sys_util: timerfd: Methods don't need to me mut

Because TimerFd is a wrapper around a 'File' that is never modified
there isn't a need for a mutable borrow. The kernel already handles the
interior mutability of the underlying file descriptor.

Change-Id: I7ae068cc54050b0021d00620b561335b2ae0ba16
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosvm/+/2161625
Reviewed-by: Dylan Reid <dgreid@chromium.org>
Reviewed-by: Zach Reizner <zachr@chromium.org>
Tested-by: Dylan Reid <dgreid@chromium.org>
Tested-by: kokoro <noreply+kokoro@google.com>
Commit-Queue: Dylan Reid <dgreid@chromium.org>

2 files changed, 6 insertions, 6 deletions

diff --git a/src/linux.rs b/src/linux.rs
index 8690ff7..c8eb478 100644
--- a/src/linux.rs
+++ b/src/linux.rs
@@ -1767,7 +1767,7 @@ fn run_control(
     }
 
     // Balance available memory between guest and host every second.
-    let mut balancemem_timer = TimerFd::new().map_err(Error::CreateTimerFd)?;
+    let balancemem_timer = TimerFd::new().map_err(Error::CreateTimerFd)?;
     if Path::new(LOWMEM_AVAILABLE).exists() {
         // Create timer request balloon stats every 1s.
         poll_ctx
diff --git a/sys_util/src/timerfd.rs b/sys_util/src/timerfd.rs
index 8e5d91b..f2a3ff8 100644
--- a/sys_util/src/timerfd.rs
+++ b/sys_util/src/timerfd.rs
@@ -34,7 +34,7 @@ impl TimerFd {
     /// Sets the timer to expire after `dur`.  If `interval` is not `None` it represents
     /// the period for repeated expirations after the initial expiration.  Otherwise
     /// the timer will expire just once.  Cancels any existing duration and repeating interval.
-    pub fn reset(&mut self, dur: Duration, interval: Option<Duration>) -> Result<()> {
+    pub fn reset(&self, dur: Duration, interval: Option<Duration>) -> Result<()> {
         // Safe because we are zero-initializing a struct with only primitive member fields.
         let mut spec: libc::itimerspec = unsafe { mem::zeroed() };
         spec.it_value.tv_sec = dur.as_secs() as libc::time_t;
@@ -61,7 +61,7 @@ impl TimerFd {
     /// Waits until the timer expires.  The return value represents the number of times the timer
     /// has expired since the last time `wait` was called.  If the timer has not yet expired once
     /// this call will block until it does.
-    pub fn wait(&mut self) -> Result<u64> {
+    pub fn wait(&self) -> Result<u64> {
         let mut count = 0u64;
 
         // Safe because this will only modify |buf| and we check the return value.
@@ -96,7 +96,7 @@ impl TimerFd {
     }
 
     /// Disarms the timer.
-    pub fn clear(&mut self) -> Result<()> {
+    pub fn clear(&self) -> Result<()> {
         // Safe because we are zero-initializing a struct with only primitive member fields.
         let spec: libc::itimerspec = unsafe { mem::zeroed() };
 
@@ -222,7 +222,7 @@ mod tests {
 
     #[test]
     fn one_shot() {
-        let mut tfd = TimerFd::new().expect("failed to create timerfd");
+        let tfd = TimerFd::new().expect("failed to create timerfd");
         assert_eq!(tfd.is_armed().unwrap(), false);
 
         let dur = Duration::from_millis(200);
@@ -239,7 +239,7 @@ mod tests {
 
     #[test]
     fn repeating() {
-        let mut tfd = TimerFd::new().expect("failed to create timerfd");
+        let tfd = TimerFd::new().expect("failed to create timerfd");
 
         let dur = Duration::from_millis(200);
         let interval = Duration::from_millis(100);