qcow2: Make cache=writethrough default

The performance of qcow2 has improved meanwhile, so we don't need to
special-case it any more. Switch the default to write-through caching
like all other block drivers.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

1 files changed, 0 insertions, 8 deletions

diff --git a/block/qcow2.c b/block/qcow2.c
index 20c114b139..9a7c666ee7 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -145,14 +145,6 @@ static int qcow_open(BlockDriverState *bs, const char *filename, int flags)
     QCowHeader header;
     uint64_t ext_end;
 
-    /* Performance is terrible right now with cache=writethrough due mainly
-     * to reference count updates.  If the user does not explicitly specify
-     * a caching type, force to writeback caching.
-     */
-    if ((flags & BDRV_O_CACHE_DEF)) {
-        flags |= BDRV_O_CACHE_WB;
-        flags &= ~BDRV_O_CACHE_DEF;
-    }
     ret = bdrv_file_open(&s->hd, filename, flags);
     if (ret < 0)
         return ret;