Break COW PTE if madvise() modify the pte entry of COW-ed PTE. Following are the list of flags which need to break COW PTE. However, like MADV_HUGEPAGE and MADV_MERGEABLE, we should handle it respectively. - MADV_DONTNEED: It calls to zap_page_range() which already be handled. - MADV_FREE: It uses walk_page_range() with madvise_free_pte_range() to free the page by itself, so add break_cow_pte(). - MADV_REMOVE: Same as MADV_FREE, it remove the page by itself, so add break_cow_pte_range(). - MADV_COLD: Similar to MAD_FREE, break COW PTE before pageout. - MADV_POPULATE: Let GUP deal with it. Signed-off-by: Chih-En Lin <shiyn.lin@xxxxxxxxx> --- mm/madvise.c | 13 +++++++++++++ 1 file changed, 13 insertions(+) diff --git a/mm/madvise.c b/mm/madvise.c index b6ea204d4e23..8b815942f286 100644 --- a/mm/madvise.c +++ b/mm/madvise.c @@ -428,6 +428,9 @@ static int madvise_cold_or_pageout_pte_range(pmd_t *pmd, if (pmd_trans_unstable(pmd)) return 0; #endif + if (break_cow_pte(vma, pmd, addr)) + return 0; + tlb_change_page_size(tlb, PAGE_SIZE); orig_pte = pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl); flush_tlb_batched_pending(mm); @@ -629,6 +632,10 @@ static int madvise_free_pte_range(pmd_t *pmd, unsigned long addr, if (pmd_trans_unstable(pmd)) return 0; + /* We should only allocate PTE. */ + if (break_cow_pte(vma, pmd, addr)) + goto next; + tlb_change_page_size(tlb, PAGE_SIZE); orig_pte = pte = pte_offset_map_lock(mm, pmd, addr, &ptl); flush_tlb_batched_pending(mm); @@ -989,6 +996,12 @@ static long madvise_remove(struct vm_area_struct *vma, if ((vma->vm_flags & (VM_SHARED|VM_WRITE)) != (VM_SHARED|VM_WRITE)) return -EACCES; + error = break_cow_pte_range(vma, start, end); + if (error < 0) + return error; + else if (error > 0) + return -ENOMEM; + offset = (loff_t)(start - vma->vm_start) + ((loff_t)vma->vm_pgoff << PAGE_SHIFT); -- 2.34.1
