xattr hash error in 4.13-rc with overlayfs over ext4

[Miklos Szeredi]

I get the following error on fsck:

Pass 1: Checking inodes, blocks, and sizes
Extended attribute in inode 3093 has a hash (2257320705) which is invalid
Clear<y>? yes
Inode 3093, i_blocks is 16, should be 8.  Fix<y>? yes

To reproduce:

[mount ext4 image]
mkdir xattrhashtest
cd xattrhashtest/
mkdir upper lower work mnt
cd lower/
echo foo > bar
ln bar baz
mount -t overlay overlay -olowerdir=lower,upperdir=upper,workdir=work mnt
cd mnt/
echo xxx >> bar
[umount and fsck]

Reverting commit daf8328172df ("ext4: eliminate xattr entry e_hash
recalculation for removes") fixes it.

Might be an ext4 or overlayfs bug.  Let me know what you think.

Thanks,
Miklos