[PATCH 1/2] btrfs: add necessary comments about tickets_id

[Wang Xiaoguang <wangxg.fnst@cn.fujitsu.com>]

Tickets_id's name may result in some misunderstandings,  it just indicates
the next ticket will be handled and is not stored per ticket.

Fixes: ce12965 ("btrfs: introduce tickets_id to determine whether
asynchronous metadata reclaim work makes progress")
Signed-off-by: Wang Xiaoguang <wangxg.fnst@cn.fujitsu.com>
---
 fs/btrfs/ctree.h | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 0b8ce2b..9307084 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -429,6 +429,10 @@ struct btrfs_space_info {
 	struct list_head ro_bgs;
 	struct list_head priority_tickets;
 	struct list_head tickets;
+	/*
+	 * tickets_id just indicates the next ticket will be handled, so note
+	 * it's not stored per ticket.
+	 */
 	u64 tickets_id;
 
 	struct rw_semaphore groups_sem;
-- 
2.5.0