[Cluster-devel] Recording extents in GFS2

[Steven Whitehouse <swhiteho@redhat.com>]

Hi,

On 11/12/2020 16:38, Abhijith Das wrote:
> Hi all,
>
> With a recent set of patches, we nearly eliminated the per_node statfs
> change files by recording that info in the journal. The files and some
> recovery code remain only for backward compatibility. Similarly, I'd
> like to get rid of the per_node quota change files and record that
> info in the journal as well.
>
> I've been talking to Andreas and Bob a bit about this and I'm
> investigating how we can record extents as we allocate and deallocate
> blocks instead of writing whole blocks. I'm looking into how XFS does
> this.
>
> We could have a new journal block type that adds a list of extents to
> inodes with alloc/dealloc info. We could add in quota (uid/gid) info
> to this as well. If we can do this right, the representation of
> alloc/dealloc becomes compact and consequently we use journal space
> more efficiently. We can hopefully avoid cases where we need to zero
> out blocks during allocation as well.
>
> I'm sending this out to start a discussion and to get ideas/comments/pointers.
>
> Cheers!
> --Abhi
>
I think you need to propose something a bit more concrete. For example 
what will the data structures look like? How many entries will fit in a 
journal block at different block sizes? How will we ensure that this is 
backwards compatible? That will make it easier to have the discussions,

Steve.