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

source code of linux/fs/erofs/compress.h