On Fri, Apr 03, 2020 at 12:56:57AM +0530, Naresh Kamboju wrote: > [ 734.876355] old_addr: 0xbfe00000, new_addr: 0xbfc00000, old_end: 0xc0000000 The ranges are overlapping. We don't expect it. mremap(2) never does this. shift_arg_pages() only moves range downwards. It should be safe. Could you try this: diff --git a/mm/mremap.c b/mm/mremap.c index af363063ea23..ddd5337de395 100644 --- a/mm/mremap.c +++ b/mm/mremap.c @@ -205,10 +205,14 @@ static bool move_normal_pmd(struct vm_area_struct *vma, unsigned long old_addr, return false; /* - * The destination pmd shouldn't be established, free_pgtables() - * should have release it. + * mremap(2) clears the new place, so the new_pmd is expected to be + * clear. + * + * But move_page_tables() is also called from shift_arg_pages() that + * allows for overlapping address ranges. The shift_arg_pages() case + * is also safe as we only move page tables downwards. */ - if (WARN_ON(!pmd_none(*new_pmd))) + if (WARN_ON(!pmd_none(*new_pmd) && old_addr > new_addr)) return false; /* -- Kirill A. Shutemov
