[PATCH] fault-injection capabilities infrastructure

This patch provides base functions implement to fault-injection
capabilities.

- The function should_fail() is taken from failmalloc-1.0
  (http://www.nongnu.org/failmalloc/)

[akpm@osdl.org: cleanups, comments, add __init]
Cc: <okuji@enbug.org>
Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Signed-off-by: Don Mullis <dwm@meer.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

lib/fault-inject.c

@@ -0,0 +1,183 @@
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/random.h>
+#include <linux/stat.h>
+#include <linux/types.h>
+#include <linux/fs.h>
+#include <linux/module.h>
+#include <linux/fault-inject.h>
+
+/*
+ * setup_fault_attr() is a helper function for various __setup handlers, so it
+ * returns 0 on error, because that is what __setup handlers do.
+ */
+int __init setup_fault_attr(struct fault_attr *attr, char *str)
+{
+	unsigned long probability;
+	unsigned long interval;
+	int times;
+	int space;
+
+	/* "<interval>,<probability>,<space>,<times>" */
+	if (sscanf(str, "%lu,%lu,%d,%d",
+			&interval, &probability, &space, &times) < 4) {
+		printk(KERN_WARNING
+			"FAULT_INJECTION: failed to parse arguments\n");
+		return 0;
+	}
+
+	attr->probability = probability;
+	attr->interval = interval;
+	atomic_set(&attr->times, times);
+	atomic_set(&attr->space, space);
+
+	return 1;
+}
+
+static void fail_dump(struct fault_attr *attr)
+{
+	if (attr->verbose > 0)
+		printk(KERN_NOTICE "FAULT_INJECTION: forcing a failure\n");
+	if (attr->verbose > 1)
+		dump_stack();
+}
+
+#define atomic_dec_not_zero(v)		atomic_add_unless((v), -1, 0)
+
+/*
+ * This code is stolen from failmalloc-1.0
+ * http://www.nongnu.org/failmalloc/
+ */
+
+int should_fail(struct fault_attr *attr, ssize_t size)
+{
+	if (atomic_read(&attr->times) == 0)
+		return 0;
+
+	if (atomic_read(&attr->space) > size) {
+		atomic_sub(size, &attr->space);
+		return 0;
+	}
+
+	if (attr->interval > 1) {
+		attr->count++;
+		if (attr->count % attr->interval)
+			return 0;
+	}
+
+	if (attr->probability > random32() % 100)
+		goto fail;
+
+	return 0;
+
+fail:
+	fail_dump(attr);
+
+	if (atomic_read(&attr->times) != -1)
+		atomic_dec_not_zero(&attr->times);
+
+	return 1;
+}
+
+#ifdef CONFIG_FAULT_INJECTION_DEBUG_FS
+
+static void debugfs_ul_set(void *data, u64 val)
+{
+	*(unsigned long *)data = val;
+}
+
+static u64 debugfs_ul_get(void *data)
+{
+	return *(unsigned long *)data;
+}
+
+DEFINE_SIMPLE_ATTRIBUTE(fops_ul, debugfs_ul_get, debugfs_ul_set, "%llu\n");
+
+static struct dentry *debugfs_create_ul(const char *name, mode_t mode,
+				struct dentry *parent, unsigned long *value)
+{
+	return debugfs_create_file(name, mode, parent, value, &fops_ul);
+}
+
+static void debugfs_atomic_t_set(void *data, u64 val)
+{
+	atomic_set((atomic_t *)data, val);
+}
+
+static u64 debugfs_atomic_t_get(void *data)
+{
+	return atomic_read((atomic_t *)data);
+}
+
+DEFINE_SIMPLE_ATTRIBUTE(fops_atomic_t, debugfs_atomic_t_get,
+			debugfs_atomic_t_set, "%lld\n");
+
+static struct dentry *debugfs_create_atomic_t(const char *name, mode_t mode,
+				struct dentry *parent, atomic_t *value)
+{
+	return debugfs_create_file(name, mode, parent, value, &fops_atomic_t);
+}
+
+void cleanup_fault_attr_dentries(struct fault_attr *attr)
+{
+	debugfs_remove(attr->dentries.probability_file);
+	attr->dentries.probability_file = NULL;
+
+	debugfs_remove(attr->dentries.interval_file);
+	attr->dentries.interval_file = NULL;
+
+	debugfs_remove(attr->dentries.times_file);
+	attr->dentries.times_file = NULL;
+
+	debugfs_remove(attr->dentries.space_file);
+	attr->dentries.space_file = NULL;
+
+	debugfs_remove(attr->dentries.verbose_file);
+	attr->dentries.verbose_file = NULL;
+
+	if (attr->dentries.dir)
+		WARN_ON(!simple_empty(attr->dentries.dir));
+
+	debugfs_remove(attr->dentries.dir);
+	attr->dentries.dir = NULL;
+}
+
+int init_fault_attr_dentries(struct fault_attr *attr, const char *name)
+{
+	mode_t mode = S_IFREG | S_IRUSR | S_IWUSR;
+	struct dentry *dir;
+
+	memset(&attr->dentries, 0, sizeof(attr->dentries));
+
+	dir = debugfs_create_dir(name, NULL);
+	if (!dir)
+		goto fail;
+	attr->dentries.dir = dir;
+
+	attr->dentries.probability_file =
+		debugfs_create_ul("probability", mode, dir, &attr->probability);
+
+	attr->dentries.interval_file =
+		debugfs_create_ul("interval", mode, dir, &attr->interval);
+
+	attr->dentries.times_file =
+		debugfs_create_atomic_t("times", mode, dir, &attr->times);
+
+	attr->dentries.space_file =
+		debugfs_create_atomic_t("space", mode, dir, &attr->space);
+
+	attr->dentries.verbose_file =
+		debugfs_create_ul("verbose", mode, dir, &attr->verbose);
+
+	if (!attr->dentries.probability_file || !attr->dentries.interval_file
+	    || !attr->dentries.times_file || !attr->dentries.space_file
+	    || !attr->dentries.verbose_file)
+		goto fail;
+
+	return 0;
+fail:
+	cleanup_fault_attr_dentries(attr);
+	return -ENOMEM;
+}
+
+#endif /* CONFIG_FAULT_INJECTION_DEBUG_FS */