[dm-devel] [patch 5/5] block: use a driver-specific handler for the "inflight" value

[Mikulas Patocka]

On Thu, 8 Nov 2018, Christoph Hellwig wrote:

> On Tue, Nov 06, 2018 at 10:35:03PM +0100, Mikulas Patocka wrote:
> > Device mapper was converted to percpu inflight counters. In order to
> > display the correct values in the "inflight" sysfs file, we need a custom
> > callback that sums the percpu counters.
> 
> The attribute that calls this is per-partition, while your method
> is per-queue, so there is some impedence mismatch here.

Device mapper doesn't use partitions.

> Is there any way you could look into just making the generic code
> use percpu counters?

In the next merge window, single-queue request-based block drivers will be 
eliminated - all the drivers will be multiqueue. So, they won't use 
the in_flight variables at all.

in_flight will be only use by bio-based stacking drivers like md.

> Also please cc linux-block on patches that touch the generic block
> code.

Mikulas