logical_disk: cache volume info, read free space live, tolerate failing volumes (#2691)

Co-authored-by: Claude <noreply@anthropic.com>
Signed-off-by: Claude <noreply@anthropic.com>

internal/headers/kernel32/disk_space.go

@@ -0,0 +1,81 @@
+// SPDX-License-Identifier: Apache-2.0
+//
+// Copyright The Prometheus Authors
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//go:build windows
+
+package kernel32
+
+import (
+	"errors"
+	"fmt"
+	"unsafe"
+
+	"golang.org/x/sys/windows"
+)
+
+//nolint:gochecknoglobals
+var procGetDiskSpaceInformationW = modkernel32.NewProc("GetDiskSpaceInformationW")
+
+// ErrDiskSpaceInformationUnavailable is returned by GetDiskSpaceInformation on Windows versions
+// before Windows 10 1809 and Windows Server 2019, which lack GetDiskSpaceInformationW.
+var ErrDiskSpaceInformationUnavailable = errors.New("GetDiskSpaceInformationW is not available")
+
+// DiskSpaceInformation contains disk space information for a volume.
+// 📑 https://learn.microsoft.com/en-us/windows/win32/api/fileapi/ns-fileapi-disk_space_information
+type DiskSpaceInformation struct {
+	ActualTotalAllocationUnits           uint64
+	ActualAvailableAllocationUnits       uint64
+	ActualPoolUnavailableAllocationUnits uint64
+	CallerTotalAllocationUnits           uint64
+	CallerAvailableAllocationUnits       uint64
+	CallerPoolUnavailableAllocationUnits uint64
+	UsedAllocationUnits                  uint64
+	TotalReservedAllocationUnits         uint64
+	VolumeStorageReserveAllocationUnits  uint64
+	AvailableCommittedAllocationUnits    uint64
+	PoolAvailableAllocationUnits         uint64
+	SectorsPerAllocationUnit             uint32
+	BytesPerSector                       uint32
+}
+
+// AllocationUnitSize returns the size of an allocation unit in bytes.
+func (d DiskSpaceInformation) AllocationUnitSize() uint64 {
+	return uint64(d.SectorsPerAllocationUnit) * uint64(d.BytesPerSector)
+}
+
+// GetDiskSpaceInformation returns the disk space information of the volume with the root path rootPath.
+// Unlike GetDiskFreeSpaceEx, it reports the size of the volume regardless of disk quotas.
+// 📑 https://learn.microsoft.com/en-us/windows/win32/api/fileapi/nf-fileapi-getdiskspaceinformationw
+func GetDiskSpaceInformation(rootPath *uint16) (DiskSpaceInformation, error) {
+	var info DiskSpaceInformation
+
+	if err := procGetDiskSpaceInformationW.Find(); err != nil {
+		return info, fmt.Errorf("%w: %w", ErrDiskSpaceInformationUnavailable, err)
+	}
+
+	hr, _, _ := procGetDiskSpaceInformationW.Call(
+		uintptr(unsafe.Pointer(rootPath)),
+		uintptr(unsafe.Pointer(&info)),
+	)
+	if int32(hr) < 0 {
+		if uint32(hr)&0xFFFF0000 == 0x80070000 {
+			return info, fmt.Errorf("GetDiskSpaceInformationW failed: %w", windows.Errno(uint32(hr)&0xFFFF))
+		}
+
+		return info, fmt.Errorf("GetDiskSpaceInformationW failed: HRESULT 0x%08X", uint32(hr))
+	}
+
+	return info, nil
+}