My suggestion would be to ask nfs@lists.sourceforge.net. Trond and Chuck Lever both seem to hang out there, and discuss changes to the linux nfs client. Alternately, the source might have some interesting comments. This might be an interesting start. I'll admit I did a quick check, and didn't find anything specific regarding snapshot support.
http://lxr.linux.no/source/fs/nfs/?v=2.6.18
-Blake
On 11/6/06, Stephen C. Losen scl@sasha.acc.virginia.edu wrote:
We installed the latest kernel update for Red Hat FC5 (forgot the kernel version number) and we noticed a nifty new NFS client feature. The kernel is "snapshot aware" which means that when you "stat()" something in a snapshot, the device number is different from the live filesystem. Furthermore, different snapshots have different device numbers.
I can see where this is a very nice feature, because it solves some difficulties with snapshots.
o You can now run "find /mountpoint -mount" (or -xdev) to avoid dropping into the .snapshot tree.
o You can now "diff" a live file and a snapshot copy of the file because many versions of diff simply return no differences when two files have the same device and inode number.
o You can now "cp" a snapshot copy of a file on top of the live file. This used to fail because cp checks the device and inode number to prevent you from copying a file on top of itself.
However, we have some locally written software that expects the live filesystem and snapshot to have the same device number. The person who wrote the software is wondering if this change in NFS behavior is a bug, or fluke, or experimental, or if the Linux developers intend for the Linux kernel to behave this way from now on. Can this behavior be enabled/disabled ? If no one knows offhand, where might I go to find out?
Steve Losen scl@virginia.edu phone: 434-924-0640
University of Virginia ITC Unix Support