To: Tejun Heo <tj@kernel.org>
CC: miklos@szeredi.hu, mszeredi@suse.cz, linux-kernel@vger.kernel.org,
       fuse-devel@lists.sourceforge.net, polynomial-c@gentoo.org,
       akpm@linux-foundation.org
In-reply-to: <4B73EE68.4070004@kernel.org> (message from Tejun Heo on Thu, 11
	Feb 2010 20:47:52 +0900)
Subject: Re: [fuse-devel] [PATCH] FUSE/CUSE: implement direct mmap support
References: <4B70FBE4.7050700@kernel.org> <E1NerZ6-0007N6-UY@pomaz-ex.szeredi.hu> <4B7296DF.207@kernel.org> <E1NfAl6-0000o4-8Z@pomaz-ex.szeredi.hu> <4B729F07.8020704@kernel.org> <E1NfBTc-0000vk-59@pomaz-ex.szeredi.hu> <4B72A802.6040009@kernel.org> <E1NfE50-0001EK-Ao@pomaz-ex.szeredi.hu> <4B7344A4.1030607@kernel.org> <E1NfVOi-0002l9-5l@pomaz-ex.szeredi.hu> <4B73EE68.4070004@kernel.org>
Message-Id: <E1NfYFm-00034C-Pd@pomaz-ex.szeredi.hu>
From: Miklos Szeredi <miklos@szeredi.hu>
Date: Thu, 11 Feb 2010 13:34:42 +0100
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 856
Lines: 21

On Thu, 11 Feb 2010, Tejun Heo wrote:
> It's not like it's something completely foreign.  It's a limitation
> which can also be found in shared memory and the server side mmap
> doesn't really have much to do with it.  It's also necessary to avoid
> aliasing issues among clients.

What aliasing issues among clients?  That's a job for the arch
dependent part of mmap.  And as you said, there's not a lot the driver
can do (except play with ->vm_pgoff) to influence the address
selection.

And playing with ->vm_pgoff is *not* a valid thing to do for the
client, at least not on "normal" mmaps.

Thanks,
Miklos
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