new helper: file_inode(file)

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/drivers/scsi/st.c b/drivers/scsi/st.c
index 98156a9..3e2b371 100644
--- a/drivers/scsi/st.c
+++ b/drivers/scsi/st.c
@@ -977,7 +977,7 @@
 	struct st_modedef *STm;
 	struct st_partstat *STps;
 	char *name = tape_name(STp);
-	struct inode *inode = filp->f_path.dentry->d_inode;
+	struct inode *inode = file_inode(filp);
 	int mode = TAPE_MODE(inode);
 
 	STp->ready = ST_READY;