qcow2: Fix bdrv_write_compressed error handling

If during allocation of compressed clusters the cluster was already allocated
uncompressed, fail and properly release the l2_table (the latter avoids a
failed assertion).

While at it, make it return some real error numbers instead of -1.
Signed-off-by: NKevin Wolf <kwolf@redhat.com>
Reviewed-by: NDong Xu Wang <wdongxu@linux.vnet.ibm.com>

block/qcow2-cluster.c

@@ -568,8 +568,10 @@ uint64_t qcow2_alloc_compressed_cluster_offset(BlockDriverState *bs,
     }
 
     cluster_offset = be64_to_cpu(l2_table[l2_index]);
-    if (cluster_offset & QCOW_OFLAG_COPIED)
-        return cluster_offset & ~QCOW_OFLAG_COPIED;
+    if (cluster_offset & QCOW_OFLAG_COPIED) {
+        qcow2_cache_put(bs, s->l2_table_cache, (void**) &l2_table);
+        return 0;
+    }
 
     if (cluster_offset)
         qcow2_free_any_clusters(bs, cluster_offset, 1);

block/qcow2.c

@@ -1053,8 +1053,8 @@ static int qcow2_write_compressed(BlockDriverState *bs, int64_t sector_num,
                        Z_DEFLATED, -12,
                        9, Z_DEFAULT_STRATEGY);
     if (ret != 0) {
-        g_free(out_buf);
-        return -1;
+        ret = -EINVAL;
+        goto fail;
     }
 
     strm.avail_in = s->cluster_size;
@@ -1064,9 +1064,9 @@ static int qcow2_write_compressed(BlockDriverState *bs, int64_t sector_num,
 
     ret = deflate(&strm, Z_FINISH);
     if (ret != Z_STREAM_END && ret != Z_OK) {
-        g_free(out_buf);
         deflateEnd(&strm);
-        return -1;
+        ret = -EINVAL;
+        goto fail;
     }
     out_len = strm.next_out - out_buf;
 
@@ -1074,22 +1074,29 @@ static int qcow2_write_compressed(BlockDriverState *bs, int64_t sector_num,
 
     if (ret != Z_STREAM_END || out_len >= s->cluster_size) {
         /* could not compress: write normal cluster */
-        bdrv_write(bs, sector_num, buf, s->cluster_sectors);
+        ret = bdrv_write(bs, sector_num, buf, s->cluster_sectors);
+        if (ret < 0) {
+            goto fail;
+        }
     } else {
         cluster_offset = qcow2_alloc_compressed_cluster_offset(bs,
             sector_num << 9, out_len);
-        if (!cluster_offset)
-            return -1;
+        if (!cluster_offset) {
+            ret = -EIO;
+            goto fail;
+        }
         cluster_offset &= s->cluster_offset_mask;
         BLKDBG_EVENT(bs->file, BLKDBG_WRITE_COMPRESSED);
-        if (bdrv_pwrite(bs->file, cluster_offset, out_buf, out_len) != out_len) {
-            g_free(out_buf);
-            return -1;
+        ret = bdrv_pwrite(bs->file, cluster_offset, out_buf, out_len);
+        if (ret < 0) {
+            goto fail;
         }
     }
 
+    ret = 0;
+fail:
     g_free(out_buf);
-    return 0;
+    return ret;
 }
 
 static BlockDriverAIOCB *qcow2_aio_flush(BlockDriverState *bs,