validation: add CChainState::m_disabled and ChainMan::isUsable

and remove m_snapshot_validated. This state can now be inferred by the
number of isUsable chainstates.

m_disabled is used to signal that a chainstate should no longer be used
by validation logic; it is used as a sentinel when background validation
completes or if the snapshot chainstate is found to be invalid.

isUsable is a convenience method that incorporates m_disabled.

1 files changed, 10 insertions, 9 deletions

diff --git a/src/validation.cpp b/src/validation.cpp
index 70ea99e6df..9b5875319e 100644
--- a/src/validation.cpp
+++ b/src/validation.cpp
@@ -4859,12 +4859,8 @@ std::vector<Chainstate*> ChainstateManager::GetAll()
     LOCK(::cs_main);
     std::vector<Chainstate*> out;
 
-    if (!IsSnapshotValidated() && m_ibd_chainstate) {
-        out.push_back(m_ibd_chainstate.get());
-    }
-
-    if (m_snapshot_chainstate) {
-        out.push_back(m_snapshot_chainstate.get());
+    for (Chainstate* cs : {m_ibd_chainstate.get(), m_snapshot_chainstate.get()}) {
+        if (this->IsUsable(cs)) out.push_back(cs);
     }
 
     return out;
@@ -5263,17 +5259,22 @@ bool ChainstateManager::IsSnapshotActive() const
 void ChainstateManager::MaybeRebalanceCaches()
 {
     AssertLockHeld(::cs_main);
-    if (m_ibd_chainstate && !m_snapshot_chainstate) {
+    bool ibd_usable = this->IsUsable(m_ibd_chainstate.get());
+    bool snapshot_usable = this->IsUsable(m_snapshot_chainstate.get());
+    assert(ibd_usable || snapshot_usable);
+
+    if (ibd_usable && !snapshot_usable) {
         LogPrintf("[snapshot] allocating all cache to the IBD chainstate\n");
         // Allocate everything to the IBD chainstate.
         m_ibd_chainstate->ResizeCoinsCaches(m_total_coinstip_cache, m_total_coinsdb_cache);
     }
-    else if (m_snapshot_chainstate && !m_ibd_chainstate) {
+    else if (snapshot_usable && !ibd_usable) {
+        // If background validation has completed and snapshot is our active chain...
         LogPrintf("[snapshot] allocating all cache to the snapshot chainstate\n");
         // Allocate everything to the snapshot chainstate.
         m_snapshot_chainstate->ResizeCoinsCaches(m_total_coinstip_cache, m_total_coinsdb_cache);
     }
-    else if (m_ibd_chainstate && m_snapshot_chainstate) {
+    else if (ibd_usable && snapshot_usable) {
         // If both chainstates exist, determine who needs more cache based on IBD status.
         //
         // Note: shrink caches first so that we don't inadvertently overwhelm available memory.