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         unsigned int spd_pages = spd->nr_pages;
 180         int ret, do_wakeup, page_nr;
 181
 182         ret = 0;
 183         do_wakeup = 0;
 184         page_nr = 0;
 185
 186         if (pipe->inode)
 187                 mutex_lock(&pipe->inode->i_mutex);
 188
 189         for (;;) {
 190                 if (!pipe->readers) {
 191                         send_sig(SIGPIPE, current, 0);
 192                         if (!ret)
 193                                 ret = -EPIPE;
 194                         break;
 195                 }
 196
 197                 if (pipe->nrbufs < PIPE_BUFFERS) {
 198                         int newbuf = (pipe->curbuf + pipe->nrbufs) & (PIPE_BUFFERS - 1);
 199                         struct pipe_buffer *buf = pipe->bufs + newbuf;
 200
 201                         buf->page = spd->pages[page_nr];
 202                         buf->offset = spd->partial[page_nr].offset;
 203                         buf->len = spd->partial[page_nr].len;
 204                         buf->ops = spd->ops;
 205                         if (spd->flags & SPLICE_F_GIFT)
 206                                 buf->flags |= PIPE_BUF_FLAG_GIFT;
 207
 208                         pipe->nrbufs++;
 209                         page_nr++;
 210                         ret += buf->len;
 211
 212                         if (pipe->inode)
 213                                 do_wakeup = 1;
 214
 215                         if (!--spd->nr_pages)
 216                                 break;
 217                         if (pipe->nrbufs < PIPE_BUFFERS)
 218                                 continue;
 219
 220                         break;
 221                 }
 222
 223                 if (spd->flags & SPLICE_F_NONBLOCK) {
 224                         if (!ret)
 225                                 ret = -EAGAIN;
 226                         break;
 227                 }
 228
 229                 if (signal_pending(current)) {
 230                         if (!ret)
 231                                 ret = -ERESTARTSYS;
 232                         break;
 233                 }
 234
 235                 if (do_wakeup) {
 236                         smp_mb();
 237                         if (waitqueue_active(&pipe->wait))
 238                                 wake_up_interruptible_sync(&pipe->wait);
 239                         kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
 240                         do_wakeup = 0;
 241                 }
 242
 243                 pipe->waiting_writers++;
 244                 pipe_wait(pipe);
 245                 pipe->waiting_writers--;
 246         }
 247
 248         if (pipe->inode) {
 249                 mutex_unlock(&pipe->inode->i_mutex);
 250
 251                 if (do_wakeup) {
 252                         smp_mb();
 253                         if (waitqueue_active(&pipe->wait))
 254                                 wake_up_interruptible(&pipe->wait);
 255                         kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
 256                 }
 257         }
 258
 259         while (page_nr < spd_pages)
 260                 page_cache_release(spd->pages[page_nr++]);
 261
 262         return ret;
 263 }
 264
 265 static int
 266 __generic_file_splice_read(struct file *in, loff_t *ppos,
 267                            struct pipe_inode_info *pipe, size_t len,
 268                            unsigned int flags)
 269 {
 270         struct address_space *mapping = in->f_mapping;
 271         unsigned int loff, nr_pages;
 272         struct page *pages[PIPE_BUFFERS];
 273         struct partial_page partial[PIPE_BUFFERS];
 274         struct page *page;
 275         pgoff_t index, end_index;
 276         loff_t isize;
 277         int error, page_nr;
 278         struct splice_pipe_desc spd = {
 279                 .pages = pages,
 280                 .partial = partial,
 281                 .flags = flags,
 282                 .ops = &page_cache_pipe_buf_ops,
 283         };
 284
 285         index = *ppos >> PAGE_CACHE_SHIFT;
 286         loff = *ppos & ~PAGE_CACHE_MASK;
 287         nr_pages = (len + loff + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
 288
 289         if (nr_pages > PIPE_BUFFERS)
 290                 nr_pages = PIPE_BUFFERS;
 291
 292         /*
 293          * Don't try to 2nd guess the read-ahead logic, call into
 294          * page_cache_readahead() like the page cache reads would do.
 295          */
 296         page_cache_readahead(mapping, &in->f_ra, in, index, nr_pages);
 297
 298         /*
 299          * Now fill in the holes:
 300          */
 301         error = 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 fill_it:
 420                 /*
 421                  * i_size must be checked after PageUptodate.
 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                         unsigned int plen;
 434
 435                         /*
 436                          * max good bytes in this page
 437                          */
 438                         plen = ((isize - 1) & ~PAGE_CACHE_MASK) + 1;
 439                         if (plen <= loff)
 440                                 break;
 441
 442                         /*
 443                          * force quit after adding this page
 444                          */
 445                         this_len = min(this_len, plen - loff);
 446                         len = this_len;
 447                 }
 448
 449                 partial[page_nr].offset = loff;
 450                 partial[page_nr].len = this_len;
 451                 len -= this_len;
 452                 loff = 0;
 453                 spd.nr_pages++;
 454                 index++;
 455         }
 456
 457         /*
 458          * Release any pages at the end, if we quit early. 'page_nr' is how far
 459          * we got, 'nr_pages' is how many pages are in the map.
 460          */
 461         while (page_nr < nr_pages)
 462                 page_cache_release(pages[page_nr++]);
 463
 464         if (spd.nr_pages)
 465                 return splice_to_pipe(pipe, &spd);
 466
 467         return error;
 468 }
 469
 470 /**
 471  * generic_file_splice_read - splice data from file to a pipe
 472  * @in:         file to splice from
 473  * @pipe:       pipe to splice to
 474  * @len:        number of bytes to splice
 475  * @flags:      splice modifier flags
 476  *
 477  * Will read pages from given file and fill them into a pipe.
 478  */
 479 ssize_t generic_file_splice_read(struct file *in, loff_t *ppos,
 480                                  struct pipe_inode_info *pipe, size_t len,
 481                                  unsigned int flags)
 482 {
 483         ssize_t spliced;
 484         int ret;
 485         loff_t isize, left;
 486
 487         isize = i_size_read(in->f_mapping->host);
 488         if (unlikely(*ppos >= isize))
 489                 return 0;
 490
 491         left = isize - *ppos;
 492         if (unlikely(left < len))
 493                 len = left;
 494
 495         ret = 0;
 496         spliced = 0;
 497         while (len) {
 498                 ret = __generic_file_splice_read(in, ppos, pipe, len, flags);
 499
 500                 if (ret < 0)
 501                         break;
 502                 else if (!ret) {
 503                         if (spliced)
 504                                 break;
 505                         if (flags & SPLICE_F_NONBLOCK) {
 506                                 ret = -EAGAIN;
 507                                 break;
 508                         }
 509                 }
 510
 511                 *ppos += ret;
 512                 len -= ret;
 513                 spliced += ret;
 514         }
 515
 516         if (spliced)
 517                 return spliced;
 518
 519         return ret;
 520 }
 521
 522 EXPORT_SYMBOL(generic_file_splice_read);
 523
 524 /*
 525  * Send 'sd->len' bytes to socket from 'sd->file' at position 'sd->pos'
 526  * using sendpage(). Return the number of bytes sent.
 527  */
 528 static int pipe_to_sendpage(struct pipe_inode_info *pipe,
 529                             struct pipe_buffer *buf, struct splice_desc *sd)
 530 {
 531         struct file *file = sd->file;
 532         loff_t pos = sd->pos;
 533         int ret, more;
 534
 535         ret = buf->ops->pin(pipe, buf);
 536         if (!ret) {
 537                 more = (sd->flags & SPLICE_F_MORE) || sd->len < sd->total_len;
 538
 539                 ret = file->f_op->sendpage(file, buf->page, buf->offset,
 540                                            sd->len, &pos, more);
 541         }
 542
 543         return ret;
 544 }
 545
 546 /*
 547  * This is a little more tricky than the file -> pipe splicing. There are
 548  * basically three cases:
 549  *
 550  *      - Destination page already exists in the address space and there
 551  *        are users of it. For that case we have no other option that
 552  *        copying the data. Tough luck.
 553  *      - Destination page already exists in the address space, but there
 554  *        are no users of it. Make sure it's uptodate, then drop it. Fall
 555  *        through to last case.
 556  *      - Destination page does not exist, we can add the pipe page to
 557  *        the page cache and avoid the copy.
 558  *
 559  * If asked to move pages to the output file (SPLICE_F_MOVE is set in
 560  * sd->flags), we attempt to migrate pages from the pipe to the output
 561  * file address space page cache. This is possible if no one else has
 562  * the pipe page referenced outside of the pipe and page cache. If
 563  * SPLICE_F_MOVE isn't set, or we cannot move the page, we simply create
 564  * a new page in the output file page cache and fill/dirty that.
 565  */
 566 static int pipe_to_file(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
 567                         struct splice_desc *sd)
 568 {
 569         struct file *file = sd->file;
 570         struct address_space *mapping = file->f_mapping;
 571         unsigned int offset, this_len;
 572         struct page *page;
 573         pgoff_t index;
 574         int ret;
 575
 576         /*
 577          * make sure the data in this buffer is uptodate
 578          */
 579         ret = buf->ops->pin(pipe, buf);
 580         if (unlikely(ret))
 581                 return ret;
 582
 583         index = sd->pos >> PAGE_CACHE_SHIFT;
 584         offset = sd->pos & ~PAGE_CACHE_MASK;
 585
 586         this_len = sd->len;
 587         if (this_len + offset > PAGE_CACHE_SIZE)
 588                 this_len = PAGE_CACHE_SIZE - offset;
 589
 590 find_page:
 591         page = find_lock_page(mapping, index);
 592         if (!page) {
 593                 ret = -ENOMEM;
 594                 page = page_cache_alloc_cold(mapping);
 595                 if (unlikely(!page))
 596                         goto out_ret;
 597
 598                 /*
 599                  * This will also lock the page
 600                  */
 601                 ret = add_to_page_cache_lru(page, mapping, index,
 602                                             GFP_KERNEL);
 603                 if (unlikely(ret))
 604                         goto out;
 605         }
 606
 607         ret = mapping->a_ops->prepare_write(file, page, offset, offset+this_len);
 608         if (unlikely(ret)) {
 609                 loff_t isize = i_size_read(mapping->host);
 610
 611                 if (ret != AOP_TRUNCATED_PAGE)
 612                         unlock_page(page);
 613                 page_cache_release(page);
 614                 if (ret == AOP_TRUNCATED_PAGE)
 615                         goto find_page;
 616
 617                 /*
 618                  * prepare_write() may have instantiated a few blocks
 619                  * outside i_size.  Trim these off again.
 620                  */
 621                 if (sd->pos + this_len > isize)
 622                         vmtruncate(mapping->host, isize);
 623
 624                 goto out_ret;
 625         }
 626
 627         if (buf->page != page) {
 628                 /*
 629                  * Careful, ->map() uses KM_USER0!
 630                  */
 631                 char *src = buf->ops->map(pipe, buf, 1);
 632                 char *dst = kmap_atomic(page, KM_USER1);
 633
 634                 memcpy(dst + offset, src + buf->offset, this_len);
 635                 flush_dcache_page(page);
 636                 kunmap_atomic(dst, KM_USER1);
 637                 buf->ops->unmap(pipe, buf, src);
 638         }
 639
 640         ret = mapping->a_ops->commit_write(file, page, offset, offset+this_len);
 641         if (ret) {
 642                 if (ret == AOP_TRUNCATED_PAGE) {
 643                         page_cache_release(page);
 644                         goto find_page;
 645                 }
 646                 if (ret < 0)
 647                         goto out;
 648                 /*
 649                  * Partial write has happened, so 'ret' already initialized by
 650                  * number of bytes written, Where is nothing we have to do here.
 651                  */
 652         } else
 653                 ret = this_len;
 654         /*
 655          * Return the number of bytes written and mark page as
 656          * accessed, we are now done!
 657          */
 658         mark_page_accessed(page);
 659 out:
 660         page_cache_release(page);
 661         unlock_page(page);
 662 out_ret:
 663         return ret;
 664 }
 665
 666 /*
 667  * Pipe input worker. Most of this logic works like a regular pipe, the
 668  * key here is the 'actor' worker passed in that actually moves the data
 669  * to the wanted destination. See pipe_to_file/pipe_to_sendpage above.
 670  */
 671 ssize_t __splice_from_pipe(struct pipe_inode_info *pipe,
 672                            struct file *out, loff_t *ppos, size_t len,
 673                            unsigned int flags, splice_actor *actor)
 674 {
 675         int ret, do_wakeup, err;
 676         struct splice_desc sd;
 677
 678         ret = 0;
 679         do_wakeup = 0;
 680
 681         sd.total_len = len;
 682         sd.flags = flags;
 683         sd.file = out;
 684         sd.pos = *ppos;
 685
 686         for (;;) {
 687                 if (pipe->nrbufs) {
 688                         struct pipe_buffer *buf = pipe->bufs + pipe->curbuf;
 689                         const struct pipe_buf_operations *ops = buf->ops;
 690
 691                         sd.len = buf->len;
 692                         if (sd.len > sd.total_len)
 693                                 sd.len = sd.total_len;
 694
 695                         err = actor(pipe, buf, &sd);
 696                         if (err <= 0) {
 697                                 if (!ret && err != -ENODATA)
 698                                         ret = err;
 699
 700                                 break;
 701                         }
 702
 703                         ret += err;
 704                         buf->offset += err;
 705                         buf->len -= err;
 706
 707                         sd.len -= err;
 708                         sd.pos += err;
 709                         sd.total_len -= err;
 710                         if (sd.len)
 711                                 continue;
 712
 713                         if (!buf->len) {
 714                                 buf->ops = NULL;
 715                                 ops->release(pipe, buf);
 716                                 pipe->curbuf = (pipe->curbuf + 1) & (PIPE_BUFFERS - 1);
 717                                 pipe->nrbufs--;
 718                                 if (pipe->inode)
 719                                         do_wakeup = 1;
 720                         }
 721
 722                         if (!sd.total_len)
 723                                 break;
 724                 }
 725
 726                 if (pipe->nrbufs)
 727                         continue;
 728                 if (!pipe->writers)
 729                         break;
 730                 if (!pipe->waiting_writers) {
 731                         if (ret)
 732                                 break;
 733                 }
 734
 735                 if (flags & SPLICE_F_NONBLOCK) {
 736                         if (!ret)
 737                                 ret = -EAGAIN;
 738                         break;
 739                 }
 740
 741                 if (signal_pending(current)) {
 742                         if (!ret)
 743                                 ret = -ERESTARTSYS;
 744                         break;
 745                 }
 746
 747                 if (do_wakeup) {
 748                         smp_mb();
 749                         if (waitqueue_active(&pipe->wait))
 750                                 wake_up_interruptible_sync(&pipe->wait);
 751                         kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
 752                         do_wakeup = 0;
 753                 }
 754
 755                 pipe_wait(pipe);
 756         }
 757
 758         if (do_wakeup) {
 759                 smp_mb();
 760                 if (waitqueue_active(&pipe->wait))
 761                         wake_up_interruptible(&pipe->wait);
 762                 kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
 763         }
 764
 765         return ret;
 766 }
 767 EXPORT_SYMBOL(__splice_from_pipe);
 768
 769 ssize_t splice_from_pipe(struct pipe_inode_info *pipe, struct file *out,
 770                          loff_t *ppos, size_t len, unsigned int flags,
 771                          splice_actor *actor)
 772 {
 773         ssize_t ret;
 774         struct inode *inode = out->f_mapping->host;
 775
 776         /*
 777          * The actor worker might be calling ->prepare_write and
 778          * ->commit_write. Most of the time, these expect i_mutex to
 779          * be held. Since this may result in an ABBA deadlock with
 780          * pipe->inode, we have to order lock acquiry here.
 781          */
 782         inode_double_lock(inode, pipe->inode);
 783         ret = __splice_from_pipe(pipe, out, ppos, len, flags, actor);
 784         inode_double_unlock(inode, pipe->inode);
 785
 786         return ret;
 787 }
 788
 789 /**
 790  * generic_file_splice_write_nolock - generic_file_splice_write without mutexes
 791  * @pipe:       pipe info
 792  * @out:        file to write to
 793  * @len:        number of bytes to splice
 794  * @flags:      splice modifier flags
 795  *
 796  * Will either move or copy pages (determined by @flags options) from
 797  * the given pipe inode to the given file. The caller is responsible
 798  * for acquiring i_mutex on both inodes.
 799  *
 800  */
 801 ssize_t
 802 generic_file_splice_write_nolock(struct pipe_inode_info *pipe, struct file *out,
 803                                  loff_t *ppos, size_t len, unsigned int flags)
 804 {
 805         struct address_space *mapping = out->f_mapping;
 806         struct inode *inode = mapping->host;
 807         ssize_t ret;
 808         int err;
 809
 810         err = remove_suid(out->f_path.dentry);
 811         if (unlikely(err))
 812                 return err;
 813
 814         ret = __splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_file);
 815         if (ret > 0) {
 816                 unsigned long nr_pages;
 817
 818                 *ppos += ret;
 819                 nr_pages = (ret + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
 820
 821                 /*
 822                  * If file or inode is SYNC and we actually wrote some data,
 823                  * sync it.
 824                  */
 825                 if (unlikely((out->f_flags & O_SYNC) || IS_SYNC(inode))) {
 826                         err = generic_osync_inode(inode, mapping,
 827                                                   OSYNC_METADATA|OSYNC_DATA);
 828
 829                         if (err)
 830                                 ret = err;
 831                 }
 832                 balance_dirty_pages_ratelimited_nr(mapping, nr_pages);
 833         }
 834
 835         return ret;
 836 }
 837
 838 EXPORT_SYMBOL(generic_file_splice_write_nolock);
 839
 840 /**
 841  * generic_file_splice_write - splice data from a pipe to a file
 842  * @pipe:       pipe info
 843  * @out:        file to write to
 844  * @len:        number of bytes to splice
 845  * @flags:      splice modifier flags
 846  *
 847  * Will either move or copy pages (determined by @flags options) from
 848  * the given pipe inode to the given file.
 849  *
 850  */
 851 ssize_t
 852 generic_file_splice_write(struct pipe_inode_info *pipe, struct file *out,
 853                           loff_t *ppos, size_t len, unsigned int flags)
 854 {
 855         struct address_space *mapping = out->f_mapping;
 856         struct inode *inode = mapping->host;
 857         ssize_t ret;
 858         int err;
 859
 860         err = should_remove_suid(out->f_path.dentry);
 861         if (unlikely(err)) {
 862                 mutex_lock(&inode->i_mutex);
 863                 err = __remove_suid(out->f_path.dentry, err);
 864                 mutex_unlock(&inode->i_mutex);
 865                 if (err)
 866                         return err;
 867         }
 868
 869         ret = splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_file);
 870         if (ret > 0) {
 871                 unsigned long nr_pages;
 872
 873                 *ppos += ret;
 874                 nr_pages = (ret + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
 875
 876                 /*
 877                  * If file or inode is SYNC and we actually wrote some data,
 878                  * sync it.
 879                  */
 880                 if (unlikely((out->f_flags & O_SYNC) || IS_SYNC(inode))) {
 881                         mutex_lock(&inode->i_mutex);
 882                         err = generic_osync_inode(inode, mapping,
 883                                                   OSYNC_METADATA|OSYNC_DATA);
 884                         mutex_unlock(&inode->i_mutex);
 885
 886                         if (err)
 887                                 ret = err;
 888                 }
 889                 balance_dirty_pages_ratelimited_nr(mapping, nr_pages);
 890         }
 891
 892         return ret;
 893 }
 894
 895 EXPORT_SYMBOL(generic_file_splice_write);
 896
 897 /**
 898  * generic_splice_sendpage - splice data from a pipe to a socket
 899  * @inode:      pipe inode
 900  * @out:        socket to write to
 901  * @len:        number of bytes to splice
 902  * @flags:      splice modifier flags
 903  *
 904  * Will send @len bytes from the pipe to a network socket. No data copying
 905  * is involved.
 906  *
 907  */
 908 ssize_t generic_splice_sendpage(struct pipe_inode_info *pipe, struct file *out,
 909                                 loff_t *ppos, size_t len, unsigned int flags)
 910 {
 911         return splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_sendpage);
 912 }
 913
 914 EXPORT_SYMBOL(generic_splice_sendpage);
 915
 916 /*
 917  * Attempt to initiate a splice from pipe to file.
 918  */
 919 static long do_splice_from(struct pipe_inode_info *pipe, struct file *out,
 920                            loff_t *ppos, size_t len, unsigned int flags)
 921 {
 922         int ret;
 923
 924         if (unlikely(!out->f_op || !out->f_op->splice_write))
 925                 return -EINVAL;
 926
 927         if (unlikely(!(out->f_mode & FMODE_WRITE)))
 928                 return -EBADF;
 929
 930         ret = rw_verify_area(WRITE, out, ppos, len);
 931         if (unlikely(ret < 0))
 932                 return ret;
 933
 934         return out->f_op->splice_write(pipe, out, ppos, len, flags);
 935 }
 936
 937 /*
 938  * Attempt to initiate a splice from a file to a pipe.
 939  */
 940 static long do_splice_to(struct file *in, loff_t *ppos,
 941                          struct pipe_inode_info *pipe, size_t len,
 942                          unsigned int flags)
 943 {
 944         int ret;
 945
 946         if (unlikely(!in->f_op || !in->f_op->splice_read))
 947                 return -EINVAL;
 948
 949         if (unlikely(!(in->f_mode & FMODE_READ)))
 950                 return -EBADF;
 951
 952         ret = rw_verify_area(READ, in, ppos, len);
 953         if (unlikely(ret < 0))
 954                 return ret;
 955
 956         return in->f_op->splice_read(in, ppos, pipe, len, flags);
 957 }
 958
 959 long do_splice_direct(struct file *in, loff_t *ppos, struct file *out,
 960                       size_t len, unsigned int flags)
 961 {
 962         struct pipe_inode_info *pipe;
 963         long ret, bytes;
 964         loff_t out_off;
 965         umode_t i_mode;
 966         int i;
 967
 968         /*
 969          * We require the input being a regular file, as we don't want to
 970          * randomly drop data for eg socket -> socket splicing. Use the
 971          * piped splicing for that!
 972          */
 973         i_mode = in->f_path.dentry->d_inode->i_mode;
 974         if (unlikely(!S_ISREG(i_mode) && !S_ISBLK(i_mode)))
 975                 return -EINVAL;
 976
 977         /*
 978          * neither in nor out is a pipe, setup an internal pipe attached to
 979          * 'out' and transfer the wanted data from 'in' to 'out' through that
 980          */
 981         pipe = current->splice_pipe;
 982         if (unlikely(!pipe)) {
 983                 pipe = alloc_pipe_info(NULL);
 984                 if (!pipe)
 985                         return -ENOMEM;
 986
 987                 /*
 988                  * We don't have an immediate reader, but we'll read the stuff
 989                  * out of the pipe right after the splice_to_pipe(). So set
 990                  * PIPE_READERS appropriately.
 991                  */
 992                 pipe->readers = 1;
 993
 994                 current->splice_pipe = pipe;
 995         }
 996
 997         /*
 998          * Do the splice.
 999          */
1000         ret = 0;
1001         bytes = 0;
1002         out_off = 0;
1003
1004         while (len) {
1005                 size_t read_len, max_read_len;
1006
1007                 /*
1008                  * Do at most PIPE_BUFFERS pages worth of transfer:
1009                  */
1010                 max_read_len = min(len, (size_t)(PIPE_BUFFERS*PAGE_SIZE));
1011
1012                 ret = do_splice_to(in, ppos, pipe, max_read_len, flags);
1013                 if (unlikely(ret < 0))
1014                         goto out_release;
1015
1016                 read_len = ret;
1017
1018                 /*
1019                  * NOTE: nonblocking mode only applies to the input. We
1020                  * must not do the output in nonblocking mode as then we
1021                  * could get stuck data in the internal pipe:
1022                  */
1023                 ret = do_splice_from(pipe, out, &out_off, read_len,
1024                                      flags & ~SPLICE_F_NONBLOCK);
1025                 if (unlikely(ret < 0))
1026                         goto out_release;
1027
1028                 bytes += ret;
1029                 len -= ret;
1030
1031                 /*
1032                  * In nonblocking mode, if we got back a short read then
1033                  * that was due to either an IO error or due to the
1034                  * pagecache entry not being there. In the IO error case
1035                  * the _next_ splice attempt will produce a clean IO error
1036                  * return value (not a short read), so in both cases it's
1037                  * correct to break out of the loop here:
1038                  */
1039                 if ((flags & SPLICE_F_NONBLOCK) && (read_len < max_read_len))
1040                         break;
1041         }
1042
1043         pipe->nrbufs = pipe->curbuf = 0;
1044
1045         return bytes;
1046
1047 out_release:
1048         /*
1049          * If we did an incomplete transfer we must release
1050          * the pipe buffers in question:
1051          */
1052         for (i = 0; i < PIPE_BUFFERS; i++) {
1053                 struct pipe_buffer *buf = pipe->bufs + i;
1054
1055                 if (buf->ops) {
1056                         buf->ops->release(pipe, buf);
1057                         buf->ops = NULL;
1058                 }
1059         }
1060         pipe->nrbufs = pipe->curbuf = 0;
1061
1062         /*
1063          * If we transferred some data, return the number of bytes:
1064          */
1065         if (bytes > 0)
1066                 return bytes;
1067
1068         return ret;
1069 }
1070
1071 /*
1072  * After the inode slimming patch, i_pipe/i_bdev/i_cdev share the same
1073  * location, so checking ->i_pipe is not enough to verify that this is a
1074  * pipe.
1075  */
1076 static inline struct pipe_inode_info *pipe_info(struct inode *inode)
1077 {
1078         if (S_ISFIFO(inode->i_mode))
1079                 return inode->i_pipe;
1080
1081         return NULL;
1082 }
1083
1084 /*
1085  * Determine where to splice to/from.
1086  */
1087 static long do_splice(struct file *in, loff_t __user *off_in,
1088                       struct file *out, loff_t __user *off_out,
1089                       size_t len, unsigned int flags)
1090 {
1091         struct pipe_inode_info *pipe;
1092         loff_t offset, *off;
1093         long ret;
1094
1095         pipe = pipe_info(in->f_path.dentry->d_inode);
1096         if (pipe) {
1097                 if (off_in)
1098                         return -ESPIPE;
1099                 if (off_out) {
1100                         if (out->f_op->llseek == no_llseek)
1101                                 return -EINVAL;
1102                         if (copy_from_user(&offset, off_out, sizeof(loff_t)))
1103                                 return -EFAULT;
1104                         off = &offset;
1105                 } else
1106                         off = &out->f_pos;
1107
1108                 ret = do_splice_from(pipe, out, off, len, flags);
1109
1110                 if (off_out && copy_to_user(off_out, off, sizeof(loff_t)))
1111                         ret = -EFAULT;
1112
1113                 return ret;
1114         }
1115
1116         pipe = pipe_info(out->f_path.dentry->d_inode);
1117         if (pipe) {
1118                 if (off_out)
1119                         return -ESPIPE;
1120                 if (off_in) {
1121                         if (in->f_op->llseek == no_llseek)
1122                                 return -EINVAL;
1123                         if (copy_from_user(&offset, off_in, sizeof(loff_t)))
1124                                 return -EFAULT;
1125                         off = &offset;
1126                 } else
1127                         off = &in->f_pos;
1128
1129                 ret = do_splice_to(in, off, pipe, len, flags);
1130
1131                 if (off_in && copy_to_user(off_in, off, sizeof(loff_t)))
1132                         ret = -EFAULT;
1133
1134                 return ret;
1135         }
1136
1137         return -EINVAL;
1138 }
1139
1140 /*
1141  * Map an iov into an array of pages and offset/length tupples. With the
1142  * partial_page structure, we can map several non-contiguous ranges into
1143  * our ones pages[] map instead of splitting that operation into pieces.
1144  * Could easily be exported as a generic helper for other users, in which
1145  * case one would probably want to add a 'max_nr_pages' parameter as well.
1146  */
1147 static int get_iovec_page_array(const struct iovec __user *iov,
1148                                 unsigned int nr_vecs, struct page **pages,
1149                                 struct partial_page *partial, int aligned)
1150 {
1151         int buffers = 0, error = 0;
1152
1153         /*
1154          * It's ok to take the mmap_sem for reading, even
1155          * across a "get_user()".
1156          */
1157         down_read(&current->mm->mmap_sem);
1158
1159         while (nr_vecs) {
1160                 unsigned long off, npages;
1161                 void __user *base;
1162                 size_t len;
1163                 int i;
1164
1165                 /*
1166                  * Get user address base and length for this iovec.
1167                  */
1168                 error = get_user(base, &iov->iov_base);
1169                 if (unlikely(error))
1170                         break;
1171                 error = get_user(len, &iov->iov_len);
1172                 if (unlikely(error))
1173                         break;
1174
1175                 /*
1176                  * Sanity check this iovec. 0 read succeeds.
1177                  */
1178                 if (unlikely(!len))
1179                         break;
1180                 error = -EFAULT;
1181                 if (unlikely(!base))
1182                         break;
1183
1184                 /*
1185                  * Get this base offset and number of pages, then map
1186                  * in the user pages.
1187                  */
1188                 off = (unsigned long) base & ~PAGE_MASK;
1189
1190                 /*
1191                  * If asked for alignment, the offset must be zero and the
1192                  * length a multiple of the PAGE_SIZE.
1193                  */
1194                 error = -EINVAL;
1195                 if (aligned && (off || len & ~PAGE_MASK))
1196                         break;
1197
1198                 npages = (off + len + PAGE_SIZE - 1) >> PAGE_SHIFT;
1199                 if (npages > PIPE_BUFFERS - buffers)
1200                         npages = PIPE_BUFFERS - buffers;
1201
1202                 error = get_user_pages(current, current->mm,
1203                                        (unsigned long) base, npages, 0, 0,
1204                                        &pages[buffers], NULL);
1205
1206                 if (unlikely(error <= 0))
1207                         break;
1208
1209                 /*
1210                  * Fill this contiguous range into the partial page map.
1211                  */
1212                 for (i = 0; i < error; i++) {
1213                         const int plen = min_t(size_t, len, PAGE_SIZE - off);
1214
1215                         partial[buffers].offset = off;
1216                         partial[buffers].len = plen;
1217
1218                         off = 0;
1219                         len -= plen;
1220                         buffers++;
1221                 }
1222
1223                 /*
1224                  * We didn't complete this iov, stop here since it probably
1225                  * means we have to move some of this into a pipe to
1226                  * be able to continue.
1227                  */
1228                 if (len)
1229                         break;
1230
1231                 /*
1232                  * Don't continue if we mapped fewer pages than we asked for,
1233                  * or if we mapped the max number of pages that we have
1234                  * room for.
1235                  */
1236                 if (error < npages || buffers == PIPE_BUFFERS)
1237                         break;
1238
1239                 nr_vecs--;
1240                 iov++;
1241         }
1242
1243         up_read(&current->mm->mmap_sem);
1244
1245         if (buffers)
1246                 return buffers;
1247
1248         return error;
1249 }
1250
1251 /*
1252  * vmsplice splices a user address range into a pipe. It can be thought of
1253  * as splice-from-memory, where the regular splice is splice-from-file (or
1254  * to file). In both cases the output is a pipe, naturally.
1255  *
1256  * Note that vmsplice only supports splicing _from_ user memory to a pipe,
1257  * not the other way around. Splicing from user memory is a simple operation
1258  * that can be supported without any funky alignment restrictions or nasty
1259  * vm tricks. We simply map in the user memory and fill them into a pipe.
1260  * The reverse isn't quite as easy, though. There are two possible solutions
1261  * for that:
1262  *
1263  *      - memcpy() the data internally, at which point we might as well just
1264  *        do a regular read() on the buffer anyway.
1265  *      - Lots of nasty vm tricks, that are neither fast nor flexible (it
1266  *        has restriction limitations on both ends of the pipe).
1267  *
1268  * Alas, it isn't here.
1269  *
1270  */
1271 static long do_vmsplice(struct file *file, const struct iovec __user *iov,
1272                         unsigned long nr_segs, unsigned int flags)
1273 {
1274         struct pipe_inode_info *pipe;
1275         struct page *pages[PIPE_BUFFERS];
1276         struct partial_page partial[PIPE_BUFFERS];
1277         struct splice_pipe_desc spd = {
1278                 .pages = pages,
1279                 .partial = partial,
1280                 .flags = flags,
1281                 .ops = &user_page_pipe_buf_ops,
1282         };
1283
1284         pipe = pipe_info(file->f_path.dentry->d_inode);
1285         if (!pipe)
1286                 return -EBADF;
1287         if (unlikely(nr_segs > UIO_MAXIOV))
1288                 return -EINVAL;
1289         else if (unlikely(!nr_segs))
1290                 return 0;
1291
1292         spd.nr_pages = get_iovec_page_array(iov, nr_segs, pages, partial,
1293                                             flags & SPLICE_F_GIFT);
1294         if (spd.nr_pages <= 0)
1295                 return spd.nr_pages;
1296
1297         return splice_to_pipe(pipe, &spd);
1298 }
1299
1300 asmlinkage long sys_vmsplice(int fd, const struct iovec __user *iov,
1301                              unsigned long nr_segs, unsigned int flags)
1302 {
1303         struct file *file;
1304         long error;
1305         int fput;
1306
1307         error = -EBADF;
1308         file = fget_light(fd, &fput);
1309         if (file) {
1310                 if (file->f_mode & FMODE_WRITE)
1311                         error = do_vmsplice(file, iov, nr_segs, flags);
1312
1313                 fput_light(file, fput);
1314         }
1315
1316         return error;
1317 }
1318
1319 asmlinkage long sys_splice(int fd_in, loff_t __user *off_in,
1320                            int fd_out, loff_t __user *off_out,
1321                            size_t len, unsigned int flags)
1322 {
1323         long error;
1324         struct file *in, *out;
1325         int fput_in, fput_out;
1326
1327         if (unlikely(!len))
1328                 return 0;
1329
1330         error = -EBADF;
1331         in = fget_light(fd_in, &fput_in);
1332         if (in) {
1333                 if (in->f_mode & FMODE_READ) {
1334                         out = fget_light(fd_out, &fput_out);
1335                         if (out) {
1336                                 if (out->f_mode & FMODE_WRITE)
1337                                         error = do_splice(in, off_in,
1338                                                           out, off_out,
1339                                                           len, flags);
1340                                 fput_light(out, fput_out);
1341                         }
1342                 }
1343
1344                 fput_light(in, fput_in);
1345         }
1346
1347         return error;
1348 }
1349
1350 /*
1351  * Make sure there's data to read. Wait for input if we can, otherwise
1352  * return an appropriate error.
1353  */
1354 static int link_ipipe_prep(struct pipe_inode_info *pipe, unsigned int flags)
1355 {
1356         int ret;
1357
1358         /*
1359          * Check ->nrbufs without the inode lock first. This function
1360          * is speculative anyways, so missing one is ok.
1361          */
1362         if (pipe->nrbufs)
1363                 return 0;
1364
1365         ret = 0;
1366         mutex_lock(&pipe->inode->i_mutex);
1367
1368         while (!pipe->nrbufs) {
1369                 if (signal_pending(current)) {
1370                         ret = -ERESTARTSYS;
1371                         break;
1372                 }
1373                 if (!pipe->writers)
1374                         break;
1375                 if (!pipe->waiting_writers) {
1376                         if (flags & SPLICE_F_NONBLOCK) {
1377                                 ret = -EAGAIN;
1378                                 break;
1379                         }
1380                 }
1381                 pipe_wait(pipe);
1382         }
1383
1384         mutex_unlock(&pipe->inode->i_mutex);
1385         return ret;
1386 }
1387
1388 /*
1389  * Make sure there's writeable room. Wait for room if we can, otherwise
1390  * return an appropriate error.
1391  */
1392 static int link_opipe_prep(struct pipe_inode_info *pipe, unsigned int flags)
1393 {
1394         int ret;
1395
1396         /*
1397          * Check ->nrbufs without the inode lock first. This function
1398          * is speculative anyways, so missing one is ok.
1399          */
1400         if (pipe->nrbufs < PIPE_BUFFERS)
1401                 return 0;
1402
1403         ret = 0;
1404         mutex_lock(&pipe->inode->i_mutex);
1405
1406         while (pipe->nrbufs >= PIPE_BUFFERS) {
1407                 if (!pipe->readers) {
1408                         send_sig(SIGPIPE, current, 0);
1409                         ret = -EPIPE;
1410                         break;
1411                 }
1412                 if (flags & SPLICE_F_NONBLOCK) {
1413                         ret = -EAGAIN;
1414                         break;
1415                 }
1416                 if (signal_pending(current)) {
1417                         ret = -ERESTARTSYS;
1418                         break;
1419                 }
1420                 pipe->waiting_writers++;
1421                 pipe_wait(pipe);
1422                 pipe->waiting_writers--;
1423         }
1424
1425         mutex_unlock(&pipe->inode->i_mutex);
1426         return ret;
1427 }
1428
1429 /*
1430  * Link contents of ipipe to opipe.
1431  */
1432 static int link_pipe(struct pipe_inode_info *ipipe,
1433                      struct pipe_inode_info *opipe,
1434                      size_t len, unsigned int flags)
1435 {
1436         struct pipe_buffer *ibuf, *obuf;
1437         int ret = 0, i = 0, nbuf;
1438
1439         /*
1440          * Potential ABBA deadlock, work around it by ordering lock
1441          * grabbing by inode address. Otherwise two different processes
1442          * could deadlock (one doing tee from A -> B, the other from B -> A).
1443          */
1444         inode_double_lock(ipipe->inode, opipe->inode);
1445
1446         do {
1447                 if (!opipe->readers) {
1448                         send_sig(SIGPIPE, current, 0);
1449                         if (!ret)
1450                                 ret = -EPIPE;
1451                         break;
1452                 }
1453
1454                 /*
1455                  * If we have iterated all input buffers or ran out of
1456                  * output room, break.
1457                  */
1458                 if (i >= ipipe->nrbufs || opipe->nrbufs >= PIPE_BUFFERS)
1459                         break;
1460
1461                 ibuf = ipipe->bufs + ((ipipe->curbuf + i) & (PIPE_BUFFERS - 1));
1462                 nbuf = (opipe->curbuf + opipe->nrbufs) & (PIPE_BUFFERS - 1);
1463
1464                 /*
1465                  * Get a reference to this pipe buffer,
1466                  * so we can copy the contents over.
1467                  */
1468                 ibuf->ops->get(ipipe, ibuf);
1469
1470                 obuf = opipe->bufs + nbuf;
1471                 *obuf = *ibuf;
1472
1473                 /*
1474                  * Don't inherit the gift flag, we need to
1475                  * prevent multiple steals of this page.
1476                  */
1477                 obuf->flags &= ~PIPE_BUF_FLAG_GIFT;
1478
1479                 if (obuf->len > len)
1480                         obuf->len = len;
1481
1482                 opipe->nrbufs++;
1483                 ret += obuf->len;
1484                 len -= obuf->len;
1485                 i++;
1486         } while (len);
1487
1488         inode_double_unlock(ipipe->inode, opipe->inode);
1489
1490         /*
1491          * If we put data in the output pipe, wakeup any potential readers.
1492          */
1493         if (ret > 0) {
1494                 smp_mb();
1495                 if (waitqueue_active(&opipe->wait))
1496                         wake_up_interruptible(&opipe->wait);
1497                 kill_fasync(&opipe->fasync_readers, SIGIO, POLL_IN);
1498         }
1499
1500         return ret;
1501 }
1502
1503 /*
1504  * This is a tee(1) implementation that works on pipes. It doesn't copy
1505  * any data, it simply references the 'in' pages on the 'out' pipe.
1506  * The 'flags' used are the SPLICE_F_* variants, currently the only
1507  * applicable one is SPLICE_F_NONBLOCK.
1508  */
1509 static long do_tee(struct file *in, struct file *out, size_t len,
1510                    unsigned int flags)
1511 {
1512         struct pipe_inode_info *ipipe = pipe_info(in->f_path.dentry->d_inode);
1513         struct pipe_inode_info *opipe = pipe_info(out->f_path.dentry->d_inode);
1514         int ret = -EINVAL;
1515
1516         /*
1517          * Duplicate the contents of ipipe to opipe without actually
1518          * copying the data.
1519          */
1520         if (ipipe && opipe && ipipe != opipe) {
1521                 /*
1522                  * Keep going, unless we encounter an error. The ipipe/opipe
1523                  * ordering doesn't really matter.
1524                  */
1525                 ret = link_ipipe_prep(ipipe, flags);
1526                 if (!ret) {
1527                         ret = link_opipe_prep(opipe, flags);
1528                         if (!ret) {
1529                                 ret = link_pipe(ipipe, opipe, len, flags);
1530                                 if (!ret && (flags & SPLICE_F_NONBLOCK))
1531                                         ret = -EAGAIN;
1532                         }
1533                 }
1534         }
1535
1536         return ret;
1537 }
1538
1539 asmlinkage long sys_tee(int fdin, int fdout, size_t len, unsigned int flags)
1540 {
1541         struct file *in;
1542         int error, fput_in;
1543
1544         if (unlikely(!len))
1545                 return 0;
1546
1547         error = -EBADF;
1548         in = fget_light(fdin, &fput_in);
1549         if (in) {
1550                 if (in->f_mode & FMODE_READ) {
1551                         int fput_out;
1552                         struct file *out = fget_light(fdout, &fput_out);
1553
1554                         if (out) {
1555                                 if (out->f_mode & FMODE_WRITE)
1556                                         error = do_tee(in, out, len, flags);
1557                                 fput_light(out, fput_out);
1558                         }
1559                 }
1560                 fput_light(in, fput_in);
1561         }
1562
1563         return error;
1564 }