hw/xen: Implement XenStore watches
Starts out fairly simple: a hash table of watches based on the path.
Except there can be multiple watches on the same path, so the watch ends
up being a simple linked list, and the head of that list is in the hash
table. Which makes removal a bit of a PITA but it's not so bad; we just
special-case "I had to remove the head of the list and now I have to
replace it in / remove it from the hash table". And if we don't remove
the head, it's a simple linked-list operation.
We do need to fire watches on *deleted* nodes, so instead of just a simple
xs_node_unref() on the topmost victim, we need to recurse down and fire
watches on them all.
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Reviewed-by: Paul Durrant <paul@xen.org>
diff --git a/tests/unit/test-xs-node.c b/tests/unit/test-xs-node.c
index c78d5bd..19000b6 100644
--- a/tests/unit/test-xs-node.c
+++ b/tests/unit/test-xs-node.c
@@ -34,10 +34,14 @@
{
int err;
+ xs_impl_reset_watches(s, DOMID_GUEST);
+ g_assert(!s->nr_domu_watches);
+
err = xs_impl_rm(s, DOMID_QEMU, XBT_NULL, "/local");
g_assert(!err);
g_assert(s->nr_nodes == 1);
+ g_hash_table_unref(s->watches);
xs_node_unref(s->root);
g_free(s);
@@ -65,6 +69,14 @@
return err;
}
+static void watch_cb(void *_str, const char *path, const char *token)
+{
+ GString *str = _str;
+
+ g_string_append(str, path);
+ g_string_append(str, token);
+}
+
static XenstoreImplState *setup(void)
{
XenstoreImplState *s = xs_impl_create();
@@ -75,6 +87,7 @@
err = write_str(s, DOMID_QEMU, XBT_NULL, abspath, "");
g_assert(!err);
+ g_assert(s->nr_nodes == 4);
g_free(abspath);
@@ -93,6 +106,8 @@
{
GByteArray *data = g_byte_array_new();
XenstoreImplState *s = setup();
+ GString *guest_watches = g_string_new(NULL);
+ GString *qemu_watches = g_string_new(NULL);
GList *items = NULL;
XsNode *old_root;
uint64_t gencnt;
@@ -100,6 +115,20 @@
g_assert(s);
+ err = xs_impl_watch(s, DOMID_GUEST, "some", "guestwatch",
+ watch_cb, guest_watches);
+ g_assert(!err);
+ g_assert(guest_watches->len == strlen("someguestwatch"));
+ g_assert(!strcmp(guest_watches->str, "someguestwatch"));
+ g_string_truncate(guest_watches, 0);
+
+ err = xs_impl_watch(s, 0, "/local/domain/1/some", "qemuwatch",
+ watch_cb, qemu_watches);
+ g_assert(!err);
+ g_assert(qemu_watches->len == strlen("/local/domain/1/someqemuwatch"));
+ g_assert(!strcmp(qemu_watches->str, "/local/domain/1/someqemuwatch"));
+ g_string_truncate(qemu_watches, 0);
+
/* Read gives ENOENT when it should */
err = xs_impl_read(s, DOMID_GUEST, XBT_NULL, "foo", data);
g_assert(err == ENOENT);
@@ -109,6 +138,14 @@
"something");
g_assert(s->nr_nodes == 7);
g_assert(!err);
+ g_assert(!strcmp(guest_watches->str,
+ "some/relative/pathguestwatch"));
+ g_assert(!strcmp(qemu_watches->str,
+ "/local/domain/1/some/relative/pathqemuwatch"));
+
+ g_string_truncate(qemu_watches, 0);
+ g_string_truncate(guest_watches, 0);
+ xs_impl_reset_watches(s, 0);
/* Read gives back what we wrote */
err = xs_impl_read(s, DOMID_GUEST, XBT_NULL, "some/relative/path", data);
@@ -123,6 +160,8 @@
g_assert(!err);
g_assert(data->len == strlen("something"));
+ g_assert(!qemu_watches->len);
+ g_assert(!guest_watches->len);
/* Keep a copy, to force COW mode */
old_root = xs_node_ref(s->root);
@@ -132,12 +171,18 @@
"something else");
g_assert(!err);
g_assert(s->nr_nodes == 8);
+ g_assert(!qemu_watches->len);
+ g_assert(!strcmp(guest_watches->str, "some/relative/path2guestwatch"));
+ g_string_truncate(guest_watches, 0);
/* Overwrite an existing node */
err = write_str(s, DOMID_GUEST, XBT_NULL, "some/relative/path",
"another thing");
g_assert(!err);
g_assert(s->nr_nodes == 8);
+ g_assert(!qemu_watches->len);
+ g_assert(!strcmp(guest_watches->str, "some/relative/pathguestwatch"));
+ g_string_truncate(guest_watches, 0);
/* We can list the two files we wrote */
err = xs_impl_directory(s, DOMID_GUEST, XBT_NULL, "some/relative", &gencnt,
@@ -151,9 +196,38 @@
g_assert(!items->next->next);
g_list_free_full(items, g_free);
+ err = xs_impl_unwatch(s, DOMID_GUEST, "some", "guestwatch",
+ watch_cb, guest_watches);
+ g_assert(!err);
+
+ err = xs_impl_unwatch(s, DOMID_GUEST, "some", "guestwatch",
+ watch_cb, guest_watches);
+ g_assert(err == ENOENT);
+
+ err = xs_impl_watch(s, DOMID_GUEST, "some/relative/path2", "watchp2",
+ watch_cb, guest_watches);
+ g_assert(!err);
+ g_assert(guest_watches->len == strlen("some/relative/path2watchp2"));
+ g_assert(!strcmp(guest_watches->str, "some/relative/path2watchp2"));
+ g_string_truncate(guest_watches, 0);
+
+ err = xs_impl_watch(s, DOMID_GUEST, "/local/domain/1/some/relative",
+ "watchrel", watch_cb, guest_watches);
+ g_assert(!err);
+ g_assert(guest_watches->len ==
+ strlen("/local/domain/1/some/relativewatchrel"));
+ g_assert(!strcmp(guest_watches->str,
+ "/local/domain/1/some/relativewatchrel"));
+ g_string_truncate(guest_watches, 0);
+
/* Write somewhere else which already existed */
err = write_str(s, DOMID_GUEST, XBT_NULL, "some/relative", "moredata");
g_assert(!err);
+ g_assert(s->nr_nodes == 8);
+
+ g_assert(!strcmp(guest_watches->str,
+ "/local/domain/1/some/relativewatchrel"));
+ g_string_truncate(guest_watches, 0);
g_byte_array_set_size(data, 0);
err = xs_impl_read(s, DOMID_GUEST, XBT_NULL, "some/relative", data);
@@ -164,6 +238,7 @@
/* Overwrite existing data */
err = write_str(s, DOMID_GUEST, XBT_NULL, "some/relative", "otherdata");
g_assert(!err);
+ g_string_truncate(guest_watches, 0);
g_byte_array_set_size(data, 0);
err = xs_impl_read(s, DOMID_GUEST, XBT_NULL, "some/relative", data);
@@ -176,11 +251,21 @@
g_assert(!err);
g_assert(s->nr_nodes == 5);
+ /* Each watch fires with the least specific relevant path */
+ g_assert(strstr(guest_watches->str,
+ "some/relative/path2watchp2"));
+ g_assert(strstr(guest_watches->str,
+ "/local/domain/1/some/relativewatchrel"));
+ g_string_truncate(guest_watches, 0);
+
g_byte_array_set_size(data, 0);
err = xs_impl_read(s, DOMID_GUEST, XBT_NULL, "some/relative", data);
g_assert(err == ENOENT);
g_byte_array_unref(data);
+ xs_impl_reset_watches(s, DOMID_GUEST);
+ g_string_free(qemu_watches, true);
+ g_string_free(guest_watches, true);
xs_node_unref(old_root);
xs_impl_delete(s);
}
