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From 56152f8d7cb931e6172a9e44bec7fe274716a240 Mon Sep 17 00:00:00 2001
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From: John Snow <jsnow@redhat.com>
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Date: Wed, 6 Feb 2019 22:12:37 +0100
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Subject: [PATCH 27/33] bitmap: Update count after a merge
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RH-Author: John Snow <jsnow@redhat.com>
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Message-id: <20190206221243.7407-18-jsnow@redhat.com>
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Patchwork-id: 84282
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O-Subject: [RHEL-7.7 qemu-kvm-rhev PATCH v2 17/23] bitmap: Update count after a merge
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Bugzilla: 1658343
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RH-Acked-by: Thomas Huth <thuth@redhat.com>
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RH-Acked-by: Laurent Vivier <lvivier@redhat.com>
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RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
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From: Eric Blake <eblake@redhat.com>
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We need an accurate count of the number of bits set in a bitmap
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after a merge. In particular, since the merge operation short-circuits
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a merge from an empty source, if you have bitmaps A, B, and C where
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B started empty, then merge C into B, and B into A, an inaccurate
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count meant that A did not get the contents of C.
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In the worst case, we may falsely regard the bitmap as empty when
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it has had new writes merged into it.
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Fixes: be58721db
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CC: qemu-stable@nongnu.org
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Signed-off-by: Eric Blake <eblake@redhat.com>
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Signed-off-by: John Snow <jsnow@redhat.com>
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Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
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Message-id: 20181002233314.30159-1-jsnow@redhat.com
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Signed-off-by: John Snow <jsnow@redhat.com>
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(cherry picked from commit d1dde7149e376d72b422a529ec4bf3ed47f3ba30)
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Signed-off-by: John Snow <jsnow@redhat.com>
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Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
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---
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util/hbitmap.c | 3 +++
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1 file changed, 3 insertions(+)
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diff --git a/util/hbitmap.c b/util/hbitmap.c
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index d5aca51..8d402c5 100644
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--- a/util/hbitmap.c
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+++ b/util/hbitmap.c
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@@ -759,6 +759,9 @@ bool hbitmap_merge(const HBitmap *a, const HBitmap *b, HBitmap *result)
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}
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}
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+ /* Recompute the dirty count */
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+ result->count = hb_count_between(result, 0, result->size - 1);
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+
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return true;
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}
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--
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1.8.3.1
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