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/mm_inline.h>
  25 #include <linux/swap.h>
  26 #include <linux/writeback.h>
  27 #include <linux/buffer_head.h>
  28 #include <linux/module.h>
  29 #include <linux/syscalls.h>
  30 #include <linux/uio.h>
  31 #include <linux/security.h>
  32
  33 /*
  34  * Attempt to steal a page from a pipe buffer. This should perhaps go into
  35  * a vm helper function, it's already simplified quite a bit by the
  36  * addition of remove_mapping(). If success is returned, the caller may
  37  * attempt to reuse this page for another destination.
  38  */
  39 static int page_cache_pipe_buf_steal(struct pipe_inode_info *pipe,
  40                                      struct pipe_buffer *buf)
  41 {
  42         struct page *page = buf->page;
  43         struct address_space *mapping;
  44
  45         lock_page(page);
  46
  47         mapping = page_mapping(page);
  48         if (mapping) {
  49                 WARN_ON(!PageUptodate(page));
  50
  51                 /*
  52                  * At least for ext2 with nobh option, we need to wait on
  53                  * writeback completing on this page, since we'll remove it
  54                  * from the pagecache.  Otherwise truncate wont wait on the
  55                  * page, allowing the disk blocks to be reused by someone else
  56                  * before we actually wrote our data to them. fs corruption
  57                  * ensues.
  58                  */
  59                 wait_on_page_writeback(page);
  60
  61                 if (PagePrivate(page))
  62                         try_to_release_page(page, GFP_KERNEL);
  63
  64                 /*
  65                  * If we succeeded in removing the mapping, set LRU flag
  66                  * and return good.
  67                  */
  68                 if (remove_mapping(mapping, page)) {
  69                         buf->flags |= PIPE_BUF_FLAG_LRU;
  70                         return 0;
  71                 }
  72         }
  73
  74         /*
  75          * Raced with truncate or failed to remove page from current
  76          * address space, unlock and return failure.
  77          */
  78         unlock_page(page);
  79         return 1;
  80 }
  81
  82 static void page_cache_pipe_buf_release(struct pipe_inode_info *pipe,
  83                                         struct pipe_buffer *buf)
  84 {
  85         page_cache_release(buf->page);
  86         buf->flags &= ~PIPE_BUF_FLAG_LRU;
  87 }
  88
  89 /*
  90  * Check whether the contents of buf is OK to access. Since the content
  91  * is a page cache page, IO may be in flight.
  92  */
  93 static int page_cache_pipe_buf_confirm(struct pipe_inode_info *pipe,
  94                                        struct pipe_buffer *buf)
  95 {
  96         struct page *page = buf->page;
  97         int err;
  98
  99         if (!PageUptodate(page)) {
 100                 lock_page(page);
 101
 102                 /*
 103                  * Page got truncated/unhashed. This will cause a 0-byte
 104                  * splice, if this is the first page.
 105                  */
 106                 if (!page->mapping) {
 107                         err = -ENODATA;
 108                         goto error;
 109                 }
 110
 111                 /*
 112                  * Uh oh, read-error from disk.
 113                  */
 114                 if (!PageUptodate(page)) {
 115                         err = -EIO;
 116                         goto error;
 117                 }
 118
 119                 /*
 120                  * Page is ok afterall, we are done.
 121                  */
 122                 unlock_page(page);
 123         }
 124
 125         return 0;
 126 error:
 127         unlock_page(page);
 128         return err;
 129 }
 130
 131 static const struct pipe_buf_operations page_cache_pipe_buf_ops = {
 132         .can_merge = 0,
 133         .map = generic_pipe_buf_map,
 134         .unmap = generic_pipe_buf_unmap,
 135         .confirm = page_cache_pipe_buf_confirm,
 136         .release = page_cache_pipe_buf_release,
 137         .steal = page_cache_pipe_buf_steal,
 138         .get = generic_pipe_buf_get,
 139 };
 140
 141 static int user_page_pipe_buf_steal(struct pipe_inode_info *pipe,
 142                                     struct pipe_buffer *buf)
 143 {
 144         if (!(buf->flags & PIPE_BUF_FLAG_GIFT))
 145                 return 1;
 146
 147         buf->flags |= PIPE_BUF_FLAG_LRU;
 148         return generic_pipe_buf_steal(pipe, buf);
 149 }
 150
 151 static const struct pipe_buf_operations user_page_pipe_buf_ops = {
 152         .can_merge = 0,
 153         .map = generic_pipe_buf_map,
 154         .unmap = generic_pipe_buf_unmap,
 155         .confirm = generic_pipe_buf_confirm,
 156         .release = page_cache_pipe_buf_release,
 157         .steal = user_page_pipe_buf_steal,
 158         .get = generic_pipe_buf_get,
 159 };
 160
 161 /**
 162  * splice_to_pipe - fill passed data into a pipe
 163  * @pipe:       pipe to fill
 164  * @spd:        data to fill
 165  *
 166  * Description:
 167  *    @spd contains a map of pages and len/offset tuples, along with
 168  *    the struct pipe_buf_operations associated with these pages. This
 169  *    function will link that data to the pipe.
 170  *
 171  */
 172 ssize_t splice_to_pipe(struct pipe_inode_info *pipe,
 173                        struct splice_pipe_desc *spd)
 174 {
 175         unsigned int spd_pages = spd->nr_pages;
 176         int ret, do_wakeup, page_nr;
 177
 178         ret = 0;
 179         do_wakeup = 0;
 180         page_nr = 0;
 181
 182         if (pipe->inode)
 183                 mutex_lock(&pipe->inode->i_mutex);
 184
 185         for (;;) {
 186                 if (!pipe->readers) {
 187                         send_sig(SIGPIPE, current, 0);
 188                         if (!ret)
 189                                 ret = -EPIPE;
 190                         break;
 191                 }
 192
 193                 if (pipe->nrbufs < PIPE_BUFFERS) {
 194                         int newbuf = (pipe->curbuf + pipe->nrbufs) & (PIPE_BUFFERS - 1);
 195                         struct pipe_buffer *buf = pipe->bufs + newbuf;
 196
 197                         buf->page = spd->pages[page_nr];
 198                         buf->offset = spd->partial[page_nr].offset;
 199                         buf->len = spd->partial[page_nr].len;
 200                         buf->private = spd->partial[page_nr].private;
 201                         buf->ops = spd->ops;
 202                         if (spd->flags & SPLICE_F_GIFT)
 203                                 buf->flags |= PIPE_BUF_FLAG_GIFT;
 204
 205                         pipe->nrbufs++;
 206                         page_nr++;
 207                         ret += buf->len;
 208
 209                         if (pipe->inode)
 210                                 do_wakeup = 1;
 211
 212                         if (!--spd->nr_pages)
 213                                 break;
 214                         if (pipe->nrbufs < PIPE_BUFFERS)
 215                                 continue;
 216
 217                         break;
 218                 }
 219
 220                 if (spd->flags & SPLICE_F_NONBLOCK) {
 221                         if (!ret)
 222                                 ret = -EAGAIN;
 223                         break;
 224                 }
 225
 226                 if (signal_pending(current)) {
 227                         if (!ret)
 228                                 ret = -ERESTARTSYS;
 229                         break;
 230                 }
 231
 232                 if (do_wakeup) {
 233                         smp_mb();
 234                         if (waitqueue_active(&pipe->wait))
 235                                 wake_up_interruptible_sync(&pipe->wait);
 236                         kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
 237                         do_wakeup = 0;
 238                 }
 239
 240                 pipe->waiting_writers++;
 241                 pipe_wait(pipe);
 242                 pipe->waiting_writers--;
 243         }
 244
 245         if (pipe->inode) {
 246                 mutex_unlock(&pipe->inode->i_mutex);
 247
 248                 if (do_wakeup) {
 249                         smp_mb();
 250                         if (waitqueue_active(&pipe->wait))
 251                                 wake_up_interruptible(&pipe->wait);
 252                         kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
 253                 }
 254         }
 255
 256         while (page_nr < spd_pages)
 257                 page_cache_release(spd->pages[page_nr++]);
 258
 259         return ret;
 260 }
 261
 262 static int
 263 __generic_file_splice_read(struct file *in, loff_t *ppos,
 264                            struct pipe_inode_info *pipe, size_t len,
 265                            unsigned int flags)
 266 {
 267         struct address_space *mapping = in->f_mapping;
 268         unsigned int loff, nr_pages, req_pages;
 269         struct page *pages[PIPE_BUFFERS];
 270         struct partial_page partial[PIPE_BUFFERS];
 271         struct page *page;
 272         pgoff_t index, end_index;
 273         loff_t isize;
 274         int error, page_nr;
 275         struct splice_pipe_desc spd = {
 276                 .pages = pages,
 277                 .partial = partial,
 278                 .flags = flags,
 279                 .ops = &page_cache_pipe_buf_ops,
 280         };
 281
 282         index = *ppos >> PAGE_CACHE_SHIFT;
 283         loff = *ppos & ~PAGE_CACHE_MASK;
 284         req_pages = (len + loff + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
 285         nr_pages = min(req_pages, (unsigned)PIPE_BUFFERS);
 286
 287         /*
 288          * Lookup the (hopefully) full range of pages we need.
 289          */
 290         spd.nr_pages = find_get_pages_contig(mapping, index, nr_pages, pages);
 291         index += spd.nr_pages;
 292
 293         /*
 294          * If find_get_pages_contig() returned fewer pages than we needed,
 295          * readahead/allocate the rest and fill in the holes.
 296          */
 297         if (spd.nr_pages < nr_pages)
 298                 page_cache_sync_readahead(mapping, &in->f_ra, in,
 299                                 index, req_pages - spd.nr_pages);
 300
 301         error = 0;
 302         while (spd.nr_pages < nr_pages) {
 303                 /*
 304                  * Page could be there, find_get_pages_contig() breaks on
 305                  * the first hole.
 306                  */
 307                 page = find_get_page(mapping, index);
 308                 if (!page) {
 309                         /*
 310                          * page didn't exist, allocate one.
 311                          */
 312                         page = page_cache_alloc_cold(mapping);
 313                         if (!page)
 314                                 break;
 315
 316                         error = add_to_page_cache_lru(page, mapping, index,
 317                                               GFP_KERNEL);
 318                         if (unlikely(error)) {
 319                                 page_cache_release(page);
 320                                 if (error == -EEXIST)
 321                                         continue;
 322                                 break;
 323                         }
 324                         /*
 325                          * add_to_page_cache() locks the page, unlock it
 326                          * to avoid convoluting the logic below even more.
 327                          */
 328                         unlock_page(page);
 329                 }
 330
 331                 pages[spd.nr_pages++] = page;
 332                 index++;
 333         }
 334
 335         /*
 336          * Now loop over the map and see if we need to start IO on any
 337          * pages, fill in the partial map, etc.
 338          */
 339         index = *ppos >> PAGE_CACHE_SHIFT;
 340         nr_pages = spd.nr_pages;
 341         spd.nr_pages = 0;
 342         for (page_nr = 0; page_nr < nr_pages; page_nr++) {
 343                 unsigned int this_len;
 344
 345                 if (!len)
 346                         break;
 347
 348                 /*
 349                  * this_len is the max we'll use from this page
 350                  */
 351                 this_len = min_t(unsigned long, len, PAGE_CACHE_SIZE - loff);
 352                 page = pages[page_nr];
 353
 354                 if (PageReadahead(page))
 355                         page_cache_async_readahead(mapping, &in->f_ra, in,
 356                                         page, index, req_pages - page_nr);
 357
 358                 /*
 359                  * If the page isn't uptodate, we may need to start io on it
 360                  */
 361                 if (!PageUptodate(page)) {
 362                         /*
 363                          * If in nonblock mode then dont block on waiting
 364                          * for an in-flight io page
 365                          */
 366                         if (flags & SPLICE_F_NONBLOCK) {
 367                                 if (TestSetPageLocked(page))
 368                                         break;
 369                         } else
 370                                 lock_page(page);
 371
 372                         /*
 373                          * page was truncated, stop here. if this isn't the
 374                          * first page, we'll just complete what we already
 375                          * added
 376                          */
 377                         if (!page->mapping) {
 378                                 unlock_page(page);
 379                                 break;
 380                         }
 381                         /*
 382                          * page was already under io and is now done, great
 383                          */
 384                         if (PageUptodate(page)) {
 385                                 unlock_page(page);
 386                                 goto fill_it;
 387                         }
 388
 389                         /*
 390                          * need to read in the page
 391                          */
 392                         error = mapping->a_ops->readpage(in, page);
 393                         if (unlikely(error)) {
 394                                 /*
 395                                  * We really should re-lookup the page here,
 396                                  * but it complicates things a lot. Instead
 397                                  * lets just do what we already stored, and
 398                                  * we'll get it the next time we are called.
 399                                  */
 400                                 if (error == AOP_TRUNCATED_PAGE)
 401                                         error = 0;
 402
 403                                 break;
 404                         }
 405                 }
 406 fill_it:
 407                 /*
 408                  * i_size must be checked after PageUptodate.
 409                  */
 410                 isize = i_size_read(mapping->host);
 411                 end_index = (isize - 1) >> PAGE_CACHE_SHIFT;
 412                 if (unlikely(!isize || index > end_index))
 413                         break;
 414
 415                 /*
 416                  * if this is the last page, see if we need to shrink
 417                  * the length and stop
 418                  */
 419                 if (end_index == index) {
 420                         unsigned int plen;
 421
 422                         /*
 423                          * max good bytes in this page
 424                          */
 425                         plen = ((isize - 1) & ~PAGE_CACHE_MASK) + 1;
 426                         if (plen <= loff)
 427                                 break;
 428
 429                         /*
 430                          * force quit after adding this page
 431                          */
 432                         this_len = min(this_len, plen - loff);
 433                         len = this_len;
 434                 }
 435
 436                 partial[page_nr].offset = loff;
 437                 partial[page_nr].len = this_len;
 438                 len -= this_len;
 439                 loff = 0;
 440                 spd.nr_pages++;
 441                 index++;
 442         }
 443
 444         /*
 445          * Release any pages at the end, if we quit early. 'page_nr' is how far
 446          * we got, 'nr_pages' is how many pages are in the map.
 447          */
 448         while (page_nr < nr_pages)
 449                 page_cache_release(pages[page_nr++]);
 450         in->f_ra.prev_index = index;
 451
 452         if (spd.nr_pages)
 453                 return splice_to_pipe(pipe, &spd);
 454
 455         return error;
 456 }
 457
 458 /**
 459  * generic_file_splice_read - splice data from file to a pipe
 460  * @in:         file to splice from
 461  * @ppos:       position in @in
 462  * @pipe:       pipe to splice to
 463  * @len:        number of bytes to splice
 464  * @flags:      splice modifier flags
 465  *
 466  * Description:
 467  *    Will read pages from given file and fill them into a pipe. Can be
 468  *    used as long as the address_space operations for the source implements
 469  *    a readpage() hook.
 470  *
 471  */
 472 ssize_t generic_file_splice_read(struct file *in, loff_t *ppos,
 473                                  struct pipe_inode_info *pipe, size_t len,
 474                                  unsigned int flags)
 475 {
 476         ssize_t spliced;
 477         int ret;
 478         loff_t isize, left;
 479
 480         isize = i_size_read(in->f_mapping->host);
 481         if (unlikely(*ppos >= isize))
 482                 return 0;
 483
 484         left = isize - *ppos;
 485         if (unlikely(left < len))
 486                 len = left;
 487
 488         ret = 0;
 489         spliced = 0;
 490         while (len && !spliced) {
 491                 ret = __generic_file_splice_read(in, ppos, pipe, len, flags);
 492
 493                 if (ret < 0)
 494                         break;
 495                 else if (!ret) {
 496                         if (spliced)
 497                                 break;
 498                         if (flags & SPLICE_F_NONBLOCK) {
 499                                 ret = -EAGAIN;
 500                                 break;
 501                         }
 502                 }
 503
 504                 *ppos += ret;
 505                 len -= ret;
 506                 spliced += ret;
 507         }
 508
 509         if (spliced)
 510                 return spliced;
 511
 512         return ret;
 513 }
 514
 515 EXPORT_SYMBOL(generic_file_splice_read);
 516
 517 /*
 518  * Send 'sd->len' bytes to socket from 'sd->file' at position 'sd->pos'
 519  * using sendpage(). Return the number of bytes sent.
 520  */
 521 static int pipe_to_sendpage(struct pipe_inode_info *pipe,
 522                             struct pipe_buffer *buf, struct splice_desc *sd)
 523 {
 524         struct file *file = sd->u.file;
 525         loff_t pos = sd->pos;
 526         int ret, more;
 527
 528         ret = buf->ops->confirm(pipe, buf);
 529         if (!ret) {
 530                 more = (sd->flags & SPLICE_F_MORE) || sd->len < sd->total_len;
 531
 532                 ret = file->f_op->sendpage(file, buf->page, buf->offset,
 533                                            sd->len, &pos, more);
 534         }
 535
 536         return ret;
 537 }
 538
 539 /*
 540  * This is a little more tricky than the file -> pipe splicing. There are
 541  * basically three cases:
 542  *
 543  *      - Destination page already exists in the address space and there
 544  *        are users of it. For that case we have no other option that
 545  *        copying the data. Tough luck.
 546  *      - Destination page already exists in the address space, but there
 547  *        are no users of it. Make sure it's uptodate, then drop it. Fall
 548  *        through to last case.
 549  *      - Destination page does not exist, we can add the pipe page to
 550  *        the page cache and avoid the copy.
 551  *
 552  * If asked to move pages to the output file (SPLICE_F_MOVE is set in
 553  * sd->flags), we attempt to migrate pages from the pipe to the output
 554  * file address space page cache. This is possible if no one else has
 555  * the pipe page referenced outside of the pipe and page cache. If
 556  * SPLICE_F_MOVE isn't set, or we cannot move the page, we simply create
 557  * a new page in the output file page cache and fill/dirty that.
 558  */
 559 static int pipe_to_file(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
 560                         struct splice_desc *sd)
 561 {
 562         struct file *file = sd->u.file;
 563         struct address_space *mapping = file->f_mapping;
 564         unsigned int offset, this_len;
 565         struct page *page;
 566         pgoff_t index;
 567         int ret;
 568
 569         /*
 570          * make sure the data in this buffer is uptodate
 571          */
 572         ret = buf->ops->confirm(pipe, buf);
 573         if (unlikely(ret))
 574                 return ret;
 575
 576         index = sd->pos >> PAGE_CACHE_SHIFT;
 577         offset = sd->pos & ~PAGE_CACHE_MASK;
 578
 579         this_len = sd->len;
 580         if (this_len + offset > PAGE_CACHE_SIZE)
 581                 this_len = PAGE_CACHE_SIZE - offset;
 582
 583 find_page:
 584         page = find_lock_page(mapping, index);
 585         if (!page) {
 586                 ret = -ENOMEM;
 587                 page = page_cache_alloc_cold(mapping);
 588                 if (unlikely(!page))
 589                         goto out_ret;
 590
 591                 /*
 592                  * This will also lock the page
 593                  */
 594                 ret = add_to_page_cache_lru(page, mapping, index,
 595                                             GFP_KERNEL);
 596                 if (unlikely(ret))
 597                         goto out_release;
 598         }
 599
 600         ret = mapping->a_ops->prepare_write(file, page, offset, offset+this_len);
 601         if (unlikely(ret)) {
 602                 loff_t isize = i_size_read(mapping->host);
 603
 604                 if (ret != AOP_TRUNCATED_PAGE)
 605                         unlock_page(page);
 606                 page_cache_release(page);
 607                 if (ret == AOP_TRUNCATED_PAGE)
 608                         goto find_page;
 609
 610                 /*
 611                  * prepare_write() may have instantiated a few blocks
 612                  * outside i_size.  Trim these off again.
 613                  */
 614                 if (sd->pos + this_len > isize)
 615                         vmtruncate(mapping->host, isize);
 616
 617                 goto out_ret;
 618         }
 619
 620         if (buf->page != page) {
 621                 /*
 622                  * Careful, ->map() uses KM_USER0!
 623                  */
 624                 char *src = buf->ops->map(pipe, buf, 1);
 625                 char *dst = kmap_atomic(page, KM_USER1);
 626
 627                 memcpy(dst + offset, src + buf->offset, this_len);
 628                 flush_dcache_page(page);
 629                 kunmap_atomic(dst, KM_USER1);
 630                 buf->ops->unmap(pipe, buf, src);
 631         }
 632
 633         ret = mapping->a_ops->commit_write(file, page, offset, offset+this_len);
 634         if (ret) {
 635                 if (ret == AOP_TRUNCATED_PAGE) {
 636                         page_cache_release(page);
 637                         goto find_page;
 638                 }
 639                 if (ret < 0)
 640                         goto out;
 641                 /*
 642                  * Partial write has happened, so 'ret' already initialized by
 643                  * number of bytes written, Where is nothing we have to do here.
 644                  */
 645         } else
 646                 ret = this_len;
 647         /*
 648          * Return the number of bytes written and mark page as
 649          * accessed, we are now done!
 650          */
 651         mark_page_accessed(page);
 652 out:
 653         unlock_page(page);
 654 out_release:
 655         page_cache_release(page);
 656 out_ret:
 657         return ret;
 658 }
 659
 660 /**
 661  * __splice_from_pipe - splice data from a pipe to given actor
 662  * @pipe:       pipe to splice from
 663  * @sd:         information to @actor
 664  * @actor:      handler that splices the data
 665  *
 666  * Description:
 667  *    This function does little more than loop over the pipe and call
 668  *    @actor to do the actual moving of a single struct pipe_buffer to
 669  *    the desired destination. See pipe_to_file, pipe_to_sendpage, or
 670  *    pipe_to_user.
 671  *
 672  */
 673 ssize_t __splice_from_pipe(struct pipe_inode_info *pipe, struct splice_desc *sd,
 674                            splice_actor *actor)
 675 {
 676         int ret, do_wakeup, err;
 677
 678         ret = 0;
 679         do_wakeup = 0;
 680
 681         for (;;) {
 682                 if (pipe->nrbufs) {
 683                         struct pipe_buffer *buf = pipe->bufs + pipe->curbuf;
 684                         const struct pipe_buf_operations *ops = buf->ops;
 685
 686                         sd->len = buf->len;
 687                         if (sd->len > sd->total_len)
 688                                 sd->len = sd->total_len;
 689
 690                         err = actor(pipe, buf, sd);
 691                         if (err <= 0) {
 692                                 if (!ret && err != -ENODATA)
 693                                         ret = err;
 694
 695                                 break;
 696                         }
 697
 698                         ret += err;
 699                         buf->offset += err;
 700                         buf->len -= err;
 701
 702                         sd->len -= err;
 703                         sd->pos += err;
 704                         sd->total_len -= err;
 705                         if (sd->len)
 706                                 continue;
 707
 708                         if (!buf->len) {
 709                                 buf->ops = NULL;
 710                                 ops->release(pipe, buf);
 711                                 pipe->curbuf = (pipe->curbuf + 1) & (PIPE_BUFFERS - 1);
 712                                 pipe->nrbufs--;
 713                                 if (pipe->inode)
 714                                         do_wakeup = 1;
 715                         }
 716
 717                         if (!sd->total_len)
 718                                 break;
 719                 }
 720
 721                 if (pipe->nrbufs)
 722                         continue;
 723                 if (!pipe->writers)
 724                         break;
 725                 if (!pipe->waiting_writers) {
 726                         if (ret)
 727                                 break;
 728                 }
 729
 730                 if (sd->flags & SPLICE_F_NONBLOCK) {
 731                         if (!ret)
 732                                 ret = -EAGAIN;
 733                         break;
 734                 }
 735
 736                 if (signal_pending(current)) {
 737                         if (!ret)
 738                                 ret = -ERESTARTSYS;
 739                         break;
 740                 }
 741
 742                 if (do_wakeup) {
 743                         smp_mb();
 744                         if (waitqueue_active(&pipe->wait))
 745                                 wake_up_interruptible_sync(&pipe->wait);
 746                         kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
 747                         do_wakeup = 0;
 748                 }
 749
 750                 pipe_wait(pipe);
 751         }
 752
 753         if (do_wakeup) {
 754                 smp_mb();
 755                 if (waitqueue_active(&pipe->wait))
 756                         wake_up_interruptible(&pipe->wait);
 757                 kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
 758         }
 759
 760         return ret;
 761 }
 762 EXPORT_SYMBOL(__splice_from_pipe);
 763
 764 /**
 765  * splice_from_pipe - splice data from a pipe to a file
 766  * @pipe:       pipe to splice from
 767  * @out:        file to splice to
 768  * @ppos:       position in @out
 769  * @len:        how many bytes to splice
 770  * @flags:      splice modifier flags
 771  * @actor:      handler that splices the data
 772  *
 773  * Description:
 774  *    See __splice_from_pipe. This function locks the input and output inodes,
 775  *    otherwise it's identical to __splice_from_pipe().
 776  *
 777  */
 778 ssize_t splice_from_pipe(struct pipe_inode_info *pipe, struct file *out,
 779                          loff_t *ppos, size_t len, unsigned int flags,
 780                          splice_actor *actor)
 781 {
 782         ssize_t ret;
 783         struct inode *inode = out->f_mapping->host;
 784         struct splice_desc sd = {
 785                 .total_len = len,
 786                 .flags = flags,
 787                 .pos = *ppos,
 788                 .u.file = out,
 789         };
 790
 791         /*
 792          * The actor worker might be calling ->prepare_write and
 793          * ->commit_write. Most of the time, these expect i_mutex to
 794          * be held. Since this may result in an ABBA deadlock with
 795          * pipe->inode, we have to order lock acquiry here.
 796          */
 797         inode_double_lock(inode, pipe->inode);
 798         ret = __splice_from_pipe(pipe, &sd, actor);
 799         inode_double_unlock(inode, pipe->inode);
 800
 801         return ret;
 802 }
 803
 804 /**
 805  * generic_file_splice_write_nolock - generic_file_splice_write without mutexes
 806  * @pipe:       pipe info
 807  * @out:        file to write to
 808  * @ppos:       position in @out
 809  * @len:        number of bytes to splice
 810  * @flags:      splice modifier flags
 811  *
 812  * Description:
 813  *    Will either move or copy pages (determined by @flags options) from
 814  *    the given pipe inode to the given file. The caller is responsible
 815  *    for acquiring i_mutex on both inodes.
 816  *
 817  */
 818 ssize_t
 819 generic_file_splice_write_nolock(struct pipe_inode_info *pipe, struct file *out,
 820                                  loff_t *ppos, size_t len, unsigned int flags)
 821 {
 822         struct address_space *mapping = out->f_mapping;
 823         struct inode *inode = mapping->host;
 824         struct splice_desc sd = {
 825                 .total_len = len,
 826                 .flags = flags,
 827                 .pos = *ppos,
 828                 .u.file = out,
 829         };
 830         ssize_t ret;
 831         int err;
 832
 833         err = remove_suid(out->f_path.dentry);
 834         if (unlikely(err))
 835                 return err;
 836
 837         ret = __splice_from_pipe(pipe, &sd, pipe_to_file);
 838         if (ret > 0) {
 839                 unsigned long nr_pages;
 840
 841                 *ppos += ret;
 842                 nr_pages = (ret + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
 843
 844                 /*
 845                  * If file or inode is SYNC and we actually wrote some data,
 846                  * sync it.
 847                  */
 848                 if (unlikely((out->f_flags & O_SYNC) || IS_SYNC(inode))) {
 849                         err = generic_osync_inode(inode, mapping,
 850                                                   OSYNC_METADATA|OSYNC_DATA);
 851
 852                         if (err)
 853                                 ret = err;
 854                 }
 855                 balance_dirty_pages_ratelimited_nr(mapping, nr_pages);
 856         }
 857
 858         return ret;
 859 }
 860
 861 EXPORT_SYMBOL(generic_file_splice_write_nolock);
 862
 863 /**
 864  * generic_file_splice_write - splice data from a pipe to a file
 865  * @pipe:       pipe info
 866  * @out:        file to write to
 867  * @ppos:       position in @out
 868  * @len:        number of bytes to splice
 869  * @flags:      splice modifier flags
 870  *
 871  * Description:
 872  *    Will either move or copy pages (determined by @flags options) from
 873  *    the given pipe inode to the given file.
 874  *
 875  */
 876 ssize_t
 877 generic_file_splice_write(struct pipe_inode_info *pipe, struct file *out,
 878                           loff_t *ppos, size_t len, unsigned int flags)
 879 {
 880         struct address_space *mapping = out->f_mapping;
 881         struct inode *inode = mapping->host;
 882         ssize_t ret;
 883         int err;
 884
 885         err = should_remove_suid(out->f_path.dentry);
 886         if (unlikely(err)) {
 887                 mutex_lock(&inode->i_mutex);
 888                 err = __remove_suid(out->f_path.dentry, err);
 889                 mutex_unlock(&inode->i_mutex);
 890                 if (err)
 891                         return err;
 892         }
 893
 894         ret = splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_file);
 895         if (ret > 0) {
 896                 unsigned long nr_pages;
 897
 898                 *ppos += ret;
 899                 nr_pages = (ret + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
 900
 901                 /*
 902                  * If file or inode is SYNC and we actually wrote some data,
 903                  * sync it.
 904                  */
 905                 if (unlikely((out->f_flags & O_SYNC) || IS_SYNC(inode))) {
 906                         mutex_lock(&inode->i_mutex);
 907                         err = generic_osync_inode(inode, mapping,
 908                                                   OSYNC_METADATA|OSYNC_DATA);
 909                         mutex_unlock(&inode->i_mutex);
 910
 911                         if (err)
 912                                 ret = err;
 913                 }
 914                 balance_dirty_pages_ratelimited_nr(mapping, nr_pages);
 915         }
 916
 917         return ret;
 918 }
 919
 920 EXPORT_SYMBOL(generic_file_splice_write);
 921
 922 /**
 923  * generic_splice_sendpage - splice data from a pipe to a socket
 924  * @pipe:       pipe to splice from
 925  * @out:        socket to write to
 926  * @ppos:       position in @out
 927  * @len:        number of bytes to splice
 928  * @flags:      splice modifier flags
 929  *
 930  * Description:
 931  *    Will send @len bytes from the pipe to a network socket. No data copying
 932  *    is involved.
 933  *
 934  */
 935 ssize_t generic_splice_sendpage(struct pipe_inode_info *pipe, struct file *out,
 936                                 loff_t *ppos, size_t len, unsigned int flags)
 937 {
 938         return splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_sendpage);
 939 }
 940
 941 EXPORT_SYMBOL(generic_splice_sendpage);
 942
 943 /*
 944  * Attempt to initiate a splice from pipe to file.
 945  */
 946 static long do_splice_from(struct pipe_inode_info *pipe, struct file *out,
 947                            loff_t *ppos, size_t len, unsigned int flags)
 948 {
 949         int ret;
 950
 951         if (unlikely(!out->f_op || !out->f_op->splice_write))
 952                 return -EINVAL;
 953
 954         if (unlikely(!(out->f_mode & FMODE_WRITE)))
 955                 return -EBADF;
 956
 957         ret = rw_verify_area(WRITE, out, ppos, len);
 958         if (unlikely(ret < 0))
 959                 return ret;
 960
 961         ret = security_file_permission(out, MAY_WRITE);
 962         if (unlikely(ret < 0))
 963                 return ret;
 964
 965         return out->f_op->splice_write(pipe, out, ppos, len, flags);
 966 }
 967
 968 /*
 969  * Attempt to initiate a splice from a file to a pipe.
 970  */
 971 static long do_splice_to(struct file *in, loff_t *ppos,
 972                          struct pipe_inode_info *pipe, size_t len,
 973                          unsigned int flags)
 974 {
 975         int ret;
 976
 977         if (unlikely(!in->f_op || !in->f_op->splice_read))
 978                 return -EINVAL;
 979
 980         if (unlikely(!(in->f_mode & FMODE_READ)))
 981                 return -EBADF;
 982
 983         ret = rw_verify_area(READ, in, ppos, len);
 984         if (unlikely(ret < 0))
 985                 return ret;
 986
 987         ret = security_file_permission(in, MAY_READ);
 988         if (unlikely(ret < 0))
 989                 return ret;
 990
 991         return in->f_op->splice_read(in, ppos, pipe, len, flags);
 992 }
 993
 994 /**
 995  * splice_direct_to_actor - splices data directly between two non-pipes
 996  * @in:         file to splice from
 997  * @sd:         actor information on where to splice to
 998  * @actor:      handles the data splicing
 999  *
1000  * Description:
1001  *    This is a special case helper to splice directly between two
1002  *    points, without requiring an explicit pipe. Internally an allocated
1003  *    pipe is cached in the process, and reused during the lifetime of
1004  *    that process.
1005  *
1006  */
1007 ssize_t splice_direct_to_actor(struct file *in, struct splice_desc *sd,
1008                                splice_direct_actor *actor)
1009 {
1010         struct pipe_inode_info *pipe;
1011         long ret, bytes;
1012         umode_t i_mode;
1013         size_t len;
1014         int i, flags;
1015
1016         /*
1017          * We require the input being a regular file, as we don't want to
1018          * randomly drop data for eg socket -> socket splicing. Use the
1019          * piped splicing for that!
1020          */
1021         i_mode = in->f_path.dentry->d_inode->i_mode;
1022         if (unlikely(!S_ISREG(i_mode) && !S_ISBLK(i_mode)))
1023                 return -EINVAL;
1024
1025         /*
1026          * neither in nor out is a pipe, setup an internal pipe attached to
1027          * 'out' and transfer the wanted data from 'in' to 'out' through that
1028          */
1029         pipe = current->splice_pipe;
1030         if (unlikely(!pipe)) {
1031                 pipe = alloc_pipe_info(NULL);
1032                 if (!pipe)
1033                         return -ENOMEM;
1034
1035                 /*
1036                  * We don't have an immediate reader, but we'll read the stuff
1037                  * out of the pipe right after the splice_to_pipe(). So set
1038                  * PIPE_READERS appropriately.
1039                  */
1040                 pipe->readers = 1;
1041
1042                 current->splice_pipe = pipe;
1043         }
1044
1045         /*
1046          * Do the splice.
1047          */
1048         ret = 0;
1049         bytes = 0;
1050         len = sd->total_len;
1051         flags = sd->flags;
1052
1053         /*
1054          * Don't block on output, we have to drain the direct pipe.
1055          */
1056         sd->flags &= ~SPLICE_F_NONBLOCK;
1057
1058         while (len) {
1059                 size_t read_len;
1060                 loff_t pos = sd->pos;
1061
1062                 ret = do_splice_to(in, &pos, pipe, len, flags);
1063                 if (unlikely(ret <= 0))
1064                         goto out_release;
1065
1066                 read_len = ret;
1067                 sd->total_len = read_len;
1068
1069                 /*
1070                  * NOTE: nonblocking mode only applies to the input. We
1071                  * must not do the output in nonblocking mode as then we
1072                  * could get stuck data in the internal pipe:
1073                  */
1074                 ret = actor(pipe, sd);
1075                 if (unlikely(ret <= 0))
1076                         goto out_release;
1077
1078                 bytes += ret;
1079                 len -= ret;
1080                 sd->pos = pos;
1081
1082                 if (ret < read_len)
1083                         goto out_release;
1084         }
1085
1086         pipe->nrbufs = pipe->curbuf = 0;
1087         return bytes;
1088
1089 out_release:
1090         /*
1091          * If we did an incomplete transfer we must release
1092          * the pipe buffers in question:
1093          */
1094         for (i = 0; i < PIPE_BUFFERS; i++) {
1095                 struct pipe_buffer *buf = pipe->bufs + i;
1096
1097                 if (buf->ops) {
1098                         buf->ops->release(pipe, buf);
1099                         buf->ops = NULL;
1100                 }
1101         }
1102         pipe->nrbufs = pipe->curbuf = 0;
1103
1104         /*
1105          * If we transferred some data, return the number of bytes:
1106          */
1107         if (bytes > 0)
1108                 return bytes;
1109
1110         return ret;
1111
1112 }
1113 EXPORT_SYMBOL(splice_direct_to_actor);
1114
1115 static int direct_splice_actor(struct pipe_inode_info *pipe,
1116                                struct splice_desc *sd)
1117 {
1118         struct file *file = sd->u.file;
1119
1120         return do_splice_from(pipe, file, &sd->pos, sd->total_len, sd->flags);
1121 }
1122
1123 /**
1124  * do_splice_direct - splices data directly between two files
1125  * @in:         file to splice from
1126  * @ppos:       input file offset
1127  * @out:        file to splice to
1128  * @len:        number of bytes to splice
1129  * @flags:      splice modifier flags
1130  *
1131  * Description:
1132  *    For use by do_sendfile(). splice can easily emulate sendfile, but
1133  *    doing it in the application would incur an extra system call
1134  *    (splice in + splice out, as compared to just sendfile()). So this helper
1135  *    can splice directly through a process-private pipe.
1136  *
1137  */
1138 long do_splice_direct(struct file *in, loff_t *ppos, struct file *out,
1139                       size_t len, unsigned int flags)
1140 {
1141         struct splice_desc sd = {
1142                 .len            = len,
1143                 .total_len      = len,
1144                 .flags          = flags,
1145                 .pos            = *ppos,
1146                 .u.file         = out,
1147         };
1148         long ret;
1149
1150         ret = splice_direct_to_actor(in, &sd, direct_splice_actor);
1151         if (ret > 0)
1152                 *ppos += ret;
1153
1154         return ret;
1155 }
1156
1157 /*
1158  * After the inode slimming patch, i_pipe/i_bdev/i_cdev share the same
1159  * location, so checking ->i_pipe is not enough to verify that this is a
1160  * pipe.
1161  */
1162 static inline struct pipe_inode_info *pipe_info(struct inode *inode)
1163 {
1164         if (S_ISFIFO(inode->i_mode))
1165                 return inode->i_pipe;
1166
1167         return NULL;
1168 }
1169
1170 /*
1171  * Determine where to splice to/from.
1172  */
1173 static long do_splice(struct file *in, loff_t __user *off_in,
1174                       struct file *out, loff_t __user *off_out,
1175                       size_t len, unsigned int flags)
1176 {
1177         struct pipe_inode_info *pipe;
1178         loff_t offset, *off;
1179         long ret;
1180
1181         pipe = pipe_info(in->f_path.dentry->d_inode);
1182         if (pipe) {
1183                 if (off_in)
1184                         return -ESPIPE;
1185                 if (off_out) {
1186                         if (out->f_op->llseek == no_llseek)
1187                                 return -EINVAL;
1188                         if (copy_from_user(&offset, off_out, sizeof(loff_t)))
1189                                 return -EFAULT;
1190                         off = &offset;
1191                 } else
1192                         off = &out->f_pos;
1193
1194                 ret = do_splice_from(pipe, out, off, len, flags);
1195
1196                 if (off_out && copy_to_user(off_out, off, sizeof(loff_t)))
1197                         ret = -EFAULT;
1198
1199                 return ret;
1200         }
1201
1202         pipe = pipe_info(out->f_path.dentry->d_inode);
1203         if (pipe) {
1204                 if (off_out)
1205                         return -ESPIPE;
1206                 if (off_in) {
1207                         if (in->f_op->llseek == no_llseek)
1208                                 return -EINVAL;
1209                         if (copy_from_user(&offset, off_in, sizeof(loff_t)))
1210                                 return -EFAULT;
1211                         off = &offset;
1212                 } else
1213                         off = &in->f_pos;
1214
1215                 ret = do_splice_to(in, off, pipe, len, flags);
1216
1217                 if (off_in && copy_to_user(off_in, off, sizeof(loff_t)))
1218                         ret = -EFAULT;
1219
1220                 return ret;
1221         }
1222
1223         return -EINVAL;
1224 }
1225
1226 /*
1227  * Map an iov into an array of pages and offset/length tupples. With the
1228  * partial_page structure, we can map several non-contiguous ranges into
1229  * our ones pages[] map instead of splitting that operation into pieces.
1230  * Could easily be exported as a generic helper for other users, in which
1231  * case one would probably want to add a 'max_nr_pages' parameter as well.
1232  */
1233 static int get_iovec_page_array(const struct iovec __user *iov,
1234                                 unsigned int nr_vecs, struct page **pages,
1235                                 struct partial_page *partial, int aligned)
1236 {
1237         int buffers = 0, error = 0;
1238
1239         /*
1240          * It's ok to take the mmap_sem for reading, even
1241          * across a "get_user()".
1242          */
1243         down_read(&current->mm->mmap_sem);
1244
1245         while (nr_vecs) {
1246                 unsigned long off, npages;
1247                 void __user *base;
1248                 size_t len;
1249                 int i;
1250
1251                 /*
1252                  * Get user address base and length for this iovec.
1253                  */
1254                 error = get_user(base, &iov->iov_base);
1255                 if (unlikely(error))
1256                         break;
1257                 error = get_user(len, &iov->iov_len);
1258                 if (unlikely(error))
1259                         break;
1260
1261                 /*
1262                  * Sanity check this iovec. 0 read succeeds.
1263                  */
1264                 if (unlikely(!len))
1265                         break;
1266                 error = -EFAULT;
1267                 if (unlikely(!base))
1268                         break;
1269
1270                 /*
1271                  * Get this base offset and number of pages, then map
1272                  * in the user pages.
1273                  */
1274                 off = (unsigned long) base & ~PAGE_MASK;
1275
1276                 /*
1277                  * If asked for alignment, the offset must be zero and the
1278                  * length a multiple of the PAGE_SIZE.
1279                  */
1280                 error = -EINVAL;
1281                 if (aligned && (off || len & ~PAGE_MASK))
1282                         break;
1283
1284                 npages = (off + len + PAGE_SIZE - 1) >> PAGE_SHIFT;
1285                 if (npages > PIPE_BUFFERS - buffers)
1286                         npages = PIPE_BUFFERS - buffers;
1287
1288                 error = get_user_pages(current, current->mm,
1289                                        (unsigned long) base, npages, 0, 0,
1290                                        &pages[buffers], NULL);
1291
1292                 if (unlikely(error <= 0))
1293                         break;
1294
1295                 /*
1296                  * Fill this contiguous range into the partial page map.
1297                  */
1298                 for (i = 0; i < error; i++) {
1299                         const int plen = min_t(size_t, len, PAGE_SIZE - off);
1300
1301                         partial[buffers].offset = off;
1302                         partial[buffers].len = plen;
1303
1304                         off = 0;
1305                         len -= plen;
1306                         buffers++;
1307                 }
1308
1309                 /*
1310                  * We didn't complete this iov, stop here since it probably
1311                  * means we have to move some of this into a pipe to
1312                  * be able to continue.
1313                  */
1314                 if (len)
1315                         break;
1316
1317                 /*
1318                  * Don't continue if we mapped fewer pages than we asked for,
1319                  * or if we mapped the max number of pages that we have
1320                  * room for.
1321                  */
1322                 if (error < npages || buffers == PIPE_BUFFERS)
1323                         break;
1324
1325                 nr_vecs--;
1326                 iov++;
1327         }
1328
1329         up_read(&current->mm->mmap_sem);
1330
1331         if (buffers)
1332                 return buffers;
1333
1334         return error;
1335 }
1336
1337 static int pipe_to_user(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
1338                         struct splice_desc *sd)
1339 {
1340         char *src;
1341         int ret;
1342
1343         ret = buf->ops->confirm(pipe, buf);
1344         if (unlikely(ret))
1345                 return ret;
1346
1347         /*
1348          * See if we can use the atomic maps, by prefaulting in the
1349          * pages and doing an atomic copy
1350          */
1351         if (!fault_in_pages_writeable(sd->u.userptr, sd->len)) {
1352                 src = buf->ops->map(pipe, buf, 1);
1353                 ret = __copy_to_user_inatomic(sd->u.userptr, src + buf->offset,
1354                                                         sd->len);
1355                 buf->ops->unmap(pipe, buf, src);
1356                 if (!ret) {
1357                         ret = sd->len;
1358                         goto out;
1359                 }
1360         }
1361
1362         /*
1363          * No dice, use slow non-atomic map and copy
1364          */
1365         src = buf->ops->map(pipe, buf, 0);
1366
1367         ret = sd->len;
1368         if (copy_to_user(sd->u.userptr, src + buf->offset, sd->len))
1369                 ret = -EFAULT;
1370
1371 out:
1372         if (ret > 0)
1373                 sd->u.userptr += ret;
1374         buf->ops->unmap(pipe, buf, src);
1375         return ret;
1376 }
1377
1378 /*
1379  * For lack of a better implementation, implement vmsplice() to userspace
1380  * as a simple copy of the pipes pages to the user iov.
1381  */
1382 static long vmsplice_to_user(struct file *file, const struct iovec __user *iov,
1383                              unsigned long nr_segs, unsigned int flags)
1384 {
1385         struct pipe_inode_info *pipe;
1386         struct splice_desc sd;
1387         ssize_t size;
1388         int error;
1389         long ret;
1390
1391         pipe = pipe_info(file->f_path.dentry->d_inode);
1392         if (!pipe)
1393                 return -EBADF;
1394
1395         if (pipe->inode)
1396                 mutex_lock(&pipe->inode->i_mutex);
1397
1398         error = ret = 0;
1399         while (nr_segs) {
1400                 void __user *base;
1401                 size_t len;
1402
1403                 /*
1404                  * Get user address base and length for this iovec.
1405                  */
1406                 error = get_user(base, &iov->iov_base);
1407                 if (unlikely(error))
1408                         break;
1409                 error = get_user(len, &iov->iov_len);
1410                 if (unlikely(error))
1411                         break;
1412
1413                 /*
1414                  * Sanity check this iovec. 0 read succeeds.
1415                  */
1416                 if (unlikely(!len))
1417                         break;
1418                 if (unlikely(!base)) {
1419                         error = -EFAULT;
1420                         break;
1421                 }
1422
1423                 sd.len = 0;
1424                 sd.total_len = len;
1425                 sd.flags = flags;
1426                 sd.u.userptr = base;
1427                 sd.pos = 0;
1428
1429                 size = __splice_from_pipe(pipe, &sd, pipe_to_user);
1430                 if (size < 0) {
1431                         if (!ret)
1432                                 ret = size;
1433
1434                         break;
1435                 }
1436
1437                 ret += size;
1438
1439                 if (size < len)
1440                         break;
1441
1442                 nr_segs--;
1443                 iov++;
1444         }
1445
1446         if (pipe->inode)
1447                 mutex_unlock(&pipe->inode->i_mutex);
1448
1449         if (!ret)
1450                 ret = error;
1451
1452         return ret;
1453 }
1454
1455 /*
1456  * vmsplice splices a user address range into a pipe. It can be thought of
1457  * as splice-from-memory, where the regular splice is splice-from-file (or
1458  * to file). In both cases the output is a pipe, naturally.
1459  */
1460 static long vmsplice_to_pipe(struct file *file, const struct iovec __user *iov,
1461                              unsigned long nr_segs, unsigned int flags)
1462 {
1463         struct pipe_inode_info *pipe;
1464         struct page *pages[PIPE_BUFFERS];
1465         struct partial_page partial[PIPE_BUFFERS];
1466         struct splice_pipe_desc spd = {
1467                 .pages = pages,
1468                 .partial = partial,
1469                 .flags = flags,
1470                 .ops = &user_page_pipe_buf_ops,
1471         };
1472
1473         pipe = pipe_info(file->f_path.dentry->d_inode);
1474         if (!pipe)
1475                 return -EBADF;
1476
1477         spd.nr_pages = get_iovec_page_array(iov, nr_segs, pages, partial,
1478                                             flags & SPLICE_F_GIFT);
1479         if (spd.nr_pages <= 0)
1480                 return spd.nr_pages;
1481
1482         return splice_to_pipe(pipe, &spd);
1483 }
1484
1485 /*
1486  * Note that vmsplice only really supports true splicing _from_ user memory
1487  * to a pipe, not the other way around. Splicing from user memory is a simple
1488  * operation that can be supported without any funky alignment restrictions
1489  * or nasty vm tricks. We simply map in the user memory and fill them into
1490  * a pipe. The reverse isn't quite as easy, though. There are two possible
1491  * solutions for that:
1492  *
1493  *      - memcpy() the data internally, at which point we might as well just
1494  *        do a regular read() on the buffer anyway.
1495  *      - Lots of nasty vm tricks, that are neither fast nor flexible (it
1496  *        has restriction limitations on both ends of the pipe).
1497  *
1498  * Currently we punt and implement it as a normal copy, see pipe_to_user().
1499  *
1500  */
1501 asmlinkage long sys_vmsplice(int fd, const struct iovec __user *iov,
1502                              unsigned long nr_segs, unsigned int flags)
1503 {
1504         struct file *file;
1505         long error;
1506         int fput;
1507
1508         if (unlikely(nr_segs > UIO_MAXIOV))
1509                 return -EINVAL;
1510         else if (unlikely(!nr_segs))
1511                 return 0;
1512
1513         error = -EBADF;
1514         file = fget_light(fd, &fput);
1515         if (file) {
1516                 if (file->f_mode & FMODE_WRITE)
1517                         error = vmsplice_to_pipe(file, iov, nr_segs, flags);
1518                 else if (file->f_mode & FMODE_READ)
1519                         error = vmsplice_to_user(file, iov, nr_segs, flags);
1520
1521                 fput_light(file, fput);
1522         }
1523
1524         return error;
1525 }
1526
1527 asmlinkage long sys_splice(int fd_in, loff_t __user *off_in,
1528                            int fd_out, loff_t __user *off_out,
1529                            size_t len, unsigned int flags)
1530 {
1531         long error;
1532         struct file *in, *out;
1533         int fput_in, fput_out;
1534
1535         if (unlikely(!len))
1536                 return 0;
1537
1538         error = -EBADF;
1539         in = fget_light(fd_in, &fput_in);
1540         if (in) {
1541                 if (in->f_mode & FMODE_READ) {
1542                         out = fget_light(fd_out, &fput_out);
1543                         if (out) {
1544                                 if (out->f_mode & FMODE_WRITE)
1545                                         error = do_splice(in, off_in,
1546                                                           out, off_out,
1547                                                           len, flags);
1548                                 fput_light(out, fput_out);
1549                         }
1550                 }
1551
1552                 fput_light(in, fput_in);
1553         }
1554
1555         return error;
1556 }
1557
1558 /*
1559  * Make sure there's data to read. Wait for input if we can, otherwise
1560  * return an appropriate error.
1561  */
1562 static int link_ipipe_prep(struct pipe_inode_info *pipe, unsigned int flags)
1563 {
1564         int ret;
1565
1566         /*
1567          * Check ->nrbufs without the inode lock first. This function
1568          * is speculative anyways, so missing one is ok.
1569          */
1570         if (pipe->nrbufs)
1571                 return 0;
1572
1573         ret = 0;
1574         mutex_lock(&pipe->inode->i_mutex);
1575
1576         while (!pipe->nrbufs) {
1577                 if (signal_pending(current)) {
1578                         ret = -ERESTARTSYS;
1579                         break;
1580                 }
1581                 if (!pipe->writers)
1582                         break;
1583                 if (!pipe->waiting_writers) {
1584                         if (flags & SPLICE_F_NONBLOCK) {
1585                                 ret = -EAGAIN;
1586                                 break;
1587                         }
1588                 }
1589                 pipe_wait(pipe);
1590         }
1591
1592         mutex_unlock(&pipe->inode->i_mutex);
1593         return ret;
1594 }
1595
1596 /*
1597  * Make sure there's writeable room. Wait for room if we can, otherwise
1598  * return an appropriate error.
1599  */
1600 static int link_opipe_prep(struct pipe_inode_info *pipe, unsigned int flags)
1601 {
1602         int ret;
1603
1604         /*
1605          * Check ->nrbufs without the inode lock first. This function
1606          * is speculative anyways, so missing one is ok.
1607          */
1608         if (pipe->nrbufs < PIPE_BUFFERS)
1609                 return 0;
1610
1611         ret = 0;
1612         mutex_lock(&pipe->inode->i_mutex);
1613
1614         while (pipe->nrbufs >= PIPE_BUFFERS) {
1615                 if (!pipe->readers) {
1616                         send_sig(SIGPIPE, current, 0);
1617                         ret = -EPIPE;
1618                         break;
1619                 }
1620                 if (flags & SPLICE_F_NONBLOCK) {
1621                         ret = -EAGAIN;
1622                         break;
1623                 }
1624                 if (signal_pending(current)) {
1625                         ret = -ERESTARTSYS;
1626                         break;
1627                 }
1628                 pipe->waiting_writers++;
1629                 pipe_wait(pipe);
1630                 pipe->waiting_writers--;
1631         }
1632
1633         mutex_unlock(&pipe->inode->i_mutex);
1634         return ret;
1635 }
1636
1637 /*
1638  * Link contents of ipipe to opipe.
1639  */
1640 static int link_pipe(struct pipe_inode_info *ipipe,
1641                      struct pipe_inode_info *opipe,
1642                      size_t len, unsigned int flags)
1643 {
1644         struct pipe_buffer *ibuf, *obuf;
1645         int ret = 0, i = 0, nbuf;
1646
1647         /*
1648          * Potential ABBA deadlock, work around it by ordering lock
1649          * grabbing by inode address. Otherwise two different processes
1650          * could deadlock (one doing tee from A -> B, the other from B -> A).
1651          */
1652         inode_double_lock(ipipe->inode, opipe->inode);
1653
1654         do {
1655                 if (!opipe->readers) {
1656                         send_sig(SIGPIPE, current, 0);
1657                         if (!ret)
1658                                 ret = -EPIPE;
1659                         break;
1660                 }
1661
1662                 /*
1663                  * If we have iterated all input buffers or ran out of
1664                  * output room, break.
1665                  */
1666                 if (i >= ipipe->nrbufs || opipe->nrbufs >= PIPE_BUFFERS)
1667                         break;
1668
1669                 ibuf = ipipe->bufs + ((ipipe->curbuf + i) & (PIPE_BUFFERS - 1));
1670                 nbuf = (opipe->curbuf + opipe->nrbufs) & (PIPE_BUFFERS - 1);
1671
1672                 /*
1673                  * Get a reference to this pipe buffer,
1674                  * so we can copy the contents over.
1675                  */
1676                 ibuf->ops->get(ipipe, ibuf);
1677
1678                 obuf = opipe->bufs + nbuf;
1679                 *obuf = *ibuf;
1680
1681                 /*
1682                  * Don't inherit the gift flag, we need to
1683                  * prevent multiple steals of this page.
1684                  */
1685                 obuf->flags &= ~PIPE_BUF_FLAG_GIFT;
1686
1687                 if (obuf->len > len)
1688                         obuf->len = len;
1689
1690                 opipe->nrbufs++;
1691                 ret += obuf->len;
1692                 len -= obuf->len;
1693                 i++;
1694         } while (len);
1695
1696         inode_double_unlock(ipipe->inode, opipe->inode);
1697
1698         /*
1699          * If we put data in the output pipe, wakeup any potential readers.
1700          */
1701         if (ret > 0) {
1702                 smp_mb();
1703                 if (waitqueue_active(&opipe->wait))
1704                         wake_up_interruptible(&opipe->wait);
1705                 kill_fasync(&opipe->fasync_readers, SIGIO, POLL_IN);
1706         }
1707
1708         return ret;
1709 }
1710
1711 /*
1712  * This is a tee(1) implementation that works on pipes. It doesn't copy
1713  * any data, it simply references the 'in' pages on the 'out' pipe.
1714  * The 'flags' used are the SPLICE_F_* variants, currently the only
1715  * applicable one is SPLICE_F_NONBLOCK.
1716  */
1717 static long do_tee(struct file *in, struct file *out, size_t len,
1718                    unsigned int flags)
1719 {
1720         struct pipe_inode_info *ipipe = pipe_info(in->f_path.dentry->d_inode);
1721         struct pipe_inode_info *opipe = pipe_info(out->f_path.dentry->d_inode);
1722         int ret = -EINVAL;
1723
1724         /*
1725          * Duplicate the contents of ipipe to opipe without actually
1726          * copying the data.
1727          */
1728         if (ipipe && opipe && ipipe != opipe) {
1729                 /*
1730                  * Keep going, unless we encounter an error. The ipipe/opipe
1731                  * ordering doesn't really matter.
1732                  */
1733                 ret = link_ipipe_prep(ipipe, flags);
1734                 if (!ret) {
1735                         ret = link_opipe_prep(opipe, flags);
1736                         if (!ret) {
1737                                 ret = link_pipe(ipipe, opipe, len, flags);
1738                                 if (!ret && (flags & SPLICE_F_NONBLOCK))
1739                                         ret = -EAGAIN;
1740                         }
1741                 }
1742         }
1743
1744         return ret;
1745 }
1746
1747 asmlinkage long sys_tee(int fdin, int fdout, size_t len, unsigned int flags)
1748 {
1749         struct file *in;
1750         int error, fput_in;
1751
1752         if (unlikely(!len))
1753                 return 0;
1754
1755         error = -EBADF;
1756         in = fget_light(fdin, &fput_in);
1757         if (in) {
1758                 if (in->f_mode & FMODE_READ) {
1759                         int fput_out;
1760                         struct file *out = fget_light(fdout, &fput_out);
1761
1762                         if (out) {
1763                                 if (out->f_mode & FMODE_WRITE)
1764                                         error = do_tee(in, out, len, flags);
1765                                 fput_light(out, fput_out);
1766                         }
1767                 }
1768                 fput_light(in, fput_in);
1769         }
1770
1771         return error;
1772 }