NFSv4.1: Delay callback processing when there are referring triples

If CB_SEQUENCE tells us that the processing of this request depends on
the completion of one or more referring triples (see RFC 5661 Section
2.10.6.3), delay the callback processing until after the RPC requests
being referred to have completed.
If we end up delaying for more than 1/2 second, then fall back to
returning NFS4ERR_DELAY in reply to the callback.

Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>

1 files changed, 21 insertions, 1 deletions

diff --git a/fs/nfs/nfs4session.c b/fs/nfs/nfs4session.c
index c1f4c208f38a..b62973045a3e 100644
--- a/fs/nfs/nfs4session.c
+++ b/fs/nfs/nfs4session.c
@@ -28,6 +28,7 @@ static void nfs4_init_slot_table(struct nfs4_slot_table *tbl, const char *queue)
         tbl->highest_used_slotid = NFS4_NO_SLOT;
         spin_lock_init(&tbl->slot_tbl_lock);
         rpc_init_priority_wait_queue(&tbl->slot_tbl_waitq, queue);
+        init_waitqueue_head(&tbl->slot_waitq);
         init_completion(&tbl->complete);
 }
 
@@ -192,7 +193,8 @@ static int nfs4_slot_get_seqid(struct nfs4_slot_table  *tbl, u32 slotid,
  * RPC call in question is still in flight. This function is mainly
  * intended for use by the callback channel.
  */
-bool nfs4_slot_seqid_in_use(struct nfs4_slot_table *tbl, u32 slotid, u32 seq_nr)
+static bool nfs4_slot_seqid_in_use(struct nfs4_slot_table *tbl,
+                u32 slotid, u32 seq_nr)
 {
         u32 cur_seq;
         bool ret = false;
@@ -206,6 +208,24 @@ bool nfs4_slot_seqid_in_use(struct nfs4_slot_table *tbl, u32 slotid, u32 seq_nr)
 }
 
 /*
+ * nfs4_slot_wait_on_seqid - wait until a slot sequence id is complete
+ *
+ * Given a slot table, slot id and sequence number, wait until the
+ * corresponding RPC call completes. This function is mainly
+ * intended for use by the callback channel.
+ */
+int nfs4_slot_wait_on_seqid(struct nfs4_slot_table *tbl,
+                u32 slotid, u32 seq_nr,
+                unsigned long timeout)
+{
+        if (wait_event_timeout(tbl->slot_waitq,
+                        !nfs4_slot_seqid_in_use(tbl, slotid, seq_nr),
+                        timeout) == 0)
+                return -ETIMEDOUT;
+        return 0;
+}
+
+/*
  * nfs4_alloc_slot - efficiently look for a free slot
  *
  * nfs4_alloc_slot looks for an unset bit in the used_slots bitmap.