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>

2 files changed, 27 insertions, 35 deletions

diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index 9e2e1c7291db..a51a7537f3f6 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -3331,15 +3331,12 @@ static struct nfs4_lockdata *nfs4_alloc_lockdata(struct file_lock *fl,
 
         p->arg.fh = NFS_FH(inode);
         p->arg.fl = &p->fl;
-        if (!(lsp->ls_seqid.flags & NFS_SEQID_CONFIRMED)) {
-                p->arg.open_seqid = nfs_alloc_seqid(&lsp->ls_state->owner->so_seqid);
-                if (p->arg.open_seqid == NULL)
-                        goto out_free;
-
-        }
+        p->arg.open_seqid = nfs_alloc_seqid(&lsp->ls_state->owner->so_seqid);
+        if (p->arg.open_seqid == NULL)
+                goto out_free;
         p->arg.lock_seqid = nfs_alloc_seqid(&lsp->ls_seqid);
         if (p->arg.lock_seqid == NULL)
-                goto out_free;
+                goto out_free_seqid;
         p->arg.lock_stateid = &lsp->ls_stateid;
         p->arg.lock_owner.clientid = server->nfs_client->cl_clientid;
         p->arg.lock_owner.id = lsp->ls_id.id;
@@ -3348,9 +3345,9 @@ static struct nfs4_lockdata *nfs4_alloc_lockdata(struct file_lock *fl,
         p->ctx = get_nfs_open_context(ctx);
         memcpy(&p->fl, fl, sizeof(p->fl));
         return p;
+out_free_seqid:
+        nfs_free_seqid(p->arg.open_seqid);
 out_free:
-        if (p->arg.open_seqid != NULL)
-                nfs_free_seqid(p->arg.open_seqid);
         kfree(p);
         return NULL;
 }
@@ -3368,20 +3365,16 @@ static void nfs4_lock_prepare(struct rpc_task *task, void *calldata)
         };
 
         dprintk("%s: begin!\n", __FUNCTION__);
+        if (nfs_wait_on_sequence(data->arg.lock_seqid, task) != 0)
+                return;
         /* Do we need to do an open_to_lock_owner? */
         if (!(data->arg.lock_seqid->sequence->flags & NFS_SEQID_CONFIRMED)) {
                 if (nfs_wait_on_sequence(data->arg.open_seqid, task) != 0)
                         return;
                 data->arg.open_stateid = &state->stateid;
                 data->arg.new_lock_owner = 1;
-                /* Retest in case we raced... */
-                if (!(data->arg.lock_seqid->sequence->flags & NFS_SEQID_CONFIRMED))
-                        goto do_rpc;
-        }
-        if (nfs_wait_on_sequence(data->arg.lock_seqid, task) != 0)
-                return;
-        data->arg.new_lock_owner = 0;
-do_rpc: 
+        } else
+                data->arg.new_lock_owner = 0;
         data->timestamp = jiffies;
         rpc_call_setup(task, &msg, 0);
         dprintk("%s: done!, ret = %d\n", __FUNCTION__, data->rpc_status);
@@ -3419,6 +3412,7 @@ static void nfs4_lock_release(void *calldata)
         struct nfs4_lockdata *data = calldata;
 
         dprintk("%s: begin!\n", __FUNCTION__);
+        nfs_free_seqid(data->arg.open_seqid);
         if (data->cancelled != 0) {
                 struct rpc_task *task;
                 task = nfs4_do_unlck(&data->fl, data->ctx, data->lsp,
@@ -3428,8 +3422,6 @@ static void nfs4_lock_release(void *calldata)
                 dprintk("%s: cancelling lock!\n", __FUNCTION__);
         } else
                 nfs_free_seqid(data->arg.lock_seqid);
-        if (data->arg.open_seqid != NULL)
-                nfs_free_seqid(data->arg.open_seqid);
         nfs4_put_lock_state(data->lsp);
         put_nfs_open_context(data->ctx);
         kfree(data);
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;
 }