From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from relay.sgi.com (relay2.corp.sgi.com [137.38.102.29]) by oss.sgi.com (Postfix) with ESMTP id 1E18C7CA2 for ; Tue, 29 Mar 2016 19:22:25 -0500 (CDT) Received: from cuda.sgi.com (cuda2.sgi.com [192.48.176.25]) by relay2.corp.sgi.com (Postfix) with ESMTP id E6AF4304053 for ; Tue, 29 Mar 2016 17:22:21 -0700 (PDT) Received: from ipmail05.adl6.internode.on.net (ipmail05.adl6.internode.on.net [150.101.137.143]) by cuda.sgi.com with ESMTP id Gcafrkq9eMtKG128 for ; Tue, 29 Mar 2016 17:22:19 -0700 (PDT) Date: Wed, 30 Mar 2016 11:16:08 +1100 From: Dave Chinner Subject: Re: [PATCH] xfs: disallow rw remount on fs with unknown ro-compat features Message-ID: <20160330001608.GG30721@dastard> References: <56FAD75C.80502@redhat.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <56FAD75C.80502@redhat.com> List-Id: XFS Filesystem from SGI List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: xfs-bounces@oss.sgi.com Sender: xfs-bounces@oss.sgi.com To: Eric Sandeen Cc: xfs-oss On Tue, Mar 29, 2016 at 02:28:28PM -0500, Eric Sandeen wrote: > Today, a kernel which refuses to mount a filesystem read-write > due to unknown ro-compat features can still transition to read-write > via the remount path. The old kernel is most likely none the wiser, > because it's unaware of the new feature, and isn't using it. However, > writing to the filesystem may well corrupt metadata related to that > new feature, and moving to a newer kernel which understand the feature > will have problems. > > Right now the only ro-compat feature we have is the free inode btree, > which showed up in v3.16. It would be good to push this back to > all the active stable kernels, I think, so that if anyone is using > newer mkfs (which enables the finobt feature) with older kernel > releases, they'll be protected. Ok, so the bug was introduced with the original extended feature masks in commit e721f50 ("xfs: implement extended feature masks"), which was introduced in 3.10. So it will need to go back to stable kernels all the way back to 3.10, right? Cheers, Dave. -- Dave Chinner david@fromorbit.com _______________________________________________ xfs mailing list xfs@oss.sgi.com http://oss.sgi.com/mailman/listinfo/xfs