[PATCH 1/4] btrfs-progs: tune use the latest bdev in fs_devices for super_copy

[Anand Jain <anand.jain@oracle.com>]

Currently, btrfstune relies on the superblock of the device specified
in the btrfstune argument for fs_info::super_copy. However, it should
use fs_devices::latest_bdev, as it points to the device with the highest
fs_devices::generation number. This will contain the superblock updates
that other devices may have missed and we can now support reuniting
devices following failures of btrfstune -m|M|u|U as in the patches:

   btrfs-progs: add support to fix superblock with CHANGING_FSID_V2 flag
   btrfs-progs: recover from the failed btrfstune -m|M

Signed-off-by: Anand Jain <anand.jain@oracle.com>
---
 tune/main.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/tune/main.c b/tune/main.c
index 902c9d97956e..2d8f2b012caf 100644
--- a/tune/main.c
+++ b/tune/main.c
@@ -345,6 +345,9 @@ int BOX_MAIN(btrfstune)(int argc, char *argv[])
 		goto free_out;
 	}
 
+	if (change_metadata_uuid || random_fsid || new_fsid_str)
+		ctree_flags |= OPEN_CTREE_USE_LATEST_BDEV;
+
 	root = open_ctree_fd(fd, device, 0, ctree_flags);
 
 	if (!root) {
-- 
2.38.1