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Date: Fri, 19 Jul 2019 08:05:02 +0200
From: Michal Hocko <mhocko@kernel.org>
To: David Hildenbrand <david@redhat.com>
Subject: Re: [PATCH v3 10/11] mm/memory_hotplug: Make
 unregister_memory_block_under_nodes() never fail
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Cc: linux-s390@vger.kernel.org, linux-ia64@vger.kernel.org,
 linux-sh@vger.kernel.org, Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
 Mark Brown <broonie@kernel.org>, "Rafael J. Wysocki" <rafael@kernel.org>,
 linux-kernel@vger.kernel.org, Wei Yang <richard.weiyang@gmail.com>,
 linux-mm@kvack.org, "David S. Miller" <davem@davemloft.net>,
 Jonathan Cameron <Jonathan.Cameron@huawei.com>,
 Alex Deucher <alexander.deucher@amd.com>, Igor Mammedov <imammedo@redhat.com>,
 akpm@linux-foundation.org, Chris Wilson <chris@chris-wilson.co.uk>,
 linuxppc-dev@lists.ozlabs.org, Dan Williams <dan.j.williams@intel.com>,
 linux-arm-kernel@lists.infradead.org, Oscar Salvador <osalvador@suse.de>
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 <linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org>

On Mon 15-07-19 13:10:33, David Hildenbrand wrote:
> On 01.07.19 12:27, Michal Hocko wrote:
> > On Mon 01-07-19 11:36:44, Oscar Salvador wrote:
> >> On Mon, Jul 01, 2019 at 10:51:44AM +0200, Michal Hocko wrote:
> >>> Yeah, we do not allow to offline multi zone (node) ranges so the current
> >>> code seems to be over engineered.
> >>>
> >>> Anyway, I am wondering why do we have to strictly check for already
> >>> removed nodes links. Is the sysfs code going to complain we we try to
> >>> remove again?
> >>
> >> No, sysfs will silently "fail" if the symlink has already been removed.
> >> At least that is what I saw last time I played with it.
> >>
> >> I guess the question is what if sysfs handling changes in the future
> >> and starts dropping warnings when trying to remove a symlink is not there.
> >> Maybe that is unlikely to happen?
> > 
> > And maybe we handle it then rather than have a static allocation that
> > everybody with hotremove configured has to pay for.
> > 
> 
> So what's the suggestion? Dropping the nodemask_t completely and calling
> sysfs_remove_link() on already potentially removed links?

Yes. In a follow up patch.
-- 
Michal Hocko
SUSE Labs