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Date: Fri, 7 Jul 2017 14:15:58 +0530
From: Anshuman Khandual <khandual@...ux.vnet.ibm.com>
To: Mike Kravetz <mike.kravetz@...cle.com>, linux-mm@...ck.org,
linux-api@...r.kernel.org, linux-kernel@...r.kernel.org
Cc: Andrew Morton <akpm@...ux-foundation.org>,
Andrea Arcangeli <aarcange@...hat.com>,
Michal Hocko <mhocko@...e.com>, Aaron Lu <aaron.lu@...el.com>,
"Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>
Subject: Re: [RFC PATCH 1/1] mm/mremap: add MREMAP_MIRROR flag for existing
mirroring functionality
On 07/06/2017 09:47 PM, Mike Kravetz wrote:
> The mremap system call has the ability to 'mirror' parts of an existing
> mapping. To do so, it creates a new mapping that maps the same pages as
> the original mapping, just at a different virtual address. This
> functionality has existed since at least the 2.6 kernel.
>
> This patch simply adds a new flag to mremap which will make this
> functionality part of the API. It maintains backward compatibility with
> the existing way of requesting mirroring (old_size == 0).
>
> If this new MREMAP_MIRROR flag is specified, then new_size must equal
> old_size. In addition, the MREMAP_MAYMOVE flag must be specified.
Yeah it all looks good. But why is this requirement that if
MREMAP_MAYMOVE is specified then old_size and new_size must
be equal.
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