }
 594
 595         ret = mapping->a_ops->prepare_write(file, page, offset, offset+this_len);
 596         if (unlikely(ret)) {
 597                 loff_t isize = i_size_read(mapping->host);
 598
 599                 if (ret != AOP_TRUNCATED_PAGE)
 600                         unlock_page(page);
 601                 page_cache_release(page);
 602                 if (ret == AOP_TRUNCATED_PAGE)
 603                         goto find_page;
 604
 605                 /*
 606                  * prepare_write() may have instantiated a few blocks
 607                  * outside i_size.  Trim these off again.
 608                  */
 609                 if (sd->pos + this_len > isize)
 610                         vmtruncate(mapping->host, isize);
 611
 612                 goto out_ret;
 613         }
 614
 615         if (buf->page != page) {
 616                 /*
 617                  * Careful, ->map() uses KM_USER0!
 618                  */
 619                 char *src = buf->ops->map(pipe, buf, 1);
 620                 char *dst = kmap_atomic(page, KM_USER1);
 621
 622                 memcpy(dst + offset, src + buf->offset, this_len);
 623                 flush_dcache_page(page);
 624                 kunmap_atomic(dst, KM_USER1);
 625                 buf->ops->unmap(pipe, buf, src);
 626         }
 627
 628         ret = mapping->a_ops->commit_write(file, page, offset, offset+this_len);
 629         if (ret) {
 630                 if (ret == AOP_TRUNCATED_PAGE) {
 631                         page_cache_release(page);
 632                         goto find_page;
 633                 }
 634                 if (ret < 0)
 635                         goto out;
 636                 /*
 637                  * Partial write has happened, so 'ret' already initialized by
 638                  * number of bytes written, Where is nothing we have to do here.
 639                  */
 640         } else
 641                 ret = this_len;
 642         /*
 643          * Return the number of bytes written and mark page as
 644          * accessed, we are now done!
 645          */
 646         mark_page_accessed(page);
 647         balance_dirty_pages_ratelimited(mapping);
 648 out:
 649         page_cache_release(page);
 650         unlock_page(page);
 651 out_ret:
 652         return ret;
 653 }
 654
 655 /*
 656  * Pipe input worker. Most of this logic works like a regular pipe, the
 657  * key here is the 'actor' worker passed in that actually moves the data
 658  * to the wanted destination. See pipe_to_file/pipe_to_sendpage above.
 659  */
 660 ssize_t __splice_from_pipe(struct pipe_inode_info *pipe,
 661                            struct file *out, loff_t *ppos, size_t len,
 662                            unsigned int flags, splice_actor *actor)
 663 {
 664         int ret, do_wakeup, err;
 665         struct splice_desc sd;
 666
 667         ret = 0;
 668         do_wakeup = 0;
 669
 670         sd.total_len = len;
 671         sd.flags = flags;
 672         sd.file = out;
 673         sd.pos = *ppos;
 674
 675         for (;;) {
 676                 if (pipe->nrbufs) {
 677                         struct pipe_buffer *buf = pipe->bufs + pipe->curbuf;
 678                         const struct pipe_buf_operations *ops = buf->ops;
 679
 680                         sd.len = buf->len;
 681                         if (sd.len > sd.total_len)
 682                                 sd.len = sd.total_len;
 683
 684                         err = actor(pipe, buf, &sd);
 685                         if (err <= 0) {
 686                                 if (!ret && err != -ENODATA)
 687                                         ret = err;
 688
 689                                 break;
 690                         }
 691
 692                         ret += err;
 693                         buf->offset += err;
 694                         buf->len -= err;
 695
 696                         sd.len -= err;
 697                         sd.pos += err;
 698                         sd.total_len -= err;
 699                         if (sd.len)
 700                                 continue;
 701
 702                         if (!buf->len) {
 703                                 buf->ops = NULL;
 704                                 ops->release(pipe, buf);
 705                                 pipe->curbuf = (pipe->curbuf + 1) & (PIPE_BUFFERS - 1);
 706                                 pipe->nrbufs--;
 707                                 if (pipe->inode)
 708                                         do_wakeup = 1;
 709                         }
 710
 711                         if (!sd.total_len)
 712                                 break;
 713                 }
 714
 715                 if (pipe->nrbufs)
 716                         continue;
 717                 if (!pipe->writers)
 718                         break;
 719                 if (!pipe->waiting_writers) {
 720                         if (ret)
 721                                 break;
 722                 }
 723
 724                 if (flags & SPLICE_F_NONBLOCK) {
 725                         if (!ret)
 726                                 ret = -EAGAIN;
 727                         break;
 728                 }
 729
 730                 if (signal_pending(current)) {
 731                         if (!ret)
 732                                 ret = -ERESTARTSYS;
 733                         break;
 734                 }
 735
 736                 if (do_wakeup) {
 737                         smp_mb();
 738                         if (waitqueue_active(&pipe->wait))
 739                                 wake_up_interruptible_sync(&pipe->wait);
 740                         kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
 741                         do_wakeup = 0;
 742                 }
 743
 744                 pipe_wait(pipe);
 745         }
 746
 747         if (do_wakeup) {
 748                 smp_mb();
 749                 if (waitqueue_active(&pipe->wait))
 750                         wake_up_interruptible(&pipe->wait);
 751                 kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
 752         }
 753
 754         return ret;
 755 }
 756 EXPORT_SYMBOL(__splice_from_pipe);
 757
 758 ssize_t splice_from_pipe(struct pipe_inode_info *pipe, struct file *out,
 759                          loff_t *ppos, size_t len, unsigned int flags,
 760                          splice_actor *actor)
 761 {
 762         ssize_t ret;
 763         struct inode *inode = out->f_mapping->host;
 764
 765         /*
 766          * The actor worker might be calling ->prepare_write and
 767          * ->commit_write. Most of the time, these expect i_mutex to
 768          * be held. Since this may result in an ABBA deadlock with
 769          * pipe->inode, we have to order lock acquiry here.
 770          */
 771         inode_double_lock(inode, pipe->inode);
 772         ret = __splice_from_pipe(pipe, out, ppos, len, flags, actor);
 773         inode_double_unlock(inode, pipe->inode);
 774
 775         return ret;
 776 }
 777
 778 /**
 779  * generic_file_splice_write_nolock - generic_file_splice_write without mutexes
 780  * @pipe:       pipe info
 781  * @out:        file to write to
 782  * @len:        number of bytes to splice
 783  * @flags:      splice modifier flags
 784  *
 785  * Will either move or copy pages (determined by @flags options) from
 786  * the given pipe inode to the given file. The caller is responsible
 787  * for acquiring i_mutex on both inodes.
 788  *
 789  */
 790 ssize_t
 791 generic_file_splice_write_nolock(struct pipe_inode_info *pipe, struct file *out,
 792                                  loff_t *ppos, size_t len, unsigned int flags)
 793 {
 794         struct address_space *mapping = out->f_mapping;
 795         struct inode *inode = mapping->host;
 796         ssize_t ret;
 797         int err;
 798
 799         err = remove_suid(out->f_path.dentry);
 800         if (unlikely(err))
 801                 return err;
 802
 803         ret = __splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_file);
 804         if (ret > 0) {
 805                 *ppos += ret;
 806
 807                 /*
 808                  * If file or inode is SYNC and we actually wrote some data,
 809                  * sync it.
 810                  */
 811                 if (unlikely((out->f_flags & O_SYNC) || IS_SYNC(inode))) {
 812                         err = generic_osync_inode(inode, mapping,
 813                                                   OSYNC_METADATA|OSYNC_DATA);
 814
 815                         if (err)
 816                                 ret = err;
 817                 }
 818         }
 819
 820         return ret;
 821 }
 822
 823 EXPORT_SYMBOL(generic_file_splice_write_nolock);
 824
 825 /**
 826  * generic_file_splice_write - splice data from a pipe to a file
 827  * @pipe:       pipe info
 828  * @out:        file to write to
 829  * @len:        number of bytes to splice
 830  * @flags:      splice modifier flags
 831  *
 832  * Will either move or copy pages (determined by @flags options) from
 833  * the given pipe inode to the given file.
 834  *
 835  */
 836 ssize_t
 837 generic_file_splice_write(struct pipe_inode_info *pipe, struct file *out,
 838                           loff_t *ppos, size_t len, unsigned int flags)
 839 {
 840         struct address_space *mapping = out->f_mapping;
 841         struct inode *inode = mapping->host;
 842         ssize_t ret;
 843         int err;
 844
 845         err = should_remove_suid(out->f_path.dentry);
 846         if (unlikely(err)) {
 847                 mutex_lock(&inode->i_mutex);
 848                 err = __remove_suid(out->f_path.dentry, err);
 849                 mutex_unlock(&inode->i_mutex);
 850                 if (err)
 851                         return err;
 852         }
 853
 854         ret = splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_file);
 855         if (ret > 0) {
 856                 *ppos += ret;
 857
 858                 /*
 859                  * If file or inode is SYNC and we actually wrote some data,
 860                  * sync it.
 861                  */
 862                 if (unlikely((out->f_flags & O_SYNC) || IS_SYNC(inode))) {
 863                         mutex_lock(&inode->i_mutex);
 864                         err = generic_osync_inode(inode, mapping,
 865                                                   OSYNC_METADATA|OSYNC_DATA);
 866                         mutex_unlock(&inode->i_mutex);
 867
 868                         if (err)
 869                                 ret = err;
 870                 }
 871         }
 872
 873         return ret;
 874 }
 875
 876 EXPORT_SYMBOL(generic_file_splice_write);
 877
 878 /**
 879  * generic_splice_sendpage - splice data from a pipe to a socket
 880  * @inode:      pipe inode
 881  * @out:        socket to write to
 882  * @len:        number of bytes to splice
 883  * @flags:      splice modifier flags
 884  *
 885  * Will send @len bytes from the pipe to a network socket. No data copying
 886  * is involved.
 887  *
 888  */
 889 ssize_t generic_splice_sendpage(struct pipe_inode_info *pipe, struct file *out,
 890                                 loff_t *ppos, size_t len, unsigned int flags)
 891 {
 892         return splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_sendpage);
 893 }
 894
 895 EXPORT_SYMBOL(generic_splice_sendpage);
 896
 897 /*
 898  * Attempt to initiate a splice from pipe to file.
 899  */
 900 static long do_splice_from(struct pipe_inode_info *pipe, struct file *out,
 901                            loff_t *ppos, size_t len, unsigned int flags)
 902 {
 903         int ret;
 904
 905         if (unlikely(!out->f_op || !out->f_op->splice_write))
 906                 return -EINVAL;
 907
 908         if (unlikely(!(out->f_mode & FMODE_WRITE)))
 909                 return -EBADF;
 910
 911         ret = rw_verify_area(WRITE, out, ppos, len);
 912         if (unlikely(ret < 0))
 913                 return ret;
 914
 915         return out->f_op->splice_write(pipe, out, ppos, len, flags);
 916 }
 917
 918 /*
 919  * Attempt to initiate a splice from a file to a pipe.
 920  */
 921 static long do_splice_to(struct file *in, loff_t *ppos,
 922                          struct pipe_inode_info *pipe, size_t len,
 923                          unsigned int flags)
 924 {
 925         loff_t isize, left;
 926         int ret;
 927
 928         if (unlikely(!in->f_op || !in->f_op->splice_read))
 929                 return -EINVAL;
 930
 931         if (unlikely(!(in->f_mode & FMODE_READ)))
 932                 return -EBADF;
 933
 934         ret = rw_verify_area(READ, in, ppos, len);
 935         if (unlikely(ret < 0))
 936                 return ret;
 937
 938         isize = i_size_read(in->f_mapping->host);
 939         if (unlikely(*ppos >= isize))
 940                 return 0;
 941
 942         left = isize - *ppos;
 943         if (unlikely(left < len))
 944                 len = left;
 945
 946         return in->f_op->splice_read(in, ppos, pipe, len, flags);
 947 }
 948
 949 long do_splice_direct(struct file *in, loff_t *ppos, struct file *out,
 950                       size_t len, unsigned int flags)
 951 {
 952         struct pipe_inode_info *pipe;
 953         long ret, bytes;
 954         loff_t out_off;
 955         umode_t i_mode;
 956         int i;
 957
 958         /*
 959          * We require the input being a regular file, as we don't want to
 960          * randomly drop data for eg socket -> socket splicing. Use the
 961          * piped splicing for that!
 962          */
 963         i_mode = in->f_path.dentry->d_inode->i_mode;
 964         if (unlikely(!S_ISREG(i_mode) && !S_ISBLK(i_mode)))
 965                 return -EINVAL;
 966
 967         /*
 968          * neither in nor out is a pipe, setup an internal pipe attached to
 969          * 'out' and transfer the wanted data from 'in' to 'out' through that
 970          */
 971         pipe = current->splice_pipe;
 972         if (unlikely(!pipe)) {
 973                 pipe = alloc_pipe_info(NULL);
 974                 if (!pipe)
 975                         return -ENOMEM;
 976
 977                 /*
 978                  * We don't have an immediate reader, but we'll read the stuff
 979                  * out of the pipe right after the splice_to_pipe(). So set
 980                  * PIPE_READERS appropriately.
 981                  */
 982                 pipe->readers = 1;
 983
 984                 current->splice_pipe = pipe;
 985         }
 986
 987         /*
 988          * Do the splice.
 989          */
 990         ret = 0;
 991         bytes = 0;
 992         out_off = 0;
 993
 994         while (len) {
 995                 size_t read_len, max_read_len;
 996
 997                 /*
 998                  * Do at most PIPE_BUFFERS pages worth of transfer:
 999                  */
1000                 max_read_len = min(len, (size_t)(PIPE_BUFFERS*PAGE_SIZE));
1001
1002                 ret = do_splice_to(in, ppos, pipe, max_read_len, flags);
1003                 if (unlikely(ret < 0))
1004                         goto out_release;
1005
1006                 read_len = ret;
1007
1008                 /*
1009                  * NOTE: nonblocking mode only applies to the input. We
1010                  * must not do the output in nonblocking mode as then we
1011                  * could get stuck data in the internal pipe:
1012                  */
1013                 ret = do_splice_from(pipe, out, &out_off, read_len,
1014                                      flags & ~SPLICE_F_NONBLOCK);
1015                 if (unlikely(ret < 0))
1016                         goto out_release;
1017
1018                 bytes += ret;
1019                 len -= ret;
1020
1021                 /*
1022                  * In nonblocking mode, if we got back a short read then
1023                  * that was due to either an IO error or due to the
1024                  * pagecache entry not being there. In the IO error case
1025                  * the _next_ splice attempt will produce a clean IO error
1026                  * return value (not a short read), so in both cases it's
1027                  * correct to break out of the loop here:
1028                  */
1029                 if ((flags & SPLICE_F_NONBLOCK) && (read_len < max_read_len))
1030                         break;
1031         }
1032
1033         pipe->nrbufs = pipe->curbuf = 0;
1034
1035         return bytes;
1036
1037 out_release:
1038         /*
1039          * If we did an incomplete transfer we must release
1040          * the pipe buffers in question:
1041          */
1042         for (i = 0; i < PIPE_BUFFERS; i++) {
1043                 struct pipe_buffer *buf = pipe->bufs + i;
1044
1045                 if (buf->ops) {
1046                         buf->ops->release(pipe, buf);
1047                         buf->ops = NULL;
1048                 }
1049         }
1050         pipe->nrbufs = pipe->curbuf = 0;
1051
1052         /*
1053          * If we transferred some data, return the number of bytes:
1054          */
1055         if (bytes > 0)
1056                 return bytes;
1057
1058         return ret;
1059 }
1060
1061 EXPORT_SYMBOL(do_splice_direct);
1062
1063 /*
1064  * After the inode slimming patch, i_pipe/i_bdev/i_cdev share the same
1065  * location, so checking ->i_pipe is not enough to verify that this is a
1066  * pipe.
1067  */
1068 static inline struct pipe_inode_info *pipe_info(struct inode *inode)
1069 {
1070         if (S_ISFIFO(inode->i_mode))
1071                 return inode->i_pipe;
1072
1073         return NULL;
1074 }
1075
1076 /*
1077  * Determine where to splice to/from.
1078  */
1079 static long do_splice(struct file *in, loff_t __user *off_in,
1080                       struct file *out, loff_t __user *off_out,
1081                       size_t len, unsigned int flags)
1082 {
1083         struct pipe_inode_info *pipe;
1084         loff_t offset, *off;
1085         long ret;
1086
1087         pipe = pipe_info(in->f_path.dentry->d_inode);
1088         if (pipe) {
1089                 if (off_in)
1090                         return -ESPIPE;
1091                 if (off_out) {
1092                         if (out->f_op->llseek == no_llseek)
1093                                 return -EINVAL;
1094                         if (copy_from_user(&offset, off_out, sizeof(loff_t)))
1095                                 return -EFAULT;
1096                         off = &offset;
1097                 } else
1098                         off = &out->f_pos;
1099
1100                 ret = do_splice_from(pipe, out, off, len, flags);
1101
1102                 if (off_out && copy_to_user(off_out, off, sizeof(loff_t)))
1103                         ret = -EFAULT;
1104
1105                 return ret;
1106         }
1107
1108         pipe = pipe_info(out->f_path.dentry->d_inode);
1109         if (pipe) {
1110                 if (off_out)
1111                         return -ESPIPE;
1112                 if (off_in) {
1113                         if (in->f_op->llseek == no_llseek)
1114                                 return -EINVAL;
1115                         if (copy_from_user(&offset, off_in, sizeof(loff_t)))
1116                                 return -EFAULT;
1117                         off = &offset;
1118                 } else
1119                         off = &in->f_pos;
1120
1121                 ret = do_splice_to(in, off, pipe, len, flags);
1122
1123                 if (off_in && copy_to_user(off_in, off, sizeof(loff_t)))
1124                         ret = -EFAULT;
1125
1126                 return ret;
1127         }
1128
1129         return -EINVAL;
1130 }
1131
1132 /*
1133  * Map an iov into an array of pages and offset/length tupples. With the
1134  * partial_page structure, we can map several non-contiguous ranges into
1135  * our ones pages[] map instead of splitting that operation into pieces.
1136  * Could easily be exported as a generic helper for other users, in which
1137  * case one would probably want to add a 'max_nr_pages' parameter as well.
1138  */
1139 static int get_iovec_page_array(const struct iovec __user *iov,
1140                                 unsigned int nr_vecs, struct page **pages,
1141                                 struct partial_page *partial, int aligned)
1142 {
1143         int buffers = 0, error = 0;
1144
1145         /*
1146          * It's ok to take the mmap_sem for reading, even
1147          * across a "get_user()".
1148          */
1149         down_read(&current->mm->mmap_sem);
1150
1151         while (nr_vecs) {
1152                 unsigned long off, npages;
1153                 void __user *base;
1154                 size_t len;
1155                 int i;
1156
1157                 /*
1158                  * Get user address base and length for this iovec.
1159                  */
1160                 error = get_user(base, &iov->iov_base);
1161                 if (unlikely(error))
1162                         break;
1163                 error = get_user(len, &iov->iov_len);
1164                 if (unlikely(error))
1165                         break;
1166
1167                 /*
1168                  * Sanity check this iovec. 0 read succeeds.
1169                  */
1170                 if (unlikely(!len))
1171                         break;
1172                 error = -EFAULT;
1173                 if (unlikely(!base))
1174                         break;
1175
1176                 /*
1177                  * Get this base offset and number of pages, then map
1178                  * in the user pages.
1179                  */
1180                 off = (unsigned long) base & ~PAGE_MASK;
1181
1182                 /*
1183                  * If asked for alignment, the offset must be zero and the
1184                  * length a multiple of the PAGE_SIZE.
1185                  */
1186                 error = -EINVAL;
1187                 if (aligned && (off || len & ~PAGE_MASK))
1188                         break;
1189
1190                 npages = (off + len + PAGE_SIZE - 1) >> PAGE_SHIFT;
1191                 if (npages > PIPE_BUFFERS - buffers)
1192                         npages = PIPE_BUFFERS - buffers;
1193
1194                 error = get_user_pages(current, current->mm,
1195                                        (unsigned long) base, npages, 0, 0,
1196                                        &pages[buffers], NULL);
1197
1198                 if (unlikely(error <= 0))
1199                         break;
1200
1201                 /*
1202                  * Fill this contiguous range into the partial page map.
1203                  */
1204                 for (i = 0; i < error; i++) {
1205                         const int plen = min_t(size_t, len, PAGE_SIZE - off);
1206
1207                         partial[buffers].offset = off;
1208                         partial[buffers].len = plen;
1209
1210                         off = 0;
1211                         len -= plen;
1212                         buffers++;
1213                 }
1214
1215                 /*
1216                  * We didn't complete this iov, stop here since it probably
1217                  * means we have to move some of this into a pipe to
1218                  * be able to continue.
1219                  */
1220                 if (len)
1221                         break;
1222
1223                 /*
1224                  * Don't continue if we mapped fewer pages than we asked for,
1225                  * or if we mapped the max number of pages that we have
1226                  * room for.
1227                  */
1228                 if (error < npages || buffers == PIPE_BUFFERS)
1229                         break;
1230
1231                 nr_vecs--;
1232                 iov++;
1233         }
1234
1235         up_read(&current->mm->mmap_sem);
1236
1237         if (buffers)
1238                 return buffers;
1239
1240         return error;
1241 }
1242
1243 /*
1244  * vmsplice splices a user address range into a pipe. It can be thought of
1245  * as splice-from-memory, where the regular splice is splice-from-file (or
1246  * to file). In both cases the output is a pipe, naturally.
1247  *
1248  * Note that vmsplice only supports splicing _from_ user memory to a pipe,
1249  * not the other way around. Splicing from user memory is a simple operation
1250  * that can be supported without any funky alignment restrictions or nasty
1251  * vm tricks. We simply map in the user memory and fill them into a pipe.
1252  * The reverse isn't quite as easy, though. There are two possible solutions
1253  * for that:
1254  *
1255  *      - memcpy() the data internally, at which point we might as well just
1256  *        do a regular read() on the buffer anyway.
1257  *      - Lots of nasty vm tricks, that are neither fast nor flexible (it
1258  *        has restriction limitations on both ends of the pipe).
1259  *
1260  * Alas, it isn't here.
1261  *
1262  */
1263 static long do_vmsplice(struct file *file, const struct iovec __user *iov,
1264                         unsigned long nr_segs, unsigned int flags)
1265 {
1266         struct pipe_inode_info *pipe;
1267         struct page *pages[PIPE_BUFFERS];
1268         struct partial_page partial[PIPE_BUFFERS];
1269         struct splice_pipe_desc spd = {
1270                 .pages = pages,
1271                 .partial = partial,
1272                 .flags = flags,
1273                 .ops = &user_page_pipe_buf_ops,
1274         };
1275
1276         pipe = pipe_info(file->f_path.dentry->d_inode);
1277         if (!pipe)
1278                 return -EBADF;
1279         if (unlikely(nr_segs > UIO_MAXIOV))
1280                 return -EINVAL;
1281         else if (unlikely(!nr_segs))
1282                 return 0;
1283
1284         spd.nr_pages = get_iovec_page_array(iov, nr_segs, pages, partial,
1285                                             flags & SPLICE_F_GIFT);
1286         if (spd.nr_pages <= 0)
1287                 return spd.nr_pages;
1288
1289         return splice_to_pipe(pipe, &spd);
1290 }
1291
1292 asmlinkage long sys_vmsplice(int fd, const struct iovec __user *iov,
1293                              unsigned long nr_segs, unsigned int flags)
1294 {
1295         struct file *file;
1296         long error;
1297         int fput;
1298
1299         error = -EBADF;
1300         file = fget_light(fd, &fput);
1301         if (file) {
1302                 if (file->f_mode & FMODE_WRITE)
1303                         error = do_vmsplice(file, iov, nr_segs, flags);
1304
1305                 fput_light(file, fput);
1306         }
1307
1308         return error;
1309 }
1310
1311 asmlinkage long sys_splice(int fd_in, loff_t __user *off_in,
1312                            int fd_out, loff_t __user *off_out,
1313                            size_t len, unsigned int flags)
1314 {
1315         long error;
1316         struct file *in, *out;
1317         int fput_in, fput_out;
1318
1319         if (unlikely(!len))
1320                 return 0;
1321
1322         error = -EBADF;
1323         in = fget_light(fd_in, &fput_in);
1324         if (in) {
1325                 if (in->f_mode & FMODE_READ) {
1326                         out = fget_light(fd_out, &fput_out);
1327                         if (out) {
1328                                 if (out->f_mode & FMODE_WRITE)
1329                                         error = do_splice(in, off_in,
1330                                                           out, off_out,
1331                                                           len, flags);
1332                                 fput_light(out, fput_out);
1333                         }
1334                 }
1335
1336                 fput_light(in, fput_in);
1337         }
1338
1339         return error;
1340 }
1341
1342 /*
1343  * Make sure there's data to read. Wait for input if we can, otherwise
1344  * return an appropriate error.
1345  */
1346 static int link_ipipe_prep(struct pipe_inode_info *pipe, unsigned int flags)
1347 {
1348         int ret;
1349
1350         /*
1351          * Check ->nrbufs without the inode lock first. This function
1352          * is speculative anyways, so missing one is ok.
1353          */
1354         if (pipe->nrbufs)
1355                 return 0;
1356
1357         ret = 0;
1358         mutex_lock(&pipe->inode->i_mutex);
1359
1360         while (!pipe->nrbufs) {
1361                 if (signal_pending(current)) {
1362                         ret = -ERESTARTSYS;
1363                         break;
1364                 }
1365                 if (!pipe->writers)
1366                         break;
1367                 if (!pipe->waiting_writers) {
1368                         if (flags & SPLICE_F_NONBLOCK) {
1369                                 ret = -EAGAIN;
1370                                 break;
1371                         }
1372                 }
1373                 pipe_wait(pipe);
1374         }
1375
1376         mutex_unlock(&pipe->inode->i_mutex);
1377         return ret;
1378 }
1379
1380 /*
1381  * Make sure there's writeable room. Wait for room if we can, otherwise
1382  * return an appropriate error.
1383  */
1384 static int link_opipe_prep(struct pipe_inode_info *pipe, unsigned int flags)
1385 {
1386         int ret;
1387
1388         /*
1389          * Check ->nrbufs without the inode lock first. This function
1390          * is speculative anyways, so missing one is ok.
1391          */
1392         if (pipe->nrbufs < PIPE_BUFFERS)
1393                 return 0;
1394
1395         ret = 0;
1396         mutex_lock(&pipe->inode->i_mutex);
1397
1398         while (pipe->nrbufs >= PIPE_BUFFERS) {
1399                 if (!pipe->readers) {
1400                         send_sig(SIGPIPE, current, 0);
1401                         ret = -EPIPE;
1402                         break;
1403                 }
1404                 if (flags & SPLICE_F_NONBLOCK) {
1405                         ret = -EAGAIN;
1406                         break;
1407                 }
1408                 if (signal_pending(current)) {
1409                         ret = -ERESTARTSYS;
1410                         break;
1411                 }
1412                 pipe->waiting_writers++;
1413                 pipe_wait(pipe);
1414                 pipe->waiting_writers--;
1415         }
1416
1417         mutex_unlock(&pipe->inode->i_mutex);
1418         return ret;
1419 }
1420
1421 /*
1422  * Link contents of ipipe to opipe.
1423  */
1424 static int link_pipe(struct pipe_inode_info *ipipe,
1425                      struct pipe_inode_info *opipe,
1426                      size_t len, unsigned int flags)
1427 {
1428         struct pipe_buffer *ibuf, *obuf;
1429         int ret = 0, i = 0, nbuf;
1430
1431         /*
1432          * Potential ABBA deadlock, work around it by ordering lock
1433          * grabbing by inode address. Otherwise two different processes
1434          * could deadlock (one doing tee from A -> B, the other from B -> A).
1435          */
1436         inode_double_lock(ipipe->inode, opipe->inode);
1437
1438         do {
1439                 if (!opipe->readers) {
1440                         send_sig(SIGPIPE, current, 0);
1441                         if (!ret)
1442                                 ret = -EPIPE;
1443                         break;
1444                 }
1445
1446                 /*
1447                  * If we have iterated all input buffers or ran out of
1448                  * output room, break.
1449                  */
1450                 if (i >= ipipe->nrbufs || opipe->nrbufs >= PIPE_BUFFERS)
1451                         break;
1452
1453                 ibuf = ipipe->bufs + ((ipipe->curbuf + i) & (PIPE_BUFFERS - 1));
1454                 nbuf = (opipe->curbuf + opipe->nrbufs) & (PIPE_BUFFERS - 1);
1455
1456                 /*
1457                  * Get a reference to this pipe buffer,
1458                  * so we can copy the contents over.
1459                  */
1460                 ibuf->ops->get(ipipe, ibuf);
1461
1462                 obuf = opipe->bufs + nbuf;
1463                 *obuf = *ibuf;
1464
1465                 /*
1466                  * Don't inherit the gift flag, we need to
1467                  * prevent multiple steals of this page.
1468                  */
1469                 obuf->flags &= ~PIPE_BUF_FLAG_GIFT;
1470
1471                 if (obuf->len > len)
1472                         obuf->len = len;
1473
1474                 opipe->nrbufs++;
1475                 ret += obuf->len;
1476                 len -= obuf->len;
1477                 i++;
1478         } while (len);
1479
1480         inode_double_unlock(ipipe->inode, opipe->inode);
1481
1482         /*
1483          * If we put data in the output pipe, wakeup any potential readers.
1484          */
1485         if (ret > 0) {
1486                 smp_mb();
1487                 if (waitqueue_active(&opipe->wait))
1488                         wake_up_interruptible(&opipe->wait);
1489                 kill_fasync(&opipe->fasync_readers, SIGIO, POLL_IN);
1490         }
1491
1492         return ret;
1493 }
1494
1495 /*
1496  * This is a tee(1) implementation that works on pipes. It doesn't copy
1497  * any data, it simply references the 'in' pages on the 'out' pipe.
1498  * The 'flags' used are the SPLICE_F_* variants, currently the only
1499  * applicable one is SPLICE_F_NONBLOCK.
1500  */
1501 static long do_tee(struct file *in, struct file *out, size_t len,
1502                    unsigned int flags)
1503 {
1504         struct pipe_inode_info *ipipe = pipe_info(in->f_path.dentry->d_inode);
1505         struct pipe_inode_info *opipe = pipe_info(out->f_path.dentry->d_inode);
1506         int ret = -EINVAL;
1507
1508         /*
1509          * Duplicate the contents of ipipe to opipe without actually
1510          * copying the data.
1511          */
1512         if (ipipe && opipe && ipipe != opipe) {
1513                 /*
1514                  * Keep going, unless we encounter an error. The ipipe/opipe
1515                  * ordering doesn't really matter.
1516                  */
1517                 ret = link_ipipe_prep(ipipe, flags);
1518                 if (!ret) {
1519                         ret = link_opipe_prep(opipe, flags);
1520                         if (!ret) {
1521                                 ret = link_pipe(ipipe, opipe, len, flags);
1522                                 if (!ret && (flags & SPLICE_F_NONBLOCK))
1523                                         ret = -EAGAIN;
1524                         }
1525                 }
1526         }
1527
1528         return ret;
1529 }
1530
1531 asmlinkage long sys_tee(int fdin, int fdout, size_t len, unsigned int flags)
1532 {
1533         struct file *in;
1534         int error, fput_in;
1535
1536         if (unlikely(!len))
1537                 return 0;
1538
1539         error = -EBADF;
1540         in = fget_light(fdin, &fput_in);
1541         if (in) {
1542                 if (in->f_mode & FMODE_READ) {
1543                         int fput_out;
1544                         struct file *out = fget_light(fdout, &fput_out);
1545
1546                         if (out) {
1547                                 if (out->f_mode & FMODE_WRITE)
1548                                         error = do_tee(in, out, len, flags);
1549                                 fput_light(out, fput_out);
1550                         }
1551                 }
1552                 fput_light(in, fput_in);
1553         }
1554
1555         return error;
1556 }