curtin-dev team mailing list archive

[Ryan Harper <rharper@xxxxxxxxxxx>]

> Michael Hudson-Doyle (mwhudson) wrote 6 minutes ago:
> I'm not sure what "really disks" means on a philosophical level <wink> but yes

Maybe I'm missing the <wink> here, but just for the folks following along I'll
be explicit.

I'm referring to multipath partitions which a linear mapping to offsets on the
multipath path disk in the device-mapper table.   Device-mapper will create
additional device-mapper devices (/dev/dm-1, /dev/dm-2) which according to
sysfs, udev and any other linux tool, are of type disk.  For example, in sysfs
/sys/class/block/dm-1 can be a "partition" and /sys/class/block/dm-1/partition
will not exist.

The mutipath software stack has conventions to determine which dm devices are
representing partitions by exporting values like DM_PART and prefixing dm
names with part- ; etc.

This code makes use of these multipath convensions.


> this is for multipath. I found that there was a currently-unused function in
> multipath.py that does most of what we want so I changed it to return the
> partition number as well and changed this code. (it used udev rather than
> sysfs pokery but well. no real difference).

OK, sounds good!  I'll review.

> On the subject of mocks, get_blockdev_for_partition is currently untested.
> Tests could be written but you'd have to mock so many filesystem accesses that
> it would be incredibly fragile and I'm not sure what value it would bring.
>
> You must have thought about a more generic way to mock the filesystem by now,
> surely, like something where you supply a dictionary mapping paths to
> content and mocks for the various os.path.* functions get set up for you?
> Did you ever write anything for this I can steal? :)


I think the closes thing we have is using tests/unittests/helpers.py:dir2dict
and populate_dir and FilesystemMocking unittest class'[1] reRoot() method which
effectively applies a chroot prefix to the operations.


1. https://github.com/canonical/cloud-init/blob/master/cloudinit/tests/helpers.py#L242




-- 
https://code.launchpad.net/~mwhudson/curtin/+git/curtin/+merge/396462
Your team curtin developers is requested to review the proposed merge of ~mwhudson/curtin:fix-multipath-partition-verification-2 into curtin:master.