block_util: add FixedVhd for its Disk type

This commit introduces a generic type `FixedVhd` for its sync and async
disk I/O types, and the disk I/O types will use it directly instead of
maintaining a file themselves.

Signed-off-by: Yu Li <liyu.yukiteru@bytedance.com>

block_util/src/fixed_vhd.rs

@@ -0,0 +1,87 @@
+// Copyright © 2021 Intel Corporation
+//
+// SPDX-License-Identifier: Apache-2.0
+
+use crate::vhd::VhdFooter;
+use std::fs::File;
+use std::io::{Read, Seek, SeekFrom, Write};
+use std::os::unix::io::{AsRawFd, RawFd};
+
+#[derive(Debug)]
+pub struct FixedVhd {
+    file: File,
+    size: u64,
+    position: u64,
+}
+
+impl FixedVhd {
+    pub fn new(mut file: File) -> std::io::Result<Self> {
+        let footer = VhdFooter::new(&mut file)?;
+
+        Ok(Self {
+            file,
+            size: footer.current_size(),
+            position: 0,
+        })
+    }
+
+    pub fn size(&self) -> u64 {
+        self.size
+    }
+}
+
+impl AsRawFd for FixedVhd {
+    fn as_raw_fd(&self) -> RawFd {
+        self.file.as_raw_fd()
+    }
+}
+
+impl Read for FixedVhd {
+    fn read(&mut self, buf: &mut [u8]) -> std::io::Result<usize> {
+        match self.file.read(buf) {
+            Ok(r) => {
+                self.position = self.position.checked_add(r.try_into().unwrap()).unwrap();
+                Ok(r)
+            }
+            Err(e) => Err(e),
+        }
+    }
+}
+
+impl Write for FixedVhd {
+    fn write(&mut self, buf: &[u8]) -> std::io::Result<usize> {
+        match self.file.write(buf) {
+            Ok(r) => {
+                self.position = self.position.checked_add(r.try_into().unwrap()).unwrap();
+                Ok(r)
+            }
+            Err(e) => Err(e),
+        }
+    }
+
+    fn flush(&mut self) -> std::io::Result<()> {
+        self.file.sync_all()
+    }
+}
+
+impl Seek for FixedVhd {
+    fn seek(&mut self, newpos: SeekFrom) -> std::io::Result<u64> {
+        match self.file.seek(newpos) {
+            Ok(pos) => {
+                self.position = pos;
+                Ok(pos)
+            }
+            Err(e) => Err(e),
+        }
+    }
+}
+
+impl Clone for FixedVhd {
+    fn clone(&self) -> Self {
+        Self {
+            file: self.file.try_clone().expect("FixedVhd cloning failed"),
+            size: self.size,
+            position: self.position,
+        }
+    }
+}

block_util/src/fixed_vhd_async.rs

@@ -5,36 +5,28 @@
 use crate::async_io::{
     AsyncIo, AsyncIoError, AsyncIoResult, DiskFile, DiskFileError, DiskFileResult,
 };
+use crate::fixed_vhd::FixedVhd;
 use crate::raw_async::RawFileAsync;
-use crate::vhd::VhdFooter;
 use std::fs::File;
 use std::os::unix::io::{AsRawFd, RawFd};
 use vmm_sys_util::eventfd::EventFd;
 
-pub struct FixedVhdDiskAsync {
-    file: File,
-    size: u64,
-}
+pub struct FixedVhdDiskAsync(FixedVhd);
 
 impl FixedVhdDiskAsync {
-    pub fn new(mut file: File) -> std::io::Result<Self> {
-        let footer = VhdFooter::new(&mut file)?;
-
-        Ok(FixedVhdDiskAsync {
-            file,
-            size: footer.current_size(),
-        })
+    pub fn new(file: File) -> std::io::Result<Self> {
+        Ok(Self(FixedVhd::new(file)?))
     }
 }
 
 impl DiskFile for FixedVhdDiskAsync {
     fn size(&mut self) -> DiskFileResult<u64> {
-        Ok(self.size)
+        Ok(self.0.size())
     }
 
     fn new_async_io(&self, ring_depth: u32) -> DiskFileResult<Box<dyn AsyncIo>> {
         Ok(Box::new(
-            FixedVhdAsync::new(self.file.as_raw_fd(), ring_depth, self.size)
+            FixedVhdAsync::new(self.0.as_raw_fd(), ring_depth, self.0.size())
                 .map_err(DiskFileError::NewAsyncIo)?,
         ) as Box<dyn AsyncIo>)
     }

block_util/src/fixed_vhd_sync.rs

@@ -5,36 +5,28 @@
 use crate::async_io::{
     AsyncIo, AsyncIoError, AsyncIoResult, DiskFile, DiskFileError, DiskFileResult,
 };
+use crate::fixed_vhd::FixedVhd;
 use crate::raw_sync::RawFileSync;
-use crate::vhd::VhdFooter;
 use std::fs::File;
 use std::os::unix::io::{AsRawFd, RawFd};
 use vmm_sys_util::eventfd::EventFd;
 
-pub struct FixedVhdDiskSync {
-    file: File,
-    size: u64,
-}
+pub struct FixedVhdDiskSync(FixedVhd);
 
 impl FixedVhdDiskSync {
-    pub fn new(mut file: File) -> std::io::Result<Self> {
-        let footer = VhdFooter::new(&mut file)?;
-
-        Ok(FixedVhdDiskSync {
-            file,
-            size: footer.current_size(),
-        })
+    pub fn new(file: File) -> std::io::Result<Self> {
+        Ok(Self(FixedVhd::new(file)?))
     }
 }
 
 impl DiskFile for FixedVhdDiskSync {
     fn size(&mut self) -> DiskFileResult<u64> {
-        Ok(self.size)
+        Ok(self.0.size())
     }
 
     fn new_async_io(&self, _ring_depth: u32) -> DiskFileResult<Box<dyn AsyncIo>> {
         Ok(Box::new(
-            FixedVhdSync::new(self.file.as_raw_fd(), self.size)
+            FixedVhdSync::new(self.0.as_raw_fd(), self.0.size())
                 .map_err(DiskFileError::NewAsyncIo)?,
         ) as Box<dyn AsyncIo>)
     }

block_util/src/lib.rs

@@ -12,6 +12,7 @@
 extern crate log;
 
 pub mod async_io;
+pub mod fixed_vhd;
 #[cfg(feature = "io_uring")]
 /// Enabled with the `"io_uring"` feature
 pub mod fixed_vhd_async;