[PATCH RFC hotfixes 1/2] mm/slab: decouple SLAB_NO_SHEAVES from SLAB_NO_OBJ_EXT

["Harry Yoo (Oracle)" <harry@kernel.org>]

Bootstrap caches are created with SLAB_NO_OBJ_EXT to disallow sheaves
and obj_exts.

To allow disabling obj_exts while allowing sheaves, decouple
SLAB_NO_SHEAVES from SLAB_NO_OBJ_EXT. Bootstrap caches now have both
SLAB_NO_SHEAVES and SLAB_NO_OBJ_EXT.

No functional change intended.

Cc: stable@vger.kernel.org
Fixes: e47c897a2949 ("slab: add sheaves to most caches")
Signed-off-by: Harry Yoo (Oracle) <harry@kernel.org>
---
 include/linux/slab.h | 13 +++++++++++--
 mm/slub.c            | 10 ++++++----
 2 files changed, 17 insertions(+), 6 deletions(-)

diff --git a/include/linux/slab.h b/include/linux/slab.h
index 51f03f18c9a7..08d7b6c9c4d6 100644
--- a/include/linux/slab.h
+++ b/include/linux/slab.h
@@ -58,10 +58,13 @@ enum _slab_flag_bits {
 #endif
 	_SLAB_OBJECT_POISON,
 	_SLAB_CMPXCHG_DOUBLE,
+#ifdef CONFIG_SLAB_OBJ_EXT
 	_SLAB_NO_OBJ_EXT,
-#if defined(CONFIG_SLAB_OBJ_EXT) && defined(CONFIG_64BIT)
+#ifdef CONFIG_64BIT
 	_SLAB_OBJ_EXT_IN_OBJ,
 #endif
+#endif
+	_SLAB_NO_SHEAVES,
 	_SLAB_FLAGS_LAST_BIT
 };
 
@@ -239,8 +242,14 @@ enum _slab_flag_bits {
 #endif
 #define SLAB_TEMPORARY		SLAB_RECLAIM_ACCOUNT	/* Objects are short-lived */
 
-/* Slab created using create_boot_cache */
+/* Slab caches without obj_exts array */
+#ifdef CONFIG_SLAB_OBJ_EXT
 #define SLAB_NO_OBJ_EXT		__SLAB_FLAG_BIT(_SLAB_NO_OBJ_EXT)
+#else
+#define SLAB_NO_OBJ_EXT		__SLAB_FLAG_UNUSED
+#endif
+
+#define SLAB_NO_SHEAVES		__SLAB_FLAG_BIT(_SLAB_NO_SHEAVES)
 
 #if defined(CONFIG_SLAB_OBJ_EXT) && defined(CONFIG_64BIT)
 #define SLAB_OBJ_EXT_IN_OBJ	__SLAB_FLAG_BIT(_SLAB_OBJ_EXT_IN_OBJ)
diff --git a/mm/slub.c b/mm/slub.c
index 9f754cf1c187..efc85053ae84 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -7777,12 +7777,12 @@ static unsigned int calculate_sheaf_capacity(struct kmem_cache *s,
 		return 0;
 
 	/*
-	 * Bootstrap caches can't have sheaves for now (SLAB_NO_OBJ_EXT).
+	 * Bootstrap caches can't have sheaves for now (SLAB_NO_SHEAVES).
 	 * SLAB_NOLEAKTRACE caches (e.g., kmemleak's object_cache) must not
 	 * have sheaves to avoid recursion when sheaf allocation triggers
 	 * kmemleak tracking.
 	 */
-	if (s->flags & (SLAB_NO_OBJ_EXT | SLAB_NOLEAKTRACE))
+	if (s->flags & (SLAB_NO_SHEAVES | SLAB_NOLEAKTRACE))
 		return 0;
 
 	/*
@@ -8559,7 +8559,8 @@ void __init kmem_cache_init(void)
 
 	create_boot_cache(kmem_cache_node, "kmem_cache_node",
 			sizeof(struct kmem_cache_node),
-			SLAB_HWCACHE_ALIGN | SLAB_NO_OBJ_EXT, 0, 0);
+			SLAB_HWCACHE_ALIGN | SLAB_NO_SHEAVES | SLAB_NO_OBJ_EXT,
+			0, 0);
 
 	hotplug_node_notifier(slab_memory_callback, SLAB_CALLBACK_PRI);
 
@@ -8569,7 +8570,8 @@ void __init kmem_cache_init(void)
 	create_boot_cache(kmem_cache, "kmem_cache",
 			offsetof(struct kmem_cache, per_node) +
 				nr_node_ids * sizeof(struct kmem_cache_per_node_ptrs),
-			SLAB_HWCACHE_ALIGN | SLAB_NO_OBJ_EXT, 0, 0);
+			SLAB_HWCACHE_ALIGN | SLAB_NO_SHEAVES | SLAB_NO_OBJ_EXT,
+			0, 0);
 
 	kmem_cache = bootstrap(&boot_kmem_cache);
 	kmem_cache_node = bootstrap(&boot_kmem_cache_node);

-- 
2.53.0