linux-kernel - [PATCH 2/5] Drivers: hv: balloon: Correctly update onlined page count

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Message-Id: <1502050376-23662-2-git-send-email-kys@exchange.microsoft.com>
Date:   Sun,  6 Aug 2017 13:12:53 -0700
From:   kys@...hange.microsoft.com
To:     gregkh@...uxfoundation.org, linux-kernel@...r.kernel.org,
        devel@...uxdriverproject.org, olaf@...fle.de, apw@...onical.com,
        vkuznets@...hat.com, jasowang@...hat.com,
        leann.ogasawara@...onical.com, marcelo.cerri@...onical.com,
        sthemmin@...rosoft.com
Cc:     Alex Ng <alexng@...sages.microsoft.com>,
        "K. Y. Srinivasan" <kys@...rosoft.com>
Subject: [PATCH 2/5] Drivers: hv: balloon: Correctly update onlined page count

From: Alex Ng <alexng@...sages.microsoft.com>

Previously, num_pages_onlined was updated using value from memory online
notifier. This is incorrect because they assume that all hot-added pages
are online, even though we only online the amount that's backed by the
host. We should update num_pages_onlined only when the balloon driver
marks a page as online.

Signed-off-by: Alex Ng <alexng@...sages.microsoft.com>
Signed-off-by: K. Y. Srinivasan <kys@...rosoft.com>
---
 drivers/hv/hv_balloon.c |    7 +++----
 1 files changed, 3 insertions(+), 4 deletions(-)

diff --git a/drivers/hv/hv_balloon.c b/drivers/hv/hv_balloon.c
index f5728de..0a5c318 100644
--- a/drivers/hv/hv_balloon.c
+++ b/drivers/hv/hv_balloon.c
@@ -584,10 +584,6 @@ static int hv_memory_notifier(struct notifier_block *nb, unsigned long val,
 
 	switch (val) {
 	case MEM_ONLINE:
-		spin_lock_irqsave(&dm_device.ha_lock, flags);
-		dm_device.num_pages_onlined += mem->nr_pages;
-		spin_unlock_irqrestore(&dm_device.ha_lock, flags);
-		/* Fall through */
 	case MEM_CANCEL_ONLINE:
 		if (dm_device.ha_waiting) {
 			dm_device.ha_waiting = false;
@@ -644,6 +640,9 @@ static void hv_page_online_one(struct hv_hotadd_state *has, struct page *pg)
 	__online_page_set_limits(pg);
 	__online_page_increment_counters(pg);
 	__online_page_free(pg);
+
+	WARN_ON_ONCE(!spin_is_locked(&dm_device.ha_lock));
+	dm_device.num_pages_onlined++;
 }
 
 static void hv_bring_pgs_online(struct hv_hotadd_state *has,
-- 
1.7.1