[syzbot] [erofs?] [fat?] WARNING in erofs_kill_sb

[Christoph Hellwig]

On Mon, Jul 31, 2023 at 06:58:14PM +0800, Gao Xiang wrote:
> Previously, deactivate_locked_super() or .kill_sb() will only be
> called after fill_super is called, and .s_magic will be set at
> the very beginning of erofs_fc_fill_super().
>
> After ("fs: open block device after superblock creation"), such
> convension is changed now.  Yet at a quick glance,
>
> WARN_ON(sb->s_magic != EROFS_SUPER_MAGIC);
>
> in erofs_kill_sb() can be removed since deactivate_locked_super()
> will also be called if setup_bdev_super() is falled.  I'd suggest
> that removing this WARN_ON() in the related commit, or as
> a following commit of the related branch of the pull request if
> possible.

Agreed.  I wonder if we should really call into ->kill_sb before
calling into fill_super, but I need to carefull look into the
details.