On 17/06/2020 16.42, Javier González wrote:
On 17.06.2020 09:43, Christoph Hellwig wrote:
On Tue, Jun 16, 2020 at 12:41:42PM +0200, Javier González wrote:
On 16.06.2020 08:34, Keith Busch wrote:
Add support for NVM Express Zoned Namespaces (ZNS) Command Set defined
in NVM Express TP4053. Zoned namespaces are discovered based on their
Command Set Identifier reported in the namespaces Namespace
Identification Descriptor list. A successfully discovered Zoned
Namespace will be registered with the block layer as a host managed
zoned block device with Zone Append command support. A namespace that
does not support append is not supported by the driver.
Why are we enforcing the append command? Append is optional on the
current ZNS specification, so we should not make this mandatory in the
implementation. See specifics below.
Because Append is the way to go and we've moved the Linux zoned block
I/O stack to required it, as should have been obvious to anyone
following linux-block in the last few months. I also have to say I'm
really tired of the stupid politics tha your company started in the
NVMe working group, and will say that these do not matter for Linux
development at all. If you think it is worthwhile to support devices
without Zone Append you can contribute support for them on top of this
series by porting the SCSI Zone Append Emulation code to NVMe.
And I'm not even going to read the rest of this thread as I'm on a
vacation that I badly needed because of the Samsung TWG bullshit.
My intention is to support some Samsung ZNS devices that will not enable
append. I do not think this is an unreasonable thing to do. How / why
append ended up being an optional feature in the ZNS TP is orthogonal to
this conversation. Bullshit or not, it ends up on devices that we would
like to support one way or another.
I do not believe any of us have said that it is unreasonable to support.
We've only asked that you make the patches for it.
All of us have communicated why Zone Append is a great addition to the
Linux kernel. Also, as Christoph points out, this has not been a secret
for the past couple of months, and as Martin pointed out, have been a
wanted feature for the past decade in the Linux community.
I do want to politely point out, that you've got a very clear signal
from the key storage maintainers. Each of them is part of the planet's
best of the best and most well-respected software developers, that
literally have built the storage stack that most of the world depends
on. The storage stack that recently sent manned rockets into space. They
each unanimously said that the Zone Append command is the right approach
for the Linux kernel to reduce the overhead of I/O tracking for zoned
block devices. It may be worth bringing this information to your
engineering organization, and also potentially consider Zone Append
support for devices that you intend to used with the Linux kernel
storage stack.
Another approach, is to use SPDK, and bypass the Linux kernel. This
might even be an advantage, your customers does not have to wait on the
Linux distribution being released with a long term release, before they
can even get started and deploy in volume. I.e., they will actually get
faster to market, and your company will be able to sell more drives.
