[PATCH v4 04/22] mm/slab: move and refactor __kmem_cache_alias()

Vlastimil Babka
2026-01-23T06:53:21Z

Move __kmem_cache_alias() to slab_common.c since it's called by
__kmem_cache_create_args() and calls find_mergeable() that both
are in this file. We can remove two slab.h declarations and make
them static. Instead declare sysfs_slab_alias() from slub.c so
that __kmem_cache_alias() can keep calling it.

Add args parameter to __kmem_cache_alias() and find_mergeable() instead
of align and ctor. With that we can also move the checks for usersize
and sheaf_capacity there from __kmem_cache_create_args() and make the
result more symmetric with slab_unmergeable().

No functional changes intended.

Reviewed-by: Harry Yoo <harry.yoo@oracle.com>
Reviewed-by: Suren Baghdasaryan <surenb@google.com>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
---
mm/slab.h | 8 +++-----
mm/slab_common.c | 44 +++++++++++++++++++++++++++++++++++++-------
mm/slub.c | 30 +-----------------------------
3 files changed, 41 insertions(+), 41 deletions(-)

diff --git a/mm/slab.h b/mm/slab.h
index e767aa7e91b0..cb48ce5014ba 100644
--- a/mm/slab.h
+++ b/mm/slab.h
@@ -281,9 +281,12 @@ struct kmem_cache {
#define SLAB_SUPPORTS_SYSFS 1
void sysfs_slab_unlink(struct kmem_cache *s);
void sysfs_slab_release(struct kmem_cache *s);
+int sysfs_slab_alias(struct kmem_cache *, const char *);
#else
static inline void sysfs_slab_unlink(struct kmem_cache *s) { }
static inline void sysfs_slab_release(struct kmem_cache *s) { }
+static inline int sysfs_slab_alias(struct kmem_cache *s, const char *p)
+ { return 0; }
#endif

void *fixup_red_left(struct kmem_cache *s, void *p);
@@ -400,11 +403,6 @@ extern void create_boot_cache(struct kmem_cache *, const char *name,
unsigned int useroffset, unsigned int usersize);

int slab_unmergeable(struct kmem_cache *s);
-struct kmem_cache *find_mergeable(unsigned size, unsigned align,
- slab_flags_t flags, const char *name, void (*ctor)(void *));
-struct kmem_cache *
-__kmem_cache_alias(const char *name, unsigned int size, unsigned int align,
- slab_flags_t flags, void (*ctor)(void *));

slab_flags_t kmem_cache_flags(slab_flags_t flags, const char *name);

diff --git a/mm/slab_common.c b/mm/slab_common.c
index e691ede0e6a8..ee245a880603 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -174,15 +174,22 @@ int slab_unmergeable(struct kmem_cache *s)
return 0;
}

-struct kmem_cache *find_mergeable(unsigned int size, unsigned int align,
- slab_flags_t flags, const char *name, void (*ctor)(void *))
+static struct kmem_cache *find_mergeable(unsigned int size, slab_flags_t flags,
+ const char *name, struct kmem_cache_args *args)
{
struct kmem_cache *s;
+ unsigned int align;

if (slab_nomerge)
return NULL;

- if (ctor)
+ if (args->ctor)
+ return NULL;
+
+ if (IS_ENABLED(CONFIG_HARDENED_USERCOPY) && args->usersize)
+ return NULL;
+
+ if (args->sheaf_capacity)
return NULL;

flags = kmem_cache_flags(flags, name);
@@ -191,7 +198,7 @@ struct kmem_cache *find_mergeable(unsigned int size, unsigned int align,
return NULL;

size = ALIGN(size, sizeof(void *));
- align = calculate_alignment(flags, align, size);
+ align = calculate_alignment(flags, args->align, size);
size = ALIGN(size, align);

list_for_each_entry_reverse(s, &slab_caches, list) {
@@ -252,6 +259,31 @@ static struct kmem_cache *create_cache(const char *name,
return ERR_PTR(err);
}

+static struct kmem_cache *
+__kmem_cache_alias(const char *name, unsigned int size, slab_flags_t flags,
+ struct kmem_cache_args *args)
+{
+ struct kmem_cache *s;
+
+ s = find_mergeable(size, flags, name, args);
+ if (s) {
+ if (sysfs_slab_alias(s, name))
+ pr_err("SLUB: Unable to add cache alias %s to sysfs\n",
+ name);
+
+ s->refcount++;
+
+ /*
+ * Adjust the object sizes so that we clear
+ * the complete object on kzalloc.
+ */
+ s->object_size = max(s->object_size, size);
+ s->inuse = max(s->inuse, ALIGN(size, sizeof(void *)));
+ }
+
+ return s;
+}
+
/**
* __kmem_cache_create_args - Create a kmem cache.
* @name: A string which is used in /proc/slabinfo to identify this cache.
@@ -323,9 +355,7 @@ struct kmem_cache *__kmem_cache_create_args(const char *name,
object_size - args->usersize < args->useroffset))
args->usersize = args->useroffset = 0;

- if (!args->usersize && !args->sheaf_capacity)
- s = __kmem_cache_alias(name, object_size, args->align, flags,
- args->ctor);
+ s = __kmem_cache_alias(name, object_size, flags, args);
if (s)
goto out_unlock;

diff --git a/mm/slub.c b/mm/slub.c
index 4eb60e99abd7..9d86c0505dcd 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -350,11 +350,8 @@ enum track_item { TRACK_ALLOC, TRACK_FREE };

#ifdef SLAB_SUPPORTS_SYSFS
static int sysfs_slab_add(struct kmem_cache *);
-static int sysfs_slab_alias(struct kmem_cache *, const char *);
#else
static inline int sysfs_slab_add(struct kmem_cache *s) { return 0; }
-static inline int sysfs_slab_alias(struct kmem_cache *s, const char *p)
- { return 0; }
#endif

#if defined(CONFIG_DEBUG_FS) && defined(CONFIG_SLUB_DEBUG)
@@ -8570,31 +8567,6 @@ void __init kmem_cache_init_late(void)
WARN_ON(!flushwq);
}

-struct kmem_cache *
-__kmem_cache_alias(const char *name, unsigned int size, unsigned int align,
- slab_flags_t flags, void (*ctor)(void *))
-{
- struct kmem_cache *s;
-
- s = find_mergeable(size, align, flags, name, ctor);
- if (s) {
- if (sysfs_slab_alias(s, name))
- pr_err("SLUB: Unable to add cache alias %s to sysfs\n",
- name);
-
- s->refcount++;
-
- /*
- * Adjust the object sizes so that we clear
- * the complete object on kzalloc.
- */
- s->object_size = max(s->object_size, size);
- s->inuse = max(s->inuse, ALIGN(size, sizeof(void *)));
- }
-
- return s;
-}
-
int do_kmem_cache_create(struct kmem_cache *s, const char *name,
unsigned int size, struct kmem_cache_args *args,
slab_flags_t flags)
@@ -9827,7 +9799,7 @@ struct saved_alias {

static struct saved_alias *alias_list;

-static int sysfs_slab_alias(struct kmem_cache *s, const char *name)
+int sysfs_slab_alias(struct kmem_cache *s, const char *name)
{
struct saved_alias *al;

--
2.52.0