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:   Thu, 7 Jul 2022 11:08:02 +0800
From:   Miaohe Lin <linmiaohe@...wei.com>
To:     HORIGUCHI NAOYA(堀口 直也) 
        <naoya.horiguchi@....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 2022/7/7 9:35, HORIGUCHI NAOYA(堀口 直也) wrote:
> On Wed, Jul 06, 2022 at 11:06:28PM +0000, HORIGUCHI NAOYA(堀口 直也) wrote:
>> 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;

IIUC, even if we return 0 here, the caller will still do TestClearPageHWPoison(please see below
code diff) and succeeds to unpoison the page. Or am I miss something?

@@ -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) {

> 
> No, I meant "if (HPageRawHwpUnreliable(hpage))", sorry for the noise :(

No, thanks for your hard work!

> 
> - Naoya Horiguchi

Thanks.

>