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Store ENOSYS in a global to avoid unnecessary system calls

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This commit is contained in:
Nicolas Koch 2018-05-17 14:10:14 +02:00
parent a5e2942861
commit 09d03bc245
1 changed files with 25 additions and 10 deletions
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35
src/libstd/sys/unix/fs.rs
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@ -781,6 +781,11 @@ pub fn copy(from: &Path, to: &Path) -> io::Result<u64> {
#[cfg(any(target_os = "linux", target_os = "android"))]
pub fn copy(from: &Path, to: &Path) -> io::Result<u64> {
use fs::{File, set_permissions};
use sync::atomic::{AtomicBool, Ordering};
// Kernel prior to 4.5 don't have copy_file_range
// We store the availability in a global to avoid unneccessary syscalls
static HAS_COPY_FILE_RANGE: AtomicBool = AtomicBool::new(true);
unsafe fn copy_file_range(
fd_in: libc::c_int,
@ -820,16 +825,26 @@ pub fn copy(from: &Path, to: &Path) -> io::Result<u64> {
} else {
(len - written) as usize
};
let copy_result = unsafe {
// We actually don't have to adjust the offsets,
// because copy_file_range adjusts the file offset automatically
cvt(copy_file_range(reader.as_raw_fd(),
ptr::null_mut(),
writer.as_raw_fd(),
ptr::null_mut(),
bytes_to_copy,
0)
)
let copy_result = if HAS_COPY_FILE_RANGE.load(Ordering::Relaxed) {
let copy_result = unsafe {
// We actually don't have to adjust the offsets,
// because copy_file_range adjusts the file offset automatically
cvt(copy_file_range(reader.as_raw_fd(),
ptr::null_mut(),
writer.as_raw_fd(),
ptr::null_mut(),
bytes_to_copy,
0)
)
};
if let Err(ref copy_err) = copy_result {
if let Some(libc::ENOSYS) = copy_err.raw_os_error() {
HAS_COPY_FILE_RANGE.store(false, Ordering::Relaxed);
}
}
copy_result
} else {
Err(io::Error::from_raw_os_error(libc::ENOSYS))
};
match copy_result {
Ok(ret) => written += ret as u64,