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Subject: Re: [LSF/MM TOPIC] Discuss least bad options for resolving
 longterm-GUP usage by RDMA
From:   Chuck Lever <chuck.lever@oracle.com>
In-Reply-To: <20190207052310.GA22726@ziepe.ca>
Date:   Thu, 7 Feb 2019 10:04:55 -0500
Cc:     Dave Chinner <david@fromorbit.com>,
        Doug Ledford <dledford@redhat.com>,
        Christopher Lameter <cl@linux.com>,
        Matthew Wilcox <willy@infradead.org>, Jan Kara <jack@suse.cz>,
        Ira Weiny <ira.weiny@intel.com>,
        lsf-pc@lists.linux-foundation.org,
        linux-rdma <linux-rdma@vger.kernel.org>, linux-mm@kvack.org,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        John Hubbard <jhubbard@nvidia.com>,
        Jerome Glisse <jglisse@redhat.com>,
        Dan Williams <dan.j.williams@intel.com>,
        Michal Hocko <mhocko@kernel.org>
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To:     Jason Gunthorpe <jgg@ziepe.ca>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk


> On Feb 7, 2019, at 12:23 AM, Jason Gunthorpe <jgg@ziepe.ca> wrote:
> 
> On Thu, Feb 07, 2019 at 02:52:58PM +1100, Dave Chinner wrote:
> 
>> Requiring ODP capable hardware and applications that control RDMA
>> access to use file leases and be able to cancel/recall client side
>> delegations (like NFS is already able to do!) seems like a pretty
> 
> So, what happens on NFS if the revoke takes too long?

NFS distinguishes between "recall" and "revoke". Dave used "recall"
here, it means that the server recalls the client's delegation. If
the client doesn't respond, the server revokes the delegation
unilaterally and other users are allowed to proceed.


--
Chuck Lever