16da0b38fSAlexey Dobriyanconfig EXT4_FS 26da0b38fSAlexey Dobriyan tristate "The Extended 4 (ext4) filesystem" 36da0b38fSAlexey Dobriyan select JBD2 46da0b38fSAlexey Dobriyan select CRC16 56da0b38fSAlexey Dobriyan help 66da0b38fSAlexey Dobriyan This is the next generation of the ext3 filesystem. 76da0b38fSAlexey Dobriyan 86da0b38fSAlexey Dobriyan Unlike the change from ext2 filesystem to ext3 filesystem, 96da0b38fSAlexey Dobriyan the on-disk format of ext4 is not forwards compatible with 106da0b38fSAlexey Dobriyan ext3; it is based on extent maps and it supports 48-bit 116da0b38fSAlexey Dobriyan physical block numbers. The ext4 filesystem also supports delayed 126da0b38fSAlexey Dobriyan allocation, persistent preallocation, high resolution time stamps, 136da0b38fSAlexey Dobriyan and a number of other features to improve performance and speed 146da0b38fSAlexey Dobriyan up fsck time. For more information, please see the web pages at 156da0b38fSAlexey Dobriyan http://ext4.wiki.kernel.org. 166da0b38fSAlexey Dobriyan 176da0b38fSAlexey Dobriyan The ext4 filesystem will support mounting an ext3 186da0b38fSAlexey Dobriyan filesystem; while there will be some performance gains from 196da0b38fSAlexey Dobriyan the delayed allocation and inode table readahead, the best 206da0b38fSAlexey Dobriyan performance gains will require enabling ext4 features in the 21692105b8SMatt LaPlante filesystem, or formatting a new filesystem as an ext4 226da0b38fSAlexey Dobriyan filesystem initially. 236da0b38fSAlexey Dobriyan 246da0b38fSAlexey Dobriyan To compile this file system support as a module, choose M here. The 256da0b38fSAlexey Dobriyan module will be called ext4. 266da0b38fSAlexey Dobriyan 276da0b38fSAlexey Dobriyan If unsure, say N. 286da0b38fSAlexey Dobriyan 296da0b38fSAlexey Dobriyanconfig EXT4DEV_COMPAT 306da0b38fSAlexey Dobriyan bool "Enable ext4dev compatibility" 316da0b38fSAlexey Dobriyan depends on EXT4_FS 326da0b38fSAlexey Dobriyan help 336da0b38fSAlexey Dobriyan Starting with 2.6.28, the name of the ext4 filesystem was 346da0b38fSAlexey Dobriyan renamed from ext4dev to ext4. Unfortunately there are some 356da0b38fSAlexey Dobriyan legacy userspace programs (such as klibc's fstype) have 366da0b38fSAlexey Dobriyan "ext4dev" hardcoded. 376da0b38fSAlexey Dobriyan 386da0b38fSAlexey Dobriyan To enable backwards compatibility so that systems that are 396da0b38fSAlexey Dobriyan still expecting to mount ext4 filesystems using ext4dev, 4043b38520SManish Katiyar choose Y here. This feature will go away by 2.6.31, so 416da0b38fSAlexey Dobriyan please arrange to get your userspace programs fixed! 426da0b38fSAlexey Dobriyan 436da0b38fSAlexey Dobriyanconfig EXT4_FS_XATTR 446da0b38fSAlexey Dobriyan bool "Ext4 extended attributes" 456da0b38fSAlexey Dobriyan depends on EXT4_FS 466da0b38fSAlexey Dobriyan default y 476da0b38fSAlexey Dobriyan help 486da0b38fSAlexey Dobriyan Extended attributes are name:value pairs associated with inodes by 496da0b38fSAlexey Dobriyan the kernel or by users (see the attr(5) manual page, or visit 506da0b38fSAlexey Dobriyan <http://acl.bestbits.at/> for details). 516da0b38fSAlexey Dobriyan 526da0b38fSAlexey Dobriyan If unsure, say N. 536da0b38fSAlexey Dobriyan 546da0b38fSAlexey Dobriyan You need this for POSIX ACL support on ext4. 556da0b38fSAlexey Dobriyan 566da0b38fSAlexey Dobriyanconfig EXT4_FS_POSIX_ACL 576da0b38fSAlexey Dobriyan bool "Ext4 POSIX Access Control Lists" 586da0b38fSAlexey Dobriyan depends on EXT4_FS_XATTR 596da0b38fSAlexey Dobriyan select FS_POSIX_ACL 606da0b38fSAlexey Dobriyan help 616da0b38fSAlexey Dobriyan POSIX Access Control Lists (ACLs) support permissions for users and 626da0b38fSAlexey Dobriyan groups beyond the owner/group/world scheme. 636da0b38fSAlexey Dobriyan 646da0b38fSAlexey Dobriyan To learn more about Access Control Lists, visit the POSIX ACLs for 656da0b38fSAlexey Dobriyan Linux website <http://acl.bestbits.at/>. 666da0b38fSAlexey Dobriyan 676da0b38fSAlexey Dobriyan If you don't know what Access Control Lists are, say N 686da0b38fSAlexey Dobriyan 696da0b38fSAlexey Dobriyanconfig EXT4_FS_SECURITY 706da0b38fSAlexey Dobriyan bool "Ext4 Security Labels" 716da0b38fSAlexey Dobriyan depends on EXT4_FS_XATTR 726da0b38fSAlexey Dobriyan help 736da0b38fSAlexey Dobriyan Security labels support alternative access control models 746da0b38fSAlexey Dobriyan implemented by security modules like SELinux. This option 756da0b38fSAlexey Dobriyan enables an extended attribute handler for file security 766da0b38fSAlexey Dobriyan labels in the ext4 filesystem. 776da0b38fSAlexey Dobriyan 786da0b38fSAlexey Dobriyan If you are not using a security module that requires using 796da0b38fSAlexey Dobriyan extended attributes for file security labels, say N. 80*6ba495e9STheodore Ts'o 81*6ba495e9STheodore Ts'oconfig EXT4_DEBUG 82*6ba495e9STheodore Ts'o bool "EXT4 debugging support" 83*6ba495e9STheodore Ts'o depends on EXT4_FS 84*6ba495e9STheodore Ts'o help 85*6ba495e9STheodore Ts'o Enables run-time debugging support for the ext4 filesystem. 86*6ba495e9STheodore Ts'o 87*6ba495e9STheodore Ts'o If you select Y here, then you will be able to turn on debugging 88*6ba495e9STheodore Ts'o with a command such as "echo 1 > /sys/kernel/debug/ext4/mballoc-debug" 89