libext2fs: add new function ext2fs_extent_set_bmap()

Allows unmapping or remapping single mapped logical blocks,
and mapping currently unmapped blocks.

Also implements ext2fs_extent_fix_parents() to fix parent
index logical starts, if the first index of a node changes
its logical start block.

Currently this can result in unnecessary new single-block extents; I
think perhaps ext2fs_extent_insert should grow a flag to request
merging with a nearby extent?

Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
3 files changed