This patch is similar to one I posted yesterday for 2.6. It fixes the
following race conditions in nbd:
 
1) adds locking and properly orders the code in NBD_CLEAR_SOCK to
eliminate races with other code
 
2) adds an lo->sock check to nbd_clear_que to eliminate races between
do_nbd_request and nbd_clear_que, which resulted in the dequeuing of
active requests
 
3) adds an lo->sock check to NBD_DO_IT to eliminate races with
NBD_CLEAR_SOCK, which caused an Oops when "nbd-client -d" was called
 

Marcelo,

If we can get this into 2.4.22, that would be great. I know there's at
least one person who's consistently getting oopses with nbd.

Thanks,
Paul