[PULL 27/30] ssh: Support BDRV_REQ_ZERO_WRITE for truncate

[Kevin Wolf]

From: Eric Blake <address@hidden>

Our .bdrv_has_zero_init_truncate can detect when the remote side
always zero fills; we can reuse that same knowledge to implement
BDRV_REQ_ZERO_WRITE by ignoring it when the server gives it to us for
free.

Signed-off-by: Eric Blake <address@hidden>
Message-Id: <address@hidden>
Reviewed-by: Richard W.M. Jones <address@hidden>
Signed-off-by: Kevin Wolf <address@hidden>
---
 block/ssh.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/block/ssh.c b/block/ssh.c
index 9eb33df859..f9e08a4900 100644
--- a/block/ssh.c
+++ b/block/ssh.c
@@ -883,6 +883,10 @@ static int ssh_file_open(BlockDriverState *bs, QDict 
*options, int bdrv_flags,
     /* Go non-blocking. */
     ssh_set_blocking(s->session, 0);
 
+    if (s->attrs->type == SSH_FILEXFER_TYPE_REGULAR) {
+        bs->supported_truncate_flags = BDRV_REQ_ZERO_WRITE;
+    }
+
     qapi_free_BlockdevOptionsSsh(opts);
 
     return 0;
-- 
2.25.3