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From 9bffc974294d823d42b4b4d51e44abd26f7147a6 Mon Sep 17 00:00:00 2001
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From: Max Reitz <mreitz@redhat.com>
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Date: Sat, 13 Jun 2015 16:22:33 +0200
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Subject: [PATCH 39/42] qcow2: Respect new_block in alloc_refcount_block()
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Message-id: <1434212556-3927-40-git-send-email-mreitz@redhat.com>
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Patchwork-id: 66058
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O-Subject: [RHEL-7.2 qemu-kvm PATCH 39/42] qcow2: Respect new_block in alloc_refcount_block()
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Bugzilla: 1129893
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RH-Acked-by: Jeffrey Cody <jcody@redhat.com>
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RH-Acked-by: Fam Zheng <famz@redhat.com>
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RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
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BZ: 1129893
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When choosing a new place for the refcount table, alloc_refcount_block()
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tries to infer the number of clusters used so far from its argument
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cluster_index (which comes from the idea that if any cluster with an
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index greater than cluster_index was in use, the refcount table would
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have to be big enough already to describe cluster_index).
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However, there is a cluster that may be at or after cluster_index, and
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which is not covered by the refcount structures, and that is the new
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refcount block new_block. Therefore, it should be taken into account for
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the blocks_used calculation.
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Also, because new_block already describes (or is intended to describe)
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cluster_index, we may not put the new refcount structures there.
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Signed-off-by: Max Reitz <mreitz@redhat.com>
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Message-id: 1423598552-24301-2-git-send-email-mreitz@redhat.com
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Reviewed-by: Eric Blake <eblake@redhat.com>
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Reviewed-by: Kevin Wolf <kwolf@redhat.com>
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Signed-off-by: Max Reitz <mreitz@redhat.com>
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(cherry picked from commit 14a58a4e0c2e98a7d9232e1c229a531ca231133b)
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Signed-off-by: Max Reitz <mreitz@redhat.com>
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Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
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---
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block/qcow2-refcount.c | 16 ++++++++++++++--
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1 file changed, 14 insertions(+), 2 deletions(-)
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diff --git a/block/qcow2-refcount.c b/block/qcow2-refcount.c
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index 87b932c..cee5b1f 100644
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--- a/block/qcow2-refcount.c
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+++ b/block/qcow2-refcount.c
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@@ -319,8 +319,20 @@ static int alloc_refcount_block(BlockDriverState *bs,
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*/
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BLKDBG_EVENT(bs->file, BLKDBG_REFTABLE_GROW);
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- /* Calculate the number of refcount blocks needed so far */
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- uint64_t blocks_used = DIV_ROUND_UP(cluster_index, s->refcount_block_size);
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+ /* Calculate the number of refcount blocks needed so far; this will be the
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+ * basis for calculating the index of the first cluster used for the
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+ * self-describing refcount structures which we are about to create.
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+ *
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+ * Because we reached this point, there cannot be any refcount entries for
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+ * cluster_index or higher indices yet. However, because new_block has been
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+ * allocated to describe that cluster (and it will assume this role later
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+ * on), we cannot use that index; also, new_block may actually have a higher
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+ * cluster index than cluster_index, so it needs to be taken into account
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+ * here (and 1 needs to be added to its value because that cluster is used).
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+ */
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+ uint64_t blocks_used = DIV_ROUND_UP(MAX(cluster_index + 1,
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+ (new_block >> s->cluster_bits) + 1),
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+ s->refcount_block_size);
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if (blocks_used > QCOW_MAX_REFTABLE_SIZE / sizeof(uint64_t)) {
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return -EFBIG;
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--
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1.8.3.1
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