16da0b38fSAlexey Dobriyanconfig EXT4_FS 26da0b38fSAlexey Dobriyan tristate "The Extended 4 (ext4) filesystem" 36da0b38fSAlexey Dobriyan select JBD2 46da0b38fSAlexey Dobriyan select CRC16 50441984aSDarrick J. Wong select CRYPTO 60441984aSDarrick J. Wong select CRYPTO_CRC32C 76da0b38fSAlexey Dobriyan help 86da0b38fSAlexey Dobriyan This is the next generation of the ext3 filesystem. 96da0b38fSAlexey Dobriyan 106da0b38fSAlexey Dobriyan Unlike the change from ext2 filesystem to ext3 filesystem, 116da0b38fSAlexey Dobriyan the on-disk format of ext4 is not forwards compatible with 126da0b38fSAlexey Dobriyan ext3; it is based on extent maps and it supports 48-bit 136da0b38fSAlexey Dobriyan physical block numbers. The ext4 filesystem also supports delayed 146da0b38fSAlexey Dobriyan allocation, persistent preallocation, high resolution time stamps, 156da0b38fSAlexey Dobriyan and a number of other features to improve performance and speed 166da0b38fSAlexey Dobriyan up fsck time. For more information, please see the web pages at 176da0b38fSAlexey Dobriyan http://ext4.wiki.kernel.org. 186da0b38fSAlexey Dobriyan 196da0b38fSAlexey Dobriyan The ext4 filesystem will support mounting an ext3 206da0b38fSAlexey Dobriyan filesystem; while there will be some performance gains from 216da0b38fSAlexey Dobriyan the delayed allocation and inode table readahead, the best 226da0b38fSAlexey Dobriyan performance gains will require enabling ext4 features in the 23692105b8SMatt LaPlante filesystem, or formatting a new filesystem as an ext4 246da0b38fSAlexey Dobriyan filesystem initially. 256da0b38fSAlexey Dobriyan 266da0b38fSAlexey Dobriyan To compile this file system support as a module, choose M here. The 276da0b38fSAlexey Dobriyan module will be called ext4. 286da0b38fSAlexey Dobriyan 296da0b38fSAlexey Dobriyan If unsure, say N. 306da0b38fSAlexey Dobriyan 3124b58424STheodore Ts'oconfig EXT4_USE_FOR_EXT23 3224b58424STheodore Ts'o bool "Use ext4 for ext2/ext3 file systems" 3384c66473SDavid Howells depends on EXT4_FS 34a214238dSTheodore Ts'o depends on EXT3_FS=n || EXT2_FS=n 3524b58424STheodore Ts'o default y 3624b58424STheodore Ts'o help 3724b58424STheodore Ts'o Allow the ext4 file system driver code to be used for ext2 or 3824b58424STheodore Ts'o ext3 file system mounts. This allows users to reduce their 3924b58424STheodore Ts'o compiled kernel size by using one file system driver for 4024b58424STheodore Ts'o ext2, ext3, and ext4 file systems. 4124b58424STheodore Ts'o 426da0b38fSAlexey Dobriyanconfig EXT4_FS_POSIX_ACL 436da0b38fSAlexey Dobriyan bool "Ext4 POSIX Access Control Lists" 44*96465efeSValerie Aurora depends on EXT4_FS 456da0b38fSAlexey Dobriyan select FS_POSIX_ACL 466da0b38fSAlexey Dobriyan help 476da0b38fSAlexey Dobriyan POSIX Access Control Lists (ACLs) support permissions for users and 486da0b38fSAlexey Dobriyan groups beyond the owner/group/world scheme. 496da0b38fSAlexey Dobriyan 506da0b38fSAlexey Dobriyan To learn more about Access Control Lists, visit the POSIX ACLs for 516da0b38fSAlexey Dobriyan Linux website <http://acl.bestbits.at/>. 526da0b38fSAlexey Dobriyan 536da0b38fSAlexey Dobriyan If you don't know what Access Control Lists are, say N 546da0b38fSAlexey Dobriyan 556da0b38fSAlexey Dobriyanconfig EXT4_FS_SECURITY 566da0b38fSAlexey Dobriyan bool "Ext4 Security Labels" 57*96465efeSValerie Aurora depends on EXT4_FS 586da0b38fSAlexey Dobriyan help 596da0b38fSAlexey Dobriyan Security labels support alternative access control models 606da0b38fSAlexey Dobriyan implemented by security modules like SELinux. This option 616da0b38fSAlexey Dobriyan enables an extended attribute handler for file security 626da0b38fSAlexey Dobriyan labels in the ext4 filesystem. 636da0b38fSAlexey Dobriyan 646da0b38fSAlexey Dobriyan If you are not using a security module that requires using 656da0b38fSAlexey Dobriyan extended attributes for file security labels, say N. 666ba495e9STheodore Ts'o 676ba495e9STheodore Ts'oconfig EXT4_DEBUG 686ba495e9STheodore Ts'o bool "EXT4 debugging support" 696ba495e9STheodore Ts'o depends on EXT4_FS 706ba495e9STheodore Ts'o help 716ba495e9STheodore Ts'o Enables run-time debugging support for the ext4 filesystem. 726ba495e9STheodore Ts'o 736ba495e9STheodore Ts'o If you select Y here, then you will be able to turn on debugging 746ba495e9STheodore Ts'o with a command such as "echo 1 > /sys/kernel/debug/ext4/mballoc-debug" 75