From: David Sterba <dsterba@suse.cz>
To: "Joshua Schüler" <joshua.schueler@gmail.com>
Cc: "Miguel Negrão" <miguel.negrao-lists@friendlyvirus.org>,
"list, btrfs" <linux-btrfs@vger.kernel.org>
Subject: Re: btrfs send 3.11 vs 3.12
Date: Thu, 23 Jan 2014 15:41:07 +0100 [thread overview]
Message-ID: <20140123144107.GN6498@twin.jikos.cz> (raw)
In-Reply-To: <52E10B06.4080703@gmail.com>
On Thu, Jan 23, 2014 at 01:28:54PM +0100, Joshua Schüler wrote:
> btrfs guarantees backward compatibility since 3.13(?), but never
> guaranteed forward compatibility.
Isnt' this the opposite way? Forward means that old fs will be mountable
on a newer kernel.
I don't know what you mean by 'backward compatibility is guaranteed
since 3.13'. There are some features that get turned on automatically if
used for the first time, but not all of them prevent mounting on an
older kernel. Exmaple is the uuid tree, "generation v2" that's been
introduced with send. Older kernel ignores the changes and newer kernel
is usually able to recognize that the data are not all-ok and recovers
itself or allows the user to do so manually.
> So it is not yet supported to mount the fs with an older kernel once
> it was mounted with a newer one.
That's right, but in practice is not that bad.
> Especially when using features that are under heavy development right now.
Which features do you mean? Once a feature is introduced, the format
and incompatibility bits should not change. The code may change, and
does of course, but always in a compatible way.
next prev parent reply other threads:[~2014-01-23 14:41 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-01-23 9:22 btrfs send 3.11 vs 3.12 Miguel Negrão
2014-01-23 12:28 ` Joshua Schüler
2014-01-23 14:41 ` David Sterba [this message]
2014-01-23 14:19 ` Josef Bacik
2014-01-23 17:58 ` Miguel Negrão
2014-01-24 12:55 ` Felix Blanke
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