From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752694AbcAUUDq (ORCPT ); Thu, 21 Jan 2016 15:03:46 -0500 Received: from mail2-relais-roc.national.inria.fr ([192.134.164.83]:40297 "EHLO mail2-relais-roc.national.inria.fr" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751122AbcAUUDo (ORCPT ); Thu, 21 Jan 2016 15:03:44 -0500 X-IronPort-AV: E=Sophos;i="5.22,327,1449529200"; d="scan'208";a="198616674" Date: Thu, 21 Jan 2016 21:03:42 +0100 (CET) From: Julia Lawall X-X-Sender: jll@localhost6.localdomain6 To: Rasmus Villemoes cc: Konrad Rzeszutek Wilk , Julia Lawall , linux-mm@kvack.org, kernel-janitors@vger.kernel.org, linux-kernel@vger.kernel.org, Boris Ostrovsky , David Vrabel , xen-devel@lists.xenproject.org Subject: Re: [PATCH] cleancache: constify cleancache_ops structure In-Reply-To: <8760ymln3q.fsf@rasmusvillemoes.dk> Message-ID: References: <1450904784-17139-1-git-send-email-Julia.Lawall@lip6.fr> <20160120222000.GA6765@char.us.oracle.com> <8760ymln3q.fsf@rasmusvillemoes.dk> User-Agent: Alpine 2.02 (DEB 1266 2009-07-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 21 Jan 2016, Rasmus Villemoes wrote: > On Wed, Jan 20 2016, Konrad Rzeszutek Wilk wrote: > > > On Wed, Dec 23, 2015 at 10:06:24PM +0100, Julia Lawall wrote: > >> The cleancache_ops structure is never modified, so declare it as const. > >> > >> This also removes the __read_mostly declaration on the cleancache_ops > >> variable declaration, since it seems redundant with const. > >> > >> Done with the help of Coccinelle. > >> > >> Signed-off-by: Julia Lawall > >> > >> --- > >> > >> Not sure that the __read_mostly change is correct. Does it apply to the > >> variable, or to what the variable points to? > > > > It should just put the structure in the right section (.rodata). > > > > Thanks for the patch! > > The __read_mostly marker should probably be left there... I sent a corrected version this afternoon. > > >> */ > >> -static struct cleancache_ops *cleancache_ops __read_mostly; > >> +static const struct cleancache_ops *cleancache_ops; > >> > >> /* > >> * Counters available via /sys/kernel/debug/cleancache (if debugfs is > >> @@ -49,7 +49,7 @@ static void cleancache_register_ops_sb(struct super_block *sb, void *unused) > >> /* > >> * Register operations for cleancache. Returns 0 on success. > >> */ > >> -int cleancache_register_ops(struct cleancache_ops *ops) > >> +int cleancache_register_ops(const struct cleancache_ops *ops) > >> { > >> if (cmpxchg(&cleancache_ops, NULL, ops)) > >> return -EBUSY; > >> > > I don't know this code, but I assume that this is mostly a one-time > thing, so once cleancache_ops gets its value assigned, it doesn't > change, and that's what the __read_mostly is about (it applies to the > object declared, not whatever it happens to point to). > > (Also, the commit message is slightly inaccurate: it is > tmem_cleancache_ops which is never changed and hence declared const; > changing the various pointers to it to const is just a necessary followup). OK, in general, I have referred to the type rather than the structure name in these patches, since there can be more than one structure. julia