Merge remote-tracking branch 'remotes/kevin/tags/for-upstream' into staging

Patches for 5.2.0-rc3:

- qcow2: Fix corruption on write_zeroes with MAY_UNMAP

# gpg: Signature made Tue 24 Nov 2020 14:23:36 GMT
# gpg:                using RSA key DC3DEB159A9AF95D3D7456FE7F09B272C88F2FD6
# gpg:                issuer "kwolf@redhat.com"
# gpg: Good signature from "Kevin Wolf <kwolf@redhat.com>" [full]
# Primary key fingerprint: DC3D EB15 9A9A F95D 3D74  56FE 7F09 B272 C88F 2FD6

* remotes/kevin/tags/for-upstream:
  qcow2: Fix corruption on write_zeroes with MAY_UNMAP

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

1 files changed, 6 insertions, 3 deletions

diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c
index 485b4cb92e..bd0597842f 100644
--- a/block/qcow2-cluster.c
+++ b/block/qcow2-cluster.c
@@ -2010,14 +2010,17 @@ static int zero_in_l2_slice(BlockDriverState *bs, uint64_t offset,
             continue;
         }
 
+        /* First update L2 entries */
         qcow2_cache_entry_mark_dirty(s->l2_table_cache, l2_slice);
-        if (unmap) {
-            qcow2_free_any_cluster(bs, old_l2_entry, QCOW2_DISCARD_REQUEST);
-        }
         set_l2_entry(s, l2_slice, l2_index + i, new_l2_entry);
         if (has_subclusters(s)) {
             set_l2_bitmap(s, l2_slice, l2_index + i, new_l2_bitmap);
         }
+
+        /* Then decrease the refcount */
+        if (unmap) {
+            qcow2_free_any_cluster(bs, old_l2_entry, QCOW2_DISCARD_REQUEST);
+        }
     }
 
     qcow2_cache_put(s->l2_table_cache, (void **) &l2_slice);