NFSv4.1: keep seq_res.sr_slot as pointer rather than an index

Having to explicitly initialize sr_slotid to NFS4_MAX_SLOT_TABLE
resulted in numerous bugs.  Keeping the current slot as a pointer
to the slot table is more straight forward and robust as it's
implicitly set up to NULL wherever the seq_res member is initialized
to zeroes.
Signed-off-by: Benny Halevy <bhalevy@panasas.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

fs/nfs/nfs4proc.c

@@ -334,10 +334,12 @@ static void renew_lease(const struct nfs_server *server, unsigned long timestamp
  * Must be called while holding tbl->slot_tbl_lock
  */
 static void
-nfs4_free_slot(struct nfs4_slot_table *tbl, u8 free_slotid)
+nfs4_free_slot(struct nfs4_slot_table *tbl, struct nfs4_slot *free_slot)
 {
+	int free_slotid = free_slot - tbl->slots;
 	int slotid = free_slotid;
 
+	BUG_ON(slotid < 0 || slotid >= NFS4_MAX_SLOT_TABLE);
 	/* clear used bit in bitmap */
 	__clear_bit(slotid, tbl->used_slots);
 
@@ -379,7 +381,7 @@ static void nfs41_sequence_free_slot(struct nfs4_sequence_res *res)
 	struct nfs4_slot_table *tbl;
 
 	tbl = &res->sr_session->fc_slot_table;
-	if (res->sr_slotid == NFS4_MAX_SLOT_TABLE) {
+	if (!res->sr_slot) {
 		/* just wake up the next guy waiting since
 		 * we may have not consumed a slot after all */
 		dprintk("%s: No slot\n", __func__);
@@ -387,17 +389,15 @@ static void nfs41_sequence_free_slot(struct nfs4_sequence_res *res)
 	}
 
 	spin_lock(&tbl->slot_tbl_lock);
-	nfs4_free_slot(tbl, res->sr_slotid);
+	nfs4_free_slot(tbl, res->sr_slot);
 	nfs41_check_drain_session_complete(res->sr_session);
 	spin_unlock(&tbl->slot_tbl_lock);
-	res->sr_slotid = NFS4_MAX_SLOT_TABLE;
+	res->sr_slot = NULL;
 }
 
 static int nfs41_sequence_done(struct rpc_task *task, struct nfs4_sequence_res *res)
 {
 	unsigned long timestamp;
-	struct nfs4_slot_table *tbl;
-	struct nfs4_slot *slot;
 	struct nfs_client *clp;
 
 	/*
@@ -410,17 +410,14 @@ static int nfs41_sequence_done(struct rpc_task *task, struct nfs4_sequence_res *
 		res->sr_status = NFS_OK;
 
 	/* -ERESTARTSYS can result in skipping nfs41_sequence_setup */
-	if (res->sr_slotid == NFS4_MAX_SLOT_TABLE)
+	if (!res->sr_slot)
 		goto out;
 
-	tbl = &res->sr_session->fc_slot_table;
-	slot = tbl->slots + res->sr_slotid;
-
 	/* Check the SEQUENCE operation status */
 	switch (res->sr_status) {
 	case 0:
 		/* Update the slot's sequence and clientid lease timer */
-		++slot->seq_nr;
+		++res->sr_slot->seq_nr;
 		timestamp = res->sr_renewal_time;
 		clp = res->sr_session->clp;
 		do_renew_lease(clp, timestamp);
@@ -433,12 +430,14 @@ static int nfs41_sequence_done(struct rpc_task *task, struct nfs4_sequence_res *
 		 * returned NFS4ERR_DELAY as per Section 2.10.6.2
 		 * of RFC5661.
 		 */
-		dprintk("%s: slot=%d seq=%d: Operation in progress\n",
-				__func__, res->sr_slotid, slot->seq_nr);
+		dprintk("%s: slot=%ld seq=%d: Operation in progress\n",
+			__func__,
+			res->sr_slot - res->sr_session->fc_slot_table.slots,
+			res->sr_slot->seq_nr);
 		goto out_retry;
 	default:
 		/* Just update the slot sequence no. */
-		++slot->seq_nr;
+		++res->sr_slot->seq_nr;
 	}
 out:
 	/* The session may be reset by one of the error handlers. */
@@ -505,10 +504,9 @@ static int nfs41_setup_sequence(struct nfs4_session *session,
 
 	dprintk("--> %s\n", __func__);
 	/* slot already allocated? */
-	if (res->sr_slotid != NFS4_MAX_SLOT_TABLE)
+	if (res->sr_slot != NULL)
 		return 0;
 
-	res->sr_slotid = NFS4_MAX_SLOT_TABLE;
 	tbl = &session->fc_slot_table;
 
 	spin_lock(&tbl->slot_tbl_lock);
@@ -550,7 +548,7 @@ static int nfs41_setup_sequence(struct nfs4_session *session,
 	dprintk("<-- %s slotid=%d seqid=%d\n", __func__, slotid, slot->seq_nr);
 
 	res->sr_session = session;
-	res->sr_slotid = slotid;
+	res->sr_slot = slot;
 	res->sr_renewal_time = jiffies;
 	res->sr_status_flags = 0;
 	/*
@@ -576,8 +574,9 @@ int nfs4_setup_sequence(const struct nfs_server *server,
 		goto out;
 	}
 
-	dprintk("--> %s clp %p session %p sr_slotid %d\n",
-		__func__, session->clp, session, res->sr_slotid);
+	dprintk("--> %s clp %p session %p sr_slot %ld\n",
+		__func__, session->clp, session, res->sr_slot ?
+			res->sr_slot - session->fc_slot_table.slots : -1);
 
 	ret = nfs41_setup_sequence(session, args, res, cache_reply,
 				   task);
@@ -650,7 +649,7 @@ static int nfs4_call_sync_sequence(struct nfs_server *server,
 		.callback_data = &data
 	};
 
-	res->sr_slotid = NFS4_MAX_SLOT_TABLE;
+	res->sr_slot = NULL;
 	if (privileged)
 		task_setup.callback_ops = &nfs41_call_priv_sync_ops;
 	task = rpc_run_task(&task_setup);
@@ -735,7 +734,6 @@ static void nfs4_init_opendata_res(struct nfs4_opendata *p)
 	p->o_res.server = p->o_arg.server;
 	nfs_fattr_init(&p->f_attr);
 	nfs_fattr_init(&p->dir_attr);
-	p->o_res.seq_res.sr_slotid = NFS4_MAX_SLOT_TABLE;
 }
 
 static struct nfs4_opendata *nfs4_opendata_alloc(struct path *path,
@@ -1975,7 +1973,6 @@ int nfs4_do_close(struct path *path, struct nfs4_state *state, gfp_t gfp_mask, i
 	calldata->res.fattr = &calldata->fattr;
 	calldata->res.seqid = calldata->arg.seqid;
 	calldata->res.server = server;
-	calldata->res.seq_res.sr_slotid = NFS4_MAX_SLOT_TABLE;
 	path_get(path);
 	calldata->path = *path;
 
@@ -2550,7 +2547,7 @@ static void nfs4_proc_unlink_setup(struct rpc_message *msg, struct inode *dir)
 
 	args->bitmask = server->cache_consistency_bitmask;
 	res->server = server;
-	res->seq_res.sr_slotid = NFS4_MAX_SLOT_TABLE;
+	res->seq_res.sr_slot = NULL;
 	msg->rpc_proc = &nfs4_procedures[NFSPROC4_CLNT_REMOVE];
 }
 
@@ -2576,7 +2573,6 @@ static void nfs4_proc_rename_setup(struct rpc_message *msg, struct inode *dir)
 	msg->rpc_proc = &nfs4_procedures[NFSPROC4_CLNT_RENAME];
 	arg->bitmask = server->attr_bitmask;
 	res->server = server;
-	res->seq_res.sr_slotid = NFS4_MAX_SLOT_TABLE;
 }
 
 static int nfs4_proc_rename_done(struct rpc_task *task, struct inode *old_dir,
@@ -3646,7 +3642,6 @@ static int _nfs4_proc_delegreturn(struct inode *inode, struct rpc_cred *cred, co
 	memcpy(&data->stateid, stateid, sizeof(data->stateid));
 	data->res.fattr = &data->fattr;
 	data->res.server = server;
-	data->res.seq_res.sr_slotid = NFS4_MAX_SLOT_TABLE;
 	nfs_fattr_init(data->res.fattr);
 	data->timestamp = jiffies;
 	data->rpc_status = 0;
@@ -3799,7 +3794,6 @@ static struct nfs4_unlockdata *nfs4_alloc_unlockdata(struct file_lock *fl,
 	p->arg.fl = &p->fl;
 	p->arg.seqid = seqid;
 	p->res.seqid = seqid;
-	p->res.seq_res.sr_slotid = NFS4_MAX_SLOT_TABLE;
 	p->arg.stateid = &lsp->ls_stateid;
 	p->lsp = lsp;
 	atomic_inc(&lsp->ls_count);
@@ -3979,7 +3973,6 @@ static struct nfs4_lockdata *nfs4_alloc_lockdata(struct file_lock *fl,
 	p->arg.lock_owner.clientid = server->nfs_client->cl_clientid;
 	p->arg.lock_owner.id = lsp->ls_id.id;
 	p->res.lock_seqid = p->arg.lock_seqid;
-	p->res.seq_res.sr_slotid = NFS4_MAX_SLOT_TABLE;
 	p->lsp = lsp;
 	p->server = server;
 	atomic_inc(&lsp->ls_count);
@@ -4612,7 +4605,6 @@ int nfs4_proc_get_lease_time(struct nfs_client *clp, struct nfs_fsinfo *fsinfo)
 	};
 	int status;
 
-	res.lr_seq_res.sr_slotid = NFS4_MAX_SLOT_TABLE;
 	dprintk("--> %s\n", __func__);
 	task = rpc_run_task(&task_setup);
 
@@ -5105,12 +5097,11 @@ static struct rpc_task *_nfs41_proc_sequence(struct nfs_client *clp, struct rpc_
 
 	if (!atomic_inc_not_zero(&clp->cl_count))
 		return ERR_PTR(-EIO);
-	calldata = kmalloc(sizeof(*calldata), GFP_NOFS);
+	calldata = kzalloc(sizeof(*calldata), GFP_NOFS);
 	if (calldata == NULL) {
 		nfs_put_client(clp);
 		return ERR_PTR(-ENOMEM);
 	}
-	calldata->res.sr_slotid = NFS4_MAX_SLOT_TABLE;
 	msg.rpc_argp = &calldata->args;
 	msg.rpc_resp = &calldata->res;
 	calldata->clp = clp;
@@ -5242,7 +5233,6 @@ static int nfs41_proc_reclaim_complete(struct nfs_client *clp)
 		goto out;
 	calldata->clp = clp;
 	calldata->arg.one_fs = 0;
-	calldata->res.seq_res.sr_slotid = NFS4_MAX_SLOT_TABLE;
 
 	msg.rpc_argp = &calldata->arg;
 	msg.rpc_resp = &calldata->res;

fs/nfs/nfs4xdr.c

@@ -4665,7 +4665,6 @@ static int decode_sequence(struct xdr_stream *xdr,
 			   struct rpc_rqst *rqstp)
 {
 #if defined(CONFIG_NFS_V4_1)
-	struct nfs4_slot *slot;
 	struct nfs4_sessionid id;
 	u32 dummy;
 	int status;
@@ -4697,15 +4696,14 @@ static int decode_sequence(struct xdr_stream *xdr,
 		goto out_overflow;
 
 	/* seqid */
-	slot = &res->sr_session->fc_slot_table.slots[res->sr_slotid];
 	dummy = be32_to_cpup(p++);
-	if (dummy != slot->seq_nr) {
+	if (dummy != res->sr_slot->seq_nr) {
 		dprintk("%s Invalid sequence number\n", __func__);
 		goto out_err;
 	}
 	/* slot id */
 	dummy = be32_to_cpup(p++);
-	if (dummy != res->sr_slotid) {
+	if (dummy != res->sr_slot - res->sr_session->fc_slot_table.slots) {
 		dprintk("%s Invalid slot id\n", __func__);
 		goto out_err;
 	}

fs/nfs/read.c

@@ -46,7 +46,6 @@ struct nfs_read_data *nfs_readdata_alloc(unsigned int pagecount)
 		memset(p, 0, sizeof(*p));
 		INIT_LIST_HEAD(&p->pages);
 		p->npages = pagecount;
-		p->res.seq_res.sr_slotid = NFS4_MAX_SLOT_TABLE;
 		if (pagecount <= ARRAY_SIZE(p->page_array))
 			p->pagevec = p->page_array;
 		else {

fs/nfs/unlink.c

@@ -262,7 +262,6 @@ nfs_async_unlink(struct inode *dir, struct dentry *dentry)
 		status = PTR_ERR(data->cred);
 		goto out_free;
 	}
-	data->res.seq_res.sr_slotid = NFS4_MAX_SLOT_TABLE;
 	data->res.dir_attr = &data->dir_attr;
 
 	status = -EBUSY;
@@ -427,7 +426,7 @@ nfs_async_rename(struct inode *old_dir, struct inode *new_dir,
 		.flags = RPC_TASK_ASYNC,
 	};
 
-	data = kmalloc(sizeof(*data), GFP_KERNEL);
+	data = kzalloc(sizeof(*data), GFP_KERNEL);
 	if (data == NULL)
 		return ERR_PTR(-ENOMEM);
 	task_setup_data.callback_data = data,

fs/nfs/write.c

@@ -55,7 +55,6 @@ struct nfs_write_data *nfs_commitdata_alloc(void)
 	if (p) {
 		memset(p, 0, sizeof(*p));
 		INIT_LIST_HEAD(&p->pages);
-		p->res.seq_res.sr_slotid = NFS4_MAX_SLOT_TABLE;
 	}
 	return p;
 }
@@ -75,7 +74,6 @@ struct nfs_write_data *nfs_writedata_alloc(unsigned int pagecount)
 		memset(p, 0, sizeof(*p));
 		INIT_LIST_HEAD(&p->pages);
 		p->npages = pagecount;
-		p->res.seq_res.sr_slotid = NFS4_MAX_SLOT_TABLE;
 		if (pagecount <= ARRAY_SIZE(p->page_array))
 			p->pagevec = p->page_array;
 		else {

include/linux/nfs_xdr.h

@@ -170,7 +170,7 @@ struct nfs4_sequence_args {
 
 struct nfs4_sequence_res {
 	struct nfs4_session	*sr_session;
-	u8			sr_slotid;	/* slot used to send request */
+	struct nfs4_slot	*sr_slot;	/* slot used to send request */
 	int			sr_status;	/* sequence operation status */
 	unsigned long		sr_renewal_time;
 	u32			sr_status_flags;