LXR linux/fs/erofs/compress.h

   1/* SPDX-License-Identifier: GPL-2.0-only */
   2/*
   3 * Copyright (C) 2019 HUAWEI, Inc.
   4 *             https://www.huawei.com/
   5 */
   6#ifndef __EROFS_FS_COMPRESS_H
   7#define __EROFS_FS_COMPRESS_H
   8
   9#include "internal.h"
  10
  11enum {
  12        Z_EROFS_COMPRESSION_SHIFTED = Z_EROFS_COMPRESSION_MAX,
  13        Z_EROFS_COMPRESSION_RUNTIME_MAX
  14};
  15
  16struct z_erofs_decompress_req {
  17        struct super_block *sb;
  18        struct page **in, **out;
  19
  20        unsigned short pageofs_out;
  21        unsigned int inputsize, outputsize;
  22
  23        /* indicate the algorithm will be used for decompression */
  24        unsigned int alg;
  25        bool inplace_io, partial_decoding;
  26};
  27
  28/* some special page->private (unsigned long, see below) */
  29#define Z_EROFS_SHORTLIVED_PAGE         (-1UL << 2)
  30#define Z_EROFS_PREALLOCATED_PAGE       (-2UL << 2)
  31
  32/*
  33 * For all pages in a pcluster, page->private should be one of
  34 * Type                         Last 2bits      page->private
  35 * short-lived page             00              Z_EROFS_SHORTLIVED_PAGE
  36 * preallocated page (tryalloc) 00              Z_EROFS_PREALLOCATED_PAGE
  37 * cached/managed page          00              pointer to z_erofs_pcluster
  38 * online page (file-backed,    01/10/11        sub-index << 2 | count
  39 *              some pages can be used for inplace I/O)
  40 *
  41 * page->mapping should be one of
  42 * Type                 page->mapping
  43 * short-lived page     NULL
  44 * preallocated page    NULL
  45 * cached/managed page  non-NULL or NULL (invalidated/truncated page)
  46 * online page          non-NULL
  47 *
  48 * For all managed pages, PG_private should be set with 1 extra refcount,
  49 * which is used for page reclaim / migration.
  50 */
  51
  52/*
  53 * short-lived pages are pages directly from buddy system with specific
  54 * page->private (no need to set PagePrivate since these are non-LRU /
  55 * non-movable pages and bypass reclaim / migration code).
  56 */
  57static inline bool z_erofs_is_shortlived_page(struct page *page)
  58{
  59        if (page->private != Z_EROFS_SHORTLIVED_PAGE)
  60                return false;
  61
  62        DBG_BUGON(page->mapping);
  63        return true;
  64}
  65
  66static inline bool z_erofs_put_shortlivedpage(struct list_head *pagepool,
  67                                              struct page *page)
  68{
  69        if (!z_erofs_is_shortlived_page(page))
  70                return false;
  71
  72        /* short-lived pages should not be used by others at the same time */
  73        if (page_ref_count(page) > 1) {
  74                put_page(page);
  75        } else {
  76                /* follow the pcluster rule above. */
  77                set_page_private(page, 0);
  78                list_add(&page->lru, pagepool);
  79        }
  80        return true;
  81}
  82
  83int z_erofs_decompress(struct z_erofs_decompress_req *rq,
  84                       struct list_head *pagepool);
  85
  86#endif
  87