[PATCH] nvme: implement support for nvme relaxed effects

[Chaitanya Kulkarni]

>> The command associated with this structure should only be submitted
>> when there is no outstanding Admin command that affects any namespace
>> and no Admin command should be submitted that affects any namespace
>> until this command is complete.
>>
>> IOW, don't we need to freeze the admin queue when controller sets the CSER
>> value to 01b until command is completed ? or it is not done/needed for
>> a specific reason ?
> 
> The user is trying to submit an admin command, which wouldn't be
> possible if we freeze the admin queue. We'd need another mechanism to
> allow just the user's command, then a way to defeat it if that command
> times out (we send admin commands as part of a reset sequence).
> 
> All that adds complications to the driver, and since there hasn't been
> any communicated need to have the driver enforce this policy, we just
> leave it up to user space to know what they're doing.

I did write a patch to see if we can do it without adding bunch of code,
but no, it doesn't really bring that much of a benefit vs complicating
exiting code as mentioned above.

I think this patch is okay then.

-ck