From owner-svn-src-all@FreeBSD.ORG Tue Sep 29 17:00:06 2009 Return-Path: Delivered-To: svn-src-all@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 7B7ED1065670; Tue, 29 Sep 2009 17:00:06 +0000 (UTC) (envelope-from rwatson@FreeBSD.org) Received: from cyrus.watson.org (cyrus.watson.org [65.122.17.42]) by mx1.freebsd.org (Postfix) with ESMTP id 49E008FC1E; Tue, 29 Sep 2009 17:00:06 +0000 (UTC) Received: from fledge.watson.org (fledge.watson.org [65.122.17.41]) by cyrus.watson.org (Postfix) with ESMTPS id DD51946B03; Tue, 29 Sep 2009 13:00:05 -0400 (EDT) Date: Tue, 29 Sep 2009 18:00:05 +0100 (BST) From: Robert Watson X-X-Sender: robert@fledge.watson.org To: Marcel Moolenaar In-Reply-To: <1F22EA6A-2793-45CE-9669-3FFD550CF4E2@mac.com> Message-ID: References: <200909282352.n8SNql1n069970@svn.freebsd.org> <200909290749.08764.jhb@freebsd.org> <1F22EA6A-2793-45CE-9669-3FFD550CF4E2@mac.com> User-Agent: Alpine 2.00 (BSF 1167 2008-08-23) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed Cc: svn-src-head@freebsd.org, svn-src-all@freebsd.org, Marcel Moolenaar , src-committers@freebsd.org, John Baldwin Subject: Re: svn commit: r197608 - head/sys/geom/part X-BeenThere: svn-src-all@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: "SVN commit messages for the entire src tree \(except for " user" and " projects" \)" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 29 Sep 2009 17:00:06 -0000 On Tue, 29 Sep 2009, Marcel Moolenaar wrote: >> Why do you check for zeros at all? AFAIK, the only real check is for AA55 >> at the end of the sector (and having an MBR or other Extended MBR partition >> entry point at the sector in question). The '96' thing seems rather >> arbitrary in the code, and I think the zero's check is overly restrictive. > > Only checking for a signature that 99% of the boot blocks have isn't enough. > The msdos file system has that signature and the check for all-zeroes is to > prevent false positives there. And, as I recall, the msdosfs check has been gradually getting weaker over time as the constraints it places on things like cylinder counts become obsolete. It's not quite that we'll mount msdosfs on any random pile of bytes, but it might be getting there... Robert