From: Patrick Caulfield <pcaulfie@redhat.com>
Date: Thu, 1 Nov 2007 10:30:12 +0000
Subject: [dlm] Don't overwrite castparam if it's NULL
Message-id: 4729AAB4.7010307@redhat.com
O-Subject: [RHEL5.2 PATCH] bz#318061 Don't overwrite castparam if it's NULL
Bugzilla: 318061

If the castaddr passed to the userland API is NULL then don't overwrite the
existing castparam. This allows a different thread to cancel a lock request
and the CANCEL AST gets delivered to the original thread.

Signed-Off-By: Patrick Caulfield <pcaulfie@redhat.com>

diff --git a/fs/dlm/lock.c b/fs/dlm/lock.c
index de8b3ca..23c332f 100644
--- a/fs/dlm/lock.c
+++ b/fs/dlm/lock.c
@@ -4430,7 +4430,8 @@ int dlm_user_unlock(struct dlm_ls *ls, struct dlm_user_args *ua_tmp,
 
 	if (lvb_in && ua->lksb.sb_lvbptr)
 		memcpy(ua->lksb.sb_lvbptr, lvb_in, DLM_USER_LVB_LEN);
-	ua->castparam = ua_tmp->castparam;
+	if (ua_tmp->castparam)
+		ua->castparam = ua_tmp->castparam;
 	ua->user_lksb = ua_tmp->user_lksb;
 
 	error = set_unlock_args(flags, ua, &args);
@@ -4475,7 +4476,8 @@ int dlm_user_cancel(struct dlm_ls *ls, struct dlm_user_args *ua_tmp,
 		goto out;
 
 	ua = (struct dlm_user_args *)lkb->lkb_astparam;
-	ua->castparam = ua_tmp->castparam;
+	if (ua_tmp->castparam)
+		ua->castparam = ua_tmp->castparam;
 	ua->user_lksb = ua_tmp->user_lksb;
 
 	error = set_unlock_args(flags, ua, &args);