trace sys_write errors for low FDs

src/syscall/fs.rs

@@ -855,6 +855,7 @@ pub fn sys_read(fd: FileHandle, buf: UserSliceWo, token: &mut CleanLockToken) ->
     Ok(bytes_read)
 }
 pub fn sys_write(fd: FileHandle, buf: UserSliceRo, token: &mut CleanLockToken) -> Result<usize> {
+    let result = (|| {
     let (bytes_written, desc_arc, desc) =
         file_op_generic_ext(fd, token, |scheme, desc_arc, desc, token| {
             let offset = if desc.internal_flags.contains(InternalFlags::POSITIONED) {
@@ -879,4 +880,10 @@ pub fn sys_write(fd: FileHandle, buf: UserSliceRo, token: &mut CleanLockToken) -
     guard.io_syscw = guard.io_syscw.saturating_add(1);
     guard.io_write_bytes = guard.io_write_bytes.saturating_add(bytes_written as u64);
     Ok(bytes_written)
+    })();
+    if result.is_err() && fd.get() <= 10 {
+        let name = context::current().read(token.token()).name;
+        info!("sys_write fd={} ctx='{}' err={:?}", fd.get(), name, result.as_ref().err());
+    }
+    result
 }