In brief

    int reflink(const char *oldpath, const char *newpath, int preserve);
    int reflinkat(int olddirfd, const char *oldpath,
                  int newdirfd, const char *newpath,
      		  int preserve,  int flags);

A call to reflink() causes newpath to look like a copy of oldpath. If preserve is REFLINK_ATTR_PRESERVE, then the entire security state of oldpath will be replicated for the new file; this is a privileged operation. Otherwise (if preserve is REFLINK_ATTR_NONE), newpath will get a new security state as if it were an entirely new file. The reflinkat() form adds the ability to supply the starting directories for relative paths and flags like the other *at() system calls. For more information, see the documentation file at the top of the reflink() patch.

Joel's patch adds reflink() support for the ocfs2 filesystem; it's not clear whether other filesystems will get reflink() support in 2.6.32 or not.

A stable debugfs?. Recurring linux-kernel arguments tend to focus on vitally important issues - like where debugfs should be mounted. The official word is that it belongs on /sys/kernel/debug, but there have been ongoing problems with rogue developers mounting it on unofficial places like /debug instead. Greg Kroah-Hartman defends /sys/kernel/debug by noting that debugfs is for kernel developers only; there's no reason for users to be interested in it.

Except, of course, that there is. The increasing utility of the ftrace framework is making it more interesting beyond kernel development circles. That led Steven Rostedt to make a suggestion:

Steven would like a new virtual filesystem for stable kernel ABIs which is easier to work with than sysfs and which can be mounted in a more typing-friendly location. Responses to the suggestion have been scarce so far; somebody will probably need to post a patch to get a real discussion going.

data=guarded. Chris Mason has posted a new version of the ext3 data=guarded mode patch. The guarded mode works to ensure that data blocks arrive on disk before any metadata changes which reference those blocks. The goal is to provide the performance benefits of the data=writeback mode while avoiding the potential information disclosure (after a crash) problems with that mode. Chris had mentioned in the past that he would like to merge this code for 2.6.32; the latest posting, though, suggests that some work still needs to be done, so it might not be ready in time.