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Date:   Thu, 7 Apr 2022 10:14:53 +1000
From:   Dave Chinner <david@fromorbit.com>
To:     "J. Bruce Fields" <bfields@fieldses.org>
Cc:     Chuck Lever <chuck.lever@oracle.com>, linux-nfs@vger.kernel.org,
        linux-fsdevel@vger.kernel.org
Subject: Re: sporadic hangs on generic/186
Message-ID: <20220407001453.GE1609613@dread.disaster.area>
References: <20220406195424.GA1242@fieldses.org>
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On Wed, Apr 06, 2022 at 03:54:24PM -0400, J. Bruce Fields wrote:
> In the last couple days I've started getting hangs on xfstests
> generic/186 on upstream.  I also notice the test completes after 10+
> hours (usually it takes about 5 minutes).  Sometimes this is accompanied
> by "nfs: RPC call returned error 12" on the client.

#define ENOMEM          12      /* Out of memory */

So either the client or the server is running out of memory
somewhere?

> Test description is:
> 
> # Ensuring that copy on write in buffered mode works when free space
> # is heavily fragmented.
> #   - Create two files
> #   - Reflink the odd blocks of the first file into a third file.
> #   - Reflink the even blocks of the second file into the third file.
> #   - Try to fragment the free space by allocating a huge file and
> #     punching out every other block.
> #   - CoW across the halfway mark.
> #   - Check that the files are now different where we say they're
> #   different.

It's using clone_file_range and hole punch, so I'm assuming that
this is nfsv4 client side testing? In which case, the behaviour is
going to be largely dependent on the server side implementation of
these functions? Does reverting the client or the server to an older
kernel resolve the issue?

Cheers,

Dave.
-- 
Dave Chinner
david@fromorbit.com