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Re: [patch for-4.7] mm, compaction: prevent VM_BUG_ON when terminating freeing scanner

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On Wed, Jun 29, 2016 at 02:47:20PM -0700, David Rientjes wrote:
> It's possible to isolate some freepages in a pageblock and then fail 
> split_free_page() due to the low watermark check.  In this case, we hit 
> VM_BUG_ON() because the freeing scanner terminated early without a 
> contended lock or enough freepages.
> 
> This should never have been a VM_BUG_ON() since it's not a fatal 
> condition.  It should have been a VM_WARN_ON() at best, or even handled 
> gracefully.
> 
> Regardless, we need to terminate anytime the full pageblock scan was not 
> done.  The logic belongs in isolate_freepages_block(), so handle its state
> gracefully by terminating the pageblock loop and making a note to restart 
> at the same pageblock next time since it was not possible to complete the 
> scan this time.
> 
> Reported-by: Minchan Kim <minchan@kernel.org>
> Signed-off-by: David Rientjes <rientjes@google.com>
Tested-by: Minchan Kim <minchan@kernel.org>

I don't know you sill send updated version based on Joonsoo again.
Anyway, this patch itself doesn't trigger VM_BUG_ON in my test. 

Thanks.

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[patch for-4.7] mm, compaction: prevent VM_BUG_ON when terminating  freeing scanner David Rientjes <rientjes@google.com> - 2016-06-30 00:00 +0200
  Re: [patch for-4.7] mm, compaction: prevent VM_BUG_ON when  terminating freeing scanner Greg KH <greg@kroah.com> - 2016-06-30 00:50 +0200
  Re: [patch for-4.7] mm, compaction: prevent VM_BUG_ON when  terminating freeing scanner Vlastimil Babka <vbabka@suse.cz> - 2016-06-30 09:20 +0200
    Re: [patch for-4.7] mm, compaction: prevent VM_BUG_ON when terminating  freeing scanner David Rientjes <rientjes@google.com> - 2016-07-05 23:10 +0200
      Re: [patch for-4.7] mm, compaction: prevent VM_BUG_ON when  terminating freeing scanner Vlastimil Babka <vbabka@suse.cz> - 2016-07-05 23:40 +0200
      Re: [patch for-4.7] mm, compaction: prevent VM_BUG_ON when  terminating freeing scanner Joonsoo Kim <iamjoonsoo.kim@lge.com> - 2016-07-06 03:40 +0200
        Re: [patch for-4.7] mm, compaction: prevent VM_BUG_ON when  terminating freeing scanner Minchan Kim <minchan@kernel.org> - 2016-07-06 04:00 +0200
  Re: [patch for-4.7] mm, compaction: prevent VM_BUG_ON when  terminating freeing scanner Joonsoo Kim <iamjoonsoo.kim@lge.com> - 2016-07-06 03:40 +0200
  Re: [patch for-4.7] mm, compaction: prevent VM_BUG_ON when  terminating freeing scanner Minchan Kim <minchan@kernel.org> - 2016-07-06 08:50 +0200

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