On 2/28/22, 2:44 PM, "Benjamin Marzinski" wrote:
> So unless I'm missing something, we'd only really want this for removing
> a kpartx device, in the case where somehow you have /dev/loopXpY
> partitions without the LO_FLAGS_PARTSCAN flag set on the disk. That
That's correct. We only want this option so that once PARTSCAN flag is set,
Kpartx -d can delete /dev/loopXpY.
> seems like it shouldn't happen in the first place. Obviously, you
> showed that it can with parted. But I would argue that this is a bug in
> parted. If parted is creating partitions, it should set
> LO_FLAGS_PARTSCAN so the partition nodes get cleaned up.
> I suppose kpartx could check if there are partition devices for the loop
> device, and if so, it could set LO_FLAGS_PARTSCAN before doing the
Would removing all partition nodes (/dev/loop0pY) on kpartx -d be a better solution.?
> remove. But setting it unilaterally would just cause it to create an
> extra set of devices that would only serve to confuse people (and lvm).
-P should be used only when partition scan needs to be enabled - only on need basis.
> Also, the actual partition /dev/loopXpY will always get removed. It's
> just the devnode that stays around, and that won't confuse lvm. This
The example below shows that /dev/loop0p1 is not removed which is confusing the LVM.
> isn't that odd for loop devices. The /dev/loopX devnodes will stay
> around once you're done with them, regardless of whether you create the
> loop device will kpartx or losetup.
That's correct.
But loop device when setup with losetup -P option does remove /dev/loopXpY on detach
Hoping to achieve the same functionality in kpartx.
>>
>> // workaround - losetup -P
>> # kpartx -a -v test.img // First kpartx
>> # ls -l /dev/loop0*
>> brw-rw----. 1 root disk 7, 0 Feb 22 20:05 /dev/loop0
>>
>> # parted -a none -s /dev/loop0 mkpart primary 64s 100000s
>> # parted -a none -s /dev/loop0 set 1 lvm on
>> # kpartx -d test.img
>> # ls -l /dev/loop0*
>> brw-rw----. 1 root disk 7, 0 Feb 22 20:05 /dev/loop0
>> brw-rw----. 1 root disk 259, 0 Feb 22 20:05 /dev/loop0p1
>>
>> # kpartx -av test.img //Second kpartx
>> # ls -l /dev/mapper/loop0*
>> lrwxrwxrwx. 1 root root 7 Feb 22 20:53 loop0p1 -> ../dm-2
>>
>> # pvcreate /dev/mapper/loop0p1
>> # pvscan
>> WARNING: Not using device /dev/loop0p1 for PV <UUID>
>> WARNING: PV <UUID> prefers device /dev/mapper/loop0p1 because device is in dm subsystem.
> So this example shows exactly why I don't want both /dev/loopXpY and
> /dev/mapper/loopXpY. Whenever we use your -P option we can run into
> this situation, right?
In the above example, the first `kpartx -a` could benefit from `-P` option and would remove /dev/loop0p1 on kpartx -d.
This is to avoid having both /dev/loop0p1 and /dev/mapper/loop0p1.
The second `kpartx -a` does not need a partition scan and `-P` option should not be provided.
However, yes, you are right - if it is specified in this case, it would create both /dev/loop0p1 and /dev/mapper/loop0p1
- which then would have to be deleted and recreated without the `-P` option.
Maybe a warning message here would help - something like `-P` option should be used only while creating new partitions.
Thanks,
Ritika
--
dm-devel mailing list
dm-devel@xxxxxxxxxx
https://listman.redhat.com/mailman/listinfo/dm-devel
