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