linux-kernel - [RFC PATCH 13/30] mm/slab: introduce SLAB_NO_OBJ_EXT to avoid obj

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Date:   Tue, 30 Aug 2022 14:49:02 -0700
From:   Suren Baghdasaryan <surenb@...gle.com>
To:     akpm@...ux-foundation.org
Cc:     kent.overstreet@...ux.dev, mhocko@...e.com, vbabka@...e.cz,
        hannes@...xchg.org, roman.gushchin@...ux.dev, mgorman@...e.de,
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Subject: [RFC PATCH 13/30] 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/slab.c            | 2 +-
 mm/slub.c            | 5 +++--
 3 files changed, 11 insertions(+), 3 deletions(-)

diff --git a/include/linux/slab.h b/include/linux/slab.h
index 0fefdf528e0d..55ae3ea864a4 100644
--- a/include/linux/slab.h
+++ b/include/linux/slab.h
@@ -124,6 +124,13 @@
 #define SLAB_RECLAIM_ACCOUNT	((slab_flags_t __force)0x00020000U)
 #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/slab.c b/mm/slab.c
index 10e96137b44f..ba97aeef7ec1 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -1233,7 +1233,7 @@ 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);
 	list_add(&kmem_cache->list, &slab_caches);
 	slab_state = PARTIAL;
 
diff --git a/mm/slub.c b/mm/slub.c
index 862dbd9af4f5..80199d5ac7c9 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -4825,7 +4825,8 @@ 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);
 
 	register_hotmemory_notifier(&slab_memory_callback_nb);
 
@@ -4835,7 +4836,7 @@ 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);
-- 
2.37.2.672.g94769d06f0-goog