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-rw-r--r--fs/btrfs/ctree.h20
1 files changed, 17 insertions, 3 deletions
diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index e20f40649917..ffc081e11277 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -2204,10 +2204,24 @@ struct btrfs_ioctl_defrag_range_args {
#define BTRFS_TEMPORARY_ITEM_KEY 248
/*
- * Persistantly 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
/*
* Persistantly stores the device replace state in the device tree.
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