mm, slab: use an enum to define SLAB_ cache creation flags

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>
Acked-by: David Rientjes <rientjes@google.com>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>

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.

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
 
 /*