Re: [[Patch mdadm] 2/5] Move the files mdmon opens into /dev/ to support handoff after pivotroot

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Dan Williams wrote:
On Thu, Feb 4, 2010 at 11:45 AM, Doug Ledford <dledford@xxxxxxxxxx> wrote:
To be fair, if post-hoc versus initial made any difference what so ever,
then so would the fact that I wouldn't have chosen to have these files
exist at all.  I would have made incremental assembly work without a map
file and I would have made imsm superblock handling be in the kernel.
So, I'm dealing with the consequences of decisions I didn't make and
wouldn't have made.  I don't think it's then fair to put some sort of
'premeditated' versus 'dealing with the situation' bias on my response.

On the argument about where to place the mdmon files I am now torn
between the "Neil" and "Doug" positions, but on the decision of where
to place imsm superblock handling I stand behind the design decision
to put it in userspace.

1/ If you take a look at native md superblock support you see that the
support code is duplicated between kernel-space and user space, having
it all handled in userspace means only one code base to maintain
(elegant aspect #1).

That is the decision which I question. Having anything mission critical in user space means that there suddenly arise ownership, privilege and scheduling issues which just don't exist for things in the kernel.

Just my opinion, I believe it introduces additional points of failure. Perhaps like crypto it could be called from user or kernel space but live in the kernel.

--
Bill Davidsen <davidsen@xxxxxxx>
 "We can't solve today's problems by using the same thinking we
  used in creating them." - Einstein

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