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 #include "internal.h"
12 #define CREATE_TRACE_POINTS
13 #include <trace/events/fscache.h>
14
15 EXPORT_TRACEPOINT_SYMBOL(fscache_access_cache);
16 EXPORT_TRACEPOINT_SYMBOL(fscache_access_volume);
17 EXPORT_TRACEPOINT_SYMBOL(fscache_access);
18
19 struct workqueue_struct *fscache_wq;
20 EXPORT_SYMBOL(fscache_wq);
21
22 /*
23 * Mixing scores (in bits) for (7,20):
24 * Input delta: 1-bit 2-bit
25 * 1 round: 330.3 9201.6
26 * 2 rounds: 1246.4 25475.4
27 * 3 rounds: 1907.1 31295.1
28 * 4 rounds: 2042.3 31718.6
29 * Perfect: 2048 31744
30 * (32*64) (32*31/2 * 64)
31 */
32 #define HASH_MIX(x, y, a) \
33 ( x ^= (a), \
34 y ^= x, x = rol32(x, 7),\
35 x += y, y = rol32(y,20),\
36 y *= 9 )
37
38 static inline unsigned int fold_hash(unsigned long x, unsigned long y)
39 {
40 /* Use arch-optimized multiply if one exists */
41 return __hash_32(y ^ __hash_32(x));
42 }
43
44 /*
45 * Generate a hash. This is derived from full_name_hash(), but we want to be
46 * sure it is arch independent and that it doesn't change as bits of the
47 * computed hash value might appear on disk. The caller must guarantee that
48 * the source data is a multiple of four bytes in size.
49 */
50 unsigned int fscache_hash(unsigned int salt, const void *data, size_t len)
51 {
52 const __le32 *p = data;
53 unsigned int a, x = 0, y = salt, n = len / sizeof(__le32);
54
55 for (; n; n--) {
56 a = le32_to_cpu(*p++);
57 HASH_MIX(x, y, a);
58 }
59 return fold_hash(x, y);
60 }
61
62 /*
63 * initialise the fs caching module
64 */
65 int __init fscache_init(void)
66 {
67 int ret = -ENOMEM;
68
69 fscache_wq = alloc_workqueue("fscache", WQ_UNBOUND | WQ_FREEZABLE, 0);
70 if (!fscache_wq)
71 goto error_wq;
72
73 ret = fscache_proc_init();
74 if (ret < 0)
75 goto error_proc;
76
77 fscache_cookie_jar = kmem_cache_create("fscache_cookie_jar",
78 sizeof(struct fscache_cookie),
79 0, 0, NULL);
80 if (!fscache_cookie_jar) {
81 pr_notice("Failed to allocate a cookie jar\n");
82 ret = -ENOMEM;
83 goto error_cookie_jar;
84 }
85
86 pr_notice("FS-Cache loaded\n");
87 return 0;
88
89 error_cookie_jar:
90 fscache_proc_cleanup();
91 error_proc:
92 destroy_workqueue(fscache_wq);
93 error_wq:
94 return ret;
95 }
96
97 /*
98 * clean up on module removal
99 */
100 void __exit fscache_exit(void)
101 {
102 _enter("");
103
104 kmem_cache_destroy(fscache_cookie_jar);
105 fscache_proc_cleanup();
106 destroy_workqueue(fscache_wq);
107 pr_notice("FS-Cache unloaded\n");
108 }
109
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