make ReadChunk not require mutable self.

That way we can reduce lock contentions because we lock for much shorter
times.

src/backup/read_chunk.rs

@@ -11,10 +11,10 @@ use super::datastore::DataStore;
 /// The ReadChunk trait allows reading backup data chunks (local or remote)
 pub trait ReadChunk {
     /// Returns the encoded chunk data
-    fn read_raw_chunk(&mut self, digest: &[u8; 32]) -> Result<DataBlob, Error>;
+    fn read_raw_chunk(&self, digest: &[u8; 32]) -> Result<DataBlob, Error>;
 
     /// Returns the decoded chunk data
-    fn read_chunk(&mut self, digest: &[u8; 32]) -> Result<Vec<u8>, Error>;
+    fn read_chunk(&self, digest: &[u8; 32]) -> Result<Vec<u8>, Error>;
 }
 
 #[derive(Clone)]
@@ -33,7 +33,7 @@ impl LocalChunkReader {
 }
 
 impl ReadChunk for LocalChunkReader {
-    fn read_raw_chunk(&mut self, digest: &[u8; 32]) -> Result<DataBlob, Error> {
+    fn read_raw_chunk(&self, digest: &[u8; 32]) -> Result<DataBlob, Error> {
         let (path, _) = self.store.chunk_path(digest);
         let raw_data = proxmox::tools::fs::file_get_contents(&path)?;
         let chunk = DataBlob::from_raw(raw_data)?;
@@ -42,7 +42,7 @@ impl ReadChunk for LocalChunkReader {
         Ok(chunk)
     }
 
-    fn read_chunk(&mut self, digest: &[u8; 32]) -> Result<Vec<u8>, Error> {
+    fn read_chunk(&self, digest: &[u8; 32]) -> Result<Vec<u8>, Error> {
         let chunk = ReadChunk::read_raw_chunk(self, digest)?;
 
         let raw_data = chunk.decode(self.crypt_config.as_ref().map(Arc::as_ref))?;
@@ -56,20 +56,20 @@ impl ReadChunk for LocalChunkReader {
 pub trait AsyncReadChunk: Send {
     /// Returns the encoded chunk data
     fn read_raw_chunk<'a>(
-        &'a mut self,
+        &'a self,
         digest: &'a [u8; 32],
     ) -> Pin<Box<dyn Future<Output = Result<DataBlob, Error>> + Send + 'a>>;
 
     /// Returns the decoded chunk data
     fn read_chunk<'a>(
-        &'a mut self,
+        &'a self,
         digest: &'a [u8; 32],
     ) -> Pin<Box<dyn Future<Output = Result<Vec<u8>, Error>> + Send + 'a>>;
 }
 
 impl AsyncReadChunk for LocalChunkReader {
     fn read_raw_chunk<'a>(
-        &'a mut self,
+        &'a self,
         digest: &'a [u8; 32],
     ) -> Pin<Box<dyn Future<Output = Result<DataBlob, Error>> + Send + 'a>> {
         Box::pin(async move{
@@ -84,7 +84,7 @@ impl AsyncReadChunk for LocalChunkReader {
     }
 
     fn read_chunk<'a>(
-        &'a mut self,
+        &'a self,
         digest: &'a [u8; 32],
     ) -> Pin<Box<dyn Future<Output = Result<Vec<u8>, Error>> + Send + 'a>> {
         Box::pin(async move {