mm/mmap.c: use helper mlock_future_check()

Use helper mlock_future_check() to check whether it's safe to enlarge the
locked_vm to simplify the code.  Minor readability improvement.

Link: https://lkml.kernel.org/r/20220402032231.64974-1-linmiaohe@huawei.comSigned-off-by: NMiaohe Lin <linmiaohe@huawei.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>

mm/mmap.c

@@ -2354,15 +2354,8 @@ static int acct_stack_growth(struct vm_area_struct *vma,
 		return -ENOMEM;
 
 	/* mlock limit tests */
-	if (vma->vm_flags & VM_LOCKED) {
-		unsigned long locked;
-		unsigned long limit;
-		locked = mm->locked_vm + grow;
-		limit = rlimit(RLIMIT_MEMLOCK);
-		limit >>= PAGE_SHIFT;
-		if (locked > limit && !capable(CAP_IPC_LOCK))
+	if (mlock_future_check(mm, vma->vm_flags, grow << PAGE_SHIFT))
 		return -ENOMEM;
-	}
 
 	/* Check to ensure the stack will not grow into a hugetlb-only region */
 	new_start = (vma->vm_flags & VM_GROWSUP) ? vma->vm_start :