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 <[email protected]> >> Tested-by: Dmitry Osipenko <[email protected]> >> --- >> 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. >> + 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 -- Wei Yang Help you, Help me
