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 and fixing the initial implementation
  13  * bugs.
  14  *
  15  * Copyright (C) 2005 Jens Axboe <axboe@suse.de>
  16  * Copyright (C) 2005 Linus Torvalds <torvalds@osdl.org>
  17  *
  18  */
  19 #include <linux/fs.h>
  20 #include <linux/file.h>
  21 #include <linux/pagemap.h>
  22 #include <linux/pipe_fs_i.h>
  23 #include <linux/mm_inline.h>
  24 #include <linux/swap.h>
  25 #include <linux/writeback.h>
  26 #include <linux/buffer_head.h>
  27 #include <linux/module.h>
  28 #include <linux/syscalls.h>
  29
  30 /*
  31  * Passed to the actors
  32  */
  33 struct splice_desc {
  34         unsigned int len, total_len;    /* current and remaining length */
  35         unsigned int flags;             /* splice flags */
  36         struct file *file;              /* file to read/write */
  37         loff_t pos;                     /* file position */
  38 };
  39
  40 /*
  41  * Attempt to steal a page from a pipe buffer. This should perhaps go into
  42  * a vm helper function, it's already simplified quite a bit by the
  43  * addition of remove_mapping(). If success is returned, the caller may
  44  * attempt to reuse this page for another destination.
  45  */
  46 static int page_cache_pipe_buf_steal(struct pipe_inode_info *info,
  47                                      struct pipe_buffer *buf)
  48 {
  49         struct page *page = buf->page;
  50         struct address_space *mapping = page_mapping(page);
  51
  52         WARN_ON(!PageLocked(page));
  53         WARN_ON(!PageUptodate(page));
  54
  55         /*
  56          * At least for ext2 with nobh option, we need to wait on writeback
  57          * completing on this page, since we'll remove it from the pagecache.
  58          * Otherwise truncate wont wait on the page, allowing the disk
  59          * blocks to be reused by someone else before we actually wrote our
  60          * data to them. fs corruption ensues.
  61          */
  62         wait_on_page_writeback(page);
  63
  64         if (PagePrivate(page))
  65                 try_to_release_page(page, mapping_gfp_mask(mapping));
  66
  67         if (!remove_mapping(mapping, page))
  68                 return 1;
  69
  70         buf->flags |= PIPE_BUF_FLAG_STOLEN | PIPE_BUF_FLAG_LRU;
  71         return 0;
  72 }
  73
  74 static void page_cache_pipe_buf_release(struct pipe_inode_info *info,
  75                                         struct pipe_buffer *buf)
  76 {
  77         page_cache_release(buf->page);
  78         buf->page = NULL;
  79         buf->flags &= ~(PIPE_BUF_FLAG_STOLEN | PIPE_BUF_FLAG_LRU);
  80 }
  81
  82 static void *page_cache_pipe_buf_map(struct file *file,
  83                                      struct pipe_inode_info *info,
  84                                      struct pipe_buffer *buf)
  85 {
  86         struct page *page = buf->page;
  87         int err;
  88
  89         if (!PageUptodate(page)) {
  90                 lock_page(page);
  91
  92                 /*
  93                  * Page got truncated/unhashed. This will cause a 0-byte
  94                  * splice, if this is the first page
  95                  */
  96                 if (!page->mapping) {
  97                         err = -ENODATA;
  98                         goto error;
  99                 }
 100
 101                 /*
 102                  * uh oh, read-error from disk
 103                  */
 104                 if (!PageUptodate(page)) {
 105                         err = -EIO;
 106                         goto error;
 107                 }
 108
 109                 /*
 110                  * page is ok afterall, fall through to mapping
 111                  */
 112                 unlock_page(page);
 113         }
 114
 115         return kmap(page);
 116 error:
 117         unlock_page(page);
 118         return ERR_PTR(err);
 119 }
 120
 121 static void page_cache_pipe_buf_unmap(struct pipe_inode_info *info,
 122                                       struct pipe_buffer *buf)
 123 {
 124         kunmap(buf->page);
 125 }
 126
 127 static struct pipe_buf_operations page_cache_pipe_buf_ops = {
 128         .can_merge = 0,
 129         .map = page_cache_pipe_buf_map,
 130         .unmap = page_cache_pipe_buf_unmap,
 131         .release = page_cache_pipe_buf_release,
 132         .steal = page_cache_pipe_buf_steal,
 133 };
 134
 135 /*
 136  * Pipe output worker. This sets up our pipe format with the page cache
 137  * pipe buffer operations. Otherwise very similar to the regular pipe_writev().
 138  */
 139 static ssize_t move_to_pipe(struct inode *inode, struct page **pages,
 140                             int nr_pages, unsigned long offset,
 141                             unsigned long len, unsigned int flags)
 142 {
 143         struct pipe_inode_info *info;
 144         int ret, do_wakeup, i;
 145
 146         ret = 0;
 147         do_wakeup = 0;
 148         i = 0;
 149
 150         mutex_lock(PIPE_MUTEX(*inode));
 151
 152         info = inode->i_pipe;
 153         for (;;) {
 154                 int bufs;
 155
 156                 if (!PIPE_READERS(*inode)) {
 157                         send_sig(SIGPIPE, current, 0);
 158                         if (!ret)
 159                                 ret = -EPIPE;
 160                         break;
 161                 }
 162
 163                 bufs = info->nrbufs;
 164                 if (bufs < PIPE_BUFFERS) {
 165                         int newbuf = (info->curbuf + bufs) & (PIPE_BUFFERS - 1);
 166                         struct pipe_buffer *buf = info->bufs + newbuf;
 167                         struct page *page = pages[i++];
 168                         unsigned long this_len;
 169
 170                         this_len = PAGE_CACHE_SIZE - offset;
 171                         if (this_len > len)
 172                                 this_len = len;
 173
 174                         buf->page = page;
 175                         buf->offset = offset;
 176                         buf->len = this_len;
 177                         buf->ops = &page_cache_pipe_buf_ops;
 178                         info->nrbufs = ++bufs;
 179                         do_wakeup = 1;
 180
 181                         ret += this_len;
 182                         len -= this_len;
 183                         offset = 0;
 184                         if (!--nr_pages)
 185                                 break;
 186                         if (!len)
 187                                 break;
 188                         if (bufs < PIPE_BUFFERS)
 189                                 continue;
 190
 191                         break;
 192                 }
 193
 194                 if (flags & SPLICE_F_NONBLOCK) {
 195                         if (!ret)
 196                                 ret = -EAGAIN;
 197                         break;
 198                 }
 199
 200                 if (signal_pending(current)) {
 201                         if (!ret)
 202                                 ret = -ERESTARTSYS;
 203                         break;
 204                 }
 205
 206                 if (do_wakeup) {
 207                         smp_mb();
 208                         if (waitqueue_active(PIPE_WAIT(*inode)))
 209                                 wake_up_interruptible_sync(PIPE_WAIT(*inode));
 210                         kill_fasync(PIPE_FASYNC_READERS(*inode), SIGIO,
 211                                     POLL_IN);
 212                         do_wakeup = 0;
 213                 }
 214
 215                 PIPE_WAITING_WRITERS(*inode)++;
 216                 pipe_wait(inode);
 217                 PIPE_WAITING_WRITERS(*inode)--;
 218         }
 219
 220         mutex_unlock(PIPE_MUTEX(*inode));
 221
 222         if (do_wakeup) {
 223                 smp_mb();
 224                 if (waitqueue_active(PIPE_WAIT(*inode)))
 225                         wake_up_interruptible(PIPE_WAIT(*inode));
 226                 kill_fasync(PIPE_FASYNC_READERS(*inode), SIGIO, POLL_IN);
 227         }
 228
 229         while (i < nr_pages)
 230                 page_cache_release(pages[i++]);
 231
 232         return ret;
 233 }
 234
 235 static int __generic_file_splice_read(struct file *in, struct inode *pipe,
 236                                       size_t len, unsigned int flags)
 237 {
 238         struct address_space *mapping = in->f_mapping;
 239         unsigned int offset, nr_pages;
 240         struct page *pages[PIPE_BUFFERS];
 241         struct page *page;
 242         pgoff_t index;
 243         int i;
 244
 245         index = in->f_pos >> PAGE_CACHE_SHIFT;
 246         offset = in->f_pos & ~PAGE_CACHE_MASK;
 247         nr_pages = (len + offset + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
 248
 249         if (nr_pages > PIPE_BUFFERS)
 250                 nr_pages = PIPE_BUFFERS;
 251
 252         /*
 253          * initiate read-ahead on this page range
 254          */
 255         do_page_cache_readahead(mapping, in, index, nr_pages);
 256
 257         /*
 258          * now fill in the holes
 259          */
 260         for (i = 0; i < nr_pages; i++, index++) {
 261                 /*
 262                  * no page there, look one up / create it
 263                  */
 264                 page = find_or_create_page(mapping, index,
 265                                                    mapping_gfp_mask(mapping));
 266                 if (!page)
 267                         break;
 268
 269                 if (PageUptodate(page))
 270                         unlock_page(page);
 271                 else {
 272                         int error = mapping->a_ops->readpage(in, page);
 273
 274                         if (unlikely(error)) {
 275                                 page_cache_release(page);
 276                                 break;
 277                         }
 278                 }
 279                 pages[i] = page;
 280         }
 281
 282         if (i)
 283                 return move_to_pipe(pipe, pages, i, offset, len, flags);
 284
 285         return 0;
 286 }
 287
 288 /**
 289  * generic_file_splice_read - splice data from file to a pipe
 290  * @in:         file to splice from
 291  * @pipe:       pipe to splice to
 292  * @len:        number of bytes to splice
 293  * @flags:      splice modifier flags
 294  *
 295  * Will read pages from given file and fill them into a pipe.
 296  *
 297  */
 298 ssize_t generic_file_splice_read(struct file *in, struct inode *pipe,
 299                                  size_t len, unsigned int flags)
 300 {
 301         ssize_t spliced;
 302         int ret;
 303
 304         ret = 0;
 305         spliced = 0;
 306         while (len) {
 307                 ret = __generic_file_splice_read(in, pipe, len, flags);
 308
 309                 if (ret <= 0)
 310                         break;
 311
 312                 in->f_pos += ret;
 313                 len -= ret;
 314                 spliced += ret;
 315
 316                 if (!(flags & SPLICE_F_NONBLOCK))
 317                         continue;
 318                 ret = -EAGAIN;
 319                 break;
 320         }
 321
 322         if (spliced)
 323                 return spliced;
 324
 325         return ret;
 326 }
 327
 328 EXPORT_SYMBOL(generic_file_splice_read);
 329
 330 /*
 331  * Send 'sd->len' bytes to socket from 'sd->file' at position 'sd->pos'
 332  * using sendpage().
 333  */
 334 static int pipe_to_sendpage(struct pipe_inode_info *info,
 335                             struct pipe_buffer *buf, struct splice_desc *sd)
 336 {
 337         struct file *file = sd->file;
 338         loff_t pos = sd->pos;
 339         unsigned int offset;
 340         ssize_t ret;
 341         void *ptr;
 342         int more;
 343
 344         /*
 345          * sub-optimal, but we are limited by the pipe ->map. we don't
 346          * need a kmap'ed buffer here, we just want to make sure we
 347          * have the page pinned if the pipe page originates from the
 348          * page cache
 349          */
 350         ptr = buf->ops->map(file, info, buf);
 351         if (IS_ERR(ptr))
 352                 return PTR_ERR(ptr);
 353
 354         offset = pos & ~PAGE_CACHE_MASK;
 355         more = (sd->flags & SPLICE_F_MORE) || sd->len < sd->total_len;
 356
 357         ret = file->f_op->sendpage(file, buf->page, offset, sd->len, &pos,more);
 358
 359         buf->ops->unmap(info, buf);
 360         if (ret == sd->len)
 361                 return 0;
 362
 363         return -EIO;
 364 }
 365
 366 /*
 367  * This is a little more tricky than the file -> pipe splicing. There are
 368  * basically three cases:
 369  *
 370  *      - Destination page already exists in the address space and there
 371  *        are users of it. For that case we have no other option that
 372  *        copying the data. Tough luck.
 373  *      - Destination page already exists in the address space, but there
 374  *        are no users of it. Make sure it's uptodate, then drop it. Fall
 375  *        through to last case.
 376  *      - Destination page does not exist, we can add the pipe page to
 377  *        the page cache and avoid the copy.
 378  *
 379  * If asked to move pages to the output file (SPLICE_F_MOVE is set in
 380  * sd->flags), we attempt to migrate pages from the pipe to the output
 381  * file address space page cache. This is possible if no one else has
 382  * the pipe page referenced outside of the pipe and page cache. If
 383  * SPLICE_F_MOVE isn't set, or we cannot move the page, we simply create
 384  * a new page in the output file page cache and fill/dirty that.
 385  */
 386 static int pipe_to_file(struct pipe_inode_info *info, struct pipe_buffer *buf,
 387                         struct splice_desc *sd)
 388 {
 389         struct file *file = sd->file;
 390         struct address_space *mapping = file->f_mapping;
 391         gfp_t gfp_mask = mapping_gfp_mask(mapping);
 392         unsigned int offset;
 393         struct page *page;
 394         pgoff_t index;
 395         char *src;
 396         int ret;
 397
 398         /*
 399          * make sure the data in this buffer is uptodate
 400          */
 401         src = buf->ops->map(file, info, buf);
 402         if (IS_ERR(src))
 403                 return PTR_ERR(src);
 404
 405         index = sd->pos >> PAGE_CACHE_SHIFT;
 406         offset = sd->pos & ~PAGE_CACHE_MASK;
 407
 408         /*
 409          * reuse buf page, if SPLICE_F_MOVE is set
 410          */
 411         if (sd->flags & SPLICE_F_MOVE) {
 412                 /*
 413                  * If steal succeeds, buf->page is now pruned from the vm
 414                  * side (LRU and page cache) and we can reuse it.
 415                  */
 416                 if (buf->ops->steal(info, buf))
 417                         goto find_page;
 418
 419                 /*
 420                  * this will also set the page locked
 421                  */
 422                 page = buf->page;
 423                 if (add_to_page_cache(page, mapping, index, gfp_mask))
 424                         goto find_page;
 425
 426                 if (!(buf->flags & PIPE_BUF_FLAG_LRU))
 427                         lru_cache_add(page);
 428         } else {
 429 find_page:
 430                 ret = -ENOMEM;
 431                 page = find_or_create_page(mapping, index, gfp_mask);
 432                 if (!page)
 433                         goto out_nomem;
 434
 435                 /*
 436                  * If the page is uptodate, it is also locked. If it isn't
 437                  * uptodate, we can mark it uptodate if we are filling the
 438                  * full page. Otherwise we need to read it in first...
 439                  */
 440                 if (!PageUptodate(page)) {
 441                         if (sd->len < PAGE_CACHE_SIZE) {
 442                                 ret = mapping->a_ops->readpage(file, page);
 443                                 if (unlikely(ret))
 444                                         goto out;
 445
 446                                 lock_page(page);
 447
 448                                 if (!PageUptodate(page)) {
 449                                         /*
 450                                          * page got invalidated, repeat
 451                                          */
 452                                         if (!page->mapping) {
 453                                                 unlock_page(page);
 454                                                 page_cache_release(page);
 455                                                 goto find_page;
 456                                         }
 457                                         ret = -EIO;
 458                                         goto out;
 459                                 }
 460                         } else {
 461                                 WARN_ON(!PageLocked(page));
 462                                 SetPageUptodate(page);
 463                         }
 464                 }
 465         }
 466
 467         ret = mapping->a_ops->prepare_write(file, page, 0, sd->len);
 468         if (ret == AOP_TRUNCATED_PAGE) {
 469                 page_cache_release(page);
 470                 goto find_page;
 471         } else if (ret)
 472                 goto out;
 473
 474         if (!(buf->flags & PIPE_BUF_FLAG_STOLEN)) {
 475                 char *dst = kmap_atomic(page, KM_USER0);
 476
 477                 memcpy(dst + offset, src + buf->offset, sd->len);
 478                 flush_dcache_page(page);
 479                 kunmap_atomic(dst, KM_USER0);
 480         }
 481
 482         ret = mapping->a_ops->commit_write(file, page, 0, sd->len);
 483         if (ret == AOP_TRUNCATED_PAGE) {
 484                 page_cache_release(page);
 485                 goto find_page;
 486         } else if (ret)
 487                 goto out;
 488
 489         mark_page_accessed(page);
 490         balance_dirty_pages_ratelimited(mapping);
 491 out:
 492         if (!(buf->flags & PIPE_BUF_FLAG_STOLEN)) {
 493                 page_cache_release(page);
 494                 unlock_page(page);
 495         }
 496 out_nomem:
 497         buf->ops->unmap(info, buf);
 498         return ret;
 499 }
 500
 501 typedef int (splice_actor)(struct pipe_inode_info *, struct pipe_buffer *,
 502                            struct splice_desc *);
 503
 504 /*
 505  * Pipe input worker. Most of this logic works like a regular pipe, the
 506  * key here is the 'actor' worker passed in that actually moves the data
 507  * to the wanted destination. See pipe_to_file/pipe_to_sendpage above.
 508  */
 509 static ssize_t move_from_pipe(struct inode *inode, struct file *out,
 510                               size_t len, unsigned int flags,
 511                               splice_actor *actor)
 512 {
 513         struct pipe_inode_info *info;
 514         int ret, do_wakeup, err;
 515         struct splice_desc sd;
 516
 517         ret = 0;
 518         do_wakeup = 0;
 519
 520         sd.total_len = len;
 521         sd.flags = flags;
 522         sd.file = out;
 523         sd.pos = out->f_pos;
 524
 525         mutex_lock(PIPE_MUTEX(*inode));
 526
 527         info = inode->i_pipe;
 528         for (;;) {
 529                 int bufs = info->nrbufs;
 530
 531                 if (bufs) {
 532                         int curbuf = info->curbuf;
 533                         struct pipe_buffer *buf = info->bufs + curbuf;
 534                         struct pipe_buf_operations *ops = buf->ops;
 535
 536                         sd.len = buf->len;
 537                         if (sd.len > sd.total_len)
 538                                 sd.len = sd.total_len;
 539
 540                         err = actor(info, buf, &sd);
 541                         if (err) {
 542                                 if (!ret && err != -ENODATA)
 543                                         ret = err;
 544
 545                                 break;
 546                         }
 547
 548                         ret += sd.len;
 549                         buf->offset += sd.len;
 550                         buf->len -= sd.len;
 551                         if (!buf->len) {
 552                                 buf->ops = NULL;
 553                                 ops->release(info, buf);
 554                                 curbuf = (curbuf + 1) & (PIPE_BUFFERS - 1);
 555                                 info->curbuf = curbuf;
 556                                 info->nrbufs = --bufs;
 557                                 do_wakeup = 1;
 558                         }
 559
 560                         sd.pos += sd.len;
 561                         sd.total_len -= sd.len;
 562                         if (!sd.total_len)
 563                                 break;
 564                 }
 565
 566                 if (bufs)
 567                         continue;
 568                 if (!PIPE_WRITERS(*inode))
 569                         break;
 570                 if (!PIPE_WAITING_WRITERS(*inode)) {
 571                         if (ret)
 572                                 break;
 573                 }
 574
 575                 if (flags & SPLICE_F_NONBLOCK) {
 576                         if (!ret)
 577                                 ret = -EAGAIN;
 578                         break;
 579                 }
 580
 581                 if (signal_pending(current)) {
 582                         if (!ret)
 583                                 ret = -ERESTARTSYS;
 584                         break;
 585                 }
 586
 587                 if (do_wakeup) {
 588                         smp_mb();
 589                         if (waitqueue_active(PIPE_WAIT(*inode)))
 590                                 wake_up_interruptible_sync(PIPE_WAIT(*inode));
 591                         kill_fasync(PIPE_FASYNC_WRITERS(*inode),SIGIO,POLL_OUT);
 592                         do_wakeup = 0;
 593                 }
 594
 595                 pipe_wait(inode);
 596         }
 597
 598         mutex_unlock(PIPE_MUTEX(*inode));
 599
 600         if (do_wakeup) {
 601                 smp_mb();
 602                 if (waitqueue_active(PIPE_WAIT(*inode)))
 603                         wake_up_interruptible(PIPE_WAIT(*inode));
 604                 kill_fasync(PIPE_FASYNC_WRITERS(*inode), SIGIO, POLL_OUT);
 605         }
 606
 607         mutex_lock(&out->f_mapping->host->i_mutex);
 608         out->f_pos = sd.pos;
 609         mutex_unlock(&out->f_mapping->host->i_mutex);
 610         return ret;
 611
 612 }
 613
 614 /**
 615  * generic_file_splice_write - splice data from a pipe to a file
 616  * @inode:      pipe inode
 617  * @out:        file to write to
 618  * @len:        number of bytes to splice
 619  * @flags:      splice modifier flags
 620  *
 621  * Will either move or copy pages (determined by @flags options) from
 622  * the given pipe inode to the given file.
 623  *
 624  */
 625 ssize_t generic_file_splice_write(struct inode *inode, struct file *out,
 626                                   size_t len, unsigned int flags)
 627 {
 628         struct address_space *mapping = out->f_mapping;
 629         ssize_t ret = move_from_pipe(inode, out, len, flags, pipe_to_file);
 630
 631         /*
 632          * if file or inode is SYNC and we actually wrote some data, sync it
 633          */
 634         if (unlikely((out->f_flags & O_SYNC) || IS_SYNC(mapping->host))
 635             && ret > 0) {
 636                 struct inode *inode = mapping->host;
 637                 int err;
 638
 639                 mutex_lock(&inode->i_mutex);
 640                 err = generic_osync_inode(mapping->host, mapping,
 641                                                 OSYNC_METADATA|OSYNC_DATA);
 642                 mutex_unlock(&inode->i_mutex);
 643
 644                 if (err)
 645                         ret = err;
 646         }
 647
 648         return ret;
 649 }
 650
 651 EXPORT_SYMBOL(generic_file_splice_write);
 652
 653 /**
 654  * generic_splice_sendpage - splice data from a pipe to a socket
 655  * @inode:      pipe inode
 656  * @out:        socket to write to
 657  * @len:        number of bytes to splice
 658  * @flags:      splice modifier flags
 659  *
 660  * Will send @len bytes from the pipe to a network socket. No data copying
 661  * is involved.
 662  *
 663  */
 664 ssize_t generic_splice_sendpage(struct inode *inode, struct file *out,
 665                                 size_t len, unsigned int flags)
 666 {
 667         return move_from_pipe(inode, out, len, flags, pipe_to_sendpage);
 668 }
 669
 670 EXPORT_SYMBOL(generic_splice_sendpage);
 671
 672 /*
 673  * Attempt to initiate a splice from pipe to file.
 674  */
 675 static long do_splice_from(struct inode *pipe, struct file *out, size_t len,
 676                            unsigned int flags)
 677 {
 678         loff_t pos;
 679         int ret;
 680
 681         if (!out->f_op || !out->f_op->splice_write)
 682                 return -EINVAL;
 683
 684         if (!(out->f_mode & FMODE_WRITE))
 685                 return -EBADF;
 686
 687         pos = out->f_pos;
 688         ret = rw_verify_area(WRITE, out, &pos, len);
 689         if (unlikely(ret < 0))
 690                 return ret;
 691
 692         return out->f_op->splice_write(pipe, out, len, flags);
 693 }
 694
 695 /*
 696  * Attempt to initiate a splice from a file to a pipe.
 697  */
 698 static long do_splice_to(struct file *in, struct inode *pipe, size_t len,
 699                          unsigned int flags)
 700 {
 701         loff_t pos, isize, left;
 702         int ret;
 703
 704         if (!in->f_op || !in->f_op->splice_read)
 705                 return -EINVAL;
 706
 707         if (!(in->f_mode & FMODE_READ))
 708                 return -EBADF;
 709
 710         pos = in->f_pos;
 711         ret = rw_verify_area(READ, in, &pos, len);
 712         if (unlikely(ret < 0))
 713                 return ret;
 714
 715         isize = i_size_read(in->f_mapping->host);
 716         if (unlikely(in->f_pos >= isize))
 717                 return 0;
 718
 719         left = isize - in->f_pos;
 720         if (left < len)
 721                 len = left;
 722
 723         return in->f_op->splice_read(in, pipe, len, flags);
 724 }
 725
 726 /*
 727  * Determine where to splice to/from.
 728  */
 729 static long do_splice(struct file *in, struct file *out, size_t len,
 730                       unsigned int flags)
 731 {
 732         struct inode *pipe;
 733
 734         pipe = in->f_dentry->d_inode;
 735         if (pipe->i_pipe)
 736                 return do_splice_from(pipe, out, len, flags);
 737
 738         pipe = out->f_dentry->d_inode;
 739         if (pipe->i_pipe)
 740                 return do_splice_to(in, pipe, len, flags);
 741
 742         return -EINVAL;
 743 }
 744
 745 asmlinkage long sys_splice(int fdin, int fdout, size_t len, unsigned int flags)
 746 {
 747         long error;
 748         struct file *in, *out;
 749         int fput_in, fput_out;
 750
 751         if (unlikely(!len))
 752                 return 0;
 753
 754         error = -EBADF;
 755         in = fget_light(fdin, &fput_in);
 756         if (in) {
 757                 if (in->f_mode & FMODE_READ) {
 758                         out = fget_light(fdout, &fput_out);
 759                         if (out) {
 760                                 if (out->f_mode & FMODE_WRITE)
 761                                         error = do_splice(in, out, len, flags);
 762                                 fput_light(out, fput_out);
 763                         }
 764                 }
 765
 766                 fput_light(in, fput_in);
 767         }
 768
 769         return error;
 770 }