closes[t:2542] Fix bug in loader: need to hold ydb lock around pre_acquire_table lock

Let LOADER_USE_PUTS trigger #2440 optimization.  DB_PRELOCKED_WRITE in loader flags prevents pre_acquire_table_lock from being called

git-svn-id: file:///svn/toku/tokudb@19586 c7de825b-a66e-492c-adef-691d508d4ae1

src/loader.c

@@ -160,20 +160,22 @@ int toku_loader_create_loader(DB_ENV *env,
     loader->close                  = toku_loader_close;
     loader->abort                  = toku_loader_abort;
 
-    int r;
+    int r = 0;
     // lock tables and check empty
     for(int i=0;i<N;i++) {
-        r = toku_db_pre_acquire_table_lock(dbs[i], txn, TRUE);
-        if ( r!=0 ) {
-            free_loader(loader);
-            return -1;
+        if (!(loader_flags&DB_PRELOCKED_WRITE)) {
+            toku_ydb_lock(); //Must hold ydb lock for pre_acquire
+            r = toku_db_pre_acquire_table_lock(dbs[i], txn, FALSE);
+            toku_ydb_unlock();
+            if (r!=0) break;
         }
         r = verify_empty(dbs[i], txn);
+        if (r!=0) break;
+    }
     if ( r!=0 ) {
         free_loader(loader);
         return -1;
     }
-    }
 
     brt_compare_func compare_functions[N];
     for (int i=0; i<N; i++) {

src/ydb.c

@@ -5053,7 +5053,7 @@ int toku_db_pre_acquire_table_lock(DB *db, DB_TXN *txn, BOOL just_lock) {
         DB *dbs[1] = {db};
         uint32_t db_flags[1]  = {DB_NOOVERWRITE};
         uint32_t dbt_flags[1] = {0};
-        uint32_t loader_flags = 0;
+        uint32_t loader_flags = DB_PRELOCKED_WRITE; //Don't recursively prelock
         DB_ENV *env = db->dbenv;
 
         toku_ydb_unlock(); //Cannot hold ydb lock when creating loader