io-uring: add readable/writable

src/io_uring/sys.rs

@@ -2,6 +2,7 @@
 
 use {
     crate::utils::oserror::OsError,
+    std::mem::MaybeUninit,
     uapi::{c, OwnedFd},
 };
 
@@ -23,6 +24,12 @@ pub struct io_uring_sqe {
     pub __pad2: [u64; 2],
 }
 
+impl Default for io_uring_sqe {
+    fn default() -> Self {
+        unsafe { MaybeUninit::zeroed().assume_init() }
+    }
+}
+
 #[repr(C)]
 #[derive(Copy, Clone)]
 pub union io_uring_sqe_union1 {