[RFC] probably bug in current ext3/jbd

[Alex Tomas]

hi!

ext3/jbd use b_committed_data buffer in order to prevent
allocation of blocks which were freed in non-committed
transaction. I think there is bug in this code. look,

some thread                               commit thread
----------------------------------------------------------
get_undo_access(#1)
dirty_buffer(#1)
stop_journal()

                                           start commit

start_journal()
get_undo_access(#1):
   1) wait for #1 to be
      in t_forget_list

                                           write #1 to log
                                           put #1 onto t_forget_list

   2) b_commit_data exists,
      finish get_undo_access()

                                           for_each_bh_in_forget_list() {
                                              if (jh->b_committed_data) {
                                                  kfree(jh->b_committed_data);
                                                  jh->b_committed_data = NULL;
                                              }
                                           }

                                           
/* using of b_committed_data */

b_committed_data is NULL ?

with best regards, Alex