SAFE public projects git trees. - safe/jmp/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 and fixing the initial implementation
  13  * bugs.
  14  *
  15  * Copyright (C) 2005 Jens Axboe <axboe@suse.de>
  16  * Copyright (C) 2005 Linus Torvalds <torvalds@osdl.org>
  17  *
  18  */
  19 #include <linux/fs.h>
  20 #include <linux/file.h>
  21 #include <linux/pagemap.h>
  22 #include <linux/pipe_fs_i.h>
  23 #include <linux/mm_inline.h>
  24 #include <linux/swap.h>
  25 #include <linux/writeback.h>
  26 #include <linux/buffer_head.h>
  27 #include <linux/module.h>
  28 #include <linux/syscalls.h>
  29
  30 /*
  31  * Passed to the actors
  32  */
  33 struct splice_desc {
  34         unsigned int len, total_len;    /* current and remaining length */
  35         unsigned int flags;             /* splice flags */
  36         struct file *file;              /* file to read/write */
  37         loff_t pos;                     /* file position */
  38 };
  39
  40 static int page_cache_pipe_buf_steal(struct pipe_inode_info *info,
  41                                      struct pipe_buffer *buf)
  42 {
  43         struct page *page = buf->page;
  44         struct address_space *mapping = page_mapping(page);
  45
  46         WARN_ON(!PageLocked(page));
  47         WARN_ON(!PageUptodate(page));
  48
  49         if (PagePrivate(page))
  50                 try_to_release_page(page, mapping_gfp_mask(mapping));
  51
  52         if (!remove_mapping(mapping, page))
  53                 return 1;
  54
  55         if (PageLRU(page)) {
  56                 struct zone *zone = page_zone(page);
  57
  58                 spin_lock_irq(&zone->lru_lock);
  59                 BUG_ON(!PageLRU(page));
  60                 __ClearPageLRU(page);
  61                 del_page_from_lru(zone, page);
  62                 spin_unlock_irq(&zone->lru_lock);
  63         }
  64
  65         return 0;
  66 }
  67
  68 static void page_cache_pipe_buf_release(struct pipe_inode_info *info,
  69                                         struct pipe_buffer *buf)
  70 {
  71         page_cache_release(buf->page);
  72         buf->page = NULL;
  73 }
  74
  75 static void *page_cache_pipe_buf_map(struct file *file,
  76                                      struct pipe_inode_info *info,
  77                                      struct pipe_buffer *buf)
  78 {
  79         struct page *page = buf->page;
  80
  81         lock_page(page);
  82
  83         if (!PageUptodate(page)) {
  84                 unlock_page(page);
  85                 return ERR_PTR(-EIO);
  86         }
  87
  88         if (!page->mapping) {
  89                 unlock_page(page);
  90                 return ERR_PTR(-ENODATA);
  91         }
  92
  93         return kmap(buf->page);
  94 }
  95
  96 static void page_cache_pipe_buf_unmap(struct pipe_inode_info *info,
  97                                       struct pipe_buffer *buf)
  98 {
  99         unlock_page(buf->page);
 100         kunmap(buf->page);
 101 }
 102
 103 static struct pipe_buf_operations page_cache_pipe_buf_ops = {
 104         .can_merge = 0,
 105         .map = page_cache_pipe_buf_map,
 106         .unmap = page_cache_pipe_buf_unmap,
 107         .release = page_cache_pipe_buf_release,
 108         .steal = page_cache_pipe_buf_steal,
 109 };
 110
 111 static ssize_t move_to_pipe(struct inode *inode, struct page **pages,
 112                             int nr_pages, unsigned long offset,
 113                             unsigned long len, unsigned int flags)
 114 {
 115         struct pipe_inode_info *info;
 116         int ret, do_wakeup, i;
 117
 118         ret = 0;
 119         do_wakeup = 0;
 120         i = 0;
 121
 122         mutex_lock(PIPE_MUTEX(*inode));
 123
 124         info = inode->i_pipe;
 125         for (;;) {
 126                 int bufs;
 127
 128                 if (!PIPE_READERS(*inode)) {
 129                         send_sig(SIGPIPE, current, 0);
 130                         if (!ret)
 131                                 ret = -EPIPE;
 132                         break;
 133                 }
 134
 135                 bufs = info->nrbufs;
 136                 if (bufs < PIPE_BUFFERS) {
 137                         int newbuf = (info->curbuf + bufs) & (PIPE_BUFFERS - 1);
 138                         struct pipe_buffer *buf = info->bufs + newbuf;
 139                         struct page *page = pages[i++];
 140                         unsigned long this_len;
 141
 142                         this_len = PAGE_CACHE_SIZE - offset;
 143                         if (this_len > len)
 144                                 this_len = len;
 145
 146                         buf->page = page;
 147                         buf->offset = offset;
 148                         buf->len = this_len;
 149                         buf->ops = &page_cache_pipe_buf_ops;
 150                         info->nrbufs = ++bufs;
 151                         do_wakeup = 1;
 152
 153                         ret += this_len;
 154                         len -= this_len;
 155                         offset = 0;
 156                         if (!--nr_pages)
 157                                 break;
 158                         if (!len)
 159                                 break;
 160                         if (bufs < PIPE_BUFFERS)
 161                                 continue;
 162
 163                         break;
 164                 }
 165
 166                 if (flags & SPLICE_F_NONBLOCK) {
 167                         if (!ret)
 168                                 ret = -EAGAIN;
 169                         break;
 170                 }
 171
 172                 if (signal_pending(current)) {
 173                         if (!ret)
 174                                 ret = -ERESTARTSYS;
 175                         break;
 176                 }
 177
 178                 if (do_wakeup) {
 179                         wake_up_interruptible_sync(PIPE_WAIT(*inode));
 180                         kill_fasync(PIPE_FASYNC_READERS(*inode), SIGIO,
 181                                     POLL_IN);
 182                         do_wakeup = 0;
 183                 }
 184
 185                 PIPE_WAITING_WRITERS(*inode)++;
 186                 pipe_wait(inode);
 187                 PIPE_WAITING_WRITERS(*inode)--;
 188         }
 189
 190         mutex_unlock(PIPE_MUTEX(*inode));
 191
 192         if (do_wakeup) {
 193                 wake_up_interruptible(PIPE_WAIT(*inode));
 194                 kill_fasync(PIPE_FASYNC_READERS(*inode), SIGIO, POLL_IN);
 195         }
 196
 197         while (i < nr_pages)
 198                 page_cache_release(pages[i++]);
 199
 200         return ret;
 201 }
 202
 203 static int __generic_file_splice_read(struct file *in, struct inode *pipe,
 204                                       size_t len, unsigned int flags)
 205 {
 206         struct address_space *mapping = in->f_mapping;
 207         unsigned int offset, nr_pages;
 208         struct page *pages[PIPE_BUFFERS], *shadow[PIPE_BUFFERS];
 209         struct page *page;
 210         pgoff_t index, pidx;
 211         int i, j;
 212
 213         index = in->f_pos >> PAGE_CACHE_SHIFT;
 214         offset = in->f_pos & ~PAGE_CACHE_MASK;
 215         nr_pages = (len + offset + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
 216
 217         if (nr_pages > PIPE_BUFFERS)
 218                 nr_pages = PIPE_BUFFERS;
 219
 220         /*
 221          * initiate read-ahead on this page range
 222          */
 223         do_page_cache_readahead(mapping, in, index, nr_pages);
 224
 225         /*
 226          * Get as many pages from the page cache as possible..
 227          * Start IO on the page cache entries we create (we
 228          * can assume that any pre-existing ones we find have
 229          * already had IO started on them).
 230          */
 231         i = find_get_pages(mapping, index, nr_pages, pages);
 232
 233         /*
 234          * common case - we found all pages and they are contiguous,
 235          * kick them off
 236          */
 237         if (i && (pages[i - 1]->index == index + i - 1))
 238                 goto splice_them;
 239
 240         /*
 241          * fill shadow[] with pages at the right locations, so we only
 242          * have to fill holes
 243          */
 244         memset(shadow, 0, nr_pages * sizeof(struct page *));
 245         for (j = 0; j < i; j++)
 246                 shadow[pages[j]->index - index] = pages[j];
 247
 248         /*
 249          * now fill in the holes
 250          */
 251         for (i = 0, pidx = index; i < nr_pages; pidx++, i++) {
 252                 int error;
 253
 254                 if (shadow[i])
 255                         continue;
 256
 257                 /*
 258                  * no page there, look one up / create it
 259                  */
 260                 page = find_or_create_page(mapping, pidx,
 261                                                    mapping_gfp_mask(mapping));
 262                 if (!page)
 263                         break;
 264
 265                 if (PageUptodate(page))
 266                         unlock_page(page);
 267                 else {
 268                         error = mapping->a_ops->readpage(in, page);
 269
 270                         if (unlikely(error)) {
 271                                 page_cache_release(page);
 272                                 break;
 273                         }
 274                 }
 275                 shadow[i] = page;
 276         }
 277
 278         if (!i) {
 279                 for (i = 0; i < nr_pages; i++) {
 280                          if (shadow[i])
 281                                 page_cache_release(shadow[i]);
 282                 }
 283                 return 0;
 284         }
 285
 286         memcpy(pages, shadow, i * sizeof(struct page *));
 287
 288         /*
 289          * Now we splice them into the pipe..
 290          */
 291 splice_them:
 292         return move_to_pipe(pipe, pages, i, offset, len, flags);
 293 }
 294
 295 ssize_t generic_file_splice_read(struct file *in, struct inode *pipe,
 296                                  size_t len, unsigned int flags)
 297 {
 298         ssize_t spliced;
 299         int ret;
 300
 301         ret = 0;
 302         spliced = 0;
 303         while (len) {
 304                 ret = __generic_file_splice_read(in, pipe, len, flags);
 305
 306                 if (ret <= 0)
 307                         break;
 308
 309                 in->f_pos += ret;
 310                 len -= ret;
 311                 spliced += ret;
 312
 313                 if (!(flags & SPLICE_F_NONBLOCK))
 314                         continue;
 315                 ret = -EAGAIN;
 316                 break;
 317         }
 318
 319         if (spliced)
 320                 return spliced;
 321
 322         return ret;
 323 }
 324
 325 /*
 326  * Send 'sd->len' bytes to socket from 'sd->file' at position 'sd->pos'
 327  * using sendpage().
 328  */
 329 static int pipe_to_sendpage(struct pipe_inode_info *info,
 330                             struct pipe_buffer *buf, struct splice_desc *sd)
 331 {
 332         struct file *file = sd->file;
 333         loff_t pos = sd->pos;
 334         unsigned int offset;
 335         ssize_t ret;
 336         void *ptr;
 337
 338         /*
 339          * sub-optimal, but we are limited by the pipe ->map. we don't
 340          * need a kmap'ed buffer here, we just want to make sure we
 341          * have the page pinned if the pipe page originates from the
 342          * page cache
 343          */
 344         ptr = buf->ops->map(file, info, buf);
 345         if (IS_ERR(ptr))
 346                 return PTR_ERR(ptr);
 347
 348         offset = pos & ~PAGE_CACHE_MASK;
 349
 350         ret = file->f_op->sendpage(file, buf->page, offset, sd->len, &pos,
 351                                         sd->len < sd->total_len);
 352
 353         buf->ops->unmap(info, buf);
 354         if (ret == sd->len)
 355                 return 0;
 356
 357         return -EIO;
 358 }
 359
 360 /*
 361  * This is a little more tricky than the file -> pipe splicing. There are
 362  * basically three cases:
 363  *
 364  *      - Destination page already exists in the address space and there
 365  *        are users of it. For that case we have no other option that
 366  *        copying the data. Tough luck.
 367  *      - Destination page already exists in the address space, but there
 368  *        are no users of it. Make sure it's uptodate, then drop it. Fall
 369  *        through to last case.
 370  *      - Destination page does not exist, we can add the pipe page to
 371  *        the page cache and avoid the copy.
 372  *
 373  * For now we just do the slower thing and always copy pages over, it's
 374  * easier than migrating pages from the pipe to the target file. For the
 375  * case of doing file | file splicing, the migrate approach had some LRU
 376  * nastiness...
 377  */
 378 static int pipe_to_file(struct pipe_inode_info *info, struct pipe_buffer *buf,
 379                         struct splice_desc *sd)
 380 {
 381         struct file *file = sd->file;
 382         struct address_space *mapping = file->f_mapping;
 383         unsigned int offset;
 384         struct page *page;
 385         pgoff_t index;
 386         char *src;
 387         int ret, stolen;
 388
 389         /*
 390          * after this, page will be locked and unmapped
 391          */
 392         src = buf->ops->map(file, info, buf);
 393         if (IS_ERR(src))
 394                 return PTR_ERR(src);
 395
 396         index = sd->pos >> PAGE_CACHE_SHIFT;
 397         offset = sd->pos & ~PAGE_CACHE_MASK;
 398         stolen = 0;
 399
 400         /*
 401          * reuse buf page, if SPLICE_F_MOVE is set
 402          */
 403         if (sd->flags & SPLICE_F_MOVE) {
 404                 if (buf->ops->steal(info, buf))
 405                         goto find_page;
 406
 407                 page = buf->page;
 408                 stolen = 1;
 409                 if (add_to_page_cache_lru(page, mapping, index,
 410                                                 mapping_gfp_mask(mapping)))
 411                         goto find_page;
 412         } else {
 413 find_page:
 414                 ret = -ENOMEM;
 415                 page = find_or_create_page(mapping, index,
 416                                                 mapping_gfp_mask(mapping));
 417                 if (!page)
 418                         goto out;
 419
 420                 /*
 421                  * If the page is uptodate, it is also locked. If it isn't
 422                  * uptodate, we can mark it uptodate if we are filling the
 423                  * full page. Otherwise we need to read it in first...
 424                  */
 425                 if (!PageUptodate(page)) {
 426                         if (sd->len < PAGE_CACHE_SIZE) {
 427                                 ret = mapping->a_ops->readpage(file, page);
 428                                 if (unlikely(ret))
 429                                         goto out;
 430
 431                                 lock_page(page);
 432
 433                                 if (!PageUptodate(page)) {
 434                                         /*
 435                                          * page got invalidated, repeat
 436                                          */
 437                                         if (!page->mapping) {
 438                                                 unlock_page(page);
 439                                                 page_cache_release(page);
 440                                                 goto find_page;
 441                                         }
 442                                         ret = -EIO;
 443                                         goto out;
 444                                 }
 445                         } else {
 446                                 WARN_ON(!PageLocked(page));
 447                                 SetPageUptodate(page);
 448                         }
 449                 }
 450         }
 451
 452         ret = mapping->a_ops->prepare_write(file, page, 0, sd->len);
 453         if (ret == AOP_TRUNCATED_PAGE) {
 454                 page_cache_release(page);
 455                 goto find_page;
 456         } else if (ret)
 457                 goto out;
 458
 459         if (!stolen) {
 460                 char *dst = kmap_atomic(page, KM_USER0);
 461
 462                 memcpy(dst + offset, src + buf->offset, sd->len);
 463                 flush_dcache_page(page);
 464                 kunmap_atomic(dst, KM_USER0);
 465         }
 466
 467         ret = mapping->a_ops->commit_write(file, page, 0, sd->len);
 468         if (ret == AOP_TRUNCATED_PAGE) {
 469                 page_cache_release(page);
 470                 goto find_page;
 471         } else if (ret)
 472                 goto out;
 473
 474         balance_dirty_pages_ratelimited(mapping);
 475 out:
 476         if (!stolen) {
 477                 page_cache_release(page);
 478                 unlock_page(page);
 479         }
 480         buf->ops->unmap(info, buf);
 481         return ret;
 482 }
 483
 484 typedef int (splice_actor)(struct pipe_inode_info *, struct pipe_buffer *,
 485                            struct splice_desc *);
 486
 487 static ssize_t move_from_pipe(struct inode *inode, struct file *out,
 488                               size_t len, unsigned int flags,
 489                               splice_actor *actor)
 490 {
 491         struct pipe_inode_info *info;
 492         int ret, do_wakeup, err;
 493         struct splice_desc sd;
 494
 495         ret = 0;
 496         do_wakeup = 0;
 497
 498         sd.total_len = len;
 499         sd.flags = flags;
 500         sd.file = out;
 501         sd.pos = out->f_pos;
 502
 503         mutex_lock(PIPE_MUTEX(*inode));
 504
 505         info = inode->i_pipe;
 506         for (;;) {
 507                 int bufs = info->nrbufs;
 508
 509                 if (bufs) {
 510                         int curbuf = info->curbuf;
 511                         struct pipe_buffer *buf = info->bufs + curbuf;
 512                         struct pipe_buf_operations *ops = buf->ops;
 513
 514                         sd.len = buf->len;
 515                         if (sd.len > sd.total_len)
 516                                 sd.len = sd.total_len;
 517
 518                         err = actor(info, buf, &sd);
 519                         if (err) {
 520                                 if (!ret && err != -ENODATA)
 521                                         ret = err;
 522
 523                                 break;
 524                         }
 525
 526                         ret += sd.len;
 527                         buf->offset += sd.len;
 528                         buf->len -= sd.len;
 529                         if (!buf->len) {
 530                                 buf->ops = NULL;
 531                                 ops->release(info, buf);
 532                                 curbuf = (curbuf + 1) & (PIPE_BUFFERS - 1);
 533                                 info->curbuf = curbuf;
 534                                 info->nrbufs = --bufs;
 535                                 do_wakeup = 1;
 536                         }
 537
 538                         sd.pos += sd.len;
 539                         sd.total_len -= sd.len;
 540                         if (!sd.total_len)
 541                                 break;
 542                 }
 543
 544                 if (bufs)
 545                         continue;
 546                 if (!PIPE_WRITERS(*inode))
 547                         break;
 548                 if (!PIPE_WAITING_WRITERS(*inode)) {
 549                         if (ret)
 550                                 break;
 551                 }
 552
 553                 if (flags & SPLICE_F_NONBLOCK) {
 554                         if (!ret)
 555                                 ret = -EAGAIN;
 556                         break;
 557                 }
 558
 559                 if (signal_pending(current)) {
 560                         if (!ret)
 561                                 ret = -ERESTARTSYS;
 562                         break;
 563                 }
 564
 565                 if (do_wakeup) {
 566                         wake_up_interruptible_sync(PIPE_WAIT(*inode));
 567                         kill_fasync(PIPE_FASYNC_WRITERS(*inode),SIGIO,POLL_OUT);
 568                         do_wakeup = 0;
 569                 }
 570
 571                 pipe_wait(inode);
 572         }
 573
 574         mutex_unlock(PIPE_MUTEX(*inode));
 575
 576         if (do_wakeup) {
 577                 wake_up_interruptible(PIPE_WAIT(*inode));
 578                 kill_fasync(PIPE_FASYNC_WRITERS(*inode), SIGIO, POLL_OUT);
 579         }
 580
 581         mutex_lock(&out->f_mapping->host->i_mutex);
 582         out->f_pos = sd.pos;
 583         mutex_unlock(&out->f_mapping->host->i_mutex);
 584         return ret;
 585
 586 }
 587
 588 ssize_t generic_file_splice_write(struct inode *inode, struct file *out,
 589                                   size_t len, unsigned int flags)
 590 {
 591         struct address_space *mapping = out->f_mapping;
 592         ssize_t ret = move_from_pipe(inode, out, len, flags, pipe_to_file);
 593
 594         /*
 595          * if file or inode is SYNC and we actually wrote some data, sync it
 596          */
 597         if (unlikely((out->f_flags & O_SYNC) || IS_SYNC(mapping->host))
 598             && ret > 0) {
 599                 struct inode *inode = mapping->host;
 600                 int err;
 601
 602                 mutex_lock(&inode->i_mutex);
 603                 err = generic_osync_inode(mapping->host, mapping,
 604                                                 OSYNC_METADATA|OSYNC_DATA);
 605                 mutex_unlock(&inode->i_mutex);
 606
 607                 if (err)
 608                         ret = err;
 609         }
 610
 611         return ret;
 612 }
 613
 614 ssize_t generic_splice_sendpage(struct inode *inode, struct file *out,
 615                                 size_t len, unsigned int flags)
 616 {
 617         return move_from_pipe(inode, out, len, flags, pipe_to_sendpage);
 618 }
 619
 620 EXPORT_SYMBOL(generic_file_splice_write);
 621 EXPORT_SYMBOL(generic_file_splice_read);
 622
 623 static long do_splice_from(struct inode *pipe, struct file *out, size_t len,
 624                            unsigned int flags)
 625 {
 626         loff_t pos;
 627         int ret;
 628
 629         if (!out->f_op || !out->f_op->splice_write)
 630                 return -EINVAL;
 631
 632         if (!(out->f_mode & FMODE_WRITE))
 633                 return -EBADF;
 634
 635         pos = out->f_pos;
 636         ret = rw_verify_area(WRITE, out, &pos, len);
 637         if (unlikely(ret < 0))
 638                 return ret;
 639
 640         return out->f_op->splice_write(pipe, out, len, flags);
 641 }
 642
 643 static long do_splice_to(struct file *in, struct inode *pipe, size_t len,
 644                          unsigned int flags)
 645 {
 646         loff_t pos, isize, left;
 647         int ret;
 648
 649         if (!in->f_op || !in->f_op->splice_read)
 650                 return -EINVAL;
 651
 652         if (!(in->f_mode & FMODE_READ))
 653                 return -EBADF;
 654
 655         pos = in->f_pos;
 656         ret = rw_verify_area(READ, in, &pos, len);
 657         if (unlikely(ret < 0))
 658                 return ret;
 659
 660         isize = i_size_read(in->f_mapping->host);
 661         if (unlikely(in->f_pos >= isize))
 662                 return 0;
 663
 664         left = isize - in->f_pos;
 665         if (left < len)
 666                 len = left;
 667
 668         return in->f_op->splice_read(in, pipe, len, flags);
 669 }
 670
 671 static long do_splice(struct file *in, struct file *out, size_t len,
 672                       unsigned int flags)
 673 {
 674         struct inode *pipe;
 675
 676         pipe = in->f_dentry->d_inode;
 677         if (pipe->i_pipe)
 678                 return do_splice_from(pipe, out, len, flags);
 679
 680         pipe = out->f_dentry->d_inode;
 681         if (pipe->i_pipe)
 682                 return do_splice_to(in, pipe, len, flags);
 683
 684         return -EINVAL;
 685 }
 686
 687 asmlinkage long sys_splice(int fdin, int fdout, size_t len, unsigned int flags)
 688 {
 689         long error;
 690         struct file *in, *out;
 691         int fput_in, fput_out;
 692
 693         if (unlikely(!len))
 694                 return 0;
 695
 696         error = -EBADF;
 697         in = fget_light(fdin, &fput_in);
 698         if (in) {
 699                 if (in->f_mode & FMODE_READ) {
 700                         out = fget_light(fdout, &fput_out);
 701                         if (out) {
 702                                 if (out->f_mode & FMODE_WRITE)
 703                                         error = do_splice(in, out, len, flags);
 704                                 fput_light(out, fput_out);
 705                         }
 706                 }
 707
 708                 fput_light(in, fput_in);
 709         }
 710
 711         return error;
 712 }