mke2fs: check extents feature when bigalloc feature is enabled

When bigalloc feature is enabled in mkfs, extents feature also needs
to be enabled.  But now when bigalloc feature is enabled without
extents feature, users will not get any warning messages until they
try to mount this file system.

Signed-off-by: Zheng Liu <wenqing.lz@taobao.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
1 file changed