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  * Created by Gao Xiang <gaoxiang25@huawei.com>
   6  */
   7 #ifndef __EROFS_FS_COMPRESS_H
   8 #define __EROFS_FS_COMPRESS_H
   9
  10 #include "internal.h"
  11
  12 enum {
  13         Z_EROFS_COMPRESSION_SHIFTED = Z_EROFS_COMPRESSION_MAX,
  14         Z_EROFS_COMPRESSION_RUNTIME_MAX
  15 };
  16
  17 struct z_erofs_decompress_req {
  18         struct super_block *sb;
  19         struct page **in, **out;
  20
  21         unsigned short pageofs_out;
  22         unsigned int inputsize, outputsize;
  23
  24         /* indicate the algorithm will be used for decompression */
  25         unsigned int alg;
  26         bool inplace_io, partial_decoding;
  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  */
  58 static 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
  67 static inline bool z_erofs_put_shortlivedpage(struct list_head *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                 set_page_private(page, 0);
  79                 list_add(&page->lru, pagepool);
  80         }
  81         return true;
  82 }
  83
  84 int z_erofs_decompress(struct z_erofs_decompress_req *rq,
  85                        struct list_head *pagepool);
  86
  87 #endif
  88