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Shutemov" To: Wei Yang 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 Message-ID: <20200706100729.y2wbkpc4tyvjojzg@box> References: <20200626135216.24314-1-richard.weiyang@linux.alibaba.com> <20200626135216.24314-4-richard.weiyang@linux.alibaba.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200626135216.24314-4-richard.weiyang@linux.alibaba.com> X-Rspamd-Queue-Id: 65DCD18003F18 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam04 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: 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 > Tested-by: Dmitry Osipenko > --- > 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. > + if (extent > next - new_addr) > + extent = next - new_addr; > old_pmd = get_old_pmd(vma->vm_mm, old_addr); > if (!old_pmd) > continue; > @@ -301,9 +304,6 @@ unsigned long move_page_tables(struct vm_area_struct *vma, > > if (pte_alloc(new_vma->vm_mm, new_pmd)) > break; > - next = (new_addr + PMD_SIZE) & PMD_MASK; > - if (extent > next - new_addr) > - extent = next - new_addr; > move_ptes(vma, old_pmd, old_addr, old_addr + extent, new_vma, > new_pmd, new_addr, need_rmap_locks); > } > -- > 2.20.1 (Apple Git-117) > -- Kirill A. Shutemov