Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755602AbXJHUFd (ORCPT ); Mon, 8 Oct 2007 16:05:33 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752933AbXJHUFY (ORCPT ); Mon, 8 Oct 2007 16:05:24 -0400 Received: from extu-mxob-1.symantec.com ([216.10.194.28]:44466 "EHLO extu-mxob-1.symantec.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751503AbXJHUFX (ORCPT ); Mon, 8 Oct 2007 16:05:23 -0400 Date: Mon, 8 Oct 2007 14:37:59 +0100 (BST) From: Hugh Dickins X-X-Sender: hugh@blonde.wat.veritas.com To: Yan Zheng cc: Nick Piggin , Miklos Szeredi , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, akpm@linux-foundation.org Subject: Re: [PATCH]fix VM_CAN_NONLINEAR check in sys_remap_file_pages In-Reply-To: <3d0408630710080445j4dea115emdfe29aac26814536@mail.gmail.com> Message-ID: References: <3d0408630710080445j4dea115emdfe29aac26814536@mail.gmail.com> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2005 Lines: 49 On Mon, 8 Oct 2007, Yan Zheng wrote: > > The test for VM_CAN_NONLINEAR always fails Good catch indeed. Though I was puzzled how we do nonlinear at all, until I realized it's "The test for not VM_CAN_NONLINEAR always fails". It's not as serious as it appears, since code further down has been added more recently to simulate nonlinear on non-RAM-backed filesystems, instead of going the real nonlinear way; so most filesystems are now not required to do what VM_CAN_NONLINEAR was put in to ensure they could do. I'm confused as to where that leaves us: is this actually a fix that needs to go into 2.6.23? or will it suddenly disable a system call which has been silently working fine on various filesystems which did not add VM_CAN_NONLINEAR? could we just rip out VM_CAN_NONLINEAR? I hope Nick or Miklos is clearer on what the risks are. (Apologies for all the "not"s and "non"s here, I'm embarrassed after just criticizing Ingo's SCHED_NO_NO_OMIT_FRAME_POINTER!) Hugh > > Signed-off-by: Yan Zheng > ---- > diff -ur linux-2.6.23-rc9/mm/fremap.c linux/mm/fremap.c > --- linux-2.6.23-rc9/mm/fremap.c 2007-10-07 15:03:33.000000000 +0800 > +++ linux/mm/fremap.c 2007-10-08 19:33:44.000000000 +0800 > @@ -160,7 +160,7 @@ > if (vma->vm_private_data && !(vma->vm_flags & VM_NONLINEAR)) > goto out; > > - if (!vma->vm_flags & VM_CAN_NONLINEAR) > + if (!(vma->vm_flags & VM_CAN_NONLINEAR)) > goto out; > > if (end <= start || start < vma->vm_start || end > vma->vm_end) > - > 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/ > - 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/