[PATCH 096/117] Staging: hv: netvsc: Further cleanup reference counting of netvsc_device

[K. Y. Srinivasan]

Further cleanup reference counting of netvsc_device. Since once the device
is marked for destruction, we only allow incoming traffic to drain out
outstanding sends, we can simplify reference counting.

Signed-off-by: K. Y. Srinivasan <k...@microsoft.com>
Signed-off-by: Haiyang Zhang <haiya...@microsoft.com>
---
 drivers/staging/hv/netvsc.c |   27 ++++++++++++++++++---------
 1 files changed, 18 insertions(+), 9 deletions(-)

diff --git a/drivers/staging/hv/netvsc.c b/drivers/staging/hv/netvsc.c
index 4ef17d8..16a80b1 100644
--- a/drivers/staging/hv/netvsc.c
+++ b/drivers/staging/hv/netvsc.c
@@ -17,6 +17,7 @@
  * Authors:
  *   Haiyang Zhang <haiya...@microsoft.com>
  *   Hank Janssen  <hjans...@microsoft.com>
+ *   K. Y. Srinivasan <k...@microsoft.com>
  */
 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
 
@@ -40,8 +41,7 @@ static struct netvsc_device *alloc_net_device(struct 
hv_device *device)
        if (!net_device)
                return NULL;
 
-       /* Set to 2 to allow both inbound and outbound traffic */
-       net_device->refcnt = 2;
+       net_device->refcnt = 1;
 
        net_device->destroy = false;
        net_device->dev = device;
@@ -50,7 +50,6 @@ static struct netvsc_device *alloc_net_device(struct 
hv_device *device)
        return net_device;
 }
 
-/* Get the net device object iff exists and its refcount > 1 */
 static struct netvsc_device *get_outbound_net_device(struct hv_device *device)
 {
        struct netvsc_device *net_device;
@@ -58,7 +57,7 @@ static struct netvsc_device *get_outbound_net_device(struct 
hv_device *device)
 
        spin_lock_irqsave(&device->ext_lock, flags);
        net_device = device->ext;
-       if (net_device && (net_device->refcnt > 1) &&
+       if (net_device && (net_device->refcnt) &&
                !net_device->destroy)
                net_device->refcnt++;
        else
@@ -68,7 +67,6 @@ static struct netvsc_device *get_outbound_net_device(struct 
hv_device *device)
        return net_device;
 }
 
-/* Get the net device object iff exists and its refcount > 0 */
 static struct netvsc_device *get_inbound_net_device(struct hv_device *device)
 {
        struct netvsc_device *net_device;
@@ -76,11 +74,23 @@ static struct netvsc_device *get_inbound_net_device(struct 
hv_device *device)
 
        spin_lock_irqsave(&device->ext_lock, flags);
        net_device = device->ext;
-       if (net_device && net_device->refcnt)
-               net_device->refcnt++;
-       else
+
+       if (!net_device)
+               goto cleanup;
+
+       /*
+        * If the device is being destroyed; allow incoming
+        * traffic only to cleanup outstanding requests.
+        */
+       if (net_device->destroy &&
+               (atomic_read(&net_device->num_outstanding_sends) == 0)) {
                net_device = NULL;
+               goto cleanup;
+       }
 
+       net_device->refcnt++;
+
+cleanup:
        spin_unlock_irqrestore(&device->ext_lock, flags);
        return net_device;
 }
@@ -400,7 +410,6 @@ int netvsc_device_remove(struct hv_device *device)
        netvsc_disconnect_vsp(net_device);
 
        spin_lock_irqsave(&device->ext_lock, flags);
-       net_device->refcnt--;
        device->ext = NULL;
        spin_unlock_irqrestore(&device->ext_lock, flags);
 
-- 
1.7.4.1

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