fs: restore nobh

fs: restore nobh

Implement nobh in new aops.  This is a bit tricky.  FWIW, nobh_truncate is
now implemented in a way that does not create blocks in sparse regions,
which is a silly thing for it to have been doing (isn't it?)

ext2 survives fsx and fsstress. jfs is converted as well... ext3
should be easy to do (but not done yet).

[[email protected]: coding-style fixes]
Cc: Badari Pulavarty <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>