Add a rustix::fs::STATX_ATTR_MOUNT_ROOT constant.

Add a `STATX_ATTR_MOUNT_ROOT` constant for musl libc compat

src/backend/libc/c.rs

@@ -14,6 +14,12 @@ pub(crate) const PROC_SUPER_MAGIC: u32 = 0x0000_9fa0;
 #[cfg(all(linux_kernel, target_env = "musl"))]
 pub(crate) const NFS_SUPER_MAGIC: u32 = 0x0000_6969;
 
+/// `STATX_ATTR_MOUNT_ROOT`—Address of the root of a mount
+#[cfg(all(linux_kernel, target_env = "musl"))]
+pub(crate) const STATX_ATTR_MOUNT_ROOT: c_int = 0x2000;
+#[cfg(all(linux_kernel, not(target_env = "musl")))]
+pub(crate) const STATX_ATTR_MOUNT_ROOT: c_int = libc::STATX_ATTR_MOUNT_ROOT;
+
 #[cfg(feature = "process")]
 #[cfg(not(any(target_os = "espidf", target_os = "wasi")))]
 pub(crate) const EXIT_SIGNALED_SIGABRT: c_int = 128 + SIGABRT as c_int;

src/backend/linux_raw/c.rs

@@ -38,8 +38,8 @@ pub(crate) use linux_raw_sys::general::epoll_event;
     )
 ))]
 pub(crate) use linux_raw_sys::general::{
-    AT_FDCWD, NFS_SUPER_MAGIC, O_LARGEFILE, PROC_SUPER_MAGIC, UTIME_NOW, UTIME_OMIT, XATTR_CREATE,
-    XATTR_REPLACE,
+    AT_FDCWD, NFS_SUPER_MAGIC, O_LARGEFILE, PROC_SUPER_MAGIC, STATX_ATTR_MOUNT_ROOT, UTIME_NOW,
+    UTIME_OMIT, XATTR_CREATE, XATTR_REPLACE,
 };
 
 pub(crate) use linux_raw_sys::ioctl::{BLKPBSZGET, BLKSSZGET, FICLONE};

src/fs/mod.rs

@@ -116,6 +116,8 @@ pub use sendfile::sendfile;
 pub use special::*;
 #[cfg(linux_kernel)]
 pub use statx::statx;
+#[cfg(all(linux_kernel, target_env = "musl"))]
+pub use statx::STATX_ATTR_MOUNT_ROOT;
 #[cfg(not(any(
     target_os = "espidf",
     target_os = "redox",

src/fs/statx.rs

@@ -10,6 +10,10 @@ use backend::fs::syscalls::statx as _statx;
 #[cfg(not(feature = "linux_4_11"))]
 use compat::statx as _statx;
 
+/// `STATX_ATTR_MOUNT_ROOT`—Address of the root of a mount
+#[allow(dead_code)]
+pub const STATX_ATTR_MOUNT_ROOT: u32 = backend::c::STATX_ATTR_MOUNT_ROOT as u32;
+
 /// `statx(dirfd, path, flags, mask, statxbuf)`
 ///
 /// This function returns [`io::Errno::NOSYS`] if `statx` is not available on