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
15EXPORT_TRACEPOINT_SYMBOL(fscache_access_cache);
16EXPORT_TRACEPOINT_SYMBOL(fscache_access_volume);
17EXPORT_TRACEPOINT_SYMBOL(fscache_access);
18
19struct workqueue_struct *fscache_wq;
20EXPORT_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
38static inline unsigned int fold_hash(unsigned long x, unsigned long y)
39{
40 /* Use arch-optimized multiply if one exists */
41 return __hash_32(val: y ^ __hash_32(val: 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 */
50unsigned 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 */
65int __init fscache_init(void)
66{
67 int ret = -ENOMEM;
68
69 fscache_wq = alloc_workqueue(fmt: "fscache", flags: WQ_UNBOUND | WQ_FREEZABLE, max_active: 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(name: "fscache_cookie_jar",
78 size: sizeof(struct fscache_cookie),
79 align: 0, flags: 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
89error_cookie_jar:
90 fscache_proc_cleanup();
91error_proc:
92 destroy_workqueue(wq: fscache_wq);
93error_wq:
94 return ret;
95}
96
97/*
98 * clean up on module removal
99 */
100void __exit fscache_exit(void)
101{
102 _enter("");
103
104 kmem_cache_destroy(s: fscache_cookie_jar);
105 fscache_proc_cleanup();
106 destroy_workqueue(wq: fscache_wq);
107 pr_notice("FS-Cache unloaded\n");
108}
109

source code of linux/fs/netfs/fscache_main.c