Date:   Thu, 11 Nov 2021 13:05:11 +0100
From:   Jiri Pirko <jiri@resnulli.us>
To:     Jason Gunthorpe <jgg@nvidia.com>
Cc:     Jakub Kicinski <kuba@kernel.org>, Jiri Pirko <jiri@nvidia.com>,
        Leon Romanovsky <leon@kernel.org>,
        Ido Schimmel <idosch@idosch.org>,
        "David S . Miller" <davem@davemloft.net>,
        linux-kernel@vger.kernel.org, netdev@vger.kernel.org,
        edwin.peer@broadcom.com
Subject: Re: [PATCH net-next] devlink: Require devlink lock during device
 reload
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Tue, Nov 09, 2021 at 07:24:27PM CET, jgg@nvidia.com wrote:
>On Tue, Nov 09, 2021 at 08:20:42AM -0800, Jakub Kicinski wrote:
>> On Tue, 9 Nov 2021 11:33:35 -0400 Jason Gunthorpe wrote:
>> > > > I once sketched out fixing this by removing the need to hold the
>> > > > per_net_rwsem just for list iteration, which in turn avoids holding it
>> > > > over the devlink reload paths. It seemed like a reasonable step toward
>> > > > finer grained locking.  
>> > > 
>> > > Seems to me the locking is just a symptom.  
>> > 
>> > My fear is this reload during net ns destruction is devlink uAPI now
>> > and, yes it may be only a symptom, but the root cause may be unfixable
>> > uAPI constraints.
>> 
>> If I'm reading this right it locks up 100% of the time, what is a uAPI
>> for? DoS? ;)
>> 
>> Hence my questions about the actual use cases.
>
>Removing namespace support from devlink would solve the crasher. I
>certainly didn't feel bold enough to suggest such a thing :)
>
>If no other devlink driver cares about this it is probably the best
>idea.

Devlink namespace support is not generic, not related to any driver.

>
>Jason