Auto merge of #122079 - tbu-:pr_copy_file_range_probe, r=the8472 · model-checking/verify-rust-std@bc346a0 (original) (raw)
`@@ -560,6 +560,12 @@ pub(super) fn copy_regular_files(reader: RawFd, writer: RawFd, max_len: u64) ->
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`// We store the availability in a global to avoid unnecessary syscalls
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`static HAS_COPY_FILE_RANGE: AtomicU8 = AtomicU8::new(NOT_PROBED);
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``
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let mut have_probed = match HAS_COPY_FILE_RANGE.load(Ordering::Relaxed) {
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NOT_PROBED => false,
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UNAVAILABLE => return CopyResult::Fallback(0),
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_ => true,
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};
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`syscall! {
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`fn copy_file_range(
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` fd_in: libc::c_int,
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`@@ -571,25 +577,22 @@ pub(super) fn copy_regular_files(reader: RawFd, writer: RawFd, max_len: u64) ->
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`) -> libc::ssize_t
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`}
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``
`-
match HAS_COPY_FILE_RANGE.load(Ordering::Relaxed) {
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``
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NOT_PROBED => {
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``
`-
// EPERM can indicate seccomp filters or an immutable file.
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``
`-
// To distinguish these cases we probe with invalid file descriptors which should result in EBADF if the syscall is supported
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``
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// and some other error (ENOSYS or EPERM) if it's not available
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let result = unsafe {
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cvt(copy_file_range(INVALID_FD, ptr::null_mut(), INVALID_FD, ptr::null_mut(), 1, 0))
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``
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};
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if matches!(result.map_err(|e| e.raw_os_error()), Err(Some(EBADF))) {
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HAS_COPY_FILE_RANGE.store(AVAILABLE, Ordering::Relaxed);
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} else {
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``
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HAS_COPY_FILE_RANGE.store(UNAVAILABLE, Ordering::Relaxed);
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``
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return CopyResult::Fallback(0);
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``
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}
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fn probe_copy_file_range_support() -> u8 {
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// In some cases, we cannot determine availability from the first
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// copy_file_range call. In this case, we probe with an invalid file
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// descriptor so that the results are easily interpretable.
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match unsafe {
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cvt(copy_file_range(INVALID_FD, ptr::null_mut(), INVALID_FD, ptr::null_mut(), 1, 0))
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.map_err(|e| e.raw_os_error())
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} {
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Err(Some(EPERM | ENOSYS)) => UNAVAILABLE,
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Err(Some(EBADF)) => AVAILABLE,
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Ok(_) => panic!("unexpected copy_file_range probe success"),
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// Treat other errors as the syscall
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// being unavailable.
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Err(_) => UNAVAILABLE,
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`}
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``
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UNAVAILABLE => return CopyResult::Fallback(0),
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_ => {}
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`-
};
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}
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``
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`let mut written = 0u64;
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`while written < max_len {
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`@@ -604,6 +607,11 @@ pub(super) fn copy_regular_files(reader: RawFd, writer: RawFd, max_len: u64) ->
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`cvt(copy_file_range(reader, ptr::null_mut(), writer, ptr::null_mut(), bytes_to_copy, 0))
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`};
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``
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if !have_probed && copy_result.is_ok() {
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have_probed = true;
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HAS_COPY_FILE_RANGE.store(AVAILABLE, Ordering::Relaxed);
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}
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`match copy_result {
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`Ok(0) if written == 0 => {
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`// fallback to work around several kernel bugs where copy_file_range will fail to
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`@@ -619,7 +627,28 @@ pub(super) fn copy_regular_files(reader: RawFd, writer: RawFd, max_len: u64) ->
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`return match err.raw_os_error() {
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`// when file offset + max_length > u64::MAX
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`Some(EOVERFLOW) => CopyResult::Fallback(written),
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Some(ENOSYS | EXDEV | EINVAL | EPERM | EOPNOTSUPP | EBADF) if written == 0 => {
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Some(raw_os_error @ (ENOSYS | EXDEV | EINVAL | EPERM | EOPNOTSUPP | EBADF))
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if written == 0 =>
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{
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if !have_probed {
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let available = if matches!(raw_os_error, ENOSYS | EOPNOTSUPP | EPERM) {
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// EPERM can indicate seccomp filters or an
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// immutable file. To distinguish these
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// cases we probe with invalid file
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// descriptors which should result in EBADF
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// if the syscall is supported and EPERM or
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// ENOSYS if it's not available.
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//
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// For EOPNOTSUPP, see below. In the case of
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// ENOSYS, we try to cover for faulty FUSE
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// drivers.
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probe_copy_file_range_support()
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} else {
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AVAILABLE
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};
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HAS_COPY_FILE_RANGE.store(available, Ordering::Relaxed);
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}
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`// Try fallback io::copy if either:
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`// - Kernel version is < 4.5 (ENOSYS¹)
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`// - Files are mounted on different fs (EXDEV)
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