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Message-ID: <3D268E19.B68559F6@zip.com.au>
Date: Fri, 05 Jul 2002 23:28:41 -0700
From: Andrew Morton <akpm@zip.com.au>
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To: Rik van Riel <riel@conectiva.com.br>
CC: linux-kernel@vger.kernel.org, linux-mm@kvack.org,
       Linus Torvalds <torvalds@transmeta.com>
Subject: Re: [PATCH][RFT](2) minimal rmap for 2.5 - akpm tested
References: <Pine.LNX.4.44L.0207060228460.8346-100000@imladris.surriel.com>
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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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