linux-kernel - Re: [PATCH] memory-hotplug: Fix bad area access on dissolve_free_huge

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Message-ID: <57E2B60A.2060200@linux.intel.com>
Date:   Wed, 21 Sep 2016 09:32:10 -0700
From:   Dave Hansen <dave.hansen@...ux.intel.com>
To:     Michal Hocko <mhocko@...nel.org>
Cc:     Rui Teng <rui.teng@...ux.vnet.ibm.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        "Aneesh Kumar K . V" <aneesh.kumar@...ux.vnet.ibm.com>,
        Paul Gortmaker <paul.gortmaker@...driver.com>,
        Santhosh G <santhog4@...ibm.com>
Subject: Re: [PATCH] memory-hotplug: Fix bad area access on
 dissolve_free_huge_pages()

On 09/21/2016 09:27 AM, Michal Hocko wrote:
> That was not my point. I wasn't very clear probably. Offlining can fail
> which shouldn't be really surprising. There might be a kernel allocation
> in the particular block which cannot be migrated so failures are to be
> expected. I just do not see how offlining in the middle of a gigantic
> page is any different from having any other unmovable allocation in a
> block. That being said, why don't we simply refuse to offline a block
> which is in the middle of a gigantic page.

Don't we want to minimize the things that can cause an offline to fail?
 The code to fix it here doesn't seem too bad.