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block: qcow: refactor: extract method cache_l2_cluster()

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There are several copy-pasted code fragments in impl QcowFile. All of
them add L2 entry to the cache and one of them (in file_offset_write())
does also allocating new L2 entry if necessary.

Fold all these code fragments (except of one in l2_table() which does
error handling in special way) into cache_l2_cluster() method without
changing the logic.
This will make the code more compact and clean.

Signed-off-by: Eugene Korenevsky <ekorenevsky@aliyun.com>
This commit is contained in:
Eugene Korenevsky 2025-11-02 01:51:24 +03:00 • committed by Rob Bradford
parent e3fa27e251
commit 3791062b23
1 changed files with 41 additions and 65 deletions
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106
block/src/qcow/mod.rs
View file

@ -1070,21 +1070,7 @@ impl QcowFile {
let l2_index = self.l2_table_index(address) as usize;
if !self.l2_cache.contains_key(l1_index) {
// Not in the cache.
let table =
VecCache::from_vec(Self::read_l2_cluster(&mut self.raw_file, l2_addr_disk)?);
let l1_table = &self.l1_table;
let raw_file = &mut self.raw_file;
self.l2_cache.insert(l1_index, table, |index, evicted| {
raw_file.write_pointer_table(
l1_table[index],
evicted.get_values(),
CLUSTER_USED_FLAG,
)
})?;
};
self.cache_l2_cluster(l1_index, l2_addr_disk, false)?;
let cluster_addr = self.l2_cache.get(l1_index).unwrap()[l2_index];
if cluster_addr == 0 {
@ -1109,28 +1095,9 @@ impl QcowFile {
let mut set_refcounts = Vec::new();
if !self.l2_cache.contains_key(l1_index) {
// Not in the cache.
let l2_table = if l2_addr_disk == 0 {
// Allocate a new cluster to store the L2 table and update the L1 table to point
// to the new table.
let new_addr: u64 = self.get_new_cluster(None)?;
// The cluster refcount starts at one meaning it is used but doesn't need COW.
set_refcounts.push((new_addr, 1));
self.l1_table[l1_index] = new_addr;
VecCache::new(self.l2_entries as usize)
} else {
VecCache::from_vec(Self::read_l2_cluster(&mut self.raw_file, l2_addr_disk)?)
};
let l1_table = &self.l1_table;
let raw_file = &mut self.raw_file;
self.l2_cache.insert(l1_index, l2_table, |index, evicted| {
raw_file.write_pointer_table(
l1_table[index],
evicted.get_values(),
CLUSTER_USED_FLAG,
)
})?;
if let Some(new_addr) = self.cache_l2_cluster(l1_index, l2_addr_disk, true)? {
// The cluster refcount starts at one meaning it is used but doesn't need COW.
set_refcounts.push((new_addr, 1));
}
let cluster_addr = match self.l2_cache.get(l1_index).unwrap()[l2_index] {
@ -1247,20 +1214,7 @@ impl QcowFile {
return Ok(false);
}
if !self.l2_cache.contains_key(l1_index) {
// Not in the cache.
let table =
VecCache::from_vec(Self::read_l2_cluster(&mut self.raw_file, l2_addr_disk)?);
let l1_table = &self.l1_table;
let raw_file = &mut self.raw_file;
self.l2_cache.insert(l1_index, table, |index, evicted| {
raw_file.write_pointer_table(
l1_table[index],
evicted.get_values(),
CLUSTER_USED_FLAG,
)
})?;
}
self.cache_l2_cluster(l1_index, l2_addr_disk, false)?;
let cluster_addr = self.l2_cache.get(l1_index).unwrap()[l2_index];
// If cluster_addr != 0, the cluster is allocated.
@ -1319,20 +1273,7 @@ impl QcowFile {
return Ok(());
}
if !self.l2_cache.contains_key(l1_index) {
// Not in the cache.
let table =
VecCache::from_vec(Self::read_l2_cluster(&mut self.raw_file, l2_addr_disk)?);
let l1_table = &self.l1_table;
let raw_file = &mut self.raw_file;
self.l2_cache.insert(l1_index, table, |index, evicted| {
raw_file.write_pointer_table(
l1_table[index],
evicted.get_values(),
CLUSTER_USED_FLAG,
)
})?;
}
self.cache_l2_cluster(l1_index, l2_addr_disk, false)?;
let cluster_addr = self.l2_cache.get(l1_index).unwrap()[l2_index];
if cluster_addr == 0 {
@ -1417,6 +1358,41 @@ impl QcowFile {
.collect())
}
// Put an L2 cluster to the cache with evicting less-used cluster
// The new cluster may be allocated if necessary
// (may_alloc argument is true and l2_addr_disk == 0)
fn cache_l2_cluster(
&mut self,
l1_index: usize,
l2_addr_disk: u64,
may_alloc: bool,
) -> std::io::Result<Option<u64>> {
let mut new_cluster: Option<u64> = None;
if !self.l2_cache.contains_key(l1_index) {
// Not in the cache.
let l2_table = if may_alloc && l2_addr_disk == 0 {
// Allocate a new cluster to store the L2 table and update the L1 table to point
// to the new table.
let new_addr: u64 = self.get_new_cluster(None)?;
new_cluster = Some(new_addr);
self.l1_table[l1_index] = new_addr;
VecCache::new(self.l2_entries as usize)
} else {
VecCache::from_vec(Self::read_l2_cluster(&mut self.raw_file, l2_addr_disk)?)
};
let l1_table = &self.l1_table;
let raw_file = &mut self.raw_file;
self.l2_cache.insert(l1_index, l2_table, |index, evicted| {
raw_file.write_pointer_table(
l1_table[index],
evicted.get_values(),
CLUSTER_USED_FLAG,
)
})?;
}
Ok(new_cluster)
}
// 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.