[Qemu-devel] [PATCH v4 1/6] Postcopy: Avoid 0 length discards

["Dr. David Alan Gilbert (git)" <dgilbert@redhat.com>]

From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>

The discard code in migration/ram.c would send request for
zero length discards in the case where no discards were needed.
It doesn't appear to have had any bad effect.

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: Denis V. Lunev <den@openvz.org>
---
 migration/ram.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/migration/ram.c b/migration/ram.c
index 3f05738..e96c2af 100644
--- a/migration/ram.c
+++ b/migration/ram.c
@@ -1557,7 +1557,9 @@ static int postcopy_send_discard_bm_ram(MigrationState *ms,
             } else {
                 discard_length = zero - one;
             }
-            postcopy_discard_send_range(ms, pds, one, discard_length);
+            if (discard_length) {
+                postcopy_discard_send_range(ms, pds, one, discard_length);
+            }
             current = one + discard_length;
         } else {
             current = one;
-- 
2.5.5