[pbs-devel] [PATCH v2 proxmox-backup 3/4] garbage collection: bypass cache if gc-cache-capacity is 0

[Christian Ebner]

Since commit 1e7639bf ("fixup minimum lru capacity") the LRU cache
capacity is set to a minimum value of 1 to avoid issues with the edge
case of 0 capacity.

In commit f1a711c8 ("garbage collection: set phase1 LRU cache
capacity by tuning option") this was not taken into account, allowing
to set values in the range [0, 8*1024*1024] via the datastores tuning
parameters.

Bypass the cache by making it optional and do not use it if the cache
capacity is set to 0, which implies it being disabled.

Signed-off-by: Christian Ebner <c.ebner at proxmox.com>
---
changes since version 1:
- not present in previous version

 pbs-datastore/src/datastore.rs | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/pbs-datastore/src/datastore.rs b/pbs-datastore/src/datastore.rs
index cbf78ecb6..dbff84bf3 100644
--- a/pbs-datastore/src/datastore.rs
+++ b/pbs-datastore/src/datastore.rs
@@ -1072,7 +1072,7 @@ impl DataStore {
         &self,
         index: Box<dyn IndexFile>,
         file_name: &Path, // only used for error reporting
-        chunk_lru_cache: &mut LruCache<[u8; 32], ()>,
+        chunk_lru_cache: &mut Option<LruCache<[u8; 32], ()>>,
         status: &mut GarbageCollectionStatus,
         worker: &dyn WorkerTaskContext,
     ) -> Result<(), Error> {
@@ -1085,8 +1085,10 @@ impl DataStore {
             let digest = index.index_digest(pos).unwrap();
 
             // Avoid multiple expensive atime updates by utimensat
-            if chunk_lru_cache.insert(*digest, ()) {
-                continue;
+            if let Some(chunk_lru_cache) = chunk_lru_cache {
+                if chunk_lru_cache.insert(*digest, ()) {
+                    continue;
+                }
             }
 
             if !self.inner.chunk_store.cond_touch_chunk(digest, false)? {
@@ -1130,7 +1132,11 @@ impl DataStore {
         let mut unprocessed_index_list = self.list_index_files()?;
         let mut index_count = unprocessed_index_list.len();
 
-        let mut chunk_lru_cache = LruCache::new(cache_capacity);
+        let mut chunk_lru_cache = if cache_capacity > 0 {
+            Some(LruCache::new(cache_capacity))
+        } else {
+            None
+        };
         let mut processed_index_files = 0;
         let mut last_percentage: usize = 0;
 
-- 
2.39.5