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Implement Metadata:from_statx for Linux MetadataExt trait #156269

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Implement Metadata:from_statx for Linux MetadataExt trait #156269

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75 changes: 75 additions & 0 deletions library/std/src/os/linux/fs.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -7,7 +7,25 @@
use crate::fs::Metadata;
#[allow(deprecated)]
use crate::os::linux::raw;
use crate::os::raw::{c_uint, c_void};
use crate::sys::AsInner;
use crate::sys::fs::cfg_has_statx;
cfg_has_statx! {{
use crate::sys::fs::FileAttr;
use crate::sys::FromInner;
} else {
use crate::sys::unsupported;
}}

/// This is the [`statx`] mask expected by [`Metadata::from_statx`], which sets both
/// `STATX_BASIC_STATS` and `STATX_BTIME`. See the [Linux man page] for statx for more
/// details.
///
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/// [`statx`]: https://docs.rs/libc/latest/libc/struct.statx.html
/// [Linux man page]: https://man7.org/linux/man-pages/man2/statx.2.html
#[unstable(feature = "metadata_statx", issue = "156268")]
#[cfg(any(target_env = "gnu", target_env = "musl", target_os = "android", target_os = "l4re"))]
pub const STATX_MASK: c_uint = libc::STATX_BASIC_STATS | libc::STATX_BTIME;
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/// OS-specific extensions to [`fs::Metadata`].
///
Expand Down Expand Up @@ -42,6 +60,52 @@ pub trait MetadataExt {
#[allow(deprecated)]
fn as_raw_stat(&self) -> &raw::stat;

/// Creates a [`Metadata`] from a const void pointer populated by the [`statx`] syscall.
///
/// Currently [`Metadata::from_statx`] is only supported on Linux platforms.
///
/// # Safety
///
/// The caller must take care to provide a valid const void pointer containing information
/// populated by the [`statx`] syscall. In particular, the provided pointer should contain
/// statx information pertaining to the mask [`STATX_MASK`], so that there will be no
/// uninitialized data encountered in constructing [`Metadata`].
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///
/// Note that the relevant information is copied out of the structure and the pointer is
/// not retained past the call.
///
/// [`Metadata`]: crate::fs::Metadata
/// [`statx`]: https://docs.rs/libc/latest/libc/struct.statx.html
///
/// ```no_run
/// #![feature(metadata_statx)]
/// use libc::statx;
/// use std::ffi::c_void;
/// use std::fs::{write, Metadata};
/// use std::io;
/// use std::os::linux::fs::{MetadataExt, STATX_MASK};
///
/// fn main() -> io::Result<()> {
/// write("hello.txt", "Hello World!")?;
/// let mut buf = Box::<statx>::new_uninit();
/// unsafe {
/// libc::statx(
/// libc::AT_FDCWD,
/// "hello.txt".as_ptr().cast(),
/// libc::AT_STATX_SYNC_AS_STAT,
/// STATX_MASK,
/// buf.as_mut_ptr().cast()
/// );
/// }
/// let statxbuf: Box<statx> = unsafe { buf.assume_init() };
/// let metadata = unsafe { Metadata::from_statx(&*statxbuf as *const statx as *const c_void) };
/// assert_eq!(metadata.len(), 12); // "Hello World!" is 12 bytes
/// Ok(())
/// }
/// ```
#[unstable(feature = "metadata_statx", issue = "156268")]
unsafe fn from_statx(statxbuf: *const c_void) -> Self;

/// Returns the device ID on which this file resides.
///
/// # Examples
Expand Down Expand Up @@ -354,6 +418,17 @@ impl MetadataExt for Metadata {
&*(self.as_inner().as_inner() as *const libc::stat64 as *const raw::stat)
}
}
cfg_has_statx! {
{
unsafe fn from_statx(statxbuf: *const c_void) -> Metadata {
Metadata::from_inner(FileAttr::from_statx(*(statxbuf as *const libc::statx)))
}
} else {
unsafe fn from_statx(statxbuf: *const c_void) -> Self {
unsupported();
}
}
}
fn st_dev(&self) -> u64 {
self.as_inner().as_inner().st_dev as u64
}
Expand Down
2 changes: 2 additions & 0 deletions library/std/src/sys/fs/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -11,6 +11,8 @@ cfg_select! {
use unix as imp;
#[cfg(any(target_os = "linux", target_os = "android"))]
pub(super) use unix::CachedFileMetadata;
#[cfg(target_os = "linux")]
pub(crate) use unix::cfg_has_statx;
#[cfg(not(any(target_os = "fuchsia", target_os = "wasi")))]
pub use unix::chroot;
#[cfg(not(target_os = "wasi"))]
Expand Down
94 changes: 59 additions & 35 deletions library/std/src/sys/fs/unix.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -123,6 +123,9 @@ macro_rules! cfg_has_statx {
};
}

#[cfg(target_os = "linux")]
pub(crate) use cfg_has_statx;

cfg_has_statx! {{
#[derive(Clone)]
pub struct FileAttr {
Expand All @@ -131,7 +134,7 @@ cfg_has_statx! {{
}

#[derive(Clone)]
struct StatxExtraFields {
pub struct StatxExtraFields {
// This is needed to check if btime is supported by the filesystem.
stx_mask: u32,
stx_btime: libc::statx_timestamp,
Expand Down Expand Up @@ -210,40 +213,7 @@ cfg_has_statx! {{
STATX_SAVED_STATE.store(STATX_STATE::Present as u8, Ordering::Relaxed);
}

// We cannot fill `stat64` exhaustively because of private padding fields.
let mut stat: stat64 = mem::zeroed();
// `c_ulong` on gnu-mips, `dev_t` otherwise
stat.st_dev = libc::makedev(buf.stx_dev_major, buf.stx_dev_minor) as _;
stat.st_ino = buf.stx_ino as libc::ino64_t;
stat.st_nlink = buf.stx_nlink as libc::nlink_t;
stat.st_mode = buf.stx_mode as libc::mode_t;
stat.st_uid = buf.stx_uid as libc::uid_t;
stat.st_gid = buf.stx_gid as libc::gid_t;
stat.st_rdev = libc::makedev(buf.stx_rdev_major, buf.stx_rdev_minor) as _;
stat.st_size = buf.stx_size as off64_t;
stat.st_blksize = buf.stx_blksize as libc::blksize_t;
stat.st_blocks = buf.stx_blocks as libc::blkcnt64_t;
stat.st_atime = buf.stx_atime.tv_sec as libc::time_t;
// `i64` on gnu-x86_64-x32, `c_ulong` otherwise.
stat.st_atime_nsec = buf.stx_atime.tv_nsec as _;
stat.st_mtime = buf.stx_mtime.tv_sec as libc::time_t;
stat.st_mtime_nsec = buf.stx_mtime.tv_nsec as _;
stat.st_ctime = buf.stx_ctime.tv_sec as libc::time_t;
stat.st_ctime_nsec = buf.stx_ctime.tv_nsec as _;

let extra = StatxExtraFields {
stx_mask: buf.stx_mask,
stx_btime: buf.stx_btime,
// Store full times to avoid 32-bit `time_t` truncation.
#[cfg(target_pointer_width = "32")]
stx_atime: buf.stx_atime,
#[cfg(target_pointer_width = "32")]
stx_ctime: buf.stx_ctime,
#[cfg(target_pointer_width = "32")]
stx_mtime: buf.stx_mtime,
};

Some(Ok(FileAttr { stat, statx_extra_fields: Some(extra) }))
Some(Ok(FileAttr::from_statx(buf)))
}

} else {
Expand Down Expand Up @@ -480,11 +450,65 @@ pub struct DirBuilder {
struct Mode(mode_t);

cfg_has_statx! {{
impl StatxExtraFields {
/// Constructs `StatxExtraFields` from a given `libc::statx` struct
///
/// SAFETY:
/// The caller must take care to provide a `libc::statx` buffer that is
/// populated by the statx syscall with the flags `STATX_BASIC_STATS`
/// and `STATX_BTIME` enabled
pub unsafe fn from_statx(buf: libc::statx) -> Self {
StatxExtraFields {
stx_mask: buf.stx_mask,
stx_btime: buf.stx_btime,
// Store full times to avoid 32-bit `time_t` truncation.
#[cfg(target_pointer_width = "32")]
stx_atime: buf.stx_atime,
#[cfg(target_pointer_width = "32")]
stx_ctime: buf.stx_ctime,
#[cfg(target_pointer_width = "32")]
stx_mtime: buf.stx_mtime,
}
}
}
impl FileAttr {
fn from_stat64(stat: stat64) -> Self {
Self { stat, statx_extra_fields: None }
}

/// Constructs `FileAttr` from a given `libc::statx` struct
///
/// SAFETY:
/// The caller must take care to provide a `libc::statx` buffer that is
/// populated by the statx syscall with the flags `STATX_BASIC_STATS`
/// and `STATX_BTIME` enabled
pub unsafe fn from_statx(buf: libc::statx) -> Self {
// We cannot fill `stat64` exhaustively because of private padding fields.
let mut stat: libc::stat64 = mem::zeroed();
// `c_ulong` on gnu-mips, `dev_t` otherwise
stat.st_dev = libc::makedev((buf).stx_dev_major, (buf).stx_dev_minor) as _;
stat.st_ino = buf.stx_ino as libc::ino64_t;
stat.st_nlink = buf.stx_nlink as libc::nlink_t;
stat.st_mode = buf.stx_mode as libc::mode_t;
stat.st_uid = buf.stx_uid as libc::uid_t;
stat.st_gid = buf.stx_gid as libc::gid_t;
stat.st_rdev = libc::makedev(buf.stx_rdev_major, buf.stx_rdev_minor) as _;
stat.st_size = buf.stx_size as libc::off64_t;
stat.st_blksize = buf.stx_blksize as libc::blksize_t;
stat.st_blocks = buf.stx_blocks as libc::blkcnt64_t;
stat.st_atime = buf.stx_atime.tv_sec as libc::time_t;
// `i64` on gnu-x86_64-x32, `c_ulong` otherwise.
stat.st_atime_nsec = buf.stx_atime.tv_nsec as _;
stat.st_mtime = buf.stx_mtime.tv_sec as libc::time_t;
stat.st_mtime_nsec = buf.stx_mtime.tv_nsec as _;
stat.st_ctime = buf.stx_ctime.tv_sec as libc::time_t;
stat.st_ctime_nsec = buf.stx_ctime.tv_nsec as _;

let statx_extra_fields = Some(StatxExtraFields::from_statx(buf));

Self {stat, statx_extra_fields}
}

#[cfg(target_pointer_width = "32")]
pub fn stx_mtime(&self) -> Option<&libc::statx_timestamp> {
if let Some(ext) = &self.statx_extra_fields {
Expand Down
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