lib/idr.c: use RCU_INIT_POINTER(x, NULL)

Replace rcu_assign_pointer(x, NULL) with RCU_INIT_POINTER(x, NULL)

The rcu_assign_pointer() ensures that the initialization of a structure
is carried out before storing a pointer to that structure.  And in the
case of the NULL pointer, there is no structure to initialize.

So, rcu_assign_pointer(p, NULL) can be safely converted to
RCU_INIT_POINTER(p, NULL)

Signed-off-by: Monam Agarwal <monamagarwal123@gmail.com>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

lib/idr.c

@@ -533,7 +533,7 @@ static void sub_remove(struct idr *idp, int shift, int id)
 	n = id & IDR_MASK;
 	if (likely(p != NULL && test_bit(n, p->bitmap))) {
 		__clear_bit(n, p->bitmap);
-		rcu_assign_pointer(p->ary[n], NULL);
+		RCU_INIT_POINTER(p->ary[n], NULL);
 		to_free = NULL;
 		while(*paa && ! --((**paa)->count)){
 			if (to_free)
@@ -602,7 +602,7 @@ static void __idr_remove_all(struct idr *idp)
 
 	n = idp->layers * IDR_BITS;
 	p = idp->top;
-	rcu_assign_pointer(idp->top, NULL);
+	RCU_INIT_POINTER(idp->top, NULL);
 	max = idr_max(idp->layers);
 
 	id = 0;