get rid of block_write_begin_newtrunc

Move the call to vmtruncate to get rid of accessive blocks to the callers
in preparation of the new truncate sequence and rename the non-truncating
version to block_write_begin.

While we're at it also remove several unused arguments to block_write_begin.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/block_dev.c b/fs/block_dev.c
index 65a0c26..63c9d60 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -308,9 +308,8 @@
 			loff_t pos, unsigned len, unsigned flags,
 			struct page **pagep, void **fsdata)
 {
-	*pagep = NULL;
-	return block_write_begin_newtrunc(file, mapping, pos, len, flags,
-				pagep, fsdata, blkdev_get_block);
+	return block_write_begin(mapping, pos, len, flags, pagep,
+				 blkdev_get_block);
 }
 
 static int blkdev_write_end(struct file *file, struct address_space *mapping,