Re: [PATCH] mm: page_alloc: validate buddy before check its migratetype.

[Steven Rostedt <rostedt@goodmis.org>]

On Wed, 30 Mar 2022 18:12:38 -0400
Zi Yan <zi.yan@sent.com> wrote:

> From: Zi Yan <ziy@nvidia.com>
> 
> Whenever a buddy page is found, page_is_buddy() should be called to
> check its validity. Add the missing check during pageblock merge check.
> 
> Fixes: 1dd214b8f21c ("mm: page_alloc: avoid merging non-fallbackable pageblocks with others")

Link: https://lore.kernel.org/all/20220330154208.71aca532@gandalf.local.home/

> 
> Reported-by: Steven Rostedt <rostedt@goodmis.org>

Tested-by: Steven Rostedt (Google) <rostedt@goodmis.org>

-- Steve

> Signed-off-by: Zi Yan <ziy@nvidia.com>
> ---
>  mm/page_alloc.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index bdc8f60ae462..6c6af8658775 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -1108,6 +1108,9 @@ 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