RE: [External] Re: [PATCH 3/5] s390, dcssblk: Allow a NULL-kaddr to ->direct_access()

[Huaisheng HS1 Ye]

From: Christian Borntraeger <borntraeger@xxxxxxxxxx>
Sent: Tuesday, July 24, 2018 7:16 PM
> >> So you are trading of a load + add (dev_info->start should be cache hot) against a
> >> compare+branch . Not sure that this is always a win.
> >
> > Hmm...the calculation process of pfn is more complicated than kaddr. I think you agree to
> check pfn but not sure kaddr, right?
> > From the logical consistency of code, I think it shall be better to give pfn and kaddr similar
> treatment.
> 
> Reading it again, its more that I do not like the patch description. It reads
> like an optimization, (and I think it is not) but it should rather read more
> like "with an upcoming change kaddr can be NULL" or so.

Thanks for suggestion, I will reword the patch description during next submission.
Does the patch itself need to be modified? If has, any suggestion is welcome.

Cheers,
Huaisheng Ye