e2fsck: salvage under-sized dirents by removing them

e2fsck: salvage under-sized dirents by removing them

If the directory processing code ends up pointing to a directory entry
that's so close to the end of the block that there's not even space
for a rec_len/name_len, just substitute dummy values that will force
e2fsck to extend the previous entry to cover the remaining space.  We
can't use the helper methods to extract rec_len because that's reading
off the end of the buffer.

This isn't an issue with non-inline directories because the directory
check buffer is zero-extended so that fsck won't blow up.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>