Re: [PATCH 2/2] mm: ksm: Support hwpoison for ksm page

[xialonglong <xialonglong1@huawei.com>]

Thank you very much for your reply. Your suggestion is indeed very 
helpful and I will take some time to consider how to implement it. Once 
I have a clear plan, I will send a separate patch to make it happen.

Best regards,
Longlong Xia
在 2023/3/31 13:42, HORIGUCHI NAOYA(堀口 直也) 写道:
> On Thu, Mar 30, 2023 at 03:45:01PM +0800, Longlong Xia wrote:
>> hwpoison_user_mappings() is updated to support ksm pages, and add
>> collect_procs_ksm() to collect processes when the error hit an ksm
>> page. The difference from collect_procs_anon() is that it also needs
>> to traverse the rmap-item list on the stable node of the ksm page.
>> At the same time, add_to_kill_ksm() is added to handle ksm pages. And
>> task_in_to_kill_list() is added to avoid duplicate addition of tsk to
>> the to_kill list. This is because when scanning the list, if the pages
>> that make up the ksm page all come from the same process, they may be
>> added repeatedly.
>>
>> Signed-off-by: Longlong Xia <xialonglong1@huawei.com>
> 
> I don't find any specific issue by code review for now, so I'll try to
> test your patches.
> 
> I have one comment about duplicated KSM pages.  It seems that KSM controls
> page duplication by limiting deduplication factor with max_page_sharing,
> primarily for performance reason.  But I think it's imporant from memory
> RAS's viewpoint too because that means we could allow recovery from memory
> errors on a KSM page by making affected processes to switch to the duplicated
> pages (without killing the processes!).  Maybe this might be beyond the scope
> of this patchset and I'm not sure how hard it is, but if you are interested
> in this issue, that's really nice.
> 
> Thanks,
> Naoya Horiguchi