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. 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