nfsd4: allow restarting callbacks

If we lose the backchannel and then the client repairs the problem,
resend any callbacks.

We use a new cb_done flag to track whether there is still work to be
done for the callback or whether it can be destroyed with the rpc.

Signed-off-by: J. Bruce Fields <bfields@redhat.com>

3 files changed, 32 insertions, 6 deletions

diff --git a/fs/nfsd/nfs4callback.c b/fs/nfsd/nfs4callback.c
index 69955e98e086..f1d9dd45553a 100644
--- a/fs/nfsd/nfs4callback.c
+++ b/fs/nfsd/nfs4callback.c
@@ -639,6 +639,10 @@ static void nfsd4_cb_prepare(struct rpc_task *task, void *calldata)
                 if (!nfsd41_cb_get_slot(clp, task))
                         return;
         }
+        cb->cb_done = false;
+        spin_lock(&clp->cl_lock);
+        list_add(&cb->cb_per_client, &clp->cl_callbacks);
+        spin_unlock(&clp->cl_lock);
         rpc_call_start(task);
 }
 
@@ -681,8 +685,11 @@ static void nfsd4_cb_recall_done(struct rpc_task *task, void *calldata)
                 return;
         }
 
+        if (cb->cb_done)
+                return;
         switch (task->tk_status) {
         case 0:
+                cb->cb_done = true;
                 return;
         case -EBADHANDLE:
         case -NFS4ERR_BAD_STATEID:
@@ -695,7 +702,7 @@ static void nfsd4_cb_recall_done(struct rpc_task *task, void *calldata)
                 if (current_rpc_client != task->tk_client) {
                         /* queue a callback on the new connection: */
                         atomic_inc(&dp->dl_count);
-                        nfsd4_cb_recall(dp);
+                        run_nfsd4_cb(&dp->dl_recall);
                         return;
                 }
         }
@@ -704,16 +711,23 @@ static void nfsd4_cb_recall_done(struct rpc_task *task, void *calldata)
                 task->tk_status = 0;
                 rpc_restart_call_prepare(task);
                 return;
-        } else
-                nfsd4_mark_cb_down(clp, task->tk_status);
+        }
+        nfsd4_mark_cb_down(clp, task->tk_status);
+        cb->cb_done = true;
 }
 
 static void nfsd4_cb_recall_release(void *calldata)
 {
         struct nfsd4_callback *cb = calldata;
+        struct nfs4_client *clp = cb->cb_clp;
         struct nfs4_delegation *dp = container_of(cb, struct nfs4_delegation, dl_recall);
 
-        nfs4_put_delegation(dp);
+        if (cb->cb_done) {
+                spin_lock(&clp->cl_lock);
+                list_del(&cb->cb_per_client);
+                spin_unlock(&clp->cl_lock);
+                nfs4_put_delegation(dp);
+        }
 }
 
 static const struct rpc_call_ops nfsd4_cb_recall_ops = {
@@ -808,8 +822,13 @@ static void nfsd4_process_cb_update(struct nfsd4_callback *cb)
         spin_unlock(&clp->cl_lock);
 
         err = setup_callback_client(clp, &conn, ses);
-        if (err)
+        if (err) {
                 warn_no_callback_path(clp, err);
+                return;
+        }
+        /* Yay, the callback channel's back! Restart any callbacks: */
+        list_for_each_entry(cb, &clp->cl_callbacks, cb_per_client)
+                run_nfsd4_cb(cb);
 }
 
 void nfsd4_do_callback_rpc(struct work_struct *w)
@@ -834,10 +853,11 @@ void nfsd4_do_callback_rpc(struct work_struct *w)
 void nfsd4_cb_recall(struct nfs4_delegation *dp)
 {
         struct nfsd4_callback *cb = &dp->dl_recall;
+        struct nfs4_client *clp = dp->dl_client;
 
         dp->dl_retries = 1;
         cb->cb_op = dp;
-        cb->cb_clp = dp->dl_client;
+        cb->cb_clp = clp;
         cb->cb_msg.rpc_proc = &nfs4_cb_procedures[NFSPROC4_CLNT_CB_RECALL];
         cb->cb_msg.rpc_argp = cb;
         cb->cb_msg.rpc_resp = cb;
@@ -846,5 +866,7 @@ void nfsd4_cb_recall(struct nfs4_delegation *dp)
         cb->cb_ops = &nfsd4_cb_recall_ops;
         dp->dl_retries = 1;
 
+        cb->cb_done = true;
+
         run_nfsd4_cb(&dp->dl_recall);
 }
diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
index 408957cf6016..6e1f9aadd439 100644
--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -1077,6 +1077,7 @@ static struct nfs4_client *create_client(struct xdr_netobj name, char *recdir,
         INIT_LIST_HEAD(&clp->cl_openowners);
         INIT_LIST_HEAD(&clp->cl_delegations);
         INIT_LIST_HEAD(&clp->cl_lru);
+        INIT_LIST_HEAD(&clp->cl_callbacks);
         spin_lock_init(&clp->cl_lock);
         INIT_WORK(&clp->cl_cb_null.cb_work, nfsd4_do_callback_rpc);
         clp->cl_time = get_seconds();
diff --git a/fs/nfsd/state.h b/fs/nfsd/state.h
index 4e5bdfd9169c..3074656ba7bf 100644
--- a/fs/nfsd/state.h
+++ b/fs/nfsd/state.h
@@ -68,10 +68,12 @@ typedef struct {
 struct nfsd4_callback {
         void *cb_op;
         struct nfs4_client *cb_clp;
+        struct list_head cb_per_client;
         u32 cb_minorversion;
         struct rpc_message cb_msg;
         const struct rpc_call_ops *cb_ops;
         struct work_struct cb_work;
+        bool cb_done;
 };
 
 struct nfs4_delegation {
@@ -248,6 +250,7 @@ struct nfs4_client {
         int                     cl_cb_state;
         struct nfsd4_callback   cl_cb_null;
         struct nfsd4_session    *cl_cb_session;
+        struct list_head        cl_callbacks; /* list of in-progress callbacks */
 
         /* for all client information that callback code might need: */
         spinlock_t              cl_lock;