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

[Rao, Vinay]

-----Original Message-----
From: Christoph Hellwig <hch at lst.de> 
Sent: Monday, May 3, 2021 12:23 PM
To: Keith Busch
Cc: Rao, Vinay; Chaitanya Kulkarni; Belanger, Martin; Hayes, Stuart; Tarikere, Madhu; Christoph Hellwig; Martin Belanger; linux-nvme at lists.infradead.org; axboe at fb.com; sagi at grimberg.me
Subject: Re: [PATCH 1/1] nvme-fabrics: Generate uevent on namespace AENs


[EXTERNAL EMAIL] 

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).

>> Just wanted to check if there is any plan to implement the code change of forcing the RAE bit for all log pages that the kernel cares about is taken up?  Can you please let us know what the plan is to address the problem.