sysfs: trim spaces in device hidden check

[clwluvw]

The hidden file might have an endline, so the check for equals to 1 would not be true. Trimming the spaces would help to cover this case.

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[k8s-ci-robot]

Hi @clwluvw. Thanks for your PR.

I'm waiting for a google member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

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[iwankgb]

/ok-to-test

[clwluvw]

/retest

[clwluvw]

Hi @iwankgb - Can you please help here with why the CI is not happy?

[ringerc]

If you see errors like Failed to get disk map: open /sys/block/nvme0c0n1/dev: no such file or directory but

# cat  /sys/block/nvme0c0n1/hidden    
1

then this might well be the problem. Check:

# od -x /sys/block/nvme0c0n1/hidden
0000000 0a31
0000002

Here, my hidden files have a leading linefeed, which means they won't match == "1".

[clwluvw]

Here, my hidden files have a leading linefeed, which means they won't match == "1".

This PR must actually have addressed such. Are you running a version >= v0.51.0?

[ringerc]

@clwluvw Yes - I've been able to verify that Red Hat OpenShift (v4.18) is currently shipping a kubelet openshift-kubelet-4.18.0-202505060638.p0.gaf98ede.assembly.stream.el9 that embeds an older fork of cadvisor based on v0.49.0 (https://github.com/openshift/google-cadvisor/tree/v0.49.0-openshift-4.17-3) that omits this fix.

I raised openshift#30 to ask them to backport the fix. Thanks very much for writing the fix.

I don't think this fix is entirely comprehensive - see #3693 for details. But it will prevent problems with hidden devices as are used in multi-path I/O systems, so it'll solve the immediate problem.