From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx182.postini.com [74.125.245.182]) by kanga.kvack.org (Postfix) with SMTP id 531376B0083 for ; Wed, 23 May 2012 11:03:56 -0400 (EDT) Message-ID: <4FBCFBE0.2080803@parallels.com> Date: Wed, 23 May 2012 19:01:52 +0400 From: Glauber Costa MIME-Version: 1.0 Subject: Re: [PATCH] slab+slob: dup name string References: <1337613539-29108-1-git-send-email-glommer@parallels.com> <4FBBAE95.6080608@parallels.com> <1337773595.3013.15.camel@dabdike.int.hansenpartnership.com> <4FBCD328.6060406@parallels.com> <1337775878.3013.16.camel@dabdike.int.hansenpartnership.com> In-Reply-To: Content-Type: text/plain; charset="ISO-8859-1"; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Christoph Lameter Cc: James Bottomley , David Rientjes , linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, linux-mm@kvack.org, Pekka Enberg On 05/23/2012 06:48 PM, Christoph Lameter wrote: > On Wed, 23 May 2012, James Bottomley wrote: > >>>> So, why not simply patch slab to rely on the string lifetime being the >>>> cache lifetime (or beyond) and therefore not having it take a copy? > > Well thats they way it was for a long time. There must be some reason that > someone started to add this copying business.... Pekka? > From git: commit 84c1cf62465e2fb0a692620dcfeb52323ab03d48 Author: Pekka Enberg Date: Tue Sep 14 23:21:12 2010 +0300 SLUB: Fix merged slab cache names As explained by Linus "I'm Proud to be an American" Torvalds: Looking at the merging code, I actually think it's totally buggy. If you have something like this: - load module A: create slab cache A - load module B: create slab cache B that can merge with A - unload module A - "cat /proc/slabinfo": BOOM. Oops. exactly because the name is not handled correctly, and you'll have module B holding open a slab cache that has a name pointer that points to module A that no longer exists. So if I understand it correctly, this is mostly because the name string outlives the cache in the slub case, because of merging ? -- 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