From: Mike Kravetz <mike.kravetz@oracle.com>
To: Michal Hocko <mhocko@kernel.org>,
Anshuman Khandual <khandual@linux.vnet.ibm.com>
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
akpm@linux-foundation.org
Subject: Re: [PATCH] mm/mremap: Document MREMAP_FIXED dependency on MREMAP_MAYMOVE
Date: Mon, 10 Jul 2017 10:31:29 -0700 [thread overview]
Message-ID: <40c61daf-da2c-bab9-99d0-a7d7147f4514@oracle.com> (raw)
In-Reply-To: <20170710134130.GA19645@dhcp22.suse.cz>
On 07/10/2017 06:41 AM, Michal Hocko wrote:
> On Mon 10-07-17 17:02:11, Anshuman Khandual wrote:
>> In the header file, just specify the dependency of MREMAP_FIXED
>> on MREMAP_MAYMOVE and make it explicit for the user space.
>
> I really fail to see a point of this patch. The depency belongs to the
> code and it seems that we already enforce it
> if (flags & MREMAP_FIXED && !(flags & MREMAP_MAYMOVE))
> return ret;
>
> So what is the point here?
Agree, I am not sure of your reasoning.
If to assist the programmer, there is no need as this is clearly specified
in the man page:
"If MREMAP_FIXED is specified, then MREMAP_MAYMOVE must also be
specified."
--
Mike Kravetz
>
>> Signed-off-by: Anshuman Khandual <khandual@linux.vnet.ibm.com>
>> ---
>> include/uapi/linux/mman.h | 6 ++++--
>> 1 file changed, 4 insertions(+), 2 deletions(-)
>>
>> diff --git a/include/uapi/linux/mman.h b/include/uapi/linux/mman.h
>> index ade4acd..8cae3f6 100644
>> --- a/include/uapi/linux/mman.h
>> +++ b/include/uapi/linux/mman.h
>> @@ -3,8 +3,10 @@
>>
>> #include <asm/mman.h>
>>
>> -#define MREMAP_MAYMOVE 1
>> -#define MREMAP_FIXED 2
>> +#define MREMAP_MAYMOVE 1 /* VMA can move after remap and resize */
>> +#define MREMAP_FIXED 2 /* VMA can remap at particular address */
>> +
>> +/* NOTE: MREMAP_FIXED must be set with MREMAP_MAYMOVE, not alone */
>>
>> #define OVERCOMMIT_GUESS 0
>> #define OVERCOMMIT_ALWAYS 1
>> --
>> 1.8.5.2
>>
>> --
>> To unsubscribe, send a message with 'unsubscribe linux-mm' in
>> the body to majordomo@kvack.org. For more info on Linux MM,
>> see: http://www.linux-mm.org/ .
>> Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
>
--
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next prev parent reply other threads:[~2017-07-10 17:31 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-07-10 11:32 Anshuman Khandual
2017-07-10 13:41 ` Michal Hocko
2017-07-10 17:31 ` Mike Kravetz [this message]
2017-07-11 2:15 ` Anshuman Khandual
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