From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759891Ab3BYXf6 (ORCPT ); Mon, 25 Feb 2013 18:35:58 -0500 Received: from mail.linuxfoundation.org ([140.211.169.12]:55944 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759853Ab3BYXf4 (ORCPT ); Mon, 25 Feb 2013 18:35:56 -0500 Date: Mon, 25 Feb 2013 15:35:54 -0800 From: Andrew Morton To: Simon Horman Cc: Zhang Yanfei , "Eric W. Biederman" , "kexec@lists.infradead.org" , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH v2] kexec: Use min_t to simplify logic Message-Id: <20130225153554.19cde4b4.akpm@linux-foundation.org> In-Reply-To: <20130225003651.GD17964@verge.net.au> References: <512A25A1.4040002@gmail.com> <20130225003651.GD17964@verge.net.au> X-Mailer: Sylpheed 3.0.2 (GTK+ 2.20.1; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 25 Feb 2013 09:36:51 +0900 Simon Horman wrote: > On Sun, Feb 24, 2013 at 10:37:21PM +0800, Zhang Yanfei wrote: > > From: Zhang Yanfei > > > > This is just a tweak: using min_t to simplify logic of variable > > assignments. > > > > v2: > > - Rewrite patch description as Simon suggested. > > - Fix an inappropriate if test introduced by v1. Thanks Simon. > > Hi Zhang, > > thanks for the update. > > Signed-off-by: Simon Horman Signed-off-by: implies that you were involved in the development or patch delivery. Were you? If not, an Acked-by or Reviewed-by is more appropriate. Also, the need to use min_t rather than min is a sign that the types are screwed up. Let's take a look. > > > > diff --git a/kernel/kexec.c b/kernel/kexec.c > > index 2436ffc..effd655 100644 > > --- a/kernel/kexec.c > > +++ b/kernel/kexec.c > > @@ -822,13 +822,8 @@ static int kimage_load_normal_segment(struct kimage *image, > > /* Start with a clear page */ > > clear_page(ptr); > > ptr += maddr & ~PAGE_MASK; > > - mchunk = PAGE_SIZE - (maddr & ~PAGE_MASK); > > - if (mchunk > mbytes) > > - mchunk = mbytes; > > - > > - uchunk = mchunk; > > - if (uchunk > ubytes) > > - uchunk = ubytes; > > + mchunk = min_t(size_t, mbytes, PAGE_SIZE - (maddr & ~PAGE_MASK)); > > + uchunk = min_t(size_t, ubytes, mchunk); The types of ubytes and mbytes are clearly wrong. They are initialised from a size_t and they are manipulated alongside size_t's. The types of PAGE_SIZE and PAGE_MASK are vague - iirc they once had different types on different architectures, so some form of casting is unavoidable here. > > result = copy_from_user(ptr, buf, uchunk); > > kunmap(page); > > @@ -874,13 +869,9 @@ static int kimage_load_crash_segment(struct kimage *image, > > } > > ptr = kmap(page); > > ptr += maddr & ~PAGE_MASK; > > - mchunk = PAGE_SIZE - (maddr & ~PAGE_MASK); > > - if (mchunk > mbytes) > > - mchunk = mbytes; > > - > > - uchunk = mchunk; > > - if (uchunk > ubytes) { > > - uchunk = ubytes; > > + mchunk = min_t(size_t, mbytes, PAGE_SIZE - (maddr & ~PAGE_MASK)); > > + uchunk = min_t(size_t, ubytes, mchunk); > > + if (mchunk > uchunk) { > > /* Zero the trailing part of the page */ > > memset(ptr + uchunk, 0, mchunk - uchunk); > > } Again, mybtes and ubytes have the wrong type. > > @@ -1461,8 +1452,7 @@ void vmcoreinfo_append_str(const char *fmt, ...) > > r = vsnprintf(buf, sizeof(buf), fmt, args); > > va_end(args); > > > > - if (r + vmcoreinfo_size > vmcoreinfo_max_size) > > - r = vmcoreinfo_max_size - vmcoreinfo_size; > > + r = min_t(size_t, r, vmcoreinfo_max_size - vmcoreinfo_size); > > > > memcpy(&vmcoreinfo_data[vmcoreinfo_size], buf, r); vmcoreinfo_max_size is a size_t and vmcoreinfo_size is a size_t and memcpy's `size' argument is a size_t. Therefore the type of `r' should be... what? int! bzzzzt.