Optimize mutex usage.

storage/maria/ma_blockrec.c:
  Unlock bitmaps earlier (no reason to have them unlocked over _ma_write_clr())
storage/maria/ma_extra.c:
  Don't lock THR_LOCK_maria for HA_EXTRA_PREPARE_FOR_RENAME (upper level ensures that we are not opening the same table during this call)
  We don't need to have share->intern_lock locked over _ma_flush_table_files()
storage/maria/ma_open.c:
  Update comment

storage/maria/ma_blockrec.c

@@ -3643,6 +3643,7 @@ my_bool _ma_write_abort_block_record(MARIA_HA *info)
       }
     }
   }
+  _ma_bitmap_unlock(share);
   if (share->now_transactional)
   {
     if (_ma_write_clr(info, info->cur_row.orig_undo_lsn,
@@ -3652,7 +3653,6 @@ my_bool _ma_write_abort_block_record(MARIA_HA *info)
                       &lsn, (void*) 0))
       res= 1;
   }
-  _ma_bitmap_unlock(share);
   _ma_unpin_all_pages_and_finalize_row(info, lsn);
   DBUG_RETURN(res);
 }

storage/maria/ma_extra.c

@@ -319,7 +319,6 @@ int maria_extra(MARIA_HA *info, enum ha_extra_function function,
     my_bool do_flush= test(function != HA_EXTRA_PREPARE_FOR_DROP);
     my_bool save_global_changed;
     enum flush_type type;
-    pthread_mutex_lock(&THR_LOCK_maria);
     /*
       This share, to have last_version=0, needs to save all its data/index
       blocks to disk if this is not for a DROP TABLE. Otherwise they would be
@@ -353,12 +352,14 @@ int maria_extra(MARIA_HA *info, enum ha_extra_function function,
     type= do_flush ? FLUSH_RELEASE : FLUSH_IGNORE_CHANGED;
     save_global_changed= share->global_changed;
     share->global_changed= 1;                 /* Don't increment open count */
+    pthread_mutex_unlock(&share->intern_lock);
     if (_ma_flush_table_files(info, MARIA_FLUSH_DATA | MARIA_FLUSH_INDEX,
                               type, type))
     {
       error=my_errno;
       share->changed= 1;
     }
+    pthread_mutex_lock(&share->intern_lock);
     share->global_changed= save_global_changed;
     if (info->opt_flag & (READ_CACHE_USED | WRITE_CACHE_USED))
     {
@@ -395,10 +396,9 @@ int maria_extra(MARIA_HA *info, enum ha_extra_function function,
         error= my_errno;
       share->bitmap.changed_not_flushed= 0;
     }
-    /* For protection against Checkpoint, we set under intern_lock: */
+    /* last_version must be protected by intern_lock; See collect_tables() */
     share->last_version= 0L;			/* Impossible version */
     pthread_mutex_unlock(&share->intern_lock);
-    pthread_mutex_unlock(&THR_LOCK_maria);
     break;
   }
   case HA_EXTRA_PREPARE_FOR_FORCED_CLOSE:

storage/maria/ma_open.c

@@ -922,7 +922,7 @@ MARIA_HA *maria_open(const char *name, int mode, uint open_flags)
     {
       /*
         We must have internal_lock before bitmap_lock because we call
-        _ma_flush_tables_files() with internal_lock locked.
+        _ma_flush_table_files() with internal_lock locked.
       */
       pthread_mutex_lock(&share->intern_lock);
       pthread_mutex_lock(&share->bitmap.bitmap_lock);