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

[<gregkh@linuxfoundation.org>]

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 <stable@vger.kernel.org> 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 <jsimmons@infradead.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: James Simmons <jsimmons@infradead.org>
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