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@kernel.dk> 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/splice.h> 24 #include <linux/memcontrol.h> 25 #include <linux/mm_inline.h> 26 #include <linux/swap.h> 27 #include <linux/writeback.h> 28 #include <linux/buffer_head.h> 29 #include <linux/module.h> 30 #include <linux/syscalls.h> 31 #include <linux/uio.h> 32 #include <linux/security.h> 33 34 /* 35 * Attempt to steal a page from a pipe buffer. This should perhaps go into 36 * a vm helper function, it's already simplified quite a bit by the 37 * addition of remove_mapping(). If success is returned, the caller may 38 * attempt to reuse this page for another destination. 39 */ 40 static int page_cache_pipe_buf_steal(struct pipe_inode_info *pipe, 41 struct pipe_buffer *buf) 42 { 43 struct page *page = buf->page; 44 struct address_space *mapping; 45 46 lock_page(page); 47 48 mapping = page_mapping(page); 49 if (mapping) { 50 WARN_ON(!PageUptodate(page)); 51 52 /* 53 * At least for ext2 with nobh option, we need to wait on 54 * writeback completing on this page, since we'll remove it 55 * from the pagecache. Otherwise truncate wont wait on the 56 * page, allowing the disk blocks to be reused by someone else 57 * before we actually wrote our data to them. fs corruption 58 * ensues. 59 */ 60 wait_on_page_writeback(page); 61 62 if (page_has_private(page) && 63 !try_to_release_page(page, GFP_KERNEL)) 64 goto out_unlock; 65 66 /* 67 * If we succeeded in removing the mapping, set LRU flag 68 * and return good. 69 */ 70 if (remove_mapping(mapping, page)) { 71 buf->flags |= PIPE_BUF_FLAG_LRU; 72 return 0; 73 } 74 } 75 76 /* 77 * Raced with truncate or failed to remove page from current 78 * address space, unlock and return failure. 79 */ 80 out_unlock: 81 unlock_page(page); 82 return 1; 83 } 84 85 static void page_cache_pipe_buf_release(struct pipe_inode_info *pipe, 86 struct pipe_buffer *buf) 87 { 88 page_cache_release(buf->page); 89 buf->flags &= ~PIPE_BUF_FLAG_LRU; 90 } 91 92 /* 93 * Check whether the contents of buf is OK to access. Since the content 94 * is a page cache page, IO may be in flight. 95 */ 96 static int page_cache_pipe_buf_confirm(struct pipe_inode_info *pipe, 97 struct pipe_buffer *buf) 98 { 99 struct page *page = buf->page; 100 int err; 101 102 if (!PageUptodate(page)) { 103 lock_page(page); 104 105 /* 106 * Page got truncated/unhashed. This will cause a 0-byte 107 * splice, if this is the first page. 108 */ 109 if (!page->mapping) { 110 err = -ENODATA; 111 goto error; 112 } 113 114 /* 115 * Uh oh, read-error from disk. 116 */ 117 if (!PageUptodate(page)) { 118 err = -EIO; 119 goto error; 120 } 121 122 /* 123 * Page is ok afterall, we are done. 124 */ 125 unlock_page(page); 126 } 127 128 return 0; 129 error: 130 unlock_page(page); 131 return err; 132 } 133 134 static const struct pipe_buf_operations page_cache_pipe_buf_ops = { 135 .can_merge = 0, 136 .map = generic_pipe_buf_map, 137 .unmap = generic_pipe_buf_unmap, 138 .confirm = page_cache_pipe_buf_confirm, 139 .release = page_cache_pipe_buf_release, 140 .steal = page_cache_pipe_buf_steal, 141 .get = generic_pipe_buf_get, 142 }; 143 144 static int user_page_pipe_buf_steal(struct pipe_inode_info *pipe, 145 struct pipe_buffer *buf) 146 { 147 if (!(buf->flags & PIPE_BUF_FLAG_GIFT)) 148 return 1; 149 150 buf->flags |= PIPE_BUF_FLAG_LRU; 151 return generic_pipe_buf_steal(pipe, buf); 152 } 153 154 static const struct pipe_buf_operations user_page_pipe_buf_ops = { 155 .can_merge = 0, 156 .map = generic_pipe_buf_map, 157 .unmap = generic_pipe_buf_unmap, 158 .confirm = generic_pipe_buf_confirm, 159 .release = page_cache_pipe_buf_release, 160 .steal = user_page_pipe_buf_steal, 161 .get = generic_pipe_buf_get, 162 }; 163 164 /** 165 * splice_to_pipe - fill passed data into a pipe 166 * @pipe: pipe to fill 167 * @spd: data to fill 168 * 169 * Description: 170 * @spd contains a map of pages and len/offset tuples, along with 171 * the struct pipe_buf_operations associated with these pages. This 172 * function will link that data to the pipe. 173 * 174 */ 175 ssize_t splice_to_pipe(struct pipe_inode_info *pipe, 176 struct splice_pipe_desc *spd) 177 { 178 unsigned int spd_pages = spd->nr_pages; 179 int ret, do_wakeup, page_nr; 180 181 ret = 0; 182 do_wakeup = 0; 183 page_nr = 0; 184 185 pipe_lock(pipe); 186 187 for (;;) { 188 if (!pipe->readers) { 189 send_sig(SIGPIPE, current, 0); 190 if (!ret) 191 ret = -EPIPE; 192 break; 193 } 194 195 if (pipe->nrbufs < PIPE_BUFFERS) { 196 int newbuf = (pipe->curbuf + pipe->nrbufs) & (PIPE_BUFFERS - 1); 197 struct pipe_buffer *buf = pipe->bufs + newbuf; 198 199 buf->page = spd->pages[page_nr]; 200 buf->offset = spd->partial[page_nr].offset; 201 buf->len = spd->partial[page_nr].len; 202 buf->private = spd->partial[page_nr].private; 203 buf->ops = spd->ops; 204 if (spd->flags & SPLICE_F_GIFT) 205 buf->flags |= PIPE_BUF_FLAG_GIFT; 206 207 pipe->nrbufs++; 208 page_nr++; 209 ret += buf->len; 210 211 if (pipe->inode) 212 do_wakeup = 1; 213 214 if (!--spd->nr_pages) 215 break; 216 if (pipe->nrbufs < PIPE_BUFFERS) 217 continue; 218 219 break; 220 } 221 222 if (spd->flags & SPLICE_F_NONBLOCK) { 223 if (!ret) 224 ret = -EAGAIN; 225 break; 226 } 227 228 if (signal_pending(current)) { 229 if (!ret) 230 ret = -ERESTARTSYS; 231 break; 232 } 233 234 if (do_wakeup) { 235 smp_mb(); 236 if (waitqueue_active(&pipe->wait)) 237 wake_up_interruptible_sync(&pipe->wait); 238 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN); 239 do_wakeup = 0; 240 } 241 242 pipe->waiting_writers++; 243 pipe_wait(pipe); 244 pipe->waiting_writers--; 245 } 246 247 pipe_unlock(pipe); 248 249 if (do_wakeup) { 250 smp_mb(); 251 if (waitqueue_active(&pipe->wait)) 252 wake_up_interruptible(&pipe->wait); 253 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN); 254 } 255 256 while (page_nr < spd_pages) 257 spd->spd_release(spd, page_nr++); 258 259 return ret; 260 } 261 262 static void spd_release_page(struct splice_pipe_desc *spd, unsigned int i) 263 { 264 page_cache_release(spd->pages[i]); 265 } 266 267 static int 268 __generic_file_splice_read(struct file *in, loff_t *ppos, 269 struct pipe_inode_info *pipe, size_t len, 270 unsigned int flags) 271 { 272 struct address_space *mapping = in->f_mapping; 273 unsigned int loff, nr_pages, req_pages; 274 struct page *pages[PIPE_BUFFERS]; 275 struct partial_page partial[PIPE_BUFFERS]; 276 struct page *page; 277 pgoff_t index, end_index; 278 loff_t isize; 279 int error, page_nr; 280 struct splice_pipe_desc spd = { 281 .pages = pages, 282 .partial = partial, 283 .flags = flags, 284 .ops = &page_cache_pipe_buf_ops, 285 .spd_release = spd_release_page, 286 }; 287 288 index = *ppos >> PAGE_CACHE_SHIFT; 289 loff = *ppos & ~PAGE_CACHE_MASK; 290 req_pages = (len + loff + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT; 291 nr_pages = min(req_pages, (unsigned)PIPE_BUFFERS); 292 293 /* 294 * Lookup the (hopefully) full range of pages we need. 295 */ 296 spd.nr_pages = find_get_pages_contig(mapping, index, nr_pages, pages); 297 index += spd.nr_pages; 298 299 /* 300 * If find_get_pages_contig() returned fewer pages than we needed, 301 * readahead/allocate the rest and fill in the holes. 302 */ 303 if (spd.nr_pages < nr_pages) 304 page_cache_sync_readahead(mapping, &in->f_ra, in, 305 index, req_pages - spd.nr_pages); 306 307 error = 0; 308 while (spd.nr_pages < nr_pages) { 309 /* 310 * Page could be there, find_get_pages_contig() breaks on 311 * the first hole. 312 */ 313 page = find_get_page(mapping, index); 314 if (!page) { 315 /* 316 * page didn't exist, allocate one. 317 */ 318 page = page_cache_alloc_cold(mapping); 319 if (!page) 320 break; 321 322 error = add_to_page_cache_lru(page, mapping, index, 323 mapping_gfp_mask(mapping)); 324 if (unlikely(error)) { 325 page_cache_release(page); 326 if (error == -EEXIST) 327 continue; 328 break; 329 } 330 /* 331 * add_to_page_cache() locks the page, unlock it 332 * to avoid convoluting the logic below even more. 333 */ 334 unlock_page(page); 335 } 336 337 pages[spd.nr_pages++] = page; 338 index++; 339 } 340 341 /* 342 * Now loop over the map and see if we need to start IO on any 343 * pages, fill in the partial map, etc. 344 */ 345 index = *ppos >> PAGE_CACHE_SHIFT; 346 nr_pages = spd.nr_pages; 347 spd.nr_pages = 0; 348 for (page_nr = 0; page_nr < nr_pages; page_nr++) { 349 unsigned int this_len; 350 351 if (!len) 352 break; 353 354 /* 355 * this_len is the max we'll use from this page 356 */ 357 this_len = min_t(unsigned long, len, PAGE_CACHE_SIZE - loff); 358 page = pages[page_nr]; 359 360 if (PageReadahead(page)) 361 page_cache_async_readahead(mapping, &in->f_ra, in, 362 page, index, req_pages - page_nr); 363 364 /* 365 * If the page isn't uptodate, we may need to start io on it 366 */ 367 if (!PageUptodate(page)) { 368 /* 369 * If in nonblock mode then dont block on waiting 370 * for an in-flight io page 371 */ 372 if (flags & SPLICE_F_NONBLOCK) { 373 if (!trylock_page(page)) { 374 error = -EAGAIN; 375 break; 376 } 377 } else 378 lock_page(page); 379 380 /* 381 * Page was truncated, or invalidated by the 382 * filesystem. Redo the find/create, but this time the 383 * page is kept locked, so there's no chance of another 384 * race with truncate/invalidate. 385 */ 386 if (!page->mapping) { 387 unlock_page(page); 388 page = find_or_create_page(mapping, index, 389 mapping_gfp_mask(mapping)); 390 391 if (!page) { 392 error = -ENOMEM; 393 break; 394 } 395 page_cache_release(pages[page_nr]); 396 pages[page_nr] = page; 397 } 398 /* 399 * page was already under io and is now done, great 400 */ 401 if (PageUptodate(page)) { 402 unlock_page(page); 403 goto fill_it; 404 } 405 406 /* 407 * need to read in the page 408 */ 409 error = mapping->a_ops->readpage(in, page); 410 if (unlikely(error)) { 411 /* 412 * We really should re-lookup the page here, 413 * but it complicates things a lot. Instead 414 * lets just do what we already stored, and 415 * we'll get it the next time we are called. 416 */ 417 if (error == AOP_TRUNCATED_PAGE) 418 error = 0; 419 420 break; 421 } 422 } 423 fill_it: 424 /* 425 * i_size must be checked after PageUptodate. 426 */ 427 isize = i_size_read(mapping->host); 428 end_index = (isize - 1) >> PAGE_CACHE_SHIFT; 429 if (unlikely(!isize || index > end_index)) 430 break; 431 432 /* 433 * if this is the last page, see if we need to shrink 434 * the length and stop 435 */ 436 if (end_index == index) { 437 unsigned int plen; 438 439 /* 440 * max good bytes in this page 441 */ 442 plen = ((isize - 1) & ~PAGE_CACHE_MASK) + 1; 443 if (plen <= loff) 444 break; 445 446 /* 447 * force quit after adding this page 448 */ 449 this_len = min(this_len, plen - loff); 450 len = this_len; 451 } 452 453 partial[page_nr].offset = loff; 454 partial[page_nr].len = this_len; 455 len -= this_len; 456 loff = 0; 457 spd.nr_pages++; 458 index++; 459 } 460 461 /* 462 * Release any pages at the end, if we quit early. 'page_nr' is how far 463 * we got, 'nr_pages' is how many pages are in the map. 464 */ 465 while (page_nr < nr_pages) 466 page_cache_release(pages[page_nr++]); 467 in->f_ra.prev_pos = (loff_t)index << PAGE_CACHE_SHIFT; 468 469 if (spd.nr_pages) 470 return splice_to_pipe(pipe, &spd); 471 472 return error; 473 } 474 475 /** 476 * generic_file_splice_read - splice data from file to a pipe 477 * @in: file to splice from 478 * @ppos: position in @in 479 * @pipe: pipe to splice to 480 * @len: number of bytes to splice 481 * @flags: splice modifier flags 482 * 483 * Description: 484 * Will read pages from given file and fill them into a pipe. Can be 485 * used as long as the address_space operations for the source implements 486 * a readpage() hook. 487 * 488 */ 489 ssize_t generic_file_splice_read(struct file *in, loff_t *ppos, 490 struct pipe_inode_info *pipe, size_t len, 491 unsigned int flags) 492 { 493 loff_t isize, left; 494 int ret; 495 496 isize = i_size_read(in->f_mapping->host); 497 if (unlikely(*ppos >= isize)) 498 return 0; 499 500 left = isize - *ppos; 501 if (unlikely(left < len)) 502 len = left; 503 504 ret = __generic_file_splice_read(in, ppos, pipe, len, flags); 505 if (ret > 0) { 506 *ppos += ret; 507 file_accessed(in); 508 } 509 510 return ret; 511 } 512 EXPORT_SYMBOL(generic_file_splice_read); 513 514 static const struct pipe_buf_operations default_pipe_buf_ops = { 515 .can_merge = 0, 516 .map = generic_pipe_buf_map, 517 .unmap = generic_pipe_buf_unmap, 518 .confirm = generic_pipe_buf_confirm, 519 .release = generic_pipe_buf_release, 520 .steal = generic_pipe_buf_steal, 521 .get = generic_pipe_buf_get, 522 }; 523 524 static ssize_t kernel_readv(struct file *file, const struct iovec *vec, 525 unsigned long vlen, loff_t offset) 526 { 527 mm_segment_t old_fs; 528 loff_t pos = offset; 529 ssize_t res; 530 531 old_fs = get_fs(); 532 set_fs(get_ds()); 533 /* The cast to a user pointer is valid due to the set_fs() */ 534 res = vfs_readv(file, (const struct iovec __user *)vec, vlen, &pos); 535 set_fs(old_fs); 536 537 return res; 538 } 539 540 static ssize_t kernel_write(struct file *file, const char *buf, size_t count, 541 loff_t pos) 542 { 543 mm_segment_t old_fs; 544 ssize_t res; 545 546 old_fs = get_fs(); 547 set_fs(get_ds()); 548 /* The cast to a user pointer is valid due to the set_fs() */ 549 res = vfs_write(file, (const char __user *)buf, count, &pos); 550 set_fs(old_fs); 551 552 return res; 553 } 554 555 ssize_t default_file_splice_read(struct file *in, loff_t *ppos, 556 struct pipe_inode_info *pipe, size_t len, 557 unsigned int flags) 558 { 559 unsigned int nr_pages; 560 unsigned int nr_freed; 561 size_t offset; 562 struct page *pages[PIPE_BUFFERS]; 563 struct partial_page partial[PIPE_BUFFERS]; 564 struct iovec vec[PIPE_BUFFERS]; 565 pgoff_t index; 566 ssize_t res; 567 size_t this_len; 568 int error; 569 int i; 570 struct splice_pipe_desc spd = { 571 .pages = pages, 572 .partial = partial, 573 .flags = flags, 574 .ops = &default_pipe_buf_ops, 575 .spd_release = spd_release_page, 576 }; 577 578 index = *ppos >> PAGE_CACHE_SHIFT; 579 offset = *ppos & ~PAGE_CACHE_MASK; 580 nr_pages = (len + offset + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT; 581 582 for (i = 0; i < nr_pages && i < PIPE_BUFFERS && len; i++) { 583 struct page *page; 584 585 page = alloc_page(GFP_USER); 586 error = -ENOMEM; 587 if (!page) 588 goto err; 589 590 this_len = min_t(size_t, len, PAGE_CACHE_SIZE - offset); 591 vec[i].iov_base = (void __user *) page_address(page); 592 vec[i].iov_len = this_len; 593 pages[i] = page; 594 spd.nr_pages++; 595 len -= this_len; 596 offset = 0; 597 } 598 599 res = kernel_readv(in, vec, spd.nr_pages, *ppos); 600 if (res < 0) { 601 error = res; 602 goto err; 603 } 604 605 error = 0; 606 if (!res) 607 goto err; 608 609 nr_freed = 0; 610 for (i = 0; i < spd.nr_pages; i++) { 611 this_len = min_t(size_t, vec[i].iov_len, res); 612 partial[i].offset = 0; 613 partial[i].len = this_len; 614 if (!this_len) { 615 __free_page(pages[i]); 616 pages[i] = NULL; 617 nr_freed++; 618 } 619 res -= this_len; 620 } 621 spd.nr_pages -= nr_freed; 622 623 res = splice_to_pipe(pipe, &spd); 624 if (res > 0) 625 *ppos += res; 626 627 return res; 628 629 err: 630 for (i = 0; i < spd.nr_pages; i++) 631 __free_page(pages[i]); 632 633 return error; 634 } 635 EXPORT_SYMBOL(default_file_splice_read); 636 637 /* 638 * Send 'sd->len' bytes to socket from 'sd->file' at position 'sd->pos' 639 * using sendpage(). Return the number of bytes sent. 640 */ 641 static int pipe_to_sendpage(struct pipe_inode_info *pipe, 642 struct pipe_buffer *buf, struct splice_desc *sd) 643 { 644 struct file *file = sd->u.file; 645 loff_t pos = sd->pos; 646 int ret, more; 647 648 ret = buf->ops->confirm(pipe, buf); 649 if (!ret) { 650 more = (sd->flags & SPLICE_F_MORE) || sd->len < sd->total_len; 651 if (file->f_op && file->f_op->sendpage) 652 ret = file->f_op->sendpage(file, buf->page, buf->offset, 653 sd->len, &pos, more); 654 else 655 ret = -EINVAL; 656 } 657 658 return ret; 659 } 660 661 /* 662 * This is a little more tricky than the file -> pipe splicing. There are 663 * basically three cases: 664 * 665 * - Destination page already exists in the address space and there 666 * are users of it. For that case we have no other option that 667 * copying the data. Tough luck. 668 * - Destination page already exists in the address space, but there 669 * are no users of it. Make sure it's uptodate, then drop it. Fall 670 * through to last case. 671 * - Destination page does not exist, we can add the pipe page to 672 * the page cache and avoid the copy. 673 * 674 * If asked to move pages to the output file (SPLICE_F_MOVE is set in 675 * sd->flags), we attempt to migrate pages from the pipe to the output 676 * file address space page cache. This is possible if no one else has 677 * the pipe page referenced outside of the pipe and page cache. If 678 * SPLICE_F_MOVE isn't set, or we cannot move the page, we simply create 679 * a new page in the output file page cache and fill/dirty that. 680 */ 681 int pipe_to_file(struct pipe_inode_info *pipe, struct pipe_buffer *buf, 682 struct splice_desc *sd) 683 { 684 struct file *file = sd->u.file; 685 struct address_space *mapping = file->f_mapping; 686 unsigned int offset, this_len; 687 struct page *page; 688 void *fsdata; 689 int ret; 690 691 /* 692 * make sure the data in this buffer is uptodate 693 */ 694 ret = buf->ops->confirm(pipe, buf); 695 if (unlikely(ret)) 696 return ret; 697 698 offset = sd->pos & ~PAGE_CACHE_MASK; 699 700 this_len = sd->len; 701 if (this_len + offset > PAGE_CACHE_SIZE) 702 this_len = PAGE_CACHE_SIZE - offset; 703 704 ret = pagecache_write_begin(file, mapping, sd->pos, this_len, 705 AOP_FLAG_UNINTERRUPTIBLE, &page, &fsdata); 706 if (unlikely(ret)) 707 goto out; 708 709 if (buf->page != page) { 710 /* 711 * Careful, ->map() uses KM_USER0! 712 */ 713 char *src = buf->ops->map(pipe, buf, 1); 714 char *dst = kmap_atomic(page, KM_USER1); 715 716 memcpy(dst + offset, src + buf->offset, this_len); 717 flush_dcache_page(page); 718 kunmap_atomic(dst, KM_USER1); 719 buf->ops->unmap(pipe, buf, src); 720 } 721 ret = pagecache_write_end(file, mapping, sd->pos, this_len, this_len, 722 page, fsdata); 723 out: 724 return ret; 725 } 726 EXPORT_SYMBOL(pipe_to_file); 727 728 static void wakeup_pipe_writers(struct pipe_inode_info *pipe) 729 { 730 smp_mb(); 731 if (waitqueue_active(&pipe->wait)) 732 wake_up_interruptible(&pipe->wait); 733 kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT); 734 } 735 736 /** 737 * splice_from_pipe_feed - feed available data from a pipe to a file 738 * @pipe: pipe to splice from 739 * @sd: information to @actor 740 * @actor: handler that splices the data 741 * 742 * Description: 743 * This function loops over the pipe and calls @actor to do the 744 * actual moving of a single struct pipe_buffer to the desired 745 * destination. It returns when there's no more buffers left in 746 * the pipe or if the requested number of bytes (@sd->total_len) 747 * have been copied. It returns a positive number (one) if the 748 * pipe needs to be filled with more data, zero if the required 749 * number of bytes have been copied and -errno on error. 750 * 751 * This, together with splice_from_pipe_{begin,end,next}, may be 752 * used to implement the functionality of __splice_from_pipe() when 753 * locking is required around copying the pipe buffers to the 754 * destination. 755 */ 756 int splice_from_pipe_feed(struct pipe_inode_info *pipe, struct splice_desc *sd, 757 splice_actor *actor) 758 { 759 int ret; 760 761 while (pipe->nrbufs) { 762 struct pipe_buffer *buf = pipe->bufs + pipe->curbuf; 763 const struct pipe_buf_operations *ops = buf->ops; 764 765 sd->len = buf->len; 766 if (sd->len > sd->total_len) 767 sd->len = sd->total_len; 768 769 ret = actor(pipe, buf, sd); 770 if (ret <= 0) { 771 if (ret == -ENODATA) 772 ret = 0; 773 return ret; 774 } 775 buf->offset += ret; 776 buf->len -= ret; 777 778 sd->num_spliced += ret; 779 sd->len -= ret; 780 sd->pos += ret; 781 sd->total_len -= ret; 782 783 if (!buf->len) { 784 buf->ops = NULL; 785 ops->release(pipe, buf); 786 pipe->curbuf = (pipe->curbuf + 1) & (PIPE_BUFFERS - 1); 787 pipe->nrbufs--; 788 if (pipe->inode) 789 sd->need_wakeup = true; 790 } 791 792 if (!sd->total_len) 793 return 0; 794 } 795 796 return 1; 797 } 798 EXPORT_SYMBOL(splice_from_pipe_feed); 799 800 /** 801 * splice_from_pipe_next - wait for some data to splice from 802 * @pipe: pipe to splice from 803 * @sd: information about the splice operation 804 * 805 * Description: 806 * This function will wait for some data and return a positive 807 * value (one) if pipe buffers are available. It will return zero 808 * or -errno if no more data needs to be spliced. 809 */ 810 int splice_from_pipe_next(struct pipe_inode_info *pipe, struct splice_desc *sd) 811 { 812 while (!pipe->nrbufs) { 813 if (!pipe->writers) 814 return 0; 815 816 if (!pipe->waiting_writers && sd->num_spliced) 817 return 0; 818 819 if (sd->flags & SPLICE_F_NONBLOCK) 820 return -EAGAIN; 821 822 if (signal_pending(current)) 823 return -ERESTARTSYS; 824 825 if (sd->need_wakeup) { 826 wakeup_pipe_writers(pipe); 827 sd->need_wakeup = false; 828 } 829 830 pipe_wait(pipe); 831 } 832 833 return 1; 834 } 835 EXPORT_SYMBOL(splice_from_pipe_next); 836 837 /** 838 * splice_from_pipe_begin - start splicing from pipe 839 * @sd: information about the splice operation 840 * 841 * Description: 842 * This function should be called before a loop containing 843 * splice_from_pipe_next() and splice_from_pipe_feed() to 844 * initialize the necessary fields of @sd. 845 */ 846 void splice_from_pipe_begin(struct splice_desc *sd) 847 { 848 sd->num_spliced = 0; 849 sd->need_wakeup = false; 850 } 851 EXPORT_SYMBOL(splice_from_pipe_begin); 852 853 /** 854 * splice_from_pipe_end - finish splicing from pipe 855 * @pipe: pipe to splice from 856 * @sd: information about the splice operation 857 * 858 * Description: 859 * This function will wake up pipe writers if necessary. It should 860 * be called after a loop containing splice_from_pipe_next() and 861 * splice_from_pipe_feed(). 862 */ 863 void splice_from_pipe_end(struct pipe_inode_info *pipe, struct splice_desc *sd) 864 { 865 if (sd->need_wakeup) 866 wakeup_pipe_writers(pipe); 867 } 868 EXPORT_SYMBOL(splice_from_pipe_end); 869 870 /** 871 * __splice_from_pipe - splice data from a pipe to given actor 872 * @pipe: pipe to splice from 873 * @sd: information to @actor 874 * @actor: handler that splices the data 875 * 876 * Description: 877 * This function does little more than loop over the pipe and call 878 * @actor to do the actual moving of a single struct pipe_buffer to 879 * the desired destination. See pipe_to_file, pipe_to_sendpage, or 880 * pipe_to_user. 881 * 882 */ 883 ssize_t __splice_from_pipe(struct pipe_inode_info *pipe, struct splice_desc *sd, 884 splice_actor *actor) 885 { 886 int ret; 887 888 splice_from_pipe_begin(sd); 889 do { 890 ret = splice_from_pipe_next(pipe, sd); 891 if (ret > 0) 892 ret = splice_from_pipe_feed(pipe, sd, actor); 893 } while (ret > 0); 894 splice_from_pipe_end(pipe, sd); 895 896 return sd->num_spliced ? sd->num_spliced : ret; 897 } 898 EXPORT_SYMBOL(__splice_from_pipe); 899 900 /** 901 * splice_from_pipe - splice data from a pipe to a file 902 * @pipe: pipe to splice from 903 * @out: file to splice to 904 * @ppos: position in @out 905 * @len: how many bytes to splice 906 * @flags: splice modifier flags 907 * @actor: handler that splices the data 908 * 909 * Description: 910 * See __splice_from_pipe. This function locks the pipe inode, 911 * otherwise it's identical to __splice_from_pipe(). 912 * 913 */ 914 ssize_t splice_from_pipe(struct pipe_inode_info *pipe, struct file *out, 915 loff_t *ppos, size_t len, unsigned int flags, 916 splice_actor *actor) 917 { 918 ssize_t ret; 919 struct splice_desc sd = { 920 .total_len = len, 921 .flags = flags, 922 .pos = *ppos, 923 .u.file = out, 924 }; 925 926 pipe_lock(pipe); 927 ret = __splice_from_pipe(pipe, &sd, actor); 928 pipe_unlock(pipe); 929 930 return ret; 931 } 932 933 /** 934 * generic_file_splice_write - splice data from a pipe to a file 935 * @pipe: pipe info 936 * @out: file to write to 937 * @ppos: position in @out 938 * @len: number of bytes to splice 939 * @flags: splice modifier flags 940 * 941 * Description: 942 * Will either move or copy pages (determined by @flags options) from 943 * the given pipe inode to the given file. 944 * 945 */ 946 ssize_t 947 generic_file_splice_write(struct pipe_inode_info *pipe, struct file *out, 948 loff_t *ppos, size_t len, unsigned int flags) 949 { 950 struct address_space *mapping = out->f_mapping; 951 struct inode *inode = mapping->host; 952 struct splice_desc sd = { 953 .total_len = len, 954 .flags = flags, 955 .pos = *ppos, 956 .u.file = out, 957 }; 958 ssize_t ret; 959 960 pipe_lock(pipe); 961 962 splice_from_pipe_begin(&sd); 963 do { 964 ret = splice_from_pipe_next(pipe, &sd); 965 if (ret <= 0) 966 break; 967 968 mutex_lock_nested(&inode->i_mutex, I_MUTEX_CHILD); 969 ret = file_remove_suid(out); 970 if (!ret) { 971 file_update_time(out); 972 ret = splice_from_pipe_feed(pipe, &sd, pipe_to_file); 973 } 974 mutex_unlock(&inode->i_mutex); 975 } while (ret > 0); 976 splice_from_pipe_end(pipe, &sd); 977 978 pipe_unlock(pipe); 979 980 if (sd.num_spliced) 981 ret = sd.num_spliced; 982 983 if (ret > 0) { 984 unsigned long nr_pages; 985 int err; 986 987 nr_pages = (ret + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT; 988 989 err = generic_write_sync(out, *ppos, ret); 990 if (err) 991 ret = err; 992 else 993 *ppos += ret; 994 balance_dirty_pages_ratelimited_nr(mapping, nr_pages); 995 } 996 997 return ret; 998 } 999 1000 EXPORT_SYMBOL(generic_file_splice_write); 1001 1002 static int write_pipe_buf(struct pipe_inode_info *pipe, struct pipe_buffer *buf, 1003 struct splice_desc *sd) 1004 { 1005 int ret; 1006 void *data; 1007 1008 ret = buf->ops->confirm(pipe, buf); 1009 if (ret) 1010 return ret; 1011 1012 data = buf->ops->map(pipe, buf, 0); 1013 ret = kernel_write(sd->u.file, data + buf->offset, sd->len, sd->pos); 1014 buf->ops->unmap(pipe, buf, data); 1015 1016 return ret; 1017 } 1018 1019 static ssize_t default_file_splice_write(struct pipe_inode_info *pipe, 1020 struct file *out, loff_t *ppos, 1021 size_t len, unsigned int flags) 1022 { 1023 ssize_t ret; 1024 1025 ret = splice_from_pipe(pipe, out, ppos, len, flags, write_pipe_buf); 1026 if (ret > 0) 1027 *ppos += ret; 1028 1029 return ret; 1030 } 1031 1032 /** 1033 * generic_splice_sendpage - splice data from a pipe to a socket 1034 * @pipe: pipe to splice from 1035 * @out: socket to write to 1036 * @ppos: position in @out 1037 * @len: number of bytes to splice 1038 * @flags: splice modifier flags 1039 * 1040 * Description: 1041 * Will send @len bytes from the pipe to a network socket. No data copying 1042 * is involved. 1043 * 1044 */ 1045 ssize_t generic_splice_sendpage(struct pipe_inode_info *pipe, struct file *out, 1046 loff_t *ppos, size_t len, unsigned int flags) 1047 { 1048 return splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_sendpage); 1049 } 1050 1051 EXPORT_SYMBOL(generic_splice_sendpage); 1052 1053 /* 1054 * Attempt to initiate a splice from pipe to file. 1055 */ 1056 static long do_splice_from(struct pipe_inode_info *pipe, struct file *out, 1057 loff_t *ppos, size_t len, unsigned int flags) 1058 { 1059 ssize_t (*splice_write)(struct pipe_inode_info *, struct file *, 1060 loff_t *, size_t, unsigned int); 1061 int ret; 1062 1063 if (unlikely(!(out->f_mode & FMODE_WRITE))) 1064 return -EBADF; 1065 1066 if (unlikely(out->f_flags & O_APPEND)) 1067 return -EINVAL; 1068 1069 ret = rw_verify_area(WRITE, out, ppos, len); 1070 if (unlikely(ret < 0)) 1071 return ret; 1072 1073 if (out->f_op && out->f_op->splice_write) 1074 splice_write = out->f_op->splice_write; 1075 else 1076 splice_write = default_file_splice_write; 1077 1078 return splice_write(pipe, out, ppos, len, flags); 1079 } 1080 1081 /* 1082 * Attempt to initiate a splice from a file to a pipe. 1083 */ 1084 static long do_splice_to(struct file *in, loff_t *ppos, 1085 struct pipe_inode_info *pipe, size_t len, 1086 unsigned int flags) 1087 { 1088 ssize_t (*splice_read)(struct file *, loff_t *, 1089 struct pipe_inode_info *, size_t, unsigned int); 1090 int ret; 1091 1092 if (unlikely(!(in->f_mode & FMODE_READ))) 1093 return -EBADF; 1094 1095 ret = rw_verify_area(READ, in, ppos, len); 1096 if (unlikely(ret < 0)) 1097 return ret; 1098 1099 if (in->f_op && in->f_op->splice_read) 1100 splice_read = in->f_op->splice_read; 1101 else 1102 splice_read = default_file_splice_read; 1103 1104 return splice_read(in, ppos, pipe, len, flags); 1105 } 1106 1107 /** 1108 * splice_direct_to_actor - splices data directly between two non-pipes 1109 * @in: file to splice from 1110 * @sd: actor information on where to splice to 1111 * @actor: handles the data splicing 1112 * 1113 * Description: 1114 * This is a special case helper to splice directly between two 1115 * points, without requiring an explicit pipe. Internally an allocated 1116 * pipe is cached in the process, and reused during the lifetime of 1117 * that process. 1118 * 1119 */ 1120 ssize_t splice_direct_to_actor(struct file *in, struct splice_desc *sd, 1121 splice_direct_actor *actor) 1122 { 1123 struct pipe_inode_info *pipe; 1124 long ret, bytes; 1125 umode_t i_mode; 1126 size_t len; 1127 int i, flags; 1128 1129 /* 1130 * We require the input being a regular file, as we don't want to 1131 * randomly drop data for eg socket -> socket splicing. Use the 1132 * piped splicing for that! 1133 */ 1134 i_mode = in->f_path.dentry->d_inode->i_mode; 1135 if (unlikely(!S_ISREG(i_mode) && !S_ISBLK(i_mode))) 1136 return -EINVAL; 1137 1138 /* 1139 * neither in nor out is a pipe, setup an internal pipe attached to 1140 * 'out' and transfer the wanted data from 'in' to 'out' through that 1141 */ 1142 pipe = current->splice_pipe; 1143 if (unlikely(!pipe)) { 1144 pipe = alloc_pipe_info(NULL); 1145 if (!pipe) 1146 return -ENOMEM; 1147 1148 /* 1149 * We don't have an immediate reader, but we'll read the stuff 1150 * out of the pipe right after the splice_to_pipe(). So set 1151 * PIPE_READERS appropriately. 1152 */ 1153 pipe->readers = 1; 1154 1155 current->splice_pipe = pipe; 1156 } 1157 1158 /* 1159 * Do the splice. 1160 */ 1161 ret = 0; 1162 bytes = 0; 1163 len = sd->total_len; 1164 flags = sd->flags; 1165 1166 /* 1167 * Don't block on output, we have to drain the direct pipe. 1168 */ 1169 sd->flags &= ~SPLICE_F_NONBLOCK; 1170 1171 while (len) { 1172 size_t read_len; 1173 loff_t pos = sd->pos, prev_pos = pos; 1174 1175 ret = do_splice_to(in, &pos, pipe, len, flags); 1176 if (unlikely(ret <= 0)) 1177 goto out_release; 1178 1179 read_len = ret; 1180 sd->total_len = read_len; 1181 1182 /* 1183 * NOTE: nonblocking mode only applies to the input. We 1184 * must not do the output in nonblocking mode as then we 1185 * could get stuck data in the internal pipe: 1186 */ 1187 ret = actor(pipe, sd); 1188 if (unlikely(ret <= 0)) { 1189 sd->pos = prev_pos; 1190 goto out_release; 1191 } 1192 1193 bytes += ret; 1194 len -= ret; 1195 sd->pos = pos; 1196 1197 if (ret < read_len) { 1198 sd->pos = prev_pos + ret; 1199 goto out_release; 1200 } 1201 } 1202 1203 done: 1204 pipe->nrbufs = pipe->curbuf = 0; 1205 file_accessed(in); 1206 return bytes; 1207 1208 out_release: 1209 /* 1210 * If we did an incomplete transfer we must release 1211 * the pipe buffers in question: 1212 */ 1213 for (i = 0; i < PIPE_BUFFERS; i++) { 1214 struct pipe_buffer *buf = pipe->bufs + i; 1215 1216 if (buf->ops) { 1217 buf->ops->release(pipe, buf); 1218 buf->ops = NULL; 1219 } 1220 } 1221 1222 if (!bytes) 1223 bytes = ret; 1224 1225 goto done; 1226 } 1227 EXPORT_SYMBOL(splice_direct_to_actor); 1228 1229 static int direct_splice_actor(struct pipe_inode_info *pipe, 1230 struct splice_desc *sd) 1231 { 1232 struct file *file = sd->u.file; 1233 1234 return do_splice_from(pipe, file, &sd->pos, sd->total_len, sd->flags); 1235 } 1236 1237 /** 1238 * do_splice_direct - splices data directly between two files 1239 * @in: file to splice from 1240 * @ppos: input file offset 1241 * @out: file to splice to 1242 * @len: number of bytes to splice 1243 * @flags: splice modifier flags 1244 * 1245 * Description: 1246 * For use by do_sendfile(). splice can easily emulate sendfile, but 1247 * doing it in the application would incur an extra system call 1248 * (splice in + splice out, as compared to just sendfile()). So this helper 1249 * can splice directly through a process-private pipe. 1250 * 1251 */ 1252 long do_splice_direct(struct file *in, loff_t *ppos, struct file *out, 1253 size_t len, unsigned int flags) 1254 { 1255 struct splice_desc sd = { 1256 .len = len, 1257 .total_len = len, 1258 .flags = flags, 1259 .pos = *ppos, 1260 .u.file = out, 1261 }; 1262 long ret; 1263 1264 ret = splice_direct_to_actor(in, &sd, direct_splice_actor); 1265 if (ret > 0) 1266 *ppos = sd.pos; 1267 1268 return ret; 1269 } 1270 1271 static int splice_pipe_to_pipe(struct pipe_inode_info *ipipe, 1272 struct pipe_inode_info *opipe, 1273 size_t len, unsigned int flags); 1274 /* 1275 * After the inode slimming patch, i_pipe/i_bdev/i_cdev share the same 1276 * location, so checking ->i_pipe is not enough to verify that this is a 1277 * pipe. 1278 */ 1279 static inline struct pipe_inode_info *pipe_info(struct inode *inode) 1280 { 1281 if (S_ISFIFO(inode->i_mode)) 1282 return inode->i_pipe; 1283 1284 return NULL; 1285 } 1286 1287 /* 1288 * Determine where to splice to/from. 1289 */ 1290 static long do_splice(struct file *in, loff_t __user *off_in, 1291 struct file *out, loff_t __user *off_out, 1292 size_t len, unsigned int flags) 1293 { 1294 struct pipe_inode_info *ipipe; 1295 struct pipe_inode_info *opipe; 1296 loff_t offset, *off; 1297 long ret; 1298 1299 ipipe = pipe_info(in->f_path.dentry->d_inode); 1300 opipe = pipe_info(out->f_path.dentry->d_inode); 1301 1302 if (ipipe && opipe) { 1303 if (off_in || off_out) 1304 return -ESPIPE; 1305 1306 if (!(in->f_mode & FMODE_READ)) 1307 return -EBADF; 1308 1309 if (!(out->f_mode & FMODE_WRITE)) 1310 return -EBADF; 1311 1312 /* Splicing to self would be fun, but... */ 1313 if (ipipe == opipe) 1314 return -EINVAL; 1315 1316 return splice_pipe_to_pipe(ipipe, opipe, len, flags); 1317 } 1318 1319 if (ipipe) { 1320 if (off_in) 1321 return -ESPIPE; 1322 if (off_out) { 1323 if (!out->f_op || !out->f_op->llseek || 1324 out->f_op->llseek == no_llseek) 1325 return -EINVAL; 1326 if (copy_from_user(&offset, off_out, sizeof(loff_t))) 1327 return -EFAULT; 1328 off = &offset; 1329 } else 1330 off = &out->f_pos; 1331 1332 ret = do_splice_from(ipipe, out, off, len, flags); 1333 1334 if (off_out && copy_to_user(off_out, off, sizeof(loff_t))) 1335 ret = -EFAULT; 1336 1337 return ret; 1338 } 1339 1340 if (opipe) { 1341 if (off_out) 1342 return -ESPIPE; 1343 if (off_in) { 1344 if (!in->f_op || !in->f_op->llseek || 1345 in->f_op->llseek == no_llseek) 1346 return -EINVAL; 1347 if (copy_from_user(&offset, off_in, sizeof(loff_t))) 1348 return -EFAULT; 1349 off = &offset; 1350 } else 1351 off = &in->f_pos; 1352 1353 ret = do_splice_to(in, off, opipe, len, flags); 1354 1355 if (off_in && copy_to_user(off_in, off, sizeof(loff_t))) 1356 ret = -EFAULT; 1357 1358 return ret; 1359 } 1360 1361 return -EINVAL; 1362 } 1363 1364 /* 1365 * Map an iov into an array of pages and offset/length tupples. With the 1366 * partial_page structure, we can map several non-contiguous ranges into 1367 * our ones pages[] map instead of splitting that operation into pieces. 1368 * Could easily be exported as a generic helper for other users, in which 1369 * case one would probably want to add a 'max_nr_pages' parameter as well. 1370 */ 1371 static int get_iovec_page_array(const struct iovec __user *iov, 1372 unsigned int nr_vecs, struct page **pages, 1373 struct partial_page *partial, int aligned) 1374 { 1375 int buffers = 0, error = 0; 1376 1377 while (nr_vecs) { 1378 unsigned long off, npages; 1379 struct iovec entry; 1380 void __user *base; 1381 size_t len; 1382 int i; 1383 1384 error = -EFAULT; 1385 if (copy_from_user(&entry, iov, sizeof(entry))) 1386 break; 1387 1388 base = entry.iov_base; 1389 len = entry.iov_len; 1390 1391 /* 1392 * Sanity check this iovec. 0 read succeeds. 1393 */ 1394 error = 0; 1395 if (unlikely(!len)) 1396 break; 1397 error = -EFAULT; 1398 if (!access_ok(VERIFY_READ, base, len)) 1399 break; 1400 1401 /* 1402 * Get this base offset and number of pages, then map 1403 * in the user pages. 1404 */ 1405 off = (unsigned long) base & ~PAGE_MASK; 1406 1407 /* 1408 * If asked for alignment, the offset must be zero and the 1409 * length a multiple of the PAGE_SIZE. 1410 */ 1411 error = -EINVAL; 1412 if (aligned && (off || len & ~PAGE_MASK)) 1413 break; 1414 1415 npages = (off + len + PAGE_SIZE - 1) >> PAGE_SHIFT; 1416 if (npages > PIPE_BUFFERS - buffers) 1417 npages = PIPE_BUFFERS - buffers; 1418 1419 error = get_user_pages_fast((unsigned long)base, npages, 1420 0, &pages[buffers]); 1421 1422 if (unlikely(error <= 0)) 1423 break; 1424 1425 /* 1426 * Fill this contiguous range into the partial page map. 1427 */ 1428 for (i = 0; i < error; i++) { 1429 const int plen = min_t(size_t, len, PAGE_SIZE - off); 1430 1431 partial[buffers].offset = off; 1432 partial[buffers].len = plen; 1433 1434 off = 0; 1435 len -= plen; 1436 buffers++; 1437 } 1438 1439 /* 1440 * We didn't complete this iov, stop here since it probably 1441 * means we have to move some of this into a pipe to 1442 * be able to continue. 1443 */ 1444 if (len) 1445 break; 1446 1447 /* 1448 * Don't continue if we mapped fewer pages than we asked for, 1449 * or if we mapped the max number of pages that we have 1450 * room for. 1451 */ 1452 if (error < npages || buffers == PIPE_BUFFERS) 1453 break; 1454 1455 nr_vecs--; 1456 iov++; 1457 } 1458 1459 if (buffers) 1460 return buffers; 1461 1462 return error; 1463 } 1464 1465 static int pipe_to_user(struct pipe_inode_info *pipe, struct pipe_buffer *buf, 1466 struct splice_desc *sd) 1467 { 1468 char *src; 1469 int ret; 1470 1471 ret = buf->ops->confirm(pipe, buf); 1472 if (unlikely(ret)) 1473 return ret; 1474 1475 /* 1476 * See if we can use the atomic maps, by prefaulting in the 1477 * pages and doing an atomic copy 1478 */ 1479 if (!fault_in_pages_writeable(sd->u.userptr, sd->len)) { 1480 src = buf->ops->map(pipe, buf, 1); 1481 ret = __copy_to_user_inatomic(sd->u.userptr, src + buf->offset, 1482 sd->len); 1483 buf->ops->unmap(pipe, buf, src); 1484 if (!ret) { 1485 ret = sd->len; 1486 goto out; 1487 } 1488 } 1489 1490 /* 1491 * No dice, use slow non-atomic map and copy 1492 */ 1493 src = buf->ops->map(pipe, buf, 0); 1494 1495 ret = sd->len; 1496 if (copy_to_user(sd->u.userptr, src + buf->offset, sd->len)) 1497 ret = -EFAULT; 1498 1499 buf->ops->unmap(pipe, buf, src); 1500 out: 1501 if (ret > 0) 1502 sd->u.userptr += ret; 1503 return ret; 1504 } 1505 1506 /* 1507 * For lack of a better implementation, implement vmsplice() to userspace 1508 * as a simple copy of the pipes pages to the user iov. 1509 */ 1510 static long vmsplice_to_user(struct file *file, const struct iovec __user *iov, 1511 unsigned long nr_segs, unsigned int flags) 1512 { 1513 struct pipe_inode_info *pipe; 1514 struct splice_desc sd; 1515 ssize_t size; 1516 int error; 1517 long ret; 1518 1519 pipe = pipe_info(file->f_path.dentry->d_inode); 1520 if (!pipe) 1521 return -EBADF; 1522 1523 pipe_lock(pipe); 1524 1525 error = ret = 0; 1526 while (nr_segs) { 1527 void __user *base; 1528 size_t len; 1529 1530 /* 1531 * Get user address base and length for this iovec. 1532 */ 1533 error = get_user(base, &iov->iov_base); 1534 if (unlikely(error)) 1535 break; 1536 error = get_user(len, &iov->iov_len); 1537 if (unlikely(error)) 1538 break; 1539 1540 /* 1541 * Sanity check this iovec. 0 read succeeds. 1542 */ 1543 if (unlikely(!len)) 1544 break; 1545 if (unlikely(!base)) { 1546 error = -EFAULT; 1547 break; 1548 } 1549 1550 if (unlikely(!access_ok(VERIFY_WRITE, base, len))) { 1551 error = -EFAULT; 1552 break; 1553 } 1554 1555 sd.len = 0; 1556 sd.total_len = len; 1557 sd.flags = flags; 1558 sd.u.userptr = base; 1559 sd.pos = 0; 1560 1561 size = __splice_from_pipe(pipe, &sd, pipe_to_user); 1562 if (size < 0) { 1563 if (!ret) 1564 ret = size; 1565 1566 break; 1567 } 1568 1569 ret += size; 1570 1571 if (size < len) 1572 break; 1573 1574 nr_segs--; 1575 iov++; 1576 } 1577 1578 pipe_unlock(pipe); 1579 1580 if (!ret) 1581 ret = error; 1582 1583 return ret; 1584 } 1585 1586 /* 1587 * vmsplice splices a user address range into a pipe. It can be thought of 1588 * as splice-from-memory, where the regular splice is splice-from-file (or 1589 * to file). In both cases the output is a pipe, naturally. 1590 */ 1591 static long vmsplice_to_pipe(struct file *file, const struct iovec __user *iov, 1592 unsigned long nr_segs, unsigned int flags) 1593 { 1594 struct pipe_inode_info *pipe; 1595 struct page *pages[PIPE_BUFFERS]; 1596 struct partial_page partial[PIPE_BUFFERS]; 1597 struct splice_pipe_desc spd = { 1598 .pages = pages, 1599 .partial = partial, 1600 .flags = flags, 1601 .ops = &user_page_pipe_buf_ops, 1602 .spd_release = spd_release_page, 1603 }; 1604 1605 pipe = pipe_info(file->f_path.dentry->d_inode); 1606 if (!pipe) 1607 return -EBADF; 1608 1609 spd.nr_pages = get_iovec_page_array(iov, nr_segs, pages, partial, 1610 flags & SPLICE_F_GIFT); 1611 if (spd.nr_pages <= 0) 1612 return spd.nr_pages; 1613 1614 return splice_to_pipe(pipe, &spd); 1615 } 1616 1617 /* 1618 * Note that vmsplice only really supports true splicing _from_ user memory 1619 * to a pipe, not the other way around. Splicing from user memory is a simple 1620 * operation that can be supported without any funky alignment restrictions 1621 * or nasty vm tricks. We simply map in the user memory and fill them into 1622 * a pipe. The reverse isn't quite as easy, though. There are two possible 1623 * solutions for that: 1624 * 1625 * - memcpy() the data internally, at which point we might as well just 1626 * do a regular read() on the buffer anyway. 1627 * - Lots of nasty vm tricks, that are neither fast nor flexible (it 1628 * has restriction limitations on both ends of the pipe). 1629 * 1630 * Currently we punt and implement it as a normal copy, see pipe_to_user(). 1631 * 1632 */ 1633 SYSCALL_DEFINE4(vmsplice, int, fd, const struct iovec __user *, iov, 1634 unsigned long, nr_segs, unsigned int, flags) 1635 { 1636 struct file *file; 1637 long error; 1638 int fput; 1639 1640 if (unlikely(nr_segs > UIO_MAXIOV)) 1641 return -EINVAL; 1642 else if (unlikely(!nr_segs)) 1643 return 0; 1644 1645 error = -EBADF; 1646 file = fget_light(fd, &fput); 1647 if (file) { 1648 if (file->f_mode & FMODE_WRITE) 1649 error = vmsplice_to_pipe(file, iov, nr_segs, flags); 1650 else if (file->f_mode & FMODE_READ) 1651 error = vmsplice_to_user(file, iov, nr_segs, flags); 1652 1653 fput_light(file, fput); 1654 } 1655 1656 return error; 1657 } 1658 1659 SYSCALL_DEFINE6(splice, int, fd_in, loff_t __user *, off_in, 1660 int, fd_out, loff_t __user *, off_out, 1661 size_t, len, unsigned int, flags) 1662 { 1663 long error; 1664 struct file *in, *out; 1665 int fput_in, fput_out; 1666 1667 if (unlikely(!len)) 1668 return 0; 1669 1670 error = -EBADF; 1671 in = fget_light(fd_in, &fput_in); 1672 if (in) { 1673 if (in->f_mode & FMODE_READ) { 1674 out = fget_light(fd_out, &fput_out); 1675 if (out) { 1676 if (out->f_mode & FMODE_WRITE) 1677 error = do_splice(in, off_in, 1678 out, off_out, 1679 len, flags); 1680 fput_light(out, fput_out); 1681 } 1682 } 1683 1684 fput_light(in, fput_in); 1685 } 1686 1687 return error; 1688 } 1689 1690 /* 1691 * Make sure there's data to read. Wait for input if we can, otherwise 1692 * return an appropriate error. 1693 */ 1694 static int ipipe_prep(struct pipe_inode_info *pipe, unsigned int flags) 1695 { 1696 int ret; 1697 1698 /* 1699 * Check ->nrbufs without the inode lock first. This function 1700 * is speculative anyways, so missing one is ok. 1701 */ 1702 if (pipe->nrbufs) 1703 return 0; 1704 1705 ret = 0; 1706 pipe_lock(pipe); 1707 1708 while (!pipe->nrbufs) { 1709 if (signal_pending(current)) { 1710 ret = -ERESTARTSYS; 1711 break; 1712 } 1713 if (!pipe->writers) 1714 break; 1715 if (!pipe->waiting_writers) { 1716 if (flags & SPLICE_F_NONBLOCK) { 1717 ret = -EAGAIN; 1718 break; 1719 } 1720 } 1721 pipe_wait(pipe); 1722 } 1723 1724 pipe_unlock(pipe); 1725 return ret; 1726 } 1727 1728 /* 1729 * Make sure there's writeable room. Wait for room if we can, otherwise 1730 * return an appropriate error. 1731 */ 1732 static int opipe_prep(struct pipe_inode_info *pipe, unsigned int flags) 1733 { 1734 int ret; 1735 1736 /* 1737 * Check ->nrbufs without the inode lock first. This function 1738 * is speculative anyways, so missing one is ok. 1739 */ 1740 if (pipe->nrbufs < PIPE_BUFFERS) 1741 return 0; 1742 1743 ret = 0; 1744 pipe_lock(pipe); 1745 1746 while (pipe->nrbufs >= PIPE_BUFFERS) { 1747 if (!pipe->readers) { 1748 send_sig(SIGPIPE, current, 0); 1749 ret = -EPIPE; 1750 break; 1751 } 1752 if (flags & SPLICE_F_NONBLOCK) { 1753 ret = -EAGAIN; 1754 break; 1755 } 1756 if (signal_pending(current)) { 1757 ret = -ERESTARTSYS; 1758 break; 1759 } 1760 pipe->waiting_writers++; 1761 pipe_wait(pipe); 1762 pipe->waiting_writers--; 1763 } 1764 1765 pipe_unlock(pipe); 1766 return ret; 1767 } 1768 1769 /* 1770 * Splice contents of ipipe to opipe. 1771 */ 1772 static int splice_pipe_to_pipe(struct pipe_inode_info *ipipe, 1773 struct pipe_inode_info *opipe, 1774 size_t len, unsigned int flags) 1775 { 1776 struct pipe_buffer *ibuf, *obuf; 1777 int ret = 0, nbuf; 1778 bool input_wakeup = false; 1779 1780 1781 retry: 1782 ret = ipipe_prep(ipipe, flags); 1783 if (ret) 1784 return ret; 1785 1786 ret = opipe_prep(opipe, flags); 1787 if (ret) 1788 return ret; 1789 1790 /* 1791 * Potential ABBA deadlock, work around it by ordering lock 1792 * grabbing by pipe info address. Otherwise two different processes 1793 * could deadlock (one doing tee from A -> B, the other from B -> A). 1794 */ 1795 pipe_double_lock(ipipe, opipe); 1796 1797 do { 1798 if (!opipe->readers) { 1799 send_sig(SIGPIPE, current, 0); 1800 if (!ret) 1801 ret = -EPIPE; 1802 break; 1803 } 1804 1805 if (!ipipe->nrbufs && !ipipe->writers) 1806 break; 1807 1808 /* 1809 * Cannot make any progress, because either the input 1810 * pipe is empty or the output pipe is full. 1811 */ 1812 if (!ipipe->nrbufs || opipe->nrbufs >= PIPE_BUFFERS) { 1813 /* Already processed some buffers, break */ 1814 if (ret) 1815 break; 1816 1817 if (flags & SPLICE_F_NONBLOCK) { 1818 ret = -EAGAIN; 1819 break; 1820 } 1821 1822 /* 1823 * We raced with another reader/writer and haven't 1824 * managed to process any buffers. A zero return 1825 * value means EOF, so retry instead. 1826 */ 1827 pipe_unlock(ipipe); 1828 pipe_unlock(opipe); 1829 goto retry; 1830 } 1831 1832 ibuf = ipipe->bufs + ipipe->curbuf; 1833 nbuf = (opipe->curbuf + opipe->nrbufs) % PIPE_BUFFERS; 1834 obuf = opipe->bufs + nbuf; 1835 1836 if (len >= ibuf->len) { 1837 /* 1838 * Simply move the whole buffer from ipipe to opipe 1839 */ 1840 *obuf = *ibuf; 1841 ibuf->ops = NULL; 1842 opipe->nrbufs++; 1843 ipipe->curbuf = (ipipe->curbuf + 1) % PIPE_BUFFERS; 1844 ipipe->nrbufs--; 1845 input_wakeup = true; 1846 } else { 1847 /* 1848 * Get a reference to this pipe buffer, 1849 * so we can copy the contents over. 1850 */ 1851 ibuf->ops->get(ipipe, ibuf); 1852 *obuf = *ibuf; 1853 1854 /* 1855 * Don't inherit the gift flag, we need to 1856 * prevent multiple steals of this page. 1857 */ 1858 obuf->flags &= ~PIPE_BUF_FLAG_GIFT; 1859 1860 obuf->len = len; 1861 opipe->nrbufs++; 1862 ibuf->offset += obuf->len; 1863 ibuf->len -= obuf->len; 1864 } 1865 ret += obuf->len; 1866 len -= obuf->len; 1867 } while (len); 1868 1869 pipe_unlock(ipipe); 1870 pipe_unlock(opipe); 1871 1872 /* 1873 * If we put data in the output pipe, wakeup any potential readers. 1874 */ 1875 if (ret > 0) { 1876 smp_mb(); 1877 if (waitqueue_active(&opipe->wait)) 1878 wake_up_interruptible(&opipe->wait); 1879 kill_fasync(&opipe->fasync_readers, SIGIO, POLL_IN); 1880 } 1881 if (input_wakeup) 1882 wakeup_pipe_writers(ipipe); 1883 1884 return ret; 1885 } 1886 1887 /* 1888 * Link contents of ipipe to opipe. 1889 */ 1890 static int link_pipe(struct pipe_inode_info *ipipe, 1891 struct pipe_inode_info *opipe, 1892 size_t len, unsigned int flags) 1893 { 1894 struct pipe_buffer *ibuf, *obuf; 1895 int ret = 0, i = 0, nbuf; 1896 1897 /* 1898 * Potential ABBA deadlock, work around it by ordering lock 1899 * grabbing by pipe info address. Otherwise two different processes 1900 * could deadlock (one doing tee from A -> B, the other from B -> A). 1901 */ 1902 pipe_double_lock(ipipe, opipe); 1903 1904 do { 1905 if (!opipe->readers) { 1906 send_sig(SIGPIPE, current, 0); 1907 if (!ret) 1908 ret = -EPIPE; 1909 break; 1910 } 1911 1912 /* 1913 * If we have iterated all input buffers or ran out of 1914 * output room, break. 1915 */ 1916 if (i >= ipipe->nrbufs || opipe->nrbufs >= PIPE_BUFFERS) 1917 break; 1918 1919 ibuf = ipipe->bufs + ((ipipe->curbuf + i) & (PIPE_BUFFERS - 1)); 1920 nbuf = (opipe->curbuf + opipe->nrbufs) & (PIPE_BUFFERS - 1); 1921 1922 /* 1923 * Get a reference to this pipe buffer, 1924 * so we can copy the contents over. 1925 */ 1926 ibuf->ops->get(ipipe, ibuf); 1927 1928 obuf = opipe->bufs + nbuf; 1929 *obuf = *ibuf; 1930 1931 /* 1932 * Don't inherit the gift flag, we need to 1933 * prevent multiple steals of this page. 1934 */ 1935 obuf->flags &= ~PIPE_BUF_FLAG_GIFT; 1936 1937 if (obuf->len > len) 1938 obuf->len = len; 1939 1940 opipe->nrbufs++; 1941 ret += obuf->len; 1942 len -= obuf->len; 1943 i++; 1944 } while (len); 1945 1946 /* 1947 * return EAGAIN if we have the potential of some data in the 1948 * future, otherwise just return 0 1949 */ 1950 if (!ret && ipipe->waiting_writers && (flags & SPLICE_F_NONBLOCK)) 1951 ret = -EAGAIN; 1952 1953 pipe_unlock(ipipe); 1954 pipe_unlock(opipe); 1955 1956 /* 1957 * If we put data in the output pipe, wakeup any potential readers. 1958 */ 1959 if (ret > 0) { 1960 smp_mb(); 1961 if (waitqueue_active(&opipe->wait)) 1962 wake_up_interruptible(&opipe->wait); 1963 kill_fasync(&opipe->fasync_readers, SIGIO, POLL_IN); 1964 } 1965 1966 return ret; 1967 } 1968 1969 /* 1970 * This is a tee(1) implementation that works on pipes. It doesn't copy 1971 * any data, it simply references the 'in' pages on the 'out' pipe. 1972 * The 'flags' used are the SPLICE_F_* variants, currently the only 1973 * applicable one is SPLICE_F_NONBLOCK. 1974 */ 1975 static long do_tee(struct file *in, struct file *out, size_t len, 1976 unsigned int flags) 1977 { 1978 struct pipe_inode_info *ipipe = pipe_info(in->f_path.dentry->d_inode); 1979 struct pipe_inode_info *opipe = pipe_info(out->f_path.dentry->d_inode); 1980 int ret = -EINVAL; 1981 1982 /* 1983 * Duplicate the contents of ipipe to opipe without actually 1984 * copying the data. 1985 */ 1986 if (ipipe && opipe && ipipe != opipe) { 1987 /* 1988 * Keep going, unless we encounter an error. The ipipe/opipe 1989 * ordering doesn't really matter. 1990 */ 1991 ret = ipipe_prep(ipipe, flags); 1992 if (!ret) { 1993 ret = opipe_prep(opipe, flags); 1994 if (!ret) 1995 ret = link_pipe(ipipe, opipe, len, flags); 1996 } 1997 } 1998 1999 return ret; 2000 } 2001 2002 SYSCALL_DEFINE4(tee, int, fdin, int, fdout, size_t, len, unsigned int, flags) 2003 { 2004 struct file *in; 2005 int error, fput_in; 2006 2007 if (unlikely(!len)) 2008 return 0; 2009 2010 error = -EBADF; 2011 in = fget_light(fdin, &fput_in); 2012 if (in) { 2013 if (in->f_mode & FMODE_READ) { 2014 int fput_out; 2015 struct file *out = fget_light(fdout, &fput_out); 2016 2017 if (out) { 2018 if (out->f_mode & FMODE_WRITE) 2019 error = do_tee(in, out, len, flags); 2020 fput_light(out, fput_out); 2021 } 2022 } 2023 fput_light(in, fput_in); 2024 } 2025 2026 return error; 2027 } 2028