Re: [Xen-devel] [PATCH v3 5/7] libxl: support unmapping static shared memory areas during domain destruction

[Zhongze Liu <blackskygg@xxxxxxxxx>]

Oops, The address lines were somehow dropped by my mail client.
Adding Wei.

2017-11-09 10:06 GMT+08:00 Zhongze Liu <blackskygg@xxxxxxxxx>:
> Hi Wei,
>
> 2017-11-01 23:55 GMT+08:00 Wei Liu <wei.liu2@xxxxxxxxxx>:
>> On Thu, Oct 19, 2017 at 10:36:33AM +0800, Zhongze Liu wrote:
>>> Add libxl__sshm_del to unmap static shared memory areas mapped by
>>> libxl__sshm_add during domain creation. The unmapping process is:
>>>
>>> * For a master: decrease the refcount of the sshm region, if the refcount
>>>   reaches 0, cleanup the whole sshm path.
>>> * For a slave: unmap the shared pages, and cleanup related xs entries.
>>>   decrease the refcount of the sshm region, if the refcount reaches 0,
>>>   cleanup the whole sshm path.
>>>
>>
>> This appears to be in line with what we discussed.
>>
>> I would like to see some explanation for: if one or more of the things
>> the code does fail half way, the system is still going to be in a
>> consistent state. Most notably, there isn't going to be any page leaked
>> with uncleaned refs.
>>
>
> The unmapping code is invoked during the domain destruction process, so
> we can't roll back. Everything done here is a "best effort": even if the code
> fails half way, what I could do is to report the errors and proceed anyway.
>
> I might be totally wrong. So please correct me.
>
>>> +
>>> +        rc = libxl__xs_transaction_commit(gc, &xt);
>>> +        if (!rc) break;
>>> +        if (rc < 0) goto out;
>>> +         isretry = true;
>>
>> Indentation.
>
> Cheers,
>
> Zhongze Liu

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