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authorPeter Xu <peterx@redhat.com>2021-03-13 08:07:26 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2021-03-13 22:27:30 +0300
commit97a7e4733b9b221d012ae68fcd3b3251febf6341 (patch)
tree3d10cd8230f56f3b1b1dca122d3220f37b86a1cf /mm
parentca7e0457efefca9eeee8c42a89a7f450651d555b (diff)
downloadlinux-97a7e4733b9b221d012ae68fcd3b3251febf6341.tar.xz
mm: introduce page_needs_cow_for_dma() for deciding whether cow
We've got quite a few places (pte, pmd, pud) that explicitly checked against whether we should break the cow right now during fork(). It's easier to provide a helper, especially before we work the same thing on hugetlbfs. Since we'll reference is_cow_mapping() in mm.h, move it there too. Actually it suites mm.h more since internal.h is mm/ only, but mm.h is exported to the whole kernel. With that we should expect another patch to use is_cow_mapping() whenever we can across the kernel since we do use it quite a lot but it's always done with raw code against VM_* flags. Link: https://lkml.kernel.org/r/20210217233547.93892-4-peterx@redhat.com Signed-off-by: Peter Xu <peterx@redhat.com> Reviewed-by: Jason Gunthorpe <jgg@ziepe.ca> Cc: Alexey Dobriyan <adobriyan@gmail.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Christoph Hellwig <hch@lst.de> Cc: Daniel Vetter <daniel@ffwll.ch> Cc: David Airlie <airlied@linux.ie> Cc: David Gibson <david@gibson.dropbear.id.au> Cc: Gal Pressman <galpress@amazon.com> Cc: Jan Kara <jack@suse.cz> Cc: Jann Horn <jannh@google.com> Cc: Kirill Shutemov <kirill@shutemov.name> Cc: Kirill Tkhai <ktkhai@virtuozzo.com> Cc: Matthew Wilcox <willy@infradead.org> Cc: Miaohe Lin <linmiaohe@huawei.com> Cc: Mike Kravetz <mike.kravetz@oracle.com> Cc: Mike Rapoport <rppt@linux.vnet.ibm.com> Cc: Roland Scheidegger <sroland@vmware.com> Cc: VMware Graphics <linux-graphics-maintainer@vmware.com> Cc: Wei Zhang <wzam@amazon.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm')
-rw-r--r--mm/huge_memory.c8
-rw-r--r--mm/internal.h5
-rw-r--r--mm/memory.c8
3 files changed, 3 insertions, 18 deletions
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;