xref: /openbmc/linux/mm/slab.c (revision 8957261c)

// SPDX-License-Identifier: GPL-2.0
/*
 * linux/mm/slab.c
 * Written by Mark Hemment, 1996/97.
 * (markhe@nextd.demon.co.uk)
 *
 * kmem_cache_destroy() + some cleanup - 1999 Andrea Arcangeli
 *
 * Major cleanup, different bufctl logic, per-cpu arrays
 *	(c) 2000 Manfred Spraul
 *
 * Cleanup, make the head arrays unconditional, preparation for NUMA
 * 	(c) 2002 Manfred Spraul
 *
 * An implementation of the Slab Allocator as described in outline in;
 *	UNIX Internals: The New Frontiers by Uresh Vahalia
 *	Pub: Prentice Hall	ISBN 0-13-101908-2
 * or with a little more detail in;
 *	The Slab Allocator: An Object-Caching Kernel Memory Allocator
 *	Jeff Bonwick (Sun Microsystems).
 *	Presented at: USENIX Summer 1994 Technical Conference
 *
 * The memory is organized in caches, one cache for each object type.
 * (e.g. inode_cache, dentry_cache, buffer_head, vm_area_struct)
 * Each cache consists out of many slabs (they are small (usually one
 * page long) and always contiguous), and each slab contains multiple
 * initialized objects.
 *
 * This means, that your constructor is used only for newly allocated
 * slabs and you must pass objects with the same initializations to
 * kmem_cache_free.
 *
 * Each cache can only support one memory type (GFP_DMA, GFP_HIGHMEM,
 * normal). If you need a special memory type, then must create a new
 * cache for that memory type.
 *
 * In order to reduce fragmentation, the slabs are sorted in 3 groups:
 *   full slabs with 0 free objects
 *   partial slabs
 *   empty slabs with no allocated objects
 *
 * If partial slabs exist, then new allocations come from these slabs,
 * otherwise from empty slabs or new slabs are allocated.
 *
 * kmem_cache_destroy() CAN CRASH if you try to allocate from the cache
 * during kmem_cache_destroy(). The caller must prevent concurrent allocs.
 *
 * Each cache has a short per-cpu head array, most allocs
 * and frees go into that array, and if that array overflows, then 1/2
 * of the entries in the array are given back into the global cache.
 * The head array is strictly LIFO and should improve the cache hit rates.
 * On SMP, it additionally reduces the spinlock operations.
 *
 * The c_cpuarray may not be read with enabled local interrupts -
 * it's changed with a smp_call_function().
 *
 * SMP synchronization:
 *  constructors and destructors are called without any locking.
 *  Several members in struct kmem_cache and struct slab never change, they
 *	are accessed without any locking.
 *  The per-cpu arrays are never accessed from the wrong cpu, no locking,
 *  	and local interrupts are disabled so slab code is preempt-safe.
 *  The non-constant members are protected with a per-cache irq spinlock.
 *
 * Many thanks to Mark Hemment, who wrote another per-cpu slab patch
 * in 2000 - many ideas in the current implementation are derived from
 * his patch.
 *
 * Further notes from the original documentation:
 *
 * 11 April '97.  Started multi-threading - markhe
 *	The global cache-chain is protected by the mutex 'slab_mutex'.
 *	The sem is only needed when accessing/extending the cache-chain, which
 *	can never happen inside an interrupt (kmem_cache_create(),
 *	kmem_cache_shrink() and kmem_cache_reap()).
 *
 *	At present, each engine can be growing a cache.  This should be blocked.
 *
 * 15 March 2005. NUMA slab allocator.
 *	Shai Fultheim <shai@scalex86.org>.
 *	Shobhit Dayal <shobhit@calsoftinc.com>
 *	Alok N Kataria <alokk@calsoftinc.com>
 *	Christoph Lameter <christoph@lameter.com>
 *
 *	Modified the slab allocator to be node aware on NUMA systems.
 *	Each node has its own list of partial, free and full slabs.
 *	All object allocations for a node occur from node specific slab lists.
 */

#include	<linux/slab.h>
#include	<linux/mm.h>
#include	<linux/poison.h>
#include	<linux/swap.h>
#include	<linux/cache.h>
#include	<linux/interrupt.h>
#include	<linux/init.h>
#include	<linux/compiler.h>
#include	<linux/cpuset.h>
#include	<linux/proc_fs.h>
#include	<linux/seq_file.h>
#include	<linux/notifier.h>
#include	<linux/kallsyms.h>
#include	<linux/kfence.h>
#include	<linux/cpu.h>
#include	<linux/sysctl.h>
#include	<linux/module.h>
#include	<linux/rcupdate.h>
#include	<linux/string.h>
#include	<linux/uaccess.h>
#include	<linux/nodemask.h>
#include	<linux/kmemleak.h>
#include	<linux/mempolicy.h>
#include	<linux/mutex.h>
#include	<linux/fault-inject.h>
#include	<linux/rtmutex.h>
#include	<linux/reciprocal_div.h>
#include	<linux/debugobjects.h>
#include	<linux/memory.h>
#include	<linux/prefetch.h>
#include	<linux/sched/task_stack.h>

#include	<net/sock.h>

#include	<asm/cacheflush.h>
#include	<asm/tlbflush.h>
#include	<asm/page.h>

#include <trace/events/kmem.h>

#include	"internal.h"

#include	"slab.h"

/*
 * DEBUG	- 1 for kmem_cache_create() to honour; SLAB_RED_ZONE & SLAB_POISON.
 *		  0 for faster, smaller code (especially in the critical paths).
 *
 * STATS	- 1 to collect stats for /proc/slabinfo.
 *		  0 for faster, smaller code (especially in the critical paths).
 *
 * FORCED_DEBUG	- 1 enables SLAB_RED_ZONE and SLAB_POISON (if possible)
 */

#ifdef CONFIG_DEBUG_SLAB
#define	DEBUG		1
#define	STATS		1
#define	FORCED_DEBUG	1
#else
#define	DEBUG		0
#define	STATS		0
#define	FORCED_DEBUG	0
#endif

/* Shouldn't this be in a header file somewhere? */
#define	BYTES_PER_WORD		sizeof(void *)
#define	REDZONE_ALIGN		max(BYTES_PER_WORD, __alignof__(unsigned long long))

#ifndef ARCH_KMALLOC_FLAGS
#define ARCH_KMALLOC_FLAGS SLAB_HWCACHE_ALIGN
#endif

#define FREELIST_BYTE_INDEX (((PAGE_SIZE >> BITS_PER_BYTE) \
				<= SLAB_OBJ_MIN_SIZE) ? 1 : 0)

#if FREELIST_BYTE_INDEX
typedef unsigned char freelist_idx_t;
#else
typedef unsigned short freelist_idx_t;
#endif

#define SLAB_OBJ_MAX_NUM ((1 << sizeof(freelist_idx_t) * BITS_PER_BYTE) - 1)

/*
 * struct array_cache
 *
 * Purpose:
 * - LIFO ordering, to hand out cache-warm objects from _alloc
 * - reduce the number of linked list operations
 * - reduce spinlock operations
 *
 * The limit is stored in the per-cpu structure to reduce the data cache
 * footprint.
 *
 */
struct array_cache {
	unsigned int avail;
	unsigned int limit;
	unsigned int batchcount;
	unsigned int touched;
	void *entry[];	/*
			 * Must have this definition in here for the proper
			 * alignment of array_cache. Also simplifies accessing
			 * the entries.
			 */
};

struct alien_cache {
	spinlock_t lock;
	struct array_cache ac;
};

/*
 * Need this for bootstrapping a per node allocator.
 */
#define NUM_INIT_LISTS (2 * MAX_NUMNODES)
static struct kmem_cache_node __initdata init_kmem_cache_node[NUM_INIT_LISTS];
#define	CACHE_CACHE 0
#define	SIZE_NODE (MAX_NUMNODES)

static int drain_freelist(struct kmem_cache *cache,
			struct kmem_cache_node *n, int tofree);
static void free_block(struct kmem_cache *cachep, void **objpp, int len,
			int node, struct list_head *list);
static void slabs_destroy(struct kmem_cache *cachep, struct list_head *list);
static int enable_cpucache(struct kmem_cache *cachep, gfp_t gfp);
static void cache_reap(struct work_struct *unused);

static inline void fixup_objfreelist_debug(struct kmem_cache *cachep,
						void **list);
static inline void fixup_slab_list(struct kmem_cache *cachep,
				struct kmem_cache_node *n, struct slab *slab,
				void **list);

#define INDEX_NODE kmalloc_index(sizeof(struct kmem_cache_node))

static void kmem_cache_node_init(struct kmem_cache_node *parent)
{
	INIT_LIST_HEAD(&parent->slabs_full);
	INIT_LIST_HEAD(&parent->slabs_partial);
	INIT_LIST_HEAD(&parent->slabs_free);
	parent->total_slabs = 0;
	parent->free_slabs = 0;
	parent->shared = NULL;
	parent->alien = NULL;
	parent->colour_next = 0;
	raw_spin_lock_init(&parent->list_lock);
	parent->free_objects = 0;
	parent->free_touched = 0;
}

#define MAKE_LIST(cachep, listp, slab, nodeid)				\
	do {								\
		INIT_LIST_HEAD(listp);					\
		list_splice(&get_node(cachep, nodeid)->slab, listp);	\
	} while (0)

#define	MAKE_ALL_LISTS(cachep, ptr, nodeid)				\
	do {								\
	MAKE_LIST((cachep), (&(ptr)->slabs_full), slabs_full, nodeid);	\
	MAKE_LIST((cachep), (&(ptr)->slabs_partial), slabs_partial, nodeid); \
	MAKE_LIST((cachep), (&(ptr)->slabs_free), slabs_free, nodeid);	\
	} while (0)

#define CFLGS_OBJFREELIST_SLAB	((slab_flags_t __force)0x40000000U)
#define CFLGS_OFF_SLAB		((slab_flags_t __force)0x80000000U)
#define	OBJFREELIST_SLAB(x)	((x)->flags & CFLGS_OBJFREELIST_SLAB)
#define	OFF_SLAB(x)	((x)->flags & CFLGS_OFF_SLAB)

#define BATCHREFILL_LIMIT	16
/*
 * Optimization question: fewer reaps means less probability for unnecessary
 * cpucache drain/refill cycles.
 *
 * OTOH the cpuarrays can contain lots of objects,
 * which could lock up otherwise freeable slabs.
 */
#define REAPTIMEOUT_AC		(2*HZ)
#define REAPTIMEOUT_NODE	(4*HZ)

#if STATS
#define	STATS_INC_ACTIVE(x)	((x)->num_active++)
#define	STATS_DEC_ACTIVE(x)	((x)->num_active--)
#define	STATS_INC_ALLOCED(x)	((x)->num_allocations++)
#define	STATS_INC_GROWN(x)	((x)->grown++)
#define	STATS_ADD_REAPED(x, y)	((x)->reaped += (y))
#define	STATS_SET_HIGH(x)						\
	do {								\
		if ((x)->num_active > (x)->high_mark)			\
			(x)->high_mark = (x)->num_active;		\
	} while (0)
#define	STATS_INC_ERR(x)	((x)->errors++)
#define	STATS_INC_NODEALLOCS(x)	((x)->node_allocs++)
#define	STATS_INC_NODEFREES(x)	((x)->node_frees++)
#define STATS_INC_ACOVERFLOW(x)   ((x)->node_overflow++)
#define	STATS_SET_FREEABLE(x, i)					\
	do {								\
		if ((x)->max_freeable < i)				\
			(x)->max_freeable = i;				\
	} while (0)
#define STATS_INC_ALLOCHIT(x)	atomic_inc(&(x)->allochit)
#define STATS_INC_ALLOCMISS(x)	atomic_inc(&(x)->allocmiss)
#define STATS_INC_FREEHIT(x)	atomic_inc(&(x)->freehit)
#define STATS_INC_FREEMISS(x)	atomic_inc(&(x)->freemiss)
#else
#define	STATS_INC_ACTIVE(x)	do { } while (0)
#define	STATS_DEC_ACTIVE(x)	do { } while (0)
#define	STATS_INC_ALLOCED(x)	do { } while (0)
#define	STATS_INC_GROWN(x)	do { } while (0)
#define	STATS_ADD_REAPED(x, y)	do { (void)(y); } while (0)
#define	STATS_SET_HIGH(x)	do { } while (0)
#define	STATS_INC_ERR(x)	do { } while (0)
#define	STATS_INC_NODEALLOCS(x)	do { } while (0)
#define	STATS_INC_NODEFREES(x)	do { } while (0)
#define STATS_INC_ACOVERFLOW(x)   do { } while (0)
#define	STATS_SET_FREEABLE(x, i) do { } while (0)
#define STATS_INC_ALLOCHIT(x)	do { } while (0)
#define STATS_INC_ALLOCMISS(x)	do { } while (0)
#define STATS_INC_FREEHIT(x)	do { } while (0)
#define STATS_INC_FREEMISS(x)	do { } while (0)
#endif

#if DEBUG

/*
 * memory layout of objects:
 * 0		: objp
 * 0 .. cachep->obj_offset - BYTES_PER_WORD - 1: padding. This ensures that
 * 		the end of an object is aligned with the end of the real
 * 		allocation. Catches writes behind the end of the allocation.
 * cachep->obj_offset - BYTES_PER_WORD .. cachep->obj_offset - 1:
 * 		redzone word.
 * cachep->obj_offset: The real object.
 * cachep->size - 2* BYTES_PER_WORD: redzone word [BYTES_PER_WORD long]
 * cachep->size - 1* BYTES_PER_WORD: last caller address
 *					[BYTES_PER_WORD long]
 */
static int obj_offset(struct kmem_cache *cachep)
{
	return cachep->obj_offset;
}

static unsigned long long *dbg_redzone1(struct kmem_cache *cachep, void *objp)
{
	BUG_ON(!(cachep->flags & SLAB_RED_ZONE));
	return (unsigned long long *) (objp + obj_offset(cachep) -
				      sizeof(unsigned long long));
}

static unsigned long long *dbg_redzone2(struct kmem_cache *cachep, void *objp)
{
	BUG_ON(!(cachep->flags & SLAB_RED_ZONE));
	if (cachep->flags & SLAB_STORE_USER)
		return (unsigned long long *)(objp + cachep->size -
					      sizeof(unsigned long long) -
					      REDZONE_ALIGN);
	return (unsigned long long *) (objp + cachep->size -
				       sizeof(unsigned long long));
}

static void **dbg_userword(struct kmem_cache *cachep, void *objp)
{
	BUG_ON(!(cachep->flags & SLAB_STORE_USER));
	return (void **)(objp + cachep->size - BYTES_PER_WORD);
}

#else

#define obj_offset(x)			0
#define dbg_redzone1(cachep, objp)	({BUG(); (unsigned long long *)NULL;})
#define dbg_redzone2(cachep, objp)	({BUG(); (unsigned long long *)NULL;})
#define dbg_userword(cachep, objp)	({BUG(); (void **)NULL;})

#endif

/*
 * Do not go above this order unless 0 objects fit into the slab or
 * overridden on the command line.
 */
#define	SLAB_MAX_ORDER_HI	1
#define	SLAB_MAX_ORDER_LO	0
static int slab_max_order = SLAB_MAX_ORDER_LO;
static bool slab_max_order_set __initdata;

static inline void *index_to_obj(struct kmem_cache *cache,
				 const struct slab *slab, unsigned int idx)
{
	return slab->s_mem + cache->size * idx;
}

#define BOOT_CPUCACHE_ENTRIES	1
/* internal cache of cache description objs */
static struct kmem_cache kmem_cache_boot = {
	.batchcount = 1,
	.limit = BOOT_CPUCACHE_ENTRIES,
	.shared = 1,
	.size = sizeof(struct kmem_cache),
	.name = "kmem_cache",
};

static DEFINE_PER_CPU(struct delayed_work, slab_reap_work);

static inline struct array_cache *cpu_cache_get(struct kmem_cache *cachep)
{
	return this_cpu_ptr(cachep->cpu_cache);
}

/*
 * Calculate the number of objects and left-over bytes for a given buffer size.
 */
static unsigned int cache_estimate(unsigned long gfporder, size_t buffer_size,
		slab_flags_t flags, size_t *left_over)
{
	unsigned int num;
	size_t slab_size = PAGE_SIZE << gfporder;

	/*
	 * The slab management structure can be either off the slab or
	 * on it. For the latter case, the memory allocated for a
	 * slab is used for:
	 *
	 * - @buffer_size bytes for each object
	 * - One freelist_idx_t for each object
	 *
	 * We don't need to consider alignment of freelist because
	 * freelist will be at the end of slab page. The objects will be
	 * at the correct alignment.
	 *
	 * If the slab management structure is off the slab, then the
	 * alignment will already be calculated into the size. Because
	 * the slabs are all pages aligned, the objects will be at the
	 * correct alignment when allocated.
	 */
	if (flags & (CFLGS_OBJFREELIST_SLAB | CFLGS_OFF_SLAB)) {
		num = slab_size / buffer_size;
		*left_over = slab_size % buffer_size;
	} else {
		num = slab_size / (buffer_size + sizeof(freelist_idx_t));
		*left_over = slab_size %
			(buffer_size + sizeof(freelist_idx_t));
	}

	return num;
}

#if DEBUG
#define slab_error(cachep, msg) __slab_error(__func__, cachep, msg)

static void __slab_error(const char *function, struct kmem_cache *cachep,
			char *msg)
{
	pr_err("slab error in %s(): cache `%s': %s\n",
	       function, cachep->name, msg);
	dump_stack();
	add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);
}
#endif

/*
 * By default on NUMA we use alien caches to stage the freeing of
 * objects allocated from other nodes. This causes massive memory
 * inefficiencies when using fake NUMA setup to split memory into a
 * large number of small nodes, so it can be disabled on the command
 * line
  */

static int use_alien_caches __read_mostly = 1;
static int __init noaliencache_setup(char *s)
{
	use_alien_caches = 0;
	return 1;
}
__setup("noaliencache", noaliencache_setup);

static int __init slab_max_order_setup(char *str)
{
	get_option(&str, &slab_max_order);
	slab_max_order = slab_max_order < 0 ? 0 :
				min(slab_max_order, MAX_ORDER);
	slab_max_order_set = true;

	return 1;
}
__setup("slab_max_order=", slab_max_order_setup);

#ifdef CONFIG_NUMA
/*
 * Special reaping functions for NUMA systems called from cache_reap().
 * These take care of doing round robin flushing of alien caches (containing
 * objects freed on different nodes from which they were allocated) and the
 * flushing of remote pcps by calling drain_node_pages.
 */
static DEFINE_PER_CPU(unsigned long, slab_reap_node);

static void init_reap_node(int cpu)
{
	per_cpu(slab_reap_node, cpu) = next_node_in(cpu_to_mem(cpu),
						    node_online_map);
}

static void next_reap_node(void)
{
	int node = __this_cpu_read(slab_reap_node);

	node = next_node_in(node, node_online_map);
	__this_cpu_write(slab_reap_node, node);
}

#else
#define init_reap_node(cpu) do { } while (0)
#define next_reap_node(void) do { } while (0)
#endif

/*
 * Initiate the reap timer running on the target CPU.  We run at around 1 to 2Hz
 * via the workqueue/eventd.
 * Add the CPU number into the expiration time to minimize the possibility of
 * the CPUs getting into lockstep and contending for the global cache chain
 * lock.
 */
static void start_cpu_timer(int cpu)
{
	struct delayed_work *reap_work = &per_cpu(slab_reap_work, cpu);

	if (reap_work->work.func == NULL) {
		init_reap_node(cpu);
		INIT_DEFERRABLE_WORK(reap_work, cache_reap);
		schedule_delayed_work_on(cpu, reap_work,
					__round_jiffies_relative(HZ, cpu));
	}
}

static void init_arraycache(struct array_cache *ac, int limit, int batch)
{
	if (ac) {
		ac->avail = 0;
		ac->limit = limit;
		ac->batchcount = batch;
		ac->touched = 0;
	}
}

static struct array_cache *alloc_arraycache(int node, int entries,
					    int batchcount, gfp_t gfp)
{
	size_t memsize = sizeof(void *) * entries + sizeof(struct array_cache);
	struct array_cache *ac = NULL;

	ac = kmalloc_node(memsize, gfp, node);
	/*
	 * The array_cache structures contain pointers to free object.
	 * However, when such objects are allocated or transferred to another
	 * cache the pointers are not cleared and they could be counted as
	 * valid references during a kmemleak scan. Therefore, kmemleak must
	 * not scan such objects.
	 */
	kmemleak_no_scan(ac);
	init_arraycache(ac, entries, batchcount);
	return ac;
}

static noinline void cache_free_pfmemalloc(struct kmem_cache *cachep,
					struct slab *slab, void *objp)
{
	struct kmem_cache_node *n;
	int slab_node;
	LIST_HEAD(list);

	slab_node = slab_nid(slab);
	n = get_node(cachep, slab_node);

	raw_spin_lock(&n->list_lock);
	free_block(cachep, &objp, 1, slab_node, &list);
	raw_spin_unlock(&n->list_lock);

	slabs_destroy(cachep, &list);
}

/*
 * Transfer objects in one arraycache to another.
 * Locking must be handled by the caller.
 *
 * Return the number of entries transferred.
 */
static int transfer_objects(struct array_cache *to,
		struct array_cache *from, unsigned int max)
{
	/* Figure out how many entries to transfer */
	int nr = min3(from->avail, max, to->limit - to->avail);

	if (!nr)
		return 0;

	memcpy(to->entry + to->avail, from->entry + from->avail - nr,
			sizeof(void *) *nr);

	from->avail -= nr;
	to->avail += nr;
	return nr;
}

/* &alien->lock must be held by alien callers. */
static __always_inline void __free_one(struct array_cache *ac, void *objp)
{
	/* Avoid trivial double-free. */
	if (IS_ENABLED(CONFIG_SLAB_FREELIST_HARDENED) &&
	    WARN_ON_ONCE(ac->avail > 0 && ac->entry[ac->avail - 1] == objp))
		return;
	ac->entry[ac->avail++] = objp;
}

#ifndef CONFIG_NUMA

#define drain_alien_cache(cachep, alien) do { } while (0)
#define reap_alien(cachep, n) do { } while (0)

static inline struct alien_cache **alloc_alien_cache(int node,
						int limit, gfp_t gfp)
{
	return NULL;
}

static inline void free_alien_cache(struct alien_cache **ac_ptr)
{
}

static inline int cache_free_alien(struct kmem_cache *cachep, void *objp)
{
	return 0;
}

static inline gfp_t gfp_exact_node(gfp_t flags)
{
	return flags & ~__GFP_NOFAIL;
}

#else	/* CONFIG_NUMA */

static struct alien_cache *__alloc_alien_cache(int node, int entries,
						int batch, gfp_t gfp)
{
	size_t memsize = sizeof(void *) * entries + sizeof(struct alien_cache);
	struct alien_cache *alc = NULL;

	alc = kmalloc_node(memsize, gfp, node);
	if (alc) {
		kmemleak_no_scan(alc);
		init_arraycache(&alc->ac, entries, batch);
		spin_lock_init(&alc->lock);
	}
	return alc;
}

static struct alien_cache **alloc_alien_cache(int node, int limit, gfp_t gfp)
{
	struct alien_cache **alc_ptr;
	int i;

	if (limit > 1)
		limit = 12;
	alc_ptr = kcalloc_node(nr_node_ids, sizeof(void *), gfp, node);
	if (!alc_ptr)
		return NULL;

	for_each_node(i) {
		if (i == node || !node_online(i))
			continue;
		alc_ptr[i] = __alloc_alien_cache(node, limit, 0xbaadf00d, gfp);
		if (!alc_ptr[i]) {
			for (i--; i >= 0; i--)
				kfree(alc_ptr[i]);
			kfree(alc_ptr);
			return NULL;
		}
	}
	return alc_ptr;
}

static void free_alien_cache(struct alien_cache **alc_ptr)
{
	int i;

	if (!alc_ptr)
		return;
	for_each_node(i)
	    kfree(alc_ptr[i]);
	kfree(alc_ptr);
}

static void __drain_alien_cache(struct kmem_cache *cachep,
				struct array_cache *ac, int node,
				struct list_head *list)
{
	struct kmem_cache_node *n = get_node(cachep, node);

	if (ac->avail) {
		raw_spin_lock(&n->list_lock);
		/*
		 * Stuff objects into the remote nodes shared array first.
		 * That way we could avoid the overhead of putting the objects
		 * into the free lists and getting them back later.
		 */
		if (n->shared)
			transfer_objects(n->shared, ac, ac->limit);

		free_block(cachep, ac->entry, ac->avail, node, list);
		ac->avail = 0;
		raw_spin_unlock(&n->list_lock);
	}
}

/*
 * Called from cache_reap() to regularly drain alien caches round robin.
 */
static void reap_alien(struct kmem_cache *cachep, struct kmem_cache_node *n)
{
	int node = __this_cpu_read(slab_reap_node);

	if (n->alien) {
		struct alien_cache *alc = n->alien[node];
		struct array_cache *ac;

		if (alc) {
			ac = &alc->ac;
			if (ac->avail && spin_trylock_irq(&alc->lock)) {
				LIST_HEAD(list);

				__drain_alien_cache(cachep, ac, node, &list);
				spin_unlock_irq(&alc->lock);
				slabs_destroy(cachep, &list);
			}
		}
	}
}

static void drain_alien_cache(struct kmem_cache *cachep,
				struct alien_cache **alien)
{
	int i = 0;
	struct alien_cache *alc;
	struct array_cache *ac;
	unsigned long flags;

	for_each_online_node(i) {
		alc = alien[i];
		if (alc) {
			LIST_HEAD(list);

			ac = &alc->ac;
			spin_lock_irqsave(&alc->lock, flags);
			__drain_alien_cache(cachep, ac, i, &list);
			spin_unlock_irqrestore(&alc->lock, flags);
			slabs_destroy(cachep, &list);
		}
	}
}

static int __cache_free_alien(struct kmem_cache *cachep, void *objp,
				int node, int slab_node)
{
	struct kmem_cache_node *n;
	struct alien_cache *alien = NULL;
	struct array_cache *ac;
	LIST_HEAD(list);

	n = get_node(cachep, node);
	STATS_INC_NODEFREES(cachep);
	if (n->alien && n->alien[slab_node]) {
		alien = n->alien[slab_node];
		ac = &alien->ac;
		spin_lock(&alien->lock);
		if (unlikely(ac->avail == ac->limit)) {
			STATS_INC_ACOVERFLOW(cachep);
			__drain_alien_cache(cachep, ac, slab_node, &list);
		}
		__free_one(ac, objp);
		spin_unlock(&alien->lock);
		slabs_destroy(cachep, &list);
	} else {
		n = get_node(cachep, slab_node);
		raw_spin_lock(&n->list_lock);
		free_block(cachep, &objp, 1, slab_node, &list);
		raw_spin_unlock(&n->list_lock);
		slabs_destroy(cachep, &list);
	}
	return 1;
}

static inline int cache_free_alien(struct kmem_cache *cachep, void *objp)
{
	int slab_node = slab_nid(virt_to_slab(objp));
	int node = numa_mem_id();
	/*
	 * Make sure we are not freeing an object from another node to the array
	 * cache on this cpu.
	 */
	if (likely(node == slab_node))
		return 0;

	return __cache_free_alien(cachep, objp, node, slab_node);
}

/*
 * Construct gfp mask to allocate from a specific node but do not reclaim or
 * warn about failures.
 */
static inline gfp_t gfp_exact_node(gfp_t flags)
{
	return (flags | __GFP_THISNODE | __GFP_NOWARN) & ~(__GFP_RECLAIM|__GFP_NOFAIL);
}
#endif

static int init_cache_node(struct kmem_cache *cachep, int node, gfp_t gfp)
{
	struct kmem_cache_node *n;

	/*
	 * Set up the kmem_cache_node for cpu before we can
	 * begin anything. Make sure some other cpu on this
	 * node has not already allocated this
	 */
	n = get_node(cachep, node);
	if (n) {
		raw_spin_lock_irq(&n->list_lock);
		n->free_limit = (1 + nr_cpus_node(node)) * cachep->batchcount +
				cachep->num;
		raw_spin_unlock_irq(&n->list_lock);

		return 0;
	}

	n = kmalloc_node(sizeof(struct kmem_cache_node), gfp, node);
	if (!n)
		return -ENOMEM;

	kmem_cache_node_init(n);
	n->next_reap = jiffies + REAPTIMEOUT_NODE +
		    ((unsigned long)cachep) % REAPTIMEOUT_NODE;

	n->free_limit =
		(1 + nr_cpus_node(node)) * cachep->batchcount + cachep->num;

	/*
	 * The kmem_cache_nodes don't come and go as CPUs
	 * come and go.  slab_mutex provides sufficient
	 * protection here.
	 */
	cachep->node[node] = n;

	return 0;
}

#if defined(CONFIG_NUMA) || defined(CONFIG_SMP)
/*
 * Allocates and initializes node for a node on each slab cache, used for
 * either memory or cpu hotplug.  If memory is being hot-added, the kmem_cache_node
 * will be allocated off-node since memory is not yet online for the new node.
 * When hotplugging memory or a cpu, existing nodes are not replaced if
 * already in use.
 *
 * Must hold slab_mutex.
 */
static int init_cache_node_node(int node)
{
	int ret;
	struct kmem_cache *cachep;

	list_for_each_entry(cachep, &slab_caches, list) {
		ret = init_cache_node(cachep, node, GFP_KERNEL);
		if (ret)
			return ret;
	}

	return 0;
}
#endif

static int setup_kmem_cache_node(struct kmem_cache *cachep,
				int node, gfp_t gfp, bool force_change)
{
	int ret = -ENOMEM;
	struct kmem_cache_node *n;
	struct array_cache *old_shared = NULL;
	struct array_cache *new_shared = NULL;
	struct alien_cache **new_alien = NULL;
	LIST_HEAD(list);

	if (use_alien_caches) {
		new_alien = alloc_alien_cache(node, cachep->limit, gfp);
		if (!new_alien)
			goto fail;
	}

	if (cachep->shared) {
		new_shared = alloc_arraycache(node,
			cachep->shared * cachep->batchcount, 0xbaadf00d, gfp);
		if (!new_shared)
			goto fail;
	}

	ret = init_cache_node(cachep, node, gfp);
	if (ret)
		goto fail;

	n = get_node(cachep, node);
	raw_spin_lock_irq(&n->list_lock);
	if (n->shared && force_change) {
		free_block(cachep, n->shared->entry,
				n->shared->avail, node, &list);
		n->shared->avail = 0;
	}

	if (!n->shared || force_change) {
		old_shared = n->shared;
		n->shared = new_shared;
		new_shared = NULL;
	}

	if (!n->alien) {
		n->alien = new_alien;
		new_alien = NULL;
	}

	raw_spin_unlock_irq(&n->list_lock);
	slabs_destroy(cachep, &list);

	/*
	 * To protect lockless access to n->shared during irq disabled context.
	 * If n->shared isn't NULL in irq disabled context, accessing to it is
	 * guaranteed to be valid until irq is re-enabled, because it will be
	 * freed after synchronize_rcu().
	 */
	if (old_shared && force_change)
		synchronize_rcu();

fail:
	kfree(old_shared);
	kfree(new_shared);
	free_alien_cache(new_alien);

	return ret;
}

#ifdef CONFIG_SMP

static void cpuup_canceled(long cpu)
{
	struct kmem_cache *cachep;
	struct kmem_cache_node *n = NULL;
	int node = cpu_to_mem(cpu);
	const struct cpumask *mask = cpumask_of_node(node);

	list_for_each_entry(cachep, &slab_caches, list) {
		struct array_cache *nc;
		struct array_cache *shared;
		struct alien_cache **alien;
		LIST_HEAD(list);

		n = get_node(cachep, node);
		if (!n)
			continue;

		raw_spin_lock_irq(&n->list_lock);

		/* Free limit for this kmem_cache_node */
		n->free_limit -= cachep->batchcount;

		/* cpu is dead; no one can alloc from it. */
		nc = per_cpu_ptr(cachep->cpu_cache, cpu);
		free_block(cachep, nc->entry, nc->avail, node, &list);
		nc->avail = 0;

		if (!cpumask_empty(mask)) {
			raw_spin_unlock_irq(&n->list_lock);
			goto free_slab;
		}

		shared = n->shared;
		if (shared) {
			free_block(cachep, shared->entry,
				   shared->avail, node, &list);
			n->shared = NULL;
		}

		alien = n->alien;
		n->alien = NULL;

		raw_spin_unlock_irq(&n->list_lock);

		kfree(shared);
		if (alien) {
			drain_alien_cache(cachep, alien);
			free_alien_cache(alien);
		}

free_slab:
		slabs_destroy(cachep, &list);
	}
	/*
	 * In the previous loop, all the objects were freed to
	 * the respective cache's slabs,  now we can go ahead and
	 * shrink each nodelist to its limit.
	 */
	list_for_each_entry(cachep, &slab_caches, list) {
		n = get_node(cachep, node);
		if (!n)
			continue;
		drain_freelist(cachep, n, INT_MAX);
	}
}

static int cpuup_prepare(long cpu)
{
	struct kmem_cache *cachep;
	int node = cpu_to_mem(cpu);
	int err;

	/*
	 * We need to do this right in the beginning since
	 * alloc_arraycache's are going to use this list.
	 * kmalloc_node allows us to add the slab to the right
	 * kmem_cache_node and not this cpu's kmem_cache_node
	 */
	err = init_cache_node_node(node);
	if (err < 0)
		goto bad;

	/*
	 * Now we can go ahead with allocating the shared arrays and
	 * array caches
	 */
	list_for_each_entry(cachep, &slab_caches, list) {
		err = setup_kmem_cache_node(cachep, node, GFP_KERNEL, false);
		if (err)
			goto bad;
	}

	return 0;
bad:
	cpuup_canceled(cpu);
	return -ENOMEM;
}

int slab_prepare_cpu(unsigned int cpu)
{
	int err;

	mutex_lock(&slab_mutex);
	err = cpuup_prepare(cpu);
	mutex_unlock(&slab_mutex);
	return err;
}

/*
 * This is called for a failed online attempt and for a successful
 * offline.
 *
 * Even if all the cpus of a node are down, we don't free the
 * kmem_cache_node of any cache. This is to avoid a race between cpu_down, and
 * a kmalloc allocation from another cpu for memory from the node of
 * the cpu going down.  The kmem_cache_node structure is usually allocated from
 * kmem_cache_create() and gets destroyed at kmem_cache_destroy().
 */
int slab_dead_cpu(unsigned int cpu)
{
	mutex_lock(&slab_mutex);
	cpuup_canceled(cpu);
	mutex_unlock(&slab_mutex);
	return 0;
}
#endif

static int slab_online_cpu(unsigned int cpu)
{
	start_cpu_timer(cpu);
	return 0;
}

static int slab_offline_cpu(unsigned int cpu)
{
	/*
	 * Shutdown cache reaper. Note that the slab_mutex is held so
	 * that if cache_reap() is invoked it cannot do anything
	 * expensive but will only modify reap_work and reschedule the
	 * timer.
	 */
	cancel_delayed_work_sync(&per_cpu(slab_reap_work, cpu));
	/* Now the cache_reaper is guaranteed to be not running. */
	per_cpu(slab_reap_work, cpu).work.func = NULL;
	return 0;
}

#if defined(CONFIG_NUMA)
/*
 * Drains freelist for a node on each slab cache, used for memory hot-remove.
 * Returns -EBUSY if all objects cannot be drained so that the node is not
 * removed.
 *
 * Must hold slab_mutex.
 */
static int __meminit drain_cache_node_node(int node)
{
	struct kmem_cache *cachep;
	int ret = 0;

	list_for_each_entry(cachep, &slab_caches, list) {
		struct kmem_cache_node *n;

		n = get_node(cachep, node);
		if (!n)
			continue;

		drain_freelist(cachep, n, INT_MAX);

		if (!list_empty(&n->slabs_full) ||
		    !list_empty(&n->slabs_partial)) {
			ret = -EBUSY;
			break;
		}
	}
	return ret;
}

static int __meminit slab_memory_callback(struct notifier_block *self,
					unsigned long action, void *arg)
{
	struct memory_notify *mnb = arg;
	int ret = 0;
	int nid;

	nid = mnb->status_change_nid;
	if (nid < 0)
		goto out;

	switch (action) {
	case MEM_GOING_ONLINE:
		mutex_lock(&slab_mutex);
		ret = init_cache_node_node(nid);
		mutex_unlock(&slab_mutex);
		break;
	case MEM_GOING_OFFLINE:
		mutex_lock(&slab_mutex);
		ret = drain_cache_node_node(nid);
		mutex_unlock(&slab_mutex);
		break;
	case MEM_ONLINE:
	case MEM_OFFLINE:
	case MEM_CANCEL_ONLINE:
	case MEM_CANCEL_OFFLINE:
		break;
	}
out:
	return notifier_from_errno(ret);
}
#endif /* CONFIG_NUMA */

/*
 * swap the static kmem_cache_node with kmalloced memory
 */
static void __init init_list(struct kmem_cache *cachep, struct kmem_cache_node *list,
				int nodeid)
{
	struct kmem_cache_node *ptr;

	ptr = kmalloc_node(sizeof(struct kmem_cache_node), GFP_NOWAIT, nodeid);
	BUG_ON(!ptr);

	memcpy(ptr, list, sizeof(struct kmem_cache_node));
	/*
	 * Do not assume that spinlocks can be initialized via memcpy:
	 */
	raw_spin_lock_init(&ptr->list_lock);

	MAKE_ALL_LISTS(cachep, ptr, nodeid);
	cachep->node[nodeid] = ptr;
}

/*
 * For setting up all the kmem_cache_node for cache whose buffer_size is same as
 * size of kmem_cache_node.
 */
static void __init set_up_node(struct kmem_cache *cachep, int index)
{
	int node;

	for_each_online_node(node) {
		cachep->node[node] = &init_kmem_cache_node[index + node];
		cachep->node[node]->next_reap = jiffies +
		    REAPTIMEOUT_NODE +
		    ((unsigned long)cachep) % REAPTIMEOUT_NODE;
	}
}

/*
 * Initialisation.  Called after the page allocator have been initialised and
 * before smp_init().
 */
void __init kmem_cache_init(void)
{
	int i;

	kmem_cache = &kmem_cache_boot;

	if (!IS_ENABLED(CONFIG_NUMA) || num_possible_nodes() == 1)
		use_alien_caches = 0;

	for (i = 0; i < NUM_INIT_LISTS; i++)
		kmem_cache_node_init(&init_kmem_cache_node[i]);

	/*
	 * Fragmentation resistance on low memory - only use bigger
	 * page orders on machines with more than 32MB of memory if
	 * not overridden on the command line.
	 */
	if (!slab_max_order_set && totalram_pages() > (32 << 20) >> PAGE_SHIFT)
		slab_max_order = SLAB_MAX_ORDER_HI;

	/* Bootstrap is tricky, because several objects are allocated
	 * from caches that do not exist yet:
	 * 1) initialize the kmem_cache cache: it contains the struct
	 *    kmem_cache structures of all caches, except kmem_cache itself:
	 *    kmem_cache is statically allocated.
	 *    Initially an __init data area is used for the head array and the
	 *    kmem_cache_node structures, it's replaced with a kmalloc allocated
	 *    array at the end of the bootstrap.
	 * 2) Create the first kmalloc cache.
	 *    The struct kmem_cache for the new cache is allocated normally.
	 *    An __init data area is used for the head array.
	 * 3) Create the remaining kmalloc caches, with minimally sized
	 *    head arrays.
	 * 4) Replace the __init data head arrays for kmem_cache and the first
	 *    kmalloc cache with kmalloc allocated arrays.
	 * 5) Replace the __init data for kmem_cache_node for kmem_cache and
	 *    the other cache's with kmalloc allocated memory.
	 * 6) Resize the head arrays of the kmalloc caches to their final sizes.
	 */

	/* 1) create the kmem_cache */

	/*
	 * struct kmem_cache size depends on nr_node_ids & nr_cpu_ids
	 */
	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);
	list_add(&kmem_cache->list, &slab_caches);
	slab_state = PARTIAL;

	/*
	 * Initialize the caches that provide memory for the  kmem_cache_node
	 * structures first.  Without this, further allocations will bug.
	 */
	new_kmalloc_cache(INDEX_NODE, KMALLOC_NORMAL, ARCH_KMALLOC_FLAGS);
	slab_state = PARTIAL_NODE;
	setup_kmalloc_cache_index_table();

	/* 5) Replace the bootstrap kmem_cache_node */
	{
		int nid;

		for_each_online_node(nid) {
			init_list(kmem_cache, &init_kmem_cache_node[CACHE_CACHE + nid], nid);

			init_list(kmalloc_caches[KMALLOC_NORMAL][INDEX_NODE],
					  &init_kmem_cache_node[SIZE_NODE + nid], nid);
		}
	}

	create_kmalloc_caches(ARCH_KMALLOC_FLAGS);
}

void __init kmem_cache_init_late(void)
{
	struct kmem_cache *cachep;

	/* 6) resize the head arrays to their final sizes */
	mutex_lock(&slab_mutex);
	list_for_each_entry(cachep, &slab_caches, list)
		if (enable_cpucache(cachep, GFP_NOWAIT))
			BUG();
	mutex_unlock(&slab_mutex);

	/* Done! */
	slab_state = FULL;

#ifdef CONFIG_NUMA
	/*
	 * Register a memory hotplug callback that initializes and frees
	 * node.
	 */
	hotplug_memory_notifier(slab_memory_callback, SLAB_CALLBACK_PRI);
#endif

	/*
	 * The reap timers are started later, with a module init call: That part
	 * of the kernel is not yet operational.
	 */
}

static int __init cpucache_init(void)
{
	int ret;

	/*
	 * Register the timers that return unneeded pages to the page allocator
	 */
	ret = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "SLAB online",
				slab_online_cpu, slab_offline_cpu);
	WARN_ON(ret < 0);

	return 0;
}
__initcall(cpucache_init);

static noinline void
slab_out_of_memory(struct kmem_cache *cachep, gfp_t gfpflags, int nodeid)
{
#if DEBUG
	struct kmem_cache_node *n;
	unsigned long flags;
	int node;
	static DEFINE_RATELIMIT_STATE(slab_oom_rs, DEFAULT_RATELIMIT_INTERVAL,
				      DEFAULT_RATELIMIT_BURST);

	if ((gfpflags & __GFP_NOWARN) || !__ratelimit(&slab_oom_rs))
		return;

	pr_warn("SLAB: Unable to allocate memory on node %d, gfp=%#x(%pGg)\n",
		nodeid, gfpflags, &gfpflags);
	pr_warn("  cache: %s, object size: %d, order: %d\n",
		cachep->name, cachep->size, cachep->gfporder);

	for_each_kmem_cache_node(cachep, node, n) {
		unsigned long total_slabs, free_slabs, free_objs;

		raw_spin_lock_irqsave(&n->list_lock, flags);
		total_slabs = n->total_slabs;
		free_slabs = n->free_slabs;
		free_objs = n->free_objects;
		raw_spin_unlock_irqrestore(&n->list_lock, flags);

		pr_warn("  node %d: slabs: %ld/%ld, objs: %ld/%ld\n",
			node, total_slabs - free_slabs, total_slabs,
			(total_slabs * cachep->num) - free_objs,
			total_slabs * cachep->num);
	}
#endif
}

/*
 * Interface to system's page allocator. No need to hold the
 * kmem_cache_node ->list_lock.
 *
 * If we requested dmaable memory, we will get it. Even if we
 * did not request dmaable memory, we might get it, but that
 * would be relatively rare and ignorable.
 */
static struct slab *kmem_getpages(struct kmem_cache *cachep, gfp_t flags,
								int nodeid)
{
	struct folio *folio;
	struct slab *slab;

	flags |= cachep->allocflags;

	folio = (struct folio *) __alloc_pages_node(nodeid, flags, cachep->gfporder);
	if (!folio) {
		slab_out_of_memory(cachep, flags, nodeid);
		return NULL;
	}

	slab = folio_slab(folio);

	account_slab(slab, cachep->gfporder, cachep, flags);
	__folio_set_slab(folio);
	/* Make the flag visible before any changes to folio->mapping */
	smp_wmb();
	/* Record if ALLOC_NO_WATERMARKS was set when allocating the slab */
	if (sk_memalloc_socks() && folio_is_pfmemalloc(folio))
		slab_set_pfmemalloc(slab);

	return slab;
}

/*
 * Interface to system's page release.
 */
static void kmem_freepages(struct kmem_cache *cachep, struct slab *slab)
{
	int order = cachep->gfporder;
	struct folio *folio = slab_folio(slab);

	BUG_ON(!folio_test_slab(folio));
	__slab_clear_pfmemalloc(slab);
	page_mapcount_reset(&folio->page);
	folio->mapping = NULL;
	/* Make the mapping reset visible before clearing the flag */
	smp_wmb();
	__folio_clear_slab(folio);

	mm_account_reclaimed_pages(1 << order);
	unaccount_slab(slab, order, cachep);
	__free_pages(&folio->page, order);
}

static void kmem_rcu_free(struct rcu_head *head)
{
	struct kmem_cache *cachep;
	struct slab *slab;

	slab = container_of(head, struct slab, rcu_head);
	cachep = slab->slab_cache;

	kmem_freepages(cachep, slab);
}

#if DEBUG
static inline bool is_debug_pagealloc_cache(struct kmem_cache *cachep)
{
	return debug_pagealloc_enabled_static() && OFF_SLAB(cachep) &&
			((cachep->size % PAGE_SIZE) == 0);
}

#ifdef CONFIG_DEBUG_PAGEALLOC
static void slab_kernel_map(struct kmem_cache *cachep, void *objp, int map)
{
	if (!is_debug_pagealloc_cache(cachep))
		return;

	__kernel_map_pages(virt_to_page(objp), cachep->size / PAGE_SIZE, map);
}

#else
static inline void slab_kernel_map(struct kmem_cache *cachep, void *objp,
				int map) {}

#endif

static void poison_obj(struct kmem_cache *cachep, void *addr, unsigned char val)
{
	int size = cachep->object_size;
	addr = &((char *)addr)[obj_offset(cachep)];

	memset(addr, val, size);
	*(unsigned char *)(addr + size - 1) = POISON_END;
}

static void dump_line(char *data, int offset, int limit)
{
	int i;
	unsigned char error = 0;
	int bad_count = 0;

	pr_err("%03x: ", offset);
	for (i = 0; i < limit; i++) {
		if (data[offset + i] != POISON_FREE) {
			error = data[offset + i];
			bad_count++;
		}
	}
	print_hex_dump(KERN_CONT, "", 0, 16, 1,
			&data[offset], limit, 1);

	if (bad_count == 1) {
		error ^= POISON_FREE;
		if (!(error & (error - 1))) {
			pr_err("Single bit error detected. Probably bad RAM.\n");
#ifdef CONFIG_X86
			pr_err("Run memtest86+ or a similar memory test tool.\n");
#else
			pr_err("Run a memory test tool.\n");
#endif
		}
	}
}
#endif

#if DEBUG

static void print_objinfo(struct kmem_cache *cachep, void *objp, int lines)
{
	int i, size;
	char *realobj;

	if (cachep->flags & SLAB_RED_ZONE) {
		pr_err("Redzone: 0x%llx/0x%llx\n",
		       *dbg_redzone1(cachep, objp),
		       *dbg_redzone2(cachep, objp));
	}

	if (cachep->flags & SLAB_STORE_USER)
		pr_err("Last user: (%pSR)\n", *dbg_userword(cachep, objp));
	realobj = (char *)objp + obj_offset(cachep);
	size = cachep->object_size;
	for (i = 0; i < size && lines; i += 16, lines--) {
		int limit;
		limit = 16;
		if (i + limit > size)
			limit = size - i;
		dump_line(realobj, i, limit);
	}
}

static void check_poison_obj(struct kmem_cache *cachep, void *objp)
{
	char *realobj;
	int size, i;
	int lines = 0;

	if (is_debug_pagealloc_cache(cachep))
		return;

	realobj = (char *)objp + obj_offset(cachep);
	size = cachep->object_size;

	for (i = 0; i < size; i++) {
		char exp = POISON_FREE;
		if (i == size - 1)
			exp = POISON_END;
		if (realobj[i] != exp) {
			int limit;
			/* Mismatch ! */
			/* Print header */
			if (lines == 0) {
				pr_err("Slab corruption (%s): %s start=%px, len=%d\n",
				       print_tainted(), cachep->name,
				       realobj, size);
				print_objinfo(cachep, objp, 0);
			}
			/* Hexdump the affected line */
			i = (i / 16) * 16;
			limit = 16;
			if (i + limit > size)
				limit = size - i;
			dump_line(realobj, i, limit);
			i += 16;
			lines++;
			/* Limit to 5 lines */
			if (lines > 5)
				break;
		}
	}
	if (lines != 0) {
		/* Print some data about the neighboring objects, if they
		 * exist:
		 */
		struct slab *slab = virt_to_slab(objp);
		unsigned int objnr;

		objnr = obj_to_index(cachep, slab, objp);
		if (objnr) {
			objp = index_to_obj(cachep, slab, objnr - 1);
			realobj = (char *)objp + obj_offset(cachep);
			pr_err("Prev obj: start=%px, len=%d\n", realobj, size);
			print_objinfo(cachep, objp, 2);
		}
		if (objnr + 1 < cachep->num) {
			objp = index_to_obj(cachep, slab, objnr + 1);
			realobj = (char *)objp + obj_offset(cachep);
			pr_err("Next obj: start=%px, len=%d\n", realobj, size);
			print_objinfo(cachep, objp, 2);
		}
	}
}
#endif

#if DEBUG
static void slab_destroy_debugcheck(struct kmem_cache *cachep,
						struct slab *slab)
{
	int i;

	if (OBJFREELIST_SLAB(cachep) && cachep->flags & SLAB_POISON) {
		poison_obj(cachep, slab->freelist - obj_offset(cachep),
			POISON_FREE);
	}

	for (i = 0; i < cachep->num; i++) {
		void *objp = index_to_obj(cachep, slab, i);

		if (cachep->flags & SLAB_POISON) {
			check_poison_obj(cachep, objp);
			slab_kernel_map(cachep, objp, 1);
		}
		if (cachep->flags & SLAB_RED_ZONE) {
			if (*dbg_redzone1(cachep, objp) != RED_INACTIVE)
				slab_error(cachep, "start of a freed object was overwritten");
			if (*dbg_redzone2(cachep, objp) != RED_INACTIVE)
				slab_error(cachep, "end of a freed object was overwritten");
		}
	}
}
#else
static void slab_destroy_debugcheck(struct kmem_cache *cachep,
						struct slab *slab)
{
}
#endif

/**
 * slab_destroy - destroy and release all objects in a slab
 * @cachep: cache pointer being destroyed
 * @slab: slab being destroyed
 *
 * Destroy all the objs in a slab, and release the mem back to the system.
 * Before calling the slab must have been unlinked from the cache. The
 * kmem_cache_node ->list_lock is not held/needed.
 */
static void slab_destroy(struct kmem_cache *cachep, struct slab *slab)
{
	void *freelist;

	freelist = slab->freelist;
	slab_destroy_debugcheck(cachep, slab);
	if (unlikely(cachep->flags & SLAB_TYPESAFE_BY_RCU))
		call_rcu(&slab->rcu_head, kmem_rcu_free);
	else
		kmem_freepages(cachep, slab);

	/*
	 * From now on, we don't use freelist
	 * although actual page can be freed in rcu context
	 */
	if (OFF_SLAB(cachep))
		kfree(freelist);
}

/*
 * Update the size of the caches before calling slabs_destroy as it may
 * recursively call kfree.
 */
static void slabs_destroy(struct kmem_cache *cachep, struct list_head *list)
{
	struct slab *slab, *n;

	list_for_each_entry_safe(slab, n, list, slab_list) {
		list_del(&slab->slab_list);
		slab_destroy(cachep, slab);
	}
}

/**
 * calculate_slab_order - calculate size (page order) of slabs
 * @cachep: pointer to the cache that is being created
 * @size: size of objects to be created in this cache.
 * @flags: slab allocation flags
 *
 * Also calculates the number of objects per slab.
 *
 * This could be made much more intelligent.  For now, try to avoid using
 * high order pages for slabs.  When the gfp() functions are more friendly
 * towards high-order requests, this should be changed.
 *
 * Return: number of left-over bytes in a slab
 */
static size_t calculate_slab_order(struct kmem_cache *cachep,
				size_t size, slab_flags_t flags)
{
	size_t left_over = 0;
	int gfporder;

	for (gfporder = 0; gfporder <= KMALLOC_MAX_ORDER; gfporder++) {
		unsigned int num;
		size_t remainder;

		num = cache_estimate(gfporder, size, flags, &remainder);
		if (!num)
			continue;

		/* Can't handle number of objects more than SLAB_OBJ_MAX_NUM */
		if (num > SLAB_OBJ_MAX_NUM)
			break;

		if (flags & CFLGS_OFF_SLAB) {
			struct kmem_cache *freelist_cache;
			size_t freelist_size;
			size_t freelist_cache_size;

			freelist_size = num * sizeof(freelist_idx_t);
			if (freelist_size > KMALLOC_MAX_CACHE_SIZE) {
				freelist_cache_size = PAGE_SIZE << get_order(freelist_size);
			} else {
				freelist_cache = kmalloc_slab(freelist_size, 0u, _RET_IP_);
				if (!freelist_cache)
					continue;
				freelist_cache_size = freelist_cache->size;

				/*
				 * Needed to avoid possible looping condition
				 * in cache_grow_begin()
				 */
				if (OFF_SLAB(freelist_cache))
					continue;
			}

			/* check if off slab has enough benefit */
			if (freelist_cache_size > cachep->size / 2)
				continue;
		}

		/* Found something acceptable - save it away */
		cachep->num = num;
		cachep->gfporder = gfporder;
		left_over = remainder;

		/*
		 * A VFS-reclaimable slab tends to have most allocations
		 * as GFP_NOFS and we really don't want to have to be allocating
		 * higher-order pages when we are unable to shrink dcache.
		 */
		if (flags & SLAB_RECLAIM_ACCOUNT)
			break;

		/*
		 * Large number of objects is good, but very large slabs are
		 * currently bad for the gfp()s.
		 */
		if (gfporder >= slab_max_order)
			break;

		/*
		 * Acceptable internal fragmentation?
		 */
		if (left_over * 8 <= (PAGE_SIZE << gfporder))
			break;
	}
	return left_over;
}

static struct array_cache __percpu *alloc_kmem_cache_cpus(
		struct kmem_cache *cachep, int entries, int batchcount)
{
	int cpu;
	size_t size;
	struct array_cache __percpu *cpu_cache;

	size = sizeof(void *) * entries + sizeof(struct array_cache);
	cpu_cache = __alloc_percpu(size, sizeof(void *));

	if (!cpu_cache)
		return NULL;

	for_each_possible_cpu(cpu) {
		init_arraycache(per_cpu_ptr(cpu_cache, cpu),
				entries, batchcount);
	}

	return cpu_cache;
}

static int __ref setup_cpu_cache(struct kmem_cache *cachep, gfp_t gfp)
{
	if (slab_state >= FULL)
		return enable_cpucache(cachep, gfp);

	cachep->cpu_cache = alloc_kmem_cache_cpus(cachep, 1, 1);
	if (!cachep->cpu_cache)
		return 1;

	if (slab_state == DOWN) {
		/* Creation of first cache (kmem_cache). */
		set_up_node(kmem_cache, CACHE_CACHE);
	} else if (slab_state == PARTIAL) {
		/* For kmem_cache_node */
		set_up_node(cachep, SIZE_NODE);
	} else {
		int node;

		for_each_online_node(node) {
			cachep->node[node] = kmalloc_node(
				sizeof(struct kmem_cache_node), gfp, node);
			BUG_ON(!cachep->node[node]);
			kmem_cache_node_init(cachep->node[node]);
		}
	}

	cachep->node[numa_mem_id()]->next_reap =
			jiffies + REAPTIMEOUT_NODE +
			((unsigned long)cachep) % REAPTIMEOUT_NODE;

	cpu_cache_get(cachep)->avail = 0;
	cpu_cache_get(cachep)->limit = BOOT_CPUCACHE_ENTRIES;
	cpu_cache_get(cachep)->batchcount = 1;
	cpu_cache_get(cachep)->touched = 0;
	cachep->batchcount = 1;
	cachep->limit = BOOT_CPUCACHE_ENTRIES;
	return 0;
}

slab_flags_t kmem_cache_flags(unsigned int object_size,
	slab_flags_t flags, const char *name)
{
	return flags;
}

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 *cachep;

	cachep = find_mergeable(size, align, flags, name, ctor);
	if (cachep) {
		cachep->refcount++;

		/*
		 * Adjust the object sizes so that we clear
		 * the complete object on kzalloc.
		 */
		cachep->object_size = max_t(int, cachep->object_size, size);
	}
	return cachep;
}

static bool set_objfreelist_slab_cache(struct kmem_cache *cachep,
			size_t size, slab_flags_t flags)
{
	size_t left;

	cachep->num = 0;

	/*
	 * If slab auto-initialization on free is enabled, store the freelist
	 * off-slab, so that its contents don't end up in one of the allocated
	 * objects.
	 */
	if (unlikely(slab_want_init_on_free(cachep)))
		return false;

	if (cachep->ctor || flags & SLAB_TYPESAFE_BY_RCU)
		return false;

	left = calculate_slab_order(cachep, size,
			flags | CFLGS_OBJFREELIST_SLAB);
	if (!cachep->num)
		return false;

	if (cachep->num * sizeof(freelist_idx_t) > cachep->object_size)
		return false;

	cachep->colour = left / cachep->colour_off;

	return true;
}

static bool set_off_slab_cache(struct kmem_cache *cachep,
			size_t size, slab_flags_t flags)
{
	size_t left;

	cachep->num = 0;

	/*
	 * Always use on-slab management when SLAB_NOLEAKTRACE
	 * to avoid recursive calls into kmemleak.
	 */
	if (flags & SLAB_NOLEAKTRACE)
		return false;

	/*
	 * Size is large, assume best to place the slab management obj
	 * off-slab (should allow better packing of objs).
	 */
	left = calculate_slab_order(cachep, size, flags | CFLGS_OFF_SLAB);
	if (!cachep->num)
		return false;

	/*
	 * If the slab has been placed off-slab, and we have enough space then
	 * move it on-slab. This is at the expense of any extra colouring.
	 */
	if (left >= cachep->num * sizeof(freelist_idx_t))
		return false;

	cachep->colour = left / cachep->colour_off;

	return true;
}

static bool set_on_slab_cache(struct kmem_cache *cachep,
			size_t size, slab_flags_t flags)
{
	size_t left;

	cachep->num = 0;

	left = calculate_slab_order(cachep, size, flags);
	if (!cachep->num)
		return false;

	cachep->colour = left / cachep->colour_off;

	return true;
}

/*
 * __kmem_cache_create - Create a cache.
 * @cachep: cache management descriptor
 * @flags: SLAB flags
 *
 * Returns zero on success, nonzero on failure.
 *
 * The flags are
 *
 * %SLAB_POISON - Poison the slab with a known test pattern (a5a5a5a5)
 * to catch references to uninitialised memory.
 *
 * %SLAB_RED_ZONE - Insert `Red' zones around the allocated memory to check
 * for buffer overruns.
 *
 * %SLAB_HWCACHE_ALIGN - Align the objects in this cache to a hardware
 * cacheline.  This can be beneficial if you're counting cycles as closely
 * as davem.
 */
int __kmem_cache_create(struct kmem_cache *cachep, slab_flags_t flags)
{
	size_t ralign = BYTES_PER_WORD;
	gfp_t gfp;
	int err;
	unsigned int size = cachep->size;

#if DEBUG
#if FORCED_DEBUG
	/*
	 * Enable redzoning and last user accounting, except for caches with
	 * large objects, if the increased size would increase the object size
	 * above the next power of two: caches with object sizes just above a
	 * power of two have a significant amount of internal fragmentation.
	 */
	if (size < 4096 || fls(size - 1) == fls(size-1 + REDZONE_ALIGN +
						2 * sizeof(unsigned long long)))
		flags |= SLAB_RED_ZONE | SLAB_STORE_USER;
	if (!(flags & SLAB_TYPESAFE_BY_RCU))
		flags |= SLAB_POISON;
#endif
#endif

	/*
	 * Check that size is in terms of words.  This is needed to avoid
	 * unaligned accesses for some archs when redzoning is used, and makes
	 * sure any on-slab bufctl's are also correctly aligned.
	 */
	size = ALIGN(size, BYTES_PER_WORD);

	if (flags & SLAB_RED_ZONE) {
		ralign = REDZONE_ALIGN;
		/* If redzoning, ensure that the second redzone is suitably
		 * aligned, by adjusting the object size accordingly. */
		size = ALIGN(size, REDZONE_ALIGN);
	}

	/* 3) caller mandated alignment */
	if (ralign < cachep->align) {
		ralign = cachep->align;
	}
	/* disable debug if necessary */
	if (ralign > __alignof__(unsigned long long))
		flags &= ~(SLAB_RED_ZONE | SLAB_STORE_USER);
	/*
	 * 4) Store it.
	 */
	cachep->align = ralign;
	cachep->colour_off = cache_line_size();
	/* Offset must be a multiple of the alignment. */
	if (cachep->colour_off < cachep->align)
		cachep->colour_off = cachep->align;

	if (slab_is_available())
		gfp = GFP_KERNEL;
	else
		gfp = GFP_NOWAIT;

#if DEBUG

	/*
	 * Both debugging options require word-alignment which is calculated
	 * into align above.
	 */
	if (flags & SLAB_RED_ZONE) {
		/* add space for red zone words */
		cachep->obj_offset += sizeof(unsigned long long);
		size += 2 * sizeof(unsigned long long);
	}
	if (flags & SLAB_STORE_USER) {
		/* user store requires one word storage behind the end of
		 * the real object. But if the second red zone needs to be
		 * aligned to 64 bits, we must allow that much space.
		 */
		if (flags & SLAB_RED_ZONE)
			size += REDZONE_ALIGN;
		else
			size += BYTES_PER_WORD;
	}
#endif

	kasan_cache_create(cachep, &size, &flags);

	size = ALIGN(size, cachep->align);
	/*
	 * We should restrict the number of objects in a slab to implement
	 * byte sized index. Refer comment on SLAB_OBJ_MIN_SIZE definition.
	 */
	if (FREELIST_BYTE_INDEX && size < SLAB_OBJ_MIN_SIZE)
		size = ALIGN(SLAB_OBJ_MIN_SIZE, cachep->align);

#if DEBUG
	/*
	 * To activate debug pagealloc, off-slab management is necessary
	 * requirement. In early phase of initialization, small sized slab
	 * doesn't get initialized so it would not be possible. So, we need
	 * to check size >= 256. It guarantees that all necessary small
	 * sized slab is initialized in current slab initialization sequence.
	 */
	if (debug_pagealloc_enabled_static() && (flags & SLAB_POISON) &&
		size >= 256 && cachep->object_size > cache_line_size()) {
		if (size < PAGE_SIZE || size % PAGE_SIZE == 0) {
			size_t tmp_size = ALIGN(size, PAGE_SIZE);

			if (set_off_slab_cache(cachep, tmp_size, flags)) {
				flags |= CFLGS_OFF_SLAB;
				cachep->obj_offset += tmp_size - size;
				size = tmp_size;
				goto done;
			}
		}
	}
#endif

	if (set_objfreelist_slab_cache(cachep, size, flags)) {
		flags |= CFLGS_OBJFREELIST_SLAB;
		goto done;
	}

	if (set_off_slab_cache(cachep, size, flags)) {
		flags |= CFLGS_OFF_SLAB;
		goto done;
	}

	if (set_on_slab_cache(cachep, size, flags))
		goto done;

	return -E2BIG;

done:
	cachep->freelist_size = cachep->num * sizeof(freelist_idx_t);
	cachep->flags = flags;
	cachep->allocflags = __GFP_COMP;
	if (flags & SLAB_CACHE_DMA)
		cachep->allocflags |= GFP_DMA;
	if (flags & SLAB_CACHE_DMA32)
		cachep->allocflags |= GFP_DMA32;
	if (flags & SLAB_RECLAIM_ACCOUNT)
		cachep->allocflags |= __GFP_RECLAIMABLE;
	cachep->size = size;
	cachep->reciprocal_buffer_size = reciprocal_value(size);

#if DEBUG
	/*
	 * If we're going to use the generic kernel_map_pages()
	 * poisoning, then it's going to smash the contents of
	 * the redzone and userword anyhow, so switch them off.
	 */
	if (IS_ENABLED(CONFIG_PAGE_POISONING) &&
		(cachep->flags & SLAB_POISON) &&
		is_debug_pagealloc_cache(cachep))
		cachep->flags &= ~(SLAB_RED_ZONE | SLAB_STORE_USER);
#endif

	err = setup_cpu_cache(cachep, gfp);
	if (err) {
		__kmem_cache_release(cachep);
		return err;
	}

	return 0;
}

#if DEBUG
static void check_irq_off(void)
{
	BUG_ON(!irqs_disabled());
}

static void check_irq_on(void)
{
	BUG_ON(irqs_disabled());
}

static void check_mutex_acquired(void)
{
	BUG_ON(!mutex_is_locked(&slab_mutex));
}

static void check_spinlock_acquired(struct kmem_cache *cachep)
{
#ifdef CONFIG_SMP
	check_irq_off();
	assert_raw_spin_locked(&get_node(cachep, numa_mem_id())->list_lock);
#endif
}

static void check_spinlock_acquired_node(struct kmem_cache *cachep, int node)
{
#ifdef CONFIG_SMP
	check_irq_off();
	assert_raw_spin_locked(&get_node(cachep, node)->list_lock);
#endif
}

#else
#define check_irq_off()	do { } while(0)
#define check_irq_on()	do { } while(0)
#define check_mutex_acquired()	do { } while(0)
#define check_spinlock_acquired(x) do { } while(0)
#define check_spinlock_acquired_node(x, y) do { } while(0)
#endif

static void drain_array_locked(struct kmem_cache *cachep, struct array_cache *ac,
				int node, bool free_all, struct list_head *list)
{
	int tofree;

	if (!ac || !ac->avail)
		return;

	tofree = free_all ? ac->avail : (ac->limit + 4) / 5;
	if (tofree > ac->avail)
		tofree = (ac->avail + 1) / 2;

	free_block(cachep, ac->entry, tofree, node, list);
	ac->avail -= tofree;
	memmove(ac->entry, &(ac->entry[tofree]), sizeof(void *) * ac->avail);
}

static void do_drain(void *arg)
{
	struct kmem_cache *cachep = arg;
	struct array_cache *ac;
	int node = numa_mem_id();
	struct kmem_cache_node *n;
	LIST_HEAD(list);

	check_irq_off();
	ac = cpu_cache_get(cachep);
	n = get_node(cachep, node);
	raw_spin_lock(&n->list_lock);
	free_block(cachep, ac->entry, ac->avail, node, &list);
	raw_spin_unlock(&n->list_lock);
	ac->avail = 0;
	slabs_destroy(cachep, &list);
}

static void drain_cpu_caches(struct kmem_cache *cachep)
{
	struct kmem_cache_node *n;
	int node;
	LIST_HEAD(list);

	on_each_cpu(do_drain, cachep, 1);
	check_irq_on();
	for_each_kmem_cache_node(cachep, node, n)
		if (n->alien)
			drain_alien_cache(cachep, n->alien);

	for_each_kmem_cache_node(cachep, node, n) {
		raw_spin_lock_irq(&n->list_lock);
		drain_array_locked(cachep, n->shared, node, true, &list);
		raw_spin_unlock_irq(&n->list_lock);

		slabs_destroy(cachep, &list);
	}
}

/*
 * Remove slabs from the list of free slabs.
 * Specify the number of slabs to drain in tofree.
 *
 * Returns the actual number of slabs released.
 */
static int drain_freelist(struct kmem_cache *cache,
			struct kmem_cache_node *n, int tofree)
{
	struct list_head *p;
	int nr_freed;
	struct slab *slab;

	nr_freed = 0;
	while (nr_freed < tofree && !list_empty(&n->slabs_free)) {

		raw_spin_lock_irq(&n->list_lock);
		p = n->slabs_free.prev;
		if (p == &n->slabs_free) {
			raw_spin_unlock_irq(&n->list_lock);
			goto out;
		}

		slab = list_entry(p, struct slab, slab_list);
		list_del(&slab->slab_list);
		n->free_slabs--;
		n->total_slabs--;
		/*
		 * Safe to drop the lock. The slab is no longer linked
		 * to the cache.
		 */
		n->free_objects -= cache->num;
		raw_spin_unlock_irq(&n->list_lock);
		slab_destroy(cache, slab);
		nr_freed++;

		cond_resched();
	}
out:
	return nr_freed;
}

bool __kmem_cache_empty(struct kmem_cache *s)
{
	int node;
	struct kmem_cache_node *n;

	for_each_kmem_cache_node(s, node, n)
		if (!list_empty(&n->slabs_full) ||
		    !list_empty(&n->slabs_partial))
			return false;
	return true;
}

int __kmem_cache_shrink(struct kmem_cache *cachep)
{
	int ret = 0;
	int node;
	struct kmem_cache_node *n;

	drain_cpu_caches(cachep);

	check_irq_on();
	for_each_kmem_cache_node(cachep, node, n) {
		drain_freelist(cachep, n, INT_MAX);

		ret += !list_empty(&n->slabs_full) ||
			!list_empty(&n->slabs_partial);
	}
	return (ret ? 1 : 0);
}

int __kmem_cache_shutdown(struct kmem_cache *cachep)
{
	return __kmem_cache_shrink(cachep);
}

void __kmem_cache_release(struct kmem_cache *cachep)
{
	int i;
	struct kmem_cache_node *n;

	cache_random_seq_destroy(cachep);

	free_percpu(cachep->cpu_cache);

	/* NUMA: free the node structures */
	for_each_kmem_cache_node(cachep, i, n) {
		kfree(n->shared);
		free_alien_cache(n->alien);
		kfree(n);
		cachep->node[i] = NULL;
	}
}

/*
 * Get the memory for a slab management obj.
 *
 * For a slab cache when the slab descriptor is off-slab, the
 * slab descriptor can't come from the same cache which is being created,
 * Because if it is the case, that means we defer the creation of
 * the kmalloc_{dma,}_cache of size sizeof(slab descriptor) to this point.
 * And we eventually call down to __kmem_cache_create(), which
 * in turn looks up in the kmalloc_{dma,}_caches for the desired-size one.
 * This is a "chicken-and-egg" problem.
 *
 * So the off-slab slab descriptor shall come from the kmalloc_{dma,}_caches,
 * which are all initialized during kmem_cache_init().
 */
static void *alloc_slabmgmt(struct kmem_cache *cachep,
				   struct slab *slab, int colour_off,
				   gfp_t local_flags, int nodeid)
{
	void *freelist;
	void *addr = slab_address(slab);

	slab->s_mem = addr + colour_off;
	slab->active = 0;

	if (OBJFREELIST_SLAB(cachep))
		freelist = NULL;
	else if (OFF_SLAB(cachep)) {
		/* Slab management obj is off-slab. */
		freelist = kmalloc_node(cachep->freelist_size,
					      local_flags, nodeid);
	} else {
		/* We will use last bytes at the slab for freelist */
		freelist = addr + (PAGE_SIZE << cachep->gfporder) -
				cachep->freelist_size;
	}

	return freelist;
}

static inline freelist_idx_t get_free_obj(struct slab *slab, unsigned int idx)
{
	return ((freelist_idx_t *) slab->freelist)[idx];
}

static inline void set_free_obj(struct slab *slab,
					unsigned int idx, freelist_idx_t val)
{
	((freelist_idx_t *)(slab->freelist))[idx] = val;
}

static void cache_init_objs_debug(struct kmem_cache *cachep, struct slab *slab)
{
#if DEBUG
	int i;

	for (i = 0; i < cachep->num; i++) {
		void *objp = index_to_obj(cachep, slab, i);

		if (cachep->flags & SLAB_STORE_USER)
			*dbg_userword(cachep, objp) = NULL;

		if (cachep->flags & SLAB_RED_ZONE) {
			*dbg_redzone1(cachep, objp) = RED_INACTIVE;
			*dbg_redzone2(cachep, objp) = RED_INACTIVE;
		}
		/*
		 * Constructors are not allowed to allocate memory from the same
		 * cache which they are a constructor for.  Otherwise, deadlock.
		 * They must also be threaded.
		 */
		if (cachep->ctor && !(cachep->flags & SLAB_POISON)) {
			kasan_unpoison_object_data(cachep,
						   objp + obj_offset(cachep));
			cachep->ctor(objp + obj_offset(cachep));
			kasan_poison_object_data(
				cachep, objp + obj_offset(cachep));
		}

		if (cachep->flags & SLAB_RED_ZONE) {
			if (*dbg_redzone2(cachep, objp) != RED_INACTIVE)
				slab_error(cachep, "constructor overwrote the end of an object");
			if (*dbg_redzone1(cachep, objp) != RED_INACTIVE)
				slab_error(cachep, "constructor overwrote the start of an object");
		}
		/* need to poison the objs? */
		if (cachep->flags & SLAB_POISON) {
			poison_obj(cachep, objp, POISON_FREE);
			slab_kernel_map(cachep, objp, 0);
		}
	}
#endif
}

#ifdef CONFIG_SLAB_FREELIST_RANDOM
/* Hold information during a freelist initialization */
struct freelist_init_state {
	unsigned int pos;
	unsigned int *list;
	unsigned int count;
};

/*
 * Initialize the state based on the randomization method available.
 * return true if the pre-computed list is available, false otherwise.
 */
static bool freelist_state_initialize(struct freelist_init_state *state,
				struct kmem_cache *cachep,
				unsigned int count)
{
	bool ret;
	if (!cachep->random_seq) {
		ret = false;
	} else {
		state->list = cachep->random_seq;
		state->count = count;
		state->pos = get_random_u32_below(count);
		ret = true;
	}
	return ret;
}

/* Get the next entry on the list and randomize it using a random shift */
static freelist_idx_t next_random_slot(struct freelist_init_state *state)
{
	if (state->pos >= state->count)
		state->pos = 0;
	return state->list[state->pos++];
}

/* Swap two freelist entries */
static void swap_free_obj(struct slab *slab, unsigned int a, unsigned int b)
{
	swap(((freelist_idx_t *) slab->freelist)[a],
		((freelist_idx_t *) slab->freelist)[b]);
}

/*
 * Shuffle the freelist initialization state based on pre-computed lists.
 * return true if the list was successfully shuffled, false otherwise.
 */
static bool shuffle_freelist(struct kmem_cache *cachep, struct slab *slab)
{
	unsigned int objfreelist = 0, i, rand, count = cachep->num;
	struct freelist_init_state state;
	bool precomputed;

	if (count < 2)
		return false;

	precomputed = freelist_state_initialize(&state, cachep, count);

	/* Take a random entry as the objfreelist */
	if (OBJFREELIST_SLAB(cachep)) {
		if (!precomputed)
			objfreelist = count - 1;
		else
			objfreelist = next_random_slot(&state);
		slab->freelist = index_to_obj(cachep, slab, objfreelist) +
						obj_offset(cachep);
		count--;
	}

	/*
	 * On early boot, generate the list dynamically.
	 * Later use a pre-computed list for speed.
	 */
	if (!precomputed) {
		for (i = 0; i < count; i++)
			set_free_obj(slab, i, i);

		/* Fisher-Yates shuffle */
		for (i = count - 1; i > 0; i--) {
			rand = get_random_u32_below(i + 1);
			swap_free_obj(slab, i, rand);
		}
	} else {
		for (i = 0; i < count; i++)
			set_free_obj(slab, i, next_random_slot(&state));
	}

	if (OBJFREELIST_SLAB(cachep))
		set_free_obj(slab, cachep->num - 1, objfreelist);

	return true;
}
#else
static inline bool shuffle_freelist(struct kmem_cache *cachep,
				struct slab *slab)
{
	return false;
}
#endif /* CONFIG_SLAB_FREELIST_RANDOM */

static void cache_init_objs(struct kmem_cache *cachep,
			    struct slab *slab)
{
	int i;
	void *objp;
	bool shuffled;

	cache_init_objs_debug(cachep, slab);

	/* Try to randomize the freelist if enabled */
	shuffled = shuffle_freelist(cachep, slab);

	if (!shuffled && OBJFREELIST_SLAB(cachep)) {
		slab->freelist = index_to_obj(cachep, slab, cachep->num - 1) +
						obj_offset(cachep);
	}

	for (i = 0; i < cachep->num; i++) {
		objp = index_to_obj(cachep, slab, i);
		objp = kasan_init_slab_obj(cachep, objp);

		/* constructor could break poison info */
		if (DEBUG == 0 && cachep->ctor) {
			kasan_unpoison_object_data(cachep, objp);
			cachep->ctor(objp);
			kasan_poison_object_data(cachep, objp);
		}

		if (!shuffled)
			set_free_obj(slab, i, i);
	}
}

static void *slab_get_obj(struct kmem_cache *cachep, struct slab *slab)
{
	void *objp;

	objp = index_to_obj(cachep, slab, get_free_obj(slab, slab->active));
	slab->active++;

	return objp;
}

static void slab_put_obj(struct kmem_cache *cachep,
			struct slab *slab, void *objp)
{
	unsigned int objnr = obj_to_index(cachep, slab, objp);
#if DEBUG
	unsigned int i;

	/* Verify double free bug */
	for (i = slab->active; i < cachep->num; i++) {
		if (get_free_obj(slab, i) == objnr) {
			pr_err("slab: double free detected in cache '%s', objp %px\n",
			       cachep->name, objp);
			BUG();
		}
	}
#endif
	slab->active--;
	if (!slab->freelist)
		slab->freelist = objp + obj_offset(cachep);

	set_free_obj(slab, slab->active, objnr);
}

/*
 * Grow (by 1) the number of slabs within a cache.  This is called by
 * kmem_cache_alloc() when there are no active objs left in a cache.
 */
static struct slab *cache_grow_begin(struct kmem_cache *cachep,
				gfp_t flags, int nodeid)
{
	void *freelist;
	size_t offset;
	gfp_t local_flags;
	int slab_node;
	struct kmem_cache_node *n;
	struct slab *slab;

	/*
	 * Be lazy and only check for valid flags here,  keeping it out of the
	 * critical path in kmem_cache_alloc().
	 */
	if (unlikely(flags & GFP_SLAB_BUG_MASK))
		flags = kmalloc_fix_flags(flags);

	WARN_ON_ONCE(cachep->ctor && (flags & __GFP_ZERO));
	local_flags = flags & (GFP_CONSTRAINT_MASK|GFP_RECLAIM_MASK);

	check_irq_off();
	if (gfpflags_allow_blocking(local_flags))
		local_irq_enable();

	/*
	 * Get mem for the objs.  Attempt to allocate a physical page from
	 * 'nodeid'.
	 */
	slab = kmem_getpages(cachep, local_flags, nodeid);
	if (!slab)
		goto failed;

	slab_node = slab_nid(slab);
	n = get_node(cachep, slab_node);

	/* Get colour for the slab, and cal the next value. */
	n->colour_next++;
	if (n->colour_next >= cachep->colour)
		n->colour_next = 0;

	offset = n->colour_next;
	if (offset >= cachep->colour)
		offset = 0;

	offset *= cachep->colour_off;

	/*
	 * Call kasan_poison_slab() before calling alloc_slabmgmt(), so
	 * page_address() in the latter returns a non-tagged pointer,
	 * as it should be for slab pages.
	 */
	kasan_poison_slab(slab);

	/* Get slab management. */
	freelist = alloc_slabmgmt(cachep, slab, offset,
			local_flags & ~GFP_CONSTRAINT_MASK, slab_node);
	if (OFF_SLAB(cachep) && !freelist)
		goto opps1;

	slab->slab_cache = cachep;
	slab->freelist = freelist;

	cache_init_objs(cachep, slab);

	if (gfpflags_allow_blocking(local_flags))
		local_irq_disable();

	return slab;

opps1:
	kmem_freepages(cachep, slab);
failed:
	if (gfpflags_allow_blocking(local_flags))
		local_irq_disable();
	return NULL;
}

static void cache_grow_end(struct kmem_cache *cachep, struct slab *slab)
{
	struct kmem_cache_node *n;
	void *list = NULL;

	check_irq_off();

	if (!slab)
		return;

	INIT_LIST_HEAD(&slab->slab_list);
	n = get_node(cachep, slab_nid(slab));

	raw_spin_lock(&n->list_lock);
	n->total_slabs++;
	if (!slab->active) {
		list_add_tail(&slab->slab_list, &n->slabs_free);
		n->free_slabs++;
	} else
		fixup_slab_list(cachep, n, slab, &list);

	STATS_INC_GROWN(cachep);
	n->free_objects += cachep->num - slab->active;
	raw_spin_unlock(&n->list_lock);

	fixup_objfreelist_debug(cachep, &list);
}

#if DEBUG

/*
 * Perform extra freeing checks:
 * - detect bad pointers.
 * - POISON/RED_ZONE checking
 */
static void kfree_debugcheck(const void *objp)
{
	if (!virt_addr_valid(objp)) {
		pr_err("kfree_debugcheck: out of range ptr %lxh\n",
		       (unsigned long)objp);
		BUG();
	}
}

static inline void verify_redzone_free(struct kmem_cache *cache, void *obj)
{
	unsigned long long redzone1, redzone2;

	redzone1 = *dbg_redzone1(cache, obj);
	redzone2 = *dbg_redzone2(cache, obj);

	/*
	 * Redzone is ok.
	 */
	if (redzone1 == RED_ACTIVE && redzone2 == RED_ACTIVE)
		return;

	if (redzone1 == RED_INACTIVE && redzone2 == RED_INACTIVE)
		slab_error(cache, "double free detected");
	else
		slab_error(cache, "memory outside object was overwritten");

	pr_err("%px: redzone 1:0x%llx, redzone 2:0x%llx\n",
	       obj, redzone1, redzone2);
}

static void *cache_free_debugcheck(struct kmem_cache *cachep, void *objp,
				   unsigned long caller)
{
	unsigned int objnr;
	struct slab *slab;

	BUG_ON(virt_to_cache(objp) != cachep);

	objp -= obj_offset(cachep);
	kfree_debugcheck(objp);
	slab = virt_to_slab(objp);

	if (cachep->flags & SLAB_RED_ZONE) {
		verify_redzone_free(cachep, objp);
		*dbg_redzone1(cachep, objp) = RED_INACTIVE;
		*dbg_redzone2(cachep, objp) = RED_INACTIVE;
	}
	if (cachep->flags & SLAB_STORE_USER)
		*dbg_userword(cachep, objp) = (void *)caller;

	objnr = obj_to_index(cachep, slab, objp);

	BUG_ON(objnr >= cachep->num);
	BUG_ON(objp != index_to_obj(cachep, slab, objnr));

	if (cachep->flags & SLAB_POISON) {
		poison_obj(cachep, objp, POISON_FREE);
		slab_kernel_map(cachep, objp, 0);
	}
	return objp;
}

#else
#define kfree_debugcheck(x) do { } while(0)
#define cache_free_debugcheck(x, objp, z) (objp)
#endif

static inline void fixup_objfreelist_debug(struct kmem_cache *cachep,
						void **list)
{
#if DEBUG
	void *next = *list;
	void *objp;

	while (next) {
		objp = next - obj_offset(cachep);
		next = *(void **)next;
		poison_obj(cachep, objp, POISON_FREE);
	}
#endif
}

static inline void fixup_slab_list(struct kmem_cache *cachep,
				struct kmem_cache_node *n, struct slab *slab,
				void **list)
{
	/* move slabp to correct slabp list: */
	list_del(&slab->slab_list);
	if (slab->active == cachep->num) {
		list_add(&slab->slab_list, &n->slabs_full);
		if (OBJFREELIST_SLAB(cachep)) {
#if DEBUG
			/* Poisoning will be done without holding the lock */
			if (cachep->flags & SLAB_POISON) {
				void **objp = slab->freelist;

				*objp = *list;
				*list = objp;
			}
#endif
			slab->freelist = NULL;
		}
	} else
		list_add(&slab->slab_list, &n->slabs_partial);
}

/* Try to find non-pfmemalloc slab if needed */
static noinline struct slab *get_valid_first_slab(struct kmem_cache_node *n,
					struct slab *slab, bool pfmemalloc)
{
	if (!slab)
		return NULL;

	if (pfmemalloc)
		return slab;

	if (!slab_test_pfmemalloc(slab))
		return slab;

	/* No need to keep pfmemalloc slab if we have enough free objects */
	if (n->free_objects > n->free_limit) {
		slab_clear_pfmemalloc(slab);
		return slab;
	}

	/* Move pfmemalloc slab to the end of list to speed up next search */
	list_del(&slab->slab_list);
	if (!slab->active) {
		list_add_tail(&slab->slab_list, &n->slabs_free);
		n->free_slabs++;
	} else
		list_add_tail(&slab->slab_list, &n->slabs_partial);

	list_for_each_entry(slab, &n->slabs_partial, slab_list) {
		if (!slab_test_pfmemalloc(slab))
			return slab;
	}

	n->free_touched = 1;
	list_for_each_entry(slab, &n->slabs_free, slab_list) {
		if (!slab_test_pfmemalloc(slab)) {
			n->free_slabs--;
			return slab;
		}
	}

	return NULL;
}

static struct slab *get_first_slab(struct kmem_cache_node *n, bool pfmemalloc)
{
	struct slab *slab;

	assert_raw_spin_locked(&n->list_lock);
	slab = list_first_entry_or_null(&n->slabs_partial, struct slab,
					slab_list);
	if (!slab) {
		n->free_touched = 1;
		slab = list_first_entry_or_null(&n->slabs_free, struct slab,
						slab_list);
		if (slab)
			n->free_slabs--;
	}

	if (sk_memalloc_socks())
		slab = get_valid_first_slab(n, slab, pfmemalloc);

	return slab;
}

static noinline void *cache_alloc_pfmemalloc(struct kmem_cache *cachep,
				struct kmem_cache_node *n, gfp_t flags)
{
	struct slab *slab;
	void *obj;
	void *list = NULL;

	if (!gfp_pfmemalloc_allowed(flags))
		return NULL;

	raw_spin_lock(&n->list_lock);
	slab = get_first_slab(n, true);
	if (!slab) {
		raw_spin_unlock(&n->list_lock);
		return NULL;
	}

	obj = slab_get_obj(cachep, slab);
	n->free_objects--;

	fixup_slab_list(cachep, n, slab, &list);

	raw_spin_unlock(&n->list_lock);
	fixup_objfreelist_debug(cachep, &list);

	return obj;
}

/*
 * Slab list should be fixed up by fixup_slab_list() for existing slab
 * or cache_grow_end() for new slab
 */
static __always_inline int alloc_block(struct kmem_cache *cachep,
		struct array_cache *ac, struct slab *slab, int batchcount)
{
	/*
	 * There must be at least one object available for
	 * allocation.
	 */
	BUG_ON(slab->active >= cachep->num);

	while (slab->active < cachep->num && batchcount--) {
		STATS_INC_ALLOCED(cachep);
		STATS_INC_ACTIVE(cachep);
		STATS_SET_HIGH(cachep);

		ac->entry[ac->avail++] = slab_get_obj(cachep, slab);
	}

	return batchcount;
}

static void *cache_alloc_refill(struct kmem_cache *cachep, gfp_t flags)
{
	int batchcount;
	struct kmem_cache_node *n;
	struct array_cache *ac, *shared;
	int node;
	void *list = NULL;
	struct slab *slab;

	check_irq_off();
	node = numa_mem_id();

	ac = cpu_cache_get(cachep);
	batchcount = ac->batchcount;
	if (!ac->touched && batchcount > BATCHREFILL_LIMIT) {
		/*
		 * If there was little recent activity on this cache, then
		 * perform only a partial refill.  Otherwise we could generate
		 * refill bouncing.
		 */
		batchcount = BATCHREFILL_LIMIT;
	}
	n = get_node(cachep, node);

	BUG_ON(ac->avail > 0 || !n);
	shared = READ_ONCE(n->shared);
	if (!n->free_objects && (!shared || !shared->avail))
		goto direct_grow;

	raw_spin_lock(&n->list_lock);
	shared = READ_ONCE(n->shared);

	/* See if we can refill from the shared array */
	if (shared && transfer_objects(ac, shared, batchcount)) {
		shared->touched = 1;
		goto alloc_done;
	}

	while (batchcount > 0) {
		/* Get slab alloc is to come from. */
		slab = get_first_slab(n, false);
		if (!slab)
			goto must_grow;

		check_spinlock_acquired(cachep);

		batchcount = alloc_block(cachep, ac, slab, batchcount);
		fixup_slab_list(cachep, n, slab, &list);
	}

must_grow:
	n->free_objects -= ac->avail;
alloc_done:
	raw_spin_unlock(&n->list_lock);
	fixup_objfreelist_debug(cachep, &list);

direct_grow:
	if (unlikely(!ac->avail)) {
		/* Check if we can use obj in pfmemalloc slab */
		if (sk_memalloc_socks()) {
			void *obj = cache_alloc_pfmemalloc(cachep, n, flags);

			if (obj)
				return obj;
		}

		slab = cache_grow_begin(cachep, gfp_exact_node(flags), node);

		/*
		 * cache_grow_begin() can reenable interrupts,
		 * then ac could change.
		 */
		ac = cpu_cache_get(cachep);
		if (!ac->avail && slab)
			alloc_block(cachep, ac, slab, batchcount);
		cache_grow_end(cachep, slab);

		if (!ac->avail)
			return NULL;
	}
	ac->touched = 1;

	return ac->entry[--ac->avail];
}

#if DEBUG
static void *cache_alloc_debugcheck_after(struct kmem_cache *cachep,
				gfp_t flags, void *objp, unsigned long caller)
{
	WARN_ON_ONCE(cachep->ctor && (flags & __GFP_ZERO));
	if (!objp || is_kfence_address(objp))
		return objp;
	if (cachep->flags & SLAB_POISON) {
		check_poison_obj(cachep, objp);
		slab_kernel_map(cachep, objp, 1);
		poison_obj(cachep, objp, POISON_INUSE);
	}
	if (cachep->flags & SLAB_STORE_USER)
		*dbg_userword(cachep, objp) = (void *)caller;

	if (cachep->flags & SLAB_RED_ZONE) {
		if (*dbg_redzone1(cachep, objp) != RED_INACTIVE ||
				*dbg_redzone2(cachep, objp) != RED_INACTIVE) {
			slab_error(cachep, "double free, or memory outside object was overwritten");
			pr_err("%px: redzone 1:0x%llx, redzone 2:0x%llx\n",
			       objp, *dbg_redzone1(cachep, objp),
			       *dbg_redzone2(cachep, objp));
		}
		*dbg_redzone1(cachep, objp) = RED_ACTIVE;
		*dbg_redzone2(cachep, objp) = RED_ACTIVE;
	}

	objp += obj_offset(cachep);
	if (cachep->ctor && cachep->flags & SLAB_POISON)
		cachep->ctor(objp);
	if ((unsigned long)objp & (arch_slab_minalign() - 1)) {
		pr_err("0x%px: not aligned to arch_slab_minalign()=%u\n", objp,
		       arch_slab_minalign());
	}
	return objp;
}
#else
#define cache_alloc_debugcheck_after(a, b, objp, d) (objp)
#endif

static inline void *____cache_alloc(struct kmem_cache *cachep, gfp_t flags)
{
	void *objp;
	struct array_cache *ac;

	check_irq_off();

	ac = cpu_cache_get(cachep);
	if (likely(ac->avail)) {
		ac->touched = 1;
		objp = ac->entry[--ac->avail];

		STATS_INC_ALLOCHIT(cachep);
		goto out;
	}

	STATS_INC_ALLOCMISS(cachep);
	objp = cache_alloc_refill(cachep, flags);
	/*
	 * the 'ac' may be updated by cache_alloc_refill(),
	 * and kmemleak_erase() requires its correct value.
	 */
	ac = cpu_cache_get(cachep);

out:
	/*
	 * To avoid a false negative, if an object that is in one of the
	 * per-CPU caches is leaked, we need to make sure kmemleak doesn't
	 * treat the array pointers as a reference to the object.
	 */
	if (objp)
		kmemleak_erase(&ac->entry[ac->avail]);
	return objp;
}

#ifdef CONFIG_NUMA
static void *____cache_alloc_node(struct kmem_cache *, gfp_t, int);

/*
 * Try allocating on another node if PFA_SPREAD_SLAB is a mempolicy is set.
 *
 * If we are in_interrupt, then process context, including cpusets and
 * mempolicy, may not apply and should not be used for allocation policy.
 */
static void *alternate_node_alloc(struct kmem_cache *cachep, gfp_t flags)
{
	int nid_alloc, nid_here;

	if (in_interrupt() || (flags & __GFP_THISNODE))
		return NULL;
	nid_alloc = nid_here = numa_mem_id();
	if (cpuset_do_slab_mem_spread() && (cachep->flags & SLAB_MEM_SPREAD))
		nid_alloc = cpuset_slab_spread_node();
	else if (current->mempolicy)
		nid_alloc = mempolicy_slab_node();
	if (nid_alloc != nid_here)
		return ____cache_alloc_node(cachep, flags, nid_alloc);
	return NULL;
}

/*
 * Fallback function if there was no memory available and no objects on a
 * certain node and fall back is permitted. First we scan all the
 * available node for available objects. If that fails then we
 * perform an allocation without specifying a node. This allows the page
 * allocator to do its reclaim / fallback magic. We then insert the
 * slab into the proper nodelist and then allocate from it.
 */
static void *fallback_alloc(struct kmem_cache *cache, gfp_t flags)
{
	struct zonelist *zonelist;
	struct zoneref *z;
	struct zone *zone;
	enum zone_type highest_zoneidx = gfp_zone(flags);
	void *obj = NULL;
	struct slab *slab;
	int nid;
	unsigned int cpuset_mems_cookie;

	if (flags & __GFP_THISNODE)
		return NULL;

retry_cpuset:
	cpuset_mems_cookie = read_mems_allowed_begin();
	zonelist = node_zonelist(mempolicy_slab_node(), flags);

retry:
	/*
	 * Look through allowed nodes for objects available
	 * from existing per node queues.
	 */
	for_each_zone_zonelist(zone, z, zonelist, highest_zoneidx) {
		nid = zone_to_nid(zone);

		if (cpuset_zone_allowed(zone, flags) &&
			get_node(cache, nid) &&
			get_node(cache, nid)->free_objects) {
				obj = ____cache_alloc_node(cache,
					gfp_exact_node(flags), nid);
				if (obj)
					break;
		}
	}

	if (!obj) {
		/*
		 * This allocation will be performed within the constraints
		 * of the current cpuset / memory policy requirements.
		 * We may trigger various forms of reclaim on the allowed
		 * set and go into memory reserves if necessary.
		 */
		slab = cache_grow_begin(cache, flags, numa_mem_id());
		cache_grow_end(cache, slab);
		if (slab) {
			nid = slab_nid(slab);
			obj = ____cache_alloc_node(cache,
				gfp_exact_node(flags), nid);

			/*
			 * Another processor may allocate the objects in
			 * the slab since we are not holding any locks.
			 */
			if (!obj)
				goto retry;
		}
	}

	if (unlikely(!obj && read_mems_allowed_retry(cpuset_mems_cookie)))
		goto retry_cpuset;
	return obj;
}

/*
 * An interface to enable slab creation on nodeid
 */
static void *____cache_alloc_node(struct kmem_cache *cachep, gfp_t flags,
				int nodeid)
{
	struct slab *slab;
	struct kmem_cache_node *n;
	void *obj = NULL;
	void *list = NULL;

	VM_BUG_ON(nodeid < 0 || nodeid >= MAX_NUMNODES);
	n = get_node(cachep, nodeid);
	BUG_ON(!n);

	check_irq_off();
	raw_spin_lock(&n->list_lock);
	slab = get_first_slab(n, false);
	if (!slab)
		goto must_grow;

	check_spinlock_acquired_node(cachep, nodeid);

	STATS_INC_NODEALLOCS(cachep);
	STATS_INC_ACTIVE(cachep);
	STATS_SET_HIGH(cachep);

	BUG_ON(slab->active == cachep->num);

	obj = slab_get_obj(cachep, slab);
	n->free_objects--;

	fixup_slab_list(cachep, n, slab, &list);

	raw_spin_unlock(&n->list_lock);
	fixup_objfreelist_debug(cachep, &list);
	return obj;

must_grow:
	raw_spin_unlock(&n->list_lock);
	slab = cache_grow_begin(cachep, gfp_exact_node(flags), nodeid);
	if (slab) {
		/* This slab isn't counted yet so don't update free_objects */
		obj = slab_get_obj(cachep, slab);
	}
	cache_grow_end(cachep, slab);

	return obj ? obj : fallback_alloc(cachep, flags);
}

static __always_inline void *
__do_cache_alloc(struct kmem_cache *cachep, gfp_t flags, int nodeid)
{
	void *objp = NULL;
	int slab_node = numa_mem_id();

	if (nodeid == NUMA_NO_NODE) {
		if (current->mempolicy || cpuset_do_slab_mem_spread()) {
			objp = alternate_node_alloc(cachep, flags);
			if (objp)
				goto out;
		}
		/*
		 * Use the locally cached objects if possible.
		 * However ____cache_alloc does not allow fallback
		 * to other nodes. It may fail while we still have
		 * objects on other nodes available.
		 */
		objp = ____cache_alloc(cachep, flags);
		nodeid = slab_node;
	} else if (nodeid == slab_node) {
		objp = ____cache_alloc(cachep, flags);
	} else if (!get_node(cachep, nodeid)) {
		/* Node not bootstrapped yet */
		objp = fallback_alloc(cachep, flags);
		goto out;
	}

	/*
	 * We may just have run out of memory on the local node.
	 * ____cache_alloc_node() knows how to locate memory on other nodes
	 */
	if (!objp)
		objp = ____cache_alloc_node(cachep, flags, nodeid);
out:
	return objp;
}
#else

static __always_inline void *
__do_cache_alloc(struct kmem_cache *cachep, gfp_t flags, int nodeid __maybe_unused)
{
	return ____cache_alloc(cachep, flags);
}

#endif /* CONFIG_NUMA */

static __always_inline void *
slab_alloc_node(struct kmem_cache *cachep, struct list_lru *lru, gfp_t flags,
		int nodeid, size_t orig_size, unsigned long caller)
{
	unsigned long save_flags;
	void *objp;
	struct obj_cgroup *objcg = NULL;
	bool init = false;

	flags &= gfp_allowed_mask;
	cachep = slab_pre_alloc_hook(cachep, lru, &objcg, 1, flags);
	if (unlikely(!cachep))
		return NULL;

	objp = kfence_alloc(cachep, orig_size, flags);
	if (unlikely(objp))
		goto out;

	local_irq_save(save_flags);
	objp = __do_cache_alloc(cachep, flags, nodeid);
	local_irq_restore(save_flags);
	objp = cache_alloc_debugcheck_after(cachep, flags, objp, caller);
	prefetchw(objp);
	init = slab_want_init_on_alloc(flags, cachep);

out:
	slab_post_alloc_hook(cachep, objcg, flags, 1, &objp, init,
				cachep->object_size);
	return objp;
}

static __always_inline void *
slab_alloc(struct kmem_cache *cachep, struct list_lru *lru, gfp_t flags,
	   size_t orig_size, unsigned long caller)
{
	return slab_alloc_node(cachep, lru, flags, NUMA_NO_NODE, orig_size,
			       caller);
}

/*
 * Caller needs to acquire correct kmem_cache_node's list_lock
 * @list: List of detached free slabs should be freed by caller
 */
static void free_block(struct kmem_cache *cachep, void **objpp,
			int nr_objects, int node, struct list_head *list)
{
	int i;
	struct kmem_cache_node *n = get_node(cachep, node);
	struct slab *slab;

	n->free_objects += nr_objects;

	for (i = 0; i < nr_objects; i++) {
		void *objp;
		struct slab *slab;

		objp = objpp[i];

		slab = virt_to_slab(objp);
		list_del(&slab->slab_list);
		check_spinlock_acquired_node(cachep, node);
		slab_put_obj(cachep, slab, objp);
		STATS_DEC_ACTIVE(cachep);

		/* fixup slab chains */
		if (slab->active == 0) {
			list_add(&slab->slab_list, &n->slabs_free);
			n->free_slabs++;
		} else {
			/* Unconditionally move a slab to the end of the
			 * partial list on free - maximum time for the
			 * other objects to be freed, too.
			 */
			list_add_tail(&slab->slab_list, &n->slabs_partial);
		}
	}

	while (n->free_objects > n->free_limit && !list_empty(&n->slabs_free)) {
		n->free_objects -= cachep->num;

		slab = list_last_entry(&n->slabs_free, struct slab, slab_list);
		list_move(&slab->slab_list, list);
		n->free_slabs--;
		n->total_slabs--;
	}
}

static void cache_flusharray(struct kmem_cache *cachep, struct array_cache *ac)
{
	int batchcount;
	struct kmem_cache_node *n;
	int node = numa_mem_id();
	LIST_HEAD(list);

	batchcount = ac->batchcount;

	check_irq_off();
	n = get_node(cachep, node);
	raw_spin_lock(&n->list_lock);
	if (n->shared) {
		struct array_cache *shared_array = n->shared;
		int max = shared_array->limit - shared_array->avail;
		if (max) {
			if (batchcount > max)
				batchcount = max;
			memcpy(&(shared_array->entry[shared_array->avail]),
			       ac->entry, sizeof(void *) * batchcount);
			shared_array->avail += batchcount;
			goto free_done;
		}
	}

	free_block(cachep, ac->entry, batchcount, node, &list);
free_done:
#if STATS
	{
		int i = 0;
		struct slab *slab;

		list_for_each_entry(slab, &n->slabs_free, slab_list) {
			BUG_ON(slab->active);

			i++;
		}
		STATS_SET_FREEABLE(cachep, i);
	}
#endif
	raw_spin_unlock(&n->list_lock);
	ac->avail -= batchcount;
	memmove(ac->entry, &(ac->entry[batchcount]), sizeof(void *)*ac->avail);
	slabs_destroy(cachep, &list);
}

/*
 * Release an obj back to its cache. If the obj has a constructed state, it must
 * be in this state _before_ it is released.  Called with disabled ints.
 */
static __always_inline void __cache_free(struct kmem_cache *cachep, void *objp,
					 unsigned long caller)
{
	bool init;

	memcg_slab_free_hook(cachep, virt_to_slab(objp), &objp, 1);

	if (is_kfence_address(objp)) {
		kmemleak_free_recursive(objp, cachep->flags);
		__kfence_free(objp);
		return;
	}

	/*
	 * As memory initialization might be integrated into KASAN,
	 * kasan_slab_free and initialization memset must be
	 * kept together to avoid discrepancies in behavior.
	 */
	init = slab_want_init_on_free(cachep);
	if (init && !kasan_has_integrated_init())
		memset(objp, 0, cachep->object_size);
	/* KASAN might put objp into memory quarantine, delaying its reuse. */
	if (kasan_slab_free(cachep, objp, init))
		return;

	/* Use KCSAN to help debug racy use-after-free. */
	if (!(cachep->flags & SLAB_TYPESAFE_BY_RCU))
		__kcsan_check_access(objp, cachep->object_size,
				     KCSAN_ACCESS_WRITE | KCSAN_ACCESS_ASSERT);

	___cache_free(cachep, objp, caller);
}

void ___cache_free(struct kmem_cache *cachep, void *objp,
		unsigned long caller)
{
	struct array_cache *ac = cpu_cache_get(cachep);

	check_irq_off();
	kmemleak_free_recursive(objp, cachep->flags);
	objp = cache_free_debugcheck(cachep, objp, caller);

	/*
	 * Skip calling cache_free_alien() when the platform is not numa.
	 * This will avoid cache misses that happen while accessing slabp (which
	 * is per page memory  reference) to get nodeid. Instead use a global
	 * variable to skip the call, which is mostly likely to be present in
	 * the cache.
	 */
	if (nr_online_nodes > 1 && cache_free_alien(cachep, objp))
		return;

	if (ac->avail < ac->limit) {
		STATS_INC_FREEHIT(cachep);
	} else {
		STATS_INC_FREEMISS(cachep);
		cache_flusharray(cachep, ac);
	}

	if (sk_memalloc_socks()) {
		struct slab *slab = virt_to_slab(objp);

		if (unlikely(slab_test_pfmemalloc(slab))) {
			cache_free_pfmemalloc(cachep, slab, objp);
			return;
		}
	}

	__free_one(ac, objp);
}

static __always_inline
void *__kmem_cache_alloc_lru(struct kmem_cache *cachep, struct list_lru *lru,
			     gfp_t flags)
{
	void *ret = slab_alloc(cachep, lru, flags, cachep->object_size, _RET_IP_);

	trace_kmem_cache_alloc(_RET_IP_, ret, cachep, flags, NUMA_NO_NODE);

	return ret;
}

void *kmem_cache_alloc(struct kmem_cache *cachep, gfp_t flags)
{
	return __kmem_cache_alloc_lru(cachep, NULL, flags);
}
EXPORT_SYMBOL(kmem_cache_alloc);

void *kmem_cache_alloc_lru(struct kmem_cache *cachep, struct list_lru *lru,
			   gfp_t flags)
{
	return __kmem_cache_alloc_lru(cachep, lru, flags);
}
EXPORT_SYMBOL(kmem_cache_alloc_lru);

static __always_inline void
cache_alloc_debugcheck_after_bulk(struct kmem_cache *s, gfp_t flags,
				  size_t size, void **p, unsigned long caller)
{
	size_t i;

	for (i = 0; i < size; i++)
		p[i] = cache_alloc_debugcheck_after(s, flags, p[i], caller);
}

int kmem_cache_alloc_bulk(struct kmem_cache *s, gfp_t flags, size_t size,
			  void **p)
{
	struct obj_cgroup *objcg = NULL;
	unsigned long irqflags;
	size_t i;

	s = slab_pre_alloc_hook(s, NULL, &objcg, size, flags);
	if (!s)
		return 0;

	local_irq_save(irqflags);
	for (i = 0; i < size; i++) {
		void *objp = kfence_alloc(s, s->object_size, flags) ?:
			     __do_cache_alloc(s, flags, NUMA_NO_NODE);

		if (unlikely(!objp))
			goto error;
		p[i] = objp;
	}
	local_irq_restore(irqflags);

	cache_alloc_debugcheck_after_bulk(s, flags, size, p, _RET_IP_);

	/*
	 * memcg and kmem_cache debug support and memory initialization.
	 * Done outside of the IRQ disabled section.
	 */
	slab_post_alloc_hook(s, objcg, flags, size, p,
			slab_want_init_on_alloc(flags, s), s->object_size);
	/* FIXME: Trace call missing. Christoph would like a bulk variant */
	return size;
error:
	local_irq_restore(irqflags);
	cache_alloc_debugcheck_after_bulk(s, flags, i, p, _RET_IP_);
	slab_post_alloc_hook(s, objcg, flags, i, p, false, s->object_size);
	kmem_cache_free_bulk(s, i, p);
	return 0;
}
EXPORT_SYMBOL(kmem_cache_alloc_bulk);

/**
 * kmem_cache_alloc_node - Allocate an object on the specified node
 * @cachep: The cache to allocate from.
 * @flags: See kmalloc().
 * @nodeid: node number of the target node.
 *
 * Identical to kmem_cache_alloc but it will allocate memory on the given
 * node, which can improve the performance for cpu bound structures.
 *
 * Fallback to other node is possible if __GFP_THISNODE is not set.
 *
 * Return: pointer to the new object or %NULL in case of error
 */
void *kmem_cache_alloc_node(struct kmem_cache *cachep, gfp_t flags, int nodeid)
{
	void *ret = slab_alloc_node(cachep, NULL, flags, nodeid, cachep->object_size, _RET_IP_);

	trace_kmem_cache_alloc(_RET_IP_, ret, cachep, flags, nodeid);

	return ret;
}
EXPORT_SYMBOL(kmem_cache_alloc_node);

void *__kmem_cache_alloc_node(struct kmem_cache *cachep, gfp_t flags,
			     int nodeid, size_t orig_size,
			     unsigned long caller)
{
	return slab_alloc_node(cachep, NULL, flags, nodeid,
			       orig_size, caller);
}

#ifdef CONFIG_PRINTK
void __kmem_obj_info(struct kmem_obj_info *kpp, void *object, struct slab *slab)
{
	struct kmem_cache *cachep;
	unsigned int objnr;
	void *objp;

	kpp->kp_ptr = object;
	kpp->kp_slab = slab;
	cachep = slab->slab_cache;
	kpp->kp_slab_cache = cachep;
	objp = object - obj_offset(cachep);
	kpp->kp_data_offset = obj_offset(cachep);
	slab = virt_to_slab(objp);
	objnr = obj_to_index(cachep, slab, objp);
	objp = index_to_obj(cachep, slab, objnr);
	kpp->kp_objp = objp;
	if (DEBUG && cachep->flags & SLAB_STORE_USER)
		kpp->kp_ret = *dbg_userword(cachep, objp);
}
#endif

static __always_inline
void __do_kmem_cache_free(struct kmem_cache *cachep, void *objp,
			  unsigned long caller)
{
	unsigned long flags;

	local_irq_save(flags);
	debug_check_no_locks_freed(objp, cachep->object_size);
	if (!(cachep->flags & SLAB_DEBUG_OBJECTS))
		debug_check_no_obj_freed(objp, cachep->object_size);
	__cache_free(cachep, objp, caller);
	local_irq_restore(flags);
}

void __kmem_cache_free(struct kmem_cache *cachep, void *objp,
		       unsigned long caller)
{
	__do_kmem_cache_free(cachep, objp, caller);
}

/**
 * kmem_cache_free - Deallocate an object
 * @cachep: The cache the allocation was from.
 * @objp: The previously allocated object.
 *
 * Free an object which was previously allocated from this
 * cache.
 */
void kmem_cache_free(struct kmem_cache *cachep, void *objp)
{
	cachep = cache_from_obj(cachep, objp);
	if (!cachep)
		return;

	trace_kmem_cache_free(_RET_IP_, objp, cachep);
	__do_kmem_cache_free(cachep, objp, _RET_IP_);
}
EXPORT_SYMBOL(kmem_cache_free);

void kmem_cache_free_bulk(struct kmem_cache *orig_s, size_t size, void **p)
{
	unsigned long flags;

	local_irq_save(flags);
	for (int i = 0; i < size; i++) {
		void *objp = p[i];
		struct kmem_cache *s;

		if (!orig_s) {
			struct folio *folio = virt_to_folio(objp);

			/* called via kfree_bulk */
			if (!folio_test_slab(folio)) {
				local_irq_restore(flags);
				free_large_kmalloc(folio, objp);
				local_irq_save(flags);
				continue;
			}
			s = folio_slab(folio)->slab_cache;
		} else {
			s = cache_from_obj(orig_s, objp);
		}

		if (!s)
			continue;

		debug_check_no_locks_freed(objp, s->object_size);
		if (!(s->flags & SLAB_DEBUG_OBJECTS))
			debug_check_no_obj_freed(objp, s->object_size);

		__cache_free(s, objp, _RET_IP_);
	}
	local_irq_restore(flags);

	/* FIXME: add tracing */
}
EXPORT_SYMBOL(kmem_cache_free_bulk);

/*
 * This initializes kmem_cache_node or resizes various caches for all nodes.
 */
static int setup_kmem_cache_nodes(struct kmem_cache *cachep, gfp_t gfp)
{
	int ret;
	int node;
	struct kmem_cache_node *n;

	for_each_online_node(node) {
		ret = setup_kmem_cache_node(cachep, node, gfp, true);
		if (ret)
			goto fail;

	}

	return 0;

fail:
	if (!cachep->list.next) {
		/* Cache is not active yet. Roll back what we did */
		node--;
		while (node >= 0) {
			n = get_node(cachep, node);
			if (n) {
				kfree(n->shared);
				free_alien_cache(n->alien);
				kfree(n);
				cachep->node[node] = NULL;
			}
			node--;
		}
	}
	return -ENOMEM;
}

/* Always called with the slab_mutex held */
static int do_tune_cpucache(struct kmem_cache *cachep, int limit,
			    int batchcount, int shared, gfp_t gfp)
{
	struct array_cache __percpu *cpu_cache, *prev;
	int cpu;

	cpu_cache = alloc_kmem_cache_cpus(cachep, limit, batchcount);
	if (!cpu_cache)
		return -ENOMEM;

	prev = cachep->cpu_cache;
	cachep->cpu_cache = cpu_cache;
	/*
	 * Without a previous cpu_cache there's no need to synchronize remote
	 * cpus, so skip the IPIs.
	 */
	if (prev)
		kick_all_cpus_sync();

	check_irq_on();
	cachep->batchcount = batchcount;
	cachep->limit = limit;
	cachep->shared = shared;

	if (!prev)
		goto setup_node;

	for_each_online_cpu(cpu) {
		LIST_HEAD(list);
		int node;
		struct kmem_cache_node *n;
		struct array_cache *ac = per_cpu_ptr(prev, cpu);

		node = cpu_to_mem(cpu);
		n = get_node(cachep, node);
		raw_spin_lock_irq(&n->list_lock);
		free_block(cachep, ac->entry, ac->avail, node, &list);
		raw_spin_unlock_irq(&n->list_lock);
		slabs_destroy(cachep, &list);
	}
	free_percpu(prev);

setup_node:
	return setup_kmem_cache_nodes(cachep, gfp);
}

/* Called with slab_mutex held always */
static int enable_cpucache(struct kmem_cache *cachep, gfp_t gfp)
{
	int err;
	int limit = 0;
	int shared = 0;
	int batchcount = 0;

	err = cache_random_seq_create(cachep, cachep->num, gfp);
	if (err)
		goto end;

	/*
	 * The head array serves three purposes:
	 * - create a LIFO ordering, i.e. return objects that are cache-warm
	 * - reduce the number of spinlock operations.
	 * - reduce the number of linked list operations on the slab and
	 *   bufctl chains: array operations are cheaper.
	 * The numbers are guessed, we should auto-tune as described by
	 * Bonwick.
	 */
	if (cachep->size > 131072)
		limit = 1;
	else if (cachep->size > PAGE_SIZE)
		limit = 8;
	else if (cachep->size > 1024)
		limit = 24;
	else if (cachep->size > 256)
		limit = 54;
	else
		limit = 120;

	/*
	 * CPU bound tasks (e.g. network routing) can exhibit cpu bound
	 * allocation behaviour: Most allocs on one cpu, most free operations
	 * on another cpu. For these cases, an efficient object passing between
	 * cpus is necessary. This is provided by a shared array. The array
	 * replaces Bonwick's magazine layer.
	 * On uniprocessor, it's functionally equivalent (but less efficient)
	 * to a larger limit. Thus disabled by default.
	 */
	shared = 0;
	if (cachep->size <= PAGE_SIZE && num_possible_cpus() > 1)
		shared = 8;

#if DEBUG
	/*
	 * With debugging enabled, large batchcount lead to excessively long
	 * periods with disabled local interrupts. Limit the batchcount
	 */
	if (limit > 32)
		limit = 32;
#endif
	batchcount = (limit + 1) / 2;
	err = do_tune_cpucache(cachep, limit, batchcount, shared, gfp);
end:
	if (err)
		pr_err("enable_cpucache failed for %s, error %d\n",
		       cachep->name, -err);
	return err;
}

/*
 * Drain an array if it contains any elements taking the node lock only if
 * necessary. Note that the node listlock also protects the array_cache
 * if drain_array() is used on the shared array.
 */
static void drain_array(struct kmem_cache *cachep, struct kmem_cache_node *n,
			 struct array_cache *ac, int node)
{
	LIST_HEAD(list);

	/* ac from n->shared can be freed if we don't hold the slab_mutex. */
	check_mutex_acquired();

	if (!ac || !ac->avail)
		return;

	if (ac->touched) {
		ac->touched = 0;
		return;
	}

	raw_spin_lock_irq(&n->list_lock);
	drain_array_locked(cachep, ac, node, false, &list);
	raw_spin_unlock_irq(&n->list_lock);

	slabs_destroy(cachep, &list);
}

/**
 * cache_reap - Reclaim memory from caches.
 * @w: work descriptor
 *
 * Called from workqueue/eventd every few seconds.
 * Purpose:
 * - clear the per-cpu caches for this CPU.
 * - return freeable pages to the main free memory pool.
 *
 * If we cannot acquire the cache chain mutex then just give up - we'll try
 * again on the next iteration.
 */
static void cache_reap(struct work_struct *w)
{
	struct kmem_cache *searchp;
	struct kmem_cache_node *n;
	int node = numa_mem_id();
	struct delayed_work *work = to_delayed_work(w);

	if (!mutex_trylock(&slab_mutex))
		/* Give up. Setup the next iteration. */
		goto out;

	list_for_each_entry(searchp, &slab_caches, list) {
		check_irq_on();

		/*
		 * We only take the node lock if absolutely necessary and we
		 * have established with reasonable certainty that
		 * we can do some work if the lock was obtained.
		 */
		n = get_node(searchp, node);

		reap_alien(searchp, n);

		drain_array(searchp, n, cpu_cache_get(searchp), node);

		/*
		 * These are racy checks but it does not matter
		 * if we skip one check or scan twice.
		 */
		if (time_after(n->next_reap, jiffies))
			goto next;

		n->next_reap = jiffies + REAPTIMEOUT_NODE;

		drain_array(searchp, n, n->shared, node);

		if (n->free_touched)
			n->free_touched = 0;
		else {
			int freed;

			freed = drain_freelist(searchp, n, (n->free_limit +
				5 * searchp->num - 1) / (5 * searchp->num));
			STATS_ADD_REAPED(searchp, freed);
		}
next:
		cond_resched();
	}
	check_irq_on();
	mutex_unlock(&slab_mutex);
	next_reap_node();
out:
	/* Set up the next iteration */
	schedule_delayed_work_on(smp_processor_id(), work,
				round_jiffies_relative(REAPTIMEOUT_AC));
}

void get_slabinfo(struct kmem_cache *cachep, struct slabinfo *sinfo)
{
	unsigned long active_objs, num_objs, active_slabs;
	unsigned long total_slabs = 0, free_objs = 0, shared_avail = 0;
	unsigned long free_slabs = 0;
	int node;
	struct kmem_cache_node *n;

	for_each_kmem_cache_node(cachep, node, n) {
		check_irq_on();
		raw_spin_lock_irq(&n->list_lock);

		total_slabs += n->total_slabs;
		free_slabs += n->free_slabs;
		free_objs += n->free_objects;

		if (n->shared)
			shared_avail += n->shared->avail;

		raw_spin_unlock_irq(&n->list_lock);
	}
	num_objs = total_slabs * cachep->num;
	active_slabs = total_slabs - free_slabs;
	active_objs = num_objs - free_objs;

	sinfo->active_objs = active_objs;
	sinfo->num_objs = num_objs;
	sinfo->active_slabs = active_slabs;
	sinfo->num_slabs = total_slabs;
	sinfo->shared_avail = shared_avail;
	sinfo->limit = cachep->limit;
	sinfo->batchcount = cachep->batchcount;
	sinfo->shared = cachep->shared;
	sinfo->objects_per_slab = cachep->num;
	sinfo->cache_order = cachep->gfporder;
}

void slabinfo_show_stats(struct seq_file *m, struct kmem_cache *cachep)
{
#if STATS
	{			/* node stats */
		unsigned long high = cachep->high_mark;
		unsigned long allocs = cachep->num_allocations;
		unsigned long grown = cachep->grown;
		unsigned long reaped = cachep->reaped;
		unsigned long errors = cachep->errors;
		unsigned long max_freeable = cachep->max_freeable;
		unsigned long node_allocs = cachep->node_allocs;
		unsigned long node_frees = cachep->node_frees;
		unsigned long overflows = cachep->node_overflow;

		seq_printf(m, " : globalstat %7lu %6lu %5lu %4lu %4lu %4lu %4lu %4lu %4lu",
			   allocs, high, grown,
			   reaped, errors, max_freeable, node_allocs,
			   node_frees, overflows);
	}
	/* cpu stats */
	{
		unsigned long allochit = atomic_read(&cachep->allochit);
		unsigned long allocmiss = atomic_read(&cachep->allocmiss);
		unsigned long freehit = atomic_read(&cachep->freehit);
		unsigned long freemiss = atomic_read(&cachep->freemiss);

		seq_printf(m, " : cpustat %6lu %6lu %6lu %6lu",
			   allochit, allocmiss, freehit, freemiss);
	}
#endif
}

#define MAX_SLABINFO_WRITE 128
/**
 * slabinfo_write - Tuning for the slab allocator
 * @file: unused
 * @buffer: user buffer
 * @count: data length
 * @ppos: unused
 *
 * Return: %0 on success, negative error code otherwise.
 */
ssize_t slabinfo_write(struct file *file, const char __user *buffer,
		       size_t count, loff_t *ppos)
{
	char kbuf[MAX_SLABINFO_WRITE + 1], *tmp;
	int limit, batchcount, shared, res;
	struct kmem_cache *cachep;

	if (count > MAX_SLABINFO_WRITE)
		return -EINVAL;
	if (copy_from_user(&kbuf, buffer, count))
		return -EFAULT;
	kbuf[MAX_SLABINFO_WRITE] = '\0';

	tmp = strchr(kbuf, ' ');
	if (!tmp)
		return -EINVAL;
	*tmp = '\0';
	tmp++;
	if (sscanf(tmp, " %d %d %d", &limit, &batchcount, &shared) != 3)
		return -EINVAL;

	/* Find the cache in the chain of caches. */
	mutex_lock(&slab_mutex);
	res = -EINVAL;
	list_for_each_entry(cachep, &slab_caches, list) {
		if (!strcmp(cachep->name, kbuf)) {
			if (limit < 1 || batchcount < 1 ||
					batchcount > limit || shared < 0) {
				res = 0;
			} else {
				res = do_tune_cpucache(cachep, limit,
						       batchcount, shared,
						       GFP_KERNEL);
			}
			break;
		}
	}
	mutex_unlock(&slab_mutex);
	if (res >= 0)
		res = count;
	return res;
}

#ifdef CONFIG_HARDENED_USERCOPY
/*
 * Rejects incorrectly sized objects and objects that are to be copied
 * to/from userspace but do not fall entirely within the containing slab
 * cache's usercopy region.
 *
 * Returns NULL if check passes, otherwise const char * to name of cache
 * to indicate an error.
 */
void __check_heap_object(const void *ptr, unsigned long n,
			 const struct slab *slab, bool to_user)
{
	struct kmem_cache *cachep;
	unsigned int objnr;
	unsigned long offset;

	ptr = kasan_reset_tag(ptr);

	/* Find and validate object. */
	cachep = slab->slab_cache;
	objnr = obj_to_index(cachep, slab, (void *)ptr);
	BUG_ON(objnr >= cachep->num);

	/* Find offset within object. */
	if (is_kfence_address(ptr))
		offset = ptr - kfence_object_start(ptr);
	else
		offset = ptr - index_to_obj(cachep, slab, objnr) - obj_offset(cachep);

	/* Allow address range falling entirely within usercopy region. */
	if (offset >= cachep->useroffset &&
	    offset - cachep->useroffset <= cachep->usersize &&
	    n <= cachep->useroffset - offset + cachep->usersize)
		return;

	usercopy_abort("SLAB object", cachep->name, to_user, offset, n);
}
#endif /* CONFIG_HARDENED_USERCOPY */