.

wcfs/wcfs.go

@@ -82,7 +82,7 @@
 // where /bigfile/<bigfileX> represent bigfile data as of revision <revX>.
 //
 // Unless accessed {head,@<revX>}/bigfile/<bigfileX> are not automatically visible in
-// wcfs filesystem. Similarly @<revX>/ become visible only after accessed.
+// wcfs filesystem. Similarly @<revX>/ become visible only after access.
 //
 //
 // Invalidation protocol
@@ -244,18 +244,16 @@ package main
 // 2) head/bigfile/* of all bigfiles represent state as of zhead.At .
 // 3) for head/bigfile/* the following invariant is maintained:
 //
-//	#blk ∈ OS file cache    =>    ZBlk(#blk) + all BTree/Bucket that lead to it  ∈ zhead cache
-//	                              (ZBlk* in ghost state(%))
+//	#blk ∈ OS file cache    =>    ZBlk(#blk) + all BTree/Bucket that lead to it  ∈ zhead cache(%)
 //
 //    The invariant helps on invalidation: if we see a changed oid, and
 //    zhead.cache.lookup(oid) = ø -> we know we don't have to invalidate OS
 //    cache for any part of any file (even if oid relates to a file block - that
 //    block is not cached and will trigger ZODB load on file read).
 //
-//    Currently we maintain this invariant by simply never evicting LOBTree/LOBucket
-//    objects from ZODB Connection cache (LOBucket keeps references to ZBlk* and
-//    so ZBlk* also stay in cache in ghost form). In the future we may want to
-//    try to synchronize to kernel freeing its pagecache pages.
+//    Currently we maintain this invariant by simply never evicting ZBlk/LOBTree/LOBucket
+//    objects from ZODB Connection cache. In the future we may want to try to
+//    synchronize to kernel freeing its pagecache pages.
 //
 // 4) when we receive an invalidation message from ZODB - we process it and
 //    propagate invalidations to OS file cache of head/bigfile/*:
@@ -545,11 +543,11 @@ func (cc *zodbCacheControl) WantEvict(obj zodb.IPersistent) bool {
 	default:
 		return true
 
+	case *ZBlk0:
+	case *ZBlk1:
 	case *btree.LOBTree:
 	case *btree.LOBucket:
 
-	// ZBlk* are kept referenced by a LOBucket, so they don't go away from Connection.cache.objtab
-
 	// FIXME we need to keep ZBigFile in cache: even if we keep a pointer
 	// to ZBigFile, but it is allowed to drop its state, it will release
 	// pointer to LOBTree object and, consequently, that LOBTree object,