This is the next generation of the ext3 filesystem. Unlike the change from ext2 filesystem to ext3 filesystem, the on-disk format of ext4 is not forwards compatible with ext3; it is based on extent maps and it supports 48-bit physical block numbers. The ext4 filesystem also supports delayed allocation, persistent preallocation, high resolution time stamps, and a number of other features to improve performance and speed up fsck time. For more information, please see the web pages at http://ext4.wiki.kernel.org. The ext4 filesystem will support mounting an ext3 filesystem; while there will be some performance gains from the delayed allocation and inode table readahead, the best performance gains will require enabling ext4 features in the filesystem, or formatting a new filesystem as an ext4 filesystem initially. To compile this file system support as a module, choose M here. The module will be called ext4. If unsure, say N.
Allow the ext4 file system driver code to be used for ext2 or ext3 file system mounts. This allows users to reduce their compiled kernel size by using one file system driver for ext2, ext3, and ext4 file systems.
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 ext4.
POSIX Access Control Lists (ACLs) support permissions for users and groups beyond the owner/group/world scheme. To learn more about Access Control Lists, visit the POSIX ACLs for Linux website <http://acl.bestbits.at/>. If you don't know what Access Control Lists are, say N
Security labels support alternative access control models implemented by security modules like SELinux. This option enables an extended attribute handler for file security labels in the ext4 filesystem. If you are not using a security module that requires using extended attributes for file security labels, say N.
Enables run-time debugging support for the ext4 filesystem. If you select Y here, then you will be able to turn on debugging with a command such as "echo 1 > /sys/kernel/debug/ext4/mballoc-debug"