Rik van Riel wrote:

Hi,

Almost the same patch as before, except this one has had
a few hours of testing by Andrew Morton and two bugs have
been ironed out, most notably the truncate_complete_page()
race.  This patch is probably safe since Andrew got bored
when no new bugs showed up ...

The box died, but not due to rmap.  We have a lock ranking
bug:

        do_exit
        ->mmput
          ->exit_mmap                           page_table_lock
            ->removed_shared_vm_struct
              ->lock_vma_mappings               i_shared_lock

versus

        do_truncate
        ->notify_change
          ->inode_setattr
            ->vmtruncate                        i_shared_lock
              ->vmtruncate_list
                ->zap_page_range                page_table_lock

It seems that in 2.5.16, a call to remove_shared_vm_struct() was
added to exit_mmap(), inside mm->page_table_lock.

That ranking conflicts with truncate.

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