[PATCH 1/1] nvme-fabrics: Generate uevent on namespace AENs

[Hannes Reinecke]

On 5/3/21 8:52 AM, Christoph Hellwig wrote:
> On Fri, Apr 30, 2021 at 09:21:04AM -0700, Keith Busch wrote:
>> On Fri, Apr 30, 2021 at 05:14:55AM +0000, Rao, Vinay wrote:
>>> + Madhu
>>>
>>> Hi Chaitanya, 
>>>
>>> Some of the AEN's like ANA state change and Name Space attribute change events are of interest outside the NVME driver. 
>>>
>>> It would be good to consider these events to be propagated up to user space. I am not yet convinced on how propagating this above to user space is problematic.
>>
>> The namespace attribute change event pairs with the Changed Namespace
>> List log, and reading that log will change the result for a subsequent
>> reader. User space racing with the kernel on a log access when there are
>> read side effects creates non-deterministic behavior, and that is
>> problematic.
> 
> The only way I could think of making this work is by:
> 
> forcing the RAE bit on for all log pages that the kernel cares about,
> and only delivering the uevent on controllers that actually do support
> the RAE bit (IIRC it got added in 1.3, but I'd have to check).
> 
Yep, that sounds like a good idea.
I would even go so far as to inhibit any user-space commands which read
those log pages and which have the RAE bit _not_ set, as this has the
potential of messing up the kernel operations...

Cheers,

Hannes
-- 
Dr. Hannes Reinecke		           Kernel Storage Architect
hare at suse.de			                  +49 911 74053 688
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