Following:
commit 13a488ad6c85976074f78f80a06414914890703c
Author: Yosry Ahmed <yosryahmed@google.com>
Date:   Mon Oct 7 19:21:16 2024 +0000

    mm: z3fold: deprecate CONFIG_Z3FOLD

    The z3fold compressed pages allocator is rarely used, most users use
    zsmalloc.  The only disadvantage of zsmalloc in comparison is the
    dependency on MMU, and zbud is a more common option for !MMU as it was the
    default zswap allocator for a long time.

    Historically, zsmalloc had worse latency than zbud and z3fold but offered
    better memory savings.  This is no longer the case as shown by a simple
    recent analysis [1].  That analysis showed that z3fold does not have any
    advantage over zsmalloc or zbud considering both performance and memory
    usage.  In a kernel build test on tmpfs in a limited cgroup, z3fold took
    3% more time and used 1.8% more memory.  The latency of zswap_load() was
    7% higher, and that of zswap_store() was 10% higher.  Zsmalloc is better
    in all metrics.

    Moreover, z3fold apparently has latent bugs, which was made noticeable by
    a recent soft lockup bug report with z3fold [2].  Switching to zsmalloc
    not only fixed the problem, but also reduced the swap usage from 6~8G to
    1~2G.  Other users have also reported being bitten by mistakenly enabling
    z3fold.

    Other than hurting users, z3fold is repeatedly causing wasted engineering
    effort.  Apart from investigating the above bug, it came up in multiple
    development discussions (e.g.  [3]) as something we need to handle, when
    there aren't any legit users (at least not intentionally).

    The natural course of action is to deprecate z3fold, and remove in a few
    cycles if no objections are raised from active users.  Next on the list
    should be zbud, as it offers marginal latency gains at the cost of huge
    memory waste when compared to zsmalloc.  That one will need to wait until
    zsmalloc does not depend on MMU.




We should likely:
* set CONFIG_ZSWAP_ZPOOL_DEFAULT_Z3FOLD_DEPRECATED=n
* set CONFIG_ZSWAP_ZPOOL_DEFAULT_ZSMALLOC=y and
CONFIG_ZSWAP_ZPOOL_DEFAULT_ZBUD=n