[PATCH V3 3/3] nvme: retry commands based on ACRE flag

[Christoph Hellwig]

On Sat, Jan 16, 2021 at 03:26:02AM +0900, Minwoo Im wrote:
> > I am not sure we should ignore the FAILFAST for non-path errors. If we
> > need retryable admin commands, we should let the driver provide a way
> > for callers to dispatch requests without that flag.
> 
> Understood.  I thought the opposite way about FAILFAST in case with
> acre, if device is enabled with acre, all commands would be retried
> regardless to FAILFAST...  Thanks for pointing that out!
> 
> How do you think which one is right choice to go with if a user-space
> application(e.g., nvme-cli) wants a command to be retired in case of
> ACRE && Error && !DNR:
> 
>   - User-space application should figure out !DNR and retry the command.
>     (Maybe we are not able to easily figure out exact status code from
>     the user-space application by the return value).
> 
>   - Driver should retry the command right before putting result up to
>     the user-space even it's a FAILFAST request.
> 
> Thanks,

We could come up with a version of the ioctls that use the normal
retry mechanisms.  nvme_passthru_cmd64 has two reserved fields we
could use for UAPI flags like this.