text: // 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/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 page *page,
  				void **list);
  static int slab_early_init = 1;
  
  #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;
  	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 unnessary
   * 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, struct page *page,
  				 unsigned int idx)
  {
  	return page->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 - 1);
  	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 page *page, void *objp)
  {
  	struct kmem_cache_node *n;
  	int page_node;
  	LIST_HEAD(list);
  
  	page_node = page_to_nid(page);
  	n = get_node(cachep, page_node);
  
  	spin_lock(&n->list_lock);
  	free_block(cachep, &objp, 1, page_node, &list);
  	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;
  }
  
  #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 void *alternate_node_alloc(struct kmem_cache *cachep,
  		gfp_t flags)
  {
  	return NULL;
  }
  
  static inline void *____cache_alloc_node(struct kmem_cache *cachep,
  		 gfp_t flags, int nodeid)
  {
  	return NULL;
  }
  
  static inline gfp_t gfp_exact_node(gfp_t flags)
  {
  	return flags & ~__GFP_NOFAIL;
  }
  
  #else	/* CONFIG_NUMA */
  
  static void *____cache_alloc_node(struct kmem_cache *, gfp_t, int);
  static void *alternate_node_alloc(struct kmem_cache *, gfp_t);
  
  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) {
  		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;
  		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 page_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[page_node]) {
  		alien = n->alien[page_node];
  		ac = &alien->ac;
  		spin_lock(&alien->lock);
  		if (unlikely(ac->avail == ac->limit)) {
  			STATS_INC_ACOVERFLOW(cachep);
  			__drain_alien_cache(cachep, ac, page_node, &list);
  		}
  		ac->entry[ac->avail++] = objp;
  		spin_unlock(&alien->lock);
  		slabs_destroy(cachep, &list);
  	} else {
  		n = get_node(cachep, page_node);
  		spin_lock(&n->list_lock);
  		free_block(cachep, &objp, 1, page_node, &list);
  		spin_unlock(&n->list_lock);
  		slabs_destroy(cachep, &list);
  	}
  	return 1;
  }
  
  static inline int cache_free_alien(struct kmem_cache *cachep, void *objp)
  {
  	int page_node = page_to_nid(virt_to_page(objp));
  	int node = numa_mem_id();
  	/*
  	 * Make sure we are not freeing a object from another node to the array
  	 * cache on this cpu.
  	 */
  	if (likely(node == page_node))
  		return 0;
  
  	return __cache_free_alien(cachep, objp, node, page_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) {
  		spin_lock_irq(&n->list_lock);
  		n->free_limit = (1 + nr_cpus_node(node)) * cachep->batchcount +
  				cachep->num;
  		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 is sufficient
  	 * protection here.
  	 */
  	cachep->node[node] = n;
  
  	return 0;
  }
  
  #if (defined(CONFIG_NUMA) && defined(CONFIG_MEMORY_HOTPLUG)) || 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 node 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);
  	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;
  	}
  
  	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;
  
  		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)) {
  			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;
  
  		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_list3 of any cache. This 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 list3 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) && defined(CONFIG_MEMORY_HOTPLUG)
  /*
   * 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 && CONFIG_MEMORY_HOTPLUG */
  
  /*
   * 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:
  	 */
  	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);
  	memcg_link_cache(kmem_cache, NULL);
  	slab_state = PARTIAL;
  
  	/*
  	 * Initialize the caches that provide memory for the  kmem_cache_node
  	 * structures first.  Without this, further allocations will bug.
  	 */
  	kmalloc_caches[KMALLOC_NORMAL][INDEX_NODE] = create_kmalloc_cache(
  				kmalloc_info[INDEX_NODE].name,
  				kmalloc_size(INDEX_NODE), ARCH_KMALLOC_FLAGS,
  				0, kmalloc_size(INDEX_NODE));
  	slab_state = PARTIAL_NODE;
  	setup_kmalloc_cache_index_table();
  
  	slab_early_init = 0;
  
  	/* 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;
  
  		spin_lock_irqsave(&n->list_lock, flags);
  		total_slabs = n->total_slabs;
  		free_slabs = n->free_slabs;
  		free_objs = n->free_objects;
  		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 page *kmem_getpages(struct kmem_cache *cachep, gfp_t flags,
  								int nodeid)
  {
  	struct page *page;
  
  	flags |= cachep->allocflags;
  
  	page = __alloc_pages_node(nodeid, flags, cachep->gfporder);
  	if (!page) {
  		slab_out_of_memory(cachep, flags, nodeid);
  		return NULL;
  	}
  
  	if (charge_slab_page(page, flags, cachep->gfporder, cachep)) {
  		__free_pages(page, cachep->gfporder);
  		return NULL;
  	}
  
  	__SetPageSlab(page);
  	/* Record if ALLOC_NO_WATERMARKS was set when allocating the slab */
  	if (sk_memalloc_socks() && page_is_pfmemalloc(page))
  		SetPageSlabPfmemalloc(page);
  
  	return page;
  }
  
  /*
   * Interface to system's page release.
   */
  static void kmem_freepages(struct kmem_cache *cachep, struct page *page)
  {
  	int order = cachep->gfporder;
  
  	BUG_ON(!PageSlab(page));
  	__ClearPageSlabPfmemalloc(page);
  	__ClearPageSlab(page);
  	page_mapcount_reset(page);
  	page->mapping = NULL;
  
  	if (current->reclaim_state)
  		current->reclaim_state->reclaimed_slab += 1 << order;
  	uncharge_slab_page(page, order, cachep);
  	__free_pages(page, order);
  }
  
  static void kmem_rcu_free(struct rcu_head *head)
  {
  	struct kmem_cache *cachep;
  	struct page *page;
  
  	page = container_of(head, struct page, rcu_head);
  	cachep = page->slab_cache;
  
  	kmem_freepages(cachep, page);
  }
  
  #if DEBUG
  static bool is_debug_pagealloc_cache(struct kmem_cache *cachep)
  {
  	if (debug_pagealloc_enabled_static() && OFF_SLAB(cachep) &&
  		(cachep->size % PAGE_SIZE) == 0)
  		return true;
  
  	return false;
  }
  
  #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 page *page = virt_to_head_page(objp);
  		unsigned int objnr;
  
  		objnr = obj_to_index(cachep, page, objp);
  		if (objnr) {
  			objp = index_to_obj(cachep, page, 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, page, 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 page *page)
  {
  	int i;
  
  	if (OBJFREELIST_SLAB(cachep) && cachep->flags & SLAB_POISON) {
  		poison_obj(cachep, page->freelist - obj_offset(cachep),
  			POISON_FREE);
  	}
  
  	for (i = 0; i < cachep->num; i++) {
  		void *objp = index_to_obj(cachep, page, 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 page *page)
  {
  }
  #endif
  
  /**
   * slab_destroy - destroy and release all objects in a slab
   * @cachep: cache pointer being destroyed
   * @page: page pointer being destroyed
   *
   * Destroy all the objs in a slab page, and release the mem back to the system.
   * Before calling the slab page 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 page *page)
  {
  	void *freelist;
  
  	freelist = page->freelist;
  	slab_destroy_debugcheck(cachep, page);
  	if (unlikely(cachep->flags & SLAB_TYPESAFE_BY_RCU))
  		call_rcu(&page->rcu_head, kmem_rcu_free);
  	else
  		kmem_freepages(cachep, page);
  
  	/*
  	 * From now on, we don't use freelist
  	 * although actual page can be freed in rcu context
  	 */
  	if (OFF_SLAB(cachep))
  		kmem_cache_free(cachep->freelist_cache, freelist);
  }
  
  static void slabs_destroy(struct kmem_cache *cachep, struct list_head *list)
  {
  	struct page *page, *n;
  
  	list_for_each_entry_safe(page, n, list, slab_list) {
  		list_del(&page->slab_list);
  		slab_destroy(cachep, page);
  	}
  }
  
  /**
   * 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;
  
  			freelist_size = num * sizeof(freelist_idx_t);
  			freelist_cache = kmalloc_slab(freelist_size, 0u);
  			if (!freelist_cache)
  				continue;
  
  			/*
  			 * 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,
  	void (*ctor)(void *))
  {
  	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 a ptr to the cache on success, NULL on failure.
   * Cannot be called within a int, but can be interrupted.
   * The @ctor is run when new pages are allocated by the cache.
   *
   * 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.
   *
   * Return: a pointer to the created cache or %NULL in case of error
   */
  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
  
  	if (OFF_SLAB(cachep)) {
  		cachep->freelist_cache =
  			kmalloc_slab(cachep->freelist_size, 0u);
  	}
  
  	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_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_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);
  	spin_lock(&n->list_lock);
  	free_block(cachep, ac->entry, ac->avail, node, &list);
  	spin_unlock(&n->list_lock);
  	slabs_destroy(cachep, &list);
  	ac->avail = 0;
  }
  
  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) {
  		spin_lock_irq(&n->list_lock);
  		drain_array_locked(cachep, n->shared, node, true, &list);
  		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 page *page;
  
  	nr_freed = 0;
  	while (nr_freed < tofree && !list_empty(&n->slabs_free)) {
  
  		spin_lock_irq(&n->list_lock);
  		p = n->slabs_free.prev;
  		if (p == &n->slabs_free) {
  			spin_unlock_irq(&n->list_lock);
  			goto out;
  		}
  
  		page = list_entry(p, struct page, slab_list);
  		list_del(&page->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;
  		spin_unlock_irq(&n->list_lock);
  		slab_destroy(cache, page);
  		nr_freed++;
  	}
  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);
  }
  
  #ifdef CONFIG_MEMCG
  void __kmemcg_cache_deactivate(struct kmem_cache *cachep)
  {
  	__kmem_cache_shrink(cachep);
  }
  
  void __kmemcg_cache_deactivate_after_rcu(struct kmem_cache *s)
  {
  }
  #endif
  
  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 disired-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 page *page, int colour_off,
  				   gfp_t local_flags, int nodeid)
  {
  	void *freelist;
  	void *addr = page_address(page);
  
  	page->s_mem = addr + colour_off;
  	page->active = 0;
  
  	if (OBJFREELIST_SLAB(cachep))
  		freelist = NULL;
  	else if (OFF_SLAB(cachep)) {
  		/* Slab management obj is off-slab. */
  		freelist = kmem_cache_alloc_node(cachep->freelist_cache,
  					      local_flags, nodeid);
  		if (!freelist)
  			return NULL;
  	} 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 page *page, unsigned int idx)
  {
  	return ((freelist_idx_t *)page->freelist)[idx];
  }
  
  static inline void set_free_obj(struct page *page,
  					unsigned int idx, freelist_idx_t val)
  {
  	((freelist_idx_t *)(page->freelist))[idx] = val;
  }
  
  static void cache_init_objs_debug(struct kmem_cache *cachep, struct page *page)
  {
  #if DEBUG
  	int i;
  
  	for (i = 0; i < cachep->num; i++) {
  		void *objp = index_to_obj(cachep, page, 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 */
  union freelist_init_state {
  	struct {
  		unsigned int pos;
  		unsigned int *list;
  		unsigned int count;
  	};
  	struct rnd_state rnd_state;
  };
  
  /*
   * Initialize the state based on the randomization methode available.
   * return true if the pre-computed list is available, false otherwize.
   */
  static bool freelist_state_initialize(union freelist_init_state *state,
  				struct kmem_cache *cachep,
  				unsigned int count)
  {
  	bool ret;
  	unsigned int rand;
  
  	/* Use best entropy available to define a random shift */
  	rand = get_random_int();
  
  	/* Use a random state if the pre-computed list is not available */
  	if (!cachep->random_seq) {
  		prandom_seed_state(&state->rnd_state, rand);
  		ret = false;
  	} else {
  		state->list = cachep->random_seq;
  		state->count = count;
  		state->pos = rand % 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(union 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 page *page, unsigned int a, unsigned int b)
  {
  	swap(((freelist_idx_t *)page->freelist)[a],
  		((freelist_idx_t *)page->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 page *page)
  {
  	unsigned int objfreelist = 0, i, rand, count = cachep->num;
  	union 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);
  		page->freelist = index_to_obj(cachep, page, 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(page, i, i);
  
  		/* Fisher-Yates shuffle */
  		for (i = count - 1; i > 0; i--) {
  			rand = prandom_u32_state(&state.rnd_state);
  			rand %= (i + 1);
  			swap_free_obj(page, i, rand);
  		}
  	} else {
  		for (i = 0; i < count; i++)
  			set_free_obj(page, i, next_random_slot(&state));
  	}
  
  	if (OBJFREELIST_SLAB(cachep))
  		set_free_obj(page, cachep->num - 1, objfreelist);
  
  	return true;
  }
  #else
  static inline bool shuffle_freelist(struct kmem_cache *cachep,
  				struct page *page)
  {
  	return false;
  }
  #endif /* CONFIG_SLAB_FREELIST_RANDOM */
  
  static void cache_init_objs(struct kmem_cache *cachep,
  			    struct page *page)
  {
  	int i;
  	void *objp;
  	bool shuffled;
  
  	cache_init_objs_debug(cachep, page);
  
  	/* Try to randomize the freelist if enabled */
  	shuffled = shuffle_freelist(cachep, page);
  
  	if (!shuffled && OBJFREELIST_SLAB(cachep)) {
  		page->freelist = index_to_obj(cachep, page, cachep->num - 1) +
  						obj_offset(cachep);
  	}
  
  	for (i = 0; i < cachep->num; i++) {
  		objp = index_to_obj(cachep, page, 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(page, i, i);
  	}
  }
  
  static void *slab_get_obj(struct kmem_cache *cachep, struct page *page)
  {
  	void *objp;
  
  	objp = index_to_obj(cachep, page, get_free_obj(page, page->active));
  	page->active++;
  
  	return objp;
  }
  
  static void slab_put_obj(struct kmem_cache *cachep,
  			struct page *page, void *objp)
  {
  	unsigned int objnr = obj_to_index(cachep, page, objp);
  #if DEBUG
  	unsigned int i;
  
  	/* Verify double free bug */
  	for (i = page->active; i < cachep->num; i++) {
  		if (get_free_obj(page, i) == objnr) {
  			pr_err("slab: double free detected in cache '%s', objp %px\n",
  			       cachep->name, objp);
  			BUG();
  		}
  	}
  #endif
  	page->active--;
  	if (!page->freelist)
  		page->freelist = objp + obj_offset(cachep);
  
  	set_free_obj(page, page->active, objnr);
  }
  
  /*
   * Map pages beginning at addr to the given cache and slab. This is required
   * for the slab allocator to be able to lookup the cache and slab of a
   * virtual address for kfree, ksize, and slab debugging.
   */
  static void slab_map_pages(struct kmem_cache *cache, struct page *page,
  			   void *freelist)
  {
  	page->slab_cache = cache;
  	page->freelist = freelist;
  }
  
  /*
   * 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 page *cache_grow_begin(struct kmem_cache *cachep,
  				gfp_t flags, int nodeid)
  {
  	void *freelist;
  	size_t offset;
  	gfp_t local_flags;
  	int page_node;
  	struct kmem_cache_node *n;
  	struct page *page;
  
  	/*
  	 * 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)) {
  		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();
  	}
  	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'.
  	 */
  	page = kmem_getpages(cachep, local_flags, nodeid);
  	if (!page)
  		goto failed;
  
  	page_node = page_to_nid(page);
  	n = get_node(cachep, page_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(page);
  
  	/* Get slab management. */
  	freelist = alloc_slabmgmt(cachep, page, offset,
  			local_flags & ~GFP_CONSTRAINT_MASK, page_node);
  	if (OFF_SLAB(cachep) && !freelist)
  		goto opps1;
  
  	slab_map_pages(cachep, page, freelist);
  
  	cache_init_objs(cachep, page);
  
  	if (gfpflags_allow_blocking(local_flags))
  		local_irq_disable();
  
  	return page;
  
  opps1:
  	kmem_freepages(cachep, page);
  failed:
  	if (gfpflags_allow_blocking(local_flags))
  		local_irq_disable();
  	return NULL;
  }
  
  static void cache_grow_end(struct kmem_cache *cachep, struct page *page)
  {
  	struct kmem_cache_node *n;
  	void *list = NULL;
  
  	check_irq_off();
  
  	if (!page)
  		return;
  
  	INIT_LIST_HEAD(&page->slab_list);
  	n = get_node(cachep, page_to_nid(page));
  
  	spin_lock(&n->list_lock);
  	n->total_slabs++;
  	if (!page->active) {
  		list_add_tail(&page->slab_list, &n->slabs_free);
  		n->free_slabs++;
  	} else
  		fixup_slab_list(cachep, n, page, &list);
  
  	STATS_INC_GROWN(cachep);
  	n->free_objects += cachep->num - page->active;
  	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 page *page;
  
  	BUG_ON(virt_to_cache(objp) != cachep);
  
  	objp -= obj_offset(cachep);
  	kfree_debugcheck(objp);
  	page = virt_to_head_page(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, page, objp);
  
  	BUG_ON(objnr >= cachep->num);
  	BUG_ON(objp != index_to_obj(cachep, page, 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 page *page,
  				void **list)
  {
  	/* move slabp to correct slabp list: */
  	list_del(&page->slab_list);
  	if (page->active == cachep->num) {
  		list_add(&page->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 = page->freelist;
  
  				*objp = *list;
  				*list = objp;
  			}
  #endif
  			page->freelist = NULL;
  		}
  	} else
  		list_add(&page->slab_list, &n->slabs_partial);
  }
  
  /* Try to find non-pfmemalloc slab if needed */
  static noinline struct page *get_valid_first_slab(struct kmem_cache_node *n,
  					struct page *page, bool pfmemalloc)
  {
  	if (!page)
  		return NULL;
  
  	if (pfmemalloc)
  		return page;
  
  	if (!PageSlabPfmemalloc(page))
  		return page;
  
  	/* No need to keep pfmemalloc slab if we have enough free objects */
  	if (n->free_objects > n->free_limit) {
  		ClearPageSlabPfmemalloc(page);
  		return page;
  	}
  
  	/* Move pfmemalloc slab to the end of list to speed up next search */
  	list_del(&page->slab_list);
  	if (!page->active) {
  		list_add_tail(&page->slab_list, &n->slabs_free);
  		n->free_slabs++;
  	} else
  		list_add_tail(&page->slab_list, &n->slabs_partial);
  
  	list_for_each_entry(page, &n->slabs_partial, slab_list) {
  		if (!PageSlabPfmemalloc(page))
  			return page;
  	}
  
  	n->free_touched = 1;
  	list_for_each_entry(page, &n->slabs_free, slab_list) {
  		if (!PageSlabPfmemalloc(page)) {
  			n->free_slabs--;
  			return page;
  		}
  	}
  
  	return NULL;
  }
  
  static struct page *get_first_slab(struct kmem_cache_node *n, bool pfmemalloc)
  {
  	struct page *page;
  
  	assert_spin_locked(&n->list_lock);
  	page = list_first_entry_or_null(&n->slabs_partial, struct page,
  					slab_list);
  	if (!page) {
  		n->free_touched = 1;
  		page = list_first_entry_or_null(&n->slabs_free, struct page,
  						slab_list);
  		if (page)
  			n->free_slabs--;
  	}
  
  	if (sk_memalloc_socks())
  		page = get_valid_first_slab(n, page, pfmemalloc);
  
  	return page;
  }
  
  static noinline void *cache_alloc_pfmemalloc(struct kmem_cache *cachep,
  				struct kmem_cache_node *n, gfp_t flags)
  {
  	struct page *page;
  	void *obj;
  	void *list = NULL;
  
  	if (!gfp_pfmemalloc_allowed(flags))
  		return NULL;
  
  	spin_lock(&n->list_lock);
  	page = get_first_slab(n, true);
  	if (!page) {
  		spin_unlock(&n->list_lock);
  		return NULL;
  	}
  
  	obj = slab_get_obj(cachep, page);
  	n->free_objects--;
  
  	fixup_slab_list(cachep, n, page, &list);
  
  	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 page *page, int batchcount)
  {
  	/*
  	 * There must be at least one object available for
  	 * allocation.
  	 */
  	BUG_ON(page->active >= cachep->num);
  
  	while (page->active < cachep->num && batchcount--) {
  		STATS_INC_ALLOCED(cachep);
  		STATS_INC_ACTIVE(cachep);
  		STATS_SET_HIGH(cachep);
  
  		ac->entry[ac->avail++] = slab_get_obj(cachep, page);
  	}
  
  	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 page *page;
  
  	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;
  
  	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. */
  		page = get_first_slab(n, false);
  		if (!page)
  			goto must_grow;
  
  		check_spinlock_acquired(cachep);
  
  		batchcount = alloc_block(cachep, ac, page, batchcount);
  		fixup_slab_list(cachep, n, page, &list);
  	}
  
  must_grow:
  	n->free_objects -= ac->avail;
  alloc_done:
  	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;
  		}
  
  		page = 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 && page)
  			alloc_block(cachep, ac, page, batchcount);
  		cache_grow_end(cachep, page);
  
  		if (!ac->avail)
  			return NULL;
  	}
  	ac->touched = 1;
  
  	return ac->entry[--ac->avail];
  }
  
  static inline void cache_alloc_debugcheck_before(struct kmem_cache *cachep,
  						gfp_t flags)
  {
  	might_sleep_if(gfpflags_allow_blocking(flags));
  }
  
  #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)
  		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 (ARCH_SLAB_MINALIGN &&
  	    ((unsigned long)objp & (ARCH_SLAB_MINALIGN-1))) {
  		pr_err("0x%px: not aligned to ARCH_SLAB_MINALIGN=%d\n",
  		       objp, (int)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
  /*
   * 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 high_zoneidx = gfp_zone(flags);
  	void *obj = NULL;
  	struct page *page;
  	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, high_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.
  		 */
  		page = cache_grow_begin(cache, flags, numa_mem_id());
  		cache_grow_end(cache, page);
  		if (page) {
  			nid = page_to_nid(page);
  			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;
  }
  
  /*
   * A interface to enable slab creation on nodeid
   */
  static void *____cache_alloc_node(struct kmem_cache *cachep, gfp_t flags,
  				int nodeid)
  {
  	struct page *page;
  	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();
  	spin_lock(&n->list_lock);
  	page = get_first_slab(n, false);
  	if (!page)
  		goto must_grow;
  
  	check_spinlock_acquired_node(cachep, nodeid);
  
  	STATS_INC_NODEALLOCS(cachep);
  	STATS_INC_ACTIVE(cachep);
  	STATS_SET_HIGH(cachep);
  
  	BUG_ON(page->active == cachep->num);
  
  	obj = slab_get_obj(cachep, page);
  	n->free_objects--;
  
  	fixup_slab_list(cachep, n, page, &list);
  
  	spin_unlock(&n->list_lock);
  	fixup_objfreelist_debug(cachep, &list);
  	return obj;
  
  must_grow:
  	spin_unlock(&n->list_lock);
  	page = cache_grow_begin(cachep, gfp_exact_node(flags), nodeid);
  	if (page) {
  		/* This slab isn't counted yet so don't update free_objects */
  		obj = slab_get_obj(cachep, page);
  	}
  	cache_grow_end(cachep, page);
  
  	return obj ? obj : fallback_alloc(cachep, flags);
  }
  
  static __always_inline void *
  slab_alloc_node(struct kmem_cache *cachep, gfp_t flags, int nodeid,
  		   unsigned long caller)
  {
  	unsigned long save_flags;
  	void *ptr;
  	int slab_node = numa_mem_id();
  
  	flags &= gfp_allowed_mask;
  	cachep = slab_pre_alloc_hook(cachep, flags);
  	if (unlikely(!cachep))
  		return NULL;
  
  	cache_alloc_debugcheck_before(cachep, flags);
  	local_irq_save(save_flags);
  
  	if (nodeid == NUMA_NO_NODE)
  		nodeid = slab_node;
  
  	if (unlikely(!get_node(cachep, nodeid))) {
  		/* Node not bootstrapped yet */
  		ptr = fallback_alloc(cachep, flags);
  		goto out;
  	}
  
  	if (nodeid == slab_node) {
  		/*
  		 * 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.
  		 */
  		ptr = ____cache_alloc(cachep, flags);
  		if (ptr)
  			goto out;
  	}
  	/* ___cache_alloc_node can fall back to other nodes */
  	ptr = ____cache_alloc_node(cachep, flags, nodeid);
    out:
  	local_irq_restore(save_flags);
  	ptr = cache_alloc_debugcheck_after(cachep, flags, ptr, caller);
  
  	if (unlikely(slab_want_init_on_alloc(flags, cachep)) && ptr)
  		memset(ptr, 0, cachep->object_size);
  
  	slab_post_alloc_hook(cachep, flags, 1, &ptr);
  	return ptr;
  }
  
  static __always_inline void *
  __do_cache_alloc(struct kmem_cache *cache, gfp_t flags)
  {
  	void *objp;
  
  	if (current->mempolicy || cpuset_do_slab_mem_spread()) {
  		objp = alternate_node_alloc(cache, flags);
  		if (objp)
  			goto out;
  	}
  	objp = ____cache_alloc(cache, flags);
  
  	/*
  	 * 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(cache, flags, numa_mem_id());
  
    out:
  	return objp;
  }
  #else
  
  static __always_inline void *
  __do_cache_alloc(struct kmem_cache *cachep, gfp_t flags)
  {
  	return ____cache_alloc(cachep, flags);
  }
  
  #endif /* CONFIG_NUMA */
  
  static __always_inline void *
  slab_alloc(struct kmem_cache *cachep, gfp_t flags, unsigned long caller)
  {
  	unsigned long save_flags;
  	void *objp;
  
  	flags &= gfp_allowed_mask;
  	cachep = slab_pre_alloc_hook(cachep, flags);
  	if (unlikely(!cachep))
  		return NULL;
  
  	cache_alloc_debugcheck_before(cachep, flags);
  	local_irq_save(save_flags);
  	objp = __do_cache_alloc(cachep, flags);
  	local_irq_restore(save_flags);
  	objp = cache_alloc_debugcheck_after(cachep, flags, objp, caller);
  	prefetchw(objp);
  
  	if (unlikely(slab_want_init_on_alloc(flags, cachep)) && objp)
  		memset(objp, 0, cachep->object_size);
  
  	slab_post_alloc_hook(cachep, flags, 1, &objp);
  	return objp;
  }
  
  /*
   * 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 page *page;
  
  	n->free_objects += nr_objects;
  
  	for (i = 0; i < nr_objects; i++) {
  		void *objp;
  		struct page *page;
  
  		objp = objpp[i];
  
  		page = virt_to_head_page(objp);
  		list_del(&page->slab_list);
  		check_spinlock_acquired_node(cachep, node);
  		slab_put_obj(cachep, page, objp);
  		STATS_DEC_ACTIVE(cachep);
  
  		/* fixup slab chains */
  		if (page->active == 0) {
  			list_add(&page->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(&page->slab_list, &n->slabs_partial);
  		}
  	}
  
  	while (n->free_objects > n->free_limit && !list_empty(&n->slabs_free)) {
  		n->free_objects -= cachep->num;
  
  		page = list_last_entry(&n->slabs_free, struct page, slab_list);
  		list_move(&page->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);
  	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 page *page;
  
  		list_for_each_entry(page, &n->slabs_free, slab_list) {
  			BUG_ON(page->active);
  
  			i++;
  		}
  		STATS_SET_FREEABLE(cachep, i);
  	}
  #endif
  	spin_unlock(&n->list_lock);
  	slabs_destroy(cachep, &list);
  	ac->avail -= batchcount;
  	memmove(ac->entry, &(ac->entry[batchcount]), sizeof(void *)*ac->avail);
  }
  
  /*
   * 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)
  {
  	/* Put the object into the quarantine, don't touch it for now. */
  	if (kasan_slab_free(cachep, objp, _RET_IP_))
  		return;
  
  	___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();
  	if (unlikely(slab_want_init_on_free(cachep)))
  		memset(objp, 0, cachep->object_size);
  	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 page *page = virt_to_head_page(objp);
  
  		if (unlikely(PageSlabPfmemalloc(page))) {
  			cache_free_pfmemalloc(cachep, page, objp);
  			return;
  		}
  	}
  
  	ac->entry[ac->avail++] = objp;
  }
  
  /**
   * kmem_cache_alloc - Allocate an object
   * @cachep: The cache to allocate from.
   * @flags: See kmalloc().
   *
   * Allocate an object from this cache.  The flags are only relevant
   * if the cache has no available objects.
   *
   * Return: pointer to the new object or %NULL in case of error
   */
  void *kmem_cache_alloc(struct kmem_cache *cachep, gfp_t flags)
  {
  	void *ret = slab_alloc(cachep, flags, _RET_IP_);
  
  	trace_kmem_cache_alloc(_RET_IP_, ret,
  			       cachep->object_size, cachep->size, flags);
  
  	return ret;
  }
  EXPORT_SYMBOL(kmem_cache_alloc);
  
  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)
  {
  	size_t i;
  
  	s = slab_pre_alloc_hook(s, flags);
  	if (!s)
  		return 0;
  
  	cache_alloc_debugcheck_before(s, flags);
  
  	local_irq_disable();
  	for (i = 0; i < size; i++) {
  		void *objp = __do_cache_alloc(s, flags);
  
  		if (unlikely(!objp))
  			goto error;
  		p[i] = objp;
  	}
  	local_irq_enable();
  
  	cache_alloc_debugcheck_after_bulk(s, flags, size, p, _RET_IP_);
  
  	/* Clear memory outside IRQ disabled section */
  	if (unlikely(slab_want_init_on_alloc(flags, s)))
  		for (i = 0; i < size; i++)
  			memset(p[i], 0, s->object_size);
  
  	slab_post_alloc_hook(s, flags, size, p);
  	/* FIXME: Trace call missing. Christoph would like a bulk variant */
  	return size;
  error:
  	local_irq_enable();
  	cache_alloc_debugcheck_after_bulk(s, flags, i, p, _RET_IP_);
  	slab_post_alloc_hook(s, flags, i, p);
  	__kmem_cache_free_bulk(s, i, p);
  	return 0;
  }
  EXPORT_SYMBOL(kmem_cache_alloc_bulk);
  
  #ifdef CONFIG_TRACING
  void *
  kmem_cache_alloc_trace(struct kmem_cache *cachep, gfp_t flags, size_t size)
  {
  	void *ret;
  
  	ret = slab_alloc(cachep, flags, _RET_IP_);
  
  	ret = kasan_kmalloc(cachep, ret, size, flags);
  	trace_kmalloc(_RET_IP_, ret,
  		      size, cachep->size, flags);
  	return ret;
  }
  EXPORT_SYMBOL(kmem_cache_alloc_trace);
  #endif
  
  #ifdef CONFIG_NUMA
  /**
   * 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, flags, nodeid, _RET_IP_);
  
  	trace_kmem_cache_alloc_node(_RET_IP_, ret,
  				    cachep->object_size, cachep->size,
  				    flags, nodeid);
  
  	return ret;
  }
  EXPORT_SYMBOL(kmem_cache_alloc_node);
  
  #ifdef CONFIG_TRACING
  void *kmem_cache_alloc_node_trace(struct kmem_cache *cachep,
  				  gfp_t flags,
  				  int nodeid,
  				  size_t size)
  {
  	void *ret;
  
  	ret = slab_alloc_node(cachep, flags, nodeid, _RET_IP_);
  
  	ret = kasan_kmalloc(cachep, ret, size, flags);
  	trace_kmalloc_node(_RET_IP_, ret,
  			   size, cachep->size,
  			   flags, nodeid);
  	return ret;
  }
  EXPORT_SYMBOL(kmem_cache_alloc_node_trace);
  #endif
  
  static __always_inline void *
  __do_kmalloc_node(size_t size, gfp_t flags, int node, unsigned long caller)
  {
  	struct kmem_cache *cachep;
  	void *ret;
  
  	if (unlikely(size > KMALLOC_MAX_CACHE_SIZE))
  		return NULL;
  	cachep = kmalloc_slab(size, flags);
  	if (unlikely(ZERO_OR_NULL_PTR(cachep)))
  		return cachep;
  	ret = kmem_cache_alloc_node_trace(cachep, flags, node, size);
  	ret = kasan_kmalloc(cachep, ret, size, flags);
  
  	return ret;
  }
  
  void *__kmalloc_node(size_t size, gfp_t flags, int node)
  {
  	return __do_kmalloc_node(size, flags, node, _RET_IP_);
  }
  EXPORT_SYMBOL(__kmalloc_node);
  
  void *__kmalloc_node_track_caller(size_t size, gfp_t flags,
  		int node, unsigned long caller)
  {
  	return __do_kmalloc_node(size, flags, node, caller);
  }
  EXPORT_SYMBOL(__kmalloc_node_track_caller);
  #endif /* CONFIG_NUMA */
  
  /**
   * __do_kmalloc - allocate memory
   * @size: how many bytes of memory are required.
   * @flags: the type of memory to allocate (see kmalloc).
   * @caller: function caller for debug tracking of the caller
   *
   * Return: pointer to the allocated memory or %NULL in case of error
   */
  static __always_inline void *__do_kmalloc(size_t size, gfp_t flags,
  					  unsigned long caller)
  {
  	struct kmem_cache *cachep;
  	void *ret;
  
  	if (unlikely(size > KMALLOC_MAX_CACHE_SIZE))
  		return NULL;
  	cachep = kmalloc_slab(size, flags);
  	if (unlikely(ZERO_OR_NULL_PTR(cachep)))
  		return cachep;
  	ret = slab_alloc(cachep, flags, caller);
  
  	ret = kasan_kmalloc(cachep, ret, size, flags);
  	trace_kmalloc(caller, ret,
  		      size, cachep->size, flags);
  
  	return ret;
  }
  
  void *__kmalloc(size_t size, gfp_t flags)
  {
  	return __do_kmalloc(size, flags, _RET_IP_);
  }
  EXPORT_SYMBOL(__kmalloc);
  
  void *__kmalloc_track_caller(size_t size, gfp_t flags, unsigned long caller)
  {
  	return __do_kmalloc(size, flags, caller);
  }
  EXPORT_SYMBOL(__kmalloc_track_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)
  {
  	unsigned long flags;
  	cachep = cache_from_obj(cachep, objp);
  	if (!cachep)
  		return;
  
  	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, _RET_IP_);
  	local_irq_restore(flags);
  
  	trace_kmem_cache_free(_RET_IP_, objp);
  }
  EXPORT_SYMBOL(kmem_cache_free);
  
  void kmem_cache_free_bulk(struct kmem_cache *orig_s, size_t size, void **p)
  {
  	struct kmem_cache *s;
  	size_t i;
  
  	local_irq_disable();
  	for (i = 0; i < size; i++) {
  		void *objp = p[i];
  
  		if (!orig_s) /* called via kfree_bulk */
  			s = virt_to_cache(objp);
  		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_enable();
  
  	/* FIXME: add tracing */
  }
  EXPORT_SYMBOL(kmem_cache_free_bulk);
  
  /**
   * kfree - free previously allocated memory
   * @objp: pointer returned by kmalloc.
   *
   * If @objp is NULL, no operation is performed.
   *
   * Don't free memory not originally allocated by kmalloc()
   * or you will run into trouble.
   */
  void kfree(const void *objp)
  {
  	struct kmem_cache *c;
  	unsigned long flags;
  
  	trace_kfree(_RET_IP_, objp);
  
  	if (unlikely(ZERO_OR_NULL_PTR(objp)))
  		return;
  	local_irq_save(flags);
  	kfree_debugcheck(objp);
  	c = virt_to_cache(objp);
  	if (!c) {
  		local_irq_restore(flags);
  		return;
  	}
  	debug_check_no_locks_freed(objp, c->object_size);
  
  	debug_check_no_obj_freed(objp, c->object_size);
  	__cache_free(c, (void *)objp, _RET_IP_);
  	local_irq_restore(flags);
  }
  EXPORT_SYMBOL(kfree);
  
  /*
   * 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);
  		spin_lock_irq(&n->list_lock);
  		free_block(cachep, ac->entry, ac->avail, node, &list);
  		spin_unlock_irq(&n->list_lock);
  		slabs_destroy(cachep, &list);
  	}
  	free_percpu(prev);
  
  setup_node:
  	return setup_kmem_cache_nodes(cachep, gfp);
  }
  
  static int do_tune_cpucache(struct kmem_cache *cachep, int limit,
  				int batchcount, int shared, gfp_t gfp)
  {
  	int ret;
  	struct kmem_cache *c;
  
  	ret = __do_tune_cpucache(cachep, limit, batchcount, shared, gfp);
  
  	if (slab_state < FULL)
  		return ret;
  
  	if ((ret < 0) || !is_root_cache(cachep))
  		return ret;
  
  	lockdep_assert_held(&slab_mutex);
  	for_each_memcg_cache(c, cachep) {
  		/* return value determined by the root cache only */
  		__do_tune_cpucache(c, limit, batchcount, shared, gfp);
  	}
  
  	return ret;
  }
  
  /* 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;
  
  	if (!is_root_cache(cachep)) {
  		struct kmem_cache *root = memcg_root_cache(cachep);
  		limit = root->limit;
  		shared = root->shared;
  		batchcount = root->batchcount;
  	}
  
  	if (limit && shared && batchcount)
  		goto skip_setup;
  	/*
  	 * 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;
  skip_setup:
  	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;
  	}
  
  	spin_lock_irq(&n->list_lock);
  	drain_array_locked(cachep, ac, node, false, &list);
  	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();
  		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;
  
  		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, struct page *page,
  			 bool to_user)
  {
  	struct kmem_cache *cachep;
  	unsigned int objnr;
  	unsigned long offset;
  
  	ptr = kasan_reset_tag(ptr);
  
  	/* Find and validate object. */
  	cachep = page->slab_cache;
  	objnr = obj_to_index(cachep, page, (void *)ptr);
  	BUG_ON(objnr >= cachep->num);
  
  	/* Find offset within object. */
  	offset = ptr - index_to_obj(cachep, page, 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;
  
  	/*
  	 * If the copy is still within the allocated object, produce
  	 * a warning instead of rejecting the copy. This is intended
  	 * to be a temporary method to find any missing usercopy
  	 * whitelists.
  	 */
  	if (usercopy_fallback &&
  	    offset <= cachep->object_size &&
  	    n <= cachep->object_size - offset) {
  		usercopy_warn("SLAB object", cachep->name, to_user, offset, n);
  		return;
  	}
  
  	usercopy_abort("SLAB object", cachep->name, to_user, offset, n);
  }
  #endif /* CONFIG_HARDENED_USERCOPY */
  
  /**
   * __ksize -- Uninstrumented ksize.
   * @objp: pointer to the object
   *
   * Unlike ksize(), __ksize() is uninstrumented, and does not provide the same
   * safety checks as ksize() with KASAN instrumentation enabled.
   *
   * Return: size of the actual memory used by @objp in bytes
   */
  size_t __ksize(const void *objp)
  {
  	struct kmem_cache *c;
  	size_t size;
  
  	BUG_ON(!objp);
  	if (unlikely(objp == ZERO_SIZE_PTR))
  		return 0;
  
  	c = virt_to_cache(objp);
  	size = c ? c->object_size : 0;
  
  	return size;
  }
  EXPORT_SYMBOL(__ksize);
  