[Qemu-devel] [PATCH v1 3/3] qcow2: check for NULL l2meta

[Hu Tao]

In case of do preallocating metadata with a large cluster size,
qcow2_alloc_cluster_offset() can allocate nothing and returns
a NULL l2meta. This patch checks for it and link2 l2 with only
valid l2meta.

Signed-off-by: Hu Tao <hu...@cn.fujitsu.com>
---
 block/qcow2.c | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/block/qcow2.c b/block/qcow2.c
index 46860d5..380c240 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -1399,18 +1399,20 @@ static int preallocate(BlockDriverState *bs)
     offset = 0;
 
     while (nb_sectors) {
-        num = MIN(nb_sectors, INT_MAX >> 9);
+        num = MIN(nb_sectors, INT_MAX >> BDRV_SECTOR_BITS);
         ret = qcow2_alloc_cluster_offset(bs, offset, &num,
                                          &host_offset, &meta);
         if (ret < 0) {
             return ret;
         }
 
-        ret = qcow2_alloc_cluster_link_l2(bs, meta);
-        if (ret < 0) {
-            qcow2_free_any_clusters(bs, meta->alloc_offset, meta->nb_clusters,
-                                    QCOW2_DISCARD_NEVER);
-            return ret;
+        if (meta) {
+            ret = qcow2_alloc_cluster_link_l2(bs, meta);
+            if (ret < 0) {
+                qcow2_free_any_clusters(bs, meta->alloc_offset,
+                                        meta->nb_clusters, 
QCOW2_DISCARD_NEVER);
+                return ret;
+            }
         }
 
         /* There are no dependent requests, but we need to remove our request
-- 
1.7.11.7