linux-ext4 - Re: [RFC PATCH 0/7] dax, ext4: Synchronous page faults

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Date:   Mon, 14 Aug 2017 10:30:12 +0200
From:   Jan Kara <jack@...e.cz>
To:     Christoph Hellwig <hch@...radead.org>
Cc:     Dan Williams <dan.j.williams@...el.com>, Jan Kara <jack@...e.cz>,
        linux-nvdimm <linux-nvdimm@...ts.01.org>,
        Dave Chinner <david@...morbit.com>, linux-xfs@...r.kernel.org,
        Andy Lutomirski <luto@...nel.org>,
        Linux FS Devel <linux-fsdevel@...r.kernel.org>,
        "linux-ext4@...r.kernel.org" <linux-ext4@...r.kernel.org>
Subject: Re: [RFC PATCH 0/7] dax, ext4: Synchronous page faults

On Sun 13-08-17 02:25:56, Christoph Hellwig wrote:
> On Sat, Aug 12, 2017 at 07:44:14PM -0700, Dan Williams wrote:
> > How about MAP_SYNC == (MAP_SHARED|MAP_PRIVATE)? On older kernels that
> > should get -EINVAL, and on new kernels it means SYNC+SHARED.
> 
> Cute trick, but I'd hate to waster it just for our little flag.
> 
> How about:
> 
> #define __MAP_VALIDATE		MAP_SHARED|MAP_PRIVATE
> #define MAP_SYNC		0x??? | __MAP_VALIDATE
> 
> so that we can reuse that trick for any new flag?

Heh, that's such an ugly hack that it is cute ;)... I'll use this
definition of MAP_SYNC in my patches and send new version of the series
(probably today in the afternoon if the testing goes fine).

								Honza

-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR