2 files changed, 30 insertions, 0 deletions

diff --git a/fs/nfsd/nfs4recover.c b/fs/nfsd/nfs4recover.c
index b4289060ebaf..bf3a3575d060 100644
--- a/fs/nfsd/nfs4recover.c
+++ b/fs/nfsd/nfs4recover.c
@@ -1265,6 +1265,22 @@ nfsd4_umh_cltrack_init(struct net *net)
 }
 
 static void
+nfsd4_cltrack_upcall_lock(struct nfs4_client *clp)
+{
+        wait_on_bit_lock(&clp->cl_flags, NFSD4_CLIENT_UPCALL_LOCK,
+                         TASK_UNINTERRUPTIBLE);
+}
+
+static void
+nfsd4_cltrack_upcall_unlock(struct nfs4_client *clp)
+{
+        smp_mb__before_atomic();
+        clear_bit(NFSD4_CLIENT_UPCALL_LOCK, &clp->cl_flags);
+        smp_mb__after_atomic();
+        wake_up_bit(&clp->cl_flags, NFSD4_CLIENT_UPCALL_LOCK);
+}
+
+static void
 nfsd4_umh_cltrack_create(struct nfs4_client *clp)
 {
         char *hexid, *has_session, *grace_start;
@@ -1275,9 +1291,14 @@ nfsd4_umh_cltrack_create(struct nfs4_client *clp)
                 dprintk("%s: can't allocate memory for upcall!\n", __func__);
                 return;
         }
+
         has_session = nfsd4_cltrack_client_has_session(clp);
         grace_start = nfsd4_cltrack_grace_start(nn->boot_time);
+
+        nfsd4_cltrack_upcall_lock(clp);
         nfsd4_umh_cltrack_upcall("create", hexid, has_session, grace_start);
+        nfsd4_cltrack_upcall_unlock(clp);
+
         kfree(has_session);
         kfree(grace_start);
         kfree(hexid);
@@ -1293,7 +1314,11 @@ nfsd4_umh_cltrack_remove(struct nfs4_client *clp)
                 dprintk("%s: can't allocate memory for upcall!\n", __func__);
                 return;
         }
+
+        nfsd4_cltrack_upcall_lock(clp);
         nfsd4_umh_cltrack_upcall("remove", hexid, NULL, NULL);
+        nfsd4_cltrack_upcall_unlock(clp);
+
         kfree(hexid);
 }
 
@@ -1311,7 +1336,11 @@ nfsd4_umh_cltrack_check(struct nfs4_client *clp)
 
         has_session = nfsd4_cltrack_client_has_session(clp);
         legacy = nfsd4_cltrack_legacy_recdir(&clp->cl_name);
+
+        nfsd4_cltrack_upcall_lock(clp);
         ret = nfsd4_umh_cltrack_upcall("check", hexid, has_session, legacy);
+        nfsd4_cltrack_upcall_unlock(clp);
+
         kfree(has_session);
         kfree(legacy);
         kfree(hexid);
diff --git a/fs/nfsd/state.h b/fs/nfsd/state.h
index 854f0c574ccf..62a82ab06cf1 100644
--- a/fs/nfsd/state.h
+++ b/fs/nfsd/state.h
@@ -306,6 +306,7 @@ struct nfs4_client {
 #define NFSD4_CLIENT_STABLE             (2)     /* client on stable storage */
 #define NFSD4_CLIENT_RECLAIM_COMPLETE   (3)     /* reclaim_complete done */
 #define NFSD4_CLIENT_CONFIRMED          (4)     /* client is confirmed */
+#define NFSD4_CLIENT_UPCALL_LOCK        (5)     /* upcall serialization */
 #define NFSD4_CLIENT_CB_FLAG_MASK       (1 << NFSD4_CLIENT_CB_UPDATE | \
                                          1 << NFSD4_CLIENT_CB_KILL)
         unsigned long           cl_flags;