btrfs: zoned: calculate free space from zone capacity

Now that we introduced capacity in a block group, we need to calculate free
space using the capacity instead of the length. Thus, bytes we account
capacity - alloc_pointer as free, and account bytes [capacity, length] as
zone unusable.
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/block-group.c

@@ -2484,7 +2484,8 @@ struct btrfs_block_group *btrfs_make_block_group(struct btrfs_trans_handle *tran
 	 */
 	trace_btrfs_add_block_group(fs_info, cache, 1);
 	btrfs_update_space_info(fs_info, cache->flags, size, bytes_used,
-				cache->bytes_super, 0, &cache->space_info);
+				cache->bytes_super, cache->zone_unusable,
+				&cache->space_info);
 	btrfs_update_global_block_rsv(fs_info);
 
 	link_block_group(cache);
@@ -2599,7 +2600,9 @@ void btrfs_dec_block_group_ro(struct btrfs_block_group *cache)
 	if (!--cache->ro) {
 		if (btrfs_is_zoned(cache->fs_info)) {
 			/* Migrate zone_unusable bytes back */
-			cache->zone_unusable = cache->alloc_offset - cache->used;
+			cache->zone_unusable =
+				(cache->alloc_offset - cache->used) +
+				(cache->length - cache->zone_capacity);
 			sinfo->bytes_zone_unusable += cache->zone_unusable;
 			sinfo->bytes_readonly -= cache->zone_unusable;
 		}

fs/btrfs/extent-tree.c

@@ -3796,7 +3796,8 @@ static int do_allocation_zoned(struct btrfs_block_group *block_group,
 		goto out;
 	}
 
-	avail = block_group->length - block_group->alloc_offset;
+	WARN_ON_ONCE(block_group->alloc_offset > block_group->zone_capacity);
+	avail = block_group->zone_capacity - block_group->alloc_offset;
 	if (avail < num_bytes) {
 		if (ffe_ctl->max_extent_size < avail) {
 			/*

fs/btrfs/free-space-cache.c

@@ -2539,10 +2539,15 @@ static int __btrfs_add_free_space_zoned(struct btrfs_block_group *block_group,
 	u64 offset = bytenr - block_group->start;
 	u64 to_free, to_unusable;
 	const int bg_reclaim_threshold = READ_ONCE(fs_info->bg_reclaim_threshold);
+	bool initial = (size == block_group->length);
+
+	WARN_ON(!initial && offset + size > block_group->zone_capacity);
 
 	spin_lock(&ctl->tree_lock);
 	if (!used)
 		to_free = size;
+	else if (initial)
+		to_free = block_group->zone_capacity;
 	else if (offset >= block_group->alloc_offset)
 		to_free = size;
 	else if (offset + size <= block_group->alloc_offset)
@@ -2755,7 +2760,7 @@ void btrfs_dump_free_space(struct btrfs_block_group *block_group,
 	 */
 	if (btrfs_is_zoned(fs_info)) {
 		btrfs_info(fs_info, "free space %llu",
-			   block_group->length - block_group->alloc_offset);
+			   block_group->zone_capacity - block_group->alloc_offset);
 		return;
 	}
 

fs/btrfs/zoned.c

@@ -1265,8 +1265,9 @@ void btrfs_calc_zone_unusable(struct btrfs_block_group *cache)
 		return;
 
 	WARN_ON(cache->bytes_super != 0);
-	unusable = cache->alloc_offset - cache->used;
-	free = cache->length - cache->alloc_offset;
+	unusable = (cache->alloc_offset - cache->used) +
+		   (cache->length - cache->zone_capacity);
+	free = cache->zone_capacity - cache->alloc_offset;
 
 	/* We only need ->free_space in ALLOC_SEQ block groups */
 	cache->last_byte_to_unpin = (u64)-1;