linux-kernel - [PATCH 08/16] tsacct: add 64-bit btime field

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Date:   Fri,  8 Nov 2019 22:32:46 +0100
From:   Arnd Bergmann <arnd@...db.de>
To:     y2038@...ts.linaro.org
Cc:     linux-kernel@...r.kernel.org, Arnd Bergmann <arnd@...db.de>,
        Thomas Gleixner <tglx@...utronix.de>,
        Kate Stewart <kstewart@...uxfoundation.org>
Subject: [PATCH 08/16] tsacct: add 64-bit btime field

As there is only a 32-bit ac_btime field in taskstat and
we should handle dates after the overflow, add a new field
with the same information but 64-bit width that can hold
a full time64_t.

Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
 include/uapi/linux/taskstats.h | 5 ++++-
 kernel/tsacct.c                | 1 +
 2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/include/uapi/linux/taskstats.h b/include/uapi/linux/taskstats.h
index 7d3ea366e93b..ccbd08709321 100644
--- a/include/uapi/linux/taskstats.h
+++ b/include/uapi/linux/taskstats.h
@@ -34,7 +34,7 @@
  */
 
 
-#define TASKSTATS_VERSION	9
+#define TASKSTATS_VERSION	10
 #define TS_COMM_LEN		32	/* should be >= TASK_COMM_LEN
 					 * in linux/sched.h */
 
@@ -169,6 +169,9 @@ struct taskstats {
 	/* Delay waiting for thrashing page */
 	__u64	thrashing_count;
 	__u64	thrashing_delay_total;
+
+	/* v10: 64-bit btime to avoid overflow */
+	__u64	ac_btime64;		/* 64-bit begin time */
 };
 
 
diff --git a/kernel/tsacct.c b/kernel/tsacct.c
index ab12616ee6fb..257ffb993ea2 100644
--- a/kernel/tsacct.c
+++ b/kernel/tsacct.c
@@ -36,6 +36,7 @@ void bacct_add_tsk(struct user_namespace *user_ns,
 	/* Convert to seconds for btime (note y2106 limit) */
 	btime = ktime_get_real_seconds() - div_u64(delta, USEC_PER_SEC);
 	stats->ac_btime = clamp_t(time64_t, btime, 0, U32_MAX);
+	stats->ac_btime64 = btime;
 
 	if (thread_group_leader(tsk)) {
 		stats->ac_exitcode = tsk->exit_code;
-- 
2.20.0