Looked at your patch and then at our xfs code in the tree and
the existing code is different than what yours is based on.
I then noticed in the logs Nathan has actually made changes for this:
----------------------------
revision 1.254
date: 2006/07/17 10:46:05; author: nathans; state: Exp; lines: +20 -5
modid: xfs-linux-melb:xfs-kern:26565a
Update XFS for i_blksize removal from generic inode structure
----------------------------
I even reviewed the change (and I don't remember it - getting old).
I looked at the mods scheduled for 2.6.19 and this is one of them.
So the fix for this is coming soon (and the fix is different from the
one above).