mm: disable preemption in apply_to_pte_range

Impact: bugfix

Lazy mmu mode needs preemption disabled, so if we're apply to
init_mm (which doesn't require any pte locks), then explicitly
disable preemption.  (Do it unconditionally after checking we've
successfully done the allocation to simplify the error handling.)

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/mm/memory.c b/mm/memory.c
index baa999e87cd2..b80cc31292b1 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1718,6 +1718,7 @@ static int apply_to_pte_range(struct mm_struct *mm, pmd_t *pmd,
 
         BUG_ON(pmd_huge(*pmd));
 
+        preempt_disable();
         arch_enter_lazy_mmu_mode();
 
         token = pmd_pgtable(*pmd);
@@ -1729,6 +1730,7 @@ static int apply_to_pte_range(struct mm_struct *mm, pmd_t *pmd,
         } while (pte++, addr += PAGE_SIZE, addr != end);
 
         arch_leave_lazy_mmu_mode();
+        preempt_enable();
 
         if (mm != &init_mm)
                 pte_unmap_unlock(pte-1, ptl);