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Re: [PATCH] mm: memcontrol: do not recurse in direct reclaim

From Johannes Weiner <hannes@cmpxchg.org>
Newsgroups linux.kernel
Subject Re: [PATCH] mm: memcontrol: do not recurse in direct reclaim
Date 2016-10-25 17:10 +0200
Message-ID <swbwt-7hI-29@gated-at.bofh.it> (permalink)
References <svUci-4bt-25@gated-at.bofh.it> <sw5U5-3BL-9@gated-at.bofh.it> <swaK5-6KY-1@gated-at.bofh.it> <swbd8-6Vq-21@gated-at.bofh.it>
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On Tue, Oct 25, 2016 at 04:45:44PM +0200, Michal Hocko wrote:
> On Tue 25-10-16 10:10:50, Johannes Weiner wrote:
> > Like other direct reclaimers, mark tasks in memcg reclaim PF_MEMALLOC
> > to avoid recursing into any other form of direct reclaim. Then let
> > recursive charges from PF_MEMALLOC contexts bypass the cgroup limit.
> 
> Should we mark this for stable (up to 4.5) which changed the out-out to
> opt-in?

Yes, good point.

Internally, we're pulling it into our 4.6 tree as well. The commit
that fixes the particular bug we encountered in btrfs is a9bb7e620efd
("memcg: only account kmem allocations marked as __GFP_ACCOUNT") in
4.5+, so you could argue that we don't need the backport in kernels
with this commit. And I'm not aware of other manifestations of this
problem. But the unbounded recursion hole is still there, technically,
so we might just want to put it into all stable kernels and be safe.

So either

Cc: <stable@vger.kernel.org>	# up to and including 4.5

or, and I'm leaning toward that, simply

Cc: <stable@vger.kernel.org>

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Thread

[PATCH] mm: memcontrol: do not recurse in direct reclaim Johannes Weiner <hannes@cmpxchg.org> - 2016-10-24 22:40 +0200
  Re: [PATCH] mm: memcontrol: do not recurse in direct reclaim Michal Hocko <mhocko@kernel.org> - 2016-10-25 11:10 +0200
    Re: [PATCH] mm: memcontrol: do not recurse in direct reclaim Johannes Weiner <hannes@cmpxchg.org> - 2016-10-25 16:20 +0200
      Re: [PATCH] mm: memcontrol: do not recurse in direct reclaim Michal Hocko <mhocko@kernel.org> - 2016-10-25 16:50 +0200
        Re: [PATCH] mm: memcontrol: do not recurse in direct reclaim Johannes Weiner <hannes@cmpxchg.org> - 2016-10-25 17:10 +0200
          Re: [PATCH] mm: memcontrol: do not recurse in direct reclaim Michal Hocko <mhocko@kernel.org> - 2016-10-25 17:10 +0200

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