linux-kernel - Re: [RFC PATCH 1/3] mm: Drop locked from isolate_migratepages

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Message-ID: <CAKgT0UcRFqXUOJ+QjgtjdQE6A7EMgAc_v9b7+mXy-ZJLvG2AgQ@mail.gmail.com>
Date:   Thu, 13 Aug 2020 07:32:46 -0700
From:   Alexander Duyck <alexander.duyck@...il.com>
To:     Alex Shi <alex.shi@...ux.alibaba.com>
Cc:     Yang Shi <yang.shi@...ux.alibaba.com>,
        kbuild test robot <lkp@...el.com>,
        Rong Chen <rong.a.chen@...el.com>,
        Konstantin Khlebnikov <khlebnikov@...dex-team.ru>,
        "Kirill A. Shutemov" <kirill@...temov.name>,
        Hugh Dickins <hughd@...gle.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Daniel Jordan <daniel.m.jordan@...cle.com>,
        linux-mm <linux-mm@...ck.org>,
        Shakeel Butt <shakeelb@...gle.com>,
        Matthew Wilcox <willy@...radead.org>,
        Johannes Weiner <hannes@...xchg.org>,
        Tejun Heo <tj@...nel.org>, cgroups@...r.kernel.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        Wei Yang <richard.weiyang@...il.com>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Joonsoo Kim <iamjoonsoo.kim@....com>
Subject: Re: [RFC PATCH 1/3] mm: Drop locked from isolate_migratepages_block

On Wed, Aug 12, 2020 at 11:57 PM Alex Shi <alex.shi@...ux.alibaba.com> wrote:
>
>
>
> 在 2020/8/13 下午12:02, Alexander Duyck 写道:
> > From: Alexander Duyck <alexander.h.duyck@...ux.intel.com>
> >
> > We can drop the need for the locked variable by making use of the
> > lruvec_holds_page_lru_lock function. By doing this we can avoid some rcu
> > locking ugliness for the case where the lruvec is still holding the LRU
> > lock associated with the page. Instead we can just use the lruvec and if it
> > is NULL we assume the lock was released.
> >
> > Signed-off-by: Alexander Duyck <alexander.h.duyck@...ux.intel.com>
> > ---
> >  mm/compaction.c |   45 ++++++++++++++++++++-------------------------
> >  1 file changed, 20 insertions(+), 25 deletions(-)
>
> Thanks a lot!
> Don't know if community is ok if we keep the patch following whole patchset alone?

I am fine with you squashing it with another patch if you want. In
theory this could probably be squashed in with the earlier patch I
submitted that introduced lruvec_holds_page_lru_lock or some other
patch. It is mostly just a cleanup anyway as it gets us away from
needing to hold the RCU read lock in the case that we already have the
correct lruvec.