[dm-devel] dm thin: superblock may write succeed before other metadata blocks because of wirting metadata in async mode.

[Joe Thornber]

On Wed, Jun 20, 2018 at 01:03:57PM -0400, monty wrote:
> Hi, Mike and Joe. Thanks for your reply. I read __commit_transaction
> many times and didn't find any problem of 2-phase commit. I use
> md-raid1(PCIe nvme and md-raid5) in write-behind mode to store dm-thin
> metadata.
> Test case:
> 1. I do copy-diff test on thin device and then reboot my machine.
> 2. Rebuild our device stack and exec "vgchang -ay".
> The thin-pool can not be established(details_root become a bitmap node
> and metadata's bitmap_root become a btree_node).

As you simplify your setup does the problem go away?  eg, turn off write-behind, use just the nvme dev etc.

The only effect of your change is to call flush twice rather than once.

- Joe