1 //! Linux `statx`.
2
3 use crate::fd::AsFd;
4 use crate::fs::AtFlags;
5 use crate::{backend, io, path};
6 use backend::fs::types::{Statx, StatxFlags};
7
8 #[cfg(feature = "linux_4_11")]
9 use backend::fs::syscalls::statx as _statx;
10 #[cfg(not(feature = "linux_4_11"))]
11 use compat::statx as _statx;
12
13 /// `statx(dirfd, path, flags, mask, statxbuf)`
14 ///
15 /// This function returns [`io::Errno::NOSYS`] if `statx` is not available on
16 /// the platform, such as Linux before 4.11. This also includes older Docker
17 /// versions where the actual syscall fails with different error codes; rustix
18 /// handles this and translates them into `NOSYS`.
19 ///
20 /// # References
21 /// - [Linux]
22 ///
23 /// # Examples
24 ///
25 /// ```
26 /// # use std::path::Path;
27 /// # use std::io;
28 /// # use rustix::fs::{AtFlags, StatxFlags};
29 /// # use rustix::fd::BorrowedFd;
30 /// /// Try to determine if the provided path is a mount root. Will return
31 /// /// `Ok(None)` if the kernel is not new enough to support `statx` or
32 /// /// [`libc::STATX_ATTR_MOUNT_ROOT`].
33 /// fn is_mountpoint(root: BorrowedFd<'_>, path: &Path) -> io::Result<Option<bool>> {
34 /// use rustix::fs::{AtFlags, StatxFlags};
35 ///
36 /// let mountroot_flag = libc::STATX_ATTR_MOUNT_ROOT as u64;
37 /// match rustix::fs::statx(
38 /// root,
39 /// path,
40 /// AtFlags::NO_AUTOMOUNT | AtFlags::SYMLINK_NOFOLLOW,
41 /// StatxFlags::empty(),
42 /// ) {
43 /// Ok(r) => {
44 /// let present = (r.stx_attributes_mask & mountroot_flag) > 0;
45 /// Ok(present.then(|| r.stx_attributes & mountroot_flag > 0))
46 /// }
47 /// Err(e) if e == rustix::io::Errno::NOSYS => Ok(None),
48 /// Err(e) => Err(e.into()),
49 /// }
50 /// }
51 /// ```
52 ///
53 /// [Linux]: https://man7.org/linux/man-pages/man2/statx.2.html
54 #[inline]
statx<P: path::Arg, Fd: AsFd>( dirfd: Fd, path: P, flags: AtFlags, mask: StatxFlags, ) -> io::Result<Statx>55 pub fn statx<P: path::Arg, Fd: AsFd>(
56 dirfd: Fd,
57 path: P,
58 flags: AtFlags,
59 mask: StatxFlags,
60 ) -> io::Result<Statx> {
61 path.into_with_c_str(|path| _statx(dirfd.as_fd(), path, flags, mask))
62 }
63
64 #[cfg(not(feature = "linux_4_11"))]
65 mod compat {
66 use crate::fd::BorrowedFd;
67 use crate::ffi::CStr;
68 use crate::fs::AtFlags;
69 use crate::{backend, io};
70 use core::sync::atomic::{AtomicU8, Ordering};
71
72 use backend::fs::types::{Statx, StatxFlags};
73
74 // Linux kernel prior to 4.11 and old versions of Docker don't support
75 // `statx`. We store the availability in a global to avoid unnecessary
76 // syscalls.
77 //
78 // 0: Unknown
79 // 1: Not available
80 // 2: Available
81 static STATX_STATE: AtomicU8 = AtomicU8::new(0);
82
83 #[inline]
statx( dirfd: BorrowedFd<'_>, path: &CStr, flags: AtFlags, mask: StatxFlags, ) -> io::Result<Statx>84 pub fn statx(
85 dirfd: BorrowedFd<'_>,
86 path: &CStr,
87 flags: AtFlags,
88 mask: StatxFlags,
89 ) -> io::Result<Statx> {
90 match STATX_STATE.load(Ordering::Relaxed) {
91 0 => statx_init(dirfd, path, flags, mask),
92 1 => Err(io::Errno::NOSYS),
93 _ => backend::fs::syscalls::statx(dirfd, path, flags, mask),
94 }
95 }
96
97 /// The first `statx` call. We don't know if `statx` is available yet.
statx_init( dirfd: BorrowedFd<'_>, path: &CStr, flags: AtFlags, mask: StatxFlags, ) -> io::Result<Statx>98 fn statx_init(
99 dirfd: BorrowedFd<'_>,
100 path: &CStr,
101 flags: AtFlags,
102 mask: StatxFlags,
103 ) -> io::Result<Statx> {
104 match backend::fs::syscalls::statx(dirfd, path, flags, mask) {
105 Err(io::Errno::NOSYS) => statx_error_nosys(),
106 Err(io::Errno::PERM) => statx_error_perm(),
107 result => {
108 STATX_STATE.store(2, Ordering::Relaxed);
109 result
110 }
111 }
112 }
113
114 /// The first `statx` call failed with `NOSYS` (or something we're treating
115 /// like `NOSYS`).
116 #[cold]
statx_error_nosys() -> io::Result<Statx>117 fn statx_error_nosys() -> io::Result<Statx> {
118 STATX_STATE.store(1, Ordering::Relaxed);
119 Err(io::Errno::NOSYS)
120 }
121
122 /// The first `statx` call failed with `PERM`.
123 #[cold]
statx_error_perm() -> io::Result<Statx>124 fn statx_error_perm() -> io::Result<Statx> {
125 // Some old versions of Docker have `statx` fail with `PERM` when it
126 // isn't recognized. Check whether `statx` really is available, and if
127 // so, fail with `PERM`, and if not, treat it like `NOSYS`.
128 if backend::fs::syscalls::is_statx_available() {
129 STATX_STATE.store(2, Ordering::Relaxed);
130 Err(io::Errno::PERM)
131 } else {
132 statx_error_nosys()
133 }
134 }
135 }
136