Change in vdsm[master]: storage: set block schedule elevator using udev

Alon Bar-Lev alonbl at redhat.com
Tue Nov 6 20:03:43 UTC 2012


Alon Bar-Lev has posted comments on this change.

Change subject: storage: set block schedule elevator using udev
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Patch Set 1:

Hi,

If someone wanted to override the setting for specific disk, he would have written udev rule and not change kernel command-line.

And even if this was the case, we can name our rule to be loaded as earliest to allow existing rule override.

If someone changed the kernel command-line manually he violated our support profile, as we assume deadline, and assume vdsm is a SLAVE hypervisor bootstrapped using supported method.

But if that is *REALLY* what bothering you (someone manually set the kernel command-line with unsupported setting), then I can read the /proc/cmdline in the udev script and simply do nothing if a setting in the kernel command-line exists. Maybe we should also support people who compile their own rhel kernel with different default?

BTW: Current bootstrap implementation will override this manual setting anyway during bootstrap, so we do not support manual changes. But let's ignore reality for now.

I think it is a mistake to go in this route, as we were the one who messed with kernel command-line in the first place. This was invalid decision that was taken at that time. Had we done this today we would have used udev to achieve the same. Because we had done this in kernel command-line we forced the user to [maybe] customize it at same place instead of flexible udev rule. Leaving this in kernel command-line because of previous poor decision is not a great argument if we want to clean up this bootstrap corner.

We can have a text within release notes to alert these advanced users to move their customization to udev, so the 3 (max) people who are effected will know what to do.

As I wrote previously, the question is which component is the owner of setting the iosched, vdsm or bootstrap. If this is rejected from vdsm and go into bootstrap domain, it will be implemented as udev rule too, I believe this belongs to vdsm.

Alon

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Gerrit-MessageType: comment
Gerrit-Change-Id: I0a8de1c861bf4570509599b6f47235ed38cc424d
Gerrit-PatchSet: 1
Gerrit-Project: vdsm
Gerrit-Branch: master
Gerrit-Owner: Alon Bar-Lev <alonbl at redhat.com>
Gerrit-Reviewer: Adam Litke <agl at us.ibm.com>
Gerrit-Reviewer: Alon Bar-Lev <alonbl at redhat.com>
Gerrit-Reviewer: Ayal Baron <abaron at redhat.com>
Gerrit-Reviewer: Barak Azulay <bazulay at redhat.com>
Gerrit-Reviewer: Dan Kenigsberg <danken at redhat.com>
Gerrit-Reviewer: Douglas Schilling Landgraf <dougsland at redhat.com>
Gerrit-Reviewer: Eduardo <ewarszaw at redhat.com>
Gerrit-Reviewer: Fabian Deutsch <fabiand at fedoraproject.org>
Gerrit-Reviewer: Federico Simoncelli <fsimonce at redhat.com>
Gerrit-Reviewer: Itamar Heim <iheim at redhat.com>
Gerrit-Reviewer: Mark Wu <wudxw at linux.vnet.ibm.com>
Gerrit-Reviewer: Saggi Mizrahi <smizrahi at redhat.com>


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