new helper: file_inode(file)

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/mm/fadvise.c b/mm/fadvise.c
index a47f0f5..6deaa6c 100644
--- a/mm/fadvise.c
+++ b/mm/fadvise.c
@@ -38,7 +38,7 @@
 	if (!f.file)
 		return -EBADF;
 
-	if (S_ISFIFO(f.file->f_path.dentry->d_inode->i_mode)) {
+	if (S_ISFIFO(file_inode(f.file)->i_mode)) {
 		ret = -ESPIPE;
 		goto out;
 	}