[CC'd to linux-mm at Rik's suggestion]

This is a first attempt at a fix for what I /think/ is a potential race
condition in getblk. There seems to be a small window where multiple
buffer_heads could be added to the hash table for the same block. The patch
compiles, but I've not tried running it yet. Any thoughts?

-- 
The very concept of PNP is a lovely dream that simply does not translate to
reality. The confusion of manually doing stuff is nothing compared to the
confusion of computers trying to do stuff and getting it wrong, which they
gleefully do with great enthusiasm. -- Jinx Tigr in the SDM