[PATCH 3.16 058/125] KVM: s390/mm: Fix page table locking vs. split pmd lock

Greg Kroah-Hartman
2014-09-03T23:10:08Z

From: Christian Borntraeger <borntraeger@de.ibm.com>

commit 55e4283c3eb1d850893f645dd695c9c75d5fa1fc upstream.

commit ec66ad66a0de87866be347b5ecc83bd46427f53b (s390/mm: enable
split page table lock for PMD level) activated the split pmd lock
for s390. Turns out that we missed one place: We also have to take
the pmd lock instead of the page table lock when we reallocate the
page tables (==> changing entries in the PMD) during sie enablement.

Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
arch/s390/mm/pgtable.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)

--- a/arch/s390/mm/pgtable.c
+++ b/arch/s390/mm/pgtable.c
@@ -1279,6 +1279,7 @@ static unsigned long page_table_realloc_
{
unsigned long next, *table, *new;
struct page *page;
+ spinlock_t *ptl;
pmd_t *pmd;

pmd = pmd_offset(pud, addr);
@@ -1296,7 +1297,7 @@ again:
if (!new)
return -ENOMEM;

- spin_lock(&mm->page_table_lock);
+ ptl = pmd_lock(mm, pmd);
if (likely((unsigned long *) pmd_deref(*pmd) == table)) {
/* Nuke pmd entry pointing to the "short" page table */
pmdp_flush_lazy(mm, addr, pmd);
@@ -1310,7 +1311,7 @@ again:
page_table_free_rcu(tlb, table);
new = NULL;
}
- spin_unlock(&mm->page_table_lock);
+ spin_unlock(ptl);
if (new) {
page_table_free_pgste(new);
goto again;