Re: [PATCH V2 3/4] blk-mq: fix dispatch from sw queue

On Mon, Dec 17, 2018 at 12:08:57PM +0100, Christoph Hellwig wrote:

On Mon, Dec 17, 2018 at 06:42:47PM +0800, Ming Lei wrote:

quoted

When requst is added to rq list of sw queue(ctx), the rq may be from
different hctx, after multi queue mapping is introduced.

So we have to put the request into one per-queue-type list inside
sw queue, otherwise the request may be dispatched to wrong hw queue.

Hmm.  For one I don't think splitting the lock makes sense even for
split lists.
Second, do we really need different lists, or just take

It depends if the driver/existed blk-mq code can work well if one
request is dispatched to wrong hctx.

the type into account when dispatching from rq_list?  I'm not really

This way may be inefficient since the whole list has to be iterated once
for finding all requests aimed to one specific hctx.


Thanks,
Ming