linux-kernel - Re: WARNING: CPU: 1 PID: 14735 at fs/dcache.c:365 dentry

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Date:   Wed, 20 Jul 2022 03:22:30 +0100
From:   Al Viro <viro@...iv.linux.org.uk>
To:     Helge Deller <deller@....de>
Cc:     Hillf Danton <hdanton@...a.com>, linux-kernel@...r.kernel.org,
        linux-parisc@...r.kernel.org
Subject: Re: WARNING: CPU: 1 PID: 14735 at fs/dcache.c:365
 dentry_free+0x100/0x128

On Tue, Jul 19, 2022 at 06:32:04PM +0200, Helge Deller wrote:
> > --- a/fs/dcache.c
> > +++ b/fs/dcache.c
> > @@ -605,8 +605,12 @@ static void __dentry_kill(struct dentry
> >  		spin_unlock(&parent->d_lock);
> >  	if (dentry->d_inode)
> >  		dentry_unlink_inode(dentry);
> > -	else
> > +	else {
> > +		if (unlikely(d_in_lookup(dentry))) {
> > +			__d_lookup_done(dentry);
> > +		}
> >  		spin_unlock(&dentry->d_lock);
> > +	}

Ugh...  If that triggers, we really have a problem.  I don't see any
way for that to happen (well, short of generally fucked refcounting -
stray dput() on wrong address and all bets are off)