linux-kernel - [PATCH 2/3] hugetlbfs: add missing TLB flush to hugetlb

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Date:	Fri, 04 Apr 2008 18:51:06 +0200
From:	Gerald Schaefer <gerald.schaefer@...ibm.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	linux-kernel@...r.kernel.org, linux-s390@...r.kernel.org,
	schwidefsky@...ibm.com, Ingo Molnar <mingo@...e.hu>,
	"David S. Miller" <davem@...emloft.net>,
	Tony Luck <tony.luck@...el.com>,
	Paul Mackerras <paulus@...ba.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Paul Mundt <lethal@...ux-sh.org>
Subject: [PATCH 2/3] hugetlbfs: add missing TLB flush to hugetlb_cow()

Subject: [PATCH 2/3] hugetlbfs: add missing TLB flush to hugetlb_cow()

From: Gerald Schaefer <gerald.schaefer@...ibm.com>

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 <schwidefsky@...ibm.com>
Signed-off-by: Gerald Schaefer <gerald.schaefer@...ibm.com>
---

 include/asm-ia64/hugetlb.h    |    5 +++++
 include/asm-powerpc/hugetlb.h |    5 +++++
 include/asm-sh/hugetlb.h      |    5 +++++
 include/asm-sparc64/hugetlb.h |    5 +++++
 include/asm-x86/hugetlb.h     |    5 +++++
 mm/hugetlb.c                  |    1 +
 6 files changed, 26 insertions(+)

Index: linux-2.6.25-rc8/mm/hugetlb.c
===================================================================
--- linux-2.6.25-rc8.orig/mm/hugetlb.c
+++ linux-2.6.25-rc8/mm/hugetlb.c
@@ -875,6 +875,7 @@ static int hugetlb_cow(struct mm_struct 
 	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 */
Index: linux-2.6.25-rc8/include/asm-ia64/hugetlb.h
===================================================================
--- linux-2.6.25-rc8.orig/include/asm-ia64/hugetlb.h
+++ linux-2.6.25-rc8/include/asm-ia64/hugetlb.h
@@ -34,4 +34,9 @@ static inline pte_t huge_ptep_get_and_cl
 	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 */
Index: linux-2.6.25-rc8/include/asm-powerpc/hugetlb.h
===================================================================
--- linux-2.6.25-rc8.orig/include/asm-powerpc/hugetlb.h
+++ linux-2.6.25-rc8/include/asm-powerpc/hugetlb.h
@@ -34,4 +34,9 @@ static inline void hugetlb_prefault_arch
 {
 }
 
+static inline void huge_ptep_clear_flush(struct vm_area_struct *vma,
+					 unsigned long addr, pte_t *ptep)
+{
+}
+
 #endif /* _ASM_POWERPC_HUGETLB_H */
Index: linux-2.6.25-rc8/include/asm-sh/hugetlb.h
===================================================================
--- linux-2.6.25-rc8.orig/include/asm-sh/hugetlb.h
+++ linux-2.6.25-rc8/include/asm-sh/hugetlb.h
@@ -46,4 +46,9 @@ static inline pte_t huge_ptep_get_and_cl
 	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 */
Index: linux-2.6.25-rc8/include/asm-sparc64/hugetlb.h
===================================================================
--- linux-2.6.25-rc8.orig/include/asm-sparc64/hugetlb.h
+++ linux-2.6.25-rc8/include/asm-sparc64/hugetlb.h
@@ -39,4 +39,9 @@ static inline void hugetlb_free_pgd_rang
 	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 */
Index: linux-2.6.25-rc8/include/asm-x86/hugetlb.h
===================================================================
--- linux-2.6.25-rc8.orig/include/asm-x86/hugetlb.h
+++ linux-2.6.25-rc8/include/asm-x86/hugetlb.h
@@ -46,4 +46,9 @@ static inline pte_t huge_ptep_get_and_cl
 	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 */


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