e2fsck: correctly handle inline directories when large_dir is enabled.

e2fsck: correctly handle inline directories when large_dir is enabled.

Historically, e2fsck has required that directories not contain holes.
(In fact, as of this writing, ext4 still requires this to be the
case.)  Commit ae9efd05a98 ("e2fsck: 3 level hash tree directory
optimization") removed this requirement if the large_dir feature is
enabled; however, the way it was done caused it to incorrectly handle
inline directories.

To reproduce the problem fixed by this commit:

truncate -s 100000000 ext4.img
misc/mke2fs -t ext4 -I 512 -O 'inline_data,large_dir' ext4.img
mkdir m
sudo mount ext4.img m
mkdir m/aa
sudo umount m
e2fsck/e2fsck -f -n ext4.img

The last command gives this output:

[root@localhost e2fsprogs-kernel]# e2fsck/e2fsck -f -n ext4-2.img
e2fsck 1.45.2 (27-May-2019)
Pass 1: Checking inodes, blocks, and sizes
Pass 2: Checking directory structure
Pass 3: Checking directory connectivity
'..' in /aa (12) is <The NULL inode> (0), should be / (2).
Fix? no

Pass 4: Checking reference counts
Inode 2 ref count is 4, should be 3.  Fix? no

Inode 12 ref count is 2, should be 1.  Fix? no

Pass 5: Checking group summary information

ext4-2.img: ********** WARNING: Filesystem still has errors **********

ext4-2.img: 12/24384 files (0.0% non-contiguous), 17874/97656 blocks

Reported-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Signed-off-by: Artem Blagodarenko <c17828@cray.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>