linux-kernel - Re: [PATCH v2 3/3] mm: use PF_ONLY_HEAD for PG_active and PG

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <alpine.LSU.2.11.2103011215260.4616@eggly.anvils>
Date:   Mon, 1 Mar 2021 12:16:19 -0800 (PST)
From:   Hugh Dickins <hughd@...gle.com>
To:     Yu Zhao <yuzhao@...gle.com>
cc:     "Kirill A. Shutemov" <kirill@...temov.name>,
        Matthew Wilcox <willy@...radead.org>,
        akpm@...ux-foundation.org, alex.shi@...ux.alibaba.com,
        vbabka@...e.cz, guro@...com, hannes@...xchg.org, hughd@...gle.com,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        mhocko@...nel.org, vdavydov.dev@...il.com
Subject: Re: [PATCH v2 3/3] mm: use PF_ONLY_HEAD for PG_active and
 PG_unevictable

On Mon, 1 Mar 2021, Yu Zhao wrote:
> On Mon, Mar 01, 2021 at 02:50:07PM +0300, Kirill A. Shutemov wrote:
> > On Fri, Feb 26, 2021 at 12:13:14PM +0000, Matthew Wilcox wrote:
> > > On Fri, Feb 26, 2021 at 02:17:18AM -0700, Yu Zhao wrote:
> > > > All places but one test, set or clear PG_active and PG_unevictable on
> > > > small or head pages. Use compound_head() explicitly for that singleton
> > > > so the rest can rid of redundant compound_head().
> > > 
> > > How do you know it's only one place?  I really wish you'd work with me
> > > on folios.  They make the compiler prove that it's not a tail page.
> > 
> > +1 to this.
> > 
> > The problem with compound_head() is systemic and ad-hoc solution to few
> > page flags will only complicate the picture.
> 
> Well, I call it an incremental improvement, and how exactly does it
> complicate the picture?
> 
> I see your point: you prefer a complete replacement. But my point is
> not about the preference; it's about presenting an option: I'm not
> saying we have to go with this series; I'm saying if you don't want
> to wait, here is something quick but not perfect.

+1 to this.

Hugh