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Subject[RFC PATCH 13/30] mm/slab: introduce SLAB_NO_OBJ_EXT to avoid obj_ext creation
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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@google.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
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