linux-kernel - Re: [PATCH v2] mm: Add MREMAP

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Message-ID: <20200203130940.enfvdsbn42hhoaki@box>
Date:   Mon, 3 Feb 2020 16:09:40 +0300
From:   "Kirill A. Shutemov" <kirill@...temov.name>
To:     Brian Geffon <bgeffon@...gle.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        "Michael S . Tsirkin" <mst@...hat.com>,
        Arnd Bergmann <arnd@...db.de>,
        LKML <linux-kernel@...r.kernel.org>,
        linux-mm <linux-mm@...ck.org>, linux-api@...r.kernel.org,
        Andy Lutomirski <luto@...capital.net>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Sonny Rao <sonnyrao@...gle.com>,
        Minchan Kim <minchan@...nel.org>,
        Joel Fernandes <joel@...lfernandes.org>,
        Yu Zhao <yuzhao@...gle.com>, Jesse Barnes <jsbarnes@...gle.com>
Subject: Re: [PATCH v2] mm: Add MREMAP_DONTUNMAP to mremap().

On Sun, Feb 02, 2020 at 05:17:53AM +0100, Brian Geffon wrote:
> On Wed, Jan 29, 2020 at 11:46 AM Kirill A. Shutemov
> <kirill@...temov.name> wrote:
> > Any better options for the flag name? (I have none)
> 
> The other option is that it's broken up into two new flags the first
> MREMAP_MUSTMOVE which can be used regardless of whether or not you're
> leaving the original mapping mapped. This would do exactly what it
> describes: move the mapping to a new address with or without
> MREMAP_FIXED, this keeps consistency with MAYMOVE.
> 
> The second flag would be the new MREMAP_DONTUNMAP flag which requires
> MREMAP_MUSTMOVE, again with or without MREMAP_FIXED.
> 
> What are your thoughts on this?

Sounds reasonable.

MREMAP_DONTUNMAP doesn't really convey that you move pages to the new
mapping, but leave empty mapping behind. But I guess there's only so much
you can encode into the name. (Patch to the man page should do the rest)

-- 
 Kirill A. Shutemov