xref: /linux/mm/slab_common.c (revision 918e25291ce95ef26c288234b088e9d433ecd94e)

// SPDX-License-Identifier: GPL-2.0
/*
 * Slab allocator functions that are independent of the allocator strategy
 *
 * (C) 2012 Christoph Lameter <cl@gentwo.org>
 */
#include <linux/slab.h>

#include <linux/mm.h>
#include <linux/poison.h>
#include <linux/interrupt.h>
#include <linux/memory.h>
#include <linux/cache.h>
#include <linux/compiler.h>
#include <linux/kfence.h>
#include <linux/module.h>
#include <linux/cpu.h>
#include <linux/uaccess.h>
#include <linux/seq_file.h>
#include <linux/dma-mapping.h>
#include <linux/swiotlb.h>
#include <linux/proc_fs.h>
#include <linux/debugfs.h>
#include <linux/kmemleak.h>
#include <linux/kasan.h>
#include <asm/cacheflush.h>
#include <asm/tlbflush.h>
#include <asm/page.h>
#include <linux/memcontrol.h>
#include <linux/stackdepot.h>
#include <trace/events/rcu.h>

#include "../kernel/rcu/rcu.h"
#include "internal.h"
#include "slab.h"

#define CREATE_TRACE_POINTS
#include <trace/events/kmem.h>

enum slab_state slab_state;
LIST_HEAD(slab_caches);
DEFINE_MUTEX(slab_mutex);
struct kmem_cache *kmem_cache;

/*
 * Set of flags that will prevent slab merging.
 * Any flag that adds per-object metadata should be included,
 * since slab merging can update s->inuse that affects the metadata layout.
 */
#define SLAB_NEVER_MERGE (SLAB_DEBUG_FLAGS | SLAB_TYPESAFE_BY_RCU | \
		SLAB_NOLEAKTRACE | SLAB_FAILSLAB | SLAB_NO_MERGE | \
		SLAB_OBJ_EXT_IN_OBJ)

#define SLAB_MERGE_SAME (SLAB_RECLAIM_ACCOUNT | SLAB_CACHE_DMA | \
			 SLAB_CACHE_DMA32 | SLAB_ACCOUNT | SLAB_MAY_ACCOUNT)

/*
 * Merge control. If this is set then no merging of slab caches will occur.
 */
static bool slab_nomerge = !IS_ENABLED(CONFIG_SLAB_MERGE_DEFAULT);

static int __init setup_slab_nomerge(char *str)
{
	slab_nomerge = true;
	return 1;
}

static int __init setup_slab_merge(char *str)
{
	slab_nomerge = false;
	return 1;
}

__setup_param("slub_nomerge", slub_nomerge, setup_slab_nomerge, 0);
__setup_param("slub_merge", slub_merge, setup_slab_merge, 0);

__setup("slab_nomerge", setup_slab_nomerge);
__setup("slab_merge", setup_slab_merge);

/*
 * Determine the size of a slab object
 */
unsigned int kmem_cache_size(struct kmem_cache *s)
{
	return s->object_size;
}
EXPORT_SYMBOL(kmem_cache_size);

#ifdef CONFIG_DEBUG_VM

static bool kmem_cache_is_duplicate_name(const char *name)
{
	struct kmem_cache *s;

	list_for_each_entry(s, &slab_caches, list) {
		if (!strcmp(s->name, name))
			return true;
	}

	return false;
}

static int kmem_cache_sanity_check(const char *name, unsigned int size)
{
	if (!name || in_interrupt() || size > KMALLOC_MAX_SIZE) {
		pr_err("kmem_cache_create(%s) integrity check failed\n", name);
		return -EINVAL;
	}

	/* Duplicate names will confuse slabtop, et al */
	WARN(kmem_cache_is_duplicate_name(name),
			"kmem_cache of name '%s' already exists\n", name);

	WARN_ON(strchr(name, ' '));	/* It confuses parsers */
	return 0;
}
#else
static inline int kmem_cache_sanity_check(const char *name, unsigned int size)
{
	return 0;
}
#endif

/*
 * Figure out what the alignment of the objects will be given a set of
 * flags, a user specified alignment and the size of the objects.
 */
static unsigned int calculate_alignment(slab_flags_t flags,
		unsigned int align, unsigned int size)
{
	/*
	 * If the user wants hardware cache aligned objects then follow that
	 * suggestion if the object is sufficiently large.
	 *
	 * The hardware cache alignment cannot override the specified
	 * alignment though. If that is greater then use it.
	 */
	if (flags & SLAB_HWCACHE_ALIGN) {
		unsigned int ralign;

		ralign = cache_line_size();
		while (size <= ralign / 2)
			ralign /= 2;
		align = max(align, ralign);
	}

	align = max(align, arch_slab_minalign());

	return ALIGN(align, sizeof(void *));
}

/*
 * Find a mergeable slab cache
 */
int slab_unmergeable(struct kmem_cache *s)
{
	if (slab_nomerge || (s->flags & SLAB_NEVER_MERGE))
		return 1;

	if (s->ctor)
		return 1;

#ifdef CONFIG_HARDENED_USERCOPY
	if (s->usersize)
		return 1;
#endif

	/*
	 * We may have set a slab to be unmergeable during bootstrap.
	 */
	if (s->refcount < 0)
		return 1;

	return 0;
}

bool slab_args_unmergeable(struct kmem_cache_args *args, slab_flags_t flags)
{
	if (slab_nomerge)
		return true;

	if (args->ctor)
		return true;

	if (IS_ENABLED(CONFIG_HARDENED_USERCOPY) && args->usersize)
		return true;

	if (flags & SLAB_NEVER_MERGE)
		return true;

	return false;
}

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

	flags = kmem_cache_flags(flags, name);
	if (slab_args_unmergeable(args, flags))
		return NULL;

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

	list_for_each_entry_reverse(s, &slab_caches, list) {
		if (slab_unmergeable(s))
			continue;

		if (size > s->size)
			continue;

		if ((flags & SLAB_MERGE_SAME) != (s->flags & SLAB_MERGE_SAME))
			continue;
		/*
		 * Check if alignment is compatible.
		 * Courtesy of Adrian Drzewiecki
		 */
		if ((s->size & ~(align - 1)) != s->size)
			continue;

		if (s->size - size >= sizeof(void *))
			continue;

		return s;
	}
	return NULL;
}

static struct kmem_cache *create_cache(const char *name,
				       unsigned int object_size,
				       struct kmem_cache_args *args,
				       slab_flags_t flags)
{
	struct kmem_cache *s;
	int err;

	/* If a custom freelist pointer is requested make sure it's sane. */
	err = -EINVAL;
	if (args->use_freeptr_offset &&
	    (args->freeptr_offset >= object_size ||
	     (!(flags & SLAB_TYPESAFE_BY_RCU) && !args->ctor) ||
	     !IS_ALIGNED(args->freeptr_offset, __alignof__(freeptr_t))))
		goto out;

	err = -ENOMEM;
	s = kmem_cache_zalloc(kmem_cache, GFP_KERNEL);
	if (!s)
		goto out;
	err = do_kmem_cache_create(s, name, object_size, args, flags);
	if (err)
		goto out_free_cache;

	s->refcount = 1;
	list_add(&s->list, &slab_caches);
	return s;

out_free_cache:
	kmem_cache_free(kmem_cache, s);
out:
	return ERR_PTR(err);
}

static struct kmem_cache *
__kmem_cache_alias(const char *name, unsigned int size, slab_flags_t flags,
		   struct kmem_cache_args *args)
{
	struct kmem_cache *s;

	s = find_mergeable(size, flags, name, args);
	if (s) {
		if (sysfs_slab_alias(s, name))
			pr_err("SLUB: Unable to add cache alias %s to sysfs\n",
			       name);

		s->refcount++;

		/*
		 * Adjust the object sizes so that we clear
		 * the complete object on kzalloc.
		 */
		s->object_size = max(s->object_size, size);
		s->inuse = max(s->inuse, ALIGN(size, sizeof(void *)));
	}

	return s;
}

/**
 * __kmem_cache_create_args - Create a kmem cache.
 * @name: A string which is used in /proc/slabinfo to identify this cache.
 * @object_size: The size of objects to be created in this cache.
 * @args: Additional arguments for the cache creation (see
 *        &struct kmem_cache_args).
 * @flags: See the descriptions of individual flags. The common ones are listed
 *         in the description below.
 *
 * Not to be called directly, use the kmem_cache_create() wrapper with the same
 * parameters.
 *
 * Commonly used @flags:
 *
 * &SLAB_ACCOUNT - Account allocations to memcg.
 *
 * &SLAB_HWCACHE_ALIGN - Align objects on cache line boundaries.
 *
 * &SLAB_RECLAIM_ACCOUNT - Objects are reclaimable.
 *
 * &SLAB_TYPESAFE_BY_RCU - Slab page (not individual objects) freeing delayed
 * by a grace period - see the full description before using.
 *
 * Context: Cannot be called within a interrupt, but can be interrupted.
 *
 * Return: a pointer to the cache on success, NULL on failure.
 */
struct kmem_cache *__kmem_cache_create_args(const char *name,
					    unsigned int object_size,
					    struct kmem_cache_args *args,
					    slab_flags_t flags)
{
	struct kmem_cache *s = NULL;
	const char *cache_name;
	int err;

#ifdef CONFIG_SLUB_DEBUG
	/*
	 * If no slab_debug was enabled globally, the static key is not yet
	 * enabled by setup_slub_debug(). Enable it if the cache is being
	 * created with any of the debugging flags passed explicitly.
	 * It's also possible that this is the first cache created with
	 * SLAB_STORE_USER and we should init stack_depot for it.
	 */
	if (flags & SLAB_DEBUG_FLAGS)
		static_branch_enable(&slub_debug_enabled);
	if (flags & SLAB_STORE_USER)
		stack_depot_init();
#else
	flags &= ~SLAB_DEBUG_FLAGS;
#endif

	/*
	 * Caches with specific capacity are special enough. It's simpler to
	 * make them unmergeable.
	 */
	if (args->sheaf_capacity)
		flags |= SLAB_NO_MERGE;

	mutex_lock(&slab_mutex);

	err = kmem_cache_sanity_check(name, object_size);
	if (err) {
		goto out_unlock;
	}

	if (flags & ~SLAB_FLAGS_PERMITTED) {
		err = -EINVAL;
		goto out_unlock;
	}

	/*
	 * For now we assume any cache can be used with __GFP_ACCOUNT and thus
	 * may need to store objcg pointers for objects
	 */
	if (!mem_cgroup_kmem_disabled())
		flags |= SLAB_MAY_ACCOUNT;

	/* Fail closed on bad usersize of useroffset values. */
	if (!IS_ENABLED(CONFIG_HARDENED_USERCOPY) ||
	    WARN_ON(!args->usersize && args->useroffset) ||
	    WARN_ON(object_size < args->usersize ||
		    object_size - args->usersize < args->useroffset))
		args->usersize = args->useroffset = 0;

	s = __kmem_cache_alias(name, object_size, flags, args);
	if (s)
		goto out_unlock;

	cache_name = kstrdup_const(name, GFP_KERNEL);
	if (!cache_name) {
		err = -ENOMEM;
		goto out_unlock;
	}

	args->align = calculate_alignment(flags, args->align, object_size);
	s = create_cache(cache_name, object_size, args, flags);
	if (IS_ERR(s)) {
		err = PTR_ERR(s);
		kfree_const(cache_name);
	}

out_unlock:
	mutex_unlock(&slab_mutex);

	if (err) {
		if (flags & SLAB_PANIC)
			panic("%s: Failed to create slab '%s'. Error %d\n",
				__func__, name, err);
		else {
			pr_warn("%s(%s) failed with error %d\n",
				__func__, name, err);
			dump_stack();
		}
		return NULL;
	}
	return s;
}
EXPORT_SYMBOL(__kmem_cache_create_args);

static struct kmem_cache *kmem_buckets_cache __ro_after_init;

/**
 * kmem_buckets_create - Create a set of caches that handle dynamic sized
 *			 allocations via kmem_buckets_alloc()
 * @name: A prefix string which is used in /proc/slabinfo to identify this
 *	  cache. The individual caches with have their sizes as the suffix.
 * @flags: SLAB flags (see kmem_cache_create() for details).
 * @useroffset: Starting offset within an allocation that may be copied
 *		to/from userspace.
 * @usersize: How many bytes, starting at @useroffset, may be copied
 *		to/from userspace.
 * @ctor: A constructor for the objects, run when new allocations are made.
 *
 * Cannot be called within an interrupt, but can be interrupted.
 *
 * Return: a pointer to the cache on success, NULL on failure. When
 * CONFIG_SLAB_BUCKETS is not enabled, ZERO_SIZE_PTR is returned, and
 * subsequent calls to kmem_buckets_alloc() will fall back to kmalloc().
 * (i.e. callers only need to check for NULL on failure.)
 */
kmem_buckets *kmem_buckets_create(const char *name, slab_flags_t flags,
				  unsigned int useroffset,
				  unsigned int usersize,
				  void (*ctor)(void *))
{
	unsigned long mask = 0;
	unsigned int idx;
	kmem_buckets *b;

	BUILD_BUG_ON(ARRAY_SIZE(kmalloc_caches[KMALLOC_NORMAL]) > BITS_PER_LONG);

	/*
	 * When the separate buckets API is not built in, just return
	 * a non-NULL value for the kmem_buckets pointer, which will be
	 * unused when performing allocations.
	 */
	if (!IS_ENABLED(CONFIG_SLAB_BUCKETS))
		return ZERO_SIZE_PTR;

	if (WARN_ON(!kmem_buckets_cache))
		return NULL;

	b = kmem_cache_alloc(kmem_buckets_cache, GFP_KERNEL|__GFP_ZERO);
	if (WARN_ON(!b))
		return NULL;

	flags |= SLAB_NO_MERGE;

	for (idx = 0; idx < ARRAY_SIZE(kmalloc_caches[KMALLOC_NORMAL]); idx++) {
		char *short_size, *cache_name;
		unsigned int cache_useroffset, cache_usersize;
		unsigned int size, aligned_idx;

		if (!kmalloc_caches[KMALLOC_NORMAL][idx])
			continue;

		size = kmalloc_caches[KMALLOC_NORMAL][idx]->object_size;
		if (!size)
			continue;

		short_size = strchr(kmalloc_caches[KMALLOC_NORMAL][idx]->name, '-');
		if (WARN_ON(!short_size))
			goto fail;

		if (useroffset >= size) {
			cache_useroffset = 0;
			cache_usersize = 0;
		} else {
			cache_useroffset = useroffset;
			cache_usersize = min(size - cache_useroffset, usersize);
		}

		aligned_idx = __kmalloc_index(size, false);
		if (!(*b)[aligned_idx]) {
			cache_name = kasprintf(GFP_KERNEL, "%s-%s", name, short_size + 1);
			if (WARN_ON(!cache_name))
				goto fail;
			(*b)[aligned_idx] = kmem_cache_create_usercopy(cache_name, size,
					0, flags, cache_useroffset,
					cache_usersize, ctor);
			kfree(cache_name);
			if (WARN_ON(!(*b)[aligned_idx]))
				goto fail;
			set_bit(aligned_idx, &mask);
		}
		if (idx != aligned_idx)
			(*b)[idx] = (*b)[aligned_idx];
	}

	return b;

fail:
	for_each_set_bit(idx, &mask, ARRAY_SIZE(kmalloc_caches[KMALLOC_NORMAL]))
		kmem_cache_destroy((*b)[idx]);
	kmem_cache_free(kmem_buckets_cache, b);

	return NULL;
}
EXPORT_SYMBOL(kmem_buckets_create);

/*
 * For a given kmem_cache, kmem_cache_destroy() should only be called
 * once or there will be a use-after-free problem. The actual deletion
 * and release of the kobject does not need slab_mutex or cpu_hotplug_lock
 * protection. So they are now done without holding those locks.
 */
static void kmem_cache_release(struct kmem_cache *s)
{
	kfence_shutdown_cache(s);
	if (__is_defined(SLAB_SUPPORTS_SYSFS) && slab_state >= FULL)
		sysfs_slab_release(s);
	else
		slab_kmem_cache_release(s);
}

void slab_kmem_cache_release(struct kmem_cache *s)
{
	__kmem_cache_release(s);
	kfree_const(s->name);
	kmem_cache_free(kmem_cache, s);
}

void kmem_cache_destroy(struct kmem_cache *s)
{
	int err;

	if (unlikely(!s) || !kasan_check_byte(s))
		return;

	/* in-flight kfree_rcu()'s may include objects from our cache */
	kvfree_rcu_barrier_on_cache(s);

	if (IS_ENABLED(CONFIG_SLUB_RCU_DEBUG) &&
	    (s->flags & SLAB_TYPESAFE_BY_RCU)) {
		/*
		 * Under CONFIG_SLUB_RCU_DEBUG, when objects in a
		 * SLAB_TYPESAFE_BY_RCU slab are freed, SLUB will internally
		 * defer their freeing with call_rcu().
		 * Wait for such call_rcu() invocations here before actually
		 * destroying the cache.
		 *
		 * It doesn't matter that we haven't looked at the slab refcount
		 * yet - slabs with SLAB_TYPESAFE_BY_RCU can't be merged, so
		 * the refcount should be 1 here.
		 */
		rcu_barrier();
	}

	/* Wait for deferred work from kmalloc/kfree_nolock() */
	deferred_work_barrier();

	cpus_read_lock();
	mutex_lock(&slab_mutex);

	s->refcount--;
	if (s->refcount) {
		mutex_unlock(&slab_mutex);
		cpus_read_unlock();
		return;
	}

	/* free asan quarantined objects */
	kasan_cache_shutdown(s);

	err = __kmem_cache_shutdown(s);
	if (!slab_in_kunit_test())
		WARN(err, "%s %s: Slab cache still has objects when called from %pS",
		     __func__, s->name, (void *)_RET_IP_);

	list_del(&s->list);

	mutex_unlock(&slab_mutex);
	cpus_read_unlock();

	if (slab_state >= FULL)
		sysfs_slab_unlink(s);
	debugfs_slab_release(s);

	if (err)
		return;

	if (s->flags & SLAB_TYPESAFE_BY_RCU)
		rcu_barrier();

	kmem_cache_release(s);
}
EXPORT_SYMBOL(kmem_cache_destroy);

/**
 * kmem_cache_shrink - Shrink a cache.
 * @cachep: The cache to shrink.
 *
 * Releases as many slabs as possible for a cache.
 * To help debugging, a zero exit status indicates all slabs were released.
 *
 * Return: %0 if all slabs were released, non-zero otherwise
 */
int kmem_cache_shrink(struct kmem_cache *cachep)
{
	kasan_cache_shrink(cachep);

	return __kmem_cache_shrink(cachep);
}
EXPORT_SYMBOL(kmem_cache_shrink);

bool slab_is_available(void)
{
	return slab_state >= UP;
}

#ifdef CONFIG_PRINTK
static void kmem_obj_info(struct kmem_obj_info *kpp, void *object, struct slab *slab)
{
	if (__kfence_obj_info(kpp, object, slab))
		return;
	__kmem_obj_info(kpp, object, slab);
}

/**
 * kmem_dump_obj - Print available slab provenance information
 * @object: slab object for which to find provenance information.
 *
 * This function uses pr_cont(), so that the caller is expected to have
 * printed out whatever preamble is appropriate.  The provenance information
 * depends on the type of object and on how much debugging is enabled.
 * For a slab-cache object, the fact that it is a slab object is printed,
 * and, if available, the slab name, return address, and stack trace from
 * the allocation and last free path of that object.
 *
 * Return: %true if the pointer is to a not-yet-freed object from
 * kmalloc() or kmem_cache_alloc(), either %true or %false if the pointer
 * is to an already-freed object, and %false otherwise.
 */
bool kmem_dump_obj(void *object)
{
	char *cp = IS_ENABLED(CONFIG_MMU) ? "" : "/vmalloc";
	int i;
	struct slab *slab;
	unsigned long ptroffset;
	struct kmem_obj_info kp = { };

	/* Some arches consider ZERO_SIZE_PTR to be a valid address. */
	if (object < (void *)PAGE_SIZE || !virt_addr_valid(object))
		return false;
	slab = virt_to_slab(object);
	if (!slab)
		return false;

	kmem_obj_info(&kp, object, slab);
	if (kp.kp_slab_cache)
		pr_cont(" slab%s %s", cp, kp.kp_slab_cache->name);
	else
		pr_cont(" slab%s", cp);
	if (is_kfence_address(object))
		pr_cont(" (kfence)");
	if (kp.kp_objp)
		pr_cont(" start %px", kp.kp_objp);
	if (kp.kp_data_offset)
		pr_cont(" data offset %lu", kp.kp_data_offset);
	if (kp.kp_objp) {
		ptroffset = ((char *)object - (char *)kp.kp_objp) - kp.kp_data_offset;
		pr_cont(" pointer offset %lu", ptroffset);
	}
	if (kp.kp_slab_cache && kp.kp_slab_cache->object_size)
		pr_cont(" size %u", kp.kp_slab_cache->object_size);
	if (kp.kp_ret)
		pr_cont(" allocated at %pS\n", kp.kp_ret);
	else
		pr_cont("\n");
	for (i = 0; i < ARRAY_SIZE(kp.kp_stack); i++) {
		if (!kp.kp_stack[i])
			break;
		pr_info("    %pS\n", kp.kp_stack[i]);
	}

	if (kp.kp_free_stack[0])
		pr_cont(" Free path:\n");

	for (i = 0; i < ARRAY_SIZE(kp.kp_free_stack); i++) {
		if (!kp.kp_free_stack[i])
			break;
		pr_info("    %pS\n", kp.kp_free_stack[i]);
	}

	return true;
}
EXPORT_SYMBOL_GPL(kmem_dump_obj);
#endif

/* Create a cache during boot when no slab services are available yet */
void __init create_boot_cache(struct kmem_cache *s, const char *name,
		unsigned int size, slab_flags_t flags,
		unsigned int useroffset, unsigned int usersize)
{
	int err;
	unsigned int align = ARCH_KMALLOC_MINALIGN;
	struct kmem_cache_args kmem_args = {};

	/*
	 * kmalloc caches guarantee alignment of at least the largest
	 * power-of-two divisor of the size. For power-of-two sizes,
	 * it is the size itself.
	 */
	if (flags & SLAB_KMALLOC)
		align = max(align, 1U << (ffs(size) - 1));
	kmem_args.align = calculate_alignment(flags, align, size);

#ifdef CONFIG_HARDENED_USERCOPY
	kmem_args.useroffset = useroffset;
	kmem_args.usersize = usersize;
#endif

	err = do_kmem_cache_create(s, name, size, &kmem_args, flags);

	if (err)
		panic("Creation of kmalloc slab %s size=%u failed. Reason %d\n",
					name, size, err);

	s->refcount = -1;	/* Exempt from merging for now */
}

static struct kmem_cache *__init create_kmalloc_cache(const char *name,
						      unsigned int size,
						      slab_flags_t flags)
{
	struct kmem_cache *s = kmem_cache_zalloc(kmem_cache, GFP_NOWAIT);

	if (!s)
		panic("Out of memory when creating slab %s\n", name);

	create_boot_cache(s, name, size, flags | SLAB_KMALLOC, 0, size);
	list_add(&s->list, &slab_caches);
	s->refcount = 1;
	return s;
}

kmem_buckets kmalloc_caches[NR_KMALLOC_TYPES] __ro_after_init =
{ /* initialization for https://llvm.org/pr42570 */ };
EXPORT_SYMBOL(kmalloc_caches);

#ifdef CONFIG_KMALLOC_PARTITION_RANDOM
unsigned long random_kmalloc_seed __ro_after_init;
EXPORT_SYMBOL(random_kmalloc_seed);
#endif

/*
 * Conversion table for small slabs sizes / 8 to the index in the
 * kmalloc array. This is necessary for slabs < 192 since we have non power
 * of two cache sizes there. The size of larger slabs can be determined using
 * fls.
 */
u8 kmalloc_size_index[24] __ro_after_init = {
	3,	/* 8 */
	4,	/* 16 */
	5,	/* 24 */
	5,	/* 32 */
	6,	/* 40 */
	6,	/* 48 */
	6,	/* 56 */
	6,	/* 64 */
	1,	/* 72 */
	1,	/* 80 */
	1,	/* 88 */
	1,	/* 96 */
	7,	/* 104 */
	7,	/* 112 */
	7,	/* 120 */
	7,	/* 128 */
	2,	/* 136 */
	2,	/* 144 */
	2,	/* 152 */
	2,	/* 160 */
	2,	/* 168 */
	2,	/* 176 */
	2,	/* 184 */
	2	/* 192 */
};

size_t kmalloc_size_roundup(size_t size)
{
	if (size && size <= KMALLOC_MAX_CACHE_SIZE) {
		struct kmem_cache *s;

		/*
		 * The flags don't matter since size_index is common to all.
		 * Neither does the caller for just getting ->object_size.
		 */
		s = kmalloc_slab(size, NULL, GFP_KERNEL, __kmalloc_token(0),
				 SLAB_ALLOC_DEFAULT);
		return s->object_size;
	}

	/* Above the smaller buckets, size is a multiple of page size. */
	if (size && size <= KMALLOC_MAX_SIZE)
		return PAGE_SIZE << get_order(size);

	/*
	 * Return 'size' for 0 - kmalloc() returns ZERO_SIZE_PTR
	 * and very large size - kmalloc() may fail.
	 */
	return size;

}
EXPORT_SYMBOL(kmalloc_size_roundup);

#ifdef CONFIG_ZONE_DMA
#define KMALLOC_DMA_NAME(sz)	.name[KMALLOC_DMA] = "dma-kmalloc-" #sz,
#else
#define KMALLOC_DMA_NAME(sz)
#endif

#ifdef CONFIG_MEMCG
#define KMALLOC_CGROUP_NAME(sz)	.name[KMALLOC_CGROUP] = "kmalloc-cg-" #sz,
#else
#define KMALLOC_CGROUP_NAME(sz)
#endif

#ifndef CONFIG_SLUB_TINY
#define KMALLOC_RCL_NAME(sz)	.name[KMALLOC_RECLAIM] = "kmalloc-rcl-" #sz,
#else
#define KMALLOC_RCL_NAME(sz)
#endif

#ifdef CONFIG_KMALLOC_PARTITION_CACHES
#define __KMALLOC_PARTITION_CONCAT(a, b) a ## b
#define KMALLOC_PARTITION_NAME(N, sz) __KMALLOC_PARTITION_CONCAT(KMA_PART_, N)(sz)
#define KMA_PART_1(sz)                  .name[KMALLOC_PARTITION_START +  1] = "kmalloc-part-01-" #sz,
#define KMA_PART_2(sz)  KMA_PART_1(sz)  .name[KMALLOC_PARTITION_START +  2] = "kmalloc-part-02-" #sz,
#define KMA_PART_3(sz)  KMA_PART_2(sz)  .name[KMALLOC_PARTITION_START +  3] = "kmalloc-part-03-" #sz,
#define KMA_PART_4(sz)  KMA_PART_3(sz)  .name[KMALLOC_PARTITION_START +  4] = "kmalloc-part-04-" #sz,
#define KMA_PART_5(sz)  KMA_PART_4(sz)  .name[KMALLOC_PARTITION_START +  5] = "kmalloc-part-05-" #sz,
#define KMA_PART_6(sz)  KMA_PART_5(sz)  .name[KMALLOC_PARTITION_START +  6] = "kmalloc-part-06-" #sz,
#define KMA_PART_7(sz)  KMA_PART_6(sz)  .name[KMALLOC_PARTITION_START +  7] = "kmalloc-part-07-" #sz,
#define KMA_PART_8(sz)  KMA_PART_7(sz)  .name[KMALLOC_PARTITION_START +  8] = "kmalloc-part-08-" #sz,
#define KMA_PART_9(sz)  KMA_PART_8(sz)  .name[KMALLOC_PARTITION_START +  9] = "kmalloc-part-09-" #sz,
#define KMA_PART_10(sz) KMA_PART_9(sz)  .name[KMALLOC_PARTITION_START + 10] = "kmalloc-part-10-" #sz,
#define KMA_PART_11(sz) KMA_PART_10(sz) .name[KMALLOC_PARTITION_START + 11] = "kmalloc-part-11-" #sz,
#define KMA_PART_12(sz) KMA_PART_11(sz) .name[KMALLOC_PARTITION_START + 12] = "kmalloc-part-12-" #sz,
#define KMA_PART_13(sz) KMA_PART_12(sz) .name[KMALLOC_PARTITION_START + 13] = "kmalloc-part-13-" #sz,
#define KMA_PART_14(sz) KMA_PART_13(sz) .name[KMALLOC_PARTITION_START + 14] = "kmalloc-part-14-" #sz,
#define KMA_PART_15(sz) KMA_PART_14(sz) .name[KMALLOC_PARTITION_START + 15] = "kmalloc-part-15-" #sz,
#else // CONFIG_KMALLOC_PARTITION_CACHES
#define KMALLOC_PARTITION_NAME(N, sz)
#endif

#ifdef CONFIG_SLAB_OBJ_EXT
#define KMALLOC_NO_OBJ_EXT_NAME(sz) .name[KMALLOC_NO_OBJ_EXT] = "kmalloc-no-objext-" #sz,
#else
#define KMALLOC_NO_OBJ_EXT_NAME(sz)
#endif

#define INIT_KMALLOC_INFO(__size, __short_size)			\
{								\
	.name[KMALLOC_NORMAL]  = "kmalloc-" #__short_size,	\
	KMALLOC_RCL_NAME(__short_size)				\
	KMALLOC_CGROUP_NAME(__short_size)			\
	KMALLOC_DMA_NAME(__short_size)				\
	KMALLOC_PARTITION_NAME(KMALLOC_PARTITION_CACHES_NR, __short_size)	\
	KMALLOC_NO_OBJ_EXT_NAME(__short_size)			\
	.size = __size,						\
}

/*
 * kmalloc_info[] is to make slab_debug=,kmalloc-xx option work at boot time.
 * kmalloc_index() supports up to 2^21=2MB, so the final entry of the table is
 * kmalloc-2M.
 */
const struct kmalloc_info_struct kmalloc_info[] __initconst = {
	INIT_KMALLOC_INFO(0, 0),
	INIT_KMALLOC_INFO(96, 96),
	INIT_KMALLOC_INFO(192, 192),
	INIT_KMALLOC_INFO(8, 8),
	INIT_KMALLOC_INFO(16, 16),
	INIT_KMALLOC_INFO(32, 32),
	INIT_KMALLOC_INFO(64, 64),
	INIT_KMALLOC_INFO(128, 128),
	INIT_KMALLOC_INFO(256, 256),
	INIT_KMALLOC_INFO(512, 512),
	INIT_KMALLOC_INFO(1024, 1k),
	INIT_KMALLOC_INFO(2048, 2k),
	INIT_KMALLOC_INFO(4096, 4k),
	INIT_KMALLOC_INFO(8192, 8k),
	INIT_KMALLOC_INFO(16384, 16k),
	INIT_KMALLOC_INFO(32768, 32k),
	INIT_KMALLOC_INFO(65536, 64k),
	INIT_KMALLOC_INFO(131072, 128k),
	INIT_KMALLOC_INFO(262144, 256k),
	INIT_KMALLOC_INFO(524288, 512k),
	INIT_KMALLOC_INFO(1048576, 1M),
	INIT_KMALLOC_INFO(2097152, 2M)
};

/*
 * Patch up the size_index table if we have strange large alignment
 * requirements for the kmalloc array. This is only the case for
 * MIPS it seems. The standard arches will not generate any code here.
 *
 * Largest permitted alignment is 256 bytes due to the way we
 * handle the index determination for the smaller caches.
 *
 * Make sure that nothing crazy happens if someone starts tinkering
 * around with ARCH_KMALLOC_MINALIGN
 */
void __init setup_kmalloc_cache_index_table(void)
{
	unsigned int i;

	BUILD_BUG_ON(KMALLOC_MIN_SIZE > 256 ||
		!is_power_of_2(KMALLOC_MIN_SIZE));

	for (i = 8; i < KMALLOC_MIN_SIZE; i += 8) {
		unsigned int elem = size_index_elem(i);

		if (elem >= ARRAY_SIZE(kmalloc_size_index))
			break;
		kmalloc_size_index[elem] = KMALLOC_SHIFT_LOW;
	}

	if (KMALLOC_MIN_SIZE >= 64) {
		/*
		 * The 96 byte sized cache is not used if the alignment
		 * is 64 byte.
		 */
		for (i = 64 + 8; i <= 96; i += 8)
			kmalloc_size_index[size_index_elem(i)] = 7;

	}

	if (KMALLOC_MIN_SIZE >= 128) {
		/*
		 * The 192 byte sized cache is not used if the alignment
		 * is 128 byte. Redirect kmalloc to use the 256 byte cache
		 * instead.
		 */
		for (i = 128 + 8; i <= 192; i += 8)
			kmalloc_size_index[size_index_elem(i)] = 8;
	}
}

static unsigned int __kmalloc_minalign(void)
{
	unsigned int minalign = dma_get_cache_alignment();

	if (IS_ENABLED(CONFIG_DMA_BOUNCE_UNALIGNED_KMALLOC) &&
	    is_swiotlb_allocated())
		minalign = ARCH_KMALLOC_MINALIGN;

	return max(minalign, arch_slab_minalign());
}

static void __init
new_kmalloc_cache(int idx, enum kmalloc_cache_type type)
{
	slab_flags_t flags = 0;
	unsigned int minalign = __kmalloc_minalign();
	unsigned int aligned_size = kmalloc_info[idx].size;
	int aligned_idx = idx;

	if ((KMALLOC_RECLAIM != KMALLOC_NORMAL) && (type == KMALLOC_RECLAIM)) {
		flags |= SLAB_RECLAIM_ACCOUNT;
	} else if (IS_ENABLED(CONFIG_MEMCG) && (type == KMALLOC_CGROUP)) {
		if (mem_cgroup_kmem_disabled()) {
			kmalloc_caches[type][idx] = kmalloc_caches[KMALLOC_NORMAL][idx];
			return;
		}
		flags |= SLAB_ACCOUNT;
	} else if (IS_ENABLED(CONFIG_SLAB_OBJ_EXT) && type == KMALLOC_NO_OBJ_EXT) {
		if (!need_kmalloc_no_objext()) {
			kmalloc_caches[type][idx] = kmalloc_caches[KMALLOC_NORMAL][idx];
			return;
		}
		flags |= SLAB_NO_OBJ_EXT | SLAB_NO_MERGE;
	} else if (IS_ENABLED(CONFIG_ZONE_DMA) && (type == KMALLOC_DMA)) {
		flags |= SLAB_CACHE_DMA;
	}

#ifdef CONFIG_KMALLOC_PARTITION_CACHES
	if (type >= KMALLOC_PARTITION_START && type <= KMALLOC_PARTITION_END)
		flags |= SLAB_NO_MERGE;
#endif

	/*
	 * If memcg_kmem is enabled and this is a KMALLOC_NORMAL cache and not
	 * aliased with any other type, make sure it's never merged with any other
	 * cache.
	 *
	 * In other cases the kmalloc cache may end up being used for a
	 * __GFP_ACCOUNT allocation so mark it as such. The exception is a
	 * KMALLOC_NO_OBJ_EXT cache.
	 */
	if (!mem_cgroup_kmem_disabled()) {
		if (type == KMALLOC_NORMAL && KMALLOC_RECLAIM != KMALLOC_NORMAL)
			flags |= SLAB_NO_MERGE;
		else if (!(flags & SLAB_NO_OBJ_EXT))
			flags |= SLAB_MAY_ACCOUNT;
	}

	if (minalign > ARCH_KMALLOC_MINALIGN) {
		aligned_size = ALIGN(aligned_size, minalign);
		aligned_idx = __kmalloc_index(aligned_size, false);
	}

	if (!kmalloc_caches[type][aligned_idx])
		kmalloc_caches[type][aligned_idx] = create_kmalloc_cache(
					kmalloc_info[aligned_idx].name[type],
					aligned_size, flags);
	if (idx != aligned_idx)
		kmalloc_caches[type][idx] = kmalloc_caches[type][aligned_idx];
}

/*
 * Create the kmalloc array. Some of the regular kmalloc arrays
 * may already have been created because they were needed to
 * enable allocations for slab creation.
 */
void __init create_kmalloc_caches(void)
{
	int i;
	enum kmalloc_cache_type type;

	/*
	 * Including KMALLOC_CGROUP if CONFIG_MEMCG defined
	 */
	for (type = KMALLOC_NORMAL; type < NR_KMALLOC_TYPES; type++) {
		/* Caches that are NOT of the two-to-the-power-of size. */
		if (KMALLOC_MIN_SIZE <= 32)
			new_kmalloc_cache(1, type);
		if (KMALLOC_MIN_SIZE <= 64)
			new_kmalloc_cache(2, type);

		/* Caches that are of the two-to-the-power-of size. */
		for (i = KMALLOC_SHIFT_LOW; i <= KMALLOC_SHIFT_HIGH; i++)
			new_kmalloc_cache(i, type);
	}
#ifdef CONFIG_KMALLOC_PARTITION_RANDOM
	random_kmalloc_seed = get_random_u64();
#endif

	/* Kmalloc array is now usable */
	slab_state = UP;

	if (IS_ENABLED(CONFIG_SLAB_BUCKETS))
		kmem_buckets_cache = kmem_cache_create("kmalloc_buckets",
						       sizeof(kmem_buckets),
						       0, SLAB_NO_MERGE, NULL);
}

gfp_t kmalloc_fix_flags(gfp_t flags)
{
	gfp_t invalid_mask = flags & GFP_SLAB_BUG_MASK;

	flags &= ~GFP_SLAB_BUG_MASK;
	pr_warn("Unexpected gfp: %#x (%pGg). Fixing up to gfp: %#x (%pGg). Fix your code!\n",
			invalid_mask, &invalid_mask, flags, &flags);
	dump_stack();

	return flags;
}

#ifdef CONFIG_SLAB_FREELIST_RANDOM
/* Randomize a generic freelist */
static void freelist_randomize(unsigned int *list,
			       unsigned int count)
{
	unsigned int rand;
	unsigned int i;

	for (i = 0; i < count; i++)
		list[i] = i;

	/* Fisher-Yates shuffle */
	for (i = count - 1; i > 0; i--) {
		rand = get_random_u32_below(i + 1);
		swap(list[i], list[rand]);
	}
}

/* Create a random sequence per cache */
int cache_random_seq_create(struct kmem_cache *cachep, unsigned int count,
				    gfp_t gfp)
{

	if (count < 2 || cachep->random_seq)
		return 0;

	cachep->random_seq = kcalloc(count, sizeof(unsigned int), gfp);
	if (!cachep->random_seq)
		return -ENOMEM;

	freelist_randomize(cachep->random_seq, count);
	return 0;
}

/* Destroy the per-cache random freelist sequence */
void cache_random_seq_destroy(struct kmem_cache *cachep)
{
	kfree(cachep->random_seq);
	cachep->random_seq = NULL;
}
#endif /* CONFIG_SLAB_FREELIST_RANDOM */

#ifdef CONFIG_SLUB_DEBUG
#define SLABINFO_RIGHTS (0400)

static void print_slabinfo_header(struct seq_file *m)
{
	/*
	 * Output format version, so at least we can change it
	 * without _too_ many complaints.
	 */
	seq_puts(m, "slabinfo - version: 2.1\n");
	seq_puts(m, "# name            <active_objs> <num_objs> <objsize> <objperslab> <pagesperslab>");
	seq_puts(m, " : tunables <limit> <batchcount> <sharedfactor>");
	seq_puts(m, " : slabdata <active_slabs> <num_slabs> <sharedavail>");
	seq_putc(m, '\n');
}

static void *slab_start(struct seq_file *m, loff_t *pos)
{
	mutex_lock(&slab_mutex);
	return seq_list_start(&slab_caches, *pos);
}

static void *slab_next(struct seq_file *m, void *p, loff_t *pos)
{
	return seq_list_next(p, &slab_caches, pos);
}

static void slab_stop(struct seq_file *m, void *p)
{
	mutex_unlock(&slab_mutex);
}

static void cache_show(struct kmem_cache *s, struct seq_file *m)
{
	struct slabinfo sinfo;

	memset(&sinfo, 0, sizeof(sinfo));
	get_slabinfo(s, &sinfo);

	seq_printf(m, "%-17s %6lu %6lu %6u %4u %4d",
		   s->name, sinfo.active_objs, sinfo.num_objs, s->size,
		   sinfo.objects_per_slab, (1 << sinfo.cache_order));

	seq_printf(m, " : tunables %4u %4u %4u",
		   sinfo.limit, sinfo.batchcount, sinfo.shared);
	seq_printf(m, " : slabdata %6lu %6lu %6lu",
		   sinfo.active_slabs, sinfo.num_slabs, sinfo.shared_avail);
	seq_putc(m, '\n');
}

static int slab_show(struct seq_file *m, void *p)
{
	struct kmem_cache *s = list_entry(p, struct kmem_cache, list);

	if (p == slab_caches.next)
		print_slabinfo_header(m);
	cache_show(s, m);
	return 0;
}

void dump_unreclaimable_slab(void)
{
	struct kmem_cache *s;
	struct slabinfo sinfo;

	/*
	 * Here acquiring slab_mutex is risky since we don't prefer to get
	 * sleep in oom path. But, without mutex hold, it may introduce a
	 * risk of crash.
	 * Use mutex_trylock to protect the list traverse, dump nothing
	 * without acquiring the mutex.
	 */
	if (!mutex_trylock(&slab_mutex)) {
		pr_warn("excessive unreclaimable slab but cannot dump stats\n");
		return;
	}

	pr_info("Unreclaimable slab info:\n");
	pr_info("Name                      Used          Total\n");

	list_for_each_entry(s, &slab_caches, list) {
		if (s->flags & SLAB_RECLAIM_ACCOUNT)
			continue;

		get_slabinfo(s, &sinfo);

		if (sinfo.num_objs > 0)
			pr_info("%-17s %10luKB %10luKB\n", s->name,
				(sinfo.active_objs * s->size) / 1024,
				(sinfo.num_objs * s->size) / 1024);
	}
	mutex_unlock(&slab_mutex);
}

/*
 * slabinfo_op - iterator that generates /proc/slabinfo
 *
 * Output layout:
 * cache-name
 * num-active-objs
 * total-objs
 * object size
 * num-active-slabs
 * total-slabs
 * num-pages-per-slab
 * + further values on SMP and with statistics enabled
 */
static const struct seq_operations slabinfo_op = {
	.start = slab_start,
	.next = slab_next,
	.stop = slab_stop,
	.show = slab_show,
};

static int slabinfo_open(struct inode *inode, struct file *file)
{
	return seq_open(file, &slabinfo_op);
}

static const struct proc_ops slabinfo_proc_ops = {
	.proc_flags	= PROC_ENTRY_PERMANENT,
	.proc_open	= slabinfo_open,
	.proc_read	= seq_read,
	.proc_lseek	= seq_lseek,
	.proc_release	= seq_release,
};

static int __init slab_proc_init(void)
{
	proc_create("slabinfo", SLABINFO_RIGHTS, NULL, &slabinfo_proc_ops);
	return 0;
}
module_init(slab_proc_init);

#endif /* CONFIG_SLUB_DEBUG */

/**
 * kfree_sensitive - Clear sensitive information in memory before freeing
 * @p: object to free memory of
 *
 * The memory of the object @p points to is zeroed before freed.
 * If @p is %NULL, kfree_sensitive() does nothing.
 *
 * Note: this function zeroes the whole allocated buffer which can be a good
 * deal bigger than the requested buffer size passed to kmalloc(). So be
 * careful when using this function in performance sensitive code.
 */
void kfree_sensitive(const void *p)
{
	size_t ks;
	void *mem = (void *)p;

	ks = ksize(mem);
	if (ks) {
		kasan_unpoison_range(mem, ks);
		memzero_explicit(mem, ks);
	}
	kfree(mem);
}
EXPORT_SYMBOL(kfree_sensitive);

#ifdef CONFIG_BPF_SYSCALL
#include <linux/btf.h>

__bpf_kfunc_start_defs();

__bpf_kfunc struct kmem_cache *bpf_get_kmem_cache(u64 addr)
{
	struct slab *slab;

	if (!virt_addr_valid((void *)(long)addr))
		return NULL;

	slab = virt_to_slab((void *)(long)addr);
	return slab ? slab->slab_cache : NULL;
}

__bpf_kfunc_end_defs();
#endif /* CONFIG_BPF_SYSCALL */

/* Tracepoints definitions. */
EXPORT_TRACEPOINT_SYMBOL(kmalloc);
EXPORT_TRACEPOINT_SYMBOL(kmem_cache_alloc);
EXPORT_TRACEPOINT_SYMBOL(kfree);
EXPORT_TRACEPOINT_SYMBOL(kmem_cache_free);

void kfree_call_rcu_nolock(struct kvfree_rcu_head *head, void *ptr)
{
	struct slab *slab;

	if (!IS_ENABLED(CONFIG_KVFREE_RCU_BATCHED))
		goto fallback;

	if (unlikely(is_vmalloc_addr(ptr)))
		goto fallback;

	slab = virt_to_slab(ptr);
	if (unlikely(!slab))
		goto fallback;

	if (unlikely(IS_ENABLED(CONFIG_NUMA) && slab_nid(slab) != numa_mem_id()))
		goto fallback;

	if (unlikely(!__kfree_rcu_sheaf(slab->slab_cache, ptr, SLAB_FREE_NOLOCK)))
		goto fallback;

	return;

fallback:
	defer_kfree_rcu(head);
}
EXPORT_SYMBOL_GPL(kfree_call_rcu_nolock);

#ifndef CONFIG_KVFREE_RCU_BATCHED

void kvfree_call_rcu(struct kvfree_rcu_head *head, void *ptr)
{
	if (head) {
		kasan_record_aux_stack(ptr);
		call_rcu(&head->head, kvfree_rcu_cb);
		return;
	}

	// kvfree_rcu(one_arg) call.
	might_sleep();
	synchronize_rcu();
	kvfree(ptr);
}
EXPORT_SYMBOL_GPL(kvfree_call_rcu);

void kvfree_rcu_barrier(void)
{
	deferred_work_barrier();
	rcu_barrier();
}

void kvfree_rcu_barrier_on_cache(struct kmem_cache *s)
{
	deferred_work_barrier();
	rcu_barrier();
}

void __init kvfree_rcu_init(void)
{
}

#else /* CONFIG_KVFREE_RCU_BATCHED */

/*
 * This rcu parameter is runtime-read-only. It reflects
 * a minimum allowed number of objects which can be cached
 * per-CPU. Object size is equal to one page. This value
 * can be changed at boot time.
 */
static int rcu_min_cached_objs = 5;
module_param(rcu_min_cached_objs, int, 0444);

// A page shrinker can ask for pages to be freed to make them
// available for other parts of the system. This usually happens
// under low memory conditions, and in that case we should also
// defer page-cache filling for a short time period.
//
// The default value is 5 seconds, which is long enough to reduce
// interference with the shrinker while it asks other systems to
// drain their caches.
static int rcu_delay_page_cache_fill_msec = 5000;
module_param(rcu_delay_page_cache_fill_msec, int, 0444);

static struct workqueue_struct *rcu_reclaim_wq;

/* Maximum number of jiffies to wait before draining a batch. */
#define KFREE_DRAIN_JIFFIES (5 * HZ)
#define KFREE_N_BATCHES 2
#define FREE_N_CHANNELS 2

/**
 * struct kvfree_rcu_bulk_data - single block to store kvfree_rcu() pointers
 * @list: List node. All blocks are linked between each other
 * @gp_snap: Snapshot of RCU state for objects placed to this bulk
 * @nr_records: Number of active pointers in the array
 * @records: Array of the kvfree_rcu() pointers
 */
struct kvfree_rcu_bulk_data {
	struct list_head list;
	struct rcu_gp_seq gp_snap;
	unsigned long nr_records;
	void *records[] __counted_by(nr_records);
};

/*
 * This macro defines how many entries the "records" array
 * will contain. It is based on the fact that the size of
 * kvfree_rcu_bulk_data structure becomes exactly one page.
 */
#define KVFREE_BULK_MAX_ENTR \
	((PAGE_SIZE - sizeof(struct kvfree_rcu_bulk_data)) / sizeof(void *))

/**
 * struct kfree_rcu_cpu_work - single batch of kfree_rcu() requests
 * @rcu_work: Let queue_rcu_work() invoke workqueue handler after grace period
 * @head_free: List of kfree_rcu() objects waiting for a grace period
 * @head_free_gp_snap: Grace-period snapshot to check for attempted premature frees.
 * @bulk_head_free: Bulk-List of kvfree_rcu() objects waiting for a grace period
 * @krcp: Pointer to @kfree_rcu_cpu structure
 */

struct kfree_rcu_cpu_work {
	struct rcu_work rcu_work;
	struct kvfree_rcu_head *head_free;
	struct rcu_gp_seq head_free_gp_snap;
	struct list_head bulk_head_free[FREE_N_CHANNELS];
	struct kfree_rcu_cpu *krcp;
};

/**
 * struct kfree_rcu_cpu - batch up kfree_rcu() requests for RCU grace period
 * @head: List of kfree_rcu() objects not yet waiting for a grace period
 * @head_gp_snap: Snapshot of RCU state for objects placed to "@head"
 * @bulk_head: Bulk-List of kvfree_rcu() objects not yet waiting for a grace period
 * @krw_arr: Array of batches of kfree_rcu() objects waiting for a grace period
 * @lock: Synchronize access to this structure
 * @monitor_work: Promote @head to @head_free after KFREE_DRAIN_JIFFIES
 * @initialized: The @rcu_work fields have been initialized
 * @head_count: Number of objects in rcu_head singular list
 * @bulk_count: Number of objects in bulk-list
 * @bkvcache:
 *	A simple cache list that contains objects for reuse purpose.
 *	In order to save some per-cpu space the list is singular.
 *	Even though it is lockless an access has to be protected by the
 *	per-cpu lock.
 * @page_cache_work: A work to refill the cache when it is empty
 * @backoff_page_cache_fill: Delay cache refills
 * @work_in_progress: Indicates that page_cache_work is running
 * @hrtimer: A hrtimer for scheduling a page_cache_work
 * @nr_bkv_objs: number of allocated objects at @bkvcache.
 *
 * This is a per-CPU structure.  The reason that it is not included in
 * the rcu_data structure is to permit this code to be extracted from
 * the RCU files.  Such extraction could allow further optimization of
 * the interactions with the slab allocators.
 */
struct kfree_rcu_cpu {
	// Objects queued on a linked list
	// through their rcu_head structures.
	struct kvfree_rcu_head *head;
	unsigned long head_gp_snap;
	atomic_t head_count;

	// Objects queued on a bulk-list.
	struct list_head bulk_head[FREE_N_CHANNELS];
	atomic_t bulk_count[FREE_N_CHANNELS];

	struct kfree_rcu_cpu_work krw_arr[KFREE_N_BATCHES];
	raw_spinlock_t lock;
	struct delayed_work monitor_work;
	bool initialized;

	struct delayed_work page_cache_work;
	atomic_t backoff_page_cache_fill;
	atomic_t work_in_progress;
	struct hrtimer hrtimer;

	struct llist_head bkvcache;
	int nr_bkv_objs;
};

static DEFINE_PER_CPU(struct kfree_rcu_cpu, krc) = {
	.lock = __RAW_SPIN_LOCK_UNLOCKED(krc.lock),
};

static __always_inline void
debug_rcu_bhead_unqueue(struct kvfree_rcu_bulk_data *bhead)
{
#ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD
	int i;

	for (i = 0; i < bhead->nr_records; i++)
		debug_rcu_head_unqueue((struct rcu_head *)(bhead->records[i]));
#endif
}

static inline struct kfree_rcu_cpu *
krc_this_cpu_lock(unsigned long *flags)
{
	struct kfree_rcu_cpu *krcp;

	local_irq_save(*flags);	// For safely calling this_cpu_ptr().
	krcp = this_cpu_ptr(&krc);
	raw_spin_lock(&krcp->lock);

	return krcp;
}

static inline void
krc_this_cpu_unlock(struct kfree_rcu_cpu *krcp, unsigned long flags)
{
	raw_spin_unlock_irqrestore(&krcp->lock, flags);
}

static inline struct kvfree_rcu_bulk_data *
get_cached_bnode(struct kfree_rcu_cpu *krcp)
{
	if (!krcp->nr_bkv_objs)
		return NULL;

	WRITE_ONCE(krcp->nr_bkv_objs, krcp->nr_bkv_objs - 1);
	return (struct kvfree_rcu_bulk_data *)
		llist_del_first(&krcp->bkvcache);
}

static inline bool
put_cached_bnode(struct kfree_rcu_cpu *krcp,
	struct kvfree_rcu_bulk_data *bnode)
{
	// Check the limit.
	if (krcp->nr_bkv_objs >= rcu_min_cached_objs)
		return false;

	llist_add((struct llist_node *) bnode, &krcp->bkvcache);
	WRITE_ONCE(krcp->nr_bkv_objs, krcp->nr_bkv_objs + 1);
	return true;
}

static int
drain_page_cache(struct kfree_rcu_cpu *krcp)
{
	unsigned long flags;
	struct llist_node *page_list, *pos, *n;
	int freed = 0;

	if (!rcu_min_cached_objs)
		return 0;

	raw_spin_lock_irqsave(&krcp->lock, flags);
	page_list = llist_del_all(&krcp->bkvcache);
	WRITE_ONCE(krcp->nr_bkv_objs, 0);
	raw_spin_unlock_irqrestore(&krcp->lock, flags);

	llist_for_each_safe(pos, n, page_list) {
		free_page((unsigned long)pos);
		freed++;
	}

	return freed;
}

static void
kvfree_rcu_bulk(struct kfree_rcu_cpu *krcp,
	struct kvfree_rcu_bulk_data *bnode, int idx)
{
	unsigned long flags;
	int i;

	if (!WARN_ON_ONCE(!poll_state_synchronize_rcu_full(&bnode->gp_snap))) {
		debug_rcu_bhead_unqueue(bnode);
		rcu_lock_acquire(&rcu_callback_map);
		if (idx == 0) { // kmalloc() / kfree().
			trace_rcu_invoke_kfree_bulk_callback(
				"slab", bnode->nr_records,
				bnode->records);

			kfree_bulk(bnode->nr_records, bnode->records);
		} else { // vmalloc() / vfree().
			for (i = 0; i < bnode->nr_records; i++) {
				trace_rcu_invoke_kvfree_callback(
					"slab", bnode->records[i], 0);

				vfree(bnode->records[i]);
			}
		}
		rcu_lock_release(&rcu_callback_map);
	}

	raw_spin_lock_irqsave(&krcp->lock, flags);
	if (put_cached_bnode(krcp, bnode))
		bnode = NULL;
	raw_spin_unlock_irqrestore(&krcp->lock, flags);

	if (bnode)
		free_page((unsigned long) bnode);

	cond_resched_tasks_rcu_qs();
}

static void
kvfree_rcu_list(struct kvfree_rcu_head *head)
{
	struct kvfree_rcu_head *next;

	for (; head; head = next) {
		void *ptr = kvmalloc_obj_start_addr(head);
		unsigned long offset = (void *) head - ptr;

		next = head->next;
		debug_rcu_head_unqueue((struct rcu_head *)ptr);
		rcu_lock_acquire(&rcu_callback_map);
		trace_rcu_invoke_kvfree_callback("slab", head, offset);

		kvfree(ptr);

		rcu_lock_release(&rcu_callback_map);
		cond_resched_tasks_rcu_qs();
	}
}

/*
 * This function is invoked in workqueue context after a grace period.
 * It frees all the objects queued on ->bulk_head_free or ->head_free.
 */
static void kfree_rcu_work(struct work_struct *work)
{
	unsigned long flags;
	struct kvfree_rcu_bulk_data *bnode, *n;
	struct list_head bulk_head[FREE_N_CHANNELS];
	struct kvfree_rcu_head *head;
	struct kfree_rcu_cpu *krcp;
	struct kfree_rcu_cpu_work *krwp;
	struct rcu_gp_seq head_gp_snap;
	int i;

	krwp = container_of(to_rcu_work(work),
		struct kfree_rcu_cpu_work, rcu_work);
	krcp = krwp->krcp;

	raw_spin_lock_irqsave(&krcp->lock, flags);
	// Channels 1 and 2.
	for (i = 0; i < FREE_N_CHANNELS; i++)
		list_replace_init(&krwp->bulk_head_free[i], &bulk_head[i]);

	// Channel 3.
	head = krwp->head_free;
	krwp->head_free = NULL;
	head_gp_snap = krwp->head_free_gp_snap;
	raw_spin_unlock_irqrestore(&krcp->lock, flags);

	// Handle the first two channels.
	for (i = 0; i < FREE_N_CHANNELS; i++) {
		// Start from the tail page, so a GP is likely passed for it.
		list_for_each_entry_safe(bnode, n, &bulk_head[i], list)
			kvfree_rcu_bulk(krcp, bnode, i);
	}

	/*
	 * This is used when the "bulk" path can not be used for the
	 * double-argument of kvfree_rcu().  This happens when the
	 * page-cache is empty, which means that objects are instead
	 * queued on a linked list through their rcu_head structures.
	 * This list is named "Channel 3".
	 */
	if (head && !WARN_ON_ONCE(!poll_state_synchronize_rcu_full(&head_gp_snap)))
		kvfree_rcu_list(head);
}

static bool kfree_rcu_sheaf(void *obj)
{
	struct kmem_cache *s;
	struct slab *slab;
	unsigned int free_flags = SLAB_FREE_DEFAULT;

	/*
	 * It is not safe to spin on PREEMPT_RT because the kernel might be
	 * holding a raw spinlock and slab acquires sleeping locks.
	 */
	if (IS_ENABLED(CONFIG_PREEMPT_RT))
		free_flags = SLAB_FREE_NOLOCK;

	if (is_vmalloc_addr(obj))
		return false;

	slab = virt_to_slab(obj);
	if (unlikely(!slab))
		return false;

	s = slab->slab_cache;
	if (likely(!IS_ENABLED(CONFIG_NUMA) || slab_nid(slab) == numa_mem_id()))
		return __kfree_rcu_sheaf(s, obj, free_flags);

	return false;
}

static bool
need_offload_krc(struct kfree_rcu_cpu *krcp)
{
	int i;

	for (i = 0; i < FREE_N_CHANNELS; i++)
		if (!list_empty(&krcp->bulk_head[i]))
			return true;

	return !!READ_ONCE(krcp->head);
}

static bool
need_wait_for_krwp_work(struct kfree_rcu_cpu_work *krwp)
{
	int i;

	for (i = 0; i < FREE_N_CHANNELS; i++)
		if (!list_empty(&krwp->bulk_head_free[i]))
			return true;

	return !!krwp->head_free;
}

static int krc_count(struct kfree_rcu_cpu *krcp)
{
	int sum = atomic_read(&krcp->head_count);
	int i;

	for (i = 0; i < FREE_N_CHANNELS; i++)
		sum += atomic_read(&krcp->bulk_count[i]);

	return sum;
}

static void
__schedule_delayed_monitor_work(struct kfree_rcu_cpu *krcp)
{
	long delay, delay_left;

	delay = krc_count(krcp) >= KVFREE_BULK_MAX_ENTR ? 1:KFREE_DRAIN_JIFFIES;
	if (delayed_work_pending(&krcp->monitor_work)) {
		delay_left = krcp->monitor_work.timer.expires - jiffies;
		if (delay < delay_left)
			mod_delayed_work(rcu_reclaim_wq, &krcp->monitor_work, delay);
		return;
	}
	queue_delayed_work(rcu_reclaim_wq, &krcp->monitor_work, delay);
}

static void
schedule_delayed_monitor_work(struct kfree_rcu_cpu *krcp)
{
	unsigned long flags;

	raw_spin_lock_irqsave(&krcp->lock, flags);
	__schedule_delayed_monitor_work(krcp);
	raw_spin_unlock_irqrestore(&krcp->lock, flags);
}

static void
kvfree_rcu_drain_ready(struct kfree_rcu_cpu *krcp)
{
	struct list_head bulk_ready[FREE_N_CHANNELS];
	struct kvfree_rcu_bulk_data *bnode, *n;
	struct kvfree_rcu_head *head_ready = NULL;
	unsigned long flags;
	int i;

	raw_spin_lock_irqsave(&krcp->lock, flags);
	for (i = 0; i < FREE_N_CHANNELS; i++) {
		INIT_LIST_HEAD(&bulk_ready[i]);

		list_for_each_entry_safe_reverse(bnode, n, &krcp->bulk_head[i], list) {
			if (!poll_state_synchronize_rcu_full(&bnode->gp_snap))
				break;

			atomic_sub(bnode->nr_records, &krcp->bulk_count[i]);
			list_move(&bnode->list, &bulk_ready[i]);
		}
	}

	if (krcp->head && poll_state_synchronize_rcu(krcp->head_gp_snap)) {
		head_ready = krcp->head;
		atomic_set(&krcp->head_count, 0);
		WRITE_ONCE(krcp->head, NULL);
	}
	raw_spin_unlock_irqrestore(&krcp->lock, flags);

	for (i = 0; i < FREE_N_CHANNELS; i++) {
		list_for_each_entry_safe(bnode, n, &bulk_ready[i], list)
			kvfree_rcu_bulk(krcp, bnode, i);
	}

	if (head_ready)
		kvfree_rcu_list(head_ready);
}

/*
 * Return: %true if a work is queued, %false otherwise.
 */
static bool
kvfree_rcu_queue_batch(struct kfree_rcu_cpu *krcp)
{
	unsigned long flags;
	bool queued = false;
	int i, j;

	raw_spin_lock_irqsave(&krcp->lock, flags);

	// Attempt to start a new batch.
	for (i = 0; i < KFREE_N_BATCHES; i++) {
		struct kfree_rcu_cpu_work *krwp = &(krcp->krw_arr[i]);

		// Try to detach bulk_head or head and attach it, only when
		// all channels are free.  Any channel is not free means at krwp
		// there is on-going rcu work to handle krwp's free business.
		if (need_wait_for_krwp_work(krwp))
			continue;

		// kvfree_rcu_drain_ready() might handle this krcp, if so give up.
		if (need_offload_krc(krcp)) {
			// Channel 1 corresponds to the SLAB-pointer bulk path.
			// Channel 2 corresponds to vmalloc-pointer bulk path.
			for (j = 0; j < FREE_N_CHANNELS; j++) {
				if (list_empty(&krwp->bulk_head_free[j])) {
					atomic_set(&krcp->bulk_count[j], 0);
					list_replace_init(&krcp->bulk_head[j],
						&krwp->bulk_head_free[j]);
				}
			}

			// Channel 3 corresponds to both SLAB and vmalloc
			// objects queued on the linked list.
			if (!krwp->head_free) {
				krwp->head_free = krcp->head;
				get_state_synchronize_rcu_full(&krwp->head_free_gp_snap);
				atomic_set(&krcp->head_count, 0);
				WRITE_ONCE(krcp->head, NULL);
			}

			// One work is per one batch, so there are three
			// "free channels", the batch can handle. Break
			// the loop since it is done with this CPU thus
			// queuing an RCU work is _always_ success here.
			queued = queue_rcu_work(rcu_reclaim_wq, &krwp->rcu_work);
			WARN_ON_ONCE(!queued);
			break;
		}
	}

	raw_spin_unlock_irqrestore(&krcp->lock, flags);
	return queued;
}

/*
 * This function is invoked after the KFREE_DRAIN_JIFFIES timeout.
 */
static void kfree_rcu_monitor(struct work_struct *work)
{
	struct kfree_rcu_cpu *krcp = container_of(work,
		struct kfree_rcu_cpu, monitor_work.work);

	// Drain ready for reclaim.
	kvfree_rcu_drain_ready(krcp);

	// Queue a batch for a rest.
	kvfree_rcu_queue_batch(krcp);

	// If there is nothing to detach, it means that our job is
	// successfully done here. In case of having at least one
	// of the channels that is still busy we should rearm the
	// work to repeat an attempt. Because previous batches are
	// still in progress.
	if (need_offload_krc(krcp))
		schedule_delayed_monitor_work(krcp);
}

static void fill_page_cache_func(struct work_struct *work)
{
	struct kvfree_rcu_bulk_data *bnode;
	struct kfree_rcu_cpu *krcp =
		container_of(work, struct kfree_rcu_cpu,
			page_cache_work.work);
	unsigned long flags;
	int nr_pages;
	bool pushed;
	int i;

	nr_pages = atomic_read(&krcp->backoff_page_cache_fill) ?
		1 : rcu_min_cached_objs;

	for (i = READ_ONCE(krcp->nr_bkv_objs); i < nr_pages; i++) {
		bnode = (struct kvfree_rcu_bulk_data *)
			__get_free_page(GFP_KERNEL | __GFP_NORETRY | __GFP_NOMEMALLOC | __GFP_NOWARN);

		if (!bnode)
			break;

		raw_spin_lock_irqsave(&krcp->lock, flags);
		pushed = put_cached_bnode(krcp, bnode);
		raw_spin_unlock_irqrestore(&krcp->lock, flags);

		if (!pushed) {
			free_page((unsigned long) bnode);
			break;
		}
	}

	atomic_set(&krcp->work_in_progress, 0);
	atomic_set(&krcp->backoff_page_cache_fill, 0);
}

// Record ptr in a page managed by krcp, with the pre-krc_this_cpu_lock()
// state specified by flags.  If can_alloc is true, the caller must
// be schedulable and not be holding any locks or mutexes that might be
// acquired by the memory allocator or anything that it might invoke.
// Returns true if ptr was successfully recorded, else the caller must
// use a fallback.
static inline bool
add_ptr_to_bulk_krc_lock(struct kfree_rcu_cpu **krcp,
	unsigned long *flags, void *ptr, bool can_alloc)
{
	struct kvfree_rcu_bulk_data *bnode;
	int idx;

	*krcp = krc_this_cpu_lock(flags);
	if (unlikely(!(*krcp)->initialized))
		return false;

	idx = !!is_vmalloc_addr(ptr);
	bnode = list_first_entry_or_null(&(*krcp)->bulk_head[idx],
		struct kvfree_rcu_bulk_data, list);

	/* Check if a new block is required. */
	if (!bnode || bnode->nr_records == KVFREE_BULK_MAX_ENTR) {
		bnode = get_cached_bnode(*krcp);
		if (!bnode && can_alloc) {
			krc_this_cpu_unlock(*krcp, *flags);

			// __GFP_NORETRY - allows a light-weight direct reclaim
			// what is OK from minimizing of fallback hitting point of
			// view. Apart of that it forbids any OOM invoking what is
			// also beneficial since we are about to release memory soon.
			//
			// __GFP_NOMEMALLOC - prevents from consuming of all the
			// memory reserves. Please note we have a fallback path.
			//
			// __GFP_NOWARN - it is supposed that an allocation can
			// be failed under low memory or high memory pressure
			// scenarios.
			bnode = (struct kvfree_rcu_bulk_data *)
				__get_free_page(GFP_KERNEL | __GFP_NORETRY | __GFP_NOMEMALLOC | __GFP_NOWARN);
			raw_spin_lock_irqsave(&(*krcp)->lock, *flags);
		}

		if (!bnode)
			return false;

		// Initialize the new block and attach it.
		bnode->nr_records = 0;
		list_add(&bnode->list, &(*krcp)->bulk_head[idx]);
	}

	// Finally insert and update the GP for this page.
	bnode->nr_records++;
	bnode->records[bnode->nr_records - 1] = ptr;
	get_state_synchronize_rcu_full(&bnode->gp_snap);
	atomic_inc(&(*krcp)->bulk_count[idx]);

	return true;
}

static enum hrtimer_restart
schedule_page_work_fn(struct hrtimer *t)
{
	struct kfree_rcu_cpu *krcp =
		container_of(t, struct kfree_rcu_cpu, hrtimer);

	queue_delayed_work(system_highpri_wq, &krcp->page_cache_work, 0);
	return HRTIMER_NORESTART;
}

static void
run_page_cache_worker(struct kfree_rcu_cpu *krcp)
{
	// If cache disabled, bail out.
	if (!rcu_min_cached_objs)
		return;

	if (rcu_scheduler_active == RCU_SCHEDULER_RUNNING &&
			!atomic_xchg(&krcp->work_in_progress, 1)) {
		if (atomic_read(&krcp->backoff_page_cache_fill)) {
			queue_delayed_work(rcu_reclaim_wq,
				&krcp->page_cache_work,
					msecs_to_jiffies(rcu_delay_page_cache_fill_msec));
		} else {
			hrtimer_setup(&krcp->hrtimer, schedule_page_work_fn, CLOCK_MONOTONIC,
				      HRTIMER_MODE_REL);
			hrtimer_start(&krcp->hrtimer, 0, HRTIMER_MODE_REL);
		}
	}
}

void __init kfree_rcu_scheduler_running(void)
{
	int cpu;

	for_each_possible_cpu(cpu) {
		struct kfree_rcu_cpu *krcp = per_cpu_ptr(&krc, cpu);

		if (need_offload_krc(krcp))
			schedule_delayed_monitor_work(krcp);
	}
}

/*
 * Queue a request for lazy invocation of the appropriate free routine
 * after a grace period.  Please note that three paths are maintained,
 * two for the common case using arrays of pointers and a third one that
 * is used only when the main paths cannot be used, for example, due to
 * memory pressure.
 *
 * Each kvfree_call_rcu() request is added to a batch. The batch will be drained
 * every KFREE_DRAIN_JIFFIES number of jiffies. All the objects in the batch will
 * be free'd in workqueue context. This allows us to: batch requests together to
 * reduce the number of grace periods during heavy kfree_rcu()/kvfree_rcu() load.
 */
void kvfree_call_rcu(struct kvfree_rcu_head *head, void *ptr)
{
	unsigned long flags;
	struct kfree_rcu_cpu *krcp;
	bool success;

	/*
	 * Please note there is a limitation for the head-less
	 * variant, that is why there is a clear rule for such
	 * objects: it can be used from might_sleep() context
	 * only. For other places please embed an rcu_head to
	 * your data.
	 */
	if (!head)
		might_sleep();

	if (kfree_rcu_sheaf(ptr))
		return;

	// Queue the object but don't yet schedule the batch.
	if (debug_rcu_head_queue(ptr)) {
		// Probable double kfree_rcu(), just leak.
		WARN_ONCE(1, "%s(): Double-freed call. rcu_head %p\n",
			  __func__, head);

		// Mark as success and leave.
		return;
	}

	kasan_record_aux_stack(ptr);
	success = add_ptr_to_bulk_krc_lock(&krcp, &flags, ptr, !head);
	if (!success) {
		run_page_cache_worker(krcp);

		if (head == NULL)
			// Inline if kvfree_rcu(one_arg) call.
			goto unlock_return;

		head->next = krcp->head;
		WRITE_ONCE(krcp->head, head);
		atomic_inc(&krcp->head_count);

		// Take a snapshot for this krcp.
		krcp->head_gp_snap = get_state_synchronize_rcu();
		success = true;
	}

	/*
	 * The kvfree_rcu() caller considers the pointer freed at this point
	 * and likely removes any references to it. Since the actual slab
	 * freeing (and kmemleak_free()) is deferred, tell kmemleak to ignore
	 * this object (no scanning or false positives reporting).
	 */
	kmemleak_ignore(ptr);

	// Set timer to drain after KFREE_DRAIN_JIFFIES.
	if (rcu_scheduler_active == RCU_SCHEDULER_RUNNING)
		__schedule_delayed_monitor_work(krcp);

unlock_return:
	krc_this_cpu_unlock(krcp, flags);

	/*
	 * Inline kvfree() after synchronize_rcu(). We can do
	 * it from might_sleep() context only, so the current
	 * CPU can pass the QS state.
	 */
	if (!success) {
		debug_rcu_head_unqueue((struct rcu_head *) ptr);
		synchronize_rcu();
		kvfree(ptr);
	}
}
EXPORT_SYMBOL_GPL(kvfree_call_rcu);

static inline void __kvfree_rcu_barrier(void)
{
	struct kfree_rcu_cpu_work *krwp;
	struct kfree_rcu_cpu *krcp;
	bool queued;
	int i, cpu;

	/*
	 * Firstly we detach objects and queue them over an RCU-batch
	 * for all CPUs. Finally queued works are flushed for each CPU.
	 *
	 * Please note. If there are outstanding batches for a particular
	 * CPU, those have to be finished first following by queuing a new.
	 */
	for_each_possible_cpu(cpu) {
		krcp = per_cpu_ptr(&krc, cpu);

		/*
		 * Check if this CPU has any objects which have been queued for a
		 * new GP completion. If not(means nothing to detach), we are done
		 * with it. If any batch is pending/running for this "krcp", below
		 * per-cpu flush_rcu_work() waits its completion(see last step).
		 */
		if (!need_offload_krc(krcp))
			continue;

		while (1) {
			/*
			 * If we are not able to queue a new RCU work it means:
			 * - batches for this CPU are still in flight which should
			 *   be flushed first and then repeat;
			 * - no objects to detach, because of concurrency.
			 */
			queued = kvfree_rcu_queue_batch(krcp);

			/*
			 * Bail out, if there is no need to offload this "krcp"
			 * anymore. As noted earlier it can run concurrently.
			 */
			if (queued || !need_offload_krc(krcp))
				break;

			/* There are ongoing batches. */
			for (i = 0; i < KFREE_N_BATCHES; i++) {
				krwp = &(krcp->krw_arr[i]);
				flush_rcu_work(&krwp->rcu_work);
			}
		}
	}

	/*
	 * Now we guarantee that all objects are flushed.
	 */
	for_each_possible_cpu(cpu) {
		krcp = per_cpu_ptr(&krc, cpu);

		/*
		 * A monitor work can drain ready to reclaim objects
		 * directly. Wait its completion if running or pending.
		 */
		cancel_delayed_work_sync(&krcp->monitor_work);

		for (i = 0; i < KFREE_N_BATCHES; i++) {
			krwp = &(krcp->krw_arr[i]);
			flush_rcu_work(&krwp->rcu_work);
		}
	}
}

/**
 * kvfree_rcu_barrier - Wait until all in-flight kvfree_rcu() complete.
 *
 * Note that a single argument of kvfree_rcu() call has a slow path that
 * triggers synchronize_rcu() following by freeing a pointer. It is done
 * before the return from the function. Therefore for any single-argument
 * call that will result in a kfree() to a cache that is to be destroyed
 * during module exit, it is developer's responsibility to ensure that all
 * such calls have returned before the call to kmem_cache_destroy().
 */
void kvfree_rcu_barrier(void)
{
	flush_all_rcu_sheaves();
	__kvfree_rcu_barrier();
}

/**
 * kvfree_rcu_barrier_on_cache - Wait for in-flight kvfree_rcu() calls on a
 *                               specific slab cache.
 * @s: slab cache to wait for
 *
 * See the description of kvfree_rcu_barrier() for details.
 */
void kvfree_rcu_barrier_on_cache(struct kmem_cache *s)
{
	/* kfree_rcu_nolock() might have deferred frees even without sheaves */
	deferred_work_barrier();

	if (cache_has_sheaves(s)) {
		cpus_read_lock();
		flush_rcu_sheaves_on_cache(s);
		cpus_read_unlock();
	}

	rcu_barrier();
	__kvfree_rcu_barrier();
}

static unsigned long
kfree_rcu_shrink_count(struct shrinker *shrink, struct shrink_control *sc)
{
	int cpu;
	unsigned long count = 0;

	/* Snapshot count of all CPUs */
	for_each_possible_cpu(cpu) {
		struct kfree_rcu_cpu *krcp = per_cpu_ptr(&krc, cpu);

		count += krc_count(krcp);
		count += READ_ONCE(krcp->nr_bkv_objs);
		atomic_set(&krcp->backoff_page_cache_fill, 1);
	}

	return count == 0 ? SHRINK_EMPTY : count;
}

static unsigned long
kfree_rcu_shrink_scan(struct shrinker *shrink, struct shrink_control *sc)
{
	int cpu, freed = 0;

	for_each_possible_cpu(cpu) {
		int count;
		struct kfree_rcu_cpu *krcp = per_cpu_ptr(&krc, cpu);

		count = krc_count(krcp);
		count += drain_page_cache(krcp);
		kfree_rcu_monitor(&krcp->monitor_work.work);

		sc->nr_to_scan -= count;
		freed += count;

		if (sc->nr_to_scan <= 0)
			break;
	}

	return freed == 0 ? SHRINK_STOP : freed;
}

void __init kvfree_rcu_init(void)
{
	int cpu;
	int i, j;
	struct shrinker *kfree_rcu_shrinker;

	rcu_reclaim_wq = alloc_workqueue("kvfree_rcu_reclaim",
			WQ_UNBOUND | WQ_MEM_RECLAIM, 0);
	WARN_ON(!rcu_reclaim_wq);

	/* Clamp it to [0:100] seconds interval. */
	if (rcu_delay_page_cache_fill_msec < 0 ||
		rcu_delay_page_cache_fill_msec > 100 * MSEC_PER_SEC) {

		rcu_delay_page_cache_fill_msec =
			clamp(rcu_delay_page_cache_fill_msec, 0,
				(int) (100 * MSEC_PER_SEC));

		pr_info("Adjusting rcutree.rcu_delay_page_cache_fill_msec to %d ms.\n",
			rcu_delay_page_cache_fill_msec);
	}

	for_each_possible_cpu(cpu) {
		struct kfree_rcu_cpu *krcp = per_cpu_ptr(&krc, cpu);

		for (i = 0; i < KFREE_N_BATCHES; i++) {
			INIT_RCU_WORK(&krcp->krw_arr[i].rcu_work, kfree_rcu_work);
			krcp->krw_arr[i].krcp = krcp;

			for (j = 0; j < FREE_N_CHANNELS; j++)
				INIT_LIST_HEAD(&krcp->krw_arr[i].bulk_head_free[j]);
		}

		for (i = 0; i < FREE_N_CHANNELS; i++)
			INIT_LIST_HEAD(&krcp->bulk_head[i]);

		INIT_DELAYED_WORK(&krcp->monitor_work, kfree_rcu_monitor);
		INIT_DELAYED_WORK(&krcp->page_cache_work, fill_page_cache_func);
		krcp->initialized = true;
	}

	kfree_rcu_shrinker = shrinker_alloc(0, "slab-kvfree-rcu");
	if (!kfree_rcu_shrinker) {
		pr_err("Failed to allocate kfree_rcu() shrinker!\n");
		return;
	}

	kfree_rcu_shrinker->count_objects = kfree_rcu_shrink_count;
	kfree_rcu_shrinker->scan_objects = kfree_rcu_shrink_scan;

	shrinker_register(kfree_rcu_shrinker);
}

#endif /* CONFIG_KVFREE_RCU_BATCHED */