[xenial][PATCH] vmbus: fix missing signaling in hv_signal_on_read()

[Marcelo Henrique Cerri]

From: Dexuan Cui <decui at microsoft.com>

BugLink: http://bugs.launchpad.net/bugs/1826416

[Fixes upstream in a much larger set of patches that are not worth backporting
to 4.9 - gregkh]

When the space available before start of reading (cached_write_sz)
is the same as the host required space (pending_sz), we need to
still signal host.

Fixes: 433e19cf33d3 ("Drivers: hv: vmbus: finally fix hv_need_to_signal_on_read()")

Signed-off-by: John Starks <jon.Starks at microsoft.com>
Signed-off-by: Dexuan Cui <decui at microsoft.com>
Signed-off-by: Stephen Hemminger <sthemmin at microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
(cherry picked from commit 13c5e97701091f9b02ded0c68809f8a6b08c747a)
Signed-off-by: Marcelo Henrique Cerri <marcelo.cerri at canonical.com>
---
 include/linux/hyperv.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/include/linux/hyperv.h b/include/linux/hyperv.h
index c92a083bcf16..f55a4c0c1475 100644
--- a/include/linux/hyperv.h
+++ b/include/linux/hyperv.h
@@ -1520,11 +1520,11 @@ static inline  void hv_signal_on_read(struct vmbus_channel *channel)
 
 	cur_write_sz = hv_get_bytes_to_write(rbi);
 
-	if (cur_write_sz < pending_sz)
+	if (cur_write_sz <= pending_sz)
 		return;
 
 	cached_write_sz = hv_get_cached_bytes_to_write(rbi);
-	if (cached_write_sz < pending_sz)
+	if (cached_write_sz <= pending_sz)
 		vmbus_setevent(channel);
 
 	return;
-- 
2.20.1