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Auto merge of #65094 - oxalica:linux-statx, r=alexcrichton

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Prefer statx on linux if available

This PR make `metadata`-related functions try to invoke `statx` first on Linux if available,
making `std::fs::Metadata::created` work on Linux with `statx` supported.

It follows the discussion in #61386 , and will fix #59743

The implementation of this PR is simply converting `struct statx` into `struct stat64` with
extra fields for `btime` if `statx` succeeds, since other fields are not currently used.

---

I also did a separated benchmark for `fs::metadata`, `stat64`, `statx`, and `statx` with conversion to `stat64`.
It shows that `statx` with conversion is even more faster than pure `statx`.
I think it's due to `sizeof stat64 == 114` but `sizeof statx == 256`.

Anyway, the bare implementation of `statx` with conversion is only about 0.2% slower than the original impl (`stat64`-family).
With heap-allocation counted (~8.5% of total cost), the difference between `stat` and `statx` (with or without conversion) is just nothing.

Therefore, I think it is not urgent to use bare `struct statx` as underlying representation now.
There is no need to break `std::os::linux::fs::MetadataExt::as_raw_stat` (https://github.com/rust-lang/rust/pull/61386#issuecomment-538074018)

[Separated bare benchmarks](https://gist.github.com/oxalica/c4073ecb202c599fe41b7f15f86dc79c):
```
metadata_ok             time:   [529.41 ns 529.77 ns 530.19 ns]
metadata_err            time:   [538.71 ns 539.39 ns 540.35 ns]
stat64_ok               time:   [484.32 ns 484.53 ns 484.75 ns]
stat64_err              time:   [481.77 ns 482.00 ns 482.24 ns]
statx_ok                time:   [488.07 ns 488.35 ns 488.62 ns]
statx_err               time:   [487.74 ns 488.00 ns 488.27 ns]
statx_cvt_ok            time:   [485.05 ns 485.28 ns 485.53 ns]
statx_cvt_err           time:   [485.23 ns 485.45 ns 485.67 ns]
```

r? @alexcrichton
This commit is contained in:
bors 2019-10-19 22:01:30 +00:00
commit 22eec92882
2 changed files with 235 additions and 14 deletions
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22
src/libstd/fs.rs
View File

@ -1090,13 +1090,14 @@ impl Metadata {
/// Returns the creation time listed in this metadata.
///
/// The returned value corresponds to the `birthtime` field of `stat` on
/// Unix platforms and the `ftCreationTime` field on Windows platforms.
/// The returned value corresponds to the `btime` field of `statx` on
/// Linux kernel starting from to 4.11, the `birthtime` field of `stat` on other
/// Unix platforms, and the `ftCreationTime` field on Windows platforms.
///
/// # Errors
///
/// This field may not be available on all platforms, and will return an
/// `Err` on platforms where it is not available.
/// `Err` on platforms or filesystems where it is not available.
///
/// # Examples
///
@ -1109,7 +1110,7 @@ impl Metadata {
/// if let Ok(time) = metadata.created() {
/// println!("{:?}", time);
/// } else {
/// println!("Not supported on this platform");
/// println!("Not supported on this platform or filesystem");
/// }
/// Ok(())
/// }
@ -3443,5 +3444,18 @@ mod tests {
check!(a.created());
check!(b.created());
}
if cfg!(target_os = "linux") {
// Not always available
match (a.created(), b.created()) {
(Ok(t1), Ok(t2)) => assert!(t1 <= t2),
(Err(e1), Err(e2)) if e1.kind() == ErrorKind::Other &&
e2.kind() == ErrorKind::Other => {}
(a, b) => panic!(
"creation time must be always supported or not supported: {:?} {:?}",
a, b,
),
}
}
}
}

227
src/libstd/sys/unix/fs.rs
View File

@ -41,11 +41,138 @@ pub use crate::sys_common::fs::remove_dir_all;
pub struct File(FileDesc);
#[derive(Clone)]
pub struct FileAttr {
stat: stat64,
// FIXME: This should be available on Linux with all `target_arch` and `target_env`.
// https://github.com/rust-lang/libc/issues/1545
macro_rules! cfg_has_statx {
({ $($then_tt:tt)* } else { $($else_tt:tt)* }) => {
cfg_if::cfg_if! {
if #[cfg(all(target_os = "linux", target_env = "gnu", any(
target_arch = "x86",
target_arch = "arm",
// target_arch = "mips",
target_arch = "powerpc",
target_arch = "x86_64",
// target_arch = "aarch64",
target_arch = "powerpc64",
// target_arch = "mips64",
// target_arch = "s390x",
target_arch = "sparc64",
)))] {
$($then_tt)*
} else {
$($else_tt)*
}
}
};
($($block_inner:tt)*) => {
#[cfg(all(target_os = "linux", target_env = "gnu", any(
target_arch = "x86",
target_arch = "arm",
// target_arch = "mips",
target_arch = "powerpc",
target_arch = "x86_64",
// target_arch = "aarch64",
target_arch = "powerpc64",
// target_arch = "mips64",
// target_arch = "s390x",
target_arch = "sparc64",
)))]
{
$($block_inner)*
}
};
}
cfg_has_statx! {{
#[derive(Clone)]
pub struct FileAttr {
stat: stat64,
statx_extra_fields: Option<StatxExtraFields>,
}
#[derive(Clone)]
struct StatxExtraFields {
// This is needed to check if btime is supported by the filesystem.
stx_mask: u32,
stx_btime: libc::statx_timestamp,
}
// We prefer `statx` on Linux if available, which contains file creation time.
// Default `stat64` contains no creation time.
unsafe fn try_statx(
fd: c_int,
path: *const libc::c_char,
flags: i32,
mask: u32,
) -> Option<io::Result<FileAttr>> {
use crate::sync::atomic::{AtomicBool, Ordering};
// Linux kernel prior to 4.11 or glibc prior to glibc 2.28 don't support `statx`
// We store the availability in a global to avoid unnecessary syscalls
static HAS_STATX: AtomicBool = AtomicBool::new(true);
syscall! {
fn statx(
fd: c_int,
pathname: *const libc::c_char,
flags: c_int,
mask: libc::c_uint,
statxbuf: *mut libc::statx
) -> c_int
}
if !HAS_STATX.load(Ordering::Relaxed) {
return None;
}
let mut buf: libc::statx = mem::zeroed();
let ret = cvt(statx(fd, path, flags, mask, &mut buf));
match ret {
Err(err) => match err.raw_os_error() {
Some(libc::ENOSYS) => {
HAS_STATX.store(false, Ordering::Relaxed);
return None;
}
_ => return Some(Err(err)),
}
Ok(_) => {
// 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,
};
Some(Ok(FileAttr { stat, statx_extra_fields: Some(extra) }))
}
}
}
} else {
#[derive(Clone)]
pub struct FileAttr {
stat: stat64,
}
}}
// all DirEntry's will have a reference to this struct
struct InnerReadDir {
dirp: Dir,
@ -97,6 +224,20 @@ pub struct FileType { mode: mode_t }
#[derive(Debug)]
pub struct DirBuilder { mode: mode_t }
cfg_has_statx! {{
impl FileAttr {
fn from_stat64(stat: stat64) -> Self {
Self { stat, statx_extra_fields: None }
}
}
} else {
impl FileAttr {
fn from_stat64(stat: stat64) -> Self {
Self { stat }
}
}
}}
impl FileAttr {
pub fn size(&self) -> u64 { self.stat.st_size as u64 }
pub fn perm(&self) -> FilePermissions {
@ -164,6 +305,22 @@ impl FileAttr {
target_os = "macos",
target_os = "ios")))]
pub fn created(&self) -> io::Result<SystemTime> {
cfg_has_statx! {
if let Some(ext) = &self.statx_extra_fields {
return if (ext.stx_mask & libc::STATX_BTIME) != 0 {
Ok(SystemTime::from(libc::timespec {
tv_sec: ext.stx_btime.tv_sec as libc::time_t,
tv_nsec: ext.stx_btime.tv_nsec as _,
}))
} else {
Err(io::Error::new(
io::ErrorKind::Other,
"creation time is not available for the filesystem",
))
};
}
}
Err(io::Error::new(io::ErrorKind::Other,
"creation time is not available on this platform \
currently"))
@ -306,12 +463,25 @@ impl DirEntry {
#[cfg(any(target_os = "linux", target_os = "emscripten", target_os = "android"))]
pub fn metadata(&self) -> io::Result<FileAttr> {
let fd = cvt(unsafe {dirfd(self.dir.inner.dirp.0)})?;
let fd = cvt(unsafe { dirfd(self.dir.inner.dirp.0) })?;
let name = self.entry.d_name.as_ptr();
cfg_has_statx! {
if let Some(ret) = unsafe { try_statx(
fd,
name,
libc::AT_SYMLINK_NOFOLLOW | libc::AT_STATX_SYNC_AS_STAT,
libc::STATX_ALL,
) } {
return ret;
}
}
let mut stat: stat64 = unsafe { mem::zeroed() };
cvt(unsafe {
fstatat64(fd, self.entry.d_name.as_ptr(), &mut stat, libc::AT_SYMLINK_NOFOLLOW)
fstatat64(fd, name, &mut stat, libc::AT_SYMLINK_NOFOLLOW)
})?;
Ok(FileAttr { stat })
Ok(FileAttr::from_stat64(stat))
}
#[cfg(not(any(target_os = "linux", target_os = "emscripten", target_os = "android")))]
@ -517,11 +687,24 @@ impl File {
}
pub fn file_attr(&self) -> io::Result<FileAttr> {
let fd = self.0.raw();
cfg_has_statx! {
if let Some(ret) = unsafe { try_statx(
fd,
b"\0" as *const _ as *const libc::c_char,
libc::AT_EMPTY_PATH | libc::AT_STATX_SYNC_AS_STAT,
libc::STATX_ALL,
) } {
return ret;
}
}
let mut stat: stat64 = unsafe { mem::zeroed() };
cvt(unsafe {
fstat64(self.0.raw(), &mut stat)
fstat64(fd, &mut stat)
})?;
Ok(FileAttr { stat })
Ok(FileAttr::from_stat64(stat))
}
pub fn fsync(&self) -> io::Result<()> {
@ -798,20 +981,44 @@ pub fn link(src: &Path, dst: &Path) -> io::Result<()> {
pub fn stat(p: &Path) -> io::Result<FileAttr> {
let p = cstr(p)?;
cfg_has_statx! {
if let Some(ret) = unsafe { try_statx(
libc::AT_FDCWD,
p.as_ptr(),
libc::AT_STATX_SYNC_AS_STAT,
libc::STATX_ALL,
) } {
return ret;
}
}
let mut stat: stat64 = unsafe { mem::zeroed() };
cvt(unsafe {
stat64(p.as_ptr(), &mut stat)
})?;
Ok(FileAttr { stat })
Ok(FileAttr::from_stat64(stat))
}
pub fn lstat(p: &Path) -> io::Result<FileAttr> {
let p = cstr(p)?;
cfg_has_statx! {
if let Some(ret) = unsafe { try_statx(
libc::AT_FDCWD,
p.as_ptr(),
libc::AT_SYMLINK_NOFOLLOW | libc::AT_STATX_SYNC_AS_STAT,
libc::STATX_ALL,
) } {
return ret;
}
}
let mut stat: stat64 = unsafe { mem::zeroed() };
cvt(unsafe {
lstat64(p.as_ptr(), &mut stat)
})?;
Ok(FileAttr { stat })
Ok(FileAttr::from_stat64(stat))
}
pub fn canonicalize(p: &Path) -> io::Result<PathBuf> {