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

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Message-ID: <20220713115401.GA2824071@hori.linux.bs1.fc.nec.co.jp>
Date:   Wed, 13 Jul 2022 11:54:02 +0000
From:   HORIGUCHI NAOYA(堀口　直也) 
        <naoya.horiguchi@....com>
To:     Miaohe Lin <linmiaohe@...wei.com>
CC:     Naoya Horiguchi <naoya.horiguchi@...ux.dev>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        David Hildenbrand <david@...hat.com>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Liu Shixin <liushixin2@...wei.com>,
        Yang Shi <shy828301@...il.com>,
        Oscar Salvador <osalvador@...e.de>,
        Muchun Song <songmuchun@...edance.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [mm-unstable PATCH v6 4/8] mm, hwpoison: make unpoison aware of
 raw error info in hwpoisoned hugepage

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@....com>
> > 
> > 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@....com>
> > Reported-by: kernel test robot <lkp@...el.com>
> 
> 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@...wei.com>

Thank you.
- Naoya Horiguchi

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