block: always open drivers in writeback mode
Formats are entirely in charge of flushes for metadata writes. For
guest-initiated writes, a writethrough cache is faked in the block layer.
So we can always open in writeback mode.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
diff --git a/block.c b/block.c
index e4396a6..48528fd 100644
--- a/block.c
+++ b/block.c
@@ -649,12 +649,13 @@
bs->opaque = g_malloc0(drv->instance_size);
bs->enable_write_cache = !!(flags & BDRV_O_CACHE_WB);
+ open_flags = flags | BDRV_O_CACHE_WB;
/*
* Clear flags that are internal to the block layer before opening the
* image.
*/
- open_flags = flags & ~(BDRV_O_SNAPSHOT | BDRV_O_NO_BACKING);
+ open_flags &= ~(BDRV_O_SNAPSHOT | BDRV_O_NO_BACKING);
/*
* Snapshots should be writable.
