DIAG: log dup2 self-buf (filetable refresh) euid + duplicate_file result

src/syscall/fs.rs

@@ -322,7 +322,25 @@ pub fn dup2(
         if buf.is_empty() {
             return Ok(new_fd);
         }
-        let new_file = duplicate_file(fd, buf, false, token)?;
+        let dbg_euid = {
+            let cur = context::current();
+            let g = cur.read(token.token());
+            g.euid
+        };
+        let new_file = match duplicate_file(fd, buf, false, token) {
+            Ok(f) => {
+                warn!("DIAG dup2-self-buf euid={dbg_euid} fd={} duplicate_file=OK", fd.get());
+                f
+            }
+            Err(e) => {
+                warn!(
+                    "DIAG dup2-self-buf euid={dbg_euid} fd={} duplicate_file=ERR errno={}",
+                    fd.get(),
+                    e.errno
+                );
+                return Err(e);
+            }
+        };
         let old_file = {
             let current_lock = context::current();
             let mut current = current_lock.read(token.token());