Re: [RFC PATCH v2 00/18] scsi: scsi_error: Introduce new error handle mechanism

[Hannes Reinecke]

On 9/26/23 14:57, Wenchao Hao wrote:
> On 2023/9/26 1:54, Mike Christie wrote:
> > On 9/25/23 10:07 AM, Wenchao Hao wrote:
> > > On 2023/9/25 22:55, Christoph Hellwig wrote:
> > > > Before we add another new error handling mechanism we need to fix the
> > > > old one first.  Hannes' work on not passing the scsi_cmnd to the 
> > > > various
> > > > reset handlers hasn't made a lot of progress in the last five years and
> > > > we'll need to urgently fix that first before adding even more
> > > > complexity.
> > > I observed Hannes's patches posted about one year ago, it has not been
> > > applied yet. I don't know if he is still working on it.
> > >
> > > My patches do not depend much on that work, I think the conflict can be
> > > solved fast between two changes.
> >
> > I think we want to figure out Hannes's patches first.
> >
> > For a new EH design we will want to be able to do multiple TMFs in 
> > parallel
> > on the same host/target right?
>
> It's not necessary to do multiple TMFs in parallel, it's ok to make sure
> each TMFs do not affect each other.
>
> For example, we have two devices: 0:0:0:0 and 0:0:0:1
>
> Both of them request device reset, they do not happened in parallel, but
> would in serial. If 0:0:0:0 is performing device reset in progress, 0:0:0:1
> just wait 0:0:0:0 to finish.
Well, not quite. Any higher-order TMFs are serialized by virtue of 
SCSI-EH, but command aborts (which also devolve down to TMFs on certain 
drivers) do run in parallel, and there we will be requiring multiple TMFs.

Cheers,

Hannes
--
Dr. Hannes Reinecke                Kernel Storage Architect
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