linux-kernel - Re: [PATCH v6 3/5] mm: introduce mmap3 for safely defining new mmap flags

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Date:   Fri, 25 Aug 2017 19:16:07 +0300
From:   "Kirill A. Shutemov" <kirill@...temov.name>
To:     Christoph Hellwig <hch@...radead.org>
Cc:     Dan Williams <dan.j.williams@...el.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Jan Kara <jack@...e.cz>, Arnd Bergmann <arnd@...db.de>,
        "linux-nvdimm@...ts.01.org" <linux-nvdimm@...ts.01.org>,
        Linux API <linux-api@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        linux-xfs@...r.kernel.org, Linux MM <linux-mm@...ck.org>,
        Andy Lutomirski <luto@...nel.org>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        linux-parisc@...r.kernel.org
Subject: Re: [PATCH v6 3/5] mm: introduce mmap3 for safely defining new mmap
 flags

On Fri, Aug 25, 2017 at 09:02:36AM -0700, Christoph Hellwig wrote:
> On Fri, Aug 25, 2017 at 06:58:03PM +0300, Kirill A. Shutemov wrote:
> > Not all archs are ready for this:
> > 
> > arch/parisc/include/uapi/asm/mman.h:#define MAP_TYPE    0x03            /* Mask for type of mapping */
> > arch/parisc/include/uapi/asm/mman.h:#define MAP_FIXED   0x04            /* Interpret addr exactly */
> 
> I'd be happy to say that we should not care about parisc for
> persistent memory.  We'll just have to find a way to exclude
> parisc without making life too ugly.

I don't think creapling mmap() interface for one arch is the right way to
go. I think the interface should be universal.

I may imagine MAP_DIRECT can be useful not only for persistent memory.
For tmpfs instead of mlock()?

-- 
 Kirill A. Shutemov