From: Tejun Heo <tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
To: Benjamin Berg <benjamin-cdvu00un1VgdHxzADdlk8Q@public.gmane.org>
Cc: cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
Subject: Re: [BUG] NULL pointer de-ref when setting io.cost.qos on LUKS devices
Date: Wed, 4 Mar 2020 11:42:05 -0500 [thread overview]
Message-ID: <20200304164205.GH189690@mtj.thefacebook.com> (raw)
In-Reply-To: <24bd31cdaa3ea945908bc11cea05d6aae6929240.camel-cdvu00un1VgdHxzADdlk8Q@public.gmane.org>
Hello, Benjamin.
On Tue, Mar 03, 2020 at 03:40:38PM +0100, Benjamin Berg wrote:
> I believe systemd tries to resolve to /dev/sda but that seems to fail
> for me. So I think there is a bug in that code; I'll verify that and
> submit a fix if so.
>
> Which device should actually be selected? Is it /dev/sda or the mapper
> device that / is mounted from?
Right now, the situation isn't great with dm. When pagecache
writebacks go through dm, in some cases including dm-crypt, the cgroup
ownership information is completely lost and all writes end up being
issued as the root cgroup, so it breaks down when dm is in use.
In the longer term, what we wanna do is controlling at physical
devices (sda here) and then updating dm so that it can maintain and
propagate the ownership correctly but we aren't there yet.
Thanks.
--
tejun
next prev parent reply other threads:[~2020-03-04 16:42 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-03 14:13 [BUG] NULL pointer de-ref when setting io.cost.qos on LUKS devices Benjamin Berg
[not found] ` <1dbdcbb0c8db70a08aac467311a80abcf7779575.camel-cdvu00un1VgdHxzADdlk8Q@public.gmane.org>
2020-03-03 14:19 ` Tejun Heo
[not found] ` <20200303141902.GB189690-146+VewaZzwNjtGbbfXrCEEOCMrvLtNR@public.gmane.org>
2020-03-03 14:40 ` Benjamin Berg
[not found] ` <24bd31cdaa3ea945908bc11cea05d6aae6929240.camel-cdvu00un1VgdHxzADdlk8Q@public.gmane.org>
2020-03-04 16:42 ` Tejun Heo [this message]
[not found] ` <20200304164205.GH189690-146+VewaZzwNjtGbbfXrCEEOCMrvLtNR@public.gmane.org>
2020-03-05 10:31 ` Benjamin Berg
[not found] ` <71515f7a143937ab9ab11625485659bb7288f024.camel-cdvu00un1VgdHxzADdlk8Q@public.gmane.org>
2020-03-05 15:20 ` Tejun Heo
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