From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-bk0-f50.google.com (mail-bk0-f50.google.com [209.85.214.50]) by kanga.kvack.org (Postfix) with ESMTP id D31A56B0031 for ; Tue, 1 Apr 2014 12:08:08 -0400 (EDT) Received: by mail-bk0-f50.google.com with SMTP id w10so1362193bkz.37 for ; Tue, 01 Apr 2014 09:08:08 -0700 (PDT) Received: from kirsi1.inet.fi (mta-out.inet.fi. [195.156.147.13]) by mx.google.com with ESMTP id qa8si9387494bkb.50.2014.04.01.09.08.06 for ; Tue, 01 Apr 2014 09:08:06 -0700 (PDT) Date: Tue, 1 Apr 2014 19:07:38 +0300 From: "Kirill A. Shutemov" Subject: Re: [PATCH RFC] drivers/char/mem: byte generating devices and poisoned mappings Message-ID: <20140401160738.GA15175@node.dhcp.inet.fi> References: <20140331211607.26784.43976.stgit@zurg> <20140401103617.GA10882@node.dhcp.inet.fi> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: owner-linux-mm@kvack.org List-ID: To: Konstantin Khlebnikov Cc: "linux-mm@kvack.org" , Linux Kernel Mailing List , Hugh Dickins , Yury Gribov , Alexandr Andreev , Vassili Karpov , Andrew Morton , "Kirill A. Shutemov" 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 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 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org