[PATCH] fault-injection capabilities infrastructure
[linux-2.6.git] / lib / fault-inject.c
1 #include <linux/kernel.h>
2 #include <linux/init.h>
3 #include <linux/random.h>
4 #include <linux/stat.h>
5 #include <linux/types.h>
6 #include <linux/fs.h>
7 #include <linux/module.h>
8 #include <linux/fault-inject.h>
9
10 /*
11  * setup_fault_attr() is a helper function for various __setup handlers, so it
12  * returns 0 on error, because that is what __setup handlers do.
13  */
14 int __init setup_fault_attr(struct fault_attr *attr, char *str)
15 {
16         unsigned long probability;
17         unsigned long interval;
18         int times;
19         int space;
20
21         /* "<interval>,<probability>,<space>,<times>" */
22         if (sscanf(str, "%lu,%lu,%d,%d",
23                         &interval, &probability, &space, &times) < 4) {
24                 printk(KERN_WARNING
25                         "FAULT_INJECTION: failed to parse arguments\n");
26                 return 0;
27         }
28
29         attr->probability = probability;
30         attr->interval = interval;
31         atomic_set(&attr->times, times);
32         atomic_set(&attr->space, space);
33
34         return 1;
35 }
36
37 static void fail_dump(struct fault_attr *attr)
38 {
39         if (attr->verbose > 0)
40                 printk(KERN_NOTICE "FAULT_INJECTION: forcing a failure\n");
41         if (attr->verbose > 1)
42                 dump_stack();
43 }
44
45 #define atomic_dec_not_zero(v)          atomic_add_unless((v), -1, 0)
46
47 /*
48  * This code is stolen from failmalloc-1.0
49  * http://www.nongnu.org/failmalloc/
50  */
51
52 int should_fail(struct fault_attr *attr, ssize_t size)
53 {
54         if (atomic_read(&attr->times) == 0)
55                 return 0;
56
57         if (atomic_read(&attr->space) > size) {
58                 atomic_sub(size, &attr->space);
59                 return 0;
60         }
61
62         if (attr->interval > 1) {
63                 attr->count++;
64                 if (attr->count % attr->interval)
65                         return 0;
66         }
67
68         if (attr->probability > random32() % 100)
69                 goto fail;
70
71         return 0;
72
73 fail:
74         fail_dump(attr);
75
76         if (atomic_read(&attr->times) != -1)
77                 atomic_dec_not_zero(&attr->times);
78
79         return 1;
80 }
81
82 #ifdef CONFIG_FAULT_INJECTION_DEBUG_FS
83
84 static void debugfs_ul_set(void *data, u64 val)
85 {
86         *(unsigned long *)data = val;
87 }
88
89 static u64 debugfs_ul_get(void *data)
90 {
91         return *(unsigned long *)data;
92 }
93
94 DEFINE_SIMPLE_ATTRIBUTE(fops_ul, debugfs_ul_get, debugfs_ul_set, "%llu\n");
95
96 static struct dentry *debugfs_create_ul(const char *name, mode_t mode,
97                                 struct dentry *parent, unsigned long *value)
98 {
99         return debugfs_create_file(name, mode, parent, value, &fops_ul);
100 }
101
102 static void debugfs_atomic_t_set(void *data, u64 val)
103 {
104         atomic_set((atomic_t *)data, val);
105 }
106
107 static u64 debugfs_atomic_t_get(void *data)
108 {
109         return atomic_read((atomic_t *)data);
110 }
111
112 DEFINE_SIMPLE_ATTRIBUTE(fops_atomic_t, debugfs_atomic_t_get,
113                         debugfs_atomic_t_set, "%lld\n");
114
115 static struct dentry *debugfs_create_atomic_t(const char *name, mode_t mode,
116                                 struct dentry *parent, atomic_t *value)
117 {
118         return debugfs_create_file(name, mode, parent, value, &fops_atomic_t);
119 }
120
121 void cleanup_fault_attr_dentries(struct fault_attr *attr)
122 {
123         debugfs_remove(attr->dentries.probability_file);
124         attr->dentries.probability_file = NULL;
125
126         debugfs_remove(attr->dentries.interval_file);
127         attr->dentries.interval_file = NULL;
128
129         debugfs_remove(attr->dentries.times_file);
130         attr->dentries.times_file = NULL;
131
132         debugfs_remove(attr->dentries.space_file);
133         attr->dentries.space_file = NULL;
134
135         debugfs_remove(attr->dentries.verbose_file);
136         attr->dentries.verbose_file = NULL;
137
138         if (attr->dentries.dir)
139                 WARN_ON(!simple_empty(attr->dentries.dir));
140
141         debugfs_remove(attr->dentries.dir);
142         attr->dentries.dir = NULL;
143 }
144
145 int init_fault_attr_dentries(struct fault_attr *attr, const char *name)
146 {
147         mode_t mode = S_IFREG | S_IRUSR | S_IWUSR;
148         struct dentry *dir;
149
150         memset(&attr->dentries, 0, sizeof(attr->dentries));
151
152         dir = debugfs_create_dir(name, NULL);
153         if (!dir)
154                 goto fail;
155         attr->dentries.dir = dir;
156
157         attr->dentries.probability_file =
158                 debugfs_create_ul("probability", mode, dir, &attr->probability);
159
160         attr->dentries.interval_file =
161                 debugfs_create_ul("interval", mode, dir, &attr->interval);
162
163         attr->dentries.times_file =
164                 debugfs_create_atomic_t("times", mode, dir, &attr->times);
165
166         attr->dentries.space_file =
167                 debugfs_create_atomic_t("space", mode, dir, &attr->space);
168
169         attr->dentries.verbose_file =
170                 debugfs_create_ul("verbose", mode, dir, &attr->verbose);
171
172         if (!attr->dentries.probability_file || !attr->dentries.interval_file
173             || !attr->dentries.times_file || !attr->dentries.space_file
174             || !attr->dentries.verbose_file)
175                 goto fail;
176
177         return 0;
178 fail:
179         cleanup_fault_attr_dentries(attr);
180         return -ENOMEM;
181 }
182
183 #endif /* CONFIG_FAULT_INJECTION_DEBUG_FS */