fault-inject: allow configuration via configfs

This provides a helper function to allow configuration of fault-injection
for configfs-based drivers.

The config items created by this function have the same interface as the
one created under debugfs by fault_create_debugfs_attr().

Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Link: https://lore.kernel.org/r/20230327143733.14599-2-akinobu.mita@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

include/linux/fault-inject.h

@@ -6,6 +6,7 @@
 
 #include <linux/types.h>
 #include <linux/debugfs.h>
+#include <linux/configfs.h>
 #include <linux/ratelimit.h>
 #include <linux/atomic.h>
 
@@ -65,6 +66,27 @@ static inline struct dentry *fault_create_debugfs_attr(const char *name,
 
 #endif /* CONFIG_FAULT_INJECTION_DEBUG_FS */
 
+#ifdef CONFIG_FAULT_INJECTION_CONFIGFS
+
+struct fault_config {
+	struct fault_attr attr;
+	struct config_group group;
+};
+
+void fault_config_init(struct fault_config *config, const char *name);
+
+#else /* CONFIG_FAULT_INJECTION_CONFIGFS */
+
+struct fault_config {
+};
+
+static inline void fault_config_init(struct fault_config *config,
+			const char *name)
+{
+}
+
+#endif /* CONFIG_FAULT_INJECTION_CONFIGFS */
+
 #endif /* CONFIG_FAULT_INJECTION */
 
 struct kmem_cache;

lib/Kconfig.debug

@@ -1958,9 +1958,20 @@ config FAIL_SUNRPC
 	  Provide fault-injection capability for SunRPC and
 	  its consumers.
 
+config FAULT_INJECTION_CONFIGFS
+	bool "Configfs interface for fault-injection capabilities"
+	depends on FAULT_INJECTION && CONFIGFS_FS
+	help
+	  This option allows configfs-based drivers to dynamically configure
+	  fault-injection via configfs.  Each parameter for driver-specific
+	  fault-injection can be made visible as a configfs attribute in a
+	  configfs group.
+
+
 config FAULT_INJECTION_STACKTRACE_FILTER
 	bool "stacktrace filter for fault-injection capabilities"
-	depends on FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORT
+	depends on FAULT_INJECTION
+	depends on (FAULT_INJECTION_DEBUG_FS || FAULT_INJECTION_CONFIGFS) && STACKTRACE_SUPPORT
 	select STACKTRACE
 	depends on FRAME_POINTER || MIPS || PPC || S390 || MICROBLAZE || ARM || ARC || X86
 	help

lib/fault-inject.c

@@ -244,3 +244,194 @@ struct dentry *fault_create_debugfs_attr(const char *name,
 EXPORT_SYMBOL_GPL(fault_create_debugfs_attr);
 
 #endif /* CONFIG_FAULT_INJECTION_DEBUG_FS */
+
+#ifdef CONFIG_FAULT_INJECTION_CONFIGFS
+
+/* These configfs attribute utilities are copied from drivers/block/null_blk/main.c */
+
+static ssize_t fault_uint_attr_show(unsigned int val, char *page)
+{
+	return snprintf(page, PAGE_SIZE, "%u\n", val);
+}
+
+static ssize_t fault_ulong_attr_show(unsigned long val, char *page)
+{
+	return snprintf(page, PAGE_SIZE, "%lu\n", val);
+}
+
+static ssize_t fault_bool_attr_show(bool val, char *page)
+{
+	return snprintf(page, PAGE_SIZE, "%u\n", val);
+}
+
+static ssize_t fault_atomic_t_attr_show(atomic_t val, char *page)
+{
+	return snprintf(page, PAGE_SIZE, "%d\n", atomic_read(&val));
+}
+
+static ssize_t fault_uint_attr_store(unsigned int *val, const char *page, size_t count)
+{
+	unsigned int tmp;
+	int result;
+
+	result = kstrtouint(page, 0, &tmp);
+	if (result < 0)
+		return result;
+
+	*val = tmp;
+	return count;
+}
+
+static ssize_t fault_ulong_attr_store(unsigned long *val, const char *page, size_t count)
+{
+	int result;
+	unsigned long tmp;
+
+	result = kstrtoul(page, 0, &tmp);
+	if (result < 0)
+		return result;
+
+	*val = tmp;
+	return count;
+}
+
+static ssize_t fault_bool_attr_store(bool *val, const char *page, size_t count)
+{
+	bool tmp;
+	int result;
+
+	result = kstrtobool(page, &tmp);
+	if (result < 0)
+		return result;
+
+	*val = tmp;
+	return count;
+}
+
+static ssize_t fault_atomic_t_attr_store(atomic_t *val, const char *page, size_t count)
+{
+	int tmp;
+	int result;
+
+	result = kstrtoint(page, 0, &tmp);
+	if (result < 0)
+		return result;
+
+	atomic_set(val, tmp);
+	return count;
+}
+
+#define CONFIGFS_ATTR_NAMED(_pfx, _name, _attr_name)	\
+static struct configfs_attribute _pfx##attr_##_name = {	\
+	.ca_name	= _attr_name,			\
+	.ca_mode	= 0644,				\
+	.ca_owner	= THIS_MODULE,			\
+	.show		= _pfx##_name##_show,		\
+	.store		= _pfx##_name##_store,		\
+}
+
+static struct fault_config *to_fault_config(struct config_item *item)
+{
+	return container_of(to_config_group(item), struct fault_config, group);
+}
+
+#define FAULT_CONFIGFS_ATTR_NAMED(NAME, ATTR_NAME, MEMBER, TYPE)				\
+static ssize_t fault_##NAME##_show(struct config_item *item, char *page)			\
+{												\
+	return fault_##TYPE##_attr_show(to_fault_config(item)->attr.MEMBER, page);		\
+}												\
+static ssize_t fault_##NAME##_store(struct config_item *item, const char *page, size_t count)	\
+{												\
+	struct fault_config *config = to_fault_config(item);					\
+	return fault_##TYPE##_attr_store(&config->attr.MEMBER, page, count);			\
+}												\
+CONFIGFS_ATTR_NAMED(fault_, NAME, ATTR_NAME)
+
+#define FAULT_CONFIGFS_ATTR(NAME, TYPE)	\
+	FAULT_CONFIGFS_ATTR_NAMED(NAME, __stringify(NAME), NAME, TYPE)
+
+FAULT_CONFIGFS_ATTR(probability, ulong);
+FAULT_CONFIGFS_ATTR(interval, ulong);
+FAULT_CONFIGFS_ATTR(times, atomic_t);
+FAULT_CONFIGFS_ATTR(space, atomic_t);
+FAULT_CONFIGFS_ATTR(verbose, ulong);
+FAULT_CONFIGFS_ATTR_NAMED(ratelimit_interval, "verbose_ratelimit_interval_ms",
+		ratelimit_state.interval, uint);
+FAULT_CONFIGFS_ATTR_NAMED(ratelimit_burst, "verbose_ratelimit_burst",
+		ratelimit_state.burst, uint);
+FAULT_CONFIGFS_ATTR_NAMED(task_filter, "task-filter", task_filter, bool);
+
+#ifdef CONFIG_FAULT_INJECTION_STACKTRACE_FILTER
+
+static ssize_t fault_stacktrace_depth_show(struct config_item *item, char *page)
+{
+	return fault_ulong_attr_show(to_fault_config(item)->attr.stacktrace_depth, page);
+}
+
+static ssize_t fault_stacktrace_depth_store(struct config_item *item, const char *page,
+		size_t count)
+{
+	int result;
+	unsigned long tmp;
+
+	result = kstrtoul(page, 0, &tmp);
+	if (result < 0)
+		return result;
+
+	to_fault_config(item)->attr.stacktrace_depth =
+		min_t(unsigned long, tmp, MAX_STACK_TRACE_DEPTH);
+
+	return count;
+}
+
+CONFIGFS_ATTR_NAMED(fault_, stacktrace_depth, "stacktrace-depth");
+
+static ssize_t fault_xul_attr_show(unsigned long val, char *page)
+{
+	return snprintf(page, PAGE_SIZE,
+			sizeof(val) == sizeof(u32) ? "0x%08lx\n" : "0x%016lx\n", val);
+}
+
+static ssize_t fault_xul_attr_store(unsigned long *val, const char *page, size_t count)
+{
+	return fault_ulong_attr_store(val, page, count);
+}
+
+FAULT_CONFIGFS_ATTR_NAMED(require_start, "require-start", require_start, xul);
+FAULT_CONFIGFS_ATTR_NAMED(require_end, "require-end", require_end, xul);
+FAULT_CONFIGFS_ATTR_NAMED(reject_start, "reject-start", reject_start, xul);
+FAULT_CONFIGFS_ATTR_NAMED(reject_end, "reject-end", reject_end, xul);
+
+#endif /* CONFIG_FAULT_INJECTION_STACKTRACE_FILTER */
+
+static struct configfs_attribute *fault_config_attrs[] = {
+	&fault_attr_probability,
+	&fault_attr_interval,
+	&fault_attr_times,
+	&fault_attr_space,
+	&fault_attr_verbose,
+	&fault_attr_ratelimit_interval,
+	&fault_attr_ratelimit_burst,
+	&fault_attr_task_filter,
+#ifdef CONFIG_FAULT_INJECTION_STACKTRACE_FILTER
+	&fault_attr_stacktrace_depth,
+	&fault_attr_require_start,
+	&fault_attr_require_end,
+	&fault_attr_reject_start,
+	&fault_attr_reject_end,
+#endif /* CONFIG_FAULT_INJECTION_STACKTRACE_FILTER */
+	NULL,
+};
+
+static const struct config_item_type fault_config_type = {
+	.ct_attrs	= fault_config_attrs,
+	.ct_owner	= THIS_MODULE,
+};
+
+void fault_config_init(struct fault_config *config, const char *name)
+{
+	config_group_init_type_name(&config->group, name, &fault_config_type);
+}
+EXPORT_SYMBOL_GPL(fault_config_init);
+
+#endif /* CONFIG_FAULT_INJECTION_CONFIGFS */