Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1946024AbXBPRhL (ORCPT ); Fri, 16 Feb 2007 12:37:11 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1946023AbXBPRhL (ORCPT ); Fri, 16 Feb 2007 12:37:11 -0500 Received: from gepetto.dc.ltu.se ([130.240.42.40]:55128 "EHLO gepetto.dc.ltu.se" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1946018AbXBPRhJ (ORCPT ); Fri, 16 Feb 2007 12:37:09 -0500 Message-ID: <45D5EBB9.4080903@student.ltu.se> Date: Fri, 16 Feb 2007 18:36:57 +0100 From: Richard Knutsson User-Agent: Thunderbird 1.5.0.9 (X11/20070212) MIME-Version: 1.0 To: "Robert P. J. Day" CC: Andreas Schwab , linux-mm@kvack.org, tony.luck@intel.com, linux-ia64@vger.kernel.org, Kernel Janitors List , linux-kernel@vger.kernel.org Subject: Re: [KJ] [PATCH] is_power_of_2 in ia64mm References: <1171627435.6127.0.camel@wriver-t81fb058.linuxcoe> <45D5C789.1090607@student.ltu.se> <45D5D47F.3000303@student.ltu.se> <45D5DE6F.6030604@student.ltu.se> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2478 Lines: 77 Robert P. J. Day wrote: > i'm not clear on what the possible problem is here: > > On Fri, 16 Feb 2007, Richard Knutsson wrote: > > >> Andreas Schwab wrote: >> >>> Richard Knutsson writes: >>> >>> >>>> Andreas Schwab wrote: >>>> >>>> >>>>> Richard Knutsson writes: >>>>> >>>>> >>>>> >>>>>> Vignesh Babu BM wrote: >>>>>> >>>>>> >>>>>>> @@ -175,7 +176,7 @@ static int __init hugetlb_setup_sz(char *str) >>>>>>> tr_pages = 0x15557000UL; >>>>>>> size = memparse(str, &str); >>>>>>> - if (*str || (size & (size-1)) || !(tr_pages & size) || >>>>>>> + if (*str || !is_power_of_2(size) || !(tr_pages & size) || >>>>>>> size <= PAGE_SIZE || >>>>>>> size >= (1UL << PAGE_SHIFT << MAX_ORDER)) { >>>>>>> printk(KERN_WARNING "Invalid huge page size specified\n"); >>>>>>> >>>>>>> >>>>>> As we talked about before; is this really correct? !is_power_of_2(0) == >>>>>> true while (0 & (0-1)) == 0. >>>>>> >>>>>> >>>>> size == 0 is also covered by the next two conditions, so the overall value >>>>> does not change. >>>>> >>>>> >>>> Yes, but is it meant to state that 'size' is not a power of two? >>>> >>>> >>> What else can it mean? >>> >> What about !one_or_less_bit()? It has not been implemented (yet?) >> but been discussed. >> > > but whether or not it's been implemented doesn't change whether or not > the code above can be simplified. given what's being tested, and the > error message about whether a page size is valid, it seems fairly > clear that this is a power of two test. what's the problem? > Fsck, I can't see that. But if that is what's intended, well then... (5 min later) Ok, now I think I see it. Sorry for the noise.. > >> It ended by concluding that is_power_of_2() should be fixed up first >> and then we can see about it. >> > > there's nothing about is_power_of_2() that needs "fixing". it's > correct as it's currently implemented. > Oh, I didn't mean that is_power_of_2() need to be fixed, I meant fixing/replacing the kernel with is_power_of_2(). Todays lesson: don't try to code while you have a cold... Richard Knutsson - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/