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block: qcow: Refactor refcount update into helper method

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Add set_cluster_refcount_track_freed() helper to consolidate the
common pattern of setting a cluster refcount and tracking freed
refblocks. This reduces code duplication and improves readability.

Signed-off-by: Anatol Belski <anbelski@linux.microsoft.com>
This commit is contained in:
Anatol Belski 2025-12-02 15:19:53 +01:00 • committed by Rob Bradford
parent f56adb8a5a
commit c940f6642f
1 changed files with 15 additions and 8 deletions
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23
block/src/qcow/mod.rs
View file

@ -1235,8 +1235,7 @@ impl QcowFile {
.get_cluster_refcount(&mut self.raw_file, addr)
.map_err(|e| std::io::Error::other(Error::GettingRefcount(e)))?;
if refcount > 0 {
let mut newly_unref = self.set_cluster_refcount(addr, refcount - 1)?;
self.unref_clusters.append(&mut newly_unref);
self.set_cluster_refcount_track_freed(addr, refcount - 1)?;
}
addr += self.raw_file.cluster_size();
}
@ -1262,8 +1261,7 @@ impl QcowFile {
};
for (addr, count) in set_refcounts {
let mut newly_unref = self.set_cluster_refcount(addr, count)?;
self.unref_clusters.append(&mut newly_unref);
self.set_cluster_refcount_track_freed(addr, count)?;
}
Ok(cluster_addr + self.raw_file.cluster_offset(address))
@ -1331,8 +1329,7 @@ impl QcowFile {
fn append_data_cluster(&mut self, initial_data: Option<Vec<u8>>) -> std::io::Result<u64> {
let new_addr: u64 = self.get_new_cluster(initial_data)?;
// The cluster refcount starts at one indicating it is used but doesn't need COW.
let mut newly_unref = self.set_cluster_refcount(new_addr, 1)?;
self.unref_clusters.append(&mut newly_unref);
self.set_cluster_refcount_track_freed(new_addr, 1)?;
Ok(new_addr)
}
@ -1437,8 +1434,7 @@ impl QcowFile {
}
let new_refcount = refcount - 1;
let mut newly_unref = self.set_cluster_refcount(cluster_addr, new_refcount)?;
self.unref_clusters.append(&mut newly_unref);
self.set_cluster_refcount_track_freed(cluster_addr, new_refcount)?;
// Rewrite the L2 entry to remove the cluster mapping.
// unwrap is safe as we just checked/inserted this entry.
@ -1523,6 +1519,17 @@ impl QcowFile {
Ok(new_cluster)
}
// Set the refcount for a cluster and add any unreferenced clusters to the unref list.
fn set_cluster_refcount_track_freed(
&mut self,
address: u64,
refcount: u16,
) -> std::io::Result<()> {
let mut newly_unref = self.set_cluster_refcount(address, refcount)?;
self.unref_clusters.append(&mut newly_unref);
Ok(())
}
// 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.