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From:   Qian Cai <cai@lca.pw>
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Subject: Re: [PATCH v2] mm/hugetlb: fix a addressing exception caused by huge_pte_offset()
Date:   Sat, 22 Feb 2020 06:50:42 -0500
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References: <f274b368-6fdb-2ae3-160e-fd8b105b9ac4@huawei.com>
Cc:     akpm@linux-foundation.org, mike.kravetz@oracle.com,
        kirill.shutemov@linux.intel.com, linux-kernel@vger.kernel.org,
        arei.gonglei@huawei.com, weidong.huang@huawei.com,
        weifuqiang@huawei.com, kvm@vger.kernel.org, linux-mm@kvack.org,
        Matthew Wilcox <willy@infradead.org>,
        Sean Christopherson <sean.j.christopherson@intel.com>,
        stable@vger.kernel.org
In-Reply-To: <f274b368-6fdb-2ae3-160e-fd8b105b9ac4@huawei.com>
To:     "Longpeng (Mike)" <longpeng2@huawei.com>
Sender: linux-kernel-owner@vger.kernel.org
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> On Feb 22, 2020, at 1:33 AM, Longpeng (Mike) <longpeng2@huawei.com> wrote:=

>=20
> As explained in the commit messages, it's for safe(e.g. avoid the compilie=
r
> mischief). You can also find the same usage in the ARM64's huge_pte_offset=
() in
> arch/arm64/mm/hugetlbpage.c

Rather than blindly copy over there, are those correct here? What kind of ba=
d compiler optimizations exactly do they try to prevent? Until we understand=
 those details, blindly adding READ_ONCE() will only hide other problems.=