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Subject: Re: [PATCH v1 1/4] xprtrdma: Remove support for FMR memory
 registration
From:   Chuck Lever <chuck.lever@oracle.com>
In-Reply-To: <20181119224143.GL4890@ziepe.ca>
Date:   Mon, 19 Nov 2018 17:56:54 -0500
Cc:     Bart Van Assche <bvanassche@acm.org>,
        linux-rdma <linux-rdma@vger.kernel.org>,
        Linux NFS Mailing List <linux-nfs@vger.kernel.org>,
        Lijun Ou <oulijun@huawei.com>, umalhi@cisco.com,
        zhongjiang@huawei.com, venkata.s.dhanalakota@intel.com,
        Dennis Dalessandro <dennis.dalessandro@intel.com>
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Message-Id: <1172062C-E8CB-4F37-905D-F40EC8D9270C@oracle.com>
References: <20181119153707.10832.42881.stgit@manet.1015granger.net>
 <20181119154551.10832.5498.stgit@manet.1015granger.net>
 <1542644197.185366.50.camel@acm.org> <20181119224143.GL4890@ziepe.ca>
To:     Jason Gunthorpe <jgg@ziepe.ca>
Sender: linux-nfs-owner@vger.kernel.org
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> On Nov 19, 2018, at 5:41 PM, Jason Gunthorpe <jgg@ziepe.ca> wrote:
>=20
> On Mon, Nov 19, 2018 at 08:16:37AM -0800, Bart Van Assche wrote:
>> On Mon, 2018-11-19 at 10:45 -0500, Chuck Lever wrote:
>>> FMR is not supported on most recent RDMA devices. It is also slower
>>> and less secure than FRWR. As discussed during the RDMA BoF at LPC
>>> 2018, it is time to remove support for FMR in the NFS/RDMA client
>>> stack. NFS/RDMA server-side uses either local memory registration or
>>> FRWR.  There is no change required there to deprecate FMR.
>>>=20
>>> There are a few Infiniband/RoCE devices in the kernel tree that do
>>> not support MEM_MGT_EXTENSIONS, and therefore will no longer support
>>> client-side NFS/RDMA. These are:
>>>=20
>>> - mthca
>>> - qib
>=20
> Ooh, qib was not in the list when we talked on this in plumbers. That
> does change things.=20
>=20
> Dennis: Could qib be changed? HFI1 supports FRWR right?
>=20
>>> - usnic
>>> - hns (RoCE)
>>=20
>> Can someone from Intel comment on how many of their customers rely on =
the qib
>> driver?
>>=20
>> Can someone from Cisco comment on how many of their customers rely on =
the usnic
>> driver?
>=20
> Ignore usnic, it is not a RDMA driver
>=20
>> Can someone from Huawei comment on how many of their customers rely =
on the hns
>> driver?
>=20
> Nor was this, this is an actively used driver..
>=20
> Could hns do FRWR? It is very disappointing that such a new driver
> does not support FRWR.
>=20
> I guess it is worth stating again that FMR is deprecated. People are
> going to be disappointed if they try to submit new drivers that don't
> support FRWR :(

My methodology was to search for whether each driver asserts
IB_DEVICE_MEM_MGT_EXTENSIONS in device_cap_flags.

Interestingly, nes and ocrdma assert it, but qib and hns do not.


--
Chuck Lever