diff options
| -rw-r--r-- | mm/huge_memory.c | 39 |
1 files changed, 35 insertions, 4 deletions
diff --git a/mm/huge_memory.c b/mm/huge_memory.c index e60837dc785c..bade35ef563b 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -941,6 +941,37 @@ unlock: spin_unlock(ptl); } +/* + * Save CONFIG_DEBUG_PAGEALLOC from faulting falsely on tail pages + * during copy_user_huge_page()'s copy_page_rep(): in the case when + * the source page gets split and a tail freed before copy completes. + * Called under pmd_lock of checked pmd, so safe from splitting itself. + */ +static void get_user_huge_page(struct page *page) +{ + if (IS_ENABLED(CONFIG_DEBUG_PAGEALLOC)) { + struct page *endpage = page + HPAGE_PMD_NR; + + atomic_add(HPAGE_PMD_NR, &page->_count); + while (++page < endpage) + get_huge_page_tail(page); + } else { + get_page(page); + } +} + +static void put_user_huge_page(struct page *page) +{ + if (IS_ENABLED(CONFIG_DEBUG_PAGEALLOC)) { + struct page *endpage = page + HPAGE_PMD_NR; + + while (page < endpage) + put_page(page++); + } else { + put_page(page); + } +} + static int do_huge_pmd_wp_page_fallback(struct mm_struct *mm, struct vm_area_struct *vma, unsigned long address, @@ -1074,7 +1105,7 @@ int do_huge_pmd_wp_page(struct mm_struct *mm, struct vm_area_struct *vma, ret |= VM_FAULT_WRITE; goto out_unlock; } - get_page(page); + get_user_huge_page(page); spin_unlock(ptl); alloc: if (transparent_hugepage_enabled(vma) && @@ -1095,7 +1126,7 @@ alloc: split_huge_page(page); ret |= VM_FAULT_FALLBACK; } - put_page(page); + put_user_huge_page(page); } count_vm_event(THP_FAULT_FALLBACK); goto out; @@ -1105,7 +1136,7 @@ alloc: put_page(new_page); if (page) { split_huge_page(page); - put_page(page); + put_user_huge_page(page); } else split_huge_page_pmd(vma, address, pmd); ret |= VM_FAULT_FALLBACK; @@ -1127,7 +1158,7 @@ alloc: spin_lock(ptl); if (page) - put_page(page); + put_user_huge_page(page); if (unlikely(!pmd_same(*pmd, orig_pmd))) { spin_unlock(ptl); mem_cgroup_uncharge_page(new_page); |