linux-kernel - Re: [PATCH v8 11/12] zram: fix crashes with cpu hotplug multistate

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Date:   Fri, 15 Oct 2021 10:31:31 -0700
From:   Luis Chamberlain <mcgrof@...nel.org>
To:     Ming Lei <ming.lei@...hat.com>
Cc:     tj@...nel.org, gregkh@...uxfoundation.org,
        akpm@...ux-foundation.org, minchan@...nel.org, jeyu@...nel.org,
        shuah@...nel.org, bvanassche@....org, dan.j.williams@...el.com,
        joe@...ches.com, tglx@...utronix.de, keescook@...omium.org,
        rostedt@...dmis.org, linux-spdx@...r.kernel.org,
        linux-doc@...r.kernel.org, linux-block@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, linux-kselftest@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v8 11/12] zram: fix crashes with cpu hotplug multistate

On Fri, Oct 15, 2021 at 04:36:11PM +0800, Ming Lei wrote:
> On Thu, Oct 14, 2021 at 05:22:40PM -0700, Luis Chamberlain wrote:
> > On Fri, Oct 15, 2021 at 07:52:04AM +0800, Ming Lei wrote:
> ...
> > > 
> > > We need to understand the exact reason why there is still cpuhp node
> > > left, can you share us the exact steps for reproducing the issue?
> > > Otherwise we may have to trace and narrow down the reason.
> > 
> > See my commit log for my own fix for this issue.
> 
> OK, thanks!
> 
> I can reproduce the issue, and the reason is that reset_store fails
> zram_remove() when unloading module, then the warning is caused.
> 
> The top 3 patches in the following tree can fix the issue:
> 
> https://github.com/ming1/linux/commits/my_v5.15-blk-dev

Thanks for trying an alternative fix! A crash stops yes, however this
also ends up leaving the driver in an unrecoverable state after a few
tries. Ie, you CTRL-C the scripts and try again over and over again and
the driver ends up in a situation where it just says:

zram: Can't change algorithm for initialized device

And the zram module can't be removed at that point.

  Luis