Re: [PATCH v2] dm-delay: Prevent zoned write reordering on suspend

[Mikulas Patocka <mpatocka@redhat.com>]

On Tue, 22 Apr 2025, Damien Le Moal wrote:

> It is not because you do not see a clean solution that there is not one. So
> unless you have completely made up your mind already and are not willing to

I haven't made up my mind completely.

> I do not understand what you are talking about. A zoned DM device is zoned
> because it is on top of a zoned device. That bottom zoned device may be another
> DM target or a real zoned device. For the real zoned device, zone write plugging
> is always used so it does not matter if the host controller does or does not
> preserve command order.

I understand that. I don't understand why can't DM devices also use write 
plugging. What kind of problem are you trying to fix - a performance 
problem or a correctness problem?

> There will always be at most 1 in-flight write per zone, which makes 
> reordering of commands completely irrelevant for write commands success.

If reordering is irrelevant for the underlying device, why is it relevant 
for DM?

If the host controller may reorder commands (as you say), why can't DM do 
it?

Mikulas