[Qemu-devel] [PATCH] rbd : disable rbd_cache_writethrough_until_flush for cache=unsafe

[Alexandre Derumier]

ceph force writethrough until a flush is detected.
With cache=unsafe, we never send flush.
So we need to tell to ceph
to set rbd_cache_writethrough_until_flush=false in this case.

This speedup a lot qemu-img convert which use cache=unsafe by default

Signed-off-by: Alexandre Derumier <address@hidden>
---
 block/rbd.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/block/rbd.c b/block/rbd.c
index 0106fea..f3af6c8 100644
--- a/block/rbd.c
+++ b/block/rbd.c
@@ -552,6 +552,10 @@ static int qemu_rbd_open(BlockDriverState *bs, QDict 
*options, int flags,
         rados_conf_set(s->cluster, "rbd_cache", "true");
     }
 
+    if (flags & BDRV_O_NO_FLUSH) {
+        rados_conf_set(s->cluster, "rbd_cache_writethrough_until_flush", 
"false");
+    }
+
     r = rados_connect(s->cluster);
     if (r < 0) {
         error_setg_errno(errp, -r, "error connecting");
-- 
2.1.4