Re: [PATCH v6 0/4] Add MMC software queue support

[Arnd Bergmann]

On Wed, Nov 27, 2019 at 10:00 AM Christoph Hellwig <hch@xxxxxxxxxxxxx> wrote:
>
> On Tue, Nov 26, 2019 at 12:17:15PM +0100, Hannes Reinecke wrote:
>  If requests are batched enough we could just drain
> and switch every time an other partition access comes in.  Especially
> so if people only use partitions for boot partitions and other rarely
> used areas.

We only support a single user partition plus up to two boot partitions that
are accessed rarely, I don't think there is any reason to optimize switching
between them.

The only change that I think we need here is to change the partition switch
from something that is done synchronously during ->queue_rq() to
something that fits better into normal scheme of sending a cmd to
the device, returning BLK_STS_RESOURCE from ->queue_rq.
Possibly this could even be turned into a standard struct request that is
added between two normal requests for different partitions at some
point, if this simplifies the logic (I suspect it won't, but it may be worth
a try).

      Arnd