1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * Copyright (C) 2007 Jens Axboe <jens.axboe@oracle.com> 4 * 5 * Scatterlist handling helpers. 6 */ 7 #include <linux/export.h> 8 #include <linux/slab.h> 9 #include <linux/scatterlist.h> 10 #include <linux/highmem.h> 11 #include <linux/kmemleak.h> 12 13 /** 14 * sg_next - return the next scatterlist entry in a list 15 * @sg: The current sg entry 16 * 17 * Description: 18 * Usually the next entry will be @sg@ + 1, but if this sg element is part 19 * of a chained scatterlist, it could jump to the start of a new 20 * scatterlist array. 21 * 22 **/ 23 struct scatterlist *sg_next(struct scatterlist *sg) 24 { 25 if (sg_is_last(sg)) 26 return NULL; 27 28 sg++; 29 if (unlikely(sg_is_chain(sg))) 30 sg = sg_chain_ptr(sg); 31 32 return sg; 33 } 34 EXPORT_SYMBOL(sg_next); 35 36 /** 37 * sg_nents - return total count of entries in scatterlist 38 * @sg: The scatterlist 39 * 40 * Description: 41 * Allows to know how many entries are in sg, taking into account 42 * chaining as well 43 * 44 **/ 45 int sg_nents(struct scatterlist *sg) 46 { 47 int nents; 48 for (nents = 0; sg; sg = sg_next(sg)) 49 nents++; 50 return nents; 51 } 52 EXPORT_SYMBOL(sg_nents); 53 54 /** 55 * sg_nents_for_len - return total count of entries in scatterlist 56 * needed to satisfy the supplied length 57 * @sg: The scatterlist 58 * @len: The total required length 59 * 60 * Description: 61 * Determines the number of entries in sg that are required to meet 62 * the supplied length, taking into account chaining as well 63 * 64 * Returns: 65 * the number of sg entries needed, negative error on failure 66 * 67 **/ 68 int sg_nents_for_len(struct scatterlist *sg, u64 len) 69 { 70 int nents; 71 u64 total; 72 73 if (!len) 74 return 0; 75 76 for (nents = 0, total = 0; sg; sg = sg_next(sg)) { 77 nents++; 78 total += sg->length; 79 if (total >= len) 80 return nents; 81 } 82 83 return -EINVAL; 84 } 85 EXPORT_SYMBOL(sg_nents_for_len); 86 87 /** 88 * sg_last - return the last scatterlist entry in a list 89 * @sgl: First entry in the scatterlist 90 * @nents: Number of entries in the scatterlist 91 * 92 * Description: 93 * Should only be used casually, it (currently) scans the entire list 94 * to get the last entry. 95 * 96 * Note that the @sgl@ pointer passed in need not be the first one, 97 * the important bit is that @nents@ denotes the number of entries that 98 * exist from @sgl@. 99 * 100 **/ 101 struct scatterlist *sg_last(struct scatterlist *sgl, unsigned int nents) 102 { 103 struct scatterlist *sg, *ret = NULL; 104 unsigned int i; 105 106 for_each_sg(sgl, sg, nents, i) 107 ret = sg; 108 109 BUG_ON(!sg_is_last(ret)); 110 return ret; 111 } 112 EXPORT_SYMBOL(sg_last); 113 114 /** 115 * sg_init_table - Initialize SG table 116 * @sgl: The SG table 117 * @nents: Number of entries in table 118 * 119 * Notes: 120 * If this is part of a chained sg table, sg_mark_end() should be 121 * used only on the last table part. 122 * 123 **/ 124 void sg_init_table(struct scatterlist *sgl, unsigned int nents) 125 { 126 memset(sgl, 0, sizeof(*sgl) * nents); 127 sg_init_marker(sgl, nents); 128 } 129 EXPORT_SYMBOL(sg_init_table); 130 131 /** 132 * sg_init_one - Initialize a single entry sg list 133 * @sg: SG entry 134 * @buf: Virtual address for IO 135 * @buflen: IO length 136 * 137 **/ 138 void sg_init_one(struct scatterlist *sg, const void *buf, unsigned int buflen) 139 { 140 sg_init_table(sg, 1); 141 sg_set_buf(sg, buf, buflen); 142 } 143 EXPORT_SYMBOL(sg_init_one); 144 145 /* 146 * The default behaviour of sg_alloc_table() is to use these kmalloc/kfree 147 * helpers. 148 */ 149 static struct scatterlist *sg_kmalloc(unsigned int nents, gfp_t gfp_mask) 150 { 151 if (nents == SG_MAX_SINGLE_ALLOC) { 152 /* 153 * Kmemleak doesn't track page allocations as they are not 154 * commonly used (in a raw form) for kernel data structures. 155 * As we chain together a list of pages and then a normal 156 * kmalloc (tracked by kmemleak), in order to for that last 157 * allocation not to become decoupled (and thus a 158 * false-positive) we need to inform kmemleak of all the 159 * intermediate allocations. 160 */ 161 void *ptr = (void *) __get_free_page(gfp_mask); 162 kmemleak_alloc(ptr, PAGE_SIZE, 1, gfp_mask); 163 return ptr; 164 } else 165 return kmalloc_array(nents, sizeof(struct scatterlist), 166 gfp_mask); 167 } 168 169 static void sg_kfree(struct scatterlist *sg, unsigned int nents) 170 { 171 if (nents == SG_MAX_SINGLE_ALLOC) { 172 kmemleak_free(sg); 173 free_page((unsigned long) sg); 174 } else 175 kfree(sg); 176 } 177 178 /** 179 * __sg_free_table - Free a previously mapped sg table 180 * @table: The sg table header to use 181 * @max_ents: The maximum number of entries per single scatterlist 182 * @nents_first_chunk: Number of entries int the (preallocated) first 183 * scatterlist chunk, 0 means no such preallocated first chunk 184 * @free_fn: Free function 185 * @num_ents: Number of entries in the table 186 * 187 * Description: 188 * Free an sg table previously allocated and setup with 189 * __sg_alloc_table(). The @max_ents value must be identical to 190 * that previously used with __sg_alloc_table(). 191 * 192 **/ 193 void __sg_free_table(struct sg_table *table, unsigned int max_ents, 194 unsigned int nents_first_chunk, sg_free_fn *free_fn, 195 unsigned int num_ents) 196 { 197 struct scatterlist *sgl, *next; 198 unsigned curr_max_ents = nents_first_chunk ?: max_ents; 199 200 if (unlikely(!table->sgl)) 201 return; 202 203 sgl = table->sgl; 204 while (num_ents) { 205 unsigned int alloc_size = num_ents; 206 unsigned int sg_size; 207 208 /* 209 * If we have more than max_ents segments left, 210 * then assign 'next' to the sg table after the current one. 211 * sg_size is then one less than alloc size, since the last 212 * element is the chain pointer. 213 */ 214 if (alloc_size > curr_max_ents) { 215 next = sg_chain_ptr(&sgl[curr_max_ents - 1]); 216 alloc_size = curr_max_ents; 217 sg_size = alloc_size - 1; 218 } else { 219 sg_size = alloc_size; 220 next = NULL; 221 } 222 223 num_ents -= sg_size; 224 if (nents_first_chunk) 225 nents_first_chunk = 0; 226 else 227 free_fn(sgl, alloc_size); 228 sgl = next; 229 curr_max_ents = max_ents; 230 } 231 232 table->sgl = NULL; 233 } 234 EXPORT_SYMBOL(__sg_free_table); 235 236 /** 237 * sg_free_append_table - Free a previously allocated append sg table. 238 * @table: The mapped sg append table header 239 * 240 **/ 241 void sg_free_append_table(struct sg_append_table *table) 242 { 243 __sg_free_table(&table->sgt, SG_MAX_SINGLE_ALLOC, 0, sg_kfree, 244 table->total_nents); 245 } 246 EXPORT_SYMBOL(sg_free_append_table); 247 248 249 /** 250 * sg_free_table - Free a previously allocated sg table 251 * @table: The mapped sg table header 252 * 253 **/ 254 void sg_free_table(struct sg_table *table) 255 { 256 __sg_free_table(table, SG_MAX_SINGLE_ALLOC, 0, sg_kfree, 257 table->orig_nents); 258 } 259 EXPORT_SYMBOL(sg_free_table); 260 261 /** 262 * __sg_alloc_table - Allocate and initialize an sg table with given allocator 263 * @table: The sg table header to use 264 * @nents: Number of entries in sg list 265 * @max_ents: The maximum number of entries the allocator returns per call 266 * @nents_first_chunk: Number of entries int the (preallocated) first 267 * scatterlist chunk, 0 means no such preallocated chunk provided by user 268 * @gfp_mask: GFP allocation mask 269 * @alloc_fn: Allocator to use 270 * 271 * Description: 272 * This function returns a @table @nents long. The allocator is 273 * defined to return scatterlist chunks of maximum size @max_ents. 274 * Thus if @nents is bigger than @max_ents, the scatterlists will be 275 * chained in units of @max_ents. 276 * 277 * Notes: 278 * If this function returns non-0 (eg failure), the caller must call 279 * __sg_free_table() to cleanup any leftover allocations. 280 * 281 **/ 282 int __sg_alloc_table(struct sg_table *table, unsigned int nents, 283 unsigned int max_ents, struct scatterlist *first_chunk, 284 unsigned int nents_first_chunk, gfp_t gfp_mask, 285 sg_alloc_fn *alloc_fn) 286 { 287 struct scatterlist *sg, *prv; 288 unsigned int left; 289 unsigned curr_max_ents = nents_first_chunk ?: max_ents; 290 unsigned prv_max_ents; 291 292 memset(table, 0, sizeof(*table)); 293 294 if (nents == 0) 295 return -EINVAL; 296 #ifdef CONFIG_ARCH_NO_SG_CHAIN 297 if (WARN_ON_ONCE(nents > max_ents)) 298 return -EINVAL; 299 #endif 300 301 left = nents; 302 prv = NULL; 303 do { 304 unsigned int sg_size, alloc_size = left; 305 306 if (alloc_size > curr_max_ents) { 307 alloc_size = curr_max_ents; 308 sg_size = alloc_size - 1; 309 } else 310 sg_size = alloc_size; 311 312 left -= sg_size; 313 314 if (first_chunk) { 315 sg = first_chunk; 316 first_chunk = NULL; 317 } else { 318 sg = alloc_fn(alloc_size, gfp_mask); 319 } 320 if (unlikely(!sg)) { 321 /* 322 * Adjust entry count to reflect that the last 323 * entry of the previous table won't be used for 324 * linkage. Without this, sg_kfree() may get 325 * confused. 326 */ 327 if (prv) 328 table->nents = ++table->orig_nents; 329 330 return -ENOMEM; 331 } 332 333 sg_init_table(sg, alloc_size); 334 table->nents = table->orig_nents += sg_size; 335 336 /* 337 * If this is the first mapping, assign the sg table header. 338 * If this is not the first mapping, chain previous part. 339 */ 340 if (prv) 341 sg_chain(prv, prv_max_ents, sg); 342 else 343 table->sgl = sg; 344 345 /* 346 * If no more entries after this one, mark the end 347 */ 348 if (!left) 349 sg_mark_end(&sg[sg_size - 1]); 350 351 prv = sg; 352 prv_max_ents = curr_max_ents; 353 curr_max_ents = max_ents; 354 } while (left); 355 356 return 0; 357 } 358 EXPORT_SYMBOL(__sg_alloc_table); 359 360 /** 361 * sg_alloc_table - Allocate and initialize an sg table 362 * @table: The sg table header to use 363 * @nents: Number of entries in sg list 364 * @gfp_mask: GFP allocation mask 365 * 366 * Description: 367 * Allocate and initialize an sg table. If @nents@ is larger than 368 * SG_MAX_SINGLE_ALLOC a chained sg table will be setup. 369 * 370 **/ 371 int sg_alloc_table(struct sg_table *table, unsigned int nents, gfp_t gfp_mask) 372 { 373 int ret; 374 375 ret = __sg_alloc_table(table, nents, SG_MAX_SINGLE_ALLOC, 376 NULL, 0, gfp_mask, sg_kmalloc); 377 if (unlikely(ret)) 378 sg_free_table(table); 379 return ret; 380 } 381 EXPORT_SYMBOL(sg_alloc_table); 382 383 static struct scatterlist *get_next_sg(struct sg_append_table *table, 384 struct scatterlist *cur, 385 unsigned long needed_sges, 386 gfp_t gfp_mask) 387 { 388 struct scatterlist *new_sg, *next_sg; 389 unsigned int alloc_size; 390 391 if (cur) { 392 next_sg = sg_next(cur); 393 /* Check if last entry should be keeped for chainning */ 394 if (!sg_is_last(next_sg) || needed_sges == 1) 395 return next_sg; 396 } 397 398 alloc_size = min_t(unsigned long, needed_sges, SG_MAX_SINGLE_ALLOC); 399 new_sg = sg_kmalloc(alloc_size, gfp_mask); 400 if (!new_sg) 401 return ERR_PTR(-ENOMEM); 402 sg_init_table(new_sg, alloc_size); 403 if (cur) { 404 table->total_nents += alloc_size - 1; 405 __sg_chain(next_sg, new_sg); 406 } else { 407 table->sgt.sgl = new_sg; 408 table->total_nents = alloc_size; 409 } 410 return new_sg; 411 } 412 413 static bool pages_are_mergeable(struct page *a, struct page *b) 414 { 415 if (page_to_pfn(a) != page_to_pfn(b) + 1) 416 return false; 417 if (!zone_device_pages_have_same_pgmap(a, b)) 418 return false; 419 return true; 420 } 421 422 /** 423 * sg_alloc_append_table_from_pages - Allocate and initialize an append sg 424 * table from an array of pages 425 * @sgt_append: The sg append table to use 426 * @pages: Pointer to an array of page pointers 427 * @n_pages: Number of pages in the pages array 428 * @offset: Offset from start of the first page to the start of a buffer 429 * @size: Number of valid bytes in the buffer (after offset) 430 * @max_segment: Maximum size of a scatterlist element in bytes 431 * @left_pages: Left pages caller have to set after this call 432 * @gfp_mask: GFP allocation mask 433 * 434 * Description: 435 * In the first call it allocate and initialize an sg table from a list of 436 * pages, else reuse the scatterlist from sgt_append. Contiguous ranges of 437 * the pages are squashed into a single scatterlist entry up to the maximum 438 * size specified in @max_segment. A user may provide an offset at a start 439 * and a size of valid data in a buffer specified by the page array. The 440 * returned sg table is released by sg_free_append_table 441 * 442 * Returns: 443 * 0 on success, negative error on failure 444 * 445 * Notes: 446 * If this function returns non-0 (eg failure), the caller must call 447 * sg_free_append_table() to cleanup any leftover allocations. 448 * 449 * In the fist call, sgt_append must by initialized. 450 */ 451 int sg_alloc_append_table_from_pages(struct sg_append_table *sgt_append, 452 struct page **pages, unsigned int n_pages, unsigned int offset, 453 unsigned long size, unsigned int max_segment, 454 unsigned int left_pages, gfp_t gfp_mask) 455 { 456 unsigned int chunks, cur_page, seg_len, i, prv_len = 0; 457 unsigned int added_nents = 0; 458 struct scatterlist *s = sgt_append->prv; 459 struct page *last_pg; 460 461 /* 462 * The algorithm below requires max_segment to be aligned to PAGE_SIZE 463 * otherwise it can overshoot. 464 */ 465 max_segment = ALIGN_DOWN(max_segment, PAGE_SIZE); 466 if (WARN_ON(max_segment < PAGE_SIZE)) 467 return -EINVAL; 468 469 if (IS_ENABLED(CONFIG_ARCH_NO_SG_CHAIN) && sgt_append->prv) 470 return -EOPNOTSUPP; 471 472 if (sgt_append->prv) { 473 unsigned long next_pfn = (page_to_phys(sg_page(sgt_append->prv)) + 474 sgt_append->prv->offset + sgt_append->prv->length) / PAGE_SIZE; 475 476 if (WARN_ON(offset)) 477 return -EINVAL; 478 479 /* Merge contiguous pages into the last SG */ 480 prv_len = sgt_append->prv->length; 481 if (page_to_pfn(pages[0]) == next_pfn) { 482 last_pg = pfn_to_page(next_pfn - 1); 483 while (n_pages && pages_are_mergeable(pages[0], last_pg)) { 484 if (sgt_append->prv->length + PAGE_SIZE > max_segment) 485 break; 486 sgt_append->prv->length += PAGE_SIZE; 487 last_pg = pages[0]; 488 pages++; 489 n_pages--; 490 } 491 if (!n_pages) 492 goto out; 493 } 494 } 495 496 /* compute number of contiguous chunks */ 497 chunks = 1; 498 seg_len = 0; 499 for (i = 1; i < n_pages; i++) { 500 seg_len += PAGE_SIZE; 501 if (seg_len >= max_segment || 502 !pages_are_mergeable(pages[i], pages[i - 1])) { 503 chunks++; 504 seg_len = 0; 505 } 506 } 507 508 /* merging chunks and putting them into the scatterlist */ 509 cur_page = 0; 510 for (i = 0; i < chunks; i++) { 511 unsigned int j, chunk_size; 512 513 /* look for the end of the current chunk */ 514 seg_len = 0; 515 for (j = cur_page + 1; j < n_pages; j++) { 516 seg_len += PAGE_SIZE; 517 if (seg_len >= max_segment || 518 !pages_are_mergeable(pages[j], pages[j - 1])) 519 break; 520 } 521 522 /* Pass how many chunks might be left */ 523 s = get_next_sg(sgt_append, s, chunks - i + left_pages, 524 gfp_mask); 525 if (IS_ERR(s)) { 526 /* 527 * Adjust entry length to be as before function was 528 * called. 529 */ 530 if (sgt_append->prv) 531 sgt_append->prv->length = prv_len; 532 return PTR_ERR(s); 533 } 534 chunk_size = ((j - cur_page) << PAGE_SHIFT) - offset; 535 sg_set_page(s, pages[cur_page], 536 min_t(unsigned long, size, chunk_size), offset); 537 added_nents++; 538 size -= chunk_size; 539 offset = 0; 540 cur_page = j; 541 } 542 sgt_append->sgt.nents += added_nents; 543 sgt_append->sgt.orig_nents = sgt_append->sgt.nents; 544 sgt_append->prv = s; 545 out: 546 if (!left_pages) 547 sg_mark_end(s); 548 return 0; 549 } 550 EXPORT_SYMBOL(sg_alloc_append_table_from_pages); 551 552 /** 553 * sg_alloc_table_from_pages_segment - Allocate and initialize an sg table from 554 * an array of pages and given maximum 555 * segment. 556 * @sgt: The sg table header to use 557 * @pages: Pointer to an array of page pointers 558 * @n_pages: Number of pages in the pages array 559 * @offset: Offset from start of the first page to the start of a buffer 560 * @size: Number of valid bytes in the buffer (after offset) 561 * @max_segment: Maximum size of a scatterlist element in bytes 562 * @gfp_mask: GFP allocation mask 563 * 564 * Description: 565 * Allocate and initialize an sg table from a list of pages. Contiguous 566 * ranges of the pages are squashed into a single scatterlist node up to the 567 * maximum size specified in @max_segment. A user may provide an offset at a 568 * start and a size of valid data in a buffer specified by the page array. 569 * 570 * The returned sg table is released by sg_free_table. 571 * 572 * Returns: 573 * 0 on success, negative error on failure 574 */ 575 int sg_alloc_table_from_pages_segment(struct sg_table *sgt, struct page **pages, 576 unsigned int n_pages, unsigned int offset, 577 unsigned long size, unsigned int max_segment, 578 gfp_t gfp_mask) 579 { 580 struct sg_append_table append = {}; 581 int err; 582 583 err = sg_alloc_append_table_from_pages(&append, pages, n_pages, offset, 584 size, max_segment, 0, gfp_mask); 585 if (err) { 586 sg_free_append_table(&append); 587 return err; 588 } 589 memcpy(sgt, &append.sgt, sizeof(*sgt)); 590 WARN_ON(append.total_nents != sgt->orig_nents); 591 return 0; 592 } 593 EXPORT_SYMBOL(sg_alloc_table_from_pages_segment); 594 595 #ifdef CONFIG_SGL_ALLOC 596 597 /** 598 * sgl_alloc_order - allocate a scatterlist and its pages 599 * @length: Length in bytes of the scatterlist. Must be at least one 600 * @order: Second argument for alloc_pages() 601 * @chainable: Whether or not to allocate an extra element in the scatterlist 602 * for scatterlist chaining purposes 603 * @gfp: Memory allocation flags 604 * @nent_p: [out] Number of entries in the scatterlist that have pages 605 * 606 * Returns: A pointer to an initialized scatterlist or %NULL upon failure. 607 */ 608 struct scatterlist *sgl_alloc_order(unsigned long long length, 609 unsigned int order, bool chainable, 610 gfp_t gfp, unsigned int *nent_p) 611 { 612 struct scatterlist *sgl, *sg; 613 struct page *page; 614 unsigned int nent, nalloc; 615 u32 elem_len; 616 617 nent = round_up(length, PAGE_SIZE << order) >> (PAGE_SHIFT + order); 618 /* Check for integer overflow */ 619 if (length > (nent << (PAGE_SHIFT + order))) 620 return NULL; 621 nalloc = nent; 622 if (chainable) { 623 /* Check for integer overflow */ 624 if (nalloc + 1 < nalloc) 625 return NULL; 626 nalloc++; 627 } 628 sgl = kmalloc_array(nalloc, sizeof(struct scatterlist), 629 gfp & ~GFP_DMA); 630 if (!sgl) 631 return NULL; 632 633 sg_init_table(sgl, nalloc); 634 sg = sgl; 635 while (length) { 636 elem_len = min_t(u64, length, PAGE_SIZE << order); 637 page = alloc_pages(gfp, order); 638 if (!page) { 639 sgl_free_order(sgl, order); 640 return NULL; 641 } 642 643 sg_set_page(sg, page, elem_len, 0); 644 length -= elem_len; 645 sg = sg_next(sg); 646 } 647 WARN_ONCE(length, "length = %lld\n", length); 648 if (nent_p) 649 *nent_p = nent; 650 return sgl; 651 } 652 EXPORT_SYMBOL(sgl_alloc_order); 653 654 /** 655 * sgl_alloc - allocate a scatterlist and its pages 656 * @length: Length in bytes of the scatterlist 657 * @gfp: Memory allocation flags 658 * @nent_p: [out] Number of entries in the scatterlist 659 * 660 * Returns: A pointer to an initialized scatterlist or %NULL upon failure. 661 */ 662 struct scatterlist *sgl_alloc(unsigned long long length, gfp_t gfp, 663 unsigned int *nent_p) 664 { 665 return sgl_alloc_order(length, 0, false, gfp, nent_p); 666 } 667 EXPORT_SYMBOL(sgl_alloc); 668 669 /** 670 * sgl_free_n_order - free a scatterlist and its pages 671 * @sgl: Scatterlist with one or more elements 672 * @nents: Maximum number of elements to free 673 * @order: Second argument for __free_pages() 674 * 675 * Notes: 676 * - If several scatterlists have been chained and each chain element is 677 * freed separately then it's essential to set nents correctly to avoid that a 678 * page would get freed twice. 679 * - All pages in a chained scatterlist can be freed at once by setting @nents 680 * to a high number. 681 */ 682 void sgl_free_n_order(struct scatterlist *sgl, int nents, int order) 683 { 684 struct scatterlist *sg; 685 struct page *page; 686 int i; 687 688 for_each_sg(sgl, sg, nents, i) { 689 if (!sg) 690 break; 691 page = sg_page(sg); 692 if (page) 693 __free_pages(page, order); 694 } 695 kfree(sgl); 696 } 697 EXPORT_SYMBOL(sgl_free_n_order); 698 699 /** 700 * sgl_free_order - free a scatterlist and its pages 701 * @sgl: Scatterlist with one or more elements 702 * @order: Second argument for __free_pages() 703 */ 704 void sgl_free_order(struct scatterlist *sgl, int order) 705 { 706 sgl_free_n_order(sgl, INT_MAX, order); 707 } 708 EXPORT_SYMBOL(sgl_free_order); 709 710 /** 711 * sgl_free - free a scatterlist and its pages 712 * @sgl: Scatterlist with one or more elements 713 */ 714 void sgl_free(struct scatterlist *sgl) 715 { 716 sgl_free_order(sgl, 0); 717 } 718 EXPORT_SYMBOL(sgl_free); 719 720 #endif /* CONFIG_SGL_ALLOC */ 721 722 void __sg_page_iter_start(struct sg_page_iter *piter, 723 struct scatterlist *sglist, unsigned int nents, 724 unsigned long pgoffset) 725 { 726 piter->__pg_advance = 0; 727 piter->__nents = nents; 728 729 piter->sg = sglist; 730 piter->sg_pgoffset = pgoffset; 731 } 732 EXPORT_SYMBOL(__sg_page_iter_start); 733 734 static int sg_page_count(struct scatterlist *sg) 735 { 736 return PAGE_ALIGN(sg->offset + sg->length) >> PAGE_SHIFT; 737 } 738 739 bool __sg_page_iter_next(struct sg_page_iter *piter) 740 { 741 if (!piter->__nents || !piter->sg) 742 return false; 743 744 piter->sg_pgoffset += piter->__pg_advance; 745 piter->__pg_advance = 1; 746 747 while (piter->sg_pgoffset >= sg_page_count(piter->sg)) { 748 piter->sg_pgoffset -= sg_page_count(piter->sg); 749 piter->sg = sg_next(piter->sg); 750 if (!--piter->__nents || !piter->sg) 751 return false; 752 } 753 754 return true; 755 } 756 EXPORT_SYMBOL(__sg_page_iter_next); 757 758 static int sg_dma_page_count(struct scatterlist *sg) 759 { 760 return PAGE_ALIGN(sg->offset + sg_dma_len(sg)) >> PAGE_SHIFT; 761 } 762 763 bool __sg_page_iter_dma_next(struct sg_dma_page_iter *dma_iter) 764 { 765 struct sg_page_iter *piter = &dma_iter->base; 766 767 if (!piter->__nents || !piter->sg) 768 return false; 769 770 piter->sg_pgoffset += piter->__pg_advance; 771 piter->__pg_advance = 1; 772 773 while (piter->sg_pgoffset >= sg_dma_page_count(piter->sg)) { 774 piter->sg_pgoffset -= sg_dma_page_count(piter->sg); 775 piter->sg = sg_next(piter->sg); 776 if (!--piter->__nents || !piter->sg) 777 return false; 778 } 779 780 return true; 781 } 782 EXPORT_SYMBOL(__sg_page_iter_dma_next); 783 784 /** 785 * sg_miter_start - start mapping iteration over a sg list 786 * @miter: sg mapping iter to be started 787 * @sgl: sg list to iterate over 788 * @nents: number of sg entries 789 * 790 * Description: 791 * Starts mapping iterator @miter. 792 * 793 * Context: 794 * Don't care. 795 */ 796 void sg_miter_start(struct sg_mapping_iter *miter, struct scatterlist *sgl, 797 unsigned int nents, unsigned int flags) 798 { 799 memset(miter, 0, sizeof(struct sg_mapping_iter)); 800 801 __sg_page_iter_start(&miter->piter, sgl, nents, 0); 802 WARN_ON(!(flags & (SG_MITER_TO_SG | SG_MITER_FROM_SG))); 803 miter->__flags = flags; 804 } 805 EXPORT_SYMBOL(sg_miter_start); 806 807 static bool sg_miter_get_next_page(struct sg_mapping_iter *miter) 808 { 809 if (!miter->__remaining) { 810 struct scatterlist *sg; 811 812 if (!__sg_page_iter_next(&miter->piter)) 813 return false; 814 815 sg = miter->piter.sg; 816 817 miter->__offset = miter->piter.sg_pgoffset ? 0 : sg->offset; 818 miter->piter.sg_pgoffset += miter->__offset >> PAGE_SHIFT; 819 miter->__offset &= PAGE_SIZE - 1; 820 miter->__remaining = sg->offset + sg->length - 821 (miter->piter.sg_pgoffset << PAGE_SHIFT) - 822 miter->__offset; 823 miter->__remaining = min_t(unsigned long, miter->__remaining, 824 PAGE_SIZE - miter->__offset); 825 } 826 827 return true; 828 } 829 830 /** 831 * sg_miter_skip - reposition mapping iterator 832 * @miter: sg mapping iter to be skipped 833 * @offset: number of bytes to plus the current location 834 * 835 * Description: 836 * Sets the offset of @miter to its current location plus @offset bytes. 837 * If mapping iterator @miter has been proceeded by sg_miter_next(), this 838 * stops @miter. 839 * 840 * Context: 841 * Don't care. 842 * 843 * Returns: 844 * true if @miter contains the valid mapping. false if end of sg 845 * list is reached. 846 */ 847 bool sg_miter_skip(struct sg_mapping_iter *miter, off_t offset) 848 { 849 sg_miter_stop(miter); 850 851 while (offset) { 852 off_t consumed; 853 854 if (!sg_miter_get_next_page(miter)) 855 return false; 856 857 consumed = min_t(off_t, offset, miter->__remaining); 858 miter->__offset += consumed; 859 miter->__remaining -= consumed; 860 offset -= consumed; 861 } 862 863 return true; 864 } 865 EXPORT_SYMBOL(sg_miter_skip); 866 867 /** 868 * sg_miter_next - proceed mapping iterator to the next mapping 869 * @miter: sg mapping iter to proceed 870 * 871 * Description: 872 * Proceeds @miter to the next mapping. @miter should have been started 873 * using sg_miter_start(). On successful return, @miter->page, 874 * @miter->addr and @miter->length point to the current mapping. 875 * 876 * Context: 877 * May sleep if !SG_MITER_ATOMIC. 878 * 879 * Returns: 880 * true if @miter contains the next mapping. false if end of sg 881 * list is reached. 882 */ 883 bool sg_miter_next(struct sg_mapping_iter *miter) 884 { 885 sg_miter_stop(miter); 886 887 /* 888 * Get to the next page if necessary. 889 * __remaining, __offset is adjusted by sg_miter_stop 890 */ 891 if (!sg_miter_get_next_page(miter)) 892 return false; 893 894 miter->page = sg_page_iter_page(&miter->piter); 895 miter->consumed = miter->length = miter->__remaining; 896 897 if (miter->__flags & SG_MITER_ATOMIC) 898 miter->addr = kmap_atomic(miter->page) + miter->__offset; 899 else 900 miter->addr = kmap(miter->page) + miter->__offset; 901 902 return true; 903 } 904 EXPORT_SYMBOL(sg_miter_next); 905 906 /** 907 * sg_miter_stop - stop mapping iteration 908 * @miter: sg mapping iter to be stopped 909 * 910 * Description: 911 * Stops mapping iterator @miter. @miter should have been started 912 * using sg_miter_start(). A stopped iteration can be resumed by 913 * calling sg_miter_next() on it. This is useful when resources (kmap) 914 * need to be released during iteration. 915 * 916 * Context: 917 * Don't care otherwise. 918 */ 919 void sg_miter_stop(struct sg_mapping_iter *miter) 920 { 921 WARN_ON(miter->consumed > miter->length); 922 923 /* drop resources from the last iteration */ 924 if (miter->addr) { 925 miter->__offset += miter->consumed; 926 miter->__remaining -= miter->consumed; 927 928 if (miter->__flags & SG_MITER_TO_SG) 929 flush_dcache_page(miter->page); 930 931 if (miter->__flags & SG_MITER_ATOMIC) { 932 WARN_ON_ONCE(!pagefault_disabled()); 933 kunmap_atomic(miter->addr); 934 } else 935 kunmap(miter->page); 936 937 miter->page = NULL; 938 miter->addr = NULL; 939 miter->length = 0; 940 miter->consumed = 0; 941 } 942 } 943 EXPORT_SYMBOL(sg_miter_stop); 944 945 /** 946 * sg_copy_buffer - Copy data between a linear buffer and an SG list 947 * @sgl: The SG list 948 * @nents: Number of SG entries 949 * @buf: Where to copy from 950 * @buflen: The number of bytes to copy 951 * @skip: Number of bytes to skip before copying 952 * @to_buffer: transfer direction (true == from an sg list to a 953 * buffer, false == from a buffer to an sg list) 954 * 955 * Returns the number of copied bytes. 956 * 957 **/ 958 size_t sg_copy_buffer(struct scatterlist *sgl, unsigned int nents, void *buf, 959 size_t buflen, off_t skip, bool to_buffer) 960 { 961 unsigned int offset = 0; 962 struct sg_mapping_iter miter; 963 unsigned int sg_flags = SG_MITER_ATOMIC; 964 965 if (to_buffer) 966 sg_flags |= SG_MITER_FROM_SG; 967 else 968 sg_flags |= SG_MITER_TO_SG; 969 970 sg_miter_start(&miter, sgl, nents, sg_flags); 971 972 if (!sg_miter_skip(&miter, skip)) 973 return 0; 974 975 while ((offset < buflen) && sg_miter_next(&miter)) { 976 unsigned int len; 977 978 len = min(miter.length, buflen - offset); 979 980 if (to_buffer) 981 memcpy(buf + offset, miter.addr, len); 982 else 983 memcpy(miter.addr, buf + offset, len); 984 985 offset += len; 986 } 987 988 sg_miter_stop(&miter); 989 990 return offset; 991 } 992 EXPORT_SYMBOL(sg_copy_buffer); 993 994 /** 995 * sg_copy_from_buffer - Copy from a linear buffer to an SG list 996 * @sgl: The SG list 997 * @nents: Number of SG entries 998 * @buf: Where to copy from 999 * @buflen: The number of bytes to copy 1000 * 1001 * Returns the number of copied bytes. 1002 * 1003 **/ 1004 size_t sg_copy_from_buffer(struct scatterlist *sgl, unsigned int nents, 1005 const void *buf, size_t buflen) 1006 { 1007 return sg_copy_buffer(sgl, nents, (void *)buf, buflen, 0, false); 1008 } 1009 EXPORT_SYMBOL(sg_copy_from_buffer); 1010 1011 /** 1012 * sg_copy_to_buffer - Copy from an SG list to a linear buffer 1013 * @sgl: The SG list 1014 * @nents: Number of SG entries 1015 * @buf: Where to copy to 1016 * @buflen: The number of bytes to copy 1017 * 1018 * Returns the number of copied bytes. 1019 * 1020 **/ 1021 size_t sg_copy_to_buffer(struct scatterlist *sgl, unsigned int nents, 1022 void *buf, size_t buflen) 1023 { 1024 return sg_copy_buffer(sgl, nents, buf, buflen, 0, true); 1025 } 1026 EXPORT_SYMBOL(sg_copy_to_buffer); 1027 1028 /** 1029 * sg_pcopy_from_buffer - Copy from a linear buffer to an SG list 1030 * @sgl: The SG list 1031 * @nents: Number of SG entries 1032 * @buf: Where to copy from 1033 * @buflen: The number of bytes to copy 1034 * @skip: Number of bytes to skip before copying 1035 * 1036 * Returns the number of copied bytes. 1037 * 1038 **/ 1039 size_t sg_pcopy_from_buffer(struct scatterlist *sgl, unsigned int nents, 1040 const void *buf, size_t buflen, off_t skip) 1041 { 1042 return sg_copy_buffer(sgl, nents, (void *)buf, buflen, skip, false); 1043 } 1044 EXPORT_SYMBOL(sg_pcopy_from_buffer); 1045 1046 /** 1047 * sg_pcopy_to_buffer - Copy from an SG list to a linear buffer 1048 * @sgl: The SG list 1049 * @nents: Number of SG entries 1050 * @buf: Where to copy to 1051 * @buflen: The number of bytes to copy 1052 * @skip: Number of bytes to skip before copying 1053 * 1054 * Returns the number of copied bytes. 1055 * 1056 **/ 1057 size_t sg_pcopy_to_buffer(struct scatterlist *sgl, unsigned int nents, 1058 void *buf, size_t buflen, off_t skip) 1059 { 1060 return sg_copy_buffer(sgl, nents, buf, buflen, skip, true); 1061 } 1062 EXPORT_SYMBOL(sg_pcopy_to_buffer); 1063 1064 /** 1065 * sg_zero_buffer - Zero-out a part of a SG list 1066 * @sgl: The SG list 1067 * @nents: Number of SG entries 1068 * @buflen: The number of bytes to zero out 1069 * @skip: Number of bytes to skip before zeroing 1070 * 1071 * Returns the number of bytes zeroed. 1072 **/ 1073 size_t sg_zero_buffer(struct scatterlist *sgl, unsigned int nents, 1074 size_t buflen, off_t skip) 1075 { 1076 unsigned int offset = 0; 1077 struct sg_mapping_iter miter; 1078 unsigned int sg_flags = SG_MITER_ATOMIC | SG_MITER_TO_SG; 1079 1080 sg_miter_start(&miter, sgl, nents, sg_flags); 1081 1082 if (!sg_miter_skip(&miter, skip)) 1083 return false; 1084 1085 while (offset < buflen && sg_miter_next(&miter)) { 1086 unsigned int len; 1087 1088 len = min(miter.length, buflen - offset); 1089 memset(miter.addr, 0, len); 1090 1091 offset += len; 1092 } 1093 1094 sg_miter_stop(&miter); 1095 return offset; 1096 } 1097 EXPORT_SYMBOL(sg_zero_buffer); 1098