nfs41: setup_sequence method

Allocate a slot in the session slot table and set the sequence op arguments.

Called at the rpc prepare stage.

Add a status to nfs41_sequence_res, initialize it to one so that we catch
rpc level failures which do not go through decode_sequence which sets
the new status field.

Note that upon an rpc level failure, we don't know if the server processed the
sequence operation or not. Proceed as if the server did process the sequence
operation.

Signed-off-by: Rahul Iyer <iyer@netapp.com>
[nfs41: sequence args use slotid]
[nfs41: find slot return slotid]
Signed-off-by: Andy Adamson <andros@netapp.com>
Signed-off-by: Benny Halevy <bhalevy@panasas.com>
[nfs41: remove SEQ4_STATUS_USE_TK_STATUS]
As per 11-14-08 review
[move extern declaration from nfs41: sequence setup/done support]
[removed sa_session definition, changed sa_cache_this into a u8 to reduce footprint]
Signed-off-by: Andy Adamson <andros@netapp.com>
Signed-off-by: Benny Halevy <bhalevy@panasas.com>
[nfs41: rpc_sleep_on slot_tbl_waitq must be called under slot_tbl_lock]
    Otherwise there's a race (we've hit) with nfs4_free_slot where
    nfs41_setup_sequence sees a full slot table, unlocks slot_tbl_lock,
    nfs4_free_slots happen concurrently and call rpc_wake_up_next
    where there's nobody to wake up yet, context goes back to
    nfs41_setup_sequence which goes to sleep when the slot table
    is actually empty now and there's no-one to wake it up anymore.
Signed-off-by: Benny Halevy <bhalevy@panasas.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

1 files changed, 32 insertions, 2 deletions

diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index a0946a0d116e..c9618080317e 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -280,6 +280,8 @@ static void renew_lease(const struct nfs_server *server, unsigned long timestamp
  * If found, we mark the slot as used, update the highest_used_slotid,
  * and respectively set up the sequence operation args.
  * The slot number is returned if found, or NFS4_MAX_SLOT_TABLE otherwise.
+ *
+ * Note: must be called with under the slot_tbl_lock.
  */
 static u8
 nfs4_find_slot(struct nfs4_slot_table *tbl, struct rpc_task *task)
@@ -288,7 +290,6 @@ nfs4_find_slot(struct nfs4_slot_table *tbl, struct rpc_task *task)
         u8 ret_id = NFS4_MAX_SLOT_TABLE;
         BUILD_BUG_ON((u8)NFS4_MAX_SLOT_TABLE != (int)NFS4_MAX_SLOT_TABLE);
 
-        spin_lock(&tbl->slot_tbl_lock);
         dprintk("--> %s used_slots=%04lx highest_used=%d max_slots=%d\n",
                 __func__, tbl->used_slots[0], tbl->highest_used_slotid,
                 tbl->max_slots);
@@ -302,7 +303,6 @@ nfs4_find_slot(struct nfs4_slot_table *tbl, struct rpc_task *task)
 out:
         dprintk("<-- %s used_slots=%04lx highest_used=%d slotid=%d \n",
                 __func__, tbl->used_slots[0], tbl->highest_used_slotid, ret_id);
-        spin_unlock(&tbl->slot_tbl_lock);
         return ret_id;
 }
 
@@ -312,12 +312,42 @@ static int nfs41_setup_sequence(struct nfs4_session *session,
                                 int cache_reply,
                                 struct rpc_task *task)
 {
+        struct nfs4_slot *slot;
+        struct nfs4_slot_table *tbl;
+        u8 slotid;
+
+        dprintk("--> %s\n", __func__);
         /* slot already allocated? */
         if (res->sr_slotid != NFS4_MAX_SLOT_TABLE)
                 return 0;
 
         memset(res, 0, sizeof(*res));
         res->sr_slotid = NFS4_MAX_SLOT_TABLE;
+        tbl = &session->fc_slot_table;
+
+        spin_lock(&tbl->slot_tbl_lock);
+        slotid = nfs4_find_slot(tbl, task);
+        if (slotid == NFS4_MAX_SLOT_TABLE) {
+                rpc_sleep_on(&tbl->slot_tbl_waitq, task, NULL);
+                spin_unlock(&tbl->slot_tbl_lock);
+                dprintk("<-- %s: no free slots\n", __func__);
+                return -EAGAIN;
+        }
+        spin_unlock(&tbl->slot_tbl_lock);
+
+        slot = tbl->slots + slotid;
+        args->sa_slotid = slotid;
+        args->sa_cache_this = cache_reply;
+
+        dprintk("<-- %s slotid=%d seqid=%d\n", __func__, slotid, slot->seq_nr);
+
+        res->sr_slotid = slotid;
+        res->sr_renewal_time = jiffies;
+        /*
+         * sr_status is only set in decode_sequence, and so will remain
+         * set to 1 if an rpc level failure occurs.
+         */
+        res->sr_status = 1;
         return 0;
 }