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-rw-r--r--mm/huge_memory.c28
1 files changed, 28 insertions, 0 deletions
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index faadc449cca5..da397779a6d4 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1074,6 +1074,24 @@ int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm,
src_page = pmd_page(pmd);
VM_BUG_ON_PAGE(!PageHead(src_page), src_page);
+
+ /*
+ * If this page is a potentially pinned page, split and retry the fault
+ * with smaller page size. Normally this should not happen because the
+ * userspace should use MADV_DONTFORK upon pinned regions. This is a
+ * 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))) {
+ pte_free(dst_mm, pgtable);
+ spin_unlock(src_ptl);
+ spin_unlock(dst_ptl);
+ __split_huge_pmd(vma, src_pmd, addr, false, NULL);
+ return -EAGAIN;
+ }
+
get_page(src_page);
page_dup_rmap(src_page, true);
add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR);
@@ -1177,6 +1195,16 @@ int copy_huge_pud(struct mm_struct *dst_mm, struct mm_struct *src_mm,
/* No huge zero pud yet */
}
+ /* 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)))) {
+ spin_unlock(src_ptl);
+ spin_unlock(dst_ptl);
+ __split_huge_pud(vma, src_pud, addr);
+ return -EAGAIN;
+ }
+
pudp_set_wrprotect(src_mm, addr, src_pud);
pud = pud_mkold(pud_wrprotect(pud));
set_pud_at(dst_mm, addr, dst_pud, pud);