[f2fs-dev] [PATCH v3 0/1] f2fs: zns zone-capacity support

[Aravind R. <ara...@wd...>]

NVM Express Zoned Namespace command set specification allows host software
to communicate with a NVM subsystem using zones. ZNS defines a host-managed
zoned block device model for NVMe devices. It divides the logical address
space of a namespace into zones. Each zone provides a LBA range that
shall be written sequentially. An explicit reset of zone is needed to write to
the zone again.

ZNS defines a per-zone capacity which can be equal or less than the
zone-size. Zone-capacity is the number of usable blocks in the zone.
This patchset implements support for ZNS devices with a zone-capacity
that is less that the device zone-size.

This patch checks if zone-capacity is less than zone-size, if it is,
then any segment which starts after the zone-capacity is marked as
not-free in the free segment bitmap at initial mount time. These segments
are marked as permanently used so they are not allocated for writes and
consequently not needed to be garbage collected. In case the zone-capacity
is not aligned to default segment size(2MB), then a segment can start
before the zone-capacity and span across zone-capacity boundary.
Such spanning segments are also considered as usable segments. It tracks
the usable blocks in a spanning segment, so that during writes and GC,
usable blocks in spanning segment is calculated to ensure writes/reads
do not cross the zone-capacity boundary.

This patch is based on the git tree
git://git.kernel.org/pub/scm/linux/kernel/git/jaegeuk/f2fs.git branch dev
and requires the below patch in order to build.
https://lore.kernel.org/linux-nvme/202...@ls.../T/#m19e0197ae1837b7fe959b13fbc2a859b1f2abc1e

The above patch has been merged to the nvme-5.9 branch in the git tree:
git://git.infradead.org/nvme.git

Aravind Ramesh (1):
  f2fs: support zone capacity less than zone size

 Documentation/filesystems/f2fs.rst |  15 +++
 fs/f2fs/f2fs.h                     |   5 +
 fs/f2fs/gc.c                       |  25 +++--
 fs/f2fs/gc.h                       |  44 +++++++-
 fs/f2fs/segment.c                  | 156 ++++++++++++++++++++++++++---
 fs/f2fs/segment.h                  |  26 +++--
 fs/f2fs/super.c                    |  41 ++++++--
 7 files changed, 275 insertions(+), 37 deletions(-)

-- 
2.19.1