1 /* 2 * "splice": joining two ropes together by interweaving their strands. 3 * 4 * This is the "extended pipe" functionality, where a pipe is used as 5 * an arbitrary in-memory buffer. Think of a pipe as a small kernel 6 * buffer that you can use to transfer data from one end to the other. 7 * 8 * The traditional unix read/write is extended with a "splice()" operation 9 * that transfers data buffers to or from a pipe buffer. 10 * 11 * Named by Larry McVoy, original implementation from Linus, extended by 12 * Jens to support splicing to files, network, direct splicing, etc and 13 * fixing lots of bugs. 14 * 15 * Copyright (C) 2005-2006 Jens Axboe <axboe@kernel.dk> 16 * Copyright (C) 2005-2006 Linus Torvalds <torvalds@osdl.org> 17 * Copyright (C) 2006 Ingo Molnar <mingo@elte.hu> 18 * 19 */ 20 #include <linux/fs.h> 21 #include <linux/file.h> 22 #include <linux/pagemap.h> 23 #include <linux/splice.h> 24 #include <linux/memcontrol.h> 25 #include <linux/mm_inline.h> 26 #include <linux/swap.h> 27 #include <linux/writeback.h> 28 #include <linux/export.h> 29 #include <linux/syscalls.h> 30 #include <linux/uio.h> 31 #include <linux/security.h> 32 #include <linux/gfp.h> 33 #include <linux/socket.h> 34 #include <linux/compat.h> 35 #include "internal.h" 36 37 /* 38 * Attempt to steal a page from a pipe buffer. This should perhaps go into 39 * a vm helper function, it's already simplified quite a bit by the 40 * addition of remove_mapping(). If success is returned, the caller may 41 * attempt to reuse this page for another destination. 42 */ 43 static int page_cache_pipe_buf_steal(struct pipe_inode_info *pipe, 44 struct pipe_buffer *buf) 45 { 46 struct page *page = buf->page; 47 struct address_space *mapping; 48 49 lock_page(page); 50 51 mapping = page_mapping(page); 52 if (mapping) { 53 WARN_ON(!PageUptodate(page)); 54 55 /* 56 * At least for ext2 with nobh option, we need to wait on 57 * writeback completing on this page, since we'll remove it 58 * from the pagecache. Otherwise truncate wont wait on the 59 * page, allowing the disk blocks to be reused by someone else 60 * before we actually wrote our data to them. fs corruption 61 * ensues. 62 */ 63 wait_on_page_writeback(page); 64 65 if (page_has_private(page) && 66 !try_to_release_page(page, GFP_KERNEL)) 67 goto out_unlock; 68 69 /* 70 * If we succeeded in removing the mapping, set LRU flag 71 * and return good. 72 */ 73 if (remove_mapping(mapping, page)) { 74 buf->flags |= PIPE_BUF_FLAG_LRU; 75 return 0; 76 } 77 } 78 79 /* 80 * Raced with truncate or failed to remove page from current 81 * address space, unlock and return failure. 82 */ 83 out_unlock: 84 unlock_page(page); 85 return 1; 86 } 87 88 static void page_cache_pipe_buf_release(struct pipe_inode_info *pipe, 89 struct pipe_buffer *buf) 90 { 91 page_cache_release(buf->page); 92 buf->flags &= ~PIPE_BUF_FLAG_LRU; 93 } 94 95 /* 96 * Check whether the contents of buf is OK to access. Since the content 97 * is a page cache page, IO may be in flight. 98 */ 99 static int page_cache_pipe_buf_confirm(struct pipe_inode_info *pipe, 100 struct pipe_buffer *buf) 101 { 102 struct page *page = buf->page; 103 int err; 104 105 if (!PageUptodate(page)) { 106 lock_page(page); 107 108 /* 109 * Page got truncated/unhashed. This will cause a 0-byte 110 * splice, if this is the first page. 111 */ 112 if (!page->mapping) { 113 err = -ENODATA; 114 goto error; 115 } 116 117 /* 118 * Uh oh, read-error from disk. 119 */ 120 if (!PageUptodate(page)) { 121 err = -EIO; 122 goto error; 123 } 124 125 /* 126 * Page is ok afterall, we are done. 127 */ 128 unlock_page(page); 129 } 130 131 return 0; 132 error: 133 unlock_page(page); 134 return err; 135 } 136 137 const struct pipe_buf_operations page_cache_pipe_buf_ops = { 138 .can_merge = 0, 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 .confirm = generic_pipe_buf_confirm, 158 .release = page_cache_pipe_buf_release, 159 .steal = user_page_pipe_buf_steal, 160 .get = generic_pipe_buf_get, 161 }; 162 163 static void wakeup_pipe_readers(struct pipe_inode_info *pipe) 164 { 165 smp_mb(); 166 if (waitqueue_active(&pipe->wait)) 167 wake_up_interruptible(&pipe->wait); 168 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN); 169 } 170 171 /** 172 * splice_to_pipe - fill passed data into a pipe 173 * @pipe: pipe to fill 174 * @spd: data to fill 175 * 176 * Description: 177 * @spd contains a map of pages and len/offset tuples, along with 178 * the struct pipe_buf_operations associated with these pages. This 179 * function will link that data to the pipe. 180 * 181 */ 182 ssize_t splice_to_pipe(struct pipe_inode_info *pipe, 183 struct splice_pipe_desc *spd) 184 { 185 unsigned int spd_pages = spd->nr_pages; 186 int ret, do_wakeup, page_nr; 187 188 ret = 0; 189 do_wakeup = 0; 190 page_nr = 0; 191 192 pipe_lock(pipe); 193 194 for (;;) { 195 if (!pipe->readers) { 196 send_sig(SIGPIPE, current, 0); 197 if (!ret) 198 ret = -EPIPE; 199 break; 200 } 201 202 if (pipe->nrbufs < pipe->buffers) { 203 int newbuf = (pipe->curbuf + pipe->nrbufs) & (pipe->buffers - 1); 204 struct pipe_buffer *buf = pipe->bufs + newbuf; 205 206 buf->page = spd->pages[page_nr]; 207 buf->offset = spd->partial[page_nr].offset; 208 buf->len = spd->partial[page_nr].len; 209 buf->private = spd->partial[page_nr].private; 210 buf->ops = spd->ops; 211 if (spd->flags & SPLICE_F_GIFT) 212 buf->flags |= PIPE_BUF_FLAG_GIFT; 213 214 pipe->nrbufs++; 215 page_nr++; 216 ret += buf->len; 217 218 if (pipe->files) 219 do_wakeup = 1; 220 221 if (!--spd->nr_pages) 222 break; 223 if (pipe->nrbufs < pipe->buffers) 224 continue; 225 226 break; 227 } 228 229 if (spd->flags & SPLICE_F_NONBLOCK) { 230 if (!ret) 231 ret = -EAGAIN; 232 break; 233 } 234 235 if (signal_pending(current)) { 236 if (!ret) 237 ret = -ERESTARTSYS; 238 break; 239 } 240 241 if (do_wakeup) { 242 smp_mb(); 243 if (waitqueue_active(&pipe->wait)) 244 wake_up_interruptible_sync(&pipe->wait); 245 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN); 246 do_wakeup = 0; 247 } 248 249 pipe->waiting_writers++; 250 pipe_wait(pipe); 251 pipe->waiting_writers--; 252 } 253 254 pipe_unlock(pipe); 255 256 if (do_wakeup) 257 wakeup_pipe_readers(pipe); 258 259 while (page_nr < spd_pages) 260 spd->spd_release(spd, page_nr++); 261 262 return ret; 263 } 264 EXPORT_SYMBOL_GPL(splice_to_pipe); 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(const struct pipe_inode_info *pipe, struct splice_pipe_desc *spd) 276 { 277 unsigned int buffers = ACCESS_ONCE(pipe->buffers); 278 279 spd->nr_pages_max = buffers; 280 if (buffers <= PIPE_DEF_BUFFERS) 281 return 0; 282 283 spd->pages = kmalloc(buffers * sizeof(struct page *), GFP_KERNEL); 284 spd->partial = kmalloc(buffers * sizeof(struct partial_page), GFP_KERNEL); 285 286 if (spd->pages && spd->partial) 287 return 0; 288 289 kfree(spd->pages); 290 kfree(spd->partial); 291 return -ENOMEM; 292 } 293 294 void splice_shrink_spd(struct splice_pipe_desc *spd) 295 { 296 if (spd->nr_pages_max <= PIPE_DEF_BUFFERS) 297 return; 298 299 kfree(spd->pages); 300 kfree(spd->partial); 301 } 302 303 static int 304 __generic_file_splice_read(struct file *in, loff_t *ppos, 305 struct pipe_inode_info *pipe, size_t len, 306 unsigned int flags) 307 { 308 struct address_space *mapping = in->f_mapping; 309 unsigned int loff, nr_pages, req_pages; 310 struct page *pages[PIPE_DEF_BUFFERS]; 311 struct partial_page partial[PIPE_DEF_BUFFERS]; 312 struct page *page; 313 pgoff_t index, end_index; 314 loff_t isize; 315 int error, page_nr; 316 struct splice_pipe_desc spd = { 317 .pages = pages, 318 .partial = partial, 319 .nr_pages_max = PIPE_DEF_BUFFERS, 320 .flags = flags, 321 .ops = &page_cache_pipe_buf_ops, 322 .spd_release = spd_release_page, 323 }; 324 325 if (splice_grow_spd(pipe, &spd)) 326 return -ENOMEM; 327 328 index = *ppos >> PAGE_CACHE_SHIFT; 329 loff = *ppos & ~PAGE_CACHE_MASK; 330 req_pages = (len + loff + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT; 331 nr_pages = min(req_pages, spd.nr_pages_max); 332 333 /* 334 * Lookup the (hopefully) full range of pages we need. 335 */ 336 spd.nr_pages = find_get_pages_contig(mapping, index, nr_pages, spd.pages); 337 index += spd.nr_pages; 338 339 /* 340 * If find_get_pages_contig() returned fewer pages than we needed, 341 * readahead/allocate the rest and fill in the holes. 342 */ 343 if (spd.nr_pages < nr_pages) 344 page_cache_sync_readahead(mapping, &in->f_ra, in, 345 index, req_pages - spd.nr_pages); 346 347 error = 0; 348 while (spd.nr_pages < nr_pages) { 349 /* 350 * Page could be there, find_get_pages_contig() breaks on 351 * the first hole. 352 */ 353 page = find_get_page(mapping, index); 354 if (!page) { 355 /* 356 * page didn't exist, allocate one. 357 */ 358 page = page_cache_alloc_cold(mapping); 359 if (!page) 360 break; 361 362 error = add_to_page_cache_lru(page, mapping, index, 363 mapping_gfp_constraint(mapping, GFP_KERNEL)); 364 if (unlikely(error)) { 365 page_cache_release(page); 366 if (error == -EEXIST) 367 continue; 368 break; 369 } 370 /* 371 * add_to_page_cache() locks the page, unlock it 372 * to avoid convoluting the logic below even more. 373 */ 374 unlock_page(page); 375 } 376 377 spd.pages[spd.nr_pages++] = page; 378 index++; 379 } 380 381 /* 382 * Now loop over the map and see if we need to start IO on any 383 * pages, fill in the partial map, etc. 384 */ 385 index = *ppos >> PAGE_CACHE_SHIFT; 386 nr_pages = spd.nr_pages; 387 spd.nr_pages = 0; 388 for (page_nr = 0; page_nr < nr_pages; page_nr++) { 389 unsigned int this_len; 390 391 if (!len) 392 break; 393 394 /* 395 * this_len is the max we'll use from this page 396 */ 397 this_len = min_t(unsigned long, len, PAGE_CACHE_SIZE - loff); 398 page = spd.pages[page_nr]; 399 400 if (PageReadahead(page)) 401 page_cache_async_readahead(mapping, &in->f_ra, in, 402 page, index, req_pages - page_nr); 403 404 /* 405 * If the page isn't uptodate, we may need to start io on it 406 */ 407 if (!PageUptodate(page)) { 408 lock_page(page); 409 410 /* 411 * Page was truncated, or invalidated by the 412 * filesystem. Redo the find/create, but this time the 413 * page is kept locked, so there's no chance of another 414 * race with truncate/invalidate. 415 */ 416 if (!page->mapping) { 417 unlock_page(page); 418 page = find_or_create_page(mapping, index, 419 mapping_gfp_mask(mapping)); 420 421 if (!page) { 422 error = -ENOMEM; 423 break; 424 } 425 page_cache_release(spd.pages[page_nr]); 426 spd.pages[page_nr] = page; 427 } 428 /* 429 * page was already under io and is now done, great 430 */ 431 if (PageUptodate(page)) { 432 unlock_page(page); 433 goto fill_it; 434 } 435 436 /* 437 * need to read in the page 438 */ 439 error = mapping->a_ops->readpage(in, page); 440 if (unlikely(error)) { 441 /* 442 * We really should re-lookup the page here, 443 * but it complicates things a lot. Instead 444 * lets just do what we already stored, and 445 * we'll get it the next time we are called. 446 */ 447 if (error == AOP_TRUNCATED_PAGE) 448 error = 0; 449 450 break; 451 } 452 } 453 fill_it: 454 /* 455 * i_size must be checked after PageUptodate. 456 */ 457 isize = i_size_read(mapping->host); 458 end_index = (isize - 1) >> PAGE_CACHE_SHIFT; 459 if (unlikely(!isize || index > end_index)) 460 break; 461 462 /* 463 * if this is the last page, see if we need to shrink 464 * the length and stop 465 */ 466 if (end_index == index) { 467 unsigned int plen; 468 469 /* 470 * max good bytes in this page 471 */ 472 plen = ((isize - 1) & ~PAGE_CACHE_MASK) + 1; 473 if (plen <= loff) 474 break; 475 476 /* 477 * force quit after adding this page 478 */ 479 this_len = min(this_len, plen - loff); 480 len = this_len; 481 } 482 483 spd.partial[page_nr].offset = loff; 484 spd.partial[page_nr].len = this_len; 485 len -= this_len; 486 loff = 0; 487 spd.nr_pages++; 488 index++; 489 } 490 491 /* 492 * Release any pages at the end, if we quit early. 'page_nr' is how far 493 * we got, 'nr_pages' is how many pages are in the map. 494 */ 495 while (page_nr < nr_pages) 496 page_cache_release(spd.pages[page_nr++]); 497 in->f_ra.prev_pos = (loff_t)index << PAGE_CACHE_SHIFT; 498 499 if (spd.nr_pages) 500 error = splice_to_pipe(pipe, &spd); 501 502 splice_shrink_spd(&spd); 503 return error; 504 } 505 506 /** 507 * generic_file_splice_read - splice data from file to a pipe 508 * @in: file to splice from 509 * @ppos: position in @in 510 * @pipe: pipe to splice to 511 * @len: number of bytes to splice 512 * @flags: splice modifier flags 513 * 514 * Description: 515 * Will read pages from given file and fill them into a pipe. Can be 516 * used as long as the address_space operations for the source implements 517 * a readpage() hook. 518 * 519 */ 520 ssize_t generic_file_splice_read(struct file *in, loff_t *ppos, 521 struct pipe_inode_info *pipe, size_t len, 522 unsigned int flags) 523 { 524 loff_t isize, left; 525 int ret; 526 527 if (IS_DAX(in->f_mapping->host)) 528 return default_file_splice_read(in, ppos, pipe, len, flags); 529 530 isize = i_size_read(in->f_mapping->host); 531 if (unlikely(*ppos >= isize)) 532 return 0; 533 534 left = isize - *ppos; 535 if (unlikely(left < len)) 536 len = left; 537 538 ret = __generic_file_splice_read(in, ppos, pipe, len, flags); 539 if (ret > 0) { 540 *ppos += ret; 541 file_accessed(in); 542 } 543 544 return ret; 545 } 546 EXPORT_SYMBOL(generic_file_splice_read); 547 548 static const struct pipe_buf_operations default_pipe_buf_ops = { 549 .can_merge = 0, 550 .confirm = generic_pipe_buf_confirm, 551 .release = generic_pipe_buf_release, 552 .steal = generic_pipe_buf_steal, 553 .get = generic_pipe_buf_get, 554 }; 555 556 static int generic_pipe_buf_nosteal(struct pipe_inode_info *pipe, 557 struct pipe_buffer *buf) 558 { 559 return 1; 560 } 561 562 /* Pipe buffer operations for a socket and similar. */ 563 const struct pipe_buf_operations nosteal_pipe_buf_ops = { 564 .can_merge = 0, 565 .confirm = generic_pipe_buf_confirm, 566 .release = generic_pipe_buf_release, 567 .steal = generic_pipe_buf_nosteal, 568 .get = generic_pipe_buf_get, 569 }; 570 EXPORT_SYMBOL(nosteal_pipe_buf_ops); 571 572 static ssize_t kernel_readv(struct file *file, const struct iovec *vec, 573 unsigned long vlen, loff_t offset) 574 { 575 mm_segment_t old_fs; 576 loff_t pos = offset; 577 ssize_t res; 578 579 old_fs = get_fs(); 580 set_fs(get_ds()); 581 /* The cast to a user pointer is valid due to the set_fs() */ 582 res = vfs_readv(file, (const struct iovec __user *)vec, vlen, &pos); 583 set_fs(old_fs); 584 585 return res; 586 } 587 588 ssize_t kernel_write(struct file *file, const char *buf, size_t count, 589 loff_t pos) 590 { 591 mm_segment_t old_fs; 592 ssize_t res; 593 594 old_fs = get_fs(); 595 set_fs(get_ds()); 596 /* The cast to a user pointer is valid due to the set_fs() */ 597 res = vfs_write(file, (__force const char __user *)buf, count, &pos); 598 set_fs(old_fs); 599 600 return res; 601 } 602 EXPORT_SYMBOL(kernel_write); 603 604 ssize_t default_file_splice_read(struct file *in, loff_t *ppos, 605 struct pipe_inode_info *pipe, size_t len, 606 unsigned int flags) 607 { 608 unsigned int nr_pages; 609 unsigned int nr_freed; 610 size_t offset; 611 struct page *pages[PIPE_DEF_BUFFERS]; 612 struct partial_page partial[PIPE_DEF_BUFFERS]; 613 struct iovec *vec, __vec[PIPE_DEF_BUFFERS]; 614 ssize_t res; 615 size_t this_len; 616 int error; 617 int i; 618 struct splice_pipe_desc spd = { 619 .pages = pages, 620 .partial = partial, 621 .nr_pages_max = PIPE_DEF_BUFFERS, 622 .flags = flags, 623 .ops = &default_pipe_buf_ops, 624 .spd_release = spd_release_page, 625 }; 626 627 if (splice_grow_spd(pipe, &spd)) 628 return -ENOMEM; 629 630 res = -ENOMEM; 631 vec = __vec; 632 if (spd.nr_pages_max > PIPE_DEF_BUFFERS) { 633 vec = kmalloc(spd.nr_pages_max * sizeof(struct iovec), GFP_KERNEL); 634 if (!vec) 635 goto shrink_ret; 636 } 637 638 offset = *ppos & ~PAGE_CACHE_MASK; 639 nr_pages = (len + offset + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT; 640 641 for (i = 0; i < nr_pages && i < spd.nr_pages_max && len; i++) { 642 struct page *page; 643 644 page = alloc_page(GFP_USER); 645 error = -ENOMEM; 646 if (!page) 647 goto err; 648 649 this_len = min_t(size_t, len, PAGE_CACHE_SIZE - offset); 650 vec[i].iov_base = (void __user *) page_address(page); 651 vec[i].iov_len = this_len; 652 spd.pages[i] = page; 653 spd.nr_pages++; 654 len -= this_len; 655 offset = 0; 656 } 657 658 res = kernel_readv(in, vec, spd.nr_pages, *ppos); 659 if (res < 0) { 660 error = res; 661 goto err; 662 } 663 664 error = 0; 665 if (!res) 666 goto err; 667 668 nr_freed = 0; 669 for (i = 0; i < spd.nr_pages; i++) { 670 this_len = min_t(size_t, vec[i].iov_len, res); 671 spd.partial[i].offset = 0; 672 spd.partial[i].len = this_len; 673 if (!this_len) { 674 __free_page(spd.pages[i]); 675 spd.pages[i] = NULL; 676 nr_freed++; 677 } 678 res -= this_len; 679 } 680 spd.nr_pages -= nr_freed; 681 682 res = splice_to_pipe(pipe, &spd); 683 if (res > 0) 684 *ppos += res; 685 686 shrink_ret: 687 if (vec != __vec) 688 kfree(vec); 689 splice_shrink_spd(&spd); 690 return res; 691 692 err: 693 for (i = 0; i < spd.nr_pages; i++) 694 __free_page(spd.pages[i]); 695 696 res = error; 697 goto shrink_ret; 698 } 699 EXPORT_SYMBOL(default_file_splice_read); 700 701 /* 702 * Send 'sd->len' bytes to socket from 'sd->file' at position 'sd->pos' 703 * using sendpage(). Return the number of bytes sent. 704 */ 705 static int pipe_to_sendpage(struct pipe_inode_info *pipe, 706 struct pipe_buffer *buf, struct splice_desc *sd) 707 { 708 struct file *file = sd->u.file; 709 loff_t pos = sd->pos; 710 int more; 711 712 if (!likely(file->f_op->sendpage)) 713 return -EINVAL; 714 715 more = (sd->flags & SPLICE_F_MORE) ? MSG_MORE : 0; 716 717 if (sd->len < sd->total_len && pipe->nrbufs > 1) 718 more |= MSG_SENDPAGE_NOTLAST; 719 720 return file->f_op->sendpage(file, buf->page, buf->offset, 721 sd->len, &pos, more); 722 } 723 724 static void wakeup_pipe_writers(struct pipe_inode_info *pipe) 725 { 726 smp_mb(); 727 if (waitqueue_active(&pipe->wait)) 728 wake_up_interruptible(&pipe->wait); 729 kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT); 730 } 731 732 /** 733 * splice_from_pipe_feed - feed available data from a pipe to a file 734 * @pipe: pipe to splice from 735 * @sd: information to @actor 736 * @actor: handler that splices the data 737 * 738 * Description: 739 * This function loops over the pipe and calls @actor to do the 740 * actual moving of a single struct pipe_buffer to the desired 741 * destination. It returns when there's no more buffers left in 742 * the pipe or if the requested number of bytes (@sd->total_len) 743 * have been copied. It returns a positive number (one) if the 744 * pipe needs to be filled with more data, zero if the required 745 * number of bytes have been copied and -errno on error. 746 * 747 * This, together with splice_from_pipe_{begin,end,next}, may be 748 * used to implement the functionality of __splice_from_pipe() when 749 * locking is required around copying the pipe buffers to the 750 * destination. 751 */ 752 static int splice_from_pipe_feed(struct pipe_inode_info *pipe, struct splice_desc *sd, 753 splice_actor *actor) 754 { 755 int ret; 756 757 while (pipe->nrbufs) { 758 struct pipe_buffer *buf = pipe->bufs + pipe->curbuf; 759 const struct pipe_buf_operations *ops = buf->ops; 760 761 sd->len = buf->len; 762 if (sd->len > sd->total_len) 763 sd->len = sd->total_len; 764 765 ret = buf->ops->confirm(pipe, buf); 766 if (unlikely(ret)) { 767 if (ret == -ENODATA) 768 ret = 0; 769 return ret; 770 } 771 772 ret = actor(pipe, buf, sd); 773 if (ret <= 0) 774 return ret; 775 776 buf->offset += ret; 777 buf->len -= ret; 778 779 sd->num_spliced += ret; 780 sd->len -= ret; 781 sd->pos += ret; 782 sd->total_len -= ret; 783 784 if (!buf->len) { 785 buf->ops = NULL; 786 ops->release(pipe, buf); 787 pipe->curbuf = (pipe->curbuf + 1) & (pipe->buffers - 1); 788 pipe->nrbufs--; 789 if (pipe->files) 790 sd->need_wakeup = true; 791 } 792 793 if (!sd->total_len) 794 return 0; 795 } 796 797 return 1; 798 } 799 800 /** 801 * splice_from_pipe_next - wait for some data to splice from 802 * @pipe: pipe to splice from 803 * @sd: information about the splice operation 804 * 805 * Description: 806 * This function will wait for some data and return a positive 807 * value (one) if pipe buffers are available. It will return zero 808 * or -errno if no more data needs to be spliced. 809 */ 810 static int splice_from_pipe_next(struct pipe_inode_info *pipe, struct splice_desc *sd) 811 { 812 /* 813 * Check for signal early to make process killable when there are 814 * always buffers available 815 */ 816 if (signal_pending(current)) 817 return -ERESTARTSYS; 818 819 while (!pipe->nrbufs) { 820 if (!pipe->writers) 821 return 0; 822 823 if (!pipe->waiting_writers && sd->num_spliced) 824 return 0; 825 826 if (sd->flags & SPLICE_F_NONBLOCK) 827 return -EAGAIN; 828 829 if (signal_pending(current)) 830 return -ERESTARTSYS; 831 832 if (sd->need_wakeup) { 833 wakeup_pipe_writers(pipe); 834 sd->need_wakeup = false; 835 } 836 837 pipe_wait(pipe); 838 } 839 840 return 1; 841 } 842 843 /** 844 * splice_from_pipe_begin - start splicing from pipe 845 * @sd: information about the splice operation 846 * 847 * Description: 848 * This function should be called before a loop containing 849 * splice_from_pipe_next() and splice_from_pipe_feed() to 850 * initialize the necessary fields of @sd. 851 */ 852 static void splice_from_pipe_begin(struct splice_desc *sd) 853 { 854 sd->num_spliced = 0; 855 sd->need_wakeup = false; 856 } 857 858 /** 859 * splice_from_pipe_end - finish splicing from pipe 860 * @pipe: pipe to splice from 861 * @sd: information about the splice operation 862 * 863 * Description: 864 * This function will wake up pipe writers if necessary. It should 865 * be called after a loop containing splice_from_pipe_next() and 866 * splice_from_pipe_feed(). 867 */ 868 static void splice_from_pipe_end(struct pipe_inode_info *pipe, struct splice_desc *sd) 869 { 870 if (sd->need_wakeup) 871 wakeup_pipe_writers(pipe); 872 } 873 874 /** 875 * __splice_from_pipe - splice data from a pipe to given actor 876 * @pipe: pipe to splice from 877 * @sd: information to @actor 878 * @actor: handler that splices the data 879 * 880 * Description: 881 * This function does little more than loop over the pipe and call 882 * @actor to do the actual moving of a single struct pipe_buffer to 883 * the desired destination. See pipe_to_file, pipe_to_sendpage, or 884 * pipe_to_user. 885 * 886 */ 887 ssize_t __splice_from_pipe(struct pipe_inode_info *pipe, struct splice_desc *sd, 888 splice_actor *actor) 889 { 890 int ret; 891 892 splice_from_pipe_begin(sd); 893 do { 894 cond_resched(); 895 ret = splice_from_pipe_next(pipe, sd); 896 if (ret > 0) 897 ret = splice_from_pipe_feed(pipe, sd, actor); 898 } while (ret > 0); 899 splice_from_pipe_end(pipe, sd); 900 901 return sd->num_spliced ? sd->num_spliced : ret; 902 } 903 EXPORT_SYMBOL(__splice_from_pipe); 904 905 /** 906 * splice_from_pipe - splice data from a pipe to a file 907 * @pipe: pipe to splice from 908 * @out: file to splice to 909 * @ppos: position in @out 910 * @len: how many bytes to splice 911 * @flags: splice modifier flags 912 * @actor: handler that splices the data 913 * 914 * Description: 915 * See __splice_from_pipe. This function locks the pipe inode, 916 * otherwise it's identical to __splice_from_pipe(). 917 * 918 */ 919 ssize_t splice_from_pipe(struct pipe_inode_info *pipe, struct file *out, 920 loff_t *ppos, size_t len, unsigned int flags, 921 splice_actor *actor) 922 { 923 ssize_t ret; 924 struct splice_desc sd = { 925 .total_len = len, 926 .flags = flags, 927 .pos = *ppos, 928 .u.file = out, 929 }; 930 931 pipe_lock(pipe); 932 ret = __splice_from_pipe(pipe, &sd, actor); 933 pipe_unlock(pipe); 934 935 return ret; 936 } 937 938 /** 939 * iter_file_splice_write - splice data from a pipe to a file 940 * @pipe: pipe info 941 * @out: file to write to 942 * @ppos: position in @out 943 * @len: number of bytes to splice 944 * @flags: splice modifier flags 945 * 946 * Description: 947 * Will either move or copy pages (determined by @flags options) from 948 * the given pipe inode to the given file. 949 * This one is ->write_iter-based. 950 * 951 */ 952 ssize_t 953 iter_file_splice_write(struct pipe_inode_info *pipe, struct file *out, 954 loff_t *ppos, size_t len, unsigned int flags) 955 { 956 struct splice_desc sd = { 957 .total_len = len, 958 .flags = flags, 959 .pos = *ppos, 960 .u.file = out, 961 }; 962 int nbufs = pipe->buffers; 963 struct bio_vec *array = kcalloc(nbufs, sizeof(struct bio_vec), 964 GFP_KERNEL); 965 ssize_t ret; 966 967 if (unlikely(!array)) 968 return -ENOMEM; 969 970 pipe_lock(pipe); 971 972 splice_from_pipe_begin(&sd); 973 while (sd.total_len) { 974 struct iov_iter from; 975 size_t left; 976 int n, idx; 977 978 ret = splice_from_pipe_next(pipe, &sd); 979 if (ret <= 0) 980 break; 981 982 if (unlikely(nbufs < pipe->buffers)) { 983 kfree(array); 984 nbufs = pipe->buffers; 985 array = kcalloc(nbufs, sizeof(struct bio_vec), 986 GFP_KERNEL); 987 if (!array) { 988 ret = -ENOMEM; 989 break; 990 } 991 } 992 993 /* build the vector */ 994 left = sd.total_len; 995 for (n = 0, idx = pipe->curbuf; left && n < pipe->nrbufs; n++, idx++) { 996 struct pipe_buffer *buf = pipe->bufs + idx; 997 size_t this_len = buf->len; 998 999 if (this_len > left) 1000 this_len = left; 1001 1002 if (idx == pipe->buffers - 1) 1003 idx = -1; 1004 1005 ret = buf->ops->confirm(pipe, buf); 1006 if (unlikely(ret)) { 1007 if (ret == -ENODATA) 1008 ret = 0; 1009 goto done; 1010 } 1011 1012 array[n].bv_page = buf->page; 1013 array[n].bv_len = this_len; 1014 array[n].bv_offset = buf->offset; 1015 left -= this_len; 1016 } 1017 1018 iov_iter_bvec(&from, ITER_BVEC | WRITE, array, n, 1019 sd.total_len - left); 1020 ret = vfs_iter_write(out, &from, &sd.pos); 1021 if (ret <= 0) 1022 break; 1023 1024 sd.num_spliced += ret; 1025 sd.total_len -= ret; 1026 *ppos = sd.pos; 1027 1028 /* dismiss the fully eaten buffers, adjust the partial one */ 1029 while (ret) { 1030 struct pipe_buffer *buf = pipe->bufs + pipe->curbuf; 1031 if (ret >= buf->len) { 1032 const struct pipe_buf_operations *ops = buf->ops; 1033 ret -= buf->len; 1034 buf->len = 0; 1035 buf->ops = NULL; 1036 ops->release(pipe, buf); 1037 pipe->curbuf = (pipe->curbuf + 1) & (pipe->buffers - 1); 1038 pipe->nrbufs--; 1039 if (pipe->files) 1040 sd.need_wakeup = true; 1041 } else { 1042 buf->offset += ret; 1043 buf->len -= ret; 1044 ret = 0; 1045 } 1046 } 1047 } 1048 done: 1049 kfree(array); 1050 splice_from_pipe_end(pipe, &sd); 1051 1052 pipe_unlock(pipe); 1053 1054 if (sd.num_spliced) 1055 ret = sd.num_spliced; 1056 1057 return ret; 1058 } 1059 1060 EXPORT_SYMBOL(iter_file_splice_write); 1061 1062 static int write_pipe_buf(struct pipe_inode_info *pipe, struct pipe_buffer *buf, 1063 struct splice_desc *sd) 1064 { 1065 int ret; 1066 void *data; 1067 loff_t tmp = sd->pos; 1068 1069 data = kmap(buf->page); 1070 ret = __kernel_write(sd->u.file, data + buf->offset, sd->len, &tmp); 1071 kunmap(buf->page); 1072 1073 return ret; 1074 } 1075 1076 static ssize_t default_file_splice_write(struct pipe_inode_info *pipe, 1077 struct file *out, loff_t *ppos, 1078 size_t len, unsigned int flags) 1079 { 1080 ssize_t ret; 1081 1082 ret = splice_from_pipe(pipe, out, ppos, len, flags, write_pipe_buf); 1083 if (ret > 0) 1084 *ppos += ret; 1085 1086 return ret; 1087 } 1088 1089 /** 1090 * generic_splice_sendpage - splice data from a pipe to a socket 1091 * @pipe: pipe to splice from 1092 * @out: socket to write to 1093 * @ppos: position in @out 1094 * @len: number of bytes to splice 1095 * @flags: splice modifier flags 1096 * 1097 * Description: 1098 * Will send @len bytes from the pipe to a network socket. No data copying 1099 * is involved. 1100 * 1101 */ 1102 ssize_t generic_splice_sendpage(struct pipe_inode_info *pipe, struct file *out, 1103 loff_t *ppos, size_t len, unsigned int flags) 1104 { 1105 return splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_sendpage); 1106 } 1107 1108 EXPORT_SYMBOL(generic_splice_sendpage); 1109 1110 /* 1111 * Attempt to initiate a splice from pipe to file. 1112 */ 1113 static long do_splice_from(struct pipe_inode_info *pipe, struct file *out, 1114 loff_t *ppos, size_t len, unsigned int flags) 1115 { 1116 ssize_t (*splice_write)(struct pipe_inode_info *, struct file *, 1117 loff_t *, size_t, unsigned int); 1118 1119 if (out->f_op->splice_write) 1120 splice_write = out->f_op->splice_write; 1121 else 1122 splice_write = default_file_splice_write; 1123 1124 return splice_write(pipe, out, ppos, len, flags); 1125 } 1126 1127 /* 1128 * Attempt to initiate a splice from a file to a pipe. 1129 */ 1130 static long do_splice_to(struct file *in, loff_t *ppos, 1131 struct pipe_inode_info *pipe, size_t len, 1132 unsigned int flags) 1133 { 1134 ssize_t (*splice_read)(struct file *, loff_t *, 1135 struct pipe_inode_info *, size_t, unsigned int); 1136 int ret; 1137 1138 if (unlikely(!(in->f_mode & FMODE_READ))) 1139 return -EBADF; 1140 1141 ret = rw_verify_area(READ, in, ppos, len); 1142 if (unlikely(ret < 0)) 1143 return ret; 1144 1145 if (in->f_op->splice_read) 1146 splice_read = in->f_op->splice_read; 1147 else 1148 splice_read = default_file_splice_read; 1149 1150 return splice_read(in, ppos, pipe, len, flags); 1151 } 1152 1153 /** 1154 * splice_direct_to_actor - splices data directly between two non-pipes 1155 * @in: file to splice from 1156 * @sd: actor information on where to splice to 1157 * @actor: handles the data splicing 1158 * 1159 * Description: 1160 * This is a special case helper to splice directly between two 1161 * points, without requiring an explicit pipe. Internally an allocated 1162 * pipe is cached in the process, and reused during the lifetime of 1163 * that process. 1164 * 1165 */ 1166 ssize_t splice_direct_to_actor(struct file *in, struct splice_desc *sd, 1167 splice_direct_actor *actor) 1168 { 1169 struct pipe_inode_info *pipe; 1170 long ret, bytes; 1171 umode_t i_mode; 1172 size_t len; 1173 int i, flags, more; 1174 1175 /* 1176 * We require the input being a regular file, as we don't want to 1177 * randomly drop data for eg socket -> socket splicing. Use the 1178 * piped splicing for that! 1179 */ 1180 i_mode = file_inode(in)->i_mode; 1181 if (unlikely(!S_ISREG(i_mode) && !S_ISBLK(i_mode))) 1182 return -EINVAL; 1183 1184 /* 1185 * neither in nor out is a pipe, setup an internal pipe attached to 1186 * 'out' and transfer the wanted data from 'in' to 'out' through that 1187 */ 1188 pipe = current->splice_pipe; 1189 if (unlikely(!pipe)) { 1190 pipe = alloc_pipe_info(); 1191 if (!pipe) 1192 return -ENOMEM; 1193 1194 /* 1195 * We don't have an immediate reader, but we'll read the stuff 1196 * out of the pipe right after the splice_to_pipe(). So set 1197 * PIPE_READERS appropriately. 1198 */ 1199 pipe->readers = 1; 1200 1201 current->splice_pipe = pipe; 1202 } 1203 1204 /* 1205 * Do the splice. 1206 */ 1207 ret = 0; 1208 bytes = 0; 1209 len = sd->total_len; 1210 flags = sd->flags; 1211 1212 /* 1213 * Don't block on output, we have to drain the direct pipe. 1214 */ 1215 sd->flags &= ~SPLICE_F_NONBLOCK; 1216 more = sd->flags & SPLICE_F_MORE; 1217 1218 while (len) { 1219 size_t read_len; 1220 loff_t pos = sd->pos, prev_pos = pos; 1221 1222 ret = do_splice_to(in, &pos, pipe, len, flags); 1223 if (unlikely(ret <= 0)) 1224 goto out_release; 1225 1226 read_len = ret; 1227 sd->total_len = read_len; 1228 1229 /* 1230 * If more data is pending, set SPLICE_F_MORE 1231 * If this is the last data and SPLICE_F_MORE was not set 1232 * initially, clears it. 1233 */ 1234 if (read_len < len) 1235 sd->flags |= SPLICE_F_MORE; 1236 else if (!more) 1237 sd->flags &= ~SPLICE_F_MORE; 1238 /* 1239 * NOTE: nonblocking mode only applies to the input. We 1240 * must not do the output in nonblocking mode as then we 1241 * could get stuck data in the internal pipe: 1242 */ 1243 ret = actor(pipe, sd); 1244 if (unlikely(ret <= 0)) { 1245 sd->pos = prev_pos; 1246 goto out_release; 1247 } 1248 1249 bytes += ret; 1250 len -= ret; 1251 sd->pos = pos; 1252 1253 if (ret < read_len) { 1254 sd->pos = prev_pos + ret; 1255 goto out_release; 1256 } 1257 } 1258 1259 done: 1260 pipe->nrbufs = pipe->curbuf = 0; 1261 file_accessed(in); 1262 return bytes; 1263 1264 out_release: 1265 /* 1266 * If we did an incomplete transfer we must release 1267 * the pipe buffers in question: 1268 */ 1269 for (i = 0; i < pipe->buffers; i++) { 1270 struct pipe_buffer *buf = pipe->bufs + i; 1271 1272 if (buf->ops) { 1273 buf->ops->release(pipe, buf); 1274 buf->ops = NULL; 1275 } 1276 } 1277 1278 if (!bytes) 1279 bytes = ret; 1280 1281 goto done; 1282 } 1283 EXPORT_SYMBOL(splice_direct_to_actor); 1284 1285 static int direct_splice_actor(struct pipe_inode_info *pipe, 1286 struct splice_desc *sd) 1287 { 1288 struct file *file = sd->u.file; 1289 1290 return do_splice_from(pipe, file, sd->opos, sd->total_len, 1291 sd->flags); 1292 } 1293 1294 /** 1295 * do_splice_direct - splices data directly between two files 1296 * @in: file to splice from 1297 * @ppos: input file offset 1298 * @out: file to splice to 1299 * @opos: output file offset 1300 * @len: number of bytes to splice 1301 * @flags: splice modifier flags 1302 * 1303 * Description: 1304 * For use by do_sendfile(). splice can easily emulate sendfile, but 1305 * doing it in the application would incur an extra system call 1306 * (splice in + splice out, as compared to just sendfile()). So this helper 1307 * can splice directly through a process-private pipe. 1308 * 1309 */ 1310 long do_splice_direct(struct file *in, loff_t *ppos, struct file *out, 1311 loff_t *opos, size_t len, unsigned int flags) 1312 { 1313 struct splice_desc sd = { 1314 .len = len, 1315 .total_len = len, 1316 .flags = flags, 1317 .pos = *ppos, 1318 .u.file = out, 1319 .opos = opos, 1320 }; 1321 long ret; 1322 1323 if (unlikely(!(out->f_mode & FMODE_WRITE))) 1324 return -EBADF; 1325 1326 if (unlikely(out->f_flags & O_APPEND)) 1327 return -EINVAL; 1328 1329 ret = rw_verify_area(WRITE, out, opos, len); 1330 if (unlikely(ret < 0)) 1331 return ret; 1332 1333 ret = splice_direct_to_actor(in, &sd, direct_splice_actor); 1334 if (ret > 0) 1335 *ppos = sd.pos; 1336 1337 return ret; 1338 } 1339 EXPORT_SYMBOL(do_splice_direct); 1340 1341 static int splice_pipe_to_pipe(struct pipe_inode_info *ipipe, 1342 struct pipe_inode_info *opipe, 1343 size_t len, unsigned int flags); 1344 1345 /* 1346 * Determine where to splice to/from. 1347 */ 1348 static long do_splice(struct file *in, loff_t __user *off_in, 1349 struct file *out, loff_t __user *off_out, 1350 size_t len, unsigned int flags) 1351 { 1352 struct pipe_inode_info *ipipe; 1353 struct pipe_inode_info *opipe; 1354 loff_t offset; 1355 long ret; 1356 1357 ipipe = get_pipe_info(in); 1358 opipe = get_pipe_info(out); 1359 1360 if (ipipe && opipe) { 1361 if (off_in || off_out) 1362 return -ESPIPE; 1363 1364 if (!(in->f_mode & FMODE_READ)) 1365 return -EBADF; 1366 1367 if (!(out->f_mode & FMODE_WRITE)) 1368 return -EBADF; 1369 1370 /* Splicing to self would be fun, but... */ 1371 if (ipipe == opipe) 1372 return -EINVAL; 1373 1374 return splice_pipe_to_pipe(ipipe, opipe, len, flags); 1375 } 1376 1377 if (ipipe) { 1378 if (off_in) 1379 return -ESPIPE; 1380 if (off_out) { 1381 if (!(out->f_mode & FMODE_PWRITE)) 1382 return -EINVAL; 1383 if (copy_from_user(&offset, off_out, sizeof(loff_t))) 1384 return -EFAULT; 1385 } else { 1386 offset = out->f_pos; 1387 } 1388 1389 if (unlikely(!(out->f_mode & FMODE_WRITE))) 1390 return -EBADF; 1391 1392 if (unlikely(out->f_flags & O_APPEND)) 1393 return -EINVAL; 1394 1395 ret = rw_verify_area(WRITE, out, &offset, len); 1396 if (unlikely(ret < 0)) 1397 return ret; 1398 1399 file_start_write(out); 1400 ret = do_splice_from(ipipe, out, &offset, len, flags); 1401 file_end_write(out); 1402 1403 if (!off_out) 1404 out->f_pos = offset; 1405 else if (copy_to_user(off_out, &offset, sizeof(loff_t))) 1406 ret = -EFAULT; 1407 1408 return ret; 1409 } 1410 1411 if (opipe) { 1412 if (off_out) 1413 return -ESPIPE; 1414 if (off_in) { 1415 if (!(in->f_mode & FMODE_PREAD)) 1416 return -EINVAL; 1417 if (copy_from_user(&offset, off_in, sizeof(loff_t))) 1418 return -EFAULT; 1419 } else { 1420 offset = in->f_pos; 1421 } 1422 1423 ret = do_splice_to(in, &offset, opipe, len, flags); 1424 1425 if (!off_in) 1426 in->f_pos = offset; 1427 else if (copy_to_user(off_in, &offset, sizeof(loff_t))) 1428 ret = -EFAULT; 1429 1430 return ret; 1431 } 1432 1433 return -EINVAL; 1434 } 1435 1436 /* 1437 * Map an iov into an array of pages and offset/length tupples. With the 1438 * partial_page structure, we can map several non-contiguous ranges into 1439 * our ones pages[] map instead of splitting that operation into pieces. 1440 * Could easily be exported as a generic helper for other users, in which 1441 * case one would probably want to add a 'max_nr_pages' parameter as well. 1442 */ 1443 static int get_iovec_page_array(const struct iovec __user *iov, 1444 unsigned int nr_vecs, struct page **pages, 1445 struct partial_page *partial, bool aligned, 1446 unsigned int pipe_buffers) 1447 { 1448 int buffers = 0, error = 0; 1449 1450 while (nr_vecs) { 1451 unsigned long off, npages; 1452 struct iovec entry; 1453 void __user *base; 1454 size_t len; 1455 int i; 1456 1457 error = -EFAULT; 1458 if (copy_from_user(&entry, iov, sizeof(entry))) 1459 break; 1460 1461 base = entry.iov_base; 1462 len = entry.iov_len; 1463 1464 /* 1465 * Sanity check this iovec. 0 read succeeds. 1466 */ 1467 error = 0; 1468 if (unlikely(!len)) 1469 break; 1470 error = -EFAULT; 1471 if (!access_ok(VERIFY_READ, base, len)) 1472 break; 1473 1474 /* 1475 * Get this base offset and number of pages, then map 1476 * in the user pages. 1477 */ 1478 off = (unsigned long) base & ~PAGE_MASK; 1479 1480 /* 1481 * If asked for alignment, the offset must be zero and the 1482 * length a multiple of the PAGE_SIZE. 1483 */ 1484 error = -EINVAL; 1485 if (aligned && (off || len & ~PAGE_MASK)) 1486 break; 1487 1488 npages = (off + len + PAGE_SIZE - 1) >> PAGE_SHIFT; 1489 if (npages > pipe_buffers - buffers) 1490 npages = pipe_buffers - buffers; 1491 1492 error = get_user_pages_fast((unsigned long)base, npages, 1493 0, &pages[buffers]); 1494 1495 if (unlikely(error <= 0)) 1496 break; 1497 1498 /* 1499 * Fill this contiguous range into the partial page map. 1500 */ 1501 for (i = 0; i < error; i++) { 1502 const int plen = min_t(size_t, len, PAGE_SIZE - off); 1503 1504 partial[buffers].offset = off; 1505 partial[buffers].len = plen; 1506 1507 off = 0; 1508 len -= plen; 1509 buffers++; 1510 } 1511 1512 /* 1513 * We didn't complete this iov, stop here since it probably 1514 * means we have to move some of this into a pipe to 1515 * be able to continue. 1516 */ 1517 if (len) 1518 break; 1519 1520 /* 1521 * Don't continue if we mapped fewer pages than we asked for, 1522 * or if we mapped the max number of pages that we have 1523 * room for. 1524 */ 1525 if (error < npages || buffers == pipe_buffers) 1526 break; 1527 1528 nr_vecs--; 1529 iov++; 1530 } 1531 1532 if (buffers) 1533 return buffers; 1534 1535 return error; 1536 } 1537 1538 static int pipe_to_user(struct pipe_inode_info *pipe, struct pipe_buffer *buf, 1539 struct splice_desc *sd) 1540 { 1541 int n = copy_page_to_iter(buf->page, buf->offset, sd->len, sd->u.data); 1542 return n == sd->len ? n : -EFAULT; 1543 } 1544 1545 /* 1546 * For lack of a better implementation, implement vmsplice() to userspace 1547 * as a simple copy of the pipes pages to the user iov. 1548 */ 1549 static long vmsplice_to_user(struct file *file, const struct iovec __user *uiov, 1550 unsigned long nr_segs, unsigned int flags) 1551 { 1552 struct pipe_inode_info *pipe; 1553 struct splice_desc sd; 1554 long ret; 1555 struct iovec iovstack[UIO_FASTIOV]; 1556 struct iovec *iov = iovstack; 1557 struct iov_iter iter; 1558 1559 pipe = get_pipe_info(file); 1560 if (!pipe) 1561 return -EBADF; 1562 1563 ret = import_iovec(READ, uiov, nr_segs, 1564 ARRAY_SIZE(iovstack), &iov, &iter); 1565 if (ret < 0) 1566 return ret; 1567 1568 sd.total_len = iov_iter_count(&iter); 1569 sd.len = 0; 1570 sd.flags = flags; 1571 sd.u.data = &iter; 1572 sd.pos = 0; 1573 1574 if (sd.total_len) { 1575 pipe_lock(pipe); 1576 ret = __splice_from_pipe(pipe, &sd, pipe_to_user); 1577 pipe_unlock(pipe); 1578 } 1579 1580 kfree(iov); 1581 return ret; 1582 } 1583 1584 /* 1585 * vmsplice splices a user address range into a pipe. It can be thought of 1586 * as splice-from-memory, where the regular splice is splice-from-file (or 1587 * to file). In both cases the output is a pipe, naturally. 1588 */ 1589 static long vmsplice_to_pipe(struct file *file, const struct iovec __user *iov, 1590 unsigned long nr_segs, unsigned int flags) 1591 { 1592 struct pipe_inode_info *pipe; 1593 struct page *pages[PIPE_DEF_BUFFERS]; 1594 struct partial_page partial[PIPE_DEF_BUFFERS]; 1595 struct splice_pipe_desc spd = { 1596 .pages = pages, 1597 .partial = partial, 1598 .nr_pages_max = PIPE_DEF_BUFFERS, 1599 .flags = flags, 1600 .ops = &user_page_pipe_buf_ops, 1601 .spd_release = spd_release_page, 1602 }; 1603 long ret; 1604 1605 pipe = get_pipe_info(file); 1606 if (!pipe) 1607 return -EBADF; 1608 1609 if (splice_grow_spd(pipe, &spd)) 1610 return -ENOMEM; 1611 1612 spd.nr_pages = get_iovec_page_array(iov, nr_segs, spd.pages, 1613 spd.partial, false, 1614 spd.nr_pages_max); 1615 if (spd.nr_pages <= 0) 1616 ret = spd.nr_pages; 1617 else 1618 ret = splice_to_pipe(pipe, &spd); 1619 1620 splice_shrink_spd(&spd); 1621 return ret; 1622 } 1623 1624 /* 1625 * Note that vmsplice only really supports true splicing _from_ user memory 1626 * to a pipe, not the other way around. Splicing from user memory is a simple 1627 * operation that can be supported without any funky alignment restrictions 1628 * or nasty vm tricks. We simply map in the user memory and fill them into 1629 * a pipe. The reverse isn't quite as easy, though. There are two possible 1630 * solutions for that: 1631 * 1632 * - memcpy() the data internally, at which point we might as well just 1633 * do a regular read() on the buffer anyway. 1634 * - Lots of nasty vm tricks, that are neither fast nor flexible (it 1635 * has restriction limitations on both ends of the pipe). 1636 * 1637 * Currently we punt and implement it as a normal copy, see pipe_to_user(). 1638 * 1639 */ 1640 SYSCALL_DEFINE4(vmsplice, int, fd, const struct iovec __user *, iov, 1641 unsigned long, nr_segs, unsigned int, flags) 1642 { 1643 struct fd f; 1644 long error; 1645 1646 if (unlikely(nr_segs > UIO_MAXIOV)) 1647 return -EINVAL; 1648 else if (unlikely(!nr_segs)) 1649 return 0; 1650 1651 error = -EBADF; 1652 f = fdget(fd); 1653 if (f.file) { 1654 if (f.file->f_mode & FMODE_WRITE) 1655 error = vmsplice_to_pipe(f.file, iov, nr_segs, flags); 1656 else if (f.file->f_mode & FMODE_READ) 1657 error = vmsplice_to_user(f.file, iov, nr_segs, flags); 1658 1659 fdput(f); 1660 } 1661 1662 return error; 1663 } 1664 1665 #ifdef CONFIG_COMPAT 1666 COMPAT_SYSCALL_DEFINE4(vmsplice, int, fd, const struct compat_iovec __user *, iov32, 1667 unsigned int, nr_segs, unsigned int, flags) 1668 { 1669 unsigned i; 1670 struct iovec __user *iov; 1671 if (nr_segs > UIO_MAXIOV) 1672 return -EINVAL; 1673 iov = compat_alloc_user_space(nr_segs * sizeof(struct iovec)); 1674 for (i = 0; i < nr_segs; i++) { 1675 struct compat_iovec v; 1676 if (get_user(v.iov_base, &iov32[i].iov_base) || 1677 get_user(v.iov_len, &iov32[i].iov_len) || 1678 put_user(compat_ptr(v.iov_base), &iov[i].iov_base) || 1679 put_user(v.iov_len, &iov[i].iov_len)) 1680 return -EFAULT; 1681 } 1682 return sys_vmsplice(fd, iov, nr_segs, flags); 1683 } 1684 #endif 1685 1686 SYSCALL_DEFINE6(splice, int, fd_in, loff_t __user *, off_in, 1687 int, fd_out, loff_t __user *, off_out, 1688 size_t, len, unsigned int, flags) 1689 { 1690 struct fd in, out; 1691 long error; 1692 1693 if (unlikely(!len)) 1694 return 0; 1695 1696 error = -EBADF; 1697 in = fdget(fd_in); 1698 if (in.file) { 1699 if (in.file->f_mode & FMODE_READ) { 1700 out = fdget(fd_out); 1701 if (out.file) { 1702 if (out.file->f_mode & FMODE_WRITE) 1703 error = do_splice(in.file, off_in, 1704 out.file, off_out, 1705 len, flags); 1706 fdput(out); 1707 } 1708 } 1709 fdput(in); 1710 } 1711 return error; 1712 } 1713 1714 /* 1715 * Make sure there's data to read. Wait for input if we can, otherwise 1716 * return an appropriate error. 1717 */ 1718 static int ipipe_prep(struct pipe_inode_info *pipe, unsigned int flags) 1719 { 1720 int ret; 1721 1722 /* 1723 * Check ->nrbufs without the inode lock first. This function 1724 * is speculative anyways, so missing one is ok. 1725 */ 1726 if (pipe->nrbufs) 1727 return 0; 1728 1729 ret = 0; 1730 pipe_lock(pipe); 1731 1732 while (!pipe->nrbufs) { 1733 if (signal_pending(current)) { 1734 ret = -ERESTARTSYS; 1735 break; 1736 } 1737 if (!pipe->writers) 1738 break; 1739 if (!pipe->waiting_writers) { 1740 if (flags & SPLICE_F_NONBLOCK) { 1741 ret = -EAGAIN; 1742 break; 1743 } 1744 } 1745 pipe_wait(pipe); 1746 } 1747 1748 pipe_unlock(pipe); 1749 return ret; 1750 } 1751 1752 /* 1753 * Make sure there's writeable room. Wait for room if we can, otherwise 1754 * return an appropriate error. 1755 */ 1756 static int opipe_prep(struct pipe_inode_info *pipe, unsigned int flags) 1757 { 1758 int ret; 1759 1760 /* 1761 * Check ->nrbufs without the inode lock first. This function 1762 * is speculative anyways, so missing one is ok. 1763 */ 1764 if (pipe->nrbufs < pipe->buffers) 1765 return 0; 1766 1767 ret = 0; 1768 pipe_lock(pipe); 1769 1770 while (pipe->nrbufs >= pipe->buffers) { 1771 if (!pipe->readers) { 1772 send_sig(SIGPIPE, current, 0); 1773 ret = -EPIPE; 1774 break; 1775 } 1776 if (flags & SPLICE_F_NONBLOCK) { 1777 ret = -EAGAIN; 1778 break; 1779 } 1780 if (signal_pending(current)) { 1781 ret = -ERESTARTSYS; 1782 break; 1783 } 1784 pipe->waiting_writers++; 1785 pipe_wait(pipe); 1786 pipe->waiting_writers--; 1787 } 1788 1789 pipe_unlock(pipe); 1790 return ret; 1791 } 1792 1793 /* 1794 * Splice contents of ipipe to opipe. 1795 */ 1796 static int splice_pipe_to_pipe(struct pipe_inode_info *ipipe, 1797 struct pipe_inode_info *opipe, 1798 size_t len, unsigned int flags) 1799 { 1800 struct pipe_buffer *ibuf, *obuf; 1801 int ret = 0, nbuf; 1802 bool input_wakeup = false; 1803 1804 1805 retry: 1806 ret = ipipe_prep(ipipe, flags); 1807 if (ret) 1808 return ret; 1809 1810 ret = opipe_prep(opipe, flags); 1811 if (ret) 1812 return ret; 1813 1814 /* 1815 * Potential ABBA deadlock, work around it by ordering lock 1816 * grabbing by pipe info address. Otherwise two different processes 1817 * could deadlock (one doing tee from A -> B, the other from B -> A). 1818 */ 1819 pipe_double_lock(ipipe, opipe); 1820 1821 do { 1822 if (!opipe->readers) { 1823 send_sig(SIGPIPE, current, 0); 1824 if (!ret) 1825 ret = -EPIPE; 1826 break; 1827 } 1828 1829 if (!ipipe->nrbufs && !ipipe->writers) 1830 break; 1831 1832 /* 1833 * Cannot make any progress, because either the input 1834 * pipe is empty or the output pipe is full. 1835 */ 1836 if (!ipipe->nrbufs || opipe->nrbufs >= opipe->buffers) { 1837 /* Already processed some buffers, break */ 1838 if (ret) 1839 break; 1840 1841 if (flags & SPLICE_F_NONBLOCK) { 1842 ret = -EAGAIN; 1843 break; 1844 } 1845 1846 /* 1847 * We raced with another reader/writer and haven't 1848 * managed to process any buffers. A zero return 1849 * value means EOF, so retry instead. 1850 */ 1851 pipe_unlock(ipipe); 1852 pipe_unlock(opipe); 1853 goto retry; 1854 } 1855 1856 ibuf = ipipe->bufs + ipipe->curbuf; 1857 nbuf = (opipe->curbuf + opipe->nrbufs) & (opipe->buffers - 1); 1858 obuf = opipe->bufs + nbuf; 1859 1860 if (len >= ibuf->len) { 1861 /* 1862 * Simply move the whole buffer from ipipe to opipe 1863 */ 1864 *obuf = *ibuf; 1865 ibuf->ops = NULL; 1866 opipe->nrbufs++; 1867 ipipe->curbuf = (ipipe->curbuf + 1) & (ipipe->buffers - 1); 1868 ipipe->nrbufs--; 1869 input_wakeup = true; 1870 } else { 1871 /* 1872 * Get a reference to this pipe buffer, 1873 * so we can copy the contents over. 1874 */ 1875 ibuf->ops->get(ipipe, ibuf); 1876 *obuf = *ibuf; 1877 1878 /* 1879 * Don't inherit the gift flag, we need to 1880 * prevent multiple steals of this page. 1881 */ 1882 obuf->flags &= ~PIPE_BUF_FLAG_GIFT; 1883 1884 obuf->len = len; 1885 opipe->nrbufs++; 1886 ibuf->offset += obuf->len; 1887 ibuf->len -= obuf->len; 1888 } 1889 ret += obuf->len; 1890 len -= obuf->len; 1891 } while (len); 1892 1893 pipe_unlock(ipipe); 1894 pipe_unlock(opipe); 1895 1896 /* 1897 * If we put data in the output pipe, wakeup any potential readers. 1898 */ 1899 if (ret > 0) 1900 wakeup_pipe_readers(opipe); 1901 1902 if (input_wakeup) 1903 wakeup_pipe_writers(ipipe); 1904 1905 return ret; 1906 } 1907 1908 /* 1909 * Link contents of ipipe to opipe. 1910 */ 1911 static int link_pipe(struct pipe_inode_info *ipipe, 1912 struct pipe_inode_info *opipe, 1913 size_t len, unsigned int flags) 1914 { 1915 struct pipe_buffer *ibuf, *obuf; 1916 int ret = 0, i = 0, nbuf; 1917 1918 /* 1919 * Potential ABBA deadlock, work around it by ordering lock 1920 * grabbing by pipe info address. Otherwise two different processes 1921 * could deadlock (one doing tee from A -> B, the other from B -> A). 1922 */ 1923 pipe_double_lock(ipipe, opipe); 1924 1925 do { 1926 if (!opipe->readers) { 1927 send_sig(SIGPIPE, current, 0); 1928 if (!ret) 1929 ret = -EPIPE; 1930 break; 1931 } 1932 1933 /* 1934 * If we have iterated all input buffers or ran out of 1935 * output room, break. 1936 */ 1937 if (i >= ipipe->nrbufs || opipe->nrbufs >= opipe->buffers) 1938 break; 1939 1940 ibuf = ipipe->bufs + ((ipipe->curbuf + i) & (ipipe->buffers-1)); 1941 nbuf = (opipe->curbuf + opipe->nrbufs) & (opipe->buffers - 1); 1942 1943 /* 1944 * Get a reference to this pipe buffer, 1945 * so we can copy the contents over. 1946 */ 1947 ibuf->ops->get(ipipe, ibuf); 1948 1949 obuf = opipe->bufs + nbuf; 1950 *obuf = *ibuf; 1951 1952 /* 1953 * Don't inherit the gift flag, we need to 1954 * prevent multiple steals of this page. 1955 */ 1956 obuf->flags &= ~PIPE_BUF_FLAG_GIFT; 1957 1958 if (obuf->len > len) 1959 obuf->len = len; 1960 1961 opipe->nrbufs++; 1962 ret += obuf->len; 1963 len -= obuf->len; 1964 i++; 1965 } while (len); 1966 1967 /* 1968 * return EAGAIN if we have the potential of some data in the 1969 * future, otherwise just return 0 1970 */ 1971 if (!ret && ipipe->waiting_writers && (flags & SPLICE_F_NONBLOCK)) 1972 ret = -EAGAIN; 1973 1974 pipe_unlock(ipipe); 1975 pipe_unlock(opipe); 1976 1977 /* 1978 * If we put data in the output pipe, wakeup any potential readers. 1979 */ 1980 if (ret > 0) 1981 wakeup_pipe_readers(opipe); 1982 1983 return ret; 1984 } 1985 1986 /* 1987 * This is a tee(1) implementation that works on pipes. It doesn't copy 1988 * any data, it simply references the 'in' pages on the 'out' pipe. 1989 * The 'flags' used are the SPLICE_F_* variants, currently the only 1990 * applicable one is SPLICE_F_NONBLOCK. 1991 */ 1992 static long do_tee(struct file *in, struct file *out, size_t len, 1993 unsigned int flags) 1994 { 1995 struct pipe_inode_info *ipipe = get_pipe_info(in); 1996 struct pipe_inode_info *opipe = get_pipe_info(out); 1997 int ret = -EINVAL; 1998 1999 /* 2000 * Duplicate the contents of ipipe to opipe without actually 2001 * copying the data. 2002 */ 2003 if (ipipe && opipe && ipipe != opipe) { 2004 /* 2005 * Keep going, unless we encounter an error. The ipipe/opipe 2006 * ordering doesn't really matter. 2007 */ 2008 ret = ipipe_prep(ipipe, flags); 2009 if (!ret) { 2010 ret = opipe_prep(opipe, flags); 2011 if (!ret) 2012 ret = link_pipe(ipipe, opipe, len, flags); 2013 } 2014 } 2015 2016 return ret; 2017 } 2018 2019 SYSCALL_DEFINE4(tee, int, fdin, int, fdout, size_t, len, unsigned int, flags) 2020 { 2021 struct fd in; 2022 int error; 2023 2024 if (unlikely(!len)) 2025 return 0; 2026 2027 error = -EBADF; 2028 in = fdget(fdin); 2029 if (in.file) { 2030 if (in.file->f_mode & FMODE_READ) { 2031 struct fd out = fdget(fdout); 2032 if (out.file) { 2033 if (out.file->f_mode & FMODE_WRITE) 2034 error = do_tee(in.file, out.file, 2035 len, flags); 2036 fdput(out); 2037 } 2038 } 2039 fdput(in); 2040 } 2041 2042 return error; 2043 } 2044