On Sat, 2021-06-12 at 08:43 +0800, Ian Kent wrote:
> On Sat, 2021-06-12 at 00:07 +0000, Al Viro wrote:
> > On Wed, Jun 09, 2021 at 04:50:27PM +0800, Ian Kent wrote:
> >
> > > + if (d_really_is_negative(dentry)) {
> > > + struct dentry *d_parent = dget_parent(dentry);
> > > + struct kernfs_node *parent;
> >
> > What the hell is dget_parent() for? You don't do anything blocking
> > here, so why not simply grab dentry->d_lock - that'll stabilize
> > the value of ->d_parent just fine. Just don't forget to drop the
> > lock before returning and that's it...
>
> Thanks Al, I'll change it.
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?
>
> >
> > > + /* If the kernfs parent node has changed discard
> > > and
> > > + * proceed to ->lookup.
> > > + */
> > > + parent = kernfs_dentry_node(d_parent);
> > > + if (parent) {
> > > + if (kernfs_dir_changed(parent, dentry)) {
> > > + dput(d_parent);
> > > + return 0;
> > > + }
> > > + }
> > > + dput(d_parent);
> > > +
> > > + /* The kernfs node doesn't exist, leave the
> > > dentry
> > > + * negative and return success.
> > > + */
> > > + return 1;
> > > + }
>
