ov3.c question

[John Newman]

from storage/ov3/ov3.c:

 do {
        oldinode = ge->indexinode;
        if (low < ge->low)
            low = ge->low;
        if (high > ge->high)
            high = ge->high;
        base = ge->base;
    } while (ge->indexinode != oldinode);

What's the significance of the loop in this piece 
of code?  I've just been perusing the source trying
to determine why some of our group overviews keep 
showing up corrupted (obviously unrelated).

-- 
				 
John