[PATCH v2] qcow2-bitmap: Fix uint64_t left-shift overflow

[Tuguoyi]

In check_constraints_on_bitmap(), the sanity check on the
granularity will cause uint64_t integer left-shift overflow
when cluster_size is 2M and the granularity is BIGGER than
32K. As a result, for a qcow2 disk with cluster_size set to
2M, we could not even create a dirty bitmap with default
granularity. This patch fix the issue by dividing @len by
granularity instead.

Signed-off-by: Guoyi Tu <address@hidden>
---
 block/qcow2-bitmap.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/block/qcow2-bitmap.c b/block/qcow2-bitmap.c
index 98294a7..71ac822 100644
--- a/block/qcow2-bitmap.c
+++ b/block/qcow2-bitmap.c
@@ -172,8 +172,8 @@ static int check_constraints_on_bitmap(BlockDriverState *bs,
     }
 
     if ((len > (uint64_t)BME_MAX_PHYS_SIZE << granularity_bits) ||
-        (len > (uint64_t)BME_MAX_TABLE_SIZE * s->cluster_size <<
-               granularity_bits))
+        (DIV_ROUND_UP(len, granularity) > (uint64_t)BME_MAX_TABLE_SIZE *
+                s->cluster_size))
     {
         error_setg(errp, "Too much space will be occupied by the bitmap. "
                    "Use larger granularity");
-- 
2.7.4