Re: [PATCH 10/14] blk-mq: initial support for multiple queue maps

From: Bart Van Assche
Date: Mon Oct 29 2018 - 15:40:39 EST

On Mon, 2018-10-29 at 10:37 -0600, Jens Axboe wrote:
+AD4 -static int cpu+AF8-to+AF8-queue+AF8-index(unsigned int nr+AF8-queues, const int cpu)
+AD4 +-static int cpu+AF8-to+AF8-queue+AF8-index(struct blk+AF8-mq+AF8-queue+AF8-map +ACo-qmap,
+AD4 +- unsigned int nr+AF8-queues, const int cpu)
+AD4 +AHs
+AD4 - return cpu +ACU nr+AF8-queues+ADs
+AD4 +- return qmap-+AD4-queue+AF8-offset +- (cpu +ACU nr+AF8-queues)+ADs
+AD4 +AH0
+AD4 +AFs ... +AF0
+AD4 --- a/include/linux/blk-mq.h
+AD4 +-+-+- b/include/linux/blk-mq.h
+AD4 +AEAAQA -78,10 +-78,11 +AEAAQA struct blk+AF8-mq+AF8-hw+AF8-ctx +AHs
+AD4 struct blk+AF8-mq+AF8-queue+AF8-map +AHs
+AD4 unsigned int +ACo-mq+AF8-map+ADs
+AD4 unsigned int nr+AF8-queues+ADs
+AD4 +- unsigned int queue+AF8-offset+ADs
+AD4 +AH0AOw

I think it's unfortunate that the blk-mq core uses the .queue+AF8-offset member but
that mapping functions in block drivers are responsible for setting that member.
Since the block driver mapping functions have to set,
how about adding a loop in blk+AF8-mq+AF8-update+AF8-queue+AF8-map() that derives .queue+AF8-offset
from .nr+AF8-queues from previous array entries?