Commit fa778fff wired up support to send the NBD_CMD_WRITE_ZEROES,
but forgot to inform the block layer that FUA unmapping of zeroes is
supported. Without BDRV_REQ_MAY_UNMAP listed as a supported flag,
the block layer will always insist on the NBD layer passing
NBD_CMD_FLAG_NO_HOLE, resulting in the server always allocating
things even when it was desired to let the server punch holes.
Similarly, failing to set BDRV_REQ_FUA means that the client may
send unnecessary NBD_CMD_FLUSH when it could have instead used the
NBD_CMD_FLAG_FUA bit.
CC: qemu-sta...@nongnu.org
Signed-off-by: Eric Blake <ebl...@redhat.com>
---
block/nbd-client.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/block/nbd-client.c b/block/nbd-client.c
index 2a302de..3779c6c 100644
--- a/block/nbd-client.c
+++ b/block/nbd-client.c
@@ -415,6 +415,10 @@ int nbd_client_init(BlockDriverState *bs,
}
if (client->nbdflags & NBD_FLAG_SEND_FUA) {
bs->supported_write_flags = BDRV_REQ_FUA;
+ bs->supported_zero_flags |= BDRV_REQ_FUA;
+ }
+ if (client->nbdflags & NBD_FLAG_SEND_WRITE_ZEROES) {
+ bs->supported_zero_flags |= BDRV_REQ_MAY_UNMAP;
}
qemu_co_mutex_init(&client->send_mutex);
--
2.7.4
