xref: /kernel/linux/linux-6.6/fs/fscache/main.c (revision 62306a36) 
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(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 */
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("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
98error_cookie_jar:
99	fscache_proc_cleanup();
100error_proc:
101	destroy_workqueue(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(fscache_cookie_jar);
116	fscache_proc_cleanup();
117	destroy_workqueue(fscache_wq);
118	pr_notice("Unloaded\n");
119}
120
121module_exit(fscache_exit);
122