Unavailable BSL is still functional for backup / restore

[danfengliu]

What steps did you take and what happened:
A GCP bucket BSL is Unavailable, but backup / restore is still functional well.
The reason is I had a top-level directory named dir-1.

Spec:
  Default:  true
  Object Storage:
    Bucket:  test-1
  Provider:  gcp
Status:
  Last Synced Time:      2024-05-09T08:28:24Z
  Last Validation Time:  2024-05-09T08:27:44Z
  Message:               BackupStorageLocation "default" is unavailable: Backup store contains invalid top-level directories: [dir-1]
  Phase:                 Unavailable

What did you expect to happen:
Since other top-level directories do not effect backup/restore, why check that?

The following information will help us better understand what's going on:

If you are using velero v1.7.0+:
Please use velero debug --backup <backupname> --restore <restorename> to generate the support bundle, and attach to this issue, more options please refer to velero debug --help

If you are using earlier versions:
Please provide the output of the following commands (Pasting long output into a GitHub gist or other pastebin is fine.)

• kubectl logs deployment/velero -n velero
• velero backup describe <backupname> or kubectl get backup/<backupname> -n velero -o yaml
• velero backup logs <backupname>
• velero restore describe <restorename> or kubectl get restore/<restorename> -n velero -o yaml
• velero restore logs <restorename>

Anything else you would like to add:

Environment:

• Velero version (use velero version):
• Velero features (use velero client config get features):
• Kubernetes version (use kubectl version):
• Kubernetes installer & version:
• Cloud provider or hardware configuration:
• OS (e.g. from /etc/os-release):

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[blackpiglet]

Two points need discussion in this issue.

velero/pkg/persistence/object_store_layout.go

Lines 32 to 50 in 7563a45

	func NewObjectStoreLayout(prefix string) *ObjectStoreLayout {
	if prefix != "" && !strings.HasSuffix(prefix, "/") {
	prefix = prefix + "/"
	}
	subdirs := map[string]string{
	"backups": path.Join(prefix, "backups") + "/",
	"restores": path.Join(prefix, "restores") + "/",
	"restic": path.Join(prefix, "restic") + "/",
	"metadata": path.Join(prefix, "metadata") + "/",
	"plugins": path.Join(prefix, "plugins") + "/",
	"kopia": path.Join(prefix, "kopia") + "/",
	}
	return &ObjectStoreLayout{
	rootPrefix: prefix,
	subdirs: subdirs,
	}
	}

• Whether the backup repository layout change logic still is needed? The layout-checking logic is introduced in issue Enable sharing bucket between Ark and Restic #576. That issue is used to integrate the Restic repository into the Ark repository. The original issue of the checking doesn't exist anymore, but the data integration check is still valuable.
• Whether the backup and restore associated with that BSL should be processed when the BSL is in an unavailable state?

[blackpiglet]

The agreement of the Velero team is making the Unavailable BSL stop from taking backup and restore.