mirror of https://github.com/xemu-project/xemu.git
hw/xen: Watches on XenStore transactions
Firing watches on the nodes that still exist is relatively easy; just walk the tree and look at the nodes with refcount of one. Firing watches on *deleted* nodes is more fun. We add 'modified_in_tx' and 'deleted_in_tx' flags to each node. Nodes with those flags cannot be shared, as they will always be unique to the transaction in which they were created. When xs_node_walk would need to *create* a node as scaffolding and it encounters a deleted_in_tx node, it can resurrect it simply by clearing its deleted_in_tx flag. If that node originally had any *data*, they're gone, and the modified_in_tx flag will have been set when it was first deleted. We then attempt to send appropriate watches when the transaction is committed, properly delete the deleted_in_tx nodes, and remove the modified_in_tx flag from the others. Signed-off-by: David Woodhouse <dwmw@amazon.co.uk> Reviewed-by: Paul Durrant <paul@xen.org>
This commit is contained in:
David Woodhouse
parent
7248b87cb0
commit
7cabbdb70d
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@ -32,6 +32,8 @@ typedef struct XsNode {
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GByteArray *content;
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GHashTable *children;
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uint64_t gencnt;
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bool deleted_in_tx;
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bool modified_in_tx;
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#ifdef XS_NODE_UNIT_TEST
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gchar *name; /* debug only */
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#endif
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@ -153,6 +155,13 @@ static XsNode *xs_node_copy(XsNode *old)
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XsNode *n = xs_node_new();
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n->gencnt = old->gencnt;
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#ifdef XS_NODE_UNIT_TEST
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if (n->name) {
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n->name = g_strdup(old->name);
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}
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#endif
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if (old->children) {
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n->children = g_hash_table_new_full(g_str_hash, g_str_equal, g_free,
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(GDestroyNotify)xs_node_unref);
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@ -221,6 +230,9 @@ struct walk_op {
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bool mutating;
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bool create_dirs;
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bool in_transaction;
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/* Tracking during recursion so we know which is first. */
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bool deleted_in_tx;
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};
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static void fire_watches(struct walk_op *op, bool parents)
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@ -277,6 +289,9 @@ static int xs_node_add_content(XsNode **n, struct walk_op *op)
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g_byte_array_unref((*n)->content);
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}
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(*n)->content = g_byte_array_ref(data);
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if (op->tx_id != XBT_NULL) {
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(*n)->modified_in_tx = true;
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}
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return 0;
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}
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@ -333,10 +348,62 @@ static int node_rm_recurse(gpointer key, gpointer value, gpointer user_data)
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return this_inplace;
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}
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static XsNode *xs_node_copy_deleted(XsNode *old, struct walk_op *op);
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static void copy_deleted_recurse(gpointer key, gpointer value,
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gpointer user_data)
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{
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struct walk_op *op = user_data;
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GHashTable *siblings = op->op_opaque2;
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XsNode *n = xs_node_copy_deleted(value, op);
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/*
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* Reinsert the deleted_in_tx copy of the node into the parent's
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* 'children' hash table. Having stashed it from op->op_opaque2
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* before the recursive call to xs_node_copy_deleted() scribbled
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* over it.
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*/
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g_hash_table_insert(siblings, g_strdup(key), n);
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}
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static XsNode *xs_node_copy_deleted(XsNode *old, struct walk_op *op)
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{
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XsNode *n = xs_node_new();
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n->gencnt = old->gencnt;
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#ifdef XS_NODE_UNIT_TEST
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if (old->name) {
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n->name = g_strdup(old->name);
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}
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#endif
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if (old->children) {
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n->children = g_hash_table_new_full(g_str_hash, g_str_equal, g_free,
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(GDestroyNotify)xs_node_unref);
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op->op_opaque2 = n->children;
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g_hash_table_foreach(old->children, copy_deleted_recurse, op);
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}
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n->deleted_in_tx = true;
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/* If it gets resurrected we only fire a watch if it lost its content */
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if (old->content) {
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n->modified_in_tx = true;
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}
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op->new_nr_nodes--;
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return n;
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}
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static int xs_node_rm(XsNode **n, struct walk_op *op)
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{
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bool this_inplace = op->inplace;
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if (op->tx_id != XBT_NULL) {
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/* It's not trivial to do inplace handling for this one */
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XsNode *old = *n;
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*n = xs_node_copy_deleted(old, op);
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xs_node_unref(old);
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return 0;
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}
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/* Fire watches for, and count, nodes in the subtree which get deleted */
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if ((*n)->children) {
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g_hash_table_foreach_remove((*n)->children, node_rm_recurse, op);
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@ -408,6 +475,10 @@ static int xs_node_walk(XsNode **n, struct walk_op *op)
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}
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if (child) {
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if (child->deleted_in_tx) {
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assert(child->ref == 1);
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/* Cannot actually set child->deleted_in_tx = false until later */
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}
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xs_node_ref(child);
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/*
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* Now we own it too. But if we can modify inplace, that's going to
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@ -475,6 +546,15 @@ static int xs_node_walk(XsNode **n, struct walk_op *op)
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xs_node_unref(old);
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}
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/*
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* If we resurrected a deleted_in_tx node, we can mark it as no longer
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* deleted now that we know the overall operation has succeeded.
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*/
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if (op->create_dirs && child && child->deleted_in_tx) {
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op->new_nr_nodes++;
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child->deleted_in_tx = false;
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}
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/*
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* The child may be NULL here, for a remove operation. Either way,
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* xs_node_add_child() will do the right thing and return a value
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@ -709,8 +789,69 @@ int xs_impl_transaction_start(XenstoreImplState *s, unsigned int dom_id,
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return 0;
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}
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static gboolean tx_commit_walk(gpointer key, gpointer value,
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gpointer user_data)
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{
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struct walk_op *op = user_data;
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int path_len = strlen(op->path);
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int key_len = strlen(key);
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bool fire_parents = true;
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XsWatch *watch;
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XsNode *n = value;
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if (n->ref != 1) {
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return false;
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}
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if (n->deleted_in_tx) {
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/*
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* We fire watches on our parents if we are the *first* node
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* to be deleted (the topmost one). This matches the behaviour
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* when deleting in the live tree.
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*/
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fire_parents = !op->deleted_in_tx;
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/* Only used on the way down so no need to clear it later */
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op->deleted_in_tx = true;
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}
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assert(key_len + path_len + 2 <= sizeof(op->path));
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op->path[path_len] = '/';
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memcpy(op->path + path_len + 1, key, key_len + 1);
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watch = g_hash_table_lookup(op->s->watches, op->path);
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if (watch) {
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op->watches = g_list_append(op->watches, watch);
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}
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if (n->children) {
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g_hash_table_foreach_remove(n->children, tx_commit_walk, op);
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}
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if (watch) {
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op->watches = g_list_remove(op->watches, watch);
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}
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/*
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* Don't fire watches if this node was only copied because a
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* descendent was changed. The modified_in_tx flag indicates the
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* ones which were really changed.
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*/
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if (n->modified_in_tx || n->deleted_in_tx) {
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fire_watches(op, fire_parents);
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n->modified_in_tx = false;
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}
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op->path[path_len] = '\0';
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/* Deleted nodes really do get expunged when we commit */
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return n->deleted_in_tx;
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}
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static int transaction_commit(XenstoreImplState *s, XsTransaction *tx)
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{
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struct walk_op op;
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XsNode **n;
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if (s->root_tx != tx->base_tx) {
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return EAGAIN;
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}
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@ -720,10 +861,18 @@ static int transaction_commit(XenstoreImplState *s, XsTransaction *tx)
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s->root_tx = tx->tx_id;
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s->nr_nodes = tx->nr_nodes;
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init_walk_op(s, &op, XBT_NULL, tx->dom_id, "/", &n);
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op.deleted_in_tx = false;
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op.mutating = true;
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/*
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* XX: Walk the new root and fire watches on any node which has a
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* Walk the new root and fire watches on any node which has a
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* refcount of one (which is therefore unique to this transaction).
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*/
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if (s->root->children) {
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g_hash_table_foreach_remove(s->root->children, tx_commit_walk, &op);
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}
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return 0;
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}
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@ -347,7 +347,13 @@ static void do_test_xs_node_tx(bool fail, bool commit)
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} else {
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g_assert(!err);
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}
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g_assert(!watches->len);
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if (commit && !fail) {
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g_assert(!strcmp(watches->str,
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"some/relative/pathwatch"));
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g_string_truncate(watches, 0);
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} else {
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g_assert(!watches->len);
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}
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g_assert(s->nr_nodes == 7);
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err = xs_impl_unwatch(s, DOMID_GUEST, "some", "watch",
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@ -386,6 +392,226 @@ static void test_xs_node_tx_succeed(void)
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do_test_xs_node_tx(false, true);
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}
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static void test_xs_node_tx_rm(void)
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{
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XenstoreImplState *s = setup();
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GString *watches = g_string_new(NULL);
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GByteArray *data = g_byte_array_new();
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unsigned int tx_id = XBT_NULL;
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int err;
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g_assert(s);
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/* Set a watch */
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err = xs_impl_watch(s, DOMID_GUEST, "some", "watch",
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watch_cb, watches);
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g_assert(!err);
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g_assert(watches->len == strlen("somewatch"));
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g_assert(!strcmp(watches->str, "somewatch"));
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g_string_truncate(watches, 0);
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/* Write something */
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err = write_str(s, DOMID_GUEST, XBT_NULL, "some/deep/dark/relative/path",
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"something");
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g_assert(!err);
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g_assert(s->nr_nodes == 9);
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g_assert(!strcmp(watches->str,
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"some/deep/dark/relative/pathwatch"));
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g_string_truncate(watches, 0);
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/* Create a transaction */
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err = xs_impl_transaction_start(s, DOMID_GUEST, &tx_id);
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g_assert(!err);
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/* Delete the tree in the transaction */
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err = xs_impl_rm(s, DOMID_GUEST, tx_id, "some/deep/dark");
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g_assert(!err);
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g_assert(s->nr_nodes == 9);
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g_assert(!watches->len);
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err = xs_impl_read(s, DOMID_GUEST, XBT_NULL, "some/deep/dark/relative/path",
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data);
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g_assert(!err);
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g_assert(data->len == strlen("something"));
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g_assert(!memcmp(data->data, "something", data->len));
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g_byte_array_set_size(data, 0);
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/* Commit the transaction */
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err = xs_impl_transaction_end(s, DOMID_GUEST, tx_id, true);
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g_assert(!err);
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g_assert(s->nr_nodes == 6);
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g_assert(!strcmp(watches->str, "some/deep/darkwatch"));
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g_string_truncate(watches, 0);
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/* Now the node is gone */
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err = xs_impl_read(s, DOMID_GUEST, XBT_NULL, "some/deep/dark/relative/path",
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data);
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g_assert(err == ENOENT);
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g_byte_array_unref(data);
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err = xs_impl_unwatch(s, DOMID_GUEST, "some", "watch",
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watch_cb, watches);
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g_assert(!err);
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g_string_free(watches, true);
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xs_impl_delete(s);
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}
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static void test_xs_node_tx_resurrect(void)
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{
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XenstoreImplState *s = setup();
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GString *watches = g_string_new(NULL);
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GByteArray *data = g_byte_array_new();
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unsigned int tx_id = XBT_NULL;
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int err;
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g_assert(s);
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/* Write something */
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err = write_str(s, DOMID_GUEST, XBT_NULL, "some/deep/dark/relative/path",
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"something");
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g_assert(!err);
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g_assert(s->nr_nodes == 9);
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/* This node will be wiped and resurrected */
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err = write_str(s, DOMID_GUEST, XBT_NULL, "some/deep/dark",
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"foo");
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g_assert(!err);
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g_assert(s->nr_nodes == 9);
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/* Set a watch */
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err = xs_impl_watch(s, DOMID_GUEST, "some", "watch",
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watch_cb, watches);
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g_assert(!err);
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g_assert(watches->len == strlen("somewatch"));
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g_assert(!strcmp(watches->str, "somewatch"));
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g_string_truncate(watches, 0);
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/* Create a transaction */
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err = xs_impl_transaction_start(s, DOMID_GUEST, &tx_id);
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g_assert(!err);
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/* Delete the tree in the transaction */
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err = xs_impl_rm(s, DOMID_GUEST, tx_id, "some/deep");
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g_assert(!err);
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g_assert(s->nr_nodes == 9);
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g_assert(!watches->len);
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/* Resurrect part of it */
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err = write_str(s, DOMID_GUEST, tx_id, "some/deep/dark/different/path",
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"something");
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g_assert(!err);
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g_assert(s->nr_nodes == 9);
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/* Commit the transaction */
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err = xs_impl_transaction_end(s, DOMID_GUEST, tx_id, true);
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g_assert(!err);
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g_assert(s->nr_nodes == 9);
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/* lost data */
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g_assert(strstr(watches->str, "some/deep/dark/different/pathwatch"));
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/* topmost deleted */
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g_assert(strstr(watches->str, "some/deep/dark/relativewatch"));
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/* lost data */
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g_assert(strstr(watches->str, "some/deep/darkwatch"));
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g_string_truncate(watches, 0);
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/* Now the node is gone */
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err = xs_impl_read(s, DOMID_GUEST, XBT_NULL, "some/deep/dark/relative/path",
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data);
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g_assert(err == ENOENT);
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g_byte_array_unref(data);
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err = xs_impl_unwatch(s, DOMID_GUEST, "some", "watch",
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watch_cb, watches);
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g_assert(!err);
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g_string_free(watches, true);
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xs_impl_delete(s);
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}
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static void test_xs_node_tx_resurrect2(void)
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{
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XenstoreImplState *s = setup();
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GString *watches = g_string_new(NULL);
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GByteArray *data = g_byte_array_new();
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unsigned int tx_id = XBT_NULL;
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int err;
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g_assert(s);
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/* Write something */
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err = write_str(s, DOMID_GUEST, XBT_NULL, "some/deep/dark/relative/path",
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"something");
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g_assert(!err);
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g_assert(s->nr_nodes == 9);
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/* Another node to remain shared */
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err = write_str(s, DOMID_GUEST, XBT_NULL, "some/place/safe", "keepme");
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g_assert(!err);
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g_assert(s->nr_nodes == 11);
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/* This node will be wiped and resurrected */
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err = write_str(s, DOMID_GUEST, XBT_NULL, "some/deep/dark",
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"foo");
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g_assert(!err);
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g_assert(s->nr_nodes == 11);
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/* Set a watch */
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err = xs_impl_watch(s, DOMID_GUEST, "some", "watch",
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watch_cb, watches);
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g_assert(!err);
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g_assert(watches->len == strlen("somewatch"));
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g_assert(!strcmp(watches->str, "somewatch"));
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g_string_truncate(watches, 0);
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/* Create a transaction */
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err = xs_impl_transaction_start(s, DOMID_GUEST, &tx_id);
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g_assert(!err);
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/* Delete the tree in the transaction */
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err = xs_impl_rm(s, DOMID_GUEST, tx_id, "some/deep");
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g_assert(!err);
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g_assert(s->nr_nodes == 11);
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g_assert(!watches->len);
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/* Resurrect part of it */
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err = write_str(s, DOMID_GUEST, tx_id, "some/deep/dark/relative/path",
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"something");
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g_assert(!err);
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g_assert(s->nr_nodes == 11);
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/* Commit the transaction */
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err = xs_impl_transaction_end(s, DOMID_GUEST, tx_id, true);
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g_assert(!err);
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g_assert(s->nr_nodes == 11);
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/* lost data */
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g_assert(strstr(watches->str, "some/deep/dark/relative/pathwatch"));
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||||
/* lost data */
|
||||
g_assert(strstr(watches->str, "some/deep/darkwatch"));
|
||||
|
||||
g_string_truncate(watches, 0);
|
||||
|
||||
/* Now the node is gone */
|
||||
err = xs_impl_read(s, DOMID_GUEST, XBT_NULL, "some/deep/dark/relative/path",
|
||||
data);
|
||||
g_assert(!err);
|
||||
g_assert(data->len == strlen("something"));
|
||||
g_assert(!memcmp(data->data, "something", data->len));
|
||||
|
||||
g_byte_array_unref(data);
|
||||
|
||||
err = xs_impl_unwatch(s, DOMID_GUEST, "some", "watch",
|
||||
watch_cb, watches);
|
||||
g_assert(!err);
|
||||
|
||||
g_string_free(watches, true);
|
||||
xs_impl_delete(s);
|
||||
}
|
||||
|
||||
int main(int argc, char **argv)
|
||||
{
|
||||
g_test_init(&argc, &argv, NULL);
|
||||
|
|
@ -395,6 +621,9 @@ int main(int argc, char **argv)
|
|||
g_test_add_func("/xs_node/tx_abort", test_xs_node_tx_abort);
|
||||
g_test_add_func("/xs_node/tx_fail", test_xs_node_tx_fail);
|
||||
g_test_add_func("/xs_node/tx_succeed", test_xs_node_tx_succeed);
|
||||
g_test_add_func("/xs_node/tx_rm", test_xs_node_tx_rm);
|
||||
g_test_add_func("/xs_node/tx_resurrect", test_xs_node_tx_resurrect);
|
||||
g_test_add_func("/xs_node/tx_resurrect2", test_xs_node_tx_resurrect2);
|
||||
|
||||
return g_test_run();
|
||||
}
|
||||
|
|
|
|||
Loading…
Reference in New Issue