devlink: Add method for time-stamp on reporter's dump

When setting the dump's time-stamp, use ktime_get_real in addition to
jiffies. This simplifies the user space implementation and bypasses
some inconsistent behavior with translating jiffies to current time.
The time taken is transformed into nsec, to comply with y2038 issue.

Fixes: c8e1da0 ("devlink: Add health report functionality")
Signed-off-by: Aya Levin <ayal@mellanox.com>
Acked-by: Jiri Pirko <jiri@mellanox.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/uapi/linux/devlink.h

@@ -421,6 +421,7 @@ enum devlink_attr {
 
 	DEVLINK_ATTR_RELOAD_FAILED,			/* u8 0 or 1 */
 
+	DEVLINK_ATTR_HEALTH_REPORTER_DUMP_TS_NS,	/* u64 */
 	/* add new attributes above here, update the policy in devlink.c */
 
 	__DEVLINK_ATTR_MAX,

net/core/devlink.c

@@ -4618,6 +4618,7 @@ struct devlink_health_reporter {
 	bool auto_recover;
 	u8 health_state;
 	u64 dump_ts;
+	u64 dump_real_ts;
 	u64 error_count;
 	u64 recovery_count;
 	u64 last_recovery_ts;
@@ -4790,6 +4791,7 @@ static int devlink_health_do_dump(struct devlink_health_reporter *reporter,
 		goto dump_err;
 
 	reporter->dump_ts = jiffies;
+	reporter->dump_real_ts = ktime_get_real_ns();
 
 	return 0;
 
@@ -4952,6 +4954,10 @@ devlink_nl_health_reporter_fill(struct sk_buff *msg,
 			      jiffies_to_msecs(reporter->dump_ts),
 			      DEVLINK_ATTR_PAD))
 		goto reporter_nest_cancel;
+	if (reporter->dump_fmsg &&
+	    nla_put_u64_64bit(msg, DEVLINK_ATTR_HEALTH_REPORTER_DUMP_TS_NS,
+			      reporter->dump_real_ts, DEVLINK_ATTR_PAD))
+		goto reporter_nest_cancel;
 
 	nla_nest_end(msg, reporter_attr);
 	genlmsg_end(msg, hdr);