Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Date:   Thu, 1 Feb 2018 23:42:33 +0000
From:   Roman Gushchin <guro@fb.com>
To:     Eric Dumazet <edumazet@google.com>
CC:     "David S. Miller" <davem@davemloft.net>,
        netdev <netdev@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>,
        kernel-team <kernel-team@fb.com>,
        Johannes Weiner <hannes@cmpxchg.org>, Tejun Heo <tj@kernel.org>
Subject: Re: [PATCH net] net: memcontrol: charge allocated memory after
 mem_cgroup_sk_alloc()
Message-ID: <20180201234226.GA14400@castle>
References: <20180125001911.15597-1-guro@fb.com>
 <20180125.120302.1117695034222616751.davem@davemloft.net>
 <20180131215401.GA8956@castle>
 <20180201.101655.1316424669256047119.davem@davemloft.net>
 <20180201202158.GA11477@castle.DHCP.thefacebook.com>
 <CANn89iLBOUZNxNqrECvZ7ktX8uu0j3REiZaqTwr=SP-U=vAPpQ@mail.gmail.com>
 <20180201225542.GA13072@castle>
 <CANn89i+mTRsYDikt9VhfbdHo1f5F5tXbZj54679nY_Fy1QS1Vg@mail.gmail.com>
MIME-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-Disposition: inline
In-Reply-To: <CANn89i+mTRsYDikt9VhfbdHo1f5F5tXbZj54679nY_Fy1QS1Vg@mail.gmail.com>
User-Agent: Mutt/1.9.1 (2017-09-22)
Received-SPF: None (protection.outlook.com: fb.com does not designate
 permitted sender hosts)
SpamDiagnosticOutput: 1:99
SpamDiagnosticMetadata: NSPM
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 01 Feb 2018 23:42:45.7394 (UTC)
X-MS-Exchange-CrossTenant-Network-Message-Id: 4b09be9b-2150-4c3c-5bc2-08d569cd7fcf
X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted
X-MS-Exchange-CrossTenant-Id: 8ae927fe-1255-47a7-a2af-5f3a069daaa2
X-MS-Exchange-Transport-CrossTenantHeadersStamped: SN2PR15MB1088
X-OriginatorOrg: fb.com
X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2018-02-01_07:,,
 signatures=0
X-Proofpoint-Spam-Reason: safe
X-FB-Internal: Safe
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On Thu, Feb 01, 2018 at 03:27:14PM -0800, Eric Dumazet wrote:
> Well, this memcg stuff is so confusing.
> 
> My recollection is that we had :
> 
> 
> https://git.kernel.org/pub/scm/linux/kernel/git/davem/net.git/commit/?id=d979a39d7242e0601bf9b60e89628fb8ac577179
> 
> https://git.kernel.org/pub/scm/linux/kernel/git/davem/net.git/commit/?id=75cb070960ade40fba5de32138390f3c85c90941
> 
> https://git.kernel.org/pub/scm/linux/kernel/git/davem/net.git/commit/?id=c0576e3975084d4699b7bfef578613fb8e1144f6
> 
> And commit a590b90d472f2c176c140576ee3ab44df7f67839 as well
> 
> Honestly bug was closed months ago for us, based on stack traces on the wild.
> 
> No C repro or whatever, but reproducing it would be a matter of
> having a TCP listener constantly doing a
> socket()/setsockopt(REUSEADDR)/bind()/listen()/close() in a loop,
> while connections are attempted to the listening port.

Oh, I see...

Then I think that we should return memcg_sk_alloc() back to the bh context,
where cgroup_sk_alloc() is, and repeat all the tricks to avoid copying
dead cgroups/memcg pointers. Do you agree?

I'll try to master a patch and reproduce the issue.

Thanks!