linux-kernel - Re: [PATCH] nvme: make controller 'state' sysfs attribute pollable

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Message-ID: <20170921051915.cfj2j5vu4bjqn5za@linux-x5ow.site>
Date:   Thu, 21 Sep 2017 07:19:15 +0200
From:   Johannes Thumshirn <jthumshirn@...e.de>
To:     Christoph Hellwig <hch@....de>
Cc:     Sagi Grimberg <sagi@...mberg.me>,
        Keith Busch <keith.busch@...el.com>,
        Hannes Reinecke <hare@...e.de>,
        Linux NVMe Mailinglist <linux-nvme@...ts.infradead.org>,
        Linux Kernel Mailinglist <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] nvme: make controller 'state' sysfs attribute pollable

On Wed, Sep 20, 2017 at 04:59:31PM +0200, Christoph Hellwig wrote:
> On Wed, Sep 20, 2017 at 12:40:32PM +0200, Johannes Thumshirn wrote:
> > Notify sysfs about changes of a nvme controller so user-space can watch the
> > file via poll() or select() in order to react to a state change.
> 
> Userspace has no business polling for the state.

So why exposing it then in the first time? I know you don't want dm-mpath in
NVMe (neither do I) but we have to have something until your patchset and ANA
is merged. And with this patch it's trivial to build a path checker that just
looks at the state attribute in sysfs.

-- 
Johannes Thumshirn                                          Storage
jthumshirn@...e.de                                +49 911 74053 689
SUSE LINUX GmbH, Maxfeldstr. 5, 90409 Nürnberg
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