1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107
// Copyright 2018-2022 System76 <info@system76.com>
// SPDX-License-Identifier: MIT
use libc::*;
use std::{ffi::CString, io, ops::Deref, os::unix::ffi::OsStrExt, path::Path, ptr};
/// Unmount trait which enables any type that implements it to be upgraded into an `UnmountDrop`.
pub trait Unmount {
/// Unmount this mount with the given `flags`.
///
/// This will also detach the loopback device that the mount is assigned to, if
/// it was associated with a loopback device.
fn unmount(&self, flags: UnmountFlags) -> io::Result<()>;
/// Upgrades `Self` into an `UnmountDrop`, which will unmount the mount when it is dropped.
fn into_unmount_drop(self, flags: UnmountFlags) -> UnmountDrop<Self>
where
Self: Sized,
{
UnmountDrop { mount: self, flags }
}
}
/// Unmounts the underlying mounted device upon drop.
pub struct UnmountDrop<T: Unmount> {
pub(crate) mount: T,
pub(crate) flags: UnmountFlags,
}
impl<T: Unmount> UnmountDrop<T> {
/// Modify the previously-set unmount flags.
pub fn set_unmount_flags(&mut self, flags: UnmountFlags) {
self.flags = flags;
}
}
impl<T: Unmount> Deref for UnmountDrop<T> {
type Target = T;
fn deref(&self) -> &T {
&self.mount
}
}
impl<T: Unmount> Drop for UnmountDrop<T> {
fn drop(&mut self) {
let _ = self.mount.unmount(self.flags);
}
}
bitflags! {
/// Flags which may be specified when unmounting a file system.
pub struct UnmountFlags: c_int {
/// Force unmount even if busy. This can cause data loss. (Only for NFS mounts.)
const FORCE = MNT_FORCE;
/// Perform a lazy unmount: make the mount point unavailable for new accesses,
/// and actually perform the unmount when the mount point ceases to be busy.
const DETACH = MNT_DETACH;
/// Mark the mount point as expired. If a mount point is not currently in use,
/// then an initial call to umount2() with this flag fails with the error EAGAIN,
/// but marks the mount point as expired. The mount point remains expired as
/// long as it isn't accessed by any process. A second umount2() call specifying
/// MNT_EXPIRE unmounts an expired mount point. This flag cannot be specified with
/// either MNT_FORCE or MNT_DETACH.
const EXPIRE = MNT_EXPIRE;
/// Don't dereference target if it is a symbolic link. This flag allows security
/// problems to be avoided in set-user-ID-root programs that allow unprivileged
/// users to unmount file systems.
const NOFOLLOW = O_NOFOLLOW;
}
}
/// Unmounts the device at `path` using the provided `UnmountFlags`.
///
/// This will not detach a loopback device if the mount was attached to one. This behavior may
/// change in the future, once the [loopdev](https://crates.io/crates/loopdev) crate supports
/// querying loopback device info.
///
/// ```rust,no_run
/// extern crate sys_mount;
///
/// use sys_mount::{unmount, UnmountFlags};
///
/// fn main() {
/// // Unmount device at `/target/path` lazily.
/// let result = unmount("/target/path", UnmountFlags::DETACH);
/// }
/// ```
pub fn unmount<P: AsRef<Path>>(path: P, flags: UnmountFlags) -> io::Result<()> {
let mount = CString::new(path.as_ref().as_os_str().as_bytes().to_owned());
let mount_ptr = mount
.as_ref()
.ok()
.map_or(ptr::null(), |cstr| cstr.as_ptr());
unsafe { unmount_(mount_ptr, flags) }
}
pub(crate) unsafe fn unmount_(mount_ptr: *const c_char, flags: UnmountFlags) -> io::Result<()> {
match umount2(mount_ptr, flags.bits()) {
0 => Ok(()),
_err => Err(io::Error::last_os_error()),
}
}