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Subject: Re: [PATCH v4 1/9] hugetlb: Pass vma into huge_pte_alloc()
From:   Mike Kravetz <mike.kravetz@oracle.com>
To:     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>,
        =?UTF-8?Q?Michal_Koutn=c3=bd?= <mkoutny@suse.com>,
        Michel Lespinasse <walken@google.com>,
        Mike Rapoport <rppt@linux.vnet.ibm.com>,
        Nicholas Piggin <npiggin@gmail.com>,
        Peter Xu <peterx@redhat.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>
Cc:     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>,
        Oliver Upton <oupton@google.com>
References: <20210128224819.2651899-2-axelrasmussen@google.com>
 <20210128234242.2677079-1-axelrasmussen@google.com>
 <67fc15f3-3182-206b-451b-1622f6657092@oracle.com>
Message-ID: <f1afa616-c4f5-daaa-6865-8bbc3c93b71a@oracle.com>
Date:   Mon, 1 Feb 2021 13:53:14 -0800
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On 2/1/21 1:38 PM, Mike Kravetz wrote:
> On 1/28/21 3:42 PM, Axel Rasmussen wrote:
>> From: Peter Xu <peterx@redhat.com>
>>
>> It is a preparation work to be able to behave differently in the per
>> architecture huge_pte_alloc() according to different VMA attributes.
>>
>> Signed-off-by: Peter Xu <peterx@redhat.com>
>> [axelrasmussen@google.com: fixed typo in arch/mips/mm/hugetlbpage.c]
>> Signed-off-by: Axel Rasmussen <axelrasmussen@google.com>
>> ---
>>  arch/arm64/mm/hugetlbpage.c   | 2 +-
>>  arch/ia64/mm/hugetlbpage.c    | 3 ++-
>>  arch/mips/mm/hugetlbpage.c    | 4 ++--
>>  arch/parisc/mm/hugetlbpage.c  | 2 +-
>>  arch/powerpc/mm/hugetlbpage.c | 3 ++-
>>  arch/s390/mm/hugetlbpage.c    | 2 +-
>>  arch/sh/mm/hugetlbpage.c      | 2 +-
>>  arch/sparc/mm/hugetlbpage.c   | 2 +-
>>  include/linux/hugetlb.h       | 2 +-
>>  mm/hugetlb.c                  | 6 +++---
>>  mm/userfaultfd.c              | 2 +-
>>  11 files changed, 16 insertions(+), 14 deletions(-)
> 
> Sorry for the delay in reviewing.
> 
> huge_pmd_share() will do a find_vma() to get the vma.  So, it would be
> 'possible' to not add an extra argument to huge_pmd_alloc() and simply
> do the uffd_disable_huge_pmd_share() check inside vma_shareable.  This
> would reduce the amount of modified code, but would not be as efficient.
> I prefer passing the vma argument as is done here.
> 
> Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>


Another thought.

We should pass the vma to huge_pmd_share to avoid the find_vma.

-- 
Mike Kravetz