| Message ID | 1362405755-3308-6-git-send-email-stefanha@redhat.com |
|---|---|
| State | New |
| Headers | show |
diff --git a/block/qcow2-refcount.c b/block/qcow2-refcount.c index 3d29d30..92519ea 100644 --- a/block/qcow2-refcount.c +++ b/block/qcow2-refcount.c @@ -532,8 +532,6 @@ static int update_cluster_refcount(BlockDriverState *bs, return ret; } - bdrv_flush(bs->file); - return get_refcount(bs, cluster_index); }
The update_cluster_refcount() function increments/decrements a cluster's refcount and then returns the new refcount value. There is no need to flush since both update_cluster_refcount() callers already take care of this: 1. qcow2_alloc_bytes() calls update_cluster_refcount() when compressed sectors will be appended to an existing cluster with enough free space. qcow2_alloc_bytes() already flushes so there is no need to do so in update_cluster_refcount(). 2. qcow2_update_snapshot_refcount() sets a cache dependency on refcounts if it needs to update L2 entries. It also flushes before completing. Removing this flush significantly speeds up qcow2 snapshot creation: $ qemu-img create -f qcow2 test.qcow2 -o size=50G,preallocation=metadata $ time qemu-img snapshot -c new test.qcow2 Time drops from more than 3 minutes to under 1 second. Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com> --- block/qcow2-refcount.c | 2 -- 1 file changed, 2 deletions(-)