alistair23-linux/mm/slab.h

/* SPDX-License-Identifier: GPL-2.0 */
#ifndef MM_SLAB_H
#define MM_SLAB_H
/*
 * Internal slab definitions
 */

#ifdef CONFIG_SLOB
/*
 * Common fields provided in kmem_cache by all slab allocators
 * This struct is either used directly by the allocator (SLOB)
 * or the allocator must include definitions for all fields
 * provided in kmem_cache_common in their definition of kmem_cache.
 *
 * Once we can do anonymous structs (C11 standard) we could put a
 * anonymous struct definition in these allocators so that the
 * separate allocations in the kmem_cache structure of SLAB and
 * SLUB is no longer needed.
 */
struct kmem_cache {
	unsigned int object_size;/* The original size of the object */
	unsigned int size;	/* The aligned/padded/added on size  */
	unsigned int align;	/* Alignment as calculated */
	slab_flags_t flags;	/* Active flags on the slab */
	unsigned int useroffset;/* Usercopy region offset */
	unsigned int usersize;	/* Usercopy region size */
	const char *name;	/* Slab name for sysfs */
	int refcount;		/* Use counter */
	void (*ctor)(void *);	/* Called on object slot creation */
	struct list_head list;	/* List of all slab caches on the system */
};

#else /* !CONFIG_SLOB */

struct memcg_cache_array {
	struct rcu_head rcu;
	struct kmem_cache *entries[0];
};

/*
 * This is the main placeholder for memcg-related information in kmem caches.
 * Both the root cache and the child caches will have it. For the root cache,
 * this will hold a dynamically allocated array large enough to hold
 * information about the currently limited memcgs in the system. To allow the
 * array to be accessed without taking any locks, on relocation we free the old
 * version only after a grace period.
 *
 * Root and child caches hold different metadata.
 *
 * @root_cache:	Common to root and child caches.  NULL for root, pointer to
 *		the root cache for children.
 *
 * The following fields are specific to root caches.
 *
 * @memcg_caches: kmemcg ID indexed table of child caches.  This table is
 *		used to index child cachces during allocation and cleared
 *		early during shutdown.
 *
 * @root_caches_node: List node for slab_root_caches list.
 *
 * @children:	List of all child caches.  While the child caches are also
 *		reachable through @memcg_caches, a child cache remains on
 *		this list until it is actually destroyed.
 *
 * The following fields are specific to child caches.
 *
 * @memcg:	Pointer to the memcg this cache belongs to.
 *
 * @children_node: List node for @root_cache->children list.
 *
 * @kmem_caches_node: List node for @memcg->kmem_caches list.
 */
struct memcg_cache_params {
	struct kmem_cache *root_cache;
	union {
		struct {
			struct memcg_cache_array __rcu *memcg_caches;
			struct list_head __root_caches_node;
			struct list_head children;
			bool dying;
		};
		struct {
			struct mem_cgroup *memcg;
			struct list_head children_node;
			struct list_head kmem_caches_node;
			struct percpu_ref refcnt;

			void (*work_fn)(struct kmem_cache *);
			union {
				struct rcu_head rcu_head;
				struct work_struct work;
			};
		};
	};
};
#endif /* CONFIG_SLOB */

#ifdef CONFIG_SLAB
#include <linux/slab_def.h>
#endif

#ifdef CONFIG_SLUB
#include <linux/slub_def.h>
#endif

#include <linux/memcontrol.h>
#include <linux/fault-inject.h>
#include <linux/kasan.h>
#include <linux/kmemleak.h>
#include <linux/random.h>
#include <linux/sched/mm.h>

/*
 * State of the slab allocator.
 *
 * This is used to describe the states of the allocator during bootup.
 * Allocators use this to gradually bootstrap themselves. Most allocators
 * have the problem that the structures used for managing slab caches are
 * allocated from slab caches themselves.
 */
enum slab_state {
	DOWN,			/* No slab functionality yet */
	PARTIAL,		/* SLUB: kmem_cache_node available */
	PARTIAL_NODE,		/* SLAB: kmalloc size for node struct available */
	UP,			/* Slab caches usable but not all extras yet */
	FULL			/* Everything is working */
};

extern enum slab_state slab_state;

/* The slab cache mutex protects the management structures during changes */
extern struct mutex slab_mutex;

/* The list of all slab caches on the system */
extern struct list_head slab_caches;

/* The slab cache that manages slab cache information */
extern struct kmem_cache *kmem_cache;

/* A table of kmalloc cache names and sizes */
extern const struct kmalloc_info_struct {
	const char *name;
	unsigned int size;
} kmalloc_info[];

#ifndef CONFIG_SLOB
/* Kmalloc array related functions */
void setup_kmalloc_cache_index_table(void);
void create_kmalloc_caches(slab_flags_t);

/* Find the kmalloc slab corresponding for a certain size */
struct kmem_cache *kmalloc_slab(size_t, gfp_t);
#endif


/* Functions provided by the slab allocators */
int __kmem_cache_create(struct kmem_cache *, slab_flags_t flags);

struct kmem_cache *create_kmalloc_cache(const char *name, unsigned int size,
			slab_flags_t flags, unsigned int useroffset,
			unsigned int usersize);
extern void create_boot_cache(struct kmem_cache *, const char *name,
			unsigned int size, slab_flags_t flags,
			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 *));
#ifndef CONFIG_SLOB
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(unsigned int object_size,
	slab_flags_t flags, const char *name,
	void (*ctor)(void *));
#else
static inline struct kmem_cache *
__kmem_cache_alias(const char *name, unsigned int size, unsigned int align,
		   slab_flags_t flags, void (*ctor)(void *))
{ return NULL; }

static inline slab_flags_t kmem_cache_flags(unsigned int object_size,
	slab_flags_t flags, const char *name,
	void (*ctor)(void *))
{
	return flags;
}
#endif


/* Legal flag mask for kmem_cache_create(), for various configurations */
#define SLAB_CORE_FLAGS (SLAB_HWCACHE_ALIGN | SLAB_CACHE_DMA | \
			 SLAB_CACHE_DMA32 | SLAB_PANIC | \
			 SLAB_TYPESAFE_BY_RCU | SLAB_DEBUG_OBJECTS )

#if defined(CONFIG_DEBUG_SLAB)
#define SLAB_DEBUG_FLAGS (SLAB_RED_ZONE | SLAB_POISON | SLAB_STORE_USER)
#elif defined(CONFIG_SLUB_DEBUG)
#define SLAB_DEBUG_FLAGS (SLAB_RED_ZONE | SLAB_POISON | SLAB_STORE_USER | \
			  SLAB_TRACE | SLAB_CONSISTENCY_CHECKS)
#else
#define SLAB_DEBUG_FLAGS (0)
#endif

#if defined(CONFIG_SLAB)
#define SLAB_CACHE_FLAGS (SLAB_MEM_SPREAD | SLAB_NOLEAKTRACE | \
			  SLAB_RECLAIM_ACCOUNT | SLAB_TEMPORARY | \
			  SLAB_ACCOUNT)
#elif defined(CONFIG_SLUB)
#define SLAB_CACHE_FLAGS (SLAB_NOLEAKTRACE | SLAB_RECLAIM_ACCOUNT | \
			  SLAB_TEMPORARY | SLAB_ACCOUNT)
#else
#define SLAB_CACHE_FLAGS (0)
#endif

/* Common flags available with current configuration */
#define CACHE_CREATE_MASK (SLAB_CORE_FLAGS | SLAB_DEBUG_FLAGS | SLAB_CACHE_FLAGS)

/* Common flags permitted for kmem_cache_create */
#define SLAB_FLAGS_PERMITTED (SLAB_CORE_FLAGS | \
			      SLAB_RED_ZONE | \
			      SLAB_POISON | \
			      SLAB_STORE_USER | \
			      SLAB_TRACE | \
			      SLAB_CONSISTENCY_CHECKS | \
			      SLAB_MEM_SPREAD | \
			      SLAB_NOLEAKTRACE | \
			      SLAB_RECLAIM_ACCOUNT | \
			      SLAB_TEMPORARY | \
			      SLAB_ACCOUNT)

bool __kmem_cache_empty(struct kmem_cache *);
int __kmem_cache_shutdown(struct kmem_cache *);
void __kmem_cache_release(struct kmem_cache *);
int __kmem_cache_shrink(struct kmem_cache *);
void __kmemcg_cache_deactivate(struct kmem_cache *s);
void __kmemcg_cache_deactivate_after_rcu(struct kmem_cache *s);
void slab_kmem_cache_release(struct kmem_cache *);
void kmem_cache_shrink_all(struct kmem_cache *s);

struct seq_file;
struct file;

struct slabinfo {
	unsigned long active_objs;
	unsigned long num_objs;
	unsigned long active_slabs;
	unsigned long num_slabs;
	unsigned long shared_avail;
	unsigned int limit;
	unsigned int batchcount;
	unsigned int shared;
	unsigned int objects_per_slab;
	unsigned int cache_order;
};

void get_slabinfo(struct kmem_cache *s, struct slabinfo *sinfo);
void slabinfo_show_stats(struct seq_file *m, struct kmem_cache *s);
ssize_t slabinfo_write(struct file *file, const char __user *buffer,
		       size_t count, loff_t *ppos);

/*
 * Generic implementation of bulk operations
 * These are useful for situations in which the allocator cannot
 * perform optimizations. In that case segments of the object listed
 * may be allocated or freed using these operations.
 */
void __kmem_cache_free_bulk(struct kmem_cache *, size_t, void **);
int __kmem_cache_alloc_bulk(struct kmem_cache *, gfp_t, size_t, void **);

static inline int cache_vmstat_idx(struct kmem_cache *s)
{
	return (s->flags & SLAB_RECLAIM_ACCOUNT) ?
		NR_SLAB_RECLAIMABLE : NR_SLAB_UNRECLAIMABLE;
}

#ifdef CONFIG_MEMCG_KMEM

/* List of all root caches. */
extern struct list_head		slab_root_caches;
#define root_caches_node	memcg_params.__root_caches_node

/*
 * Iterate over all memcg caches of the given root cache. The caller must hold
 * slab_mutex.
 */
#define for_each_memcg_cache(iter, root) \
	list_for_each_entry(iter, &(root)->memcg_params.children, \
			    memcg_params.children_node)

static inline bool is_root_cache(struct kmem_cache *s)
{
	return !s->memcg_params.root_cache;
}

static inline bool slab_equal_or_root(struct kmem_cache *s,
				      struct kmem_cache *p)
{
	return p == s || p == s->memcg_params.root_cache;
}

/*
 * We use suffixes to the name in memcg because we can't have caches
 * created in the system with the same name. But when we print them
 * locally, better refer to them with the base name
 */
static inline const char *cache_name(struct kmem_cache *s)
{
	if (!is_root_cache(s))
		s = s->memcg_params.root_cache;
	return s->name;
}

static inline struct kmem_cache *memcg_root_cache(struct kmem_cache *s)
{
	if (is_root_cache(s))
		return s;
	return s->memcg_params.root_cache;
}

/*
 * Expects a pointer to a slab page. Please note, that PageSlab() check
 * isn't sufficient, as it returns true also for tail compound slab pages,
 * which do not have slab_cache pointer set.
 * So this function assumes that the page can pass PageSlab() && !PageTail()
 * check.
 *
 * The kmem_cache can be reparented asynchronously. The caller must ensure
 * the memcg lifetime, e.g. by taking rcu_read_lock() or cgroup_mutex.
 */
static inline struct mem_cgroup *memcg_from_slab_page(struct page *page)
{
	struct kmem_cache *s;

	s = READ_ONCE(page->slab_cache);
	if (s && !is_root_cache(s))
		return READ_ONCE(s->memcg_params.memcg);

	return NULL;
}

/*
 * Charge the slab page belonging to the non-root kmem_cache.
 * Can be called for non-root kmem_caches only.
 */
static __always_inline int memcg_charge_slab(struct page *page,
					     gfp_t gfp, int order,
					     struct kmem_cache *s)
{
	struct mem_cgroup *memcg;
	struct lruvec *lruvec;
	int ret;

	rcu_read_lock();
	memcg = READ_ONCE(s->memcg_params.memcg);
	while (memcg && !css_tryget_online(&memcg->css))
		memcg = parent_mem_cgroup(memcg);
	rcu_read_unlock();

	if (unlikely(!memcg || mem_cgroup_is_root(memcg))) {
		mod_node_page_state(page_pgdat(page), cache_vmstat_idx(s),
				    (1 << order));
		percpu_ref_get_many(&s->memcg_params.refcnt, 1 << order);
		return 0;
	}

	ret = memcg_kmem_charge_memcg(page, gfp, order, memcg);
	if (ret)
		goto out;

	lruvec = mem_cgroup_lruvec(page_pgdat(page), memcg);
	mod_lruvec_state(lruvec, cache_vmstat_idx(s), 1 << order);

	/* transer try_charge() page references to kmem_cache */
	percpu_ref_get_many(&s->memcg_params.refcnt, 1 << order);
	css_put_many(&memcg->css, 1 << order);
out:
	css_put(&memcg->css);
	return ret;
}

/*
 * Uncharge a slab page belonging to a non-root kmem_cache.
 * Can be called for non-root kmem_caches only.
 */
static __always_inline void memcg_uncharge_slab(struct page *page, int order,
						struct kmem_cache *s)
{
	struct mem_cgroup *memcg;
	struct lruvec *lruvec;

	rcu_read_lock();
	memcg = READ_ONCE(s->memcg_params.memcg);
	if (likely(!mem_cgroup_is_root(memcg))) {
		lruvec = mem_cgroup_lruvec(page_pgdat(page), memcg);
		mod_lruvec_state(lruvec, cache_vmstat_idx(s), -(1 << order));
		memcg_kmem_uncharge_memcg(page, order, memcg);
	} else {
		mod_node_page_state(page_pgdat(page), cache_vmstat_idx(s),
				    -(1 << order));
	}
	rcu_read_unlock();

	percpu_ref_put_many(&s->memcg_params.refcnt, 1 << order);
}

extern void slab_init_memcg_params(struct kmem_cache *);
extern void memcg_link_cache(struct kmem_cache *s, struct mem_cgroup *memcg);

#else /* CONFIG_MEMCG_KMEM */

/* If !memcg, all caches are root. */
#define slab_root_caches	slab_caches
#define root_caches_node	list

#define for_each_memcg_cache(iter, root) \
	for ((void)(iter), (void)(root); 0; )

static inline bool is_root_cache(struct kmem_cache *s)
{
	return true;
}

static inline bool slab_equal_or_root(struct kmem_cache *s,
				      struct kmem_cache *p)
{
	return s == p;
}

static inline const char *cache_name(struct kmem_cache *s)
{
	return s->name;
}

static inline struct kmem_cache *memcg_root_cache(struct kmem_cache *s)
{
	return s;
}

static inline struct mem_cgroup *memcg_from_slab_page(struct page *page)
{
	return NULL;
}

static inline int memcg_charge_slab(struct page *page, gfp_t gfp, int order,
				    struct kmem_cache *s)
{
	return 0;
}

static inline void memcg_uncharge_slab(struct page *page, int order,
				       struct kmem_cache *s)
{
}

static inline void slab_init_memcg_params(struct kmem_cache *s)
{
}

static inline void memcg_link_cache(struct kmem_cache *s,
				    struct mem_cgroup *memcg)
{
}

#endif /* CONFIG_MEMCG_KMEM */

static inline struct kmem_cache *virt_to_cache(const void *obj)
{
	struct page *page;

	page = virt_to_head_page(obj);
	if (WARN_ONCE(!PageSlab(page), "%s: Object is not a Slab page!\n",
					__func__))
		return NULL;
	return page->slab_cache;
}

static __always_inline int charge_slab_page(struct page *page,
					    gfp_t gfp, int order,
					    struct kmem_cache *s)
{
	if (is_root_cache(s)) {
		mod_node_page_state(page_pgdat(page), cache_vmstat_idx(s),
				    1 << order);
		return 0;
	}

	return memcg_charge_slab(page, gfp, order, s);
}

static __always_inline void uncharge_slab_page(struct page *page, int order,
					       struct kmem_cache *s)
{
	if (is_root_cache(s)) {
		mod_node_page_state(page_pgdat(page), cache_vmstat_idx(s),
				    -(1 << order));
		return;
	}

	memcg_uncharge_slab(page, order, s);
}

static inline struct kmem_cache *cache_from_obj(struct kmem_cache *s, void *x)
{
	struct kmem_cache *cachep;

	/*
	 * When kmemcg is not being used, both assignments should return the
	 * same value. but we don't want to pay the assignment price in that
	 * case. If it is not compiled in, the compiler should be smart enough
	 * to not do even the assignment. In that case, slab_equal_or_root
	 * will also be a constant.
	 */
	if (!memcg_kmem_enabled() &&
	    !IS_ENABLED(CONFIG_SLAB_FREELIST_HARDENED) &&
	    !unlikely(s->flags & SLAB_CONSISTENCY_CHECKS))
		return s;

	cachep = virt_to_cache(x);
	WARN_ONCE(cachep && !slab_equal_or_root(cachep, s),
		  "%s: Wrong slab cache. %s but object is from %s\n",
		  __func__, s->name, cachep->name);
	return cachep;
}

static inline size_t slab_ksize(const struct kmem_cache *s)
{
#ifndef CONFIG_SLUB
	return s->object_size;

#else /* CONFIG_SLUB */
# ifdef CONFIG_SLUB_DEBUG
	/*
	 * Debugging requires use of the padding between object
	 * and whatever may come after it.
	 */
	if (s->flags & (SLAB_RED_ZONE | SLAB_POISON))
		return s->object_size;
# endif
	if (s->flags & SLAB_KASAN)
		return s->object_size;
	/*
	 * If we have the need to store the freelist pointer
	 * back there or track user information then we can
	 * only use the space before that information.
	 */
	if (s->flags & (SLAB_TYPESAFE_BY_RCU | SLAB_STORE_USER))
		return s->inuse;
	/*
	 * Else we can use all the padding etc for the allocation
	 */
	return s->size;
#endif
}

static inline struct kmem_cache *slab_pre_alloc_hook(struct kmem_cache *s,
						     gfp_t flags)
{
	flags &= gfp_allowed_mask;

	fs_reclaim_acquire(flags);
	fs_reclaim_release(flags);

	might_sleep_if(gfpflags_allow_blocking(flags));

	if (should_failslab(s, flags))
		return NULL;

	if (memcg_kmem_enabled() &&
	    ((flags & __GFP_ACCOUNT) || (s->flags & SLAB_ACCOUNT)))
		return memcg_kmem_get_cache(s);

	return s;
}

static inline void slab_post_alloc_hook(struct kmem_cache *s, gfp_t flags,
					size_t size, void **p)
{
	size_t i;

	flags &= gfp_allowed_mask;
	for (i = 0; i < size; i++) {
		p[i] = kasan_slab_alloc(s, p[i], flags);
		/* As p[i] might get tagged, call kmemleak hook after KASAN. */
		kmemleak_alloc_recursive(p[i], s->object_size, 1,
					 s->flags, flags);
	}

	if (memcg_kmem_enabled())
		memcg_kmem_put_cache(s);
}

#ifndef CONFIG_SLOB
/*
 * The slab lists for all objects.
 */
struct kmem_cache_node {
	spinlock_t list_lock;

#ifdef CONFIG_SLAB
	struct list_head slabs_partial;	/* partial list first, better asm code */
	struct list_head slabs_full;
	struct list_head slabs_free;
	unsigned long total_slabs;	/* length of all slab lists */
	unsigned long free_slabs;	/* length of free slab list only */
	unsigned long free_objects;
	unsigned int free_limit;
	unsigned int colour_next;	/* Per-node cache coloring */
	struct array_cache *shared;	/* shared per node */
	struct alien_cache **alien;	/* on other nodes */
	unsigned long next_reap;	/* updated without locking */
	int free_touched;		/* updated without locking */
#endif

#ifdef CONFIG_SLUB
	unsigned long nr_partial;
	struct list_head partial;
#ifdef CONFIG_SLUB_DEBUG
	atomic_long_t nr_slabs;
	atomic_long_t total_objects;
	struct list_head full;
#endif
#endif

};

static inline struct kmem_cache_node *get_node(struct kmem_cache *s, int node)
{
	return s->node[node];
}

/*
 * Iterator over all nodes. The body will be executed for each node that has
 * a kmem_cache_node structure allocated (which is true for all online nodes)
 */
#define for_each_kmem_cache_node(__s, __node, __n) \
	for (__node = 0; __node < nr_node_ids; __node++) \
		 if ((__n = get_node(__s, __node)))

#endif

void *slab_start(struct seq_file *m, loff_t *pos);
void *slab_next(struct seq_file *m, void *p, loff_t *pos);
void slab_stop(struct seq_file *m, void *p);
void *memcg_slab_start(struct seq_file *m, loff_t *pos);
void *memcg_slab_next(struct seq_file *m, void *p, loff_t *pos);
void memcg_slab_stop(struct seq_file *m, void *p);
int memcg_slab_show(struct seq_file *m, void *p);

#if defined(CONFIG_SLAB) || defined(CONFIG_SLUB_DEBUG)
void dump_unreclaimable_slab(void);
#else
static inline void dump_unreclaimable_slab(void)
{
}
#endif

void ___cache_free(struct kmem_cache *cache, void *x, unsigned long addr);

#ifdef CONFIG_SLAB_FREELIST_RANDOM
int cache_random_seq_create(struct kmem_cache *cachep, unsigned int count,
			gfp_t gfp);
void cache_random_seq_destroy(struct kmem_cache *cachep);
#else
static inline int cache_random_seq_create(struct kmem_cache *cachep,
					unsigned int count, gfp_t gfp)
{
	return 0;
}
static inline void cache_random_seq_destroy(struct kmem_cache *cachep) { }
#endif /* CONFIG_SLAB_FREELIST_RANDOM */

static inline bool slab_want_init_on_alloc(gfp_t flags, struct kmem_cache *c)
{
	if (static_branch_unlikely(&init_on_alloc)) {
		if (c->ctor)
			return false;
		if (c->flags & (SLAB_TYPESAFE_BY_RCU | SLAB_POISON))
			return flags & __GFP_ZERO;
		return true;
	}
	return flags & __GFP_ZERO;
}

static inline bool slab_want_init_on_free(struct kmem_cache *c)
{
	if (static_branch_unlikely(&init_on_free))
		return !(c->ctor ||
			 (c->flags & (SLAB_TYPESAFE_BY_RCU | SLAB_POISON)));
	return false;
}

#endif /* MM_SLAB_H */