linux-kernel - Re: [PATCH v2 4/5] mm: memory_hotplug: Add memory hotremove probe device

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Message-Id: <20171204124419.GB10599@samekh>
Date:   Mon, 4 Dec 2017 12:44:19 +0000
From:   Andrea Reale <ar@...ux.vnet.ibm.com>
To:     Michal Hocko <mhocko@...nel.org>
Cc:     linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, m.bielski@...tualopensystems.com,
        arunks@....qualcomm.com, mark.rutland@....com,
        scott.branden@...adcom.com, will.deacon@....com,
        qiuxishi@...wei.com, catalin.marinas@....com, realean2@...ibm.com
Subject: Re: [PATCH v2 4/5] mm: memory_hotplug: Add memory hotremove probe
 device

On Mon  4 Dec 2017, 13:33, Michal Hocko wrote:
> On Mon 04-12-17 11:51:29, Andrea Reale wrote:
> > On Thu 30 Nov 2017, 15:49, Michal Hocko wrote:
> > > On Thu 23-11-17 11:14:52, Andrea Reale wrote:
> > > > Adding a "remove" sysfs handle that can be used to trigger
> > > > memory hotremove manually, exactly simmetrically with
> > > > what happens with the "probe" device for hot-add.
> > > > 
> > > > This is usueful for architecture that do not rely on
> > > > ACPI for memory hot-remove.
> > > 
> > > As already said elsewhere, this really has to check the online status of
> > > the range and fail some is still online.
> > > 
> > 
> > This is actually still done in remove_memory() (patch 2/5) with
> > walk_memory_range. We just return an error rather than BUGing().
> > 
> > Or are you referring to something else?
> 
> But you are not returning that error to the caller, are you?
> 
> [...]

Oh, I see your point. Yes, indeed we should have returned it. Thanks for
catching the issue.

> > > > +	nid = memory_add_physaddr_to_nid(phys_addr);
> > > > +	ret = lock_device_hotplug_sysfs();
> > > > +	if (ret)
> > > > +		return ret;
> > > > +
> > > > +	remove_memory(nid, phys_addr,
> > > > +			 MIN_MEMORY_BLOCK_SIZE * sections_per_block);
> > > > +	unlock_device_hotplug();
> > > > +	return count;

Thanks,
Andrea
> 
> -- 
> Michal Hocko
> SUSE Labs
>