nfs41: call free slot from nfs4_restart_rpc

nfs41_sequence_free_slot can be called multiple times on SEQUENCE operation
errors.
No reason to inline nfs4_restart_rpc

Reported-by: Trond Myklebust <trond.myklebust@netapp.com>

nfs_writeback_done and nfs_readpage_retry call nfs4_restart_rpc outside the
error handler, and the slot is not freed prior to restarting in the rpc_prepare
state during session reset.

Fix this by moving the call to nfs41_sequence_free_slot from the error
path of nfs41_sequence_done into nfs4_restart_rpc, and by removing the test
for NFS4CLNT_SESSION_SETUP.
Always free slot and goto the rpc prepare state on async errors.

Signed-off-by: Andy Adamson <andros@netapp.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
diff --git a/fs/nfs/read.c b/fs/nfs/read.c
index 12c9e66..3e04fb9 100644
--- a/fs/nfs/read.c
+++ b/fs/nfs/read.c
@@ -368,7 +368,8 @@
 	argp->offset += resp->count;
 	argp->pgbase += resp->count;
 	argp->count -= resp->count;
-	nfs4_restart_rpc(task, NFS_SERVER(data->inode)->nfs_client);
+	nfs4_restart_rpc(task, NFS_SERVER(data->inode)->nfs_client,
+			 &data->res.seq_res);
 	return;
 out:
 	nfs4_sequence_free_slot(NFS_SERVER(data->inode)->nfs_client,