Ext4dev extended attributes

configname: CONFIG_EXT4DEV_FS_XATTR

Linux Kernel Configuration
└─>File systems
└─>Ext4dev extended attributes
In linux kernel since version 2.6.20 (release Date: 2007-02-04)  
Extended attributes are name:value pairs associated with inodes by
the kernel or by users (see the attr(5) manual page, or visit
<http://acl.bestbits.at/> for details).

If unsure, say N.

You need this for POSIX ACL support on ext4dev/ext4.