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 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         if (PagePrivate(page))
  56                 try_to_release_page(page, mapping_gfp_mask(mapping));
  57
  58         if (!remove_mapping(mapping, page))
  59                 return 1;
  60
  61         if (PageLRU(page)) {
  62                 struct zone *zone = page_zone(page);
  63
  64                 spin_lock_irq(&zone->lru_lock);
  65                 BUG_ON(!PageLRU(page));
  66                 __ClearPageLRU(page);
  67                 del_page_from_lru(zone, page);
  68                 spin_unlock_irq(&zone->lru_lock);
  69         }
  70
  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 }
  80
  81 static void *page_cache_pipe_buf_map(struct file *file,
  82                                      struct pipe_inode_info *info,
  83                                      struct pipe_buffer *buf)
  84 {
  85         struct page *page = buf->page;
  86
  87         lock_page(page);
  88
  89         if (!PageUptodate(page)) {
  90                 unlock_page(page);
  91                 return ERR_PTR(-EIO);
  92         }
  93
  94         if (!page->mapping) {
  95                 unlock_page(page);
  96                 return ERR_PTR(-ENODATA);
  97         }
  98
  99         return kmap(buf->page);
 100 }
 101
 102 static void page_cache_pipe_buf_unmap(struct pipe_inode_info *info,
 103                                       struct pipe_buffer *buf)
 104 {
 105         unlock_page(buf->page);
 106         kunmap(buf->page);
 107 }
 108
 109 static struct pipe_buf_operations page_cache_pipe_buf_ops = {
 110         .can_merge = 0,
 111         .map = page_cache_pipe_buf_map,
 112         .unmap = page_cache_pipe_buf_unmap,
 113         .release = page_cache_pipe_buf_release,
 114         .steal = page_cache_pipe_buf_steal,
 115 };
 116
 117 /*
 118  * Pipe output worker. This sets up our pipe format with the page cache
 119  * pipe buffer operations. Otherwise very similar to the regular pipe_writev().
 120  */
 121 static ssize_t move_to_pipe(struct inode *inode, struct page **pages,
 122                             int nr_pages, unsigned long offset,
 123                             unsigned long len, unsigned int flags)
 124 {
 125         struct pipe_inode_info *info;
 126         int ret, do_wakeup, i;
 127
 128         ret = 0;
 129         do_wakeup = 0;
 130         i = 0;
 131
 132         mutex_lock(PIPE_MUTEX(*inode));
 133
 134         info = inode->i_pipe;
 135         for (;;) {
 136                 int bufs;
 137
 138                 if (!PIPE_READERS(*inode)) {
 139                         send_sig(SIGPIPE, current, 0);
 140                         if (!ret)
 141                                 ret = -EPIPE;
 142                         break;
 143                 }
 144
 145                 bufs = info->nrbufs;
 146                 if (bufs < PIPE_BUFFERS) {
 147                         int newbuf = (info->curbuf + bufs) & (PIPE_BUFFERS - 1);
 148                         struct pipe_buffer *buf = info->bufs + newbuf;
 149                         struct page *page = pages[i++];
 150                         unsigned long this_len;
 151
 152                         this_len = PAGE_CACHE_SIZE - offset;
 153                         if (this_len > len)
 154                                 this_len = len;
 155
 156                         buf->page = page;
 157                         buf->offset = offset;
 158                         buf->len = this_len;
 159                         buf->ops = &page_cache_pipe_buf_ops;
 160                         info->nrbufs = ++bufs;
 161                         do_wakeup = 1;
 162
 163                         ret += this_len;
 164                         len -= this_len;
 165                         offset = 0;
 166                         if (!--nr_pages)
 167                                 break;
 168                         if (!len)
 169                                 break;
 170                         if (bufs < PIPE_BUFFERS)
 171                                 continue;
 172
 173                         break;
 174                 }
 175
 176                 if (flags & SPLICE_F_NONBLOCK) {
 177                         if (!ret)
 178                                 ret = -EAGAIN;
 179                         break;
 180                 }
 181
 182                 if (signal_pending(current)) {
 183                         if (!ret)
 184                                 ret = -ERESTARTSYS;
 185                         break;
 186                 }
 187
 188                 if (do_wakeup) {
 189                         wake_up_interruptible_sync(PIPE_WAIT(*inode));
 190                         kill_fasync(PIPE_FASYNC_READERS(*inode), SIGIO,
 191                                     POLL_IN);
 192                         do_wakeup = 0;
 193                 }
 194
 195                 PIPE_WAITING_WRITERS(*inode)++;
 196                 pipe_wait(inode);
 197                 PIPE_WAITING_WRITERS(*inode)--;
 198         }
 199
 200         mutex_unlock(PIPE_MUTEX(*inode));
 201
 202         if (do_wakeup) {
 203                 wake_up_interruptible(PIPE_WAIT(*inode));
 204                 kill_fasync(PIPE_FASYNC_READERS(*inode), SIGIO, POLL_IN);
 205         }
 206
 207         while (i < nr_pages)
 208                 page_cache_release(pages[i++]);
 209
 210         return ret;
 211 }
 212
 213 static int __generic_file_splice_read(struct file *in, struct inode *pipe,
 214                                       size_t len, unsigned int flags)
 215 {
 216         struct address_space *mapping = in->f_mapping;
 217         unsigned int offset, nr_pages;
 218         struct page *pages[PIPE_BUFFERS], *shadow[PIPE_BUFFERS];
 219         struct page *page;
 220         pgoff_t index, pidx;
 221         int i, j;
 222
 223         index = in->f_pos >> PAGE_CACHE_SHIFT;
 224         offset = in->f_pos & ~PAGE_CACHE_MASK;
 225         nr_pages = (len + offset + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
 226
 227         if (nr_pages > PIPE_BUFFERS)
 228                 nr_pages = PIPE_BUFFERS;
 229
 230         /*
 231          * initiate read-ahead on this page range
 232          */
 233         do_page_cache_readahead(mapping, in, index, nr_pages);
 234
 235         /*
 236          * Get as many pages from the page cache as possible..
 237          * Start IO on the page cache entries we create (we
 238          * can assume that any pre-existing ones we find have
 239          * already had IO started on them).
 240          */
 241         i = find_get_pages(mapping, index, nr_pages, pages);
 242
 243         /*
 244          * common case - we found all pages and they are contiguous,
 245          * kick them off
 246          */
 247         if (i && (pages[i - 1]->index == index + i - 1))
 248                 goto splice_them;
 249
 250         /*
 251          * fill shadow[] with pages at the right locations, so we only
 252          * have to fill holes
 253          */
 254         memset(shadow, 0, nr_pages * sizeof(struct page *));
 255         for (j = 0; j < i; j++)
 256                 shadow[pages[j]->index - index] = pages[j];
 257
 258         /*
 259          * now fill in the holes
 260          */
 261         for (i = 0, pidx = index; i < nr_pages; pidx++, i++) {
 262                 int error;
 263
 264                 if (shadow[i])
 265                         continue;
 266
 267                 /*
 268                  * no page there, look one up / create it
 269                  */
 270                 page = find_or_create_page(mapping, pidx,
 271                                                    mapping_gfp_mask(mapping));
 272                 if (!page)
 273                         break;
 274
 275                 if (PageUptodate(page))
 276                         unlock_page(page);
 277                 else {
 278                         error = mapping->a_ops->readpage(in, page);
 279
 280                         if (unlikely(error)) {
 281                                 page_cache_release(page);
 282                                 break;
 283                         }
 284                 }
 285                 shadow[i] = page;
 286         }
 287
 288         if (!i) {
 289                 for (i = 0; i < nr_pages; i++) {
 290                          if (shadow[i])
 291                                 page_cache_release(shadow[i]);
 292                 }
 293                 return 0;
 294         }
 295
 296         memcpy(pages, shadow, i * sizeof(struct page *));
 297
 298         /*
 299          * Now we splice them into the pipe..
 300          */
 301 splice_them:
 302         return move_to_pipe(pipe, pages, i, offset, len, flags);
 303 }
 304
 305 /**
 306  * generic_file_splice_read - splice data from file to a pipe
 307  * @in:         file to splice from
 308  * @pipe:       pipe to splice to
 309  * @len:        number of bytes to splice
 310  * @flags:      splice modifier flags
 311  *
 312  * Will read pages from given file and fill them into a pipe.
 313  *
 314  */
 315 ssize_t generic_file_splice_read(struct file *in, struct inode *pipe,
 316                                  size_t len, unsigned int flags)
 317 {
 318         ssize_t spliced;
 319         int ret;
 320
 321         ret = 0;
 322         spliced = 0;
 323         while (len) {
 324                 ret = __generic_file_splice_read(in, pipe, len, flags);
 325
 326                 if (ret <= 0)
 327                         break;
 328
 329                 in->f_pos += ret;
 330                 len -= ret;
 331                 spliced += ret;
 332
 333                 if (!(flags & SPLICE_F_NONBLOCK))
 334                         continue;
 335                 ret = -EAGAIN;
 336                 break;
 337         }
 338
 339         if (spliced)
 340                 return spliced;
 341
 342         return ret;
 343 }
 344
 345 EXPORT_SYMBOL(generic_file_splice_read);
 346
 347 /*
 348  * Send 'sd->len' bytes to socket from 'sd->file' at position 'sd->pos'
 349  * using sendpage().
 350  */
 351 static int pipe_to_sendpage(struct pipe_inode_info *info,
 352                             struct pipe_buffer *buf, struct splice_desc *sd)
 353 {
 354         struct file *file = sd->file;
 355         loff_t pos = sd->pos;
 356         unsigned int offset;
 357         ssize_t ret;
 358         void *ptr;
 359         int more;
 360
 361         /*
 362          * sub-optimal, but we are limited by the pipe ->map. we don't
 363          * need a kmap'ed buffer here, we just want to make sure we
 364          * have the page pinned if the pipe page originates from the
 365          * page cache
 366          */
 367         ptr = buf->ops->map(file, info, buf);
 368         if (IS_ERR(ptr))
 369                 return PTR_ERR(ptr);
 370
 371         offset = pos & ~PAGE_CACHE_MASK;
 372         more = (sd->flags & SPLICE_F_MORE) || sd->len < sd->total_len;
 373
 374         ret = file->f_op->sendpage(file, buf->page, offset, sd->len, &pos,more);
 375
 376         buf->ops->unmap(info, buf);
 377         if (ret == sd->len)
 378                 return 0;
 379
 380         return -EIO;
 381 }
 382
 383 /*
 384  * This is a little more tricky than the file -> pipe splicing. There are
 385  * basically three cases:
 386  *
 387  *      - Destination page already exists in the address space and there
 388  *        are users of it. For that case we have no other option that
 389  *        copying the data. Tough luck.
 390  *      - Destination page already exists in the address space, but there
 391  *        are no users of it. Make sure it's uptodate, then drop it. Fall
 392  *        through to last case.
 393  *      - Destination page does not exist, we can add the pipe page to
 394  *        the page cache and avoid the copy.
 395  *
 396  * If asked to move pages to the output file (SPLICE_F_MOVE is set in
 397  * sd->flags), we attempt to migrate pages from the pipe to the output
 398  * file address space page cache. This is possible if no one else has
 399  * the pipe page referenced outside of the pipe and page cache. If
 400  * SPLICE_F_MOVE isn't set, or we cannot move the page, we simply create
 401  * a new page in the output file page cache and fill/dirty that.
 402  */
 403 static int pipe_to_file(struct pipe_inode_info *info, struct pipe_buffer *buf,
 404                         struct splice_desc *sd)
 405 {
 406         struct file *file = sd->file;
 407         struct address_space *mapping = file->f_mapping;
 408         unsigned int offset;
 409         struct page *page;
 410         pgoff_t index;
 411         char *src;
 412         int ret, stolen;
 413
 414         /*
 415          * after this, page will be locked and unmapped
 416          */
 417         src = buf->ops->map(file, info, buf);
 418         if (IS_ERR(src))
 419                 return PTR_ERR(src);
 420
 421         index = sd->pos >> PAGE_CACHE_SHIFT;
 422         offset = sd->pos & ~PAGE_CACHE_MASK;
 423         stolen = 0;
 424
 425         /*
 426          * reuse buf page, if SPLICE_F_MOVE is set
 427          */
 428         if (sd->flags & SPLICE_F_MOVE) {
 429                 /*
 430                  * If steal succeeds, buf->page is now pruned from the vm
 431                  * side (LRU and page cache) and we can reuse it.
 432                  */
 433                 if (buf->ops->steal(info, buf))
 434                         goto find_page;
 435
 436                 page = buf->page;
 437                 stolen = 1;
 438                 if (add_to_page_cache_lru(page, mapping, index,
 439                                                 mapping_gfp_mask(mapping)))
 440                         goto find_page;
 441         } else {
 442 find_page:
 443                 ret = -ENOMEM;
 444                 page = find_or_create_page(mapping, index,
 445                                                 mapping_gfp_mask(mapping));
 446                 if (!page)
 447                         goto out;
 448
 449                 /*
 450                  * If the page is uptodate, it is also locked. If it isn't
 451                  * uptodate, we can mark it uptodate if we are filling the
 452                  * full page. Otherwise we need to read it in first...
 453                  */
 454                 if (!PageUptodate(page)) {
 455                         if (sd->len < PAGE_CACHE_SIZE) {
 456                                 ret = mapping->a_ops->readpage(file, page);
 457                                 if (unlikely(ret))
 458                                         goto out;
 459
 460                                 lock_page(page);
 461
 462                                 if (!PageUptodate(page)) {
 463                                         /*
 464                                          * page got invalidated, repeat
 465                                          */
 466                                         if (!page->mapping) {
 467                                                 unlock_page(page);
 468                                                 page_cache_release(page);
 469                                                 goto find_page;
 470                                         }
 471                                         ret = -EIO;
 472                                         goto out;
 473                                 }
 474                         } else {
 475                                 WARN_ON(!PageLocked(page));
 476                                 SetPageUptodate(page);
 477                         }
 478                 }
 479         }
 480
 481         ret = mapping->a_ops->prepare_write(file, page, 0, sd->len);
 482         if (ret == AOP_TRUNCATED_PAGE) {
 483                 page_cache_release(page);
 484                 goto find_page;
 485         } else if (ret)
 486                 goto out;
 487
 488         if (!stolen) {
 489                 char *dst = kmap_atomic(page, KM_USER0);
 490
 491                 memcpy(dst + offset, src + buf->offset, sd->len);
 492                 flush_dcache_page(page);
 493                 kunmap_atomic(dst, KM_USER0);
 494         }
 495
 496         ret = mapping->a_ops->commit_write(file, page, 0, sd->len);
 497         if (ret == AOP_TRUNCATED_PAGE) {
 498                 page_cache_release(page);
 499                 goto find_page;
 500         } else if (ret)
 501                 goto out;
 502
 503         balance_dirty_pages_ratelimited(mapping);
 504 out:
 505         if (!stolen) {
 506                 page_cache_release(page);
 507                 unlock_page(page);
 508         }
 509         buf->ops->unmap(info, buf);
 510         return ret;
 511 }
 512
 513 typedef int (splice_actor)(struct pipe_inode_info *, struct pipe_buffer *,
 514                            struct splice_desc *);
 515
 516 /*
 517  * Pipe input worker. Most of this logic works like a regular pipe, the
 518  * key here is the 'actor' worker passed in that actually moves the data
 519  * to the wanted destination. See pipe_to_file/pipe_to_sendpage above.
 520  */
 521 static ssize_t move_from_pipe(struct inode *inode, struct file *out,
 522                               size_t len, unsigned int flags,
 523                               splice_actor *actor)
 524 {
 525         struct pipe_inode_info *info;
 526         int ret, do_wakeup, err;
 527         struct splice_desc sd;
 528
 529         ret = 0;
 530         do_wakeup = 0;
 531
 532         sd.total_len = len;
 533         sd.flags = flags;
 534         sd.file = out;
 535         sd.pos = out->f_pos;
 536
 537         mutex_lock(PIPE_MUTEX(*inode));
 538
 539         info = inode->i_pipe;
 540         for (;;) {
 541                 int bufs = info->nrbufs;
 542
 543                 if (bufs) {
 544                         int curbuf = info->curbuf;
 545                         struct pipe_buffer *buf = info->bufs + curbuf;
 546                         struct pipe_buf_operations *ops = buf->ops;
 547
 548                         sd.len = buf->len;
 549                         if (sd.len > sd.total_len)
 550                                 sd.len = sd.total_len;
 551
 552                         err = actor(info, buf, &sd);
 553                         if (err) {
 554                                 if (!ret && err != -ENODATA)
 555                                         ret = err;
 556
 557                                 break;
 558                         }
 559
 560                         ret += sd.len;
 561                         buf->offset += sd.len;
 562                         buf->len -= sd.len;
 563                         if (!buf->len) {
 564                                 buf->ops = NULL;
 565                                 ops->release(info, buf);
 566                                 curbuf = (curbuf + 1) & (PIPE_BUFFERS - 1);
 567                                 info->curbuf = curbuf;
 568                                 info->nrbufs = --bufs;
 569                                 do_wakeup = 1;
 570                         }
 571
 572                         sd.pos += sd.len;
 573                         sd.total_len -= sd.len;
 574                         if (!sd.total_len)
 575                                 break;
 576                 }
 577
 578                 if (bufs)
 579                         continue;
 580                 if (!PIPE_WRITERS(*inode))
 581                         break;
 582                 if (!PIPE_WAITING_WRITERS(*inode)) {
 583                         if (ret)
 584                                 break;
 585                 }
 586
 587                 if (flags & SPLICE_F_NONBLOCK) {
 588                         if (!ret)
 589                                 ret = -EAGAIN;
 590                         break;
 591                 }
 592
 593                 if (signal_pending(current)) {
 594                         if (!ret)
 595                                 ret = -ERESTARTSYS;
 596                         break;
 597                 }
 598
 599                 if (do_wakeup) {
 600                         wake_up_interruptible_sync(PIPE_WAIT(*inode));
 601                         kill_fasync(PIPE_FASYNC_WRITERS(*inode),SIGIO,POLL_OUT);
 602                         do_wakeup = 0;
 603                 }
 604
 605                 pipe_wait(inode);
 606         }
 607
 608         mutex_unlock(PIPE_MUTEX(*inode));
 609
 610         if (do_wakeup) {
 611                 wake_up_interruptible(PIPE_WAIT(*inode));
 612                 kill_fasync(PIPE_FASYNC_WRITERS(*inode), SIGIO, POLL_OUT);
 613         }
 614
 615         mutex_lock(&out->f_mapping->host->i_mutex);
 616         out->f_pos = sd.pos;
 617         mutex_unlock(&out->f_mapping->host->i_mutex);
 618         return ret;
 619
 620 }
 621
 622 /**
 623  * generic_file_splice_write - splice data from a pipe to a file
 624  * @inode:      pipe inode
 625  * @out:        file to write to
 626  * @len:        number of bytes to splice
 627  * @flags:      splice modifier flags
 628  *
 629  * Will either move or copy pages (determined by @flags options) from
 630  * the given pipe inode to the given file.
 631  *
 632  */
 633 ssize_t generic_file_splice_write(struct inode *inode, struct file *out,
 634                                   size_t len, unsigned int flags)
 635 {
 636         struct address_space *mapping = out->f_mapping;
 637         ssize_t ret = move_from_pipe(inode, out, len, flags, pipe_to_file);
 638
 639         /*
 640          * if file or inode is SYNC and we actually wrote some data, sync it
 641          */
 642         if (unlikely((out->f_flags & O_SYNC) || IS_SYNC(mapping->host))
 643             && ret > 0) {
 644                 struct inode *inode = mapping->host;
 645                 int err;
 646
 647                 mutex_lock(&inode->i_mutex);
 648                 err = generic_osync_inode(mapping->host, mapping,
 649                                                 OSYNC_METADATA|OSYNC_DATA);
 650                 mutex_unlock(&inode->i_mutex);
 651
 652                 if (err)
 653                         ret = err;
 654         }
 655
 656         return ret;
 657 }
 658
 659 EXPORT_SYMBOL(generic_file_splice_write);
 660
 661 /**
 662  * generic_splice_sendpage - splice data from a pipe to a socket
 663  * @inode:      pipe inode
 664  * @out:        socket to write to
 665  * @len:        number of bytes to splice
 666  * @flags:      splice modifier flags
 667  *
 668  * Will send @len bytes from the pipe to a network socket. No data copying
 669  * is involved.
 670  *
 671  */
 672 ssize_t generic_splice_sendpage(struct inode *inode, struct file *out,
 673                                 size_t len, unsigned int flags)
 674 {
 675         return move_from_pipe(inode, out, len, flags, pipe_to_sendpage);
 676 }
 677
 678 EXPORT_SYMBOL(generic_splice_sendpage);
 679
 680 /*
 681  * Attempt to initiate a splice from pipe to file.
 682  */
 683 static long do_splice_from(struct inode *pipe, struct file *out, size_t len,
 684                            unsigned int flags)
 685 {
 686         loff_t pos;
 687         int ret;
 688
 689         if (!out->f_op || !out->f_op->splice_write)
 690                 return -EINVAL;
 691
 692         if (!(out->f_mode & FMODE_WRITE))
 693                 return -EBADF;
 694
 695         pos = out->f_pos;
 696         ret = rw_verify_area(WRITE, out, &pos, len);
 697         if (unlikely(ret < 0))
 698                 return ret;
 699
 700         return out->f_op->splice_write(pipe, out, len, flags);
 701 }
 702
 703 /*
 704  * Attempt to initiate a splice from a file to a pipe.
 705  */
 706 static long do_splice_to(struct file *in, struct inode *pipe, size_t len,
 707                          unsigned int flags)
 708 {
 709         loff_t pos, isize, left;
 710         int ret;
 711
 712         if (!in->f_op || !in->f_op->splice_read)
 713                 return -EINVAL;
 714
 715         if (!(in->f_mode & FMODE_READ))
 716                 return -EBADF;
 717
 718         pos = in->f_pos;
 719         ret = rw_verify_area(READ, in, &pos, len);
 720         if (unlikely(ret < 0))
 721                 return ret;
 722
 723         isize = i_size_read(in->f_mapping->host);
 724         if (unlikely(in->f_pos >= isize))
 725                 return 0;
 726
 727         left = isize - in->f_pos;
 728         if (left < len)
 729                 len = left;
 730
 731         return in->f_op->splice_read(in, pipe, len, flags);
 732 }
 733
 734 /*
 735  * Determine where to splice to/from.
 736  */
 737 static long do_splice(struct file *in, struct file *out, size_t len,
 738                       unsigned int flags)
 739 {
 740         struct inode *pipe;
 741
 742         pipe = in->f_dentry->d_inode;
 743         if (pipe->i_pipe)
 744                 return do_splice_from(pipe, out, len, flags);
 745
 746         pipe = out->f_dentry->d_inode;
 747         if (pipe->i_pipe)
 748                 return do_splice_to(in, pipe, len, flags);
 749
 750         return -EINVAL;
 751 }
 752
 753 asmlinkage long sys_splice(int fdin, int fdout, size_t len, unsigned int flags)
 754 {
 755         long error;
 756         struct file *in, *out;
 757         int fput_in, fput_out;
 758
 759         if (unlikely(!len))
 760                 return 0;
 761
 762         error = -EBADF;
 763         in = fget_light(fdin, &fput_in);
 764         if (in) {
 765                 if (in->f_mode & FMODE_READ) {
 766                         out = fget_light(fdout, &fput_out);
 767                         if (out) {
 768                                 if (out->f_mode & FMODE_WRITE)
 769                                         error = do_splice(in, out, len, flags);
 770                                 fput_light(out, fput_out);
 771                         }
 772                 }
 773
 774                 fput_light(in, fput_in);
 775         }
 776
 777         return error;
 778 }