.BR mke2fs .
The
.B \-R
-option is still accepted for backwards compatibility. The
-following extended options are supported:
+option is still accepted for backwards compatibility, but is deprecated.
+The following extended options are supported:
.RS 1.2i
.TP
.BI mmp_update_interval= interval
.TP
.B bigalloc
.br
-This feature enables clustered allocation, so that the unit of
+This feature enables clustered block allocation, so that the unit of
allocation is a power of two number of blocks. That is, each bit in the
what had traditionally been known as the block allocation bitmap now
indicates whether a cluster is in use or not, where a cluster is by
.TP
.B dir_index
.br
-Use hashed b-trees to speed up lookups in large directories.
+Use hashed b-trees to speed up name lookups in large directories.
.TP
.B dir_nlink
.br
.TP
.B extra_isize
.br
-This feature enables storage of nanosecond timestamps and creation
-time, if the inode size is larger than 256 bytes or larger.
+This feature reserves a specific amount of space in each inode for
+extended metadata such as nanosecond timestamps and file creation time,
+even if the current kernel does not current need to reserve this much
+space. Without this feature, the kernel will reserve the amount of
+space for features currently it currently needs, and the rest may be
+consumed by extended attributes.
+
+For this feature to be useful the inode size must be 256 bytes in size
+or larger.
.TP
.B ext_attr
.br
.\" .TP
.\" .B metadata_csum
.\" .br
-.\" Filesystem supports metadata checksumming. This feature enables a
-.\" superset of the functionality of the
+.\" Filesystem supports metadata checksumming. This feature stores
+.\" checksums for all of the filesystem metadata (superblock, group
+.\" descriptor blocks, inode and block bitmaps, directories, and
+.\" extent tree blocks). The checksum algorithm used for the metadata
+.\" blocks is different than the one used for group descriptors with the
.\" .B uninit_bg
-.\" feature.
+.\" feature, these two features are incompatible and
+.\" .B metadata_csum
+.\" will be used preferentially instead of
+.\" .BR uninit_bg .
.\" .br
.\" .B Future feature, available in e2fsprogs 1.43-WIP
.TP
.BR e2fsck (8)
time. The result is that it can speed up filesystem creation time noticeably
(if lazy_itable_init is enabled).
-.IP
-This first e2fsck run after enabling this feature will take the
-full time, but subsequent e2fsck runs will take only a fraction of the
-original time, depending on how full the file system is.
-It is only supported by the ext4 filesystem in recent Linux kernels.
.RE
.TP
.B \-q