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/export.h> 29 #include <linux/syscalls.h> 30 #include <linux/uio.h> 31 #include <linux/security.h> 32 #include <linux/gfp.h> 33 #include <linux/socket.h> 34 35 /* 36 * Attempt to steal a page from a pipe buffer. This should perhaps go into 37 * a vm helper function, it's already simplified quite a bit by the 38 * addition of remove_mapping(). If success is returned, the caller may 39 * attempt to reuse this page for another destination. 40 */ 41 static int page_cache_pipe_buf_steal(struct pipe_inode_info *pipe, 42 struct pipe_buffer *buf) 43 { 44 struct page *page = buf->page; 45 struct address_space *mapping; 46 47 lock_page(page); 48 49 mapping = page_mapping(page); 50 if (mapping) { 51 WARN_ON(!PageUptodate(page)); 52 53 /* 54 * At least for ext2 with nobh option, we need to wait on 55 * writeback completing on this page, since we'll remove it 56 * from the pagecache. Otherwise truncate wont wait on the 57 * page, allowing the disk blocks to be reused by someone else 58 * before we actually wrote our data to them. fs corruption 59 * ensues. 60 */ 61 wait_on_page_writeback(page); 62 63 if (page_has_private(page) && 64 !try_to_release_page(page, GFP_KERNEL)) 65 goto out_unlock; 66 67 /* 68 * If we succeeded in removing the mapping, set LRU flag 69 * and return good. 70 */ 71 if (remove_mapping(mapping, page)) { 72 buf->flags |= PIPE_BUF_FLAG_LRU; 73 return 0; 74 } 75 } 76 77 /* 78 * Raced with truncate or failed to remove page from current 79 * address space, unlock and return failure. 80 */ 81 out_unlock: 82 unlock_page(page); 83 return 1; 84 } 85 86 static void page_cache_pipe_buf_release(struct pipe_inode_info *pipe, 87 struct pipe_buffer *buf) 88 { 89 page_cache_release(buf->page); 90 buf->flags &= ~PIPE_BUF_FLAG_LRU; 91 } 92 93 /* 94 * Check whether the contents of buf is OK to access. Since the content 95 * is a page cache page, IO may be in flight. 96 */ 97 static int page_cache_pipe_buf_confirm(struct pipe_inode_info *pipe, 98 struct pipe_buffer *buf) 99 { 100 struct page *page = buf->page; 101 int err; 102 103 if (!PageUptodate(page)) { 104 lock_page(page); 105 106 /* 107 * Page got truncated/unhashed. This will cause a 0-byte 108 * splice, if this is the first page. 109 */ 110 if (!page->mapping) { 111 err = -ENODATA; 112 goto error; 113 } 114 115 /* 116 * Uh oh, read-error from disk. 117 */ 118 if (!PageUptodate(page)) { 119 err = -EIO; 120 goto error; 121 } 122 123 /* 124 * Page is ok afterall, we are done. 125 */ 126 unlock_page(page); 127 } 128 129 return 0; 130 error: 131 unlock_page(page); 132 return err; 133 } 134 135 const struct pipe_buf_operations page_cache_pipe_buf_ops = { 136 .can_merge = 0, 137 .map = generic_pipe_buf_map, 138 .unmap = generic_pipe_buf_unmap, 139 .confirm = page_cache_pipe_buf_confirm, 140 .release = page_cache_pipe_buf_release, 141 .steal = page_cache_pipe_buf_steal, 142 .get = generic_pipe_buf_get, 143 }; 144 145 static int user_page_pipe_buf_steal(struct pipe_inode_info *pipe, 146 struct pipe_buffer *buf) 147 { 148 if (!(buf->flags & PIPE_BUF_FLAG_GIFT)) 149 return 1; 150 151 buf->flags |= PIPE_BUF_FLAG_LRU; 152 return generic_pipe_buf_steal(pipe, buf); 153 } 154 155 static const struct pipe_buf_operations user_page_pipe_buf_ops = { 156 .can_merge = 0, 157 .map = generic_pipe_buf_map, 158 .unmap = generic_pipe_buf_unmap, 159 .confirm = generic_pipe_buf_confirm, 160 .release = page_cache_pipe_buf_release, 161 .steal = user_page_pipe_buf_steal, 162 .get = generic_pipe_buf_get, 163 }; 164 165 static void wakeup_pipe_readers(struct pipe_inode_info *pipe) 166 { 167 smp_mb(); 168 if (waitqueue_active(&pipe->wait)) 169 wake_up_interruptible(&pipe->wait); 170 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN); 171 } 172 173 /** 174 * splice_to_pipe - fill passed data into a pipe 175 * @pipe: pipe to fill 176 * @spd: data to fill 177 * 178 * Description: 179 * @spd contains a map of pages and len/offset tuples, along with 180 * the struct pipe_buf_operations associated with these pages. This 181 * function will link that data to the pipe. 182 * 183 */ 184 ssize_t splice_to_pipe(struct pipe_inode_info *pipe, 185 struct splice_pipe_desc *spd) 186 { 187 unsigned int spd_pages = spd->nr_pages; 188 int ret, do_wakeup, page_nr; 189 190 ret = 0; 191 do_wakeup = 0; 192 page_nr = 0; 193 194 pipe_lock(pipe); 195 196 for (;;) { 197 if (!pipe->readers) { 198 send_sig(SIGPIPE, current, 0); 199 if (!ret) 200 ret = -EPIPE; 201 break; 202 } 203 204 if (pipe->nrbufs < pipe->buffers) { 205 int newbuf = (pipe->curbuf + pipe->nrbufs) & (pipe->buffers - 1); 206 struct pipe_buffer *buf = pipe->bufs + newbuf; 207 208 buf->page = spd->pages[page_nr]; 209 buf->offset = spd->partial[page_nr].offset; 210 buf->len = spd->partial[page_nr].len; 211 buf->private = spd->partial[page_nr].private; 212 buf->ops = spd->ops; 213 if (spd->flags & SPLICE_F_GIFT) 214 buf->flags |= PIPE_BUF_FLAG_GIFT; 215 216 pipe->nrbufs++; 217 page_nr++; 218 ret += buf->len; 219 220 if (pipe->inode) 221 do_wakeup = 1; 222 223 if (!--spd->nr_pages) 224 break; 225 if (pipe->nrbufs < pipe->buffers) 226 continue; 227 228 break; 229 } 230 231 if (spd->flags & SPLICE_F_NONBLOCK) { 232 if (!ret) 233 ret = -EAGAIN; 234 break; 235 } 236 237 if (signal_pending(current)) { 238 if (!ret) 239 ret = -ERESTARTSYS; 240 break; 241 } 242 243 if (do_wakeup) { 244 smp_mb(); 245 if (waitqueue_active(&pipe->wait)) 246 wake_up_interruptible_sync(&pipe->wait); 247 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN); 248 do_wakeup = 0; 249 } 250 251 pipe->waiting_writers++; 252 pipe_wait(pipe); 253 pipe->waiting_writers--; 254 } 255 256 pipe_unlock(pipe); 257 258 if (do_wakeup) 259 wakeup_pipe_readers(pipe); 260 261 while (page_nr < spd_pages) 262 spd->spd_release(spd, page_nr++); 263 264 return ret; 265 } 266 267 void spd_release_page(struct splice_pipe_desc *spd, unsigned int i) 268 { 269 page_cache_release(spd->pages[i]); 270 } 271 272 /* 273 * Check if we need to grow the arrays holding pages and partial page 274 * descriptions. 275 */ 276 int splice_grow_spd(struct pipe_inode_info *pipe, struct splice_pipe_desc *spd) 277 { 278 if (pipe->buffers <= PIPE_DEF_BUFFERS) 279 return 0; 280 281 spd->pages = kmalloc(pipe->buffers * sizeof(struct page *), GFP_KERNEL); 282 spd->partial = kmalloc(pipe->buffers * sizeof(struct partial_page), GFP_KERNEL); 283 284 if (spd->pages && spd->partial) 285 return 0; 286 287 kfree(spd->pages); 288 kfree(spd->partial); 289 return -ENOMEM; 290 } 291 292 void splice_shrink_spd(struct pipe_inode_info *pipe, 293 struct splice_pipe_desc *spd) 294 { 295 if (pipe->buffers <= PIPE_DEF_BUFFERS) 296 return; 297 298 kfree(spd->pages); 299 kfree(spd->partial); 300 } 301 302 static int 303 __generic_file_splice_read(struct file *in, loff_t *ppos, 304 struct pipe_inode_info *pipe, size_t len, 305 unsigned int flags) 306 { 307 struct address_space *mapping = in->f_mapping; 308 unsigned int loff, nr_pages, req_pages; 309 struct page *pages[PIPE_DEF_BUFFERS]; 310 struct partial_page partial[PIPE_DEF_BUFFERS]; 311 struct page *page; 312 pgoff_t index, end_index; 313 loff_t isize; 314 int error, page_nr; 315 struct splice_pipe_desc spd = { 316 .pages = pages, 317 .partial = partial, 318 .flags = flags, 319 .ops = &page_cache_pipe_buf_ops, 320 .spd_release = spd_release_page, 321 }; 322 323 if (splice_grow_spd(pipe, &spd)) 324 return -ENOMEM; 325 326 index = *ppos >> PAGE_CACHE_SHIFT; 327 loff = *ppos & ~PAGE_CACHE_MASK; 328 req_pages = (len + loff + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT; 329 nr_pages = min(req_pages, pipe->buffers); 330 331 /* 332 * Lookup the (hopefully) full range of pages we need. 333 */ 334 spd.nr_pages = find_get_pages_contig(mapping, index, nr_pages, spd.pages); 335 index += spd.nr_pages; 336 337 /* 338 * If find_get_pages_contig() returned fewer pages than we needed, 339 * readahead/allocate the rest and fill in the holes. 340 */ 341 if (spd.nr_pages < nr_pages) 342 page_cache_sync_readahead(mapping, &in->f_ra, in, 343 index, req_pages - spd.nr_pages); 344 345 error = 0; 346 while (spd.nr_pages < nr_pages) { 347 /* 348 * Page could be there, find_get_pages_contig() breaks on 349 * the first hole. 350 */ 351 page = find_get_page(mapping, index); 352 if (!page) { 353 /* 354 * page didn't exist, allocate one. 355 */ 356 page = page_cache_alloc_cold(mapping); 357 if (!page) 358 break; 359 360 error = add_to_page_cache_lru(page, mapping, index, 361 GFP_KERNEL); 362 if (unlikely(error)) { 363 page_cache_release(page); 364 if (error == -EEXIST) 365 continue; 366 break; 367 } 368 /* 369 * add_to_page_cache() locks the page, unlock it 370 * to avoid convoluting the logic below even more. 371 */ 372 unlock_page(page); 373 } 374 375 spd.pages[spd.nr_pages++] = page; 376 index++; 377 } 378 379 /* 380 * Now loop over the map and see if we need to start IO on any 381 * pages, fill in the partial map, etc. 382 */ 383 index = *ppos >> PAGE_CACHE_SHIFT; 384 nr_pages = spd.nr_pages; 385 spd.nr_pages = 0; 386 for (page_nr = 0; page_nr < nr_pages; page_nr++) { 387 unsigned int this_len; 388 389 if (!len) 390 break; 391 392 /* 393 * this_len is the max we'll use from this page 394 */ 395 this_len = min_t(unsigned long, len, PAGE_CACHE_SIZE - loff); 396 page = spd.pages[page_nr]; 397 398 if (PageReadahead(page)) 399 page_cache_async_readahead(mapping, &in->f_ra, in, 400 page, index, req_pages - page_nr); 401 402 /* 403 * If the page isn't uptodate, we may need to start io on it 404 */ 405 if (!PageUptodate(page)) { 406 lock_page(page); 407 408 /* 409 * Page was truncated, or invalidated by the 410 * filesystem. Redo the find/create, but this time the 411 * page is kept locked, so there's no chance of another 412 * race with truncate/invalidate. 413 */ 414 if (!page->mapping) { 415 unlock_page(page); 416 page = find_or_create_page(mapping, index, 417 mapping_gfp_mask(mapping)); 418 419 if (!page) { 420 error = -ENOMEM; 421 break; 422 } 423 page_cache_release(spd.pages[page_nr]); 424 spd.pages[page_nr] = page; 425 } 426 /* 427 * page was already under io and is now done, great 428 */ 429 if (PageUptodate(page)) { 430 unlock_page(page); 431 goto fill_it; 432 } 433 434 /* 435 * need to read in the page 436 */ 437 error = mapping->a_ops->readpage(in, page); 438 if (unlikely(error)) { 439 /* 440 * We really should re-lookup the page here, 441 * but it complicates things a lot. Instead 442 * lets just do what we already stored, and 443 * we'll get it the next time we are called. 444 */ 445 if (error == AOP_TRUNCATED_PAGE) 446 error = 0; 447 448 break; 449 } 450 } 451 fill_it: 452 /* 453 * i_size must be checked after PageUptodate. 454 */ 455 isize = i_size_read(mapping->host); 456 end_index = (isize - 1) >> PAGE_CACHE_SHIFT; 457 if (unlikely(!isize || index > end_index)) 458 break; 459 460 /* 461 * if this is the last page, see if we need to shrink 462 * the length and stop 463 */ 464 if (end_index == index) { 465 unsigned int plen; 466 467 /* 468 * max good bytes in this page 469 */ 470 plen = ((isize - 1) & ~PAGE_CACHE_MASK) + 1; 471 if (plen <= loff) 472 break; 473 474 /* 475 * force quit after adding this page 476 */ 477 this_len = min(this_len, plen - loff); 478 len = this_len; 479 } 480 481 spd.partial[page_nr].offset = loff; 482 spd.partial[page_nr].len = this_len; 483 len -= this_len; 484 loff = 0; 485 spd.nr_pages++; 486 index++; 487 } 488 489 /* 490 * Release any pages at the end, if we quit early. 'page_nr' is how far 491 * we got, 'nr_pages' is how many pages are in the map. 492 */ 493 while (page_nr < nr_pages) 494 page_cache_release(spd.pages[page_nr++]); 495 in->f_ra.prev_pos = (loff_t)index << PAGE_CACHE_SHIFT; 496 497 if (spd.nr_pages) 498 error = splice_to_pipe(pipe, &spd); 499 500 splice_shrink_spd(pipe, &spd); 501 return error; 502 } 503 504 /** 505 * generic_file_splice_read - splice data from file to a pipe 506 * @in: file to splice from 507 * @ppos: position in @in 508 * @pipe: pipe to splice to 509 * @len: number of bytes to splice 510 * @flags: splice modifier flags 511 * 512 * Description: 513 * Will read pages from given file and fill them into a pipe. Can be 514 * used as long as the address_space operations for the source implements 515 * a readpage() hook. 516 * 517 */ 518 ssize_t generic_file_splice_read(struct file *in, loff_t *ppos, 519 struct pipe_inode_info *pipe, size_t len, 520 unsigned int flags) 521 { 522 loff_t isize, left; 523 int ret; 524 525 isize = i_size_read(in->f_mapping->host); 526 if (unlikely(*ppos >= isize)) 527 return 0; 528 529 left = isize - *ppos; 530 if (unlikely(left < len)) 531 len = left; 532 533 ret = __generic_file_splice_read(in, ppos, pipe, len, flags); 534 if (ret > 0) { 535 *ppos += ret; 536 file_accessed(in); 537 } 538 539 return ret; 540 } 541 EXPORT_SYMBOL(generic_file_splice_read); 542 543 static const struct pipe_buf_operations default_pipe_buf_ops = { 544 .can_merge = 0, 545 .map = generic_pipe_buf_map, 546 .unmap = generic_pipe_buf_unmap, 547 .confirm = generic_pipe_buf_confirm, 548 .release = generic_pipe_buf_release, 549 .steal = generic_pipe_buf_steal, 550 .get = generic_pipe_buf_get, 551 }; 552 553 static ssize_t kernel_readv(struct file *file, const struct iovec *vec, 554 unsigned long vlen, loff_t offset) 555 { 556 mm_segment_t old_fs; 557 loff_t pos = offset; 558 ssize_t res; 559 560 old_fs = get_fs(); 561 set_fs(get_ds()); 562 /* The cast to a user pointer is valid due to the set_fs() */ 563 res = vfs_readv(file, (const struct iovec __user *)vec, vlen, &pos); 564 set_fs(old_fs); 565 566 return res; 567 } 568 569 static ssize_t kernel_write(struct file *file, const char *buf, size_t count, 570 loff_t pos) 571 { 572 mm_segment_t old_fs; 573 ssize_t res; 574 575 old_fs = get_fs(); 576 set_fs(get_ds()); 577 /* The cast to a user pointer is valid due to the set_fs() */ 578 res = vfs_write(file, (const char __user *)buf, count, &pos); 579 set_fs(old_fs); 580 581 return res; 582 } 583 584 ssize_t default_file_splice_read(struct file *in, loff_t *ppos, 585 struct pipe_inode_info *pipe, size_t len, 586 unsigned int flags) 587 { 588 unsigned int nr_pages; 589 unsigned int nr_freed; 590 size_t offset; 591 struct page *pages[PIPE_DEF_BUFFERS]; 592 struct partial_page partial[PIPE_DEF_BUFFERS]; 593 struct iovec *vec, __vec[PIPE_DEF_BUFFERS]; 594 ssize_t res; 595 size_t this_len; 596 int error; 597 int i; 598 struct splice_pipe_desc spd = { 599 .pages = pages, 600 .partial = partial, 601 .flags = flags, 602 .ops = &default_pipe_buf_ops, 603 .spd_release = spd_release_page, 604 }; 605 606 if (splice_grow_spd(pipe, &spd)) 607 return -ENOMEM; 608 609 res = -ENOMEM; 610 vec = __vec; 611 if (pipe->buffers > PIPE_DEF_BUFFERS) { 612 vec = kmalloc(pipe->buffers * sizeof(struct iovec), GFP_KERNEL); 613 if (!vec) 614 goto shrink_ret; 615 } 616 617 offset = *ppos & ~PAGE_CACHE_MASK; 618 nr_pages = (len + offset + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT; 619 620 for (i = 0; i < nr_pages && i < pipe->buffers && len; i++) { 621 struct page *page; 622 623 page = alloc_page(GFP_USER); 624 error = -ENOMEM; 625 if (!page) 626 goto err; 627 628 this_len = min_t(size_t, len, PAGE_CACHE_SIZE - offset); 629 vec[i].iov_base = (void __user *) page_address(page); 630 vec[i].iov_len = this_len; 631 spd.pages[i] = page; 632 spd.nr_pages++; 633 len -= this_len; 634 offset = 0; 635 } 636 637 res = kernel_readv(in, vec, spd.nr_pages, *ppos); 638 if (res < 0) { 639 error = res; 640 goto err; 641 } 642 643 error = 0; 644 if (!res) 645 goto err; 646 647 nr_freed = 0; 648 for (i = 0; i < spd.nr_pages; i++) { 649 this_len = min_t(size_t, vec[i].iov_len, res); 650 spd.partial[i].offset = 0; 651 spd.partial[i].len = this_len; 652 if (!this_len) { 653 __free_page(spd.pages[i]); 654 spd.pages[i] = NULL; 655 nr_freed++; 656 } 657 res -= this_len; 658 } 659 spd.nr_pages -= nr_freed; 660 661 res = splice_to_pipe(pipe, &spd); 662 if (res > 0) 663 *ppos += res; 664 665 shrink_ret: 666 if (vec != __vec) 667 kfree(vec); 668 splice_shrink_spd(pipe, &spd); 669 return res; 670 671 err: 672 for (i = 0; i < spd.nr_pages; i++) 673 __free_page(spd.pages[i]); 674 675 res = error; 676 goto shrink_ret; 677 } 678 EXPORT_SYMBOL(default_file_splice_read); 679 680 /* 681 * Send 'sd->len' bytes to socket from 'sd->file' at position 'sd->pos' 682 * using sendpage(). Return the number of bytes sent. 683 */ 684 static int pipe_to_sendpage(struct pipe_inode_info *pipe, 685 struct pipe_buffer *buf, struct splice_desc *sd) 686 { 687 struct file *file = sd->u.file; 688 loff_t pos = sd->pos; 689 int more; 690 691 if (!likely(file->f_op && file->f_op->sendpage)) 692 return -EINVAL; 693 694 more = (sd->flags & SPLICE_F_MORE) ? MSG_MORE : 0; 695 if (sd->len < sd->total_len) 696 more |= MSG_SENDPAGE_NOTLAST; 697 return file->f_op->sendpage(file, buf->page, buf->offset, 698 sd->len, &pos, more); 699 } 700 701 /* 702 * This is a little more tricky than the file -> pipe splicing. There are 703 * basically three cases: 704 * 705 * - Destination page already exists in the address space and there 706 * are users of it. For that case we have no other option that 707 * copying the data. Tough luck. 708 * - Destination page already exists in the address space, but there 709 * are no users of it. Make sure it's uptodate, then drop it. Fall 710 * through to last case. 711 * - Destination page does not exist, we can add the pipe page to 712 * the page cache and avoid the copy. 713 * 714 * If asked to move pages to the output file (SPLICE_F_MOVE is set in 715 * sd->flags), we attempt to migrate pages from the pipe to the output 716 * file address space page cache. This is possible if no one else has 717 * the pipe page referenced outside of the pipe and page cache. If 718 * SPLICE_F_MOVE isn't set, or we cannot move the page, we simply create 719 * a new page in the output file page cache and fill/dirty that. 720 */ 721 int pipe_to_file(struct pipe_inode_info *pipe, struct pipe_buffer *buf, 722 struct splice_desc *sd) 723 { 724 struct file *file = sd->u.file; 725 struct address_space *mapping = file->f_mapping; 726 unsigned int offset, this_len; 727 struct page *page; 728 void *fsdata; 729 int ret; 730 731 offset = sd->pos & ~PAGE_CACHE_MASK; 732 733 this_len = sd->len; 734 if (this_len + offset > PAGE_CACHE_SIZE) 735 this_len = PAGE_CACHE_SIZE - offset; 736 737 ret = pagecache_write_begin(file, mapping, sd->pos, this_len, 738 AOP_FLAG_UNINTERRUPTIBLE, &page, &fsdata); 739 if (unlikely(ret)) 740 goto out; 741 742 if (buf->page != page) { 743 char *src = buf->ops->map(pipe, buf, 1); 744 char *dst = kmap_atomic(page); 745 746 memcpy(dst + offset, src + buf->offset, this_len); 747 flush_dcache_page(page); 748 kunmap_atomic(dst); 749 buf->ops->unmap(pipe, buf, src); 750 } 751 ret = pagecache_write_end(file, mapping, sd->pos, this_len, this_len, 752 page, fsdata); 753 out: 754 return ret; 755 } 756 EXPORT_SYMBOL(pipe_to_file); 757 758 static void wakeup_pipe_writers(struct pipe_inode_info *pipe) 759 { 760 smp_mb(); 761 if (waitqueue_active(&pipe->wait)) 762 wake_up_interruptible(&pipe->wait); 763 kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT); 764 } 765 766 /** 767 * splice_from_pipe_feed - feed available data from a pipe to a file 768 * @pipe: pipe to splice from 769 * @sd: information to @actor 770 * @actor: handler that splices the data 771 * 772 * Description: 773 * This function loops over the pipe and calls @actor to do the 774 * actual moving of a single struct pipe_buffer to the desired 775 * destination. It returns when there's no more buffers left in 776 * the pipe or if the requested number of bytes (@sd->total_len) 777 * have been copied. It returns a positive number (one) if the 778 * pipe needs to be filled with more data, zero if the required 779 * number of bytes have been copied and -errno on error. 780 * 781 * This, together with splice_from_pipe_{begin,end,next}, may be 782 * used to implement the functionality of __splice_from_pipe() when 783 * locking is required around copying the pipe buffers to the 784 * destination. 785 */ 786 int splice_from_pipe_feed(struct pipe_inode_info *pipe, struct splice_desc *sd, 787 splice_actor *actor) 788 { 789 int ret; 790 791 while (pipe->nrbufs) { 792 struct pipe_buffer *buf = pipe->bufs + pipe->curbuf; 793 const struct pipe_buf_operations *ops = buf->ops; 794 795 sd->len = buf->len; 796 if (sd->len > sd->total_len) 797 sd->len = sd->total_len; 798 799 ret = buf->ops->confirm(pipe, buf); 800 if (unlikely(ret)) { 801 if (ret == -ENODATA) 802 ret = 0; 803 return ret; 804 } 805 806 ret = actor(pipe, buf, sd); 807 if (ret <= 0) 808 return ret; 809 810 buf->offset += ret; 811 buf->len -= ret; 812 813 sd->num_spliced += ret; 814 sd->len -= ret; 815 sd->pos += ret; 816 sd->total_len -= ret; 817 818 if (!buf->len) { 819 buf->ops = NULL; 820 ops->release(pipe, buf); 821 pipe->curbuf = (pipe->curbuf + 1) & (pipe->buffers - 1); 822 pipe->nrbufs--; 823 if (pipe->inode) 824 sd->need_wakeup = true; 825 } 826 827 if (!sd->total_len) 828 return 0; 829 } 830 831 return 1; 832 } 833 EXPORT_SYMBOL(splice_from_pipe_feed); 834 835 /** 836 * splice_from_pipe_next - wait for some data to splice from 837 * @pipe: pipe to splice from 838 * @sd: information about the splice operation 839 * 840 * Description: 841 * This function will wait for some data and return a positive 842 * value (one) if pipe buffers are available. It will return zero 843 * or -errno if no more data needs to be spliced. 844 */ 845 int splice_from_pipe_next(struct pipe_inode_info *pipe, struct splice_desc *sd) 846 { 847 while (!pipe->nrbufs) { 848 if (!pipe->writers) 849 return 0; 850 851 if (!pipe->waiting_writers && sd->num_spliced) 852 return 0; 853 854 if (sd->flags & SPLICE_F_NONBLOCK) 855 return -EAGAIN; 856 857 if (signal_pending(current)) 858 return -ERESTARTSYS; 859 860 if (sd->need_wakeup) { 861 wakeup_pipe_writers(pipe); 862 sd->need_wakeup = false; 863 } 864 865 pipe_wait(pipe); 866 } 867 868 return 1; 869 } 870 EXPORT_SYMBOL(splice_from_pipe_next); 871 872 /** 873 * splice_from_pipe_begin - start splicing from pipe 874 * @sd: information about the splice operation 875 * 876 * Description: 877 * This function should be called before a loop containing 878 * splice_from_pipe_next() and splice_from_pipe_feed() to 879 * initialize the necessary fields of @sd. 880 */ 881 void splice_from_pipe_begin(struct splice_desc *sd) 882 { 883 sd->num_spliced = 0; 884 sd->need_wakeup = false; 885 } 886 EXPORT_SYMBOL(splice_from_pipe_begin); 887 888 /** 889 * splice_from_pipe_end - finish splicing from pipe 890 * @pipe: pipe to splice from 891 * @sd: information about the splice operation 892 * 893 * Description: 894 * This function will wake up pipe writers if necessary. It should 895 * be called after a loop containing splice_from_pipe_next() and 896 * splice_from_pipe_feed(). 897 */ 898 void splice_from_pipe_end(struct pipe_inode_info *pipe, struct splice_desc *sd) 899 { 900 if (sd->need_wakeup) 901 wakeup_pipe_writers(pipe); 902 } 903 EXPORT_SYMBOL(splice_from_pipe_end); 904 905 /** 906 * __splice_from_pipe - splice data from a pipe to given actor 907 * @pipe: pipe to splice from 908 * @sd: information to @actor 909 * @actor: handler that splices the data 910 * 911 * Description: 912 * This function does little more than loop over the pipe and call 913 * @actor to do the actual moving of a single struct pipe_buffer to 914 * the desired destination. See pipe_to_file, pipe_to_sendpage, or 915 * pipe_to_user. 916 * 917 */ 918 ssize_t __splice_from_pipe(struct pipe_inode_info *pipe, struct splice_desc *sd, 919 splice_actor *actor) 920 { 921 int ret; 922 923 splice_from_pipe_begin(sd); 924 do { 925 ret = splice_from_pipe_next(pipe, sd); 926 if (ret > 0) 927 ret = splice_from_pipe_feed(pipe, sd, actor); 928 } while (ret > 0); 929 splice_from_pipe_end(pipe, sd); 930 931 return sd->num_spliced ? sd->num_spliced : ret; 932 } 933 EXPORT_SYMBOL(__splice_from_pipe); 934 935 /** 936 * splice_from_pipe - splice data from a pipe to a file 937 * @pipe: pipe to splice from 938 * @out: file to splice to 939 * @ppos: position in @out 940 * @len: how many bytes to splice 941 * @flags: splice modifier flags 942 * @actor: handler that splices the data 943 * 944 * Description: 945 * See __splice_from_pipe. This function locks the pipe inode, 946 * otherwise it's identical to __splice_from_pipe(). 947 * 948 */ 949 ssize_t splice_from_pipe(struct pipe_inode_info *pipe, struct file *out, 950 loff_t *ppos, size_t len, unsigned int flags, 951 splice_actor *actor) 952 { 953 ssize_t ret; 954 struct splice_desc sd = { 955 .total_len = len, 956 .flags = flags, 957 .pos = *ppos, 958 .u.file = out, 959 }; 960 961 pipe_lock(pipe); 962 ret = __splice_from_pipe(pipe, &sd, actor); 963 pipe_unlock(pipe); 964 965 return ret; 966 } 967 968 /** 969 * generic_file_splice_write - splice data from a pipe to a file 970 * @pipe: pipe info 971 * @out: file to write to 972 * @ppos: position in @out 973 * @len: number of bytes to splice 974 * @flags: splice modifier flags 975 * 976 * Description: 977 * Will either move or copy pages (determined by @flags options) from 978 * the given pipe inode to the given file. 979 * 980 */ 981 ssize_t 982 generic_file_splice_write(struct pipe_inode_info *pipe, struct file *out, 983 loff_t *ppos, size_t len, unsigned int flags) 984 { 985 struct address_space *mapping = out->f_mapping; 986 struct inode *inode = mapping->host; 987 struct splice_desc sd = { 988 .total_len = len, 989 .flags = flags, 990 .pos = *ppos, 991 .u.file = out, 992 }; 993 ssize_t ret; 994 995 pipe_lock(pipe); 996 997 splice_from_pipe_begin(&sd); 998 do { 999 ret = splice_from_pipe_next(pipe, &sd); 1000 if (ret <= 0) 1001 break; 1002 1003 mutex_lock_nested(&inode->i_mutex, I_MUTEX_CHILD); 1004 ret = file_remove_suid(out); 1005 if (!ret) { 1006 ret = file_update_time(out); 1007 if (!ret) 1008 ret = splice_from_pipe_feed(pipe, &sd, 1009 pipe_to_file); 1010 } 1011 mutex_unlock(&inode->i_mutex); 1012 } while (ret > 0); 1013 splice_from_pipe_end(pipe, &sd); 1014 1015 pipe_unlock(pipe); 1016 1017 if (sd.num_spliced) 1018 ret = sd.num_spliced; 1019 1020 if (ret > 0) { 1021 unsigned long nr_pages; 1022 int err; 1023 1024 nr_pages = (ret + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT; 1025 1026 err = generic_write_sync(out, *ppos, ret); 1027 if (err) 1028 ret = err; 1029 else 1030 *ppos += ret; 1031 balance_dirty_pages_ratelimited_nr(mapping, nr_pages); 1032 } 1033 1034 return ret; 1035 } 1036 1037 EXPORT_SYMBOL(generic_file_splice_write); 1038 1039 static int write_pipe_buf(struct pipe_inode_info *pipe, struct pipe_buffer *buf, 1040 struct splice_desc *sd) 1041 { 1042 int ret; 1043 void *data; 1044 1045 data = buf->ops->map(pipe, buf, 0); 1046 ret = kernel_write(sd->u.file, data + buf->offset, sd->len, sd->pos); 1047 buf->ops->unmap(pipe, buf, data); 1048 1049 return ret; 1050 } 1051 1052 static ssize_t default_file_splice_write(struct pipe_inode_info *pipe, 1053 struct file *out, loff_t *ppos, 1054 size_t len, unsigned int flags) 1055 { 1056 ssize_t ret; 1057 1058 ret = splice_from_pipe(pipe, out, ppos, len, flags, write_pipe_buf); 1059 if (ret > 0) 1060 *ppos += ret; 1061 1062 return ret; 1063 } 1064 1065 /** 1066 * generic_splice_sendpage - splice data from a pipe to a socket 1067 * @pipe: pipe to splice from 1068 * @out: socket to write to 1069 * @ppos: position in @out 1070 * @len: number of bytes to splice 1071 * @flags: splice modifier flags 1072 * 1073 * Description: 1074 * Will send @len bytes from the pipe to a network socket. No data copying 1075 * is involved. 1076 * 1077 */ 1078 ssize_t generic_splice_sendpage(struct pipe_inode_info *pipe, struct file *out, 1079 loff_t *ppos, size_t len, unsigned int flags) 1080 { 1081 return splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_sendpage); 1082 } 1083 1084 EXPORT_SYMBOL(generic_splice_sendpage); 1085 1086 /* 1087 * Attempt to initiate a splice from pipe to file. 1088 */ 1089 static long do_splice_from(struct pipe_inode_info *pipe, struct file *out, 1090 loff_t *ppos, size_t len, unsigned int flags) 1091 { 1092 ssize_t (*splice_write)(struct pipe_inode_info *, struct file *, 1093 loff_t *, size_t, unsigned int); 1094 int ret; 1095 1096 if (unlikely(!(out->f_mode & FMODE_WRITE))) 1097 return -EBADF; 1098 1099 if (unlikely(out->f_flags & O_APPEND)) 1100 return -EINVAL; 1101 1102 ret = rw_verify_area(WRITE, out, ppos, len); 1103 if (unlikely(ret < 0)) 1104 return ret; 1105 1106 if (out->f_op && out->f_op->splice_write) 1107 splice_write = out->f_op->splice_write; 1108 else 1109 splice_write = default_file_splice_write; 1110 1111 return splice_write(pipe, out, ppos, len, flags); 1112 } 1113 1114 /* 1115 * Attempt to initiate a splice from a file to a pipe. 1116 */ 1117 static long do_splice_to(struct file *in, loff_t *ppos, 1118 struct pipe_inode_info *pipe, size_t len, 1119 unsigned int flags) 1120 { 1121 ssize_t (*splice_read)(struct file *, loff_t *, 1122 struct pipe_inode_info *, size_t, unsigned int); 1123 int ret; 1124 1125 if (unlikely(!(in->f_mode & FMODE_READ))) 1126 return -EBADF; 1127 1128 ret = rw_verify_area(READ, in, ppos, len); 1129 if (unlikely(ret < 0)) 1130 return ret; 1131 1132 if (in->f_op && in->f_op->splice_read) 1133 splice_read = in->f_op->splice_read; 1134 else 1135 splice_read = default_file_splice_read; 1136 1137 return splice_read(in, ppos, pipe, len, flags); 1138 } 1139 1140 /** 1141 * splice_direct_to_actor - splices data directly between two non-pipes 1142 * @in: file to splice from 1143 * @sd: actor information on where to splice to 1144 * @actor: handles the data splicing 1145 * 1146 * Description: 1147 * This is a special case helper to splice directly between two 1148 * points, without requiring an explicit pipe. Internally an allocated 1149 * pipe is cached in the process, and reused during the lifetime of 1150 * that process. 1151 * 1152 */ 1153 ssize_t splice_direct_to_actor(struct file *in, struct splice_desc *sd, 1154 splice_direct_actor *actor) 1155 { 1156 struct pipe_inode_info *pipe; 1157 long ret, bytes; 1158 umode_t i_mode; 1159 size_t len; 1160 int i, flags; 1161 1162 /* 1163 * We require the input being a regular file, as we don't want to 1164 * randomly drop data for eg socket -> socket splicing. Use the 1165 * piped splicing for that! 1166 */ 1167 i_mode = in->f_path.dentry->d_inode->i_mode; 1168 if (unlikely(!S_ISREG(i_mode) && !S_ISBLK(i_mode))) 1169 return -EINVAL; 1170 1171 /* 1172 * neither in nor out is a pipe, setup an internal pipe attached to 1173 * 'out' and transfer the wanted data from 'in' to 'out' through that 1174 */ 1175 pipe = current->splice_pipe; 1176 if (unlikely(!pipe)) { 1177 pipe = alloc_pipe_info(NULL); 1178 if (!pipe) 1179 return -ENOMEM; 1180 1181 /* 1182 * We don't have an immediate reader, but we'll read the stuff 1183 * out of the pipe right after the splice_to_pipe(). So set 1184 * PIPE_READERS appropriately. 1185 */ 1186 pipe->readers = 1; 1187 1188 current->splice_pipe = pipe; 1189 } 1190 1191 /* 1192 * Do the splice. 1193 */ 1194 ret = 0; 1195 bytes = 0; 1196 len = sd->total_len; 1197 flags = sd->flags; 1198 1199 /* 1200 * Don't block on output, we have to drain the direct pipe. 1201 */ 1202 sd->flags &= ~SPLICE_F_NONBLOCK; 1203 1204 while (len) { 1205 size_t read_len; 1206 loff_t pos = sd->pos, prev_pos = pos; 1207 1208 ret = do_splice_to(in, &pos, pipe, len, flags); 1209 if (unlikely(ret <= 0)) 1210 goto out_release; 1211 1212 read_len = ret; 1213 sd->total_len = read_len; 1214 1215 /* 1216 * NOTE: nonblocking mode only applies to the input. We 1217 * must not do the output in nonblocking mode as then we 1218 * could get stuck data in the internal pipe: 1219 */ 1220 ret = actor(pipe, sd); 1221 if (unlikely(ret <= 0)) { 1222 sd->pos = prev_pos; 1223 goto out_release; 1224 } 1225 1226 bytes += ret; 1227 len -= ret; 1228 sd->pos = pos; 1229 1230 if (ret < read_len) { 1231 sd->pos = prev_pos + ret; 1232 goto out_release; 1233 } 1234 } 1235 1236 done: 1237 pipe->nrbufs = pipe->curbuf = 0; 1238 file_accessed(in); 1239 return bytes; 1240 1241 out_release: 1242 /* 1243 * If we did an incomplete transfer we must release 1244 * the pipe buffers in question: 1245 */ 1246 for (i = 0; i < pipe->buffers; i++) { 1247 struct pipe_buffer *buf = pipe->bufs + i; 1248 1249 if (buf->ops) { 1250 buf->ops->release(pipe, buf); 1251 buf->ops = NULL; 1252 } 1253 } 1254 1255 if (!bytes) 1256 bytes = ret; 1257 1258 goto done; 1259 } 1260 EXPORT_SYMBOL(splice_direct_to_actor); 1261 1262 static int direct_splice_actor(struct pipe_inode_info *pipe, 1263 struct splice_desc *sd) 1264 { 1265 struct file *file = sd->u.file; 1266 1267 return do_splice_from(pipe, file, &file->f_pos, sd->total_len, 1268 sd->flags); 1269 } 1270 1271 /** 1272 * do_splice_direct - splices data directly between two files 1273 * @in: file to splice from 1274 * @ppos: input file offset 1275 * @out: file to splice to 1276 * @len: number of bytes to splice 1277 * @flags: splice modifier flags 1278 * 1279 * Description: 1280 * For use by do_sendfile(). splice can easily emulate sendfile, but 1281 * doing it in the application would incur an extra system call 1282 * (splice in + splice out, as compared to just sendfile()). So this helper 1283 * can splice directly through a process-private pipe. 1284 * 1285 */ 1286 long do_splice_direct(struct file *in, loff_t *ppos, struct file *out, 1287 size_t len, unsigned int flags) 1288 { 1289 struct splice_desc sd = { 1290 .len = len, 1291 .total_len = len, 1292 .flags = flags, 1293 .pos = *ppos, 1294 .u.file = out, 1295 }; 1296 long ret; 1297 1298 ret = splice_direct_to_actor(in, &sd, direct_splice_actor); 1299 if (ret > 0) 1300 *ppos = sd.pos; 1301 1302 return ret; 1303 } 1304 1305 static int splice_pipe_to_pipe(struct pipe_inode_info *ipipe, 1306 struct pipe_inode_info *opipe, 1307 size_t len, unsigned int flags); 1308 1309 /* 1310 * Determine where to splice to/from. 1311 */ 1312 static long do_splice(struct file *in, loff_t __user *off_in, 1313 struct file *out, loff_t __user *off_out, 1314 size_t len, unsigned int flags) 1315 { 1316 struct pipe_inode_info *ipipe; 1317 struct pipe_inode_info *opipe; 1318 loff_t offset, *off; 1319 long ret; 1320 1321 ipipe = get_pipe_info(in); 1322 opipe = get_pipe_info(out); 1323 1324 if (ipipe && opipe) { 1325 if (off_in || off_out) 1326 return -ESPIPE; 1327 1328 if (!(in->f_mode & FMODE_READ)) 1329 return -EBADF; 1330 1331 if (!(out->f_mode & FMODE_WRITE)) 1332 return -EBADF; 1333 1334 /* Splicing to self would be fun, but... */ 1335 if (ipipe == opipe) 1336 return -EINVAL; 1337 1338 return splice_pipe_to_pipe(ipipe, opipe, len, flags); 1339 } 1340 1341 if (ipipe) { 1342 if (off_in) 1343 return -ESPIPE; 1344 if (off_out) { 1345 if (!(out->f_mode & FMODE_PWRITE)) 1346 return -EINVAL; 1347 if (copy_from_user(&offset, off_out, sizeof(loff_t))) 1348 return -EFAULT; 1349 off = &offset; 1350 } else 1351 off = &out->f_pos; 1352 1353 ret = do_splice_from(ipipe, out, off, len, flags); 1354 1355 if (off_out && copy_to_user(off_out, off, sizeof(loff_t))) 1356 ret = -EFAULT; 1357 1358 return ret; 1359 } 1360 1361 if (opipe) { 1362 if (off_out) 1363 return -ESPIPE; 1364 if (off_in) { 1365 if (!(in->f_mode & FMODE_PREAD)) 1366 return -EINVAL; 1367 if (copy_from_user(&offset, off_in, sizeof(loff_t))) 1368 return -EFAULT; 1369 off = &offset; 1370 } else 1371 off = &in->f_pos; 1372 1373 ret = do_splice_to(in, off, opipe, len, flags); 1374 1375 if (off_in && copy_to_user(off_in, off, sizeof(loff_t))) 1376 ret = -EFAULT; 1377 1378 return ret; 1379 } 1380 1381 return -EINVAL; 1382 } 1383 1384 /* 1385 * Map an iov into an array of pages and offset/length tupples. With the 1386 * partial_page structure, we can map several non-contiguous ranges into 1387 * our ones pages[] map instead of splitting that operation into pieces. 1388 * Could easily be exported as a generic helper for other users, in which 1389 * case one would probably want to add a 'max_nr_pages' parameter as well. 1390 */ 1391 static int get_iovec_page_array(const struct iovec __user *iov, 1392 unsigned int nr_vecs, struct page **pages, 1393 struct partial_page *partial, bool aligned, 1394 unsigned int pipe_buffers) 1395 { 1396 int buffers = 0, error = 0; 1397 1398 while (nr_vecs) { 1399 unsigned long off, npages; 1400 struct iovec entry; 1401 void __user *base; 1402 size_t len; 1403 int i; 1404 1405 error = -EFAULT; 1406 if (copy_from_user(&entry, iov, sizeof(entry))) 1407 break; 1408 1409 base = entry.iov_base; 1410 len = entry.iov_len; 1411 1412 /* 1413 * Sanity check this iovec. 0 read succeeds. 1414 */ 1415 error = 0; 1416 if (unlikely(!len)) 1417 break; 1418 error = -EFAULT; 1419 if (!access_ok(VERIFY_READ, base, len)) 1420 break; 1421 1422 /* 1423 * Get this base offset and number of pages, then map 1424 * in the user pages. 1425 */ 1426 off = (unsigned long) base & ~PAGE_MASK; 1427 1428 /* 1429 * If asked for alignment, the offset must be zero and the 1430 * length a multiple of the PAGE_SIZE. 1431 */ 1432 error = -EINVAL; 1433 if (aligned && (off || len & ~PAGE_MASK)) 1434 break; 1435 1436 npages = (off + len + PAGE_SIZE - 1) >> PAGE_SHIFT; 1437 if (npages > pipe_buffers - buffers) 1438 npages = pipe_buffers - buffers; 1439 1440 error = get_user_pages_fast((unsigned long)base, npages, 1441 0, &pages[buffers]); 1442 1443 if (unlikely(error <= 0)) 1444 break; 1445 1446 /* 1447 * Fill this contiguous range into the partial page map. 1448 */ 1449 for (i = 0; i < error; i++) { 1450 const int plen = min_t(size_t, len, PAGE_SIZE - off); 1451 1452 partial[buffers].offset = off; 1453 partial[buffers].len = plen; 1454 1455 off = 0; 1456 len -= plen; 1457 buffers++; 1458 } 1459 1460 /* 1461 * We didn't complete this iov, stop here since it probably 1462 * means we have to move some of this into a pipe to 1463 * be able to continue. 1464 */ 1465 if (len) 1466 break; 1467 1468 /* 1469 * Don't continue if we mapped fewer pages than we asked for, 1470 * or if we mapped the max number of pages that we have 1471 * room for. 1472 */ 1473 if (error < npages || buffers == pipe_buffers) 1474 break; 1475 1476 nr_vecs--; 1477 iov++; 1478 } 1479 1480 if (buffers) 1481 return buffers; 1482 1483 return error; 1484 } 1485 1486 static int pipe_to_user(struct pipe_inode_info *pipe, struct pipe_buffer *buf, 1487 struct splice_desc *sd) 1488 { 1489 char *src; 1490 int ret; 1491 1492 /* 1493 * See if we can use the atomic maps, by prefaulting in the 1494 * pages and doing an atomic copy 1495 */ 1496 if (!fault_in_pages_writeable(sd->u.userptr, sd->len)) { 1497 src = buf->ops->map(pipe, buf, 1); 1498 ret = __copy_to_user_inatomic(sd->u.userptr, src + buf->offset, 1499 sd->len); 1500 buf->ops->unmap(pipe, buf, src); 1501 if (!ret) { 1502 ret = sd->len; 1503 goto out; 1504 } 1505 } 1506 1507 /* 1508 * No dice, use slow non-atomic map and copy 1509 */ 1510 src = buf->ops->map(pipe, buf, 0); 1511 1512 ret = sd->len; 1513 if (copy_to_user(sd->u.userptr, src + buf->offset, sd->len)) 1514 ret = -EFAULT; 1515 1516 buf->ops->unmap(pipe, buf, src); 1517 out: 1518 if (ret > 0) 1519 sd->u.userptr += ret; 1520 return ret; 1521 } 1522 1523 /* 1524 * For lack of a better implementation, implement vmsplice() to userspace 1525 * as a simple copy of the pipes pages to the user iov. 1526 */ 1527 static long vmsplice_to_user(struct file *file, const struct iovec __user *iov, 1528 unsigned long nr_segs, unsigned int flags) 1529 { 1530 struct pipe_inode_info *pipe; 1531 struct splice_desc sd; 1532 ssize_t size; 1533 int error; 1534 long ret; 1535 1536 pipe = get_pipe_info(file); 1537 if (!pipe) 1538 return -EBADF; 1539 1540 pipe_lock(pipe); 1541 1542 error = ret = 0; 1543 while (nr_segs) { 1544 void __user *base; 1545 size_t len; 1546 1547 /* 1548 * Get user address base and length for this iovec. 1549 */ 1550 error = get_user(base, &iov->iov_base); 1551 if (unlikely(error)) 1552 break; 1553 error = get_user(len, &iov->iov_len); 1554 if (unlikely(error)) 1555 break; 1556 1557 /* 1558 * Sanity check this iovec. 0 read succeeds. 1559 */ 1560 if (unlikely(!len)) 1561 break; 1562 if (unlikely(!base)) { 1563 error = -EFAULT; 1564 break; 1565 } 1566 1567 if (unlikely(!access_ok(VERIFY_WRITE, base, len))) { 1568 error = -EFAULT; 1569 break; 1570 } 1571 1572 sd.len = 0; 1573 sd.total_len = len; 1574 sd.flags = flags; 1575 sd.u.userptr = base; 1576 sd.pos = 0; 1577 1578 size = __splice_from_pipe(pipe, &sd, pipe_to_user); 1579 if (size < 0) { 1580 if (!ret) 1581 ret = size; 1582 1583 break; 1584 } 1585 1586 ret += size; 1587 1588 if (size < len) 1589 break; 1590 1591 nr_segs--; 1592 iov++; 1593 } 1594 1595 pipe_unlock(pipe); 1596 1597 if (!ret) 1598 ret = error; 1599 1600 return ret; 1601 } 1602 1603 /* 1604 * vmsplice splices a user address range into a pipe. It can be thought of 1605 * as splice-from-memory, where the regular splice is splice-from-file (or 1606 * to file). In both cases the output is a pipe, naturally. 1607 */ 1608 static long vmsplice_to_pipe(struct file *file, const struct iovec __user *iov, 1609 unsigned long nr_segs, unsigned int flags) 1610 { 1611 struct pipe_inode_info *pipe; 1612 struct page *pages[PIPE_DEF_BUFFERS]; 1613 struct partial_page partial[PIPE_DEF_BUFFERS]; 1614 struct splice_pipe_desc spd = { 1615 .pages = pages, 1616 .partial = partial, 1617 .flags = flags, 1618 .ops = &user_page_pipe_buf_ops, 1619 .spd_release = spd_release_page, 1620 }; 1621 long ret; 1622 1623 pipe = get_pipe_info(file); 1624 if (!pipe) 1625 return -EBADF; 1626 1627 if (splice_grow_spd(pipe, &spd)) 1628 return -ENOMEM; 1629 1630 spd.nr_pages = get_iovec_page_array(iov, nr_segs, spd.pages, 1631 spd.partial, false, 1632 pipe->buffers); 1633 if (spd.nr_pages <= 0) 1634 ret = spd.nr_pages; 1635 else 1636 ret = splice_to_pipe(pipe, &spd); 1637 1638 splice_shrink_spd(pipe, &spd); 1639 return ret; 1640 } 1641 1642 /* 1643 * Note that vmsplice only really supports true splicing _from_ user memory 1644 * to a pipe, not the other way around. Splicing from user memory is a simple 1645 * operation that can be supported without any funky alignment restrictions 1646 * or nasty vm tricks. We simply map in the user memory and fill them into 1647 * a pipe. The reverse isn't quite as easy, though. There are two possible 1648 * solutions for that: 1649 * 1650 * - memcpy() the data internally, at which point we might as well just 1651 * do a regular read() on the buffer anyway. 1652 * - Lots of nasty vm tricks, that are neither fast nor flexible (it 1653 * has restriction limitations on both ends of the pipe). 1654 * 1655 * Currently we punt and implement it as a normal copy, see pipe_to_user(). 1656 * 1657 */ 1658 SYSCALL_DEFINE4(vmsplice, int, fd, const struct iovec __user *, iov, 1659 unsigned long, nr_segs, unsigned int, flags) 1660 { 1661 struct file *file; 1662 long error; 1663 int fput; 1664 1665 if (unlikely(nr_segs > UIO_MAXIOV)) 1666 return -EINVAL; 1667 else if (unlikely(!nr_segs)) 1668 return 0; 1669 1670 error = -EBADF; 1671 file = fget_light(fd, &fput); 1672 if (file) { 1673 if (file->f_mode & FMODE_WRITE) 1674 error = vmsplice_to_pipe(file, iov, nr_segs, flags); 1675 else if (file->f_mode & FMODE_READ) 1676 error = vmsplice_to_user(file, iov, nr_segs, flags); 1677 1678 fput_light(file, fput); 1679 } 1680 1681 return error; 1682 } 1683 1684 SYSCALL_DEFINE6(splice, int, fd_in, loff_t __user *, off_in, 1685 int, fd_out, loff_t __user *, off_out, 1686 size_t, len, unsigned int, flags) 1687 { 1688 long error; 1689 struct file *in, *out; 1690 int fput_in, fput_out; 1691 1692 if (unlikely(!len)) 1693 return 0; 1694 1695 error = -EBADF; 1696 in = fget_light(fd_in, &fput_in); 1697 if (in) { 1698 if (in->f_mode & FMODE_READ) { 1699 out = fget_light(fd_out, &fput_out); 1700 if (out) { 1701 if (out->f_mode & FMODE_WRITE) 1702 error = do_splice(in, off_in, 1703 out, off_out, 1704 len, flags); 1705 fput_light(out, fput_out); 1706 } 1707 } 1708 1709 fput_light(in, fput_in); 1710 } 1711 1712 return error; 1713 } 1714 1715 /* 1716 * Make sure there's data to read. Wait for input if we can, otherwise 1717 * return an appropriate error. 1718 */ 1719 static int ipipe_prep(struct pipe_inode_info *pipe, unsigned int flags) 1720 { 1721 int ret; 1722 1723 /* 1724 * Check ->nrbufs without the inode lock first. This function 1725 * is speculative anyways, so missing one is ok. 1726 */ 1727 if (pipe->nrbufs) 1728 return 0; 1729 1730 ret = 0; 1731 pipe_lock(pipe); 1732 1733 while (!pipe->nrbufs) { 1734 if (signal_pending(current)) { 1735 ret = -ERESTARTSYS; 1736 break; 1737 } 1738 if (!pipe->writers) 1739 break; 1740 if (!pipe->waiting_writers) { 1741 if (flags & SPLICE_F_NONBLOCK) { 1742 ret = -EAGAIN; 1743 break; 1744 } 1745 } 1746 pipe_wait(pipe); 1747 } 1748 1749 pipe_unlock(pipe); 1750 return ret; 1751 } 1752 1753 /* 1754 * Make sure there's writeable room. Wait for room if we can, otherwise 1755 * return an appropriate error. 1756 */ 1757 static int opipe_prep(struct pipe_inode_info *pipe, unsigned int flags) 1758 { 1759 int ret; 1760 1761 /* 1762 * Check ->nrbufs without the inode lock first. This function 1763 * is speculative anyways, so missing one is ok. 1764 */ 1765 if (pipe->nrbufs < pipe->buffers) 1766 return 0; 1767 1768 ret = 0; 1769 pipe_lock(pipe); 1770 1771 while (pipe->nrbufs >= pipe->buffers) { 1772 if (!pipe->readers) { 1773 send_sig(SIGPIPE, current, 0); 1774 ret = -EPIPE; 1775 break; 1776 } 1777 if (flags & SPLICE_F_NONBLOCK) { 1778 ret = -EAGAIN; 1779 break; 1780 } 1781 if (signal_pending(current)) { 1782 ret = -ERESTARTSYS; 1783 break; 1784 } 1785 pipe->waiting_writers++; 1786 pipe_wait(pipe); 1787 pipe->waiting_writers--; 1788 } 1789 1790 pipe_unlock(pipe); 1791 return ret; 1792 } 1793 1794 /* 1795 * Splice contents of ipipe to opipe. 1796 */ 1797 static int splice_pipe_to_pipe(struct pipe_inode_info *ipipe, 1798 struct pipe_inode_info *opipe, 1799 size_t len, unsigned int flags) 1800 { 1801 struct pipe_buffer *ibuf, *obuf; 1802 int ret = 0, nbuf; 1803 bool input_wakeup = false; 1804 1805 1806 retry: 1807 ret = ipipe_prep(ipipe, flags); 1808 if (ret) 1809 return ret; 1810 1811 ret = opipe_prep(opipe, flags); 1812 if (ret) 1813 return ret; 1814 1815 /* 1816 * Potential ABBA deadlock, work around it by ordering lock 1817 * grabbing by pipe info address. Otherwise two different processes 1818 * could deadlock (one doing tee from A -> B, the other from B -> A). 1819 */ 1820 pipe_double_lock(ipipe, opipe); 1821 1822 do { 1823 if (!opipe->readers) { 1824 send_sig(SIGPIPE, current, 0); 1825 if (!ret) 1826 ret = -EPIPE; 1827 break; 1828 } 1829 1830 if (!ipipe->nrbufs && !ipipe->writers) 1831 break; 1832 1833 /* 1834 * Cannot make any progress, because either the input 1835 * pipe is empty or the output pipe is full. 1836 */ 1837 if (!ipipe->nrbufs || opipe->nrbufs >= opipe->buffers) { 1838 /* Already processed some buffers, break */ 1839 if (ret) 1840 break; 1841 1842 if (flags & SPLICE_F_NONBLOCK) { 1843 ret = -EAGAIN; 1844 break; 1845 } 1846 1847 /* 1848 * We raced with another reader/writer and haven't 1849 * managed to process any buffers. A zero return 1850 * value means EOF, so retry instead. 1851 */ 1852 pipe_unlock(ipipe); 1853 pipe_unlock(opipe); 1854 goto retry; 1855 } 1856 1857 ibuf = ipipe->bufs + ipipe->curbuf; 1858 nbuf = (opipe->curbuf + opipe->nrbufs) & (opipe->buffers - 1); 1859 obuf = opipe->bufs + nbuf; 1860 1861 if (len >= ibuf->len) { 1862 /* 1863 * Simply move the whole buffer from ipipe to opipe 1864 */ 1865 *obuf = *ibuf; 1866 ibuf->ops = NULL; 1867 opipe->nrbufs++; 1868 ipipe->curbuf = (ipipe->curbuf + 1) & (ipipe->buffers - 1); 1869 ipipe->nrbufs--; 1870 input_wakeup = true; 1871 } else { 1872 /* 1873 * Get a reference to this pipe buffer, 1874 * so we can copy the contents over. 1875 */ 1876 ibuf->ops->get(ipipe, ibuf); 1877 *obuf = *ibuf; 1878 1879 /* 1880 * Don't inherit the gift flag, we need to 1881 * prevent multiple steals of this page. 1882 */ 1883 obuf->flags &= ~PIPE_BUF_FLAG_GIFT; 1884 1885 obuf->len = len; 1886 opipe->nrbufs++; 1887 ibuf->offset += obuf->len; 1888 ibuf->len -= obuf->len; 1889 } 1890 ret += obuf->len; 1891 len -= obuf->len; 1892 } while (len); 1893 1894 pipe_unlock(ipipe); 1895 pipe_unlock(opipe); 1896 1897 /* 1898 * If we put data in the output pipe, wakeup any potential readers. 1899 */ 1900 if (ret > 0) 1901 wakeup_pipe_readers(opipe); 1902 1903 if (input_wakeup) 1904 wakeup_pipe_writers(ipipe); 1905 1906 return ret; 1907 } 1908 1909 /* 1910 * Link contents of ipipe to opipe. 1911 */ 1912 static int link_pipe(struct pipe_inode_info *ipipe, 1913 struct pipe_inode_info *opipe, 1914 size_t len, unsigned int flags) 1915 { 1916 struct pipe_buffer *ibuf, *obuf; 1917 int ret = 0, i = 0, nbuf; 1918 1919 /* 1920 * Potential ABBA deadlock, work around it by ordering lock 1921 * grabbing by pipe info address. Otherwise two different processes 1922 * could deadlock (one doing tee from A -> B, the other from B -> A). 1923 */ 1924 pipe_double_lock(ipipe, opipe); 1925 1926 do { 1927 if (!opipe->readers) { 1928 send_sig(SIGPIPE, current, 0); 1929 if (!ret) 1930 ret = -EPIPE; 1931 break; 1932 } 1933 1934 /* 1935 * If we have iterated all input buffers or ran out of 1936 * output room, break. 1937 */ 1938 if (i >= ipipe->nrbufs || opipe->nrbufs >= opipe->buffers) 1939 break; 1940 1941 ibuf = ipipe->bufs + ((ipipe->curbuf + i) & (ipipe->buffers-1)); 1942 nbuf = (opipe->curbuf + opipe->nrbufs) & (opipe->buffers - 1); 1943 1944 /* 1945 * Get a reference to this pipe buffer, 1946 * so we can copy the contents over. 1947 */ 1948 ibuf->ops->get(ipipe, ibuf); 1949 1950 obuf = opipe->bufs + nbuf; 1951 *obuf = *ibuf; 1952 1953 /* 1954 * Don't inherit the gift flag, we need to 1955 * prevent multiple steals of this page. 1956 */ 1957 obuf->flags &= ~PIPE_BUF_FLAG_GIFT; 1958 1959 if (obuf->len > len) 1960 obuf->len = len; 1961 1962 opipe->nrbufs++; 1963 ret += obuf->len; 1964 len -= obuf->len; 1965 i++; 1966 } while (len); 1967 1968 /* 1969 * return EAGAIN if we have the potential of some data in the 1970 * future, otherwise just return 0 1971 */ 1972 if (!ret && ipipe->waiting_writers && (flags & SPLICE_F_NONBLOCK)) 1973 ret = -EAGAIN; 1974 1975 pipe_unlock(ipipe); 1976 pipe_unlock(opipe); 1977 1978 /* 1979 * If we put data in the output pipe, wakeup any potential readers. 1980 */ 1981 if (ret > 0) 1982 wakeup_pipe_readers(opipe); 1983 1984 return ret; 1985 } 1986 1987 /* 1988 * This is a tee(1) implementation that works on pipes. It doesn't copy 1989 * any data, it simply references the 'in' pages on the 'out' pipe. 1990 * The 'flags' used are the SPLICE_F_* variants, currently the only 1991 * applicable one is SPLICE_F_NONBLOCK. 1992 */ 1993 static long do_tee(struct file *in, struct file *out, size_t len, 1994 unsigned int flags) 1995 { 1996 struct pipe_inode_info *ipipe = get_pipe_info(in); 1997 struct pipe_inode_info *opipe = get_pipe_info(out); 1998 int ret = -EINVAL; 1999 2000 /* 2001 * Duplicate the contents of ipipe to opipe without actually 2002 * copying the data. 2003 */ 2004 if (ipipe && opipe && ipipe != opipe) { 2005 /* 2006 * Keep going, unless we encounter an error. The ipipe/opipe 2007 * ordering doesn't really matter. 2008 */ 2009 ret = ipipe_prep(ipipe, flags); 2010 if (!ret) { 2011 ret = opipe_prep(opipe, flags); 2012 if (!ret) 2013 ret = link_pipe(ipipe, opipe, len, flags); 2014 } 2015 } 2016 2017 return ret; 2018 } 2019 2020 SYSCALL_DEFINE4(tee, int, fdin, int, fdout, size_t, len, unsigned int, flags) 2021 { 2022 struct file *in; 2023 int error, fput_in; 2024 2025 if (unlikely(!len)) 2026 return 0; 2027 2028 error = -EBADF; 2029 in = fget_light(fdin, &fput_in); 2030 if (in) { 2031 if (in->f_mode & FMODE_READ) { 2032 int fput_out; 2033 struct file *out = fget_light(fdout, &fput_out); 2034 2035 if (out) { 2036 if (out->f_mode & FMODE_WRITE) 2037 error = do_tee(in, out, len, flags); 2038 fput_light(out, fput_out); 2039 } 2040 } 2041 fput_light(in, fput_in); 2042 } 2043 2044 return error; 2045 } 2046