Re: [mm-unstable PATCH v6 4/8] mm, hwpoison: make unpoison aware of raw error info in hwpoisoned hugepage

[HORIGUCHI NAOYA(堀口 直也)]

On Wed, Jul 13, 2022 at 12:24:46PM +0800, Miaohe Lin wrote:
> On 2022/7/12 11:28, Naoya Horiguchi wrote:
> > From: Naoya Horiguchi <naoya.horiguchi@xxxxxxx>
> > 
> > Raw error info list needs to be removed when hwpoisoned hugetlb is
> > unpoisoned.  And unpoison handler needs to know how many errors there
> > are in the target hugepage. So add them.
> > 
> > HPageVmemmapOptimized(hpage) and HPageRawHwpUnreliable(hpage)) can't be
> > unpoisoned, so let's skip them.
> > 
> > Signed-off-by: Naoya Horiguchi <naoya.horiguchi@xxxxxxx>
> > Reported-by: kernel test robot <lkp@xxxxxxxxx>
> 
> This patch looks good to me with some nits below.
> 
> > ---
> ...
> >  
> > -void hugetlb_clear_page_hwpoison(struct page *hpage)
> > +static unsigned long free_raw_hwp_pages(struct page *hpage, bool move_flag)
> >  {
> >  	struct llist_head *head;
> >  	struct llist_node *t, *tnode;
> > +	unsigned long count = 0;
> >  
> > -	if (!HPageRawHwpUnreliable(hpage))
> > -		ClearPageHWPoison(hpage);
> > +	/*
> > +	 * HPageVmemmapOptimized hugepages can't be unpoisoned because
> > +	 * struct pages for tail pages are required to free hwpoisoned
> > +	 * hugepages.  HPageRawHwpUnreliable hugepages shouldn't be
> > +	 * unpoisoned by definition.
> > +	 */
> > +	if (HPageVmemmapOptimized(hpage) || HPageRawHwpUnreliable(hpage))
> 
> If move_flag == false, i.e. in unpoison case, tail pages are not touched. So HPageVmemmapOptimized
> can be ignored in this case? Or leave it as above to keep the code simple?

Oh, right.  We can make HPageVmemmapOptimized() more conditional.

> 
> > +		return 0;
> >  	head = raw_hwp_list_head(hpage);
> >  	llist_for_each_safe(tnode, t, head->first) {
> >  		struct raw_hwp_page *p = container_of(tnode, struct raw_hwp_page, node);
> >  
> > -		SetPageHWPoison(p->page);
> > +		if (move_flag)
> > +			SetPageHWPoison(p->page);
> >  		kfree(p);
> > +		count++;
> >  	}
> >  	llist_del_all(head);
> > +	return count;
> > +}
> > +
> > +void hugetlb_clear_page_hwpoison(struct page *hpage)
> > +{
> > +	if (!HPageRawHwpUnreliable(hpage))
> 
> It seems we can return here if HPageRawHwpUnreliable as there's nothing to do?

OK, I'll update this, too.

> 
> Anyway, for what it worth,
> 
> Reviewed-by: Miaohe Lin <linmiaohe@xxxxxxxxxx>

Thank you.
- Naoya Horiguchi

> 
> Thanks.
> 
> > +		ClearPageHWPoison(hpage);
> > +	free_raw_hwp_pages(hpage, true);
> >  }
> >  
> >  /*