examples/loop: handle io command by async/await

async/await can handling io handle in async style, meantime the
written Rust code can be just like sync programming.

This way is very helpful for writing complicated ublk target.

Signed-off-by: Ming Lei <tom.leiming@gmail.com>

README.md

@@ -116,6 +116,9 @@ see [`test_ublk_null_async():tests/basic.rs`](tests/basic.rs)
 Queue wide data is per-thread and can be shared in io handler by
 Rc() & RefCell().
 
+ * [`examples/loop.rs`](examples/loop.rs): the whole example using async/await
+
+
 ## Test
 
 You can run the test of the library with ```cargo test```

examples/loop.rs

@@ -2,10 +2,11 @@ use anyhow::Result;
 use io_uring::{opcode, squeue, types};
 use libublk::dev_flags::*;
 use libublk::io::{UblkDev, UblkIOCtx, UblkQueue};
-use libublk::{ctrl::UblkCtrl, UblkError, UblkIORes};
+use libublk::{ctrl::UblkCtrl, exe::Executor, exe::UringOpFuture, UblkError, UblkIORes};
 use log::trace;
 use serde::Serialize;
 use std::os::unix::io::AsRawFd;
+use std::rc::Rc;
 
 #[derive(Debug, Serialize)]
 struct LoJson {
@@ -56,15 +57,14 @@ fn lo_init_tgt(dev: &mut UblkDev, lo: &LoopTgt) -> Result<serde_json::Value, Ubl
     )
 }
 
-fn loop_queue_tgt_io(q: &UblkQueue, tag: u16, _io: &UblkIOCtx) {
+async fn lo_handle_io_cmd(q: &UblkQueue<'_>, tag: u16, _data: u64) {
     // either start to handle or retry
     let _iod = q.get_iod(tag);
     let iod = unsafe { &*_iod };
-
     let off = (iod.start_sector << 9) as u64;
     let bytes = (iod.nr_sectors << 9) as u32;
     let op = iod.op_flags & 0xff;
-    let data = UblkIOCtx::build_user_data(tag as u16, op, 0, true);
+    let data = UblkIOCtx::build_user_data_async(tag as u16, op, 0);
     let buf_addr = q.get_io_buf_addr(tag);
 
     if op == libublk::sys::UBLK_IO_OP_WRITE_ZEROES || op == libublk::sys::UBLK_IO_OP_DISCARD {
@@ -115,30 +115,19 @@ fn loop_queue_tgt_io(q: &UblkQueue, tag: u16, _io: &UblkIOCtx) {
                     .expect("submission fail");
             }
         }
-        _ => q.complete_io_cmd(tag, Err(UblkError::OtherError(-libc::EINVAL))),
-    };
-}
-
-fn _lo_handle_io(q: &UblkQueue, tag: u16, i: &UblkIOCtx) {
-    // our IO on backing file is done
-    if i.is_tgt_io() {
-        let user_data = i.user_data();
-        let res = i.result();
-        let cqe_tag = UblkIOCtx::user_data_to_tag(user_data);
-
-        assert!(cqe_tag == tag as u32);
-
-        if res != -(libc::EAGAIN) {
-            q.complete_io_cmd(tag, Ok(UblkIORes::Result(res)));
+        _ => {
+            q.complete_io_cmd(tag, Err(UblkError::OtherError(-libc::EINVAL)));
             return;
         }
-    }
+    };
 
-    loop_queue_tgt_io(q, tag, i);
+    // wait until the io_uring IO completed
+    let res = UringOpFuture { user_data: data }.await;
+    q.complete_io_cmd(tag, Ok(UblkIORes::Result(res)));
 }
 
 fn test_add() {
-    let back_file = std::env::args().nth(2).unwrap();
+    let back_file = std::env::args().nth(3).unwrap();
     let _pid = unsafe { libc::fork() };
 
     if _pid == 0 {
@@ -162,12 +151,20 @@ fn test_add() {
             let tgt_init = |dev: &mut UblkDev| lo_init_tgt(dev, &lo);
             let (mut ctrl, dev) = sess.create_devices(tgt_init).unwrap();
             let q_fn = move |qid: u16, _dev: &UblkDev| {
-                let lo_io_handler =
-                    move |q: &UblkQueue, tag: u16, io: &UblkIOCtx| _lo_handle_io(q, tag, io);
-
-                UblkQueue::new(qid, _dev)
-                    .unwrap()
-                    .wait_and_handle_io(lo_io_handler);
+                let q_rc = Rc::new(UblkQueue::new(qid as u16, &_dev).unwrap());
+                let exe_rc = Rc::new(Executor::new(_dev.get_nr_ios()));
+                let q = q_rc.clone();
+                let exe = exe_rc.clone();
+
+                let lo_io_handler = move |_q: &UblkQueue, tag: u16, io: &UblkIOCtx| {
+                    let q = q_rc.clone();
+                    let data = io.user_data();
+
+                    exe.spawn(tag as u16, async move {
+                        lo_handle_io_cmd(&q, tag, data).await;
+                    });
+                };
+                q.wait_and_handle_io_cmd(&exe_rc, lo_io_handler);
             };
 
             sess.run_target(&mut ctrl, &dev, q_fn, |dev_id| {