3.16.7-ckt3 -stable review patch.  If anyone has any objections, please let me 
know.

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

From: Andrew Morton <a...@linux-foundation.org>

commit 91b57191cfd152c02ded0745250167d0263084f8 upstream.

In some android devices, there will be a "divide by zero" exception.
vmpr->scanned could be zero before spin_lock(&vmpr->sr_lock).

Addresses https://bugzilla.kernel.org/show_bug.cgi?id=88051

[a...@linux-foundation.org: neaten]
Reported-by: ji_ang <ji_...@163.com>
Cc: Anton Vorontsov <anton.voront...@linaro.org>
Signed-off-by: Andrew Morton <a...@linux-foundation.org>
Signed-off-by: Linus Torvalds <torva...@linux-foundation.org>
Signed-off-by: Luis Henriques <luis.henriq...@canonical.com>
---
 mm/vmpressure.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/mm/vmpressure.c b/mm/vmpressure.c
index d4042e75f7c7..c5afd573d7da 100644
--- a/mm/vmpressure.c
+++ b/mm/vmpressure.c
@@ -165,6 +165,7 @@ static void vmpressure_work_fn(struct work_struct *work)
        unsigned long scanned;
        unsigned long reclaimed;
 
+       spin_lock(&vmpr->sr_lock);
        /*
         * Several contexts might be calling vmpressure(), so it is
         * possible that the work was rescheduled again before the old
@@ -173,11 +174,12 @@ static void vmpressure_work_fn(struct work_struct *work)
         * here. No need for any locks here since we don't care if
         * vmpr->reclaimed is in sync.
         */
-       if (!vmpr->scanned)
+       scanned = vmpr->scanned;
+       if (!scanned) {
+               spin_unlock(&vmpr->sr_lock);
                return;
+       }
 
-       spin_lock(&vmpr->sr_lock);
-       scanned = vmpr->scanned;
        reclaimed = vmpr->reclaimed;
        vmpr->scanned = 0;
        vmpr->reclaimed = 0;
-- 
2.1.3

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