Linus, I've got the first of BKL-removal ext2 patches ready to
go.  It removes BKL from ext2_get_block() and guts of ext2_truncate().
The only place where we hold BKL on these paths is in dquot.c - probably
can be easily dealt with, but threading quota is a separate story.

	Inode metadata (pointers to blocks, both in inode itself and in
indirect blocks, preallocation data and allocation goal) are protected
by rwlock - EXT2_I(inode)->i_meta_lock.

	Next steps will involve threading the group descriptors and bitmaps
handling - lock_super() uses in ext2 are going to die.  However, that's
a separate story - let's do that step-by-step.

	I suspect that patch below will take care of almost all BKL contention
from ext2 - we still have BKL held over directory operations, but for regular
files that's it.