Re: memrlimit controller merge to mainline

[Balbir Singh <balbir-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org>]

Hugh Dickins wrote:
> On Fri, 25 Jul 2008, Balbir Singh wrote:
>> I'll try and recreate the problem and fix it. If memrlimit_cgroup_uncharge_as()
>> created the problem, it's most likely related to mm->owner not being correct and
>> we are dereferencing the wrong memory.
>>
>> Thanks for the bug report, I'll look further.
> 
> Good luck!  I have only seen it once, on a dual-core laptop; though
> I don't remember to try swapoff while busy as often as I should (be
> sure to alternate between a couple or more of swapareas, so you can
> swap a new one on just before swapping an old one off, to be pretty
> sure of success).
> 

Thanks, that's very useful information. I would have never tried juggling swap
devices otherwise.

> May be easier to find in the source: my suspicion is that a bad
> mm_users assumption will come into it.  But I realize now that it
> could be entirely unrelated to memrlimit, just that uncharge_as
> was the one to get hit by bad refcounting elsewhere.
> 
> Oh, that reminds me, I never reported back on my res_counter warnings
> at shutdown: never saw them again, once I added in the set of changes
> you came up with shortly after that - thanks.
> 

I am glad those messages are gone, thanks for the bug report. I find bug fixing
more exciting that kernel development on most occasions.


-- 
	Warm Regards,
	Balbir Singh
	Linux Technology Center
	IBM, ISTL