dm-zoned-reclaim.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (C) 2017 Western Digital Corporation or its affiliates.
 *
 * This file is released under the GPL.
 */

#include "dm-zoned.h"

#include <linux/module.h>

#define	DM_MSG_PREFIX		"zoned reclaim"

struct dmz_reclaim {
	struct dmz_metadata     *metadata;

	struct delayed_work	work;
	struct workqueue_struct *wq;

	struct dm_kcopyd_client	*kc;
	struct dm_kcopyd_throttle kc_throttle;
	int			kc_err;

	int			dev_idx;

	unsigned long		flags;

	/* Last target access time */
	unsigned long		atime;
};

/*
 * Reclaim state flags.
 */
enum {
	DMZ_RECLAIM_KCOPY,
};

/*
 * Number of seconds of target BIO inactivity to consider the target idle.
 */
#define DMZ_IDLE_PERIOD			(10UL * HZ)

/*
 * Percentage of unmapped (free) random zones below which reclaim starts
 * even if the target is busy.
 */
#define DMZ_RECLAIM_LOW_UNMAP_ZONES	30

/*
 * Percentage of unmapped (free) random zones above which reclaim will
 * stop if the target is busy.
 */
#define DMZ_RECLAIM_HIGH_UNMAP_ZONES	50

/*
 * Align a sequential zone write pointer to chunk_block.
 */
static int dmz_reclaim_align_wp(struct dmz_reclaim *zrc, struct dm_zone *zone,
				sector_t block)
{
	struct dmz_metadata *zmd = zrc->metadata;
	struct dmz_dev *dev = zone->dev;
	sector_t wp_block = zone->wp_block;
	unsigned int nr_blocks;
	int ret;

	if (wp_block == block)
		return 0;

	if (wp_block > block)
		return -EIO;

	/*
	 * Zeroout the space between the write
	 * pointer and the requested position.
	 */
	nr_blocks = block - wp_block;
	ret = blkdev_issue_zeroout(dev->bdev,
				   dmz_start_sect(zmd, zone) + dmz_blk2sect(wp_block),
				   dmz_blk2sect(nr_blocks), GFP_NOIO, 0);
	if (ret) {
		dmz_dev_err(dev,
			    "Align zone %u wp %llu to %llu (wp+%u) blocks failed %d",
			    zone->id, (unsigned long long)wp_block,
			    (unsigned long long)block, nr_blocks, ret);
		dmz_check_bdev(dev);
		return ret;
	}

	zone->wp_block = block;

	return 0;
}

/*
 * dm_kcopyd_copy end notification.
 */
static void dmz_reclaim_kcopy_end(int read_err, unsigned long write_err,
				  void *context)
{
	struct dmz_reclaim *zrc = context;

	if (read_err || write_err)
		zrc->kc_err = -EIO;
	else
		zrc->kc_err = 0;

	clear_bit_unlock(DMZ_RECLAIM_KCOPY, &zrc->flags);
	smp_mb__after_atomic();
	wake_up_bit(&zrc->flags, DMZ_RECLAIM_KCOPY);
}

/*
 * Copy valid blocks of src_zone into dst_zone.
 */
static int dmz_reclaim_copy(struct dmz_reclaim *zrc,
			    struct dm_zone *src_zone, struct dm_zone *dst_zone)
{
	struct dmz_metadata *zmd = zrc->metadata;
	struct dm_io_region src, dst;
	sector_t block = 0, end_block;
	sector_t nr_blocks;
	sector_t src_zone_block;
	sector_t dst_zone_block;
	unsigned long flags = 0;
	int ret;

	if (dmz_is_seq(src_zone))
		end_block = src_zone->wp_block;
	else
		end_block = dmz_zone_nr_blocks(zmd);
	src_zone_block = dmz_start_block(zmd, src_zone);
	dst_zone_block = dmz_start_block(zmd, dst_zone);

	if (dmz_is_seq(dst_zone))
		set_bit(DM_KCOPYD_WRITE_SEQ, &flags);

	while (block < end_block) {
		if (src_zone->dev->flags & DMZ_BDEV_DYING)
			return -EIO;
		if (dst_zone->dev->flags & DMZ_BDEV_DYING)
			return -EIO;

		if (dmz_reclaim_should_terminate(src_zone))
			return -EINTR;

		/* Get a valid region from the source zone */
		ret = dmz_first_valid_block(zmd, src_zone, &block);
		if (ret <= 0)
			return ret;
		nr_blocks = ret;

		/*
		 * If we are writing in a sequential zone, we must make sure
		 * that writes are sequential. So Zeroout any eventual hole
		 * between writes.
		 */
		if (dmz_is_seq(dst_zone)) {
			ret = dmz_reclaim_align_wp(zrc, dst_zone, block);
			if (ret)
				return ret;
		}

		src.bdev = src_zone->dev->bdev;
		src.sector = dmz_blk2sect(src_zone_block + block);
		src.count = dmz_blk2sect(nr_blocks);

		dst.bdev = dst_zone->dev->bdev;
		dst.sector = dmz_blk2sect(dst_zone_block + block);
		dst.count = src.count;

		/* Copy the valid region */
		set_bit(DMZ_RECLAIM_KCOPY, &zrc->flags);
		dm_kcopyd_copy(zrc->kc, &src, 1, &dst, flags,
			       dmz_reclaim_kcopy_end, zrc);

		/* Wait for copy to complete */
		wait_on_bit_io(&zrc->flags, DMZ_RECLAIM_KCOPY,
			       TASK_UNINTERRUPTIBLE);
		if (zrc->kc_err)
			return zrc->kc_err;

		block += nr_blocks;
		if (dmz_is_seq(dst_zone))
			dst_zone->wp_block = block;
	}

	return 0;
}

/*
 * Move valid blocks of dzone buffer zone into dzone (after its write pointer)
 * and free the buffer zone.
 */
static int dmz_reclaim_buf(struct dmz_reclaim *zrc, struct dm_zone *dzone)
{
	struct dm_zone *bzone = dzone->bzone;
	sector_t chunk_block = dzone->wp_block;
	struct dmz_metadata *zmd = zrc->metadata;
	int ret;

	DMDEBUG("(%s/%u): Chunk %u, move buf zone %u (weight %u) to data zone %u (weight %u)",
		dmz_metadata_label(zmd), zrc->dev_idx,
		dzone->chunk, bzone->id, dmz_weight(bzone),
		dzone->id, dmz_weight(dzone));

	/* Flush data zone into the buffer zone */
	ret = dmz_reclaim_copy(zrc, bzone, dzone);
	if (ret < 0)
		return ret;

	dmz_lock_flush(zmd);

	/* Validate copied blocks */
	ret = dmz_merge_valid_blocks(zmd, bzone, dzone, chunk_block);
	if (ret == 0) {
		/* Free the buffer zone */
		dmz_invalidate_blocks(zmd, bzone, 0, dmz_zone_nr_blocks(zmd));
		dmz_lock_map(zmd);
		dmz_unmap_zone(zmd, bzone);
		dmz_unlock_zone_reclaim(dzone);
		dmz_free_zone(zmd, bzone);
		dmz_unlock_map(zmd);
	}

	dmz_unlock_flush(zmd);

	return ret;
}

/*
 * Merge valid blocks of dzone into its buffer zone and free dzone.
 */
static int dmz_reclaim_seq_data(struct dmz_reclaim *zrc, struct dm_zone *dzone)
{
	unsigned int chunk = dzone->chunk;
	struct dm_zone *bzone = dzone->bzone;
	struct dmz_metadata *zmd = zrc->metadata;
	int ret = 0;

	DMDEBUG("(%s/%u): Chunk %u, move data zone %u (weight %u) to buf zone %u (weight %u)",
		dmz_metadata_label(zmd), zrc->dev_idx,
		chunk, dzone->id, dmz_weight(dzone),
		bzone->id, dmz_weight(bzone));

	/* Flush data zone into the buffer zone */
	ret = dmz_reclaim_copy(zrc, dzone, bzone);
	if (ret < 0)
		return ret;

	dmz_lock_flush(zmd);

	/* Validate copied blocks */
	ret = dmz_merge_valid_blocks(zmd, dzone, bzone, 0);
	if (ret == 0) {
		/*
		 * Free the data zone and remap the chunk to
		 * the buffer zone.
		 */
		dmz_invalidate_blocks(zmd, dzone, 0, dmz_zone_nr_blocks(zmd));
		dmz_lock_map(zmd);
		dmz_unmap_zone(zmd, bzone);
		dmz_unmap_zone(zmd, dzone);
		dmz_unlock_zone_reclaim(dzone);
		dmz_free_zone(zmd, dzone);
		dmz_map_zone(zmd, bzone, chunk);
		dmz_unlock_map(zmd);
	}

	dmz_unlock_flush(zmd);

	return ret;
}

/*
 * Move valid blocks of the random data zone dzone into a free sequential zone.
 * Once blocks are moved, remap the zone chunk to the sequential zone.
 */
static int dmz_reclaim_rnd_data(struct dmz_reclaim *zrc, struct dm_zone *dzone)
{
	unsigned int chunk = dzone->chunk;
	struct dm_zone *szone = NULL;
	struct dmz_metadata *zmd = zrc->metadata;
	int ret;
	int alloc_flags = DMZ_ALLOC_SEQ;

	/* Get a free random or sequential zone */
	dmz_lock_map(zmd);
again:
	szone = dmz_alloc_zone(zmd, zrc->dev_idx,
			       alloc_flags | DMZ_ALLOC_RECLAIM);
	if (!szone && alloc_flags == DMZ_ALLOC_SEQ && dmz_nr_cache_zones(zmd)) {
		alloc_flags = DMZ_ALLOC_RND;
		goto again;
	}
	dmz_unlock_map(zmd);
	if (!szone)
		return -ENOSPC;

	DMDEBUG("(%s/%u): Chunk %u, move %s zone %u (weight %u) to %s zone %u",
		dmz_metadata_label(zmd), zrc->dev_idx, chunk,
		dmz_is_cache(dzone) ? "cache" : "rnd",
		dzone->id, dmz_weight(dzone),
		dmz_is_rnd(szone) ? "rnd" : "seq", szone->id);

	/* Flush the random data zone into the sequential zone */
	ret = dmz_reclaim_copy(zrc, dzone, szone);

	dmz_lock_flush(zmd);

	if (ret == 0) {
		/* Validate copied blocks */
		ret = dmz_copy_valid_blocks(zmd, dzone, szone);
	}
	if (ret) {
		/* Free the sequential zone */
		dmz_lock_map(zmd);
		dmz_free_zone(zmd, szone);
		dmz_unlock_map(zmd);
	} else {
		/* Free the data zone and remap the chunk */
		dmz_invalidate_blocks(zmd, dzone, 0, dmz_zone_nr_blocks(zmd));
		dmz_lock_map(zmd);
		dmz_unmap_zone(zmd, dzone);
		dmz_unlock_zone_reclaim(dzone);
		dmz_free_zone(zmd, dzone);
		dmz_map_zone(zmd, szone, chunk);
		dmz_unlock_map(zmd);
	}

	dmz_unlock_flush(zmd);

	return ret;
}

/*
 * Reclaim an empty zone.
 */
static void dmz_reclaim_empty(struct dmz_reclaim *zrc, struct dm_zone *dzone)
{
	struct dmz_metadata *zmd = zrc->metadata;

	dmz_lock_flush(zmd);
	dmz_lock_map(zmd);
	dmz_unmap_zone(zmd, dzone);
	dmz_unlock_zone_reclaim(dzone);
	dmz_free_zone(zmd, dzone);
	dmz_unlock_map(zmd);
	dmz_unlock_flush(zmd);
}

/*
 * Test if the target device is idle.
 */
static inline int dmz_target_idle(struct dmz_reclaim *zrc)
{
	return time_is_before_jiffies(zrc->atime + DMZ_IDLE_PERIOD);
}

/*
 * Find a candidate zone for reclaim and process it.
 */
static int dmz_do_reclaim(struct dmz_reclaim *zrc)
{
	struct dmz_metadata *zmd = zrc->metadata;
	struct dm_zone *dzone;
	struct dm_zone *rzone;
	unsigned long start;
	int ret;

	/* Get a data zone */
	dzone = dmz_get_zone_for_reclaim(zmd, zrc->dev_idx,
					 dmz_target_idle(zrc));
	if (!dzone) {
		DMDEBUG("(%s/%u): No zone found to reclaim",
			dmz_metadata_label(zmd), zrc->dev_idx);
		return -EBUSY;
	}
	rzone = dzone;

	start = jiffies;
	if (dmz_is_cache(dzone) || dmz_is_rnd(dzone)) {
		if (!dmz_weight(dzone)) {
			/* Empty zone */
			dmz_reclaim_empty(zrc, dzone);
			ret = 0;
		} else {
			/*
			 * Reclaim the random data zone by moving its
			 * valid data blocks to a free sequential zone.
			 */
			ret = dmz_reclaim_rnd_data(zrc, dzone);
		}
	} else {
		struct dm_zone *bzone = dzone->bzone;
		sector_t chunk_block = 0;

		ret = dmz_first_valid_block(zmd, bzone, &chunk_block);
		if (ret < 0)
			goto out;

		if (ret == 0 || chunk_block >= dzone->wp_block) {
			/*
			 * The buffer zone is empty or its valid blocks are
			 * after the data zone write pointer.
			 */
			ret = dmz_reclaim_buf(zrc, dzone);
			rzone = bzone;
		} else {
			/*
			 * Reclaim the data zone by merging it into the
			 * buffer zone so that the buffer zone itself can
			 * be later reclaimed.
			 */
			ret = dmz_reclaim_seq_data(zrc, dzone);
		}
	}
out:
	if (ret) {
		if (ret == -EINTR)
			DMDEBUG("(%s/%u): reclaim zone %u interrupted",
				dmz_metadata_label(zmd), zrc->dev_idx,
				rzone->id);
		else
			DMDEBUG("(%s/%u): Failed to reclaim zone %u, err %d",
				dmz_metadata_label(zmd), zrc->dev_idx,
				rzone->id, ret);
		dmz_unlock_zone_reclaim(dzone);
		return ret;
	}

	ret = dmz_flush_metadata(zrc->metadata);
	if (ret) {
		DMDEBUG("(%s/%u): Metadata flush for zone %u failed, err %d",
			dmz_metadata_label(zmd), zrc->dev_idx, rzone->id, ret);
		return ret;
	}

	DMDEBUG("(%s/%u): Reclaimed zone %u in %u ms",
		dmz_metadata_label(zmd), zrc->dev_idx,
		rzone->id, jiffies_to_msecs(jiffies - start));
	return 0;
}

static unsigned int dmz_reclaim_percentage(struct dmz_reclaim *zrc)
{
	struct dmz_metadata *zmd = zrc->metadata;
	unsigned int nr_cache = dmz_nr_cache_zones(zmd);
	unsigned int nr_unmap, nr_zones;

	if (nr_cache) {
		nr_zones = nr_cache;
		nr_unmap = dmz_nr_unmap_cache_zones(zmd);
	} else {
		nr_zones = dmz_nr_rnd_zones(zmd, zrc->dev_idx);
		nr_unmap = dmz_nr_unmap_rnd_zones(zmd, zrc->dev_idx);
	}
	if (nr_unmap <= 1)
		return 0;
	return nr_unmap * 100 / nr_zones;
}

/*
 * Test if reclaim is necessary.
 */
static bool dmz_should_reclaim(struct dmz_reclaim *zrc, unsigned int p_unmap)
{
	unsigned int nr_reclaim;

	nr_reclaim = dmz_nr_rnd_zones(zrc->metadata, zrc->dev_idx);

	if (dmz_nr_cache_zones(zrc->metadata)) {
		/*
		 * The first device in a multi-device
		 * setup only contains cache zones, so
		 * never start reclaim there.
		 */
		if (zrc->dev_idx == 0)
			return false;
		nr_reclaim += dmz_nr_cache_zones(zrc->metadata);
	}

	/* Reclaim when idle */
	if (dmz_target_idle(zrc) && nr_reclaim)
		return true;

	/* If there are still plenty of cache zones, do not reclaim */
	if (p_unmap >= DMZ_RECLAIM_HIGH_UNMAP_ZONES)
		return false;

	/*
	 * If the percentage of unmapped cache zones is low,
	 * reclaim even if the target is busy.
	 */
	return p_unmap <= DMZ_RECLAIM_LOW_UNMAP_ZONES;
}

/*
 * Reclaim work function.
 */
static void dmz_reclaim_work(struct work_struct *work)
{
	struct dmz_reclaim *zrc = container_of(work, struct dmz_reclaim, work.work);
	struct dmz_metadata *zmd = zrc->metadata;
	unsigned int p_unmap;
	int ret;

	if (dmz_dev_is_dying(zmd))
		return;

	p_unmap = dmz_reclaim_percentage(zrc);
	if (!dmz_should_reclaim(zrc, p_unmap)) {
		mod_delayed_work(zrc->wq, &zrc->work, DMZ_IDLE_PERIOD);
		return;
	}

	/*
	 * We need to start reclaiming random zones: set up zone copy
	 * throttling to either go fast if we are very low on random zones
	 * and slower if there are still some free random zones to avoid
	 * as much as possible to negatively impact the user workload.
	 */
	if (dmz_target_idle(zrc) || p_unmap < DMZ_RECLAIM_LOW_UNMAP_ZONES / 2) {
		/* Idle or very low percentage: go fast */
		zrc->kc_throttle.throttle = 100;
	} else {
		/* Busy but we still have some random zone: throttle */
		zrc->kc_throttle.throttle = min(75U, 100U - p_unmap / 2);
	}

	DMDEBUG("(%s/%u): Reclaim (%u): %s, %u%% free zones (%u/%u cache %u/%u random)",
		dmz_metadata_label(zmd), zrc->dev_idx,
		zrc->kc_throttle.throttle,
		(dmz_target_idle(zrc) ? "Idle" : "Busy"),
		p_unmap, dmz_nr_unmap_cache_zones(zmd),
		dmz_nr_cache_zones(zmd),
		dmz_nr_unmap_rnd_zones(zmd, zrc->dev_idx),
		dmz_nr_rnd_zones(zmd, zrc->dev_idx));

	ret = dmz_do_reclaim(zrc);
	if (ret && ret != -EINTR) {
		if (!dmz_check_dev(zmd))
			return;
	}

	dmz_schedule_reclaim(zrc);
}

/*
 * Initialize reclaim.
 */
int dmz_ctr_reclaim(struct dmz_metadata *zmd,
		    struct dmz_reclaim **reclaim, int idx)
{
	struct dmz_reclaim *zrc;
	int ret;

	zrc = kzalloc(sizeof(struct dmz_reclaim), GFP_KERNEL);
	if (!zrc)
		return -ENOMEM;

	zrc->metadata = zmd;
	zrc->atime = jiffies;
	zrc->dev_idx = idx;

	/* Reclaim kcopyd client */
	zrc->kc = dm_kcopyd_client_create(&zrc->kc_throttle);
	if (IS_ERR(zrc->kc)) {
		ret = PTR_ERR(zrc->kc);
		zrc->kc = NULL;
		goto err;
	}

	/* Reclaim work */
	INIT_DELAYED_WORK(&zrc->work, dmz_reclaim_work);
	zrc->wq = alloc_ordered_workqueue("dmz_rwq_%s_%d", WQ_MEM_RECLAIM,
					  dmz_metadata_label(zmd), idx);
	if (!zrc->wq) {
		ret = -ENOMEM;
		goto err;
	}

	*reclaim = zrc;
	queue_delayed_work(zrc->wq, &zrc->work, 0);

	return 0;
err:
	if (zrc->kc)
		dm_kcopyd_client_destroy(zrc->kc);
	kfree(zrc);

	return ret;
}

/*
 * Terminate reclaim.
 */
void dmz_dtr_reclaim(struct dmz_reclaim *zrc)
{
	cancel_delayed_work_sync(&zrc->work);
	destroy_workqueue(zrc->wq);
	dm_kcopyd_client_destroy(zrc->kc);
	kfree(zrc);
}

/*
 * Suspend reclaim.
 */
void dmz_suspend_reclaim(struct dmz_reclaim *zrc)
{
	cancel_delayed_work_sync(&zrc->work);
}

/*
 * Resume reclaim.
 */
void dmz_resume_reclaim(struct dmz_reclaim *zrc)
{
	queue_delayed_work(zrc->wq, &zrc->work, DMZ_IDLE_PERIOD);
}

/*
 * BIO accounting.
 */
void dmz_reclaim_bio_acc(struct dmz_reclaim *zrc)
{
	zrc->atime = jiffies;
}

/*
 * Start reclaim if necessary.
 */
void dmz_schedule_reclaim(struct dmz_reclaim *zrc)
{
	unsigned int p_unmap = dmz_reclaim_percentage(zrc);

	if (dmz_should_reclaim(zrc, p_unmap))
		mod_delayed_work(zrc->wq, &zrc->work, 0);
}