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@suse.de>
  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/pipe_fs_i.h>
  24 #include <linux/mm_inline.h>
  25 #include <linux/swap.h>
  26 #include <linux/writeback.h>
  27 #include <linux/buffer_head.h>
  28 #include <linux/module.h>
  29 #include <linux/syscalls.h>
  30 #include <linux/uio.h>
  31
  32 struct partial_page {
  33         unsigned int offset;
  34         unsigned int len;
  35 };
  36
  37 /*
  38  * Passed to splice_to_pipe
  39  */
  40 struct splice_pipe_desc {
  41         struct page **pages;            /* page map */
  42         struct partial_page *partial;   /* pages[] may not be contig */
  43         int nr_pages;                   /* number of pages in map */
  44         unsigned int flags;             /* splice flags */
  45         struct pipe_buf_operations *ops;/* ops associated with output pipe */
  46 };
  47
  48 /*
  49  * Attempt to steal a page from a pipe buffer. This should perhaps go into
  50  * a vm helper function, it's already simplified quite a bit by the
  51  * addition of remove_mapping(). If success is returned, the caller may
  52  * attempt to reuse this page for another destination.
  53  */
  54 static int page_cache_pipe_buf_steal(struct pipe_inode_info *info,
  55                                      struct pipe_buffer *buf)
  56 {
  57         struct page *page = buf->page;
  58         struct address_space *mapping = page_mapping(page);
  59
  60         lock_page(page);
  61
  62         WARN_ON(!PageUptodate(page));
  63
  64         /*
  65          * At least for ext2 with nobh option, we need to wait on writeback
  66          * completing on this page, since we'll remove it from the pagecache.
  67          * Otherwise truncate wont wait on the page, allowing the disk
  68          * blocks to be reused by someone else before we actually wrote our
  69          * data to them. fs corruption ensues.
  70          */
  71         wait_on_page_writeback(page);
  72
  73         if (PagePrivate(page))
  74                 try_to_release_page(page, mapping_gfp_mask(mapping));
  75
  76         if (!remove_mapping(mapping, page)) {
  77                 unlock_page(page);
  78                 return 1;
  79         }
  80
  81         buf->flags |= PIPE_BUF_FLAG_STOLEN | PIPE_BUF_FLAG_LRU;
  82         return 0;
  83 }
  84
  85 static void page_cache_pipe_buf_release(struct pipe_inode_info *info,
  86                                         struct pipe_buffer *buf)
  87 {
  88         page_cache_release(buf->page);
  89         buf->page = NULL;
  90         buf->flags &= ~(PIPE_BUF_FLAG_STOLEN | PIPE_BUF_FLAG_LRU);
  91 }
  92
  93 static void *page_cache_pipe_buf_map(struct file *file,
  94                                      struct pipe_inode_info *info,
  95                                      struct pipe_buffer *buf)
  96 {
  97         struct page *page = buf->page;
  98         int err;
  99
 100         if (!PageUptodate(page)) {
 101                 lock_page(page);
 102
 103                 /*
 104                  * Page got truncated/unhashed. This will cause a 0-byte
 105                  * splice, if this is the first page.
 106                  */
 107                 if (!page->mapping) {
 108                         err = -ENODATA;
 109                         goto error;
 110                 }
 111
 112                 /*
 113                  * Uh oh, read-error from disk.
 114                  */
 115                 if (!PageUptodate(page)) {
 116                         err = -EIO;
 117                         goto error;
 118                 }
 119
 120                 /*
 121                  * Page is ok afterall, fall through to mapping.
 122                  */
 123                 unlock_page(page);
 124         }
 125
 126         return kmap(page);
 127 error:
 128         unlock_page(page);
 129         return ERR_PTR(err);
 130 }
 131
 132 static void page_cache_pipe_buf_unmap(struct pipe_inode_info *info,
 133                                       struct pipe_buffer *buf)
 134 {
 135         kunmap(buf->page);
 136 }
 137
 138 static void *user_page_pipe_buf_map(struct file *file,
 139                                     struct pipe_inode_info *pipe,
 140                                     struct pipe_buffer *buf)
 141 {
 142         return kmap(buf->page);
 143 }
 144
 145 static void user_page_pipe_buf_unmap(struct pipe_inode_info *pipe,
 146                                      struct pipe_buffer *buf)
 147 {
 148         kunmap(buf->page);
 149 }
 150
 151 static void page_cache_pipe_buf_get(struct pipe_inode_info *info,
 152                                     struct pipe_buffer *buf)
 153 {
 154         page_cache_get(buf->page);
 155 }
 156
 157 static struct pipe_buf_operations page_cache_pipe_buf_ops = {
 158         .can_merge = 0,
 159         .map = page_cache_pipe_buf_map,
 160         .unmap = page_cache_pipe_buf_unmap,
 161         .release = page_cache_pipe_buf_release,
 162         .steal = page_cache_pipe_buf_steal,
 163         .get = page_cache_pipe_buf_get,
 164 };
 165
 166 static int user_page_pipe_buf_steal(struct pipe_inode_info *pipe,
 167                                     struct pipe_buffer *buf)
 168 {
 169         return 1;
 170 }
 171
 172 static struct pipe_buf_operations user_page_pipe_buf_ops = {
 173         .can_merge = 0,
 174         .map = user_page_pipe_buf_map,
 175         .unmap = user_page_pipe_buf_unmap,
 176         .release = page_cache_pipe_buf_release,
 177         .steal = user_page_pipe_buf_steal,
 178         .get = page_cache_pipe_buf_get,
 179 };
 180
 181 /*
 182  * Pipe output worker. This sets up our pipe format with the page cache
 183  * pipe buffer operations. Otherwise very similar to the regular pipe_writev().
 184  */
 185 static ssize_t splice_to_pipe(struct pipe_inode_info *pipe,
 186                               struct splice_pipe_desc *spd)
 187 {
 188         int ret, do_wakeup, page_nr;
 189
 190         ret = 0;
 191         do_wakeup = 0;
 192         page_nr = 0;
 193
 194         if (pipe->inode)
 195                 mutex_lock(&pipe->inode->i_mutex);
 196
 197         for (;;) {
 198                 if (!pipe->readers) {
 199                         send_sig(SIGPIPE, current, 0);
 200                         if (!ret)
 201                                 ret = -EPIPE;
 202                         break;
 203                 }
 204
 205                 if (pipe->nrbufs < PIPE_BUFFERS) {
 206                         int newbuf = (pipe->curbuf + pipe->nrbufs) & (PIPE_BUFFERS - 1);
 207                         struct pipe_buffer *buf = pipe->bufs + newbuf;
 208
 209                         buf->page = spd->pages[page_nr];
 210                         buf->offset = spd->partial[page_nr].offset;
 211                         buf->len = spd->partial[page_nr].len;
 212                         buf->ops = spd->ops;
 213                         pipe->nrbufs++;
 214                         page_nr++;
 215                         ret += buf->len;
 216
 217                         if (pipe->inode)
 218                                 do_wakeup = 1;
 219
 220                         if (!--spd->nr_pages)
 221                                 break;
 222                         if (pipe->nrbufs < PIPE_BUFFERS)
 223                                 continue;
 224
 225                         break;
 226                 }
 227
 228                 if (spd->flags & SPLICE_F_NONBLOCK) {
 229                         if (!ret)
 230                                 ret = -EAGAIN;
 231                         break;
 232                 }
 233
 234                 if (signal_pending(current)) {
 235                         if (!ret)
 236                                 ret = -ERESTARTSYS;
 237                         break;
 238                 }
 239
 240                 if (do_wakeup) {
 241                         smp_mb();
 242                         if (waitqueue_active(&pipe->wait))
 243                                 wake_up_interruptible_sync(&pipe->wait);
 244                         kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
 245                         do_wakeup = 0;
 246                 }
 247
 248                 pipe->waiting_writers++;
 249                 pipe_wait(pipe);
 250                 pipe->waiting_writers--;
 251         }
 252
 253         if (pipe->inode)
 254                 mutex_unlock(&pipe->inode->i_mutex);
 255
 256         if (do_wakeup) {
 257                 smp_mb();
 258                 if (waitqueue_active(&pipe->wait))
 259                         wake_up_interruptible(&pipe->wait);
 260                 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
 261         }
 262
 263         while (page_nr < spd->nr_pages)
 264                 page_cache_release(spd->pages[page_nr++]);
 265
 266         return ret;
 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;
 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         size_t total_len;
 282         int error;
 283         struct splice_pipe_desc spd = {
 284                 .pages = pages,
 285                 .partial = partial,
 286                 .flags = flags,
 287                 .ops = &page_cache_pipe_buf_ops,
 288         };
 289
 290         index = *ppos >> PAGE_CACHE_SHIFT;
 291         loff = *ppos & ~PAGE_CACHE_MASK;
 292         nr_pages = (len + loff + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
 293
 294         if (nr_pages > PIPE_BUFFERS)
 295                 nr_pages = PIPE_BUFFERS;
 296
 297         /*
 298          * Initiate read-ahead on this page range. however, don't call into
 299          * read-ahead if this is a non-zero offset (we are likely doing small
 300          * chunk splice and the page is already there) for a single page.
 301          */
 302         if (!loff || spd.nr_pages > 1)
 303                 do_page_cache_readahead(mapping, in, index, spd.nr_pages);
 304
 305         /*
 306          * Now fill in the holes:
 307          */
 308         error = 0;
 309         total_len = 0;
 310         for (spd.nr_pages = 0; spd.nr_pages < nr_pages; spd.nr_pages++, index++) {
 311                 unsigned int this_len;
 312
 313                 if (!len)
 314                         break;
 315
 316                 /*
 317                  * this_len is the max we'll use from this page
 318                  */
 319                 this_len = min_t(unsigned long, len, PAGE_CACHE_SIZE - loff);
 320 find_page:
 321                 /*
 322                  * lookup the page for this index
 323                  */
 324                 page = find_get_page(mapping, index);
 325                 if (!page) {
 326                         /*
 327                          * page didn't exist, allocate one
 328                          */
 329                         page = page_cache_alloc_cold(mapping);
 330                         if (!page)
 331                                 break;
 332
 333                         error = add_to_page_cache_lru(page, mapping, index,
 334                                                 mapping_gfp_mask(mapping));
 335                         if (unlikely(error)) {
 336                                 page_cache_release(page);
 337                                 break;
 338                         }
 339
 340                         goto readpage;
 341                 }
 342
 343                 /*
 344                  * If the page isn't uptodate, we may need to start io on it
 345                  */
 346                 if (!PageUptodate(page)) {
 347                         /*
 348                          * If in nonblock mode then dont block on waiting
 349                          * for an in-flight io page
 350                          */
 351                         if (flags & SPLICE_F_NONBLOCK)
 352                                 break;
 353
 354                         lock_page(page);
 355
 356                         /*
 357                          * page was truncated, stop here. if this isn't the
 358                          * first page, we'll just complete what we already
 359                          * added
 360                          */
 361                         if (!page->mapping) {
 362                                 unlock_page(page);
 363                                 page_cache_release(page);
 364                                 break;
 365                         }
 366                         /*
 367                          * page was already under io and is now done, great
 368                          */
 369                         if (PageUptodate(page)) {
 370                                 unlock_page(page);
 371                                 goto fill_it;
 372                         }
 373
 374 readpage:
 375                         /*
 376                          * need to read in the page
 377                          */
 378                         error = mapping->a_ops->readpage(in, page);
 379
 380                         if (unlikely(error)) {
 381                                 page_cache_release(page);
 382                                 if (error == AOP_TRUNCATED_PAGE)
 383                                         goto find_page;
 384                                 break;
 385                         }
 386
 387                         /*
 388                          * i_size must be checked after ->readpage().
 389                          */
 390                         isize = i_size_read(mapping->host);
 391                         end_index = (isize - 1) >> PAGE_CACHE_SHIFT;
 392                         if (unlikely(!isize || index > end_index)) {
 393                                 page_cache_release(page);
 394                                 break;
 395                         }
 396
 397                         /*
 398                          * if this is the last page, see if we need to shrink
 399                          * the length and stop
 400                          */
 401                         if (end_index == index) {
 402                                 loff = PAGE_CACHE_SIZE - (isize & ~PAGE_CACHE_MASK);
 403                                 if (total_len + loff > isize) {
 404                                         page_cache_release(page);
 405                                         break;
 406                                 }
 407                                 /*
 408                                  * force quit after adding this page
 409                                  */
 410                                 nr_pages = spd.nr_pages;
 411                                 this_len = min(this_len, loff);
 412                                 loff = 0;
 413                         }
 414                 }
 415 fill_it:
 416                 pages[spd.nr_pages] = page;
 417                 partial[spd.nr_pages].offset = loff;
 418                 partial[spd.nr_pages].len = this_len;
 419                 len -= this_len;
 420                 total_len += this_len;
 421                 loff = 0;
 422         }
 423
 424         if (spd.nr_pages)
 425                 return splice_to_pipe(pipe, &spd);
 426
 427         return error;
 428 }
 429
 430 /**
 431  * generic_file_splice_read - splice data from file to a pipe
 432  * @in:         file to splice from
 433  * @pipe:       pipe to splice to
 434  * @len:        number of bytes to splice
 435  * @flags:      splice modifier flags
 436  *
 437  * Will read pages from given file and fill them into a pipe.
 438  */
 439 ssize_t generic_file_splice_read(struct file *in, loff_t *ppos,
 440                                  struct pipe_inode_info *pipe, size_t len,
 441                                  unsigned int flags)
 442 {
 443         ssize_t spliced;
 444         int ret;
 445
 446         ret = 0;
 447         spliced = 0;
 448
 449         while (len) {
 450                 ret = __generic_file_splice_read(in, ppos, pipe, len, flags);
 451
 452                 if (ret < 0)
 453                         break;
 454                 else if (!ret) {
 455                         if (spliced)
 456                                 break;
 457                         if (flags & SPLICE_F_NONBLOCK) {
 458                                 ret = -EAGAIN;
 459                                 break;
 460                         }
 461                 }
 462
 463                 *ppos += ret;
 464                 len -= ret;
 465                 spliced += ret;
 466         }
 467
 468         if (spliced)
 469                 return spliced;
 470
 471         return ret;
 472 }
 473
 474 EXPORT_SYMBOL(generic_file_splice_read);
 475
 476 /*
 477  * Send 'sd->len' bytes to socket from 'sd->file' at position 'sd->pos'
 478  * using sendpage(). Return the number of bytes sent.
 479  */
 480 static int pipe_to_sendpage(struct pipe_inode_info *info,
 481                             struct pipe_buffer *buf, struct splice_desc *sd)
 482 {
 483         struct file *file = sd->file;
 484         loff_t pos = sd->pos;
 485         ssize_t ret;
 486         void *ptr;
 487         int more;
 488
 489         /*
 490          * Sub-optimal, but we are limited by the pipe ->map. We don't
 491          * need a kmap'ed buffer here, we just want to make sure we
 492          * have the page pinned if the pipe page originates from the
 493          * page cache.
 494          */
 495         ptr = buf->ops->map(file, info, buf);
 496         if (IS_ERR(ptr))
 497                 return PTR_ERR(ptr);
 498
 499         more = (sd->flags & SPLICE_F_MORE) || sd->len < sd->total_len;
 500
 501         ret = file->f_op->sendpage(file, buf->page, buf->offset, sd->len,
 502                                    &pos, more);
 503
 504         buf->ops->unmap(info, buf);
 505         return ret;
 506 }
 507
 508 /*
 509  * This is a little more tricky than the file -> pipe splicing. There are
 510  * basically three cases:
 511  *
 512  *      - Destination page already exists in the address space and there
 513  *        are users of it. For that case we have no other option that
 514  *        copying the data. Tough luck.
 515  *      - Destination page already exists in the address space, but there
 516  *        are no users of it. Make sure it's uptodate, then drop it. Fall
 517  *        through to last case.
 518  *      - Destination page does not exist, we can add the pipe page to
 519  *        the page cache and avoid the copy.
 520  *
 521  * If asked to move pages to the output file (SPLICE_F_MOVE is set in
 522  * sd->flags), we attempt to migrate pages from the pipe to the output
 523  * file address space page cache. This is possible if no one else has
 524  * the pipe page referenced outside of the pipe and page cache. If
 525  * SPLICE_F_MOVE isn't set, or we cannot move the page, we simply create
 526  * a new page in the output file page cache and fill/dirty that.
 527  */
 528 static int pipe_to_file(struct pipe_inode_info *info, struct pipe_buffer *buf,
 529                         struct splice_desc *sd)
 530 {
 531         struct file *file = sd->file;
 532         struct address_space *mapping = file->f_mapping;
 533         gfp_t gfp_mask = mapping_gfp_mask(mapping);
 534         unsigned int offset, this_len;
 535         struct page *page;
 536         pgoff_t index;
 537         char *src;
 538         int ret;
 539
 540         /*
 541          * make sure the data in this buffer is uptodate
 542          */
 543         src = buf->ops->map(file, info, buf);
 544         if (IS_ERR(src))
 545                 return PTR_ERR(src);
 546
 547         index = sd->pos >> PAGE_CACHE_SHIFT;
 548         offset = sd->pos & ~PAGE_CACHE_MASK;
 549
 550         this_len = sd->len;
 551         if (this_len + offset > PAGE_CACHE_SIZE)
 552                 this_len = PAGE_CACHE_SIZE - offset;
 553
 554         /*
 555          * Reuse buf page, if SPLICE_F_MOVE is set.
 556          */
 557         if (sd->flags & SPLICE_F_MOVE) {
 558                 /*
 559                  * If steal succeeds, buf->page is now pruned from the vm
 560                  * side (LRU and page cache) and we can reuse it. The page
 561                  * will also be looked on successful return.
 562                  */
 563                 if (buf->ops->steal(info, buf))
 564                         goto find_page;
 565
 566                 page = buf->page;
 567                 if (add_to_page_cache(page, mapping, index, gfp_mask))
 568                         goto find_page;
 569
 570                 if (!(buf->flags & PIPE_BUF_FLAG_LRU))
 571                         lru_cache_add(page);
 572         } else {
 573 find_page:
 574                 page = find_lock_page(mapping, index);
 575                 if (!page) {
 576                         ret = -ENOMEM;
 577                         page = page_cache_alloc_cold(mapping);
 578                         if (unlikely(!page))
 579                                 goto out_nomem;
 580
 581                         /*
 582                          * This will also lock the page
 583                          */
 584                         ret = add_to_page_cache_lru(page, mapping, index,
 585                                                     gfp_mask);
 586                         if (unlikely(ret))
 587                                 goto out;
 588                 }
 589
 590                 /*
 591                  * We get here with the page locked. If the page is also
 592                  * uptodate, we don't need to do more. If it isn't, we
 593                  * may need to bring it in if we are not going to overwrite
 594                  * the full page.
 595                  */
 596                 if (!PageUptodate(page)) {
 597                         if (this_len < PAGE_CACHE_SIZE) {
 598                                 ret = mapping->a_ops->readpage(file, page);
 599                                 if (unlikely(ret))
 600                                         goto out;
 601
 602                                 lock_page(page);
 603
 604                                 if (!PageUptodate(page)) {
 605                                         /*
 606                                          * Page got invalidated, repeat.
 607                                          */
 608                                         if (!page->mapping) {
 609                                                 unlock_page(page);
 610                                                 page_cache_release(page);
 611                                                 goto find_page;
 612                                         }
 613                                         ret = -EIO;
 614                                         goto out;
 615                                 }
 616                         } else
 617                                 SetPageUptodate(page);
 618                 }
 619         }
 620
 621         ret = mapping->a_ops->prepare_write(file, page, offset, offset+this_len);
 622         if (ret == AOP_TRUNCATED_PAGE) {
 623                 page_cache_release(page);
 624                 goto find_page;
 625         } else if (ret)
 626                 goto out;
 627
 628         if (!(buf->flags & PIPE_BUF_FLAG_STOLEN)) {
 629                 char *dst = kmap_atomic(page, KM_USER0);
 630
 631                 memcpy(dst + offset, src + buf->offset, this_len);
 632                 flush_dcache_page(page);
 633                 kunmap_atomic(dst, KM_USER0);
 634         }
 635
 636         ret = mapping->a_ops->commit_write(file, page, offset, offset+this_len);
 637         if (ret == AOP_TRUNCATED_PAGE) {
 638                 page_cache_release(page);
 639                 goto find_page;
 640         } else if (ret)
 641                 goto out;
 642
 643         /*
 644          * Return the number of bytes written.
 645          */
 646         ret = this_len;
 647         mark_page_accessed(page);
 648         balance_dirty_pages_ratelimited(mapping);
 649 out:
 650         if (!(buf->flags & PIPE_BUF_FLAG_STOLEN))
 651                 page_cache_release(page);
 652
 653         unlock_page(page);
 654 out_nomem:
 655         buf->ops->unmap(info, buf);
 656         return ret;
 657 }
 658
 659 /*
 660  * Pipe input worker. Most of this logic works like a regular pipe, the
 661  * key here is the 'actor' worker passed in that actually moves the data
 662  * to the wanted destination. See pipe_to_file/pipe_to_sendpage above.
 663  */
 664 ssize_t splice_from_pipe(struct pipe_inode_info *pipe, struct file *out,
 665                          loff_t *ppos, size_t len, unsigned int flags,
 666                          splice_actor *actor)
 667 {
 668         int ret, do_wakeup, err;
 669         struct splice_desc sd;
 670
 671         ret = 0;
 672         do_wakeup = 0;
 673
 674         sd.total_len = len;
 675         sd.flags = flags;
 676         sd.file = out;
 677         sd.pos = *ppos;
 678
 679         if (pipe->inode)
 680                 mutex_lock(&pipe->inode->i_mutex);
 681
 682         for (;;) {
 683                 if (pipe->nrbufs) {
 684                         struct pipe_buffer *buf = pipe->bufs + pipe->curbuf;
 685                         struct pipe_buf_operations *ops = buf->ops;
 686
 687                         sd.len = buf->len;
 688                         if (sd.len > sd.total_len)
 689                                 sd.len = sd.total_len;
 690
 691                         err = actor(pipe, buf, &sd);
 692                         if (err <= 0) {
 693                                 if (!ret && err != -ENODATA)
 694                                         ret = err;
 695
 696                                 break;
 697                         }
 698
 699                         ret += err;
 700                         buf->offset += err;
 701                         buf->len -= err;
 702
 703                         sd.len -= err;
 704                         sd.pos += err;
 705                         sd.total_len -= err;
 706                         if (sd.len)
 707                                 continue;
 708
 709                         if (!buf->len) {
 710                                 buf->ops = NULL;
 711                                 ops->release(pipe, buf);
 712                                 pipe->curbuf = (pipe->curbuf + 1) & (PIPE_BUFFERS - 1);
 713                                 pipe->nrbufs--;
 714                                 if (pipe->inode)
 715                                         do_wakeup = 1;
 716                         }
 717
 718                         if (!sd.total_len)
 719                                 break;
 720                 }
 721
 722                 if (pipe->nrbufs)
 723                         continue;
 724                 if (!pipe->writers)
 725                         break;
 726                 if (!pipe->waiting_writers) {
 727                         if (ret)
 728                                 break;
 729                 }
 730
 731                 if (flags & SPLICE_F_NONBLOCK) {
 732                         if (!ret)
 733                                 ret = -EAGAIN;
 734                         break;
 735                 }
 736
 737                 if (signal_pending(current)) {
 738                         if (!ret)
 739                                 ret = -ERESTARTSYS;
 740                         break;
 741                 }
 742
 743                 if (do_wakeup) {
 744                         smp_mb();
 745                         if (waitqueue_active(&pipe->wait))
 746                                 wake_up_interruptible_sync(&pipe->wait);
 747                         kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
 748                         do_wakeup = 0;
 749                 }
 750
 751                 pipe_wait(pipe);
 752         }
 753
 754         if (pipe->inode)
 755                 mutex_unlock(&pipe->inode->i_mutex);
 756
 757         if (do_wakeup) {
 758                 smp_mb();
 759                 if (waitqueue_active(&pipe->wait))
 760                         wake_up_interruptible(&pipe->wait);
 761                 kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
 762         }
 763
 764         return ret;
 765 }
 766
 767 /**
 768  * generic_file_splice_write - splice data from a pipe to a file
 769  * @pipe:       pipe info
 770  * @out:        file to write to
 771  * @len:        number of bytes to splice
 772  * @flags:      splice modifier flags
 773  *
 774  * Will either move or copy pages (determined by @flags options) from
 775  * the given pipe inode to the given file.
 776  *
 777  */
 778 ssize_t
 779 generic_file_splice_write(struct pipe_inode_info *pipe, struct file *out,
 780                           loff_t *ppos, size_t len, unsigned int flags)
 781 {
 782         struct address_space *mapping = out->f_mapping;
 783         ssize_t ret;
 784
 785         ret = splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_file);
 786         if (ret > 0) {
 787                 struct inode *inode = mapping->host;
 788
 789                 *ppos += ret;
 790
 791                 /*
 792                  * If file or inode is SYNC and we actually wrote some data,
 793                  * sync it.
 794                  */
 795                 if (unlikely((out->f_flags & O_SYNC) || IS_SYNC(inode))) {
 796                         int err;
 797
 798                         mutex_lock(&inode->i_mutex);
 799                         err = generic_osync_inode(inode, mapping,
 800                                                   OSYNC_METADATA|OSYNC_DATA);
 801                         mutex_unlock(&inode->i_mutex);
 802
 803                         if (err)
 804                                 ret = err;
 805                 }
 806         }
 807
 808         return ret;
 809 }
 810
 811 EXPORT_SYMBOL(generic_file_splice_write);
 812
 813 /**
 814  * generic_splice_sendpage - splice data from a pipe to a socket
 815  * @inode:      pipe inode
 816  * @out:        socket to write to
 817  * @len:        number of bytes to splice
 818  * @flags:      splice modifier flags
 819  *
 820  * Will send @len bytes from the pipe to a network socket. No data copying
 821  * is involved.
 822  *
 823  */
 824 ssize_t generic_splice_sendpage(struct pipe_inode_info *pipe, struct file *out,
 825                                 loff_t *ppos, size_t len, unsigned int flags)
 826 {
 827         return splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_sendpage);
 828 }
 829
 830 EXPORT_SYMBOL(generic_splice_sendpage);
 831
 832 /*
 833  * Attempt to initiate a splice from pipe to file.
 834  */
 835 static long do_splice_from(struct pipe_inode_info *pipe, struct file *out,
 836                            loff_t *ppos, size_t len, unsigned int flags)
 837 {
 838         int ret;
 839
 840         if (unlikely(!out->f_op || !out->f_op->splice_write))
 841                 return -EINVAL;
 842
 843         if (unlikely(!(out->f_mode & FMODE_WRITE)))
 844                 return -EBADF;
 845
 846         ret = rw_verify_area(WRITE, out, ppos, len);
 847         if (unlikely(ret < 0))
 848                 return ret;
 849
 850         return out->f_op->splice_write(pipe, out, ppos, len, flags);
 851 }
 852
 853 /*
 854  * Attempt to initiate a splice from a file to a pipe.
 855  */
 856 static long do_splice_to(struct file *in, loff_t *ppos,
 857                          struct pipe_inode_info *pipe, size_t len,
 858                          unsigned int flags)
 859 {
 860         loff_t isize, left;
 861         int ret;
 862
 863         if (unlikely(!in->f_op || !in->f_op->splice_read))
 864                 return -EINVAL;
 865
 866         if (unlikely(!(in->f_mode & FMODE_READ)))
 867                 return -EBADF;
 868
 869         ret = rw_verify_area(READ, in, ppos, len);
 870         if (unlikely(ret < 0))
 871                 return ret;
 872
 873         isize = i_size_read(in->f_mapping->host);
 874         if (unlikely(*ppos >= isize))
 875                 return 0;
 876
 877         left = isize - *ppos;
 878         if (unlikely(left < len))
 879                 len = left;
 880
 881         return in->f_op->splice_read(in, ppos, pipe, len, flags);
 882 }
 883
 884 long do_splice_direct(struct file *in, loff_t *ppos, struct file *out,
 885                       size_t len, unsigned int flags)
 886 {
 887         struct pipe_inode_info *pipe;
 888         long ret, bytes;
 889         loff_t out_off;
 890         umode_t i_mode;
 891         int i;
 892
 893         /*
 894          * We require the input being a regular file, as we don't want to
 895          * randomly drop data for eg socket -> socket splicing. Use the
 896          * piped splicing for that!
 897          */
 898         i_mode = in->f_dentry->d_inode->i_mode;
 899         if (unlikely(!S_ISREG(i_mode) && !S_ISBLK(i_mode)))
 900                 return -EINVAL;
 901
 902         /*
 903          * neither in nor out is a pipe, setup an internal pipe attached to
 904          * 'out' and transfer the wanted data from 'in' to 'out' through that
 905          */
 906         pipe = current->splice_pipe;
 907         if (unlikely(!pipe)) {
 908                 pipe = alloc_pipe_info(NULL);
 909                 if (!pipe)
 910                         return -ENOMEM;
 911
 912                 /*
 913                  * We don't have an immediate reader, but we'll read the stuff
 914                  * out of the pipe right after the splice_to_pipe(). So set
 915                  * PIPE_READERS appropriately.
 916                  */
 917                 pipe->readers = 1;
 918
 919                 current->splice_pipe = pipe;
 920         }
 921
 922         /*
 923          * Do the splice.
 924          */
 925         ret = 0;
 926         bytes = 0;
 927         out_off = 0;
 928
 929         while (len) {
 930                 size_t read_len, max_read_len;
 931
 932                 /*
 933                  * Do at most PIPE_BUFFERS pages worth of transfer:
 934                  */
 935                 max_read_len = min(len, (size_t)(PIPE_BUFFERS*PAGE_SIZE));
 936
 937                 ret = do_splice_to(in, ppos, pipe, max_read_len, flags);
 938                 if (unlikely(ret < 0))
 939                         goto out_release;
 940
 941                 read_len = ret;
 942
 943                 /*
 944                  * NOTE: nonblocking mode only applies to the input. We
 945                  * must not do the output in nonblocking mode as then we
 946                  * could get stuck data in the internal pipe:
 947                  */
 948                 ret = do_splice_from(pipe, out, &out_off, read_len,
 949                                      flags & ~SPLICE_F_NONBLOCK);
 950                 if (unlikely(ret < 0))
 951                         goto out_release;
 952
 953                 bytes += ret;
 954                 len -= ret;
 955
 956                 /*
 957                  * In nonblocking mode, if we got back a short read then
 958                  * that was due to either an IO error or due to the
 959                  * pagecache entry not being there. In the IO error case
 960                  * the _next_ splice attempt will produce a clean IO error
 961                  * return value (not a short read), so in both cases it's
 962                  * correct to break out of the loop here:
 963                  */
 964                 if ((flags & SPLICE_F_NONBLOCK) && (read_len < max_read_len))
 965                         break;
 966         }
 967
 968         pipe->nrbufs = pipe->curbuf = 0;
 969
 970         return bytes;
 971
 972 out_release:
 973         /*
 974          * If we did an incomplete transfer we must release
 975          * the pipe buffers in question:
 976          */
 977         for (i = 0; i < PIPE_BUFFERS; i++) {
 978                 struct pipe_buffer *buf = pipe->bufs + i;
 979
 980                 if (buf->ops) {
 981                         buf->ops->release(pipe, buf);
 982                         buf->ops = NULL;
 983                 }
 984         }
 985         pipe->nrbufs = pipe->curbuf = 0;
 986
 987         /*
 988          * If we transferred some data, return the number of bytes:
 989          */
 990         if (bytes > 0)
 991                 return bytes;
 992
 993         return ret;
 994 }
 995
 996 EXPORT_SYMBOL(do_splice_direct);
 997
 998 /*
 999  * Determine where to splice to/from.
1000  */
1001 static long do_splice(struct file *in, loff_t __user *off_in,
1002                       struct file *out, loff_t __user *off_out,
1003                       size_t len, unsigned int flags)
1004 {
1005         struct pipe_inode_info *pipe;
1006         loff_t offset, *off;
1007         long ret;
1008
1009         pipe = in->f_dentry->d_inode->i_pipe;
1010         if (pipe) {
1011                 if (off_in)
1012                         return -ESPIPE;
1013                 if (off_out) {
1014                         if (out->f_op->llseek == no_llseek)
1015                                 return -EINVAL;
1016                         if (copy_from_user(&offset, off_out, sizeof(loff_t)))
1017                                 return -EFAULT;
1018                         off = &offset;
1019                 } else
1020                         off = &out->f_pos;
1021
1022                 ret = do_splice_from(pipe, out, off, len, flags);
1023
1024                 if (off_out && copy_to_user(off_out, off, sizeof(loff_t)))
1025                         ret = -EFAULT;
1026
1027                 return ret;
1028         }
1029
1030         pipe = out->f_dentry->d_inode->i_pipe;
1031         if (pipe) {
1032                 if (off_out)
1033                         return -ESPIPE;
1034                 if (off_in) {
1035                         if (in->f_op->llseek == no_llseek)
1036                                 return -EINVAL;
1037                         if (copy_from_user(&offset, off_in, sizeof(loff_t)))
1038                                 return -EFAULT;
1039                         off = &offset;
1040                 } else
1041                         off = &in->f_pos;
1042
1043                 ret = do_splice_to(in, off, pipe, len, flags);
1044
1045                 if (off_in && copy_to_user(off_in, off, sizeof(loff_t)))
1046                         ret = -EFAULT;
1047
1048                 return ret;
1049         }
1050
1051         return -EINVAL;
1052 }
1053
1054 /*
1055  * Map an iov into an array of pages and offset/length tupples. With the
1056  * partial_page structure, we can map several non-contiguous ranges into
1057  * our ones pages[] map instead of splitting that operation into pieces.
1058  * Could easily be exported as a generic helper for other users, in which
1059  * case one would probably want to add a 'max_nr_pages' parameter as well.
1060  */
1061 static int get_iovec_page_array(const struct iovec __user *iov,
1062                                 unsigned int nr_vecs, struct page **pages,
1063                                 struct partial_page *partial)
1064 {
1065         int buffers = 0, error = 0;
1066
1067         /*
1068          * It's ok to take the mmap_sem for reading, even
1069          * across a "get_user()".
1070          */
1071         down_read(&current->mm->mmap_sem);
1072
1073         while (nr_vecs) {
1074                 unsigned long off, npages;
1075                 void __user *base;
1076                 size_t len;
1077                 int i;
1078
1079                 /*
1080                  * Get user address base and length for this iovec.
1081                  */
1082                 error = get_user(base, &iov->iov_base);
1083                 if (unlikely(error))
1084                         break;
1085                 error = get_user(len, &iov->iov_len);
1086                 if (unlikely(error))
1087                         break;
1088
1089                 /*
1090                  * Sanity check this iovec. 0 read succeeds.
1091                  */
1092                 if (unlikely(!len))
1093                         break;
1094                 error = -EFAULT;
1095                 if (unlikely(!base))
1096                         break;
1097
1098                 /*
1099                  * Get this base offset and number of pages, then map
1100                  * in the user pages.
1101                  */
1102                 off = (unsigned long) base & ~PAGE_MASK;
1103                 npages = (off + len + PAGE_SIZE - 1) >> PAGE_SHIFT;
1104                 if (npages > PIPE_BUFFERS - buffers)
1105                         npages = PIPE_BUFFERS - buffers;
1106
1107                 error = get_user_pages(current, current->mm,
1108                                        (unsigned long) base, npages, 0, 0,
1109                                        &pages[buffers], NULL);
1110
1111                 if (unlikely(error <= 0))
1112                         break;
1113
1114                 /*
1115                  * Fill this contiguous range into the partial page map.
1116                  */
1117                 for (i = 0; i < error; i++) {
1118                         const int plen = min_t(size_t, len, PAGE_SIZE) - off;
1119
1120                         partial[buffers].offset = off;
1121                         partial[buffers].len = plen;
1122
1123                         off = 0;
1124                         len -= plen;
1125                         buffers++;
1126                 }
1127
1128                 /*
1129                  * We didn't complete this iov, stop here since it probably
1130                  * means we have to move some of this into a pipe to
1131                  * be able to continue.
1132                  */
1133                 if (len)
1134                         break;
1135
1136                 /*
1137                  * Don't continue if we mapped fewer pages than we asked for,
1138                  * or if we mapped the max number of pages that we have
1139                  * room for.
1140                  */
1141                 if (error < npages || buffers == PIPE_BUFFERS)
1142                         break;
1143
1144                 nr_vecs--;
1145                 iov++;
1146         }
1147
1148         up_read(&current->mm->mmap_sem);
1149
1150         if (buffers)
1151                 return buffers;
1152
1153         return error;
1154 }
1155
1156 /*
1157  * vmsplice splices a user address range into a pipe. It can be thought of
1158  * as splice-from-memory, where the regular splice is splice-from-file (or
1159  * to file). In both cases the output is a pipe, naturally.
1160  *
1161  * Note that vmsplice only supports splicing _from_ user memory to a pipe,
1162  * not the other way around. Splicing from user memory is a simple operation
1163  * that can be supported without any funky alignment restrictions or nasty
1164  * vm tricks. We simply map in the user memory and fill them into a pipe.
1165  * The reverse isn't quite as easy, though. There are two possible solutions
1166  * for that:
1167  *
1168  *      - memcpy() the data internally, at which point we might as well just
1169  *        do a regular read() on the buffer anyway.
1170  *      - Lots of nasty vm tricks, that are neither fast nor flexible (it
1171  *        has restriction limitations on both ends of the pipe).
1172  *
1173  * Alas, it isn't here.
1174  *
1175  */
1176 static long do_vmsplice(struct file *file, const struct iovec __user *iov,
1177                         unsigned long nr_segs, unsigned int flags)
1178 {
1179         struct pipe_inode_info *pipe = file->f_dentry->d_inode->i_pipe;
1180         struct page *pages[PIPE_BUFFERS];
1181         struct partial_page partial[PIPE_BUFFERS];
1182         struct splice_pipe_desc spd = {
1183                 .pages = pages,
1184                 .partial = partial,
1185                 .flags = flags,
1186                 .ops = &user_page_pipe_buf_ops,
1187         };
1188
1189         if (unlikely(!pipe))
1190                 return -EBADF;
1191         if (unlikely(nr_segs > UIO_MAXIOV))
1192                 return -EINVAL;
1193         else if (unlikely(!nr_segs))
1194                 return 0;
1195
1196         spd.nr_pages = get_iovec_page_array(iov, nr_segs, pages, partial);
1197         if (spd.nr_pages <= 0)
1198                 return spd.nr_pages;
1199
1200         return splice_to_pipe(pipe, &spd);
1201 }
1202
1203 asmlinkage long sys_vmsplice(int fd, const struct iovec __user *iov,
1204                              unsigned long nr_segs, unsigned int flags)
1205 {
1206         struct file *file;
1207         long error;
1208         int fput;
1209
1210         error = -EBADF;
1211         file = fget_light(fd, &fput);
1212         if (file) {
1213                 if (file->f_mode & FMODE_WRITE)
1214                         error = do_vmsplice(file, iov, nr_segs, flags);
1215
1216                 fput_light(file, fput);
1217         }
1218
1219         return error;
1220 }
1221
1222 asmlinkage long sys_splice(int fd_in, loff_t __user *off_in,
1223                            int fd_out, loff_t __user *off_out,
1224                            size_t len, unsigned int flags)
1225 {
1226         long error;
1227         struct file *in, *out;
1228         int fput_in, fput_out;
1229
1230         if (unlikely(!len))
1231                 return 0;
1232
1233         error = -EBADF;
1234         in = fget_light(fd_in, &fput_in);
1235         if (in) {
1236                 if (in->f_mode & FMODE_READ) {
1237                         out = fget_light(fd_out, &fput_out);
1238                         if (out) {
1239                                 if (out->f_mode & FMODE_WRITE)
1240                                         error = do_splice(in, off_in,
1241                                                           out, off_out,
1242                                                           len, flags);
1243                                 fput_light(out, fput_out);
1244                         }
1245                 }
1246
1247                 fput_light(in, fput_in);
1248         }
1249
1250         return error;
1251 }
1252
1253 /*
1254  * Link contents of ipipe to opipe.
1255  */
1256 static int link_pipe(struct pipe_inode_info *ipipe,
1257                      struct pipe_inode_info *opipe,
1258                      size_t len, unsigned int flags)
1259 {
1260         struct pipe_buffer *ibuf, *obuf;
1261         int ret, do_wakeup, i, ipipe_first;
1262
1263         ret = do_wakeup = ipipe_first = 0;
1264
1265         /*
1266          * Potential ABBA deadlock, work around it by ordering lock
1267          * grabbing by inode address. Otherwise two different processes
1268          * could deadlock (one doing tee from A -> B, the other from B -> A).
1269          */
1270         if (ipipe->inode < opipe->inode) {
1271                 ipipe_first = 1;
1272                 mutex_lock(&ipipe->inode->i_mutex);
1273                 mutex_lock(&opipe->inode->i_mutex);
1274         } else {
1275                 mutex_lock(&opipe->inode->i_mutex);
1276                 mutex_lock(&ipipe->inode->i_mutex);
1277         }
1278
1279         for (i = 0;; i++) {
1280                 if (!opipe->readers) {
1281                         send_sig(SIGPIPE, current, 0);
1282                         if (!ret)
1283                                 ret = -EPIPE;
1284                         break;
1285                 }
1286                 if (ipipe->nrbufs - i) {
1287                         ibuf = ipipe->bufs + ((ipipe->curbuf + i) & (PIPE_BUFFERS - 1));
1288
1289                         /*
1290                          * If we have room, fill this buffer
1291                          */
1292                         if (opipe->nrbufs < PIPE_BUFFERS) {
1293                                 int nbuf = (opipe->curbuf + opipe->nrbufs) & (PIPE_BUFFERS - 1);
1294
1295                                 /*
1296                                  * Get a reference to this pipe buffer,
1297                                  * so we can copy the contents over.
1298                                  */
1299                                 ibuf->ops->get(ipipe, ibuf);
1300
1301                                 obuf = opipe->bufs + nbuf;
1302                                 *obuf = *ibuf;
1303
1304                                 if (obuf->len > len)
1305                                         obuf->len = len;
1306
1307                                 opipe->nrbufs++;
1308                                 do_wakeup = 1;
1309                                 ret += obuf->len;
1310                                 len -= obuf->len;
1311
1312                                 if (!len)
1313                                         break;
1314                                 if (opipe->nrbufs < PIPE_BUFFERS)
1315                                         continue;
1316                         }
1317
1318                         /*
1319                          * We have input available, but no output room.
1320                          * If we already copied data, return that. If we
1321                          * need to drop the opipe lock, it must be ordered
1322                          * last to avoid deadlocks.
1323                          */
1324                         if ((flags & SPLICE_F_NONBLOCK) || !ipipe_first) {
1325                                 if (!ret)
1326                                         ret = -EAGAIN;
1327                                 break;
1328                         }
1329                         if (signal_pending(current)) {
1330                                 if (!ret)
1331                                         ret = -ERESTARTSYS;
1332                                 break;
1333                         }
1334                         if (do_wakeup) {
1335                                 smp_mb();
1336                                 if (waitqueue_active(&opipe->wait))
1337                                         wake_up_interruptible(&opipe->wait);
1338                                 kill_fasync(&opipe->fasync_readers, SIGIO, POLL_IN);
1339                                 do_wakeup = 0;
1340                         }
1341
1342                         opipe->waiting_writers++;
1343                         pipe_wait(opipe);
1344                         opipe->waiting_writers--;
1345                         continue;
1346                 }
1347
1348                 /*
1349                  * No input buffers, do the usual checks for available
1350                  * writers and blocking and wait if necessary
1351                  */
1352                 if (!ipipe->writers)
1353                         break;
1354                 if (!ipipe->waiting_writers) {
1355                         if (ret)
1356                                 break;
1357                 }
1358                 /*
1359                  * pipe_wait() drops the ipipe mutex. To avoid deadlocks
1360                  * with another process, we can only safely do that if
1361                  * the ipipe lock is ordered last.
1362                  */
1363                 if ((flags & SPLICE_F_NONBLOCK) || ipipe_first) {
1364                         if (!ret)
1365                                 ret = -EAGAIN;
1366                         break;
1367                 }
1368                 if (signal_pending(current)) {
1369                         if (!ret)
1370                                 ret = -ERESTARTSYS;
1371                         break;
1372                 }
1373
1374                 if (waitqueue_active(&ipipe->wait))
1375                         wake_up_interruptible_sync(&ipipe->wait);
1376                 kill_fasync(&ipipe->fasync_writers, SIGIO, POLL_OUT);
1377
1378                 pipe_wait(ipipe);
1379         }
1380
1381         mutex_unlock(&ipipe->inode->i_mutex);
1382         mutex_unlock(&opipe->inode->i_mutex);
1383
1384         if (do_wakeup) {
1385                 smp_mb();
1386                 if (waitqueue_active(&opipe->wait))
1387                         wake_up_interruptible(&opipe->wait);
1388                 kill_fasync(&opipe->fasync_readers, SIGIO, POLL_IN);
1389         }
1390
1391         return ret;
1392 }
1393
1394 /*
1395  * This is a tee(1) implementation that works on pipes. It doesn't copy
1396  * any data, it simply references the 'in' pages on the 'out' pipe.
1397  * The 'flags' used are the SPLICE_F_* variants, currently the only
1398  * applicable one is SPLICE_F_NONBLOCK.
1399  */
1400 static long do_tee(struct file *in, struct file *out, size_t len,
1401                    unsigned int flags)
1402 {
1403         struct pipe_inode_info *ipipe = in->f_dentry->d_inode->i_pipe;
1404         struct pipe_inode_info *opipe = out->f_dentry->d_inode->i_pipe;
1405
1406         /*
1407          * Link ipipe to the two output pipes, consuming as we go along.
1408          */
1409         if (ipipe && opipe)
1410                 return link_pipe(ipipe, opipe, len, flags);
1411
1412         return -EINVAL;
1413 }
1414
1415 asmlinkage long sys_tee(int fdin, int fdout, size_t len, unsigned int flags)
1416 {
1417         struct file *in;
1418         int error, fput_in;
1419
1420         if (unlikely(!len))
1421                 return 0;
1422
1423         error = -EBADF;
1424         in = fget_light(fdin, &fput_in);
1425         if (in) {
1426                 if (in->f_mode & FMODE_READ) {
1427                         int fput_out;
1428                         struct file *out = fget_light(fdout, &fput_out);
1429
1430                         if (out) {
1431                                 if (out->f_mode & FMODE_WRITE)
1432                                         error = do_tee(in, out, len, flags);
1433                                 fput_light(out, fput_out);
1434                         }
1435                 }
1436                 fput_light(in, fput_in);
1437         }
1438
1439         return error;
1440 }