Re: [RFC PATCH 3/3] blk-mq: Remove generation seqeunce

hch
2018-07-19T13:19:04Z

On Wed, Jul 18, 2018 at 03:17:11PM -0600, Keith Busch wrote:
> And there may be other drivers that don't want their completions
> ignored, so breaking them again is also a step in the wrong direction.
>
> There are not that many blk-mq drivers, so we can go through them all.

I think the point is that SCSI is the biggest user by both the number
of low-level drivers sitting under the midlayer, and also by usage.

We need to be very careful not to break it. Note that this doesn't
mean that I don't want to eventually move away from just ignoring
completions in timeout state for SCSI. I'd just rather rever 4.18
to a clean known state instead of doctoring around late in the rc
phase.

> Most don't even implement .timeout, so they never know that condition
> ever happened. Others always return BLK_EH_RESET_TIMER without doing
> anythign else, so the 'new' behavior would have to be better for those,
> too.

And we should never even hit the timeout handler for those as it
is rather pointless (although it looks we currently do..).