I saw your talk about driverfs at OLS and it got my attention.  When 
my BKL debugging patch showed some use of the BKL in driverfs, I was 
very dissapointed (you can blame Greg if you want).

text from dmesg after BKL debugging patch:
release of recursive BKL hold, depth: 1
[ 0]main:492
[ 1]inode:149

I see no reason to hold the BKL in your situation.  I replaced it with 
i_sem in some places and just plain removed it in others.  I believe 
that you get all of the protection that you need from dcache_lock in 
the dentry insert and activate.  Can you prove me wrong?

-- 
Dave Hansen
haveblue@us.ibm.com