[PATCH] net: kunit: move struct net_devmem_dmabuf_binding off stack

[Arnd Bergmann <arnd@kernel.org>]

From: Arnd Bergmann <arnd@arndb.de>

The net_devmem_dmabuf_binding structure is really way too big to
live on the stack, and causes warnings on my randconfig build machine
with a reasonable per-function limit:

net/core/net_test.c: In function 'netmem_ref_test_tcp_devmem_recv':
net/core/net_test.c:1720:1: error: the frame size of 1744 bytes is larger than 1536 bytes [-Werror=frame-larger-than=]
 1720 | }
      | ^
net/core/net_test.c: In function 'netmem_ref_test_skb_segment':
net/core/net_test.c:1477:1: error: the frame size of 1584 bytes is larger than 1536 bytes [-Werror=frame-larger-than=]

Since the binding object is never used concurrently in multiple tests,
avoid this by just having a global copy of it and reinitializing it
for every user.

Fixes: 2285346afc99 ("net: kunit: test netmem, page_pool, and skb frag refcounting")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
I don't particularly like this workaround, as global variables are
always hacky like this. If anyone has a better idea to avoid the
last stack structure, let's do that instead.

Without the patch, I run into this every few randconfig builds,
which did not happen on linux-next before the merge window.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
 net/core/net_test.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/net/core/net_test.c b/net/core/net_test.c
index 976d14896251..19f422300d9c 100644
--- a/net/core/net_test.c
+++ b/net/core/net_test.c
@@ -984,13 +984,14 @@ static void netmem_ref_test_pp_page(struct kunit *test)
 #endif
 
 #if defined(CONFIG_PAGE_POOL) && defined(CONFIG_NET_DEVMEM)
+static struct net_devmem_dmabuf_binding binding;
+
 static void dummy_percpu_ref_release(struct percpu_ref *ref)
 {
 }
 
 static void netmem_ref_test_net_iov(struct kunit *test)
 {
-	struct net_devmem_dmabuf_binding binding = {};
 	struct page_pool_params pp_params = {
 		.order = 0,
 		.pool_size = 4,
@@ -1003,6 +1004,7 @@ static void netmem_ref_test_net_iov(struct kunit *test)
 	long base_ref;
 	int err;
 
+	memset(&binding, 0, sizeof(binding));
 	err = percpu_ref_init(&binding.ref, dummy_percpu_ref_release,
 			      PERCPU_REF_INIT_ATOMIC, GFP_KERNEL);
 	KUNIT_ASSERT_EQ(test, err, 0);
@@ -1145,7 +1147,6 @@ static void netmem_ref_test_release_data(struct kunit *test)
 		.nid = NUMA_NO_NODE,
 	};
 	struct sk_buff *skb, *clone1, *clone2, *ext;
-	struct net_devmem_dmabuf_binding binding = {};
 	struct net_iov niov = {};
 	struct page_pool *pool;
 	struct page *page;
@@ -1154,6 +1155,7 @@ static void netmem_ref_test_release_data(struct kunit *test)
 	int base_ref;
 	int i;
 
+	memset(&binding, 0, sizeof(binding));
 	pool = page_pool_create(&pp_params);
 	KUNIT_ASSERT_FALSE(test, IS_ERR(pool));
 	page = page_pool_dev_alloc_pages(pool);
@@ -1335,7 +1337,6 @@ static void netmem_ref_test_skb_segment(struct kunit *test)
 		.flags = SKBFL_ZEROCOPY_ENABLE,
 	};
 	struct sk_buff *head, *list, *segs, *seg;
-	struct net_devmem_dmabuf_binding binding = {};
 	struct net_iov niov = {};
 	struct page *pp_page, *reg_page;
 	netmem_ref pp_nm, niov_nm;
@@ -1343,6 +1344,7 @@ static void netmem_ref_test_skb_segment(struct kunit *test)
 	long base_pp_ref, base_iov_ref;
 	int base_pp_page_ref, base_reg_ref;
 
+	memset(&binding, 0, sizeof(binding));
 	pool = page_pool_create(&pp_params);
 	KUNIT_ASSERT_FALSE(test, IS_ERR(pool));
 	pp_page = page_pool_dev_alloc_pages(pool);
@@ -1634,7 +1636,6 @@ static void netmem_ref_test_try_coalesce(struct kunit *test)
 		.nid = NUMA_NO_NODE,
 	};
 	struct sk_buff *to, *from, *clone;
-	struct net_devmem_dmabuf_binding binding = {};
 	struct net_iov niov = {};
 	struct page *pp_page, *reg_page;
 	netmem_ref pp_nm, niov_nm;
@@ -1644,6 +1645,7 @@ static void netmem_ref_test_try_coalesce(struct kunit *test)
 	bool fragstolen;
 	int delta;
 
+	memset(&binding, 0, sizeof(binding));
 	pool = page_pool_create(&pp_params);
 	KUNIT_ASSERT_FALSE(test, IS_ERR(pool));
 	pp_page = page_pool_dev_alloc_pages(pool);
@@ -1766,7 +1768,6 @@ static void netmem_ref_test_tcp_devmem_recv(struct kunit *test)
 		.pool_size = 4,
 		.nid = NUMA_NO_NODE,
 	};
-	struct net_devmem_dmabuf_binding binding = {};
 	struct msghdr msg = {};
 	struct dmabuf_token token;
 	struct dmabuf_cmsg *cmsg;
@@ -1780,6 +1781,7 @@ static void netmem_ref_test_tcp_devmem_recv(struct kunit *test)
 	long base_iov_ref;
 	int ret;
 
+	memset(&binding, 0, sizeof(binding));
 	KUNIT_ASSERT_EQ(test,
 			sock_create_kern(&init_net, AF_INET, SOCK_STREAM,
 					 IPPROTO_TCP, &sock),
-- 
2.53.0