Yosry Ahmed writes:
The z3fold compressed pages allocator is not widely 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.
In hopes of having a single compressed pages allocator at some point,
and following in the footsteps of SLAB, deprecate z3fold. Rename the
user-visible option so that users with CONFIG_Z3FOLD=y get a new prompt
with explanation during make oldconfig. Remove CONFIG_Z3FOLD=y from
defconfigs.
Existing users, if any, should voice their objections. Otherwise, we can
remove z3fold in a few releases.
Signed-off-by: Yosry Ahmed <yosryahmed@xxxxxxxxxx>
Acked-by: Chris Down <chris@xxxxxxxxxxxxxx>
Thanks. We are definitely hurting users as well by keeping this around with its
known issues when writeback is disabled, for example.
---
I have limited understanding of Kconfigs. I modelled this after commit
eb07c4f39c3e ("mm/slab: rename CONFIG_SLAB to CONFIG_SLAB_DEPRECATED"),
but one difference is that CONFIG_Z3FOLD is a tristate. I made
CONFIG_Z3FOLD_DEPRECATED a boolean config, and CONFIG_Z3FOLD default y
so that it is on by default if CONFIG_Z3FOLD_DEPRECATED is selected. I
am not sure if that's the correct way to do this.
---
arch/loongarch/configs/loongson3_defconfig | 1 -
arch/powerpc/configs/ppc64_defconfig | 1 -
mm/Kconfig | 13 +++++++++++--
3 files changed, 11 insertions(+), 4 deletions(-)
diff --git a/arch/loongarch/configs/loongson3_defconfig b/arch/loongarch/configs/loongson3_defconfig
index 33795e4a5bd63..89b66b6c6a1d5 100644
--- a/arch/loongarch/configs/loongson3_defconfig
+++ b/arch/loongarch/configs/loongson3_defconfig
@@ -85,7 +85,6 @@ CONFIG_ZPOOL=y
CONFIG_ZSWAP=y
CONFIG_ZSWAP_COMPRESSOR_DEFAULT_ZSTD=y
CONFIG_ZBUD=y
-CONFIG_Z3FOLD=y
CONFIG_ZSMALLOC=m
# CONFIG_COMPAT_BRK is not set
CONFIG_MEMORY_HOTPLUG=y
diff --git a/arch/powerpc/configs/ppc64_defconfig b/arch/powerpc/configs/ppc64_defconfig
index 544a65fda77bc..d39284489aa26 100644
--- a/arch/powerpc/configs/ppc64_defconfig
+++ b/arch/powerpc/configs/ppc64_defconfig
@@ -81,7 +81,6 @@ CONFIG_MODULE_SIG_SHA512=y
CONFIG_PARTITION_ADVANCED=y
CONFIG_BINFMT_MISC=m
CONFIG_ZSWAP=y
-CONFIG_Z3FOLD=y
CONFIG_ZSMALLOC=y
# CONFIG_SLAB_MERGE_DEFAULT is not set
CONFIG_SLAB_FREELIST_RANDOM=y
diff --git a/mm/Kconfig b/mm/Kconfig
index 1902cfe4cc4f5..bc6cc97c08349 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -193,15 +193,24 @@ config ZBUD
deterministic reclaim properties that make it preferable to a higher
density approach when reclaim will be used.
-config Z3FOLD
- tristate "3:1 compression allocator (z3fold)"
+config Z3FOLD_DEPRECATED
+ bool "3:1 compression allocator (z3fold) (DEPRECATED)"
depends on ZSWAP
help
+ Deprecated and scheduled for removal in a few cycles. If you have
+ a good reason for using Z3FOLD rather than ZSMALLOC or ZBUD, please
+ contact linux-mm@xxxxxxxxx and the zswap maintainers.
+
A special purpose allocator for storing compressed pages.
It is designed to store up to three compressed pages per physical
page. It is a ZBUD derivative so the simplicity and determinism are
still there.
+config Z3FOLD
+ tristate
+ default y
+ depends on Z3FOLD_DEPRECATED
+
config ZSMALLOC
tristate
prompt "N:1 compression allocator (zsmalloc)" if ZSWAP
--
2.43.0.275.g3460e3d667-goog
