linux-kernel - [PATCH 2/2] hv_balloon: do adjust_managed_page

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Date:   Wed,  2 Dec 2020 17:12:45 +0100
From:   Vitaly Kuznetsov <vkuznets@...hat.com>
To:     linux-hyperv@...r.kernel.org
Cc:     Wei Liu <wei.liu@...nel.org>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Michael Kelley <mikelley@...rosoft.com>,
        Dexuan Cui <decui@...rosoft.com>,
        David Hildenbrand <david@...hat.com>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: [PATCH 2/2] hv_balloon: do adjust_managed_page_count() when ballooning/un-ballooning

Unlike virtio_balloon/virtio_mem/xen balloon drivers, Hyper-V balloon driver
does not adjust managed pages count when ballooning/un-ballooning and this leads
to incorrect stats being reported, e.g. unexpected 'free' output.

Note, the calculation in post_status() seems to remain correct: ballooned out
pages are never 'available' and we manually add dm->num_pages_ballooned to
'commited'.

Suggested-by: David Hildenbrand <david@...hat.com>
Signed-off-by: Vitaly Kuznetsov <vkuznets@...hat.com>
---
 drivers/hv/hv_balloon.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/hv/hv_balloon.c b/drivers/hv/hv_balloon.c
index da3b6bd2367c..8c471823a5af 100644
--- a/drivers/hv/hv_balloon.c
+++ b/drivers/hv/hv_balloon.c
@@ -1198,6 +1198,7 @@ static void free_balloon_pages(struct hv_dynmem_device *dm,
 		__ClearPageOffline(pg);
 		__free_page(pg);
 		dm->num_pages_ballooned--;
+		adjust_managed_page_count(pg, 1);
 	}
 }
 
@@ -1238,8 +1239,10 @@ static unsigned int alloc_balloon_pages(struct hv_dynmem_device *dm,
 			split_page(pg, get_order(alloc_unit << PAGE_SHIFT));
 
 		/* mark all pages offline */
-		for (j = 0; j < alloc_unit; j++)
+		for (j = 0; j < alloc_unit; j++) {
 			__SetPageOffline(pg + j);
+			adjust_managed_page_count(pg + j, -1);
+		}
 
 		bl_resp->range_count++;
 		bl_resp->range_array[i].finfo.start_page =
-- 
2.26.2