Note this is a modified backport that does not SAVE the new fields, but does load them. (#24074)

Original:
Start saving/loading prior_roots(_with_hash) to snapshot (#23844)

    * Start saving/loading prior_roots(_with_hash) to snapshot

    * Update runtime/src/accounts_index.rs

    Co-authored-by: Michael Vines <mvines@gmail.com>

    * Update runtime/src/accounts_index.rs

    Co-authored-by: Michael Vines <mvines@gmail.com>

    * update comment

    Co-authored-by: Michael Vines <mvines@gmail.com>
    (cherry picked from commit 396b49a7c1)

Co-authored-by: Jeff Washington (jwash) <wash678@gmail.com>

runtime/src/serde_snapshot.rs

@@ -23,6 +23,7 @@ use {
     solana_measure::measure::Measure,
     solana_sdk::{
         clock::{Epoch, Slot, UnixTimestamp},
+        deserialize_utils::default_on_eof,
         epoch_schedule::EpochSchedule,
         fee_calculator::{FeeCalculator, FeeRateGovernor},
         genesis_config::GenesisConfig,
@@ -67,6 +68,12 @@ struct AccountsDbFields<T>(
     StoredMetaWriteVersion,
     Slot,
     BankHashInfo,
+    /// all slots that were roots within the last epoch
+    #[serde(deserialize_with = "default_on_eof")]
+    Vec<Slot>,
+    /// slots that were roots within the last epoch for which we care about the hash value
+    #[serde(deserialize_with = "default_on_eof")]
+    Vec<(Slot, Hash)>,
 );
 
 /// Helper type to wrap BufReader streams when deserializing and reconstructing from either just a
@@ -86,9 +93,9 @@ struct SnapshotAccountsDbFields<T> {
 
 impl<T> SnapshotAccountsDbFields<T> {
     /// Collapse the SnapshotAccountsDbFields into a single AccountsDbFields.  If there is no
-    /// incremental snapshot, this returns the AccountsDbFields from the full snapshot.  Otherwise
+    /// incremental snapshot, this returns the AccountsDbFields from the full snapshot.
-    /// this uses the version, slot, and bank hash info from the incremental snapshot, then the
+    /// Otherwise, use the AccountsDbFields from the incremental snapshot, and a combination
-    /// combination of the storages from both the full and incremental snapshots.
+    /// of the storages from both the full and incremental snapshots.
     fn collapse_into(self) -> Result<AccountsDbFields<T>, Error> {
         match self.incremental_snapshot_accounts_db_fields {
             None => Ok(self.full_snapshot_accounts_db_fields),
@@ -97,6 +104,8 @@ impl<T> SnapshotAccountsDbFields<T> {
                 incremental_snapshot_version,
                 incremental_snapshot_slot,
                 incremental_snapshot_bank_hash_info,
+                incremental_snapshot_prior_roots,
+                incremental_snapshot_prior_roots_with_hash,
             )) => {
                 let full_snapshot_storages = self.full_snapshot_accounts_db_fields.0;
                 let full_snapshot_slot = self.full_snapshot_accounts_db_fields.2;
@@ -119,6 +128,8 @@ impl<T> SnapshotAccountsDbFields<T> {
                     incremental_snapshot_version,
                     incremental_snapshot_slot,
                     incremental_snapshot_bank_hash_info,
+                    incremental_snapshot_prior_roots,
+                    incremental_snapshot_prior_roots_with_hash,
                 ))
             }
         }
@@ -418,6 +429,8 @@ where
         snapshot_version,
         snapshot_slot,
         snapshot_bank_hash_info,
+        _snapshot_prior_roots,
+        _snapshot_prior_roots_with_hash,
     ) = snapshot_accounts_db_fields.collapse_into()?;
 
     let snapshot_storages = snapshot_storages.into_iter().collect::<Vec<_>>();

sdk/src/deserialize_utils.rs

@@ -12,6 +12,7 @@ where
     let result = T::deserialize(d);
     match result {
         Err(err) if err.to_string() == "io error: unexpected end of file" => Ok(T::default()),
+        Err(err) if err.to_string() == "io error: failed to fill whole buffer" => Ok(T::default()),
         result => result,
     }
 }