From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756493AbbE2Rg1 (ORCPT ); Fri, 29 May 2015 13:36:27 -0400 Received: from imap.thunk.org ([74.207.234.97]:37148 "EHLO imap.thunk.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756345AbbE2RgP (ORCPT ); Fri, 29 May 2015 13:36:15 -0400 Date: Fri, 29 May 2015 13:36:09 -0400 From: "Theodore Ts'o" To: Richard Weinberger Cc: "Enrico Weigelt, metux IT consult" , "Luis R. Rodriguez" , "backports@vger.kernel.org" , "linux-kernel@vger.kernel.org" , Julia Lawall Subject: Re: Uses of Linux backports in the industry Message-ID: <20150529173609.GF18540@thunk.org> Mail-Followup-To: Theodore Ts'o , Richard Weinberger , "Enrico Weigelt, metux IT consult" , "Luis R. Rodriguez" , "backports@vger.kernel.org" , "linux-kernel@vger.kernel.org" , Julia Lawall References: <55687D72.3070904@melag.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.23 (2014-03-12) X-SA-Exim-Connect-IP: X-SA-Exim-Mail-From: tytso@thunk.org X-SA-Exim-Scanned: No (on imap.thunk.org); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, May 29, 2015 at 05:01:00PM +0200, Richard Weinberger wrote: > On Fri, May 29, 2015 at 4:53 PM, Enrico Weigelt, metux IT consult > wrote: > > Am 29.05.2015 um 04:54 schrieb Luis R. Rodriguez: > > Actually, I really wonder why folks are sticking to ancient kernels on > > newer hardware. > > Enterprise distribution kernels. Or "special" kernels like PREEMPT_RT. > Sometimes the vendor BSP is that horrid that a customer cannot afford > to forward port it > but wants recent stuff. So you need to backport... Yep. The technique I used for the backporting ext4 encryption into the 3.10 android-common git tree in AOSP was to drop in the 3.18 versions of fs/ext4 and fs/jbd2 into the 3.10 tree (along with the associaed include files in include/linux and include/trace/events, of course), and then fix things up until they built correctly (using cherry-picks and in some cases, reverting some changes in the 3.18 version of fs/ext4). After I was sure the transplant of the 3.18 version of ext4 had "taken" correctly, with no test regressions, only then did I cherry-pick all of the ext4 encryption changes on top of 3.10. The backport of ext4 encryption to the 3.18 version of android-common should be much easier. :-) Unfortunately, I also have to do a backport to the 3.14 android-common branch as well. Yes, it's ugly, but there still are some SOC and drivers that aren't available on newer kernels. Basically, the handset vendors need to lean a lot harder on the SOC and other peripheral (cell radios, GPS, etc., etc.). :-( - Ted