Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753834Ab0AEI6E (ORCPT ); Tue, 5 Jan 2010 03:58:04 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753480Ab0AEI6D (ORCPT ); Tue, 5 Jan 2010 03:58:03 -0500 Received: from bombadil.infradead.org ([18.85.46.34]:45485 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750716Ab0AEI6A (ORCPT ); Tue, 5 Jan 2010 03:58:00 -0500 Subject: Re: [RFC][PATCH 6/8] mm: handle_speculative_fault() From: Peter Zijlstra To: Linus Torvalds Cc: KAMEZAWA Hiroyuki , "Paul E. McKenney" , "linux-kernel@vger.kernel.org" , "linux-mm@kvack.org" , "minchan.kim@gmail.com" , cl@linux-foundation.org, "hugh.dickins" , Nick Piggin , Ingo Molnar In-Reply-To: References: <20100104182429.833180340@chello.nl> <20100104182813.753545361@chello.nl> <20100105092559.1de8b613.kamezawa.hiroyu@jp.fujitsu.com> Content-Type: text/plain; charset="UTF-8" Date: Tue, 05 Jan 2010 09:57:14 +0100 Message-ID: <1262681834.2400.31.camel@laptop> Mime-Version: 1.0 X-Mailer: Evolution 2.28.1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1060 Lines: 21 On Mon, 2010-01-04 at 19:13 -0800, Linus Torvalds wrote: > Or put another way: if the vma was a writable mapping, a user may do > > munmap(mapping, size); > > and the backing file is still active and writable AFTER THE MUNMAP! This > can be a huge problem for something that wants to unmount the volume, for > example, or depends on the whole writability-vs-executability thing. The > user may have unmapped it, and expects the file to be immediately > non-busy, but with the delayed free that isn't the case any more. If it were only unmount it would be rather easy to fix by putting that RCU synchronization in unmount, unmount does a lot of sync things anyway. But I suspect there's more cases where that non-busy matters (but I'd need to educate myself on filesystems/vfs to come up with any). -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/