On 10/15/23 23:17, Christoph Hellwig wrote:
On Fri, Oct 06, 2023 at 05:19:52PM +0900, Damien Le Moal wrote:
Your change seem to assume that it makes sense to be able to combine CDL with
lifetime hints. But does it really ?
Yes, it does.
CDL is of dubious value for solid state
media and as far as I know,
No, it's pretty useful and I'd bet my 2 cents that it will eventually
show up in relevant standards and devices.
Even if it wasn't making our user interfaces exclusive would be a
massive pain.
The other question here if you really want to keep the bit separation approach
is: do we really need up to 64 different lifetime hints ? While the scsi
standard allows that much, does this many different lifetime make sense in
practice ? Can we ever think of a usecase that needs more than say 8 different
liftimes (3 bits) ? If you limit the number of possible lifetime hints to 8,
then we can keep 4 bits unused in the hint field for future features.
Yes, I think this is the smoking gun. We should be fine with a much
more limited number of lifetime hints, i.e. the user interface only
exposes 5 hints, and supporting more in the in-kernel interfaces seems
of rather doubtfuŀ use.
Thanks for the feedback Christoph. I will address this feedback in the
next version of this patch series.
Bart.
