NFSv4: Add functions to order RPC calls

 NFSv4 file state-changing functions such as OPEN, CLOSE, LOCK,... are all
 labelled with "sequence identifiers" in order to prevent the server from
 reordering RPC requests, as this could cause its file state to
 become out of sync with the client.

 Currently the NFS client code enforces this ordering locally using
 semaphores to restrict access to structures until the RPC call is done.
 This, of course, only works with synchronous RPC calls, since the
 user process must first grab the semaphore.
 By dropping semaphores, and instead teaching the RPC engine to hold
 the RPC calls until they are ready to be sent, we can extend this
 process to work nicely with asynchronous RPC calls too.

 This patch adds a new list called "rpc_sequence" that defines the order
 of the RPC calls to be sent. We add one such list for each state_owner.
 When an RPC call is ready to be sent, it checks if it is top of the
 rpc_sequence list. If so, it proceeds. If not, it goes back to sleep,
 and loops until it hits top of the list.
 Once the RPC call has completed, it can then bump the sequence id counter,
 and remove itself from the rpc_sequence list, and then wake up the next
 sleeper.

 Note that the state_owner sequence ids and lock_owner sequence ids are
 all indexed to the same rpc_sequence list, so OPEN, LOCK,... requests
 are all ordered w.r.t. each other.

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

1 files changed, 35 insertions, 8 deletions

diff --git a/fs/nfs/nfs4xdr.c b/fs/nfs/nfs4xdr.c
index 6c564ef..fcd28a2 100644
--- a/fs/nfs/nfs4xdr.c
+++ b/fs/nfs/nfs4xdr.c
@@ -604,7 +604,7 @@ static int encode_close(struct xdr_stream *xdr, const struct nfs_closeargs *arg)
 
 	RESERVE_SPACE(8+sizeof(arg->stateid.data));
 	WRITE32(OP_CLOSE);
-	WRITE32(arg->seqid);
+	WRITE32(arg->seqid->sequence->counter);
 	WRITEMEM(arg->stateid.data, sizeof(arg->stateid.data));
 	
 	return 0;
@@ -732,9 +732,9 @@ static int encode_lock(struct xdr_stream *xdr, const struct nfs_lockargs *arg)
 		struct nfs_open_to_lock *ol = opargs->u.open_lock;
 
 		RESERVE_SPACE(40);
-		WRITE32(ol->open_seqid);
+		WRITE32(ol->open_seqid->sequence->counter);
 		WRITEMEM(&ol->open_stateid, sizeof(ol->open_stateid));
-		WRITE32(ol->lock_seqid);
+		WRITE32(ol->lock_seqid->sequence->counter);
 		WRITE64(ol->lock_owner.clientid);
 		WRITE32(4);
 		WRITE32(ol->lock_owner.id);
@@ -744,7 +744,7 @@ static int encode_lock(struct xdr_stream *xdr, const struct nfs_lockargs *arg)
 
 		RESERVE_SPACE(20);
 		WRITEMEM(&el->stateid, sizeof(el->stateid));
-		WRITE32(el->seqid);
+		WRITE32(el->seqid->sequence->counter);
 	}
 
 	return 0;
@@ -775,7 +775,7 @@ static int encode_locku(struct xdr_stream *xdr, const struct nfs_lockargs *arg)
 	RESERVE_SPACE(44);
 	WRITE32(OP_LOCKU);
 	WRITE32(arg->type);
-	WRITE32(opargs->seqid);
+	WRITE32(opargs->seqid->sequence->counter);
 	WRITEMEM(&opargs->stateid, sizeof(opargs->stateid));
 	WRITE64(arg->offset);
 	WRITE64(arg->length);
@@ -826,7 +826,7 @@ static inline void encode_openhdr(struct xdr_stream *xdr, const struct nfs_opena
  */
 	RESERVE_SPACE(8);
 	WRITE32(OP_OPEN);
-	WRITE32(arg->seqid);
+	WRITE32(arg->seqid->sequence->counter);
 	encode_share_access(xdr, arg->open_flags);
 	RESERVE_SPACE(16);
 	WRITE64(arg->clientid);
@@ -941,7 +941,7 @@ static int encode_open_confirm(struct xdr_stream *xdr, const struct nfs_open_con
 	RESERVE_SPACE(8+sizeof(arg->stateid.data));
 	WRITE32(OP_OPEN_CONFIRM);
 	WRITEMEM(arg->stateid.data, sizeof(arg->stateid.data));
-	WRITE32(arg->seqid);
+	WRITE32(arg->seqid->sequence->counter);
 
 	return 0;
 }
@@ -953,7 +953,7 @@ static int encode_open_downgrade(struct xdr_stream *xdr, const struct nfs_closea
 	RESERVE_SPACE(8+sizeof(arg->stateid.data));
 	WRITE32(OP_OPEN_DOWNGRADE);
 	WRITEMEM(arg->stateid.data, sizeof(arg->stateid.data));
-	WRITE32(arg->seqid);
+	WRITE32(arg->seqid->sequence->counter);
 	encode_share_access(xdr, arg->open_flags);
 	return 0;
 }
@@ -1416,6 +1416,9 @@ static int nfs4_xdr_enc_close(struct rpc_rqst *req, uint32_t *p, struct nfs_clos
         };
         int status;
 
+	status = nfs_wait_on_sequence(args->seqid, req->rq_task);
+	if (status != 0)
+		goto out;
         xdr_init_encode(&xdr, &req->rq_snd_buf, p);
         encode_compound_hdr(&xdr, &hdr);
         status = encode_putfh(&xdr, args->fh);
@@ -1437,6 +1440,9 @@ static int nfs4_xdr_enc_open(struct rpc_rqst *req, uint32_t *p, struct nfs_opena
 	};
 	int status;
 
+	status = nfs_wait_on_sequence(args->seqid, req->rq_task);
+	if (status != 0)
+		goto out;
 	xdr_init_encode(&xdr, &req->rq_snd_buf, p);
 	encode_compound_hdr(&xdr, &hdr);
 	status = encode_putfh(&xdr, args->fh);
@@ -1464,6 +1470,9 @@ static int nfs4_xdr_enc_open_confirm(struct rpc_rqst *req, uint32_t *p, struct n
 	};
 	int status;
 
+	status = nfs_wait_on_sequence(args->seqid, req->rq_task);
+	if (status != 0)
+		goto out;
 	xdr_init_encode(&xdr, &req->rq_snd_buf, p);
 	encode_compound_hdr(&xdr, &hdr);
 	status = encode_putfh(&xdr, args->fh);
@@ -1485,6 +1494,9 @@ static int nfs4_xdr_enc_open_noattr(struct rpc_rqst *req, uint32_t *p, struct nf
 	};
 	int status;
 
+	status = nfs_wait_on_sequence(args->seqid, req->rq_task);
+	if (status != 0)
+		goto out;
 	xdr_init_encode(&xdr, &req->rq_snd_buf, p);
 	encode_compound_hdr(&xdr, &hdr);
 	status = encode_putfh(&xdr, args->fh);
@@ -1506,6 +1518,9 @@ static int nfs4_xdr_enc_open_downgrade(struct rpc_rqst *req, uint32_t *p, struct
 	};
 	int status;
 
+	status = nfs_wait_on_sequence(args->seqid, req->rq_task);
+	if (status != 0)
+		goto out;
 	xdr_init_encode(&xdr, &req->rq_snd_buf, p);
 	encode_compound_hdr(&xdr, &hdr);
 	status = encode_putfh(&xdr, args->fh);
@@ -1525,8 +1540,17 @@ static int nfs4_xdr_enc_lock(struct rpc_rqst *req, uint32_t *p, struct nfs_locka
 	struct compound_hdr hdr = {
 		.nops   = 2,
 	};
+	struct nfs_lock_opargs *opargs = args->u.lock;
+	struct nfs_seqid *seqid;
 	int status;
 
+	if (opargs->new_lock_owner)
+		seqid = opargs->u.open_lock->lock_seqid;
+	else
+		seqid = opargs->u.exist_lock->seqid;
+	status = nfs_wait_on_sequence(seqid, req->rq_task);
+	if (status != 0)
+		goto out;
 	xdr_init_encode(&xdr, &req->rq_snd_buf, p);
 	encode_compound_hdr(&xdr, &hdr);
 	status = encode_putfh(&xdr, args->fh);
@@ -1569,6 +1593,9 @@ static int nfs4_xdr_enc_locku(struct rpc_rqst *req, uint32_t *p, struct nfs_lock
 	};
 	int status;
 
+	status = nfs_wait_on_sequence(args->u.locku->seqid, req->rq_task);
+	if (status != 0)
+		goto out;
 	xdr_init_encode(&xdr, &req->rq_snd_buf, p);
 	encode_compound_hdr(&xdr, &hdr);
 	status = encode_putfh(&xdr, args->fh);