misc: clippy: add needless_pass_by_value

This is a follow-up of [0].

# Advantages

- This saves dozens of unneeded clone()s across the whole code base
- Makes it much easier to reason about how parameters are used
  (often we passed owned Arc/Rc versions without actually needing
  ownership)

# Exceptions

For certain code paths, the alternatives would require awkward or overly
complex code, and in some cases the functions are the logical owners of
the values they take. In those cases, I've added
#[allow(clippy::needless_pass_by_value)].

This does not mean that one should not improve this in the future.

[0] 6a86c157af

Signed-off-by: Philipp Schuster <philipp.schuster@cyberus-technology.de>
On-behalf-of: SAP philipp.schuster@sap.com

virtio-devices/src/vhost_user/blk.rs

@@ -297,7 +297,7 @@ impl VirtioDevice for Blk {
 
         let mut handler = self.vu_common.activate(
             mem,
-            queues,
+            &queues,
             interrupt_cb,
             self.common.acked_features,
             backend_req_handler,
@@ -316,7 +316,7 @@ impl VirtioDevice for Blk {
             Thread::VirtioVhostBlock,
             &mut epoll_threads,
             &self.exit_evt,
-            move || handler.run(paused, paused_sync.unwrap()),
+            move || handler.run(&paused, paused_sync.as_ref().unwrap()),
         )?;
         self.epoll_thread = Some(epoll_threads.remove(0));
 

virtio-devices/src/vhost_user/fs.rs

@@ -277,7 +277,7 @@ impl VirtioDevice for Fs {
 
         let mut handler = self.vu_common.activate(
             mem,
-            queues,
+            &queues,
             interrupt_cb,
             self.common.acked_features,
             backend_req_handler,
@@ -295,7 +295,7 @@ impl VirtioDevice for Fs {
             Thread::VirtioVhostFs,
             &mut epoll_threads,
             &self.exit_evt,
-            move || handler.run(paused, paused_sync.unwrap()),
+            move || handler.run(&paused, paused_sync.as_ref().unwrap()),
         )?;
         self.epoll_thread = Some(epoll_threads.remove(0));
 

virtio-devices/src/vhost_user/mod.rs

@@ -183,8 +183,8 @@ pub struct VhostUserEpollHandler<S: VhostUserFrontendReqHandler> {
 impl<S: VhostUserFrontendReqHandler> VhostUserEpollHandler<S> {
     pub fn run(
         &mut self,
-        paused: Arc<AtomicBool>,
-        paused_sync: Arc<Barrier>,
+        paused: &AtomicBool,
+        paused_sync: &Barrier,
     ) -> std::result::Result<(), EpollHelperError> {
         let mut helper = EpollHelper::new(&self.kill_evt, &self.pause_evt)?;
         helper.add_event_custom(
@@ -221,14 +221,16 @@ impl<S: VhostUserFrontendReqHandler> VhostUserEpollHandler<S> {
             )))
         })?;
 
+        let queues = self
+            .queues
+            .iter()
+            .map(|(i, q, e)| (*i, vm_virtio::clone_queue(q), e.try_clone().unwrap()))
+            .collect::<Vec<_>>();
         // Initialize the backend
         vhost_user
             .reinitialize_vhost_user(
                 self.mem.memory().deref(),
-                self.queues
-                    .iter()
-                    .map(|(i, q, e)| (*i, vm_virtio::clone_queue(q), e.try_clone().unwrap()))
-                    .collect(),
+                &queues,
                 self.virtio_interrupt.as_ref(),
                 self.acked_features,
                 self.acked_protocol_features,
@@ -305,7 +307,7 @@ impl VhostUserCommon {
     pub fn activate<T: VhostUserFrontendReqHandler>(
         &mut self,
         mem: GuestMemoryAtomic<GuestMemoryMmap>,
-        queues: Vec<(usize, Queue, EventFd)>,
+        queues: &[(usize, Queue, EventFd)],
         interrupt_cb: Arc<dyn VirtioInterrupt>,
         acked_features: u64,
         backend_req_handler: Option<FrontendReqHandler<T>>,
@@ -325,14 +327,15 @@ impl VhostUserCommon {
             return Err(ActivateError::BadActivate);
         }
         let vu = self.vu.as_ref().unwrap();
+        let queues = queues
+            .iter()
+            .map(|(i, q, e)| (*i, vm_virtio::clone_queue(q), e.try_clone().unwrap()))
+            .collect::<Vec<_>>();
         vu.lock()
             .unwrap()
             .setup_vhost_user(
                 &mem.memory(),
-                queues
-                    .iter()
-                    .map(|(i, q, e)| (*i, vm_virtio::clone_queue(q), e.try_clone().unwrap()))
-                    .collect(),
+                &queues,
                 interrupt_cb.as_ref(),
                 acked_features,
                 &backend_req_handler,

virtio-devices/src/vhost_user/net.rs

@@ -336,7 +336,7 @@ impl VirtioDevice for Net {
                 Thread::VirtioVhostNetCtl,
                 &mut epoll_threads,
                 &self.exit_evt,
-                move || ctrl_handler.run_ctrl(paused, paused_sync.unwrap()),
+                move || ctrl_handler.run_ctrl(&paused, paused_sync.as_ref().unwrap()),
             )?;
             self.ctrl_queue_epoll_thread = Some(epoll_threads.remove(0));
         }
@@ -353,7 +353,7 @@ impl VirtioDevice for Net {
 
         let mut handler = self.vu_common.activate(
             mem,
-            queues,
+            &queues,
             interrupt_cb,
             backend_acked_features,
             backend_req_handler,
@@ -371,7 +371,7 @@ impl VirtioDevice for Net {
             Thread::VirtioVhostNet,
             &mut epoll_threads,
             &self.exit_evt,
-            move || handler.run(paused, paused_sync.unwrap()),
+            move || handler.run(&paused, paused_sync.as_ref().unwrap()),
         )?;
         self.epoll_thread = Some(epoll_threads.remove(0));
 

virtio-devices/src/vhost_user/vu_common_ctrl.rs

@@ -156,7 +156,7 @@ impl VhostUserHandle {
     pub fn setup_vhost_user<S: VhostUserFrontendReqHandler>(
         &mut self,
         mem: &GuestMemoryMmap,
-        queues: Vec<(usize, Queue, EventFd)>,
+        queues: &[(usize, Queue, EventFd)],
         virtio_interrupt: &dyn VirtioInterrupt,
         acked_features: u64,
         backend_req_handler: &Option<FrontendReqHandler<S>>,
@@ -340,7 +340,7 @@ impl VhostUserHandle {
     pub fn reinitialize_vhost_user<S: VhostUserFrontendReqHandler>(
         &mut self,
         mem: &GuestMemoryMmap,
-        queues: Vec<(usize, Queue, EventFd)>,
+        queues: &[(usize, Queue, EventFd)],
         virtio_interrupt: &dyn VirtioInterrupt,
         acked_features: u64,
         acked_protocol_features: u64,