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Subject: Re: [PATCH v2 3/3] nvme: fire discovery log page change events to
 userspace
To:     Christoph Hellwig <hch@lst.de>
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        linux-nvme@lists.infradead.org,
        Keith Busch <keith.busch@intel.com>,
        James Smart <james.smart@broadcom.com>,
        linux-kernel@vger.kernel.org, Hannes Reinecke <hare@suse.de>
References: <20190712180211.26333-1-sagi@grimberg.me>
 <20190712180211.26333-4-sagi@grimberg.me> <20190822002328.GP9511@lst.de>
 <205d06ab-fedc-739d-323f-b358aff2cbfe@grimberg.me>
 <e4603511-6dae-e26d-12a9-e9fa727a8d03@grimberg.me>
 <20190826065639.GA11036@lst.de> <20190826075916.GA30396@kroah.com>
 <ac168168-fed2-2b57-493e-e88261ead73b@grimberg.me>
 <20190830055514.GC8492@lst.de>
From:   Sagi Grimberg <sagi@grimberg.me>
Message-ID: <4555a281-3cbc-0890-ce85-385c06ca912b@grimberg.me>
Date:   Fri, 30 Aug 2019 11:08:19 -0700
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>>> Yes we do, userspace should use it to order events.  Does udev not
>>> handle that properly today?
>>
>> The problem is not ordering of events, its really about the fact that
>> the chardev can be removed and reallocated for a different controller
>> (could be a completely different discovery controller) by the time
>> that userspace handles the event.
> 
> The same is generally true for lot of kernel devices.  We could reduce
> the chance by using the idr cyclic allocator.

Well, it was raised by Hannes and James, so I'll ask them respond here
because I don't mind having it this way. I personally think that this
is a better approach than having a cyclic idr allocator. In general, I
don't necessarily think that this is a good idea to have cyclic
controller enumerations if we don't absolutely have to...