blktests failures with v5.19-rc1

[Shinichiro Kawasaki]

Bjorn, FYI. This lockdep warning disappeared with kernel version v6.1. I
bisected and found the commit 2d7f9f8c1815 ("kernfs: Improve kernfs_drain() and
always call on removal.") avoided the issue. This commit touches kernfs_drain()
and __kernfs_remove(), and modifies the condition to lock kernfs_rwsem. I think
it explains why the lockdep disappeared. No longer need to work on this issue :)

-- 
Shin'ichiro Kawasaki