[PATCH v2 2/2] nvme: support io stats on the mpath device

[Jens Axboe]

On 10/3/22 3:43 AM, Sagi Grimberg wrote:
> Our mpath stack device is just a shim that selects a bottom namespace
> and submits the bio to it without any fancy splitting. This also means
> that we don't clone the bio or have any context to the bio beyond
> submission. However it really sucks that we don't see the mpath device
> io stats.
> 
> Given that the mpath device can't do that without adding some context
> to it, we let the bottom device do it on its behalf (somewhat similar
> to the approach taken in nvme_trace_bio_complete).
> 
> When the IO starts, we account the request for multipath IO stats using
> REQ_NVME_MPATH_IO_STATS nvme_request flag to avoid queue io stats disable
> in the middle of the request.

Reviewed-by: Jens Axboe <axboe at kernel.dk>

-- 
Jens Axboe