linux-kernel - [PATCH 4.9 025/116] staging: lustre: ldlm: pl

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Message-Id: <20170106213910.048576026@linuxfoundation.org>
Date:   Fri,  6 Jan 2017 22:43:07 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, James Simmons <jsimmons@...radead.org>,
        Arnd Bergmann <arnd@...db.de>
Subject: [PATCH 4.9 025/116] staging: lustre: ldlm: pl_recalc time handling is wrong

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Arnd Bergmann <arnd@...db.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@...radead.org>
Signed-off-by: Arnd Bergmann <arnd@...db.de>
Reviewed-by: James Simmons <jsimmons@...radead.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.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);