vmm: Simplify some of the io_uring code

Small patch creating a dedicated `block_io_uring_is_supported()`
function for the non-io_uring case, so that we can simplify the
code in the DeviceManager.

Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>

block_util/src/lib.rs

@@ -14,13 +14,15 @@ extern crate log;
 extern crate serde_derive;
 
 #[cfg(feature = "io_uring")]
-use io_uring::{opcode, squeue, IoUring, Probe};
+use io_uring::Probe;
+use io_uring::{opcode, squeue, IoUring};
 use serde::ser::{Serialize, SerializeStruct, Serializer};
 use std::cmp;
 use std::io::{self, Read, Seek, SeekFrom, Write};
 use std::os::linux::fs::MetadataExt;
 #[cfg(feature = "io_uring")]
-use std::os::unix::io::{AsRawFd, RawFd};
+use std::os::unix::io::AsRawFd;
+use std::os::unix::io::RawFd;
 use std::path::PathBuf;
 use std::result;
 use virtio_bindings::bindings::virtio_blk::*;
@@ -266,7 +268,6 @@ impl Request {
         Ok(len)
     }
 
-    #[cfg(feature = "io_uring")]
     pub fn execute_io_uring(
         &self,
         mem: &GuestMemoryMmap,
@@ -565,3 +566,8 @@ pub fn block_io_uring_is_supported() -> bool {
 
     true
 }
+
+#[cfg(not(feature = "io_uring"))]
+pub fn block_io_uring_is_supported() -> bool {
+    false
+}

virtio-devices/src/lib.rs

@@ -31,7 +31,6 @@ use std::io;
 mod device;
 pub mod balloon;
 pub mod block;
-#[cfg(feature = "io_uring")]
 pub mod block_io_uring;
 mod console;
 pub mod epoll_helper;
@@ -48,7 +47,6 @@ pub mod vsock;
 
 pub use self::balloon::*;
 pub use self::block::*;
-#[cfg(feature = "io_uring")]
 pub use self::block_io_uring::*;
 pub use self::console::*;
 pub use self::device::*;

vmm/src/device_manager.rs

@@ -36,7 +36,6 @@ use arch::layout;
 use arch::layout::{APIC_START, IOAPIC_SIZE, IOAPIC_START};
 #[cfg(target_arch = "aarch64")]
 use arch::DeviceType;
-#[cfg(feature = "io_uring")]
 use block_util::block_io_uring_is_supported;
 #[cfg(target_arch = "aarch64")]
 use devices::gic;
@@ -1754,8 +1753,6 @@ impl DeviceManager {
                 .map_err(DeviceManagerError::DetectImageType)?;
             let (virtio_device, migratable_device) = match image_type {
                 ImageType::Raw => {
-                    #[cfg(feature = "io_uring")]
-                    {
                     // Use asynchronous backend relying on io_uring if the
                     // syscalls are supported.
                     if block_io_uring_is_supported() {
@@ -1806,33 +1803,6 @@ impl DeviceManager {
                         )
                     }
                 }
-
-                    #[cfg(not(feature = "io_uring"))]
-                    {
-                        let dev = Arc::new(Mutex::new(
-                            virtio_devices::Block::new(
-                                id.clone(),
-                                raw_img,
-                                disk_cfg
-                                    .path
-                                    .as_ref()
-                                    .ok_or(DeviceManagerError::NoDiskPath)?
-                                    .clone(),
-                                disk_cfg.readonly,
-                                disk_cfg.iommu,
-                                disk_cfg.num_queues,
-                                disk_cfg.queue_size,
-                                self.seccomp_action.clone(),
-                            )
-                            .map_err(DeviceManagerError::CreateVirtioBlock)?,
-                        ));
-
-                        (
-                            Arc::clone(&dev) as VirtioDeviceArc,
-                            dev as Arc<Mutex<dyn Migratable>>,
-                        )
-                    }
-                }
                 ImageType::Qcow2 => {
                     let qcow_img =
                         QcowFile::from(raw_img).map_err(DeviceManagerError::QcowDeviceCreate)?;