sysfs.h: add __ATTR_RW() macro

A number of parts of the kernel created their own version of this, might
as well have the sysfs core provide it instead.
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Tested-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

include/linux/sysfs.h

@@ -79,6 +79,8 @@ struct attribute_group {
 	.show	= _name##_show,					\
 }
 
+#define __ATTR_RW(_name) __ATTR(_name, 0644, _name##_show, _name##_store)
+
 #define __ATTR_NULL { .attr = { .name = NULL } }
 
 #ifdef CONFIG_DEBUG_LOCK_ALLOC

kernel/events/core.c

@@ -6234,8 +6234,6 @@ perf_event_mux_interval_ms_store(struct device *dev,
 	return count;
 }
 
-#define __ATTR_RW(attr) __ATTR(attr, 0644, attr##_show, attr##_store)
-
 static struct device_attribute pmu_dev_attrs[] = {
 	__ATTR_RO(type),
 	__ATTR_RW(perf_event_mux_interval_ms),

mm/backing-dev.c

@@ -232,8 +232,6 @@ static ssize_t stable_pages_required_show(struct device *dev,
 			bdi_cap_stable_pages_required(bdi) ? 1 : 0);
 }
 
-#define __ATTR_RW(attr) __ATTR(attr, 0644, attr##_show, attr##_store)
-
 static struct device_attribute bdi_dev_attrs[] = {
 	__ATTR_RW(read_ahead_kb),
 	__ATTR_RW(min_ratio),