linux-kernel - [PATCH v3 07/35] mm/slab: introduce SLAB_NO_OBJ_EXT to avoid obj

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Date: Mon, 12 Feb 2024 13:38:53 -0800
From: Suren Baghdasaryan <surenb@...gle.com>
To: akpm@...ux-foundation.org
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Subject: [PATCH v3 07/35] mm/slab: introduce SLAB_NO_OBJ_EXT to avoid obj_ext creation

Slab extension objects can't be allocated before slab infrastructure is
initialized. Some caches, like kmem_cache and kmem_cache_node, are created
before slab infrastructure is initialized. Objects from these caches can't
have extension objects. Introduce SLAB_NO_OBJ_EXT slab flag to mark these
caches and avoid creating extensions for objects allocated from these
slabs.

Signed-off-by: Suren Baghdasaryan <surenb@...gle.com>
---
 include/linux/slab.h | 7 +++++++
 mm/slub.c            | 5 +++--
 2 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/include/linux/slab.h b/include/linux/slab.h
index b5f5ee8308d0..3ac2fc830f0f 100644
--- a/include/linux/slab.h
+++ b/include/linux/slab.h
@@ -164,6 +164,13 @@
 #endif
 #define SLAB_TEMPORARY		SLAB_RECLAIM_ACCOUNT	/* Objects are short-lived */
 
+#ifdef CONFIG_SLAB_OBJ_EXT
+/* Slab created using create_boot_cache */
+#define SLAB_NO_OBJ_EXT         ((slab_flags_t __force)0x20000000U)
+#else
+#define SLAB_NO_OBJ_EXT         0
+#endif
+
 /*
  * ZERO_SIZE_PTR will be returned for zero sized kmalloc requests.
  *
diff --git a/mm/slub.c b/mm/slub.c
index 1eb1050814aa..9fd96238ed39 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -5650,7 +5650,8 @@ void __init kmem_cache_init(void)
 		node_set(node, slab_nodes);
 
 	create_boot_cache(kmem_cache_node, "kmem_cache_node",
-		sizeof(struct kmem_cache_node), SLAB_HWCACHE_ALIGN, 0, 0);
+			sizeof(struct kmem_cache_node),
+			SLAB_HWCACHE_ALIGN | SLAB_NO_OBJ_EXT, 0, 0);
 
 	hotplug_memory_notifier(slab_memory_callback, SLAB_CALLBACK_PRI);
 
@@ -5660,7 +5661,7 @@ void __init kmem_cache_init(void)
 	create_boot_cache(kmem_cache, "kmem_cache",
 			offsetof(struct kmem_cache, node) +
 				nr_node_ids * sizeof(struct kmem_cache_node *),
-		       SLAB_HWCACHE_ALIGN, 0, 0);
+			SLAB_HWCACHE_ALIGN | SLAB_NO_OBJ_EXT, 0, 0);
 
 	kmem_cache = bootstrap(&boot_kmem_cache);
 	kmem_cache_node = bootstrap(&boot_kmem_cache_node);
-- 
2.43.0.687.g38aa6559b0-goog