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internal/hostcollect/statfs_linux.go

@@ -0,0 +1,39 @@
+//go:build linux
+
+package hostcollect
+
+import "syscall"
+
+// statFS reads capacity and inode usage for one mount point. statfs(2) is a read-only
+// syscall that needs no capability, which keeps the agent inside cap_drop: [ALL].
+//
+// "Used" follows df: total blocks minus free blocks, so the filesystem's reserved
+// blocks count as used rather than as available headroom the operator does not have.
+func statFS(path string) (FilesystemUsage, error) {
+	var stat syscall.Statfs_t
+	if err := syscall.Statfs(path, &stat); err != nil {
+		return FilesystemUsage{}, err
+	}
+	blockSize := uint64(stat.Bsize) //nolint:gosec,unconvert // Bsize is int64 on some arches, uint32 on others
+	if blockSize == 0 {
+		return FilesystemUsage{}, nil
+	}
+	blocks := stat.Blocks
+	free := stat.Bfree
+	if free > blocks {
+		free = blocks
+	}
+	usage := FilesystemUsage{
+		CapacityBytes: blocks * blockSize,
+		UsedBytes:     (blocks - free) * blockSize,
+		InodesTotal:   stat.Files,
+	}
+	if stat.Files > 0 {
+		freeInodes := stat.Ffree
+		if freeInodes > stat.Files {
+			freeInodes = stat.Files
+		}
+		usage.InodesUsed = stat.Files - freeInodes
+	}
+	return usage, nil
+}