jbd2: checksum data blocks that are stored in the journal

Calculate and verify checksums of each data block being stored in the journal.

Signed-off-by: Darrick J. Wong <djwong@us.ibm.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

diff --cc fs/jbd2/commit.c
Simple merge

diff --cc fs/jbd2/journal.c
Simple merge

diff --cc fs/jbd2/recovery.c
Simple merge