linux/lib/scatterlist.c
<<
>>
Prefs
   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 **/
  23struct 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}
  34EXPORT_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 **/
  45int sg_nents(struct scatterlist *sg)
  46{
  47        int nents;
  48        for (nents = 0; sg; sg = sg_next(sg))
  49                nents++;
  50        return nents;
  51}
  52EXPORT_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 **/
  68int 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}
  85EXPORT_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 **/
 101struct 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}
 112EXPORT_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 **/
 124void sg_init_table(struct scatterlist *sgl, unsigned int nents)
 125{
 126        memset(sgl, 0, sizeof(*sgl) * nents);
 127        sg_init_marker(sgl, nents);
 128}
 129EXPORT_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 **/
 138void 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}
 143EXPORT_SYMBOL(sg_init_one);
 144
 145/*
 146 * The default behaviour of sg_alloc_table() is to use these kmalloc/kfree
 147 * helpers.
 148 */
 149static 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
 169static 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 **/
 192void __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}
 232EXPORT_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 **/
 239void sg_free_table(struct sg_table *table)
 240{
 241        __sg_free_table(table, SG_MAX_SINGLE_ALLOC, false, sg_kfree);
 242}
 243EXPORT_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 **/
 266int __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}
 342EXPORT_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 **/
 355int 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}
 366EXPORT_SYMBOL(sg_alloc_table);
 367
 368static 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 */
 428struct 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;
 518out:
 519        if (!left_pages)
 520                sg_mark_end(s);
 521        return s;
 522}
 523EXPORT_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 */
 545int 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}
 552EXPORT_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 */
 567struct 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}
 611EXPORT_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 */
 621struct 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}
 626EXPORT_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 */
 641void 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}
 656EXPORT_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 */
 663void sgl_free_order(struct scatterlist *sgl, int order)
 664{
 665        sgl_free_n_order(sgl, INT_MAX, order);
 666}
 667EXPORT_SYMBOL(sgl_free_order);
 668
 669/**
 670 * sgl_free - free a scatterlist and its pages
 671 * @sgl: Scatterlist with one or more elements
 672 */
 673void sgl_free(struct scatterlist *sgl)
 674{
 675        sgl_free_order(sgl, 0);
 676}
 677EXPORT_SYMBOL(sgl_free);
 678
 679#endif /* CONFIG_SGL_ALLOC */
 680
 681void __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}
 691EXPORT_SYMBOL(__sg_page_iter_start);
 692
 693static int sg_page_count(struct scatterlist *sg)
 694{
 695        return PAGE_ALIGN(sg->offset + sg->length) >> PAGE_SHIFT;
 696}
 697
 698bool __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}
 715EXPORT_SYMBOL(__sg_page_iter_next);
 716
 717static int sg_dma_page_count(struct scatterlist *sg)
 718{
 719        return PAGE_ALIGN(sg->offset + sg_dma_len(sg)) >> PAGE_SHIFT;
 720}
 721
 722bool __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}
 741EXPORT_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 */
 755void 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}
 764EXPORT_SYMBOL(sg_miter_start);
 765
 766static 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 */
 807bool 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}
 825EXPORT_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 */
 844bool 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}
 865EXPORT_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 */
 881void 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}
 906EXPORT_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 **/
 921size_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}
 955EXPORT_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 **/
 967size_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}
 972EXPORT_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 **/
 984size_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}
 989EXPORT_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 **/
1002size_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}
1007EXPORT_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 **/
1020size_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}
1025EXPORT_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 **/
1036size_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}
1060EXPORT_SYMBOL(sg_zero_buffer);
1061