hugetlbfs: add missing TLB flush to hugetlb_cow()

A cow break on a hugetlbfs page with page_count > 1 will set a new pte with set_huge_pte_at(), w/o any tlb flush operation. The old pte will remain in the tlb and subsequent write access to the page will result in a page fault loop, for as long as it may take until the tlb is flushed from somewhere else. This patch introduces an architecture-specific huge_ptep_clear_flush() function, which is called before the the set_huge_pte_at() in hugetlb_cow(). ATTENTION: This is just a nop on all architectures for now, the s390 implementation will come with our large page patch later. Other architectures should define their own huge_ptep_clear_flush() if needed. Acked-by: Martin Schwidefsky <[email protected]> Signed-off-by: Gerald Schaefer <[email protected]> Cc: Paul Mundt <[email protected]> Cc: "Luck, Tony" <[email protected]> Cc: Ingo Molnar <[email protected]> Cc: Thomas Gleixner <[email protected]> Cc: "David S. Miller" <[email protected]> Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]>
josf · Apr 28, 2008 · 8fe627e · 8fe627e
1 parent 6d77907
commit 8fe627e
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diff --git a/include/asm-ia64/hugetlb.h b/include/asm-ia64/hugetlb.h
@@ -34,4 +34,9 @@ static inline pte_t huge_ptep_get_and_clear(struct mm_struct *mm,
 	return ptep_get_and_clear(mm, addr, ptep);
 }
 
+static inline void huge_ptep_clear_flush(struct vm_area_struct *vma,
+					 unsigned long addr, pte_t *ptep)
+{
+}
+
 #endif /* _ASM_IA64_HUGETLB_H */
diff --git a/include/asm-powerpc/hugetlb.h b/include/asm-powerpc/hugetlb.h
@@ -34,4 +34,9 @@ static inline void hugetlb_prefault_arch_hook(struct mm_struct *mm)
 {
 }
 
+static inline void huge_ptep_clear_flush(struct vm_area_struct *vma,
+					 unsigned long addr, pte_t *ptep)
+{
+}
+
 #endif /* _ASM_POWERPC_HUGETLB_H */
diff --git a/include/asm-sh/hugetlb.h b/include/asm-sh/hugetlb.h
@@ -46,4 +46,9 @@ static inline pte_t huge_ptep_get_and_clear(struct mm_struct *mm,
 	return ptep_get_and_clear(mm, addr, ptep);
 }
 
+static inline void huge_ptep_clear_flush(struct vm_area_struct *vma,
+					 unsigned long addr, pte_t *ptep)
+{
+}
+
 #endif /* _ASM_SH_HUGETLB_H */
diff --git a/include/asm-sparc64/hugetlb.h b/include/asm-sparc64/hugetlb.h
@@ -39,4 +39,9 @@ static inline void hugetlb_free_pgd_range(struct mmu_gather **tlb,
 	free_pgd_range(tlb, addr, end, floor, ceiling);
 }
 
+static inline void huge_ptep_clear_flush(struct vm_area_struct *vma,
+					 unsigned long addr, pte_t *ptep)
+{
+}
+
 #endif /* _ASM_SPARC64_HUGETLB_H */
diff --git a/include/asm-x86/hugetlb.h b/include/asm-x86/hugetlb.h
@@ -46,4 +46,9 @@ static inline pte_t huge_ptep_get_and_clear(struct mm_struct *mm,
 	return ptep_get_and_clear(mm, addr, ptep);
 }
 
+static inline void huge_ptep_clear_flush(struct vm_area_struct *vma,
+					 unsigned long addr, pte_t *ptep)
+{
+}
+
 #endif /* _ASM_X86_HUGETLB_H */
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
@@ -892,6 +892,7 @@ static int hugetlb_cow(struct mm_struct *mm, struct vm_area_struct *vma,
 	ptep = huge_pte_offset(mm, address & HPAGE_MASK);
 	if (likely(pte_same(*ptep, pte))) {
 		/* Break COW */
+		huge_ptep_clear_flush(vma, address, ptep);
 		set_huge_pte_at(mm, address, ptep,
 				make_huge_pte(vma, new_page, 1));
 		/* Make the old page be freed below */