[PATCH] NVMe: Re-introduce nvmeq->q_suspended

[Jens Axboe]

On 11/21/2014 06:07 PM, Keith Busch wrote:
> On Fri, 21 Nov 2014, Sam Bradshaw wrote:
>> At some point in the blk-mq transition, q_suspended was removed.  This
>> patch adds it back to address two failure modes, both illustrated in
>> the attached snippet.  First, it protects the ioctl path from
>> inadvertently dereferencing invalid nvme_queue data structures during
>> device shutdown/reset.  Second, it protects against a double
>> free_irq() if the shutdown/reset/resume sequence doesn't recover a
>> flaky controller.
> 
> I could have sworn there was a better way to suspend at the
> request_queue level with blk-mq so we don't need this in the driver. The
> blk_start/stop_queue is close, but doesn't work in the ioctl path. Maybe
> I'm thinking blk-mq freeze, but that's not exported for drivers.

The freeze stuff should work. I've got a prelim patch that allows
attach/detach of the namespace/block parts, the first prep patch is
exporting the freeze bits.

-- 
Jens Axboe