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Date: Tue, 10 Sep 2024 17:10:53 +0200
From: Christoph Hellwig <hch@lst.de>
To: Brian Foster <bfoster@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>, zlang@kernel.org, djwong@kernel.org,
	fstests@vger.kernel.org, linux-xfs@vger.kernel.org
Subject: Re: [PATCH] xfs: test log recovery for extent frees right after
 growfs
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References: <20240910043127.3480554-1-hch@lst.de> <ZuBVhszqs-fKmc9X@bfoster>
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On Tue, Sep 10, 2024 at 10:19:50AM -0400, Brian Foster wrote:
> No real issue with the test, but I wonder if we could do something more
> generic. Various XFS shutdown and log recovery issues went undetected
> for a while until we started adding more of the generic stress tests
> currently categorized in the recoveryloop group.
> 
> So for example, I'm wondering if you took something like generic/388 or
> 475 and modified it to start with a smallish fs, grew it in 1GB or
> whatever increments on each loop iteration, and then ran the same
> generic stress/timeout/shutdown/recovery sequence, would that eventually
> reproduce the issue you've fixed? I don't think reproducibility would
> need to be 100% for the test to be useful, fwiw.
> 
> Note that I'm assuming we don't have something like that already. I see
> growfs and shutdown tests in tests/xfs/group.list, but nothing in both
> groups and I haven't looked through the individual tests. Just a
> thought.

It turns out reproducing this bug was surprisingly complicated.
After a growfs we can now dip into reserves that made the test1
file start filling up the existing AGs first for a while, and thus
the error injection would hit on that and never even reach a new
AG.

So while agree with your sentiment and like the highlevel idea, I
suspect it will need a fair amount of work to actually be useful.
Right now I'm too busy with various projects to look into it
unfortunately.