diff --git a/lib/fault-inject.c b/lib/fault-inject.c
new file mode 100644
index 0000000..cf7b129
--- /dev/null
+++ b/lib/fault-inject.c
@@ -0,0 +1,258 @@
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/random.h>
+#include <linux/sched.h>
+#include <linux/stat.h>
+#include <linux/types.h>
+#include <linux/fs.h>
+#include <linux/export.h>
+#include <linux/interrupt.h>
+#include <linux/stacktrace.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 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;
+}
+EXPORT_SYMBOL_GPL(setup_fault_attr);
+
+static void fail_dump(struct fault_attr *attr)
+{
+	if (attr->verbose > 0 && __ratelimit(&attr->ratelimit_state)) {
+		printk(KERN_NOTICE "FAULT_INJECTION: forcing a failure.\n"
+		       "name %pd, interval %lu, probability %lu, "
+		       "space %d, times %d\n", attr->dname,
+		       attr->interval, attr->probability,
+		       atomic_read(&attr->space),
+		       atomic_read(&attr->times));
+		if (attr->verbose > 1)
+			dump_stack();
+	}
+}
+
+#define atomic_dec_not_zero(v)		atomic_add_unless((v), -1, 0)
+
+static bool fail_task(struct fault_attr *attr, struct task_struct *task)
+{
+	return in_task() && task->make_it_fail;
+}
+
+#define MAX_STACK_TRACE_DEPTH 32
+
+#ifdef CONFIG_FAULT_INJECTION_STACKTRACE_FILTER
+
+static bool fail_stacktrace(struct fault_attr *attr)
+{
+	struct stack_trace trace;
+	int depth = attr->stacktrace_depth;
+	unsigned long entries[MAX_STACK_TRACE_DEPTH];
+	int n;
+	bool found = (attr->require_start == 0 && attr->require_end == ULONG_MAX);
+
+	if (depth == 0)
+		return found;
+
+	trace.nr_entries = 0;
+	trace.entries = entries;
+	trace.max_entries = depth;
+	trace.skip = 1;
+
+	save_stack_trace(&trace);
+	for (n = 0; n < trace.nr_entries; n++) {
+		if (attr->reject_start <= entries[n] &&
+			       entries[n] < attr->reject_end)
+			return false;
+		if (attr->require_start <= entries[n] &&
+			       entries[n] < attr->require_end)
+			found = true;
+	}
+	return found;
+}
+
+#else
+
+static inline bool fail_stacktrace(struct fault_attr *attr)
+{
+	return true;
+}
+
+#endif /* CONFIG_FAULT_INJECTION_STACKTRACE_FILTER */
+
+/*
+ * This code is stolen from failmalloc-1.0
+ * http://www.nongnu.org/failmalloc/
+ */
+
+bool should_fail(struct fault_attr *attr, ssize_t size)
+{
+	if (in_task()) {
+		unsigned int fail_nth = READ_ONCE(current->fail_nth);
+
+		if (fail_nth) {
+			if (!WRITE_ONCE(current->fail_nth, fail_nth - 1))
+				goto fail;
+
+			return false;
+		}
+	}
+
+	/* No need to check any other properties if the probability is 0 */
+	if (attr->probability == 0)
+		return false;
+
+	if (attr->task_filter && !fail_task(attr, current))
+		return false;
+
+	if (atomic_read(&attr->times) == 0)
+		return false;
+
+	if (atomic_read(&attr->space) > size) {
+		atomic_sub(size, &attr->space);
+		return false;
+	}
+
+	if (attr->interval > 1) {
+		attr->count++;
+		if (attr->count % attr->interval)
+			return false;
+	}
+
+	if (attr->probability <= prandom_u32() % 100)
+		return false;
+
+	if (!fail_stacktrace(attr))
+		return false;
+
+fail:
+	fail_dump(attr);
+
+	if (atomic_read(&attr->times) != -1)
+		atomic_dec_not_zero(&attr->times);
+
+	return true;
+}
+EXPORT_SYMBOL_GPL(should_fail);
+
+#ifdef CONFIG_FAULT_INJECTION_DEBUG_FS
+
+static int debugfs_ul_set(void *data, u64 val)
+{
+	*(unsigned long *)data = val;
+	return 0;
+}
+
+static int debugfs_ul_get(void *data, u64 *val)
+{
+	*val = *(unsigned long *)data;
+	return 0;
+}
+
+DEFINE_SIMPLE_ATTRIBUTE(fops_ul, debugfs_ul_get, debugfs_ul_set, "%llu\n");
+
+static struct dentry *debugfs_create_ul(const char *name, umode_t mode,
+				struct dentry *parent, unsigned long *value)
+{
+	return debugfs_create_file(name, mode, parent, value, &fops_ul);
+}
+
+#ifdef CONFIG_FAULT_INJECTION_STACKTRACE_FILTER
+
+static int debugfs_stacktrace_depth_set(void *data, u64 val)
+{
+	*(unsigned long *)data =
+		min_t(unsigned long, val, MAX_STACK_TRACE_DEPTH);
+
+	return 0;
+}
+
+DEFINE_SIMPLE_ATTRIBUTE(fops_stacktrace_depth, debugfs_ul_get,
+			debugfs_stacktrace_depth_set, "%llu\n");
+
+static struct dentry *debugfs_create_stacktrace_depth(
+	const char *name, umode_t mode,
+	struct dentry *parent, unsigned long *value)
+{
+	return debugfs_create_file(name, mode, parent, value,
+				   &fops_stacktrace_depth);
+}
+
+#endif /* CONFIG_FAULT_INJECTION_STACKTRACE_FILTER */
+
+struct dentry *fault_create_debugfs_attr(const char *name,
+			struct dentry *parent, struct fault_attr *attr)
+{
+	umode_t mode = S_IFREG | S_IRUSR | S_IWUSR;
+	struct dentry *dir;
+
+	dir = debugfs_create_dir(name, parent);
+	if (!dir)
+		return ERR_PTR(-ENOMEM);
+
+	if (!debugfs_create_ul("probability", mode, dir, &attr->probability))
+		goto fail;
+	if (!debugfs_create_ul("interval", mode, dir, &attr->interval))
+		goto fail;
+	if (!debugfs_create_atomic_t("times", mode, dir, &attr->times))
+		goto fail;
+	if (!debugfs_create_atomic_t("space", mode, dir, &attr->space))
+		goto fail;
+	if (!debugfs_create_ul("verbose", mode, dir, &attr->verbose))
+		goto fail;
+	if (!debugfs_create_u32("verbose_ratelimit_interval_ms", mode, dir,
+				&attr->ratelimit_state.interval))
+		goto fail;
+	if (!debugfs_create_u32("verbose_ratelimit_burst", mode, dir,
+				&attr->ratelimit_state.burst))
+		goto fail;
+	if (!debugfs_create_bool("task-filter", mode, dir, &attr->task_filter))
+		goto fail;
+
+#ifdef CONFIG_FAULT_INJECTION_STACKTRACE_FILTER
+
+	if (!debugfs_create_stacktrace_depth("stacktrace-depth", mode, dir,
+				&attr->stacktrace_depth))
+		goto fail;
+	if (!debugfs_create_ul("require-start", mode, dir,
+				&attr->require_start))
+		goto fail;
+	if (!debugfs_create_ul("require-end", mode, dir, &attr->require_end))
+		goto fail;
+	if (!debugfs_create_ul("reject-start", mode, dir, &attr->reject_start))
+		goto fail;
+	if (!debugfs_create_ul("reject-end", mode, dir, &attr->reject_end))
+		goto fail;
+
+#endif /* CONFIG_FAULT_INJECTION_STACKTRACE_FILTER */
+
+	attr->dname = dget(dir);
+	return dir;
+fail:
+	debugfs_remove_recursive(dir);
+
+	return ERR_PTR(-ENOMEM);
+}
+EXPORT_SYMBOL_GPL(fault_create_debugfs_attr);
+
+#endif /* CONFIG_FAULT_INJECTION_DEBUG_FS */