diff mbox series

btrfs: comment about fsid and metadata_uuid relationship

Message ID 0b71460e3a52cf77cd0f7d533e28d2502e285c11.1693820430.git.anand.jain@oracle.com (mailing list archive)
State New, archived
Headers show
Series btrfs: comment about fsid and metadata_uuid relationship | expand

Commit Message

Anand Jain Sept. 6, 2023, 4:16 p.m. UTC 
Add a comment explaining the relationship between fsid and metadata_uuid
in the on-disk superblock and the in-memory struct btrfs_fs_devices.

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

Comments

David Sterba Sept. 6, 2023, 4:45 p.m. UTC | #1 
On Thu, Sep 07, 2023 at 12:16:41AM +0800, Anand Jain wrote:
> Add a comment explaining the relationship between fsid and metadata_uuid
> in the on-disk superblock and the in-memory struct btrfs_fs_devices.
> 
> Signed-off-by: Anand Jain <anand.jain@oracle.com>

Added to misc-next, thanks.
diff mbox series

Patch

diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h
index 2128a032c3b7..576bfcb5b764 100644
--- a/fs/btrfs/volumes.h
+++ b/fs/btrfs/volumes.h
@@ -290,6 +290,15 @@  struct btrfs_fs_devices {
 	 * - Following shall be true at all times:
 	 *   - metadata_uuid == btrfs_header::fsid
 	 *   - metadata_uuid == btrfs_dev_item::fsid
+	 *
+	 * - Relations between fsid and metadata_uuid in sb and fs_devices:
+	 *   - Normal:
+	 *       fs_devices->fsid == fs_devices->metadata_uuid == sb->fsid
+	 *       sb->metadata_uuid == 0
+	 *
+	 *   - When the BTRFS_FEATURE_INCOMPAT_METADATA_UUID flag is set:
+	 *       fs_devices->fsid == sb->fsid
+	 *       fs_devices->metadata_uuid == sb->metadata_uuid
 	 */
 	u8 metadata_uuid[BTRFS_FSID_SIZE];