Re: [PATCH] nvme: allow ANA support to be independent of native multipathing

From: Hannes Reinecke <hare@suse.de>
To: Christoph Hellwig <hch@lst.de>
Cc: Mike Snitzer <snitzer@redhat.com>,
	linux-nvme@lists.infradead.org,
	Keith Busch <keith.busch@intel.com>,
	Sagi Grimberg <sagi@grimberg.me>,
	axboe@kernel.dk, Martin Wilck <mwilck@suse.com>,
	lijie <lijie34@huawei.com>,
	xose.vazquez@gmail.com, chengjike.cheng@huawei.com,
	shenhong09@huawei.com, dm-devel@redhat.com,
	wangzhoumengjian@huawei.com, christophe.varoqui@opensvc.com,
	bmarzins@redhat.com, sschremm@netapp.com,
	linux-block@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] nvme: allow ANA support to be independent of native multipathing
Date: Fri, 16 Nov 2018 11:06:32 +0100	[thread overview]
Message-ID: <bbaf4637-209c-5cfe-2749-3fcc54f7a35f@suse.de> (raw)
In-Reply-To: <20181116094947.GA19296@lst.de>

On 11/16/18 10:49 AM, Christoph Hellwig wrote:
> On Fri, Nov 16, 2018 at 10:40:40AM +0100, Hannes Reinecke wrote:
>>>> Introduce ability to always re-read ANA log page as required due to ANA
>>>> error and make current ANA state available via sysfs -- even if native
>>>> multipathing is disabled on the host (e.g. nvme_core.multipath=N).
>>>
>>> The first part I could see, but I still want to make it conditional
>>> in some way as nvme is going into deeply embedded setups, and I don't
>>> want to carry the weight of the ANA code around for everyone.
>>>
>> Can you clarify this a bit?
>> We _do_ have the NVME multipath config option to deconfigure the whole
>> thing during compile time; that isn't influenced with this patch.
>> So are you worried about the size of the ANA implementation itself?
>> Or are you worried about the size of the ANA structures?
> 
> I just see the next step of wanting to move ANA code into the core
> which is implied above.

Really, I couldn't care less _where_ the ANA code lives.
If the size of which is any concern we can even make it configurable of 
sorts.

>>
>>> The second I fundamentally disagree with.  And even if you found agreement
>>> it would have to be in a separate patch as it is a separate feature.
>>>
>> Why? Where's the problem with re-reading the ANA log pages if we get an
>> event indicating that we should?
> 
> "second" here means the sysfs file.
> 
Ok, so would you be happy with making ANA support configurable?

Cheers,

Hannes
-- 
Dr. Hannes Reinecke		   Teamlead Storage & Networking
hare@suse.de			               +49 911 74053 688
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