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 /*
  33  * Passed to the actors
  34  */
  35 struct splice_desc {
  36         unsigned int len, total_len;    /* current and remaining length */
  37         unsigned int flags;             /* splice flags */
  38         struct file *file;              /* file to read/write */
  39         loff_t pos;                     /* file position */
  40 };
  41
  42 struct partial_page {
  43         unsigned int offset;
  44         unsigned int len;
  45 };
  46
  47 /*
  48  * Passed to move_to_pipe
  49  */
  50 struct splice_pipe_desc {
  51         struct page **pages;            /* page map */
  52         struct partial_page *partial;   /* pages[] may not be contig */
  53         int nr_pages;                   /* number of pages in map */
  54         unsigned int flags;             /* splice flags */
  55         struct pipe_buf_operations *ops;/* ops associated with output pipe */
  56 };
  57
  58 /*
  59  * Attempt to steal a page from a pipe buffer. This should perhaps go into
  60  * a vm helper function, it's already simplified quite a bit by the
  61  * addition of remove_mapping(). If success is returned, the caller may
  62  * attempt to reuse this page for another destination.
  63  */
  64 static int page_cache_pipe_buf_steal(struct pipe_inode_info *info,
  65                                      struct pipe_buffer *buf)
  66 {
  67         struct page *page = buf->page;
  68         struct address_space *mapping = page_mapping(page);
  69
  70         lock_page(page);
  71
  72         WARN_ON(!PageUptodate(page));
  73
  74         /*
  75          * At least for ext2 with nobh option, we need to wait on writeback
  76          * completing on this page, since we'll remove it from the pagecache.
  77          * Otherwise truncate wont wait on the page, allowing the disk
  78          * blocks to be reused by someone else before we actually wrote our
  79          * data to them. fs corruption ensues.
  80          */
  81         wait_on_page_writeback(page);
  82
  83         if (PagePrivate(page))
  84                 try_to_release_page(page, mapping_gfp_mask(mapping));
  85
  86         if (!remove_mapping(mapping, page)) {
  87                 unlock_page(page);
  88                 return 1;
  89         }
  90
  91         buf->flags |= PIPE_BUF_FLAG_STOLEN | PIPE_BUF_FLAG_LRU;
  92         return 0;
  93 }
  94
  95 static void page_cache_pipe_buf_release(struct pipe_inode_info *info,
  96                                         struct pipe_buffer *buf)
  97 {
  98         page_cache_release(buf->page);
  99         buf->page = NULL;
 100         buf->flags &= ~(PIPE_BUF_FLAG_STOLEN | PIPE_BUF_FLAG_LRU);
 101 }
 102
 103 static void *page_cache_pipe_buf_map(struct file *file,
 104                                      struct pipe_inode_info *info,
 105                                      struct pipe_buffer *buf)
 106 {
 107         struct page *page = buf->page;
 108         int err;
 109
 110         if (!PageUptodate(page)) {
 111                 lock_page(page);
 112
 113                 /*
 114                  * Page got truncated/unhashed. This will cause a 0-byte
 115                  * splice, if this is the first page.
 116                  */
 117                 if (!page->mapping) {
 118                         err = -ENODATA;
 119                         goto error;
 120                 }
 121
 122                 /*
 123                  * Uh oh, read-error from disk.
 124                  */
 125                 if (!PageUptodate(page)) {
 126                         err = -EIO;
 127                         goto error;
 128                 }
 129
 130                 /*
 131                  * Page is ok afterall, fall through to mapping.
 132                  */
 133                 unlock_page(page);
 134         }
 135
 136         return kmap(page);
 137 error:
 138         unlock_page(page);
 139         return ERR_PTR(err);
 140 }
 141
 142 static void page_cache_pipe_buf_unmap(struct pipe_inode_info *info,
 143                                       struct pipe_buffer *buf)
 144 {
 145         kunmap(buf->page);
 146 }
 147
 148 static void *user_page_pipe_buf_map(struct file *file,
 149                                     struct pipe_inode_info *pipe,
 150                                     struct pipe_buffer *buf)
 151 {
 152         return kmap(buf->page);
 153 }
 154
 155 static void user_page_pipe_buf_unmap(struct pipe_inode_info *pipe,
 156                                      struct pipe_buffer *buf)
 157 {
 158         kunmap(buf->page);
 159 }
 160
 161 static void page_cache_pipe_buf_get(struct pipe_inode_info *info,
 162                                     struct pipe_buffer *buf)
 163 {
 164         page_cache_get(buf->page);
 165 }
 166
 167 static struct pipe_buf_operations page_cache_pipe_buf_ops = {
 168         .can_merge = 0,
 169         .map = page_cache_pipe_buf_map,
 170         .unmap = page_cache_pipe_buf_unmap,
 171         .release = page_cache_pipe_buf_release,
 172         .steal = page_cache_pipe_buf_steal,
 173         .get = page_cache_pipe_buf_get,
 174 };
 175
 176 static int user_page_pipe_buf_steal(struct pipe_inode_info *pipe,
 177                                     struct pipe_buffer *buf)
 178 {
 179         return 1;
 180 }
 181
 182 static struct pipe_buf_operations user_page_pipe_buf_ops = {
 183         .can_merge = 0,
 184         .map = user_page_pipe_buf_map,
 185         .unmap = user_page_pipe_buf_unmap,
 186         .release = page_cache_pipe_buf_release,
 187         .steal = user_page_pipe_buf_steal,
 188         .get = page_cache_pipe_buf_get,
 189 };
 190
 191 /*
 192  * Pipe output worker. This sets up our pipe format with the page cache
 193  * pipe buffer operations. Otherwise very similar to the regular pipe_writev().
 194  */
 195 static ssize_t move_to_pipe(struct pipe_inode_info *pipe,
 196                             struct splice_pipe_desc *spd)
 197 {
 198         int ret, do_wakeup, page_nr;
 199
 200         ret = 0;
 201         do_wakeup = 0;
 202         page_nr = 0;
 203
 204         if (pipe->inode)
 205                 mutex_lock(&pipe->inode->i_mutex);
 206
 207         for (;;) {
 208                 if (!pipe->readers) {
 209                         send_sig(SIGPIPE, current, 0);
 210                         if (!ret)
 211                                 ret = -EPIPE;
 212                         break;
 213                 }
 214
 215                 if (pipe->nrbufs < PIPE_BUFFERS) {
 216                         int newbuf = (pipe->curbuf + pipe->nrbufs) & (PIPE_BUFFERS - 1);
 217                         struct pipe_buffer *buf = pipe->bufs + newbuf;
 218
 219                         buf->page = spd->pages[page_nr];
 220                         buf->offset = spd->partial[page_nr].offset;
 221                         buf->len = spd->partial[page_nr].len;
 222                         buf->ops = spd->ops;
 223                         pipe->nrbufs++;
 224                         page_nr++;
 225                         ret += buf->len;
 226
 227                         if (pipe->inode)
 228                                 do_wakeup = 1;
 229
 230                         if (!--spd->nr_pages)
 231                                 break;
 232                         if (pipe->nrbufs < PIPE_BUFFERS)
 233                                 continue;
 234
 235                         break;
 236                 }
 237
 238                 if (spd->flags & SPLICE_F_NONBLOCK) {
 239                         if (!ret)
 240                                 ret = -EAGAIN;
 241                         break;
 242                 }
 243
 244                 if (signal_pending(current)) {
 245                         if (!ret)
 246                                 ret = -ERESTARTSYS;
 247                         break;
 248                 }
 249
 250                 if (do_wakeup) {
 251                         smp_mb();
 252                         if (waitqueue_active(&pipe->wait))
 253                                 wake_up_interruptible_sync(&pipe->wait);
 254                         kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
 255                         do_wakeup = 0;
 256                 }
 257
 258                 pipe->waiting_writers++;
 259                 pipe_wait(pipe);
 260                 pipe->waiting_writers--;
 261         }
 262
 263         if (pipe->inode)
 264                 mutex_unlock(&pipe->inode->i_mutex);
 265
 266         if (do_wakeup) {
 267                 smp_mb();
 268                 if (waitqueue_active(&pipe->wait))
 269                         wake_up_interruptible(&pipe->wait);
 270                 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
 271         }
 272
 273         while (page_nr < spd->nr_pages)
 274                 page_cache_release(spd->pages[page_nr++]);
 275
 276         return ret;
 277 }
 278
 279 static int
 280 __generic_file_splice_read(struct file *in, loff_t *ppos,
 281                            struct pipe_inode_info *pipe, size_t len,
 282                            unsigned int flags)
 283 {
 284         struct address_space *mapping = in->f_mapping;
 285         unsigned int loff, nr_pages;
 286         struct page *pages[PIPE_BUFFERS];
 287         struct partial_page partial[PIPE_BUFFERS];
 288         struct page *page;
 289         pgoff_t index, end_index;
 290         loff_t isize;
 291         size_t total_len;
 292         int error;
 293         struct splice_pipe_desc spd = {
 294                 .pages = pages,
 295                 .partial = partial,
 296                 .flags = flags,
 297                 .ops = &page_cache_pipe_buf_ops,
 298         };
 299
 300         index = *ppos >> PAGE_CACHE_SHIFT;
 301         loff = *ppos & ~PAGE_CACHE_MASK;
 302         nr_pages = (len + loff + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
 303
 304         if (nr_pages > PIPE_BUFFERS)
 305                 nr_pages = PIPE_BUFFERS;
 306
 307         /*
 308          * Initiate read-ahead on this page range. however, don't call into
 309          * read-ahead if this is a non-zero offset (we are likely doing small
 310          * chunk splice and the page is already there) for a single page.
 311          */
 312         if (!loff || spd.nr_pages > 1)
 313                 do_page_cache_readahead(mapping, in, index, spd.nr_pages);
 314
 315         /*
 316          * Now fill in the holes:
 317          */
 318         error = 0;
 319         total_len = 0;
 320         for (spd.nr_pages = 0; spd.nr_pages < nr_pages; spd.nr_pages++, index++) {
 321                 unsigned int this_len;
 322
 323                 if (!len)
 324                         break;
 325
 326                 /*
 327                  * this_len is the max we'll use from this page
 328                  */
 329                 this_len = min_t(unsigned long, len, PAGE_CACHE_SIZE - loff);
 330 find_page:
 331                 /*
 332                  * lookup the page for this index
 333                  */
 334                 page = find_get_page(mapping, index);
 335                 if (!page) {
 336                         /*
 337                          * page didn't exist, allocate one
 338                          */
 339                         page = page_cache_alloc_cold(mapping);
 340                         if (!page)
 341                                 break;
 342
 343                         error = add_to_page_cache_lru(page, mapping, index,
 344                                                 mapping_gfp_mask(mapping));
 345                         if (unlikely(error)) {
 346                                 page_cache_release(page);
 347                                 break;
 348                         }
 349
 350                         goto readpage;
 351                 }
 352
 353                 /*
 354                  * If the page isn't uptodate, we may need to start io on it
 355                  */
 356                 if (!PageUptodate(page)) {
 357                         /*
 358                          * If in nonblock mode then dont block on waiting
 359                          * for an in-flight io page
 360                          */
 361                         if (flags & SPLICE_F_NONBLOCK)
 362                                 break;
 363
 364                         lock_page(page);
 365
 366                         /*
 367                          * page was truncated, stop here. if this isn't the
 368                          * first page, we'll just complete what we already
 369                          * added
 370                          */
 371                         if (!page->mapping) {
 372                                 unlock_page(page);
 373                                 page_cache_release(page);
 374                                 break;
 375                         }
 376                         /*
 377                          * page was already under io and is now done, great
 378                          */
 379                         if (PageUptodate(page)) {
 380                                 unlock_page(page);
 381                                 goto fill_it;
 382                         }
 383
 384 readpage:
 385                         /*
 386                          * need to read in the page
 387                          */
 388                         error = mapping->a_ops->readpage(in, page);
 389
 390                         if (unlikely(error)) {
 391                                 page_cache_release(page);
 392                                 if (error == AOP_TRUNCATED_PAGE)
 393                                         goto find_page;
 394                                 break;
 395                         }
 396
 397                         /*
 398                          * i_size must be checked after ->readpage().
 399                          */
 400                         isize = i_size_read(mapping->host);
 401                         end_index = (isize - 1) >> PAGE_CACHE_SHIFT;
 402                         if (unlikely(!isize || index > end_index)) {
 403                                 page_cache_release(page);
 404                                 break;
 405                         }
 406
 407                         /*
 408                          * if this is the last page, see if we need to shrink
 409                          * the length and stop
 410                          */
 411                         if (end_index == index) {
 412                                 loff = PAGE_CACHE_SIZE - (isize & ~PAGE_CACHE_MASK);
 413                                 if (total_len + loff > isize) {
 414                                         page_cache_release(page);
 415                                         break;
 416                                 }
 417                                 /*
 418                                  * force quit after adding this page
 419                                  */
 420                                 nr_pages = spd.nr_pages;
 421                                 this_len = min(this_len, loff);
 422                                 loff = 0;
 423                         }
 424                 }
 425 fill_it:
 426                 pages[spd.nr_pages] = page;
 427                 partial[spd.nr_pages].offset = loff;
 428                 partial[spd.nr_pages].len = this_len;
 429                 len -= this_len;
 430                 total_len += this_len;
 431                 loff = 0;
 432         }
 433
 434         if (spd.nr_pages)
 435                 return move_to_pipe(pipe, &spd);
 436
 437         return error;
 438 }
 439
 440 /**
 441  * generic_file_splice_read - splice data from file to a pipe
 442  * @in:         file to splice from
 443  * @pipe:       pipe to splice to
 444  * @len:        number of bytes to splice
 445  * @flags:      splice modifier flags
 446  *
 447  * Will read pages from given file and fill them into a pipe.
 448  */
 449 ssize_t generic_file_splice_read(struct file *in, loff_t *ppos,
 450                                  struct pipe_inode_info *pipe, size_t len,
 451                                  unsigned int flags)
 452 {
 453         ssize_t spliced;
 454         int ret;
 455
 456         ret = 0;
 457         spliced = 0;
 458
 459         while (len) {
 460                 ret = __generic_file_splice_read(in, ppos, pipe, len, flags);
 461
 462                 if (ret < 0)
 463                         break;
 464                 else if (!ret) {
 465                         if (spliced)
 466                                 break;
 467                         if (flags & SPLICE_F_NONBLOCK) {
 468                                 ret = -EAGAIN;
 469                                 break;
 470                         }
 471                 }
 472
 473                 *ppos += ret;
 474                 len -= ret;
 475                 spliced += ret;
 476         }
 477
 478         if (spliced)
 479                 return spliced;
 480
 481         return ret;
 482 }
 483
 484 EXPORT_SYMBOL(generic_file_splice_read);
 485
 486 /*
 487  * Send 'sd->len' bytes to socket from 'sd->file' at position 'sd->pos'
 488  * using sendpage(). Return the number of bytes sent.
 489  */
 490 static int pipe_to_sendpage(struct pipe_inode_info *info,
 491                             struct pipe_buffer *buf, struct splice_desc *sd)
 492 {
 493         struct file *file = sd->file;
 494         loff_t pos = sd->pos;
 495         ssize_t ret;
 496         void *ptr;
 497         int more;
 498
 499         /*
 500          * Sub-optimal, but we are limited by the pipe ->map. We don't
 501          * need a kmap'ed buffer here, we just want to make sure we
 502          * have the page pinned if the pipe page originates from the
 503          * page cache.
 504          */
 505         ptr = buf->ops->map(file, info, buf);
 506         if (IS_ERR(ptr))
 507                 return PTR_ERR(ptr);
 508
 509         more = (sd->flags & SPLICE_F_MORE) || sd->len < sd->total_len;
 510
 511         ret = file->f_op->sendpage(file, buf->page, buf->offset, sd->len,
 512                                    &pos, more);
 513
 514         buf->ops->unmap(info, buf);
 515         return ret;
 516 }
 517
 518 /*
 519  * This is a little more tricky than the file -> pipe splicing. There are
 520  * basically three cases:
 521  *
 522  *      - Destination page already exists in the address space and there
 523  *        are users of it. For that case we have no other option that
 524  *        copying the data. Tough luck.
 525  *      - Destination page already exists in the address space, but there
 526  *        are no users of it. Make sure it's uptodate, then drop it. Fall
 527  *        through to last case.
 528  *      - Destination page does not exist, we can add the pipe page to
 529  *        the page cache and avoid the copy.
 530  *
 531  * If asked to move pages to the output file (SPLICE_F_MOVE is set in
 532  * sd->flags), we attempt to migrate pages from the pipe to the output
 533  * file address space page cache. This is possible if no one else has
 534  * the pipe page referenced outside of the pipe and page cache. If
 535  * SPLICE_F_MOVE isn't set, or we cannot move the page, we simply create
 536  * a new page in the output file page cache and fill/dirty that.
 537  */
 538 static int pipe_to_file(struct pipe_inode_info *info, struct pipe_buffer *buf,
 539                         struct splice_desc *sd)
 540 {
 541         struct file *file = sd->file;
 542         struct address_space *mapping = file->f_mapping;
 543         gfp_t gfp_mask = mapping_gfp_mask(mapping);
 544         unsigned int offset, this_len;
 545         struct page *page;
 546         pgoff_t index;
 547         char *src;
 548         int ret;
 549
 550         /*
 551          * make sure the data in this buffer is uptodate
 552          */
 553         src = buf->ops->map(file, info, buf);
 554         if (IS_ERR(src))
 555                 return PTR_ERR(src);
 556
 557         index = sd->pos >> PAGE_CACHE_SHIFT;
 558         offset = sd->pos & ~PAGE_CACHE_MASK;
 559
 560         this_len = sd->len;
 561         if (this_len + offset > PAGE_CACHE_SIZE)
 562                 this_len = PAGE_CACHE_SIZE - offset;
 563
 564         /*
 565          * Reuse buf page, if SPLICE_F_MOVE is set.
 566          */
 567         if (sd->flags & SPLICE_F_MOVE) {
 568                 /*
 569                  * If steal succeeds, buf->page is now pruned from the vm
 570                  * side (LRU and page cache) and we can reuse it. The page
 571                  * will also be looked on successful return.
 572                  */
 573                 if (buf->ops->steal(info, buf))
 574                         goto find_page;
 575
 576                 page = buf->page;
 577                 if (add_to_page_cache(page, mapping, index, gfp_mask))
 578                         goto find_page;
 579
 580                 if (!(buf->flags & PIPE_BUF_FLAG_LRU))
 581                         lru_cache_add(page);
 582         } else {
 583 find_page:
 584                 page = find_lock_page(mapping, index);
 585                 if (!page) {
 586                         ret = -ENOMEM;
 587                         page = page_cache_alloc_cold(mapping);
 588                         if (unlikely(!page))
 589                                 goto out_nomem;
 590
 591                         /*
 592                          * This will also lock the page
 593                          */
 594                         ret = add_to_page_cache_lru(page, mapping, index,
 595                                                     gfp_mask);
 596                         if (unlikely(ret))
 597                                 goto out;
 598                 }
 599
 600                 /*
 601                  * We get here with the page locked. If the page is also
 602                  * uptodate, we don't need to do more. If it isn't, we
 603                  * may need to bring it in if we are not going to overwrite
 604                  * the full page.
 605                  */
 606                 if (!PageUptodate(page)) {
 607                         if (this_len < PAGE_CACHE_SIZE) {
 608                                 ret = mapping->a_ops->readpage(file, page);
 609                                 if (unlikely(ret))
 610                                         goto out;
 611
 612                                 lock_page(page);
 613
 614                                 if (!PageUptodate(page)) {
 615                                         /*
 616                                          * Page got invalidated, repeat.
 617                                          */
 618                                         if (!page->mapping) {
 619                                                 unlock_page(page);
 620                                                 page_cache_release(page);
 621                                                 goto find_page;
 622                                         }
 623                                         ret = -EIO;
 624                                         goto out;
 625                                 }
 626                         } else
 627                                 SetPageUptodate(page);
 628                 }
 629         }
 630
 631         ret = mapping->a_ops->prepare_write(file, page, offset, offset+this_len);
 632         if (ret == AOP_TRUNCATED_PAGE) {
 633                 page_cache_release(page);
 634                 goto find_page;
 635         } else if (ret)
 636                 goto out;
 637
 638         if (!(buf->flags & PIPE_BUF_FLAG_STOLEN)) {
 639                 char *dst = kmap_atomic(page, KM_USER0);
 640
 641                 memcpy(dst + offset, src + buf->offset, this_len);
 642                 flush_dcache_page(page);
 643                 kunmap_atomic(dst, KM_USER0);
 644         }
 645
 646         ret = mapping->a_ops->commit_write(file, page, offset, offset+this_len);
 647         if (ret == AOP_TRUNCATED_PAGE) {
 648                 page_cache_release(page);
 649                 goto find_page;
 650         } else if (ret)
 651                 goto out;
 652
 653         /*
 654          * Return the number of bytes written.
 655          */
 656         ret = this_len;
 657         mark_page_accessed(page);
 658         balance_dirty_pages_ratelimited(mapping);
 659 out:
 660         if (!(buf->flags & PIPE_BUF_FLAG_STOLEN))
 661                 page_cache_release(page);
 662
 663         unlock_page(page);
 664 out_nomem:
 665         buf->ops->unmap(info, buf);
 666         return ret;
 667 }
 668
 669 typedef int (splice_actor)(struct pipe_inode_info *, struct pipe_buffer *,
 670                            struct splice_desc *);
 671
 672 /*
 673  * Pipe input worker. Most of this logic works like a regular pipe, the
 674  * key here is the 'actor' worker passed in that actually moves the data
 675  * to the wanted destination. See pipe_to_file/pipe_to_sendpage above.
 676  */
 677 static ssize_t move_from_pipe(struct pipe_inode_info *pipe, struct file *out,
 678                               loff_t *ppos, size_t len, unsigned int flags,
 679                               splice_actor *actor)
 680 {
 681         int ret, do_wakeup, err;
 682         struct splice_desc sd;
 683
 684         ret = 0;
 685         do_wakeup = 0;
 686
 687         sd.total_len = len;
 688         sd.flags = flags;
 689         sd.file = out;
 690         sd.pos = *ppos;
 691
 692         if (pipe->inode)
 693                 mutex_lock(&pipe->inode->i_mutex);
 694
 695         for (;;) {
 696                 if (pipe->nrbufs) {
 697                         struct pipe_buffer *buf = pipe->bufs + pipe->curbuf;
 698                         struct pipe_buf_operations *ops = buf->ops;
 699
 700                         sd.len = buf->len;
 701                         if (sd.len > sd.total_len)
 702                                 sd.len = sd.total_len;
 703
 704                         err = actor(pipe, buf, &sd);
 705                         if (err <= 0) {
 706                                 if (!ret && err != -ENODATA)
 707                                         ret = err;
 708
 709                                 break;
 710                         }
 711
 712                         ret += err;
 713                         buf->offset += err;
 714                         buf->len -= err;
 715
 716                         sd.len -= err;
 717                         sd.pos += err;
 718                         sd.total_len -= err;
 719                         if (sd.len)
 720                                 continue;
 721
 722                         if (!buf->len) {
 723                                 buf->ops = NULL;
 724                                 ops->release(pipe, buf);
 725                                 pipe->curbuf = (pipe->curbuf + 1) & (PIPE_BUFFERS - 1);
 726                                 pipe->nrbufs--;
 727                                 if (pipe->inode)
 728                                         do_wakeup = 1;
 729                         }
 730
 731                         if (!sd.total_len)
 732                                 break;
 733                 }
 734
 735                 if (pipe->nrbufs)
 736                         continue;
 737                 if (!pipe->writers)
 738                         break;
 739                 if (!pipe->waiting_writers) {
 740                         if (ret)
 741                                 break;
 742                 }
 743
 744                 if (flags & SPLICE_F_NONBLOCK) {
 745                         if (!ret)
 746                                 ret = -EAGAIN;
 747                         break;
 748                 }
 749
 750                 if (signal_pending(current)) {
 751                         if (!ret)
 752                                 ret = -ERESTARTSYS;
 753                         break;
 754                 }
 755
 756                 if (do_wakeup) {
 757                         smp_mb();
 758                         if (waitqueue_active(&pipe->wait))
 759                                 wake_up_interruptible_sync(&pipe->wait);
 760                         kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
 761                         do_wakeup = 0;
 762                 }
 763
 764                 pipe_wait(pipe);
 765         }
 766
 767         if (pipe->inode)
 768                 mutex_unlock(&pipe->inode->i_mutex);
 769
 770         if (do_wakeup) {
 771                 smp_mb();
 772                 if (waitqueue_active(&pipe->wait))
 773                         wake_up_interruptible(&pipe->wait);
 774                 kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
 775         }
 776
 777         return ret;
 778 }
 779
 780 /**
 781  * generic_file_splice_write - splice data from a pipe to a file
 782  * @pipe:       pipe info
 783  * @out:        file to write to
 784  * @len:        number of bytes to splice
 785  * @flags:      splice modifier flags
 786  *
 787  * Will either move or copy pages (determined by @flags options) from
 788  * the given pipe inode to the given file.
 789  *
 790  */
 791 ssize_t
 792 generic_file_splice_write(struct pipe_inode_info *pipe, struct file *out,
 793                           loff_t *ppos, size_t len, unsigned int flags)
 794 {
 795         struct address_space *mapping = out->f_mapping;
 796         ssize_t ret;
 797
 798         ret = move_from_pipe(pipe, out, ppos, len, flags, pipe_to_file);
 799         if (ret > 0) {
 800                 struct inode *inode = mapping->host;
 801
 802                 *ppos += ret;
 803
 804                 /*
 805                  * If file or inode is SYNC and we actually wrote some data,
 806                  * sync it.
 807                  */
 808                 if (unlikely((out->f_flags & O_SYNC) || IS_SYNC(inode))) {
 809                         int err;
 810
 811                         mutex_lock(&inode->i_mutex);
 812                         err = generic_osync_inode(inode, mapping,
 813                                                   OSYNC_METADATA|OSYNC_DATA);
 814                         mutex_unlock(&inode->i_mutex);
 815
 816                         if (err)
 817                                 ret = err;
 818                 }
 819         }
 820
 821         return ret;
 822 }
 823
 824 EXPORT_SYMBOL(generic_file_splice_write);
 825
 826 /**
 827  * generic_splice_sendpage - splice data from a pipe to a socket
 828  * @inode:      pipe inode
 829  * @out:        socket to write to
 830  * @len:        number of bytes to splice
 831  * @flags:      splice modifier flags
 832  *
 833  * Will send @len bytes from the pipe to a network socket. No data copying
 834  * is involved.
 835  *
 836  */
 837 ssize_t generic_splice_sendpage(struct pipe_inode_info *pipe, struct file *out,
 838                                 loff_t *ppos, size_t len, unsigned int flags)
 839 {
 840         return move_from_pipe(pipe, out, ppos, len, flags, pipe_to_sendpage);
 841 }
 842
 843 EXPORT_SYMBOL(generic_splice_sendpage);
 844
 845 /*
 846  * Attempt to initiate a splice from pipe to file.
 847  */
 848 static long do_splice_from(struct pipe_inode_info *pipe, struct file *out,
 849                            loff_t *ppos, size_t len, unsigned int flags)
 850 {
 851         int ret;
 852
 853         if (unlikely(!out->f_op || !out->f_op->splice_write))
 854                 return -EINVAL;
 855
 856         if (unlikely(!(out->f_mode & FMODE_WRITE)))
 857                 return -EBADF;
 858
 859         ret = rw_verify_area(WRITE, out, ppos, len);
 860         if (unlikely(ret < 0))
 861                 return ret;
 862
 863         return out->f_op->splice_write(pipe, out, ppos, len, flags);
 864 }
 865
 866 /*
 867  * Attempt to initiate a splice from a file to a pipe.
 868  */
 869 static long do_splice_to(struct file *in, loff_t *ppos,
 870                          struct pipe_inode_info *pipe, size_t len,
 871                          unsigned int flags)
 872 {
 873         loff_t isize, left;
 874         int ret;
 875
 876         if (unlikely(!in->f_op || !in->f_op->splice_read))
 877                 return -EINVAL;
 878
 879         if (unlikely(!(in->f_mode & FMODE_READ)))
 880                 return -EBADF;
 881
 882         ret = rw_verify_area(READ, in, ppos, len);
 883         if (unlikely(ret < 0))
 884                 return ret;
 885
 886         isize = i_size_read(in->f_mapping->host);
 887         if (unlikely(*ppos >= isize))
 888                 return 0;
 889
 890         left = isize - *ppos;
 891         if (unlikely(left < len))
 892                 len = left;
 893
 894         return in->f_op->splice_read(in, ppos, pipe, len, flags);
 895 }
 896
 897 long do_splice_direct(struct file *in, loff_t *ppos, struct file *out,
 898                       size_t len, unsigned int flags)
 899 {
 900         struct pipe_inode_info *pipe;
 901         long ret, bytes;
 902         loff_t out_off;
 903         umode_t i_mode;
 904         int i;
 905
 906         /*
 907          * We require the input being a regular file, as we don't want to
 908          * randomly drop data for eg socket -> socket splicing. Use the
 909          * piped splicing for that!
 910          */
 911         i_mode = in->f_dentry->d_inode->i_mode;
 912         if (unlikely(!S_ISREG(i_mode) && !S_ISBLK(i_mode)))
 913                 return -EINVAL;
 914
 915         /*
 916          * neither in nor out is a pipe, setup an internal pipe attached to
 917          * 'out' and transfer the wanted data from 'in' to 'out' through that
 918          */
 919         pipe = current->splice_pipe;
 920         if (unlikely(!pipe)) {
 921                 pipe = alloc_pipe_info(NULL);
 922                 if (!pipe)
 923                         return -ENOMEM;
 924
 925                 /*
 926                  * We don't have an immediate reader, but we'll read the stuff
 927                  * out of the pipe right after the move_to_pipe(). So set
 928                  * PIPE_READERS appropriately.
 929                  */
 930                 pipe->readers = 1;
 931
 932                 current->splice_pipe = pipe;
 933         }
 934
 935         /*
 936          * Do the splice.
 937          */
 938         ret = 0;
 939         bytes = 0;
 940         out_off = 0;
 941
 942         while (len) {
 943                 size_t read_len, max_read_len;
 944
 945                 /*
 946                  * Do at most PIPE_BUFFERS pages worth of transfer:
 947                  */
 948                 max_read_len = min(len, (size_t)(PIPE_BUFFERS*PAGE_SIZE));
 949
 950                 ret = do_splice_to(in, ppos, pipe, max_read_len, flags);
 951                 if (unlikely(ret < 0))
 952                         goto out_release;
 953
 954                 read_len = ret;
 955
 956                 /*
 957                  * NOTE: nonblocking mode only applies to the input. We
 958                  * must not do the output in nonblocking mode as then we
 959                  * could get stuck data in the internal pipe:
 960                  */
 961                 ret = do_splice_from(pipe, out, &out_off, read_len,
 962                                      flags & ~SPLICE_F_NONBLOCK);
 963                 if (unlikely(ret < 0))
 964                         goto out_release;
 965
 966                 bytes += ret;
 967                 len -= ret;
 968
 969                 /*
 970                  * In nonblocking mode, if we got back a short read then
 971                  * that was due to either an IO error or due to the
 972                  * pagecache entry not being there. In the IO error case
 973                  * the _next_ splice attempt will produce a clean IO error
 974                  * return value (not a short read), so in both cases it's
 975                  * correct to break out of the loop here:
 976                  */
 977                 if ((flags & SPLICE_F_NONBLOCK) && (read_len < max_read_len))
 978                         break;
 979         }
 980
 981         pipe->nrbufs = pipe->curbuf = 0;
 982
 983         return bytes;
 984
 985 out_release:
 986         /*
 987          * If we did an incomplete transfer we must release
 988          * the pipe buffers in question:
 989          */
 990         for (i = 0; i < PIPE_BUFFERS; i++) {
 991                 struct pipe_buffer *buf = pipe->bufs + i;
 992
 993                 if (buf->ops) {
 994                         buf->ops->release(pipe, buf);
 995                         buf->ops = NULL;
 996                 }
 997         }
 998         pipe->nrbufs = pipe->curbuf = 0;
 999
1000         /*
1001          * If we transferred some data, return the number of bytes:
1002          */
1003         if (bytes > 0)
1004                 return bytes;
1005
1006         return ret;
1007 }
1008
1009 EXPORT_SYMBOL(do_splice_direct);
1010
1011 /*
1012  * Determine where to splice to/from.
1013  */
1014 static long do_splice(struct file *in, loff_t __user *off_in,
1015                       struct file *out, loff_t __user *off_out,
1016                       size_t len, unsigned int flags)
1017 {
1018         struct pipe_inode_info *pipe;
1019         loff_t offset, *off;
1020         long ret;
1021
1022         pipe = in->f_dentry->d_inode->i_pipe;
1023         if (pipe) {
1024                 if (off_in)
1025                         return -ESPIPE;
1026                 if (off_out) {
1027                         if (out->f_op->llseek == no_llseek)
1028                                 return -EINVAL;
1029                         if (copy_from_user(&offset, off_out, sizeof(loff_t)))
1030                                 return -EFAULT;
1031                         off = &offset;
1032                 } else
1033                         off = &out->f_pos;
1034
1035                 ret = do_splice_from(pipe, out, off, len, flags);
1036
1037                 if (off_out && copy_to_user(off_out, off, sizeof(loff_t)))
1038                         ret = -EFAULT;
1039
1040                 return ret;
1041         }
1042
1043         pipe = out->f_dentry->d_inode->i_pipe;
1044         if (pipe) {
1045                 if (off_out)
1046                         return -ESPIPE;
1047                 if (off_in) {
1048                         if (in->f_op->llseek == no_llseek)
1049                                 return -EINVAL;
1050                         if (copy_from_user(&offset, off_in, sizeof(loff_t)))
1051                                 return -EFAULT;
1052                         off = &offset;
1053                 } else
1054                         off = &in->f_pos;
1055
1056                 ret = do_splice_to(in, off, pipe, len, flags);
1057
1058                 if (off_in && copy_to_user(off_in, off, sizeof(loff_t)))
1059                         ret = -EFAULT;
1060
1061                 return ret;
1062         }
1063
1064         return -EINVAL;
1065 }
1066
1067 /*
1068  * Map an iov into an array of pages and offset/length tupples. With the
1069  * partial_page structure, we can map several non-contiguous ranges into
1070  * our ones pages[] map instead of splitting that operation into pieces.
1071  * Could easily be exported as a generic helper for other users, in which
1072  * case one would probably want to add a 'max_nr_pages' parameter as well.
1073  */
1074 static int get_iovec_page_array(const struct iovec __user *iov,
1075                                 unsigned int nr_vecs, struct page **pages,
1076                                 struct partial_page *partial)
1077 {
1078         int buffers = 0, error = 0;
1079
1080         /*
1081          * It's ok to take the mmap_sem for reading, even
1082          * across a "get_user()".
1083          */
1084         down_read(&current->mm->mmap_sem);
1085
1086         while (nr_vecs) {
1087                 unsigned long off, npages;
1088                 void __user *base;
1089                 size_t len;
1090                 int i;
1091
1092                 /*
1093                  * Get user address base and length for this iovec.
1094                  */
1095                 error = get_user(base, &iov->iov_base);
1096                 if (unlikely(error))
1097                         break;
1098                 error = get_user(len, &iov->iov_len);
1099                 if (unlikely(error))
1100                         break;
1101
1102                 /*
1103                  * Sanity check this iovec. 0 read succeeds.
1104                  */
1105                 if (unlikely(!len))
1106                         break;
1107                 error = -EFAULT;
1108                 if (unlikely(!base))
1109                         break;
1110
1111                 /*
1112                  * Get this base offset and number of pages, then map
1113                  * in the user pages.
1114                  */
1115                 off = (unsigned long) base & ~PAGE_MASK;
1116                 npages = (off + len + PAGE_SIZE - 1) >> PAGE_SHIFT;
1117                 if (npages > PIPE_BUFFERS - buffers)
1118                         npages = PIPE_BUFFERS - buffers;
1119
1120                 error = get_user_pages(current, current->mm,
1121                                        (unsigned long) base, npages, 0, 0,
1122                                        &pages[buffers], NULL);
1123
1124                 if (unlikely(error <= 0))
1125                         break;
1126
1127                 /*
1128                  * Fill this contiguous range into the partial page map.
1129                  */
1130                 for (i = 0; i < error; i++) {
1131                         const int plen = min_t(size_t, len, PAGE_SIZE) - off;
1132
1133                         partial[buffers].offset = off;
1134                         partial[buffers].len = plen;
1135
1136                         off = 0;
1137                         len -= plen;
1138                         buffers++;
1139                 }
1140
1141                 /*
1142                  * We didn't complete this iov, stop here since it probably
1143                  * means we have to move some of this into a pipe to
1144                  * be able to continue.
1145                  */
1146                 if (len)
1147                         break;
1148
1149                 /*
1150                  * Don't continue if we mapped fewer pages than we asked for,
1151                  * or if we mapped the max number of pages that we have
1152                  * room for.
1153                  */
1154                 if (error < npages || buffers == PIPE_BUFFERS)
1155                         break;
1156
1157                 nr_vecs--;
1158                 iov++;
1159         }
1160
1161         up_read(&current->mm->mmap_sem);
1162
1163         if (buffers)
1164                 return buffers;
1165
1166         return error;
1167 }
1168
1169 /*
1170  * vmsplice splices a user address range into a pipe. It can be thought of
1171  * as splice-from-memory, where the regular splice is splice-from-file (or
1172  * to file). In both cases the output is a pipe, naturally.
1173  *
1174  * Note that vmsplice only supports splicing _from_ user memory to a pipe,
1175  * not the other way around. Splicing from user memory is a simple operation
1176  * that can be supported without any funky alignment restrictions or nasty
1177  * vm tricks. We simply map in the user memory and fill them into a pipe.
1178  * The reverse isn't quite as easy, though. There are two possible solutions
1179  * for that:
1180  *
1181  *      - memcpy() the data internally, at which point we might as well just
1182  *        do a regular read() on the buffer anyway.
1183  *      - Lots of nasty vm tricks, that are neither fast nor flexible (it
1184  *        has restriction limitations on both ends of the pipe).
1185  *
1186  * Alas, it isn't here.
1187  *
1188  */
1189 static long do_vmsplice(struct file *file, const struct iovec __user *iov,
1190                         unsigned long nr_segs, unsigned int flags)
1191 {
1192         struct pipe_inode_info *pipe = file->f_dentry->d_inode->i_pipe;
1193         struct page *pages[PIPE_BUFFERS];
1194         struct partial_page partial[PIPE_BUFFERS];
1195         struct splice_pipe_desc spd = {
1196                 .pages = pages,
1197                 .partial = partial,
1198                 .flags = flags,
1199                 .ops = &user_page_pipe_buf_ops,
1200         };
1201
1202         if (unlikely(!pipe))
1203                 return -EBADF;
1204         if (unlikely(nr_segs > UIO_MAXIOV))
1205                 return -EINVAL;
1206         else if (unlikely(!nr_segs))
1207                 return 0;
1208
1209         spd.nr_pages = get_iovec_page_array(iov, nr_segs, pages, partial);
1210         if (spd.nr_pages <= 0)
1211                 return spd.nr_pages;
1212
1213         return move_to_pipe(pipe, &spd);
1214 }
1215
1216 asmlinkage long sys_vmsplice(int fd, const struct iovec __user *iov,
1217                              unsigned long nr_segs, unsigned int flags)
1218 {
1219         struct file *file;
1220         long error;
1221         int fput;
1222
1223         error = -EBADF;
1224         file = fget_light(fd, &fput);
1225         if (file) {
1226                 if (file->f_mode & FMODE_WRITE)
1227                         error = do_vmsplice(file, iov, nr_segs, flags);
1228
1229                 fput_light(file, fput);
1230         }
1231
1232         return error;
1233 }
1234
1235 asmlinkage long sys_splice(int fd_in, loff_t __user *off_in,
1236                            int fd_out, loff_t __user *off_out,
1237                            size_t len, unsigned int flags)
1238 {
1239         long error;
1240         struct file *in, *out;
1241         int fput_in, fput_out;
1242
1243         if (unlikely(!len))
1244                 return 0;
1245
1246         error = -EBADF;
1247         in = fget_light(fd_in, &fput_in);
1248         if (in) {
1249                 if (in->f_mode & FMODE_READ) {
1250                         out = fget_light(fd_out, &fput_out);
1251                         if (out) {
1252                                 if (out->f_mode & FMODE_WRITE)
1253                                         error = do_splice(in, off_in,
1254                                                           out, off_out,
1255                                                           len, flags);
1256                                 fput_light(out, fput_out);
1257                         }
1258                 }
1259
1260                 fput_light(in, fput_in);
1261         }
1262
1263         return error;
1264 }
1265
1266 /*
1267  * Link contents of ipipe to opipe.
1268  */
1269 static int link_pipe(struct pipe_inode_info *ipipe,
1270                      struct pipe_inode_info *opipe,
1271                      size_t len, unsigned int flags)
1272 {
1273         struct pipe_buffer *ibuf, *obuf;
1274         int ret, do_wakeup, i, ipipe_first;
1275
1276         ret = do_wakeup = ipipe_first = 0;
1277
1278         /*
1279          * Potential ABBA deadlock, work around it by ordering lock
1280          * grabbing by inode address. Otherwise two different processes
1281          * could deadlock (one doing tee from A -> B, the other from B -> A).
1282          */
1283         if (ipipe->inode < opipe->inode) {
1284                 ipipe_first = 1;
1285                 mutex_lock(&ipipe->inode->i_mutex);
1286                 mutex_lock(&opipe->inode->i_mutex);
1287         } else {
1288                 mutex_lock(&opipe->inode->i_mutex);
1289                 mutex_lock(&ipipe->inode->i_mutex);
1290         }
1291
1292         for (i = 0;; i++) {
1293                 if (!opipe->readers) {
1294                         send_sig(SIGPIPE, current, 0);
1295                         if (!ret)
1296                                 ret = -EPIPE;
1297                         break;
1298                 }
1299                 if (ipipe->nrbufs - i) {
1300                         ibuf = ipipe->bufs + ((ipipe->curbuf + i) & (PIPE_BUFFERS - 1));
1301
1302                         /*
1303                          * If we have room, fill this buffer
1304                          */
1305                         if (opipe->nrbufs < PIPE_BUFFERS) {
1306                                 int nbuf = (opipe->curbuf + opipe->nrbufs) & (PIPE_BUFFERS - 1);
1307
1308                                 /*
1309                                  * Get a reference to this pipe buffer,
1310                                  * so we can copy the contents over.
1311                                  */
1312                                 ibuf->ops->get(ipipe, ibuf);
1313
1314                                 obuf = opipe->bufs + nbuf;
1315                                 *obuf = *ibuf;
1316
1317                                 if (obuf->len > len)
1318                                         obuf->len = len;
1319
1320                                 opipe->nrbufs++;
1321                                 do_wakeup = 1;
1322                                 ret += obuf->len;
1323                                 len -= obuf->len;
1324
1325                                 if (!len)
1326                                         break;
1327                                 if (opipe->nrbufs < PIPE_BUFFERS)
1328                                         continue;
1329                         }
1330
1331                         /*
1332                          * We have input available, but no output room.
1333                          * If we already copied data, return that. If we
1334                          * need to drop the opipe lock, it must be ordered
1335                          * last to avoid deadlocks.
1336                          */
1337                         if ((flags & SPLICE_F_NONBLOCK) || !ipipe_first) {
1338                                 if (!ret)
1339                                         ret = -EAGAIN;
1340                                 break;
1341                         }
1342                         if (signal_pending(current)) {
1343                                 if (!ret)
1344                                         ret = -ERESTARTSYS;
1345                                 break;
1346                         }
1347                         if (do_wakeup) {
1348                                 smp_mb();
1349                                 if (waitqueue_active(&opipe->wait))
1350                                         wake_up_interruptible(&opipe->wait);
1351                                 kill_fasync(&opipe->fasync_readers, SIGIO, POLL_IN);
1352                                 do_wakeup = 0;
1353                         }
1354
1355                         opipe->waiting_writers++;
1356                         pipe_wait(opipe);
1357                         opipe->waiting_writers--;
1358                         continue;
1359                 }
1360
1361                 /*
1362                  * No input buffers, do the usual checks for available
1363                  * writers and blocking and wait if necessary
1364                  */
1365                 if (!ipipe->writers)
1366                         break;
1367                 if (!ipipe->waiting_writers) {
1368                         if (ret)
1369                                 break;
1370                 }
1371                 /*
1372                  * pipe_wait() drops the ipipe mutex. To avoid deadlocks
1373                  * with another process, we can only safely do that if
1374                  * the ipipe lock is ordered last.
1375                  */
1376                 if ((flags & SPLICE_F_NONBLOCK) || ipipe_first) {
1377                         if (!ret)
1378                                 ret = -EAGAIN;
1379                         break;
1380                 }
1381                 if (signal_pending(current)) {
1382                         if (!ret)
1383                                 ret = -ERESTARTSYS;
1384                         break;
1385                 }
1386
1387                 if (waitqueue_active(&ipipe->wait))
1388                         wake_up_interruptible_sync(&ipipe->wait);
1389                 kill_fasync(&ipipe->fasync_writers, SIGIO, POLL_OUT);
1390
1391                 pipe_wait(ipipe);
1392         }
1393
1394         mutex_unlock(&ipipe->inode->i_mutex);
1395         mutex_unlock(&opipe->inode->i_mutex);
1396
1397         if (do_wakeup) {
1398                 smp_mb();
1399                 if (waitqueue_active(&opipe->wait))
1400                         wake_up_interruptible(&opipe->wait);
1401                 kill_fasync(&opipe->fasync_readers, SIGIO, POLL_IN);
1402         }
1403
1404         return ret;
1405 }
1406
1407 /*
1408  * This is a tee(1) implementation that works on pipes. It doesn't copy
1409  * any data, it simply references the 'in' pages on the 'out' pipe.
1410  * The 'flags' used are the SPLICE_F_* variants, currently the only
1411  * applicable one is SPLICE_F_NONBLOCK.
1412  */
1413 static long do_tee(struct file *in, struct file *out, size_t len,
1414                    unsigned int flags)
1415 {
1416         struct pipe_inode_info *ipipe = in->f_dentry->d_inode->i_pipe;
1417         struct pipe_inode_info *opipe = out->f_dentry->d_inode->i_pipe;
1418
1419         /*
1420          * Link ipipe to the two output pipes, consuming as we go along.
1421          */
1422         if (ipipe && opipe)
1423                 return link_pipe(ipipe, opipe, len, flags);
1424
1425         return -EINVAL;
1426 }
1427
1428 asmlinkage long sys_tee(int fdin, int fdout, size_t len, unsigned int flags)
1429 {
1430         struct file *in;
1431         int error, fput_in;
1432
1433         if (unlikely(!len))
1434                 return 0;
1435
1436         error = -EBADF;
1437         in = fget_light(fdin, &fput_in);
1438         if (in) {
1439                 if (in->f_mode & FMODE_READ) {
1440                         int fput_out;
1441                         struct file *out = fget_light(fdout, &fput_out);
1442
1443                         if (out) {
1444                                 if (out->f_mode & FMODE_WRITE)
1445                                         error = do_tee(in, out, len, flags);
1446                                 fput_light(out, fput_out);
1447                         }
1448                 }
1449                 fput_light(in, fput_in);
1450         }
1451
1452         return error;
1453 }