Method set_cluster_refcount

block/src/qcow/mod.rs:1898–1960

Set the refcount for a cluster with the given address. Returns a list of any refblocks that can be reused, this happens when a refblock is moved, the old location can be reused.

(&mut self, address: u64, refcount: u64)

    // Returns a list of any refblocks that can be reused, this happens when a refblock is moved,
    // the old location can be reused.
    fn set_cluster_refcount(&mut self, address: u64, refcount: u64) -> std::io::Result<Vec<u64>> {
        let mut added_clusters = Vec::new();
        let mut unref_clusters = Vec::new();
        let mut refcount_set = false;
        let mut new_cluster = None;

        while !refcount_set {
            match self.refcounts.set_cluster_refcount(
                &mut self.raw_file,
                address,
                refcount,
                new_cluster.take(),
            ) {
                Ok(None) => {
                    refcount_set = true;
                }
                Ok(Some(freed_cluster)) => {
                    // Recursively set the freed refcount block's refcount to 0
                    let mut freed = self.set_cluster_refcount(freed_cluster, 0)?;
                    unref_clusters.append(&mut freed);
                    refcount_set = true;
                }
                Err(refcount::Error::EvictingRefCounts(e)) => {
                    return Err(e);
                }
                Err(refcount::Error::InvalidIndex) => {
                    self.set_corrupt_bit_best_effort();
                    return Err(std::io::Error::from_raw_os_error(EINVAL));
                }
                Err(refcount::Error::NeedCluster(addr)) => {
                    // Read the address and call set_cluster_refcount again.
                    new_cluster = Some((
                        addr,
                        VecCache::from_vec(self.raw_file.read_refcount_block(addr)?),
                    ));
                }
                Err(refcount::Error::NeedNewCluster) => {
                    // Allocate the cluster and call set_cluster_refcount again.
                    let addr = self.get_new_cluster(None)?;
                    added_clusters.push(addr);
                    new_cluster = Some((
                        addr,
                        VecCache::new(self.refcounts.refcounts_per_block() as usize),
                    ));
                }
                Err(refcount::Error::ReadingRefCounts(e)) => {
                    return Err(e);
                }
                Err(refcount::Error::RefcountOverflow { .. }) => {
                    return Err(std::io::Error::from_raw_os_error(EINVAL));
                }
                Err(refcount::Error::RefblockUnaligned(_)) => {
                    self.set_corrupt_bit_best_effort();
                    return Err(io::Error::from_raw_os_error(EIO));
                }
            }
        }