io_uring: count ctx refs separately from reqs

Currently batch free handles request memory freeing and ctx ref putting
together. Separate them and use different counters, that will be needed
for reusing reqs memory.
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

fs/io_uring.c

@@ -2227,6 +2227,7 @@ static void io_free_req(struct io_kiocb *req)
 struct req_batch {
 	void *reqs[IO_IOPOLL_BATCH];
 	int to_free;
+	int ctx_refs;
 
 	struct task_struct	*task;
 	int			task_refs;
@@ -2236,6 +2237,7 @@ static inline void io_init_req_batch(struct req_batch *rb)
 {
 	rb->to_free = 0;
 	rb->task_refs = 0;
+	rb->ctx_refs = 0;
 	rb->task = NULL;
 }
 
@@ -2243,7 +2245,6 @@ static void __io_req_free_batch_flush(struct io_ring_ctx *ctx,
 				      struct req_batch *rb)
 {
 	kmem_cache_free_bulk(req_cachep, rb->to_free, rb->reqs);
-	percpu_ref_put_many(&ctx->refs, rb->to_free);
 	rb->to_free = 0;
 }
 
@@ -2256,6 +2257,8 @@ static void io_req_free_batch_finish(struct io_ring_ctx *ctx,
 		io_put_task(rb->task, rb->task_refs);
 		rb->task = NULL;
 	}
+	if (rb->ctx_refs)
+		percpu_ref_put_many(&ctx->refs, rb->ctx_refs);
 }
 
 static void io_req_free_batch(struct req_batch *rb, struct io_kiocb *req)
@@ -2269,6 +2272,7 @@ static void io_req_free_batch(struct req_batch *rb, struct io_kiocb *req)
 		rb->task_refs = 0;
 	}
 	rb->task_refs++;
+	rb->ctx_refs++;
 
 	io_dismantle_req(req);
 	rb->reqs[rb->to_free++] = req;