Uses file io as default method to access account storages (#4365)

Author: brooksprumo

CHANGELOG.md

@@ -17,7 +17,7 @@ Release channels have their own copy of this changelog:
 * Changes
   * CLI:
     * Add global `--skip-preflight` option for skipping preflight checks on all transactions sent through RPC. This flag, along with `--use-rpc`, can improve success rate with program deployments using the public RPC nodes.
-  * Unhide `--accounts-db-access-storages-method` for agave-validator and agave-ledger-tool
+  * Unhide `--accounts-db-access-storages-method` for agave-validator and agave-ledger-tool and change default to `file`
   * Remove tracer stats from banking-trace. `banking-trace` directory should be cleared when restarting on v2.2 for first time. It will not break if not cleared, but the file will be a mix of new/old format. (#4043)
 
 ## [2.1.0]

accounts-db/src/accounts_db.rs

@@ -511,7 +511,7 @@ pub const ACCOUNTS_DB_CONFIG_FOR_TESTING: AccountsDbConfig = AccountsDbConfig {
     create_ancient_storage: CreateAncientStorage::Pack,
     partitioned_epoch_rewards_config: DEFAULT_PARTITIONED_EPOCH_REWARDS_CONFIG,
     test_skip_rewrites_but_include_in_bank_hash: false,
-    storage_access: StorageAccess::Mmap,
+    storage_access: StorageAccess::File,
     scan_filter_for_shrinking: ScanFilter::OnlyAbnormalWithVerify,
     enable_experimental_accumulator_hash: false,
     verify_experimental_accumulator_hash: false,
@@ -538,7 +538,7 @@ pub const ACCOUNTS_DB_CONFIG_FOR_BENCHMARKS: AccountsDbConfig = AccountsDbConfig
     create_ancient_storage: CreateAncientStorage::Pack,
     partitioned_epoch_rewards_config: DEFAULT_PARTITIONED_EPOCH_REWARDS_CONFIG,
     test_skip_rewrites_but_include_in_bank_hash: false,
-    storage_access: StorageAccess::Mmap,
+    storage_access: StorageAccess::File,
     scan_filter_for_shrinking: ScanFilter::OnlyAbnormalWithVerify,
     enable_experimental_accumulator_hash: false,
     verify_experimental_accumulator_hash: false,

accounts-db/src/accounts_file.rs

@@ -50,10 +50,11 @@ pub enum MatchAccountOwnerError {
 
 #[derive(Debug, Default, Clone, Copy, PartialEq, Eq)]
 pub enum StorageAccess {
-    #[default]
     /// storages should be accessed by Mmap
     Mmap,
+    /// storages should be accessed by File I/O
     /// ancient storages are created by 1-shot write to pack multiple accounts together more efficiently with new formats
+    #[default]
     File,
 }