Re: [PATCH v6 3/7] kernfs: use VFS negative dentry caching

[Ian Kent]

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:
> 
> > 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().