Re: [PATCH 0/8 v1] Remove FMR support from RDMA drivers

From: Dennis Dalessandro <dennis.dalessandro@intel.com>
To: Jason Gunthorpe <jgg@mellanox.com>
Cc: Leon Romanovsky <leon@kernel.org>,
	Max Gurtovoy <maxg@mellanox.com>,
	bvanassche@acm.org, linux-rdma@vger.kernel.org,
	dledford@redhat.com, sagi@grimberg.me, israelr@mellanox.com,
	shlomin@mellanox.com, "Marciniszyn,
	Mike" <mike.marciniszyn@intel.com>
Subject: Re: [PATCH 0/8 v1] Remove FMR support from RDMA drivers
Date: Tue, 19 May 2020 10:37:07 -0400	[thread overview]
Message-ID: <5563b8da-faf3-1af5-33d0-fe5a6d7291a1@intel.com> (raw)
In-Reply-To: <20200519143030.GA23839@mellanox.com>

On 5/19/2020 10:30 AM, Jason Gunthorpe wrote:
> On Tue, May 19, 2020 at 10:26:37AM -0400, Dennis Dalessandro wrote:
>> On 5/19/2020 10:19 AM, Leon Romanovsky wrote:
>>> On Tue, May 19, 2020 at 10:53:52AM -0300, Jason Gunthorpe wrote:
>>>> On Tue, May 19, 2020 at 09:43:14AM -0400, Dennis Dalessandro wrote:
>>>>> On 5/18/2020 2:10 PM, Jason Gunthorpe wrote:
>>>>>> On Mon, May 18, 2020 at 11:20:04AM -0400, Dennis Dalessandro wrote:
>>>>>>> On 5/14/2020 8:02 AM, Max Gurtovoy wrote:
>>>>>>>> This series removes the support for FMR mode to register memory. This ancient
>>>>>>>> mode is unsafe and not maintained/tested in the last few years. It also doesn't
>>>>>>>> have any reasonable advantage over other memory registration methods such as
>>>>>>>> FRWR (that is implemented in all the recent RDMA adapters). This series should
>>>>>>>> be reviewed and approved by the maintainer of the effected drivers and I
>>>>>>>> suggest to test it as well.
>>>>>>>>
>>>>>>>> The tests that I made for this series (fio benchmarks and fio verify data):
>>>>>>>> 1. iSER initiator on ConnectX-4
>>>>>>>> 2. iSER initiator on ConnectX-3
>>>>>>>> 3. SRP initiator on ConnectX-4 (loopback to SRP target)
>>>>>>>> 4. SRP initiator on ConnectX-3
>>>>>>>>
>>>>>>>> Not tested:
>>>>>>>> 1. RDS
>>>>>>>> 2. mthca
>>>>>>>> 3. rdmavt
>>>>>>>
>>>>>>> This will effectively kill qib which uses rdmavt. It's gonna have to be a
>>>>>>> NAK from me.
>>>>>>
>>>>>> Are you objecting the SRP and iSER changes too?
>>>>>
>>>>> No, just want to keep basic verbs support at least. NFS already dropped,
>>>>> similarly we are ok with dropping it from SRP/iSER as a next step.
>>>>
>>>> So you see a major user in RDS for qib?
>>>
>>> Didn't we agree to drop it from RDS too?
>>>
>>
>> Just basic verbs application support is enough for qib I think. I don't see
>> any major use of RDS.
> 
> Well, once the in-kernel users of an API are gone that API will be
> purged. This is standard kernel policy.
> 
> So you can't NAK this series on the grounds you want to keep an API
> without users, presumably for out of tree modules...
> 

Maybe I need to look at this again. I thought it would kill off user 
access as well. We don't need any kernel ULPs.

-Denny