linux-kernel - [PATCH] RDMA/core: reduce stack using in nldev_stat_get

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Message-Id: <20250620113335.3776965-1-arnd@kernel.org>
Date: Fri, 20 Jun 2025 13:33:26 +0200
From: Arnd Bergmann <arnd@...nel.org>
To: Jason Gunthorpe <jgg@...pe.ca>,
	Leon Romanovsky <leon@...nel.org>
Cc: Arnd Bergmann <arnd@...db.de>,
	Chiara Meiohas <cmeiohas@...dia.com>,
	Mark Zhang <markzhang@...dia.com>,
	Michael Guralnik <michaelgur@...dia.com>,
	linux-rdma@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH] RDMA/core: reduce stack using in nldev_stat_get_doit()

From: Arnd Bergmann <arnd@...db.de>

In the s390 defconfig, gcc-10 and earlier end up inlining three functions
into nldev_stat_get_doit(), and each of them uses some 600 bytes of stack.

The result is a function with an overly large stack frame and a warning:

drivers/infiniband/core/nldev.c:2466:1: error: the frame size of 1720 bytes is larger than 1280 bytes [-Werror=frame-larger-than=]

Mark the three functions noinline_for_stack to prevent this, ensuring
that only one copy of the nlattr array is on the stack of each function.

Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
 drivers/infiniband/core/nldev.c | 22 ++++++++++++----------
 1 file changed, 12 insertions(+), 10 deletions(-)

diff --git a/drivers/infiniband/core/nldev.c b/drivers/infiniband/core/nldev.c
index a872643e8039..e9b7a6419291 100644
--- a/drivers/infiniband/core/nldev.c
+++ b/drivers/infiniband/core/nldev.c
@@ -1469,10 +1469,11 @@ static const struct nldev_fill_res_entry fill_entries[RDMA_RESTRACK_MAX] = {
 
 };
 
-static int res_get_common_doit(struct sk_buff *skb, struct nlmsghdr *nlh,
-			       struct netlink_ext_ack *extack,
-			       enum rdma_restrack_type res_type,
-			       res_fill_func_t fill_func)
+static noinline_for_stack int
+res_get_common_doit(struct sk_buff *skb, struct nlmsghdr *nlh,
+		    struct netlink_ext_ack *extack,
+		    enum rdma_restrack_type res_type,
+		    res_fill_func_t fill_func)
 {
 	const struct nldev_fill_res_entry *fe = &fill_entries[res_type];
 	struct nlattr *tb[RDMA_NLDEV_ATTR_MAX];
@@ -2263,10 +2264,10 @@ static int nldev_stat_del_doit(struct sk_buff *skb, struct nlmsghdr *nlh,
 	return ret;
 }
 
-static int stat_get_doit_default_counter(struct sk_buff *skb,
-					 struct nlmsghdr *nlh,
-					 struct netlink_ext_ack *extack,
-					 struct nlattr *tb[])
+static noinline_for_stack int
+stat_get_doit_default_counter(struct sk_buff *skb, struct nlmsghdr *nlh,
+			      struct netlink_ext_ack *extack,
+			      struct nlattr *tb[])
 {
 	struct rdma_hw_stats *stats;
 	struct nlattr *table_attr;
@@ -2356,8 +2357,9 @@ static int stat_get_doit_default_counter(struct sk_buff *skb,
 	return ret;
 }
 
-static int stat_get_doit_qp(struct sk_buff *skb, struct nlmsghdr *nlh,
-			    struct netlink_ext_ack *extack, struct nlattr *tb[])
+static noinline_for_stack int
+stat_get_doit_qp(struct sk_buff *skb, struct nlmsghdr *nlh,
+		 struct netlink_ext_ack *extack, struct nlattr *tb[])
 
 {
 	static enum rdma_nl_counter_mode mode;
-- 
2.39.5