Add support for 'path' field in volumeContext

[wongma7]

Is this a bug fix or adding new feature? feature

What is this PR about? / Why do we need it? fixes #46.

the path must exist on the filesystem beforehand else mounting will fail.

depends on #48

no docs updates yet--I plan to do document all doc changes in one PR if that's okay.

What testing is done?
on kube master:

apiVersion: v1
kind: PersistentVolume
metadata:
  name: efs-pv
spec:
  capacity:
    storage: 5Gi
  volumeMode: Filesystem
  accessModes:
    - ReadWriteOnce
  persistentVolumeReclaimPolicy: Recycle
  storageClassName: efs-sc
  csi:
    driver: efs.csi.aws.com
    volumeHandle: fs-c2a43e69
    volumeAttributes:
      path: "/a/b"

I0718 20:50:34.587437       1 node.go:49] NodePublishVolume: called with args volume_id:"fs-c2a43e69" target_path:"/var/lib/kubelet/pods/a7d6f292-afd5-469a-93da-b6e46f382e08/volumes/kubernetes.io~csi/efs-pv/mount" volume_capability:<mount:<> access_mode:<mode:SINGLE_NODE_WRITER > > volume_context:<key:"path" value:"/a/b" >
I0718 20:50:34.587497       1 node.go:103] NodePublishVolume: creating dir /var/lib/kubelet/pods/a7d6f292-afd5-469a-93da-b6e46f382e08/volumes/kubernetes.io~csi/efs-pv/mount
I0718 20:50:34.587524       1 node.go:108] NodePublishVolume: mounting fs-c2a43e69:/a/b at /var/lib/kubelet/pods/a7d6f292-afd5-469a-93da-b6e46f382e08/volumes/kubernetes.io~csi/efs-pv/mount with options []
I0718 20:50:34.587534       1 mount_linux.go:146] Mounting cmd (mount) with arguments ([-t efs fs-c2a43e69:/a/b /var/lib/kubelet/pods/a7d6f292-afd5-469a-93da-b6e46f382e08/volumes/kubernetes.io~csi/efs-pv/mount])
...
I0718 20:53:28.621904       1 node.go:118] NodeUnpublishVolume: called with args volume_id:"fs-c2a43e69" target_path:"/var/lib/kubelet/pods/a7d6f292-afd5-469a-93da-b6e46f382e08/volumes/kubernetes.io~csi/efs-pv/mount"
I0718 20:53:28.621963       1 node.go:125] NodeUnpublishVolume: unmounting /var/lib/kubelet/pods/a7d6f292-afd5-469a-93da-b6e46f382e08/volumes/kubernetes.io~csi/efs-pv/mount
I0718 20:53:28.621969       1 mount_linux.go:211] Unmounting /var/lib/kubelet/pods/a7d6f292-afd5-469a-93da-b6e46f382e08/volumes/kubernetes.io~csi/efs-pv/mount

[leakingtapan]

the path must exist on the filesystem beforehand else mounting will fail.

How will it fail when the path doesn't exist? Could you give more test output for this case?

[wongma7]

Like so:

  Warning  FailedMount  0s (x3 over 3s)  kubelet, 127.0.0.1  MountVolume.SetUp failed for volume "efs-pv" : rpc error: code = Internal desc = Could not mount "fs-c2a43e69:/asdf/qwer" at "/var/lib/kubelet/pods/6e1b1dd0-7f11-44ac-ad1c-5b54f1a04b9c/volumes/kubernetes.io~csi/efs-pv/mount": mount failed: exit status 32
Mounting command: mount
Mounting arguments: -t efs fs-c2a43e69:/asdf/qwer /var/lib/kubelet/pods/6e1b1dd0-7f11-44ac-ad1c-5b54f1a04b9c/volumes/kubernetes.io~csi/efs-pv/mount
Output: mount.nfs4: mounting fs-c2a43e69.efs.us-west-2.amazonaws.com:/asdf/qwer failed, reason given by server: No such file or directory

[leakingtapan]

Thx for providing the details of error message.

I think requiring user to create the directory before mounting is a hard requirement that could affect user experience. Especially when there is not other Kubernetes native way to create the directory, user will have to mount the EFS fs somewhere and create the directory manually or build some automation by themselves for each path before they can use the volume.

Created a new issue to track this: #63

[leakingtapan]

Can you also check if EFS supports mounting a file instead of directory?

[leakingtapan]

The change looks good to me.
/lgtm

[wongma7]

No file mounting allowed:
$ sudo mount fs-c2a43e69.efs.us-west-2.amazonaws.com:/out.txt -t efs a
mount.nfs4: mount spec fs-c2a43e69.efs.us-west-2.amazonaws.com:/out.txt or point /home/fedora/a is not a directory

[leakingtapan]

/approve

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