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[4/9] btrfs: add comment about metadata_uuid in btrfs_fs_devices

Message ID 3ba05b04df59f1549a3026326ff4a70d6abc302d.1684826247.git.anand.jain@oracle.com (mailing list archive)
State New, archived
Headers show
Series btrfs: metadata_uuid refactors part1 | expand

Commit Message

Anand Jain May 23, 2023, 10:03 a.m. UTC 
Add comment about metadata_uuid in btrfs_fs_devices.
No functional change.

Signed-off-by: Anand Jain <anand.jain@oracle.com>
---
 fs/btrfs/volumes.h | 9 +++++++++
 1 file changed, 9 insertions(+)
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Patch

diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h
index a9a86c9220b3..35d135bcdee4 100644
--- a/fs/btrfs/volumes.h
+++ b/fs/btrfs/volumes.h
@@ -280,7 +280,16 @@  enum btrfs_read_policy {
 
 struct btrfs_fs_devices {
 	u8 fsid[BTRFS_FSID_SIZE]; /* FS specific uuid */
+
+	/*
+	 * UUID written into the btree blocks:
+	 * Relations:
+	 *   metadata_uuid != fsid must set BTRFS_FEATURE_INCOMPAT_METADATA_UUID
+	 *   metadata_uuid == btrfs_header::fsid at all times.
+	 *   metadata_uuid == btrfs_dev_item::fsid at all times.
+	 */
 	u8 metadata_uuid[BTRFS_FSID_SIZE];
+
 	struct list_head fs_list;
 
 	/*