mirror of
https://github.com/cloud-hypervisor/cloud-hypervisor.git
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block: qcow: Extract rebuild_refcounts() function
Pull rebuild_refcounts out of QcowFile so QcowFile can be removed in a follow up commit. This function is still required by parse_qcow(). Assisted-by: Claude:claude-opus-4-7 Signed-off-by: Rob Bradford <rbradford@meta.com>
This commit is contained in:
Rob Bradford
@@ -545,7 +545,7 @@ pub(crate) fn parse_qcow(
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// Skip refcount rebuilding for readonly files.
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if refcount_rebuild_required && is_writable {
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QcowFile::rebuild_refcounts(&mut raw_file, header.clone())?;
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rebuild_refcounts(&mut raw_file, header.clone())?;
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}
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let entries_per_cluster = cluster_size / size_of::<u64>() as u64;
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@@ -1055,326 +1055,6 @@ impl QcowFile {
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Ok(())
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}
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/// Rebuild the reference count tables.
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fn rebuild_refcounts(raw_file: &mut QcowRawFile, header: QcowHeader) -> BlockResult<()> {
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fn add_ref(
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refcounts: &mut [u64],
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cluster_size: u64,
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cluster_address: u64,
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max_refcount: u64,
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refcount_bits: u64,
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) -> Result<()> {
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let idx = (cluster_address / cluster_size) as usize;
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if idx >= refcounts.len() {
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return Err(Error::InvalidClusterIndex);
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}
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if refcounts[idx] >= max_refcount {
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return Err(Error::RefcountOverflow(refcount::Error::RefcountOverflow {
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value: refcounts[idx] + 1,
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max: max_refcount,
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refcount_bits,
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}));
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}
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refcounts[idx] += 1;
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Ok(())
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}
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// Add a reference to the first cluster (header plus extensions).
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fn set_header_refcount(
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refcounts: &mut [u64],
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cluster_size: u64,
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max_refcount: u64,
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refcount_bits: u64,
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) -> Result<()> {
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add_ref(refcounts, cluster_size, 0, max_refcount, refcount_bits)
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}
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// Add references to the L1 table clusters.
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fn set_l1_refcounts(
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refcounts: &mut [u64],
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header: &QcowHeader,
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cluster_size: u64,
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max_refcount: u64,
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refcount_bits: u64,
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) -> Result<()> {
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let entries_per_cluster = cluster_size / size_of::<u64>() as u64;
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let l1_clusters = div_round_up_u64(u64::from(header.l1_size), entries_per_cluster);
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let l1_table_offset = header.l1_table_offset;
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for i in 0..l1_clusters {
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add_ref(
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refcounts,
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cluster_size,
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l1_table_offset + i * cluster_size,
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max_refcount,
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refcount_bits,
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)?;
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}
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Ok(())
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}
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// Traverse the L1 and L2 tables to find all reachable data clusters.
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fn set_data_refcounts(
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refcounts: &mut [u64],
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header: &QcowHeader,
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cluster_size: u64,
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raw_file: &mut QcowRawFile,
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max_refcount: u64,
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refcount_bits: u64,
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) -> Result<()> {
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let l1_table = raw_file
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.read_pointer_table(
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header.l1_table_offset,
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u64::from(header.l1_size),
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Some(L1_TABLE_OFFSET_MASK),
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)
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.map_err(Error::ReadingPointers)?;
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for l1_index in 0..header.l1_size as usize {
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let l2_addr_disk = *l1_table.get(l1_index).ok_or(Error::InvalidIndex)?;
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if l2_addr_disk != 0 {
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// Add a reference to the L2 table cluster itself.
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add_ref(
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refcounts,
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cluster_size,
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l2_addr_disk,
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max_refcount,
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refcount_bits,
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)?;
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// Read the L2 table and find all referenced data clusters.
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let l2_table = raw_file
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.read_pointer_table(
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l2_addr_disk,
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cluster_size / size_of::<u64>() as u64,
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Some(L2_TABLE_OFFSET_MASK),
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)
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.map_err(Error::ReadingPointers)?;
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for data_cluster_addr in l2_table {
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if data_cluster_addr != 0 {
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add_ref(
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refcounts,
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cluster_size,
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data_cluster_addr,
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max_refcount,
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refcount_bits,
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)?;
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}
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}
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}
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}
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Ok(())
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}
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// Add references to the top-level refcount table clusters.
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fn set_refcount_table_refcounts(
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refcounts: &mut [u64],
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header: &QcowHeader,
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cluster_size: u64,
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max_refcount: u64,
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refcount_bits: u64,
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) -> Result<()> {
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let refcount_table_offset = header.refcount_table_offset;
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for i in 0..u64::from(header.refcount_table_clusters) {
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add_ref(
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refcounts,
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cluster_size,
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refcount_table_offset + i * cluster_size,
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max_refcount,
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refcount_bits,
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)?;
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}
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Ok(())
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}
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// Allocate clusters for refblocks.
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// This needs to be done last so that we have the correct refcounts for all other
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// clusters.
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fn alloc_refblocks(
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refcounts: &mut [u64],
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cluster_size: u64,
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refblock_clusters: u64,
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max_refcount: u64,
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refcount_bits: u64,
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) -> Result<Vec<u64>> {
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let mut ref_table = vec![0; refblock_clusters as usize];
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let mut first_free_cluster: u64 = 0;
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for refblock_addr in &mut ref_table {
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loop {
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if first_free_cluster >= refcounts.len() as u64 {
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return Err(Error::NotEnoughSpaceForRefcounts);
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}
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if refcounts[first_free_cluster as usize] == 0 {
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break;
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}
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first_free_cluster += 1;
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}
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*refblock_addr = first_free_cluster * cluster_size;
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add_ref(
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refcounts,
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cluster_size,
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*refblock_addr,
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max_refcount,
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refcount_bits,
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)?;
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first_free_cluster += 1;
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}
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Ok(ref_table)
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}
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// Write the updated reference count blocks and reftable.
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fn write_refblocks(
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refcounts: &[u64],
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mut header: QcowHeader,
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ref_table: &[u64],
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raw_file: &mut QcowRawFile,
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refcount_block_entries: u64,
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) -> Result<()> {
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// Rewrite the header with lazy refcounts enabled while we are rebuilding the tables.
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header.compatible_features |= COMPATIBLE_FEATURES_LAZY_REFCOUNTS;
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raw_file.file_mut().rewind().map_err(Error::SeekingFile)?;
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header.write_to(raw_file.file_mut())?;
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for (i, refblock_addr) in ref_table.iter().enumerate() {
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// Write a block of refcounts to the location indicated by refblock_addr.
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let refblock_start = i * (refcount_block_entries as usize);
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let refblock_end = min(
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refcounts.len(),
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refblock_start + refcount_block_entries as usize,
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);
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let refblock = &refcounts[refblock_start..refblock_end];
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raw_file
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.write_refcount_block(*refblock_addr, refblock)
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.map_err(Error::WritingHeader)?;
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// If this is the last (partial) cluster, pad it out to a full refblock cluster.
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if refblock.len() < refcount_block_entries as usize {
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let refblock_padding =
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vec![0u64; refcount_block_entries as usize - refblock.len()];
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let byte_offset =
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refblock.len() as u64 * raw_file.cluster_size() / refcount_block_entries;
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raw_file
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.write_refcount_block(*refblock_addr + byte_offset, &refblock_padding)
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.map_err(Error::WritingHeader)?;
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}
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}
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// Rewrite the top-level refcount table.
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raw_file
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.write_pointer_table_direct(header.refcount_table_offset, ref_table.iter())
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.map_err(Error::WritingHeader)?;
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// Rewrite the header again, now with lazy refcounts disabled.
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header.compatible_features &= !COMPATIBLE_FEATURES_LAZY_REFCOUNTS;
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raw_file.file_mut().rewind().map_err(Error::SeekingFile)?;
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header.write_to(raw_file.file_mut())?;
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Ok(())
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}
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let cluster_size = raw_file.cluster_size();
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let file_size = raw_file
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.file_mut()
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.metadata()
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.map_err(|e| BlockError::new(BlockErrorKind::Io, Error::GettingFileSize(e)))?
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.len();
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let refcount_bits = 1u64 << header.refcount_order;
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let max_refcount = if refcount_bits == 64 {
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u64::MAX
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} else {
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(1u64 << refcount_bits) - 1
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};
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let refcount_block_entries = cluster_size * 8 / refcount_bits;
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let pointers_per_cluster = cluster_size / size_of::<u64>() as u64;
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let data_clusters = div_round_up_u64(header.size, cluster_size);
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let l2_clusters = div_round_up_u64(data_clusters, pointers_per_cluster);
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let l1_clusters = div_round_up_u64(l2_clusters, pointers_per_cluster);
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let header_clusters = div_round_up_u64(size_of::<QcowHeader>() as u64, cluster_size);
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let max_clusters = data_clusters + l2_clusters + l1_clusters + header_clusters;
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let mut max_valid_cluster_index = max_clusters;
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let refblock_clusters = div_round_up_u64(max_valid_cluster_index, refcount_block_entries);
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let reftable_clusters = div_round_up_u64(refblock_clusters, pointers_per_cluster);
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// Account for refblocks and the ref table size needed to address them.
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let refblocks_for_refs = div_round_up_u64(
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refblock_clusters + reftable_clusters,
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refcount_block_entries,
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);
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let reftable_clusters_for_refs =
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div_round_up_u64(refblocks_for_refs, refcount_block_entries);
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max_valid_cluster_index += refblock_clusters + reftable_clusters;
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max_valid_cluster_index += refblocks_for_refs + reftable_clusters_for_refs;
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if max_valid_cluster_index > MAX_RAM_POINTER_TABLE_SIZE {
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return Err(BlockError::new(
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BlockErrorKind::CorruptImage,
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Error::InvalidRefcountTableSize(max_valid_cluster_index),
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));
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}
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let max_valid_cluster_offset = max_valid_cluster_index * cluster_size;
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if max_valid_cluster_offset < file_size - cluster_size {
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return Err(BlockError::new(
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BlockErrorKind::CorruptImage,
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Error::InvalidRefcountTableSize(max_valid_cluster_offset),
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));
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}
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let mut refcounts = vec![0; max_valid_cluster_index as usize];
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// Find all references clusters and rebuild refcounts.
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set_header_refcount(&mut refcounts, cluster_size, max_refcount, refcount_bits)
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.map_err(|e| BlockError::new(BlockErrorKind::Io, e))?;
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set_l1_refcounts(
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&mut refcounts,
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&header,
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cluster_size,
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max_refcount,
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refcount_bits,
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)
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.map_err(|e| BlockError::new(BlockErrorKind::Io, e))?;
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set_data_refcounts(
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&mut refcounts,
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&header,
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cluster_size,
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raw_file,
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max_refcount,
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refcount_bits,
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)
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.map_err(|e| BlockError::new(BlockErrorKind::Io, e))?;
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set_refcount_table_refcounts(
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&mut refcounts,
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&header,
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cluster_size,
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max_refcount,
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refcount_bits,
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)
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.map_err(|e| BlockError::new(BlockErrorKind::Io, e))?;
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// Allocate clusters to store the new reference count blocks.
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let ref_table = alloc_refblocks(
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&mut refcounts,
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cluster_size,
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refblock_clusters,
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max_refcount,
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refcount_bits,
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)
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.map_err(|e| BlockError::new(BlockErrorKind::Io, e))?;
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// Write updated reference counts and point the reftable at them.
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write_refblocks(
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&refcounts,
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header,
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&ref_table,
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raw_file,
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refcount_block_entries,
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)
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.map_err(|e| BlockError::new(BlockErrorKind::Io, e))
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}
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// Limits the range so that it doesn't exceed the virtual size of the file.
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fn limit_range_file(&self, address: u64, count: usize) -> usize {
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if address.checked_add(count as u64).is_none() || address > self.virtual_size() {
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@@ -2095,6 +1775,324 @@ impl QcowFile {
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}
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}
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/// Rebuild the reference count tables.
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fn rebuild_refcounts(raw_file: &mut QcowRawFile, header: QcowHeader) -> BlockResult<()> {
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fn add_ref(
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refcounts: &mut [u64],
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cluster_size: u64,
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cluster_address: u64,
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max_refcount: u64,
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refcount_bits: u64,
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) -> Result<()> {
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let idx = (cluster_address / cluster_size) as usize;
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if idx >= refcounts.len() {
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return Err(Error::InvalidClusterIndex);
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}
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if refcounts[idx] >= max_refcount {
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return Err(Error::RefcountOverflow(refcount::Error::RefcountOverflow {
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value: refcounts[idx] + 1,
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max: max_refcount,
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refcount_bits,
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}));
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}
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refcounts[idx] += 1;
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Ok(())
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}
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// Add a reference to the first cluster (header plus extensions).
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fn set_header_refcount(
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refcounts: &mut [u64],
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cluster_size: u64,
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max_refcount: u64,
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refcount_bits: u64,
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) -> Result<()> {
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add_ref(refcounts, cluster_size, 0, max_refcount, refcount_bits)
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}
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// Add references to the L1 table clusters.
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fn set_l1_refcounts(
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refcounts: &mut [u64],
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header: &QcowHeader,
|
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cluster_size: u64,
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max_refcount: u64,
|
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refcount_bits: u64,
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) -> Result<()> {
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let entries_per_cluster = cluster_size / size_of::<u64>() as u64;
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let l1_clusters = div_round_up_u64(u64::from(header.l1_size), entries_per_cluster);
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let l1_table_offset = header.l1_table_offset;
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for i in 0..l1_clusters {
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add_ref(
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refcounts,
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cluster_size,
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l1_table_offset + i * cluster_size,
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max_refcount,
|
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refcount_bits,
|
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)?;
|
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}
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Ok(())
|
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}
|
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|
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// Traverse the L1 and L2 tables to find all reachable data clusters.
|
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fn set_data_refcounts(
|
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refcounts: &mut [u64],
|
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header: &QcowHeader,
|
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cluster_size: u64,
|
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raw_file: &mut QcowRawFile,
|
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max_refcount: u64,
|
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refcount_bits: u64,
|
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) -> Result<()> {
|
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let l1_table = raw_file
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.read_pointer_table(
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header.l1_table_offset,
|
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u64::from(header.l1_size),
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Some(L1_TABLE_OFFSET_MASK),
|
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)
|
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.map_err(Error::ReadingPointers)?;
|
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for l1_index in 0..header.l1_size as usize {
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let l2_addr_disk = *l1_table.get(l1_index).ok_or(Error::InvalidIndex)?;
|
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if l2_addr_disk != 0 {
|
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// Add a reference to the L2 table cluster itself.
|
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add_ref(
|
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refcounts,
|
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cluster_size,
|
||||
l2_addr_disk,
|
||||
max_refcount,
|
||||
refcount_bits,
|
||||
)?;
|
||||
|
||||
// Read the L2 table and find all referenced data clusters.
|
||||
let l2_table = raw_file
|
||||
.read_pointer_table(
|
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l2_addr_disk,
|
||||
cluster_size / size_of::<u64>() as u64,
|
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Some(L2_TABLE_OFFSET_MASK),
|
||||
)
|
||||
.map_err(Error::ReadingPointers)?;
|
||||
for data_cluster_addr in l2_table {
|
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if data_cluster_addr != 0 {
|
||||
add_ref(
|
||||
refcounts,
|
||||
cluster_size,
|
||||
data_cluster_addr,
|
||||
max_refcount,
|
||||
refcount_bits,
|
||||
)?;
|
||||
}
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
Ok(())
|
||||
}
|
||||
|
||||
// Add references to the top-level refcount table clusters.
|
||||
fn set_refcount_table_refcounts(
|
||||
refcounts: &mut [u64],
|
||||
header: &QcowHeader,
|
||||
cluster_size: u64,
|
||||
max_refcount: u64,
|
||||
refcount_bits: u64,
|
||||
) -> Result<()> {
|
||||
let refcount_table_offset = header.refcount_table_offset;
|
||||
for i in 0..u64::from(header.refcount_table_clusters) {
|
||||
add_ref(
|
||||
refcounts,
|
||||
cluster_size,
|
||||
refcount_table_offset + i * cluster_size,
|
||||
max_refcount,
|
||||
refcount_bits,
|
||||
)?;
|
||||
}
|
||||
Ok(())
|
||||
}
|
||||
|
||||
// Allocate clusters for refblocks.
|
||||
// This needs to be done last so that we have the correct refcounts for all other
|
||||
// clusters.
|
||||
fn alloc_refblocks(
|
||||
refcounts: &mut [u64],
|
||||
cluster_size: u64,
|
||||
refblock_clusters: u64,
|
||||
max_refcount: u64,
|
||||
refcount_bits: u64,
|
||||
) -> Result<Vec<u64>> {
|
||||
let mut ref_table = vec![0; refblock_clusters as usize];
|
||||
let mut first_free_cluster: u64 = 0;
|
||||
for refblock_addr in &mut ref_table {
|
||||
loop {
|
||||
if first_free_cluster >= refcounts.len() as u64 {
|
||||
return Err(Error::NotEnoughSpaceForRefcounts);
|
||||
}
|
||||
if refcounts[first_free_cluster as usize] == 0 {
|
||||
break;
|
||||
}
|
||||
first_free_cluster += 1;
|
||||
}
|
||||
|
||||
*refblock_addr = first_free_cluster * cluster_size;
|
||||
add_ref(
|
||||
refcounts,
|
||||
cluster_size,
|
||||
*refblock_addr,
|
||||
max_refcount,
|
||||
refcount_bits,
|
||||
)?;
|
||||
|
||||
first_free_cluster += 1;
|
||||
}
|
||||
|
||||
Ok(ref_table)
|
||||
}
|
||||
|
||||
// Write the updated reference count blocks and reftable.
|
||||
fn write_refblocks(
|
||||
refcounts: &[u64],
|
||||
mut header: QcowHeader,
|
||||
ref_table: &[u64],
|
||||
raw_file: &mut QcowRawFile,
|
||||
refcount_block_entries: u64,
|
||||
) -> Result<()> {
|
||||
// Rewrite the header with lazy refcounts enabled while we are rebuilding the tables.
|
||||
header.compatible_features |= COMPATIBLE_FEATURES_LAZY_REFCOUNTS;
|
||||
raw_file.file_mut().rewind().map_err(Error::SeekingFile)?;
|
||||
header.write_to(raw_file.file_mut())?;
|
||||
|
||||
for (i, refblock_addr) in ref_table.iter().enumerate() {
|
||||
// Write a block of refcounts to the location indicated by refblock_addr.
|
||||
let refblock_start = i * (refcount_block_entries as usize);
|
||||
let refblock_end = min(
|
||||
refcounts.len(),
|
||||
refblock_start + refcount_block_entries as usize,
|
||||
);
|
||||
let refblock = &refcounts[refblock_start..refblock_end];
|
||||
raw_file
|
||||
.write_refcount_block(*refblock_addr, refblock)
|
||||
.map_err(Error::WritingHeader)?;
|
||||
|
||||
// If this is the last (partial) cluster, pad it out to a full refblock cluster.
|
||||
if refblock.len() < refcount_block_entries as usize {
|
||||
let refblock_padding = vec![0u64; refcount_block_entries as usize - refblock.len()];
|
||||
let byte_offset =
|
||||
refblock.len() as u64 * raw_file.cluster_size() / refcount_block_entries;
|
||||
raw_file
|
||||
.write_refcount_block(*refblock_addr + byte_offset, &refblock_padding)
|
||||
.map_err(Error::WritingHeader)?;
|
||||
}
|
||||
}
|
||||
|
||||
// Rewrite the top-level refcount table.
|
||||
raw_file
|
||||
.write_pointer_table_direct(header.refcount_table_offset, ref_table.iter())
|
||||
.map_err(Error::WritingHeader)?;
|
||||
|
||||
// Rewrite the header again, now with lazy refcounts disabled.
|
||||
header.compatible_features &= !COMPATIBLE_FEATURES_LAZY_REFCOUNTS;
|
||||
raw_file.file_mut().rewind().map_err(Error::SeekingFile)?;
|
||||
header.write_to(raw_file.file_mut())?;
|
||||
|
||||
Ok(())
|
||||
}
|
||||
|
||||
let cluster_size = raw_file.cluster_size();
|
||||
|
||||
let file_size = raw_file
|
||||
.file_mut()
|
||||
.metadata()
|
||||
.map_err(|e| BlockError::new(BlockErrorKind::Io, Error::GettingFileSize(e)))?
|
||||
.len();
|
||||
|
||||
let refcount_bits = 1u64 << header.refcount_order;
|
||||
let max_refcount = if refcount_bits == 64 {
|
||||
u64::MAX
|
||||
} else {
|
||||
(1u64 << refcount_bits) - 1
|
||||
};
|
||||
let refcount_block_entries = cluster_size * 8 / refcount_bits;
|
||||
let pointers_per_cluster = cluster_size / size_of::<u64>() as u64;
|
||||
let data_clusters = div_round_up_u64(header.size, cluster_size);
|
||||
let l2_clusters = div_round_up_u64(data_clusters, pointers_per_cluster);
|
||||
let l1_clusters = div_round_up_u64(l2_clusters, pointers_per_cluster);
|
||||
let header_clusters = div_round_up_u64(size_of::<QcowHeader>() as u64, cluster_size);
|
||||
let max_clusters = data_clusters + l2_clusters + l1_clusters + header_clusters;
|
||||
let mut max_valid_cluster_index = max_clusters;
|
||||
let refblock_clusters = div_round_up_u64(max_valid_cluster_index, refcount_block_entries);
|
||||
let reftable_clusters = div_round_up_u64(refblock_clusters, pointers_per_cluster);
|
||||
// Account for refblocks and the ref table size needed to address them.
|
||||
let refblocks_for_refs = div_round_up_u64(
|
||||
refblock_clusters + reftable_clusters,
|
||||
refcount_block_entries,
|
||||
);
|
||||
let reftable_clusters_for_refs = div_round_up_u64(refblocks_for_refs, refcount_block_entries);
|
||||
max_valid_cluster_index += refblock_clusters + reftable_clusters;
|
||||
max_valid_cluster_index += refblocks_for_refs + reftable_clusters_for_refs;
|
||||
|
||||
if max_valid_cluster_index > MAX_RAM_POINTER_TABLE_SIZE {
|
||||
return Err(BlockError::new(
|
||||
BlockErrorKind::CorruptImage,
|
||||
Error::InvalidRefcountTableSize(max_valid_cluster_index),
|
||||
));
|
||||
}
|
||||
|
||||
let max_valid_cluster_offset = max_valid_cluster_index * cluster_size;
|
||||
if max_valid_cluster_offset < file_size - cluster_size {
|
||||
return Err(BlockError::new(
|
||||
BlockErrorKind::CorruptImage,
|
||||
Error::InvalidRefcountTableSize(max_valid_cluster_offset),
|
||||
));
|
||||
}
|
||||
|
||||
let mut refcounts = vec![0; max_valid_cluster_index as usize];
|
||||
|
||||
// Find all references clusters and rebuild refcounts.
|
||||
set_header_refcount(&mut refcounts, cluster_size, max_refcount, refcount_bits)
|
||||
.map_err(|e| BlockError::new(BlockErrorKind::Io, e))?;
|
||||
set_l1_refcounts(
|
||||
&mut refcounts,
|
||||
&header,
|
||||
cluster_size,
|
||||
max_refcount,
|
||||
refcount_bits,
|
||||
)
|
||||
.map_err(|e| BlockError::new(BlockErrorKind::Io, e))?;
|
||||
set_data_refcounts(
|
||||
&mut refcounts,
|
||||
&header,
|
||||
cluster_size,
|
||||
raw_file,
|
||||
max_refcount,
|
||||
refcount_bits,
|
||||
)
|
||||
.map_err(|e| BlockError::new(BlockErrorKind::Io, e))?;
|
||||
set_refcount_table_refcounts(
|
||||
&mut refcounts,
|
||||
&header,
|
||||
cluster_size,
|
||||
max_refcount,
|
||||
refcount_bits,
|
||||
)
|
||||
.map_err(|e| BlockError::new(BlockErrorKind::Io, e))?;
|
||||
|
||||
// Allocate clusters to store the new reference count blocks.
|
||||
let ref_table = alloc_refblocks(
|
||||
&mut refcounts,
|
||||
cluster_size,
|
||||
refblock_clusters,
|
||||
max_refcount,
|
||||
refcount_bits,
|
||||
)
|
||||
.map_err(|e| BlockError::new(BlockErrorKind::Io, e))?;
|
||||
|
||||
// Write updated reference counts and point the reftable at them.
|
||||
write_refblocks(
|
||||
&refcounts,
|
||||
header,
|
||||
&ref_table,
|
||||
raw_file,
|
||||
refcount_block_entries,
|
||||
)
|
||||
.map_err(|e| BlockError::new(BlockErrorKind::Io, e))
|
||||
}
|
||||
|
||||
impl AsRawFd for QcowFile {
|
||||
fn as_raw_fd(&self) -> RawFd {
|
||||
self.raw_file.as_raw_fd()
|
||||
|
||||
Reference in New Issue
Block a user