1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /* General filesystem local caching manager
3 *
4 * Copyright (C) 2004-2007 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 <linux/sched.h>
12 #include <linux/completion.h>
13 #include <linux/slab.h>
14 #include <linux/seq_file.h>
15 #define CREATE_TRACE_POINTS
16 #include "internal.h"
17
18 MODULE_DESCRIPTION("FS Cache Manager");
19 MODULE_AUTHOR("Red Hat, Inc.");
20 MODULE_LICENSE("GPL");
21
22 unsigned fscache_defer_lookup = 1;
23 module_param_named(defer_lookup, fscache_defer_lookup, uint,
24 S_IWUSR | S_IRUGO);
25 MODULE_PARM_DESC(fscache_defer_lookup,
26 "Defer cookie lookup to background thread");
27
28 unsigned fscache_defer_create = 1;
29 module_param_named(defer_create, fscache_defer_create, uint,
30 S_IWUSR | S_IRUGO);
31 MODULE_PARM_DESC(fscache_defer_create,
32 "Defer cookie creation to background thread");
33
34 unsigned fscache_debug;
35 module_param_named(debug, fscache_debug, uint,
36 S_IWUSR | S_IRUGO);
37 MODULE_PARM_DESC(fscache_debug,
38 "FS-Cache debugging mask");
39
40 struct kobject *fscache_root;
41 struct workqueue_struct *fscache_object_wq;
42 struct workqueue_struct *fscache_op_wq;
43
44 DEFINE_PER_CPU(wait_queue_head_t, fscache_object_cong_wait);
45
46 /* these values serve as lower bounds, will be adjusted in fscache_init() */
47 static unsigned fscache_object_max_active = 4;
48 static unsigned fscache_op_max_active = 2;
49
50 #ifdef CONFIG_SYSCTL
51 static struct ctl_table_header *fscache_sysctl_header;
52
fscache_max_active_sysctl(struct ctl_table * table,int write,void * buffer,size_t * lenp,loff_t * ppos)53 static int fscache_max_active_sysctl(struct ctl_table *table, int write,
54 void *buffer, size_t *lenp, loff_t *ppos)
55 {
56 struct workqueue_struct **wqp = table->extra1;
57 unsigned int *datap = table->data;
58 int ret;
59
60 ret = proc_dointvec(table, write, buffer, lenp, ppos);
61 if (ret == 0)
62 workqueue_set_max_active(*wqp, *datap);
63 return ret;
64 }
65
66 static struct ctl_table fscache_sysctls[] = {
67 {
68 .procname = "object_max_active",
69 .data = &fscache_object_max_active,
70 .maxlen = sizeof(unsigned),
71 .mode = 0644,
72 .proc_handler = fscache_max_active_sysctl,
73 .extra1 = &fscache_object_wq,
74 },
75 {
76 .procname = "operation_max_active",
77 .data = &fscache_op_max_active,
78 .maxlen = sizeof(unsigned),
79 .mode = 0644,
80 .proc_handler = fscache_max_active_sysctl,
81 .extra1 = &fscache_op_wq,
82 },
83 {}
84 };
85
86 static struct ctl_table fscache_sysctls_root[] = {
87 {
88 .procname = "fscache",
89 .mode = 0555,
90 .child = fscache_sysctls,
91 },
92 {}
93 };
94 #endif
95
96 /*
97 * Mixing scores (in bits) for (7,20):
98 * Input delta: 1-bit 2-bit
99 * 1 round: 330.3 9201.6
100 * 2 rounds: 1246.4 25475.4
101 * 3 rounds: 1907.1 31295.1
102 * 4 rounds: 2042.3 31718.6
103 * Perfect: 2048 31744
104 * (32*64) (32*31/2 * 64)
105 */
106 #define HASH_MIX(x, y, a) \
107 ( x ^= (a), \
108 y ^= x, x = rol32(x, 7),\
109 x += y, y = rol32(y,20),\
110 y *= 9 )
111
fold_hash(unsigned long x,unsigned long y)112 static inline unsigned int fold_hash(unsigned long x, unsigned long y)
113 {
114 /* Use arch-optimized multiply if one exists */
115 return __hash_32(y ^ __hash_32(x));
116 }
117
118 /*
119 * Generate a hash. This is derived from full_name_hash(), but we want to be
120 * sure it is arch independent and that it doesn't change as bits of the
121 * computed hash value might appear on disk. The caller also guarantees that
122 * the hashed data will be a series of aligned 32-bit words.
123 */
fscache_hash(unsigned int salt,unsigned int * data,unsigned int n)124 unsigned int fscache_hash(unsigned int salt, unsigned int *data, unsigned int n)
125 {
126 unsigned int a, x = 0, y = salt;
127
128 for (; n; n--) {
129 a = *data++;
130 HASH_MIX(x, y, a);
131 }
132 return fold_hash(x, y);
133 }
134
135 /*
136 * initialise the fs caching module
137 */
fscache_init(void)138 static int __init fscache_init(void)
139 {
140 unsigned int nr_cpus = num_possible_cpus();
141 unsigned int cpu;
142 int ret;
143
144 fscache_object_max_active =
145 clamp_val(nr_cpus,
146 fscache_object_max_active, WQ_UNBOUND_MAX_ACTIVE);
147
148 ret = -ENOMEM;
149 fscache_object_wq = alloc_workqueue("fscache_object", WQ_UNBOUND,
150 fscache_object_max_active);
151 if (!fscache_object_wq)
152 goto error_object_wq;
153
154 fscache_op_max_active =
155 clamp_val(fscache_object_max_active / 2,
156 fscache_op_max_active, WQ_UNBOUND_MAX_ACTIVE);
157
158 ret = -ENOMEM;
159 fscache_op_wq = alloc_workqueue("fscache_operation", WQ_UNBOUND,
160 fscache_op_max_active);
161 if (!fscache_op_wq)
162 goto error_op_wq;
163
164 for_each_possible_cpu(cpu)
165 init_waitqueue_head(&per_cpu(fscache_object_cong_wait, cpu));
166
167 ret = fscache_proc_init();
168 if (ret < 0)
169 goto error_proc;
170
171 #ifdef CONFIG_SYSCTL
172 ret = -ENOMEM;
173 fscache_sysctl_header = register_sysctl_table(fscache_sysctls_root);
174 if (!fscache_sysctl_header)
175 goto error_sysctl;
176 #endif
177
178 fscache_cookie_jar = kmem_cache_create("fscache_cookie_jar",
179 sizeof(struct fscache_cookie),
180 0, 0, NULL);
181 if (!fscache_cookie_jar) {
182 pr_notice("Failed to allocate a cookie jar\n");
183 ret = -ENOMEM;
184 goto error_cookie_jar;
185 }
186
187 fscache_root = kobject_create_and_add("fscache", kernel_kobj);
188 if (!fscache_root)
189 goto error_kobj;
190
191 pr_notice("Loaded\n");
192 return 0;
193
194 error_kobj:
195 kmem_cache_destroy(fscache_cookie_jar);
196 error_cookie_jar:
197 #ifdef CONFIG_SYSCTL
198 unregister_sysctl_table(fscache_sysctl_header);
199 error_sysctl:
200 #endif
201 fscache_proc_cleanup();
202 error_proc:
203 destroy_workqueue(fscache_op_wq);
204 error_op_wq:
205 destroy_workqueue(fscache_object_wq);
206 error_object_wq:
207 return ret;
208 }
209
210 fs_initcall(fscache_init);
211
212 /*
213 * clean up on module removal
214 */
fscache_exit(void)215 static void __exit fscache_exit(void)
216 {
217 _enter("");
218
219 kobject_put(fscache_root);
220 kmem_cache_destroy(fscache_cookie_jar);
221 #ifdef CONFIG_SYSCTL
222 unregister_sysctl_table(fscache_sysctl_header);
223 #endif
224 fscache_proc_cleanup();
225 destroy_workqueue(fscache_op_wq);
226 destroy_workqueue(fscache_object_wq);
227 pr_notice("Unloaded\n");
228 }
229
230 module_exit(fscache_exit);
231