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 */