From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from relay.sgi.com (relay3.corp.sgi.com [198.149.34.15]) by oss.sgi.com (Postfix) with ESMTP id 78FF97CA2 for ; Tue, 29 Mar 2016 19:27:19 -0500 (CDT) Received: from cuda.sgi.com (cuda1.sgi.com [192.48.157.11]) by relay3.corp.sgi.com (Postfix) with ESMTP id F07C3AC004 for ; Tue, 29 Mar 2016 17:27:18 -0700 (PDT) Received: from mx1.redhat.com (mx1.redhat.com [209.132.183.28]) by cuda.sgi.com with ESMTP id WrVOfuC6NK1kJugv (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NO) for ; Tue, 29 Mar 2016 17:27:18 -0700 (PDT) Subject: Re: [PATCH] xfs: disallow rw remount on fs with unknown ro-compat features References: <56FAD75C.80502@redhat.com> <20160330001608.GG30721@dastard> From: Eric Sandeen Message-ID: <56FB1D64.1080700@redhat.com> Date: Tue, 29 Mar 2016 19:27:16 -0500 MIME-Version: 1.0 In-Reply-To: <20160330001608.GG30721@dastard> 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: Dave Chinner Cc: xfs-oss On 3/29/16 7:16 PM, Dave Chinner wrote: > 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. > Yeah, that seems right; it's not when the first ro-compat feature was introduced, it was when the handling was introduced, right? If you need to massage the cc:stable line feel free, of course. ie: Cc: # 3.10.x- I think. -Eric _______________________________________________ xfs mailing list xfs@oss.sgi.com http://oss.sgi.com/mailman/listinfo/xfs