[extfs] status report 8

[gnehzuil]

Status:

 * Make ext2fs read ext4 extents in read-only mode.

 * Make ext2fs support DIR_NLINK feautre.

 * Add flex groups data structure and a function to initialize it. 
FLEX_BG feature doesn't required in read-only mode.

 * UNINIT_BG feature doesn't required in read-only mode.

 * Calculate extra_isize variable in ext2_mountfs() function. 
EXTRA_ISIZE feature doesn't required in read-only mode.


Plan for next week:

 * Implement DIR_INDEX feature and make ext2fs can read hash directory 
index in read-only mode. This feature is the last one I need to 
implement the feature.

 * There is a bug in changing into a directory with DIR_NLINK feature 
and the number of directories is greater than 32000. When I change into 
a directory, it will get a panic. The panic occur in calling 
softdep_deallocate_dependencies() function. So I think this is an I/O 
error about buffer.


lz