linux-ext4 - xattr hash error in 4.13-rc with overlayfs over ext4

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Date:   Thu, 27 Jul 2017 14:37:35 +0200
From:   Miklos Szeredi <miklos@...redi.hu>
To:     Tahsin Erdogan <tahsin@...gle.com>
Cc:     "Theodore Ts'o" <tytso@....edu>,
        "linux-ext4@...r.kernel.org" <linux-ext4@...r.kernel.org>,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        "linux-unionfs@...r.kernel.org" <linux-unionfs@...r.kernel.org>
Subject: xattr hash error in 4.13-rc with overlayfs over ext4

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