diff options
| -rw-r--r-- | include/linux/mm.h | 21 | ||||
| -rw-r--r-- | mm/huge_memory.c | 8 | ||||
| -rw-r--r-- | mm/internal.h | 5 | ||||
| -rw-r--r-- | mm/memory.c | 8 |
4 files changed, 24 insertions, 18 deletions
diff --git a/include/linux/mm.h b/include/linux/mm.h index 77e64e3eac80..64a71bf20536 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -1300,6 +1300,27 @@ static inline bool page_maybe_dma_pinned(struct page *page) GUP_PIN_COUNTING_BIAS; } +static inline bool is_cow_mapping(vm_flags_t flags) +{ + return (flags & (VM_SHARED | VM_MAYWRITE)) == VM_MAYWRITE; +} + +/* + * This should most likely only be called during fork() to see whether we + * should break the cow immediately for a page on the src mm. + */ +static inline bool page_needs_cow_for_dma(struct vm_area_struct *vma, + struct page *page) +{ + if (!is_cow_mapping(vma->vm_flags)) + return false; + + if (!atomic_read(&vma->vm_mm->has_pinned)) + return false; + + return page_maybe_dma_pinned(page); +} + #if defined(CONFIG_SPARSEMEM) && !defined(CONFIG_SPARSEMEM_VMEMMAP) #define SECTION_IN_PAGE_FLAGS #endif diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 395c75111d33..da1d63a41aec 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -1100,9 +1100,7 @@ int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm, * best effort that the pinned pages won't be replaced by another * random page during the coming copy-on-write. */ - if (unlikely(is_cow_mapping(vma->vm_flags) && - atomic_read(&src_mm->has_pinned) && - page_maybe_dma_pinned(src_page))) { + if (unlikely(page_needs_cow_for_dma(vma, src_page))) { pte_free(dst_mm, pgtable); spin_unlock(src_ptl); spin_unlock(dst_ptl); @@ -1214,9 +1212,7 @@ int copy_huge_pud(struct mm_struct *dst_mm, struct mm_struct *src_mm, } /* Please refer to comments in copy_huge_pmd() */ - if (unlikely(is_cow_mapping(vma->vm_flags) && - atomic_read(&src_mm->has_pinned) && - page_maybe_dma_pinned(pud_page(pud)))) { + if (unlikely(page_needs_cow_for_dma(vma, pud_page(pud)))) { spin_unlock(src_ptl); spin_unlock(dst_ptl); __split_huge_pud(vma, src_pud, addr); diff --git a/mm/internal.h b/mm/internal.h index 9902648f2206..1432feec62df 100644 --- a/mm/internal.h +++ b/mm/internal.h @@ -296,11 +296,6 @@ static inline unsigned int buddy_order(struct page *page) */ #define buddy_order_unsafe(page) READ_ONCE(page_private(page)) -static inline bool is_cow_mapping(vm_flags_t flags) -{ - return (flags & (VM_SHARED | VM_MAYWRITE)) == VM_MAYWRITE; -} - /* * These three helpers classifies VMAs for virtual memory accounting. */ diff --git a/mm/memory.c b/mm/memory.c index c8e357627318..523230005db1 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -809,12 +809,8 @@ copy_present_page(struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma pte_t *dst_pte, pte_t *src_pte, unsigned long addr, int *rss, struct page **prealloc, pte_t pte, struct page *page) { - struct mm_struct *src_mm = src_vma->vm_mm; struct page *new_page; - if (!is_cow_mapping(src_vma->vm_flags)) - return 1; - /* * What we want to do is to check whether this page may * have been pinned by the parent process. If so, @@ -828,9 +824,7 @@ copy_present_page(struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma * the page count. That might give false positives for * for pinning, but it will work correctly. */ - if (likely(!atomic_read(&src_mm->has_pinned))) - return 1; - if (likely(!page_maybe_dma_pinned(page))) + if (likely(!page_needs_cow_for_dma(src_vma, page))) return 1; new_page = *prealloc; |