Re: [PATCH v4 0/2] rust: zpool: add abstraction for zpool drivers

[Vitaly Wool <vitaly.wool@konsulko.se>]

> On Aug 26, 2025, at 2:44 PM, Johannes Weiner <hannes@cmpxchg.org> wrote:
> 
> On Sat, Aug 23, 2025 at 03:04:19PM +0200, Vitaly Wool wrote:
>> Zpool is a common frontend for memory storage pool implementations.
>> These pools are typically used to store compressed memory objects,
>> e. g. for Zswap, the lightweight compressed cache for swap pages.
>> 
>> This patch provides the interface to use Zpool in Rust kernel code,
>> thus enabling Rust implementations of Zpool allocators for Zswap.
> 
> The zpool indirection is on its way out.
> 
> When you submitted an alternate allocator backend recently, the
> resounding feedback from the zswap maintainers was that improvements
> should happen to zsmalloc incrementally. It is a lot of code and has a
> lot of features that go beyond allocation strategy. We do not want to
> fork it and fragment this space again with niche, incomplete backends.
> 
> It's frustrating that you not only ignored this, but then went ahead
> and made other people invest their time and effort into this as well.
> 

I don’t think we have a consensus on that.

And zblock is, after some additional improvements, just better than zsmalloc in all meaningful aspects, let alone the simplicity. It is fas easier to implement in Rust than zsmalloc, too. Besides, zram is a good candidate to be rewritten in Rust as well and after that is done, zblock will be even safer and faster. So while not being “incomplete", it’s zsmalloc that is becoming a niche backend moving forward, and I would argue that it could make more sense to eventually obsolete *it* rather than the zpool API.

~Vitaly