From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx116.postini.com [74.125.245.116]) by kanga.kvack.org (Postfix) with SMTP id 1A5776B0032 for ; Mon, 17 Jun 2013 18:33:24 -0400 (EDT) Date: Mon, 17 Jun 2013 15:33:22 -0700 From: Andrew Morton Subject: Re: [PATCH] thp: define HPAGE_PMD_* constans as BUILD_BUG() if !THP Message-Id: <20130617153322.f3cecaa54aacd465fedb7c36@linux-foundation.org> In-Reply-To: <20130617222703.D8C4AE0090@blue.fi.intel.com> References: <1371506740-14606-1-git-send-email-kirill.shutemov@linux.intel.com> <20130617151417.f7610d56b4b43ced30c40133@linux-foundation.org> <20130617222703.D8C4AE0090@blue.fi.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: "Kirill A. Shutemov" Cc: "Aneesh Kumar K.V" , Andrea Arcangeli , linux-kernel@vger.kernel.org, linux-mm@kvack.org On Tue, 18 Jun 2013 01:27:03 +0300 (EEST) "Kirill A. Shutemov" wrote: > > > #else /* CONFIG_TRANSPARENT_HUGEPAGE */ > > > +#define HPAGE_PMD_SHIFT ({ BUILD_BUG(); 0; }) > > > +#define HPAGE_PMD_MASK ({ BUILD_BUG(); 0; }) > > > +#define HPAGE_PMD_SIZE ({ BUILD_BUG(); 0; }) > > > > > > > We've done this sort of thing before and it blew up. We do want to be > > able to use things like HPAGE_PMD_foo in global-var initialisers and > > definitions, but the problem is that BUILD_BUG() can't be used outside > > functions. > > I don't see how it's a blocker. For global variables, we will have to use > #ifdefs, but the approach is still useful for in-function code. OK. Current mainline uses BUILD_BUG() here, so I guess the change won't break anything. Yet. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org