Re: [BUG] Crash on x86_32 for: mm: page_alloc: avoid merging non-fallbackable pageblocks with others

From: Steven Rostedt <rostedt@goodmis.org>
To: Zi Yan <ziy@nvidia.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
	LKML <linux-kernel@vger.kernel.org>,
	Mel Gorman <mgorman@techsingularity.net>,
	David Hildenbrand <david@redhat.com>,
	Vlastimil Babka <vbabka@suse.cz>,
	Mike Rapoport <rppt@linux.ibm.com>,
	Oscar Salvador <osalvador@suse.de>,
	Andrew Morton <akpm@linux-foundation.org>,
	Linux-MM <linux-mm@kvack.org>
Subject: Re: [BUG] Crash on x86_32 for: mm: page_alloc: avoid merging non-fallbackable pageblocks with others
Date: Wed, 30 Mar 2022 16:53:37 -0400	[thread overview]
Message-ID: <20220330165337.7138810e@gandalf.local.home> (raw)
In-Reply-To: <B7789993-75EC-4F74-B4E6-AF1CC2CBD9D4@nvidia.com>

On Wed, 30 Mar 2022 16:29:28 -0400
Zi Yan <ziy@nvidia.com> wrote:

> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index bdc8f60ae462..83a90e2973b7 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -1108,6 +1108,8 @@ static inline void __free_one_page(struct page *page,
> 
>                 buddy_pfn = __find_buddy_pfn(pfn, order);
>                 buddy = page + (buddy_pfn - pfn);
> +               if (!page_is_buddy(page, buddy, order))
> +                       goto done_merging;
>                 buddy_mt = get_pageblock_migratetype(buddy);
> 
>                 if (migratetype != buddy_mt
> 

The above did not apply to Linus's tree, nor even the problem commit
(before or after), but I found where the code is, and added it manually.

It does appear to allow the machine to boot.

-- Steve