tools/xenstore: add wrapper for tdb_fetch()

Add a wrapper function for tdb_fetch taking the name of the node in
the data base as a parameter. Let it return a data pointer and the
length of the data via a length pointer provided as additional
parameter.

Move logging of the TDB access from the callers into the wrapper.

This enables to make set_tdb_key() and tdb_ctx static.

This is in preparation to replace TDB with a more simple data storage.

Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Julien Grall <jgrall@amazon.com>

tools/xenstore/xenstored_core.c

@@ -85,7 +85,7 @@ bool keep_orphans = false;
 static int reopen_log_pipe[2];
 static int reopen_log_pipe0_pollfd_idx = -1;
 char *tracefile = NULL;
-TDB_CONTEXT *tdb_ctx = NULL;
+static TDB_CONTEXT *tdb_ctx = NULL;
 unsigned int trace_flags = TRACE_OBJ | TRACE_IO;
 
 static const char *sockmsg_string(enum xsd_sockmsg_type type);
@@ -556,7 +556,7 @@ static void initialize_fds(int *p_sock_pollfd_idx, int *ptimeout)
 	}
 }
 
-void set_tdb_key(const char *name, TDB_DATA *key)
+static void set_tdb_key(const char *name, TDB_DATA *key)
 {
 	/*
 	 * Dropping const is fine here, as the key will never be modified
@@ -566,25 +566,39 @@ void set_tdb_key(const char *name, TDB_DATA *key)
 	key->dsize = strlen(name);
 }
 
+struct xs_tdb_record_hdr *db_fetch(const char *db_name, size_t *size)
+{
+	TDB_DATA key, data;
+
+	set_tdb_key(db_name, &key);
+	data = tdb_fetch(tdb_ctx, key);
+	if (!data.dptr) {
+		errno = (tdb_error(tdb_ctx) == TDB_ERR_NOEXIST) ? ENOENT : EIO;
+		*size = 0;
+	} else {
+		*size = data.dsize;
+		trace_tdb("read %s size %zu\n", db_name,
+			  *size + strlen(db_name));
+	}
+
+	return (struct xs_tdb_record_hdr *)data.dptr;
+}
+
 static void get_acc_data(const char *name, struct node_account_data *acc)
 {
-	TDB_DATA key, old_data;
+	size_t size;
 	struct xs_tdb_record_hdr *hdr;
 
 	if (acc->memory < 0) {
-		set_tdb_key(name, &key);
-		old_data = tdb_fetch(tdb_ctx, key);
+		hdr = db_fetch(name, &size);
 		/* No check for error, as the node might not exist. */
-		if (old_data.dptr == NULL) {
+		if (hdr == NULL) {
 			acc->memory = 0;
 		} else {
-			trace_tdb("read %s size %zu\n", name,
-				  old_data.dsize + key.dsize);
-			hdr = (void *)old_data.dptr;
-			acc->memory = old_data.dsize;
+			acc->memory = size;
 			acc->domid = hdr->perms[0].id;
 		}
-		talloc_free(old_data.dptr);
+		talloc_free(hdr);
 	}
 }
 
@@ -698,7 +712,7 @@ int db_delete(struct connection *conn, const char *name,
 struct node *read_node(struct connection *conn, const void *ctx,
 		       const char *name)
 {
-	TDB_DATA key, data;
+	size_t size;
 	struct xs_tdb_record_hdr *hdr;
 	struct node *node;
 	const char *db_name;
@@ -717,29 +731,24 @@ struct node *read_node(struct connection *conn, const void *ctx,
 	}
 
 	db_name = transaction_prepend(conn, name);
-	set_tdb_key(db_name, &key);
+	hdr = db_fetch(db_name, &size);
 
-	data = tdb_fetch(tdb_ctx, key);
-
-	if (data.dptr == NULL) {
-		if (tdb_error(tdb_ctx) == TDB_ERR_NOEXIST) {
+	if (hdr == NULL) {
+		if (errno == ENOENT) {
 			node->generation = NO_GENERATION;
 			err = access_node(conn, node, NODE_ACCESS_READ, NULL);
 			errno = err ? : ENOENT;
 		} else {
-			log("TDB error on read: %s", tdb_errorstr(tdb_ctx));
+			log("DB error on read: %s", strerror(errno));
 			errno = EIO;
 		}
 		goto error;
 	}
 
-	trace_tdb("read %s size %zu\n", key.dptr, data.dsize + key.dsize);
-
 	node->parent = NULL;
-	talloc_steal(node, data.dptr);
+	talloc_steal(node, hdr);
 
 	/* Datalen, childlen, number of permissions */
-	hdr = (void *)data.dptr;
 	node->generation = hdr->generation;
 	node->perms.num = hdr->num_perms;
 	node->datalen = hdr->datalen;
@@ -748,7 +757,7 @@ struct node *read_node(struct connection *conn, const void *ctx,
 	/* Permissions are struct xs_permissions. */
 	node->perms.p = hdr->perms;
 	node->acc.domid = get_node_owner(node);
-	node->acc.memory = data.dsize;
+	node->acc.memory = size;
 	if (domain_adjust_node_perms(node))
 		goto error;
 

tools/xenstore/xenstored_core.h

@@ -315,7 +315,6 @@ do {						\
 		trace("tdb: " __VA_ARGS__);	\
 } while (0)
 
-extern TDB_CONTEXT *tdb_ctx;
 extern int dom0_domid;
 extern int dom0_event;
 extern int priv_domid;
@@ -364,7 +363,7 @@ extern xengnttab_handle **xgt_handle;
 int remember_string(struct hashtable *hash, const char *str);
 
 /* Data base access functions. */
-void set_tdb_key(const char *name, TDB_DATA *key);
+struct xs_tdb_record_hdr *db_fetch(const char *db_name, size_t *size);
 int db_write(struct connection *conn, const char *db_name, void *data,
 	     size_t size, struct node_account_data *acc,
 	     enum write_node_mode mode, bool no_quota_check);

tools/xenstore/xenstored_transaction.c

@@ -356,25 +356,21 @@ static int finalize_transaction(struct connection *conn,
 				struct transaction *trans, bool *is_corrupt)
 {
 	struct accessed_node *i, *n;
-	TDB_DATA key, ta_key, data;
+	size_t size;
 	struct xs_tdb_record_hdr *hdr;
 	uint64_t gen;
 
 	list_for_each_entry_safe(i, n, &trans->accessed, list) {
 		if (i->check_gen) {
-			set_tdb_key(i->node, &key);
-			data = tdb_fetch(tdb_ctx, key);
-			hdr = (void *)data.dptr;
-			if (!data.dptr) {
-				if (tdb_error(tdb_ctx) != TDB_ERR_NOEXIST)
-					return EIO;
+			hdr = db_fetch(i->node, &size);
+			if (!hdr) {
+				if (errno != ENOENT)
+					return errno;
 				gen = NO_GENERATION;
 			} else {
-				trace_tdb("read %s size %zu\n", key.dptr,
-					  key.dsize + data.dsize);
 				gen = hdr->generation;
 			}
-			talloc_free(data.dptr);
+			talloc_free(hdr);
 			if (i->generation != gen)
 				return EAGAIN;
 		}
@@ -392,21 +388,16 @@ static int finalize_transaction(struct connection *conn,
 
 	while ((i = list_top(&trans->accessed, struct accessed_node, list))) {
 		if (i->ta_node) {
-			set_tdb_key(i->trans_name, &ta_key);
-			data = tdb_fetch(tdb_ctx, ta_key);
-			if (data.dptr) {
+			hdr = db_fetch(i->trans_name, &size);
+			if (hdr) {
 				enum write_node_mode mode;
 
-				trace_tdb("read %s size %zu\n", ta_key.dptr,
-					  ta_key.dsize + data.dsize);
-				hdr = (void *)data.dptr;
 				hdr->generation = ++generation;
 				mode = (i->generation == NO_GENERATION)
 				       ? NODE_CREATE : NODE_MODIFY;
-				*is_corrupt |= db_write(conn, i->node,
-							data.dptr, data.dsize,
-							NULL, mode, true);
-				talloc_free(data.dptr);
+				*is_corrupt |= db_write(conn, i->node, hdr,
+							size, NULL, mode, true);
+				talloc_free(hdr);
 				if (db_delete(conn, i->trans_name, NULL))
 					*is_corrupt = true;
 			} else {