[patch 08/10] Add missing TLB flush to hugetlb_cow().

Martin Schwidefsky
2008-03-12T17:35:01Z

[-- Attachment #1: 108-hugetlb-tlbflush.diff --]
[-- Type: text/plain, Size: 2224 bytes --]

From: Gerald Schaefer <geraldsc@de.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().

Cc: Andi Kleen <ak@suse.de>
Cc: David S. Miller <davem@davemloft.net>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Paul Mundt <lethal@linux-sh.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tony Luck <tony.luck@intel.com>
Signed-off-by: Gerald Schaefer <geraldsc@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
---

include/linux/hugetlb.h | 4 ++++
mm/hugetlb.c | 1 +
2 files changed, 5 insertions(+)

Index: quilt-2.6/include/linux/hugetlb.h
===================================================================
--- quilt-2.6.orig/include/linux/hugetlb.h
+++ quilt-2.6/include/linux/hugetlb.h
@@ -80,6 +80,10 @@ static inline int prepare_hugepage_range
int prepare_hugepage_range(unsigned long addr, unsigned long len);
#endif

+#ifndef ARCH_HAS_HUGEPAGE_CLEAR_FLUSH
+#define huge_ptep_clear_flush(vma, addr, ptep) do { } while (0)
+#endif
+
#ifndef ARCH_HAS_SETCLEAR_HUGE_PTE
#define set_huge_pte_at(mm, addr, ptep, pte) set_pte_at(mm, addr, ptep, pte)
#define huge_ptep_get_and_clear(mm, addr, ptep) ptep_get_and_clear(mm, addr, ptep)
Index: quilt-2.6/mm/hugetlb.c
===================================================================
--- quilt-2.6.orig/mm/hugetlb.c
+++ quilt-2.6/mm/hugetlb.c
@@ -864,6 +864,7 @@ 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 */

--
blue skies,
Martin.

"Reality continues to ruin my life." - Calvin.