dm zoned: separate random and cache zones

Instead of lumping emulated zones together with random zones we
should be handling them as separate 'cache' zones. This improves
code readability and allows an easier implementation of different
cache policies.

Also add additional allocation flags, to separate the type (cache,
random, or sequential) from the purpose (eg reclaim).

Also switch the allocation policy to not use random zones as buffer
zones if cache zones are present. This avoids a performance drop when
all cache zones are used.

Signed-off-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Damien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>

1 files changed, 92 insertions, 31 deletions

diff --git a/drivers/md/dm-zoned-metadata.c b/drivers/md/dm-zoned-metadata.c
index fa7bcb28e952..6c009a8b36a4 100644
--- a/drivers/md/dm-zoned-metadata.c
+++ b/drivers/md/dm-zoned-metadata.c
@@ -166,6 +166,7 @@ struct dmz_metadata {
 	unsigned int		nr_meta_blocks;
 	unsigned int		nr_meta_zones;
 	unsigned int		nr_data_zones;
+	unsigned int		nr_cache_zones;
 	unsigned int		nr_rnd_zones;
 	unsigned int		nr_reserved_seq;
 	unsigned int		nr_chunks;
@@ -196,6 +197,11 @@ struct dmz_metadata {
 	struct list_head	unmap_rnd_list;
 	struct list_head	map_rnd_list;
 
+	unsigned int		nr_cache;
+	atomic_t		unmap_nr_cache;
+	struct list_head	unmap_cache_list;
+	struct list_head	map_cache_list;
+
 	unsigned int		nr_seq;
 	atomic_t		unmap_nr_seq;
 	struct list_head	unmap_seq_list;
@@ -301,6 +307,16 @@ unsigned int dmz_nr_unmap_rnd_zones(struct dmz_metadata *zmd)
 	return atomic_read(&zmd->unmap_nr_rnd);
 }
 
+unsigned int dmz_nr_cache_zones(struct dmz_metadata *zmd)
+{
+	return zmd->nr_cache;
+}
+
+unsigned int dmz_nr_unmap_cache_zones(struct dmz_metadata *zmd)
+{
+	return atomic_read(&zmd->unmap_nr_cache);
+}
+
 unsigned int dmz_nr_seq_zones(struct dmz_metadata *zmd)
 {
 	return zmd->nr_seq;
@@ -1390,9 +1406,9 @@ static void dmz_emulate_zones(struct dmz_metadata *zmd, struct dmz_dev *dev)
 		atomic_set(&zone->refcount, 0);
 		zone->id = idx;
 		zone->chunk = DMZ_MAP_UNMAPPED;
-		set_bit(DMZ_RND, &zone->flags);
+		set_bit(DMZ_CACHE, &zone->flags);
 		zone->wp_block = 0;
-		zmd->nr_rnd_zones++;
+		zmd->nr_cache_zones++;
 		zmd->nr_useable_zones++;
 		if (dev->capacity - zone_offset < zmd->zone_nr_sectors) {
 			/* Disable runt zone */
@@ -1647,7 +1663,9 @@ static int dmz_load_mapping(struct dmz_metadata *zmd)
 		dzone->chunk = chunk;
 		dmz_get_zone_weight(zmd, dzone);
 
-		if (dmz_is_rnd(dzone))
+		if (dmz_is_cache(dzone))
+			list_add_tail(&dzone->link, &zmd->map_cache_list);
+		else if (dmz_is_rnd(dzone))
 			list_add_tail(&dzone->link, &zmd->map_rnd_list);
 		else
 			list_add_tail(&dzone->link, &zmd->map_seq_list);
@@ -1664,7 +1682,7 @@ static int dmz_load_mapping(struct dmz_metadata *zmd)
 		}
 
 		bzone = dmz_get(zmd, bzone_id);
-		if (!dmz_is_rnd(bzone)) {
+		if (!dmz_is_rnd(bzone) && !dmz_is_cache(bzone)) {
 			dmz_zmd_err(zmd, "Chunk %u mapping: invalid buffer zone %u",
 				    chunk, bzone_id);
 			return -EIO;
@@ -1676,7 +1694,10 @@ static int dmz_load_mapping(struct dmz_metadata *zmd)
 		bzone->bzone = dzone;
 		dzone->bzone = bzone;
 		dmz_get_zone_weight(zmd, bzone);
-		list_add_tail(&bzone->link, &zmd->map_rnd_list);
+		if (dmz_is_cache(bzone))
+			list_add_tail(&bzone->link, &zmd->map_cache_list);
+		else
+			list_add_tail(&bzone->link, &zmd->map_rnd_list);
 next:
 		chunk++;
 		e++;
@@ -1693,8 +1714,12 @@ next:
 		dzone = dmz_get(zmd, i);
 		if (dmz_is_meta(dzone))
 			continue;
+		if (dmz_is_offline(dzone))
+			continue;
 
-		if (dmz_is_rnd(dzone))
+		if (dmz_is_cache(dzone))
+			zmd->nr_cache++;
+		else if (dmz_is_rnd(dzone))
 			zmd->nr_rnd++;
 		else
 			zmd->nr_seq++;
@@ -1707,7 +1732,10 @@ next:
 		/* Unmapped data zone */
 		set_bit(DMZ_DATA, &dzone->flags);
 		dzone->chunk = DMZ_MAP_UNMAPPED;
-		if (dmz_is_rnd(dzone)) {
+		if (dmz_is_cache(dzone)) {
+			list_add_tail(&dzone->link, &zmd->unmap_cache_list);
+			atomic_inc(&zmd->unmap_nr_cache);
+		} else if (dmz_is_rnd(dzone)) {
 			list_add_tail(&dzone->link, &zmd->unmap_rnd_list);
 			atomic_inc(&zmd->unmap_nr_rnd);
 		} else if (atomic_read(&zmd->nr_reserved_seq_zones) < zmd->nr_reserved_seq) {
@@ -1751,6 +1779,9 @@ static void __dmz_lru_zone(struct dmz_metadata *zmd, struct dm_zone *zone)
 	if (dmz_is_seq(zone)) {
 		/* LRU rotate sequential zone */
 		list_add_tail(&zone->link, &zmd->map_seq_list);
+	} else if (dmz_is_cache(zone)) {
+		/* LRU rotate cache zone */
+		list_add_tail(&zone->link, &zmd->map_cache_list);
 	} else {
 		/* LRU rotate random zone */
 		list_add_tail(&zone->link, &zmd->map_rnd_list);
@@ -1826,17 +1857,19 @@ static void dmz_wait_for_reclaim(struct dmz_metadata *zmd, struct dm_zone *zone)
 }
 
 /*
- * Select a random write zone for reclaim.
+ * Select a cache or random write zone for reclaim.
  */
 static struct dm_zone *dmz_get_rnd_zone_for_reclaim(struct dmz_metadata *zmd)
 {
 	struct dm_zone *dzone = NULL;
 	struct dm_zone *zone;
+	struct list_head *zone_list = &zmd->map_rnd_list;
 
-	if (list_empty(&zmd->map_rnd_list))
-		return ERR_PTR(-EBUSY);
+	/* If we have cache zones select from the cache zone list */
+	if (zmd->nr_cache)
+		zone_list = &zmd->map_cache_list;
 
-	list_for_each_entry(zone, &zmd->map_rnd_list, link) {
+	list_for_each_entry(zone, zone_list, link) {
 		if (dmz_is_buf(zone))
 			dzone = zone->bzone;
 		else
@@ -1855,9 +1888,6 @@ static struct dm_zone *dmz_get_seq_zone_for_reclaim(struct dmz_metadata *zmd)
 {
 	struct dm_zone *zone;
 
-	if (list_empty(&zmd->map_seq_list))
-		return ERR_PTR(-EBUSY);
-
 	list_for_each_entry(zone, &zmd->map_seq_list, link) {
 		if (!zone->bzone)
 			continue;
@@ -1907,6 +1937,7 @@ struct dm_zone *dmz_get_chunk_mapping(struct dmz_metadata *zmd, unsigned int chu
 	unsigned int dzone_id;
 	struct dm_zone *dzone = NULL;
 	int ret = 0;
+	int alloc_flags = zmd->nr_cache ? DMZ_ALLOC_CACHE : DMZ_ALLOC_RND;
 
 	dmz_lock_map(zmd);
 again:
@@ -1921,7 +1952,7 @@ again:
 			goto out;
 
 		/* Allocate a random zone */
-		dzone = dmz_alloc_zone(zmd, DMZ_ALLOC_RND);
+		dzone = dmz_alloc_zone(zmd, alloc_flags);
 		if (!dzone) {
 			if (dmz_dev_is_dying(zmd)) {
 				dzone = ERR_PTR(-EIO);
@@ -2014,6 +2045,7 @@ struct dm_zone *dmz_get_chunk_buffer(struct dmz_metadata *zmd,
 				     struct dm_zone *dzone)
 {
 	struct dm_zone *bzone;
+	int alloc_flags = zmd->nr_cache ? DMZ_ALLOC_CACHE : DMZ_ALLOC_RND;
 
 	dmz_lock_map(zmd);
 again:
@@ -2022,7 +2054,7 @@ again:
 		goto out;
 
 	/* Allocate a random zone */
-	bzone = dmz_alloc_zone(zmd, DMZ_ALLOC_RND);
+	bzone = dmz_alloc_zone(zmd, alloc_flags);
 	if (!bzone) {
 		if (dmz_dev_is_dying(zmd)) {
 			bzone = ERR_PTR(-EIO);
@@ -2039,7 +2071,10 @@ again:
 	bzone->chunk = dzone->chunk;
 	bzone->bzone = dzone;
 	dzone->bzone = bzone;
-	list_add_tail(&bzone->link, &zmd->map_rnd_list);
+	if (dmz_is_cache(bzone))
+		list_add_tail(&bzone->link, &zmd->map_cache_list);
+	else
+		list_add_tail(&bzone->link, &zmd->map_rnd_list);
 out:
 	dmz_unlock_map(zmd);
 
@@ -2055,31 +2090,46 @@ struct dm_zone *dmz_alloc_zone(struct dmz_metadata *zmd, unsigned long flags)
 	struct list_head *list;
 	struct dm_zone *zone;
 
-	if (flags & DMZ_ALLOC_RND)
+	if (flags & DMZ_ALLOC_CACHE)
+		list = &zmd->unmap_cache_list;
+	else if (flags & DMZ_ALLOC_RND)
 		list = &zmd->unmap_rnd_list;
 	else
 		list = &zmd->unmap_seq_list;
+
 again:
 	if (list_empty(list)) {
 		/*
-		 * No free zone: if this is for reclaim, allow using the
-		 * reserved sequential zones.
+		 * No free zone: return NULL if this is for not reclaim.
 		 */
-		if (!(flags & DMZ_ALLOC_RECLAIM) ||
-		    list_empty(&zmd->reserved_seq_zones_list))
+		if (!(flags & DMZ_ALLOC_RECLAIM))
 			return NULL;
-
-		zone = list_first_entry(&zmd->reserved_seq_zones_list,
-					struct dm_zone, link);
-		list_del_init(&zone->link);
-		atomic_dec(&zmd->nr_reserved_seq_zones);
+		/*
+		 * Use sequential write zones if we started off with random
+		 * zones and the list is empty
+		 */
+		if (list == &zmd->unmap_rnd_list) {
+			list = &zmd->unmap_seq_list;
+			goto again;
+		}
+		/*
+		 * Fallback to the reserved sequential zones
+		 */
+		zone = list_first_entry_or_null(&zmd->reserved_seq_zones_list,
+						struct dm_zone, link);
+		if (zone) {
+			list_del_init(&zone->link);
+			atomic_dec(&zmd->nr_reserved_seq_zones);
+		}
 		return zone;
 	}
 
 	zone = list_first_entry(list, struct dm_zone, link);
 	list_del_init(&zone->link);
 
-	if (dmz_is_rnd(zone))
+	if (dmz_is_cache(zone))
+		atomic_dec(&zmd->unmap_nr_cache);
+	else if (dmz_is_rnd(zone))
 		atomic_dec(&zmd->unmap_nr_rnd);
 	else
 		atomic_dec(&zmd->unmap_nr_seq);
@@ -2110,7 +2160,10 @@ void dmz_free_zone(struct dmz_metadata *zmd, struct dm_zone *zone)
 		dmz_reset_zone(zmd, zone);
 
 	/* Return the zone to its type unmap list */
-	if (dmz_is_rnd(zone)) {
+	if (dmz_is_cache(zone)) {
+		list_add_tail(&zone->link, &zmd->unmap_cache_list);
+		atomic_inc(&zmd->unmap_nr_cache);
+	} else if (dmz_is_rnd(zone)) {
 		list_add_tail(&zone->link, &zmd->unmap_rnd_list);
 		atomic_inc(&zmd->unmap_nr_rnd);
 	} else if (atomic_read(&zmd->nr_reserved_seq_zones) <
@@ -2136,7 +2189,9 @@ void dmz_map_zone(struct dmz_metadata *zmd, struct dm_zone *dzone,
 	dmz_set_chunk_mapping(zmd, chunk, dzone->id,
 			      DMZ_MAP_UNMAPPED);
 	dzone->chunk = chunk;
-	if (dmz_is_rnd(dzone))
+	if (dmz_is_cache(dzone))
+		list_add_tail(&dzone->link, &zmd->map_cache_list);
+	else if (dmz_is_rnd(dzone))
 		list_add_tail(&dzone->link, &zmd->map_rnd_list);
 	else
 		list_add_tail(&dzone->link, &zmd->map_seq_list);
@@ -2711,6 +2766,10 @@ int dmz_ctr_metadata(struct dmz_dev *dev, int num_dev,
 	INIT_LIST_HEAD(&zmd->unmap_rnd_list);
 	INIT_LIST_HEAD(&zmd->map_rnd_list);
 
+	atomic_set(&zmd->unmap_nr_cache, 0);
+	INIT_LIST_HEAD(&zmd->unmap_cache_list);
+	INIT_LIST_HEAD(&zmd->map_cache_list);
+
 	atomic_set(&zmd->unmap_nr_seq, 0);
 	INIT_LIST_HEAD(&zmd->unmap_seq_list);
 	INIT_LIST_HEAD(&zmd->map_seq_list);
@@ -2733,7 +2792,7 @@ int dmz_ctr_metadata(struct dmz_dev *dev, int num_dev,
 	/* Set metadata zones starting from sb_zone */
 	for (i = 0; i < zmd->nr_meta_zones << 1; i++) {
 		zone = dmz_get(zmd, zmd->sb[0].zone->id + i);
-		if (!dmz_is_rnd(zone)) {
+		if (!dmz_is_rnd(zone) && !dmz_is_cache(zone)) {
 			dmz_zmd_err(zmd,
 				    "metadata zone %d is not random", i);
 			ret = -ENXIO;
@@ -2785,6 +2844,8 @@ int dmz_ctr_metadata(struct dmz_dev *dev, int num_dev,
 		      zmd->nr_meta_zones * 2);
 	dmz_zmd_debug(zmd, "  %u data zones for %u chunks",
 		      zmd->nr_data_zones, zmd->nr_chunks);
+	dmz_zmd_debug(zmd, "    %u cache zones (%u unmapped)",
+		      zmd->nr_cache, atomic_read(&zmd->unmap_nr_cache));
 	dmz_zmd_debug(zmd, "    %u random zones (%u unmapped)",
 		      zmd->nr_rnd, atomic_read(&zmd->unmap_nr_rnd));
 	dmz_zmd_debug(zmd, "    %u sequential zones (%u unmapped)",