From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([209.51.188.92]:34634) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1gklfK-0002IW-71 for qemu-devel@nongnu.org; Sat, 19 Jan 2019 03:07:43 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1gklfJ-0004FD-7Y for qemu-devel@nongnu.org; Sat, 19 Jan 2019 03:07:42 -0500 Date: Sat, 19 Jan 2019 08:07:12 +0000 From: "Richard W.M. Jones" Message-ID: <20190119080712.GY27120@redhat.com> References: <20190117193658.16413-1-eblake@redhat.com> <38eca33c-cbea-6948-0e05-86a5e0bbeb00@virtuozzo.com> <928553ea-9694-acc6-1c5f-5a09afc2c64c@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <928553ea-9694-acc6-1c5f-5a09afc2c64c@redhat.com> Subject: Re: [Qemu-devel] [PATCH v4 00/21] nbd: add qemu-nbd --list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Eric Blake Cc: Vladimir Sementsov-Ogievskiy , "qemu-devel@nongnu.org" , "nsoffer@redhat.com" , "jsnow@redhat.com" , "qemu-block@nongnu.org" On Fri, Jan 18, 2019 at 04:47:42PM -0600, Eric Blake wrote: > It matches the code, but I just learned the code is buggy for anything > larger than 5. According to > http://tldp.org/HOWTO/Large-Disk-HOWTO-13.html, MBR Extended/Logical > partitions form a linked-list, something like: > > MBR: EBR1 EBR2 > +----------+ +----------+ +----------+ > + Part 1 + |->+ Part 5 + |->+ Part 6 + > + Part 2 + | + Next --------| + 0 + > + Part 3 + | + 0 + + 0 + > + Part 4 ------- + 0 + + 0 + > +----------+ +----------+ +----------+ Wikipedia's description is a bit better: https://en.wikipedia.org/wiki/Extended_boot_record In fact it's not strictly a linked list because the start record of each entry is relative to the extended partition start. It's all a bit weird. But you're right, nbdkit can neither read (nbdkit-partition-filter) nor write (nbdkit-partitioning-plugin) MBR logical partitions so we can't test interop or tell people to use nbdkit for this corner case. Rich. -- Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones Read my programming and virtualization blog: http://rwmj.wordpress.com Fedora Windows cross-compiler. Compile Windows programs, test, and build Windows installers. Over 100 libraries supported. http://fedoraproject.org/wiki/MinGW