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
11 enum {
12 Z_EROFS_COMPRESSION_SHIFTED = Z_EROFS_COMPRESSION_MAX,
13 Z_EROFS_COMPRESSION_RUNTIME_MAX
14 };
15
16 struct 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 */
z_erofs_is_shortlived_page(struct page * page)57 static 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
z_erofs_put_shortlivedpage(struct list_head * pagepool,struct page * page)66 static 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
83 int z_erofs_decompress(struct z_erofs_decompress_req *rq,
84 struct list_head *pagepool);
85
86 #endif
87
