Re: [PATCH 00/11] scsi: libsas: Remove in_interrupt() check

[John Garry]

On 11/01/2021 13:43, Ahmed S. Darwish wrote:
> Hi John, Jason,
>
> On Tue, Dec 22, 2020 at 12:54:58PM +0000, John Garry wrote:
> > On 22/12/2020 12:30, Jason Yan wrote:
> > > >       return event;
> > > >
> > > >
> > > > So default for phy->ha->event_thres is 32, and I can't imagine that
> > > The default value is 1024.
> > Ah, 32 is the minimum allowed set via sysfs.
> >
> > > > anyone has ever reconfigured this via sysfs or even required a value
> > > > that large. Maybe Jason (cc'ed) knows better. It's an arbitrary
> > > > value to say that the PHY is malfunctioning. I do note that there is
> > > > the circular path sas_alloc_event() -> sas_notify_phy_event() ->
> > > > sas_alloc_event() there also.
> > > >
> > > > Anyway, if the 32x event memories were per-allocated, maybe there is
> > > > a clean method to manage this memory, which even works in atomic
> > > > context, so we could avoid this rework (ignoring the context bugs
> > > > you reported for a moment). I do also note that the sas_event_cache
> > > > size is not huge.
> > > Pre-allocated memory is an option.(Which we have tried at the very
> > > beginnig by Wang Yijing.)
> > Right, I remember this, but I think the concern was having a proper method
> > to manage this pre-allocated memory then. And same problem now.
> >
> > > Or directly use GFP_ATOMIC is maybe better than passing flags from lldds.
> > I think that if we don't really need this, then should not use it.
> Kind reminder. Do we have any consensus here?

Hi Ahmed,

To me, what you're doing seems fine.

I was looking for some API to manage small memory pools and which is 
atomic safe to avoid passing the context flag, but I didn't find such a 
thing.

Just one other thing to mention:
I have a patch to remove the indirection in libsas notifiers:
https://github.com/hisilicon/kernel-dev/commit/87fcd7e113dc05b7933260e7fa4588dc3730cc2a

I was going to send it today. Hopefully, if community has no problem 
with it, you can make your changes with that in mind.

Thanks,
John