linux-kernel - Re: [PATCH v12 08/11] mm: Clear arch specific VM flags on protection change

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Message-ID: <fd08210e-a6af-c3f5-3807-9ffe9dad66b0@oracle.com>
Date:   Mon, 5 Mar 2018 13:38:02 -0700
From:   Khalid Aziz <khalid.aziz@...cle.com>
To:     Dave Hansen <dave.hansen@...ux.intel.com>,
        akpm@...ux-foundation.org, davem@...emloft.net
Cc:     mhocko@...e.com, jack@...e.cz, kirill.shutemov@...ux.intel.com,
        ross.zwisler@...ux.intel.com, willy@...radead.org,
        hughd@...gle.com, n-horiguchi@...jp.nec.com, mgorman@...e.de,
        jglisse@...hat.com, dave.jiang@...el.com, dan.j.williams@...el.com,
        anthony.yznaga@...cle.com, nadav.amit@...il.com,
        zi.yan@...rutgers.edu, aarcange@...hat.com,
        khandual@...ux.vnet.ibm.com, aneesh.kumar@...ux.vnet.ibm.com,
        henry.willard@...cle.com, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, sparclinux@...r.kernel.org,
        Khalid Aziz <khalid@...ehiking.org>
Subject: Re: [PATCH v12 08/11] mm: Clear arch specific VM flags on protection
 change

On 03/05/2018 12:23 PM, Dave Hansen wrote:
> On 02/21/2018 09:15 AM, Khalid Aziz wrote:
>> +/* Arch-specific flags to clear when updating VM flags on protection change */
>> +#ifndef VM_ARCH_CLEAR
>> +# define VM_ARCH_CLEAR	VM_NONE
>> +#endif
>> +#define VM_FLAGS_CLEAR	(ARCH_VM_PKEY_FLAGS | VM_ARCH_CLEAR)
> 
> Shouldn't this be defining
> 
> # define VM_ARCH_CLEAR	ARCH_VM_PKEY_FLAGS
> 
> on x86?

ARCH_VM_PKEY_FLAGS is used by x86 as well as powerpc. On those two 
architectures VM_FLAGS_CLEAR will end up being ARCH_VM_PKEY_FLAGS and 
thus current behavior will be retained. Defining VM_ARCH_CLEAR to be 
ARCH_VM_PKEY_FLAGS on x86 will just result in VM_FLAGS_CLEAR to be 
(ARCH_VM_PKEY_FLAGS | ARCH_VM_PKEY_FLAGS) which is superfluous.

--
Khalid