NFSv4: Fix open_to_lock_owner sequenceid allocation...

NFSv4 file locking is currently completely broken since it doesn't respect
the OPEN sequencing when it is given an unconfirmed lock_owner and needs to
do an open_to_lock_owner. Worse: it breaks the sunrpc rules by doing a
GFP_KERNEL allocation inside an rpciod callback.

Fix is to preallocate the open seqid structure in nfs4_alloc_lockdata if we
see that the lock_owner is unconfirmed.
Then, in nfs4_lock_prepare() we wait for either the open_seqid, if
the lock_owner is still unconfirmed, or else fall back to waiting on the
standard lock_seqid.
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

fs/nfs/nfs4proc.c

@@ -3331,6 +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.lock_seqid = nfs_alloc_seqid(&lsp->ls_seqid);
 	if (p->arg.lock_seqid == NULL)
 		goto out_free;
@@ -3343,6 +3349,8 @@ static struct nfs4_lockdata *nfs4_alloc_lockdata(struct file_lock *fl,
 	memcpy(&p->fl, fl, sizeof(p->fl));
 	return p;
 out_free:
+	if (p->arg.open_seqid != NULL)
+		nfs_free_seqid(p->arg.open_seqid);
 	kfree(p);
 	return NULL;
 }
@@ -3359,23 +3367,23 @@ static void nfs4_lock_prepare(struct rpc_task *task, void *calldata)
 		.rpc_cred = sp->so_cred,
 	};
 
-	if (nfs_wait_on_sequence(data->arg.lock_seqid, task) != 0)
-		return;
 	dprintk("%s: begin!\n", __FUNCTION__);
 	/* Do we need to do an open_to_lock_owner? */
 	if (!(data->arg.lock_seqid->sequence->flags & NFS_SEQID_CONFIRMED)) {
-		data->arg.open_seqid = nfs_alloc_seqid(&sp->so_seqid);
-		if (data->arg.open_seqid == NULL) {
-			data->rpc_status = -ENOMEM;
-			task->tk_action = NULL;
-			goto out;
-		}
+		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:	
 	data->timestamp = jiffies;
 	rpc_call_setup(task, &msg, 0);
-out:
 	dprintk("%s: done!, ret = %d\n", __FUNCTION__, data->rpc_status);
 }
 
@@ -3411,8 +3419,6 @@ static void nfs4_lock_release(void *calldata)
 	struct nfs4_lockdata *data = calldata;
 
 	dprintk("%s: begin!\n", __FUNCTION__);
-	if (data->arg.open_seqid != NULL)
-		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,
@@ -3422,6 +3428,8 @@ 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);