From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from terminus.zytor.com ([198.137.202.10]:56465 "EHLO mail.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750721AbaETX3Z (ORCPT ); Tue, 20 May 2014 19:29:25 -0400 Message-ID: <537BE54B.3060603@zytor.com> Date: Tue, 20 May 2014 16:29:15 -0700 From: "H. Peter Anvin" MIME-Version: 1.0 To: "linux-btrfs@vger.kernel.org" CC: Chris Mason Subject: Re: Formalizing the use of Boot Area B References: <537403E3.6090902@zytor.com> In-Reply-To: <537403E3.6090902@zytor.com> Content-Type: text/plain; charset=UTF-8 Sender: linux-btrfs-owner@vger.kernel.org List-ID: On 05/14/2014 05:01 PM, H. Peter Anvin wrote: > It turns out that the primary 64K "Boot Area A" is too small for some > applications and/or some architectures. > > When I discussed this with Chris Mason, he pointed out that the area > beyond the superblock is also unused, up until at least the megabyte > point (from my reading of the mkfs code, it is actually slightly more > than a megabyte.) > > This is present in all versions of mkfs.btrfs that has the superblock at > 64K (some very early ones had the superblock at 16K, but that format is > no longer supported), so all that is needed is formalizing the specs as > to the use of this area. > > My suggestion is that 64-128K is reserved for extension of the > superblock and/or any other filesystem uses, and 128-1024K is defined as > Boot Area B. However, if there may be reason to reserve more, then we > should do that. Hence requesting a formal decision as to the extent and > ownership of this area. > > -hpa > Ping on this? If I don't hear back on this I will probably just go ahead and use 128K-1024K. -hpa