Merge tag 'for-6.9/dm-vdo' of git://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm

Pull device mapper VDO target from Mike Snitzer:
 "Introduce the DM vdo target which provides block-level deduplication,
  compression, and thin provisioning. Please see:

      Documentation/admin-guide/device-mapper/vdo.rst
      Documentation/admin-guide/device-mapper/vdo-design.rst

  The DM vdo target handles its concurrency by pinning an IO, and
  subsequent stages of handling that IO, to a particular VDO thread.
  This aspect of VDO is "unique" but its overall implementation is very
  tightly coupled to its mostly lockless threading model. As such, VDO
  is not easily changed to use more traditional finer-grained locking
  and Linux workqueues. Please see the "Zones and Threading" section of
  vdo-design.rst

  The DM vdo target has been used in production for many years but has
  seen significant changes over the past ~6 years to prepare it for
  upstream inclusion. The codebase is still large but it is isolated to
  drivers/md/dm-vdo/ and has been made considerably more approachable
  and maintainable.

  Matt Sakai has been added to the MAINTAINERS file to reflect that he
  will send VDO changes upstream through the DM subsystem maintainers"

* tag 'for-6.9/dm-vdo' of git://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm: (142 commits)
  dm vdo: document minimum metadata size requirements
  dm vdo: remove meaningless version number constant
  dm vdo: remove vdo_perform_once
  dm vdo block-map: Remove stray semicolon
  dm vdo string-utils: change from uds_ to vdo_ namespace
  dm vdo logger: change from uds_ to vdo_ namespace
  dm vdo funnel-queue: change from uds_ to vdo_ namespace
  dm vdo indexer: fix use after free
  dm vdo logger: remove log level to string conversion code
  dm vdo: document log_level parameter
  dm vdo: add 'log_level' module parameter
  dm vdo: remove all sysfs interfaces
  dm vdo target: eliminate inappropriate uses of UDS_SUCCESS
  dm vdo indexer: update ASSERT and ASSERT_LOG_ONLY usage
  dm vdo encodings: update some stale comments
  dm vdo permassert: audit all of ASSERT to test for VDO_SUCCESS
  dm-vdo funnel-workqueue: return VDO_SUCCESS from make_simple_work_queue
  dm vdo thread-utils: return VDO_SUCCESS on vdo_create_thread success
  dm vdo int-map: return VDO_SUCCESS on success
  dm vdo: check for VDO_SUCCESS return value from memory-alloc functions
  ...

1 files changed, 108 insertions, 0 deletions

diff --git a/drivers/md/dm-vdo/thread-utils.c b/drivers/md/dm-vdo/thread-utils.c
new file mode 100644
index 000000000000..ec08478dd013
--- /dev/null
+++ b/drivers/md/dm-vdo/thread-utils.c
@@ -0,0 +1,108 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright 2023 Red Hat
+ */
+
+#include "thread-utils.h"
+
+#include <asm/current.h>
+#include <linux/delay.h>
+#include <linux/kthread.h>
+#include <linux/mutex.h>
+#include <linux/types.h>
+
+#include "errors.h"
+#include "logger.h"
+#include "memory-alloc.h"
+
+static struct hlist_head thread_list;
+static struct mutex thread_mutex;
+
+struct thread {
+	void (*thread_function)(void *thread_data);
+	void *thread_data;
+	struct hlist_node thread_links;
+	struct task_struct *thread_task;
+	struct completion thread_done;
+};
+
+void vdo_initialize_threads_mutex(void)
+{
+	mutex_init(&thread_mutex);
+}
+
+static int thread_starter(void *arg)
+{
+	struct registered_thread allocating_thread;
+	struct thread *thread = arg;
+
+	thread->thread_task = current;
+	mutex_lock(&thread_mutex);
+	hlist_add_head(&thread->thread_links, &thread_list);
+	mutex_unlock(&thread_mutex);
+	vdo_register_allocating_thread(&allocating_thread, NULL);
+	thread->thread_function(thread->thread_data);
+	vdo_unregister_allocating_thread();
+	complete(&thread->thread_done);
+	return 0;
+}
+
+int vdo_create_thread(void (*thread_function)(void *), void *thread_data,
+		      const char *name, struct thread **new_thread)
+{
+	char *name_colon = strchr(name, ':');
+	char *my_name_colon = strchr(current->comm, ':');
+	struct task_struct *task;
+	struct thread *thread;
+	int result;
+
+	result = vdo_allocate(1, struct thread, __func__, &thread);
+	if (result != VDO_SUCCESS) {
+		vdo_log_warning("Error allocating memory for %s", name);
+		return result;
+	}
+
+	thread->thread_function = thread_function;
+	thread->thread_data = thread_data;
+	init_completion(&thread->thread_done);
+	/*
+	 * Start the thread, with an appropriate thread name.
+	 *
+	 * If the name supplied contains a colon character, use that name. This causes uds module
+	 * threads to have names like "uds:callbackW" and the main test runner thread to be named
+	 * "zub:runtest".
+	 *
+	 * Otherwise if the current thread has a name containing a colon character, prefix the name
+	 * supplied with the name of the current thread up to (and including) the colon character.
+	 * Thus when the "kvdo0:dedupeQ" thread opens an index session, all the threads associated
+	 * with that index will have names like "kvdo0:foo".
+	 *
+	 * Otherwise just use the name supplied. This should be a rare occurrence.
+	 */
+	if ((name_colon == NULL) && (my_name_colon != NULL)) {
+		task = kthread_run(thread_starter, thread, "%.*s:%s",
+				   (int) (my_name_colon - current->comm), current->comm,
+				   name);
+	} else {
+		task = kthread_run(thread_starter, thread, "%s", name);
+	}
+
+	if (IS_ERR(task)) {
+		vdo_free(thread);
+		return PTR_ERR(task);
+	}
+
+	*new_thread = thread;
+	return VDO_SUCCESS;
+}
+
+void vdo_join_threads(struct thread *thread)
+{
+	while (wait_for_completion_interruptible(&thread->thread_done))
+		fsleep(1000);
+
+	mutex_lock(&thread_mutex);
+	hlist_del(&thread->thread_links);
+	mutex_unlock(&thread_mutex);
+	vdo_free(thread);
+}