From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Thu, 31 Jan 2008 17:48:19 -0800 (PST) From: Christoph Lameter Subject: Re: mmu_notifier: close hole in fork In-Reply-To: <20080201000158.GT7185@v2.random> Message-ID: References: <20080131045750.855008281@sgi.com> <20080131045812.785269387@sgi.com> <20080131123118.GK7185@v2.random> <20080201000158.GT7185@v2.random> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org Return-Path: To: Andrea Arcangeli Cc: Robin Holt , Avi Kivity , Izik Eidus , kvm-devel@lists.sourceforge.net, Peter Zijlstra , steiner@sgi.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, daniel.blueman@quadrics.com List-ID: On Fri, 1 Feb 2008, Andrea Arcangeli wrote: > Good catch! This was missing also in my #v5 (KVM doesn't need that > because the only possible cows on sptes can be generated by ksm, but > it would have been a problem for GRU). The more I think about it, the How do you think the GRU should know when to drop the refcount? There is no page table and thus no way of tracking that a refcount was taken. Without the refcount you cannot defer the freeing of the page. So shootdown on invalidate_range_begin and lock out until invalidate_range_end seems to be the only workable solution. BTW what do you think about adding a flag parameter to the invalidate calls that allows shooting down writable ptes only? That could be useful for COW and page_mkclean. So #define MMU_ATOMIC 1 #define MMU_WRITABLE 2 insted of the atomic parameter? -- 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