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

Commit Message

Kevin Wolf May 8, 2020, 12:41 p.m. UTC

From: Eric Blake <[e-mail]>

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 <[e-mail]>
Message-Id: <[e-mail]>
Reviewed-by: Richard W.M. Jones <[e-mail]>
Signed-off-by: Kevin Wolf <[e-mail]>
---
 block/ssh.c | 4 ++++
 1 file changed, 4 insertions(+)

Patch

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;