libublk: add device flag of UBLK_DEV_F_NOT_ALLOC_IO_BUF

Add UBLK_DEV_F_NOT_ALLOC_IO_BUF so that target code can allocate their own buffer for handling io command. Signed-off-by: Ming Lei <tom.leiming@gmail.com>
ublk-org · Oct 11, 2023 · f266a24 · f266a24
1 parent 0d36513
commit f266a24
Show file tree

Hide file tree

Showing 3 changed files with 34 additions and 3 deletions.
diff --git a/src/io.rs b/src/io.rs
@@ -453,7 +453,9 @@ 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.dev_info.flags & (super::sys::UBLK_F_USER_COPY as u64)) == 0
+                        && (dev.flags & super::dev_flags::UBLK_DEV_F_NOT_ALLOC_IO_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
@@ -24,8 +24,13 @@ pub mod dev_flags {
     /// tell UblkCtrl that we are recovering one old device
     pub const UBLK_DEV_F_RECOVER_DEV: u32 = 1u32 << 2;
 
-    pub const UBLK_DEV_F_ALL: u32 =
-        UBLK_DEV_F_COMP_BATCH | UBLK_DEV_F_ADD_DEV | UBLK_DEV_F_RECOVER_DEV;
+    /// don't allocate io buffer for me
+    pub const UBLK_DEV_F_NOT_ALLOC_IO_BUF: 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_NOT_ALLOC_IO_BUF;
 }
 
 /// Ublk Fat completion result

diff --git a/tests/basic.rs b/tests/basic.rs
@@ -413,4 +413,28 @@ mod tests {
         let sz = core::mem::size_of::<Result<UblkIORes, UblkError>>();
         assert!(sz == 32);
     }
+
+    #[test]
+    fn test_not_alloc_io_buf() {
+        let depth = 64_u32;
+        let sess = UblkSessionBuilder::default()
+            .name("no_buf")
+            .depth(depth)
+            .nr_queues(1_u32)
+            .dev_flags(UBLK_DEV_F_ADD_DEV | UBLK_DEV_F_NOT_ALLOC_IO_BUF)
+            .build()
+            .unwrap();
+
+        let tgt_init = |dev: &mut UblkDev| {
+            dev.set_default_params(250_u64 << 30);
+            Ok(serde_json::json!({}))
+        };
+        let (mut ctrl, dev) = sess.create_devices(tgt_init).unwrap();
+        let q = UblkQueue::new(0, &dev).unwrap();
+
+        for i in 0..depth {
+            assert!(q.get_io_buf_addr(i as u16) == std::ptr::null_mut());
+        }
+        ctrl.stop_dev(&dev).unwrap();
+    }
 }