From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail203.messagelabs.com (mail203.messagelabs.com [216.82.254.243]) by kanga.kvack.org (Postfix) with ESMTP id 955166B003D for ; Thu, 19 Feb 2009 13:30:16 -0500 (EST) Date: Thu, 19 Feb 2009 18:28:55 +0000 (GMT) From: Hugh Dickins Subject: Re: [patch 1/7] slab: introduce kzfree() In-Reply-To: <1235066556.3166.26.camel@calx> Message-ID: References: <499BE7F8.80901@csr.com> <1234954488.24030.46.camel@penberg-laptop> <20090219101336.9556.A69D9226@jp.fujitsu.com> <1235034817.29813.6.camel@penberg-laptop> <1235066556.3166.26.camel@calx> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org To: Matt Mackall Cc: Pekka Enberg , KOSAKI Motohiro , David Vrabel , Johannes Weiner , Andrew Morton , Chas Williams , Evgeniy Polyakov , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Christoph Lameter , Nick Piggin List-ID: On Thu, 19 Feb 2009, Matt Mackall wrote: > On Thu, 2009-02-19 at 16:34 +0000, Hugh Dickins wrote: > > On Thu, 19 Feb 2009, Pekka Enberg wrote: > > > On Thu, 2009-02-19 at 10:22 +0900, KOSAKI Motohiro wrote: > > > > > > > > poisonig is transparent feature from caller. > > > > but the caller of kzfree() know to fill memory and it should know. > > > > > > Debatable, sure, but doesn't seem like a big enough reason to make > > > kzfree() differ from kfree(). > > > > There may be more important things for us to worry about, > > but I do strongly agree with KOSAKI-san on this. > > > > kzfree() already differs from kfree() by a "z": that "z" says please > > zero the buffer pointed to; "const" says it won't modify the buffer > > pointed to. What sense does kzfree(const void *) make? Why is > > keeping the declarations the same apart from the "z" desirable? > > > > By all means refuse to add kzfree(), but please don't add it with const. > > > > I can see that the "const" in kfree(const void *) is debatable > > [looks to see how userspace free() is defined: without a const], > > I can see that it might be nice to have some "goesaway" attribute > > for such pointers instead; but I don't see how you can argue for > > kzalloc(const void *). ^^^^^^^^^^^^^^^^^^^^^ (Of course I meant to say "kzfree(const void *)" there.) > > This is what Linus said last time this came up: > > http://lkml.org/lkml/2008/1/16/227 Thanks for that, I remember it now. Okay, that's some justification for kfree(const void *). But I fail to see it as a justification for kzfree(const void *): if someone has "const char *string = kmalloc(size)" and then wants that string zeroed before it is freed, then I think it's quite right to cast out the const when calling kzfree(). Hugh -- 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