From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail137.messagelabs.com (mail137.messagelabs.com [216.82.249.19]) by kanga.kvack.org (Postfix) with SMTP id B8DF46B004F for ; Fri, 27 Feb 2009 09:56:43 -0500 (EST) Received: by fxm18 with SMTP id 18so1160161fxm.38 for ; Fri, 27 Feb 2009 06:56:41 -0800 (PST) MIME-Version: 1.0 In-Reply-To: <20090127210727.GA9592@us.ibm.com> References: <4973AEEC.70504@gmail.com> <20090119175919.GA7476@us.ibm.com> <20090126223350.610b0283.akpm@linux-foundation.org> <20090127210727.GA9592@us.ibm.com> Date: Fri, 27 Feb 2009 15:56:40 +0100 Message-ID: <25e057c00902270656x1781d04er5703058e47df455f@mail.gmail.com> Subject: Re: [PATCH] mm: get_nid_for_pfn() returns int From: roel kluin Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Sender: owner-linux-mm@kvack.org To: Gary Hade Cc: Andrew Morton , Ingo Molnar , lkml , linux-mm@kvack.org, y-goto@jp.fujitsu.com List-ID: >> > > get_nid_for_pfn() returns int >> > My mistake. =A0Good catch. >> Presumably the (nid < 0) case has never happened. > > We do know that it is happening on one system while creating > a symlink for a memory section so it should also happen on > the same system if unregister_mem_sect_under_nodes() were > called to remove the same symlink. > > The test was actually added in response to a problem with an > earlier version reported by Yasunori Goto where one or more > of the leading pages of a memory section on the 2nd node of > one of his systems was uninitialized because I believe they > coincided with a memory hole. =A0The earlier version did not > ignore uninitialized pages and determined the nid by considering > only the 1st page of each memory section. =A0This caused the > symlink to the 1st memory section on the 2nd node to be > incorrectly created in /sys/devices/system/node/node0 instead > of /sys/devices/system/node/node1. =A0The problem was fixed by > adding the test to skip over uninitialized pages. > > I suspect we have not seen any reports of the non-removal > of a symlink due to the incorrect declaration of the nid > variable in unregister_mem_sect_under_nodes() because > =A0- systems where a memory section could have an uninitialized > =A0 =A0range of leading pages are probably rare. > =A0- memory remove is probably not done very frequently on the > =A0 =A0systems that are capable of demonstrating the problem. > =A0- lingering symlink(s) that should have been removed may > =A0 =A0have simply gone unnoticed. >> >> Should we retain the test? > > Yes. > >> >> Is silently skipping the node in that case desirable behaviour? > > It actually silently skips pages (not nodes) in it's quest > for valid nids for all the nodes that the memory section scans. > This is definitely desirable. > > I hope this answers your questions. This still isn't applied, was it lost? Roel -- 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