From: Alasdair G Kergon on
On Fri, May 21, 2010 at 08:51:49PM +0200, Kay Sievers wrote:
> The kernel itself creates /dev/mapper/control today.

Must have missed that patch:)
Userspace lvm and dm code is certainly not tied to that today.

The device node that userspace lvm and dm tools use is under the
complete control of this userspace code: it chooses the name, and
creates or fixes it if it doesn't already exist with the required
properties: anything devtmpfs is relevant only if it guessed the
right name that this *completely independent* userspace code
chooses to use and already created it exactly as required.

If we were to move to a fixed name for the control device and hand
control of that name to the kernel, then obviously this userspace
code would need adjusting to respect that.

Alasdair

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From: Luca Berra on
On Fri, May 21, 2010 at 08:51:49PM +0200, Kay Sievers wrote:
>On Fri, May 21, 2010 at 20:23, Alasdair G Kergon <agk(a)redhat.com> wrote:
>> On Fri, May 21, 2010 at 03:55:21PM +0200, Kay Sievers wrote:
>>> >> On my box without this patch:
>>> >> � dmsetup version
>>> >> � Library version: � 1.02.42 (2010-01-14)
>>> >> � /proc/misc: No entry for device-mapper found
>>> >> � Is device-mapper driver missing from kernel?
>>> >> � Failure to communicate with kernel device-mapper driver.
>>
>> (Curiously this is not an issue I remember anyone raising with me as a problem
>> before.)
I am fairly sure i did report that, i even tried moving the module
loading framework from lvm2 to device mapper, but the resulting code
sucked too much to submit, the idea was to load device-mapper module,
and all target modules on first use.

>Because distros go the easy and stupid way and just load everything
>they configured as a module. :) That is something to solve, or at
>least avoid and hide a bit.
In this case we were forced to preload dm-mod to work around the issue
;)

>
>I think its all covered with this patch. :) But if yo have any better
>idea, let us know.

what patch?

L.
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From: Alasdair G Kergon on
On Tue, May 25, 2010 at 07:33:41AM +0200, Luca Berra wrote:
> what patch?

Peter Rajnoha is working on a final version of this, which includes
tweaking the userspace logic to give supremacy to devtmpfs.

Alasdair

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