fs: move inode_dio_wait calls into ->setattr

Let filesystems handle waiting for direct I/O requests themselves instead
of doing it beforehand.  This means filesystem-specific locks to prevent
new dio referenes from appearing can be held.  This is important to allow
generalizing i_dio_count to non-DIO_LOCKING filesystems.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/gfs2/bmap.c b/fs/gfs2/bmap.c
index e65493a..2cd0e56 100644
--- a/fs/gfs2/bmap.c
+++ b/fs/gfs2/bmap.c
@@ -1224,6 +1224,8 @@
 	if (ret)
 		return ret;
 
+	inode_dio_wait(inode);
+
 	oldsize = inode->i_size;
 	if (newsize >= oldsize)
 		return do_grow(inode, newsize);