lists  /  announce  owl-users  owl-dev  john-users  john-dev  passwdqc-users  yescrypt  popa3d-users  /  oss-security  kernel-hardening  musl  sabotage  tlsify  passwords  /  crypt-dev  xvendor  /  Bugtraq  Full-Disclosure  linux-kernel  linux-netdev  linux-ext4  PHC 
Open Source and information security mailing list archives
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date:	Thu, 24 Sep 2015 10:17:19 -0600
From:	Jens Axboe <>
To:	Tejun Heo <>, Artem Bityutskiy <>
CC:	"Theodore Ts'o" <>, <>,
	<>, <>,
	<>, <>,
	<>, <>,
	<>, <>,
	Dexuan Cui <>
Subject: Re: [PATCH cgroup/for-4.3-fixes] cgroup, writeback: don't enable
 cgroup writeback on traditional hierarchies

On 09/23/2015 03:07 PM, Tejun Heo wrote:
> inode_cgwb_enabled() gates cgroup writeback support.  If it returns
> true, each inode is attached to the corresponding memory domain which
> gets mapped to io domain.  It currently only tests whether the
> filesystem and bdi support cgroup writeback; however, cgroup writeback
> support doesn't work on traditional hierarchies and thus it should
> also test whether memcg and iocg are on the default hierarchy.
> This caused traditional hierarchy setups to hit the cgroup writeback
> path inadvertently and ended up creating separate writeback domains
> for each memcg and mapping them all to the root iocg uncovering a
> couple issues in the cgroup writeback path.
> cgroup writeback was never meant to be enabled on traditional
> hierarchies.  Make inode_cgwb_enabled() test whether both memcg and
> iocg are on the default hierarchy.
> Signed-off-by: Tejun Heo <>
> Reported-by: Artem Bityutskiy <>
> Reported-by: Dexuan Cui <>
> Link:
> Link:
> ---
> Hello,
> So, this should make the regression go away.  It doesn't fix the
> underlying bugs but they shouldn't get triggered by people not
> experimenting with cgroup.
> I'm gonna keep digging the underlying issues but this should make the
> regressions go away.  If it's okay, I think it'd be better to route
> this through cgroup/for-4.3-fixes as it's gonna cause a conflict with
> for-4.4 branch and handling the merge there is easier.
> Thanks.
>   include/linux/backing-dev.h |   11 +++++++++--
>   1 file changed, 9 insertions(+), 2 deletions(-)

I'll ack this since it works around both the corruption issue and the 
performance regression, so we can avoid having to revert parts of this. 
And I know you'll keep hunting and get the real issue fixed in the mean 

Acked-by: Jens Axboe <>

Jens Axboe

To unsubscribe from this list: send the line "unsubscribe linux-ext4" in
the body of a message to
More majordomo info at

Powered by blists - more mailing lists