Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752205AbbB1BS6 (ORCPT ); Fri, 27 Feb 2015 20:18:58 -0500 Received: from mail.linuxfoundation.org ([140.211.169.12]:49494 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750843AbbB1BS5 (ORCPT ); Fri, 27 Feb 2015 20:18:57 -0500 Date: Fri, 27 Feb 2015 17:18:11 -0800 From: Andrew Morton To: Danesh Petigara Cc: , , , , , , , , Subject: Re: [PATCH v2] mm: cma: fix CMA aligned offset calculation Message-Id: <20150227171811.c9f6d0ca.akpm@linux-foundation.org> In-Reply-To: <54F114D0.3060306@broadcom.com> References: <1424821185-16956-1-git-send-email-dpetigara@broadcom.com> <20150227132443.e17d574d45451f10f413f065@linux-foundation.org> <54F10358.1050102@broadcom.com> <20150227155458.697b7701d0a67ff7b4f3d9cb@linux-foundation.org> <54F114D0.3060306@broadcom.com> X-Mailer: Sylpheed 2.7.1 (GTK+ 2.18.9; x86_64-redhat-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1855 Lines: 48 On Fri, 27 Feb 2015 17:07:28 -0800 Danesh Petigara wrote: > On 2/27/2015 3:54 PM, Andrew Morton wrote: > > On Fri, 27 Feb 2015 15:52:56 -0800 Danesh Petigara wrote: > > > >> On 2/27/2015 1:24 PM, Andrew Morton wrote: > >>> On Tue, 24 Feb 2015 15:39:45 -0800 Danesh Petigara wrote: > >>> > >>>> The CMA aligned offset calculation is incorrect for > >>>> non-zero order_per_bit values. > >>>> > >>>> For example, if cma->order_per_bit=1, cma->base_pfn= > >>>> 0x2f800000 and align_order=12, the function returns > >>>> a value of 0x17c00 instead of 0x400. > >>>> > >>>> This patch fixes the CMA aligned offset calculation. > >>> > >>> When fixing a bug please always describe the end-user visible effects > >>> of that bug. > >>> > >>> Without that information others are unable to understand why you are > >>> recommending a -stable backport. > >>> > >> > >> Thank you for the feedback. I had no crash logs to show, nevertheless, I > >> agree that a sentence describing potential effects of the bug would've > >> helped. > > > > What was the reason for adding a cc:stable? > > > > It was added since the commit that introduced the incorrect logic > (b5be83e) was already picked up by v3.19. argh. afaict the bug will, under some conditions cause cma_alloc() to report that no suitable free area is available in the arena when in fact such regions *are* available. So it's effectively a bogus ENOMEM. Correct? If so, what are the conditions under which this will occur? This isn't hard - I want to know what the patch *does*! -- 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/