From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1762292AbXGJULL (ORCPT ); Tue, 10 Jul 2007 16:11:11 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1758095AbXGJUK4 (ORCPT ); Tue, 10 Jul 2007 16:10:56 -0400 Received: from extu-mxob-2.symantec.com ([216.10.194.135]:7386 "EHLO extu-mxob-2.symantec.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756557AbXGJUKz (ORCPT ); Tue, 10 Jul 2007 16:10:55 -0400 Date: Tue, 10 Jul 2007 21:10:11 +0100 (BST) From: Hugh Dickins X-X-Sender: hugh@blonde.wat.veritas.com To: William Tambe cc: Stas Sergeev , "Rohland, Hans-Christoph" , linux-kernel@vger.kernel.org Subject: Re: Concerning a post that you made about expandable anonymous shared mappings In-Reply-To: <4692E5DF.7080304@gmail.com> Message-ID: References: <468562F6.4010604@gmail.com> <46893F97.7080200@aknet.ru> <4692E5DF.7080304@gmail.com> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-Brightmail-Verdict: VlJEQwAAAAIAAAABAAAAAAAAAAEAAAAAAAAABGluYm94AGxpbnV4LWtlcm5lbEB2Z2VyLmtlcm5lbC5vcmcAaGFucy1jaHJpc3RvcGgucm9obGFuZEBzYXAuY29tAHRhbWJld2lsbGlhbUBnbWFpbC5jb20Ac3RzcEBha25ldC5ydQA= X-Brightmail-Tracker: AAAAAA== Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 9 Jul 2007, William Tambe wrote: > Hugh Dickins wrote: > > > > I've come right around to your original view, Stas, and William's: > > if that mmap creates such an object, then the expanding mremap really > > ought to be useful, and allow the underlying object to be expanded. > > The shared anonymous object is already anomalous: expanding it on > > fault makes it more consistent with its own nature, not less. > > ... > > Here's a patch against 2.6.22-rc7: would you, Stas, put your > > Signed-off-by into this, and accept authorship - although I'm > > sending this back to you, it's very much your idea, and only > > trivially modified from your three-year-old patch by me. If > > you're agreeable, I can then forward it or its shmem_zero_fault > > equivalent to Andrew when we see which way 2.6.23 is going. >... > Will this patch be added to stable versions of the linux kernel? > Please let me know. I confess that the lukewarm response from Stas cooled my enthusiasm, and left me feeling that perhaps I'm an idiot to be adding such a feature so many years too late; and my old caution about the way a child could use up memory not freed on child's exit, unknown to parent, returned to haunt me. That could be documented for new usages, but I just don't know what usages are already out there, and fear I'd be introducing an exploit. It most certainly will not be added to a stable version of the linux kernel, if by that you mean 2.6.22.N or 2.6.21.N etc. Though it can be viewed as a bugfix, the patch as it stands seems in danger of introducing its own bug, and it's just too much of a feature to be suitable for a -stable release. But more probably you meant, will it be in 2.6.23 or 2.6.24? Sorry to be such a vacillatiing wimp, but I don't know. How well are you managing with the shm_open approach? Hugh