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Date:   Fri, 12 Feb 2021 17:14:04 -0500
From:   Peter Xu <peterx@redhat.com>
To:     Mike Kravetz <mike.kravetz@oracle.com>
Cc:     Axel Rasmussen <axelrasmussen@google.com>,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        Alexey Dobriyan <adobriyan@gmail.com>,
        Andrea Arcangeli <aarcange@redhat.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Anshuman Khandual <anshuman.khandual@arm.com>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Chinwen Chang <chinwen.chang@mediatek.com>,
        Huang Ying <ying.huang@intel.com>,
        Ingo Molnar <mingo@redhat.com>, Jann Horn <jannh@google.com>,
        Jerome Glisse <jglisse@redhat.com>,
        Lokesh Gidra <lokeshgidra@google.com>,
        "Matthew Wilcox (Oracle)" <willy@infradead.org>,
        Michael Ellerman <mpe@ellerman.id.au>,
        Michal =?utf-8?Q?Koutn=C3=BD?= <mkoutny@suse.com>,
        Michel Lespinasse <walken@google.com>,
        Mike Rapoport <rppt@linux.vnet.ibm.com>,
        Nicholas Piggin <npiggin@gmail.com>, Shaohua Li <shli@fb.com>,
        Shawn Anastasio <shawn@anastas.io>,
        Steven Rostedt <rostedt@goodmis.org>,
        Steven Price <steven.price@arm.com>,
        Vlastimil Babka <vbabka@suse.cz>, linux-kernel@vger.kernel.org,
        linux-fsdevel@vger.kernel.org, linux-mm@kvack.org,
        Adam Ruprecht <ruprecht@google.com>,
        Cannon Matthews <cannonmatthews@google.com>,
        "Dr . David Alan Gilbert" <dgilbert@redhat.com>,
        David Rientjes <rientjes@google.com>,
        Mina Almasry <almasrymina@google.com>,
        Oliver Upton <oupton@google.com>
Subject: Re: [PATCH v5 04/10] hugetlb/userfaultfd: Unshare all pmds for
 hugetlbfs when register wp
Message-ID: <20210212221404.GE3171@xz-x1>
References: <20210210212200.1097784-1-axelrasmussen@google.com>
 <20210210212200.1097784-5-axelrasmussen@google.com>
 <517f3477-cb80-6dc9-bda0-b147dea68f95@oracle.com>
 <20210212211856.GD3171@xz-x1>
 <a32b5427-0560-fa24-450c-376c427dd166@oracle.com>
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On Fri, Feb 12, 2021 at 01:34:03PM -0800, Mike Kravetz wrote:
> I'm good with the new MMU_NOTIFY_HUGETLB_UNSHARE and agree with your reasoning
> for adding it.  I really did not know enough about usage which caused me to
> question.

It actually is a good question..  Because after a 2nd thought I cannot think of
any mmu notifier usage to explicitly listen to huge pmd unshare event - it
could be just a too internal impl detail of hugetlbfs.  I think any new flag
should justify itself when introduced.  Before I could justify it, I think
MMU_NOTIFIER_CLEAR is indeed more suitable.

Thanks,

-- 
Peter Xu