From mboxrd@z Thu Jan 1 00:00:00 1970 From: Nick Piggin Subject: Re: [PATCH 03/33] mm: slub: add knowledge of reserve pages Date: Wed, 31 Oct 2007 22:25:06 +1100 Message-ID: <200710312225.07249.nickpiggin@yahoo.com.au> References: <20071030160401.296770000@chello.nl> <200710312146.03351.nickpiggin@yahoo.com.au> <1193833072.27652.167.camel@twins> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Cc: Linus Torvalds , Andrew Morton , linux-kernel@vger.kernel.org, linux-mm@kvack.org, netdev@vger.kernel.org, trond.myklebust@fys.uio.no To: Peter Zijlstra Return-path: Received: from smtp106.mail.mud.yahoo.com ([209.191.85.216]:43426 "HELO smtp106.mail.mud.yahoo.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1753268AbXJaMmo (ORCPT ); Wed, 31 Oct 2007 08:42:44 -0400 In-Reply-To: <1193833072.27652.167.camel@twins> Content-Disposition: inline Sender: netdev-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On Wednesday 31 October 2007 23:17, Peter Zijlstra wrote: > On Wed, 2007-10-31 at 21:46 +1100, Nick Piggin wrote: > > And I'd prevent these ones from doing so. > > > > Without keeping track of "reserve" pages, which doesn't feel > > too clean. > > The problem with that is that once a slab was allocated with the right > allocation context, anybody can get objects from these slabs. [snip] I understand that. > So we either reserve a page per object, which for 32 byte objects is a > large waste, or we stop anybody who doesn't have the right permissions > from obtaining objects. I took the latter approach. What I'm saying is that the slab allocator slowpath should always just check watermarks against the current task. Instead of this ->reserve stuff.