Fix UUID mismatch after partition table is modified

[yasminvalim]

BUG REPORTED:

OCP 4.17 Single node subsequent reboot after initial install fails.

SOLUTION:
Switch from using lsblk to blkid -p in the get_filesystem_uuid() function to bypass cached device information and retrieve fresh filesystem UUIDs.

[gemini-code-assist]

Code Review

This pull request aims to fix a race condition where outdated partition information, specifically UUIDs, could be used after a partition resize. The approach is to force a reread of the partition table and wait for udev events to settle before collecting device information.

The change to make reread_partition_table public is correct. However, the implementation in rootmap.rs has a couple of issues. It attempts to reread the partition table on what is likely a partition device instead of the parent whole-disk device, and it silently ignores errors which could cause the fix to be ineffective. My review includes a suggestion to address these points by finding the parent device and propagating errors.

With the suggested change, the fix should be more robust and reliable.

[jlebon]

Hmm, I don't think rereading the partition table is the fix for https://issues.redhat.com/browse/OCPBUGS-57573. The issue there has nothing to do with a stale partition table. The issue is that the rootfs filesystem UUID is stale.

To quote my comment from that bug:

Note to CoreOS devs: I think the easiest fix for this is to switch the rdcore rootmap code to use the blkid helper for this instead of lsblk:

coreos-installer/src/blockdev.rs

Line 818 in d8c6a21

pub fn blkid_single(dev: &Path) -> Result<HashMap<String, String>> {

I.e. get_filesystem_uuid() is what we call below when generating the root= karg; that function currently calls lsblk_single, but let's have it instead call blkid_single which uses blkid -p to bypass the cache.

[yasminvalim]

Thanks for your review, @jlebon. I guess I understand better what happened now, I am new to this codebase so thank you for the explanation about the problem. I updated with the right fix :)