MDEV-30209 Race condition between fil_node_open_file() and renaming files

mtr_t::commit_file(): Protect the rename operation with fil_system.mutex like we used to do before commit 2e43af6 in order to prevent fil_node_open_file() from running concurrently. In other words, fil_system.mutex will protect the consistency of fil_node_t::name and the file name in the file system. This race condition should be very hard to trigger. We would need a low value of innodb_open_files or table_cache limit so that fil_space_t::try_to_close() will be invoked frequently. Simultaneously with a RENAME operation, something (such as a write of a data page) would have to try to open the file.

Author: dr-m

storage/innobase/mtr/mtr0mtr.cc

@@ -385,15 +385,15 @@ bool mtr_t::commit_file(fil_space_t &space, const char *name)
 
  if (name)
  {
+ char *new_name= mem_strdup(name);
+ mysql_mutex_lock(&fil_system.mutex);
  success= os_file_rename(innodb_data_file_key, old_name, name);
-
  if (success)
- {
- mysql_mutex_lock(&fil_system.mutex);
- space.chain.start->name= mem_strdup(name);
- mysql_mutex_unlock(&fil_system.mutex);
- ut_free(old_name);
- }
+ space.chain.start->name= new_name;
+ else
+ old_name= new_name;
+ mysql_mutex_unlock(&fil_system.mutex);
+ ut_free(old_name);
  }
  else
  {