From mboxrd@z Thu Jan 1 00:00:00 1970 From: Richard Knutsson Date: Fri, 16 Feb 2007 16:40:15 +0000 Subject: Re: [KJ] [PATCH] is_power_of_2 in ia64mm Message-Id: <45D5DE6F.6030604@student.ltu.se> List-Id: References: <1171627435.6127.0.camel@wriver-t81fb058.linuxcoe> <45D5C789.1090607@student.ltu.se> <45D5D47F.3000303@student.ltu.se> In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Andreas Schwab Cc: Vignesh Babu BM , Kernel Janitors List , linux-mm@kvack.org, tony.luck@intel.com, linux-ia64@vger.kernel.org, linux-kernel@vger.kernel.org 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. It ended by concluding that is_power_of_2() should be fixed up first and then we can see about it. And as I stated before; !is_power_of_2(size) != (size & (size-1))! It may be a bug but then we have to be sure it is suppose to be the power of 2. Richard Knutsson