io_uring: fix memory leak when cache init fail

Exit the percpu ref when cache init fails to free the data memory with
in struct percpu_ref.

Fixes: 206aefde ("io_uring: reduce/pack size of io_ring_ctx")
Signed-off-by: Guixin Liu <kanie@linux.alibaba.com>
Reviewed-by: Gabriel Krisman Bertazi <krisman@suse.de>
Link: https://lore.kernel.org/r/20240923100512.64638-1-kanie@linux.alibaba.comSigned-off-by: Jens Axboe <axboe@kernel.dk>

io_uring/io_uring.c

@@ -321,7 +321,7 @@ static __cold struct io_ring_ctx *io_ring_ctx_alloc(struct io_uring_params *p)
 			    sizeof(struct io_kiocb));
 	ret |= io_futex_cache_init(ctx);
 	if (ret)
-		goto err;
+		goto free_ref;
 	init_completion(&ctx->ref_comp);
 	xa_init_flags(&ctx->personalities, XA_FLAGS_ALLOC1);
 	mutex_init(&ctx->uring_lock);
@@ -349,6 +349,9 @@ static __cold struct io_ring_ctx *io_ring_ctx_alloc(struct io_uring_params *p)
 	io_napi_init(ctx);
 
 	return ctx;
+
+free_ref:
+	percpu_ref_exit(&ctx->refs);
 err:
 	io_alloc_cache_free(&ctx->rsrc_node_cache, kfree);
 	io_alloc_cache_free(&ctx->apoll_cache, kfree);