1// SPDX-License-Identifier: GPL-2.0-or-later
2/* General filesystem local caching manager
3 *
4 * Copyright (C) 2021 Red Hat, Inc. All Rights Reserved.
5 * Written by David Howells (dhowells@redhat.com)
6 */
7
8#define FSCACHE_DEBUG_LEVEL CACHE
9#include <linux/module.h>
10#include <linux/init.h>
11#define CREATE_TRACE_POINTS
12#include "internal.h"
13
14MODULE_DESCRIPTION("FS Cache Manager");
15MODULE_AUTHOR("Red Hat, Inc.");
16MODULE_LICENSE("GPL");
17
18unsigned fscache_debug;
19module_param_named(debug, fscache_debug, uint,
20 S_IWUSR | S_IRUGO);
21MODULE_PARM_DESC(fscache_debug,
22 "FS-Cache debugging mask");
23
24EXPORT_TRACEPOINT_SYMBOL(fscache_access_cache);
25EXPORT_TRACEPOINT_SYMBOL(fscache_access_volume);
26EXPORT_TRACEPOINT_SYMBOL(fscache_access);
27
28struct workqueue_struct *fscache_wq;
29EXPORT_SYMBOL(fscache_wq);
30
31/*
32 * Mixing scores (in bits) for (7,20):
33 * Input delta: 1-bit 2-bit
34 * 1 round: 330.3 9201.6
35 * 2 rounds: 1246.4 25475.4
36 * 3 rounds: 1907.1 31295.1
37 * 4 rounds: 2042.3 31718.6
38 * Perfect: 2048 31744
39 * (32*64) (32*31/2 * 64)
40 */
41#define HASH_MIX(x, y, a) \
42 ( x ^= (a), \
43 y ^= x, x = rol32(x, 7),\
44 x += y, y = rol32(y,20),\
45 y *= 9 )
46
47static inline unsigned int fold_hash(unsigned long x, unsigned long y)
48{
49 /* Use arch-optimized multiply if one exists */
50 return __hash_32(val: y ^ __hash_32(val: x));
51}
52
53/*
54 * Generate a hash. This is derived from full_name_hash(), but we want to be
55 * sure it is arch independent and that it doesn't change as bits of the
56 * computed hash value might appear on disk. The caller must guarantee that
57 * the source data is a multiple of four bytes in size.
58 */
59unsigned int fscache_hash(unsigned int salt, const void *data, size_t len)
60{
61 const __le32 *p = data;
62 unsigned int a, x = 0, y = salt, n = len / sizeof(__le32);
63
64 for (; n; n--) {
65 a = le32_to_cpu(*p++);
66 HASH_MIX(x, y, a);
67 }
68 return fold_hash(x, y);
69}
70
71/*
72 * initialise the fs caching module
73 */
74static int __init fscache_init(void)
75{
76 int ret = -ENOMEM;
77
78 fscache_wq = alloc_workqueue(fmt: "fscache", flags: WQ_UNBOUND | WQ_FREEZABLE, max_active: 0);
79 if (!fscache_wq)
80 goto error_wq;
81
82 ret = fscache_proc_init();
83 if (ret < 0)
84 goto error_proc;
85
86 fscache_cookie_jar = kmem_cache_create(name: "fscache_cookie_jar",
87 size: sizeof(struct fscache_cookie),
88 align: 0, flags: 0, NULL);
89 if (!fscache_cookie_jar) {
90 pr_notice("Failed to allocate a cookie jar\n");
91 ret = -ENOMEM;
92 goto error_cookie_jar;
93 }
94
95 pr_notice("Loaded\n");
96 return 0;
97
98error_cookie_jar:
99 fscache_proc_cleanup();
100error_proc:
101 destroy_workqueue(wq: fscache_wq);
102error_wq:
103 return ret;
104}
105
106fs_initcall(fscache_init);
107
108/*
109 * clean up on module removal
110 */
111static void __exit fscache_exit(void)
112{
113 _enter("");
114
115 kmem_cache_destroy(s: fscache_cookie_jar);
116 fscache_proc_cleanup();
117 destroy_workqueue(wq: fscache_wq);
118 pr_notice("Unloaded\n");
119}
120
121module_exit(fscache_exit);
122

source code of linux/fs/fscache/main.c