Re: fs: GPF in bd_mount

[Al Viro]

On Sun, Sep 04, 2016 at 12:43:28PM +0200, Dmitry Vyukov wrote:

AFAICS, it's been introduced in commit 3684aa7099e0ab1038a1a1bf717ae60ffc3018d1
Author: Shaohua Li <shli@xxxxxx>
Date:   Mon Feb 22 15:27:40 2016 -0700

    block-dev: enable writeback cgroup support

See if you can reproduce it after the following:

ed fs/block_dev.c <<'EOF'
/bd_mount/
/if/s/dent/!IS_ERR(dent)/
wq
EOF

Said that, I'm not sure why mount_pseudo() would be returning any errors;
rejection should happen in the caller (due to MS_NOUSER in the flags), but
I don't understand what would trigger it on mount_pseudo() level...