linux-kernel - Re: [PATCH -rc7] mm/huge_memory: mark huge_zero

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Message-Id: <20240514141439.55fba39c81c1af55c9a100e1@linux-foundation.org>
Date: Tue, 14 May 2024 14:14:39 -0700
From: Andrew Morton <akpm@...ux-foundation.org>
To: Miaohe Lin <linmiaohe@...wei.com>
Cc: <shy828301@...il.com>, <nao.horiguchi@...il.com>,
 <xuyu@...ux.alibaba.com>, <linux-mm@...ck.org>,
 <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH -rc7] mm/huge_memory: mark huge_zero_page reserved

On Sat, 11 May 2024 11:54:35 +0800 Miaohe Lin <linmiaohe@...wei.com> wrote:

> When I did memory failure tests recently, below panic occurs:
> 
>  kernel BUG at include/linux/mm.h:1135!
>  invalid opcode: 0000 [#1] PREEMPT SMP NOPTI
>  CPU: 9 PID: 137 Comm: kswapd1 Not tainted 6.9.0-rc4-00491-gd5ce28f156fe-dirty #14
>
> ...
>
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -208,6 +208,7 @@ static bool get_huge_zero_page(void)
>  		__free_pages(zero_page, compound_order(zero_page));
>  		goto retry;
>  	}
> +	__SetPageReserved(zero_page);
>  	WRITE_ONCE(huge_zero_pfn, page_to_pfn(zero_page));
>  
>  	/* We take additional reference here. It will be put back by shrinker */
> @@ -260,6 +261,7 @@ static unsigned long shrink_huge_zero_page_scan(struct shrinker *shrink,
>  		struct page *zero_page = xchg(&huge_zero_page, NULL);
>  		BUG_ON(zero_page == NULL);
>  		WRITE_ONCE(huge_zero_pfn, ~0UL);
> +		__ClearPageReserved(zero_page);
>  		__free_pages(zero_page, compound_order(zero_page));
>  		return HPAGE_PMD_NR;
>  	}

This causes a bit of a mess when staged ahead of mm-stable.  So to
avoid disruption I staged it behind mm-stable.  This means that when
the -stable maintainers try to merge it, they will ask for a fixed up
version for older kernels so you can please just send them this
version.

To facilitate this I added the below adjustment:

(btw, shouldn't get_huge_zero_page() and shrink_huge_zero_page_scan()
be renamed to *_folio_*?)


From: Andrew Morton <akpm@...ux-foundation.org>
Subject: mm-huge_memory-mark-huge_zero_page-reserved-fix
Date: Tue May 14 01:53:37 PM PDT 2024

Update it for 5691753d73a2 ("mm: convert huge_zero_page to huge_zero_folio")

Cc: Matthew Wilcox (Oracle) <willy@...radead.org>
Cc: David Hildenbrand <david@...hat.com>
Cc: Miaohe Lin <linmiaohe@...wei.com>
Cc: Naoya Horiguchi <nao.horiguchi@...il.com>
Cc: Xu Yu <xuyu@...ux.alibaba.com>
Cc: Yang Shi <shy828301@...il.com>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
---

 mm/huge_memory.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/mm/huge_memory.c~mm-huge_memory-mark-huge_zero_page-reserved-fix
+++ a/mm/huge_memory.c
@@ -212,7 +212,7 @@ retry:
 		folio_put(zero_folio);
 		goto retry;
 	}
-	__SetPageReserved(zero_page);
+	__folio_set_reserved(zero_folio);
 	WRITE_ONCE(huge_zero_pfn, folio_pfn(zero_folio));
 
 	/* We take additional reference here. It will be put back by shrinker */
@@ -265,7 +265,7 @@ static unsigned long shrink_huge_zero_pa
 		struct folio *zero_folio = xchg(&huge_zero_folio, NULL);
 		BUG_ON(zero_folio == NULL);
 		WRITE_ONCE(huge_zero_pfn, ~0UL);
-		__ClearPageReserved(zero_page);
+		__folio_clear_reserved(zero_folio);
 		folio_put(zero_folio);
 		return HPAGE_PMD_NR;
 	}
_