linux-kernel - Re: next-20190708: kernel BUG at lib/lockref.c:189, softlockups in shrink

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Message-ID: <20190711072423.GA4219@amd>
Date:   Thu, 11 Jul 2019 09:24:23 +0200
From:   Pavel Machek <pavel@....cz>
To:     Al Viro <viro@...iv.linux.org.uk>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        kernel list <linux-kernel@...r.kernel.org>,
        sfr@...b.auug.org.au
Subject: Re: next-20190708: kernel BUG at lib/lockref.c:189, softlockups in
 shrink_dcache...?

On Thu 2019-07-11 01:25:27, Al Viro wrote:
> On Wed, Jul 10, 2019 at 05:09:12PM -0700, Andrew Morton wrote:
> > On Wed, 10 Jul 2019 22:13:11 +0200 Pavel Machek <pavel@....cz> wrote:
> > 
> > > Hi!
> > > 
> > > I'm getting some nastyness from lockref / memory management.
> > > 
> > > Any ideas? Any ideas who to talk to?
> > > 
> > 
> > I'd be suspecting Al's a99d7580f66e737 ("Teach shrink_dcache_parent()
> > to cope with mixed-filesystem shrink lists").
> 
> It is, and it's already fixed.  See 9bdebc2bd1c4 with fixes folded in;
> the incremental is
> 
> diff --git a/fs/dcache.c b/fs/dcache.c
> index d8732cf2e302..01b8cae41a71 100644
> --- a/fs/dcache.c
> +++ b/fs/dcache.c
> @@ -1555,7 +1555,9 @@ void shrink_dcache_parent(struct dentry *parent)
>  		d_walk(parent, &data, select_collect2);
>  		if (data.victim) {
>  			struct dentry *parent;
> +			spin_lock(&data.victim->d_lock);
>  			if (!shrink_lock_dentry(data.victim)) {
> +				spin_unlock(&data.victim->d_lock);
>  				rcu_read_unlock();
>  			} else {
>  				rcu_read_unlock();

Thanks! It only happened once under high load, so it seems it will not
be coming back.
								Pavel
								
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

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