git.oblomov.eu Git - linux-2.6/blob - fs/splice.c

   1 /*
   2  * "splice": joining two ropes together by interweaving their strands.
   3  *
   4  * This is the "extended pipe" functionality, where a pipe is used as
   5  * an arbitrary in-memory buffer. Think of a pipe as a small kernel
   6  * buffer that you can use to transfer data from one end to the other.
   7  *
   8  * The traditional unix read/write is extended with a "splice()" operation
   9  * that transfers data buffers to or from a pipe buffer.
  10  *
  11  * Named by Larry McVoy, original implementation from Linus, extended by
  12  * Jens to support splicing to files, 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 (PagePrivate(page) && !try_to_release_page(page, GFP_KERNEL))
  63                         goto out_unlock;
  64
  65                 /*
  66                  * If we succeeded in removing the mapping, set LRU flag
  67                  * and return good.
  68                  */
  69                 if (remove_mapping(mapping, page)) {
  70                         buf->flags |= PIPE_BUF_FLAG_LRU;
  71                         return 0;
  72                 }
  73         }
  74
  75         /*
  76          * Raced with truncate or failed to remove page from current
  77          * address space, unlock and return failure.
  78          */
  79 out_unlock:
  80         unlock_page(page);
  81         return 1;
  82 }
  83
  84 static void page_cache_pipe_buf_release(struct pipe_inode_info *pipe,
  85                                         struct pipe_buffer *buf)
  86 {
  87         page_cache_release(buf->page);
  88         buf->flags &= ~PIPE_BUF_FLAG_LRU;
  89 }
  90
  91 /*
  92  * Check whether the contents of buf is OK to access. Since the content
  93  * is a page cache page, IO may be in flight.
  94  */
  95 static int page_cache_pipe_buf_confirm(struct pipe_inode_info *pipe,
  96                                        struct pipe_buffer *buf)
  97 {
  98         struct page *page = buf->page;
  99         int err;
 100
 101         if (!PageUptodate(page)) {
 102                 lock_page(page);
 103
 104                 /*
 105                  * Page got truncated/unhashed. This will cause a 0-byte
 106                  * splice, if this is the first page.
 107                  */
 108                 if (!page->mapping) {
 109                         err = -ENODATA;
 110                         goto error;
 111                 }
 112
 113                 /*
 114                  * Uh oh, read-error from disk.
 115                  */
 116                 if (!PageUptodate(page)) {
 117                         err = -EIO;
 118                         goto error;
 119                 }
 120
 121                 /*
 122                  * Page is ok afterall, we are done.
 123                  */
 124                 unlock_page(page);
 125         }
 126
 127         return 0;
 128 error:
 129         unlock_page(page);
 130         return err;
 131 }
 132
 133 static const struct pipe_buf_operations page_cache_pipe_buf_ops = {
 134         .can_merge = 0,
 135         .map = generic_pipe_buf_map,
 136         .unmap = generic_pipe_buf_unmap,
 137         .confirm = page_cache_pipe_buf_confirm,
 138         .release = page_cache_pipe_buf_release,
 139         .steal = page_cache_pipe_buf_steal,
 140         .get = generic_pipe_buf_get,
 141 };
 142
 143 static int user_page_pipe_buf_steal(struct pipe_inode_info *pipe,
 144                                     struct pipe_buffer *buf)
 145 {
 146         if (!(buf->flags & PIPE_BUF_FLAG_GIFT))
 147                 return 1;
 148
 149         buf->flags |= PIPE_BUF_FLAG_LRU;
 150         return generic_pipe_buf_steal(pipe, buf);
 151 }
 152
 153 static const struct pipe_buf_operations user_page_pipe_buf_ops = {
 154         .can_merge = 0,
 155         .map = generic_pipe_buf_map,
 156         .unmap = generic_pipe_buf_unmap,
 157         .confirm = generic_pipe_buf_confirm,
 158         .release = page_cache_pipe_buf_release,
 159         .steal = user_page_pipe_buf_steal,
 160         .get = generic_pipe_buf_get,
 161 };
 162
 163 /**
 164  * splice_to_pipe - fill passed data into a pipe
 165  * @pipe:       pipe to fill
 166  * @spd:        data to fill
 167  *
 168  * Description:
 169  *    @spd contains a map of pages and len/offset tuples, along with
 170  *    the struct pipe_buf_operations associated with these pages. This
 171  *    function will link that data to the pipe.
 172  *
 173  */
 174 ssize_t splice_to_pipe(struct pipe_inode_info *pipe,
 175                        struct splice_pipe_desc *spd)
 176 {
 177         unsigned int spd_pages = spd->nr_pages;
 178         int ret, do_wakeup, page_nr;
 179
 180         ret = 0;
 181         do_wakeup = 0;
 182         page_nr = 0;
 183
 184         if (pipe->inode)
 185                 mutex_lock(&pipe->inode->i_mutex);
 186
 187         for (;;) {
 188                 if (!pipe->readers) {
 189                         send_sig(SIGPIPE, current, 0);
 190                         if (!ret)
 191                                 ret = -EPIPE;
 192                         break;
 193                 }
 194
 195                 if (pipe->nrbufs < PIPE_BUFFERS) {
 196                         int newbuf = (pipe->curbuf + pipe->nrbufs) & (PIPE_BUFFERS - 1);
 197                         struct pipe_buffer *buf = pipe->bufs + newbuf;
 198
 199                         buf->page = spd->pages[page_nr];
 200                         buf->offset = spd->partial[page_nr].offset;
 201                         buf->len = spd->partial[page_nr].len;
 202                         buf->private = spd->partial[page_nr].private;
 203                         buf->ops = spd->ops;
 204                         if (spd->flags & SPLICE_F_GIFT)
 205                                 buf->flags |= PIPE_BUF_FLAG_GIFT;
 206
 207                         pipe->nrbufs++;
 208                         page_nr++;
 209                         ret += buf->len;
 210
 211                         if (pipe->inode)
 212                                 do_wakeup = 1;
 213
 214                         if (!--spd->nr_pages)
 215                                 break;
 216                         if (pipe->nrbufs < PIPE_BUFFERS)
 217                                 continue;
 218
 219                         break;
 220                 }
 221
 222                 if (spd->flags & SPLICE_F_NONBLOCK) {
 223                         if (!ret)
 224                                 ret = -EAGAIN;
 225                         break;
 226                 }
 227
 228                 if (signal_pending(current)) {
 229                         if (!ret)
 230                                 ret = -ERESTARTSYS;
 231                         break;
 232                 }
 233
 234                 if (do_wakeup) {
 235                         smp_mb();
 236                         if (waitqueue_active(&pipe->wait))
 237                                 wake_up_interruptible_sync(&pipe->wait);
 238                         kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
 239                         do_wakeup = 0;
 240                 }
 241
 242                 pipe->waiting_writers++;
 243                 pipe_wait(pipe);
 244                 pipe->waiting_writers--;
 245         }
 246
 247         if (pipe->inode) {
 248                 mutex_unlock(&pipe->inode->i_mutex);
 249
 250                 if (do_wakeup) {
 251                         smp_mb();
 252                         if (waitqueue_active(&pipe->wait))
 253                                 wake_up_interruptible(&pipe->wait);
 254                         kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
 255                 }
 256         }
 257
 258         while (page_nr < spd_pages)
 259                 spd->spd_release(spd, page_nr++);
 260
 261         return ret;
 262 }
 263
 264 static void spd_release_page(struct splice_pipe_desc *spd, unsigned int i)
 265 {
 266         page_cache_release(spd->pages[i]);
 267 }
 268
 269 static int
 270 __generic_file_splice_read(struct file *in, loff_t *ppos,
 271                            struct pipe_inode_info *pipe, size_t len,
 272                            unsigned int flags)
 273 {
 274         struct address_space *mapping = in->f_mapping;
 275         unsigned int loff, nr_pages, req_pages;
 276         struct page *pages[PIPE_BUFFERS];
 277         struct partial_page partial[PIPE_BUFFERS];
 278         struct page *page;
 279         pgoff_t index, end_index;
 280         loff_t isize;
 281         int error, page_nr;
 282         struct splice_pipe_desc spd = {
 283                 .pages = pages,
 284                 .partial = partial,
 285                 .flags = flags,
 286                 .ops = &page_cache_pipe_buf_ops,
 287                 .spd_release = spd_release_page,
 288         };
 289
 290         index = *ppos >> PAGE_CACHE_SHIFT;
 291         loff = *ppos & ~PAGE_CACHE_MASK;
 292         req_pages = (len + loff + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
 293         nr_pages = min(req_pages, (unsigned)PIPE_BUFFERS);
 294
 295         /*
 296          * Lookup the (hopefully) full range of pages we need.
 297          */
 298         spd.nr_pages = find_get_pages_contig(mapping, index, nr_pages, pages);
 299         index += spd.nr_pages;
 300
 301         /*
 302          * If find_get_pages_contig() returned fewer pages than we needed,
 303          * readahead/allocate the rest and fill in the holes.
 304          */
 305         if (spd.nr_pages < nr_pages)
 306                 page_cache_sync_readahead(mapping, &in->f_ra, in,
 307                                 index, req_pages - spd.nr_pages);
 308
 309         error = 0;
 310         while (spd.nr_pages < nr_pages) {
 311                 /*
 312                  * Page could be there, find_get_pages_contig() breaks on
 313                  * the first hole.
 314                  */
 315                 page = find_get_page(mapping, index);
 316                 if (!page) {
 317                         /*
 318                          * page didn't exist, allocate one.
 319                          */
 320                         page = page_cache_alloc_cold(mapping);
 321                         if (!page)
 322                                 break;
 323
 324                         error = add_to_page_cache_lru(page, mapping, index,
 325                                                 mapping_gfp_mask(mapping));
 326                         if (unlikely(error)) {
 327                                 page_cache_release(page);
 328                                 if (error == -EEXIST)
 329                                         continue;
 330                                 break;
 331                         }
 332                         /*
 333                          * add_to_page_cache() locks the page, unlock it
 334                          * to avoid convoluting the logic below even more.
 335                          */
 336                         unlock_page(page);
 337                 }
 338
 339                 pages[spd.nr_pages++] = page;
 340                 index++;
 341         }
 342
 343         /*
 344          * Now loop over the map and see if we need to start IO on any
 345          * pages, fill in the partial map, etc.
 346          */
 347         index = *ppos >> PAGE_CACHE_SHIFT;
 348         nr_pages = spd.nr_pages;
 349         spd.nr_pages = 0;
 350         for (page_nr = 0; page_nr < nr_pages; page_nr++) {
 351                 unsigned int this_len;
 352
 353                 if (!len)
 354                         break;
 355
 356                 /*
 357                  * this_len is the max we'll use from this page
 358                  */
 359                 this_len = min_t(unsigned long, len, PAGE_CACHE_SIZE - loff);
 360                 page = pages[page_nr];
 361
 362                 if (PageReadahead(page))
 363                         page_cache_async_readahead(mapping, &in->f_ra, in,
 364                                         page, index, req_pages - page_nr);
 365
 366                 /*
 367                  * If the page isn't uptodate, we may need to start io on it
 368                  */
 369                 if (!PageUptodate(page)) {
 370                         /*
 371                          * If in nonblock mode then dont block on waiting
 372                          * for an in-flight io page
 373                          */
 374                         if (flags & SPLICE_F_NONBLOCK) {
 375                                 if (!trylock_page(page)) {
 376                                         error = -EAGAIN;
 377                                         break;
 378                                 }
 379                         } else
 380                                 lock_page(page);
 381
 382                         /*
 383                          * Page was truncated, or invalidated by the
 384                          * filesystem.  Redo the find/create, but this time the
 385                          * page is kept locked, so there's no chance of another
 386                          * race with truncate/invalidate.
 387                          */
 388                         if (!page->mapping) {
 389                                 unlock_page(page);
 390                                 page = find_or_create_page(mapping, index,
 391                                                 mapping_gfp_mask(mapping));
 392
 393                                 if (!page) {
 394                                         error = -ENOMEM;
 395                                         break;
 396                                 }
 397                                 page_cache_release(pages[page_nr]);
 398                                 pages[page_nr] = page;
 399                         }
 400                         /*
 401                          * page was already under io and is now done, great
 402                          */
 403                         if (PageUptodate(page)) {
 404                                 unlock_page(page);
 405                                 goto fill_it;
 406                         }
 407
 408                         /*
 409                          * need to read in the page
 410                          */
 411                         error = mapping->a_ops->readpage(in, page);
 412                         if (unlikely(error)) {
 413                                 /*
 414                                  * We really should re-lookup the page here,
 415                                  * but it complicates things a lot. Instead
 416                                  * lets just do what we already stored, and
 417                                  * we'll get it the next time we are called.
 418                                  */
 419                                 if (error == AOP_TRUNCATED_PAGE)
 420                                         error = 0;
 421
 422                                 break;
 423                         }
 424                 }
 425 fill_it:
 426                 /*
 427                  * i_size must be checked after PageUptodate.
 428                  */
 429                 isize = i_size_read(mapping->host);
 430                 end_index = (isize - 1) >> PAGE_CACHE_SHIFT;
 431                 if (unlikely(!isize || index > end_index))
 432                         break;
 433
 434                 /*
 435                  * if this is the last page, see if we need to shrink
 436                  * the length and stop
 437                  */
 438                 if (end_index == index) {
 439                         unsigned int plen;
 440
 441                         /*
 442                          * max good bytes in this page
 443                          */
 444                         plen = ((isize - 1) & ~PAGE_CACHE_MASK) + 1;
 445                         if (plen <= loff)
 446                                 break;
 447
 448                         /*
 449                          * force quit after adding this page
 450                          */
 451                         this_len = min(this_len, plen - loff);
 452                         len = this_len;
 453                 }
 454
 455                 partial[page_nr].offset = loff;
 456                 partial[page_nr].len = this_len;
 457                 len -= this_len;
 458                 loff = 0;
 459                 spd.nr_pages++;
 460                 index++;
 461         }
 462
 463         /*
 464          * Release any pages at the end, if we quit early. 'page_nr' is how far
 465          * we got, 'nr_pages' is how many pages are in the map.
 466          */
 467         while (page_nr < nr_pages)
 468                 page_cache_release(pages[page_nr++]);
 469         in->f_ra.prev_pos = (loff_t)index << PAGE_CACHE_SHIFT;
 470
 471         if (spd.nr_pages)
 472                 return splice_to_pipe(pipe, &spd);
 473
 474         return error;
 475 }
 476
 477 /**
 478  * generic_file_splice_read - splice data from file to a pipe
 479  * @in:         file to splice from
 480  * @ppos:       position in @in
 481  * @pipe:       pipe to splice to
 482  * @len:        number of bytes to splice
 483  * @flags:      splice modifier flags
 484  *
 485  * Description:
 486  *    Will read pages from given file and fill them into a pipe. Can be
 487  *    used as long as the address_space operations for the source implements
 488  *    a readpage() hook.
 489  *
 490  */
 491 ssize_t generic_file_splice_read(struct file *in, loff_t *ppos,
 492                                  struct pipe_inode_info *pipe, size_t len,
 493                                  unsigned int flags)
 494 {
 495         loff_t isize, left;
 496         int ret;
 497
 498         isize = i_size_read(in->f_mapping->host);
 499         if (unlikely(*ppos >= isize))
 500                 return 0;
 501
 502         left = isize - *ppos;
 503         if (unlikely(left < len))
 504                 len = left;
 505
 506         ret = __generic_file_splice_read(in, ppos, pipe, len, flags);
 507         if (ret > 0)
 508                 *ppos += ret;
 509
 510         return ret;
 511 }
 512
 513 EXPORT_SYMBOL(generic_file_splice_read);
 514
 515 /*
 516  * Send 'sd->len' bytes to socket from 'sd->file' at position 'sd->pos'
 517  * using sendpage(). Return the number of bytes sent.
 518  */
 519 static int pipe_to_sendpage(struct pipe_inode_info *pipe,
 520                             struct pipe_buffer *buf, struct splice_desc *sd)
 521 {
 522         struct file *file = sd->u.file;
 523         loff_t pos = sd->pos;
 524         int ret, more;
 525
 526         ret = buf->ops->confirm(pipe, buf);
 527         if (!ret) {
 528                 more = (sd->flags & SPLICE_F_MORE) || sd->len < sd->total_len;
 529
 530                 ret = file->f_op->sendpage(file, buf->page, buf->offset,
 531                                            sd->len, &pos, more);
 532         }
 533
 534         return ret;
 535 }
 536
 537 /*
 538  * This is a little more tricky than the file -> pipe splicing. There are
 539  * basically three cases:
 540  *
 541  *      - Destination page already exists in the address space and there
 542  *        are users of it. For that case we have no other option that
 543  *        copying the data. Tough luck.
 544  *      - Destination page already exists in the address space, but there
 545  *        are no users of it. Make sure it's uptodate, then drop it. Fall
 546  *        through to last case.
 547  *      - Destination page does not exist, we can add the pipe page to
 548  *        the page cache and avoid the copy.
 549  *
 550  * If asked to move pages to the output file (SPLICE_F_MOVE is set in
 551  * sd->flags), we attempt to migrate pages from the pipe to the output
 552  * file address space page cache. This is possible if no one else has
 553  * the pipe page referenced outside of the pipe and page cache. If
 554  * SPLICE_F_MOVE isn't set, or we cannot move the page, we simply create
 555  * a new page in the output file page cache and fill/dirty that.
 556  */
 557 static int pipe_to_file(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
 558                         struct splice_desc *sd)
 559 {
 560         struct file *file = sd->u.file;
 561         struct address_space *mapping = file->f_mapping;
 562         unsigned int offset, this_len;
 563         struct page *page;
 564         void *fsdata;
 565         int ret;
 566
 567         /*
 568          * make sure the data in this buffer is uptodate
 569          */
 570         ret = buf->ops->confirm(pipe, buf);
 571         if (unlikely(ret))
 572                 return ret;
 573
 574         offset = sd->pos & ~PAGE_CACHE_MASK;
 575
 576         this_len = sd->len;
 577         if (this_len + offset > PAGE_CACHE_SIZE)
 578                 this_len = PAGE_CACHE_SIZE - offset;
 579
 580         ret = pagecache_write_begin(file, mapping, sd->pos, this_len,
 581                                 AOP_FLAG_UNINTERRUPTIBLE, &page, &fsdata);
 582         if (unlikely(ret))
 583                 goto out;
 584
 585         if (buf->page != page) {
 586                 /*
 587                  * Careful, ->map() uses KM_USER0!
 588                  */
 589                 char *src = buf->ops->map(pipe, buf, 1);
 590                 char *dst = kmap_atomic(page, KM_USER1);
 591
 592                 memcpy(dst + offset, src + buf->offset, this_len);
 593                 flush_dcache_page(page);
 594                 kunmap_atomic(dst, KM_USER1);
 595                 buf->ops->unmap(pipe, buf, src);
 596         }
 597         ret = pagecache_write_end(file, mapping, sd->pos, this_len, this_len,
 598                                 page, fsdata);
 599 out:
 600         return ret;
 601 }
 602
 603 /**
 604  * __splice_from_pipe - splice data from a pipe to given actor
 605  * @pipe:       pipe to splice from
 606  * @sd:         information to @actor
 607  * @actor:      handler that splices the data
 608  *
 609  * Description:
 610  *    This function does little more than loop over the pipe and call
 611  *    @actor to do the actual moving of a single struct pipe_buffer to
 612  *    the desired destination. See pipe_to_file, pipe_to_sendpage, or
 613  *    pipe_to_user.
 614  *
 615  */
 616 ssize_t __splice_from_pipe(struct pipe_inode_info *pipe, struct splice_desc *sd,
 617                            splice_actor *actor)
 618 {
 619         int ret, do_wakeup, err;
 620
 621         ret = 0;
 622         do_wakeup = 0;
 623
 624         for (;;) {
 625                 if (pipe->nrbufs) {
 626                         struct pipe_buffer *buf = pipe->bufs + pipe->curbuf;
 627                         const struct pipe_buf_operations *ops = buf->ops;
 628
 629                         sd->len = buf->len;
 630                         if (sd->len > sd->total_len)
 631                                 sd->len = sd->total_len;
 632
 633                         err = actor(pipe, buf, sd);
 634                         if (err <= 0) {
 635                                 if (!ret && err != -ENODATA)
 636                                         ret = err;
 637
 638                                 break;
 639                         }
 640
 641                         ret += err;
 642                         buf->offset += err;
 643                         buf->len -= err;
 644
 645                         sd->len -= err;
 646                         sd->pos += err;
 647                         sd->total_len -= err;
 648                         if (sd->len)
 649                                 continue;
 650
 651                         if (!buf->len) {
 652                                 buf->ops = NULL;
 653                                 ops->release(pipe, buf);
 654                                 pipe->curbuf = (pipe->curbuf + 1) & (PIPE_BUFFERS - 1);
 655                                 pipe->nrbufs--;
 656                                 if (pipe->inode)
 657                                         do_wakeup = 1;
 658                         }
 659
 660                         if (!sd->total_len)
 661                                 break;
 662                 }
 663
 664                 if (pipe->nrbufs)
 665                         continue;
 666                 if (!pipe->writers)
 667                         break;
 668                 if (!pipe->waiting_writers) {
 669                         if (ret)
 670                                 break;
 671                 }
 672
 673                 if (sd->flags & SPLICE_F_NONBLOCK) {
 674                         if (!ret)
 675                                 ret = -EAGAIN;
 676                         break;
 677                 }
 678
 679                 if (signal_pending(current)) {
 680                         if (!ret)
 681                                 ret = -ERESTARTSYS;
 682                         break;
 683                 }
 684
 685                 if (do_wakeup) {
 686                         smp_mb();
 687                         if (waitqueue_active(&pipe->wait))
 688                                 wake_up_interruptible_sync(&pipe->wait);
 689                         kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
 690                         do_wakeup = 0;
 691                 }
 692
 693                 pipe_wait(pipe);
 694         }
 695
 696         if (do_wakeup) {
 697                 smp_mb();
 698                 if (waitqueue_active(&pipe->wait))
 699                         wake_up_interruptible(&pipe->wait);
 700                 kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
 701         }
 702
 703         return ret;
 704 }
 705 EXPORT_SYMBOL(__splice_from_pipe);
 706
 707 /**
 708  * splice_from_pipe - splice data from a pipe to a file
 709  * @pipe:       pipe to splice from
 710  * @out:        file to splice to
 711  * @ppos:       position in @out
 712  * @len:        how many bytes to splice
 713  * @flags:      splice modifier flags
 714  * @actor:      handler that splices the data
 715  *
 716  * Description:
 717  *    See __splice_from_pipe. This function locks the input and output inodes,
 718  *    otherwise it's identical to __splice_from_pipe().
 719  *
 720  */
 721 ssize_t splice_from_pipe(struct pipe_inode_info *pipe, struct file *out,
 722                          loff_t *ppos, size_t len, unsigned int flags,
 723                          splice_actor *actor)
 724 {
 725         ssize_t ret;
 726         struct inode *inode = out->f_mapping->host;
 727         struct splice_desc sd = {
 728                 .total_len = len,
 729                 .flags = flags,
 730                 .pos = *ppos,
 731                 .u.file = out,
 732         };
 733
 734         /*
 735          * The actor worker might be calling ->write_begin and
 736          * ->write_end. Most of the time, these expect i_mutex to
 737          * be held. Since this may result in an ABBA deadlock with
 738          * pipe->inode, we have to order lock acquiry here.
 739          */
 740         inode_double_lock(inode, pipe->inode);
 741         ret = __splice_from_pipe(pipe, &sd, actor);
 742         inode_double_unlock(inode, pipe->inode);
 743
 744         return ret;
 745 }
 746
 747 /**
 748  * generic_file_splice_write_nolock - generic_file_splice_write without mutexes
 749  * @pipe:       pipe info
 750  * @out:        file to write to
 751  * @ppos:       position in @out
 752  * @len:        number of bytes to splice
 753  * @flags:      splice modifier flags
 754  *
 755  * Description:
 756  *    Will either move or copy pages (determined by @flags options) from
 757  *    the given pipe inode to the given file. The caller is responsible
 758  *    for acquiring i_mutex on both inodes.
 759  *
 760  */
 761 ssize_t
 762 generic_file_splice_write_nolock(struct pipe_inode_info *pipe, struct file *out,
 763                                  loff_t *ppos, size_t len, unsigned int flags)
 764 {
 765         struct address_space *mapping = out->f_mapping;
 766         struct inode *inode = mapping->host;
 767         struct splice_desc sd = {
 768                 .total_len = len,
 769                 .flags = flags,
 770                 .pos = *ppos,
 771                 .u.file = out,
 772         };
 773         ssize_t ret;
 774         int err;
 775
 776         err = file_remove_suid(out);
 777         if (unlikely(err))
 778                 return err;
 779
 780         ret = __splice_from_pipe(pipe, &sd, pipe_to_file);
 781         if (ret > 0) {
 782                 unsigned long nr_pages;
 783
 784                 *ppos += ret;
 785                 nr_pages = (ret + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
 786
 787                 /*
 788                  * If file or inode is SYNC and we actually wrote some data,
 789                  * sync it.
 790                  */
 791                 if (unlikely((out->f_flags & O_SYNC) || IS_SYNC(inode))) {
 792                         err = generic_osync_inode(inode, mapping,
 793                                                   OSYNC_METADATA|OSYNC_DATA);
 794
 795                         if (err)
 796                                 ret = err;
 797                 }
 798                 balance_dirty_pages_ratelimited_nr(mapping, nr_pages);
 799         }
 800
 801         return ret;
 802 }
 803
 804 EXPORT_SYMBOL(generic_file_splice_write_nolock);
 805
 806 /**
 807  * generic_file_splice_write - splice data from a pipe to a file
 808  * @pipe:       pipe info
 809  * @out:        file to write to
 810  * @ppos:       position in @out
 811  * @len:        number of bytes to splice
 812  * @flags:      splice modifier flags
 813  *
 814  * Description:
 815  *    Will either move or copy pages (determined by @flags options) from
 816  *    the given pipe inode to the given file.
 817  *
 818  */
 819 ssize_t
 820 generic_file_splice_write(struct pipe_inode_info *pipe, struct file *out,
 821                           loff_t *ppos, size_t len, unsigned int flags)
 822 {
 823         struct address_space *mapping = out->f_mapping;
 824         struct inode *inode = mapping->host;
 825         struct splice_desc sd = {
 826                 .total_len = len,
 827                 .flags = flags,
 828                 .pos = *ppos,
 829                 .u.file = out,
 830         };
 831         ssize_t ret;
 832
 833         inode_double_lock(inode, pipe->inode);
 834         ret = file_remove_suid(out);
 835         if (likely(!ret))
 836                 ret = __splice_from_pipe(pipe, &sd, pipe_to_file);
 837         inode_double_unlock(inode, pipe->inode);
 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                         int err;
 850
 851                         mutex_lock(&inode->i_mutex);
 852                         err = generic_osync_inode(inode, mapping,
 853                                                   OSYNC_METADATA|OSYNC_DATA);
 854                         mutex_unlock(&inode->i_mutex);
 855
 856                         if (err)
 857                                 ret = err;
 858                 }
 859                 balance_dirty_pages_ratelimited_nr(mapping, nr_pages);
 860         }
 861
 862         return ret;
 863 }
 864
 865 EXPORT_SYMBOL(generic_file_splice_write);
 866
 867 /**
 868  * generic_splice_sendpage - splice data from a pipe to a socket
 869  * @pipe:       pipe to splice from
 870  * @out:        socket to write to
 871  * @ppos:       position in @out
 872  * @len:        number of bytes to splice
 873  * @flags:      splice modifier flags
 874  *
 875  * Description:
 876  *    Will send @len bytes from the pipe to a network socket. No data copying
 877  *    is involved.
 878  *
 879  */
 880 ssize_t generic_splice_sendpage(struct pipe_inode_info *pipe, struct file *out,
 881                                 loff_t *ppos, size_t len, unsigned int flags)
 882 {
 883         return splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_sendpage);
 884 }
 885
 886 EXPORT_SYMBOL(generic_splice_sendpage);
 887
 888 /*
 889  * Attempt to initiate a splice from pipe to file.
 890  */
 891 static long do_splice_from(struct pipe_inode_info *pipe, struct file *out,
 892                            loff_t *ppos, size_t len, unsigned int flags)
 893 {
 894         int ret;
 895
 896         if (unlikely(!out->f_op || !out->f_op->splice_write))
 897                 return -EINVAL;
 898
 899         if (unlikely(!(out->f_mode & FMODE_WRITE)))
 900                 return -EBADF;
 901
 902         if (unlikely(out->f_flags & O_APPEND))
 903                 return -EINVAL;
 904
 905         ret = rw_verify_area(WRITE, out, ppos, len);
 906         if (unlikely(ret < 0))
 907                 return ret;
 908
 909         return out->f_op->splice_write(pipe, out, ppos, len, flags);
 910 }
 911
 912 /*
 913  * Attempt to initiate a splice from a file to a pipe.
 914  */
 915 static long do_splice_to(struct file *in, loff_t *ppos,
 916                          struct pipe_inode_info *pipe, size_t len,
 917                          unsigned int flags)
 918 {
 919         int ret;
 920
 921         if (unlikely(!in->f_op || !in->f_op->splice_read))
 922                 return -EINVAL;
 923
 924         if (unlikely(!(in->f_mode & FMODE_READ)))
 925                 return -EBADF;
 926
 927         ret = rw_verify_area(READ, in, ppos, len);
 928         if (unlikely(ret < 0))
 929                 return ret;
 930
 931         return in->f_op->splice_read(in, ppos, pipe, len, flags);
 932 }
 933
 934 /**
 935  * splice_direct_to_actor - splices data directly between two non-pipes
 936  * @in:         file to splice from
 937  * @sd:         actor information on where to splice to
 938  * @actor:      handles the data splicing
 939  *
 940  * Description:
 941  *    This is a special case helper to splice directly between two
 942  *    points, without requiring an explicit pipe. Internally an allocated
 943  *    pipe is cached in the process, and reused during the lifetime of
 944  *    that process.
 945  *
 946  */
 947 ssize_t splice_direct_to_actor(struct file *in, struct splice_desc *sd,
 948                                splice_direct_actor *actor)
 949 {
 950         struct pipe_inode_info *pipe;
 951         long ret, bytes;
 952         umode_t i_mode;
 953         size_t len;
 954         int i, flags;
 955
 956         /*
 957          * We require the input being a regular file, as we don't want to
 958          * randomly drop data for eg socket -> socket splicing. Use the
 959          * piped splicing for that!
 960          */
 961         i_mode = in->f_path.dentry->d_inode->i_mode;
 962         if (unlikely(!S_ISREG(i_mode) && !S_ISBLK(i_mode)))
 963                 return -EINVAL;
 964
 965         /*
 966          * neither in nor out is a pipe, setup an internal pipe attached to
 967          * 'out' and transfer the wanted data from 'in' to 'out' through that
 968          */
 969         pipe = current->splice_pipe;
 970         if (unlikely(!pipe)) {
 971                 pipe = alloc_pipe_info(NULL);
 972                 if (!pipe)
 973                         return -ENOMEM;
 974
 975                 /*
 976                  * We don't have an immediate reader, but we'll read the stuff
 977                  * out of the pipe right after the splice_to_pipe(). So set
 978                  * PIPE_READERS appropriately.
 979                  */
 980                 pipe->readers = 1;
 981
 982                 current->splice_pipe = pipe;
 983         }
 984
 985         /*
 986          * Do the splice.
 987          */
 988         ret = 0;
 989         bytes = 0;
 990         len = sd->total_len;
 991         flags = sd->flags;
 992
 993         /*
 994          * Don't block on output, we have to drain the direct pipe.
 995          */
 996         sd->flags &= ~SPLICE_F_NONBLOCK;
 997
 998         while (len) {
 999                 size_t read_len;
1000                 loff_t pos = sd->pos, prev_pos = pos;
1001
1002                 ret = do_splice_to(in, &pos, pipe, len, flags);
1003                 if (unlikely(ret <= 0))
1004                         goto out_release;
1005
1006                 read_len = ret;
1007                 sd->total_len = read_len;
1008
1009                 /*
1010                  * NOTE: nonblocking mode only applies to the input. We
1011                  * must not do the output in nonblocking mode as then we
1012                  * could get stuck data in the internal pipe:
1013                  */
1014                 ret = actor(pipe, sd);
1015                 if (unlikely(ret <= 0)) {
1016                         sd->pos = prev_pos;
1017                         goto out_release;
1018                 }
1019
1020                 bytes += ret;
1021                 len -= ret;
1022                 sd->pos = pos;
1023
1024                 if (ret < read_len) {
1025                         sd->pos = prev_pos + ret;
1026                         goto out_release;
1027                 }
1028         }
1029
1030 done:
1031         pipe->nrbufs = pipe->curbuf = 0;
1032         file_accessed(in);
1033         return bytes;
1034
1035 out_release:
1036         /*
1037          * If we did an incomplete transfer we must release
1038          * the pipe buffers in question:
1039          */
1040         for (i = 0; i < PIPE_BUFFERS; i++) {
1041                 struct pipe_buffer *buf = pipe->bufs + i;
1042
1043                 if (buf->ops) {
1044                         buf->ops->release(pipe, buf);
1045                         buf->ops = NULL;
1046                 }
1047         }
1048
1049         if (!bytes)
1050                 bytes = ret;
1051
1052         goto done;
1053 }
1054 EXPORT_SYMBOL(splice_direct_to_actor);
1055
1056 static int direct_splice_actor(struct pipe_inode_info *pipe,
1057                                struct splice_desc *sd)
1058 {
1059         struct file *file = sd->u.file;
1060
1061         return do_splice_from(pipe, file, &sd->pos, sd->total_len, sd->flags);
1062 }
1063
1064 /**
1065  * do_splice_direct - splices data directly between two files
1066  * @in:         file to splice from
1067  * @ppos:       input file offset
1068  * @out:        file to splice to
1069  * @len:        number of bytes to splice
1070  * @flags:      splice modifier flags
1071  *
1072  * Description:
1073  *    For use by do_sendfile(). splice can easily emulate sendfile, but
1074  *    doing it in the application would incur an extra system call
1075  *    (splice in + splice out, as compared to just sendfile()). So this helper
1076  *    can splice directly through a process-private pipe.
1077  *
1078  */
1079 long do_splice_direct(struct file *in, loff_t *ppos, struct file *out,
1080                       size_t len, unsigned int flags)
1081 {
1082         struct splice_desc sd = {
1083                 .len            = len,
1084                 .total_len      = len,
1085                 .flags          = flags,
1086                 .pos            = *ppos,
1087                 .u.file         = out,
1088         };
1089         long ret;
1090
1091         ret = splice_direct_to_actor(in, &sd, direct_splice_actor);
1092         if (ret > 0)
1093                 *ppos = sd.pos;
1094
1095         return ret;
1096 }
1097
1098 /*
1099  * After the inode slimming patch, i_pipe/i_bdev/i_cdev share the same
1100  * location, so checking ->i_pipe is not enough to verify that this is a
1101  * pipe.
1102  */
1103 static inline struct pipe_inode_info *pipe_info(struct inode *inode)
1104 {
1105         if (S_ISFIFO(inode->i_mode))
1106                 return inode->i_pipe;
1107
1108         return NULL;
1109 }
1110
1111 /*
1112  * Determine where to splice to/from.
1113  */
1114 static long do_splice(struct file *in, loff_t __user *off_in,
1115                       struct file *out, loff_t __user *off_out,
1116                       size_t len, unsigned int flags)
1117 {
1118         struct pipe_inode_info *pipe;
1119         loff_t offset, *off;
1120         long ret;
1121
1122         pipe = pipe_info(in->f_path.dentry->d_inode);
1123         if (pipe) {
1124                 if (off_in)
1125                         return -ESPIPE;
1126                 if (off_out) {
1127                         if (out->f_op->llseek == no_llseek)
1128                                 return -EINVAL;
1129                         if (copy_from_user(&offset, off_out, sizeof(loff_t)))
1130                                 return -EFAULT;
1131                         off = &offset;
1132                 } else
1133                         off = &out->f_pos;
1134
1135                 ret = do_splice_from(pipe, out, off, len, flags);
1136
1137                 if (off_out && copy_to_user(off_out, off, sizeof(loff_t)))
1138                         ret = -EFAULT;
1139
1140                 return ret;
1141         }
1142
1143         pipe = pipe_info(out->f_path.dentry->d_inode);
1144         if (pipe) {
1145                 if (off_out)
1146                         return -ESPIPE;
1147                 if (off_in) {
1148                         if (in->f_op->llseek == no_llseek)
1149                                 return -EINVAL;
1150                         if (copy_from_user(&offset, off_in, sizeof(loff_t)))
1151                                 return -EFAULT;
1152                         off = &offset;
1153                 } else
1154                         off = &in->f_pos;
1155
1156                 ret = do_splice_to(in, off, pipe, len, flags);
1157
1158                 if (off_in && copy_to_user(off_in, off, sizeof(loff_t)))
1159                         ret = -EFAULT;
1160
1161                 return ret;
1162         }
1163
1164         return -EINVAL;
1165 }
1166
1167 /*
1168  * Map an iov into an array of pages and offset/length tupples. With the
1169  * partial_page structure, we can map several non-contiguous ranges into
1170  * our ones pages[] map instead of splitting that operation into pieces.
1171  * Could easily be exported as a generic helper for other users, in which
1172  * case one would probably want to add a 'max_nr_pages' parameter as well.
1173  */
1174 static int get_iovec_page_array(const struct iovec __user *iov,
1175                                 unsigned int nr_vecs, struct page **pages,
1176                                 struct partial_page *partial, int aligned)
1177 {
1178         int buffers = 0, error = 0;
1179
1180         while (nr_vecs) {
1181                 unsigned long off, npages;
1182                 struct iovec entry;
1183                 void __user *base;
1184                 size_t len;
1185                 int i;
1186
1187                 error = -EFAULT;
1188                 if (copy_from_user(&entry, iov, sizeof(entry)))
1189                         break;
1190
1191                 base = entry.iov_base;
1192                 len = entry.iov_len;
1193
1194                 /*
1195                  * Sanity check this iovec. 0 read succeeds.
1196                  */
1197                 error = 0;
1198                 if (unlikely(!len))
1199                         break;
1200                 error = -EFAULT;
1201                 if (!access_ok(VERIFY_READ, base, len))
1202                         break;
1203
1204                 /*
1205                  * Get this base offset and number of pages, then map
1206                  * in the user pages.
1207                  */
1208                 off = (unsigned long) base & ~PAGE_MASK;
1209
1210                 /*
1211                  * If asked for alignment, the offset must be zero and the
1212                  * length a multiple of the PAGE_SIZE.
1213                  */
1214                 error = -EINVAL;
1215                 if (aligned && (off || len & ~PAGE_MASK))
1216                         break;
1217
1218                 npages = (off + len + PAGE_SIZE - 1) >> PAGE_SHIFT;
1219                 if (npages > PIPE_BUFFERS - buffers)
1220                         npages = PIPE_BUFFERS - buffers;
1221
1222                 error = get_user_pages_fast((unsigned long)base, npages,
1223                                         0, &pages[buffers]);
1224
1225                 if (unlikely(error <= 0))
1226                         break;
1227
1228                 /*
1229                  * Fill this contiguous range into the partial page map.
1230                  */
1231                 for (i = 0; i < error; i++) {
1232                         const int plen = min_t(size_t, len, PAGE_SIZE - off);
1233
1234                         partial[buffers].offset = off;
1235                         partial[buffers].len = plen;
1236
1237                         off = 0;
1238                         len -= plen;
1239                         buffers++;
1240                 }
1241
1242                 /*
1243                  * We didn't complete this iov, stop here since it probably
1244                  * means we have to move some of this into a pipe to
1245                  * be able to continue.
1246                  */
1247                 if (len)
1248                         break;
1249
1250                 /*
1251                  * Don't continue if we mapped fewer pages than we asked for,
1252                  * or if we mapped the max number of pages that we have
1253                  * room for.
1254                  */
1255                 if (error < npages || buffers == PIPE_BUFFERS)
1256                         break;
1257
1258                 nr_vecs--;
1259                 iov++;
1260         }
1261
1262         if (buffers)
1263                 return buffers;
1264
1265         return error;
1266 }
1267
1268 static int pipe_to_user(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
1269                         struct splice_desc *sd)
1270 {
1271         char *src;
1272         int ret;
1273
1274         ret = buf->ops->confirm(pipe, buf);
1275         if (unlikely(ret))
1276                 return ret;
1277
1278         /*
1279          * See if we can use the atomic maps, by prefaulting in the
1280          * pages and doing an atomic copy
1281          */
1282         if (!fault_in_pages_writeable(sd->u.userptr, sd->len)) {
1283                 src = buf->ops->map(pipe, buf, 1);
1284                 ret = __copy_to_user_inatomic(sd->u.userptr, src + buf->offset,
1285                                                         sd->len);
1286                 buf->ops->unmap(pipe, buf, src);
1287                 if (!ret) {
1288                         ret = sd->len;
1289                         goto out;
1290                 }
1291         }
1292
1293         /*
1294          * No dice, use slow non-atomic map and copy
1295          */
1296         src = buf->ops->map(pipe, buf, 0);
1297
1298         ret = sd->len;
1299         if (copy_to_user(sd->u.userptr, src + buf->offset, sd->len))
1300                 ret = -EFAULT;
1301
1302         buf->ops->unmap(pipe, buf, src);
1303 out:
1304         if (ret > 0)
1305                 sd->u.userptr += ret;
1306         return ret;
1307 }
1308
1309 /*
1310  * For lack of a better implementation, implement vmsplice() to userspace
1311  * as a simple copy of the pipes pages to the user iov.
1312  */
1313 static long vmsplice_to_user(struct file *file, const struct iovec __user *iov,
1314                              unsigned long nr_segs, unsigned int flags)
1315 {
1316         struct pipe_inode_info *pipe;
1317         struct splice_desc sd;
1318         ssize_t size;
1319         int error;
1320         long ret;
1321
1322         pipe = pipe_info(file->f_path.dentry->d_inode);
1323         if (!pipe)
1324                 return -EBADF;
1325
1326         if (pipe->inode)
1327                 mutex_lock(&pipe->inode->i_mutex);
1328
1329         error = ret = 0;
1330         while (nr_segs) {
1331                 void __user *base;
1332                 size_t len;
1333
1334                 /*
1335                  * Get user address base and length for this iovec.
1336                  */
1337                 error = get_user(base, &iov->iov_base);
1338                 if (unlikely(error))
1339                         break;
1340                 error = get_user(len, &iov->iov_len);
1341                 if (unlikely(error))
1342                         break;
1343
1344                 /*
1345                  * Sanity check this iovec. 0 read succeeds.
1346                  */
1347                 if (unlikely(!len))
1348                         break;
1349                 if (unlikely(!base)) {
1350                         error = -EFAULT;
1351                         break;
1352                 }
1353
1354                 if (unlikely(!access_ok(VERIFY_WRITE, base, len))) {
1355                         error = -EFAULT;
1356                         break;
1357                 }
1358
1359                 sd.len = 0;
1360                 sd.total_len = len;
1361                 sd.flags = flags;
1362                 sd.u.userptr = base;
1363                 sd.pos = 0;
1364
1365                 size = __splice_from_pipe(pipe, &sd, pipe_to_user);
1366                 if (size < 0) {
1367                         if (!ret)
1368                                 ret = size;
1369
1370                         break;
1371                 }
1372
1373                 ret += size;
1374
1375                 if (size < len)
1376                         break;
1377
1378                 nr_segs--;
1379                 iov++;
1380         }
1381
1382         if (pipe->inode)
1383                 mutex_unlock(&pipe->inode->i_mutex);
1384
1385         if (!ret)
1386                 ret = error;
1387
1388         return ret;
1389 }
1390
1391 /*
1392  * vmsplice splices a user address range into a pipe. It can be thought of
1393  * as splice-from-memory, where the regular splice is splice-from-file (or
1394  * to file). In both cases the output is a pipe, naturally.
1395  */
1396 static long vmsplice_to_pipe(struct file *file, const struct iovec __user *iov,
1397                              unsigned long nr_segs, unsigned int flags)
1398 {
1399         struct pipe_inode_info *pipe;
1400         struct page *pages[PIPE_BUFFERS];
1401         struct partial_page partial[PIPE_BUFFERS];
1402         struct splice_pipe_desc spd = {
1403                 .pages = pages,
1404                 .partial = partial,
1405                 .flags = flags,
1406                 .ops = &user_page_pipe_buf_ops,
1407                 .spd_release = spd_release_page,
1408         };
1409
1410         pipe = pipe_info(file->f_path.dentry->d_inode);
1411         if (!pipe)
1412                 return -EBADF;
1413
1414         spd.nr_pages = get_iovec_page_array(iov, nr_segs, pages, partial,
1415                                             flags & SPLICE_F_GIFT);
1416         if (spd.nr_pages <= 0)
1417                 return spd.nr_pages;
1418
1419         return splice_to_pipe(pipe, &spd);
1420 }
1421
1422 /*
1423  * Note that vmsplice only really supports true splicing _from_ user memory
1424  * to a pipe, not the other way around. Splicing from user memory is a simple
1425  * operation that can be supported without any funky alignment restrictions
1426  * or nasty vm tricks. We simply map in the user memory and fill them into
1427  * a pipe. The reverse isn't quite as easy, though. There are two possible
1428  * solutions for that:
1429  *
1430  *      - memcpy() the data internally, at which point we might as well just
1431  *        do a regular read() on the buffer anyway.
1432  *      - Lots of nasty vm tricks, that are neither fast nor flexible (it
1433  *        has restriction limitations on both ends of the pipe).
1434  *
1435  * Currently we punt and implement it as a normal copy, see pipe_to_user().
1436  *
1437  */
1438 asmlinkage long sys_vmsplice(int fd, const struct iovec __user *iov,
1439                              unsigned long nr_segs, unsigned int flags)
1440 {
1441         struct file *file;
1442         long error;
1443         int fput;
1444
1445         if (unlikely(nr_segs > UIO_MAXIOV))
1446                 return -EINVAL;
1447         else if (unlikely(!nr_segs))
1448                 return 0;
1449
1450         error = -EBADF;
1451         file = fget_light(fd, &fput);
1452         if (file) {
1453                 if (file->f_mode & FMODE_WRITE)
1454                         error = vmsplice_to_pipe(file, iov, nr_segs, flags);
1455                 else if (file->f_mode & FMODE_READ)
1456                         error = vmsplice_to_user(file, iov, nr_segs, flags);
1457
1458                 fput_light(file, fput);
1459         }
1460
1461         return error;
1462 }
1463
1464 asmlinkage long sys_splice(int fd_in, loff_t __user *off_in,
1465                            int fd_out, loff_t __user *off_out,
1466                            size_t len, unsigned int flags)
1467 {
1468         long error;
1469         struct file *in, *out;
1470         int fput_in, fput_out;
1471
1472         if (unlikely(!len))
1473                 return 0;
1474
1475         error = -EBADF;
1476         in = fget_light(fd_in, &fput_in);
1477         if (in) {
1478                 if (in->f_mode & FMODE_READ) {
1479                         out = fget_light(fd_out, &fput_out);
1480                         if (out) {
1481                                 if (out->f_mode & FMODE_WRITE)
1482                                         error = do_splice(in, off_in,
1483                                                           out, off_out,
1484                                                           len, flags);
1485                                 fput_light(out, fput_out);
1486                         }
1487                 }
1488
1489                 fput_light(in, fput_in);
1490         }
1491
1492         return error;
1493 }
1494
1495 /*
1496  * Make sure there's data to read. Wait for input if we can, otherwise
1497  * return an appropriate error.
1498  */
1499 static int link_ipipe_prep(struct pipe_inode_info *pipe, unsigned int flags)
1500 {
1501         int ret;
1502
1503         /*
1504          * Check ->nrbufs without the inode lock first. This function
1505          * is speculative anyways, so missing one is ok.
1506          */
1507         if (pipe->nrbufs)
1508                 return 0;
1509
1510         ret = 0;
1511         mutex_lock(&pipe->inode->i_mutex);
1512
1513         while (!pipe->nrbufs) {
1514                 if (signal_pending(current)) {
1515                         ret = -ERESTARTSYS;
1516                         break;
1517                 }
1518                 if (!pipe->writers)
1519                         break;
1520                 if (!pipe->waiting_writers) {
1521                         if (flags & SPLICE_F_NONBLOCK) {
1522                                 ret = -EAGAIN;
1523                                 break;
1524                         }
1525                 }
1526                 pipe_wait(pipe);
1527         }
1528
1529         mutex_unlock(&pipe->inode->i_mutex);
1530         return ret;
1531 }
1532
1533 /*
1534  * Make sure there's writeable room. Wait for room if we can, otherwise
1535  * return an appropriate error.
1536  */
1537 static int link_opipe_prep(struct pipe_inode_info *pipe, unsigned int flags)
1538 {
1539         int ret;
1540
1541         /*
1542          * Check ->nrbufs without the inode lock first. This function
1543          * is speculative anyways, so missing one is ok.
1544          */
1545         if (pipe->nrbufs < PIPE_BUFFERS)
1546                 return 0;
1547
1548         ret = 0;
1549         mutex_lock(&pipe->inode->i_mutex);
1550
1551         while (pipe->nrbufs >= PIPE_BUFFERS) {
1552                 if (!pipe->readers) {
1553                         send_sig(SIGPIPE, current, 0);
1554                         ret = -EPIPE;
1555                         break;
1556                 }
1557                 if (flags & SPLICE_F_NONBLOCK) {
1558                         ret = -EAGAIN;
1559                         break;
1560                 }
1561                 if (signal_pending(current)) {
1562                         ret = -ERESTARTSYS;
1563                         break;
1564                 }
1565                 pipe->waiting_writers++;
1566                 pipe_wait(pipe);
1567                 pipe->waiting_writers--;
1568         }
1569
1570         mutex_unlock(&pipe->inode->i_mutex);
1571         return ret;
1572 }
1573
1574 /*
1575  * Link contents of ipipe to opipe.
1576  */
1577 static int link_pipe(struct pipe_inode_info *ipipe,
1578                      struct pipe_inode_info *opipe,
1579                      size_t len, unsigned int flags)
1580 {
1581         struct pipe_buffer *ibuf, *obuf;
1582         int ret = 0, i = 0, nbuf;
1583
1584         /*
1585          * Potential ABBA deadlock, work around it by ordering lock
1586          * grabbing by inode address. Otherwise two different processes
1587          * could deadlock (one doing tee from A -> B, the other from B -> A).
1588          */
1589         inode_double_lock(ipipe->inode, opipe->inode);
1590
1591         do {
1592                 if (!opipe->readers) {
1593                         send_sig(SIGPIPE, current, 0);
1594                         if (!ret)
1595                                 ret = -EPIPE;
1596                         break;
1597                 }
1598
1599                 /*
1600                  * If we have iterated all input buffers or ran out of
1601                  * output room, break.
1602                  */
1603                 if (i >= ipipe->nrbufs || opipe->nrbufs >= PIPE_BUFFERS)
1604                         break;
1605
1606                 ibuf = ipipe->bufs + ((ipipe->curbuf + i) & (PIPE_BUFFERS - 1));
1607                 nbuf = (opipe->curbuf + opipe->nrbufs) & (PIPE_BUFFERS - 1);
1608
1609                 /*
1610                  * Get a reference to this pipe buffer,
1611                  * so we can copy the contents over.
1612                  */
1613                 ibuf->ops->get(ipipe, ibuf);
1614
1615                 obuf = opipe->bufs + nbuf;
1616                 *obuf = *ibuf;
1617
1618                 /*
1619                  * Don't inherit the gift flag, we need to
1620                  * prevent multiple steals of this page.
1621                  */
1622                 obuf->flags &= ~PIPE_BUF_FLAG_GIFT;
1623
1624                 if (obuf->len > len)
1625                         obuf->len = len;
1626
1627                 opipe->nrbufs++;
1628                 ret += obuf->len;
1629                 len -= obuf->len;
1630                 i++;
1631         } while (len);
1632
1633         /*
1634          * return EAGAIN if we have the potential of some data in the
1635          * future, otherwise just return 0
1636          */
1637         if (!ret && ipipe->waiting_writers && (flags & SPLICE_F_NONBLOCK))
1638                 ret = -EAGAIN;
1639
1640         inode_double_unlock(ipipe->inode, opipe->inode);
1641
1642         /*
1643          * If we put data in the output pipe, wakeup any potential readers.
1644          */
1645         if (ret > 0) {
1646                 smp_mb();
1647                 if (waitqueue_active(&opipe->wait))
1648                         wake_up_interruptible(&opipe->wait);
1649                 kill_fasync(&opipe->fasync_readers, SIGIO, POLL_IN);
1650         }
1651
1652         return ret;
1653 }
1654
1655 /*
1656  * This is a tee(1) implementation that works on pipes. It doesn't copy
1657  * any data, it simply references the 'in' pages on the 'out' pipe.
1658  * The 'flags' used are the SPLICE_F_* variants, currently the only
1659  * applicable one is SPLICE_F_NONBLOCK.
1660  */
1661 static long do_tee(struct file *in, struct file *out, size_t len,
1662                    unsigned int flags)
1663 {
1664         struct pipe_inode_info *ipipe = pipe_info(in->f_path.dentry->d_inode);
1665         struct pipe_inode_info *opipe = pipe_info(out->f_path.dentry->d_inode);
1666         int ret = -EINVAL;
1667
1668         /*
1669          * Duplicate the contents of ipipe to opipe without actually
1670          * copying the data.
1671          */
1672         if (ipipe && opipe && ipipe != opipe) {
1673                 /*
1674                  * Keep going, unless we encounter an error. The ipipe/opipe
1675                  * ordering doesn't really matter.
1676                  */
1677                 ret = link_ipipe_prep(ipipe, flags);
1678                 if (!ret) {
1679                         ret = link_opipe_prep(opipe, flags);
1680                         if (!ret)
1681                                 ret = link_pipe(ipipe, opipe, len, flags);
1682                 }
1683         }
1684
1685         return ret;
1686 }
1687
1688 asmlinkage long sys_tee(int fdin, int fdout, size_t len, unsigned int flags)
1689 {
1690         struct file *in;
1691         int error, fput_in;
1692
1693         if (unlikely(!len))
1694                 return 0;
1695
1696         error = -EBADF;
1697         in = fget_light(fdin, &fput_in);
1698         if (in) {
1699                 if (in->f_mode & FMODE_READ) {
1700                         int fput_out;
1701                         struct file *out = fget_light(fdout, &fput_out);
1702
1703                         if (out) {
1704                                 if (out->f_mode & FMODE_WRITE)
1705                                         error = do_tee(in, out, len, flags);
1706                                 fput_light(out, fput_out);
1707                         }
1708                 }
1709                 fput_light(in, fput_in);
1710         }
1711
1712         return error;
1713 }