Re: [PATCHv3 00/11] dm-zoned: metadata version 2

[Mike Snitzer <snitzer@redhat.com>]

On Tue, Apr 14 2020 at  2:38am -0400,
Hannes Reinecke <hare@suse.de> wrote:

> On 4/11/20 2:30 PM, Bob Liu wrote:
> >On 4/9/20 2:45 PM, Hannes Reinecke wrote:
> >>Hi all,
> >>
> >>this patchset adds a new metadata version 2, which brings the following
> >>improvements:
> >>- UUIDs and labels: Adding three more fields to the metadata containing
> >>   the dm-zoned device UUID and label, and the device UUID. This allows
> >>   for an unique identification of the devices, so that several dm-zoned
> >>   sets can coexist and have a persistent identification.
> >>- Extend random zones by an additional regular disk device: A regular
> >>   block device can be added together with the zoned block device, providing
> >>   additional (emulated) random write zones. With this it's possible to
> >>   handle sequential zones only devices; also there will be a speed-up if
> >>   the regular block device resides on a fast medium. The regular block device
> >>   is placed logically in front of the zoned block device, so that metadata
> >>   and mapping tables reside on the regular block device, not the zoned device.
> >>- Tertiary superblock support: In addition to the two existing sets of metadata
> >>   another, tertiary, superblock is written to the first block of the zoned
> >>   block device. This superblock is for identification only; the generation
> >>   number is set to '0' and the block itself it never updated. The additional
> >>   metadate like bitmap tables etc are not copied.
> >>
> >>To handle this, some changes to the original handling are introduced:
> >>- Zones are now equidistant. Originally, runt zones were ignored, and
> >>   not counted when sizing the mapping tables. With the dual device setup
> >>   runt zones might occur at the end of the regular block device, making
> >>   direct translation between zone number and sector/block number complex.
> >>   For metadata version 2 all zones are considered to be of the same size,
> >>   and runt zones are simply marked as 'offline' to have them ignored when
> >>   allocating a new zone.
> >>- The block number in the superblock is now the global number, and refers to
> >>   the location of the superblock relative to the resulting device-mapper
> >>   device. Which means that the tertiary superblock contains absolute block
> >>   addresses, which needs to be translated to the relative device addresses
> >>   to find the referenced block.
> >>
> >>There is an accompanying patchset for dm-zoned-tools for writing and checking
> >>this new metadata.
> >>
> >>As usual, comments and reviews are welcome.
> >>
> >>Changes to v2:
> >>- Kill dmz_id()
> >>- Include reviews from Damien
> >>- Sanitize uuid handling as suggested by John Dorminy
> >>
> >
> >This series looks good to me, feel free to add my
> >Reviewed-by: Bob Liu <bob.liu@oracle.com>
> >
> >By the way, have you completed the patches for regular device support?
> >I was considering rebase my previous patches to this series but not sure is it still necessary.

Bob, not trying to be overly critical but if you couldn't answer your
question how did you feel comfortable providing your Reviewed-by to this
patchset?  That Reviewed-by _must_ mean something.

Mike


> I have combined both patchsets, this one now also included regular
> device support. So no need to resend from your side.
> 
> Cheers,
> 
> Hannes
> -- 
> Dr. Hannes Reinecke            Teamlead Storage & Networking
> hare@suse.de                               +49 911 74053 688
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