From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from ipmail06.adl2.internode.on.net ([150.101.137.129]:8890 "EHLO ipmail06.adl2.internode.on.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726258AbeJFGlK (ORCPT ); Sat, 6 Oct 2018 02:41:10 -0400 Date: Sat, 6 Oct 2018 09:40:09 +1000 From: Dave Chinner Subject: Re: [PATCH] xfs: move the define for superblock magic to uapi Message-ID: <20181005234009.GJ12041@dastard> References: <20181005122741.5100-1-kilobyte@angband.pl> <20181005160600.GR19324@magnolia> <20181005181032.pal6fwt7ebijvqu4@angband.pl> <20181005182356.GA19324@magnolia> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181005182356.GA19324@magnolia> Sender: linux-xfs-owner@vger.kernel.org List-ID: List-Id: xfs To: "Darrick J. Wong" Cc: Adam Borowski , linux-xfs@vger.kernel.org On Fri, Oct 05, 2018 at 11:23:56AM -0700, Darrick J. Wong wrote: > On Fri, Oct 05, 2018 at 08:10:32PM +0200, Adam Borowski wrote: > > On Fri, Oct 05, 2018 at 09:06:00AM -0700, Darrick J. Wong wrote: > > > On Fri, Oct 05, 2018 at 02:27:41PM +0200, Adam Borowski wrote: > > > > Needed by users of fstatfs(). > > > > > > NAK. > > > > > > The XFS superblock magic number is part of the on-disk format definition > > > of XFS. It belongs with all the other on-disk format definitions in this > > > file. > > > > > > I don't think it's a good idea for userspace to associate s_magic with > > > userspace API feature sets, though the cat's long escaped the bag on > > > that one. > > > > > > With that being reality, "the XFS superblock magic number" has a > > > different semantic meaning than "the agreed upon statfs.f_type value for > > > XFS", which means the latter should have a different symbol name to > > > reflect that difference. > > > > Ie, you'd be ok with the same value to be defined in two places -- do I > > understand this right? > > > > > > --- a/fs/xfs/libxfs/xfs_format.h > > > > -#define XFS_SB_MAGIC 0x58465342 /* 'XFSB' */ > > > > +#define XFS_SB_MAGIC XFS_SUPER_MAGIC /* 0x58465342 = 'XFSB' */ > > > > --- a/include/uapi/linux/magic.h > > > > #define JFFS2_SUPER_MAGIC 0x72b6 > > > > +#define XFS_SUPER_MAGIC 0x58465342 /* "XFSB" */ > > > > #define PSTOREFS_MAGIC 0x6165676C > > Sorry, hit send too fast. > > include/uapi/linux/magic.h would get: > > #define XFS_STATFS_MAGIC 0x58465342 /* 'XFSB' */ $ man statfs |grep 0x5846 XFS_SUPER_MAGIC 0x58465342 $ -Dave. -- Dave Chinner david@fromorbit.com