Be stricter with copy_file_range probe results

library/std/src/sys/pal/unix/kernel_copy.rs

@@ -607,42 +607,44 @@ pub(super) fn copy_regular_files(reader: RawFd, writer: RawFd, max_len: u64) ->
  Ok(0) => return CopyResult::Ended(written), // reached EOF
  Ok(ret) => written += ret as u64,
  Err(err) => {
- let raw_os_error = match err.raw_os_error() {
- Some(raw) => raw,
- _ => return CopyResult::Error(err, written),
- };
- return match raw_os_error {
+ return match err.raw_os_error() {
  // when file offset + max_length > u64::MAX
- EOVERFLOW => CopyResult::Fallback(written),
- ENOSYS | EXDEV | EINVAL | EPERM | EOPNOTSUPP | EBADF if written == 0 => {
+ Some(EOVERFLOW) => CopyResult::Fallback(written),
+ Some(raw_os_error @ (ENOSYS | EXDEV | EINVAL | EPERM | EOPNOTSUPP | EBADF))
+ if written == 0 =>
+ {
  if !have_probed {
- if raw_os_error == ENOSYS {
- HAS_COPY_FILE_RANGE.store(UNAVAILABLE, Ordering::Relaxed);
- } else {
- // EPERM can indicate seccomp filters or an
- // immutable file. To distinguish these cases
- // we probe with invalid file descriptors which
- // should result in EBADF if the syscall is
- // supported and some other error (ENOSYS or
- // EPERM) if it's not available.
- let result = unsafe {
- cvt(copy_file_range(
- INVALID_FD,
- ptr::null_mut(),
- INVALID_FD,
- ptr::null_mut(),
- 1,
- 0,
- ))
- };
-
- if matches!(result.map_err(|e| e.raw_os_error()), Err(Some(EBADF)))
- {
- HAS_COPY_FILE_RANGE.store(AVAILABLE, Ordering::Relaxed);
- } else {
- HAS_COPY_FILE_RANGE.store(UNAVAILABLE, Ordering::Relaxed);
+ let available = match raw_os_error {
+ EPERM => {
+ // EPERM can indicate seccomp filters or an
+ // immutable file. To distinguish these
+ // cases we probe with invalid file
+ // descriptors which should result in EBADF
+ // if the syscall is supported and EPERM or
+ // ENOSYS if it's not available.
+ match unsafe {
+ cvt(copy_file_range(
+ INVALID_FD,
+ ptr::null_mut(),
+ INVALID_FD,
+ ptr::null_mut(),
+ 1,
+ 0,
+ ))
+ .map_err(|e| e.raw_os_error())
+ } {
+ Err(Some(EPERM | ENOSYS)) => UNAVAILABLE,
+ Err(Some(EBADF)) => AVAILABLE,
+ Ok(_) => panic!("unexpected copy_file_range probe success"),
+ // Treat other errors as the syscall
+ // being unavailable.
+ Err(_) => UNAVAILABLE,
+ }
  }
- }
+ ENOSYS => UNAVAILABLE,
+ _ => AVAILABLE,
+ };
+ HAS_COPY_FILE_RANGE.store(available, Ordering::Relaxed);
  }
 
  // Try fallback io::copy if either: