optimize sysfs device and attribute cache

Add negative cache for attributes and look for device in cache before doing
any sysfs access. (Three times speed up for a stupid 1000 rules SYSFS file).

Signed-off-by: Kay Sievers <kay.sievers@suse.de>

1 files changed, 1 insertions, 0 deletions

diff --git a/udev.h b/udev.h
index 0c7ca12f10..2652d46ada 100644
--- a/udev.h
+++ b/udev.h
@@ -54,6 +54,7 @@ struct udev_rules;
 
 struct sysfs_device {
 	struct list_head node;			/* for device cache */
+	struct sysfs_device *parent;		/* already cached parent*/
 	char devpath[PATH_SIZE];
 	char subsystem[NAME_SIZE];		/* $class/$bus/"drivers" */
 	char kernel_name[NAME_SIZE];		/* device instance name */