dm zoned: allocate temporary superblock for tertiary devices

Checking the tertiary superblock just consists of validating UUIDs,
crcs, and the generation number; it doesn't have contents which would
be required during the actual operation.

So allocate a temporary superblock when checking tertiary devices to
avoid having to store it together with the 'real' superblocks.
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>

drivers/md/dm-zoned-metadata.c

@@ -174,7 +174,7 @@ struct dmz_metadata {
 	/* Zone information array */
 	struct xarray		zones;
 
-	struct dmz_sb		sb[3];
+	struct dmz_sb		sb[2];
 	unsigned int		mblk_primary;
 	unsigned int		sb_version;
 	u64			sb_gen;
@@ -1016,10 +1016,11 @@ int dmz_flush_metadata(struct dmz_metadata *zmd)
 /*
  * Check super block.
  */
-static int dmz_check_sb(struct dmz_metadata *zmd, unsigned int set)
+static int dmz_check_sb(struct dmz_metadata *zmd, struct dmz_sb *dsb,
+			bool tertiary)
 {
-	struct dmz_super *sb = zmd->sb[set].sb;
-	struct dmz_dev *dev = zmd->sb[set].dev;
+	struct dmz_super *sb = dsb->sb;
+	struct dmz_dev *dev = dsb->dev;
 	unsigned int nr_meta_zones, nr_data_zones;
 	u32 crc, stored_crc;
 	u64 gen;
@@ -1036,7 +1037,7 @@ static int dmz_check_sb(struct dmz_metadata *zmd, unsigned int set)
 			    DMZ_META_VER, zmd->sb_version);
 		return -EINVAL;
 	}
-	if ((zmd->sb_version < 1) && (set == 2)) {
+	if (zmd->sb_version < 2 && tertiary) {
 		dmz_dev_err(dev, "Tertiary superblocks are not supported");
 		return -EINVAL;
 	}
@@ -1080,7 +1081,7 @@ static int dmz_check_sb(struct dmz_metadata *zmd, unsigned int set)
 			return -ENXIO;
 		}
 
-		if (set == 2) {
+		if (tertiary) {
 			/*
 			 * Generation number should be 0, but it doesn't
 			 * really matter if it isn't.
@@ -1129,14 +1130,13 @@ static int dmz_check_sb(struct dmz_metadata *zmd, unsigned int set)
 /*
  * Read the first or second super block from disk.
  */
-static int dmz_read_sb(struct dmz_metadata *zmd, unsigned int set)
+static int dmz_read_sb(struct dmz_metadata *zmd, struct dmz_sb *sb, int set)
 {
 	dmz_zmd_debug(zmd, "read superblock set %d dev %s block %llu",
-		      set, zmd->sb[set].dev->name,
-		      zmd->sb[set].block);
+		      set, sb->dev->name, sb->block);
 
-	return dmz_rdwr_block(zmd->sb[set].dev, REQ_OP_READ,
-			      zmd->sb[set].block, zmd->sb[set].mblk->page);
+	return dmz_rdwr_block(sb->dev, REQ_OP_READ,
+			      sb->block, sb->mblk->page);
 }
 
 /*
@@ -1164,7 +1164,7 @@ static int dmz_lookup_secondary_sb(struct dmz_metadata *zmd)
 	zmd->sb[1].zone = dmz_get(zmd, zone_id + 1);
 	zmd->sb[1].dev = zmd->sb[0].dev;
 	for (i = 1; i < zmd->nr_rnd_zones; i++) {
-		if (dmz_read_sb(zmd, 1) != 0)
+		if (dmz_read_sb(zmd, &zmd->sb[1], 1) != 0)
 			break;
 		if (le32_to_cpu(zmd->sb[1].sb->magic) == DMZ_MAGIC)
 			return 0;
@@ -1181,9 +1181,9 @@ static int dmz_lookup_secondary_sb(struct dmz_metadata *zmd)
 }
 
 /*
- * Read the first or second super block from disk.
+ * Read a super block from disk.
  */
-static int dmz_get_sb(struct dmz_metadata *zmd, unsigned int set)
+static int dmz_get_sb(struct dmz_metadata *zmd, struct dmz_sb *sb, int set)
 {
 	struct dmz_mblock *mblk;
 	int ret;
@@ -1193,14 +1193,14 @@ static int dmz_get_sb(struct dmz_metadata *zmd, unsigned int set)
 	if (!mblk)
 		return -ENOMEM;
 
-	zmd->sb[set].mblk = mblk;
-	zmd->sb[set].sb = mblk->data;
+	sb->mblk = mblk;
+	sb->sb = mblk->data;
 
 	/* Read super block */
-	ret = dmz_read_sb(zmd, set);
+	ret = dmz_read_sb(zmd, sb, set);
 	if (ret) {
 		dmz_free_mblock(zmd, mblk);
-		zmd->sb[set].mblk = NULL;
+		sb->mblk = NULL;
 		return ret;
 	}
 
@@ -1274,13 +1274,13 @@ static int dmz_load_sb(struct dmz_metadata *zmd)
 	/* Read and check the primary super block */
 	zmd->sb[0].block = dmz_start_block(zmd, zmd->sb[0].zone);
 	zmd->sb[0].dev = dmz_zone_to_dev(zmd, zmd->sb[0].zone);
-	ret = dmz_get_sb(zmd, 0);
+	ret = dmz_get_sb(zmd, &zmd->sb[0], 0);
 	if (ret) {
 		dmz_dev_err(zmd->sb[0].dev, "Read primary super block failed");
 		return ret;
 	}
 
-	ret = dmz_check_sb(zmd, 0);
+	ret = dmz_check_sb(zmd, &zmd->sb[0], false);
 
 	/* Read and check secondary super block */
 	if (ret == 0) {
@@ -1293,7 +1293,7 @@ static int dmz_load_sb(struct dmz_metadata *zmd)
 		}
 		zmd->sb[1].block = dmz_start_block(zmd, zmd->sb[1].zone);
 		zmd->sb[1].dev = zmd->sb[0].dev;
-		ret = dmz_get_sb(zmd, 1);
+		ret = dmz_get_sb(zmd, &zmd->sb[1], 1);
 	} else
 		ret = dmz_lookup_secondary_sb(zmd);
 
@@ -1302,7 +1302,7 @@ static int dmz_load_sb(struct dmz_metadata *zmd)
 		return ret;
 	}
 
-	ret = dmz_check_sb(zmd, 1);
+	ret = dmz_check_sb(zmd, &zmd->sb[1], false);
 	if (ret == 0)
 		sb_good[1] = true;
 
@@ -1347,20 +1347,40 @@ static int dmz_load_sb(struct dmz_metadata *zmd)
 		      "Using super block %u (gen %llu)",
 		      zmd->mblk_primary, zmd->sb_gen);
 
-	if ((zmd->sb_version > 1) && zmd->sb[2].zone) {
-		zmd->sb[2].block = dmz_start_block(zmd, zmd->sb[2].zone);
-		zmd->sb[2].dev = dmz_zone_to_dev(zmd, zmd->sb[2].zone);
-		ret = dmz_get_sb(zmd, 2);
+	if (zmd->sb_version > 1) {
+		int i;
+		struct dmz_sb *sb;
+
+		sb = kzalloc(sizeof(struct dmz_sb), GFP_KERNEL);
+		if (!sb)
+			return -ENOMEM;
+		for (i = 1; i < zmd->nr_devs; i++) {
+			sb->block = 0;
+			sb->zone = dmz_get(zmd, zmd->dev[i].zone_offset);
+			sb->dev = &zmd->dev[i];
+			if (!dmz_is_meta(sb->zone)) {
+				dmz_dev_err(sb->dev,
+					    "Tertiary super block zone %u not marked as metadata zone",
+					    sb->zone->id);
+				ret = -EINVAL;
+				goto out_kfree;
+			}
+			ret = dmz_get_sb(zmd, sb, i + 1);
 			if (ret) {
-			dmz_dev_err(zmd->sb[2].dev,
+				dmz_dev_err(sb->dev,
 					    "Read tertiary super block failed");
-			return ret;
+				dmz_free_mblock(zmd, sb->mblk);
+				goto out_kfree;
 			}
-		ret = dmz_check_sb(zmd, 2);
+			ret = dmz_check_sb(zmd, sb, true);
+			dmz_free_mblock(zmd, sb->mblk);
 			if (ret == -EINVAL)
-			return ret;
+				goto out_kfree;
 		}
-	return 0;
+	out_kfree:
+		kfree(sb);
+	}
+	return ret;
 }
 
 /*
@@ -1417,12 +1437,15 @@ static int dmz_init_zone(struct blk_zone *blkz, unsigned int num, void *data)
 				zmd->sb[0].zone = zone;
 			}
 		}
-		if (zmd->nr_devs > 1 && !zmd->sb[2].zone) {
-			/* Tertiary superblock zone */
-			zmd->sb[2].zone = zone;
+		if (zmd->nr_devs > 1 && num == 0) {
+			/*
+			 * Tertiary superblock zones are always at the
+			 * start of the zoned devices, so mark them
+			 * as metadata zone.
+			 */
+			set_bit(DMZ_META, &zone->flags);
 		}
 	}
-
 	return 0;
 }
 
@@ -2860,16 +2883,6 @@ int dmz_ctr_metadata(struct dmz_dev *dev, int num_dev,
 		}
 		set_bit(DMZ_META, &zone->flags);
 	}
-	if (zmd->sb[2].zone) {
-		zone = dmz_get(zmd, zmd->sb[2].zone->id);
-		if (!zone) {
-			dmz_zmd_err(zmd,
-				    "Tertiary metadata zone not present");
-			ret = -ENXIO;
-			goto err;
-		}
-		set_bit(DMZ_META, &zone->flags);
-	}
 	/* Load mapping table */
 	ret = dmz_load_mapping(zmd);
 	if (ret)