linux-kernel - Re: [PATCH] mm: Fix the pgtable leak

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Date:   Mon, 18 Feb 2019 09:33:35 +0100
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Minchan Kim <minchan@...nel.org>
Cc:     linux-mm <linux-mm@...ck.org>, LKML <linux-kernel@...r.kernel.org>,
        Johannes Weiner <hannes@...xchg.org>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        Michal Hocko <mhocko@...e.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Hugh Dickins <hughd@...gle.com>,
        Liu Bo <bo.liu@...ux.alibaba.com>, stable@...r.kernel.org
Subject: Re: [PATCH] mm: Fix the pgtable leak

On Mon, Feb 18, 2019 at 05:20:26PM +0900, Minchan Kim wrote:
> On Thu, Feb 14, 2019 at 04:23:52PM +0900, Minchan Kim wrote:
> > On Wed, Feb 13, 2019 at 02:36:24PM +0100, Greg KH wrote:
> > > On Wed, Feb 13, 2019 at 08:29:00PM +0900, Minchan Kim wrote:
> > > > [1] was backported to v4.9 stable tree but it introduces pgtable
> > > > memory leak because with fault retrial, preallocated pagetable
> > > > could be leaked in second iteration.
> > > > To fix the problem, this patch backport [2].
> > > > 
> > > > [1] 5cf3e5ff95876, mm, memcg: fix reclaim deadlock with writeback
> > > 
> > > This is really commit 63f3655f9501 ("mm, memcg: fix reclaim deadlock
> > > with writeback") which was in 4.9.152, 4.14.94, 4.19.16, and 4.20.3 as
> > > well as 5.0-rc2.
> > 
> > Since 4.10, we has [2] so it should be okay other (tree > 4.10)
> > 
> > > 
> > > > [2] b0b9b3df27d10, mm: stop leaking PageTables
> > > 
> > > This commit was in 4.10, so I am guessing that this really is just a
> > > backport of that commit?
> > 
> > Yub.
> > 
> > > 
> > > If so, it's not the full backport, why not take the whole thing?  Why
> > > only cherry-pick one chunk of it?  Why do we not need the other parts?
> > 
> > Because [2] actually aims for fixing [3] which was introduced at 4.10.
> > Since then, [1] relies on the chunk I sent. Thus we don't need other part
> > for 4.9.
> > 
> > [3] 953c66c2b22a ("mm: THP page cache support for ppc64")
> 
> Hi Greg,
> 
> Any chance to look into this patch?

You sent it on Thursday, it is Monday, I tried to actually take the
weekend off :)

It's in my queue, relax, it has good company with a few other hundred
stable patches being requested...

greg k-h