From 56152f8d7cb931e6172a9e44bec7fe274716a240 Mon Sep 17 00:00:00 2001
From: John Snow <jsnow@redhat.com>
Date: Wed, 6 Feb 2019 22:12:37 +0100
Subject: [PATCH 27/33] bitmap: Update count after a merge

RH-Author: John Snow <jsnow@redhat.com>
Message-id: <20190206221243.7407-18-jsnow@redhat.com>
Patchwork-id: 84282
O-Subject: [RHEL-7.7 qemu-kvm-rhev PATCH v2 17/23] bitmap: Update count after a merge
Bugzilla: 1658343
RH-Acked-by: Thomas Huth <thuth@redhat.com>
RH-Acked-by: Laurent Vivier <lvivier@redhat.com>
RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>

From: Eric Blake <eblake@redhat.com>

We need an accurate count of the number of bits set in a bitmap
after a merge. In particular, since the merge operation short-circuits
a merge from an empty source, if you have bitmaps A, B, and C where
B started empty, then merge C into B, and B into A, an inaccurate
count meant that A did not get the contents of C.

In the worst case, we may falsely regard the bitmap as empty when
it has had new writes merged into it.

Fixes: be58721db
CC: qemu-stable@nongnu.org
Signed-off-by: Eric Blake <eblake@redhat.com>
Signed-off-by: John Snow <jsnow@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-id: 20181002233314.30159-1-jsnow@redhat.com
Signed-off-by: John Snow <jsnow@redhat.com>
(cherry picked from commit d1dde7149e376d72b422a529ec4bf3ed47f3ba30)
Signed-off-by: John Snow <jsnow@redhat.com>
Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
---
 util/hbitmap.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/util/hbitmap.c b/util/hbitmap.c
index d5aca51..8d402c5 100644
--- a/util/hbitmap.c
+++ b/util/hbitmap.c
@@ -759,6 +759,9 @@ bool hbitmap_merge(const HBitmap *a, const HBitmap *b, HBitmap *result)
         }
     }
 
+    /* Recompute the dirty count */
+    result->count = hb_count_between(result, 0, result->size - 1);
+
     return true;
 }
 
-- 
1.8.3.1