linux-kernel - Re: [PATCH 00/11] scsi: libsas: Remove in

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Date:   Mon, 11 Jan 2021 14:43:26 +0100
From:   "Ahmed S. Darwish" <a.darwish@...utronix.de>
To:     John Garry <john.garry@...wei.com>, Jason Yan <yanaijie@...wei.com>
Cc:     Hannes Reinecke <hare@...e.com>,
        "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        Daniel Wagner <dwagner@...e.de>,
        Artur Paszkiewicz <artur.paszkiewicz@...el.com>,
        Jack Wang <jinpu.wang@...ud.ionos.com>,
        linux-scsi@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        "Sebastian A. Siewior" <bigeasy@...utronix.de>
Subject: Re: [PATCH 00/11] scsi: libsas: Remove in_interrupt() check

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?

Thanks,

--
Ahmed S. Darwish
Linutronix GmbH