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Message-ID: <YtGo7GS5l4WxZA/R@casper.infradead.org>
Date: Fri, 15 Jul 2022 18:50:36 +0100
From: Matthew Wilcox <willy@...radead.org>
To: Zhou Guanghui <zhouguanghui1@...wei.com>
Cc: akpm@...ux-foundation.org, linux-kernel@...r.kernel.org,
linux-mm@...ck.org
Subject: Re: [PATCH] mm/huge_memory: Return from zap_huge_pmd after WARN_ONCE.
On Fri, Jul 15, 2022 at 09:22:38AM +0000, Zhou Guanghui wrote:
> After WARN_ONCE is processed, the subsequent page judgment results
> in NULL pointer access. It is more reasonable to return from the
> function here.
I'm not sure this is a good idea. Probably better to crash than
continue.
> Signed-off-by: Zhou Guanghui <zhouguanghui1@...wei.com>
> ---
> mm/huge_memory.c | 5 ++++-
> 1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> index 834f288b3769..7f5ccca6792a 100644
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -1601,8 +1601,11 @@ int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
> entry = pmd_to_swp_entry(orig_pmd);
> page = pfn_swap_entry_to_page(entry);
> flush_needed = 0;
> - } else
> + } else {
> + spin_unlock(ptl);
> WARN_ONCE(1, "Non present huge pmd without pmd migration enabled!");
> + return 1;
> + }
>
> if (PageAnon(page)) {
> zap_deposited_table(tlb->mm, pmd);
> --
> 2.17.1
>
>
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