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List:       linux-xfs
Subject:    Re: [RFC PATCH] xfs/179: modify test to trigger refcount update bugs
From:       Yang, Xiao/杨 晓 <yangx.jy () fujitsu ! com>
Date:       2022-11-30 10:07:14
Message-ID: 480d7699-5971-9125-0669-a4e77b641c5b () fujitsu ! com
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On 2022/11/30 6:06, Darrick J. Wong wrote:
> From: Darrick J. Wong<djwong@kernel.org>
> 
> Upon enabling fsdax + reflink for XFS, this test began to report
> refcount metadata corruptions after being run.  Specifically, xfs_repair
> noticed single-block refcount records that could be combined but had not
> been.
> 
> The root cause of this is improper MAXREFCOUNT edge case handling in
> xfs_refcount_merge_extents.  When we're trying to find candidates for a
> record merge, we compute the refcount of the merged record, but without
> accounting for the fact that once a record hits rc_refcount ==
> MAXREFCOUNT, it is pinned that way forever.
> 
> Adjust this test to use a sub-filesize write for one of the COW writes,
> because this is how we force the extent merge code to run.
Hi Darrick,

Cool, it is reliable to reproduce the same issue in non-DAX mode.
Reviewed-by: Xiao Yang <yangx.jy@fujitsu.com>
Tested-by: Xiao Yang <yangx.jy@fujitsu.com>

Best Regards,
Xiao Yang
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