Move the call to vmtruncate to get rid of accessive blocks to the only
remaining caller and rename the non-truncating version to nobh_write_begin.
Get rid of the superflous file argument to it while we're at it.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>