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[RFC,1/6] slab: introduce kmem_cache_setup()

Message ID 20240902-work-kmem_cache_args-v1-1-27d05bc05128@kernel.org (mailing list archive)
State New
Headers show
Series slab: add kmem_cache_setup() | expand

Commit Message

Christian Brauner Sept. 2, 2024, 3:31 p.m. UTC
Replace the custom kmem_cache_*() functions with a unified
kmem_cache_setup() function that is based on struct kmem_cache_args and
will replace kmem_cache_create(), kmem_cache_create_usercopy(), and
kmem_cache_create_rcu().

The @name, @object_size, and @flags parameters are passed separately as
they are nearly universally used. The rest of the arguments moves into
struct kmem_cache_args.

A new "use_freeptr_offset" boolean is added as zero is a valid freelist
pointer offset. The boolean allows callers to avoid having to do
anything special if they don't care about freelist pointer offsets (most
callers don't).

Signed-off-by: Christian Brauner <brauner@kernel.org>
---
 Documentation/core-api/memory-allocation.rst |  10 +--
 include/linux/slab.h                         |  21 ++++++
 mm/slab_common.c                             | 102 +++++++++++++++++----------
 3 files changed, 91 insertions(+), 42 deletions(-)
diff mbox series

Patch

diff --git a/Documentation/core-api/memory-allocation.rst b/Documentation/core-api/memory-allocation.rst
index 8b84eb4bdae7..83ae3021c89a 100644
--- a/Documentation/core-api/memory-allocation.rst
+++ b/Documentation/core-api/memory-allocation.rst
@@ -166,11 +166,11 @@  documentation. Note that `kvmalloc` may return memory that is not
 physically contiguous.
 
 If you need to allocate many identical objects you can use the slab
-cache allocator. The cache should be set up with kmem_cache_create() or
-kmem_cache_create_usercopy() before it can be used. The second function
-should be used if a part of the cache might be copied to the userspace.
-After the cache is created kmem_cache_alloc() and its convenience
-wrappers can allocate memory from that cache.
+cache allocator. The cache should be set up with kmem_cache_setup()
+before it can be used. The second function should be used if a part of
+the cache might be copied to the userspace. After the cache is created
+kmem_cache_alloc() and its convenience wrappers can allocate memory from
+that cache.
 
 When the allocated memory is no longer needed it must be freed.
 
diff --git a/include/linux/slab.h b/include/linux/slab.h
index 5b2da2cf31a8..41135ea03299 100644
--- a/include/linux/slab.h
+++ b/include/linux/slab.h
@@ -240,6 +240,27 @@  struct mem_cgroup;
  */
 bool slab_is_available(void);
 
+/**
+ * @align: The required alignment for the objects.
+ * @useroffset: Usercopy region offset
+ * @usersize: Usercopy region size
+ * @freeptr_offset: Custom offset for the free pointer in RCU caches
+ * @use_freeptr_offset: Whether a @freeptr_offset is used
+ * @ctor: A constructor for the objects.
+ */
+struct kmem_cache_args {
+	unsigned int align;
+	unsigned int useroffset;
+	unsigned int usersize;
+	unsigned int freeptr_offset;
+	bool use_freeptr_offset;
+	void (*ctor)(void *);
+};
+
+struct kmem_cache *kmem_cache_setup(const char *name, unsigned int object_size,
+				    struct kmem_cache_args *args,
+				    slab_flags_t flags);
+
 struct kmem_cache *kmem_cache_create(const char *name, unsigned int size,
 			unsigned int align, slab_flags_t flags,
 			void (*ctor)(void *));
diff --git a/mm/slab_common.c b/mm/slab_common.c
index 95db3702f8d6..515ad422cf30 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -202,22 +202,22 @@  struct kmem_cache *find_mergeable(unsigned int size, unsigned int align,
 }
 
 static struct kmem_cache *create_cache(const char *name,
-		unsigned int object_size, unsigned int freeptr_offset,
-		unsigned int align, slab_flags_t flags,
-		unsigned int useroffset, unsigned int usersize,
-		void (*ctor)(void *))
+				       unsigned int object_size,
+				       struct kmem_cache_args *args,
+				       slab_flags_t flags)
 {
 	struct kmem_cache *s;
 	int err;
 
-	if (WARN_ON(useroffset + usersize > object_size))
-		useroffset = usersize = 0;
+	if (WARN_ON(args->useroffset + args->usersize > object_size))
+		args->useroffset = args->usersize = 0;
 
 	/* If a custom freelist pointer is requested make sure it's sane. */
 	err = -EINVAL;
-	if (freeptr_offset != UINT_MAX &&
-	    (freeptr_offset >= object_size || !(flags & SLAB_TYPESAFE_BY_RCU) ||
-	     !IS_ALIGNED(freeptr_offset, sizeof(freeptr_t))))
+	if (args->use_freeptr_offset &&
+	    (args->freeptr_offset >= object_size ||
+	     !(flags & SLAB_TYPESAFE_BY_RCU) ||
+	     !IS_ALIGNED(args->freeptr_offset, sizeof(freeptr_t))))
 		goto out;
 
 	err = -ENOMEM;
@@ -227,12 +227,15 @@  static struct kmem_cache *create_cache(const char *name,
 
 	s->name = name;
 	s->size = s->object_size = object_size;
-	s->rcu_freeptr_offset = freeptr_offset;
-	s->align = align;
-	s->ctor = ctor;
+	if (args->use_freeptr_offset)
+		s->rcu_freeptr_offset = args->freeptr_offset;
+	else
+		s->rcu_freeptr_offset = UINT_MAX;
+	s->align = args->align;
+	s->ctor = args->ctor;
 #ifdef CONFIG_HARDENED_USERCOPY
-	s->useroffset = useroffset;
-	s->usersize = usersize;
+	s->useroffset = args->useroffset;
+	s->usersize = args->usersize;
 #endif
 	err = __kmem_cache_create(s, flags);
 	if (err)
@@ -248,12 +251,22 @@  static struct kmem_cache *create_cache(const char *name,
 	return ERR_PTR(err);
 }
 
-static struct kmem_cache *
-do_kmem_cache_create_usercopy(const char *name,
-		  unsigned int size, unsigned int freeptr_offset,
-		  unsigned int align, slab_flags_t flags,
-		  unsigned int useroffset, unsigned int usersize,
-		  void (*ctor)(void *))
+/**
+ * kmem_cache_setup - Create a kmem cache
+ * @name: A string which is used in /proc/slabinfo to identify this cache.
+ * @object_size: The size of objects to be created in this cache.
+ * @args: Arguments for the cache creation (see struct kmem_cache_args).
+ *
+ * Cannot be called within a interrupt, but can be interrupted.
+ * The @ctor is run when new pages are allocated by the cache.
+ *
+ * See %SLAB_* flags for an explanation of individual @flags.
+ *
+ * Return: a pointer to the cache on success, NULL on failure.
+ */
+struct kmem_cache *kmem_cache_setup(const char *name, unsigned int object_size,
+				    struct kmem_cache_args *args,
+				    slab_flags_t flags)
 {
 	struct kmem_cache *s = NULL;
 	const char *cache_name;
@@ -275,7 +288,7 @@  do_kmem_cache_create_usercopy(const char *name,
 
 	mutex_lock(&slab_mutex);
 
-	err = kmem_cache_sanity_check(name, size);
+	err = kmem_cache_sanity_check(name, object_size);
 	if (err) {
 		goto out_unlock;
 	}
@@ -296,12 +309,14 @@  do_kmem_cache_create_usercopy(const char *name,
 
 	/* Fail closed on bad usersize of useroffset values. */
 	if (!IS_ENABLED(CONFIG_HARDENED_USERCOPY) ||
-	    WARN_ON(!usersize && useroffset) ||
-	    WARN_ON(size < usersize || size - usersize < useroffset))
-		usersize = useroffset = 0;
-
-	if (!usersize)
-		s = __kmem_cache_alias(name, size, align, flags, ctor);
+	    WARN_ON(!args->usersize && args->useroffset) ||
+	    WARN_ON(object_size < args->usersize ||
+		    object_size - args->usersize < args->useroffset))
+		args->usersize = args->useroffset = 0;
+
+	if (!args->usersize)
+		s = __kmem_cache_alias(name, object_size, args->align, flags,
+				       args->ctor);
 	if (s)
 		goto out_unlock;
 
@@ -311,9 +326,8 @@  do_kmem_cache_create_usercopy(const char *name,
 		goto out_unlock;
 	}
 
-	s = create_cache(cache_name, size, freeptr_offset,
-			 calculate_alignment(flags, align, size),
-			 flags, useroffset, usersize, ctor);
+	args->align = calculate_alignment(flags, args->align, object_size);
+	s = create_cache(cache_name, object_size, args, flags);
 	if (IS_ERR(s)) {
 		err = PTR_ERR(s);
 		kfree_const(cache_name);
@@ -335,6 +349,7 @@  do_kmem_cache_create_usercopy(const char *name,
 	}
 	return s;
 }
+EXPORT_SYMBOL(kmem_cache_setup);
 
 /**
  * kmem_cache_create_usercopy - Create a cache with a region suitable
@@ -370,8 +385,14 @@  kmem_cache_create_usercopy(const char *name, unsigned int size,
 			   unsigned int useroffset, unsigned int usersize,
 			   void (*ctor)(void *))
 {
-	return do_kmem_cache_create_usercopy(name, size, UINT_MAX, align, flags,
-					     useroffset, usersize, ctor);
+	return kmem_cache_setup(name, size,
+				&(struct kmem_cache_args){
+					.align = align,
+					.ctor = ctor,
+					.useroffset = useroffset,
+					.usersize = usersize,
+				},
+				flags);
 }
 EXPORT_SYMBOL(kmem_cache_create_usercopy);
 
@@ -404,8 +425,12 @@  struct kmem_cache *
 kmem_cache_create(const char *name, unsigned int size, unsigned int align,
 		slab_flags_t flags, void (*ctor)(void *))
 {
-	return do_kmem_cache_create_usercopy(name, size, UINT_MAX, align, flags,
-					     0, 0, ctor);
+	return kmem_cache_setup(name, size,
+				&(struct kmem_cache_args){
+					.align = align,
+					.ctor = ctor,
+				},
+				flags);
 }
 EXPORT_SYMBOL(kmem_cache_create);
 
@@ -442,9 +467,12 @@  struct kmem_cache *kmem_cache_create_rcu(const char *name, unsigned int size,
 					 unsigned int freeptr_offset,
 					 slab_flags_t flags)
 {
-	return do_kmem_cache_create_usercopy(name, size, freeptr_offset, 0,
-					     flags | SLAB_TYPESAFE_BY_RCU, 0, 0,
-					     NULL);
+	return kmem_cache_setup(name, size,
+				&(struct kmem_cache_args){
+					.freeptr_offset = freeptr_offset,
+					.use_freeptr_offset = true,
+				},
+				flags | SLAB_TYPESAFE_BY_RCU);
 }
 EXPORT_SYMBOL(kmem_cache_create_rcu);