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Please (help) improve support for linux-vserver

To: xfs@xxxxxxxxxxx
Subject: Please (help) improve support for linux-vserver
From: Andras Korn <korn-xfs@xxxxxxxxxxxxxx>
Date: Sun, 16 Dec 2012 23:39:53 +0100
User-agent: Mutt/1.5.21 (2010-09-15)
Hi,

I'm a user of xfs and linux-vserver (http://linux-vserver.org/).

I'd like vserver to work better with xfs (or vice versa) and am trying to
proxy between the two development communities (which in the case of vserver
is not very large).

vservers are basically chroots on steroids: the host runs a single kernel,
but it isolates processes running in the guests from each other. There is a
"copy on write hardlink breaking" feature that allows you to hardlink files
(such as libc6) of different guests together (so that they only get mapped
into memory once), and have the kernel break the link if the inode is opened
for writing (by creating a copy and returning a FD to the copy).

This feature relies on inode flags (like the 'immutable' bit). vserver adds
two fields to the inode (the other is used to tag inodes with a context ID).

The kernel parts work, but xfs_repair breaks such filesystems because it
thinks the flags are invalid.

I approached David Chinner and Eric Sandeen about this on IRC, and they said
that the first step towards any improvement would be to share with this list
the parts of the vserver patch that affect xfs, so that's what I'm doing
now.

Please find attached the output of

filterdiff -i '*xfs*' patch-3.7-vs2.3.5.1.diff

(the latter was obtained from http://vserver.13thfloor.at/Experimental/ but
the xfs specific parts apparently haven't changed in a while).

Andras

-- 
                     Andras Korn <korn at elan.rulez.org>
                                 I ? Unicode.

Attachment: vserver-xfs.diff
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