fuse integration: add POSIX compliance test suite

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test/fuse_integration/directio_linux.go

@@ -0,0 +1,21 @@
+//go:build linux
+
+package fuse
+
+import (
+	"syscall"
+)
+
+// Direct I/O support for Linux
+
+const (
+	O_DIRECT = 0x4000 // Direct I/O flag for Linux
+)
+
+func openDirectIO(path string, flags int, mode uint32) (int, error) {
+	return syscall.Open(path, flags|O_DIRECT, mode)
+}
+
+func isDirectIOSupported() bool {
+	return true
+}