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