From e244550b42399370c11a4685a1da1954ec8c269e Mon Sep 17 00:00:00 2001 From: David Sterba Date: Tue, 1 Nov 2016 13:32:26 +0100 Subject: btrfs-progs: introduce key type for persistent permanent items The number of distinct key types is not that big that we could waste one for something new we want to store in the tree. Similar to the temporary items, we'll introduce a new name for an existing key value and use the objectid for further extension. The victim is the BTRFS_DEV_STATS_KEY (248). The device stats are an example of a permanent item. [ kernel patch 50c2d5abe64c1726b48d292a2ab04f60e8238933 ] Signed-off-by: David Sterba --- ctree.h | 20 +++++++++++++++++--- 1 file changed, 17 insertions(+), 3 deletions(-) (limited to 'ctree.h') diff --git a/ctree.h b/ctree.h index dc4b35c2..255ebad9 100644 --- a/ctree.h +++ b/ctree.h @@ -1229,10 +1229,24 @@ struct btrfs_root { #define BTRFS_TEMPORARY_ITEM_KEY 248 /* - * Persistently stores the io stats in the device tree. - * One key for all stats, (0, BTRFS_DEV_STATS_KEY, devid). + * Obsolete name, see BTRFS_PERSISTENT_ITEM_KEY */ -#define BTRFS_DEV_STATS_KEY 249 +#define BTRFS_DEV_STATS_KEY 249 + +/* + * The key type for tree items that are stored persistently and usually exist + * for a long period, eg. filesystem lifetime. The item kinds can be status + * information, stats or preference values. The item can exist in any tree. + * + * [subtype, BTRFS_PERSISTENT_ITEM_KEY, data] + * + * Existing items: + * + * - device statistics, store IO stats in the device tree, one key for all + * stats + * (0, BTRFS_DEV_STATS_KEY, 0) + */ +#define BTRFS_PERSISTENT_ITEM_KEY 249 /* * Persistently stores the device replace state in the device tree. -- cgit v1.2.3