2.4, XFS, and DM [LWN.net]

As reported last week, many users had requested that the XFS filesystem be added to the 2.4 kernel despite Marcelo's stated intent to go into a maintenance-only mode. Those users have prevailed: Marcelo has announced that, after a review by Christoph Hellwig, XFS has been merged into his 2.4 tree. It will thus show up in the first 2.4.24 prepatch, whenever that is released.

What has gone into 2.4 is, in fact, not the full XFS patch. Two subsystems have been left out:

DMAPI (Data Management API). This is an interface which allows the filesystem to communicate with hierarchical storage management systems.
ACLs. Access control lists require more general extended attribute support, which has never been merged into 2.4.

Users needing those features in XFS will have to run 2.6 to get them. Most users, however, will most likely be happy with the core XFS filesystem.

Meanwhile, a new request has been heard: could the device mapper (LVM2) code be merged? Marcelo's answer was direct: "I believe 2.6 is the right place for the device mapper." That would seem to be the end of the matter, but arguments are now being marshalled to try to get Marcelo to change his mind. This posting by Kevin Corry covers the relevant points quite well:

LVM2 is a lot nicer. The user-space tools, many taken from IBM's EVMS project, are easier to work with, and the device mapper code provides many capabilities that simply are unavailable in LVM1.
LVM1 itself has been removed from the 2.6 kernel (though LVM2 does provide backward compatibility). Putting LVM2 into 2.4 would make the transition easier for LVM users; they could get their volume sets working with LVM2 before having to commit to the new kernel.

The forward compatibility argument strikes a chord with many participants in the discussion, but Marcelo is, for now, adamant. One never knows, though; he previously has taken equally strong positions against ACPI and, of course, XFS, but been won over in the end.

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2.4, XFS, and DM

Posted Dec 11, 2003 18:29 UTC (Thu) by snitm (subscriber, #4031) [Link]

As a 2.4 device mapper user I find Marcelo's adamant "I won't merge it" approach to be very short-cited; Kevin Corry was right on the money with his take on its inclusion; there is no _real_ reason this change shouldn't be merged other than Marcelo has his head in the sand. He isn't taking the time to appreciate how minimal/non-invasive the DM changes really are.

Oh but Marcelo will gladly merge in Cyclades drivers (granted they don't touch common code paths of the kernel); maybe IBM needs to hire Marcelo to do their (and the communities') bidding...

2.4, XFS, and DM

Posted Dec 11, 2003 20:20 UTC (Thu) by Luyseyal (guest, #15693) [Link]

> Oh but Marcelo will gladly merge in Cyclades drivers

Yes, but that's a common, typical, non-invasive driver update to a stable kernel. That happens all the time.

1) Marcelo wants to be perceived as conservative, though able to be convinced now and then.

2) Marcelo probably has not allocated the time to verify how invasive the changes are. I mean, why have Hellwig review XFS if this is not the case?

Perhaps LVM2 people should have a 3rd party review their code as well...

-l

2.4, XFS, and DM

Posted Dec 11, 2003 23:16 UTC (Thu) by wolfrider (guest, #3105) [Link]

...And perhaps 2.4 needs a new maintainer.

2.4, XFS, and DM

Posted Dec 13, 2003 19:24 UTC (Sat) by giraffedata (subscriber, #1954) [Link]

Or alternatively, maybe people who don't like what Marcello is producing should stop using it. Marcello doesn't have a monopoly on Linux kernel distribution; plenty of other people distribute similar Linux kernels to Marcelo's with somewhat different choices as to what to include, and if none of those are right, there's nothing to stop someone from starting yet another.

It seems to me that someone who objects to Marcelo's performance is really objecting to the fact that lots of other people find no fault with it. Those other people are what keep Marcello's work relevant.

2.4, XFS, and DM

Posted Dec 19, 2003 18:02 UTC (Fri) by huaz (guest, #10168) [Link]

> 2) Marcelo probably has not allocated the time to verify how
> invasive the changes are. I mean, why have Hellwig review XFS
> if this is not the case?

No time? Then quit!

The reason that Chris, not Marcelo, reviewed the change is, as well said by Marcelo himself, "I don't know VFS well" (or something to that extent).

Folks, Marcelo apparently is not as competent as Alan, Andrew or Linus, so he has to be conservative. The fact that he could be "won over" is the only plus.