From: "Kirill A. Shutemov" <kirill@shutemov.name>
To: Wei Yang <richard.weiyang@linux.alibaba.com>
Cc: akpm@linux-foundation.org, kirill.shutemov@linux.intel.com,
yang.shi@linux.alibaba.com, vbabka@suse.cz, willy@infradead.org,
thomas_os@shipmail.org, thellstrom@vmware.com,
anshuman.khandual@arm.com, sean.j.christopherson@intel.com,
aneesh.kumar@linux.ibm.com, peterx@redhat.com, walken@google.com,
linux-kernel@vger.kernel.org, linux-mm@kvack.org,
digetx@gmail.com
Subject: Re: [RESEND Patch v2 3/4] mm/mremap: calculate extent in one place
Date: Tue, 7 Jul 2020 13:47:22 +0300 [thread overview]
Message-ID: <20200707104722.j3awgkz4ncgm2bss@box> (raw)
In-Reply-To: <20200707013856.GA27805@L-31X9LVDL-1304.local>
On Tue, Jul 07, 2020 at 09:38:56AM +0800, Wei Yang wrote:
> On Mon, Jul 06, 2020 at 01:07:29PM +0300, Kirill A. Shutemov wrote:
> >On Fri, Jun 26, 2020 at 09:52:15PM +0800, Wei Yang wrote:
> >> Page tables is moved on the base of PMD. This requires both source
> >> and destination range should meet the requirement.
> >>
> >> Current code works well since move_huge_pmd() and move_normal_pmd()
> >> would check old_addr and new_addr again. And then return to move_ptes()
> >> if the either of them is not aligned.
> >>
> >> In stead of calculating the extent separately, it is better to calculate
> >> in one place, so we know it is not necessary to try move pmd. By doing
> >> so, the logic seems a little clear.
> >>
> >> Signed-off-by: Wei Yang <richard.weiyang@linux.alibaba.com>
> >> Tested-by: Dmitry Osipenko <digetx@gmail.com>
> >> ---
> >> mm/mremap.c | 6 +++---
> >> 1 file changed, 3 insertions(+), 3 deletions(-)
> >>
> >> diff --git a/mm/mremap.c b/mm/mremap.c
> >> index de27b12c8a5a..a30b3e86cc99 100644
> >> --- a/mm/mremap.c
> >> +++ b/mm/mremap.c
> >> @@ -258,6 +258,9 @@ unsigned long move_page_tables(struct vm_area_struct *vma,
> >> extent = next - old_addr;
> >> if (extent > old_end - old_addr)
> >> extent = old_end - old_addr;
> >> + next = (new_addr + PMD_SIZE) & PMD_MASK;
> >
> >Please use round_up() for both 'next' calculations.
> >
>
> I took another close look into this, seems this is not a good suggestion.
>
> round_up(new_addr, PMD_SIZE)
>
> would be new_addr when new_addr is PMD_SIZE aligned, which is not what we
> expect.
Maybe round_down(new_addr + PMD_SIZE, PMD_SIZE)?
--
Kirill A. Shutemov
next prev parent reply other threads:[~2020-07-07 10:47 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-26 13:52 [RESEND Patch v2 0/4] mm/mremap: cleanup move_page_tables() a little Wei Yang
2020-06-26 13:52 ` [RESEND Patch v2 1/4] mm/mremap: format the check in move_normal_pmd() same as move_huge_pmd() Wei Yang
2020-07-06 10:06 ` Kirill A. Shutemov
2020-06-26 13:52 ` [RESEND Patch v2 2/4] mm/mremap: it is sure to have enough space when extent meets requirement Wei Yang
2020-06-26 13:52 ` [RESEND Patch v2 3/4] mm/mremap: calculate extent in one place Wei Yang
2020-07-06 10:07 ` Kirill A. Shutemov
2020-07-07 1:38 ` Wei Yang
2020-07-07 10:47 ` Kirill A. Shutemov [this message]
2020-07-07 12:53 ` Wei Yang
2020-06-26 13:52 ` [RESEND Patch v2 4/4] mm/mremap: start addresses are properly aligned Wei Yang
2020-07-06 10:08 ` [RESEND Patch v2 0/4] mm/mremap: cleanup move_page_tables() a little Kirill A. Shutemov
2020-07-06 22:06 ` Wei Yang
2020-07-06 23:04 ` Andrew Morton
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