[PATCH 5/8] Drivers: hv: util: Pass the channel information during the init call

["K. Y. Srinivasan" <kys@microsoft.com>]

Pass the channel information to the util drivers that need to defer
reading the channel while they are processing a request. This would address
the following issue reported by Vitaly:

Commit 3cace4a61610 ("Drivers: hv: utils: run polling callback always in
interrupt context") removed direct *_transaction.state = HVUTIL_READY
assignments from *_handle_handshake() functions introducing the following
race: if a userspace daemon connects before we get first non-negotiation
request from the server hv_poll_channel() won't set transaction state to
HVUTIL_READY as (!channel) condition will fail, we set it to non-NULL on
the first real request from the server.

Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Reported-by: Vitaly Kuznetsov <vkuznets@redhat.com>
---
 drivers/hv/hv_fcopy.c    |    2 +-
 drivers/hv/hv_kvp.c      |    2 +-
 drivers/hv/hv_snapshot.c |    2 +-
 drivers/hv/hv_util.c     |    1 +
 include/linux/hyperv.h   |    1 +
 5 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/hv/hv_fcopy.c b/drivers/hv/hv_fcopy.c
index c37a71e..23c7079 100644
--- a/drivers/hv/hv_fcopy.c
+++ b/drivers/hv/hv_fcopy.c
@@ -251,7 +251,6 @@ void hv_fcopy_onchannelcallback(void *context)
 		 */
 
 		fcopy_transaction.recv_len = recvlen;
-		fcopy_transaction.recv_channel = channel;
 		fcopy_transaction.recv_req_id = requestid;
 		fcopy_transaction.fcopy_msg = fcopy_msg;
 
@@ -317,6 +316,7 @@ static void fcopy_on_reset(void)
 int hv_fcopy_init(struct hv_util_service *srv)
 {
 	recv_buffer = srv->recv_buffer;
+	fcopy_transaction.recv_channel = srv->channel;
 
 	/*
 	 * When this driver loads, the user level daemon that
diff --git a/drivers/hv/hv_kvp.c b/drivers/hv/hv_kvp.c
index d4ab81b..9b9b370 100644
--- a/drivers/hv/hv_kvp.c
+++ b/drivers/hv/hv_kvp.c
@@ -639,7 +639,6 @@ void hv_kvp_onchannelcallback(void *context)
 			 */
 
 			kvp_transaction.recv_len = recvlen;
-			kvp_transaction.recv_channel = channel;
 			kvp_transaction.recv_req_id = requestid;
 			kvp_transaction.kvp_msg = kvp_msg;
 
@@ -688,6 +687,7 @@ int
 hv_kvp_init(struct hv_util_service *srv)
 {
 	recv_buffer = srv->recv_buffer;
+	kvp_transaction.recv_channel = srv->channel;
 
 	/*
 	 * When this driver loads, the user level daemon that
diff --git a/drivers/hv/hv_snapshot.c b/drivers/hv/hv_snapshot.c
index 67def4a..3fba14e 100644
--- a/drivers/hv/hv_snapshot.c
+++ b/drivers/hv/hv_snapshot.c
@@ -263,7 +263,6 @@ void hv_vss_onchannelcallback(void *context)
 			 */
 
 			vss_transaction.recv_len = recvlen;
-			vss_transaction.recv_channel = channel;
 			vss_transaction.recv_req_id = requestid;
 			vss_transaction.msg = (struct hv_vss_msg *)vss_msg;
 
@@ -337,6 +336,7 @@ hv_vss_init(struct hv_util_service *srv)
 		return -ENOTSUPP;
 	}
 	recv_buffer = srv->recv_buffer;
+	vss_transaction.recv_channel = srv->channel;
 
 	/*
 	 * When this driver loads, the user level daemon that
diff --git a/drivers/hv/hv_util.c b/drivers/hv/hv_util.c
index 7994ec2..d5acaa2 100644
--- a/drivers/hv/hv_util.c
+++ b/drivers/hv/hv_util.c
@@ -322,6 +322,7 @@ static int util_probe(struct hv_device *dev,
 	srv->recv_buffer = kmalloc(PAGE_SIZE * 4, GFP_KERNEL);
 	if (!srv->recv_buffer)
 		return -ENOMEM;
+	srv->channel = dev->channel;
 	if (srv->util_init) {
 		ret = srv->util_init(srv);
 		if (ret) {
diff --git a/include/linux/hyperv.h b/include/linux/hyperv.h
index d23dab0..aa0fadc 100644
--- a/include/linux/hyperv.h
+++ b/include/linux/hyperv.h
@@ -1251,6 +1251,7 @@ u64 hv_do_hypercall(u64 control, void *input, void *output);
 
 struct hv_util_service {
 	u8 *recv_buffer;
+	void *channel;
 	void (*util_cb)(void *);
 	int (*util_init)(struct hv_util_service *);
 	void (*util_deinit)(void);
-- 
1.7.4.1