From mboxrd@z Thu Jan  1 00:00:00 1970
From: guanjunxiong@huawei.com (Guan Junxiong)
Date: Tue, 1 Aug 2017 19:59:30 +0800
Subject: [PATCH 7/7] nvme: Send change uevent when AEN completes
In-Reply-To: <20170717152232.GC24365@localhost.localdomain>
References: <1499444581-28268-1-git-send-email-keith.busch@intel.com>
 <1499444581-28268-8-git-send-email-keith.busch@intel.com>
 <20170707181436.GC24427@lst.de>
 <20170713212955.GD14716@localhost.localdomain>
 <20170714125309.GA26975@lst.de>
 <20170714151624.GA24157@localhost.localdomain>
 <20170715084218.GA23189@lst.de>
 <20170717152232.GC24365@localhost.localdomain>
Message-ID: <64083244-85fb-ce9b-951b-efaa00f4eab4@huawei.com>

Hi, Keith

Any update about this patch?  We are keen on planning to use this kind of
feature to handle some events of controller/subsystem with multipath-tools.

Thanks

Best wishes
Guan Junxiong

On 2017/7/17 23:22, Keith Busch wrote:
> On Sat, Jul 15, 2017@10:42:18AM +0200, Christoph Hellwig wrote:
>>
>> Take the Changed Namespace List log page for example.
>>
>> We get an AER, and then both schedule a log page read in the kernel
>> (as we should, patch pending) and send the uevent.  As soon as the
>> read the log page in the kernel to clear the log page we get another
>> event due to another namespace change, but not userspace manages to
>> read the log page before the kernel acts on the next AER, so the
>> kernel won't see the changes.
>>
>> And yes, this is probably a little constructed, but we'll get more
>> log pages with similar semantics, so I am worried a bit about this.
> 
> That event needs to already be handled by the driver without relying
> on the Changed Namespace List log, like when the list exceeds the log
> size. But okay, I see the concern in general if reading a log page may
> change the results.
> 
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