linux-kernel - Re: [PATCH mm-unstable v2 4/5] mm: restart if multiple traversals raced

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Message-ID: <cjvz3rhv2wkoev3gwikb72x4ecwx76lpdvxvur3qdzpnykyvvb@k44wu2ec2htf>
Date: Tue, 20 Aug 2024 13:59:52 +0200
From: Michal Koutný <mkoutny@...e.com>
To: Kinsey Ho <kinseyho@...gle.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org, 
	linux-kernel@...r.kernel.org, cgroups@...r.kernel.org, Yosry Ahmed <yosryahmed@...gle.com>, 
	Roman Gushchin <roman.gushchin@...ux.dev>, Johannes Weiner <hannes@...xchg.org>, 
	Michal Hocko <mhocko@...nel.org>, Shakeel Butt <shakeel.butt@...ux.dev>, 
	Muchun Song <muchun.song@...ux.dev>, Tejun Heo <tj@...nel.org>, Zefan Li <lizefan.x@...edance.com>
Subject: Re: [PATCH mm-unstable v2 4/5] mm: restart if multiple traversals
 raced

On Fri, Aug 16, 2024 at 12:27:27PM GMT, Kinsey Ho <kinseyho@...gle.com> wrote:
> Hi Michal,
> 
> > I may be missing (literal) context but I'd suggest not moving the memcg
> > assignment and leverage
> >         if (memcg != NULL)
> >                 css_put(memcg->css)
> > so that the is-root comparison needn't be repeated.
> 
> I might also be misunderstanding you with respect to the is-root
> comparison – the reason the memcg assignment is moved is because it is
> possible that on the restart added in this patch, css could be NULL.

I've played with this applied up to 4/5 and I see more changes would be
needed to preserve the function. Please disregard my initial suggestion
':-)

Michal

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