linux-kernel - Re: [PATCH RFC] drivers/char/mem: byte generating devices and poisoned mappings

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Message-ID: <20140401160738.GA15175@node.dhcp.inet.fi>
Date:	Tue, 1 Apr 2014 19:07:38 +0300
From:	"Kirill A. Shutemov" <kirill@...temov.name>
To:	Konstantin Khlebnikov <koct9i@...il.com>
Cc:	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Hugh Dickins <hughd@...gle.com>,
	Yury Gribov <y.gribov@...sung.com>,
	Alexandr Andreev <aandreev@...allels.com>,
	Vassili Karpov <av1474@...tv.ru>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Subject: Re: [PATCH RFC] drivers/char/mem: byte generating devices and
 poisoned mappings

On Tue, Apr 01, 2014 at 07:15:31PM +0400, Konstantin Khlebnikov wrote:
> On Tue, Apr 1, 2014 at 2:36 PM, Kirill A. Shutemov <kirill@...temov.name> wrote:
> > On Tue, Apr 01, 2014 at 01:16:07AM +0400, Konstantin Khlebnikov wrote:
> >> This patch adds 256 virtual character devices: /dev/byte0, ..., /dev/byte255.
> >> Each works like /dev/zero but generates memory filled with particular byte.
> >
> > Shouldn't /dev/byte0 be an alias for /dev/zero?
> > I see you reuse ZERO_PAGE(0) for that, but what about all these special
> > cases /dev/zero has?
> 
> What special cases? I found rss-accounting part, you've mentioned coredump.

I'm not sure what else is there. It's probably good idea to check all
users of vm_normal_page().

One thing is zero page coloring which some archs have.

-- 
 Kirill A. Shutemov
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