On 2019/9/9 22:59, Al Viro wrote:
> On Mon, Sep 09, 2019 at 10:10:00PM +0800, zhengbin (A) wrote:
>
> Hmm... So your theory is that what you are seeing is the insertion
> into the list done by list_add() exposing an earlier ->next pointer
> to those who might be doing lockless walk through the list.
> Potentially up to the last barrier done before the list_add()...
>
>> We can solute it in 2 ways:
>>
>> 1. add a smp_wmb between __d_alloc and list_add(&dentry->d_child, &parent->d_subdirs)
>> 2. revert commit ebaaa80e8f20 ("lockless next_positive()")
> I want to take another look at the ->d_subdirs/->d_child readers...
> I agree that the above sounds plausible, but I really want to be
> sure about the exclusion we have for those accesses.
>
> I'm not sure that smp_wmb() alone would suffice, BTW - the reader side
> loop would need to be careful as well.
>
> Which architecture it was, again? arm64?
arm64
>
> .
>
