block: Fix max nb_sectors in bdrv_make_zero

In bdrv_rw_co we report -EINVAL for nb_sectors > INT_MAX /
BDRV_SECTOR_SIZE, so a caller shouldn't exceed it.
Signed-off-by: NFam Zheng <famz@redhat.com>
Reviewed-by: NMarkus Armbruster <armbru@redhat.com>
Message-id: 1415603264-21497-1-git-send-email-famz@redhat.com
Signed-off-by: NStefan Hajnoczi <stefanha@redhat.com>

block.c

@@ -2790,8 +2790,8 @@ int bdrv_make_zero(BlockDriverState *bs, BdrvRequestFlags flags)
         if (nb_sectors <= 0) {
             return 0;
         }
-        if (nb_sectors > INT_MAX) {
-            nb_sectors = INT_MAX;
+        if (nb_sectors > INT_MAX / BDRV_SECTOR_SIZE) {
+            nb_sectors = INT_MAX / BDRV_SECTOR_SIZE;
         }
         ret = bdrv_get_block_status(bs, sector_num, nb_sectors, &n);
         if (ret < 0) {