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Date:   Tue, 8 Jun 2021 13:20:15 -0400
To:     Frank van der Linden <fllinden@amazon.com>
Cc:     Wang Yugui <wangyugui@e16-tech.com>, linux-nfs@vger.kernel.org
Subject: Re: nfsd dead loop when xfstests generic/531
Message-ID: <20210608172015.GB22685@fieldses.org>
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 <20210601165535.GA3102@dev-dsk-fllinden-2c-d7720709.us-west-2.amazon.com>
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From:   bfields@fieldses.org (J. Bruce Fields)
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On Tue, Jun 01, 2021 at 04:55:35PM +0000, Frank van der Linden wrote:
> On Mon, May 31, 2021 at 12:59:51PM +0800, Wang Yugui wrote:
> > 
> > 
> > Hi,
> > 
> > nfsd dead loop when xfstests generic/531
> > 
> > linux kernel of nfs server: 5.10.41
> > linux kernel of nfs client: 5.10.41
> > 
> > 
> > nfsd dead loop when xfstests generic/531
> > 
> > linux kernel of nfs server: 5.10.41
> > linux kernel of nfs client: 5.10.41
> 
> This is a known issue. generic/531 opens a large number of files, causing
> the nfsd file cache code to walk a very long LRU list of open files. For
> v4, there will be a lot of long term opens (because of the OPEN call),
> and they all end up on that list.
> 
> So, the basic issue is, that the nfsd file cache is a good match for
> v3 semantics, but less so for v4 semantics.
> 
> I posted an experimental patch to work around the issue:
> 
> https://lore.kernel.org/linux-nfs/20201020183718.14618-4-trondmy@kernel.org/T/#m869aa427f125afee2af9a89d569c6b98e12e516f
> 
> The rhashtable patch has issues, so disregard that one, but the other one
> is a basic fix for this issue. It has one other issue that I noticed (refcount
> error), but that is easily fixed.
> 
> I should update the patch and formally post it..

That would be great.

--b.