Re: [PATCH v2] xen/balloon: Don't continue ballooning when BP_ECANCELED is encountered

[Boris Ostrovsky <boris.ostrovsky@oracle.com>]

On 10/09/2014 01:17 PM, David Vrabel wrote:
> On 07/10/14 22:00, Boris Ostrovsky wrote:
>> Commit 3dcf63677d4e ("xen/balloon: cancel ballooning if adding new
>> memory failed") makes reserve_additional_memory() return BP_ECANCELED
>> when an error is encountered. This error, however, is ignored by the
>> caller (balloon_process()) since it is overwritten by subsequent call
>> to update_schedule(). This results in continuous attempts to add more
>> memory, all of which are likely to fail again.
>>
>> We should stop trying to schedule next iteration of ballooning when
>> the current one has failed.
> What triggers this bug?  I could never work out what it was.

I don't know, I haven't been able to reproduce it neither. It's clearly 
something in AWS.

But once you hit it (which you can do by simulating add_memory() return 
an error) you will keep retrying, getting the same error back and 
flooding the log.

-boris

>
> Applied to stable/for-linus-3.18
>
> David