commit 
f1f1007644ff ("mm: add new mmgrab() helper") added a
helper that we missed out on.
Signed-off-by: Palmer Dabbelt <palmer@sifive.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Atish Patra <atish.patra@wdc.com>
Signed-off-by: Palmer Dabbelt <palmer@sifive.com>
 
 #include <linux/irq.h>
 #include <linux/of.h>
 #include <linux/sched/task_stack.h>
+#include <linux/sched/mm.h>
 #include <asm/irq.h>
 #include <asm/mmu_context.h>
 #include <asm/tlbflush.h>
        struct mm_struct *mm = &init_mm;
 
        /* All kernel threads share the same mm context.  */
-       atomic_inc(&mm->mm_count);
+       mmgrab(mm);
        current->active_mm = mm;
 
        trap_init();