diff --git a/src/io.rs b/src/io.rs
index 08b893c..6bd7d3d 100644
--- a/src/io.rs
+++ b/src/io.rs
@@ -4,6 +4,7 @@ use super::{ctrl::UblkCtrl, sys, UblkError, UblkIORes};
 use io_uring::{cqueue, opcode, squeue, types, IoUring};
 use log::{error, info, trace};
 use serde::{Deserialize, Serialize};
+use std::cell::RefCell;
 use std::fs;
 use std::os::unix::io::AsRawFd;
 
@@ -357,6 +358,59 @@ impl UblkQueueCtx {
 const UBLK_QUEUE_STOPPING: u32 = 1_u32 << 0;
 const UBLK_QUEUE_IDLE: u32 = 1_u32 << 1;
 
+#[derive(Debug, Clone, Default)]
+pub struct UblkQueueState {
+    cmd_inflight: u32,
+    state: u32,
+}
+
+impl UblkQueueState {
+    pub fn new() -> Self {
+        Self {
+            ..Default::default()
+        }
+    }
+
+    #[inline(always)]
+    fn queue_is_quiesced(&self) -> bool {
+        self.cmd_inflight == 0
+    }
+
+    #[inline(always)]
+    fn queue_is_done(&self) -> bool {
+        self.is_stopping() && self.queue_is_quiesced()
+    }
+
+    #[inline(always)]
+    fn get_nr_cmd_inflight(&self) -> u32 {
+        self.cmd_inflight
+    }
+
+    #[inline(always)]
+    fn is_stopping(&self) -> bool {
+        (self.state & UBLK_QUEUE_STOPPING) != 0
+    }
+
+    #[inline(always)]
+    fn is_idle(&self) -> bool {
+        (self.state & UBLK_QUEUE_IDLE) != 0
+    }
+
+    #[inline(always)]
+    fn inc_cmd_inflight(&mut self) {
+        self.cmd_inflight += 1;
+    }
+
+    #[inline(always)]
+    fn dec_cmd_inflight(&mut self) {
+        self.cmd_inflight -= 1;
+    }
+
+    fn mark_stopping(&mut self) {
+        self.state |= UBLK_QUEUE_STOPPING;
+    }
+}
+
 /// UBLK queue abstraction
 ///
 /// UblkQueue is the core part of the whole stack, which communicates with
@@ -377,9 +431,8 @@ pub struct UblkQueue<'a> {
     io_cmd_buf: u64,
     //ops: Box<dyn UblkQueueImpl>,
     pub dev: &'a UblkDev,
-    cmd_inflight: u32,
-    q_state: u32,
     bufs: Vec<*mut u8>,
+    state: RefCell<UblkQueueState>,
     q_ring: IoUring<squeue::Entry>,
 }
 
@@ -512,8 +565,10 @@ impl UblkQueue<'_> {
             q_depth: depth,
             io_cmd_buf: io_cmd_buf as u64,
             dev,
-            cmd_inflight: 0,
-            q_state: 0,
+            state: RefCell::new(UblkQueueState {
+                cmd_inflight: 0,
+                state: 0,
+            }),
             q_ring: ring,
             bufs,
         };
@@ -538,7 +593,8 @@ impl UblkQueue<'_> {
     #[inline(always)]
     #[allow(unused_assignments)]
     fn queue_io_cmd(&mut self, tag: u16, cmd_op: u32, buf_addr: u64, res: i32) -> i32 {
-        if (self.q_state & UBLK_QUEUE_STOPPING) != 0 {
+        let mut state = self.state.borrow_mut();
+        if state.is_stopping() {
             return 0;
         }
 
@@ -562,14 +618,15 @@ impl UblkQueue<'_> {
                 .expect("submission fail");
         }
 
-        self.cmd_inflight += 1;
+        state.inc_cmd_inflight();
+
         trace!(
             "{}: (qid {} tag {} cmd_op {}) stopping {}",
             "queue_io_cmd",
             self.q_id,
             tag,
             cmd_op,
-            (self.q_state & UBLK_QUEUE_STOPPING) != 0
+            state.is_stopping(),
         );
 
         1
@@ -597,16 +654,6 @@ impl UblkQueue<'_> {
         }
     }
 
-    #[inline(always)]
-    fn queue_is_idle(&self) -> bool {
-        self.cmd_inflight == 0
-    }
-
-    #[inline(always)]
-    fn queue_is_done(&self) -> bool {
-        (self.q_state & UBLK_QUEUE_STOPPING) != 0 && self.queue_is_idle()
-    }
-
     #[inline(always)]
     fn complete_ios(&mut self, tag: usize, res: Result<UblkIORes, UblkError>) {
         match res {
@@ -657,16 +704,18 @@ impl UblkQueue<'_> {
         let tag = UblkIOCtx::user_data_to_tag(data);
         let cmd_op = UblkIOCtx::user_data_to_op(data);
 
-        trace!(
-            "{}: res {} (qid {} tag {} cmd_op {} target {}) state {}",
-            "handle_cqe",
-            res,
-            self.q_id,
-            tag,
-            cmd_op,
-            is_target_io(data),
-            self.q_state,
-        );
+        {
+            trace!(
+                "{}: res {} (qid {} tag {} cmd_op {} target {}) state {:?}",
+                "handle_cqe",
+                res,
+                self.q_id,
+                tag,
+                cmd_op,
+                is_target_io(data),
+                self.state.borrow(),
+            );
+        }
 
         if is_target_io(data) {
             let res = e.result();
@@ -686,10 +735,13 @@ impl UblkQueue<'_> {
             return;
         }
 
-        self.cmd_inflight -= 1;
+        {
+            let mut state = self.state.borrow_mut();
+            state.dec_cmd_inflight();
 
-        if res == sys::UBLK_IO_RES_ABORT {
-            self.q_state |= UBLK_QUEUE_STOPPING;
+            if res == sys::UBLK_IO_RES_ABORT {
+                state.mark_stopping();
+            }
         }
 
         if res == sys::UBLK_IO_RES_OK as i32 {
@@ -724,13 +776,14 @@ impl UblkQueue<'_> {
 
     #[inline(always)]
     fn wait_ios(&mut self, to_wait: usize) -> Result<i32, UblkError> {
+        let state = self.state.borrow();
         info!(
             "dev{}-q{}: to_submit {} inflight cmd {} stopping {}",
             self.dev.dev_info.dev_id,
             self.q_id,
             0,
-            self.cmd_inflight,
-            (self.q_state & UBLK_QUEUE_STOPPING)
+            state.get_nr_cmd_inflight(),
+            state.is_stopping(),
         );
 
         let ret = self
@@ -743,8 +796,8 @@ impl UblkQueue<'_> {
             "submit result {}, nr_cqes {} stop {} idle {}",
             ret,
             nr_cqes,
-            (self.q_state & UBLK_QUEUE_STOPPING),
-            (self.q_state & UBLK_QUEUE_IDLE)
+            state.is_stopping(),
+            state.is_idle(),
         );
         Ok(nr_cqes)
     }
@@ -803,7 +856,7 @@ impl UblkQueue<'_> {
     where
         F: FnMut(&mut UblkIOCtx) -> Result<UblkIORes, UblkError>,
     {
-        if self.queue_is_done() && self.q_ring.submission().is_empty() {
+        if self.state.borrow().queue_is_done() && self.q_ring.submission().is_empty() {
             return Err(UblkError::QueueIsDown(-libc::ENODEV));
         }