From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from dax.scot.redhat.com (sct@dax.scot.redhat.com [195.89.149.242]) by kvack.org (8.8.7/8.8.7) with ESMTP id PAA19877 for ; Wed, 13 Jan 1999 15:21:19 -0500 Date: Wed, 13 Jan 1999 20:21:08 GMT Message-Id: <199901132021.UAA06949@dax.scot.redhat.com> From: "Stephen C. Tweedie" MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Subject: Re: Why don't shared anonymous mappings work? In-Reply-To: References: <199901061523.IAA14788@nyx10.nyx.net> Sender: owner-linux-mm@kvack.org To: "Eric W. Biederman" Cc: Colin Plumb , linux-mm@kvack.org, Stephen Tweedie List-ID: Hi, On 06 Jan 1999 23:55:03 -0600, ebiederm+eric@ccr.net (Eric W. Biederman) said: > And of course the last reason I just thought of, which is probably the > real reason. Currenlty anonymous pages if the are writable are > assumed to have exactly one mapping, or if it is in the swap cache the > page is assumed to be read only. > So reusing the swap inode could be a real problem. Yes. The _only_ reason we can't do anonymous pages right now is the VM's assumption that all swap cache pages are read-only. Once we relax that, the only thing left is the initialisation of anonymous page ptes (remembering that when we fill in a demand-zero anonymous shared page, we will have to update that page's pte in every mm which shares the page). Other than that, allowing writable swap-cache pages is all that is required. It's just too much of a potential destabiliser to add this close to 2.2.0. --Stephen -- This is a majordomo managed list. To unsubscribe, send a message with the body 'unsubscribe linux-mm me@address' to: majordomo@kvack.org