linux-kernel - Re: [RFC PATCH V2 2/10] mm: expose is_mem_section

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Message-ID: <20200107133623.GJ32178@dhcp22.suse.cz>
Date:   Tue, 7 Jan 2020 14:36:23 +0100
From:   Michal Hocko <mhocko@...nel.org>
To:     lantianyu1986@...il.com
Cc:     kys@...rosoft.com, haiyangz@...rosoft.com, sthemmin@...rosoft.com,
        sashal@...nel.org, akpm@...ux-foundation.org,
        michael.h.kelley@...rosoft.com, david@...hat.com,
        Tianyu Lan <Tianyu.Lan@...rosoft.com>,
        linux-hyperv@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, vkuznets@...hat.com, eric.devolder@...cle.com,
        vbabka@...e.cz, osalvador@...e.de, pavel.tatashin@...rosoft.com,
        rppt@...ux.ibm.com
Subject: Re: [RFC PATCH V2 2/10] mm: expose is_mem_section_removable() symbol

On Tue 07-01-20 21:09:42, lantianyu1986@...il.com wrote:
> From: Tianyu Lan <Tianyu.Lan@...rosoft.com>
> 
> Hyper-V balloon driver will use is_mem_section_removable() to
> check whether memory block is removable or not when receive
> memory hot remove msg. Expose it.

I do not think this is a good idea. The check is inherently racy. Why
cannot the balloon driver simply hotremove the region when asked?
-- 
Michal Hocko
SUSE Labs