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Kubernetes Submit Queue authored
Automatic merge from submit-queue (batch tested with PRs 59674, 60059, 60220, 58916, 60336). If you want to cherry-pick this change to another branch, please follow the instructions <a href="https://github.com/kubernetes/community/blob/master/contributors/devel/cherry-picks.md">here</a>. Support rbd-nbd for mounting operations on Ceph rbd volumes **What this PR does / why we need it**: This PR improves Ceph RBD support by allowing the pkg/volume/rbd to use the rbd-nbd client. This client is based on the common and broadly adopted (librados) librbd library, and it is being actively developed and maintained as part of the ceph upstream code base, unlike krbd. **Which issue(s) this PR fixes**: Fixes https://github.com/kubernetes/kubernetes/issues/32266 **Special notes for your reviewer**: rbd-nbd will be used for Ceph rbd volumes if rbd fails. Some inspiration was pulled from these PRs #38936 & #55866. **Test Description**: Tested against a k8s cluster with centos/7 as the host os. rbd-nbd installed from package rbd-nbd-10.2.3.rpm. Tested: 1. Fall-through to current rbd map/unmap when no rbd-nbd tools are found. 2. Map/Unmap through rbd-nbd. 3. Detecting image already mapped to a nbd device and skipping additional mapping. 4. Detecting image already mapped to a rbd device and skipping additional mapping through nbd. 5. Unmap in hosts having mixed rbd and nbd devices (caused by fall-throughs for some images). 6. Map failure in rbd-nbd due to missing image. 7. Map failure in rbd-nbd due to unreachable mon. 8. Fall-through to current rbd map when rbd-nbd map fails for any reason. **Release note**: ```release-note K8s supports rbd-nbd for Ceph rbd volume mounts. ```
