powerpc: Fix __get_user_pages_fast() irq handling

__get_user_pages_fast() may be called with interrupts disabled (see e.g.
get_futex_key() in kernel/futex.c) and therefore should use local_irq_save()
and local_irq_restore() instead of local_irq_disable()/enable().

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
CC: <stable@vger.kernel.org> [v3.12]
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

1 files changed, 3 insertions, 2 deletions

diff --git a/arch/powerpc/mm/gup.c b/arch/powerpc/mm/gup.c
index 6936547018b8..c5f734e20b0f 100644
--- a/arch/powerpc/mm/gup.c
+++ b/arch/powerpc/mm/gup.c
@@ -123,6 +123,7 @@ int __get_user_pages_fast(unsigned long start, int nr_pages, int write,
         struct mm_struct *mm = current->mm;
         unsigned long addr, len, end;
         unsigned long next;
+        unsigned long flags;
         pgd_t *pgdp;
         int nr = 0;
 
@@ -156,7 +157,7 @@ int __get_user_pages_fast(unsigned long start, int nr_pages, int write,
          * So long as we atomically load page table pointers versus teardown,
          * we can follow the address down to the the page and take a ref on it.
          */
-        local_irq_disable();
+        local_irq_save(flags);
 
         pgdp = pgd_offset(mm, addr);
         do {
@@ -179,7 +180,7 @@ int __get_user_pages_fast(unsigned long start, int nr_pages, int write,
                         break;
         } while (pgdp++, addr = next, addr != end);
 
-        local_irq_enable();
+        local_irq_restore(flags);
 
         return nr;
 }