linux-kernel - Re: [mm-unstable PATCH v4 5/9] mm, hwpoison: make unpoison aware of raw error info in hwpoisoned hugepage

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Date:   Wed, 6 Jul 2022 23:06:28 +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 v4 5/9] mm, hwpoison: make unpoison aware of
 raw error info in hwpoisoned hugepage

On Wed, Jul 06, 2022 at 10:58:53AM +0800, Miaohe Lin wrote:
> On 2022/7/4 9:33, 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.
> > 
> > Signed-off-by: Naoya Horiguchi <naoya.horiguchi@....com>
> > ---
> > @@ -2287,6 +2301,7 @@ int unpoison_memory(unsigned long pfn)
> 
> Is it safe to unpoison hugepage when HPageRawHwpUnreliable? I'm afraid because
> some raw error info is missing..

Ah, right. We need prevent it.  I'll fix it by inserting the check.

 static inline long free_raw_hwp_pages(struct page *hpage, bool move_flag)
 {
         struct llist_head *head;
         struct llist_node *t, *tnode;
         long count = 0;
 
+        if (!HPageRawHwpUnreliable(hpage))
+                return 0;

Thanks,
Naoya Horiguchi

> Thanks.
> 
> >  	struct page *p;
> >  	int ret = -EBUSY;
> >  	int freeit = 0;
> > +	long count = 1;
> >  	static DEFINE_RATELIMIT_STATE(unpoison_rs, DEFAULT_RATELIMIT_INTERVAL,
> >  					DEFAULT_RATELIMIT_BURST);
> >  
> > @@ -2334,6 +2349,8 @@ int unpoison_memory(unsigned long pfn)
> >  
> >  	ret = get_hwpoison_page(p, MF_UNPOISON);
> >  	if (!ret) {
> > +		if (PageHuge(p))
> > +			count = free_raw_hwp_pages(page, false);
> >  		ret = TestClearPageHWPoison(page) ? 0 : -EBUSY;
> >  	} else if (ret < 0) {
> >  		if (ret == -EHWPOISON) {
> > @@ -2342,6 +2359,8 @@ int unpoison_memory(unsigned long pfn)
> >  			unpoison_pr_info("Unpoison: failed to grab page %#lx\n",
> >  					 pfn, &unpoison_rs);
> >  	} else {
> > +		if (PageHuge(p))
> > +			count = free_raw_hwp_pages(page, false);
> >  		freeit = !!TestClearPageHWPoison(p);
> >  
> >  		put_page(page);
> > @@ -2354,7 +2373,7 @@ int unpoison_memory(unsigned long pfn)
> >  unlock_mutex:
> >  	mutex_unlock(&mf_mutex);
> >  	if (!ret || freeit) {
> > -		num_poisoned_pages_dec();
> > +		num_poisoned_pages_sub(count);
> >  		unpoison_pr_info("Unpoison: Software-unpoisoned page %#lx\n",
> >  				 page_to_pfn(p), &unpoison_rs);
> >  	}
> >