efivarfs: Update inode modification time for successful writes

Some applications want to be able to see when EFI variables
have been updated.

Update the modification time for successful writes.

Reported-by: Lennart Poettering <[email protected]>
Signed-off-by: Tony Luck <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Ard Biesheuvel <[email protected]>

Author: aegl

fs/efivarfs/file.c

@@ -51,6 +51,7 @@ static ssize_t efivarfs_file_write(struct file *file,
 	} else {
 		inode_lock(inode);
 		i_size_write(inode, datasize + sizeof(attributes));
+		inode->i_mtime = current_time(inode);
 		inode_unlock(inode);
 	}