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Date:   Mon, 20 Jan 2020 15:14:33 +0100
From:   Michal Hocko <mhocko@kernel.org>
To:     Tianyu Lan <Tianyu.Lan@microsoft.com>
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>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
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        vkuznets <vkuznets@redhat.com>,
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        "vbabka@suse.cz" <vbabka@suse.cz>,
        "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
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On Fri 17-01-20 16:35:03, Tianyu Lan wrote:
[...]
> > Could you describe your usecase in more details please?
> 
> Hyper-V sends hot-remove request message which just contains requested
> page number but not provide detail range. So Hyper-V driver needs to search
> suitable memory block in system memory to return back to host if there is no
> memory hot-add before. So I used the is_mem_section_removable() do such check.

As David described, you would be much better of by using
alloc_contig_range to find a memory that would be suitable for
hotremoving without any races.
-- 
Michal Hocko
SUSE Labs