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List:       linux-xfs
Subject:    Re: [PATCHSET v2 0/2] fstests: fix cpu hotplug mess
From:       Dave Chinner <david () fromorbit ! com>
Date:       2023-08-30 22:57:09
Message-ID: ZO/JRddbU8llvrs4 () dread ! disaster ! area
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On Tue, Aug 29, 2023 at 04:07:52PM -0700, Darrick J. Wong wrote:
> Hi all,
> 
> Ritesh and Eric separately reported crashes in XFS's hook function for
> CPU hot remove if the remove event races with a filesystem being
> mounted.  I also noticed via generic/650 that once in a while the log
> will shut down over an apparent overrun of a transaction reservation;
> this turned out to be due to CIL percpu list aggregation failing to pick
> up the percpu list items from a dying CPU.
> 
> Either way, the solution here is to eliminate the need for a CPU dying
> hook by using a private cpumask to track which CPUs have added to their
> percpu lists directly, and iterating with that mask.  This fixes the log
> problems and (I think) solves a theoretical UAF bug in the inodegc code
> too.
> 
> v2: fix a few put_cpu uses, add necessary memory barriers, and use
>     atomic cpumask operations
> 
> If you're going to start using this code, I strongly recommend pulling
> from my git trees, which are linked below.
> 
> This has been running on the djcloud for months with no problems.  Enjoy!
> Comments and questions are, as always, welcome.

These changes look good.

Reviewed-by: Dave Chinner <dchinner@redhat.com>

-- 
Dave Chinner
david@fromorbit.com
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