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//! Linux `statx`.
use crate::fd::{AsFd, BorrowedFd};
use crate::ffi::CStr;
use crate::fs::AtFlags;
use crate::{imp, io, path};
use core::sync::atomic::{AtomicU8, Ordering};
pub use imp::fs::types::{Statx, StatxFlags, StatxTimestamp};
/// `statx(dirfd, path, flags, mask, statxbuf)`
///
/// This function returns [`io::Errno::NOSYS`] if `statx` is not available on
/// the platform, such as Linux before 4.11. This also includes older Docker
/// versions where the actual syscall fails with different error codes; Rustix
/// handles this and translates them into `NOSYS`.
///
/// # References
/// - [Linux]
///
/// [Linux]: https://man7.org/linux/man-pages/man2/statx.2.html
#[inline]
pub fn statx<P: path::Arg, Fd: AsFd>(
dirfd: Fd,
path: P,
flags: AtFlags,
mask: StatxFlags,
) -> io::Result<Statx> {
path.into_with_c_str(|path| _statx(dirfd.as_fd(), path, flags, mask))
}
// Linux kernel prior to 4.11 old versions of Docker don't support `statx`. We
// store the availability in a global to avoid unnecessary syscalls.
//
// 0: Unknown
// 1: Not available
// 2: Available
static STATX_STATE: AtomicU8 = AtomicU8::new(0);
#[inline]
fn _statx(
dirfd: BorrowedFd<'_>,
path: &CStr,
flags: AtFlags,
mask: StatxFlags,
) -> io::Result<Statx> {
match STATX_STATE.load(Ordering::Relaxed) {
0 => statx_init(dirfd, path, flags, mask),
1 => Err(io::Errno::NOSYS),
_ => imp::fs::syscalls::statx(dirfd, path, flags, mask),
}
}
/// The first `statx` call. We don't know if `statx` is available yet.
fn statx_init(
dirfd: BorrowedFd<'_>,
path: &CStr,
flags: AtFlags,
mask: StatxFlags,
) -> io::Result<Statx> {
match imp::fs::syscalls::statx(dirfd, path, flags, mask) {
Err(io::Errno::NOSYS) => statx_error_nosys(),
Err(io::Errno::PERM) => statx_error_perm(),
result => {
STATX_STATE.store(2, Ordering::Relaxed);
result
}
}
}
/// The first `statx` call failed with `NOSYS` (or something we're treating
/// like `NOSYS`).
#[cold]
fn statx_error_nosys() -> io::Result<Statx> {
STATX_STATE.store(1, Ordering::Relaxed);
Err(io::Errno::NOSYS)
}
/// The first `statx` call failed with `PERM`.
#[cold]
fn statx_error_perm() -> io::Result<Statx> {
// Some old versions of Docker have `statx` fail with `PERM` when it isn't
// recognized. Check whether `statx` really is available, and if so, fail
// with `PERM`, and if not, treat it like `NOSYS`.
if imp::fs::syscalls::is_statx_available() {
STATX_STATE.store(2, Ordering::Relaxed);
Err(io::Errno::PERM)
} else {
statx_error_nosys()
}
}
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