[PATCH v4 2/6] btrfs: add comments for device counts in struct btrfs_fs_devices

[Josef Bacik <josef@toxicpanda.com>]

From: Anand Jain <anand.jain@oracle.com>

A bug was was checking a wrong device count before we delete the struct
btrfs_fs_devices in btrfs_rm_device(). To avoid future confusion and
easy reference add a comment about the various device counts that we have
in the struct btrfs_fs_devices.

Signed-off-by: Anand Jain <anand.jain@oracle.com>
---
 fs/btrfs/volumes.h | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h
index 83075d6855db..c7ac43d8a7e8 100644
--- a/fs/btrfs/volumes.h
+++ b/fs/btrfs/volumes.h
@@ -236,11 +236,30 @@ struct btrfs_fs_devices {
 	bool fsid_change;
 	struct list_head fs_list;
 
+	/*
+	 * Number of devices under this fsid including missing and
+	 * replace-target device and excludes seed devices.
+	 */
 	u64 num_devices;
+
+	/*
+	 * The number of devices that successfully opened, including
+	 * replace-target, excludes seed devices.
+	 */
 	u64 open_devices;
+
+	/* The number of devices that are under the chunk allocation list. */
 	u64 rw_devices;
+
+	/* Count of missing devices under this fsid excluding seed device. */
 	u64 missing_devices;
 	u64 total_rw_bytes;
+
+	/*
+	 * Count of devices from btrfs_super_block::num_devices for this fsid,
+	 * which includes the seed device, excludes the transient replace-target
+	 * device.
+	 */
 	u64 total_devices;
 
 	/* Highest generation number of seen devices */
-- 
2.26.3