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 acount 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 acount 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 * 186 * Description: 187 * Free an sg table previously allocated and setup with 188 * __sg_alloc_table(). The @max_ents value must be identical to 189 * that previously used with __sg_alloc_table(). 190 * 191 **/ 192 void __sg_free_table(struct sg_table *table, unsigned int max_ents, 193 unsigned int nents_first_chunk, sg_free_fn *free_fn) 194 { 195 struct scatterlist *sgl, *next; 196 unsigned curr_max_ents = nents_first_chunk ?: max_ents; 197 198 if (unlikely(!table->sgl)) 199 return; 200 201 sgl = table->sgl; 202 while (table->orig_nents) { 203 unsigned int alloc_size = table->orig_nents; 204 unsigned int sg_size; 205 206 /* 207 * If we have more than max_ents segments left, 208 * then assign 'next' to the sg table after the current one. 209 * sg_size is then one less than alloc size, since the last 210 * element is the chain pointer. 211 */ 212 if (alloc_size > curr_max_ents) { 213 next = sg_chain_ptr(&sgl[curr_max_ents - 1]); 214 alloc_size = curr_max_ents; 215 sg_size = alloc_size - 1; 216 } else { 217 sg_size = alloc_size; 218 next = NULL; 219 } 220 221 table->orig_nents -= sg_size; 222 if (nents_first_chunk) 223 nents_first_chunk = 0; 224 else 225 free_fn(sgl, alloc_size); 226 sgl = next; 227 curr_max_ents = max_ents; 228 } 229 230 table->sgl = NULL; 231 } 232 EXPORT_SYMBOL(__sg_free_table); 233 234 /** 235 * sg_free_table - Free a previously allocated sg table 236 * @table: The mapped sg table header 237 * 238 **/ 239 void sg_free_table(struct sg_table *table) 240 { 241 __sg_free_table(table, SG_MAX_SINGLE_ALLOC, false, sg_kfree); 242 } 243 EXPORT_SYMBOL(sg_free_table); 244 245 /** 246 * __sg_alloc_table - Allocate and initialize an sg table with given allocator 247 * @table: The sg table header to use 248 * @nents: Number of entries in sg list 249 * @max_ents: The maximum number of entries the allocator returns per call 250 * @nents_first_chunk: Number of entries int the (preallocated) first 251 * scatterlist chunk, 0 means no such preallocated chunk provided by user 252 * @gfp_mask: GFP allocation mask 253 * @alloc_fn: Allocator to use 254 * 255 * Description: 256 * This function returns a @table @nents long. The allocator is 257 * defined to return scatterlist chunks of maximum size @max_ents. 258 * Thus if @nents is bigger than @max_ents, the scatterlists will be 259 * chained in units of @max_ents. 260 * 261 * Notes: 262 * If this function returns non-0 (eg failure), the caller must call 263 * __sg_free_table() to cleanup any leftover allocations. 264 * 265 **/ 266 int __sg_alloc_table(struct sg_table *table, unsigned int nents, 267 unsigned int max_ents, struct scatterlist *first_chunk, 268 unsigned int nents_first_chunk, gfp_t gfp_mask, 269 sg_alloc_fn *alloc_fn) 270 { 271 struct scatterlist *sg, *prv; 272 unsigned int left; 273 unsigned curr_max_ents = nents_first_chunk ?: max_ents; 274 unsigned prv_max_ents; 275 276 memset(table, 0, sizeof(*table)); 277 278 if (nents == 0) 279 return -EINVAL; 280 #ifdef CONFIG_ARCH_NO_SG_CHAIN 281 if (WARN_ON_ONCE(nents > max_ents)) 282 return -EINVAL; 283 #endif 284 285 left = nents; 286 prv = NULL; 287 do { 288 unsigned int sg_size, alloc_size = left; 289 290 if (alloc_size > curr_max_ents) { 291 alloc_size = curr_max_ents; 292 sg_size = alloc_size - 1; 293 } else 294 sg_size = alloc_size; 295 296 left -= sg_size; 297 298 if (first_chunk) { 299 sg = first_chunk; 300 first_chunk = NULL; 301 } else { 302 sg = alloc_fn(alloc_size, gfp_mask); 303 } 304 if (unlikely(!sg)) { 305 /* 306 * Adjust entry count to reflect that the last 307 * entry of the previous table won't be used for 308 * linkage. Without this, sg_kfree() may get 309 * confused. 310 */ 311 if (prv) 312 table->nents = ++table->orig_nents; 313 314 return -ENOMEM; 315 } 316 317 sg_init_table(sg, alloc_size); 318 table->nents = table->orig_nents += sg_size; 319 320 /* 321 * If this is the first mapping, assign the sg table header. 322 * If this is not the first mapping, chain previous part. 323 */ 324 if (prv) 325 sg_chain(prv, prv_max_ents, sg); 326 else 327 table->sgl = sg; 328 329 /* 330 * If no more entries after this one, mark the end 331 */ 332 if (!left) 333 sg_mark_end(&sg[sg_size - 1]); 334 335 prv = sg; 336 prv_max_ents = curr_max_ents; 337 curr_max_ents = max_ents; 338 } while (left); 339 340 return 0; 341 } 342 EXPORT_SYMBOL(__sg_alloc_table); 343 344 /** 345 * sg_alloc_table - Allocate and initialize an sg table 346 * @table: The sg table header to use 347 * @nents: Number of entries in sg list 348 * @gfp_mask: GFP allocation mask 349 * 350 * Description: 351 * Allocate and initialize an sg table. If @nents@ is larger than 352 * SG_MAX_SINGLE_ALLOC a chained sg table will be setup. 353 * 354 **/ 355 int sg_alloc_table(struct sg_table *table, unsigned int nents, gfp_t gfp_mask) 356 { 357 int ret; 358 359 ret = __sg_alloc_table(table, nents, SG_MAX_SINGLE_ALLOC, 360 NULL, 0, gfp_mask, sg_kmalloc); 361 if (unlikely(ret)) 362 __sg_free_table(table, SG_MAX_SINGLE_ALLOC, 0, sg_kfree); 363 364 return ret; 365 } 366 EXPORT_SYMBOL(sg_alloc_table); 367 368 static struct scatterlist *get_next_sg(struct sg_table *table, 369 struct scatterlist *cur, 370 unsigned long needed_sges, 371 gfp_t gfp_mask) 372 { 373 struct scatterlist *new_sg, *next_sg; 374 unsigned int alloc_size; 375 376 if (cur) { 377 next_sg = sg_next(cur); 378 /* Check if last entry should be keeped for chainning */ 379 if (!sg_is_last(next_sg) || needed_sges == 1) 380 return next_sg; 381 } 382 383 alloc_size = min_t(unsigned long, needed_sges, SG_MAX_SINGLE_ALLOC); 384 new_sg = sg_kmalloc(alloc_size, gfp_mask); 385 if (!new_sg) 386 return ERR_PTR(-ENOMEM); 387 sg_init_table(new_sg, alloc_size); 388 if (cur) { 389 __sg_chain(next_sg, new_sg); 390 table->orig_nents += alloc_size - 1; 391 } else { 392 table->sgl = new_sg; 393 table->orig_nents = alloc_size; 394 table->nents = 0; 395 } 396 return new_sg; 397 } 398 399 /** 400 * __sg_alloc_table_from_pages - Allocate and initialize an sg table from 401 * an array of pages 402 * @sgt: The sg table header to use 403 * @pages: Pointer to an array of page pointers 404 * @n_pages: Number of pages in the pages array 405 * @offset: Offset from start of the first page to the start of a buffer 406 * @size: Number of valid bytes in the buffer (after offset) 407 * @max_segment: Maximum size of a scatterlist element in bytes 408 * @prv: Last populated sge in sgt 409 * @left_pages: Left pages caller have to set after this call 410 * @gfp_mask: GFP allocation mask 411 * 412 * Description: 413 * If @prv is NULL, allocate and initialize an sg table from a list of pages, 414 * else reuse the scatterlist passed in at @prv. 415 * Contiguous ranges of the pages are squashed into a single scatterlist 416 * entry up to the maximum size specified in @max_segment. A user may 417 * provide an offset at a start and a size of valid data in a buffer 418 * specified by the page array. 419 * 420 * Returns: 421 * Last SGE in sgt on success, PTR_ERR on otherwise. 422 * The allocation in @sgt must be released by sg_free_table. 423 * 424 * Notes: 425 * If this function returns non-0 (eg failure), the caller must call 426 * sg_free_table() to cleanup any leftover allocations. 427 */ 428 struct scatterlist *__sg_alloc_table_from_pages(struct sg_table *sgt, 429 struct page **pages, unsigned int n_pages, unsigned int offset, 430 unsigned long size, unsigned int max_segment, 431 struct scatterlist *prv, unsigned int left_pages, 432 gfp_t gfp_mask) 433 { 434 unsigned int chunks, cur_page, seg_len, i, prv_len = 0; 435 unsigned int added_nents = 0; 436 struct scatterlist *s = prv; 437 438 /* 439 * The algorithm below requires max_segment to be aligned to PAGE_SIZE 440 * otherwise it can overshoot. 441 */ 442 max_segment = ALIGN_DOWN(max_segment, PAGE_SIZE); 443 if (WARN_ON(max_segment < PAGE_SIZE)) 444 return ERR_PTR(-EINVAL); 445 446 if (IS_ENABLED(CONFIG_ARCH_NO_SG_CHAIN) && prv) 447 return ERR_PTR(-EOPNOTSUPP); 448 449 if (prv) { 450 unsigned long paddr = (page_to_pfn(sg_page(prv)) * PAGE_SIZE + 451 prv->offset + prv->length) / 452 PAGE_SIZE; 453 454 if (WARN_ON(offset)) 455 return ERR_PTR(-EINVAL); 456 457 /* Merge contiguous pages into the last SG */ 458 prv_len = prv->length; 459 while (n_pages && page_to_pfn(pages[0]) == paddr) { 460 if (prv->length + PAGE_SIZE > max_segment) 461 break; 462 prv->length += PAGE_SIZE; 463 paddr++; 464 pages++; 465 n_pages--; 466 } 467 if (!n_pages) 468 goto out; 469 } 470 471 /* compute number of contiguous chunks */ 472 chunks = 1; 473 seg_len = 0; 474 for (i = 1; i < n_pages; i++) { 475 seg_len += PAGE_SIZE; 476 if (seg_len >= max_segment || 477 page_to_pfn(pages[i]) != page_to_pfn(pages[i - 1]) + 1) { 478 chunks++; 479 seg_len = 0; 480 } 481 } 482 483 /* merging chunks and putting them into the scatterlist */ 484 cur_page = 0; 485 for (i = 0; i < chunks; i++) { 486 unsigned int j, chunk_size; 487 488 /* look for the end of the current chunk */ 489 seg_len = 0; 490 for (j = cur_page + 1; j < n_pages; j++) { 491 seg_len += PAGE_SIZE; 492 if (seg_len >= max_segment || 493 page_to_pfn(pages[j]) != 494 page_to_pfn(pages[j - 1]) + 1) 495 break; 496 } 497 498 /* Pass how many chunks might be left */ 499 s = get_next_sg(sgt, s, chunks - i + left_pages, gfp_mask); 500 if (IS_ERR(s)) { 501 /* 502 * Adjust entry length to be as before function was 503 * called. 504 */ 505 if (prv) 506 prv->length = prv_len; 507 return s; 508 } 509 chunk_size = ((j - cur_page) << PAGE_SHIFT) - offset; 510 sg_set_page(s, pages[cur_page], 511 min_t(unsigned long, size, chunk_size), offset); 512 added_nents++; 513 size -= chunk_size; 514 offset = 0; 515 cur_page = j; 516 } 517 sgt->nents += added_nents; 518 out: 519 if (!left_pages) 520 sg_mark_end(s); 521 return s; 522 } 523 EXPORT_SYMBOL(__sg_alloc_table_from_pages); 524 525 /** 526 * sg_alloc_table_from_pages - Allocate and initialize an sg table from 527 * an array of pages 528 * @sgt: The sg table header to use 529 * @pages: Pointer to an array of page pointers 530 * @n_pages: Number of pages in the pages array 531 * @offset: Offset from start of the first page to the start of a buffer 532 * @size: Number of valid bytes in the buffer (after offset) 533 * @gfp_mask: GFP allocation mask 534 * 535 * Description: 536 * Allocate and initialize an sg table from a list of pages. Contiguous 537 * ranges of the pages are squashed into a single scatterlist node. A user 538 * may provide an offset at a start and a size of valid data in a buffer 539 * specified by the page array. The returned sg table is released by 540 * sg_free_table. 541 * 542 * Returns: 543 * 0 on success, negative error on failure 544 */ 545 int sg_alloc_table_from_pages(struct sg_table *sgt, struct page **pages, 546 unsigned int n_pages, unsigned int offset, 547 unsigned long size, gfp_t gfp_mask) 548 { 549 return PTR_ERR_OR_ZERO(__sg_alloc_table_from_pages(sgt, pages, n_pages, 550 offset, size, UINT_MAX, NULL, 0, gfp_mask)); 551 } 552 EXPORT_SYMBOL(sg_alloc_table_from_pages); 553 554 #ifdef CONFIG_SGL_ALLOC 555 556 /** 557 * sgl_alloc_order - allocate a scatterlist and its pages 558 * @length: Length in bytes of the scatterlist. Must be at least one 559 * @order: Second argument for alloc_pages() 560 * @chainable: Whether or not to allocate an extra element in the scatterlist 561 * for scatterlist chaining purposes 562 * @gfp: Memory allocation flags 563 * @nent_p: [out] Number of entries in the scatterlist that have pages 564 * 565 * Returns: A pointer to an initialized scatterlist or %NULL upon failure. 566 */ 567 struct scatterlist *sgl_alloc_order(unsigned long long length, 568 unsigned int order, bool chainable, 569 gfp_t gfp, unsigned int *nent_p) 570 { 571 struct scatterlist *sgl, *sg; 572 struct page *page; 573 unsigned int nent, nalloc; 574 u32 elem_len; 575 576 nent = round_up(length, PAGE_SIZE << order) >> (PAGE_SHIFT + order); 577 /* Check for integer overflow */ 578 if (length > (nent << (PAGE_SHIFT + order))) 579 return NULL; 580 nalloc = nent; 581 if (chainable) { 582 /* Check for integer overflow */ 583 if (nalloc + 1 < nalloc) 584 return NULL; 585 nalloc++; 586 } 587 sgl = kmalloc_array(nalloc, sizeof(struct scatterlist), 588 gfp & ~GFP_DMA); 589 if (!sgl) 590 return NULL; 591 592 sg_init_table(sgl, nalloc); 593 sg = sgl; 594 while (length) { 595 elem_len = min_t(u64, length, PAGE_SIZE << order); 596 page = alloc_pages(gfp, order); 597 if (!page) { 598 sgl_free_order(sgl, order); 599 return NULL; 600 } 601 602 sg_set_page(sg, page, elem_len, 0); 603 length -= elem_len; 604 sg = sg_next(sg); 605 } 606 WARN_ONCE(length, "length = %lld\n", length); 607 if (nent_p) 608 *nent_p = nent; 609 return sgl; 610 } 611 EXPORT_SYMBOL(sgl_alloc_order); 612 613 /** 614 * sgl_alloc - allocate a scatterlist and its pages 615 * @length: Length in bytes of the scatterlist 616 * @gfp: Memory allocation flags 617 * @nent_p: [out] Number of entries in the scatterlist 618 * 619 * Returns: A pointer to an initialized scatterlist or %NULL upon failure. 620 */ 621 struct scatterlist *sgl_alloc(unsigned long long length, gfp_t gfp, 622 unsigned int *nent_p) 623 { 624 return sgl_alloc_order(length, 0, false, gfp, nent_p); 625 } 626 EXPORT_SYMBOL(sgl_alloc); 627 628 /** 629 * sgl_free_n_order - free a scatterlist and its pages 630 * @sgl: Scatterlist with one or more elements 631 * @nents: Maximum number of elements to free 632 * @order: Second argument for __free_pages() 633 * 634 * Notes: 635 * - If several scatterlists have been chained and each chain element is 636 * freed separately then it's essential to set nents correctly to avoid that a 637 * page would get freed twice. 638 * - All pages in a chained scatterlist can be freed at once by setting @nents 639 * to a high number. 640 */ 641 void sgl_free_n_order(struct scatterlist *sgl, int nents, int order) 642 { 643 struct scatterlist *sg; 644 struct page *page; 645 int i; 646 647 for_each_sg(sgl, sg, nents, i) { 648 if (!sg) 649 break; 650 page = sg_page(sg); 651 if (page) 652 __free_pages(page, order); 653 } 654 kfree(sgl); 655 } 656 EXPORT_SYMBOL(sgl_free_n_order); 657 658 /** 659 * sgl_free_order - free a scatterlist and its pages 660 * @sgl: Scatterlist with one or more elements 661 * @order: Second argument for __free_pages() 662 */ 663 void sgl_free_order(struct scatterlist *sgl, int order) 664 { 665 sgl_free_n_order(sgl, INT_MAX, order); 666 } 667 EXPORT_SYMBOL(sgl_free_order); 668 669 /** 670 * sgl_free - free a scatterlist and its pages 671 * @sgl: Scatterlist with one or more elements 672 */ 673 void sgl_free(struct scatterlist *sgl) 674 { 675 sgl_free_order(sgl, 0); 676 } 677 EXPORT_SYMBOL(sgl_free); 678 679 #endif /* CONFIG_SGL_ALLOC */ 680 681 void __sg_page_iter_start(struct sg_page_iter *piter, 682 struct scatterlist *sglist, unsigned int nents, 683 unsigned long pgoffset) 684 { 685 piter->__pg_advance = 0; 686 piter->__nents = nents; 687 688 piter->sg = sglist; 689 piter->sg_pgoffset = pgoffset; 690 } 691 EXPORT_SYMBOL(__sg_page_iter_start); 692 693 static int sg_page_count(struct scatterlist *sg) 694 { 695 return PAGE_ALIGN(sg->offset + sg->length) >> PAGE_SHIFT; 696 } 697 698 bool __sg_page_iter_next(struct sg_page_iter *piter) 699 { 700 if (!piter->__nents || !piter->sg) 701 return false; 702 703 piter->sg_pgoffset += piter->__pg_advance; 704 piter->__pg_advance = 1; 705 706 while (piter->sg_pgoffset >= sg_page_count(piter->sg)) { 707 piter->sg_pgoffset -= sg_page_count(piter->sg); 708 piter->sg = sg_next(piter->sg); 709 if (!--piter->__nents || !piter->sg) 710 return false; 711 } 712 713 return true; 714 } 715 EXPORT_SYMBOL(__sg_page_iter_next); 716 717 static int sg_dma_page_count(struct scatterlist *sg) 718 { 719 return PAGE_ALIGN(sg->offset + sg_dma_len(sg)) >> PAGE_SHIFT; 720 } 721 722 bool __sg_page_iter_dma_next(struct sg_dma_page_iter *dma_iter) 723 { 724 struct sg_page_iter *piter = &dma_iter->base; 725 726 if (!piter->__nents || !piter->sg) 727 return false; 728 729 piter->sg_pgoffset += piter->__pg_advance; 730 piter->__pg_advance = 1; 731 732 while (piter->sg_pgoffset >= sg_dma_page_count(piter->sg)) { 733 piter->sg_pgoffset -= sg_dma_page_count(piter->sg); 734 piter->sg = sg_next(piter->sg); 735 if (!--piter->__nents || !piter->sg) 736 return false; 737 } 738 739 return true; 740 } 741 EXPORT_SYMBOL(__sg_page_iter_dma_next); 742 743 /** 744 * sg_miter_start - start mapping iteration over a sg list 745 * @miter: sg mapping iter to be started 746 * @sgl: sg list to iterate over 747 * @nents: number of sg entries 748 * 749 * Description: 750 * Starts mapping iterator @miter. 751 * 752 * Context: 753 * Don't care. 754 */ 755 void sg_miter_start(struct sg_mapping_iter *miter, struct scatterlist *sgl, 756 unsigned int nents, unsigned int flags) 757 { 758 memset(miter, 0, sizeof(struct sg_mapping_iter)); 759 760 __sg_page_iter_start(&miter->piter, sgl, nents, 0); 761 WARN_ON(!(flags & (SG_MITER_TO_SG | SG_MITER_FROM_SG))); 762 miter->__flags = flags; 763 } 764 EXPORT_SYMBOL(sg_miter_start); 765 766 static bool sg_miter_get_next_page(struct sg_mapping_iter *miter) 767 { 768 if (!miter->__remaining) { 769 struct scatterlist *sg; 770 771 if (!__sg_page_iter_next(&miter->piter)) 772 return false; 773 774 sg = miter->piter.sg; 775 776 miter->__offset = miter->piter.sg_pgoffset ? 0 : sg->offset; 777 miter->piter.sg_pgoffset += miter->__offset >> PAGE_SHIFT; 778 miter->__offset &= PAGE_SIZE - 1; 779 miter->__remaining = sg->offset + sg->length - 780 (miter->piter.sg_pgoffset << PAGE_SHIFT) - 781 miter->__offset; 782 miter->__remaining = min_t(unsigned long, miter->__remaining, 783 PAGE_SIZE - miter->__offset); 784 } 785 786 return true; 787 } 788 789 /** 790 * sg_miter_skip - reposition mapping iterator 791 * @miter: sg mapping iter to be skipped 792 * @offset: number of bytes to plus the current location 793 * 794 * Description: 795 * Sets the offset of @miter to its current location plus @offset bytes. 796 * If mapping iterator @miter has been proceeded by sg_miter_next(), this 797 * stops @miter. 798 * 799 * Context: 800 * Don't care if @miter is stopped, or not proceeded yet. 801 * Otherwise, preemption disabled if the SG_MITER_ATOMIC is set. 802 * 803 * Returns: 804 * true if @miter contains the valid mapping. false if end of sg 805 * list is reached. 806 */ 807 bool sg_miter_skip(struct sg_mapping_iter *miter, off_t offset) 808 { 809 sg_miter_stop(miter); 810 811 while (offset) { 812 off_t consumed; 813 814 if (!sg_miter_get_next_page(miter)) 815 return false; 816 817 consumed = min_t(off_t, offset, miter->__remaining); 818 miter->__offset += consumed; 819 miter->__remaining -= consumed; 820 offset -= consumed; 821 } 822 823 return true; 824 } 825 EXPORT_SYMBOL(sg_miter_skip); 826 827 /** 828 * sg_miter_next - proceed mapping iterator to the next mapping 829 * @miter: sg mapping iter to proceed 830 * 831 * Description: 832 * Proceeds @miter to the next mapping. @miter should have been started 833 * using sg_miter_start(). On successful return, @miter->page, 834 * @miter->addr and @miter->length point to the current mapping. 835 * 836 * Context: 837 * Preemption disabled if SG_MITER_ATOMIC. Preemption must stay disabled 838 * till @miter is stopped. May sleep if !SG_MITER_ATOMIC. 839 * 840 * Returns: 841 * true if @miter contains the next mapping. false if end of sg 842 * list is reached. 843 */ 844 bool sg_miter_next(struct sg_mapping_iter *miter) 845 { 846 sg_miter_stop(miter); 847 848 /* 849 * Get to the next page if necessary. 850 * __remaining, __offset is adjusted by sg_miter_stop 851 */ 852 if (!sg_miter_get_next_page(miter)) 853 return false; 854 855 miter->page = sg_page_iter_page(&miter->piter); 856 miter->consumed = miter->length = miter->__remaining; 857 858 if (miter->__flags & SG_MITER_ATOMIC) 859 miter->addr = kmap_atomic(miter->page) + miter->__offset; 860 else 861 miter->addr = kmap(miter->page) + miter->__offset; 862 863 return true; 864 } 865 EXPORT_SYMBOL(sg_miter_next); 866 867 /** 868 * sg_miter_stop - stop mapping iteration 869 * @miter: sg mapping iter to be stopped 870 * 871 * Description: 872 * Stops mapping iterator @miter. @miter should have been started 873 * using sg_miter_start(). A stopped iteration can be resumed by 874 * calling sg_miter_next() on it. This is useful when resources (kmap) 875 * need to be released during iteration. 876 * 877 * Context: 878 * Preemption disabled if the SG_MITER_ATOMIC is set. Don't care 879 * otherwise. 880 */ 881 void sg_miter_stop(struct sg_mapping_iter *miter) 882 { 883 WARN_ON(miter->consumed > miter->length); 884 885 /* drop resources from the last iteration */ 886 if (miter->addr) { 887 miter->__offset += miter->consumed; 888 miter->__remaining -= miter->consumed; 889 890 if ((miter->__flags & SG_MITER_TO_SG) && 891 !PageSlab(miter->page)) 892 flush_kernel_dcache_page(miter->page); 893 894 if (miter->__flags & SG_MITER_ATOMIC) { 895 WARN_ON_ONCE(preemptible()); 896 kunmap_atomic(miter->addr); 897 } else 898 kunmap(miter->page); 899 900 miter->page = NULL; 901 miter->addr = NULL; 902 miter->length = 0; 903 miter->consumed = 0; 904 } 905 } 906 EXPORT_SYMBOL(sg_miter_stop); 907 908 /** 909 * sg_copy_buffer - Copy data between a linear buffer and an SG list 910 * @sgl: The SG list 911 * @nents: Number of SG entries 912 * @buf: Where to copy from 913 * @buflen: The number of bytes to copy 914 * @skip: Number of bytes to skip before copying 915 * @to_buffer: transfer direction (true == from an sg list to a 916 * buffer, false == from a buffer to an sg list) 917 * 918 * Returns the number of copied bytes. 919 * 920 **/ 921 size_t sg_copy_buffer(struct scatterlist *sgl, unsigned int nents, void *buf, 922 size_t buflen, off_t skip, bool to_buffer) 923 { 924 unsigned int offset = 0; 925 struct sg_mapping_iter miter; 926 unsigned int sg_flags = SG_MITER_ATOMIC; 927 928 if (to_buffer) 929 sg_flags |= SG_MITER_FROM_SG; 930 else 931 sg_flags |= SG_MITER_TO_SG; 932 933 sg_miter_start(&miter, sgl, nents, sg_flags); 934 935 if (!sg_miter_skip(&miter, skip)) 936 return 0; 937 938 while ((offset < buflen) && sg_miter_next(&miter)) { 939 unsigned int len; 940 941 len = min(miter.length, buflen - offset); 942 943 if (to_buffer) 944 memcpy(buf + offset, miter.addr, len); 945 else 946 memcpy(miter.addr, buf + offset, len); 947 948 offset += len; 949 } 950 951 sg_miter_stop(&miter); 952 953 return offset; 954 } 955 EXPORT_SYMBOL(sg_copy_buffer); 956 957 /** 958 * sg_copy_from_buffer - Copy from a linear buffer to an SG list 959 * @sgl: The SG list 960 * @nents: Number of SG entries 961 * @buf: Where to copy from 962 * @buflen: The number of bytes to copy 963 * 964 * Returns the number of copied bytes. 965 * 966 **/ 967 size_t sg_copy_from_buffer(struct scatterlist *sgl, unsigned int nents, 968 const void *buf, size_t buflen) 969 { 970 return sg_copy_buffer(sgl, nents, (void *)buf, buflen, 0, false); 971 } 972 EXPORT_SYMBOL(sg_copy_from_buffer); 973 974 /** 975 * sg_copy_to_buffer - Copy from an SG list to a linear buffer 976 * @sgl: The SG list 977 * @nents: Number of SG entries 978 * @buf: Where to copy to 979 * @buflen: The number of bytes to copy 980 * 981 * Returns the number of copied bytes. 982 * 983 **/ 984 size_t sg_copy_to_buffer(struct scatterlist *sgl, unsigned int nents, 985 void *buf, size_t buflen) 986 { 987 return sg_copy_buffer(sgl, nents, buf, buflen, 0, true); 988 } 989 EXPORT_SYMBOL(sg_copy_to_buffer); 990 991 /** 992 * sg_pcopy_from_buffer - Copy from a linear buffer to an SG list 993 * @sgl: The SG list 994 * @nents: Number of SG entries 995 * @buf: Where to copy from 996 * @buflen: The number of bytes to copy 997 * @skip: Number of bytes to skip before copying 998 * 999 * Returns the number of copied bytes. 1000 * 1001 **/ 1002 size_t sg_pcopy_from_buffer(struct scatterlist *sgl, unsigned int nents, 1003 const void *buf, size_t buflen, off_t skip) 1004 { 1005 return sg_copy_buffer(sgl, nents, (void *)buf, buflen, skip, false); 1006 } 1007 EXPORT_SYMBOL(sg_pcopy_from_buffer); 1008 1009 /** 1010 * sg_pcopy_to_buffer - Copy from an SG list to a linear buffer 1011 * @sgl: The SG list 1012 * @nents: Number of SG entries 1013 * @buf: Where to copy to 1014 * @buflen: The number of bytes to copy 1015 * @skip: Number of bytes to skip before copying 1016 * 1017 * Returns the number of copied bytes. 1018 * 1019 **/ 1020 size_t sg_pcopy_to_buffer(struct scatterlist *sgl, unsigned int nents, 1021 void *buf, size_t buflen, off_t skip) 1022 { 1023 return sg_copy_buffer(sgl, nents, buf, buflen, skip, true); 1024 } 1025 EXPORT_SYMBOL(sg_pcopy_to_buffer); 1026 1027 /** 1028 * sg_zero_buffer - Zero-out a part of a SG list 1029 * @sgl: The SG list 1030 * @nents: Number of SG entries 1031 * @buflen: The number of bytes to zero out 1032 * @skip: Number of bytes to skip before zeroing 1033 * 1034 * Returns the number of bytes zeroed. 1035 **/ 1036 size_t sg_zero_buffer(struct scatterlist *sgl, unsigned int nents, 1037 size_t buflen, off_t skip) 1038 { 1039 unsigned int offset = 0; 1040 struct sg_mapping_iter miter; 1041 unsigned int sg_flags = SG_MITER_ATOMIC | SG_MITER_TO_SG; 1042 1043 sg_miter_start(&miter, sgl, nents, sg_flags); 1044 1045 if (!sg_miter_skip(&miter, skip)) 1046 return false; 1047 1048 while (offset < buflen && sg_miter_next(&miter)) { 1049 unsigned int len; 1050 1051 len = min(miter.length, buflen - offset); 1052 memset(miter.addr, 0, len); 1053 1054 offset += len; 1055 } 1056 1057 sg_miter_stop(&miter); 1058 return offset; 1059 } 1060 EXPORT_SYMBOL(sg_zero_buffer); 1061