On Fri, Mar 25, 2016 at 4:05 AM, Yan, Zheng <zyan@xxxxxxxxxx> wrote:
>
>> On Mar 24, 2016, at 21:55, Ilya Dryomov <idryomov@xxxxxxxxx> wrote:
>>
>> On Thu, Mar 24, 2016 at 2:18 PM, Yan, Zheng <zyan@xxxxxxxxxx> wrote:
>>>
>>>> On Mar 24, 2016, at 18:26, Ilya Dryomov <idryomov@xxxxxxxxx> wrote:
>>
>> [ snip ]
>>
>>>> TBH I still can't wrap my head around lockless layout/namespace pointer
>>>> updates and how that can ever work reliably…
>>>
>>> see Documentation/RCU/rcuref.txt. How RCU is used in my code is similar to the second example.
>>
>> It's the higher-level cephfs code and installing new namespaces in the
>> middle of whatever else that might be going on that I'm worried about.
>> See my other mail, I'd like to hear what exactly is being achieved with
>> this approach and have you considered reusing i_ceph_lock (or others,
>> of which there are plenty).
>
> Updating namespace pointer is protected by i_ceph_lock, For read
> access of the namespace, using i_ceph_lock does not provide any extra
> guarantee. This approach provides lockless access of namespace, it’s
> convenient for functions that do not know i_ceph_lock.
Could you name some of these functions?
Thanks,
Ilya
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