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
14 MODULE_DESCRIPTION("FS Cache Manager");
15 MODULE_AUTHOR("Red Hat, Inc.");
16 MODULE_LICENSE("GPL");
17
18 unsigned fscache_debug;
19 module_param_named(debug, fscache_debug, uint,
20 S_IWUSR | S_IRUGO);
21 MODULE_PARM_DESC(fscache_debug,
22 "FS-Cache debugging mask");
23
24 EXPORT_TRACEPOINT_SYMBOL(fscache_access_cache);
25 EXPORT_TRACEPOINT_SYMBOL(fscache_access_volume);
26 EXPORT_TRACEPOINT_SYMBOL(fscache_access);
27
28 struct workqueue_struct *fscache_wq;
29 EXPORT_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
fold_hash(unsigned long x,unsigned long y)47 static inline unsigned int fold_hash(unsigned long x, unsigned long y)
48 {
49 /* Use arch-optimized multiply if one exists */
50 return __hash_32(y ^ __hash_32(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 */
fscache_hash(unsigned int salt,const void * data,size_t len)59 unsigned 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 */
fscache_init(void)74 static int __init fscache_init(void)
75 {
76 int ret = -ENOMEM;
77
78 fscache_wq = alloc_workqueue("fscache", WQ_UNBOUND | WQ_FREEZABLE, 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("fscache_cookie_jar",
87 sizeof(struct fscache_cookie),
88 0, 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
98 error_cookie_jar:
99 fscache_proc_cleanup();
100 error_proc:
101 destroy_workqueue(fscache_wq);
102 error_wq:
103 return ret;
104 }
105
106 fs_initcall(fscache_init);
107
108 /*
109 * clean up on module removal
110 */
fscache_exit(void)111 static void __exit fscache_exit(void)
112 {
113 _enter("");
114
115 kmem_cache_destroy(fscache_cookie_jar);
116 fscache_proc_cleanup();
117 destroy_workqueue(fscache_wq);
118 pr_notice("Unloaded\n");
119 }
120
121 module_exit(fscache_exit);
122
