[Libguestfs] [RFC PATCH] resize: add support for MBR logical partitions some question
Hu Tao
hutao at cn.fujitsu.com
Wed Sep 17 01:49:26 UTC 2014
On Mon, Sep 15, 2014 at 10:54:17AM +0100, Richard W.M. Jones wrote:
> On Mon, Sep 15, 2014 at 05:47:03PM +0800, Hu Tao wrote:
> > Hi Rich,
> >
> > On Mon, Sep 08, 2014 at 03:13:32PM +0100, Richard W.M. Jones wrote:
> > > On Tue, Aug 26, 2014 at 06:16:50PM +0800, Hu Tao wrote:
> > > > Hi,
> > > >
> > > > The attached patch adds support for resizing MBR logical partitions. The
> > > > failure is still there, I can't get any helpful information from lsof.
> > > > Any suggestions?
> > >
> > > I don't see the error:
> > >
> > > Error: Error informing the kernel about modifications to partition /dev/sdb5
> > >
> > > However I do see this error:
> > >
> > > virt-resize: error: libguestfs error: copy_device_to_device:
> > > copy_device_to_device_stub: /dev/sdb5: No such file or directory
> >
> > I've found the reason of this error. It's because of a bug of this patch
> > related to --expand. I tested it with --resize so haven't been able to
> > find the bug. I'll send the updated patch later.
> >
> > >
> > > For debugging with lsof, I would need to actually see the trace output
> > > and the lsof output. See what I wrote here:
> > >
> > > https://www.redhat.com/archives/libguestfs/2014-July/msg00051.html
> >
> > Thanks, I'll post lsof output and trace output.
>
> This weekend I found a bug that might be similar to this one. See:
>
> https://bugzilla.redhat.com/show_bug.cgi?id=1141451
>
> If it's the same thing, it might be fixed by calling 'udev_settle'
> after copy_device_to_device (see daemon/copy.c).
Thanks, I'll check it out.
>
> > >
> > > > + p_part_num: int; (* partition number *)
> > >
> > > I think you should split out this change into a separate patch. It's
> > > uncontroversial to keep p_part_num in the structure, and will simplify
> > > review of the patch.
> >
> > Okay.
> >
> > >
> > > > + mutable p_partitions : partition list; (* MBR logical partitions. Non-empty
> > > > + list implies extended partition
> > >
> > > I'm very unclear about this change to the structure.
> > >
> > > Originally 'type partition' is a single primary/extended partition,
> > > and we keep a list of them. That's simple to understand.
> > >
> > > After this patch, how does it work?
> > >
> > > Looking at the rest of the patch it seemed to me that you'd probably
> > > want to keep the list of logical partitions as a completely separate
> > > list.
> >
> > Yes, it is the list of logical partitions.
>
> So let's make that clear by having a separate list.
Working on it.
>
> > > > (* Helper function calculates the surplus space, given the total
> > > > * required so far for the current partition layout, compared to
> > > > * the size of the target disk. If the return value >= 0 then it's
> > > > @@ -816,29 +911,31 @@ read the man page virt-resize(1).
> > > > printf "**********\n\n";
> > > > printf "Summary of changes:\n\n";
> > > >
> > > > - List.iter (
> > > > - fun ({ p_name = name; p_part = { G.part_size = oldsize }} as p) ->
> > > > + let rec print_summary p =
> > > > let text =
> > > > match p.p_operation with
> > > > | OpCopy ->
> > > > - sprintf (f_"%s: This partition will be left alone.") name
> > > > + sprintf (f_"%s: This partition will be left alone.") p.p_name
> > > > | OpIgnore ->
> > > > - sprintf (f_"%s: This partition will be created, but the contents will be ignored (ie. not copied to the target).") name
> > > > + sprintf (f_"%s: This partition will be created, but the contents will be ignored (ie. not copied to the target).") p.p_name
> > > > | OpDelete ->
> > > > - sprintf (f_"%s: This partition will be deleted.") name
> > > > + sprintf (f_"%s: This partition will be deleted.") p.p_name
> > > > | OpResize newsize ->
> > > > sprintf (f_"%s: This partition will be resized from %s to %s.")
> > > > - name (human_size oldsize) (human_size newsize) ^
> > > > + p.p_name (human_size p.p_part.G.part_size) (human_size newsize) ^
> > > > if can_expand_content p.p_type then (
> > > > sprintf (f_" The %s on %s will be expanded using the '%s' method.")
> > > > (string_of_partition_content_no_size p.p_type)
> > > > - name
> > > > + p.p_name
> > > > (string_of_expand_content_method
> > > > (expand_content_method p.p_type))
> > > > ) else "" in
> > >
> > > This bit seems to rename a variable for no particular reason. If you
> > > think this is simpler to read, then please submit it as a separate
> > > patch. Otherwise leave it out.
> >
> > Okay.
> >
> > >
> > >
> > > > + let g =
> > > > + g#shutdown ();
> > > > + g#close ();
> > > > +
> > > > + let g = new G.guestfs () in
> > > > + if trace then g#set_trace true;
> > > > + if verbose then g#set_verbose true;
> > > > + let _, { URI.path = path; protocol = protocol;
> > > > + server = server; username = username;
> > > > + password = password } = infile in
> > > > + g#add_drive ?format ~readonly:true ~protocol ?server ?username ?secret:password path;
> > > > + (* The output disk is being created, so use cache=unsafe here. *)
> > > > + g#add_drive ?format:output_format ~readonly:false ~cachemode:"unsafe"
> > > > + outfile;
> > > > + if not quiet then Progress.set_up_progress_bar ~machine_readable g;
> > > > + g#launch ();
> > > > + g in
> > >
> > > What's this bit for?
> >
> > It's for restarting the guest so the kernel can re-read the partition
> > table, otherwise even if the logical partitions have been added
> > successfully, the kernel can't read them for writing.
> >
> > >
> > >
> > > ----------------------------------------------------------------------
> > >
> > > How are you testing this? It really needs a script that tests this
> > > case, since it obviously makes the code a lot more complex. Also when
> > > you see the error message, what virt-resize and other commands are you
> > > using?
> >
> > Basically I was using virt-resize --resize to test the patch, other
> > commands are very similar with you script, except that I pre-created the
> > image with partitions and some contents in them. I think a test script
> > is a good idea, should I add it to the repo?
>
> Yes, definitely it needs a test.
Sure.
Regards,
Hu
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