From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f46.google.com (mail-pa0-f46.google.com [209.85.220.46]) by kanga.kvack.org (Postfix) with ESMTP id B65126B0035 for ; Thu, 31 Jul 2014 10:13:24 -0400 (EDT) Received: by mail-pa0-f46.google.com with SMTP id lj1so3699470pab.19 for ; Thu, 31 Jul 2014 07:13:24 -0700 (PDT) Received: from mga09.intel.com (mga09.intel.com. [134.134.136.24]) by mx.google.com with ESMTP id ki8si159955pdb.319.2014.07.31.07.13.21 for ; Thu, 31 Jul 2014 07:13:21 -0700 (PDT) Date: Thu, 31 Jul 2014 10:13:15 -0400 From: Matthew Wilcox Subject: Re: [PATCH v8 04/22] Change direct_access calling convention Message-ID: <20140731141315.GT6754@linux.intel.com> References: <53D9174C.7040906@gmail.com> <20140730194503.GQ6754@linux.intel.com> <53DA165E.8040601@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <53DA165E.8040601@gmail.com> Sender: owner-linux-mm@kvack.org List-ID: To: Boaz Harrosh Cc: Matthew Wilcox , linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org On Thu, Jul 31, 2014 at 01:11:42PM +0300, Boaz Harrosh wrote: > >>> + if (size < 0) > >> > >> if(size < PAGE_SIZE), No? > > > > No, absolutely not. PAGE_SIZE is unsigned long, which (if I understand > > my C integer promotions correctly) means that 'size' gets promoted to > > an unsigned long, and we compare them unsigned, so errors will never be > > caught by this check. > > Good point I agree that you need a cast ie. > > if(size < (long)PAGE_SIZE) > > The reason I'm saying this is because of a bug I actually hit when > playing with partitioning and fdisk, it came out that the last partition's > size was not page aligned, and code that checked for (< 0) crashed because > prd returned the last two sectors of the partition, since your API is sector > based this can happen for you here, before you are memseting a PAGE_SIZE > you need to test there is space, No? Not in ext2/ext4. It requires block size == PAGE_SIZE, so it's never going to request the last partial block in a partition. -- 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