From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail6.bemta12.messagelabs.com (mail6.bemta12.messagelabs.com [216.82.250.247]) by kanga.kvack.org (Postfix) with ESMTP id 123316B01A7 for ; Fri, 2 Sep 2011 18:32:15 -0400 (EDT) Date: Fri, 2 Sep 2011 15:32:04 -0700 From: Andrew Morton Subject: Re: [Revert] Re: [PATCH] mm: sync vmalloc address space page tables in alloc_vm_area() Message-Id: <20110902153204.59a928c1.akpm@linux-foundation.org> In-Reply-To: <4E60C067.4010600@citrix.com> References: <1314877863-21977-1-git-send-email-david.vrabel@citrix.com> <20110901161134.GA8979@dumpdata.com> <4E5FED1A.1000300@goop.org> <20110901141754.76cef93b.akpm@linux-foundation.org> <4E60C067.4010600@citrix.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: David Vrabel Cc: Jeremy Fitzhardinge , Konrad Rzeszutek Wilk , "linux-kernel@vger.kernel.org" , "namhyung@gmail.com" , "rientjes@google.com" , "linux-mm@kvack.org" , "xen-devel@lists.xensource.com" , "paulmck@linux.vnet.ibm.com" On Fri, 2 Sep 2011 12:39:19 +0100 David Vrabel wrote: > Xen backend drivers (e.g., blkback and netback) would sometimes fail > to map grant pages into the vmalloc address space allocated with > alloc_vm_area(). The GNTTABOP_map_grant_ref would fail because Xen > could not find the page (in the L2 table) containing the PTEs it > needed to update. > > (XEN) mm.c:3846:d0 Could not find L1 PTE for address fbb42000 > > netback and blkback were making the hypercall from a kernel thread > where task->active_mm != &init_mm and alloc_vm_area() was only > updating the page tables for init_mm. The usual method of deferring > the update to the page tables of other processes (i.e., after taking a > fault) doesn't work as a fault cannot occur during the hypercall. > > This would work on some systems depending on what else was using > vmalloc. > > Fix this by reverting ef691947d8a3d479e67652312783aedcf629320a > (vmalloc: remove vmalloc_sync_all() from alloc_vm_area()) and add a > comment to explain why it's needed. oookay, I queued this for 3.1 and tagged it for a 3.0.x backport. I *think* that's the outcome of this discussion, for the short-term? -- 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/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org