linux-kernel - Re: [PATCH 0/4] mm: Use slab_list list

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Message-ID: <20190312171921.GB32504@tower.DHCP.thefacebook.com>
Date:   Tue, 12 Mar 2019 17:19:25 +0000
From:   Roman Gushchin <guro@...com>
To:     "Tobin C. Harding" <me@...in.cc>
CC:     Matthew Wilcox <willy@...radead.org>,
        "Tobin C. Harding" <tobin@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "Christoph Lameter" <cl@...ux.com>,
        Pekka Enberg <penberg@...nel.org>,
        David Rientjes <rientjes@...gle.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 0/4] mm: Use slab_list list_head instead of lru

On Tue, Mar 12, 2019 at 01:01:53PM +1100, Tobin C. Harding wrote:
> On Tue, Mar 12, 2019 at 12:22:23AM +0000, Roman Gushchin wrote:
> > On Mon, Mar 11, 2019 at 04:16:33PM -0700, Matthew Wilcox wrote:
> > > On Mon, Mar 11, 2019 at 08:49:23PM +0000, Roman Gushchin wrote:
> > > > The patchset looks good to me, however I'd add some clarifications
> > > > why switching from lru to slab_list is safe.
> > > > 
> > > > My understanding is that the slab_list fields isn't currently in use,
> > > > but it's not that obvious that putting slab_list and next/pages/pobjects
> > > > fields into a union is safe (for the slub case).
> > > 
> > > It's already in a union.
> > > 
> > > struct page {
> > >         union {
> > >                 struct {        /* Page cache and anonymous pages */
> > >                         struct list_head lru;
> > > ...
> > >                 struct {        /* slab, slob and slub */
> > >                         union {
> > >                                 struct list_head slab_list;     /* uses lru */
> > >                                 struct {        /* Partial pages */
> > >                                         struct page *next;
> > > 
> > > slab_list and lru are in the same bits.  Once this patch set is in,
> > > we can remove the enigmatic 'uses lru' comment that I added.
> > 
> > Ah, perfect, thanks! Makes total sense then.
> > 
> > Tobin, can you, please, add a note to the commit message?
> > With the note:
> > Reviewed-by: Roman Gushchin <guro@...com>
> 
> Awesome, thanks.  That's for all 4 patches or excluding 2?

To all 4, given that you'll add some explanations to the commit message.

Thanks!