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Commit d6ab0198 authored by Zijian Zhang's avatar Zijian Zhang Committed by Greg Kroah-Hartman
Browse files

selftests: fix OOM in msg_zerocopy selftest 



[ Upstream commit af2b7e5b741aaae9ffbba2c660def434e07aa241 ]

In selftests/net/msg_zerocopy.c, it has a while loop keeps calling sendmsg
on a socket with MSG_ZEROCOPY flag, and it will recv the notifications
until the socket is not writable. Typically, it will start the receiving
process after around 30+ sendmsgs. However, as the introduction of commit
dfa2f0483360 ("tcp: get rid of sysctl_tcp_adv_win_scale"), the sender is
always writable and does not get any chance to run recv notifications.
The selftest always exits with OUT_OF_MEMORY because the memory used by
opt_skb exceeds the net.core.optmem_max. Meanwhile, it could be set to a
different value to trigger OOM on older kernels too.

Thus, we introduce "cfg_notification_limit" to force sender to receive
notifications after some number of sendmsgs.

Fixes: 07b65c5b ("test: add msg_zerocopy test")
Signed-off-by: default avatarZijian Zhang <zijianzhang@bytedance.com>
Signed-off-by: default avatarXiaochun Lu <xiaochun.lu@bytedance.com>
Reviewed-by: default avatarWillem de Bruijn <willemb@google.com>
Link: https://patch.msgid.link/20240701225349.3395580-2-zijianzhang@bytedance.com


Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
Signed-off-by: default avatarSasha Levin <sashal@kernel.org>
parent 6a8a4fd0

tools/testing/selftests/net/msg_zerocopy.c

+11 −1
Original line number Diff line number Diff line
@@ -85,6 +85,7 @@ static bool cfg_rx; 
static int  cfg_runtime_ms	= 4200;

static int  cfg_verbose;

static int  cfg_waittime_ms	= 500;

static int  cfg_notification_limit = 32;

static bool cfg_zerocopy;



static socklen_t cfg_alen;
@@ -95,6 +96,7 @@ static char payload[IP_MAXPACKET]; 
static long packets, bytes, completions, expected_completions;

static int  zerocopied = -1;

static uint32_t next_completion;

static uint32_t sends_since_notify;



static unsigned long gettimeofday_ms(void)

{
@@ -208,6 +210,7 @@ static bool do_sendmsg(int fd, struct msghdr *msg, bool do_zerocopy, int domain) 
		error(1, errno, "send");

	if (cfg_verbose && ret != len)

		fprintf(stderr, "send: ret=%u != %u\n", ret, len);

	sends_since_notify++;



	if (len) {

		packets++;
@@ -460,6 +463,7 @@ static bool do_recv_completion(int fd, int domain) 
static void do_recv_completions(int fd, int domain)

{

	while (do_recv_completion(fd, domain)) {}

	sends_since_notify = 0;

}



/* Wait for all remaining completions on the errqueue */
@@ -549,6 +553,9 @@ static void do_tx(int domain, int type, int protocol) 
		else

			do_sendmsg(fd, &msg, cfg_zerocopy, domain);



		if (cfg_zerocopy && sends_since_notify >= cfg_notification_limit)

			do_recv_completions(fd, domain);



		while (!do_poll(fd, POLLOUT)) {

			if (cfg_zerocopy)

				do_recv_completions(fd, domain);
@@ -707,7 +714,7 @@ static void parse_opts(int argc, char **argv) 


	cfg_payload_len = max_payload_len;



	while ((c = getopt(argc, argv, "46c:C:D:i:mp:rs:S:t:vz")) != -1) {

	while ((c = getopt(argc, argv, "46c:C:D:i:l:mp:rs:S:t:vz")) != -1) {

		switch (c) {

		case '4':

			if (cfg_family != PF_UNSPEC)
@@ -735,6 +742,9 @@ static void parse_opts(int argc, char **argv) 
			if (cfg_ifindex == 0)

				error(1, errno, "invalid iface: %s", optarg);

			break;

		case 'l':

			cfg_notification_limit = strtoul(optarg, NULL, 0);

			break;

		case 'm':

			cfg_cork_mixed = true;

			break;