Chen Hanxiao
2015-May-08 14:26 UTC
Re: [Libguestfs] [PATCH 00/10] virt-resize: add support for resizing MBR logical partitions
On 04/30/2015 06:51 PM, Chen, Hanxiao wrote:> Hi, Rich > >> -----Original Message----- >> From: Richard W.M. Jones [mailto:rjones@redhat.com] >> Sent: Wednesday, April 29, 2015 7:04 PM >> To: Chen, Hanxiao/陈 晗霄 >> Cc: libguestfs@redhat.com >> Subject: Re: [Libguestfs] [PATCH 00/10] virt-resize: add support for resizing MBR >> logical partitions >> >> On Wed, Apr 29, 2015 at 09:19:24AM +0000, Chen, Hanxiao wrote: >>> commit 6e989fd709fea37430398cbb7c01c52cd44bd1ac already did this: >>> we had p_mbr_p_type : partition_type in type partition. >>> Like what MBR/EBR did, this patchset use `partition_type`: >>> >>> /dev/sda3: >>> partition data: 3 210763776-420478975 (209715200 bytes) >>> bootable: false >>> partition ID: 0x5 >>> content: extended partition >>> label: (none) >>> GUID: (none) >>> *partition type: extended* >>> /dev/sda5: >>> partition data: 5 211812352-222298111 (10485760 bytes) >>> bootable: false >>> partition ID: 0x83 >>> content: unknown data >>> label: (none) >>> GUID: (none) >>> *partition type: logical* >>> >>> As we could only had one extended partition, >>> all logical partitions belong to that extended partition, >>> so current type partition of virt-resize can reflect logical/extended partition >> model. >> >> The specific problem is that the extended partition (eg /dev/sda3) >> contains the logical partition (/dev/sda5). Having a flat list >> doesn't express that at all. > We had at most 4 PTE in MBR, in PTE, a partition type is on +04h, > value 05h or 0fh shows it's an extended partition. > From extended partition's EBR, we got logical partitions. > > sda1-- sda2 -- sda3 -- sda4 > ^ > | > sda5 -- sda6 > > I think we do not need to show this specially, > just use the original design: > logical partitions existed in extended partition, an implicit relations. > > So a flat list can do this: > We mark each members, then a tree view above could be rebuilt precisely > from plat list.Hi, Rich Any comments on this? Regards, - Chen> > > In this patchset, logical partitions are not filter out, it did: > > 1) partitions list: sda1 sda2 sda3 sda5 > every member of partitions got a member `partition type` > > 2) calculate surplus > > 3) then filter out logical partitions list: > logical_partitions: sda5 > partitions: sda1 sda2 sda3 > do something to it (calculate_target_partitions...) > > 4) part_add to 'non-logical' partitions and logical partitions, > then concrete them together for the original partition list. > > 5) copy_partition (ignore extended partitions, for we had logical partition > in partitions list, we copy data from there) > >> I agree it is very hard to express this, because extended partitions >> just work so differently from how any sensible partition scheme should >> work (because they are a big hack). But perhaps: >> >> - flat list of primary partitions (as now, the global 'partitions') > members of partitions list whose partition type is 'primary' >> - one MBR extended partition (as a new global variable) > member of partitions list whose partition type is 'extended'. > >> - flat list of logical partitions > members of partitions list whose partition type is 'logical'. > > So I think we do not need 2 list and a global variable, > if we want to know something, just do a List.filter. > >> would do it? It still has the problem that the extended partition is >> a bit like a primary partition, yet isn't in the partitions list. > For the point of PTE's view, it does. > PS: In my patch, it's in partitions list :) > > Regards > - Chen > >>>> It's very hard to understand what changes are being made. The commits >>>> are not grouped in a way that makes them easily understandable to me. >>> I'll try to regroup them and make the patchset easy to review. >> Thanks, >> >> Rich. >> >> -- >> Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones >> Read my programming and virtualization blog: http://rwmj.wordpress.com >> virt-p2v converts physical machines to virtual machines. Boot with a >> live CD or over the network (PXE) and turn machines into KVM guests. >> http://libguestfs.org/virt-v2v
Richard W.M. Jones
2015-May-08 14:38 UTC
Re: [Libguestfs] [PATCH 00/10] virt-resize: add support for resizing MBR logical partitions
On Fri, May 08, 2015 at 10:26:22PM +0800, Chen Hanxiao wrote:> > On 04/30/2015 06:51 PM, Chen, Hanxiao wrote: > > Hi, Rich > > > >> -----Original Message----- > >> From: Richard W.M. Jones [mailto:rjones@redhat.com] > >> Sent: Wednesday, April 29, 2015 7:04 PM > >> To: Chen, Hanxiao/陈 晗霄 > >> Cc: libguestfs@redhat.com > >> Subject: Re: [Libguestfs] [PATCH 00/10] virt-resize: add support for resizing MBR > >> logical partitions > >> > >> On Wed, Apr 29, 2015 at 09:19:24AM +0000, Chen, Hanxiao wrote: > >>> commit 6e989fd709fea37430398cbb7c01c52cd44bd1ac already did this: > >>> we had p_mbr_p_type : partition_type in type partition. > >>> Like what MBR/EBR did, this patchset use `partition_type`: > >>> > >>> /dev/sda3: > >>> partition data: 3 210763776-420478975 (209715200 bytes) > >>> bootable: false > >>> partition ID: 0x5 > >>> content: extended partition > >>> label: (none) > >>> GUID: (none) > >>> *partition type: extended* > >>> /dev/sda5: > >>> partition data: 5 211812352-222298111 (10485760 bytes) > >>> bootable: false > >>> partition ID: 0x83 > >>> content: unknown data > >>> label: (none) > >>> GUID: (none) > >>> *partition type: logical* > >>> > >>> As we could only had one extended partition, > >>> all logical partitions belong to that extended partition, > >>> so current type partition of virt-resize can reflect logical/extended partition > >> model. > >> > >> The specific problem is that the extended partition (eg /dev/sda3) > >> contains the logical partition (/dev/sda5). Having a flat list > >> doesn't express that at all. > > We had at most 4 PTE in MBR, in PTE, a partition type is on +04h, > > value 05h or 0fh shows it's an extended partition. > > From extended partition's EBR, we got logical partitions. > > > > sda1-- sda2 -- sda3 -- sda4 > > ^ > > | > > sda5 -- sda6 > > > > I think we do not need to show this specially, > > just use the original design: > > logical partitions existed in extended partition, an implicit relations. > > > > So a flat list can do this: > > We mark each members, then a tree view above could be rebuilt precisely > > from plat list. > Hi, Rich > > Any comments on this?As I said in my original email, my opinion is still that the code would be clearer if it expressed the peculiar structure of MBR extended/logical partitions directly in the structures. There's really a high hurdle for these changes. They must be: - easy to review - absolutely not break existing uses of virt-resize We're nowhere near there at the moment. There's no good testing, there are no patches for review which look sound. Rich. -- Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones Read my programming and virtualization blog: http://rwmj.wordpress.com virt-builder quickly builds VMs from scratch http://libguestfs.org/virt-builder.1.html
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