Received-SPF: softfail (google.com: domain of transitioning linux-nfs-owner@vger.kernel.org does not designate 23.128.96.19 as permitted sender) client-ip=23.128.96.19;
Date:   Wed, 1 Jun 2022 19:05:48 -0400
To:     Frank van der Linden <fllinden@amazon.com>
Cc:     Chuck Lever III <chuck.lever@oracle.com>,
        Wang Yugui <wangyugui@e16-tech.com>,
        Linux NFS Mailing List <linux-nfs@vger.kernel.org>,
        Matthew Wilcox <matthew.wilcox@oracle.com>,
        Liam Howlett <liam.howlett@oracle.com>
Subject: Re: filecache LRU performance regression
Message-ID: <20220601230548.GA29667@fieldses.org>
References: <5C7024DA-A792-4091-BFDE-CEED59BC1B69@oracle.com>
 <20220527203721.GA10628@dev-dsk-fllinden-2c-d7720709.us-west-2.amazon.com>
 <ADD1751A-7F67-4729-BFFC-D6938CA963A0@oracle.com>
 <BED36887-054D-4DC9-A5F1-CB6DD1F0DC16@oracle.com>
 <20220601161003.GA20483@dev-dsk-fllinden-2c-d7720709.us-west-2.amazon.com>
 <4C14DB3A-A5C1-41A9-8293-DF4FC2459600@oracle.com>
 <20220601211827.GA11605@dev-dsk-fllinden-2c-d7720709.us-west-2.amazon.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20220601211827.GA11605@dev-dsk-fllinden-2c-d7720709.us-west-2.amazon.com>
User-Agent: Mutt/1.5.21 (2010-09-15)
From:   bfields@fieldses.org (J. Bruce Fields)
Precedence: bulk

On Wed, Jun 01, 2022 at 09:18:27PM +0000, Frank van der Linden wrote:
> A related issue: there is currently no upper limit that I can see
> on the number of active OPENs for a client. So essentially, a
> client can run a server out of resources by doing a very large
> number of OPENs.
> 
> Should there be an upper limit, above which requests are either
> denied, or old state is invalidated?

Could be, if only to prevent abuse.  It doesn't seem to be a problem
people hit in practice, though.

Delegations add a bit of a wrinkle, as they allow the client do do opens
and locks locally without limit, and denying them during recovery from a
delegation break is ugly.

--b.