Adding upstream version 6.9.7.upstream/6.9.7

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 739 insertions, 0 deletions

diff --git a/drivers/md/dm-vdo/indexer/index-session.c b/drivers/md/dm-vdo/indexer/index-session.c
new file mode 100644
index 0000000000..aee0914d60
--- /dev/null
+++ b/drivers/md/dm-vdo/indexer/index-session.c
@@ -0,0 +1,739 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright 2023 Red Hat
+ */
+
+#include "index-session.h"
+
+#include <linux/atomic.h>
+
+#include "logger.h"
+#include "memory-alloc.h"
+#include "time-utils.h"
+
+#include "funnel-requestqueue.h"
+#include "index.h"
+#include "index-layout.h"
+
+/*
+ * The index session contains a lock (the request_mutex) which ensures that only one thread can
+ * change the state of its index at a time. The state field indicates the current state of the
+ * index through a set of descriptive flags. The request_mutex must be notified whenever a
+ * non-transient state flag is cleared. The request_mutex is also used to count the number of
+ * requests currently in progress so that they can be drained when suspending or closing the index.
+ *
+ * If the index session is suspended shortly after opening an index, it may have to suspend during
+ * a rebuild. Depending on the size of the index, a rebuild may take a significant amount of time,
+ * so UDS allows the rebuild to be paused in order to suspend the session in a timely manner. When
+ * the index session is resumed, the rebuild can continue from where it left off. If the index
+ * session is shut down with a suspended rebuild, the rebuild progress is abandoned and the rebuild
+ * will start from the beginning the next time the index is loaded. The mutex and status fields in
+ * the index_load_context are used to record the state of any interrupted rebuild.
+ */
+
+enum index_session_flag_bit {
+	IS_FLAG_BIT_START = 8,
+	/* The session has started loading an index but not completed it. */
+	IS_FLAG_BIT_LOADING = IS_FLAG_BIT_START,
+	/* The session has loaded an index, which can handle requests. */
+	IS_FLAG_BIT_LOADED,
+	/* The session's index has been permanently disabled. */
+	IS_FLAG_BIT_DISABLED,
+	/* The session's index is suspended. */
+	IS_FLAG_BIT_SUSPENDED,
+	/* The session is handling some index state change. */
+	IS_FLAG_BIT_WAITING,
+	/* The session's index is closing and draining requests. */
+	IS_FLAG_BIT_CLOSING,
+	/* The session is being destroyed and is draining requests. */
+	IS_FLAG_BIT_DESTROYING,
+};
+
+enum index_session_flag {
+	IS_FLAG_LOADED = (1 << IS_FLAG_BIT_LOADED),
+	IS_FLAG_LOADING = (1 << IS_FLAG_BIT_LOADING),
+	IS_FLAG_DISABLED = (1 << IS_FLAG_BIT_DISABLED),
+	IS_FLAG_SUSPENDED = (1 << IS_FLAG_BIT_SUSPENDED),
+	IS_FLAG_WAITING = (1 << IS_FLAG_BIT_WAITING),
+	IS_FLAG_CLOSING = (1 << IS_FLAG_BIT_CLOSING),
+	IS_FLAG_DESTROYING = (1 << IS_FLAG_BIT_DESTROYING),
+};
+
+/* Release a reference to an index session. */
+static void release_index_session(struct uds_index_session *index_session)
+{
+	mutex_lock(&index_session->request_mutex);
+	if (--index_session->request_count == 0)
+		uds_broadcast_cond(&index_session->request_cond);
+	mutex_unlock(&index_session->request_mutex);
+}
+
+/*
+ * Acquire a reference to the index session for an asynchronous index request. The reference must
+ * eventually be released with a corresponding call to release_index_session().
+ */
+static int get_index_session(struct uds_index_session *index_session)
+{
+	unsigned int state;
+	int result = UDS_SUCCESS;
+
+	mutex_lock(&index_session->request_mutex);
+	index_session->request_count++;
+	state = index_session->state;
+	mutex_unlock(&index_session->request_mutex);
+
+	if (state == IS_FLAG_LOADED) {
+		return UDS_SUCCESS;
+	} else if (state & IS_FLAG_DISABLED) {
+		result = UDS_DISABLED;
+	} else if ((state & IS_FLAG_LOADING) ||
+		   (state & IS_FLAG_SUSPENDED) ||
+		   (state & IS_FLAG_WAITING)) {
+		result = -EBUSY;
+	} else {
+		result = UDS_NO_INDEX;
+	}
+
+	release_index_session(index_session);
+	return result;
+}
+
+int uds_launch_request(struct uds_request *request)
+{
+	size_t internal_size;
+	int result;
+
+	if (request->callback == NULL) {
+		vdo_log_error("missing required callback");
+		return -EINVAL;
+	}
+
+	switch (request->type) {
+	case UDS_DELETE:
+	case UDS_POST:
+	case UDS_QUERY:
+	case UDS_QUERY_NO_UPDATE:
+	case UDS_UPDATE:
+		break;
+	default:
+		vdo_log_error("received invalid callback type");
+		return -EINVAL;
+	}
+
+	/* Reset all internal fields before processing. */
+	internal_size =
+		sizeof(struct uds_request) - offsetof(struct uds_request, zone_number);
+	// FIXME should be using struct_group for this instead
+	memset((char *) request + sizeof(*request) - internal_size, 0, internal_size);
+
+	result = get_index_session(request->session);
+	if (result != UDS_SUCCESS)
+		return result;
+
+	request->found = false;
+	request->unbatched = false;
+	request->index = request->session->index;
+
+	uds_enqueue_request(request, STAGE_TRIAGE);
+	return UDS_SUCCESS;
+}
+
+static void enter_callback_stage(struct uds_request *request)
+{
+	if (request->status != UDS_SUCCESS) {
+		/* All request errors are considered unrecoverable */
+		mutex_lock(&request->session->request_mutex);
+		request->session->state |= IS_FLAG_DISABLED;
+		mutex_unlock(&request->session->request_mutex);
+	}
+
+	uds_request_queue_enqueue(request->session->callback_queue, request);
+}
+
+static inline void count_once(u64 *count_ptr)
+{
+	WRITE_ONCE(*count_ptr, READ_ONCE(*count_ptr) + 1);
+}
+
+static void update_session_stats(struct uds_request *request)
+{
+	struct session_stats *session_stats = &request->session->stats;
+
+	count_once(&session_stats->requests);
+
+	switch (request->type) {
+	case UDS_POST:
+		if (request->found)
+			count_once(&session_stats->posts_found);
+		else
+			count_once(&session_stats->posts_not_found);
+
+		if (request->location == UDS_LOCATION_IN_OPEN_CHAPTER)
+			count_once(&session_stats->posts_found_open_chapter);
+		else if (request->location == UDS_LOCATION_IN_DENSE)
+			count_once(&session_stats->posts_found_dense);
+		else if (request->location == UDS_LOCATION_IN_SPARSE)
+			count_once(&session_stats->posts_found_sparse);
+		break;
+
+	case UDS_UPDATE:
+		if (request->found)
+			count_once(&session_stats->updates_found);
+		else
+			count_once(&session_stats->updates_not_found);
+		break;
+
+	case UDS_DELETE:
+		if (request->found)
+			count_once(&session_stats->deletions_found);
+		else
+			count_once(&session_stats->deletions_not_found);
+		break;
+
+	case UDS_QUERY:
+	case UDS_QUERY_NO_UPDATE:
+		if (request->found)
+			count_once(&session_stats->queries_found);
+		else
+			count_once(&session_stats->queries_not_found);
+		break;
+
+	default:
+		request->status = VDO_ASSERT(false, "unknown request type: %d",
+					     request->type);
+	}
+}
+
+static void handle_callbacks(struct uds_request *request)
+{
+	struct uds_index_session *index_session = request->session;
+
+	if (request->status == UDS_SUCCESS)
+		update_session_stats(request);
+
+	request->status = uds_status_to_errno(request->status);
+	request->callback(request);
+	release_index_session(index_session);
+}
+
+static int __must_check make_empty_index_session(struct uds_index_session **index_session_ptr)
+{
+	int result;
+	struct uds_index_session *session;
+
+	result = vdo_allocate(1, struct uds_index_session, __func__, &session);
+	if (result != VDO_SUCCESS)
+		return result;
+
+	mutex_init(&session->request_mutex);
+	uds_init_cond(&session->request_cond);
+	mutex_init(&session->load_context.mutex);
+	uds_init_cond(&session->load_context.cond);
+
+	result = uds_make_request_queue("callbackW", &handle_callbacks,
+					&session->callback_queue);
+	if (result != UDS_SUCCESS) {
+		vdo_free(session);
+		return result;
+	}
+
+	*index_session_ptr = session;
+	return UDS_SUCCESS;
+}
+
+int uds_create_index_session(struct uds_index_session **session)
+{
+	if (session == NULL) {
+		vdo_log_error("missing session pointer");
+		return -EINVAL;
+	}
+
+	return uds_status_to_errno(make_empty_index_session(session));
+}
+
+static int __must_check start_loading_index_session(struct uds_index_session *index_session)
+{
+	int result;
+
+	mutex_lock(&index_session->request_mutex);
+	if (index_session->state & IS_FLAG_SUSPENDED) {
+		vdo_log_info("Index session is suspended");
+		result = -EBUSY;
+	} else if (index_session->state != 0) {
+		vdo_log_info("Index is already loaded");
+		result = -EBUSY;
+	} else {
+		index_session->state |= IS_FLAG_LOADING;
+		result = UDS_SUCCESS;
+	}
+	mutex_unlock(&index_session->request_mutex);
+	return result;
+}
+
+static void finish_loading_index_session(struct uds_index_session *index_session,
+					 int result)
+{
+	mutex_lock(&index_session->request_mutex);
+	index_session->state &= ~IS_FLAG_LOADING;
+	if (result == UDS_SUCCESS)
+		index_session->state |= IS_FLAG_LOADED;
+
+	uds_broadcast_cond(&index_session->request_cond);
+	mutex_unlock(&index_session->request_mutex);
+}
+
+static int initialize_index_session(struct uds_index_session *index_session,
+				    enum uds_open_index_type open_type)
+{
+	int result;
+	struct uds_configuration *config;
+
+	result = uds_make_configuration(&index_session->parameters, &config);
+	if (result != UDS_SUCCESS) {
+		vdo_log_error_strerror(result, "Failed to allocate config");
+		return result;
+	}
+
+	memset(&index_session->stats, 0, sizeof(index_session->stats));
+	result = uds_make_index(config, open_type, &index_session->load_context,
+				enter_callback_stage, &index_session->index);
+	if (result != UDS_SUCCESS)
+		vdo_log_error_strerror(result, "Failed to make index");
+	else
+		uds_log_configuration(config);
+
+	uds_free_configuration(config);
+	return result;
+}
+
+static const char *get_open_type_string(enum uds_open_index_type open_type)
+{
+	switch (open_type) {
+	case UDS_CREATE:
+		return "creating index";
+	case UDS_LOAD:
+		return "loading or rebuilding index";
+	case UDS_NO_REBUILD:
+		return "loading index";
+	default:
+		return "unknown open method";
+	}
+}
+
+/*
+ * Open an index under the given session. This operation will fail if the
+ * index session is suspended, or if there is already an open index.
+ */
+int uds_open_index(enum uds_open_index_type open_type,
+		   const struct uds_parameters *parameters,
+		   struct uds_index_session *session)
+{
+	int result;
+	char name[BDEVNAME_SIZE];
+
+	if (parameters == NULL) {
+		vdo_log_error("missing required parameters");
+		return -EINVAL;
+	}
+	if (parameters->bdev == NULL) {
+		vdo_log_error("missing required block device");
+		return -EINVAL;
+	}
+	if (session == NULL) {
+		vdo_log_error("missing required session pointer");
+		return -EINVAL;
+	}
+
+	result = start_loading_index_session(session);
+	if (result != UDS_SUCCESS)
+		return uds_status_to_errno(result);
+
+	session->parameters = *parameters;
+	format_dev_t(name, parameters->bdev->bd_dev);
+	vdo_log_info("%s: %s", get_open_type_string(open_type), name);
+
+	result = initialize_index_session(session, open_type);
+	if (result != UDS_SUCCESS)
+		vdo_log_error_strerror(result, "Failed %s",
+				       get_open_type_string(open_type));
+
+	finish_loading_index_session(session, result);
+	return uds_status_to_errno(result);
+}
+
+static void wait_for_no_requests_in_progress(struct uds_index_session *index_session)
+{
+	mutex_lock(&index_session->request_mutex);
+	while (index_session->request_count > 0) {
+		uds_wait_cond(&index_session->request_cond,
+			      &index_session->request_mutex);
+	}
+	mutex_unlock(&index_session->request_mutex);
+}
+
+static int __must_check save_index(struct uds_index_session *index_session)
+{
+	wait_for_no_requests_in_progress(index_session);
+	return uds_save_index(index_session->index);
+}
+
+static void suspend_rebuild(struct uds_index_session *session)
+{
+	mutex_lock(&session->load_context.mutex);
+	switch (session->load_context.status) {
+	case INDEX_OPENING:
+		session->load_context.status = INDEX_SUSPENDING;
+
+		/* Wait until the index indicates that it is not replaying. */
+		while ((session->load_context.status != INDEX_SUSPENDED) &&
+		       (session->load_context.status != INDEX_READY)) {
+			uds_wait_cond(&session->load_context.cond,
+				      &session->load_context.mutex);
+		}
+
+		break;
+
+	case INDEX_READY:
+		/* Index load does not need to be suspended. */
+		break;
+
+	case INDEX_SUSPENDED:
+	case INDEX_SUSPENDING:
+	case INDEX_FREEING:
+	default:
+		/* These cases should not happen. */
+		VDO_ASSERT_LOG_ONLY(false, "Bad load context state %u",
+				    session->load_context.status);
+		break;
+	}
+	mutex_unlock(&session->load_context.mutex);
+}
+
+/*
+ * Suspend index operation, draining all current index requests and preventing new index requests
+ * from starting. Optionally saves all index data before returning.
+ */
+int uds_suspend_index_session(struct uds_index_session *session, bool save)
+{
+	int result = UDS_SUCCESS;
+	bool no_work = false;
+	bool rebuilding = false;
+
+	/* Wait for any current index state change to complete. */
+	mutex_lock(&session->request_mutex);
+	while (session->state & IS_FLAG_CLOSING)
+		uds_wait_cond(&session->request_cond, &session->request_mutex);
+
+	if ((session->state & IS_FLAG_WAITING) || (session->state & IS_FLAG_DESTROYING)) {
+		no_work = true;
+		vdo_log_info("Index session is already changing state");
+		result = -EBUSY;
+	} else if (session->state & IS_FLAG_SUSPENDED) {
+		no_work = true;
+	} else if (session->state & IS_FLAG_LOADING) {
+		session->state |= IS_FLAG_WAITING;
+		rebuilding = true;
+	} else if (session->state & IS_FLAG_LOADED) {
+		session->state |= IS_FLAG_WAITING;
+	} else {
+		no_work = true;
+		session->state |= IS_FLAG_SUSPENDED;
+		uds_broadcast_cond(&session->request_cond);
+	}
+	mutex_unlock(&session->request_mutex);
+
+	if (no_work)
+		return uds_status_to_errno(result);
+
+	if (rebuilding)
+		suspend_rebuild(session);
+	else if (save)
+		result = save_index(session);
+	else
+		result = uds_flush_index_session(session);
+
+	mutex_lock(&session->request_mutex);
+	session->state &= ~IS_FLAG_WAITING;
+	session->state |= IS_FLAG_SUSPENDED;
+	uds_broadcast_cond(&session->request_cond);
+	mutex_unlock(&session->request_mutex);
+	return uds_status_to_errno(result);
+}
+
+static int replace_device(struct uds_index_session *session, struct block_device *bdev)
+{
+	int result;
+
+	result = uds_replace_index_storage(session->index, bdev);
+	if (result != UDS_SUCCESS)
+		return result;
+
+	session->parameters.bdev = bdev;
+	return UDS_SUCCESS;
+}
+
+/*
+ * Resume index operation after being suspended. If the index is suspended and the supplied block
+ * device differs from the current backing store, the index will start using the new backing store.
+ */
+int uds_resume_index_session(struct uds_index_session *session,
+			     struct block_device *bdev)
+{
+	int result = UDS_SUCCESS;
+	bool no_work = false;
+	bool resume_replay = false;
+
+	mutex_lock(&session->request_mutex);
+	if (session->state & IS_FLAG_WAITING) {
+		vdo_log_info("Index session is already changing state");
+		no_work = true;
+		result = -EBUSY;
+	} else if (!(session->state & IS_FLAG_SUSPENDED)) {
+		/* If not suspended, just succeed. */
+		no_work = true;
+		result = UDS_SUCCESS;
+	} else {
+		session->state |= IS_FLAG_WAITING;
+		if (session->state & IS_FLAG_LOADING)
+			resume_replay = true;
+	}
+	mutex_unlock(&session->request_mutex);
+
+	if (no_work)
+		return result;
+
+	if ((session->index != NULL) && (bdev != session->parameters.bdev)) {
+		result = replace_device(session, bdev);
+		if (result != UDS_SUCCESS) {
+			mutex_lock(&session->request_mutex);
+			session->state &= ~IS_FLAG_WAITING;
+			uds_broadcast_cond(&session->request_cond);
+			mutex_unlock(&session->request_mutex);
+			return uds_status_to_errno(result);
+		}
+	}
+
+	if (resume_replay) {
+		mutex_lock(&session->load_context.mutex);
+		switch (session->load_context.status) {
+		case INDEX_SUSPENDED:
+			session->load_context.status = INDEX_OPENING;
+			/* Notify the index to start replaying again. */
+			uds_broadcast_cond(&session->load_context.cond);
+			break;
+
+		case INDEX_READY:
+			/* There is no index rebuild to resume. */
+			break;
+
+		case INDEX_OPENING:
+		case INDEX_SUSPENDING:
+		case INDEX_FREEING:
+		default:
+			/* These cases should not happen; do nothing. */
+			VDO_ASSERT_LOG_ONLY(false, "Bad load context state %u",
+					    session->load_context.status);
+			break;
+		}
+		mutex_unlock(&session->load_context.mutex);
+	}
+
+	mutex_lock(&session->request_mutex);
+	session->state &= ~IS_FLAG_WAITING;
+	session->state &= ~IS_FLAG_SUSPENDED;
+	uds_broadcast_cond(&session->request_cond);
+	mutex_unlock(&session->request_mutex);
+	return UDS_SUCCESS;
+}
+
+static int save_and_free_index(struct uds_index_session *index_session)
+{
+	int result = UDS_SUCCESS;
+	bool suspended;
+	struct uds_index *index = index_session->index;
+
+	if (index == NULL)
+		return UDS_SUCCESS;
+
+	mutex_lock(&index_session->request_mutex);
+	suspended = (index_session->state & IS_FLAG_SUSPENDED);
+	mutex_unlock(&index_session->request_mutex);
+
+	if (!suspended) {
+		result = uds_save_index(index);
+		if (result != UDS_SUCCESS)
+			vdo_log_warning_strerror(result,
+						 "ignoring error from save_index");
+	}
+	uds_free_index(index);
+	index_session->index = NULL;
+
+	/*
+	 * Reset all index state that happens to be in the index
+	 * session, so it doesn't affect any future index.
+	 */
+	mutex_lock(&index_session->load_context.mutex);
+	index_session->load_context.status = INDEX_OPENING;
+	mutex_unlock(&index_session->load_context.mutex);
+
+	mutex_lock(&index_session->request_mutex);
+	/* Only the suspend bit will remain relevant. */
+	index_session->state &= IS_FLAG_SUSPENDED;
+	mutex_unlock(&index_session->request_mutex);
+
+	return result;
+}
+
+/* Save and close the current index. */
+int uds_close_index(struct uds_index_session *index_session)
+{
+	int result = UDS_SUCCESS;
+
+	/* Wait for any current index state change to complete. */
+	mutex_lock(&index_session->request_mutex);
+	while ((index_session->state & IS_FLAG_WAITING) ||
+	       (index_session->state & IS_FLAG_CLOSING)) {
+		uds_wait_cond(&index_session->request_cond,
+			      &index_session->request_mutex);
+	}
+
+	if (index_session->state & IS_FLAG_SUSPENDED) {
+		vdo_log_info("Index session is suspended");
+		result = -EBUSY;
+	} else if ((index_session->state & IS_FLAG_DESTROYING) ||
+		   !(index_session->state & IS_FLAG_LOADED)) {
+		/* The index doesn't exist, hasn't finished loading, or is being destroyed. */
+		result = UDS_NO_INDEX;
+	} else {
+		index_session->state |= IS_FLAG_CLOSING;
+	}
+	mutex_unlock(&index_session->request_mutex);
+	if (result != UDS_SUCCESS)
+		return uds_status_to_errno(result);
+
+	vdo_log_debug("Closing index");
+	wait_for_no_requests_in_progress(index_session);
+	result = save_and_free_index(index_session);
+	vdo_log_debug("Closed index");
+
+	mutex_lock(&index_session->request_mutex);
+	index_session->state &= ~IS_FLAG_CLOSING;
+	uds_broadcast_cond(&index_session->request_cond);
+	mutex_unlock(&index_session->request_mutex);
+	return uds_status_to_errno(result);
+}
+
+/* This will save and close an open index before destroying the session. */
+int uds_destroy_index_session(struct uds_index_session *index_session)
+{
+	int result;
+	bool load_pending = false;
+
+	vdo_log_debug("Destroying index session");
+
+	/* Wait for any current index state change to complete. */
+	mutex_lock(&index_session->request_mutex);
+	while ((index_session->state & IS_FLAG_WAITING) ||
+	       (index_session->state & IS_FLAG_CLOSING)) {
+		uds_wait_cond(&index_session->request_cond,
+			      &index_session->request_mutex);
+	}
+
+	if (index_session->state & IS_FLAG_DESTROYING) {
+		mutex_unlock(&index_session->request_mutex);
+		vdo_log_info("Index session is already closing");
+		return -EBUSY;
+	}
+
+	index_session->state |= IS_FLAG_DESTROYING;
+	load_pending = ((index_session->state & IS_FLAG_LOADING) &&
+			(index_session->state & IS_FLAG_SUSPENDED));
+	mutex_unlock(&index_session->request_mutex);
+
+	if (load_pending) {
+		/* Tell the index to terminate the rebuild. */
+		mutex_lock(&index_session->load_context.mutex);
+		if (index_session->load_context.status == INDEX_SUSPENDED) {
+			index_session->load_context.status = INDEX_FREEING;
+			uds_broadcast_cond(&index_session->load_context.cond);
+		}
+		mutex_unlock(&index_session->load_context.mutex);
+
+		/* Wait until the load exits before proceeding. */
+		mutex_lock(&index_session->request_mutex);
+		while (index_session->state & IS_FLAG_LOADING) {
+			uds_wait_cond(&index_session->request_cond,
+				      &index_session->request_mutex);
+		}
+		mutex_unlock(&index_session->request_mutex);
+	}
+
+	wait_for_no_requests_in_progress(index_session);
+	result = save_and_free_index(index_session);
+	uds_request_queue_finish(index_session->callback_queue);
+	index_session->callback_queue = NULL;
+	vdo_log_debug("Destroyed index session");
+	vdo_free(index_session);
+	return uds_status_to_errno(result);
+}
+
+/* Wait until all callbacks for index operations are complete. */
+int uds_flush_index_session(struct uds_index_session *index_session)
+{
+	wait_for_no_requests_in_progress(index_session);
+	uds_wait_for_idle_index(index_session->index);
+	return UDS_SUCCESS;
+}
+
+/* Statistics collection is intended to be thread-safe. */
+static void collect_stats(const struct uds_index_session *index_session,
+			  struct uds_index_stats *stats)
+{
+	const struct session_stats *session_stats = &index_session->stats;
+
+	stats->current_time = ktime_to_seconds(current_time_ns(CLOCK_REALTIME));
+	stats->posts_found = READ_ONCE(session_stats->posts_found);
+	stats->in_memory_posts_found = READ_ONCE(session_stats->posts_found_open_chapter);
+	stats->dense_posts_found = READ_ONCE(session_stats->posts_found_dense);
+	stats->sparse_posts_found = READ_ONCE(session_stats->posts_found_sparse);
+	stats->posts_not_found = READ_ONCE(session_stats->posts_not_found);
+	stats->updates_found = READ_ONCE(session_stats->updates_found);
+	stats->updates_not_found = READ_ONCE(session_stats->updates_not_found);
+	stats->deletions_found = READ_ONCE(session_stats->deletions_found);
+	stats->deletions_not_found = READ_ONCE(session_stats->deletions_not_found);
+	stats->queries_found = READ_ONCE(session_stats->queries_found);
+	stats->queries_not_found = READ_ONCE(session_stats->queries_not_found);
+	stats->requests = READ_ONCE(session_stats->requests);
+}
+
+int uds_get_index_session_stats(struct uds_index_session *index_session,
+				struct uds_index_stats *stats)
+{
+	if (stats == NULL) {
+		vdo_log_error("received a NULL index stats pointer");
+		return -EINVAL;
+	}
+
+	collect_stats(index_session, stats);
+	if (index_session->index != NULL) {
+		uds_get_index_stats(index_session->index, stats);
+	} else {
+		stats->entries_indexed = 0;
+		stats->memory_used = 0;
+		stats->collisions = 0;
+		stats->entries_discarded = 0;
+	}
+
+	return UDS_SUCCESS;
+}
+
+void uds_wait_cond(struct cond_var *cv, struct mutex *mutex)
+{
+	DEFINE_WAIT(__wait);
+
+	prepare_to_wait(&cv->wait_queue, &__wait, TASK_IDLE);
+	mutex_unlock(mutex);
+	schedule();
+	finish_wait(&cv->wait_queue, &__wait);
+	mutex_lock(mutex);
+}