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 <[email protected]>
  16  * Copyright (C) 2005-2006 Linus Torvalds <[email protected]>
  17  * Copyright (C) 2006 Ingo Molnar <[email protected]>
  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 #include <linux/gfp.h>
  34
  35 /*
  36  * Attempt to steal a page from a pipe buffer. This should perhaps go into
  37  * a vm helper function, it's already simplified quite a bit by the
  38  * addition of remove_mapping(). If success is returned, the caller may
  39  * attempt to reuse this page for another destination.
  40  */
  41 static int page_cache_pipe_buf_steal(struct pipe_inode_info *pipe,
  42                                      struct pipe_buffer *buf)
  43 {
  44         struct page *page = buf->page;
  45         struct address_space *mapping;
  46
  47         lock_page(page);
  48
  49         mapping = page_mapping(page);
  50         if (mapping) {
  51                 WARN_ON(!PageUptodate(page));
  52
  53                 /*
  54                  * At least for ext2 with nobh option, we need to wait on
  55                  * writeback completing on this page, since we'll remove it
  56                  * from the pagecache.  Otherwise truncate wont wait on the
  57                  * page, allowing the disk blocks to be reused by someone else
  58                  * before we actually wrote our data to them. fs corruption
  59                  * ensues.
  60                  */
  61                 wait_on_page_writeback(page);
  62
  63                 if (page_has_private(page) &&
  64                     !try_to_release_page(page, GFP_KERNEL))
  65                         goto out_unlock;
  66
  67                 /*
  68                  * If we succeeded in removing the mapping, set LRU flag
  69                  * and return good.
  70                  */
  71                 if (remove_mapping(mapping, page)) {
  72                         buf->flags |= PIPE_BUF_FLAG_LRU;
  73                         return 0;
  74                 }
  75         }
  76
  77         /*
  78          * Raced with truncate or failed to remove page from current
  79          * address space, unlock and return failure.
  80          */
  81 out_unlock:
  82         unlock_page(page);
  83         return 1;
  84 }
  85
  86 static void page_cache_pipe_buf_release(struct pipe_inode_info *pipe,
  87                                         struct pipe_buffer *buf)
  88 {
  89         page_cache_release(buf->page);
  90         buf->flags &= ~PIPE_BUF_FLAG_LRU;
  91 }
  92
  93 /*
  94  * Check whether the contents of buf is OK to access. Since the content
  95  * is a page cache page, IO may be in flight.
  96  */
  97 static int page_cache_pipe_buf_confirm(struct pipe_inode_info *pipe,
  98                                        struct pipe_buffer *buf)
  99 {
 100         struct page *page = buf->page;
 101         int err;
 102
 103         if (!PageUptodate(page)) {
 104                 lock_page(page);
 105
 106                 /*
 107                  * Page got truncated/unhashed. This will cause a 0-byte
 108                  * splice, if this is the first page.
 109                  */
 110                 if (!page->mapping) {
 111                         err = -ENODATA;
 112                         goto error;
 113                 }
 114
 115                 /*
 116                  * Uh oh, read-error from disk.
 117                  */
 118                 if (!PageUptodate(page)) {
 119                         err = -EIO;
 120                         goto error;
 121                 }
 122
 123                 /*
 124                  * Page is ok afterall, we are done.
 125                  */
 126                 unlock_page(page);
 127         }
 128
 129         return 0;
 130 error:
 131         unlock_page(page);
 132         return err;
 133 }
 134
 135 static const struct pipe_buf_operations page_cache_pipe_buf_ops = {
 136         .can_merge = 0,
 137         .map = generic_pipe_buf_map,
 138         .unmap = generic_pipe_buf_unmap,
 139         .confirm = page_cache_pipe_buf_confirm,
 140         .release = page_cache_pipe_buf_release,
 141         .steal = page_cache_pipe_buf_steal,
 142         .get = generic_pipe_buf_get,
 143 };
 144
 145 static int user_page_pipe_buf_steal(struct pipe_inode_info *pipe,
 146                                     struct pipe_buffer *buf)
 147 {
 148         if (!(buf->flags & PIPE_BUF_FLAG_GIFT))
 149                 return 1;
 150
 151         buf->flags |= PIPE_BUF_FLAG_LRU;
 152         return generic_pipe_buf_steal(pipe, buf);
 153 }
 154
 155 static const struct pipe_buf_operations user_page_pipe_buf_ops = {
 156         .can_merge = 0,
 157         .map = generic_pipe_buf_map,
 158         .unmap = generic_pipe_buf_unmap,
 159         .confirm = generic_pipe_buf_confirm,
 160         .release = page_cache_pipe_buf_release,
 161         .steal = user_page_pipe_buf_steal,
 162         .get = generic_pipe_buf_get,
 163 };
 164
 165 /**
 166  * splice_to_pipe - fill passed data into a pipe
 167  * @pipe:       pipe to fill
 168  * @spd:        data to fill
 169  *
 170  * Description:
 171  *    @spd contains a map of pages and len/offset tuples, along with
 172  *    the struct pipe_buf_operations associated with these pages. This
 173  *    function will link that data to the pipe.
 174  *
 175  */
 176 ssize_t splice_to_pipe(struct pipe_inode_info *pipe,
 177                        struct splice_pipe_desc *spd)
 178 {
 179         unsigned int spd_pages = spd->nr_pages;
 180         int ret, do_wakeup, page_nr;
 181
 182         ret = 0;
 183         do_wakeup = 0;
 184         page_nr = 0;
 185
 186         pipe_lock(pipe);
 187
 188         for (;;) {
 189                 if (!pipe->readers) {
 190                         send_sig(SIGPIPE, current, 0);
 191                         if (!ret)
 192                                 ret = -EPIPE;
 193                         break;
 194                 }
 195
 196                 if (pipe->nrbufs < PIPE_BUFFERS) {
 197                         int newbuf = (pipe->curbuf + pipe->nrbufs) & (PIPE_BUFFERS - 1);
 198                         struct pipe_buffer *buf = pipe->bufs + newbuf;
 199
 200                         buf->page = spd->pages[page_nr];
 201                         buf->offset = spd->partial[page_nr].offset;
 202                         buf->len = spd->partial[page_nr].len;
 203                         buf->private = spd->partial[page_nr].private;
 204                         buf->ops = spd->ops;
 205                         if (spd->flags & SPLICE_F_GIFT)
 206                                 buf->flags |= PIPE_BUF_FLAG_GIFT;
 207
 208                         pipe->nrbufs++;
 209                         page_nr++;
 210                         ret += buf->len;
 211
 212                         if (pipe->inode)
 213                                 do_wakeup = 1;
 214
 215                         if (!--spd->nr_pages)
 216                                 break;
 217                         if (pipe->nrbufs < PIPE_BUFFERS)
 218                                 continue;
 219
 220                         break;
 221                 }
 222
 223                 if (spd->flags & SPLICE_F_NONBLOCK) {
 224                         if (!ret)
 225                                 ret = -EAGAIN;
 226                         break;
 227                 }
 228
 229                 if (signal_pending(current)) {
 230                         if (!ret)
 231                                 ret = -ERESTARTSYS;
 232                         break;
 233                 }
 234
 235                 if (do_wakeup) {
 236                         smp_mb();
 237                         if (waitqueue_active(&pipe->wait))
 238                                 wake_up_interruptible_sync(&pipe->wait);
 239                         kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
 240                         do_wakeup = 0;
 241                 }
 242
 243                 pipe->waiting_writers++;
 244                 pipe_wait(pipe);
 245                 pipe->waiting_writers--;
 246         }
 247
 248         pipe_unlock(pipe);
 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         while (page_nr < spd_pages)
 258                 spd->spd_release(spd, page_nr++);
 259
 260         return ret;
 261 }
 262
 263 static void spd_release_page(struct splice_pipe_desc *spd, unsigned int i)
 264 {
 265         page_cache_release(spd->pages[i]);
 266 }
 267
 268 static int
 269 __generic_file_splice_read(struct file *in, loff_t *ppos,
 270                            struct pipe_inode_info *pipe, size_t len,
 271                            unsigned int flags)
 272 {
 273         struct address_space *mapping = in->f_mapping;
 274         unsigned int loff, nr_pages, req_pages;
 275         struct page *pages[PIPE_BUFFERS];
 276         struct partial_page partial[PIPE_BUFFERS];
 277         struct page *page;
 278         pgoff_t index, end_index;
 279         loff_t isize;
 280         int error, page_nr;
 281         struct splice_pipe_desc spd = {
 282                 .pages = pages,
 283                 .partial = partial,
 284                 .flags = flags,
 285                 .ops = &page_cache_pipe_buf_ops,
 286                 .spd_release = spd_release_page,
 287         };
 288
 289         index = *ppos >> PAGE_CACHE_SHIFT;
 290         loff = *ppos & ~PAGE_CACHE_MASK;
 291         req_pages = (len + loff + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
 292         nr_pages = min(req_pages, (unsigned)PIPE_BUFFERS);
 293
 294         /*
 295          * Lookup the (hopefully) full range of pages we need.
 296          */
 297         spd.nr_pages = find_get_pages_contig(mapping, index, nr_pages, pages);
 298         index += spd.nr_pages;
 299
 300         /*
 301          * If find_get_pages_contig() returned fewer pages than we needed,
 302          * readahead/allocate the rest and fill in the holes.
 303          */
 304         if (spd.nr_pages < nr_pages)
 305                 page_cache_sync_readahead(mapping, &in->f_ra, in,
 306                                 index, req_pages - spd.nr_pages);
 307
 308         error = 0;
 309         while (spd.nr_pages < nr_pages) {
 310                 /*
 311                  * Page could be there, find_get_pages_contig() breaks on
 312                  * the first hole.
 313                  */
 314                 page = find_get_page(mapping, index);
 315                 if (!page) {
 316                         /*
 317                          * page didn't exist, allocate one.
 318                          */
 319                         page = page_cache_alloc_cold(mapping);
 320                         if (!page)
 321                                 break;
 322
 323                         error = add_to_page_cache_lru(page, mapping, index,
 324                                                 mapping_gfp_mask(mapping));
 325                         if (unlikely(error)) {
 326                                 page_cache_release(page);
 327                                 if (error == -EEXIST)
 328                                         continue;
 329                                 break;
 330                         }
 331                         /*
 332                          * add_to_page_cache() locks the page, unlock it
 333                          * to avoid convoluting the logic below even more.
 334                          */
 335                         unlock_page(page);
 336                 }
 337
 338                 pages[spd.nr_pages++] = page;
 339                 index++;
 340         }
 341
 342         /*
 343          * Now loop over the map and see if we need to start IO on any
 344          * pages, fill in the partial map, etc.
 345          */
 346         index = *ppos >> PAGE_CACHE_SHIFT;
 347         nr_pages = spd.nr_pages;
 348         spd.nr_pages = 0;
 349         for (page_nr = 0; page_nr < nr_pages; page_nr++) {
 350                 unsigned int this_len;
 351
 352                 if (!len)
 353                         break;
 354
 355                 /*
 356                  * this_len is the max we'll use from this page
 357                  */
 358                 this_len = min_t(unsigned long, len, PAGE_CACHE_SIZE - loff);
 359                 page = pages[page_nr];
 360
 361                 if (PageReadahead(page))
 362                         page_cache_async_readahead(mapping, &in->f_ra, in,
 363                                         page, index, req_pages - page_nr);
 364
 365                 /*
 366                  * If the page isn't uptodate, we may need to start io on it
 367                  */
 368                 if (!PageUptodate(page)) {
 369                         /*
 370                          * If in nonblock mode then dont block on waiting
 371                          * for an in-flight io page
 372                          */
 373                         if (flags & SPLICE_F_NONBLOCK) {
 374                                 if (!trylock_page(page)) {
 375                                         error = -EAGAIN;
 376                                         break;
 377                                 }
 378                         } else
 379                                 lock_page(page);
 380
 381                         /*
 382                          * Page was truncated, or invalidated by the
 383                          * filesystem.  Redo the find/create, but this time the
 384                          * page is kept locked, so there's no chance of another
 385                          * race with truncate/invalidate.
 386                          */
 387                         if (!page->mapping) {
 388                                 unlock_page(page);
 389                                 page = find_or_create_page(mapping, index,
 390                                                 mapping_gfp_mask(mapping));
 391
 392                                 if (!page) {
 393                                         error = -ENOMEM;
 394                                         break;
 395                                 }
 396                                 page_cache_release(pages[page_nr]);
 397                                 pages[page_nr] = page;
 398                         }
 399                         /*
 400                          * page was already under io and is now done, great
 401                          */
 402                         if (PageUptodate(page)) {
 403                                 unlock_page(page);
 404                                 goto fill_it;
 405                         }
 406
 407                         /*
 408                          * need to read in the page
 409                          */
 410                         error = mapping->a_ops->readpage(in, page);
 411                         if (unlikely(error)) {
 412                                 /*
 413                                  * We really should re-lookup the page here,
 414                                  * but it complicates things a lot. Instead
 415                                  * lets just do what we already stored, and
 416                                  * we'll get it the next time we are called.
 417                                  */
 418                                 if (error == AOP_TRUNCATED_PAGE)
 419                                         error = 0;
 420
 421                                 break;
 422                         }
 423                 }
 424 fill_it:
 425                 /*
 426                  * i_size must be checked after PageUptodate.
 427                  */
 428                 isize = i_size_read(mapping->host);
 429                 end_index = (isize - 1) >> PAGE_CACHE_SHIFT;
 430                 if (unlikely(!isize || index > end_index))
 431                         break;
 432
 433                 /*
 434                  * if this is the last page, see if we need to shrink
 435                  * the length and stop
 436                  */
 437                 if (end_index == index) {
 438                         unsigned int plen;
 439
 440                         /*
 441                          * max good bytes in this page
 442                          */
 443                         plen = ((isize - 1) & ~PAGE_CACHE_MASK) + 1;
 444                         if (plen <= loff)
 445                                 break;
 446
 447                         /*
 448                          * force quit after adding this page
 449                          */
 450                         this_len = min(this_len, plen - loff);
 451                         len = this_len;
 452                 }
 453
 454                 partial[page_nr].offset = loff;
 455                 partial[page_nr].len = this_len;
 456                 len -= this_len;
 457                 loff = 0;
 458                 spd.nr_pages++;
 459                 index++;
 460         }
 461
 462         /*
 463          * Release any pages at the end, if we quit early. 'page_nr' is how far
 464          * we got, 'nr_pages' is how many pages are in the map.
 465          */
 466         while (page_nr < nr_pages)
 467                 page_cache_release(pages[page_nr++]);
 468         in->f_ra.prev_pos = (loff_t)index << PAGE_CACHE_SHIFT;
 469
 470         if (spd.nr_pages)
 471                 return splice_to_pipe(pipe, &spd);
 472
 473         return error;
 474 }
 475
 476 /**
 477  * generic_file_splice_read - splice data from file to a pipe
 478  * @in:         file to splice from
 479  * @ppos:       position in @in
 480  * @pipe:       pipe to splice to
 481  * @len:        number of bytes to splice
 482  * @flags:      splice modifier flags
 483  *
 484  * Description:
 485  *    Will read pages from given file and fill them into a pipe. Can be
 486  *    used as long as the address_space operations for the source implements
 487  *    a readpage() hook.
 488  *
 489  */
 490 ssize_t generic_file_splice_read(struct file *in, loff_t *ppos,
 491                                  struct pipe_inode_info *pipe, size_t len,
 492                                  unsigned int flags)
 493 {
 494         loff_t isize, left;
 495         int ret;
 496
 497         isize = i_size_read(in->f_mapping->host);
 498         if (unlikely(*ppos >= isize))
 499                 return 0;
 500
 501         left = isize - *ppos;
 502         if (unlikely(left < len))
 503                 len = left;
 504
 505         ret = __generic_file_splice_read(in, ppos, pipe, len, flags);
 506         if (ret > 0) {
 507                 *ppos += ret;
 508                 file_accessed(in);
 509         }
 510
 511         return ret;
 512 }
 513 EXPORT_SYMBOL(generic_file_splice_read);
 514
 515 static const struct pipe_buf_operations default_pipe_buf_ops = {
 516         .can_merge = 0,
 517         .map = generic_pipe_buf_map,
 518         .unmap = generic_pipe_buf_unmap,
 519         .confirm = generic_pipe_buf_confirm,
 520         .release = generic_pipe_buf_release,
 521         .steal = generic_pipe_buf_steal,
 522         .get = generic_pipe_buf_get,
 523 };
 524
 525 static ssize_t kernel_readv(struct file *file, const struct iovec *vec,
 526                             unsigned long vlen, loff_t offset)
 527 {
 528         mm_segment_t old_fs;
 529         loff_t pos = offset;
 530         ssize_t res;
 531
 532         old_fs = get_fs();
 533         set_fs(get_ds());
 534         /* The cast to a user pointer is valid due to the set_fs() */
 535         res = vfs_readv(file, (const struct iovec __user *)vec, vlen, &pos);
 536         set_fs(old_fs);
 537
 538         return res;
 539 }
 540
 541 static ssize_t kernel_write(struct file *file, const char *buf, size_t count,
 542                             loff_t pos)
 543 {
 544         mm_segment_t old_fs;
 545         ssize_t res;
 546
 547         old_fs = get_fs();
 548         set_fs(get_ds());
 549         /* The cast to a user pointer is valid due to the set_fs() */
 550         res = vfs_write(file, (const char __user *)buf, count, &pos);
 551         set_fs(old_fs);
 552
 553         return res;
 554 }
 555
 556 ssize_t default_file_splice_read(struct file *in, loff_t *ppos,
 557                                  struct pipe_inode_info *pipe, size_t len,
 558                                  unsigned int flags)
 559 {
 560         unsigned int nr_pages;
 561         unsigned int nr_freed;
 562         size_t offset;
 563         struct page *pages[PIPE_BUFFERS];
 564         struct partial_page partial[PIPE_BUFFERS];
 565         struct iovec vec[PIPE_BUFFERS];
 566         pgoff_t index;
 567         ssize_t res;
 568         size_t this_len;
 569         int error;
 570         int i;
 571         struct splice_pipe_desc spd = {
 572                 .pages = pages,
 573                 .partial = partial,
 574                 .flags = flags,
 575                 .ops = &default_pipe_buf_ops,
 576                 .spd_release = spd_release_page,
 577         };
 578
 579         index = *ppos >> PAGE_CACHE_SHIFT;
 580         offset = *ppos & ~PAGE_CACHE_MASK;
 581         nr_pages = (len + offset + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
 582
 583         for (i = 0; i < nr_pages && i < PIPE_BUFFERS && len; i++) {
 584                 struct page *page;
 585
 586                 page = alloc_page(GFP_USER);
 587                 error = -ENOMEM;
 588                 if (!page)
 589                         goto err;
 590
 591                 this_len = min_t(size_t, len, PAGE_CACHE_SIZE - offset);
 592                 vec[i].iov_base = (void __user *) page_address(page);
 593                 vec[i].iov_len = this_len;
 594                 pages[i] = page;
 595                 spd.nr_pages++;
 596                 len -= this_len;
 597                 offset = 0;
 598         }
 599
 600         res = kernel_readv(in, vec, spd.nr_pages, *ppos);
 601         if (res < 0) {
 602                 error = res;
 603                 goto err;
 604         }
 605
 606         error = 0;
 607         if (!res)
 608                 goto err;
 609
 610         nr_freed = 0;
 611         for (i = 0; i < spd.nr_pages; i++) {
 612                 this_len = min_t(size_t, vec[i].iov_len, res);
 613                 partial[i].offset = 0;
 614                 partial[i].len = this_len;
 615                 if (!this_len) {
 616                         __free_page(pages[i]);
 617                         pages[i] = NULL;
 618                         nr_freed++;
 619                 }
 620                 res -= this_len;
 621         }
 622         spd.nr_pages -= nr_freed;
 623
 624         res = splice_to_pipe(pipe, &spd);
 625         if (res > 0)
 626                 *ppos += res;
 627
 628         return res;
 629
 630 err:
 631         for (i = 0; i < spd.nr_pages; i++)
 632                 __free_page(pages[i]);
 633
 634         return error;
 635 }
 636 EXPORT_SYMBOL(default_file_splice_read);
 637
 638 /*
 639  * Send 'sd->len' bytes to socket from 'sd->file' at position 'sd->pos'
 640  * using sendpage(). Return the number of bytes sent.
 641  */
 642 static int pipe_to_sendpage(struct pipe_inode_info *pipe,
 643                             struct pipe_buffer *buf, struct splice_desc *sd)
 644 {
 645         struct file *file = sd->u.file;
 646         loff_t pos = sd->pos;
 647         int ret, more;
 648
 649         ret = buf->ops->confirm(pipe, buf);
 650         if (!ret) {
 651                 more = (sd->flags & SPLICE_F_MORE) || sd->len < sd->total_len;
 652                 if (file->f_op && file->f_op->sendpage)
 653                         ret = file->f_op->sendpage(file, buf->page, buf->offset,
 654                                                    sd->len, &pos, more);
 655                 else
 656                         ret = -EINVAL;
 657         }
 658
 659         return ret;
 660 }
 661
 662 /*
 663  * This is a little more tricky than the file -> pipe splicing. There are
 664  * basically three cases:
 665  *
 666  *      - Destination page already exists in the address space and there
 667  *        are users of it. For that case we have no other option that
 668  *        copying the data. Tough luck.
 669  *      - Destination page already exists in the address space, but there
 670  *        are no users of it. Make sure it's uptodate, then drop it. Fall
 671  *        through to last case.
 672  *      - Destination page does not exist, we can add the pipe page to
 673  *        the page cache and avoid the copy.
 674  *
 675  * If asked to move pages to the output file (SPLICE_F_MOVE is set in
 676  * sd->flags), we attempt to migrate pages from the pipe to the output
 677  * file address space page cache. This is possible if no one else has
 678  * the pipe page referenced outside of the pipe and page cache. If
 679  * SPLICE_F_MOVE isn't set, or we cannot move the page, we simply create
 680  * a new page in the output file page cache and fill/dirty that.
 681  */
 682 int pipe_to_file(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
 683                  struct splice_desc *sd)
 684 {
 685         struct file *file = sd->u.file;
 686         struct address_space *mapping = file->f_mapping;
 687         unsigned int offset, this_len;
 688         struct page *page;
 689         void *fsdata;
 690         int ret;
 691
 692         /*
 693          * make sure the data in this buffer is uptodate
 694          */
 695         ret = buf->ops->confirm(pipe, buf);
 696         if (unlikely(ret))
 697                 return ret;
 698
 699         offset = sd->pos & ~PAGE_CACHE_MASK;
 700
 701         this_len = sd->len;
 702         if (this_len + offset > PAGE_CACHE_SIZE)
 703                 this_len = PAGE_CACHE_SIZE - offset;
 704
 705         ret = pagecache_write_begin(file, mapping, sd->pos, this_len,
 706                                 AOP_FLAG_UNINTERRUPTIBLE, &page, &fsdata);
 707         if (unlikely(ret))
 708                 goto out;
 709
 710         if (buf->page != page) {
 711                 /*
 712                  * Careful, ->map() uses KM_USER0!
 713                  */
 714                 char *src = buf->ops->map(pipe, buf, 1);
 715                 char *dst = kmap_atomic(page, KM_USER1);
 716
 717                 memcpy(dst + offset, src + buf->offset, this_len);
 718                 flush_dcache_page(page);
 719                 kunmap_atomic(dst, KM_USER1);
 720                 buf->ops->unmap(pipe, buf, src);
 721         }
 722         ret = pagecache_write_end(file, mapping, sd->pos, this_len, this_len,
 723                                 page, fsdata);
 724 out:
 725         return ret;
 726 }
 727 EXPORT_SYMBOL(pipe_to_file);
 728
 729 static void wakeup_pipe_writers(struct pipe_inode_info *pipe)
 730 {
 731         smp_mb();
 732         if (waitqueue_active(&pipe->wait))
 733                 wake_up_interruptible(&pipe->wait);
 734         kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
 735 }
 736
 737 /**
 738  * splice_from_pipe_feed - feed available data from a pipe to a file
 739  * @pipe:       pipe to splice from
 740  * @sd:         information to @actor
 741  * @actor:      handler that splices the data
 742  *
 743  * Description:
 744  *    This function loops over the pipe and calls @actor to do the
 745  *    actual moving of a single struct pipe_buffer to the desired
 746  *    destination.  It returns when there's no more buffers left in
 747  *    the pipe or if the requested number of bytes (@sd->total_len)
 748  *    have been copied.  It returns a positive number (one) if the
 749  *    pipe needs to be filled with more data, zero if the required
 750  *    number of bytes have been copied and -errno on error.
 751  *
 752  *    This, together with splice_from_pipe_{begin,end,next}, may be
 753  *    used to implement the functionality of __splice_from_pipe() when
 754  *    locking is required around copying the pipe buffers to the
 755  *    destination.
 756  */
 757 int splice_from_pipe_feed(struct pipe_inode_info *pipe, struct splice_desc *sd,
 758                           splice_actor *actor)
 759 {
 760         int ret;
 761
 762         while (pipe->nrbufs) {
 763                 struct pipe_buffer *buf = pipe->bufs + pipe->curbuf;
 764                 const struct pipe_buf_operations *ops = buf->ops;
 765
 766                 sd->len = buf->len;
 767                 if (sd->len > sd->total_len)
 768                         sd->len = sd->total_len;
 769
 770                 ret = actor(pipe, buf, sd);
 771                 if (ret <= 0) {
 772                         if (ret == -ENODATA)
 773                                 ret = 0;
 774                         return ret;
 775                 }
 776                 buf->offset += ret;
 777                 buf->len -= ret;
 778
 779                 sd->num_spliced += ret;
 780                 sd->len -= ret;
 781                 sd->pos += ret;
 782                 sd->total_len -= ret;
 783
 784                 if (!buf->len) {
 785                         buf->ops = NULL;
 786                         ops->release(pipe, buf);
 787                         pipe->curbuf = (pipe->curbuf + 1) & (PIPE_BUFFERS - 1);
 788                         pipe->nrbufs--;
 789                         if (pipe->inode)
 790                                 sd->need_wakeup = true;
 791                 }
 792
 793                 if (!sd->total_len)
 794                         return 0;
 795         }
 796
 797         return 1;
 798 }
 799 EXPORT_SYMBOL(splice_from_pipe_feed);
 800
 801 /**
 802  * splice_from_pipe_next - wait for some data to splice from
 803  * @pipe:       pipe to splice from
 804  * @sd:         information about the splice operation
 805  *
 806  * Description:
 807  *    This function will wait for some data and return a positive
 808  *    value (one) if pipe buffers are available.  It will return zero
 809  *    or -errno if no more data needs to be spliced.
 810  */
 811 int splice_from_pipe_next(struct pipe_inode_info *pipe, struct splice_desc *sd)
 812 {
 813         while (!pipe->nrbufs) {
 814                 if (!pipe->writers)
 815                         return 0;
 816
 817                 if (!pipe->waiting_writers && sd->num_spliced)
 818                         return 0;
 819
 820                 if (sd->flags & SPLICE_F_NONBLOCK)
 821                         return -EAGAIN;
 822
 823                 if (signal_pending(current))
 824                         return -ERESTARTSYS;
 825
 826                 if (sd->need_wakeup) {
 827                         wakeup_pipe_writers(pipe);
 828                         sd->need_wakeup = false;
 829                 }
 830
 831                 pipe_wait(pipe);
 832         }
 833
 834         return 1;
 835 }
 836 EXPORT_SYMBOL(splice_from_pipe_next);
 837
 838 /**
 839  * splice_from_pipe_begin - start splicing from pipe
 840  * @sd:         information about the splice operation
 841  *
 842  * Description:
 843  *    This function should be called before a loop containing
 844  *    splice_from_pipe_next() and splice_from_pipe_feed() to
 845  *    initialize the necessary fields of @sd.
 846  */
 847 void splice_from_pipe_begin(struct splice_desc *sd)
 848 {
 849         sd->num_spliced = 0;
 850         sd->need_wakeup = false;
 851 }
 852 EXPORT_SYMBOL(splice_from_pipe_begin);
 853
 854 /**
 855  * splice_from_pipe_end - finish splicing from pipe
 856  * @pipe:       pipe to splice from
 857  * @sd:         information about the splice operation
 858  *
 859  * Description:
 860  *    This function will wake up pipe writers if necessary.  It should
 861  *    be called after a loop containing splice_from_pipe_next() and
 862  *    splice_from_pipe_feed().
 863  */
 864 void splice_from_pipe_end(struct pipe_inode_info *pipe, struct splice_desc *sd)
 865 {
 866         if (sd->need_wakeup)
 867                 wakeup_pipe_writers(pipe);
 868 }
 869 EXPORT_SYMBOL(splice_from_pipe_end);
 870
 871 /**
 872  * __splice_from_pipe - splice data from a pipe to given actor
 873  * @pipe:       pipe to splice from
 874  * @sd:         information to @actor
 875  * @actor:      handler that splices the data
 876  *
 877  * Description:
 878  *    This function does little more than loop over the pipe and call
 879  *    @actor to do the actual moving of a single struct pipe_buffer to
 880  *    the desired destination. See pipe_to_file, pipe_to_sendpage, or
 881  *    pipe_to_user.
 882  *
 883  */
 884 ssize_t __splice_from_pipe(struct pipe_inode_info *pipe, struct splice_desc *sd,
 885                            splice_actor *actor)
 886 {
 887         int ret;
 888
 889         splice_from_pipe_begin(sd);
 890         do {
 891                 ret = splice_from_pipe_next(pipe, sd);
 892                 if (ret > 0)
 893                         ret = splice_from_pipe_feed(pipe, sd, actor);
 894         } while (ret > 0);
 895         splice_from_pipe_end(pipe, sd);
 896
 897         return sd->num_spliced ? sd->num_spliced : ret;
 898 }
 899 EXPORT_SYMBOL(__splice_from_pipe);
 900
 901 /**
 902  * splice_from_pipe - splice data from a pipe to a file
 903  * @pipe:       pipe to splice from
 904  * @out:        file to splice to
 905  * @ppos:       position in @out
 906  * @len:        how many bytes to splice
 907  * @flags:      splice modifier flags
 908  * @actor:      handler that splices the data
 909  *
 910  * Description:
 911  *    See __splice_from_pipe. This function locks the pipe inode,
 912  *    otherwise it's identical to __splice_from_pipe().
 913  *
 914  */
 915 ssize_t splice_from_pipe(struct pipe_inode_info *pipe, struct file *out,
 916                          loff_t *ppos, size_t len, unsigned int flags,
 917                          splice_actor *actor)
 918 {
 919         ssize_t ret;
 920         struct splice_desc sd = {
 921                 .total_len = len,
 922                 .flags = flags,
 923                 .pos = *ppos,
 924                 .u.file = out,
 925         };
 926
 927         pipe_lock(pipe);
 928         ret = __splice_from_pipe(pipe, &sd, actor);
 929         pipe_unlock(pipe);
 930
 931         return ret;
 932 }
 933
 934 /**
 935  * generic_file_splice_write - splice data from a pipe to a file
 936  * @pipe:       pipe info
 937  * @out:        file to write to
 938  * @ppos:       position in @out
 939  * @len:        number of bytes to splice
 940  * @flags:      splice modifier flags
 941  *
 942  * Description:
 943  *    Will either move or copy pages (determined by @flags options) from
 944  *    the given pipe inode to the given file.
 945  *
 946  */
 947 ssize_t
 948 generic_file_splice_write(struct pipe_inode_info *pipe, struct file *out,
 949                           loff_t *ppos, size_t len, unsigned int flags)
 950 {
 951         struct address_space *mapping = out->f_mapping;
 952         struct inode *inode = mapping->host;
 953         struct splice_desc sd = {
 954                 .total_len = len,
 955                 .flags = flags,
 956                 .pos = *ppos,
 957                 .u.file = out,
 958         };
 959         ssize_t ret;
 960
 961         pipe_lock(pipe);
 962
 963         splice_from_pipe_begin(&sd);
 964         do {
 965                 ret = splice_from_pipe_next(pipe, &sd);
 966                 if (ret <= 0)
 967                         break;
 968
 969                 mutex_lock_nested(&inode->i_mutex, I_MUTEX_CHILD);
 970                 ret = file_remove_suid(out);
 971                 if (!ret) {
 972                         file_update_time(out);
 973                         ret = splice_from_pipe_feed(pipe, &sd, pipe_to_file);
 974                 }
 975                 mutex_unlock(&inode->i_mutex);
 976         } while (ret > 0);
 977         splice_from_pipe_end(pipe, &sd);
 978
 979         pipe_unlock(pipe);
 980
 981         if (sd.num_spliced)
 982                 ret = sd.num_spliced;
 983
 984         if (ret > 0) {
 985                 unsigned long nr_pages;
 986                 int err;
 987
 988                 nr_pages = (ret + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
 989
 990                 err = generic_write_sync(out, *ppos, ret);
 991                 if (err)
 992                         ret = err;
 993                 else
 994                         *ppos += ret;
 995                 balance_dirty_pages_ratelimited_nr(mapping, nr_pages);
 996         }
 997
 998         return ret;
 999 }
1000
1001 EXPORT_SYMBOL(generic_file_splice_write);
1002
1003 static int write_pipe_buf(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
1004                           struct splice_desc *sd)
1005 {
1006         int ret;
1007         void *data;
1008
1009         ret = buf->ops->confirm(pipe, buf);
1010         if (ret)
1011                 return ret;
1012
1013         data = buf->ops->map(pipe, buf, 0);
1014         ret = kernel_write(sd->u.file, data + buf->offset, sd->len, sd->pos);
1015         buf->ops->unmap(pipe, buf, data);
1016
1017         return ret;
1018 }
1019
1020 static ssize_t default_file_splice_write(struct pipe_inode_info *pipe,
1021                                          struct file *out, loff_t *ppos,
1022                                          size_t len, unsigned int flags)
1023 {
1024         ssize_t ret;
1025
1026         ret = splice_from_pipe(pipe, out, ppos, len, flags, write_pipe_buf);
1027         if (ret > 0)
1028                 *ppos += ret;
1029
1030         return ret;
1031 }
1032
1033 /**
1034  * generic_splice_sendpage - splice data from a pipe to a socket
1035  * @pipe:       pipe to splice from
1036  * @out:        socket to write to
1037  * @ppos:       position in @out
1038  * @len:        number of bytes to splice
1039  * @flags:      splice modifier flags
1040  *
1041  * Description:
1042  *    Will send @len bytes from the pipe to a network socket. No data copying
1043  *    is involved.
1044  *
1045  */
1046 ssize_t generic_splice_sendpage(struct pipe_inode_info *pipe, struct file *out,
1047                                 loff_t *ppos, size_t len, unsigned int flags)
1048 {
1049         return splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_sendpage);
1050 }
1051
1052 EXPORT_SYMBOL(generic_splice_sendpage);
1053
1054 /*
1055  * Attempt to initiate a splice from pipe to file.
1056  */
1057 static long do_splice_from(struct pipe_inode_info *pipe, struct file *out,
1058                            loff_t *ppos, size_t len, unsigned int flags)
1059 {
1060         ssize_t (*splice_write)(struct pipe_inode_info *, struct file *,
1061                                 loff_t *, size_t, unsigned int);
1062         int ret;
1063
1064         if (unlikely(!(out->f_mode & FMODE_WRITE)))
1065                 return -EBADF;
1066
1067         if (unlikely(out->f_flags & O_APPEND))
1068                 return -EINVAL;
1069
1070         ret = rw_verify_area(WRITE, out, ppos, len);
1071         if (unlikely(ret < 0))
1072                 return ret;
1073
1074         if (out->f_op && out->f_op->splice_write)
1075                 splice_write = out->f_op->splice_write;
1076         else
1077                 splice_write = default_file_splice_write;
1078
1079         return splice_write(pipe, out, ppos, len, flags);
1080 }
1081
1082 /*
1083  * Attempt to initiate a splice from a file to a pipe.
1084  */
1085 static long do_splice_to(struct file *in, loff_t *ppos,
1086                          struct pipe_inode_info *pipe, size_t len,
1087                          unsigned int flags)
1088 {
1089         ssize_t (*splice_read)(struct file *, loff_t *,
1090                                struct pipe_inode_info *, size_t, unsigned int);
1091         int ret;
1092
1093         if (unlikely(!(in->f_mode & FMODE_READ)))
1094                 return -EBADF;
1095
1096         ret = rw_verify_area(READ, in, ppos, len);
1097         if (unlikely(ret < 0))
1098                 return ret;
1099
1100         if (in->f_op && in->f_op->splice_read)
1101                 splice_read = in->f_op->splice_read;
1102         else
1103                 splice_read = default_file_splice_read;
1104
1105         return splice_read(in, ppos, pipe, len, flags);
1106 }
1107
1108 /**
1109  * splice_direct_to_actor - splices data directly between two non-pipes
1110  * @in:         file to splice from
1111  * @sd:         actor information on where to splice to
1112  * @actor:      handles the data splicing
1113  *
1114  * Description:
1115  *    This is a special case helper to splice directly between two
1116  *    points, without requiring an explicit pipe. Internally an allocated
1117  *    pipe is cached in the process, and reused during the lifetime of
1118  *    that process.
1119  *
1120  */
1121 ssize_t splice_direct_to_actor(struct file *in, struct splice_desc *sd,
1122                                splice_direct_actor *actor)
1123 {
1124         struct pipe_inode_info *pipe;
1125         long ret, bytes;
1126         umode_t i_mode;
1127         size_t len;
1128         int i, flags;
1129
1130         /*
1131          * We require the input being a regular file, as we don't want to
1132          * randomly drop data for eg socket -> socket splicing. Use the
1133          * piped splicing for that!
1134          */
1135         i_mode = in->f_path.dentry->d_inode->i_mode;
1136         if (unlikely(!S_ISREG(i_mode) && !S_ISBLK(i_mode)))
1137                 return -EINVAL;
1138
1139         /*
1140          * neither in nor out is a pipe, setup an internal pipe attached to
1141          * 'out' and transfer the wanted data from 'in' to 'out' through that
1142          */
1143         pipe = current->splice_pipe;
1144         if (unlikely(!pipe)) {
1145                 pipe = alloc_pipe_info(NULL);
1146                 if (!pipe)
1147                         return -ENOMEM;
1148
1149                 /*
1150                  * We don't have an immediate reader, but we'll read the stuff
1151                  * out of the pipe right after the splice_to_pipe(). So set
1152                  * PIPE_READERS appropriately.
1153                  */
1154                 pipe->readers = 1;
1155
1156                 current->splice_pipe = pipe;
1157         }
1158
1159         /*
1160          * Do the splice.
1161          */
1162         ret = 0;
1163         bytes = 0;
1164         len = sd->total_len;
1165         flags = sd->flags;
1166
1167         /*
1168          * Don't block on output, we have to drain the direct pipe.
1169          */
1170         sd->flags &= ~SPLICE_F_NONBLOCK;
1171
1172         while (len) {
1173                 size_t read_len;
1174                 loff_t pos = sd->pos, prev_pos = pos;
1175
1176                 ret = do_splice_to(in, &pos, pipe, len, flags);
1177                 if (unlikely(ret <= 0))
1178                         goto out_release;
1179
1180                 read_len = ret;
1181                 sd->total_len = read_len;
1182
1183                 /*
1184                  * NOTE: nonblocking mode only applies to the input. We
1185                  * must not do the output in nonblocking mode as then we
1186                  * could get stuck data in the internal pipe:
1187                  */
1188                 ret = actor(pipe, sd);
1189                 if (unlikely(ret <= 0)) {
1190                         sd->pos = prev_pos;
1191                         goto out_release;
1192                 }
1193
1194                 bytes += ret;
1195                 len -= ret;
1196                 sd->pos = pos;
1197
1198                 if (ret < read_len) {
1199                         sd->pos = prev_pos + ret;
1200                         goto out_release;
1201                 }
1202         }
1203
1204 done:
1205         pipe->nrbufs = pipe->curbuf = 0;
1206         file_accessed(in);
1207         return bytes;
1208
1209 out_release:
1210         /*
1211          * If we did an incomplete transfer we must release
1212          * the pipe buffers in question:
1213          */
1214         for (i = 0; i < PIPE_BUFFERS; i++) {
1215                 struct pipe_buffer *buf = pipe->bufs + i;
1216
1217                 if (buf->ops) {
1218                         buf->ops->release(pipe, buf);
1219                         buf->ops = NULL;
1220                 }
1221         }
1222
1223         if (!bytes)
1224                 bytes = ret;
1225
1226         goto done;
1227 }
1228 EXPORT_SYMBOL(splice_direct_to_actor);
1229
1230 static int direct_splice_actor(struct pipe_inode_info *pipe,
1231                                struct splice_desc *sd)
1232 {
1233         struct file *file = sd->u.file;
1234
1235         return do_splice_from(pipe, file, &sd->pos, sd->total_len, sd->flags);
1236 }
1237
1238 /**
1239  * do_splice_direct - splices data directly between two files
1240  * @in:         file to splice from
1241  * @ppos:       input file offset
1242  * @out:        file to splice to
1243  * @len:        number of bytes to splice
1244  * @flags:      splice modifier flags
1245  *
1246  * Description:
1247  *    For use by do_sendfile(). splice can easily emulate sendfile, but
1248  *    doing it in the application would incur an extra system call
1249  *    (splice in + splice out, as compared to just sendfile()). So this helper
1250  *    can splice directly through a process-private pipe.
1251  *
1252  */
1253 long do_splice_direct(struct file *in, loff_t *ppos, struct file *out,
1254                       size_t len, unsigned int flags)
1255 {
1256         struct splice_desc sd = {
1257                 .len            = len,
1258                 .total_len      = len,
1259                 .flags          = flags,
1260                 .pos            = *ppos,
1261                 .u.file         = out,
1262         };
1263         long ret;
1264
1265         ret = splice_direct_to_actor(in, &sd, direct_splice_actor);
1266         if (ret > 0)
1267                 *ppos = sd.pos;
1268
1269         return ret;
1270 }
1271
1272 static int splice_pipe_to_pipe(struct pipe_inode_info *ipipe,
1273                                struct pipe_inode_info *opipe,
1274                                size_t len, unsigned int flags);
1275 /*
1276  * After the inode slimming patch, i_pipe/i_bdev/i_cdev share the same
1277  * location, so checking ->i_pipe is not enough to verify that this is a
1278  * pipe.
1279  */
1280 static inline struct pipe_inode_info *pipe_info(struct inode *inode)
1281 {
1282         if (S_ISFIFO(inode->i_mode))
1283                 return inode->i_pipe;
1284
1285         return NULL;
1286 }
1287
1288 /*
1289  * Determine where to splice to/from.
1290  */
1291 static long do_splice(struct file *in, loff_t __user *off_in,
1292                       struct file *out, loff_t __user *off_out,
1293                       size_t len, unsigned int flags)
1294 {
1295         struct pipe_inode_info *ipipe;
1296         struct pipe_inode_info *opipe;
1297         loff_t offset, *off;
1298         long ret;
1299
1300         ipipe = pipe_info(in->f_path.dentry->d_inode);
1301         opipe = pipe_info(out->f_path.dentry->d_inode);
1302
1303         if (ipipe && opipe) {
1304                 if (off_in || off_out)
1305                         return -ESPIPE;
1306
1307                 if (!(in->f_mode & FMODE_READ))
1308                         return -EBADF;
1309
1310                 if (!(out->f_mode & FMODE_WRITE))
1311                         return -EBADF;
1312
1313                 /* Splicing to self would be fun, but... */
1314                 if (ipipe == opipe)
1315                         return -EINVAL;
1316
1317                 return splice_pipe_to_pipe(ipipe, opipe, len, flags);
1318         }
1319
1320         if (ipipe) {
1321                 if (off_in)
1322                         return -ESPIPE;
1323                 if (off_out) {
1324                         if (!out->f_op || !out->f_op->llseek ||
1325                             out->f_op->llseek == no_llseek)
1326                                 return -EINVAL;
1327                         if (copy_from_user(&offset, off_out, sizeof(loff_t)))
1328                                 return -EFAULT;
1329                         off = &offset;
1330                 } else
1331                         off = &out->f_pos;
1332
1333                 ret = do_splice_from(ipipe, out, off, len, flags);
1334
1335                 if (off_out && copy_to_user(off_out, off, sizeof(loff_t)))
1336                         ret = -EFAULT;
1337
1338                 return ret;
1339         }
1340
1341         if (opipe) {
1342                 if (off_out)
1343                         return -ESPIPE;
1344                 if (off_in) {
1345                         if (!in->f_op || !in->f_op->llseek ||
1346                             in->f_op->llseek == no_llseek)
1347                                 return -EINVAL;
1348                         if (copy_from_user(&offset, off_in, sizeof(loff_t)))
1349                                 return -EFAULT;
1350                         off = &offset;
1351                 } else
1352                         off = &in->f_pos;
1353
1354                 ret = do_splice_to(in, off, opipe, len, flags);
1355
1356                 if (off_in && copy_to_user(off_in, off, sizeof(loff_t)))
1357                         ret = -EFAULT;
1358
1359                 return ret;
1360         }
1361
1362         return -EINVAL;
1363 }
1364
1365 /*
1366  * Map an iov into an array of pages and offset/length tupples. With the
1367  * partial_page structure, we can map several non-contiguous ranges into
1368  * our ones pages[] map instead of splitting that operation into pieces.
1369  * Could easily be exported as a generic helper for other users, in which
1370  * case one would probably want to add a 'max_nr_pages' parameter as well.
1371  */
1372 static int get_iovec_page_array(const struct iovec __user *iov,
1373                                 unsigned int nr_vecs, struct page **pages,
1374                                 struct partial_page *partial, int aligned)
1375 {
1376         int buffers = 0, error = 0;
1377
1378         while (nr_vecs) {
1379                 unsigned long off, npages;
1380                 struct iovec entry;
1381                 void __user *base;
1382                 size_t len;
1383                 int i;
1384
1385                 error = -EFAULT;
1386                 if (copy_from_user(&entry, iov, sizeof(entry)))
1387                         break;
1388
1389                 base = entry.iov_base;
1390                 len = entry.iov_len;
1391
1392                 /*
1393                  * Sanity check this iovec. 0 read succeeds.
1394                  */
1395                 error = 0;
1396                 if (unlikely(!len))
1397                         break;
1398                 error = -EFAULT;
1399                 if (!access_ok(VERIFY_READ, base, len))
1400                         break;
1401
1402                 /*
1403                  * Get this base offset and number of pages, then map
1404                  * in the user pages.
1405                  */
1406                 off = (unsigned long) base & ~PAGE_MASK;
1407
1408                 /*
1409                  * If asked for alignment, the offset must be zero and the
1410                  * length a multiple of the PAGE_SIZE.
1411                  */
1412                 error = -EINVAL;
1413                 if (aligned && (off || len & ~PAGE_MASK))
1414                         break;
1415
1416                 npages = (off + len + PAGE_SIZE - 1) >> PAGE_SHIFT;
1417                 if (npages > PIPE_BUFFERS - buffers)
1418                         npages = PIPE_BUFFERS - buffers;
1419
1420                 error = get_user_pages_fast((unsigned long)base, npages,
1421                                         0, &pages[buffers]);
1422
1423                 if (unlikely(error <= 0))
1424                         break;
1425
1426                 /*
1427                  * Fill this contiguous range into the partial page map.
1428                  */
1429                 for (i = 0; i < error; i++) {
1430                         const int plen = min_t(size_t, len, PAGE_SIZE - off);
1431
1432                         partial[buffers].offset = off;
1433                         partial[buffers].len = plen;
1434
1435                         off = 0;
1436                         len -= plen;
1437                         buffers++;
1438                 }
1439
1440                 /*
1441                  * We didn't complete this iov, stop here since it probably
1442                  * means we have to move some of this into a pipe to
1443                  * be able to continue.
1444                  */
1445                 if (len)
1446                         break;
1447
1448                 /*
1449                  * Don't continue if we mapped fewer pages than we asked for,
1450                  * or if we mapped the max number of pages that we have
1451                  * room for.
1452                  */
1453                 if (error < npages || buffers == PIPE_BUFFERS)
1454                         break;
1455
1456                 nr_vecs--;
1457                 iov++;
1458         }
1459
1460         if (buffers)
1461                 return buffers;
1462
1463         return error;
1464 }
1465
1466 static int pipe_to_user(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
1467                         struct splice_desc *sd)
1468 {
1469         char *src;
1470         int ret;
1471
1472         ret = buf->ops->confirm(pipe, buf);
1473         if (unlikely(ret))
1474                 return ret;
1475
1476         /*
1477          * See if we can use the atomic maps, by prefaulting in the
1478          * pages and doing an atomic copy
1479          */
1480         if (!fault_in_pages_writeable(sd->u.userptr, sd->len)) {
1481                 src = buf->ops->map(pipe, buf, 1);
1482                 ret = __copy_to_user_inatomic(sd->u.userptr, src + buf->offset,
1483                                                         sd->len);
1484                 buf->ops->unmap(pipe, buf, src);
1485                 if (!ret) {
1486                         ret = sd->len;
1487                         goto out;
1488                 }
1489         }
1490
1491         /*
1492          * No dice, use slow non-atomic map and copy
1493          */
1494         src = buf->ops->map(pipe, buf, 0);
1495
1496         ret = sd->len;
1497         if (copy_to_user(sd->u.userptr, src + buf->offset, sd->len))
1498                 ret = -EFAULT;
1499
1500         buf->ops->unmap(pipe, buf, src);
1501 out:
1502         if (ret > 0)
1503                 sd->u.userptr += ret;
1504         return ret;
1505 }
1506
1507 /*
1508  * For lack of a better implementation, implement vmsplice() to userspace
1509  * as a simple copy of the pipes pages to the user iov.
1510  */
1511 static long vmsplice_to_user(struct file *file, const struct iovec __user *iov,
1512                              unsigned long nr_segs, unsigned int flags)
1513 {
1514         struct pipe_inode_info *pipe;
1515         struct splice_desc sd;
1516         ssize_t size;
1517         int error;
1518         long ret;
1519
1520         pipe = pipe_info(file->f_path.dentry->d_inode);
1521         if (!pipe)
1522                 return -EBADF;
1523
1524         pipe_lock(pipe);
1525
1526         error = ret = 0;
1527         while (nr_segs) {
1528                 void __user *base;
1529                 size_t len;
1530
1531                 /*
1532                  * Get user address base and length for this iovec.
1533                  */
1534                 error = get_user(base, &iov->iov_base);
1535                 if (unlikely(error))
1536                         break;
1537                 error = get_user(len, &iov->iov_len);
1538                 if (unlikely(error))
1539                         break;
1540
1541                 /*
1542                  * Sanity check this iovec. 0 read succeeds.
1543                  */
1544                 if (unlikely(!len))
1545                         break;
1546                 if (unlikely(!base)) {
1547                         error = -EFAULT;
1548                         break;
1549                 }
1550
1551                 if (unlikely(!access_ok(VERIFY_WRITE, base, len))) {
1552                         error = -EFAULT;
1553                         break;
1554                 }
1555
1556                 sd.len = 0;
1557                 sd.total_len = len;
1558                 sd.flags = flags;
1559                 sd.u.userptr = base;
1560                 sd.pos = 0;
1561
1562                 size = __splice_from_pipe(pipe, &sd, pipe_to_user);
1563                 if (size < 0) {
1564                         if (!ret)
1565                                 ret = size;
1566
1567                         break;
1568                 }
1569
1570                 ret += size;
1571
1572                 if (size < len)
1573                         break;
1574
1575                 nr_segs--;
1576                 iov++;
1577         }
1578
1579         pipe_unlock(pipe);
1580
1581         if (!ret)
1582                 ret = error;
1583
1584         return ret;
1585 }
1586
1587 /*
1588  * vmsplice splices a user address range into a pipe. It can be thought of
1589  * as splice-from-memory, where the regular splice is splice-from-file (or
1590  * to file). In both cases the output is a pipe, naturally.
1591  */
1592 static long vmsplice_to_pipe(struct file *file, const struct iovec __user *iov,
1593                              unsigned long nr_segs, unsigned int flags)
1594 {
1595         struct pipe_inode_info *pipe;
1596         struct page *pages[PIPE_BUFFERS];
1597         struct partial_page partial[PIPE_BUFFERS];
1598         struct splice_pipe_desc spd = {
1599                 .pages = pages,
1600                 .partial = partial,
1601                 .flags = flags,
1602                 .ops = &user_page_pipe_buf_ops,
1603                 .spd_release = spd_release_page,
1604         };
1605
1606         pipe = pipe_info(file->f_path.dentry->d_inode);
1607         if (!pipe)
1608                 return -EBADF;
1609
1610         spd.nr_pages = get_iovec_page_array(iov, nr_segs, pages, partial,
1611                                             flags & SPLICE_F_GIFT);
1612         if (spd.nr_pages <= 0)
1613                 return spd.nr_pages;
1614
1615         return splice_to_pipe(pipe, &spd);
1616 }
1617
1618 /*
1619  * Note that vmsplice only really supports true splicing _from_ user memory
1620  * to a pipe, not the other way around. Splicing from user memory is a simple
1621  * operation that can be supported without any funky alignment restrictions
1622  * or nasty vm tricks. We simply map in the user memory and fill them into
1623  * a pipe. The reverse isn't quite as easy, though. There are two possible
1624  * solutions for that:
1625  *
1626  *      - memcpy() the data internally, at which point we might as well just
1627  *        do a regular read() on the buffer anyway.
1628  *      - Lots of nasty vm tricks, that are neither fast nor flexible (it
1629  *        has restriction limitations on both ends of the pipe).
1630  *
1631  * Currently we punt and implement it as a normal copy, see pipe_to_user().
1632  *
1633  */
1634 SYSCALL_DEFINE4(vmsplice, int, fd, const struct iovec __user *, iov,
1635                 unsigned long, nr_segs, unsigned int, flags)
1636 {
1637         struct file *file;
1638         long error;
1639         int fput;
1640
1641         if (unlikely(nr_segs > UIO_MAXIOV))
1642                 return -EINVAL;
1643         else if (unlikely(!nr_segs))
1644                 return 0;
1645
1646         error = -EBADF;
1647         file = fget_light(fd, &fput);
1648         if (file) {
1649                 if (file->f_mode & FMODE_WRITE)
1650                         error = vmsplice_to_pipe(file, iov, nr_segs, flags);
1651                 else if (file->f_mode & FMODE_READ)
1652                         error = vmsplice_to_user(file, iov, nr_segs, flags);
1653
1654                 fput_light(file, fput);
1655         }
1656
1657         return error;
1658 }
1659
1660 SYSCALL_DEFINE6(splice, int, fd_in, loff_t __user *, off_in,
1661                 int, fd_out, loff_t __user *, off_out,
1662                 size_t, len, unsigned int, flags)
1663 {
1664         long error;
1665         struct file *in, *out;
1666         int fput_in, fput_out;
1667
1668         if (unlikely(!len))
1669                 return 0;
1670
1671         error = -EBADF;
1672         in = fget_light(fd_in, &fput_in);
1673         if (in) {
1674                 if (in->f_mode & FMODE_READ) {
1675                         out = fget_light(fd_out, &fput_out);
1676                         if (out) {
1677                                 if (out->f_mode & FMODE_WRITE)
1678                                         error = do_splice(in, off_in,
1679                                                           out, off_out,
1680                                                           len, flags);
1681                                 fput_light(out, fput_out);
1682                         }
1683                 }
1684
1685                 fput_light(in, fput_in);
1686         }
1687
1688         return error;
1689 }
1690
1691 /*
1692  * Make sure there's data to read. Wait for input if we can, otherwise
1693  * return an appropriate error.
1694  */
1695 static int ipipe_prep(struct pipe_inode_info *pipe, unsigned int flags)
1696 {
1697         int ret;
1698
1699         /*
1700          * Check ->nrbufs without the inode lock first. This function
1701          * is speculative anyways, so missing one is ok.
1702          */
1703         if (pipe->nrbufs)
1704                 return 0;
1705
1706         ret = 0;
1707         pipe_lock(pipe);
1708
1709         while (!pipe->nrbufs) {
1710                 if (signal_pending(current)) {
1711                         ret = -ERESTARTSYS;
1712                         break;
1713                 }
1714                 if (!pipe->writers)
1715                         break;
1716                 if (!pipe->waiting_writers) {
1717                         if (flags & SPLICE_F_NONBLOCK) {
1718                                 ret = -EAGAIN;
1719                                 break;
1720                         }
1721                 }
1722                 pipe_wait(pipe);
1723         }
1724
1725         pipe_unlock(pipe);
1726         return ret;
1727 }
1728
1729 /*
1730  * Make sure there's writeable room. Wait for room if we can, otherwise
1731  * return an appropriate error.
1732  */
1733 static int opipe_prep(struct pipe_inode_info *pipe, unsigned int flags)
1734 {
1735         int ret;
1736
1737         /*
1738          * Check ->nrbufs without the inode lock first. This function
1739          * is speculative anyways, so missing one is ok.
1740          */
1741         if (pipe->nrbufs < PIPE_BUFFERS)
1742                 return 0;
1743
1744         ret = 0;
1745         pipe_lock(pipe);
1746
1747         while (pipe->nrbufs >= PIPE_BUFFERS) {
1748                 if (!pipe->readers) {
1749                         send_sig(SIGPIPE, current, 0);
1750                         ret = -EPIPE;
1751                         break;
1752                 }
1753                 if (flags & SPLICE_F_NONBLOCK) {
1754                         ret = -EAGAIN;
1755                         break;
1756                 }
1757                 if (signal_pending(current)) {
1758                         ret = -ERESTARTSYS;
1759                         break;
1760                 }
1761                 pipe->waiting_writers++;
1762                 pipe_wait(pipe);
1763                 pipe->waiting_writers--;
1764         }
1765
1766         pipe_unlock(pipe);
1767         return ret;
1768 }
1769
1770 /*
1771  * Splice contents of ipipe to opipe.
1772  */
1773 static int splice_pipe_to_pipe(struct pipe_inode_info *ipipe,
1774                                struct pipe_inode_info *opipe,
1775                                size_t len, unsigned int flags)
1776 {
1777         struct pipe_buffer *ibuf, *obuf;
1778         int ret = 0, nbuf;
1779         bool input_wakeup = false;
1780
1781
1782 retry:
1783         ret = ipipe_prep(ipipe, flags);
1784         if (ret)
1785                 return ret;
1786
1787         ret = opipe_prep(opipe, flags);
1788         if (ret)
1789                 return ret;
1790
1791         /*
1792          * Potential ABBA deadlock, work around it by ordering lock
1793          * grabbing by pipe info address. Otherwise two different processes
1794          * could deadlock (one doing tee from A -> B, the other from B -> A).
1795          */
1796         pipe_double_lock(ipipe, opipe);
1797
1798         do {
1799                 if (!opipe->readers) {
1800                         send_sig(SIGPIPE, current, 0);
1801                         if (!ret)
1802                                 ret = -EPIPE;
1803                         break;
1804                 }
1805
1806                 if (!ipipe->nrbufs && !ipipe->writers)
1807                         break;
1808
1809                 /*
1810                  * Cannot make any progress, because either the input
1811                  * pipe is empty or the output pipe is full.
1812                  */
1813                 if (!ipipe->nrbufs || opipe->nrbufs >= PIPE_BUFFERS) {
1814                         /* Already processed some buffers, break */
1815                         if (ret)
1816                                 break;
1817
1818                         if (flags & SPLICE_F_NONBLOCK) {
1819                                 ret = -EAGAIN;
1820                                 break;
1821                         }
1822
1823                         /*
1824                          * We raced with another reader/writer and haven't
1825                          * managed to process any buffers.  A zero return
1826                          * value means EOF, so retry instead.
1827                          */
1828                         pipe_unlock(ipipe);
1829                         pipe_unlock(opipe);
1830                         goto retry;
1831                 }
1832
1833                 ibuf = ipipe->bufs + ipipe->curbuf;
1834                 nbuf = (opipe->curbuf + opipe->nrbufs) % PIPE_BUFFERS;
1835                 obuf = opipe->bufs + nbuf;
1836
1837                 if (len >= ibuf->len) {
1838                         /*
1839                          * Simply move the whole buffer from ipipe to opipe
1840                          */
1841                         *obuf = *ibuf;
1842                         ibuf->ops = NULL;
1843                         opipe->nrbufs++;
1844                         ipipe->curbuf = (ipipe->curbuf + 1) % PIPE_BUFFERS;
1845                         ipipe->nrbufs--;
1846                         input_wakeup = true;
1847                 } else {
1848                         /*
1849                          * Get a reference to this pipe buffer,
1850                          * so we can copy the contents over.
1851                          */
1852                         ibuf->ops->get(ipipe, ibuf);
1853                         *obuf = *ibuf;
1854
1855                         /*
1856                          * Don't inherit the gift flag, we need to
1857                          * prevent multiple steals of this page.
1858                          */
1859                         obuf->flags &= ~PIPE_BUF_FLAG_GIFT;
1860
1861                         obuf->len = len;
1862                         opipe->nrbufs++;
1863                         ibuf->offset += obuf->len;
1864                         ibuf->len -= obuf->len;
1865                 }
1866                 ret += obuf->len;
1867                 len -= obuf->len;
1868         } while (len);
1869
1870         pipe_unlock(ipipe);
1871         pipe_unlock(opipe);
1872
1873         /*
1874          * If we put data in the output pipe, wakeup any potential readers.
1875          */
1876         if (ret > 0) {
1877                 smp_mb();
1878                 if (waitqueue_active(&opipe->wait))
1879                         wake_up_interruptible(&opipe->wait);
1880                 kill_fasync(&opipe->fasync_readers, SIGIO, POLL_IN);
1881         }
1882         if (input_wakeup)
1883                 wakeup_pipe_writers(ipipe);
1884
1885         return ret;
1886 }
1887
1888 /*
1889  * Link contents of ipipe to opipe.
1890  */
1891 static int link_pipe(struct pipe_inode_info *ipipe,
1892                      struct pipe_inode_info *opipe,
1893                      size_t len, unsigned int flags)
1894 {
1895         struct pipe_buffer *ibuf, *obuf;
1896         int ret = 0, i = 0, nbuf;
1897
1898         /*
1899          * Potential ABBA deadlock, work around it by ordering lock
1900          * grabbing by pipe info address. Otherwise two different processes
1901          * could deadlock (one doing tee from A -> B, the other from B -> A).
1902          */
1903         pipe_double_lock(ipipe, opipe);
1904
1905         do {
1906                 if (!opipe->readers) {
1907                         send_sig(SIGPIPE, current, 0);
1908                         if (!ret)
1909                                 ret = -EPIPE;
1910                         break;
1911                 }
1912
1913                 /*
1914                  * If we have iterated all input buffers or ran out of
1915                  * output room, break.
1916                  */
1917                 if (i >= ipipe->nrbufs || opipe->nrbufs >= PIPE_BUFFERS)
1918                         break;
1919
1920                 ibuf = ipipe->bufs + ((ipipe->curbuf + i) & (PIPE_BUFFERS - 1));
1921                 nbuf = (opipe->curbuf + opipe->nrbufs) & (PIPE_BUFFERS - 1);
1922
1923                 /*
1924                  * Get a reference to this pipe buffer,
1925                  * so we can copy the contents over.
1926                  */
1927                 ibuf->ops->get(ipipe, ibuf);
1928
1929                 obuf = opipe->bufs + nbuf;
1930                 *obuf = *ibuf;
1931
1932                 /*
1933                  * Don't inherit the gift flag, we need to
1934                  * prevent multiple steals of this page.
1935                  */
1936                 obuf->flags &= ~PIPE_BUF_FLAG_GIFT;
1937
1938                 if (obuf->len > len)
1939                         obuf->len = len;
1940
1941                 opipe->nrbufs++;
1942                 ret += obuf->len;
1943                 len -= obuf->len;
1944                 i++;
1945         } while (len);
1946
1947         /*
1948          * return EAGAIN if we have the potential of some data in the
1949          * future, otherwise just return 0
1950          */
1951         if (!ret && ipipe->waiting_writers && (flags & SPLICE_F_NONBLOCK))
1952                 ret = -EAGAIN;
1953
1954         pipe_unlock(ipipe);
1955         pipe_unlock(opipe);
1956
1957         /*
1958          * If we put data in the output pipe, wakeup any potential readers.
1959          */
1960         if (ret > 0) {
1961                 smp_mb();
1962                 if (waitqueue_active(&opipe->wait))
1963                         wake_up_interruptible(&opipe->wait);
1964                 kill_fasync(&opipe->fasync_readers, SIGIO, POLL_IN);
1965         }
1966
1967         return ret;
1968 }
1969
1970 /*
1971  * This is a tee(1) implementation that works on pipes. It doesn't copy
1972  * any data, it simply references the 'in' pages on the 'out' pipe.
1973  * The 'flags' used are the SPLICE_F_* variants, currently the only
1974  * applicable one is SPLICE_F_NONBLOCK.
1975  */
1976 static long do_tee(struct file *in, struct file *out, size_t len,
1977                    unsigned int flags)
1978 {
1979         struct pipe_inode_info *ipipe = pipe_info(in->f_path.dentry->d_inode);
1980         struct pipe_inode_info *opipe = pipe_info(out->f_path.dentry->d_inode);
1981         int ret = -EINVAL;
1982
1983         /*
1984          * Duplicate the contents of ipipe to opipe without actually
1985          * copying the data.
1986          */
1987         if (ipipe && opipe && ipipe != opipe) {
1988                 /*
1989                  * Keep going, unless we encounter an error. The ipipe/opipe
1990                  * ordering doesn't really matter.
1991                  */
1992                 ret = ipipe_prep(ipipe, flags);
1993                 if (!ret) {
1994                         ret = opipe_prep(opipe, flags);
1995                         if (!ret)
1996                                 ret = link_pipe(ipipe, opipe, len, flags);
1997                 }
1998         }
1999
2000         return ret;
2001 }
2002
2003 SYSCALL_DEFINE4(tee, int, fdin, int, fdout, size_t, len, unsigned int, flags)
2004 {
2005         struct file *in;
2006         int error, fput_in;
2007
2008         if (unlikely(!len))
2009                 return 0;
2010
2011         error = -EBADF;
2012         in = fget_light(fdin, &fput_in);
2013         if (in) {
2014                 if (in->f_mode & FMODE_READ) {
2015                         int fput_out;
2016                         struct file *out = fget_light(fdout, &fput_out);
2017
2018                         if (out) {
2019                                 if (out->f_mode & FMODE_WRITE)
2020                                         error = do_tee(in, out, len, flags);
2021                                 fput_light(out, fput_out);
2022                         }
2023                 }
2024                 fput_light(in, fput_in);
2025         }
2026
2027         return error;
2028 }