Merge pull request #49918 from torredil/dev-1.33

Add docs for KEP-4876: Mutable CSINode Allocatable Property

Author: k8s-ci-robot

content/en/docs/concepts/storage/storage-limits.md

@@ -79,4 +79,33 @@ Refer to the [CSI specifications](https://github.com/container-storage-interface
 
 * For volumes managed by in-tree plugins that have been migrated to a CSI driver, the maximum number of volumes will be the one reported by the CSI driver.
 
+### Mutable CSI Node Allocatable Count
+
+{{< feature-state state="alpha" for_k8s_version="v1.33" >}}
+
+CSI drivers can dynamically adjust the maximum number of volumes that can be attached to a Node at runtime. This enhances scheduling accuracy and reduces pod scheduling failures due to changes in resource availability.
+
+This is an alpha feature and is disabled by default.
+
+To use this feature, you must enable the `MutableCSINodeAllocatableCount` feature gate on the following components:
+
+- `kube-apiserver`
+- `kubelet`
+
+#### Periodic Updates
+
+When enabled, CSI drivers can request periodic updates to their volume limits by setting the `nodeAllocatableUpdatePeriodSeconds` field in the `CSIDriver` specification. For example:
+
+```yaml
+apiVersion: storage.k8s.io/v1
+kind: CSIDriver
+metadata:
+  name: hostpath.csi.k8s.io
+spec:
+  nodeAllocatableUpdatePeriodSeconds: 60
+```
+
+Kubelet will periodically call the corresponding CSI driver’s `NodeGetInfo` endpoint to refresh the maximum number of attachable volumes, using the interval specified in `nodeAllocatableUpdatePeriodSeconds`. The minimum allowed value for this field is 10 seconds.
+
+Additionally, if a volume attachment operation fails with a `ResourceExhausted` error (gRPC code 8), Kubernetes triggers an immediate update to the allocatable volume count for that Node.
 

content/en/docs/reference/command-line-tools-reference/feature-gates/MutableCSINodeAllocatableCount.md

@@ -0,0 +1,13 @@
+---
+title: MutableCSINodeAllocatableCount
+content_type: feature_gate
+_build:
+  list: never
+  render: false
+
+stages:
+  - stage: alpha
+    defaultValue: false
+    fromVersion: "1.33"
+---
+When this feature gate is enabled, the `CSINode.Spec.Drivers[*].Allocatable.Count` field becomes mutable, and a new field, `NodeAllocatableUpdatePeriodSeconds`, is available in the `CSIDriver` object. This allows periodic updates to a node's reported allocatable volume capacity, preventing stateful pods from becoming stuck due to outdated information that `kube-scheduler` relies on.