Re: [PATCH 2/2] ext4: implement cgroup writeback support

[Artem Bityutskiy <dedekind1@gmail.com>]

On Wed, 2015-09-23 at 16:48 -0400, Theodore Ts'o wrote:
> On Wed, Sep 23, 2015 at 10:47:16PM +0300, Artem Bityutskiy wrote:
> > And, by the way, I forgot this detail - I cut AC power off at the
> > end, then put it back on after a 20 seconds delay. I mean, this is
> > a
> > clean reboot, but with power cut at the end.
> 
> Is this reproducible without the power cut?  And what model SSD are
> you using, and are you sure that it has Power Loss Protection (many
> SSD vendors use power loss protection as the price discrimination
> feature between consumer-grade SSD and enterprise-grade SSD's that
> cost $$$).  If this problem wasn't showing up with 4.2, and is only
> failing with 4.3-rcX, then it might not be a hardware issue --- but
> it's also possible that there was a timing issue which was hiding a
> hardware problem.  So for the purposes of debugging, removing the
> power cut from the set of variables is a useful thing to do.

Ted, you are right that the problem may be anywhere, but since Tejun's
patch fixes it, I decided to not spend time on testing without AC power
cuts.

But I checked and on of my boxes uses an HDD, and it shows the same
problem, which makes the theory of imperfect SSD firmware being
involved less likely.

Thanks,
Artem.