block: async_io: Remove unnecessary mut from reference

warning: this argument is a mutable reference, but not used mutably
  --> block/src/async_io.rs:68:28
   |
68 |     fn query_block_size(f: &mut File, block_size_type: BlockSize) -> std::io::Result<u64> {
   |                            ^^^^^^^^^ help: consider changing to: `&File`
   |
   = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#needless_pass_by_ref_mut

Signed-off-by: Rob Bradford <rbradford@rivosinc.com>

block/src/async_io.rs

@@ -51,7 +51,7 @@ enum BlockSize {
 }
 
 impl DiskTopology {
-    fn is_block_device(f: &mut File) -> std::io::Result<bool> {
+    fn is_block_device(f: &File) -> std::io::Result<bool> {
         let mut stat = std::mem::MaybeUninit::<libc::stat>::uninit();
         // SAFETY: FFI call with a valid fd and buffer
         let ret = unsafe { libc::fstat(f.as_raw_fd(), stat.as_mut_ptr()) };
@@ -65,7 +65,7 @@ impl DiskTopology {
     }
 
     // libc::ioctl() takes different types on different architectures
-    fn query_block_size(f: &mut File, block_size_type: BlockSize) -> std::io::Result<u64> {
+    fn query_block_size(f: &File, block_size_type: BlockSize) -> std::io::Result<u64> {
         let mut block_size = 0;
         // SAFETY: FFI call with correct arguments
         let ret = unsafe {
@@ -87,7 +87,7 @@ impl DiskTopology {
         Ok(block_size)
     }
 
-    pub fn probe(f: &mut File) -> std::io::Result<Self> {
+    pub fn probe(f: &File) -> std::io::Result<Self> {
         if !Self::is_block_device(f)? {
             return Ok(DiskTopology::default());
         }

block/src/raw_async.rs

@@ -36,7 +36,7 @@ impl DiskFile for RawFileDisk {
     }
 
     fn topology(&mut self) -> DiskTopology {
-        if let Ok(topology) = DiskTopology::probe(&mut self.file) {
+        if let Ok(topology) = DiskTopology::probe(&self.file) {
             topology
         } else {
             warn!("Unable to get device topology. Using default topology");

block/src/raw_sync.rs

@@ -33,7 +33,7 @@ impl DiskFile for RawFileDiskSync {
     }
 
     fn topology(&mut self) -> DiskTopology {
-        if let Ok(topology) = DiskTopology::probe(&mut self.file) {
+        if let Ok(topology) = DiskTopology::probe(&self.file) {
             topology
         } else {
             warn!("Unable to get device topology. Using default topology");