[PATCH 10/40] mm/slab: introduce SLAB_NO_OBJ_EXT to avoid obj_ext creation

Suren Baghdasaryan
2023-05-01T16:57:32Z

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 6b3e155b70bf..99a146f3cedf 100644
--- a/include/linux/slab.h
+++ b/include/linux/slab.h
@@ -147,6 +147,13 @@
#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/slab.c b/mm/slab.c
index bb57f7fdbae1..ccc76f7455e9 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -1232,7 +1232,7 @@ 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 c87628cd8a9a..507b71372ee4 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -5020,7 +5020,8 @@ 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);

@@ -5030,7 +5031,7 @@ 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);
--
2.40.1.495.gc816e09b53d-goog