[dm-devel] Re: [PATCH 1/3] block: add alt_size

[Kay Sievers]

On Sat, May 9, 2009 at 16:04, Tejun Heo <tj at kernel.org> wrote:
> Kay Sievers wrote:
>> What does "alt_" stand for? I think that should be more descriptive in
>> an exported interface.
>
> Alternative.
>
>> And can we please keep the "size_*" in front of the name, so that they
>> group together?
>
> Maybe, but size_alt?  Any better ideas?

"size_limit"
"size_restricted"
"size_clipped"
"size_constrain"

anything that ideally would express that this is smaller than the
actual "size", and that is is a "configured" value and not some
hardware property.

>> Also, values with magic block counts, while there is no way to get the
>> blocksize with the same interface, are pretty weird. I think the
>> current "size" attribute is just a bug.
>
> Logical block size is fixed at 512 bytes.  Offset and size are always
> represented in multiples of 512 bytes and only get converted to
> hardware block size in the lld.

Oh, good. Didn't know that this will always be 512, even for devices
with a native size larger than this.

>> Not sure, how that should be solved, by adding a "blocksize" attribute
>> that is always in the same context as the current "size*" values, or
>> by just using bytes for new attributes here.
>>
>> Almost all tools I've seen using these attributes, have hardcoded *
>> 512 in there, which may cause trouble pretty soon. And this is mostly
>> a failure of the interface and not of the users, I think.
>
> No, it will never break.  It will always be 512.

Cool. No problem then. :)

> For userlevel exporting, it might have been better to use just bytes
> there as preformance isn't really an issue, but, well, it's already
> determined, so..

Right, but if it can not change, it's fine, I guess.

Thanks,
Kay