[PATCH v2 0/3] cleanup of SLAB_ flags

[PATCH v2 0/3] cleanup of SLAB_ flags

[Vlastimil Babka]

This started by the report that SLAB_MEM_SPREAD flag is dead (Patch 1).
Then in the alloc profiling series we realized it's too easy to reuse an
existing SLAB_ flag's value when defining a new one, by mistake.
Thus let the compiler do that for us via a new helper enum (Patch 2).
When checking if more flags are dead or could be removed, didn't spot
any, but found out the SLAB_KASAN handling of preventing cache merging
can be simplified since we now have an explicit SLAB_NO_MERGE (Patch 3).

The SLAB_MEM_SPREAD flag is now marked as unused and for removal, and
has a value of 0 so it's a no-op. Patches to remove its usage can/will
be submitted to respective subsystems independently of this series - the
flag is already dead as of v6.8-rc1 with SLAB removed. The removal of
dead cpuset_do_slab_mem_spread() code can also be submitted
independently.

Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
---
Changes in v2:
- Collect R-b, T-b (thanks!)
- Unify all disabled flags's value to a sparse-happy zero with a new macro (lkp/sparse).
- Rename __SF_BIT to __SLAB_FLAG_BIT (Roman Gushchin)
- Rewrod kasan_cache_create() comment (Andrey Konovalov)
- Link to v1: https://lore.kernel.org/r/20240220-slab-cleanup-flags-v1-0-e657e373944a@suse.cz

---
Vlastimil Babka (3):
      mm, slab: deprecate SLAB_MEM_SPREAD flag
      mm, slab: use an enum to define SLAB_ cache creation flags
      mm, slab, kasan: replace kasan_never_merge() with SLAB_NO_MERGE

 include/linux/kasan.h |  6 ----
 include/linux/slab.h  | 97 ++++++++++++++++++++++++++++++++++++---------------
 mm/kasan/generic.c    | 22 ++++--------
 mm/slab.h             |  1 -
 mm/slab_common.c      |  2 +-
 mm/slub.c             |  6 ++--
 6 files changed, 79 insertions(+), 55 deletions(-)
---
base-commit: 6613476e225e090cc9aad49be7fa504e290dd33d
change-id: 20240219-slab-cleanup-flags-c864415ecc8e

Best regards,
-- 
Vlastimil Babka <vbabka@suse.cz>

[PATCH v2 1/3] mm, slab: deprecate SLAB_MEM_SPREAD flag

[Vlastimil Babka]

The SLAB_MEM_SPREAD flag used to be implemented in SLAB, which was
removed.  SLUB instead relies on the page allocator's NUMA policies.
Change the flag's value to 0 to free up the value it had, and mark it
for full removal once all users are gone.

Reported-by: Steven Rostedt <rostedt@goodmis.org>
Closes: https://lore.kernel.org/all/20240131172027.10f64405@gandalf.local.home/
Reviewed-and-tested-by: Xiongwei Song <xiongwei.song@windriver.com>
Reviewed-by: Chengming Zhou <chengming.zhou@linux.dev>
Reviewed-by: Roman Gushchin <roman.gushchin@linux.dev>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
---
 include/linux/slab.h | 5 +++--
 mm/slab.h            | 1 -
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/include/linux/slab.h b/include/linux/slab.h
index b5f5ee8308d0..b1675ff6b904 100644
--- a/include/linux/slab.h
+++ b/include/linux/slab.h
@@ -96,8 +96,6 @@
  */
 /* Defer freeing slabs to RCU */
 #define SLAB_TYPESAFE_BY_RCU	((slab_flags_t __force)0x00080000U)
-/* Spread some memory over cpuset */
-#define SLAB_MEM_SPREAD		((slab_flags_t __force)0x00100000U)
 /* Trace allocations and frees */
 #define SLAB_TRACE		((slab_flags_t __force)0x00200000U)
 
@@ -164,6 +162,9 @@
 #endif
 #define SLAB_TEMPORARY		SLAB_RECLAIM_ACCOUNT	/* Objects are short-lived */
 
+/* Obsolete unused flag, to be removed */
+#define SLAB_MEM_SPREAD		((slab_flags_t __force)0U)
+
 /*
  * ZERO_SIZE_PTR will be returned for zero sized kmalloc requests.
  *
diff --git a/mm/slab.h b/mm/slab.h
index 54deeb0428c6..f4534eefb35d 100644
--- a/mm/slab.h
+++ b/mm/slab.h
@@ -469,7 +469,6 @@ static inline bool is_kmalloc_cache(struct kmem_cache *s)
 			      SLAB_STORE_USER | \
 			      SLAB_TRACE | \
 			      SLAB_CONSISTENCY_CHECKS | \
-			      SLAB_MEM_SPREAD | \
 			      SLAB_NOLEAKTRACE | \
 			      SLAB_RECLAIM_ACCOUNT | \
 			      SLAB_TEMPORARY | \

-- 
2.43.2

[PATCH v2 2/3] mm, slab: use an enum to define SLAB_ cache creation flags

[Vlastimil Babka]

The values of SLAB_ cache creation flags are defined by hand, which is
tedious and error-prone. Use an enum to assign the bit number and a
__SLAB_FLAG_BIT() macro to #define the final flags.

This renumbers the flag values, which is OK as they are only used
internally.

Also define a __SLAB_FLAG_UNUSED macro to assign value to flags disabled
by their respective config options in a unified and sparse-friendly way.

Reviewed-and-tested-by: Xiongwei Song <xiongwei.song@windriver.com>
Reviewed-by: Chengming Zhou <chengming.zhou@linux.dev>
Reviewed-by: Roman Gushchin <roman.gushchin@linux.dev>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
---
 include/linux/slab.h | 94 +++++++++++++++++++++++++++++++++++++---------------
 mm/slub.c            |  6 ++--
 2 files changed, 70 insertions(+), 30 deletions(-)

diff --git a/include/linux/slab.h b/include/linux/slab.h
index b1675ff6b904..f6323763cd61 100644
--- a/include/linux/slab.h
+++ b/include/linux/slab.h
@@ -21,29 +21,69 @@
 #include <linux/cleanup.h>
 #include <linux/hash.h>
 
+enum _slab_flag_bits {
+	_SLAB_CONSISTENCY_CHECKS,
+	_SLAB_RED_ZONE,
+	_SLAB_POISON,
+	_SLAB_KMALLOC,
+	_SLAB_HWCACHE_ALIGN,
+	_SLAB_CACHE_DMA,
+	_SLAB_CACHE_DMA32,
+	_SLAB_STORE_USER,
+	_SLAB_PANIC,
+	_SLAB_TYPESAFE_BY_RCU,
+	_SLAB_TRACE,
+#ifdef CONFIG_DEBUG_OBJECTS
+	_SLAB_DEBUG_OBJECTS,
+#endif
+	_SLAB_NOLEAKTRACE,
+	_SLAB_NO_MERGE,
+#ifdef CONFIG_FAILSLAB
+	_SLAB_FAILSLAB,
+#endif
+#ifdef CONFIG_MEMCG_KMEM
+	_SLAB_ACCOUNT,
+#endif
+#ifdef CONFIG_KASAN_GENERIC
+	_SLAB_KASAN,
+#endif
+	_SLAB_NO_USER_FLAGS,
+#ifdef CONFIG_KFENCE
+	_SLAB_SKIP_KFENCE,
+#endif
+#ifndef CONFIG_SLUB_TINY
+	_SLAB_RECLAIM_ACCOUNT,
+#endif
+	_SLAB_OBJECT_POISON,
+	_SLAB_CMPXCHG_DOUBLE,
+	_SLAB_FLAGS_LAST_BIT
+};
+
+#define __SLAB_FLAG_BIT(nr)	((slab_flags_t __force)(1U << (nr)))
+#define __SLAB_FLAG_UNUSED	((slab_flags_t __force)(0U))
 
 /*
  * Flags to pass to kmem_cache_create().
  * The ones marked DEBUG need CONFIG_SLUB_DEBUG enabled, otherwise are no-op
  */
 /* DEBUG: Perform (expensive) checks on alloc/free */
-#define SLAB_CONSISTENCY_CHECKS	((slab_flags_t __force)0x00000100U)
+#define SLAB_CONSISTENCY_CHECKS	__SLAB_FLAG_BIT(_SLAB_CONSISTENCY_CHECKS)
 /* DEBUG: Red zone objs in a cache */
-#define SLAB_RED_ZONE		((slab_flags_t __force)0x00000400U)
+#define SLAB_RED_ZONE		__SLAB_FLAG_BIT(_SLAB_RED_ZONE)
 /* DEBUG: Poison objects */
-#define SLAB_POISON		((slab_flags_t __force)0x00000800U)
+#define SLAB_POISON		__SLAB_FLAG_BIT(_SLAB_POISON)
 /* Indicate a kmalloc slab */
-#define SLAB_KMALLOC		((slab_flags_t __force)0x00001000U)
+#define SLAB_KMALLOC		__SLAB_FLAG_BIT(_SLAB_KMALLOC)
 /* Align objs on cache lines */
-#define SLAB_HWCACHE_ALIGN	((slab_flags_t __force)0x00002000U)
+#define SLAB_HWCACHE_ALIGN	__SLAB_FLAG_BIT(_SLAB_HWCACHE_ALIGN)
 /* Use GFP_DMA memory */
-#define SLAB_CACHE_DMA		((slab_flags_t __force)0x00004000U)
+#define SLAB_CACHE_DMA		__SLAB_FLAG_BIT(_SLAB_CACHE_DMA)
 /* Use GFP_DMA32 memory */
-#define SLAB_CACHE_DMA32	((slab_flags_t __force)0x00008000U)
+#define SLAB_CACHE_DMA32	__SLAB_FLAG_BIT(_SLAB_CACHE_DMA32)
 /* DEBUG: Store the last owner for bug hunting */
-#define SLAB_STORE_USER		((slab_flags_t __force)0x00010000U)
+#define SLAB_STORE_USER		__SLAB_FLAG_BIT(_SLAB_STORE_USER)
 /* Panic if kmem_cache_create() fails */
-#define SLAB_PANIC		((slab_flags_t __force)0x00040000U)
+#define SLAB_PANIC		__SLAB_FLAG_BIT(_SLAB_PANIC)
 /*
  * SLAB_TYPESAFE_BY_RCU - **WARNING** READ THIS!
  *
@@ -95,19 +135,19 @@
  * Note that SLAB_TYPESAFE_BY_RCU was originally named SLAB_DESTROY_BY_RCU.
  */
 /* Defer freeing slabs to RCU */
-#define SLAB_TYPESAFE_BY_RCU	((slab_flags_t __force)0x00080000U)
+#define SLAB_TYPESAFE_BY_RCU	__SLAB_FLAG_BIT(_SLAB_TYPESAFE_BY_RCU)
 /* Trace allocations and frees */
-#define SLAB_TRACE		((slab_flags_t __force)0x00200000U)
+#define SLAB_TRACE		__SLAB_FLAG_BIT(_SLAB_TRACE)
 
 /* Flag to prevent checks on free */
 #ifdef CONFIG_DEBUG_OBJECTS
-# define SLAB_DEBUG_OBJECTS	((slab_flags_t __force)0x00400000U)
+# define SLAB_DEBUG_OBJECTS	__SLAB_FLAG_BIT(_SLAB_DEBUG_OBJECTS)
 #else
-# define SLAB_DEBUG_OBJECTS	0
+# define SLAB_DEBUG_OBJECTS	__SLAB_FLAG_UNUSED
 #endif
 
 /* Avoid kmemleak tracing */
-#define SLAB_NOLEAKTRACE	((slab_flags_t __force)0x00800000U)
+#define SLAB_NOLEAKTRACE	__SLAB_FLAG_BIT(_SLAB_NOLEAKTRACE)
 
 /*
  * Prevent merging with compatible kmem caches. This flag should be used
@@ -119,25 +159,25 @@
  * - performance critical caches, should be very rare and consulted with slab
  *   maintainers, and not used together with CONFIG_SLUB_TINY
  */
-#define SLAB_NO_MERGE		((slab_flags_t __force)0x01000000U)
+#define SLAB_NO_MERGE		__SLAB_FLAG_BIT(_SLAB_NO_MERGE)
 
 /* Fault injection mark */
 #ifdef CONFIG_FAILSLAB
-# define SLAB_FAILSLAB		((slab_flags_t __force)0x02000000U)
+# define SLAB_FAILSLAB		__SLAB_FLAG_BIT(_SLAB_FAILSLAB)
 #else
-# define SLAB_FAILSLAB		0
+# define SLAB_FAILSLAB		__SLAB_FLAG_UNUSED
 #endif
 /* Account to memcg */
 #ifdef CONFIG_MEMCG_KMEM
-# define SLAB_ACCOUNT		((slab_flags_t __force)0x04000000U)
+# define SLAB_ACCOUNT		__SLAB_FLAG_BIT(_SLAB_ACCOUNT)
 #else
-# define SLAB_ACCOUNT		0
+# define SLAB_ACCOUNT		__SLAB_FLAG_UNUSED
 #endif
 
 #ifdef CONFIG_KASAN_GENERIC
-#define SLAB_KASAN		((slab_flags_t __force)0x08000000U)
+#define SLAB_KASAN		__SLAB_FLAG_BIT(_SLAB_KASAN)
 #else
-#define SLAB_KASAN		0
+#define SLAB_KASAN		__SLAB_FLAG_UNUSED
 #endif
 
 /*
@@ -145,25 +185,25 @@
  * Intended for caches created for self-tests so they have only flags
  * specified in the code and other flags are ignored.
  */
-#define SLAB_NO_USER_FLAGS	((slab_flags_t __force)0x10000000U)
+#define SLAB_NO_USER_FLAGS	__SLAB_FLAG_BIT(_SLAB_NO_USER_FLAGS)
 
 #ifdef CONFIG_KFENCE
-#define SLAB_SKIP_KFENCE	((slab_flags_t __force)0x20000000U)
+#define SLAB_SKIP_KFENCE	__SLAB_FLAG_BIT(_SLAB_SKIP_KFENCE)
 #else
-#define SLAB_SKIP_KFENCE	0
+#define SLAB_SKIP_KFENCE	__SLAB_FLAG_UNUSED
 #endif
 
 /* The following flags affect the page allocator grouping pages by mobility */
 /* Objects are reclaimable */
 #ifndef CONFIG_SLUB_TINY
-#define SLAB_RECLAIM_ACCOUNT	((slab_flags_t __force)0x00020000U)
+#define SLAB_RECLAIM_ACCOUNT	__SLAB_FLAG_BIT(_SLAB_RECLAIM_ACCOUNT)
 #else
-#define SLAB_RECLAIM_ACCOUNT	((slab_flags_t __force)0)
+#define SLAB_RECLAIM_ACCOUNT	__SLAB_FLAG_UNUSED
 #endif
 #define SLAB_TEMPORARY		SLAB_RECLAIM_ACCOUNT	/* Objects are short-lived */
 
 /* Obsolete unused flag, to be removed */
-#define SLAB_MEM_SPREAD		((slab_flags_t __force)0U)
+#define SLAB_MEM_SPREAD		__SLAB_FLAG_UNUSED
 
 /*
  * ZERO_SIZE_PTR will be returned for zero sized kmalloc requests.
diff --git a/mm/slub.c b/mm/slub.c
index 2ef88bbf56a3..2934ef5f3cff 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -306,13 +306,13 @@ static inline bool kmem_cache_has_cpu_partial(struct kmem_cache *s)
 
 /* Internal SLUB flags */
 /* Poison object */
-#define __OBJECT_POISON		((slab_flags_t __force)0x80000000U)
+#define __OBJECT_POISON		__SLAB_FLAG_BIT(_SLAB_OBJECT_POISON)
 /* Use cmpxchg_double */
 
 #ifdef system_has_freelist_aba
-#define __CMPXCHG_DOUBLE	((slab_flags_t __force)0x40000000U)
+#define __CMPXCHG_DOUBLE	__SLAB_FLAG_BIT(_SLAB_CMPXCHG_DOUBLE)
 #else
-#define __CMPXCHG_DOUBLE	((slab_flags_t __force)0U)
+#define __CMPXCHG_DOUBLE	__SLAB_FLAG_UNUSED
 #endif
 
 /*

-- 
2.43.2

[PATCH v2 3/3] mm, slab, kasan: replace kasan_never_merge() with SLAB_NO_MERGE

[Vlastimil Babka]

The SLAB_KASAN flag prevents merging of caches in some configurations,
which is handled in a rather complicated way via kasan_never_merge().
Since we now have a generic SLAB_NO_MERGE flag, we can instead use it
for KASAN caches in addition to SLAB_KASAN in those configurations,
and simplify the SLAB_NEVER_MERGE handling.

Tested-by: Xiongwei Song <xiongwei.song@windriver.com>
Reviewed-by: Chengming Zhou <chengming.zhou@linux.dev>
Reviewed-by: Andrey Konovalov <andreyknvl@gmail.com>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
---
 include/linux/kasan.h |  6 ------
 mm/kasan/generic.c    | 22 ++++++----------------
 mm/slab_common.c      |  2 +-
 3 files changed, 7 insertions(+), 23 deletions(-)

diff --git a/include/linux/kasan.h b/include/linux/kasan.h
index dbb06d789e74..70d6a8f6e25d 100644
--- a/include/linux/kasan.h
+++ b/include/linux/kasan.h
@@ -429,7 +429,6 @@ struct kasan_cache {
 };
 
 size_t kasan_metadata_size(struct kmem_cache *cache, bool in_object);
-slab_flags_t kasan_never_merge(void);
 void kasan_cache_create(struct kmem_cache *cache, unsigned int *size,
 			slab_flags_t *flags);
 
@@ -446,11 +445,6 @@ static inline size_t kasan_metadata_size(struct kmem_cache *cache,
 {
 	return 0;
 }
-/* And thus nothing prevents cache merging. */
-static inline slab_flags_t kasan_never_merge(void)
-{
-	return 0;
-}
 /* And no cache-related metadata initialization is required. */
 static inline void kasan_cache_create(struct kmem_cache *cache,
 				      unsigned int *size,
diff --git a/mm/kasan/generic.c b/mm/kasan/generic.c
index df6627f62402..27297dc4a55b 100644
--- a/mm/kasan/generic.c
+++ b/mm/kasan/generic.c
@@ -334,14 +334,6 @@ DEFINE_ASAN_SET_SHADOW(f3);
 DEFINE_ASAN_SET_SHADOW(f5);
 DEFINE_ASAN_SET_SHADOW(f8);
 
-/* Only allow cache merging when no per-object metadata is present. */
-slab_flags_t kasan_never_merge(void)
-{
-	if (!kasan_requires_meta())
-		return 0;
-	return SLAB_KASAN;
-}
-
 /*
  * Adaptive redzone policy taken from the userspace AddressSanitizer runtime.
  * For larger allocations larger redzones are used.
@@ -370,15 +362,13 @@ void kasan_cache_create(struct kmem_cache *cache, unsigned int *size,
 		return;
 
 	/*
-	 * SLAB_KASAN is used to mark caches that are sanitized by KASAN
-	 * and that thus have per-object metadata.
-	 * Currently this flag is used in two places:
-	 * 1. In slab_ksize() to account for per-object metadata when
-	 *    calculating the size of the accessible memory within the object.
-	 * 2. In slab_common.c via kasan_never_merge() to prevent merging of
-	 *    caches with per-object metadata.
+	 * SLAB_KASAN is used to mark caches that are sanitized by KASAN and
+	 * that thus have per-object metadata. Currently, this flag is used in
+	 * slab_ksize() to account for per-object metadata when calculating the
+	 * size of the accessible memory within the object. Additionally, we use
+	 * SLAB_NO_MERGE to prevent merging of caches with per-object metadata.
 	 */
-	*flags |= SLAB_KASAN;
+	*flags |= SLAB_KASAN | SLAB_NO_MERGE;
 
 	ok_size = *size;
 
diff --git a/mm/slab_common.c b/mm/slab_common.c
index 238293b1dbe1..7cfa2f1ce655 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -50,7 +50,7 @@ static DECLARE_WORK(slab_caches_to_rcu_destroy_work,
  */
 #define SLAB_NEVER_MERGE (SLAB_RED_ZONE | SLAB_POISON | SLAB_STORE_USER | \
 		SLAB_TRACE | SLAB_TYPESAFE_BY_RCU | SLAB_NOLEAKTRACE | \
-		SLAB_FAILSLAB | SLAB_NO_MERGE | kasan_never_merge())
+		SLAB_FAILSLAB | SLAB_NO_MERGE)
 
 #define SLAB_MERGE_SAME (SLAB_RECLAIM_ACCOUNT | SLAB_CACHE_DMA | \
 			 SLAB_CACHE_DMA32 | SLAB_ACCOUNT)

-- 
2.43.2

Re: [PATCH v2 1/3] mm, slab: deprecate SLAB_MEM_SPREAD flag

[David Rientjes]

On Fri, 23 Feb 2024, Vlastimil Babka wrote:

> The SLAB_MEM_SPREAD flag used to be implemented in SLAB, which was
> removed.  SLUB instead relies on the page allocator's NUMA policies.
> Change the flag's value to 0 to free up the value it had, and mark it
> for full removal once all users are gone.
> 
> Reported-by: Steven Rostedt <rostedt@goodmis.org>
> Closes: https://lore.kernel.org/all/20240131172027.10f64405@gandalf.local.home/
> Reviewed-and-tested-by: Xiongwei Song <xiongwei.song@windriver.com>
> Reviewed-by: Chengming Zhou <chengming.zhou@linux.dev>
> Reviewed-by: Roman Gushchin <roman.gushchin@linux.dev>
> Signed-off-by: Vlastimil Babka <vbabka@suse.cz>

Acked-by: David Rientjes <rientjes@google.com>

Re: [PATCH v2 2/3] mm, slab: use an enum to define SLAB_ cache creation flags

[David Rientjes]

On Fri, 23 Feb 2024, Vlastimil Babka wrote:

> The values of SLAB_ cache creation flags are defined by hand, which is
> tedious and error-prone. Use an enum to assign the bit number and a
> __SLAB_FLAG_BIT() macro to #define the final flags.
> 
> This renumbers the flag values, which is OK as they are only used
> internally.
> 
> Also define a __SLAB_FLAG_UNUSED macro to assign value to flags disabled
> by their respective config options in a unified and sparse-friendly way.
> 
> Reviewed-and-tested-by: Xiongwei Song <xiongwei.song@windriver.com>
> Reviewed-by: Chengming Zhou <chengming.zhou@linux.dev>
> Reviewed-by: Roman Gushchin <roman.gushchin@linux.dev>
> Signed-off-by: Vlastimil Babka <vbabka@suse.cz>

Acked-by: David Rientjes <rientjes@google.com>

Re: [PATCH v2 3/3] mm, slab, kasan: replace kasan_never_merge() with SLAB_NO_MERGE

[David Rientjes]

On Fri, 23 Feb 2024, Vlastimil Babka wrote:

> The SLAB_KASAN flag prevents merging of caches in some configurations,
> which is handled in a rather complicated way via kasan_never_merge().
> Since we now have a generic SLAB_NO_MERGE flag, we can instead use it
> for KASAN caches in addition to SLAB_KASAN in those configurations,
> and simplify the SLAB_NEVER_MERGE handling.
> 
> Tested-by: Xiongwei Song <xiongwei.song@windriver.com>
> Reviewed-by: Chengming Zhou <chengming.zhou@linux.dev>
> Reviewed-by: Andrey Konovalov <andreyknvl@gmail.com>
> Signed-off-by: Vlastimil Babka <vbabka@suse.cz>

Tested-by: David Rientjes <rientjes@google.com>

Re: [PATCH v2 0/3] cleanup of SLAB_ flags

[Vlastimil Babka]

On 2/23/24 19:27, Vlastimil Babka wrote:
> This started by the report that SLAB_MEM_SPREAD flag is dead (Patch 1).
> Then in the alloc profiling series we realized it's too easy to reuse an
> existing SLAB_ flag's value when defining a new one, by mistake.
> Thus let the compiler do that for us via a new helper enum (Patch 2).
> When checking if more flags are dead or could be removed, didn't spot
> any, but found out the SLAB_KASAN handling of preventing cache merging
> can be simplified since we now have an explicit SLAB_NO_MERGE (Patch 3).
> 
> The SLAB_MEM_SPREAD flag is now marked as unused and for removal, and
> has a value of 0 so it's a no-op. Patches to remove its usage can/will
> be submitted to respective subsystems independently of this series - the
> flag is already dead as of v6.8-rc1 with SLAB removed. The removal of
> dead cpuset_do_slab_mem_spread() code can also be submitted
> independently.
> 
> Signed-off-by: Vlastimil Babka <vbabka@suse.cz>

Pushed to slab/for-next

> ---
> Changes in v2:
> - Collect R-b, T-b (thanks!)
> - Unify all disabled flags's value to a sparse-happy zero with a new macro (lkp/sparse).
> - Rename __SF_BIT to __SLAB_FLAG_BIT (Roman Gushchin)
> - Rewrod kasan_cache_create() comment (Andrey Konovalov)
> - Link to v1: https://lore.kernel.org/r/20240220-slab-cleanup-flags-v1-0-e657e373944a@suse.cz
> 
> ---
> Vlastimil Babka (3):
>       mm, slab: deprecate SLAB_MEM_SPREAD flag
>       mm, slab: use an enum to define SLAB_ cache creation flags
>       mm, slab, kasan: replace kasan_never_merge() with SLAB_NO_MERGE
> 
>  include/linux/kasan.h |  6 ----
>  include/linux/slab.h  | 97 ++++++++++++++++++++++++++++++++++++---------------
>  mm/kasan/generic.c    | 22 ++++--------
>  mm/slab.h             |  1 -
>  mm/slab_common.c      |  2 +-
>  mm/slub.c             |  6 ++--
>  6 files changed, 79 insertions(+), 55 deletions(-)
> ---
> base-commit: 6613476e225e090cc9aad49be7fa504e290dd33d
> change-id: 20240219-slab-cleanup-flags-c864415ecc8e
> 
> Best regards,