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From:   Tianyu Lan <Tianyu.Lan@microsoft.com>
To:     Michal Hocko <mhocko@kernel.org>
CC:     David Hildenbrand <david@redhat.com>,
        "lantianyu1986@gmail.com" <lantianyu1986@gmail.com>,
        KY Srinivasan <kys@microsoft.com>,
        Haiyang Zhang <haiyangz@microsoft.com>,
        Stephen Hemminger <sthemmin@microsoft.com>,
        "sashal@kernel.org" <sashal@kernel.org>,
        "akpm@linux-foundation.org" <akpm@linux-foundation.org>,
        Michael Kelley <mikelley@microsoft.com>,
        "linux-hyperv@vger.kernel.org" <linux-hyperv@vger.kernel.org>,
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        "osalvador@suse.de" <osalvador@suse.de>,
        Pasha Tatashin <Pavel.Tatashin@microsoft.com>,
        "rppt@linux.ibm.com" <rppt@linux.ibm.com>
Subject: RE: [EXTERNAL] Re: [RFC PATCH V2 2/10] mm: expose
 is_mem_section_removable() symbol
Thread-Topic: [EXTERNAL] Re: [RFC PATCH V2 2/10] mm: expose
 is_mem_section_removable() symbol
Thread-Index: AQHVxV94OmmoHHYtiky82H1ysWWO7qfj7JsAgAS1vtCAAVMkgIADb8/Q
Date:   Fri, 17 Jan 2020 16:35:03 +0000
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> From: Michal Hocko <mhocko@kernel.org>=0A=
> Sent: Tuesday, January 14, 2020 5:51 PM=0A=
> To: Tianyu Lan <Tianyu.Lan@microsoft.com>=0A=
> Cc: David Hildenbrand <david@redhat.com>; lantianyu1986@gmail.com; KY=0A=
> Srinivasan <kys@microsoft.com>; Haiyang Zhang <haiyangz@microsoft.com>;=
=0A=
> Stephen Hemminger <sthemmin@microsoft.com>; sashal@kernel.org;=0A=
> akpm@linux-foundation.org; Michael Kelley <mikelley@microsoft.com>; linux=
-=0A=
> hyperv@vger.kernel.org; linux-kernel@vger.kernel.org; linux-mm@kvack.org;=
=0A=
> vkuznets <vkuznets@redhat.com>; eric.devolder@oracle.com; vbabka@suse.cz;=
=0A=
> osalvador@suse.de; Pasha Tatashin <Pavel.Tatashin@microsoft.com>;=0A=
> rppt@linux.ibm.com=0A=
> Subject: Re: [EXTERNAL] Re: [RFC PATCH V2 2/10] mm: expose=0A=
> is_mem_section_removable() symbol=0A=
> =0A=
> On Mon 13-01-20 14:49:38, Tianyu Lan wrote:=0A=
> > Hi David & Michal:=0A=
> > 	Thanks for your review. Some memory blocks are not suitable for hot-=
=0A=
> plug.=0A=
> > If not check memory block's removable, offline_pages() will report=0A=
> > some failure error e.g, "failed due to memory holes" and  "failure to=
=0A=
> > isolate range". I think the check maybe added into=0A=
> > offline_and_remove_memory()? This may help to not create/expose a new=
=0A=
> interface to do such check in module.=0A=
> =0A=
> Why is a log message a problem in the first place. The operation has fail=
ed=0A=
> afterall. Does the driver try to offline an arbitrary memory?=0A=
=0A=
Yes.=0A=
=0A=
> Could you describe your usecase in more details please?=0A=
=0A=
Hyper-V sends hot-remove request message which just contains requested=0A=
page number but not provide detail range. So Hyper-V driver needs to search=
=0A=
suitable memory block in system memory to return back to host if there is n=
o=0A=
memory hot-add before. So I used the is_mem_section_removable() do such che=
ck.=0A=
=0A=
=0A=