return log;
}
+/* The reference held by the hash table does not count towards the reference
+ * count. When a new object is created, it initially has a reference count of
+ * 1 for the creator, and similarly fetching an item from the hash table will
+ * also create a reference. If the reference count drops to zero,
+ * bluesky_cloudlog_unref attempts to remove the object from the hash
+ * table--but there is a potential race since another thread might read the
+ * object from the hash table at the same time. So an object with a reference
+ * count of zero may still be resurrected, in which case we need to abort the
+ * destruction. Once the object is gone from the hash table, and if the
+ * reference count is still zero, it can actually be deleted. */
void bluesky_cloudlog_ref(BlueSkyCloudLog *log)
{
if (log == NULL)
return;
if (g_atomic_int_dec_and_test(&log->refcount)) {
- g_print("Cloud log refcount dropped to zero.\n");
+ BlueSkyFS *fs = log->fs;
+
+ g_mutex_lock(fs->lock);
+ if (g_atomic_int_get(&log->refcount) > 0) {
+ g_mutex_unlock(fs->lock);
+ return;
+ }
+
+ g_hash_table_remove(fs->locations, &log->id);
+ g_mutex_unlock(fs->lock);
+
+ g_mutex_free(log->lock);
+ g_cond_free(log->cond);
+ g_array_unref(log->pointers);
+ bluesky_string_unref(log->data);
+ g_free(log);
}
}
BlueSkyCloudLog *log2
= (BlueSkyCloudLog *)g_hash_table_lookup(log->fs->locations, &id);
// TODO: refcount
- g_mutex_unlock(log->fs->lock);
g_assert(log2 != NULL);
+ bluesky_cloudlog_ref(log2);
+ g_mutex_unlock(log->fs->lock);
bluesky_cloudlog_serialize(log2, state);
+ bluesky_cloudlog_unref(log2);
}
+ g_mutex_lock(log->lock);
+ bluesky_cloudlog_fetch(log);
g_assert(log->data != NULL);
log->location = state->location;
g_string_append_len(state->data, log->data->data, log->data->len);
log->location_flags |= CLOUDLOG_CLOUD;
+ g_mutex_unlock(log->lock);
return log->location;
}
void bluesky_cloudlog_write_log(BlueSkyFS *fs)
{
- g_print("Starting cloudlog write...\n");
-
BlueSkyCloudLogState *state = fs->log_state;
if (state->data == NULL)
state->data = g_string_new("");
}
if (state->data->len > 0) {
- g_print("Serialized %zd bytes of data\n", state->data->len);
+ g_print("Serialized %zd bytes of data to cloud\n", state->data->len);
BlueSkyStoreAsync *async = bluesky_store_async_new(fs->store);
async->op = STORE_OP_PUT;
state->data = NULL;
}
+
+/* Ensure that a cloud log item is loaded in memory, and if not read it in.
+ * TODO: Make asynchronous, and make this also fetch from the cloud. Right now
+ * we only read from the log. Log item must be locked. */
+void bluesky_cloudlog_fetch(BlueSkyCloudLog *log)
+{
+ if (log->data != NULL)
+ return;
+
+ g_print("Re-mapping log entry %d/%d/%d...\n",
+ log->log_seq, log->log_offset, log->log_size);
+
+ g_assert(log->location_flags & CLOUDLOG_JOURNAL);
+
+ log->data = bluesky_log_map_object(log->fs->log, log->log_seq,
+ log->log_offset, log->log_size);
+
+ g_cond_broadcast(log->cond);
+}