1 files changed, 560 insertions, 0 deletions
diff --git a/drivers/md/dm-vdo/flush.c b/drivers/md/dm-vdo/flush.c
new file mode 100644
index 0000000000..57e87f0d70
--- /dev/null
+++ b/drivers/md/dm-vdo/flush.c
@@ -0,0 +1,560 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright 2023 Red Hat
+ */
+
+#include "flush.h"
+
+#include <linux/mempool.h>
+#include <linux/spinlock.h>
+
+#include "logger.h"
+#include "memory-alloc.h"
+#include "permassert.h"
+
+#include "admin-state.h"
+#include "completion.h"
+#include "io-submitter.h"
+#include "logical-zone.h"
+#include "slab-depot.h"
+#include "types.h"
+#include "vdo.h"
+
+struct flusher {
+	struct vdo_completion completion;
+	/* The vdo to which this flusher belongs */
+	struct vdo *vdo;
+	/* The administrative state of the flusher */
+	struct admin_state state;
+	/* The current flush generation of the vdo */
+	sequence_number_t flush_generation;
+	/* The first unacknowledged flush generation */
+	sequence_number_t first_unacknowledged_generation;
+	/* The queue of flush requests waiting to notify other threads */
+	struct vdo_wait_queue notifiers;
+	/* The queue of flush requests waiting for VIOs to complete */
+	struct vdo_wait_queue pending_flushes;
+	/* The flush generation for which notifications are being sent */
+	sequence_number_t notify_generation;
+	/* The logical zone to notify next */
+	struct logical_zone *logical_zone_to_notify;
+	/* The ID of the thread on which flush requests should be made */
+	thread_id_t thread_id;
+	/* The pool of flush requests */
+	mempool_t *flush_pool;
+	/* Bios waiting for a flush request to become available */
+	struct bio_list waiting_flush_bios;
+	/* The lock to protect the previous fields */
+	spinlock_t lock;
+	/* The rotor for selecting the bio queue for submitting flush bios */
+	zone_count_t bio_queue_rotor;
+	/* The number of flushes submitted to the current bio queue */
+	int flush_count;
+};
+
+/**
+ * assert_on_flusher_thread() - Check that we are on the flusher thread.
+ * @flusher: The flusher.
+ * @caller: The function which is asserting.
+ */
+static inline void assert_on_flusher_thread(struct flusher *flusher, const char *caller)
+{
+	VDO_ASSERT_LOG_ONLY((vdo_get_callback_thread_id() == flusher->thread_id),
+			    "%s() called from flusher thread", caller);
+}
+
+/**
+ * as_flusher() - Convert a generic vdo_completion to a flusher.
+ * @completion: The completion to convert.
+ *
+ * Return: The completion as a flusher.
+ */
+static struct flusher *as_flusher(struct vdo_completion *completion)
+{
+	vdo_assert_completion_type(completion, VDO_FLUSH_NOTIFICATION_COMPLETION);
+	return container_of(completion, struct flusher, completion);
+}
+
+/**
+ * completion_as_vdo_flush() - Convert a generic vdo_completion to a vdo_flush.
+ * @completion: The completion to convert.
+ *
+ * Return: The completion as a vdo_flush.
+ */
+static inline struct vdo_flush *completion_as_vdo_flush(struct vdo_completion *completion)
+{
+	vdo_assert_completion_type(completion, VDO_FLUSH_COMPLETION);
+	return container_of(completion, struct vdo_flush, completion);
+}
+
+/**
+ * vdo_waiter_as_flush() - Convert a vdo_flush's generic wait queue entry back to the vdo_flush.
+ * @waiter: The wait queue entry to convert.
+ *
+ * Return: The wait queue entry as a vdo_flush.
+ */
+static struct vdo_flush *vdo_waiter_as_flush(struct vdo_waiter *waiter)
+{
+	return container_of(waiter, struct vdo_flush, waiter);
+}
+
+static void *allocate_flush(gfp_t gfp_mask, void *pool_data)
+{
+	struct vdo_flush *flush = NULL;
+
+	if ((gfp_mask & GFP_NOWAIT) == GFP_NOWAIT) {
+		flush = vdo_allocate_memory_nowait(sizeof(struct vdo_flush), __func__);
+	} else {
+		int result = vdo_allocate(1, struct vdo_flush, __func__, &flush);
+
+		if (result != VDO_SUCCESS)
+			vdo_log_error_strerror(result, "failed to allocate spare flush");
+	}
+
+	if (flush != NULL) {
+		struct flusher *flusher = pool_data;
+
+		vdo_initialize_completion(&flush->completion, flusher->vdo,
+					  VDO_FLUSH_COMPLETION);
+	}
+
+	return flush;
+}
+
+static void free_flush(void *element, void *pool_data __always_unused)
+{
+	vdo_free(element);
+}
+
+/**
+ * vdo_make_flusher() - Make a flusher for a vdo.
+ * @vdo: The vdo which owns the flusher.
+ *
+ * Return: VDO_SUCCESS or an error.
+ */
+int vdo_make_flusher(struct vdo *vdo)
+{
+	int result = vdo_allocate(1, struct flusher, __func__, &vdo->flusher);
+
+	if (result != VDO_SUCCESS)
+		return result;
+
+	vdo->flusher->vdo = vdo;
+	vdo->flusher->thread_id = vdo->thread_config.packer_thread;
+	vdo_set_admin_state_code(&vdo->flusher->state, VDO_ADMIN_STATE_NORMAL_OPERATION);
+	vdo_initialize_completion(&vdo->flusher->completion, vdo,
+				  VDO_FLUSH_NOTIFICATION_COMPLETION);
+
+	spin_lock_init(&vdo->flusher->lock);
+	bio_list_init(&vdo->flusher->waiting_flush_bios);
+	vdo->flusher->flush_pool = mempool_create(1, allocate_flush, free_flush,
+						  vdo->flusher);
+	return ((vdo->flusher->flush_pool == NULL) ? -ENOMEM : VDO_SUCCESS);
+}
+
+/**
+ * vdo_free_flusher() - Free a flusher.
+ * @flusher: The flusher to free.
+ */
+void vdo_free_flusher(struct flusher *flusher)
+{
+	if (flusher == NULL)
+		return;
+
+	if (flusher->flush_pool != NULL)
+		mempool_destroy(vdo_forget(flusher->flush_pool));
+	vdo_free(flusher);
+}
+
+/**
+ * vdo_get_flusher_thread_id() - Get the ID of the thread on which flusher functions should be
+ *                               called.
+ * @flusher: The flusher to query.
+ *
+ * Return: The ID of the thread which handles the flusher.
+ */
+thread_id_t vdo_get_flusher_thread_id(struct flusher *flusher)
+{
+	return flusher->thread_id;
+}
+
+static void notify_flush(struct flusher *flusher);
+static void vdo_complete_flush(struct vdo_flush *flush);
+
+/**
+ * finish_notification() - Finish the notification process.
+ * @completion: The flusher completion.
+ *
+ * Finishes the notification process by checking if any flushes have completed and then starting
+ * the notification of the next flush request if one came in while the current notification was in
+ * progress. This callback is registered in flush_packer_callback().
+ */
+static void finish_notification(struct vdo_completion *completion)
+{
+	struct flusher *flusher = as_flusher(completion);
+
+	assert_on_flusher_thread(flusher, __func__);
+
+	vdo_waitq_enqueue_waiter(&flusher->pending_flushes,
+				 vdo_waitq_dequeue_waiter(&flusher->notifiers));
+	vdo_complete_flushes(flusher);
+	if (vdo_waitq_has_waiters(&flusher->notifiers))
+		notify_flush(flusher);
+}
+
+/**
+ * flush_packer_callback() - Flush the packer.
+ * @completion: The flusher completion.
+ *
+ * Flushes the packer now that all of the logical and physical zones have been notified of the new
+ * flush request. This callback is registered in increment_generation().
+ */
+static void flush_packer_callback(struct vdo_completion *completion)
+{
+	struct flusher *flusher = as_flusher(completion);
+
+	vdo_increment_packer_flush_generation(flusher->vdo->packer);
+	vdo_launch_completion_callback(completion, finish_notification,
+				       flusher->thread_id);
+}
+
+/**
+ * increment_generation() - Increment the flush generation in a logical zone.
+ * @completion: The flusher as a completion.
+ *
+ * If there are more logical zones, go on to the next one, otherwise, prepare the physical zones.
+ * This callback is registered both in notify_flush() and in itself.
+ */
+static void increment_generation(struct vdo_completion *completion)
+{
+	struct flusher *flusher = as_flusher(completion);
+	struct logical_zone *zone = flusher->logical_zone_to_notify;
+
+	vdo_increment_logical_zone_flush_generation(zone, flusher->notify_generation);
+	if (zone->next == NULL) {
+		vdo_launch_completion_callback(completion, flush_packer_callback,
+					       flusher->thread_id);
+		return;
+	}
+
+	flusher->logical_zone_to_notify = zone->next;
+	vdo_launch_completion_callback(completion, increment_generation,
+				       flusher->logical_zone_to_notify->thread_id);
+}
+
+/**
+ * notify_flush() - Launch a flush notification.
+ * @flusher: The flusher doing the notification.
+ */
+static void notify_flush(struct flusher *flusher)
+{
+	struct vdo_flush *flush =
+		vdo_waiter_as_flush(vdo_waitq_get_first_waiter(&flusher->notifiers));
+
+	flusher->notify_generation = flush->flush_generation;
+	flusher->logical_zone_to_notify = &flusher->vdo->logical_zones->zones[0];
+	flusher->completion.requeue = true;
+	vdo_launch_completion_callback(&flusher->completion, increment_generation,
+				       flusher->logical_zone_to_notify->thread_id);
+}
+
+/**
+ * flush_vdo() - Start processing a flush request.
+ * @completion: A flush request (as a vdo_completion)
+ *
+ * This callback is registered in launch_flush().
+ */
+static void flush_vdo(struct vdo_completion *completion)
+{
+	struct vdo_flush *flush = completion_as_vdo_flush(completion);
+	struct flusher *flusher = completion->vdo->flusher;
+	bool may_notify;
+	int result;
+
+	assert_on_flusher_thread(flusher, __func__);
+	result = VDO_ASSERT(vdo_is_state_normal(&flusher->state),
+			    "flusher is in normal operation");
+	if (result != VDO_SUCCESS) {
+		vdo_enter_read_only_mode(flusher->vdo, result);
+		vdo_complete_flush(flush);
+		return;
+	}
+
+	flush->flush_generation = flusher->flush_generation++;
+	may_notify = !vdo_waitq_has_waiters(&flusher->notifiers);
+	vdo_waitq_enqueue_waiter(&flusher->notifiers, &flush->waiter);
+	if (may_notify)
+		notify_flush(flusher);
+}
+
+/**
+ * check_for_drain_complete() - Check whether the flusher has drained.
+ * @flusher: The flusher.
+ */
+static void check_for_drain_complete(struct flusher *flusher)
+{
+	bool drained;
+
+	if (!vdo_is_state_draining(&flusher->state) ||
+	    vdo_waitq_has_waiters(&flusher->pending_flushes))
+		return;
+
+	spin_lock(&flusher->lock);
+	drained = bio_list_empty(&flusher->waiting_flush_bios);
+	spin_unlock(&flusher->lock);
+
+	if (drained)
+		vdo_finish_draining(&flusher->state);
+}
+
+/**
+ * vdo_complete_flushes() - Attempt to complete any flushes which might have finished.
+ * @flusher: The flusher.
+ */
+void vdo_complete_flushes(struct flusher *flusher)
+{
+	sequence_number_t oldest_active_generation = U64_MAX;
+	struct logical_zone *zone;
+
+	assert_on_flusher_thread(flusher, __func__);
+
+	for (zone = &flusher->vdo->logical_zones->zones[0]; zone != NULL; zone = zone->next)
+		oldest_active_generation =
+			min(oldest_active_generation,
+			    READ_ONCE(zone->oldest_active_generation));
+
+	while (vdo_waitq_has_waiters(&flusher->pending_flushes)) {
+		struct vdo_flush *flush =
+			vdo_waiter_as_flush(vdo_waitq_get_first_waiter(&flusher->pending_flushes));
+
+		if (flush->flush_generation >= oldest_active_generation)
+			return;
+
+		VDO_ASSERT_LOG_ONLY((flush->flush_generation ==
+				     flusher->first_unacknowledged_generation),
+				    "acknowledged next expected flush, %llu, was: %llu",
+				    (unsigned long long) flusher->first_unacknowledged_generation,
+				    (unsigned long long) flush->flush_generation);
+		vdo_waitq_dequeue_waiter(&flusher->pending_flushes);
+		vdo_complete_flush(flush);
+		flusher->first_unacknowledged_generation++;
+	}
+
+	check_for_drain_complete(flusher);
+}
+
+/**
+ * vdo_dump_flusher() - Dump the flusher, in a thread-unsafe fashion.
+ * @flusher: The flusher.
+ */
+void vdo_dump_flusher(const struct flusher *flusher)
+{
+	vdo_log_info("struct flusher");
+	vdo_log_info("  flush_generation=%llu first_unacknowledged_generation=%llu",
+		     (unsigned long long) flusher->flush_generation,
+		     (unsigned long long) flusher->first_unacknowledged_generation);
+	vdo_log_info("  notifiers queue is %s; pending_flushes queue is %s",
+		     (vdo_waitq_has_waiters(&flusher->notifiers) ? "not empty" : "empty"),
+		     (vdo_waitq_has_waiters(&flusher->pending_flushes) ? "not empty" : "empty"));
+}
+
+/**
+ * initialize_flush() - Initialize a vdo_flush structure.
+ * @flush: The flush to initialize.
+ * @vdo: The vdo being flushed.
+ *
+ * Initializes a vdo_flush structure, transferring all the bios in the flusher's waiting_flush_bios
+ * list to it. The caller MUST already hold the lock.
+ */
+static void initialize_flush(struct vdo_flush *flush, struct vdo *vdo)
+{
+	bio_list_init(&flush->bios);
+	bio_list_merge(&flush->bios, &vdo->flusher->waiting_flush_bios);
+	bio_list_init(&vdo->flusher->waiting_flush_bios);
+}
+
+static void launch_flush(struct vdo_flush *flush)
+{
+	struct vdo_completion *completion = &flush->completion;
+
+	vdo_prepare_completion(completion, flush_vdo, flush_vdo,
+			       completion->vdo->thread_config.packer_thread, NULL);
+	vdo_enqueue_completion(completion, VDO_DEFAULT_Q_FLUSH_PRIORITY);
+}
+
+/**
+ * vdo_launch_flush() - Function called to start processing a flush request.
+ * @vdo: The vdo.
+ * @bio: The bio containing an empty flush request.
+ *
+ * This is called when we receive an empty flush bio from the block layer, and before acknowledging
+ * a non-empty bio with the FUA flag set.
+ */
+void vdo_launch_flush(struct vdo *vdo, struct bio *bio)
+{
+	/*
+	 * Try to allocate a vdo_flush to represent the flush request. If the allocation fails,
+	 * we'll deal with it later.
+	 */
+	struct vdo_flush *flush = mempool_alloc(vdo->flusher->flush_pool, GFP_NOWAIT);
+	struct flusher *flusher = vdo->flusher;
+	const struct admin_state_code *code = vdo_get_admin_state_code(&flusher->state);
+
+	VDO_ASSERT_LOG_ONLY(!code->quiescent, "Flushing not allowed in state %s",
+			    code->name);
+
+	spin_lock(&flusher->lock);
+
+	/* We have a new bio to start. Add it to the list. */
+	bio_list_add(&flusher->waiting_flush_bios, bio);
+
+	if (flush == NULL) {
+		spin_unlock(&flusher->lock);
+		return;
+	}
+
+	/* We have flushes to start. Capture them in the vdo_flush structure. */
+	initialize_flush(flush, vdo);
+	spin_unlock(&flusher->lock);
+
+	/* Finish launching the flushes. */
+	launch_flush(flush);
+}
+
+/**
+ * release_flush() - Release a vdo_flush structure that has completed its work.
+ * @flush: The completed flush structure to re-use or free.
+ *
+ * If there are any pending flush requests whose vdo_flush allocation failed, they will be launched
+ * by immediately re-using the released vdo_flush. If there is no spare vdo_flush, the released
+ * structure will become the spare. Otherwise, the vdo_flush will be freed.
+ */
+static void release_flush(struct vdo_flush *flush)
+{
+	bool relaunch_flush;
+	struct flusher *flusher = flush->completion.vdo->flusher;
+
+	spin_lock(&flusher->lock);
+	if (bio_list_empty(&flusher->waiting_flush_bios)) {
+		relaunch_flush = false;
+	} else {
+		/* We have flushes to start. Capture them in a flush request. */
+		initialize_flush(flush, flusher->vdo);
+		relaunch_flush = true;
+	}
+	spin_unlock(&flusher->lock);
+
+	if (relaunch_flush) {
+		/* Finish launching the flushes. */
+		launch_flush(flush);
+		return;
+	}
+
+	mempool_free(flush, flusher->flush_pool);
+}
+
+/**
+ * vdo_complete_flush_callback() - Function called to complete and free a flush request, registered
+ *                                 in vdo_complete_flush().
+ * @completion: The flush request.
+ */
+static void vdo_complete_flush_callback(struct vdo_completion *completion)
+{
+	struct vdo_flush *flush = completion_as_vdo_flush(completion);
+	struct vdo *vdo = completion->vdo;
+	struct bio *bio;
+
+	while ((bio = bio_list_pop(&flush->bios)) != NULL) {
+		/*
+		 * We're not acknowledging this bio now, but we'll never touch it again, so this is
+		 * the last chance to account for it.
+		 */
+		vdo_count_bios(&vdo->stats.bios_acknowledged, bio);
+
+		/* Update the device, and send it on down... */
+		bio_set_dev(bio, vdo_get_backing_device(vdo));
+		atomic64_inc(&vdo->stats.flush_out);
+		submit_bio_noacct(bio);
+	}
+
+
+	/*
+	 * Release the flush structure, freeing it, re-using it as the spare, or using it to launch
+	 * any flushes that had to wait when allocations failed.
+	 */
+	release_flush(flush);
+}
+
+/**
+ * select_bio_queue() - Select the bio queue on which to finish a flush request.
+ * @flusher: The flusher finishing the request.
+ */
+static thread_id_t select_bio_queue(struct flusher *flusher)
+{
+	struct vdo *vdo = flusher->vdo;
+	zone_count_t bio_threads = flusher->vdo->thread_config.bio_thread_count;
+	int interval;
+
+	if (bio_threads == 1)
+		return vdo->thread_config.bio_threads[0];
+
+	interval = vdo->device_config->thread_counts.bio_rotation_interval;
+	if (flusher->flush_count == interval) {
+		flusher->flush_count = 1;
+		flusher->bio_queue_rotor = ((flusher->bio_queue_rotor + 1) % bio_threads);
+	} else {
+		flusher->flush_count++;
+	}
+
+	return vdo->thread_config.bio_threads[flusher->bio_queue_rotor];
+}
+
+/**
+ * vdo_complete_flush() - Complete and free a vdo flush request.
+ * @flush: The flush request.
+ */
+static void vdo_complete_flush(struct vdo_flush *flush)
+{
+	struct vdo_completion *completion = &flush->completion;
+
+	vdo_prepare_completion(completion, vdo_complete_flush_callback,
+			       vdo_complete_flush_callback,
+			       select_bio_queue(completion->vdo->flusher), NULL);
+	vdo_enqueue_completion(completion, BIO_Q_FLUSH_PRIORITY);
+}
+
+/**
+ * initiate_drain() - Initiate a drain.
+ *
+ * Implements vdo_admin_initiator_fn.
+ */
+static void initiate_drain(struct admin_state *state)
+{
+	check_for_drain_complete(container_of(state, struct flusher, state));
+}
+
+/**
+ * vdo_drain_flusher() - Drain the flusher.
+ * @flusher: The flusher to drain.
+ * @completion: The completion to finish when the flusher has drained.
+ *
+ * Drains the flusher by preventing any more VIOs from entering the flusher and then flushing. The
+ * flusher will be left in the suspended state.
+ */
+void vdo_drain_flusher(struct flusher *flusher, struct vdo_completion *completion)
+{
+	assert_on_flusher_thread(flusher, __func__);
+	vdo_start_draining(&flusher->state, VDO_ADMIN_STATE_SUSPENDING, completion,
+			   initiate_drain);
+}
+
+/**
+ * vdo_resume_flusher() - Resume a flusher which has been suspended.
+ * @flusher: The flusher to resume.
+ * @parent: The completion to finish when the flusher has resumed.
+ */
+void vdo_resume_flusher(struct flusher *flusher, struct vdo_completion *parent)
+{
+	assert_on_flusher_thread(flusher, __func__);
+	vdo_continue_completion(parent, vdo_resume_if_quiescent(&flusher->state));
+}