[Xen-changelog] [qemu-upstream-unstable] qcow2: count_contiguous_clusters and compression

[patchbot@xxxxxxx]

commit 4a5bf69f78e20a64f35770612ee897da4d80082e
Author:     Max Reitz <mreitz@xxxxxxxxxx>
AuthorDate: Fri Sep 27 12:14:15 2013 +0200
Commit:     Michael Roth <mdroth@xxxxxxxxxxxxxxxxxx>
CommitDate: Mon Dec 9 11:40:30 2013 -0600

    qcow2: count_contiguous_clusters and compression
    
    The function is not intended to be used on compressed clusters and will
    not work correctly, if used anyway, since L2E_OFFSET_MASK is not the
    right mask for determining the offset of compressed clusters. Therefore,
    assert that the first cluster is not compressed and always include the
    compression flag in the mask of significant flags, i.e., stop the search
    as soon as a compressed cluster occurs.
    
    Signed-off-by: Max Reitz <mreitz@xxxxxxxxxx>
    Signed-off-by: Kevin Wolf <kwolf@xxxxxxxxxx>
    (cherry picked from commit 15684a474286cc2c6106c756ddd095a21d058970)
    
    Signed-off-by: Michael Roth <mdroth@xxxxxxxxxxxxxxxxxx>
---
 block/qcow2-cluster.c |    7 +++++--
 1 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c
index cca76d4..fd3054b 100644
--- a/block/qcow2-cluster.c
+++ b/block/qcow2-cluster.c
@@ -266,12 +266,15 @@ static int count_contiguous_clusters(uint64_t 
nb_clusters, int cluster_size,
         uint64_t *l2_table, uint64_t start, uint64_t stop_flags)
 {
     int i;
-    uint64_t mask = stop_flags | L2E_OFFSET_MASK;
-    uint64_t offset = be64_to_cpu(l2_table[0]) & mask;
+    uint64_t mask = stop_flags | L2E_OFFSET_MASK | QCOW2_CLUSTER_COMPRESSED;
+    uint64_t first_entry = be64_to_cpu(l2_table[0]);
+    uint64_t offset = first_entry & mask;
 
     if (!offset)
         return 0;
 
+    assert(qcow2_get_cluster_type(first_entry) != QCOW2_CLUSTER_COMPRESSED);
+
     for (i = start; i < start + nb_clusters; i++) {
         uint64_t l2_entry = be64_to_cpu(l2_table[i]) & mask;
         if (offset + (uint64_t) i * cluster_size != l2_entry) {
--
generated by git-patchbot for /home/xen/git/qemu-upstream-unstable.git

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