Re: [PATCH 0/2] New zoned loop block device driver

[Ming Lei <ming.lei@redhat.com>]

On Wed, Jan 08, 2025 at 05:39:33PM +0800, Ming Lei wrote:
> On Wed, Jan 08, 2025 at 10:09:12AM +0100, Christoph Hellwig wrote:
> > On Wed, Jan 08, 2025 at 04:13:01PM +0800, Ming Lei wrote:
> > > It is backed by virtual memory, which can be big enough because of swap, and
> > 
> > Good luck getting half way decent performance out of swapping for a 50TB
> > data set.  Or even a partially filled one which really is the use case
> > here so it might only be a TB or so.
> > 
> > > it is also easy to extend to file backed support since zloop doesn't store
> > > zone meta data, which is similar to ram backed zoned actually.
> > 
> > No, zloop does store write point in the file sizse of each zone.  That's
> > sorta the whole point becauce it enables things like mount and even
> > power fail testing.
> > 
> > All of this is mentioned explicitly in the commit logs, documentation and
> > code comments, so claiming something else here feels a bit uninformed.
> 
> OK, looks one smart idea.
> 
> It is easy to extend rublk/zoned in this way with io_uring io emulation, :-)

Here it is:

https://github.com/ublk-org/rublk/commits/file-backed-zoned/

Top two commits implement the feature by command line `--path $zdir`:

	[rublk]# git diff --stat=80 HEAD^^...
	 src/zoned.rs   | 397 +++++++++++++++++++++++++++++++++++++++++++++++----------
	 tests/basic.rs |  49 ++++---
	 2 files changed, 363 insertions(+), 83 deletions(-)

It takes 280 new LoC:

    - support both ram-back and file-back
    - completely async io_uring IO emulation for zoned read/write IO
    - include selftest code for running mkfs.btrfs/mount/read & write IO/umount


Thanks,
Ming