ocfs2: Fix writeout in ocfs2_data_convert_worker()

Commit f1f540688eae66c274ff1c1133b5d9c687b28f58 "optimized"
ocfs2_data_convert_worker() to "only do work for regular files".
Unfortunately, I left out a '!', which casued it to *skip* regular files.
This was hidden from testing until recently because the default data
journaling mode (data=ordered) doesn't exercise this code.

Signed-off-by: Mark Fasheh <mark.fasheh@oracle.com>
Signed-off-by: Joel Becker <joel.becker@oracle.com>

fs/ocfs2/dlmglue.c

@@ -3042,7 +3042,7 @@ static int ocfs2_data_convert_worker(struct ocfs2_lock_res *lockres,
        	inode = ocfs2_lock_res_inode(lockres);
 	mapping = inode->i_mapping;
 
-	if (S_ISREG(inode->i_mode))
+	if (!S_ISREG(inode->i_mode))
 		goto out;
 
 	/*