async-libfuse: import async-libfuse

Import async_fuse of github.com/datenlord/datenlord as initial
version of async-libfuse
Signed-off-by: Njingxiaolu <lujingxiao@huawei.com>

Cargo.toml

+[package]
+name = "async_fuse"
+version = "0.1.0"
+authors = ["Pu Wang <nicolas.weeks@gmail.com>"]
+edition = "2018"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+anyhow = "1.0.31"
+env_logger = "0.6.0"
+futures = "0.3.5"
+futures-core = "0.3.5"
+futures-io = "0.3.5"
+futures-util = "0.3.5"
+lazy_static = "1.4.0"
+libc = "0.2"
+log = "0.4.6"
+nix = "0.17.0"
+pin-project-lite ="0.1.7"
+smol = "0.1.11"
+
+[features]
+abi-7-9 = []
+abi-7-10 = ["abi-7-9"]
+abi-7-11 = ["abi-7-10"]
+abi-7-12 = ["abi-7-11"]
+abi-7-13 = ["abi-7-12"]
+abi-7-14 = ["abi-7-13"]
+abi-7-15 = ["abi-7-14"]
+abi-7-16 = ["abi-7-15"]
+abi-7-17 = ["abi-7-16"]
+abi-7-18 = ["abi-7-17"]
+abi-7-19 = ["abi-7-18"]

License/LICENSE

+                     木兰宽松许可证, 第2版
+
+   木兰宽松许可证， 第2版 
+   2020年1月 http://license.coscl.org.cn/MulanPSL2
+
+
+   您对“软件”的复制、使用、修改及分发受木兰宽松许可证，第2版（“本许可证”）的如下条款的约束：
+
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+
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+
+   4. 分发限制
+
+      您可以在任何媒介中将“软件”以源程序形式或可执行形式重新分发，不论修改与否，但您必须向接收者提供“本许可证”的副本，并保留“软件”中的版权、商标、专利及免责声明。
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+
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+   如何将木兰宽松许可证，第2版，应用到您的软件
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+
+      2， 请您在软件包的一级目录下创建以“LICENSE”为名的文件，将整个许可证文本放入该文件中；
+
+      3， 请将如下声明文本放入每个源文件的头部注释中。
+
+   Copyright (c) [Year] [name of copyright holder]
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+   You can use this software according to the terms and conditions of the Mulan PSL v2. 
+   You may obtain a copy of Mulan PSL v2 at:
+            http://license.coscl.org.cn/MulanPSL2 
+   THIS SOFTWARE IS PROVIDED ON AN "AS IS" BASIS, WITHOUT WARRANTIES OF ANY KIND, EITHER EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO NON-INFRINGEMENT, MERCHANTABILITY OR FIT FOR A PARTICULAR PURPOSE.  
+   See the Mulan PSL v2 for more details.  
+
+
+                     Mulan Permissive Software License，Version 2
+
+   Mulan Permissive Software License，Version 2 (Mulan PSL v2)
+   January 2020 http://license.coscl.org.cn/MulanPSL2
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+   See the Mulan PSL v2 for more details.  

src/channel.rs

+use anyhow::{anyhow, Context, Result};
+use nix::{
+    fcntl::{self, FcntlArg, FdFlag, OFlag},
+    ioctl_read,
+    sys::stat::Mode,
+    unistd::close,
+};
+use std::os::unix::io::RawFd;
+
+use super::session::Session;
+
+#[derive(Debug)]
+pub(crate) struct Channel {
+    // channel fd cloned from session fd
+    chan_fd: RawFd,
+}
+
+impl Channel {
+    #[allow(dead_code)]
+    pub async fn new(session: &Session) -> Result<Channel> {
+        let devname = "/dev/fuse";
+        let clonefd = fcntl::open(devname, OFlag::O_RDWR | OFlag::O_CLOEXEC, Mode::empty());
+
+        let clonefd = match clonefd {
+            Err(err) => {
+                return Err(anyhow!("fuse: failed to open {:?}: {:?}", devname, err));
+            }
+            Ok(fd) => fd,
+        };
+
+        if let Err(err) = fcntl::fcntl(clonefd, FcntlArg::F_SETFD(FdFlag::FD_CLOEXEC)) {
+            return Err(anyhow::anyhow!(
+                "fuse: failed to set clonefd to FD_CLOEXEC: {:?}",
+                err
+            ));
+        }
+
+        ioctl_read!(clone, 299, 0, i32);
+        let mut masterfd = session.fd();
+        let res = unsafe { clone(clonefd, &mut masterfd) };
+        if let Err(err) = res {
+            close(clonefd).context("fuse: failed to close clone device")?;
+            return Err(anyhow::anyhow!(
+                "fuse: failed to clone device fd: {:?}\n",
+                err
+            ));
+        }
+
+        Ok(Channel { chan_fd: clonefd })
+    }
+
+    #[allow(dead_code)]
+    pub fn fd(&self) -> RawFd {
+        self.chan_fd
+    }
+}

src/fs/dir.rs

+use nix::sys::stat::SFlag;
+use std::ffi::{CStr, OsStr, OsString};
+use std::os::unix::ffi::OsStrExt;
+use std::os::unix::io::RawFd;
+use std::ptr;
+
+use super::super::protocol::INum;
+
+#[cfg(target_os = "linux")]
+use libc::{dirent64 as dirent, readdir64_r as readdir_r};
+
+#[cfg(not(target_os = "linux"))]
+use libc::{dirent, readdir_r};
+
+#[derive(Debug)]
+pub(crate) struct Dir(ptr::NonNull<libc::DIR>);
+
+impl Dir {
+    /// Converts from a file descriptor, closing it on success or failure.
+    pub fn from_fd(fd: RawFd) -> nix::Result<Self> {
+        let d = unsafe { libc::fdopendir(fd) };
+        if d.is_null() {
+            let e = nix::Error::last();
+            unsafe { libc::close(fd) };
+            return Err(e);
+        };
+        // Always guaranteed to be non-null by the previous check
+        Ok(Dir(ptr::NonNull::new(d).unwrap()))
+    }
+}
+
+// `Dir` is safe to pass from one thread to another, as it's not reference-counted.
+unsafe impl Send for Dir {}
+
+#[derive(Debug)]
+pub(crate) struct DirEntry {
+    ino: INum,
+    entry_type: SFlag,
+    name: OsString,
+}
+
+impl DirEntry {
+    pub fn new(ino: INum, name: OsString, entry_type: SFlag) -> Self {
+        Self {
+            ino,
+            name,
+            entry_type,
+        }
+    }
+    /// Returns the inode number (`d_ino`) of the underlying `dirent`.
+    pub fn ino(&self) -> u64 {
+        self.ino
+    }
+
+    /// Returns the bare file name of this directory entry without any other leading path component.
+    pub fn entry_name(&self) -> &OsStr {
+        self.name.as_os_str()
+    }
+
+    /// Returns the type of this directory entry, if known.
+    ///
+    /// See platform `readdir(3)` or `dirent(5)` manpage for when the file type is known;
+    /// notably, some Linux filesystems don't implement this. The caller should use `stat` or
+    /// `fstat` if this returns `None`.
+    pub fn entry_type(&self) -> SFlag {
+        self.entry_type
+    }
+
+    fn from_dirent(de: dirent) -> Self {
+        let ino = de.d_ino as INum;
+
+        let name = unsafe { OsStr::from_bytes(CStr::from_ptr(de.d_name.as_ptr()).to_bytes()) };
+
+        let entry_type = match de.d_type {
+            libc::DT_FIFO => SFlag::S_IFIFO,
+            libc::DT_CHR => SFlag::S_IFCHR,
+            libc::DT_BLK => SFlag::S_IFBLK,
+            libc::DT_DIR => SFlag::S_IFDIR,
+            libc::DT_REG => SFlag::S_IFREG,
+            libc::DT_LNK => SFlag::S_IFLNK,
+            libc::DT_SOCK => SFlag::S_IFSOCK,
+            /* libc::DT_UNKNOWN | */ _ => panic!("failed to recognize file type"),
+        };
+
+        Self {
+            ino,
+            name: name.into(),
+            entry_type,
+        }
+    }
+}
+
+impl Iterator for Dir {
+    type Item = nix::Result<DirEntry>;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        unsafe {
+            // Note: POSIX specifies that portable applications should dynamically allocate a
+            // buffer with room for a `d_name` field of size `pathconf(..., _PC_NAME_MAX)` plus 1
+            // for the NUL byte. It doesn't look like the std library does this; it just uses
+            // fixed-sized buffers (and libc's dirent seems to be sized so this is appropriate).
+            // Probably fine here too then.
+            let mut ent = std::mem::MaybeUninit::<dirent>::uninit();
+            let mut result = ptr::null_mut();
+            if let Err(e) =
+                nix::errno::Errno::result(readdir_r(self.0.as_ptr(), ent.as_mut_ptr(), &mut result))
+            {
+                return Some(Err(e));
+            }
+            if result.is_null() {
+                return None;
+            }
+            assert_eq!(result, ent.as_mut_ptr());
+            let dirent = ent.assume_init();
+            Some(Ok(DirEntry::from_dirent(dirent)))
+        }
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use futures::stream::StreamExt;
+    use nix::fcntl::{self, OFlag};
+    use nix::sys::stat::Mode;
+    use smol::blocking;
+
+    use super::Dir;
+
+    #[test]
+    fn test_dir() -> nix::Result<()> {
+        smol::run(async {
+            let oflags = OFlag::O_RDONLY | OFlag::O_DIRECTORY;
+            let fd = blocking!(fcntl::open(".", oflags, Mode::empty()))?;
+            let dir = Dir::from_fd(fd)?;
+            let mut dir = smol::iter(dir);
+
+            while let Some(entry) = dir.next().await {
+                let entry = entry?;
+                println!(
+                    "read file name={:?}, ino={}, type:={:?}",
+                    entry.entry_name(),
+                    entry.ino(),
+                    entry.entry_type()
+                );
+            }
+
+            Ok(())
+        })
+    }
+}

src/fs/util.rs

+use anyhow::{self, Context};
+use log::debug;
+use nix::fcntl::{self, OFlag};
+use nix::sys::stat::{self, FileStat, Mode, SFlag};
+use smol::blocking;
+use std::ffi::OsString;
+use std::os::unix::io::RawFd;
+use std::path::Path;
+use std::time::{Duration, SystemTime, UNIX_EPOCH};
+
+use super::super::protocol::{FuseAttr, INum};
+
+#[derive(Clone, Copy, Debug)]
+pub struct FileAttr {
+    /// Inode number
+    pub ino: INum,
+    /// Size in bytes
+    pub size: u64,
+    /// Size in blocks
+    pub blocks: u64,
+    /// Time of last access
+    pub atime: SystemTime,
+    /// Time of last modification
+    pub mtime: SystemTime,
+    /// Time of last change
+    pub ctime: SystemTime,
+    /// Time of creation (macOS only)
+    pub crtime: SystemTime,
+    /// Kind of file (directory, file, pipe, etc)
+    pub kind: SFlag,
+    /// Permissions
+    pub perm: u16,
+    /// Number of hard links
+    pub nlink: u32,
+    /// User id
+    pub uid: u32,
+    /// Group id
+    pub gid: u32,
+    /// Rdev
+    pub rdev: u32,
+    /// Flags (macOS only, see chflags(2))
+    pub flags: u32,
+}
+
+pub fn parse_oflag(flags: u32) -> OFlag {
+    debug_assert!(
+        flags < std::i32::MAX as u32,
+        "helper_parse_oflag() found flags={} overflow, larger than u16::MAX",
+        flags,
+    );
+    let oflags = OFlag::from_bits_truncate(flags as i32);
+    debug!("helper_parse_oflag() read file flags={:?}", oflags);
+    oflags
+}
+
+pub fn parse_mode(mode: u32) -> Mode {
+    debug_assert!(
+        mode < std::u16::MAX as u32,
+        "helper_parse_mode() found mode={} overflow, larger than u16::MAX",
+        mode,
+    );
+
+    #[cfg(target_os = "linux")]
+    let fmode = Mode::from_bits_truncate(mode);
+    #[cfg(target_os = "macos")]
+    let fmode = Mode::from_bits_truncate(mode as u16);
+    debug!("helper_parse_mode() read file mode={:?}", fmode);
+    fmode
+}
+
+pub fn parse_mode_bits(mode: u32) -> u16 {
+    #[cfg(target_os = "linux")]
+    let bits = parse_mode(mode).bits() as u16;
+    #[cfg(target_os = "macos")]
+    let bits = parse_mode(mode).bits();
+
+    bits
+}
+
+pub fn parse_sflag(flags: u32) -> SFlag {
+    debug_assert!(
+        flags < std::u16::MAX as u32,
+        "parse_sflag() found flags={} overflow, larger than u16::MAX",
+        flags,
+    );
+
+    #[cfg(target_os = "linux")]
+    let sflag = SFlag::from_bits_truncate(flags);
+    #[cfg(target_os = "macos")]
+    let sflag = SFlag::from_bits_truncate(flags as u16);
+    debug!("convert_sflag() read file type={:?}", sflag);
+    sflag
+}
+
+pub async fn open_dir(path: impl AsRef<Path>) -> nix::Result<RawFd> {
+    let oflags = OFlag::O_RDONLY | OFlag::O_DIRECTORY;
+    let path = path.as_ref().to_path_buf();
+    let dfd = blocking!(fcntl::open(path.as_os_str(), oflags, Mode::empty()))?;
+    Ok(dfd)
+}
+
+pub async fn open_dir_at(dfd: RawFd, child_name: OsString) -> nix::Result<RawFd> {
+    let oflags = OFlag::O_RDONLY | OFlag::O_DIRECTORY;
+    let dir_fd = blocking!(fcntl::openat(
+        dfd,
+        child_name.as_os_str(),
+        oflags,
+        Mode::empty()
+    ))?;
+    Ok(dir_fd)
+}
+
+pub async fn load_attr(fd: RawFd) -> nix::Result<FileAttr> {
+    let st = blocking!(stat::fstat(fd))?;
+
+    #[cfg(target_os = "macos")]
+    fn build_crtime(st: &FileStat) -> Option<SystemTime> {
+        UNIX_EPOCH.checked_add(Duration::new(
+            st.st_birthtime as u64,
+            st.st_birthtime_nsec as u32,
+        ))
+    }
+    #[cfg(target_os = "linux")]
+    fn build_crtime(_st: &FileStat) -> Option<SystemTime> {
+        None
+    }
+
+    let atime = UNIX_EPOCH.checked_add(Duration::new(st.st_atime as u64, st.st_atime_nsec as u32));
+    let mtime = UNIX_EPOCH.checked_add(Duration::new(st.st_mtime as u64, st.st_mtime_nsec as u32));
+    let ctime = UNIX_EPOCH.checked_add(Duration::new(st.st_ctime as u64, st.st_ctime_nsec as u32));
+    let crtime = build_crtime(&st);
+
+    let perm = parse_mode_bits(st.st_mode as u32);
+    debug!("load_attr() got file permission={}", perm);
+    let kind = parse_sflag(st.st_mode as u32);
+
+    let nt = SystemTime::now();
+    let attr = FileAttr {
+        ino: st.st_ino,
+        size: st.st_size as u64,
+        blocks: st.st_blocks as u64,
+        atime: atime.unwrap_or(nt),
+        mtime: mtime.unwrap_or(nt),
+        ctime: ctime.unwrap_or(nt),
+        crtime: crtime.unwrap_or(nt),
+        kind,
+        perm,
+        nlink: st.st_nlink as u32,
+        uid: st.st_uid,
+        gid: st.st_gid,
+        rdev: st.st_rdev as u32,
+        #[cfg(target_os = "linux")]
+        flags: 0,
+        #[cfg(target_os = "macos")]
+        flags: st.st_flags,
+    };
+    Ok(attr)
+}
+
+pub fn time_from_system_time(system_time: &SystemTime) -> anyhow::Result<(u64, u32)> {
+    let duration = system_time.duration_since(UNIX_EPOCH).context(format!(
+        "failed to convert SystemTime={:?} to Duration",
+        system_time
+    ))?;
+    Ok((duration.as_secs(), duration.subsec_nanos()))
+}
+
+pub fn mode_from_kind_and_perm(kind: SFlag, perm: u16) -> u32 {
+    (match kind {
+        SFlag::S_IFIFO => libc::S_IFIFO,
+        SFlag::S_IFCHR => libc::S_IFCHR,
+        SFlag::S_IFBLK => libc::S_IFBLK,
+        SFlag::S_IFDIR => libc::S_IFDIR,
+        SFlag::S_IFREG => libc::S_IFREG,
+        SFlag::S_IFLNK => libc::S_IFLNK,
+        SFlag::S_IFSOCK => libc::S_IFSOCK,
+        _ => panic!("unknown SFlag type={:?}", kind),
+    }) as u32
+        | perm as u32
+}
+
+pub fn convert_to_fuse_attr(attr: FileAttr) -> anyhow::Result<FuseAttr> {
+    let (atime_secs, atime_nanos) = time_from_system_time(&attr.atime)?;
+    let (mtime_secs, mtime_nanos) = time_from_system_time(&attr.mtime)?;
+    let (ctime_secs, ctime_nanos) = time_from_system_time(&attr.ctime)?;
+    #[cfg(target_os = "macos")]
+    let (crtime_secs, crtime_nanos) = time_from_system_time(&attr.crtime)?;
+
+    Ok(FuseAttr {
+        ino: attr.ino,
+        size: attr.size,
+        blocks: attr.blocks,
+        atime: atime_secs,
+        mtime: mtime_secs,
+        ctime: ctime_secs,
+        #[cfg(target_os = "macos")]
+        crtime: crtime_secs,
+        atimensec: atime_nanos,
+        mtimensec: mtime_nanos,
+        ctimensec: ctime_nanos,
+        #[cfg(target_os = "macos")]
+        crtimensec: crtime_nanos,
+        mode: mode_from_kind_and_perm(attr.kind, attr.perm),
+        nlink: attr.nlink,
+        uid: attr.uid,
+        gid: attr.gid,
+        rdev: attr.rdev,
+        #[cfg(target_os = "macos")]
+        flags: attr.flags,
+        #[cfg(feature = "abi-7-9")]
+        blksize: 0, // TODO: find a proper way to set block size
+        #[cfg(feature = "abi-7-9")]
+        padding: 0,
+    })
+}

src/fuse_read.rs

+use futures::io::AsyncRead;
+use futures::stream::Stream;
+use futures::task::{Context, Poll};
+use log::debug;
+use pin_project_lite::pin_project;
+use std::iter;
+use std::pin::Pin;
+
+pin_project! {
+    #[derive(Debug)]
+    pub(crate) struct FuseBufReadStream<R> {
+        #[pin]
+        reader: R,
+        buf: Vec<u8>,
+        cap: usize,
+    }
+}
+
+impl<R: AsyncRead> FuseBufReadStream<R> {
+    #[allow(dead_code)]
+    pub fn with_capacity(capacity: usize, reader: R) -> FuseBufReadStream<R> {
+        FuseBufReadStream {
+            reader,
+            buf: iter::repeat(0u8).take(capacity).collect(),
+            cap: capacity,
+        }
+    }
+}
+
+impl<R: AsyncRead> Stream for FuseBufReadStream<R> {
+    type Item = std::io::Result<Vec<u8>>;
+
+    fn poll_next(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
+        let this = self.project();
+
+        unsafe {
+            this.buf.set_len(this.buf.capacity());
+        }
+        let read_size = futures_core::ready!(this.reader.poll_read(cx, this.buf))?;
+        debug!("FuseBufReadStream read {} bytes", read_size);
+        if read_size == 0 {
+            return Poll::Ready(None);
+        }
+        unsafe {
+            this.buf.set_len(read_size);
+        }
+
+        Poll::Ready(Some(Ok(std::mem::replace(
+            this.buf,
+            // TODO: FIXME! It should preallocate all Vec<u8> buffers before reading
+            iter::repeat(0u8).take(*this.cap).collect(),
+        ))))
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use futures::prelude::*;
+    use futures::stream::StreamExt;
+    use smol::{self, blocking};
+    use std::fs::{self, File};
+    use std::io;
+
+    use super::FuseBufReadStream;
+
+    #[test]
+    fn test_for_each_concurrent() -> io::Result<()> {
+        smol::run(async move {
+            let capacity = 1024;
+            let dir = blocking!(fs::read_dir("./src"))?;
+            let dir = smol::iter(dir);
+            dir.try_for_each_concurrent(2, |entry| async move {
+                let path = entry.path();
+                if path.is_dir() {
+                    println!("skip directory: {:?}", path);
+                } else {
+                    println!("read file: {:?}", path);
+                    let file = blocking!(File::open(path))?;
+                    let file = smol::reader(file);
+                    FuseBufReadStream::with_capacity(capacity, file)
+                        .for_each_concurrent(10, |res| async move {
+                            match res {
+                                Ok(byte_vec) => {
+                                    println!("read {} bytes", byte_vec.len());
+                                    let output_length = 16;
+                                    if byte_vec.len() > output_length {
+                                        println!(
+                                            "first {} bytes: {:?}",
+                                            output_length,
+                                            &byte_vec[..output_length]
+                                        );
+                                    } else {
+                                        println!("total bytes: {:?}", byte_vec);
+                                    }
+                                    // Ok::<(), Error>(())
+                                }
+                                Err(err) => {
+                                    println!("read file failed, the error is: {:?}", err);
+                                }
+                            }
+                        })
+                        .await;
+                }
+                Ok(())
+            })
+            .await?;
+            Ok(())
+        })
+    }
+}

src/main.rs

+use log::debug;
+
+mod channel;
+mod fs;
+mod fuse_read;
+mod fuse_reply;
+mod fuse_request;
+mod mount;
+mod protocol;
+mod session;
+use session::*;
+
+fn main() -> anyhow::Result<()> {
+    env_logger::init();
+    let mountpoint = match std::env::args_os().nth(1) {
+        Some(path) => path,
+        None => {
+            return Err(anyhow::anyhow!(
+                "no mount path input, the usage: {} <MOUNTPOINT>",
+                std::env::args().next().unwrap(), // safe to use unwrap here
+            ));
+        }
+    };
+    debug!("mount point: {:?}", mountpoint);
+
+    smol::run(async move {
+        let ss = Session::new(&mountpoint).await?;
+        ss.run().await?;
+        Ok(())
+    })
+}
+
+#[cfg(test)]
+mod test {
+    mod integration_tests;
+    mod test_util;
+
+    use futures::prelude::*;
+    use futures::stream::StreamExt;
+    use smol::{self, blocking};
+    use std::fs::{self, File};
+    use std::io;
+
+    #[test]
+    fn test_async_iter() -> io::Result<()> {
+        smol::run(async move {
+            let dir = blocking!(fs::read_dir("."))?;
+            let mut dir = smol::iter(dir);
+            while let Some(entry) = dir.next().await {
+                let path = entry?.path();
+                if path.is_file() {
+                    println!("read file: {:?}", path);
+                    let file = blocking!(File::open(path))?;
+                    let mut file = smol::reader(file);
+                    let mut buf = vec![];
+                    file.read_to_end(&mut buf).await?;
+                    let output_length = 16;
+                    if buf.len() > output_length {
+                        println!("first {} bytes: {:?}", output_length, &buf[..output_length]);
+                    } else {
+                        println!("total bytes: {:?}", buf);
+                    }
+                } else {
+                    println!("skip directory: {:?}", path);
+                }
+            }
+            Ok(())
+        })
+    }
+}

src/mount.rs

+use anyhow::{self, Context};
+use log::{debug, info};
+use nix::fcntl::{self, OFlag};
+use nix::sys::stat::{self, Mode};
+use smol::blocking;
+use std::ffi::CString;
+use std::fs;
+use std::os::raw::c_void;
+use std::os::unix::io::RawFd;
+use std::path::Path;
+
+use param::*;
+
+#[cfg(target_os = "linux")]
+mod param {
+    // https://github.com/torvalds/linux/blob/master/include/uapi/linux/mount.h#L11
+    // TODO: use mount flags from libc
+    // pub const MS_RDONLY: u64 = 1; // Mount read-only
+    pub const MS_NOSUID: u64 = 2; // Ignore suid and sgid bits
+    pub const MS_NODEV: u64 = 4; // Disallow access to device special files
+    pub const MNT_FORCE: i32 = 1; // Force un-mount
+}
+
+#[cfg(target_os = "macos")]
+mod param {
+    // https://github.com/apple/darwin-xnu/blob/master/bsd/sys/mount.h#L288
+    // TODO: use mount flags from libc
+    // pub const MNT_RDONLY: i32 = 0x00000001; // read only filesystem
+    pub const MNT_NOSUID: i32 = 0x00000008; // don't honor setuid bits on fs
+    pub const MNT_NODEV: i32 = 0x00000010; // don't interpret special files
+    pub const MNT_FORCE: i32 = 0x00080000; // force unmount or readonly change
+    pub const MNT_NOUSERXATTR: i32 = 0x01000000; // Don't allow user extended attributes
+    pub const MNT_NOATIME: i32 = 0x10000000; // disable update of file access time
+
+    pub const PAGE_SIZE: u32 = 4096;
+
+    pub const FUSE_DEFAULT_BLOCKSIZE: u32 = 4096;
+    pub const FUSE_DEFAULT_DAEMON_TIMEOUT: u32 = 60; // seconds
+    pub const FUSE_DEFAULT_IOSIZE: u32 = 16 * PAGE_SIZE;
+
+    pub const FUSE_IOC_MAGIC: u8 = b'F';
+    pub const FUSE_IOC_TYPE_MODE: u8 = 5;
+
+    pub const FUSE_FSSUBTYPE_UNKNOWN: u32 = 0;
+    pub const FUSE_MOPT_DEBUG: u64 = 0x0000000000000040;
+    pub const FUSE_MOPT_FSNAME: u64 = 0x0000000000001000;
+    pub const FUSE_MOPT_NO_APPLEXATTR: u64 = 0x0000000000800000;
+
+    use libc::size_t;
+    pub const MFSTYPENAMELEN: size_t = 16; // length of fs type name including null
+    pub const MAXPATHLEN: size_t = 1024; //PATH_MAX
+
+    #[repr(C)]
+    pub(crate) struct FuseMountArgs {
+        pub mntpath: [u8; MAXPATHLEN],        // path to the mount point
+        pub fsname: [u8; MAXPATHLEN],         // file system description string
+        pub fstypename: [u8; MFSTYPENAMELEN], // file system type name
+        pub volname: [u8; MAXPATHLEN],        // volume name
+        pub altflags: u64,                    // see mount-time flags below
+        pub blocksize: u32,                   // fictitious block size of our "storage"
+        pub daemon_timeout: u32,              // timeout in seconds for upcalls to daemon
+        pub fsid: u32,                        // optional custom value for part of fsid[0]
+        pub fssubtype: u32,                   // file system sub type id
+        pub iosize: u32,                      // maximum size for reading or writing
+        pub random: u32,                      // random "secret" from device
+        pub rdev: u32,                        // dev_t for the /dev/osxfuse{n} in question
+    }
+}
+
+#[cfg(target_os = "linux")]
+pub async fn umount(short_path: impl AsRef<Path>) -> anyhow::Result<()> {
+    use nix::unistd;
+    use std::process::Command;
+
+    let mount_path = short_path.as_ref().to_path_buf();
+    blocking!(
+        let mntpnt = mount_path.as_os_str();
+
+        if unistd::geteuid().is_root() {
+            // direct umount
+            #[cfg(target_arch = "aarch64")]
+            let result = unsafe { libc::umount2(mntpnt as *const _ as *const u8, MNT_FORCE) };
+            #[cfg(target_arch = "x86_64")]
+            let result =
+                unsafe { libc::umount2(mntpnt as *const _ as *const u8 as *const i8, MNT_FORCE) };
+
+            if result == 0 {
+                Ok(())
+            } else {
+                Err(anyhow::anyhow!(
+                    "failed to umount fuse device, the error is: {}",
+                    nix::Error::last(),
+                ))
+            }
+        } else {
+            // use fusermount to umount
+            let umount_handle = Command::new("fusermount")
+                .arg("-uz") // lazy umount
+                .arg(mntpnt)
+                .output()
+                .expect("fusermount command failed to start");
+            if umount_handle.status.success() {
+                Ok(())
+            } else {
+                let stderr = String::from_utf8_lossy(&umount_handle.stderr);
+                debug!("fusermount failed to umount, the error is: {}", &stderr);
+                Err(anyhow::anyhow!(
+                    "fusermount failed to umount fuse device, the error is: {}",
+                    &stderr,
+                ))
+            }
+        }
+    )
+}
+
+#[cfg(target_os = "linux")]
+pub async fn mount(mount_point: impl AsRef<Path>) -> anyhow::Result<RawFd> {
+    use nix::unistd;
+
+    if unistd::geteuid().is_root() {
+        // direct umount
+        direct_mount(mount_point).await
+    } else {
+        // use fusermount to mount
+        fuser_mount(mount_point).await
+    }
+}
+
+#[cfg(target_os = "linux")]
+async fn fuser_mount(mount_point: impl AsRef<Path>) -> anyhow::Result<RawFd> {
+    use nix::cmsg_space;
+    use nix::sys::socket::{
+        self, AddressFamily, ControlMessageOwned, MsgFlags, SockFlag, SockType,
+    };
+    use nix::sys::uio::IoVec;
+    use std::process::Command;
+
+    let mount_path = mount_point.as_ref().to_path_buf();
+
+    let (local, remote) = blocking!(socket::socketpair(
+        AddressFamily::Unix,
+        SockType::Stream,
+        None,
+        SockFlag::empty(),
+    ))
+    .context("failed to create socket pair")?;
+
+    let mount_handle = blocking!(Command::new("fusermount")
+        .arg("-o")
+        // fusermount option allow_other only allowed if user_allow_other is set in /etc/fuse.conf
+        .arg("nosuid,nodev,noexec,nonempty") // rw,async,noatime,auto_unmount,allow_other
+        .arg(mount_path.as_os_str())
+        .env("_FUSE_COMMFD", remote.to_string())
+        .output())
+    .context("fusermount command failed to start")?;
+
+    assert!(
+        mount_handle.status.success(),
+        "failed to run fusermount, the error is: {}",
+        String::from_utf8_lossy(&mount_handle.stderr),
+    );
+    info!(
+        "fusermount path={:?} to FUSE device successfully!",
+        mount_point.as_ref(),
+    );
+
+    blocking!(
+        let mut buf = [0u8; 5];
+        let iov = [IoVec::from_mut_slice(&mut buf[..])];
+        let mut cmsgspace = cmsg_space!([RawFd; 1]);
+        let msg = socket::recvmsg(local, &iov, Some(&mut cmsgspace), MsgFlags::empty())
+            .context("failed to receive from fusermount")?;
+
+        let mut mount_fd = -1;
+        for cmsg in msg.cmsgs() {
+            if let ControlMessageOwned::ScmRights(fd) = cmsg {
+                debug_assert_eq!(fd.len(), 1);
+                mount_fd = fd[0];
+            } else {
+                panic!("unexpected cmsg");
+            }
+        }
+
+        debug_assert_ne!(mount_fd, -1);
+        Ok(mount_fd)
+    )
+}
+
+#[cfg(target_os = "linux")]
+async fn direct_mount(mount_point: impl AsRef<Path>) -> anyhow::Result<RawFd> {
+    use nix::sys::stat::SFlag;
+    use nix::unistd;
+
+    let mount_point = mount_point.as_ref().to_path_buf();
+
+    let devpath = Path::new("/dev/fuse");
+
+    let dev_fd = blocking!(fcntl::open(devpath, OFlag::O_RDWR, Mode::empty()))
+        .context("failed to open fuse device")?;
+
+    let full_path = blocking!(fs::canonicalize(mount_point))?;
+    let cstr_path = full_path
+        .to_str()
+        .expect("full mount path to string failed");
+
+    let mntpath = CString::new(cstr_path).expect("CString::new failed");
+    let fstype = CString::new("fuse").expect("CString::new failed");
+    let fsname = CString::new("/dev/fuse").expect("CString::new failed");
+
+    let mnt_sb =
+        blocking!(stat::stat(&full_path)).context("failed to get the file stat of mount point")?;
+
+    let opts = format!(
+        "fd={},rootmode={:o},user_id={},group_id={}",
+        dev_fd,
+        mnt_sb.st_mode & SFlag::S_IFMT.bits(),
+        unistd::getuid().as_raw(),
+        unistd::getgid().as_raw()
+    );
+    let opts = CString::new(&*opts).expect("CString::new failed");
+    debug!("direct mount opts={:?}", &opts);
+    blocking!(
+        let result = unsafe { libc::mount(
+            fsname.as_ptr(),
+            mntpath.as_ptr(),
+            fstype.as_ptr(),
+            MS_NOSUID | MS_NODEV,
+            opts.as_ptr() as *const c_void,
+        )};
+        if result == 0 {
+            info!("mount path={:?} to FUSE device={:?} successfully!", mntpath, devpath);
+            Ok(dev_fd)
+        } else {
+            // let e = Errno::from_i32(errno::errno());
+            // debug!("errno={},the error is: {:?}", errno::errno(), e);
+            // let mount_fail_str = "mount failed!";
+            // #[cfg(target_arch = "aarch64")]
+            // libc::perror(mount_fail_str.as_ptr());
+            // #[cfg(target_arch = "x86_64")]
+            // libc::perror(mount_fail_str.as_ptr() as *const i8);
+
+            Err(anyhow::anyhow!(
+                "failed to mount to fuse device, the error is: {}",
+                nix::Error::last(),
+            ))
+        }
+    )
+}
+
+#[cfg(any(target_os = "macos"))]
+pub async fn umount(mount_point: impl AsRef<Path>) -> nix::Result<()> {
+    let mntpnt = mount_point.as_ref().to_path_buf();
+    blocking!(
+        let mntpnt = mntpnt.as_os_str();
+        let res = unsafe { libc::unmount(mntpnt as *const _ as *const u8 as *const i8, MNT_FORCE) };
+        if res < 0 {
+            Err(nix::Error::last())
+        } else {
+            Ok(())
+        }
+    )
+}
+
+#[cfg(any(target_os = "macos"))]
+pub async fn mount(mount_point: impl AsRef<Path>) -> anyhow::Result<RawFd> {
+    let mount_point = mount_point.as_ref().to_path_buf();
+    let devpath = Path::new("/dev/osxfuse1");
+
+    let fd = blocking!(fcntl::open(devpath, OFlag::O_RDWR, Mode::empty()))
+        .context("failed to open fuse device")?;
+
+    let sb = blocking!(stat::fstat(fd).context("failed to get the file stat of fuse device"))?;
+
+    // use ioctl to read device random secret
+    // osxfuse/support/mount_osxfuse/mount_osxfuse.c#L1099
+    // result = ioctl(fd, FUSEDEVIOCGETRANDOM, &drandom);
+    // FUSEDEVIOCGETRANDOM // osxfuse/common/fuse_ioctl.h#L43
+    let drandom = blocking!(
+        let mut drandom: u32 = 0;
+        nix::ioctl_read!(fuse_read_random, FUSE_IOC_MAGIC, FUSE_IOC_TYPE_MODE, u32);
+        let result = unsafe { fuse_read_random(fd, &mut drandom as *mut _)? };
+        debug_assert_eq!(result, 0);
+        debug!("successfully read drandom={}", drandom);
+        Ok::<_, anyhow::Error>(drandom)
+    )?;
+
+    let full_path = blocking!(fs::canonicalize(mount_point))?;
+    let cstr_path = full_path
+        .to_str()
+        .expect("full mount path to string failed");
+
+    let mntpath = CString::new(cstr_path)?;
+    let fstype = CString::new("osxfuse")?;
+    let fsname = CString::new("macfuse")?;
+    let fstypename = CString::new("")?;
+    let volname = CString::new("OSXFUSE Volume 0 (macfuse)")?;
+
+    // (fuse_mount_args) args = {
+    //     mntpath = "/private/tmp/hello"
+    //     fsname = "macfuse@osxfuse0"
+    //     fstypename = ""
+    //     volname = "OSXFUSE Volume 0 (macfuse)"
+    //     altflags = 64
+    //     blocksize = 4096
+    //     daemon_timeout = 60
+    //     fsid = 0
+    //     fssubtype = 0
+    //     iosize = 65536
+    //     random = 1477356727
+    //     rdev = 587202560
+    //   }
+    fn copy_slice<T: Copy>(from: &[T], to: &mut [T]) {
+        debug_assert!(to.len() >= from.len());
+        to[..from.len()].copy_from_slice(&from);
+    }
+    let mut mntpath_slice = [0u8; MAXPATHLEN];
+    copy_slice(mntpath.as_bytes(), &mut mntpath_slice);
+    let mut fsname_slice = [0u8; MAXPATHLEN];
+    copy_slice(fsname.as_bytes(), &mut fsname_slice);
+    let mut fstypename_slice = [0u8; MFSTYPENAMELEN];
+    copy_slice(fstypename.as_bytes(), &mut fstypename_slice);
+    let mut volname_slice = [0u8; MAXPATHLEN];
+    copy_slice(volname.as_bytes(), &mut volname_slice);
+
+    let mut mnt_args = FuseMountArgs {
+        mntpath: mntpath_slice,
+        fsname: fsname_slice,
+        fstypename: fstypename_slice,
+        volname: volname_slice,
+        altflags: FUSE_MOPT_DEBUG | FUSE_MOPT_FSNAME | FUSE_MOPT_NO_APPLEXATTR,
+        blocksize: FUSE_DEFAULT_BLOCKSIZE,
+        daemon_timeout: FUSE_DEFAULT_DAEMON_TIMEOUT,
+        fsid: 0,
+        fssubtype: FUSE_FSSUBTYPE_UNKNOWN,
+        iosize: FUSE_DEFAULT_IOSIZE,
+        random: drandom,
+        rdev: sb.st_rdev as u32,
+    };
+
+    blocking!(
+        let result = unsafe {
+            libc::mount(
+                fstype.as_ptr(),
+                mntpath.as_ptr(),
+                MNT_NOSUID | MNT_NODEV | MNT_NOUSERXATTR | MNT_NOATIME,
+                &mut mnt_args as *mut _ as *mut c_void,
+            )
+        };
+        if result == 0 {
+            info!("mount path={:?} to FUSE device={:?} successfully!", mntpath, devpath);
+            Ok(fd)
+        } else {
+            // let e = Errno::from_i32(errno::errno());
+            // error!("errno={}, the error is: {:?}", errno::errno(), e);
+            // let mount_fail_str = "mount failed!";
+            // unsafe { libc::perror(mount_fail_str.as_ptr() as *const i8); }
+
+            Err(anyhow::anyhow!(
+                "failed to mount to fuse device, the error is: {}",
+                nix::Error::last(),
+            ))
+        }
+    )
+}

src/test/test_util.rs

+use log::{debug, info}; // warn, error
+use smol::Task;
+use std::fs;
+use std::path::Path;
+use std::thread::{self, JoinHandle};
+use std::time::Duration;
+
+use super::super::{mount, session::Session};
+
+pub const DEFAULT_MOUNT_DIR: &str = "../fuse_test";
+pub const FILE_CONTENT: &str = "0123456789ABCDEF";
+
+pub fn setup(mount_path: impl AsRef<Path>) -> anyhow::Result<JoinHandle<()>> {
+    env_logger::init();
+    let mut mount_dir = mount_path.as_ref().to_path_buf();
+    mount_dir = smol::block_on(async move {
+        let result = mount::umount(&mount_dir).await;
+        if result.is_ok() {
+            debug!("umounted {:?} before setup", mount_dir);
+        }
+        mount_dir
+    });
+
+    if mount_dir.exists() {
+        fs::remove_dir_all(&mount_dir)?;
+    }
+    fs::create_dir_all(&mount_dir)?;
+    let abs_root_path = fs::canonicalize(&mount_dir)?;
+
+    let fs_task = Task::spawn(async move {
+        async fn run_fs(mount_point: impl AsRef<Path>) -> anyhow::Result<()> {
+            let ss = Session::new(mount_point).await?;
+            ss.run().await?;
+            Ok(())
+        };
+        if let Err(e) = run_fs(&abs_root_path).await {
+            panic!("failed to run filesystem, the error is: {}", e);
+        }
+    });
+    // do not block main thread
+    let th = thread::spawn(|| {
+        smol::run(async { fs_task.await });
+        debug!("spawned a thread for smol::run()");
+    });
+    debug!("async_fuse task spawned");
+    let seconds = 2;
+    debug!("sleep {} seconds for setup", seconds);
+    thread::sleep(Duration::new(seconds, 0));
+
+    info!("setup finished");
+    Ok(th)
+}
+
+pub fn teardown(mount_dir: impl AsRef<Path>, th: JoinHandle<()>) -> anyhow::Result<()> {
+    info!("begin teardown");
+    let seconds = 1;
+    debug!("sleep {} seconds for teardown", seconds);
+    thread::sleep(Duration::new(seconds, 0));
+
+    smol::block_on(async {
+        mount::umount(&mount_dir).await.unwrap(); // TODO: remove unwrap()
+    });
+    let abs_mount_path = fs::canonicalize(mount_dir)?;
+    fs::remove_dir_all(&abs_mount_path)?;
+    th.join().unwrap(); // TODO: remove unwrap()
+    Ok(())
+}