block: add aio disk backend

Signed-off-by: Thomas Barrett <tbarrett@crusoeenergy.com>

block/src/lib.rs

@@ -24,6 +24,7 @@ pub mod qcow_sync;
 ///
 /// Enabled with the `"io_uring"` feature
 pub mod raw_async;
+pub mod raw_async_aio;
 pub mod raw_sync;
 pub mod vhd;
 pub mod vhdx;
@@ -61,6 +62,7 @@ use vm_memory::{
     GuestMemoryError, GuestMemoryLoadGuard,
 };
 use vm_virtio::{AccessPlatform, Translatable};
+use vmm_sys_util::aio;
 use vmm_sys_util::eventfd::EventFd;
 use vmm_sys_util::{ioctl_io_nr, ioctl_ioc_nr};
 
@@ -565,6 +567,11 @@ unsafe impl ByteValued for VirtioBlockConfig {}
 // SAFETY: data structure only contain a series of integers
 unsafe impl ByteValued for VirtioBlockGeometry {}
 
+/// Check if aio can be used on the current system.
+pub fn block_aio_is_supported() -> bool {
+    aio::IoContext::new(1).is_ok()
+}
+
 /// Check if io_uring for block device can be used on the current system, as
 /// it correctly supports the expected io_uring features.
 pub fn block_io_uring_is_supported() -> bool {

block/src/raw_async_aio.rs

@@ -0,0 +1,138 @@
+use crate::async_io::{
+    AsyncIo, AsyncIoError, AsyncIoResult, DiskFile, DiskFileError, DiskFileResult,
+};
+use crate::DiskTopology;
+use std::fs::File;
+use std::io::{Seek, SeekFrom};
+use std::os::unix::io::{AsRawFd, RawFd};
+use vmm_sys_util::aio;
+use vmm_sys_util::eventfd::EventFd;
+
+pub struct RawFileDiskAio {
+    file: File,
+}
+
+impl RawFileDiskAio {
+    pub fn new(file: File) -> Self {
+        RawFileDiskAio { file }
+    }
+}
+
+impl DiskFile for RawFileDiskAio {
+    fn size(&mut self) -> DiskFileResult<u64> {
+        self.file
+            .seek(SeekFrom::End(0))
+            .map_err(DiskFileError::Size)
+    }
+
+    fn new_async_io(&self, ring_depth: u32) -> DiskFileResult<Box<dyn AsyncIo>> {
+        Ok(Box::new(
+            RawFileAsyncAio::new(self.file.as_raw_fd(), ring_depth)
+                .map_err(DiskFileError::NewAsyncIo)?,
+        ) as Box<dyn AsyncIo>)
+    }
+
+    fn topology(&mut self) -> DiskTopology {
+        if let Ok(topology) = DiskTopology::probe(&self.file) {
+            topology
+        } else {
+            warn!("Unable to get device topology. Using default topology");
+            DiskTopology::default()
+        }
+    }
+}
+
+pub struct RawFileAsyncAio {
+    fd: RawFd,
+    ctx: aio::IoContext,
+    eventfd: EventFd,
+}
+
+impl RawFileAsyncAio {
+    pub fn new(fd: RawFd, queue_depth: u32) -> std::io::Result<Self> {
+        let eventfd = EventFd::new(libc::EFD_NONBLOCK)?;
+        let ctx = aio::IoContext::new(queue_depth)?;
+
+        Ok(RawFileAsyncAio { fd, ctx, eventfd })
+    }
+}
+
+impl AsyncIo for RawFileAsyncAio {
+    fn notifier(&self) -> &EventFd {
+        &self.eventfd
+    }
+
+    fn read_vectored(
+        &mut self,
+        offset: libc::off_t,
+        iovecs: &[libc::iovec],
+        user_data: u64,
+    ) -> AsyncIoResult<()> {
+        let iocbs = [&mut aio::IoControlBlock {
+            aio_fildes: self.fd.as_raw_fd() as u32,
+            aio_lio_opcode: aio::IOCB_CMD_PREADV as u16,
+            aio_buf: iovecs.as_ptr() as u64,
+            aio_nbytes: iovecs.len() as u64,
+            aio_offset: offset,
+            aio_data: user_data,
+            aio_flags: aio::IOCB_FLAG_RESFD,
+            aio_resfd: self.eventfd.as_raw_fd() as u32,
+            ..Default::default()
+        }];
+        let _ = self
+            .ctx
+            .submit(&iocbs[..])
+            .map_err(AsyncIoError::ReadVectored)?;
+
+        Ok(())
+    }
+
+    fn write_vectored(
+        &mut self,
+        offset: libc::off_t,
+        iovecs: &[libc::iovec],
+        user_data: u64,
+    ) -> AsyncIoResult<()> {
+        let iocbs = [&mut aio::IoControlBlock {
+            aio_fildes: self.fd.as_raw_fd() as u32,
+            aio_lio_opcode: aio::IOCB_CMD_PWRITEV as u16,
+            aio_buf: iovecs.as_ptr() as u64,
+            aio_nbytes: iovecs.len() as u64,
+            aio_offset: offset,
+            aio_data: user_data,
+            aio_flags: aio::IOCB_FLAG_RESFD,
+            aio_resfd: self.eventfd.as_raw_fd() as u32,
+            ..Default::default()
+        }];
+        let _ = self
+            .ctx
+            .submit(&iocbs[..])
+            .map_err(AsyncIoError::WriteVectored)?;
+
+        Ok(())
+    }
+
+    fn fsync(&mut self, user_data: Option<u64>) -> AsyncIoResult<()> {
+        let iocbs = [&mut aio::IoControlBlock {
+            aio_fildes: self.fd.as_raw_fd() as u32,
+            aio_lio_opcode: aio::IOCB_CMD_FSYNC as u16,
+            aio_data: user_data.unwrap_or(0),
+            aio_flags: aio::IOCB_FLAG_RESFD,
+            aio_resfd: self.eventfd.as_raw_fd() as u32,
+            ..Default::default()
+        }];
+        let _ = self.ctx.submit(&iocbs[..]).map_err(AsyncIoError::Fsync)?;
+
+        Ok(())
+    }
+
+    fn next_completed_request(&mut self) -> Option<(u64, i32)> {
+        let mut events: [aio::IoEvent; 1] = [aio::IoEvent::default()];
+        let rc = self.ctx.get_events(0, &mut events, None).unwrap();
+        if rc == 0 {
+            None
+        } else {
+            Some((events[0].data, events[0].res as i32))
+        }
+    }
+}