NFSv4: Clean up the OPEN/CLOSE serialisation code

Reduce the time spent locking the rpc_sequence structure by queuing the
nfs_seqid only when we are ready to take the lock (when calling
nfs_wait_on_sequence).

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

1 files changed, 16 insertions, 16 deletions

diff --git a/fs/nfs/nfs4state.c b/fs/nfs/nfs4state.c
index 5a39c6f78acf..bf94c6e0a503 100644
--- a/fs/nfs/nfs4state.c
+++ b/fs/nfs/nfs4state.c
@@ -644,27 +644,26 @@ void nfs4_copy_stateid(nfs4_stateid *dst, struct nfs4_state *state, fl_owner_t f
 
 struct nfs_seqid *nfs_alloc_seqid(struct nfs_seqid_counter *counter)
 {
-        struct rpc_sequence *sequence = counter->sequence;
         struct nfs_seqid *new;
 
         new = kmalloc(sizeof(*new), GFP_KERNEL);
         if (new != NULL) {
                 new->sequence = counter;
-                spin_lock(&sequence->lock);
-                list_add_tail(&new->list, &sequence->list);
-                spin_unlock(&sequence->lock);
+                INIT_LIST_HEAD(&new->list);
         }
         return new;
 }
 
 void nfs_free_seqid(struct nfs_seqid *seqid)
 {
-        struct rpc_sequence *sequence = seqid->sequence->sequence;
+        if (!list_empty(&seqid->list)) {
+                struct rpc_sequence *sequence = seqid->sequence->sequence;
 
-        spin_lock(&sequence->lock);
-        list_del(&seqid->list);
-        spin_unlock(&sequence->lock);
-        rpc_wake_up(&sequence->wait);
+                spin_lock(&sequence->lock);
+                list_del(&seqid->list);
+                spin_unlock(&sequence->lock);
+                rpc_wake_up(&sequence->wait);
+        }
         kfree(seqid);
 }
 
@@ -675,6 +674,7 @@ void nfs_free_seqid(struct nfs_seqid *seqid)
  */
 static void nfs_increment_seqid(int status, struct nfs_seqid *seqid)
 {
+        BUG_ON(list_first_entry(&seqid->sequence->sequence->list, struct nfs_seqid, list) != seqid);
         switch (status) {
                 case 0:
                         break;
@@ -726,15 +726,15 @@ int nfs_wait_on_sequence(struct nfs_seqid *seqid, struct rpc_task *task)
         struct rpc_sequence *sequence = seqid->sequence->sequence;
         int status = 0;
 
-        if (sequence->list.next == &seqid->list)
-                goto out;
         spin_lock(&sequence->lock);
-        if (sequence->list.next != &seqid->list) {
-                rpc_sleep_on(&sequence->wait, task, NULL, NULL);
-                status = -EAGAIN;
-        }
+        if (list_empty(&seqid->list))
+                list_add_tail(&seqid->list, &sequence->list);
+        if (list_first_entry(&sequence->list, struct nfs_seqid, list) == seqid)
+                goto unlock;
+        rpc_sleep_on(&sequence->wait, task, NULL, NULL);
+        status = -EAGAIN;
+unlock:
         spin_unlock(&sequence->lock);
-out:
         return status;
 }