libxfs: ensure btree root split sets blkno correctly

libxfs: ensure btree root split sets blkno correctly

For CRC enabled filesystems, the BMBT is rooted in an inode, so it
passes through a difference code path on root splits to the
freespace and inode btrees. The inode based btree root has a
corruption problem on split - it's the same problem we saw in the
directory/attr code where headers are memcpy()d from one block to
another without updating the self describing metadata.

Simple fix - when copying the header out of the root block, make
sure the block number is updated correctly.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Review-by: Mark Tinguely <tinguely@sgi.com>
Signed-off-by: Rich Johnston <rjohnston@sgi.com>