On 16.06.2020 14:06, Matias Bjørling wrote:
On 16/06/2020 14.00, Javier González wrote:
On 16.06.2020 13:18, Matias Bjørling wrote:
On 16/06/2020 12.41, 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.
There is already general support in the kernel for the zone append
command. Feel free to submit patches to emulate the support. It is
outside the scope of this patchset.
It is fine that the kernel supports append, but the ZNS specification
does not impose the implementation for append, so the driver should not
do that either.
ZNS SSDs that choose to leave append as a non-implemented optional
command should not rely on emulated SW support, specially when
traditional writes work very fine for a large part of current ZNS use
cases.
Please, remove this virtual constraint.
The Zone Append command is mandatory for zoned block devices. Please
see https://lwn.net/Articles/818709/ for the background.
I do not see anywhere in the block layer that append is mandatory for
zoned devices. Append is emulated on ZBC, but beyond that there is no
mandatory bits. Please explain.
Please submitpatches if you want to have support for ZNS devices that
does not implement the Zone Append command. It is outside the scope
of this patchset.
That we will.
