From: Michal Hocko <mhocko@kernel.org>
To: Li Xinhai <lixinhai.lxh@gmail.com>
Cc: "linux-mm@kvack.org" <linux-mm@kvack.org>,
akpm <akpm@linux-foundation.org>,
"kirill.shutemov" <kirill.shutemov@linux.intel.com>,
Mike Kravetz <mike.kravetz@oracle.com>
Subject: Re: [PATCH v4] mm/page_vma_mapped.c: Explicitly compare pfn for normal, hugetlbfs and THP page
Date: Wed, 15 Jan 2020 10:31:48 +0100 [thread overview]
Message-ID: <20200115093148.GZ19428@dhcp22.suse.cz> (raw)
In-Reply-To: <202001142147485028116@gmail.com>
On Tue 14-01-20 21:47:51, Li Xinhai wrote:
> On 2020-01-14 at 17:25 Michal Hocko wrote:
> >On Sat 11-01-20 10:18:05, Li Xinhai wrote:
> >> When check_pte, pfn of normal, hugetlbfs and THP page need be compared.
> >> The current implementation apply comparison as
> >> - normal 4K page: page_pfn <= pfn < page_pfn + 1
> >> - hugetlbfs page: page_pfn <= pfn < page_pfn + HPAGE_PMD_NR
> >> - THP page: page_pfn <= pfn < page_pfn + HPAGE_PMD_NR
> >> in pfn_in_hpage. For hugetlbfs page, it should be
> >> page_pfn == pfn
> >>
> >> Now, change pfn_in_hpage to pfn_is_match to highlight that comparison
> >> is not only for THP and explicitly compare for these cases.
> >
> >Why is this important to do. I have asked and Mike had the same feeling
> >that the patch is missing any real justification. Why do we need this
> >change? It is great that you have dropped VM_BUG_ON btw.
> >
> I think it is important to make the code clear, as said, comparing hugetlbfs page
> in range page_pfn <= pfn < page_pfn + HPAGE_PMD_NR is confusion.
I am sorry but I do not really see a big confusion here. It is probably
a matter of taste. If others consider this an improvement then I will
not stand in the way but I consider the justification insuficient for
merging.
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2020-01-15 9:31 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-11 10:18 Li Xinhai
2020-01-13 22:38 ` Andrew Morton
2020-01-14 14:24 ` Li Xinhai
2020-01-14 9:25 ` Michal Hocko
2020-01-14 13:47 ` Li Xinhai
2020-01-15 9:31 ` Michal Hocko [this message]
2020-01-16 0:40 ` Mike Kravetz
2020-01-16 10:29 ` Michal Hocko
2020-09-02 22:26 ` Yang Shi
2020-09-03 8:02 ` Michal Hocko
2020-09-03 16:08 ` Yang Shi
2020-09-04 1:22 ` Yang Shi
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