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

   1 /*
   2  * "splice": joining two ropes together by interweaving their strands.
   3  *
   4  * This is the "extended pipe" functionality, where a pipe is used as
   5  * an arbitrary in-memory buffer. Think of a pipe as a small kernel
   6  * buffer that you can use to transfer data from one end to the other.
   7  *
   8  * The traditional unix read/write is extended with a "splice()" operation
   9  * that transfers data buffers to or from a pipe buffer.
  10  *
  11  * Named by Larry McVoy, original implementation from Linus, extended by
  12  * Jens to support splicing to files, network, direct splicing, etc and
  13  * fixing lots of bugs.
  14  *
  15  * Copyright (C) 2005-2006 Jens Axboe <axboe@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         while (page_nr < spd_pages)
 259                 page_cache_release(spd->pages[page_nr++]);
 260
 261         return ret;
 262 }
 263
 264 static int
 265 __generic_file_splice_read(struct file *in, loff_t *ppos,
 266                            struct pipe_inode_info *pipe, size_t len,
 267                            unsigned int flags)
 268 {
 269         struct address_space *mapping = in->f_mapping;
 270         unsigned int loff, nr_pages;
 271         struct page *pages[PIPE_BUFFERS];
 272         struct partial_page partial[PIPE_BUFFERS];
 273         struct page *page;
 274         pgoff_t index, end_index;
 275         loff_t isize;
 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
 302         /*
 303          * Lookup the (hopefully) full range of pages we need.
 304          */
 305         spd.nr_pages = find_get_pages_contig(mapping, index, nr_pages, pages);
 306
 307         /*
 308          * If find_get_pages_contig() returned fewer pages than we needed,
 309          * allocate the rest.
 310          */
 311         index += spd.nr_pages;
 312         while (spd.nr_pages < nr_pages) {
 313                 /*
 314                  * Page could be there, find_get_pages_contig() breaks on
 315                  * the first hole.
 316                  */
 317                 page = find_get_page(mapping, index);
 318                 if (!page) {
 319                         /*
 320                          * Make sure the read-ahead engine is notified
 321                          * about this failure.
 322                          */
 323                         handle_ra_miss(mapping, &in->f_ra, index);
 324
 325                         /*
 326                          * page didn't exist, allocate one.
 327                          */
 328                         page = page_cache_alloc_cold(mapping);
 329                         if (!page)
 330                                 break;
 331
 332                         error = add_to_page_cache_lru(page, mapping, index,
 333                                               GFP_KERNEL);
 334                         if (unlikely(error)) {
 335                                 page_cache_release(page);
 336                                 if (error == -EEXIST)
 337                                         continue;
 338                                 break;
 339                         }
 340                         /*
 341                          * add_to_page_cache() locks the page, unlock it
 342                          * to avoid convoluting the logic below even more.
 343                          */
 344                         unlock_page(page);
 345                 }
 346
 347                 pages[spd.nr_pages++] = page;
 348                 index++;
 349         }
 350
 351         /*
 352          * Now loop over the map and see if we need to start IO on any
 353          * pages, fill in the partial map, etc.
 354          */
 355         index = *ppos >> PAGE_CACHE_SHIFT;
 356         nr_pages = spd.nr_pages;
 357         spd.nr_pages = 0;
 358         for (page_nr = 0; page_nr < nr_pages; page_nr++) {
 359                 unsigned int this_len;
 360
 361                 if (!len)
 362                         break;
 363
 364                 /*
 365                  * this_len is the max we'll use from this page
 366                  */
 367                 this_len = min_t(unsigned long, len, PAGE_CACHE_SIZE - loff);
 368                 page = pages[page_nr];
 369
 370                 /*
 371                  * If the page isn't uptodate, we may need to start io on it
 372                  */
 373                 if (!PageUptodate(page)) {
 374                         /*
 375                          * If in nonblock mode then dont block on waiting
 376                          * for an in-flight io page
 377                          */
 378                         if (flags & SPLICE_F_NONBLOCK) {
 379                                 if (TestSetPageLocked(page))
 380                                         break;
 381                         } else
 382                                 lock_page(page);
 383
 384                         /*
 385                          * page was truncated, stop here. if this isn't the
 386                          * first page, we'll just complete what we already
 387                          * added
 388                          */
 389                         if (!page->mapping) {
 390                                 unlock_page(page);
 391                                 break;
 392                         }
 393                         /*
 394                          * page was already under io and is now done, great
 395                          */
 396                         if (PageUptodate(page)) {
 397                                 unlock_page(page);
 398                                 goto fill_it;
 399                         }
 400
 401                         /*
 402                          * need to read in the page
 403                          */
 404                         error = mapping->a_ops->readpage(in, page);
 405                         if (unlikely(error)) {
 406                                 /*
 407                                  * We really should re-lookup the page here,
 408                                  * but it complicates things a lot. Instead
 409                                  * lets just do what we already stored, and
 410                                  * we'll get it the next time we are called.
 411                                  */
 412                                 if (error == AOP_TRUNCATED_PAGE)
 413                                         error = 0;
 414
 415                                 break;
 416                         }
 417                 }
 418 fill_it:
 419                 /*
 420                  * i_size must be checked after PageUptodate.
 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                         unsigned int plen;
 433
 434                         /*
 435                          * max good bytes in this page
 436                          */
 437                         plen = ((isize - 1) & ~PAGE_CACHE_MASK) + 1;
 438                         if (plen <= loff)
 439                                 break;
 440
 441                         /*
 442                          * force quit after adding this page
 443                          */
 444                         this_len = min(this_len, plen - loff);
 445                         len = this_len;
 446                 }
 447
 448                 partial[page_nr].offset = loff;
 449                 partial[page_nr].len = this_len;
 450                 len -= this_len;
 451                 loff = 0;
 452                 spd.nr_pages++;
 453                 index++;
 454         }
 455
 456         /*
 457          * Release any pages at the end, if we quit early. 'page_nr' is how far
 458          * we got, 'nr_pages' is how many pages are in the map.
 459          */
 460         while (page_nr < nr_pages)
 461                 page_cache_release(pages[page_nr++]);
 462
 463         if (spd.nr_pages)
 464                 return splice_to_pipe(pipe, &spd);
 465
 466         return error;
 467 }
 468
 469 /**
 470  * generic_file_splice_read - splice data from file to a pipe
 471  * @in:         file to splice from
 472  * @pipe:       pipe to splice to
 473  * @len:        number of bytes to splice
 474  * @flags:      splice modifier flags
 475  *
 476  * Will read pages from given file and fill them into a pipe.
 477  */
 478 ssize_t generic_file_splice_read(struct file *in, loff_t *ppos,
 479                                  struct pipe_inode_info *pipe, size_t len,
 480                                  unsigned int flags)
 481 {
 482         ssize_t spliced;
 483         int ret;
 484         loff_t isize, left;
 485
 486         isize = i_size_read(in->f_mapping->host);
 487         if (unlikely(*ppos >= isize))
 488                 return 0;
 489
 490         left = isize - *ppos;
 491         if (unlikely(left < len))
 492                 len = left;
 493
 494         ret = 0;
 495         spliced = 0;
 496         while (len) {
 497                 ret = __generic_file_splice_read(in, ppos, pipe, len, flags);
 498
 499                 if (ret < 0)
 500                         break;
 501                 else if (!ret) {
 502                         if (spliced)
 503                                 break;
 504                         if (flags & SPLICE_F_NONBLOCK) {
 505                                 ret = -EAGAIN;
 506                                 break;
 507                         }
 508                 }
 509
 510                 *ppos += ret;
 511                 len -= ret;
 512                 spliced += ret;
 513         }
 514
 515         if (spliced)
 516                 return spliced;
 517
 518         return ret;
 519 }
 520
 521 EXPORT_SYMBOL(generic_file_splice_read);
 522
 523 /*
 524  * Send 'sd->len' bytes to socket from 'sd->file' at position 'sd->pos'
 525  * using sendpage(). Return the number of bytes sent.
 526  */
 527 static int pipe_to_sendpage(struct pipe_inode_info *pipe,
 528                             struct pipe_buffer *buf, struct splice_desc *sd)
 529 {
 530         struct file *file = sd->file;
 531         loff_t pos = sd->pos;
 532         int ret, more;
 533
 534         ret = buf->ops->pin(pipe, buf);
 535         if (!ret) {
 536                 more = (sd->flags & SPLICE_F_MORE) || sd->len < sd->total_len;
 537
 538                 ret = file->f_op->sendpage(file, buf->page, buf->offset,
 539                                            sd->len, &pos, more);
 540         }
 541
 542         return ret;
 543 }
 544
 545 /*
 546  * This is a little more tricky than the file -> pipe splicing. There are
 547  * basically three cases:
 548  *
 549  *      - Destination page already exists in the address space and there
 550  *        are users of it. For that case we have no other option that
 551  *        copying the data. Tough luck.
 552  *      - Destination page already exists in the address space, but there
 553  *        are no users of it. Make sure it's uptodate, then drop it. Fall
 554  *        through to last case.
 555  *      - Destination page does not exist, we can add the pipe page to
 556  *        the page cache and avoid the copy.
 557  *
 558  * If asked to move pages to the output file (SPLICE_F_MOVE is set in
 559  * sd->flags), we attempt to migrate pages from the pipe to the output
 560  * file address space page cache. This is possible if no one else has
 561  * the pipe page referenced outside of the pipe and page cache. If
 562  * SPLICE_F_MOVE isn't set, or we cannot move the page, we simply create
 563  * a new page in the output file page cache and fill/dirty that.
 564  */
 565 static int pipe_to_file(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
 566                         struct splice_desc *sd)
 567 {
 568         struct file *file = sd->file;
 569         struct address_space *mapping = file->f_mapping;
 570         unsigned int offset, this_len;
 571         struct page *page;
 572         pgoff_t index;
 573         int ret;
 574
 575         /*
 576          * make sure the data in this buffer is uptodate
 577          */
 578         ret = buf->ops->pin(pipe, buf);
 579         if (unlikely(ret))
 580                 return ret;
 581
 582         index = sd->pos >> PAGE_CACHE_SHIFT;
 583         offset = sd->pos & ~PAGE_CACHE_MASK;
 584
 585         this_len = sd->len;
 586         if (this_len + offset > PAGE_CACHE_SIZE)
 587                 this_len = PAGE_CACHE_SIZE - offset;
 588
 589 find_page:
 590         page = find_lock_page(mapping, index);
 591         if (!page) {
 592                 ret = -ENOMEM;
 593                 page = page_cache_alloc_cold(mapping);
 594                 if (unlikely(!page))
 595                         goto out_ret;
 596
 597                 /*
 598                  * This will also lock the page
 599                  */
 600                 ret = add_to_page_cache_lru(page, mapping, index,
 601                                             GFP_KERNEL);
 602                 if (unlikely(ret))
 603                         goto out;
 604         }
 605
 606         ret = mapping->a_ops->prepare_write(file, page, offset, offset+this_len);
 607         if (unlikely(ret)) {
 608                 loff_t isize = i_size_read(mapping->host);
 609
 610                 if (ret != AOP_TRUNCATED_PAGE)
 611                         unlock_page(page);
 612                 page_cache_release(page);
 613                 if (ret == AOP_TRUNCATED_PAGE)
 614                         goto find_page;
 615
 616                 /*
 617                  * prepare_write() may have instantiated a few blocks
 618                  * outside i_size.  Trim these off again.
 619                  */
 620                 if (sd->pos + this_len > isize)
 621                         vmtruncate(mapping->host, isize);
 622
 623                 goto out_ret;
 624         }
 625
 626         if (buf->page != page) {
 627                 /*
 628                  * Careful, ->map() uses KM_USER0!
 629                  */
 630                 char *src = buf->ops->map(pipe, buf, 1);
 631                 char *dst = kmap_atomic(page, KM_USER1);
 632
 633                 memcpy(dst + offset, src + buf->offset, this_len);
 634                 flush_dcache_page(page);
 635                 kunmap_atomic(dst, KM_USER1);
 636                 buf->ops->unmap(pipe, buf, src);
 637         }
 638
 639         ret = mapping->a_ops->commit_write(file, page, offset, offset+this_len);
 640         if (ret) {
 641                 if (ret == AOP_TRUNCATED_PAGE) {
 642                         page_cache_release(page);
 643                         goto find_page;
 644                 }
 645                 if (ret < 0)
 646                         goto out;
 647                 /*
 648                  * Partial write has happened, so 'ret' already initialized by
 649                  * number of bytes written, Where is nothing we have to do here.
 650                  */
 651         } else
 652                 ret = this_len;
 653         /*
 654          * Return the number of bytes written and mark page as
 655          * accessed, we are now done!
 656          */
 657         mark_page_accessed(page);
 658 out:
 659         page_cache_release(page);
 660         unlock_page(page);
 661 out_ret:
 662         return ret;
 663 }
 664
 665 /*
 666  * Pipe input worker. Most of this logic works like a regular pipe, the
 667  * key here is the 'actor' worker passed in that actually moves the data
 668  * to the wanted destination. See pipe_to_file/pipe_to_sendpage above.
 669  */
 670 ssize_t __splice_from_pipe(struct pipe_inode_info *pipe,
 671                            struct file *out, loff_t *ppos, size_t len,
 672                            unsigned int flags, splice_actor *actor)
 673 {
 674         int ret, do_wakeup, err;
 675         struct splice_desc sd;
 676
 677         ret = 0;
 678         do_wakeup = 0;
 679
 680         sd.total_len = len;
 681         sd.flags = flags;
 682         sd.file = out;
 683         sd.pos = *ppos;
 684
 685         for (;;) {
 686                 if (pipe->nrbufs) {
 687                         struct pipe_buffer *buf = pipe->bufs + pipe->curbuf;
 688                         const struct pipe_buf_operations *ops = buf->ops;
 689
 690                         sd.len = buf->len;
 691                         if (sd.len > sd.total_len)
 692                                 sd.len = sd.total_len;
 693
 694                         err = actor(pipe, buf, &sd);
 695                         if (err <= 0) {
 696                                 if (!ret && err != -ENODATA)
 697                                         ret = err;
 698
 699                                 break;
 700                         }
 701
 702                         ret += err;
 703                         buf->offset += err;
 704                         buf->len -= err;
 705
 706                         sd.len -= err;
 707                         sd.pos += err;
 708                         sd.total_len -= err;
 709                         if (sd.len)
 710                                 continue;
 711
 712                         if (!buf->len) {
 713                                 buf->ops = NULL;
 714                                 ops->release(pipe, buf);
 715                                 pipe->curbuf = (pipe->curbuf + 1) & (PIPE_BUFFERS - 1);
 716                                 pipe->nrbufs--;
 717                                 if (pipe->inode)
 718                                         do_wakeup = 1;
 719                         }
 720
 721                         if (!sd.total_len)
 722                                 break;
 723                 }
 724
 725                 if (pipe->nrbufs)
 726                         continue;
 727                 if (!pipe->writers)
 728                         break;
 729                 if (!pipe->waiting_writers) {
 730                         if (ret)
 731                                 break;
 732                 }
 733
 734                 if (flags & SPLICE_F_NONBLOCK) {
 735                         if (!ret)
 736                                 ret = -EAGAIN;
 737                         break;
 738                 }
 739
 740                 if (signal_pending(current)) {
 741                         if (!ret)
 742                                 ret = -ERESTARTSYS;
 743                         break;
 744                 }
 745
 746                 if (do_wakeup) {
 747                         smp_mb();
 748                         if (waitqueue_active(&pipe->wait))
 749                                 wake_up_interruptible_sync(&pipe->wait);
 750                         kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
 751                         do_wakeup = 0;
 752                 }
 753
 754                 pipe_wait(pipe);
 755         }
 756
 757         if (do_wakeup) {
 758                 smp_mb();
 759                 if (waitqueue_active(&pipe->wait))
 760                         wake_up_interruptible(&pipe->wait);
 761                 kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
 762         }
 763
 764         return ret;
 765 }
 766 EXPORT_SYMBOL(__splice_from_pipe);
 767
 768 ssize_t splice_from_pipe(struct pipe_inode_info *pipe, struct file *out,
 769                          loff_t *ppos, size_t len, unsigned int flags,
 770                          splice_actor *actor)
 771 {
 772         ssize_t ret;
 773         struct inode *inode = out->f_mapping->host;
 774
 775         /*
 776          * The actor worker might be calling ->prepare_write and
 777          * ->commit_write. Most of the time, these expect i_mutex to
 778          * be held. Since this may result in an ABBA deadlock with
 779          * pipe->inode, we have to order lock acquiry here.
 780          */
 781         inode_double_lock(inode, pipe->inode);
 782         ret = __splice_from_pipe(pipe, out, ppos, len, flags, actor);
 783         inode_double_unlock(inode, pipe->inode);
 784
 785         return ret;
 786 }
 787
 788 /**
 789  * generic_file_splice_write_nolock - generic_file_splice_write without mutexes
 790  * @pipe:       pipe info
 791  * @out:        file to write to
 792  * @len:        number of bytes to splice
 793  * @flags:      splice modifier flags
 794  *
 795  * Will either move or copy pages (determined by @flags options) from
 796  * the given pipe inode to the given file. The caller is responsible
 797  * for acquiring i_mutex on both inodes.
 798  *
 799  */
 800 ssize_t
 801 generic_file_splice_write_nolock(struct pipe_inode_info *pipe, struct file *out,
 802                                  loff_t *ppos, size_t len, unsigned int flags)
 803 {
 804         struct address_space *mapping = out->f_mapping;
 805         struct inode *inode = mapping->host;
 806         ssize_t ret;
 807         int err;
 808
 809         err = remove_suid(out->f_path.dentry);
 810         if (unlikely(err))
 811                 return err;
 812
 813         ret = __splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_file);
 814         if (ret > 0) {
 815                 unsigned long nr_pages;
 816
 817                 *ppos += ret;
 818                 nr_pages = (ret + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
 819
 820                 /*
 821                  * If file or inode is SYNC and we actually wrote some data,
 822                  * sync it.
 823                  */
 824                 if (unlikely((out->f_flags & O_SYNC) || IS_SYNC(inode))) {
 825                         err = generic_osync_inode(inode, mapping,
 826                                                   OSYNC_METADATA|OSYNC_DATA);
 827
 828                         if (err)
 829                                 ret = err;
 830                 }
 831                 balance_dirty_pages_ratelimited_nr(mapping, nr_pages);
 832         }
 833
 834         return ret;
 835 }
 836
 837 EXPORT_SYMBOL(generic_file_splice_write_nolock);
 838
 839 /**
 840  * generic_file_splice_write - splice data from a pipe to a file
 841  * @pipe:       pipe info
 842  * @out:        file to write to
 843  * @len:        number of bytes to splice
 844  * @flags:      splice modifier flags
 845  *
 846  * Will either move or copy pages (determined by @flags options) from
 847  * the given pipe inode to the given file.
 848  *
 849  */
 850 ssize_t
 851 generic_file_splice_write(struct pipe_inode_info *pipe, struct file *out,
 852                           loff_t *ppos, size_t len, unsigned int flags)
 853 {
 854         struct address_space *mapping = out->f_mapping;
 855         struct inode *inode = mapping->host;
 856         ssize_t ret;
 857         int err;
 858
 859         err = should_remove_suid(out->f_path.dentry);
 860         if (unlikely(err)) {
 861                 mutex_lock(&inode->i_mutex);
 862                 err = __remove_suid(out->f_path.dentry, err);
 863                 mutex_unlock(&inode->i_mutex);
 864                 if (err)
 865                         return err;
 866         }
 867
 868         ret = splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_file);
 869         if (ret > 0) {
 870                 unsigned long nr_pages;
 871
 872                 *ppos += ret;
 873                 nr_pages = (ret + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
 874
 875                 /*
 876                  * If file or inode is SYNC and we actually wrote some data,
 877                  * sync it.
 878                  */
 879                 if (unlikely((out->f_flags & O_SYNC) || IS_SYNC(inode))) {
 880                         mutex_lock(&inode->i_mutex);
 881                         err = generic_osync_inode(inode, mapping,
 882                                                   OSYNC_METADATA|OSYNC_DATA);
 883                         mutex_unlock(&inode->i_mutex);
 884
 885                         if (err)
 886                                 ret = err;
 887                 }
 888                 balance_dirty_pages_ratelimited_nr(mapping, nr_pages);
 889         }
 890
 891         return ret;
 892 }
 893
 894 EXPORT_SYMBOL(generic_file_splice_write);
 895
 896 /**
 897  * generic_splice_sendpage - splice data from a pipe to a socket
 898  * @inode:      pipe inode
 899  * @out:        socket to write to
 900  * @len:        number of bytes to splice
 901  * @flags:      splice modifier flags
 902  *
 903  * Will send @len bytes from the pipe to a network socket. No data copying
 904  * is involved.
 905  *
 906  */
 907 ssize_t generic_splice_sendpage(struct pipe_inode_info *pipe, struct file *out,
 908                                 loff_t *ppos, size_t len, unsigned int flags)
 909 {
 910         return splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_sendpage);
 911 }
 912
 913 EXPORT_SYMBOL(generic_splice_sendpage);
 914
 915 /*
 916  * Attempt to initiate a splice from pipe to file.
 917  */
 918 static long do_splice_from(struct pipe_inode_info *pipe, struct file *out,
 919                            loff_t *ppos, size_t len, unsigned int flags)
 920 {
 921         int ret;
 922
 923         if (unlikely(!out->f_op || !out->f_op->splice_write))
 924                 return -EINVAL;
 925
 926         if (unlikely(!(out->f_mode & FMODE_WRITE)))
 927                 return -EBADF;
 928
 929         ret = rw_verify_area(WRITE, out, ppos, len);
 930         if (unlikely(ret < 0))
 931                 return ret;
 932
 933         return out->f_op->splice_write(pipe, out, ppos, len, flags);
 934 }
 935
 936 /*
 937  * Attempt to initiate a splice from a file to a pipe.
 938  */
 939 static long do_splice_to(struct file *in, loff_t *ppos,
 940                          struct pipe_inode_info *pipe, size_t len,
 941                          unsigned int flags)
 942 {
 943         int ret;
 944
 945         if (unlikely(!in->f_op || !in->f_op->splice_read))
 946                 return -EINVAL;
 947
 948         if (unlikely(!(in->f_mode & FMODE_READ)))
 949                 return -EBADF;
 950
 951         ret = rw_verify_area(READ, in, ppos, len);
 952         if (unlikely(ret < 0))
 953                 return ret;
 954
 955         return in->f_op->splice_read(in, ppos, pipe, len, flags);
 956 }
 957
 958 long do_splice_direct(struct file *in, loff_t *ppos, struct file *out,
 959                       size_t len, unsigned int flags)
 960 {
 961         struct pipe_inode_info *pipe;
 962         long ret, bytes;
 963         loff_t out_off;
 964         umode_t i_mode;
 965         int i;
 966
 967         /*
 968          * We require the input being a regular file, as we don't want to
 969          * randomly drop data for eg socket -> socket splicing. Use the
 970          * piped splicing for that!
 971          */
 972         i_mode = in->f_path.dentry->d_inode->i_mode;
 973         if (unlikely(!S_ISREG(i_mode) && !S_ISBLK(i_mode)))
 974                 return -EINVAL;
 975
 976         /*
 977          * neither in nor out is a pipe, setup an internal pipe attached to
 978          * 'out' and transfer the wanted data from 'in' to 'out' through that
 979          */
 980         pipe = current->splice_pipe;
 981         if (unlikely(!pipe)) {
 982                 pipe = alloc_pipe_info(NULL);
 983                 if (!pipe)
 984                         return -ENOMEM;
 985
 986                 /*
 987                  * We don't have an immediate reader, but we'll read the stuff
 988                  * out of the pipe right after the splice_to_pipe(). So set
 989                  * PIPE_READERS appropriately.
 990                  */
 991                 pipe->readers = 1;
 992
 993                 current->splice_pipe = pipe;
 994         }
 995
 996         /*
 997          * Do the splice.
 998          */
 999         ret = 0;
1000         bytes = 0;
1001         out_off = 0;
1002
1003         while (len) {
1004                 size_t read_len, max_read_len;
1005
1006                 /*
1007                  * Do at most PIPE_BUFFERS pages worth of transfer:
1008                  */
1009                 max_read_len = min(len, (size_t)(PIPE_BUFFERS*PAGE_SIZE));
1010
1011                 ret = do_splice_to(in, ppos, pipe, max_read_len, flags);
1012                 if (unlikely(ret < 0))
1013                         goto out_release;
1014
1015                 read_len = ret;
1016
1017                 /*
1018                  * NOTE: nonblocking mode only applies to the input. We
1019                  * must not do the output in nonblocking mode as then we
1020                  * could get stuck data in the internal pipe:
1021                  */
1022                 ret = do_splice_from(pipe, out, &out_off, read_len,
1023                                      flags & ~SPLICE_F_NONBLOCK);
1024                 if (unlikely(ret < 0))
1025                         goto out_release;
1026
1027                 bytes += ret;
1028                 len -= ret;
1029
1030                 /*
1031                  * In nonblocking mode, if we got back a short read then
1032                  * that was due to either an IO error or due to the
1033                  * pagecache entry not being there. In the IO error case
1034                  * the _next_ splice attempt will produce a clean IO error
1035                  * return value (not a short read), so in both cases it's
1036                  * correct to break out of the loop here:
1037                  */
1038                 if ((flags & SPLICE_F_NONBLOCK) && (read_len < max_read_len))
1039                         break;
1040         }
1041
1042         pipe->nrbufs = pipe->curbuf = 0;
1043
1044         return bytes;
1045
1046 out_release:
1047         /*
1048          * If we did an incomplete transfer we must release
1049          * the pipe buffers in question:
1050          */
1051         for (i = 0; i < PIPE_BUFFERS; i++) {
1052                 struct pipe_buffer *buf = pipe->bufs + i;
1053
1054                 if (buf->ops) {
1055                         buf->ops->release(pipe, buf);
1056                         buf->ops = NULL;
1057                 }
1058         }
1059         pipe->nrbufs = pipe->curbuf = 0;
1060
1061         /*
1062          * If we transferred some data, return the number of bytes:
1063          */
1064         if (bytes > 0)
1065                 return bytes;
1066
1067         return ret;
1068 }
1069
1070 /*
1071  * After the inode slimming patch, i_pipe/i_bdev/i_cdev share the same
1072  * location, so checking ->i_pipe is not enough to verify that this is a
1073  * pipe.
1074  */
1075 static inline struct pipe_inode_info *pipe_info(struct inode *inode)
1076 {
1077         if (S_ISFIFO(inode->i_mode))
1078                 return inode->i_pipe;
1079
1080         return NULL;
1081 }
1082
1083 /*
1084  * Determine where to splice to/from.
1085  */
1086 static long do_splice(struct file *in, loff_t __user *off_in,
1087                       struct file *out, loff_t __user *off_out,
1088                       size_t len, unsigned int flags)
1089 {
1090         struct pipe_inode_info *pipe;
1091         loff_t offset, *off;
1092         long ret;
1093
1094         pipe = pipe_info(in->f_path.dentry->d_inode);
1095         if (pipe) {
1096                 if (off_in)
1097                         return -ESPIPE;
1098                 if (off_out) {
1099                         if (out->f_op->llseek == no_llseek)
1100                                 return -EINVAL;
1101                         if (copy_from_user(&offset, off_out, sizeof(loff_t)))
1102                                 return -EFAULT;
1103                         off = &offset;
1104                 } else
1105                         off = &out->f_pos;
1106
1107                 ret = do_splice_from(pipe, out, off, len, flags);
1108
1109                 if (off_out && copy_to_user(off_out, off, sizeof(loff_t)))
1110                         ret = -EFAULT;
1111
1112                 return ret;
1113         }
1114
1115         pipe = pipe_info(out->f_path.dentry->d_inode);
1116         if (pipe) {
1117                 if (off_out)
1118                         return -ESPIPE;
1119                 if (off_in) {
1120                         if (in->f_op->llseek == no_llseek)
1121                                 return -EINVAL;
1122                         if (copy_from_user(&offset, off_in, sizeof(loff_t)))
1123                                 return -EFAULT;
1124                         off = &offset;
1125                 } else
1126                         off = &in->f_pos;
1127
1128                 ret = do_splice_to(in, off, pipe, len, flags);
1129
1130                 if (off_in && copy_to_user(off_in, off, sizeof(loff_t)))
1131                         ret = -EFAULT;
1132
1133                 return ret;
1134         }
1135
1136         return -EINVAL;
1137 }
1138
1139 /*
1140  * Map an iov into an array of pages and offset/length tupples. With the
1141  * partial_page structure, we can map several non-contiguous ranges into
1142  * our ones pages[] map instead of splitting that operation into pieces.
1143  * Could easily be exported as a generic helper for other users, in which
1144  * case one would probably want to add a 'max_nr_pages' parameter as well.
1145  */
1146 static int get_iovec_page_array(const struct iovec __user *iov,
1147                                 unsigned int nr_vecs, struct page **pages,
1148                                 struct partial_page *partial, int aligned)
1149 {
1150         int buffers = 0, error = 0;
1151
1152         /*
1153          * It's ok to take the mmap_sem for reading, even
1154          * across a "get_user()".
1155          */
1156         down_read(&current->mm->mmap_sem);
1157
1158         while (nr_vecs) {
1159                 unsigned long off, npages;
1160                 void __user *base;
1161                 size_t len;
1162                 int i;
1163
1164                 /*
1165                  * Get user address base and length for this iovec.
1166                  */
1167                 error = get_user(base, &iov->iov_base);
1168                 if (unlikely(error))
1169                         break;
1170                 error = get_user(len, &iov->iov_len);
1171                 if (unlikely(error))
1172                         break;
1173
1174                 /*
1175                  * Sanity check this iovec. 0 read succeeds.
1176                  */
1177                 if (unlikely(!len))
1178                         break;
1179                 error = -EFAULT;
1180                 if (unlikely(!base))
1181                         break;
1182
1183                 /*
1184                  * Get this base offset and number of pages, then map
1185                  * in the user pages.
1186                  */
1187                 off = (unsigned long) base & ~PAGE_MASK;
1188
1189                 /*
1190                  * If asked for alignment, the offset must be zero and the
1191                  * length a multiple of the PAGE_SIZE.
1192                  */
1193                 error = -EINVAL;
1194                 if (aligned && (off || len & ~PAGE_MASK))
1195                         break;
1196
1197                 npages = (off + len + PAGE_SIZE - 1) >> PAGE_SHIFT;
1198                 if (npages > PIPE_BUFFERS - buffers)
1199                         npages = PIPE_BUFFERS - buffers;
1200
1201                 error = get_user_pages(current, current->mm,
1202                                        (unsigned long) base, npages, 0, 0,
1203                                        &pages[buffers], NULL);
1204
1205                 if (unlikely(error <= 0))
1206                         break;
1207
1208                 /*
1209                  * Fill this contiguous range into the partial page map.
1210                  */
1211                 for (i = 0; i < error; i++) {
1212                         const int plen = min_t(size_t, len, PAGE_SIZE - off);
1213
1214                         partial[buffers].offset = off;
1215                         partial[buffers].len = plen;
1216
1217                         off = 0;
1218                         len -= plen;
1219                         buffers++;
1220                 }
1221
1222                 /*
1223                  * We didn't complete this iov, stop here since it probably
1224                  * means we have to move some of this into a pipe to
1225                  * be able to continue.
1226                  */
1227                 if (len)
1228                         break;
1229
1230                 /*
1231                  * Don't continue if we mapped fewer pages than we asked for,
1232                  * or if we mapped the max number of pages that we have
1233                  * room for.
1234                  */
1235                 if (error < npages || buffers == PIPE_BUFFERS)
1236                         break;
1237
1238                 nr_vecs--;
1239                 iov++;
1240         }
1241
1242         up_read(&current->mm->mmap_sem);
1243
1244         if (buffers)
1245                 return buffers;
1246
1247         return error;
1248 }
1249
1250 /*
1251  * vmsplice splices a user address range into a pipe. It can be thought of
1252  * as splice-from-memory, where the regular splice is splice-from-file (or
1253  * to file). In both cases the output is a pipe, naturally.
1254  *
1255  * Note that vmsplice only supports splicing _from_ user memory to a pipe,
1256  * not the other way around. Splicing from user memory is a simple operation
1257  * that can be supported without any funky alignment restrictions or nasty
1258  * vm tricks. We simply map in the user memory and fill them into a pipe.
1259  * The reverse isn't quite as easy, though. There are two possible solutions
1260  * for that:
1261  *
1262  *      - memcpy() the data internally, at which point we might as well just
1263  *        do a regular read() on the buffer anyway.
1264  *      - Lots of nasty vm tricks, that are neither fast nor flexible (it
1265  *        has restriction limitations on both ends of the pipe).
1266  *
1267  * Alas, it isn't here.
1268  *
1269  */
1270 static long do_vmsplice(struct file *file, const struct iovec __user *iov,
1271                         unsigned long nr_segs, unsigned int flags)
1272 {
1273         struct pipe_inode_info *pipe;
1274         struct page *pages[PIPE_BUFFERS];
1275         struct partial_page partial[PIPE_BUFFERS];
1276         struct splice_pipe_desc spd = {
1277                 .pages = pages,
1278                 .partial = partial,
1279                 .flags = flags,
1280                 .ops = &user_page_pipe_buf_ops,
1281         };
1282
1283         pipe = pipe_info(file->f_path.dentry->d_inode);
1284         if (!pipe)
1285                 return -EBADF;
1286         if (unlikely(nr_segs > UIO_MAXIOV))
1287                 return -EINVAL;
1288         else if (unlikely(!nr_segs))
1289                 return 0;
1290
1291         spd.nr_pages = get_iovec_page_array(iov, nr_segs, pages, partial,
1292                                             flags & SPLICE_F_GIFT);
1293         if (spd.nr_pages <= 0)
1294                 return spd.nr_pages;
1295
1296         return splice_to_pipe(pipe, &spd);
1297 }
1298
1299 asmlinkage long sys_vmsplice(int fd, const struct iovec __user *iov,
1300                              unsigned long nr_segs, unsigned int flags)
1301 {
1302         struct file *file;
1303         long error;
1304         int fput;
1305
1306         error = -EBADF;
1307         file = fget_light(fd, &fput);
1308         if (file) {
1309                 if (file->f_mode & FMODE_WRITE)
1310                         error = do_vmsplice(file, iov, nr_segs, flags);
1311
1312                 fput_light(file, fput);
1313         }
1314
1315         return error;
1316 }
1317
1318 asmlinkage long sys_splice(int fd_in, loff_t __user *off_in,
1319                            int fd_out, loff_t __user *off_out,
1320                            size_t len, unsigned int flags)
1321 {
1322         long error;
1323         struct file *in, *out;
1324         int fput_in, fput_out;
1325
1326         if (unlikely(!len))
1327                 return 0;
1328
1329         error = -EBADF;
1330         in = fget_light(fd_in, &fput_in);
1331         if (in) {
1332                 if (in->f_mode & FMODE_READ) {
1333                         out = fget_light(fd_out, &fput_out);
1334                         if (out) {
1335                                 if (out->f_mode & FMODE_WRITE)
1336                                         error = do_splice(in, off_in,
1337                                                           out, off_out,
1338                                                           len, flags);
1339                                 fput_light(out, fput_out);
1340                         }
1341                 }
1342
1343                 fput_light(in, fput_in);
1344         }
1345
1346         return error;
1347 }
1348
1349 /*
1350  * Make sure there's data to read. Wait for input if we can, otherwise
1351  * return an appropriate error.
1352  */
1353 static int link_ipipe_prep(struct pipe_inode_info *pipe, unsigned int flags)
1354 {
1355         int ret;
1356
1357         /*
1358          * Check ->nrbufs without the inode lock first. This function
1359          * is speculative anyways, so missing one is ok.
1360          */
1361         if (pipe->nrbufs)
1362                 return 0;
1363
1364         ret = 0;
1365         mutex_lock(&pipe->inode->i_mutex);
1366
1367         while (!pipe->nrbufs) {
1368                 if (signal_pending(current)) {
1369                         ret = -ERESTARTSYS;
1370                         break;
1371                 }
1372                 if (!pipe->writers)
1373                         break;
1374                 if (!pipe->waiting_writers) {
1375                         if (flags & SPLICE_F_NONBLOCK) {
1376                                 ret = -EAGAIN;
1377                                 break;
1378                         }
1379                 }
1380                 pipe_wait(pipe);
1381         }
1382
1383         mutex_unlock(&pipe->inode->i_mutex);
1384         return ret;
1385 }
1386
1387 /*
1388  * Make sure there's writeable room. Wait for room if we can, otherwise
1389  * return an appropriate error.
1390  */
1391 static int link_opipe_prep(struct pipe_inode_info *pipe, unsigned int flags)
1392 {
1393         int ret;
1394
1395         /*
1396          * Check ->nrbufs without the inode lock first. This function
1397          * is speculative anyways, so missing one is ok.
1398          */
1399         if (pipe->nrbufs < PIPE_BUFFERS)
1400                 return 0;
1401
1402         ret = 0;
1403         mutex_lock(&pipe->inode->i_mutex);
1404
1405         while (pipe->nrbufs >= PIPE_BUFFERS) {
1406                 if (!pipe->readers) {
1407                         send_sig(SIGPIPE, current, 0);
1408                         ret = -EPIPE;
1409                         break;
1410                 }
1411                 if (flags & SPLICE_F_NONBLOCK) {
1412                         ret = -EAGAIN;
1413                         break;
1414                 }
1415                 if (signal_pending(current)) {
1416                         ret = -ERESTARTSYS;
1417                         break;
1418                 }
1419                 pipe->waiting_writers++;
1420                 pipe_wait(pipe);
1421                 pipe->waiting_writers--;
1422         }
1423
1424         mutex_unlock(&pipe->inode->i_mutex);
1425         return ret;
1426 }
1427
1428 /*
1429  * Link contents of ipipe to opipe.
1430  */
1431 static int link_pipe(struct pipe_inode_info *ipipe,
1432                      struct pipe_inode_info *opipe,
1433                      size_t len, unsigned int flags)
1434 {
1435         struct pipe_buffer *ibuf, *obuf;
1436         int ret = 0, i = 0, nbuf;
1437
1438         /*
1439          * Potential ABBA deadlock, work around it by ordering lock
1440          * grabbing by inode address. Otherwise two different processes
1441          * could deadlock (one doing tee from A -> B, the other from B -> A).
1442          */
1443         inode_double_lock(ipipe->inode, opipe->inode);
1444
1445         do {
1446                 if (!opipe->readers) {
1447                         send_sig(SIGPIPE, current, 0);
1448                         if (!ret)
1449                                 ret = -EPIPE;
1450                         break;
1451                 }
1452
1453                 /*
1454                  * If we have iterated all input buffers or ran out of
1455                  * output room, break.
1456                  */
1457                 if (i >= ipipe->nrbufs || opipe->nrbufs >= PIPE_BUFFERS)
1458                         break;
1459
1460                 ibuf = ipipe->bufs + ((ipipe->curbuf + i) & (PIPE_BUFFERS - 1));
1461                 nbuf = (opipe->curbuf + opipe->nrbufs) & (PIPE_BUFFERS - 1);
1462
1463                 /*
1464                  * Get a reference to this pipe buffer,
1465                  * so we can copy the contents over.
1466                  */
1467                 ibuf->ops->get(ipipe, ibuf);
1468
1469                 obuf = opipe->bufs + nbuf;
1470                 *obuf = *ibuf;
1471
1472                 /*
1473                  * Don't inherit the gift flag, we need to
1474                  * prevent multiple steals of this page.
1475                  */
1476                 obuf->flags &= ~PIPE_BUF_FLAG_GIFT;
1477
1478                 if (obuf->len > len)
1479                         obuf->len = len;
1480
1481                 opipe->nrbufs++;
1482                 ret += obuf->len;
1483                 len -= obuf->len;
1484                 i++;
1485         } while (len);
1486
1487         inode_double_unlock(ipipe->inode, opipe->inode);
1488
1489         /*
1490          * If we put data in the output pipe, wakeup any potential readers.
1491          */
1492         if (ret > 0) {
1493                 smp_mb();
1494                 if (waitqueue_active(&opipe->wait))
1495                         wake_up_interruptible(&opipe->wait);
1496                 kill_fasync(&opipe->fasync_readers, SIGIO, POLL_IN);
1497         }
1498
1499         return ret;
1500 }
1501
1502 /*
1503  * This is a tee(1) implementation that works on pipes. It doesn't copy
1504  * any data, it simply references the 'in' pages on the 'out' pipe.
1505  * The 'flags' used are the SPLICE_F_* variants, currently the only
1506  * applicable one is SPLICE_F_NONBLOCK.
1507  */
1508 static long do_tee(struct file *in, struct file *out, size_t len,
1509                    unsigned int flags)
1510 {
1511         struct pipe_inode_info *ipipe = pipe_info(in->f_path.dentry->d_inode);
1512         struct pipe_inode_info *opipe = pipe_info(out->f_path.dentry->d_inode);
1513         int ret = -EINVAL;
1514
1515         /*
1516          * Duplicate the contents of ipipe to opipe without actually
1517          * copying the data.
1518          */
1519         if (ipipe && opipe && ipipe != opipe) {
1520                 /*
1521                  * Keep going, unless we encounter an error. The ipipe/opipe
1522                  * ordering doesn't really matter.
1523                  */
1524                 ret = link_ipipe_prep(ipipe, flags);
1525                 if (!ret) {
1526                         ret = link_opipe_prep(opipe, flags);
1527                         if (!ret) {
1528                                 ret = link_pipe(ipipe, opipe, len, flags);
1529                                 if (!ret && (flags & SPLICE_F_NONBLOCK))
1530                                         ret = -EAGAIN;
1531                         }
1532                 }
1533         }
1534
1535         return ret;
1536 }
1537
1538 asmlinkage long sys_tee(int fdin, int fdout, size_t len, unsigned int flags)
1539 {
1540         struct file *in;
1541         int error, fput_in;
1542
1543         if (unlikely(!len))
1544                 return 0;
1545
1546         error = -EBADF;
1547         in = fget_light(fdin, &fput_in);
1548         if (in) {
1549                 if (in->f_mode & FMODE_READ) {
1550                         int fput_out;
1551                         struct file *out = fget_light(fdout, &fput_out);
1552
1553                         if (out) {
1554                                 if (out->f_mode & FMODE_WRITE)
1555                                         error = do_tee(in, out, len, flags);
1556                                 fput_light(out, fput_out);
1557                         }
1558                 }
1559                 fput_light(in, fput_in);
1560         }
1561
1562         return error;
1563 }