1 /* General filesystem local caching manager
2 *
3 * Copyright (C) 2004-2007 Red Hat, Inc. All Rights Reserved.
4 * Written by David Howells (dhowells@redhat.com)
5 *
6 * This program is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU General Public License
8 * as published by the Free Software Foundation; either version
9 * 2 of the License, or (at your option) any later version.
10 */
11
12 #define FSCACHE_DEBUG_LEVEL CACHE
13 #include <linux/module.h>
14 #include <linux/init.h>
15 #include <linux/sched.h>
16 #include <linux/completion.h>
17 #include <linux/slab.h>
18 #include <linux/seq_file.h>
19 #define CREATE_TRACE_POINTS
20 #include "internal.h"
21
22 MODULE_DESCRIPTION("FS Cache Manager");
23 MODULE_AUTHOR("Red Hat, Inc.");
24 MODULE_LICENSE("GPL");
25
26 unsigned fscache_defer_lookup = 1;
27 module_param_named(defer_lookup, fscache_defer_lookup, uint,
28 S_IWUSR | S_IRUGO);
29 MODULE_PARM_DESC(fscache_defer_lookup,
30 "Defer cookie lookup to background thread");
31
32 unsigned fscache_defer_create = 1;
33 module_param_named(defer_create, fscache_defer_create, uint,
34 S_IWUSR | S_IRUGO);
35 MODULE_PARM_DESC(fscache_defer_create,
36 "Defer cookie creation to background thread");
37
38 unsigned fscache_debug;
39 module_param_named(debug, fscache_debug, uint,
40 S_IWUSR | S_IRUGO);
41 MODULE_PARM_DESC(fscache_debug,
42 "FS-Cache debugging mask");
43
44 struct kobject *fscache_root;
45 struct workqueue_struct *fscache_object_wq;
46 struct workqueue_struct *fscache_op_wq;
47
48 DEFINE_PER_CPU(wait_queue_head_t, fscache_object_cong_wait);
49
50 /* these values serve as lower bounds, will be adjusted in fscache_init() */
51 static unsigned fscache_object_max_active = 4;
52 static unsigned fscache_op_max_active = 2;
53
54 #ifdef CONFIG_SYSCTL
55 static struct ctl_table_header *fscache_sysctl_header;
56
fscache_max_active_sysctl(struct ctl_table * table,int write,void __user * buffer,size_t * lenp,loff_t * ppos)57 static int fscache_max_active_sysctl(struct ctl_table *table, int write,
58 void __user *buffer,
59 size_t *lenp, loff_t *ppos)
60 {
61 struct workqueue_struct **wqp = table->extra1;
62 unsigned int *datap = table->data;
63 int ret;
64
65 ret = proc_dointvec(table, write, buffer, lenp, ppos);
66 if (ret == 0)
67 workqueue_set_max_active(*wqp, *datap);
68 return ret;
69 }
70
71 static struct ctl_table fscache_sysctls[] = {
72 {
73 .procname = "object_max_active",
74 .data = &fscache_object_max_active,
75 .maxlen = sizeof(unsigned),
76 .mode = 0644,
77 .proc_handler = fscache_max_active_sysctl,
78 .extra1 = &fscache_object_wq,
79 },
80 {
81 .procname = "operation_max_active",
82 .data = &fscache_op_max_active,
83 .maxlen = sizeof(unsigned),
84 .mode = 0644,
85 .proc_handler = fscache_max_active_sysctl,
86 .extra1 = &fscache_op_wq,
87 },
88 {}
89 };
90
91 static struct ctl_table fscache_sysctls_root[] = {
92 {
93 .procname = "fscache",
94 .mode = 0555,
95 .child = fscache_sysctls,
96 },
97 {}
98 };
99 #endif
100
101 /*
102 * Mixing scores (in bits) for (7,20):
103 * Input delta: 1-bit 2-bit
104 * 1 round: 330.3 9201.6
105 * 2 rounds: 1246.4 25475.4
106 * 3 rounds: 1907.1 31295.1
107 * 4 rounds: 2042.3 31718.6
108 * Perfect: 2048 31744
109 * (32*64) (32*31/2 * 64)
110 */
111 #define HASH_MIX(x, y, a) \
112 ( x ^= (a), \
113 y ^= x, x = rol32(x, 7),\
114 x += y, y = rol32(y,20),\
115 y *= 9 )
116
fold_hash(unsigned long x,unsigned long y)117 static inline unsigned int fold_hash(unsigned long x, unsigned long y)
118 {
119 /* Use arch-optimized multiply if one exists */
120 return __hash_32(y ^ __hash_32(x));
121 }
122
123 /*
124 * Generate a hash. This is derived from full_name_hash(), but we want to be
125 * sure it is arch independent and that it doesn't change as bits of the
126 * computed hash value might appear on disk. The caller also guarantees that
127 * the hashed data will be a series of aligned 32-bit words.
128 */
fscache_hash(unsigned int salt,unsigned int * data,unsigned int n)129 unsigned int fscache_hash(unsigned int salt, unsigned int *data, unsigned int n)
130 {
131 unsigned int a, x = 0, y = salt;
132
133 for (; n; n--) {
134 a = *data++;
135 HASH_MIX(x, y, a);
136 }
137 return fold_hash(x, y);
138 }
139
140 /*
141 * initialise the fs caching module
142 */
fscache_init(void)143 static int __init fscache_init(void)
144 {
145 unsigned int nr_cpus = num_possible_cpus();
146 unsigned int cpu;
147 int ret;
148
149 fscache_object_max_active =
150 clamp_val(nr_cpus,
151 fscache_object_max_active, WQ_UNBOUND_MAX_ACTIVE);
152
153 ret = -ENOMEM;
154 fscache_object_wq = alloc_workqueue("fscache_object", WQ_UNBOUND,
155 fscache_object_max_active);
156 if (!fscache_object_wq)
157 goto error_object_wq;
158
159 fscache_op_max_active =
160 clamp_val(fscache_object_max_active / 2,
161 fscache_op_max_active, WQ_UNBOUND_MAX_ACTIVE);
162
163 ret = -ENOMEM;
164 fscache_op_wq = alloc_workqueue("fscache_operation", WQ_UNBOUND,
165 fscache_op_max_active);
166 if (!fscache_op_wq)
167 goto error_op_wq;
168
169 for_each_possible_cpu(cpu)
170 init_waitqueue_head(&per_cpu(fscache_object_cong_wait, cpu));
171
172 ret = fscache_proc_init();
173 if (ret < 0)
174 goto error_proc;
175
176 #ifdef CONFIG_SYSCTL
177 ret = -ENOMEM;
178 fscache_sysctl_header = register_sysctl_table(fscache_sysctls_root);
179 if (!fscache_sysctl_header)
180 goto error_sysctl;
181 #endif
182
183 fscache_cookie_jar = kmem_cache_create("fscache_cookie_jar",
184 sizeof(struct fscache_cookie),
185 0, 0, NULL);
186 if (!fscache_cookie_jar) {
187 pr_notice("Failed to allocate a cookie jar\n");
188 ret = -ENOMEM;
189 goto error_cookie_jar;
190 }
191
192 fscache_root = kobject_create_and_add("fscache", kernel_kobj);
193 if (!fscache_root)
194 goto error_kobj;
195
196 pr_notice("Loaded\n");
197 return 0;
198
199 error_kobj:
200 kmem_cache_destroy(fscache_cookie_jar);
201 error_cookie_jar:
202 #ifdef CONFIG_SYSCTL
203 unregister_sysctl_table(fscache_sysctl_header);
204 error_sysctl:
205 #endif
206 fscache_proc_cleanup();
207 error_proc:
208 destroy_workqueue(fscache_op_wq);
209 error_op_wq:
210 destroy_workqueue(fscache_object_wq);
211 error_object_wq:
212 return ret;
213 }
214
215 fs_initcall(fscache_init);
216
217 /*
218 * clean up on module removal
219 */
fscache_exit(void)220 static void __exit fscache_exit(void)
221 {
222 _enter("");
223
224 kobject_put(fscache_root);
225 kmem_cache_destroy(fscache_cookie_jar);
226 #ifdef CONFIG_SYSCTL
227 unregister_sysctl_table(fscache_sysctl_header);
228 #endif
229 fscache_proc_cleanup();
230 destroy_workqueue(fscache_op_wq);
231 destroy_workqueue(fscache_object_wq);
232 pr_notice("Unloaded\n");
233 }
234
235 module_exit(fscache_exit);
236