linux-kernel - Re: [PATCH 2/4] mm: memcontrol: reign in the CONFIG space madness

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Date:	Sat, 12 Dec 2015 12:20:57 -0500
From:	Johannes Weiner <hannes@...xchg.org>
To:	Vladimir Davydov <vdavydov@...tuozzo.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Michal Hocko <mhocko@...e.cz>, linux-mm@...ck.org,
	cgroups@...r.kernel.org, linux-kernel@...r.kernel.org,
	kernel-team@...com
Subject: Re: [PATCH 2/4] mm: memcontrol: reign in the CONFIG space madness

On Sat, Dec 12, 2015 at 07:33:32PM +0300, Vladimir Davydov wrote:
> On Fri, Dec 11, 2015 at 02:54:11PM -0500, Johannes Weiner wrote:
> > What CONFIG_INET and CONFIG_LEGACY_KMEM guard inside the memory
> > controller code is insignificant, having these conditionals is not
> > worth the complication and fragility that comes with them.
> > 
> > Signed-off-by: Johannes Weiner <hannes@...xchg.org>
> 
> Acked-by: Vladimir Davydov <vdavydov@...tuozzo.com>
> 
> > @@ -4374,17 +4342,11 @@ static void mem_cgroup_css_free(struct cgroup_subsys_state *css)
> >  {
> >  	struct mem_cgroup *memcg = mem_cgroup_from_css(css);
> >  
> > -#ifdef CONFIG_INET
> >  	if (cgroup_subsys_on_dfl(memory_cgrp_subsys) && !cgroup_memory_nosocket)
> >  		static_branch_dec(&memcg_sockets_enabled_key);
> > -#endif
> > -
> > -	memcg_free_kmem(memcg);
> 
> I wonder where the second call to memcg_free_kmem comes from. Luckily,
> it couldn't result in a breakage. And now it's removed.

Lol, I had to double check my trees to see what's going on as I don't
remember this being part of the patch. But it looks like the double
free came from the "net: drop tcp_memcontrol.c" patch and I must have
removed it again during conflict resolution when rebasing this patch
on top of yours. I must have thought git's auto-merge added it.

However, this causes an underflow of the kmem static branch, so we
will have to fix this directly in "net: drop tcp_memcontrol.c".

Andrew, could you please pick this up? However, it's important to also
then remove the hunk above from THIS patch, the one that deletes the
excessive memcg_free_kmem(). We need exactly one memcg_free_kmem() in
mem_cgroup_css_free(). :-)

>From 94a14b7b0f7ed5b5ac88ca285a7e8ec3215ea59c Mon Sep 17 00:00:00 2001
From: Johannes Weiner <hannes@...xchg.org>
Date: Sat, 12 Dec 2015 12:14:31 -0500
Subject: [PATCH] net: drop tcp_memcontrol.c fix

Signed-off-by: Johannes Weiner <hannes@...xchg.org>
---
 mm/memcontrol.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 5cf7fd2..a4ce8d3 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -4386,8 +4386,6 @@ static void mem_cgroup_css_free(struct cgroup_subsys_state *css)
 		static_branch_dec(&memcg_sockets_enabled_key);
 #endif
 
-	memcg_free_kmem(memcg);
-
 	__mem_cgroup_free(memcg);
 }
 
-- 
2.6.4
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