[PATCHv2 4/7] nvme: export I/O requeue count when no path is available via sysfs

[Sagi Grimberg]

> When the NVMe namespace head determines that there is no currently
> available path to handle I/O (for example, while a controller is
> resetting/connecting or due to a transient link failure), incoming
> I/Os are added to the requeue list.
>
> Currently, there is no visibility into how many I/Os have been requeued
> in this situation. Add a new sysfs counter, requeue_no_available_path,
> to expose the number of I/Os that were requeued due to the absence of
> an available path.
>
> This statistic can help users understand I/O slowdowns or stalls caused
> by temporary path unavailability, and can be consumed by monitoring
> tools such as nvme-top for real-time observability.

Other than the debugfs comment, would it make sense to have a reset
functionality to these files (via write to the file)?

Other than that, patch makes sense to me.