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
  11struct z_erofs_decompress_req {
  12        struct super_block *sb;
  13        struct page **in, **out;
  14
  15        unsigned short pageofs_in, pageofs_out;
  16        unsigned int inputsize, outputsize;
  17
  18        /* indicate the algorithm will be used for decompression */
  19        unsigned int alg;
  20        bool inplace_io, partial_decoding;
  21};
  22
  23struct z_erofs_decompressor {
  24        int (*decompress)(struct z_erofs_decompress_req *rq,
  25                          struct page **pagepool);
  26        char *name;
  27};
  28
  29/* some special page->private (unsigned long, see below) */
  30#define Z_EROFS_SHORTLIVED_PAGE         (-1UL << 2)
  31#define Z_EROFS_PREALLOCATED_PAGE       (-2UL << 2)
  32
  33/*
  34 * For all pages in a pcluster, page->private should be one of
  35 * Type                         Last 2bits      page->private
  36 * short-lived page             00              Z_EROFS_SHORTLIVED_PAGE
  37 * preallocated page (tryalloc) 00              Z_EROFS_PREALLOCATED_PAGE
  38 * cached/managed page          00              pointer to z_erofs_pcluster
  39 * online page (file-backed,    01/10/11        sub-index << 2 | count
  40 *              some pages can be used for inplace I/O)
  41 *
  42 * page->mapping should be one of
  43 * Type                 page->mapping
  44 * short-lived page     NULL
  45 * preallocated page    NULL
  46 * cached/managed page  non-NULL or NULL (invalidated/truncated page)
  47 * online page          non-NULL
  48 *
  49 * For all managed pages, PG_private should be set with 1 extra refcount,
  50 * which is used for page reclaim / migration.
  51 */
  52
  53/*
  54 * short-lived pages are pages directly from buddy system with specific
  55 * page->private (no need to set PagePrivate since these are non-LRU /
  56 * non-movable pages and bypass reclaim / migration code).
  57 */
  58static inline bool z_erofs_is_shortlived_page(struct page *page)
  59{
  60        if (page->private != Z_EROFS_SHORTLIVED_PAGE)
  61                return false;
  62
  63        DBG_BUGON(page->mapping);
  64        return true;
  65}
  66
  67static inline bool z_erofs_put_shortlivedpage(struct page **pagepool,
  68                                              struct page *page)
  69{
  70        if (!z_erofs_is_shortlived_page(page))
  71                return false;
  72
  73        /* short-lived pages should not be used by others at the same time */
  74        if (page_ref_count(page) > 1) {
  75                put_page(page);
  76        } else {
  77                /* follow the pcluster rule above. */
  78                erofs_pagepool_add(pagepool, page);
  79        }
  80        return true;
  81}
  82
  83#define MNGD_MAPPING(sbi)       ((sbi)->managed_cache->i_mapping)
  84static inline bool erofs_page_is_managed(const struct erofs_sb_info *sbi,
  85                                         struct page *page)
  86{
  87        return page->mapping == MNGD_MAPPING(sbi);
  88}
  89
  90int z_erofs_fixup_insize(struct z_erofs_decompress_req *rq, const char *padbuf,
  91                         unsigned int padbufsize);
  92int z_erofs_decompress(struct z_erofs_decompress_req *rq,
  93                       struct page **pagepool);
  94
  95/* prototypes for specific algorithms */
  96int z_erofs_lzma_decompress(struct z_erofs_decompress_req *rq,
  97                            struct page **pagepool);
  98#endif
  99