On Sat, 2021-06-12 at 01:51 +0000, Al Viro wrote:

On Sat, Jun 12, 2021 at 09:08:05AM +0800, Ian Kent wrote:

quoted

But if I change to take the read lock to ensure there's no
operation
in progress for the revision check I would need the dget_parent(),
yes?

WTF for?  ->d_parent can change *ONLY* when ->d_lock is held on all
dentries involved (including old and new parents).

Understood, thanks.

And it very definitely does *not* change for negative dentries.  I
mean,
look at the very beginning of __d_move().