[032/141] mm/THP: use pmd_populate() to update the pmd with pgtable_t pointer

Steven Rostedt
2013-07-03T19:03:13Z

[-- Attachment #1: 0032-mm-THP-use-pmd_populate-to-update-the-pmd-with-pgtab.patch --]
[-- Type: text/plain, Size: 1761 bytes --]

3.6.11.6 stable review patch.
If anyone has any objections, please let me know.

------------------

From: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>

[ Upstream commit 7c3425123ddfdc5f48e7913ff59d908789712b18 ]

We should not use set_pmd_at to update pmd_t with pgtable_t pointer.
set_pmd_at is used to set pmd with huge pte entries and architectures
like ppc64, clear few flags from the pte when saving a new entry.
Without this change we observe bad pte errors like below on ppc64 with
THP enabled.

BUG: Bad page map in process ld mm=0xc000001ee39f4780 pte:7fc3f37848000001 pmd:c000001ec0000000

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Reviewed-by: Andrea Arcangeli <aarcange@redhat.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
mm/huge_memory.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 141dbb6..29301d4 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1954,7 +1954,12 @@ static void collapse_huge_page(struct mm_struct *mm,
pte_unmap(pte);
spin_lock(&mm->page_table_lock);
BUG_ON(!pmd_none(*pmd));
- set_pmd_at(mm, address, pmd, _pmd);
+ /*
+ * We can only use set_pmd_at when establishing
+ * hugepmds and never for establishing regular pmds that
+ * points to regular pagetables. Use pmd_populate for that
+ */
+ pmd_populate(mm, pmd, pmd_pgtable(_pmd));
spin_unlock(&mm->page_table_lock);
anon_vma_unlock(vma->anon_vma);
goto out;
--
1.7.10.4