Patch "staging: lustre: ldlm: pl_recalc time handling is wrong" has been added to the 4.9-stable tree

This is a note to let you know that I've just added the patch titled

    staging: lustre: ldlm: pl_recalc time handling is wrong

to the 4.9-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     staging-lustre-ldlm-pl_recalc-time-handling-is-wrong.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let [off-list ref] know about it.

From b8cb86fd95bb461c3496e1f4b4083b198c963a9c Mon Sep 17 00:00:00 2001

From: Arnd Bergmann <arnd@arndb.de>
Date: Thu, 10 Nov 2016 16:21:20 +0100
Subject: staging: lustre: ldlm: pl_recalc time handling is wrong

From: Arnd Bergmann <arnd@arndb.de>

commit b8cb86fd95bb461c3496e1f4b4083b198c963a9c upstream.

James Simmons reports:

The ldlm_pool field pl_recalc_time is set to the current
monotonic clock value but the interval period is calculated
with the wall clock. This means the interval period will
always be far larger than the pl_recalc_period, which is
just a small interval time period. The correct thing to
do is to use monotomic clock current value instead of the
wall clocks value when calculating recalc_interval_sec.

This broke when I converted the 32-bit get_seconds() into
ktime_get_{real_,}seconds() inconsistently. Either
one of those two would have worked, but mixing them
does not.

Staying with the original intention of the patch, this
changes the ktime_get_seconds() calls into ktime_get_real_seconds(),
using real time instead of mononic time.

Fixes: 8f83409cf238 ("staging/lustre: use 64-bit time for pl_recalc")
Reported-by: James Simmons <redacted>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: James Simmons <redacted>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/staging/lustre/lustre/ldlm/ldlm_pool.c |    8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

--- a/drivers/staging/lustre/lustre/ldlm/ldlm_pool.c
+++ b/drivers/staging/lustre/lustre/ldlm/ldlm_pool.c

@@ -356,10 +356,10 @@ static int ldlm_pool_recalc(struct ldlm_
 	u32 recalc_interval_sec;
 	int count;
 
-	recalc_interval_sec = ktime_get_seconds() - pl->pl_recalc_time;
+	recalc_interval_sec = ktime_get_real_seconds() - pl->pl_recalc_time;
 	if (recalc_interval_sec > 0) {
 		spin_lock(&pl->pl_lock);
-		recalc_interval_sec = ktime_get_seconds() - pl->pl_recalc_time;
+		recalc_interval_sec = ktime_get_real_seconds() - pl->pl_recalc_time;
 
 		if (recalc_interval_sec > 0) {
 			/*

@@ -382,7 +382,7 @@ static int ldlm_pool_recalc(struct ldlm_
 				    count);
 	}
 
-	recalc_interval_sec = pl->pl_recalc_time - ktime_get_seconds() +
+	recalc_interval_sec = pl->pl_recalc_time - ktime_get_real_seconds() +
 			      pl->pl_recalc_period;
 	if (recalc_interval_sec <= 0) {
 		/* DEBUG: should be re-removed after LU-4536 is fixed */

@@ -657,7 +657,7 @@ int ldlm_pool_init(struct ldlm_pool *pl,
 
 	spin_lock_init(&pl->pl_lock);
 	atomic_set(&pl->pl_granted, 0);
-	pl->pl_recalc_time = ktime_get_seconds();
+	pl->pl_recalc_time = ktime_get_real_seconds();
 	atomic_set(&pl->pl_lock_volume_factor, 1);
 
 	atomic_set(&pl->pl_grant_rate, 0);

Patches currently in stable-queue which might be from arnd@arndb.de are

queue-4.9/staging-lustre-ldlm-pl_recalc-time-handling-is-wrong.patch
queue-4.9/arm64-tegra-add-vdd_gpu-regulator-to-jetson-tx1.patch