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 #include <linux/gfp.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 static 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 /** 166 * splice_to_pipe - fill passed data into a pipe 167 * @pipe: pipe to fill 168 * @spd: data to fill 169 * 170 * Description: 171 * @spd contains a map of pages and len/offset tuples, along with 172 * the struct pipe_buf_operations associated with these pages. This 173 * function will link that data to the pipe. 174 * 175 */ 176 ssize_t splice_to_pipe(struct pipe_inode_info *pipe, 177 struct splice_pipe_desc *spd) 178 { 179 unsigned int spd_pages = spd->nr_pages; 180 int ret, do_wakeup, page_nr; 181 182 ret = 0; 183 do_wakeup = 0; 184 page_nr = 0; 185 186 pipe_lock(pipe); 187 188 for (;;) { 189 if (!pipe->readers) { 190 send_sig(SIGPIPE, current, 0); 191 if (!ret) 192 ret = -EPIPE; 193 break; 194 } 195 196 if (pipe->nrbufs < pipe->buffers) { 197 int newbuf = (pipe->curbuf + pipe->nrbufs) & (pipe->buffers - 1); 198 struct pipe_buffer *buf = pipe->bufs + newbuf; 199 200 buf->page = spd->pages[page_nr]; 201 buf->offset = spd->partial[page_nr].offset; 202 buf->len = spd->partial[page_nr].len; 203 buf->private = spd->partial[page_nr].private; 204 buf->ops = spd->ops; 205 if (spd->flags & SPLICE_F_GIFT) 206 buf->flags |= PIPE_BUF_FLAG_GIFT; 207 208 pipe->nrbufs++; 209 page_nr++; 210 ret += buf->len; 211 212 if (pipe->inode) 213 do_wakeup = 1; 214 215 if (!--spd->nr_pages) 216 break; 217 if (pipe->nrbufs < pipe->buffers) 218 continue; 219 220 break; 221 } 222 223 if (spd->flags & SPLICE_F_NONBLOCK) { 224 if (!ret) 225 ret = -EAGAIN; 226 break; 227 } 228 229 if (signal_pending(current)) { 230 if (!ret) 231 ret = -ERESTARTSYS; 232 break; 233 } 234 235 if (do_wakeup) { 236 smp_mb(); 237 if (waitqueue_active(&pipe->wait)) 238 wake_up_interruptible_sync(&pipe->wait); 239 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN); 240 do_wakeup = 0; 241 } 242 243 pipe->waiting_writers++; 244 pipe_wait(pipe); 245 pipe->waiting_writers--; 246 } 247 248 pipe_unlock(pipe); 249 250 if (do_wakeup) { 251 smp_mb(); 252 if (waitqueue_active(&pipe->wait)) 253 wake_up_interruptible(&pipe->wait); 254 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN); 255 } 256 257 while (page_nr < spd_pages) 258 spd->spd_release(spd, page_nr++); 259 260 return ret; 261 } 262 263 static void spd_release_page(struct splice_pipe_desc *spd, unsigned int i) 264 { 265 page_cache_release(spd->pages[i]); 266 } 267 268 /* 269 * Check if we need to grow the arrays holding pages and partial page 270 * descriptions. 271 */ 272 int splice_grow_spd(struct pipe_inode_info *pipe, struct splice_pipe_desc *spd) 273 { 274 if (pipe->buffers <= PIPE_DEF_BUFFERS) 275 return 0; 276 277 spd->pages = kmalloc(pipe->buffers * sizeof(struct page *), GFP_KERNEL); 278 spd->partial = kmalloc(pipe->buffers * sizeof(struct partial_page), GFP_KERNEL); 279 280 if (spd->pages && spd->partial) 281 return 0; 282 283 kfree(spd->pages); 284 kfree(spd->partial); 285 return -ENOMEM; 286 } 287 288 void splice_shrink_spd(struct pipe_inode_info *pipe, 289 struct splice_pipe_desc *spd) 290 { 291 if (pipe->buffers <= PIPE_DEF_BUFFERS) 292 return; 293 294 kfree(spd->pages); 295 kfree(spd->partial); 296 } 297 298 static int 299 __generic_file_splice_read(struct file *in, loff_t *ppos, 300 struct pipe_inode_info *pipe, size_t len, 301 unsigned int flags) 302 { 303 struct address_space *mapping = in->f_mapping; 304 unsigned int loff, nr_pages, req_pages; 305 struct page *pages[PIPE_DEF_BUFFERS]; 306 struct partial_page partial[PIPE_DEF_BUFFERS]; 307 struct page *page; 308 pgoff_t index, end_index; 309 loff_t isize; 310 int error, page_nr; 311 struct splice_pipe_desc spd = { 312 .pages = pages, 313 .partial = partial, 314 .flags = flags, 315 .ops = &page_cache_pipe_buf_ops, 316 .spd_release = spd_release_page, 317 }; 318 319 if (splice_grow_spd(pipe, &spd)) 320 return -ENOMEM; 321 322 index = *ppos >> PAGE_CACHE_SHIFT; 323 loff = *ppos & ~PAGE_CACHE_MASK; 324 req_pages = (len + loff + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT; 325 nr_pages = min(req_pages, pipe->buffers); 326 327 /* 328 * Lookup the (hopefully) full range of pages we need. 329 */ 330 spd.nr_pages = find_get_pages_contig(mapping, index, nr_pages, spd.pages); 331 index += spd.nr_pages; 332 333 /* 334 * If find_get_pages_contig() returned fewer pages than we needed, 335 * readahead/allocate the rest and fill in the holes. 336 */ 337 if (spd.nr_pages < nr_pages) 338 page_cache_sync_readahead(mapping, &in->f_ra, in, 339 index, req_pages - spd.nr_pages); 340 341 error = 0; 342 while (spd.nr_pages < nr_pages) { 343 /* 344 * Page could be there, find_get_pages_contig() breaks on 345 * the first hole. 346 */ 347 page = find_get_page(mapping, index); 348 if (!page) { 349 /* 350 * page didn't exist, allocate one. 351 */ 352 page = page_cache_alloc_cold(mapping); 353 if (!page) 354 break; 355 356 error = add_to_page_cache_lru(page, mapping, index, 357 GFP_KERNEL); 358 if (unlikely(error)) { 359 page_cache_release(page); 360 if (error == -EEXIST) 361 continue; 362 break; 363 } 364 /* 365 * add_to_page_cache() locks the page, unlock it 366 * to avoid convoluting the logic below even more. 367 */ 368 unlock_page(page); 369 } 370 371 spd.pages[spd.nr_pages++] = page; 372 index++; 373 } 374 375 /* 376 * Now loop over the map and see if we need to start IO on any 377 * pages, fill in the partial map, etc. 378 */ 379 index = *ppos >> PAGE_CACHE_SHIFT; 380 nr_pages = spd.nr_pages; 381 spd.nr_pages = 0; 382 for (page_nr = 0; page_nr < nr_pages; page_nr++) { 383 unsigned int this_len; 384 385 if (!len) 386 break; 387 388 /* 389 * this_len is the max we'll use from this page 390 */ 391 this_len = min_t(unsigned long, len, PAGE_CACHE_SIZE - loff); 392 page = spd.pages[page_nr]; 393 394 if (PageReadahead(page)) 395 page_cache_async_readahead(mapping, &in->f_ra, in, 396 page, index, req_pages - page_nr); 397 398 /* 399 * If the page isn't uptodate, we may need to start io on it 400 */ 401 if (!PageUptodate(page)) { 402 /* 403 * If in nonblock mode then dont block on waiting 404 * for an in-flight io page 405 */ 406 if (flags & SPLICE_F_NONBLOCK) { 407 if (!trylock_page(page)) { 408 error = -EAGAIN; 409 break; 410 } 411 } else 412 lock_page(page); 413 414 /* 415 * Page was truncated, or invalidated by the 416 * filesystem. Redo the find/create, but this time the 417 * page is kept locked, so there's no chance of another 418 * race with truncate/invalidate. 419 */ 420 if (!page->mapping) { 421 unlock_page(page); 422 page = find_or_create_page(mapping, index, 423 mapping_gfp_mask(mapping)); 424 425 if (!page) { 426 error = -ENOMEM; 427 break; 428 } 429 page_cache_release(spd.pages[page_nr]); 430 spd.pages[page_nr] = page; 431 } 432 /* 433 * page was already under io and is now done, great 434 */ 435 if (PageUptodate(page)) { 436 unlock_page(page); 437 goto fill_it; 438 } 439 440 /* 441 * need to read in the page 442 */ 443 error = mapping->a_ops->readpage(in, page); 444 if (unlikely(error)) { 445 /* 446 * We really should re-lookup the page here, 447 * but it complicates things a lot. Instead 448 * lets just do what we already stored, and 449 * we'll get it the next time we are called. 450 */ 451 if (error == AOP_TRUNCATED_PAGE) 452 error = 0; 453 454 break; 455 } 456 } 457 fill_it: 458 /* 459 * i_size must be checked after PageUptodate. 460 */ 461 isize = i_size_read(mapping->host); 462 end_index = (isize - 1) >> PAGE_CACHE_SHIFT; 463 if (unlikely(!isize || index > end_index)) 464 break; 465 466 /* 467 * if this is the last page, see if we need to shrink 468 * the length and stop 469 */ 470 if (end_index == index) { 471 unsigned int plen; 472 473 /* 474 * max good bytes in this page 475 */ 476 plen = ((isize - 1) & ~PAGE_CACHE_MASK) + 1; 477 if (plen <= loff) 478 break; 479 480 /* 481 * force quit after adding this page 482 */ 483 this_len = min(this_len, plen - loff); 484 len = this_len; 485 } 486 487 spd.partial[page_nr].offset = loff; 488 spd.partial[page_nr].len = this_len; 489 len -= this_len; 490 loff = 0; 491 spd.nr_pages++; 492 index++; 493 } 494 495 /* 496 * Release any pages at the end, if we quit early. 'page_nr' is how far 497 * we got, 'nr_pages' is how many pages are in the map. 498 */ 499 while (page_nr < nr_pages) 500 page_cache_release(spd.pages[page_nr++]); 501 in->f_ra.prev_pos = (loff_t)index << PAGE_CACHE_SHIFT; 502 503 if (spd.nr_pages) 504 error = splice_to_pipe(pipe, &spd); 505 506 splice_shrink_spd(pipe, &spd); 507 return error; 508 } 509 510 /** 511 * generic_file_splice_read - splice data from file to a pipe 512 * @in: file to splice from 513 * @ppos: position in @in 514 * @pipe: pipe to splice to 515 * @len: number of bytes to splice 516 * @flags: splice modifier flags 517 * 518 * Description: 519 * Will read pages from given file and fill them into a pipe. Can be 520 * used as long as the address_space operations for the source implements 521 * a readpage() hook. 522 * 523 */ 524 ssize_t generic_file_splice_read(struct file *in, loff_t *ppos, 525 struct pipe_inode_info *pipe, size_t len, 526 unsigned int flags) 527 { 528 loff_t isize, left; 529 int ret; 530 531 isize = i_size_read(in->f_mapping->host); 532 if (unlikely(*ppos >= isize)) 533 return 0; 534 535 left = isize - *ppos; 536 if (unlikely(left < len)) 537 len = left; 538 539 ret = __generic_file_splice_read(in, ppos, pipe, len, flags); 540 if (ret > 0) { 541 *ppos += ret; 542 file_accessed(in); 543 } 544 545 return ret; 546 } 547 EXPORT_SYMBOL(generic_file_splice_read); 548 549 static const struct pipe_buf_operations default_pipe_buf_ops = { 550 .can_merge = 0, 551 .map = generic_pipe_buf_map, 552 .unmap = generic_pipe_buf_unmap, 553 .confirm = generic_pipe_buf_confirm, 554 .release = generic_pipe_buf_release, 555 .steal = generic_pipe_buf_steal, 556 .get = generic_pipe_buf_get, 557 }; 558 559 static ssize_t kernel_readv(struct file *file, const struct iovec *vec, 560 unsigned long vlen, loff_t offset) 561 { 562 mm_segment_t old_fs; 563 loff_t pos = offset; 564 ssize_t res; 565 566 old_fs = get_fs(); 567 set_fs(get_ds()); 568 /* The cast to a user pointer is valid due to the set_fs() */ 569 res = vfs_readv(file, (const struct iovec __user *)vec, vlen, &pos); 570 set_fs(old_fs); 571 572 return res; 573 } 574 575 static ssize_t kernel_write(struct file *file, const char *buf, size_t count, 576 loff_t pos) 577 { 578 mm_segment_t old_fs; 579 ssize_t res; 580 581 old_fs = get_fs(); 582 set_fs(get_ds()); 583 /* The cast to a user pointer is valid due to the set_fs() */ 584 res = vfs_write(file, (const char __user *)buf, count, &pos); 585 set_fs(old_fs); 586 587 return res; 588 } 589 590 ssize_t default_file_splice_read(struct file *in, loff_t *ppos, 591 struct pipe_inode_info *pipe, size_t len, 592 unsigned int flags) 593 { 594 unsigned int nr_pages; 595 unsigned int nr_freed; 596 size_t offset; 597 struct page *pages[PIPE_DEF_BUFFERS]; 598 struct partial_page partial[PIPE_DEF_BUFFERS]; 599 struct iovec *vec, __vec[PIPE_DEF_BUFFERS]; 600 pgoff_t index; 601 ssize_t res; 602 size_t this_len; 603 int error; 604 int i; 605 struct splice_pipe_desc spd = { 606 .pages = pages, 607 .partial = partial, 608 .flags = flags, 609 .ops = &default_pipe_buf_ops, 610 .spd_release = spd_release_page, 611 }; 612 613 if (splice_grow_spd(pipe, &spd)) 614 return -ENOMEM; 615 616 res = -ENOMEM; 617 vec = __vec; 618 if (pipe->buffers > PIPE_DEF_BUFFERS) { 619 vec = kmalloc(pipe->buffers * sizeof(struct iovec), GFP_KERNEL); 620 if (!vec) 621 goto shrink_ret; 622 } 623 624 index = *ppos >> PAGE_CACHE_SHIFT; 625 offset = *ppos & ~PAGE_CACHE_MASK; 626 nr_pages = (len + offset + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT; 627 628 for (i = 0; i < nr_pages && i < pipe->buffers && len; i++) { 629 struct page *page; 630 631 page = alloc_page(GFP_USER); 632 error = -ENOMEM; 633 if (!page) 634 goto err; 635 636 this_len = min_t(size_t, len, PAGE_CACHE_SIZE - offset); 637 vec[i].iov_base = (void __user *) page_address(page); 638 vec[i].iov_len = this_len; 639 spd.pages[i] = page; 640 spd.nr_pages++; 641 len -= this_len; 642 offset = 0; 643 } 644 645 res = kernel_readv(in, vec, spd.nr_pages, *ppos); 646 if (res < 0) { 647 error = res; 648 goto err; 649 } 650 651 error = 0; 652 if (!res) 653 goto err; 654 655 nr_freed = 0; 656 for (i = 0; i < spd.nr_pages; i++) { 657 this_len = min_t(size_t, vec[i].iov_len, res); 658 spd.partial[i].offset = 0; 659 spd.partial[i].len = this_len; 660 if (!this_len) { 661 __free_page(spd.pages[i]); 662 spd.pages[i] = NULL; 663 nr_freed++; 664 } 665 res -= this_len; 666 } 667 spd.nr_pages -= nr_freed; 668 669 res = splice_to_pipe(pipe, &spd); 670 if (res > 0) 671 *ppos += res; 672 673 shrink_ret: 674 if (vec != __vec) 675 kfree(vec); 676 splice_shrink_spd(pipe, &spd); 677 return res; 678 679 err: 680 for (i = 0; i < spd.nr_pages; i++) 681 __free_page(spd.pages[i]); 682 683 res = error; 684 goto shrink_ret; 685 } 686 EXPORT_SYMBOL(default_file_splice_read); 687 688 /* 689 * Send 'sd->len' bytes to socket from 'sd->file' at position 'sd->pos' 690 * using sendpage(). Return the number of bytes sent. 691 */ 692 static int pipe_to_sendpage(struct pipe_inode_info *pipe, 693 struct pipe_buffer *buf, struct splice_desc *sd) 694 { 695 struct file *file = sd->u.file; 696 loff_t pos = sd->pos; 697 int ret, more; 698 699 ret = buf->ops->confirm(pipe, buf); 700 if (!ret) { 701 more = (sd->flags & SPLICE_F_MORE) || sd->len < sd->total_len; 702 if (file->f_op && file->f_op->sendpage) 703 ret = file->f_op->sendpage(file, buf->page, buf->offset, 704 sd->len, &pos, more); 705 else 706 ret = -EINVAL; 707 } 708 709 return ret; 710 } 711 712 /* 713 * This is a little more tricky than the file -> pipe splicing. There are 714 * basically three cases: 715 * 716 * - Destination page already exists in the address space and there 717 * are users of it. For that case we have no other option that 718 * copying the data. Tough luck. 719 * - Destination page already exists in the address space, but there 720 * are no users of it. Make sure it's uptodate, then drop it. Fall 721 * through to last case. 722 * - Destination page does not exist, we can add the pipe page to 723 * the page cache and avoid the copy. 724 * 725 * If asked to move pages to the output file (SPLICE_F_MOVE is set in 726 * sd->flags), we attempt to migrate pages from the pipe to the output 727 * file address space page cache. This is possible if no one else has 728 * the pipe page referenced outside of the pipe and page cache. If 729 * SPLICE_F_MOVE isn't set, or we cannot move the page, we simply create 730 * a new page in the output file page cache and fill/dirty that. 731 */ 732 int pipe_to_file(struct pipe_inode_info *pipe, struct pipe_buffer *buf, 733 struct splice_desc *sd) 734 { 735 struct file *file = sd->u.file; 736 struct address_space *mapping = file->f_mapping; 737 unsigned int offset, this_len; 738 struct page *page; 739 void *fsdata; 740 int ret; 741 742 /* 743 * make sure the data in this buffer is uptodate 744 */ 745 ret = buf->ops->confirm(pipe, buf); 746 if (unlikely(ret)) 747 return ret; 748 749 offset = sd->pos & ~PAGE_CACHE_MASK; 750 751 this_len = sd->len; 752 if (this_len + offset > PAGE_CACHE_SIZE) 753 this_len = PAGE_CACHE_SIZE - offset; 754 755 ret = pagecache_write_begin(file, mapping, sd->pos, this_len, 756 AOP_FLAG_UNINTERRUPTIBLE, &page, &fsdata); 757 if (unlikely(ret)) 758 goto out; 759 760 if (buf->page != page) { 761 /* 762 * Careful, ->map() uses KM_USER0! 763 */ 764 char *src = buf->ops->map(pipe, buf, 1); 765 char *dst = kmap_atomic(page, KM_USER1); 766 767 memcpy(dst + offset, src + buf->offset, this_len); 768 flush_dcache_page(page); 769 kunmap_atomic(dst, KM_USER1); 770 buf->ops->unmap(pipe, buf, src); 771 } 772 ret = pagecache_write_end(file, mapping, sd->pos, this_len, this_len, 773 page, fsdata); 774 out: 775 return ret; 776 } 777 EXPORT_SYMBOL(pipe_to_file); 778 779 static void wakeup_pipe_writers(struct pipe_inode_info *pipe) 780 { 781 smp_mb(); 782 if (waitqueue_active(&pipe->wait)) 783 wake_up_interruptible(&pipe->wait); 784 kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT); 785 } 786 787 /** 788 * splice_from_pipe_feed - feed available data from a pipe to a file 789 * @pipe: pipe to splice from 790 * @sd: information to @actor 791 * @actor: handler that splices the data 792 * 793 * Description: 794 * This function loops over the pipe and calls @actor to do the 795 * actual moving of a single struct pipe_buffer to the desired 796 * destination. It returns when there's no more buffers left in 797 * the pipe or if the requested number of bytes (@sd->total_len) 798 * have been copied. It returns a positive number (one) if the 799 * pipe needs to be filled with more data, zero if the required 800 * number of bytes have been copied and -errno on error. 801 * 802 * This, together with splice_from_pipe_{begin,end,next}, may be 803 * used to implement the functionality of __splice_from_pipe() when 804 * locking is required around copying the pipe buffers to the 805 * destination. 806 */ 807 int splice_from_pipe_feed(struct pipe_inode_info *pipe, struct splice_desc *sd, 808 splice_actor *actor) 809 { 810 int ret; 811 812 while (pipe->nrbufs) { 813 struct pipe_buffer *buf = pipe->bufs + pipe->curbuf; 814 const struct pipe_buf_operations *ops = buf->ops; 815 816 sd->len = buf->len; 817 if (sd->len > sd->total_len) 818 sd->len = sd->total_len; 819 820 ret = actor(pipe, buf, sd); 821 if (ret <= 0) { 822 if (ret == -ENODATA) 823 ret = 0; 824 return ret; 825 } 826 buf->offset += ret; 827 buf->len -= ret; 828 829 sd->num_spliced += ret; 830 sd->len -= ret; 831 sd->pos += ret; 832 sd->total_len -= ret; 833 834 if (!buf->len) { 835 buf->ops = NULL; 836 ops->release(pipe, buf); 837 pipe->curbuf = (pipe->curbuf + 1) & (pipe->buffers - 1); 838 pipe->nrbufs--; 839 if (pipe->inode) 840 sd->need_wakeup = true; 841 } 842 843 if (!sd->total_len) 844 return 0; 845 } 846 847 return 1; 848 } 849 EXPORT_SYMBOL(splice_from_pipe_feed); 850 851 /** 852 * splice_from_pipe_next - wait for some data to splice from 853 * @pipe: pipe to splice from 854 * @sd: information about the splice operation 855 * 856 * Description: 857 * This function will wait for some data and return a positive 858 * value (one) if pipe buffers are available. It will return zero 859 * or -errno if no more data needs to be spliced. 860 */ 861 int splice_from_pipe_next(struct pipe_inode_info *pipe, struct splice_desc *sd) 862 { 863 while (!pipe->nrbufs) { 864 if (!pipe->writers) 865 return 0; 866 867 if (!pipe->waiting_writers && sd->num_spliced) 868 return 0; 869 870 if (sd->flags & SPLICE_F_NONBLOCK) 871 return -EAGAIN; 872 873 if (signal_pending(current)) 874 return -ERESTARTSYS; 875 876 if (sd->need_wakeup) { 877 wakeup_pipe_writers(pipe); 878 sd->need_wakeup = false; 879 } 880 881 pipe_wait(pipe); 882 } 883 884 return 1; 885 } 886 EXPORT_SYMBOL(splice_from_pipe_next); 887 888 /** 889 * splice_from_pipe_begin - start splicing from pipe 890 * @sd: information about the splice operation 891 * 892 * Description: 893 * This function should be called before a loop containing 894 * splice_from_pipe_next() and splice_from_pipe_feed() to 895 * initialize the necessary fields of @sd. 896 */ 897 void splice_from_pipe_begin(struct splice_desc *sd) 898 { 899 sd->num_spliced = 0; 900 sd->need_wakeup = false; 901 } 902 EXPORT_SYMBOL(splice_from_pipe_begin); 903 904 /** 905 * splice_from_pipe_end - finish splicing from pipe 906 * @pipe: pipe to splice from 907 * @sd: information about the splice operation 908 * 909 * Description: 910 * This function will wake up pipe writers if necessary. It should 911 * be called after a loop containing splice_from_pipe_next() and 912 * splice_from_pipe_feed(). 913 */ 914 void splice_from_pipe_end(struct pipe_inode_info *pipe, struct splice_desc *sd) 915 { 916 if (sd->need_wakeup) 917 wakeup_pipe_writers(pipe); 918 } 919 EXPORT_SYMBOL(splice_from_pipe_end); 920 921 /** 922 * __splice_from_pipe - splice data from a pipe to given actor 923 * @pipe: pipe to splice from 924 * @sd: information to @actor 925 * @actor: handler that splices the data 926 * 927 * Description: 928 * This function does little more than loop over the pipe and call 929 * @actor to do the actual moving of a single struct pipe_buffer to 930 * the desired destination. See pipe_to_file, pipe_to_sendpage, or 931 * pipe_to_user. 932 * 933 */ 934 ssize_t __splice_from_pipe(struct pipe_inode_info *pipe, struct splice_desc *sd, 935 splice_actor *actor) 936 { 937 int ret; 938 939 splice_from_pipe_begin(sd); 940 do { 941 ret = splice_from_pipe_next(pipe, sd); 942 if (ret > 0) 943 ret = splice_from_pipe_feed(pipe, sd, actor); 944 } while (ret > 0); 945 splice_from_pipe_end(pipe, sd); 946 947 return sd->num_spliced ? sd->num_spliced : ret; 948 } 949 EXPORT_SYMBOL(__splice_from_pipe); 950 951 /** 952 * splice_from_pipe - splice data from a pipe to a file 953 * @pipe: pipe to splice from 954 * @out: file to splice to 955 * @ppos: position in @out 956 * @len: how many bytes to splice 957 * @flags: splice modifier flags 958 * @actor: handler that splices the data 959 * 960 * Description: 961 * See __splice_from_pipe. This function locks the pipe inode, 962 * otherwise it's identical to __splice_from_pipe(). 963 * 964 */ 965 ssize_t splice_from_pipe(struct pipe_inode_info *pipe, struct file *out, 966 loff_t *ppos, size_t len, unsigned int flags, 967 splice_actor *actor) 968 { 969 ssize_t ret; 970 struct splice_desc sd = { 971 .total_len = len, 972 .flags = flags, 973 .pos = *ppos, 974 .u.file = out, 975 }; 976 977 pipe_lock(pipe); 978 ret = __splice_from_pipe(pipe, &sd, actor); 979 pipe_unlock(pipe); 980 981 return ret; 982 } 983 984 /** 985 * generic_file_splice_write - splice data from a pipe to a file 986 * @pipe: pipe info 987 * @out: file to write to 988 * @ppos: position in @out 989 * @len: number of bytes to splice 990 * @flags: splice modifier flags 991 * 992 * Description: 993 * Will either move or copy pages (determined by @flags options) from 994 * the given pipe inode to the given file. 995 * 996 */ 997 ssize_t 998 generic_file_splice_write(struct pipe_inode_info *pipe, struct file *out, 999 loff_t *ppos, size_t len, unsigned int flags) 1000 { 1001 struct address_space *mapping = out->f_mapping; 1002 struct inode *inode = mapping->host; 1003 struct splice_desc sd = { 1004 .total_len = len, 1005 .flags = flags, 1006 .pos = *ppos, 1007 .u.file = out, 1008 }; 1009 ssize_t ret; 1010 1011 pipe_lock(pipe); 1012 1013 splice_from_pipe_begin(&sd); 1014 do { 1015 ret = splice_from_pipe_next(pipe, &sd); 1016 if (ret <= 0) 1017 break; 1018 1019 mutex_lock_nested(&inode->i_mutex, I_MUTEX_CHILD); 1020 ret = file_remove_suid(out); 1021 if (!ret) { 1022 file_update_time(out); 1023 ret = splice_from_pipe_feed(pipe, &sd, pipe_to_file); 1024 } 1025 mutex_unlock(&inode->i_mutex); 1026 } while (ret > 0); 1027 splice_from_pipe_end(pipe, &sd); 1028 1029 pipe_unlock(pipe); 1030 1031 if (sd.num_spliced) 1032 ret = sd.num_spliced; 1033 1034 if (ret > 0) { 1035 unsigned long nr_pages; 1036 int err; 1037 1038 nr_pages = (ret + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT; 1039 1040 err = generic_write_sync(out, *ppos, ret); 1041 if (err) 1042 ret = err; 1043 else 1044 *ppos += ret; 1045 balance_dirty_pages_ratelimited_nr(mapping, nr_pages); 1046 } 1047 1048 return ret; 1049 } 1050 1051 EXPORT_SYMBOL(generic_file_splice_write); 1052 1053 static int write_pipe_buf(struct pipe_inode_info *pipe, struct pipe_buffer *buf, 1054 struct splice_desc *sd) 1055 { 1056 int ret; 1057 void *data; 1058 1059 ret = buf->ops->confirm(pipe, buf); 1060 if (ret) 1061 return ret; 1062 1063 data = buf->ops->map(pipe, buf, 0); 1064 ret = kernel_write(sd->u.file, data + buf->offset, sd->len, sd->pos); 1065 buf->ops->unmap(pipe, buf, data); 1066 1067 return ret; 1068 } 1069 1070 static ssize_t default_file_splice_write(struct pipe_inode_info *pipe, 1071 struct file *out, loff_t *ppos, 1072 size_t len, unsigned int flags) 1073 { 1074 ssize_t ret; 1075 1076 ret = splice_from_pipe(pipe, out, ppos, len, flags, write_pipe_buf); 1077 if (ret > 0) 1078 *ppos += ret; 1079 1080 return ret; 1081 } 1082 1083 /** 1084 * generic_splice_sendpage - splice data from a pipe to a socket 1085 * @pipe: pipe to splice from 1086 * @out: socket to write to 1087 * @ppos: position in @out 1088 * @len: number of bytes to splice 1089 * @flags: splice modifier flags 1090 * 1091 * Description: 1092 * Will send @len bytes from the pipe to a network socket. No data copying 1093 * is involved. 1094 * 1095 */ 1096 ssize_t generic_splice_sendpage(struct pipe_inode_info *pipe, struct file *out, 1097 loff_t *ppos, size_t len, unsigned int flags) 1098 { 1099 return splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_sendpage); 1100 } 1101 1102 EXPORT_SYMBOL(generic_splice_sendpage); 1103 1104 /* 1105 * Attempt to initiate a splice from pipe to file. 1106 */ 1107 static long do_splice_from(struct pipe_inode_info *pipe, struct file *out, 1108 loff_t *ppos, size_t len, unsigned int flags) 1109 { 1110 ssize_t (*splice_write)(struct pipe_inode_info *, struct file *, 1111 loff_t *, size_t, unsigned int); 1112 int ret; 1113 1114 if (unlikely(!(out->f_mode & FMODE_WRITE))) 1115 return -EBADF; 1116 1117 if (unlikely(out->f_flags & O_APPEND)) 1118 return -EINVAL; 1119 1120 ret = rw_verify_area(WRITE, out, ppos, len); 1121 if (unlikely(ret < 0)) 1122 return ret; 1123 1124 if (out->f_op && out->f_op->splice_write) 1125 splice_write = out->f_op->splice_write; 1126 else 1127 splice_write = default_file_splice_write; 1128 1129 return splice_write(pipe, out, ppos, len, flags); 1130 } 1131 1132 /* 1133 * Attempt to initiate a splice from a file to a pipe. 1134 */ 1135 static long do_splice_to(struct file *in, loff_t *ppos, 1136 struct pipe_inode_info *pipe, size_t len, 1137 unsigned int flags) 1138 { 1139 ssize_t (*splice_read)(struct file *, loff_t *, 1140 struct pipe_inode_info *, size_t, unsigned int); 1141 int ret; 1142 1143 if (unlikely(!(in->f_mode & FMODE_READ))) 1144 return -EBADF; 1145 1146 ret = rw_verify_area(READ, in, ppos, len); 1147 if (unlikely(ret < 0)) 1148 return ret; 1149 1150 if (in->f_op && in->f_op->splice_read) 1151 splice_read = in->f_op->splice_read; 1152 else 1153 splice_read = default_file_splice_read; 1154 1155 return splice_read(in, ppos, pipe, len, flags); 1156 } 1157 1158 /** 1159 * splice_direct_to_actor - splices data directly between two non-pipes 1160 * @in: file to splice from 1161 * @sd: actor information on where to splice to 1162 * @actor: handles the data splicing 1163 * 1164 * Description: 1165 * This is a special case helper to splice directly between two 1166 * points, without requiring an explicit pipe. Internally an allocated 1167 * pipe is cached in the process, and reused during the lifetime of 1168 * that process. 1169 * 1170 */ 1171 ssize_t splice_direct_to_actor(struct file *in, struct splice_desc *sd, 1172 splice_direct_actor *actor) 1173 { 1174 struct pipe_inode_info *pipe; 1175 long ret, bytes; 1176 umode_t i_mode; 1177 size_t len; 1178 int i, flags; 1179 1180 /* 1181 * We require the input being a regular file, as we don't want to 1182 * randomly drop data for eg socket -> socket splicing. Use the 1183 * piped splicing for that! 1184 */ 1185 i_mode = in->f_path.dentry->d_inode->i_mode; 1186 if (unlikely(!S_ISREG(i_mode) && !S_ISBLK(i_mode))) 1187 return -EINVAL; 1188 1189 /* 1190 * neither in nor out is a pipe, setup an internal pipe attached to 1191 * 'out' and transfer the wanted data from 'in' to 'out' through that 1192 */ 1193 pipe = current->splice_pipe; 1194 if (unlikely(!pipe)) { 1195 pipe = alloc_pipe_info(NULL); 1196 if (!pipe) 1197 return -ENOMEM; 1198 1199 /* 1200 * We don't have an immediate reader, but we'll read the stuff 1201 * out of the pipe right after the splice_to_pipe(). So set 1202 * PIPE_READERS appropriately. 1203 */ 1204 pipe->readers = 1; 1205 1206 current->splice_pipe = pipe; 1207 } 1208 1209 /* 1210 * Do the splice. 1211 */ 1212 ret = 0; 1213 bytes = 0; 1214 len = sd->total_len; 1215 flags = sd->flags; 1216 1217 /* 1218 * Don't block on output, we have to drain the direct pipe. 1219 */ 1220 sd->flags &= ~SPLICE_F_NONBLOCK; 1221 1222 while (len) { 1223 size_t read_len; 1224 loff_t pos = sd->pos, prev_pos = pos; 1225 1226 ret = do_splice_to(in, &pos, pipe, len, flags); 1227 if (unlikely(ret <= 0)) 1228 goto out_release; 1229 1230 read_len = ret; 1231 sd->total_len = read_len; 1232 1233 /* 1234 * NOTE: nonblocking mode only applies to the input. We 1235 * must not do the output in nonblocking mode as then we 1236 * could get stuck data in the internal pipe: 1237 */ 1238 ret = actor(pipe, sd); 1239 if (unlikely(ret <= 0)) { 1240 sd->pos = prev_pos; 1241 goto out_release; 1242 } 1243 1244 bytes += ret; 1245 len -= ret; 1246 sd->pos = pos; 1247 1248 if (ret < read_len) { 1249 sd->pos = prev_pos + ret; 1250 goto out_release; 1251 } 1252 } 1253 1254 done: 1255 pipe->nrbufs = pipe->curbuf = 0; 1256 file_accessed(in); 1257 return bytes; 1258 1259 out_release: 1260 /* 1261 * If we did an incomplete transfer we must release 1262 * the pipe buffers in question: 1263 */ 1264 for (i = 0; i < pipe->buffers; i++) { 1265 struct pipe_buffer *buf = pipe->bufs + i; 1266 1267 if (buf->ops) { 1268 buf->ops->release(pipe, buf); 1269 buf->ops = NULL; 1270 } 1271 } 1272 1273 if (!bytes) 1274 bytes = ret; 1275 1276 goto done; 1277 } 1278 EXPORT_SYMBOL(splice_direct_to_actor); 1279 1280 static int direct_splice_actor(struct pipe_inode_info *pipe, 1281 struct splice_desc *sd) 1282 { 1283 struct file *file = sd->u.file; 1284 1285 return do_splice_from(pipe, file, &file->f_pos, sd->total_len, 1286 sd->flags); 1287 } 1288 1289 /** 1290 * do_splice_direct - splices data directly between two files 1291 * @in: file to splice from 1292 * @ppos: input file offset 1293 * @out: file to splice to 1294 * @len: number of bytes to splice 1295 * @flags: splice modifier flags 1296 * 1297 * Description: 1298 * For use by do_sendfile(). splice can easily emulate sendfile, but 1299 * doing it in the application would incur an extra system call 1300 * (splice in + splice out, as compared to just sendfile()). So this helper 1301 * can splice directly through a process-private pipe. 1302 * 1303 */ 1304 long do_splice_direct(struct file *in, loff_t *ppos, struct file *out, 1305 size_t len, unsigned int flags) 1306 { 1307 struct splice_desc sd = { 1308 .len = len, 1309 .total_len = len, 1310 .flags = flags, 1311 .pos = *ppos, 1312 .u.file = out, 1313 }; 1314 long ret; 1315 1316 ret = splice_direct_to_actor(in, &sd, direct_splice_actor); 1317 if (ret > 0) 1318 *ppos = sd.pos; 1319 1320 return ret; 1321 } 1322 1323 static int splice_pipe_to_pipe(struct pipe_inode_info *ipipe, 1324 struct pipe_inode_info *opipe, 1325 size_t len, unsigned int flags); 1326 /* 1327 * After the inode slimming patch, i_pipe/i_bdev/i_cdev share the same 1328 * location, so checking ->i_pipe is not enough to verify that this is a 1329 * pipe. 1330 */ 1331 static inline struct pipe_inode_info *pipe_info(struct inode *inode) 1332 { 1333 if (S_ISFIFO(inode->i_mode)) 1334 return inode->i_pipe; 1335 1336 return NULL; 1337 } 1338 1339 /* 1340 * Determine where to splice to/from. 1341 */ 1342 static long do_splice(struct file *in, loff_t __user *off_in, 1343 struct file *out, loff_t __user *off_out, 1344 size_t len, unsigned int flags) 1345 { 1346 struct pipe_inode_info *ipipe; 1347 struct pipe_inode_info *opipe; 1348 loff_t offset, *off; 1349 long ret; 1350 1351 ipipe = pipe_info(in->f_path.dentry->d_inode); 1352 opipe = pipe_info(out->f_path.dentry->d_inode); 1353 1354 if (ipipe && opipe) { 1355 if (off_in || off_out) 1356 return -ESPIPE; 1357 1358 if (!(in->f_mode & FMODE_READ)) 1359 return -EBADF; 1360 1361 if (!(out->f_mode & FMODE_WRITE)) 1362 return -EBADF; 1363 1364 /* Splicing to self would be fun, but... */ 1365 if (ipipe == opipe) 1366 return -EINVAL; 1367 1368 return splice_pipe_to_pipe(ipipe, opipe, len, flags); 1369 } 1370 1371 if (ipipe) { 1372 if (off_in) 1373 return -ESPIPE; 1374 if (off_out) { 1375 if (!(out->f_mode & FMODE_PWRITE)) 1376 return -EINVAL; 1377 if (copy_from_user(&offset, off_out, sizeof(loff_t))) 1378 return -EFAULT; 1379 off = &offset; 1380 } else 1381 off = &out->f_pos; 1382 1383 ret = do_splice_from(ipipe, out, off, len, flags); 1384 1385 if (off_out && copy_to_user(off_out, off, sizeof(loff_t))) 1386 ret = -EFAULT; 1387 1388 return ret; 1389 } 1390 1391 if (opipe) { 1392 if (off_out) 1393 return -ESPIPE; 1394 if (off_in) { 1395 if (!(in->f_mode & FMODE_PREAD)) 1396 return -EINVAL; 1397 if (copy_from_user(&offset, off_in, sizeof(loff_t))) 1398 return -EFAULT; 1399 off = &offset; 1400 } else 1401 off = &in->f_pos; 1402 1403 ret = do_splice_to(in, off, opipe, len, flags); 1404 1405 if (off_in && copy_to_user(off_in, off, sizeof(loff_t))) 1406 ret = -EFAULT; 1407 1408 return ret; 1409 } 1410 1411 return -EINVAL; 1412 } 1413 1414 /* 1415 * Map an iov into an array of pages and offset/length tupples. With the 1416 * partial_page structure, we can map several non-contiguous ranges into 1417 * our ones pages[] map instead of splitting that operation into pieces. 1418 * Could easily be exported as a generic helper for other users, in which 1419 * case one would probably want to add a 'max_nr_pages' parameter as well. 1420 */ 1421 static int get_iovec_page_array(const struct iovec __user *iov, 1422 unsigned int nr_vecs, struct page **pages, 1423 struct partial_page *partial, int aligned, 1424 unsigned int pipe_buffers) 1425 { 1426 int buffers = 0, error = 0; 1427 1428 while (nr_vecs) { 1429 unsigned long off, npages; 1430 struct iovec entry; 1431 void __user *base; 1432 size_t len; 1433 int i; 1434 1435 error = -EFAULT; 1436 if (copy_from_user(&entry, iov, sizeof(entry))) 1437 break; 1438 1439 base = entry.iov_base; 1440 len = entry.iov_len; 1441 1442 /* 1443 * Sanity check this iovec. 0 read succeeds. 1444 */ 1445 error = 0; 1446 if (unlikely(!len)) 1447 break; 1448 error = -EFAULT; 1449 if (!access_ok(VERIFY_READ, base, len)) 1450 break; 1451 1452 /* 1453 * Get this base offset and number of pages, then map 1454 * in the user pages. 1455 */ 1456 off = (unsigned long) base & ~PAGE_MASK; 1457 1458 /* 1459 * If asked for alignment, the offset must be zero and the 1460 * length a multiple of the PAGE_SIZE. 1461 */ 1462 error = -EINVAL; 1463 if (aligned && (off || len & ~PAGE_MASK)) 1464 break; 1465 1466 npages = (off + len + PAGE_SIZE - 1) >> PAGE_SHIFT; 1467 if (npages > pipe_buffers - buffers) 1468 npages = pipe_buffers - buffers; 1469 1470 error = get_user_pages_fast((unsigned long)base, npages, 1471 0, &pages[buffers]); 1472 1473 if (unlikely(error <= 0)) 1474 break; 1475 1476 /* 1477 * Fill this contiguous range into the partial page map. 1478 */ 1479 for (i = 0; i < error; i++) { 1480 const int plen = min_t(size_t, len, PAGE_SIZE - off); 1481 1482 partial[buffers].offset = off; 1483 partial[buffers].len = plen; 1484 1485 off = 0; 1486 len -= plen; 1487 buffers++; 1488 } 1489 1490 /* 1491 * We didn't complete this iov, stop here since it probably 1492 * means we have to move some of this into a pipe to 1493 * be able to continue. 1494 */ 1495 if (len) 1496 break; 1497 1498 /* 1499 * Don't continue if we mapped fewer pages than we asked for, 1500 * or if we mapped the max number of pages that we have 1501 * room for. 1502 */ 1503 if (error < npages || buffers == pipe_buffers) 1504 break; 1505 1506 nr_vecs--; 1507 iov++; 1508 } 1509 1510 if (buffers) 1511 return buffers; 1512 1513 return error; 1514 } 1515 1516 static int pipe_to_user(struct pipe_inode_info *pipe, struct pipe_buffer *buf, 1517 struct splice_desc *sd) 1518 { 1519 char *src; 1520 int ret; 1521 1522 ret = buf->ops->confirm(pipe, buf); 1523 if (unlikely(ret)) 1524 return ret; 1525 1526 /* 1527 * See if we can use the atomic maps, by prefaulting in the 1528 * pages and doing an atomic copy 1529 */ 1530 if (!fault_in_pages_writeable(sd->u.userptr, sd->len)) { 1531 src = buf->ops->map(pipe, buf, 1); 1532 ret = __copy_to_user_inatomic(sd->u.userptr, src + buf->offset, 1533 sd->len); 1534 buf->ops->unmap(pipe, buf, src); 1535 if (!ret) { 1536 ret = sd->len; 1537 goto out; 1538 } 1539 } 1540 1541 /* 1542 * No dice, use slow non-atomic map and copy 1543 */ 1544 src = buf->ops->map(pipe, buf, 0); 1545 1546 ret = sd->len; 1547 if (copy_to_user(sd->u.userptr, src + buf->offset, sd->len)) 1548 ret = -EFAULT; 1549 1550 buf->ops->unmap(pipe, buf, src); 1551 out: 1552 if (ret > 0) 1553 sd->u.userptr += ret; 1554 return ret; 1555 } 1556 1557 /* 1558 * For lack of a better implementation, implement vmsplice() to userspace 1559 * as a simple copy of the pipes pages to the user iov. 1560 */ 1561 static long vmsplice_to_user(struct file *file, const struct iovec __user *iov, 1562 unsigned long nr_segs, unsigned int flags) 1563 { 1564 struct pipe_inode_info *pipe; 1565 struct splice_desc sd; 1566 ssize_t size; 1567 int error; 1568 long ret; 1569 1570 pipe = pipe_info(file->f_path.dentry->d_inode); 1571 if (!pipe) 1572 return -EBADF; 1573 1574 pipe_lock(pipe); 1575 1576 error = ret = 0; 1577 while (nr_segs) { 1578 void __user *base; 1579 size_t len; 1580 1581 /* 1582 * Get user address base and length for this iovec. 1583 */ 1584 error = get_user(base, &iov->iov_base); 1585 if (unlikely(error)) 1586 break; 1587 error = get_user(len, &iov->iov_len); 1588 if (unlikely(error)) 1589 break; 1590 1591 /* 1592 * Sanity check this iovec. 0 read succeeds. 1593 */ 1594 if (unlikely(!len)) 1595 break; 1596 if (unlikely(!base)) { 1597 error = -EFAULT; 1598 break; 1599 } 1600 1601 if (unlikely(!access_ok(VERIFY_WRITE, base, len))) { 1602 error = -EFAULT; 1603 break; 1604 } 1605 1606 sd.len = 0; 1607 sd.total_len = len; 1608 sd.flags = flags; 1609 sd.u.userptr = base; 1610 sd.pos = 0; 1611 1612 size = __splice_from_pipe(pipe, &sd, pipe_to_user); 1613 if (size < 0) { 1614 if (!ret) 1615 ret = size; 1616 1617 break; 1618 } 1619 1620 ret += size; 1621 1622 if (size < len) 1623 break; 1624 1625 nr_segs--; 1626 iov++; 1627 } 1628 1629 pipe_unlock(pipe); 1630 1631 if (!ret) 1632 ret = error; 1633 1634 return ret; 1635 } 1636 1637 /* 1638 * vmsplice splices a user address range into a pipe. It can be thought of 1639 * as splice-from-memory, where the regular splice is splice-from-file (or 1640 * to file). In both cases the output is a pipe, naturally. 1641 */ 1642 static long vmsplice_to_pipe(struct file *file, const struct iovec __user *iov, 1643 unsigned long nr_segs, unsigned int flags) 1644 { 1645 struct pipe_inode_info *pipe; 1646 struct page *pages[PIPE_DEF_BUFFERS]; 1647 struct partial_page partial[PIPE_DEF_BUFFERS]; 1648 struct splice_pipe_desc spd = { 1649 .pages = pages, 1650 .partial = partial, 1651 .flags = flags, 1652 .ops = &user_page_pipe_buf_ops, 1653 .spd_release = spd_release_page, 1654 }; 1655 long ret; 1656 1657 pipe = pipe_info(file->f_path.dentry->d_inode); 1658 if (!pipe) 1659 return -EBADF; 1660 1661 if (splice_grow_spd(pipe, &spd)) 1662 return -ENOMEM; 1663 1664 spd.nr_pages = get_iovec_page_array(iov, nr_segs, spd.pages, 1665 spd.partial, flags & SPLICE_F_GIFT, 1666 pipe->buffers); 1667 if (spd.nr_pages <= 0) 1668 ret = spd.nr_pages; 1669 else 1670 ret = splice_to_pipe(pipe, &spd); 1671 1672 splice_shrink_spd(pipe, &spd); 1673 return ret; 1674 } 1675 1676 /* 1677 * Note that vmsplice only really supports true splicing _from_ user memory 1678 * to a pipe, not the other way around. Splicing from user memory is a simple 1679 * operation that can be supported without any funky alignment restrictions 1680 * or nasty vm tricks. We simply map in the user memory and fill them into 1681 * a pipe. The reverse isn't quite as easy, though. There are two possible 1682 * solutions for that: 1683 * 1684 * - memcpy() the data internally, at which point we might as well just 1685 * do a regular read() on the buffer anyway. 1686 * - Lots of nasty vm tricks, that are neither fast nor flexible (it 1687 * has restriction limitations on both ends of the pipe). 1688 * 1689 * Currently we punt and implement it as a normal copy, see pipe_to_user(). 1690 * 1691 */ 1692 SYSCALL_DEFINE4(vmsplice, int, fd, const struct iovec __user *, iov, 1693 unsigned long, nr_segs, unsigned int, flags) 1694 { 1695 struct file *file; 1696 long error; 1697 int fput; 1698 1699 if (unlikely(nr_segs > UIO_MAXIOV)) 1700 return -EINVAL; 1701 else if (unlikely(!nr_segs)) 1702 return 0; 1703 1704 error = -EBADF; 1705 file = fget_light(fd, &fput); 1706 if (file) { 1707 if (file->f_mode & FMODE_WRITE) 1708 error = vmsplice_to_pipe(file, iov, nr_segs, flags); 1709 else if (file->f_mode & FMODE_READ) 1710 error = vmsplice_to_user(file, iov, nr_segs, flags); 1711 1712 fput_light(file, fput); 1713 } 1714 1715 return error; 1716 } 1717 1718 SYSCALL_DEFINE6(splice, int, fd_in, loff_t __user *, off_in, 1719 int, fd_out, loff_t __user *, off_out, 1720 size_t, len, unsigned int, flags) 1721 { 1722 long error; 1723 struct file *in, *out; 1724 int fput_in, fput_out; 1725 1726 if (unlikely(!len)) 1727 return 0; 1728 1729 error = -EBADF; 1730 in = fget_light(fd_in, &fput_in); 1731 if (in) { 1732 if (in->f_mode & FMODE_READ) { 1733 out = fget_light(fd_out, &fput_out); 1734 if (out) { 1735 if (out->f_mode & FMODE_WRITE) 1736 error = do_splice(in, off_in, 1737 out, off_out, 1738 len, flags); 1739 fput_light(out, fput_out); 1740 } 1741 } 1742 1743 fput_light(in, fput_in); 1744 } 1745 1746 return error; 1747 } 1748 1749 /* 1750 * Make sure there's data to read. Wait for input if we can, otherwise 1751 * return an appropriate error. 1752 */ 1753 static int ipipe_prep(struct pipe_inode_info *pipe, unsigned int flags) 1754 { 1755 int ret; 1756 1757 /* 1758 * Check ->nrbufs without the inode lock first. This function 1759 * is speculative anyways, so missing one is ok. 1760 */ 1761 if (pipe->nrbufs) 1762 return 0; 1763 1764 ret = 0; 1765 pipe_lock(pipe); 1766 1767 while (!pipe->nrbufs) { 1768 if (signal_pending(current)) { 1769 ret = -ERESTARTSYS; 1770 break; 1771 } 1772 if (!pipe->writers) 1773 break; 1774 if (!pipe->waiting_writers) { 1775 if (flags & SPLICE_F_NONBLOCK) { 1776 ret = -EAGAIN; 1777 break; 1778 } 1779 } 1780 pipe_wait(pipe); 1781 } 1782 1783 pipe_unlock(pipe); 1784 return ret; 1785 } 1786 1787 /* 1788 * Make sure there's writeable room. Wait for room if we can, otherwise 1789 * return an appropriate error. 1790 */ 1791 static int opipe_prep(struct pipe_inode_info *pipe, unsigned int flags) 1792 { 1793 int ret; 1794 1795 /* 1796 * Check ->nrbufs without the inode lock first. This function 1797 * is speculative anyways, so missing one is ok. 1798 */ 1799 if (pipe->nrbufs < pipe->buffers) 1800 return 0; 1801 1802 ret = 0; 1803 pipe_lock(pipe); 1804 1805 while (pipe->nrbufs >= pipe->buffers) { 1806 if (!pipe->readers) { 1807 send_sig(SIGPIPE, current, 0); 1808 ret = -EPIPE; 1809 break; 1810 } 1811 if (flags & SPLICE_F_NONBLOCK) { 1812 ret = -EAGAIN; 1813 break; 1814 } 1815 if (signal_pending(current)) { 1816 ret = -ERESTARTSYS; 1817 break; 1818 } 1819 pipe->waiting_writers++; 1820 pipe_wait(pipe); 1821 pipe->waiting_writers--; 1822 } 1823 1824 pipe_unlock(pipe); 1825 return ret; 1826 } 1827 1828 /* 1829 * Splice contents of ipipe to opipe. 1830 */ 1831 static int splice_pipe_to_pipe(struct pipe_inode_info *ipipe, 1832 struct pipe_inode_info *opipe, 1833 size_t len, unsigned int flags) 1834 { 1835 struct pipe_buffer *ibuf, *obuf; 1836 int ret = 0, nbuf; 1837 bool input_wakeup = false; 1838 1839 1840 retry: 1841 ret = ipipe_prep(ipipe, flags); 1842 if (ret) 1843 return ret; 1844 1845 ret = opipe_prep(opipe, flags); 1846 if (ret) 1847 return ret; 1848 1849 /* 1850 * Potential ABBA deadlock, work around it by ordering lock 1851 * grabbing by pipe info address. Otherwise two different processes 1852 * could deadlock (one doing tee from A -> B, the other from B -> A). 1853 */ 1854 pipe_double_lock(ipipe, opipe); 1855 1856 do { 1857 if (!opipe->readers) { 1858 send_sig(SIGPIPE, current, 0); 1859 if (!ret) 1860 ret = -EPIPE; 1861 break; 1862 } 1863 1864 if (!ipipe->nrbufs && !ipipe->writers) 1865 break; 1866 1867 /* 1868 * Cannot make any progress, because either the input 1869 * pipe is empty or the output pipe is full. 1870 */ 1871 if (!ipipe->nrbufs || opipe->nrbufs >= opipe->buffers) { 1872 /* Already processed some buffers, break */ 1873 if (ret) 1874 break; 1875 1876 if (flags & SPLICE_F_NONBLOCK) { 1877 ret = -EAGAIN; 1878 break; 1879 } 1880 1881 /* 1882 * We raced with another reader/writer and haven't 1883 * managed to process any buffers. A zero return 1884 * value means EOF, so retry instead. 1885 */ 1886 pipe_unlock(ipipe); 1887 pipe_unlock(opipe); 1888 goto retry; 1889 } 1890 1891 ibuf = ipipe->bufs + ipipe->curbuf; 1892 nbuf = (opipe->curbuf + opipe->nrbufs) & (opipe->buffers - 1); 1893 obuf = opipe->bufs + nbuf; 1894 1895 if (len >= ibuf->len) { 1896 /* 1897 * Simply move the whole buffer from ipipe to opipe 1898 */ 1899 *obuf = *ibuf; 1900 ibuf->ops = NULL; 1901 opipe->nrbufs++; 1902 ipipe->curbuf = (ipipe->curbuf + 1) & (ipipe->buffers - 1); 1903 ipipe->nrbufs--; 1904 input_wakeup = true; 1905 } else { 1906 /* 1907 * Get a reference to this pipe buffer, 1908 * so we can copy the contents over. 1909 */ 1910 ibuf->ops->get(ipipe, ibuf); 1911 *obuf = *ibuf; 1912 1913 /* 1914 * Don't inherit the gift flag, we need to 1915 * prevent multiple steals of this page. 1916 */ 1917 obuf->flags &= ~PIPE_BUF_FLAG_GIFT; 1918 1919 obuf->len = len; 1920 opipe->nrbufs++; 1921 ibuf->offset += obuf->len; 1922 ibuf->len -= obuf->len; 1923 } 1924 ret += obuf->len; 1925 len -= obuf->len; 1926 } while (len); 1927 1928 pipe_unlock(ipipe); 1929 pipe_unlock(opipe); 1930 1931 /* 1932 * If we put data in the output pipe, wakeup any potential readers. 1933 */ 1934 if (ret > 0) { 1935 smp_mb(); 1936 if (waitqueue_active(&opipe->wait)) 1937 wake_up_interruptible(&opipe->wait); 1938 kill_fasync(&opipe->fasync_readers, SIGIO, POLL_IN); 1939 } 1940 if (input_wakeup) 1941 wakeup_pipe_writers(ipipe); 1942 1943 return ret; 1944 } 1945 1946 /* 1947 * Link contents of ipipe to opipe. 1948 */ 1949 static int link_pipe(struct pipe_inode_info *ipipe, 1950 struct pipe_inode_info *opipe, 1951 size_t len, unsigned int flags) 1952 { 1953 struct pipe_buffer *ibuf, *obuf; 1954 int ret = 0, i = 0, nbuf; 1955 1956 /* 1957 * Potential ABBA deadlock, work around it by ordering lock 1958 * grabbing by pipe info address. Otherwise two different processes 1959 * could deadlock (one doing tee from A -> B, the other from B -> A). 1960 */ 1961 pipe_double_lock(ipipe, opipe); 1962 1963 do { 1964 if (!opipe->readers) { 1965 send_sig(SIGPIPE, current, 0); 1966 if (!ret) 1967 ret = -EPIPE; 1968 break; 1969 } 1970 1971 /* 1972 * If we have iterated all input buffers or ran out of 1973 * output room, break. 1974 */ 1975 if (i >= ipipe->nrbufs || opipe->nrbufs >= opipe->buffers) 1976 break; 1977 1978 ibuf = ipipe->bufs + ((ipipe->curbuf + i) & (ipipe->buffers-1)); 1979 nbuf = (opipe->curbuf + opipe->nrbufs) & (opipe->buffers - 1); 1980 1981 /* 1982 * Get a reference to this pipe buffer, 1983 * so we can copy the contents over. 1984 */ 1985 ibuf->ops->get(ipipe, ibuf); 1986 1987 obuf = opipe->bufs + nbuf; 1988 *obuf = *ibuf; 1989 1990 /* 1991 * Don't inherit the gift flag, we need to 1992 * prevent multiple steals of this page. 1993 */ 1994 obuf->flags &= ~PIPE_BUF_FLAG_GIFT; 1995 1996 if (obuf->len > len) 1997 obuf->len = len; 1998 1999 opipe->nrbufs++; 2000 ret += obuf->len; 2001 len -= obuf->len; 2002 i++; 2003 } while (len); 2004 2005 /* 2006 * return EAGAIN if we have the potential of some data in the 2007 * future, otherwise just return 0 2008 */ 2009 if (!ret && ipipe->waiting_writers && (flags & SPLICE_F_NONBLOCK)) 2010 ret = -EAGAIN; 2011 2012 pipe_unlock(ipipe); 2013 pipe_unlock(opipe); 2014 2015 /* 2016 * If we put data in the output pipe, wakeup any potential readers. 2017 */ 2018 if (ret > 0) { 2019 smp_mb(); 2020 if (waitqueue_active(&opipe->wait)) 2021 wake_up_interruptible(&opipe->wait); 2022 kill_fasync(&opipe->fasync_readers, SIGIO, POLL_IN); 2023 } 2024 2025 return ret; 2026 } 2027 2028 /* 2029 * This is a tee(1) implementation that works on pipes. It doesn't copy 2030 * any data, it simply references the 'in' pages on the 'out' pipe. 2031 * The 'flags' used are the SPLICE_F_* variants, currently the only 2032 * applicable one is SPLICE_F_NONBLOCK. 2033 */ 2034 static long do_tee(struct file *in, struct file *out, size_t len, 2035 unsigned int flags) 2036 { 2037 struct pipe_inode_info *ipipe = pipe_info(in->f_path.dentry->d_inode); 2038 struct pipe_inode_info *opipe = pipe_info(out->f_path.dentry->d_inode); 2039 int ret = -EINVAL; 2040 2041 /* 2042 * Duplicate the contents of ipipe to opipe without actually 2043 * copying the data. 2044 */ 2045 if (ipipe && opipe && ipipe != opipe) { 2046 /* 2047 * Keep going, unless we encounter an error. The ipipe/opipe 2048 * ordering doesn't really matter. 2049 */ 2050 ret = ipipe_prep(ipipe, flags); 2051 if (!ret) { 2052 ret = opipe_prep(opipe, flags); 2053 if (!ret) 2054 ret = link_pipe(ipipe, opipe, len, flags); 2055 } 2056 } 2057 2058 return ret; 2059 } 2060 2061 SYSCALL_DEFINE4(tee, int, fdin, int, fdout, size_t, len, unsigned int, flags) 2062 { 2063 struct file *in; 2064 int error, fput_in; 2065 2066 if (unlikely(!len)) 2067 return 0; 2068 2069 error = -EBADF; 2070 in = fget_light(fdin, &fput_in); 2071 if (in) { 2072 if (in->f_mode & FMODE_READ) { 2073 int fput_out; 2074 struct file *out = fget_light(fdout, &fput_out); 2075 2076 if (out) { 2077 if (out->f_mode & FMODE_WRITE) 2078 error = do_tee(in, out, len, flags); 2079 fput_light(out, fput_out); 2080 } 2081 } 2082 fput_light(in, fput_in); 2083 } 2084 2085 return error; 2086 } 2087