NFSv4: Final tweak to sequence id

 Sacrifice queueing fairness for performance.

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

2 files changed, 14 insertions, 11 deletions

diff --git a/fs/nfs/nfs4_fs.h b/fs/nfs/nfs4_fs.h
index 45bff1d1a513..5c0dd26d0985 100644
--- a/fs/nfs/nfs4_fs.h
+++ b/fs/nfs/nfs4_fs.h
@@ -110,8 +110,8 @@ struct nfs_seqid_counter {
 };
 
 struct nfs_seqid {
-        struct list_head list;
         struct nfs_seqid_counter *sequence;
+        struct list_head list;
 };
 
 static inline void nfs_confirm_seqid(struct nfs_seqid_counter *seqid, int status)
diff --git a/fs/nfs/nfs4state.c b/fs/nfs/nfs4state.c
index da0861db57fb..c59ef90e956b 100644
--- a/fs/nfs/nfs4state.c
+++ b/fs/nfs/nfs4state.c
@@ -670,15 +670,12 @@ 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;
 }
@@ -687,10 +684,12 @@ void nfs_free_seqid(struct nfs_seqid *seqid)
 {
         struct rpc_sequence *sequence = seqid->sequence->sequence;
 
-        spin_lock(&sequence->lock);
-        list_del(&seqid->list);
-        rpc_wake_up(&sequence->wait);
-        spin_unlock(&sequence->lock);
+        if (!list_empty(&seqid->list)) {
+                spin_lock(&sequence->lock);
+                list_del(&seqid->list);
+                spin_unlock(&sequence->lock);
+        }
+        rpc_wake_up_next(&sequence->wait);
         kfree(seqid);
 }
 
@@ -746,12 +745,16 @@ 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) {
+        if (!list_empty(&sequence->list)) {
                 rpc_sleep_on(&sequence->wait, task, NULL, NULL);
                 status = -EAGAIN;
-        }
+        } else
+                list_add(&seqid->list, &sequence->list);
         spin_unlock(&sequence->lock);
+out:
         return status;
 }