new helper: file_inode(file)

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

mm/fadvise.c

@@ -38,7 +38,7 @@ SYSCALL_DEFINE(fadvise64_64)(int fd, loff_t offset, loff_t len, int advice)
 	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;
 	}