diff --git a/crates/runc-shim/src/synchronous/runc.rs b/crates/runc-shim/src/synchronous/runc.rs
index df07eb1..1df4bf8 100644
--- a/crates/runc-shim/src/synchronous/runc.rs
+++ b/crates/runc-shim/src/synchronous/runc.rs
@@ -36,7 +36,7 @@ use shim::api::*;
 use shim::console::ConsoleSocket;
 use shim::error::{Error, Result};
 use shim::io::Stdio;
-use shim::monitor::{monitor_subscribe, ExitEvent, Subject, Subscription, Topic};
+use shim::monitor::{monitor_subscribe, wait_pid, ExitEvent, Subject, Subscription, Topic};
 use shim::mount::mount_rootfs;
 use shim::protos::api::ProcessInfo;
 use shim::protos::cgroups::metrics::Metrics;
@@ -672,17 +672,3 @@ where
     }
     "".to_string()
 }
-
-fn wait_pid(pid: i32, s: Subscription) -> i32 {
-    loop {
-        if let Ok(ExitEvent {
-            subject: Subject::Pid(epid),
-            exit_code: code,
-        }) = s.rx.recv()
-        {
-            if pid == epid {
-                return code;
-            }
-        }
-    }
-}
diff --git a/crates/shim/Cargo.toml b/crates/shim/Cargo.toml
index 625fbc3..29c70ff 100644
--- a/crates/shim/Cargo.toml
+++ b/crates/shim/Cargo.toml
@@ -32,6 +32,8 @@ uuid = { version = "1.0.0", features = ["v4"] }
 signal-hook = "0.3.13"
 oci-spec = "0.5.4"
 prctl = "1.0.0"
+page_size = "0.4.2"
+regex = "1"
 
 containerd-shim-protos = { path = "../shim-protos", version = "0.2.0" }
 
diff --git a/crates/shim/src/mount.rs b/crates/shim/src/mount.rs
index ad38536..d49445d 100644
--- a/crates/shim/src/mount.rs
+++ b/crates/shim/src/mount.rs
@@ -16,14 +16,21 @@
 #![allow(unused)]
 
 use std::collections::HashMap;
+use std::env;
 use std::ops::{BitAnd, BitAndAssign, BitOr, BitOrAssign, Not};
 use std::path::Path;
 
 use lazy_static::lazy_static;
+use log::error;
 #[cfg(target_os = "linux")]
 use nix::mount::{mount, MsFlags};
+#[cfg(target_os = "linux")]
+use nix::unistd::{fork, ForkResult};
+use regex::Regex;
 
 use crate::error::{Error, Result};
+#[cfg(not(feature = "async"))]
+use crate::monitor::{monitor_subscribe, wait_pid, Topic};
 
 #[cfg(target_os = "linux")]
 struct Flag {
@@ -31,6 +38,8 @@ struct Flag {
     flags: MsFlags,
 }
 
+const OVERLAY_LOWERDIR_PREFIX: &str = "lowerdir=";
+
 #[cfg(target_os = "linux")]
 lazy_static! {
     static ref MOUNT_FLAGS: HashMap<&'static str, Flag> = {
@@ -223,6 +232,300 @@ lazy_static! {
     static ref MS_BIND_RO: MsFlags = MsFlags::MS_BIND.bitor(MsFlags::MS_RDONLY);
 }
 
+fn options_size(options: &[String]) -> usize {
+    options.iter().fold(0, |sum, x| sum + x.len())
+}
+
+fn longest_common_prefix(dirs: &[String]) -> Option<String> {
+    if dirs.is_empty() {
+        return None;
+    }
+    if dirs.len() == 1 {
+        if dirs[0].is_empty() {
+            return None;
+        }
+        return Some(dirs[0].to_string());
+    }
+
+    let min = dirs.iter().min().unwrap();
+    let max = dirs.iter().max().unwrap();
+    let min_chars = min.chars().collect::<Vec<char>>();
+    let max_chars = max.chars().collect::<Vec<char>>();
+    let mut i = 0;
+    while i < min_chars.len() && i < max_chars.len() {
+        if min_chars[i] != max_chars[i] {
+            if i == 0 {
+                return None;
+            }
+            return Some(min[0..i].to_string());
+        }
+        i += 1;
+    }
+
+    if min.is_empty() {
+        None
+    } else {
+        Some(min.to_string())
+    }
+}
+
+// NOTE: the snapshot id is based on digits.
+// in order to avoid to get snapshots/x, shoule be back to parent dir.
+// however, there is assumption that the common dir is ${root}/io.containerd.v1.overlayfs/snapshots.
+#[cfg(target_os = "linux")]
+fn trim_flawed_dir(s: &str) -> String {
+    let r = Regex::new(r"((/[^/]+)+/)([^/]*)").unwrap();
+    r.replace(s, "$1").to_string()
+}
+
+#[cfg(target_os = "linux")]
+struct LowerdirCompactor {
+    options: Vec<String>,
+    lowerdirs: Option<Vec<String>>,
+    lowerdir_prefix: Option<String>,
+}
+
+#[cfg(target_os = "linux")]
+impl LowerdirCompactor {
+    fn new(options: &[String]) -> Self {
+        Self {
+            options: options.to_vec(),
+            lowerdirs: None,
+            lowerdir_prefix: None,
+        }
+    }
+
+    fn lowerdirs(&mut self) -> &mut Self {
+        self.lowerdirs = Some(
+            self.options
+                .iter()
+                .filter(|x| x.starts_with(OVERLAY_LOWERDIR_PREFIX))
+                .map(|x| x.strip_prefix(OVERLAY_LOWERDIR_PREFIX).unwrap_or(x))
+                .flat_map(|x| x.split(':'))
+                .map(str::to_string)
+                .collect(),
+        );
+        self
+    }
+
+    fn lowerdir_prefix(&mut self) -> &mut Self {
+        self.lowerdir_prefix = self
+            .lowerdirs
+            .as_ref()
+            .filter(|x| x.len() > 1)
+            .map(|x| longest_common_prefix(x))
+            .unwrap_or(None)
+            .filter(|x| x != "/")
+            .map(|x| trim_flawed_dir(&x))
+            .filter(|x| !x.is_empty() && x != "/");
+        self
+    }
+
+    fn compact(&mut self) -> (Option<String>, Vec<String>) {
+        self.lowerdirs().lowerdir_prefix();
+        if let Some(chdir) = &self.lowerdir_prefix {
+            let lowerdir_str = self
+                .lowerdirs
+                .as_ref()
+                .unwrap_or(&Vec::new())
+                .iter()
+                .map(|x| x.strip_prefix(chdir).unwrap_or(x))
+                .collect::<Vec<&str>>()
+                .join(":");
+            let replace = |x: &str| -> String {
+                if x.starts_with(OVERLAY_LOWERDIR_PREFIX) {
+                    format!("{}{}", OVERLAY_LOWERDIR_PREFIX, lowerdir_str)
+                } else {
+                    x.to_string()
+                }
+            };
+            (
+                self.lowerdir_prefix.clone(),
+                self.options
+                    .iter()
+                    .map(|x| replace(x))
+                    .collect::<Vec<String>>(),
+            )
+        } else {
+            (None, self.options.to_vec())
+        }
+    }
+}
+
+enum MountExitCode {
+    NixUnknownErr,
+    ChdirErr,
+    Success,
+    NixOtherErr(i32),
+}
+
+impl From<i32> for MountExitCode {
+    fn from(code: i32) -> Self {
+        match code {
+            -2 => MountExitCode::NixUnknownErr,
+            -1 => MountExitCode::ChdirErr,
+            0 => MountExitCode::Success,
+            _ => MountExitCode::NixOtherErr(code),
+        }
+    }
+}
+
+impl From<MountExitCode> for i32 {
+    fn from(code: MountExitCode) -> Self {
+        match code {
+            MountExitCode::NixUnknownErr => -2,
+            MountExitCode::ChdirErr => -1,
+            MountExitCode::Success => 0,
+            MountExitCode::NixOtherErr(errno) => errno,
+        }
+    }
+}
+
+impl From<nix::errno::Errno> for MountExitCode {
+    fn from(err: nix::errno::Errno) -> Self {
+        match err {
+            nix::errno::Errno::UnknownErrno => MountExitCode::NixUnknownErr,
+            _ => MountExitCode::NixOtherErr(err as i32),
+        }
+    }
+}
+
+impl From<MountExitCode> for nix::errno::Errno {
+    fn from(code: MountExitCode) -> Self {
+        match code {
+            MountExitCode::NixOtherErr(errno) => nix::errno::Errno::from_i32(errno),
+            _ => nix::errno::Errno::UnknownErrno,
+        }
+    }
+}
+
+impl From<MountExitCode> for Result<()> {
+    fn from(code: MountExitCode) -> Self {
+        match code {
+            MountExitCode::NixUnknownErr => Err(other!(
+                "mount process exit unexpectedly, exit code: {}",
+                nix::errno::Errno::from(code)
+            )),
+            MountExitCode::ChdirErr => Err(other!("mount process exit unexpectedly: chdir failed")),
+            MountExitCode::Success => Ok(()),
+            MountExitCode::NixOtherErr(errno) => Err(other!(
+                "mount process exit unexpectedly, exit code: {}",
+                nix::errno::Errno::from_i32(errno)
+            )),
+        }
+    }
+}
+
+#[cfg(not(feature = "async"))]
+#[cfg(target_os = "linux")]
+pub fn mount_rootfs(
+    fs_type: Option<&str>,
+    source: Option<&str>,
+    options: &[String],
+    target: impl AsRef<Path>,
+) -> Result<()> {
+    //TODO add helper to mount fuse
+    let max_size = page_size::get();
+    // avoid hitting one page limit of mount argument buffer
+    //
+    // NOTE: 512 id a buffer during pagesize check.
+    let (chdir, options) =
+        if fs_type.unwrap_or("") == "overlay" && options_size(options) >= max_size - 512 {
+            LowerdirCompactor::new(options).compact()
+        } else {
+            (None, options.to_vec())
+        };
+
+    let mut flags: MsFlags = MsFlags::from_bits(0).unwrap();
+    let mut data = Vec::new();
+    options.iter().for_each(|x| {
+        if let Some(f) = MOUNT_FLAGS.get(x.as_str()) {
+            if f.clear {
+                flags.bitand_assign(f.flags.not());
+            } else {
+                flags.bitor_assign(f.flags)
+            }
+        } else {
+            data.push(x.as_str())
+        }
+    });
+
+    let opt = data.join(",");
+    if opt.len() > max_size {
+        return Err(other!("mount option is too long"));
+    }
+
+    let data = if !data.is_empty() {
+        Some(opt.as_str())
+    } else {
+        None
+    };
+
+    let s = monitor_subscribe(Topic::All)?;
+    match unsafe { fork() } {
+        Ok(ForkResult::Parent { child, .. }) => {
+            let code: MountExitCode = wait_pid(i32::from(child), s).into();
+            code.into()
+        }
+        Ok(ForkResult::Child) => {
+            if let Some(workdir) = chdir {
+                env::set_current_dir(Path::new(&workdir)).unwrap_or_else(|_| {
+                    unsafe { libc::_exit(i32::from(MountExitCode::ChdirErr)) };
+                });
+            }
+            // mount with non-propagation first, or remount with changed data
+            let oflags = flags.bitand(PROPAGATION_TYPES.not());
+            let zero: MsFlags = MsFlags::from_bits(0).unwrap();
+            if flags.bitand(MsFlags::MS_REMOUNT).eq(&zero) || data != None {
+                mount(source, target.as_ref(), fs_type, oflags, data).unwrap_or_else(|err| {
+                    error!(
+                        "Mount {:?} to {} failed: {}",
+                        source,
+                        target.as_ref().display(),
+                        err
+                    );
+                    let code: MountExitCode = err.into();
+                    unsafe { libc::_exit(code.into()) };
+                });
+            }
+            // change the propagation type
+            if flags.bitand(*PROPAGATION_TYPES).ne(&zero) {
+                mount::<str, Path, str, str>(None, target.as_ref(), None, *MS_PROPAGATION, None)
+                    .unwrap_or_else(|err| {
+                        error!(
+                            "Change {} mount propagation faied: {}",
+                            target.as_ref().display(),
+                            err
+                        );
+                        let code: MountExitCode = err.into();
+                        unsafe { libc::_exit(code.into()) };
+                    });
+            }
+            if oflags.bitand(*MS_BIND_RO).eq(&MS_BIND_RO) {
+                mount::<str, Path, str, str>(
+                    None,
+                    target.as_ref(),
+                    None,
+                    oflags.bitor(MsFlags::MS_REMOUNT),
+                    None,
+                )
+                .unwrap_or_else(|err| {
+                    error!(
+                        "Change {} read-only failed: {}",
+                        target.as_ref().display(),
+                        err
+                    );
+                    let code: MountExitCode = err.into();
+                    unsafe { libc::_exit(code.into()) };
+                });
+            }
+            unsafe { libc::_exit(i32::from(MountExitCode::Success)) };
+        }
+        Err(_) => Err(other!("fork mount process failed")),
+    }
+}
+
+#[cfg(feature = "async")]
 #[cfg(target_os = "linux")]
 pub fn mount_rootfs(
     fs_type: Option<&str>,
@@ -299,3 +602,111 @@ pub fn mount_rootfs(
 ) -> Result<()> {
     Err(Error::Unimplemented("start".to_string()))
 }
+
+#[cfg(test)]
+#[cfg(target_os = "linux")]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_trim_flawed_dir() {
+        let mut tcases: Vec<(&str, String)> = Vec::new();
+        tcases.push(("/.foo-_bar/foo", "/.foo-_bar/".to_string()));
+        tcases.push(("/.foo-_bar/foo/", "/.foo-_bar/foo/".to_string()));
+        tcases.push(("/.foo-_bar/foo/bar", "/.foo-_bar/foo/".to_string()));
+        tcases.push(("/.foo-_bar/foo/bar/", "/.foo-_bar/foo/bar/".to_string()));
+        for (case, expected) in tcases {
+            let res = trim_flawed_dir(case);
+            assert_eq!(res, expected);
+        }
+    }
+
+    #[test]
+    fn test_longest_common_prefix() {
+        let mut tcases: Vec<(Vec<String>, Option<String>)> = Vec::new();
+        tcases.push((vec![], None));
+        tcases.push((vec!["foo".to_string()], Some("foo".to_string())));
+        tcases.push((vec!["foo".to_string(), "bar".to_string()], None));
+        tcases.push((
+            vec!["foo".to_string(), "foo".to_string()],
+            Some("foo".to_string()),
+        ));
+        tcases.push((
+            vec!["foo".to_string(), "foobar".to_string()],
+            Some("foo".to_string()),
+        ));
+        tcases.push((
+            vec!["foo".to_string(), "".to_string(), "foobar".to_string()],
+            None,
+        ));
+        for (case, expected) in tcases {
+            let res = longest_common_prefix(&case);
+            assert_eq!(res, expected);
+        }
+    }
+
+    #[test]
+    fn test_compact_lowerdir_option() {
+        let mut tcases: Vec<(Vec<String>, Option<String>, Vec<String>)> = Vec::new();
+        tcases.push((
+            vec!["workdir=a".to_string()],
+            None,
+            vec!["workdir=a".to_string()],
+        ));
+        tcases.push((
+            vec!["workdir=a".to_string(), "lowerdir=b".to_string()],
+            None,
+            vec!["workdir=a".to_string(), "lowerdir=b".to_string()],
+        ));
+        tcases.push((
+            vec!["lowerdir=/snapshots/1/fs:/snapshots/10/fs".to_string()],
+            Some("/snapshots/".to_string()),
+            vec!["lowerdir=1/fs:10/fs".to_string()],
+        ));
+        tcases.push((
+            vec![
+                "workdir=a".to_string(),
+                "lowerdir=/snapshots/1/fs:/snapshots/10/fs".to_string(),
+            ],
+            Some("/snapshots/".to_string()),
+            vec!["workdir=a".to_string(), "lowerdir=1/fs:10/fs".to_string()],
+        ));
+        tcases.push((
+            vec!["lowerdir=/snapshots/1/fs:/snapshots/10/fs:/snapshots/2/fs".to_string()],
+            Some("/snapshots/".to_string()),
+            vec!["lowerdir=1/fs:10/fs:2/fs".to_string()],
+        ));
+        tcases.push((
+            vec![
+                "workdir=a".to_string(),
+                "lowerdir=/snapshots/1/fs:/snapshots/10/fs:/snapshots/2/fs".to_string(),
+            ],
+            Some("/snapshots/".to_string()),
+            vec![
+                "workdir=a".to_string(),
+                "lowerdir=1/fs:10/fs:2/fs".to_string(),
+            ],
+        ));
+        tcases.push((
+            vec!["lowerdir=/snapshots/1/fs:/other_snapshots/1/fs".to_string()],
+            None,
+            vec!["lowerdir=/snapshots/1/fs:/other_snapshots/1/fs".to_string()],
+        ));
+        tcases.push((
+            vec![
+                "workdir=a".to_string(),
+                "lowerdir=/snapshots/1/fs:/other_snapshots/1/fs".to_string(),
+            ],
+            None,
+            vec![
+                "workdir=a".to_string(),
+                "lowerdir=/snapshots/1/fs:/other_snapshots/1/fs".to_string(),
+            ],
+        ));
+        for (case, expected_chdir, expected_options) in tcases {
+            let (chdir, options) = LowerdirCompactor::new(&case).compact();
+            assert_eq!(chdir, expected_chdir);
+            assert_eq!(options, expected_options);
+        }
+    }
+}
diff --git a/crates/shim/src/synchronous/monitor.rs b/crates/shim/src/synchronous/monitor.rs
index ef6feef..5f2f49d 100644
--- a/crates/shim/src/synchronous/monitor.rs
+++ b/crates/shim/src/synchronous/monitor.rs
@@ -135,3 +135,17 @@ impl Drop for Subscription {
         });
     }
 }
+
+pub fn wait_pid(pid: i32, s: Subscription) -> i32 {
+    loop {
+        if let Ok(ExitEvent {
+            subject: Subject::Pid(epid),
+            exit_code: code,
+        }) = s.rx.recv()
+        {
+            if pid == epid {
+                return code;
+            }
+        }
+    }
+}