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

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

From: Christian Borntraeger <borntrae...@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 <borntrae...@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidef...@de.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gre...@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;


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