btrfs-progs: mkfs: add dev stats and device items

The kernel adds a zeroed btrfs_dev_stats_item for each device on the
first mount. Preempt this by doing it at mkfs time.

Signed-off-by: Mark Harmstone <[email protected]>
Signed-off-by: David Sterba <[email protected]>

Author: maharmstone

kernel-shared/ctree.h

@@ -831,6 +831,16 @@ static inline u64 btrfs_dev_stats_value(const struct extent_buffer *eb,
 	return val;
 }
 
+static inline void btrfs_set_dev_stats_value(struct extent_buffer *eb,
+					     struct btrfs_dev_stats_item *ptr,
+					     int index, u64 val)
+{
+	write_extent_buffer(eb, &val,
+			    offsetof(struct btrfs_dev_stats_item, values) +
+			     ((unsigned long)ptr) + (index * sizeof(u64)),
+			    sizeof(val));
+}
+
 /* struct btrfs_ioctl_search_header */
 static inline u64 btrfs_search_header_transid(struct btrfs_ioctl_search_header *sh)
 {

kernel-shared/volumes.c

@@ -1135,6 +1135,7 @@ int btrfs_add_device(struct btrfs_trans_handle *trans,
 	int ret;
 	struct btrfs_path *path;
 	struct btrfs_dev_item *dev_item;
+	struct btrfs_dev_stats_item *dev_stats;
 	struct extent_buffer *leaf;
 	struct btrfs_key key;
 	struct btrfs_root *root = fs_info->chunk_root;
@@ -1149,6 +1150,7 @@ int btrfs_add_device(struct btrfs_trans_handle *trans,
 	if (ret)
 		goto out;
 
+	/* Add DEV_ITEM. */
 	key.objectid = BTRFS_DEV_ITEMS_OBJECTID;
 	key.type = BTRFS_DEV_ITEM_KEY;
 	key.offset = free_devid;
@@ -1182,6 +1184,27 @@ int btrfs_add_device(struct btrfs_trans_handle *trans,
 			    BTRFS_UUID_SIZE);
 	btrfs_mark_buffer_dirty(leaf);
 	fs_info->fs_devices->total_rw_bytes += device->total_bytes;
+
+	btrfs_release_path(path);
+
+	/* Add DEV STATS item. */
+	key.objectid = BTRFS_DEV_STATS_OBJECTID;
+	key.type = BTRFS_PERSISTENT_ITEM_KEY;
+	key.offset = free_devid;
+
+	ret = btrfs_insert_empty_item(trans, fs_info->dev_root, path, &key,
+				      sizeof(*dev_stats));
+	if (ret)
+		goto out;
+
+	leaf = path->nodes[0];
+	dev_stats = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_dev_stats_item);
+
+	for (int i = 0; i < BTRFS_DEV_STAT_VALUES_MAX; i++)
+		btrfs_set_dev_stats_value(leaf, dev_stats, i, 0);
+
+	btrfs_mark_buffer_dirty(leaf);
+
 	ret = 0;
 
 out:

mkfs/common.c

@@ -369,6 +369,7 @@ int make_btrfs(int fd, struct btrfs_mkfs_config *cfg)
 	struct btrfs_chunk *chunk;
 	struct btrfs_dev_item *dev_item;
 	struct btrfs_dev_extent *dev_extent;
+	struct btrfs_dev_stats_item *dev_stats;
 	enum btrfs_mkfs_block blocks[MKFS_BLOCK_COUNT];
 	u8 chunk_tree_uuid[BTRFS_UUID_SIZE];
 	u8 *ptr;
@@ -673,8 +674,25 @@ int make_btrfs(int fd, struct btrfs_mkfs_config *cfg)
 	memset(buf->data + sizeof(struct btrfs_header), 0,
 		cfg->nodesize - sizeof(struct btrfs_header));
 	nritems = 0;
-	itemoff = cfg->leaf_data_size - sizeof(struct btrfs_dev_extent);
+	itemoff = cfg->leaf_data_size;
+
+	/* Add a DEV_STATS item for device 1. */
+	itemoff -= sizeof(struct btrfs_dev_stats_item);
+	btrfs_set_disk_key_objectid(&disk_key, BTRFS_DEV_STATS_OBJECTID);
+	btrfs_set_disk_key_type(&disk_key, BTRFS_PERSISTENT_ITEM_KEY);
+	btrfs_set_disk_key_offset(&disk_key, 1);
+	btrfs_set_item_key(buf, &disk_key, nritems);
+	btrfs_set_item_offset(buf, nritems, itemoff);
+	btrfs_set_item_size(buf, nritems, sizeof(struct btrfs_dev_stats_item));
+	dev_stats = btrfs_item_ptr(buf, nritems, struct btrfs_dev_stats_item);
+
+	for (i = 0; i < BTRFS_DEV_STAT_VALUES_MAX; i++)
+		btrfs_set_dev_stats_value(buf, dev_stats, i, 0);
+
+	nritems++;
 
+	/* Add the DEV_EXTENT item for the system chunk. */
+	itemoff -= sizeof(struct btrfs_dev_extent);
 	btrfs_set_disk_key_objectid(&disk_key, 1);
 	btrfs_set_disk_key_offset(&disk_key, system_group_offset);
 	btrfs_set_disk_key_type(&disk_key, BTRFS_DEV_EXTENT_KEY);