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

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Message-ID: <20181116094947.GA19296@lst.de>
Date:   Fri, 16 Nov 2018 10:49:47 +0100
From:   Christoph Hellwig <hch@....de>
To:     Hannes Reinecke <hare@...e.de>
Cc:     Christoph Hellwig <hch@....de>, Mike Snitzer <snitzer@...hat.com>,
        linux-nvme@...ts.infradead.org,
        Keith Busch <keith.busch@...el.com>,
        Sagi Grimberg <sagi@...mberg.me>, axboe@...nel.dk,
        Martin Wilck <mwilck@...e.com>, lijie <lijie34@...wei.com>,
        xose.vazquez@...il.com, chengjike.cheng@...wei.com,
        shenhong09@...wei.com, dm-devel@...hat.com,
        wangzhoumengjian@...wei.com, christophe.varoqui@...nsvc.com,
        bmarzins@...hat.com, sschremm@...app.com,
        linux-block@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] nvme: allow ANA support to be independent of native
 multipathing

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.
>
>> 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.