[PATCH v2] landlock: Use kmem for landlock_object

Use kmem_cache replace kzalloc() calls with kmem_cache_zalloc() for
struct landlock_object and update the related dependencies to improve
memory allocation and deallocation performance. This patch does not
change kfree() and kfree_rcu() calls because according to kernel commit
ae65a5211d90("mm/slab: document kfree() as allowed for
kmem_cache_alloc() objects"), starting from kernel 6.4 with
CONFIG_SLOB, kfree() is safe to use for such objects.

Signed-off-by: Ayush Tiwari <[email protected]>
---

Changes in v2: Used clang-format and corrected the removal of kfree_rcu.
Tried to use KMEM macro but due to lack of cache pointer in that macro,
had to explicitly define landlock_object_cache, as done in security.c.

 security/landlock/object.c | 12 +++++++++++-
 security/landlock/object.h |  2 ++
 security/landlock/setup.c  |  1 +
 3 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/security/landlock/object.c b/security/landlock/object.c
index 1f50612f0185..cfc367725624 100644
--- a/security/landlock/object.c
+++ b/security/landlock/object.c
@@ -17,6 +17,15 @@
 
 #include "object.h"
 
+static struct kmem_cache *landlock_object_cache;
+
+void __init landlock_object_cache_init(void)
+{
+	landlock_object_cache = kmem_cache_create(
+		"landlock_object_cache", sizeof(struct landlock_object), 0,
+		SLAB_PANIC, NULL);
+}
+
 struct landlock_object *
 landlock_create_object(const struct landlock_object_underops *const underops,
 		       void *const underobj)
@@ -25,7 +34,8 @@ landlock_create_object(const struct landlock_object_underops *const underops,
 
 	if (WARN_ON_ONCE(!underops || !underobj))
 		return ERR_PTR(-ENOENT);
-	new_object = kzalloc(sizeof(*new_object), GFP_KERNEL_ACCOUNT);
+	new_object =
+		kmem_cache_zalloc(landlock_object_cache, GFP_KERNEL_ACCOUNT);
 	if (!new_object)
 		return ERR_PTR(-ENOMEM);
 	refcount_set(&new_object->usage, 1);
diff --git a/security/landlock/object.h b/security/landlock/object.h
index 5f28c35e8aa8..d9967ef16ec1 100644
--- a/security/landlock/object.h
+++ b/security/landlock/object.h
@@ -15,6 +15,8 @@
 
 struct landlock_object;
 
+void __init landlock_object_cache_init(void);
+
 /**
  * struct landlock_object_underops - Operations on an underlying object
  */
diff --git a/security/landlock/setup.c b/security/landlock/setup.c
index f6dd33143b7f..525820fc03ec 100644
--- a/security/landlock/setup.c
+++ b/security/landlock/setup.c
@@ -33,6 +33,7 @@ const struct lsm_id landlock_lsmid = {
 
 static int __init landlock_init(void)
 {
+	landlock_object_cache_init();
 	landlock_add_cred_hooks();
 	landlock_add_ptrace_hooks();
 	landlock_add_fs_hooks();
-- 
2.40.1