[Qemu-devel] [PATCH v3 3/4] 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.

Replace 9 and 512 with BDRV_SECTOR_BITS, BDRV_SECTOR_SIZE
respectively while at the function.

Reviewed-by: Max Reitz <address@hidden>
Signed-off-by: Hu Tao <address@hidden>
---
 block/qcow2.c | 25 ++++++++++++++-----------
 1 file changed, 14 insertions(+), 11 deletions(-)

diff --git a/block/qcow2.c b/block/qcow2.c
index a0596ec..e4e06f9 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -1395,22 +1395,24 @@ static int preallocate(BlockDriverState *bs)
     int ret;
     QCowL2Meta *meta;
 
-    nb_sectors = bdrv_getlength(bs) >> 9;
+    nb_sectors = bdrv_getlength(bs) >> BDRV_SECTOR_BITS;
     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
@@ -1422,7 +1424,7 @@ static int preallocate(BlockDriverState *bs)
         /* TODO Preallocate data if requested */
 
         nb_sectors -= num;
-        offset += num << 9;
+        offset += num << BDRV_SECTOR_BITS;
     }
 
     /*
@@ -1431,9 +1433,10 @@ static int preallocate(BlockDriverState *bs)
      * EOF). Extend the image to the last allocated sector.
      */
     if (host_offset != 0) {
-        uint8_t buf[512];
-        memset(buf, 0, 512);
-        ret = bdrv_write(bs->file, (host_offset >> 9) + num - 1, buf, 1);
+        uint8_t buf[BDRV_SECTOR_SIZE];
+        memset(buf, 0, BDRV_SECTOR_SIZE);
+        ret = bdrv_write(bs->file, (host_offset >> BDRV_SECTOR_BITS) + num - 1,
+                         buf, 1);
         if (ret < 0) {
             return ret;
         }
-- 
1.8.5.2.229.g4448466