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/splice.h>
  24 #include <linux/memcontrol.h>
  25 #include <linux/mm_inline.h>
  26 #include <linux/swap.h>
  27 #include <linux/writeback.h>
  28 #include <linux/buffer_head.h>
  29 #include <linux/module.h>
  30 #include <linux/syscalls.h>
  31 #include <linux/uio.h>
  32 #include <linux/security.h>
  33
  34 /*
  35  * Attempt to steal a page from a pipe buffer. This should perhaps go into
  36  * a vm helper function, it's already simplified quite a bit by the
  37  * addition of remove_mapping(). If success is returned, the caller may
  38  * attempt to reuse this page for another destination.
  39  */
  40 static int page_cache_pipe_buf_steal(struct pipe_inode_info *pipe,
  41                                      struct pipe_buffer *buf)
  42 {
  43         struct page *page = buf->page;
  44         struct address_space *mapping;
  45
  46         lock_page(page);
  47
  48         mapping = page_mapping(page);
  49         if (mapping) {
  50                 WARN_ON(!PageUptodate(page));
  51
  52                 /*
  53                  * At least for ext2 with nobh option, we need to wait on
  54                  * writeback completing on this page, since we'll remove it
  55                  * from the pagecache.  Otherwise truncate wont wait on the
  56                  * page, allowing the disk blocks to be reused by someone else
  57                  * before we actually wrote our data to them. fs corruption
  58                  * ensues.
  59                  */
  60                 wait_on_page_writeback(page);
  61
  62                 if (page_has_private(page) &&
  63                     !try_to_release_page(page, GFP_KERNEL))
  64                         goto out_unlock;
  65
  66                 /*
  67                  * If we succeeded in removing the mapping, set LRU flag
  68                  * and return good.
  69                  */
  70                 if (remove_mapping(mapping, page)) {
  71                         buf->flags |= PIPE_BUF_FLAG_LRU;
  72                         return 0;
  73                 }
  74         }
  75
  76         /*
  77          * Raced with truncate or failed to remove page from current
  78          * address space, unlock and return failure.
  79          */
  80 out_unlock:
  81         unlock_page(page);
  82         return 1;
  83 }
  84
  85 static void page_cache_pipe_buf_release(struct pipe_inode_info *pipe,
  86                                         struct pipe_buffer *buf)
  87 {
  88         page_cache_release(buf->page);
  89         buf->flags &= ~PIPE_BUF_FLAG_LRU;
  90 }
  91
  92 /*
  93  * Check whether the contents of buf is OK to access. Since the content
  94  * is a page cache page, IO may be in flight.
  95  */
  96 static int page_cache_pipe_buf_confirm(struct pipe_inode_info *pipe,
  97                                        struct pipe_buffer *buf)
  98 {
  99         struct page *page = buf->page;
 100         int err;
 101
 102         if (!PageUptodate(page)) {
 103                 lock_page(page);
 104
 105                 /*
 106                  * Page got truncated/unhashed. This will cause a 0-byte
 107                  * splice, if this is the first page.
 108                  */
 109                 if (!page->mapping) {
 110                         err = -ENODATA;
 111                         goto error;
 112                 }
 113
 114                 /*
 115                  * Uh oh, read-error from disk.
 116                  */
 117                 if (!PageUptodate(page)) {
 118                         err = -EIO;
 119                         goto error;
 120                 }
 121
 122                 /*
 123                  * Page is ok afterall, we are done.
 124                  */
 125                 unlock_page(page);
 126         }
 127
 128         return 0;
 129 error:
 130         unlock_page(page);
 131         return err;
 132 }
 133
 134 static const struct pipe_buf_operations page_cache_pipe_buf_ops = {
 135         .can_merge = 0,
 136         .map = generic_pipe_buf_map,
 137         .unmap = generic_pipe_buf_unmap,
 138         .confirm = page_cache_pipe_buf_confirm,
 139         .release = page_cache_pipe_buf_release,
 140         .steal = page_cache_pipe_buf_steal,
 141         .get = generic_pipe_buf_get,
 142 };
 143
 144 static int user_page_pipe_buf_steal(struct pipe_inode_info *pipe,
 145                                     struct pipe_buffer *buf)
 146 {
 147         if (!(buf->flags & PIPE_BUF_FLAG_GIFT))
 148                 return 1;
 149
 150         buf->flags |= PIPE_BUF_FLAG_LRU;
 151         return generic_pipe_buf_steal(pipe, buf);
 152 }
 153
 154 static const struct pipe_buf_operations user_page_pipe_buf_ops = {
 155         .can_merge = 0,
 156         .map = generic_pipe_buf_map,
 157         .unmap = generic_pipe_buf_unmap,
 158         .confirm = generic_pipe_buf_confirm,
 159         .release = page_cache_pipe_buf_release,
 160         .steal = user_page_pipe_buf_steal,
 161         .get = generic_pipe_buf_get,
 162 };
 163
 164 /**
 165  * splice_to_pipe - fill passed data into a pipe
 166  * @pipe:       pipe to fill
 167  * @spd:        data to fill
 168  *
 169  * Description:
 170  *    @spd contains a map of pages and len/offset tuples, along with
 171  *    the struct pipe_buf_operations associated with these pages. This
 172  *    function will link that data to the pipe.
 173  *
 174  */
 175 ssize_t splice_to_pipe(struct pipe_inode_info *pipe,
 176                        struct splice_pipe_desc *spd)
 177 {
 178         unsigned int spd_pages = spd->nr_pages;
 179         int ret, do_wakeup, page_nr;
 180
 181         ret = 0;
 182         do_wakeup = 0;
 183         page_nr = 0;
 184
 185         if (pipe->inode)
 186                 mutex_lock(&pipe->inode->i_mutex);
 187
 188         for (;;) {
 189                 if (!pipe->readers) {
 190                         send_sig(SIGPIPE, current, 0);
 191                         if (!ret)
 192                                 ret = -EPIPE;
 193                         break;
 194                 }
 195
 196                 if (pipe->nrbufs < PIPE_BUFFERS) {
 197                         int newbuf = (pipe->curbuf + pipe->nrbufs) & (PIPE_BUFFERS - 1);
 198                         struct pipe_buffer *buf = pipe->bufs + newbuf;
 199
 200                         buf->page = spd->pages[page_nr];
 201                         buf->offset = spd->partial[page_nr].offset;
 202                         buf->len = spd->partial[page_nr].len;
 203                         buf->private = spd->partial[page_nr].private;
 204                         buf->ops = spd->ops;
 205                         if (spd->flags & SPLICE_F_GIFT)
 206                                 buf->flags |= PIPE_BUF_FLAG_GIFT;
 207
 208                         pipe->nrbufs++;
 209                         page_nr++;
 210                         ret += buf->len;
 211
 212                         if (pipe->inode)
 213                                 do_wakeup = 1;
 214
 215                         if (!--spd->nr_pages)
 216                                 break;
 217                         if (pipe->nrbufs < PIPE_BUFFERS)
 218                                 continue;
 219
 220                         break;
 221                 }
 222
 223                 if (spd->flags & SPLICE_F_NONBLOCK) {
 224                         if (!ret)
 225                                 ret = -EAGAIN;
 226                         break;
 227                 }
 228
 229                 if (signal_pending(current)) {
 230                         if (!ret)
 231                                 ret = -ERESTARTSYS;
 232                         break;
 233                 }
 234
 235                 if (do_wakeup) {
 236                         smp_mb();
 237                         if (waitqueue_active(&pipe->wait))
 238                                 wake_up_interruptible_sync(&pipe->wait);
 239                         kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
 240                         do_wakeup = 0;
 241                 }
 242
 243                 pipe->waiting_writers++;
 244                 pipe_wait(pipe);
 245                 pipe->waiting_writers--;
 246         }
 247
 248         if (pipe->inode) {
 249                 mutex_unlock(&pipe->inode->i_mutex);
 250
 251                 if (do_wakeup) {
 252                         smp_mb();
 253                         if (waitqueue_active(&pipe->wait))
 254                                 wake_up_interruptible(&pipe->wait);
 255                         kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
 256                 }
 257         }
 258
 259         while (page_nr < spd_pages)
 260                 spd->spd_release(spd, page_nr++);
 261
 262         return ret;
 263 }
 264
 265 static void spd_release_page(struct splice_pipe_desc *spd, unsigned int i)
 266 {
 267         page_cache_release(spd->pages[i]);
 268 }
 269
 270 static int
 271 __generic_file_splice_read(struct file *in, loff_t *ppos,
 272                            struct pipe_inode_info *pipe, size_t len,
 273                            unsigned int flags)
 274 {
 275         struct address_space *mapping = in->f_mapping;
 276         unsigned int loff, nr_pages, req_pages;
 277         struct page *pages[PIPE_BUFFERS];
 278         struct partial_page partial[PIPE_BUFFERS];
 279         struct page *page;
 280         pgoff_t index, end_index;
 281         loff_t isize;
 282         int error, page_nr;
 283         struct splice_pipe_desc spd = {
 284                 .pages = pages,
 285                 .partial = partial,
 286                 .flags = flags,
 287                 .ops = &page_cache_pipe_buf_ops,
 288                 .spd_release = spd_release_page,
 289         };
 290
 291         index = *ppos >> PAGE_CACHE_SHIFT;
 292         loff = *ppos & ~PAGE_CACHE_MASK;
 293         req_pages = (len + loff + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
 294         nr_pages = min(req_pages, (unsigned)PIPE_BUFFERS);
 295
 296         /*
 297          * Lookup the (hopefully) full range of pages we need.
 298          */
 299         spd.nr_pages = find_get_pages_contig(mapping, index, nr_pages, pages);
 300         index += spd.nr_pages;
 301
 302         /*
 303          * If find_get_pages_contig() returned fewer pages than we needed,
 304          * readahead/allocate the rest and fill in the holes.
 305          */
 306         if (spd.nr_pages < nr_pages)
 307                 page_cache_sync_readahead(mapping, &in->f_ra, in,
 308                                 index, req_pages - spd.nr_pages);
 309
 310         error = 0;
 311         while (spd.nr_pages < nr_pages) {
 312                 /*
 313                  * Page could be there, find_get_pages_contig() breaks on
 314                  * the first hole.
 315                  */
 316                 page = find_get_page(mapping, index);
 317                 if (!page) {
 318                         /*
 319                          * page didn't exist, allocate one.
 320                          */
 321                         page = page_cache_alloc_cold(mapping);
 322                         if (!page)
 323                                 break;
 324
 325                         error = add_to_page_cache_lru(page, mapping, index,
 326                                                 mapping_gfp_mask(mapping));
 327                         if (unlikely(error)) {
 328                                 page_cache_release(page);
 329                                 if (error == -EEXIST)
 330                                         continue;
 331                                 break;
 332                         }
 333                         /*
 334                          * add_to_page_cache() locks the page, unlock it
 335                          * to avoid convoluting the logic below even more.
 336                          */
 337                         unlock_page(page);
 338                 }
 339
 340                 pages[spd.nr_pages++] = page;
 341                 index++;
 342         }
 343
 344         /*
 345          * Now loop over the map and see if we need to start IO on any
 346          * pages, fill in the partial map, etc.
 347          */
 348         index = *ppos >> PAGE_CACHE_SHIFT;
 349         nr_pages = spd.nr_pages;
 350         spd.nr_pages = 0;
 351         for (page_nr = 0; page_nr < nr_pages; page_nr++) {
 352                 unsigned int this_len;
 353
 354                 if (!len)
 355                         break;
 356
 357                 /*
 358                  * this_len is the max we'll use from this page
 359                  */
 360                 this_len = min_t(unsigned long, len, PAGE_CACHE_SIZE - loff);
 361                 page = pages[page_nr];
 362
 363                 if (PageReadahead(page))
 364                         page_cache_async_readahead(mapping, &in->f_ra, in,
 365                                         page, index, req_pages - page_nr);
 366
 367                 /*
 368                  * If the page isn't uptodate, we may need to start io on it
 369                  */
 370                 if (!PageUptodate(page)) {
 371                         /*
 372                          * If in nonblock mode then dont block on waiting
 373                          * for an in-flight io page
 374                          */
 375                         if (flags & SPLICE_F_NONBLOCK) {
 376                                 if (!trylock_page(page)) {
 377                                         error = -EAGAIN;
 378                                         break;
 379                                 }
 380                         } else
 381                                 lock_page(page);
 382
 383                         /*
 384                          * Page was truncated, or invalidated by the
 385                          * filesystem.  Redo the find/create, but this time the
 386                          * page is kept locked, so there's no chance of another
 387                          * race with truncate/invalidate.
 388                          */
 389                         if (!page->mapping) {
 390                                 unlock_page(page);
 391                                 page = find_or_create_page(mapping, index,
 392                                                 mapping_gfp_mask(mapping));
 393
 394                                 if (!page) {
 395                                         error = -ENOMEM;
 396                                         break;
 397                                 }
 398                                 page_cache_release(pages[page_nr]);
 399                                 pages[page_nr] = page;
 400                         }
 401                         /*
 402                          * page was already under io and is now done, great
 403                          */
 404                         if (PageUptodate(page)) {
 405                                 unlock_page(page);
 406                                 goto fill_it;
 407                         }
 408
 409                         /*
 410                          * need to read in the page
 411                          */
 412                         error = mapping->a_ops->readpage(in, page);
 413                         if (unlikely(error)) {
 414                                 /*
 415                                  * We really should re-lookup the page here,
 416                                  * but it complicates things a lot. Instead
 417                                  * lets just do what we already stored, and
 418                                  * we'll get it the next time we are called.
 419                                  */
 420                                 if (error == AOP_TRUNCATED_PAGE)
 421                                         error = 0;
 422
 423                                 break;
 424                         }
 425                 }
 426 fill_it:
 427                 /*
 428                  * i_size must be checked after PageUptodate.
 429                  */
 430                 isize = i_size_read(mapping->host);
 431                 end_index = (isize - 1) >> PAGE_CACHE_SHIFT;
 432                 if (unlikely(!isize || index > end_index))
 433                         break;
 434
 435                 /*
 436                  * if this is the last page, see if we need to shrink
 437                  * the length and stop
 438                  */
 439                 if (end_index == index) {
 440                         unsigned int plen;
 441
 442                         /*
 443                          * max good bytes in this page
 444                          */
 445                         plen = ((isize - 1) & ~PAGE_CACHE_MASK) + 1;
 446                         if (plen <= loff)
 447                                 break;
 448
 449                         /*
 450                          * force quit after adding this page
 451                          */
 452                         this_len = min(this_len, plen - loff);
 453                         len = this_len;
 454                 }
 455
 456                 partial[page_nr].offset = loff;
 457                 partial[page_nr].len = this_len;
 458                 len -= this_len;
 459                 loff = 0;
 460                 spd.nr_pages++;
 461                 index++;
 462         }
 463
 464         /*
 465          * Release any pages at the end, if we quit early. 'page_nr' is how far
 466          * we got, 'nr_pages' is how many pages are in the map.
 467          */
 468         while (page_nr < nr_pages)
 469                 page_cache_release(pages[page_nr++]);
 470         in->f_ra.prev_pos = (loff_t)index << PAGE_CACHE_SHIFT;
 471
 472         if (spd.nr_pages)
 473                 return splice_to_pipe(pipe, &spd);
 474
 475         return error;
 476 }
 477
 478 /**
 479  * generic_file_splice_read - splice data from file to a pipe
 480  * @in:         file to splice from
 481  * @ppos:       position in @in
 482  * @pipe:       pipe to splice to
 483  * @len:        number of bytes to splice
 484  * @flags:      splice modifier flags
 485  *
 486  * Description:
 487  *    Will read pages from given file and fill them into a pipe. Can be
 488  *    used as long as the address_space operations for the source implements
 489  *    a readpage() hook.
 490  *
 491  */
 492 ssize_t generic_file_splice_read(struct file *in, loff_t *ppos,
 493                                  struct pipe_inode_info *pipe, size_t len,
 494                                  unsigned int flags)
 495 {
 496         loff_t isize, left;
 497         int ret;
 498
 499         isize = i_size_read(in->f_mapping->host);
 500         if (unlikely(*ppos >= isize))
 501                 return 0;
 502
 503         left = isize - *ppos;
 504         if (unlikely(left < len))
 505                 len = left;
 506
 507         ret = __generic_file_splice_read(in, ppos, pipe, len, flags);
 508         if (ret > 0)
 509                 *ppos += ret;
 510
 511         return ret;
 512 }
 513
 514 EXPORT_SYMBOL(generic_file_splice_read);
 515
 516 /*
 517  * Send 'sd->len' bytes to socket from 'sd->file' at position 'sd->pos'
 518  * using sendpage(). Return the number of bytes sent.
 519  */
 520 static int pipe_to_sendpage(struct pipe_inode_info *pipe,
 521                             struct pipe_buffer *buf, struct splice_desc *sd)
 522 {
 523         struct file *file = sd->u.file;
 524         loff_t pos = sd->pos;
 525         int ret, more;
 526
 527         ret = buf->ops->confirm(pipe, buf);
 528         if (!ret) {
 529                 more = (sd->flags & SPLICE_F_MORE) || sd->len < sd->total_len;
 530
 531                 ret = file->f_op->sendpage(file, buf->page, buf->offset,
 532                                            sd->len, &pos, more);
 533         }
 534
 535         return ret;
 536 }
 537
 538 /*
 539  * This is a little more tricky than the file -> pipe splicing. There are
 540  * basically three cases:
 541  *
 542  *      - Destination page already exists in the address space and there
 543  *        are users of it. For that case we have no other option that
 544  *        copying the data. Tough luck.
 545  *      - Destination page already exists in the address space, but there
 546  *        are no users of it. Make sure it's uptodate, then drop it. Fall
 547  *        through to last case.
 548  *      - Destination page does not exist, we can add the pipe page to
 549  *        the page cache and avoid the copy.
 550  *
 551  * If asked to move pages to the output file (SPLICE_F_MOVE is set in
 552  * sd->flags), we attempt to migrate pages from the pipe to the output
 553  * file address space page cache. This is possible if no one else has
 554  * the pipe page referenced outside of the pipe and page cache. If
 555  * SPLICE_F_MOVE isn't set, or we cannot move the page, we simply create
 556  * a new page in the output file page cache and fill/dirty that.
 557  */
 558 static int pipe_to_file(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
 559                         struct splice_desc *sd)
 560 {
 561         struct file *file = sd->u.file;
 562         struct address_space *mapping = file->f_mapping;
 563         unsigned int offset, this_len;
 564         struct page *page;
 565         void *fsdata;
 566         int ret;
 567
 568         /*
 569          * make sure the data in this buffer is uptodate
 570          */
 571         ret = buf->ops->confirm(pipe, buf);
 572         if (unlikely(ret))
 573                 return ret;
 574
 575         offset = sd->pos & ~PAGE_CACHE_MASK;
 576
 577         this_len = sd->len;
 578         if (this_len + offset > PAGE_CACHE_SIZE)
 579                 this_len = PAGE_CACHE_SIZE - offset;
 580
 581         ret = pagecache_write_begin(file, mapping, sd->pos, this_len,
 582                                 AOP_FLAG_UNINTERRUPTIBLE, &page, &fsdata);
 583         if (unlikely(ret))
 584                 goto out;
 585
 586         if (buf->page != page) {
 587                 /*
 588                  * Careful, ->map() uses KM_USER0!
 589                  */
 590                 char *src = buf->ops->map(pipe, buf, 1);
 591                 char *dst = kmap_atomic(page, KM_USER1);
 592
 593                 memcpy(dst + offset, src + buf->offset, this_len);
 594                 flush_dcache_page(page);
 595                 kunmap_atomic(dst, KM_USER1);
 596                 buf->ops->unmap(pipe, buf, src);
 597         }
 598         ret = pagecache_write_end(file, mapping, sd->pos, this_len, this_len,
 599                                 page, fsdata);
 600 out:
 601         return ret;
 602 }
 603
 604 /**
 605  * __splice_from_pipe - splice data from a pipe to given actor
 606  * @pipe:       pipe to splice from
 607  * @sd:         information to @actor
 608  * @actor:      handler that splices the data
 609  *
 610  * Description:
 611  *    This function does little more than loop over the pipe and call
 612  *    @actor to do the actual moving of a single struct pipe_buffer to
 613  *    the desired destination. See pipe_to_file, pipe_to_sendpage, or
 614  *    pipe_to_user.
 615  *
 616  */
 617 ssize_t __splice_from_pipe(struct pipe_inode_info *pipe, struct splice_desc *sd,
 618                            splice_actor *actor)
 619 {
 620         int ret, do_wakeup, err;
 621
 622         ret = 0;
 623         do_wakeup = 0;
 624
 625         for (;;) {
 626                 if (pipe->nrbufs) {
 627                         struct pipe_buffer *buf = pipe->bufs + pipe->curbuf;
 628                         const struct pipe_buf_operations *ops = buf->ops;
 629
 630                         sd->len = buf->len;
 631                         if (sd->len > sd->total_len)
 632                                 sd->len = sd->total_len;
 633
 634                         err = actor(pipe, buf, sd);
 635                         if (err <= 0) {
 636                                 if (!ret && err != -ENODATA)
 637                                         ret = err;
 638
 639                                 break;
 640                         }
 641
 642                         ret += err;
 643                         buf->offset += err;
 644                         buf->len -= err;
 645
 646                         sd->len -= err;
 647                         sd->pos += err;
 648                         sd->total_len -= err;
 649                         if (sd->len)
 650                                 continue;
 651
 652                         if (!buf->len) {
 653                                 buf->ops = NULL;
 654                                 ops->release(pipe, buf);
 655                                 pipe->curbuf = (pipe->curbuf + 1) & (PIPE_BUFFERS - 1);
 656                                 pipe->nrbufs--;
 657                                 if (pipe->inode)
 658                                         do_wakeup = 1;
 659                         }
 660
 661                         if (!sd->total_len)
 662                                 break;
 663                 }
 664
 665                 if (pipe->nrbufs)
 666                         continue;
 667                 if (!pipe->writers)
 668                         break;
 669                 if (!pipe->waiting_writers) {
 670                         if (ret)
 671                                 break;
 672                 }
 673
 674                 if (sd->flags & SPLICE_F_NONBLOCK) {
 675                         if (!ret)
 676                                 ret = -EAGAIN;
 677                         break;
 678                 }
 679
 680                 if (signal_pending(current)) {
 681                         if (!ret)
 682                                 ret = -ERESTARTSYS;
 683                         break;
 684                 }
 685
 686                 if (do_wakeup) {
 687                         smp_mb();
 688                         if (waitqueue_active(&pipe->wait))
 689                                 wake_up_interruptible_sync(&pipe->wait);
 690                         kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
 691                         do_wakeup = 0;
 692                 }
 693
 694                 pipe_wait(pipe);
 695         }
 696
 697         if (do_wakeup) {
 698                 smp_mb();
 699                 if (waitqueue_active(&pipe->wait))
 700                         wake_up_interruptible(&pipe->wait);
 701                 kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
 702         }
 703
 704         return ret;
 705 }
 706 EXPORT_SYMBOL(__splice_from_pipe);
 707
 708 /**
 709  * splice_from_pipe - splice data from a pipe to a file
 710  * @pipe:       pipe to splice from
 711  * @out:        file to splice to
 712  * @ppos:       position in @out
 713  * @len:        how many bytes to splice
 714  * @flags:      splice modifier flags
 715  * @actor:      handler that splices the data
 716  *
 717  * Description:
 718  *    See __splice_from_pipe. This function locks the input and output inodes,
 719  *    otherwise it's identical to __splice_from_pipe().
 720  *
 721  */
 722 ssize_t splice_from_pipe(struct pipe_inode_info *pipe, struct file *out,
 723                          loff_t *ppos, size_t len, unsigned int flags,
 724                          splice_actor *actor)
 725 {
 726         ssize_t ret;
 727         struct inode *inode = out->f_mapping->host;
 728         struct splice_desc sd = {
 729                 .total_len = len,
 730                 .flags = flags,
 731                 .pos = *ppos,
 732                 .u.file = out,
 733         };
 734
 735         /*
 736          * The actor worker might be calling ->write_begin and
 737          * ->write_end. Most of the time, these expect i_mutex to
 738          * be held. Since this may result in an ABBA deadlock with
 739          * pipe->inode, we have to order lock acquiry here.
 740          */
 741         inode_double_lock(inode, pipe->inode);
 742         ret = __splice_from_pipe(pipe, &sd, actor);
 743         inode_double_unlock(inode, pipe->inode);
 744
 745         return ret;
 746 }
 747
 748 /**
 749  * generic_file_splice_write_nolock - generic_file_splice_write without mutexes
 750  * @pipe:       pipe info
 751  * @out:        file to write to
 752  * @ppos:       position in @out
 753  * @len:        number of bytes to splice
 754  * @flags:      splice modifier flags
 755  *
 756  * Description:
 757  *    Will either move or copy pages (determined by @flags options) from
 758  *    the given pipe inode to the given file. The caller is responsible
 759  *    for acquiring i_mutex on both inodes.
 760  *
 761  */
 762 ssize_t
 763 generic_file_splice_write_nolock(struct pipe_inode_info *pipe, struct file *out,
 764                                  loff_t *ppos, size_t len, unsigned int flags)
 765 {
 766         struct address_space *mapping = out->f_mapping;
 767         struct inode *inode = mapping->host;
 768         struct splice_desc sd = {
 769                 .total_len = len,
 770                 .flags = flags,
 771                 .pos = *ppos,
 772                 .u.file = out,
 773         };
 774         ssize_t ret;
 775         int err;
 776
 777         err = file_remove_suid(out);
 778         if (unlikely(err))
 779                 return err;
 780
 781         ret = __splice_from_pipe(pipe, &sd, pipe_to_file);
 782         if (ret > 0) {
 783                 unsigned long nr_pages;
 784
 785                 *ppos += ret;
 786                 nr_pages = (ret + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
 787
 788                 /*
 789                  * If file or inode is SYNC and we actually wrote some data,
 790                  * sync it.
 791                  */
 792                 if (unlikely((out->f_flags & O_SYNC) || IS_SYNC(inode))) {
 793                         err = generic_osync_inode(inode, mapping,
 794                                                   OSYNC_METADATA|OSYNC_DATA);
 795
 796                         if (err)
 797                                 ret = err;
 798                 }
 799                 balance_dirty_pages_ratelimited_nr(mapping, nr_pages);
 800         }
 801
 802         return ret;
 803 }
 804
 805 EXPORT_SYMBOL(generic_file_splice_write_nolock);
 806
 807 /**
 808  * generic_file_splice_write - splice data from a pipe to a file
 809  * @pipe:       pipe info
 810  * @out:        file to write to
 811  * @ppos:       position in @out
 812  * @len:        number of bytes to splice
 813  * @flags:      splice modifier flags
 814  *
 815  * Description:
 816  *    Will either move or copy pages (determined by @flags options) from
 817  *    the given pipe inode to the given file.
 818  *
 819  */
 820 ssize_t
 821 generic_file_splice_write(struct pipe_inode_info *pipe, struct file *out,
 822                           loff_t *ppos, size_t len, unsigned int flags)
 823 {
 824         struct address_space *mapping = out->f_mapping;
 825         struct inode *inode = mapping->host;
 826         struct splice_desc sd = {
 827                 .total_len = len,
 828                 .flags = flags,
 829                 .pos = *ppos,
 830                 .u.file = out,
 831         };
 832         ssize_t ret;
 833
 834         inode_double_lock(inode, pipe->inode);
 835         ret = file_remove_suid(out);
 836         if (likely(!ret))
 837                 ret = __splice_from_pipe(pipe, &sd, pipe_to_file);
 838         inode_double_unlock(inode, pipe->inode);
 839         if (ret > 0) {
 840                 unsigned long nr_pages;
 841
 842                 *ppos += ret;
 843                 nr_pages = (ret + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
 844
 845                 /*
 846                  * If file or inode is SYNC and we actually wrote some data,
 847                  * sync it.
 848                  */
 849                 if (unlikely((out->f_flags & O_SYNC) || IS_SYNC(inode))) {
 850                         int err;
 851
 852                         mutex_lock(&inode->i_mutex);
 853                         err = generic_osync_inode(inode, mapping,
 854                                                   OSYNC_METADATA|OSYNC_DATA);
 855                         mutex_unlock(&inode->i_mutex);
 856
 857                         if (err)
 858                                 ret = err;
 859                 }
 860                 balance_dirty_pages_ratelimited_nr(mapping, nr_pages);
 861         }
 862
 863         return ret;
 864 }
 865
 866 EXPORT_SYMBOL(generic_file_splice_write);
 867
 868 /**
 869  * generic_splice_sendpage - splice data from a pipe to a socket
 870  * @pipe:       pipe to splice from
 871  * @out:        socket to write to
 872  * @ppos:       position in @out
 873  * @len:        number of bytes to splice
 874  * @flags:      splice modifier flags
 875  *
 876  * Description:
 877  *    Will send @len bytes from the pipe to a network socket. No data copying
 878  *    is involved.
 879  *
 880  */
 881 ssize_t generic_splice_sendpage(struct pipe_inode_info *pipe, struct file *out,
 882                                 loff_t *ppos, size_t len, unsigned int flags)
 883 {
 884         return splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_sendpage);
 885 }
 886
 887 EXPORT_SYMBOL(generic_splice_sendpage);
 888
 889 /*
 890  * Attempt to initiate a splice from pipe to file.
 891  */
 892 static long do_splice_from(struct pipe_inode_info *pipe, struct file *out,
 893                            loff_t *ppos, size_t len, unsigned int flags)
 894 {
 895         int ret;
 896
 897         if (unlikely(!out->f_op || !out->f_op->splice_write))
 898                 return -EINVAL;
 899
 900         if (unlikely(!(out->f_mode & FMODE_WRITE)))
 901                 return -EBADF;
 902
 903         if (unlikely(out->f_flags & O_APPEND))
 904                 return -EINVAL;
 905
 906         ret = rw_verify_area(WRITE, out, ppos, len);
 907         if (unlikely(ret < 0))
 908                 return ret;
 909
 910         return out->f_op->splice_write(pipe, out, ppos, len, flags);
 911 }
 912
 913 /*
 914  * Attempt to initiate a splice from a file to a pipe.
 915  */
 916 static long do_splice_to(struct file *in, loff_t *ppos,
 917                          struct pipe_inode_info *pipe, size_t len,
 918                          unsigned int flags)
 919 {
 920         int ret;
 921
 922         if (unlikely(!in->f_op || !in->f_op->splice_read))
 923                 return -EINVAL;
 924
 925         if (unlikely(!(in->f_mode & FMODE_READ)))
 926                 return -EBADF;
 927
 928         ret = rw_verify_area(READ, in, ppos, len);
 929         if (unlikely(ret < 0))
 930                 return ret;
 931
 932         return in->f_op->splice_read(in, ppos, pipe, len, flags);
 933 }
 934
 935 /**
 936  * splice_direct_to_actor - splices data directly between two non-pipes
 937  * @in:         file to splice from
 938  * @sd:         actor information on where to splice to
 939  * @actor:      handles the data splicing
 940  *
 941  * Description:
 942  *    This is a special case helper to splice directly between two
 943  *    points, without requiring an explicit pipe. Internally an allocated
 944  *    pipe is cached in the process, and reused during the lifetime of
 945  *    that process.
 946  *
 947  */
 948 ssize_t splice_direct_to_actor(struct file *in, struct splice_desc *sd,
 949                                splice_direct_actor *actor)
 950 {
 951         struct pipe_inode_info *pipe;
 952         long ret, bytes;
 953         umode_t i_mode;
 954         size_t len;
 955         int i, flags;
 956
 957         /*
 958          * We require the input being a regular file, as we don't want to
 959          * randomly drop data for eg socket -> socket splicing. Use the
 960          * piped splicing for that!
 961          */
 962         i_mode = in->f_path.dentry->d_inode->i_mode;
 963         if (unlikely(!S_ISREG(i_mode) && !S_ISBLK(i_mode)))
 964                 return -EINVAL;
 965
 966         /*
 967          * neither in nor out is a pipe, setup an internal pipe attached to
 968          * 'out' and transfer the wanted data from 'in' to 'out' through that
 969          */
 970         pipe = current->splice_pipe;
 971         if (unlikely(!pipe)) {
 972                 pipe = alloc_pipe_info(NULL);
 973                 if (!pipe)
 974                         return -ENOMEM;
 975
 976                 /*
 977                  * We don't have an immediate reader, but we'll read the stuff
 978                  * out of the pipe right after the splice_to_pipe(). So set
 979                  * PIPE_READERS appropriately.
 980                  */
 981                 pipe->readers = 1;
 982
 983                 current->splice_pipe = pipe;
 984         }
 985
 986         /*
 987          * Do the splice.
 988          */
 989         ret = 0;
 990         bytes = 0;
 991         len = sd->total_len;
 992         flags = sd->flags;
 993
 994         /*
 995          * Don't block on output, we have to drain the direct pipe.
 996          */
 997         sd->flags &= ~SPLICE_F_NONBLOCK;
 998
 999         while (len) {
1000                 size_t read_len;
1001                 loff_t pos = sd->pos, prev_pos = pos;
1002
1003                 ret = do_splice_to(in, &pos, pipe, len, flags);
1004                 if (unlikely(ret <= 0))
1005                         goto out_release;
1006
1007                 read_len = ret;
1008                 sd->total_len = read_len;
1009
1010                 /*
1011                  * NOTE: nonblocking mode only applies to the input. We
1012                  * must not do the output in nonblocking mode as then we
1013                  * could get stuck data in the internal pipe:
1014                  */
1015                 ret = actor(pipe, sd);
1016                 if (unlikely(ret <= 0)) {
1017                         sd->pos = prev_pos;
1018                         goto out_release;
1019                 }
1020
1021                 bytes += ret;
1022                 len -= ret;
1023                 sd->pos = pos;
1024
1025                 if (ret < read_len) {
1026                         sd->pos = prev_pos + ret;
1027                         goto out_release;
1028                 }
1029         }
1030
1031 done:
1032         pipe->nrbufs = pipe->curbuf = 0;
1033         file_accessed(in);
1034         return bytes;
1035
1036 out_release:
1037         /*
1038          * If we did an incomplete transfer we must release
1039          * the pipe buffers in question:
1040          */
1041         for (i = 0; i < PIPE_BUFFERS; i++) {
1042                 struct pipe_buffer *buf = pipe->bufs + i;
1043
1044                 if (buf->ops) {
1045                         buf->ops->release(pipe, buf);
1046                         buf->ops = NULL;
1047                 }
1048         }
1049
1050         if (!bytes)
1051                 bytes = ret;
1052
1053         goto done;
1054 }
1055 EXPORT_SYMBOL(splice_direct_to_actor);
1056
1057 static int direct_splice_actor(struct pipe_inode_info *pipe,
1058                                struct splice_desc *sd)
1059 {
1060         struct file *file = sd->u.file;
1061
1062         return do_splice_from(pipe, file, &sd->pos, sd->total_len, sd->flags);
1063 }
1064
1065 /**
1066  * do_splice_direct - splices data directly between two files
1067  * @in:         file to splice from
1068  * @ppos:       input file offset
1069  * @out:        file to splice to
1070  * @len:        number of bytes to splice
1071  * @flags:      splice modifier flags
1072  *
1073  * Description:
1074  *    For use by do_sendfile(). splice can easily emulate sendfile, but
1075  *    doing it in the application would incur an extra system call
1076  *    (splice in + splice out, as compared to just sendfile()). So this helper
1077  *    can splice directly through a process-private pipe.
1078  *
1079  */
1080 long do_splice_direct(struct file *in, loff_t *ppos, struct file *out,
1081                       size_t len, unsigned int flags)
1082 {
1083         struct splice_desc sd = {
1084                 .len            = len,
1085                 .total_len      = len,
1086                 .flags          = flags,
1087                 .pos            = *ppos,
1088                 .u.file         = out,
1089         };
1090         long ret;
1091
1092         ret = splice_direct_to_actor(in, &sd, direct_splice_actor);
1093         if (ret > 0)
1094                 *ppos = sd.pos;
1095
1096         return ret;
1097 }
1098
1099 /*
1100  * After the inode slimming patch, i_pipe/i_bdev/i_cdev share the same
1101  * location, so checking ->i_pipe is not enough to verify that this is a
1102  * pipe.
1103  */
1104 static inline struct pipe_inode_info *pipe_info(struct inode *inode)
1105 {
1106         if (S_ISFIFO(inode->i_mode))
1107                 return inode->i_pipe;
1108
1109         return NULL;
1110 }
1111
1112 /*
1113  * Determine where to splice to/from.
1114  */
1115 static long do_splice(struct file *in, loff_t __user *off_in,
1116                       struct file *out, loff_t __user *off_out,
1117                       size_t len, unsigned int flags)
1118 {
1119         struct pipe_inode_info *pipe;
1120         loff_t offset, *off;
1121         long ret;
1122
1123         pipe = pipe_info(in->f_path.dentry->d_inode);
1124         if (pipe) {
1125                 if (off_in)
1126                         return -ESPIPE;
1127                 if (off_out) {
1128                         if (out->f_op->llseek == no_llseek)
1129                                 return -EINVAL;
1130                         if (copy_from_user(&offset, off_out, sizeof(loff_t)))
1131                                 return -EFAULT;
1132                         off = &offset;
1133                 } else
1134                         off = &out->f_pos;
1135
1136                 ret = do_splice_from(pipe, out, off, len, flags);
1137
1138                 if (off_out && copy_to_user(off_out, off, sizeof(loff_t)))
1139                         ret = -EFAULT;
1140
1141                 return ret;
1142         }
1143
1144         pipe = pipe_info(out->f_path.dentry->d_inode);
1145         if (pipe) {
1146                 if (off_out)
1147                         return -ESPIPE;
1148                 if (off_in) {
1149                         if (in->f_op->llseek == no_llseek)
1150                                 return -EINVAL;
1151                         if (copy_from_user(&offset, off_in, sizeof(loff_t)))
1152                                 return -EFAULT;
1153                         off = &offset;
1154                 } else
1155                         off = &in->f_pos;
1156
1157                 ret = do_splice_to(in, off, pipe, len, flags);
1158
1159                 if (off_in && copy_to_user(off_in, off, sizeof(loff_t)))
1160                         ret = -EFAULT;
1161
1162                 return ret;
1163         }
1164
1165         return -EINVAL;
1166 }
1167
1168 /*
1169  * Map an iov into an array of pages and offset/length tupples. With the
1170  * partial_page structure, we can map several non-contiguous ranges into
1171  * our ones pages[] map instead of splitting that operation into pieces.
1172  * Could easily be exported as a generic helper for other users, in which
1173  * case one would probably want to add a 'max_nr_pages' parameter as well.
1174  */
1175 static int get_iovec_page_array(const struct iovec __user *iov,
1176                                 unsigned int nr_vecs, struct page **pages,
1177                                 struct partial_page *partial, int aligned)
1178 {
1179         int buffers = 0, error = 0;
1180
1181         while (nr_vecs) {
1182                 unsigned long off, npages;
1183                 struct iovec entry;
1184                 void __user *base;
1185                 size_t len;
1186                 int i;
1187
1188                 error = -EFAULT;
1189                 if (copy_from_user(&entry, iov, sizeof(entry)))
1190                         break;
1191
1192                 base = entry.iov_base;
1193                 len = entry.iov_len;
1194
1195                 /*
1196                  * Sanity check this iovec. 0 read succeeds.
1197                  */
1198                 error = 0;
1199                 if (unlikely(!len))
1200                         break;
1201                 error = -EFAULT;
1202                 if (!access_ok(VERIFY_READ, base, len))
1203                         break;
1204
1205                 /*
1206                  * Get this base offset and number of pages, then map
1207                  * in the user pages.
1208                  */
1209                 off = (unsigned long) base & ~PAGE_MASK;
1210
1211                 /*
1212                  * If asked for alignment, the offset must be zero and the
1213                  * length a multiple of the PAGE_SIZE.
1214                  */
1215                 error = -EINVAL;
1216                 if (aligned && (off || len & ~PAGE_MASK))
1217                         break;
1218
1219                 npages = (off + len + PAGE_SIZE - 1) >> PAGE_SHIFT;
1220                 if (npages > PIPE_BUFFERS - buffers)
1221                         npages = PIPE_BUFFERS - buffers;
1222
1223                 error = get_user_pages_fast((unsigned long)base, npages,
1224                                         0, &pages[buffers]);
1225
1226                 if (unlikely(error <= 0))
1227                         break;
1228
1229                 /*
1230                  * Fill this contiguous range into the partial page map.
1231                  */
1232                 for (i = 0; i < error; i++) {
1233                         const int plen = min_t(size_t, len, PAGE_SIZE - off);
1234
1235                         partial[buffers].offset = off;
1236                         partial[buffers].len = plen;
1237
1238                         off = 0;
1239                         len -= plen;
1240                         buffers++;
1241                 }
1242
1243                 /*
1244                  * We didn't complete this iov, stop here since it probably
1245                  * means we have to move some of this into a pipe to
1246                  * be able to continue.
1247                  */
1248                 if (len)
1249                         break;
1250
1251                 /*
1252                  * Don't continue if we mapped fewer pages than we asked for,
1253                  * or if we mapped the max number of pages that we have
1254                  * room for.
1255                  */
1256                 if (error < npages || buffers == PIPE_BUFFERS)
1257                         break;
1258
1259                 nr_vecs--;
1260                 iov++;
1261         }
1262
1263         if (buffers)
1264                 return buffers;
1265
1266         return error;
1267 }
1268
1269 static int pipe_to_user(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
1270                         struct splice_desc *sd)
1271 {
1272         char *src;
1273         int ret;
1274
1275         ret = buf->ops->confirm(pipe, buf);
1276         if (unlikely(ret))
1277                 return ret;
1278
1279         /*
1280          * See if we can use the atomic maps, by prefaulting in the
1281          * pages and doing an atomic copy
1282          */
1283         if (!fault_in_pages_writeable(sd->u.userptr, sd->len)) {
1284                 src = buf->ops->map(pipe, buf, 1);
1285                 ret = __copy_to_user_inatomic(sd->u.userptr, src + buf->offset,
1286                                                         sd->len);
1287                 buf->ops->unmap(pipe, buf, src);
1288                 if (!ret) {
1289                         ret = sd->len;
1290                         goto out;
1291                 }
1292         }
1293
1294         /*
1295          * No dice, use slow non-atomic map and copy
1296          */
1297         src = buf->ops->map(pipe, buf, 0);
1298
1299         ret = sd->len;
1300         if (copy_to_user(sd->u.userptr, src + buf->offset, sd->len))
1301                 ret = -EFAULT;
1302
1303         buf->ops->unmap(pipe, buf, src);
1304 out:
1305         if (ret > 0)
1306                 sd->u.userptr += ret;
1307         return ret;
1308 }
1309
1310 /*
1311  * For lack of a better implementation, implement vmsplice() to userspace
1312  * as a simple copy of the pipes pages to the user iov.
1313  */
1314 static long vmsplice_to_user(struct file *file, const struct iovec __user *iov,
1315                              unsigned long nr_segs, unsigned int flags)
1316 {
1317         struct pipe_inode_info *pipe;
1318         struct splice_desc sd;
1319         ssize_t size;
1320         int error;
1321         long ret;
1322
1323         pipe = pipe_info(file->f_path.dentry->d_inode);
1324         if (!pipe)
1325                 return -EBADF;
1326
1327         if (pipe->inode)
1328                 mutex_lock(&pipe->inode->i_mutex);
1329
1330         error = ret = 0;
1331         while (nr_segs) {
1332                 void __user *base;
1333                 size_t len;
1334
1335                 /*
1336                  * Get user address base and length for this iovec.
1337                  */
1338                 error = get_user(base, &iov->iov_base);
1339                 if (unlikely(error))
1340                         break;
1341                 error = get_user(len, &iov->iov_len);
1342                 if (unlikely(error))
1343                         break;
1344
1345                 /*
1346                  * Sanity check this iovec. 0 read succeeds.
1347                  */
1348                 if (unlikely(!len))
1349                         break;
1350                 if (unlikely(!base)) {
1351                         error = -EFAULT;
1352                         break;
1353                 }
1354
1355                 if (unlikely(!access_ok(VERIFY_WRITE, base, len))) {
1356                         error = -EFAULT;
1357                         break;
1358                 }
1359
1360                 sd.len = 0;
1361                 sd.total_len = len;
1362                 sd.flags = flags;
1363                 sd.u.userptr = base;
1364                 sd.pos = 0;
1365
1366                 size = __splice_from_pipe(pipe, &sd, pipe_to_user);
1367                 if (size < 0) {
1368                         if (!ret)
1369                                 ret = size;
1370
1371                         break;
1372                 }
1373
1374                 ret += size;
1375
1376                 if (size < len)
1377                         break;
1378
1379                 nr_segs--;
1380                 iov++;
1381         }
1382
1383         if (pipe->inode)
1384                 mutex_unlock(&pipe->inode->i_mutex);
1385
1386         if (!ret)
1387                 ret = error;
1388
1389         return ret;
1390 }
1391
1392 /*
1393  * vmsplice splices a user address range into a pipe. It can be thought of
1394  * as splice-from-memory, where the regular splice is splice-from-file (or
1395  * to file). In both cases the output is a pipe, naturally.
1396  */
1397 static long vmsplice_to_pipe(struct file *file, const struct iovec __user *iov,
1398                              unsigned long nr_segs, unsigned int flags)
1399 {
1400         struct pipe_inode_info *pipe;
1401         struct page *pages[PIPE_BUFFERS];
1402         struct partial_page partial[PIPE_BUFFERS];
1403         struct splice_pipe_desc spd = {
1404                 .pages = pages,
1405                 .partial = partial,
1406                 .flags = flags,
1407                 .ops = &user_page_pipe_buf_ops,
1408                 .spd_release = spd_release_page,
1409         };
1410
1411         pipe = pipe_info(file->f_path.dentry->d_inode);
1412         if (!pipe)
1413                 return -EBADF;
1414
1415         spd.nr_pages = get_iovec_page_array(iov, nr_segs, pages, partial,
1416                                             flags & SPLICE_F_GIFT);
1417         if (spd.nr_pages <= 0)
1418                 return spd.nr_pages;
1419
1420         return splice_to_pipe(pipe, &spd);
1421 }
1422
1423 /*
1424  * Note that vmsplice only really supports true splicing _from_ user memory
1425  * to a pipe, not the other way around. Splicing from user memory is a simple
1426  * operation that can be supported without any funky alignment restrictions
1427  * or nasty vm tricks. We simply map in the user memory and fill them into
1428  * a pipe. The reverse isn't quite as easy, though. There are two possible
1429  * solutions for that:
1430  *
1431  *      - memcpy() the data internally, at which point we might as well just
1432  *        do a regular read() on the buffer anyway.
1433  *      - Lots of nasty vm tricks, that are neither fast nor flexible (it
1434  *        has restriction limitations on both ends of the pipe).
1435  *
1436  * Currently we punt and implement it as a normal copy, see pipe_to_user().
1437  *
1438  */
1439 SYSCALL_DEFINE4(vmsplice, int, fd, const struct iovec __user *, iov,
1440                 unsigned long, nr_segs, unsigned int, flags)
1441 {
1442         struct file *file;
1443         long error;
1444         int fput;
1445
1446         if (unlikely(nr_segs > UIO_MAXIOV))
1447                 return -EINVAL;
1448         else if (unlikely(!nr_segs))
1449                 return 0;
1450
1451         error = -EBADF;
1452         file = fget_light(fd, &fput);
1453         if (file) {
1454                 if (file->f_mode & FMODE_WRITE)
1455                         error = vmsplice_to_pipe(file, iov, nr_segs, flags);
1456                 else if (file->f_mode & FMODE_READ)
1457                         error = vmsplice_to_user(file, iov, nr_segs, flags);
1458
1459                 fput_light(file, fput);
1460         }
1461
1462         return error;
1463 }
1464
1465 SYSCALL_DEFINE6(splice, int, fd_in, loff_t __user *, off_in,
1466                 int, fd_out, loff_t __user *, off_out,
1467                 size_t, len, unsigned int, flags)
1468 {
1469         long error;
1470         struct file *in, *out;
1471         int fput_in, fput_out;
1472
1473         if (unlikely(!len))
1474                 return 0;
1475
1476         error = -EBADF;
1477         in = fget_light(fd_in, &fput_in);
1478         if (in) {
1479                 if (in->f_mode & FMODE_READ) {
1480                         out = fget_light(fd_out, &fput_out);
1481                         if (out) {
1482                                 if (out->f_mode & FMODE_WRITE)
1483                                         error = do_splice(in, off_in,
1484                                                           out, off_out,
1485                                                           len, flags);
1486                                 fput_light(out, fput_out);
1487                         }
1488                 }
1489
1490                 fput_light(in, fput_in);
1491         }
1492
1493         return error;
1494 }
1495
1496 /*
1497  * Make sure there's data to read. Wait for input if we can, otherwise
1498  * return an appropriate error.
1499  */
1500 static int link_ipipe_prep(struct pipe_inode_info *pipe, unsigned int flags)
1501 {
1502         int ret;
1503
1504         /*
1505          * Check ->nrbufs without the inode lock first. This function
1506          * is speculative anyways, so missing one is ok.
1507          */
1508         if (pipe->nrbufs)
1509                 return 0;
1510
1511         ret = 0;
1512         mutex_lock(&pipe->inode->i_mutex);
1513
1514         while (!pipe->nrbufs) {
1515                 if (signal_pending(current)) {
1516                         ret = -ERESTARTSYS;
1517                         break;
1518                 }
1519                 if (!pipe->writers)
1520                         break;
1521                 if (!pipe->waiting_writers) {
1522                         if (flags & SPLICE_F_NONBLOCK) {
1523                                 ret = -EAGAIN;
1524                                 break;
1525                         }
1526                 }
1527                 pipe_wait(pipe);
1528         }
1529
1530         mutex_unlock(&pipe->inode->i_mutex);
1531         return ret;
1532 }
1533
1534 /*
1535  * Make sure there's writeable room. Wait for room if we can, otherwise
1536  * return an appropriate error.
1537  */
1538 static int link_opipe_prep(struct pipe_inode_info *pipe, unsigned int flags)
1539 {
1540         int ret;
1541
1542         /*
1543          * Check ->nrbufs without the inode lock first. This function
1544          * is speculative anyways, so missing one is ok.
1545          */
1546         if (pipe->nrbufs < PIPE_BUFFERS)
1547                 return 0;
1548
1549         ret = 0;
1550         mutex_lock(&pipe->inode->i_mutex);
1551
1552         while (pipe->nrbufs >= PIPE_BUFFERS) {
1553                 if (!pipe->readers) {
1554                         send_sig(SIGPIPE, current, 0);
1555                         ret = -EPIPE;
1556                         break;
1557                 }
1558                 if (flags & SPLICE_F_NONBLOCK) {
1559                         ret = -EAGAIN;
1560                         break;
1561                 }
1562                 if (signal_pending(current)) {
1563                         ret = -ERESTARTSYS;
1564                         break;
1565                 }
1566                 pipe->waiting_writers++;
1567                 pipe_wait(pipe);
1568                 pipe->waiting_writers--;
1569         }
1570
1571         mutex_unlock(&pipe->inode->i_mutex);
1572         return ret;
1573 }
1574
1575 /*
1576  * Link contents of ipipe to opipe.
1577  */
1578 static int link_pipe(struct pipe_inode_info *ipipe,
1579                      struct pipe_inode_info *opipe,
1580                      size_t len, unsigned int flags)
1581 {
1582         struct pipe_buffer *ibuf, *obuf;
1583         int ret = 0, i = 0, nbuf;
1584
1585         /*
1586          * Potential ABBA deadlock, work around it by ordering lock
1587          * grabbing by inode address. Otherwise two different processes
1588          * could deadlock (one doing tee from A -> B, the other from B -> A).
1589          */
1590         inode_double_lock(ipipe->inode, opipe->inode);
1591
1592         do {
1593                 if (!opipe->readers) {
1594                         send_sig(SIGPIPE, current, 0);
1595                         if (!ret)
1596                                 ret = -EPIPE;
1597                         break;
1598                 }
1599
1600                 /*
1601                  * If we have iterated all input buffers or ran out of
1602                  * output room, break.
1603                  */
1604                 if (i >= ipipe->nrbufs || opipe->nrbufs >= PIPE_BUFFERS)
1605                         break;
1606
1607                 ibuf = ipipe->bufs + ((ipipe->curbuf + i) & (PIPE_BUFFERS - 1));
1608                 nbuf = (opipe->curbuf + opipe->nrbufs) & (PIPE_BUFFERS - 1);
1609
1610                 /*
1611                  * Get a reference to this pipe buffer,
1612                  * so we can copy the contents over.
1613                  */
1614                 ibuf->ops->get(ipipe, ibuf);
1615
1616                 obuf = opipe->bufs + nbuf;
1617                 *obuf = *ibuf;
1618
1619                 /*
1620                  * Don't inherit the gift flag, we need to
1621                  * prevent multiple steals of this page.
1622                  */
1623                 obuf->flags &= ~PIPE_BUF_FLAG_GIFT;
1624
1625                 if (obuf->len > len)
1626                         obuf->len = len;
1627
1628                 opipe->nrbufs++;
1629                 ret += obuf->len;
1630                 len -= obuf->len;
1631                 i++;
1632         } while (len);
1633
1634         /*
1635          * return EAGAIN if we have the potential of some data in the
1636          * future, otherwise just return 0
1637          */
1638         if (!ret && ipipe->waiting_writers && (flags & SPLICE_F_NONBLOCK))
1639                 ret = -EAGAIN;
1640
1641         inode_double_unlock(ipipe->inode, opipe->inode);
1642
1643         /*
1644          * If we put data in the output pipe, wakeup any potential readers.
1645          */
1646         if (ret > 0) {
1647                 smp_mb();
1648                 if (waitqueue_active(&opipe->wait))
1649                         wake_up_interruptible(&opipe->wait);
1650                 kill_fasync(&opipe->fasync_readers, SIGIO, POLL_IN);
1651         }
1652
1653         return ret;
1654 }
1655
1656 /*
1657  * This is a tee(1) implementation that works on pipes. It doesn't copy
1658  * any data, it simply references the 'in' pages on the 'out' pipe.
1659  * The 'flags' used are the SPLICE_F_* variants, currently the only
1660  * applicable one is SPLICE_F_NONBLOCK.
1661  */
1662 static long do_tee(struct file *in, struct file *out, size_t len,
1663                    unsigned int flags)
1664 {
1665         struct pipe_inode_info *ipipe = pipe_info(in->f_path.dentry->d_inode);
1666         struct pipe_inode_info *opipe = pipe_info(out->f_path.dentry->d_inode);
1667         int ret = -EINVAL;
1668
1669         /*
1670          * Duplicate the contents of ipipe to opipe without actually
1671          * copying the data.
1672          */
1673         if (ipipe && opipe && ipipe != opipe) {
1674                 /*
1675                  * Keep going, unless we encounter an error. The ipipe/opipe
1676                  * ordering doesn't really matter.
1677                  */
1678                 ret = link_ipipe_prep(ipipe, flags);
1679                 if (!ret) {
1680                         ret = link_opipe_prep(opipe, flags);
1681                         if (!ret)
1682                                 ret = link_pipe(ipipe, opipe, len, flags);
1683                 }
1684         }
1685
1686         return ret;
1687 }
1688
1689 SYSCALL_DEFINE4(tee, int, fdin, int, fdout, size_t, len, unsigned int, flags)
1690 {
1691         struct file *in;
1692         int error, fput_in;
1693
1694         if (unlikely(!len))
1695                 return 0;
1696
1697         error = -EBADF;
1698         in = fget_light(fdin, &fput_in);
1699         if (in) {
1700                 if (in->f_mode & FMODE_READ) {
1701                         int fput_out;
1702                         struct file *out = fget_light(fdout, &fput_out);
1703
1704                         if (out) {
1705                                 if (out->f_mode & FMODE_WRITE)
1706                                         error = do_tee(in, out, len, flags);
1707                                 fput_light(out, fput_out);
1708                         }
1709                 }
1710                 fput_light(in, fput_in);
1711         }
1712
1713         return error;
1714 }