From: Sagi Grimberg <sagi@grimberg.me>
To: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Christoph Hellwig <hch@lst.de>
Cc: linux-nvme@lists.infradead.org,
Keith Busch <keith.busch@intel.com>,
James Smart <james.smart@broadcom.com>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 3/3] nvme: fire discovery log page change events to userspace
Date: Thu, 29 Aug 2019 11:21:02 -0700 [thread overview]
Message-ID: <ac168168-fed2-2b57-493e-e88261ead73b@grimberg.me> (raw)
In-Reply-To: <20190826075916.GA30396@kroah.com>
>>>> You are correct that this information can be derived from sysfs, but the
>>>> main reason why we add these here, is because in udev rule we can't
>>>> just go ahead and start looking these up and parsing these..
>>>>
>>>> We could send the discovery aen with NVME_CTRL_NAME and have
>>>> then have systemd run something like:
>>>>
>>>> nvme connect-all -d nvme0 --sysfs
>>>>
>>>> and have nvme-cli retrieve all this stuff from sysfs?
>>>
>>> Actually that may be a problem.
>>>
>>> There could be a hypothetical case where after the event was fired
>>> and before it was handled, the discovery controller went away and
>>> came back again with a different controller instance, and the old
>>> instance is now a different discovery controller.
>>>
>>> This is why we need this information in the event. And we verify this
>>> information in sysfs in nvme-cli.
>>
>> Well, that must be a usual issue with uevents, right? Don't we usually
>> have a increasing serial number for that or something?
>
> 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.
next prev parent reply other threads:[~2019-08-29 18:21 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20190712180211.26333-1-sagi@grimberg.me>
[not found] ` <20190712180211.26333-4-sagi@grimberg.me>
[not found] ` <20190822002328.GP9511@lst.de>
[not found] ` <205d06ab-fedc-739d-323f-b358aff2cbfe@grimberg.me>
[not found] ` <e4603511-6dae-e26d-12a9-e9fa727a8d03@grimberg.me>
2019-08-26 6:56 ` [PATCH v2 3/3] nvme: fire discovery log page change events to userspace Christoph Hellwig
2019-08-26 7:59 ` Greg Kroah-Hartman
2019-08-29 18:21 ` Sagi Grimberg [this message]
2019-08-30 5:55 ` Christoph Hellwig
2019-08-30 18:08 ` Sagi Grimberg
2019-08-30 18:36 ` James Smart
2019-08-30 21:07 ` Sagi Grimberg
2019-08-30 22:24 ` James Smart
2019-09-09 15:10 ` Hannes Reinecke
2019-08-30 6:20 ` Greg Kroah-Hartman
2019-08-30 18:14 ` Sagi Grimberg
2019-09-02 19:33 ` Greg Kroah-Hartman
2019-09-04 1:35 ` Sagi Grimberg
2019-09-04 5:25 ` Greg Kroah-Hartman
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