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