Re: [PATCH] mm,hwpoison: return -EBUSY when page already poisoned

[Aili Yao]

On Fri, 5 Mar 2021 15:55:25 +0000
"Luck, Tony" <tony.luck@xxxxxxxxx> wrote:

> > From the walk, it seems we have got the virtual address, can we just send a SIGBUS with it?  
> 
> If the walk wins the race and the pte for the poisoned page is still valid, then yes.
> 
> But we could have:
> 
> CPU1                            CPU2
> memory_failure sets poison
> bit for struct page
> 
> 
> rmap finds page in task
> on CPU2 and sets PTE
> to not-valid-poison
> 
>                                 memory_failure returns
>                                 early because struct page
>                                 already marked as poison
> 
>                                 walk page tables looking
>                                 for mapping - don't find it
> 
> -Tony

While I don't think there is a race condition, and if you really think the pfn with SIGBUS is not
proper, I think following patch maybe one way.
I copy your abandon code, and make a little modification, and just now it pass
my simple test.

And also this is a RFC version, only valid if you think the pfn with SIGBUS is not right.

Thanks!