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agent: Simplify BareMount::mount by using nix::mount::mount

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BareMount::mount does some complicated marshalling and uses unsafe code to
call into the mount(2) system call.  However, we're already using the nix
crate which provides a more Rust-like wrapper for mount(2).  We're even
already using nix::mount::umount and nix::mount::MsFlags from the same
module.

In the same way, we can replace the direct usage of libc::umount() with
nix::mount::umount() in one of the tests.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
This commit is contained in:
David Gibson 2021-08-24 15:50:23 +10:00
parent bac849ecba
commit 49282854f1
1 changed files with 15 additions and 48 deletions
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63
src/agent/src/mount.rs
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@ -4,22 +4,18 @@
//
use std::collections::HashMap;
use std::ffi::CString;
use std::fs;
use std::fs::File;
use std::io;
use std::io::{BufRead, BufReader};
use std::iter;
use std::os::unix::fs::{MetadataExt, PermissionsExt};
use std::path::Path;
use std::ptr::null;
use std::str::FromStr;
use std::sync::Arc;
use tokio::sync::Mutex;
use libc::{c_void, mount};
use nix::mount::{self, MsFlags};
use nix::mount::MsFlags;
use nix::unistd::Gid;
use regex::Regex;
@ -184,15 +180,6 @@ impl<'a> BareMount<'a> {
#[instrument]
pub fn mount(&self) -> Result<()> {
let source;
let dest;
let fs_type;
let mut options = null();
let cstr_options: CString;
let cstr_source: CString;
let cstr_dest: CString;
let cstr_fs_type: CString;
if self.source.is_empty() {
return Err(anyhow!("need mount source"));
}
@ -201,24 +188,10 @@ impl<'a> BareMount<'a> {
return Err(anyhow!("need mount destination"));
}
cstr_source = CString::new(self.source)?;
source = cstr_source.as_ptr();
cstr_dest = CString::new(self.destination)?;
dest = cstr_dest.as_ptr();
if self.fs_type.is_empty() {
return Err(anyhow!("need mount FS type"));
}
cstr_fs_type = CString::new(self.fs_type)?;
fs_type = cstr_fs_type.as_ptr();
if !self.options.is_empty() {
cstr_options = CString::new(self.options)?;
options = cstr_options.as_ptr() as *const c_void;
}
info!(
self.logger,
"mount source={:?}, dest={:?}, fs_type={:?}, options={:?}",
@ -227,17 +200,22 @@ impl<'a> BareMount<'a> {
self.fs_type,
self.options
);
let rc = unsafe { mount(source, dest, fs_type, self.flags.bits(), options) };
if rc < 0 {
return Err(anyhow!(
nix::mount::mount(
Some(self.source),
self.destination,
Some(self.fs_type),
self.flags,
Some(self.options),
)
.map_err(|e| {
anyhow!(
"failed to mount {:?} to {:?}, with error: {}",
self.source,
self.destination,
io::Error::last_os_error()
));
}
Ok(())
e
)
})
}
}
@ -816,7 +794,7 @@ pub fn cgroups_mount(logger: &Logger, unified_cgroup_hierarchy: bool) -> Result<
#[instrument]
pub fn remove_mounts(mounts: &[String]) -> Result<()> {
for m in mounts.iter() {
mount::umount(m.as_str()).context(format!("failed to umount {:?}", m))?;
nix::mount::umount(m.as_str()).context(format!("failed to umount {:?}", m))?;
}
Ok(())
}
@ -865,7 +843,6 @@ fn parse_options(option_list: Vec<String>) -> HashMap<String, String> {
mod tests {
use super::*;
use crate::{skip_if_not_root, skip_loop_if_not_root, skip_loop_if_root};
use libc::umount;
use std::fs::metadata;
use std::fs::File;
use std::fs::OpenOptions;
@ -1023,17 +1000,7 @@ mod tests {
assert!(result.is_ok(), "{}", msg);
// Cleanup
unsafe {
let cstr_dest =
CString::new(dest_filename).expect("failed to convert dest to cstring");
let umount_dest = cstr_dest.as_ptr();
let ret = umount(umount_dest);
let msg = format!("{}: umount result: {:?}", msg, result);
assert!(ret == 0, "{}", msg);
};
nix::mount::umount(dest_filename.as_str()).unwrap();
continue;
}