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, false, 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, false, 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 /** 414 * sg_alloc_append_table_from_pages - Allocate and initialize an append sg 415 * table from an array of pages 416 * @sgt_append: The sg append table to use 417 * @pages: Pointer to an array of page pointers 418 * @n_pages: Number of pages in the pages array 419 * @offset: Offset from start of the first page to the start of a buffer 420 * @size: Number of valid bytes in the buffer (after offset) 421 * @max_segment: Maximum size of a scatterlist element in bytes 422 * @left_pages: Left pages caller have to set after this call 423 * @gfp_mask: GFP allocation mask 424 * 425 * Description: 426 * In the first call it allocate and initialize an sg table from a list of 427 * pages, else reuse the scatterlist from sgt_append. Contiguous ranges of 428 * the pages are squashed into a single scatterlist entry up to the maximum 429 * size specified in @max_segment. A user may provide an offset at a start 430 * and a size of valid data in a buffer specified by the page array. The 431 * returned sg table is released by sg_free_append_table 432 * 433 * Returns: 434 * 0 on success, negative error on failure 435 * 436 * Notes: 437 * If this function returns non-0 (eg failure), the caller must call 438 * sg_free_append_table() to cleanup any leftover allocations. 439 * 440 * In the fist call, sgt_append must by initialized. 441 */ 442 int sg_alloc_append_table_from_pages(struct sg_append_table *sgt_append, 443 struct page **pages, unsigned int n_pages, unsigned int offset, 444 unsigned long size, unsigned int max_segment, 445 unsigned int left_pages, gfp_t gfp_mask) 446 { 447 unsigned int chunks, cur_page, seg_len, i, prv_len = 0; 448 unsigned int added_nents = 0; 449 struct scatterlist *s = sgt_append->prv; 450 451 /* 452 * The algorithm below requires max_segment to be aligned to PAGE_SIZE 453 * otherwise it can overshoot. 454 */ 455 max_segment = ALIGN_DOWN(max_segment, PAGE_SIZE); 456 if (WARN_ON(max_segment < PAGE_SIZE)) 457 return -EINVAL; 458 459 if (IS_ENABLED(CONFIG_ARCH_NO_SG_CHAIN) && sgt_append->prv) 460 return -EOPNOTSUPP; 461 462 if (sgt_append->prv) { 463 unsigned long paddr = 464 (page_to_pfn(sg_page(sgt_append->prv)) * PAGE_SIZE + 465 sgt_append->prv->offset + sgt_append->prv->length) / 466 PAGE_SIZE; 467 468 if (WARN_ON(offset)) 469 return -EINVAL; 470 471 /* Merge contiguous pages into the last SG */ 472 prv_len = sgt_append->prv->length; 473 while (n_pages && page_to_pfn(pages[0]) == paddr) { 474 if (sgt_append->prv->length + PAGE_SIZE > max_segment) 475 break; 476 sgt_append->prv->length += PAGE_SIZE; 477 paddr++; 478 pages++; 479 n_pages--; 480 } 481 if (!n_pages) 482 goto out; 483 } 484 485 /* compute number of contiguous chunks */ 486 chunks = 1; 487 seg_len = 0; 488 for (i = 1; i < n_pages; i++) { 489 seg_len += PAGE_SIZE; 490 if (seg_len >= max_segment || 491 page_to_pfn(pages[i]) != page_to_pfn(pages[i - 1]) + 1) { 492 chunks++; 493 seg_len = 0; 494 } 495 } 496 497 /* merging chunks and putting them into the scatterlist */ 498 cur_page = 0; 499 for (i = 0; i < chunks; i++) { 500 unsigned int j, chunk_size; 501 502 /* look for the end of the current chunk */ 503 seg_len = 0; 504 for (j = cur_page + 1; j < n_pages; j++) { 505 seg_len += PAGE_SIZE; 506 if (seg_len >= max_segment || 507 page_to_pfn(pages[j]) != 508 page_to_pfn(pages[j - 1]) + 1) 509 break; 510 } 511 512 /* Pass how many chunks might be left */ 513 s = get_next_sg(sgt_append, s, chunks - i + left_pages, 514 gfp_mask); 515 if (IS_ERR(s)) { 516 /* 517 * Adjust entry length to be as before function was 518 * called. 519 */ 520 if (sgt_append->prv) 521 sgt_append->prv->length = prv_len; 522 return PTR_ERR(s); 523 } 524 chunk_size = ((j - cur_page) << PAGE_SHIFT) - offset; 525 sg_set_page(s, pages[cur_page], 526 min_t(unsigned long, size, chunk_size), offset); 527 added_nents++; 528 size -= chunk_size; 529 offset = 0; 530 cur_page = j; 531 } 532 sgt_append->sgt.nents += added_nents; 533 sgt_append->sgt.orig_nents = sgt_append->sgt.nents; 534 sgt_append->prv = s; 535 out: 536 if (!left_pages) 537 sg_mark_end(s); 538 return 0; 539 } 540 EXPORT_SYMBOL(sg_alloc_append_table_from_pages); 541 542 /** 543 * sg_alloc_table_from_pages_segment - Allocate and initialize an sg table from 544 * an array of pages and given maximum 545 * segment. 546 * @sgt: The sg table header to use 547 * @pages: Pointer to an array of page pointers 548 * @n_pages: Number of pages in the pages array 549 * @offset: Offset from start of the first page to the start of a buffer 550 * @size: Number of valid bytes in the buffer (after offset) 551 * @max_segment: Maximum size of a scatterlist element in bytes 552 * @gfp_mask: GFP allocation mask 553 * 554 * Description: 555 * Allocate and initialize an sg table from a list of pages. Contiguous 556 * ranges of the pages are squashed into a single scatterlist node up to the 557 * maximum size specified in @max_segment. A user may provide an offset at a 558 * start and a size of valid data in a buffer specified by the page array. 559 * 560 * The returned sg table is released by sg_free_table. 561 * 562 * Returns: 563 * 0 on success, negative error on failure 564 */ 565 int sg_alloc_table_from_pages_segment(struct sg_table *sgt, struct page **pages, 566 unsigned int n_pages, unsigned int offset, 567 unsigned long size, unsigned int max_segment, 568 gfp_t gfp_mask) 569 { 570 struct sg_append_table append = {}; 571 int err; 572 573 err = sg_alloc_append_table_from_pages(&append, pages, n_pages, offset, 574 size, max_segment, 0, gfp_mask); 575 if (err) { 576 sg_free_append_table(&append); 577 return err; 578 } 579 memcpy(sgt, &append.sgt, sizeof(*sgt)); 580 WARN_ON(append.total_nents != sgt->orig_nents); 581 return 0; 582 } 583 EXPORT_SYMBOL(sg_alloc_table_from_pages_segment); 584 585 #ifdef CONFIG_SGL_ALLOC 586 587 /** 588 * sgl_alloc_order - allocate a scatterlist and its pages 589 * @length: Length in bytes of the scatterlist. Must be at least one 590 * @order: Second argument for alloc_pages() 591 * @chainable: Whether or not to allocate an extra element in the scatterlist 592 * for scatterlist chaining purposes 593 * @gfp: Memory allocation flags 594 * @nent_p: [out] Number of entries in the scatterlist that have pages 595 * 596 * Returns: A pointer to an initialized scatterlist or %NULL upon failure. 597 */ 598 struct scatterlist *sgl_alloc_order(unsigned long long length, 599 unsigned int order, bool chainable, 600 gfp_t gfp, unsigned int *nent_p) 601 { 602 struct scatterlist *sgl, *sg; 603 struct page *page; 604 unsigned int nent, nalloc; 605 u32 elem_len; 606 607 nent = round_up(length, PAGE_SIZE << order) >> (PAGE_SHIFT + order); 608 /* Check for integer overflow */ 609 if (length > (nent << (PAGE_SHIFT + order))) 610 return NULL; 611 nalloc = nent; 612 if (chainable) { 613 /* Check for integer overflow */ 614 if (nalloc + 1 < nalloc) 615 return NULL; 616 nalloc++; 617 } 618 sgl = kmalloc_array(nalloc, sizeof(struct scatterlist), 619 gfp & ~GFP_DMA); 620 if (!sgl) 621 return NULL; 622 623 sg_init_table(sgl, nalloc); 624 sg = sgl; 625 while (length) { 626 elem_len = min_t(u64, length, PAGE_SIZE << order); 627 page = alloc_pages(gfp, order); 628 if (!page) { 629 sgl_free_order(sgl, order); 630 return NULL; 631 } 632 633 sg_set_page(sg, page, elem_len, 0); 634 length -= elem_len; 635 sg = sg_next(sg); 636 } 637 WARN_ONCE(length, "length = %lld\n", length); 638 if (nent_p) 639 *nent_p = nent; 640 return sgl; 641 } 642 EXPORT_SYMBOL(sgl_alloc_order); 643 644 /** 645 * sgl_alloc - allocate a scatterlist and its pages 646 * @length: Length in bytes of the scatterlist 647 * @gfp: Memory allocation flags 648 * @nent_p: [out] Number of entries in the scatterlist 649 * 650 * Returns: A pointer to an initialized scatterlist or %NULL upon failure. 651 */ 652 struct scatterlist *sgl_alloc(unsigned long long length, gfp_t gfp, 653 unsigned int *nent_p) 654 { 655 return sgl_alloc_order(length, 0, false, gfp, nent_p); 656 } 657 EXPORT_SYMBOL(sgl_alloc); 658 659 /** 660 * sgl_free_n_order - free a scatterlist and its pages 661 * @sgl: Scatterlist with one or more elements 662 * @nents: Maximum number of elements to free 663 * @order: Second argument for __free_pages() 664 * 665 * Notes: 666 * - If several scatterlists have been chained and each chain element is 667 * freed separately then it's essential to set nents correctly to avoid that a 668 * page would get freed twice. 669 * - All pages in a chained scatterlist can be freed at once by setting @nents 670 * to a high number. 671 */ 672 void sgl_free_n_order(struct scatterlist *sgl, int nents, int order) 673 { 674 struct scatterlist *sg; 675 struct page *page; 676 int i; 677 678 for_each_sg(sgl, sg, nents, i) { 679 if (!sg) 680 break; 681 page = sg_page(sg); 682 if (page) 683 __free_pages(page, order); 684 } 685 kfree(sgl); 686 } 687 EXPORT_SYMBOL(sgl_free_n_order); 688 689 /** 690 * sgl_free_order - free a scatterlist and its pages 691 * @sgl: Scatterlist with one or more elements 692 * @order: Second argument for __free_pages() 693 */ 694 void sgl_free_order(struct scatterlist *sgl, int order) 695 { 696 sgl_free_n_order(sgl, INT_MAX, order); 697 } 698 EXPORT_SYMBOL(sgl_free_order); 699 700 /** 701 * sgl_free - free a scatterlist and its pages 702 * @sgl: Scatterlist with one or more elements 703 */ 704 void sgl_free(struct scatterlist *sgl) 705 { 706 sgl_free_order(sgl, 0); 707 } 708 EXPORT_SYMBOL(sgl_free); 709 710 #endif /* CONFIG_SGL_ALLOC */ 711 712 void __sg_page_iter_start(struct sg_page_iter *piter, 713 struct scatterlist *sglist, unsigned int nents, 714 unsigned long pgoffset) 715 { 716 piter->__pg_advance = 0; 717 piter->__nents = nents; 718 719 piter->sg = sglist; 720 piter->sg_pgoffset = pgoffset; 721 } 722 EXPORT_SYMBOL(__sg_page_iter_start); 723 724 static int sg_page_count(struct scatterlist *sg) 725 { 726 return PAGE_ALIGN(sg->offset + sg->length) >> PAGE_SHIFT; 727 } 728 729 bool __sg_page_iter_next(struct sg_page_iter *piter) 730 { 731 if (!piter->__nents || !piter->sg) 732 return false; 733 734 piter->sg_pgoffset += piter->__pg_advance; 735 piter->__pg_advance = 1; 736 737 while (piter->sg_pgoffset >= sg_page_count(piter->sg)) { 738 piter->sg_pgoffset -= sg_page_count(piter->sg); 739 piter->sg = sg_next(piter->sg); 740 if (!--piter->__nents || !piter->sg) 741 return false; 742 } 743 744 return true; 745 } 746 EXPORT_SYMBOL(__sg_page_iter_next); 747 748 static int sg_dma_page_count(struct scatterlist *sg) 749 { 750 return PAGE_ALIGN(sg->offset + sg_dma_len(sg)) >> PAGE_SHIFT; 751 } 752 753 bool __sg_page_iter_dma_next(struct sg_dma_page_iter *dma_iter) 754 { 755 struct sg_page_iter *piter = &dma_iter->base; 756 757 if (!piter->__nents || !piter->sg) 758 return false; 759 760 piter->sg_pgoffset += piter->__pg_advance; 761 piter->__pg_advance = 1; 762 763 while (piter->sg_pgoffset >= sg_dma_page_count(piter->sg)) { 764 piter->sg_pgoffset -= sg_dma_page_count(piter->sg); 765 piter->sg = sg_next(piter->sg); 766 if (!--piter->__nents || !piter->sg) 767 return false; 768 } 769 770 return true; 771 } 772 EXPORT_SYMBOL(__sg_page_iter_dma_next); 773 774 /** 775 * sg_miter_start - start mapping iteration over a sg list 776 * @miter: sg mapping iter to be started 777 * @sgl: sg list to iterate over 778 * @nents: number of sg entries 779 * 780 * Description: 781 * Starts mapping iterator @miter. 782 * 783 * Context: 784 * Don't care. 785 */ 786 void sg_miter_start(struct sg_mapping_iter *miter, struct scatterlist *sgl, 787 unsigned int nents, unsigned int flags) 788 { 789 memset(miter, 0, sizeof(struct sg_mapping_iter)); 790 791 __sg_page_iter_start(&miter->piter, sgl, nents, 0); 792 WARN_ON(!(flags & (SG_MITER_TO_SG | SG_MITER_FROM_SG))); 793 miter->__flags = flags; 794 } 795 EXPORT_SYMBOL(sg_miter_start); 796 797 static bool sg_miter_get_next_page(struct sg_mapping_iter *miter) 798 { 799 if (!miter->__remaining) { 800 struct scatterlist *sg; 801 802 if (!__sg_page_iter_next(&miter->piter)) 803 return false; 804 805 sg = miter->piter.sg; 806 807 miter->__offset = miter->piter.sg_pgoffset ? 0 : sg->offset; 808 miter->piter.sg_pgoffset += miter->__offset >> PAGE_SHIFT; 809 miter->__offset &= PAGE_SIZE - 1; 810 miter->__remaining = sg->offset + sg->length - 811 (miter->piter.sg_pgoffset << PAGE_SHIFT) - 812 miter->__offset; 813 miter->__remaining = min_t(unsigned long, miter->__remaining, 814 PAGE_SIZE - miter->__offset); 815 } 816 817 return true; 818 } 819 820 /** 821 * sg_miter_skip - reposition mapping iterator 822 * @miter: sg mapping iter to be skipped 823 * @offset: number of bytes to plus the current location 824 * 825 * Description: 826 * Sets the offset of @miter to its current location plus @offset bytes. 827 * If mapping iterator @miter has been proceeded by sg_miter_next(), this 828 * stops @miter. 829 * 830 * Context: 831 * Don't care. 832 * 833 * Returns: 834 * true if @miter contains the valid mapping. false if end of sg 835 * list is reached. 836 */ 837 bool sg_miter_skip(struct sg_mapping_iter *miter, off_t offset) 838 { 839 sg_miter_stop(miter); 840 841 while (offset) { 842 off_t consumed; 843 844 if (!sg_miter_get_next_page(miter)) 845 return false; 846 847 consumed = min_t(off_t, offset, miter->__remaining); 848 miter->__offset += consumed; 849 miter->__remaining -= consumed; 850 offset -= consumed; 851 } 852 853 return true; 854 } 855 EXPORT_SYMBOL(sg_miter_skip); 856 857 /** 858 * sg_miter_next - proceed mapping iterator to the next mapping 859 * @miter: sg mapping iter to proceed 860 * 861 * Description: 862 * Proceeds @miter to the next mapping. @miter should have been started 863 * using sg_miter_start(). On successful return, @miter->page, 864 * @miter->addr and @miter->length point to the current mapping. 865 * 866 * Context: 867 * May sleep if !SG_MITER_ATOMIC. 868 * 869 * Returns: 870 * true if @miter contains the next mapping. false if end of sg 871 * list is reached. 872 */ 873 bool sg_miter_next(struct sg_mapping_iter *miter) 874 { 875 sg_miter_stop(miter); 876 877 /* 878 * Get to the next page if necessary. 879 * __remaining, __offset is adjusted by sg_miter_stop 880 */ 881 if (!sg_miter_get_next_page(miter)) 882 return false; 883 884 miter->page = sg_page_iter_page(&miter->piter); 885 miter->consumed = miter->length = miter->__remaining; 886 887 if (miter->__flags & SG_MITER_ATOMIC) 888 miter->addr = kmap_atomic(miter->page) + miter->__offset; 889 else 890 miter->addr = kmap(miter->page) + miter->__offset; 891 892 return true; 893 } 894 EXPORT_SYMBOL(sg_miter_next); 895 896 /** 897 * sg_miter_stop - stop mapping iteration 898 * @miter: sg mapping iter to be stopped 899 * 900 * Description: 901 * Stops mapping iterator @miter. @miter should have been started 902 * using sg_miter_start(). A stopped iteration can be resumed by 903 * calling sg_miter_next() on it. This is useful when resources (kmap) 904 * need to be released during iteration. 905 * 906 * Context: 907 * Don't care otherwise. 908 */ 909 void sg_miter_stop(struct sg_mapping_iter *miter) 910 { 911 WARN_ON(miter->consumed > miter->length); 912 913 /* drop resources from the last iteration */ 914 if (miter->addr) { 915 miter->__offset += miter->consumed; 916 miter->__remaining -= miter->consumed; 917 918 if (miter->__flags & SG_MITER_TO_SG) 919 flush_dcache_page(miter->page); 920 921 if (miter->__flags & SG_MITER_ATOMIC) { 922 WARN_ON_ONCE(!pagefault_disabled()); 923 kunmap_atomic(miter->addr); 924 } else 925 kunmap(miter->page); 926 927 miter->page = NULL; 928 miter->addr = NULL; 929 miter->length = 0; 930 miter->consumed = 0; 931 } 932 } 933 EXPORT_SYMBOL(sg_miter_stop); 934 935 /** 936 * sg_copy_buffer - Copy data between a linear buffer and an SG list 937 * @sgl: The SG list 938 * @nents: Number of SG entries 939 * @buf: Where to copy from 940 * @buflen: The number of bytes to copy 941 * @skip: Number of bytes to skip before copying 942 * @to_buffer: transfer direction (true == from an sg list to a 943 * buffer, false == from a buffer to an sg list) 944 * 945 * Returns the number of copied bytes. 946 * 947 **/ 948 size_t sg_copy_buffer(struct scatterlist *sgl, unsigned int nents, void *buf, 949 size_t buflen, off_t skip, bool to_buffer) 950 { 951 unsigned int offset = 0; 952 struct sg_mapping_iter miter; 953 unsigned int sg_flags = SG_MITER_ATOMIC; 954 955 if (to_buffer) 956 sg_flags |= SG_MITER_FROM_SG; 957 else 958 sg_flags |= SG_MITER_TO_SG; 959 960 sg_miter_start(&miter, sgl, nents, sg_flags); 961 962 if (!sg_miter_skip(&miter, skip)) 963 return 0; 964 965 while ((offset < buflen) && sg_miter_next(&miter)) { 966 unsigned int len; 967 968 len = min(miter.length, buflen - offset); 969 970 if (to_buffer) 971 memcpy(buf + offset, miter.addr, len); 972 else 973 memcpy(miter.addr, buf + offset, len); 974 975 offset += len; 976 } 977 978 sg_miter_stop(&miter); 979 980 return offset; 981 } 982 EXPORT_SYMBOL(sg_copy_buffer); 983 984 /** 985 * sg_copy_from_buffer - Copy from a linear buffer to an SG list 986 * @sgl: The SG list 987 * @nents: Number of SG entries 988 * @buf: Where to copy from 989 * @buflen: The number of bytes to copy 990 * 991 * Returns the number of copied bytes. 992 * 993 **/ 994 size_t sg_copy_from_buffer(struct scatterlist *sgl, unsigned int nents, 995 const void *buf, size_t buflen) 996 { 997 return sg_copy_buffer(sgl, nents, (void *)buf, buflen, 0, false); 998 } 999 EXPORT_SYMBOL(sg_copy_from_buffer); 1000 1001 /** 1002 * sg_copy_to_buffer - Copy from an SG list to a linear buffer 1003 * @sgl: The SG list 1004 * @nents: Number of SG entries 1005 * @buf: Where to copy to 1006 * @buflen: The number of bytes to copy 1007 * 1008 * Returns the number of copied bytes. 1009 * 1010 **/ 1011 size_t sg_copy_to_buffer(struct scatterlist *sgl, unsigned int nents, 1012 void *buf, size_t buflen) 1013 { 1014 return sg_copy_buffer(sgl, nents, buf, buflen, 0, true); 1015 } 1016 EXPORT_SYMBOL(sg_copy_to_buffer); 1017 1018 /** 1019 * sg_pcopy_from_buffer - Copy from a linear buffer to an SG list 1020 * @sgl: The SG list 1021 * @nents: Number of SG entries 1022 * @buf: Where to copy from 1023 * @buflen: The number of bytes to copy 1024 * @skip: Number of bytes to skip before copying 1025 * 1026 * Returns the number of copied bytes. 1027 * 1028 **/ 1029 size_t sg_pcopy_from_buffer(struct scatterlist *sgl, unsigned int nents, 1030 const void *buf, size_t buflen, off_t skip) 1031 { 1032 return sg_copy_buffer(sgl, nents, (void *)buf, buflen, skip, false); 1033 } 1034 EXPORT_SYMBOL(sg_pcopy_from_buffer); 1035 1036 /** 1037 * sg_pcopy_to_buffer - Copy from an SG list to a linear buffer 1038 * @sgl: The SG list 1039 * @nents: Number of SG entries 1040 * @buf: Where to copy to 1041 * @buflen: The number of bytes to copy 1042 * @skip: Number of bytes to skip before copying 1043 * 1044 * Returns the number of copied bytes. 1045 * 1046 **/ 1047 size_t sg_pcopy_to_buffer(struct scatterlist *sgl, unsigned int nents, 1048 void *buf, size_t buflen, off_t skip) 1049 { 1050 return sg_copy_buffer(sgl, nents, buf, buflen, skip, true); 1051 } 1052 EXPORT_SYMBOL(sg_pcopy_to_buffer); 1053 1054 /** 1055 * sg_zero_buffer - Zero-out a part of a SG list 1056 * @sgl: The SG list 1057 * @nents: Number of SG entries 1058 * @buflen: The number of bytes to zero out 1059 * @skip: Number of bytes to skip before zeroing 1060 * 1061 * Returns the number of bytes zeroed. 1062 **/ 1063 size_t sg_zero_buffer(struct scatterlist *sgl, unsigned int nents, 1064 size_t buflen, off_t skip) 1065 { 1066 unsigned int offset = 0; 1067 struct sg_mapping_iter miter; 1068 unsigned int sg_flags = SG_MITER_ATOMIC | SG_MITER_TO_SG; 1069 1070 sg_miter_start(&miter, sgl, nents, sg_flags); 1071 1072 if (!sg_miter_skip(&miter, skip)) 1073 return false; 1074 1075 while (offset < buflen && sg_miter_next(&miter)) { 1076 unsigned int len; 1077 1078 len = min(miter.length, buflen - offset); 1079 memset(miter.addr, 0, len); 1080 1081 offset += len; 1082 } 1083 1084 sg_miter_stop(&miter); 1085 return offset; 1086 } 1087 EXPORT_SYMBOL(sg_zero_buffer); 1088