linux-kernel - Re: Enhancing semantics with memremap()

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Date:	Tue, 31 May 2016 23:31:54 +0000
From:	"Kani, Toshimitsu" <toshi.kani@....com>
To:	"mcgrof@...nel.org" <mcgrof@...nel.org>
CC:	"toshi.kani@...com" <toshi.kani@...com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"hch@...radead.org" <hch@...radead.org>,
	"dan.j.williams@...el.com" <dan.j.williams@...el.com>,
	"x86@...nel.org" <x86@...nel.org>,
	"paulmck@...ux.vnet.ibm.com" <paulmck@...ux.vnet.ibm.com>,
	"will.deacon@....com" <will.deacon@....com>,
	"bp@...en8.de" <bp@...en8.de>,
	"julia.lawall@...6.fr" <julia.lawall@...6.fr>,
	"linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>,
	"benh@...nel.crashing.org" <benh@...nel.crashing.org>
Subject: Re: Enhancing semantics with memremap() - aliasing with memremap()

On Tue, 2016-05-31 at 19:27 +0200, Luis R. Rodriguez wrote:
> On Tue, May 31, 2016 at 07:25:14PM +0200, Luis R. Rodriguez wrote:
> > 
> > On Tue, May 31, 2016 at 09:58:28AM -0700, Christoph Hellwig wrote:
> > > 
> > > On Tue, May 24, 2016 at 04:36:42PM -0700, Luis R. Rodriguez wrote:
> > > > 
> > > > Is it a good time for that now? I would hope identifying proper
> > > > aliasing uses for memremap() might be a bit easier now than for
> > > > ioremap() given its not used as widely. It may be an easier target
> > > > to also write some grammar rules for it as well.
> > > 
> > > So you want an explicit opt-in flag to allow aliasing?  Sounds fine to
> > > me.
> >   
> > Yup! Can the default then safely already be no-aliasing then?
>
> Or if aliasing is truly not needed as often a different API, this
> maybe useful later if we pick up again module namespace stuff.

I agree that we should be able to change memremap() to fail an aliasing
request since it's a relatively new interface.  ioremap() needs to start
from adding a warning message.

Thanks,
-Toshi