From: Mike Kravetz <mike.kravetz@oracle.com>
To: Li Xinhai <lixinhai.lxh@gmail.com>, Michal Hocko <mhocko@kernel.org>
Cc: "linux-mm@kvack.org" <linux-mm@kvack.org>,
"kirill.shutemov" <kirill.shutemov@linux.intel.com>
Subject: Re: [PATCH v2] mm/page_vma_mapped.c: Detect mismatched pfn of hugetlbfs page in pfn_in_hpage()
Date: Thu, 9 Jan 2020 15:00:18 -0800 [thread overview]
Message-ID: <fb4126c6-0140-5638-137f-1eb0bc5b36f7@oracle.com> (raw)
In-Reply-To: <2020011006480540632892@gmail.com>
On 1/9/20 2:48 PM, Li Xinhai wrote:
> oops, I didn't write the code correctly. I should wrote it as
>
> if (pfn >= hpage_pfn && pfn - hpage_pfn < hpage_nr_pages(hpage)) {
> VM_BUG_ON_PAGE(PageHuge(hpage) && pfn != hpage_pfn, hpage);
> return true;
> }
>
> return false;
>
> hpage_nr_pages(hpage) give us HPAGE_PMD_NR for THP and hugetlbfs page,
> but remapping PTE to a differrnt hugetlbfs page still allowed, so put the BUG code
> into this condition is necessary. By this way, if it was not a exact match for PageHuge,
> then it is a bug.
Thank you. I think we all agree on what the proposed code is doing.
However, we would like to know why you believe this code should be added.
For example,
- Did you actually encounter this situation (PageHuge(hpage) && pfn !=
hpage_pfn)?
- Did you discover some code path where we are likely to encounter this
situation?
- Some other reason?
--
Mike Kravetz
next prev parent reply other threads:[~2020-01-09 23:00 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-09 14:26 [PATCH v2] mm/page_vma_mapped.c: Detect mismatched pfn of hugetlbfs page in pfn_in_hpage() Li Xinhai
2020-01-09 14:26 ` [PATCH] mm/page_vma_mapped.c: Exactly compare hugetlbfs page's pfn " Li Xinhai
2020-01-09 14:31 ` Li Xinhai
2020-01-09 15:00 ` [PATCH v2] mm/page_vma_mapped.c: Detect mismatched pfn of hugetlbfs page " Michal Hocko
2020-01-09 17:09 ` Mike Kravetz
2020-01-09 22:48 ` Li Xinhai
2020-01-09 23:00 ` Mike Kravetz [this message]
2020-01-10 2:52 ` Li Xinhai
2020-01-10 6:22 ` Michal Hocko
2020-01-10 7:11 ` Li Xinhai
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