From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Wed, 27 Feb 2008 14:43:41 -0800 (PST) From: Christoph Lameter Subject: Re: [patch 5/6] mmu_notifier: Support for drivers with revers maps (f.e. for XPmem) In-Reply-To: <200802201055.21343.nickpiggin@yahoo.com.au> Message-ID: References: <20080215064859.384203497@sgi.com> <20080215064933.376635032@sgi.com> <200802201055.21343.nickpiggin@yahoo.com.au> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org Return-Path: To: Nick Piggin Cc: akpm@linux-foundation.org, Andrea Arcangeli , Robin Holt , Avi Kivity , Izik Eidus , kvm-devel@lists.sourceforge.net, Peter Zijlstra , general@lists.openfabrics.org, Steve Wise , Roland Dreier , Kanoj Sarcar , steiner@sgi.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, daniel.blueman@quadrics.com List-ID: On Wed, 20 Feb 2008, Nick Piggin wrote: > I don't know how this is supposed to solve anything. The sleeping > problem happens I guess mostly in truncate. And all you are doing > is putting these rmap callbacks in page_mkclean and try_to_unmap. truncate is handled by the range invalidates. This is special code to deal with the unnap/clean of an individual page. > That doesn't seem right. To start with, the new callbacks aren't > even called in the places where invalidate_page isn't allowed to > sleep. > > The problem is unmap_mapping_range, right? And unmap_mapping_range > must walk the rmaps with the mmap lock held, which is why it can't > sleep. And it can't hold any mmap_sem so it cannot prevent address Nope. unmap_mapping_range is already handled by the range callbacks. > So in the meantime, you could have eg. a fault come in and set up a > new page for one of the processes, and that page might even get > exported via the same external driver. And now you have a totally > inconsistent view. The situation that you are imagining has already been dealt with by the earlier patches. This is only to allow sleeping while unmapping individual pages. -- 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