cifs: fix interface count calculation during refresh

The last fix to iface_count did fix the overcounting issue.
However, during each refresh, we could end up undercounting
the iface_count, if a match was found.

Fixing this by doing increments and decrements instead of
setting it to 0 before each parsing of server interfaces.

Fixes: 096bbeec7b ("smb3: interface count displayed incorrectly")
Cc: stable@vger.kernel.org # 6.1
Signed-off-by: Shyam Prasad N <sprasad@microsoft.com>
Reviewed-by: Paulo Alcantara (SUSE) <pc@cjr.nz>
Signed-off-by: Steve French <stfrench@microsoft.com>

fs/cifs/smb2ops.c

@@ -530,7 +530,6 @@ parse_server_interfaces(struct network_interface_info_ioctl_rsp *buf,
 	p = buf;
 
 	spin_lock(&ses->iface_lock);
-	ses->iface_count = 0;
 	/*
 	 * Go through iface_list and do kref_put to remove
 	 * any unused ifaces. ifaces in use will be removed
@@ -540,6 +539,7 @@ parse_server_interfaces(struct network_interface_info_ioctl_rsp *buf,
 				 iface_head) {
 		iface->is_active = 0;
 		kref_put(&iface->refcount, release_iface);
+		ses->iface_count--;
 	}
 	spin_unlock(&ses->iface_lock);
 
@@ -618,6 +618,7 @@ parse_server_interfaces(struct network_interface_info_ioctl_rsp *buf,
 				/* just get a ref so that it doesn't get picked/freed */
 				iface->is_active = 1;
 				kref_get(&iface->refcount);
+				ses->iface_count++;
 				spin_unlock(&ses->iface_lock);
 				goto next_iface;
 			} else if (ret < 0) {