Subject: [Bug 207359] MegaRAID SAS 9361 controller hang/reset

From: [email-masked]
Date: Thu, 06 Aug 2020 17:56:24 +0000

https://bugzilla.kernel.org/show_bug.cgi?id=207359

--- Comment #4 from Cameron ([email-masked]) ---
I converted the box's filesystems from BTRFS to XFS, and switched the page size
from 4k to 64k. The problem appears to be entirely gone now. I am able to
conclusively run 5.7.13 without issue, which I verified as having the
megaraid_sas controller hang problem while still running my previous BTRFS+4k
page configuration.

Unfortunately, it took a great deal of time to perform this conversion, and I
wasn't able to keep the box down even longer to test if converting to XFS and
64k pages individually resolved the issue. All I can say for certain is that
either switching to XFS, to a 64k page size, or both has fixed the problem for
me.

The backup volume is a single SATA disk that is still using BTRFS (for
snapshotting), and is not giving me any trouble. But if this has any relation
to https://bugzilla.kernel.org/show_bug.cgi?id=206123, then this may not be
conclusive due to being that SATA disks potentially may not trigger the issue.
The single disk also can't push as much IO as the RAID10 volume so that may be
another reason.

My quasi educated non-kernel-dev guess is that this is probably a bug relating
to the 4k page size. Whether or not the regular behavior of BTRFS exacerbates
this (making it easier to reproduce), is possible, but unknown.

Hopefully someone else encountering this issue will find this helpful.

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