linux-kernel - Re: [RFC 02/15] slub: Add isolate() and migrate() methods

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Message-ID: <20190308162237.GD373@cisco>
Date:   Fri, 8 Mar 2019 09:22:37 -0700
From:   Tycho Andersen <tycho@...ho.ws>
To:     Christopher Lameter <cl@...ux.com>
Cc:     "Tobin C. Harding" <tobin@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Pekka Enberg <penberg@...helsinki.fi>,
        Matthew Wilcox <willy@...radead.org>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [RFC 02/15] slub: Add isolate() and migrate() methods

On Fri, Mar 08, 2019 at 04:15:46PM +0000, Christopher Lameter wrote:
> On Fri, 8 Mar 2019, Tycho Andersen wrote:
> 
> > On Fri, Mar 08, 2019 at 03:14:13PM +1100, Tobin C. Harding wrote:
> > > diff --git a/mm/slab_common.c b/mm/slab_common.c
> > > index f9d89c1b5977..754acdb292e4 100644
> > > --- a/mm/slab_common.c
> > > +++ b/mm/slab_common.c
> > > @@ -298,6 +298,10 @@ int slab_unmergeable(struct kmem_cache *s)
> > >  	if (!is_root_cache(s))
> > >  		return 1;
> > >
> > > +	/*
> > > +	 * s->isolate and s->migrate imply s->ctor so no need to
> > > +	 * check them explicitly.
> > > +	 */
> >
> > Shouldn't this implication go the other way, i.e.
> >     s->ctor => s->isolate & s->migrate
> 
> A cache can have a constructor but the object may not be movable (I.e.
> currently dentries and inodes).

Yep, thanks. Somehow I got confused by the comment.

Tycho