Re: [XFS SUMMIT] Deprecating V4 on-disk format

From: Eric Sandeen <sandeen@sandeen.net>
To: Mike Fleetwood <mike.fleetwood@googlemail.com>,
	Emmanuel Florac <eflorac@intellique.com>
Cc: Dave Chinner <david@fromorbit.com>,
	"Darrick J. Wong" <darrick.wong@oracle.com>,
	linux-xfs@vger.kernel.org
Subject: Re: [XFS SUMMIT] Deprecating V4 on-disk format
Date: Tue, 26 May 2020 12:16:23 -0500	[thread overview]
Message-ID: <6588190a-37f4-7d9d-0def-8727770a6ef5@sandeen.net> (raw)
In-Reply-To: <CAMU1PDjKGBVqog+JRB9OmYXTsT4y_chnDTHbF9P8xCJxN=aXqA@mail.gmail.com>

On 5/21/20 3:29 AM, Mike Fleetwood wrote:
> On Wed, 20 May 2020 at 14:25, Emmanuel Florac <eflorac@intellique.com> wrote:
>>
>> Le Wed, 20 May 2020 11:14:30 +1000
>> Dave Chinner <david@fromorbit.com> écrivait:
>>
>>> Well, there's a difference between what a distro that heavily
>>> patches the upstream kernel is willing to support and what upstream
>>> supports. And, realistically, v4 is going to be around for at least
>>> one more major distro release, which means the distro support time
>>> window is still going to be in the order of 15 years.
>>
>> IIRC, RedHat/CentOS v.7.x shipped with a v5-capable mkfs.xfs, but
>> defaulted to v4. That means that unless you were extremely cautious
>> (like I am :) 99% of RH/COs v7 will be running v4 volumes for the
>> coming years. How many years, would you ask?
> 
> [Trying again hopefully without HTML]
> 
> So initial RHEL/CentOS 7 releases did create XFS v4 file systems.
> However from RHEL/CentOS 7.3 [1] (circa Nov 2016) they are creating XFS
> v5 file systems by default.

That's correct.  Still a little shocked that we switched midstream but it
worked out fine.  :)

But as Dave said downthread, distro defaults and support is unrelated to
upstream; distros already signed up to support their shipped features
for the lifetime of the OS (or whatever their support policy says)

In fact, deprecating old stuff upstream will help future distro releases
manage their support by getting rid of antiquated features and behaviors...

-Eric

> 
> [1] RHEL 7.3 Release Notes > Chapter 9. File Systems
> https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/7/html/7.3_release_notes/new_features_file_systems
> 
> 
> # cat /etc/centos-release
> CentOS Linux release 7.8.2003 (Core)
> # mkfs.xfs -V
> mkfs.xfs version 4.5.0
> # mkfs.xfs /dev/sdb13
> ...
> # xfs_db -c version -r /dev/sdb13
> versionnum [0xb4a5+0x18a] =
> V5,NLINK,DIRV2,ALIGN,LOGV2,EXTFLG,MOREBITS,ATTR2,LAZYSBCOUNT,PROJID32BIT,CRC,FTYPE
> 