Re: Race between vmtruncate and mapped areas?

[Andrew Morton]

Dave McCracken <[e-mail]> wrote:
>
> Actually it does fix it.  I added code in vmtruncate_list() to do a
>  down_write(&vma->vm_mm->mmap_sem) around the zap_page_range(), and the
>  problem went away.  It serializes against any outstanding page faults on a
>  particular page table.  New faults will see that the page is no longer in
>  the file and fail with SIGBUS.  Andrew's test case stopped failing.
> 
>  I've attached the patch so you can see what I did.
> 
>  Can anyone think of any gotchas to this solution?

mmap_sem nests outside i_shared_sem.