diff --git a/shared-scheduler/src/algorithm/ring_fifo.rs b/shared-scheduler/src/algorithm/ring_fifo.rs
index 9fa612b..eb45327 100644
--- a/shared-scheduler/src/algorithm/ring_fifo.rs
+++ b/shared-scheduler/src/algorithm/ring_fifo.rs
@@ -90,7 +90,7 @@ impl<T, const N: usize> RingQueue<T, N> {
         }
         unsafe { *self.elem[self.tail].as_mut_ptr() = value };
         self.tail = self.tail.wrapping_add(1);
-        if self.tail > N || self.tail == 0 {
+        if self.tail >= N || self.tail == 0 {
             self.tail = self.tail.wrapping_sub(N);
         }
         None // success
@@ -101,7 +101,7 @@ impl<T, const N: usize> RingQueue<T, N> {
         }
         let value = unsafe { ptr::read(self.elem[self.front].as_ptr()) };
         self.front = self.front.wrapping_add(1); // assured non empty
-        if self.front > N || self.front == 0 {
+        if self.front >= N || self.front == 0 {
             self.front = self.front.wrapping_sub(N);
         }
         Some(value)
diff --git a/tornado-kernel/src/virtio/mod.rs b/tornado-kernel/src/virtio/mod.rs
index 86da825..e874463 100644
--- a/tornado-kernel/src/virtio/mod.rs
+++ b/tornado-kernel/src/virtio/mod.rs
@@ -77,7 +77,7 @@ pub extern "C" fn virtio_virt_to_phys(vaddr: VirtualAddress) -> PhysicalAddress
 pub async fn async_virtio_blk_test() {
     let mut read_buf = [0u8; 512];
     let mut write_buf = [0u8; 512];
-    for i in 0..50 {
+    for i in 0..512 {
         write_buf.iter_mut().for_each(|byte| *byte = i as u8);
         BLOCK_DEVICE.write_block(i as usize, &write_buf).await;
         BLOCK_DEVICE.read_block(i as usize, &mut read_buf).await;