From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andi Kleen Subject: Re: DNAME_INLINE_LEN versus CONFIG_GENERIC_LOCKBREAK Date: Thu, 03 Jul 2014 12:53:01 -0700 Message-ID: <87fviite1u.fsf@tassilo.jf.intel.com> References: <8761je94wk.fsf@rasmusvillemoes.dk> Mime-Version: 1.0 Content-Type: text/plain Cc: Nick Piggin , Al Viro , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org To: Rasmus Villemoes Return-path: Received: from mga01.intel.com ([192.55.52.88]:42893 "EHLO mga01.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751392AbaGCTxG (ORCPT ); Thu, 3 Jul 2014 15:53:06 -0400 In-Reply-To: <8761je94wk.fsf@rasmusvillemoes.dk> (Rasmus Villemoes's message of "Thu, 03 Jul 2014 11:18:35 +0200") Sender: linux-fsdevel-owner@vger.kernel.org List-ID: Rasmus Villemoes writes: > In dcache.h, DNAME_INLINE_LEN is carefully chosen so that sizeof(struct > dentry) is a (specific) multiple of 64 bytes. Obviously this breaks when > certain debug options are chosen (DEBUG_LOCK_ALLOC and DEBUG_SPINLOCK), > but also, AFAICT, on architectures with CONFIG_GENERIC_LOCKBREAK. > > I'm not sure it matters, but if it does, I'd suggest putting a > BUILD_BUG_ON somewhere, protected by suitable #ifdefs, so that the code > documents the assumptions that went into the particular choice of > DNAME_INLINE_LEN (this would also help catch changes to some of the > structures embedded in struct dentry which would violate those > assumptions). The right fix would be to pad it correctly for these other variants too. Checking for magic numbers would be nasty though. -Andi -- ak@linux.intel.com -- Speaking for myself only