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/module.h> 29 #include <linux/syscalls.h> 30 #include <linux/uio.h> 31 #include <linux/security.h> 32 #include <linux/gfp.h> 33 34 /* 35 * Attempt to steal a page from a pipe buffer. This should perhaps go into 36 * a vm helper function, it's already simplified quite a bit by the 37 * addition of remove_mapping(). If success is returned, the caller may 38 * attempt to reuse this page for another destination. 39 */ 40 static int page_cache_pipe_buf_steal(struct pipe_inode_info *pipe, 41 struct pipe_buffer *buf) 42 { 43 struct page *page = buf->page; 44 struct address_space *mapping; 45 46 lock_page(page); 47 48 mapping = page_mapping(page); 49 if (mapping) { 50 WARN_ON(!PageUptodate(page)); 51 52 /* 53 * At least for ext2 with nobh option, we need to wait on 54 * writeback completing on this page, since we'll remove it 55 * from the pagecache. Otherwise truncate wont wait on the 56 * page, allowing the disk blocks to be reused by someone else 57 * before we actually wrote our data to them. fs corruption 58 * ensues. 59 */ 60 wait_on_page_writeback(page); 61 62 if (page_has_private(page) && 63 !try_to_release_page(page, GFP_KERNEL)) 64 goto out_unlock; 65 66 /* 67 * If we succeeded in removing the mapping, set LRU flag 68 * and return good. 69 */ 70 if (remove_mapping(mapping, page)) { 71 buf->flags |= PIPE_BUF_FLAG_LRU; 72 return 0; 73 } 74 } 75 76 /* 77 * Raced with truncate or failed to remove page from current 78 * address space, unlock and return failure. 79 */ 80 out_unlock: 81 unlock_page(page); 82 return 1; 83 } 84 85 static void page_cache_pipe_buf_release(struct pipe_inode_info *pipe, 86 struct pipe_buffer *buf) 87 { 88 page_cache_release(buf->page); 89 buf->flags &= ~PIPE_BUF_FLAG_LRU; 90 } 91 92 /* 93 * Check whether the contents of buf is OK to access. Since the content 94 * is a page cache page, IO may be in flight. 95 */ 96 static int page_cache_pipe_buf_confirm(struct pipe_inode_info *pipe, 97 struct pipe_buffer *buf) 98 { 99 struct page *page = buf->page; 100 int err; 101 102 if (!PageUptodate(page)) { 103 lock_page(page); 104 105 /* 106 * Page got truncated/unhashed. This will cause a 0-byte 107 * splice, if this is the first page. 108 */ 109 if (!page->mapping) { 110 err = -ENODATA; 111 goto error; 112 } 113 114 /* 115 * Uh oh, read-error from disk. 116 */ 117 if (!PageUptodate(page)) { 118 err = -EIO; 119 goto error; 120 } 121 122 /* 123 * Page is ok afterall, we are done. 124 */ 125 unlock_page(page); 126 } 127 128 return 0; 129 error: 130 unlock_page(page); 131 return err; 132 } 133 134 const struct pipe_buf_operations page_cache_pipe_buf_ops = { 135 .can_merge = 0, 136 .map = generic_pipe_buf_map, 137 .unmap = generic_pipe_buf_unmap, 138 .confirm = page_cache_pipe_buf_confirm, 139 .release = page_cache_pipe_buf_release, 140 .steal = page_cache_pipe_buf_steal, 141 .get = generic_pipe_buf_get, 142 }; 143 144 static int user_page_pipe_buf_steal(struct pipe_inode_info *pipe, 145 struct pipe_buffer *buf) 146 { 147 if (!(buf->flags & PIPE_BUF_FLAG_GIFT)) 148 return 1; 149 150 buf->flags |= PIPE_BUF_FLAG_LRU; 151 return generic_pipe_buf_steal(pipe, buf); 152 } 153 154 static const struct pipe_buf_operations user_page_pipe_buf_ops = { 155 .can_merge = 0, 156 .map = generic_pipe_buf_map, 157 .unmap = generic_pipe_buf_unmap, 158 .confirm = generic_pipe_buf_confirm, 159 .release = page_cache_pipe_buf_release, 160 .steal = user_page_pipe_buf_steal, 161 .get = generic_pipe_buf_get, 162 }; 163 164 static void wakeup_pipe_readers(struct pipe_inode_info *pipe) 165 { 166 smp_mb(); 167 if (waitqueue_active(&pipe->wait)) 168 wake_up_interruptible(&pipe->wait); 169 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN); 170 } 171 172 /** 173 * splice_to_pipe - fill passed data into a pipe 174 * @pipe: pipe to fill 175 * @spd: data to fill 176 * 177 * Description: 178 * @spd contains a map of pages and len/offset tuples, along with 179 * the struct pipe_buf_operations associated with these pages. This 180 * function will link that data to the pipe. 181 * 182 */ 183 ssize_t splice_to_pipe(struct pipe_inode_info *pipe, 184 struct splice_pipe_desc *spd) 185 { 186 unsigned int spd_pages = spd->nr_pages; 187 int ret, do_wakeup, page_nr; 188 189 ret = 0; 190 do_wakeup = 0; 191 page_nr = 0; 192 193 pipe_lock(pipe); 194 195 for (;;) { 196 if (!pipe->readers) { 197 send_sig(SIGPIPE, current, 0); 198 if (!ret) 199 ret = -EPIPE; 200 break; 201 } 202 203 if (pipe->nrbufs < pipe->buffers) { 204 int newbuf = (pipe->curbuf + pipe->nrbufs) & (pipe->buffers - 1); 205 struct pipe_buffer *buf = pipe->bufs + newbuf; 206 207 buf->page = spd->pages[page_nr]; 208 buf->offset = spd->partial[page_nr].offset; 209 buf->len = spd->partial[page_nr].len; 210 buf->private = spd->partial[page_nr].private; 211 buf->ops = spd->ops; 212 if (spd->flags & SPLICE_F_GIFT) 213 buf->flags |= PIPE_BUF_FLAG_GIFT; 214 215 pipe->nrbufs++; 216 page_nr++; 217 ret += buf->len; 218 219 if (pipe->inode) 220 do_wakeup = 1; 221 222 if (!--spd->nr_pages) 223 break; 224 if (pipe->nrbufs < pipe->buffers) 225 continue; 226 227 break; 228 } 229 230 if (spd->flags & SPLICE_F_NONBLOCK) { 231 if (!ret) 232 ret = -EAGAIN; 233 break; 234 } 235 236 if (signal_pending(current)) { 237 if (!ret) 238 ret = -ERESTARTSYS; 239 break; 240 } 241 242 if (do_wakeup) { 243 smp_mb(); 244 if (waitqueue_active(&pipe->wait)) 245 wake_up_interruptible_sync(&pipe->wait); 246 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN); 247 do_wakeup = 0; 248 } 249 250 pipe->waiting_writers++; 251 pipe_wait(pipe); 252 pipe->waiting_writers--; 253 } 254 255 pipe_unlock(pipe); 256 257 if (do_wakeup) 258 wakeup_pipe_readers(pipe); 259 260 while (page_nr < spd_pages) 261 spd->spd_release(spd, page_nr++); 262 263 return ret; 264 } 265 266 void spd_release_page(struct splice_pipe_desc *spd, unsigned int i) 267 { 268 page_cache_release(spd->pages[i]); 269 } 270 271 /* 272 * Check if we need to grow the arrays holding pages and partial page 273 * descriptions. 274 */ 275 int splice_grow_spd(struct pipe_inode_info *pipe, struct splice_pipe_desc *spd) 276 { 277 if (pipe->buffers <= PIPE_DEF_BUFFERS) 278 return 0; 279 280 spd->pages = kmalloc(pipe->buffers * sizeof(struct page *), GFP_KERNEL); 281 spd->partial = kmalloc(pipe->buffers * sizeof(struct partial_page), GFP_KERNEL); 282 283 if (spd->pages && spd->partial) 284 return 0; 285 286 kfree(spd->pages); 287 kfree(spd->partial); 288 return -ENOMEM; 289 } 290 291 void splice_shrink_spd(struct pipe_inode_info *pipe, 292 struct splice_pipe_desc *spd) 293 { 294 if (pipe->buffers <= PIPE_DEF_BUFFERS) 295 return; 296 297 kfree(spd->pages); 298 kfree(spd->partial); 299 } 300 301 static int 302 __generic_file_splice_read(struct file *in, loff_t *ppos, 303 struct pipe_inode_info *pipe, size_t len, 304 unsigned int flags) 305 { 306 struct address_space *mapping = in->f_mapping; 307 unsigned int loff, nr_pages, req_pages; 308 struct page *pages[PIPE_DEF_BUFFERS]; 309 struct partial_page partial[PIPE_DEF_BUFFERS]; 310 struct page *page; 311 pgoff_t index, end_index; 312 loff_t isize; 313 int error, page_nr; 314 struct splice_pipe_desc spd = { 315 .pages = pages, 316 .partial = partial, 317 .flags = flags, 318 .ops = &page_cache_pipe_buf_ops, 319 .spd_release = spd_release_page, 320 }; 321 322 if (splice_grow_spd(pipe, &spd)) 323 return -ENOMEM; 324 325 index = *ppos >> PAGE_CACHE_SHIFT; 326 loff = *ppos & ~PAGE_CACHE_MASK; 327 req_pages = (len + loff + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT; 328 nr_pages = min(req_pages, pipe->buffers); 329 330 /* 331 * Lookup the (hopefully) full range of pages we need. 332 */ 333 spd.nr_pages = find_get_pages_contig(mapping, index, nr_pages, spd.pages); 334 index += spd.nr_pages; 335 336 /* 337 * If find_get_pages_contig() returned fewer pages than we needed, 338 * readahead/allocate the rest and fill in the holes. 339 */ 340 if (spd.nr_pages < nr_pages) 341 page_cache_sync_readahead(mapping, &in->f_ra, in, 342 index, req_pages - spd.nr_pages); 343 344 error = 0; 345 while (spd.nr_pages < nr_pages) { 346 /* 347 * Page could be there, find_get_pages_contig() breaks on 348 * the first hole. 349 */ 350 page = find_get_page(mapping, index); 351 if (!page) { 352 /* 353 * page didn't exist, allocate one. 354 */ 355 page = page_cache_alloc_cold(mapping); 356 if (!page) 357 break; 358 359 error = add_to_page_cache_lru(page, mapping, index, 360 GFP_KERNEL); 361 if (unlikely(error)) { 362 page_cache_release(page); 363 if (error == -EEXIST) 364 continue; 365 break; 366 } 367 /* 368 * add_to_page_cache() locks the page, unlock it 369 * to avoid convoluting the logic below even more. 370 */ 371 unlock_page(page); 372 } 373 374 spd.pages[spd.nr_pages++] = page; 375 index++; 376 } 377 378 /* 379 * Now loop over the map and see if we need to start IO on any 380 * pages, fill in the partial map, etc. 381 */ 382 index = *ppos >> PAGE_CACHE_SHIFT; 383 nr_pages = spd.nr_pages; 384 spd.nr_pages = 0; 385 for (page_nr = 0; page_nr < nr_pages; page_nr++) { 386 unsigned int this_len; 387 388 if (!len) 389 break; 390 391 /* 392 * this_len is the max we'll use from this page 393 */ 394 this_len = min_t(unsigned long, len, PAGE_CACHE_SIZE - loff); 395 page = spd.pages[page_nr]; 396 397 if (PageReadahead(page)) 398 page_cache_async_readahead(mapping, &in->f_ra, in, 399 page, index, req_pages - page_nr); 400 401 /* 402 * If the page isn't uptodate, we may need to start io on it 403 */ 404 if (!PageUptodate(page)) { 405 lock_page(page); 406 407 /* 408 * Page was truncated, or invalidated by the 409 * filesystem. Redo the find/create, but this time the 410 * page is kept locked, so there's no chance of another 411 * race with truncate/invalidate. 412 */ 413 if (!page->mapping) { 414 unlock_page(page); 415 page = find_or_create_page(mapping, index, 416 mapping_gfp_mask(mapping)); 417 418 if (!page) { 419 error = -ENOMEM; 420 break; 421 } 422 page_cache_release(spd.pages[page_nr]); 423 spd.pages[page_nr] = page; 424 } 425 /* 426 * page was already under io and is now done, great 427 */ 428 if (PageUptodate(page)) { 429 unlock_page(page); 430 goto fill_it; 431 } 432 433 /* 434 * need to read in the page 435 */ 436 error = mapping->a_ops->readpage(in, page); 437 if (unlikely(error)) { 438 /* 439 * We really should re-lookup the page here, 440 * but it complicates things a lot. Instead 441 * lets just do what we already stored, and 442 * we'll get it the next time we are called. 443 */ 444 if (error == AOP_TRUNCATED_PAGE) 445 error = 0; 446 447 break; 448 } 449 } 450 fill_it: 451 /* 452 * i_size must be checked after PageUptodate. 453 */ 454 isize = i_size_read(mapping->host); 455 end_index = (isize - 1) >> PAGE_CACHE_SHIFT; 456 if (unlikely(!isize || index > end_index)) 457 break; 458 459 /* 460 * if this is the last page, see if we need to shrink 461 * the length and stop 462 */ 463 if (end_index == index) { 464 unsigned int plen; 465 466 /* 467 * max good bytes in this page 468 */ 469 plen = ((isize - 1) & ~PAGE_CACHE_MASK) + 1; 470 if (plen <= loff) 471 break; 472 473 /* 474 * force quit after adding this page 475 */ 476 this_len = min(this_len, plen - loff); 477 len = this_len; 478 } 479 480 spd.partial[page_nr].offset = loff; 481 spd.partial[page_nr].len = this_len; 482 len -= this_len; 483 loff = 0; 484 spd.nr_pages++; 485 index++; 486 } 487 488 /* 489 * Release any pages at the end, if we quit early. 'page_nr' is how far 490 * we got, 'nr_pages' is how many pages are in the map. 491 */ 492 while (page_nr < nr_pages) 493 page_cache_release(spd.pages[page_nr++]); 494 in->f_ra.prev_pos = (loff_t)index << PAGE_CACHE_SHIFT; 495 496 if (spd.nr_pages) 497 error = splice_to_pipe(pipe, &spd); 498 499 splice_shrink_spd(pipe, &spd); 500 return error; 501 } 502 503 /** 504 * generic_file_splice_read - splice data from file to a pipe 505 * @in: file to splice from 506 * @ppos: position in @in 507 * @pipe: pipe to splice to 508 * @len: number of bytes to splice 509 * @flags: splice modifier flags 510 * 511 * Description: 512 * Will read pages from given file and fill them into a pipe. Can be 513 * used as long as the address_space operations for the source implements 514 * a readpage() hook. 515 * 516 */ 517 ssize_t generic_file_splice_read(struct file *in, loff_t *ppos, 518 struct pipe_inode_info *pipe, size_t len, 519 unsigned int flags) 520 { 521 loff_t isize, left; 522 int ret; 523 524 isize = i_size_read(in->f_mapping->host); 525 if (unlikely(*ppos >= isize)) 526 return 0; 527 528 left = isize - *ppos; 529 if (unlikely(left < len)) 530 len = left; 531 532 ret = __generic_file_splice_read(in, ppos, pipe, len, flags); 533 if (ret > 0) { 534 *ppos += ret; 535 file_accessed(in); 536 } 537 538 return ret; 539 } 540 EXPORT_SYMBOL(generic_file_splice_read); 541 542 static const struct pipe_buf_operations default_pipe_buf_ops = { 543 .can_merge = 0, 544 .map = generic_pipe_buf_map, 545 .unmap = generic_pipe_buf_unmap, 546 .confirm = generic_pipe_buf_confirm, 547 .release = generic_pipe_buf_release, 548 .steal = generic_pipe_buf_steal, 549 .get = generic_pipe_buf_get, 550 }; 551 552 static ssize_t kernel_readv(struct file *file, const struct iovec *vec, 553 unsigned long vlen, loff_t offset) 554 { 555 mm_segment_t old_fs; 556 loff_t pos = offset; 557 ssize_t res; 558 559 old_fs = get_fs(); 560 set_fs(get_ds()); 561 /* The cast to a user pointer is valid due to the set_fs() */ 562 res = vfs_readv(file, (const struct iovec __user *)vec, vlen, &pos); 563 set_fs(old_fs); 564 565 return res; 566 } 567 568 static ssize_t kernel_write(struct file *file, const char *buf, size_t count, 569 loff_t pos) 570 { 571 mm_segment_t old_fs; 572 ssize_t res; 573 574 old_fs = get_fs(); 575 set_fs(get_ds()); 576 /* The cast to a user pointer is valid due to the set_fs() */ 577 res = vfs_write(file, (const char __user *)buf, count, &pos); 578 set_fs(old_fs); 579 580 return res; 581 } 582 583 ssize_t default_file_splice_read(struct file *in, loff_t *ppos, 584 struct pipe_inode_info *pipe, size_t len, 585 unsigned int flags) 586 { 587 unsigned int nr_pages; 588 unsigned int nr_freed; 589 size_t offset; 590 struct page *pages[PIPE_DEF_BUFFERS]; 591 struct partial_page partial[PIPE_DEF_BUFFERS]; 592 struct iovec *vec, __vec[PIPE_DEF_BUFFERS]; 593 ssize_t res; 594 size_t this_len; 595 int error; 596 int i; 597 struct splice_pipe_desc spd = { 598 .pages = pages, 599 .partial = partial, 600 .flags = flags, 601 .ops = &default_pipe_buf_ops, 602 .spd_release = spd_release_page, 603 }; 604 605 if (splice_grow_spd(pipe, &spd)) 606 return -ENOMEM; 607 608 res = -ENOMEM; 609 vec = __vec; 610 if (pipe->buffers > PIPE_DEF_BUFFERS) { 611 vec = kmalloc(pipe->buffers * sizeof(struct iovec), GFP_KERNEL); 612 if (!vec) 613 goto shrink_ret; 614 } 615 616 offset = *ppos & ~PAGE_CACHE_MASK; 617 nr_pages = (len + offset + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT; 618 619 for (i = 0; i < nr_pages && i < pipe->buffers && len; i++) { 620 struct page *page; 621 622 page = alloc_page(GFP_USER); 623 error = -ENOMEM; 624 if (!page) 625 goto err; 626 627 this_len = min_t(size_t, len, PAGE_CACHE_SIZE - offset); 628 vec[i].iov_base = (void __user *) page_address(page); 629 vec[i].iov_len = this_len; 630 spd.pages[i] = page; 631 spd.nr_pages++; 632 len -= this_len; 633 offset = 0; 634 } 635 636 res = kernel_readv(in, vec, spd.nr_pages, *ppos); 637 if (res < 0) { 638 error = res; 639 goto err; 640 } 641 642 error = 0; 643 if (!res) 644 goto err; 645 646 nr_freed = 0; 647 for (i = 0; i < spd.nr_pages; i++) { 648 this_len = min_t(size_t, vec[i].iov_len, res); 649 spd.partial[i].offset = 0; 650 spd.partial[i].len = this_len; 651 if (!this_len) { 652 __free_page(spd.pages[i]); 653 spd.pages[i] = NULL; 654 nr_freed++; 655 } 656 res -= this_len; 657 } 658 spd.nr_pages -= nr_freed; 659 660 res = splice_to_pipe(pipe, &spd); 661 if (res > 0) 662 *ppos += res; 663 664 shrink_ret: 665 if (vec != __vec) 666 kfree(vec); 667 splice_shrink_spd(pipe, &spd); 668 return res; 669 670 err: 671 for (i = 0; i < spd.nr_pages; i++) 672 __free_page(spd.pages[i]); 673 674 res = error; 675 goto shrink_ret; 676 } 677 EXPORT_SYMBOL(default_file_splice_read); 678 679 /* 680 * Send 'sd->len' bytes to socket from 'sd->file' at position 'sd->pos' 681 * using sendpage(). Return the number of bytes sent. 682 */ 683 static int pipe_to_sendpage(struct pipe_inode_info *pipe, 684 struct pipe_buffer *buf, struct splice_desc *sd) 685 { 686 struct file *file = sd->u.file; 687 loff_t pos = sd->pos; 688 int more; 689 690 if (!likely(file->f_op && file->f_op->sendpage)) 691 return -EINVAL; 692 693 more = (sd->flags & SPLICE_F_MORE) || sd->len < sd->total_len; 694 return file->f_op->sendpage(file, buf->page, buf->offset, 695 sd->len, &pos, more); 696 } 697 698 /* 699 * This is a little more tricky than the file -> pipe splicing. There are 700 * basically three cases: 701 * 702 * - Destination page already exists in the address space and there 703 * are users of it. For that case we have no other option that 704 * copying the data. Tough luck. 705 * - Destination page already exists in the address space, but there 706 * are no users of it. Make sure it's uptodate, then drop it. Fall 707 * through to last case. 708 * - Destination page does not exist, we can add the pipe page to 709 * the page cache and avoid the copy. 710 * 711 * If asked to move pages to the output file (SPLICE_F_MOVE is set in 712 * sd->flags), we attempt to migrate pages from the pipe to the output 713 * file address space page cache. This is possible if no one else has 714 * the pipe page referenced outside of the pipe and page cache. If 715 * SPLICE_F_MOVE isn't set, or we cannot move the page, we simply create 716 * a new page in the output file page cache and fill/dirty that. 717 */ 718 int pipe_to_file(struct pipe_inode_info *pipe, struct pipe_buffer *buf, 719 struct splice_desc *sd) 720 { 721 struct file *file = sd->u.file; 722 struct address_space *mapping = file->f_mapping; 723 unsigned int offset, this_len; 724 struct page *page; 725 void *fsdata; 726 int ret; 727 728 offset = sd->pos & ~PAGE_CACHE_MASK; 729 730 this_len = sd->len; 731 if (this_len + offset > PAGE_CACHE_SIZE) 732 this_len = PAGE_CACHE_SIZE - offset; 733 734 ret = pagecache_write_begin(file, mapping, sd->pos, this_len, 735 AOP_FLAG_UNINTERRUPTIBLE, &page, &fsdata); 736 if (unlikely(ret)) 737 goto out; 738 739 if (buf->page != page) { 740 /* 741 * Careful, ->map() uses KM_USER0! 742 */ 743 char *src = buf->ops->map(pipe, buf, 1); 744 char *dst = kmap_atomic(page, KM_USER1); 745 746 memcpy(dst + offset, src + buf->offset, this_len); 747 flush_dcache_page(page); 748 kunmap_atomic(dst, KM_USER1); 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 file_update_time(out); 1007 ret = splice_from_pipe_feed(pipe, &sd, pipe_to_file); 1008 } 1009 mutex_unlock(&inode->i_mutex); 1010 } while (ret > 0); 1011 splice_from_pipe_end(pipe, &sd); 1012 1013 pipe_unlock(pipe); 1014 1015 if (sd.num_spliced) 1016 ret = sd.num_spliced; 1017 1018 if (ret > 0) { 1019 unsigned long nr_pages; 1020 int err; 1021 1022 nr_pages = (ret + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT; 1023 1024 err = generic_write_sync(out, *ppos, ret); 1025 if (err) 1026 ret = err; 1027 else 1028 *ppos += ret; 1029 balance_dirty_pages_ratelimited_nr(mapping, nr_pages); 1030 } 1031 1032 return ret; 1033 } 1034 1035 EXPORT_SYMBOL(generic_file_splice_write); 1036 1037 static int write_pipe_buf(struct pipe_inode_info *pipe, struct pipe_buffer *buf, 1038 struct splice_desc *sd) 1039 { 1040 int ret; 1041 void *data; 1042 1043 data = buf->ops->map(pipe, buf, 0); 1044 ret = kernel_write(sd->u.file, data + buf->offset, sd->len, sd->pos); 1045 buf->ops->unmap(pipe, buf, data); 1046 1047 return ret; 1048 } 1049 1050 static ssize_t default_file_splice_write(struct pipe_inode_info *pipe, 1051 struct file *out, loff_t *ppos, 1052 size_t len, unsigned int flags) 1053 { 1054 ssize_t ret; 1055 1056 ret = splice_from_pipe(pipe, out, ppos, len, flags, write_pipe_buf); 1057 if (ret > 0) 1058 *ppos += ret; 1059 1060 return ret; 1061 } 1062 1063 /** 1064 * generic_splice_sendpage - splice data from a pipe to a socket 1065 * @pipe: pipe to splice from 1066 * @out: socket to write to 1067 * @ppos: position in @out 1068 * @len: number of bytes to splice 1069 * @flags: splice modifier flags 1070 * 1071 * Description: 1072 * Will send @len bytes from the pipe to a network socket. No data copying 1073 * is involved. 1074 * 1075 */ 1076 ssize_t generic_splice_sendpage(struct pipe_inode_info *pipe, struct file *out, 1077 loff_t *ppos, size_t len, unsigned int flags) 1078 { 1079 return splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_sendpage); 1080 } 1081 1082 EXPORT_SYMBOL(generic_splice_sendpage); 1083 1084 /* 1085 * Attempt to initiate a splice from pipe to file. 1086 */ 1087 static long do_splice_from(struct pipe_inode_info *pipe, struct file *out, 1088 loff_t *ppos, size_t len, unsigned int flags) 1089 { 1090 ssize_t (*splice_write)(struct pipe_inode_info *, struct file *, 1091 loff_t *, size_t, unsigned int); 1092 int ret; 1093 1094 if (unlikely(!(out->f_mode & FMODE_WRITE))) 1095 return -EBADF; 1096 1097 if (unlikely(out->f_flags & O_APPEND)) 1098 return -EINVAL; 1099 1100 ret = rw_verify_area(WRITE, out, ppos, len); 1101 if (unlikely(ret < 0)) 1102 return ret; 1103 1104 if (out->f_op && out->f_op->splice_write) 1105 splice_write = out->f_op->splice_write; 1106 else 1107 splice_write = default_file_splice_write; 1108 1109 return splice_write(pipe, out, ppos, len, flags); 1110 } 1111 1112 /* 1113 * Attempt to initiate a splice from a file to a pipe. 1114 */ 1115 static long do_splice_to(struct file *in, loff_t *ppos, 1116 struct pipe_inode_info *pipe, size_t len, 1117 unsigned int flags) 1118 { 1119 ssize_t (*splice_read)(struct file *, loff_t *, 1120 struct pipe_inode_info *, size_t, unsigned int); 1121 int ret; 1122 1123 if (unlikely(!(in->f_mode & FMODE_READ))) 1124 return -EBADF; 1125 1126 ret = rw_verify_area(READ, in, ppos, len); 1127 if (unlikely(ret < 0)) 1128 return ret; 1129 1130 if (in->f_op && in->f_op->splice_read) 1131 splice_read = in->f_op->splice_read; 1132 else 1133 splice_read = default_file_splice_read; 1134 1135 return splice_read(in, ppos, pipe, len, flags); 1136 } 1137 1138 /** 1139 * splice_direct_to_actor - splices data directly between two non-pipes 1140 * @in: file to splice from 1141 * @sd: actor information on where to splice to 1142 * @actor: handles the data splicing 1143 * 1144 * Description: 1145 * This is a special case helper to splice directly between two 1146 * points, without requiring an explicit pipe. Internally an allocated 1147 * pipe is cached in the process, and reused during the lifetime of 1148 * that process. 1149 * 1150 */ 1151 ssize_t splice_direct_to_actor(struct file *in, struct splice_desc *sd, 1152 splice_direct_actor *actor) 1153 { 1154 struct pipe_inode_info *pipe; 1155 long ret, bytes; 1156 umode_t i_mode; 1157 size_t len; 1158 int i, flags; 1159 1160 /* 1161 * We require the input being a regular file, as we don't want to 1162 * randomly drop data for eg socket -> socket splicing. Use the 1163 * piped splicing for that! 1164 */ 1165 i_mode = in->f_path.dentry->d_inode->i_mode; 1166 if (unlikely(!S_ISREG(i_mode) && !S_ISBLK(i_mode))) 1167 return -EINVAL; 1168 1169 /* 1170 * neither in nor out is a pipe, setup an internal pipe attached to 1171 * 'out' and transfer the wanted data from 'in' to 'out' through that 1172 */ 1173 pipe = current->splice_pipe; 1174 if (unlikely(!pipe)) { 1175 pipe = alloc_pipe_info(NULL); 1176 if (!pipe) 1177 return -ENOMEM; 1178 1179 /* 1180 * We don't have an immediate reader, but we'll read the stuff 1181 * out of the pipe right after the splice_to_pipe(). So set 1182 * PIPE_READERS appropriately. 1183 */ 1184 pipe->readers = 1; 1185 1186 current->splice_pipe = pipe; 1187 } 1188 1189 /* 1190 * Do the splice. 1191 */ 1192 ret = 0; 1193 bytes = 0; 1194 len = sd->total_len; 1195 flags = sd->flags; 1196 1197 /* 1198 * Don't block on output, we have to drain the direct pipe. 1199 */ 1200 sd->flags &= ~SPLICE_F_NONBLOCK; 1201 1202 while (len) { 1203 size_t read_len; 1204 loff_t pos = sd->pos, prev_pos = pos; 1205 1206 ret = do_splice_to(in, &pos, pipe, len, flags); 1207 if (unlikely(ret <= 0)) 1208 goto out_release; 1209 1210 read_len = ret; 1211 sd->total_len = read_len; 1212 1213 /* 1214 * NOTE: nonblocking mode only applies to the input. We 1215 * must not do the output in nonblocking mode as then we 1216 * could get stuck data in the internal pipe: 1217 */ 1218 ret = actor(pipe, sd); 1219 if (unlikely(ret <= 0)) { 1220 sd->pos = prev_pos; 1221 goto out_release; 1222 } 1223 1224 bytes += ret; 1225 len -= ret; 1226 sd->pos = pos; 1227 1228 if (ret < read_len) { 1229 sd->pos = prev_pos + ret; 1230 goto out_release; 1231 } 1232 } 1233 1234 done: 1235 pipe->nrbufs = pipe->curbuf = 0; 1236 file_accessed(in); 1237 return bytes; 1238 1239 out_release: 1240 /* 1241 * If we did an incomplete transfer we must release 1242 * the pipe buffers in question: 1243 */ 1244 for (i = 0; i < pipe->buffers; i++) { 1245 struct pipe_buffer *buf = pipe->bufs + i; 1246 1247 if (buf->ops) { 1248 buf->ops->release(pipe, buf); 1249 buf->ops = NULL; 1250 } 1251 } 1252 1253 if (!bytes) 1254 bytes = ret; 1255 1256 goto done; 1257 } 1258 EXPORT_SYMBOL(splice_direct_to_actor); 1259 1260 static int direct_splice_actor(struct pipe_inode_info *pipe, 1261 struct splice_desc *sd) 1262 { 1263 struct file *file = sd->u.file; 1264 1265 return do_splice_from(pipe, file, &file->f_pos, sd->total_len, 1266 sd->flags); 1267 } 1268 1269 /** 1270 * do_splice_direct - splices data directly between two files 1271 * @in: file to splice from 1272 * @ppos: input file offset 1273 * @out: file to splice to 1274 * @len: number of bytes to splice 1275 * @flags: splice modifier flags 1276 * 1277 * Description: 1278 * For use by do_sendfile(). splice can easily emulate sendfile, but 1279 * doing it in the application would incur an extra system call 1280 * (splice in + splice out, as compared to just sendfile()). So this helper 1281 * can splice directly through a process-private pipe. 1282 * 1283 */ 1284 long do_splice_direct(struct file *in, loff_t *ppos, struct file *out, 1285 size_t len, unsigned int flags) 1286 { 1287 struct splice_desc sd = { 1288 .len = len, 1289 .total_len = len, 1290 .flags = flags, 1291 .pos = *ppos, 1292 .u.file = out, 1293 }; 1294 long ret; 1295 1296 ret = splice_direct_to_actor(in, &sd, direct_splice_actor); 1297 if (ret > 0) 1298 *ppos = sd.pos; 1299 1300 return ret; 1301 } 1302 1303 static int splice_pipe_to_pipe(struct pipe_inode_info *ipipe, 1304 struct pipe_inode_info *opipe, 1305 size_t len, unsigned int flags); 1306 1307 /* 1308 * Determine where to splice to/from. 1309 */ 1310 static long do_splice(struct file *in, loff_t __user *off_in, 1311 struct file *out, loff_t __user *off_out, 1312 size_t len, unsigned int flags) 1313 { 1314 struct pipe_inode_info *ipipe; 1315 struct pipe_inode_info *opipe; 1316 loff_t offset, *off; 1317 long ret; 1318 1319 ipipe = get_pipe_info(in); 1320 opipe = get_pipe_info(out); 1321 1322 if (ipipe && opipe) { 1323 if (off_in || off_out) 1324 return -ESPIPE; 1325 1326 if (!(in->f_mode & FMODE_READ)) 1327 return -EBADF; 1328 1329 if (!(out->f_mode & FMODE_WRITE)) 1330 return -EBADF; 1331 1332 /* Splicing to self would be fun, but... */ 1333 if (ipipe == opipe) 1334 return -EINVAL; 1335 1336 return splice_pipe_to_pipe(ipipe, opipe, len, flags); 1337 } 1338 1339 if (ipipe) { 1340 if (off_in) 1341 return -ESPIPE; 1342 if (off_out) { 1343 if (!(out->f_mode & FMODE_PWRITE)) 1344 return -EINVAL; 1345 if (copy_from_user(&offset, off_out, sizeof(loff_t))) 1346 return -EFAULT; 1347 off = &offset; 1348 } else 1349 off = &out->f_pos; 1350 1351 ret = do_splice_from(ipipe, out, off, len, flags); 1352 1353 if (off_out && copy_to_user(off_out, off, sizeof(loff_t))) 1354 ret = -EFAULT; 1355 1356 return ret; 1357 } 1358 1359 if (opipe) { 1360 if (off_out) 1361 return -ESPIPE; 1362 if (off_in) { 1363 if (!(in->f_mode & FMODE_PREAD)) 1364 return -EINVAL; 1365 if (copy_from_user(&offset, off_in, sizeof(loff_t))) 1366 return -EFAULT; 1367 off = &offset; 1368 } else 1369 off = &in->f_pos; 1370 1371 ret = do_splice_to(in, off, opipe, len, flags); 1372 1373 if (off_in && copy_to_user(off_in, off, sizeof(loff_t))) 1374 ret = -EFAULT; 1375 1376 return ret; 1377 } 1378 1379 return -EINVAL; 1380 } 1381 1382 /* 1383 * Map an iov into an array of pages and offset/length tupples. With the 1384 * partial_page structure, we can map several non-contiguous ranges into 1385 * our ones pages[] map instead of splitting that operation into pieces. 1386 * Could easily be exported as a generic helper for other users, in which 1387 * case one would probably want to add a 'max_nr_pages' parameter as well. 1388 */ 1389 static int get_iovec_page_array(const struct iovec __user *iov, 1390 unsigned int nr_vecs, struct page **pages, 1391 struct partial_page *partial, int aligned, 1392 unsigned int pipe_buffers) 1393 { 1394 int buffers = 0, error = 0; 1395 1396 while (nr_vecs) { 1397 unsigned long off, npages; 1398 struct iovec entry; 1399 void __user *base; 1400 size_t len; 1401 int i; 1402 1403 error = -EFAULT; 1404 if (copy_from_user(&entry, iov, sizeof(entry))) 1405 break; 1406 1407 base = entry.iov_base; 1408 len = entry.iov_len; 1409 1410 /* 1411 * Sanity check this iovec. 0 read succeeds. 1412 */ 1413 error = 0; 1414 if (unlikely(!len)) 1415 break; 1416 error = -EFAULT; 1417 if (!access_ok(VERIFY_READ, base, len)) 1418 break; 1419 1420 /* 1421 * Get this base offset and number of pages, then map 1422 * in the user pages. 1423 */ 1424 off = (unsigned long) base & ~PAGE_MASK; 1425 1426 /* 1427 * If asked for alignment, the offset must be zero and the 1428 * length a multiple of the PAGE_SIZE. 1429 */ 1430 error = -EINVAL; 1431 if (aligned && (off || len & ~PAGE_MASK)) 1432 break; 1433 1434 npages = (off + len + PAGE_SIZE - 1) >> PAGE_SHIFT; 1435 if (npages > pipe_buffers - buffers) 1436 npages = pipe_buffers - buffers; 1437 1438 error = get_user_pages_fast((unsigned long)base, npages, 1439 0, &pages[buffers]); 1440 1441 if (unlikely(error <= 0)) 1442 break; 1443 1444 /* 1445 * Fill this contiguous range into the partial page map. 1446 */ 1447 for (i = 0; i < error; i++) { 1448 const int plen = min_t(size_t, len, PAGE_SIZE - off); 1449 1450 partial[buffers].offset = off; 1451 partial[buffers].len = plen; 1452 1453 off = 0; 1454 len -= plen; 1455 buffers++; 1456 } 1457 1458 /* 1459 * We didn't complete this iov, stop here since it probably 1460 * means we have to move some of this into a pipe to 1461 * be able to continue. 1462 */ 1463 if (len) 1464 break; 1465 1466 /* 1467 * Don't continue if we mapped fewer pages than we asked for, 1468 * or if we mapped the max number of pages that we have 1469 * room for. 1470 */ 1471 if (error < npages || buffers == pipe_buffers) 1472 break; 1473 1474 nr_vecs--; 1475 iov++; 1476 } 1477 1478 if (buffers) 1479 return buffers; 1480 1481 return error; 1482 } 1483 1484 static int pipe_to_user(struct pipe_inode_info *pipe, struct pipe_buffer *buf, 1485 struct splice_desc *sd) 1486 { 1487 char *src; 1488 int ret; 1489 1490 /* 1491 * See if we can use the atomic maps, by prefaulting in the 1492 * pages and doing an atomic copy 1493 */ 1494 if (!fault_in_pages_writeable(sd->u.userptr, sd->len)) { 1495 src = buf->ops->map(pipe, buf, 1); 1496 ret = __copy_to_user_inatomic(sd->u.userptr, src + buf->offset, 1497 sd->len); 1498 buf->ops->unmap(pipe, buf, src); 1499 if (!ret) { 1500 ret = sd->len; 1501 goto out; 1502 } 1503 } 1504 1505 /* 1506 * No dice, use slow non-atomic map and copy 1507 */ 1508 src = buf->ops->map(pipe, buf, 0); 1509 1510 ret = sd->len; 1511 if (copy_to_user(sd->u.userptr, src + buf->offset, sd->len)) 1512 ret = -EFAULT; 1513 1514 buf->ops->unmap(pipe, buf, src); 1515 out: 1516 if (ret > 0) 1517 sd->u.userptr += ret; 1518 return ret; 1519 } 1520 1521 /* 1522 * For lack of a better implementation, implement vmsplice() to userspace 1523 * as a simple copy of the pipes pages to the user iov. 1524 */ 1525 static long vmsplice_to_user(struct file *file, const struct iovec __user *iov, 1526 unsigned long nr_segs, unsigned int flags) 1527 { 1528 struct pipe_inode_info *pipe; 1529 struct splice_desc sd; 1530 ssize_t size; 1531 int error; 1532 long ret; 1533 1534 pipe = get_pipe_info(file); 1535 if (!pipe) 1536 return -EBADF; 1537 1538 pipe_lock(pipe); 1539 1540 error = ret = 0; 1541 while (nr_segs) { 1542 void __user *base; 1543 size_t len; 1544 1545 /* 1546 * Get user address base and length for this iovec. 1547 */ 1548 error = get_user(base, &iov->iov_base); 1549 if (unlikely(error)) 1550 break; 1551 error = get_user(len, &iov->iov_len); 1552 if (unlikely(error)) 1553 break; 1554 1555 /* 1556 * Sanity check this iovec. 0 read succeeds. 1557 */ 1558 if (unlikely(!len)) 1559 break; 1560 if (unlikely(!base)) { 1561 error = -EFAULT; 1562 break; 1563 } 1564 1565 if (unlikely(!access_ok(VERIFY_WRITE, base, len))) { 1566 error = -EFAULT; 1567 break; 1568 } 1569 1570 sd.len = 0; 1571 sd.total_len = len; 1572 sd.flags = flags; 1573 sd.u.userptr = base; 1574 sd.pos = 0; 1575 1576 size = __splice_from_pipe(pipe, &sd, pipe_to_user); 1577 if (size < 0) { 1578 if (!ret) 1579 ret = size; 1580 1581 break; 1582 } 1583 1584 ret += size; 1585 1586 if (size < len) 1587 break; 1588 1589 nr_segs--; 1590 iov++; 1591 } 1592 1593 pipe_unlock(pipe); 1594 1595 if (!ret) 1596 ret = error; 1597 1598 return ret; 1599 } 1600 1601 /* 1602 * vmsplice splices a user address range into a pipe. It can be thought of 1603 * as splice-from-memory, where the regular splice is splice-from-file (or 1604 * to file). In both cases the output is a pipe, naturally. 1605 */ 1606 static long vmsplice_to_pipe(struct file *file, const struct iovec __user *iov, 1607 unsigned long nr_segs, unsigned int flags) 1608 { 1609 struct pipe_inode_info *pipe; 1610 struct page *pages[PIPE_DEF_BUFFERS]; 1611 struct partial_page partial[PIPE_DEF_BUFFERS]; 1612 struct splice_pipe_desc spd = { 1613 .pages = pages, 1614 .partial = partial, 1615 .flags = flags, 1616 .ops = &user_page_pipe_buf_ops, 1617 .spd_release = spd_release_page, 1618 }; 1619 long ret; 1620 1621 pipe = get_pipe_info(file); 1622 if (!pipe) 1623 return -EBADF; 1624 1625 if (splice_grow_spd(pipe, &spd)) 1626 return -ENOMEM; 1627 1628 spd.nr_pages = get_iovec_page_array(iov, nr_segs, spd.pages, 1629 spd.partial, flags & SPLICE_F_GIFT, 1630 pipe->buffers); 1631 if (spd.nr_pages <= 0) 1632 ret = spd.nr_pages; 1633 else 1634 ret = splice_to_pipe(pipe, &spd); 1635 1636 splice_shrink_spd(pipe, &spd); 1637 return ret; 1638 } 1639 1640 /* 1641 * Note that vmsplice only really supports true splicing _from_ user memory 1642 * to a pipe, not the other way around. Splicing from user memory is a simple 1643 * operation that can be supported without any funky alignment restrictions 1644 * or nasty vm tricks. We simply map in the user memory and fill them into 1645 * a pipe. The reverse isn't quite as easy, though. There are two possible 1646 * solutions for that: 1647 * 1648 * - memcpy() the data internally, at which point we might as well just 1649 * do a regular read() on the buffer anyway. 1650 * - Lots of nasty vm tricks, that are neither fast nor flexible (it 1651 * has restriction limitations on both ends of the pipe). 1652 * 1653 * Currently we punt and implement it as a normal copy, see pipe_to_user(). 1654 * 1655 */ 1656 SYSCALL_DEFINE4(vmsplice, int, fd, const struct iovec __user *, iov, 1657 unsigned long, nr_segs, unsigned int, flags) 1658 { 1659 struct file *file; 1660 long error; 1661 int fput; 1662 1663 if (unlikely(nr_segs > UIO_MAXIOV)) 1664 return -EINVAL; 1665 else if (unlikely(!nr_segs)) 1666 return 0; 1667 1668 error = -EBADF; 1669 file = fget_light(fd, &fput); 1670 if (file) { 1671 if (file->f_mode & FMODE_WRITE) 1672 error = vmsplice_to_pipe(file, iov, nr_segs, flags); 1673 else if (file->f_mode & FMODE_READ) 1674 error = vmsplice_to_user(file, iov, nr_segs, flags); 1675 1676 fput_light(file, fput); 1677 } 1678 1679 return error; 1680 } 1681 1682 SYSCALL_DEFINE6(splice, int, fd_in, loff_t __user *, off_in, 1683 int, fd_out, loff_t __user *, off_out, 1684 size_t, len, unsigned int, flags) 1685 { 1686 long error; 1687 struct file *in, *out; 1688 int fput_in, fput_out; 1689 1690 if (unlikely(!len)) 1691 return 0; 1692 1693 error = -EBADF; 1694 in = fget_light(fd_in, &fput_in); 1695 if (in) { 1696 if (in->f_mode & FMODE_READ) { 1697 out = fget_light(fd_out, &fput_out); 1698 if (out) { 1699 if (out->f_mode & FMODE_WRITE) 1700 error = do_splice(in, off_in, 1701 out, off_out, 1702 len, flags); 1703 fput_light(out, fput_out); 1704 } 1705 } 1706 1707 fput_light(in, fput_in); 1708 } 1709 1710 return error; 1711 } 1712 1713 /* 1714 * Make sure there's data to read. Wait for input if we can, otherwise 1715 * return an appropriate error. 1716 */ 1717 static int ipipe_prep(struct pipe_inode_info *pipe, unsigned int flags) 1718 { 1719 int ret; 1720 1721 /* 1722 * Check ->nrbufs without the inode lock first. This function 1723 * is speculative anyways, so missing one is ok. 1724 */ 1725 if (pipe->nrbufs) 1726 return 0; 1727 1728 ret = 0; 1729 pipe_lock(pipe); 1730 1731 while (!pipe->nrbufs) { 1732 if (signal_pending(current)) { 1733 ret = -ERESTARTSYS; 1734 break; 1735 } 1736 if (!pipe->writers) 1737 break; 1738 if (!pipe->waiting_writers) { 1739 if (flags & SPLICE_F_NONBLOCK) { 1740 ret = -EAGAIN; 1741 break; 1742 } 1743 } 1744 pipe_wait(pipe); 1745 } 1746 1747 pipe_unlock(pipe); 1748 return ret; 1749 } 1750 1751 /* 1752 * Make sure there's writeable room. Wait for room if we can, otherwise 1753 * return an appropriate error. 1754 */ 1755 static int opipe_prep(struct pipe_inode_info *pipe, unsigned int flags) 1756 { 1757 int ret; 1758 1759 /* 1760 * Check ->nrbufs without the inode lock first. This function 1761 * is speculative anyways, so missing one is ok. 1762 */ 1763 if (pipe->nrbufs < pipe->buffers) 1764 return 0; 1765 1766 ret = 0; 1767 pipe_lock(pipe); 1768 1769 while (pipe->nrbufs >= pipe->buffers) { 1770 if (!pipe->readers) { 1771 send_sig(SIGPIPE, current, 0); 1772 ret = -EPIPE; 1773 break; 1774 } 1775 if (flags & SPLICE_F_NONBLOCK) { 1776 ret = -EAGAIN; 1777 break; 1778 } 1779 if (signal_pending(current)) { 1780 ret = -ERESTARTSYS; 1781 break; 1782 } 1783 pipe->waiting_writers++; 1784 pipe_wait(pipe); 1785 pipe->waiting_writers--; 1786 } 1787 1788 pipe_unlock(pipe); 1789 return ret; 1790 } 1791 1792 /* 1793 * Splice contents of ipipe to opipe. 1794 */ 1795 static int splice_pipe_to_pipe(struct pipe_inode_info *ipipe, 1796 struct pipe_inode_info *opipe, 1797 size_t len, unsigned int flags) 1798 { 1799 struct pipe_buffer *ibuf, *obuf; 1800 int ret = 0, nbuf; 1801 bool input_wakeup = false; 1802 1803 1804 retry: 1805 ret = ipipe_prep(ipipe, flags); 1806 if (ret) 1807 return ret; 1808 1809 ret = opipe_prep(opipe, flags); 1810 if (ret) 1811 return ret; 1812 1813 /* 1814 * Potential ABBA deadlock, work around it by ordering lock 1815 * grabbing by pipe info address. Otherwise two different processes 1816 * could deadlock (one doing tee from A -> B, the other from B -> A). 1817 */ 1818 pipe_double_lock(ipipe, opipe); 1819 1820 do { 1821 if (!opipe->readers) { 1822 send_sig(SIGPIPE, current, 0); 1823 if (!ret) 1824 ret = -EPIPE; 1825 break; 1826 } 1827 1828 if (!ipipe->nrbufs && !ipipe->writers) 1829 break; 1830 1831 /* 1832 * Cannot make any progress, because either the input 1833 * pipe is empty or the output pipe is full. 1834 */ 1835 if (!ipipe->nrbufs || opipe->nrbufs >= opipe->buffers) { 1836 /* Already processed some buffers, break */ 1837 if (ret) 1838 break; 1839 1840 if (flags & SPLICE_F_NONBLOCK) { 1841 ret = -EAGAIN; 1842 break; 1843 } 1844 1845 /* 1846 * We raced with another reader/writer and haven't 1847 * managed to process any buffers. A zero return 1848 * value means EOF, so retry instead. 1849 */ 1850 pipe_unlock(ipipe); 1851 pipe_unlock(opipe); 1852 goto retry; 1853 } 1854 1855 ibuf = ipipe->bufs + ipipe->curbuf; 1856 nbuf = (opipe->curbuf + opipe->nrbufs) & (opipe->buffers - 1); 1857 obuf = opipe->bufs + nbuf; 1858 1859 if (len >= ibuf->len) { 1860 /* 1861 * Simply move the whole buffer from ipipe to opipe 1862 */ 1863 *obuf = *ibuf; 1864 ibuf->ops = NULL; 1865 opipe->nrbufs++; 1866 ipipe->curbuf = (ipipe->curbuf + 1) & (ipipe->buffers - 1); 1867 ipipe->nrbufs--; 1868 input_wakeup = true; 1869 } else { 1870 /* 1871 * Get a reference to this pipe buffer, 1872 * so we can copy the contents over. 1873 */ 1874 ibuf->ops->get(ipipe, ibuf); 1875 *obuf = *ibuf; 1876 1877 /* 1878 * Don't inherit the gift flag, we need to 1879 * prevent multiple steals of this page. 1880 */ 1881 obuf->flags &= ~PIPE_BUF_FLAG_GIFT; 1882 1883 obuf->len = len; 1884 opipe->nrbufs++; 1885 ibuf->offset += obuf->len; 1886 ibuf->len -= obuf->len; 1887 } 1888 ret += obuf->len; 1889 len -= obuf->len; 1890 } while (len); 1891 1892 pipe_unlock(ipipe); 1893 pipe_unlock(opipe); 1894 1895 /* 1896 * If we put data in the output pipe, wakeup any potential readers. 1897 */ 1898 if (ret > 0) 1899 wakeup_pipe_readers(opipe); 1900 1901 if (input_wakeup) 1902 wakeup_pipe_writers(ipipe); 1903 1904 return ret; 1905 } 1906 1907 /* 1908 * Link contents of ipipe to opipe. 1909 */ 1910 static int link_pipe(struct pipe_inode_info *ipipe, 1911 struct pipe_inode_info *opipe, 1912 size_t len, unsigned int flags) 1913 { 1914 struct pipe_buffer *ibuf, *obuf; 1915 int ret = 0, i = 0, nbuf; 1916 1917 /* 1918 * Potential ABBA deadlock, work around it by ordering lock 1919 * grabbing by pipe info address. Otherwise two different processes 1920 * could deadlock (one doing tee from A -> B, the other from B -> A). 1921 */ 1922 pipe_double_lock(ipipe, opipe); 1923 1924 do { 1925 if (!opipe->readers) { 1926 send_sig(SIGPIPE, current, 0); 1927 if (!ret) 1928 ret = -EPIPE; 1929 break; 1930 } 1931 1932 /* 1933 * If we have iterated all input buffers or ran out of 1934 * output room, break. 1935 */ 1936 if (i >= ipipe->nrbufs || opipe->nrbufs >= opipe->buffers) 1937 break; 1938 1939 ibuf = ipipe->bufs + ((ipipe->curbuf + i) & (ipipe->buffers-1)); 1940 nbuf = (opipe->curbuf + opipe->nrbufs) & (opipe->buffers - 1); 1941 1942 /* 1943 * Get a reference to this pipe buffer, 1944 * so we can copy the contents over. 1945 */ 1946 ibuf->ops->get(ipipe, ibuf); 1947 1948 obuf = opipe->bufs + nbuf; 1949 *obuf = *ibuf; 1950 1951 /* 1952 * Don't inherit the gift flag, we need to 1953 * prevent multiple steals of this page. 1954 */ 1955 obuf->flags &= ~PIPE_BUF_FLAG_GIFT; 1956 1957 if (obuf->len > len) 1958 obuf->len = len; 1959 1960 opipe->nrbufs++; 1961 ret += obuf->len; 1962 len -= obuf->len; 1963 i++; 1964 } while (len); 1965 1966 /* 1967 * return EAGAIN if we have the potential of some data in the 1968 * future, otherwise just return 0 1969 */ 1970 if (!ret && ipipe->waiting_writers && (flags & SPLICE_F_NONBLOCK)) 1971 ret = -EAGAIN; 1972 1973 pipe_unlock(ipipe); 1974 pipe_unlock(opipe); 1975 1976 /* 1977 * If we put data in the output pipe, wakeup any potential readers. 1978 */ 1979 if (ret > 0) 1980 wakeup_pipe_readers(opipe); 1981 1982 return ret; 1983 } 1984 1985 /* 1986 * This is a tee(1) implementation that works on pipes. It doesn't copy 1987 * any data, it simply references the 'in' pages on the 'out' pipe. 1988 * The 'flags' used are the SPLICE_F_* variants, currently the only 1989 * applicable one is SPLICE_F_NONBLOCK. 1990 */ 1991 static long do_tee(struct file *in, struct file *out, size_t len, 1992 unsigned int flags) 1993 { 1994 struct pipe_inode_info *ipipe = get_pipe_info(in); 1995 struct pipe_inode_info *opipe = get_pipe_info(out); 1996 int ret = -EINVAL; 1997 1998 /* 1999 * Duplicate the contents of ipipe to opipe without actually 2000 * copying the data. 2001 */ 2002 if (ipipe && opipe && ipipe != opipe) { 2003 /* 2004 * Keep going, unless we encounter an error. The ipipe/opipe 2005 * ordering doesn't really matter. 2006 */ 2007 ret = ipipe_prep(ipipe, flags); 2008 if (!ret) { 2009 ret = opipe_prep(opipe, flags); 2010 if (!ret) 2011 ret = link_pipe(ipipe, opipe, len, flags); 2012 } 2013 } 2014 2015 return ret; 2016 } 2017 2018 SYSCALL_DEFINE4(tee, int, fdin, int, fdout, size_t, len, unsigned int, flags) 2019 { 2020 struct file *in; 2021 int error, fput_in; 2022 2023 if (unlikely(!len)) 2024 return 0; 2025 2026 error = -EBADF; 2027 in = fget_light(fdin, &fput_in); 2028 if (in) { 2029 if (in->f_mode & FMODE_READ) { 2030 int fput_out; 2031 struct file *out = fget_light(fdout, &fput_out); 2032 2033 if (out) { 2034 if (out->f_mode & FMODE_WRITE) 2035 error = do_tee(in, out, len, flags); 2036 fput_light(out, fput_out); 2037 } 2038 } 2039 fput_light(in, fput_in); 2040 } 2041 2042 return error; 2043 } 2044