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 if (WARN_ON(offset)) 474 return -EINVAL; 475 476 /* Merge contiguous pages into the last SG */ 477 prv_len = sgt_append->prv->length; 478 last_pg = sg_page(sgt_append->prv); 479 while (n_pages && pages_are_mergeable(last_pg, pages[0])) { 480 if (sgt_append->prv->length + PAGE_SIZE > max_segment) 481 break; 482 sgt_append->prv->length += PAGE_SIZE; 483 last_pg = pages[0]; 484 pages++; 485 n_pages--; 486 } 487 if (!n_pages) 488 goto out; 489 } 490 491 /* compute number of contiguous chunks */ 492 chunks = 1; 493 seg_len = 0; 494 for (i = 1; i < n_pages; i++) { 495 seg_len += PAGE_SIZE; 496 if (seg_len >= max_segment || 497 !pages_are_mergeable(pages[i], pages[i - 1])) { 498 chunks++; 499 seg_len = 0; 500 } 501 } 502 503 /* merging chunks and putting them into the scatterlist */ 504 cur_page = 0; 505 for (i = 0; i < chunks; i++) { 506 unsigned int j, chunk_size; 507 508 /* look for the end of the current chunk */ 509 seg_len = 0; 510 for (j = cur_page + 1; j < n_pages; j++) { 511 seg_len += PAGE_SIZE; 512 if (seg_len >= max_segment || 513 !pages_are_mergeable(pages[j], pages[j - 1])) 514 break; 515 } 516 517 /* Pass how many chunks might be left */ 518 s = get_next_sg(sgt_append, s, chunks - i + left_pages, 519 gfp_mask); 520 if (IS_ERR(s)) { 521 /* 522 * Adjust entry length to be as before function was 523 * called. 524 */ 525 if (sgt_append->prv) 526 sgt_append->prv->length = prv_len; 527 return PTR_ERR(s); 528 } 529 chunk_size = ((j - cur_page) << PAGE_SHIFT) - offset; 530 sg_set_page(s, pages[cur_page], 531 min_t(unsigned long, size, chunk_size), offset); 532 added_nents++; 533 size -= chunk_size; 534 offset = 0; 535 cur_page = j; 536 } 537 sgt_append->sgt.nents += added_nents; 538 sgt_append->sgt.orig_nents = sgt_append->sgt.nents; 539 sgt_append->prv = s; 540 out: 541 if (!left_pages) 542 sg_mark_end(s); 543 return 0; 544 } 545 EXPORT_SYMBOL(sg_alloc_append_table_from_pages); 546 547 /** 548 * sg_alloc_table_from_pages_segment - Allocate and initialize an sg table from 549 * an array of pages and given maximum 550 * segment. 551 * @sgt: The sg table header to use 552 * @pages: Pointer to an array of page pointers 553 * @n_pages: Number of pages in the pages array 554 * @offset: Offset from start of the first page to the start of a buffer 555 * @size: Number of valid bytes in the buffer (after offset) 556 * @max_segment: Maximum size of a scatterlist element in bytes 557 * @gfp_mask: GFP allocation mask 558 * 559 * Description: 560 * Allocate and initialize an sg table from a list of pages. Contiguous 561 * ranges of the pages are squashed into a single scatterlist node up to the 562 * maximum size specified in @max_segment. A user may provide an offset at a 563 * start and a size of valid data in a buffer specified by the page array. 564 * 565 * The returned sg table is released by sg_free_table. 566 * 567 * Returns: 568 * 0 on success, negative error on failure 569 */ 570 int sg_alloc_table_from_pages_segment(struct sg_table *sgt, struct page **pages, 571 unsigned int n_pages, unsigned int offset, 572 unsigned long size, unsigned int max_segment, 573 gfp_t gfp_mask) 574 { 575 struct sg_append_table append = {}; 576 int err; 577 578 err = sg_alloc_append_table_from_pages(&append, pages, n_pages, offset, 579 size, max_segment, 0, gfp_mask); 580 if (err) { 581 sg_free_append_table(&append); 582 return err; 583 } 584 memcpy(sgt, &append.sgt, sizeof(*sgt)); 585 WARN_ON(append.total_nents != sgt->orig_nents); 586 return 0; 587 } 588 EXPORT_SYMBOL(sg_alloc_table_from_pages_segment); 589 590 #ifdef CONFIG_SGL_ALLOC 591 592 /** 593 * sgl_alloc_order - allocate a scatterlist and its pages 594 * @length: Length in bytes of the scatterlist. Must be at least one 595 * @order: Second argument for alloc_pages() 596 * @chainable: Whether or not to allocate an extra element in the scatterlist 597 * for scatterlist chaining purposes 598 * @gfp: Memory allocation flags 599 * @nent_p: [out] Number of entries in the scatterlist that have pages 600 * 601 * Returns: A pointer to an initialized scatterlist or %NULL upon failure. 602 */ 603 struct scatterlist *sgl_alloc_order(unsigned long long length, 604 unsigned int order, bool chainable, 605 gfp_t gfp, unsigned int *nent_p) 606 { 607 struct scatterlist *sgl, *sg; 608 struct page *page; 609 unsigned int nent, nalloc; 610 u32 elem_len; 611 612 nent = round_up(length, PAGE_SIZE << order) >> (PAGE_SHIFT + order); 613 /* Check for integer overflow */ 614 if (length > (nent << (PAGE_SHIFT + order))) 615 return NULL; 616 nalloc = nent; 617 if (chainable) { 618 /* Check for integer overflow */ 619 if (nalloc + 1 < nalloc) 620 return NULL; 621 nalloc++; 622 } 623 sgl = kmalloc_array(nalloc, sizeof(struct scatterlist), 624 gfp & ~GFP_DMA); 625 if (!sgl) 626 return NULL; 627 628 sg_init_table(sgl, nalloc); 629 sg = sgl; 630 while (length) { 631 elem_len = min_t(u64, length, PAGE_SIZE << order); 632 page = alloc_pages(gfp, order); 633 if (!page) { 634 sgl_free_order(sgl, order); 635 return NULL; 636 } 637 638 sg_set_page(sg, page, elem_len, 0); 639 length -= elem_len; 640 sg = sg_next(sg); 641 } 642 WARN_ONCE(length, "length = %lld\n", length); 643 if (nent_p) 644 *nent_p = nent; 645 return sgl; 646 } 647 EXPORT_SYMBOL(sgl_alloc_order); 648 649 /** 650 * sgl_alloc - allocate a scatterlist and its pages 651 * @length: Length in bytes of the scatterlist 652 * @gfp: Memory allocation flags 653 * @nent_p: [out] Number of entries in the scatterlist 654 * 655 * Returns: A pointer to an initialized scatterlist or %NULL upon failure. 656 */ 657 struct scatterlist *sgl_alloc(unsigned long long length, gfp_t gfp, 658 unsigned int *nent_p) 659 { 660 return sgl_alloc_order(length, 0, false, gfp, nent_p); 661 } 662 EXPORT_SYMBOL(sgl_alloc); 663 664 /** 665 * sgl_free_n_order - free a scatterlist and its pages 666 * @sgl: Scatterlist with one or more elements 667 * @nents: Maximum number of elements to free 668 * @order: Second argument for __free_pages() 669 * 670 * Notes: 671 * - If several scatterlists have been chained and each chain element is 672 * freed separately then it's essential to set nents correctly to avoid that a 673 * page would get freed twice. 674 * - All pages in a chained scatterlist can be freed at once by setting @nents 675 * to a high number. 676 */ 677 void sgl_free_n_order(struct scatterlist *sgl, int nents, int order) 678 { 679 struct scatterlist *sg; 680 struct page *page; 681 int i; 682 683 for_each_sg(sgl, sg, nents, i) { 684 if (!sg) 685 break; 686 page = sg_page(sg); 687 if (page) 688 __free_pages(page, order); 689 } 690 kfree(sgl); 691 } 692 EXPORT_SYMBOL(sgl_free_n_order); 693 694 /** 695 * sgl_free_order - free a scatterlist and its pages 696 * @sgl: Scatterlist with one or more elements 697 * @order: Second argument for __free_pages() 698 */ 699 void sgl_free_order(struct scatterlist *sgl, int order) 700 { 701 sgl_free_n_order(sgl, INT_MAX, order); 702 } 703 EXPORT_SYMBOL(sgl_free_order); 704 705 /** 706 * sgl_free - free a scatterlist and its pages 707 * @sgl: Scatterlist with one or more elements 708 */ 709 void sgl_free(struct scatterlist *sgl) 710 { 711 sgl_free_order(sgl, 0); 712 } 713 EXPORT_SYMBOL(sgl_free); 714 715 #endif /* CONFIG_SGL_ALLOC */ 716 717 void __sg_page_iter_start(struct sg_page_iter *piter, 718 struct scatterlist *sglist, unsigned int nents, 719 unsigned long pgoffset) 720 { 721 piter->__pg_advance = 0; 722 piter->__nents = nents; 723 724 piter->sg = sglist; 725 piter->sg_pgoffset = pgoffset; 726 } 727 EXPORT_SYMBOL(__sg_page_iter_start); 728 729 static int sg_page_count(struct scatterlist *sg) 730 { 731 return PAGE_ALIGN(sg->offset + sg->length) >> PAGE_SHIFT; 732 } 733 734 bool __sg_page_iter_next(struct sg_page_iter *piter) 735 { 736 if (!piter->__nents || !piter->sg) 737 return false; 738 739 piter->sg_pgoffset += piter->__pg_advance; 740 piter->__pg_advance = 1; 741 742 while (piter->sg_pgoffset >= sg_page_count(piter->sg)) { 743 piter->sg_pgoffset -= sg_page_count(piter->sg); 744 piter->sg = sg_next(piter->sg); 745 if (!--piter->__nents || !piter->sg) 746 return false; 747 } 748 749 return true; 750 } 751 EXPORT_SYMBOL(__sg_page_iter_next); 752 753 static int sg_dma_page_count(struct scatterlist *sg) 754 { 755 return PAGE_ALIGN(sg->offset + sg_dma_len(sg)) >> PAGE_SHIFT; 756 } 757 758 bool __sg_page_iter_dma_next(struct sg_dma_page_iter *dma_iter) 759 { 760 struct sg_page_iter *piter = &dma_iter->base; 761 762 if (!piter->__nents || !piter->sg) 763 return false; 764 765 piter->sg_pgoffset += piter->__pg_advance; 766 piter->__pg_advance = 1; 767 768 while (piter->sg_pgoffset >= sg_dma_page_count(piter->sg)) { 769 piter->sg_pgoffset -= sg_dma_page_count(piter->sg); 770 piter->sg = sg_next(piter->sg); 771 if (!--piter->__nents || !piter->sg) 772 return false; 773 } 774 775 return true; 776 } 777 EXPORT_SYMBOL(__sg_page_iter_dma_next); 778 779 /** 780 * sg_miter_start - start mapping iteration over a sg list 781 * @miter: sg mapping iter to be started 782 * @sgl: sg list to iterate over 783 * @nents: number of sg entries 784 * 785 * Description: 786 * Starts mapping iterator @miter. 787 * 788 * Context: 789 * Don't care. 790 */ 791 void sg_miter_start(struct sg_mapping_iter *miter, struct scatterlist *sgl, 792 unsigned int nents, unsigned int flags) 793 { 794 memset(miter, 0, sizeof(struct sg_mapping_iter)); 795 796 __sg_page_iter_start(&miter->piter, sgl, nents, 0); 797 WARN_ON(!(flags & (SG_MITER_TO_SG | SG_MITER_FROM_SG))); 798 miter->__flags = flags; 799 } 800 EXPORT_SYMBOL(sg_miter_start); 801 802 static bool sg_miter_get_next_page(struct sg_mapping_iter *miter) 803 { 804 if (!miter->__remaining) { 805 struct scatterlist *sg; 806 807 if (!__sg_page_iter_next(&miter->piter)) 808 return false; 809 810 sg = miter->piter.sg; 811 812 miter->__offset = miter->piter.sg_pgoffset ? 0 : sg->offset; 813 miter->piter.sg_pgoffset += miter->__offset >> PAGE_SHIFT; 814 miter->__offset &= PAGE_SIZE - 1; 815 miter->__remaining = sg->offset + sg->length - 816 (miter->piter.sg_pgoffset << PAGE_SHIFT) - 817 miter->__offset; 818 miter->__remaining = min_t(unsigned long, miter->__remaining, 819 PAGE_SIZE - miter->__offset); 820 } 821 822 return true; 823 } 824 825 /** 826 * sg_miter_skip - reposition mapping iterator 827 * @miter: sg mapping iter to be skipped 828 * @offset: number of bytes to plus the current location 829 * 830 * Description: 831 * Sets the offset of @miter to its current location plus @offset bytes. 832 * If mapping iterator @miter has been proceeded by sg_miter_next(), this 833 * stops @miter. 834 * 835 * Context: 836 * Don't care. 837 * 838 * Returns: 839 * true if @miter contains the valid mapping. false if end of sg 840 * list is reached. 841 */ 842 bool sg_miter_skip(struct sg_mapping_iter *miter, off_t offset) 843 { 844 sg_miter_stop(miter); 845 846 while (offset) { 847 off_t consumed; 848 849 if (!sg_miter_get_next_page(miter)) 850 return false; 851 852 consumed = min_t(off_t, offset, miter->__remaining); 853 miter->__offset += consumed; 854 miter->__remaining -= consumed; 855 offset -= consumed; 856 } 857 858 return true; 859 } 860 EXPORT_SYMBOL(sg_miter_skip); 861 862 /** 863 * sg_miter_next - proceed mapping iterator to the next mapping 864 * @miter: sg mapping iter to proceed 865 * 866 * Description: 867 * Proceeds @miter to the next mapping. @miter should have been started 868 * using sg_miter_start(). On successful return, @miter->page, 869 * @miter->addr and @miter->length point to the current mapping. 870 * 871 * Context: 872 * May sleep if !SG_MITER_ATOMIC. 873 * 874 * Returns: 875 * true if @miter contains the next mapping. false if end of sg 876 * list is reached. 877 */ 878 bool sg_miter_next(struct sg_mapping_iter *miter) 879 { 880 sg_miter_stop(miter); 881 882 /* 883 * Get to the next page if necessary. 884 * __remaining, __offset is adjusted by sg_miter_stop 885 */ 886 if (!sg_miter_get_next_page(miter)) 887 return false; 888 889 miter->page = sg_page_iter_page(&miter->piter); 890 miter->consumed = miter->length = miter->__remaining; 891 892 if (miter->__flags & SG_MITER_ATOMIC) 893 miter->addr = kmap_atomic(miter->page) + miter->__offset; 894 else 895 miter->addr = kmap(miter->page) + miter->__offset; 896 897 return true; 898 } 899 EXPORT_SYMBOL(sg_miter_next); 900 901 /** 902 * sg_miter_stop - stop mapping iteration 903 * @miter: sg mapping iter to be stopped 904 * 905 * Description: 906 * Stops mapping iterator @miter. @miter should have been started 907 * using sg_miter_start(). A stopped iteration can be resumed by 908 * calling sg_miter_next() on it. This is useful when resources (kmap) 909 * need to be released during iteration. 910 * 911 * Context: 912 * Don't care otherwise. 913 */ 914 void sg_miter_stop(struct sg_mapping_iter *miter) 915 { 916 WARN_ON(miter->consumed > miter->length); 917 918 /* drop resources from the last iteration */ 919 if (miter->addr) { 920 miter->__offset += miter->consumed; 921 miter->__remaining -= miter->consumed; 922 923 if (miter->__flags & SG_MITER_TO_SG) 924 flush_dcache_page(miter->page); 925 926 if (miter->__flags & SG_MITER_ATOMIC) { 927 WARN_ON_ONCE(!pagefault_disabled()); 928 kunmap_atomic(miter->addr); 929 } else 930 kunmap(miter->page); 931 932 miter->page = NULL; 933 miter->addr = NULL; 934 miter->length = 0; 935 miter->consumed = 0; 936 } 937 } 938 EXPORT_SYMBOL(sg_miter_stop); 939 940 /** 941 * sg_copy_buffer - Copy data between a linear buffer and an SG list 942 * @sgl: The SG list 943 * @nents: Number of SG entries 944 * @buf: Where to copy from 945 * @buflen: The number of bytes to copy 946 * @skip: Number of bytes to skip before copying 947 * @to_buffer: transfer direction (true == from an sg list to a 948 * buffer, false == from a buffer to an sg list) 949 * 950 * Returns the number of copied bytes. 951 * 952 **/ 953 size_t sg_copy_buffer(struct scatterlist *sgl, unsigned int nents, void *buf, 954 size_t buflen, off_t skip, bool to_buffer) 955 { 956 unsigned int offset = 0; 957 struct sg_mapping_iter miter; 958 unsigned int sg_flags = SG_MITER_ATOMIC; 959 960 if (to_buffer) 961 sg_flags |= SG_MITER_FROM_SG; 962 else 963 sg_flags |= SG_MITER_TO_SG; 964 965 sg_miter_start(&miter, sgl, nents, sg_flags); 966 967 if (!sg_miter_skip(&miter, skip)) 968 return 0; 969 970 while ((offset < buflen) && sg_miter_next(&miter)) { 971 unsigned int len; 972 973 len = min(miter.length, buflen - offset); 974 975 if (to_buffer) 976 memcpy(buf + offset, miter.addr, len); 977 else 978 memcpy(miter.addr, buf + offset, len); 979 980 offset += len; 981 } 982 983 sg_miter_stop(&miter); 984 985 return offset; 986 } 987 EXPORT_SYMBOL(sg_copy_buffer); 988 989 /** 990 * sg_copy_from_buffer - Copy from a linear buffer to an SG list 991 * @sgl: The SG list 992 * @nents: Number of SG entries 993 * @buf: Where to copy from 994 * @buflen: The number of bytes to copy 995 * 996 * Returns the number of copied bytes. 997 * 998 **/ 999 size_t sg_copy_from_buffer(struct scatterlist *sgl, unsigned int nents, 1000 const void *buf, size_t buflen) 1001 { 1002 return sg_copy_buffer(sgl, nents, (void *)buf, buflen, 0, false); 1003 } 1004 EXPORT_SYMBOL(sg_copy_from_buffer); 1005 1006 /** 1007 * sg_copy_to_buffer - Copy from an SG list to a linear buffer 1008 * @sgl: The SG list 1009 * @nents: Number of SG entries 1010 * @buf: Where to copy to 1011 * @buflen: The number of bytes to copy 1012 * 1013 * Returns the number of copied bytes. 1014 * 1015 **/ 1016 size_t sg_copy_to_buffer(struct scatterlist *sgl, unsigned int nents, 1017 void *buf, size_t buflen) 1018 { 1019 return sg_copy_buffer(sgl, nents, buf, buflen, 0, true); 1020 } 1021 EXPORT_SYMBOL(sg_copy_to_buffer); 1022 1023 /** 1024 * sg_pcopy_from_buffer - Copy from a linear buffer to an SG list 1025 * @sgl: The SG list 1026 * @nents: Number of SG entries 1027 * @buf: Where to copy from 1028 * @buflen: The number of bytes to copy 1029 * @skip: Number of bytes to skip before copying 1030 * 1031 * Returns the number of copied bytes. 1032 * 1033 **/ 1034 size_t sg_pcopy_from_buffer(struct scatterlist *sgl, unsigned int nents, 1035 const void *buf, size_t buflen, off_t skip) 1036 { 1037 return sg_copy_buffer(sgl, nents, (void *)buf, buflen, skip, false); 1038 } 1039 EXPORT_SYMBOL(sg_pcopy_from_buffer); 1040 1041 /** 1042 * sg_pcopy_to_buffer - Copy from an SG list to a linear buffer 1043 * @sgl: The SG list 1044 * @nents: Number of SG entries 1045 * @buf: Where to copy to 1046 * @buflen: The number of bytes to copy 1047 * @skip: Number of bytes to skip before copying 1048 * 1049 * Returns the number of copied bytes. 1050 * 1051 **/ 1052 size_t sg_pcopy_to_buffer(struct scatterlist *sgl, unsigned int nents, 1053 void *buf, size_t buflen, off_t skip) 1054 { 1055 return sg_copy_buffer(sgl, nents, buf, buflen, skip, true); 1056 } 1057 EXPORT_SYMBOL(sg_pcopy_to_buffer); 1058 1059 /** 1060 * sg_zero_buffer - Zero-out a part of a SG list 1061 * @sgl: The SG list 1062 * @nents: Number of SG entries 1063 * @buflen: The number of bytes to zero out 1064 * @skip: Number of bytes to skip before zeroing 1065 * 1066 * Returns the number of bytes zeroed. 1067 **/ 1068 size_t sg_zero_buffer(struct scatterlist *sgl, unsigned int nents, 1069 size_t buflen, off_t skip) 1070 { 1071 unsigned int offset = 0; 1072 struct sg_mapping_iter miter; 1073 unsigned int sg_flags = SG_MITER_ATOMIC | SG_MITER_TO_SG; 1074 1075 sg_miter_start(&miter, sgl, nents, sg_flags); 1076 1077 if (!sg_miter_skip(&miter, skip)) 1078 return false; 1079 1080 while (offset < buflen && sg_miter_next(&miter)) { 1081 unsigned int len; 1082 1083 len = min(miter.length, buflen - offset); 1084 memset(miter.addr, 0, len); 1085 1086 offset += len; 1087 } 1088 1089 sg_miter_stop(&miter); 1090 return offset; 1091 } 1092 EXPORT_SYMBOL(sg_zero_buffer); 1093