ext4: Ensure zeroout blocks have no dirty metadata

ext4: Ensure zeroout blocks have no dirty metadata

commit 515f41c33a9d44a964264c9511ad2c869af1fac3 upstream (as of v2.6.33-rc3)

This fixes a bug (found by Curt Wohlgemuth) in which new blocks
returned from an extent created with ext4_ext_zeroout() can have dirty
metadata still associated with them.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Curt Wohlgemuth <curtw@google.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>