Re: [RFC][V8][PATCH 0/5] btrfs: allocation_hint mode

[Josef Bacik <josef@toxicpanda.com>]

On Mon, Dec 13, 2021 at 08:54:24PM +0100, Goffredo Baroncelli wrote:
> Gentle ping :-)
> 
> Are there anyone of the mains developer interested in supporting this patch ?
> 
> I am open to improve it if required.
> 

Sorry I missed this go by.  I like the interface, we don't have a use for
device->type yet, so this fits nicely.

I don't see the btrfs-progs patches in my inbox, and these don't apply, so
you'll definitely need to refresh for a proper review, but looking at these
patches they seem sane enough, and I like the interface.  I'd like to hear
Zygo's opinion as well.

If we're going to use device->type for this, and since we don't have a user of
device->type, I'd also like you to go ahead and re-name ->type to
->allocation_policy, that way it's clear what we're using it for now.

I'd also like some xfstests to validate the behavior so we're sure we're testing
this.  I'd want 1 test to just test the mechanics, like mkfs with different
policies and validate they're set right, change policies, add/remove disks with
different policies.

Then a second test to do something like fsstress with each set of allocation
policies to validate that we did actually allocate from the correct disks.  For
this please also test with compression on to make sure the test validation works
for both normal allocation and compression (ie it doesn't assume writing 5gib of
data == 5 gib of data usage, as compression chould give you a different value).

With that in place I think this is the correct way to implement this feature.
Thanks,

Josef