On Mon, Jul 12, 2021 at 07:16:36PM +0000, Johannes Thumshirn wrote:

On 07/07/2021 17:02, Johannes Thumshirn wrote:

quoted

On 07/07/2021 16:53, David Sterba wrote:

quoted

On Tue, Jul 06, 2021 at 06:19:22PM +0900, Johannes Thumshirn wrote:

quoted

On zoned devices we're currently not supporting any other block group
profile than the SINGLE profile, so pick it as default value otherwise a
user would have to specify it manually at mkfs time for rotational zoned
devices.

Yes this is annoying but careful with setting defaults, it's hard to
change them. And in case of zoned devices it will be possible to set
something else in the future so defaulting to single/single needs to be
justified in another way than "currently we don't support anything
else".

The SSD fallback to single is not showing as useful and there's ongoing
work to make it default to dup for metadata again. For consistency I'd
rather have simple logic for selecting defaults and give hints
eventually instead of checking random things in the system and then
selectin on behalf of the user. Unfortunatelly it's not that easy as
there are conflicting valid interests and we don't have defaults that
fits all scenarios.

Agreed, but without this patch mkfs with default parameters on a rotational
zoned device will fail with:

johannes@redsun60:btrfs-progs(master)$ sudo ./mkfs.btrfs /dev/sda
btrfs-progs v5.12.1 
See http://btrfs.wiki.kernel.org for more information.

Zoned: /dev/sda: host-managed device detected, setting zoned feature
ERROR: cannot use RAID/DUP profile in zoned mode

So defaulting to not creating a filesystem won't work either.

We could improve the error message hinting the user to specify 
"-m single -d single" on mkfs but that feels more hacky than setting 
the defaults to something working.

So what's the way to go here? The current default won't create a file
system so it's unusable.

I've updated the message to ask for -d single -m single.