[PATCH v3] mm/zsmalloc: remove CONFIG_ZSMALLOC_STAT

[PATCH v3] mm/zsmalloc: remove CONFIG_ZSMALLOC_STAT

[Xueyuan Chen]

CONFIG_ZSMALLOC_STAT only controls the debugfs interface. The class
counters are updated regardless of this option.

Remove the CONFIG_ZSMALLOC_STAT guards and rely on the debugfs API
stubs when CONFIG_DEBUG_FS=n. Skip statistics setup silently when
debugfs is unavailable.

Remove the Kconfig entry and replace the existing CONFIG_ZSMALLOC_STAT
settings with CONFIG_DEBUG_FS=y. Update the English and Chinese
documentation to match, and clarify the pool name in the debugfs path.

Suggested-by: Nhat Pham <nphamcs@gmail.com>
Reviewed-by: Nhat Pham <nphamcs@gmail.com>
Signed-off-by: Xueyuan Chen <xueyuan.chen21@gmail.com>
---
Drop CONFIG_ZSMALLOC_STAT instead of making the counters conditional. The
option only controls the debugfs interface, while the class counters are
updated unconditionally. Removing it simplifies the code.

Following Nhat's suggestion, remove CONFIG_ZSMALLOC_STAT and rely on
the existing debugfs API stubs when CONFIG_DEBUG_FS=n.
---
Changes in v3:
- Squash the three patches into one (Nhat, Sergey).
- Add Nhat's Reviewed-by.
- Update the documentation wording.
- Link to v2: https://patch.msgid.link/20261109-zsmalloc_stat-v2-0-caee41684aba@gmail.com

Changes in v2:
- Drop CONFIG_ZSMALLOC_STAT instead of making the counters conditional.
- Update configuration files and documentation.
- Link to v1: https://patch.msgid.link/20261106-zsmalloc_stat-v1-1-b574f4714adf@gmail.com
---
 Documentation/mm/zsmalloc.rst                    |  4 +--
 Documentation/translations/zh_CN/mm/zsmalloc.rst |  2 +-
 arch/s390/configs/debug_defconfig                |  2 +-
 arch/s390/configs/defconfig                      |  2 +-
 drivers/gpu/drm/ci/arm.config                    |  2 +-
 drivers/gpu/drm/ci/arm64.config                  |  2 +-
 drivers/gpu/drm/ci/x86_64.config                 |  2 +-
 mm/Kconfig                                       |  9 -------
 mm/zsmalloc.c                                    | 33 ++----------------------
 9 files changed, 10 insertions(+), 48 deletions(-)

diff --git a/Documentation/mm/zsmalloc.rst b/Documentation/mm/zsmalloc.rst
index d2bbecd78e14..4c0786378dc3 100644
--- a/Documentation/mm/zsmalloc.rst
+++ b/Documentation/mm/zsmalloc.rst
@@ -33,8 +33,8 @@ proper handle-based APIs.
 stat
 ====
 
-With CONFIG_ZSMALLOC_STAT, we could see zsmalloc internal information via
-``/sys/kernel/debug/zsmalloc/<user name>``. Here is a sample of stat output::
+With CONFIG_DEBUG_FS, we could see zsmalloc internal information via
+``/sys/kernel/debug/zsmalloc/<pool-name>``. Here is a sample of stat output::
 
  # cat /sys/kernel/debug/zsmalloc/zram0/classes
 
diff --git a/Documentation/translations/zh_CN/mm/zsmalloc.rst b/Documentation/translations/zh_CN/mm/zsmalloc.rst
index 4c8c9b1006a9..b555a07ac871 100644
--- a/Documentation/translations/zh_CN/mm/zsmalloc.rst
+++ b/Documentation/translations/zh_CN/mm/zsmalloc.rst
@@ -32,7 +32,7 @@ zs_unmap_object()解除映射。
 stat
 ====
 
-通过CONFIG_ZSMALLOC_STAT，我们可以通过 ``/sys/kernel/debug/zsmalloc/<user name>``
+启用CONFIG_DEBUG_FS，我们可以通过 ``/sys/kernel/debug/zsmalloc/<pool-name>``
 看到zsmalloc内部信息。下面是一个统计输出的例子。::
 
  # cat /sys/kernel/debug/zsmalloc/zram0/classes
diff --git a/arch/s390/configs/debug_defconfig b/arch/s390/configs/debug_defconfig
index d44674b63715..83193ef8efb9 100644
--- a/arch/s390/configs/debug_defconfig
+++ b/arch/s390/configs/debug_defconfig
@@ -100,7 +100,7 @@ CONFIG_UNIXWARE_DISKLABEL=y
 CONFIG_IOSCHED_BFQ=y
 CONFIG_BINFMT_MISC=m
 CONFIG_ZSWAP=y
-CONFIG_ZSMALLOC_STAT=y
+CONFIG_DEBUG_FS=y
 CONFIG_SLAB_BUCKETS=y
 CONFIG_SLUB_STATS=y
 # CONFIG_COMPAT_BRK is not set
diff --git a/arch/s390/configs/defconfig b/arch/s390/configs/defconfig
index e00e252d4694..694a309377d5 100644
--- a/arch/s390/configs/defconfig
+++ b/arch/s390/configs/defconfig
@@ -94,7 +94,7 @@ CONFIG_UNIXWARE_DISKLABEL=y
 CONFIG_IOSCHED_BFQ=y
 CONFIG_BINFMT_MISC=m
 CONFIG_ZSWAP=y
-CONFIG_ZSMALLOC_STAT=y
+CONFIG_DEBUG_FS=y
 CONFIG_SLAB_BUCKETS=y
 # CONFIG_COMPAT_BRK is not set
 CONFIG_MEMORY_HOTPLUG=y
diff --git a/drivers/gpu/drm/ci/arm.config b/drivers/gpu/drm/ci/arm.config
index d7c51670da2f..fc0a8a4bfb18 100644
--- a/drivers/gpu/drm/ci/arm.config
+++ b/drivers/gpu/drm/ci/arm.config
@@ -5,7 +5,7 @@ CONFIG_CRYPTO_ZSTD=y
 CONFIG_ZRAM_MEMORY_TRACKING=y
 CONFIG_ZRAM_WRITEBACK=y
 CONFIG_ZRAM=y
-CONFIG_ZSMALLOC_STAT=y
+CONFIG_DEBUG_FS=y
 
 # abootimg with a 'dummy' rootfs fails with root=/dev/nfs
 CONFIG_BLK_DEV_INITRD=n
diff --git a/drivers/gpu/drm/ci/arm64.config b/drivers/gpu/drm/ci/arm64.config
index c46125c1f80f..10b01b55a66d 100644
--- a/drivers/gpu/drm/ci/arm64.config
+++ b/drivers/gpu/drm/ci/arm64.config
@@ -5,7 +5,7 @@ CONFIG_CRYPTO_ZSTD=y
 CONFIG_ZRAM_MEMORY_TRACKING=y
 CONFIG_ZRAM_WRITEBACK=y
 CONFIG_ZRAM=y
-CONFIG_ZSMALLOC_STAT=y
+CONFIG_DEBUG_FS=y
 
 # abootimg with a 'dummy' rootfs fails with root=/dev/nfs
 CONFIG_BLK_DEV_INITRD=n
diff --git a/drivers/gpu/drm/ci/x86_64.config b/drivers/gpu/drm/ci/x86_64.config
index 7ac98a78691e..8225b806dad8 100644
--- a/drivers/gpu/drm/ci/x86_64.config
+++ b/drivers/gpu/drm/ci/x86_64.config
@@ -5,7 +5,7 @@ CONFIG_CRYPTO_ZSTD=y
 CONFIG_ZRAM_MEMORY_TRACKING=y
 CONFIG_ZRAM_WRITEBACK=y
 CONFIG_ZRAM=y
-CONFIG_ZSMALLOC_STAT=y
+CONFIG_DEBUG_FS=y
 
 CONFIG_PWM=y
 CONFIG_PM_DEVFREQ=y
diff --git a/mm/Kconfig b/mm/Kconfig
index afff1b25b543..4a77cda7f1d7 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -130,15 +130,6 @@ menu "Zsmalloc allocator options"
 
 comment "Zsmalloc is a common backend allocator for zswap & zram"
 
-config ZSMALLOC_STAT
-	bool "Export zsmalloc statistics"
-	select DEBUG_FS
-	help
-	  This option enables code in the zsmalloc to collect various
-	  statistics about what's happening in zsmalloc and exports that
-	  information to userspace via debugfs.
-	  If unsure, say N.
-
 config ZSMALLOC_CHAIN_SIZE
 	int "Maximum number of physical pages per-zspage"
 	default 8
diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
index 7ef80e0da626..104ccf3aa170 100644
--- a/mm/zsmalloc.c
+++ b/mm/zsmalloc.c
@@ -222,9 +222,7 @@ struct zs_size_stat {
 	unsigned long objs[NR_CLASS_STAT_TYPES];
 };
 
-#ifdef CONFIG_ZSMALLOC_STAT
 static struct dentry *zs_stat_root;
-#endif
 
 static size_t huge_class_size;
 
@@ -279,9 +277,7 @@ struct zs_pool {
 	/* Compact classes */
 	struct shrinker *shrinker;
 
-#ifdef CONFIG_ZSMALLOC_STAT
 	struct dentry *stat_dentry;
-#endif
 #ifdef CONFIG_COMPACTION
 	struct work_struct free_work;
 #endif
@@ -565,14 +561,10 @@ static inline unsigned long class_stat_read(struct size_class *class, int type)
 	return class->stats.objs[type];
 }
 
-#ifdef CONFIG_ZSMALLOC_STAT
-
 static void __init zs_stat_init(void)
 {
-	if (!debugfs_initialized()) {
-		pr_warn("debugfs not available, stat dir not created\n");
+	if (!debugfs_initialized())
 		return;
-	}
 
 	zs_stat_root = debugfs_create_dir("zsmalloc", NULL);
 }
@@ -650,10 +642,8 @@ DEFINE_SHOW_ATTRIBUTE(zs_stats_size);
 
 static void zs_pool_stat_create(struct zs_pool *pool, const char *name)
 {
-	if (!zs_stat_root) {
-		pr_warn("no root stat dir, not creating <%s> stat dir\n", name);
+	if (IS_ERR_OR_NULL(zs_stat_root))
 		return;
-	}
 
 	pool->stat_dentry = debugfs_create_dir(name, zs_stat_root);
 
@@ -666,25 +656,6 @@ static void zs_pool_stat_destroy(struct zs_pool *pool)
 	debugfs_remove_recursive(pool->stat_dentry);
 }
 
-#else /* CONFIG_ZSMALLOC_STAT */
-static void __init zs_stat_init(void)
-{
-}
-
-static void __exit zs_stat_exit(void)
-{
-}
-
-static inline void zs_pool_stat_create(struct zs_pool *pool, const char *name)
-{
-}
-
-static inline void zs_pool_stat_destroy(struct zs_pool *pool)
-{
-}
-#endif
-
-
 /*
  * For each size class, zspages are divided into different groups
  * depending on their usage ratio. This function returns fullness

---
base-commit: fa4ad798f6f681031775266044ba1b0cf3c670bd

--  
Best regards,
Xueyuan