text: /*
   * 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 dmz_dev		*dev;
  
  	struct delayed_work	work;
  	struct workqueue_struct *wq;
  
  	struct dm_kcopyd_client	*kc;
  	struct dm_kcopyd_throttle kc_throttle;
  	int			kc_err;
  
  	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_RND	30
  
  /*
   * Percentage of unmapped (free) random zones above which reclaim will
   * stop if the target is busy.
   */
  #define DMZ_RECLAIM_HIGH_UNMAP_RND	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;
  	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(zrc->dev->bdev,
  				   dmz_start_sect(zmd, zone) + dmz_blk2sect(wp_block),
  				   dmz_blk2sect(nr_blocks), GFP_NOIO, 0);
  	if (ret) {
  		dmz_dev_err(zrc->dev,
  			    "Align zone %u wp %llu to %llu (wp+%u) blocks failed %d",
  			    dmz_id(zmd, zone), (unsigned long long)wp_block,
  			    (unsigned long long)block, nr_blocks, ret);
  		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 dmz_dev *dev = zrc->dev;
  	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 = dev->zone_nr_blocks;
  	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) {
  		/* 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 = dev->bdev;
  		src.sector = dmz_blk2sect(src_zone_block + block);
  		src.count = dmz_blk2sect(nr_blocks);
  
  		dst.bdev = 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);
  		ret = dm_kcopyd_copy(zrc->kc, &src, 1, &dst, flags,
  				     dmz_reclaim_kcopy_end, zrc);
  		if (ret)
  			return ret;
  
  		/* 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;
  
  	dmz_dev_debug(zrc->dev,
  		      "Chunk %u, move buf zone %u (weight %u) to data zone %u (weight %u)",
  		      dzone->chunk, dmz_id(zmd, bzone), dmz_weight(bzone),
  		      dmz_id(zmd, dzone), 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, zrc->dev->zone_nr_blocks);
  		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 0;
  }
  
  /*
   * 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;
  
  	dmz_dev_debug(zrc->dev,
  		      "Chunk %u, move data zone %u (weight %u) to buf zone %u (weight %u)",
  		      chunk, dmz_id(zmd, dzone), dmz_weight(dzone),
  		      dmz_id(zmd, bzone), 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, zrc->dev->zone_nr_blocks);
  		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 0;
  }
  
  /*
   * 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;
  
  	/* Get a free sequential zone */
  	dmz_lock_map(zmd);
  	szone = dmz_alloc_zone(zmd, DMZ_ALLOC_RECLAIM);
  	dmz_unlock_map(zmd);
  	if (!szone)
  		return -ENOSPC;
  
  	dmz_dev_debug(zrc->dev,
  		      "Chunk %u, move rnd zone %u (weight %u) to seq zone %u",
  		      chunk, dmz_id(zmd, dzone), dmz_weight(dzone),
  		      dmz_id(zmd, szone));
  
  	/* 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, zrc->dev->zone_nr_blocks);
  		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 0;
  }
  
  /*
   * 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);
  }
  
  /*
   * Find a candidate zone for reclaim and process it.
   */
  static void dmz_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);
  	if (!dzone)
  		return;
  
  	start = jiffies;
  
  	if (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);
  		}
  		rzone = 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);
  			rzone = dzone;
  		}
  	}
  out:
  	if (ret) {
  		dmz_unlock_zone_reclaim(dzone);
  		return;
  	}
  
  	(void) dmz_flush_metadata(zrc->metadata);
  
  	dmz_dev_debug(zrc->dev, "Reclaimed zone %u in %u ms",
  		      dmz_id(zmd, rzone), jiffies_to_msecs(jiffies - start));
  }
  
  /*
   * 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);
  }
  
  /*
   * Test if reclaim is necessary.
   */
  static bool dmz_should_reclaim(struct dmz_reclaim *zrc)
  {
  	struct dmz_metadata *zmd = zrc->metadata;
  	unsigned int nr_rnd = dmz_nr_rnd_zones(zmd);
  	unsigned int nr_unmap_rnd = dmz_nr_unmap_rnd_zones(zmd);
  	unsigned int p_unmap_rnd = nr_unmap_rnd * 100 / nr_rnd;
  
  	/* Reclaim when idle */
  	if (dmz_target_idle(zrc) && nr_unmap_rnd < nr_rnd)
  		return true;
  
  	/* If there are still plenty of random zones, do not reclaim */
  	if (p_unmap_rnd >= DMZ_RECLAIM_HIGH_UNMAP_RND)
  		return false;
  
  	/*
  	 * If the percentage of unmappped random zones is low,
  	 * reclaim even if the target is busy.
  	 */
  	return p_unmap_rnd <= DMZ_RECLAIM_LOW_UNMAP_RND;
  }
  
  /*
   * 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 nr_rnd, nr_unmap_rnd;
  	unsigned int p_unmap_rnd;
  
  	if (!dmz_should_reclaim(zrc)) {
  		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.
  	 */
  	nr_rnd = dmz_nr_rnd_zones(zmd);
  	nr_unmap_rnd = dmz_nr_unmap_rnd_zones(zmd);
  	p_unmap_rnd = nr_unmap_rnd * 100 / nr_rnd;
  	if (dmz_target_idle(zrc) || p_unmap_rnd < DMZ_RECLAIM_LOW_UNMAP_RND / 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_rnd / 2);
  	}
  
  	dmz_dev_debug(zrc->dev,
  		      "Reclaim (%u): %s, %u%% free rnd zones (%u/%u)",
  		      zrc->kc_throttle.throttle,
  		      (dmz_target_idle(zrc) ? "Idle" : "Busy"),
  		      p_unmap_rnd, nr_unmap_rnd, nr_rnd);
  
  	dmz_reclaim(zrc);
  
  	dmz_schedule_reclaim(zrc);
  }
  
  /*
   * Initialize reclaim.
   */
  int dmz_ctr_reclaim(struct dmz_dev *dev, struct dmz_metadata *zmd,
  		    struct dmz_reclaim **reclaim)
  {
  	struct dmz_reclaim *zrc;
  	int ret;
  
  	zrc = kzalloc(sizeof(struct dmz_reclaim), GFP_KERNEL);
  	if (!zrc)
  		return -ENOMEM;
  
  	zrc->dev = dev;
  	zrc->metadata = zmd;
  	zrc->atime = jiffies;
  
  	/* 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", WQ_MEM_RECLAIM,
  					  dev->name);
  	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)
  {
  	if (dmz_should_reclaim(zrc))
  		mod_delayed_work(zrc->wq, &zrc->work, 0);
  }
  
  