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