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(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 */
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("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
89error_cookie_jar:
90	fscache_proc_cleanup();
91error_proc:
92	destroy_workqueue(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(fscache_cookie_jar);
105	fscache_proc_cleanup();
106	destroy_workqueue(fscache_wq);
107	pr_notice("FS-Cache unloaded\n");
108}
109