netdev - Re: [net-next][PATCH v2 2/2] rds: add sysctl for rds support of On-Demand-Paging

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Date:   Wed, 1 May 2019 10:54:50 -0700
From:   Santosh Shilimkar <santosh.shilimkar@...cle.com>
To:     Leon Romanovsky <leon@...nel.org>
Cc:     netdev@...r.kernel.org, davem@...emloft.net
Subject: Re: [net-next][PATCH v2 2/2] rds: add sysctl for rds support of
 On-Demand-Paging

On 5/1/2019 12:45 AM, Leon Romanovsky wrote:
> On Mon, Apr 29, 2019 at 04:37:20PM -0700, Santosh Shilimkar wrote:
>> RDS doesn't support RDMA on memory apertures that require On Demand
>> Paging (ODP), such as FS DAX memory. A sysctl is added to indicate
>> whether RDMA requiring ODP is supported.
>>
>> Reviewed-by: Håkon Bugge <haakon.bugge@...cle.com>
>> Reviewed-tested-by: Zhu Yanjun <yanjun.zhu@...cle.com>
>> Signed-off-by: Hans Westgaard Ry <hans.westgaard.ry@...cle.com>
>> Signed-off-by: Santosh Shilimkar <santosh.shilimkar@...cle.com>
>> ---
>>   net/rds/ib.h        | 1 +
>>   net/rds/ib_sysctl.c | 8 ++++++++
>>   2 files changed, 9 insertions(+)
> 
> This sysctl is not needed at all
> 
Its needed for application to check the support of the ODP support
feature which in progress. Failing the RDS_GET_MR was just one path
and we also support inline MR registration along with message request.

Basically application runs on different kernel versions and to be
portable, it will check if underneath RDS support ODP and then only
use RDMA. If not it will fallback to buffer copy mode. Hope
it clarifies.


Regards,
Santosh