diff --git a/examples/null.rs b/examples/null.rs
index d1eef16..bcf60ba 100755
--- a/examples/null.rs
+++ b/examples/null.rs
@@ -43,7 +43,15 @@ fn __test_add(id: i32, nr_queues: u32, depth: u32, ctrl_flags: u64, buf_size: u3
             .nr_queues(nr_queues)
             .io_buf_bytes(buf_size)
             .ctrl_flags(ctrl_flags)
-            .dev_flags(UBLK_DEV_F_ADD_DEV | if aio { UBLK_DEV_F_ASYNC } else { 0 })
+            .dev_flags(
+                UBLK_DEV_F_ADD_DEV
+                    | if aio { UBLK_DEV_F_ASYNC } else { 0 }
+                    | if (ctrl_flags & libublk::sys::UBLK_F_USER_COPY as u64) != 0 {
+                        UBLK_DEV_F_DONT_ALLOC_BUF
+                    } else {
+                        0
+                    },
+            )
             .build()
             .unwrap();
         let tgt_init = |dev: &mut UblkDev| {
diff --git a/examples/ramdisk.rs b/examples/ramdisk.rs
index 63415cb..8b13596 100644
--- a/examples/ramdisk.rs
+++ b/examples/ramdisk.rs
@@ -8,12 +8,11 @@ use libublk::io::{UblkDev, UblkQueue};
 use libublk::{ctrl::UblkCtrl, exe::Executor, UblkError};
 use std::rc::Rc;
 
-fn handle_io(q: &UblkQueue, tag: u16, start: u64) -> i32 {
+fn handle_io(q: &UblkQueue, tag: u16, buf_addr: *mut u8, start: u64) -> i32 {
     let iod = q.get_iod(tag);
     let off = (iod.start_sector << 9) as u64;
     let bytes = (iod.nr_sectors << 9) as i32;
     let op = iod.op_flags & 0xff;
-    let buf_addr = q.get_io_buf_addr(tag);
 
     match op {
         libublk::sys::UBLK_IO_OP_READ => unsafe {
@@ -45,7 +44,8 @@ fn rd_add_dev(dev_id: i32, buf_addr: u64, size: u64, for_add: bool) {
         UBLK_DEV_F_ADD_DEV
     } else {
         UBLK_DEV_F_RECOVER_DEV
-    } | UBLK_DEV_F_ASYNC;
+    } | UBLK_DEV_F_ASYNC
+        | UBLK_DEV_F_DONT_ALLOC_BUF;
 
     let depth = 128_u16;
     let sess = libublk::UblkSessionBuilder::default()
@@ -66,20 +66,24 @@ fn rd_add_dev(dev_id: i32, buf_addr: u64, size: u64, for_add: bool) {
 
     let exe = Executor::new(dev.get_nr_ios());
     let q_rc = Rc::new(UblkQueue::new(0, &dev).unwrap());
+    let buf_size = dev.dev_info.max_io_buf_bytes as usize;
 
     for tag in 0..depth as u16 {
         let q = q_rc.clone();
+        assert!(q.get_io_buf_addr(tag) == std::ptr::null_mut());
         exe.spawn(tag as u16, async move {
-            let addr = q.get_io_buf_addr(tag);
+            let mut buffer: Vec<u8> = vec![0; buf_size];
+            let addr = buffer.as_mut_ptr();
             let mut cmd_op = libublk::sys::UBLK_IO_FETCH_REQ;
             let mut res = 0;
+
             loop {
                 let cmd_res = q.submit_io_cmd(tag, cmd_op, addr as u64, res).await;
                 if cmd_res == libublk::sys::UBLK_IO_RES_ABORT {
                     break;
                 }
 
-                res = handle_io(&q, tag, buf_addr);
+                res = handle_io(&q, tag, addr, buf_addr);
                 cmd_op = libublk::sys::UBLK_IO_COMMIT_AND_FETCH_REQ;
             }
         });
diff --git a/src/io.rs b/src/io.rs
index 125d5f4..df38333 100644
--- a/src/io.rs
+++ b/src/io.rs
@@ -477,6 +477,12 @@ impl UblkQueue<'_> {
         let sq_depth = tgt.sq_depth;
         let cq_depth = tgt.cq_depth;
 
+        if ((dev.flags & UBLK_DEV_F_ASYNC) == 0)
+            && ((dev.dev_info.flags & (sys::UBLK_F_USER_COPY as u64)) == 0)
+            && ((dev.flags & UBLK_DEV_F_DONT_ALLOC_BUF) != 0)
+        {
+            return Err(UblkError::OtherError(-libc::EINVAL));
+        }
         let ring = IoUring::<squeue::Entry, cqueue::Entry>::builder()
             .setup_cqsize(cq_depth as u32)
             .setup_coop_taskrun()
@@ -521,7 +527,7 @@ impl UblkQueue<'_> {
             // extra io slot needn't to allocate buffer
             let addr = {
                 if i < depth {
-                    if (dev.dev_info.flags & (super::sys::UBLK_F_USER_COPY as u64)) == 0 {
+                    if (dev.flags & UBLK_DEV_F_DONT_ALLOC_BUF) == 0 {
                         super::ublk_alloc_buf(dev.dev_info.max_io_buf_bytes as usize, unsafe {
                             libc::sysconf(libc::_SC_PAGESIZE).try_into().unwrap()
                         })
diff --git a/src/lib.rs b/src/lib.rs
index 7d2ae12..957c9c3 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -28,8 +28,14 @@ pub mod dev_flags {
     /// use async/.await
     pub const UBLK_DEV_F_ASYNC: u32 = 1u32 << 3;
 
-    pub const UBLK_DEV_F_ALL: u32 =
-        UBLK_DEV_F_COMP_BATCH | UBLK_DEV_F_ADD_DEV | UBLK_DEV_F_RECOVER_DEV | UBLK_DEV_F_ASYNC;
+    /// need to preallocate io buffer
+    pub const UBLK_DEV_F_DONT_ALLOC_BUF: u32 = 1u32 << 4;
+
+    pub const UBLK_DEV_F_ALL: u32 = UBLK_DEV_F_COMP_BATCH
+        | UBLK_DEV_F_ADD_DEV
+        | UBLK_DEV_F_RECOVER_DEV
+        | UBLK_DEV_F_ASYNC
+        | UBLK_DEV_F_DONT_ALLOC_BUF;
 }
 
 /// Ublk Fat completion result
diff --git a/tests/basic.rs b/tests/basic.rs
index 8dd404e..255979c 100644
--- a/tests/basic.rs
+++ b/tests/basic.rs
@@ -95,7 +95,10 @@ mod integration {
                 .wait_and_handle_io(io_handler);
         }
 
-        __test_ublk_null(UBLK_DEV_F_ADD_DEV, null_handle_queue);
+        __test_ublk_null(
+            UBLK_DEV_F_ADD_DEV | UBLK_DEV_F_DONT_ALLOC_BUF,
+            null_handle_queue,
+        );
     }
 
     /// make one ublk-null and test if /dev/ublkbN can be created successfully
@@ -119,7 +122,7 @@ mod integration {
         }
 
         __test_ublk_null(
-            UBLK_DEV_F_ADD_DEV | UBLK_DEV_F_COMP_BATCH,
+            UBLK_DEV_F_ADD_DEV | UBLK_DEV_F_DONT_ALLOC_BUF | UBLK_DEV_F_COMP_BATCH,
             null_handle_queue_batch,
         );
     }
@@ -192,11 +195,11 @@ mod integration {
                 let __dev_data = _dev_data.clone();
 
                 exe.spawn(tag as u16, async move {
-                    let buf_addr = q.get_io_buf_addr(tag) as u64;
                     let mut cmd_op = sys::UBLK_IO_FETCH_REQ;
+                    let buf = q.get_io_buf_addr(tag);
                     let mut res = 0;
                     loop {
-                        let cmd_res = q.submit_io_cmd(tag, cmd_op, buf_addr, res).await;
+                        let cmd_res = q.submit_io_cmd(tag, cmd_op, buf as u64, res).await;
                         if cmd_res == sys::UBLK_IO_RES_ABORT {
                             break;
                         }
@@ -353,7 +356,10 @@ mod integration {
                 .wait_and_handle_io(io_handler);
         }
 
-        __test_ublk_null(UBLK_DEV_F_ADD_DEV, null_queue_mut_io);
+        __test_ublk_null(
+            UBLK_DEV_F_ADD_DEV | UBLK_DEV_F_DONT_ALLOC_BUF,
+            null_queue_mut_io,
+        );
     }
 
     /// run examples/ramdisk recovery test