From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Tue, 1 May 2001 10:36:31 +0100 From: "Stephen C. Tweedie" Subject: Re: Hopefully a simple question on /proc/pid/mem Message-ID: <20010501103631.J26638@redhat.com> References: <20010430225802.H26638@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: ; from ebiederm@xmission.com on Mon, Apr 30, 2001 at 07:13:53PM -0600 Sender: owner-linux-mm@kvack.org Return-Path: To: "Eric W. Biederman" Cc: "Stephen C. Tweedie" , "Benjamin C.R. LaHaise" , Alexander Viro , Richard F Weber , linux-mm@kvack.org List-ID: Hi, On Mon, Apr 30, 2001 at 07:13:53PM -0600, Eric W. Biederman wrote: > > Hint: think about what happens if you make a shared mapping of a > > private proc/*/mem region... > > Now that we have reusable swap cache pages we could make it work > correctly, except for the case of the first write a private mapping of > file. Not that we would want to... Think about fork. If a parent forks and then touches a private page before the child does, it's the parent which gets a new page. The supposed shared mmap of the parent now points to the child's page, not the parent's. COW basically just can't do the right thing if a page is both shared and private at the same time. --Stephen -- 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.eu.org/Linux-MM/