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UNIX remove_dir_all(): Try recursing first on the slow path #94446

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merged 3 commits into from
Mar 5, 2022
Merged

UNIX remove_dir_all(): Try recursing first on the slow path #94446

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e427333
remove_dir_all(): try recursing first instead of trying to unlink()
hkratz Feb 28, 2022
41b4423
Integrate macos x86-64 remove_dir_all() impl. Step 1: remove
hkratz Feb 28, 2022
735f60c
Integrate macos x86-64 remove_dir_all() impl. Step 2: readd
hkratz Feb 28, 2022
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205 changes: 74 additions & 131 deletions library/std/src/sys/unix/fs.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1482,140 +1482,60 @@ mod remove_dir_impl {
pub use crate::sys_common::fs::remove_dir_all;
}

// Dynamically choose implementation Macos x86-64: modern for 10.10+, fallback for older versions
#[cfg(all(target_os = "macos", target_arch = "x86_64"))]
// Modern implementation using openat(), unlinkat() and fdopendir()
#[cfg(not(any(target_os = "redox", target_os = "espidf")))]
mod remove_dir_impl {
use super::{cstr, lstat, Dir, InnerReadDir, ReadDir};
use super::{cstr, lstat, Dir, DirEntry, InnerReadDir, ReadDir};
use crate::ffi::CStr;
use crate::io;
use crate::os::unix::io::{AsRawFd, FromRawFd, IntoRawFd};
use crate::os::unix::prelude::{OwnedFd, RawFd};
use crate::path::{Path, PathBuf};
use crate::sync::Arc;
use crate::sys::weak::weak;
use crate::sys::{cvt, cvt_r};
use libc::{c_char, c_int, DIR};

pub fn openat_nofollow_dironly(parent_fd: Option<RawFd>, p: &CStr) -> io::Result<OwnedFd> {
weak!(fn openat(c_int, *const c_char, c_int) -> c_int);
let fd = cvt_r(|| unsafe {
openat.get().unwrap()(
parent_fd.unwrap_or(libc::AT_FDCWD),
p.as_ptr(),
libc::O_CLOEXEC | libc::O_RDONLY | libc::O_NOFOLLOW | libc::O_DIRECTORY,
)
})?;
Ok(unsafe { OwnedFd::from_raw_fd(fd) })
}

fn fdreaddir(dir_fd: OwnedFd) -> io::Result<(ReadDir, RawFd)> {
weak!(fn fdopendir(c_int) -> *mut DIR, "fdopendir$INODE64");
let ptr = unsafe { fdopendir.get().unwrap()(dir_fd.as_raw_fd()) };
if ptr.is_null() {
return Err(io::Error::last_os_error());
}
let dirp = Dir(ptr);
// file descriptor is automatically closed by libc::closedir() now, so give up ownership
let new_parent_fd = dir_fd.into_raw_fd();
// a valid root is not needed because we do not call any functions involving the full path
// of the DirEntrys.
let dummy_root = PathBuf::new();
Ok((
ReadDir {
inner: Arc::new(InnerReadDir { dirp, root: dummy_root }),
end_of_stream: false,
},
new_parent_fd,
))
}

fn remove_dir_all_recursive(parent_fd: Option<RawFd>, p: &Path) -> io::Result<()> {
weak!(fn unlinkat(c_int, *const c_char, c_int) -> c_int);
#[cfg(not(all(target_os = "macos", target_arch = "x86_64"),))]
use libc::{fdopendir, openat, unlinkat};
#[cfg(all(target_os = "macos", target_arch = "x86_64"))]
use macos_weak::{fdopendir, openat, unlinkat};

let pcstr = cstr(p)?;
#[cfg(all(target_os = "macos", target_arch = "x86_64"))]
mod macos_weak {
use crate::sys::weak::weak;
use libc::{c_char, c_int, DIR};

// entry is expected to be a directory, open as such
let fd = openat_nofollow_dironly(parent_fd, &pcstr)?;
fn get_openat_fn() -> Option<unsafe extern "C" fn(c_int, *const c_char, c_int) -> c_int> {
weak!(fn openat(c_int, *const c_char, c_int) -> c_int);
openat.get()
}

// open the directory passing ownership of the fd
let (dir, fd) = fdreaddir(fd)?;
for child in dir {
let child = child?;
match child.entry.d_type {
libc::DT_DIR => {
remove_dir_all_recursive(Some(fd), Path::new(&child.file_name()))?;
}
libc::DT_UNKNOWN => {
match cvt(unsafe { unlinkat.get().unwrap()(fd, child.name_cstr().as_ptr(), 0) })
{
// type unknown - try to unlink
Err(err) if err.raw_os_error() == Some(libc::EPERM) => {
// if the file is a directory unlink fails with EPERM
remove_dir_all_recursive(Some(fd), Path::new(&child.file_name()))?;
}
result => {
result?;
}
}
}
_ => {
// not a directory -> unlink
cvt(unsafe { unlinkat.get().unwrap()(fd, child.name_cstr().as_ptr(), 0) })?;
}
}
pub fn has_openat() -> bool {
get_openat_fn().is_some()
}

// unlink the directory after removing its contents
cvt(unsafe {
unlinkat.get().unwrap()(
parent_fd.unwrap_or(libc::AT_FDCWD),
pcstr.as_ptr(),
libc::AT_REMOVEDIR,
)
})?;
Ok(())
}
pub unsafe fn openat(dirfd: c_int, pathname: *const c_char, flags: c_int) -> c_int {
get_openat_fn().map(|openat| openat(dirfd, pathname, flags)).unwrap_or_else(|| {
crate::sys::unix::os::set_errno(libc::ENOSYS);
-1
})
}

fn remove_dir_all_modern(p: &Path) -> io::Result<()> {
// We cannot just call remove_dir_all_recursive() here because that would not delete a passed
// symlink. No need to worry about races, because remove_dir_all_recursive() does not recurse
// into symlinks.
let attr = lstat(p)?;
if attr.file_type().is_symlink() {
crate::fs::remove_file(p)
} else {
remove_dir_all_recursive(None, p)
pub unsafe fn fdopendir(fd: c_int) -> *mut DIR {
weak!(fn fdopendir(c_int) -> *mut DIR, "fdopendir$INODE64");
fdopendir.get().map(|fdopendir| fdopendir(fd)).unwrap_or_else(|| {
crate::sys::unix::os::set_errno(libc::ENOSYS);
crate::ptr::null_mut()
})
}
}

pub fn remove_dir_all(p: &Path) -> io::Result<()> {
weak!(fn openat(c_int, *const c_char, c_int) -> c_int);
if openat.get().is_some() {
// openat() is available with macOS 10.10+, just like unlinkat() and fdopendir()
remove_dir_all_modern(p)
} else {
// fall back to classic implementation
crate::sys_common::fs::remove_dir_all(p)
pub unsafe fn unlinkat(dirfd: c_int, pathname: *const c_char, flags: c_int) -> c_int {
weak!(fn unlinkat(c_int, *const c_char, c_int) -> c_int);
unlinkat.get().map(|unlinkat| unlinkat(dirfd, pathname, flags)).unwrap_or_else(|| {
crate::sys::unix::os::set_errno(libc::ENOSYS);
-1
})
}
}
}

// Modern implementation using openat(), unlinkat() and fdopendir()
#[cfg(not(any(
all(target_os = "macos", target_arch = "x86_64"),
target_os = "redox",
target_os = "espidf"
)))]
mod remove_dir_impl {
use super::{cstr, lstat, Dir, DirEntry, InnerReadDir, ReadDir};
use crate::ffi::CStr;
use crate::io;
use crate::os::unix::io::{AsRawFd, FromRawFd, IntoRawFd};
use crate::os::unix::prelude::{OwnedFd, RawFd};
use crate::path::{Path, PathBuf};
use crate::sync::Arc;
use crate::sys::{cvt, cvt_r};
use libc::{fdopendir, openat, unlinkat};

pub fn openat_nofollow_dironly(parent_fd: Option<RawFd>, p: &CStr) -> io::Result<OwnedFd> {
let fd = cvt_r(|| unsafe {
Expand Down Expand Up @@ -1683,8 +1603,21 @@ mod remove_dir_impl {
fn remove_dir_all_recursive(parent_fd: Option<RawFd>, p: &Path) -> io::Result<()> {
let pcstr = cstr(p)?;

// entry is expected to be a directory, open as such
let fd = openat_nofollow_dironly(parent_fd, &pcstr)?;
// try opening as directory
let fd = match openat_nofollow_dironly(parent_fd, &pcstr) {
Err(err) if err.raw_os_error() == Some(libc::ENOTDIR) => {
// not a directory - don't traverse further
return match parent_fd {
// unlink...
Some(parent_fd) => {
cvt(unsafe { unlinkat(parent_fd, pcstr.as_ptr(), 0) }).map(drop)
}
// ...unless this was supposed to be the deletion root directory
None => Err(err),
};
}
result => result?,
};

// open the directory passing ownership of the fd
let (dir, fd) = fdreaddir(fd)?;
Expand All @@ -1697,19 +1630,13 @@ mod remove_dir_impl {
Some(false) => {
cvt(unsafe { unlinkat(fd, child.name_cstr().as_ptr(), 0) })?;
}
None => match cvt(unsafe { unlinkat(fd, child.name_cstr().as_ptr(), 0) }) {
// type unknown - try to unlink
Err(err)
if err.raw_os_error() == Some(libc::EISDIR)
|| err.raw_os_error() == Some(libc::EPERM) =>
{
// if the file is a directory unlink fails with EISDIR on Linux and EPERM everyhwere else
remove_dir_all_recursive(Some(fd), Path::new(&child.file_name()))?;
}
result => {
result?;
}
},
None => {
// POSIX specifies that calling unlink()/unlinkat(..., 0) on a directory can succeed
// if the process has the appropriate privileges. This however can causing orphaned
// directories requiring an fsck e.g. on Solaris and Illumos. So we try recursing
// into it first instead of trying to unlink() it.
remove_dir_all_recursive(Some(fd), Path::new(&child.file_name()))?;
}
}
}

Expand All @@ -1720,7 +1647,7 @@ mod remove_dir_impl {
Ok(())
}

pub fn remove_dir_all(p: &Path) -> io::Result<()> {
fn remove_dir_all_modern(p: &Path) -> io::Result<()> {
// We cannot just call remove_dir_all_recursive() here because that would not delete a passed
// symlink. No need to worry about races, because remove_dir_all_recursive() does not recurse
// into symlinks.
Expand All @@ -1731,4 +1658,20 @@ mod remove_dir_impl {
remove_dir_all_recursive(None, p)
}
}

#[cfg(not(all(target_os = "macos", target_arch = "x86_64")))]
pub fn remove_dir_all(p: &Path) -> io::Result<()> {
remove_dir_all_modern(p)
}

#[cfg(all(target_os = "macos", target_arch = "x86_64"))]
pub fn remove_dir_all(p: &Path) -> io::Result<()> {
if macos_weak::has_openat() {
// openat() is available with macOS 10.10+, just like unlinkat() and fdopendir()
remove_dir_all_modern(p)
} else {
// fall back to classic implementation
crate::sys_common::fs::remove_dir_all(p)
}
}
}