io_uring: initialize percpu refcounters using PERCU_REF_ALLOW_REINIT

Percpu reference counters should now be initialized with the
PERCPU_REF_ALLOW_REINIT in order to allow switching them to the
percpu mode from the atomic mode. This is exactly what
percpu_ref_reinit() called from __io_uring_register() is supposed to
do. So let's initialize percpu refcounters with the
PERCU_REF_ALLOW_REINIT flag.
Signed-off-by: Roman Gushchin <guro@fb.com>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Dennis Zhou <dennis@kernel.org>

fs/io_uring.c

@@ -389,7 +389,8 @@ static struct io_ring_ctx *io_ring_ctx_alloc(struct io_uring_params *p)
 	if (!ctx)
 		return NULL;
 
-	if (percpu_ref_init(&ctx->refs, io_ring_ctx_ref_free, 0, GFP_KERNEL)) {
+	if (percpu_ref_init(&ctx->refs, io_ring_ctx_ref_free,
+			    PERCPU_REF_ALLOW_REINIT, GFP_KERNEL)) {
 		kfree(ctx);
 		return NULL;
 	}