Re: [PATCH v15 00/42] btrfs: zoned block device support

On Thu, Feb 04, 2021 at 07:21:39PM +0900, Naohiro Aota wrote:

This series adds zoned block device support to btrfs. Some of the patches
in the previous series are already merged as preparation patches.

Moved from for-next to misc-next.

* Log-structured superblock

Superblock (and its copies) is the only data structure in btrfs which
has a fixed location on a device. Since we cannot overwrite in a
sequential write required zone, we cannot place superblock in the
zone.

This series implements superblock log writing. It uses two zones as a
circular buffer to write updated superblocks. Once the first zone is filled
up, start writing into the second zone. The first zone will be reset once
both zones are filled. We can determine the postion of the latest
superblock by reading the write pointer information from a device.

About that, in this patchset it's still leaving superblock at the fixed
zone number while we want it at a fixed location, spanning 2 zones
regardless of their size.