cryptospore / rpms / qemu-kvm

Forked from rpms/qemu-kvm 2 years ago
Clone

Blame SOURCES/kvm-qcow2-Respect-new_block-in-alloc_refcount_block.patch

05bba0
From 9bffc974294d823d42b4b4d51e44abd26f7147a6 Mon Sep 17 00:00:00 2001
05bba0
From: Max Reitz <mreitz@redhat.com>
05bba0
Date: Sat, 13 Jun 2015 16:22:33 +0200
05bba0
Subject: [PATCH 39/42] qcow2: Respect new_block in alloc_refcount_block()
05bba0
05bba0
Message-id: <1434212556-3927-40-git-send-email-mreitz@redhat.com>
05bba0
Patchwork-id: 66058
05bba0
O-Subject: [RHEL-7.2 qemu-kvm PATCH 39/42] qcow2: Respect new_block in alloc_refcount_block()
05bba0
Bugzilla: 1129893
05bba0
RH-Acked-by: Jeffrey Cody <jcody@redhat.com>
05bba0
RH-Acked-by: Fam Zheng <famz@redhat.com>
05bba0
RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
05bba0
05bba0
BZ: 1129893
05bba0
05bba0
When choosing a new place for the refcount table, alloc_refcount_block()
05bba0
tries to infer the number of clusters used so far from its argument
05bba0
cluster_index (which comes from the idea that if any cluster with an
05bba0
index greater than cluster_index was in use, the refcount table would
05bba0
have to be big enough already to describe cluster_index).
05bba0
05bba0
However, there is a cluster that may be at or after cluster_index, and
05bba0
which is not covered by the refcount structures, and that is the new
05bba0
refcount block new_block. Therefore, it should be taken into account for
05bba0
the blocks_used calculation.
05bba0
05bba0
Also, because new_block already describes (or is intended to describe)
05bba0
cluster_index, we may not put the new refcount structures there.
05bba0
05bba0
Signed-off-by: Max Reitz <mreitz@redhat.com>
05bba0
Message-id: 1423598552-24301-2-git-send-email-mreitz@redhat.com
05bba0
Reviewed-by: Eric Blake <eblake@redhat.com>
05bba0
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
05bba0
Signed-off-by: Max Reitz <mreitz@redhat.com>
05bba0
(cherry picked from commit 14a58a4e0c2e98a7d9232e1c229a531ca231133b)
05bba0
05bba0
Signed-off-by: Max Reitz <mreitz@redhat.com>
05bba0
Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
05bba0
---
05bba0
 block/qcow2-refcount.c | 16 ++++++++++++++--
05bba0
 1 file changed, 14 insertions(+), 2 deletions(-)
05bba0
05bba0
diff --git a/block/qcow2-refcount.c b/block/qcow2-refcount.c
05bba0
index 87b932c..cee5b1f 100644
05bba0
--- a/block/qcow2-refcount.c
05bba0
+++ b/block/qcow2-refcount.c
05bba0
@@ -319,8 +319,20 @@ static int alloc_refcount_block(BlockDriverState *bs,
05bba0
      */
05bba0
     BLKDBG_EVENT(bs->file, BLKDBG_REFTABLE_GROW);
05bba0
 
05bba0
-    /* Calculate the number of refcount blocks needed so far */
05bba0
-    uint64_t blocks_used = DIV_ROUND_UP(cluster_index, s->refcount_block_size);
05bba0
+    /* Calculate the number of refcount blocks needed so far; this will be the
05bba0
+     * basis for calculating the index of the first cluster used for the
05bba0
+     * self-describing refcount structures which we are about to create.
05bba0
+     *
05bba0
+     * Because we reached this point, there cannot be any refcount entries for
05bba0
+     * cluster_index or higher indices yet. However, because new_block has been
05bba0
+     * allocated to describe that cluster (and it will assume this role later
05bba0
+     * on), we cannot use that index; also, new_block may actually have a higher
05bba0
+     * cluster index than cluster_index, so it needs to be taken into account
05bba0
+     * here (and 1 needs to be added to its value because that cluster is used).
05bba0
+     */
05bba0
+    uint64_t blocks_used = DIV_ROUND_UP(MAX(cluster_index + 1,
05bba0
+                                            (new_block >> s->cluster_bits) + 1),
05bba0
+                                        s->refcount_block_size);
05bba0
 
05bba0
     if (blocks_used > QCOW_MAX_REFTABLE_SIZE / sizeof(uint64_t)) {
05bba0
         return -EFBIG;
05bba0
-- 
05bba0
1.8.3.1
05bba0