[Ocfs2-users] Versions and features

[Sunil Mushran]

On 03/01/2011 05:35 AM, Werner Flamme wrote:
> I see the compatibility list on the mkfs.ocfs2 manpage. But I still do
> not see what features are available for any of us.

That should be listed with the docs that are made available with
the fs. Remember tools is just one half of the equation.

> I this list, the kernel my colleague uses (2.6.18) is not mentioned, the
> list starts with 2.6.20. So he has no OCFS2 at all? Nonsense, he has.
> He uses OCFS2 1.4.8 as a kernel module, and the tools show version 1.6.
> So he can use what features? Because of his kernel module it was local,
> sparse, unwritten, and inline-data. But from the tools version he should
> be able to use block64, xattr, and refcount also.

Note that EL5 is _not_ 2.6.18. That version was merely the starting
point. The kernel versions listed in mkfs manpage refer to pure
unadulterated mainline kernel versions.

If the kernel module is 1.4, then the user will be limited to the feature
set listed in the 1.4 docs. That the tools are 1.6 is incidental. To get
all the latest features, both the tools and the fs need to be the latest
version.


> My kernel (2.6.32) does show up, but the version of my kernel module
> (1.5) does not. My tools are version 1.4. So I should not be able to use
> any feature that he can't. But this is not the case, some attribute that
> my mkfs.ocfs2 introduced to the filesystem was the reason that he could
> not mount it.

In mainline, the fs version does not matter. It is the version of the
kernel that dictates the version of the fs. We have not figured out
how to automatically populate the fs version with the kernel version.

> What might this attribute have been? How will we ever find out? Only
> trial and error?
>
> What about a %F in the query string of tunefs.ocfs2 telleing all
> possible features for the installed combination of OCFS2 kernel module
> and tools? %H and %M are nice, but they only show the flags that are
> already applied. %F might show the features that are possible to handle.

modinfo maybe a better place to provide this info. But the reality is
that this is just an interim problem. If we add the list of supported
features in modinfo, the new module will be in users hands around
the same time that all users will be on the new version. Still something
for us to chew on.