[PATCH] affs: implement ->drop_inode

affs wants to truncate the inode when the last user goes away, currently it
does that through a potentially racy i_count check in ->put_inode.  But we
already have a method that's called just after the we dropped the last
reference, ->drop_inode.  This patch implements affs_drop_inode to take
advantage of this.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Cc: Roman Zippel <zippel@linux-m68k.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>