OCPBUGS-56597: Fix multipath configuration

[ravanelli]

• To ensure multipath continues working even if a path fails, the WWID must be specified both as a
  kernel argument and in /etc/multipath/wwids.
  Without these, multipath may fail to detect
  devices when paths go down, leading to device
  mapping issues.
• This PR adds mpath.wwid kernel argument needed for the installer.

[gemini-code-assist]

Summary of Changes

Hello @ravanelli, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request introduces new functionality to detect the system's multipath World Wide Identifier (WWID) by querying the multipath -ll command. The stated intent is to ensure this WWID is correctly passed as a kernel argument for robust multipath configuration, although the current implementation focuses on the detection and logging aspect, with the generated kernel argument not yet being integrated into the final kernel command line.

Highlights

• Multipath WWID Detection Logic: Introduces a new private helper function get_multipath_configured that executes the multipath -ll command, parses its output to extract the first detected World Wide Identifier (WWID), and constructs a kernel argument string in the format mpath.wwid=<WWID>.
• Integration into Rootmap Process: Calls the newly introduced get_multipath_configured() function within the rootmap function (on line 71). While the get_multipath_configured function generates the mpath.wwid kernel argument, its return value is currently not used to modify the main kargs list in the rootmap function.

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[gemini-code-assist]

Code Review

The code changes add a function to retrieve the WWID of a multipath device and add it as a kernel argument. The review suggests improvements to handle multiple WWIDs and return an error if no WWIDs are found.

[ravanelli]

Adding some notes here: RHCOS uses multipath aliases, which generate mpath device names (like mpatha, mpathb, etc.), while FCOS does not and instead shows devices as dm-0. I’m not very familiar with multipath, so I tried to get the first listed device to extract the WWID. I’m not sure if there might be other edge cases to consider when identifying the WWID, if this order would affect it.

Other than that, we still need to finish the fix adding the WWID in the /etc/multipath/wwids via overlay.d "override" for now. And enable the test in kola for it, it needs more testing before getting merged.

Editing, I just realized the formats are different for the output as well, I was using fcos as base, I will fix it:

FCOS:
[root@cosa-devsh core]# multipath -ll
0x48a4930d278dabe9 dm-0 NVME,VirtualMultipath
RHCOS:
[root@cosa-devsh core]# multipath -ll
mpatha (0x794b6a95103d982d) dm-0 NVME,VirtualMultipath

[dustymabe]

Should we validate the wwid string is in a format we expect here before we pass it as a karg?

[jlebon]

Rebased for conflicts and passed through rustfmt.

Thanks @ravanelli!